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Publication numberUS20040011380 A1
Publication typeApplication
Application numberUS 10/410,803
Publication dateJan 22, 2004
Filing dateApr 10, 2003
Priority dateJul 18, 2002
Publication number10410803, 410803, US 2004/0011380 A1, US 2004/011380 A1, US 20040011380 A1, US 20040011380A1, US 2004011380 A1, US 2004011380A1, US-A1-20040011380, US-A1-2004011380, US2004/0011380A1, US2004/011380A1, US20040011380 A1, US20040011380A1, US2004011380 A1, US2004011380A1
InventorsBing Ji, Stephen Motika, Ronald Pearlstein, Eugene Karwacki, Dingjun Wu
Original AssigneeBing Ji, Motika Stephen Andrew, Pearlstein Ronald Martin, Karwacki Eugene Joseph, Dingjun Wu
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Method for etching high dielectric constant materials and for cleaning deposition chambers for high dielectric constant materials
US 20040011380 A1
Abstract
A process for the removal of a substance from a substrate for etching and/or cleaning applications is disclosed herein. In one embodiment, there is provided a process for removing a substance having a dielectric constant greater than silicon dioxide from a substrate by reacting the substance with a reactive agent that comprises at least one member from the group consisting a halogen-containing compound, a boron-containing compound, a hydrogen-containing compound, nitrogen-containing compound, a chelating compound, a carbon-containing compound, a chlorosilane, a hydrochlorosilane, or an organochlorosilane to form a volatile product and removing the volatile product from the substrate to thereby remove the substance from the substrate.
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Claims(33)
1. A process for cleaning a substance from a reactor surface, said process comprising:
providing a reactor containing the reactor surface, wherein: (a) the reactor surface is at least partially coated with a film of the substance; (b) the substance is at least one member selected from the group consisting of a transition metal oxide, a transition metal silicate, a Group 13 metal oxide, a Group 13 metal silicate, a nitrogen containing Group 13 metal oxide, a nitrogen containing Group 13 metal silicate, a nitrogen containing transition metal oxide, a nitrogen containing transition metal silicate, or a laminate comprising at least one layer selected from the group consisting of a transition metal oxide, a transition metal silicate, a Group 13 metal oxide, a Group 13 metal silicate, a nitrogen containing transition metal oxide, a nitrogen containing transition metal silicate, a nitrogen containing Group 13 metal oxide, or a nitrogen containing Group 13 metal silicate; and (c) the substance has a dielectric constant greater than the dielectric constant of silicon dioxide;
reacting the substance with a reactive agent to form a volatile product, wherein the reactive agent comprises at least one member selected from the group consisting of a halogen-containing compound; a boron-containing compound, a carbon-containing compound, a hydrogen-containing compound, a nitrogen-containing compound, a chelating compound, a chlorosilane compound, a hydrochlorosilane compound, or an organochlorosilane compound; and
removing the volatile product from the reactor to thereby remove the substance from the surface.
2. The process of claim 1, wherein the reactor is an atomic layer deposition reactor.
3. The process of claim 1, wherein the substance is at least one member selected from the group consisting of Al2O3, HfO2, ZrO2, HfSixOy, and ZrSixOy wherein x is a number greater than 0 and y is 2x +2, and any of the aforementioned compounds containing nitrogen.
4. The process of claim 1 wherein the reactive agent is at least one member selected from the group consisting of BCl3, COCl2, HCl, Cl2, ClF3, and NFzCl3-z, where z is an integer from 0 to 2.
5. The process of claim 4, wherein the reactive agent is COCl2 formed by an in situ reaction of CO and Cl2.
6. The process of claim 4, wherein the reactive agent is BCl3.
7. The process of claim 1 wherein the reactive agent is a carbon-containing compound having the formula CxHyClz, wherein x is a number ranging from 1 to 6, y is a number ranging from 0 to 13, and z is a number ranging 1 from 14.
8. The process of claim 1, wherein the reactive agent is conveyed to the substance from a gas cylinder, a safe delivery system or a vacuum delivery system.
9. The process of claim 1, wherein the reactive agent is formed in situ by a point-of-use generator.
10. The process of claim 1, wherein the substance is contacted with the reactive agent diluted with an inert gas diluent.
11. A process for removing a substance from at least a portion of the surface of a reaction chamber, the process comprising:
providing a reaction chamber wherein at least a portion of the surface is at least partially coated with the substance and wherein the substance has a dielectric constant of 4.1 or greater and is at least one member of the group consisting of a transition metal oxide, a transition metal silicate, a Group 13 metal oxide, a Group 13 metal silicate, a nitrogen containing Group 13 metal oxide, a nitrogen containing Group 13 metal silicate, a nitrogen containing transition metal oxide, a nitrogen containing transition metal silicate, or a laminate comprising at least one layer of the group consisting of a transition metal oxide, a transition metal silicate, a Group 13 metal oxide, a Group 13 metal silicate, a nitrogen containing Group 13 metal oxide, a nitrogen containing Group 13 metal silicate, a nitrogen containing transition metal oxide, a nitrogen containing transition metal silicate;
introducing a reactive agent into the reaction chamber wherein the reactive agent comprises at least one member selected from the group consisting of a halogen-containing compound; a boron-containing compound, a carbon-containing compound, a hydrogen-containing compound, a nitrogen-containing compound, a chelating compound, a chlorosilane compound, a hydrochlorosilane compound, or an organochlorosilane compound;
exposing the reactive agent to one or more energy sources sufficient to react the substance with the reactive agent and form a volatile product; and
removing the volatile product from the reaction chamber.
12. The process of claim 11, wherein the reactive agent is conveyed to the substance from a gas cylinder, a safe delivery system or a vacuum delivery system.
13. The process of claim 11, wherein the reactive agent is formed in situ by a point-of-use generator.
14. The process of claim 11, wherein the substance is contacted with the reactive agent diluted with an inert gas diluent.
15. The process of claim 11 wherein the reactive agent is deposited onto a nonreactive support.
16. The process of claim 11 wherein the reactive agent is exposed to one or more energy sources and the exposing step is conducted prior to the introducing step.
17. The process of claim 11 wherein the reactive agent is exposed to one or more energy sources and the exposing step is conducted during at least a portion of the introducing step.
18. The process of claim 11 wherein a temperature of the exposing step is at least 150° C.
19. The process of claim 11 wherein a pressure of the exposing step is at least 10 mTorr.
20. An apparatus for removing a substance from at least one surface of a reactor, the apparatus comprising:
an at least one reactive agent selected from the group consisting of a halogen-containing compound; a boron-containing compound, a carbon-containing compound, a hydrogen-containing compound, a nitrogen-containing compound, a chelating compound, a chlorosilane compound, a hydrochlorosilane compound, or an organochlorosilane compound; and
a non-reactive support having the at least one reactive agent deposited thereupon.
21. A mixture for removing a substance from at least one surface of a reactor, the mixture comprising:
an at least one reactive agent selected from the group consisting of a halogen-containing compound; a boron-containing compound, a carbon-containing compound, a hydrogen-containing compound, a nitrogen-containing compound, a chelating compound, a chlorosilane compound, a hydrochlorosilane compound, or an organochlorosilane compound; and
an inert diluent.
22. A process for removing a substance from an at least one surface of a substrate, said process comprising:
providing the substrate wherein the substrate is at least partially coated with a film of the substance that is at least one member selected from the group consisting of a transition metal oxide, a transition metal silicate, a Group 13 metal oxide other than Al2O3, a Group 13 metal silicate, a nitrogen containing Group 13 metal oxide, a nitrogen containing Group 13 metal silicate, a nitrogen containing transition metal oxide, a nitrogen containing transition metal silicate, or a laminate comprising at least one layer of the group consisting of a transition metal oxide, a transition metal silicate, a Group 13 metal oxide, a Group 13 metal silicate, a nitrogen containing Group 13 metal oxide, a nitrogen containing Group 13 metal silicate, a nitrogen containing transition metal oxide, or a nitrogen containing transition metal silicate; and wherein the substance has a dielectric constant greater than a dielectric constant of silicon dioxide;
reacting the substance with a reactive agent to form a volatile product, wherein the reactive agent comprises at least one member from the group consisting of a halogen-containing compound ; a boron-containing compound, a carbon-containing compound, a hydrogen-containing compound, a nitrogen-containing compound, a chelating compound, a chlorosilane compound, a hydrochlorosilane compound, or an organochlorosilane compound; and
removing the volatile product from the substrate to thereby remove the substance from the substrate.
23. The process of claim 22, wherein the substance is at least one member selected from the group consisting of HfO2, ZrO2, HfSixOy, ZrSixOy where x is greater than 0 and y is 2x +2, Al2SiwOz, where w is greater than 0 and z is 2w +3, or any of the aforementioned compounds containing nitrogen.
24. The process of claim 22, wherein the substance is a laminate comprising layers of at least one material selected from the group consisting of a transition metal oxide, a transition metal silicate, a Group 13 metal oxide, a Group 13 metal silicate, a nitrogen containing transition metal oxide, a nitrogen containing transition metal silicate, a nitrogen containing Group 13 metal oxide, or a nitrogen containing Group 13 metal silicate.
25. The process of claim 22, wherein the reactive agent is at least one member selected from the group consisting of BCl3, COCl2, HCl, Cl2, ClF3, and NFzCl3-z, where z is an integer from 0 to 2.
26. The process of claim 25, wherein the substance is at least one member selected from the group consisting of HfO2, ZrO2, HfSixOy, ZrSixOy, where x is greater than 0 and y is 2x +2, Al2SiwOz, where w is greater than 0 and z is 2w +3, or any of the aforementioned compounds containing nitrogen.
27. The process of claim 25, wherein the reactive agent is COCl2 formed by an in situ reaction of CO and Cl2.
28. The process of claim 25, wherein the reactive agent is BCl3.
29. The process of claim 22 wherein the reactive agent is a carbon-containing compound having the formula CxHyClz, wherein x is a number ranging from 1 to 6, y is a number ranging from 0 to 13, and z is a number ranging 1 from 14.
30. The process of claim 22 wherein the reactive agent is conveyed to the substance from a gas cylinder, a safe delivery system or a vacuum delivery system.
31. The process of claim 22 wherein the reactive agent is formed in situ by a point-of-use generator.
32. The process of claim 22 wherein the substance is contacted with the reactive agent diluted with an inert gas diluent.
33. The process of claim 22, wherein the substance is coated on the substrate by atomic layer deposition.
Description
    CROSS-REFERENCE TO RELATED APPLICATIONS
  • [0001]
    This application is a continuation-in-part of U.S. patent application Ser. No. 10/198,509, filed Jul. 18, 2002, the disclosure of which is incorporated herein by reference in its entirety.
  • BACKGROUND OF THE INVENTION
  • [0002]
    This invention relates to a method to etch high-k dielectric materials deposited on a substrate, and a method to clean residues from the internal surfaces of a reactor in which these high-k dielectric films are deposited.
  • [0003]
    In the manufacture of semiconductor integrated circuits (IC), dielectric materials such as silicon dioxide (SiO2), silicon nitride (Si3N4), and silicon oxynitride (SiON) have been widely used as insulators for transistor gates. Such insulators are often called gate dielectrics. As IC device geometry shrinks, gate dielectric layers have become progressively thinner. When the gate dielectric layer approaches thicknesses of a few nanometers or less, conventional SiO2, Si3N4, and SiON materials undergo electric breakdown and no longer provide insulation. To maintain adequate breakdown voltage at very small thickness (≦10 nm), high dielectric constant materials (i.e., high-k materials, which for present purposes are defined as materials where k is greater than about 4.1, the k of silicon dioxide) can be used as the gate insulating layer. In addition, high-k materials can also be used as the barrier layer in deep trench capacitors for semiconductor memory chip manufacturing. The IC industry has experimented with many high-k materials. The latest and most promising high-k materials are metal oxides such as Al2O3, HfO2, ZrO2, and mixtures thereof, and metal silicates such as HfSixOy, ZrSiO4, and mixtures thereof. In some instances, nitrogen may be incorporated into these metal oxides and metal silicates high-k materials (such as HfSiON or AlSiON) to improve the dielectric constant and to suppress crystallization of high-k materials. Crystallization of high-k materials such as HfO2 causes high leakage current and device failure. Therefore, incorporation of nitrogen can dramatically improve the device reliability.
  • [0004]
    High-k materials such as Al2O3, HfO2, and ZrO2 are very stable and resistive against most of the etching reactions, which has led to their use as etch stop layers and hard mask layers in plasma etching of other materials. See, e.g., K. K. Shih et al., “Hafnium dioxide etch-stop layer for phase-shifting masks”, J. Vac. Sci. Technol. B 11(6), pp. 2130-2131 (1993); J. A. Britten, et al., “Etch-stop characteristics of Sc2O3 and HfO2 films for multilayer dielectric grating applications”, J. Vac. Sci. Technol. A 14(5), pp. 2973-2975 (1996); J. Hong et al., “Comparison of Cl2 and F2 based chemistries for the inductively coupled plasma etching of NiMnSb thin films”, J. Vac. Sci. Technol. A 17(4), pp. 1326-1330 (1999); U.S. Pat. No. 5,972,722 to Visokay et al.; U.S. Pat. No. 6,211,035 B1 to Moise et al., U.S. patent application Publication US2001/0055852 A1 to Moise et al.; and EP 1,001,459 A2 to Moise et al.
  • [0005]
    These high-k materials are typically deposited from chemical precursors that react in a deposition chamber to form films in a chemical vapor deposition (CVD) process. In some instances, these high-k materials are deposited onto semiconductor substrates (wafers) by atomic layer deposition (ALD), in which the films are deposited in controlled, nearly monoatomic layers. Apparatus and processes for performing ALD are disclosed in, e.g., U.S. Pat. No. 5,879,459 to Gadgil et al., U.S. Pat. No. 6,174,377 B1 to Doering et al., U.S. patent application Publication US2001/0011526 A1 to Doering et al., U.S. Pat. No. 6,387,185 B2 to Doering et al., WO 00/40772 to Doering et al. and WO 00/79019 A1 to Gadgil et al. This family of patents assigned to Genus, Inc. teaches that “In situ plasma cleans allow the realization of a very long time between maintenance cleaning.” (See, e.g., U.S. Pat. No. 6,387,185 B2 at column 7, lines 27-28.) However, no details of any process for plasma cleaning of ALD chambers were given in the above family of disclosures.
  • [0006]
    Plasma sources have been used to enhance atomic layer deposition processes (PE-ALD). For example, Pomarede et al. in WO 02/43115 A2 teach the use of plasma sources to generate excited reactive species that prepare/activate the substrate surface to facilitate subsequent ALD. Nguyen et al. in WO 02/43114 A2 teach the use of a pulsing plasma to enact ALD processes instead of alternating precursor chemical flows. Again, these publications do not disclose any method to clean the ALD residues after the wafers have been processed.
  • [0007]
    Although the aforementioned high-k materials are excellent gate insulators, it is very difficult to dry etch these films for pattern transfer. While the deposition process desirably generates high-k films on a substrate (typically a silicon wafer), the reactions that form these films also occur non-productively on other exposed surfaces inside of the deposition chamber. Accumulation of deposition residues results in particle shedding, degradation of deposition uniformity, and processing drifts. These effects can lead to wafer defects and subsequent device failure. Therefore, all CVD chambers, and specifically ALD chambers, must be periodically cleaned.
  • [0008]
    Due to their extreme chemical inertness, there have been few attempts to dry etch these high-k materials. J. W. Lee et al. in “Electron cyclotron resonance plasma etching of oxides and SrS and ZnS-based electroluminescent materials for flat panel displays”, J. Vac. Sci. Technol. A 16(3), pp. 1944-1948 (1998), reported several chemistries to etch various metal oxides and sulfides. The authors used very powerful plasma conditions (800 W of microwave source power, up to 450 W of RF chuck bias power, and chamber pressure of 1.5 mTorr). The result of such process conditions is very high chuck bias voltage (up to 535 V). High chuck bias voltage can greatly enhance energetic ion sputtering and sputter induced etching. The authors used Cl2/Ar, BCl3/Ar, and SF6/Ar mixture under the extreme plasma conditions to etch various materials. Al2O3 showed the slowest etch rates. In most of their experiments, Al2O3 etch rates were less than 20% of the ZnS etch rates under identical conditions. The authors also noted “Fairly similar trends were seen with BCl3/Ar discharges, with the absolute rates being ˜20% lower than that for Cl2/Ar.” While the authors' method may be used for anisotropic etching of flat panel display devices, high power plasma sputtering cannot be achieved on grounded chamber surfaces. Therefore, the authors' methods cannot be extended to clean deposition residues within ALD chambers.
  • [0009]
    Williams et al. in U.S. Pat. No. 6,238,582 B1 teach a reactive ion beam etching (RIBE) method to etch thin film head materials such as Al2O3. The patentees used a CHF3/Ar plasma as the ion source. A collimated reactive ion beam impinges upon the wafer substrate to etch thin film materials. Such collimated ion beams cannot be used to clean deposition residues from ALD chambers.
  • [0010]
    Lagendijk et al. in U.S. Pat. Nos. 5,298,075 and 5,288,662 teach a “process for thermal oxidation of silicon or cleaning of furnace tubes . . . by exposing the silicon or tube to temperatures above 700° C. while flowing a carrier gas containing oxygen and a chlorohydrocarbon having a general formula CxHxClx where x is 2, 3, or 4 over the silicon or tube. The chlorohydrocarbon is selected to readily and completely oxidize at temperature.” (See Abstract.) Oxidation of silicon into SiO2 and gettering metal contaminants (such as Na and Fe) in oxidation or diffusion furnaces is a completely different process than etching/cleaning high-k materials.
  • [0011]
    Various references discuss adding certain compounds to the plasma in order to effect the etch rate of Al2O3. The references, W. G. M. Van Den Hoek, “The Etch Mechanism for Al2O3 in Fluorine and Chlorine Based RF Dry Etch Plasmas”. Met. Res. Soc. Symp. Proc. Vol. 68 (1986), pp. 71-78 and Heiman, et al., “High Rate Reactive Ion Etching of Al2O3 and Si”, J. Vac. Sci. Tech., 17(3), May/June 1980, pp. 731-34, disclose adding a fluorine based gas or a chlorine based gas, respectively, to an Ar plasma to increase the etch rate of Al2O3. However, these studies were all under the reactive ion etch (RIE) conditions. Ion bombardment/sputter induced reactions play a much large role than chemical etching reactions. Like other prior arts, such extreme RIE conditions do not apply to cleaning grounded chamber surfaces.
  • [0012]
    In view of the dearth of art disclosing the removal of high k dielectric residues, ALD reactors have typically been cleaned by mechanical means (scrubbing or blasting) to clean up the deposition residues from the internal surfaces of the chamber and downstream equipment (e.g. pump headers and exhaust manifolds). However, mechanical cleaning methods are time-consuming, labor-intensive, and damaging to the surfaces being cleaned.
  • [0013]
    Fluorine-containing plasma-based processes (i.e., dry cleaning) are commonly used to remove residues of silicon compounds (such as polycrystalline silicon, SiO2, SiON, and Si3N4) and tungsten from the interior surfaces of chemical vapor deposition (CVD) reactors. Here, fluorine reacts with the aforementioned residues to produce SiF4, a volatile species that can be pumped out of the reactor during the cleaning process. However, fluorine-based chemistry alone is ineffective to remove the high-k dielectric materials discussed above. See, e.g., J. Hong et al., J. Vac. Sci. Technol. A, Vol. 17, pp1326-1330, 1999, wherein the authors exposed Al2O3 coated wafers to NF3/Ar based inductively coupled plasmas, and found that “the greater concentration of atomic F available at high source power contributed to thicker fluorinated surfaces, leading to the net deposition rather than etching.” In the case of high-k materials the metal fluoride product that forms is nonvolatile and, thus, difficult to remove from the reactor.
  • [0014]
    Thus, there is an urgent need for a process to chemically dry clean high-k material residues, such as Al2O3, HfO2, ZrO2, HfSixOy, ZrSixOy and mixtures thereof, residues of laminates containing high-k materials such as HfAIO, and residues from nitrogen containing high-k material such as HfAlON, from ALD chambers without venting/opening up the chamber. An effective chemical dry cleaning method will significantly increase the productivity and lower the cost-of-ownership (CoO) for ALD-based deposition processes.
  • [0015]
    All references cited herein are incorporated herein by reference in their entireties.
  • BRIEF SUMMARY OF THE INVENTION
  • [0016]
    Accordingly, the invention provides process for cleaning a substance from a reactor surface comprising: providing a reactor containing the reactor surface, wherein: (a) the reactor surface is at least partially coated with a film of the substance; (b) the substance is at least one member selected from the group consisting of a transition metal oxide, a transition metal silicate, a Group 13 metal oxide, a Group 13 metal silicate, a nitrogen containing Group 13 metal oxide, a nitrogen containing Group 13 metal silicate, a nitrogen containing transition metal oxide, a nitrogen containing transition metal silicate, or a laminate comprising at least one layer selected from the group consisting of a transition metal oxide, a transition metal silicate, a Group 13 metal oxide, a Group 13 metal silicate, a nitrogen containing transition metal oxide, a nitrogen containing transition metal silicate, a nitrogen containing Group 13 metal oxide, or a nitrogen containing Group 13 metal silicate; and (c) the substance has a dielectric constant greater than the dielectric constant of silicon dioxide; reacting the substance with a reactive agent to form a volatile product, wherein the reactive agent comprises at least one member selected from the group consisting of a halogen-containing compound; a boron-containing compound, a carbon-containing compound, a hydrogen-containing compound, a nitrogen-containing compound, a chelating compound, a chlorosilane compound, a hydrochlorosilane compound, or an organochlorosilane compound; and removing the volatile product from the reactor to thereby remove the substance from the surface.
  • [0017]
    Further provided is a process for removing a substance from a surface of a reaction chamber comprising: providing a reaction chamber wherein at least a portion of the surface is at least partially coated with the substance and wherein the substance has a dielectric constant of 4.1 or greater and is at least one member of the group consisting of a transition metal oxide, a transition metal silicate, a Group 13 metal oxide, a Group 13 metal silicate, a nitrogen containing Group 13 metal oxide, a nitrogen containing Group 13 metal silicate, a nitrogen containing transition metal oxide, a nitrogen containing transition metal silicate, or a laminate comprising at least one layer of the group consisting of a transition metal oxide, a transition metal silicate, a Group 13 metal oxide, a Group 13 metal silicate, a nitrogen containing Group 13 metal oxide, a nitrogen containing Group 13 metal silicate, a nitrogen containing transition metal oxide, a nitrogen containing transition metal silicate; introducing a reactive agent into the reaction chamber wherein the reactive agent comprises at least one member selected from the group consisting of a halogen-containing compound; a boron-containing compound, a carbon-containing compound, a hydrogen-containing compound, a nitrogen-containing compound, a chelating compound, a chlorosilane compound, a hydrochlorosilane compound, or an organochlorosilane compound; exposing the reactive agent to one or more energy sources sufficient to react the substance with the reactive agent and form a volatile product; and removing the volatile product from the reaction chamber.
  • [0018]
    Still further provided is an apparatus for removing a substance from at least one surface of a reactor comprising: an at least one reactive agent selected from the group consisting of a halogen-containing compound; a boron-containing compound, a carbon-containing compound, a hydrogen-containing compound, a nitrogen-containing compound, a chelating compound, a chlorosilane compound, a hydrochlorosilane compound, or an organochlorosilane compound; and a non-reactive support having the at least one reactive agent deposited thereupon.
  • [0019]
    Still also provided is a mixture for removing a substance from at least one surface of a reactor comprising: an at least one reactive agent selected from the group consisting of a halogen-containing compound; a boron-containing compound, a carbon-containing compound, a hydrogen-containing compound, a nitrogen-containing compound, a chelating compound, a chlorosilane compound, a hydrochlorosilane compound, or an organochlorosilane compound; and an inert diluent.
  • [0020]
    Further provided is a process for removing a substance from an at least one surface of a substrate comprising: providing the substrate wherein the substrate is at least partially coated with a film of the substance that is at least one member selected from the group consisting of a transition metal oxide, a transition metal silicate, a Group 13 metal oxide other than Al2O3, a Group 13 metal silicate, a nitrogen containing Group 13 metal oxide, a nitrogen containing Group 13 metal silicate, a nitrogen containing transition metal oxide, a nitrogen containing transition metal silicate, or a laminate comprising at least one layer of the group consisting of a transition metal oxide, a transition metal silicate, a Group 13 metal oxide, a Group 13 metal silicate, a nitrogen containing Group 13 metal oxide, a nitrogen containing Group 13 metal silicate, a nitrogen containing transition metal oxide, or a nitrogen containing transition metal silicate; and wherein the substance has a dielectric constant greater than a dielectric constant of silicon dioxide; reacting the substance with a reactive agent to form a volatile product, wherein the reactive agent comprises at least one member from the group consisting of a halogen-containing compound ; a boron-containing compound, a carbon-containing compound, a hydrogen-containing compound, a nitrogen-containing compound, a chelating compound, a chlorosilane compound, a hydrochlorosilane compound, or an organochlorosilane compound; and removing the volatile product from the substrate to thereby remove the substance from the substrate.
  • [0021]
    These and other aspects of the invention will become apparent from the following detailed description.
  • BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS
  • [0022]
    [0022]FIGS. 1a and 1 b provides an illustration of an apparatus suitable for performing chamber cleaning using an internal energy source or a remote energy source, respectively.
  • [0023]
    [0023]FIG. 2 provides an illustration of an apparatus for performing a process of the invention using plasma as the energy source.
  • [0024]
    [0024]FIG. 3 provides a graphical illustration of the relative BCl3 plasma etch rates of various high dielectric constant materials, normalized to Al2O3.
  • [0025]
    [0025]FIG. 4 provides an illustration of an apparatus for performing a process of the invention using thermal heating as the energy source
  • [0026]
    [0026]FIG. 5 provides an illustration of the etch rate dependence on lower electrode/pedestal set temperature at constant chamber pressure and BCl3 flow rate.
  • [0027]
    [0027]FIG. 6 provides an illustration of the etch rate dependence on chamber pressure at constant lower electrode set temperature and BCl3 flow rate.
  • DETAILED DESCRIPTION OF THE INVENTION
  • [0028]
    The inventive process is useful for dry-etching high-k materials and dry-cleaning chemical vapor deposition (CVD) chambers (and more specifically, ALD chambers) used to deposit high-k materials onto wafer surfaces. The material to be removed from the surface being etched or cleaned is converted from a solid non-volatile material into species that have higher volatility than the high-k materials deposited thereupon and can be subsequently removed, for example, by reactor vacuum pumps. Thus, in preferred embodiments, the invention removes a substance from a substrate using a reactive agent to volatilize the substance. Unlike wet-etching and wet-cleaning processes, dry-etching and dry-cleaning processes do not immerse the substrate in or expose the substrate to liquid chemical solutions.
  • [0029]
    In certain embodiments, the substance to be removed can be a transition metal oxide, a transition metal silicate, a Group 13 metal oxide or a Group 13 metal silicate (in accordance with the IUPAC Nomenclature of Inorganic Chemistry, Recommendations 1990, Group 13 metals include Al, Ga, In and Tl, and the transition metals occupy Groups 3-12). The substance may be a high-k material having a dielectric constant greater than that of silicon dioxide (i.e., greater than about 4.1), more preferably greater than 5, even more preferably at least 7. Preferably, the substance is at least one member selected from the group consisting of Al2O3, HfO2, ZrO2, HfSixOy, ZrSixOy, and mixtures thereof. Those skilled in the art will appreciate that the formula HfSixOy (and the formula ZrSixOy) represents a mixture of HfO2 (ZrO2) and SiO2, where x is greater than 0 and y is2x+2.
  • [0030]
    In other embodiments of the present invention, the substance may be a laminate comprising layers of at least one member selected from the group of the following materials: a transition metal oxide, a transition metal silicate, a Group 13 metal oxide, a Group 13 metal silicate, a nitrogen containing transition metal oxide, a nitrogen containing transition metal silicate, a nitrogen containing Group 13 metal oxide, or a nitrogen containing Group 13 metal silicate. The laminate is preferably alternating between at least one of the foregoing materials and, optionally, other materials such as insulating materials. For example, the laminate may be comprised of alternating layers of HfO2 and Al2O3. The laminate may also consist of a certain number of layers of a first material and a certain number of layers of a second material or, alternatively, outer layers of at least one first material and inner layers of at least one second material.
  • [0031]
    In yet a further embodiment of the present invention, the substance may be a nitrogen containing material such as a nitrogen containing transition metal oxide, a nitrogen containing transition metal silicate, a nitrogen containing Group 13 metal oxide, or a nitrogen containing Group 13 metal silicate. An example of this type of substance includes HfAlON.
  • [0032]
    As mentioned previously, the substance to be removed is reacted with a reactive agent to form a volatile product which can be readily removed from the substrate. In certain preferred embodiments, the reactive agent may be exposed to one or more energy sources sufficient to form active species which react and form the volatile product. Examples of suitable reactive agents include: a halogen-containing compound such as a chloride, bromide, or iodide compound; a boron-containing compound, a carbon-containing compound, a hydrogen-containing compound, a nitrogen-containing compound, a chelating compound, a chlorosilane compound, a hydrochlorosilane compound, an organochlorosilane compound, or a mixture thereof. Although the reactive agents used herein may be sometimes described as “gaseous”, it is understood that the chemical reagents may be delivered directly as a gas to the reactor, delivered as a vaporized liquid, a sublimed solid and/or transported by an inert diluent gas into the reactor.
  • [0033]
    The reactive agents can be delivered to the reaction chamber by a variety of means, such as, for example, conventional cylinders, safe delivery systems, vacuum delivery systems, solid or liquid-based generators that create the reactive agent at the point of use. In one embodiment of the present invention, at least one reactive agent can be added to a non-reactive liquid or gaseous diluent and applied to the substrate having the substance to be removed as a spray or other means. The reactive agent can react with the substance to form the volatile product upon exposure to one or more energy sources. In an alternative embodiment such as for chamber cleaning applications, the reactive agent(s) can be deposited onto a non-reactive support which can be introduced into the reaction chamber. The material of the non-reactive support is one that will not react with the reactive agent prior to or during exposure to one of energy sources. In certain preferred embodiments, the non-reactive support has a plurality of pores. The reactive agent(s) can be released upon exposure to one or more energy sources and react with the substance to be removed to form the volatile product.
  • [0034]
    Since the chlorides of these metals (such as AlCl3, HfCl4, ZrCl4, and SiCl4) are more volatile, it is preferred to convert these high-k substances into chlorides. This conversion is accomplished by contacting the substance to be removed with a reactive agent containing chlorine. Preferred examples of chlorine-containing reactive agents include BCl3, COCl2, HCl, Cl2, ClF3, and NFxCl3-x, where x is an integer from 0 to 2, chlorocarbons, and chlorohydrocarbons (such as CxHyClz where x is a number ranging from 1 to 6, y is a number ranging from 0 to 13, and z is a number ranging from 1 to 14). Chlorine-containing reactive agents that also contain oxygen-getter functions, such as BCl3, COCl2, chlorocarbons and chlorohydrocarbons, are more preferred because the oxygen-getter component (B, CO, C, or H) in these molecules extracts oxygen from the high-k materials and hence enhances the conversion of metal oxides and metal silicates into metal chlorides. Among the chlorine-containing and oxygen-getter gases, BCl3 is the most preferred one. In embodiments employing COCl2 as the reactive agent it can be provided in prepared form or formed by an in situ reaction of CO and Cl2. In embodiments for removing metal silicates, the reactive agent can comprise a chlorine-containing gas and a fluorine-containing gas (e.g., BCl3 and BF3), or a gas containing both fluorine and chlorine such as ClF3, and NFzCl3, where z is an integer from 0 to 2.
  • [0035]
    In addition to the reactive agents described herein, inert diluent gases such as nitrogen, CO2, helium, neon, argon, krypton, and xenon etc. can also be added. Inert diluent gases can modify the plasma characteristics and cleaning processes to better suit some specific applications. The concentration of the inert gases can range from 0 to 99%.
  • [0036]
    The process of the invention is useful for etching substances from the surfaces of a substrate. Thus, suitable substrates for the etching embodiments of the invention include, e.g., semiconductor wafers and the like. FIG. 3 shows a comparison of the relative etch rate of hafnium oxide, aluminum oxide, and zirconium oxide for one embodiment of the present invention using BCl3 as the reactive agent.
  • [0037]
    The present invention may be also suitable for cleaning substances from substrates such as surfaces of reaction chambers for CVD and/or ALD processes. The present invention is particularly suited for removing high k substances that have deposited onto the exposed surfaces of a reaction chamber such as, for example, the workpiece platform, grounded sidewalls, and/or showerhead of a typical reaction chamber.
  • [0038]
    Thermal or plasma activation and/or enhancement can significantly impact the efficacy of dry etching and dry cleaning of high-k materials. For thermal activation, the substrate can be heated up to 600° C., more preferably up to 400° C., and even more preferably up to 300° C. The pressure range is generally 10 mTorr to 760 Torr, more preferably 1 Torr to 760 Torr.
  • [0039]
    For in situ plasma activation, one can generate the plasma with a 13.56 MHz RF power supply, with RF power density at least 0.2 W/cm2, more preferably at least 0.5 W/cm2, even more preferably at least 1 W/cm2. One can also operate the in situ plasma at RF frequencies lower than 13.56 MHz to enhance ion assisted cleaning of grounded ALD chamber walls. The operating pressure is generally in the range of 2.5 mTorr to 100 Torr, more preferably 5 mTorr to 50 Torr, even more preferably 10 mTorr to 20 Torr. Optionally, one can also combine thermal and plasma enhancement for more effective cleaning of ALD chamber walls.
  • [0040]
    One can also use a remote plasma source to replace an in situ plasma to generate more reactive species. The remote plasma source can be generated by either an RF or a microwave source. In addition, reactions between remote plasma generated reactive species and high-k materials can be activated/enhanced by heating ALD reactor components to elevated temperatures up to 600° C., more preferably up to 400° C., and even more preferably up to 300° C.
  • [0041]
    Other means of activation and enhancement to the cleaning processes can also be employed. For example, one can use photon induced chemical reactions to generate reactive species and enhance the etching/cleaning reactions.
  • [0042]
    The following tables show thermochemical calculations for preferred reactions for volatilizing the substance to be removed from the substrate. In these tables, Keq represents the equilibrium constant for the reaction as written; so that the larger this value is, the more favorable the reaction will be to proceed.
    TABLE 1
    Al2O3 reaction with BCl3:
    Al2O3 + 2BCl3(g) B2O3 + 2AlCl3(g)
    Temperature (° C.) ΔH (Kcal) ΔS (Cal) ΔG (Kcal) Keq
    0.000 9.561 12.274 6.208 1.078E−005
    100.000 9.547 12.249 4.976 1.217E−003
    200.000 9.424 11.959 3.766 1.822E−002
    300.000 9.299 11.719 2.582 1.036E−001
    400.000 9.196 11.553 1.419 3.461E−001
    500.000 15.123 19.739 −0.138 1.094E+000
    600.000 15.476 20.169 −2.135 3.422E+000
    700.000 15.748 20.464 −4.167 8.629E+000
    800.000 15.951 20.664 −6.224 1.852E+001
    900.000 16.097 20.794 −8.298 3.515E+001
    1000.000 16.190 20.871 −10.381 6.056E+001
  • [0043]
    [0043]
    TABLE 2
    HfO2 reaction with BCl3:
    1.5HfO2 + 2BCl3(g) 1.5HfCl4(g) + B2O3
    Temperature (° C.) ΔH (Kcal) ΔS (Cal) ΔG (Kcal) Keq
    0.000 −17.999 −12.638 −14.547 4.367E+011
    25.000 −18.003 −12.653 −14.231 2.707E+010
    50.000 −18.025 −12.721 −13.914 2.576E+009
    75.000 −18.057 −12.817 −13.595 3.426E+008
    100.000 −18.096 −12.924 −13.273 5.950E+007
    125.000 −18.138 −13.034 −12.948 1.283E+007
    150.000 −18.182 −13.141 −12.621 3.305E+006
    175.000 −18.226 −13.242 −12.291 9.879E+005
    200.000 −18.268 −13.335 −11.959 3.346E+005
  • [0044]
    [0044]
    TABLE 3
    ZrO2 reaction with BCl3:
    1.5ZrO2 + 2BCl3(g) 1.5ZrCl4(g) + B2O3
    Temperature (° C.) ΔH (Kcal) ΔS (Cal) ΔG (Kcal) Keq
    0.000 −29.845 −12.107 −26.538 1.717E+021
    25.000 −29.825 −12.038 −26.236 1.710E+019
    50.000 −29.822 −12.026 −25.935 3.481E+017
    75.000 −29.828 −12.047 −25.634 1.239E+016
    100.000 −29.842 −12.083 −25.333 6.891E+014
    125.000 −29.858 −12.126 −25.030 5.502E+013
    150.000 −29.875 −12.168 −24.726 5.913E+012
    175.000 −29.892 −12.207 −24.422 8.142E+011
    200.000 −29.908 −12.240 −24.116 1.381E+011
  • [0045]
    [0045]
    TABLE 4
    HfO2 reaction with COCl2:
    HfO2 + 2COCl2(g) HfCl4(g) + 2CO2(g)
    Temperature (° C.) ΔH (Kcal) ΔS (Cal) ΔG (Kcal) Keq
    0.000 −20.643 41.960 −32.105 4.890E+025
    25.000 −20.649 41.940 −33.153 2.014E+024
    50.000 −20.668 41.878 −34.201 1.357E+023
    75.000 −20.699 41.787 −35.247 1.343E+022
    100.000 −20.739 41.677 −36.290 1.806E+021
    125.000 −20.786 41.554 −37.331 3.112E+020
    150.000 −20.840 41.423 −38.368 6.578E+019
    175.000 −20.900 41.285 −39.402 1.647E+019
    200.000 −20.965 41.144 −40.432 4.757E+018
  • [0046]
    [0046]
    TABLE 5
    ZrO2 reaction with COCl2:
    ZrO2 + 2COCl2(g) ZrCl4(g) + 2CO2(g)
    Temperature (° C.) ΔH (Kcal) ΔS (Cal) ΔG (Kcal) Keq
    0.000 −28.540 42.313 −40.098 1.218E+032
    25.000 −28.530 42.350 −41.157 1.483E+030
    50.000 −28.533 42.341 −42.215 3.573E+028
    75.000 −28.547 42.300 −43.273 1.469E+027
    100.000 −28.569 42.238 −44.330 9.244E+025
    125.000 −28.599 42.160 −45.385 8.215E+024
    150.000 −28.636 42.071 −46.438 9.694E+023
    175.000 −28.678 41.975 −47.489 1.448E+023
    200.000 −28.724 41 .873 −48.537 2.638E+022
  • [0047]
    [0047]
    TABLE 6
    ZrSiO4 reaction with BCl3:
    ZrSiO4 + 2.667BCl3(g) SiCl4(g) + ZrCl4(g) + 1.333B2O3
    Temperature (° C.) ΔH (Kcal) ΔS (Cal) ΔG (Kcal) Keq
    0.000 −31.065 −21.096 −25.303 1.764E+020
    25.000 −31.003 −20.879 −24.778 1.460E+018
    50.000 −30.962 −20.747 −24.258 2.554E+016
    75.000 −30.935 −20.665 −23.740 8.020E+014
    100.000 −30.916 −20.613 −23.224 4.013E+013
    125.000 −30.902 −20.577 −22.710 2.928E+012
    150.000 −30.891 −20.549 −22.196 2.914E+011
    175.000 −30.879 −20.523 −21.682 3.755E+010
    200.000 −30.867 −20.496 −21.169 6.012E+009
    225.000 −30.852 −20.466 −20.657 1.158E+009
    250.000 −30.835 −20.432 −20.146 2.612E+008
    275.000 −30.814 −20.393 −19.636 6.754E+007
    300.000 −30.790 −20.349 −19.127 1.967E+007
    325.000 −30.761 −20.300 −18.618 6.358E+006
    350.000 −30.729 −20.247 −18.112 2.252E+006
    375.000 −30.692 −20.190 −17.606 8.652E+005
    400.000 −30.652 −20.130 −17.102 3.572E+005
    425.000 −30.608 −20.066 −16.600 1.573E+005
    450.000 −22.891 −9.391 −16.100 7.349E+004
    475.000 −22.663 −9.081 −15.869 4.327E+004
    500.000 −22.443 −8.791 −15.646 2.649E+004
  • [0048]
    [0048]
    TABLE 7
    ZrSiO4 reaction with BF3 and BCl3: ZrSiO4 + 1.333BF3(g) +
    1.333BCl3(g) SiF4(g) + ZrCl4(g) + 1.333B2O3
    Temperature (° C.) ΔH (Kcal) ΔS (Cal) ΔG (Kcal) Keq
    0.000 −25.010 −21.014 −19.270 2.627E+015
    25.000 −24.951 −20.807 −18.748 5.540E+013
    50.000 −24.912 −20.681 −18.229 2.136E+012
    75.000 −24.885 −20.600 −17.713 1.319E+011
    100.000 −24.865 −20.545 −17.199 1.186E+010
    125.000 −24.849 −20.502 −16.686 1.445E+009
    150.000 −24.833 −20.463 −16.174 2.260E+008
    175.000 −24.816 −20.423 −15.663 4.354E+007
    200.000 −24.796 −20.380 −15.153 9.992E+006
    225.000 −24.772 −20.332 −14.644 2.661E+006
    250.000 −24.745 −20.278 −14.136 8.053E+005
    275.000 −24.712 −20.218 −13.630 2.721E+005
    300.000 −24.675 −20.152 −13.125 1.012E+005
    325.000 −24.633 −20.080 −12.622 4.095E+004
    350.000 −24.586 −20.003 −12.121 1.784E+004
    375.000 −24.535 −19.922 −11.622 8.303E+003
    400.000 −24.478 −19.837 −11.125 4.095E+003
    425.000 −24.418 −19.749 −10.630 2.128E+003
    450.000 −16.684 −9.050 −10.139 1.160E+003
    475.000 −16.439 −8.717 −9.917 7.894E+002
    500.000 −16.201 −8.405 −9.703 5.535E+002
  • [0049]
    Tables 1-7 show that BCl3 and COCl2 can be used as the etchants for dry etching and cleaning of the high-k materials. BCl3 (boron trichloride) is a liquefied gas at room temperature and can be readily delivered into ALD reactors for chamber cleaning. COCl2 (phosgene) is preferably provided in situ in etch or deposition reactors by reacting gaseous carbon monoxide and chlorine to form phosgene assisted by an external energy source (e.g. plasma) as follows:
  • CO(g)+Cl2(g)→COCl2
  • [0050]
    In other embodiments of the present invention such as applications that are sensitive to boron residue, chlorocarbons (CC) and hydrochlorocarbons (HCC) may be employed as the reactive agent because these compounds may contain chlorine as well as oxygen getter components (C or H). The general formula for the CC and HCC compounds is CxHyClz, where x ranges from 1 to 6, y ranges from 0 to 13, and z ranges from 1 to 14. Examples of suitable CC and HCC compounds include, but are not limited to, trans-dichloroethylene C2H2Cl2 (a.k.a. Trans-LC®), cis-dichloroethylene, 1,1-dichloroethylele, 1,1,1-trichloroethane (C2H3Cl3), or tetrachloroethylene C2Cl4, C4H4Cl4, CHCl3, and CCl4. Some CC and HCC compounds may react with high-k metal oxides without the addition of oxygen. For example, in some embodiments, tetrachloroethylene (C2Cl4) can react with Al2O3 to form volatile byproducts as follows:
  • 1.5C2Cl4(g)+Al2O3→2AlCl3(g)+3CO(g)
  • [0051]
    Table 8 illustrates that the reaction is thermodynamically favorable at temperatures above 100° C.
    TABLE 8
    Thermodynamic data for reaction:
    1.5C2Cl4(g) + Al2O3 = 2AlCl3(g) + 3CO(g)
    T (° C.) ΔH (Kcal) ΔS (Cal) ΔG (Kcal) Keq
    0.000 46.723 157.382 3.734 1.028E−003
    100.000 46.760 157.552 −12.031 1.114E+007
    200.000 46.314 156.508 −27.738 6.509E+012
    300.000 45.599 155.144 −43.322 3.317E+016
    400.000 44.704 153.709 −58.765 1.204E+019
    500.000 43.674 152.284 −74.064 8.667E+020
    600.000 42.541 150.907 −89.223 2.160E+022
    700.000 41.340 149.605 −104.248 2.594E+023
    800.000 40.087 148.380 −119.147 1.848E+024
    900.000 38.793 147.228 −133.927 8.948E+024
    1000.000 37.467 146.143 −148.595 3.236E+025
  • [0052]
    The above thermochemical calculations are illustrations of limiting cases for those chemical reactions. In addition to the limiting case reaction products such as B2O3, intermediate reaction products such as boron oxychloride (BOCl) can also be formed in reactions between high-k materials and BCl3. Intermediate reaction products such as BOCl have higher volatility and thus may further enhance the removal of high-k materials.
  • [0053]
    Other CC and HCC compounds may need the addition of oxygen to release chlorine without forming carbon residues (soot). For example, trans-dichloroethylene (C2H2Cl2) (a.k.a. Trans-LC®) can react with Al2O3 at an O2:C2H2Cl2 molar ration of 2:1, 602(g)+Al2O3+3C2H2Cl2(g)=2AlCl3(g)+6CO2(g)+3H2O(g) Table 9 shows such a reaction is thermodynamically favorable at temperatures between 0 and 1000° C.
    TABLE 9
    Thermodynamic data for reaction: 6O2(g) + Al2O3 +
    3C2H2Cl2(g) = 2AlCl3(g) + 6CO2(g) + 3H2O(g)
    T (° C.) ΔH (Kcal) ΔS (Cal) ΔG (Kcal) Keq
    0.000 −616.464 77.981 −637.764 1.000E+308
    100.000 −616.428 78.113 −645.576 1.000E+308
    200.000 −616.656 77.585 −653.365 6.559E+301
    300.000 −617.145 76.654 −661.079 1.257E+252
    400.000 −617.872 75.490 −668.688 1.316E+217
    500.000 −618.811 74.193 −676.173 1.422E+191
    600.000 −619.918 72.848 −683.525 1.261E+171
    700.000 −621.140 71.523 −690.743 1.380E+155
    800.000 −622.440 70.253 −697.832 1.340E+142
    900.000 −623.784 69.056 −704.796 2.040E+131
    1000.000 −625.138 67.947 −711.646 1.485E+122
  • [0054]
    An excess amount of oxygen is undesirable in the above reactions since excess O2 can convert metal chlorides back to metal oxides. A better way to prevent excess oxygen is to oxidize carbon only partially into CO by running the reaction under an oxygen lean condition. For example, O2:C2H2Cl2 molar ratio of 1:1 can lead to the formation of CO and AlCl3 as the byproducts:
  • 3C2H2Cl2(g)+Al2O3+3O2=2AlCl3(g)+6CO(g)+3H2O(g)
  • [0055]
    As shown in Table 10, such partial oxidation reaction is also favorable thermodynamically.
    TABLE 10
    Thermodynamic data for reaction: 3C2H2Cl2(g) +
    Al2O3 + 3O2 = 2AlCl3(g) + 6CO(g) + 3H2O(g)
    T (° C.) ΔH (Kcal) ΔS (Cal) ΔG (Kcal) Keq
    0.000 −210.973 200.961 −265.865 5.480E+212
    100.000 −210.103 203.760 −286.136 3.984E+167
    200.000 −210.055 203.905 −306.532 3.982E+141
    300.000 −210.561 202.949 −326.881 4.512E+124
    400.000 −211.485 201.470 −347.105 5.046E+112
    500.000 −212.749 199.725 −367.166 6.267E+103
    600.000 −214.276 197.870 −387.046 7.688E+096
    700.000 −215.992 196.011 −406.740 2.255E+091
    800.000 −217.847 194.197 −426.250 6.518E+086
    900.000 −219.797 192.461 −445.582 1.037E+083
    1000.000 −221.800 190.822 −464.745 6.097E+079
  • [0056]
    Instead of oxygen, chlorine (Cl2) can be added to prevent the formation of carbon soot. For example, Cl2:C2H2Cl2 molar ratio of 2:1 allows the following reaction:
  • 2Cl2(g)+Al2O3+C2H2Cl2(g)=2AlCl3(g)+H2O(g)°2CO(g)
  • [0057]
    Similarly, Cl2:C2H2Cl2 molar ratio of 4:1 allows the following reaction:
  • 4Cl2(g)+Al2O3+C2H2Cl2(g)=3.333AlCl3(g)+H2O(g)+2CO2(g)
  • [0058]
    Both reactions are thermodynamically favorable, as shown in Tables 11 and 12. The use of chlorine to control soot formation is more desirable since excess amount of chlorine helps the chlorination of metal oxides.
    TABLE 11
    Thermodynamic data for reaction: 2Cl2(g) +
    Al2O3 + C2H2Cl2(g) = 2AlCl3(g) + H2O(g) + 2CO(g)
    T (° C.) ΔH (kcal) ΔS (kcal) ΔG (kcal) Keq
    0.000 10.291 101.403 −17.407 8.479E+013
    100.000 10.619 102.465 −27.616 1.498E+016
    200.000 10.554 102.326 −37.861 3.088E+017
    300.000 10.225 101.701 −48.065 2.135E+018
    400.000 9.697 100.855 −58.194 7.859E+018
    500.000 9.005 99.900 −68.233 1.946E+019
    600.000 8.185 98.904 −78.173 3.701E+019
    700.000 7.277 97.920 −88.014 5.858E+019
    800.000 6.303 96.967 −97.758 8.134E+019
    900.000 5.280 96.056 −107.409 1.026E+020
    1000.000 4.224 95.193 −116.971 1.205E+020
  • [0059]
    [0059]
    TABLE 12
    Thermodynamic data for reaction: 4Cl2(g) + Al2O3 +
    C2H2Cl2(g) = 3.333AlCl3(g) + H2O(g) + 2CO2(g)
    T (° C.) ΔH (kcal) ΔS (kcal) ΔG (kcal) Keq
    0.000 −44.076 94.797 −69.970 9.734E+055
    100.000 −43.990 95.096 −79.475 3.562E+046
    200.000 −44.229 94.542 −88.962 1.245E+041
    300.000 −44.715 93.617 −98.372 3.262E+037
    400.000 −45.399 92.520 −107.680 9.182E+034
    500.000 −46.255 91.338 −116.873 1.096E+033
    600.000 −47.248 90.132 −125.946 3.365E+031
    700.000 −48.328 88.961 −134.900 1.988E+030
    800.000 −49.475 87.840 −143.740 1.886E+029
    900.000 −50.671 86.775 −152.470 2.550E+028
    1000.000 −51.901 85.769 −161.097 4.532E+027
  • [0060]
    In addition to the chloride compounds, the bromide and iodide compounds of these high-k materials, such as AlBr3, AlI3, HfBr4, Hfl4, ZrBr4, and Zrl4 have a volatility similar to their corresponding chlorides. Therefore, some bromo- and iodo-compounds can also be used to etch/clean these high-k materials. Bromine and iodine ions are heavier than chlorine ions, hence bromine and iodine ions can provide more effective sputtering to energize plasma-assisted etch/clean reactions with high-k materials. Bromine and iodine atoms have higher surface sticking coefficients than chlorine atoms. A higher sticking coefficient relates to a higher probability for bromine and iodine atoms/ions to be adsorbed onto the surface of high-k materials hence enhancing the bromination/iodization reactions. Desirable bromo- and iodo-compounds preferably contain an oxygen-getter function in the molecule. Examples of suitable bromine and iodine containing compounds include boron tribromide (BBr3), boron triiodide (BI3), hydrogen bromide (HBr), hydro iodide (HI), bromocarbons such as CBr4, bromohydrocarbons such as trans-dibromoethylene (C2H2Br2), iodocarbons such as Cl4, and iodohydrocarbons such as trans-diiodoethylene (C2H2I2) etc. For HfO2, the bromine and iodine chemistries are dramatically more favorable than the corresponding chlorine chemistry, as shown in tables 13-15.
    TABLE 13
    Thermodynamic data for reaction:
    1.5HfO2 + 2BCl3(g) = 1.5HfCl4(g) + B2O3
    T (° C.) ΔH (kcal) ΔS (kcal) ΔG (kcal) Keq
    0.000 −17.999 −12.638 −14.547 4.367E+011
    100.000 −18.096 −12.924 −13.273 5.950E+007
    200.000 −18.268 −13.335 −11.959 3.346E+005
    300.000 −18.413 −13.614 −10.611 1.113E+004
    400.000 −18.507 −13.765 −9.241 1.001E+003
    500.000 −12.540 −5.525 −8.268 2.175E+002
    600.000 −12.126 −5.020 −7.743 8.672E+001
    700.000 −11.790 −4.655 −7.260 4.271E+001
    800.000 −11.524 −4.395 −6.808 2.436E+001
    900.000 −11.321 −4.213 −6.378 1.543E+001
    1000.000 −11.176 −4.094 −5.963 1.056E+001
  • [0061]
    [0061]
    TABLE 14
    Thermodynamic data for reaction:
    1.5HfO2 + 2BBr3(g) = 1.5HfBr4(g) + B2O3
    T (° C.) ΔH (kcal) ΔS (kcal) ΔG (kcal) Keq
    0.000 −53.997 −10.093 −51.241 1.003E+041
    100.000 −54.122 −10.459 −50.219 2.602E+029
    200.000 −54.371 −11.049 −49.143 5.026E+022
    300.000 −54.601 −11.492 −48.014 2.042E+018
    400.000 −54.773 −11.770 −46.850 1.629E+015
    500.000 −48.872 −3.621 −46.073 1.058E+013
    600.000 −48.508 −3.178 −45.734 2.806E+011
    700.000 −48.207 −2.851 −45.433 1.600E+010
    800.000 −47.960 −2.609 −45.161 1.577E+009
    900.000 −47.761 −2.431 −44.909 2.328E+008
    1000.000 −47.606 −2.304 −44.673 4.669E+007
  • [0062]
    [0062]
    TABLE 15
    Thermodynamic data for reaction:
    1.5HfO2 + 2Bl3(g) = 1.5Hfl4(g) + B2O3
    T (° C.) ΔH (kcal) ΔS (kcal) ΔG (kcal) Keq
    0.000 −58.042 −15.921 −53.694 9.212E+042
    100.000 −58.342 −16.842 −52.057 3.104E+030
    200.000 −58.692 −17.675 −50.329 1.775E+023
    300.000 −58.991 −18.250 −48.531 3.214E+018
    400.000 −59.216 −18.614 −46.686 1.442E+015
    500.000 −53.362 −10.530 −45.221 6.080E+012
    600.000 −53.042 −10.139 −44.189 1.152E+011
    700.000 −52.784 −9.859 −43.190 5.015E+009
    800.000 −52.581 −9.660 −42.214 3.961E+008
    900.000 −52.429 −9.524 −41.256 4.856E+007
    1000.000 −52.324 −9.438 −40.308 8.315E+006
  • [0063]
    Similarly, bromine and iodine chemistries are also thermodynamically favorable for reactions with Al2O3 and ZrO2, as shown in Tables 16-18.
    TABLE 16
    Thermodynamical data for reaction:
    2BBr3(g) + Al2O3 = 2AlBr3(g) + B2O3
    T (° C.) ΔH (kcal) ΔS (kcal) ΔG (kcal) Keq
    0.000 −2.212 12.687 −5.678 3.493E+004
    100.000 −2.279 12.503 −6.944 1.168E+004
    200.000 −2.482 12.022 −8.170 5.945E+003
    300.000 −2.685 11.632 −9.352 3.683E+003
    400.000 −2.852 11.362 −10.501 2.567E+003
    500.000 3.023 19.476 −12.035 2.525E+003
    600.000 3.337 19.858 −14.003 3.200E+003
    700.000 3.579 20.122 −16.003 3.928E+003
    800.000 3.764 20.303 −18.024 4.688E+003
    900.000 3.897 20.422 −20.061 5.464E+003
    1000.000 3.985 20.494 −22.107 6.241E+003
  • [0064]
    [0064]
    TABLE 17
    Thermodynamical data for reaction:
    2BBr3(g) + 1.5ZrO2 = 1.5ZrBr4(g) + B2O3
    T (° C.) ΔH (kcal) ΔS (kcal) ΔG (kcal) Keq
    0.000 −44.096 −11.573 −40.935 5.691E+032
    100.000 −44.194 −11.861 −39.768 1.965E+023
    200.000 −44.363 −12.264 −38.560 6.495E+017
    300.000 −44.489 −12.509 −37.320 1.706E+014
    400.000 −44.545 −12.600 −36.064 5.125E+011
    500.000 −38.522 −4.282 −35.212 9.000E+009
    600.000 −38.033 −3.686 −34.815 5.186E+008
    700.000 −37.604 −3.220 −34.470 5.520E+007
    800.000 −37.229 −2.853 −34.167 9.096E+006
    900.000 −36.902 −2.561 −33.897 2.067E+006
    1000.000 −36.619 −2.330 −33.653 5.989E+005
  • [0065]
    [0065]
    TABLE 18
    Thermodynamical data for reaction:
    2Bl3(g) + 1.5ZrO2 = 1.5Zrl4(g) + B2O3
    T (° C.) ΔH (kcal) ΔS (kcal) ΔG (kcal) Keq
    0.000 −74.430 −11.695 −71.235 1.001E+057
    100.000 −74.587 −12.171 −70.045 1.067E+041
    200.000 −74.805 −12.689 −68.801 6.053E+031
    300.000 −74.972 −13.013 −67.514 5.573E+025
    400.000 −75.065 −13.163 −66.204 3.134E+021
    500.000 −69.074 −4.891 −65.293 2.873E+018
    600.000 −68.614 −4.330 −64.833 1.695E+016
    700.000 −68.212 −3.894 −64.423 2.947E+014
    800.000 −67.861 −3.549 −64.052 1.110E+013
    900.000 −67.555 −3.276 −63.711 7.411E+011
    1000.000 −67.291 −3.061 −63.394 7.642E+010
  • [0066]
    In certain embodiments, the reactive agent may comprise a chelating compound. A chelating compound, as used herein, describes a compound that contains at least two electron-rich (e.g., Lewis base) sites that could potentially interact with an electron-deficient (e.g., Lewis acid) metal atom such as, but not limited to, Zr, Al, or Hf. It is not required, however, that the plurality of sites simultaneously interact with the metal in order. Also, the chelating compound may be delivered into the reaction chamber as a conjugate acid of the basic site. Examples of these compounds may be found in U.S. Pat. No. 3,634,477. Further examples of chelating compounds include oxy-halocarbon compounds, such as chloroacetic acid, oxalyl chloride, etc., are known to be chelating compounds or agents that can react with metal oxides and metal chlorides to form volatile byproducts. Some exemplary chelating compounds may have the formula CαHβXγY67 O68 , wherein X and Y are one of the halogen atoms F, Cl, Br, and l; α is a number ranging from 1 to 6, β is a number ranging from 0 to 13, the sum of γ+δ is a number ranging from 1 to 14, and ε is a number ranging from 1 to 6. Examples of these compounds include hexafluoropetanedione (CCl3C(O)CH2C(O)CCl3) (a.k.a. Hhfac), hexachloropetanedione (CCl3C(O)CH2C(O)CCl3), hexafluoroacetone (CF3C(O)CF3) and hexachloroacetone (CCl3C(O)CCl3). For example, hexafluoropetanedione (a.k.a. Hhfac) (CF3C(O)CH2C(O)CF3, or C5H2O2F6) is a common chelating agent that can react with a wide variety of metal oxides and/or chlorides to form volatile organo-metal compounds M(hfac)x, where M is a metal ion such as Al3+, Hf4+, and Zr4+ etc. Such chelating property can be used to enhance the etching and chamber cleaning of high-k materials. In addition, these molecules can be used as an oxygen scavenger to enhance chlorination of the high-k materials. For example, one can have:
  • HfO2+C5H2O2F6+2Cl2+O2=HfCl4(g)+H2O(g)+3COF2(g)+2CO(g)
  • [0067]
    In certain embodiments of the present invention, the chlorine analog of Hhfac, hexachloropetanedione (CCl3C(O)CH2C(O)CCl3) may be more advantageous as the reactive agent since it can be both an oxygen scavenger and a chlorinating agent. These reactions can be also be assisted by thermal and/or plasma activation. For example,
  • C5H2O2Cl6+Al2O3+0.5O2=2AlCl3(g)+5CO(g)+H2O(g)
  • [0068]
    and
  • 2C5H2O2Cl6+3HfO2+O2=3HfCl4(g)+10CO(g)+2H2 2O(g)
  • [0069]
    To prevent oxidation of the metal chlorides, chlorine can be used to replace oxygen:
  • C5H2O2Cl6+Al2O3+Cl2=2AlCl3(g)+5CO(g)+2HCl(g)
  • [0070]
    Chlorosilanes, hydrochlorosilanes, and organochlorosilanes can also be effective agents to etch/clean high-k materials. Thanks to the highly stable SiO2 byproduct, these compounds can be both a very effective oxygen scavenger and a chlorinating agent. Upon exposure to a thermal or plasma source, these compounds can be just as effective as BCl3 to convert high-k materials into volatile chlorides without the potential problem of boron residue contamination. In certain embodiments, the chlorosilane, hydrochlorosilane, or organochlorosilane compound has the formula SipClqRsHt, wherein: 1≦p≦3, 1≦q≦{2p+2−(s+t)}, s and t can have any values subject to the constraint that 0≦(s+t)≦(2p+1) and R is an organic radical having 1-8 carbon atoms, including: hydrocarbyl (e.g. methyl, ethyl, phenyl, p-tolyl), halocarbyl (e.g., trichloromethyl, trifluoromethyl, pentafluoroethyl), halogenated hydrocarbyl (e.g., chloromethyl, 2,4-difluorophenyl), oxygenated hydrocarbyl (e.g., methoxy, hydroxyethyl, chlorormethoxy) and nitrogen-substituted hydrocarbyl moieties (e.g., aminomethyl, dimethylaminonomethyl, pyridyl). Exemplary reactions include:
  • 1.5SiCl4(g)+Al2O3=2AlCl3(g)+1.5SiO2
  • SiCl4(g)+HfO2=HfCl4(g)+SiO2
  • SiCl4(g)+ZrO2=ZrCl4(g)+SiO2
  • O2(g)+2SiHCl3(g)+Al2O3=2AlCl3(g)+H2O(g)+2SiO2
  • 4O2(g)+2SiCH3Cl3(g)+Al2O3=2AlCl3(g)+3H2O(g)+2SiO2+2CO2(g)
  • [0071]
    Thermodynamic calculations show that the above reactions are favorable at room temperature or moderately elevated temperatures, as shown in Tables 19-23.
    TABLE 19
    Thermodynamical data for reaction:
    1.5SiCl4(g) + Al2O3 = 2AlCl3(g) + 1.5SiO2
    T (° C.) ΔH (kcal) ΔS (kcal) ΔG (kcal) Keq
    0.000 32.037 34.471 22.621 7.927E−019
    100.000 31.880 33.990 19.196 5.703E−012
    200.000 31.647 33.439 15.825 4.895E−008
    300.000 31.400 32.967 12.506 1.702E−005
    400.000 31.178 32.608 9.228 1.009E−003
    500.000 31.009 32.373 5.980 2.039E−002
    600.000 31.097 32.475 2.742 2.059E−001
    700.000 30.702 32.047 −0.484 1.285E+000
    800.000 30.291 31.645 −3.669 5.587E+000
    900.000 30.612 31.957 −6.878 1.912E+001
    1000.000 30.204 31.623 −10.057 5.327E+001
  • [0072]
    [0072]
    TABLE 20
    Thermodynamical data for reaction:
    SiCl4(g) + HfO2 =HfCl4(g) + SiO2
    T (° C.) ΔH (kcal) ΔS (kcal) ΔG (kcal) Keq
    0.000 2.985 6.373 1.244 1.010E−001
    100.000 2.825 5.878 0.631 4.267E−001
    200.000 2.636 5.430 0.067 9.314E−001
    300.000 2.459 5.089 −0.458 1.495E+000
    400.000 2.317 4.860 −0.955 2.042E+000
    500.000 2.230 4.739 −1.434 2.543E+000
    600.000 2.330 4.857 −1.911 3.009E+000
    700.000 2.110 4.618 −2.385 3.432E+000
    800.000 1.877 4.391 −2.835 3.779E+000
    900.000 2.130 4.633 −3.306 4.129E+000
    1000.000 1.892 4.439 −3.759 4.419E+000
  • [0073]
    [0073]
    TABLE 21
    Thermodynamical data for reaction:
    SiCl4(g) + ZrO2 = ZrCl4(g) + SiO2
    T (° C.) ΔH (kcal) ΔS (kcal) ΔG (kcal) Keq
    0.000 −4.912 6.726 −6.749 2.516E+005
    100.000 −5.006 6.439 −7.408 2.185E+004
    200.000 −5.123 6.160 −8.038 5.164E+003
    300.000 −5.226 5.963 −8.643 1.977E+003
    400.000 −5.288 5.861 −9.233 9.955E+002
    500.000 −5.292 5.854 −9.818 5.966E+002
    600.000 −5.106 6.077 −10.412 4.041E+002
    700.000 −5.237 5.936 −11.013 2.975E+002
    800.000 −5.375 5.800 −11.600 2.304E+002
    900.000 −5.026 6.129 −12.216 1.887E+002
    1000.000 −5.163 6.016 −12.823 1.590E+002
  • [0074]
    [0074]
    TABLE 22
    Thermodynamical data for reaction:
    O2(g) + 2SiHCl3(g) + Al2O3 =
    2AlCl3(g) + H2O(g) + 2SiO2
    T (° C.) ΔH (kcal) ΔS (kcal) ΔG (kcal) Keq
    0.000 −134.894 4.620 −136.156 8.893E+108
    100.000 −135.412 2.993 −136.529 9.339E+079
    200.000 −135.834 1.989 −136.775 1.521E+063
    300.000 −136.187 1.309 −136.938 1.662E+052
    400.000 −136.464 0.863 −137.045 3.145E+044
    500.000 −136.643 0.612 −137.117 5.789E+038
    600.000 −136.462 0.826 −137.183 2.187E+034
    700.000 −136.917 0.333 −137.241 6.669E+030
    800.000 −137.387 −0.126 −137.251 8.991E+027
    900.000 −136.875 0.364 −137.301 3.806E+025
    1000.000 −137.329 −0.008 −137.319 3.752E+023
  • [0075]
    [0075]
    TABLE 23
    Thermodynamical data for reaction:
    4O2(g) + 2SiCH3Cl3(g) + Al2O3 =
    2AlCl3(g) + 3H2O(g) + 2SiO2 + 2CO2(g)
    T (° C.) ΔH (kcal) ΔS (kcal) ΔG (kcal) Keq
    0.000 −423.175 31.434 −431.762 1.000E+308
    100.000 −423.093 31.710 −434.925 5.650E+254
    200.000 −423.197 31.470 −438.087 2.349E+202
    300.000 −423.424 31.038 −441.213 1.797E+168
    400.000 −423.714 30.573 −444.294 1.818E+144
    500.000 −424.016 30.154 −447.329 2.878E+126
    600.000 −424.028 30.132 −450.339 5.361E+112
    700.000 −424.723 29.380 −453.314 6.510E+101
    800.000 −425.461 28.658 −456.216 8.264E+092
    900.000 −425.237 28.892 −459.132 3.469E+085
    1000.000 −425.990 28.276 −461.990 2.051E+079
  • [0076]
    In addition, other chloride compounds such as GeCl4 and related compounds can also be used to etch/clean high-k materials in a similar manner. When etching/cleaning hafnium and zirconium based high-k materials, AlCl3 can be added into the reactants to enhance the chlorination of HfO2, ZrO2, HfSixOy, and ZrSixOy etc. This is because AlCl3 can be used as an oxygen scavenger to facilitate the chlorination of HfO2 and ZrO2 etc. while forming aluminum oxychloride such as AlOCl, which is more volatile than Al2O3.
  • [0077]
    In addition to being thermodynamically favorable, a chemical reaction often requires an external energy source to overcome an activation energy barrier so that the reaction can proceed. The external energy source can be, for example, thermal heating or plasma activation. Higher temperatures can accelerate chemical reactions and make reaction byproducts more volatile. However, there may be practical limitations on temperature in production deposition chambers. Plasmas can generate more reactive species to facilitate reactions. Ions in the plasmas are accelerated by the electric field in the plasma sheath to gain energy. Energetic ions impinging upon surfaces can provide the energy needed to overcome reaction activation energy barrier. Ion bombardment also helps to volatize and remove reaction byproducts. These are common mechanisms in plasma etching/cleaning and reactive ion etching. Optionally, one can combine both thermal and plasma activation mechanisms to enhance the desired reactions for dry etching/cleaning of high-k materials. As an alternative to in situ plasma cleaning, one can use remote plasma source to generate more reactive species for cleaning high-k material residues from the deposition chambers. In addition, reactions between remote plasma generated reactive species and high-k materials can be activated and/or enhanced by heating CVD or ALD reactor components to elevated temperatures up to 600° C., more preferably up to 400° C., and even more preferably up to 300° C.
  • [0078]
    [0078]FIGS. 1a and 1 b provides an illustration of an apparatus suitable for performing chamber cleaning using an internal energy source or an external energy source, respectively. In FIG. 1a, the reactive agent (i.e., BCl3) is introduced into the substrate (i.e., reaction chamber) which has the substance to be removed or the high-k residues such as the HfO2 depicted. As shown in FIG. 1a, the substance is deposited upon at least a portion of the exposed surface within the reaction chamber, particularly, the grounded sidewalls, shower head, work piece platform, etc. The reactive agent is exposed to an external energy source, such as the RF power supply or heater shown, which creates active species such as BCl3 and Cl. The active species react with substance and form a volatile product such as HfCl4. The volatile product is removed from the chamber as shown.
  • [0079]
    [0079]FIG. 1b provides an example of an apparatus wherein the reactive agent is exposed to an external energy source such as a microwave source to produce a high density plasma of the reactive agent. The high density plasma can then be transported to the substrate (i.e., reaction chamber) having the substance to be removed and form the volatile product. The volatile product can be easily removed form the chamber via the foreline shown.
  • EXAMPLES
  • [0080]
    The invention will be illustrated in more detail with reference to the following Examples, but it should be understood that the present invention is not deemed to be limited thereto.
  • [0081]
    The following are experimental examples of utilizing the above chemistries for dry etching/cleaning of high-k materials. The experiments for examples 1 through 3 were conducted in a parallel plate capacitively coupled RF plasma reactorsimilar to the setup illustrated in FIG. 2. Sample coupons were prepared from wafers coated with high-k dielectric materials Al2O3, HfO2, and ZrO2 deposited by atomic layer deposition. For each experimental run, a sample coupon was put onto a carrier wafer and loaded onto the reactor chuck through a loadlock. Process gases were fed into the reactor from a top mounted showerhead. The chuck was then powered by a 13.56 MHz RF power source to generate the plasma. The thickness of the high-k film on a coupon was measured by ellipsometry both before and after a timed exposure of the processing plasma. Change in high-k film thickness after plasma processing is used to calculate the etch rate. In addition to etch rate, plasma dc self bias voltage (Vbias) was also measured. In examples 1-3, both the wafer and the chamber walls were kept at room temperature.
  • Example 1
  • [0082]
    Plasma Etching/Cleaning of Al2O3 Samples
  • [0083]
    Since power is one of the key processing parameters in plasma etching/cleaning, we evaluated power dependence of Al2O3 etching by BCl3 plasma. The results are listed in Table 24 below.
    TABLE 24
    RF power dependence of Al2O3 etching by BCl3 plasma
    Power density Pressure Al2O3 etch rate Vbias
    Power (W) (W/cm2) (mTorr) (nm/min) (V)
    50 0.27 500 0.0 16
    100 0.55 500 3.0 35
    200 1.10 500 9.8 58
  • [0084]
    Apparently there is a threshold power density of 0.55 W/cm2 or threshold Vbias of 35 V for etching Al2O3. Higher power density and higher Vbias resulted in higher etch rate.
  • [0085]
    Next, we investigated chamber pressure dependence of Al2O3 etching by BCl3 plasma. The results are listed in Table 25 below.
    TABLE 25
    Chamber pressure dependence of Al2O3 etching by BCl3 plasma
    Power density Pressure Al2O3 etch rate Vbias
    Power (W) (W/cm2) (mTorr) (nm/min) (V)
    100 0.55 50 7.2 91
    100 0.55 500 3.0 35
    100 0.55 1000 0.8 4
  • [0086]
    A higher etch rate was achieved at a reduced pressure. There are two factors that favor the etch reactions at reduced pressure. First, higher bias voltage at lower pressure leads to more energetic ion bombardment to help the etch reactions to overcome activation energy barrier. Second, lower pressure leads to faster desorption and diffusion of reaction byproducts. Higher Vbias also enhances physical sputtering by energetic ions. To delineate the contributions from reactive ion etching and physical sputtering, we conducted comparison runs using pure argon plasma. The results are listed in Table 26 below.
    TABLE 26
    Argon plasma etching of Al2O3
    Power density Pressure Al2O3 etch rate Vbias
    Power (W) (W/cm2) (mTorr) (nm/min) (V)
    200 1.10 5 0.6 173
    200 1.10 50 1.0 189
    200 1.10 500 −0.4 185
  • [0087]
    The data showed pure argon plasma essentially did not etch Al2O3 even with very high power and a relatively higher Vbias than that of BCl3 plasmas. This indicates that physical sputtering may not be the primary mechanism to etch Al2O3. Instead, ion bombardment enhanced chemical etching, or reactive ion etching (RIE) may be the primary mechanism.
  • [0088]
    Tables 24 and 25 showed higher power and lower pressure can increase Vdc, which in turn enhances chemical etching of high-k materials. One can also operate the RF plasma at lower frequencies. Ions transiting through a plasma sheath often exhibit a bi-modal energy distribution at lower frequencies. Bimodal ion energy distribution results in a large fraction of the ions impinging onto reactor surfaces with higher energies. This can be an effective strategy to enhance plasma cleaning of high-k deposition residues from grounded ALD chamber surfaces. At a fixed RF excitation frequency (such as 13.56 MHz), the data in Tables 24 and 25 show higher power and lower pressure can increase bias voltage, which in turn enhances chemical etching of high-k materials. Lower pressure and higher power is particularly effective to enhance plasma etching of substrates coated with high-k films. For ALD chamber cleaning, one must balance the requirements between RF powered reactor components and grounded reactor components (such as chamber walls).
  • Example 2
  • [0089]
    Plasma Etching/Cleaning of HfO2 Samples
  • [0090]
    At 500 mTorr pressure, etching of HfO2 was achieved at all power levels between 50 and 200 W. The results are listed in Table 27 below.
    TABLE 27
    BCl3 plasma etching of HfO2
    Power density Pressure HfO2 etch rate Vbias
    Power (W) (W/cm2) (mTorr) (nm/min) (V)
    50 0.27 500 1.6 14
    50 0.27 500 1.4 16
    100 0.55 500 4.7 34
    200 1.10 500 14.7 63
  • Example 3
  • [0091]
    Plasma Etching/Cleaning of ZrO2 Samples
  • [0092]
    Several experiments were conducted with ZrO2 samples using 500 mTorr pressure and various power levels between 50 and 200 W. The results are listed in Table 28 below.
    TABLE 28
    BCl3 plasma etching of HfO2
    Power density Pressure ZrO2 etch rate Vbias
    Power (W) (W/cm2) (mTorr) (nm/min) (V)
    50 0.27 500 0.3 16
    100 0.55 500 −3.8* 32
    100 0.55 500 −2.5* 45
    200 1.10 500 7.1 65
  • [0093]
    [0093]FIG. 3 shows the relative comparison of BCl3 plasma etch rates of high-k materials HfO2, Al2O3, and ZrO2 at 500 mTorr chamber pressure and 1 W/cm2 RF power density. It can be seen that HfO2 has the highest etch rate, and ZrO2 has the lowest etch rate among the three high-k materials.
  • [0094]
    Examples 4 and 5 illustrate BCl3 thermal etching/cleaning of high-k materials. FIG. 4 is a schematic of the experimental setup for examples 4 and 5. In this reactor RF power can be applied on the top electrode, and the lower electrode and the chamber walls are grounded. This reactor can be operated with both RF plasma and thermal heating during an etching/cleaning experiments. Only thermal heating was used in examples 4 and 5. The lower electrode/pedestal can be heated by an AC powered heater and controlled by the temperature controller. The temperature range of the lower electrode/pedestal is from room temperature up to 700° C. The sample and the carrier wafer were placed on the lower electrode/pedestal. Sample surface temperature is about 50° C. lower than the lower electrode set point in ambient atmosphere. Sample preparation and measurement procedures were similar to those in examples 1 through3. After sample introduction, the reactor was evacuated, and the heater was turned out. When the lower electrode reached the set point, process gases were introduced into the chamber to reach a set pressure. The sample was exposed to the process gases for a set period of time. The process gases were evacuated and the sample was retrieved from the chamber for measurement.
  • Example 4
  • [0095]
    Thermal Etching/Cleaning of Al2O3 Samples
  • [0096]
    Several experiments were conducted using BCl3 as the etchant for thermal etching/cleaning of Al2O3 samples. The process variables were lower electrode temperature, chamber pressure, and BCl3 flow rate. The results are listed in Table 29.
    TABLE 29
    BCl3 thermal etching of Al2O3
    Lower Electrode Set Chamber Pressure BCl3 Flow Rate Etch Rate
    Temperature (° C.) (Torr) (sccm) (nm/min)
    200 100 100 0.0
    350 25 100 0.1
    350 100 100 0.2
    350 100 100 0.2
    350 100 0 0.3
    350 200 100 0.3
    350 400 100 0.7
    600 100 100 0.6
  • Example 5
  • [0097]
    Thermal Etching/Cleaning of HfO2 Samples
  • [0098]
    A similar set of experiments were conducted using BCl3 as the etchant for thermal etching/cleaning of HfO2 samples. The process variables were lower electrode temperature, chamber pressure, and BCl3 flow rate. The results are listed in Table 30.
    TABLE 30
    BCl3 thermal etching of HfO2
    Lower Electrode Set Chamber Pressure BCl3 Flow Rate Etch Rate
    Temperature (° C.) (Torr) (sccm) (nm/min)
    200 100 100 0.0
    350 25 100 0.1
    350 100 100 0.6
    350 100 100 0.6
    350 100 0 0.6
    350 200 100 1.1
    350 400 100 2.4
    600 100 100 1.1
  • [0099]
    [0099]FIG. 5 examines the etch rate dependence on lower electrode temperature at constant chamber pressure and BCl3 flow rate. It can be seen that both Al2O3 and HfO2 etch rates increase at temperature increases. The etch rates of HfO2 are higher than those of Al2O3 under the same conditions.
  • [0100]
    [0100]FIG. 6 examines the etch rate dependence on chamber pressure at constant lower electrode set temperature and BCl3 flow rate. It can be seen that etch rates increase at higher pressures. At lower electrode temperature about 350° C., increasing chamber pressure is a more effective method to enhance etch rates. Again, the etch rates of HfO2 are higher than those of Al2O3 under the same conditions.
  • [0101]
    The data in Tables 29 and 30 shows that there is no strong dependence between etch rate and BCl3 flow rate. This means one can operate thermal etching/cleaning either with continuous flow of etchant gases (such as BCl3) or with static chamber at a set pressure without flow.
  • [0102]
    While the invention has been described in detail and with reference to specific examples thereof, it will be apparent to one skilled in the art that various changes and modifications can be made therein without departing from the spirit and scope thereof.
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Classifications
U.S. Classification134/1.1, 134/166.00R, 134/22.1, 134/30
International ClassificationH01L21/3065, H01L21/31, H01L21/306, B01J19/08, B08B7/00, C23C16/44
Cooperative ClassificationB08B7/0035, C23C16/4405, B08B7/00
European ClassificationC23C16/44A6, B08B7/00S, B08B7/00
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Feb 20, 2017ASAssignment
Owner name: VERSUM MATERIALS US, LLC, ARIZONA
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Effective date: 20170214