|Publication number||US20070113789 A1|
|Application number||US 11/557,462|
|Publication date||May 24, 2007|
|Filing date||Nov 7, 2006|
|Priority date||Mar 31, 2005|
|Also published as||US7132128, US20060219177|
|Publication number||11557462, 557462, US 2007/0113789 A1, US 2007/113789 A1, US 20070113789 A1, US 20070113789A1, US 2007113789 A1, US 2007113789A1, US-A1-20070113789, US-A1-2007113789, US2007/0113789A1, US2007/113789A1, US20070113789 A1, US20070113789A1, US2007113789 A1, US2007113789A1|
|Original Assignee||Tokyo Electron Limited|
|Export Citation||BiBTeX, EndNote, RefMan|
|Referenced by (5), Classifications (9)|
|External Links: USPTO, USPTO Assignment, Espacenet|
This application is a divisional of co-pending U.S. Pat. No. 7,132,128, the content of which is hereby incorporated by reference herein in its entirety. This application is also related to co-pending U.S. patent application Ser. No. 11/096,156, entitled “Method for Saturating a Carrier Gas with Precursor Vapor”, the content of which is herein incorporated by reference in its entirety.
1. Field of Invention
The present invention relates to a system for thin film deposition, and more particularly to a system for vaporizing a film precursor and delivering the vapor to a deposition chamber.
2. Description of Related Art
The introduction of copper (Cu) metal into multilayer metallization schemes for manufacturing integrated circuits can necessitate the use of diffusion barriers/liners to promote adhesion and growth of the Cu layers and to prevent diffusion of Cu into the dielectric materials. Barriers/liners that are deposited onto dielectric materials can include refractive materials, such as tungsten (W), molybdenum (Mo), and tantalum (Ta), that are non-reactive and immiscible in Cu, and can offer low electrical resistivity. Current integration schemes that integrate Cu metallization and dielectric materials can require barrier/liner deposition processes at substrate temperatures between about 400° C. and about 500° C., or lower.
For example, Cu integration schemes for technology nodes less than or equal to 130 nm currently utilize a low dielectric constant (low-k) inter-level dielectric, followed by a physical vapor deposition (PVD) TaN layer and Ta barrier layer, followed by a PVD Cu seed layer, and an electrochemical deposition (ECD) Cu fill. Generally, Ta layers are chosen for their adhesion properties (i.e., their ability to adhere on low-k films), and Ta/TaN layers are generally chosen for their barrier properties (i.e., their ability to prevent Cu diffusion into the low-k film).
As described above, significant effort has been devoted to the study and implementation of thin transition metal layers as Cu diffusion barriers, these studies including such materials as chromium, tantalum, molybdenum and tungsten. Each of these materials exhibits low miscibility in Cu. More recently, other materials, such as ruthenium (Ru) and rhodium (Rh), have been identified as potential barrier layers since they are expected to behave similarly to conventional refractory metals. However, the use of Ru or Rh can permit the use of only one barrier layer, as opposed to two layers, such as Ta/TaN. This observation is due to the adhesive and barrier properties of these materials. For example, one Ru layer can replace the Ta/TaN barrier layer. Moreover, current research is finding that the one Ru layer can further replace the Cu seed layer, and bulk Cu fill can proceed directly following Ru deposition. This observation is due to good adhesion between the Cu and the Ru layers.
Conventionally, Ru layers can be formed by thermally decomposing a ruthenium-containing precursor, such as a ruthenium carbonyl precursor, in a thermal chemical vapor deposition (TCVD) process. Material properties of Ru layers that are deposited by thermal decomposition of metal carbonyl precursors (e.g., Ru3(CO)12), can deteriorate when the substrate temperature is lowered to below about 400° C. As a result, an increase in the (electrical) resistivity of the Ru layers and poor surface morphology (e.g., the formation of nodules) at low deposition temperatures has been attributed to increased incorporation of CO reaction by-products into the thermally deposited Ru layers. Both effects can be explained by a reduced CO desorption rate from the thermal decomposition of the ruthenium carbonyl precursor at substrate temperatures below about 400° C.
Additionally, the use of metal carbonyls, such as ruthenium carbonyl, can lead to poor deposition rates due to their low vapor pressure, and the transport issues associated therewith. For instance, transport issues can include excessive decomposition of the precursor vapor on internal surfaces of the deposition system, such as on the internal surfaces of the vapor delivery system used to transport the vapor from the vaporization system to the process chamber, thus further reducing the amount of precursor vapor that reaches the substrate surface. Overall, the inventor has observed that current deposition systems suffer from such a low rate, making the deposition of such metal films impractical.
The present invention provides a deposition system for forming a thin film on a substrate in which a film precursor vaporization system is integrated with the process chamber, rather than remote therefrom. The deposition system comprises a process chamber having a substrate holder configured to support the substrate and heat the substrate, and a pumping system configured to evacuate the process chamber; and a film precursor vaporization system coupled to the process chamber above the substrate and configured to vaporize a film precursor, and to transport film precursor vapor in a carrier gas. The film precursor vaporization system comprises a housing positioned above the process chamber and having an opening in the bottom of the housing that is in general alignment with an opening in the top of the process chamber. A precursor tray is supported within the housing and an annular space is formed between the precursor tray and the housing. The precursor tray is configured to support the film precursor, and is coupled to a carrier gas supply system configured to flow the carrier gas through or over the film precursor, through the annular space, and through the opening in the bottom of the housing.
The present invention further provides a method of depositing a thin film on a substrate using the above-described deposition system. The method comprises: disposing the substrate on the substrate holder in the process chamber of the deposition system; introducing a film precursor to the film precursor vaporization system in the deposition system; flowing a carrier gas from the carrier gas supply system through the film precursor vaporization system; heating the film precursor to form the film precursor vapor in the carrier gas; and exposing the substrate to the film precursor vapor.
In the accompanying drawings:
In the following description, in order to facilitate a thorough understanding of the invention and for purposes of explanation and not limitation, specific details are set forth, such as a particular geometry of the deposition system and descriptions of various components. However, it should be understood that the invention may be practiced in other embodiments that depart from these specific details.
Referring now to the drawings, wherein like reference numerals designate identical or corresponding parts throughout the several views,
The process chamber 10 is further coupled to a vacuum pumping system 40, wherein the pumping system 40 is configured to evacuate the process chamber 10 and film precursor vaporization system 50 to a pressure suitable for forming the thin film on substrate 25, and suitable for vaporization of a film precursor (not shown) in the film precursor vaporization system 50.
Referring still to
In order to achieve the desired temperature for vaporizing the film precursor (or subliming a solid metal precursor), the film precursor vaporization system 50 is coupled to a vaporization temperature control system (not shown) configured to control the vaporization temperature. For instance, the temperature of the film precursor is generally elevated to approximately 40-45° C. in conventional systems in order to sublime, for example, ruthenium carbonyl. At this temperature, the vapor pressure of the ruthenium carbonyl, for instance, ranges from approximately 1 to approximately 3 mTorr. As the film precursor is heated to cause evaporation (or sublimation), a carrier gas is passed over the film precursor or by the film precursor. The carrier gas can include, for example, an inert gas, such as a noble gas (i.e., He, Ne, Ar, Kr, Xe), or a monoxide, such as carbon monoxide (CO), for use with metal carbonyls, or a mixture thereof. For example, a carrier gas supply system (not shown) is coupled to the film precursor vaporization system 50, and it is configured to, for instance, supply the carrier gas above the film precursor via a feed line (not shown). In another example, the carrier gas supply system is coupled to the vapor distribution system 30 and is configured to supply the carrier gas to the vapor of the film precursor via another feed line (not shown) as or after it enters the vapor distribution system 30. Although not shown, the carrier gas supply system can comprise a gas source, one or more control valves, one or more filters, and a mass flow controller. For instance, the flow rate of carrier gas can range from approximately 5 sccm (standard cubic centimeters per minute) to approximately 1000 sccm. For example, the flow rate of carrier gas can range from about 10 sccm to about 200 sccm. By way of further example, the flow rate of carrier gas can range from about 20 sccm to about 100 sccm.
Referring again to
Once film precursor vapor enters the processing zone 35, the film precursor vapor thermally decomposes upon adsorption at the substrate surface due to the elevated temperature of the substrate 25, and the thin film is formed on the substrate 25. The substrate holder 20 is configured to elevate the temperature of substrate 25, by virtue of the substrate holder 20 being coupled to a substrate temperature control system 22. For example, the substrate temperature control system 22 can be configured to elevate the temperature of substrate 25 up to approximately 500° C. In one embodiment, the substrate temperature can range from about 100° C. to about 500° C. In another embodiment, the substrate temperature can range from about 300° C. to about 400° C. Additionally, process chamber 10 can be coupled to a chamber temperature control system 12 configured to control the temperature of the chamber walls.
As described above, for example, conventional systems have contemplated operating the film precursor vaporization system 50, within a temperature range of approximately 40-45° C. for ruthenium carbonyl in order to limit metal vapor precursor decomposition, and metal vapor precursor condensation. For example, ruthenium carbonyl precursor can decompose at elevated temperatures to form by-products, such as those illustrated below:
However, within such systems having a small process window, the deposition rate becomes extremely low, due in part to the low vapor pressure of ruthenium carbonyl. For instance, the deposition rate can be as low as approximately 1 Angstrom per minute. Therefore, according to one embodiment, the vaporization temperature is elevated to be greater than or equal to approximately 40° C. Alternatively, the vaporization temperature is elevated to be greater than or equal to approximately 50° C. In an exemplary embodiment of the present invention, the vaporization temperature is elevated to be greater than or equal to approximately 60° C. In a further exemplary embodiment, the vaporization temperature is elevated to range from approximately 60-100° C., and for example from approximately 60-90° C. The elevated temperature increases the vaporization rate due to the higher vapor pressure (e.g., nearly an order of magnitude larger) and, hence, it is expected by the inventors to increase the deposition rate. It may also be desirable to periodically clean deposition system 1 following processing of one or more substrates. For example, additional details on a cleaning method and system can be obtained from co-pending U.S. patent application Ser. No. 10/998,394, filed on Nov. 29, 2004, and entitled “Method and System for Performing In-Situ Cleaning of a Deposition System” (Attorney Docket No. TTCA-005), which is herein incorporated by reference in its entirety.
As discussed above, the deposition rate is proportional to the amount of film precursor that is vaporized and transported to the substrate prior to decomposition, or condensation, or both. Therefore, in order to achieve a desired deposition rate, and to maintain consistent processing performance (i.e., deposition rate, film thickness, film uniformity, film morphology, etc.) from one substrate to the next, it is important to provide the ability to monitor, adjust, or control the flow rate of the film precursor vapor. In conventional systems, an operator may indirectly determine the flow rate of film precursor vapor by using the vaporization temperature, and a pre-determined relationship between the vaporization temperature and the flow rate. However, processes and their performance drift in time, and hence it is imperative that the flow rate is measured more accurately. For example, additional details can be obtained from co-pending U.S. patent application Ser. No. 10/998,393, filed on Nov. 29, 2004, and entitled “Method and System for Measuring a Flow Rate in a Solid Precursor Delivery System” (Attorney Docket No. TTCA-004), which is herein incorporated by reference in its entirety.
Still referring the
Referring still to
During processing, the heated substrate 125 can thermally decompose the vapor of film precursor vapor, such as a metal carbonyl precursor, and enable deposition of a thin film, such as a metal layer, on the substrate 125. According to one embodiment, the film precursor includes a solid precursor. According to another embodiment, the film precursor includes a metal precursor. According to another embodiment, the film precursor includes a solid metal precursor. According to yet another embodiment, the film precursor includes a metal carbonyl precursor. According to yet another embodiment, the film precursor can be a ruthenium carbonyl precursor, for example Ru3(CO)12. According to yet another embodiment of the invention, the film precursor can be a rhenium carbonyl precursor, for example Re2(CO)10. As will be appreciated by those skilled in the art of thermal chemical vapor deposition, other ruthenium carbonyl precursors and rhenium carbonyl precursors can be used without departing from the scope of the invention. In yet another embodiment, the film precursor can be W(CO)6, Mo(CO)6, Co2(CO)8, Rh4(CO)12, Cr(CO)6, or Os3(CO)12.
The substrate holder 120 is heated to a pre-determined temperature that is suitable for depositing, for instance, a desired Ru, Re, or other metal layer onto the substrate 125. Additionally, a heater (not shown), coupled to a chamber temperature control system 112, can be embedded in the walls of process chamber 110 to heat the chamber walls to a pre-determined temperature. The heater can maintain the temperature of the walls of process chamber 110 from about 40° C. to about 100° C., for example from about 40° C. to about 80° C. A pressure gauge (not shown) is used to measure the process chamber pressure.
Referring specifically to
Furthermore, the vapor distribution system 130 is positioned at the opening 136 provided in the bottom of the vaporization system 150 for receiving vapor precursor from the vaporization system 150 and introducing it into vapor distribution plenum 132 for distribution to the processing zone 135 through opening 137. Moreover, temperature control elements (not shown), such as concentric fluid channels configured to flow a cooled or heated fluid, are provided for controlling the temperature of the vapor distribution system 130, and thereby prevent the decomposition of the film precursor inside the vapor distribution system 130. For instance, a fluid, such as water, can be supplied to fluid channels from a vapor distribution temperature control system 138. The vapor distribution temperature control system 138 can include a fluid source, a heat exchanger, one or more temperature sensors for measuring the fluid temperature or vapor distribution plate temperature or both, and a controller configured to control the temperature of the vapor distribution plate 131 from about 20° C. to about 100° C. Referring again to both
As the film precursor is heated to cause evaporation (or sublimation), a carrier gas can be passed over the film precursor 175, or by the film precursor 175, or through the film precursor 175. For example, a carrier gas supply system 160 is coupled to the film precursor vaporization system 150 via gas line 161, and it is configured to, for instance, supply the carrier gas below the film precursor 175. Additionally, carrier gas supply system 160 can also be coupled to the precursor delivery system 105, 105′ downstream of the film precursor 175, proximate the opening 136. In
The carrier gas can include, for example, an inert gas, such as a noble gas (i.e., He, Ne, Ar, Kr, Xe), or a monoxide, such as carbon monoxide (CO), for use with metal carbonyls, or a mixture thereof. The carrier gas supply system 160 can comprise a gas source (not shown), one or more control valves (not shown), one or more filters (not shown), and a mass flow controller (not shown). For instance, the flow rate of carrier gas can range from approximately 5 sccm (standard cubic centimeters per minute) to approximately 1000 sccm. In one embodiment, for instance, the flow rate of carrier gas can range from about 10 sccm to about 200 sccm. In another embodiment, for instance, the flow rate of carrier gas can range from about 20 sccm to about 100 sccm.
Referring still to
Referring now to
Referring now to
Referring now to
Referring now to
Referring again to
As illustrated in
Referring back to the substrate holder 120 in the process chamber 110, as shown in
Referring still to
Controller 190 may be locally located relative to the deposition system 100, or it may be remotely located relative to the deposition system 100 via an internet or intranet. Thus, controller 190 can exchange data with the deposition system 100, 100′ (100″) using at least one of a direct connection, an intranet, or the internet. Controller 190 may be coupled to an intranet at a customer site (i.e., a device maker, etc.), or coupled to an intranet at a vendor site (i.e., an equipment manufacturer). Furthermore, another computer (i.e., controller, server, etc.) can access controller 190 to exchange data via at least one of a direct connection, an intranet, or the internet.
Referring now to
In 830, a precursor valve system coupled to the film precursor vaporization system is closed in order to prevent precursor vapor from exiting the film precursor vaporization system and entering the process chamber. In 840, the film precursor is heated to form a precursor vapor in the film precursor vaporization system. In 850, a carrier gas passes through, or over, the film precursor while the film precursor is heated. In 860, the flow of carrier gas is terminated. The termination of the flow of carrier gas into the film precursor vaporization system may occur once a pre-specified pressure is achieved within the film precursor vaporization system.
In 870, the substrate is heated to a substrate temperature sufficient to decompose the film precursor vapor. In 880, after a period of time sufficient to permit stabilization of the pressure and of the vaporization process in the film precursor vaporization system, the precursor valve system is opened to permit introduction of the precursor vapor to the process chamber and exposure of the heated substrate to the film precursor vapor. Prior to opening the precursor valve system and while the flow of carrier gas is terminated, the carrier gas within the film precursor vaporization system can become saturated with film precursor vapor. Given the vaporization temperature, the film precursor vapor can achieve a specific partial pressure within the volume of carrier gas. Once saturated (i.e., the partial pressure is achieved), the amount of film precursor vapor delivered to the substrate during exposure can be determined. When the precursor valve system is opened to expose the substrate to precursor vapor, the transport of the precursor vapor and carrier gas already present in the film precursor vaporization system may or may not be accompanied by an additional flow of a carrier gas. Steps 810 to 880 may be repeated successively a desired number of times to deposit a metal film on a desired number of substrates.
Although only certain exemplary embodiments of this invention have been described in detail above, those skilled in the art will readily appreciate that many modifications are possible in the exemplary embodiments without materially departing from the novel teachings and advantages of this invention. Accordingly, all such modifications are intended to be included within the scope of this invention.
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|US7351285 *||Mar 29, 2005||Apr 1, 2008||Tokyo Electron Limited||Method and system for forming a variable thickness seed layer|
|US7638002||Nov 29, 2004||Dec 29, 2009||Tokyo Electron Limited||Multi-tray film precursor evaporation system and thin film deposition system incorporating same|
|US7651570 *||Mar 31, 2005||Jan 26, 2010||Tokyo Electron Limited||Solid precursor vaporization system for use in chemical vapor deposition|
|US7708835||Feb 10, 2006||May 4, 2010||Tokyo Electron Limited||Film precursor tray for use in a film precursor evaporation system and method of using|
|US7846256||Feb 23, 2007||Dec 7, 2010||Tokyo Electron Limited||Ampule tray for and method of precursor surface area|
|U.S. Classification||118/726, 427/248.1, 438/758|
|International Classification||C23C16/00, H01L21/31|
|Cooperative Classification||C23C16/4481, C23C16/16|
|European Classification||C23C16/448B, C23C16/16|