US 20050178666 A1
Methods are provided for forming a conductor for use in electrochemical mechanical polishing. In one aspect a method is provided for processing a substrate including providing a substrate having a conductive surface, depositing a resist material on the conductive surface, patterning the resist layer to expose portions of the conductive surface, and depositing a metal layer on the exposed portions of the conductive surface by an electrochemical deposition technique.
1. A method for processing a polishing article, comprising:
providing a substrate having a conductive base structure comprising one or more fibers coated with a conductive material;
depositing a mask material on the conductive base structure;
patterning the mask layer to expose portions of the conductive base structure; and
depositing a metal layer on the exposed portions of the conductive base structure by an electrochemical deposition technique.
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12. A polishing article for processing a substrate, comprising:
a base structure including at least a fabric layer; and
a plurality of conductive contacts disposed on the fabric layer and adapted to polish a substrate.
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20. A method for processing a polishing article, comprising:
providing a substrate having a conductive base structure comprising one or more fibers coated with a conductive material;
depositing a pattern template on the conductive base structure, wherein the patterned template is adapted to expose portions of the conductive base structure; and
depositing a metal layer on the exposed portions of the conductive base structure by an electrochemical deposition technique.
This application claims benefit of U.S. provisional patent application Ser. No. 60/536,098, filed Jan. 13, 2004, which is herein incorporated by reference.
1. Field of the Invention
Embodiments of the present invention generally relate to a process for depositing a metal on a substrate.
2. Description of the Related Art
In the fabrication of integrated circuits and other electronic devices, multiple layers of conducting, semiconducting, and dielectric materials are deposited on or removed from a surface of a substrate. Thin layers of conducting, semiconducting, and dielectric materials may be deposited by a number of deposition techniques. Common deposition techniques in modern processing include physical vapor deposition (PVD), also known as sputtering, chemical vapor deposition (CVD), plasma-enhanced chemical vapor deposition (PECVD), and electrochemical plating (ECP).
As layers of materials are sequentially deposited and removed, the uppermost surface of the substrate may become non-planar across its surface and require planarization. Planarizing a surface, or “polishing” a surface, is a process where material is removed from the surface of the substrate to form a generally even, planar surface. Planarization is useful in removing undesired surface topography and surface defects, such as rough surfaces, agglomerated materials, crystal lattice damage, scratches, and contaminated layers or materials. Planarization is also useful in forming features on a substrate by removing excess deposited material used to fill the features and to provide an even surface for subsequent levels of metallization and processing.
One material increasingly utilized in integrated circuit fabrication is copper due to its desirable electrical properties. However, copper has its own special fabrication problems. For example, copper is difficult to pattern and etch and new processes and techniques, such as damascene or dual damascene processes, are being used to form copper substrate features.
In damascene processes, a feature is defined in a dielectric material and subsequently filled with copper. Dielectric materials with low dielectric constants, i.e., less than about 3, are being used in the manufacture of copper damascenes. Barrier layer materials are deposited conformally on the surfaces of the features formed in the dielectric layer prior to deposition of copper material. Copper material is then deposited over the barrier layer and the surrounding field. However, copper fill of the features usually results in excess copper material, or overburden, on the substrate surface that must be removed to form a copper filled feature in the dielectric material and prepare the substrate surface for subsequent processing. However, low dielectric constant materials, such as carbon doped silicon oxides, may deform or fracture under conventional polishing pressures (i.e., about 6 psi), called downforce, which can detrimentally affect substrate polish quality and detrimentally affect device formation. For example, relative rotational movement between the substrate and a polishing pad can induce a shear force along the substrate surface and deform the low k material to form topographical defects, which can detrimentally affect subsequent polishing.
One process for polishing copper in low dielectric materials is by polishing copper by electrochemical mechanical polishing (ECMP) techniques. ECMP techniques remove conductive material from a substrate surface by electrochemical dissolution while concurrently polishing the substrate with reduced mechanical abrasion compared to conventional CMP processes. The electrochemical dissolution is performed by applying a bias between a cathode and substrate surface to remove conductive materials from a substrate surface into a surrounding electrolyte.
In one embodiment of an ECMP system, the bias is applied by a ring of conductive contacts in electrical communication with the substrate surface in a substrate support device, such as a substrate carrier head. However, the contact ring has been observed to exhibit non-uniform distribution of current over the substrate surface, which results in non-uniform dissolution, especially during overpolishing where a ring of conductive contacts doesn't efficiently remove residues. Mechanical abrasion is performed by contacting the substrate with a conventional polishing pad and providing relative motion between the substrate and polishing pad. However, conventional polishing pads often limit electrolyte flow to the surface of the substrate. Additionally, the polishing pad may be composed of insulative materials that may interfere with the application of bias to the substrate surface and result in non-uniform or variable dissolution of material from the substrate surface.
Therefore, there is a need for a polishing article for the removal of conductive material on a substrate surface and a fabrication method to effectively provide a surface having a desired pattern.
Aspects of the invention generally provide methods for forming a conductive article for electrochemical mechanical polishing. In one aspect, a method is provided for processing a substrate including providing a substrate having a conductive base structure comprising one or more fibers coated with a conductive material, depositing a mask material on the conductive base structure, patterning the mask layer to expose portions of the conductive base structure, and depositing a metal layer on the exposed portions of the conductive base structure by an electrochemical deposition technique. In another aspect, a polishing article is provided for processing a substrate including a fabric layer and a plurality of conductive contacts disposed on the fabric and adapted to polish a substrate.
In another aspect, a method is provided for processing a polishing article including providing a substrate having a conductive base structure comprising one or more fibers coated with a conductive material, depositing a pattern template on the conductive base structure, wherein the patterned template is adapted to expose portions of the conductive base structure, and depositing a metal layer on the exposed portions of the conductive base structure by an electrochemical deposition technique.
So that the manner in which the above recited features of the present invention can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments.
The words and phrases used herein should be given their ordinary and customary meaning in the art by one skilled in the art unless otherwise further defined. Chemical-mechanical polishing should be broadly construed and includes, and is not limited to, abrading a substrate surface by chemical activity, mechanical activity, or a combination of both chemical and mechanical activity. Electropolishing should be broadly construed and includes, and is not limited to, planarizing a substrate by the application of electrochemical activity, such as by anodic dissolution.
Electrochemical mechanical polishing (ECMP) should be broadly construed and includes, and is not limited to, planarizing a substrate by the application of electrochemical activity, chemical activity, mechanical activity, or a combination of electrochemical, chemical, and mechanical activity to remove material from a substrate surface.
Electrochemical mechanical plating process (ECMPP) should be broadly construed and includes, and is not limited to, electrochemically depositing material on a substrate and generally planarizing the deposited material by the application of electrochemical activity, chemical activity, mechanical activity, or a combination of electrochemical, chemical, and mechanical activity.
Anodic dissolution should be broadly construed and includes, and is not limited to, the application of an anodic bias to a substrate directly or indirectly which results in the removal of conductive material from a substrate surface and into a surrounding electrolyte solution. Polishing surface is broadly defined as the portion of an article of manufacture that at least partially contacts a substrate surface during processing or electrically couples an article of manufacture to a substrate surface either directly through contact or indirectly through an electrically conductive medium.
The polishing article may be disposed on any apparatus capable of performing an electrochemical mechanical polishing process. One polishing tool that may be adapted to benefit from the invention is a MIRRAŽ Mesa™ chemical mechanical polisher available from Applied Materials, Inc. located in Santa Clara, Calif. An example of a suitable polishing apparatus is described in U.S. patent application Ser. No. 10/455,941, filed on Jun. 6, 2003, and incorporated by reference herein to the extent not inconsistent with the disclosure herein. Another example of a suitable polishing apparatus is described in U.S. patent application Ser. No. 10/980,888, filed on Nov. 3, 2004, and incorporated by reference herein to the extent not inconsistent with the disclosure herein.
Although the embodiments of the invention disclosed below focus primarily on polishing a substrate, it is contemplated that the teachings disclosed herein may be utilized to electroplate a substrate by reversing the polarity of the bias.
In one embodiment, the carrier head assembly 118 may be positioned over the platen assembly 142 by an arm 164 coupled to a column 130. The carrier head assembly 118 generally includes a drive system 102 coupled to a carrier head 122. The drive system 102 generally provides at least rotational motion to the carrier head 122. The carrier head 122 additionally may be actuated toward the platen assembly 142 such that the substrate 120 retained in the carrier head 122 may be disposed against a processing surface 104 of the pad assembly 106 during processing.
In one embodiment, the carrier head 122 may be a TITAN HEAD™ or TITAN PROFILER™ wafer carrier manufactured by Applied Materials, Inc., of Santa Clara, Calif. Generally, the carrier head 122 comprises a housing 124 and retaining ring 126 that define a center recess in which the substrate 120 is retained while leaving a feature side of the substrate exposed. The retaining ring 126 circumscribes the substrate 120 disposed within the carrier head 122 to prevent the substrate 120 from slipping out from under the carrier head 122 during processing. It is contemplated that other carrier heads may be utilized.
The platen assembly 142 is rotationally disposed on a base 158. A bearing 154 is disposed between the platen assembly 142 and the base 158 to facilitate rotation of the platen assembly 142 relative to the base 158. A motor 160 is coupled to the platen assembly 142 to provide rotational motion.
In one embodiment, the platen assembly 142 includes an upper plate 114 and a lower plate 148. The upper plate 114 may be fabricated from a rigid material, such as a metal or rigid plastic, and in one embodiment, is fabricated from or coated with a dielectric material, such as chlorinated polyvinyl chloride (CPVC). The upper plate 114 may have a circular, rectangular or other geometric form with a planar top surface 116. A top surface 116 of the upper plate 114 supports the pad assembly 106 thereon. The pad assembly 106 may be held to the upper plate 114 of the platen assembly 142 by magnetic attraction, static attraction, vacuum, adhesives, or the like.
The lower plate 148 is generally fabricated from a rigid material, such as aluminum and may be coupled to the upper plate 114 by any conventional means, such as a plurality of fasteners (not shown). Generally, a plurality of locating pins 146 (one is shown in
A plenum 138 is defined in the platen assembly 142 and may be partially formed in at least one of the upper or lower plates 114, 148. In the embodiment depicted in
A pad assembly 106 and at least one contact element 134 are disposed on the platen assembly 142. The contact element 134 is adapted to electrically couple the substrate 120 to a power source 166. The contact element 134 may be coupled to the platen assembly 142, part of the pad assembly 106, or a separate element and is generally positioned to maintain contact with the substrate 120 during processing. The pad assembly 106 includes an electrode (210, shown in
Alternatively, the pad assembly 106 may be configured without an electrode, in which case the electrode may be disposed upon or within the platen assembly 142. It is contemplated that multiple contact elements 134 and/or electrodes 210 may be used. The contact elements 134 and/or electrodes 210 may be independently biased.
To facilitate control of the processing station 100 as described above, a controller 180 is coupled to the processing station 100. The controller 180 is utilized to control power supplies, motors, drives, fluid supplies, valves, actuators, and other processing components of the processing station 100. The controller 180 comprises a central processing unit (CPU) 182, support circuits 186 and memory 184. The CPU 182 may be one of any form of computer processor that can be used in an industrial setting for controlling various chambers and sub-processors. The memory 184 is coupled to the CPU 182. The memory 184, or computer-readable medium, may be one or more of readily available memory such as random access memory (RAM), read only memory (ROM), floppy disk, hard disk, or any other form of digital storage, local or remote. The support circuits 186 are coupled to the CPU 182 for supporting the processor in a conventional manner. These circuits include cache, power supplies, clock circuits, input/output circuitry, subsystems, and the like.
The controller 180 may receive a metric indicative of processing performance for closed-loop process control of the processing station 100. For example, material removal in a polishing operation may be monitored by measuring and/or calculating the thickness of conductive material remaining on the substrate 120. The thickness of the material remaining on the substrate 120 may be measured and/or determined by, for example, optical measurement, interferometric end point, process voltage, process current, charge removed from the conductive material on the substrate, effluent component analysis, and other known means for detecting process attributes.
The processing surface 104 of the pad assembly 106 includes a non-conductive processing surface 202 and a conductive surface 204. In the embodiment depicted in
The passage 218 extends through the non-conductive surface 202 at least to the electrode 210 and allows an electrolyte to establish a conductive path between the substrate 120 (shown in
Optionally, an extension 222 of the permeable passage 218 (shown in phantom) may be formed in and at least partially through the electrode 210. The extension 222 may extend completely through the electrode 210. The extension 222 increases the surface area of the electrode 210 in contact with the electrolyte which improves the rate of removal of material from the surface of the substrate 120 during processing. Electrolyte from the source 170 or other fluid may optionally flow through the holes 216.
The non-conductive surface 202, or optionally the entire upper layer 212, may be fabricated from polymeric materials compatible with process chemistry, examples of which include polyurethane, polycarbonate, nylon, acrylic polymers, epoxy, fluoropolymers, PTFE, PTFA, polyphenylene sulfide (PPS), or combinations thereof, and other polishing materials used in polishing substrate surfaces. In one embodiment, the non-conductive surface 202 of the pad assembly 106 is dielectric, for example, polyurethane or other polymer. In the embodiment depicted in
In one implementation, the upper layer 212 can be manufactured, e.g., by a molding process, with the permeable passages 218 formed in the upper layer 212. In one molding process, e.g., injection molding or compression molding, the pad material cures or sets in a mold that has indentations that form the holes 216 that form the permeable passage 218. Alternatively, the upper layer 212 can be manufactured by a more conventional technique, e.g., by skiving a thin sheet of pad material from a cast block. The permeable passages 218 may be part of a porous pad material. Alternatively, the permeable passages 218 may comprise holes 216 formed by machining the upper layer 212.
Examples of pad assemblies that may be adapted to benefit from the invention are described in U.S. patent application Ser. No. 10/455,941, filed Jun. 6, 2003 by Y. Hu et al. and U.S. patent application Ser. No. 10/455,895, filed Jun. 6, 2003 by Y. Hu et al., both previously incorporated by reference.
The subpad 211 is a compressible material that is softer and more compressible than the upper layer 212. For example, the subpad can be a closed-cell foam, such as polyurethane or polysilicone with voids, so that under pressure the cells collapse and the subpad compresses. In one embodiment, the subpad 211 comprises foamed urethane. Alternatively, the subpad 211 may be formed of other materials having other structures such as a mesh, cells, or solid configurations so longs as the compressibility of the subpad 211 meets the requirements detailed below. Examples of suitable subpad 211 materials include, but are not limited to, foamed polymers, elastomers, felt, impregnated felt, and plastics compatible with the polishing chemistries.
It is permissible for the material of the subpad 211 to be laterally displaced under pressure from the substrate. The subpad 211 can have a hardness in the range of from 2-90 on the Shore A scale. In one embodiment, the subpad 211 has a Shore A hardness in the range of from about 20 or less, such as 12 or less, or 5 or less.
In addition, the subpad 211 has a thickness of, e.g., 30 mils or more. In one embodiment, the subpad 211 has a thickness of 90 mils or more. For example, the subpad may be about 95 to 500 mils thick, such as 95 to 200 mils, or 95 to 150 mils, or 95 to 125 mils.
In general, the thickness of the subpad 211 is selected to ensure that, given the compressibility of the subpad 211 and the rigidity of the upper layer 212, the upper layer will deflect at very low pressures, e.g., pressures of 0.5 psi or less, an amount at least equal to any non-uniformity in the thickness of the upper layer, e.g., about 2 mil. Compressibility may be measured as a percentage thickness change at a given pressure. For example, under a pressure of about 0.5 psi, the subpad 211 can undergo about 3% compression. For Example, a 100 mil thick subpad should have a compression of at least 2% at 0.5 psi, whereas a 200 mil thick subpad should have a compression of at least 1% at 0.5 psi. A suitable material for the subpad is PORON 4701-30 from Rogers Corporation, in Rogers, Connecticut (PORON is a trademark of Rogers Corporation).
Moreover, the subpad should be sufficiently compressible that at the operating pressures of interest, e.g., at 1 psi or less, the polishing pad assembly is below the maximum compressibility of the polishing pad assembly. The subpad can have a maximum compressibility greater than about 10%, or greater than about 20%. In one implementation, the subpad can have a compressibility of about 25% at pressures of about 1 to about 9 psi at a 0.2 in/min strain rate, with a maximum compressibility that is even higher.
In brief, at pressures of 1 psi or below (and possibly at 0.8 psi or below, or 0.5 psi or below, or 0.3 psi or below), the subpad can have a product of the compressibility and thickness (CˇD) that is greater than the non-uniformities in thickness of the cover layer. For example, at pressures of 0.8 psi or below (and possibly at 0.5 psi or below), the subpad can have a product of the compressibility and thickness (CˇD) of 2 mils or more (and possibly 3 mils or more).
Hydrostatic modulus K may be measured as applied pressure (P) divided volumetric strain (AVN), i.e., K=PV/AV. Assuming that the subpad undergoes pure compression (i.e., material is not displaced laterally under the applied pressure), then the hydrostatic modulus K equals the applied pressure divided by the compression (AD/D). Thus, assuming that the subpad undergoes at least 2% pure compression at 0.5 psi, the subpad would have a compressibility modulus K of 25 or less. On the other hand, if even lower pressures are to be used, e.g., pressures of 0.1 psi, then the subpad 211 should have a compressibility modulus of 5 or less. The subpad may have a compressibility modulus K of 50 psi or less per psi of applied pressure in the range of 0.1 to 1.0 psi. Of course, if the material of the subpad does undergo lateral displacement under compression, then the volumetric strain will be somewhat less than the compression, so the hydrostatic modulus may be somewhat higher.
Without being limited to any particular theory, this configuration permits the downward force from the substrate to “flatten out” the non-conductive surface 202 of the upper layer 212 at low pressures, even at pressures of 0.5 psi or less, such as 0.3 psi or less, such as 0.1 psi, and thus substantially compensate for the thickness non-uniformity of the upper layer. For example, the variations in thickness of the upper layer 212 are absorbed by the compression of the subpad 211, so that the processing surface remains in substantially uniform contact with the substantially planar substrate across the substrate surface. As a result, a uniform pressure can be applied to the substrate by the processing pad, thereby improving processing uniformity during low pressure processing. Consequently, materials that require low-pressure processing to avoid delamination, such as low-k dielectric materials, can be processed with an acceptable degree of uniformity. It is contemplated that the embodiments of the subpad 211 disclosed above is applicable to any embodiment of processing pad assemblies disclosed herein that have subpads.
The electrode 210 is disposed on the top surface 116 of the platen assembly 142 and may be held there by magnetic attraction, static attraction, vacuum, adhesives, or the like. In one embodiment, adhesive is used to secure the electrode 210 to the upper plate 114. It is contemplated that other layers, such as release films, liners, and/or other adhesive layers, may be disposed between the electrode 210 and the top surface 116 to facilitate ease of handling, insertion, and removal of the pad assembly 106 from the platen assembly 142.
The electrode 210 is coupled to the power source 166 and may act as a single electrode, or may comprise multiple independently biasable electrode zones isolated from each other. The electrode 210 is typically comprised of a corrosion resistant conductive material, such as metals, conductive alloys, metal coated fabrics, conductive polymers, conductive pads, and the like. Conductive metals include Sn, Ni, Cu, Au, and the like. Conductive metals also include a corrosion resistant metal such as Sn, Ni, or Au coated over an active metal such as Cu, Zn, Al, and the like. Conductive alloys include inorganic alloys and metal alloys such as bronze, brass, stainless steel, or palladium-tin alloys, among others. Metal coated fabric may be woven or non-woven with any corrosion resistant metal coating. Conductive pads may consist of conductive fillers disposed in a polymer matrix. The electrode 210 should also be fabricated of a material compatible with electrolyte chemistries to minimize cross-talk between zones when multi-zoned electrodes are utilized. For example, metals stable in the electrolyte chemistries are able to minimize zone cross-talk.
When metal is used as the material for the electrode 210, it may be a solid sheet. Alternatively, the electrode 210 may be perforated or formed of a metal screen in order to increase the adhesion to the upper layer 212 or the optional subpad 211. The electrode 210 may also be primed with an adhesion promoter to increase the adhesion to the upper layer 212 or the optional subpad 211. An electrode 210 which is perforated or formed of a metal screen also has a greater surface area which further increases the substrate removal rate during processing.
When the electrode 210 is fabricated from metal screen, a perforated metal sheet, or conductive fabric, one side of the electrode 210 may be laminated, coated, or molded with a polymer layer which penetrates the openings in the electrode 210 to further increase adhesion to the upper layer 212 or the optional subpad 211. When the electrode 210 is formed from a conductive pad, the polymer matrix of the conductive pad may have a high affinity or interaction to an adhesive applied to the upper layer 212 or the optional subpad.
The contact element 134 may be integrally or removably coupled to the upper layer 212, the electrode 210, the upper surface 116 of the platen assembly 142, or combinations thereof. In one embodiment, at least one aperture 220 is formed in at least the upper layer 212 and the optional subpad 211 of the pad assembly 106. Alternatively, the at least one aperture 220 may extend completely through the pad assembly 106, as shown in phantom at 226 in
It is contemplated that any number of contact elements 134 may be utilized in any geometric configuration across the pad assembly 106. The contact elements 134 may be disposed in any location or combination of locations on the pad assembly 106, for example, at the center, the edge, the middle, or combinations thereof. It is also contemplated that contact elements 134 may be formed in any geometric shape including, but not limited to, circles, ellipses, polygons, arcs, spirals, wavy lines, line segments, radii, and the like. For example, a centrally disposed contact element 134, as depicted in
In one embodiment of the pad assembly, the processing surface 104 of the pad assembly 106 includes a fully conductive surface 204 as described herein. In another embodiment of the pad assembly, the processing surface 104 of the pad assembly 106 includes a non-conductive processing surface 202 and a conductive surface 204. In the embodiment depicted in
In another embodiment, the contact element 134 circumscribes at least a portion of the non-conductive processing surface 202, rather than being disposed in an aperture 220. For example,
The embodiments depicted herein are illustrative only and other configurations are contemplated. Note that any of the embodiments of contact elements 134 depicted in any of
The contact elements of the polishing assembly comprise a base structure and a plurality of contacts disposed thereon. The contacts may be disposed in any location or combination of locations on the base structure of the contact element, and disposed in any pattern. The base structure may have the shape as described for the contact elements described herein.
The contacts may be disposed over the entire upper surface of the base structure or a portion of the upper surface at the center, the edge, the middle, or combinations thereof, of the base structure. The contacts may be formed in any geometric shape including, but not limited to cylinders, trapezoidal, pyramidal or truncated pyramidal shape, cube or rectangular shape, and frustoconical shapes. The top portions of the contacts may be pyramidal, rounded or planar. The contacts may also have variable be disposed with variable density in umber, for example, a higher density of contacts may be disposed at a perimeter of the contact element as opposed to a center portion. The contacts may also be disposed in any pattern including delineated rows and columns, arcuate patterns, spirals patterns, concentric rings, and the like. The contacts may also vary in size, for example, such as having dimensions of one millimeter by one millimeter or two millimeter by two millimeter, and a height between 0.1 millimeter and two millimeter.
The base structure may be formed as a metal foil or as a fabric of conductive fibers. The conductive fiber materials may comprise conductive or dielectric fibers, such as dielectric or conductive polymers or carbon-based materials, at least partially, or completely, coated or covered with a conductive material including a metal, a carbon-based material, a conductive ceramic material, a conductive alloy, or combinations thereof. The conductive fibers may be in the form of fibers or filaments to form a conductive fabric or cloth, and the conductive fibers may further be in the shape of linear fibers or one or more loops, coils, or rings of conductive fibers. Multiple layers of conductive materials, for example, multiple layers of conductive cloth or fabric, may be used to form the base structure.
Dielectric polymeric materials may be used as fiber materials. Examples of suitable dielectric fiber materials include polymeric materials, such as polyamides, polyimides, nylon polymer, polyurethane, polyester, polypropylene, polyethylene, polystyrene, polycarbonate, diene containing polymers, such as AES (polyacrylontrile ethylene styrene), acrylic polymers, or combinations thereof. The invention also contemplates the use of organic or inorganic materials that may be used as fibers described herein.
The conductive fiber material may comprise intrinsically conductive polymeric materials including polyacetylene, polyethylenedioxythiophene (PEDT), which is commercially available under the trade name Baytron™, polyaniline, polypyrrole, polythiophene, carbon-based fibers, or combinations thereof. Another example of a conductive polymer is polymer-noble metal hybrid materials. Polymer-noble metal hybrid materials are generally chemically inert with a surrounding electrolyte, such as those with noble metals that are resistant to oxidation. An example of a polymer-noble metal hybrid material is a platinum-polymer hybrid material. Examples of conductive polishing materials, including conductive fibers, are more fully described in co-pending U.S. patent application Ser. No. 10/033,732, filed on Dec. 27, 2001, entitled, “Conductive Polishing Article for Electrochemical Mechanical Polishing”, which is incorporated herein by reference in its entirety. The invention also contemplates the use of organic or inorganic materials that may be used as fibers described herein.
The fiber material may be solid or hollow in nature. The fiber length is in the range between about 1 μm and about 1000 mm with a diameter between about 0.1 μm and about 1 mm. In one aspect, the diameter of fiber may be between about 5 μm to about 200 μm with an aspect ratio of length to diameter of about 5 or greater, such as about 10 or greater, for conductive polymer composites and foams, such as conductive fibers disposed in polyurethane. The cross-sectional area of the fiber may be circular, elliptical, star-patterned, “snow flaked”, or of any other shape of manufactured dielectric or conductive fibers. High aspect ratio fibers having a length between about 5 mm and about 1000 mm in length and between about 5 μm and about 1000 μm in diameter may be used for forming meshes, loops, fabrics or cloths, of the conductive fibers. The fibers may also have an elasticity modulus in the range between about 104 psi and about 108 psi. However, the invention contemplates any elastic modulus necessary to provide for compliant, elastic fibers in the polishing articles and processes described herein.
Conductive material disposed on the conductive or dielectric fiber material generally include conductive inorganic compounds, such as a metal, a metal alloy, a carbon-based material, a conductive ceramic material, a metal inorganic compound, or combinations thereof. Examples of metal that may be used for the conductive material coatings herein include noble metals, tin, lead, copper, nickel, cobalt, and combinations thereof. Noble metals include gold, platinum, palladium, iridium, rhenium, rhodium, rhenium, ruthenium, osmium, and combinations thereof, of which tin, gold and platinum are preferred. Preferred materials include metal that have a hardness less than that of copper.
An example of a suitable conductive fiber is nylon fibers coated with tin. An example of a conductive fiber using a nucleation material is a nylon fiber coated with a copper seed layer and a tin layer disposed on the copper layer. The invention contemplates that the coating of the fibers may occur before or after interweaving of the fibers to form the fabric.
The invention also contemplates the use of other metals for the conductive material coatings than those illustrated herein. Carbon-based material includes carbon black, graphite, and carbon particles capable of being affixed to the fiber surface. Examples of ceramic materials include niobium carbide (NbC), zirconium carbide (ZrC), tantalum carbide (TaC), titanium carbide (TiC), tungsten carbide (WC), and combinations thereof. The invention also contemplates the use of other metals, other carbon-based materials, and other ceramic materials for the conductive material coatings than those illustrated herein. Metal inorganic compounds include, for example, copper sulfide or danjenite, Cu9S5, disposed on polymeric fibers, such as acrylic or nylon fibers. The danjenite coated fibers are commercially available under the tradename ThunderonŽ from Nihon Sanmo Dyeing Co., Ltd, of Japan. The ThunderonŽ fibers typically have a coating of danjenite, Cu9S5, between about 0.03 μm and about 0.1 μm and have been observed to have conductivities of about 40 Ω/cm.
The conductive coating may be disposed directly on the fiber by plating, coating, physical vapor deposition, chemical deposition, binding, or bonding of the conductive materials. Additionally, a nucleation, or seed, layer of a conductive material, for example, copper, cobalt or nickel, may be used to improve adhesion between the conductive material and the fiber material. The conductive material may be disposed on individual dielectric or conductive fibers of variable lengths as well as on shaped loops, foams, and cloths or fabrics made out of the dielectric or conductive fiber material. A seed layer is broadly defined herein as continuously or discontinuously deposited material used to promote or facilitate growth of subsequently deposited layers on a surface and to enhance interlayer adhesion of deposited materials. The invention also contemplates that any material suitable for catalyzing or nucleating an electrochemical deposition process may be used as a seed layer, for example, an organic ligand material that initiates metal deposition may be used.
The fibers may be interwoven into a conductive fabric or cloth. The conductive fabric may be manufactured by interweaving the fibers and the coating the fibers with a conductive material as described herein or the fibers may be coated with the conductive material prior to interweaving into a conductive fabric. In one embodiment of the conductive fabric, the fiber material coated with a conductive material may be interwoven to form a yarn. The yarns may be brought together to make a conductive mesh that may be used in place of the conductive fabric as the contact element.
The conductive materials are used to coat both dielectric and conductive fibers to provide a desired level of conductivity for forming the conductive polishing material. Generally, the coating of conductive material is deposited on the fiber and/or filler material to a thickness between about 0.01 μm and about 50 μm, such as between about 0.02 μm and about 10 μm. The coating typically results in fibers or fillers having resistivities less than about 100 Ω-cm, such as between about 0.001 D-cm and about 32 Ω-cm. The invention contemplates that resistivities are dependent on the materials of both the fiber and the coating used, and may exhibit resistivities of the conductive material coating, for example, platinum, which has a resistivity 9.81 μΩ-cm at 0° C. An example of a suitable conductive fiber includes a nylon fiber coated with about 0.1 μm copper, nickel, or cobalt, and about 2 μm of gold disposed on the copper, nickel, or cobalt layer, with a total diameter of the fiber between about 30 μm and about 90 μm.
The conductive fiber may be used to form a contact element having bulk or surface resistivity of about 50 Ω-cm or less, such as a resistivity of about 3 Ω-cm or less. In one aspect of the contact element, the contact element has a resistivity of about 1 Ω-cm or less. An example of a composite of the conductive polishing material and conventional polishing material includes tin or carbon coated fibers which exhibit resistivities of 1 Ω-cm or less, disposed in a conventional polishing material of polyurethane in sufficient amounts to provide a polishing article having a bulk resistivity of about 10 Ω-cm or less.
The conductive polishing materials formed from the conductive fibers described herein generally have mechanical properties that do not degrade under sustained electric fields and are resistant to degradation in acidic or basic electrolytes. The conductive material and any binder material used are combined to have equivalent mechanical properties, if applicable, of conventional polishing materials used in a conventional polishing article. For example, the conductive polishing material, either alone or in combination with a binder material, has a hardness of about 100 or less on the Shore D Hardness scale for polymeric materials as described by the American Society for Testing and Materials (ASTM), headquartered in Philadelphia, Pa. In one aspect, the conductive material has a hardness of about 80 or less on the Shore D Hardness scale for polymeric materials. The conductive polishing portion 310 generally includes a surface roughness of about 500 microns or less. The properties of the contact element are generally designed to reduce or minimize scratching of the substrate surfaces during mechanical polishing and when applying a bias to the substrate surface.
Alternatively, a metal foil may be used in the place of the conductive fabric as the base structure of the contact element. The metal foil may comprise a material including noble metals, tin, lead, copper, nickel, cobalt, and combinations thereof. Noble metals include gold, platinum, palladium, iridium, rhenium, rhodium, rhenium, ruthenium, osmium, and combinations thereof, of which tin, gold and platinum are preferred. Preferred materials include metal that have a hardness less than that of copper, such as tin. The metal foil comprises the substantially the same physical properties as the conductive fabric, for example, the same or substantially the same conductivity.
Methods for forming a polishing article having a plurality of conductive contacts will be described as follows.
A base structure of a fabric of fibers coated with a conductive material as described herein is provided to a processing apparatus at step 301. A mask material is deposited on the base structure at step 303. The mask material is patterned to expose portions of the underlying fabric layer at step 305. A metal layer is then selectively deposited on the exposed portions of the fabric layer by an electrochemical deposition process at step 307. The mask material is then removed from the base structure to form a plurality of contacts extending above the plane of the fabric layer at step 309.
Initially, a base structure is provided to deposit material thereon at step 301. The base structure comprises a layer of fabric material 310 as described herein. In one example, the base structure or fabric material 310 may comprise interwoven nylon fibers or polyester fibers coated in tin. An optional seed layer may be disposed on the nylon fiber before the deposition of tin. The base structure may be introduced into any apparatus adapted for electrochemical deposition, such as electroless and electroplating processes. Examples of suitable apparatus for electrochemical deposition include the SlimCell™ platform and the iECP™ platform, available from Applied Materials of Santa Clara, Calif.
A mask layer 320 is then deposited on the base structure 310 at step 303. The mask material may be any material suitable forming a pattern of non-conductive material on the base structure surface that may then be patterned. Suitable non-conductive material include, for example, a dielectric material, such as amorphous carbon silicon oxide, carbon-doped silicon oxide, oxygen containing silicon carbide, or silicon carbide, or a resist material, such as a photoresist material or e-beam resist material. Examples of suitable resist materials include ZEP, a resist material commercially available from Tokyo-Oka of Japan, or a chemically amplified resist (CAR) also commercially available from Tokyo-Oka of Japan.
The resist layer 320 may be deposited on the base structure 310 at any suitable thickness, for example, between about 100 angstroms (Å) and about 6000 Å thick, such as between about 2000 Å and about 4000 Å thick, and may be of any thickness desired. Preferred photoresist materials include those used to manufacture circuit boards. While the following description illustrates the use of a positive photoresist, the invention contemplates that a negative photoresist or other resist material, such as an e-beam resist, known or unknown, may be used.
A resist layer 320 may then be patterned on the fabric layer 310 to expose the underlying material at step 305. In one resist patterning process, a photoresist material is deposited, exposed to an energy source, such as ultraviolet light, through a patterned reticle to modify a portion of the photoresist, and then chemically treated or developed to remove modified or unmodified portions of the photoresist material. Alternatively, a resist material can be patterned using conventional laser or electron beam patterning equipment.
The resist material is then treated with a developing solution, such as an alkaline solution or amine solution, to remove the modified photoresist material and expose the underlying fabric layer 310 to form apertures 330 in the remaining resist material 340. The patterning process forms apertures 330 for the subsequent deposition of material therein. The patterned resist material 340 may form patterns including a matrix of elements of variable shapes and sizes depending on the desired pattern of materials deposited therein.
The base structure may then be introduced into an apparatus and a metal layer 350 deposited on the fabric layer 310 by an electrochemical process at step 307. The electrochemical process may include electroless deposition or electroplating techniques. The metal layer 350 may be any material suitable for deposition from an electrochemical process, for example, copper, nickel, cobalt, palladium, tin, titanium, tantalum, tungsten, molybdenum, platinum, iron, niobium, and combinations thereof, including alloys, may be used, of which materials softer than copper, such as tin are preferably used. The metal layer 350 may be doped, for example, with phosphorus, boron, tungsten, molybdenum, rhenium, and combinations thereof, among others. The metal layer 350 may also comprise the same material as the conductive material coating the fibers. For example, a tin metal layer may be deposited on a tin coated nylon or polyester fibers. The metal layer 350 may be deposited to any desired thickness, and may fill up all or a portion of the apertures 330 formed in the resists layer 340.
Examples of suitable electroless plating techniques are provided in commonly assigned U.S. Pat. No. 6,258,223, entitled “In-Situ Electroless Copper Seed Layer Enhancement In An Electroplating System,” filed on Jul. 9, 1999, and in co-pending U.S. publication No. 20020152955, entitled “Apparatus And Method For Depositing An Electroless Solution,” filed on Dec. 30, 1999, which are hereby incorporated by reference to the extent not inconsistent with the claimed aspects and disclosure herein.
Examples of suitable electroplating techniques are provided in commonly assigned U.S. Pat. No. 6,258,220, entitled “Electro-chemical Deposition System,” and in co-pending U.S. patent application Ser. No. 09/245,780, entitled “Electrodeposition Chemistry for Improved Filling of Apertures,” filed on Feb. 5, 1999, which are hereby incorporated by reference to the extent not inconsistent with the claimed aspects and disclosure herein. One suitable system that can be used to deposit a metal layer 230 by an electroplating or electroless process is the ElectraŽ ECP system, available from Applied Materials, Inc., of Santa Clara, Calif.
One example of a suitable electroplating technique is provided in commonly assigned U.S. patent application Ser. No. 10/351,227, entitled “Homogeneous Copper-Tin Alloy Plating For Enhancement Of Electro-Migration Resistance In Interconnects,” filed on Jan. 24, 2003, which is hereby incorporated by reference to the extent not inconsistent with the claimed aspects and disclosure herein.
For example, a tin layer may be deposited from a tin plating solution including a tin source, and optionally, one or more organic additives configured to provide a control element over the plating characteristics of the plating solution. The source for the tin ions includes, for example, SnSO4, SnCl2, or another tin containing compound acceptable to a tin electrochemical plating solution. The concentration of the tin ions in the plating solution, for example, is between about 0.1M and about 0.9M.
The plating solution may additionally contain an acid, which, for example, may be at a concentration of between about 5 g/L and about 200 g/L, and further, the plating solution may contain halide ions, such as chloride, for example, which may be at a concentration of between about 10 ppm and about 200 ppm. Exemplary acids that may be used in plating solution include sulfuric acid, phosphoric acid, and/or derivatives thereof. However, embodiments of the invention are not limited to these parameters or components.
The electroplating solution may further include one or more organic additives configured to provide a control element of the plating characteristics of the plating solution. Additives, which may be, for example, levelers, inhibitors, suppressors, brighteners, accelerators, or other additives known in the art, are typically organic materials that adsorb onto the surface of the base structure being plated. Useful suppressors typically include copolymers—ethylene oxide, propylene oxide, polyethers, such as polyethylene glycol (PEG), for example, and/or other polymers, such as polyethylene-polypropylene oxides, which adsorb on the base structure surface, slowing down deposition in the adsorbed areas. Useful accelerators typically include sulfides or disulfides, such as bis (3-sulfopropyl) disulfide, MPSA, and SPS molecules, which compete with suppressors for adsorption sites, accelerating deposition in adsorbed areas. Useful levelers typically include amines, thiadiazole, imidazole, and other nitrogen containing organics. Useful inhibitors typically include sodium benzoate and sodium sulfite, which inhibit the rate of deposition on the base structure. Additionally hydroquinone may be utilized as an inhibitor, and may be added to the plating solution at in a concentration of up to about 2500 ppm, for example.
During plating, the additives are generally consumed at the base structure surface. As such, plating systems generally include a replenishment mechanism configured to replace the additives consumed in the plating process, so that a relatively constant concentration of the additives may be maintained the plating solution. However, it is generally known that the differences in diffusion rates of the various additives may result in varying concentrations of particular additives at the top of a high aspect ratio feature compared to the bottom of the feature, thereby setting up different plating rates at the top of the feature verses the bottom of the feature. For example, suppressors may be larger molecules that diffuse slower than accelerators, and therefore, fewer suppressors may adsorb onto the bottom surface of a high aspect ratio feature than accelerators. As such, the bottom of the feature may plate at a faster rate than the top of the feature, thus increasing the fill rate of the feature. Therefore, an appropriate composition of additives in the plating solution is desired to facilitate void-free fill of high aspect ratio features.
A plating current density applied to the base structure for a tin electrodeposition process, for example, may be between about 5 mA/cm2 and about 60 mA/cm2 at a constant current density. Alternatively, the plating current density may be varied throughout the deposition process, i.e., the current density is stepped up, down, or alternated between lower and higher current densities during a plating process. For example, the current density is calculated to facilitate tin deposition in an initial stage of filling a feature, and then the current density is changed to facilitate a more heavy deposition once the feature is somewhat lined with a tin alloy at the interfaces. Additionally, the substrate support member supporting the base structure during the electrodeposition process is rotated at between about 5 RPM and about 40 RPM, for example, while the flow rate of the electroplating solution to the electroplating cell is between about 0.5 GPM and about 6.5 GPM, for example.
Embodiments of the invention contemplate that the plating cell is capable of providing generally constant hydrodynamics, so that the flow of the plating solution across the plating surface of the base structure is constant. This operates to maintain a fresh supply of tin ions at the plating surface, which is important to simultaneous plating operations, as one ion may generally deplete faster than another ion and cause non-uniformity (spatial non-homogenous alloys) in the alloy layer.
Once the metal layer is deposited, the layer may be further processed. For example, the deposited metal may be exposed to a cleaning process and/or annealed. Embodiments of the invention contemplate that an annealing process may be implemented to anneal the metal contacts with the metal of the base structure to improve structure stability. The exposure/annealing time for a tin film may be between about 5 minutes and about 1 hour, depending upon the structure desired and the thermal budget available for the process.
The resist material 340 is then removed from the base structure 310 at step 309. The resist material 340 may be removed by any suitable process presently known or that may be developed. The remaining structures 350 of the metal layer comprise the plurality of contacts.
In an alternative embodiment, the structures 350 may be formed by using disposing a template having the pattern formed thereon as a mask in place of the resist material at step 303. Then a metal layer, a conductive polymer or polymer composite, such as a tin filled polyurethane or tin coated fibers disposed in a polyurethane, may be disposed on the base structure and form structures 350 in portions of the fabric layer 310 exposed by the template. The template may then be removed with the structures 350 being formed behind. Examples of metal filled polymers and polymer-metal composites are more fully described in commonly owned U.S. patent application Ser. No. 10/455,941, filed on Jun. 6, 2003, and incorporated by reference herein to the extent not inconsistent with the disclosure herein.
While the foregoing is directed to embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.