Patent Application
20080293343
1. Field of the Invention
Embodiments of the present invention generally relate to a processing apparatus for planarizing or polishing a substrate. More particularly, the invention relates to polishing pad design for planarizing or polishing a semiconductor substrate by electrochemical mechanical planarization.
2. Description of the Related Art
In the fabrication of integrated circuits and other electronic devices on substrates, multiple layers of conductive, semiconductive, and dielectric materials are deposited on or removed from a substrate, such as a semi conductor substrate. As layers of materials are sequentially deposited and removed, the substrate may become non-planar and require planarization, in which previously deposited material is removed from the substrate to form a generally even, planar or level surface. The process is useful in removing undesired surface topography and surface defects, such as rough surfaces, agglomerated materials, crystal lattice damage and scratches. The planarization process is also useful in forming features on the substrate by removing excess deposited material used to fill the features and to provide an even or level surface for subsequent deposition and processing.
Electrochemical Mechanical Planarization (ECMP) is one exemplary process which is used to remove materials from the substrate. ECMP typically uses a pad having conductive properties and combines physical abrasion with electrochemical activity that enhances the removal of materials. The pad is attached to an apparatus having a rotating platen assembly that is adapted to couple the pad to a power source. The apparatus also has a substrate carrier, such as a polishing head, that is mounted on a carrier assembly above the pad that holds a substrate. The polishing head places the substrate in contact with the pad and is adapted to provide downward pressure, controllably urging the substrate against the pad. The pad is moved relative to the substrate by an external driving force and the polishing head typically moves relative to the moving pad. A chemical composition, such as an electrolyte, is typically provided to the surface of the pad which enhances electrochemical activity between the pad and the substrate. The ECMP apparatus may affect abrasive and/or polishing activity from frictional movement while the electrolyte combined with the conductive properties of the pad selectively removes material from the substrate.
Although ECMP has produced good results in recent years, there is an ongoing effort to develop pads that improve polishing qualities, require less conditioning, and consume less polishing solution. For example, a conductive polishing pad used in an ECMP process generally includes an anode and a cathode (or counter electrode) separated by an insulating layer and porous foam pad. The foam pad provides mechanical cushion for global flexibility. The insulating layer and porous foam pad are exposed to polishing solution and tend to trap debris and byproducts during polishing. The debris and byproducts may scratch the substrate surface if not removed. Generally, renewing the polishing solution and rinsing the polishing pad may reduce the debris and byproducts. However, the foam pad makes it difficult to rinse the polishing pad and adds consumption of polishing solution.
Therefore, there exists a need in the art for a processing article or pad that is easy to clean and reduces amount of polishing solution used.
The present invention generally provides a polishing article that is easy to clean, reduces debris and byproduct accumulation and reduces amount of polishing solution needed.
One embodiment of the present invention provides a pad assembly for processing a substrate comprising a first conductive layer having an upper surface adapted to contact the substrate, a second conductive layer disposed below the first conductive layer with an insulative layer therebetween, and a compressive layer disposed below the second conductive layer opposite the first conductive layer, wherein a plurality of recesses are formed above the second conductive layer.
Another embodiment of the present invention provides a pad assembly for processing a substrate comprising a first electrode, a compressive layer disposed on one side of the first electrode, and a plurality of discrete members coupled to the first electrode opposite the compressive layer, wherein the plurality of discrete members and the first electrode define a plurality of recesses configured to retain a processing solution therein, each of the plurality of discrete members comprises a conductive layer adapted to contact the substrate and an insulative layer disposed between the first electrode and the conductive layer.
So that the manner in which the above recited features, advantages and objects of the present invention are attained and can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to the embodiments thereof 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.
To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures.
The words and phrases used in the present invention should be given their ordinary and customary meaning in the art by one skilled in the art unless otherwise further defined. The embodiments described herein may relate to removing material from a substrate, but may be equally effective for electroplating a substrate by adjusting the polarity of an electrical source. Common reference numerals may be used in the Figures, where possible, to denote similar elements depicted in the Figures.
A processing pad assembly 222 is disposed on the platen assembly 230. The processing pad assembly 222 is configured to receive an electrical bias to perform a plating process and/or an electrochemical mechanical polishing/planarizing process.
The drive system 202 generally provides at least a rotational motion to the carrier head 186 and additionally may be actuated toward the ECMP station 102 such that a device side 115 of the substrate 114 retained in the carrier head 186, may be disposed against a processing surface 125 of the pad assembly 222 during processing.
Typically, the substrate 114 and the processing pad assembly 222 are rotated relatively to one another in an ECMP process to remove material from the device side 115 of the substrate 114. Depending on process parameters, the carrier head 186 is rotated at a rotational speed greater than, less than, or equal to, the rotational speed of the platen assembly 230. The carrier head assembly 152 is also capable of remaining fixed and may move in a path indicated by arrow 107 during processing. The carrier head assembly 152 may also provide an orbital or a sweeping motion across the processing surface 125 during processing.
In one embodiment, the processing pad assembly 222 may be adapted to releasably couple to an upper surface 260 of the platen assembly 230. The pad assembly 222 may be bound to the upper surface 260 by the use of pressure and/or temperature sensitive adhesives, allowing replacement of the pad assembly 222 by peeling the pad assembly from the upper surface 260 and applying fresh adhesive prior to placement of a new pad assembly 222. In another embodiment, the upper surface 260 of the platen assembly 230, having the processing pad assembly 222 coupled thereto, may be adapted to releasably couple to the platen assembly 230 via fasteners, such as screws.
The platen assembly 230 is typically rotationally disposed on a base 108 and is typically supported above the base 108 by a bearing 238 so that the platen assembly 230 may be rotated relative to the base 108. The platen assembly 230 may be fabricated from a rigid material, such as a metal or rigid plastic, and in one embodiment the platen assembly 230 has an upper surface 260 that is fabricated from or coated with a dielectric material, such as CPVC. The platen assembly 230 may have a circular, rectangular or other plane form and the upper surface 260 may resemble that plane form.
An electrolyte 204 may be provided from the source 248, through appropriate plumbing and controls, such as a conduit 241, to a nozzle 255 above the processing pad assembly 222 of the ECMP station 102. Optionally, an enclosure 206 may be defined in the platen assembly 230 for containing an electrolyte and facilitating ingress and egress of the electrolyte to the pad assembly 222.
In the embodiment shown in
The pad assembly 222 comprises a first conductive layer 211, a second conductive layer 212, an insulative layer 214 disposed between the first conductive layer 211 and the second conductive layer 212, and a compressive layer 216. In one embodiment, the pad assembly 222 may comprise a pad base 210 on which the rest of the layers are stacked.
In one embodiment, the first conductive layer 211 and the insulative layer 214 may form a plurality of posts or discrete members 205 extending from the second conductive layer 212.
The discrete members 205 may include any geometrical shape, such as ovals, rectangles, triangles, hexagons, octagons, or combinations thereof. A processing surface 125 is generally defined by an upper portion of each of the plurality of discrete members 205, and the plurality of apertures 209. The plurality of apertures 209 are generally defined by the open areas between the plurality of discrete members 205.
Each of the plurality of apertures 209 defines a functional cell 207 which is configured to receive an electrolyte. Each of the functional cells 207 are adapted to perform as an electrochemical cell when the electrolyte 204 is provided to the pad assembly 222, and a differential electrical bias is applied to the first conductive layer 211 and the second conductive layer 212. The second conductive layer 212 may have a continuous body, for example a whole disk, preventing the electrolyte from contacting the compressive layer 216.
In one embodiment, the plurality of apertures 209, define an open area between about 10 percent to about 90 percent, for example, between about 20 percent to about 70 percent.
The compressive layer 216 may be made of a soft material that is configured to provide compressibility to the pad assembly 222.
The pad assembly 322 comprises a first conductive layer 311, a second conductive layer 312, an insulative layer 314 disposed between the first conductive layer 311 and the second conductive layer 312. The insulative layer 314 is configured to electrically isolate the first conductive layer 311 from the second conductive layer 312. The pad assembly 322 further comprises a compressive layer 316 disposed on one side of the second conductive layer 312 opposing the insulative layer 314. The pad assembly 322 further comprises a pad base 310 on which the rest of the layers are stacked.
In one embodiment, the first conductive layer 311 and the insulative layer 314 may form a plurality of discrete members 305 extending from the second conductive layer 312. The plurality of discrete members 305 may include any geometrical shape, such as ovals, rectangles, triangles, hexagons, octagons, or combinations thereof.
A plurality of apertures 309 are formed between the plurality of discrete members 305. The plurality of apertures 309 are generally defined by the open areas between the plurality of discrete members 305. The plurality of apertures 309 are connected to one another and are configured to retain an electrolyte therein. A processing surface 325 is generally defined by an upper portion of each of the discrete members 305.
The first conductive layer 311 and second conductive layer 312 may be connected to a power source 320 during processing. The electrolyte, when retained in the plurality of apertures 309, may form an electrochemical cell with the first and second conductive layers 311, 312 to remove or deposit a conductive material from or onto a surface in contact with the process surface 325.
The second conductive layer 312 is stacked on the compressive layer 316 which is stacked on a pad base 310. The compressive layer 316 is configured to provide compressibility to the pad assembly 322. The compressive layer 316 is not in fluid communication with the plurality of apertures 309, therefore, not in contact with the electrolyte during processing. The pad base 310 is configured to support the pad assembly 322.
When used in an electrochemical processing, such as electrochemical mechanical polishing or electroplating, the pad assembly 322 presents several advantages over the state of the art pad assemblies.
First, the pad assembly 322 has a reduced resistance between electrodes, i.e. between the first conductive layer 311 and the second conductive layer 312. This may be a result of the second conductive layer 312 being a whole piece instead of being distributed in a plurality of discrete members. Additionally, less electrolyte is disposed between the first and second conductive layers 311, 312 because height of the plurality of apertures 309 is reduced. In this embodiment, only thickness of the first conductive layer 311 and the insulative layer 314 contributes to the height of the plurality of apertures 309.
Second, volume of electrolyte used during processing may be reduced. Again, this may be contributed to the reduced height of the plurality of apertures 309. The reduced volume of electrolyte used makes it possible to replace the electrolyte and rinse the pad assembly more often without increasing product costs and reducing system throughput. In one embodiment, the electrolyte may be replaced for every substrate during polishing.
Third, defects on substrates being processed may be reduced because there is less room for storing particles and by products because less layers are exposed to the electrolyte during processing. Particularly, porous layers, such as the compressive layer 316, are not in fluid communication with the electrolyte.
Fourth, chemical decomposition is also reduced because less layers are exposed to the electrolyte during processing. Particularly, the compressive layer 316, which is more prone to decomposition, is not in contact with the electrolyte.
The first conductive layer 311 may comprise a conductive polymer material. In one embodiment, the first conductive layer 311 comprises a conventional polishing material, such as polymer based pad materials compatible with the process chemistry, examples of which include polyurethane, polycarbonate, fluoropolymers, polytetraflouroethylene(PTFE), polytetraflouroacrylate (PTFA), polyphenylene sulfide (PPS), or combinations thereof. The conventional polishing material may be coated, doped, or impregnated with a process compatible conductive material and/or particles. Alternatively, the first conductive layer 311 may be a conductive polymer, such as a conductive filler material disposed in a conductive polymer matrix, such as fine tin particles in a polyurethane binder, or a conductive fabric, such as carbon fibers in a polyurethane binder.
In one embodiment, the first conductive layer 311 comprises removal particles adapted to facilitate material removal from the device side of the substrate. In one embodiment, the removal particles are conductive particles, such as particles of tin, copper, nickel, silver, gold, or combinations thereof, in a conductive polymer matrix. In another embodiment, the removal particles are abrasive particles, such as aluminum, ceria, oxides thereof and derivatives thereof, and combinations thereof, in a conductive polymer matrix. In yet another embodiment, the removal particles are a combination of abrasive and conductive particles as described herein and are interspersed within the first conductive layer 311. The first conductive layer 311 may further include a chamfer, a bevel, a square groove, or combinations thereof, which is adapted to facilitate electrolyte and polishing byproduct transportation.
The second conductive layer 312 may be fabricated from a conductive material, such as stainless steel, aluminum, gold, silver, copper, tin, nickel, among others. For example, the second conductive layer 312 may be a metal foil, a mesh made of metal wire or metal-coated wire, or a laminated metal layer on a polymer material compatible with the electrolyte, such as a polyimide, polyester, flouroethylene, polypropylene, or polyethylene sheet. In one embodiment, the second conductive layer 312 is configured to provide conformity and sufficient stiffness to allow the pad assembly to remain substantially flat alone, or in combination with the pad base 310. In one embodiment, the second conductive layer 312 comprises a copper mesh.
The insulative layer 314 may be fabricated from polymeric materials, such as polyurethane and polyurethane mixed with fillers, polycarbonate, polyphenylene sulfide (PPS), ethylene-propylene-diene-methylene (EPDM), Teflon™ polymers, or combinations thereof, and other polishing materials used in polishing substrate surfaces, such as open or closed-cell foamed polymers, elastomers, felt, impregnated felt, plastics, and like materials compatible with the processing chemistries.
The compressive layer 316 may be made of a polymer material, such as an open cell foamed polymers, closed cell foamed polymers, a MYLAR® material, heat activated adhesives, or combinations thereof. In one embodiment, the compressive layer 316 may have a hardness of about 20 Shore A to about 90 Shore A. In one embodiment, the foam layer 316 comprises open cell foam, such as a urethane material sold under the trade name PORON®, which is available from the Rogers Corporation. In one embodiment, the foam layer 316 comprises a material under the trade name PORON® 30 or PORON® 35.
In one embodiment, binding layers 321a-d may be used in between the above described layers. The binding layers 321a-d may be made of an adhesive that is compatible with process chemistry, such as heat and/or pressure sensitive adhesives known in the art.
The pad assembly 422 is similar to the pad assembly 322 illustrated in
The conductive carrier layer 415 is configured to improve uniformity across a substrate being processed. In one embodiment, the conductive carrier layer 415 comprises a conductive material, such as stainless steel, aluminum, gold, silver, copper, tin, nickel, among others. For example, the conductive carrier layer 415 may be a metal foil, a mesh made of metal wire or metal coated wire, metal coated fabric, or a laminated metal layer on a polymer material compatible with the electrolyte used in processing, such as a polyimide, polyester, flouroethylene, polypropylenen, or polyethylene sheet.
While the foregoing is directed to the illustrative embodiment 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.
