METHOD OF MANUFACTURING A CHEMICAL MECHANICAL PLANARIZATION PAD
The present disclosure relates to a process for forming a chemical mechanical planarization pad. The process includes forming a chemical mechanical planarization pad including a polymer matrix and an embedded structure by heating the polymer matrix and the embedded structure at a first temperature T1 and a first pressure P1. The chemical mechanical planarization pad is then allowed to deform at a second temperature T2 and a second pressure P2. The chemical mechanical planarization pad is then compressed at given mold cavity thickness by applying heat at a third temperature T3, wherein T1>T2, P1>P2, T1≦T3.
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The present disclosure relates to a method of manufacturing a chemical mechanical planarization pad and the chemical mechanical planarization pad formed by such method. In particular, the method may incorporate multiple forming stages during pad formation.
BACKGROUNDSemiconductor devices may be formed from a relatively flat, thin wafer of a semiconductor material, such as silicon. As the devices and layers of interconnecting circuits are deposited on the wafer, the layers may be polished to achieve a sufficiently flat surface with minimal defects before additional layers are deposited. A variety of chemical, electrochemical, and chemical mechanical polishing techniques may be employed to polish the wafers.
In chemical mechanical polishing (CMP), a polishing pad made of polymer material, such as a polyurethane, may be used in conjunction with a slurry to polish the wafers. The slurry comprises abrasive particles, such as aluminum oxide, cerium oxide, or silica, dispersed in an aqueous medium. The abrasive particles generally range in size from 20 to 200 nanometers (nm). Other agents, such as surface active agents, oxidizing agents, or pH regulators, are typically present in the slurry. The pad may also be textured, such as with grooves or perforations, to aid in the distribution of the slurry across the pad and wafer and removal of the slurry and by products therefrom.
For example, in U.S. Pat. No. 6,656,018, whose teachings are incorporated herein by reference, a pad for polishing a substrate in the presence of a slurry is disclosed, where the slurry may contain abrasive particles and a dispersive agent. The pad itself may include a work surface and a backing surface. The pad may be formed from a two-component system, a first component comprising a soluble component, a second component comprising a polymer matrix component, where the soluble component is distributed throughout at least an upper portion of the working structure and the soluble component may include fibrous materials soluble in the slurry to form a void structure in the work surface.
The polishing pad is understood to be a relatively important aspect in a chemical mechanical planarization system impacting polishing rate, resultant uniformity, planarization, etc. Accordingly, physical properties of the pads, such as specific gravity, thickness, hardness, compression modulus, compressibility and the extent of their uniformity within the pad, are understood to be key attributes of the polishing pads that influence the polishing process Improvements in controlling the desired value and uniformity of these properties may, therefore, improve the chemical mechanical planarization process.
SUMMARYAn aspect of the present disclosure relates to a process for forming a chemical mechanical planarization pad. The process includes forming a chemical mechanical planarization pad including a polymer matrix and an embedded structure by heating the polymer matrix and the embedded structure at a first temperature T1 and a first pressure P1. The chemical mechanical planarization pad is then allowed to deform at a second temperature T2 and a second pressure P2. The chemical mechanical planarization pad is then compressed at given mold cavity thickness by applying heat at a third temperature T3, wherein T1>T2, P1>P2, T1<T3.
The above-mentioned and other features of this disclosure, and the manner of attaining them, will become more apparent and better understood by reference to the following description of embodiments described herein taken in conjunction with the accompanying drawings, wherein:
The present disclosure relates to a method of manufacturing chemical mechanical planarization (CMP) pads including embedded structures. In particular, the methods herein may incorporate multiple press stages, where the pad is subjected to a compressive force, thermal energy (heat) or both, multiple times during and after pad formation. The methods utilized herein may provide improved control of pad properties and their uniformity including, in particular, pad thickness and/or specific gravity. In another embodiment, the process may provide increased process design flexibility and the ability to form multiple layer CMP pads.
Without being bound to any particular theory, it has been found that the embedded structure within a given CMP pad may act as a resilient body. Thus, after forming a CMP pad, with only a single application of heat, pressure or both, the embedded structure within a CMP pad may subsequently partially or wholly rebound or spring back to the initial dimensions exhibited by the embedded structure prior to molding causing the CMP pad to deform. This may result in variations in specific gravity, thickness and other properties of the CMP pad, which may negatively affect CMP performance. It has been found herein, that by utilizing processes that apply multiple heating and/or pressing stages to the pad, relatively tighter control of specific gravity, thickness and other pad characteristics may be maintained, which may therefore improve polishing performance.
An example of a CMP pad produced according to the multiple stage process herein includes, consists of or consists essentially of a primary or first layer 10 including an embedded structure 12 dispersed in a polymer matrix 14. The pad and embedded structure are provided such that the pad includes one or more window regions 16. In embodiments, the window region is formed such that the embedded structure is at least partially or completely removed from that portion of the pad. Optionally, one or more additional layers 18 are provided, wherein one or more physical properties may be different from those exhibited by polymer matrix 14 of the primary layer.
In embodiments, one or more additional layers are formed directly on the surface of the primary or first layer and subsequent layers during additional compression steps forming a laminate, i.e., two or more layers bonded together. If reactive polymers, including polymer precursors and crosslinking agents are provided, the polymer precursors and cross-linking agents of one layer may at least partially react with residual polymer precursors and cross-linking agents of a subsequent layer. The additional layers may be mechanically or chemically bound to the primary layer including the polymer matrix and embedded structure securing the primary or layer to additional layers. For example, an adhesive may be applied between the first and second layers, or mechanical interlocks may be provided as between the first and second layers wherein features in the second layer may lock into features provided in a first layer.
The polymer matrix and the embedded structure may individually be selected from a variety of polymeric resins. For example, the polymeric resins may include polyurethane, polyvinyl alcohol, polyacrylate, polyacrylic acids, hydroxyethylcellulose, hydroxylmethylcellulose, methylcellulose, carboxymethylcellulose, polyethylene glycol, starch, maleic acid copolymer, polysaccharides, pectin, alginate, polyethylene oxide, polycarbonate, polyester, polyamide, polypropylene, polyacrylamide, polymethylacrylate, poly(methyl methacrylate), polyacrylonitrile, polyamines, polysulfone, polyimides, various silicone compounds as well as any copolymers and derivatives thereof.
Adhesives may include acrylic, epoxy, cyanoacrylates, silicone, or phenolic adhesives. In embodiments, the adhesive may be applied as a coating or film. In other embodiments, the adhesive may be provided as a double sided adhesive tape, wherein the adhesive is carried by a film carrier formed from polyester or polyolefin thermoplastic material.
In embodiments, the polymer matrix is selected from a polymer resin that is capable of providing end point detection via use of a laser or another light source which emits light that passes through the window 16, which may then be reflected off the polished surface of a substrate. The polymer matrix may be capable of transmitting at least a portion of incident light (radiation), which may be understood as light impinging on the surface of the polymer matrix. At least 1% or more of the radiation may be transmitted through a portion of the polymer matrix, and the thickness of the pad, including all values and ranges from 1% to 99%, such as 25% to 75%, 50% to 80%, etc.
In some embodiments, the polymer matrix is formed of polyurethane prepolymers such as MDI-, IPDI- or TDI-terminated aliphatic or aromatic polyester, or polyether prepolymers may be combined with a cross-linking or curing agent with or without catalyst and additives. Examples of polyurethane pre-polymers may be sourced from ADIPRENE LF 750D and L-325 from Chemtura, IMUTHANE APC-504 from COIM and mixtures thereof. Curing agents may include bis- or tri-functional amines such as Vibracure A134 (4,4′-methylene-bis-(o-chloroaniline)), diamines such as Ethacure 100 and 300 from Albermarle and bis- or tri-hydroxyl curing agents.
In some embodiments, the polymeric resin for the embedded structure may be selected from polyacrylate, polyamide, polyethylene, polyester or combinations thereof. The embedded structure may include particles (having an aspect ratio—length to cross-sectional area—of up to 10:1), fibers (having an aspect ratio—length to cross-sectional area—of greater than 10:1), a fabric and combinations thereof. Fabric utilized in the embedded structure may be woven or non-woven. In addition, the embedded structure may exhibit a number of intersection locations 20 dispersed throughout the pad 10.
The embedded structure may also include soluble polymeric resins, which may at least partially dissolve upon exposure to water or aqueous slurry utilized in the CMP process. If present, the soluble polymeric resin may comprise from 1 to 100% by weight of the embedded structure, including all values and ranges therein, such as 50% to 100% of the embedded structure, 1 to 50% of the embedded structure, 25% to 75% of the embedded structure, etc. Examples of said soluble polymeric resins may include, but are not limited to, polyacrylates, polyvinyl alcohols, polysaccharides, dextrin, hydrosols, various complex starches, pectin, aliginates, and their copolymers and derivatives thereof. Such polymeric resins may be commercially available in the form of particles, fibers, woven or nonwoven fabrics, nettings and various porous structures.
The embedded structure may also include commercially available “fillers” including, but not limited to, clay powder, silica fume, kaolin, organic and polymeric hollow micro spheres, various plasticizers, hydro-gels and blowing agents etc.
As illustrated in
As alluded to above, the CMP pad may be formed by a process which incorporates multiple pressing stages, wherein each pressing stage may include the application of heat and pressure. Accordingly, the CMP pad is initially formed or molded in a first pressing stage and then subsequently compressed in additional pressing stages. Intervening stages may also be present between the pressing stages wherein the CMP pads may be exposed to ambient temperatures (temperatures in the range of 19° C. to 25° C., including all values and ranges therein) and atmospheric pressure (pressures in the range of 20 kPa to 100 kPa). During the multistage process, the pad may be positioned in one or more molds. For example, for each pressing stage, the pad may be placed in a different mold or the pad may be kept in the same mold through out the entirety of the process. The additional compression of the chemical mechanical planarization pad results in a reduction in the thickness variation and specific gravity variation in a given batch of pads.
The process may begin by incorporating an embedded structure into the CMP pad, the embedded structure is first contacted with the polymer matrix. For purposes of clarity and consistency, it is noted that while the embedded structure is called an embedded structure prior to being contacted with the polymer matrix, it is appreciated that the structure is not necessarily embedded until the CMP pad is formed or molded. In embodiments, the embedded structure is first placed into a mold prior to filling the mold with the polymer matrix. In other embodiments, the embedded structure is mixed into the polymer matrix prior to filling the mold. In further embodiments, a portion of the embedded structure, such as a fabric, is placed into the mold before the polymer matrix is added to the mold and another portion of the embedded structure is mixed into the polymer matrix prior to forming. Once formed, the embedded structure is at least partially embedded and, in some embodiments, wholly embedded within the polymer matrix. In embodiments where less than the entire embedded structure is surrounded by the polymer matrix, at least 50% to 100% by volume of the embedded structure is surrounded by the polymer matrix, including all values and ranges from 75% to 100%, 75% to 85%, etc., by volume is surrounded by the polymer matrix.
The embedded structure is optionally dried prior to placement in the mold. For example, the embedded structure may be dried for a period of time in the range of 30 minutes to 1200 minutes, including all values and ranges therein at 1 minute intervals. Furthermore, the drying temperature may be in the range of 37° C. to 538° C. or 100° F. to 1000° F., including all values and ranges therein at 1° C. or 1° F. increments.
Reference is now made to
During the initial forming of the pad 312, heat may be applied at a first temperature T1 to the polymer matrix and the embedded structure therein for a first duration of time D1 as illustrated in
A first compressive force or pressure P1 may also be applied to the CMP pad during the first stage of the process. The pressure applied to the pad may be in the range of 10 to 300 lbf per square inch (psi), including all values and ranges therein at 1 psi increments. Said pressure may be applied directly to the pad or alternately applied to stop-gap blocks or shims between the mold halves to maintain the desired gap thickness wherein the pad is placed.
Reference is therefore made to
During a second stage, which intervenes between pressing stages, the CMP pad may be removed from the mold for a selected time period 316, illustrated as period St. 2 in
The rebounding of the pad may cause the pad to deform, wherein the pad may expand to thicknesses that are greater than those desired at given locations along the pad. Furthermore, shrinkage of the polymer matrix may occur during the second stage, causing warpage of the pad. Accordingly, pad deformation from either shrinkage or rebound may be allowed during the second stage.
In addition, in the case of a pad formed from polymer precursors, by the end of the second stage, the matrix of the chemical mechanical pad is not completely cured. The pad may be cured to achieve 70% or greater of mechanical properties exhibited upon fully curing the pad, but less than 100%, such as in the range of 70% to 95%, 70% to 80%, etc. In embodiments, such mechanical properties include one or more of tensile strength, flexural strength, compressive strength, or combinations thereof. Preferably, such properties include tensile strength. Complete cure may occur after any additional pressing stages, (such as the third stage discussed below) wherein the pressing stages are followed by an extended thermal exposure, in a heated oven, to complete the curing of the pad.
In a third stage, the pads may then be subjected to a second pressing process 318, illustrated by period St. 3 in
The mold and/or molding press utilized during the third stage may be the same or different than the mold and/or molding press utilized during the first stage. During the third stage, the molding press may be set to maintain a given mold cavity thickness, wherein the thickness may be the desired thickness of the resulting pad, such as in the range of 0.2 mm to 4 mm, including all values and ranges therein, such as from 0.635 mm to 3.81 mm, etc. Referring again to
In embodiments, the mold cavity during the third stage is smaller than that used during the first stage. Furthermore, the size of the chemical mechanical planarization pad after the first molding stage and second intervening stage may be slightly larger than the size of the mold cavity used during the third stage and the ultimate targeted size of the chemical mechanical planarization pad. In embodiments, the size of the pad may be 1% to 10% larger than the size of the mold cavity in at least one dimension, such as thickness, diameter or both, including all values and increments in the range of 1% to 10%, such as 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%.
After the third stage, the average thickness and specific gravity of the chemical mechanical planarization pad may be different than the thickness or specific gravity provided after the first stage. For example, in embodiments the average thickness of the chemical mechanical planarization pad may be reduced. In embodiments the specific gravity may be reduced. As understood herein, the specific gravity is with reference to the specific gravity of water.
Additional stages may also be utilized in the process. For example, three, four or five pressing stages may be contemplated with optional intervening stages occurring between the pressing stages. During these additional pressing stages, the application of heat, pressure or both over time may be varied to achieve a desired CMP thickness. Further, during the optional intervening stages the application of either heat or pressure may be removed from the pad. The pad may be exposed to ambient temperature and atmospheric pressure or the pad may be quenched. The additional pressuring stages allow for relatively fine adjustment of the pad dimensions and properties.
However, as discussed further in the Examples set forth below, it was found that in utilizing a single forming process without additional compression stages having the temperature and pressure profiles described herein, the resulting pad thickness may vary within +/−10% or more of a target pad thickness. Further, the resulting pad specific gravity may also vary within +/−10% or more of a target pad specific gravity. Target thickness and specific gravity is understood as properties which the process is intended to provide. However, due to variations in a single pressing process, including material or environmental variations, the target thickness may not be obtained.
The multiple stage processes described herein, including a second and third stage, produce CMP pads that have a thickness variation of within +/−2% of the target thickness. Furthermore, the use of the multiple stage process herein produces CMP pads that have a variation in specific gravity within +/−4% of the target specific gravity.
EXAMPLE IAlso disclosed herein is an embodiment wherein the use of multiple press stages may allow for the formation of additional material layers in the CMP pad. Referring again to
For example, the first layer including the embedded matrix may be porous or the embedded matrix may dissolve causing the liquid aqueous solution used in polishing to interact with and deteriorate the adhesive fixing the CMP pad to the polishing machine. The second layer may then be employed to provide a liquid barrier between the first porous layer and the adhesive, thus preventing the interaction and deterioration of adhesive fixing of the pad to the polishing machine.
In another example, the first layer of the CMP pad including the polymer matrix and the embedded structure may be formed using a first polyurethane material exhibiting relatively low optical transmittance such as Adiprene L325 from Chemtura. A second layer may be formed comprising polyurethane with high optical transmittance, such as Immuthane APC504 from COIM. The thickness of the first layer is thus restricted for optical transmissivity reasons, and the second layer is employed to impart the desired mechanical integrity to the resulting 2-layered pad.
The two or more layered pad may be formed as described above and illustrated in
The foregoing description of several methods and embodiments has been presented for purposes of illustration. It is not intended to be exhaustive or to limit the scope of the invention to the precise steps and/or forms disclosed, and obviously many modifications and variations are possible in light of the above teaching.
Claims
1. A process for forming a chemical mechanical planarization pad, comprising:
- forming a chemical mechanical planarization pad including a polymer matrix and an embedded structure by heating said polymer matrix and said embedded structure at a first temperature T1 and a first pressure P1;
- allowing said chemical mechanical planarization pad to deform at a second temperature T2 and a second pressure P2; and
- compressing said chemical mechanical planarization pad at given mold cavity thickness by applying heat at a third temperature T3, wherein T1>T2, P1>P2, T1≦T3.
2. The process of claim 1, wherein said chemical mechanical planarization pad is formed in a mold cavity having a first mold cavity thickness and said first mold cavity thickness is greater than said given mold cavity thickness.
3. The process of claim 1, wherein combining said polymer matrix and said embedded structure includes combining a prepolymer and a cross-linking agent with said embedded structure.
4. The process of claim 1, wherein said first temperature T1 is in the range of 37° C. to 537° C. and said second temperature T2 is at least 10° C. less than the first temperature T1 and P1 is in the range of 10 lbf to 300 lbf.
5. The process of claim 1, wherein said third temperature T3 is at least 1° C. greater than said first temperature T1.
6. The process of claim 1, wherein said T1 and P1 are applied for a duration D1 of up to 300 minutes and said chemical mechanical planarization pad are exposed to T2 and P2 for a duration D2 of up to four days.
7. The process of claim 1, wherein said second temperature T2 is ambient temperature and said second pressure P2 is atmospheric pressure.
8. The process of claim 1, wherein said chemical mechanical planarization pad exhibits a first thickness after forming and a second thickness after compressing, wherein said first thickness is different from said second thickness.
9. The process of claim 8, wherein said first thickness is within +/−10% of a target thickness and said second thickness is within +/−2% of said target thickness.
10. The process of claim 1, wherein said chemical mechanical planarization pad exhibits a first specific gravity after forming and a second specific gravity after compressing, wherein said first specific gravity is different from said second specific gravity.
11. The process of claim 10, wherein said first specific gravity is +/−10% of a target specific gravity and said second specific gravity is within +/−4% said target specific gravity.
12. The process of claim 1, further comprising forming a second layer of said chemical mechanical planarization pad.
13. The process of claim 12, wherein forming said second layer occurs after forming said first layer and said second layer is formed on said first layer.
14. The process of claim 12, wherein forming said second layer occurs while compressing.
15. The process of claim 12, wherein said second layer is secured to said first layer with an adhesive.
16. The process of claim 12, wherein said second layer is secured to said first layer with interlocking features.
Type: Application
Filed: Feb 14, 2013
Publication Date: Aug 15, 2013
Applicant: INNOPAD, INC. (Wilmington, MA)
Inventor: Innopad, Inc.
Application Number: 13/766,930
International Classification: B24D 18/00 (20060101);