WO2013123105A2

WO2013123105A2 - Method of manufacturing a chemical mechanical planarization pad

Info

Publication number: WO2013123105A2
Application number: PCT/US2013/026015
Authority: WO
Inventors: John Erik Aldeborgh; Peter Renteln; Robert P. Dolan
Original assignee: Innopad, Inc.
Priority date: 2012-02-14
Filing date: 2013-02-14
Publication date: 2013-08-22
Also published as: TW201402272A; WO2013123105A3; US20130205679A1

Abstract

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.

Description

METHOD OF MANUFACTURING A CHEMICAL MECHANICAL PLANARIZATION

PAD

FIELD OF INVENTION

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.

BACKGROUND

Semiconductor 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. Patent 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.

SUMMARY

An 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 Tl and a first pressure PI. 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 Tl> T2, P1>P2, T1<T3.

BRIEF DESCRIPTION OF THE DRAWINGS

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:

FIG. 1 is a perspective view of an embodiment of a polishing pad formed by the methods described herein.

FIG. 2 is a top view of an embodiment of a polishing pad formed by the methods described herein.

FIG. 3 is a flow chart of an embodiment of a method of forming a polishing pad.

FIG. 4 is a graph of temperature versus time of an embodiment of the method herein using multiple pressing stages.

FIG. 5 is a schematic of a cross-section of a compression molding cavity.

FIG. 6 is a graph of temperature versus time of an embodiment of the method herein using a single pressing stage.

FIG. 7 is a graph of pad to pad variation in specific gravity when using a single pressing stage.

FIG. 8 is an SEM micrograph illustrating the porosity of a pad formed using a single pressing stage. FIG. 9 is a graph of pad to pad variation in specific gravity when using multiple pressing stages.

FIG. 10 is an SEM micrograph illustrating the porosity of a pad formed using a multiple pressing stages.

FIG. 11 is a graph of pad to pad variation in thickness for the same batch of urethane utilized in a single press process and a double press process.

FIG. 12 is a graph of pad to pad variation in thickness.

FIG. 13 is a graph of pad to pad variation in thickness. DESCRIPTION

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 A 134 (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 FIG. 2, the CMP pad 10 may also include one or more grooves 22 on at least one surface 24, wherein the grooves may define land areas 26 therebetween at or near the surface. While illustrated in FIG. 2 as a series of concentric rings, the grooves may also include other patterns, such as spirals, log positive and negative (counterclockwise and clockwise), or the grooves may be randomized over the surface. The grooves may be formed on the working surface of the polishing pad, which is contacted with the object to be polished or planarized during planarization. In embodiments, the grooves are formed after the pressing stages in an independent finishing operation using mechanical or laser cutting means.

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 FIGS. 3 and 4 herein which illustrate a flow chart of an embodiment of a method contemplated herein and a plot of temperature versus time while the method is performed, respectively. Once the embedded structure is optionally preloaded into the mold or mixed into polymer matrix 310, the CMP pad may be formed in a first stage through the application of heat, pressure, or a combination thereof, to the pad components (i.e., the polymer matrix and embedded structure). Processes including, for example, injection molding, compression molding, or casting the polymer matrix may be used to form the pad into a desired shape 312.

During the initial forming of the pad 312, heat may be applied at a first temperature Tl to the polymer matrix and the embedded structure therein for a first duration of time Dl as illustrated in FIG. 4 as period St. 1. The pad may generally take on the form and dimensions of the mold cavity in which the polymer matrix is positioned 314. In some embodiments, the thickness of the mold cavity, further described below, may be greater than the target thickness of the chemical mechanical planarization pad. The first stage temperature Tl may be in the range of 37 °C to 537 °C (or 100 °F to 1000 °F) including all values and ranges therein, at 1 °F increments or 1 °C increments. In addition, the first temperature Tl may be applied for a first duration Dl in the range of less than 1 minute and up to 300 minutes, including all values and ranges therein, at 1 minute increments. Such as from 1 min to 300 minutes.

A first compressive force or pressure PI 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 FIG. 5 which illustrates a schematic of a cross-section of a compression mold. As illustrated, the mold 500 includes two mold halves 512a and 512b. A cavity 510 is formed within one of the mold halves, however, in embodiments the cavity may be formed as between the mold halves as well. The mold cavity thickness MCT may be regulated, in part, by the gap height G maintained between the two mold halves and the force F applied to the two mold halves. The gap height G may be adjusted by providing shims or stop gap blocks 514 between the two cavities 512a, 512b. In embodiments, the CMP pad exhibits a thickness of t of 0.20 mm to 4.00 mm, including all values and ranges therein, such as from 0.635 mm to 3.81 mm, etc.

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 FIG. 4. As illustrated, the temperature T2 which the pad is exposed to during the second stage may be relatively less than the temperature the pad is exposed to during the first stage Tl. In one embodiment, the second temperature T2 may be at least 10 °C (or 50 °F) less than the first temperature Tl including all values and ranges therein, and a second pressure ranging from ambient atmospheric pressure to just under PI. For example, the second temperature T2 may be in the range of 10 °C to 66 °C or 50 °F to 150 °F, including all values and ranges therein at 1 °C or 1 °F increments, and the second pressure is ambient atmospheric pressure. The second stage may last for a duration D2 of 1 minute to several days (e.g. 3-4 days) and up to 4 days (48 hours) including all values and ranges therein. Thus the time period for the second stage may be equal to or greater than the time period of the first stage.

During this second stage, between the first forming stage and the third compressing stage, the embedded structure, if deformable, may rebound, i.e., recover to at least a portion of its initial shape prior to the forming/molding stage. Depending on the degree to which the embedded structure is deformed during the forming process, the embedded structure may recover to exhibit dimensions such as an overall thickness or overall diameter within at least 75 % of its initial dimensions to 100 % of its initial dimensions, including all values and ranges therein, such as within at least 80 % of its initial dimensions, within at least 90 % of its initial dimensions, etc.

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 FIG. 4, wherein the pad may be placed in a mold and the pad may be exposed to a third temperature T3 for a third duration D3. The third temperature T3 may be equal to or different from the temperature applied to the pad during the first stage Tl, and greater than the temperature T2 applied during the second stage. In some embodiments, for example, the temperature of the third stage T3 may be at least 1 °C (or 5 °F) greater than the temperature applied during the first stage. The temperature applied to the pad may be in the range of 40 °C to 649 °C (or 105 °F to 1200 °F), including all values and ranges therein, at 1 °C or 1 °F. Furthermore, the third temperature may be applied for a duration D3 in the range of 1 to 1000 minutes, including all values and ranges therein at 1 minute increments. This third duration D3, may be less than or equal to the first duration Dl or, greater than the first duration Dl but less than the second duration D2.

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 FIG. 5 a mold cavity 510 is provided in a mold 500 for use in either the forming process or compression process. The mold cavity includes two mold halves 512a and 512b. The mold cavity has a mold cavity thickness MCT, which again may be adjusted based upon thickness settings, such as the gap height G, where pressure is adjusted to achieve a selected mold cavity thickness. During the third compression stage, it may be appreciated, that the pressure within the mold cavity is varied or controlled to achieve the selected mold cavity thickness. The mold cavity thickness MCT may also be adjusted using pressure settings where thickness is adjusted, or allowed to "float", to achieve a selected pressure.

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.

FIG. 6 illustrates an example of a single press process (illustrated in solid lines), wherein heat, compressive force or both may be applied in a single stage St. 1', as compared to an embodiment of the multi-pressing stage process herein (illustrated in doted lines). The processing temperatures, and in particular, the mold temperatures, during the first stage St. 1' of a single press process may be higher than those exhibited in the multiple stage process discussed herein. In addition, the dwell time for the first stage in the single forming process may be longer than those utilized in a multiple stage process. After pressing, the pad may be removed from the mold and allowed to cool at room temperature St. 2'.

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 +1-2 % 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 I

FIG. 7 illustrates a graph of pad to pad variation in specific gravity of urethane CMP pads produced using a single press process. The process parameters were 230 °F press temperature, 140 psi mold closing pressure, 130 mils clearance or gap space (mold cavity thickness) and 16 minutes of dwell or mold time. Each of the above parameters may be controlled separately. As illustrated in the graph, 30 samples were measured. The target specific gravity was 0.940 and the target range was 0.16. The actual mean specific gravity was 0.952 and the actual range was 0.16. However, 4 of the 30 samples were either at or outside of the target range, and the CpK— an statistical indicator of variability where a CpK value of 1.0 typically indicates marginal process control capability— was a low 0.533. FIG. 8 illustrates a Scanning Electron Micrography (SEM) micrograph of a cross-section of a CMP pad produced by the aforementioned single pressing step referred to in Fig 6.

Example II

FIG. 9 illustrates a graph of pad to pad variation in specific gravity of urethane CMP pads produced using a double press process. The process parameters were: first press temperature 200 °F to 230 °F and first mold time 15 to 30 minutes; second press temperature 200 °F to 250 °F and second mold time 5 to 20 minutes; press gap for both first and second presses are set at 90 to 150 mils. As illustrated in the graph, 15 samples were measured. The target specific gravity and range were again 0.940 and 0.16, respectively. The actual mean specific gravity was 0.936 and the actual range was 0.06, respectively. Furthermore, all 15 samples were within the target as well as the process control range, and the CpK was an acceptable 1.436. While the single press process yielded high process variability and out of target specific gravities, the multiple press process yielded low process variability and zero out of spec specific gravities. FIG. 10 illustrates an SEM micrograph of a cross-section of a CMP pad produced by the double pressing process referred to in FIG. 9.

Example III

FIG. 11 illustrates an inspection history of pad to pad variation in thickness in CMP pads produced using the same batch of urethane in both a single press process and a double press process. The process parameters were 220 °F, 15 minutes press time and gap set of 130 mils for the first press; and 230 deg F, 10 minutes press time and gap set of 95 mil for the second press, respectively. As illustrated in the graph, about 400 samples were measured. The target thickness was 163.0 mil and target range was 133.0 to 193.0 mils. The mean thickness of the pads produced using a single press process was 155.3452 mils and the actual range was 141.7623 mils to 194.8765 mils. The mean thickness of the pads produced using a double press process was 162.5024 milsand the actual range was 158.1760 to 165.6703 mils.

Example IV

FIG. 12 illustrates an inspection history of pad to pad thickness variation of CMP pads produced by the conventional single press method. The process parameters were 230 °F press temperature, 21 minutes press time and 130 mils press gap, respectively. As illustrated in the graph the pad thickness varies between about 150 mils to over 200 mils.

FIG. 13 illustrates an inspection history of pad to pad thickness variation of CMP pads produced by the double press method. The process parameters were 220 °F press temperature, 21 minutes press time and 130 mils gap for the first press, and 230 °F press temperature, 10 minutes press time and 95 mils gap for the second press. As illustrated in the graph the pad thickness varies between about 169 and 180 mils.

Also 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 FIG. 1, optional layer 18 may be formed in a second or additional pressing stage. The material forming the optional layer may be selected from the polymer matrix materials discussed above. In addition, the optional layer or layers may include the same or a different embedded structure aforementioned. The optional layer or layers may also exhibit similar or different optical, chemical, mechanical and/or electrical properties as those of the first layer.

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 FIGS. 3 and 4. The second and optional additional layers may be formed simultaneously with the first layer, or individually or collectively in subsequent processing steps under T2, D2 and/or T3, D3, etc. in Fig. 3 , wherein heat and/or pressure may be applied to the pad for pre-determined time(s). When the second, or additional layers are formed, they may be formed on the prior layer, such that the prior layer may essentially form a part of the mold. Additional layer(s) thus may be similarly formed at additional pressing stages.

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 Tl and a first pressure PI;

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 Tl> 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 Tl 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 Tl and PI 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 Tl.

6. The process of claim 1, wherein said Tl and PI are applied for a duration Dl 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.