Polishing pad with endpoint window
Patent Information
- Application Number
- JP2024011870
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2024-01-04
- Filing Date
- 2024-01-30
- Publication Date
- 2026-10-30
AI Technical Summary
Conventional polishing pads with transparent windows suffer from material incompatibilities leading to defects, non-uniform polishing rates, and reduced service life due to differences in wear rates and mechanical properties between the window and polishing layer materials.
A polishing pad design featuring a recessed transparent window with a peripheral abrasive portion, where the window is non-porous and recessed below the polishing surface, minimizing material differences and stress, and ensuring a flush interface to maintain optical integrity and reduce defects.
The design extends pad life, reduces defects, and maintains uniform polishing rates by alleviating stress and deformation, enhancing the accuracy and reliability of endpoint detection during chemical mechanical polishing processes.
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Abstract
Description
[Technical field]
[0001] The field of the invention is polishing pads used in chemical mechanical polishing. [Background technology]
[0002] Chemical mechanical planarization (CMP) is a type of polishing process that is widely used to flatten or planarize layers of structures in integrated circuits or similar structures. In particular, CMP is often used to produce flat uniform layers of a given thickness in the construction of three-dimensional circuit structures by additive stacking and planarization processes. The CMP process removes excess material deposited on the substrate (e.g., wafer) surface to produce a highly planar layer of uniform thickness that extends uniformly across the substrate (e.g., wafer) area. When the uniform thickness extends across the entire wafer, it is known as global uniformity.
[0003] CMP utilizes a liquid, often called a slurry, that may contain nano-sized particles. The slurry is delivered to the surface of a rotating multi-layer polymer pad (sometimes called a polishing sheet), which is attached to a rotating platen. The polishing pad includes a polishing layer and may include a subpad. A substrate (e.g., a wafer) is mounted in a separate fixture, i.e., a carrier, with separate rotation means, and is pressed against the surface of the pad under a controlled load. This can result in high-speed relative motion between the substrate (e.g., a wafer) and the polishing pad, and consequent high-speed shear or wear on both the substrate and pad surfaces. This shear, together with the slurry particles trapped at the pad / substrate interface, wears the substrate (e.g., a wafer) surface, resulting in the removal of material from the substrate surface. Control of the removal rate and uniformity of removal are important to achieve global uniformity.
[0004] Various types of film thickness metrology can be used in conjunction with real-time control software to achieve device design goals. One approach for endpoint detection uses the transmission of light of a desired wavelength through a polishing pad, where the light reflects off the substrate being polished, and the reflected light signal then passes back to an interferometer that processes the reflected signal to determine whether polishing has reached its desired goal (e.g., film thickness, desired exposure of underlying structures, etc.). The metrology equipment can be located within the body of the platen that holds the pad. This requires that at least a portion of the polishing pad be sufficiently transparent to the light source being used to produce an acceptable signal-to-noise ratio.
[0005] For certain pad structures, the pad material itself can be transparent to the desired wavelengths of light. Alternatively, a plug of transparent polymer can be provided and an opaque material molded around it to produce a transparent window. See, for example, U.S. Pat. No. 5,605,760. A third approach is to form a pad with an opening into which a transparent window material is inserted and held in place by adhesive. See, for example, U.S. Pat. No. 5,893,796. Various versions of these pads with windows have been proposed. See, for example, U.S. Pat. No. 7,621,798, U.S. Pat. No. 8,475,228, U.S. Pat. No. 10,569,383, US2021 / 0402556, U.S. Pat. No. 9,475,168. Summary of the Invention [Problem to be solved by the invention]
[0006] The use of two different materials in the pad can cause problems during use, including one or more of the following: scratching or defects in the substrate being polished, limited useful life of the pad due to differences in wear rates between the window and the polishing layer, or adhesion problems between the transparent window material and the polishing pad material. Thus, a need remains for an improved polishing pad with a transparent window. [Means for solving the problem]
[0007] Disclosed herein is a polishing pad for chemical mechanical polishing, comprising a polishing layer having an upper polishing surface, a lower surface and a thickness, the polishing layer comprising a porous polishing material and a window region, the window region including a transparent window having an exposed upper surface and an exposed lower surface to allow light to transmit through the polishing pad in the window region, the exposed upper surface of the transparent window being recessed from the upper polishing surface, the transparent window extending from the recessed region to the lower surface of the polishing pad, the window region further including a peripheral portion of the polishing material in contact with a side edge of the transparent window, the peripheral portion of the polishing material having an upper surface that is recessed from an upper surface of the upper polishing surface, the transparent window being non-porous, a portion of the upper surface of the peripheral portion adjacent the transparent window being flush with the upper surface of the transparent window, and the exposed lower surface of the transparent window being flush with the lower surface of the polishing layer.
[0008] Reference will now be made to the drawings of exemplary embodiments, in which like elements are numbered likewise. [Brief description of the drawings]
[0009] [Figure 1] FIG. 1 is a cross-sectional view of an example of a polishing pad disclosed herein. [Diagram 2] FIG. 1 is a cross-sectional view of an example of a polishing pad disclosed herein. [Diagram 3] FIG. 1 is a cross-sectional view of an example of a polishing pad disclosed herein. [Figure 4] FIG. 2 is a plan view of the top surface of an example of a pad of the present invention, in which the optical window is rectangular. [Diagram 5] FIG. 2 is a plan view of the top surface of an example of a pad of the present invention, in which the optical window is oval shaped. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0010] Detailed Description of the Invention Disclosed herein is a polishing pad useful for chemical mechanical polishing, with a design that minimizes the risk of defects to the substrate caused by using different materials for the polishing material and the transparent window, while at the same time minimizing adhesion problems between the transparent window and the polishing material. In particular, the polishing pad includes a polishing layer and a window area. The polishing layer has an upper polishing surface and a thickness. The polishing layer includes an abrasive material. The window area is recessed from the upper polishing surface. The window area includes a transparent window having an exposed upper surface and an exposed lower surface to allow light to transmit through the polishing pad in the window area. The window area further includes a peripheral portion of the polishing material in contact with a side edge of the transparent window, the peripheral portion of the polishing material also having an upper surface recessed from the upper surface of the upper polishing surface. The peripheral portion can be a shelf. Having a window area that is recessed from the upper polishing surface of the pad and includes both the transparent window and the peripheral portion (or shelf) of the polishing material can increase the useful life of the polishing pad and reduce defects created by the different properties of the transparent window material and the polishing material.
[0011] In particular, many conventional polishing pads with transparent windows require at least a portion of the window to be flush with the upper polishing surface to ensure good transmission of light through the window and to the surface of the substrate being polished. However, because the window material is of a different composition from the polishing material, local differences in different mechanical properties, contact pressure and texture are observed during use, which may cause non-uniform polishing rates and increased wafer-scale non-uniformity. Furthermore, because polishing pads are generally dressed with bonded diamond abrasive grains to maintain a constant polishing rate during use, the difference in dressing wear rate between the upper pad material and the window during continued use may cause protrusion of the window area. It is widely recognized that the occurrence of this protrusion causes a higher level of scratch formation defects, often resulting in replacement of the pad, thus increasing production costs and scratch formation and defects on the substrate being polished. Also, differential thinning of the window during use may disturb the optical signal. The difference in thermal expansion coefficient between the polishing material and the window material may cause additional stress and deformation.
[0012] Having a recessed window area with an upper window surface recessed below the upper polishing surface, with a peripheral area of polishing material also recessed below the upper polishing surface, facilitates stress relief in the pad and also avoids protrusion of the window material above the upper polishing surface, which can cause defects or scratch formation.
[0013] 1, 2 and 3 show cross-sections of three examples of polishing pads 100 disclosed herein. The polishing pad 100 has a polishing layer 120 having an upper polishing surface 110 with a thickness a, and a window region 103. The polishing layer 120 is porous and includes a porous polishing material 101. FIGS. 1, 2 and 3 show an optional macrotexture 102 on the upper surface 100 of the polishing layer 120. The macrotexture 102 can be a groove, protrusion or raised feature for improving polishing and handling of the slurry fluid and removed material. The macrotexture can be in the form of a groove, for example, having a depth b and a width g. The macrotexture 102 can be separated from the window region 103. Alternatively, the macrotexture can intersect with a recessed peripheral portion 105 of the window region 103. The window region 103 includes a transparent window 104 having an upper surface 104a and a lower surface 104b. The transparent window 104 is non-porous to facilitate the transmission of light for optically measuring the polishing endpoint. The window area also includes a peripheral portion 105 having an upper surface 105a. The transparent window 104 extends from the upper surface 105a of the peripheral portion to the lower surface 105b of the polishing layer 120. Typically, there is no chemical bond between the transparent window 104 and the polishing layer 120. This lack of chemical bonding between the materials makes it important that the transparent window extend the entire length from the upper surface 105a to the lower surface 105b. This extension from the upper surface 105a to the lower surface 105b creates an increased contact that increases the frictional force that holds the window in place during polishing.
[0014] The transparent window 104 preferably has the same thickness measured across the transparent window 104 from the top surface 104a to the bottom surface 104b. This reduces light distortion and makes the top surface 104a of the transparent window 104 flush with the top surface 105a of the peripheral region 105. In addition, the bottom surface 104a of the transparent window 104 flush with the bottom surface 105b of the polishing layer 120. The top surface 104a of the window 104 and the top surface 105a of the peripheral portion are recessed from the upper polishing surface 110 by a distance c. The peripheral portion can be formed of the polishing material 101. The top surface 105a of the peripheral portion can form a shelf having a width dimension d. Advantageously, the dimension "d" (width of the peripheral portion or shelf) is equal to or greater than the dimension "a" (polishing layer thickness) minus dimension "c" (window recession depth) or window thickness to reduce stress resulting from compressing the porous polishing layer 120 adjacent the non-porous window 104. Most advantageously, dimension "d" (width of peripheral portion or shelf) is greater than dimension "a" (abrasive layer thickness) minus dimension "c" (window recession depth) or window thickness to reduce stresses resulting from compressing the porous abrasive layer 120 adjacent the non-porous window 104. Because window 104 is non-porous, it will not compress beyond at least 1 mm when compressed with a flat circular surface of thickness equal to the thickness of window 104. 2 On the scale of
[0015] The polishing pad 100 may include an optional subpad 106 below the polishing layer 120. The subpad 106 also includes an opening 107 having a dimension f to expose the lower surface 104b of the window 104. In FIG. 1, the dimension f is substantially similar to the dimension of the surface 104b to allow light to pass through any portion of the window material.
[0016] 2, dimension f of opening 107 is greater than window underside 104b such that peripheral portion 105 includes exposed underside 105b'. Advantageously, dimension "d" (peripheral portion or shelf width) is greater than or equal to dimension "a" (polishing layer thickness) minus dimension "c" (window recession depth) or window thickness to reduce stresses resulting from compressing porous polishing layer 120 adjacent non-porous window 104. Most advantageously, dimension "d" (peripheral portion or shelf width) is greater than dimension "a" (polishing layer thickness) minus dimension "c" (window recession depth) or window thickness to reduce stresses resulting from compressing porous polishing layer 120 adjacent non-porous window 104.
[0017] In a further example, as shown in FIG. 3, the peripheral portion 105 can include a curved upper surface 109, rather than the right angle shown in FIGS. 1 and 2. As another alternative, the transition from the upper surface 110 of the polishing layer 120 to the peripheral portion upper surface 105a can be at an angle other than 90° (i.e., an oblique transition rather than a perfectly vertical transition). A portion of the window upper surface 104a and the upper surface 105a or the curve 109 can be coplanar or substantially coplanar. In particular, in the region contacting the side edge of the window 104, at least a portion of the upper surface 105a or the curve 109 is coplanar or substantially coplanar with the upper window surface 104a. As used herein, "substantially coplanar" means that the upper window surface 104a and the surface of the polishing material in the peripheral region (e.g., 105a or 109) are at a vertical distance of less than 0.02 mm, less than 0.01 mm, or less than 0.005 mm from each other.
[0018] 4 and 5 show plan views of two examples of polishing pads 100 disclosed herein, in which 110 is the upper polishing layer, 102 is an optional groove, 104 is a window, and 105 is a peripheral portion of the window area. In FIG. 4, the window 105 and the window area 103 are substantially rectangular, and in FIG. 5, the window 105 and the window area 103 are oval. Other shapes (not shown), such as squares, circles, and other polygons, can also be used. Furthermore, the upper polishing layer can optionally include multiple windows (not shown), for example, three or more equally spaced windows. Multiple equally spaced windows reduce the time between signal measurements. This reduction in the time between signal measurements can increase the accuracy of polishing endpoint detection.
[0019] The thinness of the polishing layer at the peripheral portion of the polishing layer compared to the total polishing layer thickness can allow flexibility during use without negatively affecting the optical signal or pad life (e.g., the signal-to-noise ratio remains acceptable). In fact, the recess in the window region can extend the pad life. The depth of the recess in the window region (e.g., 103) can be adjusted to accommodate the properties of the materials (e.g., polishing material, window material) used in the pad to provide the desired flexibility during use without causing excessive harmful deformation. Similarly, the width of the peripheral portion can also be adjusted to provide the desired mechanical response for the pad material and design. For example, the recess depth c can be greater than 0.1 mm, greater than 0.2 mm, or at least 0.3 mm, and 1.1 mm or less, 1 mm or less, 0.8 mm or less, or 0.6 mm or less. The width d of the peripheral region can be, for example, at least 0.05 mm, at least 0.1 mm, at least 0.2 mm, or at least 0.3 mm, and 1.1 mm or less, 1 mm or less, 0.8 mm or less, or 0.6 mm or less. To further adjust the effective flexibility of the pad, the width f of the opening 107 can be adjusted to controllably vary the flexibility of the window area without affecting the operation of the endpoint system. By moving the subpad 106 away from the interface between the window 104 and the polishing material 101, stresses on the bond can be reduced, further improving window integrity.
[0020] The major dimension e of the window material in a direction parallel to the top polishing surface can be a dimension commonly used for windows in CMP pads. In a further example, the dimension of the window in a direction parallel to the top polishing surface is about 8-18 mm. The thickness of the window can be less than the total thickness a of the polishing layer 120 to provide a recess in the window area 103. For example, the thickness of the window can be 0.3-3 mm, 0.4-2.5 mm, 0.5-2 mm, or 0.6-1.5 mm, provided that it is no thicker than the total pad thickness, and preferably no thicker than the polishing layer.
[0021] The polishing layer can have a thickness a of 1-4, 3, or 2.5 mm. The total thickness of the polishing pad (e.g., polishing pad + subpad) is preferably 4 mm or less. As described above, the polishing layer can include an optional macrotexture (e.g., grooves). Because the macrotexture can affect the effective elastic modulus, variable adjustment of the window area recess depth c, peripheral portion width d, relative to the macrotexture or groove depth b and total polishing layer thickness a can be performed to provide the desired flexibility that is a feature of the pad design disclosed herein. For example, the window recess depth c can be 20-50% or 30-40% of the total pad thickness, or 20-50% or 30-40% of the polishing layer thickness a. As another example, the window recess depth c can be 50-90% or 60-80% of the macrotexture depth b. As another example, the peripheral portion width d can be 40-60% of the macrotexture (e.g., groove) width g. These ratios can be easily adjusted during manufacturing by the disclosed pad manufacturing method described below.
[0022] A further advantage of the present design is that it can provide a simple means for determining the end of pad life. Because the window recession depth can be small depending on the groove depth, pad conditioning wear over time is expected to cause a change in the end point signal as the window recession depth approaches zero. This change can occur before the macro-texture completely disappears, so the pad can be discontinued before any significant change in polishing performance occurs, preventing non-uniformity and defects.
[0023] The polishing material 101 of the polishing layer 120 can include a polymer. The polishing layer 101 can be opaque at the thickness a of the polishing layer 120. For example, porosity can be provided by the addition of hollow flexible polymer elements (e.g., hollow microspheres), blowing agents, foaming agents, or supercritical carbon dioxide. Examples of polymeric materials for the polishing layer include polyurethane, polycarbonate, polysulfone, nylon, polyether, polyester, polystyrene, acrylic polymers, polymethylmethacrylate, polyvinylchloride, polyvinylfluoride, polyethylene, polypropylene, polybutadiene, polyethyleneimine, polyethersulfone, polyamide, polyetherimide, polyketone, epoxy resins, silicones, copolymers thereof (e.g., polyether / polyester copolymers), and mixtures or blends thereof. The polishing layer can include a polymer that is a polyurethane formed by the reaction of one or more multifunctional isocyanates with one or more polyols. For example, polyisocyanate-terminated urethane prepolymers can be used. The polyfunctional isocyanate used to form the polishing layer of the chemical mechanical polishing pad of the present invention can be selected from the group consisting of aliphatic polyfunctional isocyanates, aromatic polyfunctional isocyanates, and mixtures thereof. For example, the polyfunctional isocyanate used to form the polishing layer of the chemical mechanical polishing pad of the present invention can be a diisocyanate selected from the group consisting of 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 4,4'-diphenylmethane diisocyanate, naphthalene-1,5-diisocyanate, tolidine diisocyanate, paraphenylene diisocyanate, xylylene diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, cyclohexane diisocyanate, and mixtures thereof. The polyfunctional isocyanate can be an isocyanate-terminated urethane prepolymer formed by the reaction of a diisocyanate with a prepolymer polyol.The isocyanate-terminated urethane prepolymer can have 2-12%, 2-10%, 4-8%, or 5-7% by weight of unreacted isocyanate (NCO) groups. The prepolymer polyol used to form the polyfunctional isocyanate-terminated urethane prepolymer can be selected from the group consisting of diols, polyols, polyol diols, copolymers thereof, and mixtures thereof. For example, the prepolymer polyol can be selected from the group consisting of polyether polyols (e.g., poly(oxytetramethylene) glycol, poly(oxypropylene) glycol, and mixtures thereof); polycarbonate polyols; polyester polyols; polycaprolactone polyols; mixtures thereof; and mixtures thereof containing one or more low molecular weight polyols selected from the group consisting of ethylene glycol; 1,2-propylene glycol; 1,3-propylene glycol; 1,2-butanediol; 1,3-butanediol; 2-methyl-1,3-propanediol; 1,4-butanediol; neopentyl glycol; 1,5-pentanediol; 3-methyl-1,5-pentanediol; 1,6-hexanediol; diethylene glycol; dipropylene glycol; and tripropylene glycol. For example, the prepolymer polyol can be selected from the group consisting of polytetramethylene ether glycol (PTMEG); ester-based polyols (e.g., ethylene adipate, butylene adipate, etc.); polypropylene ether glycol (PPG); polycaprolactone polyols; copolymers thereof; and mixtures thereof. For example, the prepolymer polyol can be selected from the group consisting of PTMEG and PPG. When the prepolymer polyol is PTMEG, the isocyanate-terminated urethane prepolymer can have an unreacted isocyanate (NCO) concentration of 2-10 wt% (more preferably 4-8 wt%; most preferably 6-7 wt%).Examples of commercially available PTMEG-based isocyanate-terminated urethane prepolymers include Imuthane® prepolymers (available from COIM USA, Inc., such as PET-80A, PET-85A, PET-90A, PET-93A, PET-95A, PET-60D, PET-70D, PET-75D); Adiprene® prepolymers (available from Chemtura, such as LF 800A, LF 900A, LF 910A, LF 930A, LF 931A, LF 939A, LF 950A, LF 952A, LF 600D, LF 601D, LF 650D, LF 667, LF 700D, LF750D, LF751D, LF752D, LF753D, and L325); Andur® prepolymers (available from Anderson Development Available from Polypropylene Company, for example, 70APLF, 80APLF, 85APLF, 90APLF, 95APLF, 60DPLF, 70APLF, 75APLF. When the prepolymer polyol is PPG, the isocyanate-terminated urethane prepolymer can have an unreacted isocyanate (NCO) concentration of 3 to 9 wt% (more preferably 4 to 8 wt%, most preferably 5 to 6 wt%). Examples of commercially available PPG-based isocyanate-terminated urethane prepolymers include Imuthane® prepolymers (available from COIM USA, Inc., e.g., PPT-80A, PPT-90A, PPT-95A, PPT-65D, PPT-75D); Adiprene® prepolymers (available from Chemtura, e.g., LFG 963A, LFG 964A, LFG 740D); and Andur® prepolymers (available from Anderson Development Company, e.g., 8000APLF, 9500APLF, 6500DPLF, 7501DPLF). The isocyanate-terminated urethane prepolymer can be a low free isocyanate-terminated urethane prepolymer having a free toluene diisocyanate (TDI) monomer content of less than 0.1% by weight. Non-TDI-based isocyanate-terminated urethane prepolymers can also be used.For example, isocyanate-terminated urethane prepolymers including those formed by the reaction of 4,4'-diphenylmethane diisocyanate (MDI) with a polyol such as polytetramethylene glycol (PTMEG) and an optional diol such as 1,4-butanediol (BDO) are acceptable. When such isocyanate-terminated urethane prepolymers are used, the unreacted isocyanate (NCO) concentration is preferably 4-10% by weight (more preferably 4-10% by weight, most preferably 5-10% by weight). Examples of commercially available isocyanate-terminated urethane prepolymers in this category include Imuthane® prepolymers (available from COIM USA, Inc., e.g., 27-85A, 27-90A, 27-95A); Andur® prepolymers (available from Anderson Development Company, e.g., IE75AP, IE80AP, IE85AP, IE90AP, IE95AP, IE98AP); and Vibrathane® prepolymers (available from Chemtura, e.g., B625, B635, B821).
[0024] The window 104 can comprise any desired polymer or polymer blend, so long as it has sufficient transparency at the wavelengths used by the optical metrology. If the window material has a hardness or thermal expansion coefficient similar to that of the material used in the polishing layer, it can be useful. Examples of window materials include polyurethane, acrylic polymers, cyclic olefin copolymers (e.g., TOPAS 8007, etc.). In pads in which the polishing layer and subpad layer are polyurethane, the use of polyurethane materials can also be useful. The window is conveniently made from an aliphatic polyisocyanate-containing material ("prepolymer"). The prepolymer is the reaction product of an aliphatic polyisocyanate (e.g., diisocyanate) and a hydroxyl-containing material. The prepolymer is then cured with a curing agent. Preferred aliphatic polyisocyanates include, but are not limited to, methylenebis-4,4'-cyclohexylisocyanate, cyclohexyl diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate, propylene-1,2-diisocyanate, tetramethylene-1,4-diisocyanate, 1,6-hexamethylene-diisocyanate, dodecane-1,12-diisocyanate, cyclobutane-1,3-diisocyanate, cyclohexane-1,3-diisocyanate, cyclohexane-1,4-diisocyanate, 1- Isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane, methylcyclohexylene diisocyanate, triisocyanate of hexamethylene diisocyanate, triisocyanate of 2,4,4-trimethyl-1,6-hexane diisocyanate, uretdione of hexamethylene diisocyanate, ethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate, dicyclohexylmethane diisocyanate, and mixtures thereof. Preferred aliphatic polyisocyanates are those having less than 10% by weight of unreacted isocyanate groups.
[0025] Advantageously, the curing agent is a polydiamine. Preferred polydiamines include, but are not limited to, diethyltoluenediamine ("DETDA"), 3,5-dimethylthio-2,4-toluenediamine and its isomers, 3,5-diethyltoluene-2,4-diamine and its isomers, such as 3,5-diethyltoluene-2,6-diamine, 4,4'-bis-(sec-butylamino)-diphenylmethane, 1,4-bis-(sec-butylamino)-benzene, 4,4'-methylene-bis-(2-chloroaniline), 4,4'-methylene-bis-(3-chloro-2,6-diethylaniline) ("MCDEA"), polytetramethylene oxide-di-p-aminobenzoate, N,N'-dialkyl Diaminodiphenylmethane, p,p'-methylenedianiline ("MDA"), m-phenylenediamine ("MPDA"), methylene-bis-2-chloroaniline ("MBOCA"), 4,4'-methylene-bis-(2-chloroaniline) ("MOCA"), 4,4'-methylene-bis-(2,6-diethylaniline) ("MDEA"), 4,4'-methylene-bis-(2,3-dichloroaniline) ("MDCA"), 4,4'-diamino-3,3'-diethyl-5,5'-dimethyldiphenylmethane, 2,2',3,3'-tetrachlorodiaminodiphenylmethane, trimethylene glycol di-p-aminobenzoate, and mixtures thereof. Preferably, the curing agent of the present invention includes 3,5-dimethylthio-2,4-toluenediamine and its isomers. Suitable polyamine curing agents include both primary and secondary amines.
[0026] In addition, other curing agents, such as diols, triols, tetraols or hydroxy-terminated curing agents, may be added to the polyurethane composition. Suitable diols, triols and tetraols include ethylene glycol, diethylene glycol, polyethylene glycol, propylene glycol, polypropylene glycol, low molecular weight polytetramethylene ether glycol, 1,3-bis(2-hydroxyethoxy)benzene, 1,3-bis-[2-(2-hydroxyethoxy)ethoxy]benzene, 1,3-bis-{2-[2-(2-hydroxyethoxy)ethoxy]ethoxy}benzene, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, resorcinol-di-(β-hydroxyethyl)ether, hydroquinone-di-(β-hydroxyethyl)ether and mixtures thereof. Preferred hydroxy-terminated curing agents include 1,3-bis(2-hydroxyethoxy)benzene, 1,3-bis-[2-(2-hydroxyethoxy)ethoxy]benzene, 1,3-bis-{2-[2-(2-hydroxyethoxy)ethoxy]ethoxy}benzene, 1,4-butanediol, and mixtures thereof. Both the hydroxy-terminated curing agent and the amine curing agent can contain one or more saturated, unsaturated, aromatic, and cyclic groups. In addition, the hydroxy-terminated curing agent and the amine curing agent can contain one or more halogen groups. The polyurethane composition can be formed with a blend or mixture of curing agents. However, if desired, the polyurethane composition can be formed with a single curing agent.
[0027] The subpad 106 can include a polymeric material. The subpad material can be more compliant than the polishing material 101 of the polishing layer 102. The subpad 106 can include a porous layer. Examples of polymeric materials for the subpad layer include polyurethane, polycarbonate, polysulfone, nylon, epoxy resin, polyether, polyester, polystyrene, acrylic polymers, polymethylmethacrylate, polyvinyl chloride, polyvinyl fluoride, polyethylene, polypropylene, polybutadiene, polyethyleneimine, polyethersulfone, polyamide, polyetherimide, polyketone, silicone, copolymers thereof (e.g., polyether / polyester copolymers), and mixtures or blends thereof.
[0028] The polishing pad 100 disclosed herein can be made by providing a plug of window material in a mold and injection molding the polishing layer around the plug. According to one approach, a thick slab of the polishing layer is formed with a thick plug and then sliced to the desired thickness a of the polishing layer 120. A recess in the window area 103 is then cut into the polishing layer 120 in the area around the plug of window material. The polishing layer may also be cut to provide the macrotexture 102. Alternatively, the pad may be cast alone around the window material 104 in a mold with the desired polishing layer depth a. When cast around the window material, the polishing pad material penetrates the irregular or rough surface of the window to provide a secure bond that allows additional processing such as skiving a polymer cake onto the polishing pad. After demolding, a recess is cut into the polishing layer in the area of the window to the desired recess depth c to form the window area 103. In this latter approach, the macro-texture 102 can be formed from the top surface of the mold, or a flat top surface can be cut back to provide the macro-texture. The cutting to form the recesses can be performed, for example, by milling. A commercially available example of a milling machine that can be used can be a CNC milling machine.
[0029] A method of using the polishing pad 100 disclosed herein includes providing a substrate to be polished, providing a polishing pad 100 disclosed herein, optionally providing a slurry on the polishing pad, contacting the polishing pad with the substrate, moving the substrate and polishing pad relative to one another (e.g., in a rotational motion), transmitting light through the transparent window 104, and detecting light reflected from the substrate back through the transparent window 104 to determine when polishing is complete. Preferably, a translucent slurry is used.
[0030] The present disclosure further includes the following aspects.
[0031] Aspect 1: A polishing pad for chemical mechanical polishing, comprising: a polishing layer having an upper polishing surface, a lower surface, and a thickness, the polishing layer comprising a porous polishing material and a window region, the window region including a transparent window having an exposed upper surface and an exposed lower surface to allow light to transmit through the polishing pad in the window region, the exposed upper surface of the transparent window being recessed from the upper polishing surface, the transparent window extending from the recessed region to the lower surface of the polishing pad, the window region further including a peripheral portion of the polishing material in contact with a side edge of the transparent window, the peripheral portion of the polishing material having an upper surface that is recessed from an upper surface of the upper polishing surface, the transparent window being non-porous, a portion of the upper surface of the peripheral portion adjacent to the transparent window being flush with the upper surface of the transparent window, and the exposed lower surface of the transparent window being flush with the lower surface of the polishing layer.
[0032] Embodiment 2: The polishing pad of embodiment 1, wherein there is no chemical bond between the transparent window and the polishing layer.
[0033] Aspect 3: The polishing pad of aspect 1 or 2, wherein the upper polishing surface comprises a macrotexture.
[0034] Embodiment 4: The polishing pad of embodiment 3, wherein the macrotexture comprises grooves.
[0035] Embodiment 5: The polishing pad of embodiment 4, wherein the grooves intersect at a peripheral portion of the window region.
[0036] Embodiment 6: The polishing pad of any one of the preceding embodiments, further comprising a subpad adjacent to the polishing layer and opposite from the top polishing surface, the subpad comprising an opening in the window area to allow light to be transmitted through the transparent window.
[0037] Embodiment 7: The polishing pad of embodiment 1, wherein the peripheral portion has a width equal to or greater than the thickness of the transparent window.
[0038] Embodiment 8: The polishing pad of embodiment 1, wherein the peripheral portion has a width greater than a thickness of the transparent window.
[0039] Aspect 9: The polishing pad of any one of the preceding aspects, wherein the upper surface of the transparent window is recessed below the polishing surface to a depth of 0.1 to 1.1 mm, preferably 0.2 to 1 mm, more preferably 0.2 to 0.8 mm, and most preferably 0.3 to 0.6 mm.
[0040] Aspect 10: The polishing pad according to any one of the preceding aspects, wherein the width of the recessed peripheral portion of the polishing material is 0.05 to 1.1 mm, preferably 0.1 to 1 mm, more preferably 0.2 to 0.8 mm, and most preferably 0.3 to 0.6 mm.
[0041] Embodiment 11: The polishing pad of any one of the preceding embodiments, wherein an upper surface of the transparent window is flush with an upper surface of the recessed peripheral portion of the polishing material at the point of contact between the window and the recessed peripheral portion of the polishing material.
[0042] Embodiment 12: The polishing pad of any one of the preceding embodiments, wherein an upper surface of the transparent window is flush with an upper surface of the recessed peripheral portion of the polishing material.
[0043] Aspect 13: A method of forming a polishing pad according to any one of the preceding aspects, comprising the steps of placing a plug of transparent window material in a mold and forming a polishing layer around the plug, and cutting away a portion of the polishing layer to form a window area including a recessed window and a recessed peripheral portion of the polishing material.
[0044] Embodiment 14: The method of embodiment 13, wherein the forming step includes forming a thick slab, which is cut into a plurality of polishing layers each having a transparent window material extending through its thickness, and the notching step includes removing an upper portion of the transparent window material.
[0045] A polishing method comprising the steps of providing a substrate to be polished, providing a polishing pad according to any one of the preceding embodiments, providing a translucent slurry on the polishing pad, moving the substrate relative to the polishing pad, transmitting light through a transparent window material, and detecting light reflected from the substrate and returning through the transparent window and the translucent slurry to determine when polishing is complete.
[0046] All ranges disclosed herein are inclusive of the endpoints, and the endpoints are independently combinable with each other (e.g., the range "up to 25% by weight, or more specifically, 5% to 20% by weight" includes the endpoints of the range "5% to 25% by weight" and all intermediate values, etc.). Moreover, stated upper and lower limits can be combined to form ranges (e.g., "at least 1% by weight or at least 2% by weight" and "up to 10 or 5% by weight" can be combined to form the ranges "1 to 10% by weight" or "1 to 5% by weight" or "2 to 10% by weight" or "2 to 5% by weight").
[0047] The present disclosure may alternatively comprise, consist of, or consist essentially of the suitable components disclosed herein. The present disclosure may additionally or alternatively be formulated to be free or substantially free of components, materials, ingredients, adjuvants, or species that are used in prior art compositions or that are otherwise not necessary for the function or accomplishment of the purpose of the present disclosure.
[0048] All patents, patent applications, and other references cited are incorporated herein by reference in their entirety, but if a term in this application contradicts or is incompatible with a term in an incorporated reference, the term from this application takes precedence over the conflicting term from the incorporated reference.
[0049] Unless otherwise specified herein, all test standards are the latest standards in effect as of the filing date of this application or, if priority is claimed, as of the filing date of the earliest priority application in which the test standards are cited.
Claims
1. Polishing pad for chemical mechanical polishing, comprising a polishing layer having an upper polishing surface, a lower surface and thickness, and including a porous polishing material and a window region, wherein the window region includes a transparent window having an exposed upper surface and an exposed lower surface for allowing light to be transmitted through the polishing pad in the window region, the exposed upper surface of the transparent window being recessed from the upper polishing surface, the transparent window extending from the recessed region to the lower surface of the polishing pad, and the window region further including a peripheral portion of the polishing material in contact with the side edge of the transparent window, the peripheral portion of the polishing material having an upper surface recessed from the upper surface of the upper polishing surface, the transparent window being non-porous, a portion of the upper surface of the peripheral portion adjacent to the transparent window being coplanar with the upper surface of the transparent window, and the exposed lower surface of the transparent window being coplanar with the lower surface of the polishing layer.
2. The polishing pad according to claim 1, wherein no chemical bond exists between the transparent window and the polishing layer.
3. The polishing pad according to claim 1, wherein the upper polishing surface includes grooves.
4. The polishing pad according to claim 3, wherein the grooves intersect in the peripheral portion of the window area.
5. The polishing pad according to claim 1, further comprising a sub-pad adjacent to the polishing layer and on the opposite side from the upper polishing surface, wherein the sub-pad includes an opening in the window region for allowing light to be transmitted through the transparent window.
6. The polishing pad according to claim 1, wherein the peripheral portion has a width greater than or equal to the thickness of the transparent window.
7. The polishing pad according to claim 1, wherein the peripheral portion has a width greater than the thickness of the transparent window.
8. A method for forming the polishing pad according to claim 1, A step of placing a plug of transparent window material into a mold and forming a polished layer around the plug, A step of cutting out a portion of the polishing layer to form a window region including a recessed window and a recessed peripheral portion of the polishing material. A method that includes this.
9. The method according to claim 8, wherein the forming step includes forming a thick slab, the thick slab being cut into a plurality of polished layers, each having a transparent window material extending through its thickness, and the notching step includes removing the upper portion of the transparent window material.
10. A process of providing a substrate to be polished, A step of providing the polishing pad according to claim 1, The steps include providing a translucent slurry onto the polishing pad, A step of moving the substrate relative to the polishing pad, A step of transmitting light through a transparent window material, detecting the light that reflects from the substrate and returns through the transparent window and translucent slurry, and determining when polishing is complete. Polishing methods including those mentioned.