Enhanced microporous polishing pad

Abstract

To provide a microporous polishing pad capable of further reducing defects caused by a polishing pad and increasing polishing rate.SOLUTION: The invention provides a porous polyurethane polishing pad that includes a porous substrate. The substrate has large pores that extend upward from a base surface and open to an upper surface. The large pores are interconnected with tertiary pores, a portion of the large pores is open to a top polishing surface and at least a portion of the large pores extend to the top polishing surface. Spring-arm sections connect a lower section and an upper section of the large pores. All spring-arm sections are in the same horizontal direction as measured from the vertical orientation and they are combined so as to increase compressibility of the polishing pad and contact area of the top polishing surface during polishing.SELECTED DRAWING: Figure 3A

Description

[Technical Field]

[0001] FIELD OF THE INVENTION The present invention relates to chemical mechanical polishing pads and methods of forming polishing pads. More particularly, the present invention relates to microporous chemical mechanical polishing pads and methods of forming microporous polishing pads. [Background technology]

[0002] In the fabrication of integrated circuits and other electronic devices, multiple layers of conductive, semiconductive, and dielectric materials are deposited on and removed from the surface of a semiconductor wafer. Thin layers of conductive, semiconductive, and dielectric materials can be deposited using several deposition techniques. Common deposition techniques in modern wafer processing include sputtering, chemical vapor deposition (CVD), plasma-enhanced chemical vapor deposition (PECVD), and physical vapor deposition (PVD), also known as electrochemical plating, among others. Common removal techniques include wet and dry isotropic and anisotropic etching, among others.

[0003] As layers of material are sequentially deposited and removed, the top surface of the wafer becomes non-planar. Subsequent semiconductor processing (such as photolithography) requires that the wafer's surface be flat, so the wafer must be planarized. Planarization helps remove undesirable surface topography and surface defects (e.g., rough surfaces, agglomerated materials, crystal lattice damage, scratches, contaminated layers or materials).

[0004] Chemical mechanical planarization, or chemical mechanical polishing (CMP), is a common technique used to planarize or polish workpieces (e.g., semiconductor wafers). In traditional CMP, a wafer carrier or polishing head is attached to a carrier assembly. The polishing head holds the wafer and positions it in contact with a polishing layer on a polishing pad mounted on a table or platen within the CMP apparatus. The carrier assembly provides controllable pressure between the wafer and the polishing pad. Simultaneously, a polishing medium (e.g., slurry) is dispensed onto the polishing pad and drawn into the gap between the wafer and the polishing layer. To perform the polishing, the polishing pad and wafer typically rotate relative to each other. As the polishing pad rotates beneath the wafer, the wafer typically sweeps over an annular polishing track or area, where the wafer surface directly faces the polishing layer. The wafer surface is polished and made planar by the chemical and mechanical action of the polishing layer and polishing medium on the surface.

[0005] The CMP process typically occurs in two or three steps on a single polishing tool. The first step planarizes the wafer and removes most of the excess material. After planarization, the next step removes any scratches or chatter marks introduced during the planarization step. The polishing pads used for these applications must be flexible and conformal to polish the substrate without scratching. Additionally, these polishing pads and slurries for these steps often require selective material removal (e.g., high TEOS-to-metal removal rates). For purposes of this specification, TEOS is a decomposition product of tetraethyloxysilicate. This is a difficult problem that manufacturers have been working on for many years, as TEOS is a harder material than metals such as copper.

[0006] Over the last several years, semiconductor manufacturers have increasingly transitioned to microporous polishing pads (e.g., Politex™ and Optivision™ polyurethane pads for finishing or final polishing operations where low defectivity is a more critical requirement) (Politex and Optivision are trademarks of one or more of DuPont de Nemours, Inc. or its affiliates). For purposes of this specification, the term microporous refers to porous polyurethane polishing pads produced by solidification from aqueous, non-aqueous, or combinations of aqueous and non-aqueous solutions. The advantage of these polishing pads is the efficient removal of fewer defects. This reduction in defects can result in a dramatic increase in wafer yield.

[0007] A particularly important polishing application is copper barrier polishing, where low defectivity is required in combination with the ability to simultaneously remove both copper and TEOS dielectrics. Consequently, TEOS removal rates are higher than copper removal rates to meet advanced wafer integration designs. Commercially available pads (e.g., Politex polishing pads) do not provide sufficiently low defectivity or high enough TEOS:Cu selectivity for future designs. Other commercially available pads contain surfactants that leach out during polishing, creating excessive amounts of foam that interfere with polishing. Furthermore, surfactants may contain alkali metals that can contaminate dielectrics and degrade the functional performance of semiconductors.

[0008] Despite the low TEOS removal rates associated with microporous polishing pads, the potential for achieving lower defectivity with microporous pads versus other pad types (e.g., IC1000™ polishing pads) has led some advanced polishing applications to transition to all-microporous pad CMP polishing operations. While these operations have fewer defects, challenges remain in further reducing pad-induced defects and increasing polishing rates. Summary of the Invention [Means for solving the problem]

[0009] One aspect of the present invention provides a porous polyurethane polishing pad comprising: a porous substrate having large pores extending upward from a base surface and opening to a top surface, the large pores interconnecting with tertiary pores, a portion of the large pores opening to a top polishing surface; At least a portion of the large pores are Up to the top polished surface , extending vertically It has lower and upper sections, where vertical is the direction perpendicular to the base surface toward the top surface, and spring arm sections connect the lower and upper sections, all of the spring arm sections being in the same horizontal direction measured from the vertical direction, and the spring arm sections are interlocked to increase the compressibility of the polishing pad and the contact area of ​​the top polishing surface during polishing. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a schematic diagram of a coagulation line used to manufacture polyurethane polymer rolls. [Figure 2] FIG. 1 is a schematic diagram of a touch roll used to create a shear zone in a polyurethane polymer roll. [Figure 3] 1 is a schematic diagram of a large perforation showing the main section, middle section, and bottom section of the large perforation before deformation by the touch roll. [Figure 3A] 1 is a schematic diagram of a large perforation showing that the spring arm section after deformation with the touch roll has a horizontal separating gap between the upper and lower sections of the large perforation. [Figure 3B] 1 is a schematic diagram of a large perforation showing that the spring arm section after deformation at the touch roll has a horizontal overlap between the upper and lower sections of the large perforation. [Figure 4] 1 is a schematic diagram of multiple large pores showing a spring arm section with a secondary large pore located adjacent to the spring arm section. [Figure 4A] FIG. 5 is a schematic view of FIG. 4 after buffing to further open the large pores, secondary pores, and upper secondary pores. [Figure 5]This is an SEM photograph of a cross section taken parallel to the roll direction. DETAILED DESCRIPTION OF THE INVENTION

[0011] The polishing pads of the present invention are useful for polishing at least one of magnetic substrates, optical substrates, and semiconductor substrates. In particular, polyurethane pads are useful for polishing semiconductor wafers. In particular, the pads are useful for polishing advanced applications (e.g., copper-barrier applications) where very low defectivity is more important than planarization capability and multiple materials must be simultaneously removed, such as copper, barrier metals, and dielectric materials (including, but not limited to, TEOS, low-k, and ultra-low-k dielectrics). For purposes of this specification, "polyurethane" refers to a product derived from a di- or polyfunctional isocyanate (e.g., polyether urea, polyisocyanurate, polyurethane, polyurea, polyurethane urea, copolymers thereof, and mixtures thereof).

[0012] A porous polyurethane polishing pad comprises a porous substrate having large pores extending upward from a base surface and opening to a top or polishing surface. The large pores are interconnected with tertiary pores. While it is possible for all pores to be open at the top surface, typically only a portion of the large pores open to the top polishing surface. At least a portion of the large pores but , up to the top polished surface , extending vertically The large pores have a lower section and an upper section. As used herein, vertical refers to a direction perpendicular to the basal surface toward the upper surface. Typically, the average diameter of the lower section of the large pores is greater than the average diameter of the upper section of the large pores.

[0013] The spring arm sections connect the lower and upper sections. All of the spring arm sections extend in the same horizontal direction, measured from the vertical direction. While it is possible for the spring arms to bend in multiple directions, pulling the web in shear typically creates spring arm sections that all extend in the same direction. As a result, the middle or spring arm sections typically have an average diameter that is smaller than the average diameter of the lower section of the large perforation. For long middle or spring arm sections, they typically have an average diameter that is smaller than the average diameter of the lower and upper sections of the large perforation.

[0014] These spring arm sections are combined to increase the compressibility of the polishing pad and the contact area of ​​the top polishing surface during polishing. Advantageously, the spring arm sections create a horizontal overlap between the lower and upper sections of the large pores. This shift of the large pores facilitates compression of the entire polishing pad. Most advantageously, the spring arm sections create a horizontal separation gap between the lower and upper sections of the large pores. The longer the spring arms, the greater the leverage and the higher the compressibility of the polishing pad. Increasing the compressibility improves the conformity of the polishing pad on the wafer, increasing the contact area and increasing the polishing rate. Advantageously, the spring arm sections have an angle of between 15 and 90 degrees measured from an upward vertical direction.

[0015] In addition to the large pores, medium pores begin adjacent to the spring arm sections of the large pores, and the medium pores have a vertical orientation. The medium pores usually begin horizontally and above the spring arm sections. Similarly, small pores begin between the medium pores and interconnect them. As indicated, the large pores are the largest and usually have a vertical height that is about twice the vertical height of the medium pores. The large pores with spring arms or connecting sections advantageously account for less than 50 percent of the total of the large pores plus the medium and small pores. The large, medium, and small pores all combine to improve the compressibility of the polishing pad.

[0016] The polishing pad advantageously has a compressibility measured by a uniaxial compression tester with a Keyence laser thickness measurement instrument configured as follows: [Table 1] The deflectometer operates by adding an initial weight 1 to a rod that presses a 5 mm diameter solid metal probe against a flat specimen, and measuring the thickness (T1) after 60 seconds. Then, after waiting another 60 seconds, a second weight is added to the rod, increasing the weight and forcing the probe further into the specimen. The measurement after another 60 seconds then represents the final thickness (T2), which is used to calculate the compressibility with the above formula. For purposes of this application, particularly the examples, all compressibility data and ranges represent values ​​measured with the test method described above.

[0017] The polishing pad advantageously has a compressibility of at least 5% in the above test. Most advantageously, the polishing pad has a compressibility of 5-10% in the above test.

[0018] Advantageously, the polishing pad has an embossed surface that forms grooves that extend to the periphery of the polishing pad. Typically, the embossing is an XY square grid pattern. However, the embossing can be any known pattern (e.g., circular, or circular and radial).

[0019] Referring to FIG. 1 , a polyurethane-water-dimethylformamide ("DMF") coating mixture 10 is coated onto a felt roll 12 by controlling a trailing blade 14 and a knife or doctor blade 16. The porous abrasive layer is fixed to a polymer film substrate or formed on a woven or nonwoven substrate to form a polishing pad. When depositing a porous abrasive layer onto a polymer substrate (e.g., a nonporous poly(ethylene terephthalate) film or sheet), it is often advantageous to use a binder (e.g., a proprietary urethane or acrylic adhesive) to enhance adhesion to the film or sheet. While these films or sheets may contain porosity, they are preferably nonporous. The advantages of a nonporous film or sheet are that it promotes uniform thickness or flatness, increases the overall stiffness of the polishing pad, reduces overall compressibility, and eliminates the slurry suction effect during polishing.

[0020] Felt roll 12, backing blade 14, and doctor blade 16 with side walls (not shown) together form a trough 18 that holds coating mixture 10. Backing blade 14 presses felt roll 12 against backup roll 20 to prevent coating mixture 10 from flowing out the back of trough 18. Backup roll 20 rotates clockwise during operation of the coating line.

[0021] Moving the trailing blade 14 toward or away from the backup roll 20 determines the width of the gap 22. The smaller the gap 22, the greater the back tension on the felt roll 12. The dotted arrow 22A indicates the change in the width of the gap 22. This is achieved by moving the trailing blade 14 toward the backup roll 20 to decrease the gap (-) and increase the tension, or by moving the trailing blade 14 away from the backup roll 20 to increase the gap (+) and decrease the tension. The tension vector A indicates the direction of the back tension on the felt roll 12. The height of the doctor blade 16 determines the thickness of the coating 24 on the felt roll 12. Because the doctor blade 16 controls the thickness of the liquid coating mixture 10, it applies near-zero or zero back tension to the felt roll 12.

[0022] A tension roller (not shown) pulls the felt roll 12 with the coating portion 24 into the water bath 26. Tension vector B indicates the direction of tension pulling both the felt roll 12 and the coating portion 24 through the water bath 26. Immediately upon immersion in the water bath 26, DMF diffuses from the coating mixture 10, replacing the water with a lower DMF concentration. This rapid diffusion creates pores in the coating portion 24. Moving the touch roll 28 up and down facilitates adjustment of the tension and compression of the felt roll 12 with the coating portion 24. Because the coating mixture 10 is a liquid-solid mixture, there is no countertension in the coating portion 24 between the doctor blade 16 and the touch roll 28. Tension in the coating portion 24 exists only after the coating portion 24 passes through the touch roll 28. The touch roll 28 rotates counterclockwise during operation of the coating line. As the large slots 30 move and engage the touch roll 28, a combination of tension and compression forces deform the slots 30. Increasing the line speed allows the substrate surrounding the slots less time to settle and cure. The substrate should be strong enough to retain its shape, but not strong enough to elastically deform and recover. This partial cure before oven curing facilitates the formation of the deformed slots 30.

[0023] Referring to FIG. 2, the combination of the counter tension on the felt roll 12 and the tensile tension of the covering portion 24 after the felt roll 12 and touch roll 28 acts to create a shear zone, shown by the dotted lines with respect to the lower shear zone boundary 32 and the upper shear zone boundary 34. Arrow C indicates the rotation direction of the touch roll 28. In the shear zone 33, between the dotted lines 32 and 34, the large perforations 30 change from vertical perforations to large vertical perforations 40 with a curved portion of the spring arm section 42 (FIG. 3A). Arrow D indicates the direction of the felt roll 12 at the touch roll 28. In the touch roll 28, tension vectors A and B pull in opposite directions through the lower shear zone boundary 32 to the upper shear zone boundary 34 or the top of the shear zone 33. The shear zone 33 defined between the lower boundary 32 and the upper boundary 34 gradually deforms the large perforations 30. Perforations 30A indicate the initial bending of the middle section. Pore ​​30B has a more pronounced bend in the middle. Pore 30C has a well-defined bend with a moderate narrowing in the middle. Pore 30D has a near-final bend with a near-final narrowing in the middle. Pore 40 represents the final large pore containing spring arm sections. These spring arm sections promote high compressibility and conformability of the final polishing pad.

[0024] Referring to Figures 3, 3A, and 3B, the large pore 30 includes a main section 50 having a teardrop shape, a mid-section 52 having a tapered neck shape, and a top section 54 having a vertical orientation and slight taper. Arrows 50A, 52A, and 54A define the heights of the main section 50, the mid-section 52, and the top section 54, respectively. Typically, the shear zone boundaries 32 and 34 extend from the top of the main section 50 through the mid-section 52 to the bottom of the top section 54. During deformation, the top of the main section 50 deforms in a tensile direction. The mid-section 52 deforms in multiple directions and laterally. The pore is stretched and narrowed by first bending from a vertical orientation to a partially horizontal-partial vertical orientation, and then bent upward from the partially horizontal-partial vertical orientation back to the vertical orientation. As the pore is stretched and narrowed, its cross-sectional area or average diameter decreases. This narrow, at least partially horizontally extending region is known as the spring arm section 60. Arrow 60A defines the height and length of the spring arm section 60. Arrow 60B defines the perpendicular bisection of the main section 50. line Vertical bisection of upper section 54 line to define an offset for the upper section. Advantageously, the spring arm section 60 has an angle of between 15 and 90 degrees from vertical. Most advantageously, the spring arm section 60 has an angle of between 25 and 80 degrees from vertical.

[0025] Referring to Figure 3A, when shear zone 33 is large, upper section 54 shifts horizontally a distance sufficient to create a horizontal gap 60B for spring arm section 60 extending beyond lower section 50 of large pore 40. Referring to Figure 3B, when shear zone 33 is small, upper section 54 shifts horizontally a distance not sufficient to create a horizontal gap 60B for spring arm section 60 extending beyond lower section 50 of large pore 40. In this case, there is a horizontal overlap between the upper section of spring arm section 60 and the outermost portion of lower section 50 of large pore 40. The force in shear zone 33 combined with the yield strength of the polymer matrix controls the final length 60A of the spring arm section.

[0026] Referring to FIG. 4, the coated felt substrate 12 includes a plurality of large pores 40 containing spring arm sections 60. The spring arm sections are interlocked to increase compressibility and contact area during polishing. A series of large secondary pores 70 begin adjacent to the spring arm sections 60. Similarly, a set of upper secondary pores 72 begin approximately midway between the secondary pores 70. Typically, the large pores 40 have the largest size. The secondary pores 70 tend to be smaller than the large pores 40 but larger than the upper secondary pores 72. The large pores 40, secondary pores 70, and upper secondary pores 72 all extend to the skin layer 76 at the top surface. Numerous micropores 78 are present subsurface, just below the skin layer 76.

[0027] After DMF removal, oven drying hardens the thermoplastic polyurethane. If necessary, a high-pressure washing and drying process further cleans the substrate. After drying, referring to Figure 4A, a buffing process removes the skin layer 76 and fine pores 78, opening the large pores 40, secondary pores 70, and upper secondary pores 72 to a controlled depth. This allows for a consistent pore count and open pore area at the top surface. During buffing, it is advantageous to use a stable abrasive that does not shed or penetrate the porous substrate. Diamond abrasives typically produce the most consistent texture and are least likely to break during buffing. After buffing, the substrate has a typical "fluff" (i.e., pore) height of 10 to 30 mils (0.25 to 0.76 mm) and an overall thickness of 30 to 60 mils (0.76 to 1.52 mm). The average large pore size ranges from 5 to 85 μm. Typical density values ​​are 0.2 to 0.5 g / cm. 3 The cross-sectional pore area is usually 10 to 30 percent, the surface roughness Ra is less than 14, and Rp is less than 40. The hardness of the polishing pad is preferably 40 to 74 in Asker C type.

[0028] In an alternative embodiment, a non-porous film serves as the base substrate. The most notable drawback of films is the potential for air bubbles to become trapped between the polishing pad and the platen of the polishing tool when a non-porous film or porous substrate is used as the base substrate in combination with an adhesive film. These bubbles distort the polishing pad and cause defects during polishing. A patterned release liner facilitates air removal and eliminates bubbles under these conditions. This causes significant problems, including uneven polishing, increased defects, increased pad wear, and reduced pad life. Using felt as the base substrate eliminates these problems because air permeates the felt and air bubbles are not trapped. Second, when an abrasive layer is applied to the film, adhesion of the abrasive layer to the film depends on the strength of the adhesive bond. Under some aggressive polishing conditions, this bond can fail, resulting in catastrophic failure. When felt is used, the abrasive layer actually penetrates to a certain depth within the felt, forming a strong, mechanically interlocked boundary layer. While woven structures are acceptable, nonwoven structures may provide additional surface area for strong bonding to porous polymer substrates. An excellent example of a suitable nonwoven structure is polyester felt impregnated with polyurethane to hold the fibers together. Typical polyester felt rolls are 0.5 to 1.5 mm thick.

[0029] The polishing pad of the present invention is suitable for polishing or planarizing at least one of a semiconductor substrate, an optical substrate, and a magnetic substrate using a polishing liquid and relative motion between the polishing pad and at least one of the semiconductor substrate, the optical substrate, and the magnetic substrate. The polishing layer has an open-cell polymer matrix. At least a portion of the open-cell structure is open to the polishing surface. The large pores have a vertical orientation. doThese large pores, contained within the solidified polymer matrix, form a "fluff" layer up to a certain "fluff" height. The height of the vertical pores is the same as the height of the "fluff" layer. The orientation of the vertical pores is formed during the solidification process. For purposes of this patent application, the vertical or up-and-down direction is perpendicular to the polishing surface. The average diameter of the vertical pores increases with distance from or below the polishing surface. The polishing layer typically has a thickness of 20 to 200 mils (0.5 to 5 mm), preferably 30 to 80 mils (0.76 to 2.0 mm). An open-cell polymer matrix having vertical pores and open channels interconnecting the vertical pores. Preferably, the open-cell polymer matrix has interconnecting pores with a diameter sufficient to allow fluid transport. These interconnecting pores have an average diameter much smaller than the average diameter of the vertical pores. The pore morphology is characterized by open-topped primary pores approximately 40 μm in size and interconnected micropores approximately 2 μm in size within the polyurethane layer.

[0030] The plurality of grooves in the polishing layer facilitates slurry distribution and removal of polishing debris. Preferably, the plurality of grooves form an orthogonal grid pattern. Typically, the grooves form an XY coordinate grid pattern in the polishing layer. The grooves have an average width measured adjacent to the polishing surface. The plurality of grooves have a debris-removal dwell time during which a point on at least one of a semiconductor substrate, an optical substrate, and a magnetic substrate rotating at a constant speed passes through the width of the plurality of grooves. The plurality of protruding land areas within the plurality of grooves are advantageously supported by tapered support structures extending outward and downward from the apex or plane of the polishing surface of the plurality of protruding land areas. Preferably, the slope is 30 to 60 degrees as measured from the plane of the polishing surface. Most preferably, the plurality of land areas have frustum or blunt apexes that form the polishing surface from a polymer matrix containing vertical pores. Typically, the protruding land areas have a shape selected from hemispherical, truncated pyramidal, truncated trapezoidal, and combinations thereof, with a plurality of linearly extending grooves between the protruding land areas. The plurality of grooves have an average depth greater than an average height of the vertical pores, and the vertical pores have an average diameter that increases the depth of at least one of the vertical pores below the polishing surface.

[0031] Melting and solidifying the thermoplastic polyurethane at the bottom of the sloping sidewalls closes most of the large and small pores, forming groove channels. Preferably, the plastic deformation of the sidewalls and the melting and solidification process form a lattice of interconnected grooves. The bottom surfaces of the groove channels have few or no open pores. This facilitates smooth debris removal and secures the microporous polishing pad within the open-pore, tapered pillow-like structure. Preferably, the grooves form a series of pillow-like structures formed from a porous matrix containing large and small pores. Preferably, the small pores have a diameter sufficient to allow the flow of deionized water between the vertical pores.

[0032] The substrate is important for forming a proper foundation. The substrate can be a polymer film or sheet. However, woven or nonwoven fibers provide the best substrate for microporous polishing pads. For purposes of this specification, microporous refers to a breathable synthetic leather formed from the aqueous displacement of organic solvents. Nonwoven felt provides an excellent substrate for most applications. Typically, these substrates are dominated by polyester fibers (e.g., polyethylene terephthalate fibers, or other polymer fibers formed by blending, carding, and needle punching).

[0033] For consistent properties, it is important that the felt has consistent thickness, density, and compressibility. Forming felt from consistent fibers with consistent physical properties results in a base substrate with consistent compressibility. To increase consistency, shrinking and non-shrinking fibers can be mixed and the felt can be passed through a hot water bath to control the density of the felt. This has the advantage that the bath temperature and residence time can be used to fine-tune the final felt density. After the felt is formed, it is sent to a polymer impregnation bath (e.g., an aqueous polyurethane solution), which coats the fibers. After the fibers are coated, the felt is cured in an oven to increase its stiffness and resilience.

[0034] Curing after coating and a subsequent buffing process control the thickness of the felt. To fine-tune the thickness, the felt can be first buffed with coarse grit, then finished with finer grit. After buffing the felt, it is preferably washed and dried to remove any grit or debris picked up during the buffing process. After drying, the felt is then prepared for the waterproofing process by entrapping dimethylformamide (DMF) on the backside. For example, perfluorocarboxylic acids and their precursors (e.g., AGC Chemical's AG-E092 Repellent for Textiles) can waterproof the top surface of the felt. After waterproofing, the felt must be dried, and an optional burning process can remove any fiber ends protruding from the top layer of the felt. The waterproof felt is then prepared for coating and solidification.

[0035] A mixture of anionic and nonionic surfactants preferably forms pores during coagulation, contributing to improved hard-soft compartment formation and optimal physical properties. For anionic surfactants, the surface-active portion of the molecule carries a negative charge. Examples of anionic surfactants include, but are not limited to, carboxylates, sulfonates, sulfates, phosphates and polyphosphates, and fluorinated anions. More specific examples include, but are not limited to, dioctyl sodium sulfosuccinate, sodium alkylbenzene sulfonate, and salts of polyoxyethylenated fatty alcohol carboxylates. In the case of nonionic surfactants, the surface-active portion does not have a significant ionic charge. Examples of nonionic surfactants include, but are not limited to, polyoxyethylene (POE) alkylphenols, POE linear alcohols, POE polyoxypropylene glycols, POE mercaptans, long-chain carboxylic acid esters, alkanolamine alkanolamides, tertiary acetylene glycols, POE silicones, N-alkylpyrrolidones, and alkyl polyglycosides. More specific examples include, but are not limited to, monoglycerides of long chain fatty acids, polyoxoethylenated alkylphenols, polyoxyethylenated alcohols, and polyoxyethylene cetyl stearyl ether. For a more complete description of anionic and nonionic surfactants, see, for example, Milton J. Rosen, "Surfactants and Interfacial Phenomena," 3rd Edition, Wiley-Interscience, 2004, Chapter 1.

[0036] Example The following examples illustrate the invention, focusing on polyurethane formulation, set control, and polishing performance.

[0037] material

[0038] In the examples, Component A represents DIC's CRISVON™ 8166NC, methylene diphenyl diisocyanate (MDI), for producing a "hard section" in thermoplastic polyurethane. Specifically, the polyurethane is a polyester-type low-elasticity polyurethane that was processed through a coagulation process to form an upper porous layer as a polishing layer. The analytical specifications for Component A are as follows: nonvolatile solids weight percent: 29.0-31.0%; viscosity at 25°C: 60,000-80,000 MPa(s); 300% modulus—17 MPa; tensile strength—55 MPa; elongation to break of at least 500%; and melting point of 195°C.

[0039] The chemical composition of component A was determined by proton and carbon-13 NMR and was as follows: [Table 2]

[0040] The first surfactant was RESAMINE CUT-30 dioctyl sodium sulfosuccinate ("DSS") purchased from Dainichiseika. The second surfactant was PL-220 polyoxyethylene alkyl ether ("EOPO") purchased from Kao Chemical.

[0041] Component A: Polyurethane Component B: Dioctyl Sodium Sulfosuccinate Surfactant Component C: Polyoxyalkylene alkyl ether surfactant Component D: Dimethylformamide (DMF)

[0042] The formulations used various combinations of components A-D formed by different solidification processes: [Table 3]

[0043] Control of pore growth and final pore morphology was achieved by using various concentrations of surfactant components B and C. The coating solution was a mixture of components A, B, C, and D used for coating, followed by water for the DMF displacement coagulation process.

[0044] Coagulated films of polyurethane formulations were prepared by laboratory drawdown tests to investigate surfactant ratios for creating porous materials. Impregnated nonwoven polyester felt was used as the substrate. The polyurethane was diluted with DMF to the design solids percentage, mixed with surfactant, degassed, equilibrated to the design temperature, and then drawn off. Coagulation was performed in a DMF / water bath, followed by washing and drying. [Table 4] Example 1 : polymer: Ingredient A Polymer concentration: 20% by weight in DMF Surfactants: DSS and EOPO Surfactant mixture concentration: DSS concentration = 0.5, 1.0, 2.0, 3.0, 4.0phr EOPO concentration = 0.5, 1.0, 2.0, 3.0, 4.0phr Coating thickness: 65 mils (1.65 mm) DMF concentration: 7% by weight Coagulation bath temperature: 30℃ Sample size: 25 Drawdown result: DSS promotes the formation of primary pores. EOPO assists in the formation of deep cylindrical pores. From this testing, it was determined that the best surfactant ratio for creating the deepest primary pores was DSS / EOPO=4:1 phr / phr.

[0045] The two surfactants controlled the coagulation mechanism and enabled primary pore growth. The DSS surfactant promoted the growth of primary pores deep at the bottom of the coated layer. The height of the "fluff" of the primary pores increased with increasing concentration of the DSS surfactant.

[0046] The combination of DSS and EOPO surfactants modulated the coagulation of the polyurethane, resulting in the formation of increased primary pores with a cylindrical upper section, instead of a pure teardrop shape without a cylindrical section. EOPO surfactant concentrations above 2.0 phr prevented the growth of primary pores, leaving only a uniform layer of micropores. This is likely due to the affinity of EOPO for the soft compartment of the polyurethane chain, which promoted solvation of the polyurethane and reduced the degree of phase separation.

[0047] The best ratio of DSS / EOPO surfactant was 4:1 phr / phr. Example 2 : Candidate formulations: Ingredient A Polymer concentration: 20% by weight, 22% by weight in DMF Surfactants: DSS and EOPO Concentration of surfactant mixture: DSS concentration = 4.0 phr EOPO concentration = 1.0 phr Coating thickness: 65 mil (1.65 mm), 90 mil (2.23 mm) DMF concentration: 7% by weight Coagulation bath temperature: 25℃、30℃、35℃ Sample size: 12 Drawdown method: Laboratory drawdown test, standard conditions result: The solidification temperature affected the pore morphology and the growth of "fluff" (i.e., pores). The solids concentration affected the pore morphology, especially the teardrop shape. Pore ​​growth could reach the bottom of the drawdown with thicker coatings, but better control of the pore morphology was needed. Example 3 : Candidate formulations: Ingredient A Polymer concentration: 20% by weight in DMF Surfactants: DSS and EOPO Concentration of surfactant mixture: DSS concentration = 4.0 phr EOPO concentration = 1.0 phr Coating thickness: 65 mils (1.65 mm) DMF concentration: 0% by weight, 7% by weight, 14% by weight Coagulation bath temperature: 20℃、30℃、40℃ Sample size: 9 Drawdowns method: Laboratory drawdown test, standard conditions result: The solidification temperature had a significant effect on the pore morphology and fluff growth. Increasing the DMF concentration prevented the formation of primary pores. The key process conditions for solidification control and pore morphology were determined as follows: Coagulation bath temperature Polymer Solids % DMF / moisture concentration Coating Thickness Example 4 : Candidate formulations: Ingredient A Polymer concentration: 20% by weight in DMF Surfactants: DSS and EOPO Concentration of surfactant mixture: DSS concentration = 3.2, 4.0, 4.8 phr EOPO concentration = 0.8, 1.0, 1.2 phr Coating thickness: 65 mils (1.65 mm) DMF concentration: 7% by weight Coagulation bath temperature: 25℃ method: Laboratory drawdown test, standard conditions Sample size: 11 Drawdown [Table 5]

[0048] Table 5 summarizes the surfactant ratios for Example 4. Table 6 provides the results for the polishing pads prepared under the conditions of Table 5. The data are summarized below based on SEM analysis. [Table 6]

[0049] Pore ​​formation was observed with pore morphology within ±1.5 sigma variation. The surfactant ratio had a significant effect on fuzz height compared to other parameters. For the substrates in Table 6, the pore structures of Samples 1, 5, and 8, with a DSS to EOPO weight percent concentration of 4:1, provided the best pore morphology.

[0050] Example 5 Film Tensile Properties [Table 7]

[0051] The above data demonstrates the excellent toughness and energy to break of the porous substrate. Note: The above properties are representative of film substrates tested according to (ASTM D886).

[0052] Polishing Protocol

[0053] Pad polishing performance was determined on 300mm blanket wafers mounted on an Applied Material Reflexion® LK 300mm CMP polishing tool. Polishing removal rate experiments were performed on copper wafers from a Novellus 300mm sheet 20K Cu electronic plate, TEOS wafers from a Novellus 300mm blanket 20k tetraethyl orthosilicate (TEOS) sheet wafer, tantalum (Ta) wafers from a Sematech 300mm sheet 1K tantalum, Black Diamond™ and Coral™ low-k dielectric wafers from a CNSE 300mm sheet 5K BD (k=3.0), and BD2S wafers from a SVTC 300mm sheet 5K BD2 (k=2.7).

[0054] All polishing experiments were performed using ACuPLANE™ LK393c4 Cu barrier slurry from Rohm and Haas Electronic Materials CMP Inc. All wafers were polished for a typical 60 seconds under standard conditions: a low pressure of 12.4 kPa (1.8 psi), a flow rate of 300 mL / min of chemical mechanical polishing composition, a table rotation speed of 93 rpm, and a carrier rotation speed of 87 rpm. A 3M-A82 diamond pad conditioner, commercially available from 3M, was used to condition the polishing pad. Table 8 lists the specifications for the 3M-A82 disk. The polishing pad was pressed through the conditioner using a downward force of 2.0 lbs (0.9 kg) for 10 minutes with the conditioner's high-pressure rinse (HPR) turned on, a platen speed of 73 rpm, and a conditioner speed of 111 rpm. During polishing, the pad was fully conditioned by the conditioner with the high pressure rinse (HPR) on, a platen speed of 73 rpm, and a conditioner speed of 111 rpm, using a down force of 2.0 lbs (0.9 kg) for only 3.2 seconds.

[0055] TEOS removal rates were determined by measuring film thickness before and after polishing using a KLA-Tencor SPECTRAFX200 metrology tool. Copper (Cu) and tantalum (Ta) removal rates were determined using a KLA-Tencor RS100C metrology tool. Defect map scans were performed using a KLA-Tencor SP2 metrology tool, and defect review was performed using a KLA-Tencor eDR-5210 metrology tool. [Table 8]

[0056] Polishing example Four examples of pads and their respective characterizations are summarized below: All pads were made with the same polyurethane / surfactant formulation with the process parameters of Sample 1 being different. [Table 9]

[0057] All of the pads described above had the pore structures shown in Figures 3A, 4, and 5. In particular, the primary pores had a spring-arm shape that promoted pad compressibility. The data above demonstrates that increasing line speed increases the compressibility of the polishing pad. Increasing compressibility increases the contact area during polishing. This increased contact area allowed the pad to operate with a softer structure that is less prone to defects.

[0058] Example 6 Polishing Performance

[0059] The removal rate and defect results are summarized in the table below.

[0060] Example 7: Polishing performance of pads 1, 4 (different batches): [Table 10] [Table 11]

[0061] The table above shows excellent polishing stability for 500 wafers when polishing copper, TEOS, and tantalum substrates. Example 7 Removal Rate [Table 12] [Table 13]

[0062] For copper removal rates, the pads of Examples 1-4A and 1-4B exhibited copper rates of 694 and 680 A / min, respectively, approximately 12% and 14% lower than that of commercial pad A. The TEOS removal rates of 1-4A and 1-4B were 1416 and 1414 A / min, similar to commercial pads A and B. The similar removal rates between commercial pad A, pad B, and the pads of Examples 1-4A and 1-4B suggest that good contact area or wear and compatibility between the pad, abrasive, and wafer facilitate effective oxide and copper removal. Example 8 Defective Performance [Table 14] [Table 15] [Table 16] [Table 17]

[0063] Polishing Pads 1-4A and 1-4B exhibited significantly fewer total defects than commercial pads A and B. The total defects averaged 73, 146, 19, and 37, while scratches and chatter marks averaged 35, 10, 4, and 1 for pads A, B, 1-4A, and 1-4B. This represented a measurable and dramatic reduction in polishing defects. High-compression pads produced at the highest line speeds tended to have the fewest total defects.

[0064] Enhanced scanning recipes were developed to improve resolution and differentiate performance. The results are summarized in the graph on the right, showing 241, 736, 34, and 85 total defects, and 126, 360, 5, and 9 scratches and chatter marks for Pads A, B, 1-4A, and 1-4B, respectively. Polishing Pads 1-4A and 1-4B averaged over 99% reduction in scratches and chatter compared to commercial Pad B and over 95% reduction compared to commercial Pad A. The highly compressible pads produced at the highest line speeds had the fewest chatter mark defects. Example 9 Pad Analysis After Polishing

[0065] To evaluate pad wear, SEM analysis was performed on the pad surface after polishing. The sampling area included the center, middle, and edge of the pad. For polishing pads 1-4A and 1-4B, all primary pores remained open, and no debris was present. No significant hanging material was observed from either pad break-in, conditioning, or wafer polishing. Furthermore, there was no significant difference in surface pore morphology from the center, middle, or edge of the pad. This suggests that consistent wear occurred throughout the pad. Furthermore, high-resolution SEM images (500x and 1000x magnification) showed a distinct secondary pore structure. Smaller pores remained open after polishing, and no debris accumulation was observed. This indicated effective slurry flow through the porous structure. No differences were observed between the center, middle, or edge of the pad.

[0066] The uniform distribution of primary pores and interconnected micropores represents one reason for the pad's excellent performance, providing satisfactory removal rates combined with excellent defectivity. The present invention demonstrated a new highly compressible structure that provides excellent polishing performance. In particular, it exhibited ultra-low defectivity, good removal rates for copper, TEOS, and barrier metals, and long pad life. In particular, the pad polished at excellent copper and TEOS rates that remained stable for multiple wafers. Furthermore, the pad exhibited significantly fewer scratches and chattering defects than conventional polishing pads. The manufacturing process used was a determining factor for the final primary and secondary pore structure. Furthermore, the manufacturing process was robust and provided reproducible pad pore morphology and polishing performance.

Claims

1. 1. A porous polyurethane polishing pad comprising: a porous substrate having large pores extending upward from a basal surface and opening to an upper surface; Equipped with The large pores are a lower main section having a teardrop shape and given by a perpendicular bisector; an intermediate spring arm section having a tapered neck shape; and an upper vertical section having a cylindrical shape and having a perpendicular bisector given by: and the average diameter of the lower section is greater than the average diameter of the upper vertical section; the intermediate spring arm section extends from the perpendicular bisector of the lower main section to the perpendicular bisector of the upper vertical section; the large pores are interconnected with the micropores; the upper vertical section of the large pore is open to a top polished surface; at least a portion of the macropores have the lower major section and the upper vertical section extending vertically to the top polished surface, the vertical direction being perpendicular to the base surface and toward the top surface; and the intermediate spring arm section connects the lower main section and the upper vertical section; the intermediate spring arm sections all have angles of 15 to 90 degrees measured from the vertical direction of a perpendicular bisector of the lower main section of the large slot; the intermediate spring arm sections create a horizontal separation gap and combine to increase the compressibility of the polishing pad and increase the contact area of ​​the top polishing surface during polishing; The above polishing pad.

2. 2. The polishing pad of claim 1, wherein the intermediate spring arm section creates a horizontal separation gap between the lower main section and a majority of the upper vertical section of the large pore.

3. 2. The polishing pad of claim 1, wherein the intermediate spring arm section creates a horizontal overlap between the lower main section and a majority of the upper vertical section of the large pore.

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