A chemical mechanical polishing pad with improved edge effect, method of making and use thereof

Abstract

The application discloses a preparation method of a chemical mechanical polishing pad with improved polishing wafer polishing "edge effect" defects, which comprises the following steps: a hole area is formed on the lower surface of a polishing track area of a polishing layer, and a polyurethane material is filled in the hole area, and the polishing layer is formed after solidification, so that the chemical mechanical polishing pad is prepared. The application also relates to the prepared chemical mechanical polishing pad and application thereof in chemical mechanical polishing. The method changes the physical properties of the polishing track area of the polishing pad, improves the hardness of the polishing layer in the center area of the polishing track, and improves the grinding rate of the center area of the wafer, so as to relieve the generation of the "edge effect".

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of chemical mechanical polishing, and particularly relates to a chemical mechanical polishing pad capable of eliminating or reducing edge effect of wafers after polishing, a preparation method and application thereof. BACKGROUND

[0002] Chemical mechanical polishing (CMP) is a technology combining chemical action and mechanical action, and its process is quite complex, with many influencing factors. First, the material on the surface of a workpiece reacts chemically with oxidizing agents, catalysts and the like in a polishing liquid to form a soft layer that is relatively easy to remove. Then, the mechanical action of abrasives in the polishing liquid and the polishing pad removes the soft layer, so that the surface of the workpiece is exposed again, and then the chemical reaction is carried out again. In this way, the polishing of the surface of the workpiece is completed in the alternating process of chemical action and mechanical action.

[0003] However, chemical mechanical polishing is often accompanied by the problem of edge effect. Edge effect refers to a phenomenon that the polishing rate at the edge of a polishing element is not uniform with the polishing rate at the center. Relative to the center, edge effect often leads to excessive removal of material at the periphery of the polishing element, i.e. so-called overpolishing, and thus uneven edge polishing profiles are generated on the polishing element, which seriously affects the yield and good rate of the polishing element.

[0004] Patent CN107813219B proposes a formula of a polishing pad, the polishing layer comprises a polyurethane reaction product of a reaction mixture of a curing agent and a polyisocyanate prepolymer, the unreacted isocyanate (NCO) concentration of the polyisocyanate prepolymer is 8.3wt% to 9.8wt%, and is formed by a polypropylene glycol (PPG) and a polytetramethylene ether glycol (PTMEG) and a polyol blend containing a hydrophilic portion of polyethylene glycol or an ethylene oxide repeating unit, toluene diisocyanate, and one or more isocyanate extenders. The polishing pad prepared from the formula provides improved (reduced) defect rate without a corresponding decrease in planarization efficiency.

[0005] Patent CN112338820A discloses a polishing pad, the polishing pad has a buffer layer formed by different compression ratios and rebound rates of combined pieces and a polishing layer stacked on the buffer layer; different combined pieces form a center circular buffer zone, one or more intermediate annular buffer zones arranged around the center buffer zone, and an outer edge annular buffer zone arranged around the intermediate buffer zone. The different compression ratios and rebound rates of the combined pieces of the buffer layer in the direction from the center to the outer edge of the polishing pad are set, and the wear rate is basically maintained during mechanical polishing, so that the surface of the wafer to be polished becomes flat, and the planarization efficiency is high.

[0006] It is necessary to eliminate or reduce the "edge effect" in the polishing process for the efficiency and energy consumption of wafer production, and it is desirable to achieve a simple and low-cost way. SUMMARY

[0007] To solve the problem of "edge effect" on the wafer surface after polishing in the prior art, the present application does not focus on reducing the polishing rate at the edge, but creatively improves the polishing rate at the center of the wafer from the structure of the polishing pad itself, and develops a new type of polishing pad, thereby completing the present application.

[0008] One object of the present application is to provide a preparation method of a chemical mechanical polishing pad with improved "edge effect".

[0009] Another object of the present application is to provide such a chemical mechanical polishing pad with improved "edge effect".

[0010] Still another object of the present application is to provide the use of such a chemical mechanical polishing pad for wafer polishing.

[0011] To achieve the above technical objects, the present application adopts the following technical solutions:

[0012] A preparation method of a chemical mechanical polishing pad with improved edge effect, comprising the steps of sequentially bonding and pressing a polishing layer, a bonding layer, a buffer layer and a release layer, wherein the polishing layer is prepared by the following steps:

[0013] 1) uniformly mixing a prepolymer A containing unreacted isocyanate groups, expanded microspheres and a curing agent, pouring into a mold by a pouring machine to obtain a polyurethane "cake", and demolding after heating and curing;

[0014] 2) obtaining a polishing layer sheet after thickness setting operation, and performing groove engraving on the upper surface of the polishing layer by a slotting machine;

[0015] 3) engraving a hole structure on the lower surface of the polishing layer, avoiding the groove position on the upper surface;

[0016] 4) uniformly pouring a prepolymer B containing unreacted isocyanate groups and a curing agent into the hole structure after mixing, and smoothing, and obtaining the polishing layer after heating and curing.

[0017] In a specific embodiment, the step 1) is obtained by a prepolymer A containing 5-10 wt% of unreacted isocyanate groups, expanded microspheres and a curing agent containing active hydrogen groups; preferably, the stoichiometric ratio of unreacted isocyanate groups in the prepolymer A to active hydrogen in the curing agent is 0.8-1.2.

[0018] In one specific embodiment, the mass fraction of unreacted isocyanate groups in the prepolymer B of step 4) is higher than the unreacted isocyanate group component in the prepolymer A of step 1) by 1-2 wt% (absolute value); preferably, the stoichiometric ratio of unreacted isocyanate groups in the prepolymer B to active hydrogen in the curing agent is 0.8-1.2.

[0019] In one specific embodiment, the polishing layer comprises a circular intermediate region, an annular polishing track region, and an outer edge region, the polishing layer radius is R, the polishing layer center to the circular intermediate region radius is R0, the polishing layer center to the outer edge of the annular polishing track region radius is R1, and the three satisfy the following relationship: 0 < R0≤ 1 / 4 * R, R0 < R1 < R.

[0020] In one specific embodiment, the hole structure engraved on the lower surface of the polishing layer in step 3) is distributed in the annular polishing track region. In a single annular region, the distance between the centers of every two non-penetrating holes along the circumferential direction is greater than or equal to 1.5 times the hole diameter and less than or equal to 3 times the hole diameter.

[0021] In one specific embodiment, the hole structure engraved on the lower surface of the polishing layer in step 3) is a hole that does not penetrate the upper surface of the polishing layer.

[0022] In one specific embodiment, the hole structure on the lower surface of the polishing layer is circular in shape; preferably, the hole diameter of the circular hole is smaller than the groove spacing of the circumferential groove on the upper surface of the polishing layer.

[0023] In one specific embodiment, the buffer layer is selected from polyurethane impregnated felt; and the adhesive layer is selected from pressure-sensitive adhesives and / or reactive hot melt adhesives.

[0024] In another aspect, the chemical mechanical polishing pad with improved edge effect prepared by the aforementioned preparation method.

[0025] In still another aspect, the use of the aforementioned chemical mechanical polishing pad with improved edge effect prepared by the aforementioned preparation method or the aforementioned chemical mechanical polishing pad with improved edge effect in chemical mechanical polishing.

[0026] Compared with the prior art, the present application has the following beneficial effects:

[0027] For the "edge effect" phenomenon, most of the current solutions are to reduce the high polishing rate at the edge by adjusting the polishing pad formula, structure, or by adjusting the equipment parameters in the polishing process. The present application breaks through the conventional thinking and improves the polishing rate of the wafer center area by increasing the hardness of the polishing layer in the polishing track center area to alleviate the "edge effect".

[0028] The method of the present application increases the hole structure on the lower surface of the polishing layer, and fills it again, and the prepolymer B, which is one of the components of the filling, contains unreacted isocyanate groups with a mass fraction higher than the isocyanate mass fraction of the prepolymer A of the polishing layer by 1-2 wt%, so as to improve the hardness of the polishing layer in the center area of the polishing track, improve the polishing rate in the center area of the wafer, and alleviate the generation of "edge effect". If it is lower than 1%, the hardness of the obtained polyurethane filling is not much different, and it does not have a significant effect on improving the polishing flatness. If it is higher than 2%, the hardness of the obtained polyurethane filling is too large, which may cause "reverse edge effect" of the center polishing rate, and even cause irreversible damage to the wafer.

[0029] Meanwhile, the present application is preferably limited in a single annular area, and the interval distance between the centers of every two non-penetrating holes in the circumferential direction. If the interval distance between the holes on the lower surface is small, the area occupied by the holes is too large, which will also cause the hardness of the polishing track area to be too large during the polishing process, and "reverse edge effect" is generated. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 is a schematic top view of the polishing layer with hole structure engraved on the lower surface of the present application.

[0031] Among them, 1 is the polishing layer, 2 is the center of the polishing layer, 3 is the circular intermediate area, 4 is the annular polishing track area, 5 is the outer edge area, 6 is the groove, 7 is the hole structure, and 8 is the hole arrangement track. DETAILED DESCRIPTION

[0032] The following examples will further illustrate the method provided by the present application, but the present application is not limited to the listed examples, and any other known changes within the scope of the claims of the present application should also be included.

[0033] The present application provides a chemical mechanical polishing pad, which comprises at least a polishing layer, a buffer layer, an adhesive layer and a release layer. The polishing layer has an upper surface facing the wafer and a lower surface bonded to the buffer layer through the adhesive layer. As shown in Figure 1 The polishing layer 1 is divided into a circular intermediate area 3, an annular polishing track area 4 and an outer edge area 5 from the inside to the outside from the center 2 of the polishing layer. The upper surface of the polishing layer can be engraved with circumferential grooves 6 and / or radial grooves (not shown). The lower surface of the polishing layer in the polishing track area has non-penetrating hole structure 7, which avoids the groove area on the upper surface of the polishing layer. The hole centers are arranged in a circular track 8 in a single annular area in the circumferential direction. Meanwhile, the hole structure is filled with polyurethane material. The polyurethane material used to fill the hole structure is the same as the raw material of the polyurethane material used to form the polishing layer, which is the reaction product of a prepolymer and a curing agent.

[0034] Specifically, the polishing layer has a radius R, the polishing layer has a radius R0 from the center of the polishing layer to the center of the circular intermediate region, and the polishing layer has a radius R1 from the center of the polishing layer to the outer edge of the annular polishing track region, and the sizes of the three satisfy the following relationship: 0 < R0 ≤ 1 / 4 * R, R0 < R1 < R.

[0035] wherein the polishing layer is obtained by reacting a prepolymer A containing 7-10 wt% of unreacted isocyanate groups, expanded microspheres, and a curing agent containing active hydrogen groups. The unreacted isocyanate group content in the prepolymer A is preferably 5.5-9.5%. For example, including but not limited to 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%. The stoichiometric ratio of unreacted isocyanate groups in the prepolymer A to active hydrogen in the curing agent is 0.8-1.2, preferably 0.85-1.15, including but not limited to 0.85, 0.9, 0.95, 1.0, 1.05, 1.1, 1.15. The unreacted isocyanate groups are selected from prepolymers obtained by reacting isocyanate with polyol, and the isocyanate is selected from, for example, methylene diphenyl diisocyanate, toluene diisocyanate, naphthalene diisocyanate, p-phenylene diisocyanate, o-toluidine diisocyanate, carbodiimide-modified diphenylmethane diisocyanate, uretonimine-modified diphenylmethane diisocyanate, biuret-modified diphenylmethane diisocyanate, isophorone diisocyanate, 1,6-hexane diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, cyclohexane diisocyanate, and mixtures thereof, but not limited thereto. The polyol is selected from, for example, at least one of polytetramethylene ether glycol, polypropylene ether glycol, polycarbonate polyol, polycaprolactone polyol, ester-based polyol of ethylene adipate or butylene adipate, for example, and can also be a copolymer or mixture thereof, but not limited thereto.

[0036] The curing agent containing active hydrogen groups used to prepare the polished layer is a polyol or polyamine curing agent. For example, it is selected from ethylene glycol, 1,2-propanediol, 1,3-propanediol, 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, tripropylene glycol, 4,4'-methylene-bis-o-chloroaniline, 4,4'-methylene-bis-(3-chloro-2,6-dichloroaniline). 4,4'-diethylaniline), dimethylthiotoluenediamine, propylene glycol di-p-aminobenzoate, 2-bis(2-aminophenylthio)ethane, 4,4'-methylene-bis-aniline, diethyltoluenediamine, 5-tert-butyl-2,4-toluenediamine, 3-tert-butyl-2,6-toluenediamine, 5-tert-pentyl-2,4-toluenediamine, 3-tert-pentyl-2,6-toluenediamine, or chlorotoluenediamine, but not limited thereto. Preferably, the curing agent is selected from at least one of 1,3-propanediol, 1,2-butanediol, 4,4'-methylene-bis-o-chloroaniline, and 4,4'-methylene-bis(3-chloro-2,6-diethylaniline).

[0037] The hollow microspheres mentioned above are, for example, polymer microspheres with shells of polyacrylonitrile or polyacrylonitrile copolymers, such as those purchased from AkzoNobel. But it is not limited to this.

[0038] In this invention, the polyurethane filling the pore structure on the lower surface of the polishing layer is obtained by reacting a prepolymer B containing unreacted isocyanate groups with a curing agent containing active hydrogen groups. The mass fraction of the unreacted isocyanate groups is 1-2 wt% higher than that of the isocyanate group component in the prepolymer A forming the polishing layer, including but not limited to 1%, 1.5%, or 2% higher; that is, the mass fraction of unreacted isocyanate groups in the prepolymer B containing unreacted isocyanate groups is, for example, 8-12%.

[0039] Similarly, the stoichiometric ratio of unreacted isocyanate groups in prepolymer B to active hydrogen in curing agent is 0.8 to 1.2, preferably 0.85 to 1.15, including but not limited to 0.85, 0.9, 0.95, 1.0, 1.05, 1.1, and 1.15.

[0040] The porous structure is located on the lower surface of the polished layer, distributed within the polishing trajectory area, and within a single annular area (e.g., Figure 1The holes are arranged along a circular trajectory 8) on the polishing pad, and the distance between the centers of every two non-through holes is greater than or equal to 1.5 times the diameter of the holes and less than or equal to 3 times the diameter of the holes. The distance between every two holes is not particularly limited, and can be the same or different. The holes are preferably circular in shape, and the diameter of the holes is less than the distance between the adjacent grooves on the upper surface of the polishing layer. The holes do not penetrate the upper surface of the polishing layer. The diameter of the holes is less than the distance between the adjacent grooves, for example, the diameter of the holes is 0.8 mm, 1 mm, 1.2 mm, 1.4 mm, 1.6 mm.

[0041] The surface of the polishing layer has a plurality of grooves. Preferably, the groove design is selected from the group consisting of concentric grooves (which can be circular or spiral), curved grooves, cross-hatched grooves (e.g., arranged as an X-Y grid on the pad surface), other regular designs (e.g., hexagonal, triangular), tire tread patterns, irregular designs (e.g., fractal patterns), and combinations thereof. More preferably, the groove design is selected from the group consisting of concentric grooves (spiral grooves), cross-hatched grooves (X-Y grid grooves), and other regular designs (hexagonal grooves, triangular grooves).

[0042] The cushioning layer material includes woven and non-woven materials, such as felted materials, spun-bond materials, and needle-punched materials. The cushioning layer material in the present application can include, for example, polymer-impregnated felt materials (e.g., polyurethane-impregnated felt materials) and woven materials (e.g., thick flannel materials).

[0043] The polishing pad in the present application further includes a bonding layer selected from a pressure-sensitive adhesive, a reactive hot-melt adhesive, or a mixture of both. The hot-melt adhesive is selected from at least one of polyolefins, ethylene-vinyl acetate, polyamides, polyesters, polyurethanes, polyvinyl chlorides, or epoxy resins. The pressure-sensitive adhesive is selected from at least one of an acryl-based adhesive (PSAV) or a rubber-based adhesive (PSA8). The main function of the bonding layer is to tightly bond the polishing layer and the cushioning layer together.

[0044] The present application also provides a method for preparing the aforementioned chemical mechanical polishing pad with improved edge effect, comprising the following steps:

[0045] First, the prepolymer A containing unreacted isocyanate groups, the expanded microspheres and the curing agent are mixed uniformly, and then poured into a mold by a casting machine to obtain a polyurethane "cake", which is demolded after heating and curing. After the thickness operation, a polishing layer sheet is obtained. The groove engraving is carried out on the upper surface of the polishing layer by a grooving machine, and the polishing track area of the polishing layer is found at the same time. The hole structure is engraved on the polishing track area of the lower surface of the polishing layer, avoiding the groove on the upper surface. The prepolymer B and the curing agent are mixed and then poured into the hole structure, and the smoothing step can be used to ensure that there is no mixture of the prepolymer B and the curing agent outside the hole. The polishing layer is obtained after heating and curing.

[0046] The obtained polishing layer is combined with the adhesive layer, the buffer layer, the release layer and the like in sequence to obtain a chemical mechanical polishing pad.

[0047] In another aspect, the aforementioned chemical mechanical polishing pad is used in chemical mechanical polishing, for example, a polishing method comprising the following steps:

[0048] A pressure is applied to the polishing element to be placed on the polishing pad;

[0049] The polishing element and the polishing pad are provided with relative motion.

[0050] The polishing method mainly uses the chemical mechanical polishing pad with the structure of the present application, and the application of the polishing equipment, the polishing process and the polishing liquid can be referred to the prior art.

[0051] The present application will be further explained and described by more specific examples below, but any limitation is not constituted.

[0052] The main raw materials used in the examples and comparative examples of the present application are as follows:

[0053] The polishing experiment is carried out on an Applied Reflexion polisher (Applied Materials) using a 300 mm wafer, in which the carrier pressure is 0.024 MPa, the slurry flow rate is 300 mL / min (Mirra polisher is 200 mL / min), the workbench rotation speed is 93 rpm, and the carrier rotation speed is 87 rpm.

[0054] Test method: Before and after each polishing experiment, the thickness of 81 test points at the same position on the wafer is measured by a four-point probe (Four Dimensions, Inc, ) tester, and the removal rate is calculated by the thickness difference. The removal rate calculation formula is as follows: Wherein, T0 is the average thickness of the 81 test points before polishing, T1 is the average thickness of the 81 test points after polishing, and ΔT avgThis represents the average thickness difference at each of the 81 points before and after polishing. The non-uniformity ratio (%NUR) is calculated from the standard deviation of the removal rate. The smaller the non-uniformity ratio, i.e., the smaller the standard deviation of the removal rate, the more uniform the polishing rate and the more uniform the polishing effect across the entire polished surface.

[0055] After polishing, the surface of the wafer is observed using an optical microscope to detect scratches. Scratches longer than 10 micrometers are counted, and the total number is the number of scratches.

[0056] Example 1

[0057] 25.5 kg of isocyanate-terminated prepolymer A (produced by Chemtura) Prepolymer LF600D (NCO content 7.12%) was preheated to 60℃. 5.2 kg of curing agent (MOCA, Jinan Lunan Chemical) was melted at 110℃. The prepolymer, curing agent, and 0.32 kg of expanded microspheres (AkzoNobel) were mixed and stirred at room temperature, and gelled at room temperature. After gelling for 15 minutes, the mixture was placed in a 100℃ oven and heated for 12 hours to obtain a polishing pad block. The polishing pad block was removed from the oven and cut into polyurethane sheets with a diameter of 508 mm. Concentric circular grooves were engraved on the upper surface of the sheet, with a groove spacing of 1.8 mm. In the polishing trajectory area on the lower surface (a ring-shaped area within 100-200 mm from the center), non-penetrating holes with a diameter of 1.5 mm were engraved around the concentric circular grooves, with a circumferential spacing of 3 mm between the centers of every two non-penetrating holes. The non-penetrating holes were prepared by mixing 10.8 kg of prepolymer B (prepolymer LF700D, NCO content 8.13%) with 3.1 kg of curing agent MOCA, and then pouring the mixture into the non-penetrating holes. After curing in a 100℃ oven for 8 hours, the final polished layer was obtained.

[0058] The polishing layer and the Dow SUBA IV buffer layer are bonded together using a acrylic adhesive (PSAV). After bonding using a laminating machine, a polishing pad is obtained. The resulting polishing pad is then subjected to polishing performance testing.

[0059] Example 2

[0060] 36.7 kg of isocyanate-terminated prepolymer A (produced by Chemtura) Prepolymer LF600D (7.12% NCO content) was preheated to 60°C. 2.4 kg of curing agent (dipropylene glycol, Aladdin) was melted at 110°C. The prepolymer, curing agent, and 0.4 kg of expanded microspheres (AkzoNobel) were mixed and stirred at room temperature, and gelled at room temperature. After gelling for 13 minutes, the mixture was placed in a 100°C oven and heated for 10 hours to obtain a polishing pad block. The polishing pad block was removed from the oven and cut into polyurethane sheets with a diameter of 508 mm. Concentric circular grooves with a groove spacing of 2.5 mm were engraved on the upper surface. In the polishing trajectory area on the lower surface (a ring-shaped area within 150–210 mm from the center), non-penetrating holes with a diameter of 2 mm were engraved around the concentric circular grooves. The center of each pair of non-penetrating holes was spaced 4.2 mm circumferentially. The non-penetrating holes are made by mixing 8.7 kg of prepolymer B (prepolymer L325, NCO content 9.11%) with 0.7 kg of curing agent dipropylene glycol, and then pouring the mixture into the non-penetrating holes. After curing in a 100℃ oven for 8 hours, the final polished layer is obtained.

[0061] The polishing layer and the Dow SUBA IV buffer layer are bonded together using a acrylic adhesive (PSAV). After bonding using a laminating machine, a polishing pad is obtained. The resulting polishing pad is then subjected to polishing performance testing.

[0062] Example 3

[0063] 35.2 kg of isocyanate-terminated prepolymer A (produced by Chemtura) Prepolymer LF1950A (NCO content 5.3%) was preheated to 60℃. 3.8 kg of curing agent (diethyltoluene diamine, Shandong Jinshengtai Chemical) was melted at 100℃. The prepolymer, curing agent, and 0.39 kg of expanded microspheres (AkzoNobel) were mixed and stirred at room temperature, and gelled at room temperature. After gelling for 15 minutes, the mixture was placed in a 105℃ oven and heated for 11 hours to obtain a polishing pad block. The polishing pad block was removed from the oven and cut into polyurethane sheets with a diameter of 508 mm. Concentric circular grooves were engraved on the upper surface of the sheet, with a groove spacing of 1.8 mm. In the polishing trajectory area on the lower surface (a ring-shaped area within 80–120 mm from the center), non-penetrating holes with a diameter of 1.5 mm were engraved around the concentric circular grooves, with a circumferential spacing of 3.5 mm between the centers of every two non-penetrating holes. The non-penetrating holes are made by mixing 9.3 kg of prepolymer B (prepolymer LF950D, NCO content 5.99%) with 1.2 kg of curing agent diethyltoluene diamine, and then pouring the mixture into the non-penetrating holes in sequence. After curing in a 100℃ oven for 8 hours, the final polished layer is obtained.

[0064] The polishing layer and the Dow SUBA IV buffer layer are bonded together using a acrylic adhesive (PSAV). After bonding using a laminating machine, a polishing pad is obtained. The resulting polishing pad is then subjected to polishing performance testing.

[0065] Comparative Example 1

[0066] 25.5 kg of isocyanate-terminated prepolymer A (produced by Chemtura) Prepolymer LF600D (NCO content 7.12%) was preheated to 60℃. 5.2 kg of curing agent (MOCA, Jinan Lunan Chemical) was melted at 110℃. The prepolymer, curing agent, and 0.32 kg of expanded microspheres (AkzoNobel) were mixed and stirred at room temperature, and gelled at room temperature. After gelling for 15 minutes, the mixture was placed in a 100℃ oven and heated for 12 hours to obtain a polishing pad block. The polishing pad block was removed from the oven and cut into polyurethane sheets with a diameter of 508 mm. Concentric grooves with a groove spacing of 1.8 mm were engraved on the upper surface of the sheet to obtain the final polishing layer.

[0067] The polishing layer and the Dow SUBAIV buffer layer are bonded together using a acrylic adhesive (PSAV). After bonding using a laminating machine, a polishing pad is obtained. The resulting polishing pad is then subjected to polishing performance testing.

[0068] Comparative Example 2

[0069] 25.5 kg of isocyanate-terminated prepolymer A (produced by Chemtura) Prepolymer LF600D (NCO content 7.12%) was preheated to 60℃. 5.2 kg of curing agent (MOCA, Jinan Lunan Chemical) was melted at 110℃. The prepolymer, curing agent, and 0.32 kg of expanded microspheres (AkzoNobel) were mixed and stirred at room temperature, and gelled at room temperature. After gelling for 15 minutes, the mixture was placed in a 100℃ oven and heated for 12 hours to obtain a polishing pad block. The polishing pad block was removed from the oven and cut into polyurethane sheets with a diameter of 508 mm. Concentric circular grooves were engraved on the upper surface of the sheet, with a groove spacing of 1.8 mm. In the polishing trajectory area on the lower surface (a ring-shaped area within 100-200 mm from the center), non-penetrating holes with a diameter of 1.5 mm were engraved around the concentric circular grooves, with a circumferential spacing of 3 mm between the centers of every two non-penetrating holes.

[0070] The polishing layer and the Dow SUBA IV buffer layer are bonded together using a acrylic adhesive (PSAV). After bonding using a laminating machine, a polishing pad is obtained. The resulting polishing pad is then subjected to polishing performance testing.

[0071] Comparative Example 3

[0072] 47.6 kg of isocyanate-terminated prepolymer A (produced by Chemtura) Prepolymer L325 (NCO content 9.11%) was preheated to 50°C. 9.4 kg of curing agent (tripropylene glycol, Aladdin) was melted at 110°C. The prepolymer, curing agent, and 0.57 kg of expanded microspheres (AkzoNobel) were mixed and stirred at room temperature, and gelled at room temperature. After gelling for 15 minutes, the mixture was placed in a 100°C oven and heated for 12 hours to obtain a polishing pad block. The polishing pad block was removed from the oven and cut into polyurethane sheets with a diameter of 508 mm. Concentric circular grooves were engraved on the upper surface of the sheet, with a groove spacing of 1.8 mm. In the polishing trajectory area on the lower surface (a ring-shaped area within 100–200 mm from the center), non-penetrating holes with a diameter of 1.5 mm were engraved around the concentric circular grooves, with a circumferential spacing of 3 mm between the centers of every two non-penetrating holes. The non-penetrating holes are made by mixing 1.9 kg of prepolymer B (prepolymer LF751D, NCO content 9.02%) with 3.1 kg of curing agent tripropylene glycol, and then pouring the mixture into the non-penetrating holes. After curing in a 100℃ oven for 8 hours, the final polished layer is obtained.

[0073] The polishing layer and the Dow SUBAIV buffer layer are bonded together using a acrylic adhesive (PSAV). After bonding using a laminating machine, a polishing pad is obtained. The resulting polishing pad is then subjected to polishing performance testing.

[0074] Comparative Example 4

[0075] 33.9 kg of isocyanate-terminated prepolymer A (produced by Chemtura) Prepolymer LF1950A (NCO content 5.3%) was preheated to 50℃. 3.4 kg of curing agent (diethyltoluene diamine, Shandong Jinshengtai Chemical) was melted at 110℃. The prepolymer, curing agent, and 0.37 kg of expanded microspheres (AkzoNobel) were mixed and stirred at room temperature, and gelled at room temperature. After gelling for 15 minutes, the mixture was placed in a 100℃ oven and heated for 12 hours to obtain a polishing pad block. The polishing pad block was removed from the oven and cut into polyurethane sheets with a diameter of 508 mm. Concentric circular grooves were engraved on the upper surface of the sheet, with a groove spacing of 1.8 mm. In the polishing trajectory area on the lower surface (a ring-shaped area within 100-200 mm from the center), non-penetrating holes with a diameter of 1.5 mm were engraved around the concentric circular grooves, with a circumferential spacing of 3 mm between the centers of every two non-penetrating holes. The non-penetrating holes are made by mixing 6.7 kg of prepolymer B (prepolymer LF700D, NCO content 8.13%) with 1.3 kg of curing agent diethyltoluene diamine, and then pouring the mixture into the non-penetrating holes in sequence. After curing in a 100℃ oven for 8 hours, the final polished layer is obtained.

[0076] The polishing layer and the Dow SUBAIV buffer layer are bonded together using a acrylic adhesive (PSAV). After bonding using a laminating machine, a polishing pad is obtained. The resulting polishing pad is then subjected to polishing performance testing.

[0077] Comparative Example 5

[0078] 25.5 kg of isocyanate-terminated prepolymer A (produced by Chemtura) Prepolymer LF600D (7.12% NCO content) was preheated to 60℃. 5.2 kg of curing agent (MOCA, Jinan Lunan Chemical) was melted at 110℃. The prepolymer, curing agent, and 0.32 kg of expanded microspheres (AkzoNobel) were mixed and stirred at room temperature, and gelled at room temperature. After gelling for 15 minutes, the mixture was placed in a 100℃ oven and heated for 12 hours to obtain a polishing pad block. The polishing pad block was removed from the oven and cut into polyurethane sheets with a diameter of 508 mm. Concentric circular grooves were engraved on the upper surface of the sheet, with a groove spacing of 1.8 mm. In the polishing trajectory area on the lower surface (a ring-shaped area within 100-200 mm from the center), non-penetrating holes with a diameter of 1.5 mm were engraved around the concentric circular grooves, with a circumferential interval of 1.8 mm between the centers of every two non-penetrating holes. The non-penetrating holes were prepared by mixing 10.8 kg of prepolymer B (prepolymer LF700D, NCO content 8.13%) with 3.1 kg of curing agent MOCA, and then pouring the mixture into the non-penetrating holes. After curing in a 100℃ oven for 8 hours, the final polished layer was obtained.

[0079] The polishing layer and the Dow SUBAIV buffer layer are bonded together using a acrylic adhesive (PSAV). After bonding using a laminating machine, a polishing pad is obtained. The resulting polishing pad is then subjected to polishing performance testing.

[0080] The obtained polishing pads were used for polishing experiments using the following methods:

[0081] Polishing experiments were conducted on 300mm wafers using an Applied Reflexion polisher (Applied Materials Corporation), with a carrier pressure of 0.024 MPa, a slurry flow rate of 300 mL / min (Mirra polisher uses 200 mL / min), a stage rotation speed of 93 rpm, and a carrier rotation speed of 87 rpm.

[0082] The non-uniform ratio value was calculated by using a four-probe tester.

[0083] Table 1 shows the non-uniform ratio test data obtained from the tests of the embodiments and comparative examples.

[0084] Table 1. Data table of non-uniform ratio test results

[0085]

[0086] As can be seen from the table, the wafers polished by the polishing pads obtained according to the methods in Examples 1 to 3 exhibit good polishing performance under the test conditions of the conventional polishing method. Comparative Example 1 is a conventional polishing pad, and its non-uniformity ratio and polishing rate, i.e. scratch, are slightly worse than those of the polishing pads of the present application. In Comparative Example 2, the non-through hole portion of the lower surface of the polishing layer is not filled with polyurethane, resulting in too low overall hardness and too low compression rate of the polishing layer, which causes a serious tendency of polishing rate decrease. In Comparative Example 3, the unreacted isocyanate contents of Prepolymers A and B are not significantly different, and no obvious beneficial effect is observed. In Comparative Example 4, the unreacted isocyanate contents of Prepolymers A and B are significantly different, which causes the filled polyurethane to have too high hardness, and plays a reverse role in relieving the edge effect. At the same time, the increased hardness also increases the number of scratches and the polishing rate. In Comparative Example 5, the spacing of the non-through holes on the lower surface of the polishing layer is narrow, resulting in a large area occupied by the non-through holes, which also produces a reverse edge effect.

[0087] Although the present application has been described in detail by the above preferred embodiments, it should be understood that the above description should not be considered as limiting the present application. Those skilled in the art can understand that some modifications or adjustments can be made to the present application under the teaching of the present specification. These modifications or adjustments should also be within the scope defined by the claims of the present application.

Claims

1. A method for preparing a chemical mechanical polishing pad with improved edge effect, comprising the steps of sequentially bonding and pressing a polishing layer, an adhesive layer, a buffer layer, and a release layer, characterized in that, The polished layer is prepared by the following steps: 1) Mix prepolymer A containing unreacted isocyanate groups, expanded microspheres and curing agent evenly, pour into mold through a casting machine to obtain polyurethane "cake", heat to cure and then demold; 2) After the thickness determination operation, a polished layer sheet is obtained, and grooves are engraved on the upper surface of the polished layer using a grooving machine; 3) Carve hole structures on the lower surface of the polished layer, avoiding the groove positions on the upper surface; 4) The prepolymer B containing unreacted isocyanate groups and the curing agent are mixed and poured evenly into the porous structure and smoothed. After heating and curing, the polished layer is obtained. In step 3), the hole structure engraved on the lower surface of the polishing layer is distributed within the annular polishing trajectory area. The mass fraction of unreacted isocyanate groups in prepolymer B in step 4) is 1-2 wt% higher than that of unreacted isocyanate groups in prepolymer A in step 1).

2. The preparation method according to claim 1, characterized in that, Step 1) is obtained by reacting prepolymer A containing 5-10 wt% unreacted isocyanate groups, expanded microspheres, and a curing agent containing active hydrogen groups.

3. The preparation method according to claim 2, characterized in that, The stoichiometric ratio of unreacted isocyanate groups in prepolymer A to active hydrogen in curing agent is 0.8 to 1.

2.

4. The preparation method according to claim 1 or 2, characterized in that, The stoichiometric ratio of unreacted isocyanate groups in prepolymer B to active hydrogen in curing agent is 0.8 to 1.

2.

5. The preparation method according to claim 1, characterized in that, The polished layer includes a circular central region, an annular polishing trajectory region, and an outer edge region. The radius of the polished layer is R, the radius from the center of the polished layer to the circular central region is R0, and the radius from the center of the polished layer to the outer edge of the annular polishing trajectory region is R1. These three satisfy the following relationship: 0 <R0≤1 / 4*R,R0<R1<R。 6. The preparation method according to claim 1 or 5, characterized in that, Within a single annular region, the circumferential distance between the centers of any two non-penetrating holes is greater than or equal to 1.5 times the hole diameter and less than or equal to 3 times the hole diameter.

7. The preparation method according to claim 1, characterized in that, In step 3), the hole structure engraved on the lower surface of the polishing layer is a hole that does not penetrate the upper surface of the polishing layer.

8. The preparation method according to claim 1, characterized in that, The hole structure located on the lower surface of the polished layer is circular in shape.

9. The preparation method according to claim 8, characterized in that, The diameter of the circular hole is smaller than the groove spacing of the circumferential grooves on the upper surface of the polished layer.

10. The preparation method according to claim 1, characterized in that, The buffer layer is selected from polyurethane-impregnated felt; the adhesive layer is selected from pressure-sensitive adhesives and / or reactive hot melt adhesives.

11. A chemical mechanical polishing pad with improved edge effect prepared by the preparation method according to any one of claims 1 to 10.

12. The application of the chemical mechanical polishing pad with improved edge effect prepared by the preparation method according to any one of claims 1 to 10 in chemical mechanical polishing.

Images