A method for manufacturing a chemical mechanical polishing pad and use thereof
By adding acid-soluble compounds to polyurethane resin and using ionizable compound solutions to prepare interconnected microporous polishing pads, the problems of uneven pore size and long cleaning time were solved, achieving efficient polishing fluid supply and efficient chemical mechanical polishing effect.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- INVENTECH MATERIALS CO LTD
- Filing Date
- 2022-10-09
- Publication Date
- 2026-06-19
AI Technical Summary
The pores of existing chemical mechanical polishing pads are uneven in size and not interconnected, resulting in uneven supply of polishing fluid, which limits their application in high-end chip manufacturing. In addition, traditional methods are time-consuming and have low polishing rates during the cleaning process, and may cause scratches on the silicon wafer surface.
By pulverizing an acid-soluble compound and adding it to a polyurethane resin mixture to form a uniform microporous structure, and then dissolving the powder with an ionizable compound solution, an interconnected microporous polishing pad is prepared, thereby improving the uniform supply of polishing fluid and polishing efficiency.
It achieves uniform supply of polishing slurry and high polishing rate, improves the flatness of the wafer surface after polishing, and improves the yield of high-end process chips.
Smart Images
Figure CN115958542B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of chemical mechanical polishing technology, B24B37 / 24, and particularly to a method for preparing a chemical mechanical polishing pad and its application. Background Technology
[0002] Semiconductor chips contain multiple layers of micro-integrated circuits. As chip integration density continues to increase, the number of circuit layers in the chip also increases, and they are formed layer by layer from bottom to top. The manufacturing of micro-integrated circuits mainly involves depositing layers onto the surface of a semiconductor wafer step by step using different deposition techniques and processes. Then, chemical etching technology is used to remove excess structures, which results in an uneven surface, directly affecting the performance of the final semiconductor chip.
[0003] Chemical mechanical polishing (CMP) is a process combining chemical reactions, mechanical friction, and hydrodynamic pressure. By combining particles with a polishing slurry, the silicon wafer is brought into contact with the polishing surface of a polishing pad, achieving a smooth and flat surface that is difficult to achieve with other planar processing methods. CMP is an important surface polishing technology in integrated circuits, removing excess material and impurities from the surface and reducing defects such as surface roughness and scratches. The CMP process generally includes two stages: rough polishing and fine polishing. Rough polishing uses a harder polishing pad to planarize the wafer and remove a large amount of excess material. Fine polishing typically uses a softer polishing pad, which has better conformability to non-planar silicon wafer surfaces. The soft polishing pad is usually prepared using a film deposition method. A key function of the polishing pad is to uniformly supply the polishing slurry to the polishing interface and provide uniform support. Polyurethane porous membranes prepared using conventional processes store polishing slurry through a teardrop-shaped pore structure (smaller at the top and larger at the bottom) and are then supplied to the polishing interface during polishing. However, the inconsistent size and lack of interconnection of these pores lead to uneven slurry supply to the polishing interface. Consequently, this prevents further improvement in the surface flatness of the workpiece, limiting its application in high-end chip manufacturing processes.
[0004] Chinese patent application CN114670119A discloses a chemical mechanical polishing pad for improving polishing efficiency and its preparation method. The method involves heating and mixing a coagulation regulator and a polyurethane solution to obtain a resin slurry. This slurry is then coagulated to form a film, providing rigid support to the resin. Finally, the coagulation regulator is removed by cleaning with a cleaning solution, resulting in a polyurethane polishing pad with a microporous, sponge-like porous structure, exhibiting high polishing efficiency. However, the cleaning process using the cleaning solution is time-consuming, resulting in large pore sizes and a low polishing rate. Furthermore, if alkali-soluble polymer powder is added to the polyurethane resin solution, and the powder is degraded with an alkaline aqueous solution after polyurethane coagulation to obtain a polyurethane porous membrane with numerous interconnected micropores, the alkaline aqueous solution degradation process is time-consuming. Moreover, the alkaline aqueous solution has a strong degradative effect on the polyurethane resin, easily leading to a decrease in resin strength and thus reducing the lifespan of the polishing pad. Simultaneously, if the powder is not completely degraded, the residual powder particles will directly cause scratches on the silicon wafer surface. Due to the above-mentioned drawbacks, this method requires very high control over the production process, making it difficult to achieve mass production. Summary of the Invention
[0005] To address the aforementioned problems, the first aspect of this invention provides a method for preparing a chemical mechanical polishing pad, comprising:
[0006] S1. The acid-soluble compound is pulverized and sieved to obtain powder;
[0007] S2. Add the powder obtained in S1 to the polyurethane resin mixture to obtain a polyurethane slurry;
[0008] S3. Coat the polyurethane slurry obtained in S2 onto a transparent film roll to obtain a polyurethane film;
[0009] S4. Immerse the polyurethane membrane obtained in S3 in an ionizable compound solution, and then wash it to obtain the final product.
[0010] In S1,
[0011] In some preferred embodiments, the acid-soluble compound is selected from at least one of metal oxides, metal hydroxides, inorganic salts, and organic salts; preferably, it is one or more of metal oxides, inorganic salts, and organic salts.
[0012] In some preferred embodiments, the metal oxide is selected from at least one of iron oxide, ferrous oxide, iron(II,III) oxide, aluminum oxide, magnesium oxide, copper oxide, cuprous oxide, silver oxide, and zinc oxide; preferably aluminum oxide.
[0013] In some preferred embodiments, the metal hydroxide is selected from at least one of iron hydroxide, copper hydroxide, magnesium hydroxide, and aluminum hydroxide.
[0014] In some preferred embodiments, the inorganic salt is selected from at least one of barium carbonate, calcium carbonate, silver carbonate, manganese carbonate, ferrous carbonate, zinc carbonate, and magnesium carbonate; preferably calcium carbonate.
[0015] In some preferred embodiments, the organic salt is selected from at least one of calcium oxalate, calcium citrate, calcium tartrate, and calcium malate; preferably calcium oxalate.
[0016] This application incorporates specific acid-soluble compounds that are insoluble or sparingly soluble in polar solvents. These compounds suspension and dispersion as tiny particles within the polyurethane resin slurry facilitate the uniform placement of these particles in the solid phase of the polyurethane during solidification. This ensures a uniform distribution and consistent pore size within the polishing pad. Subsequent immersion in an ionizable compound solution allows for rapid dissolution, removing the occupying particles and leaving interconnected micropores of appropriate size. This allows the polishing fluid to circulate within these micropores, enhancing the polishing effect of the pad.
[0017] In some preferred embodiments, the crushing refers to the process of using mechanical force to hammer, cut, squeeze, grind, etc., solid materials to make them into small pieces, granules or powder. This application does not particularly limit the crushing method.
[0018] Preferably, the pulverization method is selected from one of mechanical pulverizer pulverization, grinding mill pulverization, and air jet mill pulverization.
[0019] In some preferred embodiments, the mechanical crusher is selected from at least one of, for example, toothed crusher, blade crusher, turbine crusher, milling crusher, hammer crusher, and pressure mill crusher.
[0020] In some preferred embodiments, the grinding mill is selected from at least one of ball mills and roller mills.
[0021] In some preferred embodiments, the average particle size of the pulverized acid-soluble compound is in the micrometer range; preferably ≤20μm; more preferably ≤13μm.
[0022] In some preferred embodiments, the mesh size of the sieve is 600 to 2000 mesh; preferably 1000 mesh.
[0023] In this invention, the acid-soluble compound particles are ground and sieved to maintain relative size uniformity. The inventors discovered that when the average particle size of the acid-soluble compound is greater than 20 μm, especially greater than 13 μm, it occupies too much space in the solid phase of the polyurethane slurry, thus affecting the structure of conventional teardrop-shaped pores. This can easily lead to severe deformation of the teardrop-shaped pore structure, which is detrimental to the stability of the micromechanical structure. Simultaneously, the resulting polishing pad exhibits large pore size deviations and reduced porosity, decreasing the final polishing pad's grinding rate and increasing its non-uniformity. If powder particles of 13 μm or less are selected, the impact on the teardrop-shaped pore structure is smaller, resulting in a higher polishing pad grinding rate and a higher degree of surface planarization of the polished wafer.
[0024] In S2,
[0025] In some preferred embodiments, the polyurethane resin mixture comprises 100 parts by weight of a DMF solution of polyurethane resin, 15-65 parts by weight of a polar solvent, and 2-5 parts by weight of a surfactant.
[0026] In some preferred embodiments, the polyurethane resin mixture is prepared by dispersing a surfactant in a polar solvent and stirring until homogeneous, and then adding a DMF solution of polyurethane resin.
[0027] In some preferred embodiments, the solid content of the polyurethane resin in the DMF solution of the polyurethane resin is 20-44 wt%; preferably 25-35 wt%; more preferably 30 wt%.
[0028] In some preferred embodiments, the polar solvent is selected from at least one of dimethylformamide (DMF), dimethyl sulfoxide (DMSO), sulfolane, water, 1,4-epoxybutane (THF), and dimethylacetamide (DMA); preferably DMF.
[0029] In some preferred embodiments, the surfactant is selected from at least one of sodium dodecylbenzene sulfonate, sodium dodecyl sulfonate, butylphenol polyoxyethylene ether, sodium dioctyl succinate sulfonate, disodium fatty alcohol polyoxyethylene ether sulfosuccinate, lignin sulfonate, sodium fatty alcohol polyoxyethylene ether sulfate, and sodium lauryl sulfate; preferably sodium dioctyl succinate sulfonate.
[0030] In some preferred embodiments, the weight ratio of the polyurethane resin to the acid-soluble compound is 100:(0.5-13); preferably 100:(1-10); and more preferably 100:5.
[0031] Adding acid-soluble compounds to polyurethane resin slurry can increase the wear resistance of polished surfaces. The inventors have discovered that by rationally controlling the weight ratio of polyurethane resin to acid-soluble compounds, when the weight ratio is 100:(0.5-13), the acid-soluble compounds can be uniformly dispersed in the system under the synergistic effect of surfactants, forming a stable system. This results in polishing pads with suitable porosity, average micropore size, small pore size standard deviation, and high grinding speed while maintaining high surface flatness. However, if the content of acid-soluble compounds is too high, it will not only lead to a decrease in grinding speed but also cause a large amount of agglomeration in the system, resulting in excessively high porosity and consequently reducing the mechanical properties and wear resistance of the chemical mechanical polishing pad.
[0032] In S3,
[0033] The transparent film roll is not subject to any special limitations.
[0034] Preferably, the transparent film roll is selected from at least one of polypropylene (PP), polyethylene terephthalate (PET), polyethylene (PE), polycarbonate (PC), and acrylonitrile-butadiene-styrene terpolymer (ABS); preferably PP.
[0035] In some preferred embodiments, the polyurethane membrane is prepared by a condensation method.
[0036] In some preferred embodiments, the specific operation of the coagulation method is to send a transparent film roll coated with polyurethane slurry into a coagulation liquid for solidification, thereby obtaining the product.
[0037] In some preferred embodiments, the coating method is blade coating.
[0038] In some preferred embodiments, the condensate is selected from at least one of DMF, THF, and DMSO; preferably DMF; more preferably an aqueous solution of DMF.
[0039] In some preferred embodiments, the mass concentration of DMF in the aqueous solution of DMF is 17-30%; preferably 20-25%; and more preferably 20%.
[0040] In S4,
[0041] In some preferred embodiments, the ionizable compound solution is selected from at least one of hydrochloric acid solution, sulfuric acid solution, nitric acid solution, perchloric acid solution, carbonic acid solution, phosphoric acid solution, and boric acid solution; preferably at least one of hydrochloric acid solution, sulfuric acid solution, and nitric acid solution; more preferably hydrochloric acid solution; and even more preferably an aqueous solution of hydrochloric acid.
[0042] In some preferred embodiments, the hydrochloric acid content in the aqueous hydrochloric acid solution is 1 wt%-37 wt%; preferably 2 wt%-25 wt%; more preferably 5.0 wt%.
[0043] In this invention, the solution of the ionizable compound needs to be heated.
[0044] Preferably, the temperature of the ionizable compound solution is 55-110°C; more preferably 60-100°C; and even more preferably 60°C.
[0045] In some preferred embodiments, the cleaning solution used for cleaning is pure water.
[0046] The present invention may further include a post-treatment process after the cleaning solution treatment. The post-treatment process is a conventional post-treatment process for polishing pad fabrication in the art.
[0047] Preferably, the post-processing steps are drying, polishing, and cleaning.
[0048] A second aspect of the present invention provides a chemical mechanical polishing pad for use in the chemical mechanical polishing process of semiconductor chip manufacturing.
[0049] Compared with the prior art, the present invention has the following beneficial effects:
[0050] (1) In this invention, an acid-soluble compound is pulverized and added to a polyurethane resin mixture consisting of a DMF solution of polyurethane resin, a polar solvent, and a surfactant. During the coagulation and film formation process, while water-induced phase separation forms water droplet-shaped pores, the acid-soluble compound powder occupies space inside the polyurethane and coagulates and solidifies together. The powder is then dissolved by soaking in an ionizable compound solution. After elution, micropores can be formed in the polyurethane solid phase. These micropores are interconnected, allowing the polishing liquid to circulate within them. At the same time, the presence of these micropores makes the micromechanical structure of the polishing pad more balanced, enhancing its uniform support force on the polished object, and making the supply of polishing liquid more uniform and stable.
[0051] (2) The chemical mechanical polishing pad obtained by the present invention has an excellent polishing rate and a high degree of surface flatness of the polished wafer, which provides favorable support for improving the yield of high-end process chips. Attached Figure Description
[0052] Figure 1 A flowchart of a method for preparing a chemical mechanical polishing pad.
[0053] Figure 2 Cross-sectional electron microscope image of the chemical mechanical polishing pad obtained in Example 2.
[0054] Figure 3Cross-sectional electron microscope image of the chemical mechanical polishing pad obtained in Comparative Example 2
[0055] Figure labeling: 11 condensate, 12 ionizable compound solution, 13 cleaning solution. Detailed Implementation
[0056] Example 1
[0057] 1. A method for preparing a chemical mechanical polishing pad, comprising:
[0058] S1. The acid-soluble compound is pulverized and sieved to obtain powder;
[0059] S2. Add the powder obtained in S1 to the polyurethane resin mixture to obtain a polyurethane slurry;
[0060] S3. Coat the polyurethane slurry obtained in S2 onto a transparent film roll to obtain a polyurethane film;
[0061] S4. Immerse the polyurethane membrane obtained in S3 in ionizable compound solution 12, and then wash it to obtain the final product.
[0062] In S1,
[0063] The acid-soluble compound is a metal oxide.
[0064] The metal oxide is aluminum oxide, specifically activated aluminum oxide (activated aluminum oxide from Aluminum Corporation of China Limited).
[0065] The pulverization method is air jet milling.
[0066] The average particle size of the pulverized acid-soluble compound is ≤13μm.
[0067] The screen has a mesh size of 1000.
[0068] In S2,
[0069] The polyurethane resin mixture comprises 100 parts by weight of a DMF solution of polyurethane resin, 45 parts by weight of a polar solvent, and 2 parts by weight of a surfactant.
[0070] The polyurethane resin mixture is prepared by dispersing a surfactant in a polar solvent and stirring until homogeneous, and then adding a DMF solution of polyurethane resin.
[0071] The polyurethane resin in the DMF solution was purchased from Zhejiang Huada Resin HDW-20M.
[0072] The solid content of the polyurethane resin in the DMF solution of the polyurethane resin is 30 wt%.
[0073] The polar solvent is DMF.
[0074] The surfactant is sodium dioctyl succinate sulfonate.
[0075] The weight ratio of the polyurethane resin to the acid-soluble compound is 100:5.
[0076] like Figure 1 As shown, in S3,
[0077] The transparent film roll is made of PP (purchased from Changzhou Xinmei New Material Packaging Factory).
[0078] The polyurethane membrane is prepared by a condensation method.
[0079] The specific operation of the coagulation method is to send a transparent film roll coated with polyurethane slurry into the coagulation liquid 11 for coagulation, thereby obtaining the product.
[0080] The condensate is an aqueous solution of DMF; the mass concentration of DMF in the aqueous solution is 20%.
[0081] The coating method is blade coating.
[0082] In S4,
[0083] The ionizable compound solution is an aqueous solution of hydrochloric acid.
[0084] The hydrochloric acid aqueous solution contains 5.0 wt% hydrochloric acid.
[0085] The temperature of the ionizable compound solution 12 is 60°C.
[0086] The cleaning solution 13 used for cleaning is pure water.
[0087] The post-processing steps include drying, polishing, and cleaning.
[0088] 2. A chemical mechanical polishing pad for use in the chemical mechanical polishing process of semiconductor chip manufacturing.
[0089] Example 2
[0090] 1. A method for preparing a chemical mechanical polishing pad, which differs from Example 1 in that...
[0091] The acid-soluble compound is an inorganic salt; the inorganic salt is calcium carbonate, specifically 1000-mesh heavy calcium carbonate (Jiangxi Shengtai Chemical Co., Ltd.).
[0092] 2. A chemical mechanical polishing pad for use in the chemical mechanical polishing process of semiconductor chip manufacturing.
[0093] Example 3
[0094] 1. A method for preparing a chemical mechanical polishing pad, which differs from Example 1 in that...
[0095] The acid-soluble compound is an organic salt; the organic salt is calcium oxalate, specifically calcium oxalate monohydrate of analytical grade (CAS No.: 5794-28-5).
[0096] 2. A chemical mechanical polishing pad for use in the chemical mechanical polishing process of semiconductor chip manufacturing.
[0097] Example 4
[0098] 1. A method for preparing a chemical mechanical polishing pad, which differs from Example 2 in that...
[0099] The weight ratio of the polyurethane resin to the acid-soluble compound is 100:1.
[0100] 2. A chemical mechanical polishing pad for use in the chemical mechanical polishing process of semiconductor chip manufacturing.
[0101] Example 5
[0102] 1. A method for preparing a chemical mechanical polishing pad, which differs from Example 2 in that...
[0103] The weight ratio of the polyurethane resin to the acid-soluble compound is 10:1.
[0104] 2. A chemical mechanical polishing pad for use in the chemical mechanical polishing process of semiconductor chip manufacturing.
[0105] Example 6
[0106] 1. A method for preparing a chemical mechanical polishing pad, which differs from Example 2 in that...
[0107] The hydrochloric acid aqueous solution contains 10 wt% hydrochloric acid.
[0108] The temperature of the ionizable compound solution 12 is 25°C.
[0109] 2. A chemical mechanical polishing pad for use in the chemical mechanical polishing process of semiconductor chip manufacturing.
[0110] Comparative Example 1
[0111] 1. A method for preparing a chemical mechanical polishing pad, which differs from Example 2 in that...
[0112] The average particle size of the pulverized acid-soluble compound is ≤25μm.
[0113] The screen has a mesh size of 500.
[0114] 2. A chemical mechanical polishing pad for use in the chemical mechanical polishing process of semiconductor chip manufacturing.
[0115] Comparative Example 2
[0116] 1. A method for preparing a chemical mechanical polishing pad, which differs from Example 2 in that the weight ratio of the polyurethane resin to the acid-soluble compound is 100:20.
[0117] 2. A chemical mechanical polishing pad for use in the chemical mechanical polishing process of semiconductor chip manufacturing.
[0118] The parameters used in the preparation of the polishing pads for the examples and comparative examples are shown in Table 1.
[0119] Table 1. Preparation process parameters of polishing pads in the examples and comparative examples.
[0120]
[0121] Performance testing
[0122] The following performance tests were performed on the polishing pads provided in the examples and comparative examples, and the specific results are shown in Table 2.
[0123] 1. Size testing of interconnected micropores: The cross-sectional structure of the formed pad was observed using SEM (scanning electron microscopy) (see...). Figure 2 and Figure 3 ), observe the size of the micropores within a length of 0.2 mm; and calculate the standard deviation σ of the micropore size using formula (1).
[0124] Formula (1)
[0125] 2. Porosity of microporous membrane: A certain mass of microporous membrane (dried to constant weight) is soaked in anhydrous ethanol for 24 hours. After removal, the ethanol adsorbed on the surface is gently absorbed with filter paper, and the membrane is weighed quickly. The porosity of the microporous membrane is calculated according to formula (2).
[0126] Formula (2)
[0127] In the formula, w1 and w2 are the masses (g) of the polyurethane porous membrane before and after immersion, respectively; ρ1 is the density of the polyurethane (g / cm³). 3 ); ρ2 is the density of anhydrous ethanol (g / cm³). 3 ).
[0128] 3. Polishing Performance: Polishing studies were conducted using Anji D2000E silica polishing slurry on a single-module integrated CMP polisher manufactured by Hangzhou SIZONE Electronic Technology Inc. TEOS blanket-coated silicon wafers were used as monitor wafers to determine the polishing rate (RR). Unless otherwise specified, the polishing conditions used in all polishing experiments included: a polishing platform speed of 93 rpm; a polishing head speed of 87 rpm; and a polishing slurry flow rate of 170 mL / min. Polishing time was 90 s / wafer.
[0129] The film thickness (PRE) before polishing was measured by scanning 49 points on a silicon wafer using a FILMETRICS film thickness measurement tool (Filmetrics, Inc., USA). and subsequent membrane thickness POST To calculate the average removal amount (MEAN) at 49 locations. (Formula (3)), Standard Deviation of Removal Amount STDEV (Formula (4)), Average Removal Rate RR of Test Wafer (Formula (3)) / min) (Formula (5)), test the non-uniformity of wafer removal amount Nu (%) (Formula (6)), which reflects the degree of surface planarization of the wafer after polishing.
[0130] Formula (3)MEAN=AVERAGE(PRE-POST);
[0131] Formula (4)
[0132] Formula (5)
[0133] Formula (6)
[0134] The polishing data of the test wafer (moniter wafer) was recorded at the 26th, 52nd, 78th, 104th and 145th wafer counts. The RR and Nu of each of the five test wafers were counted and their average value was calculated as the recorded data.
[0135] Table 2. Performance test results of the examples and comparative examples.
[0136]
[0137] The test results above show that the polishing pad provided by the present invention has high flatness, uniform and fine surface pores, and interconnected micro-pores inside. It has a low defect rate and is suitable for chemical mechanical polishing processes in semiconductor chip manufacturing. It can improve the polishing rate while improving the surface flatness of the object to be polished.
Claims
1. A method of making a chemical mechanical polishing pad, characterized by, include: S1. Crush the acid-soluble compound and sieve it to obtain powder; S2. Add the powder obtained in S1 to the polyurethane resin mixture to obtain a polyurethane slurry; S3. Coat the polyurethane slurry obtained in S2 onto a transparent film roll to obtain a polyurethane film; S4. Immerse the polyurethane membrane obtained in S3 in an ionizable compound solution, and then wash it to obtain the final product. The acid-soluble compound is selected from at least one of metal oxides, metal hydroxides, inorganic salts, and organic salts; The average particle size of the pulverized acid-soluble compound is in the micrometer range, and the average particle size of the pulverized acid-soluble compound is ≤13μm; The polyurethane resin mixture includes 100 parts by weight of a DMF solution of polyurethane resin, 15-65 parts by weight of a polar solvent, and 2-5 parts by weight of a surfactant. The metal oxide is selected from at least one of iron oxide, ferrous oxide, iron(II,III) oxide, aluminum oxide, magnesium oxide, copper oxide, cuprous oxide, silver oxide, and zinc oxide. The inorganic salt is selected from at least one of barium carbonate, calcium carbonate, silver carbonate, manganese carbonate, ferrous carbonate, zinc carbonate, and magnesium carbonate. The organic salt is selected from at least one of calcium oxalate, calcium citrate, calcium tartrate, and calcium malate.
2. The method for preparing a chemical mechanical polishing pad according to claim 1, characterized in that, The metal hydroxide is selected from at least one of iron hydroxide, copper hydroxide, magnesium hydroxide, and aluminum hydroxide.
3. The method for preparing a chemical mechanical polishing pad according to claim 1, characterized in that, The ionizable compound solution is selected from at least one of hydrochloric acid solution, sulfuric acid solution, nitric acid solution, perchloric acid solution, carbonic acid solution, phosphoric acid solution, and boric acid solution.
4. The application of a chemical mechanical polishing pad prepared by the method of any one of claims 1-3 in the chemical mechanical polishing process of semiconductor chip manufacturing.