An organic piezoelectric polyurethane polishing pad and its preparation method

Abstract

This invention belongs to the field of polyurethane materials technology, and relates to an organic piezoelectric polyurethane polishing pad and its preparation method. Preparation method: In the preparation of the polyurethane polishing pad, before the reaction of polyether polyol and isocyanate, PVDF fibers are added to the polyether polyol in batches, and stirred until the PVDF fibers are uniformly dispersed in the polyether polyol. The resulting polyurethane polishing pad is the organic piezoelectric polyurethane polishing pad. The prepared organic piezoelectric polyurethane polishing pad includes a polyurethane matrix and PVDF fibers. The polyurethane matrix has a porous structure, and the PVDF fibers are distributed in the polyurethane matrix in a network structure. The method of this invention is simple, and the obtained organic piezoelectric polyurethane polishing pad has good polishing effect and polishing efficiency.

Description

Technical Field

[0001] This invention belongs to the field of polishing pad technology, and relates to an organic piezoelectric polyurethane polishing pad and its preparation method. Background Technology

[0002] In the fabrication of workpieces (such as semiconductor wafers), polishing techniques are often required to planarize the surface of the workpiece or other substrates. Chemical mechanical polishing (CMP) is a common technique used to planarize or polish workpieces and remove excess material in damascene processes, front-end online (FEOL) processes, or back-end online (BEOL) processes. In conventional CMP, a workpiece holder or polishing head is mounted on a holder assembly. The polishing head holds the workpiece and positions it in contact with the polishing surface of a polishing pad. The polishing pad is mounted on a table or platen within the CMP equipment. The holder assembly provides controlled pressure between the workpiece and the polishing pad, while polishing media (such as polishing slurry) is dispensed onto the polishing pad and drawn into the gap between the workpiece and the polishing pad. For polishing, the polishing pad and the workpiece rotate relative to each other. As the polishing pad rotates below the workpiece, the surface of the workpiece directly faces the polishing pad. The workpiece surface is polished and planarized through the chemical and mechanical action of the polishing surface and the polishing media on that surface.

[0003] Therefore, polishing pads are a crucial component in CMP that determines the surface quality of workpieces, and studying the structure and preparation methods of polishing pads is of great significance.

[0004] Existing technologies attempt to add electrospun fiber components to polishing pads to improve their performance, for example:

[0005] Patent application CN115194641A discloses a white pad with high flatness for semiconductor polishing and its preparation process. The process involves mixing a silicone matrix, epoxy resin, non-woven polyester, glass wool, non-woven synthetic fibers, and open-cell plastic foam at high temperature, and then preparing nanofibers by electrospinning. These nanofibers serve as the nanofiber interlayer, which improves the connection strength of the various structures inside the polishing pad body. This results in more uniform pressure inside the homogeneous main body layer, making it suitable for long-term and high-intensity work and helping to extend the service life of the polishing pad.

[0006] Patent application CN107053032A discloses a method for preparing a bonded abrasive polishing pad. Using zirconium propoxide as a precursor and composite epoxy resin as a medium, high-refractive-index fibers are prepared by electrospinning. These high-refractive-index fibers are then added to the polishing pad. Due to light refraction, ultraviolet light is cured on the surface of the abrasive particles. After repeated refraction by the refractive fibers, the ultraviolet light penetrates deep into the bonded abrasive polishing pad for ultraviolet curing, thereby improving the curing rate and uniform curing degree of the bonded abrasive polishing pad and thus improving its wear resistance.

[0007] However, although the polishing pads prepared by the above methods have certain improvements in wear resistance and service life, the polishing effect and efficiency in the CMP polishing process need to be improved.

[0008] Therefore, it is necessary to develop a new type of polishing pad with better polishing effect and higher polishing efficiency. Summary of the Invention

[0009] The purpose of this invention is to solve the problems existing in the prior art and to provide an organic piezoelectric polyurethane polishing pad and its preparation method.

[0010] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0011] An organic piezoelectric polyurethane polishing pad includes a polyurethane matrix and PVDF (polyvinylidene fluoride) fibers. The polyurethane matrix has a porous structure, and the PVDF fibers are distributed in the polyurethane matrix in a mesh structure.

[0012] The polyurethane polishing pad of the present invention exhibits significantly better polishing effect and efficiency than existing polyurethane polishing pads in the CMP polishing process, for the following reasons:

[0013] During CMP polishing, the polishing pad deforms under the pressure applied by the workpiece, causing a change in molecular polarity and a rearrangement of intramolecular polar bonds, leading to a redistribution of charge. The PVDF fibers within the polishing pad deform along the direction of the applied force. PVDF exists in three phase structures: α, β, and γ. When the β-phase structure within the PVDF fibers is deformed by external force, the lattice units become distorted, causing a change in the electric dipole moment. This results in a potential difference and charge separation, generating a piezoelectric effect. This creates an in-situ electric field within the polishing pad. Because the PVDF fibers are distributed in a network structure within the polyurethane matrix, the in-situ electric field generated by the PVDF fibers can be combined, increasing the overall strength of the in-situ electric field. This in-situ electric field is conducted to the surface of the polishing pad through the polishing fluid and the pores of the polyurethane matrix, combining with the surface of the material being polished, thereby improving the polishing effect and efficiency.

[0014] As a preferred technical solution:

[0015] As described above, the organic piezoelectric polyurethane polishing pad has PVDF fibers with an average length of 2-5 micrometers. PVDF fibers of this length will not affect the cross-linking of its network structure due to being too short, nor will they cause cross-linking flocculation due to being too long.

[0016] The organic piezoelectric polyurethane polishing pad described above is prepared by electrospinning PVDF fibers to obtain a nanofiber membrane, which is then broken down (using a high-speed homogenizer). The spinning solution contains 2,3-dihydrodecafluoropentane.

[0017] Hydrogen bonds are formed between 2,3-dihydrodecafluoropentane and PVDF. On one hand, fluorine atoms in 2,3-dihydrodecafluoropentane form hydrogen bonds with hydrogen atoms in PVDF; on the other hand, hydrogen atoms in 2,3-dihydrodecafluoropentane form hydrogen bonds with fluorine atoms in PVDF. The hydrogen bonds between 2,3-dihydrodecafluoropentane and β-phase PVDF are closer and more favorable than those between 2,3-dihydrodecafluoropentane and α-phase PVDF. Therefore, during electrospinning, under the influence of an applied voltage, the strong hydrogen bond interactions cause the α-phase to transform into the β-phase, thereby increasing the β-phase content of PVDF nanofibers. Since the β-phase structure is the most piezoelectric crystalline phase in PVDF, its lattice structure has lattice units of varying sizes, which can induce an electric dipole moment. When the β-phase structure in the PVDF crystal is deformed by external force, the lattice units will be distorted, causing a change in the electric dipole moment, resulting in a potential difference and charge separation, thus producing a piezoelectric effect. Therefore, increasing the β phase content can improve the piezoelectric properties of PVDF.

[0018] The preparation process of the spinning solution for the organic piezoelectric polyurethane polishing pad described above is as follows: by weight, 40-50 parts of matrix mixture, 15-30 parts of 2,3-dihydrodecafluoropentane, and 10-20 parts of deionized water are stirred and mixed, and then heated in a water bath (for 30-40 minutes at a temperature of 45-50°C), filtered to obtain filtrate, and the filtrate is placed at 70-75°C for rotary evaporation to 1 / 5 of its original volume to obtain the spinning solution;

[0019] The preparation process of the matrix mixture is as follows: PVDF is mixed with solvent A or solvent B at a mass ratio of 1:8 and then heated in a water bath (for 8-10 hours at a temperature of 55-60℃) to obtain the matrix mixture.

[0020] Solvent A is DMAc (dimethylacetamide), DMSO (dimethyl sulfoxide), DMF (dimethylformamide), or NMP (N-methyl-2-pyrrolidone);

[0021] Solvent B is a mixture of solvent A and acetone in a volume ratio of 6:4, which can more effectively improve the dissolution efficiency of PVDF.

[0022] The electrospinning process parameters for the organic piezoelectric polyurethane polishing pad described above include: electrospinner injector angle 60°, receiving distance 15cm, relative humidity 50-60%, voltage 14-20kV, and feeding speed 2-3mL / h.

[0023] The organic piezoelectric polyurethane polishing pad described above has a PVDF fiber content of 22-23 wt% and a porosity of 50-60%.

[0024] The organic piezoelectric polyurethane polishing pad described above has a Si wafer removal rate of 338.26-383.25 nm / min during the polishing process.

[0025] The present invention also provides a method for preparing an organic piezoelectric polyurethane polishing pad as described in any of the preceding claims. In the process of preparing the polyurethane polishing pad, before the reaction between the polyether polyol and the isocyanate, PVDF fibers are added to the polyether polyol in batches and stirred until the PVDF fibers are uniformly dispersed in the polyether polyol. The polyurethane polishing pad finally obtained is the organic piezoelectric polyurethane polishing pad.

[0026] As a preferred technical solution:

[0027] As described above, adding PVDF fibers in batches means adding PVDF fibers in three batches with a mass ratio of 4:3:3. Stirring is carried out during the batch addition of PVDF fibers, and stirring is continued for 20 minutes after each batch addition. The stirring speed is 1500 r / min.

[0028] The specific steps of the method described above are as follows:

[0029] (1) Add PVDF fibers to the polyether polyol in batches and stir until the PVDF fibers are uniformly dispersed in the polyether polyol to obtain component A;

[0030] (2) Mix the polyurethane prepolymer, isocyanate, water, silicone oil and catalyst, and stir until homogeneous to obtain component B;

[0031] (3) After mixing components A and B, foaming, drying, settling, cutting and polishing are carried out in sequence to obtain organic piezoelectric polyurethane polishing pad.

[0032] In the method described above, the polyether polyol is one or more of sorbitol-based polyether polyol, polypropylene glycol, and polycarbonate diol; the isocyanate is diphenylmethane diisocyanate or hexamethylene diisocyanate.

[0033] The mixture of components A and B contains 25 wt% polyether polyol, 15 wt% PVDF fiber, 25 wt% isocyanate, 1 wt% water, 1.5 wt% silicone oil, and 2.5 wt% catalyst.

[0034] The foaming temperature is 55℃ and the time is 30 minutes; the drying temperature is 50-60℃ and the time is 30 minutes; the standing temperature is 25-30℃ and the time is 36-48 hours.

[0035] Beneficial effects:

[0036] (1) The organic piezoelectric polyurethane polishing pad provided by the present invention adds PVDF fibers, which makes the prepared polishing pad have piezoelectric properties. During the polishing process, the piezoelectric effect is generated during the deformation caused by the applied pressure, which generates an in-situ electric field in the polishing pad. At the same time, the network structure of PVDF fibers can further enhance the in-situ electric field strength. The fibrous piezoelectric material can better contact the polishing liquid, thereby conducting to the surface of the polishing pad and acting on the surface of the workpiece to be polished, thus having a better polishing effect and higher polishing efficiency. The removal rate in the CMP polishing process is 338.26-383.25 nm / min.

[0037] (2) The PVDF fibers added in this invention are distributed in a mesh structure, which changes the surface structure of the polishing pad and adjusts the porosity, improving water absorption. At the same time, due to the high specific surface area and excellent mechanical properties of PVDF fibers, the anti-aging, corrosion resistance and wear resistance of the polishing pad are also enhanced, giving the polishing pad a longer lifespan. Detailed Implementation

[0038] The present invention will be further described below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0039] The following are the test methods for the relevant performance indicators in each embodiment:

[0040] Porosity: Tested in accordance with GB / T 21650.1-2008 standard.

[0041] Removal rate: The organic piezoelectric polyurethane polishing pad was processed into a flat surface using a cutting machine. After the processed organic piezoelectric polyurethane polishing pad was installed on the table of the polishing machine, it was first polished with a 200-mesh diamond grinding wheel under a pressure of 0.03 MPa for 2 hours. Then, the polished organic piezoelectric polyurethane polishing pad was used to polish three groups of 2-inch Si wafers under a pressure of 4.5 psi. The removal mass of the three groups of Si wafers before and after polishing was collected. The removal rate of the three groups of experiments was calculated according to the formula for the removal rate, and the average value was taken. The polishing slurry in the polishing process consisted of 1 wt% silica sol (manufacturer: Ningbo Risheng New Materials Co., Ltd., China, CAS No. 112926-00-8, average particle size: 130 nm) and 99 wt% deionized water. The polishing time was 15 min, the table speed was 60 r / min, the carrier speed was 60 r / min, and the slurry flow rate was 20 mL / min.

[0042] The formula for calculating the removal rate is as follows:

[0043]

[0044] In the formula, MRR is the removal rate, in nm / min; Δm is the difference in mass removed before and after polishing of the Si wafer, in g; and ρ is the density of the Si wafer, in g / cm³. 3 r is the radius of the Si wafer in cm; t is the polishing time in min.

[0045] Example 1

[0046] A method for preparing an organic piezoelectric polyurethane polishing pad, comprising the following specific steps:

[0047] (1) Preparation of raw materials;

[0048] PVDF: CAS number is 24937-79-9;

[0049] Solvent: DMAc;

[0050] 2,3-Dihydrodecafluoropentane;

[0051] Deionized water;

[0052] Polyether polyol: Manufacturer is China Jiahe Chemical Co., Ltd., brand name is Puranol RF 6282;

[0053] Polyurethane prepolymer: Manufacturer is Jinshitou Plastic Raw Materials Business Department, Zhangmutou City, Dongguan, China; Brand name: HKR76010.

[0054] Isocyanate: Diphenylmethane diisocyanate, CAS No. 101-68-8;

[0055] water;

[0056] Silicone oil: Manufacturer is Momentive Advanced Materials Group, USA; Grade: L6900;

[0057] Catalyst: Manufacturer is Momentive Advanced Materials Group, USA; Grade A33;

[0058] (2) Preparation of PVDF fibers;

[0059] (2.1) Mix PVDF and solvent at a mass ratio of 1:8 and then heat in a water bath (for 8 hours at a temperature of 55°C) to obtain a matrix mixture.

[0060] (2.2) By weight, 45 parts of matrix mixture, 25 parts of 2,3-dihydrodecafluoropentane and 15 parts of deionized water are stirred and mixed, and then heated in a water bath (30 min, 45 °C) and filtered to obtain filtrate. The filtrate is then placed at 75 °C and rotary evaporated to 1 / 5 of its original volume to obtain spinning solution.

[0061] (2.3) After obtaining a nanofiber membrane by electrospinning the spinning solution, the nanofiber membrane was broken up by a high-speed homogenizer to obtain PVDF fibers with an average length of 2 micrometers. The process parameters of electrospinning were: electrospinner injector angle 60°, receiving distance 15cm, relative humidity 55%, voltage 18kV, and feeding speed 3mL / h.

[0062] (3) Preparation of organic piezoelectric polyurethane polishing pad;

[0063] (3.1) PVDF fibers were added to the polyether polyol in three batches (with stirring during the addition process) and stirred until the PVDF fibers were uniformly dispersed in the polyether polyol to obtain component A; wherein the mass ratio of the PVDF fibers added in the three batches was 4:3:3; the stirring speed was 1500 r / min for each batch.

[0064] (3.2) Mix the polyurethane prepolymer, isocyanate, water, silicone oil and catalyst, and stir until homogeneous to obtain component B;

[0065] (3.3) After mixing components A and B, the mixture is foamed, dried, allowed to stand, cut, and polished in sequence to obtain an organic piezoelectric polyurethane polishing pad. The mixture of components A and B contains 25 wt% polyether polyol, 15 wt% PVDF fiber, 25 wt% isocyanate, 1 wt% water, 1.5 wt% silicone oil, and 2.5 wt% catalyst. The foaming temperature is 55℃ and the time is 30 min. The drying temperature is 50℃ and the time is 30 min. The standing temperature is 25℃ and the time is 36 h.

[0066] The final organic piezoelectric polyurethane polishing pad is composed of a polyurethane matrix and PVDF fibers. The polyurethane matrix has a porous structure, and the PVDF fibers are distributed in the polyurethane matrix in a mesh structure. The PVDF fiber content in the organic piezoelectric polyurethane polishing pad is 22 wt%. The porosity of the organic piezoelectric polyurethane polishing pad is 53%. The removal rate of Si wafers by the organic piezoelectric polyurethane polishing pad during the polishing process is 343.57 nm / min.

[0067] Comparative Example 1

[0068] A method for preparing a polishing pad is basically the same as in Example 1, except that step (2) is not performed; in step (3), polyether polyol is directly used as component A, and the mixture of component A and component B does not contain PVDF fiber. The amount of polyether polyol, polyurethane prepolymer, isocyanate, water, silicone oil and catalyst added is the same as in Example 1.

[0069] The final polishing pad achieved a Si wafer removal rate of 280.55 nm / min during the polishing process.

[0070] Compared to Comparative Example 1, the polishing effect and efficiency of Example 1 were significantly reduced. This is because, unlike Comparative Example 1, Example 1 incorporated PVDF fibers during the preparation of the polishing pad. During CMP polishing, the polishing pad deforms under the pressure applied by the workpiece, causing a change in molecular polarity and rearrangement of intramolecular polar bonds, resulting in a redistribution of charge. The PVDF fibers inside the polishing pad deform along the direction of force. PVDF has three phase structures: α, β, and γ. When the β phase structure in the PVDF fibers is deformed by external force, the lattice units become distorted, causing a change in the electric dipole moment, thereby generating a potential difference and charge separation, resulting in a piezoelectric effect. This generates an in-situ electric field in the polishing pad. Since the PVDF fibers are distributed in a network structure within the polyurethane matrix, the in-situ electric field generated by the PVDF fibers can be combined, increasing the overall strength of the generated in-situ electric field. The in-situ electric field is conducted to the surface of the polishing pad through the polishing fluid and the pores of the polyurethane matrix and combines with the surface of the material being polished, thus improving the polishing effect and efficiency.

[0071] Example 2

[0072] A method for preparing an organic piezoelectric polyurethane polishing pad, comprising the following specific steps:

[0073] (1) Preparation of raw materials;

[0074] PVDF: CAS number is 24937-79-9;

[0075] Solvent: DMSO;

[0076] 2,3-Dihydrodecafluoropentane;

[0077] Deionized water;

[0078] Polyether polyol: Manufacturer is China Jiahe Chemical Co., Ltd., brand name is Puranol RF 6406;

[0079] Polyurethane prepolymer: Manufacturer is Jinshitou Plastic Raw Materials Business Department, Zhangmutou City, Dongguan, China; Brand name: HKR76010.

[0080] Isocyanate: Diphenylmethane diisocyanate, CAS No. 101-68-8;

[0081] water;

[0082] Silicone oil: Manufacturer is Momentive Advanced Materials Group, USA; Grade: L6900;

[0083] Catalyst: Manufacturer is Momentive Advanced Materials Group, USA; Grade A33;

[0084] (2) Preparation of PVDF fibers;

[0085] (2.1) Mix PVDF and solvent at a mass ratio of 1:8 and then heat in a water bath (for 8 hours at a temperature of 55°C) to obtain a matrix mixture.

[0086] (2.2) By weight, 48 parts of matrix mixture, 25 parts of 2,3-dihydrodecafluoropentane and 15 parts of deionized water are stirred and mixed, and then heated in a water bath (30 min, 45 °C) and filtered to obtain filtrate. The filtrate is then placed at 75 °C and rotary evaporated to 1 / 5 of its original volume to obtain spinning solution.

[0087] (2.3) After obtaining a nanofiber membrane by electrospinning the spinning solution, the nanofiber membrane was broken up by a high-speed homogenizer to obtain PVDF fibers with an average length of 3 micrometers. The process parameters of electrospinning were: electrospinner injector angle 60°, receiving distance 15cm, relative humidity 60%, voltage 18kV, and feeding speed 2mL / h.

[0088] (3) Preparation of organic piezoelectric polyurethane polishing pad;

[0089] (3.1) PVDF fibers were added to the polyether polyol in three batches (with stirring during the addition process) and stirred until the PVDF fibers were uniformly dispersed in the polyether polyol to obtain component A; wherein the mass ratio of the PVDF fibers added in the three batches was 4:3:3; the stirring speed was 1500 r / min for each batch.

[0090] (3.2) Mix the polyurethane prepolymer, isocyanate, water, silicone oil and catalyst, and stir until homogeneous to obtain component B;

[0091] (3.3) After mixing components A and B, the mixture is foamed, dried, allowed to stand, cut, and polished in sequence to obtain an organic piezoelectric polyurethane polishing pad. The mixture of components A and B contains 25 wt% polyether polyol, 15 wt% PVDF fiber, 25 wt% isocyanate, 1 wt% water, 1.5 wt% silicone oil, and 2.5 wt% catalyst. The foaming temperature is 55℃ and the time is 30 min. The drying temperature is 55℃ and the time is 30 min. The standing temperature is 30℃ and the time is 36 h.

[0092] The final organic piezoelectric polyurethane polishing pad is composed of a polyurethane matrix and PVDF fibers. The polyurethane matrix has a porous structure, and the PVDF fibers are distributed in the polyurethane matrix in a network structure. The PVDF fiber content in the organic piezoelectric polyurethane polishing pad is 22 wt%. The porosity of the organic piezoelectric polyurethane polishing pad is 54%. The removal rate of Si wafers by the organic piezoelectric polyurethane polishing pad during the polishing process is 350.31 nm / min.

[0093] Example 3

[0094] A method for preparing an organic piezoelectric polyurethane polishing pad, comprising the following specific steps:

[0095] (1) Preparation of raw materials;

[0096] PVDF: CAS number is 24937-79-9;

[0097] Solvent: DMF;

[0098] 2,3-Dihydrodecafluoropentane;

[0099] Deionized water;

[0100] Polyether polyol: A mixture of sorbitol-based polyether polyol (manufacturer: China Jiahe Chemical Co., Ltd., brand name: Puranol RF 6482) and polypropylene glycol (CAS No.: 25322-69-4) in a mass ratio of 3:1;

[0101] Polyurethane prepolymer: Manufacturer is Jinshitou Plastic Raw Materials Business Department, Zhangmutou City, Dongguan, China; Brand name: HKR76010.

[0102] Isocyanate: Diphenylmethane diisocyanate, CAS No. 101-68-8;

[0103] water;

[0104] Silicone oil: Manufacturer is Momentive Advanced Materials Group, USA; Grade: L6900;

[0105] Catalyst: Manufacturer is Momentive Advanced Materials Group, USA; Grade A33;

[0106] (2) Preparation of PVDF fibers;

[0107] (2.1) Mix PVDF and solvent at a mass ratio of 1:8 and heat in a water bath (time: 10h, temperature: 60℃) to obtain matrix mixture;

[0108] (2.2) By weight, 50 parts of matrix mixture, 25 parts of 2,3-dihydrodecafluoropentane and 15 parts of deionized water are stirred and mixed, and then heated in a water bath (for 40 min at 50°C) and filtered to obtain filtrate. The filtrate is then placed at 70°C and evaporated to 1 / 5 of its original volume to obtain spinning solution.

[0109] (2.3) After obtaining a nanofiber membrane by electrospinning the spinning solution, the nanofiber membrane was broken up by a high-speed homogenizer to obtain PVDF fibers with an average length of 3 micrometers. The process parameters of electrospinning were: electrospinner injector angle 60°, receiving distance 15cm, relative humidity 55%, voltage 18kV, and feeding speed 2mL / h.

[0110] (3) Preparation of organic piezoelectric polyurethane polishing pad;

[0111] (3.1) PVDF fibers were added to the polyether polyol in three batches (with stirring during the addition process) and stirred until the PVDF fibers were uniformly dispersed in the polyether polyol to obtain component A; wherein the mass ratio of the PVDF fibers added in the three batches was 4:3:3; the stirring speed was 1500 r / min for each batch.

[0112] (3.2) Mix the polyurethane prepolymer, isocyanate, water, silicone oil and catalyst, and stir until homogeneous to obtain component B;

[0113] (3.3) After mixing components A and B, the mixture is foamed, dried, allowed to stand, cut, and polished in sequence to obtain an organic piezoelectric polyurethane polishing pad. The mixture of components A and B contains 25 wt% polyether polyol, 15 wt% PVDF fiber, 25 wt% isocyanate, 1 wt% water, 1.5 wt% silicone oil, and 2.5 wt% catalyst. The foaming temperature is 55℃ and the time is 30 min. The drying temperature is 60℃ and the time is 30 min. The standing temperature is 25℃ and the time is 42 h.

[0114] The final organic piezoelectric polyurethane polishing pad is composed of a polyurethane matrix and PVDF fibers. The polyurethane matrix has a porous structure, and the PVDF fibers are distributed in the polyurethane matrix in a network structure. The PVDF fiber content in the organic piezoelectric polyurethane polishing pad is 22 wt%. The porosity of the organic piezoelectric polyurethane polishing pad is 60%. The removal rate of Si wafers by the organic piezoelectric polyurethane polishing pad during the polishing process is 352.18 nm / min.

[0115] Example 4

[0116] A method for preparing an organic piezoelectric polyurethane polishing pad, comprising the following specific steps:

[0117] (1) Preparation of raw materials;

[0118] PVDF: CAS number is 24937-79-9;

[0119] Solvent: NMP;

[0120] 2,3-Dihydrodecafluoropentane;

[0121] Deionized water;

[0122] Polyether polyol: Sorbitol-based polyether polyol, manufactured by China Jiahe Chemical Co., Ltd., brand name Puranol RF 6499;

[0123] Polyurethane prepolymer: Manufacturer is Jinshitou Plastic Raw Materials Business Department, Zhangmutou City, Dongguan, China; Brand name: HKR76010.

[0124] Isocyanate: Hexamethylene diisocyanate, CAS No. 822-06-0;

[0125] water;

[0126] Silicone oil: Manufacturer is Momentive Advanced Materials Group, USA; Grade: L6900;

[0127] Catalyst: Manufacturer is Momentive Advanced Materials Group, USA; Grade A33;

[0128] (2) Preparation of PVDF fibers;

[0129] (2.1) Mix PVDF and solvent at a mass ratio of 1:8 and heat in a water bath (time: 10h, temperature: 60℃) to obtain matrix mixture;

[0130] (2.2) By weight, 40 parts of matrix mixture, 30 parts of 2,3-dihydrodecafluoropentane and 15 parts of deionized water are stirred and mixed, and then heated in a water bath (for 40 min at 50°C) and filtered to obtain filtrate. The filtrate is then placed at 70°C and rotary evaporated to 1 / 5 of its original volume to obtain spinning solution.

[0131] (2.3) After obtaining a nanofiber membrane by electrospinning the spinning solution, the nanofiber membrane was broken up by a high-speed homogenizer to obtain PVDF fibers with an average length of 3 micrometers. The process parameters of electrospinning were: electrospinner injector angle 60°, receiving distance 15cm, relative humidity 55%, voltage 16kV, and feeding speed 3mL / h.

[0132] (3) Preparation of organic piezoelectric polyurethane polishing pad;

[0133] (3.1) PVDF fibers were added to the polyether polyol in three batches (with stirring during the addition process) and stirred until the PVDF fibers were uniformly dispersed in the polyether polyol to obtain component A; wherein the mass ratio of the PVDF fibers added in the three batches was 4:3:3; the stirring speed was 1500 r / min for each batch.

[0134] (3.2) Mix the polyurethane prepolymer, isocyanate, water, silicone oil and catalyst, and stir until homogeneous to obtain component B;

[0135] (3.3) After mixing components A and B, the mixture is foamed, dried, allowed to stand, cut, and polished in sequence to obtain an organic piezoelectric polyurethane polishing pad. The mixture of components A and B contains 25 wt% polyether polyol, 15 wt% PVDF fiber, 25 wt% isocyanate, 1 wt% water, 1.5 wt% silicone oil, and 2.5 wt% catalyst. The foaming temperature is 55℃ and the time is 30 min. The drying temperature is 60℃ and the time is 30 min. The standing temperature is 30℃ and the time is 48 h.

[0136] The final organic piezoelectric polyurethane polishing pad is composed of a polyurethane matrix and PVDF fibers. The polyurethane matrix has a porous structure, and the PVDF fibers are distributed in the polyurethane matrix in a network structure. The PVDF fiber content in the organic piezoelectric polyurethane polishing pad is 22 wt%. The porosity of the organic piezoelectric polyurethane polishing pad is 50%. The removal rate of Si wafers by the organic piezoelectric polyurethane polishing pad during the polishing process is 347.52 nm / min.

[0137] Example 5

[0138] A method for preparing an organic piezoelectric polyurethane polishing pad, comprising the following specific steps:

[0139] (1) Preparation of raw materials;

[0140] PVDF: CAS number is 24937-79-9;

[0141] Solvent: A mixture of DMAc and acetone in a volume ratio of 6:4;

[0142] 2,3-Dihydrodecafluoropentane;

[0143] Deionized water;

[0144] Polyether polyol: Sorbitol-based polyether polyol, manufactured by China Jiahe Chemical Co., Ltd., brand name Puranol RF 6480;

[0145] Polyurethane prepolymer: Manufacturer is Jinshitou Plastic Raw Materials Business Department, Zhangmutou City, Dongguan, China; Brand name: HKR76010.

[0146] Isocyanate: Diphenylmethane diisocyanate, CAS No. 101-68-8;

[0147] water;

[0148] Silicone oil: Manufacturer is Momentive Advanced Materials Group, USA; Grade: L6900;

[0149] Catalyst: Manufacturer is Momentive Advanced Materials Group, USA; Grade A33;

[0150] (2) Preparation of PVDF fibers;

[0151] (2.1) Mix PVDF and solvent at a mass ratio of 1:8 and then heat in a water bath (for 8 hours at a temperature of 55°C) to obtain a matrix mixture.

[0152] (2.2) By weight, 50 parts of matrix mixture, 30 parts of 2,3-dihydrodecafluoropentane and 10 parts of deionized water are stirred and mixed, and then heated in a water bath (30 min, 45 °C) and filtered to obtain filtrate. The filtrate is then placed at 75 °C and evaporated to 1 / 5 of its original volume to obtain spinning solution.

[0153] (2.3) After obtaining a nanofiber membrane by electrospinning the spinning solution, the nanofiber membrane was broken up by a high-speed homogenizer to obtain PVDF fibers with an average length of 5 micrometers. The process parameters of electrospinning were: electrospinner injector angle 60°, receiving distance 15cm, relative humidity 55%, voltage 18kV, and feeding speed 2mL / h.

[0154] (3) Preparation of organic piezoelectric polyurethane polishing pad;

[0155] (3.1) PVDF fibers were added to the polyether polyol in three batches (with stirring during the addition process) and stirred until the PVDF fibers were uniformly dispersed in the polyether polyol to obtain component A; wherein the mass ratio of the PVDF fibers added in the three batches was 4:3:3; the stirring speed was 1500 r / min for each batch.

[0156] (3.2) Mix the polyurethane prepolymer, isocyanate, water, silicone oil and catalyst, and stir until homogeneous to obtain component B;

[0157] (3.3) After mixing components A and B, the mixture is foamed, dried, allowed to stand, cut, and polished in sequence to obtain an organic piezoelectric polyurethane polishing pad. The mixture of components A and B contains 25 wt% polyether polyol, 15 wt% PVDF fiber, 25 wt% isocyanate, 1 wt% water, 1.5 wt% silicone oil, and 2.5 wt% catalyst. The foaming temperature is 55℃ and the time is 30 min. The drying temperature is 55℃ and the time is 30 min. The standing temperature is 25℃ and the time is 36 h.

[0158] The final organic piezoelectric polyurethane polishing pad is composed of a polyurethane matrix and PVDF fibers. The polyurethane matrix has a porous structure, and the PVDF fibers are distributed in the polyurethane matrix in a network structure. The PVDF fiber content in the organic piezoelectric polyurethane polishing pad is 23 wt%. The porosity of the organic piezoelectric polyurethane polishing pad is 56%. The removal rate of Si wafers by the organic piezoelectric polyurethane polishing pad during the polishing process is 372.45 nm / min.

[0159] Example 6

[0160] A method for preparing an organic piezoelectric polyurethane polishing pad, comprising the following specific steps:

[0161] (1) Preparation of raw materials;

[0162] PVDF: CAS number is 24937-79-9;

[0163] Solvent: A mixture of DMSO and acetone in a volume ratio of 6:4;

[0164] 2,3-Dihydrodecafluoropentane;

[0165] Deionized water;

[0166] Polyether polyol: Sorbitol-based polyether polyol, manufactured by China Jiahe Chemical Co., Ltd., brand name Puranol RF 8043;

[0167] Polyurethane prepolymer: Manufacturer is Jinshitou Plastic Raw Materials Business Department, Zhangmutou City, Dongguan, China; Brand name: HKR76010.

[0168] Isocyanate: Hexamethylene diisocyanate, CAS No. 822-06-0;

[0169] water;

[0170] Silicone oil: Manufacturer is Momentive Advanced Materials Group, USA; Grade: L6900;

[0171] Catalyst: Manufacturer is Momentive Advanced Materials Group, USA; Grade A33;

[0172] (2) Preparation of PVDF fibers;

[0173] (2.1) Mix PVDF and solvent at a mass ratio of 1:8 and heat in a water bath (time: 10h, temperature: 60℃) to obtain matrix mixture;

[0174] (2.2) By weight, 50 parts of matrix mixture, 15 parts of 2,3-dihydrodecafluoropentane and 20 parts of deionized water are stirred and mixed, and then heated in a water bath (for 40 min at 45°C) and filtered to obtain filtrate. The filtrate is then placed at 75°C and evaporated to 1 / 5 of its original volume to obtain spinning solution.

[0175] (2.3) After obtaining a nanofiber membrane by electrospinning the spinning solution, the nanofiber membrane was broken up by a high-speed homogenizer to obtain PVDF fibers with an average length of 5 micrometers. The process parameters of electrospinning were: electrospinner injector angle 60°, receiving distance 15cm, relative humidity 55%, voltage 14kV, and feeding speed 2mL / h.

[0176] (3) Preparation of organic piezoelectric polyurethane polishing pad;

[0177] (3.1) PVDF fibers were added to the polyether polyol in three batches (with stirring during the addition process) and stirred until the PVDF fibers were uniformly dispersed in the polyether polyol to obtain component A; wherein the mass ratio of the PVDF fibers added in the three batches was 4:3:3; the stirring speed was 1500 r / min for each batch.

[0178] (3.2) Mix the polyurethane prepolymer, isocyanate, water, silicone oil and catalyst, and stir until homogeneous to obtain component B;

[0179] (3.3) After mixing components A and B, the mixture is foamed, dried, allowed to stand, cut, and polished in sequence to obtain an organic piezoelectric polyurethane polishing pad. The mixture of components A and B contains 25 wt% polyether polyol, 15 wt% PVDF fiber, 25 wt% isocyanate, 1 wt% water, 1.5 wt% silicone oil, and 2.5 wt% catalyst. The foaming temperature is 55℃ and the time is 30 min. The drying temperature is 55℃ and the time is 30 min. The standing temperature is 25℃ and the time is 48 h.

[0180] The final organic piezoelectric polyurethane polishing pad is composed of a polyurethane matrix and PVDF fibers. The polyurethane matrix has a porous structure, and the PVDF fibers are distributed in the polyurethane matrix in a network structure. The PVDF fiber content in the organic piezoelectric polyurethane polishing pad is 22 wt%. The porosity of the organic piezoelectric polyurethane polishing pad is 54%. The removal rate of Si wafers by the organic piezoelectric polyurethane polishing pad during the polishing process is 364.33 nm / min.

[0181] Example 7

[0182] A method for preparing an organic piezoelectric polyurethane polishing pad, comprising the following specific steps:

[0183] (1) Preparation of raw materials;

[0184] PVDF: CAS number is 24937-79-9;

[0185] Solvent: A mixture of DMF and acetone in a volume ratio of 6:4;

[0186] 2,3-Dihydrodecafluoropentane;

[0187] Deionized water;

[0188] Polyether polyol: Sorbitol-based polyether polyol, manufactured by China Jiahe Chemical Co., Ltd., brand name Puranol RF 8038;

[0189] Polyurethane prepolymer: Manufacturer is Jinshitou Plastic Raw Materials Business Department, Zhangmutou City, Dongguan, China; Brand name: HKR76010.

[0190] Isocyanate: Diphenylmethane diisocyanate, CAS No. 101-68-8;

[0191] water;

[0192] Silicone oil: Manufacturer is Momentive Advanced Materials Group, USA; Grade: L6900;

[0193] Catalyst: Manufacturer is Momentive Advanced Materials Group, USA; Grade A33;

[0194] (2) Preparation of PVDF fibers;

[0195] (2.1) Mix PVDF and solvent at a mass ratio of 1:8 and heat in a water bath (for 8 hours at a temperature of 60°C) to obtain a matrix mixture;

[0196] (2.2) By weight, 50 parts of matrix mixture, 30 parts of 2,3-dihydrodecafluoropentane and 10 parts of deionized water are stirred and mixed, and then heated in a water bath (30 min, 45 °C) and filtered to obtain filtrate. The filtrate is then placed at 75 °C and evaporated to 1 / 5 of its original volume to obtain spinning solution.

[0197] (2.3) After obtaining a nanofiber membrane by electrospinning the spinning solution, the nanofiber membrane was broken up by a high-speed homogenizer to obtain PVDF fibers with an average length of 5 micrometers. The process parameters of electrospinning were: electrospinner injector angle 60°, receiving distance 15cm, relative humidity 60%, voltage 20kV, and feeding speed 2mL / h.

[0198] (3) Preparation of organic piezoelectric polyurethane polishing pad;

[0199] (3.1) PVDF fibers were added to the polyether polyol in three batches (with stirring during the addition process) and stirred until the PVDF fibers were uniformly dispersed in the polyether polyol to obtain component A; wherein the mass ratio of the PVDF fibers added in the three batches was 4:3:3; the stirring speed was 1500 r / min for each batch.

[0200] (3.2) Mix the polyurethane prepolymer, isocyanate, water, silicone oil and catalyst, and stir until homogeneous to obtain component B;

[0201] (3.3) After mixing components A and B, the mixture is foamed, dried, allowed to stand, cut, and polished in sequence to obtain an organic piezoelectric polyurethane polishing pad. The mixture of components A and B contains 25 wt% polyether polyol, 15 wt% PVDF fiber, 25 wt% isocyanate, 1 wt% water, 1.5 wt% silicone oil, and 2.5 wt% catalyst. The foaming temperature is 55℃ and the time is 30 min. The drying temperature is 55℃ and the time is 30 min. The standing temperature is 30℃ and the time is 48 h.

[0202] The final organic piezoelectric polyurethane polishing pad is composed of a polyurethane matrix and PVDF fibers. The polyurethane matrix has a porous structure, and the PVDF fibers are distributed in the polyurethane matrix in a network structure. The PVDF fiber content in the organic piezoelectric polyurethane polishing pad is 23 wt%. The porosity of the organic piezoelectric polyurethane polishing pad is 55%. The removal rate of Si wafers by the organic piezoelectric polyurethane polishing pad during the polishing process is 383.25 nm / min.

[0203] Example 8

[0204] A method for preparing an organic piezoelectric polyurethane polishing pad is basically the same as in Example 7, except that 2,3-dihydrodecafluoropentane is not added in step (2.2).

[0205] The final organic piezoelectric polyurethane polishing pad achieved a Si wafer removal rate of 338.26 nm / min during the polishing process.

[0206] The organic piezoelectric polyurethane polishing pad of Example 7 showed a higher Si wafer removal rate during polishing than that of Example 8. This is because the 2,3-dihydrodecafluoropentane added during the preparation of the spinning solution in Example 7 forms hydrogen bonds with PVDF. On the one hand, fluorine atoms in 2,3-dihydrodecafluoropentane form hydrogen bonds with hydrogen atoms in PVDF; on the other hand, hydrogen atoms in 2,3-dihydrodecafluoropentane form hydrogen bonds with fluorine atoms in PVDF. The hydrogen bonds between 2,3-dihydrodecafluoropentane and β-phase PVDF are closer and more favorable than those between 2,3-dihydrodecafluoropentane and α-phase PVDF. Therefore, during electrospinning, under the action of an applied voltage, the strong hydrogen bond interaction causes the α-phase to transform into the β-phase, thereby increasing the β-phase content of PVDF nanofibers. Since the β-phase structure is the most piezoelectric crystal phase in PVDF material, its crystal structure has lattice units of varying sizes, which can induce the appearance of electric dipole moments. When the β-phase structure in a PVDF crystal is deformed by external force, the lattice unit will be distorted, causing a change in the electric dipole moment, which in turn produces a potential difference and charge separation, resulting in a piezoelectric effect. Therefore, increasing the β-phase content in Example 7 can improve the piezoelectric properties of PVDF, thereby leading to a higher Si wafer removal rate by the organic piezoelectric polyurethane polishing pad during the polishing process.

[0207] Example 9

[0208] A method for preparing an organic piezoelectric polyurethane polishing pad, comprising the following specific steps:

[0209] (1) Preparation of raw materials;

[0210] PVDF: CAS number is 24937-79-9;

[0211] Solvent: A mixture of NMP and acetone in a volume ratio of 6:4;

[0212] 2,3-Dihydrodecafluoropentane;

[0213] Deionized water;

[0214] Polyether polyol: polycarbonate diol, CAS number 29862-10-0;

[0215] Polyurethane prepolymer: Manufacturer is Jinshitou Plastic Raw Materials Business Department, Zhangmutou City, Dongguan, China; Brand name: HKR76010.

[0216] Isocyanate: Diphenylmethane diisocyanate, CAS No. 101-68-8;

[0217] water;

[0218] Silicone oil: Manufacturer is Momentive Advanced Materials Group, USA; Grade: L6900;

[0219] Catalyst: Manufacturer is Momentive Advanced Materials Group, USA; Grade A33;

[0220] (2) Preparation of PVDF fibers;

[0221] (2.1) Mix PVDF and solvent at a mass ratio of 1:8 and heat in a water bath (time: 10h, temperature: 60℃) to obtain matrix mixture;

[0222] (2.2) By weight, 40 parts of matrix mixture, 30 parts of 2,3-dihydrodecafluoropentane and 15 parts of deionized water are stirred and mixed, and then heated in a water bath (30 min, 50 °C) and filtered to obtain filtrate. The filtrate is then placed at 70 °C and evaporated to 1 / 5 of its original volume to obtain spinning solution.

[0223] (2.3) After obtaining a nanofiber membrane by electrospinning the spinning solution, the nanofiber membrane was broken up by a high-speed homogenizer to obtain PVDF fibers with an average length of 4 micrometers. The process parameters of electrospinning were: electrospinner injector angle 60°, receiving distance 15cm, relative humidity 55%, voltage 16kV, and feeding speed 3mL / h.

[0224] (3) Preparation of organic piezoelectric polyurethane polishing pad;

[0225] (3.1) PVDF fibers were added to the polyether polyol in three batches (with stirring during the addition process) and stirred until the PVDF fibers were uniformly dispersed in the polyether polyol to obtain component A; wherein the mass ratio of the PVDF fibers added in the three batches was 4:3:3; the stirring speed was 1500 r / min for each batch.

[0226] (3.2) Mix the polyurethane prepolymer, isocyanate, water, silicone oil and catalyst, and stir until homogeneous to obtain component B;

[0227] (3.3) After mixing components A and B, the mixture is foamed, dried, allowed to stand, cut, and polished in sequence to obtain an organic piezoelectric polyurethane polishing pad. The mixture of components A and B contains 25 wt% polyether polyol, 15 wt% PVDF fiber, 25 wt% isocyanate, 1 wt% water, 1.5 wt% silicone oil, and 2.5 wt% catalyst. The foaming temperature is 55℃ and the time is 30 min. The drying temperature is 60℃ and the time is 30 min. The standing temperature is 30℃ and the time is 48 h.

[0228] The final organic piezoelectric polyurethane polishing pad is composed of a polyurethane matrix and PVDF fibers. The polyurethane matrix has a porous structure, and the PVDF fibers are distributed in the polyurethane matrix in a mesh structure. The PVDF fiber content in the organic piezoelectric polyurethane polishing pad is 22 wt%. The porosity of the organic piezoelectric polyurethane polishing pad is 50%. The removal rate of Si wafers by the organic piezoelectric polyurethane polishing pad during the polishing process is 358.64 nm / min.

Claims

1. A method for preparing an organic piezoelectric polyurethane polishing pad, characterized in that, The organic piezoelectric polyurethane polishing pad comprises a polyurethane matrix and PVDF fibers. The polyurethane matrix has a porous structure, and the PVDF fibers are distributed in the polyurethane matrix in a mesh structure. PVDF fibers are obtained by electrospinning to produce nanofiber membranes, which are then broken down. The spinning solution contains 2,3-dihydrodecafluoropentane. The specific steps are as follows: (1) Add PVDF fibers to the polyether polyol in batches and stir until the PVDF fibers are uniformly dispersed in the polyether polyol to obtain component A; (2) Mix the polyurethane prepolymer, isocyanate, water, silicone oil and catalyst, and stir until homogeneous to obtain component B; (3) After mixing components A and B, foaming, drying, settling, cutting and polishing are carried out in sequence to obtain organic piezoelectric polyurethane polishing pad.

2. The method for preparing an organic piezoelectric polyurethane polishing pad according to claim 1, characterized in that, The average length of PVDF fibers is 2-5 micrometers.

3. The method for preparing an organic piezoelectric polyurethane polishing pad according to claim 1, characterized in that, The preparation process of the spinning solution is as follows: by weight, 40-50 parts of matrix mixture, 15-30 parts of 2,3-dihydrodecafluoropentane and 10-20 parts of deionized water are stirred and mixed, and then heated in a water bath and filtered to obtain filtrate. The filtrate is placed at 70-75℃ and evaporated to 1 / 5 of the original volume to obtain the spinning solution. The preparation process of the matrix mixture is as follows: PVDF is mixed with solvent A or solvent B at a mass ratio of 1:8 and then heated in a water bath to obtain the matrix mixture; Solvent A is DMAc, DMSO, DMF, or NMP; Solvent B is a mixture of solvent A and acetone in a volume ratio of 6:

4.

4. The method for preparing an organic piezoelectric polyurethane polishing pad according to claim 1, characterized in that, The process parameters for electrospinning include: electrospinner injector angle 60°, receiving distance 15cm, relative humidity 50-60%, voltage 14-20kV, and feeding speed 2-3mL / h.

5. The method for preparing an organic piezoelectric polyurethane polishing pad according to claim 1, characterized in that, The PVDF fiber content in the organic piezoelectric polyurethane polishing pad is 22-23 wt%; the porosity of the organic piezoelectric polyurethane polishing pad is 50-60%.

6. The method for preparing an organic piezoelectric polyurethane polishing pad according to claim 1, characterized in that, The organic piezoelectric polyurethane polishing pad achieved a Si wafer removal rate of 338.26-383.25 nm / min during the polishing process.

7. The method for preparing an organic piezoelectric polyurethane polishing pad according to claim 1, characterized in that, The polyether polyol is one or more of sorbitol-based polyether polyol, polypropylene glycol, and polycarbonate diol; the isocyanate is diphenylmethane diisocyanate or hexamethylene diisocyanate. The mixture of components A and B contains 25 wt% polyether polyol, 15 wt% PVDF fiber, 25 wt% isocyanate, 1 wt% water, 1.5 wt% silicone oil, and 2.5 wt% catalyst. The foaming temperature is 55℃ and the time is 30 minutes; the drying temperature is 50-60℃ and the time is 30 minutes; the standing temperature is 25-30℃ and the time is 36-48 hours.

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