JP7650218B2 - Polishing pad and method of manufacturing same - Google Patents

Description

The present invention relates to a polishing pad and a method for manufacturing the same.

Patent Documents 1 to 3 disclose conventional polishing pads. These polishing pads have a base material and abrasive particles. The base material is made of a binder resin and has a plurality of pores formed therein. Examples of the binder resin that can be used include polyvinylidene fluoride, epoxy resin, and PES ( polyethersulfone ). The abrasive particles are made of silica or the like and are held within the base material or the pores.

These polishing pads are manufactured through a mixing process, a molding process, and a pore-forming process. In the mixing process, a paste containing a resin solution in which a binder resin is dissolved in a solvent, abrasive particles, and a pore-forming agent is obtained. In the molding process, a sheet-shaped molded body is obtained from the paste. In the pore-forming process, the molded body undergoes a phase separation process to harden the binder resin and form pores. The front and/or back surface of the intermediate body obtained in the pore-forming process is ground to form a polishing surface for polishing the object to be polished.

The polishing pad obtained in this way is a semi-fixed type polishing pad with abrasive particles, and is used in polishing processes using the CMP (Chemical Mechanical Polishing) method, using a polishing liquid that does not contain abrasive particles or simply water as the polishing liquid.

JP 2011-49256 A JP 2021-61306 A Patent No. 6243009

Incidentally, when polishing a SiC wafer using the CMP method, for example, a rough lapping process is generally performed to adjust the thickness, followed by a finish lapping process. In these polishing processes, it is efficient to use diamond particles, which are harder than other particles, as the abrasive particles.

However, according to the inventors' test results, the above-mentioned conventional polishing pads do not provide sufficient polishing efficiency when polishing SiC wafers.

The present invention was made in consideration of the above-mentioned conventional situation, and the problem to be solved is how to achieve high polishing efficiency while using diamond particles as abrasive particles in a semi-fixed abrasive particle type polishing pad in the polishing process of wafers.

The polishing pad of the present invention comprises a base material made of a binder resin and having a plurality of pores formed therein, and abrasive particles held within the base material or within the pores, and constitutes a polishing surface for polishing an object to be polished,
The pores are composed of pores, continuous pores, and closed pores,
The continuous pores communicate with each other or communicate with the pores having a size of 1 μm or more,
The isolated pores communicate with the pores smaller than 1 μm but do not communicate with the pores equal to or larger than 1 μm,
The abrasive particles include diamond particles and silica particles,
The diamond particles and the silica particles are held in the matrix and in the interconnected pores, but are also held in the closed pores,
The diamond particles have an average particle size of 5 to 10 μm;
The silica particles have an average particle size of 0.2 μm,
The diamond particles are contained in an amount of 6 vol % or more, and the silica particles are contained in an amount of 6 vol % or more,
The effective number of particles X (X=S×N), calculated by multiplying the total area S occupied by the independent pores in a cross section parallel to the polishing surface by the number N of the diamond particles per unit area, satisfies 0.5≦X.

The inventors have thoroughly investigated why sufficient polishing efficiency cannot be obtained in the polishing process of wafers even when diamond particles are held within the pores of the base material of a semi-fixed abrasive particle polishing pad. They came to the conclusion that many diamond particles fall off from the base material during the polishing process, and that there is a shortage of diamond particles that actually contribute to the polishing process.

The aim was therefore to improve the retention of diamond particles in the base material during polishing. The researchers believed that the pore structure of the base material was important for this purpose, and came up with the idea of forming independent pores in the base material and retaining diamond particles within the independent pores. When a test was conducted using the polishing pad thus obtained to polish a wafer, it was demonstrated that sufficient polishing efficiency could be obtained. Based on these findings, the present invention was completed.

The polishing pad of the present invention contains diamond particles, which are harder than other particles, as abrasive particles. In addition, independent pores are formed in the base material, and diamond particles are held within the independent pores. An independent pore refers to a pore that exists independently in the base material or does not communicate with pores of a certain diameter or more. There is a term called continuous pores as opposed to independent pores, but continuous pores refer to pores that communicate with each other or with pores of a certain diameter or more. Pores are inevitably generated when replacing the solvent in the molded body during the manufacture of the polishing pad. In the present invention, according to the confirmation of the inventors, an independent pore refers to a pore that does not communicate with pores of 1 μm or more. The pores of the above-mentioned conventional polishing pad are continuous pores that communicate with each other or with pores of 1 μm or more, and are different from the independent pores in the polishing pad of the present invention.

According to the inventors' test results, the polishing pad of the present invention can improve the polishing efficiency when polishing, for example, a SiC wafer as the polished object. This is believed to be because the retention of diamond particles in the base material during polishing is improved, ensuring a sufficient number of diamond particles that can actually contribute to the polishing process. It is believed that the reason for the improved retention of diamond particles is that, since independent pores are formed by nucleation and growth-type phase separation, the concentration gradient is steeper than when continuous pores are formed, and the side walls are thicker than those of continuous pores, making it easier for diamond particles to be held within the independent pores.

Therefore, the polishing pad of the present invention can achieve high polishing efficiency in wafer polishing while using diamond particles as the abrasive particles of a semi-fixed abrasive pad.

The method for producing the polishing pad of the present invention is a method for producing the polishing pad of the present invention,
a mixing step of obtaining a resin solution in which the binder resin is dissolved in a solvent, the abrasive particles, and a paste containing a pore-forming agent so that a nucleation-growth type phase separation process occurs;
A molding step of obtaining a sheet-shaped body from the paste;
and a pore forming step of subjecting the molded body to the phase separation process, curing the binder resin, and forming the independent pores.
When the abrasive particles contain silica particles, the paste contains, excluding diamond particles, 25 to 30 vol. % binder resin, 0 to 10 vol. % silica particles, and 60 to 75 vol. % solvent, and is characterized in that the volume ratio of silica particles to binder resin is 0.4 or less.

In the mixing process, the volume ratio of each component of the binder resin, the solvent, and the abrasive particles is appropriately adjusted so that a nucleation growth type phase separation process occurs in the pore formation process. This causes a nucleation growth type phase separation process in the pore formation process. If nucleation growth type phase separation occurs, unlike the spinodal decomposition type phase separation process, a large number of spherical and isolated solvent rich phases are dispersed in the resin rich phase. These solvent rich phases are irregular in size and relative position, and the concentration gradient at the interface between the solvent rich phase and the resin rich phase is steep. Then, by removing the solvent and hardening the binder resin, a plurality of independent pores of irregular size and irregularly distributed can be formed in the base material. The solvent in the independent pores is discharged from the pores to the outside of the base material through continuous pores in some cases. In the base material obtained in this way, the abrasive particles are held in the base material or in the pores. And diamond particles as abrasive particles are easily held in the independent pores formed in the base material.

According to the inventors' test results, by making such a paste, the pore structure of the base material can be made to have multiple independent pores of appropriate size.

According to the present invention, it is possible to achieve high polishing efficiency in wafer polishing processing while using diamond particles as the abrasive particles of a semi-fixed abrasive particle polishing pad.

FIG. 1 is an enlarged cross-sectional view showing the polishing pads of Examples 1 to 9, which is a schematic diagram of an intermediate product after a pore forming step. FIG. 2 is an enlarged cross-sectional view showing the polishing pads of Examples 1 to 9 after the cutting process. FIG. 3 is a 1000-times magnified SEM photograph of the cross section parallel to the polishing surface of the polishing pad of Example 1. FIG. 4 is a 1000x SEM photograph of the cross section parallel to the polishing surface of the polishing pad of Example 2. FIG. 5 is a SEM photograph of the polishing pad of Example 3, taken at 2000 times, of a cross section parallel to the polishing surface. FIG. 6 is a 1000-times magnified SEM photograph of a cross section parallel to the polishing surface of the polishing pad of Example 4. FIG. 7 is a 1000-times magnified SEM photograph of the cross section parallel to the polishing surface of the polishing pad of Example 5. FIG. 8 is a 1000x SEM photograph of the cross section parallel to the polishing surface of the polishing pad of Example 6. FIG. 9 is a 1000-times magnified SEM photograph of the cross section parallel to the polishing surface of the polishing pad of Example 7. FIG. 10 is a 1000-times magnified SEM photograph of the cross section parallel to the polishing surface of the polishing pad of Example 8. FIG. 11 is a 1000-times magnification SEM photograph of a cross section parallel to the polishing surface of the polishing pad of Example 9. FIG. 12 is a 700x SEM photograph of the cross section parallel to the polishing surface of the polishing pad of Comparative Example 1. FIG. 13 is a 1000-times magnified SEM photograph of a cross section parallel to the polishing surface of the polishing pad of Comparative Example 2. FIG. 14 is a graph showing the results of examining the polishing efficiency (processing rate) for each of the polishing pads of Examples 1 and 3 to 7 and Comparative Examples 1 and 2. FIG. 15 is a graph showing the relationship between the number of effective action particles N and the polishing efficiency (processing rate) for each of the polishing pads of Examples 1, 3 to 7, and Comparative Example 1. FIG. 16 is a 2000-times magnified SEM photograph of the cross section of the polishing pad of sample A parallel to the polishing surface. FIG. 17 is a 2000-times magnification SEM photograph of the cross section of the polishing pad of sample B parallel to the polishing surface. FIG. 18 is a SEM photograph of the polishing pad of sample C, taken at 2000 times magnification, of a cross section parallel to the polishing surface. FIG. 19 is a 2000-times magnification SEM photograph of the cross section parallel to the polishing surface of the polishing pad of sample D. FIG. 20 is a 2000-times magnification SEM photograph of the cross section parallel to the polishing surface of the polishing pad of sample E. FIG. 21 is a SEM photograph of the polishing pad of sample F, taken at 2000 times, of a cross section parallel to the polishing surface. FIG. 22 is a SEM photograph of the polishing pad of sample G, taken at 2000 times, of a cross section parallel to the polishing surface. FIG. 23 is a SEM photograph of the polishing pad of sample H, taken at 2000 times magnification, of a cross section parallel to the polishing surface. FIG. 24 is a 2000-times magnification SEM photograph of a cross section parallel to the polishing surface of the polishing pad of Sample I. FIG. 25 is a graph showing the relationship between the composition ratio of the solvent, binder resin, and silica particles in the paste and the pore structure.

The pore diameter of the independent pores can be about 1 to 100 μm, and is preferably about 2 to 20 μm. The average pore diameter of the independent pores is preferably 5 to 10 μm, and more preferably 7.5 to 8.5 μm. If the average pore diameter of the independent pores is too small, it becomes difficult to hold diamond particles in the independent pores. If the average pore diameter of the independent pores is too large, it becomes difficult to maintain the rigidity of the base material. The pores formed in the base material may include continuous pores.

The number of effective particles, as shown below, can be considered as an index for evaluating the retention of diamond particles in the base material during polishing. This number of effective particles is the product of the S value and the N value (X = S x N), where S is the total area occupied by the independent pores in a cross section parallel to the polishing surface, and N is the number of diamond particles per unit area.

According to the test results of the inventors, from the viewpoint of improving the retention of diamond particles on the base material during polishing, the value of the effective particle number X is preferably 0.5≦X, more preferably 2.3 ≦X, and particularly preferably 15.9 ≦X.

The pore diameter of the independent pores can be measured by binarizing an SEM photograph of a cross section parallel to the polished surface using an image analyzer, and recognizing, for example, a black area surrounded by connected white areas in the binarized image as a single particle.

Polyethersulfone (PES ) can be used as the binder resin constituting the base material .

The diamond particles may be held within the matrix or within interconnected pores, but are held within closed pores. The diamond particles may be single crystal diamond, polycrystalline diamond, or pseudo-polycrystalline diamond.

The average particle size of the diamond particles can be about 1 to 20 μm, preferably 3 to 15 μm, and more preferably 5 to 10 μm. If the average particle size of the diamond particles is too large, they will tend to fall off and will tend to scratch the workpiece being polished. If the average particle size of the diamond particles is too small, it will be difficult to achieve sufficient polishing efficiency.

The polishing pad of the present invention may contain abrasive particles other than diamond particles. Examples of abrasive particles other than diamond particles include silica particles, ceria particles, alumina particles, zirconia particles, titania particles, manganese oxide particles, barium carbonate particles, chromium oxide particles, iron oxide particles, etc. These may be used alone or in a mixture of two or more types.

The abrasive particles preferably contain silica particles or ceria particles in addition to diamond particles. According to the inventors' test results, when a polishing pad is manufactured using silica particles or ceria particles together with diamond particles as abrasive particles, the viscosity of the paste increases and independent pores are more likely to form. Furthermore, since silica particles and ceria particles are softer than diamond particles, they can exert a buffering effect and a lubricating effect. Furthermore, ceria particles can be expected to have a chemical polishing effect. For this reason, it is expected that scratches caused by diamond particles on the polished object will be suppressed.

According to the inventors' test results, it is preferable that the polishing pad of the present invention contains 6 vol% or more of diamond particles and 6 vol% or more of silica particles. In this case, sufficient polishing efficiency can be obtained in polishing SiC wafers, and a polishing pad that can suppress scratches caused by diamond particles can be easily manufactured.

The average particle size of abrasive particles other than diamond particles, such as silica particles and ceria particles, can be about 0.05 to 0.5 μm, preferably 0.1 to 0.3 μm, and more preferably 0.15 to 0.25 μm. If the average particle size of abrasive particles other than diamond particles is too large or too small, it becomes difficult to appropriately adjust the viscosity of the paste containing the resin solution and abrasive particles.

According to the inventors' test results, it is preferable that the diamond particles have an average particle size of 5 to 10 μm, and that the silica particles or ceria particles have an average particle size of 0.2 μm. In this case, the viscosity of the paste containing the resin solution and the abrasive particles can be appropriately adjusted, making it easier to form independent pores. In addition, the cushioning and lubricating effects make it easier to prevent scratches caused by the diamond particles on the workpiece being polished.

The volume ratio of each component in the polishing pad of the present invention is preferably 24 to 43 vol% of binder resin, 9 to 23 vol% of abrasive particles including diamond particles, and 35 to 64 vol% of pores, when the entire polishing pad is taken as 100 vol%. When silica particles or ceria particles are included as abrasive particles, the volume ratio of each component is preferably 24 to 43 vol% of binder resin, 6 to 14 vol% of diamond particles, 6 to 14 vol% of silica particles or ceria particles, and 35 to 64 vol% of pores, when the entire polishing pad is taken as 100 vol%.

In the mixing step of the method for manufacturing the polishing pad of the present invention, when the abrasive particles contain silica particles, it is preferable that the paste, excluding the diamond particles, contains 25 to 30 vol% binder resin, 0 to 10 vol% silica particles, and 60 to 75 vol% solvent, and that the volume ratio of silica particles to binder resin is 0.4 or less. In this way, an appropriate closed pore structure can be formed in the base material.

The solvent may be anything that dissolves the binder resin that constitutes the base material, and examples of the solvent that can be used include N-methyl-2-pyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, and dimethylsulfoxide.

The pore former is added to adjust the pore structure formed in the base material. When an oil-based solvent is used, a water-soluble pore former can be used. Examples of water-soluble pore formers that can be used include powdered sugar made by grinding granulated sugar into a powder, cornstarch, etc.

Additives may be added to the paste as necessary, such as glycerin for adjusting the solubility of the binder resin in the solvent.

There are no particular limitations on the molding process, and the material is molded into a sheet-like molded body using a molding device such as a T-die. This molding method is not limited to this as long as it can achieve a uniform thickness to a certain extent.

In the pore formation process, for example, the molded body is immersed in a water tank whose water temperature is adjusted to 10°C or less for a specified period of time to cause a nucleation-growth type phase separation process. This results in numerous isolated, spherical solvent-rich phases that are irregular in size and relative positioning being dispersed in the resin-rich phase. During this process, the solvent in the solvent-rich phase is replaced by water due to the difference in specific gravity.

In this way, when an oil-based solvent is used in the pore formation process, an aqueous liquid such as tap water is used as the replacement liquid, and the molded body is immersed in the replacement liquid to disperse the solvent-rich phase in the resin-rich phase through a nucleation and growth type phase separation process, and at the same time, the solvent in the solvent-rich phase is replaced with the replacement liquid to remove the solvent from the molded body. At this time, each isolated solvent-rich phase is connected to the outside of the molded body through the pores formed in the resin-rich phase, and the solvent is replaced with the replacement liquid through the pores. When the solvent is removed from the molded body in this way, the resin-rich phase shrinks and hardens, and minute continuous pores are formed in the resin-rich phase. In addition, by using an aqueous liquid such as tap water as the replacement liquid and immersing the molded body in the replacement liquid, the water-soluble pore-forming agent can also be removed at the same time.

The molded body from which the solvent and pore-forming agent have been removed undergoes a drying process to become an intermediate body. The front and/or back surface of the intermediate body is cut to form an abrasive surface, which becomes the polishing pad of the present invention.

(Test 1)
<Preparation process>
The following binder resin, abrasive particles, solvent, pore former and additives were prepared.

(Binder resin)
PES (Polyethersulfone)
(Abrasive particles)
Diamond particles (average particle size: 5 μm, 10 μm)
Silica particles ( _SiO2 ) particles (average particle size: 0.2 μm)
Ceria particles ( _CeO2 ) particles (average particle size: 0.2 μm)
(solvent)
N-Methyl-2-pyrrolidone (pore former)
Granulated sugar powder (additive)
Glycerin

<Mixing step>
The binder resin, abrasive particles, solvent, pore-forming agent, and additive components were mixed in the mixing ratio (parts by mass) shown in Table 1 to obtain a paste. At this time, the volume ratio of the binder resin and the solvent was appropriately adjusted so that a nucleation-growth type phase separation process occurs in the pore-forming process. The viscosity (Pa·s) of the obtained paste at 40°C was measured using a parallel plate vibration rheometer in accordance with JIS K 7244-10. The results are also shown in Table 1. In addition, in the obtained paste, the volume ratio of the binder resin and the solvent was appropriately adjusted so that a nucleation-growth type phase separation process occurs in the pore-forming process.

<Molding process>
Each of the obtained pastes was used to obtain a sheet-like molded body using a T-die.

<Pore formation process, drying process>
The molded body was immersed for a predetermined period of time in tap water stored in a water tank and adjusted to a temperature of 10° C. or less. This caused a nucleation-growth type phase separation process to occur in the molded body, dispersing a large number of isolated spherical solvent-rich phases in the resin-rich phase, and replacing the solvent in the molded body with tap water to remove the solvent and pore-forming agent from the molded body.

The obtained intermediate 10 was left in the air at room temperature for about two days to remove moisture from the intermediate 10. A schematic cross-sectional view of the intermediate 10 of Examples 1 to 9 is shown in Figure 1.

Each intermediate 10 has a base material 20 and abrasive particles 30. The base material 20 is made of resin and has a plurality of independent pores 20a, a plurality of continuous pores (not shown), and pores (not shown). The independent pores 20a are pores that communicate with pores smaller than 1 μm, but do not communicate with pores of 1 μm or more. The continuous pores are pores that communicate with each other or with pores of 1 μm or more. The pores are pores other than the independent pores 20a and the continuous pores.

The abrasive particles 30 are diamond particles 30a and silica particles (or ceria particles) 30b. The diamond particles 30a and silica particles (or ceria particles) 30b are held within the matrix 20 and the continuous pores, but are also held within the independent pores 20a.

The surface of each intermediate body 10 is ground to form a polishing surface 40a for polishing an object to be polished, as shown in Fig. 2. In this manner, a polishing pad 40 is obtained. Each polishing pad 40 is also made of a binder resin and has a base material 20 in which a plurality of pores 20a and the like are formed, and abrasive particles 30 held within the base material 20 or within the pores including the independent pores 20a. Each polishing pad 40 is in the shape of a disk having a diameter of 300 mm and a thickness of 2 mm.

The volume ratio (vol %) of each component, density (g/cm ³ ) and durometer hardness (Shore D) of each polishing pad were measured. The results are shown in Table 2.

Figures 3 to 13 show SEM photographs of the cross section parallel to the polishing surface 40a of each polishing pad 40. As is clear from Figures 3 to 11, the polishing pads 40 of Examples 1 to 9 have an independent pore structure, and diamond particles 30a as abrasive particles 30 are held within the numerous independent pores 20a.

On the other hand, as shown in Figures 12 and 13, in the polishing pads 40 of Comparative Examples 1 and 2, no independent pore structure is formed, meaning that the base material does not have independent pores, but only continuous pores and fine pores.

For each of the polishing pads 40 of Examples 1, 3 to 7 and Comparative Examples 1 and 2, a SiC wafer was polished using a wafer polishing test device under the following processing test conditions to examine the polishing efficiency (processing rate) (μm/min).

<Test conditions>
Testing machine: Wafer polishing machine (Engis EJW-380)
Workpiece (object to be polished): SiC wafer (4 inches)
Polishing liquid: Water Polishing liquid amount: 10 ml/min Processing pressure: 20 kPa
Platen/workpiece rotation speed: 60/60 rpm

The results are shown in Figure 14. As is clear from Figure 14, the polishing pads 40 of Examples 1 and 3 to 7 all had a higher processing rate than the polishing pad 40 of Comparative Example 1. This is thought to be because the diamond particles 30a were well retained within the independent pores 20a, improving the retention of the diamond particles 30a in the base material 20 during polishing, and as a result, a sufficient amount of diamond particles 30a were able to contribute to the polishing process.

The reason why the processing rate of the polishing pad of Comparative Example 2 was improved compared to that of Comparative Example 1 is that the particle diameter of the diamond particles 30a in Comparative Example 1 was 10 μm, while the particle diameter of the diamond particles 30a in Comparative Example 2 was 5 μm. Therefore, the number of diamond particles 30a contained in the polishing pad of Comparative Example 2 was four times that of Comparative Example 1, and the number of diamond particles 30a that came into contact with the workpiece during processing increased.

(Test 2)
The retention of diamond particles 30a was evaluated for each polishing pad 40 of Examples 1 to 9 and Comparative Examples 1 and 2. That is, for each polishing pad 40 of Examples 1 to 9 and Comparative Examples 1 and 2, the SEM photograph of the cross section parallel to the polishing surface 40a was binarized by an image analyzer, and the total area S (μm ² ) occupied by the independent pores was calculated. In addition, the number N (count/μm ² ) of diamond particles 30a per unit area in the cross section parallel to the polishing surface 30a was calculated. The X (X=S×N) (count) value obtained by integrating the S value and the N value was taken as the effective number of particles. The results are shown in Table 3.

表３においては、有効作用粒子数Ｘについて、Ｘ＜０．５を×、０．５≦Ｘ＜２．０を△、２．０≦Ｘ＜１５を○、１５≦Ｘを◎と評価した。表３及び図１４から明らかなように、有効作用粒子数Ｘが他より大きな実施例７の研磨パッド４０は、他の研磨パッド４０と比べて加工レートが大きく向上していることがわかる。

In Table 3, the number of effective action particles X was evaluated as follows: X<0.5 is x, 0.5≦X<2.0 is △, 2.0≦X<15 is ◯, and 15≦X is ◎. As is clear from Table 3 and Fig. 14, the polishing pad 40 of Example 7, which has a larger number of effective action particles X than the others, has a significantly improved processing rate compared to the other polishing pads 40.

(Test 3)
The relationship between the number of effective particles X and the processing rate was investigated for each polishing pad 40 of Examples 1, 3 to 7, and Comparative Example 1. The results are shown in Figure 15. As is clear from Figure 15, it was recognized that there is an approximately proportional relationship between the number of effective particles X and the processing rate.

(Test 4)
As shown in Table 4, in the mixing step, the pastes were prepared by varying the compositions of the binder resin, silica particles, and solvent. In other words, each paste did not contain diamond particles. From each paste, polishing pads of samples A to I were obtained.

Figures 16 to 24 show SEM photographs of cross sections parallel to the polishing surface of the polishing pads of samples A to I. Table 4 and Figure 25 show the relationship between the composition ratio of the binder resin, silica particles, and solvent in the paste and the pore structure. Table 4 also shows the volume ratio of silica particles to the binder resin. In Figure 25, the pore structure of the base material was evaluated as follows: a mesh structure with no independent pores was marked with an X; a structure with independent pores but only tiny independent pores smaller than the diamond particles was marked with a △; and a good independent pore structure with many independent pores larger than the diamond particles was marked with an O.

As is clear from Table 4 and Figure 25, each paste contains 25-30 vol% binder resin, 0-10 vol% silica particles, and 60-75 vol% solvent, and the volume ratio of silica particles to binder resin is 0.4 or less, a good closed pore structure is obtained.

Although the present invention has been described above with reference to Tests 1 to 4, it goes without saying that the present invention is not limited to the above test examples, and can be modified as appropriate without departing from the spirit of the present invention.

The present invention can be used in semiconductor device manufacturing equipment.

20a... Independent pores 20... Base material 30... Abrasive particles 30a... Diamond particles 30b... Silica particles (or ceria particles)
40a...polishing surface 40...polishing pad

Claims (5)

A polishing pad having a base material made of a binder resin and having a plurality of pores formed therein, and abrasive particles held within the base material or within the pores, and constituting a polishing surface for polishing an object to be polished, comprising:
The binder resin is polyethersulfone,
The pores are composed of pores, continuous pores, and closed pores,
The continuous pores communicate with each other or communicate with the pores having a size of 1 μm or more,
The isolated pores communicate with the pores smaller than 1 μm but do not communicate with the pores equal to or larger than 1 μm,
The abrasive particles include diamond particles and silica particles,
The diamond particles and the silica particles are held in the matrix and in the interconnected pores, but are also held in the closed pores,
The diamond particles have an average particle size of 5 to 10 μm;
The silica particles have an average particle size of 0.2 μm,
The diamond particles are contained in an amount of 6 vol % or more, and the silica particles are contained in an amount of 6 vol % or more,
A polishing pad characterized in that the effective number of particles X (X = S x N) obtained by multiplying the total area S occupied by the independent pores in a cross section parallel to the polishing surface by the number of diamond particles N per unit area satisfies 0.5 ≦ X. The polishing pad according to claim 1, wherein the number of effective particles X satisfies 2.3≦X. The polishing pad according to claim 2, wherein the number of effective particles X satisfies 15.9≦X. A method for producing the polishing pad of any one of claims 1 to 3, comprising the steps of:
a mixing step of obtaining a resin solution in which the binder resin is dissolved in a solvent, the abrasive particles, and a paste containing a pore-forming agent so that a nucleation-growth type phase separation process occurs;
A molding step of obtaining a sheet-shaped body from the paste;
a pore forming step of subjecting the molded body to the phase separation process, curing the binder resin and forming the independent pores,
The abrasive particles include silica particles,
The paste contains, excluding the diamond particles, 25 to 30 vol% of the binder resin, 0 to 10 vol% of the silica particles, and 60 to 75 vol% of the solvent, and the volume ratio of the silica particles to the binder resin is 0.4 or less. The solvent is N-methyl-2-pyrrolidone,
5. The method for producing a polishing pad according to claim 4, wherein the pore-forming agent is granulated sugar.

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