JP2001088013A - Polishing pad - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polishing pad, wherein a layer to be in direct contact with a polished surface of a wafer has a plurality of independent hollows, a uniform pressure over the whole wafer surface is given, high polishing accuracy for the wafer surface is assured, abrasive grains of sufficient density is kept, a high surface porous density and improved efficiency of polishing speed are obtained, reduction of time required for dressing and reduction of dressing frequency are attained, and there is no neccessity of providing a cushion layer on a rear surface suitable for the polishing pad requiring high flat accuracy of thickness and shape. SOLUTION: This is a polishing pad made of synthetic resin whose Shore hardness is not less than 50, compression ratio is 1.3-5.5% and compression recovery rate is not less than 50%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to optical materials such as lenses and reflection mirrors, silicon wafers, glass substrates for hard disks, resin plates for information recording and ceramic plates, etc., which require high surface flatness. The present invention relates to a polishing pad that performs a flattening process at a stable and high polishing rate. The polishing pad of the present invention is preferably used particularly in a step of flattening a silicon wafer and a device having an oxide layer, a metal layer, etc. formed thereon, before laminating and forming these layers. is there.

[0002]

2. Description of the Related Art Semiconductor integrated circuits (ICs, LSIs) are typically used as materials requiring high surface flatness.
And a disk of single-crystal silicon called a silicon wafer. Silicon wafer, IC, LS
In a manufacturing process such as I, in order to form a reliable semiconductor junction of various thin films used for forming a circuit, it is required to finish the surface with high precision and flatness in each thin film forming process.

Generally, a polishing pad is fixed to a rotatable support disk called a platen, and a semiconductor wafer is fixed to a disk called a polishing head capable of revolving around itself. The relative rotation between the platen and the polishing head is generated by the two rotational motions, and a polishing slurry in which fine particles (abrasive grains) are suspended in a gap between the polishing pad and the wafer is added, so that polishing, A flattening process is performed. At this time, as the polishing pad moves over the wafer surface, the abrasive grains are pressed onto the wafer surface at the contact points. Therefore, the working surface is polished by a sliding dynamic frictional action between the wafer surface and the abrasive grains. Such polishing is usually called CPM polishing.

The polishing operation in the CMP polishing step is performed by holding abrasive grains in a slurry in which fine particles (abrasive grains) are suspended on a polishing pad to be used. Therefore, the polishing rate increases as the holding density of the abrasive grains on the polishing pad increases. For this reason, a porous material having a large number of holes is usually used as a polishing pad, and by holding the abrasive particles in the holes, it is possible to increase the holding density of the abrasive particles and increase the polishing rate. Have been done. In such a porous material, it is effective to increase the number of holes and reduce the diameter of the holes in order to increase the holding density of the abrasive grains.

Conventionally, a polyurethane foam sheet having a porosity of about 30 to 35% is generally used as a polishing pad used for the above-mentioned high precision polishing. Also,
The technique described in Japanese Patent Publication No. Hei 8-500622, which discloses a polishing pad in which hollow microspheres or a water-soluble polymer powder or the like is dispersed in a matrix resin such as polyurethane, is also known.

[0006]

However, a polishing pad using a conventional polyurethane sheet has the following problems.

(1) The above-mentioned polyurethane foam sheet used for the conventional CPM polishing has an excellent local flattening ability, but has a compression ratio of about 0.5 to 1.0%. Therefore, it is difficult to apply a uniform pressure to the entire surface of the wafer due to insufficient cushioning property. In order to obtain a sufficient cushioning property, it is necessary to increase the porosity to reduce the compression ratio of the polyurethane foam sheet to about 2%, and when the porosity is increased, the compression recovery rate and the surface hardness may decrease. Inevitable. When the compression recovery rate and the surface hardness decrease, the polishing pad is densified by repetition of compression and release of the load in the polishing step, and a problem occurs in that the processing accuracy is reduced. In order to prevent such a decrease in polishing accuracy, a soft cushion layer is usually separately provided on the back surface of the polyurethane foam sheet, and polishing is performed. Therefore, the flattening ability of the polyurethane foam sheet on the wafer surface is substantially reduced, and there is a limit in improving the processing accuracy.

(2) The polyurethane foam must be closed-cell because the polishing pad needs to surface pores by dressing when clogging occurs as described later. Closed cell polyurethane foam is generally a mixture of a polyisocyanate compound and a polyhydroxy compound in the presence of a foaming agent, injection molding in a mold and polymerization to form a block-shaped foam. is there.
Since the foam produced in this way is formed by the vaporization and expansion of the foam, the pores, that is, the bubbles, are spherical, and it is extremely difficult to reduce the pore diameter to 100 μm or less on average. Difficult, 50μ even if measured individually
m is the minimum. For this reason, the holding density of the abrasive grains is not sufficient.

(3) When a polishing operation is performed using a polishing slurry, polishing dust or deteriorated abrasive grains clog the pores,
The polishing rate is reduced, and the flat surface to be polished may be scratched (scratched), thereby deteriorating the processing characteristics. Moreover,
When the micropores become clogged, it is extremely difficult to completely excavate processing waste and the like to return to the initial state. Therefore,
Using a diamond grindstone or the like, dressing is performed to scrape the surface of the pad, and as in the initial state, a work of exposing the surface where the holes are exposed and reusing is performed. However, since the pores of the current polyurethane foam are spherical and the pore diameter is about 100 μm on average, in order to stably bring out the surface in the initial state, the surface structure must be uniform, The cross-sectional structure must be uniform, and at least a portion corresponding to the hole diameter needs to be removed by dressing. Since surface polishing by dressing can be performed only by a small thickness, when the polyurethane foam is dressed with a diamond grindstone, the time required for shaving 100 μm is as follows.
~ 2 hours are required. During this time, the wafer cannot be polished, and it is required to reduce the time required for dressing and to reduce the frequency of dressing in order to increase the wafer throughput.

(4) In order to increase the accuracy of the flatness of the surface to be polished, the thickness accuracy and the shape accuracy of the polishing pad are important. Conventional polyurethane foam sheet
The foam block obtained as described above is obtained by slicing and cutting the foam block to a thickness of about 1 to 2 mm using a band saw or the like. The thickness accuracy of the urethane sheet thus obtained is 3σ. And about 5 to 6%, which is insufficient as the precision required for a polishing pad that requires high precision flatness.

According to the technique described in Japanese Patent Application Laid-Open No. Hei 8-500622, only an example using hollow microspheres is disclosed as a polishing sheet having holes (Example 1). The pores are spherical and the pore diameter is 100
It has a spherical shape of about μm and has the same problems (1) to (4) as the above-mentioned polyurethane foam.

An image obtained by a scanning electron microscope of a typical commercially available polishing pad (IC-1000 manufactured by Rodale) was subjected to counting the number of holes using an image processing apparatus V-10 (manufactured by Toyobo Co., Ltd.). , The pore density on the surface is about 1100
Pieces / mm ² , and it is required to increase the number to increase the polishing rate.

[0013] It is an object of the present invention that the layer directly in contact with the processing surface of the wafer has a large number of independent cavities and has appropriate hardness, compressibility, and compression recovery, and
An object of the present invention is to provide a polishing pad that solves the problem (4) and satisfies the demand and does not need to provide a cushion layer on the back surface.

[0014]

The present invention relates to a polishing pad made of synthetic resin, which has a Shore D hardness of 50 or more, a compressibility of 1.3 to 5.5%, and a compression recovery rate of 50% or more. It is characterized by having.

The polishing pad having the above structure does not require the provision of a cushion layer, and as a result, can perform high-precision polishing without impairing the flattening ability inherent to the polishing layer.
That is, the processing accuracy is improved both locally and as a whole.

When the Shore D hardness is less than 50, the hardness is too low, and when the compression ratio is less than 1.3, the compression and the release of the load in the polishing step are repeated, whereby the polishing pad is densified and the processing accuracy is reduced. However, if it exceeds 5.5%, there arises a problem that planarization accuracy is reduced. Even if the compression recovery rate is less than 50%, consolidation still occurs, which is not preferable.

The compression ratio is more preferably 1.5 to 4.0.
%, Particularly preferably 1.8 to 2.5%. The synthetic resin is preferably a thermoplastic resin, particularly a high-rigidity thermoplastic resin. Higher compression recovery rate, ie 100%
It is better to be close to

The compression ratio and the compression recovery ratio are represented by the following equations. Compression rate (%) = 100 (T ₁ −T ₂ ) / T ₁ Compression recovery rate (%) = 100 (T ₃ −T ₂ ) / (T ₁ −T
₂₎ T ₁ ~T ₃ herein, using a cylindrical indenter having a diameter of 5 mm, T _1: the sheet when the load stress of 300 g / cm ² over a period of 60 seconds from the unloaded condition Thickness T _2: 1800 g / cm ² over 60 seconds from the state of T ₁
T ₃ : The thickness of the sheet when the stress of 300 g / cm ² is maintained for 60 seconds from the state of T ₂ for 60 seconds after the state of T ₂ , and the thickness of the sheet is maintained at the stress of 300 g / cm ² for 60 seconds. .

The polishing pad of the present invention is preferably a cavity-containing thermoplastic resin containing a large number of independent cavities inside.

With the above configuration, the hardness, compression ratio, and compression recovery ratio of the present invention can be easily achieved.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION As the synthetic resin constituting the polishing pad of the present invention, a thermoplastic resin having high rigidity, that is, a high compression elastic modulus is preferably used as described above. Specifically, polyethylene terephthalate (PET) is used. ) And other polyester resins, polypropylene (PP), polyethylene (PE),
Examples thereof include polyamide (PA).

As a means for forming a large number of cavities in the synthetic resin, a method of mixing an incompatible thermoplastic resin with a synthetic resin (matrix resin) and forming the incompatible thermoplastic resin as a core is preferable. is there.

When PET is used as the matrix resin constituting the polishing pad, the incompatible thermoplastic resin is
It is preferable that the resin contains at least one or more of a polystyrene resin, a polymethylpentene resin, and a polypropylene resin.

By using the above-mentioned incompatible thermoplastic resin as a thermoplastic resin which is not compatible with polyester, a void-containing polyester having a small pore diameter and a flat shape and a high surface pore density is obtained. A system sheet layer can be obtained. The term “surface” includes a surface newly obtained from the inside of the sheet, which is obtained by dressing.

When PP or PE is used as the matrix resin constituting the polishing pad, a cross-linkable polymethyl methacrylate is exemplified as a suitable incompatible thermoplastic resin.

It is preferable to use a polyester resin as a matrix resin constituting the polishing pad and use a resin in which a polystyrene resin and a specific polyolefin resin are mixed at a specific weight ratio as the incompatible thermoplastic resin. It is an aspect. Specifically, the polishing pad contains a polystyrene resin, a polymethylpentene resin, and a polypropylene resin, and the content of the polystyrene resin in the polishing pad constituting resin is a (wt%), and the content of the polymethylpentene resin is b (wt%) and the content of the polypropylene-based resin is c (wt%): 0.01 ≦ a / (b + c) ≦ 1 c / b ≦ 13 ≦ a + b + c ≦ 50 Is preferred.

When the amount of the polystyrene resin or the polymethylpentene resin used is so large that the above range is not satisfied, the incompatible thermoplastic resin tends to be coarsely dispersed and the polishing pad surface has unevenness. In the case where the heat generation occurs and the amount of the incompatible thermoplastic resin is too small to satisfy the above range, the above unevenness is improved, but there is a limit in increasing the void content of the sheet.

The shape of the polishing pad of the present invention is selected depending on the apparatus to be used and may be any of a square, a rectangle, a polygon, a circle, etc., but is preferably a circle.

It is also a preferred embodiment to provide a continuous groove on the polishing surface of the polishing pad of the present invention, that is, the surface of the independent hollow polyester sheet, which is open at the end face of the polishing pad. These grooves are effective for discharging, from the polishing surface, those that may damage the polishing surface, such as polishing dust generated by polishing. Groove depth is 0.1mm ~ 0.5mm
Degree is preferred, and 1 to the independent hollow polyester sheet surface
Preferably, they are formed at intervals of about 5 mm.
The cross-sectional shape of the groove is not particularly limited, such as an arc shape or a triangular shape.

In order to obtain the same effect as the above-described groove, it is also a preferable embodiment to provide a through-hole in the void-containing polyester sheet by a punching method or the like. The size and arrangement pitch of the through holes are not particularly limited, but the through hole diameter is preferably about 0.5 mm to 5 mm, and the distance between adjacent holes is 1.2 mm to
It is preferably 12 mm. If the diameter of the through hole is too large, the polishing effect is reduced, and the strength of the polyester sheet is also reduced. If the diameter is too small, the effect of the through hole is not sufficiently exhibited. If the distance between the adjacent holes is too small, the strength of the polyester sheet is reduced. If the distance is too large, the density of the through holes becomes too small and the effect cannot be sufficiently obtained.

When performing a polishing operation using the polishing pad of the present invention, it is a preferable embodiment to use a known auxiliary agent, for example, a lubricant or an abrasive, and specifically, alumina, ceria, silica, etc. And a slurry in which these are dispersed or suspended in water or a liquid organic compound.

In the following, a void-containing polyester film particularly suitable as the polishing pad of the present invention will be described.
Further specific characteristics and a method of manufacturing the same will be described. The void-containing polyester film preferably has a fine void ratio of 10% by volume or more, more preferably 20 to 80% by volume, and particularly preferably 25 to 50% by volume. Although not limited, the secondary transition point is preferably at least 65 ° C. If the porosity is less than 10% by volume,
If the density of the holes does not increase and exceeds 80% by volume, the strength of the pad decreases.

The porosity is calculated as follows: porosity (%) = 100 × (true specific gravity−apparent specific gravity) / true specific gravity.

The polyester for producing the polyester sheet containing independent cavities suitable in the present invention includes an aromatic dicarboxylic acid such as terephthalic acid, isophthalic acid and naphthalenedicarboxylic acid or an ester thereof, and ethylene glycol.
, Diethylene glycol, 1,4-butanediol,
Polyester produced by polycondensation with a glycol such as neopentyl glycol.

These polyesters can be obtained by directly reacting an aromatic dicarboxylic acid and a glycol, by subjecting an alkyl ester of an aromatic dicarboxylic acid to a transesterification reaction with a glycol followed by polycondensation, or by reacting an aromatic dicarboxylic acid with a diglycol. It is produced by a method such as polycondensation of an ester.

Typical examples of the above-mentioned polyesters include polyethylene terephthalate, polyethylene butylene terephthalate, and polyethylene-2,6-naphthalate. The polyester may be a homopolymer or a copolymer obtained by copolymerizing a third component. In any case, the polyester used in the present invention contains at least 70 mol%, preferably at least 80 mol%, more preferably at least 90 mol% of ethylene terephthalate units, butylene terephthalate units or ethylene-2,6-naphthalate units. Is preferred.

The incompatible thermoplastic resin used in the production of the void-containing polyester sheet in the present invention must be incompatible with the polyester described above. Specific examples include polystyrene-based resins, polyolefin-based resins, polyacryl-based resins, polycarbonate resins, polysulfone-based resins, and resins containing these as a main component. As a resin preferably used in combination, a resin containing at least one of a polyolefin resin such as a polymethylpentene resin and a polypropylene resin, and a polystyrene resin is particularly preferable.

[0038] The polystyrene resin is a thermoplastic resin having a polystyrene structure as a basic constituent element. In addition to homopolymers such as atactic polystyrene, syndiotactic polystyrene and isotactic polystyrene, other monomer components are grafted. It is meant to include a modified resin that has been polymerized or block copolymerized. Examples of the modified resin include an impact-resistant polystyrene resin, a modified polystyrene resin, and a mixture with a homopolymer or a resin such as polyphenylene ether having compatibility with these resins.

Hereinafter, a method for producing a void-containing polyester sheet suitable as a polishing pad in the present invention will be described. Even when other matrix resin is used, a polishing pad can be manufactured by a method according to this method.

In the present invention, first, a polymer mixture is prepared by mixing a polyester and a thermoplastic resin incompatible with the polyester. This polymer mixture is obtained, for example, by mixing the chips of each resin, melt-kneading them in an extruder, extruding and solidifying the mixture, previously kneading both resins by a kneader, then solidifying, and then melting again from the extruder.・ A method of solidifying by extrusion, a method of adding a thermoplastic resin incompatible with polyester in a polyester polymerization step, and stirring and dispersing chips obtained by melting and extruding to obtain a method of solidifying. Can be. The polymer sheet (unstretched sheet) obtained by solidification is usually in a non-oriented or weakly oriented state. In addition, the thermoplastic resin incompatible with the polyester exists in a form dispersed in the polyester in various shapes such as a spherical shape, an elliptical spherical shape, and a thread shape.

The polymer mixture may contain inorganic particles, if necessary, for adjusting the fine cavities and adjusting the slipperiness of the film. Examples of the inorganic particles include cerium oxide, zirconium oxide, aluminum oxide, chromium oxide, titanium oxide, silicon dioxide, calcium carbonate, barium sulfate, and the like, but are not particularly limited.

The polymer mixture thus obtained is further stretched between rolls having different speeds (roll stretching), stretched by gripping and expanding with a clip (tenter stretching), or stretched by air pressure. At least uniaxial orientation treatment is performed by (inflation stretching) or the like. At this time, peeling occurs at the interface between the polyester and the incompatible thermoplastic resin dispersed in the polyester, and a large number of cavities are generated in the polymer mixture, thereby forming a void-containing polyester sheet.

The amount of the thermoplastic resin incompatible with the polyester to be mixed with the polyester varies depending on the desired amount of fine cavities, but is preferably 3 to 50 parts by weight, more preferably 10 to 50 parts by weight, per 100 parts by weight of the polyester. ~ 40 parts by weight are preferred. If the amount is less than 3 parts by weight, there is a limit in increasing the amount of fine cavities. The higher the amount of incompatible thermoplastic resin added, the higher the density, the higher the density of pores on the surface,
However, if it exceeds 50 parts by weight, the heat resistance and strength of the polyester film may be significantly impaired, which is not preferable.

As described above, since the polishing pad of the present invention can be manufactured by extrusion molding, the density fluctuation in the thickness direction is smaller than that of a conventional polyurethane polishing pad (density fluctuation is 15 to 20%). Thus, it is possible to suppress it to about 1 to 2%.

The conditions for orienting the polymer mixture are closely related to the formation of microcavities. Therefore, the conditions for achieving this object are, for example, the most commonly performed sequential biaxial stretching step as an example, after a continuous sheet of the polymer mixture is roll-stretched in the longitudinal direction, then in the width direction. In the case of the sequential biaxial stretching method in which tenter stretching is performed, the following is performed.
In the roll stretching, it is preferable that the temperature is not higher than the secondary transition temperature of the polyester + 30 ° C. and the stretching ratio is 1.2 to 5 times in order to generate many fine cavities. In order to form a sheet stably without breaking in tenter stretching, it is preferable to set the temperature to 80 to 150 ° C. and the stretching ratio to 1.2 to 5 times. However, it is not limited to these methods.

The cavity density, porosity (foaming rate), size and shape of the cavities are determined by the amount of the incompatible thermoplastic resin, the stretching method, the stretching ratio, the properties of the inorganic particles to be added as required,
It is adjusted by the amount added. When using the conventional polyurethane, the porosity was limited to 30 to 35%,
According to the invention, the porosity can be easily adjusted over a wider range.

As the stretching method, either uniaxial stretching or biaxial stretching can be used. According to the biaxial stretching method, a sheet made of a void-containing synthetic resin having excellent heat resistance and physical properties can be obtained, but it is difficult to use a sheet having a film thickness exceeding 500 μm. The thickness of 1
mm. In the case of the uniaxial stretching method, 1
A sheet made of void-containing synthetic resin having a thickness of mm can be easily produced. Although the heat resistance is inferior to that of the biaxial stretching method, the temperature at the time of polishing does not exceed 50 ° C. and is lower than the glass transition temperature of the synthetic resin, so that no practical problem occurs.

The voids on the surface of the void-containing polyester sheet produced as described above were stretched 2.5 times each in the vertical and horizontal directions by adding an incompatible resin so that the void ratio was 30%. In this case, the density of pores on the surface of the obtained sheet is several thousands to 15,000 / mm ^2, which is much higher than that of a polishing pad obtained by a conventional technique. Since the pore diameter is small and the number is large, the abrasive grain retention density is increased. As a result, the polishing rate can be improved.

Further, by using a thermoplastic resin having a high compression modulus as exemplified by the void-containing polyester sheet, even if the compressibility of the void-containing sheet is set to 2%, which is required for a polishing pad which does not require a cushion layer, it can be compressed. Recovery rate 80-90
%, And a Shore D hardness of 65 or more can be realized. That is,
A polishing pad for CMP polishing without a cushion layer is obtained.

The shape of the voids of the void-containing polyester sheet produced by the above-described method is an ellipse (A) having a long shape as viewed from the surface direction, and a shallow bottom as viewed from the thickness direction, as shown in FIG. It is dish-shaped (B). The shape of the pores is determined by the stretching ratio in the longitudinal and transverse directions of the sheet. Usually, the longitudinal direction (sheet longitudinal direction) becomes the major axis because the transverse stretching is performed after the longitudinal stretching. And the minor axis in the thickness direction. Those having a major axis of 5 to 30 μm, a minor axis of 1 to 4 μm, and a depth of about 1 to 5 μm can be manufactured. As described above, in particular, a hole whose thickness direction is much smaller than the hole diameter (about 100 μm) of the conventional polishing pad can be obtained, so that the time required for dressing can be drastically reduced.

Further, in the production of the void-containing thermoplastic resin sheet constituting the polishing pad of the present invention, the thickness can be regulated by extrusion molding with a T-die, so that the in-plane sheet thickness accuracy is high and 3σ. At least 1-2%
Can be reduced to about. In the current sliced urethane foam, as described above, at most
It is about 6%, which clearly shows that the present invention is a polishing pad having excellent smoothness. Further, since the flatness is obtained immediately after the production, the effect that the pretreatment process of the polishing pad can be simplified can be obtained.

For the production of the void-containing thermoplastic resin sheet which is the polishing layer of the polishing pad of the present invention, a continuous step which is a usual film production step can be applied. Simpler and lower cost compared to conventional foaming urethane sheets, each of which has only a batch process, such as the foaming process, cross-linking agent addition / mixing process, injection molding process, and slicing process. Can be manufactured.

The void-containing thermoplastic resin sheet of the present invention comprises:
It can be created with any thickness. Therefore, it is of course possible to produce a material having a thickness of about 1 mm, which is employed in the current polyurethane, and a material having a thickness smaller than that.

The stretched thermoplastic resin sheet containing fine cavities can improve the dimensional stability at high temperatures when heat-set at 130 ° C. or higher, preferably 180 ° C. or higher, and can withstand local frictional heat. Is improved.

[0055]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Examples of the present invention will be described based on an example in which PET, which is a high-rigidity thermoplastic resin, is used as a synthetic resin and a sheet containing a large number of independent cavities is formed using an incompatible thermoplastic resin. I do.

The compression ratio and the compression recovery ratio were determined by using a cylindrical indenter having a diameter of 5 mm and measuring TMA of 2
T _{1 to} T ₃ were measured at 5 ° C. and determined by the following formula.

Compression rate (%) = 100 (T ₁ −T ₂ ) / T ₁ Compression recovery rate (%) = 100 (T ₃ −T ₂ ) / (T ₁ −T)
₂ ) T ₁ : Sheet thickness when 300 g / cm ² stress is applied for 60 seconds from no load T ₂ : 1800 g / cm ^{2 for} 60 seconds from T ₁
The thickness T ₃ sheets of stress when loaded with of: after the stress of 300 g / cm ² over a period of 60 seconds from the state of T _2, is the sheet thickness when 60 seconds held in stress of 300 g / cm ² .

(Preparation of Polishing Pad Sample 1) Polyethylene terephthalate (PET) 85 having an intrinsic viscosity of 0.62
Parts by weight and polystyrene having a melt flow index of 2.0 (Toporex 570-57 manufactured by Mitsui Toatsu Co., Ltd.)
U) A mixture with 15 parts by weight was supplied to a vented twin-screw extruder and kneaded, and extruded from a T-die of the extruder onto a cooling drum at a temperature of 30 ° C. to obtain an unstretched sheet having a thickness of 1800 μm. . Subsequently, the unstretched sheet was heated to 85 ° C. and stretched 3.4 times with a stretching roll. Next, the film was heated to 120 ° C. and stretched 3.2 times in the width direction with a tenter. The thickness of the sheet thus obtained is 2
35 μm, apparent specific gravity 1.005, porosity about 30
%Met. Further, four such void-containing polyester sheets were laminated via an adhesive layer to obtain a sheet (void-containing polyester sheet 1) having a thickness of 0.95 mm. (Void-containing polyester sheet 1) with a diameter of 2 mm,
After punching 5mm pitch, 300mm diameter
A polishing pad sample 1 was punched out in a disk shape of mm. The polishing pad sample 1 thus obtained is
The cavity density is 13500 pcs / mm ² , the compression ratio is 1.9%,
The compression recovery was 75% and the Shore D hardness was 67.

(Preparation of Polishing Pad Sample 2) The surface of the void-containing polyester sheet 1 used for preparing the polishing pad sample 1 was 2 mm wide and 0.4 m deep at 10 mm intervals.
A grid-shaped groove of m was formed and punched into a disk having a diameter of 300 mm to obtain a polishing pad sample 2. The polishing pad sample 2 thus obtained had a cavity density of 13500 pieces / mm ² , a compression ratio of 1.9%, a compression recovery ratio of 75%, and a Shore D hardness of 67, similarly to the polishing pad sample 1.
Met.

(Polishing pad sample 3) Intrinsic viscosity 0.6
A mixture of 85 parts by weight of polyethylene terephthalate (PET) 2 and 15 parts by weight of polypropylene having a melt flow index of 2.5 (FS2011 manufactured by Sumitomo Chemical Co., Ltd.) is supplied to a vented twin-screw extruder and kneaded. The sheet was extruded from a die onto a cooling drum at a temperature of 30 ° C. to obtain an unstretched sheet having a thickness of 3500 μm. Subsequently, the unstretched sheet was heated to 125 ° C. and stretched 5 times in a longitudinal direction by a stretching roll. Next, the film was heated to 165 ° C. with a tenter and stretched 5 times in the width direction. The sheet thus obtained had a thickness of 230 μm, a specific gravity of 0.59, and a porosity of about 35%. In addition, this hollow composite sheet
The sheets were laminated via an adhesive layer to obtain a 0.94 mm thick sheet (hollow composite sheet 2).

The surface of the obtained hollow composite sheet 2 has a diameter of 2
mm, 5 mm pitch hunting, and then punched into a disk with a diameter of 300 mm.
And The cavity density of the polishing pad sample 3 was 11500.
Pcs / mm ² , compression ratio 2.1%, compression recovery ratio 68%,
The Shore D hardness was 58.

(Polishing Pad Sample 4) A polishing pad sample 4 was a commercially available polishing pad made of polyurethane, a laminated pad of IC-1000A21 (upper layer) / SUBA400 (lower layer = cushion layer) (manufactured by Rodale).

(Polishing pad sample 5) Intrinsic viscosity 0.6
Using a mixture of 90 parts by weight of polyethylene terephthalate of No. 2 and 10 parts by weight of polystyrene having a melt flow index of 2.0, longitudinal stretching and width direction stretching were performed in the same manner as in (Cavity-containing sheet 1), 170μ
m of void-containing sheets (void-containing sheet 3).
The specific gravity of the obtained sheet is 1.31, and the void content is 6%.
Met. As in the case of the polishing pad sample 1, five sheets were laminated through an adhesive layer to form a sheet having a thickness of 0.85 mm.
The resultant was punched out into a disk shape of m to obtain a polishing pad sample 5.
The cavity density of the polishing pad sample 5 was 1000 pieces / mm.
^2. Compression rate 0.7%, compression recovery rate 89%, Shore D
The hardness was 70.

(Polishing pad sample 6) Intrinsic viscosity 0.6
Using a mixture of 60 parts by weight of polyethylene terephthalate of No. 2 and 40 parts by weight of polystyrene having a melt flow index of 2.0, longitudinal stretching and width direction stretching were carried out in the same manner as in (Void-containing sheet 1), 340μ
m of void-containing sheets (void-containing sheet 4).
The specific gravity of the obtained (cavity-containing sheet 4) was 1.31, and the void content was 6%. As in the case of the polishing pad sample 1, three sheets were laminated via an adhesive layer to form a sheet having a thickness of 1.02 mm, punched, and punched into a disk having a diameter of 300 mm. I got The cavity density of polishing pad sample 5 is 2
3000 pieces / mm ² , the compression ratio was 6.0%, the compression recovery ratio was 45%, and the Shore D hardness was 48.

[Polishing Evaluation] 500
A wafer on which a 0 Å SiO ₂ film was formed was used as a processing material for evaluation, and polishing evaluation was performed under the following conditions. As a polishing apparatus, a general lap master / LM15 (corresponding to φ4 inches) was used as a test polishing apparatus. As the polishing slurry, ceria (CeO ₂ )
Sol (manufactured by Nissan Chemical Industries, Ltd.) was used. A wafer to be processed is attached to a polishing head by water adsorption / standard backing material (NF2
00) Hold under conditions, platen (polishing pad support)
The above-mentioned polishing pad samples 1 to 6 were respectively adhered and fixed, and a polishing pressure of 200 g / cm ² , a relative speed between the polishing head and the platen of 30 m / min were given, and a polishing slurry supply speed of 110 cc / min. The polishing operation was performed for 2 minutes, and the polishing rate was measured.

[Evaluation of Non-uniformity] Rmax and Rmin were determined for 25 polished surfaces of a 4-inch wafer after polishing.
Is measured using a stylus meter, and the expression 100 × (Rmax-Rmi
n) / (Rmax + Rmin) was obtained as a numerical value (%), which was used as the evaluation result of Non-uniformity of the entire wafer surface. The results are shown in Table 1.

[0067]

[Table 1]

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of the shape of pores on a polishing surface of a polishing sheet of the present invention.

Claims (2)

[Claims] 1. A Shore D hardness of 50 or more and a compressibility of 1.
A polishing pad made of a synthetic resin, wherein the polishing pad has a compression recovery ratio of 3 to 5.5% and 50% or more. 2. The polishing pad according to claim 1, wherein the polishing pad is a cavity-containing thermoplastic resin containing a large number of independent cavities therein.