JP2009291942A - Polishing pad - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polishing pad which has a number of independent cavities in a layer in direct contact with the machining surface of a wafer to give uniform pressure to the whole surface of the wafer while machining the surface of the wafer with high accuracy, which has sufficient abrasive particle holding density and high surface cavity density to effectively improve a polishing speed while shortening a time required for dressing and reducing the frequency of dressing, and which adequately meets requirements of flatness with high thickness accuracy and shape accuracy without the need for a cushion layer provided on the reverse side. <P>SOLUTION: This synthetic resin polishing pad has a shore D hardness of 50 or more, a compression rate of 1.3-5.5%, and a compression recovery rate of 50% or more. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention stabilizes flattening processing of materials that require high surface flatness, such as optical materials such as lenses and reflecting mirrors, glass substrates for silicon wafers, hard disks, resin plates for information recording and ceramic plates, In addition, the present invention relates to a polishing pad that is performed at a high polishing rate. The polishing pad of the present invention is particularly suitable for use in a step of planarizing a silicon wafer and a device on which an oxide layer, a metal layer, etc. are formed, before further laminating and forming these layers. is there.

  A typical material that requires high surface flatness is a single crystal silicon disk called a silicon wafer for manufacturing a semiconductor integrated circuit (IC, LSI). Silicon wafers are required to have a flat surface with high precision in each thin film production process in order to form reliable semiconductor junctions of various thin films used for circuit production in the manufacturing process of IC, LSI, and the like.

In general, the polishing pad is fixed to a rotatable support disk called a platen, and the semiconductor wafer is fixed to a disk called a polishing head capable of rotating and revolving. By rotating both of them, a relative speed is generated between the platen and the polishing head, and by adding a polishing slurry in which fine particles (abrasive grains) are suspended in the gap between the polishing pad and the wafer, polishing, A flattening process is performed. At this time, when the polishing pad moves on the wafer surface, the abrasive grains are pressed onto the wafer surface at the contact point. Accordingly, polishing of the processed surface is performed by a sliding frictional action between the wafer surface and the abrasive grains. Such a polishing process is usually referred to as a CPM polishing process.

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 higher the abrasive density of the polishing pad, the higher the polishing rate. For this reason, a porous material having a large number of pores is usually used as the polishing pad. By holding the abrasive grains in the pores, it is possible to increase the retention density of the abrasive grains and increase the polishing rate. It has been broken. 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 retention density of the abrasive grains.

Conventionally, as a polishing pad used for the above-described high-precision polishing, a polyurethane foam sheet having a porosity of about 30 to 35% is generally used. Further, a technique described in Patent Document 1 that discloses a polishing pad in which hollow microspheres or water-soluble polymer powder is dispersed in a matrix resin such as polyurethane is also known.

Japanese National Patent Publication No. 8-500622

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

(1) Although the above-mentioned polyurethane foam sheet used for conventional CPM polishing is excellent in local flattening ability, the compression ratio is as small as about 0.5 to 1.0%, Therefore, it is difficult to apply a uniform pressure to the entire wafer surface because the cushioning property is insufficient. In order to obtain sufficient cushioning properties, it is necessary to increase the void ratio in order to reduce the compression ratio of the polyurethane foam sheet to about 2%. If the void ratio is increased, the compression recovery ratio and surface hardness may decrease. Inevitable. When the compression recovery rate and the surface hardness are reduced, the polishing pad is consolidated by repeated compression and release of the load in the polishing process, which causes a problem that processing accuracy is lowered. 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 ability of the polyurethane foam sheet to flatten the wafer surface is substantially reduced, and there is a limit to the improvement of processing accuracy.

(2) Since the polishing pad needs to surface pores by dressing when clogging occurs as described later, the polyurethane foam must be closed-celled. A closed-cell polyurethane foam is generally a block-shaped foam obtained by mixing a polyisocyanate compound and a polyhydroxy compound in the presence of a foaming agent, and then injecting and polymerizing the mixture in a mold. 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 the average pore diameter is 100 μm or less. It is difficult, and even when measured individually, 50 μm is the minimum. For this reason, the retention density of the abrasive grains is not sufficient.

(3) When a polishing operation is performed using a polishing slurry, polishing scraps or deteriorated abrasive grains are clogged in the pores, the polishing rate is reduced, and scratches on the flat surface to be polished may be caused. , Processing characteristics deteriorate. Moreover, when the fine holes are clogged, it is extremely difficult to completely excavate the machining waste and return to the initial state. Therefore, a diamond grinding wheel or the like is used to scrape off the pad surface called dressing, and, as in the initial state, an operation in which the surface with exposed voids is taken out and reused is performed. However, since the pores of the current polyurethane foam are spherical and the average pore diameter is about 100 μm, in order to stably bring out the surface in the initial state, the surface structure is made uniform, The cross-sectional structure must also be uniform, and at least a portion corresponding to the hole diameter must be scraped off by dressing. Since surface polishing by dressing can be performed only by a slight thickness, when dressing a polyurethane foam with a diamond grindstone, it takes 1 to 2 hours as a time required to scrape 100 μm. During this time, the wafer cannot be polished, and in order to increase the wafer throughput, it is required to reduce the time required for dressing and to reduce the dressing frequency.

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

  In addition, according to the technique described in Patent Document 1, only an example using hollow microspheres is disclosed as a polishing sheet having pores (Example 1), and the pores are spherical and have a pore diameter. Has a spherical shape of about 100 μm and has the same problems (1) to (4) as the polyurethane foam.

An image obtained by a scanning electron microscope of a typical commercially available polishing pad (Rodale IC-1000) was counted by an image processing device V-10 (manufactured by Toyobo). The hole density is about 1100 holes / mm ² , and further increase is required to improve the polishing rate.

  The object of the present invention is that the layer directly in contact with the processed surface of the wafer has a number of independent cavities, and has an appropriate hardness, compression rate, and compression recovery rate, and the above (1) to (4) An object of the present invention is to provide a polishing pad that solves the problem and satisfies the requirements, and does not require a cushion layer on the back surface.

  The present invention is a synthetic resin polishing pad having a Shore D hardness of 50 or more, a compression rate of 1.3 to 5.5%, and a compression recovery rate of 50% or more. .

  The polishing pad having the above configuration does not need to be provided with a cushion layer, and as a result, high-accuracy polishing can be performed without impairing the planarization ability inherent in the polishing layer. That is, machining accuracy is improved both locally and overall.

  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 polishing pad is consolidated by repeated compression and release of the load in the polishing process, and the processing accuracy is lowered. If it exceeds 0.5%, there arises a problem that the flattening accuracy is lowered. Even if the compression recovery rate is less than 50%, compaction still occurs, which is not preferable.

  The compression rate 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. A higher compression recovery rate, that is, closer to 100% is better.

The compression rate and the compression recovery rate are expressed 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 )
Here, T _{1 to} T ₃ use a cylindrical indenter with a diameter of 5 mm,
T ₁ : Sheet thickness when stress of 300 g / cm ^{2 is} applied over 60 seconds from the unloaded state T ₂ : Sheet thickness when stress of 1800 g / cm ^{2 is} applied over 60 seconds from the state of T ₁ Thickness T ₃ : The thickness of the sheet when the stress is 300 g / cm ² over 60 seconds from the state of T ₂ and then held 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 rate, and compression recovery rate of the present invention can be easily achieved.

The figure which showed the example of the shape of the void | hole of the polishing surface of the polishing sheet of this invention

  As the synthetic resin constituting the polishing pad of the present invention, a thermoplastic resin having a high rigidity, that is, a high compressive elastic modulus is preferably used as described above. Specifically, a polyester resin such as polyethylene terephthalate (PET), polypropylene, and the like. (PP), polyethylene (PE), polyamide (PA) and the like are exemplified.

  As a means for forming a large number of cavities in the synthetic resin, a method in which an incompatible thermoplastic resin is mixed with the synthetic resin (matrix resin) and the incompatible thermoplastic resin is formed as a core is suitable.

  When PET is used as a matrix resin constituting the polishing pad, the incompatible thermoplastic resin may contain at least one of a polystyrene resin, a polymethylpentene resin, and a polypropylene resin. Is preferred.

  By using the above-mentioned incompatible thermoplastic resin as a thermoplastic resin that is incompatible with polyester, the void-containing polyester-based sheet layer has a small and flat pore size and a high density of pores on the surface. Can be obtained. “Surface” means to include a surface newly obtained from the inside of the sheet obtained by dressing.

  When PP or PE is used as the matrix resin that constitutes the polishing pad, examples of suitable incompatible thermoplastic resins include cross-linked polymethyl methacrylate.

It is a preferred embodiment that a polyester resin is used as a matrix resin constituting the polishing pad, and a resin in which a polystyrene resin and a specific polyolefin resin are mixed at a specific weight ratio is used as an incompatible thermoplastic resin. . Specifically, it contains a polystyrene-based resin, a polymethylpentene-based resin, and a polypropylene-based resin, the polystyrene-based resin content in the polishing pad constituent resin is a (wt%), and the polymethylpentene-based resin content is b (wt%), when the polypropylene resin content is c (wt%),
0.01 ≦ a / (b + c) ≦ 1
c / b ≦ 1
3 ≦ a + b + c ≦ 50
Is preferably satisfied.

  If the amount of polystyrene resin or polymethylpentene resin used is so large that it does not meet the above range, these incompatible thermoplastic resins tend to coarsely disperse, causing unevenness on the polishing pad surface, When the amount of the incompatible thermoplastic resin is so small that it does not satisfy the above range, the above unevenness is improved, but there is a limit to 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 square, rectangle, polygon, circle and the like, but is preferably circular.

  It is also preferable to provide a groove that is continuous and opens on the end surface of the polishing pad on the polishing surface of the polishing pad of the present invention, that is, the independent hollow polyester sheet surface. These grooves are effective for discharging from the polishing surface those that may damage the polishing surface, such as polishing debris generated by polishing. The depth of the groove is preferably about 0.1 mm to 0.5 mm, and is preferably formed on the independent hollow polyester sheet surface at an interval of about 1 to 5 mm. The cross-sectional shape of the groove is not particularly limited, such as an arc shape or a triangle.

  In order to obtain the same effect as the above-mentioned groove, it is also a preferable aspect 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 12 mm. Preferably there is. If the through-hole diameter is too large, the polishing effect is reduced, and the polyester sheet strength is also reduced. If it 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 lowered, and if it is too large, the density of the through holes becomes too small and the effect cannot be obtained sufficiently.

  When performing a polishing operation using the polishing pad of the present invention, it is a preferred embodiment to use a known auxiliary agent, such as a lubricant or an abrasive, specifically, polishing of alumina, ceria, silica or the like. Examples thereof include slurries obtained by dispersing and suspending agents and water or liquid organic compounds.

  In the following, more specific characteristics and production methods of the void-containing polyester film particularly suitable as the polishing pad of the present invention 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. Moreover, although it does not limit, it is preferable that a secondary transition point is 65 degreeC or more. If the void ratio is less than 10% by volume, the density of the pores does not increase, and if it exceeds 80% by volume, the strength of the pad decreases.

The void ratio is
Cavity ratio (%) = 100 × (true specific gravity−apparent specific gravity) / true specific gravity.

  Polyesters for producing a polyester sheet containing an independent cavity suitable for the present invention include aromatic dicarboxylic acids or esters thereof such as terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid, and ethylene glycol, diethylene glycol, 1,4-butanediol. Polyester produced by polycondensation with glycol such as neopentyl glycol.

  These polyesters are obtained by directly reacting an aromatic dicarboxylic acid and a glycol, transesterifying an alkyl ester of an aromatic dicarboxylic acid and a glycol, and then polycondensing them, or by polycondensing a diglycol ester of an aromatic dicarboxylic acid. It is produced by a method such as condensation.

  Representative examples of the above polyester include polyethylene terephthalate, polyethylene butylene terephthalate, polyethylene-2,6-naphthalate, and the like. This polyester may be a homopolymer or a copolymer obtained by copolymerizing a third component. In any case, the polyester used in the present invention is a polyester having an ethylene terephthalate unit, a butylene terephthalate unit or an ethylene-2,6-naphthalate unit of 70 mol% or more, preferably 80 mol% or more, more preferably 90 mol% or more. 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 above-described polyester. Specific examples include polystyrene resins, polyolefin resins, polyacrylic resins, polycarbonate resin, polysulfone resins, and resins containing these as main components. As a preferred resin to be 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 suitable.

  Polystyrene resin is a thermoplastic resin containing a polystyrene structure as a basic component, and in addition to homopolymers such as atactic polystyrene, syndiotactic polystyrene and isotactic polystyrene, other monomer components are graft-polymerized, or It is meant to include a block copolymerized modified resin. Examples of such modified resins include impact-resistant polystyrene resins, modified polystyrene resins, and homopolymers and mixtures with resins such as polyphenylene ethers that are compatible 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 resins are used, a polishing pad can be produced by a method according to this method.

  In the present invention, first, a polymer mixture is prepared by mixing polyester and an incompatible thermoplastic resin with the polyester. This polymer mixture is obtained, for example, by mixing each resin chip and melt-kneading in an extruder, then extruding and solidifying the resin, kneading both resins in advance with a kneader, solidifying, and then melting again from the extruder Obtaining by a method such as a method of solidifying by extrusion, a method of adding incompatible thermoplastic resin to the polyester in the polyester polymerization step, and melting and extruding the chip obtained by stirring and dispersing Can do. The polymer sheet (unstretched sheet) obtained by solidification is usually in a non-oriented or weakly oriented state. Further, thermoplastic resins that are incompatible with polyester exist in various forms such as spherical, elliptical, or thread-like dispersion in polyester.

  The polymer mixture may contain inorganic particles as necessary for adjusting 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, and barium sulfate, but are not particularly limited.

  The polymer mixture thus obtained is further stretched between rolls with different speeds (roll stretching), stretched by gripping with a clip (tenter stretching) or stretched by air pressure (inflation stretching). ) Or the like to align at least one axis. At this time, peeling occurs at the interface between the polyester and the incompatible thermoplastic resin dispersed in the polyester, a large number of voids are generated in the polymer mixture, and a void-containing polyester sheet is formed.

  The addition amount of the thermoplastic resin incompatible with the polyester mixed with the polyester varies depending on the amount of the desired fine cavity, but is preferably 3 to 50 parts by weight, particularly 10 to 40 parts by weight with respect to 100 parts by weight of the polyester. Part is preferred. If it is less than 3 parts by weight, there is a limit to increasing the amount of fine cavities generated. Increasing the amount of incompatible thermoplastic resin increases, and the density of surface pores increases, which is preferable, but if it exceeds 50 parts by weight, the heat resistance and strength of the polyester film may be greatly impaired, It is not preferable.

  As described above, since the polishing pad of the present invention can be manufactured by extrusion molding, the density variation in the thickness direction is compared with a conventional polyurethane-based polishing pad (density variation is 15 to 20%). It can be suppressed to about 1 to 2%.

  The conditions for orienting the polymer mixture are closely related to the formation of fine cavities. Accordingly, the conditions for achieving this object are, for example, the most commonly performed sequential biaxial stretching step. For example, the continuous sheet of the polymer mixture is roll-stretched in the longitudinal direction and then stretched in the width direction. In the case of the sequential biaxial stretching method in which tenter stretching is performed, it is as follows. In roll stretching, in order to generate a large number of fine cavities, the temperature is preferably the second order transition temperature of the polyester + 30 ° C. or less, and the stretching ratio is preferably 1.2 to 5 times. In the tenter stretching, in order to stably form a sheet without breaking, it is preferable that the temperature is 80 to 150 ° C. and the stretching ratio is 1.2 to 5 times. However, it is not restricted to these methods.

  Cavity density, cavity ratio (foaming ratio), cavity size, shape, etc. depend on the amount of incompatible thermoplastic resin added, stretching method, stretching ratio, properties of inorganic particles added as required, added amount, etc. Adjusted. When the conventional polyurethane is used, the void ratio is limited to 30 to 35%, but according to the present invention, the void ratio can be easily adjusted to a wider range.

  As the stretching method, either uniaxial stretching or biaxial stretching can be used. According to the biaxial stretching method, an excellent void-containing synthetic resin sheet can be obtained with respect to heat resistance and physical properties, but it is difficult to have a film thickness exceeding 500 μm, and a polishing pad usually used by laminating several sheets It is necessary to set the thickness to about 1 mm. In the case of the uniaxial stretching method, a 1 mm thick void-containing synthetic resin sheet 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 not higher than the glass transition temperature of the synthetic resin, and no practical problem occurs.

The density of pores on the surface of the void-containing polyester sheet produced as described above is obtained when an incompatible resin is added so that the void ratio is 30% and stretched 2.5 times in length and width. The density of pores on the surface of the obtained sheet is several thousand to 15,000 / mm ^2, which is much larger than the polishing pad obtained by the conventional technique. Since the hole diameter is small and the number is large, the abrasive grain retention density is increased. As a result, the polishing rate can be improved.

  Moreover, even if the compression rate of the cavity-containing sheet is 2% required for a polishing pad that does not require a cushion layer by using a thermoplastic resin having a high compression modulus exemplified by the cavity-containing polyester sheet, the compression recovery rate can be reduced. 80 to 90% and a Shore D hardness of 65 or more can be realized. That is, a polishing pad for CMP polishing that does not require a cushion layer can be obtained.

  As shown in FIG. 1, the cavity shape of the cavity-containing polyester sheet produced by the above-described method is an ellipse (A) having a long shape when viewed from the surface direction, and the shape when viewed from the thickness direction is a shallow dish shape. Yes (B). The shape of the pores is determined by the stretching ratio in the longitudinal and lateral directions of the sheet. Usually, the longitudinal direction (sheet longitudinal direction) becomes the major axis and the transverse direction is the longitudinal direction after the longitudinal stretching. And the thickness direction becomes a minor axis. The major axis is 5 to 30 μm, the minor axis is 1 to 4 μm, and the depth is about 1 to 5 μm. As described above, since a hole having a thickness much smaller than the hole diameter (about 100 μm) of the polishing pad of the prior art can be obtained, 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, since the thickness can be regulated by extrusion molding with a T-die, the in-plane sheet thickness accuracy is high, and at least 1 to 3σ. It can be reduced to about 2%. In the current sliced urethane foam, as described above, at most 3σ is about 5 to 6%, and it is clear that the present invention is a polishing pad having excellent smoothness. Furthermore, since it has such flatness immediately after production, an effect that the pretreatment process of the polishing pad can be simplified is also obtained.

  For the production of the void-containing thermoplastic resin sheet that is the polishing layer of the polishing pad of the present invention, a continuous process that is a normal film manufacturing process can be applied. Like conventional foamed urethane sheets, each process is simpler and less expensive than the ones that only have 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 can be prepared with an arbitrary thickness. Accordingly, it is naturally possible to create a product having a thickness of about 1 mm, which is used in the current polyurethane, and to manufacture a product having a thickness less than that.

  The stretched thermoplastic resin sheet containing fine cavities can improve dimensional stability at high temperatures when heat-fixed at 130 ° C or higher, preferably 180 ° C or higher, and improve durability against localized frictional heat. Is done.

  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 using an incompatible thermoplastic resin.

The compression rate and the compression recovery rate were determined by the following formula using a cylindrical indenter having a diameter of 5 mm, measuring T _{1 to} T ₃ at 25 ° C. with TMA manufactured by Mac Science.

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 stress of 300 g / cm ^{2 is} applied over 60 seconds from the unloaded state T ₂ : Sheet thickness when stress of 1800 g / cm ^{2 is} applied over 60 seconds from the state of T ₁ Thickness T ₃ : The thickness of the sheet when the stress is 300 g / cm ² over 60 seconds from the state of T ₂ and then held at the stress of 300 g / cm ² for 60 seconds.

(Preparation of polishing pad sample 1)
A mixture of 85 parts by weight of polyethylene terephthalate (PET) having an intrinsic viscosity of 0.62 and 15 parts by weight of polystyrene having a melt flow index of 2.0 (Topolex 570-57U manufactured by Mitsui Toatsu Co., Ltd.) was added to a vent type twin screw extruder. The mixture was fed and kneaded and extruded from a T die of the extruder onto a cooling drum having 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 longitudinally stretched 3.4 times with a stretching roll. Next, the film was heated to 120 ° C. and stretched in the width direction by a factor of 3.2. The sheet thus obtained had a thickness of 235 μm, an apparent specific gravity of 1.005, and a porosity of about 30%. Further, four of these void-containing polyester sheets were laminated via an adhesive layer to obtain a sheet having a thickness of 0.95 mm (void-containing polyester sheet 1).
After punching the hollow-containing polyester sheet 1 with a diameter of 2 mm and a pitch of 5 mm, it was punched into a disk shape with a diameter of 300 mm to obtain a polishing pad sample 1. The thus obtained polishing pad sample 1 had a cavity density of 13500 pieces / mm ² , a compression rate of 1.9%, a compression recovery rate of 75%, and a Shore D hardness of 67.

(Preparation of polishing pad sample 2)
A grid-like groove having a width of 2 mm and a depth of 0.4 mm is formed on the surface of the void-containing polyester sheet 1 used for the production of the polishing pad sample 1 at intervals of 10 mm, and punched into a disk shape having a diameter of 300 mm. It was. The polishing pad sample 2 thus obtained had a cavity density of 13500 pieces / mm ² , a compression rate of 1.9%, a compression recovery rate of 75%, and a Shore D hardness of 67, like the polishing pad sample 1. there were.

(Polishing pad sample 3)
A mixture of 85 parts by weight of polyethylene terephthalate (PET) having an intrinsic viscosity of 0.62 and 15 parts by weight of polypropylene having a melt flow index of 2.5 (FS2011 manufactured by Sumitomo Chemical Co., Ltd.) was supplied to a bent twin screw extruder and kneaded. It was extruded from a T-die of an extruder onto a cooling drum having a temperature of 30 ° C. to obtain an unstretched sheet having a thickness of 3500 μm. Subsequently, this unstretched sheet was heated to 125 ° C. and subjected to 5-fold longitudinal stretching with a stretching roll. Subsequently, it heated at 165 degreeC with the tenter, and performed width direction extending | stretching 5 times. The thickness of the sheet thus obtained was 230 μm, the specific gravity was 0.59, and the porosity was about 35%. Further, four of these hollow sheets were laminated via an adhesive layer to obtain a sheet having 0.94 mm thickness (hollow sheet 2).

The surface of the obtained hollow sheet 2 was subjected to hunting with a diameter of 2 mm and a pitch of 5 mm, and then punched into a disk shape with a diameter of 300 mm to obtain a polishing pad sample 3. The cavity density of the polishing pad sample 3 was 11500 pieces / mm ² , the compression rate was 2.1%, the compression recovery rate was 68%, and the Shore D hardness was 58.

(Polishing pad sample 4)
A commercially available polyurethane polishing pad, IC-1000A21 (upper layer) / SUBA400 (lower layer = cushion layer) laminate pad (Rodel) was used as the polishing pad sample 4.

(Polishing pad sample 5)
Using a mixture of 90 parts by weight of polyethylene terephthalate having an intrinsic viscosity of 0.62 and 10 parts by weight of polystyrene having a melt flow index of 2.0, longitudinal stretching and stretching in the width direction were performed in the same manner as in (Cavity-containing sheet 1). This was carried out to prepare a void-containing sheet (hollow-containing sheet 3) having a thickness of 170 μm. The specific gravity of the obtained sheet was 1.31, and the void content was 6%. Similarly to the polishing pad sample 1, five sheets of this sheet were laminated through an adhesive layer to form a sheet having a thickness of 0.85 mm, punched, punched into a disk shape having a diameter of 300 mm, and the polishing pad sample 5 Got. The cavity density of the polishing pad sample 5 was 1000 / mm ² , the compression rate was 0.7%, the compression recovery rate was 89%, and the Shore D hardness was 70.

(Polishing pad sample 6)
Using a mixture of 60 parts by weight of polyethylene terephthalate having an intrinsic viscosity of 0.62 and 40 parts by weight of polystyrene having a melt flow index of 2.0, longitudinal stretching and stretching in the width direction were performed in the same manner as in (Cavity-containing sheet 1). It carried out and produced the cavity containing sheet (cavity containing sheet 4) of thickness 340 micrometers. The specific gravity of the obtained (cavity-containing sheet 4) was 1.31, and the void content was 6%. In the same manner as the polishing pad sample 1, three sheets of this sheet were laminated through an adhesive layer to form a sheet having a thickness of 1.02 mm, punched, punched into a disk shape having a diameter of 300 mm, and the polishing pad sample 5 Got. The polishing pad sample 5 had a cavity density of 23000 / mm ² , a compression rate of 6.0%, a compression recovery rate of 45%, and a Shore D hardness of 48.

[Polishing evaluation]
A wafer having a 5000 Å SiO ₂ film formed on the surface of single crystal silicon 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 (compatible with φ4 inch) was used as a test polishing apparatus. As the polishing slurry, ceria (CeO ₂ ) sol (manufactured by Nissan Chemical Co., Ltd.) was used. The wafer, which is the workpiece, is held on the polishing head under the conditions of water adsorption / standard backing material (NF200), and the above polishing pad samples 1 to 6 are attached and fixed to the platen (polishing pad support), respectively, and polished. The pressure was 200 g / cm ² , the relative speed between the polishing head and the platen was 30 m / min, the polishing operation was performed for 2 minutes at a polishing slurry supply speed of 110 cc / min, and the polishing speed was measured.

[Non-uniformity evaluation]
Rmax and Rmin are measured with a stylus meter for 25 polished surfaces of a φ4 inch wafer after polishing, and a numerical value (%) is obtained by the formula 100 × (Rmax−Rmin) / (Rmax + Rmin). The overall non-uniformity was evaluated. The results are shown in Table 1.

Claims (3)

It comprises a polyester resin as a matrix resin, and an independent cavity-containing polyester sheet containing at least one incompatible thermoplastic resin selected from the group consisting of a polystyrene resin, a polymethylpentene resin, and a polypropylene resin, The Shore D hardness is 50 or more, the compression rate is 1.3 to 5.5%, the compression recovery rate is 50% or more, and the shape of the independent cavity is 5 to 30 μm in major axis, 1 to 4 μm in minor axis, and depth 1 A polishing pad having a flat shape of ˜5 μm. The polishing pad according to claim 1, wherein the independent void-containing polyester sheet has a void ratio of 20 to 80% by volume. The polishing pad according to claim 1 or 2, wherein the content of the incompatible thermoplastic resin is 3 to 50 parts by weight with respect to 100 parts by weight of the polyester resin.