JP5356098B2 - Polishing pad and manufacturing method thereof - Google Patents

Description

  The present invention stabilizes flattening processing of optical materials such as lenses and reflecting mirrors, silicon wafers, glass substrates for hard disks, aluminum substrates, and materials that require high surface flatness such as general metal polishing processing, In addition, the present invention relates to a polishing pad that can be performed with high polishing efficiency. The polishing pad of the present invention is particularly suitable for a step of planarizing a silicon wafer and a device having an oxide layer, a metal layer, etc. formed thereon, before further laminating and forming these oxide layers and metal layers. Used for.

  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 have a highly accurate surface in each process of stacking and forming oxide layers and metal layers in order to form reliable semiconductor junctions of various thin films used for circuit formation in IC, LSI, and other manufacturing processes. It is required to finish flat. In such a polishing finishing process, a polishing pad is generally fixed to a rotatable support disk called a platen, and a workpiece such as a semiconductor wafer is fixed to a polishing head. A polishing operation is performed by generating a relative speed between the platen and the polishing head by both movements, and continuously supplying a polishing slurry containing abrasive grains onto the polishing pad.

  The polishing characteristics of the polishing pad are required to be excellent in the flatness (planarity) and in-plane uniformity of the object to be polished and to have a high polishing rate. The flatness and in-plane uniformity of the object to be polished can be improved to some extent by increasing the elastic modulus of the polishing layer. The polishing rate can be improved by using a foam containing bubbles and increasing the amount of slurry retained.

  As a polishing pad that satisfies the above characteristics, a polishing pad made of a non-foamed synthetic resin or a polishing pad made of a polyurethane foam has been proposed (Patent Documents 1 and 2).

  However, when a polishing pad made of foam is used, the contact area between the polishing object and the polishing pad is reduced, and the local surface pressure is increased, so that the surface to be polished of the polishing object is likely to be scratched. There is a problem.

  On the other hand, when a large number of semiconductor wafers are planarized using a polishing pad, the fine irregularities on the surface of the polishing pad wear out, reducing the ability to supply slurry to the processed surface of the semiconductor wafer and reducing the polishing rate. Or flattening characteristics deteriorate. For this reason, it is necessary to update and roughen (dress) the surface of the polishing pad using a dresser after the planarization of a predetermined number of semiconductor wafers. When dressing is performed for a predetermined time, innumerable fine irregularities are formed on the surface of the polishing pad, and the pad surface becomes fuzzy.

  A conventional polishing pad made of a non-foamed material has a problem that the cut rate at the time of dressing is low and the dressing takes too much time.

JP 2006-110665 A Japanese Patent No. 4128607

  An object of the present invention is to provide a polishing pad that hardly causes scratches on the surface of an object to be polished and has improved dressing properties, and a method for manufacturing the same.

  As a result of intensive studies to solve the above problems, the present inventors have found that the above object can be achieved by the polishing pad shown below, and have completed the present invention.

  That is, the present invention provides a polishing pad having a polishing layer made of non-foamed polyurethane, wherein the non-foamed polyurethane is an isocyanate terminal obtained by reacting a prepolymer raw material composition containing a diisocyanate, a high molecular weight polyol, and a low molecular weight polyol. A pre-polymer, a reaction cured product of a polyurethane raw material composition containing an isocyanate-modified product increased in number by adding three or more diisocyanates, and a chain extender, and the amount of the isocyanate-modified product added is an isocyanate-terminated prepolymer It is related with the polishing pad characterized by being 5-30 weight part with respect to 100 weight part.

  The present invention is characterized in that the polishing layer is formed of non-foamed polyurethane. As a result, the contact area between the object to be polished and the polishing layer is increased, and the surface pressure applied to the object to be polished becomes low and uniform, so that the generation of scratches on the surface to be polished can be effectively suppressed.

  Further, the present inventors also used, as a raw material for the non-foaming polyurethane, the isocyanate-terminated prepolymer and an isocyanate-modified product that has been multimerized by adding three or more diisocyanates, and these and a chain extender. By partially introducing chemical cross-links into the polymer by reaction (partially forming a three-dimensional cross-linked structure), non-foamed polyurethane becomes hard and brittle and the cut rate during dressing increases, so the pad surface is renewed. I found out that it would be easier. Moreover, regular chemical crosslinking can be introduced into the polymer by reacting the isocyanate-modified product directly with the chain extender without introducing it into the isocyanate-terminated prepolymer. Thereby, the brittleness on the entire surface of the polishing layer can be made uniform, and variations in wear can be suppressed.

  The high molecular weight polyol is a polyether polyol having a number average molecular weight of 500 to 5000, and the diisocyanate is preferably toluene diisocyanate and dicyclohexylmethane diisocyanate. The isocyanate-modified product is preferably an isocyanurate-type and / or burette-type hexamethylene diisocyanate-modified product. By using these, swelling of the non-foamed polyurethane at the time of water absorption is suppressed, and the renewability of the pad surface at the time of dressing is improved.

  It is necessary to add 5 to 30 parts by weight of the isocyanate-modified product with respect to 100 parts by weight of the isocyanate-terminated prepolymer. If the amount of the isocyanate-modified product added is less than 5 parts by weight, the rate of chemical cross-linking in the polymer becomes insufficient, so the renewability of the pad surface at the time of dressing is reduced and the foam-free polyurethane swells at the time of water absorption It becomes easy to do. On the other hand, when it exceeds 30 parts by weight, the ratio of chemical crosslinking in the polymer becomes excessive, and the hardness of the non-foamed polyurethane becomes too high, so that the surface of the polishing object is likely to be scratched.

  The non-foamed polyurethane preferably has an Asker D hardness of 65 to 80 degrees. When Asker D hardness is less than 65 degrees, the flatness of the object to be polished tends to decrease. On the other hand, when it is larger than 80 degrees, the flatness is good, but the in-plane uniformity of the object to be polished tends to decrease. In addition, scratches are likely to occur on the surface of the object to be polished.

  In addition, the polishing pad of the present invention preferably has a cut rate of 2 μm / min or more from the viewpoint of pad surface renewability.

  In addition, the present invention can be obtained by adding three or more diisocyanates to 100 parts by weight of an isocyanate-terminated prepolymer obtained by reacting a prepolymer raw material composition containing a diisocyanate, a high molecular weight polyol, and a low molecular weight polyol. The present invention relates to a method for producing a polishing pad comprising a step of mixing a first component containing 5 to 30 parts by weight of a quantified isocyanate-modified product and a second component containing a chain extender and curing to produce a non-foamed polyurethane.

  Furthermore, the present invention relates to a semiconductor device manufacturing method including a step of polishing a surface of a semiconductor wafer using the polishing pad.

Schematic configuration diagram showing an example of a polishing apparatus used in CMP polishing Schematic showing 73 film thickness measurement positions on wafer

  The polishing pad of the present invention has a polishing layer made of non-foamed polyurethane. The polishing pad of the present invention may be only the polishing layer or a laminate of the polishing layer and another layer (for example, a cushion layer).

  Polyurethane resin is a particularly preferable material for forming the polishing layer because it has excellent wear resistance and a polymer having desired physical properties can be easily obtained by variously changing the raw material composition.

  The non-foamed polyurethane is an isocyanate-modified prepolymer obtained by reacting a prepolymer raw material composition containing a diisocyanate, a high molecular weight polyol, and a low molecular weight polyol, and is multiplied by adding three or more diisocyanates. And a reaction cured product of a polyurethane raw material composition containing a chain extender.

  As the diisocyanate, a known compound in the field of polyurethane can be used without particular limitation. For example, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 2,2′-diphenylmethane diisocyanate, 2,4′-diphenylmethane diisocyanate, 4,4′-diphenylmethane diisocyanate, 1,5-naphthalene diisocyanate, p-phenylene Aromatic diisocyanates such as diisocyanate, m-phenylene diisocyanate, p-xylylene diisocyanate, m-xylylene diisocyanate, aliphatic diisocyanates such as ethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, 1,6-hexamethylene diisocyanate 1,4-cyclohexane diisocyanate, 4,4′-dicyclohexylmethane diisocyanate, isophorone diisocyanate, nor Cycloaliphatic diisocyanates such as Renan diisocyanate. These may be used alone or in combination of two or more. Of these, it is preferable to use toluene diisocyanate and dicyclohexylmethane diisocyanate in combination.

  On the other hand, the isocyanate-modified product in the present invention is a compound or a mixture thereof which has been multiplied by adding three or more diisocyanates. Examples of the modified isocyanate include 1) trimethylolpropane adduct type, 2) burette type, and 3) isocyanurate type, with isocyanurate type and burette type being particularly preferable.

  In the present invention, aliphatic diisocyanate is preferably used as the diisocyanate forming the isocyanate-modified product, and 1,6-hexamethylene diisocyanate is particularly preferably used. The isocyanate-modified product may be modified by urethane modification, allophanate modification, burette modification or the like.

  Examples of the high molecular weight polyol include polyether polyols typified by polytetramethylene ether glycol, polyester polyols typified by polybutylene adipate, polycaprolactone polyol, and a reaction product of a polyester glycol such as polycaprolactone and alkylene carbonate. Polyester polycarbonate polyol, polyester polycarbonate polyol obtained by reacting ethylene carbonate with polyhydric alcohol and then reacting the resulting reaction mixture with organic dicarboxylic acid, and polycarbonate polyol obtained by transesterification reaction between polyhydroxyl compound and aryl carbonate Etc. These may be used alone or in combination of two or more.

  The number average molecular weight of the high molecular weight polyol is not particularly limited, but is preferably 500 to 5000, more preferably 1000 to 2000, from the viewpoint of the elastic properties of the resulting polyurethane. When the number average molecular weight is less than 500, the number of hard segments is excessive and the polyurethane has low toughness. On the other hand, when the number average molecular weight exceeds 5,000, polyurethane becomes too soft, so that a polishing pad produced from this polyurethane tends to have poor planarization characteristics.

  Examples of the low molecular weight polyol include ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,3- Butanediol, 1,6-hexanediol, neopentyl glycol, 1,4-cyclohexanedimethanol, 3-methyl-1,5-pentanediol, diethylene glycol, triethylene glycol, 1,4-bis (2-hydroxyethoxy) Benzene, trimethylolpropane, glycerin, 1,2,6-hexanetriol, pentaerythritol, tetramethylolcyclohexane, methylglucoside, sorbitol, mannitol, dulcitol, sucrose, 2,2,6,6-tetrakis (hydroxymethyl) ) Cyclohexanol, diethanolamine, N- methyldiethanolamine, and triethanolamine, and the like. These may be used alone or in combination of two or more.

  Moreover, low molecular weight polyamines, such as ethylenediamine, tolylenediamine, diphenylmethanediamine, and diethylenetriamine, can also be used together as a raw material component of the isocyanate-terminated prepolymer. Also, alcohol amines such as monoethanolamine, 2- (2-aminoethylamino) ethanol, and monopropanolamine can be used in combination. These may be used alone or in combination of two or more.

  The blending amount of the low molecular weight polyol, the low molecular weight polyamine or the like is not particularly limited, and is appropriately determined depending on the characteristics required for the polishing pad (polishing layer) to be produced. However, all active hydrogen which is a raw material component of the isocyanate-terminated prepolymer It is preferable that it is 20-70 mol% of a group containing compound.

  The chain extender is an organic compound having at least two active hydrogen groups, and examples of the active hydrogen group include a hydroxyl group, a primary or secondary amino group, and a thiol group (SH). Specifically, 4,4′-methylenebis (o-chloroaniline) (MOCA), 2,6-dichloro-p-phenylenediamine, 4,4′-methylenebis (2,3-dichloroaniline), 3,5 -Bis (methylthio) -2,4-toluenediamine, 3,5-bis (methylthio) -2,6-toluenediamine, 3,5-diethyltoluene-2,4-diamine, 3,5-diethyltoluene-2 , 6-diamine, trimethylene glycol-di-p-aminobenzoate, polytetramethylene oxide-di-p-aminobenzoate, 4,4′-diamino-3,3 ′, 5,5′-tetraethyldiphenylmethane, 4, 4'-diamino-3,3'-diisopropyl-5,5'-dimethyldiphenylmethane, 4,4'-diamino-3,3 ', 5,5'-tetra Sopropyldiphenylmethane, 1,2-bis (2-aminophenylthio) ethane, 4,4′-diamino-3,3′-diethyl-5,5′-dimethyldiphenylmethane, N, N′-di-sec-butyl -4,4'-diaminodiphenylmethane, 3,3'-diethyl-4,4'-diaminodiphenylmethane, m-xylylenediamine, N, N'-di-sec-butyl-p-phenylenediamine, m-phenylenediamine And polyamines exemplified by p-xylylenediamine and the like, or the low molecular weight polyols and low molecular weight polyamines mentioned above. These may be used alone or in combination of two or more.

  It is necessary to add 5 to 30 parts by weight of the isocyanate-modified product with respect to 100 parts by weight of the isocyanate-terminated prepolymer, and preferably 5 to 20 parts by weight. In order to obtain a polishing pad having desired polishing characteristics, the number of isocyanate groups in the isocyanate component relative to the number of active hydrogen groups (hydroxyl groups, amino groups) in the chain extender is preferably 0.80 to 1.20. More preferably, it is 0.99 to 1.15. When the number of isocyanate groups is outside the above range, curing failure occurs and the required specific gravity and hardness cannot be obtained, and the polishing characteristics tend to be deteriorated.

  The non-foamed polyurethane can be produced by applying a known urethanization technique such as a melting method or a solution method, but is preferably produced by a melting method in consideration of cost, work environment and the like. In addition, you may add stabilizers, such as antioxidant, a lubricant, a pigment, a filler, an antistatic agent, and another additive as needed.

  Moreover, you may use the catalyst which accelerates | stimulates well-known polyurethane reactions, such as a tertiary amine type | system | group. The type and addition amount of the catalyst are selected in consideration of the flow time for pouring into a mold having a predetermined shape after the mixing step.

  The production of non-foamed polyurethane is a batch method in which each component is weighed and put into a container and stirred. Alternatively, each component is continuously supplied to the stirring device and stirred, and the polyurethane raw material composition is sent out. It may be a continuous production method for producing a molded product.

  In addition, the isocyanate-terminated prepolymer and the isocyanate-modified product are put into a reaction vessel, and after that, a chain extender is added and stirred, and then poured into a casting mold of a predetermined size to prepare a block. The block is shaped like a bowl or a band saw In the method of slicing using a slicer or the above-described casting step, a thin sheet may be used. Alternatively, a sheet-like non-foamed polyurethane may be obtained by extrusion from a T die.

  The non-foamed polyurethane preferably has an Asker D hardness of 65 to 80 degrees, more preferably 70 to 75 degrees.

  The polishing surface of the polishing pad (polishing layer) of the present invention that comes into contact with the object to be polished preferably has a concavo-convex structure for holding and renewing the slurry. A polishing layer made of a non-foamed material has a poor function of holding and renewing the slurry, but by forming a concavo-convex structure on the polishing surface, it is possible to efficiently hold and renew the slurry, and It is possible to prevent destruction of the object to be polished due to adsorption. The concavo-convex structure is not particularly limited as long as it is a shape that holds and renews the slurry. For example, an XY lattice groove, a concentric circular groove, a through hole, a non-penetrating hole, a polygonal column, a cylinder, a spiral groove, Examples include eccentric circular grooves, radial grooves, and combinations of these grooves. In addition, these uneven structures are generally regular, but in order to make the slurry retention and renewability desirable, the groove pitch, groove width, groove depth, etc. should be changed for each range. Is also possible.

  The method for producing the concavo-convex structure is not particularly limited. For example, a method of machine cutting using a jig such as a tool of a predetermined size, pouring a resin into a mold having a predetermined surface shape, and curing. Using a press plate having a predetermined surface shape, a method of producing a resin by pressing, a method of producing using photolithography, a method of producing using a printing technique, a carbon dioxide laser, etc. Examples include a manufacturing method using laser light.

  The thickness of the polishing layer is not particularly limited, but is usually about 0.8 to 4 mm, and preferably 1.5 to 2.5 mm. As a method for producing the polishing layer having the above thickness, a method in which the non-foamed polyurethane block is made to have a predetermined thickness using a band saw type or canna type slicer, a resin is poured into a mold having a predetermined thickness cavity, and curing is performed. And a method using a coating technique or a sheet forming technique.

  Further, the thickness variation of the polishing layer is preferably 100 μm or less. When the thickness variation exceeds 100 μm, the polishing layer has a large undulation, and there are portions where the contact state with the object to be polished is different, which adversely affects the polishing characteristics. In order to eliminate the thickness variation of the polishing layer, in general, the surface of the polishing layer is dressed with a dresser in which diamond abrasive grains are electrodeposited and fused at the initial stage of polishing. As a result, the dressing time becomes longer and the production efficiency is lowered.

  Examples of a method for suppressing the variation in the thickness of the polishing layer include a method of buffing the surface of the polishing sheet sliced to a predetermined thickness. Moreover, when buffing, it is preferable to carry out stepwise with abrasives having different particle sizes.

  The polishing pad of the present invention may be obtained by bonding the polishing layer and the cushion layer.

  The cushion layer supplements the characteristics of the polishing layer. The cushion layer is necessary in order to achieve both planarity and uniformity in a trade-off relationship in CMP. Planarity refers to the flatness of a pattern portion when a polishing object having minute irregularities generated during pattern formation is polished, and uniformity refers to the uniformity of the entire polishing object. The planarity is improved by the characteristics of the polishing layer, and the uniformity is improved by the characteristics of the cushion layer. In the polishing pad of the present invention, the cushion layer is preferably softer than the polishing layer.

  Examples of the cushion layer include fiber nonwoven fabrics such as polyester nonwoven fabric, nylon nonwoven fabric, and acrylic nonwoven fabric, resin-impregnated nonwoven fabrics such as polyester nonwoven fabric impregnated with polyurethane, polymer resin foams such as polyurethane foam and polyethylene foam, butadiene rubber, and isoprene. Examples thereof include rubber resins such as rubber and photosensitive resins.

  As a means for bonding the polishing layer and the cushion layer, for example, a method in which the polishing layer and the cushion layer are sandwiched and pressed with a double-sided tape can be mentioned.

  The double-sided tape has a general configuration in which adhesive layers are provided on both sides of a substrate such as a nonwoven fabric or a film. In consideration of preventing the slurry from penetrating into the cushion layer, it is preferable to use a film for the substrate. Examples of the composition of the adhesive layer include rubber adhesives and acrylic adhesives. Considering the content of metal ions, an acrylic adhesive is preferable because the metal ion content is low. In addition, since the composition of the polishing layer and the cushion layer may be different, the composition of each adhesive layer of the double-sided tape can be made different so that the adhesive force of each layer can be optimized.

  The polishing pad of the present invention may be provided with a double-sided tape on the surface to be bonded to the platen. As the double-sided tape, a tape having a general configuration in which an adhesive layer is provided on both surfaces of a base material can be used as described above. As a base material, a nonwoven fabric, a film, etc. are mentioned, for example. In consideration of peeling from the platen after use of the polishing pad, it is preferable to use a film for the substrate. Examples of the composition of the adhesive layer include rubber adhesives and acrylic adhesives. Considering the content of metal ions, an acrylic adhesive is preferable because the metal ion content is low.

  The semiconductor device is manufactured through a step of polishing the surface of the semiconductor wafer using the polishing pad. A semiconductor wafer is generally a laminate of a wiring metal and an oxide film on a silicon wafer. The method and apparatus for polishing the semiconductor wafer are not particularly limited. For example, as shown in FIG. 1, a polishing surface plate 2 that supports a polishing pad (polishing layer) 1 and a support table (polishing head) that supports the semiconductor wafer 4. 5 and a polishing apparatus equipped with a backing material for uniformly pressing the wafer and a supply mechanism of the abrasive 3. The polishing pad 1 is attached to the polishing surface plate 2 by attaching it with a double-sided tape, for example. The polishing surface plate 2 and the support base 5 are disposed so that the polishing pad 1 and the semiconductor wafer 4 supported on each of the polishing surface plate 2 and the support table 5 face each other, and are provided with rotating shafts 6 and 7 respectively. Further, a pressurizing mechanism for pressing the semiconductor wafer 4 against the polishing pad 1 is provided on the support base 5 side. In polishing, the semiconductor wafer 4 is pressed against the polishing pad 1 while rotating the polishing surface plate 2 and the support base 5, and polishing is performed while supplying slurry. The flow rate of the slurry, the polishing load, the polishing platen rotation speed, and the wafer rotation speed are not particularly limited, and are adjusted as appropriate.

  As a result, the protruding portion of the surface of the semiconductor wafer 4 is removed and polished flat. Thereafter, a semiconductor device is manufactured by dicing, bonding, packaging, or the like. The semiconductor device is used for an arithmetic processing device, a memory, and the like.

  Hereinafter, the present invention will be described with reference to examples, but the present invention is not limited to these examples.

[Measurement and evaluation methods]
(Measurement of number average molecular weight)
The number average molecular weight was measured by GPC (gel permeation chromatography) and converted by standard polystyrene.
GPC device: manufactured by Shimadzu Corporation, LC-10A
Column: Polymer Laboratories, (PLgel, 5 μm, 500 Å), (PLgel, 5 μm, 100 Å), and (PLgel, 5 μm, 50 Å) connected to three columns, flow rate: 1.0 ml / min Concentration: 1 .0g / l
Injection volume: 40 μl
Column temperature: 40 ° C
Eluent: Tetrahydrofuran

(Measurement of specific gravity)
This was performed according to JIS Z8807-1976. The produced non-foamed polyurethane and polyurethane foam cut into 4 cm x 8.5 cm strips (thickness: arbitrary) are used as specific gravity measurement samples, and the environment is 23 ° C ± 2 ° C and humidity is 50% ± 5%. And left to stand for 16 hours. The specific gravity was measured using a hydrometer (manufactured by Sartorius).

(Measurement of hardness)
This was performed in accordance with JIS K6253-1997. The produced non-foamed polyurethane and polyurethane foam cut into a size of 2 cm × 2 cm (thickness: arbitrary) were used as samples for hardness measurement, and the temperature was 23 ° C. ± 2 ° C. and the humidity was 50% ± 5%. Let stand for hours. At the time of measurement, the samples were overlapped to a thickness of 6 mm or more. The hardness after 1 minute was measured using a hardness meter (manufactured by Kobunshi Keiki Co., Ltd., Asker D type hardness meter).

（式中、Ｌｘはｘ方向の測定長であり、Ｌｙはｙ方向の測定長である。）
測定条件
測定面積：５００μｍ×５００μｍ（測定長５００μｍ）
スキャン速度：スキャンピッチ２０μｍ／ｓ
トレース：５１（１０μｍピッチ）
測定荷重：２ｍｇ (Measurement of surface roughness distribution)
The produced polishing pad was bonded to the platen of a polishing apparatus (Okamoto Machine Tool Co., Ltd., SPP600S). Using a dresser (M type, manufactured by Asahi Diamond), the surface of the polishing layer was dressed under the conditions of a dressing pressure of 50 g / cm ² , a platen rotation number of 35 rpm, a flowing water amount of 200 ml / min, and a dressing time of 30 minutes. After dressing, three samples (20 mm × 20 mm) were cut out at 120 ° intervals at the center position in the radial direction of the polishing pad. Using a stylus type surface level difference measuring device (P-15, manufactured by KLA Tencor), the surface roughness of each of the three samples was measured once, and the three-dimensional square root roughness Sq (μm) was calculated. And the average value (average Sq value) of the Sq values of the three samples was calculated. The average Sq value is preferably 6 to 9 μm. The three-dimensional square root roughness Sq is obtained by the following equation when the average plane is the XY plane, the vertical direction is the Z axis, and the measured surface shape curve is z = f (x, y).

(In the formula, Lx is the measurement length in the x direction, and Ly is the measurement length in the y direction.)
Measurement conditions Measurement area: 500 μm × 500 μm (measurement length 500 μm)
Scan speed: scan pitch 20 μm / s
Trace: 51 (10 μm pitch)
Measurement load: 2mg

(Cut rate measurement)
The produced polishing pad was bonded to the platen of a polishing apparatus (Okamoto Machine Tool Co., Ltd., SPP600S). Using a dresser (M type, manufactured by Asahi Diamond), the surface of the polishing layer under the conditions of a dress load of 9.7 lbf, a dress pressure of 50 g / cm ² , a platen rotation number of 35 rpm, a flow rate of 200 ml / min, and a dressing time of 30 minutes Dressed up. After dressing, a strip-shaped sample having a width of 20 mm and a length of 610 mm was cut out. The thickness was measured every 20 mm from the center of the sample (15 points on one side, 30 points in total). Then, a difference in thickness (amount of wear) from the undressed center portion was calculated at each measurement position, and an average value thereof was calculated. The cut rate is calculated by the following formula. In the present invention, the cut rate is preferably 2 μm / min or more, more preferably 2 to 3 μm / min.
Cut rate (μm / min) = average amount of wear / (0.5 × 60)

(Scratch evaluation)
SPP600S (manufactured by Okamoto Machine Tool Co., Ltd.) was used as a polishing apparatus, and scratches were evaluated using the prepared polishing pad. After polishing a 1-μm thick thermal oxide film on an 8-inch silicon wafer under the following conditions, using a surface defect detection device (Surf Scan SP1 TBI) manufactured by KLA Tencor at EE (Edge Exclusion) 5 mm The number of defects of 0.19 to 2 μm on the wafer was measured. As polishing conditions, silica slurry (SS12 Cabot) was added at a flow rate of 150 ml / min during polishing, the polishing load was 350 g / cm ² , the polishing platen rotation speed was 35 rpm, and the wafer rotation speed was 30 rpm.

(Measurement of average polishing rate)
Using an SPP600S (manufactured by Okamoto Machine Tool Co., Ltd.) as the polishing apparatus, the average polishing rate was measured using the prepared polishing pad. An 8 inch silicon wafer with a 1 μm thermal oxide film was polished for 1 minute under the following conditions, and the average polishing speed was determined from the film pressure measured after polishing at 73 specific positions on the wafer as shown in FIG. Calculated. An interference type film thickness measuring device (manufactured by Otsuka Electronics Co., Ltd.) was used for measuring the thickness of the oxide film. As polishing conditions, silica slurry (SS12 Cabot) was added at a flow rate of 150 ml / min during polishing, the polishing load was 350 g / cm ² , the polishing platen rotation speed was 35 rpm, and the wafer rotation speed was 30 rpm.

Example 1
In a container, 1229 parts by weight of toluene diisocyanate (mixture of 2,4-isomer / 2,6-isomer = 80/20), 272 parts by weight of 4,4′-dicyclohexylmethane diisocyanate, polytetramethylene ether glycol 1901 having a number average molecular weight of 1018 Part by weight and 198 parts by weight of diethylene glycol were added and reacted at 70 ° C. for 4 hours to obtain an isocyanate-terminated prepolymer. 100 parts by weight of the prepolymer and 10 parts by weight of 1,6-hexamethylene diisocyanate (Sumika Bayer Urethane Co., Ltd., Sumidur N-3300, isocyanurate type) as an isocyanate-modified product are mixed with a planetary stirring and deaerator. And defoamed. Thereafter, 32.9 weight of 4,4′-methylenebis (o-chloroaniline) melted at 120 ° C. was added to the mixed solution, mixed with a planetary stirring deaerator, and defoamed to prepare a polyurethane raw material composition. . The composition was poured into an open mold (casting container) having a length and width of 800 mm and a depth of 2.5 mm and post-cured at 100 ° C. for 16 hours to obtain a non-foamed polyurethane sheet. Next, using a buffing machine (Amitech Co., Ltd.), the surface of the sheet was buffed to a thickness of 1.27 mm to obtain a sheet with an adjusted thickness accuracy. The buffed sheet is punched out with a diameter of 61 cm, and a concentric circle having a groove width of 0.25 mm, a groove pitch of 1.50 mm, and a groove depth of 0.40 mm on the surface using a groove processing machine (manufactured by Techno). Groove processing was performed to obtain a polishing layer. A double-sided tape (manufactured by Sekisui Chemical Co., Ltd., double tack tape) was attached to the surface of the polishing layer opposite to the grooved surface using a laminator. Furthermore, the surface of the corona-treated cushion layer (manufactured by Toray Industries, Inc., polyethylene foam, Torepef, thickness 0.8 mm) was buffed and bonded to the double-sided tape using a laminator. Further, a double-sided tape was attached to the other surface of the cushion layer using a laminator to prepare a polishing pad.

Example 2
In Example 1, the addition amount of Sumidur N-3300 was changed from 10 to 5 parts by weight, and the addition amount of 4,4′-methylenebis (o-chloroaniline) was changed from 32.9 to 29.7 parts by weight. A polishing pad was produced in the same manner as in Example 1 except for the change.

Example 3
In Example 1, instead of Sumijoule N-3300, 10 parts by weight of multimerized 1,6-hexamethylene diisocyanate (manufactured by Sumika Bayer Urethane Co., Ltd., Sumijoule N-3200, Burette type) was used as an isocyanate modified product. A polishing pad was prepared in the same manner as in Example 1 except that the amount of 4,4′-methylenebis (o-chloroaniline) added was changed from 32.9 to 33.2 parts by weight.

Comparative Example 1
Example 1 was the same as Example 1 except that Sumidur N-3300 was not added and the amount of 4,4′-methylenebis (o-chloroaniline) added was changed from 32.9 parts by weight to 26.6 parts by weight. A polishing pad was produced in the same manner.

Comparative Example 2
In Example 1, the addition amount of Sumidur N-3300 was changed from 10 to 35 parts by weight, and the addition amount of 4,4′-methylenebis (o-chloroaniline) was changed from 32.9 to 48.8 parts by weight. A polishing pad was produced in the same manner as in Example 1 except for the change.

Comparative Example 3
In a container, 1229 parts by weight of toluene diisocyanate (mixture of 2,4-isomer / 2,6-isomer = 80/20), 272 parts by weight of 4,4′-dicyclohexylmethane diisocyanate, polytetramethylene ether glycol 1901 having a number average molecular weight of 1018 Part by weight and 198 parts by weight of diethylene glycol were added and reacted at 70 ° C. for 4 hours to obtain an isocyanate-terminated prepolymer. 100 parts by weight of the prepolymer, 20 parts by weight of 1,6-hexamethylene diisocyanate (manufactured by Sumika Bayer Urethane Co., Ltd., Sumidur N-3300, isocyanurate type) as a modified isocyanate, and a silicon surfactant (Toray Industries, Inc.) 3.6 parts by weight of Dow Corning Silicon, SH-192) was added to the polymerization vessel, mixed, adjusted to 80 ° C. and degassed under reduced pressure. Then, it stirred vigorously for about 4 minutes so that a bubble might be taken in in a reaction system with the rotation speed of 900 rpm using the stirring blade. Thereto was added 39.3 parts by weight of 4,4′-methylenebis (o-chloroaniline) previously melted at 120 ° C. The mixed liquid was stirred for about 70 seconds, and then poured into a pan-shaped open mold (casting container). When the fluidity of the mixed solution disappeared, it was put in an oven and post-cured at 100 ° C. for 16 hours to obtain a polyurethane foam block. The polyurethane foam block heated to about 80 ° C. was sliced using a slicer (AGW Tech, VGW-125) to obtain a polyurethane foam sheet. Next, using a buffing machine (Amitech Co., Ltd.), the surface of the sheet was buffed to a thickness of 1.27 mm to obtain a sheet with an adjusted thickness accuracy. The buffed sheet is punched out with a diameter of 61 cm, and a concentric circle having a groove width of 0.25 mm, a groove pitch of 1.50 mm, and a groove depth of 0.40 mm on the surface using a groove processing machine (manufactured by Techno). Groove processing was performed to obtain a polishing layer. Thereafter, a polishing pad was produced in the same manner as in Example 1.

1: Polishing pad (polishing layer)
2: Polishing surface plate 3: Abrasive (slurry)
4: Polishing object (semiconductor wafer)
5: Support base (polishing head)
6, 7: Rotating shaft

Claims (7)

In the polishing pad having a polishing layer made of non-foamed polyurethane, the non-foamed polyurethane is an isocyanate-terminated prepolymer obtained by reacting a prepolymer raw material composition containing diisocyanate, high molecular weight polyol, and low molecular weight polyol, three or more Is a reaction cured product of a polyurethane raw material composition containing a chain extender and an isocyanate-modified product that has been multiplied by the addition of a diisocyanate, and the added amount of the isocyanate-modified product is based on 100 parts by weight of the isocyanate-terminated prepolymer. A polishing pad comprising 5 to 30 parts by weight. The polishing pad according to claim 1, wherein the high molecular weight polyol is a polyether polyol having a number average molecular weight of 500 to 5,000, and the diisocyanate is toluene diisocyanate and dicyclohexylmethane diisocyanate. The polishing pad according to claim 1 or 2, wherein the isocyanate-modified product is an isocyanurate-type and / or burette-type hexamethylene diisocyanate-modified product. The polishing pad according to claim 1, wherein the non-foamed polyurethane has an Asker D hardness of 65 to 80 degrees. The polishing pad according to any one of claims 1 to 4, wherein the cut rate is 2 µm / min or more. Isocyanate-modified product obtained by adding three or more diisocyanates to 100 parts by weight of an isocyanate-terminated prepolymer obtained by reacting a prepolymer raw material composition containing a diisocyanate, a high molecular weight polyol, and a low molecular weight polyol. A method for producing a polishing pad comprising a step of mixing a first component containing 5 to 30 parts by weight with a second component containing a chain extender and curing to produce a non-foamed polyurethane. A method for manufacturing a semiconductor device, comprising a step of polishing a surface of a semiconductor wafer using the polishing pad according to claim 1.

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