JP2015116615A - Polishing pad and polishing method using polishing pad - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polishing pad enabling optical means to inspect a polishing target during polishing or to measure a polishing endpoint.SOLUTION: Provided is a polishing pad including a polishing layer comprising a thermoplastic polyurethane composition in which a content of nitrogen atoms deriving from isocyanate groups of thermoplastic polyurethane is 4.8 to 6.0 mass%, the polishing layer including a detection part and a remaining part, a thickness of the detection part being 0.2 to 1.0 mm and a thickness of the remaining part being 1.1 to 2.5 mm.

Description

  The present invention relates to a polishing pad useful for planarizing the surface of an insulating film and a conductor film in a semiconductor or an integrated circuit, and a polishing method using the polishing pad.

  Large scale integrated circuits (LSIs) represented by semiconductor memories have been integrated and miniaturized year by year, and as a result, the manufacturing technology has to cope with higher density, and the manufacturing process has become complicated. ing. The number of stacked semiconductor devices has also increased, and irregularities on the wafer surface such as insulating films and conductor films during the manufacture of semiconductor devices, which has not been a problem in the past, are caused by disconnections and resistance values due to the multilayered semiconductor devices. This is a cause of variation. Therefore, further planarization of the wafer surface is required.

  In addition, when manufacturing an LSI, lithography (projection exposure) is performed as a technique for forming a mask pattern on the wafer surface. With the miniaturization of semiconductor integrated circuits, the exposure wavelength is shortened and the focus of exposure is increased. The depth is very shallow. If there are irregularities on the surface of the wafer, the resolution of the mask pattern will be reduced. From this point, further flattening of the wafer surface is required.

  The planarization of the wafer surface is usually performed by a polishing apparatus using chemical mechanical polishing (CMP). As a technique for determining the polishing end point while polishing the wafer surface, a method using a laser interferometer (for example, refer to Patent Document 1) or a portion transparent to light of a specific wavelength (transmission window) There has been proposed a method using a polishing pad having a thickness (see Patent Documents 2 and 3). Patent Document 2 exemplifies a method of manufacturing a pad having a transmission plug (transmission window) by embedding the transmission plug (transmission window) in an impermeable resin in a liquid state and then curing the impermeable resin and further slicing. ing. Patent Document 3 describes a polishing pad in which a substantially transparent plug (transmission window) is disposed.

  However, the polishing pads described in Patent Documents 2 and 3 are (1) complicated to manufacture because the transmission window needs to be embedded in the polishing pad. (2) Between the transmission window and its peripheral part. If a gap is generated, it will cause the polishing slurry used for polishing to leak. (3) Since the material constituting the transmission window and the material constituting the other part are different, these are different speeds during polishing. As a result, the problem arises that cracks and tears occur around the transmission window.

  In order to solve the above-mentioned problem, a polishing pad in which the polishing surface portion and the transmission window are made of the same resin has been proposed (see Patent Document 4). Patent Document 4 describes a polishing pad including the molded article having a region where the polymer material is transparent (transmission window) and an adjacent region where the polymer material is opaque. In this Patent Document 4, when a semi-crystalline thermoplastic polymer is used to cool from the melting temperature to the glass transition temperature, a part of the part is subjected to rapid cooling treatment to impart transparency to the part. Or when the polishing pad is produced from a reactive thermosetting polymer formed from a mixture of a polymeric diol and a polymeric diamine and a diisocyanate such as diphenylmethane diisocyanate, the reaction temperature of the part forming the transmission window is changed. A method is described in which transparency is imparted to the part by changing the temperature to that of the part.

  However, in the polishing pad described in Patent Document 4, (1) the temperature control at the time of manufacture in the portion that becomes the transmission window is complicated, (2) even if the transmission window and the other portions are the same resin In addition, when transparency is imparted to the transmission window by temperature control, there is an adverse effect such as generation of scratches during polishing due to the difference in physical properties between the resin constituting the transmission window and the resin constituting the other part. There is a problem that is concerned.

U.S. Pat. No. 5,1394,941 Japanese National Patent Publication No. 11-512977 US Pat. No. 5,893,796 Special table 2003-507199 gazette

  Therefore, an object of the present invention is to provide a polishing pad capable of performing inspection of an object to be polished and measurement of a polishing end point during polishing by optical means.

According to the present invention, the above object is
[1] A polishing pad having a polishing layer comprising a thermoplastic polyurethane composition having a nitrogen atom content of 4.8 to 6.0% by mass derived from an isocyanate group of a thermoplastic polyurethane,
The polishing layer has a detection portion and other portions;
The thickness of the detection part is 0.2 to 1.0 mm,
A polishing pad having a thickness of the other part of 1.1 to 2.5 mm;
[2] The polishing pad according to [1] above, wherein the laser transmittance of the thermoplastic polyurethane composition under the following measurement conditions is 20 to 60%. Test piece: Sheet of thermoplastic polyurethane composition Test piece thickness: 0 .5mm
Laser wavelength: 660 nm
Laser power: 310μW
Distance between detection head and output head: 10 cm
Measurement position of test piece: intermediate between detection head and output head;
[3] The polishing pad of [1] or [2] above, wherein the area of the detection portion is 100 to 2,000 mm ² ;
[4] The polishing pad according to any one of [1] to [3], wherein the planar shape of the detection portion is a rectangle having a short side of 10 to 25 mm and a long side of 10 to 80 mm;
[5] The polishing pad according to any one of [1] to [4], wherein the thermoplastic polyurethane is obtained by reacting a polymer diol, an organic diisocyanate, and a chain extender;
[6] The polishing pad according to [5], wherein the polymer diol has a number average molecular weight of 1,400 to 3,600;
[7] The polishing pad of [5] or [6] above, wherein the polymer diol contains a polyester diol and / or a polyether diol;
[8] The polishing pad according to [5] or [6], wherein the polymer diol contains a polyester diol having a structural unit derived from a diol having 6 to 12 carbon atoms;
[9] The polymer diol is poly (ethylene glycol), poly (tetramethylene glycol), poly (nonamethylene adipate), poly (2-methyl-1,8-octamethylene adipate), poly (2-methyl-1, 8-octamethylene-co-nonamethylene adipate) and poly (3-methyl-1,5-pentamethylene adipate), and at least one selected from the group consisting of
The organic diisocyanate is at least one selected from the group consisting of 4,4′-diphenylmethane diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate and isophorone diisocyanate;
The chain extender is at least selected from the group consisting of 1,3-propanediol, 1,4-butanediol, neopentyl glycol, 1,5-pentanediol, 1,6-hexanediol and 1,4-cyclohexanedimethanol One of the polishing pads of [5] or [6] above;
[10] The mass ratio ([mass of polymer diol] / [total mass of organic diisocyanate and chain extender]) of the mass of the polymer diol and the total mass of the organic diisocyanate and the chain extender is 10/90 to 50 / 50, the polishing pad according to any one of the above [5] to [9];
[11] The polishing pad according to any one of [1] to [10], wherein an elastic layer is laminated on a surface of the polishing layer opposite to the polishing surface;
[12] The polishing pad according to [11] above, wherein a portion of the elastic layer positioned above the detection portion of the polishing layer is a void, or a transparent member is fitted in the void; and [13] the above [1] ] To [12] a polishing method using the polishing pad;
Is achieved by providing

  ADVANTAGE OF THE INVENTION According to this invention, the polishing pad which can perform the test | inspection of the to-be-polished object during grinding | polishing, and the measurement of a polishing end point by an optical means, and the grinding | polishing method using this polishing pad can be provided.

  The polishing pad of the present invention is a polishing pad having a polishing layer made of a thermoplastic polyurethane composition having a content of nitrogen atoms derived from isocyanate groups of thermoplastic polyurethane of 4.8 to 6.0% by mass. The layer has a detection portion and other portions, the detection portion has a thickness of 0.2 to 1.0 mm, and the other portion has a thickness of 1.1 to 2.5 mm.

  The thermoplastic polyurethane composition may be composed only of the thermoplastic polyurethane (that is, the thermoplastic polyurethane composition = thermoplastic polyurethane), or may be a mixture of the thermoplastic polyurethane and other components. As the thermoplastic polyurethane, those obtained by reacting a polymer diol, an organic diisocyanate and a chain extender are preferable from the viewpoint of light transmittance. More preferably, the thermoplastic polyurethane does not substantially have a foam structure.

  Examples of the polymer diol include polyether diol, polyester diol, and polycarbonate diol. Of these, polyether diols and polyester diols are preferred.

  Examples of the polyether diol include poly (ethylene glycol), poly (propylene glycol), poly (tetramethylene glycol), poly (methyltetramethylene glycol), and the like. Of these, poly (ethylene glycol) and poly (tetramethylene glycol) are preferred.

  The polyester diol can be obtained, for example, by subjecting an ester-forming derivative such as dicarboxylic acid or its ester or anhydride and a low molecular diol directly to an esterification reaction or transesterification according to a conventional method.

  Examples of the dicarboxylic acid include oxalic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, dodecanedioic acid, 2-methylsuccinic acid, 2-methyladipic acid, and 3-methyladipic acid. Aliphatic dicarboxylic acid obtained by dimerizing unsaturated fatty acids obtained by fractional distillation of 3-methylpentanedioic acid, 2-methyloctanedioic acid, 3,8-dimethyldecanedioic acid, 3,7-dimethyldecanedioic acid, triglyceride Aliphatic dicarboxylic acids having 2 to 48 carbon atoms (preferably 2 to 12 carbon atoms) such as acids (dimer acids) and hydrogenated products thereof (hydrogenated dimer acids); Alicyclic rings such as 1,4-cyclohexanedicarboxylic acids Formula dicarboxylic acids; aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid and orthophthalic acid. These dicarboxylic acids may be used alone or in combination of two or more. Of these, aliphatic dicarboxylic acids having 2 to 12 carbon atoms are preferred, and adipic acid is more preferred.

  A low molecular diol refers to a diol having 12 or less carbon atoms. Examples of the low molecular diol include ethylene glycol, 1,3-propanediol, 1,2-propanediol, 2-methyl-1,3-propanediol, 1,4-butanediol, neopentyl glycol, 1,5- Pentanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 2-methyl-1,8-octanediol, 1,9- Examples thereof include aliphatic diols such as nonanediol and 1,10-decanediol; and alicyclic diols such as cyclohexanedimethanol and cyclohexanediol. These low molecular diols may be used alone or in combination of two or more. The low molecular diol preferably has 6 to 12 carbon atoms, more preferably 8 to 10 carbon atoms, and still more preferably 9 carbon atoms. That is, the polyester diol preferably has a structural unit derived from a diol having 6 to 12 carbon atoms, more preferably has a structural unit derived from a diol having 8 to 10 carbon atoms, Those having a derived structural unit are more preferred.

  Polyester diols include poly (nonamethylene adipate), poly (2-methyl-1,8-octamethylene adipate), poly (2-methyl-1,8-octamethylene-co-nonamethylene adipate) and poly (3- Methyl-1,5-pentamethylene adipate) is preferred.

  The polycarbonate diol is suitably obtained by reacting a low molecular diol with a carbonate compound such as dialkyl carbonate, alkylene carbonate, or diaryl carbonate. Examples of the low molecular diol constituting the polycarbonate diol include the low molecular diols exemplified above. Examples of the dialkyl carbonate include dimethyl carbonate and diethyl carbonate. Examples of the alkylene carbonate include ethylene carbonate. Examples of the diaryl carbonate include diphenyl carbonate.

  Only one type of polymer diol may be used, or two or more types may be used in combination. The number average molecular weight of the polymer diol is preferably 1,400 to 3,600, more preferably 1,700 to 3,400, and further preferably 2,000 to 3,200. When the number average molecular weight of the polymer diol is too high, the transparency of the resulting polishing layer is reduced, and when the number average molecular weight of the polymer diol is too low, the hardness of the resulting polishing layer becomes too high and scratches are generated. It tends to occur easily. In addition, the number average molecular weight of the high molecular diol as used in this specification means the number average molecular weight calculated based on the hydroxyl value measured based on JISK1557.

  As organic diisocyanate, what is conventionally used for manufacture of a normal polyurethane can be used. Examples of the organic diisocyanate include ethylene diisocyanate, tetramethylene diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate, dodecamethylene diisocyanate, isophorone diisocyanate, Isopropylidenebis (4-cyclohexylisocyanate), cyclohexylmethane diisocyanate, methylcyclohexane diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, lysine diisocyanate, 2,6-diisocyanatomethylcaproate, bis (2-isocyanatoethyl) fumarate Bis (2-isocyanatoethyl) carbonate, 2- Aliphatic or cycloaliphatic diisocyanates such as soocyanatoethyl-2,6-diisocyanatohexanoate, cyclohexylene diisocyanate, methylcyclohexylene diisocyanate, bis (2-isocyanatoethyl) -4-cyclohexene; 2,4 ′ -Diphenylmethane diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, m-phenylene diisocyanate, p-phenylene diisocyanate, m-xylylene diisocyanate, p-xylylene diisocyanate, 1,5-naphthylene diisocyanate, 4,4′-diisocyanatobiphenyl, 3,3′-dimethyl-4,4′-diisocyanatobiphenyl, 3,3′-dimethyl-4,4′-di Socia diisocyanatodiphenylmethane, chloro-phenylene-2,4-diisocyanate, aromatic diisocyanates such as tetramethylxylylene diisocyanate. These organic diisocyanates may be used alone or in combination of two or more. Among these, 4,4′-diphenylmethane diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, and isophorone diisocyanate are preferable from the viewpoint of abrasion resistance of the polishing pad to be obtained, and 4,4′-diphenylmethane diisocyanate. Is more preferable.

  As the chain extender, those conventionally used in the production of ordinary polyurethane can be used. As the chain extender, a low molecular weight compound having a molecular weight of 300 or less and having 2 or more active hydrogen atoms capable of reacting with an isocyanate group is preferably used. For example, ethylene glycol, diethylene glycol, 1,2-propanediol, 1,3 -Propanediol, neopentyl glycol, 2,2-diethyl-1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 2,3-butanediol, 1,4-butanediol, 1 , 5-pentanediol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, 1,4-bis (β-hydroxyethoxy) benzene, 1,4-cyclohexanediol, 1,4-cyclohexanedi Methanol, bis (β-hydroxyethyl) terephthalate, 1,9-nonanediol, Diols such as m-xylylene glycol and p-xylylene glycol; ethylenediamine, trimethylenediamine, tetramethylenediamine, hexamethylenediamine, heptamethylenediamine, octamethylenediamine, nonamethylenediamine, decamethylenediamine, undecamethylenediamine , Dodecamethylenediamine, 2,2,4-trimethylhexamethylenediamine, 2,4,4-trimethylhexamethylenediamine, 3-methylpentamethylenediamine, 1,2-cyclohexanediamine, 1,3-cyclohexanediamine, 1, 4-cyclohexanediamine, 1,2-diaminopropane, hydrazine, xylylenediamine, isophoronediamine, piperazine, o-phenylenediamine, m-phenylenediamine, p-pheny Diamine, tolylenediamine, xylenediamine, adipic acid dihydrazide, isophthalic acid dihydrazide, 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenyl ether, 4,4'-bis (4-aminophenoxy) biphenyl, 4,4 '-Bis (3-aminophenoxy) biphenyl, 1,4-bis (4-aminophenoxy) benzene, 1,3-bis (4-aminophenoxy) benzene, 1,3-bis (3-aminophenoxy) benzene, 3,4′-diaminodiphenyl ether, 4,4′-diaminodiphenyl sulfone, 3,4-diaminodiphenyl sulfone, 3,3′-diaminodiphenyl sulfone, 4,4′-methylene-bis (2-chloroaniline), 3 , 3′-dimethyl-4,4′-diaminobiphenyl, , 4'-diaminodiphenyl sulfide, 2,6-diaminotoluene, 2,4-diaminochlorobenzene, 1,2-diaminoanthraquinone, 1,4-diaminoanthraquinone, 3,3'-diaminobenzophenone, 3,4-diaminobenzophenone 4,4′-diaminobenzophenone, 4,4′-diaminobibenzyl, 2,2′-diamino-1,1′-binaphthalene, 1,3-bis (4-aminophenoxy) alkane, 1,4-bis 1, n-bis (4-aminophenoxy) alkane (n is an integer of 3 to 10) such as (4-aminophenoxy) alkane and 1,5-bis (4-aminophenoxy) alkane, 1,2-bis [ 2- (4-Aminophenoxy) ethoxy] ethane, 9,9-bis (4-aminophenyl) fluorene, 4,4′-diamino Examples thereof include diamines such as benzanilide. These chain extenders may use only 1 type and may use 2 or more types together. Among these, 1,3-propanediol, 1,4-butanediol, neopentyl glycol, 1,5-pentanediol, 1,6-hexanediol and 1,4-cyclohexanedimethanol are preferable, and 1,4- Butanediol and 1,4-cyclohexanedimethanol are more preferred.

  Examples of the thermoplastic polyurethane include poly (ethylene glycol), poly (tetramethylene glycol), poly (nonamethylene adipate), poly (2-methyl-1,8-octamethylene adipate), and poly (2-methyl-1). , 8-octamethylene-co-nonamethylene adipate) and poly (3-methyl-1,5-pentamethylene adipate), at least one polymeric diol, and 4,4′-diphenylmethane diisocyanate, , 4-tolylene diisocyanate, 2,6-tolylene diisocyanate and isophorone diisocyanate, and 1,3-propanediol, 1,4-butanediol, neopentyl glycol, 1, 5-pentane Lumpur, such as those obtained by reacting at least one chain extender selected from the group consisting of 1,6-hexanediol and 1,4-cyclohexanedimethanol.

  The content of the nitrogen atom derived from the isocyanate group in the thermoplastic polyurethane is 4.8 to 6.0% by mass, preferably 4.9 to 5.8% by mass, and preferably 5.0 to 5. 8 mass% is more preferable. When the content is less than 4.8% by mass, the polishing layer made of the thermoplastic polyurethane composition tends to be too soft, and the flatness and polishing efficiency of the surface to be polished tend to decrease. On the other hand, when the content exceeds 6.0% by mass, the resulting polishing pad becomes too hard and the object to be polished tends to be scratched, and the laser transmittance of the polishing layer is high. It becomes difficult to measure the polishing end point by optical means.

  The thermoplastic polyurethane can be produced by melt-kneading the above polymer diol, organic diisocyanate, and chain extender in a predetermined ratio. The use ratio of each component is appropriately determined in consideration of physical properties to be imparted to the polishing layer made of the thermoplastic polyurethane composition, such as wear resistance. In this regard, it is preferable to use each component at a ratio of 0.95 to 1.3 mol of the isocyanate group contained in the organic diisocyanate with respect to 1 mol of the active hydrogen atom contained in the polymer diol and the chain extender. . If the ratio is less than 0.95 mol, the mechanical strength and wear resistance of the polishing layer made of the thermoplastic polyurethane composition tend to be reduced, and if it exceeds 1.3 mol, the productivity of the thermoplastic polyurethane and Storage stability tends to decrease. Isocyanate contained in organic diisocyanate with respect to 1 mol of active hydrogen atom contained in polymer diol and chain extender from the viewpoint of mechanical strength and abrasion resistance of polishing layer and productivity and storage stability of thermoplastic polyurethane It is more preferable to use each component at a ratio of 0.96 to 1.1 mol, and even more preferable to use each component at a ratio of 0.97 to 1.05 mol.

  The mass ratio of the mass of the polymer diol to the total mass of the organic diisocyanate and the chain extender ([mass of polymer diol] / [total mass of the organic diisocyanate and chain extender]) is 10/90 to 50/50. It is preferable to use each component so that If the mass ratio is less than 10/90, the resulting polishing pad becomes too hard and scratches tend to occur on the polished wafer surface, and if it exceeds 50/50, the resulting polishing pad becomes too soft. The flattening performance tends to decrease. From the viewpoint of achieving both scratch suppression and flattening performance, the mass ratio is more preferably 13/87 to 45/55, and still more preferably 16/84 to 40/60.

  It is obtained by reacting a polymer diol having a number average molecular weight of 1,400 to 3,600, an organic diisocyanate and a chain extender, and the content of nitrogen atoms derived from isocyanate groups is 4.8 to 6.0% by mass. The thermoplastic polyurethane is preferably because it has high transparency. In addition, it is more preferable that the thermoplastic polyurethane has substantially no foamed structure.

  The thermoplastic polyurethane can be produced by a known method such as a prepolymer method or a one-shot method using the above-mentioned polymer diol, organic diisocyanate and chain extender as raw materials. The thermoplastic polyurethane is preferably produced by a method of melt polymerization substantially in the absence of a solvent, and a method of continuous melt polymerization using a multi-screw extruder is more preferred.

  The thermoplastic polyurethane composition may contain components other than the thermoplastic polyurethane as long as the effects of the present invention are not impaired. Examples of such other components include fillers such as crosslinking agents, inorganic fillers, and organic fillers; crosslinking accelerators, crosslinking aids, softeners, tackifiers, anti-aging agents, foaming agents, processing aids, Adhesion imparting agent, crystal nucleating agent, heat stabilizer, weathering stabilizer, antistatic agent, colorant, lubricant, flame retardant, flame retardant aid, blooming inhibitor, mold release agent, thickener, antioxidant, etc. Is mentioned. The content of other components in the thermoplastic polyurethane composition is preferably 50% by mass or less, more preferably 20% by mass or less, and further preferably 5% by mass or less. It is particularly preferred that the thermoplastic polyurethane composition is made of thermoplastic polyurethane, that is, the polishing layer is made of thermoplastic polyurethane.

The laser transmittance of the thermoplastic polyurethane composition is preferably 20 to 60%, more preferably 25 to 60%, and even more preferably 30 to 60%. If the laser transmittance is too low, it may be difficult to measure the polishing end point by optical means. On the other hand, when the laser transmittance is higher than 60%, the polishing end point can be measured without forming the thinned portion of the detection portion on the polishing layer. Measurement conditions for the laser transmittance are as follows.
Test piece: Sheet made of thermoplastic polyurethane composition Test piece thickness: 0.5 mm
Laser wavelength: 660 nm
Laser power: 310μW
Distance between detection head and output head: 10 cm
Test piece measurement position: intermediate between detection head and output head

  A sheet made of the thermoplastic polyurethane composition used for the polishing layer is produced by extruding the thermoplastic polyurethane composition into a sheet. Although it does not restrict | limit especially as an extrusion method, For example, using extruders, such as a single screw extruder equipped with T-die, a twin screw extruder, the method of melt-extruding the said resin and using it as a sheet | seat is employable.

  If necessary, the obtained sheet can be processed into a desired size and shape by cutting, punching, cutting, or the like, or processed to a desired thickness by grinding or the like to form a polishing layer. Moreover, you may form a grid | lattice form, a concentric circle form, a spiral groove | channel, a through-hole, etc. in a polishing layer as needed.

  As a method of forming the groove, for example, a method of forming the groove by cutting the above-mentioned sheet; a heated mold, a heat ray or the like is brought into contact with the above-mentioned sheet, and the groove is formed by dissolving the contact portion. Method: A method for producing a sheet in which grooves are formed in advance by using a mold having convex portions for forming grooves, pouring the melt of the thermoplastic polyurethane composition into the mold, and then solidifying the mold. Etc.

  As a method for forming the detection portion of the polishing layer, for example, a method of cutting the pad surface and / or the back surface after forming the groove with a spindle or the like; a mold having a convex portion for forming the groove and the detection portion is used. For example, a method of manufacturing a sheet in which a groove and a detection portion are formed in advance by pouring a melt of the thermoplastic polyurethane composition and solidifying the melt.

The polishing layer is characterized by having a detection part having a thickness of 0.2 to 1.0 mm and another part having a thickness of 1.1 to 2.5 mm.
Here, the detection portion refers to a thin portion of the polishing layer formed in the vicinity of the laser irradiation window on the polishing table (platen) of the polishing apparatus, and is a groove for controlling the slurry flow formed on the entire polishing layer. Clearly distinguished. Further, in the present invention, the groove is formed in a continuous line shape and has a recess (specifically, a width in a direction perpendicular to the continuous direction) of 3 mm or less (that is, cannot be used for detection by light). Part).
On the other hand, the detection portion is formed in an elliptical shape, a circular shape, a polygonal shape, etc., and has a width (short axis for an elliptical shape, diameter for a circular shape, minimum side for a polygonal shape). A thin part exceeding 10 mm (that is, a part that can be used for detection by light). Moreover, the thickness of the above-mentioned detection part and the thickness of another part say the thickness of the part in which the groove | channel is not formed. In addition, the detection part may be only one place on the polishing pad, or may exist in two or more places.

  The thickness of the detection portion of the polishing layer is preferably 0.25 mm to 0.9 mm, and more preferably 0.3 mm to 0.8 mm. When the detection portion is too thin, the mechanical strength of the polishing layer is low, and there is a possibility of slurry leakage due to breakage. When the detection portion is too thick, light transmission tends to be inhibited.

  The thickness of the other part of the polishing layer is preferably 1.2 mm to 2.3 mm, and more preferably 1.3 mm to 2.1 mm. If the other part of the polishing layer is too thin, polishing uniformity may be reduced. In the case of a multi-layer type polishing pad having an elastic layer, if the other part of the polishing layer is too thick, the effect of the elastic layer following the warpage and waviness of the entire object to be polished may be reduced.

The area of the detection portion of the polishing layer is preferably 100～2,000Mm ^2, more preferably 200～1800Mm ^2, further preferably 300~1,600mm ^2. If the detection portion is too small, it may be difficult to measure the polishing end point by optical means, and if the detection portion is too large, the polishing characteristics of the polishing layer may change.

  The planar shape of the detection portion is preferably a rectangle having a short side of 10 to 25 mm and a long side of 10 to 80 mm, more preferably a rectangle having a short side of 10 to 23 mm and a long side of 25 to 80 mm, and a short side of 10 to 20 mm. And it is more preferable that it is a rectangle with a long side of 35 to 80 mm. Here, the planar shape of the detection portion refers to the shape of the detection portion when the surface of the polishing layer on which the detection portion is formed is viewed from above. In addition, the rectangle in the present invention means a planar quadrilateral having opposite sides with a length equal to four internal angles that are perpendicular to each other, and is a concept including a square with the short side and the long side having the same length.

  The polishing pad may be a single-layer polishing pad consisting of only one polishing layer, or a multi-layer polishing pad in which an elastic layer is laminated on the surface opposite to the polishing surface of the polishing layer. The elastic layer preferably has a hardness lower than that of the polishing layer. When the hardness of the elastic layer is lower than the hardness of the polishing layer, the hard polishing layer acts on local irregularities of the object to be polished, while the elastic layer is flexible against warping and waviness of the entire object to be polished. Therefore, as a result, both global flatness (overall flatness of the object to be polished) and local flatness (local flatness of the object to be polished) can be achieved.

  The hardness of the polishing layer in the multi-layer polishing pad is 55 or more as the JIS-D hardness because scratches are likely to occur on the surface to be polished if the local flatness of the object to be polished is too high or the hardness is too high. It is preferably 60-80, more preferably 65-75. On the other hand, if the hardness of the elastic layer is global flatness or if the hardness is too low, the rotation of the polishing table cannot be sufficiently transmitted to the polishing layer when it is affixed to the polishing table (platen) and polishing. Since stable polishing may not be performed, the JIS-C hardness is preferably 20 to 80, more preferably 30 to 70, and still more preferably 40 to 65.

  The thickness of the elastic layer is preferably 0.5 to 3 mm. When the thickness of the elastic layer is less than 0.5 mm, the follow-up effect on the warpage and waviness of the entire object to be polished may be reduced. On the other hand, when the thickness exceeds 3 mm, the entire polishing pad becomes too soft. When polishing is performed by attaching a polishing pad to a polishing table (platen), the rotation of the polishing table cannot be sufficiently transmitted to the polishing layer, and stable polishing may not be performed. The thickness of the elastic layer is more preferably 1 to 2.5 mm.

  As the material of the elastic layer, natural rubber, nitrile rubber, polybutadiene rubber, silicone rubber, etc., as well as non-woven fabrics impregnated with polyurethane currently used for general purposes (for example, “Suba400” manufactured by Nitta Haas Co., Ltd.) It is possible to employ a thermoplastic elastomer such as a polyester-based thermoplastic elastomer, a polyamide-based thermoplastic elastomer, a fluorine-based thermoplastic elastomer; a foamed plastic; a polyurethane, or the like. Among them, polyurethane is preferable because it has the flexibility required for the elastic layer and a foamed structure can be easily obtained.

  Multi-layer type polishing pads are those in which the polishing layer and the elastic layer are directly bonded, as well as those in which both layers are bonded with an adhesive, double-sided adhesive tape, etc., or there is another layer between both layers Including what to do.

  In the multi-layer type polishing pad, in order not to interfere with the inspection of the object to be polished and the measurement of the polishing end point by optical means, the elastic layer portion located above the detection portion of the polishing layer is a void, or the void It is preferable that a transparent member is fitted in the. Here, the transparent member refers to a member that is transparent to light (for example, laser light) used for optical means. Examples of the transparent member include glass, acrylic, polycarbonate, polyethylene terephthalate, vinyl chloride, polystyrene, polyurethane, and epoxy.

  The polishing pad of the present invention can be used in a polishing method such as chemical mechanical polishing together with a known polishing slurry. As the polishing slurry, for example, a liquid medium such as water or oil; an abrasive such as aluminum oxide, cerium oxide, zirconium oxide, or silicon carbide; a slurry containing components such as a base, an acid, or a surfactant can be used. In the polishing method, if necessary, a lubricating oil, a coolant, or the like may be used together with the polishing slurry.

  The polishing method uses a known apparatus (in particular, an apparatus capable of performing inspection of the object to be polished and measurement of the polishing end point by optical means during polishing) and polishing the object to be polished through the polishing slurry. This can be done by contacting the pad under pressure at a constant speed for a fixed time. Examples of the object to be polished include quartz, silicon, glass, an optical substrate, an electronic circuit substrate, a multilayer wiring substrate, and a hard disk. In particular, the object to be polished is preferably a silicon wafer or a semiconductor wafer. As a semiconductor wafer, for example, an insulating film such as silicon oxide, silicon oxyfluoride, or an organic polymer; a wiring material metal film such as copper, aluminum, or tungsten; a barrier metal film such as tantalum, titanium, tantalum nitride, or titanium nitride; Have the following.

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

[Evaluation of laser transmittance]
The thermoplastic polyurethane obtained as described below was charged into a single screw extruder (90 mmφ), and downward at a speed of 120 cm / min from a T die having a lip width of 2.0 mm at a cylinder temperature of 215 to 225 ° C. and a die temperature of 225 ° C. And a sheet having a thickness of 0.5 mm was prepared as a test piece. Next, a laser sensor LV-NH110 (wavelength 660 nm, output 310 μw) manufactured by Keyence Corporation is used, the detection head and the output head are made to face each other at a distance of 10 cm, and a test piece is vertically installed at the midpoint of the head. The transmittance was measured.

[Evaluation of end point detection by light]
A polishing pad was installed in Applied Materials' polishing apparatus “MIRRA”, and a diamond dresser “CMP-M” manufactured by Asahi Diamond Industry Co., Ltd. was used, while flowing ultrapure water at a flow rate of 200 mL / min. The surface of the polishing pad was conditioned for 30 minutes at a polishing pad rotational speed of 50 rpm and a dresser load of 5.0 lbf. Next, under the conditions of a polishing pad rotation speed of 80 rpm, a wafer rotation speed of 70 rpm, and a polishing pressure of 20 kPa, a polishing slurry (“PL-7105” manufactured by Fujimi Incorporated, ultrapure water, hydrogen peroxide solution (concentration 31 mass) %) Was mixed at a mass ratio of 1: 2: 0.09) at a flow rate of 200 mL / min, and the pattern wafer SEMATECH 854 made by SEMATECH was polished for 130 seconds. In this polishing, it was evaluated that the end point could be detected when the reflectance of the laser beam changed by 10% or more when the copper film was removed and the barrier film was exposed.

[Evaluation of scratches after removing copper film]
The polishing pad after evaluation of the end point detection performance by light was conditioned for 30 seconds at a dresser rotation speed of 120 rpm, a polishing pad rotation speed of 80 rpm, and a dresser load of 5.0 lbf while flowing ultrapure water at a flow rate of 200 mL / min. Thereafter, an 8-inch silicon wafer having a copper film without a pattern on its surface was polished for 60 seconds. Using a Surfscan SP1 manufactured by KLA-Tencor, the number of scratches having a size of 0.16 μm or more present on the wafer surface from which the copper film was removed after polishing was measured.

[Production Example 1]
Production of thermoplastic polyurethane (PU-1) Poly (tetramethylene glycol) having a number average molecular weight of 2000 [abbreviation: PTMG2000], poly (2-methyl-1,8-octamethylene-co-nonamethylene adipate having a number average molecular weight of 2000 ) [Abbreviation: PNOA2000, molar ratio of nonamethylene unit to 2-methyl-1,8-octamethylene unit = 7 to 3], 1,4-cyclohexanedimethanol [abbreviation: CHDM], 1,4-butanediol [ Abbreviation: BD] and 4,4′-diphenylmethane diisocyanate [abbreviation: MDI], the mass ratio of PTMG2000: PNOA2000: CHDM: BD: MDI is 20.1: 8.4: 5.7: 14.2: 51. 6 (content ratio of isocyanate group-derived nitrogen atom: 5.8% by mass), and The total supply amount of these is 300 g / min, and continuously supplied to a twin-screw extruder (30 mmφ, L / D = 36, cylinder temperature: 75 to 260 ° C.) rotated coaxially by a metering pump. Then, continuous melt polymerization was performed to produce a thermoplastic polyurethane. The melt of the produced thermoplastic polyurethane was continuously extruded into water in a strand shape, then chopped into pellets with a pelletizer, and the resulting pellets were dehumidified and dried at 70 ° C. for 20 hours to obtain thermoplastic polyurethane (hereinafter referred to as “polyurethane polyurethane”). , This is referred to as PU-1). The obtained PU-1 had a laser transmittance of 40%.

[Production Example 2]
Production of Thermoplastic Polyurethane (PU-2) Poly (tetramethylene glycol) with a number average molecular weight of 3000 [abbreviation: PTMG3000], CHDM, BD and MDI, and a mass ratio of PTMG3000: CHDM: BD: MDI of 21.1: 6 .3: 15.8: 56.8 (content ratio of nitrogen atom derived from isocyanate group: 6.4% by mass) and the total supply amount thereof was 300 g / min. A thermoplastic polyurethane was produced by continuously supplying to a twin screw extruder (30 mmφ, L / D = 36, cylinder temperature: 75 to 260 ° C.) rotated coaxially by a pump, and performing continuous melt polymerization. The melt of the produced thermoplastic polyurethane was continuously extruded into water in a strand shape, then chopped into pellets with a pelletizer, and the resulting pellets were dehumidified and dried at 70 ° C. for 20 hours to obtain thermoplastic polyurethane (hereinafter referred to as “polyurethane polyurethane”). This is called PU-2). The obtained PU-2 had a laser transmittance of 15%.

[Example 1]
The PU-1 obtained in Production Example 1 was charged into a single screw extruder (90 mmφ), and downward at a speed of 40 cm / min from a T-die having a lip width of 2.0 mm at a cylinder temperature of 215 to 225 ° C. and a die temperature of 225 ° C. And a sheet having a thickness of 1.5 mm was produced.
The surface of the sheet was ground to produce a uniform sheet having a thickness of 1.2 mm, and cut into a disk shape having a diameter of 510 mm. Further, a circular groove having a width of 1.0 mm, a depth of 0.7 mm, and a pitch of 6.5 mm was formed on one surface which is a polishing surface of the disk-shaped sheet. Further, a rectangular (long side 57 mm, short side 19 mm, area 1083 mm ² ) detection portion is formed on the surface opposite to the polishing surface of the polishing layer so that the long side is parallel to the diameter direction at a portion 100 mm from the center. did. The thickness of the detection part was 0.5 mm, and the thickness of the other part was 1.2 mm. In addition, “suba400” manufactured by Nitta Haas Co., Ltd. was attached as an elastic layer to the surface of the polishing layer opposite to the polishing surface to form a multilayer polishing pad. At this time, a portion of the elastic layer that was in contact with the detection portion was cut out in advance to form a void.

  As a result of attaching the obtained multilayer polishing pad to the polishing apparatus MIRRA made by AMAT and polishing the pattern wafer SEMATECH 854 made by SEMATECH, a clear change in the detected laser intensity was observed when the surface copper film was removed, Polishing end point detection by light was possible. The number of scratches on the wafer surface after removing the copper film was 100 or less.

[Example 2]
A multilayer polishing pad was prepared in the same manner as in Example 1 except that a rectangular detection portion having a long side of 40 mm, a short side of 15 mm, an area of 600 mm ² and a thickness of 0.3 mm was formed. The polishing end point of the pad could also be detected by light. The number of scratches on the wafer surface after removing the copper film was 100 or less.

[Example 3]
A multilayer polishing pad was produced in the same manner as in Example 1 except that a rectangular detection portion having a long side of 35 mm, a short side of 10 mm, an area of 350 mm ² and a thickness of 0.7 mm was formed. The polishing end point of the pad could also be detected by light. The number of scratches on the wafer surface after removing the copper film was 100 or less.

[Comparative Example 1]
The PU-1 obtained in Production Example 1 was charged into a single screw extruder (90 mmφ), and downward at a speed of 40 cm / min from a T-die having a lip width of 3.5 mm at a cylinder temperature of 215 to 225 ° C. and a die temperature of 225 ° C. And a sheet having a thickness of 3.1 mm was produced.
The surface of the sheet was ground to produce a uniform sheet having a thickness of 2.7 mm and cut into a disk shape having a diameter of 510 mm. Further, a circular groove having a width of 1.0 mm, a depth of 1.2 mm, and a pitch of 6.5 mm was formed on one surface which is a polishing surface of the disk-shaped sheet. Further, a rectangular detection portion (long side 57 mm, short side 19 mm, area 1083 mm ² ) was formed at a portion 100 mm from the center so that the long side was parallel to the diameter direction. The thickness of the detection part was 1.5 mm, and the thickness of the other part was 2.7 mm. In addition, “suba400” manufactured by Nitta Haas Co., Ltd. was attached as an elastic layer to the surface of the polishing layer opposite to the polishing surface to form a multilayer polishing pad. At this time, a portion of the elastic layer that was in contact with the detection portion was cut out in advance to form a void.

  As a result of mounting the obtained multi-layer polishing pad on the polishing apparatus MIRRA manufactured by AMAT and polishing the SEMATECH patterned wafer SEMATECH 854, no clear change in the detected laser intensity was observed when the surface copper film was removed. The polishing end point could not be detected by light. The number of scratches on the wafer surface after removing the copper film was 100 or less.

[Comparative Example 2]
A multilayer polishing pad was produced in the same manner as in Example 1 except that PU-1 was replaced with PU-2 obtained in Production Example 2. The pad could not detect the polishing end point by light. The number of scratches on the wafer surface after removing the copper film was about 1000.

  By using the polishing pad of the present invention, it is possible to inspect the object to be polished and measure the polishing end point during polishing by optical means. Such a polishing pad is useful for, for example, chemical mechanical polishing of a silicon wafer or a semiconductor wafer when manufacturing a semiconductor device.

Claims (13)

A polishing pad having a polishing layer comprising a thermoplastic polyurethane composition having a content of nitrogen atoms derived from an isocyanate group of a thermoplastic polyurethane of 4.8 to 6.0% by mass,
The polishing layer has a detection portion and other portions;
The thickness of the detection part is 0.2 to 1.0 mm,
A polishing pad having a thickness of the other part of 1.1 to 2.5 mm. The polishing pad according to claim 1, wherein the laser transmittance of the thermoplastic polyurethane composition under the following measurement conditions is 20 to 60%.
Test piece: Sheet made of thermoplastic polyurethane composition Test piece thickness: 0.5 mm
Laser wavelength: 660 nm
Laser power: 310μW
Distance between detection head and output head: 10 cm
Test piece measurement position: intermediate between detection head and output head The polishing pad according to claim 1, wherein the detection portion has an area of 100 to 2,000 mm ² .   The polishing pad according to any one of claims 1 to 3, wherein a planar shape of the detection portion is a rectangle having a short side of 10 to 25 mm and a long side of 10 to 80 mm.   The polishing pad according to any one of claims 1 to 4, wherein the thermoplastic polyurethane is obtained by reacting a polymer diol, an organic diisocyanate, and a chain extender.   The polishing pad according to claim 5, wherein the polymer diol has a number average molecular weight of 1,400 to 3,600.   The polishing pad according to claim 5 or 6, wherein the polymer diol contains a polyester diol and / or a polyether diol.   The polishing pad according to claim 5 or 6, wherein the polymer diol contains a polyester diol having a structural unit derived from a diol having 6 to 12 carbon atoms. High molecular diols are poly (ethylene glycol), poly (tetramethylene glycol), poly (nonamethylene adipate), poly (2-methyl-1,8-octamethylene adipate), poly (2-methyl-1,8-octa) Methylene-co-nonamethylene adipate) and poly (3-methyl-1,5-pentamethylene adipate), and at least one selected from the group consisting of
The organic diisocyanate is at least one selected from the group consisting of 4,4′-diphenylmethane diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate and isophorone diisocyanate;
The chain extender is at least selected from the group consisting of 1,3-propanediol, 1,4-butanediol, neopentyl glycol, 1,5-pentanediol, 1,6-hexanediol and 1,4-cyclohexanedimethanol The polishing pad according to claim 5, wherein the number is one.   The mass ratio ([mass of polymer diol] / [total mass of organic diisocyanate and chain extender]) between the mass of the polymer diol and the total mass of the organic diisocyanate and the chain extender is 10/90 to 50/50. The polishing pad as described in any one of Claims 5-9.   The polishing pad according to any one of claims 1 to 10, wherein an elastic layer is laminated on a surface of the polishing layer opposite to the polishing surface.   The polishing pad according to claim 11, wherein a portion of the elastic layer located on the detection portion of the polishing layer is a void, or a transparent member is fitted in the void.   A polishing method using the polishing pad according to claim 1.