JP4744087B2 - Polishing pad and semiconductor device manufacturing method - Google Patents

Description

  The present invention relates to a polishing pad used when planarizing irregularities on a wafer surface by chemical mechanical polishing (CMP), and more specifically, a polishing pad having a window for detecting a polishing state or the like by optical means, and the polishing pad The present invention relates to a method for manufacturing a semiconductor device using a polishing pad.

  When manufacturing a semiconductor device, a process of forming a conductive film on the wafer surface and forming a wiring layer by photolithography, etching, or the like, a process of forming an interlayer insulating film on the wiring layer, etc. These steps are performed, and irregularities made of a conductor such as metal or an insulator are generated on the wafer surface. In recent years, miniaturization of wiring and multilayer wiring have been advanced for the purpose of increasing the density of semiconductor integrated circuits, and along with this, technology for flattening the irregularities on the wafer surface has become important.

  As a method for flattening the irregularities on the wafer surface, a CMP method is generally employed. CMP is a technique of polishing using a slurry-like abrasive (hereinafter referred to as slurry) in which abrasive grains are dispersed in a state where the surface to be polished of a wafer is pressed against the polishing surface of a polishing pad.

  As shown in FIG. 1, for example, a polishing apparatus generally used in CMP includes a polishing surface plate 2 that supports a polishing pad 1, a support base (polishing head) 5 that supports an object to be polished (wafer) 4, and the like. A backing material for uniformly pressing the wafer and an abrasive supply mechanism are provided. 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 object to be polished 4 supported on each of the polishing surface plate 2 and the support base 5 are opposed to each other, and are provided with rotating shafts 6 and 7 respectively. The support 5 is provided with a pressurizing mechanism for pressing the object to be polished 4 against the polishing pad 1.

  When performing such CMP, there is a problem of determining the flatness of the wafer surface. In other words, it is necessary to detect when the desired surface characteristics or planar state is reached. Conventionally, with regard to the thickness of the oxide film, the polishing rate, and the like, a test wafer is periodically processed, and after confirming the result, a product wafer is polished.

  However, in this method, the time and cost for processing the test wafer are wasted, and the polishing result differs between the test wafer and the product wafer that have not been processed in advance due to the loading effect peculiar to CMP. If it is not actually processed, it is difficult to accurately predict the processing result.

Therefore, recently, in order to solve the above-mentioned problems, there is a demand for a method capable of detecting a point in time when desired surface characteristics and thickness are obtained in the CMP process. Various methods are used for such detection. Currently proposed detection means include
(1) Torque detection method for detecting a friction coefficient between a wafer and a pad as a change in rotational torque of a wafer holding head or a surface plate (Patent Document 1)
(2) Capacitance method for detecting the thickness of the insulating film remaining on the wafer (Patent Document 2)
(3) An optical method in which a film thickness monitoring mechanism using laser light is incorporated in a rotating surface plate (Patent Document 3, Patent Document 4)
(4) Vibration analysis method for analyzing frequency spectrum obtained from vibration or acceleration sensor attached to head or spindle (5) Differential transformer application detection method built in head (6) Friction heat and slurry between wafer and polishing pad Method of measuring reaction heat between substrate and object with infrared radiation thermometer (Patent Document 5)
(7) A method of measuring the thickness of an object to be polished by measuring the propagation time of ultrasonic waves (Patent Document 6, Patent Document 7)
(8) Method for measuring sheet resistance of metal film on wafer surface (Patent Document 8)
Etc. Currently, the method (1) is widely used, but the method (3) is becoming mainstream from the viewpoint of measurement accuracy and spatial resolution in non-contact measurement.

  Specifically, the optical detection means which is the method of (3) is to irradiate the wafer through the polishing pad through a window (light transmission region) and monitor the interference signal generated by the reflection. This is a method for detecting the end point of polishing.

  Currently, white light using a He—Ne laser light having a wavelength near 600 nm or a halogen lamp having a wavelength light in the range of 380 to 800 nm is generally used as the light beam.

  In such a method, the end point is determined by monitoring the change in the thickness of the surface layer of the wafer and knowing the approximate depth of the surface irregularities. When such a change in thickness becomes equal to the depth of the unevenness, the CMP process is terminated. Various methods have been proposed for the polishing end point detection method using such optical means and the polishing pad used in the method.

A polishing pad in which a stepped transparent plug is inserted is disclosed (Patent Document 3). Also, a polishing cloth having at least one optical window in the polishing cloth is disclosed (Patent Document 4). In addition, a polishing pad having a transparent polymer sheet that transmits solid and homogeneous light having a wavelength of 190 nm to 3500 nm at least in part is disclosed (Patent Document 9). Furthermore, a polishing pad having a transparent plug that is flush with the polishing surface is disclosed (Patent Document 10). Both are disclosed to be used as end point detection windows.
US Pat. No. 5,069,002 US Pat. No. 5,081,421 Japanese Patent Laid-Open No. 9-7985 Japanese Patent Laid-Open No. 9-36072 US Pat. No. 5,196,353 JP-A-55-106769 JP 7-135190 A US Pat. No. 5,559,428 Japanese National Patent Publication No. 11-512977 Japanese Patent Laid-Open No. 10-83977

  The window (light transmission region) described in the patent document is a long object or a circular object in the circumferential direction of the polishing pad as shown in FIGS. However, in the case of the window having the shape described above, since the window concentrates and contacts only a certain part of the wafer when polishing the wafer, the polishing is nonuniform between the portion where the window contacts and the portion where the window does not contact. There is a problem. There is also a problem that only a limited portion of the polishing profile with which the window contacts can be obtained. Furthermore, since the conventional light transmission region does not have the required optical characteristics, there is a problem that the end point detection accuracy is insufficient.

  The present invention has been made in order to solve the above-described problems, enables high-precision optical end point detection while polishing, has excellent polishing characteristics (particularly in-plane uniformity), and is accurate and has a wide range. An object of the present invention is to provide a polishing pad capable of obtaining a polishing profile of a simple wafer and a method of manufacturing a semiconductor device using the polishing pad.

  As a result of intensive studies in view of the above situation, the present inventor has found that the above-described problems can be solved by using a light transmission region having a specific structure.

That is, the present invention is a polishing pad that is used for chemical mechanical polishing and has a polishing region and a light transmission region, and the light transmission region is provided between a center portion and a peripheral end portion of the polishing pad. And the length (L) in the circumferential direction is shorter than the length (D) in the diameter direction of the polishing pad, the thickness variation is 50 μm or less , the light transmittance variation is 30% or less, The present invention relates to a polishing pad characterized in that arithmetic mean roughness (Ra) on the back side and the front side is 1 μm or less, and a material for forming the light transmission region is a non-foamed polyurethane resin .

  As described above, the light transmission region has a shape in which the circumferential length (L) is shorter than the length (D) in the diameter direction of the polishing pad. Since the light transmission regions do not concentrate and come in contact with each other uniformly on the entire surface of the wafer, the wafer can be polished uniformly and the polishing characteristics can be improved. In addition, a polishing profile of a wide range of wafers can be obtained by appropriately moving the laser interferometer in the diameter direction within a range having a light transmission region during polishing, so that the end point of the polishing process can be accurately and easily determined. It becomes possible.

  Here, the length (D) in the diameter direction refers to the length of a portion that passes through the center of gravity of the light transmission region and overlaps the light transmission region with a straight line connecting the center of the polishing pad and the peripheral edge. In addition, the circumferential length (L) is the portion of the light transmission region that overlaps the maximum with the straight line passing through the center of gravity of the light transmission region and orthogonal to the straight line connecting the center and peripheral edge of the polishing pad. Say length.

  The light transmission region is provided between the center portion and the peripheral end portion of the polishing pad. In general, since the diameter of the wafer is smaller than the radius of the polishing pad, it is sufficient to provide a light transmission region between the center and the peripheral edge of the polishing pad to obtain a wide range of wafer polishing profiles. If the region is longer than the radius of the polishing pad or about the same length as the diameter, the polishing region is reduced and the polishing efficiency is lowered, which is not preferable.

In addition, the thickness variation of the light transmission region needs to be 50 μm or less. When the thickness variation exceeds 50 μm, the light transmission region has a large undulation, and the contact state with the object to be polished varies depending on the location, which not only affects the polishing characteristics but also the optical end point. Even in detection, there is an adverse effect that accuracy is greatly reduced. Arbitrary preferred that the thickness variation in the light transmission region is 25 [mu] m or less.

The light transmission region, the light transmittance variation Ru der than 30%.

The light transmittance variation is the maximum value (TR _max ) and the minimum value of light transmittance at an arbitrary wavelength within a measurement wavelength of 400 to 700 nm, measured at an arbitrary number of points (5 mm intervals) on a straight line in the diameter direction of the polishing pad. It is a value calculated by substituting the value (TR _min ) and the average light transmittance (TR _ave ) into the following equation. For details, refer to the description of the examples.
Light transmittance variation (%) = {(TR _max −TR _min ) / TR _ave } × 100
A wide range of wafer polishing profiles can be obtained by appropriately moving the laser interferometer in the diameter direction within the range having the light transmission region during polishing, but the light transmittance is large depending on each position in the diameter direction of the light transmission region. If there is variation (if the light transmittance variation exceeds 30%), the polishing profile will also vary greatly, and it will be difficult to accurately determine the end point of the polishing process. The light transmittance variation is more preferably 15% or less, and particularly preferably 3% or less.

The light transmission region, arithmetic average roughness of the back side (Ra) is Ri der 1 [mu] m or less, good Mashiku is 0.5μm or less. Here, the back surface side refers to the surface opposite to the surface that is in close proximity (contact) with the object to be polished. That is, the surface on the polishing platen side. Since the back side of the light transmission region is not dressed or polished, the surface state from before use to after use is always constant. Therefore, the surface roughness on the back surface side of the light transmission region is particularly important for optical end point detection. By setting the arithmetic average roughness (Ra) on the back side of the light transmission region to 1 μm or less, irregular reflection of light can be suppressed and the optical end point detection accuracy can be further improved.

Further, the light transmitting area, the surface arithmetic average roughness (Ra) of Ri der 1 [mu] m or less, good Mashiku is 0.5μm or less. The surface roughness of the light transmission region on the polishing surface side (side close to the object to be polished) always changes during dressing and wafer polishing, but the arithmetic average roughness (Ra) in the initial use is set to 1 μm or less. Thus, an accurate polishing profile of the wafer can be obtained from the initial stage of polishing.

  In the present invention, the length (D) in the diameter direction of the light transmission region is preferably 2.5 times or more, and more preferably 3 times or more the circumferential length (L). In the case of less than 2.5 times, the length in the diameter direction is not sufficient, and the portion where the light beam can be irradiated onto the wafer is limited to a certain range, so that it is insufficient for detecting the film thickness of the wafer, When the length is made sufficiently long, the circumferential length (L) is also increased, resulting in a decrease in the polishing region, and the polishing efficiency tends to decrease.

  The shape of the light transmission region is preferably rectangular from the viewpoint that it can be easily manufactured. At least one light transmission region may be provided in the polishing pad, but two or more light transmission regions may be provided.

  In addition, the circumferential length (L) of the light transmission region is preferably shorter than the diameter of the wafer. If the circumferential length (L) of the light transmission region is about the diameter of the wafer, it is sufficient for film thickness detection. If the circumferential length (L) of the light transmission region is too long, the polishing region is reduced. This tends to adversely affect the polishing of the wafer.

  In the present invention, it is preferable that the length (D) of the light transmission region in the diameter direction is 1/4 to 1/2 times the diameter of the object to be polished. When the ratio is less than 1/4, the portion where the light beam can be irradiated onto the wafer is limited to a certain range, so that the film thickness detection of the wafer is insufficient or the polishing tends to be non-uniform. On the other hand, if it exceeds 1/2 times, the polishing area tends to decrease, and the polishing efficiency tends to decrease.

  In the present invention, the material for forming the light transmission region is preferably a non-foamed material. If it is a non-foamed material, light scattering can be suppressed, so that an accurate reflectance can be detected and the detection accuracy of the polishing optical end point can be increased.

  Further, it is preferable that the polishing surface of the light transmission region does not have a concavo-convex structure that holds and renews the polishing liquid. If there is macroscopic surface irregularities on the polishing side surface of the light transmission region, slurry containing additives such as abrasive grains accumulates in the recesses, and light scattering / absorption tends to affect detection accuracy. Further, it is preferable that the other surface side surface of the light transmission region does not have macro surface unevenness. This is because if there are macro surface irregularities, light scattering is likely to occur, which may affect detection accuracy.

  In the present invention, the forming material of the polishing region is preferably a fine foam. Moreover, it is preferable that the groove | channel is provided in the grinding | polishing side surface of the said grinding | polishing area | region.

  The average cell diameter of the fine foam is preferably 70 μm or less, more preferably 50 μm or less. If the average bubble diameter is 70 μm or less, planarity (flatness) is good.

Further, the specific gravity of the fine foam is preferably 0.5 to 1.0 g / cm ^3, more preferably from 0.7~0.9g / cm ^3. When the specific gravity is less than 0.5 g / cm ^3, strength of the surface of the polishing region is lowered, reduces the planarity of the polished object, also, 1.0 g / cm ³ greater than the fine surface of the polishing region The number of bubbles is reduced and planarity is good, but the polishing rate tends to be low.

  Moreover, it is preferable that the hardness of the said fine foam is 45 to 65 degree | times by an Asker D hardness, More preferably, it is 45 to 60 degree | times. When the Asker D hardness is less than 45 degrees, the planarity of the object to be polished is lowered. It is in.

Moreover, it is preferable that the compression rate of the said fine foam is 0.5 to 5.0%, More preferably, it is 0.5 to 3.0%. If the compression ratio is within the above range, both planarity and uniformity can be sufficiently achieved. The compression rate is a value calculated by the following formula.
Compression rate (%) = {(T1-T2) / T1} × 100
T1: Thickness of the fine foam when a stress load of 30 KPa (300 g / cm ² ) is held for 60 seconds from an unloaded state to the fine foam T2: Stress load of 180 KPa (1800 g / cm ² ) from the state of T1 Of fine foam when holding for 60 seconds

Moreover, it is preferable that the compression recovery rate of the said fine foam is 50 to 100%, More preferably, it is 60 to 100%. When it is less than 50%, as the repeated load is applied to the polishing region during polishing, a large change appears in the thickness of the polishing region, and the stability of the polishing characteristics tends to decrease. The compression recovery rate is a value calculated by the following formula.
Compression recovery rate (%) = {(T3-T2) / (T1-T2)} × 100
T1: Thickness of the fine foam when a stress load of 30 KPa (300 g / cm ² ) is held for 60 seconds from an unloaded state to the fine foam T2: Stress load of 180 KPa (1800 g / cm ² ) from the state of T1 Of fine foam when holding for 60 seconds From the state of T3: T2 held for 60 seconds in a no-load state, and then a fine foam when holding a stress load of 30 KPa (300 g / cm ² ) for 60 seconds Thickness

Moreover, it is preferable that the storage elastic modulus in 40 degreeC and 1 Hz of the said fine foam is 200 Mpa or more, More preferably, it is 250 Mpa or more. When the storage elastic modulus is less than 200 MPa, the strength of the surface of the polishing region decreases and the planarity of the object to be polished tends to decrease. The storage elastic modulus is an elastic modulus measured by applying a sinusoidal vibration to a fine foam using a dynamic viscoelasticity measuring device and using a tensile test jig.

  The present invention also relates to a method for manufacturing a semiconductor device including a step of polishing a surface of a semiconductor wafer using the polishing pad described above.

  The polishing pad of the present invention has a polishing region and a light transmission region.

  The material for forming the light transmission region is not particularly limited, but preferably has a light transmittance of 10% or more in the measurement wavelength region (400 to 700 nm). When the light transmittance is less than 10%, the reflected light becomes small due to the influence of slurry, dressing marks, etc. supplied during polishing, and the film thickness detection accuracy tends to be lowered or cannot be detected. Examples of the forming material include polyurethane resin, polyester resin, polyamide resin, acrylic resin, polycarbonate resin, halogen resin (polyvinyl chloride, polytetrafluoroethylene, polyvinylidene fluoride, etc.), polystyrene, olefin resin (polyethylene, polypropylene). Etc.), and epoxy resins. These may be used alone or in combination of two or more. It is preferable to use a material similar to the forming material used for the polishing region and the physical properties of the polishing region. In particular, a highly abrasion-resistant polyurethane resin that can suppress light scattering in the light transmission region due to dressing marks during polishing is desirable.

  The polyurethane resin is composed of organic isocyanate, polyol (high molecular weight polyol, low molecular weight polyol), and chain extender.

  Examples of the organic isocyanate include 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 2,2′-diphenylmethane diisocyanate, 2,4′-diphenylmethane diisocyanate, 4,4′-diphenylmethane diisocyanate, 1,5-naphthalene diisocyanate, Examples include p-phenylene diisocyanate, m-phenylene diisocyanate, p-xylylene diisocyanate, m-xylylene diisocyanate, hexamethylene diisocyanate, 1,4-cyclohexane diisocyanate, 4,4′-dicyclohexylmethane diisocyanate, and isophorone diisocyanate. . These may be used alone or in combination of two or more.

  As the organic isocyanate, in addition to the diisocyanate compound, a trifunctional or higher polyfunctional polyisocyanate compound can also be used. As a polyfunctional isocyanate compound, a series of diisocyanate adduct compounds are commercially available as Desmodur-N (manufactured by Bayer) or trade name Duranate (manufactured by Asahi Kasei Kogyo Co., Ltd.). These trifunctional or higher functional polyisocyanate compounds are preferably used by adding to the diisocyanate compound because they are easily gelled during prepolymer synthesis when used alone.

  Examples of the high molecular weight polyol include polyester polyols represented by polytetramethylene ether glycol, polyester polyols represented by polybutylene adipate, polycaprolactone polyol, and polycaprolactone. A polyester polycarbonate polyol or an ethylene carbonate exemplified by a reaction product of glycol and alkylene carbonate is reacted with a polyhydric alcohol, and then the resulting reaction mixture is reacted. Examples thereof include polyester polycarbonate polyol reacted with an organic dicarboxylic acid, and polycarbonate polycarbonate obtained by transesterification of a polyhydroxyl compound with aryl carbonate. These may be used alone or in combination of two or more.

  In addition to the high molecular weight polyols described above as polyols, ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butanediol, 1,6-hexanediol, neopentyl glycol, 1, Low molecular weight polyols such as 4-cyclohexanedimethanol, 3-methyl-1,5-pentanediol, diethylene glycol, triethylene glycol, and 1,4-bis (2-hydroxyethoxy) benzene may be used in combination.

  Chain extenders include ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butanediol, 1,6-hexanediol, neopentyl glycol, 1,4-cyclohexanedimethanol, 3 -Low molecular weight polyols such as methyl-1,5-pentanediol, diethylene glycol, triethylene glycol, 1,4-bis (2-hydroxyethoxy) benzene, or 2,4-toluenediamine, 2,6-toluenediamine, 3,5-diethyl-2,4-toluenediamine, 4,4′-di-sec-butyl-diaminodiphenylmethane, 4,4′-diaminodiphenylmethane, 3,3′-dichloro-4,4′-diaminodiphenylmethane, 2,2 ′, 3,3′-tetrachloro-4,4′-diamino Phenylmethane, 4,4'-diamino-3,3'-diethyl-5,5'-dimethyldiphenylmethane, 3,3'-diethyl-4,4'-diaminodiphenylmethane, 4,4'-methylene-bis-methylanthra Nilate, 4,4′-methylene-bis-anthranilic acid, 4,4′-diaminodiphenylsulfone, N, N′-di-sec-butyl-p-phenylenediamine, 4,4′-methylene-bis ( 3-chloro-2,6-diethylamine), 3,3′-dichloro-4,4′-diamino-5,5′-diethyldiphenylmethane, 1,2-bis (2-aminophenylthio) ethane, trimethyleneglycol Polyamines exemplified by luge-p-aminobenzoate, 3,5-bis (methylthio) -2,4-toluenediamine and the like Can. These may be used alone or in combination of two or more.

  The ratio of the organic isocyanate, polyol, and chain extender in the polyurethane resin can be appropriately changed depending on the molecular weight of each and the desired physical properties of the light transmission region produced from these. In order for the light transmission region to obtain the above characteristics, the number of isocyanate groups of the organic isocyanate with respect to the total number of functional groups (hydroxyl group + amino group) of the polyol and the chain extender is preferably 0.95 to 1.15, and more preferably. Is 0.99 to 1.10.

  The polyurethane resin can be manufactured by applying a known urethanization technique such as a melting method or a solution method, but it is preferable to manufacture the polyurethane resin by a melting method in consideration of cost, working environment, and the like.

  As the polymerization procedure of the polyurethane resin, either a prepolymer method or a one-shot method can be used, but an isocyanate-terminated prepolymer is synthesized in advance from an organic isocyanate and a polyol, and this is reacted with a chain extender. The polymer method is preferred. In addition, although the isocyanate terminal prepolymer manufactured from organic isocyanate and a polyol is marketed, if it suits this invention, polymerize the polyurethane used by this invention by a prepolymer method using them. Is also possible.

  The method for producing the light transmission region is not particularly limited, and can be produced by a known method. For example, a polyurethane resin block produced by the above method can be made to have a predetermined thickness using a band saw type or canna type slicer, a method of pouring the resin into a mold having a cavity of a predetermined thickness, a coating technique, A method using a sheet forming technique is used.

  The light transmission region has a shape in which the length (L) in the circumferential direction is shorter than the length (D) in the diameter direction of the polishing pad, and is not particularly limited as long as the thickness variation is 100 μm or less. Specifically, the shapes shown in FIGS.

  Examples of the method for adjusting the thickness variation of the light transmission region to 100 μm or less include a method of buffing the surface of a resin sheet having a predetermined thickness, a method of producing a resin sheet using a mold having high planar accuracy, and the like. It is done. The buffing is preferably performed in stages using polishing sheets having different particle sizes.

  Moreover, it is preferable that arithmetic mean roughness (Ra) of the back surface side or surface side of a light transmissive area | region is 2 micrometers or less. Examples of the method for adjusting the surface roughness include a method of buffing using a 240th or higher polishing sheet.

  The thickness of the light transmission region is not particularly limited, but is preferably equal to or less than the thickness of the polishing region. If the light transmission region is thicker than the polishing region, the object to be polished may be damaged by the protruding portion during polishing.

  The material for forming the polishing region can be used without particular limitation as long as it is normally used as the material for the polishing layer, but in the present invention, it is preferable to use a fine foam. For example, polyurethane resin, polyester resin, polyamide resin, acrylic resin, polycarbonate resin, halogen resin (polyvinyl chloride, polytetrafluoroethylene, polyvinylidene fluoride, etc.), polystyrene, olefin resin (polyethylene, polypropylene, etc.), epoxy resin And photosensitive resin. These may be used alone or in combination of two or more. The material for forming the polishing region may be the same composition as or different from the light transmission region.

  Polyurethane resin is particularly preferable as a material for forming a polishing region 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 polyurethane resin is composed of an organic isocyanate, a polyol, and a chain extender.

  The organic isocyanate to be used is not particularly limited, and examples thereof include the organic isocyanate.

  The polyol to be used is not particularly limited, and examples thereof include the high molecular weight polyols described above. In addition, the number average molecular weight of these high molecular weight polyols is not particularly limited, but is preferably 500 to 2000 from the viewpoint of the elastic characteristics of the obtained polyurethane. If the number average molecular weight is less than 500, a polyurethane using the number average molecular weight does not have sufficient elastic properties and becomes a brittle polymer. Therefore, the polishing pad manufactured from this polyurethane becomes too hard, which causes a scratch on the polishing surface of the object to be polished. Moreover, since it becomes easy to wear, it is not preferable from the viewpoint of the pad life. On the other hand, when the number average molecular weight exceeds 2000, polyurethane using the same becomes soft, so that a polishing pad produced from this polyurethane tends to have poor planarization characteristics.

  Moreover, as a polyol, the said low molecular weight polyol can also be used together other than the high molecular weight polyol mentioned above. The ratio of the high molecular weight component to the low molecular weight component in the polyol is determined by the characteristics required for the polishing region produced therefrom.

  Examples of chain extenders include polyamines exemplified by 4,4′-methylenebis (o-chloroaniline), 2,6-dichloro-p-phenylenediamine, 4,4′-methylenebis (2,3-dichloroaniline) and the like. Or the low molecular weight polyols mentioned above. These may be used alone or in combination of two or more.

  The ratio of the organic isocyanate, polyol, and chain extender in the polyurethane resin can be variously changed depending on the molecular weight of each and the desired physical properties of the polishing region produced therefrom. In order to obtain a polishing region having excellent polishing characteristics, the number of isocyanate groups of the organic isocyanate relative to the total number of functional groups (hydroxyl group + amino group) of the polyol and the chain extender is preferably 0.95 to 1.15, and more preferably Is 0.99 to 1.10.

  The polyurethane resin can be produced by the same method as described above. If necessary, stabilizers such as antioxidants, surfactants, lubricants, pigments, fillers, antistatic agents, and other additives may be added to the polyurethane resin.

  The method of finely foaming the polyurethane resin is not particularly limited, and examples thereof include a method of adding hollow beads, a method of foaming by a mechanical foaming method, a chemical foaming method, and the like. In addition, although each method may be used together, the mechanical foaming method using the silicone type surfactant which is a copolymer of polyalkylsiloxane and polyether and does not have an active hydrogen group is preferable. Examples of the silicone surfactant include SH-192 (manufactured by Toray Dow Corning Silicon) and the like as a suitable compound.

An example of a method for producing a closed cell type polyurethane foam used in the polishing region will be described below. The manufacturing method of this polyurethane foam has the following processes.
1) Stirring process for preparing a cell dispersion of isocyanate-terminated prepolymer Add a silicone surfactant to the isocyanate-terminated prepolymer, stir with a non-reactive gas, and disperse the non-reactive gas as fine bubbles to disperse the bubbles. Use liquid. When the isocyanate-terminated prepolymer is solid at room temperature, it is preheated to an appropriate temperature and melted before use.
2) Curing Agent (Chain Extender) Mixing Step A chain extender is added to the cell dispersion and mixed and stirred.
3) Curing process An isocyanate-terminated prepolymer mixed with a chain extender is cast and cured by heating.

  As the non-reactive gas used to form the fine bubbles, non-flammable gases are preferable, and specific examples include nitrogen, oxygen, carbon dioxide, rare gases such as helium and argon, and mixed gases thereof. The use of air that has been dried to remove moisture is most preferable in terms of cost.

  As a stirring device for making non-reactive gas into fine bubbles and dispersing it in an isocyanate-terminated prepolymer containing a silicone-based surfactant, a known stirring device can be used without particular limitation. Specifically, a homogenizer, a dissolver, A two-axis planetary mixer (planetary mixer) is exemplified. The shape of the stirring blade of the stirring device is not particularly limited, but it is preferable to use a whipper-type stirring blade because fine bubbles can be obtained.

  In addition, it is also a preferable aspect to use a different stirring apparatus for the stirring which produces a bubble dispersion liquid in the stirring process, and the stirring which adds and mixes the chain extender in a mixing process. In particular, the stirring in the mixing step may not be stirring that forms bubbles, and it is preferable to use a stirring device that does not involve large bubbles. As such an agitator, a planetary mixer is suitable. There is no problem even if the same stirring device is used as the stirring device for the stirring step and the mixing step, and it is also preferable to adjust the stirring conditions such as adjusting the rotation speed of the stirring blade as necessary. .

  In the method for producing the polyurethane fine foam, heating and post-curing the foam that has reacted until the foam dispersion does not flow by pouring the cell dispersion into the mold has the effect of improving the physical properties of the foam, Very suitable. The bubble dispersion may be poured into the mold and immediately placed in a heating oven for post-cure. Under such conditions, heat is not immediately transferred to the reaction components, so the bubble diameter does not increase. . The curing reaction is preferably performed at normal pressure because the bubble shape is stable.

  In the production of the polyurethane resin, a catalyst that promotes a known polyurethane reaction such as tertiary amine or organotin may be used. 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 polyurethane foam can be produced in a batch system in which each component is weighed into a container and stirred. Alternatively, each component and a non-reactive gas are continuously supplied to a stirrer and stirred to produce bubbles. It may be a continuous production method in which a dispersion is sent out to produce a molded product.

  The polishing area to be the polishing layer is manufactured by cutting the polyurethane foam prepared as described above into a predetermined size.

  It is preferable that the polishing area | region which consists of a fine foam is provided with the groove | channel for hold | maintaining and renewing a slurry in the grinding | polishing side surface which contacts a to-be-polished body. Since the polishing region is formed of a fine foam, it has a large number of openings on the polishing surface and has a function of holding the slurry. However, in order to efficiently further maintain the slurry and renew the slurry. Also, in order to prevent destruction of the object to be polished due to adsorption with the object to be polished, it is preferable to have a groove on the polishing side surface. The groove is not particularly limited as long as it is a surface shape that holds and renews the slurry. For example, XY lattice grooves, concentric circular grooves, through holes, non-through holes, polygonal columns, cylinders, spiral grooves, Examples include eccentric circular grooves, radial grooves, and combinations of these grooves. Further, the groove pitch, groove width, groove depth and the like are not particularly limited and are appropriately selected and formed. In addition, these grooves are generally regular, but the groove pitch, groove width, groove depth, etc. may be changed for each range to make the slurry retention and renewability desirable. Is possible.

  The method of forming the groove is not particularly limited. For example, a method of machine cutting using a jig such as a tool of a predetermined size, a method of pouring and curing a resin in a mold having a predetermined surface shape , A method of pressing a resin with a press plate having a predetermined surface shape, a method of forming using photolithography, a method of forming using a printing technique, and a laser beam using a carbon dioxide gas laser, etc. The method of doing is mentioned.

  Although the thickness of a grinding | polishing area | region is not specifically limited, It is about 0.8-2.0 mm. As a method of producing the polishing region of the thickness, a method of making the block of the fine foam a predetermined thickness using a band saw type or a canna type slicer, pouring resin into a mold having a cavity of a predetermined thickness, and curing And a method using a coating technique or a sheet forming technique.

  Further, the thickness variation in the polishing region is preferably 100 μm or less, and particularly preferably 50 μm or less. When the thickness variation exceeds 100 μm, the polishing region has a large undulation, and there are portions where the contact state with the object to be polished is different, which tends to adversely affect the polishing characteristics. In order to eliminate the variation in the thickness of the polishing region, the surface of the polishing region is generally dressed with a dresser in which diamond abrasive grains are electrodeposited or fused in the initial stage of polishing, but the above range is exceeded. Things will increase dressing time and reduce production efficiency. In addition, as a method for suppressing the variation in thickness, there is also a method of buffing the surface of the polishing region having a predetermined thickness. When buffing, it is preferable to carry out stepwise with abrasive sheets having different particle sizes.

  A method for manufacturing a polishing pad having a polishing region and a light transmission region is not particularly limited, and various methods can be considered. Specific examples will be described below. In the following specific examples, a polishing pad provided with a cushion layer is described, but a polishing pad without a cushion layer may be used.

  In the first example, as shown in FIG. 7, the polishing area 9 opened to a predetermined size is bonded to the double-sided tape 10, and the predetermined size is set below the polishing area 9 so as to match the opening. Then, the cushion layer 11 opened is attached. Next, the double-sided tape 12 with the release paper 13 is bonded to the cushion layer 11, and the light transmission region 8 is fitted into the opening of the polishing region 9 to be bonded.

  As a second specific example, as shown in FIG. 8, a polishing region 9 opened to a predetermined size is bonded to a double-sided tape 10, and a cushion layer 11 is bonded thereto. Thereafter, the double-sided tape 10 and the cushion layer 11 are opened to a predetermined size so as to match the opening of the polishing region 9. Next, the double-sided tape 12 with the release paper 13 is bonded to the cushion layer 11, and the light transmission region 8 is fitted into the opening of the polishing region 9 to be bonded.

  As a third specific example, as shown in FIG. 9, a polishing region 9 opened to a predetermined size is bonded to a double-sided tape 10, and a cushion layer 11 is bonded thereto. Next, the double-sided tape 12 with the release paper 13 is bonded to the opposite surface of the cushion layer 11, and then the double-sided tape 10 to the release paper 13 are opened to a predetermined size so as to match the opening of the polishing region 9. To do. In this method, the light transmission region 8 is fitted into the opening of the polishing region 9 and bonded. In this case, since the opposite side of the light transmission region 8 is in an open state and dust or the like may accumulate, it is preferable to attach a member 14 that closes it.

  As a fourth specific example, as shown in FIG. 10, a cushion layer 11 to which a double-sided tape 12 with a release paper 13 is attached is opened to a predetermined size. Next, the polishing region 9 opened to a predetermined size is bonded to the double-sided tape 10, and these are bonded so that the openings match. Then, the light transmission region 8 is fitted into the opening of the polishing region 9 and bonded. In this case, since the opposite side of the polishing region is open and dust or the like may accumulate, it is preferable to attach a member 14 that closes it.

  In the method for creating the polishing pad, the means for opening the polishing region and the cushion layer is not particularly limited. For example, a method of pressing and opening a jig having cutting ability, a laser using a carbonic acid laser or the like. Examples thereof include a method of using and a method of grinding with a jig such as a cutting tool. The size of the opening in the polishing region is not particularly limited. Further, the shape of the opening in the polishing region is not particularly limited.

  The cushion layer supplements the characteristics of the polishing region (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 polished object with minute irregularities generated during pattern formation is polished, and uniformity refers to the uniformity of the entire object to be polished. 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.

  A material for forming the cushion layer is not particularly limited. For example, a fiber nonwoven fabric such as a polyester nonwoven fabric, a nylon nonwoven fabric, and an acrylic nonwoven fabric, a resin-impregnated nonwoven fabric such as a polyester nonwoven fabric impregnated with polyurethane, a polymer resin such as a polyurethane foam and a polyethylene foam Examples thereof include rubber resins such as foam, butadiene rubber and isoprene rubber, and photosensitive resins.

  Examples of means for bonding the polishing layer used in the polishing region 9 and the cushion layer 11 include a method in which the polishing region and the cushion layer are sandwiched with a double-sided tape and pressed.

  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 region 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.

  Examples of means for attaching the cushion layer 11 and the double-sided tape 12 include a method of pressing and bonding the double-sided tape to the cushion layer.

  The double-sided tape has a general configuration in which an adhesive layer is provided on both surfaces of a base material such as a nonwoven fabric or a film as described above. In consideration of peeling from the platen after using the polishing pad, it is preferable to use a film as the base material because the tape residue and the like can be eliminated. The composition of the adhesive layer is the same as described above.

  The member 14 is not particularly limited as long as it closes the opening. However, when polishing, it must be peelable.

  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 the polishing pad 1, a support table (polishing head) 5 that supports the semiconductor wafer 4, and the wafer. This is performed using a backing material for performing uniform pressurization and a polishing apparatus equipped with a polishing agent 3 supply mechanism. 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 appropriately adjusted.

  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.

  Examples and the like specifically showing the configuration and effects of the present invention will be described below. The evaluation items in Examples and the like were measured as follows.

(Measurement of thickness variation in light transmission region)
The thickness variation in the light transmission region was measured using a Digimatic micrometer (manufactured by Mitutoyo). The thickness of the produced light transmission region was measured at intervals of 5 mm on a straight line in the D direction (diameter direction when the polishing pad was produced), and the difference between the maximum value and the minimum value was calculated. And the measurement similar to the above was performed 3 times, and the average value was made into thickness variation of the light transmission region.

(Measurement of arithmetic average roughness Ra)
Based on JIS B633, Ra was measured using P-15 manufactured by KLA-Tencor (stylus: L-stylus 2.0 μmR, 60 °). Measured by scanning at 5 mm intervals in the D direction (diameter direction when the polishing pad was produced) and L direction (circumferential direction when the polishing pad was produced) on the back side or the front side of the produced light transmission region The average value of all the measured values was calculated. And the measurement similar to the above was performed 3 times, and the average value was made into arithmetic average roughness Ra.

(Measurement of light transmittance variation)
The light transmittance in the light transmission region was measured in a measurement wavelength range of 400 to 700 nm using a spectrophotometer (manufactured by Hitachi, Ltd., U-3210 Spectro Photometer). The light transmittance variation is the maximum value (TR _max ) and the minimum value (TR _max ) of the light transmittance at an arbitrary wavelength measured at an arbitrary number of locations (5 mm intervals) on the straight line in the D direction (diameter direction when the polishing pad was produced). TR _min ) and average light transmittance (TR _ave ) are calculated by substituting them into the following equation. And the same measurement as the above was performed 3 times, the value was computed, and the average value was made into the light transmittance variation. Light transmittance variation (%) = {(TR _max −TR _min ) / TR _ave } × 100

(Average bubble diameter measurement)
A polishing region cut in parallel with a microtome cutter as thin as possible to a thickness of about 1 mm was used as a sample for measuring average bubble diameter. The sample was fixed on a slide glass, and the total bubble diameter in an arbitrary 0.2 mm × 0.2 mm range was measured using an image processing apparatus (Image Analyzer V10, manufactured by Toyobo Co., Ltd.), and the average bubble diameter was calculated.

(Specific gravity measurement)
This was performed according to JIS Z8807-1976. A polished area cut into a 4 cm × 8.5 cm strip (thickness: arbitrary) was used as a sample for measuring specific gravity, and the sample was allowed to stand for 16 hours in an environment of temperature 23 ° C. ± 2 ° C. and humidity 50% ± 5%. The specific gravity was measured using a hydrometer (manufactured by Sartorius).

(Asker D hardness measurement)
This was performed in accordance with JIS K6253-1997. A polished region cut out to a size of 2 cm × 2 cm (thickness: arbitrary) was used as a sample for hardness measurement, and was allowed to stand for 16 hours in an environment of a temperature of 23 ° C. ± 2 ° C. and a humidity of 50% ± 5%. At the time of measurement, the samples were overlapped to a thickness of 6 mm or more. The hardness was measured using a hardness meter (manufactured by Kobunshi Keiki Co., Ltd., Asker D type hardness meter).

(Measurement of compression rate and compression recovery rate)
A polishing area (polishing layer) cut into a 7 mm diameter circle (thickness: arbitrary) is used as a sample for measuring the compression rate and compression recovery rate, and left for 40 hours in an environment of temperature 23 ° C. ± 2 ° C. and humidity 50% ± 5%. did. For the measurement, a thermal analysis measuring instrument TMA (manufactured by SEIKO INSTRUMENTS, SS6000) was used to measure the compression rate and the compression recovery rate. Moreover, the calculation formula of a compression rate and a compression recovery rate is shown below.

Compression rate (%) = {(T1-T2) / T1} × 100
T1: Polishing layer thickness when holding a stress load of 30 KPa (300 g / cm ² ) for 60 seconds from an unloaded state on the polishing layer T2: Stress load of 180 KPa (1800 g / cm ² ) for 60 seconds from the state of T1 Polishing layer thickness when held

Compression recovery rate (%) = {(T3-T2) / (T1-T2)} × 100
T1: Polishing layer thickness when holding a stress load of 30 KPa (300 g / cm ² ) for 60 seconds from an unloaded state on the polishing layer T2: Stress load of 180 KPa (1800 g / cm ² ) for 60 seconds from the state of T1 Polishing layer thickness when held: T3: Polishing layer thickness when holding from 60 to 60 seconds in an unloaded state and then holding a stress load of 30 KPa (300 g / cm ² ) for 60 seconds

(Storage elastic modulus measurement)
This was performed in accordance with JIS K7198-1991. A polishing region cut into a 3 mm × 40 mm strip (thickness; arbitrary) was used as a sample for dynamic viscoelasticity measurement, and the sample was allowed to stand for 4 days in a container containing silica gel under an environmental condition of 23 ° C. The accurate width and thickness of each sheet after cutting was measured with a micrometer. For measurement, a storage elastic modulus E ′ was measured using a dynamic viscoelastic spectrometer (manufactured by Iwamoto Seisakusho, present IS Engineering Co., Ltd.). The measurement conditions at that time are shown below.
<Measurement conditions>
Measurement temperature: 40 ° C
Applied strain: 0.03%
Initial load: 20g
Frequency: 1Hz

(Evaluation of polishing characteristics)
Using SPP600S (manufactured by Okamoto Machine Tool Co., Ltd.) as a polishing apparatus, polishing characteristics were evaluated using the prepared polishing pad. The polishing rate was calculated from the time obtained by polishing about 0.5 μm of a 1-μm thermal oxide film formed on an 8-inch silicon wafer. The thickness of the oxide film was measured by using an interference type film thickness measuring device (manufactured by Otsuka Electronics Co., Ltd.) by moving it in the diameter direction of the polishing pad within a range having a light transmission region. As polishing conditions, silica slurry (SS12, manufactured by Cabot) was added as a slurry at a flow rate of 150 ml / min during polishing. The polishing load was 350 g / cm ² , the polishing platen rotation number was 35 rpm, and the wafer rotation number was 30 rpm.

  Further, the in-plane uniformity was calculated by the following formula from film thickness measurement values at arbitrary 25 points on the wafer. Note that the smaller the in-plane uniformity value, the higher the uniformity of the wafer surface.

In-plane uniformity (%) = {(film thickness maximum value−film thickness minimum value) / (film thickness maximum value + film thickness minimum value)} × 100

(Thickness detection evaluation)
Optical detection evaluation of the film thickness of the wafer was performed by the following method. As a wafer, an 8 inch silicon wafer formed by forming a thermal oxide film with a thickness of 1 μm was used, and the produced light transmission region was placed thereon. Using an interference type film thickness measuring device (manufactured by Otsuka Electronics Co., Ltd.), the film thickness was measured several times in the wavelength region of 400 to 700 nm. The calculated film thickness result and the state of peaks and valleys of interference light were confirmed, and the detection was evaluated according to the following criteria.
A: The film thickness is measured with extremely good reproducibility.
○: The film thickness is measured with good reproducibility.
X: Reproducibility is poor and detection accuracy is insufficient.

[Production of light transmission region]
Production Example 1
50 parts by weight of an isocyanate-terminated prepolymer (Uniroy, L-325, NCO content: 9.15% by weight) adjusted to a temperature of 70 ° C. was weighed in a vacuum tank, and reduced pressure (about 10 Torr) into the prepolymer. The remaining gas was degassed. 13 parts by weight of 4,4′-methylenebis (o-chloroaniline) (Ihara Chemical Co., Ltd., Iharacamine MT) dissolved at 120 ° C. was added to the defoamed prepolymer, and a hybrid mixer (Keyence Co., Ltd.) was added. For 1 minute and degassed. The mixture was poured into a mold and post-cured in an oven at 110 ° C. for 8 hours to prepare a rectangular polyurethane resin sheet (length: 57 mm, width: 19 mm). Then, both surfaces of the polyurethane resin sheet were buffed using a 240th sandpaper to produce a light transmission region (thickness of the center of gravity: about 1.98 mm). Table 1 shows the measurement results of various physical properties of the obtained light transmission region.

Production Example 2
A polyurethane resin sheet (length: 57 mm, width: 19 mm) was produced in the same manner as in Production Example 1. Then, both surfaces of the polyurethane resin sheet are first buffed using a 240th sandpaper, and then buffed using a 800th sandpaper to form a light transmission region (thickness of the center of gravity: about 1.98 mm). Produced. Table 1 shows the measurement results of various physical properties of the obtained light transmission region.

Production Example 3
125 parts by weight of a polyester polyol (number average molecular weight: 2440) obtained by polymerizing adipic acid and hexanediol and 31 parts by weight of 1,4-butanediol were mixed, and the temperature was adjusted to 70 ° C. To this mixed solution, 100 parts by weight of 4,4′-diphenylmethane diisocyanate previously adjusted to 70 ° C. was added, stirred for 1 minute using a hybrid mixer (manufactured by Keyence Corporation), and defoamed. Then, the mixed solution was poured into a container kept at 100 ° C. and post-cured at 100 ° C. for 8 hours to produce a polyurethane resin. Using this polyurethane resin, a light transmission region (length: 57 mm, width: 19 mm, thickness of the center of gravity: about 1.98 mm) was prepared by injection molding. Table 1 shows the measurement results of various physical properties of the obtained light transmission region.

Production Example 4-1 and Production Example 4-2
50 parts by weight of an isocyanate-terminated prepolymer (Uniroy, L-325, NCO content: 9.15% by weight) adjusted to a temperature of 70 ° C. was weighed in a vacuum tank, and reduced pressure (about 10 Torr) into the prepolymer. The remaining gas was degassed. 13 parts by weight of 4,4′-methylenebis (o-chloroaniline) (Ihara Chemical Co., Ltd., Iharacamine MT) dissolved at 120 ° C. was added to the defoamed prepolymer, and a hybrid mixer (Keyence Co., Ltd.) was added. For 1 minute and degassed. The mixture was poured into a mold and post-cured in an oven at 110 ° C. for 8 hours to produce a polyurethane resin block. The polyurethane resin block was sliced using a band saw type slicer (manufactured by Fecken) to produce a light transmission region (length: 57 mm, width: 19 mm, thickness of the center of gravity: about 1.98 mm). Table 1 shows the measurement results of various physical properties of the obtained light transmission region.

Production Example 5
50 parts by weight of an isocyanate-terminated prepolymer (Uniroy, L-325, NCO content: 9.15% by weight) adjusted to a temperature of 70 ° C. was weighed in a vacuum tank, and reduced pressure (about 10 Torr) into the prepolymer. The remaining gas was degassed. 13 parts by weight of 4,4′-methylenebis (o-chloroaniline) (Ihara Chemical Co., Ltd., Iharacamine MT) dissolved at 120 ° C. was added to the defoamed prepolymer, and a hybrid mixer (Keyence Co., Ltd.) was added. For 1 minute and degassed. The mixture was poured into a mold and post-cured in an oven at 110 ° C. for 8 hours to produce a polyurethane resin block. The polyurethane resin block was sliced using a band saw type slicer (manufactured by Fecken Co., Ltd.) and punched into a circular shape to produce a light transmission region (diameter: 30 mm, central portion thickness: about 1.98 mm). Table 1 shows the measurement results of various physical properties of the obtained light transmission region.

Production Example 6
50 parts by weight of an isocyanate-terminated prepolymer (Uniroy, L-325, NCO content: 9.15% by weight) adjusted to a temperature of 70 ° C. was weighed in a vacuum tank, and reduced pressure (about 10 Torr) into the prepolymer. The remaining gas was degassed. 13 parts by weight of 4,4′-methylenebis (o-chloroaniline) (Ihara Chemical Co., Ltd., Iharacamine MT) dissolved at 120 ° C. was added to the defoamed prepolymer, and a hybrid mixer (Keyence Co., Ltd.) was added. For 1 minute and degassed. The mixture was poured into a mold and post-cured in an oven at 110 ° C. for 8 hours to produce a light transmission region (length: 57 mm, width: 19 mm, center of gravity thickness: about 1.98 mm). Table 1 shows the measurement results of various physical properties of the obtained light transmission region.

[Production of polishing area]
In a reaction vessel coated with fluorine, 1000 parts by weight of filtered polyether-based prepolymer (Uniroy, Adiprene L-325, NCO concentration: 2.22 meq / g) and filtered silicone-based nonionic surfactant (Toray Industries, Inc.) -Dow silicone company make, SH192) 30 weight part was mixed, and temperature was adjusted to 80 degreeC. Using a fluorine-coated stirring blade, the mixture was vigorously stirred for about 4 minutes so that air bubbles were taken into the reaction system at a rotation speed of 900 rpm. Thereto, 260 parts by weight of 4,4′-methylenebis (o-chloroaniline) (Ihara Chemical amine, manufactured by Ihara Chemical Co., Ltd.) previously melted and filtered at 120 ° C. was added. Thereafter, stirring was continued for about 1 minute, and the reaction solution was poured into a pan-type open mold coated with fluorine. When the reaction solution lost its fluidity, it was placed in an oven and post-cured at 110 ° C. for 6 hours to obtain a polyurethane resin foam block. This polyurethane resin foam block was sliced using a band saw type slicer (manufactured by Fecken) to obtain a polyurethane resin foam sheet. Next, this sheet was subjected to surface buffing to a predetermined thickness using a buffing machine (manufactured by Amitech Co., Ltd.) to obtain a sheet with adjusted thickness accuracy (sheet thickness: about 2 mm). This buffed sheet is punched into a predetermined diameter (61 cm), and a groove processing machine (manufactured by Toho Koki Co., Ltd.) is used to make a groove width of 0.25 mm, groove pitch of 1.50 mm, and groove depth of 0.40 mm. Concentric grooves were processed. A double-sided tape (Sekisui Chemical Co., Ltd., double tack tape) was applied to the surface opposite to the grooved surface of this sheet using a laminating machine to produce a polishing region with double-sided tape. The physical properties of the polished region were an average bubble diameter of 50 μm, a specific gravity of 0.86 g / cm ³ , an Asker D hardness of 52 degrees, a compression rate of 1.1%, a compression recovery rate of 65.0%, and a storage elastic modulus of 260 MPa.

[Production of polishing pad]
Example 1
Punching holes (rectangular, D (diameter direction) = 57.5 mm, L (circumferential direction) = 19.5 mm) for fitting the light transmission region between the center portion and the peripheral end of the polishing region with the double-sided tape It was. Then, a cushion layer made of polyethylene foam (Toray Industries Inc., TORAYPEF, thickness: 0.8 mm) buffed and corona-treated is bonded to the adhesive surface of the polishing area with double-sided tape using a laminator. . Furthermore, double-sided tape was bonded to the cushion layer surface. After that, out of the hole punched out to fit the light transmission area of the polishing area, the cushion layer is punched out with a size (rectangle) of D (diameter direction) = 51 mm and L (circumferential direction) = 13 mm, and penetrates the hole I let you. Thereafter, the light transmission region produced in Production Example 1 was fitted, and a polishing pad as shown in FIG. 4 was produced. The length (D) in the diameter direction of the light transmitting region is three times the length (L) in the circumferential direction. Further, the length (D) in the diameter direction of the light transmission region with respect to the diameter of the wafer as the object to be polished was 0.28 times. Table 2 shows the polishing characteristics of the produced polishing pad.

Example 2
In Example 1, a polishing pad was produced in the same manner as in Example 1 except that the light transmission region produced in Production Example 2 was used. Table 2 shows the polishing characteristics of the produced polishing pad.

Example 3
In Example 1, a polishing pad was produced in the same manner as in Example 1 except that the light transmission region produced in Production Example 3 was used. Table 2 shows the polishing characteristics of the produced polishing pad.

Comparative Example 1
Punching holes (rectangular, D (diameter direction) = 19.5 mm, L (circumferential direction) = 57.5 mm) for fitting the light transmission region between the center and peripheral edge of the polishing region with the double-sided tape It was. Then, a cushion layer made of polyethylene foam (Toray Industries Inc., TORAYPEF, thickness: 0.8 mm) buffed and corona-treated is bonded to the adhesive surface of the polishing area with double-sided tape using a laminator. . Furthermore, double-sided tape was bonded to the cushion layer surface. After that, out of the hole punched out to fit the light transmission region of the polishing region, the cushion layer is punched out with a size (rectangle) of D (diameter direction) = 13 mm and L (circumferential direction) = 51 mm, and penetrates the hole I let you. Then, the light transmission region produced in Production Example 4-1 was fitted, and a polishing pad as shown in FIG. 11 was produced. The length (D) in the diameter direction of the light transmission region is 0.3 times the length (L) in the circumferential direction. Further, the length (D) in the diameter direction of the light transmission region with respect to the diameter of the wafer as the object to be polished was 0.09 times. Table 2 shows the polishing characteristics of the produced polishing pad.

Comparative Example 2
Punching holes (rectangular, D (diameter direction) = 57.5 mm, L (circumferential direction) = 19.5 mm) for fitting the light transmission region between the center portion and the peripheral end of the polishing region with the double-sided tape It was. Then, a cushion layer made of polyethylene foam (Toray Industries Inc., TORAYPEF, thickness: 0.8 mm) buffed and corona-treated is bonded to the adhesive surface of the polishing area with double-sided tape using a laminator. . Furthermore, double-sided tape was bonded to the cushion layer surface. After that, out of the hole punched out to fit the light transmission area of the polishing area, the cushion layer is punched out with a size (rectangle) of D (diameter direction) = 51 mm and L (circumferential direction) = 13 mm, and penetrates the hole I let you. Then, the light transmission region produced in Production Example 4-2 was fitted, and a polishing pad as shown in FIG. 4 was produced. The length (D) in the diameter direction of the light transmitting region is three times the length (L) in the circumferential direction. Further, the length (D) in the diameter direction of the light transmission region with respect to the diameter of the wafer as the object to be polished was 0.28 times. Table 2 shows the polishing characteristics of the produced polishing pad.

Comparative Example 3
A hole (circular, diameter: 30.5 mm) for embedding the light transmission region was punched between the center portion and the peripheral end portion of the polishing region with the double-sided tape. Then, a cushion layer made of polyethylene foam (Toray Industries Inc., TORAYPEF, thickness: 0.8 mm) buffed and corona-treated is bonded to the adhesive surface of the polishing area with double-sided tape using a laminator. . Furthermore, double-sided tape was bonded to the cushion layer surface. Thereafter, the cushion layer was punched out with a diameter of 24 mm out of the hole punched out to fit the light transmission region in the polishing region, and the hole was penetrated. Thereafter, the light transmission region produced in Production Example 5 was fitted, and a polishing pad as shown in FIG. 3 was produced. Further, the length of the diameter of the light transmission region with respect to the diameter of the wafer as the object to be polished was 0.15 times. Table 2 shows the polishing characteristics of the produced polishing pad.

Comparative Example 4
Punching holes (rectangular, D (diameter direction) = 57.5 mm, L (circumferential direction) = 19.5 mm) for fitting the light transmission region between the center portion and the peripheral end of the polishing region with the double-sided tape It was. Then, a cushion layer made of polyethylene foam (Toray Industries Inc., TORAYPEF, thickness: 0.8 mm) buffed and corona-treated is bonded to the adhesive surface of the polishing area with double-sided tape using a laminator. . Furthermore, double-sided tape was bonded to the cushion layer surface. After that, out of the hole punched out to fit the light transmission area of the polishing area, the cushion layer is punched out with a size (rectangle) of D (diameter direction) = 51 mm and L (circumferential direction) = 13 mm, and penetrates the hole I let you. Thereafter, the light transmission region produced in Production Example 6 was fitted, and a polishing pad as shown in FIG. 4 was produced. The length (D) in the diameter direction of the light transmitting region is three times the length (L) in the circumferential direction. Further, the length (D) in the diameter direction of the light transmission region with respect to the diameter of the wafer as the object to be polished was 0.28 times. Table 2 shows the polishing characteristics of the produced polishing pad.

表１及び表２から、光透過領域が研磨パッドの直径方向の長さ（Ｄ）に比べて円周方向の長さ（Ｌ）が短い形状をしており、さらに光透過領域の厚みバラツキが１００μｍ以下の場合には、ウエハの研磨に際してウエハのある一部分にのみ光透過領域が集中して接触することがなくウエハ全面に均一に接触するため、ウエハを均一に研磨することができ、面内均一性に優れることがわかる。また、光透過率バラツキや光透過領域の裏面側や表面側の算術平均粗さを特定範囲内に制御することにより、さらに膜厚検出精度を高めることができる。

From Table 1 and Table 2, the light transmission region has a shape with a shorter length (L) in the circumferential direction compared to the length (D) in the diameter direction of the polishing pad, and the thickness variation of the light transmission region is further reduced. In the case of 100 μm or less, since the light transmission region does not concentrate and come into contact with only a certain part of the wafer when polishing the wafer, the wafer can be uniformly polished, and the wafer can be polished uniformly. It can be seen that the uniformity is excellent. Further, the film thickness detection accuracy can be further increased by controlling the light transmittance variation and the arithmetic average roughness on the back surface side or the front surface side of the light transmission region within a specific range.

Schematic configuration diagram showing an example of a conventional polishing apparatus used in CMP polishing Schematic showing an example of a polishing pad having a conventional light transmission region Schematic which shows another example of the polishing pad which has the conventional light transmission area | region. Schematic which shows an example of the polishing pad which has the light transmissive area | region of this invention Schematic which shows another example of the polishing pad which has the light transmissive area | region of this invention. Schematic which shows another example of the polishing pad which has the light transmissive area | region of this invention. Schematic sectional view showing an example of the polishing pad of the present invention Schematic sectional view showing another example of the polishing pad of the present invention Schematic sectional view showing another example of the polishing pad of the present invention Schematic sectional view showing another example of the polishing pad of the present invention Schematic showing the polishing pad of Comparative Example 1 Schematic configuration diagram showing an example of a CMP polishing apparatus having an end point detection apparatus of the present invention

Explanation of symbols

1: Polishing pad 2: Surface plate 3: Abrasive (slurry)
4: Object to be polished (wafer)
5: object to be polished (wafer) support (polishing head)
6, 7: Rotating shaft 8: Light transmission region 9: Polishing region 10, 12: Double-sided tape 11: Cushion layer 13: Release paper (film)
14: Member for closing the opening 15: Laser interferometer 16: Laser beam

Claims (4)

A polishing pad used for chemical mechanical polishing and having a polishing region and a light transmission region, wherein the light transmission region is provided between a center portion and a peripheral end portion of the polishing pad, and the diameter of the polishing pad The length (L) in the circumferential direction is shorter than the length (D) in the direction, the thickness variation is 43 μm or less, the light transmittance variation is 29.8% or less, and the arithmetic mean on the back side roughness (Ra) of 0.93μm or less, the arithmetic average roughness of the surface side (Ra) is not more than 0.91, the material for forming the light transmitting region, non-foamed polyurethane resin der is, the polishing area The organic isocyanate, polyol, and chain extender, which are raw materials for the non-foamed polyurethane resin that is a finely foamed polyurethane resin and is a material for forming the light transmission region, are the materials for forming the polishing region. Fine raw material is an organic isocyanate foamed polyurethane resin, a polishing pad, wherein the polyol, and the same compounds der Rukoto a chain extender. The polishing pad according to claim 1, wherein the light transmission region does not have an uneven structure that holds and renews the polishing liquid on the polishing side surface. Polishing region, the polishing pad according to claim 1 or 2 grooves are provided on the polishing surface. The method of manufacturing a semiconductor device including a step of polishing a surface of a semiconductor wafer using a polishing pad according to any one of claims 1-3.

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