JP4890744B2 - Polishing pad and method for manufacturing semiconductor device - Google Patents

Description

  The present invention relates to a polishing pad used when planarizing unevenness on a wafer surface by chemical mechanical polishing (CMP), and more particularly, to detect a polishing state or the like by optical means in CMP using an acidic slurry. The present invention relates to a polishing pad having a plurality of windows and a method for manufacturing a semiconductor device using the polishing pad.

  When manufacturing a semiconductor device, a step of forming a conductive layer on the wafer surface and forming a wiring layer by photolithography, etching, or the like, or a step of forming an interlayer insulating film on the wiring layer These steps cause irregularities made of a conductor such as metal or an insulator 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 also referred to as slurry) in which abrasive grains are dispersed in a state in which a surface to be polished of a wafer is pressed against a polishing surface of a polishing pad.

  For example, as shown in FIG. 1, a polishing apparatus generally used in CMP includes a polishing surface plate 2 that supports a polishing pad 1, a support base 5 (polishing head) 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 4 to be polished against the polishing pad 1.

  In performing such CMP, there is a problem in determining the wafer surface flatness. 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.

Conventionally 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 target and object to be polished with infrared radiation thermometer (Patent Document 5)
(7) 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.

  The optical detection means which is the method of (3) is specifically by irradiating a wafer through a window (light transmission region) through a polishing pad and monitoring an 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.

  By such a method, the end point is determined by monitoring the change in the thickness of the wafer surface layer 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.

For example, a polishing pad having at least a part of a transparent polymer sheet that transmits solid and homogeneous light having a wavelength of 190 nm to 3500 nm is disclosed (Patent Documents 9 and 13). Further, a polishing pad in which a stepped transparent plug is inserted is disclosed (Patent Document 3). In addition, a polishing pad having a transparent plug that is flush with the polishing surface is disclosed (Patent Document 10). Furthermore, the translucent member contains a water-insoluble matrix material and water-soluble particles dispersed in the water-insoluble matrix material, and has a light transmittance of 400% to 800 nm of 0.1% or more. A pad is disclosed (Patent Documents 11 and 12). 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 JP 2002-324769 A JP 2002-324770 A JP 2003-48151 A

  As described above, He—Ne laser light or white light using a halogen lamp is used as the light beam. However, when white light is used, light of various wavelengths can be applied to the wafer. This is advantageous in that many wafer surface profiles can be obtained. When this white light is used as a light beam, it is necessary to improve detection accuracy over a wide wavelength range.

  In the future, with higher integration and ultra-miniaturization in semiconductor manufacturing, it is expected that the wiring width of integrated circuits will become increasingly smaller. In such cases, high-precision optical end point detection will be required. The end point detection window is not sufficiently accurate over a wide wavelength range. In particular, even when detection accuracy that is satisfactory to some extent is obtained at the start of use of the polishing pad, when polishing using an acidic polishing slurry, the light transmission region gradually becomes cloudy or deteriorates, and the end point detection accuracy decreases. There was a problem of coming. Therefore, the conventional window cannot maintain high-precision optical end point detection for a long period from the start of use to the end of use.

  The present invention has been made to solve the above-described problem, and even when polishing is performed using an acidic slurry, high-precision optical end point detection is maintained for a long period from the start of use to the end of use. An object of the present invention is to provide a polishing pad that can be manufactured and a method for 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 the following light transmission region as the light transmission region for the polishing pad.

That is, the present invention is a polishing pad used for chemical mechanical polishing and having a polishing region and a light transmission region, and the light transmission region has a thickness of 0.5 to 4 mm and a wavelength of 500 to 700 nm. The light transmittance in the entire region is 80% or more, and further, the light transmittance T ₁ (%) at the measurement wavelength λ after being immersed in a pH 4 H ₂ O ₂ aqueous solution for 24 hours, and the light at the measurement wavelength λ before immersion. Polishing characterized in that ΔT (ΔT = T ₀ −T ₁ ) (%), which is the difference from transmittance T ₀ (%), is within 10 (%) within the entire measurement wavelength range of 400 to 700 nm. Related to the pad.

  The smaller the intensity of light passing through the light transmission region of the polishing pad, the higher the precision of detecting the polishing end point and the accuracy of measuring the film thickness. Therefore, the degree of the light transmittance at the wavelength of the measurement light to be used is important for determining the detection accuracy of the polishing end point and the measurement accuracy of the film thickness. The light transmission region of the present invention has a small attenuation of light transmittance especially on the short wavelength side, and can maintain high detection accuracy in a wide wavelength range.

  Since the polishing apparatus generally used as described above uses a laser having a transmission wavelength in the vicinity of 500 to 700 nm, if the light transmittance in the wavelength region is 80% or more, high reflected light is generated. As a result, the end point detection accuracy and the film thickness detection accuracy can be improved. The light transmittance in the wavelength region is preferably 90% or more, and more preferably 95% or more. When the light transmittance is less than 80%, the reflected light becomes small and the end point detection accuracy and the film thickness detection accuracy are lowered.

Furthermore, the light transmission region of the present invention is ΔT (%) [ΔT = (light transmittance before immersion) T ₀ ) − (light after immersion) which is a difference in light transmittance before and after immersion in the H ₂ O ₂ aqueous solution. The transmittance T ₁ )] is within 10 (%) within the entire measurement wavelength range of 400 to 700 nm and is excellent in acid resistance, so that it can sufficiently withstand repeated use of the acidic slurry used during polishing. Therefore, the light transmission region does not gradually become cloudy or deteriorate, and high-precision optical end point detection can be maintained for a long period from the start of use to the end of use. The ΔT (%) is preferably within 9 (%), particularly preferably within 5 (%). When ΔT (%) is greater than 10 (%), the transparency of the light transmission region gradually decreases due to contact with the acidic slurry, so that high-precision optical end point detection should be maintained over a long period of time. I can't.

The light transmission region preferably has a light transmittance change rate of 50 (%) or less, more preferably 25, at a measurement wavelength of 400 to 700 nm represented by the following formula before immersion in an H ₂ O ₂ aqueous solution. (%) Or less.

Rate of change (%) = {(maximum light transmittance at 400 to 700 nm−minimum light transmittance at 400 to 700 nm) / maximum light transmittance at 400 to 700 nm} × 100
When the change rate of the light transmittance exceeds 50 (%), the attenuation of the intensity of the light passing through the light transmission region on the short wavelength side is increased, and the amplitude of the interference light is reduced. The film thickness measurement accuracy tends to decrease.

The light transmission region preferably has a light transmittance of 20% or more at a measurement wavelength of 400 nm, more preferably 50% or more, before immersion in an aqueous H ₂ O ₂ solution. If the light transmittance at a wavelength of 400 nm is 20% or more, a laser having a transmission wavelength in the vicinity of 400 to 700 nm can be used, and more wafer surface profiles can be obtained. The accuracy can be further increased.

The light transmission region preferably has a difference in light transmittance at a measurement wavelength of 500 to 700 nm within 5 (%), more preferably within 3 (%) before immersion in the H ₂ O ₂ aqueous solution. is there. If the difference in light transmittance at each wavelength is within 5 (%), when spectrally analyzing the film thickness of the wafer, it is possible to irradiate the wafer with a constant incident light and calculate an accurate reflectance so that the detection accuracy can be calculated. Can be increased.

  The light transmittance of the light transmission region in the present invention is a value when the thickness of the light transmission region is 1 mm, or a value when converted to a thickness of 1 mm. In general, the light transmittance varies depending on the thickness of the light transmission region according to Lambert-Beer's law. Since the light transmittance decreases as the thickness increases, it is necessary to calculate the light transmittance when the thickness is constant.

  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 for holding and updating 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, the strength of the surface of the polishing region decreases, the planarity of the object to be polished decreases, and when it exceeds 1.0 g / cm ³ , the surface of the polishing region becomes fine. The number of bubbles is reduced and planarity is good, but the polishing rate tends to be low.

  Further, the hardness of the fine foam is preferably 35 to 65 degrees in terms of Asker D hardness, more preferably 35 to 60 degrees. When the Asker D hardness is less than 35 degrees, the planarity of the object to be polished is reduced. When the Asker D hardness is more than 65 degrees, the planarity is good, but the uniformity of the object to be polished is decreased. Tend to.

  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 The thickness of the fine foam when the is held for 60 seconds The compression recovery rate of the fine foam is preferably 50 to 100%, more preferably 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 The storage elastic modulus at 40 ° C. and 1 Hz of the fine foam is preferably 150 MPa or more, and more preferably 250 MPa or more. When the storage elastic modulus is less than 150 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 at least a polishing region and a light transmission region.

The light transmission region has a thickness of 0.5 to 4 mm and a light transmittance of 80% or more in the entire region of a wavelength of 500 to 700 nm, and is further immersed for 24 hours in a pH 4 H ₂ O ₂ aqueous solution. ΔT (%), which is the difference between the light transmittance T ₁ (%) at the measurement wavelength λ and the light transmittance T ₀ (%) at the measurement wavelength λ before immersion, is within the entire measurement wavelength range of 400 to 700 nm. It is necessary to be within 10 (%).

The material for forming the light transmission region is not particularly limited as long as it is a material that expresses the above characteristics,
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.), and epoxy Resin etc. are mentioned. These resins may be used alone or in combination of two or more.

  As a means for increasing the light transmittance in the entire region of the light transmission region having a wavelength of 500 to 700 nm to 80% or more, the structure of each resin is to eliminate a skeleton having an absorption band for light of a wavelength of 500 to 700 nm. Or it is preferable to mix | blend to the extent which does not impair the required light transmittance. Another means is to reduce the length of resonance, which is the flow of electrons in the direction of the molecular chain in each resin. This is because even if the skeleton of each monomer constituting the resin does not have a large absorption in the above wavelength region, when each monomer is polymerized, a resonance structure that is the flow of electrons in the molecular chain direction develops. This is because the light absorption band is considered to easily shift to the long wavelength side. Therefore, it is preferable to insert a skeleton that cuts the resonance structure into the molecule. Furthermore, one is to reduce charge transfer between molecules. Therefore, it is preferable to use a resin including a flexible polymer chain, a polymer chain having a bulky functional group, or a polymer chain that does not contain many skeletons with high electron-withdrawing and electron-donating properties.

Further, as a means for reducing the change in light transmittance before and after immersion in a pH 4 H ₂ O ₂ aqueous solution, a method of increasing the durability of the material used in the light transmission region with respect to the acidic aqueous solution can be considered. When a material having low durability against an acidic aqueous solution is used, deterioration proceeds from the surface of the material, and the light transmittance is reduced.

  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 the polyfunctional isocyanate compound, a series of diisocyanate adduct compounds such as Desmodur-N (manufactured by Bayer) and Duranate (manufactured by Asahi Kasei Kogyo) are commercially available. 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.

As a high molecular weight polyol, a reaction product of a polyester glycol such as a polytetramethylene ether glycol, a polycaprolactone polyol, a polycaprolactone, and an alkylene carbonate, in particular, in order to improve durability against an acidic aqueous solution . A polyester polycarbonate polyol, a polyester polyol composed of adipic acid, hexanediol, and ethylene glycol , obtained by reacting a polyester polycarbonate polyol, ethylene carbonate with a polyhydric alcohol, and then reacting the resulting reaction mixture with an organic dicarboxylic acid. Use. Also, in order to improve the light transmittance, a long resonant structure high molecular weight polyol and which do not have, it is preferable to use very high molecular weight polyol having no electron withdrawing, electron donating highly skeletal structure. 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 - methyl-1,5-pentanediol, diethylene glycol, low molecular weight polyols such as triethylene glycol is used. These may be used alone or in combination of two or more . Since a compound having a Fang aromatic hydrocarbon group as the light transmittance in short wavelength side tends to decrease, such compounds have such uses. The compound electron donating group or an electron withdrawing group is bonded to an aromatic ring such as such as a halogen group or a thio group, the light transmittance tends to decrease, such compounds have such uses.

  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, it is also possible to synthesize | combine a polyurethane resin by the prepolymer method using them. .

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 is made to have a predetermined thickness using a band saw type or canna type slicer, a method in which the resin is poured into a mold having a cavity of a predetermined thickness, and a coating technique or sheet Examples include a method using a molding technique.
When there are bubbles in the light transmission region, the attenuation of the reflected light increases due to light scattering, and the polishing end point detection accuracy and the film thickness measurement accuracy tend to decrease. Therefore, in order to remove such bubbles, it is preferable to sufficiently remove gas contained in the material by reducing the pressure to 10 Torr or less before mixing the material. Moreover, in the stirring process after mixing, in the case of the stirring blade type mixer normally used, it is preferable to stir at the rotation speed of 100 rpm or less so that bubbles may not mix. In addition, the stirring step is preferably performed under reduced pressure. Furthermore, since the rotation and revolution type mixer is difficult to mix bubbles even at high rotation, it is also preferable to perform stirring and defoaming using the mixer.

  The shape and size of the light transmission region are not particularly limited, but it is preferable to have the same shape and size as the opening of the polishing region.

  The thickness of the light transmission region is 0.5 to 4 mm, preferably 0.6 to 3.5 mm. The light transmission region is preferably the same thickness as the polishing region or less. If the light transmission region is thicker than the polishing region, the wafer may be damaged by the protruding portion during polishing. On the other hand, if it is too thin, the durability will be insufficient.

  Further, the variation in the thickness of the light transmission region is preferably 100 μm or less, and more preferably 50 μm or less. When the thickness variation exceeds 100 μm, it has a large waviness and tends to affect the polishing characteristics because portions with different contact states with the wafer are generated.

  As a method of suppressing the variation in thickness, a method of buffing a sheet surface having a predetermined thickness can be mentioned. The buffing is preferably performed in stages using polishing sheets having different particle sizes. In addition, when buffing the light transmission region, the smaller the surface roughness, the better. When the surface roughness is large, the incident light is irregularly reflected on the surface of the light transmission region, so that the light transmittance is lowered and the detection accuracy tends to be lowered.

  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. By using a fine foam, the slurry can be held in the bubble portion on the surface, and the polishing rate can be increased.

Examples of the material for forming the polishing region 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.), epoxy resins, and photosensitive resins. These may be used alone or in combination of two or more. The material for forming the polishing region may be the same or different from that of the light transmission region, but it is preferable to use the same type of material as that used for 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 organic isocyanate, polyol (high molecular weight polyol, low molecular weight polyol), and chain extender.

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

  The high molecular weight polyol to be used is not particularly limited, and examples thereof include the high molecular weight polyol. 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 and causes scratches on the wafer surface. 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 2,000, polyurethane using this is too 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 besides a high molecular weight polyol.

  Further, the ratio of the high molecular weight polyol to the low molecular weight polyol 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 a method similar to the above method. 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 step for producing a cell dispersion of isocyanate-terminated prepolymer A silicone-based surfactant is added to the isocyanate-terminated prepolymer and stirred with a non-reactive gas to disperse the non-reactive gas as fine bubbles. A dispersion is obtained. 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 above cell dispersion and mixed and stirred.

3) Curing step 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 production of the polyurethane foam may be a batch method in which each component is metered into a container and stirred, and each component and a non-reactive gas are continuously supplied to the stirring device and stirred. It may be a continuous production method in which a cell 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.

  In the polishing region of the present invention, it is preferable that a groove for holding and renewing the slurry is provided on the polishing side surface in contact with the wafer. When the polishing region is formed of fine foam, it has many openings on the polishing surface and has the function of holding the slurry, but in order to more efficiently maintain the slurry and renew the slurry. Also, in order to prevent the wafer from being broken due to adsorption with the wafer, 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 0.8-4 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 variation in the thickness of 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 different contact states with respect to the wafer, 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 producing 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. 2, 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. 3, a polishing region 9 opened to a predetermined size is bonded to a double-sided tape 10, and a cushion layer 11 is bonded to the bottom. 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. 4, a polishing region 9 opened to a predetermined size is bonded to a double-sided tape 10, and a cushion layer 11 is bonded to the bottom. 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. 5, the cushion layer 11 to which the double-sided tape 12 with the release paper 13 is bonded 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 and shape of the opening in the polishing region are 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 wafer with minute irregularities generated during pattern formation is polished, and uniformity refers to the uniformity of the entire wafer. 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 5 (polishing head) 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 acidic slurry. The flow rate of the acidic slurry, the polishing load, the polishing platen rotation speed, and the wafer rotation speed are not particularly limited, and are adjusted as appropriate.

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

  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 light transmittance before immersion)
The produced light transmission region member was cut into a size of 2 cm × 6 cm (thickness: arbitrary) to obtain a sample for measuring light transmittance. Using a spectrophotometer (manufactured by Hitachi, U-3210 Spectro Photometer), the measurement was performed in a measurement wavelength range of 400 to 700 nm. The measurement results of these light transmittances were converted into light transmittances of 1 mm thickness using Lambert-Beer's law.

(Measurement of light transmittance after immersion for 24 hours to pH4 aqueous H ₂ O ₂ solution)
The produced light transmission region member was cut into a size of 2 cm × 6 cm (thickness: arbitrary) to obtain a sample for light transmittance measurement, and the sample was placed in a H ₂ O ₂ aqueous solution (50 ml, 60 ° C.) adjusted to pH 4. Soaked for 24 hours. Then, the sample was taken out, the aqueous solution on the surface was wiped off, and the measurement was performed in the measurement wavelength range of 400 to 700 nm using the spectrophotometer. The measurement results of these light transmittances were converted into light transmittances of 1 mm thickness using Lambert-Beer's law.

(Calculation of ΔT (%), which is the difference in light transmittance before and after immersion)
From the difference between the light transmittance T ₁ (%) at the measurement wavelength λ after immersion in an aqueous solution of H ₂ O _{2 at} pH 4 for 24 hours and the light transmittance T ₀ (%) at the measurement wavelength λ before immersion, ΔT (% ) Was calculated. The measurement wavelength range was 400 to 700 nm, and evaluation was performed using each light transmittance at 700, 600, 500, and 400 nm as the measurement wavelength λ.
ΔT (%) = (light transmittance T ₀ before immersion) − (light transmittance T ₁ after immersion)

(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 using an image processing apparatus (Image Analyzer V10, manufactured by Toyobo Co., Ltd.), the total bubble diameter in an arbitrary 0.2 mm × 0.2 mm range was measured, 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. The calculation formula of the compression rate and the 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 in a container containing silica gel for 4 days 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

(Film thickness detection evaluation A)
The optical detection evaluation A of the film thickness of the wafer was performed by the following method. As a wafer, an 8 inch silicon wafer formed with a thermal oxide film of 1 μm was used, and a light transmission region (thickness: 1.25 mm) before the immersion was first installed 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 results and the situation of peaks and valleys of interference light at each wavelength were confirmed, and the film thickness detection of the light transmission region before immersion was evaluated according to the following criteria. Then, the light transmission area | region after the said immersion was installed, and the same measurement was performed. Then, compared with the results before immersion, and the film thickness detecting changes in aqueous H ₂ O ₂ before and after dipping was evaluated by the following criteria.
Evaluation before immersion ○: The film thickness is measured with very good reproducibility.
Δ: The film thickness is measured with good reproducibility.
X: Reproducibility is poor and detection accuracy is insufficient.
Evaluation before and after immersion ○: The film thickness is measured with good reproducibility before and after immersion.
X: Reproducibility was poor before and after immersion, and the film thickness detection accuracy decreased due to immersion in an aqueous solution of H ₂ O ₂ .

(Film thickness detection evaluation B)
The optical detection evaluation B of the film thickness of the wafer was performed by the following method. As a wafer, an 8 inch silicon wafer formed with a thermal oxide film of 1 μm was used, and a light transmission region (thickness: 1.25 mm) before the immersion was first installed thereon. Film thickness measurement was performed several times at a wavelength of 633 nm using an interference-type film thickness measuring apparatus using a He—Ne laser. The calculated film thickness results and the situation of peaks and valleys of interference light at each wavelength were confirmed, and the film thickness detection of the light transmission region before immersion was evaluated according to the following criteria. Then, the light transmission area | region after the said immersion was installed, and the same measurement was performed. Compared with the result before immersion, the change in film thickness detection before and after immersion in the aqueous H ₂ O ₂ solution was detected and evaluated according to the following criteria.
Evaluation before immersion ○: The film thickness is measured with good reproducibility.
X: Reproducibility is poor and detection accuracy is insufficient.
Evaluation before and after immersion ○: The film thickness is measured with good reproducibility before and after immersion.
X: Reproducibility was poor before and after immersion, and the film thickness detection accuracy decreased due to immersion in an aqueous solution of H ₂ O ₂ .

(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 at which Cu was sputtered on an 8-inch silicon wafer with a thickness of 1500 mm and a Cu plating film having a thickness of 2 μm was further polished to about 1 μm. For measuring the film thickness of the Cu film, a sheet resistance measuring device (manufactured by Napson Corporation, NC-80) was used. As polishing conditions, CHS3000EM (manufactured by Shibaura Mechatronics) was added as an acidic slurry at a flow rate of 200 ml / min during polishing. The polishing load was 300 g / cm 2, the polishing platen rotation speed was 60 rpm, and the wafer rotation speed was 63 rpm. In-plane uniformity was evaluated by measuring the in-plane film thickness of the wafer polished as described above at 28 points and obtaining the in-plane uniformity by the following formula. The smaller the value of the in-plane uniformity, the better the uniformity.
In-plane uniformity (%) = {(maximum film thickness−minimum film thickness) / (maximum film thickness + minimum film thickness)} × 100

[Production of light transmission region]
Production Example 1
128 parts by weight of a polyester polyol (number average molecular weight 2050) composed of adipic acid, hexanediol, and ethylene glycol and 30 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 and stirred for about 1 minute. 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 the produced polyurethane resin, a light transmission region (length 57 mm, width 19 mm, thickness 1.25 mm) was prepared by injection molding.

Production Example 2
According to the same method as in Production Example 1, except that the polyester polyol (number average molecular weight 1720) consisting of adipic acid, hexanediol and ethylene glycol was changed to 89 parts by weight and 1,4-butanediol 31 parts by weight in Production Example 1. A light transmission region (length 57 mm, width 19 mm, thickness 1.25 mm) was produced.

Production Example 3
In Production Example 1, 75 parts by weight of polytetramethylene glycol (number average molecular weight 890) was used instead of polyester polyol, and the amount of 1,4-butanediol added was changed to 28 parts by weight. A light transmission region (length 57 mm, width 19 mm, thickness 1.25 mm) was produced by the method.

Production Example 4
In Production Example 1, a light transmissive region (by a method similar to that in Production Example 1 except that polycaprolactone polyol (number average molecular weight 2000) was changed to 120 parts by weight instead of polyester polyol and 31 parts by weight of 1,4-butanediol was used. 57 mm in length, 19 mm in width, and 1.25 mm in thickness).

Production Example 5
In a reaction vessel, 14790 parts by weight of toluene diisocyanate (mixture of 2,4-isomer / 2,6-isomer = 80/20), 3930 parts by weight of 4,4′-dicyclohexylmethane diisocyanate, polytetramethylene glycol (number average molecular weight: 1006) Molecular weight distribution: 1.7) 25150 parts by weight of diethylene glycol and 2756 parts by weight of diethylene glycol were added and stirred at 80 ° C. for 120 minutes to obtain an isocyanate-terminated prepolymer (isocyanate equivalent: 2.1 meq / g). 100 parts by weight of this prepolymer was weighed in a vacuum tank, and the gas remaining in the prepolymer was degassed by reduced pressure (about 10 Torr). 29 parts by weight of 4,4′-methylenebis (o-chloroaniline) previously melted at 120 ° C. is added to the defoamed prepolymer, and rotated using a rotating / revolving mixer (manufactured by Sinky). The mixture was stirred at several 800 rpm for about 3 minutes. The mixture was poured into a mold and post-cured in a 110 ° C. oven for 9 hours to obtain a polyurethane resin sheet. Thereafter, both surfaces of the polyurethane resin sheet were buffed to produce a light transmission region (length 57 mm, width 19 mm, thickness 1.25 mm).

Production Example 6
In Production Example 1, instead of the polyester polyol composed of adipic acid, hexanediol and ethylene glycol, 120 parts by weight of polyester polyol (number average molecular weight 2000) composed of adipic acid and ethylene glycol and 31 parts by weight of 1,4-butanediol A light transmission region (length 57 mm, width 19 mm, thickness 1.25 mm) was produced in the same manner as in Production Example 1 except that the thickness was changed.

Production Example 7
In Production Example 5, instead of 4,4′-dicyclohexylmethane diisocyanate, a light transmission region (57 mm in length, 19 mm in width, 19 mm in width, in the same manner as in Production Example 5 except that the amount was changed to 3778 parts by weight of 4,4′-diisocyanate diphenyl ether A thickness of 1.25 mm) was produced.

[Production of polishing area]
Toluene diisocyanate (mixture of 2,4-isomer / 2,6-isomer = 80/20) 14790 parts by weight, 3,4′-dicyclohexylmethane diisocyanate 3930 parts by weight, polytetramethylene glycol (number average molecular weight: 1006, molecular weight distribution) 1.7) 25150 parts by weight of diethylene glycol and 2756 parts by weight of diethylene glycol were mixed and stirred at 80 ° C. for 120 minutes to obtain an isocyanate-terminated prepolymer (isocyanate equivalent: 2.1 meq / g). In the reaction vessel, 100 parts by weight of the filtered prepolymer and 3 parts by weight of a filtered silicone-based nonionic surfactant (manufactured by Toray Dow Silicone, SH192) were mixed, and the temperature was adjusted to 80 ° C. Using a stirring blade, the mixture was vigorously stirred for about 4 minutes so that bubbles were taken into the reaction system at 900 rpm. Thereto, 26 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. Stirring was continued for about 1 minute, and then the reaction solution was poured into a pan-type open mold. 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 (Amitech Co., Ltd.) to obtain a sheet with adjusted thickness accuracy (sheet thickness: 1.27 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, groove depth of 0.40 mm. Concentric grooves were processed. Using a laminator on the surface opposite to the grooved surface of this sheet, a double-sided tape (Sekisui Chemical Co., Ltd., double tack tape) is applied, and then a light transmission area is formed at a predetermined position of the grooved sheet. A hole for fitting (thickness 1.27 mm, 57.5 mm × 19.5 mm) was punched out to prepare a polishing region with a double-sided tape. The physical properties of the produced polishing region were an average bubble diameter of 45 μm, a specific gravity of 0.86 g / cm ³ , an Asker D hardness of 53 degrees, a compression rate of 1.0%, a compression recovery rate of 65.0%, and a storage elastic modulus of 275 MPa. .

[Production of polishing pad]
Example 1
A cushioning layer made of polyethylene foam (Toray Industries Inc., TORAYPEF, thickness: 0.8 mm) buffed and corona-treated is bonded to the prepared adhesive surface of the polishing area with double-sided tape using a laminator. It was. Furthermore, double-sided tape was bonded to the cushion layer surface. Thereafter, a cushion layer having a size of 51 mm × 13 mm was punched out of the hole punched out to fit the light transmission region of the polishing region, and the hole was penetrated. Thereafter, the light transmission region produced in Production Example 1 was fitted to produce a polishing pad. Table 1 shows the polishing characteristics and the like of the produced polishing pad.

Example 2
A polishing pad was produced in the same manner as in Example 1 using the light transmission region produced in Production Example 2. Table 1 shows the polishing characteristics and the like of the produced polishing pad.

Example 3
A polishing pad was produced in the same manner as in Example 1 using the light transmission region produced in Production Example 3. Table 1 shows the polishing characteristics and the like of the produced polishing pad.

Example 4
A polishing pad was produced in the same manner as in Example 1 using the light transmission region produced in Production Example 4. Table 1 shows the polishing characteristics and the like of the produced polishing pad.

Reference example 1
A polishing pad was produced in the same manner as in Example 1 using the light transmission region produced in Production Example 5. Table 1 shows the polishing characteristics and the like of the produced polishing pad.

Comparative Example 1
A polishing pad was produced in the same manner as in Example 1 using the light transmission region produced in Production Example 6. Table 1 shows the polishing characteristics and the like of the produced polishing pad.

Comparative Example 2
A polishing pad was produced in the same manner as in Example 1 using the light transmission region produced in Production Example 7. Table 1 shows the polishing characteristics and the like of the produced polishing pad.

表１から、ΔＴが１０％以内である場合（実施例１〜４、参考例１）には、酸性スラリーを用いて研磨を行っても長期にわたり高精度の光学的終点検知を維持し続けることができる。ΔＴが１０％を超える場合（比較例１）には、酸性スラリーを用いて研磨を行った際に高精度の光学的終点検知を長期にわたり維持し続けることができない。波長５００〜７００ｎｍの全領域における光透過率が８０％未満の場合（比較例２）には、膜厚検出精度が不十分である。

From Table 1, when ΔT is within 10% (Examples 1 to 4, Reference Example 1), even if polishing is performed using acidic slurry, high-precision optical end point detection should be maintained over a long period of time. Can do. When ΔT exceeds 10% (Comparative Example 1), high-precision optical end point detection cannot be maintained for a long time when polishing is performed using an acidic slurry. When the light transmittance in the entire region of the wavelength of 500 to 700 nm is less than 80% (Comparative Example 2), the film thickness detection accuracy is insufficient.

Schematic configuration diagram showing an example of a conventional polishing apparatus used in CMP polishing 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 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 stand (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 (8)

A polishing pad used for chemical mechanical polishing, having a polishing region and a light transmission region, wherein the light transmission region is made of at least an organic isocyanate, a high molecular weight polyol, and a polyurethane resin using a chain extender as a raw material. The molecular weight polyol is at least one selected from the group consisting of polyether polyol, polycaprolactone polyol, polyester polycarbonate polyol, and polyester polyol consisting of adipic acid, hexanediol and ethylene glycol, and the chain extender is aromatic It is a low molecular weight polyol having no hydrocarbon group, the light transmission region has a thickness of 0.5 to 4 mm, a light transmittance of 90 % or more in the entire region of a wavelength of 500 to 700 nm, and a pH of 4 of H ₂ O ₂ A light transmittance T _{1 (%)} at a measurement wavelength lambda after immersion for 24 hours in a solution, which is the difference between the light transmittance T _{0 (%)} at a measurement wavelength before immersion λ ΔT (ΔT = T ₀ -T ₁ ) (%) is within 10 (%) within the entire measurement wavelength range of 400 to 700 nm, and the light transmission region is light at a measurement wavelength of 400 to 700 nm represented by the following formula before immersion. A polishing pad having a transmittance change rate of 50% or less.
Rate of change (%) = {(maximum light transmittance at 400 to 700 nm−minimum light transmittance at 400 to 700 nm) / maximum light transmittance at 400 to 700 nm} × 100 The light transmission region, before immersion, the polishing pad of claim 1 Symbol mounting light transmittance at a measurement wavelength of 400nm is 20% or more. The light transmission region, before immersion, the polishing pad according to claim 1 or 2 difference between the light transmittance at a measurement wavelength of 500~700nm is within 5 (%). Material for forming the light transmissive region, the polishing pad according to any one of claims 1 to 3 which is non-foamed. The polishing pad according to the material for forming the polishing region, claim 1-4 is a fine-cell foam. The light transmission region, a polishing pad according to any one of the polishing liquid having no claim 1-5 an uneven structure can be retained and renewed in the polishing surface. The polishing region, the polishing pad according to any one of claims 1 to 6, the grooves on the polishing surface is provided. 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 1-7.

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