JP4964420B2 - Polishing pad - Google Patents

Description

  The present invention relates to a polishing pad for use in planarizing unevenness on a surface of an object to be polished such as a semiconductor wafer by chemical mechanical polishing (CMP), and more specifically, a window for detecting a polishing state or the like by optical means. The present invention relates to a polishing pad having (light transmission region) and a method for manufacturing a semiconductor device using the 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 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.

  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. From the viewpoint of measurement accuracy and spatial resolution in non-contact measurement, an optical detection method in which a film thickness monitoring mechanism using a laser beam is incorporated in a rotating surface plate ( Patent Documents 1 and 2) are becoming mainstream.

  Specifically, the optical detection means detects a polishing end point by irradiating a wafer with a light beam through a window (light transmission region) through a polishing pad and monitoring an interference signal generated by the reflection. Is the method.

  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.

  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 Document 3). Further, a polishing pad in which a stepped transparent plug is inserted is disclosed (Patent Document 4). Also, a polishing pad having a transparent plug that is the same surface as the polishing surface is disclosed (Patent Document 5).

On the other hand, when performing the CMP process, there is a problem of metal contamination of the wafer. In the CMP process, when a wafer as a material to be polished is polished while flowing the slurry through the polishing pad, the slurry and the metal contained in the polishing pad remain on the polished wafer surface. Such metal contamination of the wafer induces a decrease in the reliability of the insulating film, generation of leakage current, abnormal film formation, etc., has a great adverse effect on the semiconductor device, and further reduces the yield. In particular, in shallow trench isolation (STI), which is the mainstream for isolating elements on a semiconductor substrate in current semiconductor manufacturing, metal contamination of the oxide film after polishing becomes a very big problem. . In STI, a predetermined shallow groove (shallow trench) is dug in the silicon wafer surface, and a SiO ₂ film is deposited and filled in the trench. Thereafter, the surface is polished to produce a region separated into oxide films. Since an element (transistor portion or the like) is manufactured in the separated region, metal contamination on the wafer surface after polishing causes a decrease in performance and reliability of the entire element. Currently, a wafer cleaning process is performed after CMP in order to reduce metal contamination of the wafer.

  However, the cleaning of the wafer has many disadvantages such as oxidation of the wiring, and it is desired to reduce the contamination by the slurry and the polishing pad. In particular, metals such as Fe ions are difficult to remove by cleaning and are likely to remain on the wafer.

  Therefore, recently, in order to solve the above problems, a polishing sheet having a high molecular weight polyethylene-based resin porous film having a metal impurity concentration of 100 ppm or less as a polishing layer has been proposed (Patent Document 6). Moreover, a polishing cloth for a semiconductor wafer having a zinc content of 200 ppm or less has been proposed (Patent Document 7).

  However, with the above metal impurity concentration, metal contamination of the wafer cannot be sufficiently prevented, and a load is applied to the wafer in the wafer cleaning process after CMP, and it is difficult to improve the device yield. .

  Further, a polishing pad using an organic intermolecular crosslinking agent that contains as little metal atoms as possible has been proposed (Patent Document 8).

However, the metal content concentration in the specific polishing pad is not clarified. Further, the mold is molded at the time of manufacturing the polishing pad, and it is impossible to reduce metal contamination on the wafer surface with the polishing pad.
US Pat. No. 5,069,002 US Pat. No. 5,081,421 Japanese National Patent Publication No. 11-512977 Japanese Patent Laid-Open No. 9-7985 Japanese Patent Laid-Open No. 10-83977 JP 2000-343411 A International Publication No. 01/15860 Pamphlet JP 2001-308045 A

  This invention solves the said subject, and provides the polishing pad which has the grinding | polishing area | region and light transmissive area | region where the content density | concentration of a specific metal is below a specific value (threshold value). Moreover, it is providing the manufacturing method of the semiconductor device using this polishing pad.

  As a result of intensive studies in view of the above situation, the present inventors have found that the above-described problems can be solved by the following polishing pad.

  That is, the present invention provides a polishing pad having a polishing region and a light transmission region, wherein the polishing region and the light transmission region each have a Fe content concentration of 0.3 ppm or less, a Ni content concentration of 1.0 ppm or less, and a Cu content. The present invention relates to a polishing pad having a content concentration of 0.5 ppm or less, a Zn content concentration of 0.1 ppm or less, and an Al content concentration of 1.2 ppm or less.

  As shown in FIGS. 2 to 8, the present inventors have found that the degree of influence on the device yield varies greatly depending on the type and concentration of metal contained in the polishing pad forming material. For example, the Fe concentration contained in the polishing pad forming material greatly affects the device yield, but the Mg and Cr content concentrations hardly affect the device yield. And it discovered that Fe, Ni, Cu, Zn, and Al had a big influence on the yield of a device. Furthermore, it has been found that when the content concentration of each metal contained in the forming material exceeds a threshold value specific to each metal, the device yield is extremely reduced.

  The content concentration value of each metal is a threshold value, and if any one of the above values is exceeded, the yield of the device is extremely lowered.

  In the present invention, the material for forming the polishing region and the light transmission region is made of polyolefin resin, polyurethane resin, (meth) acrylic resin, silicon resin, fluorine resin, polyester resin, polyamide resin, polyamideimide resin, and photosensitive resin. It is preferably at least one polymer material selected from the group, and particularly preferably a polyurethane resin.

  By using the polishing pad of the present invention, the content concentration of each metal on the wafer can be reduced. As a result, the wafer cleaning process can be performed easily, the work process can be made more efficient, the manufacturing cost can be reduced, and the load on the wafer can be reduced in the wafer cleaning process. Can be improved.

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

  In the polishing region and the light transmission region in the present invention, the Fe content concentration is 0.3 ppm or less, the Ni content concentration is 1.0 ppm or less, the Cu content concentration is 0.5 ppm or less, and the Zn content concentration is 0.1 ppm. The following is not particularly limited as long as the Al concentration is 1.2 ppm or less. In the present invention, the forming material of the polishing region and the light transmission region is made of polyolefin resin, polyurethane resin, (meth) acrylic resin, silicon resin, fluororesin, polyester resin, polyamide resin, polyamideimide resin, and photosensitive resin. It is preferable to use at least one polymer material selected from the group.

  Examples of the polyolefin resin include polyethylene, polypropylene, polyvinyl chloride, and polyvinylidene chloride.

  Examples of the fluororesin include polychlorotrifluoroethylene (PCTFE), perfluoroalkoxyalkane (PFA), polytetrafluoroethylene (PTFE), and polyvinylidene fluoride (PVDF).

  Examples of the polyester resin include polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate.

  As the photosensitive resin, a photodecomposable photosensitive resin utilizing photolysis of a diazo group or an azide group, a photodimerizing photosensitive resin utilizing a photodimerization reaction of a functional group introduced into a side chain of a linear polymer, Examples include photo-radical polymerization of olefins, photoaddition reactions of thiol groups to olefins, and ring-opening addition reactions of epoxy groups.

  In order to reduce the metal content in the polishing region and the light transmission region, the metal content in the raw material used for the resin synthesis is preferably as low as possible.

  However, even if the metal content in the raw material is reduced, it is conceivable that the metal content in the resin increases due to the resin coming into contact with the metal in the production process.

  The method for producing the polymer material is not particularly limited and can be produced by a known method. However, in the present invention, in all steps until the polymer material is produced, the raw materials and / or reaction products thereof are used. It is preferable to manufacture using a tool whose surface that is in direct contact with the metal is not a metal or a chrome-plated tool. The production process of the polymer material differs depending on the type of polymer material. For example, in the case of 1) polyurethane resin, etc., raw material measurement process, filtration process, mixing process, stirring process, casting process, 2 ) In the case of a photosensitive resin or the like, there are a raw material measurement step, a mixing step, an extrusion step, and the like. It is preferable to perform each manufacturing process so that a raw material and / or its reaction product may not contact directly with metals other than chromium in all these processes. As the method, it is in direct contact with raw materials and / or reaction products thereof such as instruments used in the production process of the polymer material, for example, a measuring container, a filter, a polymerization container, a stirring blade, a casting container, an extrusion apparatus, etc. And a method using a non-metal or chrome-plated surface.

  Examples of the non-metal surface include those made of resin or ceramic, and non-metal-coated surfaces of the instrument. Non-metallic coatings include, but are not limited to, resin coatings, ceramic coatings, diamond coatings, and the like.

  In the case of resin coating, the resin to be coated is not particularly limited as long as it has high corrosion resistance and extremely low metal contamination. In particular, a fluororesin is preferable because it has excellent corrosion resistance and extremely low metal contamination. Specific examples of the fluororesin include PFA and PTFE.

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

  The material for forming the light transmission region 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. As a forming material, in particular, a polyurethane resin having high wear resistance that can suppress light scattering in a 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 polyether polyols typified by polytetramethylene ether glycol, polyester polyols typified by polybutylene adipate, polycaprolactone polyol, and a reaction product of a polyester glycol such as polycaprolactone and alkylene carbonate. Polyester polycarbonate polyol, polyester carbonate polyol obtained by reacting ethylene carbonate with polyhydric alcohol and then reacting the resulting reaction mixture with organic dicarboxylic acid, and polycarbonate polyol obtained by transesterification reaction between polyhydroxyl compound and aryl carbonate Etc. These may be used alone or in combination of two or more.

  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-butyldiaminodiphenylmethane, 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. Rukoto can. These may be used alone or in combination of two or more.

  The ratio of the organic isocyanate, the high molecular weight polyol, the low molecular weight polyol, and the chain extender in the polyurethane resin can be appropriately changed according to the respective molecular weights and desired physical properties of the light transmission region produced from these.

  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 that case, it is preferable to manufacture using the superposition | polymerization container, the stirring blade, and the casting container which the surface which contacts the said component and / or its reaction product directly is not a metal, or was chrome-plated. It is also preferable to use a polyurethane raw material measuring container, a filter or the like whose surface is not metal or chrome plated. Furthermore, it is preferable to wash the surface of the container or the like with an acid or alkali having a very low concentration of contained metal before use.

  Usually, a metal is used for the instrument used in manufacture of polymer materials, such as a polyurethane resin, from a viewpoint of strength and the like. In particular, from the viewpoint of corrosion resistance and workability, iron, aluminum, copper, galvanized steel, stainless steel (stainless is generally an alloy made of Fe, Ni, Cr) or the like is used. Since the instrument is in direct contact with the raw material and its reaction product, the metal peeled off during manufacture is mixed into the raw material and its reaction product. Such metal contamination causes an increase in the concentration of metal contained in the raw material and its reaction product, so that the surface portion of the instrument that is in direct contact with the raw material and its reaction product is not metal or chrome plated. Manufacture using things.

  The manufacturing method of the light transmission region is not particularly limited, and can be manufactured 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. It is preferable that jigs such as the slicer and the metal mold are subjected to diamond vapor deposition or the like to eliminate the metal exposure. It is also preferable to perform chrome plating.

  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.

  In addition, it is preferable that the polishing surface of the light transmission region does not have an uneven 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.

  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. 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 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 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, 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 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 particularly preferable. Examples of the silicon 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 silicon-based surfactant is added to the isocyanate-terminated prepolymer, stirred with a non-reactive gas, and the non-reactive gas is dispersed 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.

  In the present invention, at least up to the above-described steps (until the production of the polyurethane resin), the surface is in contact with the raw material or the like and is manufactured using a non-metal or chrome-plated device.

  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 silicon-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 foam, heating and post-curing the foam that has been reacted until the cell dispersion is poured into the mold and no longer flows has the effect of improving the physical properties of the foam. Is preferred. 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 region is produced by cutting the polyurethane foam produced as described above into a predetermined size.

  Although the thickness of a grinding | polishing area | region is not specifically limited, Generally, it is 0.8-2.0 mm. As a method for producing the polishing region of the thickness, the block of the polymer material is made a predetermined thickness by using a band saw type or canna type slicer, or a resin is poured into a mold having a cavity of a predetermined thickness and cured. Or a method using a coating technique or a sheet forming technique is used. In the case of the above slicer, a process of polishing the blade edge (griding) is necessary to maintain the cutting of the blade, but in that case, the blade edge is cleaned using ultrapure water or a solvent with a very low metal content after grinding. It is preferable to do. In a jig such as a metal mold, it is preferable that the metal is not exposed by coating with resin or diamond deposition. It is also preferable to chrome-plat the surface.

  Moreover, it is preferable that the average cell diameter of a polyurethane foam is 70 micrometers or less, More preferably, it is 50 micrometers or less. If the average bubble diameter is 70 μm or less, planarity (flatness) is good.

  Moreover, it is preferable that the specific gravity of a polyurethane foam is 0.5-1.0, More preferably, it is 0.7-0.9. When the specific gravity is less than 0.5, the strength of the surface of the polishing region decreases, and the planarity of the object to be polished decreases. When the specific gravity is greater than 1.0, the number of fine bubbles on the surface of the polishing region decreases. The planarity is good, but the polishing rate tends to be small.

  Moreover, it is preferable that the hardness of a polyurethane foam is 35 to 65 degree | times by an Asker D hardness, More preferably, it is 35 to 60 degree | times. 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.

  The surface of the polishing region that comes into contact with the material to be polished preferably has a surface shape that holds and renews the slurry. The polishing area made of foam has many openings on the polishing surface and has the function of holding and renewing the slurry. However, in order to more efficiently maintain the slurry and renew the slurry, it is also necessary to be polished. In order to prevent destruction of the material to be polished due to adsorption with the material, it is preferable that the polished surface has an uneven structure. The concavo-convex structure is not particularly limited as long as the shape holds and renews the slurry. For example, an XY lattice groove, a concentric circular groove, a through hole, a non-penetrating hole, a helical groove, an eccentric circular groove, Examples include radial grooves and combinations of these grooves. In addition, these uneven structures are generally regular, but in order to make the slurry retention and renewability desirable, the groove pitch, groove width, groove depth, etc. should be changed for each range. Is also possible.

  The production method of the concavo-convex structure is not particularly limited, for example, a method of machine cutting using a jig such as a tool of a predetermined size, a resin raw material is poured into a mold having a predetermined surface shape, and cured. Using a press plate having a predetermined surface shape, a method of producing a resin by pressing, a method of producing using photolithography, a method of producing using a printing technique, a carbon dioxide laser, etc. Examples include a manufacturing method using laser light. It is preferable that the jigs such as the cutting tool and the die are subjected to diamond vapor deposition or the like to eliminate the metal exposure. It is also preferable to perform chrome plating.

  The thickness variation of the polishing region is preferably 100 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 material to be polished is different, which adversely affects the polishing characteristics. In addition, in order to eliminate the variation in the thickness of the polishing region, in general, dressing is performed on the surface of the polishing region using a dresser in which diamond abrasive grains are electrodeposited and fused in the initial stage of polishing. As a result, the dressing time becomes longer and the production efficiency is lowered.

  As a method for suppressing the variation in the thickness of the polishing region, there is a method of buffing the surface of the polishing region sliced to a predetermined thickness. When buffing is performed using a polishing belt or the like coated with abrasive grains, it is preferable that the polishing belt has a low metal content.

  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.

  First, as shown in FIG. 9, 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. 10, a polishing area 9 having 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. 11, 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. 12, 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 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 polyurethane foam and 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.

(Average bubble diameter measurement)
The produced polyurethane foam was cut as thin as possible to a thickness of 1 mm or less in parallel with a microtome cutter, and used as a sample for measuring the average cell 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. The produced polyurethane foam was cut into a 4 cm x 8.5 cm strip (thickness: arbitrary) and used as a sample for measuring the specific gravity, and allowed to stand for 16 hours in an environment of a temperature of 23 ° C ± 2 ° C and a humidity of 50% ± 5%. did. The specific gravity was measured using a hydrometer (manufactured by Sartorius).

(Hardness measurement)
This was performed in accordance with JIS K6253-1997. A sample obtained by cutting the produced polyurethane foam into a size of 2 cm × 2 cm (thickness: arbitrary) was used as a sample for hardness measurement and allowed to stand for 16 hours in an environment of temperature 23 ° C. ± 2 ° C. and humidity 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).

(Contained metal concentration measurement)
The prepared polyurethane foam for the polishing region and polyurethane for the light transmission region were carbonized and incinerated (550 ° C.), and the residue was dissolved in a 1.2N hydrochloric acid solution as a test solution. The elements in the test solution were determined by ICP emission analysis (CIROS-120, manufactured by Rigaku Corporation). The measurement results are shown in Table 1.
Measurement emission line of ICP emission analysis Fe: 259.940 nm, Ni: 231.604 nm, Cu: 324.754 nm, Zn: 213.856 nm, Al: 396.152 nm
(Evaluation of oxide breakdown voltage)
Polishing was performed using a polishing pad on which an n-type Cz-Si wafer having a plane orientation (100) and a resistivity of 10 Ωcm was produced. As a polishing apparatus, SPP600S (manufactured by Okamoto Machine Tool Co., Ltd.) was used. 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. The polishing time was 2 minutes.

  The polished oxide was removed from the polished wafer using RCA cleaning and 5% diluted HF. Thereafter, dry oxidation was performed at 900 ° C. for 2 hours. The oxide film thickness at this time was about 300 mm. An Al electrode MOS capacitor was formed on this wafer, and a 5 mmφ electrode was formed thereon. Further, the back surface of the wafer was sandblasted, and gold was evaporated to form a back electrode. A lamp voltage was applied to a 5 mmφ electrode with a polarity such that the Al electrode was (+) and the back electrode was (−).

A capacitor having an oxide film applied voltage of 7.5 MV / cm or more when the leakage current density of the oxide film was 1 μA / cm ² was determined as a good product. 100 wafers were polished, and the non-defective rate was determined from the ratio of non-defective capacitors to all capacitors. Table 1 shows the percentage of non-defective products.

Example 1
[Production of light transmission region]
A polyester polyol composed of adipic acid, hexanediol and ethylene glycol (number average molecular weight 2400) 128 parts by weight and 1,4-butanediol 30 parts by weight were weighed using a fluorine-coated measuring container, and these were fluorine-coated polymerization. The mixture was added to the container and 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 the mixture was stirred for about 1 minute using a fluorine-coated stirring blade. Then, the mixed solution was poured into a mold which was kept at 100 ° C. and chrome-plated, and post-cured at 100 ° C. for 8 hours to produce polyurethane. Using the produced polyurethane, a light transmission region (length 56.5 mm, width 19.5 mm, thickness 1.25 mm) was produced by injection molding using a chromium plated mold. In all the steps so far, the surface directly contacting with the raw material or the like was manufactured using an instrument whose surface was fluorine coated or chrome plated.

[Production of polishing area]
3000 parts by weight of a polyether-based prepolymer (manufactured by Uniroyal, Adiprene L-325; isocyanate group concentration: 2.22 meq / g), and 90 parts by weight of a silicon-based nonionic surfactant (manufactured by Dow Silicone, SH192) Were weighed using a fluorine-coated measuring container, and these were added to a fluorine-coated polymerization container and mixed to adjust the reaction temperature to 80 ° C. Using a fluorine-coated stirring blade, the mixture was vigorously stirred for about 4 minutes so that bubbles were taken into the reaction system at 900 rpm. 780 parts by weight of 4,4′-methylenebis (o-chloroaniline) (Ihara Chemical amine, Iharacamine MT) previously melted at a temperature of 120 ° C. was weighed using a measuring vessel coated with fluorine, Was added into the polymerization vessel. Stirring was continued for about 4 minutes, and then the reaction solution was poured into a fluorine-coated mold. When the fluidity of the reaction solution ceased, it was placed in an oven with a nichrome hot wire part in a separate chamber and post-cured at 110 ° C. for 6 hours to obtain a polyurethane foam block. In all the steps so far, it was manufactured using a tool whose surface directly contacting with the raw material or the like is not metal.

  Slicing the polyurethane foam block prepared above using a band saw type slicer that was washed with ultrapure water (specific resistance: 12 MΩ · cm or more) after gliding the rotary blade of the slicer, to obtain a polyurethane foam sheet It was. Next, using a buffing machine in which a polishing belt (made by Riken Corundum Co., Ltd.) in which silicon carbide is used as abrasive grains is set, the surface of the sheet is buffed to a predetermined thickness, and the thickness accuracy is adjusted. did. This buffed polyurethane foam sheet (thickness: 1.27 mm) is punched to a predetermined diameter, and a groove width is 0.25 mm, a groove pitch is 1.50 mm, and a groove depth is 0 on the sheet surface using a groove processing machine. A 40 mm concentric groove was formed.

  Using a laminating machine on the surface opposite to the grooved surface of this sheet, a double-sided tape (Sekisui Chemical Co., Ltd., double tack tape) is applied. An opening (57 mm × 20 mm) for fitting was punched out to produce a polishing area with 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, and an Asker D hardness of 53 degrees.

[Production of polishing pad]
A cushion layer made of polyethylene foam (Toray Industries Inc., TORAYPEF, thickness: 0.8 mm) buffed and corona-treated on the surface was bonded to the adhesive surface of the prepared double-sided taped polishing area using a laminator. . Next, a double-sided tape was bonded to the cushion layer surface. And the cushion layer was pierced by the magnitude | size of 51 mm x 14 mm among the hole parts pierced in order to insert the light transmissive area | region. Then, a polishing pad was produced by fitting the produced light transmission region into the opening.

Comparative Example 1
In Example 1, a polishing pad was produced in the same manner as in Example 1 except that a mold that was not chrome-plated was used when producing the light transmission region.

以上に示す結果から明らかなように、特定金属の含有濃度が閾値以下であるである高分子材料からなる研磨パッドを用いて研磨することにより、研磨後のウエハの金属汚染を低減させ、半導体デバイスの歩留まりを格段に向上させることが可能となる。

As is clear from the results shown above, by polishing using a polishing pad made of a polymer material whose specific metal content is below a threshold value, metal contamination of the wafer after polishing is reduced, and the semiconductor device It is possible to significantly improve the yield.

Schematic configuration diagram showing an example of a polishing apparatus used in CMP polishing Graph showing the relationship between Fe concentration and device yield Graph showing the relationship between Ni concentration and device yield Graph showing the relationship between Cu concentration and device yield Graph showing the relationship between Zn concentration and device yield Graph showing the relationship between Al concentration and device yield Graph showing the relationship between Mg concentration and device yield Graph showing the relationship between Cr concentration and device yield 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 (polishing sheet)
2: Polishing surface plate 3: Abrasive (slurry)
4: Material to be polished (semiconductor wafer)
5: Support base (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 (3)

In the polishing pad having the polishing region and the light transmission region, the polishing region and the light transmission region have a Fe content concentration of 0.3 ppm or less, a Ni content concentration of 1.0 ppm or less, and a Cu content concentration of 0.5 ppm, respectively. A polishing pad having a Zn concentration of 0.1 ppm or less and an Al content of 1.2 ppm or less. The forming material of the polishing region and the light transmission region is selected from the group consisting of polyolefin resin, polyurethane resin, (meth) acrylic resin, silicon resin, fluorine resin, polyester resin, polyamide resin, polyamideimide resin, and photosensitive resin. The polishing pad according to claim 1, wherein the polishing pad is at least one polymer material. A method for manufacturing a semiconductor device, comprising a step of polishing a surface of a semiconductor wafer using the polishing pad according to claim 1.

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