JP5019417B2 - Polishing pad manufacturing method and polishing pad - Google Patents

Description

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

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

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

  Conventionally, a polishing pad is produced by 1) pouring a resin material into a mold to produce a resin block, and slicing the resin block with a slicer, and 2) pouring the resin material into the mold and pressing it. A method of manufacturing in a thin sheet form, 3) A method of dissolving a raw material resin and extruding it from an extruder and directly manufacturing it into a sheet form, 4) A method of manufacturing in a direct sheet form by a reaction injection molding method It was manufactured by.

  For example, in Patent Documents 1 and 2, a polishing pad having an average cell diameter of 1 to 50 μm is manufactured by a reaction injection molding method. Moreover, in patent document 3, the polishing pad which is comprised by the extrusion foaming sheet | seat of 2 or more layers and in which the average diameter of the bubble contained in each layer differs is manufactured by the extrusion method.

  Conventional polishing pads are prepared so that the bubble diameter and the number of bubbles on the polishing surface are as uniform as possible in the surface in order to improve the polishing characteristics such as the flattening characteristics.

  However, the conventional polishing pad has a problem of center throw (a phenomenon in which the wafer central portion is difficult to be polished), and a solution to this problem has been desired.

JP 2003-62748 A JP 2004-42189 A JP 2003-220550 A

  An object of this invention is to provide the polishing pad which can improve center throw, and its manufacturing method. Moreover, it aims at providing the manufacturing method of the semiconductor device using this polishing pad.

  The present invention includes a step of dissolving a non-reactive gas under pressure in a first component including an isocyanate component and / or a second component including an active hydrogen group-containing compound, and a polyurethane composition in which the first component and the second component are mixed. A product is injected into a mold by a reaction injection molding method and foamed and cured to form a first polishing region, and the polyurethane composition is injected into a mold having the first polishing region by a reaction injection molding method. Polishing including a step of integrally forming a second polishing region that is injected and foam-cured and has a different average bubble diameter and / or average number of bubbles from the first polishing region inside and / or outside the first polishing region. The present invention relates to a pad manufacturing method.

  In the production method of the present invention, the polyurethane composition is injected into a mold having the first polishing region and the second polishing region by a reaction injection molding method and foam-cured, and then the first polishing region and the second polishing region. It is preferable to include a step of integrally forming a third polishing region having an average bubble diameter and / or an average number of bubbles different from that of the polishing region inside and / or outside the first polishing region and the second polishing region.

  According to this production method, it is possible to produce a polishing layer having a very fine cell structure and integrally formed with a plurality of polishing regions having different average cell diameters and / or average cell numbers.

  The reason why the center throw occurs is considered as follows. The polishing operation is performed by continuously supplying a polishing slurry containing abrasive grains onto the polishing pad, and it is considered that the polishing slurry is difficult to reach the center of the wafer at that time. That is, it is considered that the center throw occurs because the contact ratio with the polishing slurry is greatly different between the periphery and the center of the wafer.

  The inventors of the present invention have provided a plurality of polishing regions having different average bubble diameters and / or average bubble numbers on the polishing surface, and the average bubble diameter of the polishing region having a high rate of contact with the wafer center is determined by the ratio of contact of the wafer periphery. It has been found that center throw can be effectively suppressed by making the average bubble diameter smaller than that of a high polishing region and increasing the average number of bubbles to increase the contact ratio between the wafer center and the polishing slurry.

  In the production method of the present invention, it is preferable that 0.01 to 1% by weight of the non-reactive gas is dissolved in the first component and / or the second component with respect to the total weight of the first component and the second component. . When the non-reactive gas is less than 0.01% by weight, the polyurethane resin is not sufficiently foamed, and the surface of the polishing region is thinned. When the non-reactive gas exceeds 1% by weight, voids or extremely large are present in the polyurethane resin. There exists a space | gap and it exists in the tendency for a uniform foam to be hard to be formed.

  The non-reactive gas is preferably nitrogen and / or carbon dioxide, which has high solubility in the polyurethane raw material and is easy to handle.

  The non-reactive gas is preferably dissolved in the first component and / or the second component in a supercritical state. By setting the supercritical state, a large amount of non-reactive gas can be quickly and uniformly dissolved in the first component and / or the second component. Thereby, a very large amount of bubbles can be uniformly dispersed in the polyurethane resin.

  The polyurethane composition preferably contains 0.05 to 10% by weight of a silicon-based surfactant. When the content of the silicon-based surfactant is less than 0.05% by weight, it is difficult to obtain a polyurethane foam having ultrafine cells. On the other hand, if it exceeds 10% by weight, a polyurethane foam having high hardness tends to be difficult to obtain due to the plasticizing effect of the surfactant.

  Moreover, this invention relates to the polishing pad manufactured by the said method.

  In the polishing pad of the present invention, the second polishing region is formed inside the first polishing region, and the average bubble diameter of the second polishing region is not more than 0.9 times the average bubble size of the first polishing region. The average number of bubbles in the second polishing region is preferably 1.1 times or more than the average number of bubbles in the first polishing region. If it is out of the above range, it becomes difficult to suppress the center throw.

  In the polishing pad of the present invention, the third polishing region is formed inside the second polishing region, and the average cell diameter of the second polishing region is 0.9 times or less than the average cell size of the third polishing region. The average number of bubbles in the second polishing region is preferably 1.1 times or more than the average number of bubbles in the third polishing region. If it is out of the above range, it becomes difficult to suppress the center throw.

In the polishing pad of the present invention, each polishing region preferably has an average cell diameter of 5 to 50 μm and an average cell number of 500 to 20000 / mm ² . A polishing pad having a polishing region having the above structure is particularly excellent in polishing characteristics such as polishing speed and flattening characteristics.

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

  The method for producing a polishing pad of the present invention comprises a step of dissolving a non-reactive gas under pressure in a first component containing an isocyanate component and / or a second component containing an active hydrogen group-containing compound, the first component and the second component. A step of injecting a polyurethane composition mixed with the components into a mold by a reaction injection molding method and foam-curing to form a first polishing region; and a step of forming the first polishing region by the reaction injection molding method. A second polishing region having an average bubble diameter and / or an average number of bubbles different from that of the first polishing region is integrally formed inside and / or outside the first polishing region. Forming step.

  The first and second polishing regions constitute a polishing layer. The polishing pad of the present invention may be a polishing layer alone or a laminate of a polishing layer and another layer (for example, a cushion layer).

  As the isocyanate component, a known compound in the field of polyurethane can be used without particular limitation. As the isocyanate component, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 2,2′-diphenylmethane diisocyanate, 2,4′-diphenylmethane diisocyanate, 4,4′-diphenylmethane diisocyanate, 1,5-naphthalene diisocyanate, Aromatic diisocyanates such as p-phenylene diisocyanate, m-phenylene diisocyanate, p-xylylene diisocyanate, m-xylylene diisocyanate, ethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, 1,6-hexamethylene diisocyanate, etc. Aliphatic diisocyanates, 1,4-cyclohexane diisocyanate, 4,4′-dicyclohexylmethane diisocyanate, isophor Diisocyanate, alicyclic diisocyanates such as norbornane diisocyanate and the like. These may be used alone or in combination of two or more. Since it is preferable that the polyurethane resin has a short curing time, it is preferable to use highly reactive aromatic diisocyanates, and it is particularly preferable to use diphenylmethane diisocyanate.

  As the isocyanate component, a trifunctional or higher polyfunctional polyisocyanate compound can be used in addition to the diisocyanate compound. 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.).

  The active hydrogen group-containing compound is a compound having an active hydrogen group that reacts with an isocyanate group, and examples thereof include a polyol component (such as a high molecular weight polyol and a low molecular weight polyol), a polyamine component, and a chain extender.

  Examples of the high molecular weight polyol include those usually used in the technical field of polyurethane. Examples include polyether polyols typified by polytetramethylene ether glycol, polyethylene glycol, etc., polyester polyols typified by polybutylene adipate, polycaprolactone polyols, reactants of polyester glycols such as polycaprolactone and alkylene carbonate, etc. Polyester polycarbonate polyol obtained by reacting ethylene carbonate with polyhydric alcohol and then reacting the obtained reaction mixture with organic dicarboxylic acid, polycarbonate polyol obtained by transesterification of polyhydroxyl compound and aryl carbonate Etc. These may be used alone or in combination of two or more. In particular, it is preferable to use a terminal amine-modified high molecular weight polyol having a molecular terminal modified with an amine or the like. Moreover, it is preferable to use a trifunctional or higher molecular weight polyol.

  The number average molecular weight of these high molecular weight polyols is not particularly limited, but is preferably about 1000 to 30000 from the viewpoint of the elastic properties of the resulting polyurethane resin. When the number average molecular weight is less than 1000, the polyurethane resin obtained by using the polyurethane resin does not have sufficient elastic properties and tends to be a brittle polymer, the polishing pad made of this polyurethane resin becomes too hard, May cause scratches. Moreover, since it becomes easy to wear, it is not preferable from the viewpoint of the life of the polishing pad. On the other hand, when the number average molecular weight exceeds 30000, a polishing pad made of a polyurethane resin obtained by using this becomes soft and it is difficult to obtain a sufficiently satisfactory planarity, which is not preferable.

  In addition to the high molecular weight polyol, ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, dipropylene glycol, tripropylene glycol, 1,2-butanediol, 1,3-butanediol, 1, 4-butanediol, 2,3-butanediol, 1,6-hexanediol, neopentyl glycol, 1,4-cyclohexanedimethanol, 3-methyl-1,5-pentanediol, diethylene glycol, triethylene glycol, 1, 4-bis (2-hydroxyethoxy) benzene, trimethylolpropane, glycerin, 1,2,6-hexanetriol, pentaerythritol, tetramethylolcyclohexane, methylglucoside, sorbitol, mannitol, dulcitol, sucrose , 2,2,6,6-tetrakis (hydroxymethyl) cyclohexanol, diethanolamine, N- methyldiethanolamine, and can be used in combination of low molecular weight polyols such as triethanolamine. Moreover, low molecular weight polyamines, such as ethylenediamine, tolylenediamine, diphenylmethanediamine, and diethylenetriamine, can also be used in combination. Also, alcohol amines such as monoethanolamine, 2- (2-aminoethylamino) ethanol, and monopropanolamine can be used in combination. These low molecular weight polyols and low molecular weight polyamines may be used alone or in combination of two or more. The blending amount of the low molecular weight polyol, the low molecular weight polyamine or the like is not particularly limited, and is appropriately determined depending on the properties required for the polishing layer. In particular, if the isocyanate-terminated prepolymer has a symmetric molecular structure, it becomes easy to crystallize and the handling becomes complicated. To prevent this, propylene glycol, dipropylene glycol, tripropylene glycol, and 1,3-butanediol It is preferable to use an asymmetric glycol such as

  In the case of producing a polyurethane resin as a material for the polishing region by the prepolymer method, it is preferable to use a chain extender for curing the prepolymer. The chain extender is an organic compound having at least two active hydrogen groups, and examples of the active hydrogen group include a hydroxyl group, a primary or secondary amino group, and a thiol group (SH). Specifically, 4,4′-methylenebis (o-chloroaniline) (MOCA), 2,6-dichloro-p-phenylenediamine, 4,4′-methylenebis (2,3-dichloroaniline), 3,5 -Bis (methylthio) -2,4-toluenediamine, 3,5-bis (methylthio) -2,6-toluenediamine, 3,5-diethyltoluene-2,4-diamine, 3,5-diethyltoluene-2 , 6-diamine, trimethylene glycol-di-p-aminobenzoate, polytetramethylene oxide-di-p-aminobenzoate, 4,4′-diamino-3,3 ′, 5,5′-tetraethyldiphenylmethane, 4, 4'-diamino-3,3'-diisopropyl-5,5'-dimethyldiphenylmethane, 4,4'-diamino-3,3 ', 5,5'-tetra Sopropyldiphenylmethane, 1,2-bis (2-aminophenylthio) ethane, 4,4′-diamino-3,3′-diethyl-5,5′-dimethyldiphenylmethane, N, N′-di-sec-butyl -4,4'-diaminodiphenylmethane, 3,3'-diethyl-4,4'-diaminodiphenylmethane, m-xylylenediamine, N, N'-di-sec-butyl-p-phenylenediamine, m-phenylenediamine And polyamines exemplified by p-xylylenediamine and the like, or the above-described high molecular weight polyols, low molecular weight polyols, and low molecular weight polyamines. These may be used alone or in combination of two or more. Of these, non-halogen aromatic polyamines are preferably used. Halogen-based aromatic polyamines such as MOCA are not preferred because they contain chlorine in the molecule and have environmental disadvantages such as the generation of harmful substances such as dioxins during disposal.

  The ratio of the isocyanate component, the polyol component, the chain extender, and the like can be variously changed depending on the molecular weight of each, the desired physical properties of the polishing pad, and the like. In order to obtain a polishing pad having desired polishing characteristics, the number of isocyanate groups of the isocyanate component relative to the total number of active hydrogen groups (hydroxyl group + amino group) of the active hydrogen group-containing compound (polyol component, chain extender, etc.) is 0.00. It is preferable that it is 85-1.3, More preferably, it is 0.99-1.15. When the number of isocyanate groups is outside the above range, curing failure occurs and the required specific gravity and hardness cannot be obtained, and the polishing characteristics tend to be deteriorated.

  Polyurethane resin can be produced by either the prepolymer method or the one-shot method, but a prepolymer method in which an isocyanate-terminated prepolymer is synthesized in advance from an isocyanate component and a polyol component and then reacted with a chain extender. However, the obtained polyurethane resin has excellent physical properties and is suitable.

  In particular, in the present invention, an isocyanate-terminated prepolymer is synthesized from an aromatic diisocyanate and an asymmetric glycol, and a non-halogen aromatic polyamine and / or a terminal amine-modified high molecular weight polyol is reacted as a chain extender. preferable. In the synthesis of the isocyanate-terminated prepolymer, the aromatic diisocyanate is preferably used in an amount of 170 to 350 mol with respect to 100 mol of the asymmetric glycol.

  As the isocyanate-terminated prepolymer, those having a molecular weight of about 800 to 5000 are preferable because of excellent processability and physical characteristics.

  If necessary, a stabilizer such as a catalyst and an antioxidant, a lubricant, a pigment, a filler, an antistatic agent, and other additives may be added to the first component and / or the second component. In particular, it is preferable to add 0.05 to 10% by weight of a silicone surfactant, which is a copolymer of polyalkylsiloxane and polyether, to the polyurethane composition (first component + second component). A more preferable addition amount is 0.5 to 5% by weight. As such a silicon-based surfactant, SH-193, L-5340, SF-2938F (manufactured by Toray Dow Corning Silicone) and the like are exemplified as suitable compounds.

  Constituent components of the polyurethane resin such as the isocyanate component, polyol component, chain extender, and silicon-based surfactant may be changed in their components and mixing ratio for each polishing region as necessary.

  The non-reactive gas is preferably a gas at normal temperature and pressure and not flammable. Specific examples include nitrogen, carbon dioxide, dry air, noble gases such as chlorofluorocarbon, helium and argon, and mixed gases thereof, and nitrogen and / or carbon dioxide are particularly preferable. Moreover, you may change suitably the non-reactive gas used for every grinding | polishing area | region.

  Hereinafter, the manufacturing method of the polishing pad of the present invention by reaction injection molding (RIM) will be described in detail. 1 to 5 are schematic views showing the structure of the polishing pad of the present invention.

  The RIM molding machine used in the present invention includes a raw material tank A for storing a first component containing an isocyanate component (isocyanate-terminated prepolymer), an active hydrogen group-containing compound (a polyol component, a polyamine component, a chain extender, etc.). It is basically composed of a raw material tank B that stores two components, a gas metering device, a liquid-gas mixing unit, a hydraulic unit, a temperature control unit, a pressure control unit, a mixing head, and a RIM mold. A supercritical fluid quantitative supply device can also be used as the gas quantitative supply device.

  Although the temperature in the said raw material tank A and the raw material tank B can be adjusted suitably, it is 0-150 degreeC normally.

  In the production method of the present invention, it is preferable that the non-reactive gas is brought into a supercritical state and dissolved in the first component and / or the second component. The supercritical state is a state above the critical temperature and the critical pressure, for example, −147 ° C. or higher and 3.4 MPa or higher for nitrogen, and 31 ° C. or higher and 7.38 MPa or higher for carbon dioxide. .

  After the first component and / or the second component and the non-reactive gas are mixed in a liquid-gas mixing unit, they are mixed in a mixing head to prepare a polyurethane composition. Injection into a shaped RIM mold. And, while the reaction hardening of the polyurethane composition proceeds in the RIM mold set to a predetermined mold internal pressure, the non-reactive gas dissolved in the composition is gasified to form polyurethane. Resin is foamed to form a first polishing region made of polyurethane foam.

  Since the non-reactive gas under the saturation pressure is uniformly dissolved in the polyurethane composition, the gas is gasified at substantially the same expansion rate and expansion rate in the RIM mold in a low pressure state. As a result, a very large number of ultrafine bubbles having substantially the same cell diameter are formed uniformly in the polyurethane resin. In addition, since pressure is uniformly applied to the non-reactive gas in the RIM mold, bubbles that are very nearly spherical are formed. The bubble diameter and the number of bubbles can be appropriately adjusted by the pressure in the RIM mold, the amount of non-reactive gas dissolved, the curing time, the amount of raw material injected, and the like. The bubble diameter decreases as the pressure in the RIM mold increases. Moreover, if there is much dissolution amount of non-reactive gas, the number of bubbles will increase. The curing time can be adjusted by the catalyst, the curing temperature, and the like.

  Thereafter, the polyurethane composition is injected into a mold having a first polishing region and foam-cured by the same method as described above, and the second bubble is different in average bubble diameter and / or average bubble number from the first polishing region. A polishing region is integrally formed inside and / or outside of the first polishing region.

Each polishing region preferably has an average cell diameter of 5 to 50 μm and an average cell count of 500 to 20000 / mm ² , more preferably an average cell diameter of 5 to 30 μm and an average cell count of 1000 to 15000 / a mm ^2.

  FIG. 1 shows an example of a polishing pad 1 in which a first polishing region 3 is formed outside and a second polishing region 4 is formed inside. Conversely, the first polishing region 3 may be formed first on the inner side, and then the second polishing region 4 may be formed on the outer side. Moreover, as shown in FIG. 2, the concave 1st grinding | polishing area | region 3 may be formed in the outer side, and the 2nd grinding | polishing area | region 4 may be formed in a recess after that. Conversely, the second polishing region 4 may be formed first on the inner side, and then the concave first polishing region 3 may be formed on the outer side of the second polishing region 4.

  Also, by providing the cushion layer 5 in the RIM mold in advance, the polishing pad 1 in which the polishing layer 2 and the cushion layer 5 are integrally molded can be manufactured. According to this manufacturing method, since the process of bonding the polishing layer 2 and the cushion layer 5 can be omitted, it is preferable from the viewpoint of manufacturing efficiency. Further, when the polishing layer 2 and the cushion layer 5 are bonded with a double-sided tape or an adhesive, there is a problem that they are easily peeled off. However, according to the above manufacturing method, the polishing layer 2 is self-adhered to the cushion layer 5. It is preferable because both layers are extremely difficult to peel off. On the contrary, it is also possible to manufacture the polishing pad 1 in which the polishing layer 2 and the cushion layer 5 are integrally formed by providing the polishing layer 2 in the mold in advance and self-adhering the cushion layer 5. . However, the polishing pad 1 may be produced by bonding the polishing layer 2 and the cushion layer 5 together with a double-sided tape or the like.

  The cushion layer supplements the characteristics of the polishing layer. The cushion layer is necessary in order to achieve both planarity and uniformity in a trade-off relationship in CMP. Planarity refers to the flatness of a pattern portion when a material having fine irregularities generated during pattern formation is polished, and uniformity refers to the uniformity of the entire material 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.

  Examples of the cushion layer include 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 foam such as polyurethane foam and polyethylene foam, a butadiene rubber, Examples thereof include rubber resins such as isoprene rubber and photosensitive resins.

In the polishing pad of the present invention, the second polishing region is formed inside the first polishing region, and the average bubble diameter of the second polishing region is not more than 0.9 times the average bubble diameter of the first polishing region. Is preferable, and more preferably 0.8 times or less. The average number of bubbles in the second polishing region is preferably 1.1 times or more, more preferably 1.5 times or more, and particularly preferably 2 times or more than the average number of bubbles in the first polishing region. Specifically, the average bubble diameter of the first polishing region is 10 to 50 μm, the average number of bubbles is 500 to 18000 / mm ² , the average bubble size of the second polishing region is 5 to 40 μm, and the average number of bubbles is 600. It is preferably ˜20,000 / mm ² and has a difference in the average bubble diameter and / or the average number of bubbles.

  In the polishing pad having the structure of FIGS. 1 and 2, the width of the first polishing region 3 on the polishing surface can be appropriately adjusted according to the size of the wafer to be polished and the polishing pad. Generally, it is 5 to 50% of the radius of the polishing layer 2, and preferably 10 to 40%.

  In the manufacturing method of the polishing pad of the present invention, after the first polishing region and the second polishing region are formed by the method, the polyurethane composition is further formed by the reaction injection molding method to the first polishing region and the second polishing region. It is preferable that the third polishing region is integrally molded inside and / or outside of the first polishing region and the second polishing region by being injected into a RIM mold having foam and being cured by foaming.

  FIG. 3 shows an example of the polishing pad 1 formed with the first polishing region 3 on the outside, the second polishing region 4 in the middle, and the third polishing region 6 on the center side. The position and order of formation of each polishing region is not particularly limited, and the first polishing region is first formed on the center side, then the second polishing region is formed in the middle, and then the third polishing region is formed outside. May be.

  Further, as shown in FIG. 4, the concave first polishing region 3 is formed on the outside, and then the concave second polishing region 4 is formed in the middle, and then the third polishing region 6 is formed in the second polishing region. 4 may be formed in the recess. Conversely, the third polishing region 6 may be formed first, then the second polishing region 4 may be formed outside thereof, and then the third polishing region 6 may be formed outside thereof.

  Further, as shown in FIG. 5, by providing the light transmission region 7 in the RIM mold in advance, the polishing pad 1 in which the polishing region and the light transmission region are integrally formed can be manufactured. This manufacturing method is preferable from the viewpoint of manufacturing efficiency because it is possible to omit a step of separately forming a through hole in the polishing layer and providing a light transmission region in the through hole by bonding or the like. In addition, when the light transmission region is provided in the through hole by bonding or the like, there is a problem that the polishing slurry leaks from the gap to the back surface side. However, according to the above manufacturing method, the polishing region is self-adhered to the light transmission region. And the gap between the two regions can be completely closed. Thereby, the above problem of slurry leakage can be easily solved. However, similarly to the conventional method, a through hole may be formed in the polishing layer, and a light transmission region may be provided in the through hole by bonding or the like.

In the polishing pad of the present invention, it is preferable that the second polishing region is formed inside the first polishing region, and the third polishing region is formed inside the second polishing region. And when the average bubble diameter of adjacent grinding | polishing area | regions is compared, it is preferable that the difference of an average bubble diameter is 10% or more. Moreover, when comparing the average number of bubbles between adjacent polishing regions, the difference in the average number of bubbles is preferably 10% or more. Specifically, the average bubble diameter of the first polishing region is 10 to 50 μm, the average number of bubbles is 500 to 18000 / mm ² , the average bubble size of the second polishing region is 5 to 40 μm, and the average number of bubbles is 600. ˜20,000 / mm ² , the average bubble diameter of the third polishing region is 10 to 50 μm, the average number of bubbles is 500 to 18,000 / mm ² , and has a difference between the average bubble diameter and the average number of bubbles. Is preferred. In particular, it is preferable that the first polishing region and the third polishing region have the same average bubble diameter and average number of bubbles. In that case, the average bubble diameter of the second polishing region is preferably 0.9 times or less, more preferably 0.8 times or less than the average bubble size of the first polishing region and the third polishing region. Further, the average number of bubbles in the second polishing region is preferably 1.1 times or more, more preferably 1.5 times or more, particularly preferably 2 times the average number of bubbles in the first polishing region and the third polishing region. That's it.

  In the polishing pad having the structure of FIGS. 3 and 4, the width of each polishing region on the polishing surface can be appropriately adjusted according to the size of the wafer or polishing pad as the object to be polished. In general, the width of the first polishing region 3 is preferably 5 to 50% of the radius of the polishing layer 2, and more preferably 10 to 40%. Moreover, it is preferable that the width | variety of the 2nd grinding | polishing area | region 4 in a grinding | polishing surface is 5 to 50% of the radius of the grinding | polishing layer 2, More preferably, it is 10 to 40%. Furthermore, the width of the third polishing region 6 is preferably 20 to 80%, more preferably 25 to 70% of the diameter of the wafer.

  According to the production method of the present invention, it is possible to easily produce a polishing pad in which n (n = 2 or more) polishing regions having different average bubble diameters and / or average bubble numbers are integrated. However, as the number of polishing regions having different bubble structures increases, the center throw improvement effect does not increase. From the viewpoint of improving center throws and manufacturing costs, the number of polishing regions having different bubble structures is 2 to 2. It is preferable that there are four. Further, according to the manufacturing method of the present invention, it is possible to integrally mold a polished region having a complicated shape.

  The specific gravity of each polishing region is preferably 0.5 to 1.2. When the specific gravity is less than 0.5, the surface strength of the polishing layer decreases, and the planarity of the material to be polished tends to decrease. On the other hand, when the ratio is larger than 1.2, the number of bubbles on the surface of the polishing layer is reduced and the planarity is good, but the polishing rate tends to decrease.

  The hardness of each polishing region is preferably 30 to 80 degrees with an Asker D hardness meter. When the Asker D hardness is less than 30 degrees, the planarity of the material to be polished is lowered. When the Asker D hardness is more than 80 degrees, the planarity is good but the uniformity of the material to be polished is lowered. There is a tendency. Moreover, it is preferable that the hardness difference of each grinding | polishing area | region is 5 degrees or less. When the hardness difference exceeds 5 degrees, the uniformity of the material to be polished tends to decrease.

  The specific gravity and hardness of each polishing region can be achieved by adjusting the selection of raw materials, the amount of non-reactive gas dissolved, the injection rate of the polyurethane composition into the RIM mold, the pressure in the RIM mold, etc. Can be adjusted to the range.

  The thickness of the polishing layer is not particularly limited, but is usually about 0.8 to 4 mm, and preferably 1.0 to 2.5 mm.

  The size of the polishing layer can be appropriately adjusted according to the polishing apparatus to be used, but is usually about 50 to 200 cm in diameter.

  The polishing surface of the polishing pad (polishing layer) of the present invention that is in contact with the material to be polished preferably has a surface shape that holds and renews the slurry. The polishing layer 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 retain the slurry and renew the slurry, the polishing layer is also 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 it is a shape that holds and renews the slurry. Examples include eccentric circular grooves, radial grooves, and combinations of these grooves. In addition, these uneven structures are generally regular, but in order to make the slurry retention and renewability desirable, the groove pitch, groove width, groove depth, etc. should be changed for each range. Is also possible.

  The method for producing the concavo-convex structure is not particularly limited. For example, a method of machine cutting using a jig such as a tool of a predetermined size, or pressing a resin with a press plate having a predetermined surface shape. Examples thereof include a method, a manufacturing method using photolithography, and a manufacturing method using laser light using a carbon dioxide gas laser. In addition, using a RIM mold having a concavo-convex structure, the concavo-convex structure may be formed on the surface simultaneously with the production of each polishing region.

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

  The semiconductor device is manufactured through a step of polishing the surface of the semiconductor wafer using the polishing pad. A semiconductor wafer is generally a laminate of a wiring metal and an oxide film on a silicon wafer. The method and apparatus for polishing the semiconductor wafer are not particularly limited. For example, as shown in FIG. 6, a polishing surface plate 8 that supports the polishing pad 1, a support table (polishing head) 10 that supports the semiconductor wafer 9, and the wafer. This is performed using a backing material for performing uniform pressurization and a polishing apparatus equipped with a supply mechanism of the abrasive 11. The polishing pad 1 is attached to the polishing surface plate 8 by attaching it with a double-sided tape, for example. The polishing surface plate 8 and the support base 10 are arranged so that the polishing pad 1 and the semiconductor wafer 9 supported on each of the polishing surface plate 8 and the support table 10 face each other, and are provided with rotating shafts 12 and 13 respectively. Further, a pressure mechanism for pressing the semiconductor wafer 9 against the polishing pad 1 is provided on the support base 10 side. In polishing, the semiconductor wafer 9 is pressed against the polishing pad 1 while rotating the polishing surface plate 8 and the support base 10, 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 9 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 Hereinafter, although an Example demonstrates this invention, this invention is not limited to these Examples.

[Measurement and evaluation methods]
(Measurement of average bubble diameter and average number of bubbles)
A sample for measurement was prepared by cutting each of the polished regions as thin as possible to a thickness of 1 mm or less in parallel with a microtome cutter. The sample surface was photographed at 100 times with a scanning electron microscope (S-3500N, manufactured by Hitachi Science Systems). Then, using an image analysis software (WIN-ROOF, manufactured by MITANI Corporation), the equivalent circle diameter of all bubbles in an arbitrary range was measured, and the average bubble diameter was calculated from the measured value. Further, the average number of bubbles (number / mm ² ) in an arbitrary range was also measured.

(Specific gravity measurement)
This was performed according to JIS Z8807-1976. Each of the prepared polished areas was cut into a 4 cm × 8.5 cm strip (thickness: arbitrary) and used as a sample for measuring specific gravity, and allowed to stand for 16 hours in an environment of temperature 23 ° C. ± 2 ° C. and humidity 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. Each of the produced polishing regions was cut into a size of 2 cm × 2 cm (thickness: arbitrary) and used as a sample for hardness measurement, and was 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).

(Evaluation of center throw)
Using SPP600S (manufactured by Okamoto Machine Tool Co., Ltd.) as the polishing apparatus, the center throw was evaluated using the prepared polishing pad. As the polishing conditions, silica slurry (SS12 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 center throw was evaluated by measuring the in-plane uniformity. The in-plane uniformity was obtained by polishing for 2 minutes under the above polishing conditions using a 1-μm thermal oxide film deposited on an 8-inch silicon wafer, and before and after polishing at 25 specific positions on the wafer as shown in FIG. The maximum polishing rate and the minimum polishing rate were obtained from the film thickness measurement values, and the values were calculated by substituting them into the following formula. An interference type film thickness measuring device (manufactured by Otsuka Electronics Co., Ltd.) was used for measuring the thickness of the oxide film. In-plane uniformity of the 100th wafer is shown in Table 1. Note that the smaller the in-plane uniformity value, the higher the uniformity of the wafer surface.
In-plane uniformity (%) = {(maximum polishing rate−minimum polishing rate) / (maximum polishing rate + minimum polishing rate)} × 100

Example 1
An isocyanate-terminated prepolymer (manufactured by Bayer, Mondur PF) was placed in the raw material tank A as the first component, and the temperature was adjusted to 60 ° C. In addition, terminal tank-modified polyol (Mitsui Chemical Fine Co., Ltd., Jeffamine T-5000) 80 parts by weight as raw material tank B, 3,5-diethyltoluene-2,4-diamine and 3,5-diethyltoluene A mixture of 2,6-diamine (Albemarle, Etacure 100) 20 parts by weight, and a silicone surfactant (Toray Dow Corning Silicone, SF-2938F) 3 parts by weight was added and the temperature was increased to 60 ° C. Adjusted. In a liquid-gas mixing unit, 54 parts by weight of the first component and 0.18 parts by weight of nitrogen in the supercritical state are mixed, and 103 parts by weight of the second component and 0.36 parts by weight of nitrogen in the supercritical state are mixed. After mixing, both components were mixed in a mixing head to prepare a polyurethane composition. The polyurethane composition was immediately injected into the RIM mold (internal pressure 294 kPa, mold temperature 80 ° C.). The used RIM mold is provided with concentric circular grooves having a groove width of 0.25 mm, a groove pitch of 1.5 mm, and a groove depth of 0.4 mm for transferring onto the surface of the polyurethane foam. Thereafter, it was cured at 100 ° C. for 15 minutes and demolded to obtain polyurethane foam A. The surface of the foam A was buffed using a buffing machine (manufactured by Amitech) to obtain a polyurethane sheet with adjusted thickness accuracy. The polyurethane sheet was punched out to produce a second polishing region (diameter 450 mm, thickness 1 mm).

  Next, 54 parts by weight of the first component and 0.11 part by weight of nitrogen in the supercritical state are mixed in a liquid-gas mixing unit, and 103 parts by weight of the second component and 0.21 part by weight of nitrogen in the supercritical state. And then mixing both components in a mixing head to prepare a polyurethane composition. Then, the polyurethane composition was immediately injected into the RIM mold (internal pressure 294 kPa, mold temperature 80 ° C.) in which the second polishing region was fixed at a predetermined position. Thereafter, curing was performed at 100 ° C. for 15 minutes to integrally mold the concave polyurethane foam B outside the second polishing region. Using a buffing machine (Amitech), the surface of the foam B was buffed to form a first polishing region, and a polyurethane sheet with a adjusted thickness accuracy was obtained. The polyurethane sheet was punched out so that the second polishing region was located at the center, and a polishing layer (diameter 610 mm, thickness 1.27 mm) having the structure shown in FIG. 2 was produced.

  A double-sided tape (manufactured by Sekisui Chemical Co., Ltd., double tack tape) was attached to the surface of the polishing layer opposite to the grooved surface using a laminator. Further, the surface of the corona-treated cushion sheet (manufactured by Toray Industries, Inc., polyethylene foam, Torepef, thickness 0.8 mm) was buffed and bonded to the double-sided tape using a laminator. Further, the double-sided tape was bonded to the other surface of the cushion sheet using a laminator to prepare a polishing pad.

Example 2
In the production of the second polishing region in Example 1, 54 parts by weight of the first component and 0.11 part by weight of nitrogen in the supercritical state were mixed, and 103 parts by weight of the second component and nitrogen 0 in the supercritical state were mixed. A third polishing region (diameter 150 mm, thickness 0.8 mm) was produced in the same manner as in Example 1 except that .21 parts by weight was mixed.

  Next, 54 parts by weight of the first component and 0.14 parts by weight of nitrogen in the supercritical state are mixed in a liquid-gas mixing unit, and 103 parts by weight of the second component and 0.26 parts by weight of nitrogen in the supercritical state. And then mixing both components in a mixing head to prepare a polyurethane composition. The polyurethane composition was immediately injected into the RIM mold (internal pressure 294 kPa, mold temperature 80 ° C.) in which the third polishing region was fixed at a predetermined position. After that, curing was performed at 100 ° C. for 15 minutes to integrally mold the concave polyurethane foam C outside the third polishing region. Using a buffing machine (Amitech), the surface of the foam C was buffed to form a second polishing region, thereby obtaining a polyurethane sheet with adjusted thickness accuracy. The polyurethane sheet was punched out so that the third polishing region was located at the center to prepare a composite polishing region (diameter 450 mm, thickness 1 mm).

  Next, 54 parts by weight of the first component and 0.11 part by weight of nitrogen in the supercritical state are mixed in a liquid-gas mixing unit, and 103 parts by weight of the second component and 0.21 part by weight of nitrogen in the supercritical state. And then mixing both components in a mixing head to prepare a polyurethane composition. The polyurethane composition was immediately injected into the RIM mold (internal pressure 294 kPa, mold temperature 80 ° C.) in which the composite polishing region was fixed at a predetermined position. Thereafter, curing was performed at 100 ° C. for 15 minutes, and a concave polyurethane foam D was integrally formed outside the composite polishing region. Using a buffing machine (Amitech), the surface of the foam D was buffed to form a first polishing region, and a polyurethane sheet with a adjusted thickness accuracy was obtained. The polyurethane sheet was punched out so that the composite polishing region was located at the center, and a polishing layer (diameter 610 mm, thickness 1.27 mm) having the structure shown in FIG. 4 was produced. Thereafter, a polishing pad was produced in the same manner as in Example 1.

Comparative Example 1
In the production of the second polishing region of Example 1, a polishing region was produced in the same manner as in Example 1 except that the diameter was 610 mm and the thickness was 1.27 mm.

表１から明らかなように、気泡径及び／又は気泡数が異なる研磨領域を複数有する研磨層を用いることにより、ウエハ中心部と研磨スラリーとの接触率を高めることができ、センタースローを効果的に抑制できる。 A double-sided tape (manufactured by Sekisui Chemical Co., Ltd., double tack tape) was affixed to the surface opposite to the grooved surface of this polishing region using a laminator. Further, the surface of the corona-treated cushion sheet (manufactured by Toray Industries, Inc., polyethylene foam, Torepef, thickness 0.8 mm) was buffed and bonded to the double-sided tape using a laminator. Further, the double-sided tape was bonded to the other surface of the cushion sheet using a laminator to prepare a polishing pad.

As is apparent from Table 1, by using a polishing layer having a plurality of polishing regions having different bubble diameters and / or numbers of bubbles, the contact ratio between the wafer central portion and the polishing slurry can be increased, and the center throw is effective. Can be suppressed.

Schematic showing the structure of the polishing pad of the present invention Schematic which shows the other structure of the polishing pad of this invention Schematic which shows the other structure of the polishing pad of this invention Schematic which shows the other structure of the polishing pad of this invention Schematic which shows the other structure of the polishing pad of this invention Schematic configuration diagram showing an example of a polishing apparatus used in CMP polishing Schematic showing 25 film thickness measurement positions on wafer

Explanation of symbols

1: Polishing pad 2: Polishing layer 3: First polishing region 4: Second polishing region 5: Cushion layer 6: Third polishing region 7: Light transmission region 8: Polishing surface plate 9: Material to be polished (semiconductor wafer)
10: Support base (polishing head)
11: Abrasive (slurry)
12, 13: Rotating shaft

Claims (10)

A step of dissolving a non-reactive gas under pressure in a first component containing an isocyanate component and / or a second component containing an active hydrogen group-containing compound, and reacting a polyurethane composition obtained by mixing the first component and the second component the average cell diameter 5~50μm by the injected foamed cured in a mold by injection molding, process average cell number forming the first polishing region is 1000 to 20000 pieces / mm ^2, and the polyurethane composition , By injection injection into a mold having the first polishing region by a reaction injection molding method, the average bubble diameter is 0.9 times or less than the average bubble diameter of the first polishing region, and the average number of bubbles a method of making an abrasive pad but including a step of integrally molding the second polishing region is 1.1 times or more the average cell number of the first polishing region, on the inner side of the first polishing region. The polyurethane composition is injected into a mold having the first polishing region and the second polishing region by a reaction injection molding method and foamed and cured to have an average cell diameter of 5 to 50 μm and an average cell number of 1000 to 20000 / a third polishing region is mm ^2, it viewed including the step of integrally molded on the inner side of the front Stories second polishing region,
The average bubble diameter of the second polishing region is 0.9 times or less of the average bubble diameter of the third polishing region, and the average bubble number of the second polishing region is 1.1 times or more of the average bubble number of the third polishing region. The method for producing a polishing pad according to claim 1. The first polishing region and the third polishing region have an average number of bubbles of 5000 to 18000 / mm. ² In the second polishing region, the average number of bubbles is 11000 to 20000 / mm. ² The method for producing a polishing pad according to claim 2. The method for producing a polishing pad according to claim 2 or 3, wherein the first polishing region and the third polishing region have the same average bubble diameter and average bubble number. The first component and / or the second component, according to any one of claims 1-4 for dissolving a non-reactive gas 0.01-1% by weight relative to the total weight of the first component and the second component Manufacturing method of polishing pad. Non-reactive gas, the production method of the polishing pad according to any one of claims 1 to 5 which is a nitrogen and / or carbon dioxide. Method for producing a polishing pad according to any one of claims 1 to 6 for dissolving a non-reactive gas to the first component and / or the second component in the supercritical state. Polyurethane composition, method for producing a polishing pad according to any one of claims 1 to 7 containing a silicone surfactant 0.05 to 10 wt%. The polishing pad manufactured by the method in any one of Claims 1-8 . 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 9 .

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