JP4986274B2 - Polishing pad and manufacturing method thereof - 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, In addition, the present invention relates to 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.

  As the polishing characteristics of the polishing pad, it is required that the polishing object has excellent flatness (planarity) and in-plane uniformity and has 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.

  As a polishing pad that satisfies the above characteristics, a polishing pad made of a polyurethane resin foam has been proposed (Patent Documents 1 and 2). The polyurethane resin foam is produced by reacting an isocyanate prepolymer and a chain extender (curing agent). As the chain extender, from the viewpoint of reactivity and physical properties of the obtained polyurethane resin foam. 4,4′-methylenebis (o-chloroaniline) (hereinafter also referred to as MOCA) is used as a suitable material.

  However, MOCA contains chlorine in the molecule, and there are environmental disadvantages such as the generation of harmful substances such as dioxins when it is disposed of, so its use may be restricted or prohibited in the future. For this reason, development of a polishing pad containing no halogen has been desired.

Patent No. 3013105 Japanese Patent No. 3516874

  SUMMARY OF THE INVENTION An object of the present invention is to provide a polishing pad that has better planarization characteristics than conventional polishing pads and does not contain halogen, and a method for manufacturing the same. Moreover, it aims at providing the manufacturing method of the semiconductor device using this polishing pad.

  As a result of intensive studies to solve the above problems, the present inventors have found that the above problems can be solved by the following polishing pad, and have completed the present invention.

  The present invention relates to a polishing pad having a polishing layer comprising a polyurethane resin foam, wherein the polyurethane resin foam comprises an isocyanate-terminated prepolymer containing an isocyanate component and a high molecular weight polyol, hydroquinone, resorcin, and p-xylylene. Polishing characterized by being a reaction-cured product of a chain extender containing an ethylene oxide adduct and / or a propylene oxide adduct of at least one aromatic diol selected from the group consisting of glycol and bisphenol A Related to the pad.

  In the present invention, instead of MOCA, ethylene oxide (EO) adduct and / or propylene of at least one aromatic diol selected from the group consisting of hydroquinone, resorcin, p-xylylene glycol, and bisphenol A By using an oxide (PO) adduct (hereinafter also referred to as an aromatic diol EO / PO adduct) as a chain extender, a halogen-free polishing pad can be obtained while improving planarization characteristics as compared with conventional polishing pads. I found out that

  In this invention, it is preferable that the isocyanate component which comprises an isocyanate terminal prepolymer contains 90 mol% or more of aromatic isocyanate. The aromatic isocyanate is preferably diphenylmethane diisocyanate.

  In the present invention, the high molecular weight polyol constituting the isocyanate-terminated prepolymer is preferably polytetramethylene ether glycol having a number average molecular weight of 500 to 1,500.

  Further, the isocyanate-terminated prepolymer preferably contains a low molecular weight polyol as a raw material component.

  By using the above prepolymer, the reaction rate with the aromatic diol EO / PO adduct, which is a chain extender, can be controlled within a suitable range, which is not only preferable for work, but also in terms of moldability of polyurethane resin foam. preferable. Further, the polishing pad using the specific material is particularly excellent in the effect of improving the planarization characteristics.

  The aromatic diol EO / PO adduct is preferably a product obtained by adding 2 to 4 mol of EO and / or PO to 1 mol of the aromatic diol.

Moreover, this invention mixes the 1st component containing an isocyanate terminal prepolymer, and the 2nd component containing a chain extension agent, It hardens | cures in the manufacturing method of the polishing pad containing the process (1) which produces a polyurethane resin foam. ,
In the step (1), a silicon-based surfactant is added to the first component containing the isocyanate-terminated prepolymer so as to be 0.05 to 10% by weight in the polyurethane resin foam. After preparing a bubble dispersion in which the non-reactive gas is dispersed as fine bubbles by stirring with a reactive gas, a second component containing a chain extender is mixed in the bubble dispersion and cured to form a polyurethane resin foam. The chain extender is an ethylene oxide adduct and / or propylene oxide of at least one aromatic diol selected from the group consisting of hydroquinone, resorcin, p-xylylene glycol, and bisphenol A The present invention relates to a method for producing a polishing pad comprising an adduct.

  According to this production method, a polyurethane resin foam with high hardness having a very uniform fine cell structure can be obtained. Therefore, the polishing pad using the polyurethane resin foam has excellent planarization characteristics as compared with the conventional polishing pad.

  In the said manufacturing method, it is preferable that the isocyanate component which comprises an isocyanate terminal prepolymer contains 90 mol% or more of aromatic isocyanate. The aromatic isocyanate is preferably diphenylmethane diisocyanate.

  Moreover, in the said manufacturing method, it is preferable that the high molecular weight polyol which comprises an isocyanate terminal prepolymer is the polytetramethylene ether glycol of number average molecular weight 500-1500.

  Moreover, in the said manufacturing method, it is preferable that an isocyanate terminal prepolymer contains a low molecular weight polyol as a raw material component.

  Furthermore, in the said manufacturing method, it is preferable that aromatic diol EO / PO adduct is what EO and / or PO added 2-4 mol with respect to 1 mol of aromatic diols.

  The silicon-based surfactant needs to be added to the polyurethane resin foam in an amount of 0.05 to 10% by weight, preferably 0.5 to 10% by weight. When the amount of the silicon-based surfactant is less than 0.05% by weight, a fine-bubble foam tends to be not obtained. On the other hand, when it exceeds 10% by weight, the number of bubbles in the foam becomes too large, and it tends to be difficult to obtain a polyurethane resin foam having high hardness.

  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.

  The polishing pad of the present invention may be only a polishing layer made of a polyurethane resin foam, or may be a laminate of a polishing layer and another layer (such as a cushion layer).

  The isocyanate-terminated prepolymer used in the present invention contains at least an isocyanate component and a high molecular weight polyol as raw material components. By using an isocyanate-terminated prepolymer, the physical properties of the resulting polyurethane resin foam are excellent.

  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 diisocyanate; 1,4-cyclohexane diisocyanate, 4,4′-dicyclohexylmethane diisocyanate, isophorone diisocyanate Isocyanate, cycloaliphatic diisocyanates such as norbornane diisocyanate. These may be used alone or in combination of two or more.

  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.).

  Among the above, it is preferable to use 90 mol% or more of aromatic isocyanate, more preferably 95 mol% or more, and particularly preferably 100 mol%. The aromatic isocyanate is preferably diphenylmethane diisocyanate, more preferably 4,4'-diphenylmethane diisocyanate.

  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. Among these, it is particularly preferable to use polytetramethylene ether glycol.

  The number average molecular weight of these high molecular weight polyols is not particularly limited, but is preferably 500 to 1500 from the viewpoint of the elastic properties of the resulting polyurethane resin. When the number average molecular weight is less than 500, 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, and the surface of the object to be polished is 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 1500, 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 polyols described above, ethylene glycol, 1,2-propylene glycol, 1,3-propylene 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 (hydroxy) Chill) 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 these low molecular weight polyols, low molecular weight polyamines and the like is not particularly limited and is appropriately determined depending on the properties required for the polishing pad, but is preferably 20 to 70 mol% of the total polyol components.

The isocyanate-terminated prepolymer uses the polyol or the like and an isocyanate component, and has an equivalent ratio (NCO / H ^* ) of isocyanate group (NCO) to active hydrogen (H ^* ) of 1.2 to 5.0, preferably 1. It is produced by heating reaction in the range of 6 to 2.6. If the ratio is less than 1.2, the prepolymer tends to be solidified or gelled with a high molecular weight during synthesis. On the other hand, when it exceeds 5.0, a large amount of unreacted isocyanate remains, so that the reaction with the chain extender is accelerated and the molding processability of the polyurethane resin foam tends to deteriorate.

  In the present invention, an EO adduct and / or PO adduct of at least one aromatic diol selected from the group consisting of hydroquinone, resorcin, p-xylylene glycol, and bisphenol A is used as a chain extender.

  Although the addition amount of EO and / or PO is not particularly limited, it is preferably 2 to 4 mol with respect to 1 mol of the aromatic diol. When the added amount of EO and / or PO is out of the above range, the polyurethane resin foam becomes soft, and a satisfactory planarity tends to be hardly obtained.

  The ratio of the prepolymer to the aromatic diol EO / PO adduct can be variously changed depending on the molecular weight of each and the desired physical properties of the polishing pad produced therefrom. In order to obtain a polishing pad having desired polishing characteristics, the number of isocyanate groups of the prepolymer relative to the number of functional groups of the aromatic diol EO / PO adduct is preferably in the range of 0.95 to 1.20, more preferably 0.8. 99 to 1.15.

  Moreover, you may use the said low molecular weight polyol and / or low molecular weight polyamine with the said aromatic diol EO / PO adduct as a chain extender as needed. However, when these are used in combination, the aromatic diol EO / PO adduct is preferably used in an amount of 80 mol% or more, more preferably 90 mol% or more. When the aromatic diol EO / PO adduct is less than 80 mol%, the bubble diameter tends to be large or the bubble diameter tends to vary, and the planarization characteristics of the polishing pad tend to deteriorate.

  The polyurethane resin foam can be produced by applying a known urethanization technique such as a melting method or a solution method, but is preferably produced by a melting method in consideration of cost, work environment, and the like.

  In the production of the polyurethane resin foam, the first component containing the isocyanate-terminated prepolymer and the second component containing the chain extender are mixed and cured.

  Examples of the method for producing a polyurethane resin foam include a method of adding hollow beads, a mechanical foaming method, and a chemical foaming method.

  In particular, a mechanical foaming method using a silicon surfactant which is a copolymer of polyalkylsiloxane and polyether is preferable. Examples of suitable silicon-based nonionic surfactants include SH-193 (manufactured by Toray Dow Corning Silicone) and L-5340 (manufactured by Nippon Unica).

  If necessary, stabilizers such as antioxidants, lubricants, pigments, fillers, antistatic agents, and other additives may be added to the polyurethane resin foam.

An example of a method for producing a fine cell type polyurethane resin foam constituting the polishing pad (polishing layer) will be described below. The manufacturing method of this polyurethane resin foam has the following processes.
1) Foaming process for producing a cell dispersion of isocyanate-terminated prepolymer A silicon-based surfactant is added to the isocyanate-terminated prepolymer (first component), and the mixture is stirred in the presence of a non-reactive gas to remove the non-reactive gas. Disperse as fine bubbles to obtain a cell dispersion. When the prepolymer is solid at normal temperature, it is preheated to an appropriate temperature and melted before use.
2) Curing Agent (Chain Extender) Mixing Step A chain extender (second component) is added to the above cell dispersion, mixed and stirred to obtain a foaming reaction solution. 3) Casting process The above foaming reaction liquid is poured into a mold.
4) Curing process The foaming reaction liquid poured into the mold is heated and reacted and cured.

  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. In view of cost, it is most preferable to use air that has been dried to remove moisture.

  A known stirring device can be used without particular limitation as a stirring device for dispersing non-reactive gas in the form of fine bubbles and dispersed in the first component containing the silicon-based surfactant. Specifically, a homogenizer, a dissolver, 2 A shaft 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 cell dispersion in a foaming 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 foaming 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 a polyurethane resin foam, heating and post-curing the foam that has reacted until the foaming reaction liquid is poured into the mold and no longer flows has the effect of improving the physical properties of the foam. Is preferred. The foam reaction solution may be poured into the mold and immediately put into a heating oven for post cure, and heat is not immediately transferred to the reaction components under such conditions, so the bubble size does not increase. . The curing reaction is preferably performed at normal pressure because the bubble shape is stable.

  In the polyurethane resin foam, a known catalyst that promotes a polyurethane reaction such as tertiary amine 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.

  Polyurethane resin foam can be manufactured by batch feeding each component into a container and stirring, or by continuously supplying each component and non-reactive gas to the stirring device and stirring, It may be a continuous production method in which a dispersion is sent out to produce a molded product.

  In addition, the prepolymer that is the raw material of the polyurethane resin foam is placed in a reaction vessel, and then a chain extender is added and stirred, and then poured into a casting mold of a predetermined size to produce a block, and the block is shaped like a bowl or band saw. In the method of slicing using a slicer, or in the above-described casting step, a thin sheet may be used. Alternatively, the raw material resin may be dissolved and extruded from a T-die to directly obtain a sheet-like polyurethane resin foam.

  In this invention, it is preferable that the average cell diameter of the said polyurethane resin foam is 70 micrometers or less, More preferably, it is 30-60 micrometers. When deviating from this range, the planarity (flatness) of the polished object after polishing tends to decrease.

  The polyurethane resin foam preferably has a hardness of 50 to 65 degrees using an Asker D hardness meter. When the Asker D hardness is less than 50 degrees, the planarity of the object to be polished is lowered. When the Asker D hardness is more than 65 degrees, the planarity is good but the uniformity of the object to be polished is reduced. There is a tendency.

  The polishing surface of the polishing pad (polishing layer) of the present invention that is in contact with the object 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, it is also a subject of polishing. In order to prevent destruction of the object to be polished due to adsorption with the object, it is preferable that the polishing 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, pouring a resin into a mold having a predetermined surface shape, and curing. 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.

  The thickness variation of the polishing layer is preferably 100 μm or less. When the thickness variation exceeds 100 μm, the polishing layer has a large undulation, and there are portions where the contact state with the object to be polished is different, which adversely affects the polishing characteristics. In order to eliminate the thickness variation of the polishing layer, in general, the surface of the polishing layer is dressed with 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.

  Examples of a method for suppressing the variation in the thickness of the polishing layer include a method of buffing the surface of the polishing sheet sliced to a predetermined thickness. Moreover, when buffing, it is preferable to carry out stepwise with abrasives having different particle sizes.

  The polishing pad of the present invention may be a laminate of the polishing layer and a cushion sheet.

  The cushion sheet (cushion layer) supplements the characteristics of the polishing layer. The cushion sheet is necessary for achieving both planarity and uniformity in a trade-off relationship in CMP. Planarity refers to the flatness of a pattern portion when a polishing object having minute irregularities generated during pattern formation is polished, and uniformity refers to the uniformity of the entire polishing object. The planarity is improved by the characteristics of the polishing layer, and the uniformity is improved by the characteristics of the cushion sheet. In the polishing pad of the present invention, it is preferable to use a cushion sheet that is softer than the polishing layer.

  Examples of the cushion sheet 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.

  Examples of means for attaching the polishing layer and the cushion sheet include a method of pressing the polishing layer and the cushion sheet with a double-sided tape.

  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 penetration of the slurry into the cushion sheet, 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 layer and the cushion sheet 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.

  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 the double-sided tape, a tape having a general configuration in which an adhesive layer is provided on both surfaces of a base material can be used as described above. 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. 1, a polishing surface plate 2 that supports a polishing pad (polishing layer) 1 and a support table (polishing head) that supports the semiconductor wafer 4. 5 and a polishing apparatus equipped with a backing material for uniformly pressing the wafer and a supply mechanism of the abrasive 3. 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 Hereinafter, although an Example demonstrates this invention, this invention is not limited to these Examples.

[Measurement and evaluation methods]
(Measurement of number average molecular weight of polyol component)
The number average molecular weight of the polyol component was measured by GPC (gel permeation chromatography) and converted by standard polystyrene.
GPC device: manufactured by Shimadzu Corporation, LC-10A
Column: Polymer Laboratories, (PLgel, 5 μm, 500 mm), (PLgel, 5 μm, 100 mm), and (PLgel, 5 μm, 50 mm) connected to three columns, flow rate: 1.0 ml / min
Concentration: 1.0 g / l
Injection volume: 40 μl
Column temperature: 40 ° C
Eluent: Tetrahydrofuran

(Measurement of average bubble diameter)
A sample for measurement was prepared by cutting the produced polyurethane resin foam in parallel with a microtome cutter as thin as possible to a thickness of 1 mm or less. 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.

(Specific gravity measurement)
This was performed according to JIS Z8807-1976. The produced polyurethane resin foam 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%. I put it. The specific gravity was measured using a hydrometer (manufactured by Sartorius).

(Hardness measurement)
This was performed in accordance with JIS K6253-1997. The produced polyurethane resin foam 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 polishing characteristics)
Using SPP600S (manufactured by Okamoto Machine Tool Co., Ltd.) as a polishing apparatus, polishing characteristics were evaluated using the prepared polishing pad. The polishing rate was calculated from the time obtained by polishing about 0.5 μm of a 1-μm thermal oxide film formed on an 8-inch silicon wafer. An interference type film thickness measuring device (manufactured by Otsuka Electronics Co., Ltd.) was used for measuring the thickness of the oxide film. 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.

  In the evaluation of the planarization characteristics, after depositing a thermal oxide film of 0.5 μm on an 8-inch silicon wafer and performing predetermined patterning, an oxide film of 1 μm is deposited by p-TEOS, and an initial step of 0.5 μm is formed. A wafer with a pattern was prepared, this wafer was polished under the above-mentioned conditions, and after polishing, each step was measured to evaluate the planarization characteristics.

  Two steps were measured as the flattening characteristics. One is a local step, which is a step in a pattern in which lines having a width of 270 μm are arranged in a space of 30 μm, and the step after one minute was measured. The other is the amount of scraping. In the pattern in which lines with a width of 270 μm are arranged in a space of 30 μm and the pattern in which lines with a width of 30 μm are arranged in a space of 270 μm, the level difference between the above two patterns is 2000 mm or less. The amount of scraping of the 270 μm space was measured. When the numerical value of the local step is low, it indicates that the flattening speed in a certain time is high with respect to the unevenness of the oxide film caused by the pattern dependence on the wafer. Further, when the amount of scraping of the space is small, the amount of shaving of the portion that is not desired to be shaved is small and the flatness is high.

Example 1
In a container, 578 parts by weight of 4,4′-diphenylmethane diisocyanate (hereinafter abbreviated as MDI), 378 parts by weight of polytetramethylene ether glycol (hereinafter abbreviated as PTMG-650) having a number average molecular weight of 653, propylene glycol (hereinafter, 44 parts by weight were added and reacted at 80 ° C. for 2 hours to obtain an isocyanate-terminated prepolymer (A). 100 parts by weight of the prepolymer (A) and 3 parts by weight of a silicon surfactant (L-5340, manufactured by Nihon Unika) were added to the polymerization vessel, mixed, adjusted to 80 ° C. and degassed under reduced pressure. Then, it stirred vigorously for about 4 minutes so that a bubble might be taken in in a reaction system with the rotation speed of 900 rpm using the stirring blade. 21 parts by weight of 1,4-bis (β-hydroxyethoxy) benzene (Mitsui Chemical Fine Co., Ltd., hereinafter abbreviated as BHEB) previously melted at 140 ° C. was added thereto. The mixed solution was stirred for about 1 minute and then poured into a pan-shaped open mold (casting container). When the fluidity of the mixed solution disappeared, it was placed in an oven and post-cured at 100 ° C. for 16 hours to obtain a polyurethane resin foam block.

  The polyurethane resin foam block was sliced using a band saw type slicer to obtain a polyurethane resin foam sheet. Next, using a buffing machine (Amitech Co., Ltd.), the surface of the sheet was buffed to a thickness of 1.27 mm to obtain a sheet with an adjusted thickness accuracy. The buffed sheet is punched out with a diameter of 61 cm, and is polished by using a groove processing machine to process concentric grooves with a groove width of 0.25 mm, a groove pitch of 1.50 mm, and a groove depth of 0.40 mm. A sheet was obtained. A double-sided tape (manufactured by Sekisui Chemical Co., Ltd., double tack tape) was applied to the surface of the polishing sheet 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, a double-sided tape was attached to the other surface of the cushion sheet using a laminator to prepare a polishing pad.

Example 2
In Example 1, instead of 21 parts by weight of BHEB melted at 140 ° C., resorcin-heated EO2 mole adduct (INDSPEC Chemical, HER) 21 parts by weight was used, which was heated to 100 ° C. A polishing pad was prepared by the method described above.

Example 3
In Example 1, instead of 21 parts by weight of BHEB melted at 140 ° C., 35 parts by weight of an EO adduct of bisphenol A (manufactured by Nippon Emulsifier, BA-2 glycol) melted at 140 ° C. was used. A polishing pad was produced in the same manner.

Example 4
The container was charged with 673 parts by weight of MDI, 293 parts by weight of PTMG-650 and 34 parts by weight of PG, and reacted at 80 ° C. for 2 hours to obtain an isocyanate-terminated prepolymer (B).
In Example 1, 100 parts by weight of isocyanate-terminated prepolymer (B) was used instead of 100 parts by weight of isocyanate-terminated prepolymer (A), and BHEB was changed from 21 parts by weight to 32 parts by weight. A polishing pad was prepared by the method described above.

Example 5
The container was charged with 569 parts by weight of MDI, 371 parts by weight of PTMG-650 and 60 parts by weight of diethylene glycol (hereinafter abbreviated as DEG), and reacted at 80 ° C. for 2 hours to obtain an isocyanate-terminated prepolymer (C).
A polishing pad was prepared in the same manner as in Example 1 except that 100 parts by weight of the isocyanate-terminated prepolymer (C) was used instead of 100 parts by weight of the isocyanate-terminated prepolymer (A).

Example 6
488 parts by weight of toluene diisocyanate (mixture of 2,4-isomer / 2,6-isomer = 80/20, hereinafter abbreviated as TDI-80), 458 parts by weight of PTMG-650, 53 parts by weight of PG, It was made to react at 80 degreeC for 2 hours, and the isocyanate terminal prepolymer (D) was obtained.
In Example 1, 100 parts by weight of the isocyanate-terminated prepolymer (D) was used in place of 100 parts by weight of the isocyanate-terminated prepolymer (A), and BHEB was changed from 21 parts by weight to 25 parts by weight. A polishing pad was prepared by the method described above.

Comparative Example 1
In a container, 341 parts by weight of TDI-80 (87 mol% with respect to the total isocyanate component), 76 parts by weight of 4,4′-dicyclohexylmethane diisocyanate, 528 parts by weight of polytetramethylene ether glycol having a number average molecular weight of 1018, and 55 parts by weight of DEG Part was added and reacted at 80 ° C. for 2 hours to obtain an isocyanate-terminated prepolymer (E).
100 parts by weight of the prepolymer (E) and 3 parts by weight of a silicon surfactant (manufactured by Toray Dow Corning Silicone, SH-193) are added to the polymerization vessel, mixed, adjusted to 80 ° C. and depressurized under reduced pressure. Foamed. Then, it stirred vigorously for about 4 minutes so that a bubble might be taken in in a reaction system with the rotation speed of 900 rpm using the stirring blade. 26 parts by weight of 4,4′-methylenebis (o-chloroaniline) previously melted at 120 ° C. was added thereto. The mixed solution was stirred for about 1 minute and then poured into a pan-shaped open mold (casting container). When the fluidity of the mixed solution disappeared, it was placed in an oven and post-cured at 100 ° C. for 16 hours to obtain a polyurethane resin foam block.
A polishing pad was produced in the same manner as in Example 1 using the polyurethane resin foam block.

Reference example 1
In Comparative Example 1, in the same manner as Comparative Example 1 except that 20 parts by weight of BHEB melted at 140 ° C. was used instead of 26 parts by weight of 4,4′-methylenebis (o-chloroaniline) melted at 120 ° C. A polishing pad was prepared.

A polishing test was performed using the polishing pads obtained in Examples, Comparative Examples, and Reference Examples, and polishing characteristics were evaluated. The results are shown in Table 1.

  From the results shown in Table 1, the polishing pad of the present invention is superior in planarization characteristics as compared with the conventional polishing pad, and is excellent in terms of environment because it is halogen-free.

Schematic configuration diagram showing an example of a polishing apparatus used in CMP polishing

Explanation of symbols

1: Polishing pad (polishing layer)
2: Polishing surface plate 3: Abrasive (slurry)
4: Polishing object (semiconductor wafer)
5: Support base (polishing head)
6, 7: Rotating shaft

Claims (8)

In a polishing pad having a polishing layer made of a polyurethane resin foam (but not containing water-soluble particles) obtained by a mechanical foaming method, the polyurethane resin foam contains an isocyanate component and a high molecular weight polyol. reaction of a terminated prepolymer, a chain extender containing at least one ethylene oxide adduct of an aromatic diol and / or propylene oxide adduct selected from Les Zorushin and p- xylylene glycol or Ranaru group A polishing pad, which is a cured product. The polishing pad according to claim 1, wherein the isocyanate component contains 90 mol% or more of aromatic isocyanate. The polishing pad according to claim 2, wherein the aromatic isocyanate is diphenylmethane diisocyanate. The polishing pad according to any one of claims 1 to 3, wherein the high molecular weight polyol is polytetramethylene ether glycol having a number average molecular weight of 500 to 1,500. The polishing pad according to any one of claims 1 to 4, wherein the isocyanate-terminated prepolymer contains a low molecular weight polyol as a raw material component. The polishing pad according to any one of claims 1 to 5, wherein the addition amount of ethylene oxide and / or propylene oxide is 2 to 4 mol with respect to 1 mol of the aromatic diol. Polishing including the step (1) of mixing a first component containing an isocyanate-terminated prepolymer and a second component containing a chain extender and curing to produce a polyurethane resin foam (but not containing water-soluble particles) In the pad manufacturing method,
In the step (1), a silicon-based surfactant is added to the first component containing the isocyanate-terminated prepolymer so as to be 0.05 to 10% by weight in the polyurethane resin foam. After preparing a bubble dispersion in which the non-reactive gas is dispersed as fine bubbles by stirring with a reactive gas, a second component containing a chain extender is mixed in the bubble dispersion and cured to form a polyurethane resin foam. a step of preparing the body, the chain extender, resorcin and p- xylylene ethylene oxide adduct of alkylene glycol least one aromatic diol selected from the Le or Ranaru group and / or propylene oxide adduct A method for producing a polishing pad, comprising: 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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