JP2008168431A - Abrasive pad - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an abrasive pad used for the chemical mechanical polishing which sufficiently suppresses occurrence of scratches on a surface to be polished. <P>SOLUTION: A circular recess is formed on a non-abrasive surface side of an abrasive pad to suppress generation of excessive stresses in a center of the abrasive pad. The recess is located in a center of a surface to be polished, and its depth is 0.01-2 mm. The abrasive pad is formed of a material consisting of a water insoluble matrix and water-soluble particles dispersed in the matrix. The depth of grooves is made larger than the size of the water-soluble particles. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a polishing pad used for chemical mechanical polishing.

  In recent years, Chemical Mechanical Polishing (CMP) has attracted attention as a polishing method capable of forming a surface having excellent flatness. CMP is a technique in which polishing is performed by causing a CMP slurry (an aqueous dispersion in which abrasive grains are dispersed) to flow down on the surface of the polishing pad while sliding the polishing pad and the surface to be polished. In this CMP, it is known that the polishing result greatly depends on the properties and characteristics of the polishing pad.

  Conventionally, in CMP, a polyurethane foam containing fine bubbles is used as a polishing pad, and polishing is performed by holding a slurry in a hole (hereinafter referred to as “pore”) opened on the surface of the resin. At this time, it is known to improve the polishing rate and the polishing result by providing a groove on the surface (polishing surface) of the polishing pad (see, for example, Patent Documents 1 to 3).

  However, when polyurethane foam is used as a material for the polishing pad, it is extremely difficult to freely control foaming. Therefore, the quality of the polishing pad varies and the polishing speed and processing state vary. In particular, scratch-like surface defects (hereinafter referred to as “scratch”) may occur, and improvements are desired.

  In recent years, a polishing pad in which a water-soluble polymer is dispersed in a matrix resin has been disclosed as a polishing pad that can form pores without using a foam (see, for example, Patent Documents 4 to 7). In this technique, a water-soluble polymer dispersed in a matrix resin is dissolved in contact with a CMP slurry or water during polishing to form pores. According to this technology, there is an advantage that the dispersion state of the pores can be arbitrarily controlled, but it may not be possible to prevent the pores from being clogged during polishing or after dressing. The situation may not be achieved and a radical solution is desired.

In addition, in a conventionally known polishing pad, the supplied CMP slurry may not be uniformly dispersed on the polishing pad, which may result in an insufficient polishing rate and a non-polished surface condition. There is a need for a solution.
JP-A-11-70463 JP-A-8-216029 It is disclosed in JP-A-8-39423. Japanese National Patent Publication No. 8-500622 JP 2000-34416 A JP 2000-33552 A JP-A-2001-334455

  The present invention solves the above-described conventional problems, and an object thereof is to provide a polishing pad for use in chemical mechanical polishing in which generation of scratches on a surface to be polished is sufficiently suppressed.

  According to the present invention, the above-mentioned object of the present invention is achieved by a polishing pad for use in chemical mechanical polishing, characterized in that a recess is provided on the non-polishing surface side.

  The inventors of the present invention have studied in detail the mechanism by which a conventionally known polishing pad generates a scratch, and as a result, excessive pressure is generated particularly near the center of the pad, thereby inducing the generation of the scratch. The inventors have found that the present invention has been achieved.

  The “concave portion” opens to the non-polishing surface side of the polishing pad. The shape of the recess has a function of dispersing a local pressure increase due to pressurization by the polishing head during polishing. The position of the recess is not particularly limited, but is preferably located at the center of the pad. Here, “located in the central portion” is not limited to the case where it is positioned at the center in a mathematically strict sense, but it is sufficient that the center of the non-polishing surface of the polishing pad is positioned within the range of the recess.

  Although the shape of a recessed part is not specifically limited, It is preferable that it is circular or polygonal shape, and circular is especially preferable. When the shape of the recess is circular, the upper limit value of the diameter is preferably 100% or less, more preferably 75% or less, and particularly preferably 50% or less of the diameter of the wafer that is a non-polished product. When the shape of the recess is circular, the lower limit of the diameter is preferably 1 mm, more preferably 5 mm, regardless of the size of the wafer that is a non-polished product.

  For example, when the diameter of the non-polished wafer is 300 mm, the diameter when the recess is circular is preferably 1 to 300 mm, more preferably 1 to 225 mm, and particularly preferably 5 to 150 mm. In addition, when the diameter of the non-polished wafer is 200 mm, the diameter when the recess is circular is preferably 1 to 200 mm, more preferably 1 to 150 mm, and particularly preferably 5 to 100 mm.

  Further, the depth of the recess is preferably 0.01 mm to 2.0 mm, more preferably 0.1 mm to 1.5 mm, and particularly preferably 0.1 mm to 1.0 mm.

  The polishing pad of the present invention can be provided with a groove of any shape and other recesses on the polishing surface as required. Examples of the groove shape include concentric circular shapes, lattice grooves, spiral grooves, and radial grooves. Examples of other recesses include a case where a large number of circular or polygonal recesses are provided on the polishing surface.

  The shape of the polishing pad of the present invention is not particularly limited, and may be, for example, a disk shape or a polygonal shape, and can be appropriately selected according to the polishing apparatus to which the polishing pad of the present invention is attached and used.

  The size of the polishing pad is not particularly limited, but in the case of a disc-shaped polishing pad, for example, the diameter is 150 to 1200 mm, particularly 500 to 800 mm, the thickness is 1.0 to 5.0 mm, and particularly the thickness is 1.5 to 3.0 mm. can do.

  The polishing pad of the present invention may be composed of any material as long as it has the recesses as described above. For example, a water-insoluble matrix material and a water-soluble material dispersed in the water-insoluble matrix material. For example, a pad containing fine particles or a pad having fine bubbles in a water-insoluble matrix.

  The material constituting the “water-insoluble matrix material” is not particularly limited, but is usually organic because it is easy to be molded into a predetermined shape and a molded body having appropriate hardness and elasticity can be obtained. Material is used. As the organic material, rubber, curable resin (thermosetting resin, photocurable resin or the like is crosslinked and cured by external energy such as heat or light), a thermoplastic resin, an elastomer, or the like is used alone or in combination. be able to.

Examples of the rubber include conjugated diene rubbers such as 1,2-polybutadiene, other butadiene rubbers, isoprene rubbers, styrene-butadiene rubbers, and styrene-isoprene rubbers;
Nitrile rubbers such as acrylonitrile-butadiene rubber;
Acrylic rubber;
Ethylene-α-olefin rubbers such as ethylene-propylene rubber and ethylene-propylene-diene rubber;
Other rubbers such as butyl rubber, silicone rubber and fluoro rubber can be mentioned. These rubbers may be crosslinked with sulfur or organic peroxides.

  Examples of the cured resin include urethane resins, epoxy resins, acrylic resins, unsaturated polyester resins, polyurethane-urea resins, urea resins, silicon resins, phenol resins, vinyl ester resins, and the like. .

  Examples of the thermoplastic resin include 1,2-polybutadiene resin, polyolefin resin such as polyethylene, polystyrene resin, polyacrylic resin [(meth) acrylate resin, etc.], vinyl ester resin (excluding acrylic resin), polyester Resin, polyamide resin, fluororesin, polycarbonate resin, polyacetal resin and the like. Among these thermoplastic resins, a resin that can be chemically cross-linked by an organic peroxide or the like, or radiation cross-linked by electron beam irradiation or the like may be cross-linked or may not be cross-linked.

  Examples of the elastomer include styrene-based elastomers such as diene-based elastomers such as 1,2-polybutadiene, polyolefin-based elastomers (TPO), styrene-butadiene-styrene block copolymers (SBS), and hydrogenated block copolymers (SEBS) thereof. Examples thereof include thermoplastic elastomers such as elastomers, thermoplastic polyurethane elastomers (TPU), thermoplastic polyester elastomers (TPEE), and polyamide elastomers (TPAE), silicone resin elastomers, and fluororesin elastomers. These elastomers may be cross-linked or may not be cross-linked.

  These organic materials may be modified with an acid anhydride group, a carboxyl group, a hydroxyl group, an epoxy group, an amino group, or the like. By modification, the affinity with water-soluble particles and slurry described later can be adjusted.

  These organic materials may use only 1 type and may use 2 or more types together.

  Among these organic materials, the polishing pad of the present invention preferably contains a crosslinked polymer. By containing a cross-linked polymer, the surface roughness of the inner surface of the groove can be controlled to 20 μm or less, for example, contributing to improvement of the surface state of the non-polished surface and imparting elastic recovery force to the water-insoluble matrix material. In addition, there is an advantage that the displacement due to the shear stress applied to the polishing pad during polishing can be suppressed small. Further, it is possible to effectively suppress the water-insoluble matrix material from being excessively stretched and plastically deformed to fill the pores during polishing and dressing, and the polishing pad surface from becoming excessively fuzzy. Accordingly, there are advantages that pores can be efficiently formed even at the time of dressing, a decrease in the retention of the slurry at the time of polishing can be prevented, and further that a polishing pad that has less fuzz and does not hinder the polishing flatness can be obtained.

  As the cross-linked polymer, rubber, cured resin, cross-linked thermoplastic resin, cross-linked elastomer, and the like among the above organic materials can be used. Further, among these, a crosslinked rubber is preferable because it is stable against strong acids and strong alkalis contained in many slurries and is less softened by water absorption. Among the crosslinked rubbers, those crosslinked with an organic peroxide are particularly preferable, and crosslinked 1,2-polybutadiene is more preferable. 1,2-Polybutadiene is preferable because it has a higher hardness than other rubbers.

  The content of these cross-linked polymers in the water-insoluble matrix is not particularly limited, but when the total amount of the water-insoluble matrix material is 100% by volume, 20% by volume or more (more preferably 30% by volume or more, more preferably 40 volume% or more and 100 volume% may be sufficient). If the content of the crosslinked polymer in the water-insoluble matrix is less than 20% by volume, the effect of containing the crosslinked polymer may not be sufficiently exhibited.

  The water-insoluble matrix material containing a cross-linked polymer is an elongation remaining after rupture (hereinafter simply referred to as “breaking residue”) when a test piece made of a water-insoluble matrix material is ruptured at 80 ° C. in accordance with JIS K 6251. Elongation ") is preferably 100% or less. That is, it is preferable that the total distance between marked lines after the fracture is not more than twice the distance between marked lines before the fracture. The elongation at break is preferably 30% or less, more preferably 10% or less, and still more preferably 5% or less. If the residual elongation at break exceeds 100%, the fine pieces scraped or stretched from the surface of the polishing pad during polishing and surface renewal tend to easily block the pores, which is not preferable. This “breaking elongation at break” is the same as that in JIS K 6251 “Tensile test method for vulcanized rubber” in a tensile test at a test piece shape dumbbell shape No. 3, tensile speed 500 mm / min, test temperature 80 ° C. When the test piece is broken, the elongation is obtained by subtracting the distance between the marked lines before the test from the total distance from each marked line to the broken part of the broken and divided test pieces. In actual polishing, since heat is generated by sliding, the test is performed at a temperature of 80 ° C.

  The “water-soluble particles” are particles that are detached from the water-insoluble matrix material by contacting with the slurry that is an aqueous dispersion in the polishing pad. This desorption may be caused by dissolution by contact with water or the like contained in the slurry, or may be caused by swelling and gelation containing this water or the like. Further, this dissolution or swelling may be caused not only by water but also by contact with an aqueous mixed medium containing an alcohol solvent such as methanol.

  In addition to the effect of forming pores, the water-soluble particles have an effect of increasing the indentation hardness of the polishing pad in the polishing pad. That is, for example, by containing water-soluble particles, the Shore D hardness of the polishing pad of the present invention is preferably 35 or more, more preferably 35 to 100, still more preferably 50 to 90, particularly 60. -85. When the Shore D hardness is 35 or more, the pressure that can be applied to the object to be polished can be increased, and the polishing rate can be improved accordingly. In addition, high polishing flatness can be obtained. Therefore, it is particularly preferable that the water-soluble particles are solid bodies that can ensure sufficient indentation hardness in the polishing pad.

  The material constituting the water-soluble particles is not particularly limited, and examples thereof include organic water-soluble particles and inorganic water-soluble particles. Organic water-soluble particles include dextrin, cyclodextrin, mannitol, saccharides (lactose, etc.), celluloses (hydroxypropylcellulose, methylcellulose, etc.), starch, protein, polyvinyl alcohol, polyvinylpyrrolidone, polyacrylic acid, polyethylene oxide, Examples thereof include those formed from water-soluble photosensitive resins, sulfonated polyisoprene, sulfonated polyisoprene copolymers, and the like. Furthermore, examples of the inorganic water-soluble particles include those formed from potassium acetate, potassium nitrate, potassium carbonate, potassium hydrogen carbonate, potassium chloride, potassium bromide, potassium phosphate, magnesium nitrate, and the like. These water-soluble particles can be used alone or in combination of two or more. Further, it may be one type of water-soluble particles made of a predetermined material, or two or more types of water-soluble particles made of different materials.

  Moreover, it is preferable that the average particle diameter of water-soluble particle | grains is 0.1-500 micrometers, More preferably, it is 0.5-100 micrometers. That is, the pore size is 0.1 to 500 μm, and more preferably 0.5 to 100 μm. If the average particle size of the water-soluble particles is less than 0.1 μm, the size of the pores formed is smaller than that of the abrasive grains that are normally used, so that it is difficult to obtain a polishing pad that can sufficiently hold the slurry. On the other hand, when the thickness exceeds 500 μm, the mechanical strength and polishing rate of the polishing pad that can be obtained are excessively large and the polishing rate tends to decrease.

  The content of the water-soluble particles is preferably 90% by volume or less, more preferably 0.1 to 90% by volume when the total of the water-insoluble matrix material and the water-soluble particles is 100% by volume. Yes, more preferably 0.1 to 60% by volume, and particularly preferably 0.5 to 40% by volume. When the water-soluble particles are contained in an amount exceeding 90% by volume, it tends to be difficult to sufficiently prevent the water-soluble particles existing in the resulting polishing pad from swelling or dissolving. It may be difficult to maintain the target strength at an appropriate value.

  Further, it is preferable that the water-soluble particles are water-soluble only when exposed to the surface layer in the polishing pad, absorb moisture inside the polishing pad, and do not swell. For this reason, water-soluble particle | grains can be equipped with the outer shell which suppresses moisture absorption in at least one part of the outermost part. The outer shell may be physically adsorbed on the water-soluble particles, may be chemically bonded to the water-soluble particles, or may be in contact with the water-soluble particles by both. Examples of the material for forming such an outer shell include epoxy resin, polyimide, polyamide, polysilicate, and the like. Even if the outer shell is formed only on a part of the water-soluble particles, the above effect can be sufficiently obtained.

  The water-insoluble matrix material can contain a compatibilizing agent in order to control the affinity with the water-soluble particles and the dispersibility of the water-soluble particles in the water-insoluble matrix material. Examples of compatibilizers include polymers modified with acid anhydride groups, carboxyl groups, hydroxyl groups, epoxy groups, oxazoline groups, amino groups, block copolymers, random copolymers, and various nonionic types. Surfactant, coupling agent, etc. are mentioned.

  Furthermore, in addition to the compatibilizing agent, the water-insoluble matrix material includes abrasive grains, oxidizing agents, alkali metal hydroxides and acids, pH regulators, surfactants, scratches, which have been conventionally used as components of slurries. At least one kind such as an inhibitor can be contained. As a result, polishing can be performed by supplying only water during polishing.

  In addition, various additives such as a filler, a softener, an antioxidant, an ultraviolet absorber, an antistatic agent, a lubricant, and a plasticizer can be contained. Furthermore, reactive additives such as sulfur and peroxide can be added to react and crosslink. In particular, as fillers, materials that improve rigidity such as calcium carbonate, magnesium carbonate, talc, clay, and silica, alumina, ceria, zirconia, titanium oxide, zirconium oxide, manganese dioxide, dimanganese trioxide, barium carbonate, etc. A material having a polishing effect may be used.

  Examples of the material for the “pad having fine bubbles in the water-insoluble matrix” include polyethylene foam, polyurethane foam, and polystyrene foam.

  The method for producing the polishing pad of the present invention is not particularly limited, and the method for forming the recesses of the polishing pad is not particularly limited. For example, after a polishing pad composition to be used as a polishing pad is prepared in advance and the composition is formed into a desired general shape, the recesses can be formed by cutting or the like. Furthermore, by molding the polishing pad composition using a mold having a concave shape, the concave shape can be formed simultaneously with the rough shape of the polishing pad.

  The method for preparing the polishing pad composition is not particularly limited, and for example, it can be prepared by kneading a necessary material such as a predetermined organic material with a kneader or the like. A well-known thing can be used as a kneading machine. Examples thereof include kneaders such as rolls, kneaders, Banbury mixers, and extruders (single screw and multi screw).

  Furthermore, a polishing pad composition for producing a polishing pad containing water-soluble particles can be prepared, for example, by kneading a water-insoluble matrix material, water-soluble particles and other additives. However, it is usually kneaded by heating so that it can be easily processed during kneading, but the water-soluble particles are preferably solid at the temperature at the time of kneading. By being solid, water-soluble particles can be dispersed at the above-mentioned preferable average particle diameter regardless of the compatibility with the water-insoluble matrix material.

  Therefore, it is preferable to select the type of water-soluble particles depending on the processing temperature of the water-insoluble matrix material to be used.

  The polishing pad of the present invention may be a multi-layer type polishing pad having a support layer on the non-polishing surface side of the polishing pad as described above.

  The support layer is a layer that supports the polishing layer and the like on the back side of the polishing layer. The characteristics of the support layer are not particularly limited, but are preferably softer than the polishing layer. By providing a softer support layer, even when the polishing layer is thin (for example, 1.0 mm or less), the polishing layer is lifted during polishing, the surface of the polishing layer is curved, etc. Can be prevented and stable polishing can be performed. The hardness of the support layer is preferably 90% or less of the hardness of the polishing layer, more preferably 50 to 90%, particularly preferably 50 to 80%, and most preferably 50 to 70%. Moreover, it is preferable that the Shore D hardness of a support layer is 70 or less, More preferably, it is 60 or less, More preferably, it is 50 or less.

  The support layer may be a porous body (foam) or a non-porous body. Furthermore, the planar shape is not particularly limited, and may be the same as or different from the polishing layer. The planar shape of the support layer can be, for example, a circle or a polygon (such as a quadrangle). Moreover, although the thickness is not specifically limited, for example, 0.1-5 mm is preferable, More preferably, it can be 0.5-2 mm.

  The material constituting the support layer is not particularly limited, but it is preferable to use an organic material because it can be easily molded into a predetermined shape and properties and can be provided with appropriate elasticity. As the organic material, an organic material constituting the water-insoluble matrix material in the polishing pad can be applied. However, the organic material constituting the support layer may be a crosslinked polymer or a non-crosslinked polymer.

  The polishing pad of the present invention can be mounted on a commercially available polishing apparatus and used for CMP by a known method.

  ADVANTAGE OF THE INVENTION According to this invention, the generation | occurrence | production of the scratch in the to-be-polished surface is provided, and the polishing pad for using for chemical mechanical polishing is provided.

  Hereinafter, the present invention will be described specifically by way of examples.

[Example 1]
(1) Production of polishing pad 80 parts by volume of 1,2-polybutadiene (trade name “JSR RB830”, manufactured by JSR Corporation) which is crosslinked to form a water-insoluble matrix, and β-cyclodextrin which is water-soluble particles ( 20 parts by volume of Yokohama International Bio Laboratory Co., Ltd., trade name “Dexipal β-100”, average particle size 20 μm) were kneaded with a rudder adjusted to 160 ° C. Thereafter, 1.0 part by volume of dicumyl peroxide (manufactured by NOF Corporation, trade name “Park Mill D”) was mixed and further kneaded at 120 ° C. to obtain pellets. Next, the kneaded product was heated in a mold at 170 ° C. for 18 minutes and crosslinked to obtain a disk-shaped molded body having a diameter of 600 mm and a thickness of 2.5 mm. Thereafter, a concentric groove having a width of 0.5 mm, a pitch of 2.0 mm, and a depth of 1.0 mm was formed on the polished surface side of the molded body using a commercially available cutting machine.

  Furthermore, a circular recess having a diameter of 50 mm and a depth of 0.5 mm centered on the same position as the center of the concentric circle on the surface was formed by spot machining on the non-polished surface side.

(2) Evaluation of polishing rate and number of scratches The polishing pad manufactured above was mounted on a platen of a polishing apparatus (Ebara Manufacturing Co., Ltd., model “EPO112”) and diluted three times as a slurry for chemical mechanical polishing. Chemical vapor phase using CMS-1101 (trade name, manufactured by JSR Co., Ltd.) and using a patternless SiO2 film (PETEOS film; tetraethylorthosilicate (TEOS) as a raw material and plasma as an acceleration condition under the following conditions: A wafer having a SiO2 film formed by growth was polished, and the polishing rate and the number of scratches were evaluated. As a result, the polishing rate was 210 nm / min, and the number of scratches was 2.

Surface plate rotation speed: 70 rpm
Head rotation speed: 63 rpm
Head pressing pressure: 4 psi
Slurry supply amount: 200 mL / min Polishing time: 2 minutes The polishing rate was calculated from these film thicknesses by measuring the film thickness before and after polishing with an optical film thickness meter. In addition, the number of scratches generated on the entire surface of the polished surface was measured using a wafer defect inspection apparatus (model “KLA2351” manufactured by KLA-Tencor Corporation).

[Example 2]
In the same manner as in Example 1, pellets containing 1,2-polybutadiene, β-cyclodextrin, and dicumyl peroxide were obtained. Then, it is heated at 170 ° C. for 18 minutes in a mold having a convex shape with a diameter of 50 mm and a depth of 0.5 mm at the center of the lower mold, and is crosslinked to form a disk shape with a diameter of 600 mm and a thickness of 2.5 mm. A molded body having a recess having a diameter of 50 mm and a depth of 0.5 mm on the non-polished surface side was obtained. Thereafter, concentric grooves having a width of 0.5 mm, a pitch of 2.0 mm, and a depth of 1.0 mm were formed on the polished surface side of the molded body using a cutting machine.

  The polishing rate and the number of scratches were evaluated in the same manner as in Example 1 except that the polishing pad prepared above was used. As a result, the polishing rate was 200 nm / min, and there were 3 scratches.

[Comparative Example 1]
In the same manner as in Example 1, a disk-shaped molded body having the same size was prepared, and using a commercially available cutting machine on the polishing surface side, the width was 0.5 mm, the pitch was 2.0 mm, and the depth was 1. A polishing pad having a 0 mm concentric groove, a groove on the polishing surface side, and no recess on the non-polishing surface side was produced.

Using this polishing pad, the polishing rate and the presence or absence of scratches were evaluated in the same manner as in Example 1. As a result, the polishing rate was 200 nm / min, and there were 15 scratches.

Claims (4)

  A polishing pad for use in chemical mechanical polishing, comprising a recess on a non-polishing surface side.   The polishing pad for use in chemical mechanical polishing according to claim 1, wherein the recess is located in the center of the non-polishing surface.   The polishing pad for use in chemical mechanical polishing according to claim 1 or 2, wherein the recess has a circular or polygonal shape.   The polishing pad for use in chemical mechanical polishing according to any one of claims 1 to 3, comprising a water-insoluble matrix and water-soluble particles dispersed in the water-insoluble matrix.