JP2006100556A - Polishing pad and polishing method using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polishing pad of a low load which is excellent in flatness, removes a layer insulation film effectively at a fast speed, and reduces the generation of polishing flaws in a CMP technique for forming wiring by flattening and polishing a metallic film which is buried and grown in a wiring groove formed on the layer insulation film, and to provide a polishing method for polishing without a defect in an insulation layer by using the polishing pad. <P>SOLUTION: The modulus of elasticity in the tension of the polishing pad at room temperature is 0.1 to 2.5 Gpa. A matrix constituting the polishing surface of the pad comprises one or more kinds of polyurethane, and at least one of the polyurethanes comprises (1) an isocyanate compound and (2) active hydrogen, and a compound having a branched chain in α position carbon of a functional group with active hydrogen. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a polishing pad and a polishing method using the same in a chemical mechanical polishing technique for forming a wiring by planarizing and polishing an object to be polished such as a metal film.

In recent years, new microfabrication techniques have been developed along with higher integration and higher performance of semiconductor integrated circuits (hereinafter referred to as LSIs).
The chemical mechanical polishing (hereinafter referred to as CMP) method is one example, for example, planarization of an interlayer insulating film, formation of a metal plug, embedded wiring in an LSI manufacturing process disclosed in Patent Document 1, particularly a multilayer wiring forming process. It is a technique that is frequently used in formation.
Recently, in order to improve the performance of LSIs, the use of copper alloys as wiring materials has been attempted. However, it is difficult to finely process the copper alloy by the dry etching method frequently used in the formation of the conventional aluminum alloy wiring. Therefore, a so-called damascene method is mainly employed, in which a copper alloy thin film is deposited and embedded on an insulating film in which grooves are formed in advance, and the copper alloy thin film other than the grooves is removed by CMP to form embedded wiring. (See Patent Document 2).
A general method of metal CMP of copper alloy or the like is to apply a polishing pad on a circular polishing platen (platen), immerse the polishing pad surface with a metal polishing liquid, and press the surface on which the metal film of the base is formed Then, the polishing platen is turned with a pressure higher than 20 kPa (hereinafter referred to as polishing load) applied from the back surface, and the metal film on the convex portion is removed by mechanical friction between the polishing liquid and the convex portion of the metal film. Is.

On the other hand, with the miniaturization of wiring due to high integration of LSI, there is a problem of increase in signal delay time due to increase in inter-wiring capacitance. Further, there is a demand for further reduction of the relative dielectric constant and heat treatment process.
For example, conventionally, a SiO ₂ film by a CVD method having a relative dielectric constant of about 4.2 has been used as a material for forming an interlayer insulating film. However, the capacitance between devices is reduced and the operation speed of an LSI is improved. Therefore, a material that exhibits a lower dielectric constant is desired.
On the other hand, as a low dielectric constant material that is currently in practical use, a SiOF film by a CVD method having a relative dielectric constant of about 3.5 can be cited. Examples of the insulating material having a relative dielectric constant of 2.5 to 3.0 include organic SOG (Spin On Glass) and organic polymers.
Furthermore, as insulating materials having a relative dielectric constant of 2.5 or less, porous materials having voids in the film are considered to be promising, and studies and developments for application to LSI interlayer insulating films are actively conducted. ing.
U.S. Pat. No. 4,944,836 JP-A-2-278822

However, the above-described low dielectric constant insulating film tends to decrease the film strength as the dielectric constant of the insulating film decreases, and there is a big problem from the viewpoint of process compatibility. When applied as an interlayer film material in a Cu-damascene process, the adhesion (bondability) tends to be weak at the interface between the SiO ₂ film and the SOG film formed by the CVD method used as the cap film. . If this happens, interfacial peeling occurs in the Cu-CMP process for polishing the Cu film of the wiring metal. For this reason, when polishing the wiring metal or the like, polishing has to be performed with a low load.

  The present invention provides high-speed and low-load insulation in CMP technology in which a metal film is embedded and grown in an electrode, plug, and wiring groove pattern formed in an interlayer insulating film, and the metal film is planarized and polished to form a wiring. A polishing pad capable of polishing without causing defects in a layer and a polishing method using the same are provided.

  Also, in the CMP technology that removes the interlayer insulating film, BPSG film, and shallow trench isolation insulating film in the semiconductor device manufacturing process, it has excellent flatness and efficiently removes the insulating film at the same time. It is an object of the present invention to provide a polishing pad that can reduce the occurrence of the above. Furthermore, the present invention can be diverted to fields such as wiring boards that require a high polishing rate.

The above problems can be solved by the following polishing pad and polishing method.
That is, the polishing pad of the present invention is a polishing pad having a tensile elastic modulus at room temperature of 0.1 to 2.5 Gpa used for polishing an object to be polished by being attached to a surface plate, and the matrix constituting the polishing surface of the pad is One or more polyurethanes are included, and at least one of the polyurethanes includes 1) an isocyanate compound and 2) a compound having a branched chain at the α-position carbon of the functional group having active hydrogen and active hydrogen.

  In addition, in the polishing method of the present invention, the polishing pad is fixed on the surface plate, the object to be polished is held by the holder with the surface to be polished facing the polishing pad, and the polishing agent is placed on the polishing pad. And polishing the polishing object by relatively sliding the pad and the polishing object, wherein the polishing pad of the present invention is used for the polishing pad. Is the method.

  When metal CMP is performed using the polishing pad of the present invention, polishing can be performed at a high speed with a low load, so that the load on the interlayer insulating film is small and polishing with excellent flatness can be performed. Next generation dual damascene method can be easily implemented.

  In view of the above problems, the inventors of the present invention have developed an active hydrogen compound that is one of the constituent elements of polyurethane, which is a material of the pad, while developing CMP technology. In the case of a compound having a branched chain (hereinafter also referred to as compound (A)), the polishing rate of the object to be polished can be dramatically improved, the polishing time can be reduced, or low load polishing can be performed. It came.

  The polishing pad of the present invention is a polishing pad suitable for polishing a layer mainly composed of a metal or a layer composed of a metal and an insulating film that separates the metal mainly in a semiconductor manufacturing process. At least one polyurethane shown below is used in a matrix constituting a surface in contact with an object (hereinafter referred to as a polished surface).

  Here, the polyurethane is a polymer synthesized based on a polyaddition reaction or a polymerization reaction of an isocyanate compound and a compound having active hydrogen (an active hydrogen compound). In the present invention, the compound used as a reaction target of isocyanate is an active hydrogen-containing compound, for example, two or more polyhydroxy group-containing compounds (such as polyols) or amino group-containing compounds.

  What can be used as a polyurethane in this invention includes a thermoplastic polyurethane, a crosslinked polyurethane, a thermoplastic polyurethane prepolymer, and a crosslinked polyurethane prepolymer.

  Here, what can be used as an isocyanate compound as a raw material of polyurethane is tolylene diisocyanate, xylene diisocyanate, metaxylene diisocyanate, 4,4'-diphenylmethane diisocyanate, naphthalene diisocyanate, tolidine diisocyanate, methylcyclohexane-2,4- (or- 2,6--Diisocyanate, hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, isophorone diisocyanate and the like can be mentioned, but are not limited thereto. Moreover, what has the polyfunctional isocyanate group which made these compounds the isocyanurate body, the burette body, the adduct body, and the polymeric body can also be used. Examples of these include, but are not limited to, 4, 4 ′, 4 ″ -triphenylmethane triisocyanate, 2,4-tolylene diisocyanate cyclic trimer, and the like. . These can be used alone or as a mixture.

  Moreover, you may use the reaction product of the above isocyanate compound and the compound which has one or more active hydrogen in a molecule | numerator as an isocyanate compound. As the compounds having one or more active hydrogens in the molecule, general compounds can be widely used in addition to the active hydrogens shown below and compounds having a branched chain at the α-position carbon of the functional group having active hydrogens. For example, ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, polyethylene glycol, sorbitol, glycerin, triethanolamine, pentaerythritol, ethylenediamine, propyl Anything that can react with an isocyanate compound, such as amine, butylamine, polypropylene glycol, polytetramethylene ether glycol, poly-ε-caprolactone diol, adipate ester diol, polycarbonate diol, and mixtures and copolymers thereof Can be used.

The compound (A) in the present invention is a compound that reacts with an isocyanate compound to obtain a polyurethane, and is a compound having a branched chain at the α-position carbon of the functional group having active hydrogen and active hydrogen. For example, propylene glycol, hexylene glycol, 1,2-propanediol, 1,2-butanediol, 1,3-butanediol, 2,3-butanediol, 1,2-hexanediol, polypropylene glycol, castor oil-based polyol The representative ester and amide compounds of ricinoleic acid and the like, and mixtures, polymers, copolymers and the like thereof are not limited thereto. In particular, propylene glycol, polypropylene glycol, and castor oil-based polyol are preferable.
Among these, it is obtained by combining 4,4′-diphenylmethane diisocyanate as an isocyanate compound and polypropylene glycol, polytetramethylene ether glycol, or an ester compound of ricinoleic acid (castor oil-based polyol) as a polyol of an active hydrogen compound. Polyurethane is preferable because of its excellent moldability.

An active hydrogen compound other than the compound (A) (hereinafter referred to as the compound (B)) may be used in the reaction between the compound (A) and the isocyanate compound and contained in the same polyurethane chain. Moreover, the polyurethane of the compound (B) and the isocyanate compound may be mixed with the polyurethane using the compound (A) and used in the matrix.
As the compound (B) having at least one active hydrogen in the molecule other than the compound (A), the following general compounds can be widely used. For example, ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, polyethylene glycol, sorbitol, glycerin, triethanolamine, pentaerythritol, ethylenediamine, propyl Amine, butylamine, polytetramethylene ether glycol, poly-ε-caprolactone diol, adipate ester diol, polycarbonate diol, and the like, and mixtures and copolymers thereof other than compound (A) can react with isocyanate compounds Can all be used.

  When the polyurethane in the present invention is a thermoplastic resin, a diol is used. In the case of a thermoplastic polyurethane, by appropriately combining a short-chain diol and a long-chain diol, the ratio of the hard segment and the soft segment can be adjusted, and the elastic modulus at the use temperature can be adjusted. The thermoplastic polyurethane can be produced by a known method, for example, rapidly mixing all raw materials, heating the mixture on a conveyor belt, polymerizing while polymerizing while kneading with a single or multi-screw extruder. A melt polymerization method, a method of proceeding polymerization by dissolving a raw material in a solvent and heating can be used without particular limitation. Moreover, the preferable compounding rate in this case uses an isocyanate compound and the compound which has an active hydrogen each bifunctional, and is NCO group / active hydrogen = 0.5-1.5, More preferably, it is 0.8-1.2. Furthermore, as a final shape, a desired shape such as a pellet shape, a flake shape, or a sheet shape can be used, but in consideration of a case where it is mixed with other components, a pellet shape is more preferable.

  In the production of the polyurethane in the present invention, a catalyst can be used as necessary regardless of thermoplasticity or thermal crosslinking type. Examples of the catalyst include nitrogen-containing compounds such as triethylamine and triethylenediamine, and organometallic compounds such as dibutyltin dilaurate and tin octylate.

  In order to adjust the elastic modulus and hardness, other polyurethanes, polymer compounds such as acrylic, and plasticizers such as polyol are added to the polyurethane alone or a mixture of the above-mentioned isocyanate compound and a compound having active hydrogen. May be used. Moreover, you may add antioxidant, a pigment, an antiblocking agent, etc. However, these additives are preferably used in an amount of 90% or less, more preferably 40% or less, and still more preferably 10% or less by weight. Here, if the proportion of the additive is too large, the polishing rate may be drastically reduced.

  The matrix composed of the above materials preferably has a tensile elastic modulus at room temperature in the range of 0.1 to 2.5 GPa. More preferably, it is 0.1-1.0 GPa. More preferably, it is 0.15-0.4 GPa. If the elastic modulus is high, the polishing rate becomes high and local flatness such as dishing is improved, but the surface to be polished tends to be easily damaged. On the other hand, if the elastic modulus is low, scratches are less likely to occur and the uniformity at the wafer level is improved, but local flatness such as polishing rate and dishing tends to decrease. Here, the elastic modulus in the present invention refers to an evaluation result by dynamic elastic modulus measurement. The tensile modulus here means that a sample made of a measurement object such as the above matrix is cut into a 1 mm × 1.5 mm × 35 mm strip, and the span is 27.5 mm using a normal dynamic viscoelasticity test apparatus. The storage elastic modulus of the complex elastic modulus obtained by measuring at a frequency of 1 Hz at room temperature.

For the purpose of adjusting the elastic modulus and improving the slurry retention on the surface, it is possible to introduce inorganic and / or organic fibers or fine particles and bubbles into the matrix mainly composed of polyurethane described above.
It is desirable that inorganic fibers and / or organic fibers or fine particles are exposed to 20% or less of the area of the surface exposed portion (polishing surface) in contact with the polishing object of the polishing pad. The addition of fibers and fine particles having a positive zeta potential is particularly desirable from the viewpoint of achieving both protection of the surface to be polished and the polishing rate.

  As what can be used as an above-mentioned fiber, what made acrylic, aramid, polyamide, polyester, a cellulose, etc. into a fiber form can be especially used without a restriction | limiting. Two or more of these can be selected and mixed for use. It is more preferable to select an aramid fiber alone or as a main component. That is, aramid fibers have higher tensile strength than other general organic fibers, and when the polishing pad polishing surface according to the present invention is mechanically roughened to expose the fibers, the fibers are likely to remain on the surface. Because there is. It also has the effect of improving the durability of the polishing pad and extending the service life.

  The aramid fiber has a para type and a meta type, and the para-type aramid fiber is more suitable because it has higher mechanical strength and lower moisture absorption than the meta type fiber. As the para-aramid fiber, poly p-phenylene terephthalamide fiber and poly p-phenylene diphenyl ether terephthalamide fiber are commercially available and can be used.

Even if these use the chop which cut | disconnected the short fiber to predetermined length, the thing of several types of fiber lengths can also be mixed and used. Moreover, you may fill in resin in the form of a woven fabric or a nonwoven fabric.
An organic fiber having a fiber diameter (diameter) of 1 mm or less can be used appropriately, but is preferably 200 μm or less. Preferably it is 1-200 micrometers, More preferably, it is 5-150 micrometers. If it is too thick, the mechanical strength is too high, which causes polishing scratches and defective dresses. If it is too thin, the handleability tends to be lowered, or the durability of the pad is lowered due to insufficient strength. A fiber length of 10 mm or less can be used appropriately, but is desirably 5 mm or less. Preferably, it is 0.1-3 mm. If it is too short, the exposed fiber will not be effectively held in the pad when the pad polishing surface is mechanically roughened. If it is too long, the pad will be thickened and mixed with the elastic body that mainly constitutes the pad. May be difficult.

  When using chopped fibers, the fiber surface may be mechanically or chemically roughened beforehand or modified with a coupling material or the like in order to improve the affinity with the resin. From the viewpoint of handling, a bundle of short fiber chops coated with a very small amount of resin can be used. However, this is only required to have a holding power enough to disperse the short fibers in the matrix resin by heating during mixing with the matrix resin or by an applied shearing force. Furthermore, in addition to the main organic fibers, inorganic fibers such as glass fibers may be added.

  The content of the organic fiber is not particularly limited, but needs to be optimized depending on the softening temperature and viscosity of the elastic body mainly constituting the pad. 1 to 50% by weight of the entire pad is preferable, and more preferably 2 to 20% by weight. If the amount of fibers is small, polishing scratches on the surface to be polished of the object to be polished become prominent, and if it is too large, the moldability tends to deteriorate.

  The inorganic and organic fine particles are preferably harder than the matrix. Examples of organic substances include epoxy resins, cross-linked polyurethanes, polyamides, aramids, polyethylenes, polypropylenes, and polycarbonates. Examples of inorganic substances include silica, alumina, aluminum hydroxide, ceria, titania, zirconia, and germania, but are not limited thereto. Can be used without any problems.

  In particular, these inorganic fine particles preferably have a small particle size. The average particle diameter is preferably 1 μm or less, more preferably 0.5 μm or less. If it is too large, when used for a metal such as Cu, the polishing rate is lowered and it causes polishing scratches. However, kneading or the like becomes difficult at 0.01 μm or less. The content of the fine particles is preferably 2 to 30% in the pad.

  The polishing pad composed of the above materials is required to have a tensile elastic modulus at room temperature in the range of 0.1 to 2.5 GPa. Preferably, it is 0.2-1.0 GPa. More preferably, it is 0.3-0.7 GPa. If the elastic modulus is high, local flatness such as dishing is improved, but scratches on the polished surface tend to occur. If the elastic modulus is lowered, uniformity at the wafer level is improved, but local flatness such as polishing rate and dishing tends to be lowered.

  The method for producing the polishing pad of the present invention is not particularly defined, but can be performed by a conventionally known method. When the matrix mainly constituting the pad is made of a thermoplastic resin, the following method can be employed. First, each component is uniformly mixed (dry blended) with a Henschel mixer, a super mixer, a turnbull mixer, a ribbon blender or the like, and then melt-kneaded with a single screw extruder, a twin screw extruder, a Banbury mixer, or the like. Further, if necessary, organic fibers or particles are added, melt mixed, cooled and tableted. If water is used for cooling, the tablet must be thoroughly dried and dehydrated. The final sheet-like molded product can be produced by extruding the obtained thermoplastic resin composition tablet again through a die with an injection molding machine and rolling with a roll. Moreover, you may inject | pour into a metal mold | die.

  On the other hand, when a thermosetting resin is used as the matrix, a casting method is desirable. For example, when a two-component thermosetting resin is used, fibers or particles are dispersed in one or both of the two liquid solutions with a homomixer or the like, and the two liquids are further mixed and stirred. The mixed liquid after stirring is depressurized, and the entrained gas is degassed. The mixture is placed in a mold that can be formed into a sheet and heated at high pressure or normal pressure to be cured.

The overall thickness of the polishing pad is preferably 0.1 to 5 mm, and more preferably 0.5 to 2 mm. If necessary, this is processed to the shape of a surface plate of a predetermined polishing apparatus to obtain a final product. In addition, as a method of attaching a groove to the polishing pad, a convex part that becomes a groove of the polishing pad is provided in advance in a sheet-like mold, and a groove shape is formed on a molded product, or processing is performed using an NC lathe after forming. You can also
For fixing the polishing pad to the polishing apparatus surface plate, an adhesive such as a double-sided adhesive tape can be used on the side opposite to the polishing surface. Alternatively, it may be attached via a low elastic modulus subpad made of foamed polyurethane or the like.

Hereinafter, a polishing method using the polishing pad of the present invention will be described.
In the polishing method of the present invention, a polishing pad is fixed on a surface plate, and an object to be polished is held by a holder with the surface to be polished facing the polishing pad, and the polishing agent of the present invention is applied to the polishing pad. And polishing the polishing object by relatively sliding the pad and the polishing object. In order to relatively slide the polishing pad and the object to be polished, there is a method of rotating at least one of the holder and the surface plate. Further, the holder may be deviated from the center of rotation of the surface plate and rotate.
There is no restriction | limiting in particular in a grinding | polishing apparatus, It can use with a disk type grinding | polishing apparatus and a linear type grinding | polishing apparatus. As an example, there is a general polishing apparatus that has a surface plate that is connected to a motor or the like that can change the number of rotations, and on which a polishing pad is attached, and a holder that holds an object to be polished such as a semiconductor substrate. Specifically, there is a polishing apparatus manufactured by Ebara Corporation: model number EPO111.
There are no particular limitations on the polishing conditions, and in general, the polishing load is preferably 1 to 100 kPa. However, it is desirable to optimize the various polishing conditions according to the material and state of the object to be polished. During polishing, an abrasive is continuously supplied onto the polishing pad with a pump or the like. Although there is no restriction | limiting in this supply amount, It is preferable that the surface of a polishing pad is always covered with the abrasive | polishing agent. The abrasion and shape of the pad or the fibers and particles by polishing are regenerated by dressing.
It is desirable that the polished object after polishing is thoroughly washed in running water and then dried by removing water droplets adhering to the polished object using a spin dryer or the like.

Polishing with the polishing method of the present invention is preferably a layer mainly made of metal, more preferably a layer made of copper. For example, for example, a film mainly including a metal such as Cu, Ta, TaN, or Al, which is embedded in the composite opening of the insulating layer can be given. Specifically, in a semiconductor device manufacturing process, a barrier film is formed on an interlayer insulating film in which via holes and wiring grooves are formed by dry etching so as to completely cover an opening and an inner wall, and a metal film such as Cu is further formed thereon. And a substrate in which the opening is completely embedded.
Examples of the interlayer insulating film include a low-k silicon-based film and an organic polymer film. Examples of the silicon-based film include silica-based films such as fluorosilicate glass, organosilicate glass, silicon oxynitride, and hydrogenated silsesquioxane. Examples of the organic polymer film include a wholly aromatic low dielectric constant interlayer insulating film. In particular, organosilicate glass is preferable.
The barrier film contains one or more selected from tungsten, tungsten nitride, tungsten alloy, other tungsten compounds, titanium, titanium nitride, titanium alloys, other titanium compounds, tantalum, tantalum nitride, tantalum alloys, and other tantalum compounds. Layer.
Examples of the metal film include copper, copper alloy, copper oxide, copper alloy oxide, tungsten, tungsten alloy, silver, gold and other metal-based materials, such as copper, copper alloy, copper oxide. It is preferable that copper such as an oxide of a copper alloy is a main component.

  In addition to the films containing metal as described above, silicon oxide films formed on predetermined wiring boards, inorganic insulating films such as glass and silicon nitride, films mainly containing polysilicon, photomasks, lenses, prisms, etc. Optical glass, inorganic conductive films such as ITO, optical integrated circuits composed of glass and crystalline materials, optical switching elements, optical waveguides, optical fiber end faces, scintillator and other optical single crystals, solid state laser single crystals, blue lasers Sapphire substrates for LEDs, semiconductor single crystals such as SiC, GaP, and GaAs, glass or aluminum substrates for magnetic disks, magnetic heads, wiring boards, etc. can be polished.

The metal CMP abrasive used in the polishing method using the polishing pad of the present invention is any one of a metal oxidizer, a metal oxide solubilizer, an anticorrosive, a water-soluble polymer, and a metal laminate film interfacial peeling inhibitor. Can be used without particular limitation, but those having a pH in the range of 3 to 5 are preferred. In particular, those further containing abrasive grains are preferred, and those containing at least abrasive grains and a water-soluble polymer, particularly polyacrylic acid, are more preferred. For example, as a polishing agent for Cu, abrasive particles such as silica, alumina, ceria, titania, zirconia, and germania, an additive such as the above-mentioned metal oxide solubilizer, and an anticorrosive are dispersed in water, and further, an oxidizing agent for the above metal A polishing agent to which a peroxide is added.
As the abrasive, colloidal silica particles or alumina particles are particularly preferable. The abrasive particle content is preferably 0.1 to 20% by weight. When the particle content is small, the polishing rate tends to decrease. The abrasive particles do not limit the production method, but the average particle size is preferably 0.01 to 1.0 μm. If the average particle size is less than 0.01 μm, the polishing rate becomes too low, and if it exceeds 1.0 μm, it tends to cause scratches.

The pH of the abrasive is preferably in the range of 3 to 5, particularly preferably 3.5 to 4.5. If the pH is too low or too high, the storage stability of the abrasive tends to be reduced, which tends to cause scratches, and global flatness may be impaired. The pH can be adjusted by adding an acid component or an alkali component such as ammonia, sodium hydroxide, tetramethylammonium hydroxide (TMAH).
In the present invention, the pH of the abrasive was measured with a pH meter (for example, PH81 manufactured by Yokogawa Electric Corporation). After calibrating two points using a standard buffer solution (phthalate pH buffer solution pH: 4.21 (25 ° C.), neutral phosphate pH buffer solution pH 6.86 (25 ° C.)), the electrode was polished. The value after being stabilized after 2 minutes or more was measured.

Examples of the metal oxidizing agent include hydrogen peroxide (H ₂ O ₂ ), nitric acid, potassium periodate, hypochlorous acid, ozone water, etc. Among them, hydrogen peroxide is particularly preferable. These are used alone or in combination of two or more.
In the case where the object to be polished is a silicon substrate including an integrated circuit element, contamination by alkali metal, alkaline earth metal, halide, or the like is not desirable, so an oxidizing agent that does not contain a nonvolatile component is desirable.
However, hydrogen peroxide is most suitable because ozone water has a severe compositional change over time.
However, when the object to be applied is a glass substrate or the like that does not include a semiconductor element, an oxidizing agent that includes a nonvolatile component may be used.

The metal oxide solubilizer used in the present invention is preferably water-soluble.
An aqueous solution selected from the following group is suitable.
Formic acid, acetic acid, propionic acid, butyric acid, valeric acid, 2-methylbutyric acid, n-hexanoic acid, 3,3-dimethylbutyric acid, 2-ethylbutyric acid, 4-methylpentanoic acid, n-heptanoic acid, 2-methylhexanoic acid , N-octanoic acid, 2-ethylhexanoic acid, benzoic acid, glycolic acid, salicylic acid, glyceric acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, maleic acid, phthalic acid, malic acid, Examples thereof include tartaric acid, citric acid and the like, and salts such as ammonium salts of these organic acids, sulfuric acid, nitric acid, ammonia, ammonium salts such as ammonium persulfate, ammonium nitrate and ammonium chloride, chromic acid and the like, or a mixture thereof. These are used alone or in combination of two or more.
Of these, formic acid, malonic acid, malic acid, tartaric acid, and citric acid are preferred.

The anticorrosive agent is preferably selected from the following group.
Benzotriazole, 1-hydroxybenzotriazole, 1-dihydroxypropylbenzotriazole, 2,3-dicarboxypropylbenzotriazole, 4-hydroxybenzotriazole, 4-carboxyl (-1H-) benzotriazole, 4-carboxyl (-1H- ) Benzotriazole methyl ester, 4-carboxyl (-1H-) benzotriazole butyl ester, 4-carboxyl (-1H-) benzotriazole octyl ester, 5-hexyl benzotriazole, [1,2,3-benzotriazolyl- 1-methyl] [1,2,4-triazolyl-1-methyl] [2-ethylhexyl] amine, tolyltriazole, naphthotriazole, bis [(1-benzotriazolyl) methyl] phosphonic acid and the like. That. These are used alone or in combination of two or more.
Among these, benzotriazole, 4-hydroxybenzotriazole, 4-carboxyl (-1H-) benzotriazole butyl ester, tolyltriazole, and naphthotriazole are preferable for obtaining a low etching rate.

As the water-soluble polymer, those selected from the following group are suitable.
Polysaccharides such as alginic acid, pectic acid, carboxymethylcellulose, agar, curdlan and pullulan; amino acid salts such as glycine ammonium salt and glycine sodium salt; polyaspartic acid, polyglutamic acid, polylysine, polymalic acid, polymethacrylic acid, polymethacrylic acid Ammonium salt, polymethacrylic acid sodium salt, polyamic acid, polymaleic acid, polyitaconic acid, polyfumaric acid, poly (p-styrenecarboxylic acid), polyacrylic acid, polyacrylamide, aminopolyacrylamide, polyacrylic acid ammonium salt, polyacrylic acid Sodium salt, polyamic acid, polyamic acid ammonium salt, polyamic acid sodium salt and polycarboxylic acid such as polyglyoxylic acid, its salts, esters and derivatives; polyvinyl alcohol Vinyl polymers such as polyvinyl pyrrolidone and acrolein and the like. These are used alone or in combination of two or more.
However, when the object to be polished is a silicon substrate for a semiconductor integrated circuit or the like, contamination with an alkali metal, an alkaline earth metal, a halide or the like is not desirable, so an acid or an ammonium salt thereof is desirable.
Among these, polymethacrylic acid and polyacrylic acid are preferable.

As the metal laminate film interfacial peeling preventing agent, those selected from the following groups are suitable.
Aliphatic azoles such as 1,2,3-triazole, 1,2,4-triazole, 3-amino-1H-1,2,4-triazole; 2-methylimidazole, 4-methylimidazole, 2-ethylimidazole, Imidazoles such as 2- (isopropyl) imidazole, 2-propylimidazole and 2-butylimidazole; 2-thiohydantoin, 1- (o-tolyl) -bisguanide, 1H-1,2,3-triazolo [4,5-b ] Other nitrogen-containing compounds such as pyridine, 1,2,4-triazolo [1,5-a] pyrimidine, 3-methyl-5-pyrazole, 3,5-dimethylpyrazole, 1,3-diphenylguanidine; Mercaptobenzothiazole, 2- [2- (benzothiazolyl)] thiobutyric acid, 2- [2- (benzothiazolyl)] thio Thiazoles such as lopionic acid, 4,5-dimethylthiazole and 2-aminothiazole; thiols such as benzimidazole-2-thiol, triazinedithiol and triazinetrithiol; thioamides such as thioacetamide and thiobenzamide; ethylenethiourea and propylenethiourea And the like. These are used alone or in combination of two or more.
Among these, 1H-1,2,3-triazolo [4,5-b] pyridine, 1,3-diphenylguanidine, 3,5-dimethylpyrazole, 4,5-dimethylthiazole, and 2-aminothiazole are more preferable.

Further, as an abrasive for polishing an inorganic insulating film such as the above-described silicon oxide film, glass, silicon nitride, etc. as an object to be polished, a composition containing water, cerium oxide particles, a dispersant, and a dispersion aid is used. Can be mentioned.
In addition to the above-described materials, the abrasives generally include additives such as colorants such as dyes and pigments, pH adjusters, and solvents other than water. You may add in the range which does not impair an effect.

EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited to these examples.
(Synthesis of thermoplastic polyurethane)
(Synthesis Example 1)
In a 500 mL separable flask equipped with a stirrer under a nitrogen stream, 4,4'-diphenylmethane diisocyanate (manufactured by Wako Pure Chemical Industries, Ltd., MDI) and polypropylene glycol (manufactured by Wako Pure Chemical Industries, Ltd., PPG: Mw = 1000 g / mol) 1110 g was added, and the mixture was reacted by heating at 75 ° C. for 2 hours. Thereafter, 467 g of diethylene glycol (manufactured by Wako Pure Chemical Industries, Ltd.) was added dropwise thereto and stirred, heated to 200 ° C. and allowed to react for 1 hour. At this time, the ratio of the OCN group of MDI to the total active hydrogen of glycols was 0.91. The produced polyurethane was opened on a bat and cooled, and then pulverized by a pulverizer. This was repeated several times to synthesize a desired amount of polyurethane. Then, these were put into a twin screw extruder and kneaded under a temperature condition of 230 ° C., discharged from the die part in a strand shape, cooled with water in a clean bath, and pelletized with a strand cutter.

(Synthesis Example 2)
In a 500 mL separable flask equipped with a stirrer under a nitrogen stream, 4,4'-diphenylmethane diisocyanate (manufactured by Wako Pure Chemical Industries, Ltd., MDI) and polypropylene glycol (manufactured by Wako Pure Chemical Industries, Ltd., PPG: Mw = (1000 g / mol) and 832 g were added and reacted by heating at 75 ° C. for 2 hours. Thereafter, 496 g of diethylene glycol (manufactured by Wako Pure Chemical Industries, Ltd.) was added dropwise thereto and stirred, heated to 200 ° C. and allowed to react for 1 hour. At this time, the ratio of the OCN group of MDI to the total active hydrogen of glycols was 0.91. The produced polyurethane was opened on a bat and cooled, and then pulverized by a pulverizer. This was repeated several times to synthesize a desired amount of polyurethane. Then, these were put into a twin screw extruder and kneaded under a temperature condition of 230 ° C., discharged from the die part in a strand shape, cooled with water in a clean bath, and pelletized with a strand cutter.

(Synthesis Example 3)
Under a nitrogen stream, 4,4'-diphenylmethane diisocyanate (manufactured by Wako Pure Chemical Industries, Ltd., MDI) and polypropylene glycol (manufactured by Wako Pure Chemical Industries, Ltd., PPG: Mw = (1000 g / mol) and 757 g were added, and the mixture was reacted by heating at 75 ° C. for 2 hours. Thereafter, 451 g of diethylene glycol (manufactured by Wako Pure Chemical Industries, Ltd.) was added dropwise thereto and stirred, heated to 200 ° C., and allowed to react for 1 hour. At this time, the ratio of the OCN group of MDI to the total active hydrogen of glycols was 1.0. The produced polyurethane was opened on a bat and cooled, and then pulverized by a pulverizer. This was repeated several times to synthesize a desired amount of polyurethane. Thereafter, these were put into a twin-screw extruder and kneaded under a temperature condition of 230 ° C., discharged from the die part in a strand shape, cooled with water in a clean bath, and pelletized with a strand cutter.

(Synthesis Example 4)
In a 500 mL separable flask equipped with a stirrer under a nitrogen stream, 4,4'-diphenylmethane diisocyanate (manufactured by Wako Pure Chemical Industries, Ltd., MDI) and polypropylene glycol (manufactured by Wako Pure Chemical Industries, Ltd., PPG: Mw = 1000 g / mol) 555 g and castor oil-based diol (manufactured by Ito Oil Co., Ltd., trade name URIC H62) 234 g were added, and the mixture was heated at 75 ° C. for 2 hours. Thereafter, 451 g of diethylene glycol (manufactured by Wako Pure Chemical Industries, Ltd.) was added dropwise thereto and stirred, heated to 200 ° C., and allowed to react for 1 hour. At this time, the ratio of the OCN group of MDI to the total active hydrogen of glycols was 1.0. The produced polyurethane was opened on a bat and cooled, and then pulverized by a pulverizer. This was repeated several times to synthesize a desired amount of polyurethane. Then, these were put into a twin screw extruder and kneaded under a temperature condition of 230 ° C., discharged from the die part in a strand shape, cooled with water in a clean bath, and pelletized with a strand cutter.

(Comparative Synthesis Example 1)
In a 500 mL separable flask with a stirrer under a nitrogen stream, 4,1'-diphenylmethane diisocyanate (Wako Pure Chemical Industries, Ltd., MDI) 1251 g and polypropylene glycol (Wako Pure Chemical Industries, Ltd. PPG: Mw = 1000 g) / mol) 1665 g was added, and the mixture was heated at 75 ° C. for 2 hours. Thereafter, 409 g of diethylene glycol (manufactured by Wako Pure Chemical Industries, Ltd.) was added dropwise thereto and stirred, heated to 200 ° C., and allowed to react for 1 hour. At this time, the ratio of the OCN group of MDI to the total active hydrogen of glycols was 0.91. The produced polyurethane was opened on a bat and cooled, and then pulverized by a pulverizer. This was repeated several times to synthesize a desired amount of polyurethane. Then, these were put into a twin screw extruder and kneaded under a temperature condition of 230 ° C., discharged from the die part in a strand shape, cooled with water in a clean bath, and pelletized with a strand cutter.

(Preparation of polishing pad)
A polishing pad was prepared by the following method.
Example 1
The polyurethane pellet produced in Synthesis Example 1 was pressurized and heated in a vacuum press through a spacer having an inner dimension of 650 mm square and a thickness of 2 mm, to obtain a uniform sheet-like molded body. On this sheet, grooves having a rectangular cross-sectional shape having a depth of 0.6 mm and a width of 2.0 mm were formed in a lattice shape having a pitch of 15 mm, and then cut into a disk shape having a diameter of 600 mm. Further, a double-sided tape was bonded to the opposite side of the grooved surface to obtain a polishing pad.

(Example 2)
A polishing pad was obtained in the same manner as in Example 1 except that the polyurethane pellets produced in Synthesis Example 2 were used.
(Example 3)
A polishing pad was obtained in the same manner as in Example 1 except that the polyurethane pellets produced in Synthesis Example 3 were used.
Example 4
A polishing pad was obtained in the same manner as in Example 1 except that the polyurethane pellets produced in Synthesis Example 4 were used.

(Example 5)
Pads were molded by the following procedure using polyurethane resin HEI-CAST manufactured by Etch & K as a thermosetting resin. First, the HEI-CAST N4760A solution (castor oil-based polyol, main component: castor oil) and HEI-CAST 3400C solution (polyol mixture, main component: polyether polyol) were mixed, and this was further mixed with HEI-CAST N4760B solution (organic poly). Isocyanate mixture, main component: 4,4'-diphenylmethane diisocyanate) and defoamed, and then the mixed resin solution is poured into a mold capable of forming a sheet of 2 mm thickness and 650 cm square and heated at 80 ° C for 1 hour. Cured. Here, the mixing ratio of each raw material was N4760A: 3400C: N4760B = 100: 20: 100 by weight ratio. On this sheet, grooves having a rectangular cross-section with a depth of 0.4 mm and a width of 0.5 mm were concentrically formed with a minimum radius of 30 mm and a pitch of 1.5 mm, and then cut into a disk shape of Φ600 mm. Further, a double-sided tape was bonded to the opposite side of the grooved surface to obtain a polishing pad.

(Example 6)
Poly-p-phenylene terephthalamide fiber (DuPont “Kevlar” (registered trademark), fiber diameter 125 μm, fiber length 3 mm) as the organic fiber, and the pellet of Synthesis Example 3 as the matrix resin are melt-mixed in an extrusion molding machine, and the tablet Turned into. Here, the poly-p-phenylene terephthalamide fiber was adjusted to 5% by weight. After the tablet was dried at 120 ° C. for 5 hours with a large dryer, a sheet-like molded product having a thickness of 1.2 mm and a width of 1 m was prepared using an extrusion molding and a roll. On this sheet, grooves having a rectangular cross-sectional shape having a depth of 0.6 mm and a width of 2.0 mm were formed in a lattice shape having a pitch of 15 mm, and then cut into a disk shape having a diameter of 600 mm. Further, a double-sided tape was bonded to the opposite side of the grooved surface to obtain a polishing pad.

(Example 7)
An aramid fiber felt base material (product number 13-0796-01-25, manufactured by Toray DuPont) was used as the organic fiber, and the liquid thermosetting resin of Example 5 was added dropwise thereto, followed by pressure heating in a resin vacuum press. As a result, a 2 mm, 650 cm square sheet was formed. The fiber content calculated from the weight ratio was 5% by weight. On this sheet, grooves having a rectangular cross-section with a depth of 0.4 mm and a width of 0.5 mm were concentrically formed with a minimum radius of 30 mm and a pitch of 1.5 mm, and then cut into a disk shape of Φ600 mm. Further, a double-sided tape was bonded to the opposite side of the grooved surface to obtain a polishing pad.

(Comparative Example 1)
A polishing pad was produced in the same manner as in Example 1 except that the polyurethane resin of Comparative Synthesis Example 1 was used as the thermoplastic resin.
(Comparative Example 2)
A polishing pad was prepared in the same manner as in Example 1 except that polyurethane resin Resamine P4250 (manufactured by Dainichi Seika Kogyo Co., Ltd.) using a polycaprolactone-based diol as a thermoplastic resin was used.
(Comparative Example 3)
A polishing pad was prepared in the same manner as in Example 1 except that polyurethane resin Resamine P890 (manufactured by Dainichi Seika Kogyo Co., Ltd., unbranched polycarbonate-based both-end diol) using a polycarbonate diol as a thermoplastic resin was used. Produced.

(Evaluation of pad characteristics)
The characteristics of the produced polishing pad were evaluated according to the following.
(Tensile modulus)
The prepared polishing pad was cut into a 1 mm x 1.5 mm x 35 mm strip and measured at room temperature at a frequency of 1 Hz with a span of 27.5 mm using a dynamic viscoelasticity testing device (Rheometrix Scientific, RSA-II). The elastic modulus was obtained.

  Table 1 shows the tensile modulus of the pad determined by the above method. Comparative Example 1 has almost the same structure as Examples 1 to 3 which are the thermoplastic polyurethane pads of the present invention, but its elastic modulus is extremely low, less than 0.1 GPa. Comparative Examples 2 and 3 are commercially available thermoplastic polyurethanes, and the structure of the diol component is completely different from that of the present invention. Among these, Comparative Example 2 has the elastic modulus characteristic itself within the range of the polyurethane pad according to the present invention.

(Production of abrasive)
As an abrasive for copper, 0.37% by weight of colloidal silica having an average secondary particle size of 35 nm is added to an abrasive-free (abrasive-free) polishing liquid (slurry product name: HS-C430 manufactured by Hitachi Chemical Co., Ltd.). A polishing solution containing abrasive grains was prepared. At the time of use, it was mixed at a volume ratio of polishing liquid: hydrogen peroxide solution = 7: 3. The pH during use was 3.5.

(Metal film polishing)
Each of the above polishing pads was attached to a surface plate of a polishing apparatus, a # 160 diamond grindstone was attached, and the surface was roughened with a dresser for 30 minutes. Thereafter, using the above-mentioned abrasive, a silicon wafer substrate without wiring or having wiring formed thereon was subjected to CMP polishing as follows, and dishing was measured as an index of polishing rate, polishing scratches, and flatness.
For evaluation of the polishing rate and polishing scratches, a substrate without wiring was used, and a silicon substrate with a silicon dioxide film layer (substrate 1) without forming a wiring in which a copper film having a thickness of 1 μm was formed for polishing a metal film was used.
For dishing evaluation, a substrate having wiring formed thereon, that is, a groove having a depth of 0.5 μm is formed in silicon dioxide, and a tantalum nitride film having a thickness of 50 nm is formed as a barrier layer by a known sputtering method. A silicon substrate (substrate 2) having a stripe pattern portion in which a wiring metal portion (copper) width of 100 μm and a silicon dioxide portion width of 100 μm are alternately arranged and formed by a known heat treatment is formed by forming a copper film by the method. Used for polishing.

(Evaluation of polishing rate)
The copper film-formed wafer substrate (substrate 1) is set in a holder to which a suction pad for attaching the wafer substrate of the polishing apparatus is attached, and set on the polishing pad attached to the surface plate of the polishing apparatus with the processing surface down. . While supplying the above polishing slurry for copper at 210 ml / min, CMP polishing was performed for 1 minute at a polishing load of 14 kPa and 10 kPa, and at a rotation speed of 38 rpm between the substrate and the surface plate. The copper film thickness before and after polishing was calculated by measuring the sheet resistance value using a model number RT-7 manufactured by Napson Co., Ltd., calculating the film thickness from the resistivity, and calculating the film thickness difference before and after CMP polishing.

(Evaluation of polishing scratches)
The evaluation of scratches on the Cu film was performed by visual observation in the dark field of a metal microscope using the substrate on which the polishing rate was evaluated.

(Dishing amount)
Using the substrate (substrate 2) on which the copper wiring is formed and the copper polishing agent, the same apparatus, polishing load, rotation speed, and polishing liquid supply as the polishing rate evaluation until the barrier film is exposed at a portion other than the wiring portion. Copper polishing was performed under the condition of the amount.
Thereafter, the barrier film was polished by polishing for 30 seconds under the same conditions as the above copper polishing, except that a polishing liquid for barrier film (HS-T605, trade name of abrasives manufactured by Hitachi Chemical Co., Ltd.) was used.
From the surface shape of the stripe pattern portion in which the wiring metal portion (copper) width of 100 μm and the insulating film (silicon dioxide) portion width of 100 μm are alternately arranged with a stylus type step gauge (Veeco / Sloan Dektat 3030) The amount of film loss in the wiring metal part was measured and used as the dishing amount.

Table 2 shows the results of polishing characteristics using the pads of the above examples and comparative examples.
In each of the examples, it was confirmed that the polishing rate was dramatically higher than that of the commercially available polyurethane and the like of the comparative example, and that it was particularly useful for polishing with a low polishing load, that is, a low frictional force.

  With the commercially available thermoplastic polyurethanes shown in Comparative Examples 2 and 3, the polishing rate was slow, and as in Comparative Example 1, polishing of the pattern took 10 minutes or more and was stopped halfway. From the above comparative examples, it is shown that not only the mechanical and electrical characteristics of the matrix resin of the pad but also the chemical structure itself affects the polishing rate.

Examples 6 and 7 have the same structure as that of Example 4 and Example 5 except that they contain fibers, have a small influence on the polishing rate, and can improve dishing.
From the above examination results, it was found that if the polishing pad according to the present invention is used, the polishing rate can be maintained and the flatness can be improved while reducing the load applied to the insulating layer during CMP.

Claims (13)

  A polishing pad having a tensile modulus of elasticity at room temperature of 0.1 to 2.5 Gpa used for polishing a polishing object by being attached to a surface plate, wherein the matrix constituting the polishing surface of the pad contains one or more polyurethanes, and the polyurethane A polishing pad comprising at least one of 1) an isocyanate compound and 2) a compound having a branched chain at the α-position carbon of the functional group having active hydrogen and active hydrogen.   The polishing pad according to claim 1, wherein at least a castor oil-based polyol is used as a raw material of the polyurethane.   The polishing pad according to claim 1, wherein at least one of propylene glycol and polypropylene glycol is used as a raw material of the polyurethane.   The polishing pad according to claim 1, which has bubbles in the matrix.   The polishing pad according to claim 4, wherein the bubble content is 5 to 25%.   The polishing pad according to claim 1, wherein the matrix contains fibers.   The polishing pad according to claim 1, wherein at least one of organic and inorganic fine particles is contained in the matrix.   The polishing pad according to claim 7, wherein the content of the fine particles is 2 to 30%.   A polishing pad is fixed on a surface plate, and an object to be polished is held by a holder in a state where a surface to be polished is opposed to the polishing pad, and an abrasive is supplied onto the polishing pad. A method of polishing a polishing object by relatively sliding the object, wherein the polishing pad according to any one of claims 1 to 8 is used as the polishing pad.   The polishing method according to claim 9, wherein an abrasive containing at least polyacrylic acid and abrasive grains is used.   The polishing method according to claim 9 or 10, wherein an abrasive having a pH of 3 to 5 is used.   The polishing method according to claim 9, wherein a layer mainly made of metal is polished.   The polishing method according to claim 12, wherein a layer mainly made of copper as a metal is polished.