JP2005294661A - Polishing pad and polishing method using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polishing pad which reduces a load and improves flatness and by which an insulating film can be efficiently removed at high speed and the generation of a polishing flaw on a substrate can be reduced at the same time, and a polishing method by which polishing can be performed using the polishing pad without incurring a defect on the insulating film, in a CMP technique for forming wiring by embedding a metal film on a wiring groove pattern formed in a layer insulating film, growing, flattening and polishing such a metal film. <P>SOLUTION: A polishing pad which is fixed on a polishing plate and used for polishing is characterized by using a material, for at least a part of the surface of the polishing pad in contact with an object to be polished, of which the tensile elastic modulus at room temperature is 0.2 GPa or more, and of which the ζ-potential is positive in a pH region of a polishing agent supplied between the object to be polished and the polishing pad. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a polishing pad and a polishing method using the same in CMP technology for chemically and flatly polishing an object to be polished.

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 of them, and 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 have been formed in advance, and a 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 such as copper alloy is to fix a polishing pad on a circular polishing platen (platen) and fix the polishing pad surface with a metal polishing liquid to form a metal film of a base. The metal film of the convex portion is pressed by rotating the polishing platen while pressing the surface and applying a pressure higher than 20 kPa (hereinafter referred to as a polishing load) from the back surface, and mechanical friction between the polishing liquid and the convex portion of the metal film. Is to be removed.

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 relates to a CMP technique 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 that can be polished without being generated, and a polishing method using the same are provided.
Further, the present invention provides a CMP technique for removing an interlayer insulating film, a BPSG film, and a shallow trench isolation insulating film in a semiconductor element manufacturing process. It is an object of the present invention to provide a polishing pad that can reduce the occurrence of the above polishing scratches.

  The present invention has been made by finding an effect that a CMP polishing pad having a positive zeta charge obtains a high polishing rate when polishing a metal film formed on a substrate. However, a sufficient polishing rate can be obtained.

  That is, the first of the present invention is a polishing pad that is used for polishing while being fixed to a surface plate, and the tensile elastic modulus at room temperature is 0.2 GPa or more on at least a part of the surface of the polishing pad that contacts the object to be polished In addition, the present invention relates to a polishing pad using a material having a positive zeta potential in a pH range of an abrasive supplied between the workpiece and the polishing pad.

  The above material preferably has a zeta potential of +0.1 to +30 mV. More preferably, the material occupies 80% or more of the surface in contact with the object to be polished. The elastic modulus of the polishing pad is preferably 0.2 to 1 GPa, and is preferably made of polyurethane containing at least one of castor oil-based polyol and polypropylene glycol as a raw material.

  In the second aspect of the present invention, the polishing pad is fixed on a surface plate, the object to be polished is held by a holder with the polishing surface facing the polishing pad, and the polishing agent is polished with the polishing pad. A method of polishing the object to be polished by relatively sliding the pad and the object to be polished, wherein the pad and at least a part of the surface in contact with the object to be polished are The present invention relates to a polishing method using a material having a positive zeta potential in the pH range of the polishing agent. Here, the polishing pad is preferably the polishing pad of the present invention.

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

  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 separating the metal in a semiconductor manufacturing process. A material having a positive zeta potential in the pH range of the abrasive used during polishing is used for at least a part of the contact surface.

  The type of metal to be polished is not particularly limited as long as it is used in semiconductors, and can be applied to Au, Ag, Cu, Al, W, Ir, Pt, Ru, Ni, Ti, etc. Application to Cu is effective. Further, the present invention is applicable not only to metal but also to CMP for removing an interlayer insulating film, a BPSG film, and a shallow trench isolation insulating film in a semiconductor element manufacturing process.

  The zeta potential here is a potential at a so-called sliding surface in the distribution of counter ions generated corresponding to the charge on the surface of the substance when it contacts the liquid. Specifically, it can be measured using the electrokinetic phenomenon of the material constituting the pad. In this invention, the evaluation result by the streaming potential method using a flat plate is said. More specifically, a monitor latex (Otsuka Electronics Co., Ltd.) dispersed in a 10 mM NaCl aqueous solution adjusted to a desired pH with an aqueous HCl solution using an electrophoretic light scattering device (ELS-800, manufactured by Otsuka Electronics Co., Ltd.). )).

Examples of the material having the positive zeta potential used for the polishing pad of the present invention include polymethyl methacrylate, AS (acrylonitrile-styrene copolymer), nylon 6, nylon 66, and aramid at pH 3.5. It is done. Thermosetting and thermoplastic polyurethanes may also be used.
Polyurethane is a polymer synthesized based on polyisocyanate polyaddition reaction or polymerization reaction, and the compound used as the polyisocyanate target is an active hydrogen-containing compound, that is, two or more polyhydroxy or amino groups. Containing compounds.
Examples of the polyisocyanate include tolylene diisocyanate, diphenylmethane diisocyanate, naphthalene diisocyanate, tolidine diisocyanate, hexamethylene diisocyanate, and isophorone diisocyanate, but are not limited thereto.

Polyol is typically used as polyhydroxy, and examples of the polyol include epoxy resin-modified polyol, polyether polyol, polyester polyol, acrylic polyol, polybutadiene polyol, silicone polyol, and castor oil.
In particular, when a thermoplastic polyurethane is used, a diol is used. Examples include ethylene glycol, 1,3-propanediol, propylene glycol, 1,4-butanediol, 1,6-hexanediol, 1,5-pentanediol, polypropylene glycol, polytetramethylene ether glycol, polycaprolactone diol, castor oil Diols, adipate ester diols, polycarbonate diols, and the like.
These polyisocyanates and polyhydroxys may be used alone or in combination of two or more. In particular, when a thermoplastic polyurethane is used, the ratio of the hard segment and the soft segment can be adjusted by appropriately combining the short chain diol and the long chain diol, and the elastic modulus at the use temperature can be adjusted.

Of these, polyurethane obtained by combining diphenylmethane diisocyanate as the polyisocyanate and polypropylene glycol, polytetramethylene ether glycol, and castor oil-based polyol as the polyisocyanate is preferable because it has excellent moldability and is widely used. In particular, the polyol is preferably made of polyurethane obtained using at least one of polypropylene glycol and castor oil-based polyol.
In addition, the elastic modulus can be adjusted by adding a long-chain diol or a compatible plasticizer to these.
Even negative materials other than those described above may be positively adjusted by adding appropriate additives.

As described above, a negative material may be added to a positive material of zeta potential for the purpose of adjusting the elastic modulus, but in the case of incompatible materials, the surface in contact with the object to be polished (hereinafter referred to as the polishing pad surface). It is desirable that 80% or more of the area is a positive material having the zeta potential. Moreover, if these are made positive by performing an appropriate surface treatment, they can be used without limitation. For example, when a fiber having a negative zeta potential or a particulate substance is supplied, an appropriate surface treatment may be applied to the surface in contact with the object to be polished to adjust the surface positively.
The addition of a fiber having a positive zeta potential is particularly desirable from the viewpoint of both protection of the surface to be polished and polishing rate.

  As what can be used as an above-mentioned fiber, what made acrylic, aramid, polyamide, 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, the aramid fiber has a higher tensile strength than other general organic fibers, and when the surface of the polishing pad according to the present invention is mechanically roughened to expose the fiber, the fiber is likely to remain on the surface. Because. 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, but is desirably 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 tends to cause 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, but is preferably 5 mm or less. Preferably, it is 0.1-3 mm. If it is too short, the exposed fiber when the pad surface is mechanically roughened will not be effectively held in the pad, and if it is too long, the pad will be thickened and molded when mixed with the elastic body mainly constituting the pad. It can 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.

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 elastic body 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, 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 polishing pad including the above materials preferably has a tensile modulus of 0.2 GPa or more and is in a range of 0.2 to 2.5 GPa. More 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 tensile modulus here refers to the above polishing pad cut into 1 mm x 1.5 mm x 35 mm strips and measured at room temperature at a frequency of 1 Hz with a span of 27.5 mm using a normal dynamic viscoelasticity testing device. The storage elastic modulus of the complex elastic modulus obtained.

The entire 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 final plate shape of a predetermined polishing machine 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.

The polishing pad of the present invention as described above can be used for CMP polishing of a semiconductor substrate or the like.
Hereinafter, the polishing method of the present invention will be described.
In the polishing method of the present invention, a polishing pad is fixed on a surface plate, an object to be polished is held by a holder in a state where the polishing surface faces the polishing pad, and a polishing agent is used to And polishing the object by relatively sliding the pad and the object to be polished. 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. The polishing pad is preferably the polishing pad of the present invention described above, using a material having a positive zeta potential in the pH range of the polishing agent for at least a part of the pad surface.
There is no particular limitation on the polishing apparatus, and it can be used in a disk type polishing apparatus or a linear type polishing apparatus. As an example, there is a general polishing apparatus that includes a holder that holds an object to be polished such as a semiconductor substrate, and a surface plate that is connected to a motor or the like whose rotation speed can be changed and to which a polishing pad is attached. Specifically, there is a polishing apparatus manufactured by Ebara Corporation: model number EPO111.
There are no particular restrictions on the polishing conditions. For example, it is generally preferable that the polishing pad has a polishing load of 1 to 100 kPa, but various polishing conditions are optimized depending on the material to be polished, that is, the object to be polished. It is desirable to plan. During polishing, an abrasive is continuously supplied with a pump or the like between the polishing pad and the object to be polished, for example, on the polishing pad. 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.
The object to be polished after polishing is preferably washed in running water and then dried after removing water droplets adhering to the object to be polished using a spin dryer or the like.

Polishing with the polishing method of the present invention is preferably a layer made mainly of metal, more preferably a layer made of copper. For example, a film mainly containing a metal such as Cu, Ta, TaN, Al, etc., embedded in the composite opening of the insulating layer can be mentioned.
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.
In addition to the above films, silicon oxide films formed on predetermined wiring boards, glass, inorganic insulating films such as silicon nitride, films mainly containing polysilicon, optical glasses such as photomasks, lenses, and prisms Optical integrated circuits, optical switching elements, optical waveguides, optical fiber end faces, scintillator single crystals, solid state laser single crystals, blue laser LED sapphire, composed of inorganic conductive films such as ITO, glass and crystalline materials A substrate, a semiconductor single crystal such as SiC, GaP, or GaAs, glass for a magnetic disk, an aluminum substrate, a magnetic head, or the like can be polished.

  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 at least one 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 metal films include copper, copper alloys, copper oxides, copper alloy oxides, tungsten, tungsten alloys, silver, gold and other metal-based materials, such as copper, copper alloys and copper oxides. It is preferable that copper such as an oxide of a copper alloy is a main component.

  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 containing abrasive grains are preferred, and at least abrasive grains and a water-soluble polymer are more preferred. For example, as an abrasive for Cu, abrasive grains 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 low, the polishing rate tends to decrease. The abrasive particles do not limit the production method, but the average diameter is preferably 0.01 to 1 μm. When the average particle size is 0.01 μm or less, the polishing rate is low, and when it exceeds 1.0 μm, there is a tendency to be damaged.

The pH of the abrasive is not particularly limited, but is preferably in the range of 3 or more and 5 or less, and particularly preferably in the range of 3.5 or more and 4.5 or less. 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, Model 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.
When the substrate to be polished, that is, the substrate to be polished is a silicon substrate including an integrated circuit element, contamination by alkali metal, alkaline earth metal, halide, etc. is not desirable, so an oxidizing agent that does not contain nonvolatile components is desirable. .
However, hydrogen peroxide is most suitable because ozone water has a severe compositional change over time.
However, in the case where the substrate to be polished is a glass substrate that does not include a semiconductor element, an oxidizing agent containing 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-hexylbenzotriazole, [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. . 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, polymaleic acid, polyitaconic acid, polyfumaric acid, poly (p-styrene carboxylic acid), polyacrylic acid, polyacrylamide, aminopolyacrylamide, polyacrylic acid ammonium salt, polyacrylic acid sodium salt, Polycarboxylic acids such as polyamic acid, polyamic acid ammonium salt, polyamic acid sodium salt and polyglyoxylic acid and salts thereof; polyvinyl alcohol, polyvinyl pyrrolidone and polya Vinyl polymers such as Lorraine 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. Therefore, 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 a polishing agent for polishing the above-described inorganic insulating film such as silicon oxide film, glass, silicon nitride, etc., a composition containing water, cerium oxide particles, a dispersing agent, 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.
(Preparation of polishing pad)
A polishing pad was prepared by the following method.
(Example 1)
As a thermosetting resin, a pad was molded by the following procedure using a polyurethane resin product name HEI-CAST manufactured by Etch & Kay Co., Ltd. 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: 100: 20 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 2)
A polishing pad was produced in the same manner as in Example 1 except that the mixing ratio of each raw material was N4760A: 3400C: N4760B = 100: 100: 28 by weight.

(Example 3)
A polishing pad was produced in the same manner as in Example 1 except that the mixing ratio of each raw material was N4760A: 3400C: N4760B = 100: 100: 40 by weight.

Example 4
Poly-p-phenylene terephthalamide fiber (trade name “Kevlar” manufactured by DuPont, fiber diameter 12.5 μm, fiber length 3 mm) as organic fiber, and polyurethane resin HEI-CAST manufactured by Etch & K Co., Ltd. as thermosetting resin The pad was molded using The HEI-CAST N4760A solution and the 3400C solution, and the chopped aramid fiber were mixed with a homomixer, and the fiber was dispersed in the resin. Further, HEI-CAST N4760B solution was added and rapidly stirred and dispersed with a homomixer, and defoamed under reduced pressure. The mixing ratio of the organic fiber and each resin was HEI-CASTN4760A: 3400C: aramid fiber: N4760B = 100: 40: 10: 100 by weight ratio. The mixed resin solution was poured into a mold capable of forming a 650 cm square sheet having a thickness of 2 mm, and heated at 80 ° C. for 1 hour to be cured. 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 5)
Using an aramid fiber felt base material (product number 13-0796-01-25, manufactured by Toray DuPont) as an organic fiber, a liquid thermosetting resin is added dropwise thereto and then heated under pressure in a resin vacuum press to 2 mm. A 650 cm square sheet was formed. Here, the same thermosetting resin as in Examples 3 and 4 was used. 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 polypropylene (PP) resin tablet as a thermoplastic resin was dried at 120 ° C. for 5 hours with a large dryer, and then a sheet-shaped shaped article 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-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 2)
A commercially available foamed polyurethane pad (model number: IC1000, manufactured by Rodel) was used.

(Comparative Example 3)
A polishing pad was prepared in the same manner as in Comparative Example 1 except that polycarbonate-based polyurethane resin Rezamin P890 (trade name, manufactured by Dainichi Seika Kogyo Co., Ltd.) was used as the thermoplastic resin.

(Evaluation of pad characteristics)
The characteristics of the produced polishing pad were evaluated according to the following.
(Elastic 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.
(Zeta potential)
The surface of the sample cut out to 30 mm × 60 mm was washed. Using an electrophoretic light scattering device (ELS-800, manufactured by Otsuka Electronics Co., Ltd.), a sample was attached to a flat plate measurement cell, and a monitor latex dispersed in a 10 mM NaCl aqueous solution adjusted to pH 3.5 with an aqueous HCl solution (Otsuka) Measurement was carried out using an electronic).

  Table 1 shows the pad characteristics obtained by the above method. All examples showed positive values at pH 3.5. Moreover, PP of the comparative example and the commercially available polyurethane pad showed a negative value. Comparative Example 3 is a thermoplastic polyurethane pad having a positive zeta potential but a low elastic modulus.

(Production of abrasive)
As a polishing agent for copper, a colloidal silica having an average secondary particle diameter of 35 nm in an abrasive-free (abrasive-free) polishing liquid (abrasive 1: slurry product name HS-C430 manufactured by Hitachi Chemical Co., Ltd.) Was added to prepare a polishing solution containing abrasive grains (polishing agent 2) adjusted to 0.37% by weight. At the time of use, the abrasive was mixed at a volume ratio of abrasive: hydrogen peroxide = 7: 3. The pH during use was 3.5.

(Polishing metal films and insulating films)
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.
Using each of the polishing pads and the polishing agent, 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 polishing rate and polishing scratches, a substrate without wiring was used, and a silicon substrate (substrate 1) with a silicon dioxide film layer without wiring formation 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 copper polishing liquid (polishing agent 2) at 210 ml / min, CMP polishing was performed for 1 minute at a polishing load of 14 kPa and 10 kPa 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 Model RT-7 manufactured by Napson Co., Ltd., calculating the film thickness from the resistivity, and determining 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 1 on which the polishing rate was evaluated.

(Dishing amount)
Using a substrate (substrate 2) on which copper wiring is formed and a polishing liquid for copper (polishing agent 2), the polishing load is 14 kPa and 10 kPa until the barrier film is exposed in a portion other than the wiring portion. While supplying each polishing speed at 38 rpm and a polishing agent at 210 ml / min, copper polishing was performed with the same apparatus as the evaluation of the polishing speed.
Then, using a barrier film polishing liquid (HS-T605, Hitachi Chemical Co., Ltd. abrasive product name), polishing was performed for 30 seconds under the same polishing load, rotational speed, and abrasive supply amount as the copper polishing. The membrane was polished. 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 of the above examples and comparative examples.
In each of the examples, it was confirmed that the polishing rate was remarkably large at a low load and useful for polishing with a low polishing load, that is, a low frictional force. On the other hand, in Comparative Example 1 using a thermoplastic polymer having a negative zeta potential, the polishing rate cannot be increased. Moreover, in the comparative example 2 using a commercially available polyurethane foam, the fall of the grinding | polishing rate when a load is low is large.
On the other hand, it can be seen that even in the example using the thermoplastic polyurethane having a positive zeta potential, the polishing rate is extremely reduced in the comparative example 3, and the elastic modulus is required to be high.
Examples 4 and 5 are manufactured in the same manner as Example 3 except that fibers are included. However, since the mixing of fibers does not negatively affect the zeta potential, the influence on the polishing rate is small, and dishing can be improved. it can.

  From the above examination results, it was found that if the polishing pad according to the present invention is used, the polishing rate and the flatness can be improved while reducing the load applied to the insulating layer during CMP.

Claims (10)

  A polishing pad fixed to a surface plate and used for polishing, wherein at least a part of a surface of the polishing pad in contact with an object to be polished has a tensile elastic modulus at room temperature of 0.2 GPa or more and is polished with the object to be polished A polishing pad comprising a material having a positive zeta potential in the pH range of an abrasive supplied between the pad and the pad.   The polishing pad according to claim 1, wherein a material having a positive zeta potential in the pH region of the polishing agent is used for 80% or more of the area of the surface of the polishing pad that contacts the object to be polished.   The polishing pad according to claim 1 or 2, wherein a material having a zeta potential of +0.1 to +30 mV in the pH range of the abrasive is used for at least a part of a surface in contact with an object to be polished.   The polishing pad according to any one of claims 1 to 3, which has a tensile elastic modulus at room temperature of 0.2 to 1 GPa.   The polishing pad according to any one of claims 1 to 4, comprising a polyurethane containing at least one of castor oil-based polyol and polypropylene glycol as a raw material.   The polishing pad is fixed on a surface plate, the object to be polished is held by a holder with its polishing surface facing the polishing pad, and an abrasive is supplied between the polishing pad and the object to be polished. A method for polishing an object to be polished by relatively sliding the pad and the object to be polished, wherein at least a part of a surface of the polishing pad in contact with the object to be polished has a zeta potential in a pH region of the polishing agent. A polishing method characterized by using a material having a positive value.   The polishing method according to claim 6, wherein an abrasive containing at least polyacrylic acid and abrasive grains is used.   The polishing method according to claim 6 or 7, wherein an abrasive having a pH of 3 to 5 is used.   The polishing method according to any one of claims 6 to 8, wherein a layer mainly made of metal is polished.   The polishing method according to claim 9, wherein a layer mainly made of copper as a metal is polished.