JP4604727B2 - Additive for CMP abrasives - Google Patents

Description

  The present invention relates to an additive solution for a CMP abrasive used in semiconductor element manufacturing technology, and more specifically, in a substrate surface planarization process, particularly in an interlayer insulating film planarization process, shallow trench isolation formation process, and the like. The present invention relates to an additive solution for CMP abrasive used.

  In the present ultra-large scale integrated circuit, there is a tendency to increase the mounting density, and various fine processing techniques are being researched and developed. Already, the design rules are on the order of sub-half microns. One of the techniques that have been developed in order to satisfy such demands for strict miniaturization is a CMP (chemical mechanical polishing) technique. Since this technology can completely planarize the layer to be exposed in the manufacturing process of the semiconductor device, reduce the burden of the exposure technology, and stabilize the yield, for example, planarization of the interlayer insulating film, shallow trench This technique is essential when performing separation or the like.

  Conventionally, CMP polishing for planarizing an inorganic insulating film layer such as a silicon oxide insulating film formed by a method such as plasma-CVD (Chemical Vapor Deposition) or low-pressure CVD in a manufacturing process of a semiconductor device. Colloidal silica-based abrasives have been generally studied as agents. Colloidal silica-based abrasives are produced by growing silica particles by a method such as thermal decomposition of tetrachlorosilicic acid and adjusting pH. However, such a polishing agent has a technical problem that the polishing rate of the inorganic insulating film does not have a sufficient speed, and it is necessary to improve the low polishing rate for practical use.

In generations with a design rule of 0.5 μm or more, LOCOS (silicon local oxidation) was used for element isolation in an integrated circuit. Thereafter, when the processing dimension is further reduced, a technology with a narrow element isolation width is required, and shallow trench isolation is being used. In shallow trench isolation, CMP is used to remove an excess silicon oxide film formed on the substrate, and a stopper film having a low polishing rate is formed under the silicon oxide film in order to stop polishing. Silicon nitride or the like is used for the stopper film, and it is desirable that the polishing rate ratio between the silicon oxide film and the stopper film is large. Conventional colloidal silica-based abrasives have a polishing rate ratio of the above-described silicon oxide film and stopper film as small as about 3, and have no practical characteristics for shallow trench isolation.
On the other hand, a cerium oxide abrasive is used as a glass surface abrasive for photomasks and lenses. Cerium oxide particles have a lower hardness than silica particles and alumina particles, and therefore are less likely to scratch the polished surface, and are useful for finish mirror polishing. However, since a cerium oxide abrasive for polishing glass surfaces uses a dispersant containing a sodium salt, it cannot be directly applied as an abrasive for semiconductors.

An object of the present invention is to provide a CMP polishing agent capable of polishing a surface to be polished such as a silicon oxide insulating film at a high speed without scratching.
In addition to the above-described invention, another object of the present invention is to polish a surface to be polished such as a silicon oxide insulating film at high speed without scratching the surface to be polished without causing alkali metal contamination such as sodium ions. It is an object of the present invention to provide a CMP polishing agent capable of satisfying the requirements.
Another object of the present invention is to provide a CMP polishing agent capable of increasing the ratio of the silicon oxide insulating film polishing rate to the silicon nitride insulating film polishing rate in addition to the above invention.
Another object of the present invention is to polish a surface to be polished such as a silicon oxide insulating film at a high speed without scratching the surface to be polished without causing alkali metal contamination such as sodium ions. An object of the present invention is to provide a CMP abrasive having improved storage stability.
In addition to the above-described invention, another object of the present invention is to polish a surface to be polished such as a silicon oxide insulating film at high speed without scratching the surface to be polished without causing alkali metal contamination such as sodium ions. An object of the present invention is to provide a CMP polishing agent capable of providing a ratio of a silicon oxide insulating film polishing rate to a silicon nitride insulating film polishing rate of 50 or more.
Another object of the present invention is to provide an additive solution for a CMP abrasive used for improving storage stability in the above-described CMP abrasive.
Another object of the present invention is to provide an additive solution for CMP abrasive used for improving the flatness of the surface to be polished of a substrate.
Another object of the present invention is to provide a substrate polishing method capable of polishing a surface to be polished of a substrate without scratching.
Another object of the present invention is to provide a substrate capable of polishing a surface to be polished such as a silicon oxide insulating film at a high speed without scratching and capable of increasing the ratio of the silicon oxide film polishing rate to the silicon nitride film polishing rate to 50 or more. A polishing method is provided.

The present invention relates to the following.
(1) A CMP abrasive comprising a cerium oxide slurry containing cerium oxide particles, a dispersant and water, and an additive liquid containing a dispersant and water.
(2) The CMP polishing slurry according to (1), wherein the dispersant contained in each of the cerium oxide slurry and the additive liquid is a polymer dispersant and a polymer having an ammonium acrylate salt as a copolymerization component.
(3) The CMP polishing slurry according to (1), wherein the dispersant contained in each of the cerium oxide slurry and the additive solution is a polymer dispersant and is a polyacrylic acid ammonium salt or a polyacrylic acid amine salt.
(4) The CMP polishing slurry according to (2) or (3), wherein the polymer dispersant has a weight average molecular weight of 100 to 50,000.
(5) The content of the dispersant in the cerium oxide slurry is 0.01 to 2.0 parts by weight with respect to 100 parts by weight of the cerium oxide particles, and the content of the cerium oxide particles is 0.3 with respect to the cerium oxide slurry. (1) CMP abrasive | polishing agent which is -40weight%.
(6) The CMP abrasive | polishing agent in any one of (1)-(5) whose pH of a cerium oxide slurry is 6-10.
(7) The CMP abrasive | polishing agent in any one of (1)-(6) whose ratio of a silicon oxide film polishing rate and a silicon nitride film polishing rate is 50 or more.
(8) An additive solution for CMP abrasives containing a dispersant and water.
(9) The additive solution for CMP polishing slurry according to (8), wherein the content of the dispersant is 1 to 10% by weight.
(10) The additive for CMP polishing slurry according to (9), wherein the dispersant is polyacrylic acid ammonium salt or polyacrylic acid amine salt.
(11) The additive liquid for CMP polishing slurry according to (9), wherein the polyacrylic acid ammonium salt or the polyacrylic acid amine salt has a weight average molecular weight of 1,000 to 100,000.
(12) The additive solution for CMP polishing slurry according to (11), wherein the polyacrylic acid ammonium salt or the polyacrylic acid amine salt has a molecular weight distribution (weight average molecular weight / number average molecular weight) of from 1.005 to 1.300.
(13) The additive solution for CMP polishing slurry according to (10), wherein the proportion of free ammonia or amine that does not constitute a polyacrylic acid ammonium salt or a polyacrylic acid amine salt is 10 mol% or less.
(14) The additive solution for CMP polishing slurry according to (10), wherein the pH of the additive solution is 4 to 8.
(15) The additive liquid for CMP polishing slurry according to (10), wherein the viscosity of the additive liquid is 1.20 to 2.50 mPa · s.
(16) The substrate on which the film to be polished is formed is pressed against the polishing cloth of the polishing platen and pressed, and the CMP abrasive of any one of (1) to (7) is supplied between the film to be polished and the polishing cloth. A method for polishing a substrate, comprising moving the substrate and a polishing surface plate to polish a film to be polished.
(17) The substrate polishing method according to (16), wherein the substrate on which at least the silicon oxide film or the silicon nitride film is formed is polished.

The CMP abrasive | polishing agent of this invention is excellent in grinding | polishing to-be-polished surfaces, such as a silicon oxide film, without a flaw, and is excellent in the grinding | polishing method used for a semiconductor element manufacturing technique, especially the board | substrate for shallow trench isolation | separation Suitable for the method.
The CMP polishing agent of the present invention is also excellent in that the surface to be polished is not contaminated with alkali metal such as sodium ions, and the ratio of the silicon oxide film polishing rate / silicon nitride film polishing rate can be increased.
The CMP abrasive | polishing agent of this invention can improve the storage stability of a cerium oxide slurry, and is suitable for the grinding | polishing method used for a semiconductor element manufacturing technique.
The substrate polishing method of the present invention is excellent in polishing a surface to be polished such as a silicon oxide film at high speed without scratches, and is suitable for a polishing method used in a semiconductor element manufacturing technique.

  In general, cerium oxide is obtained by oxidizing a cerium compound of carbonate, nitrate, sulfate, or oxalate. The cerium oxide abrasive used for polishing a silicon oxide film formed by TEOS-CVD or the like has a large primary particle size and single crystal cerium oxide particles are used, but there is a tendency that polishing scratches are likely to occur. . Therefore, although the production method of the cerium oxide particles used in the present invention is not limited, it is preferable that the cerium oxide particles are polycrystalline in which single crystal particles of 5 nm to 300 nm are aggregated. Moreover, since it uses for semiconductor chip grinding | polishing, it is preferable to suppress the content rate of an alkali metal and halogens to 10 ppm or less in a cerium oxide particle.

  In the present invention, as a method for producing the cerium oxide powder, firing or oxidation using hydrogen peroxide or the like can be used. The firing temperature is preferably 350 ° C. or higher and 900 ° C. or lower. As a raw material at this time, cerium carbonate is preferable.

  Since the cerium oxide particles produced by the above method are agglomerated, it is preferably mechanically pulverized. As the pulverization method, a dry pulverization method such as a jet mill or a wet pulverization method such as a planetary bead mill is preferable.

  The cerium oxide slurry in the present invention can be obtained, for example, by dispersing a composition comprising cerium oxide particles having the above characteristics, a dispersant for cerium oxide particles in water, and water. Here, although there is no restriction | limiting in content of a cerium oxide particle, 0.3 to 40 weight% is preferable from the ease of handling of a dispersion liquid, and the range of 0.5 to 20 weight% is more preferable. Moreover, 0.01-10 weight% is preferable and, as for content of the cerium oxide particle in CMP abrasive | polishing agent when mixing a cerium oxide slurry and an addition liquid, 0.1-5 weight% is more preferable.

  As the dispersant, one or two selected from a polymer dispersant, a water-soluble anionic surfactant, a water-soluble nonionic surfactant, a water-soluble cationic surfactant and a water-soluble amphoteric surfactant. More than one compound is used. Since it is used for semiconductor chip polishing, the content of alkali metals such as sodium ions and potassium ions, halogens and sulfur in the dispersant is preferably suppressed to 10 ppm or less.

  Polymer dispersing agents include polymers of unsaturated carboxylic acids such as acrylic acid, methacrylic acid and maleic acid, or ammonium salts and amine salts thereof; unsaturated carboxylic acids such as acrylic acid, methacrylic acid and maleic acid; and acrylic acid. Alkyl acrylates such as methyl and ethyl acrylate, hydroxyalkyl acrylates such as hydroxyethyl acrylate, alkyl methacrylates such as methyl methacrylate and ethyl methacrylate, hydroxyalkyl methacrylates such as hydroxyethyl methacrylate, vinyl acetate, vinyl Examples thereof include a copolymer with a copolymerizable monomer such as alcohol, an ammonium salt or an amine salt thereof. In these polymers or copolymers, the unsaturated carboxylic acid may be converted to an ammonium salt before polymerization. Moreover, it is preferable that the ratio of unsaturated carboxylic acid in these polymers or copolymers is 1-100 mol%, and it is especially preferable that it is 10-100 mol%.

  As the dispersant, a polymer containing ammonium acrylate as a copolymerization component, ammonium polyacrylate, and amine polyacrylate are preferable. The weight average molecular weight of the polyacrylic acid ammonium or the polyacrylic acid amine salt is preferably 1,000 to 100,000, more preferably 3,000 to 60,000, and still more preferably 10,000 to 40,000. When the weight average molecular weight is less than 1,000, the cerium oxide particles tend to aggregate, and when it exceeds 100,000, the polishing rate ratio tends to decrease. Further, the molecular weight distribution (weight average molecular weight / number average molecular weight) of poly (ammonium acrylate) or poly (amine acrylate) is preferably 1.005 to 1.300, more preferably 1.100 to 1.250, and still more preferably. 1.150 to 1.200. When the molecular weight distribution is less than 1.005, the cerium oxide particles tend to aggregate, and when it exceeds 1.300, the polishing rate ratio tends to decrease. The weight average molecular weight and the number average molecular weight are those measured by gel permeation chromatography using a standard polystyrene calibration curve.

  Ammonium polyacrylate or amine salt of polyacrylate is obtained by mixing polyacrylic acid and its carboxyl group with an equimolar amount of ammonia or amine and carrying out a neutralization reaction. An amine ratio of 10 mol% or less (in other words, 90 mol% or more of the carboxyl group of polyacrylic acid is neutralized) is particularly preferable from the viewpoint of high flatness. The amount of free ammonia or amine that does not form a salt can be determined by quantifying ammonia or amine in the liquid obtained by adding an organic solvent and precipitating and filtering the polymer.

  Examples of the water-soluble anionic surfactant include lauryl sulfate triethanolamine, lauryl ammonium sulfate, polyoxyethylene alkyl ether sulfate triethanolamine, and the like.

  Examples of the water-soluble nonionic surfactant include polyoxyethylene lauryl ether, polyoxyethylene cetyl ether, polyoxyethylene stearyl ether, polyoxyethylene oleyl ether, polyoxyethylene higher alcohol ether, polyoxyethylene octyl phenyl ether. , Polyoxyethylene nonylphenyl ether, polyoxyalkylene alkyl ether, polyoxyethylene derivatives, polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan monopalmitate, polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan tristearate , Polyoxyethylene sorbitan monooleate, polyoxyethylene sorbitan trioleate, tetraoleic acid Reoxyethylene sorbit, polyethylene glycol monolaurate, polyethylene glycol monostearate, polyethylene glycol distearate, polyethylene glycol monooleate, polyoxyethylene alkylamine, polyoxyethylene hydrogenated castor oil, alkyl alkanolamide, etc. Examples of the water-soluble cationic surfactant include coconut amine acetate and stearyl amine acetate.

  Examples of the water-soluble amphoteric surfactant include lauryl betaine, stearyl betaine, lauryl dimethylamine oxide, 2-alkyl-N-carboxymethyl-N-hydroxyethyl imidazolinium betaine and the like.

  The amount of these dispersants added in the cerium oxide slurry is 0.01 weight with respect to 100 parts by weight of the cerium oxide particles from the relationship between the dispersibility of the particles in the slurry and the settling prevention, and the relationship between polishing scratches and the amount of dispersant added. The range of not less than 2.0 parts and not more than 2.0 parts by weight is preferred. Among the above dispersants, the molecular weight of the polymer dispersant is a weight average molecular weight measured by gel permeation chromatography using a standard polystyrene calibration curve, and is preferably 100 to 100,000, preferably 100 to 50,000. More preferred is 1,000 to 10,000. If the molecular weight of the dispersant is too small, a sufficient polishing rate cannot be obtained when polishing a silicon oxide film or a silicon nitride film. If the molecular weight of the dispersant is too large, the viscosity increases and the cerium oxide slurry is stored. This is because the stability is lowered.

  The pH of the cerium oxide slurry is preferably 6-10. If the pH is too low, the storage stability of the mixed solution of the cerium oxide slurry and the additive solution is reduced, and when a silicon oxide film or a silicon nitride film is polished, polishing flaws occur. If the pH is too high, the cerium oxide This is because the storage stability of the mixed liquid of the slurry and the additive liquid is lowered, and polishing flaws occur when the silicon oxide film or the silicon nitride film is polished. For adjusting the pH, a method of mixing and stirring ammonia water is used.

  As a method for dispersing these cerium oxide particles in water, a homogenizer, an ultrasonic disperser, a wet ball mill or the like can be used in addition to a dispersion treatment using a normal stirrer.

  The average particle size of the cerium oxide particles in the slurry thus prepared is preferably 0.01 μm to 1.0 μm. This is because if the average particle size of the polishing liquid is too small, the polishing rate becomes too low, and if the average particle size is too large, the film to be polished is easily damaged.

  On the other hand, the additive solution for CMP abrasive in the present invention contains a dispersant and water. As the dispersant, a dispersant for water of the cerium oxide particles used in the cerium oxide slurry described above is used, and those preferably used for the cerium oxide slurry from the viewpoint of the polishing rate ratio of the polished surface and high flatness. It is also preferably used in the additive solution. The kind of dispersant for the cerium oxide slurry and the additive solution may be the same or different. The concentration of the dispersant is preferably 1 to 10% by weight in the additive solution. If the amount is less than 1% by weight, the flatness of the polished surface tends to decrease, and if it exceeds 10% by weight, the cerium oxide particles tend to aggregate.

  The CMP polishing slurry of the present invention is prepared by separately preparing a cerium oxide slurry and an additive liquid, and mixing and using both at the time of polishing. When the cerium oxide slurry and the additive liquid are stored in a mixed state, cerium oxide particles Agglomerates, resulting in generation of polishing flaws and fluctuations in the polishing rate. For this reason, the additive solution is supplied separately from the cerium oxide slurry on the polishing platen and mixed on the polishing platen, or mixed with the cerium oxide slurry and supplied onto the polishing platen immediately before polishing. It is done. At this time, the mixing ratio of the cerium oxide slurry and the additive solution is not particularly limited as long as it finally reaches a target concentration.

  Further, the amount of the dispersant in the additive liquid used with respect to cerium oxide is determined based on the dispersibility of the particles in the slurry and the prevention of sedimentation, and the relationship between the polishing flaws and the amount of the dispersant added. The range of 0.001-2000 weight part of the dispersing agent in an additive liquid is preferable with respect to a weight part, The range of 0.01-1000 weight part is more preferable, The range of 0.01-500 weight part is more preferable. .

  The additive liquid preferably has a specific gravity of 1.005 to 1.050. The specific gravity is more preferably 1.007 to 1.040, and still more preferably 1.010 to 1.030. When the specific gravity is less than 1.005, the flatness of the polished surface tends to decrease, and when the specific gravity exceeds 1.050, the cerium oxide particles tend to aggregate. Moreover, it is preferable that pH of the additive liquid is 4-8. The pH is more preferably 5-7, still more preferably 6-7. When the pH is less than 4, the polishing rate tends to decrease, and when the pH exceeds 8, the flatness of the polished surface tends to decrease. The pH is adjusted by adding an acid or alkali such as acetic acid or aqueous ammonia to the additive solution. The additive solution preferably has a viscosity at 25 ° C. of 1.20 to 2.50 mPa · s. The viscosity is more preferably 1.30 to 2.30 mPa · s, and still more preferably 1.40 to 2.20 mPa · s. If the viscosity is less than 1.20 mPa · s, the cerium oxide particles tend to aggregate, and if it exceeds 2.50 Pa · s, the flatness of the polished surface tends to decrease.

  The CMP polishing slurry of the present invention may use the cerium oxide slurry and additive solution as they are, but non-polymer addition such as N, N-diethylethanolamine, N, N-dimethylethanolamine, aminoethylethanolamine, etc. An agent can be added to the cerium oxide slurry or the CMP additive to form a CMP abrasive. These additives are preferably used so that the final CMP abrasive has a concentration of 0.001 to 20% by weight, and more preferably 0.01 to 10% by weight. It is preferable.

Examples of a method for producing an inorganic insulating film using the CMP abrasive of the present invention include a low pressure CVD method and a plasma CVD method. Silicon oxide film formation by low-pressure CVD uses monosilane: SiH ₄ as the Si source and oxygen: O ₂ as the oxygen source. It can be obtained by performing this SiH ₄ —O ₂ oxidation reaction at a low temperature of 400 ° C. or lower. In some cases, heat treatment is performed at a temperature of 1000 ° C. or lower after CVD. When doping phosphorus: P in order to achieve surface flattening by high-temperature reflow, it is preferable to use a SiH ₄ —O ₂ —PH ₃ reaction gas. The plasma CVD method has an advantage that a chemical reaction requiring a high temperature can be performed at a low temperature under normal thermal equilibrium. There are two plasma generation methods, capacitive coupling type and inductive coupling type. As the reaction gas, a SiH ₄ —N ₂ O gas using SiH ₄ as a Si source and N ₂ O as an oxygen source and a TEOS-O ₂ gas (TEOS—) using tetraethoxysilane (TEOS) as a Si source are used. Plasma CVD method). The substrate temperature is preferably 250 to 400 ° C., and the reaction pressure is preferably 67 to 400 Pa. Thus, the silicon oxide film of the present invention may be doped with elements such as phosphorus and boron.

Similarly, in forming the silicon nitride film by the low pressure CVD method, dichlorosilane: SiH ₂ Cl ₂ is used as the Si source, and ammonia: NH ₃ is used as the nitrogen source. The SiH ₂ Cl ₂ —NH ₃ oxidation reaction is performed at a high temperature of 900 ° C. In the plasma CVD method, examples of the reactive gas include SiH ₄ —NH ₃ -based gas using SiH ₄ as the Si source and NH ₃ as the nitrogen source. The substrate temperature is preferably 300 ° C to 400 ° C.

  As a substrate, a semiconductor substrate, that is, a semiconductor substrate on which a circuit element and a wiring pattern are formed, a substrate on which a silicon oxide film layer or a silicon nitride film layer is formed on a semiconductor substrate such as a semiconductor substrate on which a circuit element is formed Can be used. By polishing the silicon oxide film layer or silicon nitride film layer formed on such a semiconductor substrate with the above-described CMP abrasive, the unevenness on the surface of the silicon oxide film layer is eliminated and the entire surface of the semiconductor substrate is made smooth. be able to. It can also be used for shallow trench isolation. In order to use for shallow trench isolation, the ratio of the silicon oxide film polishing rate to the silicon nitride film polishing rate, and the silicon oxide film polishing rate / silicon nitride film polishing rate must be 10 or more. If this ratio is too small, the difference between the polishing rate of the silicon oxide film and the polishing rate of the silicon nitride film becomes small, and polishing cannot be stopped at a predetermined position when performing shallow trench isolation. In addition, when this ratio is 50 or more, the polishing rate of the silicon nitride film is further reduced and polishing can be easily stopped, which is preferable for shallow trench isolation.

As a polishing apparatus, a general polishing apparatus having a holder for holding a semiconductor substrate and a surface plate to which a polishing cloth (pad) is attached (a motor or the like whose rotation speed can be changed) is attached. As an abrasive cloth, a general nonwoven fabric, a polyurethane foam, a porous fluororesin, etc. can be used, and there is no restriction | limiting in particular. Further, it is preferable that the polishing cloth is grooved so that the CMP abrasive is accumulated. The polishing conditions are not limited, but the rotation speed of the surface plate is preferably low rotation of 200 rpm or less so that the semiconductor substrate does not jump out, and the pressure applied to the semiconductor substrate is 1 kg / cm ² or less so that no scratches are generated after polishing. Is preferred. In order to be used for shallow trench isolation, it is necessary that scratches are less likely to occur during polishing. During polishing, slurry is continuously supplied to the polishing cloth with a pump or the like. Although there is no restriction | limiting in this supply amount, it is preferable that the surface of polishing cloth is always covered with the slurry.

  The semiconductor substrate after the polishing is preferably washed in running water, and then dried after removing water droplets adhering to the semiconductor substrate using a spin dryer or the like. After forming the planarized shallow trench in this way, an aluminum wiring is formed on the silicon oxide insulating film layer, and after forming the silicon oxide insulating film again between the wirings and on the wiring by the above method, By polishing using the above-described CMP abrasive, unevenness on the surface of the insulating film is eliminated, and a smooth surface is obtained over the entire surface of the semiconductor substrate. By repeating this process a predetermined number of times, a desired number of semiconductor layers are manufactured.

  The CMP polishing agent of the present invention includes not only a silicon oxide film formed on a semiconductor substrate, but also a silicon oxide film formed on a wiring board having a predetermined wiring, an inorganic insulating film such as glass and silicon nitride, a photomask lens・ Optical integrated circuits composed of optical glass such as prisms, inorganic conductive films such as ITO, glass and crystalline materials ・ Optical switching elements / optical waveguides, optical fiber end faces, optical single crystals such as scintillators, solid state laser single crystals A sapphire substrate for blue laser LED, a semiconductor single crystal such as SiC, GaP, and GaAS, a glass substrate for magnetic disk, a magnetic head, and the like can be polished.

  Examples of the present invention and comparative examples thereof will be shown below, and the present invention will be described more specifically. However, the present invention is not limited to these examples.

Production Example 1 (Production of cerium oxide particles)
About 1 kg of yellowish white powder was obtained by putting 2 kg of cerium carbonate hydrate in a platinum container and firing in air at 700 ° C. for 2 hours. When this powder was phase-identified by X-ray diffraction, it was confirmed to be cerium oxide. It mixed with deionized water so that it might become 10 weight% of cerium oxide powder, and it grind | pulverized for 120 minutes at 1400 rpm using the horizontal type wet ultrafine particle dispersion grinder. The obtained polishing liquid was dried at 110 ° C. for 3 hours to obtain cerium oxide particles. The cerium oxide particles have a primary particle diameter of 10 nm to 60 nm constituting a polycrystal as observed from a transmission electron microscope, and a specific surface area measurement result by the BET method is 39.5 m ² / g. I understood.

Production Example 2 (Production of cerium oxide particles)
About 1 kg of yellowish white powder was obtained by putting 2 kg of cerium carbonate hydrate in a platinum container and firing in air at 700 ° C. for 2 hours. When this powder was phase-identified by X-ray diffraction, it was confirmed to be cerium oxide. 1 kg of cerium oxide powder was dry pulverized using a jet mill. The cerium oxide particles have a primary particle size of 10 nm to 60 nm constituting a polycrystal as observed from a transmission electron microscope, and are 41.2 m ² / g as a result of measuring a specific surface area by the BET method. I understood.

Production Example 3 (Production of cerium oxide slurry)
Ammonium salt aqueous solution of polyacrylic acid copolymer having a weight average molecular weight of 10,000 obtained by copolymerizing 125 g of cerium oxide particles prepared in Preparation Example 1 of the above cerium oxide particles and acrylic acid and methyl acrylate 3: 1 (40 wt. %) 3 g and 2372 g of deionized water were mixed and subjected to ultrasonic dispersion while stirring. The ultrasonic frequency was 40 kHz, and dispersion was performed with a dispersion time of 10 minutes. The obtained slurry was filtered with a 0.8 micron filter, and further deionized water was added to obtain a 2 wt% cerium oxide slurry (A-1). The pH of the cerium oxide slurry (A-1) was 8.5. When the particle size distribution of the cerium oxide slurry (A-1) was examined with a laser diffraction particle size distribution meter, it was found that the average particle size was as small as 0.20 μm. Moreover, the particle | grains of 1.0 micrometer or less were 95.0%.

Production Example 4 (Production of cerium oxide slurry)
The cerium oxide slurry was prepared in the same manner as in the preparation example 3 of the cerium oxide slurry except that the cerium oxide slurry prepared in the preparation example 2 of cerium oxide particles was used instead of the cerium oxide particles prepared in the preparation example 1 of cerium oxide particles. A-2) was produced. The pH of this cerium oxide slurry (A-2) was 8.7. When the particle size distribution of the cerium oxide slurry (A-2) was examined, it was found that the average particle size was as small as 0.21 μm. Moreover, the particle | grains of 1.0 micrometer or less were 95.0%.

Production Example 5 (Production of cerium oxide particles)
About 1 kg of yellowish white powder was obtained by putting 2 kg of cerium carbonate hydrate into a platinum container and firing in air at 900 ° C. for 2 hours. When this powder was phase-identified by X-ray diffraction, it was confirmed to be cerium oxide. 1 kg of cerium oxide powder was dry pulverized using a jet mill. This cerium oxide particle was found to be a single crystal having a particle diameter of 80 nm to 150 nm from observation with a transmission electron microscope, and as a result of measuring the specific surface area by the BET method, it was found to be 18.5 m ² / g.

Production Example 6 (Production of cerium oxide slurry)
The cerium oxide slurry (B-1) was prepared in the same manner as the cerium oxide slurry preparation example 1 except that the cerium oxide particles prepared in comparative preparation example 1 were used instead of the cerium oxide particles prepared in preparation example 1 of the cerium oxide particles. ) Was produced. The pH of this cerium oxide slurry (B-1) was 8.4. When the particle size distribution of the cerium oxide slurry (B-1) was examined, it was found that the average particle size was as small as 0.35 μm. Moreover, the particle | grains of 1.0 micrometer or less were 85.5%.

Examples 1 to 10 and Comparative Examples 1 and 2
As shown in Table 1, a cerium oxide slurry and an additive solution were prepared to produce a CMP abrasive, and the insulating film was polished by the following method using a mixed solution of the cerium oxide slurry and the additive solution. The results are shown in Table 1.

  In Examples 1 to 5 and Examples 7 and 9, the same dispersant as that used in the cerium oxide slurry of Example 1 was used, and a predetermined amount dissolved in deionized water was used.

  The ammonium polyacrylate used as a dispersant in Examples 6, 8, and 10 was a weight average molecular weight of 10,000, a number average molecular weight of 8,333, a molecular weight distribution of 1.2, and free ammonia of 4.3 mol%. . The additive solution used in Example 6 had a viscosity of 1.46 mPa · s and a specific gravity of 1.010.

  In Comparative Example 2, the cerium oxide slurry and the additive solution in Example 1 were mixed in advance, and after 1 day, the insulating film was polished using this mixture.

(Insulating film polishing)
A silicon wafer with a diameter of 125 mm is formed by forming a silicon oxide film made by TEOS-plasma CVD method on a holder with a suction pad for attaching a substrate on a surface plate with a porous urethane resin polishing pad. The film surface was set downward and a weight was applied so that the polishing load was 300 g / cm ² . While feeding the above cerium oxide slurry (solid content: 2% by weight) and the additive liquid on the surface plate at a rate of 25 ml / min, while adjusting the nozzle so that it becomes one liquid immediately before the surface plate, The surface plate was rotated at 40 rpm for 2 minutes to polish the insulating film. After polishing, the wafer was removed from the holder, washed thoroughly with running water, and further washed with an ultrasonic cleaner for 20 minutes. After washing, water droplets were removed with a spin dryer and dried for 10 minutes with a 120 ° C. dryer. The change in film thickness before and after polishing was measured using an optical interference type film thickness measuring device, and the polishing rate was calculated.

  Similarly, a silicon nitride film produced by a low pressure CVD method instead of a silicon oxide film produced by TEOS-plasma CVD method was polished under the same conditions, a change in film thickness before and after polishing was measured, and a polishing rate was calculated. From the results of film thickness measurement, it was found that the silicon oxide film produced by the TEOS-plasma CVD method and the silicon nitride film produced by the low pressure CVD method had a uniform thickness over the entire surface of the wafer. Further, the surface of the insulating film was not scratched by visual observation under a mercury lamp light source, but was further observed in detail with a wafer appearance inspection device (Olympus AL-2000, Olympus Optical Co., Ltd., trade name).

  In the same manner, a silicon oxide film in which convex portions having a diameter of 20 μm and a height of 5,000 mm are formed at intervals of 100 μm is polished, and a dent (dishing) between the convex portion and the convex portion when the convex portion is polished. The amount was determined and the flatness was evaluated.

  As is apparent from Table 1, by using the CMP polishing agent and the substrate polishing method of the present invention, the surface to be polished such as a silicon oxide film or a silicon nitride film is contaminated with alkali metal such as sodium ions on the surface to be polished. Polishing agent capable of polishing without scratches and having a ratio of silicon oxide film polishing rate / silicon nitride film polishing rate of 50 or more, and substrate polishing method using these CMP abrasives It can be seen that

Claims (15)

The substrate on which the film to be polished is formed is pressed against the polishing cloth of the polishing surface plate and pressurized, and the substrate and the polishing surface plate are moved while the CMP abrasive is being supplied between the film to be polished and the polishing cloth. In the polishing method of the substrate to be polished,
The CMP abrasive is prepared by separately preparing a cerium oxide slurry containing cerium oxide particles, a dispersant and water, and an additive liquid containing 1% by weight or more of a dispersant and water, and mixing both during polishing. A cerium oxide slurry containing cerium oxide particles, a dispersant and water, used in a substrate polishing method,
The dispersant contained in each of the cerium oxide slurry and the additive solution is a polymer dispersant,
Polymer dispersing agent is at least one type of cerium oxide slurries selected polymers and or ammonium polyacrylate et be copolymerized component an acrylic acid ammonium salt.   The mixing is to supply the additive solution and the cerium oxide slurry separately on the polishing platen and mix them on the polishing platen, or to mix the additive solution and the cerium oxide slurry immediately before polishing, The cerium oxide slurry according to claim 1. The polishing target film includes a silicon oxide film and a silicon nitride film,
3. The cerium oxide slurry according to claim 1, wherein the cerium oxide slurry can be mixed with the additive liquid at the time of polishing to increase the polishing rate of silicon oxide film / silicon nitride film of the CMP abrasive to 10 or more. slurry.   The cerium oxide slurry according to any one of claims 1 to 3, which has a pH of 6 to 10.   The cerium oxide slurry according to any one of claims 1 to 4, wherein the weight average molecular weight of the dispersant contained in each of the cerium oxide slurry and the additive liquid is 10,000 to 40,000.   The cerium oxide slurry according to any one of claims 1 to 5, wherein a molecular weight distribution (weight average molecular weight / number average molecular weight) of a dispersant contained in each of the cerium oxide slurry and the additive liquid is 1.005 to 1.300. Cerium oxide slurry and the additive liquid of claims 1 to 6 or cerium oxide slurry according proportion of ammonia free, which does not constitute the salt of the dispersant is 10 mol% or less contained in each. The substrate on which the film to be polished is formed is pressed against the polishing cloth of the polishing surface plate and pressurized, and the substrate and the polishing surface plate are moved while the CMP abrasive is being supplied between the film to be polished and the polishing cloth. In the polishing method of the substrate to be polished,
A substrate in which the CMP abrasive is prepared by separately preparing a cerium oxide slurry containing cerium oxide particles, a dispersant and water, and an additive liquid containing a dispersant and water, and mixing both during polishing. Used in the polishing method, an additive liquid containing 1% by weight or more of a dispersant and water, and the dispersant contained in each of the cerium oxide slurry and the additive liquid is a polymer dispersant,
Polymer dispersing agent is at least one selected et or polymers and polyacrylic acid ammonium salt to copolymerizable component acrylic acid ammonium salt, adding liquid.   The mixing is to supply the additive solution and the cerium oxide slurry separately on the polishing platen and mix them on the polishing platen, or to mix the additive solution and the cerium oxide slurry immediately before polishing, The additive liquid according to claim 8. The polishing target film includes a silicon oxide film and a silicon nitride film,
The additive solution according to claim 8 or 9, wherein the additive solution can be mixed with the cerium oxide slurry at the time of polishing to increase the polishing rate of silicon oxide film / silicon nitride film of the CMP abrasive to 10 or more. .   The additive solution according to any one of claims 8 to 10, which has a viscosity at 25 ° C of 1.20 to 2.50 mPa · s.   pH is 4-8, The additive liquid in any one of Claims 8-11.   The additive solution according to any one of claims 8 to 12, wherein the weight average molecular weight of the dispersant contained in each of the cerium oxide slurry and the additive solution is 10,000 to 40,000.   The additive liquid according to any one of claims 8 to 13, wherein the molecular weight distribution (weight average molecular weight / number average molecular weight) of the dispersant contained in each of the cerium oxide slurry and the additive liquid is 1.005 to 1.300. Additive solution according to claim 8 to 14, wherein any percentage of ammonia free, which does not constitute the salt of the dispersing agent contained in each of the cerium oxide slurry and the additive liquid is 10 mol% or less.