JP2011233748A - Substrate polishing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polishing method in which improvement in polishing speed of a silicon oxide film or the like and reduction in polishing scratches can be easily performed in a CMP technology of planarizing an interlayer insulating film, a BPSG film and an STI film.SOLUTION: A polishing step is divided into a first polishing step at an initial polishing stage, and a second polishing step in which planarization is mainly performed. In the first polishing step, an abrasive material is used which contains a cerium oxide particle of which the size is larger than that of a prescribed one, and in the second polishing step, the abrasive material is used which contains the cerium oxide of which the size is smaller than that of the prescribed one. More preferably, the abrasive material contains an N-substituted polyoxyethylene compound.

Description

  The present invention is a semiconductor element manufacturing technique, a planarization process of a substrate surface, in particular, an interlayer insulation film, a planarization process of a BPSG (silicon dioxide film doped with boron and phosphorus) film, and formation of shallow trench isolation (STI). The present invention relates to a method for polishing a substrate using an abrasive used in a process or the like.

  In the current ULSI semiconductor device manufacturing process, processing technology for high density and miniaturization has been researched and developed, and one of them, CMP (Chemical Mechanical Polishing) technology, is used in the semiconductor device manufacturing process. It has become an indispensable technique when performing planarization of an interlayer insulating film, STI formation, plug and embedded metal wiring formation, and the like.

Conventionally, in a semiconductor device manufacturing process, an inorganic insulating film layer such as a silicon oxide insulating film is formed by a method such as plasma-CVD (chemical vapor deposition) or low-pressure CVD (chemical vapor deposition). As a chemical mechanical polishing agent for planarizing the inorganic insulating film layer, a fumed silica-based polishing agent is generally studied.
Fumed silica-based abrasives are produced by growing grains by a method such as thermal decomposition of tetrachlorosilicic acid and adjusting pH.
However, such an abrasive has a technical problem that the polishing rate is slow.

In addition, in the generation after design rule: 0.25 μm, STI is used for element isolation in an integrated circuit. In STI, CMP is used to remove an extra silicon oxide film formed on a substrate, and a stopper film having a slow polishing rate is formed under the silicon oxide film in order to stop polishing at an arbitrary depth. Is done.
For the stopper film, silicon nitride or the like is used, and it is desirable that the polishing rate ratio between the silicon oxide film and the stopper film is large. However, the conventional fumed silica-based polishing agent uses the above-described silicon oxide film and stopper film. The polishing rate ratio was as small as about 3, and it did not have the characteristics to withstand practical use for STI.

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 are therefore useful for finishing mirror polishing because they do not easily scratch the polished surface.
Further, the cerium oxide abrasive has an advantage that the polishing rate is faster than the silica abrasive.

In recent years, many CMP polishing agents for semiconductors using high-purity cerium oxide abrasive grains have been used. For example, the technique is disclosed in Patent Document 1.
Furthermore, Patent Document 2 discloses a technique for reducing polishing scratches by adding polyoxyalkylene alkyl ether to an abrasive.

  Further, it is known to add an additive in order to control the polishing rate of the cerium oxide abrasive and improve the flatness over the entire surface of the semiconductor substrate, which is disclosed in Patent Document 3, for example.

Japanese Patent Laid-Open No. 10-106994 JP 2001-102333 A JP-A-8-22970

  However, polishing agents using cerium oxide as described above are also required to reduce the polishing time in order to improve productivity. For this purpose, it is necessary to increase the polishing rate. . In addition, there is a demand for further reduction of polishing scratches by miniaturization of design rules for wiring and STI.

  Accordingly, the present invention provides a CMP technique for flattening an interlayer insulating film, a BPSG film, and an STI film by increasing the polishing speed in order to shorten the polishing time of a silicon oxide film and the like, and easily reducing polishing scratches after polishing. An object of the present invention is to provide a polishing method that can be performed.

The present invention relates to the following.
(1) A substrate polishing method for polishing a substrate by the following steps.
(A) The process of grind | polishing a board | substrate using the abrasive | polishing agent containing a cerium oxide particle (1st grinding | polishing process).
(B) A step of polishing the substrate with an abrasive containing cerium oxide particles having a particle size smaller than that used in step (a) (second polishing step).

  (2) The polishing agent for the first polishing step and the second polishing step both contain an N-substituted polyoxyethylene compound, and N in the N-substituted polyoxyalkylene compound includes a plurality of polyoxyalkylene groups. The method for polishing a substrate according to (1), wherein at least one alkyl group or an alkyl group via an amide bond is bonded to N.

  According to the present invention, in CMP technology for flattening an interlayer insulating film, a BPSG film, an STI, etc., the polishing speed of a silicon oxide film or the like is increased to shorten the polishing time and reduce polishing scratches after polishing. It is possible to provide a polishing method.

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 using tetraethoxysilane (TEOS) as a Si source has a larger grain size and smaller crystal distortion, that is, crystallinity. The better, the higher the speed of polishing and the higher the productivity, but there is a tendency for polishing flaws to occur. On the other hand, if the particle size is small, the polishing rate becomes slow and the productivity is lowered, but there is a tendency that polishing scratches are difficult to occur.
Therefore, the polishing time is shortened by polishing with a polishing agent having a large particle size in the first polishing step in the initial stage of polishing, and the polishing scratches are reduced with a polishing agent having a small particle size in the second polishing step in which flattening is mainly performed. As a result, the polishing time is shortened and the polishing scratches are reduced.
From this, the cerium oxide particles used in the polishing method of the present invention are not limited in its production method, but the particle size is preferably 150 to 500 nm in the first polishing step, and the particles in the second polishing step. The diameter is preferably 1 to 250 nm. Further, by increasing the particle size of the cerium oxide particles used in the first polishing step than the particle size of the cerium oxide used in the second polishing step, it is possible to improve the polishing rate and reduce polishing scratches.
Moreover, since it uses for the grinding | polishing which concerns on manufacture of a semiconductor element, it is preferable to suppress the content rate of an alkali metal and halogens to 10 ppm or less in a cerium oxide particle.

  As a method for producing the cerium oxide particles, firing or an oxidation method using hydrogen peroxide or the like can be used, and the firing temperature is preferably 350 to 900 ° C.

Since the cerium oxide particles produced by the above method are agglomerated, it is preferably mechanically pulverized. As the pulverization method, dry pulverization using a jet mill or the like, or wet pulverization using a planetary bead mill or the like can be used.
The jet mill is described, for example, in Chemical Engineering Papers, Vol. 6, No. 5, (1980), pages 527-532.

  As a method of dispersing such cerium oxide particles in water, which is a main dispersion medium, 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.

As a method for further micronizing the cerium oxide dispersed by the above method, a sedimentation classification method is used in which large particles are settled by allowing the cerium oxide dispersion to stand for a long time, and the supernatant is pumped out by a pump.
In addition, a method using a high-pressure homogenizer that causes cerium oxide particles in the dispersion medium to collide with each other at a high pressure can be used.

The average particle size of the cerium oxide particles in the abrasive is preferably 1 to 500 nm, preferably 150 to 500 nm in the first polishing step, and 1 to 250 nm in the second polishing step. Is preferred. When the average particle diameter of the cerium oxide particles is less than 1 nm, the polishing rate tends to be slow, and when it exceeds 500 nm, the film to be polished tends to be damaged. Further, by increasing the particle size of the cerium oxide particles used in the first polishing step to be larger than that of the cerium oxide used in the second polishing step, it is possible to increase the polishing rate and reduce polishing scratches.
In addition, the average particle diameter of the cerium oxide particle described here refers to the value of D50 (median diameter of volume distribution, cumulative median value) measured with a laser diffraction particle size distribution meter.

The abrasive is obtained, for example, by blending cerium oxide particles, a dispersant, and water to disperse the particles, and further adding a water-soluble polymer and an N-substituted polyoxyalkylene compound.
The concentration of the cerium oxide particles is preferably in the range of 0.1 to 20% by mass per 100% by mass of the abrasive. More preferably, it is 0.1-5 mass%, More preferably, it is 0.5-1.5 mass%. This is because if the concentration of the cerium oxide particles is too low, the polishing rate tends to be slow, and if it is too high, the particles tend to aggregate and cause polishing flaws.

  Examples of the dispersant include a water-soluble anionic dispersant, a water-soluble nonionic dispersant, a water-soluble cationic dispersant, and a water-soluble amphoteric dispersant. Moreover, the polymeric component containing an ammonium acrylate salt as a copolymerization component is preferable, for example, the polyacrylic acid ammonium, the copolymer of acrylic acid amide, and an ammonium acrylate etc. are mentioned.

Further, as the dispersant, at least one kind of a polymer dispersant containing an ammonium acrylate salt as a copolymerization component, a water-soluble anionic dispersant, a water-soluble nonionic dispersant, a water-soluble cationic dispersant. Two or more kinds of dispersants including at least one kind selected from water-soluble amphoteric dispersants may be used in combination.
Since the abrasive is used for polishing in the manufacture of semiconductor elements, 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.

  Examples of the water-soluble anionic dispersant include lauryl sulfate triethanolamine, ammonium lauryl sulfate, polyoxyethylene alkyl ether sulfate triethanolamine, and a special polycarboxylic acid type polymer dispersant.

  Examples of the water-soluble nonionic dispersant include polyethylene glycol monolaurate, polyethylene glycol monostearate, polyethylene glycol distearate, polyethylene glycol monooleate, polyoxyethylene alkylamine, polyoxyethylene hydrogenated castor oil, 2 -Hydroxyethyl methacrylate, alkyl alkanolamides and the like.

  Examples of the water-soluble cationic dispersant include polyvinyl pyrrolidone, coconut amine acetate, stearyl amine acetate and the like.

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

The amount of these dispersants added is 0.01 to 100% by mass with respect to 100% by mass of the cerium oxide particles from the relationship between the dispersibility of particles in the slurry-like abrasive and the sedimentation prevention, and the relationship between the polishing scratches and the amount of the dispersant added. A range of 10% by mass is preferred.
The weight average molecular weight of the dispersant is preferably 100 to 150,000, and more preferably 1,000 to 20,000. When the weight average molecular weight of the dispersant is less than 100, it is difficult to obtain a sufficient polishing rate when polishing the silicon oxide film or the silicon nitride film, and when the weight average molecular weight of the dispersant exceeds 150,000 This is because the viscosity may increase and the storage stability of the abrasive may decrease.
In the present invention, the weight average molecular weight is a value measured by GPC (Gel Permeation Chromatography) and converted to standard polyoxyethylene.

  In addition, as the N-substituted polyoxyalkylene compound, a plurality of polyoxyalkylene groups are bonded to N of the N-substituted polyoxyalkylene compound, and N is bonded via at least one alkyl group or amide bond. Preferred are those having an alkyl group bonded thereto, for example, dipolyoxyethylenealkylamine, dipolyoxyethylenealkyldiamine, dipolyoxyethylenealkylamide, etc., and these can be used in combination of two or more. .

Examples of the water-soluble polymer include polysaccharides such as alginic acid, pectic acid, carboxymethylcellulose, agar, curdlan and pullulan; polyacrylic acid, polyaspartic acid, polyglutamic acid, polylysine, polymalic acid, polyamic acid, ammonium polyamic acid Examples thereof include salts, polycarboxylic acids such as sodium polyamic acid and polyglyoxylic acid and salts thereof; vinyl polymers such as polyvinyl alcohol, polyvinyl pyrrolidone and polyacrolein.
These water-soluble polymers preferably have a weight average molecular weight of 500 or more. Moreover, these compounding quantities have the preferable range of 0.01-5 mass% with respect to 100 mass% of abrasive | polishing agents.

The abrasive is stored as a two-component abrasive that is divided into a cerium oxide slurry comprising cerium oxide particles, a dispersant, and water, and an additive liquid containing a water-soluble polymer and an N-substituted polyoxyalkylene compound. In addition, stable characteristics can be obtained even when stored in advance as a one-pack type abrasive containing a water-soluble polymer and an N-substituted polyoxyalkylene compound.
When the cerium oxide slurry and the additive solution are stored as a two-component abrasive, the planarization characteristics and the polishing rate can be adjusted by arbitrarily changing the composition of these two components.
When polishing with a two-component abrasive, the additive solution is sent through a separate pipe from the cerium oxide slurry, and these pipes are merged and mixed immediately before the outlet of the supply pipe and supplied onto the polishing platen Alternatively, a method of mixing with cerium oxide slurry immediately before polishing can be used.

The abrasive can be adjusted to a desired pH and used for polishing. Although there is no restriction | limiting in a pH adjuster, When using for semiconductor polishing, ammonia water and an acid component are used suitably rather than alkali metal compounds. For the pH adjustment, an ammonium salt of a water-soluble polymer that has been partially neutralized with ammonia in advance can be used.
The pH of the abrasive is preferably from 3 to 10, and if the pH is too low or too high, the storage stability of the abrasive tends to be reduced, which may cause scratches.

  The pH of the abrasive can be measured with a pH meter (for example, Model PH81 (trade name) manufactured by Yokogawa Electric Corporation). The measurement was performed after two-point calibration 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 value after the electrode is put into an abrasive and stabilized after 2 minutes or more is measured.

  In the polishing method described in the present invention, a substrate on which a film to be polished is formed is pressed against a polishing cloth of a polishing platen and pressed, and the substrate is polished while supplying the abrasive between the film to be polished and the polishing cloth. The film to be polished is polished by moving the surface plate relatively.

As a substrate, a substrate related to semiconductor element manufacture, for example, a semiconductor substrate at a stage where a circuit element and a wiring pattern are formed, a substrate having an inorganic insulating layer formed on a semiconductor substrate such as a semiconductor substrate at a stage where a circuit element is formed Is mentioned. Examples of the film to be polished include the inorganic insulating layers such as a silicon oxide film layer, a silicon nitride film layer, and a silicon oxide film layer.
By polishing the silicon oxide film layer or silicon nitride film layer formed on such a semiconductor substrate with the above-mentioned polishing agent, 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.
Abrasives 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, the silicon oxide film polishing rate / the silicon nitride film polishing rate, is preferably 10 or more. When this ratio is less than 10, the difference between the silicon oxide film polishing rate and the silicon nitride film polishing rate is small, and it becomes difficult to stop polishing at a predetermined position when performing shallow trench isolation. When this ratio is 10 or more, polishing can be easily stopped, and it is more preferable for shallow trench isolation. In addition, for use in shallow trench isolation, it is preferable that scratches are less likely to occur during polishing.

  Hereinafter, the polishing method will be described by taking the case of a semiconductor substrate on which an inorganic insulating layer is formed as an example.

As an apparatus for polishing, a holder for holding a substrate having a film to be polished such as a semiconductor substrate, a polishing surface plate to which a polishing cloth (pad) can be attached, a motor that can change the number of rotations, and the like are attached, For example, a polishing apparatus manufactured by Ebara Manufacturing Co., Ltd .: model number EPO-111 or the like can be used.
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. In addition, it is preferable that the polishing cloth is subjected to groove processing so that the abrasive is collected.
The polishing conditions are not limited, but the rotation speed of the surface plate is preferably low rotation of 200 rotations / minute or less so that the semiconductor substrate does not pop out, and the pressure (working load) applied to the semiconductor substrate is scratched after polishing. 100 kPa or less is preferable.
During polishing, an abrasive 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 abrasive | polishing agent.

The semiconductor substrate after polishing is preferably washed in running water, and then dried by removing water droplets adhering to the semiconductor substrate using a spin dryer or the like.
By polishing the inorganic insulating layer, which is the film to be polished, with the polishing agent in this way, surface irregularities can be eliminated and a smooth surface can be obtained over the entire surface of the semiconductor substrate. After the planarized shallow trench is formed, an aluminum wiring is formed on the silicon oxide insulating film layer, a silicon oxide insulating film is formed again between and on the wiring, and then polished again using an abrasive. And make it a smooth surface. By repeating this step a predetermined number of times, a semiconductor substrate having a desired number of layers can be manufactured.

  By adding the N-substituted polyoxyalkylene compound to the abrasive, polishing scratches after polishing of the film to be polished (silicon oxide film) can be reduced. Even when the N-substituted polyoxyalkylene compound is added, there is no change in the polishing agent not added and the polishing rate.

Examples of a method for manufacturing an inorganic insulating film in which an abrasive is used include a low pressure CVD method and a plasma CVD method. The silicon oxide film formation by the low pressure CVD method uses monosilane: SiH ₄ as the Si source and oxygen: O ₂ as the oxygen source. An inorganic insulating film can be obtained by performing this SiH ₄ —O ₂ -based 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.
In order to achieve surface flattening by high-temperature reflow, when doping with phosphorus: P, it is preferable to use a SiH ₄ —O ₂ —PH ₃ -based reactive 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.
The reaction as a gas, SiH ₄ as an Si source, an oxygen source as _{N 2} O was used was _SiH 4 -N ₂ O-based gas and _{TEOS-O 2} based gas using tetraethoxysilane (TEOS) in an Si source (TEOS- Plasma CVD method). The substrate temperature is preferably 250 to 400 ° C., and the reaction pressure is preferably 67 to 400 Pa.
The silicon oxide film may be doped with an element such as phosphorus or boron.
Similarly, silicon nitride film formation by low pressure CVD uses dichlorosilane: SiH ₂ Cl ₂ as a Si source and ammonia: NH ₃ as a nitrogen source. This SiH ₂ Cl ₂ —NH ₃ -based oxidation reaction can be obtained by carrying out 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.

The polishing method of the present invention can be applied not only to a silicon oxide film formed on a semiconductor substrate but also to manufacturing processes of various semiconductor devices.
For example, a silicon oxide film formed on a wiring board having a predetermined wiring, an inorganic insulating film such as glass and silicon nitride, a film mainly containing polysilicon, Al, Cu, Ti, TiN, W, Ta, TaN, etc. Optical glass such as photomasks, lenses and prisms, inorganic conductive films such as ITO, optical integrated circuits composed of glass and crystalline materials, optical switching elements, optical waveguides, optical fiber end faces, optical single crystals such as scintillators, Solid laser single crystals, blue laser LED sapphire substrates, semiconductor single crystals such as SiC, GaP, and GaAs, glass substrates for magnetic disks, magnetic heads, and the like can be polished.

  Next, the present invention will be described with reference to examples, but the present invention is not limited thereto.

Example 1
[Creation of cerium oxide slurry 1]
Cerium oxide powder: 200.0 g and deionized water: 795.0 g are mixed, an aqueous solution of ammonium polyacrylate (weight average molecular weight: 8000, 40% by mass): 5 g is added, and ultrasonic dispersion is performed with stirring. Was done. The ultrasonic frequency was 400 kHz and the dispersion time was 20 minutes.
Thereafter, 1 kg of a cerium oxide dispersion was placed in a 1 liter container and allowed to stand to perform sedimentation classification.
Classification time: After 4 hours, a supernatant of 10 mm or more from the bottom of the container was pumped up. The obtained supernatant cerium oxide dispersion was then diluted with deionized water to obtain a cerium oxide slurry 1 so that the solid content concentration was 5% by mass.
In order to measure the average particle size in the cerium oxide slurry, it was diluted to an appropriate concentration, and a refractive index of 1.93 and an absorption of 0 were obtained using a laser diffraction particle size distribution meter, Master Sizer Microplus (trade name, manufactured by Malvern). When measured, the value of D50 was 280 nm.
[Creation of cerium oxide slurry 2]
A polishing liquid was prepared in the same manner as the preparation of the polishing liquid 1 except that the classification time was set to 15 hours by sedimentation classification, and a cerium oxide slurry 2 was obtained.
Moreover, in order to measure the average particle diameter of the particle | grains in an abrasive | polishing agent with a laser diffraction type particle size distribution analyzer, as a result of measuring diluted to a suitable density | concentration, the value of D50 was 200 nm.

Ammonium polyacrylate aqueous solution (weight average molecular weight: 8000, 40% by mass): 23 g as a water-soluble polymer, and amirazine D (dipolyoxyethylene alkylamine, first compound) as an N-substituted polyoxyalkylene compound as an additive Kogyo Seiyaku Co., Ltd., trade name): 0.3 g, deionized water: 2677 g were mixed and adjusted to pH 4.8 with ammonia water (25 mass%).
Furthermore, the above-mentioned cerium oxide slurries 1 and 2 (solid content: 5% by mass): 300 g were added, and the first polishing process abrasive and the second polishing process abrasive (solid content: 0.5% by mass) were added. Produced. The abrasive pH was 5 respectively.
Moreover, in order to measure the average particle diameter of the particles in the abrasive with a laser diffraction particle size distribution analyzer, the value of D50 was 280 nm for the abrasive for the first polishing process as a result of being diluted to an appropriate concentration and measured. The polishing agent for the second polishing step was 200 nm.

(Polishing the insulating film layer)
As a polishing test wafer, a SiO ₂ film-formed wafer (diameter: 200 mm) using P-TEOS (plasma-tetraethoxysilane) was used (SiO ₂ film thickness: 1000 nm).
The polishing test wafer is set in a holder of a polishing apparatus (polishing apparatus manufactured by Ebara Manufacturing Co., Ltd .: model number EPO-111) on which a suction pad for attaching a substrate to be held is attached, and the polishing apparatus is mounted on a polishing surface plate having a diameter of 600 mm A polishing cloth made of porous urethane resin (groove shape = perforate type: manufactured by Rohm and Haas, model number IC1000) was attached. Further, the holder was placed with the insulating film (silicon oxide film) surface, which is the film to be polished, facing down, and the processing load was set to 350 gf / cm ² (34.3 kPa).
While the above polishing agent for the first polishing step was dropped on the surface plate at a rate of 200 ml / min, the surface plate and the wafer were each operated at 50 rpm, and the polishing test wafer was polished for 30 seconds. Then, the polishing test wafer was polished for 30 seconds while dropping the second polishing step abrasive in the same manner as the first polishing step abrasive.
The polished wafer was thoroughly washed with pure water and then dried.
Then, using a laser scattering surface defect inspection apparatus (Applied Material Co., Ltd., trade name: Complex 3T), the defect position on the wafer surface is measured, and the defect is observed with an electron microscope type defect inspection apparatus (Applied Material Co., Ltd., The product was observed using a trade name: SEMVision G3), and the number of polishing scratches of 0.2 μm or more was measured.
Further, the SiO ₂ film thickness before and after polishing is measured with an optical film thickness measuring instrument (trade name: Nanospec AFT5100, manufactured by Nanometrics Co., Ltd.), and the film thickness after polishing is determined from the film thickness before polishing. The subtracted value was defined as the polishing rate (unit: nm / min).
Table 1 shows the results (number of polished scratches on polished wafer: 0 / wafer, polishing rate: 403 nm / min).

(Example 2)
As a water-soluble polymer, ammonium polyacrylate aqueous solution (weight average molecular weight: 8000, 40% by mass): 23 g and deionized water: 2377 g were mixed, and adjusted to pH 4.8 with aqueous ammonia (25%). No additive was added.
Furthermore, cerium oxide slurries 1 and 2 prepared in Example 1 (solid content: 5% by mass): 300 g were added, and the first polishing step abrasive and the second polishing step abrasive (solid content: 0.00%). 5 mass%) was produced.
The abrasive pH was 5, and the average particle size of the particles in the abrasive was measured by diluting to an appropriate concentration in order to measure with a laser diffraction particle size distribution meter. The polishing slurry for the process was 280 nm, and the polishing slurry for the second polishing process was 200 nm.

(Polishing the insulating film layer)
A polishing test wafer for evaluation was polished in the same manner as in Example 1 except that the abrasive prepared above was used, and the results shown in Table 1 (number of polishing flaws: 15 / wafer, polishing rate: 407 nm / min) Got.

(Comparative Example 1)
Ammonium polyacrylate aqueous solution (weight average molecular weight: 8000, 40% by mass): 23 g as a water-soluble polymer, and amyrazine D: 0.3 g, deionized water: 2377 g as an additive were mixed, and aqueous ammonia (25%) To adjust the pH to 4.8.
Further, cerium oxide slurry 2 prepared in Example 1 (solid content: 5% by mass): 300 g was added, and the first polishing process abrasive and the second polishing process abrasive (solid content: 0.5 mass). %).
The abrasive pH was 5, and the average particle size of the particles in the abrasive was measured by diluting to an appropriate concentration in order to measure with a laser diffraction particle size distribution meter. Both the process polishing agent and the second polishing process polishing agent were 200 nm.

(Polishing the insulating film layer)
A polishing test wafer for evaluation was polished in the same manner as in Example 1 except that the abrasive prepared above was used, and the results shown in Table 1 above (number of polishing flaws / wafer, polishing rate: 246 nm / min) )
It was found that when the abrasive containing cerium oxide having the same small particle size as in the second polishing step was used in the first polishing step, the polishing rate was lowered.

(Comparative Example 2)
Except that the cerium oxide slurry 1 produced in Example 1 was used, the abrasive for the first polishing step and the abrasive for the second polishing step (solid content: 0.5% by mass) were produced in the same manner as in Comparative Example 1. .
The abrasive pH was 5, and the average particle size of the particles in the abrasive was measured by diluting to an appropriate concentration in order to measure with a laser diffraction particle size distribution meter. Both the process abrasive and the second polishing process abrasive were 280 nm.

(Polishing the insulating film layer)
A polishing test wafer for evaluation was polished in the same manner as in Example 1 except that the abrasive prepared above was used, and the results shown in Table 1 above (number of polishing flaws: 25 / wafer, polishing rate: 474 nm / min) )
It was found that when a polishing agent containing cerium oxide having a large particle size was used in the second polishing step, the number of polishing flaws was increased even when Amiradine D was added to the polishing agent.

(Comparative Example 3)
As a water-soluble polymer, ammonium polyacrylate aqueous solution (weight average molecular weight: 8000, 40% by mass): 23 g and deionized water: 2377 g were mixed, and adjusted to pH 4.8 with aqueous ammonia (25%). No additive was added.
Furthermore, cerium oxide slurry 1 produced in Example 1 (solid content: 5% by mass): 300 g was added, and the first polishing process abrasive and the second polishing process abrasive (solid content: 0.5 mass). %).
The abrasive pH was 5, and the average particle size of the particles in the abrasive was measured by diluting to an appropriate concentration in order to measure with a laser diffraction particle size distribution meter. Both the process abrasive and the second polishing process abrasive were 280 nm.

(Polishing the insulating film layer)
A polishing test wafer for evaluation was polished in the same manner as in Example 1 except that the abrasive prepared above was used, and the results shown in Table 1 above (number of polishing flaws: 40 wafers / polishing rate: 468 nm / min) )
It has been found that the number of polishing flaws is remarkably increased if an abrasive containing cerium oxide having a large particle size is used in the second polishing step, and no amylazine D is added to the abrasive.

Claims (2)

A substrate polishing method for polishing a substrate by the following steps.
(1) A step of polishing a substrate using an abrasive containing cerium oxide particles (first polishing step).
(2) A step of polishing the substrate using an abrasive containing cerium oxide particles having a particle size smaller than that used in step (1) (second polishing step).   Each of the polishing agents for the first polishing step and the second polishing step contains an N-substituted polyoxyalkylene compound, and a plurality of polyoxyalkylene groups are bonded to N of the N-substituted polyoxyalkylene compound. The substrate polishing method according to claim 1, wherein at least one alkyl group or an alkyl group via an amide bond is bonded to N.