JPH10298538A - Cerium oxide abrasive material and polishing of substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cerium oxide abrasive material capable of polishing the surface of an SiO2 insulation film, etc., at a high speed to a flawless state. SOLUTION: An Si wafer having an SiO2 insulation film produced by TEOS- CVD method is polished with a slurry polishing agent produced by using cerium oxide particles containing >=90% particles having particle diameter of 20-1,500 nm measured by electron microscope observation based on the total number of the abrasive particles and containing >=90 vol.% of particles having particle diameter of 100-1,500 nm measured by electron microscope observation based on the total volume of the particles and dispersing the above particles in a medium.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention provides a cerium oxide abrasive and a method for polishing a substrate.

[0002]

2. Description of the Related Art Conventionally, in the manufacturing process of a semiconductor device,
Colloidal silica-based polishing agents are generally studied as chemical mechanical polishing agents for planarizing an inorganic insulating film layer such as a SiO ₂ insulating film formed by a method such as plasma-CVD or low-pressure-CVD. Colloidal silica-based abrasives are produced by growing silica particles by a method such as thermal decomposition of silicic acid tetrachloride and adjusting the pH with an alkali solution containing no alkali metal such as ammonia. However, such a polishing agent does not have a sufficient polishing rate for the inorganic insulating film, and there is a technical problem of a low polishing rate for practical use.

On the other hand, cerium oxide abrasives have been used for polishing the glass surface for photomasks. Cerium oxide particles have lower hardness than silica particles and alumina particles,
Therefore, it is useful for finish mirror polishing because the polishing surface is hardly damaged. Also, cerium oxide has chemically active properties as known as strong oxidizing agents.
Taking advantage of this advantage, application to a chemical mechanical polishing agent for an insulating film is useful. However, if a cerium oxide abrasive for polishing a glass surface for a photomask is used for polishing an inorganic insulating film as it is, the particle size is large, and a polishing scratch that can be visually observed is formed on the surface of the insulating film.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a cerium oxide abrasive and a substrate polishing method capable of polishing a surface to be polished such as a SiO ₂ insulating film at a high speed without any damage.

[0005]

The cerium oxide abrasive of the present invention is obtained by dispersing cerium oxide particles having a particle diameter of 20% or more and 1500 nm or less by 90% or more of the total number of particles in a medium as observed by an electron microscope. It contains slurry. It is preferable that 90% or more of all particles having a particle diameter of 20 nm or more and 800 nm or less are observed by an electron microscope. Other cerium oxide abrasives of the present invention,
Particle size of 100 nm or more and 150 as observed by electron microscope
It includes a slurry in which cerium oxide particles having a particle size of 0 nm or less and 90% or more of the total volume are dispersed in a medium. Particle size of 100 nm or more and 800 by electron microscope observation
It is preferable that particles having a size of not more than nm be 90% or more of the total volume. In addition, the particle diameter is 300n when observed with an electron microscope.
It is preferable that particles having a size of not less than m and not more than 1500 nm account for 90% or more of the total volume.

The method of polishing a substrate according to the present invention is characterized in that a predetermined substrate is polished with the above-mentioned cerium oxide abrasive.

According to the present invention, the number of particles having a particle diameter of 20 nm or more and 1500 nm or less is 90% when observed by an electron microscope.
% Of cerium oxide particles or particles having a particle diameter of 100 nm or more and 1500 nm or less as observed by an electron microscope are 90% or more of the total volume, so that a surface to be polished such as a SiO2 insulating film is used. It was made by finding that high-speed polishing can be performed without damaging the surface.

[0008]

DETAILED DESCRIPTION OF THE INVENTION Generally, cerium oxide is a carbonate,
It is obtained by calcining cerium compounds such as sulfates and oxalates. Si formed by a TEOS-CVD method or the like
The O ₂ insulating film can be polished at a high speed as the primary particle diameter is large and the crystal distortion is small, that is, as the crystallinity is good. Therefore, the cerium oxide particles used in the present invention are produced without increasing crystallinity. Further, since it is used for polishing semiconductor chips, the content of alkali metals and halogens is 1 ppm.
It is preferable to suppress it to the following.

In the present invention, a firing method can be used as a method for producing cerium oxide particles. However, low-temperature sintering that does not increase the crystallinity as much as possible is preferable in order to produce particles that do not cause polishing scratches. Since the oxidation temperature of the cerium compound is 300 ° C., the firing temperature is 700 ° C. or more and 90 ° C.
0 ° C. or lower is preferred.

[0010] The cerium oxide slurry in the present invention comprises:
It is obtained by dispersing an aqueous solution containing cerium oxide particles produced by the above method or a composition comprising cerium oxide particles recovered from this aqueous solution, water and, if necessary, a dispersant. Here, there is no limitation on the concentration of the cerium oxide particles, but the concentration of the cerium oxide particles is set at 0.
A range of 5 to 10% by weight is preferred. As the dispersant, those containing no metal ions include acrylic acid polymers and their ammonium salts, methacrylic acid polymers and their ammonium salts, water-soluble organic polymers such as polyvinyl alcohol, ammonium lauryl sulfate, and polyoxyethylene. Water-soluble anionic surfactants such as ammonium lauryl ether sulfate, polyoxyethylene lauryl ether, water-soluble nonionic surfactants such as polyethylene glycol monostearate, monoethanolamine,
And water-soluble amines such as diethanolamine. The addition amount of these dispersants is preferably in the range of 0.01 part by weight to 5 parts by weight based on 100 parts by weight of the cerium oxide particles in view of the dispersibility and anti-settling properties of the particles in the slurry, and enhances the dispersing effect For this purpose, it is preferable that the particles are simultaneously placed in the disperser during the dispersion treatment.

As a method for dispersing these cerium oxide particles in water, a homogenizer, an ultrasonic disperser, a ball mill, or the like can be used in addition to the usual dispersion treatment using a stirrer. In particular, in order to disperse cerium oxide particles as fine particles of 1 μm or less, it is preferable to use a wet disperser such as a ball mill, a vibrating ball mill, a planetary ball mill, and a medium stirring mill. When it is desired to increase the alkalinity of the slurry, an alkaline substance not containing metal ions, such as aqueous ammonia, can be added during or after the dispersion treatment.

In the cerium oxide abrasive of the present invention, the above slurry may be used as it is, but N, N-diethylethanolamine, N, N-dimethylethanolamine,
Additives such as aminoethylethanolamine can be added to make an abrasive.

As a method for forming an inorganic insulating film using the cerium oxide abrasive of the present invention, there are a constant pressure CVD method, a plasma CVD method and the like. SiO2 by constant pressure CVD
In forming the insulating film, monosilane: SiH4 is used as a Si source, and oxygen: O2 is used as an oxygen source. This is obtained by performing the SiH4-O2-based oxidation reaction at a low temperature of about 400 DEG C. or less. When doping phosphorus: P in order to planarize the surface by high-temperature reflow, SiH4-O2-PH3 is used.
It is preferable to use a system 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. The plasma generation method includes two types, a capacitive coupling type and an inductive coupling type. As a reaction gas, a SiH4—N2O-based gas using SiH4 as a Si source and N2O as an oxygen source, and tetraethoxysilane (TEO)
S) as a source of TEOS-O2 based gas (TEOS
-Plasma CVD method). Substrate temperature is 250
The reaction pressure is preferably in the range of 67 to 400 Pa. As described above, the elements such as phosphorus and boron may be doped in the SiO2 insulating film of the present invention.

A semiconductor substrate at a stage where circuit elements and wiring patterns are formed,
A substrate in which an SiO2 insulating film layer is formed on a semiconductor substrate such as a semiconductor substrate at a stage where circuit elements are formed can be used.
By polishing the SiO2 insulating film layer formed on such a semiconductor substrate with the above-mentioned cerium oxide abrasive, S
The irregularities on the surface of the iO2 insulating film layer are eliminated, and a smooth surface is formed over the entire surface of the semiconductor substrate. Here, as a polishing apparatus, a holder for holding a semiconductor substrate and a polishing cloth (pad) are used.
A general polishing apparatus having a surface plate on which is attached (a motor or the like whose rotation speed can be changed) is attached can be used.
As a polishing cloth, general nonwoven fabric, foamed polyurethane,
A porous fluororesin or the like can be used, and there is no particular limitation. Further, it is preferable that the polishing cloth is subjected to a groove processing for storing the slurry. Although there is no limitation on the polishing conditions, the rotational speed of the platen 100rpm or lower rotational preferably so that no semiconductor protrude, pressure applied to the semiconductor substrate is a 1 kg / cm ² or less as scratches is not generated after polishing preferable. During polishing, the slurry is continuously supplied to the polishing cloth by a pump or the like. Although the supply amount is not limited, it is preferable that the surface of the polishing pad is always covered with the slurry.

After the polishing is completed, the semiconductor substrate is preferably washed well in running water, and then dried using a spin drier or the like to remove water droplets adhering to the semiconductor substrate. On this way, the SiO ₂ insulating film layer which is flattened, forming an aluminum wiring of the second layer, after forming the SiO ₂ insulating film again by the above method on the inter-wiring and the wiring, the cerium oxide By polishing using an abrasive, unevenness on the surface of the insulating film is eliminated, and a smooth surface is formed over the entire surface of the semiconductor substrate. By repeating this process a predetermined number of times, a semiconductor having a desired number of layers is manufactured.

The cerium oxide abrasive of the present invention can be used not only for an SiO ₂ insulating film formed on a semiconductor substrate but also for a SiO ₂ insulating film formed on a wiring board having predetermined wiring, glass,
Inorganic insulating films such as silicon nitride, optical glasses such as photomasks, lenses, and prisms; inorganic conductive films such as ITO; optical integrated circuits, optical switching elements, optical waveguides, and optical fibers composed of glass and crystalline materials. End face, scintillation
Used for polishing optical single crystals such as lasers, solid laser single crystals, LED sapphire substrates for blue lasers, semiconductor single crystals such as SiC, GaP, GaAs, glass substrates for magnetic disks, magnetic heads, etc. Is done. Thus the predetermined substrate in the present invention, a semiconductor substrate which SiO ₂ insulating film is formed, SiO ₂ wiring board on which an insulating film is formed, glass,
Inorganic insulating films such as silicon nitride, optical glasses such as photomasks, lenses, and prisms; inorganic conductive films such as ITO; optical integrated circuits, optical switching elements, optical waveguides, and optical fibers composed of glass and crystalline materials. End face, scintillation
Optical single crystal such as laser, solid laser single crystal, blue laser LED sapphire substrate, semiconductor single crystal such as SiC, GaP, GaAs, magnetic disk glass substrate, magnetic head, etc.

[0017]

【Example】

(Preparation of Cerium Oxide Particles) 2.5 kg of cerium carbonate hydrate (purity 99.9%) was placed in a platinum container,
Calcination in air at 2 ° C. for 2 hours gave a yellow-white powder. When this powder was identified by an X-ray diffraction method, it was confirmed that the powder was cerium oxide.

(Preparation of Cerium Oxide Slurry 1) 80 g of the above cerium oxide powder was dispersed in 800 g of deionized water, and 8 g of ammonium polyacrylate was added thereto. -5
The resulting mixture was subjected to a dispersion treatment at 2300 rpm for 30 minutes using a mold) to obtain one milky white cerium oxide slurry.
The pH of this slurry was 9.1. When the particle size distribution of this slurry was examined with a scanning electron microscope, 9
0% or more was in the range of 20 nm to 800 nm, and 90% or more of the total weight was in the range of 100 nm to 800 nm.

(Preparation of Cerium Oxide Slurry 2) 1 kg of the above cerium oxide powder was finely pulverized with a jet mill to obtain fine cerium oxide powder. This cerium oxide fine powder 1
00 g was dispersed in 1 kg of deionized water, and 10 g of ammonium polyacrylate was added thereto.
The dispersion treatment was performed for 10 minutes using the ultrasonic vibrator described above to obtain a milky white cerium oxide slurry 2. The pH of this slurry was 8.3. When the particle size distribution of this slurry was examined with a scanning electron microscope, 90% or more of the total number was in the range of 100 nm to 800 nm, and 9% of the total weight.
0% or more was distributed in the range of 300 nm to 1500 nm.

(Polishing of Insulating Film Layer) An SiO ₂ insulating film formed by a TEOS-plasma CVD method was formed on a holder to which a suction pad for mounting a substrate to be held was attached.
An i-wafer was set, a holder was placed on a surface plate on which a polishing pad made of a porous urethane resin was attached, with the insulating film facing down, and a weight was further placed so that the processing load was 160 g / cm ² . While dropping the above two kinds of cerium oxide slurries (solid content: 2.5 wt%) at a rate of 35 cc / min on the platen, the platen was rotated at 30 rpm for 3 minutes,
The insulating film was polished. After polishing, the wafer is removed from the holder, washed well with running water, and further washed with an ultrasonic cleaner.
Washed for 0 minutes. After the washing, water droplets were removed from the wafer with a spin dryer, and the wafer was dried with a dryer at 120 ° C. for 10 minutes. As a result of measuring the change in film thickness before and after polishing using an optical interference type film thickness measuring device, the slurry removed the insulating films of 640 nm and 750 nm respectively in the slurries 1 and 2 so that the slurries had uniform thickness over the front surface of the wafer. It turned out that it was. In addition, no scratch was observed on the surface of the insulating film visually.

Comparative Example SiO ₂ produced by the TEOS-CVD method in the same manner as in the example.
The Si wafer on which the insulating film was formed was polished using a commercially available silica slurry (manufactured by Cabot Corp., trade name SS225). The pH of this commercial slurry was 10.3,
It contains 12.5 wt% of SiO ₂ particles.
The polishing conditions are the same as in the embodiment. As a result, no scratches were found due to the polishing, and the polishing was performed uniformly, but only the insulating film layer of 75 nm was removed by the polishing for 3 minutes.

[0022]

According to the polishing agent of the present invention, a surface to be polished such as an SiO ₂ insulating film can be polished at high speed without being damaged.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yasushi Kurata 48 Wadai, Tsukuba, Ibaraki Pref.Hitachi Chemical Industry Co., Ltd. (72) Inventor Kiyohito Tanno 4-3-1, Higashi-cho, Hitachi, Ibaraki Hitachi Chemical Co., Ltd.Yamazaki Plant (72) Inventor Hiroto Otsuki 4-1-1, Higashi-cho, Hitachi, Ibaraki Hitachi Chemical Seiraku Industry Co., Ltd.

Claims (10)

[Claims] 1. A particle diameter of 20 n as observed by an electron microscope.
A cerium oxide abrasive comprising a slurry in which cerium oxide particles having 90% or more of the total number of particles having a size of m to 1500 nm are dispersed in a medium. 2. A particle size of 20 n as observed by an electron microscope.
2. The cerium oxide abrasive according to claim 1, wherein the number of particles having a size of m to 800 nm is 90% or more of the total number. 3. A particle size of 100 as observed by an electron microscope.
90% or less of the total volume of particles having a size of not less than nm and not more than 1500 nm
A cerium oxide abrasive containing a slurry in which the above cerium oxide particles are dispersed in a medium. 4. A particle size of 100 as observed by an electron microscope.
4. The cerium oxide abrasive according to claim 3, wherein the particles having a size of not less than nm and not more than 800 nm account for 90% or more of the total volume. 5. A particle diameter of 300 as observed by an electron microscope.
90% or less of the total volume of particles having a size of not less than nm and not more than 1500 nm
The cerium oxide abrasive according to claim 3, which is the above. 6. The cerium oxide abrasive according to claim 1, wherein the slurry contains a dispersant. 7. The cerium oxide abrasive according to claim 1, wherein the medium is water. 8. The dispersant is at least one selected from a water-soluble organic polymer, a water-soluble anionic surfactant, a water-soluble nonionic surfactant and a water-soluble amine.
A cerium oxide abrasive as described in each item. 9. The cerium oxide abrasive according to claim 1, wherein the slurry has a pH of 7 or more and 10 or less. 10. A method for polishing a substrate, comprising polishing a predetermined substrate with the cerium oxide abrasive according to any one of claims 1 to 9.