JPH11330016A - Cerium oxide polishing agent and substrate manufacturing method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable polishing without damages to a surface to be polished by using cerium oxide particles, of which assumed density measured by a stationary method is less than a specific value. SOLUTION: A cerium compound which is not solved in water is selected from trivalent cerium compound as original material, it is scattered in water and tetravalent cerium oxide particles are made by performing oxidation processing under a condition of maintaining solid state by dripping oxidation agent. An assumed density of the cerium oxide particles measured by a stationary method is made to be equal to or more than 0.80 g/ml and equal to or less than 1.30 g/ml and polishing without the damage of a surface to be polished can be performed by using such cerium oxide polishing agent. Therefore rapid polishing over the whole substrate surface becomes possible and is able to adequately correspond to making of wiring fine.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a cerium oxide abrasive, a semiconductor substrate using the cerium oxide abrasive,
The present invention relates to a method for manufacturing a substrate such as a wiring substrate.

[0002]

2. Description of the Related Art In recent years, rapid increase in density and integration of VLSIs has progressed, and there has been a demand for a multilayer aluminum wiring and a reduction in the minimum processing line width accompanying the miniaturization of the wiring pattern. Therefore, there is a demand for a flattening technique for filling the fine wiring intervals without voids in the interlayer insulating film used for these LSIs and for flattening the surface.

In general, an interlayer insulating film requiring flattening is formed by a deposition method such as a plasma CVD method and an ECR-CVD method, and a coating method such as an SOG method. Of these, the SOG method is a method in which an alkoxysilane and an alkylalkoxysilane are hydrolyzed by adding water and a catalyst in an organic solvent such as an alcohol, and a coating solution obtained by spin coating is applied, followed by heat treatment. In the method of flattening by curing, an organic SOG film in which an organic component (for example, an alkyl group) is left in the film is mainly used in order to suppress the occurrence of cracks and to form a thick film. . This organic SOG film has advantages such as low volume shrinkage upon curing, hydrophobicity, and low dielectric constant. Although this organic SOG film can be applied to local flattening, it is insufficient for global flattening due to the density of wiring. Further, as a material for forming the interlayer insulating film, application of an organic polymer resin containing no silicon as being excellent in insulating properties and adhesiveness has been promoted. Since a coating solution obtained by dissolving the organic polymer resin in an organic solvent such as alcohol is applied by spin coating, an insulating film is formed by heat treatment or the like, so that a thick film can be formed relatively easily.

[0004]

[0005] Multi-layer wiring has been developed in VLSI for high density and high integration. In particular, in logic devices, the number of layers has already been increased to four or more, and the level difference on the surface tends to increase. On the other hand, the depth of focus of a resist used for wiring patterning tends to be shallower as the wiring becomes finer, and the above-described step height increase on the surface has been regarded as a problem. Global flattening has been demanded in order to eliminate this high step. As one of the methods, chemical mechanical polishing (CMP: Chemical Mechanical) utilizing a combined effect of a chemical polishing action and a mechanical polishing action conventionally used for polishing of a Si wafer.
The application of (Polishing) is expected.

Among the insulating films, a film formed by the CVD method can be relatively easily polished by using a slurry in which colloidal silica, which has been conventionally used for polishing a Si wafer, is dispersed as an abrasive. is there. However, this CVD method has a poor embedding property in a groove having a high aspect ratio due to miniaturization of a wiring pattern, and an aspect ratio of about 3 is limited. Attempts have been made to introduce fluorine in order to lower the dielectric constant of the film, but there are still some problems such as desorption of the introduced fluorine and an increase in the hygroscopicity of the film.

On the other hand, organic SO formed by the SOG method
The G film has a good embedding property in a groove with a high aspect ratio, and is possible even with an aspect ratio of 10 or more. Further, the dielectric constant of the film is as low as about 3 as it is, and the cost of film formation can be suppressed lower than that of the CVD method.
However, polishing is liable to occur when polishing is performed with the above-mentioned abrasive using colloidal silica, and if the polishing conditions are moderated in order to prevent this, the polishing rate is extremely reduced. Furthermore, even if the polishing is performed under the same conditions, the polishing rate of the organic SOG film is very low as compared with the case of the CVD film. Therefore, development of a polishing agent capable of polishing the organic SOG film at high speed is required. Also,
Since a film using an organic polymer resin can form a film as thick as 10 μm or more by one application, it is considered to be promising for global flattening. The dielectric constant of the film is 3
Although it is as low as it is, a lower dielectric constant can be obtained by using a resin containing fluorine, and a forming method that does not use heat such as ultraviolet curing can be obtained by using an acrylate polymer. However, the hardness of this organic polymer resin is
Since the film is extremely low as compared with the film and the organic SOG film, polishing scratches occur when the film is polished with the above-mentioned abrasive using colloidal silica. If the polishing conditions are moderated until polishing scratches are no longer generated to prevent this, almost no polishing occurs. Therefore, there is a demand for the development of an abrasive that can polish a film using this organic polymer resin without generating polishing scratches.

The present invention enables global flattening,
In addition, a cerium oxide abrasive suitable for polishing an insulating film layer of an organic SOG film and an organic polymer resin film having a good embedding property between fine wirings and a low dielectric constant, and a substrate using the cerium oxide abrasive Is provided.

[0008]

The cerium oxide abrasive of the present invention comprises a slurry in which cerium oxide particles are dispersed in water, and has an apparent density of 1.0 as a cerium oxide particle measured by a static method. What is 30 g / ml or less is used. The present invention has been accomplished by using cerium oxide particles having an apparent density of 1.30 g / ml or less as measured by a static method, and finding that polishing can be performed without damaging the surface to be polished. is there.

The method for manufacturing a substrate according to the present invention includes a step of forming an insulating film layer containing an organic group or an insulating film such as an organic polymer resin on a predetermined substrate and polishing it with the cerium oxide abrasive of the present invention. It is characterized by the following.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In general, cerium oxide is a cerium compound (hydroxide, carbonate, sulfate, oxalate, etc.) obtained by separating and purifying typical rare earth minerals such as bastnaesite and mosanite. ) Is obtained by firing. The cerium oxide particles used in the present invention can also be prepared by a usual method. However, when polishing an organic SOG film, a high crystallinity of cerium oxide tends to decrease the polishing rate. It is necessary to make without. In addition, since it is used for polishing semiconductors, the content of alkali metals and halogens in particular needs to be suppressed to 2 ppm or less in order to prevent impurities from being mixed.

In the present invention, the apparent density measured by a static method is preferably 0.80 g / ml or more and 1.30 g / ml.
g / ml or less, more preferably 0.90 g / ml or more and 1.20 g / ml or less are used. When a slurry in which cerium oxide particles having an apparent density exceeding 1.30 g / ml are dispersed in water is used, 1
Since the secondary particle diameter increases, scratches occur on the polished surface after polishing. In addition, when cerium oxide particles having an apparent density of less than 0.80 g / ml are used, a sufficient polishing effect may not be obtained because the polishing rate becomes extremely low. Here, the method of measuring the apparent density includes a static measurement method and a dynamic measurement method, and there is no particular limitation, but JIS K-510
The static method specified in 1 is preferred because the measurement is simple.

In the present invention, as a method for producing cerium oxide particles, for example, (1) a cerium compound which is insoluble in water among trivalent cerium compounds is used as a starting material, and after dispersing it in water, A method of producing tetravalent cerium oxide particles by dropping an oxidizing agent and performing oxidation treatment in a solid state, (2) a water-soluble trivalent cerium compound as a starting material, An oxidizing agent is added dropwise to a water-insoluble cerium compound (precipitate) obtained by adding ammonium bicarbonate or the like to an aqueous solution in which cerium oxide is dissolved, so that the oxidizing treatment is performed in a solid state to obtain tetravalent cerium oxide particles. Method for producing (3)
A tetravalent cerium compound is used as a starting material, and a method of preparing tetravalent cerium oxide particles by making the aqueous solution neutral or alkaline by adding ammonia water to an aqueous solution in which the cerium compound is dissolved is preferably used. There is no particular limitation.

As the trivalent water-insoluble cerium compound,
Water-insoluble cerium salts such as cerium carbonate, cerium hydroxide, cerium oxalate, and cerium acetate are mentioned, and there is no particular limitation. As a method of dispersing these trivalent water-insoluble cerium compounds 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, it is preferable to perform the dispersion treatment by a ball mill, since the oxidation treatment to be performed later can be easily performed by making the dispersed particles finer. The concentration of the trivalent water-insoluble cerium compound is not particularly limited, but is preferably in the range of 1 to 30% by weight from the viewpoint of easy handling of the dispersion.
By adding an oxidizing agent to the dispersion of the trivalent water-insoluble cerium compound, the solid state is subjected to an oxidation treatment to obtain tetravalent cerium oxide particles. The oxidizing agent used here includes nitrates such as potassium nitrate, permanganates such as potassium permanganate, chromates such as potassium chromate, hydrogen peroxide, halogen, ozone, and the like. Among these, it is preferable to use hydrogen peroxide in order to prevent impurities from being mixed in with the oxidation treatment. The addition amount of the oxidizing agent is required to be 1 mol or more per 1 mol of the water-insoluble trivalent cerium compound, and is preferably in the range of 1 mol to 10 mol in order to complete the oxidation treatment.
The treatment temperature is not particularly limited, but when using a self-decomposable oxidizing agent such as hydrogen peroxide, it is preferable to start the treatment at 40 ° C. or less. Is preferably heated to 80 ° C. or higher. An aqueous solution containing cerium oxide particles obtained by performing the oxidation treatment can be directly used for the dispersion treatment. Further, cerium oxide particles can be recovered from the aqueous solution by using ordinary methods such as decantation, filtration, and centrifugation. As this recovery method, centrifugation, which can efficiently separate in a short time, is preferable. At this time, if the pH of the solution is on the acid side, precipitation of the particles is extremely slow, and solid-liquid separation becomes difficult with a general centrifuge.
It is preferable to add an alkaline substance not containing metal ions such as ammonia to adjust the pH of the solution to 8 or more before performing centrifugation. It is also effective to repeat the washing of the precipitate to reduce the impurity concentration. Cerium oxide particles are obtained by removing water from the collected precipitate using a dryer or the like. The drying temperature is not particularly limited. However, since the crystallinity of the cerium oxide particles is significantly increased at 420 ° C. or higher, it is preferable to dry at 420 ° C. or lower as low as possible.

The trivalent water-soluble cerium compound includes, but is not particularly limited to, water-soluble cerium salts such as cerium nitrate, cerium sulfate and cerium chloride. The concentration of the trivalent water-soluble cerium compound in the aqueous solution in which these are dissolved is not particularly limited, but is preferably 1 to 30% by weight because of the ease of handling of the suspension after formation of the water-insoluble cerium compound as a precipitate.
Is preferable. When an aqueous solution of ammonium hydrogen carbonate or the like is added to these aqueous solutions, a white precipitate (a water-insoluble cerium compound) is produced. Here, the concentration of ammonium bicarbonate is required to be 1.5 mol or more per 1 mol of the trivalent water-soluble cerium compound, and is preferably in the range of 1.5 mol to 30 mol in order to complete the reaction. By adding an oxidizing agent to a dispersion of a precipitate (a water-insoluble cerium compound) obtained from the trivalent water-soluble cerium compound, an oxidizing treatment is performed in a solid state to obtain tetravalent cerium oxide particles. Get. The same oxidizing agent as used in the case of the trivalent water-insoluble cerium compound can be used here. Among these, it is preferable to use hydrogen peroxide in order to prevent impurities from being mixed in with the oxidation treatment. The amount of the oxidizing agent added is trivalent water-soluble cerium compound 1
1 mol or more is required per 1 mol, and the range of 1 mol to 10 mol is preferable from the viewpoint of completing the oxidation treatment. The treatment temperature is not particularly limited, but when using a self-decomposable oxidizing agent such as hydrogen peroxide, it is preferable to start the treatment at 40 ° C. or less. Is preferably heated to 80 ° C. or higher. An aqueous solution containing cerium oxide particles obtained by performing the oxidation treatment can be directly used for the dispersion treatment. Further, cerium oxide particles can be recovered from the aqueous solution by using ordinary methods such as decantation, filtration, and centrifugation. As this recovery method, centrifugation, which can efficiently separate in a short time, is preferable. At this time, if the pH of the solution is on the acid side, the precipitation of particles is extremely slow, and solid-liquid separation becomes difficult with a general centrifuge, so an alkaline substance that does not contain metal ions such as ammonia is added. It is preferable to perform centrifugation after adjusting the pH of the solution to 8 or more. It is also effective to repeatedly wash the precipitate to reduce the content of impurities. By removing the collected sediment with a dryer etc.,
Cerium oxide particles are obtained. The drying temperature is not particularly limited. However, since the crystallinity of the cerium oxide particles is significantly increased at 420 ° C. or higher, it is preferable to dry at 420 ° C. or lower as low as possible.

Examples of the tetravalent cerium compound include cerium salts such as cerium sulfate, cerium ammonium sulfate and cerium ammonium nitrate, and are not particularly limited.
The concentration of the tetravalent cerium compound in the aqueous solution in which these are dissolved is not particularly limited, but 1 to 30% by weight of the suspension after the precipitation (cerium oxide particles) is formed.
Is preferable. These aqueous solutions are acidic, but are neutralized by adding aqueous ammonia to the aqueous solution or the like.
When made alkaline, a white precipitate (cerium oxide particles) is produced. Here, the addition amount of the aqueous ammonia is determined by the pH of the suspension.
Must be added from the initial acidity to neutrality, and it is preferable to add it slightly in excess of neutrality to alkalinity. The aqueous solution containing the cerium oxide particles obtained by performing the precipitation treatment can be directly used for the dispersion treatment. From this aqueous solution, decantation, filtration,
Cerium oxide particles can also be recovered using a conventional method such as centrifugation. As this recovery method, centrifugation, which can efficiently separate in a short time, is preferable.
It is also effective to repeatedly wash the precipitate to reduce the content of impurities. Cerium oxide particles are obtained by removing water from the collected precipitate using a dryer or the like. The drying temperature is not particularly limited. However, since the crystallinity of the cerium oxide particles is significantly increased at 420 ° C. or higher, it is preferable to dry at 420 ° C. or lower as low as possible.

[0016] 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 three methods or a composition comprising cerium oxide particles, a dispersant, and water recovered from the aqueous solution. Here, the concentration of the cerium oxide particles is not limited, but is 1 to 30 due to the ease of handling the suspension.
A range of weight% is preferred. As the dispersing agent, 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 polyoxygen. Water-soluble anionic surfactants such as ethylene lauryl ether ammonium sulfate, polyoxyethylene lauryl ether,
Examples include water-soluble nonionic surfactants such as polyethylene glycol monostearate, and water-soluble amines such as monoethanolamine and diethanolamine. The addition amount of these dispersants is preferably in the range of 0.01 parts by weight to 10 parts by weight based on 100 parts by weight of the cerium oxide particles from the viewpoint of the dispersibility and anti-settling properties of the particles in the slurry,
In order to enhance the dispersing effect, it is preferable that the particles are simultaneously placed in a disperser during the dispersion treatment. As a method of 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 dispersion treatment using a normal 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.

The insulating film used in the production of the semiconductor chip of the present invention is formed by spinning a coating solution obtained by hydrolyzing alkoxysilane and alkylalkoxysilane in an organic solvent such as alcohol by adding water and a catalyst. After coating on the substrate by a coating method, etc., it is cured by heat treatment, or after applying a coating solution in which an organic polymer resin containing no silicon is dissolved in an organic solvent such as alcohol by a spin coating method, and formed by a heat treatment or the like. It is manufactured by letting it.

Here, examples of the alkoxysilane include monomers or oligomers such as tetramethoxysilane, tetraethoxysilane, and tetrapropoxysilane, each of which can be used alone or in combination of two or more. Examples of the alkylalkoxysilane include methyltrimethoxysilane, phenyltrimethoxysilane, dimethyldimethoxysilane, diphenyldimethoxysilane, aminopropyltrimethoxysilane,
Glycidoxypropyltrimethoxysilane, 3-methacryloxypropyltrimethoxysilane, vinyltrimethoxysilane and the like can be mentioned, and these can be used alone or in combination of two or more. Here, alkoxysilanes such as fluorotrimethoxysilane and fluoromethyldimethoxysilane, those in which fluorine is bonded to Si of an alkylalkoxysilane, and alkyl groups of an alkylalkoxysilane such as trifluoromethyltrimethoxysilanetrifluoromethylmethyldimethoxysilane At least partly fluorinated ones, alkoxysilanes and alkylalkoxysilanes in which fluorine is bonded to Si can also be used. These can be used alone or in combination of two or more. Here, the proportion of the added amount of the alkoxysilane and the alkylalkoxysilane is such that the number of Si atoms derived from the siloxane bond and the number of C atoms derived from the alkyl group in the insulating film formed by these are C atoms / (Si atom It is preferable that (number + number of C atoms) ≧ 0.1. If this ratio is less than 0.1, cracks occur in the film when the insulating film is formed, and defects such as lack of the film and deterioration of the insulating property occur. Examples of the organic solvent include monohydric alcohols such as methyl alcohol and ethyl alcohol and ethers or esters thereof,
Examples thereof include polyhydric alcohols such as glycerin and ethylene glycol and ethers or esters thereof, and ketones such as acetone and methyl ethyl ketone. These can be used alone or in combination of two or more. As a catalyst, for hydrolysis, hydrochloric acid,
Examples include inorganic acids such as nitric acid and phosphoric acid, organic acids such as acetic acid and maleic acid, acids such as acid anhydrides and derivatives thereof, and alkalis such as sodium hydroxide, ammonia and methylamine.

Here, the amount of water to be added depends on the alkoxy group 1 of the alkoxysilane and the alkylalkoxysilane.
A range of less than 75% relative to 00% is preferred,
% Or more, the hydrolysis of the alkoxysilane and the alkylalkoxysilane rapidly occurs, so that the coating solution gels or becomes cloudy. The amount of the catalyst to be added is preferably from 0.1 to 5 parts by weight based on 100 parts by weight of the alkoxysilane and the alkylalkoxysilane. If the amount is less than 0.1 part by weight, the hydrolysis of the alkoxysilane and the alkylalkoxysilane will not occur. A film is not formed at the time of coating because of sufficient amount, and when the amount is more than 5 parts by weight, hydrolysis occurs rapidly and the coating solution gels. The amount of the alkoxysilane and the alkylalkoxysilane is preferably in the range of 1 to 40 parts by weight based on 100 parts by weight of the organic solvent. If the amount of the alkoxysilane and the alkylalkoxysilane is less than 1 part by weight, it is difficult to form a film at the time of coating, and if it exceeds 40 parts by weight, it is difficult to obtain a uniform film. The reaction temperature at the time of increasing the molecular weight is not particularly limited, but is preferably equal to or lower than the boiling point of the organic solvent used, and particularly preferably from 5 ° C to 70 ° C in order to control the molecular weight of the obtained hydrolyzate. There is no particular limitation on the reaction time at the time of hydrolysis, and the reaction is terminated when a predetermined molecular weight is reached. The method for measuring the molecular weight at this time is not particularly limited, but a method using a liquid chromatograph is simple and preferable.

The insulating film forming material obtained from these four components is manufactured as follows. First, it is manufactured by dispersing a predetermined amount of alkoxysilane and alkylalkoxysilane in an organic solvent, mixing water and a catalyst with this, stirring for a while, and increasing the molecular weight at room temperature or under heating.

On the other hand, organic polymer resins containing no silicon include thermosetting resins such as phenol, epoxy, unsaturated polyester, polyester, polyimide, polyamideimide, polyamide, polyurethane, polyethylene, ethylene-vinyl acetate copolymer, polypropylene,
Polystyrene, ABS resin, AS resin, polymethyl methacrylate, polyvinyl chloride, polyvinyl formalin,
Thermoplastic resins such as polytetrafluoroethylene and polytrifluoroethylene chloride are exemplified. Of these, the use of a fluororesin such as polytetrafluoroethylene or polychlorotrifluoroethylene is effective in lowering the dielectric constant of the film, and the use of a polyamideimide resin or a polyimide resin reduces the heat resistance of the film. It is effective, but there is no particular limitation.

These materials for forming an insulating film of an organic polymer resin containing no silicon are prepared as follows. When a thermosetting resin is used, a coating liquid for forming an insulating film is prepared by dissolving each monomer and / or low-molecular-weight resin in the above-mentioned organic solvent such as alcohol. Here, a commonly used curing agent, accelerator, catalyst, and the like can be used in combination for further curing. When a thermoplastic resin is used, a coating liquid for forming an insulating film is prepared by dissolving each resin in the above-described organic solvent such as alcohol. The organic solvent preferably ranges from 0 parts by weight to 900 parts by weight based on 10 parts by weight of the organic polymer resin. 9 organic solvents
When the amount exceeds 00 parts by weight, a film is hardly formed at the time of coating.

A material for forming an insulating film manufactured by the above-described method is used as a semiconductor substrate such as a semiconductor substrate in which circuit elements and wiring patterns are formed, and a semiconductor substrate in which circuit elements are formed. For example, IC
After a circuit is formed and an aluminum wiring is applied on the patterned semiconductor substrate, a heat treatment is performed at 100 ° C. or more to form an insulating film layer. Here, examples of the semiconductor substrate include a Si wafer and a GaAs wafer, but there is no particular limitation. Examples of the coating method include a spin coating method, a spraying method, and a dip coating method, and are not particularly limited. Heat treatment temperature is 3
There is no particular limitation at a temperature of 00 ° C. or higher, but there is an upper limit depending on the substrate to be used. There is no particular limitation on the heat curing time, and the heating is terminated when the physical properties of the formed film have almost reached equilibrium. The determination method at this time is not particularly limited, but measurement of the surface hardness of the film, the thickness of the film, and the like is simple and preferable. There is no particular limitation on the atmosphere during the heat treatment, but it is preferable to introduce an inert gas such as nitrogen or argon in order to reduce the elimination of the alkyl group in the alkylalkoxysilane during the heating.

An insulating film layer formed on a predetermined semiconductor substrate, that is, a semiconductor substrate on which circuit elements and wiring patterns have been formed, and a semiconductor substrate on which circuit elements have been formed, is coated with the cerium oxide slurry. By polishing, the unevenness on the surface of the insulating film layer is eliminated, and a smooth surface is formed over the entire surface of the semiconductor substrate. The insulating film layer formed on a predetermined semiconductor substrate is formed to be thicker than the thickness of the wiring, for example, at least 1.2 times the thickness of the wiring. Here, as a polishing apparatus, a holder for holding a semiconductor substrate and a polishing cloth (pad) were attached (a motor capable of changing the number of rotations can be used, and there is no particular limitation. In addition, slurry is applied to the polishing cloth. The polishing conditions are not limited, but the rotation speed of the platen is preferably low at 100 rpm or less so that the semiconductor substrate does not pop out, and the pressure applied to the semiconductor substrate is after polishing. It is preferably 1 kg / cm ² or less so as not to cause scratches.
The slurry is continuously supplied to the polishing cloth by a pump or the like. Although the supply amount at this time is not limited, it is preferable that the surface of the polishing pad is always covered with the slurry, and the supply amount per unit area is, for example, 25 ml / mi for an 18-inch platen.
A ratio of n or more is particularly preferred. This supply amount is 25ml /
If it is less than min, a sufficient polishing rate cannot be obtained, and uniform polishing cannot be obtained due to insufficient diffusion of the slurry. Further, because the influence of mechanical polishing increases, the polishing rate of the CVD film tends to increase, and the selectivity represented by the speed ratio with the organic SOG film decreases.
Selective polishing becomes impossible.

After the polishing is completed, the semiconductor substrate is thoroughly washed in running water, and then removed from hydrogen peroxide and nitric acid, sulfuric acid, ammonium carbonate, ammonium carbamate and ammonium hydrogen carbonate in order to remove cerium oxide particles attached to the surface. It is immersed in at least one of the selected liquids, washed again with water, and dried. Here, although there is no particular limitation on the immersion time, the end of the treatment can be determined at the time when bubbles generated by dissolution of the cerium oxide particles are not generated. There is no particular limitation on the immersion temperature. However, when a material having self-decomposability such as aqueous hydrogen peroxide is used, the treatment is preferably performed at 40 ° C. or lower. After washing with water, it is preferable to use a spin drier or the like to remove water droplets attached to the semiconductor substrate and then dry the semiconductor substrate.

A second layer of aluminum wiring is formed on the thus flattened insulating film layer, and an insulating film is formed again between the wirings and on the wiring by the above-described method. By polishing using
The unevenness on the surface of the insulating film layer 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 particles having a specific surface area of 25 m ² / g or more according to the present invention are more preferably those having at least one of the following characteristics. (1) The apparent density measured by the stationary method is 1.3 g / m
l or less. (2) The apparent density measured by the tap method is 1.6 g /
ml or less. (3) The half width of the main peak of the powder X-ray diffraction pattern is 0.
4 ° or more. (4) The primary particle diameter is 20 when observed by a transmission electron microscope.
90% or more of the total number of primary particles having a size of not more than nm. (5) 90% or more of the total number of primary particles having a primary particle diameter of 20 nm or less, and 90% or more of the total number of secondary particles having a secondary particle diameter of 1 μm or less in which the primary particles are aggregated. (6) 90% of the total number of secondary particles having a diameter of 1 μm or less
As described above, the contour is such that the secondary particles do not include corners smaller than 120 °. (7) The number of particles whose primary particles have an aspect ratio of 2.0 or less is 90% or more of the total number.

The slurry of the present invention in which cerium oxide particles having a specific surface area of 25 m ² / g or more are dispersed in water includes:
In addition to the cerium oxide particles of the present invention, for example, oxides or salts of rare earth metals may be added. By mixing other additives, it is possible to expect improvement in characteristics such as improvement in dispersibility, promotion of chemical reaction, improvement in sliding characteristics, and improvement in selectivity. The amount of other additives mixed is preferably 50% by weight or less of the solid content.

[0029]

EXAMPLES (Production of cerium oxide particles, 1) Cerium carbonate 50
g was added to 450 g of deionized water, and subjected to a dispersion treatment at 2800 rpm for 15 minutes using a planetary ball mill to obtain a white cerium carbonate slurry. Hydrogen peroxide solution (about 35%) while stirring this slurry 29.
After dropping 2 g, the reaction was allowed to proceed for 1 hour while stirring was continued, and then the temperature was raised to 90 ° C. using a water bath. After stirring at 90 ° C. for 1 hour, the mixture was cooled to room temperature, solid-liquid separated by a centrifugal separator, and dried with a dryer at 120 ° C. for 24 hours to obtain 30 g of a white powder. As a result of measuring the X-ray diffraction pattern of this white powder, it was identified to be cerium oxide. The specific surface area was measured by a nitrogen adsorption method. As a result, the specific surface area was 111 m ² / g.

(Preparation of Cerium Oxide Particles, Part 2) After 50 g of cerium nitrate was put in 500 g of deionized water and mixed well, an aqueous solution in which 75 g of ammonium hydrogen carbonate was dissolved in 400 g of distilled water was added dropwise while stirring was continued. The mixture was reacted at room temperature for 1 hour to obtain a white precipitate. This white precipitate was subjected to solid-liquid separation by treating with a centrifuge at 3000 rpm for 10 minutes. The white precipitate was again placed in 500 g of deionized water, dispersed well, and 60.9 g of hydrogen peroxide solution (about 35%) was added dropwise. The reaction was allowed to proceed for 1 hour while stirring was continued. And heated to 90 ° C. After stirring at 90 ° C. for 1 hour, the mixture was cooled to room temperature, solid-liquid separated by a centrifugal separator, and dried with a dryer at 120 ° C. for 24 hours to obtain 20 g of a white powder. As a result of measuring the X-ray diffraction pattern of this white powder, it was identified to be cerium oxide. Further, the specific surface area was measured by a nitrogen adsorption method, and as a result, it was 112 m ² / g.

(Preparation of Cerium Oxide Particles, Part 3) 50 g of cerium ammonium nitrate was placed in 500 g of deionized water, mixed well, and then stirred with ammonia water 27 g.
g was dissolved in 500 g of distilled water, and a white precipitate was obtained by allowing the mixture to react at room temperature for 1 hour. This white precipitate was subjected to solid-liquid separation by treating at 3000 rpm for 10 minutes using a centrifuge.
The powder was dried for 24 hours using a dryer at 0 ° C. to obtain 15 g of a white powder. As a result of measuring the X-ray diffraction pattern of this white powder, it was identified to be cerium oxide. The specific surface area was measured by the nitrogen adsorption method.
It showed 30 m ² / g.

(Preparation of Cerium Oxide Slurry) 10 g of the above cerium oxide powder was dispersed in 100 g of deionized water, 1 g of ammonium polyacrylate was added thereto, and a planetary ball mill (P-5, manufactured by Flitsch) was added. The mixture was subjected to a dispersion treatment at 2800 rpm for 30 minutes to obtain a milky white cerium oxide slurry. As a result of measuring the particle size distribution of this slurry using a Coulter counter (Type N-4, manufactured by Nikkaki Co., Ltd.), it was found that the average particle size was as small as 176 nm, and the distribution was monodisperse and relatively narrow.

(Formation of Insulating Layer) A 4-inch Si wafer on which an IC circuit was previously formed and aluminum wiring was patterned was set on a spin coater, and tetramethoxysilane (4 mol) and methyltrimethoxysilane (1 mol) were formed. ) Is hydrolyzed by adding water and nitric acid in isopropyl alcohol to obtain 5 ml of a coating solution.
Was applied on a wafer, rotated at 2,500 rpm for 30 seconds, and dried on a hot plate at 250 ° C. for 1 minute.
This wafer was set in a heating furnace and baked at 450 ° C. for 30 minutes to form an insulating layer.

(Polishing of Semiconductor) The Si wafer on which the insulating layer was formed was set on a holder to which a suction pad for attaching a substrate to be held was attached, and a polishing pad made of porous fluororesin was attached (rotation speed). The holder was mounted on a surface plate with the Si wafer surface facing down, and a 5 kg weight was further mounted thereon. While dropping the cerium oxide slurry onto the surface plate, the upper plate was rotated at 50 rpm for 4 minutes to polish the insulating film. After polishing, the Si wafer is removed from the holder, washed thoroughly in running water, immersed in a beaker containing a mixture of hydrogen peroxide and nitric acid at a ratio of 1: 1 and the beaker is set in an ultrasonic cleaner. And washed for 10 minutes. After confirming that the bubbling accompanying the dissolution of cerium oxide had subsided, the Si wafer was taken out of the beaker, water droplets were removed with a spin drier, and 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 automatic ellipsometer, the polishing removed an insulating layer of about 4000 °
It was found that the thickness was almost uniform over the entire surface of the i-wafer. Further, as a result of cutting the Si wafer and observing the cross section with a SEM, the width was 0.1 μm and the depth was 1.0 μm.
No defects such as cavities were found in the groove portions between the m wirings, indicating that sufficient embedding properties were exhibited. This process was repeated six times to form a six-layer wiring. From the SEM observation of the cross section, it was found that there was almost no step difference on the surface over the entire surface of the Si substrate in each layer, and the wiring pattern was cut with high accuracy. I understand.

Comparative Example An insulating layer was formed in the same manner as in the example, and formation of a multilayer wiring was attempted without polishing using a cerium oxide slurry.
It has been found that when the number of layers is three or more, the level difference on the surface becomes extremely large, so that the insulating property between the upper and lower layers is destroyed, and further multi-layering cannot be performed. Cerium oxide particles commercially available using the insulating layer as a reagent (specific surface area: 4 m ² / g)
As a result of trying the polishing of the insulating film with the slurry prepared in the same manner as above, the insulating film was polished to a thickness of about 4100 °, but a number of polishing scratches were generated on the surface. Was admitted. Therefore, when the weight placed on the holder was reduced from 5 kg to 1 kg, generation of polishing scratches was no longer observed. However, even if it was polished at 50 rpm for 10 minutes, only about 1000 mm was removed, and the entire surface of the Si wafer was flattened. Turned out to be extremely inefficient.

[0036]

According to the abrasive of the present invention, it is possible to polish an organic SOG film or an organic polymer resin film at high speed without causing polishing scratches. According to the method for manufacturing a substrate of the present invention, almost no surface step is formed on the entire surface of the substrate in each layer, so that it is possible to sufficiently cope with miniaturization of wiring and to realize multilayer wiring by high density and high integration. Further, since the organic SOG film or the organic polymer resin film is used as the insulating film, the burying property between the fine wirings and the reduction of the dielectric constant can be simultaneously achieved.

──────────────────────────────────────────────────の Continuing on the front page (51) Int.Cl. ⁶ Identification symbol FI H01L 21/768 H01L 21/90 P (72) Inventor Kiyoto Tanno 4-13-1 Higashicho, Hitachi City, Ibaraki Prefecture Hitachi Chemical Co., Ltd. (72) Inventor Yoshio Homma 1-280 Higashi Koigakubo, Kokubunji-shi, Tokyo Inside the Central Research Laboratory, Hitachi, Ltd.

Claims (10)

[Claims] 1. The apparent density measured by a static method is 1.
A cerium oxide abrasive for polishing an insulating film layer provided on a predetermined substrate, comprising a slurry in which cerium oxide particles of 30 g / ml or less are dispersed in water. 2. The slurry according to claim 1, wherein the slurry contains at least one dispersant selected from a water-soluble organic polymer, a water-soluble anionic surfactant, a water-soluble nonionic surfactant and a water-soluble amine. Cerium oxide abrasive. 3. The cerium oxide particles 10
The cerium oxide abrasive according to claim 2, wherein the amount is from 0.01 to 10 parts by weight based on 0 parts by weight. 4. The cerium oxide abrasive according to claim 1, wherein the slurry is an alkaline slurry. 5. A method for manufacturing a substrate, comprising: forming an insulating film layer on a predetermined substrate; and polishing the insulating film layer with the cerium oxide abrasive according to any one of claims 1 to 4. 6. The method according to claim 5, wherein the insulating film layer is an insulating film layer containing an organic group. 7. The insulating film layer is obtained by applying a coating solution obtained by adding and hydrolyzing an alkoxysilane or an alkylalkoxysilane in an organic solvent with water and a catalyst, applying the coating solution on a substrate, and then heating and curing the coating solution. A method for manufacturing a substrate according to claim 6. 8. The insulating film layer, wherein the number of Si atoms derived from a siloxane bond and the number of C atoms derived from an alkyl group in the insulating film are such that: C atoms / (Si atoms + C atoms) ≧ 0.1 8. The method for manufacturing a substrate according to claim 7, wherein said insulating film layers are related. 9. The method according to claim 5, wherein the insulating film layer is a silicon-free organic polymer resin film layer. 10. After polishing the insulating film layer, the method includes a step of washing the substrate with at least one of hydrogen peroxide and a liquid containing at least one selected from nitric acid, sulfuric acid, ammonium carbonate, ammonium carbamate and ammonium hydrogen carbonate. The method for manufacturing a substrate according to claim 5, wherein: