JPH10172934A - Composition for polishing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress a decrease in speed for polishing a surface to be polished even after repetitive use by specifying an electric conductivity of a composition for polishing containing fumed silica, basic potassium compound, and water. SOLUTION: This composition for polishing is adjusted by mixing, and dispersing or dissolving fumed silica and a basic potassium compound with/to water at a desired percentage content. The fumed silica is fabricated by, for example, burning silicon tetrachloride and hydrogen in the air and its percentage content is preferably 1 to 25wt.% of a total quantity of the composition for polishing. The basic potassium compound promotes polishing to a surface to be polished by a chemical action and also acts as a dispersant of the fumed silica. The content of the basic potassium compound is preferably 0.1 to 0.4wt.% of the total quantity of the composition for polishing. Further, the electric conductivity of the composition for polishing is 100 to 5500μS/cm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polishing composition used for polishing various industrial products such as semiconductors, photomasks, bases for various types of memory hard disks and synthetic resins or members thereof, and more particularly to device wafers in the semiconductor industry and the like. The present invention relates to a polishing composition suitable for surface flattening processing.

More specifically, the present invention has high efficiency in polishing silicon dioxide, which is a high-purity interlayer insulating film to which a CMP technique (details will be described later) is conventionally applied,
The present invention relates to a polishing composition capable of forming an excellent polishing surface, and particularly to a polishing composition having a low rate of reduction of a polishing rate of a silicon dioxide film even in recycle use and good processing stability. is there.

[0003]

2. Description of the Related Art In recent years, so-called high-tech products such as computers have been remarkably advanced, and components used in such products, for example, ULSI, have been increasing in integration and operating speed year by year. Along with this, the design rules of semiconductor devices have been miniaturized year by year, the depth of focus in the device manufacturing process has become shallower, and the flatness required for the pattern formation surface has become stricter.

Further, in order to cope with an increase in wiring resistance due to miniaturization of wiring, the wiring length is shortened by increasing the number of devices. However, steps on the surface of the formed pattern are problematic as obstacles to multilayering. Have been doing.

In performing such miniaturization and multi-layering, it is necessary to flatten a desired surface in order to remove a step during the process. Back and other planarization methods have been used.

However, although these methods can partially planarize, it is difficult to achieve global planarization (complete planarization) required for next-generation devices. 2. Description of the Related Art Flattening (Chemical Mechanical Polishing, hereinafter referred to as "CMP") by mechanochemical polishing combining mechanical or physical polishing and chemical polishing has been studied.

[0007] In addition to this CMP, in various kinds of polishing of a semiconductor wafer, attention is paid to the incorporation of metal impurities, particularly sodium, into the polishing composition. This is because if the metal impurities are not completely removed in the cleaning process after the polishing, the electrical characteristics of the semiconductor will fluctuate. For this reason, the polishing composition is required to have high purity, and the raw materials thereof are necessarily required to have high purity.

[0008]

From such a background,
As an abrasive used in the polishing composition for semiconductor wafers,
Fumed silica is often used. Among the silicas used as abrasives, fumed silica is characterized in that it is easier to obtain high-purity silica than other silicas, for example, colloidal silica, and that the polishing speed of a silicon dioxide film to be polished is high. There is. For this reason, in the conventional CMP processing, a polishing composition to which potassium hydroxide, ammonia, and others are added based on fumed silica and water is often used.

However, there is a problem that the CMP processing is expensive. This is due to the complexity of the CMP process, the need for capital investment,
This is due to the fact that consumables such as the polishing composition used for the P processing are expensive, and for other reasons.

[0010] Regarding the above polishing composition containing fumed silica, fumed silica is relatively expensive, so that cost reduction has been studied from various aspects.

As one of them, recycling of a polishing composition used for CMP processing has been considered. However, when the polishing composition is recycled, the polishing process gradually decreases the polishing rate of the polishing target surface, for example, a silicon dioxide film, as the number of times of use increases. No, there was a problem.

As a result of repeated studies to solve this problem, the present inventors have added a basic potassium compound to a polishing composition containing fumed silica and water, Conductivity of 100 to 5500 μS / cm
Thus, it has been found that, when the polishing composition is recycled, a reduction in the polishing rate of the surface to be polished, for example, a silicon dioxide film, can be suppressed, and the processing process can be stabilized. A conventional polishing composition comprising fumed silica and a basic potassium compound is used to increase the polishing rate or contains a large amount of a basic potassium compound. It had a large electrical conductivity. On the other hand, it was surprising that the polishing composition of the present invention having a specific electrical conductivity did not significantly reduce the polishing rate and did not significantly reduce the polishing rate when recycled.

[0013] The present invention provides a polishing composition used in CMP processing, which has been conventionally required to have a high purity, a high polishing rate on a surface to be polished, an excellent polished surface, and other basic properties. In addition to the performance that does not impair the typical polishing performance, especially when the polishing composition is recycled, the reduction in the polishing rate of the polished surface is small even with repeated use, stabilizing the processing process It is an object of the present invention to provide a polishing composition that can be used.

[0014]

[Means for Solving the Problems]

[Summary of the Invention] <Summary> The polishing composition of the present invention comprises fumed silica,
A polishing composition comprising a basic potassium compound and water, the electric conductivity of which is 100 to 5500 μS /
cm.

<Effect> The polishing composition of the present invention has a high polishing rate for the surface to be polished, and when recycled, has a higher electrical conductivity than conventional polishing compositions. The reduction in the rate of polishing the surface to be polished when the number of times of use is repeated is small, and the processing process can be stabilized.

[Specific description of the invention] <Fumed silica> The polishing composition of the present invention contains fumed silica as a main abrasive. The fumed silica referred to in the present invention is produced by subjecting a thermally decomposable precursor compound that gives silicon oxide, for example, a halide, particularly a chloride, to high-temperature pyrolysis (including combustion).

The fumed silica is produced, for example, by burning silicon tetrachloride and hydrogen in air. The reaction formula is as follows. SiCl ₄ + 2H ₂ + O ₂ → SiO ₂ + 4HCl The shape of the fumed silica particles generally forms secondary particles having a chain structure in which several to several tens of fine primary particles are gathered. Such fumed silica is commercially available, for example, from Aerosil Japan under the trade name Aerosil.

The fumed silica used in the present invention is for polishing a surface to be polished by a mechanical action as abrasive grains. The particle diameter is a sphere-equivalent average particle diameter calculated based on the specific surface area measured by the BET method, and is generally 5 to 80.
nm, preferably 10 to 65 nm. When the average particle size exceeds 80 nm, the surface roughness of the object to be polished may increase, or a problem such as scratch may occur.
Conversely, if it is less than 5 nm, the polishing rate becomes extremely low, which is not practical.

The content of the fumed silica used in the present invention is generally 0.1 to 50% by weight, preferably 1 to 25% by weight, based on the total amount of the polishing composition. If the content of fumed silica is too small, the polishing rate becomes extremely low and it is not practical.On the other hand, if it is too large, uniform dispersion cannot be maintained, and the viscosity of the composition becomes excessively large, making it difficult to handle. May be.

<Basic Potassium Compound> The basic potassium compound used in the polishing composition of the present invention promotes polishing of the surface to be polished by a chemical action. The basic potassium compound also functions as a dispersant for fumed silica as the main abrasive.

Any basic potassium compound can be used as long as it does not impair the effects of the present invention. Preferred basic potassium compounds include hydroxides, phosphates, pyrophosphates, phosphites,
Carbonates, silicates, borates, hypochlorites, hypobromite, and carboxylates such as gluconate, lactate, citrate, tartrate, malate, glycolate , Malonates, formates, and oxalates, and are preferably salts of weak acids.

[0022] The content of the basic potassium compound in the polishing composition is generally 0.0% based on the total amount of the polishing composition.
1 to 0.5% by weight, preferably 0.1 to 0.4% by weight,
It is. If the content of the basic potassium compound is too small, the polishing rate becomes extremely small, and conversely, if the content is too large,
When recycled, the initial polishing rate of the silicon dioxide film tends to be slightly higher, but when the number of uses is increased, the polishing rate is greatly reduced.

<Polishing Composition> The polishing composition of the present invention is generally prepared by mixing the above-mentioned components, ie, fumed silica and a basic potassium compound, in water at a desired content, and dispersing or dissolving the same. Prepared. The order of dispersing or dissolving the above-mentioned components, or various additives to be added as necessary (details described later) is not particularly limited. For example, a basic potassium compound is dissolved in a dispersion of fumed silica. Alternatively, fumed silica may be dispersed in an aqueous solution in which a basic potassium compound is dissolved. Further, the fumed silica and the basic potassium compound may be mixed with water at the same time to simultaneously perform dispersion and / or dissolution. Further, although the polishing composition of the present invention contains a basic potassium compound, a basic potassium compound may be obtained in the polishing composition. That is, a neutral or acidic potassium salt, such as potassium chloride or potassium nitrate, and a basic compound, such as sodium hydroxide, are used in combination, and the equivalent of adding a basic potassium compound in the polishing composition. It is also possible to create a state. However, in this method, the electric conductivity described later becomes too large, and the presence of extra ions causes the problem of impurities. Therefore, it is common to directly use a basic potassium compound.

In preparing the above polishing composition, various types of polishing compositions may be used depending on the purpose of maintaining and stabilizing the quality of the product, the type of the workpiece, the processing conditions, and other needs for polishing. Known additives may be further added.

That is, preferred examples of the additives to be added are (a) silicon dioxides other than fumed silica, such as colloidal silica, precipitated silica, and (b) celluloses such as cellulose. Carboxymethylcellulose and hydroxyethylcellulose, (c) water-soluble alcohols such as ethanol, propanol and ethylene glycol, (d) surfactants such as formalin condensates of sodium alkylbenzenesulfonate and naphthalenesulfonic acid, (e) organic polyanions -Based materials such as lignin sulfonates and polyacrylates, (f) inorganic salts such as ammonium sulfate, magnesium chloride, potassium acetate and aluminum nitrate, (g) water-soluble polymers (emulsifiers), e.g. If polyvinyl alcohol, (h)
Aluminum oxides, such as alumina sol, and fumed alumina, (li) zirconium oxides, such as fumed zirconia, (nu) titanium oxides, such as fumed titania, and others.

The polishing composition of the present invention is prepared as described above.
5500 μS / cm, preferably 500 to 4000 μS
/ Cm. If the electric conductivity is less than 100 μS / cm, it is difficult to obtain a sufficiently dispersed state of fumed silica in the polishing composition, and 550.
If it exceeds 0 μS / cm, when the polishing composition is recycled and used, the reduction of the polishing rate when the number of times of use is repeated becomes large. In addition, the polishing composition of the present invention usually has a pH of 7 or more in order to stably contain a basic compound.

The polishing composition of the present invention may be prepared as a stock solution having a relatively high concentration, stored or transported, and diluted at the time of actual polishing. The above-mentioned preferred concentration range is described as an actual polishing process, and it goes without saying that when such a method of use is taken, a solution having a higher concentration is obtained in a state of being stored or transported. .

The polishing composition of the present invention prepared as described above has a high purity and an excellent polished surface. Therefore, semiconductor devices, photomasks, substrates for various memory hard disks, synthetic resins and Although it can be used for other polishing, when the polishing composition of the present invention is recycled, the reduction in the polishing rate of the silicon dioxide film is suppressed even if the number of times of use is increased, and the processing stability is good. Therefore, it is suitable for the CMP processing technology of the device wafer in the semiconductor industry.

Hereinafter, the polishing composition of the present invention will be specifically described using examples. Note that the present invention is not limited to the configurations of the examples described below as long as the gist is not exceeded.

[0030]

BEST MODE FOR CARRYING OUT THE INVENTION

<Contents and Preparation of Polishing Composition> First, fumed silica (trade name: Aerosil 50, primary particle size 5) as an abrasive material
5 nm, manufactured by Nippon Aerosil Co., Ltd.) was dispersed in water using a stirrer to prepare a slurry having an abrasive concentration of 12% by weight. Then, a basic potassium compound was added to the slurry at a ratio shown in Table 1 and mixed to prepare samples of Examples 1 to 3 and Comparative Examples 1 to 3.

<Measurement of Electric Conductivity> For each of the samples of Examples 1 to 3 and Comparative Examples 1 to 3, after preparing the composition,
The electric conductivity was measured under the same conditions. The obtained results are as shown in Table 1.

<Polishing Test> Next, polishing tests were performed on the samples of Examples 1 to 3 and Comparative Examples 1 to 3. As a workpiece, a 6-inch silicon wafer (outer diameter: about 150 mm) on which a silicon dioxide film was formed by a thermal oxidation method was used, and the surface of the silicon dioxide film with the film was polished.

Polishing and recycling of the polishing composition were carried out in the following manner. First, a wafer with a silicon dioxide film was loaded into a polishing machine and polished for 3 minutes under the following conditions. Subsequently, after removing the wafer from the polishing machine, the polishing pad was washed with pure water for 1 minute using a dressing equipment. On the other hand, the polishing composition used for polishing was collected, and a filter having a mesh size of 10 μm and a mesh size of 5 μm were collected using a pump.
The resultant was sequentially filtered through a filter of m and used for the next polishing. One set of the above series of operations was performed, and this was repeated six sets.

Polishing conditions Polishing machine Single-side polishing machine (platen diameter 570 mm) Polishing machine platen Polyurethane laminated polishing pad (Ro
Del (USA) IC-1000 / Suba400) Processing pressure 490 g / cm ² Platen rotation speed 35 rpm Abrasive supply 150 cc / min

After the polishing, the wafers were sequentially washed and dried, and the polishing rate was determined by measuring the thickness reduction of the wafers by polishing at 60 points for each wafer.
Further, the rate of reduction in the polishing rate of the silicon dioxide film was determined by dividing the polishing rate of the sixth set by that of the first set. The results obtained are as shown in Table 1.

Table 1 Electric velocity Addition Conduction Polishing rate [nm / min] Maintain Basic potassium amount Rate Type of compound [g / l] [μS 1st 2nd 3rd 4th 5th 6th [%] / cm] Example 1 Potassium hydroxide 3 3500 176 176 172 174 174 172 172 97.7 Example 2 Potassium pyrophosphate 3 3200 137 137 136 136 135 135 134 97.8 Example 3 Potassium carbonate 3 3200 145 143 143 141 142 141 97.2 Comparative Example 1 Potassium hydroxide 6 5800 181 180 175 172 170 166 91.7 Comparative Example 2 Potassium pyrophosphate 6 7500 140 137 135 134 131 128 91.4 Comparative Example 3 Potassium carbonate 6 8200 149 148 143 140 140 139 136 91.2

From the results shown in Table 1, the polishing rate of the polishing composition of the present invention is hardly impaired as compared with the conventional polishing composition having a high electric conductivity, and the polishing composition is recycled. Also, when compared with the polishing composition having a high electrical conductivity, the reduction in polishing rate is small,
It can be seen that a stable polishing rate can be obtained.

No surface defects such as scratches were found on any of the wafers used in these tests, and no particular problem was found in the state of the polished surface.

[0039]

According to the polishing composition of the present invention, when it is recycled, the polishing rate is small even if it is repeatedly used, and a high polishing rate at the beginning of recycling can be stably maintained. The fact that the process can be stabilized is as described above in the Summary of the Invention.

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Kazuma Tamai 2-1-1, Nishibiwajima-cho, Nishibiwashima-cho, Nishi-Kasugai-gun, Aichi Prefecture Inside Fujimi Incorporated

Claims (5)

[Claims] 1. A polishing composition comprising fumed silica, a basic potassium compound and water, the polishing composition having an electric conductivity of 100 to 5500 μS / cm. 2. The polishing composition according to claim 1, wherein the basic potassium compound is a potassium salt of a weak acid. 3. The method of claim 1, wherein the basic potassium compound is a hydroxide, a phosphate, a pyrophosphate, a phosphite, a carbonate, a silicate,
The polishing composition according to claim 2, wherein the polishing composition is selected from the group consisting of borate, hypochlorite, hypobromite, and carboxylate. 4. The polishing method according to claim 1, wherein the content of the basic potassium compound is 0.01 to 0.5% by weight based on the total amount of the polishing composition. Composition. 5. A fumed silica having a primary particle size of 5 to 80.
The polishing composition according to any one of claims 1 to 4, wherein the polishing composition has a nm.