JPH10172937A - 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 colloidal silica, a nitrogen-containing basic compound, and water. SOLUTION: This composition for polishing is adjusted by mixing and dispersing or dissolving colloidal silica and a nitrogen-containing basic compound with/to water at a desired percentage content. The colloidal silica is aqueous colloidal silica or gel silica each including all of stable dispersing elements of amorphous silica in a liquid and its percentage content is preferably 0.1 to 30wt.% of the total quantity of the composition for polishing. The nitrogen basic compound promotes polishing to a surface to be polished by a chemical action and also acts as a dispersant of colloidal silica. Ammonia is typical of the compound and its content is preferably 0.01 to 5wt.%. Further, the electric conductivity of the composition for polishing is 30 to 1500μS/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
The present invention relates to a polishing composition that is highly efficient in polishing silicon dioxide as an interlayer insulating film to which P technology (described later in detail) is applied and can form an excellent polished surface. The present invention relates to a polishing composition having a small rate of decrease in the polishing rate of a silicon film and good processing stability.

[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. One of the reasons consumables are expensive is that fumed silica is expensive. From this point,
The use of cheaper colloidal silica is being studied. That is, it has been studied to obtain a high-purity colloidal silica by ion-exchange treatment of a relatively low-purity colloidal silica or to improve the production method, and to use the colloidal silica for a polishing composition.

On the other hand, with respect to polishing compositions containing relatively expensive fumed silica, 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.

The inventors of the present invention have conducted various studies to solve these problems.
By setting the electric conductivity to 30 to 1500 μS / cm, when the polishing composition is recycled, it is possible to suppress a reduction in the polishing rate of the surface to be polished, for example, a silicon dioxide film, and to improve the processing process. Can be stabilized. A conventional polishing composition containing colloidal silica has a higher electric conductivity than the polishing composition of the present invention because the polishing composition contains a large amount of an ionic compound in order to increase the polishing rate. I was On the contrary,
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 for CMP, which has been conventionally required to provide a high polishing rate on a surface to be polished, an excellent polished surface, and other basic polishing performance. In addition to the performance that does not impair, especially when the polishing composition is recycled, the rate of polishing the surface to be polished is small even if the number of uses is repeated,
It is an object of the present invention to provide a polishing composition that can stabilize a processing process.

[0014]

[Means for Solving the Problems]

[Summary of the Invention] <Summary> The polishing composition of the present invention comprises colloidal silica,
A polishing composition comprising a nitrogen-containing basic compound and water, the electric conductivity of which is 30 to 1500 μS / cm.
It is characterized by that.

<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] <Colloidal Silica> The polishing composition of the present invention contains colloidal silica as a main abrasive. The colloidal silica referred to in the present invention is an aqueous colloidal silica or gel, which includes all stable dispersions of amorphous silica in a liquid. The method for producing these colloidal silicas includes a wet method, a silica gel peptization method, an ion exchange method, a hydrolysis method for an organosilicon compound, and others.The method for producing the colloidal silica of the present invention includes the method of the present invention. There is no particular limitation as long as the effect is not impaired.

The colloidal silica used in the present invention preferably has a low metal content. This can be achieved by reducing the metal content by a production method and by purifying the metal content by ion exchange treatment or the like.

The colloidal silica used in the present invention is used for polishing a surface to be polished by mechanical action as abrasive grains. The particle diameter is a sphere-equivalent average particle diameter calculated from the specific surface area measured by the BET method, and generally ranges from 5 to 200.
nm, preferably 10 to 150 nm. If the average particle size exceeds 200 nm, the surface roughness of the object to be polished may increase, or problems such as scratching may occur. Conversely, if the average particle size is less than 5 nm, the polishing rate becomes extremely low and is not practical. .

The content of the colloidal silica used in the present invention is generally 0.05 to 50 with respect to the total amount of the polishing composition.
%, Preferably 0.1 to 30% by weight. If the content of colloidal silica is too small, the polishing rate becomes extremely small and is not practical, and conversely, if it is too large,
In some cases, uniform dispersion cannot be maintained, and the viscosity of the composition becomes excessive, making it difficult to handle.

<Nitrogen-containing basic compound> The nitrogen-containing basic compound used in the polishing composition of the present invention promotes polishing of the surface to be polished by a chemical action. The nitrogen-containing basic compound also functions as a dispersant for colloidal silica, which is the main abrasive.

The nitrogen-containing basic compound referred to in the present invention includes ammonium compounds, amine compounds, and others. The nitrogen-containing basic compound used is not limited as long as the effects of the present invention are not impaired. Any can be used. A representative is ammonia. Specific examples of preferred nitrogen-containing basic compounds include ammonia hydroxide, phosphate, carbonate, silicate, borate, hypochlorite, and hypobromite, and carboxylic acid. Salts include gluconate, lactate, citrate, tartrate, malate, glycolate, malonate, formate, and oxalate, and amine compounds, and are ammonium salts of weak acids Is preferred.

The content of the nitrogen-containing basic compound in the polishing composition is preferably 0.01 to 5% by weight based on the total amount of the polishing composition. When the content of the nitrogen-containing basic compound is too small, the polishing rate becomes extremely low.On the contrary, when the content is too large, the rate at which the initial silicon dioxide film is polished tends to be slightly higher when recycled. In addition, when the number of times of use is increased, a decrease in the polishing speed becomes large.

<Polishing Composition> The polishing composition of the present invention generally comprises the above-mentioned components, ie, colloidal silica,
And a nitrogen-containing basic compound at a desired content in water and dispersed or dissolved. The order of dispersing or dissolving each of the above components or various additives (details described later) as necessary is not particularly limited. For example, each additive may be dissolved in a dispersion of colloidal silica. Then, colloidal silica may be dispersed in an aqueous solution in which each additive is dissolved. Further, the colloidal silica and the nitrogen-containing basic compound may be mixed with water at the same time to simultaneously perform dispersion and / or dissolution. Furthermore, although the polishing composition of the present invention contains a nitrogen-containing basic compound, a nitrogen-containing basic compound may be obtained in the polishing composition. That is, neutral or acidic nitrogen-containing salts, such as ammonium chloride and ammonium nitrate,
And a basic compound, for example, sodium hydroxide, can be used in combination to create a state equivalent to a state in which a nitrogen-containing basic compound is added in the polishing composition. However, in this method, the electric conductivity, which will be described later, becomes too large, and the presence of extra ions causes the problem of impurities. Therefore, it is common to directly use a nitrogen-containing basic compound. Dispersion or dissolution can be performed by any method, for example, by stirring with a blade-type stirrer or dispersing or dissolving by ultrasonic dispersion. Dispersion or dissolution can be performed by any method, for example, by stirring with a blade-type stirrer or dispersing or dissolving by ultrasonic dispersion.

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 additive to be added are (a) silicon dioxides other than colloidal silica, such as fumed 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, and has an electric conductivity of 30 to 1
500 μS / cm, preferably 50 to 1200 μS / c
m. If the electric conductivity is less than 30 μS / cm, it is difficult for the polishing composition to obtain a sufficient polishing rate. If the electric conductivity exceeds 1500 μS / cm, the polishing composition is not used when recycled. When the number of times is increased, the polishing rate is greatly reduced. 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 can be used for polishing semiconductor devices, photomasks, substrates for various types of memory hard disks, synthetic resins, and other polishing materials because excellent polishing surfaces can be obtained. Although it is possible, when the polishing composition of the present invention is recycled,
Since 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, 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, colloidal silica as an abrasive was dispersed in water using a stirrer to prepare a slurry having an abrasive concentration of 20% by weight. Next, the samples of Examples 1 to 3 and Comparative Examples 1 to 3 were prepared by adding and mixing the nitrogen-containing basic compound to the slurry at the ratio shown in Table 1.

<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 speed Addition Conduction Polishing rate [nm / min] Maintained Nitrogen-containing basic amount Rate Compound type [g / l] [μS 1st 2nd 3rd 4th 5th 6th [%] / cm] Example 1 Ammonia 5 1400 100 100 100 99 100 99 99.0 Example 2 Ethylenediamine 5 760 80 80 80 80 80 80 100.0 Example 3 Phosphoric acid 1 1080 80 79 80 80 79 79 98.8 Triammonium Comparative example 1 Ammonia 60 3200 120 119 116 113 111 110 91.7 Comparative example 2 Ethylenediamine 60 2700 85 83 80 81 80 78 91.8 Comparative example 3 Phosphoric acid 60 43000 85 85 82 82 80 77 90.6 triammonium

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 Continuation of the front page (51) Int.Cl. ⁶ Identification code FI G11B 5/84 G11B 5/84 A (72) Inventor Kazu Makoto Tamai 1 Inside Fujimi Incorporated

Claims (4)

[Claims] 1. A polishing composition comprising a colloidal silica, a nitrogen-containing basic compound and water, wherein the electric conductivity is 30 to 1500 μS / cm. 2. The method of claim 1, wherein the nitrogen-containing basic compound is a hydroxide, phosphate, carbonate, silicate, borate, hypochlorite, hypobromite, and carboxylate of ammonia. The polishing composition according to any one of claims 2 and 3, wherein the polishing composition is selected from the group consisting of an amine compound. 3. The polishing composition according to claim 1, wherein the content of the nitrogen-containing basic compound is 0.01 to 5% by weight based on the total amount of the polishing composition. Composition. 4. The colloidal silica has a primary particle size of 5 to 20.
The polishing composition according to any one of claims 1 to 3, which has a thickness of 0 nm.