JPH09208933A - Composition for polishing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a polishing composition consisting essentially of water, silicon nitride fine powder and an acid, capable of polishing a layer insulating film, etc., at a high speed, excellent in surface property of polishing face, having large selective polishing rate ratio of a silicon dioxide film to a silicon nitride film and useful for semiconductor devices. SOLUTION: This composition for polishing contains (A) water, (B) silicon nitride fine powder having α type, β type or amorphous form (e.g. fine powder having 0.01-10μm average particle diameter) and (C) an acid such as gluconic acid, lactic acid, citric acid, tartaric acid, malic acid, glycolic acid, malonic acid, formic acid, oxalic acid, nitric acid or hydrochloric acid as a main component. Furthermore, the composition contains the components B and C in amounts of 0.1-50wt.% and 0.001-20wt.%, respectively, based on the total amount of the composition.

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, glass disks and synthetic resins, or members thereof, and particularly, the surface flatness of device wafers in the semiconductor industry and the like. The present invention relates to a polishing composition suitable for chemical processing. More specifically, it is possible to form an excellent polished surface with high efficiency in polishing an interlayer insulating film and a metal wiring to which a CMP technique has been conventionally applied, and at the same time, an advanced device forming technique such as element isolation. The present invention relates to a polishing composition applicable to.

[0002]

2. Description of the Related Art The progress of high-tech products such as computers in recent years has been remarkable, and for example, U
LSIs are becoming more highly integrated and faster every 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 shallow, and the flatness required for the pattern formation surface has become strict. Further, in order to cope with an increase in wiring resistance due to miniaturization of wiring, the wiring length has been shortened by increasing the number of devices, but a step at the time of pattern formation has become a problem as an obstacle to the multilayering.

In carrying out such fine / multi-layering, it is necessary to carry out some flattening for removing steps in the process. As a method therefor, spin-on-glass and resist etchback have been used so far. Etc. were used. However, with these methods, although partial planarization is possible, it is difficult to achieve the global planarization (complete planarization) required for next-generation devices, and the mechanochemical polishing ( Hereinafter, planarization by CMP (Chemical Mechanical Polishing) has been studied.

[0004]

A film mainly composed of silicon dioxide is used as an interlayer insulating film of a semiconductor device. At present, an abrasive in which fumed silica is dispersed in water is mainly used for polishing the interlayer insulating film and the metal wiring, but the obtained polishing efficiency is not sufficient, and a polishing agent having a higher polishing efficiency is desired. Has been done. The low productivity of the present abrasives is also a major impediment to the development of CMP technology.

On the other hand, the CMP technique is being studied for application other than planarization of the interlayer insulating film. Element isolation is one of such applications. As a conventional element isolation method for a semiconductor device circuit, a LOCOS method (Local Oxidation of Silicon) in which silicon is thermally oxidized using a silicon nitride film as a mask is used.
However, the so-called Bird's Beak formed by this method has been a factor that hinders the miniaturization of semiconductor devices.

On the other hand, a shallow groove (Shallow
Trench) is formed and an oxide film is deposited thereon, and then C
Shallow Trench Isolation, which flattens by MP technology, enables element isolation in a smaller area, and has been attracting attention as a technology that is compatible with future high density of semiconductor devices instead of LOCOS method. .

A technical problem in carrying out the shallow trench isolation is to finish the surface to be flattened uniformly without excess or deficiency of the stock removal by polishing, and to finish the polishing with a predetermined stock removal. In general, a silicon nitride film is arranged below a silicon dioxide film to be polished, and polishing is often performed using the silicon nitride film as a stopper.
It can be understood that, as the polishing agent used at this time, a polishing agent capable of efficiently processing a silicon dioxide film, while not polishing the silicon nitride film, is suitable. However, the conventional polishing agent has a low polishing efficiency for the silicon dioxide film and a low selective polishing rate ratio of the silicon dioxide film to the silicon nitride film, which hinders the improvement of the yield of shallow trench isolation. The selective polishing rate ratio represents how easily the silicon dioxide film is polished with respect to the silicon nitride film, and is obtained by dividing the polishing rate of the silicon dioxide film by that of the silicon nitride film.

The present invention has been made in order to solve the above-mentioned problems, and in polishing an interlayer insulating film and a metal wiring, a polishing rate is high, and at the same time, a polishing product having an excellent surface state of the polishing surface can be obtained. Another object of the present invention is to provide a polishing composition having a large selective polishing rate ratio of a silicon dioxide film to a silicon nitride film.

[0009]

DISCLOSURE OF THE INVENTION The present inventors have conducted extensive studies to obtain an excellent polishing composition comprising a composition suitable for satisfying the above-mentioned objects, and as a result, water and nitriding It has been known that the presence of an acid in the polishing agent containing silicon fine powder as a main component can improve the selective polishing rate ratio of the silicon dioxide film to the silicon nitride film and the polishing rate. The gist of the present invention resides in a polishing composition characterized by containing water and an acid in silicon nitride fine powder as a composition. Hereinafter, the present invention will be described in more detail.

Among the components of the polishing composition of the present invention, silicon nitride used as the main abrasive is, for example, in the form of α-
Silicon nitride, β-silicon nitride, amorphous silicon nitride and the like may be used, and fine powders thereof may be mixed at an arbitrary ratio and are not particularly limited. The content of the silicon nitride fine powder in the polishing composition is usually 0.1 to 50% by weight, preferably 1 to 25% by weight based on the total amount of the composition. If this is too small, the polishing rate and the selective polishing rate ratio of the silicon dioxide film to the silicon nitride film will be small, and if it is too large, uniform dispersion cannot be maintained,
In addition, the slurry viscosity becomes too large, which makes it difficult to handle. In consideration of processing accuracy and polishing rate, the average particle diameter of the particle diameter is 0.01 to 10 μm, preferably 0.05 to 3
μm (result of measurement by BET method).

The acid used as an essential additive in the components of the polishing composition of the present invention is preferably at least one kind of organic acid and inorganic acid. Among the organic acids, carboxylic acids are particularly preferable, and among the carboxylic acids, gluconic acid, lactic acid, citric acid, tartaric acid, malic acid, glycolic acid, malonic acid, formic acid, oxalic acid and the like are preferable. Of the inorganic acids, hydrochloric acid and nitric acid are particularly preferable. However, the type of acid used is not limited to the above examples.

The content of these acids varies depending on the strength of the acid, but is 0.001 to 20% by weight, preferably 0.005 to 10% by weight, based on the total amount of the polishing composition. If the amount is too small, the effect of the present invention cannot be expected.
On the contrary, if it is too much, the effect of addition does not improve,
Therefore, it is not economical.

The mechanistic details of the polishing composition of the present invention having an excellent polishing effect are unknown, but the presence of an acid determines whether the silicon nitride fine powder is dispersed in the polishing composition. It is believed that such a dispersed state has an advantageous effect in the polishing process.

The polishing composition of the present invention may be prepared by mixing the above-mentioned components, that is, silicon nitride fine powder and acid, in water at a predetermined content and stirring. The acid is dissolved in water, the silicon nitride fine powder is uniformly dispersed in this solution to form a suspension,
A polishing composition is formed. Then, the pH of this polishing composition is adjusted to 7 or less. The mixing order and the like are not particularly limited.

When preparing the above-mentioned polishing composition, depending on the purpose of maintaining the quality and stability of the product, and the necessary polishing conditions such as the type of the work piece and the processing conditions.
Various known auxiliary additives as described below may be added.

That is, as a preferred example of the auxiliary additive,
Silicon oxides such as fumed silica and colloidal silica, celluloses such as cellulose, carboxymethyl cellulose and hydroxyethyl cellulose, water-soluble alcohols such as ethanol, propanol and ethylene glycol, sodium alkylbenzene sulfonate, and formalin condensation of naphthalene sulfonic acid. Substances such as surfactants, lignin sulfonates, organic polyanion materials such as polyacrylates, ammonium sulfate, magnesium chloride, potassium acetate, inorganic salts such as aluminum nitrate, water-soluble polymers such as polyvinyl alcohol (Emulsifiers), alumina sol and the like can be mentioned.

Further, the polishing composition of the present invention can be prepared as a raw material having a relatively high concentration and used by diluting it during the actual polishing process. The above-mentioned preferable concentration range is described as the actual polishing process.

The polishing composition of the present invention prepared as described above can be used for polishing semiconductor devices, photomasks, glass disks, synthetic resins and the like, but since it has a high polishing rate, it can be used in the semiconductor industry. It is suitable for polishing the interlayer insulating film and the metal wiring in the flattening process of the device wafer. Further, since the selective polishing rate ratio of the silicon dioxide film to the silicon nitride film is also high, it is particularly suitable for shallow trench isolation.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION Results of polishing tests performed on two types of workpieces having different polishing surface materials with respect to the polishing compositions of Embodiments 1 to 11 and Comparative Embodiments 1 to 16 below. The present invention will be specifically described by presenting. In addition,
The present invention is not limited to the configurations of the embodiments described below as long as the gist thereof is not exceeded.

[Contents of Each Polishing Composition] Table 1 shows samples of comparative forms (also called comparative samples), and Table 2 shows samples of embodiments of the present invention (also called working samples). .
In Table 2, only α-silicon nitride (average particle diameter 0.12 μm) was used as the main abrasive, but in Table 1, fumed silica (average particle diameter 0.05 μm) and cerium oxide (average particle diameter 0.98 μm) were used. ), Aluminum oxide (average particle size 0.07 μm), chromium oxide (average particle size 0.20 μm)
m), zirconium oxide (average particle size 0.20 μm),
And silicon carbide (average particle size 0.60 μm), 1
Α-Silicon nitride was used as the main abrasive for the No. 5 and No. 16 comparative samples. [Preparation of Each Polishing Composition] First, each fine powder was dispersed in water using a stirrer to prepare a slurry having a main abrasive concentration of 10% by weight. The slurry was then treated with several acids.
~ Sample 1 of the embodiment by adding and mixing at a ratio shown in Table 2
-11 and Comparative Examples 1-16 were prepared for a total of 27 polishing compositions.

[Polishing test and its result] Next, the execution sample 1
11 to 11 and comparative samples 1 to 16 will be described below. As the work piece, a 6-inch silicon wafer having a silicon dioxide film formed by a thermal oxidation method and a 6-inch silicon wafer having a silicon nitride film formed by an LPCVD method (both having an outer diameter of about 1
50 mm) substrate was used to polish the film surfaces of the silicon dioxide film and the silicon nitride film, respectively.

Polishing was performed using a single-sided polishing machine (plate diameter 570 mm). A laminating polishing pad made of polyurethane (made by Rodel [US]; IC-1000
/ Suba400) was attached, a wafer with a silicon dioxide film was first loaded and polished for 1 minute, and then the wafer was replaced with a wafer with a silicon nitride film and polished for 1 minute in the same manner. The polishing conditions were a processing pressure of 490 g / cm ² , a platen rotation speed of 30 rpm, a polishing agent supply amount of 150 cc / min, and a wafer rotation speed of 30 rpm.

After polishing, each wafer was sequentially washed and dried, and the film thickness reduction of the wafer due to polishing was measured at 49 points to determine the polishing rate for each test. Further, by dividing the polishing rate of the silicon dioxide film by that of the silicon nitride film, a selective polishing rate ratio of the silicon dioxide film to the silicon nitride film (this may be abbreviated as a selection ratio) was obtained. The test results are shown in Tables 1 and 2.

[0024]

[Table 1]

[0025]

[Table 2]

From the test results shown in Tables 1 and 2, the polishing rate for the silicon dioxide film of each of the practical samples was significantly higher than that of the comparative sample except for Comparative sample 5, and the polishing rate of the practical sample was also high. It is clear that all the selection ratios are significantly higher than that of the comparative sample. Although not shown in Tables 1 and 2 above, when the polished surfaces of these were visually evaluated, both the execution sample and the comparative sample were acceptable, and defects due to processing were found. There wasn't.

[0027]

As described above, according to the present invention, a polishing composition obtained by adding an acid to water and silicon nitride fine powder does not cause surface defects on the polished surface and causes interlayer insulation. It was confirmed that it has an excellent effect that a high polishing rate can be imparted in polishing of a film and a metal wiring, and at the same time, a selective polishing rate ratio of a silicon dioxide film to a silicon nitride film can be increased in shallow trench isolation.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Noritaka Yokomichi 2-1, 1-1 Jyoryo, Nishibiwajima-cho, Nishikasugai-gun, Aichi Prefecture Fujimi Incorporated Co., Ltd.

Claims (4)

[Claims] 1. A polishing composition, wherein the main components are water, silicon nitride fine powder and an acid. 2. The acid is at least one kind of acid selected from gluconic acid, lactic acid, citric acid, tartaric acid, malic acid, glycolic acid, malonic acid, formic acid, oxalic acid, nitric acid and hydrochloric acid. The polishing composition according to claim 1. 3. A polishing composition for flattening the surface of a semiconductor device, wherein the main components are water, silicon nitride fine powder and an acid. 4. The acid is at least one kind of acid selected from gluconic acid, lactic acid, citric acid, tartaric acid, malic acid, glycolic acid, malonic acid, formic acid, oxalic acid, nitric acid and hydrochloric acid. The polishing composition for flattening the surface of a semiconductor device according to claim 3.