JP2002294224A - Polishing composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polishing composition having high selectivity such that the polishing rate of a copper film is fast while the polishing rate of a tantalum compound is slow. SOLUTION: The polishing composition comprises (A) a polishing material, (B) 2-hydroxybenzotriazole, (C) hydrogen peroxide and (D) water, where the polishing material is at least one selected among fumed silica, colloidal silica, fumed alumina and colloidal alumina.

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 semiconductors, substrates for various memory hard disks, etc., and more particularly to a polishing composition suitably used for flattening the surface of semiconductor device wafers. It is about.

[0002]

2. Description of the Related Art With the recent remarkable development of the electronics industry, transistors, ICs, LSIs, and ultra LSIs have been evolving. With the rapid increase in the degree of circuit integration in these semiconductor devices, the design of semiconductor devices has increased. The rules are becoming finer year by year, the depth of focus in the device manufacturing process is becoming shallower, and the flatness of the pattern formation surface is becoming increasingly severe.

On the other hand, in order to cover an increase in wiring resistance due to miniaturization of wiring, copper wiring having lower electric resistance is being studied from aluminum and tungsten as a wiring material. However, when copper is used for interconnection between wiring layers and wiring, after forming wiring grooves and holes on the insulating film,
Unnecessary portions on the insulating film are removed by chemical mechanical polishing (CMP) at unnecessary portions by forming a copper film by sputtering or plating.

In such a process, copper diffuses into the insulating film to lower device characteristics. Therefore, it is general to provide a tantalum or tantalum nitride layer as a barrier layer on the insulating film to prevent copper diffusion. It has become.

[0005] In the planarization CMP process of a device in which a copper film is formed on the uppermost layer, an unnecessary portion of the copper film is first polished to a surface layer of a tantalum compound formed on the insulating layer. In the next step, the tantalum compound layer on the insulating film must be polished and the polishing must be completed when the SiO ₂ surface comes out. FIG. 1 shows such a process. In the CMP polishing in this process, a polishing rate (polishing thickness per minute: Å / min) for different materials such as copper, a tantalum compound, and SiO _2.
(Polishing selectivity) is required.

That is, in step 1, the polishing rate for copper is high, and the selectivity is such that there is almost no polishing ability for tantalum compounds. Although further polishing rate is greater for Step 2 in tantalum compound SiO ₂
The smaller the polishing rate is, the more preferable it is because the excessive removal of SiO ₂ can be prevented.

[0007] Ideally, it is desired that this process can be polished with a single abrasive. However, since the selection ratio of the polishing rate for different materials cannot be changed during the process, the process is divided into two steps and different selections are made. Each CMP step is performed with two slurries having properties. In order to prevent the copper film in the grooves and holes from being excessively ground (dishing, recess, erosion), the polishing is finished in step 1 with the copper film on the tantalum compound remaining slightly. Then, in step 2, a small amount of copper and a tantalum compound remaining by using the SiO ₂ layer as a stopper are polished and removed.

The polishing composition used in step 1 needs to have a large polishing rate only for the copper film without generating surface defects (scratch) that cannot be recovered in step 2. is there.

[0009] Such a polishing composition for a copper film is disclosed in JP-A-7-233485.
At least one selected from aminoacetic acid and amidosulfuric acid
Polishing composition containing various kinds of organic acids, oxidizing agents and water,
And a method for producing a semiconductor device using the composition. Although a relatively large polishing rate for copper was obtained, it can be estimated that copper ionized by the oxidizing agent formed a chelate with the above-mentioned organic acid and became easily mechanically polished.

However, when the polishing composition is used to polish a semiconductor device having a copper film and a tantalum compound, the polishing selectivity between copper and the tantalum compound is not sufficient,
If the selectivity with respect to copper is increased, there are problems that the copper film in the wiring grooves and holes is excessively shaved and the smoothness of the copper film surface is impaired.

[0011]

SUMMARY OF THE INVENTION The present invention provides a polishing composition having a high polishing rate for a copper film and a low polishing rate for a tantalum compound and having high selectivity.

[0012]

The present invention provides (A) an abrasive, (B) 2-hydroxybenzotriazole, (C)
This is a polishing composition comprising hydrogen peroxide and (D) water. As a more preferred embodiment, the abrasive is at least one selected from fumed silica, colloidal silica, fumed alumina, and colloidal alumina, and the primary particles of the abrasive are 0.01 to 0.2 μm. The amount of the abrasive in the polishing composition is 5 to 30% by weight; the amount of 2-hydroxybenzotriazole in the polishing composition is 1 to 5% by weight; polishing of hydrogen peroxide The polishing composition has a blending amount of 0.03 to 3% by weight in the polishing composition.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION In the CMP process of a semiconductor device having a copper film and a tantalum compound, the polishing rate of copper is high, but the polishing rate of a tantalum compound is small. It has been found that a composition for use can be obtained, and a CMP process excellent in the smoothness of the copper film surface can be realized.

The abrasive used in the present invention is not particularly limited as long as it is an abrasive, but is preferably made of at least one selected from fumed silica, colloidal silica, fumed alumina, and colloidal alumina. Things. These can be used alone or in any combination. The combination and the ratio are not particularly limited.

[0015] These abrasives have a relatively small particle diameter so as to prevent scratches caused by the abrasive on the surface of the object to be polished and to prevent precipitation and change in composition during storage. Is preferred. The primary particle size of the abrasive can be observed with a scanning electron microscope.
It is preferably in the range of 01 to 0.2 μm. 0.0
If the thickness is smaller than 1 μm, the polishing rate is not easily increased, which is not preferable.

The compounding amount (compounding amount) of the abrasive in the polishing composition is preferably 5 to 30% by weight. If the compounding amount of the abrasive is too small, the mechanical polishing ability decreases and the polishing rate decreases, which is not preferable.If the compounding amount is too high, the mechanical polishing ability increases and the polishing rate of the tantalum compound may be suppressed. This is not preferable because selectivity is lowered.

The polishing composition of the present invention is characterized by containing 2-hydroxybenzotriazole.
The compounding amount in the polishing composition is desirably 0.1 to 5% by weight. When the amount of 2-hydroxybenzotriazole is small, the polishing rate of the copper film is decreased, which is not preferable. When the amount is excessively large, the polishing rate of the copper film is increased, so that the control of the polished surface becomes difficult or the polishing tends to be excessive. Not preferred. In particular, excessive use is not preferred because the smoothness of the surface of the object to be polished is impaired.

The polishing composition of the present invention is characterized by containing hydrogen peroxide. In the polishing composition of the present invention, hydrogen peroxide acts as an oxidizing agent. Hydrogen peroxide exerts an oxidizing effect on the copper film, and has a function of increasing the polishing rate of the copper film by promoting ionization. However, the compounding amount in the polishing composition is 0.03 to
Desirably, it is 3% by weight. If the amount is too high or too low, the polishing rate of the copper film decreases, which is not preferable.

The medium of the polishing composition of the present invention is water,
It is desirable that ionic impurities and metal ions are reduced as much as possible. .

The polishing composition of the present invention is produced by mixing, dissolving and dispersing the above-mentioned components, the abrasive, 2-hydroxybenzotriazole and hydrogen peroxide in water, and the mixing method is carried out by an optional apparatus. be able to. For example, blade-type rotary stirrer, ultrasonic disperser, bead mill disperser, kneader,
A ball mill or the like is applicable. Note that hydrogen peroxide may be added immediately before the polishing operation.

In addition to the above components, various polishing aids may be blended. Examples of such polishing aids include dispersing aids, rust inhibitors, defoamers, pH adjusters, fungicides, and the like, but these are used for the purpose of improving the dispersion storage stability of the slurry and the polishing rate. Added. Examples of the dispersing aid include sodium hexametaphosphate. Of course, it is needless to say that the dispersibility can be improved by adding various surfactants and the like. As the pH adjuster, acetic acid, hydrochloric acid, nitric acid and the like can be mentioned. Examples of the antifoaming agent include liquid paraffin, dimethyl silicone oil, monostearic acid, a mixture of diglycerides, and sorbitan monopalmitate.

[0022]

EXAMPLES The present invention will be specifically described with reference to Examples. <Examples 1 to 8 and Comparative Examples 1 to 4> Colloidal silica was used as an abrasive, and hydrogen peroxide and 2-hydroxybenzotriazole (2-HBT) were added in a mixing amount shown in Table 1 so as to obtain a blending amount shown in Table 1. The polishing compositions of Examples 1 to 8 and Comparative Examples 1 to 4 were obtained by mixing with ion-exchanged water filtered through a 5 μm cartridge filter and uniformly dispersing the mixture by stirring with a high-speed homogenizer. Hydrogen peroxide was mixed and used immediately before polishing.

Polishing evaluation The object to be polished is 10000Å copper by electrolytic plating on a 6-inch silicon wafer and 2000Å by sputtering.
Of tantalum (Ta) is prepared, and copper, Ta
The surface was polished.

For polishing, a single-side polishing machine having a platen diameter of 600 mm was used. A polishing pad IC-1000 / Suba400 made of Rodale (USA) is adhered to the surface plate of the polishing machine with a special double-sided tape, and a polishing composition (slurry) is prepared.
The copper and tantalum films were polished for 1 minute while flowing. The polishing conditions were a load of 300 g / cm ² and a rotation speed of the platen of 4
0 rpm, the number of rotations of the wafer was 40 rpm, and the flow rate of the abrasive composition was 200 ml / min.

After cleaning and drying the wafer, the reduced film thickness was determined to determine the polishing rate (Å / min). The ratio of the polishing rate of copper to the polishing rate of tantalum was used as the selectivity. The polished surface was observed with an optical microscope to check the polished state, and the following ranking was made. ◎: good, ：: partially poorly smooth, ×: poorly smooth, ×
×: Notably corroded and smooth NG

The measurement results are shown in Table 1.

[Table 1]

[0027]

According to the present invention, a polishing composition capable of preferentially polishing a copper film in a CMP process of a semiconductor device including a copper film, a tantalum film, and the like can be obtained, and a semiconductor device can be efficiently manufactured. can do.

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[Procedure amendment]

[Submission date] April 24, 2001 (2001.4.2
4)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Brief description of drawings

[Correction method] Added

[Correction contents]

[Brief description of the drawings]

FIG. 1 shows a process in CMP polishing.

Claims (5)

[Claims] 1. A polishing composition comprising (A) an abrasive, (B) 2-hydroxybenzotriazole, (C) hydrogen peroxide and (D) water. 2. The abrasive material is at least one selected from fumed silica, colloidal silica, fumed alumina, and colloidal alumina.
The polishing composition according to the above. 3. The abrasive has a primary particle size of 0.01 to 0.2 μm.
m, and the amount of the abrasive in the polishing composition is 5 to 30.
The polishing composition according to claim 1, which is in terms of% by weight. 4. The polishing composition according to claim 1, wherein the amount of 2-hydroxybenzotriazole in the polishing composition is 1 to 5% by weight. 5. The polishing composition according to claim 1, wherein the amount of the hydrogen peroxide in the polishing composition is 0.03 to 3% by weight.
The polishing composition according to the above.