JPH118228A - Dry-etching method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To properly dry etch an Al wiring film without generating configurational difference with pattern density by a method, wherein hydrogen atom generating gas is formed by mixing chlorine gas and trichloro-boron gas using discharge plasma. SOLUTION: In the etching of an Al wiring film, since as the working of polymerization by Al catalytic action of an organic compound, containing Al and generated in etching can be suppressed by mixing hydrogen atom H containing gas into chlorine gas Cl2 and trichloro-boron gas BCl3 gas, even if there is roughness and fineness in a wiring, the generation of configurational difference due to the roughness and fineness of pattern can be prevented. Also, by mixing the gas, which generates hydrogen atoms H at a prescribed rate using discharge plasma in conformity with the etching condition of the process such as device, treatment pressure, and gas species, etc., the generation of configurational difference due to the roughness and the fineness of pattern can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a dry etching method, and more particularly to a dry etching method suitable for etching an Al-based wiring film of a fine electronic component such as a semiconductor integrated circuit.

[0002]

2. Description of the Related Art In a conventional dry etching method of this type, etching is performed using discharge plasma containing chlorine gas and boron trichloride gas, or chlorine gas and hydrogen chloride gas. In addition, as a thing related to this kind, for example, JP-A-60-169140 is cited.

[0003]

In the above prior art,
The component serving as the sidewall protective film is reactively adsorbed at the upper part of the high aspect ratio pattern and is not transported to the lower part of the pattern. Had occurred.

It is an object of the present invention to provide a dry etching method which does not cause a shape difference due to pattern density.

[0005]

SUMMARY OF THE INVENTION The object of the present invention is to provide a method for producing Al by utilizing discharge plasma containing chlorine gas and boron trichloride gas.
In a method of etching a workpiece of a system wiring film, the method is achieved by mixing a gas that generates hydrogen atoms by discharge plasma with a chlorine gas and a boron trichloride gas.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In etching Al-based wiring films such as Al and Al alloy films and wiring films having a laminated structure having an Al alloy film (hereinafter referred to as metal etching), differences in etching shapes occur due to the density of patterns. The reason for this will be clarified by the study of the present inventors, and an example in which the present invention is implemented to eliminate the density difference will be described below.

In metal etching, shape control is performed using a side wall protective film.
A carbon compound-based reaction product, which is mainly generated when the photoresist is scraped by the incidence of ions in the plasma, is formed by re-entering the workpiece. The transport of the reaction product to the lower portion of the dense pattern portion is performed through several collisions with the pattern side wall.

[0008] In the case of etching a laminated wiring of TiN and Al or the like, the reaction products from the photoresist are present on the side wall protective film together with the reaction products. These reaction products of Ti and Al catalyze the polymerization of the carbon compound, and the reaction products from the photoresist colliding with the carbon compounds react with high probability and are adsorbed with high probability. It is difficult to transport the lower part of the pattern.

On the other hand, the amount of the reaction product supplied from the photoresist to the side wall of the sparse pattern portion is governed by the line of sight, so that the same amount of the reaction product from the photoresist as the lower part of the pattern and the upper part of the pattern is adsorbed.

[0010] Therefore, in order to eliminate the difference in density, it is necessary to lower the probability of adsorption of the reaction product so that the reaction product is similarly supplied to the lower part of the dense pattern.
It is necessary to deactivate the reaction product of Al and TiN that acts as a polymerization catalyst.

According to the supply of hydrogen or hydrogen compound gas according to the present invention, hydrogen atoms are dissociated by the discharge plasma and supplied to the surface of the workpiece. The authors' research has revealed that this hydrogen atom is very effective in deactivating the catalytic action of the reaction product of Al and TiN. This addition amount must be optimized according to the structure of the etching apparatus, the area of the sample, and the operating conditions. However, it has been found that the object of the present invention can be achieved in the range of 30 to 70 vol% with respect to the etching gas flow rate. Hereinafter, this will be clarified by some examples.

The plasma processing apparatus used was a microwave etching apparatus shown in FIG. Here, 1 is a vacuum processing chamber, and 2 is a vacuum processing chamber 1
A quartz window 3 for introducing a microwave into the sample stage 3 is disposed in the vacuum processing chamber 1 so as to face the quartz window 2, and a sample stage having an Al-based wiring film is arranged thereon. A high frequency power supply for generating a bias voltage, 5 is a quartz window 2
Is a waveguide for guiding the microwave to the vacuum processing chamber 1 and a solenoid coil 6 for forming a magnetic field in the vacuum processing chamber 1.

[Example 1] A wafer having a diameter of 8 inches, which is a workpiece to which a film was formed and patterned as shown in a sectional view of FIG. 2A, was subjected to a chlorine gas (Cl ₂ ) flow rate of 80 cc / min.
Boron trichloride gas (BCl ₃ ) is a mixed gas with a flow rate of 20 cc / min.
A microwave (μ wave) power of 800 W was used to generate a medium density plasma. Fig. 2 shows the etching result at that time.
This is shown in (b). According to this, it can be seen that the dense portion is processed into a vertical shape, but the sparse portion at the right end of the dense portion has a tapered shape and a large difference in the dense and dense shapes is generated.

Here, based on the present invention, hydrogen chloride gas (HC
FIG. 2 (c) shows the etching shape when l) was added at 100 cc / min (50 vol%). Both the sparse part and the dense part can be processed into a vertical shape, and it can be seen that the difference in the sparse and dense shape is greatly improved. When the flow rate of the hydrogen chloride gas is increased to 200 cc / min (67 vol%), the dense portion becomes thicker than the sparse portion as shown in FIG. This is probably because the adsorption coefficient was too low.

[Embodiment 2] The same sample as in Embodiment 1,
With respect to the same Cl ₂ and BCl ₃ flow rates, the dependency of the processed shape on the additional gas flow rate when the additional gas was hydrogen gas (H ₂ ) was observed. When the flow rate of the H ₂ gas was 30 cc / min (20 atm%), a good processed shape similar to that shown in FIG. 2C was obtained. On the other hand, when the flow rate of the H ₂ gas was set to 80 cc / min (40 atm%), the gas worked excessively in the same manner as in the first embodiment, and the opposite density difference was generated as in the case of FIG.

[Embodiment 3] The same sample as in Embodiment 1,
With respect to the same flow rate of Cl ₂ and BCl ₃ , the dependence of the processing shape on the flow rate of the added gas when the added gas was ammonia gas (NH ₃ ) was observed. When the flow rate of the NH ₃ gas was set to 20 cc / min (19 atm%), a good processed shape similar to that shown in FIG. 2C was obtained. On the other hand, the NH ₃ gas flow rate was set to 70 cc / min (40 atm
In the case of (%), it acts excessively in the same manner as in Example 1, and the opposite dense / dense shape difference occurs as in FIG. 2 (d).

[Embodiment 4] FIG. 3 shows a comparison between the first embodiment and the first embodiment in which the density difference is quantified when the density of the plasma is increased by changing the microwave output from 800 W to 1200 W under the same conditions as in the first embodiment. Shown in It can be seen that when the microwave power is high, the density difference is reduced with a small amount of addition. This is because, by increasing the density of the plasma, the dissociation of the introduced gas is promoted, and the supply amount of hydrogen atoms is increased.

As described above, according to the present embodiment, even when the wiring pattern is uneven in the etching of the Al-based wiring film,
By mixing H-containing gas with l ₃ and Cl ₂ gas, it is possible to suppress the polymerization action of Al-containing organic compounds generated during etching by the catalytic action of Al. The occurrence of the difference can be prevented. In addition, by mixing a gas that generates hydrogen atoms by discharge plasma at a predetermined ratio in accordance with the etching conditions of the process such as an apparatus, a processing pressure, and a gas type, the occurrence of a shape difference due to pattern sparse and dense in an optimum shape. Can be prevented.

In addition, by adding a gas having C and H components to a mixture of the boron trichloride gas, the chlorine gas, and the gas generating hydrogen atoms by the discharge plasma as shown in this embodiment, The effect of supplementing C and H of the same components as the resist is produced, and the selectivity between the resist and the metal wiring film can be further improved.
For example, a mixed gas of CH ₄ and Ar is added to a mixed gas of BCl ₃ , Cl ₂ , and HCl, or BCl ₃ , Cl ₂ , H
CH ₂ F ₂ gas or CHF ₃ gas is added to the Cl mixed gas. Thus, the selection ratio of the resist to the resist can be improved without causing a shape difference due to the pattern density. Further, here, instead of the HCl gas, a gas having H such as chloroform in addition to the above-described H ₂ and NH ₃ can be expected to have an effect.

[0020]

According to the present invention, there is an effect that the Al-based wiring film can be favorably dry-etched without causing a shape difference due to the pattern density.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a microwave etching apparatus as an example of an apparatus for performing a dry etching method of the present invention.

FIG. 2 is a longitudinal sectional view showing a processed shape of a sample having an Al-based wiring film of the present invention.

FIG. 3 is a diagram showing the dependence of the microwave output and the amount of added HCl on the pattern density difference between samples.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Vacuum processing chamber, 2 ... Quartz window, 3 ... Sample stand, 4 ... High frequency power supply, 5 ... Waveguide, 6 ... Solenoid coil.

Continued on the front page (72) Inventor Ryoji Hamazaki 794, Higashi-Toyoi, Kazamatsu, Kudamatsu City, Yamaguchi Prefecture Inside the Kasado Plant, Hitachi, Ltd. (72) Inventor Masayuki Kojima 5-2-1 Mizumoto-cho, Kodaira-shi, Tokyo Inside Semiconductor Division, Hitachi, Ltd.

Claims (8)

[Claims] In a method for etching a workpiece of an Al-based wiring film using a discharge plasma containing a chlorine gas and a boron trichloride gas, hydrogen atoms are added to the chlorine gas and the boron trichloride gas by the discharge plasma. A dry etching method comprising mixing generated gas. 2. The dry etching method according to claim 1, wherein a gas containing C and H components is added to said mixed gas. 3. An Al, Al alloy or
A dry etching method of a wiring film having a laminated structure having an Al alloy, wherein the wiring film is etched using discharge plasma of a mixed gas containing boron trichloride gas, chlorine gas, and hydrogen chloride gas. Etching method. 4. A dry etching method according to claim 3, wherein a mixed gas of CH ₄ and Ar in the mixed gas, CH ₂
A dry etching method using a mixed gas to which F ₂ gas or CHF ₃ gas is added. 5. A method for processing a workpiece using discharge plasma containing chlorine gas and boron trichloride gas, wherein hydrogen chloride gas is added in an amount of 15 vol% or more. Method. 6. A method of processing a workpiece using discharge plasma containing chlorine gas and boron trichloride gas, wherein 30 to 70 vol% of hydrogen chloride gas is added. Etching method. 7. A method for processing a workpiece using a discharge plasma containing a chlorine gas and a boron trichloride gas, wherein a hydrogen gas or a hydrogen compound gas is contained so as to contain 10% to 40% of hydrogen atoms in terms of atoms. Characterized by adding
Dry etching method for Al-based wiring film. 8. A dry etching method for an Al-based wiring film, wherein the discharge plasma according to claim 5 is an ECR discharge.