JPH05343363A - Dry etching method - Google Patents

Abstract

PURPOSE:To accurately process a fine pattern by controlling a metal thin film and particularly a film of a laminated structure in a satisfactory sectional shape. CONSTITUTION:A laminated film formed of a tungsten(W) film 5, a titanium nitride (TiN)film 4 and a titanium(Ti) film 3 is dry etched by using mixture gas of ClF3 and N2 (N2 is mixed by 30% by volume) by a reactive ion etching(RIE) method. As an etching mask, a pattern of a photoresist 6 is used. In this case, a substrate temperature is held at -20 deg.C.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a dry etching method for a metal thin film.

[0002]

2. Description of the Related Art In the process of forming electrode wiring of a semiconductor device, selective etching techniques for various metal thin films are important factors. In particular, in recent years, with higher integration of LSIs, finer wiring patterns have been required. Therefore, the importance of anisotropic dry etching of various metal thin films is also increasing.

Anisotropic dry etching of a metal thin film is to control the etching cross-sectional shape so that the side wall becomes a positive taper from the side perpendicular to the substrate surface. For example, a tungsten metal thin film or tungsten is included. It is not easy to dry-etch an alloy film with high dimensional accuracy. Conventionally, in anisotropic etching of a tungsten metal thin film or an alloy film containing tungsten, shape control has mainly utilized a side wall protection effect by deposition of sputter decomposition products from a resist on the side wall of tungsten. However, if the resist decomposition product that contributes to the side wall protection effect is insufficient and the side wall protection effect is insufficient, or if the tungsten etchant is excessive, side etching often occurs and the cross-sectional shape is inversely tapered. It was A cross-sectional shape after etching when side etching occurs is shown in FIG. If side etching occurs or the cross-sectional shape becomes an inverse taper, the reliability of the metal wiring itself deteriorates, and the coverage (coverability) of the interlayer insulating film is also increased.
Deteriorates, making it difficult to flatten.

As one of the methods for solving this problem,
For example, in the case of dry etching of a tungsten metal thin film, a method has been proposed in which SF ₆ is used as an etching gas and dry etching is performed while the substrate temperature is kept low. However, this method has a drawback that it cannot sufficiently cope with dry etching of the laminated film.

[0005]

As described above, in the conventional dry etching method for a metal thin film, side etching often occurs or the cross-sectional shape after etching becomes an inverse taper, which causes problems. However, it is difficult to suppress the side etching and the occurrence of the inverse taper shape without other adverse effects.

The present invention has been made in view of the above circumstances, and an object thereof is to process a metal thin film, particularly a film having a laminated structure, into a fine pattern with good precision by controlling the cross-sectional shape. It is to provide a dry etching method capable of performing the above.

[0007]

In order to achieve this object, the present invention uses the following means. That is, in the dry etching method according to the present invention, at the time of dry etching a metal thin film, at least one of N ₂ , O ₂ , and HBr and C are used as dry etching gas.
A gas containing 1F ₃ is used and the temperature of the substrate is kept at 0 ° C. or lower.

[0008]

In the present invention, by the above method, Cl used as an etching gas in dry etching of a metal thin film is used.
The radicals or ions of Cl and F generated by the decomposition of F ₃ gas act as an etchant for the metal thin film, and the etching proceeds. At this time, the temperature of the substrate is kept at 0 ° C. or lower. As a result, the side wall protection action is strengthened and the lateral reaction on the surface of the metal thin film is suppressed. Also, depending on N ₂ or O ₂ or HBr used as an additive gas,
Nitride or oxide or bromide is formed on the side wall of the metal thin film, and functions as a side wall protection. Therefore, side etching does not proceed.

As described above, a highly accurate etching pattern is formed. As described above, in the dry etching method of the present invention, side etching can be effectively prevented, and the metal thin film can be accurately processed into a fine pattern by controlling the cross-sectional shape well. .

[0010]

Embodiments of the present invention will be described below with reference to the drawings.

(First Embodiment) FIGS. 1A to 1C are sectional views in order of steps showing a first embodiment of the present invention.

First, referring to FIG. 1A, the semiconductor substrate 1
A silicon dioxide (SiO ₂ ) film 2 is formed on top of this, and then a titanium (Ti) film 3 with a film thickness of 25 nm and a titanium nitride (TiN) film 4 with a film thickness of 100 nm are grown on each by sputtering. Let Next, a tungsten (W) film 5 having a thickness of 0.5 μm is formed by the CVD method. Further, a pattern of the photoresist 6 is formed thereon by a known photolithography technique.

Next, as shown in FIG. 1B, reactive ion etching (RI) using a mixed gas of ClF ₃ and N ₂ is performed using the pattern of the photoresist 6 as an etching mask.
Perform E). The mixing ratio of N ₂ is 30% by volume.
Etching pressure is 10 Pa, RF power density is 1 W / cm
^{Is 2} . At this time, the temperature of the substrate is kept at -20 ° C. Tungsten (W) film 5 and titanium nitride (TiN) film 4 and titanium (Ti) film 3 during dry etching
A metal nitride 7 is formed on the surface of the side wall of the plasma, and the sputtering action of ions in the etching gas plasma does not act on this part, and it does not react with the reactive radicals in the plasma, and the side wall remains protected. . This effect is exhibited by keeping the substrate temperature at 0 ° C or lower. Therefore, the side etching does not proceed. And
As shown in FIG. 1C, the etching is performed until the surface of the SiO ₂ film 2 is reached, and the formation of the etching pattern is completed.

The etching pattern thus obtained is
Side etching is prevented, the dimensions are the same as the mask pattern, and the cross-sectional shape does not become an inverse taper.

Although a mixed gas of ClF ₃ and N ₂ is used as the etching gas in this embodiment, ClF ₃ and O ₂ are used.
Alternatively, a mixed gas of ClF ₃ and HBr may be used. Also, a combination of these gases can be used as an etching gas. Further, a gas such as Ar or He may be added to these and used.

In the present embodiment, a laminated film of tungsten, titanium nitride and titanium is selected as the object to be etched, but a metal film of tungsten (W), titanium (Ti), molybdenum (Mo) or the like. Similar effects can be obtained when dry-etching an alloy film containing a metal and a laminated film made of them.

In this embodiment, the resist is used as the etching mask material, but an inorganic substance such as silicon oxide or silicon nitride can also be used as the mask material.

Further, as the etching method, magnetron RIE or ECR etching may be used in addition to RIE.

[0019]

According to the present invention, when dry etching a metal thin film on a semiconductor substrate, at least one of N ₂ , O ₂ and HBr and ClF are used as dry etching gas.
_The gas containing ₃ and ₃ is used, and the temperature of the substrate is kept at 0 ° C. or lower. As a result, the cross-sectional shape of the metal thin film can be controlled well, and the metal thin film can be processed into a fine pattern with high accuracy.

Therefore, a great effect is brought about in further increasing the degree of integration of the LSI.

[Brief description of drawings]

FIG. 1 is a cross-sectional view in the order of a dry etching process showing an embodiment of the present invention.

FIG. 2 is a sectional view for explaining a conventional problem.

[Explanation of symbols]

1 Semiconductor Substrate 2 Silicon Dioxide (SiO ₂ ) Film 3 Titanium (Ti) Film 4 Titanium Nitride (TiN) Film 5 Tungsten (W) Film 6 Photoresist 7 Metal Nitride Film

Claims (3)

[Claims] 1. When dry etching a metal thin film on a semiconductor substrate, N ₂ as a dry etching gas,
A dry etching method characterized in that a gas containing at least one of O ₂ and HBr and ClF ₃ is used and the temperature of the substrate is kept at 0 ° C. or lower. 2. The dry etching method according to claim 1, wherein the metal thin film is a tungsten metal thin film or a thin film of an alloy containing tungsten. 3. The dry etching according to claim 1, wherein the metal thin film is a laminated film of a tungsten metal thin film or a thin film of an alloy containing tungsten and a titanium nitride thin film or a titanium metal thin film. Method.