JP3106590B2 - Dry etching method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dry etching method, and more particularly to a silicon nitride film (hereinafter referred to as "Si") used as a passivation or an interlayer film of a double metal.
N film ". ) And a phosphorus glass film (hereinafter “PSG”).
Called “film”. ) Relates to a dry etching method for a two-layer film.

[0002]

2. Description of the Related Art As shown in FIG. 3, a two-layer film 1 of this kind is coated with a photoresist mask 4 on the SiN film 2 in order to form a through hole in the film.
Dry etching is performed with a predetermined gas from above.

[0003] Dry etching of such a two-layer film 1 of the SiN film 2 and the PSG film 3 is performed by an etching apparatus provided with a gas, an oscillation frequency and a pressure corresponding to each film. In the case of the SiN film 2, FIG.
As shown in, for example, CF ₄ + O
₂ is used, and etching is performed by an etching apparatus having an oscillation frequency of 2.45 GHz. On the other hand, in the case of the PSG film 3, as shown in FIG. 3B, for example, CF ₄ + CHF ₃ + He is used as a gas, and etching is performed by an etching device having an oscillation frequency of 13.56 MHz. .

Therefore, in order to dry-etch the two-layer film 1 composed of the SiN film 2 and the PSG film 3, the etching has been performed by separate etching apparatuses corresponding to the respective films.

[0005]

In the dry etching method as described above, the SiN film 2 and the PS
Since the dry etching of the G film 3 is performed by separate etching devices corresponding to the respective films, the number of steps is increased and the respective etching rates of the SiN film 2 and the PSG film 3 are different. As shown, there is a problem that the overhang shape A may be formed.

SUMMARY OF THE INVENTION In view of the above problems, it is an object of the present invention to simultaneously etch a two-layer film of a SiN film and a PSG film with the same etching apparatus, thereby reducing man-hours and forming a good etching shape. And a dry etching method.

[0011]

The object of the present invention is to provide a dry etching method according to the present invention, in which a SiN film used as a passivation or a double metal interlayer film and a PSN film are formed.
In the dry etching method of the two-layer film with the G film, a masking of a photoresist film is performed on the SiN film, and a gas mixture of CF ₄ and He at a similar ratio is applied from above to the SiN film at a predetermined pressure. the film is etched, it continued etching in the same gas as is until the PSG film is several thousand angstroms removed, subsequent, while decreasing the flow rate of the CF _4, the PSG film with the same pressure pouring CHF ₃ of that amount This is achieved by performing the etching.

[0012]

According to the above structure, when etching the SiN film, the SiN film is etched at a predetermined pressure from above the mask of the photoresist film with a gas in which CF ₄ and He are mixed at a similar ratio. The film can be uniformly etched.

Although it is possible to etch the PSG film to the same extent, flowing a large amount of the CF ₄ also etches the photoresist film.

Therefore, as a method of increasing the selectivity of the photoresist film, the flow rate of CF ₄ is reduced,
By pouring in the corresponding amount of CHF ₃ , the etching rate of the photoresist film can be reduced.

However, the PSG film can be uniformly etched without significantly lowering the etching rate, but the SiN film has a lower etching rate due to a decrease in the flow rate of CF ₄ , and the etching uniformity is extremely poor. Therefore, the SiN film is etched with a gas in which CF ₄ and He are mixed at a similar ratio, and
Etching is continued with the same gas until the SG film is removed by several thousand angstroms, and thereafter, the flow rate of the CF ₄ is reduced, and the PSG film is etched at the same pressure while the flow rate of the CHF ₃ is reduced. It can form a shape.

Since only the kind and flow rate of the gas are changed as described above, the etching can be performed by the same etching apparatus, and the number of steps can be reduced.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the dry etching method according to the present invention will be described below in detail with reference to the accompanying drawings. As shown in FIG. 1A, the interlayer film of passivation and double metal is formed in the structure of a two-layer film 11 of a SiN film 12 and a PSG film 13. First, the photoresist film 14 is masked on the SiN film 12 by a known photolithography technique. The photoresist film 14 is 2/3 of the SiN film 12 and the PSG
The film 13 is formed to have a thickness of 1/5. This thickness is slightly suitable for miniaturization.

Next, the two-layer film 11 is
It is housed in a parallel plate type etching apparatus (not shown) having an oscillation frequency of KHz, and CF ₄ and He are deposited from above the photoresist film 14 as shown in FIG. The SiN film 12 is etched at a predetermined pressure with a large amount of gas mixed at a ratio of 1: 1.

Then, as shown in FIG. 1C, the PSG film 13 is removed by several thousand angstroms with the same gas in which CF ₄ and He are mixed at a ratio of 1: 1 as it is. Continue etching. On this occasion,
The photoresist film 14 is also etched by half its thickness. Therefore, the photoresist film 14 is set in consideration of this.

Thereafter, as shown in FIG. 1D, the flow rate of the CF ₄ is set to 1 in the same etching apparatus.
/ 3 and the same amount of CH as the reduced flow rate
The PSG film 13 is entirely etched at the same pressure by flowing F ₃ .

Next, the operation of the above embodiment will be described.
When the SiN film 12 is etched by the above-described etching apparatus, a large amount of CF ₄ is flowed, and He at a flow rate similar to this is mixed, so that etching can be performed uniformly at a constant pressure.

The PSG film 13 is also made of the CF ₄
And He can be etched to the same extent by using the same gas mixed at a ratio of 1: 1. However, if a large amount of the above-mentioned CF ₄ flows, the photoresist film 14 is also etched.

Therefore, good etching cannot be performed unless the thickness of the photoresist film 14 is made considerably thicker than the SiN film 12 and the PSG film 13. As described above, since the thickness of the photoresist film 14 must be considerably increased, it is difficult to form fine through holes in the photoresist film 14. Therefore, the selection ratio of the photoresist film to the photoresist must be further increased.

Therefore, as a method of increasing the selectivity of the photoresist film, the flow rate of the CF ₄ is reduced, and the CHF ₃ is added accordingly, whereby the etching rate of the photoresist film 14 can be reduced.

However, the PSG film 13 can be uniformly etched without significantly lowering the etching rate, but the SiN film 12 has a reduced etching rate due to a decrease in the flow rate of the CF ₄ , resulting in extremely poor etching uniformity. Worse.

Therefore, the SiN film 12 is etched at a predetermined pressure with a gas in which CF ₄ and He are mixed at a ratio of 1: 1 and the same gas is etched as it is until the PSG film 13 is removed by several thousand angstroms. Continue. Thereafter, the flow rate of the CF ₄ is reduced to 1/3, and the same flow rate of CHF ₃ is supplied to etch the PSG film 12 at the same pressure, whereby the SiN film as shown in FIG. It is possible to form a good etching shape B in which the interface between the film 12 and the PSG film 13 coincides with each other. Therefore, it is very suitable as a double metal interlayer film.

That is, dry etching can be performed by the same etching apparatus without forming the photoresist film 14 so thick, and the two-layer film 11 can be simultaneously etched in a short time.

Further, since only the kind and flow rate of the gas are changed, the etching can be performed by the same etching apparatus, and the number of steps can be reduced.

[0029]

As described above, according to the dry etching method of the present invention, the same etching apparatus
The two-layer film of the film and the PSG film are simultaneously etched to reduce the number of steps and to form an excellent etched shape, which is an excellent effect.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing one embodiment of a dry etching method according to the present invention.

FIG. 2 is a schematic view showing an etching shape of an interlayer film by a dry etching method according to the present invention.

FIG. 3 is an explanatory view showing an example of a conventional dry etching method.

FIG. 4 is a schematic view showing an etching shape of an interlayer film by a conventional dry etching method.

[Explanation of symbols]

 Reference Signs List 11 double layer film 12 SiN film 13 PSG film 14 photoresist film

Claims (1)

(57) [Claims] In a dry etching method for a two-layer film of a SiN film and a PSG film used as a passivation or a double metal interlayer film, a masking of a photoresist film is performed on the SiN film, and CF _{4 is formed} from above the SiN film. And He are mixed at a predetermined ratio with a gas at a predetermined pressure to etch the SiN film. The etching is continued with the same gas until the PSG film is removed by several thousand angstroms, and then the flow rate of the CF ₄ is reduced. And at the same pressure, pour CHF ₃ into the PS
A dry etching method, wherein the G film is etched.