JPH05160077A - Plasma etching method - Google Patents

Abstract

PURPOSE:To enable an etching device to be enhanced in throughput by a method wherein a laminated film composed of a silicon oxide film and a silicon nitride film is continuously etched in the same etching chamber. CONSTITUTION:Etching gas composed of CHF3, CF4, and Ar is used to etch a silicon oxide film, and on the other hand, etching gas composed of CHF3, CF4, Ar, and O2 is used to etch a silicon nitride. When a silicon nitrdie film is etched, the flow ratio of O2 gas to CHF3, CF4, and Ar (O2/CHF3+CF4+Ar) is set to over 20% so as to set the ratio of etching rate of SiN to SiO (SiN /SiO2) to 2 or so.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma etching method, and more particularly to a method of plasma etching a silicon oxide film and a silicon nitride film.

[0002]

2. Description of the Related Art Conventionally, when a silicon oxide film (SiO ₂ based film) is subjected to plasma etching, a C—F based gas such as CHF ₃ or CF ₄ diluted with Ar gas is used as an etching gas. Etching. When the silicon nitride film (SiN-based film) is plasma-etched, the etching gas is SF ₆ gas diluted with He gas. As described above, conventionally, optimum etching conditions have been obtained by using completely different etching gases for etching a silicon oxide film and for etching a silicon nitride film.

[0003]

However, in the above-mentioned conventional plasma etching method, since completely different etching gases are used when etching the silicon oxide film and when etching the silicon nitride film, the laminated silicon is stacked. When etching the oxide film and silicon nitride film, an etching device is used every time each film is etched.
(To be exact, there is a problem that the etching chamber) must be changed. This is because the etching gas is completely different and it is difficult to switch the etching gas with the same etching apparatus to deal with it. Therefore, the conventional plasma etching method cannot increase the throughput.

SUMMARY OF THE INVENTION An object of the present invention is to provide a plasma etching method capable of continuously etching a laminated silicon oxide film and a silicon nitride film with the same etching apparatus and increasing throughput.

[0005]

In order to achieve the above object, a plasma etching method of the present invention is a plasma etching method for etching a laminated silicon oxide film and a silicon nitride film, wherein the silicon oxide film is etched. CHF ₃ , CF ₄ as etching gas
While using Ar and Ar, CHF ₃ , CF ₄ , Ar as etching gas when etching the silicon nitride film.
And O ₂ are used.

When etching the silicon nitride film, it is desirable to set the flow rate ratio of the O ₂ gas to CHF ₃ , CF ₄ and Ar gas to 20% or more.

[0007]

According to the present invention, when etching the silicon nitride film, the etching gas (CH
Only O ₂ gas is added to F ₃ , CF ₄ and Ar). Therefore, the etching conditions for the silicon oxide film and the silicon nitride film can be set to be substantially equal, and both films can be etched by simply opening and closing the O ₂ gas system with the same etching apparatus. Therefore, the stacked silicon oxide film and silicon nitride film are continuously etched in the same etching chamber of the same etching apparatus. As a result, the throughput is improved.

The present inventor has also found that the flow rate ratio (O ₂ / (CHF ₃₎ of the above-mentioned O ₂ gas to the remaining CHF ₃ , CF ₄ and Ar gas.
+ CF ₄ + Ar)) is gradually increased from 0%, as shown in FIG. 1, the etching rates of the silicon oxide film and the silicon nitride film are reversed, and when the flow rate ratio is 20%, the etching rate ratio (SiN / It was confirmed experimentally that the SiO ₂ ) was about 2. In FIG. 1, the solid line A shows the SiN etching rate, and the broken line B shows the SiO ₂ etching rate. Therefore, when the flow rate ratio is set to 20% or more when etching the silicon nitride film on the silicon oxide film, the underlying silicon oxide film may be inadvertently etched under the etching conditions of the silicon nitride film. There is no. As shown in the figure, the etching rate ratio (SiO ₂ / SiN) is about 2 under the etching conditions (O ₂ gas = 0%) of the silicon oxide film.

[0009]

EXAMPLES The plasma etching method of the present invention will be described in detail below with reference to examples.

As shown in FIG. 2, SiO _{2 is formed} on the Si substrate 1.
A laminated film formed by laminating a film (thickness 600Å) 2, a SiN film (thickness 1200Å) 3 and a SiO ₂ film (thickness 2500Å) 4
A case of selectively etching will be described.

First, a mask 5 having a predetermined pattern is formed on the laminated film using a novolac resin-based positive resist. Next, the substrate 1 is placed in the etching chamber of a parallel plate type magnetron RIE (reactive ion etching) device having an aluminum electrode. Then, in the etching chamber, the films 4, 3 and 2 are continuously etched as follows.

First, CHF ₃ , CF is used as an etching gas.
₄ and Ar, the flow rate ratio CHF ₃ : CF ₄ : Ar = 38:
Under the condition of 5:57, a portion of the SiO ₂ film (thickness 2500Å) 4 not covered with the mask 5 is etched and removed. Subsequently, O ₂ gas was added as an etching gas,
The exposed SiN film (thickness 1200 Å) is removed by etching under the condition of the flow rate ratio CHF ₃ : CF ₄ : Ar: O ₂ = 38: 5: 37: 20. At this time, the underlying SiO ₂ film 2 is about 200Å
Etched to a degree. Then, the O ₂ gas is stopped, and only CHF ₃ , CF ₄ , and Ar are used again as the etching gas, and the remaining SiO ₂ film is formed under the condition of the flow rate ratio CHF ₃ : CF ₄ : Ar = 38: 5: 57. 2 is etched away.
At this time, the amount of the underlying Si substrate 1 etched is 20
It is less than 0Å. A vertical shape has been obtained.

As described above, according to this plasma etching method, the SiO ₂ / SiN ₄ / SiO ₂ laminated film can be continuously etched in one etching chamber of one etching apparatus. Therefore, the throughput can be improved about three times as compared with the conventional one.

[0014]

As is apparent from the above, the plasma etching method of the present invention, when etching the silicon nitride film, uses the etching gas (CHF ₃ ,
Etching is performed only by adding O ₂ gas to CF ₄ and Ar). Therefore, the etching conditions of the silicon oxide film and the silicon nitride film can be set to be substantially equal, and with the same etching apparatus (same etching chamber),
The stacked silicon oxide film and silicon nitride film can be continuously etched. Therefore, the throughput can be improved.

When etching the silicon nitride film, if the flow rate ratio of the O ₂ gas to CHF ₃ , CF ₄ and Ar gas (O ₂ / CHF ₃ + CF ₄ + Ar) is set to 20% or more, the etching is performed. Rate ratio (SiN / SiO ₂ )
Can be about 2. Therefore, it is possible to prevent the underlying silicon oxide film from being inadvertently etched under the etching conditions for the silicon nitride film.

[Brief description of drawings]

FIG. 1 is a diagram showing a relationship between a flow rate ratio of an etching gas and an etching rate.

FIG. 2 SiO ₂ / Si ₃ N ₄ / SiO ₂ to be etched
It is a figure which shows a laminated film.

[Explanation of symbols]

1 Si substrate 2, 4 SiO ₂ film 3 Si ₃ N ₄ film 5 Resist mask A Silicon oxide film etching rate B Silicon nitride film etching rate

Claims (2)

[Claims] 1. A plasma etching method for etching a laminated silicon oxide film and a silicon nitride film, wherein CHF ₃ , CF ₄ and Ar are used as etching gases when etching the silicon oxide film, while the silicon nitride film is used. A plasma etching method characterized in that CHF ₃ , CF ₄ , Ar and O ₂ are used as etching gas when etching a film. 2. The plasma etching according to claim 1, wherein when etching the silicon nitride film, a flow rate ratio of the O ₂ gas to CHF ₃ , CF ₄ and Ar gas is set to 20% or more. Method.