JPH06208977A - Dry etching method - Google Patents

Abstract

PURPOSE:To provide a method for dry etching a multilayer thin film which has little number of treating steps and in which a product of high reliability is obtained. CONSTITUTION:A method for dry etching a thin film 9 to be etched of a material 8 to be etched comprises the steps of mounting parallel electrodes 3, 4 in a reaction chamber 1 containing etching gas, mounting the material 8 to be etched having the film 9 to be etched on the one electrode 4, connecting a high frequency power source 7 to the electrode 4 on which the material 8 to be etched is mounted, and etching the film 9 to be etched. First, as etching gas, mixture gas of CF4 gas and O2 gas is used. After a multilayer film in which two or more types of thin films are laminated on the film 9 to be etched is dry etched, the mixture gas of the SF6 gas and the O2 gas is used so as to increase the thin film etching quantity of an upper layer as compared with that of a lower layer, thereby obtaining a shape corrected positive taper shape.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for processing a thin film semiconductor in the field of electronic equipment, and more particularly to a dry etching method for processing a thin film transistor for liquid crystal or the like.

[0002]

2. Description of the Related Art First, a wet etching method of a first conventional example, which has been used for etching a thin film transistor for liquid crystal and the like, will be described.

In the wet etching method of the first conventional example, an etching composition liquid suitable for various thin films is known. For example, silicon nitride (S
iNx), a mixed solution of HF and NH ₄ OH (1: 8)
(Mixing ratio of) is used. And Al, Cr, M
oSi ₂ , Mo, Ni, Ta, Ti, SiO ₂ , ITO,
Each etching composition liquid is known for a single layer film such as a-Si (amorphous silicon).

Recently, the dry etching method of the second conventional example has been used. Next, the dry etching method of the second conventional example will be described based on the reactive ion etching apparatus shown in FIG.

In FIG. 1, in the dry etching method of the second conventional example, a metal chamber (reaction chamber) 1 is
Etching gas is introduced through the gas controller 5 and is controlled to a predetermined pressure by the exhaust system 2. An anode electrode 3 is provided in the upper part of the chamber 1, and a cathode electrode 4 is provided in the lower part of the chamber 1. A substrate (etching object) 8 having a thin film (etching thin film) 9 on the surface thereof is installed on the cathode electrode 4, and an RF power source 7 is connected to the cathode electrode 4 via an impedance matching circuit 6, and the cathode electrode 4 A high-frequency discharge can be generated between the anode electrode 3 and the anode electrode 3. Utilizing plasma generated by this discharge, morphous silicon (a-Si), silicon oxide (Si
A thin film of O ₂ ), silicon nitride (SiNx) or the like is dry-etched.

[0006]

However, in the wet etching method of the first conventional example and the dry etching method of the second conventional example, there is no problem with the single layer film,
In the case of etching a multilayer thin film composed of different kinds of films, there are the following problems.

In the wet etching method of the first conventional example, it is often necessary to change the etching composition liquid for each layer, which results in an increase in many complicated operations such as a photo process corresponding thereto. Therefore, the processing facility cost of the etching composition liquid, the processing cost,
There is a problem that pollution problems will increase.

In the dry etching method of the second conventional example,
If the etching conditions for the single layer film are applied to the multilayer film as they are, the etching rate of the lower layer may be faster than the etching rate of the upper layer.In this case, the etching shape may be an inverse taper etching shape between the upper layer and the lower layer. , The etching shape has an opposite step between the upper layer and the lower layer, or the etching gas moves so as to roll up from the lower layer to the upper layer, resulting in an undercut shape having a notch (see FIG. 3). There is a problem that the film is likely to be cut and the reliability of the electronic component is impaired.

The present invention solves the above problems and provides a dry etching method for a method of etching a multilayer film of an electronic component for liquid crystal or the like, which requires a small number of processing steps and provides a highly reliable product. It is an object.

[0010]

In order to solve the above-mentioned problems, the dry etching method of the present invention has a counter electrode provided in a reaction chamber in which an etching gas is present, and one of the electrodes is provided with a thin film to be etched. In a dry etching method of holding an etching target object having a substrate, connecting a high frequency power source to the electrode holding the etching target member, and etching the etching target multilayer thin film of the etching target, the multilayer film is dry-etched and then etched. It is characterized in that dry etching is further performed in the next step in order to correct the shape.

In the dry etching method of the present invention, in order to solve the above problems, the reaction gas for dry etching the multilayer film is once mixed gas of O ₂ gas and CF ₄ gas,
The gas for correcting the shape is preferably SF ₆ mixed gas containing O ₂ gas or SF ₆ simple gas.

Further, in order to solve the above-mentioned problems, the dry etching method of the present invention uses a film including an amorphous silicon film doped from the uppermost layer, an amorphous silicon film not doped, and a silicon nitride film. is there. Further, the multilayer film of the present invention is a film including an amorphous silicon film and a silicon nitride film which are not doped from the uppermost layer. Furthermore, the present invention is a film in which the multilayer film includes an amorphous silicon film and a silicon nitride film doped from the uppermost layer.

[0013]

According to the dry etching method of the present invention, the multilayer thin film on the glass substrate is once dry-etched and then further dry-etched to correct the etching shape to a positive taper. By doing so, the dry etching method of the present invention, the etching rate of each single layer film constituting the multilayer film, the etching rate of the upper layer thin film is not necessarily equal to or higher than the etching rate of the lower layer thin film. In addition, the etching shape can always be a positive taper etching shape, the batch dry etching process of the multilayer film can be performed, and the number of steps can be reduced and the reliability can be improved.

In the dry etching method of the present invention, a mixed gas of O ₂ gas and CF ₄ gas is used once for the multilayer film, and a gas for correcting the shape is SF ₆ mixed gas containing O ₂ gas or SF ₆ gas. By using a simple substance gas, it is possible to surely make the etching shape of the limited multilayer thin film into a positive taper. Further, according to the multilayer thin film of the present invention, a positive taper etching shape can be reliably obtained.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the dry etching method of the present invention will be described with reference to FIGS.

This embodiment uses the same reactive ion etching apparatus (dry etching apparatus) shown in FIG. 1 as that used in the dry etching method of the second conventional example.

In FIG. 1, according to the dry etching method of this embodiment, an etching gas is introduced into a metal chamber (reaction chamber) 1 through a gas controller 5,
The exhaust system 2 controls the pressure to a predetermined value. An anode electrode 3 is provided in the upper part of the chamber 1, and a cathode electrode 4 is provided in the lower part of the chamber 1.
A substrate (object to be etched) 8 (size 32) having a thin film (to-be-etched thin film) 9 on its surface is formed on the cathode electrode 4.
The RF power source 7 is connected to the cathode electrode 4 through the impedance matching circuit 6 so that high frequency discharge can be generated between the cathode electrode 4 and the anode electrode 3. The thin film 9 is dry-etched using the plasma generated by this discharge. This dry etching method is a reactive ion etching method (R
It is said to be IE).

Next, the reasons for setting the etching gas species and the structure of the multilayer thin film to be etched in this embodiment will be described with reference to FIGS.
Will be explained. FIG. 3 shows a sample made by Corning 705.
9 glass substrate (320mm x 400mm) on a rectangular substrate, chromium film (Cr film) 1000Å (10), and Si on it
O ₂ film 500Å, tantalum oxide film (Ta
Ox film) 2000Å (11), nitride film (SiNx film) 2000Å (12) thereon, undoped amorphous silicon (a-Si film) 500Å
(13), doped amorphous silicon (n ⁺ a-Si film) 500Å (14) is formed thereon, and a positive resist (OFPR-5 having a thickness of about 1.8 μm) is formed thereon.
000) (16) is applied, patterning is performed to form a resist layer, and the reactive ion etching method (RIE) of FIG. 1 is used, and RF power density is 0.8 w / cm ² ,
400 sccm of CF ₄ and 100 scc of O ₂ as reaction gases
m, vacuum pressure 400 mTow, distance between cathode electrode and anode electrode 100 mm, electrode temperature 20 ° C., etching shape when etching time is 3 minutes. As shown in FIG. 3, the SiNx film, the a-Si film, and the n ⁺ a-Si film have an etching shape of a reverse taper, which easily causes disconnection after wiring in the next process, which improves the reliability of electronic parts. There is a problem of damage. This occurs due to the difference in the etching rate of each monolayer film. FIG. 4 shows the etching rate of each single layer film under the present conditions. As shown in FIG. 4, the etching rate is SiN film> n ⁺ a-Si film> a-Si film> TaOx.
Film> SiO ₂ film, resulting in the shape shown in FIG. Then the O ₂ gas 1 Samples of the shape of FIG. 3, in order to positively tapered to further correct the shape in the same Chanpa
00sccm, SF ₆ gas 300sccm, pressure 400mTow, R
FIG. 2 shows the shape when dry etching was performed for 30 seconds under the condition of F power density 0.8 w / cm ² . By correcting the shape from FIG. 2, it is possible to make the shape of the multilayer thin film into a positive taper, and it is possible to perform a dry etching process on the multilayer thin film at one time, and it is possible to reduce the number of steps and improve reliability.
Next, regarding this reason, FIG. 5 shows the etching rate of a mixed gas of SF ₆ and O ₂ . From the shape of Figure 3 to the shape of Figure 2
In order to do so, the n ⁺ a-Si film as the uppermost film and the a-Si film thereunder may be selectively etched, and the SiN film may be etched. That is, the etching rate n ⁺ a-Si
If film> a-Si film> SiN film, the shape as shown in FIG. 2 is obtained. In fact, the following characteristics are obtained from the results of Table 2 regarding the etching rate. n ⁺ a-Si> a-Si
> SiN >>TaOx> SiO ₂ . Therefore, as a whole, in the relative comparison of etching amounts including over-etching for each monolayer film, n ⁺ a-Si>a-Si> S
When the etching rate is iN>TaOx> SiO _2, a positive taper shape is obtained. From this embodiment, a positive taper shape can be obtained particularly easily in the multilayer thin film structure according to the third aspect.

The dry etching method of the present invention is not limited to the above-mentioned embodiment, and various forms are possible. For example, a large-sized glass substrate was used in this embodiment, but similar results can be obtained by using substrates of various sizes such as small-sized size and semiconductor. The reaction gas is also CF ₄ gas and O ₂
Cl ₂ , BCl ₃ , HBr, BBr ₃ ,
HCl, HI, CHF ₃ , SF ₆ , C ₂ F ₆ , N ₂ , He,
A gas such as Ar is added, or C ₆ is added to the SF ₆ simple gas or the mixed gas of SF ₆ gas and O ₂ gas as a shape-correcting reaction gas.
l ₂ , BCl ₃ , HBr, BBr ₃ , HCl, HI, C
The purpose of adjusting the etching rate ratio as a result by adding gases such as F ₄ , CHF ₃ , C ₂ F ₆ , N ₂ , He, Ar, etc., and by using reaction gases in various other gas combinations. The same result can be obtained if the above is performed.
Also, regarding the structure of the multilayer thin film, n ⁺ a-Si, a-Si, SiNx, TaO added with metals and alloys such as Al, Al alloys, Ti, Cr, Mo, MoSi.
Even if the structure includes all semiconductors such as x and SiO ₂ and insulating films, as a result, the etching rate of each single-layer film forming the multilayer film is gradually decreased from the uppermost layer film to the lowermost layer film. Needless to say, the same result can be obtained. Moreover, in the embodiment, the etching is performed in two steps,
As a result, it goes without saying that multi-step etching of two or more steps is possible. Further, in the embodiment, it is needless to say that the same chamber is used, but multi-chamber processing is also possible. Similar results can be obtained even when the substrate size is large or small.

[0020]

According to the dry etching method of the present invention, in the dry etching of the multilayer thin film, the final result is that the etching amount from the uppermost layer film to the lowermost layer film is gradually reduced. It is possible to perform dry etching at one time and obtain a positive taper etching shape.

Therefore, according to the dry etching method of the present invention, it is possible to eliminate many complicated operations and problems such as deterioration of reliability due to the shape correction which cannot be performed in the conventional example. This has the effect of obtaining highly reliable products.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a dry etching apparatus using a method according to an embodiment of the present invention.

FIG. 2 is an etching shape diagram of a multilayer thin film according to an embodiment method of the present invention.

FIG. 3 is an etching profile of a multi-layered thin film according to a conventional method.

FIG. 4 is a diagram showing etching rate characteristics with a CF ₄ / O ₂ mixed gas according to an embodiment method of the present invention.

FIG. 5 is a diagram showing etching rate characteristics with SF ₆ / O ₂ mixed gas according to an embodiment method of the present invention.

[Explanation of symbols]

 1 Chamber (Reaction Chamber) 2 Exhaust System 3 Anode Electrode 4 Cathode Electrode 5 Gas Controller 6 Impedance Matching Circuit 7 RF Power Supply (High Frequency Power Supply) 8 Substrate (Etching Object) 9 Thin Film (Etching Thin Film)

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Koichi Honda 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Hidenori Takeda 1006 Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd. (72) Inventor Daiyoshi Sekiguchi 1006 Kadoma, Kadoma-shi, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (5)

[Claims] 1. A glass substrate is placed on one electrode in a reaction chamber provided with parallel plate electrodes in which an etching gas is present, and high-frequency power is applied to the electrode on which the glass substrate is placed to form a multilayer on the glass substrate. A dry etching method, characterized in that when a thin film is dry-etched, the multilayer film is once dry-etched and then further dry-etched to correct the etching shape to a positive taper. 2. A reaction of once dry etching a multilayer film.
O gas₂Gas and CF _FourCorrects mixed gas and shape with gas
O gas to do₂SF including₆Mixed gas or SF
₆The dry etching method according to claim 1, wherein a single gas is used.
Law. 3. The dry etching method according to claim 1, wherein the multilayer film is a film including an amorphous silicon film doped from the uppermost layer, an amorphous silicon film not doped, and a silicon nitride film. 4. The dry etching method according to claim 1, wherein the multilayer film is a film including an amorphous silicon film and a silicon nitride film which are not doped from the uppermost layer. 5. The dry etching method according to claim 1, wherein the multilayer film is a film including an amorphous silicon film and a silicon nitride film doped from the uppermost layer.