JP3449741B2 - Plasma 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 method of etching an aluminum alloy film by using plasma in a process of providing aluminum wiring to a semiconductor device , or an aluminum alloy.
The aluminum alloy film and the TiN film formed underneath
It relates to a method of etching .

[0002]

2. Description of the Related Art FIG. 7 is a schematic cross-sectional view showing the structure of a plasma etching apparatus using electron cyclotron resonance (hereinafter referred to as ECR) using microwaves, and 21 in the drawing shows plasma for performing etching. It is a plasma generating chamber. The plasma generation chamber 21 has a microwave introduction window 21a of a quartz glass plate which seals the upper wall center,
A circular plasma extraction window 21b is provided at a position facing the microwave introduction window 21a at the center of the lower wall. Further, a gas supply pipe 24 for supplying a source gas to the microwave introduction window 21a is provided on the upper wall of the plasma generation chamber 21 at the outer edge of the microwave introduction window 21a.

One end of a waveguide 22 having the other end connected to a high-frequency oscillator (not shown) is connected to the microwave introduction window 21a, and a sample chamber 23 is arranged so as to face the plasma extraction window 21b. ing. Exciting coils 35 are arranged concentrically with the plasma generation chamber 21 so as to surround the plasma generation chamber 21 and one end of the waveguide 22 connected thereto so as to surround them. On the other hand, a mounting table 27 is arranged in the sample chamber 23,
On top of that, for example Al-1% via a SiO ₂ film on the Si substrate.
A sample S on which an Al alloy film of Si-0.5% Cu is deposited is mounted as it is or detachably by means such as electrostatic adsorption. Further, a gas supply pipe 25 is provided penetrating the side wall of the sample chamber 23, and an exhaust port 23a is opened in the lower wall so as to face the mounting table 27.

In order to perform etching with such an apparatus, the plasma generation chamber 21 and the sample chamber set to a required degree of vacuum.
A Cl ₂ + BCl ₃ mixed gas was supplied into 23, and a microwave was introduced into the plasma generation chamber 21 while forming a magnetic field with the excitation coil 35, and the plasma generation chamber 21 was supplied as a cavity resonator.
A Cl ₂ + BCl ₃ mixed gas is excited by ECR to generate plasma, and the plasma is formed by an exciting coil 35, and the magnetic flux density decreases toward the sample chamber 23 side. Of the sample S, and the Al alloy film is etched by using the resist formed into a predetermined pattern on the Al alloy film as a mask.

[0005]

By the way, when the Al alloy film is etched by such a method, this etching is mainly a chemical reaction and isotropic etching. Therefore, it is necessary to perform anisotropic etching. , Etched
Etching is performed while forming a protective film on the side wall of the Al alloy film. However, in the above-mentioned method, the protective film is formed only by the resist sputtering by plasma, and is not sufficient to obtain the required anisotropic shape. Therefore, in order to strengthen the protective film, depositional gases such as SiCl ₄ , CCl ₄ , CHCl ₃ , N ₂ and CF ₄ are added.

However , when N ₂ gas , for example, is added to a commonly used Cl ₂ + BCl ₃ mixed gas, BCl ₃ and N ₂ react in the ECR plasma etching apparatus to form a BN-based reaction product, This adheres to the inside of the device and causes a particle problem. Further, since the protective film reinforced by the addition of the deposition gas remains after the removal of the protective film such as ashing or wet treatment, it is corroded by chlorine contained in the residue and moisture in the atmosphere. There was a risk of this occurring. Therefore, as described in JP-A-3-104886, a method of etching an Al alloy film using a mixed gas of chlorine-based gas and nitrogen-based gas instead of the Cl ₂ + BCl ₃ mixed gas has been proposed.

According to this method, the object to be etched reacts with the etching gas only around the sample, so that the inside of the apparatus is less contaminated and the generation of particles is suppressed, and the formed protective film is easily removed. But with the resist
Since the selection ratio with respect to the Al alloy film is small, for example, the thin portion of the resist film in the step portion of the Al wiring may be excessively etched to damage the Al wiring, and the upper surface of the resist may not be uniformly etched to cause unevenness. Since it is formed, it poses a problem in the subsequent removal process of the protective film. The present invention has been made in view of the above circumstances, and the object thereof is to have a high selection ratio even when a mixed gas of a chlorine-based gas and a nitrogen-based gas is used, and an Al alloy without affecting the subsequent steps. It is to provide a plasma etching method for anisotropically etching a film.

[0008]

A plasma etching method according to a first invention is a method of plasma etching an aluminum alloy film by using a chlorine-based gas and a nitrogen-based gas as an etching gas and using a resist as a mask.
An oxide film is deposited on the resist, and the aluminum alloy film is etched by using the oxide film and the resist as a mask. Ri reactant der membrane, Si, O, N, C , of H
The oxide film on the resist is removed while forming a protective film including at least two and removable by ashing.
It characterized thereby until progression. In the plasma etching method according to the second aspect of the present invention, a chlorine-based gas and a nitrogen-based gas are used as etching gases, and the resist is used as a mask to form the aluminum alloy film and the Ti film formed under the aluminum alloy film.
In the method of collectively plasma etching the N film ,
The resist oxide film deposited on, using the oxide film and the resist as a mask, the aluminum alloy film 及
The etching of the fine TiN film on the sidewalls of the aluminum alloy film and the TiN film made cut by the etching, Ri reactant der of the etching gas, the resist and oxide film, S
At least two of i, O, N, C, and H are included,
While forming a protective film removable by sequencing, the registration
It characterized in that to proceed until the oxide film on the strike is removed. The plasma etching method according to the third invention, EC the Oite the etching in the first or second invention
You and performing with R plasma. In the plasma etching method according to the fourth aspect of the present invention, the film thickness of the oxide film in any one of the first to third aspects is 1/2 of the film thickness of the aluminum alloy film. It is characterized as follows. Furthermore, the plasma etching method according to the fifth invention is
In any one of the first to fourth inventions, Cl ₂ is used as the chlorine-based gas, and N ₂ is used as the nitrogen-based gas.

[0009]

In the present invention, the aluminum alloy film, or the aluminum alloy film and the TiN film formed thereunder are etched using the resist and the oxide film formed on the resist as a mask, so that C is used as an etching gas.
When a chlorine-based gas such as l ₂ or the like and a nitrogen-based gas such as N ₂ or the like is used, etching is performed by chlorine and nitrogen in the etching gas, a reaction product of the component of the etched oxide film and the etched resist. Further, a protective film is formed on the side wall of the aluminum alloy film, and the etching progresses under the protection of the side wall by the protective film so that a desired anisotropic shape can be obtained. Protective film to be formed, Si, O, N, C , includes two or more of H, the A Tsu sheet ring using a reactive gas obtained by adding CF ₄ gas to O ₂ gas because easily removed, it does not affect the subsequent process. Further, the selection ratio between the oxide film and the aluminum alloy film is high, and the selection ratio with respect to the resist is also improved.

Further, the oxide film deposited on the resist is removed.
Etching to progress etching until it is removed
Before ashing after, for removing the oxide film remaining
No pretreatment is required.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below with reference to the drawings showing the embodiments. Figure 1 is a schematic cross-sectional view of a sample to be etched according to the present invention, (a) is an Al alloy film, also (b) as a barrier layer deposited on the Al alloy film and the underlying
The case where the TiN film is etched is shown . In (a), the SiO ₂ film 2 as an insulating film is laminated on the Si substrate 1 ,
Al alloy film 4 on the said SiO ₂ film 2 is sedimentary. Al Go
The gold film 4 has a composition of, for example, Al-1% Si-0.5% Cu.
However, the film thicknesses of the SiO ₂ film 2 and the Al alloy film 4 are each 5,000.
Å and 10,000Å. In addition, in (b), on the Si substrate 1
On the SiO ₂ film 2 is laminated insulating film, the TiN film 3 as a barrier layer, and the Al alloy film 4 is deposited in this order. The thickness of the TiN film 3 is 1,000Å.

A resist film 5 is formed on both Al alloy films 4.
After depositing to a film thickness of 20,000Å , SO is deposited on the resist film 5.
The G film 6 is deposited so that the film thickness is 5,000 Å or less.
The film thickness of the SOG film 6 on the resist film 5, in consideration of the post-et etching process, as the resist film SOG film 6 on the 5 does not remain after the treatment, the film thickness of Al alloy film 4 as an etching target It is necessary to set it to be 1/2 or less of
Since the thickness of the protective film depends on the thickness of the SOG film 6, it has sufficient strength.
It is necessary to set so as to obtain a protective film of various degrees. Above
The thickness of the SOG film 6 that is less than 5,000 Å is 10,000 Å
It is set with respect to the film thickness of the Al alloy film 4. this
After depositing the SOG film 6 having such a film thickness, another resist film (not shown) is deposited, exposed to a predetermined pattern, and developed by wet processing.
The G film 6 is etched, it is removed by ashing using another resist film O ₂ gas used as the mask. As a result, the SOG film 6 and the resist film 5 formed into a predetermined pattern are used as a mask to expose the Al alloy film 4 or the Al alloy film 4 and the TiN film by plasma with Cl ₂ + N ₂ mixed gas
The film to be etched of the film 3 is etched until it reaches the SiO ₂ film 2. By this etching, the SOG film 6 becomes a resist
It is removed without remaining on the film 5.

FIG. 2 is a schematic cross-sectional view showing the result of etching, in which (a) and (b) correspond to (a) and (b) in FIG. 1, respectively. As is clear from Figure 2, SO
As G film 6 and the film to be etched is etched from the top of the resist film 5 to I <br/> other Ru side wall at the lower end of the film to be etched, and Si and O in the SOG film 6 is an oxide film, D
Cl and N in etching gas and etched resist
A protective film 11 is formed as a reaction product with the film 5 . Since selectivity of the SOG film 6 is high, the SOG film 6 remaining resist film 5 until it has been etched, thereby improving the apparent upper selectivity to the resist. And since the side wall of the film to be etched is protected from etching by the protective film 11,
The etching proceeds only in the direction perpendicular to the Si substrate 1, and the required anisotropic shape is obtained. Protective film 11 formed as described above
Contains at least two of Si, O, N, C and H.
Ri, after the etching process, CF ₄ gas to O ₂ gas was added
To remove the resist film 5 using the reactive gas
Easily removed by dividing ashing, the post-process
It has no effect.

On the other hand, on the resist film 5 as shown in FIG.
FIG. 4 shows the result of etching using a plasma of Cl ₂ + BCl ₃ mixed gas and Cl ₂ + N ₂ mixed gas in a conventional sample to be etched in which the SOG film 6 is not deposited.
Shown in (a) and (b). As is apparent from FIG. 4, when the former is used (a), the etching shape of the Al alloy film 4 becomes an inverse taper shape because the side wall protective film 12 of the Al alloy film 4 is weak, and when the latter is used (b), Although the etching shape of the Al alloy film 4 is good, the resist film 5 is largely etched because the selection ratio between the resist film 5 and the Al alloy film 4 is small, and the etched trace of the resist film 5 is uneven. Are formed. Further, when the SOG film 6 is not deposited, the controllability of the etching shape is inferior and the control range is narrower than when the SOG film 6 is deposited.

On the other hand, in the sample to be etched of FIG. 1A in which the SOG film 6 is deposited on the resist film 5, Cl ₂ + BCl
FIGS. 5A and 5B show the results of etching using plasma with a mixed gas of ₃ mixed gas and Cl ₂ + BCl ₃ to which N ₂ gas was further added. As is apparent from FIG. 5, when the former is used (a), since the resist film 5 is not etched, the sidewall protective film of the Al alloy film 4 is hardly formed, and the undercut occurs at the boundary between the resist film 5 and the Al alloy film 4. When the latter is used (b), since the deposition film 14 is formed by the added gas, the Al alloy film 4
6 has a forward tapered shape, and since the deposition film 14 includes the BN film even after the resist film 5 is removed by ashing, the deposition film 14 remains as shown in FIG. 6 because ashing cannot be performed.

Further, in the present invention, it is used as a mask.
Was oxide film (SOG film 6), registration after the etching treatment
Since it does not remain on the strike film 5 , the resist film 5 and the protective film
Before the ashing process described above to remove 11, SO
The process for removing the G film 6 is unnecessary.

[0017]

As described in detail above, the plasma etching method of the present invention has a high selection ratio between the Al alloy film and the oxide film, so that the patterning surface of the Al alloy film is not damaged even in a stepped portion. The present invention has excellent effects such that the required anisotropic shape can be obtained in a wide control range, the reliability of Al wiring is improved, and the number of new operations does not increase after the etching treatment by the etching of the present invention. .

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of a sample to be etched according to the present invention.

FIG. 2 is a schematic cross-sectional view showing a result of etching according to the present invention.

FIG. 3 is a schematic cross-sectional view of a conventional sample to be etched.

FIG. 4 is a schematic cross-sectional view showing a result of etching a conventional sample to be etched using plasma of Cl ₂ + BCl ₃ mixed gas and Cl ₂ + N ₂ mixed gas.

FIG. 5 shows the sample to be etched according to the present invention as Cl.₂＋ BCl₃
Mixed gas and Cl₂＋ BCl₃To N ₂Mixing gas with gas
The results of etching with plasma
It is a schematic cross-sectional view.

FIG. 6 shows a sample to be etched according to the present invention as Cl ₂ + BCl ₃
FIG. 3 is a schematic cross-sectional view showing the result of etching using plasma with a mixed gas in which N ₂ gas has been added to, and further performing ashing treatment.

FIG. 7 is a schematic cross-sectional view showing the configuration of a plasm matching device that uses ECR using microwaves.

[Explanation of symbols]

1 Si substrate 2 SiO ₂ film 3 TiN film 4 Al alloy film 5 Resist 6 SOG 11 Protective film

Continuation of the front page (56) Reference JP 61-144026 (JP, A) JP 3-116930 (JP, A) JP 1-313936 (JP, A) JP 4-165619 (JP , A) JP-A-4-332118 (JP, A) JP-A-2-49425 (JP, A) JP-A-63-58835 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB) Name) H01L 21/3213 H01L 21/3065

Claims (5)

(57) [Claims] 1. A method of plasma etching an aluminum alloy film using a resist as a mask, using a chlorine-based gas and a nitrogen-based gas as an etching gas, comprising depositing an oxide film on the resist, and masking the oxide film and the resist. as used etching of the aluminum alloy film, on the side wall of the aluminum alloy film made cut by the etching, Ri reactant der of the etching gas, the resist and the oxide film, Si, O, N, C, of H home
The oxide film on the resist is removed while forming a protective film including at least two and removable by ashing.
A plasma etching method, characterized in that the plasma etching method is performed until it reaches the temperature 2. A method of plasma-etching an aluminum alloy film and a TiN film formed thereunder all together by using chlorine gas and nitrogen gas as etching gas and using a resist as a mask. the oxide film is deposited on the resist, using the oxide film and the resist as a mask, the aluminum alloy film 及
The etching of the fine TiN film on the sidewalls of the aluminum alloy film and the TiN film made cut by the etching, Ri reactant der of the etching gas, the resist and oxide film, S
At least two of i, O, N, C, and H are included,
While forming a protective film removable by sequencing, the registration
A plasma etching method, characterized in that the oxide film on the strike is advanced until it is removed . 3. The ECR plasma is used for the etching.
The plasma etching method according to claim 1 or 2, which is carried out as follows . 4. The thickness of the oxide film is the aluminum
4. The plasma etching method according to claim 1, wherein the thickness is 1/2 or less of the thickness of the alloy film . 5. Cl ₂ is used as the chlorine-based gas ,
The plasma etching method according to claim 1 , wherein N ₂ is used as the nitrogen-based gas .