JPH04294533A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To enable a shape to be maintained to be vertical and anisotropic etching without any etching shift to be performed by using the dry etching method of a polysilicon layer or polycide with a high selection ratio for silicon oxide film and resist. CONSTITUTION:When etching a polysilicon layer 3 or polycide layers 3 and 3 which are formed through a silicon oxide film 2 on a semiconductor substrate 1 using a mask 5, a mixed gas of hydrogen bromide and nitrogen is used as an etching gas for performing anisotropic etching. Also, a mixed gas of hydrogen bromide and nitrous oxide is used as an etching gas for performing anisotropic etching. Also, anisotropic etching is performed by using a mixed gas of chlorine and nitrous oxide as an etching gas.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a semiconductor device, and more particularly to a method of dry etching a polysilicon layer or a polycide layer.

[0002] In recent years, as semiconductor devices have become faster and more highly integrated, their structures have become more and more complex, and the processes to realize these structures require more precise processing technology. There is. In the dry etching process, the etch rate ratio (selectivity) with respect to the base film is particularly important. In particular, when dry etching a polysilicon layer or polycide layer on a silicon oxide film, it is desirable to improve the selectivity to the underlying silicon oxide film.
Furthermore, dimensional accuracy and perpendicularity of shape are also desired.

0003

2. Description of the Related Art Conventionally, dry etching of silicon-based films has been carried out using a gas containing HBr with oxygen added or a gas containing chlorine with oxygen added as an etching gas. This is because these gases have a high selectivity with respect to the base oxide film (SiO2 film) and a vertical shape can be easily obtained.

FIGS. 9(a) to 9(c) are cross-sectional views for explaining a conventional example of etching, in which 1 is a Si substrate;
2 is a SiO2 film, 3 is a poly-Si layer, 4 is a WSi layer, 5
5a is a resist mask, 5a is a resist mask after etching, 15 is a sidewall adhesion film, and 16 is an undercut. FIG. 10 is a diagram showing the etch rate and selectivity of poly-Si by (HBr+O2), and FIG.
2 is a diagram showing the selectivity of poly-Si to resist by O2). Hereinafter, a conventional example of etching a polycide gate electrode will be described with reference to these figures.

Referring to FIG. 9(a), an SiO2 film 2 is formed on a Si substrate 1 by thermal oxidation, and a poly-Si layer 3 and a tungsten silicide (WSi) layer 4 are successively deposited thereon by, for example, the CVD method. W
A resist mask 5 for etching the WSi layer 4 and poly-Si layer 3 on the Si layer 4 to form a gate electrode.
form.

Refer to FIG. 9(b). After this, such a wafer 6 is placed in, for example, a parallel plate type reactive ion etching apparatus, and (HBr+O2
) gas or (Cl2 +O2) gas is supplied, and the WSi layer 4 and poly-Si layer 3 are dry etched using the resist mask 5 as a mask. At this time, during etching, a SiBrO-based adhesion film is formed on the sidewall in the case of (HBr+O2), and a SiClO-based adhesion film is formed in the case of (Cl2+O2), and these sidewall adhesion films 15 act as protective films to maintain the vertical shape. . However, a non-negligible etching shift occurs on the etched sidewall, and the base oxide film (SiO2 film) is slightly overetched.

FIG. 10 shows polyS by (HBr+O2)
FIG. 3 is a diagram showing the etch rate and selectivity of i. As seen in this figure, as O2 is added, the selectivity to SiO2 improves, so overetching does not pose a practical problem. However, as O2 is added, the selectivity to the resist rapidly decreases, and as a result, as shown in FIG. 9(b), the resist mask 5 undergoes film thinning as shown in the resist mask 5a after etching, and the etching process is reduced. The shift becomes larger.

FIG. 11 is a diagram showing the selectivity of poly-Si to resist due to (Cl 2 +O 2 ). In this case too
As 2 is added, the selectivity to resist decreases rapidly, resulting in film thinning of the resist mask after etching and an increase in etching shift.

Refer to FIG. 9(c). After that, the resist mask is peeled off, and the sidewall deposited film 15 is etched and removed. However, since SiBrO-based and SiClO-based deposited films are very strong, they can only be removed using highly concentrated hydrofluoric acid. When completely removed, the underlying SiO2 film is greatly gouged out, resulting in undercut 1.
yields 6.

[0010] Therefore, in the conventional method, etching shift and undercut occur during etching of a silicon-based film, which hinders microfabrication and hinders higher integration and higher speed of devices.

[0011]

[Problems to be Solved by the Invention] In view of the above problems, the present invention performs dry etching that has a high selectivity to the base oxide film and resist and has good pattern width accuracy when etching a polysilicon layer or polycide layer. The purpose of this invention is to provide a method that eliminates the need for wet etching that causes undercuts in the underlying oxide film.

0012

Means for Solving the Problems FIGS. 1(a) and 1(b) are sectional views for explaining an example of etching. The above problem is solved by the polysilicon layer 3 or polycide layers 3 and 4 formed on the semiconductor substrate 1 via the silicon oxide film 2.
This problem is solved by a semiconductor device manufacturing method that uses a mixed gas of hydrogen bromide and nitrogen as an etching gas to perform anisotropic etching when etching using the mask 5.

[0013] The problem is also solved by a method of manufacturing a semiconductor device in which anisotropic etching is performed using a mixed gas of hydrogen bromide and nitrous oxide as an etching gas. The problem can also be solved by a semiconductor device manufacturing method that performs anisotropic etching using a mixed gas of chlorine and nitrous oxide as an etching gas.

[0014]

[Operation] According to the experimental results of anisotropic dry etching in making the present invention, when nitrogen is mixed with hydrogen bromide, the etching of the polysilicon layer 3 or polycide layers 3 and 4 against the silicon oxide film is improved. The selection ratio increases. On the other hand, the selectivity to resist did not change significantly, but remained at 50 or more. Therefore, no film loss occurs in the resist mask 5, and the etching shift can be ignored.

When nitrogen is mixed with hydrogen bromide, a SiBrN-based adhesion film is formed on the side wall during etching, and this serves as a protective film to maintain the vertical shape. However, although this deposited film is stable under reduced pressure, it evaporates and disappears when exposed to the atmosphere after etching. Therefore, removal using hydrofluoric acid as in the conventional example is not required, and undercuts do not occur.

A mixed gas of hydrogen bromide and nitrous oxide also exhibits an effect similar to that of a mixed gas of hydrogen bromide and nitrogen. Also, when nitrous oxide is mixed with chlorine, the polysilicon layer 3 or polycide layer 3,
The etching selectivity of No. 4 is increased. On the other hand, the selectivity to resist did not change significantly, but remained at 50 or more. Therefore, no film loss occurs in the resist mask 5, and the etching shift can be ignored.

[0017] Also, during etching, Si is deposited on the sidewall.
A ClN-based adhesion film is formed, which serves as a protective film and maintains the vertical shape. However, although this deposited film is stable under reduced pressure, it evaporates and disappears when exposed to the atmosphere after etching. Therefore, removal using hydrofluoric acid as in the conventional example is not required, and undercuts do not occur.

[0018]

[Example] Fig. 7 is a conceptual diagram of a commonly used parallel plate reactive ion etching (RIE) apparatus, and Fig. 8 is a conceptual diagram of an electron cyclotron resonance (ECR) plasma etching apparatus. is a stage, 8 is a heater, 9 is a vacuum chamber, 10 is a shower head, 1
1 represents a gas supply port, 12 represents an RF power source, 13 represents a microwave oscillator, and 14 represents a coil.

An embodiment in which a gate electrode is formed by dry etching a polycide layer using such an anisotropic dry etching apparatus will be described. Figure 1(a) SiO2 with a thickness of 200 Å is deposited on the reference Si substrate 1 by thermal oxidation.
A film 2 is formed thereon, and a thickness of 15
A poly-Si layer 3 with a thickness of 00 Å and a tungsten silicide (WSi) layer 4 with a thickness of 1500 Å are successively deposited. WSi
A resist mask 5 having a width of 0.6 μm is formed on the layer 4 for etching the WSi layer 4 and poly-Si layer 3 to form a gate electrode.

Refer to FIG. 1(b) After this, such a wafer 6 is placed in the RIE apparatus shown in FIG. 7 or the ECR plasma etching apparatus shown in FIG. 8, an etching gas is supplied, and the resist mask 5 is removed. Then, dry etching of the WSi layer 4 and the poly-Si layer 3 is performed.

First Example Dry etching conditions were set as follows using the RIE apparatus. HBr+N2 95 SCCM
+5 SCCM pressure
0.1 TorrRF power
300 W (13.56 MHz) Stage temperature: 40° C. The etch rate of the poly-Si layer 3 was 300 nm/min, and the etch rate of the WSi layer 4 was also approximately the same. The selectivity for the SiO2 film 2 was approximately 100, and the selectivity for the resist mask 5 was 50 or more.

Just etch 100 on the polycide layer 6.
% over-etching was performed to completely remove the polycide layer 6. Film reduction of SiO2 film 2 (overetch amount)
is about 30 Å, which poses no practical problem at all.

The film reduction of the resist mask 5 was about 160 Å, but the width of the polycide gate electrode was 0.6 μm.
At m, the sidewall shape was vertical despite 100% overetching, and the amount of etching shift was almost zero. After being exposed to the atmosphere, the SiBrN-based protective film that had been expected to have been formed on the sidewalls of the polycide gate electrode during etching had disappeared.

Next, the mixing ratio of the etching gas HBr and N2 is determined by the etching rate of the poly-Si layer 3 and the S of the poly-Si layer 3.
The results of a detailed study on the influence on the selectivity between the iO2 film 2 and the resist mask 5 will be described.

[0025] HBr+N2 total flow rate 100 SCCM
and the flow volume ratio of N2/(HBr+N2) to 0.
Dry etching of the WSi layer 4 and the poly-Si layer 3 was carried out under the same conditions as described above except that the etching rate was changed between 20% and 20%.

FIG. 2 shows poly-Si by (HBr+N2)
FIG. 3 is a diagram showing the etch rate and selectivity of . According to Figure 2, as N2 is added to HBr, the etch rate of poly-Si and the selectivity of poly-Si to SiO2 increase significantly, reaching a peak at a mixed gas containing 5 to 10% N2, and If the amount is added above, it will decrease. On the other hand, the selectivity to resist hardly changes due to addition;
Maintains a score of 50 or higher. The addition of N2 to HBr is preferably 15% or less in terms of flow volume ratio.

Second Example Dry etching conditions were set as follows using the RIE apparatus. HBr+N2O 95 SCCM+
5 SCCM pressure
0.2 TorrRF power
300 W (13.56 MHz) Stage temperature: 40° C. The etch rate of the poly-Si layer 3 was 400 nm/min, and the etch rate of the WSi layer 4 was also approximately the same. The selectivity for the SiO2 film 2 was about 100, and the selectivity for the resist mask 5 was about 70.

Just etch 100 on the polycide layer 6.
% over-etching was performed to completely remove the polycide layer 6. Film reduction of SiO2 film 2 (overetch amount)
is about 40 Å, which poses no practical problem at all.

The thickness reduction of the resist mask 5 was about 160 Å, but the width of the polycide gate electrode was 0.6 μm.
At m, the sidewall shape was vertical despite 100% overetching, and the amount of etching shift was almost zero. After being exposed to the atmosphere, the SiBrN-based protective film that had been expected to have been formed on the sidewalls of the polycide gate electrode during etching had disappeared.

Next, we will explain the results of a detailed study on the influence of the mixing ratio of the etching gas HBr and N2O on the etch rate of the poly-Si layer 3 and the selectivity of the poly-Si layer 3 with respect to the SiO2 film 2 and the resist mask 5. do.

[0031] HBr+N2O total flow rate to 100 SCC
Dry etching of the WSi layer 4 and the poly-Si layer 3 was carried out under the same conditions as described above except that the flow volume ratio of N2 O/(HBr+N2 O) was changed between 0 and 20%.

FIG. 3 shows polyS by (HBr+N2O)
FIG. 3 is a diagram showing the etch rate and selectivity of i. According to Figure 3, as N2O is added to HBr, the etch rate of poly-Si and the selectivity of poly-Si to SiO2 increase significantly, reaching a peak at a mixed gas containing 5 to 10% N2O. , it decreases with further addition. on the other hand,
The selectivity to the resist hardly changes due to addition, but remains at about 70.

[0033] The addition of N2O to HBr is preferably 15% or less in terms of flow volume ratio. The dry etching conditions were set as follows using the RIE apparatus of the third embodiment.

Cl2 + N2 O 95
SCCM + 5 SCCM pressure 0.1 T
orrRF power 300W
(13.56MHz) Stage temperature
The etch rate of the poly-Si layer 3 at 40°C is 450 n
m/min, and the etch rate of the WSi layer 4 was also approximately the same. The selectivity for SiO2 film 2 is approximately 15
0, and the selectivity with respect to resist mask 5 was about 70.

Just etch 100 on the polycide layer 6.
% over-etching was performed to completely remove the polycide layer 6. Film reduction of SiO2 film 2 (overetch amount)
is about 30 Å, which poses no practical problem at all.

The film reduction of the resist mask 5 was about 180 Å, but the width of the polycide gate electrode was 0.6 μm.
At m, the sidewall shape was vertical despite 100% overetching, and the amount of etching shift was almost zero. After being exposed to the atmosphere, the SiClN-based protective film that had been expected to have been formed on the sidewalls of the polycide gate electrode during etching had disappeared.

Next, etching gas Cl2 and N2O
The mixing ratio of poly-Si layer 3 is the etch rate of poly-Si layer 3,
The results of a detailed study on the influence of the resist mask on the selectivity between the SiO2 film 2 and the resist mask 5 will be described.

[0038] Cl2 + N2 O total flow rate 100 SC
Dry etching of the WSi layer 4 and the poly-Si layer 3 was performed using CM as CM and changing the flow volume ratio of N2O/(Cl2+N2O) between 0 and 30%, and other conditions being the same as described above.

FIG. 4 is a diagram showing the etch rate and selectivity of poly-Si by RIE (Cl 2 +N 2 O). According to Figure 4, as N2O is added to Cl2, the etch rate of poly-Si and the selectivity of poly-Si to SiO2 increase significantly, reaching a peak at a mixed gas containing 5 to 10% N2O. , it decreases with further addition. On the other hand, the selectivity to the resist hardly changes due to addition, but remains at about 60.

[0040] The addition of N2 O to Cl2 is preferably 15% or less in terms of flow volume ratio. Fourth Example Dry etching conditions were set as follows using an ECR plasma etching apparatus.

Cl2 + N2 O 45
SCCM + 5 SCCM pressure 0.002
Torr microwave power 1.5 kW
Stage temperature: The etch rate of the room temperature poly-Si layer 3 is 300 nm/min, and the WSi
The etch rate of layer 4 was also approximately the same. The selectivity to SiO2 film 2 was about 50.

Just etch 100 on the polycide layer 6.
% over-etching was performed to completely remove the polycide layer 6. Film reduction of SiO2 film 2 (overetch amount)
is about 60 Å, which poses no practical problem at all.

[0043] The width of the polycide gate electrode is 0.6 μm.
The sidewall shape was vertical despite 100% overetching, and the amount of etching shift was almost zero. After being exposed to the atmosphere, the SiClN-based protective film that had been expected to have been formed on the sidewalls of the polycide gate electrode during etching had disappeared.

Next, etching gas Cl2 and N2O
The mixing ratio of poly-Si layer 3 is the etch rate of poly-Si layer 3,
The results of a detailed study on the influence of .

[0045] Cl2 + N2 O total flow rate is 50SCCM
Dry etching of the WSi layer 4 and the poly-Si layer 3 was carried out under the same conditions as described above, except that the flow volume ratio of N2 O/(Cl2 +N2 O) was varied between 0 and 40%.

FIG. 5 is a diagram showing the etch rate and selectivity of poly-Si by ECR (Cl 2 +N 2 O). According to Figure 5, as N2O is added to Cl2, the etch rate of poly-Si and the selectivity of poly-Si to SiO2 increase significantly, reaching a peak at a mixed gas containing 10 to 20% N2O. , it decreases with further addition.

[0047] The addition of N2 O to Cl2 is preferably 25% or less in terms of flow volume ratio. FIG. 6 is a diagram showing the relationship between overetching and etching shift amount in ECR plasma etching.

As shown in this figure, in a mixed gas (Cl2 + N2 O) containing 10% N2O, even if overetching is applied by 80%, the amount of etching shift is almost zero. On the other hand, with a gas containing only Cl2 and no N2O, the etching shift amount increases linearly to the positive side when the overetch exceeds 20%.

Although the above embodiment describes anisotropic dry etching of polycide of polySi and WSi, the method of the present invention can be used for other high melting point metals, such as M
o, Ti silicide and polySi polycide gate electrode can be vertically dry etched with a high selectivity.

[0050]

[Effect of the invention] As explained above, according to the present invention,
In anisotropic dry etching, the selectivity of the polysilicon layer or polycide layer to the silicon oxide film and resist can be increased, and the shape can be precisely maintained perpendicular to the substrate surface, and the etching shift is also small. can.

According to the present invention, a silicon-based conductive film can be processed with high precision to obtain a fine wiring pattern. The present invention is particularly effective in forming polycide gate electrodes, and contributes to higher integration and higher speed of devices.

[Brief explanation of drawings]

FIGS. 1(a) and 1(b) are cross-sectional views for explaining an example of etching.

FIG. 2 is a diagram showing the etch rate and selectivity of poly-Si by (HBr+N2).

FIG. 3 is a diagram showing the etch rate and selectivity of poly-Si by (HBr+N2O).

FIG. 4 is a diagram showing the etch rate and selectivity of poly-Si by RIE (Cl2+N2O).

FIG. 5 is a diagram showing the etch rate and selectivity of poly-Si by ECR (Cl2+N2O).

FIG. 6 is a diagram showing the relationship between overetching and the amount of etching shift.

FIG. 7 is a conceptual diagram of a parallel plate type reactive ion etching apparatus.

FIG. 8 is a conceptual diagram of an electron cyclotron resonance plasma etching apparatus.

FIGS. 9(a) to 9(c) are cross-sectional views for explaining a conventional example of etching.

FIG. 10 is a diagram showing the etch rate and selectivity of poly-Si by (HBr+O2).

FIG. 11 is a diagram showing the selectivity of poly-Si to resist due to (Cl2+O2).

[Explanation of symbols]

1 is a semiconductor substrate, Si substrate 2 is a silicon oxide film, and SiO2 film 3 is poly-Si.
The layer 4 is a WSi layer 5 is a mask, the resist mask 5a is a resist mask 6 after etching, the wafer 7 is a stage 8, the heater 9 is a vacuum chamber 10, the shower head 11 is a gas supply port 12, the RF power source 13 is a microwave The oscillator 14 has a coil 15 with an undercut sidewall adhesion film 16.

Claims (3)

[Claims] [Claim 1] A polysilicon layer (3) formed on a semiconductor substrate (1) via a silicon oxide film (2).
Alternatively, a method for manufacturing a semiconductor device characterized in that when etching the polycide layers (3, 4) using a mask (5), anisotropic etching is performed using a mixed gas of hydrogen bromide and nitrogen as an etching gas. . [Claim 2] A polysilicon layer (3) formed on a semiconductor substrate (1) via a silicon oxide film (2).
Alternatively, when etching the polycide layers (3, 4) using the mask (5), a mixed gas of hydrogen bromide and nitrous oxide is used as an etching gas to perform anisotropic etching. Production method. [Claim 3] A polysilicon layer (3) formed on a semiconductor substrate (1) via a silicon oxide film (2).
Alternatively, a method for manufacturing a semiconductor device characterized in that when etching the polycide layers (3, 4) using the mask (5), anisotropic etching is performed using a mixed gas of chlorine and nitrous oxide as an etching gas. .