JPH0382120A - Film patterning method - Google Patents

Abstract

PURPOSE:To suppress side etching by a method wherein mixed etching gas of chlorine and hydrogen bromide is used, the gas is brought into a plasmic state, it is fed to a polycrystalline silicon film and a tungsten silicide film, and the exposed tungsten silicide film and the polycrystalline silicon film are etched. CONSTITUTION:Chlorine and hydrogen bromide are brought into a plasmic state, a chemical reaction is generated by feeding the above-mentioned material in Plasmic state to films 3 and 4 which are exposed from a resist 5, and the polycrystalline silicon film 4 and the tungsten silicide film 3 are etched successively. In the above-mentioned state, a reaction product 6 is grown by the coupling of the carbon atoms, emitted from the resist 5, and the silicon atoms and the like, which are emitted from the film to be etched, are coupled with bromine atoms, the reaction product 6 is adhered to the side wall of the patterned films 3 and 4, and etching is inhibited. As a result, even when overetching is conducted for the purpose of removing the etching residue on the SiO2 film 2, side etching does not make progress, and also an undercut is not generated on the pattern.

Description

[Detailed Description of the Invention] [Summary] Regarding a method for patterning a film consisting of a polycrystalline silicon layer and a tungsten silicide layer, the purpose of this method is to improve the selectivity and pattern the cross-sectional shape of the film vertically. The polycrystalline silicon film and the tungsten silicide film, which were sequentially formed on the silicon film, are covered with a resist mask, and the tungsten silicide film and the polycrystalline silicon exposed from the resist mask are covered with a plasma of a gas containing chlorine and hydrogen bromide. The method includes etching the film and patterning the polycrystalline silicon film and the tungsten silicide film.

[Industrial application field]

The present invention relates to a method for patterning a film, and more particularly, to a method for patterning a film consisting of a polycrystalline silicon layer and a tungsten silicide layer.

[Conventional technology]

When forming electrode wiring in a semiconductor device, the fifth
As shown in the figure, a polycrystalline silicon film 41 and tungsten silicide II! 40 and 40 are sequentially formed on the substrate 42, and this two-layer structure film 43 is covered with a resist mask 44, and exposed through the resist mask 44 by reactive ion etching, electron cyclotron resonance (ECR) plasma etching, etc. I'm trying to etch some parts.

Next, the etching method will be specifically explained.

The first method is to use sulfur hexafluoride gas or a mixed gas of sulfur hexafluoride and oxygen to etch the two-layered film 43 by reactive ion etching (RIE). . The second method involves reactive ion etching using a mixed gas of chlorine and oxygen, and the third method involves etching using electron cyclotron resonance (ECR) plasma using chlorine gas. A fourth method includes etching with ECR plasma using a mixed gas of sulfur hexafluoride and Freon 113.

[Problem i1 to be solved by the invention] However, according to the first method, as shown in FIG. 6(a), undercuts are likely to occur in each of the tungsten silicide film 40 and the polycrystalline silicon film 41. In addition, when only sulfur hexafluoride gas is used, the selectivity for the base layer 45 made of 5iot is low, and when oxygen is added, the resist mask 44 is made thinner to improve the dimensional accuracy of the pattern. There is an inconvenience of lowering the value.

On the other hand, according to the second method, although the degree of undercut is small, the problem of thinning of the resist mask 44 still remains unsolved.

Further, according to the third method, by appropriately changing parameters such as the high frequency power supplied to the substrate 42, plasma power, pressure, temperature, etc., it is possible to adjust the cross-sectional shape of the pattern and the etching selection ratio with respect to the underlying layer. It is possible, but
If the parameters are adjusted so that the cross-sectional shape is vertical, the etching selectivity will be lowered. Further, if the selection ratio is adjusted to be high, an undercut as shown in FIG. 6(b) will occur in the pattern, and there is a problem that it is impossible to improve both of these at the same time.

In this case, it is also possible to divide the etching conditions into two stages, first performing etching under parameter conditions that improve the cross-sectional shape, and then changing the conditions so that the selectivity to the underlying layer 45 becomes high.

However, according to this method, as shown in FIG.
The lower electrode arrangement layer 46 is inserted through the glabella insulating film 47 consisting of h.
When a two-layer structure film 43 is formed on top and anisotropically etched, polycrystalline silicon 44 is formed on the sides of the lower wiring layer 46.
1 remained on the sidewall for 4 days, and the upper layer film 43
A problem arises in that the upper electrode wiring layer, which is formed by patterning into stripes, is short-circuited.

Therefore, it is possible to perform overetching to remove the sidewalls, but if the selectivity to the underlying Ji45 is increased, undercuts will occur in the upper layer film 43, and the cross-sectional shape of the pattern will not be vertical. If this is done, there is a problem that the selectivity becomes low and the glabellar insulating film 47 is removed.

Furthermore, according to the fourth method, both the cross-sectional shape and selection ratio cannot be improved at the same time, and furthermore, it is not desirable to use fluorocarbon gas 113 because it will be subject to fluorocarbon regulations in the future. .

The present invention has been made in view of these problems, and it is an object of the present invention to provide an etching method that can improve the selectivity and pattern the cross-sectional shape of a film vertically.

[Means to solve the problem]

The above-mentioned problem is solved by covering the polycrystalline silicon film and tungsten silicide film, which are sequentially formed on the silicon oxide film, with a resist mask, and then using plasma of a gas containing chlorine and hydrogen bromide to cover the tungsten silicide film exposed from the resist mask. The problem is solved by a film patterning method characterized in that the film and the polycrystalline silicon film are etched, and the polycrystalline silicon film and the tungsten silicide film are patterned.

In this case, the film patterning method is characterized in that the amount of hydrogen bromide added in the gas is 25% or less of the amount of chlorine added, or the etching is performed at a temperature in the range of 70°C to 150°C. This problem can be solved by a method of patterning the film.

[For production]

According to the present invention, an etching gas containing chlorine and hydrogen bromide is used to turn this into plasma. Plasma is then supplied to the tungsten silicide film and the polycrystalline silicon film to sequentially etch the tungsten silicide film and the polycrystalline silicon film exposed from the resist.

In this case, the tungsten silicide film and polycrystalline silicon film will be etched by chlorine plasma and bromine plasma, but elements such as carbon released from the resist and silicon released from the film combine with bromine, resulting in reaction products. to occur.

This reaction product adheres to the sidewalls of the patterned film and suppresses side etching, so that undercuts do not occur.

In addition, bromine has a high etching selectivity for the silicon oxide film, and the selectivity is improved compared to etching using only chlorine gas.

Furthermore, when the temperature is raised using a mixed gas of chlorine and hydrogen bromide, the etching rate of tungsten silicide films and polycrystalline silicon films increases, while the etching rate of silicon oxide films is mostly dependent on temperature. However, the selectivity to the silicon oxide film can be improved by adjusting the temperature.

In this case, if the amount of hydrogen bromide added is 25% or less of the amount of chlorine added, the etching rate of tungsten silicide increases as shown in Table 1, and the mixing ratio of chlorine and hydrogen bromide increases. However, the etching rate of the Si0g film does not change significantly. In addition, the above etching
When etching is performed at a temperature in the range from .degree. C. to 150.degree. C., the etching rate of the tungsten silicide film can be made almost the same as or higher than that of the polycrystalline silicon film, as illustrated in FIG.

Therefore, by early etching the tungsten silicide film, the underlying polycrystalline silicon film can be etched almost uniformly, reducing etching residue and shortening the overetching time. The etching selectivity for the SiO□ film can be increased.

[Example] Therefore, an example of the present invention will be described below based on the drawings.

FIG. 2 shows an etching apparatus for carrying out the present invention, and reference numeral 10 in the figure is a reaction chamber into which an etching gas is introduced. An electrode 13 connected to a power source 12 is provided,
Further, an electrostatic chuck 14 is attached to the front side of the electrode 13, and the substrate 1 is electrostatically attracted to the electrode 13 by the electrostatic chuck 14.

In addition, in the figure, the reference numeral 15 indicates the electrode 13 and the electrostatic chuck 1.
4, an optical fiber bar 17 is installed so as to face the inside of the reaction chamber 10 from the surface of the electrostatic chuck 13, and 17 determines the temperature based on the signal input from the optical fiber 16. A thermometer 19 indicates a cooling water flow pipe provided in the electrode 13, 20 indicates a DC power source for applying static electricity to the electrostatic chuck 14, and 21 indicates an exhaust port provided in the reaction chamber 10.

FIG. 1 is a cross-sectional process diagram showing an embodiment of the present invention, and reference numeral 1 in the figure is a semiconductor substrate made of silicon, germanium, etc. Human 5i(h membrane 2 is formed (Fig. 1(
a)).

In this state, a polycrystalline silicon film 3 with a thickness of 2,000 thick is formed on the SiO□ film 2, and a tungsten silicide film 4 with a thickness of 2,000 thick is formed thereon (FIG. 1(b)).
). These films 3 and 4 are formed by chemical vapor deposition or the like.

After this, a resist 5 is applied on the tungsten silicide film 4 for 1t! A stripe-like pattern with a width of 0.8 μm, for example, is formed by coating the film in a thickness of about m, and exposing and developing it.

After applying a fluorescent substance to the back of the semiconductor substrate l that has undergone such treatment, the semiconductor substrate l is placed in the reaction chamber lO of the etching apparatus described above, and the surface on which the resist 5 is formed is directed toward the gas inlet 11 side. When the semiconductor substrate 1 is brought close to the electrostatic chuck 14, the semiconductor substrate 1 is drawn toward the electrode 13 by static electricity.

Then, the gas in the reaction chamber 10 is removed from the exhaust port 21 to reduce the pressure, and chlorine (2 CI) and hydrogen bromide (HBr) are removed.
) is introduced into the reaction chamber 10 from the gas inlet 11. In this case, the pressure inside the reaction chamber 10 is set to 0.01 to 0°10 Torr.
pressure.

Also, frequency 13.56MH, hower 100~400w
A power of a magnitude of 1 is applied from the high frequency power supply 12 to the semiconductor substrate 1. Furthermore, helium gas is flowed into the gas pipe 15 at a pressure of 2 Torr to supply helium between the electrostatic chuck 14 and the semiconductor substrate 1, and heat is transferred from the semiconductor substrate 1 to the cooling water flow pipe 19 through the helium. By adjusting the temperature of the semiconductor substrate l to 10 to 90°C, or by attaching a heater (not shown) to the electrode 13,
It is adjustable up to C. The temperature of the substrate during etching is measured using a thermometer 14 based on the amount of light from the fluorescent material on the back surface of the semiconductor substrate 1.
judged by.

As a result, chlorine and hydrogen bromide are turned into plasma and supplied to the film 4.3 exposed from the resist 5 to cause a chemical reaction, and the polycrystalline silicon film 4 and the tungsten silicide film 3
are sequentially etched (Fig. 1(c)).

In this state, carbon atoms released from the resist 5 and silicon atoms released from the film to be etched combine with bromine atoms to form a reaction product 6, and this reaction product 6 forms a patterned film 4. It adheres to the sidewalls of 3 and prevents etching. Therefore, even if over-etching is performed to remove the upper etching residue on the Stag film 2, side etching does not proceed and no undercut occurs in the pattern (FIG. 1(d)).

By the way, the pressure inside the reaction chamber 10 was set to 0.05 Torr, the high frequency power was set to 300 W, and the temperature was set to 60° C.
When the etching rates of the tungsten silicide film 4, the polycrystalline silicon film 3.5iO1 film 2 were measured by changing the flow rates of chlorine and hydrogen bromide, the results shown in Table 1 were obtained.
It was confirmed that the etching rate could be controlled by changing the mixing ratio of chlorine and hydrogen bromide. In particular, the amount of change in the etching rate of the tungsten silicide film 4 increases.

space below] Here, the gas flow rates of chlorine and hydrogen bromide are each 80SC.
When the relationship between the temperature of the semiconductor substrate 1 and the etching rate was measured using a CM of 20 SCCM, a pressure of Q, 1 Torr, and a high frequency power source of 300 W, the results shown in FIG. 4 were obtained.

According to this, the etching rate of the tungsten silicide W144 and the polycrystalline silicon film 3 can be increased by increasing the temperature. Furthermore, at temperatures below 75°C, the etching rate of the polycrystalline silicon film 3 was higher than that of the tungsten silicide film 4, and at temperatures above 75°C, the etching rate of the tungsten silicide film 4 became larger.

This makes it possible to eliminate etching residues on the sidewalls 48 and the like even when patterning is performed on areas with steps as shown in FIG.

Moreover, it was confirmed that the etching rate of the Sing film 2 decreased slightly or did not change as the temperature was increased, and by increasing the temperature to 11 m, the selectivity of the polycrystalline silicon film 3 and the tungsten silicide film 4 to the Sing film 2 was increased. It becomes possible to increase the

For example, the flow rates of chlorine and bromine are each 803 CC)'l
.

20SCC? l, the pressure in the reaction chamber 10 is 0.05 Torr
, when the power of the high frequency power supply 12 is 250 W and the temperature of the semiconductor substrate 1 is 80° C., the tungsten silicide film 4 and the polycrystalline silicon lI! Both etching speeds of 3 are 23
50 entries/win, 5ift Etching speed of film 2 is 2
It was confirmed that the selectivity for the 5i(h film 2) was 10, and the cross-sectional shape of the pattern was vertical.

In addition, the flow rates of chlorine and bromine are 80SCCM and 11SCCM, respectively.
05CC, the pressure of the reaction chamber 10 is 0.05 Torr, the power of the high frequency power source 12 is 200 W, and the temperature of the semiconductor substrate 1 is 80° C., the etching rate of both the tungsten silicide film 4 and the polycrystalline silicon film 3 is 2220 people/+.
+in, Sin, etching speed of film 2 is 185 people/
+win, the selection ratio to the SiO□ film 2 is 12, and the cross-sectional shape of the pattern is vertical.

Note that if the substrate temperature is increased to 150°C or higher, problems such as changes in the shape of the resist mask pattern will occur, so for practical purposes, tungsten silicide film, polycrystalline silicon film, etc. Preferably, the membrane is etched.

Note that the above-described etching can be performed by the RIE method or by the ECR plasma etching method.

〔Effect of the invention〕

As described above, according to the present invention, an etching gas containing a mixture of chlorine and hydrogen bromide is used to turn it into plasma,
This plasma was supplied to the polycrystalline silicon film and tungsten silicide film to etch the tungsten silicide film and polycrystalline silicon film exposed from the resist, so that elements such as carbon released from the resist and silicon released from the film were etched. combines with bromine to produce a reaction product, which adheres to the sidewall of the patterned film, thereby suppressing side etching.

Furthermore, bromine has a high etching selectivity for silicon oxide films, and can improve the etching selectivity compared to the case where only chlorine gas is used for etching. Furthermore, when using a mixed gas of chlorine and hydrogen bromide, the etching rate of tungsten silicide films and polycrystalline silicon films increases as the temperature increases, while the etching rate of silicon oxide films mostly depends on temperature. Therefore, the selectivity to the silicon oxide film can be improved by temperature adjustment.

[Brief explanation of drawings]

FIG. 1 is a process diagram showing a cross section of an embodiment of the present invention. FIG. 2 is a schematic configuration diagram showing an example of an etching apparatus for implementing the present invention. FIG. 4 is a characteristic diagram showing the relationship between substrate temperature and etching rate according to the present invention; FIG. 5 is a sectional view showing an example of a conventional method; FIG. 6 is a sectional view showing an example of etching in a certain case; FIG. 7 is a sectional view showing an etching state by a conventional method. FIG. 7 is a perspective view showing another etching state by a conventional method. (Explanation of symbols) 1... Semiconductor substrate, 2 -s+oJs 3... Polycrystalline silicon film, 4... Tungsten silicide film, 5... Resist, 6... Reaction product, 10... - Reaction chamber, 11... Gas inlet, 12... High frequency power supply, 13... Electrode, 21... Exhaust port. Applicant Fujitsu Limited

Claims (3)

[Claims] (1) The polycrystalline silicon film and the tungsten silicide film formed in this order on the silicon oxide film are covered with a resist mask, and the tungsten silicide film and the tungsten silicide film exposed from the resist mask are covered with a plasma of gas containing chlorine and hydrogen bromide. A method for patterning a film, comprising etching the polycrystalline silicon film and patterning the polycrystalline silicon film and the tungsten silicide film. (2) A method for patterning a film, characterized in that the amount of hydrogen bromide added to the gas according to claim (1) is 25% or less of the amount of chlorine added. (3) The etching described in claim (1) is performed at 70°C at 15°C.
A method for patterning a film, characterized in that it is carried out at a temperature in the range of 0°C.