JPH03127826A - Dry etching method - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention]

[Summary] Regarding the dry etching method of a workpiece consisting of a layered structure of tungsten silicide and polycrystalline silicon, the workpiece is etched vertically and the polycrystalline silicon is etched with a high selectivity to the underlying silicon oxide film. The purpose of the present invention is to provide an etching method using a mask in which a resist and an insulating film that does not contain C as a constituent material are laminated above and below, and a chlorine-containing gas and a BCf3 of 10% or less for the chlorine-containing gas. , 50% or less HBr, or 50% or less Br.
a and CCl4. cia and 5iC14+ or cc
Using a second etching gas selected from a mixture of i4 and O8 or CCl4 alone, the temperature of the workpiece was increased to 15%.
A first step of etching the tungsten silicide at a temperature below 0° C., a second step of removing the resist,
Using an insulating film that does not have C as a constituent material as a mask,
using the first mixed gas at below 0°C, or HBr alone;
A third step of etching polycrystalline silicon using a third etching gas selected from a mixed gas containing mainly HBr and less than 50% CL added thereto. [Industrial Application Field] The present invention relates to a method for dry etching a workpiece having a layered structure of tungsten silicide and polycrystalline silicon. With the miniaturization of semiconductor devices, materials with a two-layer structure of tungsten silicide and polycrystalline silicon, which have relatively low resistance, are often used for gate electrodes and wiring. A dry etching method using S・F8 or CI2* is provided for etching these (VLSI Manufacturing Technology, January 14, 1989, published by Nikkei BP, Vol. 25).
However, from the viewpoint of miniaturization that is recently required, undercuts tend to occur, dimensional accuracy is poor, and the etching selectivity of polycrystalline silicon to the underlying silicon oxide film (S i O , simply called "selectivity ratio")
Therefore, there is a need for a fine pattern forming technology that meets these requirements. [Prior Art] Conventional techniques for dry etching a two-layer structure of tungsten silicide and polycrystalline silicon include the following. [i] Dry etching method using SF8 or a mixed gas of SF and 02. [Literature core: “Etching of polycide structures by SFa glow discharge using a low frequency excited parallel plate reactor: M, E. Coe, S, H, Rogers: 5solid 5tat
e technology (Japanese version), 0cto
ber 1982] [2] Reactive ion etching (RIE) method using a mixed gas of Cβ2 and 02.

[3] Using CL and gas, electron cyclotron resonance (E
CR) Dry etching method using plasma. [4] Using a mixed gas of SFj and C, Cβ2F8, E
Dry etching method using CR plasma. [5] Cni and C0g4. Cta2 and SiC Shinobu. Or cci! , 4 or 02 [Problem to be solved by the invention] However, RIE by SF (11 tends to cause undercuts. Also, when using oxygen as an additive gas, When used, it has the effect of increasing the selectivity of polycrystalline silicon to the underlying silicon oxide film (SiO2), but it is not possible to obtain a vertical shape of the two-layer structure workpiece, and it also promotes the receding of the mask material, resulting in poor dimensional accuracy. Similarly, in the case of RIE [2] using a mixed gas of Cβ2 and 03, a vertical shape of the two-layer structure workpiece cannot be obtained, and the pattern accuracy is poor because the mask material also recedes. In the etching method using electron cyclotron resonance (ECR) [3], when attempting to obtain a vertical shape of a two-layer structure workpiece, the selectivity to SiO) becomes less than 5; If you raise it up, you won't get a vertical shape. Therefore, two-step etching is being considered, which is performed under conditions that provide a vertical shape and conditions that provide a high selectivity, but if the etching time of the second step is prolonged, the shape of the polycrystalline silicon layer deteriorates. . Therefore, this etching method [3] cannot be used where there are steps. And CTCβz used in the etching method of [4]
Since Fm is a gas subject to fluorocarbon regulations, it will no longer be possible to use it. With the etching method [5], it is difficult to achieve both a high selectivity and a vertical shape. Therefore, the present invention aims to vertically etch a workpiece having a layered structure of tungsten silicide and polycrystalline silicon, and to provide an etching method in which polycrystalline silicon has a high selectivity with respect to the underlying silicon oxide film. purpose. [Means for Solving the Problems] The above-mentioned problems in the method of dry etching a workpiece having a layered structure of tungsten silicide and polycrystalline silicon are solved by the following method. (1) In a dry etching method for a workpiece consisting of a layered structure of tungsten silicide and polycrystalline silicon, a mask consisting of a resist and an insulating film that does not contain C as a constituent material is used, and a chlorine-containing gas and a chlorine-containing gas are used. A first etching gas in which a chlorine-containing gas is mixed with an additive gas consisting of one or more of 10% or less BCl3, 50% or less HBr, or 50% or less Br, or Cl
2 and CC: L, Cl2 and 5il14+ or CC
Using a second etching gas selected from a mixed gas of l4 and 02 or CC1 alone, the temperature of the workpiece was increased to 15
A first step of etching the tungsten silicide at a temperature below 0° C., a second step of removing the resist, and using an insulating film that does not have C as a constituent material as a mask.
using the first mixed gas at below 0°C, or HBr alone;
A third step of etching polycrystalline silicon using a third etching gas selected from a mixed gas mainly containing HBr and containing less than 50% Cl2. (2) A mixed gas in which one or more of nitrogen, oxygen, and a rare gas element is added to one or more of the first etching gas, second etching gas, or third etching gas in each step, It is characterized by using (1
) Dry etching method (3) The resist removing device used in the second step is a down-flow type device in which the workpiece is not directly exposed to plasma, and oxygen, or mainly oxygen, nitrogen, hydrogen, water, and the The dry etching method according to (1) or (2), characterized in that the dry etching method is carried out using a mixed gas to which 10% or less of any one or more of halogen gases is added as an ashing gas. [Operation] In order to clarify the structure of the present invention, experimental results by the present inventor will be explained below with reference to the drawings. In addition, in the figure, 1 is a silicon substrate, 2 is a 5iO- layer, 3 is polycrystalline silicon,
4 is tungsten silicide, 5 is 5iOz film mask,
6 is a resist. (First Step) When etching tungsten silicide in the first step, undercutting occurred when using an etching gas containing only chlorine (see FIG. 2). Therefore, a gas that forms a film that protects the sidewalls of tungsten silicide was added to chlorine. The additive gases are boron trichloride, hydrogen bromide, carbon tetrachloride, and silicon tetrachloride. This resulted in a vertical shape without undercuts (see Figure 3). However, this. The sidewall protective film is not formed by the action of the additive gas alone, but is a protective film formed by the action of carbon and hydrogen from the resist. This is because an SiO2 film was used as a mask material and the tungsten silicide was etched with a mixed gas of chlorine and boron trichloride, but an undercut occurred (see
(see figure). In addition, the reason why the amount of boron trichloride added is 10% or less relative to the chlorine is that if the amount added exceeds 10%, the etch rate of tungsten silicide will be below a practical level, and the shape will deteriorate and the vertical (See Figures 5 and 6). For the same reason, the amount of hydrogen bromide added was set at 50% or less (see Figure 7).
. Furthermore, it has been found that when the etching gas of the present invention is used, tungsten silicide is hardly etched when the substrate temperature is low. This is shown in FIGS. 8 and 9. Figure 8 shows the case where a mixed gas of chlorine and boron trichloride at a ratio of 6% to the chlorine is used as the etching gas, and Figure 9 shows a mixed gas of chlorine and hydrogen bromide at a ratio of 20% to the chlorine. This is the case when the etching gas is used. Therefore, in practice, it is desirable that the substrate temperature be 20° C. or higher. Note that the upper limit of the substrate temperature was set to 150° C. in consideration of the heat resistance of the resist. (Third step) When etching polycrystalline silicon with a mixed gas of chlorine and boron trichloride in the third step, it is better to use a film that does not contain carbon as a mask than to use a resist mask. Etching is possible with high selectivity. Here, Table 1 shows examples of changes in selectivity due to the influence of carbon. The etching conditions at this time were a chlorine flow rate of 80 sec.
, boron trichloride flow rate is 5 sec, r f power is 0
．． The temperature was 66 w/crrr, the pressure was 0.10 Torr, and the substrate temperature was 0°C. (Margins below) Table 1. Influence of Carbon Also, by keeping the temperature below 0°C, polycrystalline silicon can be etched without etching tungsten silicide (see Figure 8). This development was also observed when a mixed gas of chlorine and hydrogen bromide and a mixed gas of chlorine and bromine were used (see FIG. 9). Next, when hydrogen bromide alone or a mixed gas consisting of hydrogen bromide and less than 50% chlorine is used as an etching gas, polycrystalline silicon can be etched without etching tungsten silicide ( (See Figure 7). This phenomenon was also observed when a mixed gas consisting of bromine and chlorine in an amount less than 50% relative to the bromine was used. (Second step) If the resist used in the second step is removed using equipment that directly exposes the workpiece to oxygen plasma, the surface of the polycrystalline silicon exposed in the first step will oxidize and form a silicon oxide film. However, a delay time occurred in the subsequent third step of etching polycrystalline silicon. Therefore, in order to increase the throughput, it is not preferable to form the silicon oxide film. Therefore, an apparatus and process in which the silicon oxide film is difficult to form are desired. For this purpose, a down-flow type device in which the workpiece is not directly exposed to plasma is suitable. Also, for the ashing gas, it is better to use a mixed gas containing oxygen and one or more of nitrogen, hydrogen, water, or a halogen gas added at 10% or less to the oxygen, rather than using oxygen gas alone.
A silicon oxide film is difficult to form on the surface of polycrystalline silicon. Furthermore, if the amount of halogen-based gas added exceeds 10%, undercuts may occur in tungsten silicide and polycrystalline silicon, and etching in the subsequent third step may cause a decrease in selectivity. It is. [Example 1] FIG. 10 is a sectional view of a parallel plate electrode type RIE apparatus used in carrying out the present invention. In the figure, 7 is an etching chamber, 9 is a cooling water circulation mechanism, 10 is a fluorescent optical fiber thermometer, and 12 is an electrostatic sample. 13 is a He gas supply port, 11 is a He gas exhaust port, 18 is a high frequency power source,
8 is an insulator, 14 is a sample, 15 is a fluorescent material, 16 is a gas supply port, 17 is an electrostatic chuck, and 19 is a gas exhaust port. A mixed gas of, for example, Cl, z, and B CQ s was introduced into the etching chamber 7 and exhausted from the gas exhaust port 19 to maintain the pressure inside the reaction chamber at 0.05 Torr. Then, a power of 150 W to 250 W at a frequency of 13.56 MH was applied per substrate from the high frequency power source 18. Then, the sample was dry etched. The pressure of the He gas used for heat transfer was all set at 2 Torr. Also, the substrate temperature during etching was measured using a fluorescent optical fiber thermometer.
Measured at 0. FIG. 11 is a schematic diagram of a microwave downflow ashing device used for resist removal. A punching board 24 was placed between the plasma chamber 23 and the reaction chamber in which the sample 25 was placed. A heater 27 is provided inside the stage 26, and the temperature can be adjusted from 40°C to 400°C. The resist ashing conditions are as follows: pressure in the reaction chamber is 0-3 Torr, and microwave output is 1.
5KW, 02 flow rate is ILSM, stage temperature is 160℃
And so. A schematic cross-sectional view of the sample used in the present invention is shown in FIG. In the figure, a Sing film 2 with a thickness of 100 Å is formed by thermal oxidation as an insulating film on a silicon substrate 1, and a Sing film 2 with a thickness of 200 Å is formed on it by CVD (chemical vapor deposition).
polycrystalline silicon 3 is formed, and the same CV
Tungsten silicide 4 having a thickness of 2000 Å was formed by method D. Subsequently, phosphorus was implanted using the ion implantation method. Further, a Sing film 5 having a thickness of 1000 Å was formed thereon by the CVD method, and a mask pattern having a line width of 0.3 μm and a thickness of 1 μm was formed using a resist 6 thereon. Using the resist mask, CVD-S
A 5ins film mask was formed by etching the iO* film. Next, examples will be shown. Note that the shape after etching was observed using a scanning electron microscope (SEM). [Example 1] In the first step, a parallel plate type RIE apparatus shown in FIG.
Using 0s105e, rf power is 150W, pressure is 0
．． Etching of the tungsten silicide of the sample shown in Fig. 12 was carried out at a temperature of 80°C and a substrate temperature of 80°C (since there is almost no difference between the temperature of the substrate and the temperature of the workpiece, the temperature of the workpiece is hereinafter referred to as the substrate temperature). . In the subsequent second step, a microwave downflow ashing device shown in Fig. 11 is used, and the ashing gas is oxygen (the flow rate is ISLM).
), the microwave power was 1.2kw, the pressure was 0.
The resist was removed at a temperature of 80 Torr and a stage temperature of 160°C. Then, in the third step, the first
Using the parallel plate type RIE device shown in Figure 0, the etching gas was a mixed gas of chlorine and boron trichloride (the flow rate was 90%
scc+a, boron trichloride is 10 sec),
Polycrystalline silicon was etched at an RF power of 150 W, a pressure of 0.5 Torr, and a substrate temperature of 0.degree. As a result, the selectivity to the underlying silicon oxide film is 26.
Thus, the vertical shape shown in FIG. 13 was obtained.

[Example 2] In the first step, a parallel plate type RIE apparatus shown in FIG.
The tungsten silicide of the sample shown in FIG. 12 was etched using an RF power of 150 W, a pressure of 0.05 Torr, and a substrate temperature of 80°C. In the subsequent second step, oxygen (
The flow rate is ISLM), and the microwave power is 1.2k.
w, pressure is 0.80 Torr, stage temperature is 160
℃ and the resist was removed. In the third step, a parallel plate type RIE apparatus shown in FIG. 10 was used, and a mixed gas of chlorine and hydrogen bromide (flow rate was 80 sec for chlorine and 20 sec for hydrogen bromide) was used as the etching gas. Power is 250w1 Pressure is 0.05Torr
, polycrystalline silicon was etched at a substrate temperature of 0°C. As a result, the selectivity to the underlying silicon oxide film was 40, and the vertical shape shown in FIG. 12 was obtained. [Example 3] In the first step, a parallel plate type RIE apparatus shown in FIG.
The tungsten silicide of the sample shown in FIG. 12 was etched using an RF power of 150 ws, a pressure of 0.5 Torr, and a substrate temperature of 80.degree. In the subsequent second step, the microwave downflow ashing device shown in Fig. 11 is used, oxygen is used as the ashing gas (flow rate is ISLM), and the microwave power is 1.
．． The resist was removed under conditions of 2 kW, a pressure of 0.80 Torr, and a stage temperature of 160°C. In the third step, a parallel plate type RIE apparatus shown in FIG. 10 is used, and a mixed gas of chlorine and hydrogen bromide (
The flow rate is 50 sec for chlorine and 50 sec for hydrogen bromide.
m), rf power is 250W, pressure is 0,05
Polycrystalline silicon was etched at a substrate temperature of 80° C. and Torr. As a result, the selectivity to the underlying silicon oxide film was 40, and the vertical shape shown in FIG. 13 was obtained. 0 [Example 4] In the first step, a parallel plate type RIE apparatus shown in FIG.
Using 0s105e, rf power is 150W, pressure is 0
The tungsten silicide of the sample shown in FIG. 12 was etched at a temperature of 80° C., 05 Torr, and a substrate temperature of 80° C. In the subsequent second step, oxygen (
The flow rate is ISLM), and the microwave power is 1.2k.
w, pressure is 0.80 Torr, stage temperature is 160
℃ and the resist was removed. In the third step, using the parallel plate type RIE apparatus shown in FIG. 10, hydrogen bromide gas (flow rate: 50 sec
m), rf power is 250W, pressure is 0.05T
Polycrystalline silicon was etched at a substrate temperature of 80°C. As a result, the selectivity to the underlying silicon oxide film was 60, and the vertical shape shown in FIG. 13 was obtained. [Example 5] In the first step, a parallel plate type RIE apparatus shown in Fig. 10 was used, and the etching gas was a mixed gas of chlorine and hydrogen bromide (the flow rate was 80 sec for chlorine and 20 sec for hydrogen bromide).
cm) with an RF power of 250W. The pressure was 0, 05 Torr, and the substrate temperature was 80°C.
The tungsten silicide of the sample shown in FIG. 12 was etched. In the subsequent second step, the microwave downflow ashing device shown in Fig. 11 was used, oxygen was used as the ashing gas (flow rate was ISLM), the microwave power was 1.2 kW, the pressure was 0, 80 Torr, and the stage temperature was The resist was removed at 160°C. Then, in the third step, the parallel plate type RI shown in FIG.
E equipment was used, and the etching gas was a mixed gas of chlorine and boron trichloride (the flow rate was 90 sec for chlorine, 10 sec for boron trichloride, RF power was 150 W, the pressure was 0.5 Torr, and the substrate temperature was 0°C). , polycrystalline silicon was etched. As a result, the selectivity to the underlying silicon oxide film was 26, and the vertical shape shown in FIG. 12 was obtained. [Example 6] In the first step, the 10th Using the parallel plate type RIE device shown in the figure, the etching gas was a mixed gas of chlorine and hydrogen bromide (the flow rate was 80 sec for chlorine and 20 sec for hydrogen bromide).
cm), rf power is 250 W% pressure is 0.
The tungsten silicide of the sample shown in FIG. 12 was etched at a temperature of 0.05 Torr and a substrate temperature of 80.degree. In the subsequent second step, a microwave downflow ashing device shown in FIG.
The resist was removed at a ws pressure of 0, 80 Torr, and a stage temperature of 160°C. In the third step, using the parallel plate type RIE apparatus shown in FIG. 10, a mixed gas of chlorine and hydrogen bromide was used as the etching gas (the flow rate was 80 sec for chlorine and 20 sec for hydrogen bromide).
m), rf power is 250W, pressure is 0.05T
Polycrystalline silicon was etched at a substrate temperature of 0°C. As a result, the selectivity with respect to the underlying silicon oxide film was 45, and the vertical shape shown in FIG. 13 was obtained. [Example 7] In the first step, a parallel plate type RI E shown in FIG.
Using a device, a mixed gas of chlorine and hydrogen bromide is used as the etching gas (flow rate is 80 sec for chlorine and 20 sec for hydrogen bromide).
ecm), RF power is 250W, pressure is 0,
The tungsten silicide of the sample shown in FIG. 12 was etched at a temperature of 0.05 Torr and a substrate temperature of 80.degree. In the subsequent second step, a microwave downflow ashing device shown in Fig. 11 was used, oxygen was used as the ashing gas (flow rate was ISLM), and the microwave power was 1.2 kW.
The resist was removed under a pressure of 0.80 Torr and a stage temperature of 160°C. And in the third step,
Similarly, a parallel plate type RIE apparatus shown in FIG. 10 was used, and a mixed gas of chlorine and hydrogen bromide (flow rate was 50 sec for chlorine and 50 sec for hydrogen bromide) was used as the etching gas.
Polycrystalline silicon was etched at an RF power of 250 W, a pressure of 40,05 Torr, and a substrate temperature of 80°C. As a result, the selectivity to the underlying silicon oxide film was 50, and the vertical shape shown in FIG. 13 was obtained. [Example 8] In the first step, a parallel plate type RIE apparatus shown in Fig. 10 was used, and the etching gas was a mixed gas of chlorine and hydrogen bromide (the flow rate was 80 sec for chlorine and 20 sec for hydrogen bromide).
cm) with an RF power of 250W. The pressure was 0, 05 Torr, and the substrate temperature was 80°C.
The tungsten silicide of the sample shown in FIG. 11 was etched. In the subsequent second step, a microwave downflow ashing device shown in FIG. 11 was used, and oxygen (flow rate was ISLM) was added to the ashing gas. Microwave power is 1゜2kW, pressure is 0.8
The resist was removed at a temperature of 0 Torr and a stage temperature of 160°C. Then, in the third step, the first
Using the parallel plate type RIE apparatus shown in Fig. 0, using hydrogen bromide gas (flow rate: 50 sec) as the etching gas, r
Etching of polycrystalline silicon was performed at an f power of 250 W, a pressure of 0.05 Torr, and a substrate temperature of 80.degree. As a result, the selectivity to the underlying silicon oxide film was 70, and the vertical shape shown in FIG. 13 was obtained. [Example 9] In the first step in Examples 5 to 8, when bromine was used instead of hydrogen bromide in the etching gas,
Similar results corresponding to those of Examples 5 to 8 were obtained. [Example 10] In the first step, a parallel plate type RI E shown in FIG.
Using a device, the etching gas is a mixed gas of carbon tetrachloride and oxygen (the flow rate is 250 sec for carbon tetrachloride and 20 sec for oxygen).
secm), rf power is 400W, pressure is 0
．． The tungsten silicide of the sample shown in FIG. 12 was etched at a temperature of 15 Torr and a substrate temperature of 80°C. In the subsequent second step, oxygen (
The flow rate is LSLM), and the microwave power is 1.2k.
w, pressure is 0.80 orr, stage temperature is 160
℃ and the resist was removed. Then, in the third step, using the parallel plate type RIE apparatus shown in FIG. 10, a mixed gas of chlorine and boron trichloride (flow rate is 90 sec for chlorine and 10 sec for boron trichloride) is used as the etching gas. Polycrystalline silicon was etched at a power of 150 W, a pressure of 0.05 Torr, and a substrate temperature of 0°C. As a result, the selectivity to the underlying silicon oxide film is 26.
As a result, the vertical shape shown in FIG. 13 was obtained. The etching gas used in the first step is a mixed gas of chlorine and carbon tetrachloride (the flow rate is 100 sccm for chlorine, 100 secm for carbon tetrachloride), or a mixed gas of chlorine and silicon tetrachloride (the flow rate is 100 sccm for chlorine). , silicon tetrachloride (100 sec)), similar results were obtained. [Example 11] In the first step, a parallel plate RIE apparatus shown in FIG. 10 was used, and the etching gas was a mixed gas of carbon tetrachloride 7 and oxygen (the flow rate was 250 sec
, oxygen at 20 sec) and rf power at 400 sec.
The tungsten silicide of the sample shown in FIG. 12 was etched at a pressure of 0.15 Torr and a substrate temperature of 8.0°C. In the subsequent second step, the microwave downflow ashing device shown in Fig. 11 was used, oxygen was used as the ashing gas (flow rate was ISLM), the microwave power was 1.2 kW, the pressure was 0, 80 Torr, and the stage temperature was The resist was removed at 160°C. In the third step, using the parallel plate RIE apparatus shown in FIG.
Polycrystalline silicon was etched using an RF power of 250w, a pressure of 0.05 Torr, and a substrate temperature of 0°C. As a result, the selectivity to the underlying silicon oxide film was 40, and the vertical shape shown in FIG. 12 was obtained. Similar results were obtained when a mixed gas of chlorine and carbon tetrachloride or a mixed gas of chlorine and silicon tetrachloride was used as the etching gas in the first step. [Example 12] In the first step, a parallel plate type RIE apparatus shown in FIG.
secm), the rf power was 400W, and the pressure was 0.
The tungsten silicide of the sample shown in FIG. 12 was etched at a temperature of 15 orr and a substrate temperature of 80°C. In the subsequent second step, a microwave downflow ashing device shown in Fig. 11 was used, oxygen was used as the ashing gas (flow rate was ISLM), and the microwave power was 1.2 kW.
Pressure is 0, 80 Torr, stage temperature is 160
℃ and the resist was removed. Then, in the third step, using the parallel plate RIE apparatus shown in FIG. Power is 250W, pressure is 0.05Torr
Polycrystalline silicon was etched at a substrate temperature of 80°C. As a result, the selectivity to the underlying silicon oxide film was 40, and the vertical shape shown in FIG. 13 was obtained. Similar results were obtained when a mixed gas of chlorine and carbon tetrachloride or a mixed gas of chlorine and silicon tetrachloride was used as the etching gas in the first step. [Example 13] In the first step, a parallel plate type RIE apparatus shown in FIG.
secm), rf power is 250W, pressure is 0
, 15 Torr, substrate temperature 8.0°C, 12th
The tungsten silicide of the sample shown in the figure was etched. In the subsequent second step, the microwave downflow ashing device shown in Fig. 11 was used, oxygen was used as the ashing gas (flow rate was ISLM), and the microwave power was 1.2.
kW, pressure is 0.80 Torr, stage temperature is 16
The temperature was lowered to 0° C., and the resist was removed. In the third step, using the parallel plate type RIE apparatus shown in FIG. 10, hydrogen bromide gas (flow rate: 50 se
cm), rf power is 250W, pressure is 0.05
Polycrystalline silicon was etched at a substrate temperature of 80° C. and Torr. As a result, the selectivity to the underlying silicon oxide film was 60, and the vertical shape shown in FIG. 13 was obtained. Similar results were obtained when a mixed gas of chlorine and carbon tetrachloride or a mixed gas of chlorine and silicon tetrachloride was used as the etching gas in the first step. [Example 14] In the third step in Example 3.4.7.8.9.12.13, when bromine was used as the etching gas instead of hydrogen bromide, the same procedure corresponding to each example was performed. The results were obtained. [Example 15] The first step and the third step in Example 1 to Example 14
When one of nitrogen and rare gas elements was added to each etching gas during the process, the etching rate of tungsten silicide and polycrystalline silicon was slower than the respective results, but the shape did not change. The selectivity to the underlying silicon oxide film was higher than the results obtained in Examples 1 to 14. [Example 16] The first step and the third step in Example 1 to Example 15
When oxygen is added to each etching gas in the process, the etch rates of tungsten silicide and polycrystalline silicon become faster than their respective results, and the selectivity to the underlying silicon oxide film becomes higher than their respective results. Ta. Vertical shapes were also obtained. [Example 17] In the second step in Examples 1 to 16, when the ashing gas was only oxygen, there was a delay of 6 seconds in the start of etching polycrystalline silicon in the subsequent third step. For oxygen, nitrogen, hydrogen, water, 1 for the oxygen
When a mixed gas containing at least one type of halogen gas added at 0% or less was used as the ashing gas, there was no such delay time and etching of polycrystalline silicon started immediately. When a halogen-based gas exceeding 10% of the oxygen was added, the lag time did not occur, but the selectivity to the underlying oxide film was lower than the results of each example. Furthermore, when the resist was removed by exposing the workpiece to oxygen plasma, there was a 15 second delay in starting the subsequent third step of etching polycrystalline silicon. [Example 18] In Examples 1 to 17, when a 5isN4 film was used as a mask instead of the Sing film mask, the results of Examples 1 to 17 were the same. [Effects of the Invention] As explained above, according to the present invention, the two-layer structure of tungsten silicide and polycrystalline silicon can be etched vertically and with a high selectivity.
This greatly contributes to the improvement of microfabrication technology for such semiconductor devices.

[Brief explanation of the drawing]

Figure 1 shows a test sample of the method of the present invention. Figure 2 is a cross-sectional view of a workpiece with an undercut caused by etching with chlorine. Figure 3 shows a workpiece with a vertical shape obtained using only a resist mask. Figure 4 is a cross-sectional view of a workpiece with an undercut caused only by the SiOw film mask. Figure 5 is a graph showing the relationship between tungsten silicide and polycrystalline with respect to the amount of boron trichloride (BCI23) added. Figure 6 is a graph showing changes in each etch rate of silicon.
BCj2. ), Figure 7 is a graph showing changes in the etching rates of tungsten silicide and polycrystalline silicon as a function of the amount of hydrogen bromide (HBr) added, and Figure 8 is a graph showing changes in the etching rates of tungsten silicide and polycrystalline silicon depending on the amount of hydrogen bromide (HBr) added. Figure 9 is a graph showing changes in the etch rates of tungsten silicide, polycrystalline silicon, and silicon oxide films with respect to substrate temperature when a mixed gas of chlorine and boron trichloride is used. 10 is a graph showing changes in etch rates of tungsten silicide, polycrystalline silicon, and silicon oxide film with respect to substrate temperature when mixed gas is used; FIG. The figure is a schematic diagram of the microwave downflow ashing device used to implement the method of the present invention, Figure 12 is a cross-sectional view of the sample used to implement the method of the present invention, and Figure 13 is a schematic diagram of the microwave downflow ashing device used to implement the method of the present invention. FIG. 3 is a cross-sectional view showing the vertical shape of the obtained workpiece. In the figure, 1 - silicon substrate, 2 - 3 iO, layer, 3 - polycrystalline silicon, 4 - tungsten silicon side, 5 -
SiOw film mask, 6-resist, 7-etching chamber, 9-cooling water circulation mechanism, 10-fluorescent optical fiber,
12-DC power supply source for electrostatically adsorbing the sample, 13-He gas supply port, 1l-He gas exhaust port, 1
8-high frequency power supply, 8-insulator, 14-sample, 15-fluorescent material, 5 16-gas supply port, 17-electrostatic chuck, 9-gas exhaust port 6. 3 Figure 7 v Guni sword and raw etching "Figure 2 10 0 0 Ch 711]t, BCI! 3111') Amount 1 inch of etching rate guest and Figure 5 d! 21 'MDIJ + 1 BrO amount 1: Yusu 4〕5 Etsunashi ←'s refreshing. Figure 7 Kore version 凰Anti ('C) rf / ``is' (1) open t(d
z+mouth Sr) pressure crab 0.05Torr

Claims (1)

[Claims] 1. In a dry etching method for a workpiece having a layered structure of tungsten silicide and polycrystalline silicon, using a mask in which a resist and an insulating film not containing C as a constituent material are stacked vertically, A first etching gas that is a mixture of a containing gas and an additive gas consisting of one or more of 10% or less BCl_3, 50% or less HBr, or 50% or less Br, or C
A first step of etching tungsten silicide using a second etching gas selected from l_2 and CCl_4, Cl_2 and SiCl_4, a mixed gas of CCl_4 and O_2, or CCl_4 alone, and at a temperature of 150° C. or less of the workpiece. and a second step of removing the resist, using an insulating film not having the C as a constituent material as a mask.
using the first mixed gas at below 0°C, or HBr alone;
Polycrystalline silicon is etched using a third etching gas selected from a mixed gas containing mainly HBr and less than 50% Cl added. A dry etching method comprising: a third step; and a third step. 2. Nitrogen, oxygen,
3. The dry etching method according to claim 1, wherein a mixed gas containing one or more of the rare gas elements is used in each step. Oxygen, or a mixed gas mainly composed of oxygen and containing at least one of nitrogen, hydrogen, water, or a halogen gas of up to 10% added to the oxygen, using a downflow type device that is not directly exposed to plasma. 3. The dry etching method according to claim 1, wherein the dry etching method is carried out using as an ashing gas.