JPH1012598A - Semiconductor manufacturing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a semiconductor device, stabilizing a CD shift amount. SOLUTION: At the time of sequential etching processing S2 of a polysilicon film, formed on a silicon oxide film, dummy discharge S1 is performed in advance for twenty min. by using a dummy semiconductor substrate with the silicon oxide film by means of the etching device. A reaction product sticking to an etching device inner wall after dummy discharge is almost eliminated. Later, etching of a second film allows balanced state to be rached with a fewer number of sheets.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a plasma etching process.

[0002]

2. Description of the Related Art In describing a conventional plasma etching process, a plasma etching apparatus will be described first with reference to the drawings. FIG. 8 is a schematic diagram showing a configuration of a conventional plasma etching apparatus applied to the present invention. Referring to FIG. 8, a semiconductor wafer 2 is provided in reaction chamber 1.
Is mounted on the stage 3. Reaction chamber 1
A gas introduction pipe 4 for introducing a reactive gas into the reaction chamber 1 is provided at an upper portion of the reaction chamber 1. A microwave power supply 5 for generating microwaves is provided outside the reaction chamber 1. The microwave having a predetermined frequency generated by the microwave power supply 5 is introduced into the reaction chamber 1 through the waveguide 6 and the quartz window 7. A coil 8 for generating a magnetic field is provided on the outer periphery of the quartz window 7. This coil 8
As a result, a magnetic field having a predetermined magnetic flux density is applied in a direction substantially perpendicular to the surface of the semiconductor wafer 2. An exhaust port 9 is provided below the reaction chamber 1, and the inside of the reaction chamber 1 is evacuated by an exhaust means (not shown) such as a vacuum pump connected to the exhaust port 9. Is maintained.

The reaction chamber 1 is often made of a metal such as aluminum or stainless steel from the viewpoint of strength and ease of processing. When such a metal contaminates, for example, a transistor portion in a manufacturing process of a semiconductor device, there is a problem that its electrical characteristics are deteriorated and its reliability is deteriorated. Further, such a metal may be deteriorated or corroded by the impact of plasma. In order to avoid this problem, an inner wall 10 made of quartz or the like is provided inside the reaction chamber 1. This inner wall 1
Since 0 is installed in a vacuum, it is difficult to control its temperature. That is, the temperature of the inner wall 10 increases with the microwave discharge time.

In general, in mass production of semiconductor devices, for example, about 24 wafers are processed in each lot in one lot. For this reason, as described above, if the temperature of the inner wall rises with the discharge time, the etching characteristics such as the finished shape and the etching rate differ between the first sheet and the 24th sheet during the processing of one lot. Occurs. This is because the rate at which the reaction products generated by the reaction between the film to be etched or the resist and the reactive gas during the etching adhere to the inner wall depends on the temperature of the inner wall. One example is shown in FIG. This figure shows the dependence of the etching rate on the number of processed wafers when a polysilicon film is etched by chlorine plasma. As shown in FIG. 9, as the number of processed wafers increases from the first to fourth wafers, the etching rate decreases. The etching rate is substantially stable from the fifth sheet onward. This is because the temperature of the inner wall does not rise sufficiently until the fifth sheet, and SiCl _x as a reaction product
Is not sufficiently adhered to the wafer, and the amount thereof is re-adhered to the wafer.

In order to solve this problem, there is a method in which a discharge (dummy discharge) is performed using a silicon wafer immediately before the lot processing, and the lot processing is continuously performed after the inner wall is brought into a constant temperature state. FIG. 10 shows the dependence of the etching rate and the CD shift amount on the number of processed wafers when a dummy discharge is performed using a silicon wafer immediately before the lot processing. As shown in FIG. 11, an actual wafer for the lot process was used in which a silicon oxide film 11, a polysilicon film 12, and a photoresist were sequentially formed on a silicon substrate 2, and the photoresist 13 was patterned. Overetching was performed for the same time as the etching time of the polysilicon film. The etching rate was calculated based on the thickness of the polysilicon film and the etching time. Chlorine gas was used as a reactive gas.

As shown in FIG. 10, a value obtained by subtracting the line width a of the polysilicon film after etching from the line width b of the resist mask before etching is used as the CD shift amount. When the value is positive, it is called CD gain, and when the value is negative, it is called CD loss. As shown in FIG. 10, when a dummy discharge using a silicon wafer is performed,
The etching rate does not depend on the number of processed wafers and is almost constant. This is because the temperature of the inner wall of the reaction chamber becomes constant with the dummy discharge.

Further, based on the same concept as described above,
No. 851 discloses a method of performing a dummy discharge using a dummy wafer on which a film of the same quality as a film to be etched of a real wafer is formed. Also in this method, the temperature of the inner wall of the reaction chamber becomes constant with the discharge of the dummy wafer, and the etching rate is stabilized.

[0008]

However, when a silicon wafer itself is used as a dummy wafer or a silicon wafer having a film of the same quality as the film to be etched of a real wafer is used, the CD shift amount as shown below is required. There were fluctuations.

First, a silicon wafer is used as a dummy wafer.
When used as such, reactive gas is generated by dummy discharge.
Reaction product SiCl by the reaction of_xDeparts
Live. Also, for example, if the film to be etched on an actual wafer is
If it is a polysilicon film, the polysilicon film
When the dummy discharge is performed on the me wafer, the reaction product SiCl _x
Occurs. Some of the generated reaction products adhere to the inner wall
You. Therefore, after the dummy discharge,
Has a large amount of reaction products attached.

Next, when the processing of the actual wafer is started, a reaction product is generated during the main etching for etching the polysilicon film, and a part of the reaction product adheres to the inner wall. During the over-etching for etching the silicon oxide film, a part of the reaction product adhering to the inner wall is separated from the inner wall and re-adhered to the actual wafer. The reaction product re-adhered to the actual wafer becomes a sidewall protective film of the pattern of the polysilicon film. Therefore, the side walls of the pattern are hardly etched during over-etching, resulting in a CD gain.

By the way, a large amount of reaction products adhere to the inner wall before processing the actual wafer. In such a situation,
The amount of the reaction product released from the inner wall during the over-etching of the actual wafer is larger than the amount of the reaction product generated during the main etching of the actual wafer adhering to the inner wall. In addition, the amount of the reaction product generated during the main etching adheres to the inner wall is considered to be substantially the same in each actual wafer to be etched. Therefore, as the number of processed actual wafers increases, the amount of reaction products adhering to the inner wall of each actual wafer immediately before etching decreases. Therefore, the amount of reaction products re-attached during over-etching of each actual wafer is reduced, and the CD gain is reduced as shown in FIG.

Further, when the actual wafer is etched, the amount of the reaction product adhering to the inner wall during the main etching of the actual wafer and the amount of the reaction product detaching from the inner wall during the over-etching and re-adhering to the wafer are reduced. Are approximately equal and reach an equilibrium state. In such an equilibrium state,
As shown in FIG. 10, the CD shift amount becomes almost zero.

The number of processed actual wafers until the equilibrium state is reached depends on the amount of reaction products adhering to the inner wall of the actual wafer before processing. The larger the amount attached, the more actual wafers need to be processed until equilibrium is reached. That is, in the lot processing, there is a problem that the finished pattern shape of the actual wafer in the lot varies.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide a method of manufacturing a semiconductor device which suppresses a variation in a CD shift amount.

[0015]

According to a first aspect of the present invention, there is provided a method of manufacturing a semiconductor device, comprising the steps of: forming a second film formed on a first film on a semiconductor substrate into a resist patterned on the second film; Etching using the as a mask,
It has the following steps. As the dummy etching step, the first dummy film is etched in the reaction chamber using the first dummy semiconductor substrate on which the first dummy film of the same quality as the first film is formed. After the dummy etching step, the second films formed on each of the plurality of semiconductor substrates are sequentially etched in the reaction chamber.

According to this method, of the reaction products generated by the reaction between the reactive gas and the first dummy film in the dummy etching step, the amount of the reaction product adhering to the inner wall of the reaction chamber depends on the amount of the reaction product adhering to the inner wall. Much smaller than the amount that an object detaches. Therefore, the amount of the reaction product adhering to the inner wall of the reaction chamber decreases with the dummy etching time. As a result, of the plurality of semiconductor substrates, almost no reaction products adhere to the inner wall of the reaction chamber immediately before etching the second film on the first semiconductor substrate (hereinafter referred to as “initial state”).

Then, in the step of sequentially etching the second film on the semiconductor substrate, a part of the reaction product generated when the second film is etched adheres to the inner wall of the reaction chamber,
In addition, a part thereof is detached from the inner wall and reattached to the second film on the semiconductor substrate. In this way, the amount of reaction products attached to the inner wall increases. As the etching proceeds, an equilibrium state is reached in which the amount of the reaction product adhering to the inner wall and the amount of the reaction product detached from the inner wall and redeposited on the semiconductor substrate are substantially equal. At this time, the time required to reach the equilibrium state can be shortened by almost eliminating the reaction products attached to the inner wall in the initial state. That is, the number of semiconductor substrates to be processed after the first semiconductor substrate is processed until the equilibrium state is reached can be reduced. Therefore, the second semiconductor substrate formed on each of the plurality of semiconductor substrates
Variations in the CD shift amount of the film can be suppressed.

Preferably, the first dummy semiconductor substrate is formed by patterning a resist on the first dummy film.

In this case, in the dummy etching step, a part of the reaction product generated by the reaction between the reactive gas and the resist adheres to the inner wall of the reaction chamber. On the other hand, a part of the reaction product attached to the inner wall is separated from the inner wall. In this way, a certain amount of reaction product adheres to the reaction chamber wall in the initial state. Therefore, in the step of sequentially etching the second film on the semiconductor substrate, the number of semiconductor substrates to be processed before reaching the equilibrium state can be further reduced. Therefore, variation in the CD shift amount of the second film can be further suppressed.

Preferably, the dummy etching step further includes a step of etching the second dummy film in a reaction chamber using a second dummy semiconductor substrate on which a dummy film of the same quality as the second film is formed; After the step, the second semiconductor substrate formed on each of the plurality of semiconductor substrates is formed.
A step of sequentially etching the film in the reaction chamber.

In this case, the reactive gas and the second gas are etched by etching the second dummy film in the dummy etching step.
Part of the reaction product generated by the reaction with the dummy film adheres to the inner wall of the reaction chamber. On the other hand, the reaction product adhering to the inner wall of the reaction chamber is separated from the inner wall by the etching of the first dummy film. As a result, a certain amount of the reaction product adheres to the inner wall of the reaction chamber in the initial state. In addition, the amount of the reaction product is adjusted by etching the first dummy film and the second dummy film so that the second product on the semiconductor substrate in an equilibrium state is formed.
It approaches the amount of reaction products adhering to the inner wall just before etching the film. For this reason, in the step of sequentially etching the second film on the semiconductor substrate, the number of semiconductor substrates to be processed before reaching the equilibrium state can be further reduced. Therefore, variation in the CD shift amount of the second film can be further suppressed.

More preferably, the aperture ratio of the first dummy film by the resist on the first dummy semiconductor substrate is substantially the same as the aperture ratio of the second film by the resist on the semiconductor substrate.

In this case, by the etching of the first dummy film in the dummy etching step, a part of the reaction product generated by the reaction between the reactive gas and the resist adheres to the inner wall of the reaction chamber. Moreover, the amount of the reaction product generated by the reaction between the resist and the reactive gas in the step of etching the second film on the semiconductor substrate is substantially equal to the amount of the reaction product adhered to the inner wall. As a result, the amount of the reaction product attached to the inner wall of the reaction chamber in the initial state is almost equal to the amount of the reaction product attached to the inner wall immediately before the etching of the second film on the semiconductor substrate in the equilibrium state. Become equal. For this reason, in the step of sequentially etching the second film on the semiconductor substrate, the number of semiconductor substrates to be processed before reaching the equilibrium state can be further reduced. Therefore, variation in the CD shift amount of the second film can be further suppressed.

[0024]

BEST MODE FOR CARRYING OUT THE INVENTION

(Embodiment 1) Hereinafter, a plasma etching process according to Embodiment 1 of the present invention will be described with reference to the drawings. FIG.
Is an example showing the flow of the plasma etching process. Referring to FIG. 1, in the plasma etching process, first, dummy etching for dummy-discharging a dummy wafer is performed for 20 minutes (S3). Thereafter, 24 actual wafers are continuously discharged for 2 minutes each (S2).
As the actual wafer, one having a film structure having a silicon oxide film, a polysilicon film, and a patterned photoresist on a silicon substrate shown in FIG. 13 was used. As the dummy wafer, a wafer having the same silicon oxide film as the base film of the actual wafer deposited on a silicon substrate was used. Chlorine gas was used as an etching gas. As a time for the dummy discharge, a time when the temperature of the reaction chamber wall 10 and the like of the etching apparatus shown in FIG. In the present embodiment, the time is set to 20 minutes. In the actual wafer etching, the over-etching time was set to 100% of the main etching time.

Next, the processing result will be described. FIG. 2 shows the dependence of the etching rate of the actual wafer and the CD shift amount on the number of processed wafers. A silicon oxide film is formed on the dummy wafer used for the dummy etching. Therefore, the dummy etching corresponds to over-etching for etching the silicon oxide film of the actual wafer. During the overetching, a part of the reaction product adhered to the inner wall 10 of the reaction chamber mainly separates from the inner wall 10 and re-adheres to the wafer. Therefore, there is almost no reaction product adhering to the reaction chamber wall 10 after the dummy etching. With that state as an initial state, the actual wafer is first etched sequentially.

During the main etching of the first real wafer,
Some of the reaction products adhere to the inner wall 10. During the over-etching of the actual wafer, the reaction product is detached from the inner wall 10 and adheres again on the actual wafer. The reaction product re-adhered to the actual wafer acts as a sidewall protection film on the pattern sidewall of the polysilicon film. However, since the amount of the reaction product to be reattached is relatively small, the reaction product does not sufficiently function as the side wall protective film. Therefore, the side wall of the polysilicon film is etched during the over-etching. The width of the etched polysilicon film is shorter than the width of the resist before etching. That is, as shown in FIG.
The shift amount becomes a CD loss. After the first actual wafer is etched, the remaining reaction products that have not been removed by over-etching are attached to the inner wall 10.

In the subsequent etching of the actual wafer, the reaction product is detached from the inner wall 10 during the over-etching and reattached on the actual wafer. The amount of redeposition is
Before the actual wafer is etched, the reaction product is
Since it is attached to zero, the amount of the reaction product re-adhered to the previous actual wafer is larger. As a result, the amount of the reaction product acting as the sidewall protection film of the pattern increases.
Therefore, the finished shape of the pattern shifts from the CD loss to the CD gain.

When the actual wafers are sequentially etched, an equilibrium state is reached in which the amount of the reaction product adhering to the inner wall of each actual wafer is substantially equal to the amount of the reaction product detached from the inner wall and redeposited on the actual wafer. In the equilibrium state, as shown in FIG.
It has become. The change in the CD shift amount is recognized for the first few actual wafers, but the change amount is smaller than the result described in the section of the related art. In the case described in the section of the related art, a large amount of reaction products adhered to the inner wall in the initial state. On the other hand, in the case of the present embodiment, in the initial state, almost no reaction product adheres to the inner wall. That is, by eliminating almost all the reaction products attached to the inner wall in the initial state, an equilibrium state can be reached after processing three or four actual wafers.

As shown in FIG. 2, the etching rate showed a substantially constant etching rate regardless of the number of processed wafers. This is because the temperature of the inner wall 10 of the reaction chamber becomes constant during the dummy etching.

The etching rate of the silicon oxide film in this etching process is 50 ° / min. Therefore, the silicon oxide film of the dummy wafer is
By doing so, the dummy wafer can be repeatedly used for dummy discharge about several tens of times. Therefore, the manufacturing cost of the semiconductor device can be reduced.

Second Embodiment Next, a plasma etching process according to a second embodiment of the present invention will be described with reference to the drawings. FIG. 3 shows a film structure of a dummy wafer for dummy discharge used in the present embodiment. Referring to FIG. 3, the dummy wafer has a film 1 of the same quality as the base film of the actual wafer.
On top of this, a photoresist 13 is patterned.
The pattern of the resist may be different from the actual wafer,
It need not be a fine pattern. However, the aperture ratio, which is the ratio of the exposed area of the base film 11 to the wafer area, is
Desirably, it is equivalent to an actual wafer. The processing flow in the present embodiment is the same as the processing flow shown in FIG.

Next, the processing result will be described with reference to the drawings. FIG. 4 shows the dependence of the etching rate and the CD shift amount of the actual wafer on the number of processed wafers. A resist is patterned on the silicon oxide film of the dummy wafer. Therefore, in the dummy etching, a part of the reaction product generated by the reaction between the reactive gas and the resist adheres to the inner wall of the reaction chamber. On the other hand, a part of the reaction product attached to the inner wall is separated from the inner wall. Therefore, compared with the case of the first embodiment, a certain amount of the reaction product adheres to the inner wall of the reaction chamber after the dummy etching.
With that state as the initial state, the actual wafer is then sequentially etched.

During the main etching of the first actual wafer,
Some of the reaction products adhere to the inner wall 10. During the over-etching of the actual wafer, the reaction product is detached from the inner wall 10 and adheres again on the actual wafer. In addition, compared with the case of the first embodiment, since a certain amount of the reaction product is already attached in the initial state, a larger amount is attached again. Therefore, the reaction product more sufficiently acts as a sidewall protection film on the pattern sidewall of the polysilicon film of the actual wafer. This suppresses etching of the side wall of the polysilicon film during over-etching. Therefore, as compared with the case of the first embodiment, the value of the CD loss becomes smaller as shown in FIG.

Thereafter, when the actual wafer is sequentially etched, the equilibrium state is reached as described in the first embodiment, and the change in the CD shift amount becomes almost zero as shown in FIG.

In the case of the present embodiment, a certain amount of reaction product adheres to the inner wall 10 of the reaction chamber in the initial state. This reaction product functions as a sidewall protection film for the pattern. As a result, the etching of the actual wafer reaches an equilibrium state faster than in the case of the first embodiment, and the actual wafer becomes
An equilibrium state is reached after processing one sheet.

By the way, regarding the etching rate, FIG.
As shown in the figure, the etching rate was almost constant independently of the number of processed wafers. This is for the same reason as described in the first embodiment.

The photoresist etching rate in this plasma etching process is 400 ° /
min. Since the pattern of the dummy wafer used for the dummy etching need not be fine, the photoresist can be formed thick. For example, by setting the thickness to about 10 μm, one dummy wafer can be used about 10 times. Although the cost is higher than in the case of the first embodiment due to the patterning of the photoresist, the manufacturing cost can be reduced in that it can be used repeatedly.

(Embodiment 3) Next, a plasma etching process according to Embodiment 3 of the present invention will be described with reference to the drawings. FIG. 5 is a diagram showing the flow. FIG.
Referring to, this flow is performed before actual wafer processing (S2).
Dummy discharge 1 (S3) and dummy discharge 2 (S4) as dummy etching are provided. In the dummy discharge 1, a dummy wafer having a polysilicon film, which is a film of the same quality as the film exposed during the main etching of the actual wafer, was used. In the dummy discharge 2, a dummy wafer formed with a silicon oxide film, which is a film of the same quality as the base film of the actual wafer, was used.

Next, the processing result will be described. FIG. 6 shows the dependence of the etching rate and the CD shift amount of the actual wafer on the number of processed wafers. In the dummy discharge 1 (S3), a part of the reaction product generated by the reaction between the reactive gas and the polysilicon film adheres to the inner wall of the reaction chamber. In the dummy discharge 2 (S4), a part of the reaction product attached to the inner wall of the reaction chamber is separated from the inner wall. As a result, a certain amount of the reaction product adheres to the inner wall of the reaction chamber after the dummy etching. With this state as an initial state, the actual wafer is sequentially etched.

During the main etching of the first actual wafer,
Some of the reaction products adhere to the inner wall 10. During the over-etching of the actual wafer, the reaction product is detached from the inner wall 10 and adheres again on the actual wafer. In addition, this amount is close to the amount of the reaction product adhering to the inner wall immediately before etching each actual wafer in the equilibrium state of the actual wafer by performing the dummy discharge 1 and the dummy 2.
This reaction product acts more sufficiently as a sidewall protective film. This suppresses etching of the side wall of the polysilicon film during over-etching. Therefore, as shown in FIG. 6, the value of the CD loss is further reduced as compared with the case of the second embodiment.

Thereafter, when the actual wafer is sequentially etched, an equilibrium state is reached, and the amount of change of the CD shift becomes almost zero as shown in FIG.

As described above, in the case of the present embodiment, a certain amount of the reaction product adheres to the inner wall of the reaction chamber in the initial state. In addition, this amount is close to the amount of the reaction product adhering to the inner wall immediately before etching each actual wafer when the actual wafer is in an equilibrium state. The reaction product acts as a side wall protective film, so that the etching of the actual wafer reaches an equilibrium state faster than in the case of the second embodiment, and reaches an equilibrium state after processing one or two actual wafers.

By the way, as shown in FIG. 6, the etching rate was almost constant independently of the number of processed wafers. This is also for the same reason as described in the first embodiment.

The silicon oxide film and the polysilicon film of the dummy wafer used for the dummy etching have a thickness of several μm.
Thus, the dummy wafer can be used for dummy discharge several times. Although the cost is higher than in the case of the first embodiment in that an extra dummy wafer is required, the cost is lower than in the case of the second embodiment because there is no need to pattern the resist. However,
The use of two dummy wafers takes a longer time to transport than one wafer, and thus has a disadvantage in that the throughput is slightly reduced.

(Embodiment 4) Next, a plasma etching process according to Embodiment 4 of the present invention will be described with reference to the drawings. First, the plasma etching process is the same as the process flow shown in FIG. As the dummy wafer in the dummy discharge 2, a wafer having a silicon oxide film with a photoresist mask shown in FIG. 3 was used. Other conditions were the same as those described in the third embodiment.

Next, the processing result will be described with reference to the drawings. FIG. 7 shows the dependence of the etching rate of the actual wafer and the CD shift amount on the number of processed wafers. Dummy discharge 1
In (S3), a part of the reaction product generated by the reaction between the reactive gas and the polysilicon film adheres to the inner wall of the reaction chamber. In the dummy discharge 2 (S4),
Part of the reaction product attached to the inner wall of the reaction chamber is separated from the inner wall. In addition, a part of the reaction product generated by the reaction between the reactive gas and the resist adheres to the inner wall of the reaction chamber. As a result, a certain amount of the reaction product adheres to the inner wall of the reaction chamber after the dummy etching. With this state as an initial state, the actual wafer is sequentially etched.

During the main etching of the first actual wafer,
Some of the reaction products adhere to the inner wall 10. During the over-etching of the actual wafer, the reaction product is detached from the inner wall 10 and adheres again on the actual wafer. In addition, this amount is almost the same as the amount of the reaction product adhering to the inner wall immediately before etching each actual wafer in the equilibrium state of the actual wafer by performing the dummy discharge 1 and the dummy discharge 2. The reaction product functions more sufficiently as a sidewall protective film. This suppresses etching of the side wall of the polysilicon film during over-etching. Therefore, compared with the case of the third embodiment, the CD shift amount is almost 0 as shown in FIG.

In the subsequent etching of the actual wafer, as shown in FIG. 7, the amount of change in the CD shift is almost zero.

As described above, in the case of the present embodiment, a certain amount of reaction product adheres to the inner wall of the reaction chamber in the initial state. In addition, this amount is almost close to the amount of the reaction product adhering to the inner wall immediately before etching each actual wafer when the etching of the actual wafer is in an equilibrium state. This reaction product acts as a side wall protective film,
The etching of the actual wafer reaches the equilibrium state faster than in the case of the third embodiment, and as shown in FIG. 7, the equilibrium state is substantially attained from the processing of the first actual wafer.

As shown in FIG. 7, the etching rate was almost constant independently of the number of processed wafers. This is also for the same reason as described in the first embodiment.

The thickness of the silicon oxide film and the polysilicon film of the dummy wafer used for the dummy etching is set to several μm.
Thus, the dummy wafer can be used for dummy discharge several times. An extra dummy wafer is required, and the cost is slightly higher than in the first to third embodiments because the resist is patterned.

In the third and fourth embodiments, a wafer having a polysilicon film formed on a silicon substrate is used as the wafer used for the dummy discharge 1. Alternatively, the wafer may be simply a silicon wafer. Further, a wafer in which a photoresist is patterned on the silicon wafer may be used. In each case, the effects described in the third embodiment or the fourth embodiment can be obtained.

In the first to fourth embodiments, the case where the polysilicon film on the silicon oxide film is etched as a real wafer has been described. However, the present invention can be similarly applied to other film structures. For example, when patterning an aluminum film formed on a silicon oxide film, or patterning a tungsten film on a silicon oxide film, a dummy wafer corresponding to each film quality is prepared, and etching characteristics are performed by performing a dummy discharge. Can be stabilized.

The embodiment disclosed this time is merely an example, and it is intended that various embodiments can be taken within an equivalent scope of the invention described in the claims.

[0055]

According to the method of manufacturing a semiconductor device according to one aspect of the present invention, a reaction product adhering to the inner wall of the reaction chamber is separated from the inner wall of the reaction chamber by performing dummy etching, thereby forming the reaction chamber in the initial state. Reaction products adhering to the walls are almost eliminated. Thereby, the etching of the second film formed on each of the plurality of semiconductor substrates reaches an equilibrium state with a smaller number of substrates. Therefore, each second
Variations in the CD shift amount of the film can be suppressed.

Preferably, a substrate in which a resist is patterned on the first dummy film is used as the first dummy semiconductor substrate. In this case, a part of the reaction product generated by the reaction between the reactive gas and the resist due to the dummy etching adheres to the inner wall of the reaction chamber, so that a certain amount of the reaction product adheres to the inner wall in the initial state. Thereby, the etching of the second film formed on each of the plurality of semiconductor substrates reaches an equilibrium state with a smaller number of etchings. Therefore,
Variations in the CD shift amount of each second film can be further suppressed.

Preferably, the dummy etching step further includes a step of etching the second dummy film in the reaction chamber using the second dummy semiconductor substrate on which the second dummy film of the same quality as the second film is formed, After the dummy etching step, a step of sequentially etching the second film formed on each of the plurality of semiconductor substrates in the reaction chamber is included.

In this case, the amount of the reaction product adhering to the inner wall in the initial state by the dummy etching is determined by the amount of the reaction product adhering to the inner wall immediately before etching the second film on the semiconductor substrate in the equilibrium state. Approach the quantity. Thereby, the second semiconductor substrate formed on each of the plurality of semiconductor substrates is formed.
Equilibrium is reached with fewer films etched. Therefore, the variation in the CD shift amount of each second film can be further suppressed.

More preferably, the aperture ratio of the first dummy film by the resist on the first dummy semiconductor substrate is substantially the same as the aperture ratio of the second film by the resist on the semiconductor substrate.

In this case, the amount of the reaction product adhering to the inner wall in the initial state by the dummy etching is determined by the amount of the reaction product adhering to the inner wall immediately before etching the second film on the semiconductor substrate in the equilibrium state. It is almost equal to the amount.
Thereby, the etching of the second film formed on each of the plurality of semiconductor substrates is substantially equilibrated from the first substrate. Therefore, variation in the CD shift amount of each second film can be almost suppressed.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of a process flow according to Embodiment 1 of the present invention.

FIG. 2 shows an etching rate and C in Embodiment 2;
9 is a graph showing the dependence of the D shift amount on the number of processed sheets.

FIG. 3 is a diagram showing a film structure of a dummy wafer according to a second embodiment of the present invention.

FIG. 4 shows the etching rate and C in Embodiment 2;
9 is a graph showing the dependence of the D shift amount on the number of processed sheets.

FIG. 5 is a diagram showing an example of a process flow according to a third embodiment of the present invention.

FIG. 6 shows an etching rate and C in Embodiment 3;
9 is a graph showing the dependence of the D shift amount on the number of processed sheets.

FIG. 7 is a graph showing the dependence of the etching rate and the CD shift amount on the number of processed wafers in the fourth embodiment of the present invention.

FIG. 8 is a sectional view showing an example of the structure of a plasma etching apparatus.

FIG. 9 is a graph showing the dependence of the etching rate on the number of processed wafers in the related art.

FIG. 10 shows an etching rate and a CD according to a conventional technique.
9 is a graph showing the dependence of the shift amount on the number of processed sheets.

FIG. 11 is a cross-sectional view showing an actual wafer film structure according to a conventional technique and the first to fourth embodiments.

[Explanation of symbols]

1 reaction chamber, 2 semiconductor wafer, 10 inner wall, 11 silicon oxide film, 12 polysilicon film, 13 photoresist.

Claims (4)

[Claims] 1. A method of etching a second film formed on a first film on a semiconductor substrate using a resist patterned on the second film as a mask, the method comprising: Using a first dummy semiconductor substrate on which a first dummy film is formed, a dummy etching step of etching the first dummy film in a reaction chamber, and forming a dummy etching step on each of the plurality of semiconductor substrates after the dummy etching step Sequentially etching the formed second film in the reaction chamber. 2. The method according to claim 1, wherein the first dummy semiconductor substrate is formed by patterning a resist on the first dummy film. 3. The method according to claim 2, wherein the dummy etching step includes the step of:
A step of etching the second dummy film in the reaction chamber using a second dummy semiconductor substrate on which a second dummy film of the same quality as the film is formed; 3. The method of manufacturing a semiconductor device according to claim 1, further comprising a step of sequentially etching the second film formed on each of the second films in the reaction chamber. 4. 4. An aperture ratio of the first dummy film by the resist on the first dummy semiconductor substrate is substantially the same as an aperture ratio of the second film by the resist on the semiconductor substrate.
A method for manufacturing a semiconductor device according to claim 2.