JPH09260096A - Method and apparatus for matching impedance and apparatus for producing semiconductor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform automatic impedance matching to positively ignite plasma, even when the ignition point of plasma is displaced due to the change in impedance. SOLUTION: Plasma is ignited after automatically moving a stab of impedance matching device 6 to the predefined ignition point. A power monitor 5 monitors the reflection of microwaves to determine that the plasma has been successfully ignited if the reflected wave is less than a threshold value, otherwise that the plasma has not been ignited if the reflection is higher than the threshold. If not ignited, the range of impedance matching is regularly widen around the ignition point in the ignition region to find a point where the reflected wave is weaker than the threshold value, to positively ignite plasma. Thereafter, the stab is displaced again to move in to the impedance matching point to find similarly a point within the impedance matching region where the reflected wave is weaker than the threshold value, to guide to a point of impedance matching where the plasma is settled stable.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an impedance matching method and apparatus and a semiconductor manufacturing apparatus, and more particularly to a technique effective when applied to impedance matching during plasma ignition in a plasma apparatus.

[0002]

2. Description of the Related Art In recent years, in a plasma apparatus for performing processing such as thin film formation, dry etching and ashing by using plasma discharge generated by high frequency or microwave power, impedance matching for stabilizing plasma is required for stable processing. Technology is essential.

According to a study made by the present inventor, this impedance matching technique considers that the plasma ignition region and the matching region are the same, and presets the matching position at the end of plasma discharge as the ignition point. Widely known are a method of setting a matching position of impedance at the time of discharge ignition and a method of empirically considering the position as an ignition point, starting discharge from that point, and guiding to an immediate matching point.

As an example in which this type of plasma processing apparatus is described in detail, as an example of the semiconductor circuit process series "Semiconductor Plasma Process Technology", published by Sangyo Tosho Co., Ltd. on June 8, 1990, Takuo Sugano "Semiconductor Plasma Process Technology" P103- P
165, which describes the structure and characteristics of various plasma etching apparatuses.

[0005]

However, in the impedance matching technique in the plasma device as described above,
The inventors have found the following problems.

That is, the impedance is different for each processing due to the change of the load in the processing chamber for performing the plasma processing, the state of the plasma device, etc., and the ignition point of the plasma is different, which may cause the plasma not to be ignited. .

Even if the plasma is forcibly moved to the matching point without confirming the ignition of the plasma, the impedance is greatly different if the plasma is not ignited, and the plasma does not ignite or the plasma ignites. There is a problem that it takes a long time to perform the matching and the plasma processing is not stably performed.

An object of the present invention is to provide an impedance matching method and apparatus and a semiconductor manufacturing apparatus capable of automatically impedance matching a shift in the ignition point of plasma due to a change in impedance and reliably igniting the plasma. is there.

The above and other objects and novel features of the present invention will become apparent from the description of the present specification and the accompanying drawings.

[0010]

SUMMARY OF THE INVENTION Among the inventions disclosed in the present application, the outline of a representative one will be briefly described.
It is as follows.

That is, the impedance matching method of the present invention comprises a step of searching for a matching point of impedance at which plasma is ignited with reference to a preset impedance, and a stable plasma discharge is formed when the ignition of plasma is confirmed. A step of automatically shifting to a preset reference impedance matching point, and a step of automatically searching for an impedance matching point that stabilizes the plasma discharge formed with the shifted matching point as a reference. I have.

As a result, the optimum impedance matching for plasma ignition is automatically performed, so that stable plasma ignition can be performed in a short time, and plasma ignition or plasma ignition due to impedance change in the processing chamber can be prevented. It is possible to prevent the time from becoming longer.

Further, the impedance matching apparatus of the present invention monitors the ignition state of plasma in the processing chamber and impedance matching means for performing impedance matching in accordance with the impedance change in the processing chamber in which the predetermined processing of the object to be processed is performed. The plasma monitor means for outputting as a detection signal, and the matching device control means for judging whether or not the plasma is ignited based on the detection signal output from the plasma monitoring means and controlling the impedance matching means. It is a thing.

As a result, even if impedance in the processing chamber changes, optimum impedance matching for plasma ignition can be automatically performed, and stable plasma ignition can be performed in a short time.

Further, in the impedance matching device of the present invention, the plasma monitor means is composed of a directional coupler for detecting a reflected wave of plasma.

As a result, the optimum impedance matching for plasma ignition can be automatically performed at a low cost with a simple device configuration.

Further, in the impedance matching device of the present invention, the plasma monitor means is composed of a photo sensor for detecting the light amount of plasma.

Also by this, the optimum impedance matching for plasma ignition can be automatically performed at a low cost with a simple device configuration.

Further, the semiconductor manufacturing apparatus of the present invention comprises a plasma apparatus which is constructed by using the impedance matching apparatus and which carries out a predetermined treatment on an object to be treated by a chemical reaction by gas plasma.

As a result, the plasma processing of the object to be processed can be performed efficiently and stably, and the quality of products such as semiconductor devices can be improved.

Also, in the semiconductor manufacturing apparatus of the present invention, the plasma apparatus forms a thin film by plasma discharge decomposition of a reactive gas, which is a plasma CVD (Chemical Va).
por Deposition) device or a plasma etching device that performs etching by reactive gas plasma.

As a result, it is possible to efficiently and stably form a thin film on an object to be processed and to perform etching, and it is possible to improve the quality of products such as semiconductor devices.

[0023]

Embodiments of the present invention will be described below in detail with reference to the drawings.

(Embodiment 1) FIG. 1 is a diagram for explaining the structure of a plasma etching apparatus according to Embodiment 1 of the present invention, and FIG. 2 is an impedance matching point of plasma in the plasma etching apparatus according to Embodiment 1 of the present invention. It is a Smith chart figure explaining.

In the first embodiment, which is a kind of plasma device, a reactive gas plasma is utilized to require the entire surface or a specific place such as a thin film formed on the surface of a semiconductor wafer which is an object to be processed. A plasma etching apparatus (semiconductor manufacturing apparatus) 1 that etches only the thickness is provided with a microwave generator 2 that oscillates a microwave of, for example, about 2.45 GHz at the uppermost portion.

In the plasma etching apparatus 1, a waveguide 3 for guiding the microwave generated by the microwave generator 2 is provided below the microwave generator 2.
The waveguide 3 is connected to the microwave generator 2.

Further, in the plasma etching apparatus 1, an isolator 4 which absorbs the microwave in the waveguide 3 which has become a reflected wave is provided on the side portion of the waveguide 3 so as to be connected to the waveguide 3. There is.

Further, in the plasma etching apparatus 1, for example, the microwave generated from the microwave generator 2 is incident on a predetermined position below the waveguide 3 and the microwave from the process chamber described later is generated. A power monitor (plasma monitor means) 5 which is a directional coupler for monitoring reflection and reflection is provided.

Further, the plasma etching apparatus 1 is provided with an impedance matching device (impedance matching device) that performs impedance matching by installing, for example, three stubs according to the impedance change in the process chamber and controlling the interval between these stubs. Matching means) 6 is provided below the waveguide 3.

Further, in the plasma etching apparatus 1, an impedance matching controller (matching device control means) for controlling the impedance matching device 6 provided in the plasma etching device 1 based on the signal output from the power monitor 5 described above. The impedance matching controller 7 is connected to each of the power monitor 5 and the impedance matching device 6.

The power monitor 5, the impedance matching device 6 and the impedance matching controller 7 constitute an impedance matching device.

Further, the plasma etching apparatus 1 is provided below the impedance matching device 6 with a processing chamber (processing chamber) 8 made of, for example, quartz, which is a processing chamber for etching a semiconductor wafer or the like.

Further, the process chamber 8 includes an exhaust port for exhausting the inside of the process chamber 8 at the time of etching by, for example, a vacuum pump, and the process chamber 8.
A gas inlet for introducing a reactive gas for etching is provided after exhausting the inside.

Further, in the plasma etching apparatus 1, a stage 9 on which a semiconductor wafer to be processed is placed is provided below the process chamber 8.

Next, the Smith chart, which is a calculation chart for the transmission line circuit used for calculating the impedance and the reflection coefficient at each point of the transmission line circuit in FIG. 2, will be described.

In this case, the ignition region CR in the upper part of the Smith chart of FIG. 2 is the region of impedance required for plasma ignition, and the ignition point FP is
In the ignition region CR, the impedance point at which plasma ignition is most smoothly performed is shown.

Further, the impedance matching region SR located in the center of the Smith chart of FIG. 2 is a region of impedance that suppresses the reflected wave to a low level and stabilizes the plasma after ignition of the plasma. The impedance matching point TP located in the SR region indicates the point of impedance at which the reflected wave becomes the lowest and the energy contributing to the plasma becomes maximum.

Next, the operation of this embodiment will be described with reference to FIG.
This will be described with reference to FIG.

First, the inside of the process chamber 8 is evacuated by the above-mentioned vacuum pump, and when the inside of the process chamber 8 reaches a predetermined degree of vacuum, a predetermined reaction gas for etching is introduced into the process chamber 8 from the gas inlet. .

After that, a microwave serving as excitation energy for generating plasma is generated from the microwave generator 2 and guided to the process chamber 8 via the waveguide 3.

At this time, the impedance matching controller 7 controls the impedance matching device so that it is automatically located at the ignition point FP, which is a point matched with the impedance required for preset plasma ignition. Move the stub in 6.

The power monitor 5 constantly monitors the incident wave and the reflected wave of the microwave at a predetermined position of the waveguide 3, and the monitoring result by the power monitor 5 is input to the impedance matching controller 7. There is.

When the reflected wave, which is the monitoring result output from the power monitor 5, is lower than a predetermined threshold value at the reference ignition point FP, the impedance matching controller 7 determines that the plasma has ignited. to decide.

If the reflected wave output from the power monitor 5 is higher than a predetermined threshold value at the above-mentioned reference ignition point FP, the impedance matching controller 7 determines that the plasma has not ignited.

In this case, in order to obtain the impedance necessary for the ignition of the plasma, the ignition point FP is centered within the ignition region CR, and as shown by the locus KP1 in FIG. The impedance matching range is expanded in the direction to search for a point where the reflected wave becomes lower than a predetermined threshold value.

When the reflected wave becomes lower than the predetermined threshold value and the impedance matching controller 7 determines that the plasma is surely ignited, the impedance matching controller 7 controls the impedance matching device 6 again. Then, by moving the stub, the stub is moved to an impedance matching point TP in a preset impedance matching region SR in order to form a stable plasma discharge.

Also here, the monitoring result by the power monitor 5 that constantly monitors the incident wave and the reflected wave of the microwave is input to the impedance matching controller 7, and is lower than the predetermined threshold value at the impedance matching point TP. In this case, the impedance matching controller 7 determines that the plasma is in a stable state.

Similarly, when the impedance matching point TP is higher than a predetermined threshold value, the impedance matching controller 7 determines that the plasma is in an unstable state.

In this case, in order to obtain the impedance required to make the plasma stable, the locus KP2 of FIG. 2 is centered on the aforementioned impedance matching point TP within the impedance matching region SR. As shown, the impedance matching point TP
To the outer peripheral direction, the range of impedance matching is widened, a point where the reflected wave becomes lower than a predetermined threshold value is searched for, and induction to the point of impedance matching where the plasma is reliably stable is performed.

When the reflected wave becomes lower than the predetermined threshold value, the impedance matching controller 7 judges that the plasma is in a stable state, and starts the predetermined plasma etching process.

As a result, according to the first embodiment, the impedance matching controller 7 automatically performs the optimum impedance matching within the range of the ignition region CR with the preset ignition point FP as a reference when the plasma is ignited. The plasma can be ignited reliably in a short time.

Further, in the first embodiment, the reflected wave of the microwave is monitored by the power monitor 5 (FIG. 1). However, for example, the amount of light is detected in the peep window of the process chamber 8 (FIG. 1). A sensor such as a photo sensor may be provided to determine that the plasma is surely ignited when the amount of light is equal to or more than a predetermined amount.

In this case, the above-mentioned photosensor, impedance matching device 6 (FIG. 1) and impedance matching controller 7 (FIG. 1) constitute an impedance matching device.

(Embodiment 2) FIG. 3 is a diagram showing the structure of a plasma CVD apparatus according to Embodiment 2 of the present invention.

In the second embodiment, a plasma CVD apparatus (semiconductor manufacturing apparatus) 1a for forming a thin film on a semiconductor wafer, which is a kind of plasma apparatus in which plasma chemistry is introduced into a CVD technique, is provided at the top, for example, 2 .45 GHz
A microwave generator 2 that oscillates a microwave of a certain degree is provided.

Further, a waveguide 3 for guiding the microwave generated from the microwave generator 2 is provided below the microwave generator 2, and the waveguide 3 is connected to the microwave generator 2. It is connected.

Further, in the plasma CVD apparatus 1a, an isolator 4 for absorbing the microwave in the waveguide 3 which has become a reflected wave is provided on the side portion of the waveguide 3 in connection with the waveguide 3. At a predetermined position below the waveguide 3, a power monitor which is a directional coupler that monitors the incidence of the microwave generated from the microwave generator 2 and the reflection of the microwave from the process chamber described later. 5 are provided.

Further, in the plasma CVD apparatus 1a, an impedance matching device 6 for performing impedance matching is provided, for example, by installing three stubs according to the impedance change in the process chamber and controlling the interval between the stubs. It is connected to the lower portion of the waveguide 3.

Further, the plasma CVD apparatus 1a is provided with an impedance matching controller 7 for controlling the impedance matching device 6 provided in the plasma CVD apparatus 1a based on the signal output from the power monitor 5 described above. , This impedance matching controller 7
Are connected to the power monitor 5 and the impedance matching device 6, respectively.

The power monitor 5, the impedance matching device 6 and the impedance matching controller 7 constitute an impedance matching device.

Further, the plasma CVD apparatus 1a is provided below the impedance matching device 6 with a tubular reaction chamber (processing chamber) 10 made of, for example, quartz, which is a processing chamber for etching semiconductor wafers and the like. ing.

Further, a vacuum pump 11 for exhausting the inside of the reaction chamber 10 at the time of etching is provided at one end of the reaction chamber 10, and a gas introduction for introducing a reaction gas into the reaction chamber 10 is provided at the other end. A mouth 12 is provided.

In the plasma CVD apparatus 1a, the stage 9 on which the semiconductor wafer to be processed is placed is the reaction chamber 10.
It is provided at the lower part.

The operation of this embodiment will be described below.

First, the vacuum pump 1 is used to evacuate the reaction chamber 10.
1 and when the inside of the reaction chamber 10 has a predetermined degree of vacuum, a predetermined reaction gas is introduced into the reaction chamber 10 through the gas inlet 12 and a microwave as excitation energy for generating plasma is generated by the microwave generator 2 Generated from the waveguide 3
Through the reaction chamber 10.

At this time, the impedance matching controller 7 performs control and is automatically positioned at the ignition point FP (Embodiment 1, FIG. 2) which is a point matched with the impedance required for preset plasma ignition. The stub in the impedance matching device 6 is moved as described above.

The power monitor 5 constantly monitors the incident wave and the reflected wave of the microwave at a predetermined position of the waveguide 3, and the monitoring result by the power monitor 5 is input to the impedance matching controller 7. There is.

When the reflected wave which is the monitor result output from the power monitor 5 is lower than the predetermined threshold value at the reference ignition point FP, the impedance matching controller 7 determines that the plasma has ignited. If the reflected wave output from the power monitor 5 is higher than a predetermined threshold value at the ignition point FP,
Judge that the plasma has not ignited.

In this case, in order to obtain the impedance required for plasma ignition, the ignition region CR (first embodiment,
Within the range of FIG. 2), while centering on the ignition point FP described above, as shown in the locus KP1 (Embodiment 1, FIG. 2), the impedance matching range is widened from the ignition point FP to the outer peripheral direction, and a predetermined range is obtained. Search for points where the reflected wave is lower than the threshold value.

Then, when the reflected wave becomes lower than the predetermined threshold value and the impedance matching controller 7 determines that the plasma is surely ignited, the impedance matching controller 7 controls the impedance matching device 6 again. Then, the stub is moved to an impedance matching point TP (Embodiment 1, FIG. 2) in a preset impedance matching region SR (Embodiment 1, FIG. 2) for forming a stable plasma discharge. Let

Also here, the monitoring result by the power monitor 5 that constantly monitors the incident wave and the reflected wave of the microwave is input to the impedance matching controller 7, which is lower than the predetermined threshold value at the impedance matching point TP. In this case, the impedance matching controller 7 determines that the plasma is in a stable state.

Similarly, when the impedance matching point TP is higher than a predetermined threshold value, the impedance matching controller 7 determines that the plasma is in an unstable state.

In this case, in order to obtain the impedance required to make the plasma stable, the locus KP2 shown above is centered on the above-mentioned impedance matching point TP within the impedance matching region SR. , Impedance matching point T
The impedance matching range is expanded from P to the outer peripheral direction, a point where the reflected wave becomes lower than a predetermined threshold value is searched for, and induction to the impedance matching point where the plasma is reliably stable is performed.

When the reflected wave becomes lower than the predetermined threshold value, the impedance matching controller 7 judges that the plasma is surely stable and starts the predetermined plasma CVD process.

As a result, in the second embodiment, the impedance matching controller 7 automatically performs optimum impedance matching within the range of the ignition region CR with the preset ignition point FP as a reference when the plasma is ignited. The plasma can be ignited reliably in a short time.

Also in the second embodiment, the reflected wave of the microwave is monitored by the power monitor 5 (FIG. 3). However, for example, the observation window provided in the reaction chamber 10 (FIG. 3) is used. A photosensor, which is a sensor for detecting the amount of light, may be provided to determine that the plasma is surely ignited when the amount of light is equal to or more than a predetermined amount.

In this case, the above-described photosensor, impedance matching device 6 (FIG. 3) and impedance matching controller 7 (FIG. 3) constitute an impedance matching device.

Although the invention made by the inventor has been specifically described based on the embodiments of the present invention, the present invention is not limited to the above embodiments, and various modifications may be made without departing from the gist of the invention. Needless to say, it can be changed.

Further, in the first and second embodiments,
Although the plasma etching apparatus and the plasma CVD apparatus have been described, other than this, a plasma apparatus such as a plasma ashing apparatus for peeling off an organic substance or the like may be used as long as it is a plasma apparatus for performing a predetermined process on an object to be processed using plasma.

In the first and second embodiments,
The microwave was an excitation energy source for generating plasma, but this excitation energy source may be any excitation source capable of generating plasma, such as a high frequency power supply or a helicon wave.

[0081]

Advantageous effects obtained by typical ones of the inventions disclosed by the present application will be briefly described as follows.
It is as follows.

(1) According to the present invention, since optimum impedance matching is automatically performed, stable plasma ignition can be performed in a short time.

(2) Further, according to the present invention, optimum impedance matching for plasma ignition can be automatically performed at a low cost with a simple apparatus configuration.

(3) Further, in the present invention, the impedance matching device is used to construct a semiconductor manufacturing apparatus for performing plasma processing such as a plasma CVD apparatus or a plasma etching apparatus, so that plasma processing of an object to be processed can be performed efficiently. It can be carried out well and stably, and the quality of products such as semiconductor devices can be improved.

[Brief description of drawings]

FIG. 1 is a structural explanatory view of a plasma etching apparatus according to a first embodiment of the present invention.

FIG. 2 is a Smith chart diagram for explaining plasma impedance matching points in the plasma etching apparatus according to the first embodiment of the present invention.

FIG. 3 is a configuration explanatory diagram of a plasma CVD apparatus according to a second embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Plasma etching apparatus (semiconductor manufacturing apparatus) 1a Plasma CVD apparatus (semiconductor manufacturing apparatus) 2 Microwave generator 3 Waveguide 4 Isolator 5 Power monitor (plasma monitoring means) 6 Impedance matching device (impedance matching means) 7 Impedance matching controller 8 process chamber (processing room) 9 stage 10 reaction chamber (processing room) 11 vacuum pump 12 gas inlet CR ignition region FP ignition point SR impedance matching region TP impedance matching point KP1, KP2 locus

Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI Technical display location H01L 21/205 H01L 21/205 21/3065 21/302 A

Claims (7)

[Claims] 1. A step of searching a matching point of impedance at which plasma ignites with reference to a preset impedance, and a preset reference for forming a stable plasma discharge when the ignition of the plasma is confirmed. And a step of automatically searching for an impedance matching point that stabilizes the plasma discharge formed based on the transferred matching point. Impedance matching method. 2. Impedance matching means for performing impedance matching according to impedance changes in a processing chamber in which a predetermined processing of an object to be processed is performed, and plasma for monitoring the ignition state of plasma in the processing chamber and outputting it as a detection signal. An impedance matching device comprising monitor means and matcher control means for judging whether or not plasma is ignited based on the detection signal output from the plasma monitor means and for controlling the impedance matching means. . 3. The impedance matching device according to claim 2, wherein the plasma monitor means is a directional coupler that detects a reflected wave of plasma. 4. The impedance matching device according to claim 2, wherein the plasma monitor means is a photosensor for detecting the amount of plasma light. 5. A semiconductor manufacturing apparatus configured by using the impedance matching device according to claim 2, wherein plasma is used to perform a predetermined process on an object to be processed by a chemical reaction by gas plasma. A semiconductor manufacturing apparatus, which is a device. 6. The semiconductor manufacturing apparatus according to claim 5, wherein the plasma apparatus is a plasma CVD apparatus that forms a thin film by plasma discharge decomposition of a reactive gas. 7. The semiconductor manufacturing apparatus according to claim 5, wherein the plasma apparatus is a plasma etching apparatus that performs etching with a reactive gas plasma.