JP2001085410A - Method and device for etching - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an etching method, by which the ending point of etching can be detected with high accuracy at the time of etching a nitrogen-containing metallic film having a high melting point, using a carbon-free fluorine compound gas. SOLUTION: An etching method includes a process, in which a nitrogen atom-containing layer is etched in a first area by using a carbon-free etching gas, and the gas produced in the first area is introduced to a second area, where a carbon nitride is generated by generating plasma from the gas generated in the first area and a carbon-containing gas introduced to the second area. Then the luminous intensity of the carbon nitride is measured in the second area, and the time at which the luminous intensity decreases to a prescribed value is decided as the ending point of the etching on the nitrogen atom- containing layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an etching method and an etching apparatus, and more particularly to a method for etching a nitrogen-containing high melting point metal film and an etching apparatus used for the etching.

[0002]

2. Description of the Related Art In a manufacturing process of a semiconductor device, a film or a substrate is sometimes etched using reactive plasma. In such plasma etching, it is preferable to suppress damage to the semiconductor substrate. When a nitrogen-containing high melting point metal film such as tungsten nitride silicide (WSiN) used as a gate metal material of a semiconductor device is plasma-etched, a high selection is performed with respect to a film below the high melting point metal film. It is required that etching be performed at a high ratio and the end point be detected with high accuracy.

[0003] carbon compound as an etching gas WSiN refractory metal film, for example, end point detection of the etching when not using CHF ₃ is an emission line of dissociated tungsten atoms with spectrometer from WF _x is an etching product gas It was done by observing. However, it has been difficult to obtain sufficient sensitivity for detecting the end point of etching by observing the emission line of tungsten atoms in order to increase the accuracy.

On the other hand, when a nitrogen-containing high-melting-point metal film is etched using a carbon-containing etching gas, carbon nitride (CN) with extremely high sensitivity is produced. Therefore, by performing etching while observing CN emission, highly accurate etching end point detection becomes possible. About the observation of CN emission,
These are described in JP-A-58-26013 and JP-A-3-83342.

[0005]

However, in plasma etching used for manufacturing a semiconductor device, it is preferable to use an etching gas containing no carbon in order to prevent contamination by carbon or carbon compound residues. In contrast, the fluorine-based etching gas which does not contain carbon, for example because when etching the refractory metal film nitrogenous using SF ₆ CN emission is not observed, while observing the emission of tungsten as described above Since the etching is performed, it becomes difficult to detect the end point of the etching with high accuracy.

An object of the present invention is to provide an etching method and an etching apparatus capable of detecting the end point of etching with high accuracy when etching a nitrogen-containing high melting point metal film using a fluorine compound gas containing no carbon. Is to provide.

[0007]

Means for Solving the Problems The above-mentioned problems are solved in FIGS.
As illustrated in FIG. 4, the nitrogen atom-containing layer is etched in a first region using an etching gas containing no carbon, and a product gas in the first region is introduced into a second region. A carbon-containing gas is introduced into the second region to form a plasma together with the produced gas to generate carbon nitride, and the emission intensity of the carbon nitride is measured in the second region, and the emission intensity becomes a predetermined value. The problem is solved by an etching method, wherein the etching end point of the nitrogen atom-containing layer is set at the time of the attenuation.

In the above-mentioned etching method, the carbon-containing gas may be introduced from the outside into the second region, or may be obtained by etching the carbon-containing layer in the second region. Good. In the above-described etching method, the etching of the carbon-containing layer is performed using plasma of the generated gas,
This may be performed using another etching gas plasma introduced from the outside.

[0009] The above-mentioned problems are caused by an etching chamber for etching a nitrogen atom-containing layer in a reduced pressure atmosphere, a plasma discharge chamber into which a generated gas flows in the etching chamber, and a carbon-containing gas for supplying a carbon-containing gas into the plasma discharge chamber. A gas supply source; and a carbon nitride luminescence intensity measuring device for measuring luminescence intensity of carbon nitride plasma obtained by converting the carbon-containing gas and the generated gas into plasma in the plasma discharge chamber. It is solved by an etching device.

In the above etching apparatus, the carbon-containing gas supply source may be a gas supply cylinder provided outside the plasma discharge chamber to supply the carbon-containing gas in a gaseous state to the plasma discharge chamber. . In the above-described etching apparatus, the carbon-containing gas supply source includes:
The carbon-containing layer may be placed in the plasma discharge chamber and etched.

In the above-described etching apparatus, the plasma discharge chamber has a parallel plate type electrode having a first electrode supplied with high-frequency power and a second electrode connected to a constant voltage source, or an external electrode. May have a microwave guiding means for introducing a microwave from. next,
The operation of the present invention will be described.

According to the present invention, an etching region for etching a nitrogen-containing layer and a plasma discharge region for detecting an etching end point are separately provided so that a gas introduced from the etching region and a carbon-containing gas are supplied to the plasma discharge region. I have to. Therefore, since the gas introduced from the etching region is introduced into the plasma discharge region and the end point is detected there, it is not necessary to use the carbon-containing gas, which is a contamination source of the substrate, for etching the nitrogen-containing layer.

Moreover, the gas introduced from the etching region and the carbon-containing gas introduced from another region are turned into plasma,
Since the intensity of CN emission in the plasma was measured, when the nitrogen-containing layer was being etched, the gas taken into the plasma discharge region from the etching region contained nitrogen, so the CN emission intensity was measured. On the other hand, when the etching of the nitrogen-containing layer is completed, the gas introduced into the plasma discharge region does not contain nitrogen, so that the CN emission intensity decreases and the etching end point is detected.

Therefore, the end point of the etching can be detected with high sensitivity and high accuracy based on the CN emission measurement.

[0015]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an embodiment of the present invention. (First Embodiment) FIG. 1 is a configuration diagram showing a reactive ion etching apparatus according to a first embodiment of the present invention.

A cathode 2 and a counter electrode 3 are provided inside an etching chamber 1 of the reactive ion etching apparatus shown in FIG.
Are mounted so as to face each other, and the surface of the cathode electrode 2 facing the counter electrode 3 is a region where the substrate W is placed. The counter electrode 3 is electrically connected to a constant voltage source Vg such as a ground potential, and the cathode electrode 3 is connected to the constant voltage source Vg via a 13.56 MHz high frequency power supply 4, for example.

The etching chamber 1 is provided with a gas inlet 5 for supplying an etching gas between the cathode electrode 2 and the counter electrode 3, and an exhaust port 6 for discharging the gas inside from the chamber. An etching gas supply source 7 in which a reaction gas containing no carbon, for example, sulfur hexafluoride (SF ₆ ) is sealed is connected to the gas inlet 5 through an on-off valve 8.

The exhaust port 6 is connected to a vacuum pump 11 via a plasma discharge chamber 9 and a pressure adjusting device 10, and the etching chamber 1 and the plasma discharge chamber 9 are controlled by the vacuum pump 11 and the pressure adjusting device 10. Pressure. The plasma discharge chamber 9 has a cathode electrode 9a and a counter electrode 9b that face each other inside.
The cathode electrode 9a is connected to a constant voltage source Vg via a high frequency power supply 18, and the counter electrode 9b is connected to a constant voltage source Vg.
It is connected to the.

Further, the plasma discharge chamber 9 has a carbon-containing gas inlet 9c for supplying a carbon-containing gas between the cathode electrode 9a and the counter electrode 9b, and the carbon-containing gas inlet 9c has a CF. ₄ , a carbon-containing gas supply source 12 in which a carbon-containing gas such as CHF ₃ is sealed, for example, a carbon-containing gas cylinder is connected via an on-off valve 13. In the plasma discharge chamber 9, an etching reaction gas inlet 9d connected to the exhaust port 6 of the etching chamber 1 via a gas pipe 14 is provided on one side of a space between the cathode electrode 9a and the counter electrode 9b. An exhaust port 9e connected to the pressure regulator 10 and the vacuum pump 11 via the gas pipe 15 is provided on the other side of the space.

The plasma discharge chamber 9 is provided with a light receiving section of a plasma emission measuring device 16 for spectrally measuring emission lines of molecules or atoms contained in the plasma generated by the cathode electrode 9a and the counter electrode 9b. . Reference numeral 17 in FIG. 1 denotes a connection between the high-frequency power supply 4 and the cathode electrode 2 based on the measurement signal S1 of the emission intensity of a predetermined molecule or atom measured by the plasma emission measurement device 16 and the external signal S2. Is a control circuit for turning ON / OFF the switch SW.

In the above-described reactive ion etching apparatus, first, a tungsten nitride silicide (WSiN) layer, a tungsten nitride (WN layer),
A substrate W having a nitride atom-containing layer such as a titanium tungsten nitride (WTiN) layer is attached. Also, the control circuit 17
The opening / closing valve 8 is opened by the operation according to
An etching gas containing no carbon, for example, sulfur hexafluoride (SF ₆ ) gas from the etching chamber 1 through a gas inlet 8.
Introduce within. The pressure in the etching chamber 1 after the introduction of the etching gas is adjusted to be 0.5 Pa.

Then, when an etching start signal S2 is sent to the control circuit 17, the control circuit 17 turns on the switch SW to turn on the cathode electrode 2 and the high frequency power supply 4 in the etching chamber 1.
Connect. Thereby, the cathode electrode 2 and the counter electrode 3
During this time, plasma is generated to start etching of the nitrogen atom-containing layer on the substrate W, and the nitrogen-containing etching product gas generated by the etching is subjected to an etching reaction through the exhaust port 6 of the etching chamber 1 and the gas pipe 14. The gas flows from the gas inlet 9 d into the plasma discharge chamber 1.

In the plasma discharge chamber 1, an on-off valve 1 is provided.
A carbon-containing gas, for example, a CF ₄ gas or a CHF ₃ gas is supplied from a carbon-containing gas supply source 12 through the carbon gas supply port 3 and the carbon-containing gas inlet 9 c. Therefore, in the plasma discharge chamber 9,
Cathode electrode 9a and counter electrode 9 to which high-frequency power is applied
During b, an etching generation gas and a carbon-containing gas are introduced and turned into plasma to generate CN, thereby generating CN emission at a wavelength of 388 nm. The intensity of CN emission is
It is measured by the plasma emission measurement device 16. Then, it can be seen that the etching of the nitrogen-containing layer on the substrate W is in progress while the CN emission is occurring at a certain intensity. On the other hand, when the spectral intensity of CN emission measured by the plasma emission measurement device 16 is attenuated and smaller than a predetermined value, or when CN emission is not confirmed, etching of the nitrogen-containing layer on the substrate W is stopped. It can be seen that the nitrogen gas is no longer contained in the etching product gas upon completion.

Therefore, when the CN emission intensity measured by the plasma emission measurement device 16 is reduced to a predetermined value (including zero) when the nitrogen-containing layer is being etched in the etching chamber 1, the plasma The control circuit 17 receiving the signal S2 from the luminescence measuring device 16 determines that the etching is completed, and turns off the switch SW to stop the application of the high frequency power from the high frequency power supply 4 to the cathode electrode 2.

As described above, the etching product gas is introduced into the plasma generating region different from the etching region, and the etching product gas and the carbon-containing gas are turned into plasma in the plasma generating region to observe CN emission. So
When nitrogen is no longer contained in the etching product gas, C
The N emission disappears, and the end point of the etching is detected.

Thus, contamination of the substrate can be prevented by using an etching gas containing no carbon, and the end point of the etching can be detected with high accuracy by measuring CN emission in a region different from the etching. (Second Embodiment) In the first embodiment, plasma is generated by introducing an etching product gas and a carbon-containing gas exhausted from an etching region between parallel plate electrodes. However, instead of generating plasma between parallel plate electrodes, plasma may be generated using microwaves, and an embodiment thereof will be described below.

FIG. 2 is a block diagram showing a reactive ion etching apparatus according to a second embodiment of the present invention, and the same reference numerals as those in FIG. 1 denote the same elements. In FIG. 2, a plasma discharge chamber 19 and a vacuum vessel 20 are mounted in parallel between the exhaust port 6 of the etching chamber 1 and the pressure adjusting device 10 described in the first embodiment. The vacuum container 20 is configured so that the etching product gas discharged from the exhaust port 6 passes toward the vacuum pump 11.

The plasma discharge chamber 1 of the vacuum vessel 20
On the upstream side of 9, a carbon-containing gas inlet 19c for introducing a carbon-containing gas is provided. The carbon gas inlet 19
The carbon gas supply source 12 is connected to c via an on-off valve 19d. A microwave waveguide 19b drawn from a microwave source 19a is arranged around the plasma discharge chamber 19, and the microwave propagated through the microwave waveguide 19b is applied into the plasma discharge chamber 19. It has become. Further, the detection unit of the plasma emission measurement device 16 is connected to the plasma discharge chamber 19.

The rest of the configuration of the etching apparatus of the present embodiment is the same as that of the first embodiment. In the reactive ion etching apparatus as described above, similarly to the first embodiment, an etching gas containing no carbon, for example,
SF ₆ is applied to the cathode 2 and the counter electrode 3 in the etching chamber 1.
And the substrate W
When the upper nitrogen-containing layer is etched, an etching product gas generated by the etching flows through the exhaust port 6 to the plasma discharge chamber 19 and the bypass vacuum vessel 20.

From the exhaust port 6 of the etching chamber 1 to the vacuum vessel 2
A part of the etching product gas introduced into 0 flows into the plasma discharge chamber 19, and the rest is directly exhausted toward the vacuum pump 11 as it is. Further, an on-off valve 19 d and a carbon gas inlet 19 are provided from the carbon-containing gas supply source 12.
The carbon-containing gas supplied to the vacuum vessel 20 through c.
A part passes through the plasma discharge chamber 19 and flows to the vacuum pump 11, and the rest passes through the vacuum container 20 and the vacuum pump 11.
Exhausted towards.

In the plasma discharge chamber 19,
The microwave transmitted in the microwave waveguide 19b is applied to the etching product gas and the carbon-containing gas, whereby CN emission occurs in the plasma discharge chamber 19. Its CN
The light emission intensity is measured by the plasma light emission measuring device 16, and it is easy to determine whether the etching of the nitrogen-containing layer on the substrate W is in progress or completed, as in the first embodiment.

That is, when the etching proceeds in the etching chamber 1 and the etching of the nitrogen-containing layer is completed, the nitrogen component in the etching product gas rapidly decreases or disappears. The light emission intensity decreases rapidly and CN light emission is not observed. Therefore,
At the time when the intensity of the CN emission measured by the plasma emission measuring device 16 is reduced from a certain value to a predetermined value or becomes zero during the etching of the nitrogen-containing layer in the etching chamber 1,
The control circuit 17 determines that the etching process has been completed, and turns off the high-frequency power supply 4 to stop the application of the high-frequency power.

That is, in the above-described apparatus, similarly to the first embodiment, the etching reaction product gas is introduced into a plasma generation region different from the etching region, and nitrogen in the etching reaction product gas is introduced into the plasma generation region. The end point of the etching is detected by measuring the intensity of CN emission obtained by converting the newly introduced carbon into plasma. This eliminates the need to use an etching gas that does not contain carbon, which is a source of contamination, and also makes it possible to measure the CN emission in a region distant from the etching region to detect the etching end point with high accuracy.

In the present embodiment, the plasma discharge chamber 19 is connected in parallel with the vacuum vessel 20, but the gas normally used in place of the vacuum vessel 20 between the etching chamber 1 and the pressure adjusting device 10 is used. By providing a tube and connecting the plasma discharge chamber 19 in parallel with the gas tube, the apparatus according to the present embodiment can be configured using an existing etching apparatus. (Third Embodiment) In the first embodiment, an etching product gas exhausted from an etching region and a carbon-containing gas supplied from a carbon-containing gas supply source are introduced between parallel plate electrodes to generate plasma. Is occurring. However, the means for supplying carbon between the parallel plate type electrodes is not limited to a gaseous one from the beginning, and as described below, carbon is vaporized by etching a carbon-containing substrate. You may use what was done.

FIG. 3 is a block diagram showing a reactive ion etching apparatus according to a third embodiment of the present invention, wherein the same reference numerals as those in FIG. 1 denote the same elements. In FIG. 3, the plasma discharge chamber 9 connected between the exhaust port 6 of the etching chamber 1 and the pressure adjusting device 10 is not provided with a gas inlet for introducing a carbon-containing gas. A carbon-containing substrate 9f such as a carbon substrate or a silicon carbide substrate is arranged on the cathode electrode 9a in the plasma discharge chamber 9.

The rest of the configuration of the etching apparatus of the present embodiment is the same as that of the first embodiment. In the above-described etching apparatus, as in the first embodiment, while the nitrogen-containing layer on the substrate W is being etched in the etching chamber 1, a nitrogen-containing etching product gas is generated and the plasma discharge chamber 9 is generated. Leaked to

When high-frequency power is applied to the cathode electrode 9a in the plasma discharge chamber 9, the etching product gas introduced between the cathode electrode 9a and the counter electrode 9b is turned into plasma, and the carbon-containing substrate supported on the cathode electrode 9a is turned into plasma. 9f
Is etched. Then, the carbon sublimated by the etching of the carbon-containing substrate 9f reacts with the nitrogen in the etching product gas to generate CN luminescence in the plasma. Similarly to the embodiment, after the etching of the nitrogen atom-containing layer is completed in the etching chamber 1, nitrogen is not contained in the etching product gas and the CN is formed in the plasma discharge chamber 9.
No light is emitted.

Then, the point in time at which the CN emission is no longer observed is detected and set as the etching end point, and the etching in the etching chamber 1 is terminated. Therefore, also in this embodiment, since the etching end point is detected by introducing carbon downstream of the etching region, a carbon-containing reaction gas is used as an etching gas for the nitrogen atom-containing layer in order to obtain CN emission. The substrate is prevented from being contaminated by carbon, and C
By measuring the N emission intensity, it becomes possible to detect the etching end point with high sensitivity.

Note that carbon may be used as the material of the cathode electrode 9a. In this case, since the cathode electrode 9a can be used as a carbon generation source, the carbon-containing substrate 9f does not need to be placed on the cathode electrode 9a. It will be good. (Fourth Embodiment) In the above third embodiment,
As a gas for plasma-etching the carbon-containing substrate 9f in the plasma discharge chamber 9, an etching product gas flowing from the etching chamber 1 is used. When the amount of carbon vaporized is small, a sufficient CN emission intensity can be obtained. Therefore, a gas having high etching efficiency may be introduced into the plasma discharge chamber 9 as described below.

FIG. 4 is a block diagram showing a reactive ion etching apparatus according to a third embodiment of the present invention, wherein the same reference numerals as those in FIG. 1 denote the same elements. 4, the plasma discharge chamber 9 connected between the exhaust port 6 of the etching chamber 1 and the pressure adjusting device 10 has a cathode electrode 9a and a counter electrode 9b.
In order to introduce a gas for carbon etching, for example, an argon gas or a carbon-based gas, an etching gas inlet 9g is provided between the etching gas inlet 9g and the etching gas source 22 via an on-off valve 21. For example, an etching gas cylinder is connected.

A carbon-containing substrate 9f such as a carbon substrate or a silicon carbide substrate is disposed on the cathode electrode 9a in the plasma discharge chamber 9. When carbon is used as the material of the cathode electrode 9a, the carbon-containing substrate 9f may be omitted because the cathode electrode 9a can be used as a carbon generation source. Other configurations of the etching apparatus of the present embodiment are the same as those of the first embodiment.

In the above-described etching apparatus, when the nitrogen-containing layer on the substrate W is etched in the etching chamber 1 as in the first embodiment, a nitrogen-containing etching product gas is generated and flows out to the plasma discharge chamber 9. Then, from the carbon gas source 22 to the on-off valve 21 and the etching gas inlet 9 g
When an etching gas is introduced between the cathode electrode 9a and the opposing electrode 9b through the interface, and high-frequency power is applied to the cathode electrode 9a, the etching gas introduced between the cathode electrode 9a and the opposing electrode 9b is turned into a plasma to form a cathode. The carbon-containing substrate 9f supported by the electrode 9a is etched and vaporized, and a carbon-containing gas is generated in a space between the cathode region 9a and the counter electrode 9b.

As a result, plasma of the carbon-containing gas and the etching product gas is generated in the space between the cathode electrode 9a and the counter electrode 9b, and CN emission is generated in the plasma. In the same manner as in the first embodiment, after the etching of the nitrogen atom-containing layer in the etching chamber 1 is completed, almost no nitrogen is contained in the etching product gas, and the CN in the plasma discharge chamber 9 is measured. Light emission is substantially eliminated.

Then, the point in time when the CN emission is no longer observed is detected to be the etching end point, and the etching in the etching chamber 1 is terminated. Therefore, also in the present embodiment, since the etching end point is detected by introducing carbon on the downstream side of the etching region, it is not necessary to use a carbon-containing reaction gas as an etching gas for the nitrogen atom-containing layer. The contamination of the substrate by carbon is prevented, and the etching end point can be detected with high sensitivity by measuring the CN emission intensity in a region different from the etching region.

Further, since the carbon-containing gas was generated in the plasma discharge chamber 9 by plasma-etching the carbon-containing substrate 9f used as the carbon supply source, it is necessary to increase the amount of carbon to sufficiently secure CN emission. Can be. In the above-described first to fourth embodiments, a reactive ion etching apparatus is used as an apparatus for etching a nitrogen-containing layer, but another dry etching apparatus not using a parallel plate electrode may be used.

[0046]

As described above, according to the present invention, the etching region for etching the nitrogen-containing layer and the plasma discharge region for detecting the etching end point are separately provided. It can be used for etching the containing layer, and can prevent contamination of the substrate by carbon.

Further, since the gas introduced from the etching region and the carbon-containing gas introduced from another region are turned into plasma in the plasma discharge region and the intensity of CN emission in the plasma is measured, the nitrogen-containing layer is etched. When the etching of the nitrogen-containing layer is completed, the CN emission intensity decreases and the etching end point is detected, and the etching end point is detected based on the CN emission measurement. High sensitivity and high accuracy.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an apparatus according to a first embodiment of the present invention.

FIG. 2 is a configuration diagram of an apparatus showing a second embodiment of the present invention.

FIG. 3 is a configuration diagram of an apparatus according to a third embodiment of the present invention.

FIG. 4 is a configuration diagram of an apparatus according to a fourth embodiment of the present invention.

[Explanation of symbols]

1. Etching chamber, 2. Cathode electrode, 3. Counter electrode,
4 ... High frequency power supply, 5 ... Etching gas inlet, 6 ... Exhaust port, 7 ... Etching gas supply source, 8 ... Open / close valve, 9 ... Plasma discharge chamber, 10 ... Pressure adjusting device, 11 ... Vacuum pump,
12: gas supply source, 13: on-off valve, 14, 15: gas pipe, 16: plasma emission measurement device, 17: control circuit, 1
8: High frequency power supply, 19: Plasma discharge chamber, 20: Vacuum container.

Claims (7)

[Claims] 1. A method for etching a nitrogen atom-containing layer in a first region using an etching gas containing no carbon, introducing a product gas in the first region into a second region, A carbon-containing gas is introduced into the region to generate plasma with the generated gas to generate carbon nitride. The emission intensity of the carbon nitride is measured in the second region, and the emission intensity is attenuated to a predetermined value. An etching method, wherein an etching end point of the nitrogen atom-containing layer is set at a point in time. 2. The method according to claim 1, wherein the carbon-containing gas is externally introduced into the second region or is obtained by etching a carbon-containing layer in the second region. 3. The etching method according to 1. 3. The method according to claim 2, wherein the etching of the carbon-containing layer is performed by using plasma of the generated gas or by using plasma of an etching gas separately introduced from outside. Etching method. 4. An etching chamber for etching a nitrogen atom-containing layer in a reduced-pressure atmosphere, a plasma discharge chamber into which a generated gas in the etching chamber flows, and a carbon-containing gas supply source for supplying a carbon-containing gas into the plasma discharge chamber. An etching apparatus, comprising: a carbon nitride emission intensity measuring device configured to measure emission intensity of carbon nitride plasma obtained by converting the carbon-containing gas and the generated gas into plasma in the plasma discharge chamber. 5. A gas supply cylinder provided outside the plasma discharge chamber and for supplying the carbon-containing gas in a gaseous state to the plasma discharge chamber. 5. The etching apparatus according to 4. 6. The etching apparatus according to claim 4, wherein the carbon-containing gas supply source is a carbon-containing layer that is placed in the plasma discharge chamber and is etched. 7. The plasma discharge chamber has a parallel plate type electrode having a first electrode supplied with high frequency power and a second electrode connected to a constant voltage source, or receives microwaves from outside. 5. The etching apparatus according to claim 4, further comprising a microwave waveguide for introducing.