JPH06151360A - Method and apparatus for etching - Google Patents

Abstract

PURPOSE:To perform a high-accuracy and high-selectivity etching operation which gives a vertically worked shape without depending on an aspect ratio by a method wherein, during an etching and working operation, the average thickness of an ion sheath formed on the surface of a sample and the average energy of etching ions are changed periodically between two respectively different values. CONSTITUTION:A surface of a sample is etched and worked by using the discharge plasma of a gas containing a reactive gas. During the etching and working operation and in a state that the discharge plasma is generated continuously, the average thickness of an ion sheath formed on the surface of the sample and the average energy of etching ions are changed periodically between two respectively different values. For example, while a reactive gas is being introduced into a discharge tube at a definite flow rate, a microwave discharge plasma is generated. After that, in a state that the plasma is generated continuously, high-frequency electric power applied to the sample is turned on and off repeatedly, and the adsorption of a reaction seed and the desorption of a reaction product are repeated alternately.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an etching method capable of performing etching processing of high selectivity and high anisotropy by using high density plasma with low gas pressure, and an apparatus for carrying out the method. Regarding

[0002]

2. Description of the Related Art In recent years, with the increasing integration of semiconductor integrated circuits and the like, further miniaturization of etching patterns has been promoted in the manufacturing process thereof. The miniaturization of the etching pattern inevitably causes the etching process shape to have a high aspect ratio, so that the aspect ratio dependence of the etching rate has become a problem. That is, it becomes difficult to increase the etching rate as the aspect ratio increases.

In the etching process, energetic ions (hereinafter referred to as etching ions) for etching are attached to the surface of a workpiece to which reactive species (hereinafter referred to as etchant) are adsorbed.
Or simply referred to as ions) to form a reaction product of the etchant and the surface-constituting material of the workpiece by the impact of the ion, and desorb the reaction product from the surface of the workpiece. This is a process of obtaining an etching pattern. At this time, only the ions accelerated by the electric field enter the surface of the work piece with directivity, and the etchant enters the surface of the work piece from random directions. Therefore, in order to reduce the dependency of the etching rate on the aspect ratio, it is necessary to align the incident directions of the etching ions, and various measures have been taken for that purpose.

A general method for aligning the traveling directions of etching ions is to lower the gas pressure of plasma for generating etching ions. This is a method for improving the directionality of etching ions by reducing the scattering of etching ions due to collision with neutral particles in the ion sheath. However, in this case, since the density of the etchant and the etching ions themselves is lowered by lowering the gas pressure, the etching rate is inevitably lowered. Therefore, in order to prevent the decrease of the etching rate, a magnetic field is applied to the generated plasma to densify the plasma.

Further, in the processing of ultra-high integrated circuits (ULSI), thinning of masks and underlayers has progressed, and etching techniques excellent in high selectivity and low damage have been required.
To meet this requirement, the energy of etching ions has been reduced.

As an etching device of low gas pressure and low ion energy which can satisfy both of the above requirements, an etching device using a magnetic field microwave discharge (this is also called an ECR (electron cyclotron resonance) etching device). Have been put to practical use, and further improvements have been made. For example, JP-A-2-253617
The publication discloses a device in which a DC current in which an AC current is superposed is passed through an electromagnet arranged around the reaction chamber to improve the uniformity of plasma and thereby increase the etching rate. In addition, Japanese Patent Laid-Open No. 3-155620
The publication discloses an apparatus for intermittently generating plasma by switching a microwave power source for plasma generation in synchronization with an AC bias power source for accelerating ions. According to this device, it is shown that the AC bias can be efficiently matched, the loss of the bias power is reduced, and the etching rate is improved.

[0007]

In the above-mentioned conventional etching method and apparatus, in order to improve the directionality of etching ions and reduce the energy, high density plasma is generated at low gas pressure, and It has been done to reduce the magnitude of the high frequency bias power to accelerate the. In such a conventional technique, consideration is given to reducing the scattering of ions assisting the etching and improving the directionality of the ions. However, improvement in the uniformity of the accelerating electric field of the ions and sufficient etchant It cannot be said that sufficient consideration has been given to the point of supply of electricity. For this reason, for example, when etching a groove or hole pattern, there occurs a phenomenon that the supply of the etchant to the bottom of the groove or hole is insufficient, and the etching ions are incident in a substantially vertical direction even though they are incident in a high direction. There is a problem that the etching rate in the aspect ratio portion decreases and the etching depth becomes insufficient. This problem is becoming more and more important as the aspect ratio increases as the processing size becomes finer.

Further, the etching ions are bent by local electric field distortion such as mask charge-up of the workpiece,
The phenomenon that the processed shape is slanted is also becoming a problem. The phenomenon that the ions are bent is caused by the electric field concentration due to the processing step. This phenomenon is because when the plasma density is increased to increase the etching rate, the ion sheath thickness becomes relatively thin with respect to the processing step size of the etching shape, so that the ions are further bent. It is an even more serious issue.

An object of the present invention is to solve the above-mentioned problems in the prior art and to perform a highly accurate and highly selective etching method for providing a vertical processing shape having no aspect ratio dependency, and a method suitable for carrying out the method. An etching device is provided.

[0010]

The above-mentioned object is achieved by intermittently changing the output of a high-frequency power source connected to a support of a workpiece (sample) or the strength of a magnetic field applied in plasma, thereby obtaining an average ion. The sheath thickness d and the average ion energy Vs take the values of d ₁ and Vs ₁ , respectively, and d ₂ and Vs ₂ (d ₂ > d ₁ and Vs
₂ > Vs ₁ ) It is achieved by repeating alternate switching between a plurality of different states such as a state in which a value of ₂ > Vs ₁ ) is taken.

[0011]

As described above, in the etching method and apparatus of the present invention, the high-frequency wave connected to the sample stage that supports the sample to be processed under the condition that the plasma for generating the etching ions is continuously generated. Change the output of the power supply intermittently between different output values, or
By changing the magnetic field intensity applied to the plasma intermittently by the magnetic field generating means arranged around the plasma generating chamber, the average ion sheath thickness d of the plasma is intermittently changed between a thin state and a thick state. The feature is that it is changed (periodically).

First, the average ion sheath thickness d is (d = d
_{In the} thin state ( ₁ ), the output of the high frequency power supply is lowered to lower the average ion energy Vs (Vs = Vs ₁ ). Within this time, a sufficient amount of etchant is supplied while suppressing the etching reaction. After that, in a state in which the average ion sheath thickness d is increased (d = d ₂ ), the output of the high frequency power source is increased to set the average ion energy Vs to (Vs =
Vs ₂ ) to accelerate the etching reaction. However, the average ion energy Vs ₂ in this state is not so good that it is simply higher. In practice, the average ion energy Vs ₂ should be selected within a range where a high etching selectivity is obtained for the mask material used. Therefore, it is necessary to improve the etching selectivity.

As described above, in the etching method of the present invention, a predetermined etching is performed by periodically repeating the above two states in the state where the plasma for generating the etching ions is continuously generated and maintained. Is carried out. Therefore, the etching ions can be irradiated in a state where the etchant is sufficiently supplied to the high aspect ratio portion, so that the aspect ratio dependence of the etching rate, which has been a problem in the conventional technique, can be effectively relaxed. It is possible.

Further, in a state where the average thickness d of the ion sheath is thick (d ₂ ), this thickness d _{2 is set} to be 10 times or more the step size on the surface of the workpiece and shorter than the average free path of the ions. By doing so, it is possible to reduce the influence of electric field distortion and charge-up in the vicinity of the step, and allow ions to enter vertically.

In the etching method of the present invention, the supply of the etchant and the ion irradiation with relatively high energy for promoting the etching can be independently controlled, so that a good vertical etching process can be achieved.

[0016]

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

[Embodiment 1] This embodiment relates to a method of etching a sample surface while periodically changing a high frequency voltage applied to a sample to be processed in a magnetic field microwave etching apparatus.

FIG. 1 is a schematic vertical cross-sectional view showing the structure of a main part of a magnetic field microwave etching apparatus used for carrying out the etching method of the present invention. In the figure,
Microwave power generator 1, waveguide 2, microwave transparent vacuum container (discharge tube) 3, magnetic field generating electromagnetic coil 4, sample stage 5, sample temperature control mechanism 6, sample 7 to be processed, fixed potential applying electrode 8, high frequency power application power supply 9, electromagnetic coil power supply 1
0, the gas introduction system 11, the vacuum exhaust port 12, the plasma monitoring window 13 for the emission monitor, and the emission monitor processing device 14 are already used in the conventional magnetic field microwave etching device.

In the above structure, the sample 7 to be etched is placed on the sample table 5 and the inside of the discharge tube 3 is evacuated. In the state that the discharge gas containing gas is introduced,
Discharge tube 3 from microwave power generator 1 via waveguide 2
By supplying microwave power to the inside, microwave discharge plasma is generated in the discharge tube 3. In addition, the density of the generated plasma is increased by applying a magnetic field of appropriate strength to the generated plasma by the electromagnetic coil 4. In this high density plasma, the discharge gas is excited and dissociated to generate etching ions and a reactive etchant. As described above, the surface of the sample 7 is etched by the etching ions and the etchant. It should be noted that a more detailed description of the operation and function of the conventional device portion will be omitted here.

In the present embodiment, in addition to the above-mentioned conventional apparatus configuration, the high frequency power to the sample 7 is further provided in the path for applying the high frequency power from the high frequency power applying power source 9 to the sample via the sample stage 5. Is additionally provided with a chopper 15 for intermittently switching between two different application conditions, and a synchronous control mechanism 16 for synchronously controlling the chopper 15 and the magnetic field coil power supply 10 is provided. ing. The magnetic field coil power supply 1 is provided by this synchronization control mechanism 16.
By changing the supply condition of the exciting current from 0 to the electromagnetic coil 4 intermittently between two different conditions, the plasma generation condition of the plasma continuously generated and maintained in the discharge tube 3 (plasma density and ECR point ) Is intermittently and repeatedly changed between two different states, and the high frequency power applied from the high frequency power applying power source 9 to the sample 7 by the chopper 15 is synchronized with the intermittent change of the plasma generation condition. It is configured so that the application condition can be intermittently and repeatedly changed between two different conditions. Instead of using the chopper 15 described above, the output system itself of the high frequency power applying power source 9 is provided with a functional means capable of intermittently changing the high frequency power applying condition for the sample similar to the above, and the synchronous control is performed. It goes without saying that the function means may be directly controlled by the control signal from the mechanism 16. In short, any functional means capable of intermittently changing the condition for applying high-frequency power to the sample may be used.

FIG. 2 shows a basic flow chart of the etching method of the present invention, which is performed by using the apparatus configuration of FIG. Figure 2
In (a), the pressure condition of the gas introduced into the plasma is shown, and (b) is the microwave (μ
(Wave) power, (c) shows the change of the high frequency power (RF power) applied to the sample, and (d) shows the state of the change of the etching reaction mechanism performed on the sample surface. FIG. 3 is a diagram conceptually illustrating how the etching reaction mechanism changes (adsorption of reactive species and desorption of reaction products) when the sample surface is etched according to the above-described etching flow.

In the etching method of this embodiment, first, a reactive gas is introduced into the discharge tube 3 at a constant flow rate so that the gas pressure in the discharge tube 3 is kept constant ((a) of FIG. 2). On the other hand, microwave power having a constant intensity is applied to the discharge tube 3 ((b) of FIG. 2) to generate microwave discharge plasma in the discharge tube 3. After that, the high-frequency power applied to the sample 7 is repeatedly turned on and off while the plasma is continuously generated (continuous discharge) ((c) of FIG. 2). As a result, the adsorption of the reactive species and the desorption of the reaction product are alternately repeated ((d) of FIG. 2).

First, the application of high frequency power to the sample is turned off.
In the cycle time (Toff), the thickness of the ion sheath is thin and the energy of the generated etching ions is low, so that the etching hardly progresses and the etchant (reactive species) is preferentially adsorbed. And
During this period (Toff), the sample surface is covered with at least one layer of etchant (see FIG. 3A). Next, in the cycle time (Ton) when the application of the high frequency power to the sample is turned on, the thickness of the ion sheath increases,
The energy of etching ions increases, and a sufficient etching reaction proceeds (see (b) in FIG. 3).

By repeating these operations with a cycle time (T) shorter than 1 second, etching is performed in a state where the etchant is sufficiently supplied,
Etching with high reaction efficiency is achieved. Also, the supply of microwave (μ-wave) power is made periodic (intermittent),
When a pause period for microwave discharge plasma generation is provided, intermittent application of high frequency power to the sample as described above may be repeated during the period during which the plasma is generated.

A case where the silicon substrate 41 provided with the single-layer resist mask 42 as shown in FIG. 4A is etched using SF ₆ gas by using the apparatus configuration of FIG. 1 will be described. First, the silicon substrate 41 is transferred into the discharge tube 3 and cooled by the temperature control mechanism 6
Fix on top and hold the silicon substrate temperature at -130 ° C. Then, a discharge gas containing 25 sccm of SF ₆ gas was introduced into the discharge tube 3, and the pressure in the discharge tube 3 was adjusted to 10 m Torr.
Keep at r (constant). In this state, an electric current is passed through the electromagnetic coil 4, microwave power is supplied from the waveguide 2 into the discharge tube 3, and gas discharge plasma is generated in the discharge tube 3.

When this discharge plasma is generated, this time,
A control signal from the synchronous control mechanism 16 is sent to the chopper 15 provided in the connection path between the high-frequency power source 9 and the sample table 5 so that the high-frequency power is applied to the sample 7 at 0 W in 0.5 second cycles. While alternately switching between (OFF state) and 5W applied state (ON state),
Etching was performed to a depth of 3 μm in a pattern portion having an opening width Wa of 3 μm. The etching pattern shape when etching was performed by this method was as shown in FIG. On the other hand, the etching pattern shape when the high frequency power was applied to the sample 7 at a constant 5 W according to the conventional method, and the etching pattern shape was as shown in FIG.

As is clear from the comparison between FIG. 4B and FIG. 4C, the etching shape obtained by the method of this embodiment is greatly improved in terms of selectivity to resist and aspect ratio dependency. . By the way, in the conventional method, the selection ratio to the resist was about 40, whereas in the method of the present example, the selection ratio was about 100, and it was confirmed that the selection ratio was improved more than twice. Further, an etching delay of about 20% was recognized in the etching depth 44 of the pattern portion having the opening width Wb of 0.5 μm by the conventional method as compared with the etching depth 43 of the pattern portion having the opening width Wa of 3 μm. However, almost no such etching delay was observed in the etching depth 46 of the 0.5 μm pattern portion in the method of this embodiment.

The reason why the above-mentioned excellent effects are obtained in this embodiment will be described with reference to the experimental results shown in FIG. FIG. 5 shows ON-OF when high frequency power is applied to the sample.
The change in etching rate is shown when the cycle time T is changed with the same F time (Ton = Toff).
The experiment was conducted on the sample shown in FIG. 4A using the apparatus configuration of FIG. While introducing SF ₆ gas at a pressure of 10 m Torr at 25 sccm, the high frequency power applied to the sample is periodically switched between 0 W (no applied state) and 5 W (applied state) to perform etching treatment. 0.
The etching rate of the pattern portion having a width of 5 μm was examined. For comparison, the etching rate in the case of continuously applying a high-frequency power of 5 W to the sample according to the conventional method was about 3.5 μm / min, and the case of continuously applying 0 W (no applied state) Etching rate is about 0.1
It was μm / min. On the other hand, when the high frequency power applied to the sample is cyclically changed according to the present invention, when the cycle time T is as long as about 10 seconds, the etching rate decreases to about 1.5 μm / min. This cycle time T
Is shorter than 1 second, the etching rate remarkably increases, and is saturated in 0.2 seconds or less. When the cycle time T is long, this is an average etching rate when the high frequency power application is 0 W continuous and 5 W continuous, but as the cycle time T is shortened, the etchant adsorption occurs. It is considered that the above process and the process of desorption of the reaction product are efficiently performed. Under the conditions shown in FIG. 5, it is appropriate that the application time Ton of the high frequency power after the saturated adsorption of the etchant is 0.1 seconds.

Next, the sample 7 is supplied as an etchant supply time.
The effect of providing the high-frequency power non-application time Toff to the will be described with reference to the experimental results of FIG. This experiment was performed on the sample shown in FIG. 4A using the apparatus configuration shown in FIG. The cycle time Ton when the high frequency power applied to the sample 7 is 5 W is fixed to 0.1 second, and the cycle time T when the applied high frequency power is 0 W (RF off).
The change in the etching rate of the 0.5 μm pattern portion when the off was changed was examined. Other conditions were set in the same manner as in the case of the experiment shown in FIG.

As the cycle time Toff of no RF power application (RF off) is shortened, the etching rate increases,
It was almost saturated at 0.05 seconds or less. But 3.0
The etching rate of the μm pattern portion was not saturated even when it was 0.05 seconds or less, and the aspect ratio dependency was generated again. Under this condition, the supply of the etchant is almost saturated in 0.05 seconds, and the adsorption amount does not increase even if the adsorption time (Toff) is further lengthened. Therefore, the dead time increases and the etching rate decreases. But Toff time is 0.0
If the time is shorter than 5 seconds, it is considered that the amount of etchant adsorbed in the pattern portion having a high aspect ratio becomes insufficient, resulting in the aspect ratio dependency.

Now, when attempting to adsorb 3 to 4 etchants to silicon atoms present on the surface of a silicon substrate at an areal density of about 1.4 × 10 ¹⁵ per cm ² of area, 10 m Torr of At pressure, the amount of etchant incident is about 5 × 10 ¹⁸ per second, so that a required number of etchants are incident in about 1 millisecond. However, since the number of etchants reaching the bottom of the etching hole or groove is about several percent to 50% of the incident amount due to the aspect ratio, it takes at least 0.05 seconds for the adsorption amount to be saturated.
As described above, the adsorption time of at least 1 millisecond or more is required to perform the saturated gas adsorption. Therefore,
The frequency of intermittent application of high-frequency power to the sample is 1 kHz.
Must be:

When a low frequency power source is used instead of the chopper 15 and the high frequency power source 9 in the apparatus configuration of FIG. 1, the processing accuracy is lowered due to the charge-up of an insulating mask such as a resist during one cycle. Therefore, the desired effect cannot be obtained simply by applying a low-frequency sample bias. Therefore, by applying high-frequency power of 1 kHz or more to the sample by amplitude-modulating the high-frequency power with low frequency, the desired effect can be obtained. It is possible to realize highly precise and highly efficient etching processing.

In the above example, SF is used as the etching gas.
_Although the case of using ₆ gases is shown, the optimum cycle time T changes slightly even if other etching gases such as Cl ₂ and Br ₂ are used, but the application of high frequency power to the sample is intermittently changed. As a result, a similar effect was obtained.

Further, the usable etching apparatus is not limited to the magnetic field microwave plasma etching apparatus shown in the above-mentioned embodiment, and a plasma using a plasma generation mechanism such as a helical resonance type or a three-electrode type is used. Similar effects can be obtained with a plasma etching apparatus such as an etching apparatus that can independently control generation of plasma and application of high-frequency power to a sample.

In the etching method of the present invention, the etchant is sufficiently adsorbed to the sample being etched in the continuously generated plasma, and then a high frequency bias is instantaneously applied to increase the height. Since the etching is performed by the action of anisotropic ions, the ion irradiation with the low energy that does not cause a remarkable etching action may be performed at the time of adsorbing the etchant. That is, it goes without saying that the high frequency bias applied to the sample is not simply turned on and off, but switching between the high bias application state and the low bias application state may be repeated.

[Embodiment 2] This embodiment relates to a method for etching polycrystalline silicon through an oxide film mask using the magnetic field microwave etching apparatus having the apparatus configuration shown in FIG. Another purpose is to explain another effect when the high frequency power applied to the sample to be processed is intermittently changed.

FIG. 7 is a process diagram of the etching method according to this embodiment. FIG. 7A shows the shape of the sample before etching. After the thermal oxide film 72 is grown on the silicon substrate 71, the polycrystalline silicon 73 and the silicon oxide film 74 are deposited and the silicon oxide film 74 is formed. It is formed by forming an isolated pattern. This sample was etched in a reaction chamber (discharge tube) where Cl ₂ gas was introduced at a flow rate of 20 sccm and the pressure was kept constant at 10 m Torr. In the apparatus configuration of FIG. 1, the output of the applied high frequency power is set to 3 W (constant) in order to obtain a high etching selection ratio of the polycrystalline silicon 73 to the oxide film 74 without changing the high frequency power applied to the sample intermittently. When the polycrystalline silicon layer 73 was set and continuously etched, there was a phenomenon that the etching cross-sectional shape became an inverse taper shape as shown in FIG. 7B. It is considered that this is because the average thickness d of the ion sheath formed between the plasma and the sample surface is thinner than the pattern step and the accelerating electric field is low, so that it is affected by the distortion of the electric field in the pattern portion. . At this time, the etching selection ratio of the polycrystalline silicon 73 to the oxide film 74 was about 30. Using the same apparatus structure, in order to mitigate the influence of electric field distortion of the pattern portion, when the output of the high frequency power source is set to 10 W (constant) and continuous etching is performed, a vertical cross section as shown in FIG. A shape was obtained, but the etching selectivity at this time was reduced to about 10.

On the other hand, in the apparatus configuration of FIG. 1, the etching cross-sectional shape when etching is performed while repeatedly switching the high frequency power applied to the sample between 0 W and 10 W at each 0.5 second cycle is shown in FIG. d). With a vertical cross section,
The etching selectivity is about 30, and the shape and selectivity are improved. In this embodiment, since the supply of the etchant is saturated and the high-energy ions are irradiated, it is considered that efficient etching progresses and the selectivity and the processed shape are improved.

Further, in the present embodiment, since etching having almost no aspect ratio dependency is achieved, the time for overetching may be short.
It is possible to reduce scraping.

In addition, even when a pattern in which a large number of grooves (spaces) to be etched are lined up, such as lines and spaces, is etched by using the etching method of this embodiment, the same good etching characteristics as above can be obtained. Was given.

[0041]

According to the etching method of the present invention, since the etchant supply time to the sample surface and the etching ion irradiation can be controlled almost independently, a high selectivity ratio of the vertical cross-section shape with almost no aspect ratio dependency can be obtained. Since etching can be achieved, there is an effect that the pattern processing accuracy in ULSI or the like can be significantly improved. Therefore, it is particularly effective for processing a gate when the underlying oxide film is thin, processing a trench capacitor having a high aspect ratio structure, and the like. Also,
According to the etching method of the present invention, it is possible to obtain an effect that etching processing can be performed with low damage.

[Brief description of drawings]

FIG. 1 is a schematic vertical cross-sectional view showing a configuration of a main part of a magnetic field microwave etching apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram showing a parameter flow of an etching method according to an embodiment of the present invention.

FIG. 3 is a schematic diagram for explaining an etching mechanism in the etching method of the present invention.

FIG. 4 is a process explanatory view for explaining an effect obtained by the etching method of the present invention.

FIG. 5 is a curve diagram for explaining another effect obtained by the etching method of the present invention.

FIG. 6 is a curve diagram for explaining still another effect obtained by the etching method of the present invention.

FIG. 7 is a process explanatory view for explaining still another effect obtained by the etching method of the present invention.

[Explanation of symbols]

1: microwave generator 2: waveguide
3: Discharge tube, 4: Electromagnetic coil, 5: Sample stand, 6: Temperature control mechanism, 7: Sample,
8: fixed potential applying electrode, 9: high frequency power supply,
10: coil power supply, 11: gas introduction system,
12: exhaust port, 13: daylighting window,
14: light emission signal monitor, 15: chopper, 16: synchronization mechanism, 41:
Silicon substrate, 42: Resist, 4
3: etching depth, 44: etching depth, 45: etching depth, 4
6: etching depth, 71: silicon substrate,
72: Silicon oxide film, 73: Polycrystalline silicon film, 74: Silicon oxide film.

Claims (8)

[Claims] 1. An etching method for etching a sample surface using discharge plasma of a gas containing a reactive gas, wherein the discharge plasma of the sample is continuously generated during the etching process of the sample surface. An etching method characterized in that the average thickness of the ion sheath formed on the surface and the average energy of etching ions are periodically changed between different binary values. 2. When the average thickness of the ion sheath has a small value, the average energy of the etching ions also has a small value, and when the average thickness of the ion sheath has a large value, the average energy of the etching ions also has a large value. The etching method according to claim 1, wherein the etching method has a large value. 3. The etching method according to claim 1, wherein the cycle of the periodic change is 1 second or less. 4. A reaction chamber, means for holding a sample to be etched in the reaction chamber, means for generating discharge plasma of a gas containing a reactive gas in the reaction chamber, and high-frequency power to the sample. In the etching apparatus having a means for applying, a means for periodically changing the magnitude of the high frequency power applied to the sample by the high frequency power applying means is additionally provided. Etching equipment. 5. The etching method according to claim 4, wherein the discharge plasma generating means is a microwave discharge plasma generating means for generating discharge plasma using microwaves. 6. The etching apparatus according to claim 4, further comprising means for applying a magnetic field to the discharge plasma. 7. The etching apparatus according to claim 6, further comprising means for periodically changing the magnetic field strength applied to the discharge plasma by the magnetic field applying means during etching. . 8. A means for synchronizing the periodical change of the high frequency power applied to the sample with the periodical change of the magnetic field strength applied to the discharge plasma is further provided. The etching apparatus according to claim 7.