JPH03155132A - Method and apparatus for dry etching - Google Patents

Abstract

PURPOSE:To prevent contamination and damage of an object by an etching method in which a periodical potential is applied to an extraction electrode and a susceptor is moved periodically between an ion path and the outside of the path to prevent the collision with sputtered ions other than the useful ions. CONSTITUTION:A power supply 9 applies a voltage to one plate 7a, facing a plasma chamber 1, of an attraction electrode 7. The voltage is applied to spatially separate sputtered ions 81 and chlorine ions 4 according to the difference in velocity between the two kinds of ion. The frequency of the voltage is determined to obtain sufficient spatial separation of ions in the position of a specimen 3. A fixed shutter 10 is provided away from the path of ions in a process chamber 2. A susceptor 6 mounted on a shaft is rotated to a position under the ion path and the shutter 10. The angular speed of the susceptor 6 is regulated according to the degree of spatial separation of the sputtered ions 81 and the chlorine ions 4. The susceptor 6 is thus brought under the shutter 10 for protection before high-speed ions 81 pass.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a dry etching apparatus and a dry etching method for microfabrication of samples such as semiconductor wafers, and in particular to a dry etching method that does not cause contamination or damage to the sample due to impurity ions. The present invention relates to an apparatus and a dry etching method.

[Conventional technology]

As a method for microfabrication of semiconductor wafers, there is reactive ion beam etching using a reactive gas such as chlorine. In this method, as shown in FIG. 3, a plasma chamber 1 and a sample processing chamber 2 are provided adjacent to each other, an ion extraction electrode 7 is provided at the interface between the chambers, and etching gas is discharged within the plasma chamber 1. , generates ions 4 and radicals 5, accelerates the ions 4 in the plasma by the extraction electrode 7, irradiates the sample 3 placed on the sample stage 6 in the sample processing chamber 2, and also extracts the neutral radicals 5. This is a method in which the sample 3 is irradiated by leaking through the opening 17 provided in the electrode 7, and etching is performed by the action of both ions 4 and radicals 5.
It is described in detail in Publication No. 31.

In this conventional dry etching apparatus, the extraction electrode 7 consists of two electrode plates 7a arranged parallel to each other with a predetermined distance maintained between them.
Each electrode plate is provided with a large number of holes, and when the electrode 7b is at ground potential and a bias voltage is applied to the electrode 7a, the electrode 7a is connected to the electrode 7b.
An electric field is generated in the direction b, and the ions are accelerated by this electric field between the electrodes and rush into the etching chamber 2. By controlling the bias voltage applied to the extraction electrode 7, ions 4 or radicals 5 in the plasma can be selectively extracted to perform anisotropic etching, isotropic etching, fine etching, etc. on a sample such as a semiconductor wafer. This can be done with precise control.

[Problem to be solved by the invention]

In the etching method using the conventional dry etching apparatus using the above-mentioned reactive gas, the ions 4 and radicals 5 of the reactive etching gas sputter the extraction electrode 7 and the inner wall material of the plasma chamber 1. These undesirable sputtered impurities 8 include sputtered impurity atoms 80 and sputtered ions 80, and reach the sample 3 together with the ions 4 of the etching gas.

The sputtered impurities 8 are the MO of the electrode material and the plasma chamber 1.
．． Composition of stainless steel (F
e, Cr, Ni, etc.). Of these, neutral sputtered atoms 80 accumulate on the sample surface, and are driven into the sample 3 by ions 4, forming lattice defects or becoming impurities, which adversely affect the electrical and optical properties of the sample. . Since the sputtered ions 81 are accelerated by the extraction electrode 7, they are struck into the sample 3, forming lattice defects or becoming impurities.

Generally, the proportion of sputtered ions 81 in sputtered impurities 8 is about 10% at most, so it is not large in quantity;
Since it is accelerated and the kinetic energy is large, the effect is large.

SUMMARY OF THE INVENTION An object of the present invention is to provide a novel dry etching apparatus and dry etching method that solves the drawbacks of the dry etching method using the conventional dry etching apparatus described above and eliminates contamination and damage to a sample due to sputtered ions.

[Means to solve the problem]

The dry etching apparatus of the present invention includes an ion extraction electrode provided at the interface between the plasma chamber and the sample processing chamber in the vacuum apparatus, a means for applying a periodically changing potential to the extraction electrode 7, and a means for holding the sample. Mechanical means is provided for moving the sample stage alternately between a path section where ions fly in the sample processing chamber and a space where ions do not fly.

Furthermore, in the dry etching method of the present invention, ions of the etching gas are periodically drawn out toward the sample by applying a periodically changing potential to the extraction electrode of the dry etching apparatus, and at the same time, the ions of the etching gas are drawn out toward the sample. Etching is carried out by periodically moving the table between the ion path and the space where ions do not fly, thereby preventing sputtered ions other than ions of the processing gas from reaching the sample.

In order to effectively prevent sputtered ions from reaching the sample, it is effective to set the periodic potential applied to the extraction electrode to be an alternating current or pulsating current, and to synchronize the period with the period of movement of the sample stage.

As will be explained later, sputtered ions can be selectively obstructed because of the large difference in kinetic energy between the etching gas ions and the ions generated by sputtering, and the speed at which the sputtered ions move towards the sample is greater than that of the etching gas ions. Since this method takes advantage of the fact that the ion velocity is relatively smaller than the velocity of the ions, the period of the potential applied to the extraction electrode must be made small enough to make a slight difference in the velocity of the ions significant. Therefore, it is necessary to move the sample stage sufficiently quickly in synchronization with the period.

[Effect]

As described above, the ions of the etching gas in the plasma chamber are accelerated by the extraction electrode, extracted into the sample processing chamber, and reach the sample. At this time, the ions collide with the extraction electrode and the inner wall of the plasma chamber to generate sputtered impurities.

As long as a positive potential is applied to the extraction electrode, the ionized sputter ions of the sputter impurities are accelerated toward the sample processing chamber together with the etching gas ions. However, when the potential is negative or zero, it is accelerated towards the plasma chamber or remains within the plasma chamber 1 and does not come out to the sample processing chamber.

By the way, the speed of sputtering ions is generally smaller than that of primary ions, that is, etching gas ions, ranging from 1/10 to 1/10
It is said to be 1/1. Therefore, if the potential applied to the extraction electrode is an alternating current or pulsating flow, the flow of ions entering the sample processing chamber will consist of alternating groups of mainly etching gas ions and groups of mainly sputter ions. . By moving the sample stage in synchronization with this cycle, sputtered ions can be prevented from reaching the sample.

〔Example〕

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

FIG. 1 is a cross-sectional view of a first embodiment of the present invention, showing the case where the present invention is applied to a dry etching apparatus using a reactive ion beam etching method that uses electron cyclotron resonance as a means of plasma generation. .

In a vacuum apparatus, a plasma chamber 1 and a sample processing chamber 2 are provided adjacent to each other, and an opening is provided in the wall forming the boundary between the chambers to communicate the chambers. An extraction electrode 7 for extraction is provided. This ion extraction electrode 7 is composed of two electrode plates 7a and 7b arranged in parallel with a predetermined interval, and each electrode plate has a large number of openings 17. . In the illustrated embodiment, the plasma chamber 1 is an electron cyclotron resonance type plasma chamber, and a microwave waveguide 14 for plasma excitation is connected to the upper part of the plasma chamber via a quartz plate 15, and an electromagnetic waveguide for excitation of cyclotron motion is connected to the upper part of the plasma chamber. It is surrounded by a coil 16.

In the above configuration, the microwave injected into the plasma chamber 1 from the microwave waveguide 14 excites a standing wave within the plasma chamber 1. - way 1, reaction gas supply pipe 18
The etching gas such as chlorine supplied to the plasma chamber 1 is discharged by the injection microwave electric field, and the ions in the plasma generated by the discharge cause cyclotron movement by the magnetic field of the electromagnetic coil 16, and the frequency of this movement is changed by the injection. Since the frequency of the microwave is equal to that of the microwave, the microwave is resonantly absorbed, and a plasma with high ion density is formed in the center of the plasma chamber 1. As in the conventional dry etching apparatus described above, the electrode plate 7b of the extraction electrode 7 on the sample processing chamber 2 side is at ground potential.

An alternating current or pulsating voltage is supplied and applied to the electrode plate 7b on the plasma chamber 1 side from an alternating current power supply 9 provided outside the dry etching apparatus. The period is 8 sputtered ions.
In consideration of the speed difference between ions 1 and ions 4 of chlorine gas, the position of the sample 3 is set as short as possible to sufficiently spatially separate the ions 4 and the sputtered ions 81. On the other hand, in the sample processing chamber 2, a fixed shirt plate 10 is provided at a position away from the ion path and not hit by too many ions.

The sample stage 6 is attached to a rotatable shaft,
As the shaft rotates, it can be positioned in the path of ions or under the shutter plate 10. Shirt board 1
Since ion 4.8.81 does not reach the bottom of 0,
While the sample stage 6 is in this position, the sample 3 is not exposed to the sputtered ions 81. By adjusting the rotation speed of the sample stage 6 in accordance with the spatial separation between the sputtered ions 81 and the chlorine ions 4 due to the periodic potential application to the extraction electrode, the highly sputtered ions 81 can be adjusted to the position of the sample stage 6 in the path. The sample stage 6 can be retracted under the shutter plate 10 when passing through.

In contrast to a method using a dry etching apparatus and a dry etching method in which the sample 3 is evacuated to a space where sputtered ions 81 do not fly as in the present invention, for example, the sample stage 6
It is also conceivable to move the shutter plate 10 on the sample stage 6 after fixing it to prevent the sputtered ions 81 from flying. However, in the latter case, since the shutter plate 10 is always exposed to ions, there is a problem that the shutter plate 10 itself is sputtered and becomes a source of a large amount of sputtered impurities.

The present invention is advantageous in that such a problem does not occur because the shutter plate 10 can be provided in a region where the number of ions that fly is originally small.

FIG. 2 is a sectional view of a second embodiment of the invention.

Here, the configuration is such that the cycle of the alternating current or pulsating current applied to the extraction electrode 7 and the rotation cycle of the rotary sample stage 6 are controlled by a synchronization signal generator 13. It is preferable to use a pulse drive motor 12 to rotate the rotary sample stage 6, and since the other configuration is the same as that of the first embodiment, a description thereof will be omitted.

In the above embodiment, the voltage applied to the extraction electrode 7 was an alternating current or pulsating voltage, but a rectangular pulse voltage may also be used.Although chlorine was used as the etching gas in the explanation, a reactive gas such as bromine could be used. But it's okay.

Further, although an electron cyclotron resonance type is used as the plasma generating means, it goes without saying that a Kauffman type or a glow discharge type may also be used.

〔Effect of the invention〕

As explained above, if the dry etching apparatus and dry etching method of the present invention are used, etching can be performed while the sample is evacuated to a space where sputtered ions other than etching gas ions do not fly. can be significantly reduced. Therefore, it is possible to reduce contamination and damage to the sample due to sputtered ions, and it is possible to process a high-quality sample.

1 Brief Description of the Drawings Figure 1 is a sectional view of the first embodiment of the present invention, Figure 2 is a sectional view of the second embodiment of the invention, and Figure 3 is an example of a conventional dry etching apparatus. FIG.

DESCRIPTION OF SYMBOLS 1... Plasma chamber, 2... Sample processing chamber, 3... Sample, 4... Ion, 5... Radical, 6... Sample stage, 7... Extraction electrode, 8...・Sputter impurities, 9・
... AC or pulsating current power supply, 10... Shaft plate, 12.
...Pulse drive motor 13...Synchronization signal generator,
14... Microwave tube, 15... Quartz plate, 16...
- Electromagnetic coil, 17... Opening part, 18... Reaction gas supply pipe.

Claims (2)

[Claims] 1. A plasma chamber for ionizing processing gas, a sample processing chamber that is provided in contact with the plasma chamber and has a sample stage for holding the sample, and an ion ion processing chamber provided at the interface between the plasma chamber and the sample processing chamber. an extraction electrode for extraction, a means for applying a periodically changing potential to the extraction electrode, and a means for preventing the ions from flying, the sample stage being provided in a path portion where the ions fly and in the sample processing chamber. What is claimed is: 1. A dry etching apparatus, comprising at least means for making the dry etching apparatus movable alternately between the spaces. 2. A plasma chamber for ionizing processing gas, a sample processing chamber that is provided in contact with the plasma chamber and has a sample stage for holding the sample, and an ion ion processing chamber provided at the interface between the plasma chamber and the sample processing chamber. an extraction electrode for extraction, a means for applying a periodically changing potential to the extraction electrode, and a means for preventing the ions from flying, the sample stage being provided in a path portion where the ions fly and in the sample processing chamber. Using a dry etching apparatus that includes at least a means that allows the ions to move alternately between spaces, ions of the processing gas are periodically directed toward the sample by applying a periodically changing potential to the extraction electrode. A dry etching method characterized in that etching is performed by adjusting the moving period of the sample stage so as to prevent atoms and ion species other than ions of the components of the processing gas from reaching the sample.