JPS5855571A - Plasma etching apparatus - Google Patents

Abstract

PURPOSE:To provide the titled apparatus provided with a means suitable for enhancing the yield of an etching process, comprising providing a dust adsorbing electrode for adsorbing and removing dust, especially, adhered to the etching surface of a sample. CONSTITUTION:In recessed bores provided at equal intervals to the upper surface of a rotary type sample table 2 in an etching chamber 1 evacuated through an exhaust port 8, samples 6a, 6b... are accommodated. In this condition, high frequency power generated by a magnetron 11 is supplied from a supply means 12 to form plasma of a gas introduced into a reaction chamber 9 from a gas inlet 10. In this state, plasma is confined in the chamber 9 by a magnetic field generated by supplying current to an exciting coil 13 and the surfaces of the samples 6a, 6b... passing through this plasma region are subjected to plasma etching. By this mechanism, for example, dust adhered to the surface of the sample 6a is adsorbed by a first dust adsorbing electrode 14 and the dust tansferred onto the electrode 14 is adsorbed and removed by a second dust adsorbing electrode 19 to which an electric field with counter polarity is applied. That is, because the dust adhered on the surface of the sample can be removed in a contact free state directly before ethching is started, etching inferiority due to dust can be extremely reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a plasma etching apparatus, and more particularly to a plasma etching apparatus equipped with suitable means for adsorbing and removing dust adhering to the etching surface of a sample to improve the yield of an etching process. It is something.

It is generally known that dust is to be avoided in semiconductor manufacturing processes, and the current situation is to install expensive equipment such as clean rooms to remove dust as much as possible. By the way, in devices such as plasma etching equipment that process in a vacuum container, even if the inside of the container is cleaned, fine dust is generated due to two rotations of sample exchange, sliding, resist peeling, etc. Even with improvements, it is nearly impossible to eliminate dust generation. Furthermore, since it is a vacuum container, the dust may fly up and contaminate the sample due to disturbances in the airflow when evacuation starts or when there is a leak, causing inconveniences such as uneven etching or stopping the progress of etching in contaminated areas. Arise.

This was a factor that deteriorated the finished product yield.

Therefore, as a countermeasure against dust in a vacuum container, methods such as minimizing the structure that causes dust generation such as sliding and collisions, and gradually performing exhaustion and leakage are generally used. However, in the latter case, for example, the slow leak requires a time almost equivalent to the etching time, which significantly impedes the overall work efficiency, and some improvement is desired. is the current situation.

The present invention has been made in view of the above, and its purpose is to provide a plasma etching apparatus that can adsorb and remove dust adhering to the etching surface of a sample and improve the etching yield. There is a particular thing.

The first feature of the present invention is to remove dust adhering to the surface of a sample by providing a dust adsorption electrode at a position close to the surface of the sample and adsorbing the dust by the potential difference between this electrode and the dust. That's the point. The second feature is that a charging means is further provided at a position facing the sample to charge the dust on the surface of the sample with a negative charge, and the dust is charged with a negative charge to more effectively remove the dust. The structure is such that the dust can be attracted and removed by the dust adsorption electrode.

The present invention will be explained in detail below using the embodiments shown in FIGS. 1 to 3.

FIG. 1 is a sectional view showing an embodiment of the plasma etching apparatus of the present invention. In FIG. 1, reference numeral 1 denotes an etching chamber, and the etching chamber 1 is constructed of a vacuum container, and the inside thereof is evacuated through an exhaust pipe 8 to create a vacuum. Reference numeral 2 denotes a rotary sample stage, which is supported by a bearing 4 through a shaft 3 at approximately the center of the etching chamber 1, and is rotationally driven by a motor 5. A plurality of samples 5a and 6b are placed on the upper surface of the rotary sample stage 2.

... (others not shown) are provided with recessed holes 7 for accommodating the samples 5a and 5b at equal intervals in the circumferential direction.

It houses... 9 is a reaction chamber, and a gas introduction pipe 10
A high frequency power generated by a magnetron 11 is supplied to the gas introduced through the waveguide 12 to convert it into plasma,
The surfaces of the samples 5a, 5b, .
The etching surface is etched with a plasma gas.

Reference numeral 14 denotes a first dust adsorption electrode, which is provided at a position close to and facing the samples 6a, . . . , and its area is equal to that of the samples 5a,
. . . It is electrically insulated by an insulating member 15 and supported by a heir 16 so as to be freely rotatable from the outside via a shaft 17. Reference numeral 18 denotes a dust storage chamber, which is provided at a position that can accommodate the first dust adsorption electrode 14 when it rotates to the position shown by the broken line.

19 is a second dust adsorption electrode, which is the first dust adsorption electrode 14
The area of the reed is the first dust adsorption electrode 1.
It is almost the same as 4.

Reference numeral 20 denotes an insulating member that electrically insulates the second dust suction electrode 19 and mechanically seals between the lid 21 and the second dust suction electrode 19. 22 is a DC power supply, 23 is a lead terminal, and the first. The second dust adsorption electrodes 14 and 19 are configured to be able to be supplied with a potential of either positive or negative polarity by a DC power source 22 via a changeover switch 24.

During the process in which the samples 6a, . . . (silicon wafers, etc.) are introduced into the rotary sample stage 2 in the etching chamber 1, the dust that adheres to these samples 5a, . Has a charge. Alternatively, when passing through a plasma region, it is often charged in one direction or another. Therefore, by applying a positive or negative electric field to the first dust adsorption electrode 14 facing the samples 5a, . . . , the dust adhering to the surfaces of the samples 6a, . It can be adsorbed to the adsorption electrode 14. In addition, when there is only one first dust adsorption electrode 14, positive and negative electric fields are applied alternately by switching the changeover switch 24, and when multiple first dust adsorption electrodes 14 are installed, one is positive and the other is applied. By applying a negative electric field, no matter which way the dust is charged, the dust can be reliably removed from the sample 5a,...
can be adsorbed from the surface. If an electric field with a polarity opposite to that of the first dust adsorption electrode 14 is applied to the second dust adsorption electrode 19, the first dust adsorption electrode 1 that has adsorbed dust
4 comes to the position indicated by the broken line in the figure, the first dust adsorption electrode 1
4 can be removed by the second dust adsorption electrode 19.

According to the embodiment of the invention described above, sample 5a.

Immediately before the start of etching of ..., that is, sample 5a, ...
Since the dust adhering to the sample surface can be removed and cleaned without contact when the sample is transferred to the rotary sample stage 2, etching defects due to dust can be significantly reduced. Accordingly, it is possible to omit the leakage during sample exchange and the gradual exhaustion to eliminate the causes of dust generation, so that work efficiency can be significantly improved.

FIG. 2 is a sectional view showing another embodiment of the present invention, in which the same parts as those in FIG.

In FIG. 2, the dust attached to the sample 5a, . . . is neutralized and has no charge at all, or
If the charge is too weak to be adsorbed by the electric field applied to the first dust adsorption electrode 14, the sample 5a
, . . . The dust above is irradiated with a negative charge to be charged, and then the dust is attracted by the first dust adsorption electrode 14. Of course, when irradiating negative charges, damage to the samples 6a, etc. must be fully taken into account, so in the embodiment shown in FIG. A low-speed electron gun 25 that irradiates with the following accelerating voltage is used.

Other details are the same as in FIG.

FIG. 3 is a cross-sectional view of a main part of an embodiment of the low-speed electron gun 25 shown in FIG. The low-speed electron gun 25 is installed on a part of the container wall of the etching chamber 1 so as to be provided at an appropriate position substantially facing the samples 5a, .

From here, low-speed electrons are emitted toward the samples 6a, . . . . In FIG. 3, a filament 26 is suspended from lead terminals 28a and 28b which are airtightly planted on a base 27 made of an insulator. A grid 29 is connected to a lead terminal 28C attached to the base 27 so that a potential can be applied thereto. Reference numeral 30 denotes a holder which airtightly houses the base 27 and is airtightly fixed to the container wall 1a of the etching chamber 1 with screws. A hole 308 of the holder 30 has a hole in the center and serves as an anode.

Sample 5a is configured as described above.

In order to remove dust adhering to the surface of the sample prior to etching, the low-speed electron gun 25 is ignited while rotating the rotating sample stage 2 at an appropriate speed. That is, at the same time as a current is passed through the filament 26, an appropriate accelerating voltage is applied to the anode, and an appropriate bias voltage is applied to the grid 29, so that low-speed electrons are emitted toward the opposing sample 6a, . . . . As a result, the dust adhering to the samples 5a, . . . becomes negatively charged. Here, when an appropriate positive voltage is applied to the first dust adsorption electrode 14 from the lead terminal 23, the sample 5a is separated during rotation.

When the electrode 14 faces the electrode 14, negatively charged dust is attracted to the electrode 14. Therefore, a plurality of samples 6a on the rotary sample stand 2 are accommodated,...
・are cleaned one after another. After cleaning for an appropriate period of time, turn the first dust suction electrode 14 to the position shown by the dotted line, change the potential here from positive to negative, and apply a positive potential to the second dust suction electrode 19, and the above will occur. Similarly, the dust that had been adsorbed on the electrode 14 is adsorbed on the electrode 19. When etching is started after the above process has been completed, the dust has been removed much better than in the case of FIG. 1, so there are no etching defects due to dust.

Other effects are similar to the first one.

Incidentally, the dust adsorbed on the second dust adsorption electrode 19 is removed from the vehicle collection chamber 18 after a certain period of operation and is cleaned externally by mechanical means or the like.

Alternatively, an ion gun may be provided as a means to positively charge the dust on the sample f3a, . It will be done. Alternatively, the rotary sample stage 2 may be electrically insulated and, for example, a negative potential may be applied to it via a lead terminal.

Furthermore, the etching chamber 1 may be provided with an optical means 11J for observing dust on the sample surface to check the degree of cleanliness, and the cleaning may be performed while measuring the dust removal effect.

As explained above, according to the present invention, it is possible to adsorb and remove dust adhering to the etched surface of a sample, thereby improving the etching yield and significantly improving work efficiency. There is an effect.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing one embodiment of the plasma etching apparatus of the present invention, FIG. 2 is a sectional view showing another embodiment of the invention, and FIG. 3 is an embodiment of the low-speed electron gun of FIG. FIG. 1... Etching chamber, 2... Rotary sample stand, 6a. 6b...sample, 9...reaction chamber, 11...magnetron, 13...excitation coil, 14...first dust adsorption electrode, 18...dust collection chamber, 19...th 2 dust adsorption electrode, 25 (and 1 other person) Figure 1 ￥2 (2) Figure 3

Claims (1)

[Scope of Claims] 1. A plasma that excites a specific gas in a vacuum with high-frequency power to turn it into plasma, and etches the surface of a sample placed on a rotating sample stage in an etching chamber with the plasma-turned gas. Plasma etching characterized in that the etching apparatus is equipped with a dust adsorption electrode disposed close to the surface of the sample that adsorbs and removes dust adhering to the surface of the sample using a potential difference between the etching device and the sample. Device. 2. The plasma etching apparatus according to claim 1, wherein the dust adsorption electrode is configured so that the dust adsorbed to the electrode is adsorbed by a second dust adsorption electrode. 3. In a plasma etching apparatus that excites a specific gas with high-frequency power in a vacuum to turn it into plasma, and etches the surface of a sample placed on a rotating sample stage in an etching chamber with the plasma-turned gas, the sample a dust adsorption electrode disposed close to the surface of the sample that adsorbs and removes dust adhering to the surface of the sample using a potential difference between the electrode and the sample; 1. A plasma etching apparatus comprising a charging means provided at a position facing a sample. 4. The plasma etching apparatus according to claim 3, wherein the charging means is a low-speed electron gun.