JPS6273720A - Plasma processor - Google Patents

Abstract

PURPOSE:To uniformize a discharge by providing an insulator between a sample electrode and a sample. CONSTITUTION:When an alumina film 6a having 2mm or less of thickness is formed on a sample electrode 3, it can prevent a local discharge from occurring in case of etching with high frequency power of 3MHz or lower of frequency to eliminate the local degradation of a resist and the rise of an etching velocity. Further, a discharge can be uniformized by altering the thickness, and the etching velocity can be uniformized over the entire surface of a silicon wafer 1.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a plasma processing apparatus, and particularly to a plasma processing apparatus suitable for uniform plasma processing.

[Background of the invention]

Conventional plasma processing equipment uses a sample electrode made of a conductive material (eg, aluminum).

Some are made of stainless steel or carbon, and have an insulating material coated or placed on the surface of the sample electrode.

For example, as described in Japanese Patent Application Laid-Open No. 58-213427,
By covering the discharge area with a cover made of a material that is stable in the active reaction gas, such as quartz glass, contamination of the kneeling/dolling sample by reaction products can be prevented and efficient processing can be achieved. There is something I decided to do.

Also, for example, as described in Japanese Patent Publication No. 56-53853. , a so-called heavy film is interposed between the forcedly cooled sample stage and the material to be processed, and a DC circuit configured using the electrical conductivity of gas plasma is installed, and 7. It is characterized by applying a potential difference to firmly adsorb the processed material to the sample stage via the dielectric film, and uses high-frequency glow discharge! '→Epking 36 to promote heat transfer between the material to be processed and the sample stage, and to prevent the temperature rise of the resist used as a mask for transferring the fine pattern to the material to be processed. Some masks are designed to prevent thermal deterioration such as deformation and deterioration of the mask.

Furthermore, as described in Japanese Patent Publication No. 55-9464, for example, the etching speed of silicon on a silicon substrate,
In order to improve the etching speed of silicon oxide on the silicon substrate, a sample stage was installed on the electrode hill to hold the sample, and two base resins were used as the material of the sample stage.
Bu→Zumae/There is something to eng.

(7) However, there is no one in which an insulating material is provided in order to equalize the discharge in the Ifj section and perform uniform plasma processing.

[Purpose of the invention]

An object of the invention is to provide a plasma processing apparatus that can uniformize discharge and obtain uniform etching or film formation.

[Summary of the invention]

By using a low frequency, for example, a frequency below 3 MHz, the conventional 1356 MF (,
It is known that compared to etching with z, the increase in engineering is 1,111 notes. However, at frequencies below 3 Ml(z), a problem arose in that concentrated discharge occurred as shown in Figure J6.

Therefore, using a silicon wafer as a material, using a plasma processing apparatus shown in FIG. 5, in this case an etching apparatus,
An experiment was conducted to investigate the state of discharge by increasing the high frequency power density in the frequency range of 3 hours or less. 1 is the sample, in this case a silicon wafer, 2 is the processing chamber, and 3 is the sample W! , 4 is a sample surface, 5 is an insulating material, 7 is a high frequency power supply, 8 is a matching device, 9
Is it opposite? 1E is an electrode, 10 is a flow control valve, 11 is an earth shield, and 1 is an exhaust port. During the experiment, the gas was CHF, the gas was 100 SCCM, the pressure was 05 Torr, the electrode spacing was 59 IIIO, and the frequency of the four-frequency power source was I MHz.

When the high-frequency power density was increased to 2w/- or more, areas with high discharge emission intensity were visually confirmed at several locations on the outer periphery of the silicon wafer 1a.Also, a photoresist (OFPR- 800) Even when using a silicon wafer 1 that has been subjected to grain patterning, there are several defects on the outer periphery of the grain-like silicon wafer 1. It was visually observed that the portions where the discharge emission intensity was large were visually observed, and it was confirmed that the resist was deteriorated in a sub-volume manner, and that the knee f-engaging speed in the deteriorated portions was increased. The increase in processing speed was approximately 15 times greater than other parts.

Since the surface of a thermally oxidized silicon wafer is etched mainly by the ion effect, the number of ions increases in the altered area, or the acceleration energy when the ions are incident on the silicon wafer 1 increases. Don't think about it.

As a result of investigating the non-uniformity of this radiation jJ, it was found that the roughness of the silicon wafer 1 (kinuta's warpage and sample holder 4)
It was found that the sample electrode 3 was later attached to the sample electrode 3 due to the unevenness of the sample electrode 3. In order to confirm this, a small piece of aluminum of 2x2xo, st was placed on the sample electrode 3'' under the center of the Noricon wafer 1, and a discharge was caused under the same conditions as above. As a result, parts with high emission intensity of discharge were confirmed on the center surface of the silicon wafer on which the small piece of aluminum was placed and on the extreme outer periphery of 111E.

From this, it was found that providing an insulating material on the mounting surface of the silicon wafer 1 on the sample electrode 3 can improve the non-uniformity of discharge. Also, SiH.

(monosilane) gas, CHF
3. By providing an insulator in the same manner as described above in the region where the emission intensity of the discharge increases as in the case of discharge using a gas, the prospect of improving the non-uniformity of the discharge was obtained.

What has not yet been invented is a processing chamber into which a processing gas is introduced and the pressure is reduced to a predetermined pressure υF, a sample electrode provided in the processing chamber for arranging the sample, and a sample electrode provided in the processing chamber described above. 3M1 (crystal frequency power source that uses power with a frequency of less than z, and the sample electrode and the sample are directly connected to each other) It is characterized by comprising an insulating material provided on the entire surface or part of the space between the sample electrode and the sample to prevent contact between the sample electrode and the sample, thereby making it possible to uniformize the discharge and obtain uniform etching or film formation. It is something.

[Embodiments of the invention]

Hereinafter, one embodiment of the present invention will be explained with reference to FIG. 1 and FIG. 2.

FIG. 1 shows the sample electrode 3 of the plasma processing apparatus shown in FIG.
In the figure showing the details above, the same reference numerals indicate the same members, and the difference between this figure and Fig. 5 is that the sample electrode 3 is covered with an insulating material 6a), and the silicon wafer 1 is the sample The insulating material 6a of No. 3, in this case, is placed over alumina melt (film thickness: 200 μm).

When we investigated the discharge state using the plasma processing apparatus shown in Fig. 1 under the same conditions as in the previous experiment using the plasma processing apparatus shown in Fig. 5, we found that even at the maximum high frequency power density of 5 W/cd, No discharge concentration occurred. In addition, even when using a silicon wafer 1 that has been thermally oxidized and patterned with photoresist 0FPR-SOO (product name of Tokyo Ohka Kogyo Co., Ltd.) at a high frequency power density of 3 W/cd, resist deterioration and knee I No increase in the rate of rotation occurred.

Next, Fig. 2 shows the results of examining changes in the etching rate of the surface of the thermally oxidized silicon wafer 1 by changing the film thickness of the insulating (16B) alumina film between 0 and 5 plates. is CHF, , waste flow rate is 100 SCCM, surface circumference 6% power density is 3 W/d, high frequency power frequency is I MI
-b, , pressure is 0.5 TorrF line.

Ta. In this case, the insulating material 6a is alumina sprayed or an alumina plate, and the film thickness is 2 ml as shown in FIG.
11, the etching rate is reduced to about 80% compared to when the insulating material 68 is not provided.

If the value falls below this value, the processing time to process a certain film thickness will increase, and the number of sheets processed per unit time will decrease (
throughput) can no longer be ignored. Therefore, it is preferable that the alumina film thickness is 2 marks or more.

Furthermore, as shown in Figure 2, the etching rate can be increased or decreased by adjusting the thickness of the alumina film, so it is possible to reduce the variation (non-uniformity) in the etching rate of silicon wafers by adjusting the alumina film thickness. . For example, in this case, the etching rate was maximum at the center of the silicon wafer 1, and the etching rate decreased concentrically thereafter, so by increasing the thickness of the alumina film at the center of the silicon wafer 1, the etching rate could be made uniform. I was able to figure out my sexuality. In this case, the same effect can be obtained by forming the alumina film by making the surface of the sample electrode 3 into a groove and raising the alumina in a convex shape, or by processing the surface of the sample electrode 3 into a concave shape and making the surface of the alumina into flights. .

As described above, according to this embodiment, the film F72m is placed on the sample electrode 3.
Provide an alumina film with a thickness of 11 or less.
It is possible to prevent local discharges that occur when etching is performed with high frequency power of several 3 MIIz or less, and to prevent local deterioration of the resist and increase in etching speed. Furthermore, by changing the film thickness, the discharge can be made uniform, and the etching rate can be made uniform over the entire surface of the silicon wafer 1. In addition, silicon wafer 1
As a result, the etching speed becomes uniform and the yield improves. For example, for silicon wafers with a diameter of 150 cm, the yield increases from 60% to 90 cm. and can increase productivity. Further, since it is possible to prevent deterioration of the resist, appearance defects can also be prevented.

Next, a second embodiment of the present invention will be described with reference to FIG.

In this figure? jS The same reference numerals as in Fig. 1 indicate the same members, and the difference from Fig. 1 is that the insulation material 6a in Fig. 1 has a hole in the center and is provided so that it contacts only the peripheral part of the silicon wafer 1. 6b. This i! 3
A gold insulating material was provided in a width of 20 mm from the periphery of the silicon wafer 1. When the discharge state in this case was examined under the same conditions as in Section 01-Example, no discharge concentration occurred even at the maximum high frequency power density of 5 w/d.

Similar to the previous embodiment, in the case of the second embodiment, local discharge can be prevented, and local deterioration of the resist and increase in etching rate can be prevented, so that poor appearance due to resist deterioration can be avoided. In addition, the etching rate can be made uniform and the yield can be improved.

Next, a third embodiment of the present invention will be described with reference to FIG.

In this figure, the same symbols as in Figure @1 indicate the same members, and
The difference from the figure is that the insulating material 6a in FIG. That's a certain point. In this case, the insulating material 6C has a donut shape and is provided at two locations, one on the outer periphery and one on the inside of the silicon wafer 1, and supports the silicon wafer 1.

According to the embodiment of Part 3, it is possible to obtain the same effect as the second embodiment, and also to suppress the bending of the silicon wafer 1 at the center.

Note that the insulating material 6C is donut-shaped in this case, but the shape can be chosen arbitrarily, and the number of insulating materials 6C is not limited to two, but can be two or more, or even one in a star shape. good.

In the above embodiments, alumina has been used as the insulating materials 6a to 6C, but in addition to aluminum, BN may also be used.
, Sin, SiN, polytetrafluoroethylene, and the like, uniform discharge can be obtained in the same way as with alumina. When applying an insulating material to the sample electrode 3, it is necessary to take into consideration adhesion to the sample electrode 3, voltage resistance, thermal conductivity, etc. that affect the cooling effect of the wafer. In addition, if helium gas or the like is used as a heat medium to cool the wafer and people are crowded into the gap on the backside of the wafer, insulating material should be installed from time to time to prevent helium gas or other gas from leaking into the processing chamber. It is necessary to consider the seal structure.

In addition, in the case of Takeshi Kimitsu, the etching rate was discussed as a plasma processing apparatus, but film forming apparatuses such as CVD
Since the discharge is uniform for the equipment, the quality of the film deposited on the sample can be made uniform, and the appearance defects caused by differences in interference colors caused by conventional differences in film thickness can be eliminated. .

〔Effect of the invention〕

According to the present invention, an insulating material is provided between the sample 1'1E electrode and the sample. This has the effect that the discharge between the sample electrode and the opposing north pole can be made uniform, and plasma processing can be performed to obtain uniform etching or film formation.

[Brief explanation of drawings]

Figure 1 is a cross-sectional view showing plasma treatment ti1, which is an embodiment of this invention, Figure 2 is a graph showing the results of the experiment conducted according to Figure 1, and the third flash is a second example of this invention. FIG. 4, a sectional view showing a plasma processing apparatus, is a cross-sectional view of the plasma processing apparatus according to the present invention. FIG. 5 is a sectional view showing a plasma processing apparatus according to the A3 embodiment for 4 hours, FIG. 5 is a sectional view showing a conventional plasma processing apparatus, and FIG. 6 is a graph showing the results of an experiment conducted using FIG. 1...Solicon wafer, 2...m-processing x,
3...Sample electrode, 6a to 6C...Insulating material, 9...20 AhOayI (蔗悄)

Claims (1)

[Scope of Claims] 1. A processing chamber into which a processing gas is introduced and evacuated to a predetermined pressure, a sample electrode provided within the processing chamber and on which a sample is placed, and a sample electrode provided within the processing chamber and opposed to the sample electrode. a high-frequency power supply that uses power with a frequency of 3 MHz or less as a high-frequency power applied between the sample electrode and the counter electrode; A plasma processing apparatus characterized by comprising an insulating material provided on the entire surface or a part of the space between the plasma processing apparatus and the sample. 2. The plasma processing apparatus according to claim 1, wherein the insulating material is alumina and is adhered to the sample electrode.