JPH09246244A - Plasma processing apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate ununiformity in plasma density at the area between the center and peripheral area of an object to be processed even when the object becomes large in size by providing, in addition to a lower electrode consisting of an object supporting member itself, a side electrode to the surrounding or peripheral area of the object supporting member and also providing an upper electrode at the upper side of supporting member. SOLUTION: An upper electrode 15 is coupled at the upper end of a chamber 1 of a gas inlet pipe 4. Moreover, a side electrode 9 is provided to surround a lower electrode 2. A high frequency voltage to form plasma is impressed from the lower electrode 2 forming a susceptor, upper electrode 15 forming a gas injection nozzle and a side electrode 9 forming a gas injection nozzle. Therefore, drop of field intensity generated by the high frequency voltage at the area surrounding a semiconductor wafer 3 can be prevented, field intensity in the peripheral part may be maintained almost at the same degree as that in the center area and ununiformity of plasma density resulting from drop of field intensity at the peripheral part of the wafer 3 may be corrected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma processing apparatus, and more particularly, to plasma generated by a high frequency voltage in a chamber having a gas introducing portion to promote a reaction due to the gas supplied from the gas introducing portion. The present invention relates to a plasma processing apparatus, such as a plasma etching apparatus or a plasma CVD apparatus, which performs processing on an object to be processed on an object supporting member to be processed.

[0002]

Make gas plasma BACKGROUND ART on a semiconductor wafer in the chamber, for example, Si of the gas and the semiconductor wafer surface by a gas atom radicals in an excited state, SiO _2, Si
There are a plasma CVD technique and a plasma etching technique in which vapor phase growth and etching are performed by a reaction with H or the like, which are utilized in the manufacture of semiconductor devices.

As a method of forming gas plasma in the chamber, the wafer support (susceptor) is used as an electrode (lower electrode), and a high frequency (R) is applied between the electrode and the chamber itself.
In many cases, the method of applying F: Radio Frequency) voltage is adopted.

FIG. 3 is a sectional view showing an example of a conventional plasma etching apparatus adopting such a plasma forming method.

In the drawings, reference numeral 1 is a chamber, and 2 is a susceptor on which a semiconductor wafer 3 is placed, which also serves as a high frequency applying electrode (lower electrode) for plasma formation. Reference numeral 4 is a gas introduction pipe for introducing a reaction gas (for example, CF4) into the chamber 1, and 5 is a gas which is connected to the tip of the gas introduction pipe 4 inside the chamber 1 and jets the reaction gas downward onto the semiconductor wafer 3. A jet nozzle, 6 is an exhaust port of the chamber 1, 7 is a high-frequency power source for generating a high-frequency voltage for forming plasma, and the output of the power source 7 is between the lower electrode 2 forming the susceptor and the chamber 1 itself. Is applied.

The frequency of the high-frequency voltage generated by the power source 7 has been fixed to a preset value in the past.

[0007]

By the way, it is difficult for the conventional etching apparatus as shown in FIG. 3 to cope with the increase in the diameter of the wafer, and it is necessary to obtain the optimum etching condition corresponding to the etching target. There was a problem that it was difficult.

The problem will be described in detail. The larger the diameter of the wafer, the more the wafer (from the current 8 inches to 1
The diameter may be 0 or 12 inches, or even larger. ) The nonuniformity of the etching rate becomes large, and the etching rate tends to be lower in the peripheral portion than in the central portion of the wafer, and the nonuniformity has reached ± 20% in the conventional case.

Then, the inventors of the present application pursued the cause, and the plasma density in the peripheral portion was lower than that in the central portion of the wafer, and as the diameter of the wafer became larger, the difference in the plasma density, that is, the non-uniformity of the plasma density. Was found to be large.

That is, the lower the plasma density, the more inactive the reaction becomes, and the lower the etching rate becomes. Therefore, the etching rate becomes lower in the peripheral portion than in the central portion of the wafer. Will be higher. In the case of the plasma CVD apparatus, this appears as nonuniformity of the deposition rate.

Then, when the cause of the non-uniformity of the plasma density was sought, the reaction gas was supplied only from above the wafer 3, and as a result, the gas concentration on the wafer 3 was highest in the central portion of the wafer 3 and the periphery thereof. It became lower as it went to the part, and it became clear that it was one of the causes of the non-uniformity of the plasma density.

Further, the strength of the electric field on the wafer 3 due to the high frequency RF influences the plasma density, and the electric field strength at the periphery becomes insufficient as compared with the central portion due to the increase in the diameter of the wafer, which is also the reason. It was also found to be one of the causes of the decrease in plasma density on the peripheral portion.

Further, the inventor of the present application has noticed that the optimum frequency of the high frequency power source varies depending on the material to be etched, such as SiO ₂ , poly-Si and Al. FIG. 4 is a diagram showing this, that is, SiO ₂ , po.
It shows the RF frequency dependence of the etching rate and its non-uniformity for each material of ly-Si and Al. As is clear from this figure, when etching SiO ₂ , the etching rate becomes maximum at a frequency of 2 MHz and the rate nonuniformity becomes minimum. That is,
It can be said that ₂ MHz is the optimum frequency for etching SiO ₂ . However, for poly-Si, 13.56 MHz is the optimum frequency,
Since the optimum frequency is 800 KHz, it can be said that the optimum frequency differs depending on the material.

However, in the conventional case, the high frequency power source 7 is used.
The frequency of was fixed at a preset constant value and could not be changed. Therefore, conventionally, in order to perform the etching process under the optimum conditions, it is necessary to use different etching apparatuses for each material. This also applies to the plasma CVD apparatus, and the optimum frequency differs depending on the film to be formed, and it is necessary to use the plasma CVD apparatus that differs depending on the film.

As described above, changing the apparatus depending on the type of processing causes a decrease in productivity and an increase in equipment cost, and makes it difficult to cope with the recent tendency of high-mix low-volume production. .

The present invention has been made to solve such a problem, and one object thereof is to make the plasma density non-uniform even when the object to be processed becomes large in size, particularly the central part and the periphery of the object to be processed. The other purpose is to prevent nonuniformity between the parts and other parts, and another purpose is to enable the processing under optimum conditions according to the etching target, the type of processing, and the like.

[0017]

According to a first aspect of the plasma processing apparatus of the present invention, there is provided a lower electrode composed of an object supporting member itself and side electrodes provided around or laterally to the object supporting member. And an upper electrode disposed above the supporting member as an electrode for applying a high frequency voltage. Therefore, according to the first plasma processing apparatus of the present invention, not only the lower electrode, Since the upper electrode and the side electrode are also provided, it is possible to enhance the uniformity of the intensity distribution of the electric field due to the high frequency voltage on the object to be processed placed by the lower electrode. Therefore, it is possible to reduce the non-uniformity of the plasma density, especially the non-uniformity between the central part and the peripheral part of the object to be processed even if the object to be processed becomes large in size. The processing rate can be made uniform.

The second plasma processing apparatus of the present invention is characterized in that a high frequency power source for generating a high frequency voltage has a variable frequency.

Therefore, according to the second aspect of the plasma processing apparatus of the present invention, the frequency of the high frequency voltage generated by the high frequency power source can be changed according to the type of processing such as the etching target or the film formation. In addition, different types of processing can be performed at the optimum frequency for one type, and it is possible to avoid lowering productivity and increasing equipment costs, and to respond appropriately to the recent trend of high-mix low-volume production. It will be possible.

A third aspect of the plasma processing apparatus of the present invention is characterized in that the gas introducing portions are provided at the upper and side portions of the chamber.

Therefore, according to the third aspect of the plasma processing apparatus of the present invention, since the gas introducing portion is also provided on the side portion of the chamber, the reaction on the peripheral portion of the object to be treated, especially a large object to be treated. The decrease in gas concentration can be prevented by the reaction gas supplied from the gas introduction portion provided on the side of the chamber, and the concentration of the reaction gas on the surface of the object to be processed can be made uniform.

Therefore, the non-uniformity of the plasma density caused by the non-uniformity of the concentration distribution of the reaction gas, particularly the non-uniformity between the central portion and the peripheral portion of the object to be processed, should be reduced. Therefore, the processing rate of etching or deposition can be made uniform.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the illustrated embodiments.

FIG. 1 is a sectional view showing the outline of the first embodiment of the plasma processing apparatus of the present invention.

In the drawings, reference numeral 1 is a chamber, and 2 is a susceptor on which a semiconductor wafer 3 is placed, which also serves as a high frequency applying electrode (lower electrode) for plasma formation. 4 is a gas introduction pipe for introducing a reaction gas (for example, CF4) into the chamber 1, 15
Is a gas ejection nozzle and upper electrode which is connected to the tip of the gas introduction pipe 4 in the chamber 1 and ejects the reaction gas downward onto the semiconductor wafer 3 for plasma formation also between this and the chamber 1. A high frequency voltage is applied.

The gas introduction pipe 5 in the plasma processing apparatus shown in FIG. 3 is located above the lower electrode 2 similarly to the gas ejection nozzle 15 of the plasma processing apparatus shown in FIG. 1, and on the semiconductor wafer 3 on the lower electrode 2. The reaction gas was fed downwards towards the, but did not function as an electrode. On the other hand, the gas ejection nozzle 15 in this embodiment also functions as an electrode, that is, an upper electrode.

Reference numeral 6 denotes an exhaust port of the chamber 1, and reference numeral 7a denotes a high frequency power source for generating a high frequency voltage applied between the lower electrode 2 which also functions as a susceptor and the chamber 1. 8a
Is a control unit for controlling the frequency of the high frequency power supply 7a, and the frequency of the high frequency voltage can be arbitrarily changed by the control unit 8a.

Reference numeral 7b is a high frequency power source for generating a high frequency voltage applied between the upper electrode 2 which also functions as a gas ejection nozzle and the chamber 1 itself. A control unit 8b controls the frequency of the high frequency power supply 7b, and the frequency of the high frequency voltage can be arbitrarily changed by the control unit 8a.

Reference numeral 9 denotes a gas ejection nozzle (cumulative side electrode) provided so as to surround the lower electrode (susceptor) 2 and 10 denotes a gas for supplying a reaction gas from the outside of the chamber 1 to the gas ejection nozzle 9. It is an introduction pipe. In the conventional plasma processing apparatus shown in FIG. 3, the gas ejection nozzle was not present around the susceptor 2, but in the present embodiment, the gas ejection nozzle 9 is present around the susceptor 2 and the chamber is introduced through the gas introduction pipe 10. 1. A reaction gas supplied from the outside is ejected toward the center of the chamber 1. Reference numeral 7c is a high-frequency power source that generates a high-frequency voltage applied between the side electrode 9 that also functions as a gas ejection nozzle and the chamber 1 itself. A control unit 8c controls the frequency of the high frequency power supply 7c, and the frequency of the high frequency voltage can be arbitrarily changed by the control unit 8c.

According to this plasma processing apparatus, a high-frequency voltage for plasma formation is applied from any of the lower electrode 2 forming a susceptor, the upper electrode 4 forming a gas ejection nozzle, and the side electrode 9 forming a gas ejection nozzle. Therefore, it is possible to prevent the strength of the electric field generated by the high frequency voltage from decreasing on the peripheral portion of the semiconductor wafer 3, and make the electric field strength on the peripheral portion substantially the same as that on the central portion.
Therefore, it is possible to correct the non-uniformity of the plasma density due to the decrease of the electric field intensity on the peripheral portion of the wafer 3.

Further, the non-uniformity of the plasma density is caused by the wafer 3
This occurs due to the non-uniformity of the concentration distribution of the reaction gas above, but in the present embodiment, the reaction gas can be supplied also from the gas injection nozzles 9 provided on the side portions, so that on the peripheral portion of the wafer 3. It is possible to correct the decrease in the gas concentration in.

FIG. 2 shows how the etching rate changes depending on the distance from the center of the wafer 3 by comparing the conventional case with the case of the present invention. In the conventional case, the etching rate in the central portion is 600 mm / mi
n, the etching rate in the peripheral portion (100 mm) is 400 mm / min, and the difference between the etching rates is about 2
On the other hand, according to the present invention, the etching rate is about 870 mm / min from the central portion to the peripheral portion of the wafer 3, and not only the etching rate is remarkably high. However, there is almost no nonuniformity in the etching rate. The reason why the etching rate can be made considerably higher than before is that gas concentration and electric field strength, which are the two major factors that determine the plasma density, are not only on the peripheral portion but also on the central portion. It was because I was able to raise.

As described above, since the etching rate can be increased as a whole, the time required for etching can be shortened. However, the plasma density on the peripheral portion and the central portion of the wafer 3 is further increased. Can be made uniform so that the etching amount can be made uniform.
It is of great significance to be able to almost eliminate the possibility that the dimensions and characteristics of the semiconductor element will differ between the central part and the peripheral part of the wafer 3. The significance becomes larger as the diameter of the wafer becomes larger (10 inch, 12 inch, and more are expected).

Further, according to the present embodiment, it is possible to change the frequency of the high frequency voltage generated by the high frequency power supplies 7a to 7c. Therefore, the etching target can be changed according to the type of the etching target (for example, SiO ₂ , poly-Si, Al, etc.), and thus, one plasma processing apparatus can perform etching at different frequencies for different etching targets. It can be carried out. Therefore, it is possible to avoid a decrease in productivity and an increase in equipment cost, and it is possible to appropriately cope with the recent tendency of high-mix low-volume production.

For example, when etching a film made of SiO ₂ , the RF frequency is set to 2 MHz and the poly-
When etching a film made of Si, set it to 1
When setting 3.56 MHz and etching Al,
If it is set to 800 KHz, it becomes possible to perform optimum etching. Therefore, one plasma processing apparatus can be used for various etchings. Of course, this plasma processing apparatus can also be used for plasma ashing.

Further, the present invention can be applied not only to the plasma etching apparatus but also to the plasma CVD apparatus, and the same effect as that obtained by the plasma etching apparatus can be obtained.

[0037]

According to the first embodiment of the plasma processing apparatus of the present invention, not only the lower electrode but also the upper electrode and the side electrode are provided. The uniformity of the intensity distribution of the electric field can be improved. Therefore, it is possible to reduce the non-uniformity of the plasma density, especially the non-uniformity between the central part and the peripheral part of the object to be processed, even if the object to be processed becomes large in size. The processing rate can be made uniform.

According to the second plasma processing apparatus of the present invention, the frequency of the high-frequency voltage generated by the high-frequency power source can be changed according to the type of processing such as the etching target or film formation. It is possible to perform different types of processing with the optimal frequency for each type, avoid productivity decline and increase in equipment cost, and especially appropriate response to the recent trend of high-mix low-volume production. Become.

According to the third aspect of the plasma processing apparatus of the present invention, since the gas introduction portion is also provided at the side portion of the chamber, the reaction gas on the peripheral portion of the object to be treated, particularly the large object to be treated is increased. The decrease in concentration can be prevented by the reaction gas supplied from the gas introduction portion provided on the side of the chamber, and the concentration of the reaction gas on the surface of the object to be treated can be made uniform.

Therefore, the non-uniformity of the plasma density caused by the non-uniformity of the concentration distribution of the reaction gas, especially the non-uniformity between the central part and the peripheral part of the object to be processed is reduced. Therefore, the processing rate of etching or deposition can be made uniform.

[Brief description of drawings]

FIG. 1 is a sectional view showing the outline of a first embodiment of a plasma processing apparatus of the present invention.

FIG. 2 is a diagram showing a relationship between a distance from a center o of a wafer and an etching rate in comparison between the case of the above embodiment and the conventional case.

FIG. 3 is a sectional view showing an outline of a conventional example of a plasma processing apparatus.

FIG. 4 shows the dependence of etching rate on RF frequency by SiO.
It is a figure shown about ₂ , poly-Si, and Al.

[Explanation of symbols]

1 ... Chamber, 2 ... Lower electrode (also object-to-be-processed object supporting member), 3 ... Object to be processed (semiconductor wafer), 7a
7c ... Radio frequency (RF) power supply, 9 ... Side electrode (cumulative gas introduction part), 15 ... Upper electrode (cumulative gas introduction part)

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical display location H05H 1/46 H05H 1/46 A

Claims (3)

[Claims] 1. A plasma is generated by a high frequency voltage in a chamber having a gas introducing portion to promote a reaction by a gas supplied from the gas introducing portion, and to the object to be treated on the object supporting member in the chamber. In a plasma processing apparatus for performing processing, a lower electrode composed of the object supporting member itself, side electrodes provided around or lateral to the object supporting member, and an upper electrode arranged above the supporting member. And an electrode for applying a high frequency voltage. 2. A plasma is generated by a high frequency voltage in a chamber having a gas introduction part to promote a reaction by a gas supplied from the gas introduction part to the object to be processed on the object support member in the chamber. A plasma processing apparatus for performing processing, characterized in that a high frequency power source for generating a high frequency voltage has a variable frequency. 3. A plasma is generated by a high frequency voltage in a chamber having a gas introduction part to promote a reaction by the gas supplied from the gas introduction part to the object to be processed on the object support member in the chamber. A plasma processing apparatus for performing a process, wherein a gas introduction part is provided at an upper part and a side part of the chamber.