JPH08124903A - Plasma processing system and cleaning method therefor - Google Patents

Abstract

PURPOSE: To realize efficient in-situ cleaning on the wall of a processing chamber by generating a plasma, having density higher in the vicinity of the wall than in the central part of the processing chamber, and cleaning the inner wall of the processing chamber. CONSTITUTION: In a plasma processing system employing a plasma having higher density in the central part of a processing chamber than in the vicinity of the wall thereof, the inner wall of the processing chamber is cleaned by generating a plasma having higher density in the vicinity of the wall than in the central part of the processing chamber. For example, a coil 3 for high frequency inductively coupled plasma(ICP) is interposed between a microwave introduction pipe 1 and a quartz belljar. At the time of cleaning, a high frequency current is fed to the coil 3 to generate an ICP discharge thus increasing the plasma density in the vicinity of the wall. Since ions or radicals required for cleaning can be fed sufficiently to the wall, the wall can be cleaned effectively thus suppressing generation of particles and aging.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cleaning method for a plasma processing apparatus.

[0002]

2. Description of the Related Art In an electron cyclotron resonance (hereinafter abbreviated as ECR) plasma etching apparatus, since the plasma density near the wall is small, the plasma has a small effect of cleaning the inner wall of the processing chamber during etching. Therefore, as the etching process is repeated, the etching reaction products gradually adhere to the inner wall of the processing chamber. The reaction products adhering to the inner wall of the processing chamber may cause a change over time or become particles and fall onto the wafer.

Therefore, in the maintenance of the ECR plasma etching apparatus, a technique for cleaning the wall, particularly in vacuum (in-situ cleaning)
is important.

A typical wall in-situ cleaning technique is a method of cleaning a wall by generating a plasma of a reactive gas and chemically reacting with radicals generated in the plasma as in Japanese Patent Laid-Open No. 144786/1993. There is. However, this method cannot remove the chemically stable reaction products of the species by cleaning. A method for removing such reaction products is disclosed in JP-A-4-18492.
There is a method of applying a bias to a wall to accelerate ions to be incident on the wall and physically remove reaction products adhering to the wall, as in Japanese Patent Publication No. 4).

[0005]

In the conventional cleaning method, since ECR plasma is used for cleaning discharge, the plasma density near the wall is low, and radicals and ions cannot be sufficiently supplied to the wall, so that the wall cleaning efficiency is low. . According to the method disclosed in Japanese Patent Laid-Open No. 4-184924, a portion such as a metal portion to which a bias can be applied is cleaned, but a portion such as a quartz bell jar to which a bias cannot be applied is not cleaned.

An object of the present invention is to provide a method for solving these problems and efficiently performing in situ wall cleaning.

[0007]

In a plasma processing apparatus using ECR plasma, high frequency inductively coupled plasma (hereinafter referred to as ICP) is generated during cleaning to increase the plasma density near the wall.

[0008]

In contrast to the ECR plasma discharge in which the plasma density becomes smaller near the wall, the plasma density near the wall becomes higher in the ICP discharge. Therefore, the ions and radicals necessary for cleaning can be sufficiently supplied to the wall, and the wall can be effectively cleaned.

Further, in the ICP discharge, since high-energy ions can be made incident on the wall near the ICP discharge coil, it is possible to effectively clean a portion such as a quartz bell jar which is not normally biased.

[0010]

【Example】

(Embodiment 1) FIG. 1 shows an example of a plasma etching apparatus having a cleaning function of the present invention. A coil 3 for ICP discharge between the microwave waveguide 1 and the quartz bell jar 2.
It has. At the time of cleaning, a high-frequency current is passed through the coil 3 to perform ICP discharge.

Using this apparatus, continuous etching of 25 pieces of polysilicon (Poly-Si) by ECR plasma of chlorine gas and cleaning of the inner wall of the processing chamber by ICP discharge of chlorine gas for 5 minutes were repeated to obtain etching characteristics. I examined the changes.

FIG. 2 shows the relationship between the poly-Si selection ratio with respect to SiO ₂ and the number of processed wafers. ECR cleaning for comparison
The results of plasma discharge are also shown in the figure. The cleaning discharge using ECR plasma has almost no cleaning effect, and the change over time in which the selection ratio decreases as the number of processed sheets is increased. On the other hand, the IC of the present invention
It can be seen that in the cleaning discharge using P plasma, the selection ratio is recovered by the cleaning, and the high selection ratio is maintained even after the continuous treatment of 1000 sheets.

(Embodiment 2) FIG. 3 shows an example of a plasma processing apparatus having a cleaning function of the present invention. The inside of the metallic cylindrical discharge tube 8 is coated with two layers of insulating members 9 and 10. R is placed between the insulating member 9 and the insulating member 10.
A coil 3 capable of passing an F current is provided.
At the time of cleaning, a high-frequency current is passed through the coil 3 to generate ICP discharge and clean the inner wall of the processing chamber.

[0014]

Since the efficiency of in-situ cleaning is improved, the generation of particles and the change with time are reduced, and the etching can be performed cleanly and with good reproducibility.

Further, since it has become possible to effectively clean the quartz bell jar which has been difficult to perform in situ cleaning, it is not necessary to replace the dirty quartz bell jar and the maintenance cost can be reduced.

Further, since the same gas as the etching gas can be used for cleaning, there is no need for preliminary discharge (seasoning) with the etching gas after cleaning, and the processing steps can be shortened.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a plasma etching apparatus provided with a cleaning facility of the present invention.

FIG. 2 is an explanatory diagram of the dependence of the poly-Si / SiO ₂ selection ratio on the number of processed sheets.

FIG. 3 is an explanatory diagram of a plasma processing apparatus provided with the cleaning equipment of the present invention.

[Explanation of symbols]

1 ... Microwave waveguide, 2 ... Quartz bell jar, 3 ... ICP
Discharge coil, 4 ... RF power supply, 5 ... Magnetron, 7 ...
Sample table.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Internal reference number FI Technical indication location H01L 21/304 341 D 21/31 C H05H 1/46 C 9216-2G (72) Inventor Tatsumi Mizutani 1-280, Higashi Koikekubo, Kokubunji, Tokyo Inside Hitachi Central Research Laboratory (72) Inventor Kazunori Tsujimoto 1-280, Higashi Koikeku, Tokyo Kokubunji City Central Research Institute, Hitachi (72) Inventor Taka Yunoue Kokubunji 1-280 Higashi-Kengokubo Central Research Laboratory, Hitachi, Ltd.

Claims (5)

[Claims] 1. A plasma processing apparatus using plasma in which the plasma density in the center of the processing chamber is higher than the plasma density in the vicinity of the wall, and the plasma is generated in the vicinity of the wall of the processing chamber in which the plasma density is higher. A method of cleaning a plasma processing chamber, comprising cleaning an inner wall of the processing chamber. 2. A plasma processing apparatus using electron cyclotron resonance plasma, wherein the inner wall of the processing chamber is cleaned by using high frequency inductively coupled plasma discharge. 3. The method for cleaning a plasma processing apparatus according to claim 2, wherein the processing gas used for plasma processing is introduced into the processing chamber during high frequency inductive coupling plasma discharge. 4. A plasma processing apparatus having both an electron cyclotron resonance plasma discharge mechanism and a high frequency inductive coupling type plasma discharge mechanism. 5. A plasma processing apparatus having a mechanism of electron cyclotron resonance plasma discharge, comprising a coil for high-frequency inductive coupling type plasma discharge between a discharge tube and a microwave waveguide.