JPH08181117A - Pressure reducing method of plasma processor - Google Patents

Abstract

PURPOSE: To pressure-reduce a chamber even from the state of water molecules adhering to the wall surface in the device by producing plasma by feeding high-frequency power in the pressure reducing time in a plasma processor. CONSTITUTION: A chamber 1 is exhausted at low rate by an exhaust system 7. Next, Ar gas is fed in the chamber 1 from a gas introducing system 4 while feeding microwaves from a microwave introducing port 1a. At this time, plasma can be produced in the plasma producing chamber 1b by actuating an exciting coil 2. Due to the high pressure in the chamber 1, the mean free molecular stroke of the product plasma is short to be diffused within wide range in intensive contact with the inner wall surface of the chamber 1. Due to this contact, the wall surface temperature in the chamber 1 is raised thereby enabling the adhering water molecules to be vaporized.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a depressurizing method for starting an apparatus for plasma processing using microwaves, RF or the like.

[0002]

2. Description of the Related Art In the process of manufacturing a semiconductor device, a plasma processing device such as a plasma etching device or a plasma CVD device is used as a device for performing plasma processing on the semiconductor device. In such a plasma processing apparatus, a semiconductor device to be processed is loaded into a chamber, the pressure inside the chamber is reduced, and plasma processing is performed. At this time, the products generated during plasma processing adhere to the inner wall of the chamber,
The deposition amount of the product increases as the throughput of the semiconductor device increases. Therefore, the plasma treatment is temporarily stopped, the chamber is opened to the atmosphere, the interior is cleaned, for example, washed with water, and then the pressure in the chamber is reduced again to restart the plasma treatment.

[0003]

However, it takes about one day before the plasma processing is restarted after such a cleaning process. This is because the pressure (4 × 10 ^-6 to
This is because it takes time to reduce the pressure in the chamber to rr). Thus, there is a problem that the throughput of the object to be processed is lowered due to the cleaning of the plasma device.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a depressurizing method capable of shortening the depressurizing time of a plasma processing apparatus and increasing throughput by generating plasma during depressurization.

[0005]

A method of decompressing a plasma processing apparatus according to a first aspect of the present invention is a method of decompressing the inside of a plasma processing apparatus for subjecting an object to be processed to plasma processing. A first step of preliminary decompression,
A second step of supplying high frequency power into the plasma processing apparatus to generate plasma, a third step of loading the object to be processed into the plasma processing apparatus after the completion of the second step, and an exhaust system for the plasma processing. A fourth step of reducing the pressure in the processing apparatus to a predetermined pressure.

The depressurizing method of the plasma processing apparatus according to the second invention is characterized in that, in the first invention, the depressurizing rate in the first step is set lower than the depressurizing rate in the fourth step.

[0007]

In the depressurizing method of the plasma processing apparatus of the first invention,
The generated plasma ions and electrons come into contact with the inner wall of the plasma processing apparatus to rapidly raise the inner wall surface temperature. Water molecules attached during cleaning of the inside of the plasma processing apparatus are vaporized by the rise of the inner wall surface temperature, and the decompression time is shortened.

In the depressurizing method of the plasma treatment of the second invention, when the plasma is generated in the first step, depressurization is performed at a speed lower than that in the fourth step, and the mean free path of the molecules is shortened so that the molecules are separated from each other. By making it easy to contact with each other, the diffusion range of plasma is widened and the rate of rise of the inner wall temperature is increased.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below with reference to the drawings showing the embodiments. FIG. 1 is a schematic sectional view showing the structure of an ECR plasma etching apparatus used in the depressurizing method of the present invention. In the figure, 1 is a chamber, which is formed in a hollow cylindrical system. A microwave introduction port 1a for introducing microwaves is provided on one end side of the chamber 1, and a plasma generation chamber 1b is provided so as to face the microwave introduction port 1a. On the outer peripheral wall of the chamber 1, an exciting coil 2 is concentrically arranged so as to surround the plasma generation chamber 1b and a part of the microwave introduction port 1a.

In the sample chamber 1c facing the plasma generation chamber 1b, a sample table 3 is arranged at a position facing the plasma introduction port, and a wafer W as an object to be processed is placed thereon.
A gas introduction system 4 is provided on the side wall of the sample chamber 1c,
A predetermined amount of gas is introduced into the chamber 1 according to an instruction from the gas introduction control unit 5.

An exhaust system 6 and an exhaust system 7 are provided on the side wall of the sample chamber 1c. Exhaust system 6 has a diameter of 200 mm
The main valve 8, a turbo molecular pump 9 having a high exhaust capacity, an auxiliary valve 10 having a diameter of φ70 mm and a dry pump 11 which is an auxiliary pump are provided, and the exhaust system 7 is provided with a roughing valve 12 having an aperture of φ70 mm. By closing the roughing valve 12 and opening the main valve 8 and the auxiliary valve 10 to operate the turbo molecular pump 9 and the dry pump 11, the chamber 1 is evacuated to a high vacuum. Further, the main valve 8 and the auxiliary valve 10 are closed, the roughing valve 12 is opened, and the dry pump 11 is operated, so that the decompression speed in the chamber 1 can be made lower than that of the exhaust system 6.

When the wafer W is etched by using the ECR plasma etching apparatus having the above structure,
The pressure inside the chamber 1 that has been washed with water is reduced. FIG. 2 is a flow chart showing the procedure of depressurizing the chamber, and the depressurizing procedure will be described based on this. First, the main valve 8 and the auxiliary valve 10 are closed, the roughing valve 12 is opened, the dry pump 11 is operated (step S11), and the exhaust system 7 exhausts the chamber 1 at a low speed. Then, 20 sccm of Ar gas is introduced into the chamber 1 from the gas introduction system 4 (step S12), and a microwave of 1.5 kW is supplied from the microwave introduction port 1a (step S13).

At this time, when the exciting coil 2 is operated, plasma is generated in the plasma generating chamber 1b. Since the pressure inside the chamber 1 is high, the generated plasma has a short mean free path of molecules, is diffused in a wide range, and comes into intense contact with the inner wall surface of the chamber 1. Due to this contact, the temperature of the wall surface of the chamber 1 rises and the attached water molecules are vaporized (step S14).

After that, the wafer W is placed on the sample table 3 and
The roughing valve 12 is closed, the main valve 8 and the auxiliary valve 10 are opened, and the turbo molecular pump 9 and the dry pump 11 are opened.
Is operated (step S15). Since the water molecules in the chamber 1 have been removed, the inside of the chamber 1 is evacuated to a high vacuum in a short time.

FIG. 3 is a graph showing the result of decompressing the plasma processing apparatus by the method of the present invention, together with the result of the conventional method. The vertical axis represents the partial pressure of water, and the horizontal axis represents time. “O” indicates data under the conditions of the above-described embodiment, and “x” indicates data according to the conventional method in which plasma is not generated during depressurization. As is clear from the graph, the pressure inside the equipment is 4 × 10 ^-6 torr with the conventional method.
It is estimated that it takes 24 hours or more to reach the value below, but in this example, it can be seen that the value reached 4 × 10 ⁻⁶ torr in 1 hour. As described above, according to the method of the present invention, the decompression time of the chamber can be reduced.

In the above embodiment, the chamber 1 is depressurized at a low speed by the roughing pump 12 at the time of plasma generation. However, the present invention is not limited to this, and it is possible to depressurize by using a normal turbo molecular pump. The chamber 1 can be depressurized to a predetermined pressure in a shorter time than conventional. However, it is desirable to use the roughing pump 12 in order to further shorten the decompression time.

Further, although the case where the ECR plasma etching apparatus is used has been described in the above-mentioned embodiments, the present invention is not limited to this, and a plasma processing for supplying a high frequency power may be performed, for example, a CVD plasma apparatus or an RIE plasma etching. It can also be applied to devices and the like.

[0018]

As described above, according to the present invention, high-frequency power is supplied to generate plasma when the plasma processing apparatus is depressurized, so that even if water molecules adhere to the inside of the apparatus, a predetermined time is maintained. Pressure can be reduced to pressure. The present invention has such excellent effects.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing the structure of an ECR plasma etching apparatus used in the depressurizing method of the present invention.

FIG. 2 is a flowchart showing a procedure of decompressing the chamber of this embodiment.

FIG. 3 is a graph showing the result of decompressing the plasma processing apparatus by the method of the present invention.

[Explanation of symbols]

 1 Chamber 2 Excitation Coil 4 Gas Introduction System 6, 7 Exhaust System 8 Main Valve 9 Turbo Molecular Pump 11 Dry Pump 12 Roughing Valve

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical indication H01L 21/304 341 D 21/31 C H05H 1/46 C 9216-2G

Claims (2)

[Claims] 1. A method of depressurizing the inside of a plasma processing apparatus for performing plasma processing on an object to be processed, comprising a first step of prepressurizing the inside of the plasma processing apparatus by an exhaust system, and high-frequency power in the plasma processing apparatus. A second step of supplying and generating plasma, a third step of loading the object to be processed into the plasma processing apparatus after completion of the second step, and depressurizing the inside of the plasma processing apparatus to a predetermined pressure by an exhaust system. And a fourth step of: depressurizing the plasma processing apparatus. 2. The depressurizing method of the plasma processing apparatus according to claim 1, wherein the depressurizing rate in the first step is lower than the depressurizing rate in the fourth step.