JPH09260360A - Plasma processing method and apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable reducing washing time in the case of cleaning, by supplying treatment gas to a treatment chamber, reducing and discharging the pressure in the treatment chamber to be lower than or equal to a specific value, applying an RF voltage of a specified frequency to both electrodes and generating high density plasma. SOLUTION: Treatment gas is supplied to a treatment chamber 1 which has parallel plane plate type electrodes 2, 3, and pressure in the treatment chamber 1 is reduced by discharge from about 0.1Torr down to lower. An RF voltage whose frequency is 100kHz-1MHz is applied to both of the electrodes 2, 3, plasma is generated, and the inside of the treatment chamber 1 is cleaned by the generated plasma. For example, O2 gas is supplied to the treatment chamber 1, and pressure is maintained at 0.1Torr. Switches 5, 6 are connected to a low-frequency power source 7 side. Electric power whose frequency is 100kHz is applied to the electrodes 2, 3, plasma of O2 gas is generated in the treatment chamber 1, and plasma cleaning is performed.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art As disclosed in Japanese Patent Application Laid-Open No. Sho 61-5521, there is a technique for applying an RF (13.56 MHz) or AC (50 to 400 Hz) voltage to a pair of parallel plate electrodes.
However, in this known example, when such a voltage is applied to a pair of parallel plate electrodes, one electrode is moved toward the other electrode, and both electrodes are brought into a close state. No consideration has been given to the technical idea of generating plasma between the two electrodes under the RF voltage application condition.

[0003]

The above-mentioned prior art does not consider generation of high-density plasma between two electrodes.

It is an object of the present invention to provide a plasma processing method and apparatus capable of generating high density plasma and shortening the cleaning time when cleaning, for example.

[0005]

The above-mentioned object is to supply a processing gas to a processing chamber having a parallel plate type electrode therein, and to evacuate the pressure in the processing chamber from around 0.1 Torr to below.
An RF voltage having a frequency of 100 kHz to 1 MHz is applied to both electrodes of the electrode to generate plasma, and the generated plasma cleans the inside of the processing chamber, and also has parallel plate electrodes inside. A processing chamber, a gas supply device for supplying a processing gas into the processing chamber, an exhaust device for reducing the pressure in the processing chamber from around 0.1 Torr to below and generating an RF voltage having a frequency of 100 kHz to 1 MHz. It is achieved by cleaning the inside of the processing chamber with a power source connected to both electrodes of the electrode.

By the above-mentioned means, high-energy discharge with RF voltage applied is generated between the pair of electrodes, so that a high density plasma can be obtained between the two electrodes, and this plasma is used for cleaning the processing chamber, for example, for cleaning time. Can be shortened.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS.

FIG. 1 shows a plasma processing apparatus having a parallel plate type electrode in this case. Electrodes 2 and 3 are provided in the processing chamber 1 so as to face each other. The processing gas is supplied by a gas supply device (not shown), and the pressure is reduced to a predetermined pressure by an exhaust device (not shown). Electrode 2 is powered via switch 5, in this case frequency 13.56M
Hz high-frequency power supply 4. Electrode 3 is switch 6
Grounded via The other of the switches 5 and 6 is another power source for cleaning, in this case, the frequency 1
It is connected to a 00 kHz low frequency power supply 7 and is connected to the electrodes 2 and 3 by switching the switches 5 and 6.

With the apparatus having the above structure, the switch 5 is connected to the high-frequency power supply 4 side, the switch 6 is connected to the ground side, and the wafer is placed on the electrode 2. In this case, for example, CHF ₃ is supplied as a processing gas. Then, the SiO ₂ film formed on the wafer surface is etched at a predetermined pressure. Deposits such as C, CF, and Si adhere to the inner wall of the processing chamber 1 and the surfaces of the electrodes 2 and 3 due to the etching process. Next, plasma cleaning is performed to remove the deposits.

In this case, the plasma cleaning is performed by supplying O ₂ gas into the processing chamber 1 and maintaining the pressure at 0.1 Torr.
The switches 5 and 6 are connected to the low frequency power supply 7 side, and a power of 100 kHz is applied to the electrodes 2 and 3 so that the processing chamber 1
This is performed by generating O ₂ gas plasma therein. O ₂ gas is O
In a plasma state of ions and O radicals, the O ions and O radicals react with the deposits attached to the inner wall of the processing chamber 1 to remove the deposits, and have high energy accelerated by low frequency power. Since some O ions collide with the deposit to remove the deposit by sputtering, efficient plasma cleaning can be performed.

This is achieved by changing the frequency of the low-frequency power source 7 and
It was found by examining the relationship between the frequency and the cleaning speed, and as shown in FIG. 2, it was found that the cleaning speed improved as the frequency was lowered. The cleaning speed in this case is obtained by measuring a point on the side wall A in the processing chamber 1. At a frequency of 13.56 MHz when the etching process is performed, the cycle of switching between positive and negative is short, and energy for accelerating ions having a larger mass than electrons is not obtained, and a sputtering effect by ions is obtained. The cleaning rate has been reduced due to only reaction removal by radicals. The frequency at which ions start to move due to acceleration is different depending on pressure, voltage, and the like, but is generally from around 1 MHz.

Next, the frequency is kept constant at 100 kHz, and the relationship between the pressure in the processing chamber 1 and the cleaning speed is examined. As shown in FIG. 3, the cleaning speed is reduced from around 0.1 Torr to below. Was found to improve. Incidentally, points B and C are O ₂ gas in performance problems of the exhaust system 50c
Since the pressure could not be reduced to the specified pressure at c / min,
The flow rate of the O ₂ gas was 39 cc / min and 5 cc / min, respectively, and the pressure was reduced to a predetermined pressure, and the examination was performed. It is believed that the improvement in the cleaning rate is due to the longer free path length of the gas molecules, so that the ion sputtering effect is further improved.In addition, when the pressure is further reduced, the cleaning rate is reduced by ions and radicals. I think that the amount of

In the case of a frequency of 13.56 MHz, as shown in FIGS. 4 and 5, the cleaning speed is the highest at a pressure of about 0.1 Torr, and the cleaning time is shortened. However, the cleaning speed is much slower than when the frequency is lowered.

As described above, according to this embodiment, a low-frequency power supply having a frequency of 1 MHz or less is used as a plasma generation power supply during plasma cleaning, so that ions in the plasma follow the alternating electric field and collide with the processing chamber. So you can
Sputter removal by ions is added together with reaction removal by ions and radicals, so that the cleaning time can be shortened.

The processing pressure at the time of cleaning is 0.1T.
By lowering it to orr or less, there is an effect that the cleaning time can be further shortened.

Further, in the present embodiment, a low-frequency power is applied to both the electrodes 2 and 3 to generate a discharge between the processing chamber 1 and the entire inner wall surface of the processing chamber 1 and the electrodes. The plasma spreads between the electrodes 2 and 3 as well as the back surfaces of the substrates 2 and 3, and plasma cleaning can be performed on the entire surface of the processing chamber. That is, the electrodes 2,
3, a sheath layer is generated along the surfaces facing each other, and plasma generated between the sheaths is confined, so that a higher-density plasma can be obtained. To the entire processing chamber.

In this embodiment, the low-frequency power is applied to both the electrodes 2 and 3. However, the low-frequency power is applied to one of the electrodes, or the electrodes to which the low-frequency power is applied are alternately applied. Even if it is changed, the cleaning speed can be similarly improved.

In this embodiment, the high-frequency power supply 4 for processing the wafer and the low-frequency power supply 7 for performing the plasma cleaning are separated, but the processing is performed using the low-frequency power supply when processing the wafer. In this case, the electrode 2 may be connected to a low-frequency power source 7 as shown in FIG. 6, and the switch 6 may be used to switch the electrode 3 between the low-frequency power source 7 and the ground.

Further, in this embodiment, the O ₂ gas is used as the processing gas for the plasma cleaning. However, it is needless to say that the deposit differs depending on the processing of the wafer and is determined by the deposit. .

[0020]

According to the present invention, there is an effect that the cleaning time for cleaning using plasma can be shortened.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a plasma processing apparatus according to one embodiment of the present invention.

FIG. 2 is a diagram showing a relationship between a frequency and a cleaning speed.

FIG. 3 is a diagram showing the relationship between pressure and cleaning rate when the frequency is set to 100 kHz.

FIG. 4 is a diagram showing the relationship between the pressure and the cleaning speed when the frequency is 13.56 MHz.

FIG. 5 is a diagram showing the case of FIG. 4 in relation to pressure and cleaning time.

FIG. 6 is a configuration diagram showing another embodiment of the present invention.

[Explanation of symbols]

 Reference numeral 1 denotes a processing chamber, 2, 3 denotes an electrode, and 7 denotes a low-frequency power supply.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Hiroyuki Nakata Inventor Hiroyuki Nakata 111, Nishiyokote-cho, Takasaki-shi, Gunma Hitachi Ltd. Takasaki Plant

Claims (2)

[Claims] 1. A processing gas is supplied to a processing chamber having a parallel plate type electrode therein, and the pressure inside the processing chamber is evacuated to below from about 0.1 Torr to generate an RF voltage having a frequency of 100 kHz to 1 MHz. A plasma processing method comprising applying plasma to both electrodes of the electrodes to generate plasma, and cleaning the processing chamber with the generated plasma. 2. A processing chamber having a parallel plate type electrode therein, a gas supply device for supplying a processing gas into the processing chamber, and an exhaust device for evacuating the pressure in the processing chamber from about 0.1 Torr to below. And a power source connected to both electrodes of the electrode for generating an RF voltage having a frequency of 100 kHz to 1 MHz to clean the inside of the processing chamber.