JPH0641771A - Plasma treating device - Google Patents

Abstract

PURPOSE:To generate high density plasma and to efficiently perform a plasma treatment by arranging a pair of electrodes in a treatment room housing a treatment gas having prescribed pressure and applying the same RF voltage of a specific frequency to both electrodes. CONSTITUTION:The treating gas is supplied into the treatment room 1 at the inside for which a pair of the electrodes 2, 3 are arranged and the treating gas is reduced and discharged in the pressure to a prescribed level. Thereafter, the high frequency voltage is applied to the electrodes 2, 3. Treatments, such as etching are performed by the plasma generated by such constitution. The RF voltage of a frequency of 100kHz to 1MHz is applied to both electrodes 2, 3 from a high frequency power source 4 and a low frequency power source 7 in the plasma treating device. At this time, after the etching treatment is performed by applying the high frequency voltage, the treating gases such as O2 is introduced into the treatment room 1 and the pressure in the room kept at <=0.1Torr and the low frequency voltage, 100kHz for instance, is applied. Thus, hollow cathod electric discharge is generated between the electrodes and high density plasma is obtained, thereby accomplishing the plasma cleaning in a short time.

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 a plasma processing apparatus capable of generating plasma having a high plasma density suitable for plasma cleaning.

[0002]

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

[0003]

The above-mentioned prior art does not take into consideration the fact that a high density plasma is generated between two electrodes.

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

[0005]

In the present invention, an RF (radio frequency) of 100 kHz to 1 MHz is applied to both of these electrodes.
Means are provided for applying a voltage.

[0006]

By the above means, a hollow cathode discharge at RF is generated between the electrodes, so that a high density plasma can be obtained between the two electrodes, and this plasma can be used for cleaning the processing chamber to shorten the cleaning time. You can

[0007]

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

FIG. 1 shows a plasma processing apparatus having parallel plate electrodes in this case. Electrodes 2 and 3 are provided in the processing chamber 1 so as to face each other, a processing gas is supplied by a gas supply device (not shown), and the gas is evacuated to a predetermined pressure by an exhaust device (not shown). Electrode 2 is powered via switch 5, frequency 13.56M in this case
It is connected to a high frequency power source 4 of Hz. Electrode 3 is switch 6
It is grounded through. 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 low frequency power source 7 of 00 kHz 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 source 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 with a predetermined pressure. By this etching process, deposits of C, CF, Si, etc. adhere to the inner wall of the processing chamber 1 and the surfaces of the electrodes 2 and 3. Next, plasma cleaning is performed to remove the deposits.

In the plasma cleaning, in this case, O ₂ gas was supplied into the processing chamber 1 and the pressure was kept at 0.1 Torr.
The switches 5 and 6 are connected to the low frequency power source 7 side, and a power of frequency 100 kHz is applied to the electrodes 2 and 3 so that the processing chamber 1
It is performed by generating plasma of O ₂ gas inside. O ₂ gas is O
In a plasma state of ions and O radicals, the O ions and O radicals react with deposits adhering to the inner wall of the processing chamber 1 to remove the deposits, and at the same time, they are accelerated by low frequency power and have high energy. Since some O ions collide with the deposit to remove the deposit by sputtering, efficient plasma cleaning becomes possible.

This is done by changing the frequency of the low frequency power source 7,
It was found by investigating the relationship between the frequency and the cleaning speed. As shown in FIG. 2, it was found that the cleaning speed was improved as the frequency was lowered. The cleaning rate in this case is a measurement of the point on the side wall portion A in the processing chamber 1. At the frequency of 13.56 MHz when etching is performed, the energy for accelerating ions having a short positive / negative switching period and a large mass compared to electrons is not obtained, and the sputtering effect due to ions can be obtained, so ions and Only the reaction removal by radicals slows down the cleaning speed. The frequency at which the ions are accelerated and start moving varies depending on the pressure, voltage, etc., but is from around 1 MHz.

Next, when 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 increased from around 0.1 Torr to the following. Was found to improve. It should be noted that points B and C are due to a problem with the performance of the exhaust system, and O ₂ gas is 50 c.
Since it was not possible to reduce the pressure to the prescribed pressure in the condition of c / min,
The flow rate of O ₂ gas was set to 39 cc / min and 5 cc / min, respectively, and the pressure was reduced to a predetermined pressure for the examination. The cleaning speed is improved because the free path length of gas molecules is lengthened, so the ion sputtering effect is expected to be further improved. I think that the amount of will decrease.

When the frequency is 13.56 MHz, as shown in FIGS. 4 and 5, the cleaning speed is highest near the pressure of 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, since the low frequency power source with a frequency of 1 MHz or less is used as the plasma generating power source during the plasma cleaning, the ions in the plasma can be made to follow the alternating electric field and collide with the processing chamber. Therefore, the cleaning time can be shortened because sputter removal by ions is added in addition to the reaction removal by ions and radicals.

The processing pressure during cleaning is 0.1T.
By lowering it to orr or lower, the cleaning time can be further shortened.

Furthermore, in the present embodiment, low frequency power is applied to both electrodes 2 and 3 to cause discharge between the electrodes and the processing chamber 1, so that the entire inner wall surface of the processing chamber 1 and the electrode 2 are treated. The plasma spreads not only on the back surfaces of the electrodes 3 and 3, but also between the electrodes 2 and 3, so that the entire surface of the inside of the processing chamber can be cleaned. That is, the electrodes 2 and 3
Since the sheath layers are generated along the surfaces facing each other and the plasma generated between the sheaths is confined, a higher density plasma is obtained by the hollow cathode effect. Will spread from the end of the electrode to the entire processing chamber.

Although low frequency power is applied to both electrodes 2 and 3 in this embodiment, low frequency power is applied to one of the electrodes, or electrodes to which low frequency power is applied are alternately switched. Even if it does so, the cleaning speed can be similarly improved.

Further, in this embodiment, the high frequency power source 4 for processing the wafer and the low frequency power source 7 for plasma cleaning are separate, but the low frequency power source is used for processing the wafer. If yes, the sixth
As shown in the figure, the electrode 2 is connected to the low frequency power source 7,
The electrode 6 may be switched between the low frequency power source 7 and the ground by the switch 6.

Further, in the present embodiment, O ₂ gas is used as the processing gas for plasma cleaning. Needless to say, however, this deposit is different depending on the processing of the wafer and is determined by this deposit.

[0020]

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

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a plasma processing apparatus that is an 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 the pressure and the cleaning rate when the frequency is 100 kHz.

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

5 is a diagram showing the relationship between pressure and cleaning time in the case of FIG. 4;

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

[Explanation of symbols]

 1 ... Processing chamber, 2, 3 ... Electrode, 7 ... 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 chamber having a pair of electrodes therein, a gas supply device for supplying a processing gas into the processing chamber, an exhaust device for decompressing and exhausting the processing chamber to a predetermined pressure, and a pair of electrodes. A plasma processing apparatus comprising: a power supply for applying an RF voltage having a frequency of 100 kHz to 1 MHz to both. 2. The plasma processing apparatus according to claim 1, wherein the pressure in the processing chamber is 0.1 Torr or less.