JPH05206067A - Plasma control method for plasma processor - Google Patents

Abstract

PURPOSE:To maintain plasma in stable condition without extinguishing it even in low gas pressure condition (high vacuum condition), in a plasma processor. CONSTITUTION:The frequency distribution of the potential of a high frequency electrode 5a is measured with a spectrum analyzer 21. When the potential waveform of the high frequency electrode 5a, which has the peak strength in the frequency higher than the frequency of a high frequency power source 6 and has the frequency ingredients where the frequency value at that time fluctuates irregularly, is measured, the plasma control parameters such as treatment gas pressure, high frequency power, etc., are controlled. For example, the pressure of the treatment gas inside a vacuum vessel 1 is elevated a little. Hereby, plasma can be maintained in stable condition without being extinguished even in the condition that the gas pressure is low.

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 for performing plasma processing such as etching, CVD (Chemical Vapor Deposition), and sputtering on a sample substrate, and measures the frequency distribution of the potential waveform of the high frequency electrode immediately before the plasma disappears. Low gas pressure condition (high vacuum condition) by detecting condition and controlling plasma control parameters
The present invention also relates to a plasma control method in a plasma processing apparatus, which is capable of stably maintaining plasma.

[0002]

2. Description of the Related Art A high-frequency voltage is applied from a high-frequency power source to a high-frequency electrode provided inside a vacuum container to turn a processing gas introduced into the vacuum container into a plasma, and the plasma is placed on the high-frequency electrode. As a plasma processing apparatus for etching a sample substrate, for example, a plasma processing apparatus shown in FIG.

In FIG. 5, reference numeral 1 denotes a vacuum container, and the vacuum container 1 is provided with a processing gas introduction port 1a to which a processing gas introduction pipe 2 is connected and a processing gas exhaust port 1b. A gas flow rate adjusting valve 3 for adjusting the processing gas flow rate for adjusting the processing gas pressure in the vacuum container 1 is provided in the middle of the processing gas introduction pipe 2. The opening of the gas flow rate adjusting valve 3 is controlled by the gas flow rate controller 4. The other end of the processing gas introduction pipe 2 is connected to a processing gas cylinder (not shown).
It should be noted that a stop valve and the like provided in the middle of the processing gas introduction pipe 2 are not shown.

In the vacuum container 1, a high frequency electrode 5a and an anode electrode 5b are arranged as electrodes at a predetermined interval.
A sample substrate W is placed on the high frequency electrode 5a. 6 is 13.56 MHz high frequency (Radio Frequency
) A high frequency power supply for supplying electric power between the electrodes 5a and 5b,
Reference numeral 7 is a high frequency output control unit, 8 is a matching circuit for impedance matching, and 9 is a coupling capacitor for bias.

As shown in the figure, the high-frequency power source 6 has one end connected to the high-frequency electrode 5a through the high-frequency output control unit 7, the matching circuit 8 and the coupling capacitor 9 in series, and the other end connected to the anode electrode 5b. It is connected. 10a
And 10b are insulators for insulating between the electrodes 5a, 5b and the vacuum container 1.

In the plasma processing apparatus having such a structure, a processing gas such as Cl ₂ gas is introduced while exhausting the inside of the vacuum container 1 to a predetermined pressure, and a high frequency is applied between the electrodes 5a and 5b. , High frequency discharge occurs, vacuum container 1
The processing gas introduced therein is turned into plasma. In this example, the sample substrate W placed on the high-frequency electrode 4 is etched by this plasma.

In this case, when the high frequency power supplied between the electrodes 5a and 5b changes, the ions in the plasma are transferred to the sample substrate W.
The voltage (sheath voltage) for accelerating toward changes.
In order to stably obtain the optimum plasma processing conditions, the high frequency power must be controlled so that the sheath voltage is constant. Therefore, conventionally, the output of the high frequency power source 6 is kept constant to keep the sheath potential constant,
The plasma is controlled by measuring the magnitude of the sheath potential during plasma processing and adjusting the output of the high frequency power source 6 based on the measured value.

[0008]

However, in the plasma control method in the conventional plasma processing apparatus, since the sheath potential is strongly dependent on the stability of plasma,
For example, when the plasma becomes unstable, the sheath potential becomes unstable and the optimum plasma processing conditions cannot be obtained stably. In particular, the ion energy is increased to increase the mean free path of the ions. However, in a low gas pressure state where anisotropic plasma processing is possible, there is a problem that it is not easy to maintain the plasma in a stable state because the plasma tends to become unstable.

The present invention has been made in order to solve the above-mentioned conventional problems, and in a plasma processing apparatus, a stable state is achieved without extinguishing plasma even in a low gas pressure state (high vacuum state). An object of the present invention is to provide a plasma control method in a plasma processing apparatus that can be maintained.

[0010]

In order to achieve the above object, in the plasma control method in the plasma processing apparatus according to the present invention, a high frequency voltage is applied from a high frequency power source through a coupling capacitor while a sample substrate is placed. Introduce the processing gas into the vacuum container where the high frequency electrode is placed,
In a plasma control method in a plasma processing apparatus that performs plasma processing such as etching, CVD, and sputtering on a sample substrate by turning a processing gas into plasma by high-frequency discharge, a frequency distribution of a potential waveform of a high-frequency electrode is measured and Controlling plasma control parameters such as process gas pressure and high frequency power when the potential waveform having a peak intensity at a frequency higher than the frequency and a frequency component at which the frequency value fluctuates irregularly is measured. Is characterized in that the plasma is stabilized.

[0011]

In the plasma control method according to the present invention,
The frequency distribution of the potential waveform of the high frequency electrode is measured. When the plasma state becomes unstable and becomes a state just before the plasma disappears, the plasma impedance fluctuates irregularly.Therefore, due to the frequency component based on the irregular fluctuation, the peak intensity at a frequency higher than the frequency of the high frequency power source is generated. The potential waveform of the high frequency electrode that it has is measured. When the potential waveform of the high frequency electrode indicating the state immediately before the plasma is extinguished, the plasma is stably maintained without being extinguished by controlling the plasma control parameters such as the processing gas pressure and the high frequency power.

[0012]

EXAMPLES The present invention will be described below based on examples. FIG. 1 is a structural explanatory view showing an example of a plasma processing apparatus to which the method according to the present invention is applied. Note that, in FIG. 1, substantially the same parts as those shown in FIG. 5 are denoted by the same reference numerals, description thereof will be omitted, and only different points will be described.

In FIG. 1, reference numeral 21 is a spectrum analyzer device. This spectrum analyzer device 21
As shown in the figure, the frequency distribution of the potential waveform (signal) of the high-frequency electrode 5a is measured, and when the potential waveform of the high-frequency electrode 5a indicating the state immediately before plasma extinction described below is measured, detection indicating the state immediately before plasma extinction is detected. A signal is given to the gas flow rate controller 4.

Next, a plasma control method performed in the above plasma processing apparatus for performing etching will be described below. FIG. 2 is a diagram showing a potential waveform of the high-frequency electrode and a frequency distribution of the potential waveform in a state before plasma generation,
FIG. 3 is a diagram showing a potential waveform of the high-frequency electrode and a frequency distribution of the potential waveform in a state where plasma is stably generated, and FIG. 4 is a potential waveform of the high-frequency electrode in a state immediately before plasma extinction and a frequency distribution of the potential waveform. FIG. 2 to 4, (a) shows the potential waveform of the high-frequency electrode, and (b) shows the frequency distribution of the potential waveform.

First, in the state before plasma generation (generation), as shown in FIG. 2, the potential waveform of the high frequency electrode 5a is the frequency f of the high frequency power source 6 with the zero volt line as a reference.
It changes regularly with _R (13.56 MHz). Therefore, the spectrum analyzer device 21 measures the frequency of the high frequency power supply 6.

Next, when the plasma is generated in a stable state, as shown in FIG. 3, the mobility of electrons in the plasma is overwhelmingly higher than that of ions, so that a rectifying action occurs. As a result, the potential waveform of the high frequency electrode 5a regularly changes with the frequency f _R of the high frequency power source 6 in the state of being negatively biased. In this case, in the spectrum analyzer device 21, the frequency f _{R of the} high frequency power source 6
Will be measured. In addition, in FIG.
2V _p is a positive peak value, and V _f is a self-bias potential.

When etching is performed in a low gas pressure state (high vacuum state) in order to increase ion energy, the plasma state is apt to become unstable in nature, and the local extinction and generation of the plasma occur. Then, the impedance of the plasma fluctuates irregularly. for that reason,
As shown in FIG. 4, when the state immediately before the plasma is extinguished, the spectrum analyzer device 21 has a peak intensity at a frequency higher than the frequency f _R of the high frequency power source 6 and the frequency value at that time fluctuates irregularly (for example, 100 MH
The potential waveform of the high frequency electrode 5a having a frequency component of about z to 1 GHz) is measured. The potential waveform of the high-frequency electrode 5a as shown in FIG. 4 also occurs at the plasma processing start timing when the state before plasma generation shown in FIG. 2 shifts to the stable plasma generation state shown in FIG.

When the potential waveform of the high frequency electrode showing the state immediately before the extinction of the plasma is measured, the spectrum analyzer device 21 gives a detection signal indicating this to the gas flow rate controller 4. The gas flow rate controller 4 slightly increases the opening degree of the gas flow rate adjustment valve 3 in response to the detection signal indicating the state immediately before the extinction of plasma. As a result, the plasma that was in an unstable state is stabilized by slightly increasing the processing gas pressure in the vacuum container 1, and is maintained in a stable state without extinguishing the plasma in a gas pressure state lower than before. Then, etching can be performed.

For example, when reactive ion etching is performed using Cl ₂ gas, according to the method of the present invention, the gas pressure at which etching can be performed while maintaining the plasma in a stable state is 3 × 10 ^-3. I was able to get from Torr to 1 × 10 ^-3 Torr. Instead of adjusting the processing gas pressure, the high frequency power may be slightly increased to control the plasma.

In the above embodiment, the process gas is excited by the high frequency power supplied from the high frequency power source to be turned into plasma. However, the plasma control method according to the present invention is not limited to the high frequency power source and the microwave power source. f
_(M = 2.45 GHz) and a magnetic field generating means for resonating electrons in plasma at the same frequency as the microwave, and can be applied to, for example, a plasma processing apparatus configured to perform sputtering. In the case of a plasma processing apparatus in which this microwave is also used, the magnetic field strength also serves as a plasma control parameter, and the spectrum analyzer device 21 is used to measure the microwave intensity indicated by broken lines in FIGS. 2 to 4 from the potential waveform of the high frequency electrode 5a. The frequency f _{M will} also be measured. Although the spectrum analyzer device is used in the above-described embodiment, instead of this, a more inexpensive bandpass filter is used to detect a specific frequency component of the potential waveform of the high frequency electrode, and the plasma control parameter is set based on this. It may be controlled.

[0021]

As described above, according to the plasma control method in the plasma processing apparatus of the present invention, the frequency distribution of the potential waveform of the high frequency electrode is measured, and the peak intensity is obtained at a frequency higher than the frequency of the high frequency power source. When the potential waveform of the high frequency electrode has a frequency component whose frequency value fluctuates irregularly, the plasma is stabilized by controlling the plasma control parameters such as the processing gas pressure and the high frequency power. Therefore, it is possible to maintain the plasma in a stable state without extinguishing the plasma in a lower gas pressure state (high vacuum state) than in the past, and this enables etching with higher ion energy than in the past. Plasma treatment such as.

[Brief description of drawings]

FIG. 1 is a structural explanatory view showing an example of a plasma processing apparatus to which a method according to the present invention is applied.

FIG. 2 is a diagram showing a potential waveform of a high-frequency electrode and a frequency distribution of the potential waveform in a state before plasma generation, where (a) shows the potential waveform of the high-frequency electrode and (b) shows the potential waveform. It shows a frequency distribution.

FIG. 3 is a diagram showing a potential waveform of the high-frequency electrode and a frequency distribution of the potential waveform in a state where plasma is stably generated, in which (a) shows the potential waveform of the high-frequency electrode and (b) thereof. ) Indicates the frequency distribution of the potential waveform.

4A and 4B are diagrams showing the potential waveform of the high-frequency electrode and the frequency distribution of the potential waveform in the state immediately before the plasma is extinguished, where FIG. 4A shows the potential waveform of the high-frequency electrode and FIG. 4B shows the frequency of the potential waveform. It shows the distribution.

FIG. 5 is a structural explanatory view of a plasma processing apparatus for explaining a conventional technique.

[Explanation of symbols]

1 ... Vacuum container 1a ... Processing gas inlet 1b ... Processing gas exhaust port 2 ... Processing gas introducing pipe 3 ... Gas flow rate adjusting valve
4 ... Gas flow rate controller 5a ... High frequency electrode 5b ... Anode electrode 6 ... High frequency power supply 7 ... High frequency output control unit 8 ... Matching circuit 9 ... Coupling capacitor 10
a, 10b ... Insulator 21 ... Spectrum analyzer device
W ... Sample substrate

Claims (1)

[Claims] 1. A processing gas is introduced into a vacuum container in which a sample substrate is placed and a high frequency electrode to which a high frequency voltage is applied from a high frequency power source through a coupling capacitor is arranged.
In a plasma control method in a plasma processing apparatus that performs plasma processing such as etching, CVD, and sputtering on a sample substrate by turning a processing gas into plasma by high-frequency discharge, a frequency distribution of a potential waveform of a high-frequency electrode is measured and Controlling plasma control parameters such as processing gas pressure and high frequency power when the potential waveform having a peak intensity at a frequency higher than the frequency and a frequency component at which the frequency value fluctuates irregularly is measured. A plasma control method in a plasma processing apparatus, characterized in that the plasma is stabilized by the above method.