JPS58158929A - Plasma generator - Google Patents

Abstract

PURPOSE:To enable to perform an optimum processing on the titled device by a method wherein one end of a parallel-plate electrode is grounded through a variable reactance element, a high frequency power source is connected to the other end of the parallel- plate electrode, and the value of the reactance element is controlled by comparing the generated DC self-biased voltage with the set value. CONSTITUTION:The excitation of plasma is performed by applying the output of the high frequency power source 5 on an electrode 8 through a DC blocking capacitor 4. The other electrode 2 is grounded through a variable capacitor or an inductance. When plasma is generated, the DC self-biased voltage is generated at an electrode 3, the DC self-biased voltage is applied to a differential amplifier 10 through the filters on a coil 7 and the capacitor 8, and the DC self-biased voltage is compared with the set voltage of a potentiometer 9, a motor 11 is operated in accordance with the result of the above comparison, and the DC self-biased voltage is adjusted to the set voltage by controlling the value of a variable impedance 6. When the high frequency power, vacuum pressure and gas flow rate which are optimum to the processing are determined, a stabilized etching can be performed while the DC self-biased voltage value is being controlled to an appropriate value during the period wherein plasma is generated.

Description

DETAILED DESCRIPTION OF THE INVENTION One of the processes for manufacturing a semiconductor integrated circuit is the process of forming an interlayer insulating film and a final protective film. It is well known that when these films are formed by, for example, chemical vapor deposition using plasma, a high melting point substance can be formed at a low temperature of 400° C., which provides many advantages.

The present invention uses such a processing device, that is, a high-frequency power source sends energy between parallel plate electrodes provided in a vacuum container to excite plasma, and processes a semiconductor integrated circuit or the like placed on one of the electrodes. It is related to the device.

In the above plasma generation processing equipment, a negative DC voltage is generated at the electrode (to which the output of the high frequency power supply is applied) due to the difference in the mobility of electrons and ions in the plasma. Its size depends on the pressure inside the vacuum container, the type and flow rate of the flowing gas,
It varies depending on the structure and material of the container, the frequency and amount of power applied, etc. As described above, the DC self-heating and insulating pressure, which has many parameters, greatly affects the processing of semiconductor devices.

For example, when plasma di-etching is performed on a semiconductor device, if the DC self-bias voltage is large, the etching will be anisotropic, and if it is small, the etching will be isotropic.

On the other hand, if it is too large, the selectivity with the substrate will be poor and the photoresist will be damaged, and if it is too small, undercutting may occur and polymer may be deposited on the substrate after etching. Based on these factors, optimal high frequency power, vacuum pressure,
Once the gas flow rate is determined, there is an optimum value for the DC self-bias voltage.

- Conventionally, as a means of controlling the DC self-bias voltage, methods such as making the applied high-frequency power variable or vacuum pressure variable have been proposed. Since the concentration changes, it is impossible to perform constant processing, and the processing of semiconductor devices becomes extremely unstable if the vacuum pressure changes. Note that once the pressure inside the vacuum container, the amount of high-frequency power to be applied, and the type and flow rate of the flowing gas are determined, the DC self-bias voltage depends on the structure and material of the container and the structure and material of the electrodes. Due to requirements such as prevention of dirt and easy cleaning, the structure is simple. Furthermore, the material of the container is also limited in terms of contamination, and the structure and material of the electrodes are also subject to similar restrictions.

The present invention is characterized in that the DC self-bias voltage can be adjusted to a predetermined value even during plasma generation, thereby eliminating the above-mentioned drawbacks at once and allowing satisfactory processing to be performed. Next, the present invention will be explained in more detail with reference to the drawings.

, the drawing is a configuration diagram of a plasma generation processing apparatus in which the present invention is implemented. The actual device requires a gas flow rate control device on the gas inlet side, a vacuum exhaust device, a pressure control device, etc. at the vacuum exhaust port, but these are omitted in this drawing.

1 in the figure is a vacuum vessel, inside which parallel plate electrodes 2 and 8 are placed facing each other. A constant flow rate of gas is introduced into the vacuum vessel l through a gas port 12 from a gas flow control device. Further, evacuation is performed through the evacuation outlet 18 by a vacuum evacuation device with a pressure control device. Excitation of the plasma is performed by applying the output of a high frequency power source 5 to the electrode 3 through a DC blocking capacitor 4, while the other electrode 2 is grounded through a variable reactance element, that is, a variable capacitor 6 or a variable inductance coil (inductor). There is. When plasma is generated, a DC self-bias voltage is generated at the electrode 8.

This voltage passes through a filter circuit consisting of a high frequency choke coil 7 and a capacitor 8 and is applied to one input of a differential amplifier 10. Another input of the differential amplifier 10 is the setting voltage from the potentiometer 9 of the bias setter, and the differential amplifier l
O amplifies the difference between these two human forces and drives the drive unit 11 (motor, etc.)
The DC self-bias voltage is adjusted to the setting voltage (setting signal) of the bias setting device by changing the value of the variable capacitor 6 or the variable inductor connected thereto.

As explained above, once the optimal high-frequency power, vacuum pressure, and gas flow rate for processing are determined, the DC self-bias voltage can be controlled to any appropriate value using the device of the present invention during plasma generation. The effect is as described above, but to give a more specific example, since a plasma CVD apparatus using parallel plate electrodes uses an anode coupling method, the electrode on the side on which the sample wafer etc. is placed (ground side)
The potential can be made variable and an optimal film can be produced on the wafer. Furthermore, when performing plasma etching, etching can be performed while controlling the DC self-bias voltage to an optimum value.

As described above, by using the apparatus of the present invention, semiconductor processing processes using plasma can be stabilized and products with higher performance can be realized, which is a significant improvement in industry.

[Brief explanation of the drawing]

(Side 4 is a configuration diagram of a plasma generator implementing the present invention. ■... Vacuum vessel, 2.8... Electrode, 4, 8
---Capacitor, 5--High frequency power supply, 6-
・0 variable capacitor, 7... choke coil,
9...Bias voltage setter, IO...Differential amplifier, 11...Driver, l2
・■・Gas inlet, 18...Exhaust port. Patent applicant Kokusai Denki Co., Ltd. agent Okyu 1 person from outside the university

Claims (1)

[Claims] In a device that generates plasma by applying electric power from a high-frequency power source to parallel plate electrodes provided inside a vacuum container through which gas flows, one of the parallel plate electrodes is supplied with the output of the high-frequency power source, and the other electrode has a variable reactance. The variable reactance element is grounded through the element, and the high-frequency power supply side electrode (2) detects the generated DC self-bias voltage, compares it with the set voltage, and adjusts the value of the variable reactance element so as to keep the DC self-bias voltage value at a constant value. A plasma generation device characterized by comprising a DC self-bias voltage detection section and a control section.