JPS6274082A - Rf plasma cvd device - Google Patents

Abstract

PURPOSE:To always maintain the specified self-bias voltage and to form a film on a substrate with good reproducibility in the stage of forming the film by an RF plasma CVD device on the substrate by detecting the self-bias voltage generated in an RF electrode, comparing the same with a reference voltage and automatically regulating the pressure in a reaction chamber by the deviation value thereof. CONSTITUTION:A substrate electrode 13 on which the substrate 23 is attached and the RF electrode 14 are provided to face each other in a reaction chamber 10 of the RF plasma CVD device. An RF power source 16 is disposed therebetween. After the inside of the reaction chamber 10 is evacuated to a prescribed vacuum degree by an evacuation system 21, gas for film formation is supplied to a prescribed pressure from a gas source 11 and plasma discharge is generated between the two electrodes in the chamber 10 to form the tin film by the gas for film formation on the substrate 23. The self-bias voltage on the electrode 14 is detected by a detection circuit 18 and is compared with the reference voltage 20 in a comparator circuit 19. The deviation value thereof is fed back to a pressure regulating valve 22 provided to the vacuum system 21 to control the valve 22 by which the pressure in the chamber 10 is controlled to control the self-bias voltage to the same value as the reference voltage 20. The uniform film is thus formed with the good reproducibility.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an RF plasma CVD apparatus that controls a self-bias voltage to be constant.

Conventionally, in RF plasma CVD, it has been known that in order to stabilize the plasma state, it is effective to keep the self-bias voltage generated on the RF electrode side constant.

In particular, a method is known in which the stability of plasma during film formation is monitored or the lot of film-forming substrates is managed by measuring temporal changes in self-bias voltage.

In actual RF plasma CVD work, the operator manually adjusts the matching box connected to the RF main power supply, or manually adjusts the pressure regulating valve connected to the exhaust system. The self-bias voltage was kept at a constant value while visually observing the self-bias voltage as it fluctuated.

Five Lessons 1W Inuyama - One Problem However, the above-mentioned conventional method inherently requires skill because it is necessary to constantly monitor the self-bias voltage. Furthermore, such a manual method has the problem that it is not possible to automate the work.

The present invention was devised in view of the above circumstances, and an object of the present invention is to provide an RF plasma CVD apparatus that achieves plasma stabilization by automatically keeping the self-bias voltage constant without relying on manual operations. It is said that

The RF plasma CVD apparatus of the present invention has a self-bias voltage detection circuit connected to an RF main power source and an RF set of electrodes, and compares the output of the self-bias voltage detection circuit with a reference voltage. The self-bias voltage is controlled by feeding back the output of the comparison circuit to a pressure regulating valve provided in the exhaust system.

The self-bias voltage and the reference voltage are compared and the pressure regulating valve is adjusted based on the output from the comparator circuit.

The pressure inside the chamber fluctuates by adjusting the pressure regulating valve.
Therefore, the self-bias voltage fluctuates. However, as a result of comparing the magnitude relationship between the reference voltage and the self-bias voltage in the comparison circuit, the self-bias voltage is always maintained at the reference voltage.

1. Example 1 FIG. 1 is a diagram illustrating the principle of an embodiment of the present invention.

In the figure, 10 is a chamber, and a film forming gas is introduced into the +iii chamber from a gas supply source 11 via a needle valve 12.

Reference numeral 13 denotes a substrate electrode, which is normally grounded, to which the substrate is held.

Reference numeral 14 denotes an RI'' electrode provided opposite to the substrate electrode 13, and an RF power source 16 is connected between the substrate electrode 13 and the lmaF electrode 14 via a matching box 15. This is a self-bias voltage detection circuit for detecting the self-bias voltage generated in the RF group electrode 4, and the self-bias voltage detection circuit 14 includes a DC amplifier therein.Note that 17 is a low-pass filter for RF prevention. be.

19 is a comparison circuit that compares the output of the self-bias voltage detection circuit with the reference voltage 20, and the output of this comparison circuit 19 is fed back to control the opening and closing of the pressure regulating valve 22 connected to the exhaust system 21. .

The operating procedure of the RF plasma CVD apparatus configured as described above will be explained.

(2) After holding the substrate 23 on the substrate electrode 13, the pressure regulating valve 22 is opened and the inside of the chamber 10 is evacuated to a predetermined degree of vacuum.

(2) After the chamber is evacuated, a predetermined film-forming gas is introduced into the chamber from the gas source 11 while adjusting the needle valve 12, and the pressure inside the chamber is maintained at a predetermined pressure.

(2) Turn on the RF power source 15 and adjust the matching box 15 so that the plasma discharge power in the chamber reaches a predetermined value, for example, the maximum value.

■As the plasma discharge progresses, a self-bias voltage is generated on the RF electrode 14, but the value of this self-bias voltage is detected by the self-bias voltage detection circuit 18 and compared with the reference voltage 20. The signal is input to the circuit 19. The comparator circuit 19 compares the two and sends the deviation data to the pressure regulating valve 22. The pressure regulating valve 22 operates by an amount corresponding to the deviation data by an actuator installed inside the pressure regulating valve 22, thereby adjusting the pressure in the chamber. Adjust. As a result, the self-bias voltage is controlled to be the same as the reference voltage.

As is clear from FIG. 2, with the same discharge power, if the pressure inside the chamber is low, the self-bias voltage will be large, and if the pressure is high, it will be small, so it can be seen that the pressure inside the chamber can be controlled.

In the present invention, the self-bias voltage is compared with the reference voltage using a comparison circuit, and the pressure regulating valve is controlled based on the output deviation data, so that the self-bias voltage is always kept constant. Therefore, it becomes possible to form a film with good reproducibility.

[Brief explanation of drawings]

FIG. 1 is a diagram illustrating the principle of an embodiment of the present invention, and FIG. 2 is data showing the relationship between discharge power and self-bias voltage using chamber pressure as a parameter. 10. ・ ・ ・ ・ ・ ・ ・ RF voltage i1.18 ・ ・ ・ ・ ・ Self-bias voltage detection circuit, 19 ・
...Comparison [member =, 20...Reference voltage, 22...Eka = Circumference adjustment valve. Patent applicant: Shimadzu Co., Ltd. Representative: Patent attorney: Takashi Onishi Figure 1

Claims (1)

[Claims] (1) It is equipped with an RF power supply, a self-bias voltage detection circuit connected to an RF electrode, and a comparison circuit that compares the output of the self-bias voltage detection circuit with a reference voltage, and exhausts the output of the comparison circuit. RF plasma CVD characterized in that the self-bias voltage is controlled by feedback to a pressure regulating valve provided in the system.
Device.