JP2796383B2 - Plasma processing equipment - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a plasma processing apparatus.

[Conventional technology]

In a conventional plasma processing apparatus, for example,
As described in Japanese Patent No. 3827, an insulator is provided between an object to be processed and an electrode.

[Problems to be solved by the invention]

In the above prior art, no consideration is given to the discharge of the electric charge accumulated on the electrode on which the object is placed at the end of the treatment of the object, and the electric charge accumulated on the electrode is transferred through the object. Therefore, there is a problem that the thin insulating film on the object to be processed is electrically deteriorated or destroyed due to discharge to the plasma side.

 An object of the present invention is to solve the above problems.

[Means for solving the problem]

In order to achieve the above object, the discharge time constant of the electrode on which the object is placed is set longer than the plasma decay time constant,
The collector of the transistor was connected to an electrode and an earth emitter, and a sensing electrode which was in electrical contact with the plasma was provided around the object to be processed, and was connected to the base of the transistor.

[Action]

By making the discharge time constant of the electrode on which the object is placed longer than the decay time constant of the plasma, the charge accumulated in the electrode when the plasma generation power is turned off is reduced on the insulator on the plasma side on the object to be treated. It does not discharge faster than the stored charge. Since the time constant of the sensing electrode is very small and follows the plasma, the base potential of the transistor becomes lower than the emitter potential and a base current flows. The transistor amplifies this current and rapidly discharges the charge on the electrode, but the current decreases as it approaches the potential of the sensing electrode. As a result, the surface potential of the portion to be processed and the electrode potential are kept the same, so that the thin insulating film in the object to be processed is not electrically deteriorated or broken.

〔Example〕

Hereinafter, an embodiment of the present invention will be described with reference to FIG. FIG. 1 is a vertical sectional view of a dry etching apparatus for generating a plasma by electric discharge and etching a semiconductor substrate. The reaction vessel 1 has a gas introduction port 2 and an exhaust port 3, and is kept in a steady low-pressure atmosphere by exhausting while introducing a reactive gas. Semiconductor substrate 4 to be processed
The cathode 5, which is the electrode on which is mounted, is connected to a high-frequency power supply 10 via a coupling capacitor 8 and a matching box 9. Cathode 5 is attached to reaction vessel 1 by support 6. When a high-frequency electric field is introduced between the cathode 5 and the anode 7 by the high-frequency power supply 10,
Plasma is generated by the discharge, and the semiconductor substrate 4 is etched.

Reference numerals 11 to 14 are constituent elements showing the features of the present invention. Reference numeral 11 denotes a sensing electrode made of SiC (silicon carbide) having a low resistance value, which makes electrical contact with the plasma.
And a larger time constant than the plasma to the cathode 5 together with the capacitor 14. Reference numeral 12 denotes a transistor for controlling discharge of the electric charge of the cathode 5. The emitter is connected to the cathode 5, the collector is connected to the ground, and the base is connected to the sensing electrode 11.

 Hereinafter, the operation will be described with reference to FIG.

During the etching process, the potential of the cathode 5 and the potential of the sensing electrode 11 are equal, the transistor 12 is cut off, no current flows between the emitter and the collector. As the voltage is reduced, the potentials of the cathode 5 and the sensing electrode 11 begin to increase. However, since the cathode 5 has a large discharge time constant, its rise is slower than that of the sensing electrode 11. Therefore, the base potential of the transistor 12 becomes higher than the collector potential, and a base current flows. As a result, the current amplified between the collector and the emitter continues to flow until the current between the base and the emitter becomes 0, that is, the potentials of the cathode 5 and the sensing electrode 11 become equal. Thus, the potential applied to the thin insulating film in the semiconductor substrate can be reduced to 0, so that the withstand voltage of the insulating film can be prevented from deteriorating and destroyed.

For example, when a semiconductor substrate on which a 10 mm insulating film is formed and the circuit of the present invention is removed and etching is performed,
% Of the dielectric breakdown and 40% of the breakdown voltage degradation occurred, but when the circuit of this example was used, both became 0%.

〔The invention's effect〕

According to the present invention, since damage to an insulating film of a semiconductor circuit can be reduced, a semiconductor element can be efficiently produced.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a dry etching apparatus according to one embodiment of the present invention. 5 ... cathode, 7 ... anode, 10 ... high frequency power supply
11 sensing electrodes, 12 transistors, 13 coils, 14 capacitors

Claims (3)

(57) [Claims] 1. A plasma processing apparatus comprising: a sensing electrode that is in electrical contact with plasma; and an electric characteristic adjusting circuit between the plasma generation electrode and ground. 2. The electric characteristic adjusting circuit according to claim 1, wherein the electric characteristic adjusting circuit increases a discharge time constant of an electrode on which the object to be processed is mounted, and a transistor is provided between the electrode and the ground. Plasma processing equipment. 3. The method according to claim 2, wherein, at the end of the processing, the electric charge accumulated on the electrode on which the object is placed is discharged by amplifying a current flowing between the electrode and the sensing electrode by the transistor. The plasma processing apparatus as described in the above.