JPH0457325A - Plasma treating equipment - Google Patents

Abstract

PURPOSE:To enable the plasma treatment without damaging an insulating film, by arranging an exposed part on the outer periphery so as to come into contact with plasma, in the state that a substrate to be treated is arranged on an electrode, and forming a bypass circuit for making a current flowing from the exposed part flow to the earth. CONSTITUTION:In the state that a substrate to be treated is arranged on an electrode 301 on which the substrate 306 to be treated is arranged, an exposed part 302 is so formed on the outer periphery that the electrode 301 comes into DC contact with plasma. Circuits 303-305 which are connected with the electrode 301 and bypass a current are equipped. The exposed part 302 on the outer periphery collects superfluous electron current in the outer peripheral part of plasma. The current bypass circuits 303-305 make the collected current flow to the earth side via the electrode 301, thereby preventing said current from flowing to the semiconductor substrate 306 side. Hence the deterioration of breakdown strength and the dielectric breakdown of a very thin insulating film can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to plasma processing M1, and particularly to a plasma processing apparatus that is optimal for processing a semiconductor substrate having a very thin insulating film.

[Conventional technology]

Conventional devices, for example, reduce the strength of the magnetic field to prevent breakdown voltage or dielectric breakdown due to plasma treatment of a gate oxide film, which is a very thin insulating film on a semiconductor substrate, as described in Japanese Patent Application Laid-Open No. 63-23750. This was prevented by doing things like this.

[Problem to be solved by the invention]

The above-mentioned conventional technology has problems such as a reduction in plasma processing speed.

An object of the present invention is to provide a plasma processing apparatus that can prevent breakdown voltage deterioration of a very thin insulating film on a semiconductor substrate without changing plasma processing conditions, which directly affects processing speed and the like.

[Means to solve the problem]

For the above purpose, an exposed portion is provided on the outer periphery so that the electrode contacts the plasma in a DC manner when the substrate to be processed is installed on the electrode, and an exposed portion is connected to the electrode. A circuit was provided to bypass the current.

[For production]

The exposed portion of the outer periphery collects excess electron current from the plasma periphery, and the current bypass circuit functions to flow this to the ground side via the electrode and prevent it from flowing to the semiconductor substrate side.

This makes it possible to prevent breakdown voltage deterioration and dielectric breakdown of the very thin insulating film in the semiconductor substrate.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG. 1st
The figure is a cross-sectional view of a plasma dry etching apparatus for processing semiconductor substrates using plasma, to which a magnetic field is applied for high-speed processing, and in which a voltage resistance deterioration prevention circuit for an insulating film according to the present invention is added. The reactor vessel 101 has a gas introduction hole 102 and an exhaust hole 103, and is maintained in a steady low-pressure atmosphere by exhausting the reactor gas while introducing it. A cathode electrode 105 on which a semiconductor substrate 104, which is an object to be processed, is placed is connected to a high frequency power source #110 via a coupling capacitor 108 and a mapping box 109.

The cathode electrode 1i105 is attached to the reaction vessel 101 by a supporting material made of an insulator 106.

When a high frequency electric field is introduced between the anode electrode 107 and the high frequency power source 110, plasma is generated due to discharge.
The semiconductor substrate 104 is etched. A magnetic field is generated by a magnet unit 111 and introduced into the reaction chamber.

The above is a description of the operation of a normal dry etching apparatus, and below, an explanation will be given of an embodiment of the effect of the present invention in reducing damage occurring to an insulating film.

Figure 2 shows the current-voltage characteristics of plasma and the operation in an Li setting without using the present invention. The characteristics are shown by curve 202. Such property differences usually arise due to the spatial distribution of plasma properties. At this time, the wafer is at a potential indicated by point 203, and a potential difference between points 2041 and 203 is applied to the insulating film on the semiconductor substrate located near the plasma having the characteristic of curve 202.

FIG. 3 shows details of the hardware for implementing the invention. Reference numeral 301 denotes a cathode electrode, which is also shown in FIG. 1, and has a portion 302 exposed to plasma around a semiconductor substrate 306. 302 is provided with a protrusion in order to facilitate the conduction of current from the plasma. 303.304.
305 is a component that constitutes a circuit for bypassing excess molecular current, and is composed of a coil 304, a variable resistor 303, and a capacitor 305. A coil 304 and a capacitor 305 are used to prevent high frequency current from flowing.

FIG. 4 shows the operating points on the current-voltage characteristics when the circuit shown in FIG. 1183 is operated. A straight line 401 indicates the value of the variable resistor after adjustment.

Due to the variable resistor, excess electron current from the plasma between points 402 and 403 is bypassed to the ground via the variable resistor, and the current that attempts to flow into the insulating film is at most between points 402 and 404. The maximum voltage is also point 4.
The size is only between 05-406.

An experimental example will be shown to demonstrate the effect of the present invention when a semiconductor substrate (wafer) having a gate oxide film, which is a type of very thin insulating film, is actually etched using the apparatus shown in FIG.

FIG. 5 shows the results of measuring the withstand voltage of the gate oxide film after the etching process, and the gate oxide film in the shaded area has dielectric breakdown. Without connecting a resistor (resistance value =
00), when there is no exposed part, dielectric breakdown occurs from the center to the periphery of the wafer, as shown in FIG. 5(a), and the breakdown rate reaches as high as 53 inches. This is thought to be because the potential difference shown in FIG. 2 exceeded the withstand voltage of the gate oxide film, and a current flowed, causing dielectric breakdown. Next, if the resistance value is set to 50 Ω using a variable resistor and there is no exposed part, the fifth
As shown in Figure (b), dielectric breakdown occurred in the peripheral area, but the breakdown rate was reduced to 15%. The reason why there was no destruction at the center was because the excess electron current was released to the ground, and the resulting potential difference became below the destruction threshold.

The reason why dielectric breakdown still occurs at the periphery is that excess electron current is flowing through the wafer to ground.

If the value of the variable resistance is set to 50Ω and a mist outlet is also provided, the fifth
As shown in Figure (C), the current flowing around the wafer now flows without passing through the wafer, and no dielectric breakdown occurs at all.

The effects described above can also be obtained with other plasma processing apparatuses. FIG. 6 shows a magnetic field microwave dry etching device, and in the same manner as shown in FIG. This generates plasma and etches the substrate 605 placed on the table 604. A high frequency bias is introduced into the table 604 by a high frequency power supply 606 for the purpose of controlling etching characteristics. In this equipment, the introduced microwave electric field strength and high frequency bias are non-uniform, resulting in a spatial distribution of plasma characteristics, and even if the etching rate is uniform, the current-voltage characteristics will vary as in the plasma dry etching equipment described above. Non-uniformity occurs. This may cause deterioration of the withstand voltage in the insulating film, and the deterioration of the withstand voltage can be prevented by the bypass circuit shown at 607 and the protrusion provided on the table shown at 608 based on the same principle. Note that the configuration of the bypass circuit is not limited to this embodiment, and a transistor or the like may be used instead of the variable resistor. In short, any circuit that can flow a constant current can be replaced.

〔Effect of the invention〕

According to the present invention, a semiconductor substrate or the like can be plasma-treated without damaging an insulating film, so that semiconductor devices can be efficiently produced.

[Brief explanation of drawings]

4! Figure 1 is a longitudinal cross-sectional view of a main part of a plasma dry etching apparatus according to an embodiment of the present invention, Figure 2 is an operational diagram in terms of current-voltage characteristics when the present invention is not used, and Figure 3 is a hardware configuration diagram for implementing the present invention! l! Figure 4 is an operational diagram of current-voltage characteristics when the present invention is implemented;
′! Figure IA5 is a schematic plan view of the results of pressure resistance measurement, and Figure 6 is a vertical cross-sectional view of a main part of a magnetic field microwave dry etching apparatus according to another embodiment of the present invention. 303...Variable resistor, 302, song, current collection M/ Figure 1 α- Immersive G device cathode "ril pole O Z diagram Diagram Bonde > Sir No. 5 Neko Ke: Tokimura surface familiar C Figure (α) (b) (C)

Claims (1)

[Scope of Claims] 1. In a plasma processing apparatus for processing semiconductor substrates, etc., the outer periphery of the electrode is set so that the electrode is placed in direct current contact with plasma when the substrate is placed on the electrode. What is claimed is: 1. A plasma processing apparatus characterized in that an exposed part is provided in the part of the plasma processing apparatus, and a bypass circuit is provided for causing current flowing from the part to flow to ground. 2. The plasma processing apparatus according to claim 1, wherein the bypass circuit comprises a high frequency blocking circuit and a variable resistor.