JPH07263411A - Plasma etching device - Google Patents

Abstract

PURPOSE:To improve the evenness in the etching characteristics in a wafer surface by equalizing the densities of produced plasma even in the plasma etching step mainly using the ion reaction phenomenon. CONSTITUTION:Within the title etching device having opposite upper electrode 1 and lower electrode 12 in a reaction chamber 3, the lower electrode 12 is impressed with high frequency electric field while a reaction gas is fed to the reaction chamber 3 so as to etch away the specific position of an etched material film arranged on the lower electrode 12 by the plasma produced in the space between the upper electrode 1 and the lower electrode 12, the lower electrode 12 is divided into a plurality of independent concentric circles.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma etching apparatus, and more particularly to a plasma etching apparatus used for forming a fine pattern in manufacturing a semiconductor device.

[0002]

2. Description of the Related Art The dry etching method is a so-called highly anisotropic etching method capable of selectively etching only a predetermined region. This dry etching method is used for semiconductor devices such as U
This is one of the important processes in the LSI manufacturing process. There are several types of this dry etching method, and reactive ion etching (RIE) is predominant at present.

FIG. 4 is a block diagram showing a conventional plasma etching apparatus. As shown in FIG. 4, in the conventional plasma etching apparatus, an anode electrode 1 as an upper electrode and a cathode electrode 2 as a lower electrode are arranged facing each other in a chamber 3 as a reaction chamber.
Is grounded, and the reaction gas inlet 4 is provided above,
The reaction gas is supplied into the chamber 3 through a large number of openings (not shown) of the anode electrode 1 like a shower.

On the other hand, a high frequency (RF) is applied to the cathode electrode 2.
A high frequency electric field is applied by the power 6. The cathode lower power electrode 2 has a structure in which a disk portion 2a and a cylindrical portion 2b are integrated as shown in a perspective view of FIG. 5, and an etching target material film is formed on the surface of the disk 2a as shown in FIG. A substrate such as the Si wafer 7 to be arranged is arranged.

In the plasma etching apparatus having such a structure, when a high frequency electric field is applied to the cathode electrode 2 of the lower electrode and a reaction gas having an appropriate concentration is supplied into the chamber 3, the cathode electrode 2 and the anode electrode of the upper electrode are provided. Plasma is generated between 1 and 1. Ions in the plasma are vertically incident on the Si wafer 7 on the lower power electrode 2 by the high frequency electric field, and the above-described anisotropic etching proceeds.

[0006]

If the density of the plasma generated between the counter electrodes 1 and 2 is entirely uniform, the dose of ions on the entire surface of the Si wafer 7 will be substantially uniform. , The etching characteristics within the surface of the Si wafer 7 should be uniform. However, in reality, the density of the plasma becomes lower toward the end of the electrode. Therefore, there is a difference in the etching rate between the center part and the edge part of the Si wafer 7, and good etching can be performed. In turn, this led to a decrease in yield.

As a method for eliminating the non-uniform ion irradiation dose due to the difference in plasma density, there is known a method in which the temperature control of the lower electrode is changed concentrically. With this method, it is possible to improve the uniformity of the etching rate in an etching process mainly involving a radical reaction using CF ₄ or the like as a reaction gas. However, the etching rate uniformity was hardly improved in the etching mainly involving the ion reaction, which has a small temperature dependence of the etching rate.

In consideration of the above problems, the present invention is a plasma which can improve the non-uniformity of etching characteristics in a wafer surface by making the generated plasma density uniform even in the plasma etching mainly based on ion reaction. An object is to provide an etching device.

[0009]

In order to solve the above problems, a plasma etching apparatus according to claim 1 of the present invention has an upper electrode and a lower electrode facing each other in a reaction chamber, and a high frequency electric field is applied to the lower electrode. A plasma etching apparatus for supplying a reaction gas into the reaction chamber and etching a predetermined portion of the material film to be etched arranged on the lower electrode by plasma generated between the upper electrode and the lower electrode. In the above, the lower electrode is divided into a plurality of concentric circles, each of which is independent.

A plasma etching apparatus according to a second aspect of the present invention is characterized in that, in the second aspect, the lower electrode is composed of two sections, a fixed outer electrode and a movable inner electrode.

A plasma etching apparatus according to a third aspect of the present invention is the plasma etching apparatus according to the first aspect, characterized in that a gap for introducing a cooling gas is provided between the fixed outer electrode and the movable inner electrode. To do.

[0012]

According to the present invention according to claims 1 and 2, since the lower electrode 12 is divided into the inner electrode 12a and the outer electrode 12b as shown in FIGS. 1 and 2, and the inner electrode 12a is movable, At the center of the Si wafer 7, the inner electrode 1
By separating 2a, the difference in plasma density on the Si wafer 7 can be improved. Therefore, the dose of ions contributing to plasma etching can be made more uniform.

According to the third aspect of the present invention, since the gap for introducing the cooling gas is provided between the inner electrode 12a and the outer electrode 12b, the helium (H
A cooling gas such as e) can be introduced and the inner electrode 12a is separated from the Si wafer 7 or the like having the material film to be etched, whereby the temperature difference generated in the plane of the wafer 7 is improved.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of the plasma etching apparatus according to the present invention. As shown in FIG. 1, the plasma etching apparatus of this embodiment separates the cathode electrode 2 of the conventional plasma etching apparatus shown in FIG. 4 into a cylindrical inner electrode 12a and a donut-shaped outer electrode 12b as the cathode electrode 12. The structure is the same as that of the conventional device shown in FIG. Therefore, in FIG. 1, the detailed description of the configuration other than the cathode electrode 12 as the lower electrode is the same as that described above, and will be omitted.

The cathode electrode 12 (lower power electrode portion) of the plasma etching apparatus of this embodiment has a cylindrical inner electrode 12a and a donut as shown in a perspective view in FIG. 2 and an enlarged top sectional view in FIG. The outer electrode 12b has a concentric circular combination structure. A gap 13 is provided between the inner electrode 12a and the outer electrode 12b to serve as an inlet for cooling gas, such as He. Outer electrode 12b
Is fixed because it functions as a support, the inner electrode 12a is movable, and it is movable up and down on the lower side from the state where it functions as a support for the Si wafer 7.

As described above, in the plasma etching apparatus in which the lower power electrode portion is independently configured for the inner electrode 12a and the outer electrode 12b, even if the inner electrode 12a and the outer electrode 12b are set to the same potential, S the electrode 12a
By moving in a direction away from the i-wafer 7,
A potential difference can be generated between the central portion and the edge portion of the Si wafer 7 arranged on those electrodes.

The operation method of the device of this embodiment is as follows.
Etching is performed with the position of 2a set at several positions in advance, the inspection of the optimum state of the etching gas plasma is performed, and the internal electrode 12a and the external electrode 12b are fixed at the positions that meet the inspection conditions. Etching is done in the process. That is, the Si wafer 7 having the material film to be etched arranged on the outer electrode 12b arranged in the chamber (reaction chamber) 3 is fixed by the clamp ring 8.
The inner electrode 12a is lowered and fixed at the optimum position that meets the above-described inspection conditions.

In such a state, the reaction gas is introduced from the introduction port 4, and a predetermined potential is applied between the upper and lower electrodes by the RF power 6 to turn the gas into plasma and a predetermined portion of the material film to be etched on the Si wafer 7. To etch.

In this embodiment, the inner electrode 12a is replaced by the outer electrode 1
Since it is arranged at a position lower than 2b, a potential difference can be generated between the central portion and the edge portion of the Si wafer 7. This makes it possible to change the amount of ion irradiation within the wafer surface and make the etching characteristics within the wafer surface uniform within the surface. For example, the uniformity of the W plug in the wafer surface after etching back tungsten (W) is improved from about ± 3% to about ± 1%.

Regarding the temperature difference generated in the plane of the wafer 7 by separating the inner electrode 12a and the Si wafer 7, the cooling helium (He) is passed from the rear of the lower power electrode through the gap 13 between the inner electrode 12a and the outer electrode 12b.
This can be solved by supplying the gas into the chamber 3 to clean the entire surface of the Si wafer 7 and adjusting the temperature.

The plasma etching apparatus of the present invention is also effective when flattening a multi-layer wiring structure having irregularities, when a polyimide layer is formed on the multi-layer wiring, and the upper surface of the layer is etched and flattened, that is, so-called etch back is performed. Used for.

[0022]

As described above, according to the present invention, it is possible to eliminate the non-uniformity of the ion irradiation dose due to the difference in plasma density by causing a potential difference in the wafer on the lower electrode on which the wafer is placed. As a result, it is possible to eliminate the non-uniformity of etching characteristics within the wafer surface.

Furthermore, according to the present invention, the film thickness at the central portion and the edge portion of the wafer, which occurs during the film formation, particularly the film formation of the coating type organic material such as applying a polyamide solution and imidizing by heating. Can be corrected by etching and flattened.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a plasma etching apparatus according to the present invention.

FIG. 2 is a perspective view of a lower power electrode unit according to the present invention.

FIG. 3 is a diagram showing a state in which an inner electrode of a lower power electrode unit according to the present invention is lowered.

FIG. 4 is a configuration diagram of a conventional plasma etching apparatus.

FIG. 5 is a perspective view of a lower power electrode portion of a conventional plasma etching apparatus.

[Explanation of symbols]

 1 Anode Electrode (Upper Electrode) 2,12 Cathode Electrode (Lower Power Electrode) 2a Disk Part 2b Cylindrical Part 3 Chamber 4 Reactive Gas Inlet 5 Gas Exhaust 6 RF Power 7 Si Wafer 8 Clamp Spring 12a Inner Electrode 12b Outer Electrode

Claims (3)

[Claims] 1. An upper electrode and a lower electrode facing each other are provided in a reaction chamber, a high-frequency electric field is applied to the lower electrode, a reaction gas is supplied into the reaction chamber, and generated between the upper electrode and the lower electrode. In a plasma etching apparatus configured to etch a predetermined portion of a material film to be etched arranged on the lower electrode by plasma, the lower electrode is divided into a plurality of concentric circles, each of which is independent. Plasma etching equipment. 2. The plasma etching apparatus according to claim 1, wherein the lower electrode is composed of two sections, a fixed outer electrode and a movable inner electrode. 3. The plasma etching apparatus according to claim 1, wherein a gap for introducing a cooling gas is provided between the fixed outer electrode and the movable inner electrode.