JPH07207471A - Plasma etching device - Google Patents

Abstract

PURPOSE:To increase the plasma density and especially to improve the processing rate under low pressure by providing the device with a member which is in electrically negative potential to the surface of a material to be treated and with a means to give strong repulsive force to electrons in plasma. CONSTITUTION:The reaction chamber 1 is directly grounded. The cathode 3 where a wafer 12 is mounted is connected to a power supply 6 to generate plasma. The cathode 3 is supported with an insulating supporting member 11 and attached to the reaction chamber 1. An insulator 2 is disposed to face the cathode 3 and attached to seal the upper aperture of the chamber 1. The insulator 2 is insulated from the ground in a DC circuit, and the back side of the body is provided with a magnet element 9 to apply a magnetic field on the discharge space. By this constitution, strong plasma is produced in the discharge space by the magnetic field effect, and simultaneously, an ion sheath is produced by a large self bias voltage between the plasma and the cathode 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sputter etching apparatus, and more particularly to a sputter etching apparatus suitable for processing under a low pressure.

[0002]

2. Description of the Related Art A conventional device is disclosed in Japanese Patent Application Laid-Open No. 57-15538.
As described in No. 4, a parallel plate type high frequency sputter etching apparatus in which a high frequency electrode and a counter electrode are arranged in parallel with each other in a vacuum chamber, and a gas introduced from a gas introduction hole is ionized to sputter-etch a sample surface. In some cases, an introduction positive electrode having a positive potential with respect to the ground potential and having a gas introduction hole is provided.

[0003]

The above-mentioned prior art does not take into consideration the case where plasma is generated under a low pressure by utilizing the action of a magnetic field, and during the discharge generated between the high frequency electrode and the counter electrode. However, there is a problem that the electrons of the above flow quickly to the introduction positive electrode, the action of the magnetic field does not contribute much to the electrons during the discharge, and strong plasma cannot be generated.

An object of the present invention is to provide a sputter etching apparatus which makes full use of the action of a magnetic field to increase the plasma density and has a high processing speed.

[0005]

The above object can be achieved by providing a means for imparting a repulsive force to the electrons in the plasma generated above the sample by utilizing the action of the electromagnetic field.

[0006]

By preventing the electrons in the plasma space from flowing to the side opposite to the sample, and by repelling the electrons in the plasma space and retaining them, the action of the magnetic field can be sufficiently contributed to the electrons and the plasma density can be improved. Can be higher. Thereby, the processing speed of the plasma processing can be increased.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 shows a magnetic field combined sputter etching apparatus which is a plasma etching apparatus. The processing container 1 has a gas introduction port 7 and an exhaust port 8, and in this case,
A steady low-pressure atmosphere is maintained by introducing argon gas and evacuating it at the same time.

The reaction vessel 1 is directly connected to the ground. The cathode electrode 3 on which the wafer 12 is placed is connected to a high frequency power source 6 for plasma generation via a coupling capacitor 4 and a matching box 5. The cathode electrode 3 is made up of a support material 11 made of an insulating material, and the reaction container 1
Is attached to. An insulator 2 is provided on the opposite surface of the cathode electrode 3, and is attached so as to seal the upper opening of the processing container 1. The insulator 2 is galvanically isolated from the ground. On the back surface (upper side of the drawing) of the insulator 2, a magnet element 9 for introducing a magnetic field into the discharge space, that is, the upper space of the wafer 12, and a motor 10 for rotating the magnet element 9.
Is installed.

When a high-frequency voltage is applied to the cathode 3 by the high-frequency power source 6 by the apparatus thus constructed, discharge is started between the cathode 3 and the processing container 1, and the discharge spreads on the upper part of the wafer 12 so that the wafer 12 is exposed. A strong plasma is formed in the upper space by the action of the magnetic field generated by the magnet element 9. Since the processing container 1 is connected to the ground, the generated plasma is maintained at substantially the ground potential. On the other hand, the cathode electrode 3 has a DC negative potential due to the coupling capacitor 4, and an ion sheath is formed between the cathode electrode 3 and the plasma to generate a large potential difference (self-bias voltage). The insulator 2 is charged up by high-speed electrons from the plasma, that is, electrons that fly out in a direction perpendicular to the surface of the cathode electrode 3 and are added through the ion sheath,
It has a negative potential with respect to plasma, prevents electrons in the plasma from repelling and flowing into the insulator 2 side, floating many electrons in the plasma, and keeping the plasma at a high density by the action of the magnetic field. .

For example, if the silicon oxide film is sputter-etched at a high-frequency power of 400 W and an argon pressure of 5 mTorr (0.7 Pa), the etching rate is 1 in this case.
The self bias voltage was 00 nm / min and -300V. However, when the insulator 2 is used as an anode electrode and is connected to the ground as a conductor as in the conventional case, the potential difference between the anode electrode and the plasma is reduced to about 1/10, and electrons flow from the plasma to the anode electrode to cause the plasma. Since the density of electrons in the inside decreases, in this case, if the sputter etching is performed under the same conditions as above, the etching rate becomes 40 nm / min, and the processing rate decreases. In addition,
The self-bias voltage at this time was -600V.

When a conductor such as aluminum is sputter-etched, the aluminum of the wafer 12 is sputtered and a disk-shaped aluminum film similar to the shape of the wafer 12 is formed on the surface of the insulator 2. Are electrically kept in a floating state, electrons are charged in the end portion of the disk-shaped aluminum film, the plasma density in the space in the upper central portion of the wafer 12 is reduced, and the etching density distribution for the wafer 12 is reduced. Occurs in the peripheral area. In this case, the groove 2 having an overhang on the surface of the insulator 2 as shown in FIGS.
By forming 3 and making it discontinuous even if aluminum adheres, and by keeping the electron charge in each part, high density plasma can be held.

The insulating plate 2 in this case is a flat plate 21 of alumina.
And a plurality of convex rings 22 made of alumina, the convex ring 22 is fixed by being pushed into the groove of the flat plate 21 with the convex side facing the flat plate 21 side. Such groove processing of the convex ring 22 and the flat plate 21 can be easily performed if it is performed between alumina materials, and it can be fixed by inserting the convex ring 22 into the groove provided in the flat plate 21 and then sintering. If adhesive strength is required, an alumina-based adhesive may be used. There is no problem in heat resistance to plasma, and heating at about 500 ° C. is possible.

Further, in this case, the flat plate 21 is provided with the groove, but the convex ring 22 may be adhered and fixed without the groove.

According to this, when aluminum was sputter-etched under the same conditions as the previous conditions when the silicon oxide film was sputter-etched, both the sputter rate and the self-bias voltage were the same as those for the silicon oxide film.

Further, in this case, the insulating plate 2 is formed by the alumina flat plate 21 and the convex ring 22, but the same effect can be obtained even if it is constructed as shown in FIG.

The insulating plate 2 according to FIG. 4 comprises a quartz plate 24 and a resist (mask material) 25.
The quartz plate 24 is isotropically wet-etched on the back side of the pattern groove 26 so as to engrave the bottom portion of the mask material 25. As a result, a shadow portion where the sputtered metal particles do not adhere is formed in the etch groove 27.

In the present embodiment, the insulating plate 2 is entirely made of an insulating material, but a grounded conductor may be contained inside. At this time, at least the conductor on the surface in contact with the discharge space must be completely coated with an insulator.

Further, although the sidewall of the processing container 1 installed around the cathode electrode 3 is present in this embodiment, a ground electrode installed separately may be installed around the cathode electrode.

Next, another embodiment of the present invention will be described with reference to FIGS. 5, the same symbols as in FIG. 1 indicate the same members. This drawing is different from FIG. 1 in that instead of the insulator 2, a support material 13 made of an insulating material is used to form an anode electrode 14
Is attached to the processing container 1, and a DC power supply 15 for applying a negative potential to the anode electrode 14 is connected.

In this case, a wafer 12 having a silicon oxide film coated with aluminum is used. In this case, when a high frequency voltage is applied to the cathode electrode 3 by the high frequency power source 6, Electric discharge is started between the processing container 1 and the upper surface of the wafer 12, and the plasma is formed in the upper space of the wafer 12 by the action of the magnetic field generated by the magnet element 9. The generated plasma is maintained at substantially the ground potential because the processing container 1 is connected to the ground. On the other hand, the cathode electrode 3
Becomes a DC negative potential due to the coupling capacitor 4 and generates a large potential difference (self-bias voltage) with the plasma to form an ion sheath.

On the other hand, the anode electrode 14 is kept at a negative potential by the DC power supply 15 and repels high-speed electrons from the plasma, that is, electrons that fly out in a direction perpendicular to the surface of the cathode electrode 3 and pass through the ion sheath, and repel the anode electrode. 14
Since it is prevented from flowing into the side, the anode electrode 1 is compared with the conventional case in which the anode electrode 14 is connected to the ground.
A large ion sheath is formed on the 4th part. Electrons are held in the discharge space by these two sheaths, and a high-density plasma is formed under the action of a magnetic field.

FIG. 6 shows the dependence of the etching rate and the self-bias voltage on the DC voltage applied to the anode electrode when the aluminum film is etched at a high frequency power of 400 W and an argon pressure of 5 mTorr (0.7 Pa). is there. By increasing the absolute value of the DC applied voltage in the range of 100 V or less, the etching rate is increased by 2 to 3 times as compared with the conventional one in which the DC applied voltage is not applied. At this time, the self-bias voltage of the cathode electrode 3 is greatly reduced.

In this case, since the anode electrode 14 is formed of a conductor, it is not necessary to form a groove even when the aluminum film is sputter-etched as in the first embodiment.

As described above, according to this embodiment, the same effect as that of the above-mentioned one embodiment can be obtained. In particular, it is a good enemy when the material to be etched is a metal material.

[0025]

According to the present invention, since the plasma density can be increased by fully utilizing the action of the magnetic field, there is an effect that high speed processing can be performed.

[Brief description of drawings]

FIG. 1 is a vertical sectional view showing a plasma etching apparatus according to an embodiment of the present invention.

FIG. 2 is a plan view of the insulating plate viewed from AA in FIG.

3 is a sectional view of FIG. 2 viewed from B. FIG.

FIG. 4 is a cross-sectional view showing another example different from FIG.

FIG. 5 is a vertical sectional view showing a plasma etching apparatus according to another embodiment of the present invention.

6 is an explanatory diagram showing a relationship between an etching rate and a voltage when an experiment is performed using the apparatus of FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Processing container, 2 ... Insulator, 3 ... Cathode, 6 ... High frequency power supply, 9 ... Magnet element, 14 ... Anode electrode, 15 ... DC power supply.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Takeshi Oyamada 111 No. Nishiyote-cho, Takasaki-shi, Gunma Hitachi Ltd. Takasaki factory (72) Inventor Hikari Nishijima 111 No. Nishi-yokote-machi, Takasaki, Gunma Hitachi Ltd. Takasaki Factory

Claims (4)

[Claims] 1. A means for generating a plasma on an upper portion of a sample by utilizing an action of an electromagnetic field, and a means for providing a repulsive force to an electron in the plasma, the means being provided on an opposite surface of the sample. Characteristic plasma etching equipment. 2. A plasma etching apparatus for performing processing by generating plasma above a sample by utilizing the action of an electromagnetic field, wherein a member having an electrically negative potential is provided on the facing surface of the sample. And a plasma etching device. 3. A cathode electrode on which a sample is placed, an electrode surrounding the cathode electrode and electrically grounded, an insulator provided opposite to the cathode, and between the insulator and the cathode electrode. And a magnet element for applying a magnetic field to the plasma etching apparatus. 4. A cathode electrode on which a sample is placed, an electrode which surrounds the cathode electrode and is electrically grounded, a negative electrode facing the cathode, to which a negative potential is applied, and the negative electrode. A plasma etching apparatus comprising: a magnet element that applies a magnetic field between the cathode electrode and the cathode electrode.