JPH01123421A - Plasma etching apparatus - Google Patents

Abstract

PURPOSE:To perform high speed etching characterized by less damages to a pattern on a wafer, by attaching a diamagnetic material to a wafer stage, and enhancing a magnetic field required for ECR discharge by the magnetic shield effect of the diamagnetic material. CONSTITUTION:A diamagnetic material 13 comprising a ceramic based or oxide based high temperature superconductor and the like is attached in a wafer stage 5. A magnetic field coil 14 generates a magnetic field for ECR discharge. At the same time, generated magnetic lines of force are going to pass through the wafer stage 5. The magnetic lines of force M are extremely diverged on the wafer stage 5 by the diamagnetic action of the diamagnetic material 3, which is provided in the wafer stage 5. Plasma is drifted by the magnetic field formed by the magnetic lines of force M and an electric field E, which is generated by conventional high frequency discharge. The plasma acts on a wafer 5 effectively. Thus, high speed etching characterized by less damages of the pattern on the wafer 5 can be performed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) The present invention relates to a plasma etching apparatus suitable for high-speed etching of semiconductors and the like.

(Conventional technology) A conventional plasma etching apparatus is shown in FIG.

A vacuum container 1, a valve 2 for vacuum evacuation or sealing, and a valve 3 for introducing etching gas constitute a vacuum pump, etc., and a wafer that also serves as an electrode 4 for high-frequency discharge in the vacuum container 1 and an electrode on the opposite side. It is composed of a table 5, a high frequency power source 6 that generates discharge between the electrode 4 and the wafer table 5, and generates a negative voltage on the wafer table 5, and a capacitor 7. On the other hand, the wafer 8 to be etched is mounted on the wafer stand 5. In order to improve ionization in plasma discharge, a permanent magnet or the like is installed below the wafer table 5, and the configuration is such that a magnetic flux M that crosses the wafer table 5 is formed.

When etching a semiconductor wafer, in the apparatus shown in FIG. 4, an appropriate etching gas is usually introduced into the vacuum chamber 1, and appropriate power is supplied from the high frequency power source 6 to the electrode 4.
A discharge is generated between the wafer table 5 and the wafer table 5 to form plasma.

In this case, the number of ions on the wafer 8 and the energy of the ions contribute to the etching rate.

(Problem to be Solved by the Invention) A magnetic field B is generated above the wafer 8 by the permanent magnet 9 and the capacitor 7 that generates a negative bias voltage on the wafer stage 5 in order to control the number of ions and ion energy. An electric field E is generated which causes electrons and ions in the plasma to drift, forming a very bright plasma on the wafer.

In other words, the etching effect becomes greater. Furthermore, if the pressure of the gas sealed in is low, it becomes difficult to generate plasma, and the apparatus becomes complicated, such as having to use other means in combination to generate plasma.

Note that in conventional parallel plate type devices, permanent magnets are attached, but the structure is complicated to generate an appropriate magnetic field.

Further, the shape of the etching is greatly influenced by the gas pressure of the plasma, and the lower the gas pressure, the higher the anisotropy and the better the shape. The magnetic field B on the wafer is very effective for speeding up etching.

On the other hand, in devices that use electron cyclotron discharge using microwave power, electromagnets may be used instead of permanent magnets, but this requires an excitation power source, etc., resulting in a complex configuration, and it is necessary to improve the uniformity of etching. Become.

An object of the present invention is to achieve high-speed etching by means of generating plasma at a wide range of gas pressures and at the same time generating a high magnetic field on the wafer.

[Structure of the invention]

(Means for Solving the Problems) In the present invention, a diamagnetic material such as a superconducting conductor is installed in or near the wafer table.

(Function) With the above configuration, the magnetic field generated by the external magnetic field coil is bent by the wafer stand, and a magnetic field is formed in a direction parallel to the wafer stand. Magnetron discharge is generated by the enhancement of this magnetic field and the electric field due to the bias voltage applied to the wafer stage, resulting in an increase in ionized dust in the reaction gas, and the number and energy of ions required for etching are obtained, making high-speed etching possible.

(Example) FIG. 1 shows an example of the plasma etching apparatus of the present invention.

Microwave waveguide 11 to increase plasma density
is attached to the vacuum vessel 1 via the dielectric 12.

A diamagnetic material 13 such as a ceramic-based or oxide-based high-temperature superconductor is mounted inside the wafer table 5 . 'mm Cocoil 14
It is installed outside the vacuum chamber 1 in a direction opposite to the wafer table 15. A cooling water pipe is provided for cooling the wafer table 5, and a cooling water valve 15 is attached to the tip of the pipe.

The effects of etching are as follows.

By opening the valve 2, the vacuum container 1 is drawn to a sufficiently high vacuum by an exhaust system (not shown).

Thereafter, etching gas is introduced through valve 3 to an appropriate gas pressure. In order to form plasma, a high frequency electric field E is applied by a high frequency power source 6 to the space between the wafer table 5 and the vacuum container 1 as in the conventional case, but in order to obtain a higher density plasma, a magnetic field coil 14 and a microwave waveguide 11 are applied. and dielectric 1
2, an electrocyclotron discharge (
ECR).

The magnetic field coil 14 generates a magnetic field for ECR discharge, and at the same time the generated magnetic lines of force try to pass through the wafer table 5. Due to the diamagnetic effect of the diamagnetic material 13 installed in the wafer table 5, the lines of magnetic force M are extremely diverged on the wafer table 5. In other words, the magnetic field lines are distributed almost parallel to the wafer 8. The plasma is drifted by the magnetic field formed by the lines of magnetic force M and the electric field E generated by conventional high-frequency discharge, and effectively acts on the wafer 5. .

FIG. 2 is a diagram illustrating the plasma generation situation due to the magnetic field B and the electric field E. When the magnetic lines of force M try to pass through the wafer stand 5, eddy currents i flow through the diamagnetic material 13 in the wafer stand 5 so as to cancel the magnetic flux, and as a result, they cannot pass through the wafer stand 5. Therefore, a magnetic field B is generated in a direction parallel to the wafer 8, and the plasma 16 drifts between it and the electric field E of the wafer table, and a magnetron discharges on the wafer table, causing the plasma 16 to drift.
The ionization of 6 increases.

That is, the highly ionized plasma generated by the ECR discharge is transported toward the wafer table based on the magnetic lines of force, and due to the emphasis with the magnetron discharge, a denser plasma is generated on the wafer. As a result of the generation of dense plasma, the number of ions or excited gas molecules contributing to etching increases, making high-speed etching possible.

(Other Embodiments) FIG. 3 shows a magnetic field coil 14 with a plurality of drive devices 17 attached thereto. This causes the coil support point to move up and down in waves at certain time intervals. above the support point.

By optimizing the lower drive, the shaft can be adjusted to any angle, including front and rear, left and right. By doing so, the plasma on the wafer can be moved over a wide range to make etching uniform.

〔Effect of the invention〕

Since the plasma etching apparatus of the present invention has a diamagnetic material attached to the wafer table, the magnetic field required for ECR discharge can be increased by the magnetic shielding effect of the diamagnetic material, and the E
High-density plasma is generated on the wafer by CR discharge and magnetron discharge, making it possible to perform high-speed etching with little damage to patterns on the wafer.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a plasma etching apparatus according to an embodiment of the present invention, FIG. 2 is a diagram explaining the operation of the above embodiment, FIG. 3 is a diagram showing another embodiment of the present invention, and FIG. 1 is a diagram of a conventional device; FIG. 1... Vacuum container 5... Wafer stand 6...
High frequency power supply 11...Microwave waveguide 12.
...Plasma 13...Diamagnetic material 14...
Magnetic field coil agent Patent attorney Nori Ken Yudo Chika Ken Daishimaru Figure 1, 18, Figure 2, Figure 4

Claims (2)

[Claims] (1) A device for introducing and exhausting etching gas into a vacuum container, a device for forming plasma in the container by introducing a magnetic field generating coil and microwaves, a wafer stand for fixing a wafer in the container, and a wafer stand. A plasma etching apparatus characterized in that a diamagnetic material such as a ceramic-based or oxide-based superconductor is installed inside or near the plasma etching apparatus. (2) The plasma etching apparatus according to claim 1, further comprising a coil support device for rotating or moving the magnetic field generating coil.