JPH0217636A - Dry etching device - Google Patents

Abstract

PURPOSE:To make it possible to perform high density etching mainly by ions and uniform etching for a large bore wafer by providing a cavity resonator which emits microwaves and a magnet for generating a magnetic field. CONSTITUTION:A microwave generated in the outside enters to a cavity resonator 14 from a wave guide 1 and amplified, and introduced to a plasma generation room 4 through a slit 15 and a microwave permeable window 3. The window 3, the room 4 and a specimen room 8 constitute a vacuum container. It is discharged through a discharge slot 9 and an etching gas is introduced from a gas introduction tube 6, and kept at a predetermined pressure. At this time, the etching gas is converted to a plasma by microwaves and the wafer 7 is etched. Since a magnetic field for confining plasma caused by a mirror magnetic field generation coil 2 provided in the periphery and a permanent magnet for generating a multi-pole cusp magnetic field exists only in the vicinity of the side wall in the room 4, a good uniformity of the density distribution of plasma in the radial direction is obtained, microwaves from the slit 15 are efficiently absorbed in a plasma generation region 16 because of its directivity, and plasma having sufficient density can be obtained at a low pressure.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a dry etching apparatus, and particularly to a dry etching apparatus suitable for etching large diameter wafers uniformly and with high precision.

[Conventional technology]

In the dry etching process of semiconductor manufacturing, anisotropic etching is performed in which ions of an etching gas are perpendicularly incident on the wafer in order to improve the processing accuracy. However, as the density of products increases, the pattern width also becomes narrower, making further improvement of anisotropy an important issue.

It is currently believed that the etching process proceeds through the combined action of ions and neutral radicals generated in plasma. Of these, ions are caused to be incident perpendicularly to the wafer by applying an electric field. However, neutral radicals enter the wafer from completely random directions. Therefore, in order to improve the etching precision, it is possible to reduce the contribution of neutral radicals.

Since the number of neutral radicals is considered to be proportional to gas pressure, it is effective to lower the processing pressure.

Therefore, microwave etching devices that can maintain stable plasma even at low pressures have been proposed, and some have been commercialized.

The conventional microwave etching device was developed in Japanese Patent Application Laid-Open No. 57-16
As in the microwave etching apparatus described in Japanese Patent No. 4985, microwaves guided by a waveguide enter a plasma generation chamber, where electrons are excited and collide with gas molecules to ionize them. At this time, a magnetic field is applied to excite electrons more efficiently. That is, by matching the frequency of the cyclic motion of electrons due to a magnetic field to the frequency of microwaves, a resonance phenomenon, that is, an electron cyclotron (IHactron Cylotion Re5), is generated.
onaae (hereinafter referred to as 1fcRJ) and utilize this.

In the conventional microwave etching, a coil is used to create an a-field that satisfies the ICR conditions, and in order to process large-diameter wafers, a large-sized coil is required. Further, if a uniform magnetic field is generated by the coil in the ICR generation chamber, radial diffusion of plasma is suppressed, and the effect of relaxing the radial density distribution is weakened. Therefore, the density becomes non-uniform in the radial direction.

[Problem to be solved by the invention]

In the prior art, K is used to generate plasma at low pressure.
11 ICR is used, and a coil for this is required. In this case, a coil with large dust is required to process a large diameter wafer, and since there is a uniform magnetic field inside the IICR generation chamber, the uniformity of the plasma in the radial direction is poor, making it impossible to perform uniform etching processing. was there.

SUMMARY OF THE INVENTION An object of the present invention is to solve the problems of the prior art and to provide a dry etching apparatus that can generate plasma of sufficient density at low pressure, maintain the plasma uniformly, and use it for etching processing. .

[Means to solve the problem]

The purpose is to provide a cavity resonator that increases the electric field strength of microwaves and radiates microwaves to a plasma generation chamber in a sample chamber through a slit and a microwave transmission window; ,
This is achieved by installing a magnet that generates a magnetic field that confines the plasma only near the wall surface of the plasma generation chamber.

[Effect]

In plasma, electrons excited by microwaves constantly ionize gas molecules and simultaneously create new electrons. On the other hand, ions and electrons diffuse toward the wall of the plasma generation chamber and disappear there. That is, in plasma, ions and electrons are generated and annihilated at the wall surface simultaneously. Therefore, it is thought that the balance between generation and extinction maintains the plasma and determines the plasma density. In order to make the plasma more dense, it is necessary to increase the amount of production or reduce the amount of extinction. However, as the pressure is lowered, the collision frequency between gas molecules and electrons decreases, so the increase in the amount of production decreases. I can't wait. Therefore, in this case, it is effective to reduce the amount of extinction.

Even if the production amount is constant, the plasma density can be relatively increased by reducing the extinction amount.

By the way, in order to reduce the loss on the wall surface of the plasma generation chamber, it is necessary to prevent ions and electrons from going to the wall surface. For this purpose, it is possible to use a magnetic field. In other words, charged particles are difficult to diffuse in the direction perpendicular to magnetic lines of force, and when moving from a weak magnetic field to a strong magnetic field,
One possibility is to utilize the property of being reflected toward the weak magnetic field side.

On the other hand, in order to efficiently generate plasma within an area surrounded by a magnetic field, that is, to avoid generating plasma in unnecessary areas, it is necessary to skillfully control the plasma generation area (microwave absorption area). For this reason, K uses a cavity resonator to strengthen the electric field of the microwave and radiates it into the plasma through a slit provided in the cavity resonator.

In this case, the slit can be considered a type of antenna, and the directivity of the radiated microwave can be changed depending on the arrangement of the antenna, so the microwave absorption region can be controlled. Further, since the microwave emitted from the slit has a strong electric field strength, microwave absorption is good even if the ECR condition is not satisfied, and the magnetic field can be configured without being subject to this condition.

Therefore, it is possible to provide a strong magnetic field only near the wall surface of the plasma generation chamber, and as a result, the uniformity of plasma can be improved.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a longitudinal sectional view of a dry etching apparatus according to the present invention.

The dry etching apparatus of the embodiment shown in FIG. A plasma generation chamber 4, a coil 2 for generating a mirror magnetic field, which is installed around the plasma generation chamber 4, and a magnetic field which is also installed around the plasma generation chamber 4 and confines the plasma only in the vicinity of the wall surface of the plasma generation chamber 4. A permanent magnet 12 for generating a multipolar cusp magnetic field, which is a magnet.
A sample chamber 8 has a gas introduction pipe 6 for blowing etching gas into the plasma generation chamber 4, and a mounting table 17 for a wafer 7.
and an exhaust port 9 for evacuating the vacuum container including the sample chamber 8.

Then, the microwave emitted from the microwave oscillator (not shown) enters the cavity resonator 14 from the waveguide 1, is amplified here, and passes through the slit 15 and the microwave transmission window 3 to the plasma generation chamber 4. be introduced.

The microwave transmission window 3. The plasma generation chamber 4 and the sample chamber 8 form one vacuum container.

This is evacuated through the exhaust port 9 by a vacuum evacuation device (not shown), and at the same time, etching gas is introduced through the gas introduction pipe 6 and maintained at a predetermined pressure. At this time, the etching gas is turned into plasma by the microwave, and the wafer 7 is etched.

A coil 2 for generating a mirror magnetic field and a permanent magnet 12 for generating a multipolar cusp magnetic field are provided around the plasma generation chamber 4, and each generates a magnetic field as shown by lines of magnetic force 10.15. ing.

The microwave radiated from the slit 15 of the cavity resonator 14 is efficiently absorbed in the plasma generation region 16 due to its directivity.

The plasma generated in the plasma generation region 16 in the plasma generation chamber 4 is surrounded by the mirror magnetic field produced by the coil 2 on the top surface, and by the multipolar cusp magnetic field produced by the permanent magnet 12 on the side surface, so that the plasma generated in the plasma generation region 16 in the plasma generation chamber 4 is has no loss.

Furthermore, since the magnetic field that serves to confine the plasma exists near the wall surface of the plasma generation chamber 4, the uniformity of the radial density distribution of the plasma is improved.

As a result of the above, plasma with sufficient density can be obtained even at low pressure, making it possible to perform high-density etching using mainly ions.Also, since the uniformity of the plasma is improved, even large-diameter wafers can be etched uniformly. becomes.

〔Effect of the invention〕

According to the present invention described above, a cavity resonator is installed that increases the intensity of microwaves and radiates the microwaves to the plasma generation chamber in the sample chamber through the slit and the microwave transmission window, so it is sufficient even at low pressure. Since plasma of a high density can be obtained, it is possible to perform etching mainly using ions, which has the effect of increasing the density of etching.

Further, according to the present invention, a magnet is provided that generates a magnetic field that confines the plasma generated in the plasma generation area in the plasma generation chamber only near the wall surface 49 of the plasma generation chamber. Since it exists only near the wall of the chamber, the density distribution of the plasma becomes uniform, which has the effect of improving the uniformity of etching.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view showing one embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Waveguide, 2... Coil, 3... Microwave transmission window, 4... Plasma generation chamber, 5... Permanent magnet,
6... Gas introduction pipe, 7... Wafer, 8... Sample chamber, 9... Exhaust port, 10... Mirror magnetic field, 11...
Multipolar cusp magnetic field, 12... Permanent magnet that generates a magnetic field that confines plasma only near the wall of the plasma generation chamber, 1... Multipolar cusp magnetic field, 14... Cavity resonator, 1
5...Slit, 6...Plasma generation area. No. 1 P Ki + 4-'4'l' Sakaji rs-・Slif F Nob・Braz VP5 Pregnancy〉Q clan area

Claims (1)

[Claims] 1. A means for introducing microwaves, and a sample chamber for etching the substrate with plasma generated by the microwaves;
In a dry etching apparatus equipped with an evacuation device that evacuates the sample chamber and a gas introduction means that introduces an etching gas into the sample chamber, the electric field strength of the microwave is increased and the sample chamber is evacuated through a slit and a microwave transmission window. A cavity resonator that radiates microwaves into a plasma generation chamber, and a magnet that generates a magnetic field that confines plasma generated in a plasma generation region within the plasma generation chamber only in the vicinity of the wall surface of the plasma generation chamber. Characteristic dry etching equipment.