JPH0536496A - Plasma generating apparatus - Google Patents

Abstract

PURPOSE:To generate highly dense plasma even if the applied electricity is small. CONSTITUTION:A semiconductor wafer W is mounted on a holder 18 in a vacuum container 10, the vacuum container 10 is evacuated by an evacuation apparatus 14 and at the same time a reactive gas is led through a gas supplying inlet 12 to make the inside of the vacuum container 10 in a prescribed decreased pressure. Then, a prescribed a.c. voltage is applied between surfacial electrodes 22A, 22B installed in the upper and lower side of a porous plate 16 which has an electron--multiplying function and in which a large number of linear through holes are formed. In the through holes of the porous plate 16, plasma can be easily generated by the electron-multiplying function. As a result, the semiconductor wafer is etched highly precisely even by application of small amount of electricity.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma generator, and more particularly to a plasma generator capable of generating high density plasma with a small power supply.

[0002]

2. Description of the Related Art A dry etching method is one of the techniques for finely processing a semiconductor wafer. This method is mainly for microfabrication of a wafer by performing glow discharge in a reactive gas to generate plasma and treating the wafer with chemically active particles such as radicals and ions generated therein. Is to do.

In the above dry etching method, there is also a method of physically etching by accelerating and irradiating ions (charge particles) among active particles to a substrate (wafer).

As a technique for generating active particles as described above and etching a wafer, for example, JP-A-59-59
The reactive ion beam etching apparatus shown in 225525 is known.

In a conventional etching apparatus, a reactive gas is used to generate active particles such as ions and radicals.
A method of making plasma by microwaves or a high frequency of 13.56 MHz, for example, is adopted.

[0006] Usually, when active particles are generated, a magnet arranged around the plasma chamber prevents electrons and ions from reaching the inner wall of the plasma chamber, thereby deteriorating the reaction gas and impure gas and particles. It is also attempted to prevent the generation and increase the plasma density.

There is also a method of arranging a magnet for generating a magnetic field in which electrons perform cyclotron motion and generating active particles by so-called ECR plasma.

[0008]

However, in the conventional plasma generation method, in order to increase the density of the active particles, the electric power to be applied to the plasma has to be increased, and the plasma is stably generated with the electric power. There was a limit. Further, when high power is applied in this way, a high electric field is applied between the wafer and plasma, and charged particles are accelerated, so that the effect of physical sputtering is increased, the etching surface is roughened, and fine processing is performed. There was an inconvenience that it could not be done. Furthermore, ECR plasma requires a large magnet to obtain a uniform magnetic field, and therefore
There is a problem that the device becomes bulky and expensive.

The present invention has been made in order to solve the above-mentioned conventional problems, and it is possible to easily generate a high-density plasma even with a small input power, for example, plasma processing such as etching for a semiconductor wafer or the like. It is an object of the present invention to provide a plasma generator capable of performing microfabrication, which is suitable for application when performing with high precision.

[0010]

According to the present invention, there is provided a plasma generator, wherein the plasma generator is provided with a porous plate having a large number of linear through holes having an electron multiplying function. It has been achieved.

The present invention further achieves the above object more reliably by providing a mechanism for controlling the kinetic energy and direction of ions obtained from the plasma generated in the linear through hole. .

The present invention further achieves the above object more reliably by providing a mechanism for neutralizing ions obtained from the plasma generated in the linear through hole.

[0013]

In the present invention, since a perforated plate having a large number of linear through holes having an electron multiplying function is used as the plasma generating means, it is attached to both sides of the perforated plate.
By applying a predetermined voltage between the two surface electrodes,
An electron multiplication effect can be exhibited in the through hole. Therefore, when the electron multiplying effect is exhibited in the presence of a low-pressure reactive gas, the reactive gas introduced into the through holes can be easily converted into a high-density plasma.

As described above, since a high density plasma can be generated by applying a voltage which causes an electron multiplication effect between the both surface electrodes, a small amount of power is required and a few millimeters. Since the plasma can be generated in the porous plate having the following thickness, the plasma generator itself can be made extremely small.

Further, when a mechanism for controlling the kinetic energy of ions obtained from the plasma generated in the linear through-hole and the direction thereof is provided, the surface of the object to be processed is irradiated with ions of appropriate energy vertically. Therefore, highly reliable fine processing can be performed with high accuracy.

Further, when a mechanism for neutralizing ions obtained from plasma generated in the linear through holes is provided, neutral particles centered on radicals are selectively taken out,
Since the object to be treated can be treated with the neutral particles, electrostatic breakdown of the insulating film can be prevented, and further, the deflection in the irradiation direction of the neutral particles can be prevented. As a result, highly reliable and highly precise microfabrication is possible.

[0017]

Embodiments of the present invention will now be described in detail with reference to the drawings.

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

The etching apparatus (plasma generator) of the present embodiment has a vacuum container 10, a gas supply port 12 for supplying a reactive gas to the vacuum container 10, and the vacuum container 10.
And an evacuation device 14 for setting a predetermined degree of vacuum therein. Further, the vacuum container 10 is provided with a perforated plate 16 as a plasma generating means, a holder 18 on which a workpiece is placed, and a holder moving device 20 for moving the holder 18.

Surface electrodes 22A and 22B formed by depositing a metal such as aluminum by vapor deposition or the like are attached to both upper and lower surfaces of the porous plate 16, and both surface electrodes 22A and 22B are AC. A power supply 24 is connected so that a desired AC voltage can be applied between the electrodes 22A and 22B.

As shown in an enlarged view of a part of the perforated plate 16 in a partially broken state, a large number of linear through holes 16A extending in the thickness direction thereof are formed, and these through holes 16A are formed. Each of them has a function of exhibiting an electron multiplying effect by applying a predetermined voltage between both surface electrodes 22A and 22B. That is, the inner wall of the through hole 16A is formed of a resistor and has a property of emitting secondary electrons.

The porous plate is, for example, a microchannel plate (hereinafter abbreviated as MCP). This MCP has the structure shown in FIG. 2 above, and is made by assembling a number of very thin glass pipes (inner diameter is, for example, several μm to 100 μm), and the bundle is cut into slices. The thin plate has a thickness of, for example, about several mm.

When this MCP is used as the perforated plate 16, the gain of the electron multiplication function is usually about 100 to 10,000, although it varies depending on the voltage applied to the surface electrodes 20A and 20B. Further, the applied voltage may be, for example, about 1 kV, though it varies depending on the reactive gas or the like used.

Next, the operation of this embodiment will be described.

The case of using MCP as the porous plate 16 will be described. First, after mounting the semiconductor wafer W as an object to be processed on the holder 18, the inside of the vacuum container 10 is evacuated by the vacuum exhaust device 14 and a reactive gas such as chlorine (Cl ₂ ) is introduced through the gas supply port 12. Then, the vacuum container 1
The inside of 0 is set to a predetermined pressure. The arrows in FIG. 1 indicate the way in which the reactive gas, plasma, etc. flow.

Next, an AC voltage having a predetermined frequency and voltage is applied between the surface electrodes 22A and 22B by the AC power source 24 to cause discharge in the through holes 16A of the porous plate 16,
Plasma is generated by the electron multiplication effect.

When plasma is generated in the through hole 16A, active particles such as ions and radicals in the plasma are guided onto the semiconductor wafer W by a flow generated by being exhausted by the vacuum exhaust device 14. Therefore, the active particles are irradiated onto the wafer W with directivity, and the wafer W can be etched with high anisotropy.

In this embodiment, the MC
Since it is possible to generate plasma in the pores (through holes) of P (perforated plate), it is necessary to generate plasma composed of active particles of radicals and ions of extremely high density as compared with the conventional plasma generation method. You can

Since the density of the generated plasma can be controlled by adjusting the applied voltage, the etching rate can be set to a desired value over a wide range.

Further, since the semiconductor wafer W does not come into direct contact with plasma, the temperature of the wafer W hardly rises,
Therefore, the reproducibility of processing is extremely high.

FIG. 3 is a schematic sectional view showing an etching apparatus of the second embodiment according to the present invention.

The etching apparatus of this embodiment is substantially the same as the etching apparatus of the first embodiment, except that the AC power supply 24 in FIG. 1 is replaced with a DC power supply 26.

According to this embodiment, as in the case of the first embodiment, it is possible to perform highly anisotropic etching on the wafer W with a small amount of input power. At that time, of the ions in the plasma generated in the through holes 16A of the porous plate 16, only one of the ions, for example, + ions, can be used as the active particles.

FIG. 4 is a schematic sectional view showing an etching apparatus of the third embodiment according to the present invention.

The etching apparatus of the present embodiment has a porous plate 16
Between the holder 18 and the holder 18, a grid electrode 28 for controlling the kinetic energy of the ions and its direction is installed, and a DC variable power source 30 for applying a desired potential to the grid electrode 28 is installed. It is substantially the same as the etching apparatus of the first embodiment.

According to this embodiment, the grid electrode 28 is
Since the above is provided, it is possible to accurately control the energy of the ions, which are the charged particles, of the active particles guided onto the wafer W from the plasma generated in the through holes 16A of the porous plate 16.

For example, when a negative potential is applied to the grid electrode 28, only positive ions of the charged particles generated in the through hole 16A can be extracted and guided onto the wafer W.
At this time, the energy of positive ions can be controlled by adjusting the potential applied to the grid electrode 28. Further, since the moving direction of the positive ions coincides with the direction of the electric field between the grid electrode 28 and the wafer W, in the present embodiment, the positive ions are controlled to have an appropriate kinetic energy, and the positive ions are moved on the wafer W. It is possible to make the light incident vertically on.

In order to prevent the positive ions from colliding with other particles while moving between the grid electrode 28 and the wafer W and being scattered, the movement direction of the wafer W is changed. The contained space is at a low pressure, eg 1
It is desirable to set it to 0 ^-3 Torr.

On the other hand, when a positive potential is applied to the grid electrode 28, only electrons and negative ions of the charged particles can be extracted. In this case, the particles effective for the plasma treatment are negative ions, and the control of the energy and the movement direction thereof can be performed in the same manner as in the case of the positive ions, only by reversing the electric field direction.

As described above, according to this embodiment, it is possible to vertically irradiate the wafer W with the ions.
Etching can be performed with higher accuracy than in the embodiment.

FIG. 5 is a schematic sectional view showing an etching apparatus of the fourth embodiment according to the present invention.

The etching apparatus of this embodiment is the same as the third embodiment except that a porous plate 32 having an electron multiplying function for neutralizing ions is provided between the grid electrode 28 and the wafer W. Is substantially the same as

Similar to the case of the porous plate 16, the porous plate 32 is provided with surface electrodes 34A and 34B, and a desired voltage is applied to both surface electrodes 34A and 34B to increase electron emission. A DC variable electrode 36 for producing a doubling effect is connected.

In this embodiment, the grid electrode 28 is used.
When the positive ions are extracted by the above method, when the extracted positive ions pass through the perforated plate 32, a part thereof is extracted.
Since the secondary electrons collide with the wall surface of the through-hole formed in and the large amount of secondary electrons are emitted from the wall surface, the secondary electron is attached to positive ions passing through the through-hole. as a result,
The positive ions are neutralized to become a neutral beam and the wafer W
To reach.

According to this embodiment, since it is possible to etch with neutral particles centering on radicals,
When etching an insulating film such as an oxide film, the film can be prevented from being damaged by charging, and the beam of neutral particles with which the wafer W is irradiated is not deflected by the surface potential of the wafer W. Therefore, it is possible to perform etching with higher accuracy than in the case of processing with a beam containing ions.

Although the present invention has been specifically described above, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the scope of the invention.

For example, as the perforated plate, MC made of glass is used.
Not limited to P, any one can be used as long as it has an electron multiplying function.

Further, the plasma generator of the present invention is not limited to the etching device, but can be applied to any application using plasma, for example, a film forming device.

[0049]

As described above, according to the present invention, a high density plasma can be generated even with a small applied power. Therefore, when the plasma generator of the present invention is applied to plasma processing such as etching for a semiconductor wafer or the like, it is possible to perform processing with high accuracy even with a small electric power and to make the processing apparatus compact.

[Brief description of drawings]

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

FIG. 2 is an enlarged perspective view showing a main part of the etching apparatus.

FIG. 3 is a schematic sectional view showing an etching apparatus of a second embodiment according to the present invention.

FIG. 4 is a schematic sectional view showing an etching apparatus of a third embodiment according to the present invention.

FIG. 5 is a schematic sectional view showing an etching apparatus of a fourth embodiment according to the present invention.

[Explanation of symbols]

10 ... vacuum container, 12 ... Gas supply port, 14 ... vacuum exhaust device, 16, 32 ... Perforated plate, 16A ... through-hole, 22A, 22B, 34A, 34B ... Surface electrodes.

Continued front page    (72) Inventor Emi Murakawa             1 Kawasaki-cho, Chiba-shi, Chiba Kawasaki Steel Co., Ltd.             Corporate Technology Research Division (72) Inventor Osamu Kinoshita             1 Kawasaki-cho, Chiba-shi, Chiba Kawasaki Steel Co., Ltd.             Corporate Technology Research Division

Claims (3)

[Claims] 1. A plasma generator, comprising a perforated plate having a large number of linear through holes having an electron multiplication function as the plasma generating means. 2. A plasma generator according to claim 1, further comprising a mechanism for controlling kinetic energy of ions obtained from plasma generated in the linear through hole and a direction thereof. 3. The plasma generator according to claim 1, further comprising a mechanism for neutralizing ions obtained from plasma generated in the linear through hole.