JP3220528B2 - Vacuum processing equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vacuum processing apparatus for performing etching and film formation of a semiconductor device using plasma.

[0002]

2. Description of the Related Art Conventionally, in the process of performing etching and film formation for manufacturing a semiconductor device by using plasma,
A vacuum processing apparatus using parallel plate electrodes has been generally used. However, in recent years, vacuum processing apparatuses utilizing electron cyclotron resonance (ECR) and helicon waves have been widely used due to demands for fine processing of etching and vacuum processing with little damage. In these vacuum processing apparatuses, a very high-density plasma is generated even at a low pressure in a plasma generation source remote from a substrate mounting table on which a substrate to be processed is mounted, and the plasma is diffused to the vicinity of the substrate to be processed. Processing is in progress. In this case, it is possible to control the energy of ions incident on the substrate by applying a bias voltage to the substrate by applying a high frequency or DC voltage independent of the plasma generation source to the substrate mounting table. Etching with little damage has become possible. Particularly, in an etching apparatus used for the manufacture of an VLSI device, the surface of the substrate to be processed is often covered with an insulator, so that a high frequency is often used for controlling the ion energy.

[0003]

However, in any plasma generating source utilizing electron cyclotron resonance (ECR) or helicon waves, there is no electrode in a portion exposed to the plasma, that is, plasma is generated by so-called electrodeless discharge. Therefore, there is a fear that the space potential of the plasma cannot be determined. For this reason, when a bias voltage is induced in the substrate mounting table, there is a possibility that the space potential of the plasma is affected by the bias voltage. As a result, a bias voltage is induced on the substrate mounting table and the incident energy of ions is reduced.
In some cases, the control could not be carried out well, and only extremely reproducible results were obtained.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems, and an object of the present invention is to provide a vacuum processing apparatus provided with a plasma source independently of a substrate mounting table. Even if a bias voltage is induced on the mounting table, the substrate incident ion energy can be controlled with good reproducibility without affecting the space potential of the plasma generated by the plasma source, and the space potential of the plasma is independent. Another object of the present invention is to provide a vacuum processing apparatus which can be controlled in a vacuum.

[0005]

According to a first aspect of the present invention, a substrate to be processed is held by a substrate mounting table installed in a container that can be evacuated to a vacuum, and a plasma generating source installed at a position distant from the substrate mounting table. In a vacuum processing apparatus that generates plasma of an introduced gas and processes a substrate using the plasma, a conductive body whose potential can be controlled is provided between a plasma generation source and a substrate mounting table. INDUSTRIAL APPLICABILITY The present invention can be applied to an apparatus for processing a substrate using plasma in a vacuum vessel, and is suitable for, for example, an etching apparatus using plasma or a film forming apparatus using plasma.

According to a second aspect of the invention, the plasma generation source according to the first aspect of the invention is configured to generate plasma by electrodeless discharge.

In a third aspect of the present invention, the plasma generating source in the second aspect is an ECR ion source.

According to a fourth aspect of the present invention, the plasma generating source in the second aspect is a helicon wave ion source.

According to a fifth aspect of the present invention, the conductor according to the first aspect of the present invention is formed in a hollow body shape having both ends open, so that plasma is diffused through the inside of the hollow body. Examples of the shape of the hollow body include a hollow cylinder, a hollow disk, and a hollow hemisphere having an open top.

In a sixth aspect of the present invention, at least a portion of the conductor of the first aspect of the present invention which is exposed to plasma is made of graphite, pyrolytic carbon, glassy carbon, conductive silicon carbide, or conductive silicon. Any one selected from the group consisting of The conductive silicon is obtained by doping impurities into pure silicon to increase conductivity.

In a seventh aspect, the conductor according to the first aspect is grounded.

In an eighth aspect, the conductor according to the first aspect is connected to a DC power supply or a high-frequency power supply.

[0013]

According to the present invention, since a conductor whose potential can be controlled is provided between the plasma generation source and the substrate mounting table, the plasma is generated by the plasma generation source when the plasma comes into contact with the conductor. Is dependent on the potential of the conductor, and is determined to be a certain value according to the potential of the conductor. Since the substrate incident ion energy depends on the potential difference between the plasma potential and the substrate potential, if the plasma potential can be controlled using the present invention, the controllability and reproducibility of the substrate incident ion energy can be improved. Thus, high-precision substrate processing becomes possible.

When a plasma generating source such as an ECR ion source or a helicon wave ion source is used to generate plasma by electrodeless discharge, it is easy to control the floating potential of the plasma using a conductor. become.

The material of at least the portion of the conductor exposed to the plasma may be graphite, pyrolytic carbon,
The use of any one of glassy carbon, conductive silicon carbide, and conductive silicon has the following advantages. For these materials, the property that the material is etched by the plasma is superior to the property that the film is deposited on the material by the plasma with respect to the plasma of the halogen-based gas used in the etching apparatus or the like. Therefore, no film is deposited on the conductor formed of the material. if,
When a film is deposited on a conductor, the film is generally not necessarily conductive, so that the potential of the plasma may not be controlled. In general, when a metal conductor is used, the deposition of a film thereon becomes superior, and from this viewpoint, it is not preferable to use a metal conductor. Even when a film is not deposited on a metal conductor, the metal is sputtered and taken into the substrate, causing damage to the film. In addition, graphite, pyrolytic carbon,
If a carbon-based material such as glassy carbon is used as the conductor, there is a possibility that even if these are etched, they can be exhausted in the form of CO ₂ or CH ₄ . Further, when silicon which has been made conductive is used as a conductor, there is also an advantage that when a Si wafer is used as a substrate, even if the conductor is etched, it does not become an impurity to the substrate.

[0016]

FIG. 1 is a front sectional view of an embodiment of the present invention. This vacuum processing apparatus is a dry etching apparatus using a helicon wave ion source as a plasma generation source. A cylindrical helicon wave ion source 10 made of quartz is mounted above the diffusion chamber 12. An antenna 14 is provided around the helicon wave ion source 10, and a high frequency is applied from a high frequency power source 16 for source plasma. Further, an excitation coil 18 for generating a magnetic field is provided around the helicon wave ion source 10, and generates a magnetic field in the axial direction of the helicon wave ion source 10. The diffusion chamber 12 is made of aluminum, and a permanent magnet device 20 is arranged on an outer peripheral portion of the diffusion chamber 12 on the atmosphere side. Diffusion chamber 1
A substrate mounting table 22 is installed inside 2 and is connected to a high frequency power supply 24 for bias. Substrate mounting table 22
A wafer 23 is placed on top. Further, a conductor 26 in the form of a hollow cylinder made of glassy carbon is provided above the substrate mounting table 22 near the helicon wave ion source 10. The conductor 26 is connected to a power source 28 for plasma potential control.

FIG. 2 is a layout view of the permanent magnet device 20.
(A) is a plan view, and (B) is a view indicated by arrows BB in (A). In the permanent magnet device 20, when viewed in a plan view, twenty-four permanent magnet units 21 are arranged circumferentially equally so that adjacent magnetic poles have opposite polarities. Also,
As shown in (B), each permanent magnet unit 21 has a plurality of permanent magnet pieces 25 stacked vertically. A cusp magnetic field is formed in the diffusion chamber 12 by the permanent magnet device 20.

Next, the operation of the etching apparatus shown in FIG. 1 will be described. First, the diffusion chamber 12 is evacuated to a vacuum, and the wafer 23 to be etched is transferred to the substrate mounting table 22 via a load lock chamber (not shown). A poly-Si film is formed on the surface of the wafer 23 in advance, and is further patterned with a photoresist. Next, a gate valve (not shown) between the load lock chamber and the diffusion chamber 12 is closed, and a chlorine gas, which is a reactive gas, is introduced from a gas introduction pipe 29 and connected to the diffusion chamber 12. The exhaust gas is exhausted by a process gas exhaust pump (not shown). A throttle valve (not shown) for controlling the conductance is connected between the diffusion chamber 12 and the process gas exhaust pump. By controlling the opening degree, the pressure in the diffusion chamber 12 is kept constant. . In this embodiment, the pressure was set to 2 mTorr.

Next, the bias high-frequency power supply 24 is turned on, and at the same time, the source plasma high-frequency power supply 16 and the plasma potential control power supply 28 are also turned on to generate a reactive plasma of chlorine gas. Plasma is generated in a helicon mode by a high-frequency electric field induced by an antenna 14 wound around the helicon wave ion source 10. This plasma diffuses into the diffusion chamber 12 and
To reach the surface. During the plasma diffusion,
In order to prevent a situation where electrons collide with the inner wall of the diffusion chamber 12 and disappear, the cusp magnetic field is generated by the permanent magnet device 20 arranged on the outer peripheral portion of the diffusion chamber 12. Due to the cusp magnetic field, the electrons are returned to the inside of the diffusion chamber 12, and as a result, the plasma is transported to the wafer 23 in a state where the plasma disappears little. Wafer 23
Since the self-bias voltage is induced by the high frequency power supply for bias 24, ions in the plasma are accelerated toward the wafer 23, and the poly-Si on the surface of the wafer 23 can be etched by increasing the anisotropy. It is possible.

The ion incident energy on the substrate includes (1) the degree of anisotropy, (2) the degree of damage given to the substrate,
(3) It is an important factor for controlling the ratio (selectivity) of the etching rate between the substrate and the photoresist or between the substrate and the base, and controlling the incident energy of the substrate is fine etching. Important in the process. The ion incident energy on the substrate is determined by the difference between the space potential of the plasma and the self-bias voltage induced on the surface of the wafer 23. In this embodiment, since the plasma diffused in the diffusion chamber 12 comes into contact with the conductor 26, the space potential of the plasma is determined by the potential of the conductor 26. Therefore, by controlling the potential of the conductor 26 by the plasma potential control power supply 28, the energy of ions incident on the wafer 23 can be controlled, and etching with excellent controllability can be performed.

The value of the difference between the space potential of the plasma and the self-bias voltage induced on the surface of the wafer 23 depends on the process conditions. For example, when etching polysilicon with plasma of chlorine gas, the potential of the plasma is set to be higher than the potential of the wafer 23 by 50 to 100 V.

Since the entirety of the conductor 26 or the inner surface portion in contact with the plasma is made of glassy carbon which is a conductive material, the potential of the plasma has a certain value determined by the potential of the conductor 26. The plasma potential is usually
A value higher by 10 to 30 V than the potential of the conductor 26,
It is hardly affected by the bias voltage induced on the wafer 23. Therefore, it is possible to control the energy of ions incident on the wafer 23 very accurately and to perform etching with almost no damage. Further, since no deposit is formed on the glassy carbon, which is the material of the conductor 26, by plasma, the conductivity is always maintained. In addition, since glassy carbon is a material containing almost no metal impurities,
Even if the surface is etched by plasma, the wafer 2
No contamination of 3

The plasma potential can be controlled using a plasma potential control power supply 28, but the conductor 26 may be simply grounded without using the power supply 28. Even in this case, the spatial potential of the plasma is not affected by the self-bias voltage generated on the wafer 23, and etching with extremely high reproducibility can be performed. Since the plasma potential becomes 10 to 30 V when the conductor 26 is grounded, the bias voltage of the wafer 23 is controlled to make the energy of the substrate incident ions a desired value. For example, the wafer 23
Is set to the negative side by 50 to 100 V. As a result, the bias voltage of the wafer 23 is on the minus side by several tens of volts from the ground potential. If wafer 2
When it is desired to set the bias voltage of No. 3 near the ground potential, the plasma potential control power supply 28 is also required.

FIG. 3 is a perspective view showing various examples of the shape of the conductor 26. As shown in FIG. (A) is a hollow cylinder used in the embodiment of FIG. (B) is a hollow disk,
(C) is a hollow hemisphere with an open top. In any conductor, the plasma passes through the hollow interior.

FIG. 4 is a front sectional view of another embodiment of the present invention. This device uses electron cyclotron resonance (ECR)
This is a dry etching apparatus using the ion source 30 as a plasma generation source. The point that the ECR ion source 30 is mounted above the diffusion chamber 12 and the point that the conductor 26 is made of poly-Si and grounded are significantly different from the embodiment of FIG. This is almost the same as the first embodiment. Parts that are the same as in the apparatus of FIG. 1 are given the same reference numerals.

The operation of the apparatus shown in FIG. 4 will be described. First, EC
The exciting coil 32 wound around the R ion source 30 is excited to generate a magnetic field (875 gauss in this case) required for ECR resonance below the inside of the ECR ion source 30. Next, a microwave of 2.45 GHz is generated by the magnetron 34, and this is transmitted through the waveguide 36 to the ECR.
It is supplied to the ion source 30. At this time, a dense plasma is generated around a region where the ECR resonance condition is satisfied. EC
The entire inner wall of the R ion source 30 is covered with quartz glass 38 in order to prevent heavy metals from being sputtered and adhering to the wafer 23. For this reason, the spatial potential of the plasma tends to be very unstable. However, since the conductor 26 is installed in the diffusion chamber 12 as in the present embodiment, the spatial potential of the plasma is set to be lower than the ground potential by 10%. It was possible to stably maintain a high value by several volts. As a result, it was possible to perform highly reproducible etching of poly-Si with high anisotropy while obtaining a selectivity of 60 or more with respect to the silicon oxide film.

In the above two embodiments, the helicon wave ion source and the ECR ion source are used as the ion source, but other ion sources may be used. Further, the shape of the conductor may be other than the shape shown in FIG. The material of the conductor may be a conductive substance and a substance with little heavy metal contamination, and may be, for example, graphite, pyrolytic carbon, or silicon carbide. . The conductor may be mounted at any position in the diffusion chamber or ion source as long as it is exposed to the plasma. Further, the voltage applied to the conductor may be a high frequency, and the frequency can be arbitrarily selected.

Although the above two embodiments relate to an etching apparatus, the present invention can also be applied to a plasma CVD apparatus used for forming an amorphous silicon or silicon nitride film.

[0029]

According to the present invention, the space potential of the plasma can be stabilized by providing a conductor whose potential can be controlled between the plasma source and the substrate mounting table. This makes it possible to control the substrate incident ion energy with good reproducibility. When the present invention is applied to an etching apparatus, it is possible to etch a substrate with extremely high reproducibility under conditions satisfying high anisotropy and high selectivity.

[Brief description of the drawings]

FIG. 1 is a front sectional view of one embodiment of the present invention.

FIG. 2A is a plan view of a permanent magnet device, and FIG. 2B is a view taken along line BB of FIG.

FIG. 3 is a perspective view showing various shapes of a conductor.

FIG. 4 is a front sectional view of another embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Helicon wave ion source 12 ... Diffusion chamber 22 ... Substrate mounting table 23 ... Wafer 24 ... High frequency power supply for bias 26 ... Conductor 28 ... Power supply for plasma potential control 30 ... ECR ion source

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) C23F 4/00 C23C 16/50 H01L 21/3065

Claims (8)

(57) [Claims] 1. A substrate to be processed is held by a substrate mounting table installed in a container that can be evacuated to a vacuum, and plasma of an introduced gas is generated by a plasma generation source installed at a position distant from the substrate mounting table. What is claimed is: 1. A vacuum processing apparatus for processing a substrate by using plasma, wherein a conductive body whose potential can be controlled is provided between a plasma generation source and a substrate mounting table. 2. The vacuum processing apparatus according to claim 1, wherein said plasma generation source is of a type that generates plasma by electrodeless discharge. 3. The vacuum processing apparatus according to claim 2, wherein said plasma generation source is an ECR ion source. 4. The vacuum processing apparatus according to claim 2, wherein said plasma generation source is a helicon wave ion source. 5. The vacuum processing apparatus according to claim 1, wherein the conductor has a shape of a hollow body whose both ends are open, and plasma is diffused through the inside of the hollow body. 6. The material of at least a portion of the conductor exposed to plasma is graphite, pyrolytic carbon,
2. The vacuum processing apparatus according to claim 1, wherein the apparatus is any one selected from the group consisting of glassy carbon, conductive silicon carbide, and conductive silicon. 7. The vacuum processing apparatus according to claim 1, wherein the conductor is grounded. 8. The vacuum processing apparatus according to claim 1, wherein the conductor is connected to a DC power supply or a high-frequency power supply.