JP2902009B2 - Microwave plasma processing apparatus and processing method - Google Patents

Description

Description: BACKGROUND OF THE INVENTION The present invention relates to a plasma processing apparatus for manufacturing semiconductor devices, electronic components to which thin films such as liquid crystal display elements, thermal heads, thin film magnetic heads and the like are applied, and the like. In particular, the present invention relates to an apparatus and a method for performing plasma processing such as thin film formation and etching.

[Prior Art] As a conventional microwave plasma processing apparatus of this type, the one disclosed in Japanese Patent Application Laid-Open No. 59-3018 is known. In the device disclosed in the publication, a discharge tube is provided in a vacuum chamber, a coil is attached thereto, a magnetic field is applied, and a microwave having the same frequency as the electron cyclotron frequency is introduced through a waveguide, By causing the discharge, the reaction gas introduced into the vacuum chamber is decomposed, whereby the chemical vapor deposition is performed on the substrate which is the sample placed in the vacuum chamber.

However, when microwaves are introduced through a waveguide, the size of the waveguide is limited by the size of the waveguide, which makes it difficult to process a large-area substrate.

As a microwave introduction method, in addition to the method using a waveguide, Japanese Journal of Applied Physics Vol. 23, No. 8, August 1984, pp. 1101 to 1106 (JAPANESE
JOURNAL OF APPLIED PHYSICS Vol.23 No.8, August 198
4, pp. 1101 to 1106) using a Lisitano-Coil. In this method, the discharge portion can be enlarged by increasing the diameter of the Rigidano coil.

However, even with this method, it is difficult to generate uniform plasma, and the difference between the plasma density and the electron energy between the central part and the peripheral part cannot be avoided. In particular,
When the pressure is 0.1 Pa or more, the non-uniformity becomes remarkable, and it is difficult to use the apparatus as a large-area processing apparatus.

[Problems to be Solved by the Invention] By the way, plasma CVD or plasma etching using low-pressure, high-density plasma of microwave plasma is used for manufacturing a liquid crystal display element, a facsimile line sensor, and a thermal head. It is taking place. In this case, plasma processing of a large substrate or a large wafer is required with an increase in the size of the element.

On the other hand, JP-A-63-240013 discloses a reactor using a microwave horn antenna as a reactor utilizing electron cyclotron resonance.

Since this conventional device uses a microwave horn, it is considered that plasma can be generated over a wide area. Therefore, it is considered that the processing by the microwave plasma can be performed over a large area, and that a large-area substrate can be processed. Further, it is considered that a large number of substrates can be processed at one time, and the processing amount per unit time can be increased.

However, the disclosed conventional apparatus does not consider the uniformity of the density of the generated plasma. That is, in this conventional technique, the generated plasma is
Since it is localized under the influence of a magnetic field and does not exist at a constant density over a large area, it is difficult to uniformly treat a large area substrate,
The performance of the element itself and the production yield cannot be improved. Therefore, for example, it is difficult to process a liquid crystal display panel or the like using a large substrate, and there is a problem that a large wafer cannot be processed. Further, even with a small substrate, there is a problem that a large number of substrates cannot be uniformly processed at once, resulting in a low production yield.

An object of the present invention is to provide a microwave plasma processing apparatus and a processing method capable of performing processing uniformly over a large area.

[Means for Solving the Problems] In order to achieve the above object, the present invention expands a microwave to a processing area by using an electromagnetic horn, generates a large-area plasma, and partitions an insulator in the middle of a vacuum vessel. A plate is provided to enable uniform plasma processing.

The partition plate is provided so as to be arranged in the vacuum vessel and is aligned with the substrate to be processed, and is configured such that plasma exists between the substrate and the partition plate. It is preferable that the distance between the partition plate and the substrate to be processed is set so as to be close at a place where the plasma density is high and to be distant at a place where the plasma density is low. in this case,
The partition plate is preferably formed in a curved shape.

To introduce microwaves, spread the microwave with an electromagnetic horn, then introduce the microwave into the vacuum chamber through a window made of insulating material such as quartz, or vacuum seal at the seam between the waveguide and the electromagnetic horn Can be considered. In the former, the microwave can be spread without the influence of plasma, but the vacuum seal surface has a large diameter. In the latter, plasma is present in the electromagnetic horn, which has some influence on the propagation of microwaves. However, vacuum sealing can be performed on the waveguide cross section, which is advantageous in device fabrication.

A necessary condition is that the material of the window for introducing the microwave into the vacuum is an insulator and not so large in dielectric constant. Quartz is desirable in terms of heat resistance and strength. Since a large-diameter quartz window is expensive and easily destroyed by the force due to atmospheric pressure, it is more economical and more advantageous in terms of safety to perform vacuum sealing at the seam between the waveguide and the electromagnetic horn.

The vacuum container may be formed in a structure in which the whole or a part thereof has a conical shape, a quadrangular pyramid or a polygonal pyramid shape, and a microwave is introduced into the inside from a vertex thereof.
A conical, quadrangular pyramid or polygonal pyramid portion functions as an electromagnetic horn.

The electromagnetic horn is preferably made of a metal having high conductivity, for example, an aluminum alloy. Further, it is preferable to use an electromagnetic horn configured to emit a substantially plane wave from the opening. Conditions for this will be described later.

The microwave plasma processing apparatus of the present invention is particularly suitable for a microwave plasma processing apparatus having a magnetic field generating means for generating electron cyclotron resonance (ECR) at a microwave frequency in the vacuum vessel. In this case, the partition plate is provided in parallel with the substrate to be processed, and is installed so that there is an electron cyclotron resonance point between the substrate and the partition plate.

Examples of an apparatus to which the present invention is preferably applied include, for example, a microwave plasma etching apparatus using a compound containing fluorine or chlorine as a gas, a microwave plasma CVD apparatus using a compound containing silicon as a gas, and oxygen or oxygen as a gas. A microwave plasma oxidation device using nitrogen oxide is used.

[Effect] The electromagnetic horn can substantially maintain the mode of the microwave and can spread the microwave in a spherical shape centered near the entrance of the horn. In order to generate uniform plasma efficiently, it is desirable that the illuminance distribution is uniform and the phases of the waves are uniform. For that purpose, there is an optimal combination between the opening diameter and the length of the electromagnetic horn. Electromagnetic horns have a rectangular cross section and a circular cross section, and either may be used.

In order for the electromagnetic horn to emit a substantially plane wave, it is necessary for the horn to be designed optimally. In the case of a rectangular horn, the opening lengths a and b have a relationship with the horn length 1 as shown in FIG. Here, since the linear approximation is sufficient for practical use, the following conditions are preferable for the opening lengths a and b.

For a rectangular horn with a side of 1 m or less, if the aperture diameter in the electric field direction is a, the aperture diameter in the magnetic field direction is b, the length is l, and the wavelength of the microwave is λ, the shape should be determined so as to satisfy the following conditions. If this is the case, relatively uniform plasma can be obtained.

0.23l + 2λ ≦ a ≦ 0.23l + 4λ 0.2l + 1.5λ ≦ b ≦ 0.2l + 3.5λ In the case of a circular horn having a diameter of 1 m or less, if the diameter is D, it is relatively uniform if the shape is determined so as to satisfy the following conditions. Plasma can be obtained.

0.21l + 1.75λ ≦ D ≦ 0.21l + 3.75λ When performing plasma processing, radicals or ions activated by plasma are often used. To make these concentrations uniform on the substrate surface, It is effective to partition the plasma with a partition plate parallel to the substrate surface and to make the amount of plasma acting on each point on the substrate constant.

The charged particles in the magnetic field make a helical motion about the line of magnetic force, and move along the line of magnetic force. When vacuum sealing is performed at the joint between the electromagnetic horn and the waveguide, plasma is also generated inside the electromagnetic horn, but the charged particles that make up the plasma move along the magnetic lines of force, so the plasma on the magnetic lines of force that crosses the substrate becomes The line of magnetic force will contribute to the surface reaction at the point of intersection with the substrate surface. Here, the plasma corresponding to the central portion of the substrate extends to the depth of the electromagnetic horn, whereas the plasma corresponding to the peripheral portion has only a length from the substrate surface to the wall of the electromagnetic horn, and can contribute to the surface reaction. The difference in length of the number of particles will occur.

Therefore, by inserting a partition plate at a certain distance from the substrate and in parallel, the length of the plasma contributing to the surface reaction can be kept constant from the substrate to the length of the partition plate. It becomes possible.

However, in this case, it is necessary to form a magnetic field such that a point where electron cyclotron resonance occurs is located between the substrate and the partition plate. When the electron cyclotron resonance point exists in the space on the opposite side of the partition plate from the substrate, microwaves propagate only to the resonance point, so that no plasma is generated between the partition plate and the substrate.

If the design of the electromagnetic horn is not the optimal design, the illuminance distribution of the microwave tends to be strong at the center and weak at the periphery. In such a case, the plasma density in the central portion increases, and the concentration of activated radicals and ions tends to increase in the central portion. In such a case, higher uniformity can be obtained by making the partition plate a curved surface and shortening the distance to the substrate in a portion having a high concentration and increasing the distance to the substrate in a portion having a low concentration.

Therefore, according to the present invention, a large-area liquid crystal display element,
Microwave plasma can be applied to the fabrication of large-area devices, such as thermal heads, which were conventionally processed with high-frequency plasma with a lower plasma density than microwave plasma. It becomes possible.

[Example] Hereinafter, an example of the present invention will be described with reference to the drawings.

Embodiment 1 Embodiment 1 will be described with reference to FIG.

The embodiment shown in FIG. 1 includes a microwave supply unit, a processing unit, and a vacuum exhaust system.

The microwave supply unit includes a microwave source 1, a waveguide 2, an isolator 3, a tuner 4, a rectangular-circular mode converter 5, and a circular electromagnetic horn 6.

The processing unit includes a vacuum chamber 9 and a partition plate provided therein.
7b, a gas outlet tube 8 and a substrate table 10.

The vacuum chamber 9 performs vacuum sealing with the quartz window 7a immediately before entering the circular electromagnetic horn 6 from the rectangular-circular mode converter 5,
The circular electromagnetic horn 6 also serves as a part of the outer wall of the vacuum chamber 9. The vacuum sealing of the quartz window 7a is performed using a metal O-ring (not shown). In addition, the vacuum chamber 9
At the opening of the circular electromagnetic horn 6, a 3 mm thick quartz partition plate 7
Place b to separate the upper and lower plasma. Further, the vacuum chamber 9 communicates with a vacuum exhaust system via a conductance adjusting valve 12.

The evacuation system consists of a turbo molecular pump 13 and an oil rotary pump.
It has 14 and.

Next, a case where plasma etching is performed using the apparatus configured as described above will be described.

From the microwave source 1 through the waveguide 2, through the isolator 3, the tuner 4, and the rectangular-circular mode converter 5,
Microwaves were guided to the circular electromagnetic horn 6 through the quartz window 7a, where the microwaves were spread to a diameter of 300 mm and radiated into the vacuum chamber 9.

As the gas, carbon tetrafluoride containing 3% of oxygen was caused to flow at a rate of 90 cm ³ per minute through the gas blowing pipe 8 and exhausted by the turbo molecular pump 13. The pressure in the vacuum chamber should be about 0.1Pa,
It was adjusted by the conductance adjustment valve 12.

The magnetic field causes a current to flow through the coil 15 and about 0.1 T
Generated. The microwave frequency is 2.45 GHz, where the electron cyclotron resonance occurs at 0.0875T. This point is between the partition plate 7b and the substrate 11.

The opening diameter of the electromagnetic horn was 300 mm in diameter, and the length of the horn was 300 mm.

The substrate 11 is formed by forming a silicon nitride film having a thickness of 1 μm on a silicon wafer having a diameter of about 125 mm by a chemical vapor deposition method and then patterning an aluminum film having a thickness of 0.5 μm into a 3 μm line and space. Used.

When microwaves of 600 W were applied under the above conditions, almost uniform plasma was generated, and etching of the silicon nitride film occurred using the aluminum pattern as a resist. The etching rate was 0.08 to 0.085 μm per minute, which was almost uniform over the entire surface.

At this time, the quartz window 7a was heated by the microwave and ion bombardment and glowed red. However, in this embodiment, the quartz window 7a
Since the vacuum seal was performed with a metal O-ring, the seal was not deteriorated even by red heat. This is the same in other embodiments described later.

Embodiment 2 Embodiment 2 will be described with reference to FIG.

The embodiment shown in FIG. 2 includes a microwave supply unit, a processing unit, and a vacuum exhaust system, similarly to the first embodiment.

The microwave supply unit includes a microwave generation source 21 and a microwave waveguide system 22 configured similarly to the first embodiment.

The processing unit includes a vacuum chamber 29 including a rectangular electromagnetic horn 24,
Inside the vacuum chamber 29, there are provided a partition plate 26, a gas blowing pipe 25, and a substrate table (not shown) for supporting the substrate 27.

The vacuum chamber 29 is provided with a rectangular electromagnetic horn from the microwave waveguide system 22.
Immediately before entering the chamber 24, a vacuum seal is performed with the quartz window 23, and the rectangular electromagnetic horn 24 also serves as a part of the outer wall of the vacuum chamber 29. The vacuum seal of the quartz window 23 is made of metal O (not shown).
Performed in a ring. In the vacuum chamber 29, a quartz partition plate 26 having a thickness of 3 mm is placed at the opening of the rectangular electromagnetic horn 24 to separate the upper and lower plasma. Further, the vacuum chamber 29 communicates with a vacuum exhaust system via a conductance adjusting valve (not shown).

The rectangular electromagnetic horn 24 has an opening diameter in the direction of the electric field of the microwave of 500 mm, an opening diameter in the direction of the magnetic field of 420 mm, and a length of 580 mm.

A coil 30 for generating a magnetic field is arranged outside the vacuum chamber 29.

The evacuation system includes a turbo molecular pump 28a, an oil rotary pump 28b, and a conductance adjusting valve (not shown).

Next, a case where plasma etching is performed using the apparatus having the above configuration will be described.

As in the first embodiment, a 2.45 GHz microwave was guided from a microwave source 21 through a microwave waveguide system 22 to a rectangular electromagnetic horn 24.

The magnetic field was generated by passing an electric current through the coil 30 so that the electron cyclotron resonance point was between the partition plate 26 and the substrate 27.

The substrate 27 is 400 mm coated with 15 μm thick polyimide.
A 0.2 μm silicon oxide film was formed on a × 300 mm glass substrate by a plasma CVD method, and a hole pattern having a diameter of 2 μm was formed in silicon oxide.

As for the gas, oxygen was caused to flow at a rate of 200 cm ³ per minute through the gas blowing pipe 25, and the gas was exhausted by the turbo molecular pump 28a. Vacuum chamber 29
The internal pressure was about 1 Pa.

When a microwave of 2 kW was supplied from the microwave generation source 21, almost uniform plasma was generated, and the polyimide was oxidized and removed. The etching rate of the polyimide was about 1 μm per minute, and was almost constant over the entire surface.

Embodiment 3 Embodiment 3 will be described with reference to FIG.

The embodiment shown in FIG. 3 includes a microwave supply unit, a processing unit, and a vacuum exhaust system, similarly to the first and second embodiments.

The microwave supply unit includes a microwave generation source 31 and a microwave waveguide system 32 configured in the same manner as in the first embodiment.

A vacuum chamber 45 including the circular electromagnetic horn 34,
Inside the vacuum chamber 45, there are provided a partition plate 38, a gas blowing pipe 39, and a substrate table 40 for supporting the substrate 41.

The vacuum chamber 45 is provided with a circular electromagnetic horn from the microwave waveguide system 32.
Immediately before entering the chamber, vacuum sealing is performed with a quartz plate 33, and the circular electromagnetic horn 34 also serves as a part of the outer wall of the vacuum chamber 45. The vacuum sealing of the quartz window 33 is performed by a metal O-ring. In addition, a quartz partition plate 38 having a thickness of 3 mm is placed in the opening of the circular electromagnetic horn 34 to separate upper and lower plasma. Further, the vacuum chamber 45 communicates with the vacuum exhaust system via the conductance adjusting valve 42.

Outside the circular electromagnetic horn 34, coils 35 and 36 are provided. A magnetic field is generated through current through the coils 35 and 36. The electron cyclotron resonance point was located between the partition plate 38 and the substrate 41. A cover 37 made of a soft iron plate is placed on the outer periphery of the coils 35 and 36 to enhance the magnetic force.

The circular electromagnetic horn 34 has an opening diameter of 1000 mm and a length of 900 m
Set to m. With this opening diameter, ideally 2.5m-3
Although it is desirable to have a length of m, creating a vacuum chamber of 2.5 m to 3 m and applying a magnetic field close to 0.1 T to the vacuum chamber increases the size of the apparatus, increases power consumption, and has many practical problems. Therefore, although the length is shortened, the microwave does not spread sufficiently uniformly at this length, the irradiation intensity at the center becomes higher than that at the periphery, and the plasma density at the center becomes high. Therefore, in the present embodiment, the partition plate 38 is formed as a spherical surface, the central portion is brought close to the substrate, and the higher the plasma density, the shorter the length of the contributing plasma.

The evacuation system is a turbo molecular pump 43 and an oil rotary pump
44 and a conductance adjusting valve 42.

Next, a case where an amorphous silicon film is formed using the apparatus having the above configuration will be described.

From the microwave source 31 through the microwave waveguide system 32,
A 2.45 GHz microwave was guided to the circular electromagnetic horn 34. Immediately before entering the circular electromagnetic horn 34, mode conversion from rectangular to circular is performed.

As the substrate 41, a square glass substrate having a side of 600 mm was used.

As for the gas, monosilane was allowed to flow at a rate of 200 cm ³ per minute through the gas blowing pipe 39, and the gas was exhausted by the turbo molecular pump 43. The pressure in the vacuum chamber 45 is controlled by the conductance adjustment valve 42.
It was adjusted to 0.2 Pa. The substrate 41 is attached to the substrate base 40, and heated to 150 ° C.
Heated.

When microwaves of 6.5 kW were injected from the microwave generation source 31, plasma was generated over the entire space, although the central portion tended to be slightly strong, and an amorphous silicon film was formed on the glass substrate. A film of about 0.5 μm was formed in 5 minutes, and the thickness unevenness was within ± 3%.

[Effects of the Invention] According to the present invention, there is an effect that a microwave plasma can be uniformly processed over a large area. Therefore, a large-area substrate can be processed with good yield without deteriorating the performance of elements and the like. Further, a large number of substrates can be processed at a time with a high yield, and the throughput per unit time can be increased.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a microwave plasma processing apparatus according to a first embodiment of the present invention, FIG. 2 is a perspective view showing a microwave plasma processing apparatus according to a second embodiment, and FIG. FIG. 4 is a longitudinal sectional view of the plasma processing apparatus, and FIG. 4 is a graph showing the relationship between the opening lengths a and b of the rectangular horn and the horn length 1 in the optimum design. DESCRIPTION OF SYMBOLS 1 ... Microwave source, 2 ... Waveguide, 3 ... Isolator, 4 ... Tuner, 5 ... Rectangle-circular mode converter, 6 ... Circular electromagnetic horn, 7a ... Quartz window, 7b ... ... Partition plate, 8 ... Gas blowing tube, 9 ... Vacuum chamber, 10 ... Substrate stand,
11 ... board, 12 ... conductance adjustment valve, 13 ...
Turbo molecular pump, 14 ... Oil rotary pump, 15 ... Coil, 21 ... Microwave generation source, 22 ... Microwave waveguide system, 23 ... Quartz window, 24 ... Rectangular electromagnetic horn, 25 ... Gas blowing Tube, 26 Partition plate, 27 Substrate, 28a Turbo molecular pump, 29 Vacuum chamber, 30 Coil, 31 Microwave source, 32 Microwave waveguide, 33 Quartz window,
34 …… Circular electromagnetic horn, 35,36 …… Coil, 37 …… Cover, 38 …… Partition plate, 39 …… Gas outlet tube, 40 …… Substrate stand,
41 …… Substrate, 42 …… Conductance adjustment valve, 43 ……
Turbo molecular pump, 44 ... Oil rotary pump.

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Satoru Satoru 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture Inside Hitachi, Ltd. Production Engineering Laboratory Co., Ltd. (72) Mitsuo Nakatani 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture Shares (72) Kazuo Suzuki 2-9-1, Aisecho, Hitachi City, Ibaraki Prefecture Hitachi Engineering Services, Ltd. (72) Tadashi Sonobe 3-1-1, Sachimachi, Hitachi City, Ibaraki Prefecture No. 1 Hitachi, Ltd. Hitachi Plant (58) Field surveyed (Int. Cl. ⁶ , DB name) C23C 16/00-16/56 C23F 4/00-4/04 H05H 1/46 H01L 21/205, 21 / 31,21 / 365 H01L 21 / 496,21 / 86 H01L 21 / 302,21 / 3065 H01L 21/461

Claims (14)

(57) [Claims] 1. A vacuum vessel provided with a gas supply means and a vacuum exhaust means, means for introducing a microwave into the vacuum vessel,
An electromagnetic horn for spreading microwaves and irradiating a large area, and a material that allows microwaves to pass through the vacuum vessel at a position between the microwave introduction means and the substrate to be processed. A microwave plasma processing apparatus, wherein a partition plate is provided. 2. A structure in which the inside of the electromagnetic horn becomes a part of a vacuum vessel by performing vacuum sealing using a material that transmits microwaves in the waveguide or at a portion near the entrance of the electromagnetic horn. The microwave plasma processing apparatus as described in the above. 3. The microwave plasma processing apparatus according to claim 1, wherein the electromagnetic horn is configured to emit a substantially plane wave from an opening. 4. The microwave plasma according to claim 2, wherein said vacuum seal is made of a material having high heat resistance while allowing microwaves to pass therethrough, and using a heat-resistant sealing material. Processing equipment. 5. The partition plate is disposed in a vacuum vessel.
The plasma processing apparatus according to claim 1, wherein the plasma processing apparatus is provided so as to be aligned with a substrate to be processed, and is configured so that plasma exists between the substrate and the partition plate.
5. The microwave plasma processing apparatus according to 2, 3, or 4. 6. The microwave plasma processing apparatus according to claim 5, wherein the distance between the partition plate and the substrate to be processed is set to be short at a place where the plasma density is high and to be far at a place where the plasma density is low. 7. The partition plate is formed in a curved shape such that a distance between the partition plate and a substrate to be processed is short at a place where the plasma density is high and is long at a place where the plasma density is low. The microwave plasma processing apparatus as described in the above. 8. A vacuum vessel provided with a gas supply means and a vacuum exhaust means, and means for introducing microwaves into the vacuum vessel, wherein the vacuum vessel has a whole or a part thereof having a conical or square shape. A weight or a polygonal pyramid, a structure for introducing a microwave from the apex to the inside, and at a position between the microwave introduction means and the substrate to be processed,
A microwave plasma processing apparatus comprising a partition plate made of a material through which microwaves can pass. 9. An electron cyclotron resonance (ECR) at a microwave frequency in said vacuum vessel.
9. The microwave plasma processing apparatus according to claim 1, further comprising a magnetic field generating means for causing a lotron resonance. 10. The microwave plasma processing apparatus according to claim 9, wherein said partition plate is provided in parallel with a substrate to be processed, and is installed so that an electron cyclotron resonance point exists between the substrate and the partition plate. 11. The method according to claim 1, wherein a compound containing fluorine or chlorine is used as the gas.
The microwave plasma etching apparatus according to 5, 6, 7, 8, 9 or 10. 12. The method according to claim 1, wherein a compound containing silicon is used as a gas.
11. The microwave plasma CVD apparatus according to 7, 8, 9 or 10. 13. The method according to claim 1, wherein oxygen or nitrous oxide is used as the gas.
The microwave plasma oxidizing apparatus according to 7, 8, 9 or 10. 14. A vacuum vessel provided with gas supply means and vacuum exhaust means, means for introducing microwaves into the vacuum vessel, and an electromagnetic horn for spreading microwaves and irradiating a large area, and The substrate to be processed is placed in a microwave plasma processing apparatus in which a partition plate made of a material through which microwaves pass is installed at a position in the vacuum vessel between the microwave introduction means and the substrate to be processed. And subjecting the substrate to microwave plasma processing.