JPH03138853A - Microwave discharge light source device - Google Patents

Abstract

PURPOSE:To reduce the limitation on the luminous wavelength area of vacuum ultraviolet rays and obtain efficient luminescence with high intensity by forming a discharge space with a groove provided on the outer periphery of the inner conductor of a coaxial line and a plate-shaped dielectric substance covering the groove, and providing multiple discharge spaces. CONSTITUTION:A discharge space 4 is formed with a groove 51 provided on the outer periphery of the inner conductor 2 of a coaxial line and a plate-shaped dielectric substance 3 covering the groove 5a, and multiple discharge spaces 4 are provided. The discharge space 4 generating plasma via a microwave discharge for discharge luminescence is formed with the groove 51 provided on the outer periphery of the inner conductor 2 and the plate-shaped dielectric substance 3 covering the groove 51, thus the plate-shaped dielectric substance 3 permeating the light can be used, and the material of the dielectric substance 3 has no limitation. Multiple discharge spaces 4 are provided, thus luminescence with a large total light quantity is obtained. The limitation on the luminous wavelength area of vacuum ultraviolet rays can be reduced, and efficient luminescence with high intensity can be obtained.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a light source device using microwave discharge,
In particular, the present invention relates to a microwave discharge light source device that can efficiently generate vacuum ultraviolet light with high brightness.

[Prior Art] FIG. 4 is an overview diagram showing a laser oscillation device using a conventional microwave discharge light source device disclosed in Japanese Patent Application Laid-Open No. 83-184259, and FIG. 5 is a diagram showing A-A in FIG. 6 is a sectional view taken along line A, and FIG. 6 is a sectional view taken along line BB in FIG. In the figure, (20) is an electrodeless lamp with a metal plasma generation medium such as rare gas or mercury sealed inside (30).
For example, it is formed by sealing off both ends (23) of an outer tube (21) and an inner tube (22) formed into a coaxial cylindrical shape with a transparent dielectric material such as quartz. (25) is an electrodeless lamp (
20) is a metal mesh film as an inner conductor provided coaxially on the outer peripheral side of the inner tube (22), and forms a discharge space (31) between it and the outer tube (21). (34) is an outer conductor that is formed in a cylindrical shape and constitutes a microwave cavity (35) having a structure of a coaxial line, which is a type of microwave circuit, with a metal mesh film (25) as an inner conductor. The inner surface of (34) is finished as a light reflecting surface. The electrodeless lamp (20) is arranged coaxially within the microwave cavity (35). (6) has a microwave cavity (3
5) is a waveguide connected to the waveguide (6), (7) is a microwave matching window formed in the waveguide (6), and (8) is a microwave oscillator provided at the other end of the waveguide (6). The magnetron, which is
(9) is a magnetron antenna that protrudes from the magnetron (8) into the waveguide (6), and (13) is a feed port provided at the connection between the waveguide (6) and the microwave cavity (35). The waveguide (6), the microwave matching window (7), the magnetron (8), and the power feed port (13) constitute a microwave power feeding means (14). (3G) is a laser rod disposed coaxially at the center of a cylindrical microwave cavity (35), (37) and (38) are laser rods (36), respectively.
) are a total reflection mirror for laser oscillation and a partial transmission mirror for laser oscillation, which are provided facing each other at both ends of the mirror.

Next, the operation of the above device will be explained. The microwaves generated by the magnetron (8) are radiated from the magnetron antenna (9) to the waveguide (6),
) is excited into the microwave cavity (35). The excited microwave causes the discharge space (31) of the electrodeless lamp (20) to discharge and emit light. This electrodeless lamp (20
) is formed in an annular shape as shown in FIG. or,
The microwave cavity (35) is formed into a coaxial cavity by an outer conductor (34) and a metal mesh film (25) serving as an inner conductor. The light emitted from the electrodeless lamp (20) is irradiated directly or reflected by the inner surface of the outer conductor (34) to the laser rod (36), which excites the excitation medium in the laser rod (36) and causes total internal reflection. Laser oscillation is performed by a laser resonator constituted by (37) and a partially transmitting mirror (38).The oscillated laser light is extracted from the partially transmitting mirror (38) side as a laser light output.

At this time, the metal mesh film (25) as an inner conductor constituting a part of the microwave circuit and the metal mesh film (25)
A discharge space (21) formed between the outer tube (21), which is a dielectric material and serves as an incident window for microwaves, is provided opposite to the outer tube (21).
In order to cause microwave discharge in 31), the microwave is incident only from one side of the plasma. A phenomenon in which the microwave mode of the coaxial mode used as a conductor becomes dominant does not occur, and discharge can be performed in the desired microwave mode. Furthermore, when the microwave circuit forms a microwave mode having an electric field component perpendicular to the boundary between the dielectric outer tube (21) and the plasma, as in the case of the coaxial line shown in FIG. (21) and the metal mesh film (25) as an inner conductor are placed facing each other, so the metal mesh film (25) also has a perpendicular electric field component, creating an electric field that penetrates the plasma. At this time,
Even if a conductive plasma is generated, there is a metal mesh film (25) that is several orders of magnitude more conductive than the plasma facing the outer tube (21), which is the microwave incidence window, so the terminal current of the incident microwave is low. flows through this metal mesh membrane (25),
The electric field near the metal mesh film (25) is forced to be perpendicular to the surface of the metal mesh film (25), and the electric field penetrating the plasma is maintained. Therefore, the microwave penetrates into the plasma, a current flows through the plasma, and a spatially-like discharge plasma is obtained from the continuity of the current.

Since such a uniform discharge is obtained, the laser oscillation device has a high efficiency in converting microwave energy into the discharge of the electrodeless lamp (20), and the outer tube (21) of the electrodeless lamp (20) is not abnormal. There is no risk of damage due to heating.

In addition, since the microwave penetrates into the plasma and a spatially-like discharge plasma is obtained, the proportion of light directly irradiated to the laser rod (3B) from the electrodeless lamp (20) increases, and the laser rod There is also an advantage that the efficiency with which the excited substance in (36) is excited is improved, and the efficiency of the entire device is also improved.

Although the device described above is a laser oscillation device, it can be configured in various ways depending on the type of microwave circuit and the method of configuring the discharge space (31), and can be used not only as a laser oscillation device but also as a variety of light sources. can do.

Next, the structure of the light source device will be explained.

FIG. 7 is a cross-sectional view of a light source device using a coaxial line as a microwave circuit. In the figure, (51) is the inner conductor of the coaxial line, (32) is a transparent dielectric material such as quartz,
(31) is a discharge space surrounded by the inner conductor (51) and the dielectric (32), (411) is a coaxial metal mesh film provided on the outer circumferential side of the dielectric (32), and the inner conductor ( 51)
Together, they form a microwave cavity. Discharge space (31)
The light emitted by the discharge is radiated in the entire circumferential direction through a metal mesh film (411) that does not transmit microwaves but allows light to pass through. Further, by making a part of the metal mesh film (411) not a mesh but a metal light reflection film that does not transmit either light or microscopic particles, light can be focused in a desired direction.

[Problems to be Solved by the Invention] In the conventional microwave discharge light source device as described above, the dielectric (32) can only be used in the shape of a tube (vibe), so the materials are limited, and therefore, it is difficult to use vacuum ultraviolet light. The emission wavelength range is also limited, and there is a problem in that it is difficult to emit light in the shorter wavelength region.

To explain this further, the emission wavelength range of the light source required for photoexcitation processes such as photoCVD and photoetching related to semiconductor manufacturing equipment is in the vacuum ultraviolet region of 200 nm or less, so the light from the light emitting part is transmitted. The material (dielectric material in the case of the above light source device) must also allow light of 20OnI11 or less to pass through.

However, the material that can be easily obtained in the tube shape and can be used in the vacuum ultraviolet region is synthetic silica glass (minimum transmission wavelength 160 rv), which has the problem of being unable to emit light of 180 nm or less because of the glass. Ta.

This invention has been made to solve these problems, and provides a microwave discharge light source device that is less subject to limitations on the emission wavelength range of vacuum ultraviolet light and can efficiently emit light at high brightness. With the goal.

[Means for Solving the Problems] A microwave discharge light source device according to the present invention uses a microwave having a coaxial line structure that generates a microwave electric field for generating plasma by microwave discharge and performing discharge light emission. It has a circuit, and generates plasma and discharges light in the discharge space formed between a conductor wall that constitutes a part of this microwave circuit and a dielectric material provided opposite to this conductor wall. In a system in which a plasma generation medium is enclosed and a microwave circuit forms a microwave mode with an electric field component perpendicular to the boundary between the dielectric and the plasma, the discharge space is a groove formed on the outer periphery of the inner conductor of the coaxial line. , and a plate-shaped dielectric covering the groove, and a plurality of discharge spaces are provided.

[Function] In the present invention, the discharge space in which plasma is generated by microwave discharge and discharge light emission is formed by a groove provided on the outer periphery of the inner conductor and a plate-shaped dielectric covering the groove. Because of this, a plate-shaped dielectric can be used as a dielectric that transmits light, and there are no restrictions on the material of the dielectric.
There are fewer restrictions on the emission wavelength range of vacuum ultraviolet light. Further, since a plurality of the discharge spaces are provided, light emission with high brightness and a large total amount of light can be obtained.

[Example] Fig. 1 is an overview diagram showing an embodiment of the present invention, Fig. 2 is a sectional view taken along line A-A in Fig. 1, and Fig. 3 is a cross-sectional view taken along line B-B in Fig. 2. FIG. In the figure, the parts with the same reference numerals as in FIGS. 4 to 6 are the same parts, and therefore the explanation will be omitted.

(1) is the outer conductor of the coaxial line, and (2) is the inner conductor, which together with the outer conductor form a microwave cavity (15).

Note that a part of the outer conductor (1) is a metal mesh (11) that does not transmit microwaves but allows light to transmit.

(51) is a groove provided on the outer periphery of the inner conductor (2).

This groove (51) is dug from the outer peripheral surface of the inner conductor (2) toward its center, and its bottom (52) is finished to form a flat surface. Also, the long plane direction is the inner conductor (
2) is provided so as to coincide with the axial direction. (53
) is a conductive wall that constitutes a part of the microwave circuit, and in this example, it is the wall surface of the groove (5I), or in other words, the wall surface of the groove (51).
The bottom surface of is used. (3) is a plate-shaped dielectric material provided opposite to the conductor wall (53), which is a sapphire plate in this embodiment. (4) is a discharge space formed between the conductor wall (53) and the dielectric (3) by covering the groove (51) with the dielectric (3); is filled with Xe gas. In this example, the discharge space (
4) divides the outer circumference into three equal parts and provides three locations. (5) is the end plate of the microwave cavity (15), (10) is the inner conductor (2
) is a cooling waterway installed in the

Next, the operation will be explained.

The microwaves generated by the magnetron (8) are radiated from the magnetron antenna (9) to the waveguide (6),
The microwave cavity (15) is excited via the power feed port (13). The excited microwave causes the three discharge spaces (4) to discharge and emit light, and a resonance line of 147 nll1 Xe is generated. Light emitted by discharge in the discharge space (4) is radiated in the entire circumferential direction through the metal mesh (11). Moreover, by using a metal reflective film that does not transmit light or microwaves as a part of the metal mesh (11) instead of a mesh, light can be focused in a desired direction.

At this time, in the above-mentioned microwave discharge light source device, the microwave is incident only from one side of the plasma, similar to those in FIGS. A phenomenon in which the wave mode becomes dominant does not occur, and discharge can occur in the desired microwave mode. Furthermore, when the microwave circuit forms a microwave mode having an electric field component perpendicular to the boundary between the dielectric (3) and the plasma as in the coaxial line shown in FIGS. 2 and 3, FIGS. An electric field is maintained through the plasma, similar to that of FIG.

Therefore, the microwave penetrates into the plasma, a current flows through the plasma, and a spatially-like discharge plasma is obtained from the continuity of the current. Since such a uniform discharge can be obtained, the efficiency with which microwave energy is converted into discharge light emission is high, and high output discharge light emission can be obtained.

Note that the above operation operates in the same manner for all three discharge spaces.

Next, in the above embodiment, a sapphire plate was used as the dielectric (3) and Xe gas was used as the plasma generation medium, but it is difficult to form the dielectric (3) into a cylindrical shape. If a MgF2 single crystal plate is used and D2 gas is used as a plasma generation medium, vacuum ultraviolet light of 110 to 160 na+ can be emitted.

The number of discharge spaces in which discharge light is emitted is not limited to three, but can be as many as can be provided around the outer periphery of the inner conductor (2). In this manner, by providing a plurality of light sources, it is possible to emit vacuum ultraviolet light with high brightness and a large total amount of light.

Furthermore, if the inner conductor (2) is cooled by the cooling channel (10) provided, the heat caused by the discharge can be efficiently removed, and the vacuum ultraviolet transmittance of the dielectric (especially sapphire glass) (
Transmittance decreases as temperature increases).

[Effects of the Invention] As explained above, the present invention forms a discharge space in which discharge light emission occurs by a groove provided on the outer periphery of an inner conductor of a coaxial line and a plate-shaped dielectric covering this groove, and further comprises: Since a plurality of the discharge spaces are provided, the emission wavelength range of the vacuum ultraviolet light is less limited, and there is an effect that light can be emitted over a wide range, efficiently, and with high brightness.

[Brief explanation of the drawing]

Fig. 1 is an overview diagram showing one embodiment of the present invention, Fig. 2 is a cross-sectional view taken along line A-A in Fig. 1, Fig. 3 is a cross-sectional view taken along line B-B in Fig. 2, and Fig. Fig. 4 is an overview diagram showing a laser oscillation device using a conventional microwave discharge light source device, Fig. 5 is a cross-sectional view taken along line A-A in Fig. 4, and Fig. 6 is a cross-sectional view taken along line B-B in Fig. 5. FIG. 7 is a cross-sectional view of a light source device using a coaxial line as a microwave circuit. In the figure, (1) is the outer conductor, (2) is the inner conductor, and (3)
is a dielectric, (4) is a discharge space, (6) is a waveguide, (8)
is a magnetron, (14) is a microwave power supply means, (1
5) is a microwave cavity, (51) is a groove, (52) is the bottom of the groove, and (53) is a conductor wall. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (1)

[Claims] It has a microwave circuit with a coaxial line structure that generates a microwave electric field to generate plasma by microwave discharge and discharge light emission, and a conductive wall and this A plasma generating medium that generates plasma and discharges light is enclosed in a discharge space formed between a dielectric body provided opposite to a conductor wall, and a plasma generation medium that generates discharge light is enclosed in a boundary between the dielectric body and the plasma by the microwave circuit. In a microwave discharge light source device in which a microwave mode with a vertical electric field component is formed, the discharge space is formed by a groove provided on the outer periphery of an inner conductor of a coaxial line and a plate-shaped dielectric covering the groove. A microwave discharge light source device characterized in that a plurality of discharge spaces are provided.