JP3215461B2 - Microwave excitation type ultraviolet lamp device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a microwave-excited ultraviolet lamp device used as a light source in an ultraviolet photochemical process.

[0002]

2. Description of the Related Art Conventionally, excimer lasers, deuterium lamps, xenon flash lamps and the like have been known as ultraviolet light sources used in ultraviolet photochemical processes and the like. In recent years, unlike excimer lasers, excimer lamps for extracting spontaneous emission light from excimer molecules have been developed.

By the way, SiH ₄ , Si ₂ H ₆ , C ₂ H
₂ and many other gas materials used in semiconductor processes are known to have strong light absorption properties in the vacuum ultraviolet region with a wavelength of 180 nm or less. Conventionally, an excimer laser and a deuterium lamp are known. For example discharge excitation F ₂ laser is a broad excimer laser that oscillates at a wavelength of 157 nm, as narrow as about 1 nm oscillation spectrum width, and excellent wavelength selectivity.

[0004]

However [0005] In the discharge excitation F ₂ laser of ultraviolet light source described above, the optimum operation is required more high pressure 6atm, 10 MW / cm ³ or more high-density excitation efficiency Also has a problem of as low as 0.1% or less.
Further, the deuterium lamp has a problem that the emission spectrum is continuous and the efficiency is extremely low at 0.01% or less.

Further, the present inventors have developed a microwave-excited ultraviolet lamp device as the above-mentioned excimer lamp, in which a discharge portion filled with a lamp gas is provided in a cylindrical or rectangular microwave resonator. However, in such a microwave excitation type ultraviolet lamp device, the microwave electric field is
Since the electric discharge is generated at the center of the microwave resonator, the discharge portion must be provided at the center of the microwave resonator.
Therefore, when used as a light source of vacuum ultraviolet light, in order to extract vacuum ultraviolet light to the outside, the inside of the microwave resonator must be evacuated or a vacuum propagation path for vacuum ultraviolet light extraction must be provided. There was a problem.

The present invention has been made in view of such a conventional situation, and it is possible to generate vacuum ultraviolet light with high efficiency, and to easily guide it to the outside and supply it to a desired portion. It is an object of the present invention to provide a microwave-excited ultraviolet lamp device capable of performing the above operation.

[0007]

That is, a microwave excitation type ultraviolet lamp device of the present invention has an outer cylinder having a hollow structure and an inner cylinder provided coaxially so as to protrude into the outer cylinder.
And an inductor formed by a side surface of the inner cylinder and a side surface of the outer cylinder.
Between the bottom of the inner cylinder and the bottom of the outer cylinder.
Impedance component with the capacitance component
A microwave resonator configured to generate resonance by being cut off , and a predetermined lamp provided inside and adjacent to the bottom of the outer cylinder or the bottom of the inner cylinder in the microwave resonator. A discharge portion filled with gas; and a window provided at the bottom of the outer cylinder or the bottom of the inner cylinder adjacent to the discharge portion and for guiding light generated in the discharge portion. .

[0008]

In the microwave-excited ultraviolet lamp device having the above-mentioned structure, a so-called reentrant type microwave resonator having an outer tube having a hollow structure and an inner tube provided coaxially so as to protrude into the outer tube. A microwave resonator is used. For this reason, instead of the central part in the microwave resonator,
A strong microwave electric field can be formed between the opposed inner cylinder bottom and outer cylinder bottom.

Therefore, a discharge portion filled with a lamp gas is provided adjacent to the outer cylinder bottom or the inner cylinder bottom, and a window for guiding light to the outer cylinder bottom or the inner cylinder bottom adjacent to the discharge section is provided. By providing, even if it is vacuum ultraviolet light,
It can be generated with high efficiency, and can be easily led to the outside and supplied to a desired part without, for example, evacuating the inside of a microwave resonator or providing a vacuum propagation path for deriving vacuum ultraviolet light. Can be.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the microwave-excited ultraviolet lamp device of the present invention will be described below with reference to the drawings.

FIGS. 1 and 2 show the configuration of a microwave-excited ultraviolet lamp device according to an embodiment of the present invention. In the drawings, reference numeral 1 denotes a microwave resonator. The microwave resonator 1 is of a so-called reentrant type and includes a metal outer cylinder 2 formed in a hollow cylindrical shape and a metal inner cylinder 3 provided coaxially with the outer cylinder 2. It is configured. Also, the inner cylinder 3 is, as shown by the arrow in the figure,
It is configured to be able to move along the central axis of the outer cylinder 2 so that impedance matching can be achieved.

At the bottom of the outer cylinder 2, there is provided a discharge section 5 which is hermetically isolated by a disk-shaped dielectric 4 made of, for example, alumina ceramics, quartz or the like. A predetermined lamp gas, for example, a rare gas, a halogen gas, a mixed gas of a rare gas and a halogen gas,
Hydrogen gas, deuterium gas, or the like is filled. The bottom plate 6 of the outer cylinder 2 adjacent to the discharge unit 5 is made of a material having high transparency to vacuum ultraviolet light, for example, MgF ₂ , CaF ₂ , Li
A window 8 provided with a flat plate 7 made of F, sapphire, or the like is provided. The window 8 is provided with a metal mesh 9.

The metal mesh 9 is for preventing microwave leakage, and it is preferable to use a highly conductive metal, for example, a mesh of copper, aluminum or the like. In the example shown in FIG. 1, the metal mesh 9 is provided inside the discharge unit 5, but may be provided outside the flat plate 7 (outside the discharge unit 5). In addition, as shown in FIG.
When disposing the metal mesh 9 inside the mesh, it is necessary to select a mesh made of a material having high corrosion resistance. In addition, it is necessary to appropriately select the roughness of the metal mesh 9 from the relationship between the efficiency for deriving light and the leakage of microwaves. In the present embodiment, a mesh of 20 mesh was used.

The microwave resonator 1 is provided with a microwave guide 10 for transmitting a microwave from a microwave generator (not shown) including a microwave oscillator, an isolator, a directional coupler, a stub tuner, and the like. The microwave guide 10 guides the inside of the microwave resonator 1.

In the microwave-excited ultraviolet lamp device having the above-described configuration, the microwave introduced into the microwave resonator 1 by the microwave guide 10 generates an inductance between the side surface of the inner tube 3 and the side surface of the outer tube 2. Component and a capacitance component created between the bottom surface of the inner cylinder 3 and the bottom surface of the outer cylinder 2, and a strong microwave electric field is generated between the bottom surface of the inner cylinder 3 and the bottom surface of the outer cylinder 2. I do. As a result, a lamp discharge occurs in the discharge unit 5, and the vacuum ultraviolet light generated by the lamp discharge can be extracted from the window 8.

For example, a mixed gas of F ₂ and He is used as a lamp gas, a mixing ratio F ₂ / He = 5/95 (%), a gas pressure is 20 Torr, and an oscillation frequency is 2450 as a microwave oscillator.
When a CW magnetron tube of MHz is used, vacuum ultraviolet light having two peaks centered at wavelengths of 157 nm and 166 nm is obtained as shown in the graph of FIG. I got it. Note that F ₂
The fluorescence output depends on the F ₂ concentration as shown in FIG.
In the case of 10 Torr, when the microwave injection power was 185 W and 310 W, the F ₂ concentration reached the maximum at 4%, and decreased at higher values. When the F ₂ concentration was 4%, that is, the mixing ratio was F ₂ / He = 4/96 (%), and the relationship between the total pressure and the F ₂ fluorescence output was examined, as shown in FIG. _{(2) The} fluorescence output reached its maximum at a total pressure of 5 to 10 Torr. Therefore, when a mixed gas of F ₂ and He is used as the lamp gas, F ₂
Preferably, the concentration is about 3 to 5% and the total pressure is about 5 to 15 Torr. The maximum output is a microwave injection power of 310 W
At that time, it was 18.9 W, and the internal efficiency was 6.2%.

As described above, according to this embodiment, the vacuum ultraviolet light can be generated with high efficiency. In addition, the discharge unit 5
Can be provided at the end in the microwave resonator 1, so that the vacuum ultraviolet light can be easily taken out from the window 8,
It can be supplied to a desired part. That is, for example, as in the case of using a cylindrical microwave resonator or a rectangular microwave resonator, the inside of the microwave resonator is evacuated, or a vacuum region for deriving vacuum ultraviolet light is provided in the microwave resonator. There is no need to provide.

Further, the light emitting section can be made to emit surface light,
A planar crystal window (flat plate 7) can be used. Further, by moving the inner cylinder 3 along the center axis of the outer cylinder 2, good impedance matching can be achieved without using, for example, a triple stub tuner or changing the resonator length. . Further, the discharge area can be changed by changing the cross-sectional area of the inner cylinder 3.

FIG. 6 shows another embodiment. In this embodiment, instead of the discharge portion 5 of the above embodiment, the upper surface and the side surface are formed of a dielectric material 4 such as ceramics, and the lower surface is formed of Mg.
Discharge portion 5a made of a flat plate 7 made of crystal or the like of F ₂ is provided, the metal mesh 9 is provided outside of the discharge portion 5a.

In the embodiment shown in FIG. 7, instead of the microwave resonator 1 of the above embodiment, a convex portion 20 protruding toward the inner cylinder 3 is formed at the bottom of the outer cylinder 2b. This shows an example using a microwave resonator 1b arranged so as to face each other. The discharge portion 5b is provided adjacent to the upper bottom portion of the projection 20. That is, the upper part of the discharge part 5b is formed of a dielectric material 4 such as ceramics, and the lower part of the discharge part 5b is a flat plate 7 made of MgF ₂ crystal or the like provided adjacent to the upper bottom part of the convex part 20. It is formed with. A window 8 is provided so as to guide vacuum ultraviolet light from inside the convex portion 20 through the flat plate 7.

In these embodiments, effects similar to those of the above-described embodiments can be obtained. Further, the structures of the microwave resonator 1, the discharge unit 5, the window 8, and the like can be appropriately changed. For example, in the embodiment shown in FIG. It is also possible to provide it on the bottom side of the device.

An example in which the present invention is actually applied to etching will be described below. FIG. 8 is a diagram of an apparatus in which an etching cell 11 is connected to the bottom plate 6 of the microwave resonator 1 shown in FIG. The etching cell 11 is provided with an etching gas introduction pipe 12 for filling the etching cell 11 with an etching gas and an etching gas discharge pipe 13 for discharging the etching gas. Then, a sample silicon wafer 14 was placed below the window 8 for extracting vacuum ultraviolet light, and the surface was irradiated with ultraviolet light to perform etching.

A mixed gas of F ₂ and He is used as a lamp gas, the mixture ratio is F ₂ / He = 4/96 (%), and the gas pressure is 15
Torr, C with oscillation frequency of 2450 MHz as microwave oscillator
A W magnetron tube was used. Microwave injection power is 31
It was set to 0W.

FIG. 9 shows the light irradiation dependency when a silicon wafer having a 50 nm thermal oxide film (SiO ₂ ) is used as the etching sample 14. The same mixed gas of F ₂ / He (= 4/96 (%)) as the lamp gas was used as the etching gas. The total pressure of the etching gas is 50 Torr and 100 Torr
There are two types. From the figure, when the total pressure is 50 Torr and the total pressure is 100 Torr, the etching rates of the thermal oxide film are 1.76 nm, respectively.
/ s, 3.83 nm / s, etching rate of Si substrate
0.28 nm / s, 0.77 at 50 Torr and 100 Torr total pressure
nm / s. From the above, the effectiveness of the microwave excitation type ultraviolet lamp device of the present invention for etching was confirmed.

[0025]

As described above, according to the microwave-excited ultraviolet lamp device of the present invention, even if it is vacuum ultraviolet light, it can be generated with high efficiency and can be easily led out. To a desired portion.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a configuration of a main part of an embodiment of the present invention.

FIG. 2 is a plan view of FIG.

FIG. 3 is a graph showing an emission spectrum of the example device.

FIG. 4 is a graph showing a relationship between F ₂ concentration and F ₂ fluorescence output in the apparatus of the embodiment.

FIG. 5 is a graph showing the relationship between the total pressure and the F ₂ fluorescence output in the apparatus of the embodiment.

FIG. 6 is a longitudinal sectional view showing a configuration of a main part of another embodiment of the present invention.

FIG. 7 is a longitudinal sectional view showing a configuration of a main part of another embodiment of the present invention.

FIG. 8 is a longitudinal sectional view showing a configuration of a main part of an apparatus in which the present invention is applied to etching.

FIG. 9 is a graph showing light irradiation time dependency when a silicon wafer having a thermal oxide film is etched using the apparatus of FIG. 8;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Microwave resonator 2 Outer cylinder 3 Inner cylinder 4 Dielectric 5 Discharge part 6 Bottom plate 7 Flat plate 8 Window 9 Metal mesh 10 Microwave guide 11 Etching cell 12 Etching gas introduction pipe 13 Etching gas discharge pipe 14 Sample

Claims (2)

(57) [Claims] An outer tube of claim 1 hollow structure, and a tubular possess among which is provided coaxially as to protrude to the outer cylinder, the side of the inner tube
And the inductance component created by the side of the outer cylinder,
A capacity formed between the bottom surface of the inner cylinder and the bottom surface of the outer cylinder.
Impedance component and impedance component.
A microwave resonator configured to cause vibration, and a discharge unit provided adjacent to the outer cylinder bottom or the inner cylinder bottom in the microwave resonator and filled with a predetermined lamp gas therein. A microwave-excitation type ultraviolet lamp device, comprising: a window provided at the bottom of the outer cylinder or the bottom of the inner cylinder adjacent to the discharge unit, for leading out light generated in the discharge unit. 2. A micro processing apparatus according to claim 1, further comprising a processing chamber having a processing gas introduction pipe and a processing gas discharge pipe outside said window and configured to be capable of accommodating an object to be processed. Wave excitation type ultraviolet lamp device.