JP2004095441A - Excimer lamp lighting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an excimer lamp lighting device capable of lowering an impression voltage by having excimer light efficiently emitted by the pulse (intermittent) supply of high-frequency voltages in a MHz band and capable of having a high-output vacuum ultraviolet ray emitted. <P>SOLUTION: In the excimer lamp lighting device composed of an excimer lamp 1 with discharge gas generating excimer molecules by discharge filled in a discharge vessel 2 and with a dielectric arranged between at least one of a pair of electrodes 5, 6 and a discharge space, and an excimer lamp lighting circuit that is connected to the pair of electrodes 5, 6 for lighting the excimer lamp 1 by supplying it at a high-frequency voltage, the pressure of the discharge gas is 10kPa or more and the high-frequency voltage has high frequencies of 1 MHz to 1GHz pulse modulated with a frequency of 1 kHz or more and a modulation signal of 1/10 or less of the high frequencies of 1 MHz to 1 GHz and a duty ratio of 10 to 80%. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an excimer lamp lighting device that generates excimer molecules by electric discharge and uses light emitted from the excimer molecules.
[0002]
[Prior art]
2. Description of the Related Art An excimer lamp, which is one of vacuum ultraviolet light emitting lamps having a high-efficiency radiation performance, has been used for processes such as curing, dry cleaning, sterilization, surface modification, and photo-CVD using a photochemical reaction.
[0003]
As an excimer lamp, a lamp utilizing a dielectric barrier discharge is known. For example, as disclosed in Japanese Patent Application Laid-Open No. 2-7353, a discharge gas for generating excimer molecules is formed in a discharge vessel. After filling, a dielectric barrier discharge (also known as an ozonizer discharge or a silent discharge, a new edition of the “Discharge Handbook” published by the Institute of Electrical Engineers of Japan, reprinted in June 2001, reprinted in 7th edition, page 263) to generate excimer molecules, and vacuum ultraviolet from the excimer molecules It emits light.
[0004]
In an excimer lamp using such a dielectric barrier discharge, it is known that, for example, when a rectangular wave voltage having a frequency of several tens of kHz is applied to the excimer lamp, vacuum ultraviolet light having high luminous efficiency can be obtained.
[0005]
On the other hand, when vacuum ultraviolet light is emitted using an excimer lamp lighting device, it is necessary to increase the output in order to shorten the processing time, but in order to increase the output, when trying to light at a frequency of several tens of kHz, It is necessary to apply a high voltage of about 5 kV. However, such high voltages create a troublesome insulation problem for excimer lamp lighting devices.
[0006]
Therefore, in order to avoid such an insulation problem, a frequency in the MHz band, which is lower than the applied voltage at several tens of kHz, is used (for example, at a frequency of several MHz, the applied voltage is about 1 kV. The application of the dielectric barrier discharge is considered.
[0007]
[Problems to be solved by the invention]
However, in the excimer lamp device, when it is attempted to operate at a frequency in the MHz band, the amount of radiation of vacuum ultraviolet light is smaller than when operating at a frequency of several tens of kHz, that is, the emission efficiency of excimer light is poor. Occurs. The reason is described below.
[0008]
First, the phenomenon of excimer light emission will be described in detail with reference to FIG. 9 in terms of the energy level of Xe (xenon) and the electron temperature.
FIG. 9 is a diagram showing a part of the energy level of Xe. Here, the Xe atom (Xe ( ¹ S ₀ )) in the ground state obtains energy by colliding with high-energy electrons during discharge. As a result, an excited state (Xe ^* (res), Xe ^* (met)) is obtained. The Xe atom that has reached the excited state changes to an Xe excimer by three-body collision with the Xe atom in the ground state (Xe ^* + Xe ^* + Xe → Xe ₂ ^* + Xe). The Xe excimer thus generated emits vacuum ultraviolet light having a wavelength of 172 nm by being de-excited.
[0009]
Therefore, when vacuum ultraviolet light is emitted by such a process, in order to increase the amount of vacuum ultraviolet light emitted, Xe atoms in the ground state are frequently excited to increase Xe atoms in the excited state. , And the Xe atom in the excited state must be changed to Xe excimer.
[0010]
Electrons during a steady discharge have various energies, and the energies are generally several eV, and few electrons have high energies of 8 eV or more necessary to excite Xe atoms in the ground state. Therefore, in the above process, in the former process, it is necessary to increase the ratio of the number of high-energy electrons by increasing the energy distribution of electrons.
The latter process is achieved by increasing the number of Xe atoms in the discharge, which is why conventional excimer lamps operate at relatively high gas pressures of 10 kPa or more.
[0011]
However, when a high frequency of 1 MHz to 1 GHz is continuously applied to the lamp, the above process is not performed efficiently as shown in FIG.
That is, immediately after the lamp is turned on, that is, immediately after the discharge is generated, the high-frequency electromagnetic energy input into the lamp is mainly absorbed by the electrons, and only the electrons are heated to a high energy state (high electron temperature). An electron in a high energy state collides with an Xe atom to give energy to the Xe atom, and generates a large amount of Xe excimer in an excited state. However, when a sufficient time (msec order or more) elapses from the discharge generation, the above collision process reaches a steady state, the electron temperature decreases, the gas temperature (atomic temperature), and the ion temperature rise and calm down. .
[0012]
As described above, when a high frequency of 1 MHz to 1 GHz is continuously applied to the lamp, immediately after the application of the high frequency voltage, the electron temperature rises rapidly and is in a very high state, and the light output is correspondingly high. Although it increases, it calms down to a steady state thereafter, and when the gas temperature increases, the unstable excimer molecules are liable to be broken, and the light output decreases.
[0013]
Thus, the following is found from the above. That is, the input power (power consumption) when the high frequency of 1 MHz to 1 GHz is continuously supplied and the input power (power consumption) when the high frequency of 1 MHz to 1 GHz is supplied in a pulsed (intermittent) manner. Under the conditions, when a high frequency of 1 MHz to 1 GHz is supplied to the lamp in a pulsed manner (intermittently), the voltage value in the pulse ON period (output period) may be higher than that of a continuous wave. Since the discharge can completely disappear during the pulse OFF period (pause period) and the temperature of the gas can be lowered, the energy distribution of electrons can be made higher and the ratio of the number of high energy electrons can be reduced. It is possible to increase the number of excited species and, consequently, the vacuum ultraviolet light.
[0014]
An object of the present invention is to supply a high-frequency voltage in the MHz band to an excimer lamp in a pulsed manner (intermittently) based on the above findings, thereby efficiently emitting excimer light and reducing the applied voltage. Another object of the present invention is to provide an excimer lamp lighting device capable of emitting high-output vacuum ultraviolet light.
[0015]
[Means for Solving the Problems]
The present invention employs the following means in order to solve the above problems.
[0016]
The first means is an excimer lamp in which a discharge gas that generates excimer molecules by discharge is filled in a discharge vessel, and a dielectric is disposed between at least one electrode of the pair of electrodes and the discharge space, An excimer lamp lighting circuit, which is connected to the pair of electrodes and supplies a high-frequency voltage to light the excimer lamp, wherein the excimer lamp has a pressure of the discharge gas of 10 kPa or more; The high-frequency voltage supplied from the lighting circuit is a high-frequency voltage of 1 MHz to 1 GHz, and a pulse of a modulation signal having a frequency of 1 kHz or more and 1/10 or less of the high frequency of 1 MHz to 1 GHz and a duty ratio of 10 to 80%. It is characterized by being modulated.
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION
An embodiment of the present invention will be described with reference to FIGS.
FIG. 1A is a cross-sectional view of the excimer lamp in the tube axis direction, and FIG. 1B is a cross-sectional view taken along AA in FIG. 1A.
[0018]
In FIG. 1, reference numeral 1 denotes an excimer lamp, 2 denotes a discharge vessel in which a discharge gas for forming excimer molecules such as xenon gas is filled at 10 kPa or more, and is formed in a bamboo ring shape; Is an inner tube of the discharge vessel 2, 5 is a first electrode formed on the outer tube 3 of the discharge vessel 2 in a mesh pattern, and 6 is a second electrode formed on the inner tube 4 of the discharge vessel 2. It is.
[0019]
As shown in FIG. 1, the discharge vessel 2 of the excimer lamp 1 has a double-tube structure in which an outer tube 3 and an inner tube 4 made of a dielectric material are coaxially arranged, and both ends of the outer tube 3 and the inner tube 4 are provided. Is closed, during which a discharge space is formed. When a high-frequency voltage, which will be described in detail later, is applied between the first electrode 5 and the second electrode 6 from a lighting circuit to be described later, a discharge occurs in the discharge vessel 2 and the excimer generated by being excited by the discharge is generated. Vacuum ultraviolet light is generated from the molecule, and the generated vacuum ultraviolet light can be radiated outside from between the mesh-shaped first electrodes 5 of the outer tube 3.
[0020]
The excimer lamps used in the experiments described below include three types of xenon (Xe) gas of 2 kPa, 10 kPa, and 60 kPa (each converted to 25 ° C.) containing xenon (Xe) gas as a discharge gas for generating excimer molecules. Used. The discharge vessel 2 was made of synthetic quartz glass, and the outer tube 3 had an outer diameter of 26 mm, the inner tube 4 had an outer diameter of 16 mm, a length of 25 cm, and an inner volume of 63 cc.
[0021]
FIG. 2 is a block diagram showing a configuration of a lighting circuit for lighting the excimer lamp 1.
In the figure, 7 is a high frequency generating circuit for generating a high frequency (reference frequency) of 1 MHz to 1 GHz, and 8 is a high frequency (reference frequency) of 1 MHz to 1 GHz. A modulation signal generation circuit for generating a pulse modulation signal having a duty ratio of 10 to 80% which is 1/10 or less of 1 GHz, a modulation amplification circuit 9 for generating and amplifying a pulse-modulated high-frequency voltage, and a pulse modulation circuit 10 This is a matching circuit for applying the applied high-frequency voltage to the excimer lamp 1.
[0022]
FIG. 3A is a diagram illustrating a pulse-modulated high-frequency voltage applied to an excimer lamp, and FIG. 3B is a diagram illustrating a light output of vacuum ultraviolet light emitted from the excimer lamp.
As shown in the figure, according to the present invention, a frequency voltage (reference frequency) of 1 MHz to 1 GHz is applied to the excimer lamp 1 at a frequency of 1 kHz or more and 1/10 or less of 1 MHz to 1 GHz, and By applying a high-frequency voltage modulated by a pulse modulation signal having a ratio of 10 to 80% and lighting the device, excimer light can be efficiently emitted, and high-output vacuum ultraviolet light capable of reducing the applied voltage can be obtained. Can be output.
[0023]
Next, the results of experiments with an excimer lamp lighting device that led to the knowledge of applying a high-frequency voltage under the above conditions to the excimer lamp are shown in the tables of FIGS.
[0024]
In this experiment, three kinds of excimer lamps shown in FIG. 1 having xenon (Xe) gas filling pressures of 2 kPa, 10 kPa, and 60 kPa were used, and in the lighting circuit shown in FIG. The high frequency (reference frequency) is changed variously in the range of 1 GHz, and the modulation signal generating circuit 8 changes the pulse modulation frequency in the frequency range of 100 Hz to 500 MHz and the duty ratio in the range of 5 to 90%. It was done.
[0025]
In these figures, the efficiency ratio refers to the input when the high frequency (reference frequency) is continuously supplied as shown in FIG. Under the condition that the power (power consumption) is equal to the input power (power consumption) when a high frequency (reference frequency) is supplied in a pulsed (intermittent) manner as shown in FIG. Represents the ratio of the light output of vacuum ultraviolet light (172 nm wavelength) when continuously supplied to the light output of vacuum ultraviolet light (172 nm wavelength) when supplied in the other pulsed (intermittent) manner. is there. In these tables, ○ indicates the experimental results in which the efficiency ratio was particularly improved.
[0026]
As shown in FIGS. 4 to 8, the following lighting conditions were found from the experimental results.
First, as shown in the table of FIG. 4, when the reference frequency is about 800 kHz, no improvement in the efficiency ratio is observed even if the reference frequency is applied with any high-frequency voltage modulated in a pulsed (intermittent) manner. Therefore, it is understood that the reference frequency is in the range of 1 MHz to 1 GHz.
[0027]
Also, as shown in the tables of FIGS. 5 to 8, it can be seen that the lower limit value of the pulse modulation frequency must be 1 kHz or more. This is presumably because when the pulse modulation frequency is 1 kHz or less, the pulse ON period in one cycle of the pulse modulation frequency becomes longer, and as a result, the state shown in FIG. Also, as shown in the tables of FIGS. 5 to 8, the upper limit of the pulse modulation frequency does not show any improvement in the efficiency ratio when the reference frequency is 1/10 or more. For example, no improvement in the efficiency ratio is observed at half the reference frequency. This is considered to be because the pulse ON period in one cycle of the pulse modulation frequency is short, that is, the period of the reference frequency is too short, and the input power per pulse to the excimer lamp is insufficient to excite the base Xe atoms. .
[0028]
Similarly, as shown in the tables of FIGS. 5 to 8, the efficiency ratio is improved in the range of the duty ratio of 10 to 80%. If the duty ratio is 10% or less, it is considered that the pulse ON period in one cycle of the pulse modulation frequency is too short, the input power to the excimer lamp is insufficient, and there is no time to generate excimer molecules. Further, when the duty ratio is 80% or more, the pulse ON period in one cycle of the pulse modulation frequency becomes longer, so that it is considered that the state shown in FIG. 10B is exhibited during the ON period.
[0029]
【The invention's effect】
According to the first aspect of the present invention, the pressure of the discharge gas in the excimer lamp is 10 kPa or more, the high frequency voltage supplied from the excimer lamp lighting circuit is a high frequency of 1 MHz to 1 GHz, the frequency is 1 kHz or more, and the frequency is 1 MHz or more. Since the pulse modulation is performed with a modulation signal having a duty ratio of 10 to 80%, which is 1/10 or less of a high frequency of 1 GHz, the light emission efficiency of the excimer light is increased even when the excimer lamp lighting frequency is set to the MHz band. As a result, the applied voltage can be reduced, and an excimer lamp lighting device capable of increasing the output of vacuum ultraviolet light can be realized.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of an excimer lamp according to the present invention in a tube axis direction and a cross-sectional view of the excimer lamp viewed from a direction perpendicular to the tube axis direction.
FIG. 2 is a block diagram showing a configuration of a lighting circuit of an excimer lamp according to the present invention.
FIG. 3 is a diagram showing a pulse-modulated high-frequency voltage applied to an excimer lamp and an optical output of vacuum ultraviolet light emitted from the excimer lamp according to the present invention.
FIG. 4 is a table showing experimental results in an excimer lamp lighting device.
FIG. 5 is a table showing experimental results in an excimer lamp lighting device.
FIG. 6 is a table showing experimental results in an excimer lamp lighting device.
FIG. 7 is a table showing experimental results in an excimer lamp lighting device.
FIG. 8 is a table showing experimental results in an excimer lamp lighting device.
FIG. 9 is a diagram showing a part of the energy level of Xe.
FIG. 10 is a diagram showing a high-frequency voltage of 1 MHz to 1 GHz continuously applied to an excimer lamp according to the related art and an optical output of vacuum ultraviolet light radiated from the excimer lamp.
[Explanation of symbols]
REFERENCE SIGNS LIST 1 excimer lamp 2 discharge vessel 3 outer tube 4 inner tube 5 first electrode 6 second electrode 7 high-frequency generation circuit 8 modulation signal generation circuit 9 modulation amplification circuit 10 matching circuit

Claims (1)

An excimer lamp in which a discharge gas that generates excimer molecules by discharge is filled in a discharge vessel, and a dielectric is disposed between at least one of the pair of electrodes and the discharge space,
An excimer lamp lighting circuit that is connected to the pair of electrodes and supplies a high-frequency voltage to light the excimer lamp;
An excimer lamp lighting device comprising
The pressure of the discharge gas in the excimer lamp is 10 kPa or more, and the high-frequency voltage supplied from the excimer lamp lighting circuit is a high frequency of 1 MHz to 1 GHz. An excimer lamp lighting device, wherein the pulse modulation is performed with a modulation signal having a duty ratio of 10 to 80% or less.

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