JP2002151761A - Reference light source for fluorine laser - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a reference light source for stabilizing a wavelength in a practical fluorine laser device when the fluorine laser device is used as a light source of a projection aligner for a stepper or scan exposure, etc. SOLUTION: This reference light source for fluorine laser has an emission spectrum near to a laser-light wavelength emitted from a fluorine laser device and is used to stabilize the oscillated wavelength of the laser light emitted therefrom by using the emission spectral line. It is provided with a window member 3 on one end of an almost cylindrical discharging container 1 that radiates a vacuum ultraviolet light, and the container 1 contains at least either of bromine molecular and bromine compound as a light emitting substance, as well as a rare gas as a starting buffer gas. Furthermore, a pair of band-like electrodes 4a and 4b are arranged on the outer surface of the container 1, apart from each other in the lengthwise direction of the container 1 in a manner that its side is surrounded.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reference light source lamp for stabilizing the oscillation wavelength of laser light, and more particularly to a reference light source for a fluorine laser device which emits light having a wavelength of 157 nm.

[0002]

2. Description of the Related Art As semiconductor circuits become finer and more highly integrated,
The projection exposure apparatus is required to improve the resolution. For this reason, the exposure light emitted from the light source has been shortened in wavelength, and as a light source for semiconductor lithography, an ArF excimer laser device that emits light having a wavelength shorter than the emission wavelength (365 nm) of a conventional mercury lamp has been used. Has been adopted. This ArF excimer laser device has an oscillation wavelength of 193 nm and a spectral width of 0.5 pm. Recently, a fluorine (molecule) laser device having a shorter oscillation wavelength has attracted attention as a next-generation light source. This fluorine laser device has an oscillation wavelength of 157 nm (strictly, 157.6299 nm) and a spectrum width of 0.2 pm.

Since the oscillation wavelength of the ArF excimer laser device and the fluorine laser device fluctuate during the discharge operation, the laser device needs wavelength stabilization control for maintaining the oscillation wavelength at a predetermined value. The level of stabilization is ± 0.05 n in the case of an ArF excimer laser device.
m, a fluorine laser device is required with an accuracy lower than that. In order to perform such wavelength stabilization control, means for measuring the oscillation wavelength from the laser device is required. Normally, by using a reference light source whose emission light is stable (the emission wavelength does not fluctuate), the emission light from this reference light source is compared with the light to be measured (laser light) at predetermined time intervals. A method of detecting the deviation of the wavelength of the light to be measured with the deviation is used.

FIG. 9 shows a wavelength measuring device of an ArF excimer laser device. Reference light is emitted from the reference light source, and the reference light enters the beam splitter through the shutter A,
Further, the light enters a linear sensor (CCD) as a photodetector via an etalon and a condenser lens. An interference fringe (fringe) is formed on the linear sensor, and the line width and center wavelength of the radiated light of the reference light source are recognized from the position data of the fringe.

Next, the shutter A is closed, and the light to be measured (laser light) having a wavelength of about 193.4 nm from the ArF excimer laser is guided through the entrance aperture, the shutter B, and the reflecting mirror, and further to the concave reflecting mirror and the etalon. . Then, the light to be measured, which is multiply interfered by the etalon, is irradiated on a linear sensor (CCD) via a condenser lens. On this linear sensor, a fringe is formed as in the case of the reference light source, and the line width and the center wavelength of the light to be measured are calculated from the position data formed on the CCD as in the case of the reference light source.

Since the wavelength of the reference light source does not easily change, it is considered that periodic measurement after the start of the laser operation is unnecessary if the measurement is performed only once or if a computer or the like in the apparatus recognizes it beforehand. . However, the position of the interference fringes on the linear sensor also slightly changes due to the reason that the refractive index of air in the etalon fluctuates with the elapse of the laser operation and the position of the mirror slightly fluctuates. In other words, the emitted light of the reference light source does not fluctuate, but fluctuates in the measurement system.
Or you will need it frequently. In other words, even if the state of the etalon or the mirror changes, the deviation of the oscillation wavelength of the laser light can be obtained by comparing the position data formed by the reference light source and the position data formed by the laser light of the ArF laser device in that state. It can be measured.

Although the above-described conventional example has been described for the case of an ArF excimer laser device, the same applies to a fluorine laser device, and control using a reference light source is required to stabilize the wavelength of the oscillating laser light. In particular, in the case of a fluorine laser device, the oscillation wavelength is in a vacuum ultraviolet region shorter than that of the ArF excimer laser, and the wavelength slightly changes due to a change in refractive index caused by density fluctuation due to a temperature of a transmitting gaseous medium. May be observed
The line width is small and the tolerance for the deviation of the oscillation wavelength is small.
Requires a reference light source that emits light having a wavelength very close to the oscillation wavelength of the fluorine laser device.

Here, the reference light source of the fluorine laser device is described in, for example, Japanese Patent Application Laid-Open No. 2000-249600. In this document, carbon (C), iron (Fe), sodium (Na) ), Fluorine (F), magnesium (Mg), aluminum (A
l), argon (Ar), calcium (Ca), scandium (Sc), chromium (Cr), manganese (Mn),
Nickel (Ni), copper (Cu), germanium (G
e), arsenic (As), bromine (Br), and platinum (Pt) are disclosed.

However, the disclosure of this document discloses that the wavelength 1
It is merely a list of atoms that can possibly emit light even in the vicinity of 57 nm, and does not specify a practically effective light-emitting atom in consideration of the light-emission intensity. In other words, even if a reference light source is made by selecting the atoms disclosed herein as a luminescent substance, the light intensity of the light emitted by the selected atoms is too low, or the relative intensity with another wavelength. Therefore, it cannot be sufficiently used as a reference light source of a fluorine laser device used as a light source of a projection exposure apparatus (stepper or scan exposure) which is a semiconductor manufacturing apparatus. Further, this document does not disclose any structure or shape of the discharge lamp, nor does it disclose what structure or shape is excellent as a reference light source.

[0010]

An object of the present invention is to provide a reference light source for stabilizing the wavelength of a fluorine laser device that emits light having a wavelength of 157.6299 nm. It is an object of the present invention to provide a practical light source as a reference light source when used as a light source of a projection exposure apparatus such as a scanner or scan exposure.

[0011]

In order to solve the above problems, a reference light source of the present invention has an emission spectrum close to the wavelength of laser light emitted from a fluorine laser device, and utilizes this emission spectrum line. A reference light source for a fluorine laser for stabilizing the oscillation wavelength of the laser light from the fluorine laser device, the reference light source further having a window member for emitting vacuum ultraviolet light at one end of a substantially cylindrical discharge vessel. In the container, there are bromine as a luminescent substance and a rare gas as a buffer gas for starting, and on the outer surface of the discharge container, a pair of generally band-shaped electrodes surrounding the side surface is arranged in the longitudinal direction of the discharge container. It is characterized by being arranged apart from each other.

Further, the invention according to claim 2 is characterized in that, of the pair of electrodes, an electrode arranged on the window member side is electrically connected to ground. Furthermore, the invention according to claim 3 is characterized in that, of the pair of electrodes, an area of the electrode provided on the window member side is larger than an area of the other electrode. Further, the invention according to claim 4 is characterized in that the inner diameter of the discharge space formed between the pair of external electrodes is not more than の of the inner diameter of the discharge space corresponding to the portion where the external electrodes are attached. I do.
Further, the invention according to claim 5 is characterized in that an interval between the pair of external electrodes is 5 mm or more and 150 mm or less.

[0013]

According to the first aspect of the present invention, it is found that it is effective to use a bromine atom as a luminescent material as a reference light source of a fluorine (F2) laser device. The structure and shape of the arranged electrodes are specified.

Regarding the first point, by enclosing bromine in the form of bromine molecules or bromine compounds in the discharge vessel, a large number of bromine-excited atoms are generated in the discharge plasma. A desired emission spectrum close to the wavelength can be efficiently obtained, and emitted light can be extracted to the outside through the window member of the discharge vessel. In particular,
The emission spectrum of the bromine atom is 157.6387 nm, which is the oscillation wavelength of the fluorine laser of 157.6299 n.
m, and the bromine atom has a higher light intensity at this emission wavelength than other atoms, so that it has sufficient practicality as compared with other atoms.

Regarding the second point, the entire shape of the discharge vessel is substantially cylindrical, a window member is provided at one end thereof, and the outer electrode is formed by discharging a cylindrical (strip-like) one surrounding the outer side surface of the discharge vessel. The containers are closely spaced apart from each other in the longitudinal direction of the container. With such a structure, when light emission from the discharge plasma generated in the discharge vessel is extracted from the center axis of the cylinder through a window, the optically brightest position in the discharge plasma is set in the cylindrical discharge vessel. Can be generated stably in the vicinity of the center, and since the optically brightest position can be easily estimated, in connection with an optical system such as a lens or a slit at the subsequent stage,
These position adjustments can be easily performed. In addition, the external electrode type structure eliminates the need for a structure for introducing the electrode rod into the discharge vessel, and the discharge vessel can be completely hermetically sealed. For this reason, problems such as leakage of the sealed gas and generation of cracks in the sealing portion as seen in conventional lamps can be solved satisfactorily, and as a result, stable light emission can be obtained for a long time.

Next, in the invention according to claim 2, since the electrode provided on the window member side of the pair of electrodes is electrically grounded, the outer surface of the discharge vessel in the vicinity of the window member is provided with another metal flange or the like. Even when the metal parts contact, the occurrence of undesired discharge between the metal parts and the electrodes can be suppressed.

Further, in the invention according to the third aspect, similarly to the case of the second aspect, when the metal component comes into contact with the vicinity of the window member, generation of an undesired discharge between the metal component and the electrode is further increased. Can be suppressed.

Further, in the invention according to claim 4, the inner diameter of the discharge space formed between the pair of external electrodes is set to be not more than 1/2 of the inner diameter of the discharge space corresponding to the portion where the external electrodes are attached. When light emitted from the discharge plasma generated in the discharge vessel is extracted from the center axis of the cylinder through a window, the optically brightest position in the discharge plasma can be easily specified, and the desired light emission at that position The spectral intensity can be increased.

Further, in the invention according to claim 5, the distance between the pair of external electrodes is set to 5 mm or more and 150 mm or less, so that the resistance component of the discharge plasma generated in the discharge vessel is reduced to the distance between the external electrodes. Change proportionally,
Within the power range required as the reference light source, the lamp input power can be easily set and the lamp input can be finely adjusted. If the distance is less than 5 mm, a short circuit may occur due to creeping discharge between the electrodes. If the distance exceeds 150 mm, bromine atoms easily capture electrons, and the discharge starting voltage becomes unnecessarily high.

[0020]

FIG. 1 shows a reference light source for controlling the oscillation laser light of a fluorine (F2) laser device according to the present invention. The discharge vessel 1 includes a main body case 2 and a window member 3. The main body case 2 has a substantially cylindrical shape.
Formed from borosilicate glass. The window member 3 is for extracting vacuum ultraviolet light generated inside the container, and is attached so that a substantially disk-shaped member made of synthetic quartz glass closes one end of the main body case 2. Here, one end 2a of the main body case 2 is connected to a step joint of glass whose thermal expansion coefficient is slightly changed to facilitate adhesion to the window member 3. The main body case 2 can be formed of synthetic quartz glass. In this case, since the main body case 2 is made of the same material as the window member 3, the hermetic sealing structure is obtained by directly bonding without employing a step joint structure. Can be formed. The main body case 2 can also use soda-lime glass, lead glass, alumina silicate glass, or the like, and the window member 3 can use magnesium fluoride in addition to synthetic quartz glass. In this case, since magnesium fluoride has a different expansion coefficient depending on the crystal direction due to the anisotropy of the crystal structure, there is an advantage that thermal shock resistance can be reduced by sealing the magnesium fluoride with the main body case in consideration of this direction. A numerical example of a discharge vessel has a length of 15
0 mm, outer diameter 20 mm, thickness 1 mm.

A pair of generally band-shaped electrodes 4 (4a, 4b) are wound around the outer surface of the main body case 2, and connection wires from the electrodes 4 (4a, 4b) are connected to an AC power supply 5. . The electrodes 4 (4a, 4b) are arranged so as to be separated from each other in the longitudinal direction of the discharge vessel 2 as described later, and one electrode is close to the window member 3 and the other electrode is from the window member 3. Form a structure that is separated. Electrode 4
For example, a thin film made of copper and aluminum is wound around the main body case 2 in close contact therewith. Alternatively, a metal member that has been molded in advance may be attached and fixed with an adhesive or a screw. To give a numerical example, the width of each of the electrodes 4 is 10 mm, the distance between the electrode 4 a and the end of the discharge vessel is about 20 mm, and the distance between the electrode 4 b and the window member 3 is 50 mm. The distance between the electrodes will be described later.
It is selected from the range of m or more and 150 mm or less.

The inside of the discharge vessel 1 is filled with bromine molecules or a compound thereof as a light emitting component, and a rare gas as a buffer gas for starting lighting. As an example, a bromine molecule or a compound thereof has a bromine atom of, for example, 0.015 μmo.
The rare gas is filled with 2.67 kPa of argon. When this lamp is turned on,
Discharge plasma 6 is formed between electrode 4a and electrode 4b.
In some cases, the discharge plasma is uniformly formed in the entire discharge vessel, but in this example, the discharge plasma is narrowed. The bromine compounds include hydrogen bromide (HBr), ammonium bromide (NH ₄ Br), and ethylene bromide (CH ₂ B).
r ₂ ) and ethyl bromide (CH ₃ Br).

Next, the point that the discharge vessel 2 is cylindrical, the point that the window member 3 is provided at one end of the discharge vessel, and the point that the generally strip-shaped electrode is provided on the outer surface of the discharge vessel will be described. In FIG. 2A, a metal flange 20, a filter F, and a slit SL are arranged on the window member side of the discharge vessel shown in FIG. The metal flange 20 is for mounting and fixing the discharge vessel 20, and the filter F is for selecting only a desired spectral line, and has a slit SL
Is for guiding the emitted light satisfactorily toward the optical system shown in FIG. Light is guided from the slit SL to the optical system shown in FIG. FIG. 2B is a cross-sectional view of the electrode 4 at an arbitrary position.

When a predetermined high-frequency voltage is applied to the pair of electrodes 4a and 4b, a discharge plasma 6 is generated inside the discharge vessel 2. This discharge plasma can be realized as a form in which the discharge is narrowed between the electrodes 4a and 4b, as shown in the figure, depending on how to select the electrode interval, gas pressure, and high-frequency voltage. In the case of such a discharge mode, the portion indicated by x in the figure can be regarded as the optically brightest position.
The high-frequency voltage can be in the frequency range of about 50 Hz to 100 MHz, which is a commercial frequency, and the voltage waveform can be a sine wave, a rectangular wave, pulse lighting by flyback, burst lighting, or the like. Then, by adjusting the positional relationship between the discharge vessel and the slit SL with reference to the optically brightest position, the amount of light flux incident on the slit SL can be determined to be the maximum.

Since both the discharge vessel 20 and the electrode 4 are substantially cylindrical, it can be considered that a voltage is uniformly applied from all around the discharge vessel. The position of the optically brightest position x can be easily determined from only the structure of. That is,
(B) Referring to the figure, the optically brightest position x is formed at the center of the circular section, so that the window member 3 can be aligned with the center reference. This means that the shape of the reference light source used in the fluorine laser device is such that the discharge vessel is cylindrical, the window member is provided at one end of the discharge vessel, and the roughly band-shaped electrode surrounds the outer surface of the discharge vessel. This means that the provision is advantageous.

Also, in FIG.
Are arranged on the window member 3, and the electrode 4b on the side close to the window member 3 is grounded. Therefore, the discharge vessel 3 is connected to the metal flange 2.
0 and the metal flange 20
Is normally grounded, so that the metal flange 20 and the electrode 4
It is possible to suppress the occurrence of an undesired discharge during the period b.
That is, stable discharge can be maintained between the electrodes 4a and 4b. This means that if the window material inserted into the flange and part of the cylindrical discharge vessel are sealed,
It is possible to prevent an undesirable discharge from being generated in the vicinity of the seal portion, thereby eroding the seal portion and impairing the airtightness. Even if it is not a metal flange, other metal parts are often arranged in the vicinity of the window member 3, and it is effective in such a case for the same reason.

Further, as shown in FIG. 3, it is more effective in terms of the above points that the electrode 4b is grounded and the width of the electrode 4b is made larger than that of the electrode 4a. This is because even if the electrode 4b on the side close to the window member 3 is grounded, if the surface area of the metal flange 20 is larger than the surface area of the electrode 4b, electrons flying from the electrode 4a will be captured by the electrode 4b. Not the metal flange 20
This is because they may fly toward the window member 3 and accumulate in the window member 3 as a result. It is not preferable that the window member 3 is charged because airtightness is impaired, and the present invention can solve such a problem by increasing the area of the electrode 4b closer to the window member 3. For example, the electrode 4a is 10 mm and the electrode 4b is 50 mm.

Next, the point of partially reducing the inner diameter of the discharge space will be described. FIG. 4 shows an embodiment of the reference light source of the present invention, which shows a structure in which a small tube portion is provided in a part of the discharge vessel 2 to reduce the inner diameter of the discharge space. Are the same as those shown in FIG. Specifically, it is configured by forming portions 30a and 30b of the discharge vessel corresponding to portions where the external electrodes 4a and 4b are provided, and a thin tube portion 31 therebetween.

As described above, the purpose of partially forming the small diameter portion in the discharge vessel is to increase the density of bromine atoms excited in the discharge plasma and (1) reduce the apparent size of the light source. And (2) to obtain higher illuminance. In order to satisfy these two requirements, it is necessary to simultaneously achieve the optimum electron temperature of the discharge plasma for efficiently generating excited bromine atoms and increase the density of excited bromine atoms per unit volume. Here, to optimize the electron temperature of the discharge plasma, it is determined by setting the product of the gas pressure and the inner diameter of the tube to a certain constant K [Pa · cm]. Therefore, in order to make the apparent size of the light source smaller and brighter, it is necessary to reduce the inner diameter of the tube and set the gas pressure to K / D [Pa] so as to obtain an optimum electron temperature. It is possible.

Even in such a case, the vicinity of the end of the thin tube portion 31 can be regarded as the optically brightest position X, and this optical position is determined by the lens L disposed outside the window member 3. The brightest position x forms an image on the slit SL1. That is, similarly to the above, the position of the optically brightest position x that can be formed at the end of the thin tube portion 31 can be easily estimated, and the position adjustment with the lens and the slit can be easily performed. In addition, in the case of the discharge vessel of this embodiment, the present invention can be applied to an optical system in which only a slit is provided without providing a lens as in the structure shown in FIGS.
The present invention can be applied to an optical system provided with a lens in the structure of FIG. As described above, the presence or absence of the lens is a problem of the optical system for measuring the wavelength, and does not affect the structure of the reference light source.

FIGS. 5A and 5B show another embodiment of the reference light source. This embodiment shows a state where the optically brightest position x is determined to be approximately the same size as the small diameter portion when the narrow tube of the discharge vessel is extremely short or the small diameter portion is short. Such a short structure with a small diameter part allows light emission from excited atoms and molecules that may be self-absorbing.
This is an effective means for minimizing the influence of the spread of the spectral line width due to self-absorption.

Next, the structure of another discharge vessel will be described. FIG. 6 shows a structure different from the structures shown in FIGS. 2 to 5 in that the entire inner diameter of the discharge space facing the portion where the electrodes are arranged is small. In such a structure, the discharge plasma 6 is uniformly spread throughout the inside of the discharge space, and an optically brightest position x is formed in the discharge plasma 6 without taking a narrowed form. Also in this structure, the window member 3 can be arranged at an optimal position in relation to the lens L and the slit SL in consideration of the position of the optically brightest position x, as in the case of the above embodiment. The effect of can be expected. As in this embodiment, the window member 3 is located at the inner side of the discharge space.
Is large, when the optically brightest position x is regarded as a point light source, a large solid angle can be expected, and more light can be extracted.

Next, the distance between the electrodes will be described.
FIG. 10 is an example showing an equivalent circuit of the lamp of the present invention. The electrodes and the dielectric constituting the discharge vessel can be regarded as a kind of capacitor. Further, the discharge plasma generated between the electrodes 4a and 4b can be regarded as the resistance component R. That is, the lamp of the present invention is configured by connecting the capacitor Ca formed by the electrode 4a, the capacitor Cb formed by the electrode 4b, and the resistance component R of the discharge plasma in series. C0 is the capacity due to the discharge plasma, and is ignored here because it is smaller than Ca and Cb. Here, when the distance between the electrodes 4a and 4b is changed, Ca,
Cb does not change, and only the resistance component R of the discharge plasma changes. Therefore, when the voltage applied between the electrodes is held constant and the distance between the electrodes is increased, the electric input to the discharge plasma decreases, and when the voltage applied to the electrodes is increased in proportion to the distance between the electrodes, the electric power applied to the discharge plasma decreases. Electric input also increases. Based on the concept of the equivalent circuit described above, the present inventors have found that the reference light source according to the present invention has a distance between electrodes of 5 to 40 mm when the outer diameter of the discharge vessel is 5 to 40 mm and the thickness is about 0.5 to 2 mm.
It has been confirmed that the size of the optically brightest position and good light output can be obtained in the range of 150 mm.

Next, the overall structure of a fluorine laser device using such a reference light source will be described with reference to FIG. The fluorine laser device includes a laser chamber 10, a narrow-band module 20, a waveform detection optical system 30, and a control circuit 40 as main components, and emits light having a wavelength of 157 nm to function as a light source for a projection exposure apparatus. Windows are provided at both ends of the laser chamber 10, and a fluorine gas and a buffer gas mainly composed of helium are sealed in the chamber. A pair of discharge electrodes facing each other are provided inside the laser chamber 10 at a predetermined interval, and when a high-voltage pulse is applied from a high-voltage generator (not shown), a discharge is generated between the discharge electrodes to generate a laser gas. A certain fluorine gas is excited. Although the laser light is generated by this excitation, the narrowing module 20 is provided with a prism or a diffraction grating for narrowing the spectrum width of the laser light. An output mirror is provided outside the other window of the laser chamber 10, and a beam splitter 31 is provided ahead of the output mirror, from which a part of the detection light for fairening the laser light is extracted. The waveform detection optical system 30 receiving this detection light has the structure shown in FIG. 9, that is, the signal from the linear sensor in FIG.

On the other hand, a reference light source 50 using bromine as a light emitting substance
Is also incident on the waveform detection optical system 30. This description can be similarly applied only by applying the lamp of the present invention as the reference light source in FIG.
Then, the radiation light from the reference light source 50 is also transmitted to the control circuit 40 as a signal from the linear sensor. In actual operation, the laser light from the fluorine laser device is periodically measured, and the reference light source 5
The emission light from 0 will be measured. The reason for this is as described above, because the state of the optical components such as the etalon and the mirror included in the waveform detection circuit 30 is slightly changed. Each time, both lights are detected and the laser of the fluorine laser device in that state is detected. The light is measured with reference to the wavelength of the reference light source. If there is a deviation in the oscillation spectrum of the laser light from the fluorine laser device, the control circuit 40
, A signal is sent to the narrow band module 20, and the optimization is achieved by moving the diffraction grating.

FIG. 8 shows a spectrum of the reference light source of the present invention. The vertical axis indicates the relative intensity of light at each wavelength of the total radiation emitted from the reference light source. In the figure, it can be seen that a high radiation intensity is shown at a wavelength of 157.6387 nm (in the figure, the wavelength is 163n).
It also has a higher peak around m, but at 157.6.
It can be seen that a high peak also exists at 387 nm).
The reference light source is a lamp containing 0.025 μmol / cc of bromine and 6.60 kPa of argon as a rare gas.

[0037]

As described above, the reference light source for stabilizing the wavelength of the fluorine laser device according to the present invention uses a bromine atom as a light-emitting substance, and therefore has a wavelength very close to the oscillation wavelength of the fluorine laser. Since light can be extracted and the light intensity at the wavelength is higher than that of other atoms, it has sufficient practicality.

Further, the discharge vessel has a generally cylindrical shape, a window member is provided at one end thereof, and the outer electrode is formed in a cylindrical (band) shape so as to surround the outer side surface of the discharge vessel in the longitudinal direction of the discharge vessel. Since it is separated from and closely attached to the discharge vessel, an optically brightest position in the discharge plasma generated in the discharge vessel can be stably generated almost in the vicinity of the center of the cylindrical discharge vessel. The position of the brightest position can be easily estimated. For this reason, these positions can be easily adjusted in relation to an optical system such as a lens or a slit to which the emitted light is guided.

Further, the external electrode type structure eliminates the need for a structure in which an electrode rod is introduced into the discharge vessel, and the discharge vessel can be completely hermetically sealed. For this reason, problems such as leakage of the sealed gas and generation of cracks in the sealing portion as seen in conventional lamps can be solved satisfactorily, and as a result, stable light emission can be obtained for a long time.

[Brief description of the drawings]

FIG. 1 shows a basic configuration of a wavelength stabilizing reference light source of a fluorine laser device according to the present invention.

FIG. 2 shows another embodiment of the reference light source according to the present invention.

FIG. 3 shows another embodiment of the reference light source according to the present invention.

FIG. 4 shows another embodiment of the reference light source according to the present invention.

FIG. 5 shows another embodiment of the reference light source according to the present invention.

FIG. 6 shows another embodiment of the reference light source according to the present invention.

FIG. 7 is an external view of the entire reference light source and fluorine laser device of the present invention.

FIG. 8 shows a spectrum of a reference light source according to the present invention.

FIG. 9 shows a schematic diagram of a wavelength measuring device.

FIG. 10 shows an equivalent circuit of the lamp of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Discharge container 2 Main body case 3 Window member 4 Electrode 5 AC power supply 6 Discharge plasma

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5F071 AA04 BB01 CC10 DD06 DD08 GG03 HH05 JJ10 5F072 AA04 GG03 HH05 JJ20 KK01 KK05 KK07 KK08 KK09 KK15 YY09

Claims (5)

[Claims] 1. A fluorine laser having an emission spectrum close to the wavelength of laser light emitted from a fluorine laser device, and stabilizing the oscillation wavelength of the laser light from the fluorine laser device using the emission spectrum line. In the reference light source for use, the discharge lamp has a window member that emits vacuum ultraviolet light at one end of a substantially cylindrical discharge vessel, and contains bromine as a luminescent substance and a rare gas as a starting buffer gas in the vessel. A reference light source for a fluorine laser, wherein a pair of generally band-shaped electrodes surrounding the side surface of the discharge vessel are spaced apart from each other in the longitudinal direction of the discharge vessel. 2. The fluorine laser reference light source according to claim 1, wherein an electrode disposed on the window member side among the pair of electrodes is electrically connected to a ground. 3. The reference light source for a fluorine laser according to claim 2, wherein, of the pair of electrodes, an area of an electrode provided on the window member side is larger than an area of the other electrode. 4. The fluorine according to claim 1, wherein the inner diameter of the discharge space formed between the pair of electrodes is not more than 1/2 of the inner diameter of the discharge space corresponding to the portion where the external electrode is attached. Reference light source for laser. 5. The fluorine laser reference light source according to claim 1, wherein a distance between said pair of electrodes is 5 mm or more and 150 mm or less.