JP2000213983A - Power measuring device of vacuum ultraviolet laser - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power measuring device of a vacuum ultraviolet laser capable of always and exactly measuring a power of a laser light at a vacuum ultraviolet area. SOLUTION: The power measuring device 3 of a vacuum ultraviolet laser 1 for measuring a power of a laser light 11 at a vacuum ultraviolet area emitted from the vacuum ultraviolet laser 1 is provided with a fluorescent plate 15 for generating a fluorescence 14 having a strength corresponding to a power of laser lights 11, 11A incident; a fluorescence detector 17 for measuring a strength of the fluorescence 14 generated from the fluorescent plate 15; and an operation device 18 for operating the power of the laser light 11 based on the strength of the fluorescence 14 measured. Thus, the power of the laser light 11 can be measured by measuring the strength of the fluorescence 14 without directly introducing the laser light 11 to the power measuring device 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a power measuring device for measuring the power of laser light oscillated from a vacuum ultraviolet laser.

[0002]

2. Description of the Related Art Conventionally, a vacuum ultraviolet region of about 2 mm.
A vacuum ultraviolet laser that oscillates a laser beam having a wavelength of about 0 nm to 200 nm is known, and examples of such a vacuum ultraviolet laser include an ArF laser (193 nm) and an F2 laser (157 nm). The vacuum ultraviolet laser is mainly used for precision processing such as laser lithography. In order to perform such precision machining satisfactorily, the power of the laser light applied to the workpiece must be set to a predetermined value. In order to control the power of the oscillated laser light, It is necessary to measure.

FIG. 5 shows a configuration diagram of an F2 laser device having a power measuring device for measuring the power of a vacuum ultraviolet laser according to the prior art. In the same figure, F2 laser device 1
A laser chamber 2 in which a laser gas is sealed and a discharge is generated therein to oscillate a laser beam 11, a power measuring device 3 for measuring the power of the laser beam 11 emitted from the laser chamber 2, and a power measuring device A laser controller 4 that is electrically connected to the laser beam 3 and controls the power of the laser beam 11.

[0004] In the laser chamber 2, for example, fluorine (F2) and helium (He) are sealed as laser gases at a predetermined pressure ratio. A set of discharge electrodes 5, 5 is provided at a predetermined position in the laser chamber 2, and a high voltage is applied between the discharge electrodes 5, 5 from a high-voltage power supply 6 via a current introducing means (not shown). , Laser light 11
Is oscillating. The oscillated laser light 11 partially passes through a front mirror 8 provided on the front outside (right side in the figure) of the laser chamber 2 and is emitted to the outside.

In order to measure the power of the laser beam 11, a beam splitter 12 is provided on the optical axis of the laser beam 11. The laser beam 11 is transmitted to the beam splitter 1
The sample light 11A is partially reflected downward in FIG.
Then, for example, the light enters the power measuring device 3 having the photodiode 13 and the like, and the power is measured.

Then, the power measuring device 3 calculates the power of the laser beam 11 from the power of the sample beam 11A, and transmits this to the laser controller 4. The laser controller 4 outputs a command signal to the high voltage power supply 6 based on the power of the laser light 11, and controls a high voltage applied so that the power of the laser light 11 becomes a predetermined value.

[0007]

However, the above prior art has the following problems.

That is, since the wavelength of the laser beam 11 in the vacuum ultraviolet region is short, the energy of photons (photons) that is inversely proportional to the wavelength is very large. Therefore, the sample light 11
When A is incident on the power measuring device 3, the photodiode 13 is gradually degraded by the energy of the photons, the life is shortened, and the power cannot be measured accurately over a long period of time.

In addition, the measured value of the power of the laser beam 11 becomes inaccurate, so that the laser beam 11 controlled by the laser controller 4 is controlled based on the measured value.
Power fluctuates. As a result, there is a problem that the power of the laser beam 11 applied to the workpiece fluctuates and precision processing becomes defective.

The present invention has been made in view of the above problems, and has as its object to provide a vacuum ultraviolet laser power measuring apparatus capable of always accurately measuring the power of a laser beam. I have.

[0011]

In order to achieve the above object, a first object of the present invention is to provide a vacuum ultraviolet laser which measures the power of laser light in a vacuum ultraviolet region oscillated from a vacuum ultraviolet laser. In the power measuring device, a fluorescent plate that generates fluorescence having an intensity corresponding to the power of the incident laser light, a fluorescence detector that measures the intensity of the fluorescence generated from the fluorescent plate, and a laser based on the measured intensity of the fluorescence A computing device for computing the power of light.

According to the first aspect of the present invention, fluorescent light corresponding to the power of the incident laser light is generated by the fluorescent plate, and the intensity of the fluorescent light generated from the fluorescent plate is measured by the fluorescent light detector. The power of the laser beam is calculated by the calculation device based on the intensity of the fluorescence. As described above, by measuring the intensity of the fluorescent light, the power of the laser light can be measured without causing the laser light to directly enter the power measuring device. Fluorescent light has a longer wavelength than laser light in the vacuum ultraviolet region, for example, visible light, and has low photon energy, so that a photodiode or the like of a power measuring device is not damaged as in the case where laser light is incident. . Thereby, the failure of the power measuring device is reduced, and the operation rate of the vacuum ultraviolet laser is improved. In addition, since the power of the laser beam of the vacuum ultraviolet laser can always be measured accurately, precise power control can be performed based on the measured value. Accordingly, even when a vacuum ultraviolet laser is used as a light source for precision processing such as laser lithography, a workpiece can be accurately irradiated with laser light having a predetermined power, and good processing can be performed.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment according to the present invention will be described in detail with reference to the drawings. In each embodiment, the same reference numerals are given to the same elements as those used in the description of the related art and the drawings used in the description of the embodiment earlier than the embodiment, and the overlapping description will be omitted. I do.

An embodiment of the present invention will be described with reference to FIGS. In this embodiment, the vacuum ultraviolet laser is F
A description will be given taking a two-laser device as an example. FIG. 1 shows a configuration diagram of an F2 laser device provided with a power measuring device according to the present embodiment. In the figure, the F2 laser device 1
A laser chamber 2 in which a laser gas is sealed, a discharge is generated therein, and a laser beam 11 is oscillated, a power measuring device 3 for measuring the power of the laser beam 11 emitted from the laser chamber 2, and a power measuring device 3 A laser controller 4 that is electrically connected and controls the power of the laser beam 11 to a predetermined value based on the measured power of the laser beam 11.

In the laser chamber 2, for example, fluorine (F 2) and helium (He) are sealed at a predetermined pressure ratio as a laser gas.
A set of discharge electrodes 5, 5 is provided. A high voltage is applied between the discharge electrodes 5 and 5 from a high voltage power supply 6 via a current introducing means (not shown) based on an instruction from the laser controller 4 to oscillate the laser beam 11 having a wavelength of about 157 nm. I have. Generally, a high voltage applied to such an F2 laser device 1 is applied in a pulse form,
The laser beam 11 of the F2 laser device 1 oscillates in pulses.

The oscillated laser beam 11 passes through a rear window 9 provided at the rear end (left end in the figure) of the laser chamber 2 and is rearward outside the laser chamber 2 (left side in the figure).
, Is totally reflected by a rear mirror 10 provided in the laser chamber 2, passes through the laser chamber 2, and passes through a front window 7 provided at a front end of the laser chamber 2. A part of the laser beam 11 transmitted through the front window 7 is partially reflected by a front mirror 8 provided in front of the laser chamber 2 and returns to the inside of the laser chamber 2, but the remaining laser beam 11 passes through the front mirror 8. Partially transmitted and emitted to the outside. When the F2 laser device 1 is used as a light source for precision processing such as the laser lithography, a band-narrowing unit having a wavelength selection element such as an etalon or a grating may be provided instead of the rear mirror 10. is there.
This makes it possible to stabilize the wavelength of the laser beam 11 and narrow the spectral width of the wavelength, thereby more suitably performing precision processing.

On the optical axis of the laser beam 11, a beam splitter 12 for sampling a part of the laser beam 11 is provided. The laser beam 11 is partially reflected by the beam splitter 12 downward in the drawing, and enters the power measuring device 3 as sample light 11A.
The power measuring device 3 measures the power of the sample light 11A, and detects the power of the laser light 11 based on the power. Then, an electric signal corresponding to the power of the laser light 11 is output to the laser controller 4 which is electrically connected. The laser controller 4 outputs a command signal to the high-voltage power supply 6 based on the power of the laser light 11 detected by the power measuring device 3 to control the power of the laser light 11 to a predetermined value.

Hereinafter, the power measuring device 3 will be described in detail. Inside the power measuring device 3, a phosphor plate 15 having a surface coated with a phosphor 16 or contained therein is disposed on the optical axis of the incident sample light 11A. Such a fluorescent plate 15 has an intensity corresponding to the power of the incident sample light 11A and the sample light 1A.
Fluorescence 1 of wavelength longer than 1A (generally visible light)
4 is generated in a direction (downward in the figure) transmitting through the fluorescent plate 15. The generated fluorescent light 14 passes through the fluorescent plate 15 and enters a fluorescent light detector 17 that detects the intensity of the fluorescent light 14. The fluorescence detector 17 includes, for example, an optical element such as a photodiode 13 and transmits an electric signal corresponding to the intensity of the fluorescent light 14 emitted from the fluorescent plate 15 to an arithmetic unit 18 that is electrically connected. The arithmetic unit 18 performs an arithmetic operation based on the received electric signal, detects the power of the laser light 11, and transmits the value to the laser controller 4.

FIGS. 2 and 3 are graphs showing an example of the relationship between the power of the sample light 11A incident on the fluorescent plate 15 and the intensity of the fluorescent light 14 generated from the fluorescent plate 15, wherein the vertical axis represents the intensity of the fluorescent light 14, and FIG. The horizontal axis is the power of the sample light 11A. Such a relationship varies depending on the material of the phosphor 16. As shown in FIG. 2, when the power of the sample light 11A is approximately proportional to the intensity of the fluorescent light 14, the power of the sample light 11A may be calculated from the intensity of the fluorescent light 14 by multiplying by a predetermined coefficient. Further, as shown in FIG. 3, when the intensity of the sample light 11A and the intensity of the fluorescence 14 draw a curve, for example, the relationship between the two is stored in the arithmetic unit 18 as an arithmetic table, and this arithmetic operation is performed. The power of the sample light 11A may be obtained based on the table. Alternatively, the power of the sample light 11A may be calculated by approximating the curve shown in FIG.

The material of the fluorescent plate 15 is preferably such that it hardly transmits light in the vacuum ultraviolet region and transmits most of light having a wavelength close to the wavelength of the fluorescent light 14.
For example, BK7 or the like of optical glass is suitable. Thereby, the sample light 11A rarely reaches the fluorescence detector 17, and the fluorescence detector 17 is hardly damaged. Alternatively, for example, a fluorescent glass (Lumiras, trade name, manufactured by Sumita Optical Glass Co., Ltd.) containing a phosphor 16 therein
Etc. may be used. Further, as a material of the phosphor 16, a phosphate phosphor (commonly called phosphor), a rare earth ion, or the like is preferable. In order to prevent the sample light 11A irregularly reflected on the surface of the fluorescent plate 15 or the like from reaching the fluorescence detector 17, an ultraviolet ray which does not transmit light in the vacuum ultraviolet region and transmits light having a wavelength close to the wavelength of the fluorescence 14 is used. Filter 20
Is preferably provided on the front surface of the fluorescence detector 17.

Since the light in the vacuum ultraviolet region is very well absorbed by oxygen in the air, the power of the laser light 11 is greatly attenuated by passing through the air. In order to prevent this attenuation, in the present embodiment, the optical paths of the laser beam 11 and the sample beam 11A and the power measuring device 3 are covered with a sealing cover 22 to be substantially sealed as shown in FIG. Preferably, the internal space covered by the sealing cover 22 is evacuated with a vacuum pump (not shown) or purged with a gas containing no oxygen by a purge means (not shown). At this time, the arithmetic unit 1
8 may be outside sealing cover 22.

When the sample light 11A is continuously irradiated on the fluorescent plate 15 for a long time, the phosphor 16 on the portion of the sample light 11A which is irradiated by the photon energy of the sample light 11A is degraded, and the phosphor 16 is irradiated with the power of the incident sample light 11A. In some cases, the fluorescent light 14 having the reduced intensity may not be emitted.
In order to prevent the phosphor 16 from deteriorating, the fluorescent plate 1
5 is provided with a movable actuator 21 capable of moving the sample 5 by a predetermined distance in a direction perpendicular to the optical axis of the sample light 11A (the X and Y directions in the figure). Good. Then, the number of pulses of the pulsed laser light 11 is counted, and each time the sample light 11A is irradiated to the fluorescent plate 15 by a predetermined number of pulses, the moving plate 21 moves the fluorescent plate 15 by a predetermined distance to thereby generate the sample light 11A. Change the irradiation position. As a result, the deterioration of the phosphor 16 is reduced, and the life of the phosphor plate 15 is extended. In addition, phosphor 1
In order to prevent the deterioration of Sample No. 6, it is preferable to lower the power density of the sample light 11A. That is, on the optical axis of the sample light 11A and on the upstream side of the fluorescent plate 15, an optical component (neither is shown) for diffusing the sample light 11A such as a lens or a diffusion plate is arranged, and the power density is diffused. It is preferable that the sample light 11 </ b> A having a reduced height be incident on the fluorescent screen 15.

FIG. 4 shows another configuration example of the power measuring device 3 according to the present embodiment. In the figure, a phosphor 16 is coated on the surface of the fluorescent plate 15, and the fluorescent plate 15 is arranged obliquely with respect to the optical axis of the sample light 11A so that the sample light 11A has a predetermined incident angle θ. The fluorescent substance 16 generates fluorescent light 14 having an intensity corresponding to the power of the incident sample light 11A at a predetermined reflection angle φ. The generated fluorescent light 14 is received by a fluorescent light detector 17 arranged on the optical axis of the fluorescent light 14 and its intensity is measured, whereby the power of the sample light 11A can be detected.

In this embodiment, the beam splitter 12
Thus, a part of the laser light 11 is extracted as a sample light 11A, and the power of the laser light 11 is constantly measured by measuring the power of the sample light 11A. However, the present invention is not limited to such a form, and is also applicable to a case where the power of the laser beam 11 is periodically measured at predetermined time intervals (for example, once a day). It is. That is, in FIG. 1, the beam splitter 12 is not disposed during normal oscillation, and the beam splitter 1 is used only when measuring the power of the laser beam.
A total reflection mirror is arranged at substantially the same position as 2. Then, the laser beam 11 totally reflected by the total reflection mirror or a beam of the laser beam 11 reduced by a filter or the like is made incident on the power measuring device 3, and the laser beam 1 is generated based on the generated fluorescence 14.
1 may be detected. Alternatively, the power measuring device 3 is disposed on the optical axis of the laser beam 11 without providing the beam splitter 12 and the total reflection mirror, and the laser beam 1
1 may be directly measured.

As described above, according to the present embodiment, the laser light 11 or the sample light 11A is applied to the fluorescent plate 15 including the fluorescent material 16, and the intensity of the fluorescent light 14 emitted from the fluorescent plate 15 is measured. , The power of the laser beam 11 is detected. That is, the power of the laser beam 11 can be measured without causing the laser beam 11 to directly enter the power measuring device 3. Fluorescent light has a longer wavelength than laser light in the vacuum ultraviolet region, and the energy of photons is small.
The power measuring device 3 is not damaged as in the case where a laser is incident. Thereby, the failure of the power measuring device 3 is reduced, and the operation rate of the F2 laser device 1 is improved. Further, since the power of the laser beam 11 can be accurately measured for a long time, precise power control based on the measured value can be stably performed for a long time.
Thus, even when an F2 laser device is used as a light source for precision processing such as laser lithography, a workpiece can be accurately irradiated with laser light having a predetermined power, and good processing can be performed.

In this embodiment, the F2 laser device 1 has been described as an example of a vacuum ultraviolet laser.
The laser is not limited to this, and may be any laser that emits light having a wavelength in the vacuum ultraviolet region (about 20 nm to 200 nm). Examples of the vacuum ultraviolet laser include ArF laser and ArC laser.
l laser, Xe2 laser, Kr2 laser, Ar2 laser,
H2 laser, H2 Raman laser, Xe Auger laser and the like are included. The present invention is also applicable when measuring the power of these vacuum ultraviolet lasers.

Further, in the present embodiment, the laser controller 4 controls the high voltage applied to the high-voltage power supply in order to set the power to a predetermined value based on the measured value of the power of the laser beam 11. However, it is not limited to this. For example, a gas introduction unit (not shown) for introducing a laser gas into the laser chamber 2 may be controlled to control the composition of the laser gas inside the laser chamber 2.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an F2 laser device including a power measurement device according to an embodiment of the present invention.

FIG. 2 is a graph showing the relationship between the power of sample light and the intensity of fluorescence.

FIG. 3 is a graph showing the relationship between the power of sample light and the intensity of fluorescence.

FIG. 4 is a configuration diagram showing another configuration example of the power measurement device.

FIG. 5 is a configuration diagram of an F2 laser device provided with a power measuring device according to the related art.

[Explanation of symbols]

1: F2 laser device, 2: laser chamber, 3: power measuring device, 4: laser controller, 5: discharge electrode,
6: High voltage power supply, 7: Front window, 8: Front mirror, 9: Rear window, 10: Rear mirror, 1
1: laser light, 11A: sample light, 12: beam splitter, 13: photodiode, 14: fluorescence, 15:
Fluorescent plate, 16: phosphor, 17: fluorescence detector, 18: arithmetic unit, 20: ultraviolet filter, 21: moving actuator, 22: sealing cover.

Continuation of the front page F term (reference) 2G065 AA04 AB05 AB09 AB11 AB16 BA09 BA29 BC13 BC21 CA23 DA05 4E068 CA02 CC01 5F072 AA07 JJ20 YY20

Claims (1)

[Claims] A power measuring apparatus (3) for a vacuum ultraviolet laser (1) for measuring the power of a laser light (11) in a vacuum ultraviolet region oscillated from a vacuum ultraviolet laser (1). , 11A)
A fluorescent plate (15) for generating (14), a fluorescent detector (17) for measuring the intensity of the fluorescent light (14) generated from the fluorescent plate (15), and a laser based on the measured intensity of the fluorescent light (14). A power measuring device (3), comprising: a calculating device (18) for calculating the power of the light (11).