JP2000216471A - Power measurement device of f2 laser - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an F2 laser power measurement device which enables power of laser beam to be measured always accurately. SOLUTION: A power measurement device 3 of an F2 laser 1 for measuring power of laser beam 11 oscillated from the F2 laser 1 has a red light detector 17 which measures intensity of red light 14 projected to the F2 laser 1 following oscillation of the laser beam 11 and an operation device 18 for operating power of the laser beam 11 based on intensity of the measured red light 14. Since power of the laser beam 11 can be thereby measured without projecting the laser beam 11 directly to the power measurement device 3, the power measurement device 3 is hardly broken and power of the laser beam 11 can be measured always accurately.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power measuring device for measuring the power of laser light oscillated from an F2 laser.

[0002]

2. Description of the Related Art Conventionally, an F2 laser which oscillates a laser beam having a wavelength of about 157 nm has been known, and is mainly used for precision processing such as laser lithography. In order to perform such precision machining satisfactorily, the power of the laser beam applied to the workpiece must be controlled to a predetermined value. To that end, the power of the laser beam emitted from the F2 laser must be controlled. It is necessary to measure accurately.

FIG. 7 shows a configuration diagram of an F2 laser provided with a power measuring device according to the prior art. In FIG. 1, an F2 laser 1 includes a laser chamber 2 in which a laser gas is sealed, a discharge is generated therein, and a laser beam 11 is oscillated, and a power measuring device 3 for measuring the power of the laser beam 11 emitted from the laser chamber 2. And a laser controller 4 that is electrically connected to the power measuring device 3 and controls the power of the laser beam 11.

In the laser chamber 2, for example, fluorine (F 2) and helium (He) are sealed as a laser gas at a predetermined pressure ratio, and a set of discharge electrodes 5 is provided at a predetermined position in the laser chamber 2. 5 are installed. The laser beam 11 is oscillated by applying a high voltage between the discharge electrodes 5 and 5 from a high-voltage power supply 6 outside the laser chamber 2 via a current introducing means (not shown).
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 path of the laser beam 11. The laser beam 11 is transmitted to the beam splitter 1
At 2, a part thereof is reflected downward in the drawing to become a sample laser beam 11 </ b> A, which is incident on a power measuring device 3 having a power detector 13 such as a photodiode, for example, to measure its power.

Then, the power measuring device 3 calculates the power of the laser beam 11 from the power of the sample laser 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 measured value of 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 of the F2 laser is as short as about 157 nm, the energy of photons (photons) that is inversely proportional to the wavelength is very large. Therefore, when the sample laser beam 11A enters the power detector 13,
There is a problem that the power detector 13 is damaged due to photon energy due to long-term use, and its power cannot be measured accurately.

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 an F2 laser power measuring device capable of always accurately measuring the power of laser light. .

[0011]

Means for Solving the Problems, Functions and Effects In order to achieve the above object, an invention according to claim 1 is an apparatus for measuring the power of a laser beam oscillated from an F2 laser. With the oscillation of the laser light, F2
A red light detector for measuring the intensity of the red light emitted from the laser, and a calculation device for calculating the power of the laser light based on the measured intensity of the red light are provided.

According to the first aspect of the present invention, the intensity of the red light emitted from the F2 laser along with the oscillation of the laser light is measured by the red light detector, and based on the measured intensity of the red light. The power of the laser beam is calculated by the calculation device. The intensity of the red light emitted from the F2 laser and the power of the laser light have a correlation with each other, and the power of the laser light is detected by measuring the intensity, so that the laser light is directly incident on the power measuring device. It is possible to detect the power without making it. Since the red light has a longer wavelength than the laser light and the energy of the photons is smaller, the red light detector is not damaged unlike the case where the laser light is incident on the power detector. Thereby, the failure of the power measuring device is reduced, and the operation rate of the F2 laser is improved. In addition, since the power of the laser beam of the F2 laser can always be measured accurately, precise power control can be performed based on the measured value. Accordingly, even when an F2 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.

First, a first embodiment of the present invention will be described with reference to FIGS. FIG. 1 shows a configuration diagram of an F2 laser provided with a power measuring device according to the present embodiment.
In the figure, an F2 laser 1 encloses a laser gas,
A laser chamber 2 for generating a laser beam 11 by causing a discharge therein, a power measuring device 3 for measuring the power of the laser beam 11 emitted from the laser chamber 2,
The laser light 1 is electrically connected to the power measuring device 3 and
And a laser controller 4 for controlling the power of the laser beam 11 to a predetermined value based on the measured value of the power.

A laser gas, for example, fluorine (F 2) and helium (He) are sealed in the laser chamber 2 at a predetermined pressure ratio, and a set of discharge electrodes 5 is provided at a predetermined position in the laser chamber 2. , 5 are installed. Then, based on an instruction from the laser controller 4, a high voltage is applied between the discharge electrodes 5 and 5 from the high-voltage power supply 6 via a current introducing means (not shown) to oscillate the laser beam 11 having a wavelength of about 157 nm. Let me. Generally, such a high voltage applied to the F2 laser 1 is applied in a pulsed manner, and the laser beam 11 of the F2 laser 1 oscillates in a pulsed manner.

The laser beam 11 passes through a rear window 9 provided at a rear end (left end in the figure) of the laser chamber 2 and is provided outside a rear mirror (left side in the figure) of the laser chamber 2. The laser beam is totally reflected by the laser beam 2, passes through the laser chamber 2, and passes through the front window 7 provided at the front end of the laser chamber 2. The laser beam 11 transmitted through the front window 7 partially transmits through the front mirror 8 and a part of the laser beam 11 is emitted to the outside. When the F2 laser 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, a grating, or a prism is provided instead of the rear mirror 10. Sometimes. 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.

At this time, it is known that the discharge generates red light 14 having a wavelength of about 700 nm from the laser chamber 2. As shown in the figure,
The red light 14 is emitted from the laser chamber 2 coaxially with the laser light 11 so as to surround the red light 14 and is radially spread. The intensity of the red light 14 and the power of the laser light 11 have a correlation with each other, and the power of the laser light 11 can be detected by measuring the intensity of the red light 14.

Hereinafter, the power measuring device 3 according to the present embodiment will be described.
The operation when measuring the power of the laser beam 11A will now be described in detail. A beam splitter 12 for sampling a part of the laser light 11 and the red light 14 is provided on an optical path of the laser light 11 and the red light 14 emitted from the laser chamber 2. Laser light 11
A part of the red light 14 is reflected by the beam splitter 12 downward in the figure, and the sample laser light 11A and the sample red light 14A (collectively referred to as sample light 19).
And enters the power measuring device 3.

Sample light 1 incident on the power measuring device 3
Reference numeral 9 denotes an ultraviolet filter 20 which does not transmit light having a wavelength close to the wavelength of the laser light 11 (about 157 nm) and transmits light having a wavelength close to the wavelength of the red light 14 (about 700 nm). As the ultraviolet filter 20, for example, BK7 made of optical glass is suitable. Further, a gas or liquid absorbing light close to the wavelength of the laser light 11 may be sealed in a sealed container.

By passing through such an ultraviolet filter 20, the sample laser beam 1
1A is removed, and only the sample red light 14A is
And enters the red light detector 17 provided with an optical element such as a photodiode. The red light detector 17 transmits an electric signal corresponding to the intensity of the incident sample red light 14A to the arithmetic unit 18 that is electrically connected. The arithmetic device 18 performs an arithmetic operation based on the received electric signal, calculates the power of the laser light 11, and transmits the value 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 detected by the power measuring device 3 and controls the power of the laser light 11 to be a predetermined value. I have.

FIGS. 2 and 3 are graphs showing an example of the relationship between the power of the oscillated laser light 11 and the intensity of the generated red light 14, wherein the vertical axis represents the intensity of the red light 14 and the horizontal axis represents the laser. This is the power of light 11. Such a relationship between the two changes variously depending on the composition of the laser gas inside the laser chamber 2 and the like. As shown in FIG. 2, when the power of the laser light 11 and the intensity of the red light 14 are substantially proportional, the power of the laser light 11 may be calculated from the intensity of the red light 14 by multiplying by a predetermined coefficient. . As shown in FIG. 3, when the intensity of the laser light 11 and the intensity of the red light 14 draw a curve, for example, the relationship between the two is stored in the arithmetic unit 18 as an arithmetic table. The power of the laser beam 11 may be determined based on the calculation table. Alternatively, the curve shown in the figure may be approximated to a higher-order curve, and the power of the laser beam 11 may be obtained by calculation.

Since the laser beam 11 oscillated from the F2 laser 1 is very well absorbed by oxygen in the air, the power of the laser beam 11 is greatly attenuated by passing through the air. In order to prevent this attenuation, in the present embodiment, as shown in FIG. 1, the optical path of the laser light 11 is covered with a sealing cover 22, and an ultraviolet filter 20 is installed in an opening 24 provided in the sealing cover 22. . And
The internal space covered by the sealing cover 22 is evacuated by a vacuum pump (not shown) or purged with a gas containing no oxygen by a purge means (not shown). With this configuration, the laser beam 11 is prevented from being attenuated, and even if a part of the sample laser beam 11A passes through the ultraviolet filter 20, it is greatly attenuated in the air.
Light incident on the red light detector 17 due to irregular reflection or the like is reduced.

In the above embodiment, a part of the laser light 11 and the red light 14 is extracted as the sample light 19 by the beam splitter 12 and the intensity of the sample red light 14A contained in the sample light 19 is measured. Eleven powers are always measured. 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 total reflection mirror is disposed at substantially the same position as the beam splitter 12 only when measuring the power of laser light. Then, the laser light 11 and the red light 14 totally reflected by the total reflection mirror, or light obtained by reducing the laser light 11 and the red light 14 with a filter or the like is made incident on the power measuring device 3, and the intensity of the red light 14 is May be used to detect the power of the laser beam 11. Alternatively, the power measuring device 3 may be arranged on the optical path of the laser light 11 without providing the beam splitter 12 and the total reflection mirror.

As described above, according to the present embodiment, the intensity of the red light 14 emitted from the laser chamber 2 with the oscillation of the laser light 11 is measured by the red light detector 17, and the measured value is calculated. The power of the laser beam 11 is detected by calculation by the device 18. Therefore, the power of the laser light 11 can be measured without directly inputting the laser light 11 to the red light detector 17. Since the red light 14 has a longer wavelength and a smaller photon energy than the laser light 11 oscillated from the F2 laser 1,
Red light detector 1 as in the case where laser light 11 is incident
7 is not damaged. Thereby, the failure of the power measuring device 3 is reduced, and the operation rate of the F2 laser 1 is improved. Further, since the power of the laser beam 11 can be accurately measured over a long period of time, precise power control based on the measured value can be stably performed for a long period of time. Thus, even when an F2 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.

Next, a second embodiment will be described with reference to FIG. FIG. 1 is a configuration diagram of a power measurement device 3 according to the present embodiment. As described above, the red light 14 is emitted from the F2 laser 1 coaxially with the laser light 11 and spreads radially around the laser light 11. In the present embodiment, the red light detector 17 is disposed at a predetermined distance from the center of the optical axis of the laser light 11 in the vertical direction at a predetermined distance larger than the beam diameter of the laser light 11 and at a position where the red light 14 passes. ing.
By arranging the red light detector 17 at such a position, the red light detector 17 can receive only the red light 14 without receiving the laser light 11. The intensity of the red light 14 is measured by the red light detector 17, and the power of the laser light 11 is calculated by the arithmetic unit 18 based on the measured value.

At this time, in order to prevent the laser light 11 from being irregularly reflected on optical components (not shown) and incident on the red light detector 17, the ultraviolet filter (not shown) is provided in front of the red light detector 17. May be arranged. In order to improve the measurement accuracy of the red light detector 17, the red light detector 17 is used.
A red light 14 may be focused on the red light detector 17 by disposing a lens (not shown) in front of the lens. Further, an amplifier (not shown) for amplifying the signal output of the red light detector 17 may be connected between the red light detector 17 and the arithmetic unit 18.

As described above, according to the present embodiment,
Since the power of the laser beam 11 can be calculated from the intensity of the red light 14 without providing the ultraviolet filter 20 and the beam splitter 12, the configuration of the power measuring device 3 is simplified. Further, the power measurement can be performed without sampling the laser beam 11 and there is no power loss of the laser beam 11 due to the sampling.
Power increases.

Next, a third embodiment will be described with reference to FIG. FIG. 1 is a configuration diagram of a power measurement device 3 according to the present embodiment. In the figure, a laser beam 11 and a red beam 14 emitted from an F2 laser 1 (not shown) enter a beam splitter 12 placed on the optical path. The beam splitter 12 is provided with a wavelength selection coating 12A made of, for example, a dielectric multilayer film so as to reflect only light near the wavelength of the red light 14 and transmit light near the wavelength of the laser light 11. This wavelength selective coating 12
A causes the laser beam 11 to pass through the beam splitter 12. On the other hand, the red light 14 is emitted from the beam splitter 12
The light is reflected downward in the figure to enter the power measuring device 3. Accordingly, the power measurement device 3 is provided with the ultraviolet filter 20.
Is not provided, the red light detector 17 outputs the laser light 1
It is possible to receive only the red light 14 without receiving 1. The intensity of the red light 14 is measured by the red light detector 17, and the power of the laser light 11 is calculated by the arithmetic unit 18 based on the measured value. Alternatively, at this time, the wavelength selection coating 12 of the beam splitter 12 is used.
A is a coating that reflects only light near the wavelength of the laser light 11 and transmits light near the wavelength of the red light 14, and measures the intensity of the transmitted red light 14 to measure the intensity of the transmitted red light 14.
May be calculated.

FIG. 6 shows another configuration example of the power measuring device 3 according to the present embodiment. In the figure, the power measuring device 3 is provided with a central opening 26 having a diameter through which the laser light 11 passes in the center, and a mirror 25 that totally reflects light near the wavelength of the red light 14. Then, instead of the beam splitter 12 having the wavelength selection coating 12A shown in FIG. 5, this mirror 25 is arranged. As a result, the laser beam 11 passes through the central opening 26 of the mirror 25.
, The surrounding red light 14 is reflected downward by a mirror 25 in the figure, and enters the power measurement device 3. Thus, the intensity of the red light 14 is measured, and the power of the laser light 11 is calculated by the arithmetic unit 18 based on the measured value.

As described above, according to the present embodiment,
The red light 14 enters the power measuring device 3 without sampling the laser light 11, and the power of the laser light 11 can be measured. That is, the laser light 11 by sampling
Since there is no power loss, the available power of the laser beam 11 increases. Furthermore, since most of the red light 14 can be incident on the power measuring device 3, the measurement accuracy of the intensity is improved, and the power measurement of the laser light 11 can be performed more accurately.

As described above, according to the present invention, the intensity of the red light 14 emitted from the laser chamber 2 with the oscillation of the laser light 11 is measured by the red light detector 17, and the measured value is calculated by the arithmetic unit. By calculating at 18, the power of the laser beam 11 is detected. Therefore, the laser light 11
Can be measured without directly entering the red light detector 17. Red light 14
Since the wavelength is longer than the laser light 11 oscillated from the F2 laser 1 and the energy of the photons is small, the red light detector 17 is not damaged unlike the case where the laser light 11 is incident. Thereby, the failure of the power measuring device 3 is reduced, and the operation rate of the F2 laser 1 is improved. Further, since the power of the laser beam 11 can be accurately measured over a long period of time, precise power control based on the measured value can be stably performed for a long period of time. Thus, even when an F2 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.

In the present invention, it has been described that the laser controller 4 controls the high voltage applied to the high-voltage power supply 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 including a power measurement device according to a first embodiment of the present invention.

FIG. 2 is a graph showing an example of the relationship between the power of laser light and the intensity of red light.

FIG. 3 is a graph showing an example of the relationship between the power of laser light and the intensity of red light.

FIG. 4 is a configuration diagram of a power measurement device according to a second embodiment.

FIG. 5 is a configuration diagram of a power measurement device according to a third embodiment.

FIG. 6 is a configuration diagram showing another configuration example of the power measurement device according to the third embodiment.

FIG. 7 is a configuration diagram of an F2 laser provided with a power measurement device according to the related art.

[Explanation of symbols]

1: F2 laser, 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, 11: laser light, 11A: sample laser light, 12: beam splitter, 12A: wavelength selective coating, 13: photodiode, 14: red light, 14A: sample red light,
17: red light detector, 18: arithmetic unit, 19: sample light, 20: ultraviolet filter, 22: sealed cover, 23:
Lens, 24: opening, 25: mirror, 26: central opening.

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Claims (1)

[Claims] 1. A laser beam (11) oscillating from an F2 laser (1)
Power measurement system for F2 laser (1)
In (3), a red light detector (17) for measuring the intensity of red light (14) emitted from the F2 laser (1) with the oscillation of the laser light (11), and a measured red light (14) A power measurement device (3), comprising: a calculation device (18) for calculating the power of the laser beam (11) based on the intensity of the laser beam (11).