JP2003214949A - Monitoring device and ultraviolet laser device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a monitoring device and an ultraviolet laser device capable of constantly and accurately measuring pulse energy. <P>SOLUTION: The monitoring device detecting the pulse energy of a laser beam 21 having an ultraviolet wavelength is provided with a light quantity sensor 38 measuring the pulse energy of a sample beam 37 obtained by sampling a part of the leaser beam 21 and a sensor 39 for calibration calibrating the light quantity sensor 38 by measuring the pulse energy of the sample beam 37. The device has a shielding means 48 so that the sample beam 37 is not made incident when the sensor 39 for calibration is out of calibration service, and determines timing for calibration based on at least either one of an operating time T of the ultraviolet laser device or a pulse oscillation frequency C of the laser beam 21. The ultraviolet laser device is equipped with the monitoring device. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a monitor device and an ultraviolet laser device for accurately measuring pulse energy of laser light having an ultraviolet wavelength.

[0002]

2. Description of the Related Art Conventionally, in a laser device such as an excimer laser device that oscillates a laser beam having an ultraviolet wavelength, a monitor device for measuring the pulse energy of the laser beam has been known. It is shown. FIG. 18 shows an excimer laser device provided with a monitor device according to a conventional technique, and the conventional technique will be described below with reference to FIG.

The excimer laser device has a laser chamber 112 in which a laser gas containing fluorine is sealed.
Inside the laser chamber 112, a pair of main electrodes 11
4, 115 are arranged to face each other in the vertical direction in FIG. By applying a pulsed high voltage from the high-voltage power supply 123 between the main electrodes 114 and 115, discharge is caused to excite the laser gas and pulsed laser light 121 is generated.

The laser beam 121 generated inside the laser chamber 112 enters a narrowing unit 131 on the rear side (left side in FIG. 18) and is narrowed by a grating (not shown) or the like. Narrow band laser light 1
21 partially penetrates the front mirror 116,
Emit forward.

A main beam splitter 122 is arranged on the optical axis of the emitted laser light 121, and the laser light 12
A part of the sample light 137 is reflected upward in FIG.
The light amount sensor 138 is made to enter. Light intensity sensor 13
For example, 8 is generally composed of a silicon photodiode and outputs an electric signal according to the magnitude of the pulse energy of the sample light 137.

The laser controller 129 detects the pulse energy of the laser light 121 based on the output signal of the light quantity sensor 138. Then, the detected laser light 12
Based on the pulse energy of 1, the value of the high voltage applied between the high-voltage power supply 123 and the main electrodes 114 and 115 is controlled so that this becomes a desired value. This is called constant pulse energy control.

[0007]

However, the above-mentioned prior art has the following problems. That is, the laser light 121 emitted from the excimer laser device 111 or the fluorine molecular laser device has a wavelength in the ultraviolet region, and when it is irradiated for a long time, the light amount sensor 13 is emitted.
The photodiode of No. 8 is deteriorated, and it becomes difficult to measure the pulse energy accurately. Further, the main beam splitter 121 and the optical components for propagating the sample light 137 to the light quantity sensor 138 are also deteriorated by the irradiation of the laser light 121 and the like. Therefore, the intensity of the sample light 137 guided to the light amount sensor 138 is attenuated, which makes it difficult to measure the pulse energy accurately. As a result, there is a problem that even if the pulse energy constant control is performed, the pulse energy does not reach a desired value, and the exposure is not appropriately performed, for example, when the laser light 121 is applied to the exposure.

For example, if the photodiode is deteriorated and its detection sensitivity is lowered, the intensity of the output signal from the light quantity sensor 138 is reduced even if the output of the laser light 121 is not changed. The laser controller 129 is the light amount sensor 1
Based on the output signal from 38, the pulse energy constant control is performed so that it has a predetermined intensity, so that the pulse energy value becomes larger than the desired value. Further, the deterioration of the above-described optical components also causes the intensity of the sample light 137 guided to the light amount sensor 138 to be attenuated, and the same problem occurs.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a monitor device and an ultraviolet laser device capable of always accurately measuring pulse energy.

[0010]

In order to achieve the above-mentioned object, the present invention provides a sample obtained by sampling a part of laser light in a monitor device for detecting pulse energy of laser light having an ultraviolet wavelength. A light amount sensor for measuring the pulse energy of light and a calibration sensor for measuring the pulse energy of sample light to calibrate the light amount sensor are provided. As a result, the light amount sensor can be calibrated, so that the pulse energy can always be measured accurately.

Further, according to the present invention, the calibration sensor has a shielding means for preventing the sample light from entering except during calibration,
Alternatively, an attenuator for attenuating the sample light is provided. As a result, deterioration of the calibration sensor is reduced, and accurate calibration can be performed for a long period of time.

Further, according to the present invention, the shielding means or the damping means is arranged on the upstream side of the diffusion plate arranged in front of the calibration sensor. As a result, the diffusion plate is not irradiated with the sample light except at the time of calibration, and changes in characteristics such as the transmittance of the diffusion plate are unlikely to occur, so that the measurement by the calibration sensor becomes accurate.

Further, according to the present invention, the optical path of the sample light entering the light quantity sensor and the optical path of the sample light entering the calibration sensor are shielded from each other. This allows
Accurate measurement because light other than the object to be measured does not enter the sensor.

Further, according to the present invention, the optical path of the sample light incident on the light quantity sensor and the optical path of the sample light incident on the calibration sensor are common, and the sample light is measured when the pulse energy of the sample light (37) is measured. Place the light intensity sensor (38) at the position where (37) is incident, and use the sample light (37) for calibration.
It is provided with a sensor positioning means for arranging the calibration sensor (39) at a position where is incident. By making the optical path common, if the optical components on the optical path are contaminated, the light quantity sensor and the calibration sensor are equally affected, so that the calibration becomes accurate. Further, it is not necessary to provide a plurality of optical paths, which simplifies the structure of the optical paths.

The present invention further comprises a laser controller for determining the degree of deterioration of the optical component on the optical path based on the comparison between the output of the calibration sensor during initial calibration and the output during subsequent calibration. There is. As a result, it is possible to reduce the number of measurements and calibrations in the state where the optical components are deteriorated, and it is possible to measure the pulse energy accurately.

The present invention further comprises a controller for determining the degree of deterioration of the light quantity sensor based on the calibration by the calibration sensor and issuing a warning when the degree of deterioration is larger than a predetermined degree. As a result, the measurement of the pulse energy is not performed by the light quantity sensor that is greatly deteriorated, and the measurement is always performed accurately.

Further, the present invention is provided with a controller for deciding the calibration timing based on at least one of the irradiation time of the sample light to the light quantity sensor and the pulse oscillation number. Deterioration of the light amount sensor is caused by irradiating the sample light for a long time or over a large number of pulses. Therefore, by determining the calibration timing based on these factors, it is possible to perform calibration at appropriate timing.

Further, by providing such a monitor device, the ultraviolet laser device can also accurately measure the pulse energy of the laser light and accurately control the pulse energy to be constant, for example, based on this. .

[0019]

DETAILED DESCRIPTION OF THE INVENTION Embodiments of the present invention will be described in detail below with reference to the drawings. First, the first embodiment will be described. FIG. 1 shows a configuration diagram of a fluorine molecular laser device according to the present embodiment. In FIG. 1, a fluorine molecular laser device 11 includes a laser controller 29 that controls the entire device and a laser chamber 12 that seals a laser gas containing fluorine.

Inside the laser chamber 12, a pair of main electrodes 14 and 15 are arranged facing each other in the vertical direction in FIG. The laser controller 29 outputs an instruction to the high voltage power supply 23 to apply a pulsed high voltage between the main electrodes 14 and 15. As a result, discharge is caused to excite the laser gas, and pulsed fluorine molecular laser light 21 (hereinafter referred to as laser light 21) is generated.

A front window 17 and a rear window 19 for transmitting the laser light 21 are attached to the front and rear of the laser chamber 12, respectively. A front slit 26 and a rear slit 27 each having an opening are arranged in front of and behind the laser chamber 12. Laser light 2 generated inside the laser chamber 12
1 passes through the rear window 19 and enters the rear single line unit 30 (on the left side in FIG. 1).

The single line unit 30 includes, for example, two dispersion prisms 28, 28 and a rear mirror 18 that totally reflects the laser light 21. At this time, the laser light 21 has strong line light with a long wavelength (center wavelength 15
7.63 nm) and weak line light with a short wavelength (center wavelength 157.52 nm) are mixed.

Since the strong line light and the weak line light have different wavelengths, there is a difference in the refraction angle when entering and exiting the dispersion prisms 28, 28. Therefore, while the strong line light and the weak line light pass through the two dispersion prisms 28, 28, their optical paths are gradually shifted.

As a result, the strong line light that has passed through the dispersion prisms 28, 28 passes through the openings of the slits 26, 27 and exits from the front mirror 16. In contrast,
The weak line light is shifted in its optical path while passing through the two dispersion prisms 28, 28, and is blocked by either of the slits 26, 27 so that it does not oscillate. Fluorine molecular laser device 1
In No. 1, by oscillating only the strong line light in this way, the wavelength of the laser light 11 is made into a single line, and the spectral line width is narrowed.

The single line conversion unit 30 is surrounded by a single line conversion box 31. The single line box 31 is connected to a purge gas cylinder 35 which is filled with a purge gas having a low reactivity and being clean and containing no oxygen, and the inside thereof is always filled with the purge gas. Nitrogen is generally used as the purge gas,
An inert gas such as helium may be used.

The single-lined laser light 21 is
The light passes through the windows 17 and 19 and is amplified while being reflected between the front mirror 16 and the rear mirror 18. Part of the light partially passes through the front mirror 16 and is emitted forward. A main beam splitter 22 is arranged on the optical axis of the emitted laser light 21, and a part of the laser light 21 is reflected upward in FIG. Laser light 2 transmitted through the main beam splitter 22
1 enters an exposure device 25 such as a stepper and is used as the exposure light.

An optical path between the laser chamber 12 and the single line unit 30, an optical path between the laser chamber 12 and the monitor device 36, and an optical path between the laser chamber 12 and the exposure unit 25 are not shown. It is surrounded by an enclosure. A purge cylinder (not shown) filled with a low-reactivity, oxygen-free, clean purge gas is connected to the enclosure, and the interior of the enclosure is always filled with the purge gas. As a result, oxygen that absorbs ultraviolet rays is removed from the optical path, so that the laser light 21 that passes through the optical path is less likely to be absorbed by oxygen. This is the same in all the following embodiments.

Sample light 37 incident on the monitor device 36
Is partially reflected to the right in FIG. 1 by the first beam splitter 40 and enters the light amount sensor 38. Light intensity sensor 38
Is provided with, for example, a silicon photodiode as a sensor, and outputs an electric signal according to the magnitude of the pulse energy of the sample light 37. Laser controller 2
Reference numeral 9 detects the pulse energy of the laser light 21 based on the output signal of the light quantity sensor 38.

The monitor device 36 also includes a calibration sensor 39 for calibrating the light amount sensor 38. First
Part of the sample light 37 that has passed through the beam splitter 40 is reflected to the right in FIG. 1 by the second beam splitter 41, and enters the calibration sensor 39. At this time, between the second beam splitter 41 and the calibration sensor 39, there is provided a shutter 48 which is a light shielding means which can be opened and closed by a signal from the laser controller 29, so that the sample light 37 can be shielded. ing.

The sample light 37 transmitted through the second beam splitter 41 is incident on the damper 42. The damper 42 is
The laser light is very rarely reflected, and most of the sample light 37 incident on the damper 42 is absorbed. As the damper 42, in order to prevent reflection of the sample light 37, for example, an aluminum plate plated with matt black nickel is suitable.

At this time, the portion of the shutter 48 exposed to the light may be formed of an absorber such as the damper 42. Further, the shutter 48 may be tilted at about 45 degrees with respect to the optical axis of the sample light 37, and the sample light 37 reflected by the shutter 48 may be absorbed by the damper 42.

Alternatively, instead of completely blocking the sample light 37, the shutter 48 may be constituted by a light-reducing member and attenuated to the extent that the calibration sensor 39 is not deteriorated. As the light reducing member, for example, an ND filter (Neutral)
Density Filter) or a diffusion plate can be used.
When a diffuser plate is used, the diffused sample light 3
The calibration sensor 3 from the first beam splitter 40 through the shutter 48 so that 7 does not enter the light amount sensor 38.
It is desirable to cover the optical path reaching 9 with a light shielding plate or the like.

Further, as the beam splitters 40 and 41, for example, a parallel flat substrate (hereinafter referred to as an uncoated substrate) of calcium fluoride (CaF2) in which neither surface is coated is suitable. In such a beam splitter, about 9% of the incident laser light is reflected by Fresnel reflection and 91% is transmitted.

The laser controller 29 controls the value of the high voltage applied between the high-voltage power supply 23 and the main electrodes 14 and 15 so that the desired value can be obtained based on the detected pulse energy of the laser light 21. This is called constant pulse energy control. When performing constant pulse energy control during normal exposure, the shutter 48 is closed to block the sample light 37 from entering the calibration sensor 39. As a result, deterioration of the calibration sensor 39 is prevented.

FIG. 2 shows a detailed view of the monitor device 36.
As shown in FIG. 2, the monitor device 36 includes a monitor box 5
Surrounded by 1. The optical path of the sample light 37 entering the light quantity sensor 38 and the optical path of the sample light 37 entering the calibration sensor 39 are shielded from each other by the partition wall 60. Thereby, for example, the sample light 37 to be incident on the light amount sensor 38 is rarely incident on the calibration sensor 39 due to diffused reflection on the inner wall of the monitor box 51, and accurate pulse energy can be measured.

The monitor box 51 has a purge gas cylinder 55 containing a purge gas having a low reactivity and containing no oxygen.
Is connected to the inside of the monitor box 51, and the purge gas is continuously flowed inside the monitor box 51. With the purge gas,
By expelling oxygen inside the monitor box 51, the attenuation of the sample light 37, which is ultraviolet light, is prevented.
The purge gas is supplied from the vicinity of the light amount sensor 38 and the calibration sensor 39, and as shown by a dashed arrow 57, follows the optical path of the sample light 37 in the opposite direction, and the purge gas outlet 56.
Go out from. As a result, even if dust enters the inside of the monitor box 51, it is pushed by the flow of the purge gas,
Dust is less likely to adhere to the sensors 38 and 39. Further, by supplying the purge gas from the vicinity of the sensors 38 and 39, the oxygen concentration in the vicinity of the sensors 38 and 39 is particularly reduced, so that the attenuation of the sample light 37 due to oxygen is reduced and the intensity of the sample light 37 is stabilized, Measurement is also stable.

A plate-like member 54 projects from the inner wall of the monitor box 51 in the optical path of the sample light 37. As a result, the purge gas flows along the surface of the optical component in a direction substantially perpendicular to the optical axis of the sample light 37, so that dust or the like is unlikely to adhere to the surface of the optical component. In particular, as shown in FIG. 2, if the plate member 54 has a spiral shape, the flow of the purge gas flows more effectively on the surface of the optical component, which is even better.

Even if the pulse energy of the laser light 21 is controlled to be constant by the constant pulse energy control, the pulse energy distribution (beam profile) in the beam cross section may fluctuate. As a result, sample light 3
The pulse energy distribution of 7 also fluctuates. That is,
When only a part of the beam cross section of the sample light 37 is cut out and made incident on the sensors 38 and 39, the light amount of the cut out part may fluctuate due to the fluctuation of the pulse energy distribution, despite the constant control of the pulse energy. . Therefore, in order to accurately measure the optical output of the sample light 37, it is necessary to propagate the entire beam cross section of the sample light 37 to the light amount sensor 38 and the calibration sensor 39.

For this purpose, there is a means of condensing the sample light 37 by, for example, a condensing optical system so that the entire beam cross section of the sample light 37 is made incident on the sensors 38 and 39 each having a small light receiving surface area. However, in this case,
There is a problem that the energy density on the light receiving surfaces of the sensors 38 and 39 becomes too large, and the life of the sensors is significantly reduced. Further, for example, the sample light 37 is shaped so that the cross-sectional shape of the beam substantially matches the light receiving surfaces of the sensors 38 and 39 and the pulse energy distribution becomes uniform (the beam profile becomes a top hat). There is a means. However, the optical system for beam shaping is
It becomes complicated and expensive.

In this embodiment, a lens 53 is arranged in the optical path of the sample light 37. This lens 5
3, the sample light 37 is disposed in front of the light amount sensor 38 and the calibration sensor 39, and the diffuser plate 5 is provided.
The size is limited to about 2,52.

As a result, the entire beam cross section of the sample light 37 enters the diffusion plates 52, 52. Then, the sample light 37 is converted by the diffuser plates 52, 52 into a diffused beam that diffuses in a random direction. Therefore, the intensity of this diffused beam is proportional to the pulse energy of the sample light 37, and the intensity distribution is substantially uniform. As a result, the pulse energy of the sample light 37 is reflected no matter which part of the diffused beam is cut out, and the measured value does not change even if the beam profile of the laser light 21 changes. This is the same when the emission position or the traveling direction of the laser light 21 fluctuates, and the use of the diffuser plates 52, 52 causes the entire beam cross section of the beam of the sample light 37 to enter the diffuser plates 52, 52. The fluctuation of the measured value due to the above fluctuation is small.

By using the diffusing plates 52, 52 in this way, the sample light 37 is detected by the condensing optical system.
Sensor 38,39, as when focusing on 8,39.
The energy density on the light receiving surface does not increase, and its life is not significantly shortened. Also, the diffusion plate 5
2, 52 are inexpensive and simple in construction, and do not require complicated and expensive optical components such as when shaping a beam.

The diffusion plates 52, 52 are, as shown in FIG.
It is preferable to arrange a plurality of sheets at a distance of a certain amount or more. That is, by increasing or decreasing the number of the diffusion plates 52, 52, the pulse energy of the sample light 37 incident on the sensors 38, 39 can be adjusted according to the sensitivity of the sensors 38, 39. In addition, the diffusion plates 52, 5
Even if there are only two sheets, by changing the distance between the diffusion plates 52, 52 as shown by the broken line in FIG. 3,
The pulse energy of the sample light 37 incident on the sensor can be adjusted by changing the degree of collection of the sample light 37.

Furthermore, by arranging the diffusion plates 52, 52 at a certain distance or more from each other, the purge gas can flow between them. As a result, even if impurities are generated, they rarely stay between the diffusion plates 52, 52 and can be removed by the flow of the purge gas.

At this time, the diffusion plates 52, 52 and the sensor 3
Even if the intensity of the sample light is measured by disposing a fluorescent plate (not shown) that emits fluorescence when irradiated with ultraviolet rays between 8 and 39, and measuring the intensity of the fluorescence generated by the sample light. Good. The shutter 48 is provided on the diffusion plate 5
It is arranged on the upstream side of the optical axis with respect to 2, 52. The transmittance of the diffusion plates 52, 52 and the intensity of the fluorescent light generated by the fluorescent plates are not so significant as the sensitivity of the sensors 38, 39 is lowered,
It changes gradually by the irradiation of the sample light 37. In order to avoid such changes, the calibration sensor 3 should be used except during calibration.
It is preferable that the optical components of the optical path of the sample light 37 entering 8 are not irradiated with the sample light 37 as much as possible.

An example of the means for holding the optical component at this time is as follows.
Taking the holder 59 for holding the diffusion plates 52, 52 as an example,
As shown in FIG. As shown in FIG. 4, the optical component is fixed to the inner wall of the monitor box 51 by a holder 59 having an opening 58 on the periphery thereof. This allows the purge gas passing through the opening 58 to flow in the vicinity of the optical component, so that dust is less likely to adhere to the surface of the optical component.

FIG. 5 is a flowchart showing a procedure for performing the initial calibration of the light quantity sensor 38 and the calibration sensor 39 with respect to the pulse energy of the laser light 21 in the fluorine molecular laser device 11 as described above.

The laser controller 29 first detects the main electrode 1
A predetermined high voltage is applied between 4 and 15 to oscillate the laser light 21 (step S11). At this time, as shown by the broken line in FIG. 1, the calorimeter 43 is installed on the optical axis of the laser light 21 and the pulse energy of the laser light 21 is measured (step S12).

At the same time, the shutter 48 is opened and the magnitudes of the output signals of the light amount sensor 38 and the calibration sensor 39 are detected (step S13). Then, while gradually increasing the applied high voltage to change the pulse energy variously (step S12), the steps S12-
Repeat S14. In step S13, the sample light 37 is made incident on only one of the light amount sensor 38 and the calibration sensor 39, and the pulse energy measurement by the light amount sensor 38 and the calibration sensor 39 is alternately performed. May be.

FIG. 6 is a graph showing the pulse energy measured by the calorimeter 43 on the horizontal axis and the outputs of the light amount sensor 38 and the calibration sensor 39 on the vertical axis. As shown in FIG. 6, the output P1 of the light amount sensor 38 and the output P2 of the calibration sensor 39 with respect to the pulse energy E are both approximated by a straight line.

That is, the reciprocal a of the slope of the straight line in the graph
The pulse energy E can be obtained by obtaining 1 by the least square method or the like and multiplying the output P1 of the light amount sensor 38 by the reciprocal a1. Similarly, the output P2 of the calibration sensor 39
Is multiplied by the reciprocal a2 of the slope of the straight line to obtain the pulse energy E. The reciprocal of these slopes a1,
a2 is converted into conversion factors a1 and a of the sensors 38 and 39, respectively.
Call 2.

The structure of the calorimeter 43 is shown in FIG. The calorimeter 43 includes a perfect black body 44 that converts the light energy of the laser light 21 into heat with high efficiency, and a perfect black body 44.
And a thermoelectric conversion element 45 for converting the heat of the above into an electric current. As a result, it is possible to measure the pulse energy of the laser light 21 oscillated from about 1 Hz to 500 Hz, one pulse at a time. Such initial calibration by the calorimeter is performed not only when the fluorine molecular laser device 11 is assembled, but also at an appropriate timing based on the irradiation time of the sample light 37 and the number of oscillated pulses.

Next, using the light quantity sensor 38 and the calibration sensor 39 that have been initially calibrated in the above procedure, a flow chart of a procedure for performing constant pulse energy control while calibrating the light quantity sensor 38 with the calibration sensor 39 at an appropriate timing. Is shown in FIG.

First, the laser controller 29 operates the molecular fluorine laser device 11 to oscillate the laser light 21 (step S21). Then, since the light quantity sensor 38 was calibrated last time, is the light quantity sensor 38 calibrated based on at least one of the number of pulses of the laser light 21 oscillated so far and the operating time of the fluorine molecular laser device 11? It is determined whether or not (step S22).

In this judgment, for example, the pulse number C is set to a predetermined value C.
Compare with 0, and if C> C0, calibrate. Alternatively, for example, the light quantity sensor 38 has been used for the sample light 37 until now.
Is compared with a predetermined value T0, and T> T
If 0, calibrate. This is because it is considered that the more the sample light 37 is irradiated for a long period of time or a large number of pulses, the more severe the deterioration of the light amount sensor 38.

When it is determined in step S22 that the calibration is necessary, the laser controller 29 calibrates the light quantity sensor 38 based on the calibration procedure described later (step S23). This calibration is performed by correcting the conversion coefficient a1 of the light amount sensor 38. Then, the corrected conversion coefficient a1 is used as the output signal P1 of the light amount sensor 38.
And the pulse energy E is detected, and constant pulse energy control is performed (step S24), step S2.
Return to 2.

If it is determined in step S22 that it is not necessary to perform the calibration, the uncorrected conversion coefficient a1 is output to the output signal P of the light amount sensor 38 in step S24.
The pulse energy E is detected by multiplying by 1, and constant pulse energy control is performed. Incidentally, the above steps S21 to S
24, in steps other than the step S23 of performing calibration, the shutter 48 placed in front of the calibration sensor 39 is in a closed state, and the calibration sensor 39 is not irradiated with the sample light 37. There is.

FIG. 9 is a flowchart showing an example of the calibration procedure of the light amount sensor 38. First, the laser controller 2
9 oscillates the laser light 21 at a predetermined high voltage and frequency (step S31) to open the shutter 48,
The sample light 37 is made incident on both the light amount sensor 38 and the calibration sensor 39 (step S32). Incidentally, step S
In 32, as will be described later, only one of the light quantity sensor 38 and the calibration sensor 39 has the sample light 3
Alternatively, the pulse energy may be measured by the alternating sensors 38 and 39.

The laser controller 29 uses the light amount sensor 3
8 and the outputs P1 and P2 of the calibration sensor 39 to the conversion factor a
1 and a2 are respectively multiplied to calculate pulse energies E1 and E2 of the laser light 21 (step S33). As described above, since the calibration sensor 39 blocks the sample light 37 by the shutter 48 while the calibration is not performed, the deterioration thereof is much smaller than that of the light amount sensor 38. Therefore, it is considered that the pulse energy E2 obtained based on the output P2 of the calibration sensor 39 is almost close to the true pulse energy E.

The laser controller 29 compares the pulse energies E1 and E2 with each other (step S3).
4) The light amount sensor 38 calculates a correction coefficient b (= E2 / E1) for obtaining the true pulse energy E2 from the pulse energy E1 (step S35).

Then, by comparing this correction coefficient b with the correction coefficient b obtained and stored in the previous calibration, the degree of deterioration of the light quantity sensor is determined (step S3).
6) If the correction coefficient b is largely fluctuated, it is determined that the light amount sensor has significantly deteriorated since the previous calibration, the laser oscillation is stopped, and a warning signal is output (step S3).
7). For example, from the correction coefficient b in the previous calibration, 5
If it fluctuates by 0% or more, it may be determined as deterioration. The warning signal in this case is called warning 1.

In step S36, the light amount sensor 38
If it is determined that the degree of deterioration is low, the conversion coefficient a1 is updated by multiplying the calculated correction coefficient b by the conversion coefficient a1 (step S38). Then, the conversion coefficient a1 is
Deterioration of the light amount sensor is determined by comparing with the initial conversion coefficient a1 obtained using the calorimeter 43 in steps S12 to S14 (step S39).

FIG. 10 shows a graph in which the horizontal axis represents the pulse number C and the vertical axis represents the conversion coefficient a1 of the light amount sensor 38. Figure 1
As shown in 0, as the pulse number C increases, the sensitivity of the light amount sensor 38 decreases, and the conversion coefficient a1 gradually increases. In general, it is considered that the life of the light amount sensor 38 is when the conversion coefficient a1 becomes ten times as large as when the sample light 37 is irradiated to the light amount sensor 38 for the first time.

Therefore, for example, when the conversion coefficient a1 is 10 times or more, it is determined that the light amount sensor 38 has reached the end of its life, the laser oscillation is stopped, and a warning signal is output (step S40). The warning signal in this case is called warning 2.

As described above, according to the first embodiment, the light quantity sensor 38 for measuring the pulse energy of the laser light 21 and the calibration sensor 39 for calibrating the light quantity sensor 38 are provided. There is. Accordingly, the conversion coefficient a1 for obtaining the pulse energy E from the output of the light amount sensor 38 can be corrected, and the light amount sensor 38 can be corrected.
Accurate measurement by.

A shutter 48 is provided in front of the calibration sensor.
Is arranged to prevent the sample light 37 from entering the calibration sensor except during calibration such as exposure. As a result, the calibration sensor is not irradiated with the sample light 37 except at the time of calibration, so that the calibration sensor is less likely to deteriorate and the calibration is accurately performed.

When the degree of deterioration of the light quantity sensor 38 is estimated and it is determined that the deterioration is large, the laser oscillation is stopped and a warning signal is output. As a result, it is possible to always measure the pulse energy accurately. Further, since it is possible to always obtain a desired pulse energy without performing constant pulse energy control based on the measured value of the deteriorated light amount sensor 38, an exposure error occurs even when performing exposure using this. It gets harder.

In addition, as shown in FIG.
And the beam splitters 22, 40, 41 are even-numbered times before the sample light 37 enters the calibration sensor 39.
Is reflected at a predetermined angle. Sample light 3
By reflecting 7 at an even number of times at a predetermined angle, the ratio of the P-polarized component and the S-polarized component of the laser light 21 (hereinafter referred to as the polarization ratio) matches the polarization ratio of the sample light 37. Therefore, even if the polarization ratio of the laser light 21 changes, the sample light 3
The light quantity of 7 does not change, and accurate pulse energy measurement and calibration are possible.

FIG. 11 shows another configuration example of the fluorine molecular laser device 11 according to the first embodiment. As shown in FIG. 11, the molecular fluorine laser device 11 is, for example, a pneumatic cylinder (not shown), and includes a shutter 48 that is slidable substantially perpendicularly to the optical axis of the sample light 37. The shutter 48 receives the sample light 3 incident on the light quantity sensor 38.
7 optical path or sample light 3 incident on the calibration sensor 39
One of the seven optical paths is always shielded, and the sample light 37 passing through the other optical path is allowed to pass.

As a result, the sample light 37 enters only one of the light quantity sensor 38 and the calibration sensor 39. Therefore, the sample light 37 rarely enters the light amount sensor 38 when the calibration sensor 39 is measured, and the deterioration degree of the light amount sensor 38 due to the irradiation of the sample light 37 is reduced. Although the shutter 48 is slidable in FIG. 11, it may be a rotary type using a rotary solenoid as a drive source.

Next, the second embodiment will be described. 12
2 shows a configuration diagram of the fluorine molecular laser device 11 according to the second embodiment. In FIG. 12, a light amount sensor 38 and a calibration sensor 39 are mounted on the optical axis of the sample light 37 reflected by the beam splitter 40 in the right direction in FIG.
A linear movement stage 46 is arranged.

The linear movement stage 46 is movable substantially perpendicular to the optical axis of the sample light 37 by, for example, a linear bearing (not shown). Linear stage 46
It is possible to cause only one of the light amount sensor 38 and the calibration sensor 39 to appear on the optical axis of the sample light 37 by operating.

That is, when the pulse energy constant control is performed, the light amount sensor 38 is positioned on the optical axis and measurement is performed. When performing calibration, the light amount sensor 3
One of the sensor 8 and the calibration sensor 39 is alternately positioned on the optical axis to measure the pulse energy.

According to the second embodiment, the sample light 37 entering the light quantity sensor 38 and the sample light 37 entering the calibration sensor 39 pass through substantially the same optical path. Therefore, if optical components such as the beam splitter 40 on the optical path are contaminated, the measured values of the light amount sensor 38 and the calibration sensor 39 are equally affected, and accurate pulse energy measurement and calibration are possible. is there. Further, since both the sensors 38 and 39 are driven, it is not necessary to distribute the sample light 37 to a plurality of optical paths, the number of optical components is reduced, and the structure of the optical path is simplified. Furthermore, by storing the output of the calibration sensor 39 at the time of initial calibration and comparing the output when performing calibration after that with the stored output at the time of initial calibration, the output of the optical component on the optical path It becomes easy to find stains and the like.

FIG. 13 shows another example of the fluorine molecular laser device 11 according to the second embodiment. In FIG. 13, the fluorine molecular laser device 11 has a beam splitter 40 arranged on a linear movement stage 46. If the beam splitter 40 is at the 40A position, the sample light 37
Enters the light amount sensor 38 and the beam splitter 40
When it is at the 0B position, the sample light 37 is incident on the calibration sensor 39.

Instead of the beam splitter 40, a mirror that totally reflects the sample light 37 may be arranged. In this case, the damper 42 becomes unnecessary. On the other hand, by using the beam splitter 40 as shown in FIG. 13, it is possible to arrange a measuring instrument for measuring beam divergence and pointing stability in place of the damper 42 and measure these characteristics.

Next, a third embodiment will be described. 14
FIG. 9 shows a configuration diagram of the fluorine molecular laser device 11 according to the third embodiment. In FIG. 14, on the optical path of the sample light 37 reflected by the main beam splitter 22 and the first beam splitter, a movable mirror 47 having a rotary actuator (not shown) and rotatable as shown by an arrow is arranged. . As the rotary actuator, for example, a galvano scanner is suitable, and the angle of the movable mirror 47 with respect to the optical axis of the sample light 37 can be changed at high speed based on a command from the laser controller 29.

The movable mirror 47 reflects the reflected light at only one of a deep angle (corresponding to 47A in FIG. 14) and a shallow angle (corresponding to 47B in FIG. 14).
The angle of the sample light 37 with respect to the optical axis is set.
The sample light 37 (broken line) reflected at a shallow angle enters the calibration sensor 39, and the sample light 37 reflected at a deep angle enters the light amount sensor 38.

Alternatively, the sample light 37 is moved to the movable mirror 47.
Then, the light may be reflected by 90 degrees in the upward and downward directions in FIG. 14, respectively. Then, for example, when the light is reflected in the upward direction, it is incident on the light amount sensor 38, and when it is reflected in the downward direction, it is incident on the calibration sensor 39.

According to the third embodiment, by changing the angle of the movable mirror 47, whether the light is incident on the calibration sensor 39 or the light amount sensor 38 is changed. Since only the lightweight movable mirror 47 is rotated, the optical path of the sample light 37 can be switched quickly, and the time required for calibration can be shortened. Also, the first and second
Compared to moving the shutter 48 and the sensors 38 and 39 as in the embodiment, a large device such as a linear bearing is not required.

Next, a fourth embodiment will be described.
FIG. 15 shows a fluorine molecular laser device 1 according to the fourth embodiment.
The block diagram of 1 is shown. 15, the fluorine molecular laser device 11 causes the sample beam 37 reflected by the main beam splitter 22 in the upward direction in FIG. 15 to be incident on the first beam splitter 40. The sample light 37 transmitted through the first beam splitter 40 enters the damper 42 and is absorbed.

A second beam splitter 41 is arranged on the optical path of the sample light 37 reflected by the first beam splitter 40 to the right in FIG. The sample light 37 transmitted through the second beam splitter 41 is used as the calibration sensor 39.
The sample light 3 reflected by the second beam splitter 41
7 is incident on the light amount sensor 38, and the intensity is measured. In front of the calibration sensor 39 and the light amount sensor 38,
A shutter 48 capable of blocking the sample light 37 is arranged.

Thus, the transmitted light of the beam splitter is received by the calibration sensor 39, and the reflected light is received by the light amount sensor 38. As mentioned above, as a beam splitter,
An uncoated substrate of calcium fluoride is commonly used. This is because if the coating is applied, the coating may be contaminated by the irradiation of the sample light 37.

As described above, when an uncoated substrate of calcium fluoride is used as the beam splitter, about 9% of the incident laser light is reflected by Fresnel reflection and 91% is transmitted. Therefore, of the sample light 37 incident on the second beam splitter 41, about 9% is reflected and incident on the light amount sensor 38, and 91% is transmitted and incident on the calibration sensor 39.

That is, the sample light 37 having an intensity approximately 10 times that of the light quantity sensor 38 is incident on the calibration sensor 39.
As a result, the S / N ratio of the calibration sensor 39 improves, the measurement becomes accurate, and the calibration accuracy improves. Further, since the weak sample light 37 enters the light amount sensor 38 to which the sample light 37 always enters during the constant pulse energy control, the light amount sensor 38 is less likely to deteriorate.

Next, a fifth embodiment will be described. FIG.
FIG. 9 shows a configuration diagram of the fluorine molecular laser device 11 according to the fifth embodiment. In FIG. 16, a fluorine molecular laser device 1 is shown.
Reference numeral 1 denotes a first main beam splitter 22 that is permanently installed on the optical path of the laser light 21, and a second main beam splitter 49 that can be retracted and retracted on the optical path by a linear movement stage 46, for example.
It has and.

The first main beam splitter 22 shown in FIG.
The sample light 37 reflected upward in 6 is reflected rightward in FIG. 16 by the first beam splitter 40, and enters the light amount sensor 38. In addition, part of the laser light 21 that has passed through the first main beam splitter 22 is reflected downward in FIG. 16 by the second main beam splitter 49 that appears on the optical path, and is reflected by the second beam splitter 41 in FIG. The light is reflected to the right and enters the calibration sensor 39.

In this way, by making the second main beam splitter 49 retractable into and out of the optical path of the laser light 21, the optical components 49 and 41 on the optical path of the sample light 37 incident on the calibration sensor 39 are normally used. Prevents the sample light 37 from being emitted. As a result, deterioration of the optical component is extremely reduced, and thus the pulse energy of the sample light 37 entering the calibration sensor 39 is less likely to change due to the deterioration of the optical component, and the calibration sensor 3
The measurement by 9 becomes accurate.

Next, a sixth embodiment will be described. FIG. 17 shows a fluorine molecular laser device 11 according to the sixth embodiment.
FIG. In FIG. 17, the fluorine molecular laser device 11 includes a partial transmission rear mirror 50 that transmits a part of the laser light 21. As the partially transmissive rear mirror 50, it is preferable to use, for example, a parallel plane substrate of calcium fluoride, which is coated with a coating that reflects the laser beam 21 by about 99%.

A calibration sensor 39 is disposed behind the partial transmission rear mirror 50, and the partial transmission rear mirror 5 is provided.
The intensity of the sample light 61 transmitted through 0 can be measured. Calibration sensor 39 and partially transmissive rear mirror 5
A shutter 4 that can block the sample light 61 between 0 and
8 is inserted.

As described above, according to the sixth embodiment, the calibration is performed based on the intensity of the sample light 61 transmitted through the partial transmission rear mirror 50. This eliminates the need for a part of the beam splitter and reduces the number of optical components. Moreover, since the output of the laser beam 21 can be measured more directly, the measurement becomes accurate.

In FIG. 17, the partially transmissive rear mirror 50 is shown.
The pulse energy of the sample light 61 that has passed through is measured by the calibration sensor 39, and the pulse energy of the sample light 37 that branches the emitted laser light 21 is measured by the light amount sensor 38, but it may be reversed.

Although not described, the monitor device 36 in each of the above-described embodiments is surrounded by the monitor box 51 as in the first embodiment, and the inside of the monitor box 51 has a low-reactive purge gas. Is being continuously swept. Further, the description has been given by taking the fluorine molecular laser device 11 in which the wavelength is made into the single line by the dispersion prisms 28, 28, but the same is also valid for the fluorine molecular laser device 11 in which the wavelength is not made into the single line. Is. In this case, the dispersion prisms 28, 28 are unnecessary. The same applies to a fluorine molecular laser device whose wavelength is narrowed by using another narrowing means such as a grating. Further, although the explanation has been made by taking the fluorine molecular laser device as an example, a KrF excimer laser device and an Ar
The same can be applied to an excimer laser device such as an F excimer laser device. That is, any laser device that oscillates a laser beam having an ultraviolet wavelength can be similarly applied.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a fluorine molecular laser device according to a first embodiment.

FIG. 2 is a detailed view of the monitor device according to the first embodiment.

FIG. 3 is a layout view of a diffusion plate according to the first embodiment.

FIG. 4 is an explanatory diagram showing an example of a holding unit for an optical component according to the first embodiment.

FIG. 5 is a flowchart showing a procedure for performing initial calibration of the sensor.

FIG. 6 is a graph showing the relationship between pulse energy and sensor output.

FIG. 7 is an explanatory diagram showing a structure of a calorimeter.

FIG. 8 is a flowchart for performing constant pulse energy control and sensor calibration.

FIG. 9 is a flowchart showing an example of a calibration procedure of the light amount sensor.

FIG. 10 is a graph illustrating the life of the light amount sensor.

FIG. 11 is a configuration diagram of a fluorine molecular laser device according to the first embodiment.

FIG. 12 is a configuration diagram of a fluorine molecular laser device according to a second embodiment.

FIG. 13 is a configuration diagram of a fluorine molecular laser device according to a second embodiment.

FIG. 14 is a configuration diagram of a fluorine molecular laser device according to a third embodiment.

FIG. 15 is a configuration diagram of a fluorine molecular laser device according to a fourth embodiment.

FIG. 16 is a block diagram of a fluorine molecular laser device according to a fifth embodiment.

FIG. 17 is a configuration diagram of a fluorine molecular laser device according to a sixth embodiment.

FIG. 18 is a configuration diagram of an excimer laser device according to a conventional technique.

[Explanation of symbols]

11: Excimer laser device, 12: Laser chamber, 1
4: main electrode, 15: main electrode, 16: front mirror, 1
7: Front window, 18: Rear mirror, 19: Rear window, 21: Laser light, 22: Beam splitter, 23: High-voltage power supply, 24: Cross-flow fan, 25: Exposure machine, 26: Front slit, 27: Rear slit, 2
8: Dispersion prism, 29: Laser controller, 30:
Single line unit, 31: Single line box, 35: Purge gas cylinder, 36: Monitor device,
37: sample light, 38: light amount sensor, 39: calibration sensor, 40: first beam splitter, 41: second beam splitter, 42: damper, 43: calorimeter, 4
4: Perfect black body, 45: Thermoelectric conversion element, 46: Linear movement stage, 47: Movable mirror, 48: Shutter, 49: Second main beam splitter, 50: Partial transmission rear mirror, 5
1: monitor box, 52: diffuser plate, 53: lens, 5
4: plate member, 55: purge gas cylinder, 56: purge gas outlet, 58: opening, 59: holder, 60: partition wall.

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 2G065 AA04 AB05 AB09 AB14 BA09                       BB21 CA23 CA25 DA01                 5F072 AA04 JJ03 JJ05 JJ09 KK15                       RR05

Claims (9)

[Claims] 1. A monitor device for detecting the pulse energy of a laser light (21) having an ultraviolet wavelength, wherein a sample light (37) obtained by sampling a part of the laser light (21).
Monitor device comprising a light amount sensor (38) for measuring the pulse energy of the sample light (37) and a calibration sensor (39) for measuring the pulse energy of the sample light (37) to calibrate the light amount sensor (38) . 2. The monitor device according to claim 1, wherein the calibration sensor (39) is provided with a sample light (3
The shielding means (48) or the sample light (3
A monitor device provided with a damping means (48) for damping 7). 3. The monitor device according to claim 2, wherein the shielding means (48) or the damping means (48) is a calibration sensor (3).
9. A monitor device arranged upstream of a diffuser plate (52, 52) arranged in front of 9). 4. The monitor device according to claim 1, wherein an optical path of the sample light (37) incident on the light quantity sensor (38) and a sample light (39) incident on the calibration sensor (39). A monitor device characterized in that the optical path of 37) is shielded from each other. 5. The monitor device according to claim 1, wherein an optical path of the sample light (37) incident on the light amount sensor (38) and an optical path of the sample light (37) incident on the calibration sensor (39). It is common, and when measuring the pulse energy of the sample light (37), place the light quantity sensor (38) at the position where the sample light (37) enters,
A monitor device comprising a sensor positioning means (46) for arranging a calibration sensor (39) at a position where the sample light (37) enters during calibration. 6. The monitor device according to claim 5, wherein the deterioration degree of the optical component on the optical path is based on a comparison between the output of the calibration sensor (39) at the time of initial calibration and the output at the subsequent calibration. A monitor device comprising a laser controller (29) for determining whether or not the 7. The monitor device according to claim 1, wherein a deterioration degree of the light amount sensor (38) is determined based on the calibration by the calibration sensor, and when the deterioration degree is larger than a predetermined degree. Is a monitor device having a laser controller (29) for issuing a warning. 8. The monitoring device according to claim 1, wherein at least one of irradiation time (T) and pulse oscillation number (C) of the sample light (37) to the light quantity sensor (38). A monitor device comprising a laser controller (29) for determining the timing of calibration based on one side. 9. An ultraviolet laser device comprising the monitor device (36) according to any one of claims 1 to 8.