JP3417323B2 - Etalon evaluation method, etalon evaluation device, and laser oscillator - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an etalon evaluation device and an etalon evaluation method, and more particularly to a Fabry-Perot etalon evaluation method used for narrowing the bandwidth of a laser oscillator, the etalon evaluation device and the etalon. The present invention relates to a laser oscillator having a narrow band.

[0002]

2. Description of the Related Art A Fabry-Perot etalon (hereinafter abbreviated as "etalon") has conventionally been used as an element for sweeping a wavelength and analyzing a spectrum of light, and is also inserted in a laser resonator to select a laser oscillation frequency. It is used as an element that

In recent years, in order to obtain excimer laser light having a high spectral purity used as a light source of a semiconductor exposure apparatus, an etalon is inserted in a laser resonator as a filter used in the optical region.

This semiconductor exposure apparatus is a very important apparatus for manufacturing a semiconductor device whose progress of miniaturization is remarkable, and a KrF laser which is an excimer laser has already been put into practical use as a light source of this semiconductor exposure apparatus. There is.

Then, in the semiconductor exposure apparatus, if the wavelength spectrum of the light source is widened, the resolution is lowered due to the chromatic aberration of the exposure optical system.

Therefore, in the excimer laser for semiconductor exposure apparatus, it is necessary to narrow the wavelength spectrum in order to reduce the influence of this chromatic aberration.

Particularly, in recent years, the semiconductor exposure apparatus has been miniaturized year by year, and in order to meet the demand, a sub-picometer is required for the half width of the wavelength spectrum of the light source.
That is, the spectrum width of this laser is about 2 to 3 pm in half width in the past, but is now 1 p.
A half-value width of m or less has been put to practical use.

As a method for obtaining an excimer laser beam having a high spectral purity by using an etalon as described above, for example, a method described in Japanese Patent Laid-Open No. 3-87084 is known.

First, the etalon will be briefly described. FIG. 15 is a side view of the air gap etalon.

This etalon is made up of two parallel flat plates 153a and 153b having a certain reflectance as shown in FIG. It is a filter in the optical region that can selectively transmit only the wavelength determined by the reflectance and the gap interval.

In general, a plurality of spacers 152 having the same thickness are sandwiched between two parallel flat plates 153a and 153b to realize a gap interval 151 with good parallelism.

However, in manufacturing, variations in the size of the spacers and variations in the gap distance on the order of nanometers occur due to the accuracy of assembly. There is a tendency for this gap interval to vary, and there are two parallel flat plates 153a,
It is general that the 153b has a V-shape.

In the case of FIG. 15, the direction in which the variation in the gap distance is the smallest is perpendicular to the paper surface. Here, the direction from the front side to the back side of the paper is set to the direction in which the variation in the gap interval is the smallest, and in this figure, in order to make it easy to understand the variation in the gap interval, the gap interval 1
51 is exaggerated so that it becomes wider below.

Next, FIG. 16 shows a schematic diagram of the transmission characteristics of the etalon. The transmission characteristics of the etalon are as follows: Free Spectral Range (FS)
R) shows a peak for each unique wavelength pitch determined by the gap distance of the etalon. The sharpness of each peak is mainly determined by the reflectance, roughness, and parallelism of the parallel plate. The higher the reflectance, the smaller the roughness, and the higher the parallelism, the sharper the sharpness.

As described above, the laser band narrowing needs to be uniform over the entire beam.

Now, the laser beams are a, b, and
Suppose that the beam position of c is passed. At this time, looking at one peak in the transmission characteristics of the etalon, the peak wavelength is slightly shifted as shown in FIG. 17 because the etalon gap interval 151 is different at each beam transmission position.

When narrowing the band to the half width of the sub-picometer, if the gap interval 151 has a variation of several tens of nanometers, the wavelength shift is on the order of picometers, and the spread of the half width due to the variation of the gap interval is ignored. It becomes a size that cannot be done.

Therefore, when used in an excimer laser for a semiconductor exposure apparatus, the etalon is required to have a highly parallel gap distance.

The measurement of the parallelism of the etalon has an important meaning in ensuring the performance of the excimer laser for a semiconductor exposure apparatus.

FIG. 18 shows a conventional etalon evaluation apparatus. In FIG. 18, the laser light from the excimer laser light source 181 is expanded by the beam expander 182 to an appropriate beam size. This beam is diffuser 18
Irradiated to 3 and diffused in various directions, etalon 1
Irradiate 84.

The light transmitted through the etalon 184 is
An image is formed on the sensor 186 by the lens 185.

The light pattern on the surface of the sensor 186 becomes concentric interference fringes as shown by 19a in FIG.

As shown at 19a in FIG. 19, if the sensor is a vertically long line sensor, the signal 187 from the sensor at this time is as shown at 19b in FIG. 19, for example. When the pattern for three stripes can be measured in this way, since the FSR of the etalon is known, it can be used as an index indicating the half-value width of the transmission characteristic of the etalon.

More precisely, the measured full width at half maximum is the overlap of the spread of the spectrum of the laser light specified for measurement, but if the spectrum of this laser light is sufficiently narrow, the measured full width at half maximum is Indicates the characteristics of the etalon itself.

[0025]

However, according to the above configuration, it is possible to inspect whether or not the transmission characteristics of the etalon reach the required level, but it is possible to check the individual characteristics of the etalon, especially the gap distance. The variation cannot be measured.

That is, in the etalon evaluation method or evaluation device, it is required to accurately measure the uniformity of the gap distance in the laser beam plane, but conventionally, the gap under the actual use condition of the etalon is required. There is a problem that the uniformity depending on the location of the interval is not measured.

The present invention relates to a method and an apparatus for evaluating the filter characteristics of an etalon used to obtain an excimer laser beam having such high spectral purity, and a laser oscillator. An object of the present invention is to provide a laser oscillator capable of oscillating a laser beam having a higher spectral purity by using a device for accurately measuring the property and an etalon evaluated by the device for narrowing the band.

[0028]

In order to solve this problem, the present invention relates to an optical element provided between an excimer laser light source and an etalon when irradiating a laser light from the excimer laser light source on the etalon. The irradiation area of the irradiation beam can be changed by.

As a result, it becomes possible to accurately measure the variation in the etalon gap distance depending on the location, that is, the uniformity. Further, the etalon evaluated in the above-mentioned configuration is used for the laser oscillator to narrow the band of the laser beam.

[0030]

DETAILED DESCRIPTION OF THE INVENTION The present invention according to claim 1, a laser oscillator, a diffusion plate, a condenser lens, a light receiving sensor, installed fab Repeller Roetaron between the diffusion plate and the condenser lens, the Fabry In a device for measuring equi-tilt interference fringes of a Perot etalon and evaluating characteristics, the Fabry-Perot etalon is provided as means for allowing light from the laser oscillator to enter a plurality of regions of the Fabry-Perot etalon.
Immediately before Ron, relative rotation is possible with the Fabry-Perot etalon
It is an etalon evaluation device that has a slit installed in Noh . With this configuration, it is possible to accurately measure and evaluate the variation in the gap distance of the etalon depending on the location, that is, the uniformity, and the variation in the gap distance is large.
The direction can be identified, and the magnitude of variation can be evaluated .

[0031]

Alternatively, the present invention according to claim 2 is a laser.
Consists of an oscillator, a diffuser, a condenser lens, and a light receiving sensor
The Fabry-Perot etalon between the diffuser and the condenser lens.
Is installed and equilibrium interference fringes of the Fabry-Perot etalon
The measured, the apparatus for evaluating the characteristics, installation light from the laser oscillator as a means for allowing incident into a plurality of regions of the Fabry-Perot etalon, just prior to the Fabry-Perot etalon and relatively movable in the Fabry-Perot etalon This is an etalon evaluation device having a defined aperture, which allows quantitative evaluation of variations in the gap distance depending on the location.

As described in claim 3 , claim 1 or
In the apparatus described in 2 above , when an aperture and an optical system are installed between the laser oscillator and the diffusion plate and only a portion where the spectrum of the laser beam oscillated from the laser oscillator is constant is used for evaluation, higher accuracy is obtained. You can measure.

More specifically, as described in claim 4 ,
In the apparatus according to the third aspect , even if the optical system installed between the laser oscillator and the diffusion plate is a beam expander, more accurate measurement can be performed.

Alternatively, as described in claim 5 , claim 1
In the device according to any one of 1 to 4 , a narrow band excimer laser oscillator may be used as the laser oscillator.

The invention according to claim 6 is the same as claim 2.
In the above device, a line sensor is used for the sensor,
Before SL is an evaluation device and wherein placing a line sensor in the same direction as the scanning direction of the aperture is disposed just before the fab repeller Roetaron, perform more accurate measurements.

Further, an invention according to claim 7, wherein, an equal inclination interference fringe was measured by irradiating a laser beam diffused in the Fabry-Perot etalon, from the like inclination interference fringe of the fab repeller b <br/> Etaron an evaluation device for evaluating the characteristics, slit
The laser light to the Fabry-Perot etalon
Of the equi-tilt interference fringe a obtained by irradiating the reference position of
The laser light is lit using a Fabry-Perot
The interference fringes b obtained by irradiating an arbitrary position of Ron
Both are input signals, and the half-value widths of the equal-angle interference fringes a and b are
An evaluation device having means for calculating a change in the gap distance of the fab repeller Roetaron from the change, can be performed more accurate measurements.

[0038]

The invention according to claim 8 is the Fabry-Perot.
Irradiate the laser light diffused on the talon to obtain the equi-tilt interference fringes.
Is measured, and the Fabry-Perot
An evaluation device for evaluating the characteristics of a talon, wherein the laser beam is irradiated by using an aperture and an equitilt angle interference fringe a obtained by irradiating the reference position of the Fabry-Perot etalon with the laser beam. and at least the input signal interference fringes b obtained by irradiating an arbitrary position of the fab repeller Roetaron comprises means for calculating a change in the gap distance of the Fabry-Perot etalon from the amount of movement of said equal inclination interference fringe a and b It is an evaluation device and can perform more accurate measurement.

The invention according to claim 9 is the same as claim 7 or
Faburipe in apparatus according 8, the input signal
And means for converting the transmission characteristics due to the wavelength of the low etalon, before the signal after converting the transmission characteristics due to said wavelength
The evaluation device is characterized by calculating the change in the gap distance of the Fabry-Perot etalon, and can perform more accurate measurement.

The invention according to claim 10 is the same as claim 8.
In the above equipment, measure the interference fringes in one direction and the other direction from the center of the concentric circles of the equi-tilt interference fringes, and take the average value of the movement amount of each interference fringe to obtain the measurement error. It is an evaluation device characterized by correcting and calculating the change in the gap interval of the Fabry-Perot etalon,
More accurate measurement can be performed.

Further the invention of claim 11 is equal inclination interference fringe was measured by irradiating a laser beam diffused in the Fabry-Perot etalon, the gap of the fab repeller b <br/> Etaron from the like inclination interference fringe As an evaluation method for calculating changes in intervals
In the calculation method, the laser light is calculated using a slit.
Obtained by irradiating the reference position of the Fabry-Perot etalon
The laser is formed by using the equal tilt interference fringe a and the slit.
Irradiate light to any position on the Fabry-Perot etalon
From the change of the half width of the interference fringe b obtained by
This is an evaluation method characterized by calculating the change in the gap distance of the low etalon, which enables more accurate measurement.

[0043]

The invention according to claim 12 is the Fabry pe
The low etalon is irradiated with the diffused laser light to obtain an equal tilt angle.
The interference fringes are measured, and the Fabry-pet
In the evaluation method of calculating the change in the gap distance of Roetaron, calculation method, using the aperture with an equal inclination interference fringe a obtained by irradiating the laser beam to the reference position of the Fabry-Perot etalon with an aperture wherein the laser beam from the amount of movement of the interference fringes b obtained by irradiating an arbitrary position of the fab Repeller Roetaron Faburipe
An evaluation method characterized by and Turkey to calculate the change in the gap distance of the rows etalon, perform more accurate measurements.

The invention according to claim 13 is the same as claim 11.
Or 12 in the evaluation method described, off the equal inclination interference fringe
Converted to transmission characteristics according to the wavelength of the Abbey Perot etalon,
This is an evaluation method characterized in that a change in the gap distance of the Fabry-Perot etalon is calculated from the transmission characteristic depending on the wavelength, and more accurate measurement can be performed.

The invention of claim 14 is the same as claim 12
In the evaluation method described , by measuring the interference fringes in one direction and the other direction from the center of the concentric circles of the equi-tilt interference fringes, by taking the average value of the movement amount of each interference fringe,
This is an evaluation method characterized by correcting the measurement error and calculating the change in the gap interval of the Fabry-Perot etalon, which enables more accurate measurement.

Further the invention of claim 15 is a fab Repeller Roetaron inside the optical resonator placed in the laser oscillator for narrowing a laser beam, a pre-Symbol fab Repeller b <br/> Etaron claim 1 15. The evaluation device according to any one of claims 1 to 10 is used, or any one of claims 11 to 14 is used.
It was evaluated by the method of evaluation, the Faburipe from the result
With regions small change in low etalon gap spacing, before Symbol a laser oscillator characterized by narrowing the front SL laser beam oscillated from the laser oscillator, thereby high laser beam spectral purity than conventional Can be obtained.

(Embodiment 1) FIG. 1 is a schematic configuration diagram of an apparatus for evaluating variations in gap distance of an etalon according to a first embodiment of the present invention.

In FIG. 1, 11 is an excimer laser oscillator for measurement, 12 is a beam expander, 13 is a diffuser plate,
14 is a slit, 15 is a slit rotation mechanism, 16 is an etalon, 17 is a lens, 18 is a sensor, 19 is a signal, 20
Is a calculator, and 21 is a change in the gap distance of the etalon calculated by the calculator 20.

The characteristic configuration of this embodiment is that the slit 14 having the rotating mechanism 15 is inserted immediately before the etalon 16 to be measured and the calculator 20 is the sensor 1.
It has the same function as the constituent elements described in the conventional example except that the change 21 of the etalon gap interval is calculated from the signal 19 of FIG.

The positional relationship between the etalon 16 and the slit 14 is shown in FIG. Now, in FIG. 2, when the position of the slit 14 is at the position 2a, interference fringes from the sensor 18 are recorded in the same manner as in the conventional example.

The signal from the sensor 18 recorded at this time becomes a signal 3a shown in FIG. 3 after being converted into a transmission characteristic by wavelength by the calculator 20.

Thereafter, the rotating mechanism 15 rotates the position of the slit 14 to the position of 2b.

Then, the interference fringes from the sensor 18 are recorded,
The signal 3b shown in FIG. 3 is obtained after being converted into the transmission characteristic by the wavelength by the calculator 20. At this time, the signal 3a and the signal 3b are measuring the transmission characteristics of the etalon 16 at horizontally long places in different directions.

In this way, the slit 14 is rotated to record the signal at each position. And
The calculator 20 calculates the half-width Δ3a of the transmission characteristic depending on the wavelength,
.DELTA.3b ... is obtained respectively.

The full width at half maximum obtained in this way is the same for all perfectly parallel etalons, but in reality it is not parallel to the gap distance of the etalons, so it is small in a certain direction. It becomes a large value in the direction orthogonal to it.

Here, when the smallest half-value width is Δ1 and the largest half-value width is Δ2, the difference in the half-value widths at this time reflects the difference in the gap interval between the slit positions of the etalons. If the difference between Δ1 and Δ2 is Δλ, the maximum gap difference ΔL on the etalon is approximately represented by the following (Equation 1).

[0058]

[Equation 1]

Here, λ is the wavelength of the excimer laser beam output from the excimer laser oscillator 11, and FSR is the FSR value of the etalon 16.

Thus, it is possible in this way to measure the difference in gap spacing in different directions on the etalon.

As described above, in the present embodiment, the slit is rotated, the signal from the sensor is recorded, and the uniformity of the gap interval in each direction on the etalon is reliably evaluated by the calculator from the captured signal. can do.

In the present embodiment, the signal from the sensor 19 was converted into the wavelength characteristic of the etalon to find the change in the gap interval. However, the change in the gap interval is also found from the difference in the half width of the signal from the sensor 19 itself. You can ask. In that case, the difference between the smallest half-width and the largest half-width is Δx
The maximum gap difference ΔL on the etalon
Will be approximately represented by the following (Equation 2).

[0063]

[Equation 2]

In the present embodiment, the spectral width of the measuring laser beam is sufficiently narrower than the half-value width of the transmission characteristic of the etalon for the sake of simplification of description. If the spectrum of light has a spread, the uniformity of the gap spacing in each direction on the etalon can be similarly evaluated by appropriately correcting the effect of this spread by deconvolution processing or the like.

(Second Embodiment of the Invention) A second embodiment of the present invention will be described below with reference to the drawings. Figure 4
FIG. 6 is a conceptual diagram of an etalon evaluation device in a second embodiment of the present invention. In FIG. 4, reference numeral 41 denotes a measuring laser oscillator, which is typically an excimer laser oscillator in this embodiment. 42 is an aperture for controlling a laser beam used for measurement, 43 is a beam expander, 44 is a diffuser, and 45 is a diffuser.
Is an aperture for controlling the irradiation range of the etalon, 46 is a moving mechanism of the aperture 45, 47 is an etalon, 48 is a lens for converging a laser beam, 49 is a sensor, 50 is a signal taken out from the sensor, 51 is a calculator, Reference numeral 52 represents a change in the etalon gap interval calculated by the calculator 51.

Next, the operation will be described. The laser beam emitted from the excimer laser oscillator 41 has an aperture 42.
Thus, only an arbitrary part is selected. In FIG. 4, the laser beam is shown by a dotted line. The laser beam that has passed through the aperture 42 is expanded to an appropriate beam size by the beam expander 43.

This beam irradiates the etalon 47 while being diffused in various directions by the diffuser plate 44. At this time, the aperture 45 controls the portion where the laser beam irradiates the etalon 47. Further, the etalon irradiation range can be selected by moving the aperture with the aperture moving mechanism 46. The laser beam transmitted through the etalon 47 is focused on the sensor 49 by the lens 48.

The light pattern on the sensor 49 is 5 in FIG.
As shown in a, an interference pattern on a concentric circle, that is, an equal-angle interference fringe. In the present embodiment, when a line sensor is used and an interference pattern for three stripes is measured, since the FSR of the etalon 47 is known, the pattern of the equi-tilt interference fringe can be converted into a transmission characteristic according to the wavelength of the etalon, It is possible to know the full width at half maximum.

The half width obtained in this way actually includes the spread of the spectrum of the laser beam, but if the laser spectrum is known, the spread of the spectrum can be removed by deconvolution or the like, and only the characteristics of the etalon can be known. . Also, if you use a laser beam with a narrow band so that the spread of the spectrum can be ignored,
It goes without saying that the full width at half maximum of the transmission characteristics of the etalon can be obtained directly from the measured data.

The difference of this embodiment from the conventional example is that the aperture 45 and the aperture moving mechanism 46 are provided immediately before the etalon 47.
Is a point at which is installed and a point where the change in the etalon gap interval is calculated from the signal 50 from the sensor using the calculator 51. The positional relationship between the etalon 47 and the aperture 45 is shown in FIG.

In FIG. 6, the shaded portion is the aperture shielding portion, and the blackened portion is the aperture opening portion. The shaded area is the etalon. By moving the aperture, the etalon irradiation part can be changed as shown in 6a and 6b of FIG. Now, when the aperture is at 6a in FIG. 6, the interference fringes are measured in the same manner as in the conventional example and converted into the transmission characteristic according to the wavelength. Next, the aperture is moved to the position of 6b in FIG. 6 and the same measurement is performed to convert the transmission characteristic according to the wavelength. At this time, the transmission characteristics are as shown in FIG.

In FIG. 7, 7a is a wavelength transmission characteristic when the aperture arrangement is 6a in FIG. 6, and 7b is a wavelength transmission characteristic when the aperture arrangement is 6b in FIG. Here, when the etalon gap intervals are equal regardless of the location, the center positions of the transmission characteristics are completely the same. However, if there is a difference in the etalon gap intervals in 6a and 6b of FIG. 6 due to the surface accuracy and non-parallelism of the etalon, 7a of FIG.
The center position of 7b is different. If this difference is Δλ, the difference in the gap interval between 7a in FIG. 7 and 7a in FIG.
Given in.

In this way, the aperture is moved and Δ
It is possible to measure λ and use the calculator 51 to calculate the etalon gap spacing variation from the signal 50.
Further, in the present embodiment, the laser beam was used after being enlarged to an appropriate size by the cutout beam expander 43 by the aperture 42. The laser beam output from the excimer laser used in this embodiment may have a different spectral width or wavelength depending on the beam position. In such a case, by using the aperture 42 to select and use only a portion having a constant spectrum width or wavelength, the measurement accuracy is significantly improved.

As described above, the aperture is arranged immediately before the etalon, and the transmission characteristic of the etalon is measured every time the aperture is moved. It can be evaluated quantitatively.

In this embodiment, the excimer laser oscillator is used as the light source, but any kind of light source can be used as long as it can output the light whose band is narrowed to the extent that it can be corrected by the deconvolution process. Further, in this embodiment, the distribution of the etalon equitilt interference fringes is converted into the wavelength transmission characteristic.
The gap distance of the etalon can also be measured from the movement amount Δx of the equitilt interference fringes. In this case, the etalon gap distance ΔL
Is given by (Equation 2).

In this embodiment, the location where the aperture is scanned to irradiate the etalon is selected. However, a large number of apertures are provided in advance in the aperture, and the same measurement can be performed by shielding the apertures other than the desired location. Needless to say, the measurement of can be performed.

(Third Embodiment of the Invention) A third embodiment of the present invention will be described below with reference to the drawings.
FIG. 8 is a conceptual diagram of the etalon evaluation device in the third embodiment of the present invention. In FIG. 8, reference numeral 81 denotes a measuring laser oscillator, which is typically an excimer laser oscillator in this embodiment. Reference numeral 82 is an aperture for controlling a laser beam used for measurement, 83 is a beam expander, 84 is a diffusing plate, 8
Reference numeral 5 is an aperture for controlling the irradiation range of the etalon, 86 is a moving mechanism of the aperture 85, 87 is an etalon, 88 is a lens for condensing a laser beam, 89 is a sensor, and a line sensor is used in this embodiment. Reference numeral 90 is a sensor moving / rotating mechanism, 91 is a signal taken out from the sensor, 92 is a calculator, and 93 is a change in the etalon gap interval calculated from the signal 91 by the calculator 92.

Next, the operation will be described. The laser beam emitted from the excimer laser oscillator 81 has an aperture 82.
Thus, only an arbitrary part is selected. In FIG. 8, the laser beam is shown by a dotted line. The laser beam that has passed through the aperture 82 is expanded to an appropriate beam size by the beam expander 83. This beam irradiates the etalon 87 while being diffused in various directions by the diffuser plate 84. At this time, the aperture 85 controls the portion where the laser beam irradiates the etalon. Also, the aperture moving mechanism 8
By moving the aperture with 6, the etalon irradiation range can be selected. The laser beam transmitted through the etalon 87 is focused on the sensor 89 by the lens 88. The light pattern on the sensor 89 becomes a concentric interference pattern, that is, an equal-angle interference fringe, as shown at 9a in FIG.

The difference of the present embodiment from the second embodiment is that the sensor 89 is moved for 9a in FIG. 9 to measure a total of 6 stripes with 3 stripes sandwiching the center of the concentric circle.
In addition, the sensor 89, which is a line sensor, is used for the aperture 8
Install 5 in the same direction as it moves. Normal sensor 8
9 is installed at the focal position of the lens 88,
If there is a manufacturing error, the position where the sensor 89 is installed is slightly displaced from the focus position. Third Embodiment
Is effective in such cases.

FIG. 10 is a diagram showing how the equi-tilt angle interference fringes change when the etalon club spacing is evaluated using this evaluation system. In the case of FIG. 10, the sensor is installed at the focal position of the lens without error. The aperture is 10a in FIG.
Fig. 10 shows the equi-tilt angle interference fringes when it is installed and measured at the position
10a '.

Next, the equi-tilt interference fringes when the aperture is installed at the position 10b in FIG. 10 and measured are 10 in FIG.
b '. In the case where the etalon gap interval changes in 10a 'and 10b', the diameter of the equi-tilt interference fringes changes, and the movement amounts 10Δr and 10Δl of the interference fringes at this time are equal to each other. 10Δr and 10Δl are Δx in (Equation 2)
Therefore, the change ΔL in the etalon's gap interval can be obtained by the equation 2. Further, when the projection angle interference fringes are converted into the transmission characteristics depending on the wavelength of the etalon, 10Δr and 10Δl are converted into Δλ in the mathematical expression 1, so that the change ΔL in the etalon cuff interval can be obtained by the mathematical expression 1.

Therefore, when the sensor is installed at the focal position of the lens without error as shown in FIG. 10, there is no problem if only the three concentric fringes of the concentric interference fringes on one side are measured as in the second embodiment. . Next, consider the case where the sensor installation position has an error with respect to the focal position of the lens as shown in FIG. At this time, the aperture is changed to 11a and 11b in FIG.
The equi-tilt angle interference fringes measured by being installed in the space are as shown in 11a 'and 11b'. At this time, if there is a difference in the etalon gap intervals in 11a and 11b, the diameters of the concentric circles in 11a 'and 11b' change.

In the case of FIG. 11, the entire concentric circles of the equi-tilt interference fringes are displaced due to the change in the diameter of the concentric circles and the deviation from the focal position of the sensor installation location. The shift amount is approximately 11Δc shown in FIG. 11, and the shift direction is the moving direction of the aperture from 11a to 11b.
The line sensor is installed in the same direction as the moving direction. In such a case, since the movement amounts 11Δr and 11Δl of the interference fringes are not equal to each other, it is possible to accurately obtain the difference between the etalon cuff intervals simply by measuring the three fringes of the equal-angle tilt interference fringes as in the second embodiment. Can not. In the case of FIG. 11, the average value of the movement amounts 11Δr and 11Δl is the movement amount Δx of the interference fringe in the equation 2. If Δx is known, the change in the gap distance of the etalon can be obtained by using Equation 2.

Therefore, in the third embodiment, the interference fringes on both sides of the center of the concentric circle are measured, the average value of the movement amount of the interference fringes on both sides is calculated, and the change in the etalon gap interval can be obtained. I can. Also, the equi-tilt angle interference fringes 11a ',
The gap distance of the etalon can be obtained by converting b'to the transmission characteristic of the etalon depending on the wavelength. In this case, the wavelength transmission characteristic of the etalon is as shown in FIG.

Here, 12a is the wavelength transmission characteristic of the etalon when the aperture is at the position of 11a in FIG.
2b is the wavelength transmission characteristic of the etalon when the aperture is at the position of 11b. 12Δλr and 12Δλl in FIG.
Is obtained by converting 11Δr and 11Δl into wavelengths.
Since the average value of 1Δλr and 11Δλl is Δλ in Equation 1, if 12Δλr and 12Δλl are known, the distribution of the gap distance of the etalon can be measured using (Equation 1).

As described above, when there is an error in the position of the sensor that should be installed at the focal position of the lens, the equi-tilt interference fringes are measured for three stripes each for three stripes across the center of the concentric circle, for a total of six stripes. However, the variation in the gap distance of the etalon can be quantitatively evaluated from the average value of the movement amount of the center position of the transmission characteristics on both sides of the concentric circle. In this embodiment, an excimer laser oscillator is used as the light source, but any type of light source can be used as long as it is a light source that can output light with a band narrowed to the extent that it can be corrected by deconvolution processing.

In the present embodiment, the equi-tilt interference fringes are measured for a total of 6 fringes with 3 fringes sandwiching the center of the concentric circle, but if more fringes than 6 fringes are measured, the etalon gap can be more accurately measured. Interval is required.

(Fourth Embodiment) FIG. 13 is a diagram showing the structure of an optical resonator of an excimer laser oscillator according to a fourth embodiment of the present invention. In FIG. 13, 131 is a total reflection mirror,
Reference numeral 132 is a quarter-wave plate, 133 is a discharge tube, 134 is a polarization separation mirror, 135 is a prism, 136 is an etalon, 138 is a prism, and 139 is a grating.

Next, the operation of the optical resonator will be described with reference to FIG. The light 140 amplified by the laser medium in the discharge tube 133 has its propagation direction separated by the polarization separation mirror 134 depending on the polarization component, and the light of one polarization component is output as the output light 141. The light of the other polarization component passes through the polarization separation mirror 134 and becomes the transmitted light 142. Transmitted light 142
Passes through the three prisms 135, 137, 138 and the etalon 136 and enters the grating 139 while the beam size is expanded. Since the etalon 136 has wavelength selectivity here, the wavelength of the light transmitted through the etalon is narrowed.

Further, the transmitted light 142 has its wavelength spectral width narrowed by the diffraction effect of the grating. The reason for expanding the beam size using the prisms 135, 137, and 138 is to increase the efficiency of narrowing the wavelength spectrum due to diffraction of the grating.

Further, since the magnification of one prism is limited to about 3 times, three prisms are used in this embodiment. The reflected light 143 diffracted by the grating 139 passes through the polarization separation mirror 134 again and is amplified by the laser medium to become light 144, which is the quarter-wave plate 132.
Enter The light 144 is reflected by the total reflection mirror 131 to become the reflected light 145. By passing through the quarter-wave plate 132 twice, it becomes equivalent to passing through the half-wave plate, and the light is changed in one direction. 144 becomes reflected light 145 including polarized components in both directions.

Next, the reflected light 145 is amplified by the laser medium of the discharge tube 133 to become the light 140. The light 140 is output by the polarization splitting mirror 134 as a polarized light component in one direction as output light 141. On the other hand, the other polarized component becomes this processing 142 and continues oscillation.

Next, the features and effects of this embodiment will be described with reference to FIG. Figure 14 (α) shows Etalon 1
It is the figure which looked at 36 from the optical axis direction. First, a cross-sectional view of the laser beam transmitted through the etalon is shown in FIG.
4a, the spectrum of the laser beam of the output light 141 at this time is 14a 'in (β) of FIG.

Next, the etalon is evaluated by the evaluation method shown in the first to third embodiments. For example, assuming that the region 14b in the etalon 136 has the smallest change in the gap distance, the etalon is moved and rotated in the present embodiment. Then, the laser beam is transmitted through the region 14b. By doing so, the spectrum becomes like 14b 'in (β) of FIG. When 14a 'and 14b' are compared, FWHMa> FWHMb. Therefore, using the region 14b makes it possible to obtain a laser beam with higher spectral purity.

As described above, the change in the gap distance of the etalon is evaluated by using the evaluation method as in the first to third embodiments as in the present embodiment, and the region where the change in the gap distance is small is narrowed by the laser beam. A laser beam with higher spectral purity can be obtained by using it for banding.

[0096]

As described above, according to the present invention, the advantageous effect that the uniformity of the gap distance of the etalon can be accurately measured can be obtained. Further, if the etalon is evaluated according to the present invention and a region having a good gap interval is used for narrowing the band of the laser beam, the spectral purity of the laser beam can be further improved.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a configuration of an etalon evaluation device according to an embodiment of the present invention.

FIG. 2 is a schematic view showing a positional relationship between the etalon and the slit.

FIG. 3 is a schematic diagram of wavelength characteristics of the etalon.

FIG. 4 is a schematic diagram showing a configuration of an etalon evaluation device according to a second embodiment of the present invention.

FIG. 5 is a schematic diagram of equal-angle tilt fringes and wavelength transmission characteristics of the etalon.

FIG. 6 is a diagram showing a positional relationship between the etalon and the aperture.

FIG. 7 is a diagram showing wavelength characteristics of the etalon measured in the same manner.

FIG. 8 is a schematic diagram showing a configuration of an etalon evaluation device according to a third embodiment of the present invention.

FIG. 9 is a schematic diagram of an equal tilt interference fringe and a wavelength transmission characteristic of the etalon.

FIG. 10 is a diagram showing a change in equitilt angle interference fringes when the etalon's gap interval is evaluated using the same evaluation system.

FIG. 11 is a diagram showing a state of changes in equi-tilt interference fringes when the etalon's gap interval is evaluated using this evaluation system when the sensor is misaligned.

FIG. 12 is a diagram showing wavelength characteristics of the etalon measured in the same manner.

FIG. 13 is a diagram showing a configuration of an optical resonator according to a fourth embodiment of the present invention.

FIG. 14 is a diagram of the etalon viewed from the optical axis direction and a diagram showing a laser spectrum.

FIG. 15 is a diagram showing a structure of an etalon in a conventional example.

FIG. 16 is a schematic diagram of wavelength characteristics of the etalon.

FIG. 17 is a schematic diagram showing a shift of wavelength transmission characteristics in the wavelength direction due to a change in the gap distance of the etalon.

FIG. 18 is a diagram showing a configuration of the etalon evaluation device.

FIG. 19 is a schematic view of an equal tilt interference fringe and a wavelength transmission characteristic of the etalon.

[Explanation of symbols]

11 Excimer laser light source for measurement 12 beam expander 13 Diffuser 14 slits 15 Slit rotation mechanism 16 etalon 17 lenses 18 sensors 19 signals 20 calculator 21 Change in etalon gap distance 41 Excimer laser oscillator for measurement 42 Aperture 43 beam expander 44 Diffuser 45 aperture 46 Aperture moving mechanism 47 Etalon 48 lenses 49 sensors 50 signal 51 calculator 52 Etalon gap change 81 Excimer laser oscillator for measurement 82 Aperture 83 beam expander 84 Diffuser 85 Aperture 86 Aperture moving mechanism 87 Etalon 88 lens 89 sensor 90 Sensor movement rotation mechanism 91 signal 92 calculator 93 Change in gap distance of etalon 131 total reflection mirror 132 1/4 wave plate 133 discharge tube 134 Polarization separation mirror 135 prism 136 etalon 137 prism 138 prism 139 grating 140 light 141 output light 142 transmitted light 143 reflected light 144 light 145 reflected light 151 gap spacing 152 spacer 153a Parallel plate 153b Parallel plate 181 Excimer laser oscillator for measurement 182 beam expander 183 diffuser 184 etalon 185 lens 186 sensor 187 signal

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI H01S 3/225 H01S 3/223 E (72) Inventor Keitaro Takano 3-10-1 Higashisanda, Tama-ku, Kawasaki-shi, Kanagawa Matsushita Giken (72) Inventor Yuji Hashidate 3-10-1, Higashisanda, Tama-ku, Kawasaki City, Kanagawa Prefecture Matsushita Giken Co., Ltd. (72) Hidemi Takahashi 3-10-1, Higashisanda, Tama-ku, Kawasaki City, Kanagawa Prefecture Matsushita Giken Co., Ltd. (56) Reference JP-A-8-62041 (JP, A) JP-A-4-36622 (JP, A) JP-A-4-198822 (JP, A) JP-A-2-44219 ( JP, A) JP-A-1-310583 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) G01M 11/00-11/08 H01S 3/00-3/30 G01J 3 / 00-4/04 G01J 7/00-9/04 G02B 5/20-5/28

Claims (15)

(57) [Claims] 1. A laser oscillator, a diffusion plate, a condenser lens, a light receiving sensor, established the full <br/> fab Repeller Roetaron between the diffusion plate and the condenser lens, etc. inclination of the Fabry-Perot etalon In a device for measuring interference fringes and evaluating characteristics, as means for allowing light from the laser oscillator to enter a plurality of regions of the Fabry-Perot etalon ,
Just before the Fabry-Perot etalon, the Fabry-Perot
An evaluation device having a slit installed so as to be rotatable relative to the etalon . 2. A laser oscillator, a diffusion plate, a condenser lens, and a receiver.
It consists of an optical sensor and has a space between the diffuser and the condenser lens.
Installed the Fabry-Perot etalon,
Equal inclination interference fringe Talon measured, in the apparatus for evaluating the characteristics, as a means to allow the incident light from the laser oscillator into a plurality of regions of the Fabry-Perot etalon, the Fabry-Perot etalon immediately before the Fabry-Perot etalon Has an aperture installed so that it can move relative to
That the evaluation device. 3. A device according to claim 1 or 2, wherein,
An evaluation apparatus, wherein an aperture and an optical system are installed between a laser oscillator and a diffusion plate, and only a portion where a spectrum of a laser beam emitted from the laser oscillator is constant is used for evaluation. 4. The evaluation device according to claim 3 , wherein the optical system installed between the laser oscillator and the diffusion plate is a beam expander. 5. The apparatus according to any of claims 1 to 4, the evaluation device, which comprises using an excimer laser oscillator which is narrowed in the laser oscillator. Apparatus 6. The method of claim 2, wherein, using a line sensor in the sensor, the pre-SL line sensor fab
Evaluation apparatus characterized by placing in the same direction as the scanning direction of the aperture is disposed just before the repeller Roetaron. 7. irradiated with laser light diffused in the Fabry-Perot etalon, an equal inclination interference fringe is measured and an evaluation device for evaluating the characteristics of the fab repeller Roetaron from the like inclination interference fringe, the slits Using the laser light
Obtained by irradiating the reference position of the Fabry-Perot etalon
The laser is formed by using the equal tilt interference fringe a and the slit.
Irradiate light to any position on the Fabry-Perot etalon
At least an input signal interference fringes b was collected using a, and evaluated with a means for calculating a change in the fab repeller b <br/> gap spacing Etaron from a change in the half width of said equal inclination interference fringe a and b device. 8. The diffused layer in the Fabry-Perot etalon.
Laser beam is radiated to measure the equi-tilt angle interference fringes.
Evaluate the characteristics of the Fabry-Perot etalon from interference fringes
A that the evaluation device, any of the fab repeller Roetaron the laser light using the aperture with an equal inclination interference fringe a obtained by irradiating the laser beam to the reference position of the fab repeller Roetaron with aperture and at least the input signal interference fringes b obtained by irradiating the position of, <br/> evaluation having a means for calculating a change of said equal inclination interference fringe a and b gap spacing of the fab repeller Roetaron from the amount of movement of apparatus. 9. The apparatus according to claim 7 , wherein
And means for converting the input signal to the transmission characteristics due to the wavelength of the fab repeller Roetaron, and calculates the change in the gap distance of the fab repeller Roetaron from the signal after converting the transmission characteristics due to said wavelength Evaluation device. 10. The apparatus according to claim 8 , wherein interference fringes in one direction from the center of the concentric circles of the equi-tilt interference fringes and in the other direction are measured, and the average value of the movement amount of each interference fringe is calculated. by taking, correcting an error of measurement, evaluation apparatus characterized by calculating the change in the gap distance of the fab repeller <br/> Roetaron. 11. irradiated with laser light diffused in the Fabry-Perot etalon, an equal inclination interference fringe was measured, in the evaluation method of calculating the change in the gap distance of the fab repeller Roetaron from the like inclination interference fringe, calculated The method is
The laser light is lit using a Fabry-Perot
Ron's reference position and the same tilt angle interference fringe a
The slits are used to direct the laser light to the Fabry-Perot.
Half of the interference fringe b obtained by irradiating an arbitrary position of the etalon
From the change in price range, the gap of the Fabry-Perot etalon
An evaluation method characterized by calculating a change in interval . 12. A diffused Fabry-Perot etalon
Irradiate laser light and measure the interference fringes at the same tilt angle.
From the angular fringe to the gap between the Fabry-Perot etalons
In the evaluation method of calculating the interval change of calculation method, the laser light using the aperture with an equal inclination interference fringe a obtained by irradiating the laser beam to the reference position of the fab repeller Roetaron with aperture the fab Repeller <br/> interference fringes b obtained by irradiating an arbitrary position of Roetaron
Evaluation wherein the Turkey to calculate the change in the gap distance of the fab repeller Roetaron from the amount of movement of the. 13. The evaluation method according to claim 11 or 12, wherein converting the equal inclination interference fringe to the transmission characteristics of the wavelength of the fab repeller Roetaron, calculates the change in the gap distance of the fab repeller Roetaron from the transmission characteristics of the wavelength An evaluation method characterized by: 14. The evaluation method according to claim 12 , wherein
Measure the interference fringes in one direction and the other direction from the center of the concentric circles of the equi-tilt interference fringes, and correct the measurement error by taking the average value of the movement amount of each interference fringe. evaluation method characterized by calculating the change in the gap spacing br /> Bed Repeller Roetaron. 15. established a fab Repeller Roetaron inside the optical resonator, the laser oscillator for narrowing the laser beam, the fab repeller Roetaron claim 1
To claim using the evaluation device according to any one of
Were evaluated by the evaluation method according to any of claim 11 14, characterized in that the narrowing of the laser beam oscillated from the laser oscillator using a region little change in the gap distance of the fab repeller Roetaron from the result And a laser oscillator.