JPH0465640A - Method and instrument for spectrum measurement - Google Patents

Abstract

PURPOSE:To sufficiently accurately evaluate a spectrum peripheral part and to improve the resolution by providing a single-longitudinal-mode CW Ar second harmonic laser, etc., for reproducing the device function of a spectral device. CONSTITUTION:The beam from an excimer laser 1 to be tested is transmitted through a mirror 7, entered into a fiber incidence optical system 4, and diffracted spectrally by a grating spectroscope 3 according to a command from a controller 6. The tested excimer laser light which is diffracted spectrally contains position information on a wavelength axis and its spectrum is measured by a linear sensor 5 and stored. Then a shutter 8b is opened and a shutter 8a is closed. The beam of an argon half-wavelength laser 2 is reflected by a mirror 7, entered into the optical system 4, and diffracted spectrally by the spectroscope 3 and the spectrum is measured by a linear sensor 5 and stored. The spectrum width of the argon half-wavelength laser is about 0.001pm and the device function of the spectroscope 3 can sufficiently be measured.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a spectrum measuring instrument that performs precise spectroscopy by measuring the device function of the spectrometer.

[Prior Art] With advances in semiconductor exposure technology, excimer projection exposure technology using an excimer laser as a light source has been developed. However, the wavelength of excimer laser is in the deep ultraviolet region, and quartz is the only lens material with good transmittance and workability. If the projection lens is made of only quartz, achromatization is not possible, so it is necessary to limit the spectral width of the excimer laser, which is the light source, to 81 bands in order to correct chromatic aberration.

Therefore, in designing the projection lens, it is necessary to accurately measure and evaluate the spectrum of the narrow-band excimer laser.

Conventionally, the spectrum of excimer laser light has been measured using a long focus spectrometer or an etalon spectrometer using a grating with many lines per unit length.

[Problems to be Solved by the Invention] However, the above conventional example had the following drawbacks. When a grating spectrometer is used, evaluation of the peripheral part of the spectrum is determined approximately by the S/N of the sensor and is good.

However, the spectral width of excimer laser light is approximately 2 to 3
[pm]. Also, 3600 lines/mm width 110 [m
The resolution of a grating spectrometer using a grating of λ-248, 4 nm was about 05 to lO[pm]. Therefore, the evaluation of spectral width was not accurate enough.

When using a square etalon spectrometer, the resolution is (FSR/Fi
ness). FSR is a measurement range of a certain order of the etalon, and Finess is a constant related to the performance or failure of the etalon.

1"1ness is a nearly constant value of 10 to 20, so in order to increase the resolution, the FSR must be decreased. When the FSR is decreased, light of different orders overlaps,
The reliability of the evaluation of the periphery of the spectrum decreases.

As described above, the grating spectrometer has the disadvantage that although the peripheral part of the spectrum can be well evaluated, the resolution is insufficient, and the etalon spectrometer has the disadvantage that although the resolution is improved, the peripheral part of the spectrum cannot be evaluated well.

The present invention has been made in view of the above-mentioned drawbacks of the prior art, and it is an object of the present invention to provide a spectrum measuring instrument that can evaluate the peripheral part of the spectrum with sufficient precision and has improved resolution.

[Means and effects for solving the problem] To achieve the above object, according to the present invention, by providing a single longitudinal mode CW Ar double harmonic laser, etc., which reproduces the instrumental function of a spectroscopic device, , performs resolution improvement correction and precisely evaluates the peripheral part of the spectrum.

[Example] Fig. 1 is a drawing showing the configuration of an example of the present invention, in which 1 is a test excimer laser, 2 is a single longitudinal mode CW argon laser 2 with a spectral width of about 0.001 pm.
Double harmonic laser (argon half wavelength laser), 3 is a grating spectrometer, 4 is a fiber input optical system that guides light to the grating spectrometer, 5 is a linear sensor attached to the grating spectrometer, 6 is a controller, 7 is a half mirror 8a and 8b are shutters for switching between the excimer laser 1 and the argon half-wavelength laser 2 to be tested; 9 is a spectrum display that displays the calculation results from the controller 6;
10 is an optical fiber.

Based on a command from the controller 6, the shutter 8a is opened and the shutter 8b is closed. The beam of the excimer laser 1 to be tested passes through the half mirror 7 and enters the fiber input optical system 4, where it is separated by the re-grating spectrometer 3. The spectrum of the separated test excimer laser light is measured by the linear sensor 5, with the wavelength axis serving as position information, and is temporarily stored in the controller 6.

Next, based on the command from the controller 6, the shutter 8b
is opened, and the shutter 8a is closed.

The beam of the argon half-wavelength laser 2 is reflected by the half mirror 7, enters the fiber input optical system 4, is separated into spectra by the grating spectrometer 3, is spectrally measured by the linear sensor 5, and is temporarily stored in the controller 6. The spectral width of the argon half-wavelength laser is about 0.001 pm, which is sufficient to measure the device function of the grating spectrometer 3.

FIG. 2(a) shows the measured spectrum a(λ) of the excimer laser beam under test, and FIG. 2(b) shows the spectrum g(λ) of the argon half-wavelength laser beam.

Letting the actual spectrum of the excimer laser light under test be S(λ), the following relationship exists.

a(λ)zu-zs(λ')g(λ-λ')dλ'λ'The troller 6 stores a(λ) and g(λ) and solves the above integral equation to calculate S(λ). Calculate. Also, since the wavelength of the peak of g(λ) is known, the difference between the peak of a(λ) and the peak of g(λ) indicates that the test excimer laser beam a
Find the center wavelength of (λ).

FIG. 2(c) shows the calculated spectrum S(λ).

It can be seen that the minute bumps seen in the measured spectrum a(λ) are separated as seen in part A of S(λ).

As explained above, in the above embodiment, a grating spectrometer is used as a spectroscopic means to separate the test laser beam in a spectrum measuring instrument that measures the wavelength spectrum of the test laser beam, and the resolution of the laser beam to be measured and the spectroscopic means are It is equipped with an apparatus function reproduction means for reproducing the apparatus function of the spectroscopic means using a light source with a sufficiently narrow half-width compared to the above, and has an arithmetic means for correcting the spectrum data obtained from the spectroscopic means based on the apparatus function. . The laser under test is, for example, a KrF narrow-band excimer laser that oscillates at a center wavelength of 248.4 n+n. Further, the device function reproducing means is, for example, a single longitudinal mode CW argon second harmonic laser (argon half-wavelength laser) that oscillates at a center wavelength of 248.25 nm. The calculation means subtracts the device function obtained by measurement of the argon half-wavelength laser from the spectral data of the excimer laser beam under test (decomposition), and calculates the difference between the center wavelengths of both laser beams.

FIG. 3 shows the configuration of another embodiment of the invention. In this embodiment, a single longitudinal mode CW argon-dye two-wave mixed laser which oscillates at a center wavelength of 248.2 nm to 24B, 6 nm is used in place of the argon half-wavelength laser in the embodiment of FIG. Other configurations, functions and effects are similar to those of the embodiment shown in FIG. 1, but the single longitudinal mode CW Argo, N dye two-wave mixed laser can be directly tuned to the oscillation wavelength of the excimer laser.

[Effects of the Invention] As explained above, according to the present invention, the resolution of the spectrometer is corrected and the peripheral part of the spectrum is also evaluated.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of an embodiment of the present invention. FIG. 2 is a graph showing measured spectra and calculated spectra. FIG. 3 is another embodiment of the present invention. FIG. 6 Near 28: 9 = 2' Controller, Half Mirror Shutter, Spectrum Display, : Car-longitudinal mode CW argon-dye two-wave mixed laser.

Claims (7)

[Claims] (1) The test light whose spectrum is to be measured and the reference light whose spectral width is sufficiently narrow compared to the test light are separated by a common spectrometer, and based on the spectral data of the reference light detected by the spectrometer, the A spectrum measurement method characterized by performing correction calculations on spectrum data of test light detected by a device. (2) a first light source that emits test light whose spectrum is to be measured; a spectrometer that spectrally spectra the test light; and a spectrometer that spectrally has a narrower spectral width than the test light and has a spectral width that can be analyzed by the spectrometer. It is characterized by comprising: a second light source that emits light for device function reproduction; and a calculation means for correcting the spectrum of the test light based on spectral data of the test light detected by the spectrometer and the light for spectrometer function reproduction. Spectral measuring instrument. (3) The spectrum measuring instrument according to claim 2, wherein the test light is comprised of a KrF narrowband excimer laser that oscillates at a center wavelength of 248.4 nm. (4) The spectrum measuring device according to claim 2, wherein the spectroscopic device comprises a grating spectrometer. (5) The spectroscopic device function reproduction light has a center wavelength of 248.
3. The spectrum measuring instrument according to claim 2, comprising a single longitudinal mode CW argon second harmonic laser that oscillates at 25 nm. (6) The calculation means subtracts the spectrometer function data from the spectrum data of the test light, and calculates the difference between the center wavelengths of both lights.
Spectral measuring instrument as described in section. (7) The spectroscopic device function reproduction light has a center wavelength of 248.
3. The spectrum measuring instrument according to claim 2, comprising a single longitudinal mode CW argon-dye two-wave mixed laser that oscillates at a wavelength of 2 nm to 248.6 nm.