JP2006242967A - Wavelength detector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To precisely detect a wavelength of a detected light output from a detected light source, without an error, even when individual differences exist among the spectroscopes or a measuring environment is fluctuated to vary a characteristic of the spectroscope. <P>SOLUTION: This wavelength detector for detecting the wavelength of the detected light output from the detected light source, based on a wavelength of reference light emitted from a reference light source, uses as the reference light one or more of emission light beams out of three emission light beams of platinum Pt having a wavelength most approximate to a wavelength of an argon-fluorine excimer laser emission beam, and having a prescribed level or more of light intensity, when the detected light is the argon-fluorine excimer laser emission beam. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a wavelength detection device for detecting the wavelength of light such as a laser, and more particularly to a wavelength detection device suitable for detecting the wavelength of oscillation laser light from an argon fluorine (ArF) excimer laser and a krypton fluorine (KrF) excimer laser. Is.

  When an excimer laser is used as a light source for a stepper (reduction projection exposure apparatus), it is necessary to narrow the band of the oscillation laser light of the excimer laser. Furthermore, it is necessary to carry out stabilization control with high accuracy so that the center wavelength of the spectrum of the oscillation laser beam having the narrow band is not shifted during exposure.

  FIG. 19 shows a general laser wavelength stabilization control device.

  The band narrowing is performed by driving a band narrowing element such as an etalon or a grating disposed in the band narrowing module 26 via the driver 28 by the controller 20 (for example, adjusting the installation angle of the etalon or the grating). Done. During exposure, the wavelength is controlled so that the center wavelength of the spectrum does not fluctuate.

  That is, during the exposure, the absolute wavelength of the oscillation laser beam L0 is detected by always detecting the relative wavelength of the oscillation laser beam L0 with respect to the reference light in the monitor module 22.

  Next, the detection result is fed back to the controller 20, whereby the narrowband element is driven via the driver 28.

  The center wavelength of the spectrum of the laser light L0 emitted through the laser chamber 27 is fixed to the target wavelength.

  In Patent Document 1, an arsenic (As) emission line having a wavelength of 193.696 nm is used as reference light for detecting the absolute wavelength of an oscillation laser beam of an argon fluorine excimer laser (wavelength: about 193.3 nm).

  That is, the emission line emitted from the arsenic-sealed discharge lamp is made incident on the spectroscope as reference light. At the same time, an oscillating laser beam of an argon fluorine excimer laser whose wavelength is to be detected is made incident on the spectroscope as detected light. In the spectroscope, the reference light and the light to be detected are split, and an image of the split light is formed on the line sensor. The detection position on the line sensor corresponds to the detection wavelength.

  Then, the relative wavelength of the detected light with respect to the reference light is obtained from the difference in the detection position on the line sensor using the dispersion value, and the absolute wavelength of the detected light is calculated based on the obtained relative wavelength and the wavelength of the known reference light. is doing.

  Here, the dispersion value will be described. FIG. 12 shows the relationship between the sensor channel number (position on the line sensor) of the line sensor and the sensor signal intensity. The line sensor includes a plurality of light receiving channels, and the light detection position on the line sensor is determined according to the channel number in which the maximum intensity light is detected. In the line sensor, since the incident position on the line sensor differs according to the wavelength, the wavelength of light can be detected from the light detection position of the line sensor. Therefore, the wavelength of the light is determined from the channel number where the light is detected.

  The dispersion value is a wavelength (unit: nm) corresponding to the channel interval (unit: μm) of the line sensor. If the dispersion value (wavelength corresponding to the channel interval of the line sensor) can be determined, the difference between the channel number Sa that detects the reference light La and the channel number S0 that detects the detected light L0 using this dispersion value, The relative wavelength of the detected light L0 with respect to the reference light La can be obtained.

  The wavelength corresponding to the channel spacing (dispersion value) is determined by the characteristics of the spectroscope that guides light onto the sensor. The characteristics of the spectroscope are determined by the characteristic values of various optical element parts constituting the spectroscope, such as the number of grooves in the grating, the focal length of the concave mirror, and the refractive index of light in the air.

  Here, conventionally, the wavelength λ0 of the light to be detected is calculated on the assumption that the characteristics of the spectrometer are known, that is, the dispersion value is a known value.

  Specifically, a theoretical (spectroscope design) dispersion value Dt (wavelength per sensor channel) is obtained for each spectroscope based on design values such as the focal length of the concave mirror inside the spectroscope.

Then, the obtained theoretical dispersion value Dt is fixed, and the relative wavelength of the detected light L0 with respect to the reference light La is determined from the difference between the detected channel number Sa of the reference light La and the detected channel number S0 of the detected light L0. The wavelength λ0 of the detected light L0 is calculated from the obtained relative wavelength and the known wavelength λa (193.696 nm) of the reference light La.
JP-A-4-163980

  However, the characteristic values of the designed spectrometer are slightly different from the characteristic values of the actually manufactured individual spectrometers. That is, an error is included in the theoretical dispersion value Dt due to the individual difference of the spectroscope.

  The characteristics of the spectroscope change according to changes in the measurement environment, such as changes in temperature and pressure. For example, when the temperature changes, the interval between the grooves of the grating changes. When the pressure changes, the refractive index of light in the air changes. For this reason, the relationship between the detection position of the sensor and the wavelength varies with changes in temperature and pressure.

  As described above, the actual dispersion of the spectrometer is caused by the difference between the characteristics of the designed spectrometer and the characteristics of each actually manufactured spectrometer, the fluctuation of the spectrometer characteristics due to the fluctuation of the measurement environment, etc. The value D indicates a value different from the theoretical dispersion value Dt. Therefore, assuming that the spectroscope characteristics are known, that is, assuming that the theoretical dispersion value Dt is known, the difference between the detection channel number Sa of the reference light La and the detection channel number S0 of the detection light L0 is the target of the reference light La. When the relative wavelength of the detected light L0 is obtained and the wavelength λ0 of the detected light L0 is calculated from the obtained relative wavelength and the known wavelength λa (193.696 nm) of the reference light La, the obtained wavelength λ0 A detection error is included. The wavelength λ0 is required to have a detection accuracy of the order of 0.0001 nm, but this request cannot be met.

  The present invention has been made in view of such circumstances, and even if the spectroscope has individual differences or the measurement environment fluctuates, the detected light output from the detected light source is changed. It is an object of the present invention to make it possible to accurately detect the wavelength of these without error.

Therefore, in the first invention of the present invention, in order to achieve the above-described problem,
In the wavelength detection device that detects the wavelength of the detected light output from the detected light source based on the wavelength of the reference light emitted from the reference light source,
When the detected light is an argon fluorine excimer laser emission line, among the three emission lines of platinum Pt having a wavelength closest to the wavelength of the argon fluorine excimer laser emission line and having a light intensity of a certain value or more, One or more emission lines are used as the reference light.

  The first invention will be described with reference to FIG.

  That is, according to the first invention, as the reference light of the reference light source, one of the three light emission lines of platinum Pt having a wavelength closest to the wavelength of the argon fluorine excimer laser light emission line and having a light intensity of a certain level or more. The above light emission lines are used.

  Here, for example, as shown in FIG. 13, when three light emission lines LP1, LP2, LP3 of platinum Pt having a wavelength closest to the wavelength λ0 of the detected light L0 of the argon fluorine excimer laser are used as the reference light, The wavelength λ0 of the detected light L0 is detected based on the wavelengths λP1, λP2, and λP3 of the reference lights LP1, LP2, and LP3.

  As described above, according to the first aspect of the present invention, one or more light emission lines among the three light emission lines of platinum Pt having a wavelength closest to the wavelength of the argon fluorine excimer laser light emission line and having a light intensity of a certain level or more. Since it is used as the reference light, the wavelength λ0 of the detected light L0 can be detected.

  As a result, even if the spectroscope 7 has individual differences or the measurement environment fluctuates and the characteristics of the spectroscope 7 change, the wavelength λ0 of the detected light L0 output from the detected light source 1 is accurate without error. Can be detected well.

Moreover, in the second invention, in order to achieve the above-mentioned solution problem,
In the wavelength detection device for detecting the wavelength of the detected light based on the absorption line that minimizes the light intensity of the detected light output from the detected light source,
When the detected light is an argon fluorine excimer laser emission line, among the absorption lines of platinum Pt, arsenic As, neon Ne, carbon C, and germanium Ge having a wavelength approximate to the wavelength of the argon fluorine excimer laser emission line, One or more absorption lines are used as an absorption line for the argon fluorine excimer laser emission line.

  A wavelength detection apparatus according to the present invention will be described below with reference to the drawings.

  In the present embodiment, it is assumed that the wavelength of an argon fluorine (ArF) excimer laser is detected. However, the present invention can also be applied to the case of detecting the wavelength of a krypton fluorine (KrF) excimer laser. The wavelength of the krypton fluorine excimer laser is about 248.4 nm. The wavelength of the argon fluorine excimer laser is about 193.3 nm. It can also be applied to the detection of wavelengths of light other than laser light.

  FIG. 1 shows a configuration of a wavelength detection apparatus according to an embodiment.

  The detected light source 1 is a light source from which detected light L0 whose wavelength is to be detected is emitted, and is an argon fluorine excimer laser device in this embodiment. The laser beam oscillated by being discharge-excited in the laser chamber of the argon fluorine excimer laser device is amplified by reciprocating in the resonator formed by the front mirror 21 and the narrowband module 26, and is amplified from the laser extraction window. It is emitted as power oscillation laser light L0.

  On the other hand, the reference light source 2 is an arsenic (As) lamp in which neon Ne is sealed as a buffer gas. The buffer gas is enclosed in the lamp so that the lamp filament does not burn. As the arsenic lamp, a hollow cathode lamp is used. Therefore, the reference light source 2 emits a neon Ne emission line Ln having a wavelength of 193.00345 nm and an arsenic As emission line La having a wavelength of 193.7590 nm as two reference lights Ln and La having different wavelengths. Therefore, according to the present embodiment, there is an advantage that two reference lights Ln (neon) and La (arsenic) can be emitted from one reference light source 2. There is no need to prepare two reference light sources separately.

  The detected light L0 is incident on the beam splitter 5 through the lens 3. Part of the detected light L 0 is reflected by the beam splitter 5 and guided to the shutter 6. The reference lights Ln and La are incident on the beam splitter 5 through the lens 4. Some of the reference lights Ln and La are transmitted through the beam splitter 5 and guided to the shutter 6.

  Thus, the detected light L0 and the reference lights Ln and La pass through the shutter 6 and enter the spectroscope 7.

  When the detected light L0 and the reference lights Ln and La are incident on the spectroscope 7, they are first incident on the concave mirror M1 and the reflected light is incident on the grating 8 which is a diffraction grating. The diffraction angle of the grating 8 changes according to the wavelength of incident light. The detected light L0 and the reference lights Ln and La diffracted by the grating 8 are incident on the concave mirror M2, and the reflected light is guided to the sensor 10 via the reflecting mirror 9.

  The sensor 10 is a line sensor. Specifically, a one-dimensional or two-dimensional image sensor or a diode array can be used.

  If the wavelength of the light incident on the spectroscope 7 is different, the diffraction angle at the grating 8 is different and the incident position on the sensor 10 is different. As a result, the detected light L0 and the reference lights Ln and La having different wavelengths are incident on the sensor 10 after being split, and the detected light L0 and the reference light Ln incident on the spectroscope 7 according to the detection position on the sensor 10. La wavelength λ0, λn and λa can be detected. That is, the spectrum profile on the line sensor changes depending on the wavelength of light. When an etalon is used instead of the grating, the fringe pattern on the line sensor changes.

  The reference lights Ln and La emitted from the reference light source 2 and the detected light L0 emitted from the detected light source 1 may be simultaneously incident on the spectrometer 7. The reference light and the detected light are shifted in time. May enter the spectroscope 7.

  In the present embodiment, it is assumed that the excimer laser device of the detected light source 1 is used as a light source of a stepper (reduced projection exposure apparatus). In this case, it is necessary to narrow the band of the oscillation laser light L0 of the excimer laser. Furthermore, it is necessary to carry out stabilization control with high accuracy so that the center wavelength of the spectrum of the narrowband oscillation laser beam L0 does not shift during exposure.

  The band narrowing is performed by driving a band narrowing element such as an etalon or a grating disposed in the resonator of the laser chamber (for example, adjusting an installation angle of the etalon or the grating). During exposure, the wavelength is controlled so that the center wavelength of the spectrum does not fluctuate.

  For this purpose, the absolute wavelength λ0 of the oscillation laser beam L0 is detected by detecting the relative wavelength of the oscillation laser beam L0 with respect to the reference beams Ln and La during the exposure by the wavelength detector shown in FIG. Then, by feeding back the detection result, the band narrowing element is driven, and the center wavelength of the spectrum of the oscillation laser light L0 is fixed to the target wavelength.

  The controller 20 performs wavelength detection processing shown in FIG. 3 described later, and executes the above-described wavelength fixing control based on the obtained wavelength detection result.

  Here, the principle applied to this embodiment will be described.

  FIG. 2 shows a relationship between the channel number S (position on the line sensor) of the sensor 10 and the sensor signal intensity. The sensor 10 includes a plurality of light receiving channels, and the light detection position on the line sensor is determined according to the channel number where the light having the maximum intensity is detected. In the line sensor, since the incident position on the line sensor differs according to the wavelength, the wavelength of light can be detected from the light detection position of the line sensor. Therefore, the wavelength of the light is determined from the channel number where the light is detected.

  If the dispersion value D of the spectroscope 7 (wavelength corresponding to the channel interval of the line sensor 10) can be determined, the channel number Sn or Sa in which the reference light Ln or La is detected using this dispersion value D, and the target The difference from the channel number S0 where the detection light L0 is detected can be converted into the relative wavelength of the detected light L0 with respect to the reference light Ln or La. The wavelength λ0 of the detected light L0 can be calculated from the relative wavelength thus determined and the known wavelength λn (= 193.03345 nm) or λa (= 1933.7590 nm) of the reference light Ln or La.

  In the present embodiment, the actual dispersion value D is obtained in consideration of the fact that the dispersion value D of the spectroscope 7 fluctuates according to changes in the measurement environment, and the detected object is based on the obtained actual dispersion value D. It is characterized in that the wavelength λ0 of the light L0 is calculated. This will be specifically described below with reference to the flowchart shown in FIG.

  As shown in FIG. 3, first, the controller 20 opens the shutter 6 of the wavelength detecting device shown in FIG. 1, and causes the detected light L0 and the reference lights Ln and La to enter the spectroscope 7 (step 101).

  In the next step 102, the output of the sensor 10 is read.

  As shown in FIG. 2, the sensor 10 outputs sensor channel numbers Sn, S0 and Sa corresponding to the three peaks of the sensor signal intensity. Here, the wavelength λn of the neon Ne emission line is λn = 193.03345 nm (in vacuum), the wavelength λa of the arsenic As emission line is λa = 1933.7590 nm (in vacuum), and the detected light L0 Λ0 of the emission line is larger than λn and smaller than λa (λ0 = 193.3 nm).

  Therefore, S0, which is larger than the channel number Sn for detecting the neon Ne emission line and smaller than the channel number Sa for detecting the arsenic As emission line, is the channel number for detecting the oscillation laser light L0 (step 102).

  Next, the dispersion value D (wavelength per channel of the sensor 10) is calculated by the following equation (1), and the channel numbers Sn and Sa in which the two reference lights Ln and La are detected and the two reference lights are detected. Ln. Calculation is performed using known wavelengths λn (= 193.03345 nm) and λa (= 1933.7590 nm) of La.

D = (λa−λn) / (Sa−Sn) (1)
Next, the wavelength λ0 of the detected light L0 is obtained using the dispersion value D as shown in the following equation (2).

λ0 = λn + (S0−Sn) · D (2)
That is, by multiplying the dispersion value D by the difference between the channel number S0 that detects the detected light S0 and the channel number Sn that detects the reference light Ln, the relative wavelength (S0−Sn) of the detected light L0 with respect to the reference light Ln. D is obtained, and the wavelength λ0 of the detected light L0 is calculated by adding the known wavelength λn of the reference light Ln to this relative wavelength (S0−Sn). In the above equation (2), the wavelength λn and channel number Sn of neon Ne are used, but the wavelength λa and channel number Sa of arsenic As may be used instead (step 104).

  As described above, according to this embodiment, the actual dispersion value D of the spectrometer 7 is obtained, and the wavelength λ0 of the detected light L0 is calculated based on this actual dispersion value D. Even if the characteristics of the spectrometer 7 change due to a difference or a change in the measurement environment, the wavelength λ0 of the detected light L0 output from the detected light source 1 can be detected with high accuracy without error.

  In the embodiment described above, it is assumed that the relationship between the channel position S of the sensor 10 and the wavelength λ has a substantially linear relationship, as shown in the above equation (1).

  Next, a preferred embodiment when the relationship between the channel position S of the sensor 10 and the wavelength λ is not linear will be described. For example, it is suitable for use when the width per channel of the sensor 10 is not uniform.

  FIG. 4 shows the arrangement of the optical system inside the spectroscope when a Czerny-Turner type grating spectroscope 7 ′ is used instead of the spectroscope 7 in FIG.

  As shown in FIG. 4, when the light to be detected L0 and the reference lights Ln and La are incident on the spectroscope 7 ', the light is first incident on the concave mirror M1 and the reflected light is incident on the grating 8. The angle of incidence on the grating 8 is α. The exit angle of the grating 8 changes according to the wavelength of the incident light. The emission angle of the reference light Ln having the wavelength λn is βn, the emission angle of the reference light La having the wavelength λa is βa, and the emission angle of the detected light L0 having the wavelength λ0 is β0. The detected light L0 and the reference lights Ln and La diffracted by the grating 8 are incident on the concave mirror M2, and the reflected light is guided to the sensor 10 via the reflecting mirror 9. Let the focal length of the concave mirror M2 be f (mm).

  The controller 20 executes the same processing as in steps 101 and 102.

  However, in the present embodiment, the detected light L0 and the reference lights Ln and La are simultaneously incident on the spectroscope 7 to simultaneously measure three detection positions on the sensor 10. Then, the channel number Sn corresponding to the peak center wavelength is obtained by interpolating the three channel positions where the sensor signal intensity peaks. Channel numbers Sa and S0 are obtained by similar interpolation.

  Then, instead of steps 103 and 104, the following processing is executed.

  Hereinafter, the groove number density of the grating 8 is N (gr / mm), and the diffraction order of the grating 8 is m. The width of the light receiving channel of the sensor 10 per channel (channel) is MCD (mm / ch).

  Then, the following formulas (3), (4), (5), (6), and (7) are established from the relationship between the incident angle and the outgoing angle of the grating 8.

N · m · λ n = sin α + sin β n (3)
N · m · λa = sin α + sin βa (4)
N · m · λ 0 = sin α + sin β 0 (5)
βa = βn + δβna = βn + dna / f (6)
β0 = βn + δβn0 = βn + dn0 / f (7)
However, dna = (Sn−Sa) · MCDdn0 = (Sn−S0) · MCD.

Therefore, from Equation (3)-(4),
N · m (λn−λa) = sin βn−sin βa is obtained,
N · m (λn−λa) = sin βn−sin βa = k.

Substituting equation (6) into this,
sin βn−sin (βn + dna / f) = k
2sin (-dna / 2f) .cos (βn + dna / 2f) = k
Is obtained. Than this,
βn = acos (k / 2sin (-dna / 2f))-dna / 2f (8)
Is obtained.

From Equation (3) and Equation (8),
sin α = N · m · λ n −sin β n (9)
Is calculated.

From the equations (7) and (8),
sin β0 = sin [acos {k / 2 · sin (−dna / 2f) −dna / 2f} + dn0 / f] (10)
Is calculated.

Therefore, from the equations (5), (9) and (10),
λ0 = (sin α + sin β0) / (N · m) (11)
And the wavelength λ0 is calculated.

  As described above, also in this embodiment, it is possible to accurately detect the wavelength λ0 of the detected light L0 in consideration of the actual characteristic value of the spectrometer 7 ′.

  In the embodiment described above, as shown in FIG. 2, the neon Ne emission line Ln having the wavelength λn = 193.03345 nm, which is smaller than the detected light L0 having the wavelength λ0 = 1933.3 nm, and the detected light L0. The light emission line La of arsenic As having a wavelength λa = 1933.7590 nm having a wavelength larger than that of the reference light is used as the reference light. However, if the reference light has a wavelength close to the detected light L0, the type of the reference light (element Type), the magnitude of the wavelength relative to the detected light L0, and the number of reference lights are not limited.

  As shown in FIG. 5, the neon Ne emission line Ln (detection channel number Sn of the sensor 10) having a wavelength λn = 193.03345 nm, which is smaller in wavelength than the light to be detected L0, and the carbon C having a wavelength λc = 193.0905 nm The light emission line Lc (detection channel number Sc (> Sn) of the sensor 10) may be used as the reference light.

  Further, as shown in FIG. 6, the neon Ne emission line Ln (detection channel number Sn of the sensor 10) having a wavelength λn = 193.03345 nm, which is smaller in wavelength than the detected light L0, and the wavelength larger than the detected light L0. A germanium Ge light emission line Lg (detection channel number Sg of the sensor 10) having a wavelength λg = 193.4048 nm may be used as the reference light.

  Further, as shown in FIG. 7, germanium Ge emission line Lg (detection channel number Sg of sensor 10) having a wavelength λg = 193.448 nm, which has a wavelength larger than the detected light L0, and arsenic having a wavelength λa = 1933.7590 nm The As light emission line La (channel number Sa (> Sg) of the sensor 10) may be used as the reference light.

  Further, as shown in FIG. 8, the neon Ne emission line Ln (detection channel number Sn of the sensor 10) having a wavelength λn = 193.03345 nm, which has a wavelength smaller than that of the detected light L0, and the wavelength of the detected light L0, respectively. Three light emission lines Lg (detection channel number Sg of the sensor 10) of germanium Ge having a large wavelength λg = 193.408nm and an emission line La of arsenic As (channel number Sa of the sensor 10) having a wavelength λa = 1933.7590 nm. Reference light may be used.

  Further, these arsenic As, neon Ne, germanium Ge, and carbon C can be appropriately combined and used as the reference light.

  If there is a carbon lamp that emits carbon C as a reference light, it can be used. For example, in the case of the combination of neon Ne and carbon C shown in FIG. 5, a carbon (C) lamp using neon Ne as a buffer gas can be used as the reference light source 2.

  In the case of the combination of neon Ne and germanium Ge shown in FIG. 6, a germanium (Ge) lamp using neon Ne as a buffer gas can be used as the reference light source 2.

  In the case of the combination of arsenic As and germanium Ge shown in FIG. 7, a hollow cathode lamp in which arsenic As and germanium Ge are mixed can be used as the reference light source 2.

  As shown in FIG. 8, in the case of a combination of neon Ne, germanium Ge, and arsenic As, a lamp containing each element that emits light near 193 nm can be used as a reference light source.

  As shown in FIG. 8, when the reference light is used for three elements, if the two elements are sequentially selected and the dispersion value D of the spectrometer 7 is obtained from the above-described equation (1), three dispersion values are obtained. D1, D2, D3 are obtained. In this case, the average value of these three dispersion values D1, D2, and D3 may be determined as the final dispersion value D of the spectroscope 7.

  As shown in FIG. 2, when the wavelength λ0 of the detected light L0 exists between the wavelengths λn and λa of the two reference lights Ln and La, the wavelength λ0 of the detected light L0 can be accurately obtained by interpolation. The advantage is obtained. This is because the relationship between each sensor position of the line sensor 10 and the wavelength is not completely linear. As shown in FIG. 5, when the wavelength λ0 of the detected light L0 exists outside between the wavelengths λn and λc of the two reference lights Ln and Lc, it is extrapolated, so that the wavelength λ0 of the detected light L0 is detected. The accuracy will be slightly inferior.

  In the above-described embodiment, an arsenic lamp in which neon gas is sealed as a buffer gas is used as the reference light source 2. For example, two types of reference light are emitted from one reference light source 2. It is also possible to emit light from different reference light sources.

  FIG. 9 shows a configuration example using two reference light sources 11 and 12.

  As shown in FIG. 9, as reference light sources 11 and 12, an arsenic lamp 11 which emits and outputs an arsenic As light emission line La having a wavelength λa = 1933.7590 nm, and a neon Ne light emission line Ln having a wavelength λn = 193.345 nm. A neon lamp 12 that emits and outputs light is prepared, and light output from each of the reference light sources 11 and 12 is incident on the integrating sphere 13. Similarly, a detected light L 0 having a wavelength λ 0 = 193.3 nm is emitted from the detected light source 1 and incident on the integrating sphere 13 via the lens 3. The detection light L0 and the reference light La, Ln are incident on the integrating sphere 13 at the same time.

  In the integrating sphere 13, the incident light is irregularly reflected and uniformly scattered. Therefore, the two reference lights La and Ln and the detected light L0 are uniformly mixed in the integrating sphere 13 and are incident on the spectroscope 7 through the lens 14 from one light source. Since the processing after entering the light into the spectroscope 7 is the same as that of the above-described embodiment, the description thereof is omitted.

  It is desirable that the above-described two reference lights La and Ln and the detected light L0 are incident simultaneously. This is because the characteristics of the spectroscope 7 that varies depending on the environment can be measured in real time.

  Next, a wavelength detection apparatus using a Fabry-Perot etalon spectrometer will be described with reference to FIGS.

  As shown in FIG. 10, in this wavelength detection device, the oscillation laser light L 0 that is the detected light output from the detected light source 1 is partially reflected by the beam splitter 5 through the lens 3, and the diffusion plate 15. Is irradiated. The detected light L0 is scattered and emitted from the diffuser plate 15 and applied to the etalon 16. On the other hand, the reference light Ln (neon Ne emission line) and La (arsenic As emission line) output from the reference light source 2 are partially transmitted through the lens 4 by the beam splitter 5 and diffused by the diffusion plate 15. The back etalon 16 is irradiated. Here, the etalon 16 is composed of two transparent plates whose inner surfaces are partially reflecting mirrors. The etalon 16 transmits the reference lights Ln and La having different wavelengths and the detected light L0.

  The light transmitted through the etalon 16 is incident on the condenser lens 17. The condenser lens 17 is, for example, an achromatic lens subjected to chromatic aberration correction, and the chromatic aberration is corrected by passing through the achromatic condenser lens 17.

  The line sensor 18 is disposed on the focal point of the condenser lens 17. As a result, the light passing through the condenser lens 17 is imaged on the line sensor 18, and the interference fringes 19 a corresponding to the wavelength λa of the reference light La (arsenic As) and the reference light are formed on the detection surface on the line sensor 18. Interference fringes 19b corresponding to the wavelength λn of Ln (neon Ne) and interference fringes 19c corresponding to the wavelength λ0 of the detected light L0 are formed. These interference fringes are formed concentrically on the line sensor 18.

  The radius of the interference fringe 19a corresponding to arsenic As from the center position of the line sensor 18 is Ra, the radius of the interference fringe 19b corresponding to neon Ne is Rn, and the interference fringe 10c corresponding to the detected light L0 The radius is R0.

  The line sensor 18 detects radii Ra, Rn and R0 from the line sensor center to each interference fringe imaging position.

  As shown in FIG. 11, the relationship between the square R2 of the radius R from the center of the line sensor to the interference fringe imaging position and the wavelength λ of the light imaged on the line sensor 18 is a theoretically linear relationship. Is approximated by

  That is, the relationship between the squares Rn2 and Ra2 of the radii of the interference fringes 19b and 19a of the reference lights Ln and La and the wavelengths λn and λa is expressed by a linear function, and the coefficient can be obtained. Specifically, the slope of the straight line Q is determined.

  Therefore, the imaging position of the interference fringe 19c of the detected light L0, that is, the radius R0 of the interference fringe 19c is detected by the line sensor 18, so that the square of the radius R02 can be obtained. From the straight line Q shown, the wavelength λ0 corresponding to the square of the radius R02 can be obtained as the wavelength of the detected light L0.

  In the above description, the case where the oscillation laser beam of the argon fluorine (ArF) excimer laser is used as the detection light has been described. However, when the oscillation laser beam of the krypton fluorine (KrF) excimer laser is used as the detection light L0. Similarly, the wavelength λ 0 of the detected light L 0 can be detected using a reference light source that outputs an emission line having a wavelength close to the wavelength λ 0 = 248.4 nm. For example, an iron (Fe) lamp that outputs light emission lines having different levels of iron (Fe) can be used as the reference light source 2. Two emission lines with wavelengths of 248.2371 nm and 248.4188 nm are output from the iron (Fe) lamp.

  In place of the diffraction grating type spectrometer 7 shown in FIG. 1, a diffraction grating type spectrometer 7 ″ shown in FIG. 12 may be used.

  By the way, in the above-described embodiment, the emission line of neon Ne, arsenic As, carbon C, and germanium Ge is used as the reference light. However, the emission line of platinum Pt may be used as the reference light.

  Note that a hollow cathode lamp can be used as a light source for outputting platinum Pt emission lines.

  As shown in FIG. 13, platinum Pt has three emission lines LP1, LP2, and LP3 having different wavelengths.

  The wavelengths of the three emission lines LP1, LP2, and LP3 outputted from the platinum lamp are λP1 = 193.369 nm (channel number SP1 of sensor 10), λP2 = 193.243nm (channel number SP2 of sensor 10), λP3 = 193 7245 nm (channel number SP3 of sensor 10), which is close to the wavelength λ 0 = 193.3 nm of the argon fluorine excimer laser emission line.

  Therefore, only one of the three light emitting lines LP1, LP2, LP3 can be used as the reference light.

  However, if two or more of the three emission lines LP1, LP2, and LP3 are used as the reference light, the dispersion value D of the spectrometer 7 can be obtained in the same manner as in the above-described embodiment. It is possible to accurately detect the wavelength λ0 of the detected light L0 output from the single-layer detected light source 1 without error.

  In the embodiment described above, the emission line is used as the reference light for detecting the wavelength of the argon fluorine excimer laser. However, the wavelength of the argon fluorine excimer laser may be detected using the absorption line. .

  14 and 15 are diagrams showing an embodiment of a wavelength detection device that detects the wavelength of an argon fluorine excimer laser using an absorption line. However, FIG. 15 is a diagram showing an embodiment in which the spectral line width of the absorption line is narrower than the spectral line width of the argon fluorine excimer laser.

  From the detected light source 1 which is an argon fluorine excimer laser device, an oscillation laser beam L0 having a predetermined power is emitted as a detected light L0 through a front mirror 21.

  On the other hand, the absorption cell 23 is composed of platinum Pt having absorption lines BP1, BP2, and BP3 with wavelengths λP1 = 1933.4369 nm, λP2 = 1933.2243 nm, and λP3 = 1933.7245 nm as absorption lines for the emission line of the argon fluorine excimer laser. Vapor gas is enclosed.

  Here, the wavelengths λP1, λP2, and λP3 of the absorption lines BP1, BP2, and BP3 of the platinum Pt gas are the same as those of the emission lines LP1, LP2, and LP3 shown in FIG. This approximates to the wavelength λ 0 = 193.3 nm of the emission line L 0.

  Therefore, by adjusting the wavelength λ0 of the narrow-band oscillation laser light L0 to the wavelength of one or more absorption lines among the wavelengths λP1, λP2, λP3 of the absorption lines BP1, BP2, BP3, the oscillation laser light The absolute wavelength of L0 can be detected.

  In addition to the absorption lines BP1, BP2, and BP3 of platinum Pt, the wavelengths of the absorption lines of neon Ne, arsenic As, carbon C, and germanium Ge are also close to the wavelength λ0 of the emission line L0 of the argon fluorine excimer laser = 193.3 nm. is doing.

  The wavelengths of the absorption lines of these neon Ne, arsenic As, carbon C, and germanium Ge are the same as the wavelength values of the above-described emission lines shown in FIGS. 2, 5, 6, 7R> 7, and 8.

  For this reason, the wavelength λ0 of the oscillated laser beam L0 having a narrow band is selected from the absorption lines Ba, Bn, Bc, and Bg of the arsenic As, neon Ne, carbon C, and germanium Ge wavelengths λa, λn, λc, and λg. By adjusting to the wavelength of one or more absorption lines, the absolute wavelength of the oscillation laser light L0 can also be detected.

  The detected light L 0 is incident on the beam splitter 5 a in the monitor module 22. A part of the detected light L0 is reflected by the beam splitter 5a and enters the beam splitter 5b. A part of the detected light L0 passes through the beam splitter 5b and enters the absorption cell 23. The remaining detected light L0 reflected by the beam splitter 5b is irradiated to the diffuser plate 15b and then scattered, and the light intensity is detected by the photodiode 24. The detected light L0 that has passed through the absorption cell 23 is irradiated to the diffusion plate 15a. The light to be detected L0 is scattered and emitted from the diffuser plate 15a and enters the spectroscope 7. As described above, on the sensor 10, the detection position of the detected light L0 on the line sensor is determined in accordance with the channel number where the maximum intensity light is detected by the plurality of light receiving channels, and the channel where the detected light L0 is detected. The wavelength λ0 of the detected light L0 is determined from the number.

  FIG. 15 shows the spectrum of the emission line L0 when the detected light L0 of the spontaneous emission argon fluorine excimer laser is transmitted through the absorption cell 23 (with platinum Pt gas sealed). This shows how the absorption lines BP1, BP2, and BP3 having a spectral line width narrower than the line width are minimized.

  In addition, when enclosing platinum Pt gas, a through-type hollow cathode lamp may be used.

  The sensor 10 includes a plurality of light receiving channels, and the light detection position on the sensor 10 is determined according to the channel number where the light having the maximum intensity is detected. In the sensor 10, since the incident position on the sensor 10 differs according to the wavelength, the wavelength of light can be detected from the light detection position of the sensor 10. Therefore, the wavelength of the light is determined from the channel number where the light is detected.

  It is assumed that platinum Pt gas is enclosed in the absorption cell 23 now. In this case, the detected light L0 passes through the platinum Pt gas and then enters the spectroscope 7 through the diffusion plate 15a, and the light intensity of the spectrum is detected by the channel number SP on the sensor 10.

  In this case, absorption lines BP1, BP2, and BP3 of spectral line widths W1, W2, and W3 that are narrower than the emission line width W0 of the detected light L0 are included in the emission line width W0 of the detected light L0. That is, the wavelengths λP1 = 193.369 nm, λP2 = 1933.2243 nm, and λP3 = 1933.7245 nm of platinum Pt are included in the emission line width W0 of the detected light L0 having the wavelength λ0 = 193.3 nm. Therefore, the light intensity in the portion corresponding to the wavelengths λP1 = 193.369 nm, λP2 = 1933.2243 nm, λP3 = 1933.7245 nm in the emission line of the detected light L0 is minimized by the absorption lines BP1, BP2, BP3.

  Further, for example, it is assumed that a gas such as arsenic As, neon Ne, carbon C, or germanium Ge is sealed in the absorption cell 23.

  In this case, absorption lines Ba, Bn, Bc and Bg having a spectral line width narrower than the emission line width W0 of the detected light L0 are also included in the emission line width W0 of the detected light L0. That is, within the emission line width W0 of the detected light L0 having the wavelength λ0 = 193.3 nm, the wavelength λa = 1933.7590 nm of arsenic As, the wavelength λn of neon Ne = 193.34545 nm, the wavelength λc of carbon C = 193.0905 nm , The wavelength λg of germanium Ge is 193.4048 nm, respectively. Accordingly, the light intensity in the portion corresponding to the wavelengths λa = 1933.7590 nm, λn = 193.0345 nm, λc = 193.905 nm, λg = 193.048 nm in the emission line of the detected light L 0 is the absorption lines Ba, Bn, Bc. , Bg is minimized.

  FIG. 16 is a diagram showing an embodiment in which the spectral line width of the absorption line is wider than the spectral line width of the argon fluorine excimer laser.

  Also in this case, an oscillation laser beam L0 having a predetermined power is emitted from the detected light source 1 which is an argon fluorine excimer laser device as a detected light L0 via the front mirror 21.

  The detected light L 0 is incident on the beam splitter 5 a in the monitor module 22. A part of the detected light L0 is reflected by the beam splitter 5a and enters the beam splitter 5b. Part of the detected light L0 passes through the beam splitter 5b and enters the beam splitter 5c. The remaining detected light L0 reflected by the beam splitter 5b is irradiated to the diffuser plate 15b and then scattered, and the light intensity is detected by the photodiode 24. A part of the detected light L 0 is reflected by the beam splitter 5 c and is incident on the absorption cell 23. Then, the detected light L 0 passes through the absorption cell 23, and its light intensity is detected by the light intensity detector 25.

  On the other hand, a part of the detection light L0 transmitted through the beam splitter 5c is irradiated to the diffusion plate 15a. The light to be detected L0 is scattered and emitted from the diffuser plate 15a and enters the spectroscope 7. As described above, on the sensor 10, the wavelength λ0 of the detected light L0 is determined from the channel number where the light intensity of the detected light L0 is detected.

  FIG. 17 shows that the detected light L0 of the argon fluorine excimer laser is transmitted through the absorption cell 23 (containing platinum Pt gas), so that the light intensity of the emission line of the detected light L0 is greater than the spectral line width of the emission line L0. FIG. 9 shows how the absorption line BP1, BP2 or BP3 having a wide spectral line width is minimized.

  The light intensity detector 25 only needs to detect the light intensity. For example, a photodiode, a photomultiplier, or the like.

  It is assumed that platinum Pt gas is enclosed in the absorption cell 23 now. The light intensity of the light to be detected L0 is detected by a light receiving channel on the light intensity detector 25 after passing through the platinum Pt gas.

  At this time, the emission line of the detection light L0 is changed from the light intensity H1 to the minimum light intensity H2 by the absorption line having the spectral line width W1, W2, or W3 wider than the emission line width W0 of the detection light L0.

  Further, for example, it is assumed that a gas such as arsenic As, neon Ne, carbon C, or germanium Ge is sealed in the absorption cell 23. At this time, the light intensity of the detected light L0 is detected by the light receiving channel on the light intensity detector 25 after passing through the arsenic As gas, neon Ne gas, carbon C gas, or germanium Ge gas. The emission line of the detected light L0 is reduced from the light intensity H1 to the minimum light intensity H2 by the absorption line of arsenic As, neon Ne, carbon C, or germanium Ge having a spectral line width wider than the emission line width W0 of the detected light L0. To be.

  Next, taking as an example the case where platinum Pt gas is sealed in the absorption cell 23, three absorption lines BP1, BP2, and BP3 of platinum Pt having a spectral line width narrower than the emission line width of an argon fluorine excimer laser were used. Processing for detecting the wavelength of the oscillation laser beam L0 will be described with reference to FIGS.

  FIG. 18A is a flowchart of the wavelength control of the oscillation laser light L0 using the absorption line, and FIG. 18B is a diagram showing the relationship between the oscillation wavelength λ0 and the light intensity.

  In the flowchart of FIG. 18A, first, the controller 20 shown in FIG. 21 executes a wavelength calibration subroutine for fixing the center wavelength λ 0 of the spectrum of the oscillation laser light L 0 to a target wavelength based on an external command signal ( Step 200).

  When the wavelength calibration subroutine is executed, the oscillation wavelength λ0 of the oscillation laser light L0 is emitted at a predetermined initial wavelength (step 201).

  Next, in the monitor module 22 shown in FIG. 14, the light intensity of the oscillating laser light L 0 that has passed through the absorption cell 23 containing platinum Pt gas and passed through the diffusion plate 15 a and the spectroscope 7 is measured on the sensor 10. Desired. At this time, the light detection position on the sensor 10 is determined according to the channel number in which the light having the maximum intensity is detected. However, the channel number on the sensor 10 for detecting the light intensity of the spectrum of the oscillation laser light changes according to the change of the oscillation wavelength λ 0 (step 202).

  Next, the oscillation wavelength λ 0 of the oscillation laser light L 0 is changed by the controller 20 by a predetermined amount from the initial wavelength. Thus, the minimum points Z2, Z1, and Z3 at which the light intensity of the spectrum of the oscillation laser beam L0 is minimized are sequentially searched (step 203).

  Then, it is determined whether or not the oscillation wavelength λ0 has reached the calibration end wavelength (step 204).

  If it is determined that the oscillation wavelength λ0 of the oscillation laser beam L0 is not the calibration end wavelength (determination N0 in step 204), the process proceeds to step 202 and step 203 again, and the oscillation wavelength λ0 of the oscillation laser beam L0 further increases. It is changed by a predetermined amount. On the other hand, when the oscillation wavelength λ0 of the oscillation laser beam L0 becomes the calibration end wavelength (YES in step 204), the data d of the relationship between the oscillation wavelength λ0 and the light intensity is plotted as shown in FIG. (Step 205).

Then, as indicated by points Z1, Z2, and Z3 of data d in FIG. 18B, the light intensity of the spectrum of the oscillation laser light L0 detected on the sensor 10 is minimized by the absorption lines BP1, BP2, and BP3. . The wavelengths of the minimum points Z1, Z2, and Z3 correspond to the positions of the minimum points Z1, Z2, and Z3 because the wavelengths λP1 = 193.369 nm, λP2 = 193.243 nm, and λP3 = 1933.7245 nm of the absorption lines BP1, BP2, and BP3. The center wavelength λ 0 of the spectrum of the oscillation laser light L 0 incident on the light receiving channels Sz 1, Sz 2, Sz 3 on the sensor 10 is the wavelengths λ P1 = 193.369 nm, λ P2 = 193.243 nm, λ P3 = 193 of the absorption lines BP1, BP2, BP3. Calibrated at 7245 nm. As a result, the light receiving channels Sz1, Sz2, and Sz3 on the sensor 10 corresponding to the positions of the minimum points Z1, Z2, and Z3 are determined. The wavelength difference between the light receiving channels on the sensor 10 is determined by the distance between the spectroscope 7 and the sensor 10 and the lens characteristics, and can be expressed by a constant δ. Therefore, the wavelength λ0 of the unknown oscillation laser light L0 whose light intensity is detected on the sensor 10 is the wavelengths λP1 = 193.369nm, λP2 = 1933.2243nm, λP3 = 1933.7245nm of the absorption lines BP1, BP2, BP3. Using the number of channels X1, X2, X3 and the constant δ between the light receiving channels Sz1, Sz2, Sz3 and the light receiving channel SP in which the wavelength λ0 of the unknown oscillation laser light L0 is detected, the following (12): (13), (14) formula,
λ01 = 193.369 ± X1 × δ (12)
λ02 = 1933.2243 ± X2 × δ (13)
λ03 = 1933.7245 ± X3 × δ (14)
Can be determined by either Further, the average value of the three wavelengths λ01, λ02, and λ02 obtained from the above equations can be obtained as the wavelength λ0 of the final unknown oscillation laser light L0. Further, since two or more absorption lines are used, the dispersion value D of the spectroscope 7 can be obtained in the same manner as in the embodiment using two or more reference lights described above (step 206).

  Next, with reference to FIGS. 16, 18, and 19 for wavelength detection processing of the oscillation laser beam L0 using the absorption lines BP1, BP2, and BP3 of platinum Pt having a spectral line width wider than the emission line width of the argon fluorine excimer laser. To explain.

  First, the processing from steps 200 to 201 shown in FIG.

  Next, in the monitor module 22 shown in FIG. 16, the light intensity of the spectrum of the oscillation laser light L0 transmitted through the absorption cell 23 in which platinum Pt gas is sealed is detected on the light intensity detector 25 (step 202). .

  Next, the oscillation wavelength λ0 of the oscillation laser light L0 is changed by a predetermined amount from the initial wavelength by the controller 20 shown in FIG. As a result, the minimum point where the light intensity of the spectrum of the oscillation laser beam L0 detected on the light intensity detector 25 is minimized is searched (step 203).

  Next, the processing from step 204 to step 205 shown in FIG.

  As a result, the light-receiving channels Sz1 and Sz2 on the sensor 10 when the light intensity of the spectrum of the oscillation laser light L0 detected on the light intensity detector 25 in step 203 is minimized by the absorption lines BP1, BP2 and BP3. The oscillation wavelength λ0 of the oscillation laser light L0 incident on Sz3 becomes the wavelengths λP1, λP2, and λP3 of the absorption lines BP1, BP2, and BP3. Therefore, the wavelength λ0 of the unknown oscillation laser light L0 whose light intensity is detected on the sensor 10 is the wavelengths λP1 = 193.369nm, λP2 = 1933.2243nm, λP3 = 1933.7245nm of the absorption lines BP1, BP2, BP3. Using the number of channels X1, X2, X3 between the light receiving channels Sz1, Sz2, Sz3 and the light receiving channel SP in which the wavelength λ0 of the unknown oscillation laser light L0 is detected, and the constant δ, the above (12), ( 13) and (14) can be similarly obtained as the wavelength λ0 of the final unknown oscillation laser light L0 (step 206).

  When obtaining the wavelength λ0 of the unknown oscillation laser light L0, one of the three absorption lines BP1, BP2, BP3 of platinum Pt or two absorption lines may be used.

  However, if two or more of the three absorption lines BP1, BP2, and BP3 are used as in the above-described embodiment, the dispersion value D of the spectrometer 7 can be obtained, and the detected light source 1 is further increased. The wavelength λ0 of the detected light L0 output from can be accurately detected without error.

  As described above, in the argon fluorine excimer laser, when it is desired to detect the wavelength λ 0 = 193.3 nm of the oscillation laser light L 0, the absorption lines of platinum Pt, arsenic As, neon Ne, carbon C, and germanium Ge are used as absorption lines. Of these, one or more absorption lines are used as absorption lines for the argon fluorine excimer laser emission line.

  As a result, even if the spectroscope 7 has individual differences or the measurement environment fluctuates and the characteristics of the spectroscope 7 change, the wavelength λ0 of the detected light L0 output from the detected light source 1 is accurate without error. Can be detected well.

FIG. 1 is a diagram showing a configuration of an embodiment of a wavelength detection device according to the present invention. FIG. 2 is a diagram showing the relationship between the sensor channel number and the sensor signal intensity when a reference light source that outputs neon and arsenic emission lines is used. FIG. 3 is a flowchart showing a processing procedure for calculating the wavelength of the detected light. FIG. 4 is a diagram showing an arrangement configuration of the optical system in the spectroscope. FIG. 5 is a diagram showing the relationship between the sensor channel number and the sensor signal intensity when a reference light source that outputs neon and carbon emission lines is used. FIG. 6 is a diagram showing the relationship between the sensor channel number and the sensor signal intensity when a reference light source that outputs neon and germanium emission lines is used. FIG. 7 is a diagram showing the relationship between the sensor channel number and the sensor signal intensity when a reference light source that outputs germanium and arsenic emission lines is used. FIG. 8 is a diagram showing the relationship between the sensor channel number and the sensor signal intensity when a reference light source that outputs neon, germanium, and arsenic emission lines is used. FIG. 9 is a diagram illustrating a configuration example of a wavelength detection device using two reference lamps. FIG. 10 is a diagram illustrating a configuration example of a wavelength detection device using a Fabry-Perot etalon spectrometer. FIG. 11 is a diagram showing the relationship between the square of the radius of the interference fringes and the wavelength. FIG. 12 is a view showing a modification of the diffraction grating spectrometer according to the present invention. FIG. 13 is a diagram showing the relationship between the sensor channel number and the sensor signal intensity when a reference light source that outputs platinum emission lines is used. FIG. 14 is a diagram showing a configuration of an embodiment of a wavelength detection device according to the present invention. FIG. 15 is a diagram showing how the light intensity of the emission line of an argon fluorine excimer laser is minimized by a plurality of absorption lines having a spectral line width narrower than the spectral line width of the emission line. FIG. 16 is a diagram showing a modification of the embodiment of the wavelength detection device shown in FIG. FIG. 17 is a diagram showing how the light intensity of the emission line of an argon fluorine excimer laser is minimized by an absorption line having a spectral line width wider than the spectral line width of the emission line. FIG. 18A is a diagram showing a flowchart of the wavelength control of the oscillation laser beam using the absorption line, and FIG. 18B is a diagram showing the relationship between the oscillation wavelength and the light intensity. FIG. 19 is a diagram showing a general laser wavelength stabilization control device. FIG. 20 is a diagram for explaining the prior art, and is a diagram showing a relationship between a sensor channel number and a sensor signal intensity.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Light source to be detected 2 Reference light source 7, 7 'Spectrometer 10, 18 Sensor

Claims (2)

In the wavelength detection device that detects the wavelength of the detected light output from the detected light source based on the wavelength of the reference light emitted from the reference light source,
When the detected light is an argon fluorine excimer laser emission line, among the three emission lines of platinum Pt having a wavelength closest to the wavelength of the argon fluorine excimer laser emission line and having a light intensity of a certain value or more, A wavelength detection device that uses one or more emission lines as the reference light. In the wavelength detection device for detecting the wavelength of the detected light based on the absorption line that minimizes the light intensity of the detected light output from the detected light source,
When the detected light is an argon fluorine excimer laser emission line, among the absorption lines of platinum Pt, arsenic As, neon Ne, carbon C, and germanium Ge having a wavelength approximate to the wavelength of the argon fluorine excimer laser emission line, One or more absorption lines are used as an absorption line for the argon fluorine excimer laser emission line.

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