Abstract

A measurement system for quantitative registration of transient and irreversible lens effects in DUV optics induced by absorbed UV laser radiation was developed. It is based upon a strongly improved Hartmann-Shack wavefront sensor with an extreme sensitivity of ~λ/10000 rms @ 193nm, accomplishing precise on-line monitoring of wavefront deformations of a collimated test laser beam transmitted through the laser-irradiated site of a sample. Caused by the temperature dependence of the refractive index as well as thermal expansion, the initially plane wavefront of the test laser is distorted into a convex or concave lens, depending on sign and magnitude of index change and expansion. This transient wavefront distortion yields a quantitative measure of the absorption losses in the sample. In the case of fused silica, an additional permanent change indicates irreversible material compaction. Results for both fused silica and CaF2 are presented and compared.

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References

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  1. R. E. Schenker, L. Eichner, H. Vaidya, S. Vaidya, P. M. Schermerhorn, D. R. Fladd, and W. G. Oldham, “Ultraviolet damage properties of various fused silica materials,” Proc. SPIE 2428, 458–468 (1994).
    [CrossRef]
  2. W. Primak and R. Kampwirth, “The Radiation Compaction of Vitreous Silica,” J. Appl. Phys. 39(12), 5651–5658 (1968).
    [CrossRef]
  3. C. Van Peski, “Behavior of Fused Silica under 193nm Irradiation”, Technology Transfer # 00073974A-TR, International SEMATECH (2000)
  4. E. Eva and K. Mann, “Calorimetric measurement of two-photon absorption and color-center formation in ultraviolet-window materials,” Appl. Phys., A Mater. Sci. Process. 62(2), 143–149 (1996).
    [CrossRef]
  5. M. Guntau and W. Triebel, “Novel method to measure bulk absorption in optically transparent materials,” Rev. Sci. Instrum. 71(6), 2279–2282 (2000).
    [CrossRef]
  6. C. Görling, U. Leinhos, and K. Mann, “Comparative studies of absorptance behaviour of alkaline-earth fluorides at 193 nm and 157nm,” Appl. Phys. B 74(3), 259–265 (2002).
    [CrossRef]
  7. N. F. Borrelli, C. Smith, D. C. Allan, and T. P. Seward, “Densification of fused silica under 193-nm excitation,” J. Opt. Soc. Am. B 14(7), 1606–1625 (1997).
    [CrossRef]
  8. J. M. Algots, C. Steinbrecher, H. Jinbo, and S. Chuckravanen, “Optical Materials: Compaction and rarefaction affect photolithography system lifetimes,” Laser Focus World , 41(11) (2005).
  9. D. R. Neal, W. J. Alford, J. K. Gruetzner, and M. E. Warren, “Amplitude and phase beam characterization using a two-dimensional wavefront sensor,” Proc. SPIE 2870, 72 (1996).
    [CrossRef]
  10. B. Schäfer and K. Mann, “Investigation of the propagation characteristics of excimer lasers using a Hartmann-Shack sensor,” Rev. Sci. Instrum. 71(7), 2663 (2000).
    [CrossRef]
  11. B. Schäfer and K. Mann, “Determination of beam parameters and coherence properties of laser radiation by use of an extended Hartmann-Shack wave-front sensor,” Appl. Opt. 41(15), 2809–2817 (2002).
    [CrossRef] [PubMed]
  12. M. Born, and E. Wolf, Principles of Optics, (Cambridge University Press, 7th Ed.), Sect. 15.4, 823pp (2001)

2005 (1)

J. M. Algots, C. Steinbrecher, H. Jinbo, and S. Chuckravanen, “Optical Materials: Compaction and rarefaction affect photolithography system lifetimes,” Laser Focus World , 41(11) (2005).

2002 (2)

C. Görling, U. Leinhos, and K. Mann, “Comparative studies of absorptance behaviour of alkaline-earth fluorides at 193 nm and 157nm,” Appl. Phys. B 74(3), 259–265 (2002).
[CrossRef]

B. Schäfer and K. Mann, “Determination of beam parameters and coherence properties of laser radiation by use of an extended Hartmann-Shack wave-front sensor,” Appl. Opt. 41(15), 2809–2817 (2002).
[CrossRef] [PubMed]

2000 (2)

B. Schäfer and K. Mann, “Investigation of the propagation characteristics of excimer lasers using a Hartmann-Shack sensor,” Rev. Sci. Instrum. 71(7), 2663 (2000).
[CrossRef]

M. Guntau and W. Triebel, “Novel method to measure bulk absorption in optically transparent materials,” Rev. Sci. Instrum. 71(6), 2279–2282 (2000).
[CrossRef]

1997 (1)

1996 (2)

D. R. Neal, W. J. Alford, J. K. Gruetzner, and M. E. Warren, “Amplitude and phase beam characterization using a two-dimensional wavefront sensor,” Proc. SPIE 2870, 72 (1996).
[CrossRef]

E. Eva and K. Mann, “Calorimetric measurement of two-photon absorption and color-center formation in ultraviolet-window materials,” Appl. Phys., A Mater. Sci. Process. 62(2), 143–149 (1996).
[CrossRef]

1994 (1)

R. E. Schenker, L. Eichner, H. Vaidya, S. Vaidya, P. M. Schermerhorn, D. R. Fladd, and W. G. Oldham, “Ultraviolet damage properties of various fused silica materials,” Proc. SPIE 2428, 458–468 (1994).
[CrossRef]

1968 (1)

W. Primak and R. Kampwirth, “The Radiation Compaction of Vitreous Silica,” J. Appl. Phys. 39(12), 5651–5658 (1968).
[CrossRef]

Alford, W. J.

D. R. Neal, W. J. Alford, J. K. Gruetzner, and M. E. Warren, “Amplitude and phase beam characterization using a two-dimensional wavefront sensor,” Proc. SPIE 2870, 72 (1996).
[CrossRef]

Algots, J. M.

J. M. Algots, C. Steinbrecher, H. Jinbo, and S. Chuckravanen, “Optical Materials: Compaction and rarefaction affect photolithography system lifetimes,” Laser Focus World , 41(11) (2005).

Allan, D. C.

Borrelli, N. F.

Chuckravanen, S.

J. M. Algots, C. Steinbrecher, H. Jinbo, and S. Chuckravanen, “Optical Materials: Compaction and rarefaction affect photolithography system lifetimes,” Laser Focus World , 41(11) (2005).

Eichner, L.

R. E. Schenker, L. Eichner, H. Vaidya, S. Vaidya, P. M. Schermerhorn, D. R. Fladd, and W. G. Oldham, “Ultraviolet damage properties of various fused silica materials,” Proc. SPIE 2428, 458–468 (1994).
[CrossRef]

Eva, E.

E. Eva and K. Mann, “Calorimetric measurement of two-photon absorption and color-center formation in ultraviolet-window materials,” Appl. Phys., A Mater. Sci. Process. 62(2), 143–149 (1996).
[CrossRef]

Fladd, D. R.

R. E. Schenker, L. Eichner, H. Vaidya, S. Vaidya, P. M. Schermerhorn, D. R. Fladd, and W. G. Oldham, “Ultraviolet damage properties of various fused silica materials,” Proc. SPIE 2428, 458–468 (1994).
[CrossRef]

Görling, C.

C. Görling, U. Leinhos, and K. Mann, “Comparative studies of absorptance behaviour of alkaline-earth fluorides at 193 nm and 157nm,” Appl. Phys. B 74(3), 259–265 (2002).
[CrossRef]

Gruetzner, J. K.

D. R. Neal, W. J. Alford, J. K. Gruetzner, and M. E. Warren, “Amplitude and phase beam characterization using a two-dimensional wavefront sensor,” Proc. SPIE 2870, 72 (1996).
[CrossRef]

Guntau, M.

M. Guntau and W. Triebel, “Novel method to measure bulk absorption in optically transparent materials,” Rev. Sci. Instrum. 71(6), 2279–2282 (2000).
[CrossRef]

Jinbo, H.

J. M. Algots, C. Steinbrecher, H. Jinbo, and S. Chuckravanen, “Optical Materials: Compaction and rarefaction affect photolithography system lifetimes,” Laser Focus World , 41(11) (2005).

Kampwirth, R.

W. Primak and R. Kampwirth, “The Radiation Compaction of Vitreous Silica,” J. Appl. Phys. 39(12), 5651–5658 (1968).
[CrossRef]

Leinhos, U.

C. Görling, U. Leinhos, and K. Mann, “Comparative studies of absorptance behaviour of alkaline-earth fluorides at 193 nm and 157nm,” Appl. Phys. B 74(3), 259–265 (2002).
[CrossRef]

Mann, K.

C. Görling, U. Leinhos, and K. Mann, “Comparative studies of absorptance behaviour of alkaline-earth fluorides at 193 nm and 157nm,” Appl. Phys. B 74(3), 259–265 (2002).
[CrossRef]

B. Schäfer and K. Mann, “Determination of beam parameters and coherence properties of laser radiation by use of an extended Hartmann-Shack wave-front sensor,” Appl. Opt. 41(15), 2809–2817 (2002).
[CrossRef] [PubMed]

B. Schäfer and K. Mann, “Investigation of the propagation characteristics of excimer lasers using a Hartmann-Shack sensor,” Rev. Sci. Instrum. 71(7), 2663 (2000).
[CrossRef]

E. Eva and K. Mann, “Calorimetric measurement of two-photon absorption and color-center formation in ultraviolet-window materials,” Appl. Phys., A Mater. Sci. Process. 62(2), 143–149 (1996).
[CrossRef]

Neal, D. R.

D. R. Neal, W. J. Alford, J. K. Gruetzner, and M. E. Warren, “Amplitude and phase beam characterization using a two-dimensional wavefront sensor,” Proc. SPIE 2870, 72 (1996).
[CrossRef]

Oldham, W. G.

R. E. Schenker, L. Eichner, H. Vaidya, S. Vaidya, P. M. Schermerhorn, D. R. Fladd, and W. G. Oldham, “Ultraviolet damage properties of various fused silica materials,” Proc. SPIE 2428, 458–468 (1994).
[CrossRef]

Primak, W.

W. Primak and R. Kampwirth, “The Radiation Compaction of Vitreous Silica,” J. Appl. Phys. 39(12), 5651–5658 (1968).
[CrossRef]

Schäfer, B.

B. Schäfer and K. Mann, “Determination of beam parameters and coherence properties of laser radiation by use of an extended Hartmann-Shack wave-front sensor,” Appl. Opt. 41(15), 2809–2817 (2002).
[CrossRef] [PubMed]

B. Schäfer and K. Mann, “Investigation of the propagation characteristics of excimer lasers using a Hartmann-Shack sensor,” Rev. Sci. Instrum. 71(7), 2663 (2000).
[CrossRef]

Schenker, R. E.

R. E. Schenker, L. Eichner, H. Vaidya, S. Vaidya, P. M. Schermerhorn, D. R. Fladd, and W. G. Oldham, “Ultraviolet damage properties of various fused silica materials,” Proc. SPIE 2428, 458–468 (1994).
[CrossRef]

Schermerhorn, P. M.

R. E. Schenker, L. Eichner, H. Vaidya, S. Vaidya, P. M. Schermerhorn, D. R. Fladd, and W. G. Oldham, “Ultraviolet damage properties of various fused silica materials,” Proc. SPIE 2428, 458–468 (1994).
[CrossRef]

Seward, T. P.

Smith, C.

Steinbrecher, C.

J. M. Algots, C. Steinbrecher, H. Jinbo, and S. Chuckravanen, “Optical Materials: Compaction and rarefaction affect photolithography system lifetimes,” Laser Focus World , 41(11) (2005).

Triebel, W.

M. Guntau and W. Triebel, “Novel method to measure bulk absorption in optically transparent materials,” Rev. Sci. Instrum. 71(6), 2279–2282 (2000).
[CrossRef]

Vaidya, H.

R. E. Schenker, L. Eichner, H. Vaidya, S. Vaidya, P. M. Schermerhorn, D. R. Fladd, and W. G. Oldham, “Ultraviolet damage properties of various fused silica materials,” Proc. SPIE 2428, 458–468 (1994).
[CrossRef]

Vaidya, S.

R. E. Schenker, L. Eichner, H. Vaidya, S. Vaidya, P. M. Schermerhorn, D. R. Fladd, and W. G. Oldham, “Ultraviolet damage properties of various fused silica materials,” Proc. SPIE 2428, 458–468 (1994).
[CrossRef]

Warren, M. E.

D. R. Neal, W. J. Alford, J. K. Gruetzner, and M. E. Warren, “Amplitude and phase beam characterization using a two-dimensional wavefront sensor,” Proc. SPIE 2870, 72 (1996).
[CrossRef]

Appl. Opt. (1)

Appl. Phys. B (1)

C. Görling, U. Leinhos, and K. Mann, “Comparative studies of absorptance behaviour of alkaline-earth fluorides at 193 nm and 157nm,” Appl. Phys. B 74(3), 259–265 (2002).
[CrossRef]

Appl. Phys., A Mater. Sci. Process. (1)

E. Eva and K. Mann, “Calorimetric measurement of two-photon absorption and color-center formation in ultraviolet-window materials,” Appl. Phys., A Mater. Sci. Process. 62(2), 143–149 (1996).
[CrossRef]

J. Appl. Phys. (1)

W. Primak and R. Kampwirth, “The Radiation Compaction of Vitreous Silica,” J. Appl. Phys. 39(12), 5651–5658 (1968).
[CrossRef]

J. Opt. Soc. Am. B (1)

Laser Focus World (1)

J. M. Algots, C. Steinbrecher, H. Jinbo, and S. Chuckravanen, “Optical Materials: Compaction and rarefaction affect photolithography system lifetimes,” Laser Focus World , 41(11) (2005).

Proc. SPIE (2)

D. R. Neal, W. J. Alford, J. K. Gruetzner, and M. E. Warren, “Amplitude and phase beam characterization using a two-dimensional wavefront sensor,” Proc. SPIE 2870, 72 (1996).
[CrossRef]

R. E. Schenker, L. Eichner, H. Vaidya, S. Vaidya, P. M. Schermerhorn, D. R. Fladd, and W. G. Oldham, “Ultraviolet damage properties of various fused silica materials,” Proc. SPIE 2428, 458–468 (1994).
[CrossRef]

Rev. Sci. Instrum. (2)

B. Schäfer and K. Mann, “Investigation of the propagation characteristics of excimer lasers using a Hartmann-Shack sensor,” Rev. Sci. Instrum. 71(7), 2663 (2000).
[CrossRef]

M. Guntau and W. Triebel, “Novel method to measure bulk absorption in optically transparent materials,” Rev. Sci. Instrum. 71(6), 2279–2282 (2000).
[CrossRef]

Other (2)

C. Van Peski, “Behavior of Fused Silica under 193nm Irradiation”, Technology Transfer # 00073974A-TR, International SEMATECH (2000)

M. Born, and E. Wolf, Principles of Optics, (Cambridge University Press, 7th Ed.), Sect. 15.4, 823pp (2001)

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Figures (13)

Fig. 1
Fig. 1

Principle of the Hartmann-Shack wavefront sensor (cf. text)

Fig. 2
Fig. 2

Geometry and notations characterizing a cylindrical optical element during laser irradiation

Fig. 3
Fig. 3

Setup for measurement of the laser induced photo-thermal wavefront deformation

Fig. 4
Fig. 4

Recorded spot diagram (left) and reconstructed wavefront (right) of a quartz cylinder (Ø 25mm × 45mm), irradiated at 193nm with an intensity of ~ 100mW/cm2

Fig. 5
Fig. 5

, left: z-averaged temperature difference between axis and boundary vs. time calculated for a quartz cylinder (length 40mm) during alternate irradiation and cooling intervals of 27 and 81 s, respectively. Right: Measured decay of the wavefront distortion of a cylindrical quartz sample (length 40mm) after stopping irradiation.

Fig. 6
Fig. 6

, left: Calibration of the photo-thermal measurement setup using quartz sample (d=25mm, lc=45mm) with central bore (=dia. of laser beam) and resistor chain; right: peak-valley and rms wavefront deformation plotted vs. electrical power. Solid lines represent the linear fit to the measured data.

Fig. 7a
Fig. 7a

(left): Measured wrms data as a function of laser fluence (@ 150 Hz, λ=193nm, average over 5 measurements) for three uncoated quartz substrates of equal size. Right: Corresponding absorption coefficients k (calculated with calibration factors from resistor heated sample). The slopes indicate the presence of two-photon non-linear absorption

Fig. 7b
Fig. 7b

Absorption coefficients k for three uncoated quartz substrates of equal size calculated with calibration factors from numerical simulations assuming a surface absorption of 0.01%.

Fig. 8
Fig. 8

Photothermal measurement of CaF2 samples (left: ls=20mm, right: ls=70mm) using an irradiation wavelength of 248nm and 50mW/cm2 power density. A sign reversal of the thermal lens is observed.

Fig. 9
Fig. 9

FD calculations of the wavefront distortion wpv for two CaF2 samples (z axis oriented || [001]) which exhibit different signs of thermal lensing. A circular flat-top beam (Ø7mm) of 5·103 W/m2 cw power and a sample diameter of 25mm were used for calculation.

Fig. 10
Fig. 10

, left: Wavefront deformation of a quartz sample (ls=25mm) after 9 million 193nm pulses of 0.1J/cm2. The entrance and exit positions of the heating beam, projected on a plane perpendicular to the test beam axis are marked as rectangles. right: peak-valley wavefont irregularity as a function of pulse number.

Fig. 11
Fig. 11

, left: Test beam pattern of a quartz sample between crossed polarizers after 1.2·106 pulses (193nm) at 0.1 J/cm2. The rotated coordinate axes indicate the orientation with respect to the camera reference frame; right: simulated test beam pattern for δρ/ρ=4·10−6 and a flat-top beam of 3mmx1.5mm. The isolines represent transmitted intensities of 9·10−5 −9·10−4 relative to the test beam intensity.

Fig. 12
Fig. 12

Ratio: maximum intensity between crossed polarizers to maximum intensity without sample and parallel polarizers as a function of pulse number for a quartz sample of ls=25mm. Laser parameters were ν=1kHz, fluence H=0.1J/cm2.

Tables (1)

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Table 1 Material parameters of fused silica and CaF2 used in finite difference simulations

Equations (16)

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( β x β y ) i j = ( w / x w / y ) i j = 1 f ( x c x r y c y r ) i j .
w ( x , y ) = l = 0 M c l P l ( x , y ) ,
i , j [ ( l c l P l x ( x i , y j ) β x , exp . i j ) 2 + ( l c l P l y ( x i , y j ) β y , exp . i j ) 2 ] = ! min
w P V = max i j w i j min i j w i j and w r m s = N 1 / 2 i , j ( w i j w ¯ ) 2
c p ρ t δ T ( r , t ) + ( λ δ T ( r , t ) ) + μ I P ( r , t ) = 0 r G n ( λ δ T ( r , t ) + κ δ T ( r , t ) n β I p ( r , t ) e z ) = 0 r G .
δ T ( r , z , t ) = μ l s , β < < 1 P [ μ V ( r , z , t ) + β S ( r , z , t ) ] ,
n ( δ T ( r , z , t ) ) = n 0 + n T δ T ( r , z , t ) ,
δ l ( r , t ) = 0 l s u z z ( r , z , t ) d z .
Δ u ( r , t ) + 1 1 2 σ ( u ) = 2 + 2 σ 1 2 σ α δ T ( r , t ) r G n ( C ( U α δ T ) ) = p r G .
δ w ( r , t ) = ( n 0 1 ) 0 l s u z z ( r , z , t ) d z + n T 0 l s δ T ( r , z , t ) d z ~ l i n e a r i t y P [ μ V ' ( r , t ) + β S ' ( r , t ) ] .
δ w ( x cos γ d v , y , t ) = 0 l s [ ( n 0 1 ) u z z ( h , z , t ) + n T δ T ( h , z , t ) ] 1 + tan 2 γ ' d z ,
ρ ρ 0 ρ e q ρ 0 = 1 exp [ ( a I ² N ) b ] ,
δ ρ ρ = ( c I 2 N ) b ,
k = w r m s b a P l s lg ( e ) .
n r n ϕ ~ σ r σ ϕ ~ Δ ρ ρ ~ ( I ² N ) b .
I I | | = sin 2 ϕ cos 2 ϕ ( 1 cos ( 2 π ( n r n ϕ )     l s λ ) ) ~ ( n r n φ ) l s < < λ ( I ² N ) 2 b .

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