EUV Reflectometry for Determining the Optical Properties of Photoresists and Underlayer Materials Upon Irradiation at 13.5-nm

Transcription

1 EUV Reflectometry for Determining the Optical Properties of Photoresists and Underlayer Materials Upon Irradiation at 13.5-nm Grace H. Ho, 1 Fu-H. Kang, 1 Yu-H. Shih, 1 Hok-S. Fung, Hwang-W. Fu, Rikimaru Sakamoto, 3 Takafumi Endo, 3 Bang-C. Ho, 3 Yang-T. Huang, 4 and Bor-Y. Shew 1 Department of Applied Chemistry, National University of Kaohsiung, Nanzih, Kaohsiung 811, Taiwan. National Synchrotron Radiation Research Center, Hsinchu 311, Taiwan. 3 Electronic Materials Research Laboratories, Nissan Chemical Industries, Ltd., Tayama , Japan. 4 Department of Electronics Engineering, National Chiao Tung University, Hsinchu300, Taiwan

2 1. Introduction: EUV Resist Study Overview Optical properties (n,k,t) study by EUV reflectometer M. Chandhok, H. Cao, W. Yueh, E. Gullikson, R. Brainard, S. Robertson, Techniques for directly measuring the absorbance of photoresists at EUV wavelengths, Proc. of SPIE, 5374 (004) 863. Y. Kwark, J. P. Bravo-Vasquez, M. Chandhok, H. Deng, E. Gullikson, C. K. Ober, Absorbance measurement of polymers at extreme ultraviolet wavelength Correlation between experimental and theoretical calculations J. Vac. Sci. Technol. B 4 (006) 18.

3 1. Introduction: EUV Resist Study Overview Optical properties (n,k,t) by X-ray diffractometer Material study: D.J. Guerrero, C. Beaman, R. Sakamoto, T. Endo, B. Ho, Organic underlayers for EUV lithography, J. Photopolym. Sci. Technol. Vol. 1(008) 451. Quantum yield study: R. Brainard, C. Higgins, E. Hassanein, R. Matyi, A. Wuest, Film quantum yirlds od ultrahigh PAG EUV photoresists, J. Photopolym. Sci. Technol. Vol. 1(008) 457.

4 1. Introduction: EUV reflectometer for R&D Examples: (a) NIST/DARPA (c) PTB (b) ALS (a) (b) (c)

5 1. Introduction: EUV Photochemistry PMMA ablation 0.1 nm per EUV pulse at energy densities of 13 mj/cm F. Barkusky, C. Peth, A. Bayer, K. Mann, Direct photo-etching of poly methyl methacrylate using focused extreme ultraviolet radiation from a table-top laser-induced plasma source J. Appl. Phys. 101, 14908(007)

6 . Experimental: Reflectometer EUV Reflectometer of NSRRC (θ) (θ) Design detail: Poster Compact and ultrahighvacuum reflectometer for EUVL applications (MET-6)

7 . Experimental: Reflectometer Reflectivity measurement Accumulated dose vs. θ: Fresh sample Measuring the evolution of film thickness as a function of the accumulated dose Over-exposed sample - Dose independent film thickness

8 . Experimental: Samples Novolac-type underlayer material (UL) PMMA Round-robin : Composition:

9 . Experimental: n, k, T Empirical method: n : First derivative at the critical angle, k : CXRO formula Absorbance ( Dill B) = T : λ = nd cos( β 1 β ) Simulation method (Panalytical X Pert): Input: Photoabsorption cross section in cm g -1, chemical formula, scattering factor (f 1, f ) Output: Density (n, k),t n sinθ = vaccum 4π λ critical β n film β r0 n π λ R s a x i f sinθ = sinθ + i n n cos θ cos θ n =1 δ + iβ

10 3. Results: Measurement precision in a six-month period: ±9% Benchmarking results: absorbance Absorbance (um -1 ) Samples 009-Feb 008-Nov 009-May This work NISSAN CHEMICAL INDUSTRIES, LTD. EUV リソグラフィー用レジスト下層膜の開発

11 3. Results: Film integrity upon EUV radiation UL-novolac polymer: stable Round-robin resist: reactive Fresh UL D (g/cm 3 ) T (nm) Multiple exposure Fresh Over-exposed Satisfactory simulation results. Fresh = over-exposed No observable n change Thickness evolution

12 3. Results: Film integrity upon EUV radiation ½ flux,fresh ¼ flux fresh Fresh Overexposed Literature ½ flux,fresh ¼ flux fresh Fresh Overexposed Literature d (g/cm 3 ) k (um -1 ) d (g/cm 3 ) k (um -1 ) PMMA Round-robin Refractive index & absorbance stay constant against dose. Absorbance: PMMA s is ~ 0% greater than round-robin s. Ablation rate: PMMA s > round-robin s by more than 0%.

13 3. Results: Thickness evolution upon 13.5 nm irradiation Round-robin Stated thickness (nm) Fresh (nm) Overexposed (nm) T (nm) Profilometer result (nm) Profilometer measurement of the over-exposed sample Etch rate: (0.04±0.01) nm cm mj -1

14 3. Results: Thickness evolution upon 13.5 nm irradiation PMMA Etch rate : 0.13 nm cm mj -1 c.f. F. Barkusky, C. Peth, A. Bayer, K. Mann, Direct photo-etching of poly methyl methacrylate using focused extreme ultraviolet radiation from a table-top laser-induced plasma source J. Appl. Phys. 101, (007) 0.1 nm per EUV pulse at energy densities of 13 mj cm - Etch rate = nm cm mj -1 (derive from high dose)

15 1. Introduction: EUV Photochemistry PMMA ablation 0.1 nm per EUV pulse at energy densities of 13 mj/cm F. Barkusky, C. Peth, A. Bayer, K. Mann, Direct photo-etching of poly methyl methacrylate using focused extreme ultraviolet radiation from a table-top laser-induced plasma source J. Appl. Phys. 101, 14908(007)

16 4. Briefly summary EUV reflectometer is an in situ and actinic metrology tool to study EUV photonic effects on resists and underlayer materials. - Stability of thin-film samples upon EUV irradiation UL (novolac type) sample is EUV stable. PMMA and round-robin resist are not EUV stable. - The EUV ablation rate can be determined. 15 nm round-robin resist ~ (0.04±0.01) nm cm mj nm PMMA resist ~ 0.13 nm cm mj -1

17 Acknowledgement National Science Council NSC M Nissan Chemical Ind., Ltd. NUK