Surprising phase transformation of a-Si:H films under femtosecond laser impact

Vladimir A. Volodin; Mikhail D. Efremov; Grigoriy A. Kachurin; Sergey A. Kochubei; Alexander G. Cherkov; M. Deutschmann; N. Baersch

doi:10.1117/12.802366

29 April 2008 Surprising phase transformation of a-Si:H films under femtosecond laser impact

Vladimir A. Volodin, Mikhail D. Efremov, Grigoriy A. Kachurin, Sergey A. Kochubei, Alexander G. Cherkov, M. Deutschmann, N. Baersch

Author Affiliations +

Proceedings Volume 7025, Micro- and Nanoelectronics 2007; 70250I (2008) https://doi.org/10.1117/12.802366
Event: Micro- and Nanoelectronics 2007, 2007, Zvenigorod, Russian Federation

Abstract

Thin (90 nm) a-Si:H films have been crystallized on Corning 7059 glass substrates by 120 fs pulses of Ti:sapphire laser. Initial films were deposited using low-temperature plasma enhanced deposition technique. The pulses with wavelength of 800 nm, pulse energy up to 0.8 mJ, and repetition rate of 1 kHz were employed. The focused to 280 micron laser beam was raster scanned, using x-y sample translation by computer-controlled motors. The structural properties of the films were characterized by the spectroscopy of Raman scattering, excited by the argon laser (line 514,5 nm). The ablation threshold was found to be of about 65 mJ/cm². When pulse energy density was lower than ~30 mJ/cm² no structural changes were observed. In optimal regimes the films were found to be fully crystallized with fine grain structure, according to the Raman scattering data. Numerical estimates show the pulse energy density was lower than the Si melting threshold, so non-thermal "explosive" impacts may play some role. The possibility of the femtosecond laser pulses to crystallize Si films on glass substrates is shown for the first time. The results obtained are of great importance for manufacturing of polysilicon layers on non-refractory substrates for thin film microelectronics.

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Vladimir A. Volodin, Mikhail D. Efremov, Grigoriy A. Kachurin, Sergey A. Kochubei, Alexander G. Cherkov, M. Deutschmann, and N. Baersch "Surprising phase transformation of a-Si:H films under femtosecond laser impact", Proc. SPIE 7025, Micro- and Nanoelectronics 2007, 70250I (29 April 2008); https://doi.org/10.1117/12.802366

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