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Hess,

and Sigmon,

eds.

Laser and Electron-Beam Solid Interactions and Materials Processing

503

THERMALLY-ASSISTED PULSED-LASER ANNEALING OF SOS

MASAYOSHI YAMADA, KEN-ICHI YAMAZAKI, HISAKAZU KOTANI, KEIICHI YAMAMOTO, AND KENJI ABE Department of Electronics, Faculty of Engineering, Kobe University Rokkodai, Nada, Kobe 657, Japan

ABSTRACT Thermally-assisted pulsed-laser annealing has been performed on ion-implanted silicon-on-sapphire(SOS) by irradiating Q-switched(20 nsec) ruby laser light Raman scattering measurements have been made to estiduring thermally heating. It was observed that Raman shift mate the residual strain of the annealed SOS. 0 of SOS annealed in the temperature range of 400 C to 500°C was very close to that of single crystal silicon and the depolarization factor(the Raman intensity ratio of allowed z(xy)z to forbidden z(xx)z scattering configuration) was infinite, while Raman shift of SOS annealed at room temperature was shifted down 1 It was found that the to about 5 cmand the depolarization factor was finite. residual strain of SOS was relieved by the thermally-assisted pulsed-laser annealing, but the residual strain of SOS annealed at room temperature was inhomogeneous and attained to 7x10"3 The annealing temperature dependences of the residual strains were not explained well with a strictly thermal melting and recrystallization model in conjunction with the thermal expansion difference between silicon and sapphire, and suggested to need a new model.

INTRODUCTION Thin layers of silicon-on-sapphire(SOS) are currently used as a basic materiOne of the deficiencies of this al for low-power, high frequency circuitry. material is the high densities of defects formed in the Si layer near the interface, due to the heteroepitaxy, originating from lattice and thermal expansion The difference in the thermal expansion coefficients coefficients mismatches. of Si and sapphire, that of sapphire being roughly twice that of Si, causes the room temperature lateral strain of % -3×i0-3 upon cooling down from the growth 1 Bean has temperature of % 1000'C in the chemical vapor deposition(CVD) method. recently reported thin single crystal growth of SOS by molecular beam epitaxy 2 Yamada et a1 have tryed to crysat relatively low temperature of 650-800'C. tallize amorphous silicon layers rf-sputtered on sapphire by CW ion laser annealing method. Lau et al3 have improved the crystalline quality of SOS grown by CVD method through the use of implantation of Si ions and subsequent thermal annealing at relatively low temperature of about 550'C. employed Q-switched Nd-YAG laser annealing to imRoulet et al4 have first Sai-Halasz et al1 prove the crystalline quality of SOS grown by CVD method. have obtained stress-relieved regrowth of the Si on the compressed sapphire surface by the laser annealing with laser power inputs of various durations. 6 7 They ' have simply explained their laser annealing effect with such a strictly thermal melting and recrystallization model as other investigators insisted. 8 9 have proposed a