レーザー光照射によるp型Siの局所的陽極酸化とナノ構造制御

Abstract

The effect of low power helium–neon laser (632.8 nm) irradiation on the anodization of p-type silicon in hydrofluoric acid solution was studied. The laser beam of 2 mW power with a Gaussian diameter of 0.9 mm was successfully employed to control the formation of porous silicon (PS) of good quality. The photoluminescence (PL) of PS was excited by a violet laser diode (409 nm), and the spectra were acquired with an optical microscope from an area of about 60 μm in diameter on the PS surface. The microscopic distribution of the PL spectra appeared in a corresponding manner with the beam intensity distribution during the formation process. On the laser-irradiated surface the electrochemical reaction is enhanced by the current concentration due to the photoconduction in the body, while photo-excited electrons recombine with holes near the surface suppressing the reaction. Under an optimized condition PS which exhibited sharp PL at peak energy of 2.0 eV with 0.3 eV FWHM could be obtained. Though the critical condition may vary with the electrical property of employed silicon wafer, it is demonstrated that microfabrication is made possible in wet processing on p-type silicon surface by tuning only laser beam intensity of about 0.1 W/cm^2.