Microstructures formed on silicon wafer by CO2 laser irradiation

Abstract

Laser bumps have been formed on the silicon surface with anisotropic patterns induced by the pulsed CO2 laser under the backside effect conditions. The microstructures are formed with periodic patterns, and vary with the laser parameters. The parallel narrow fringes have period around 2 μm, and the fringe orientation is in parallel with the laser polarization direction. The circular fringes with spacing around 1 μm appear when the laser energy increase. The fringe patterns were found to be independent on the laser pulses, therefore are re-writable. The bump formation mechanism is considered to be thermal capillary wave effect during the material melting and resolidification processes under laser irradiation. Whereas, the laser absorption may be induced by the hot electrons, or the thermal energy resulting from the laser interaction with the backside coating material.