Photoinduced microchannels inside silicon by femtosecond pulses

We reported on the fabrication of microchannels in the interior of silicon wafers using a femtosecond laser of 800 nm wavelength, which was in the absorption region of silicon. The scanning electron micrographs showed that microchannels were induced inside the silicon wafer when the femtosecond laser beam was focused inside the wafer. The aspect ratio of the microchannel cross section decreased with the increase in scan velocity of the laser. The formation of the photoinduced microchannels probably resulted from the microexplosions due to both the linear absorption and avalanche ionization.