Ultrashort pulse laser micro drilling of silicon

Abstract

Ultrashort pulse laser processing of materials induces negligible thermal effects on materials, thereby reducing the post-processing operations, which makes the process a “green manufacturing process”. In the present research work, micro holes are fabricated in silicon using ultrashort pulse laser micromachining with pulse energy of 40 µJ at high repetition rates from 100 to 500 kHz. The hole depths obtained are 16.7, 17.8, 28.1, 33.9, and 32.2 µm at repetition rates of 100, 200, 333, 400, and 500 kHz, respectively. An analytical model is used to estimate the surface temperature obtained as 2000, 2800, 3700, 4000, and 4500 K at the center of the micro holes at repetition rates of 100, 200, 333, 400, and 500 kHz respectively. It is observed that the saturation of surface temperature occurred after a certain number of pulses. Due to the saturation of temperature after a certain number of pulses, the increase in micro hole depth gets saturated. The present investigation is beneficial for producing micro holes in silicon which are highly demanding for MEMS, photonics, solar cells, and microfluidic applications.