Interconnection for Power Electronics Using Laser Ablation

Laser-induced backside wet etching (LIBWE) is a method for the precise etching and structuring of SiO2. In this study, LIBWE is performed by using ultrashort laser pulses with a pulse duration of = 500 fs and a wavelength of = 515 nm. Saturated aqueous KMnO4 solution is the absorbing liquid for the LIBWE process. The observed etching rate is approximately 10 -3 nm/pulse, which is substantially lower than that in previous reports; it increases with increasing laser fluence. The initial etching rate decreases with higher pulse numbers until it approaches a stable value. After the LIBWE, the generated etching pits are partially covered by MnOx layers with thicknesses of tens of nanometers. However, at the etched SiO2 surface, two different laser-induced periodic surface structures (LIPSS) are found. In the center of the etching pits, LIPSS with a period of HSFL (52 2) nm are observed, whereas in the outer areas, LIPSS with a period of LSFL (390 20) nm are found. The etching mechanism for the LIBWE of SiO2 with aqueous KMnO4 solution is proposed to comprise laser-based heating, decomposition of KMnO4, and chemical etching of the SiO2 surface by the produced KOH.