Large-area femtosecond laser ablation of Silicon to create membrane with high performance CMOS-SOI RF functions

Femtosecond laser processing is a tool of increasing relevance for controlled etching of metals, semiconductors, and dielectrics with minimum collateral damage. We make use of this technique to remove silicon locally from the handler substrate of Silicon-on-Insulator (SOI) dies. By combining laser removal with XeF2 etching, we create thin membranes of SP9T switch, with the handler silicon completely removed underneath. This is done in order to mitigate the losses and non-linear products caused by capacitive coupling to the handler substrate. We demonstrate the improvement of linearity and insertion loss of a switch (Fig. 9 and Fig. 10) by employing the proposed method. This could be of potential interest for future wireless applications like 5G.