Mitigation of substrate coupling effects in RF switch by localized substrate removal using laser processing
With the evolution of radio frequency (RF)/microwave technology, there is a demand for circuits which are able to meet highly challenging RF frontend specifications. Silicon-on-insulator (SOI) technology is one of the leading platforms for upcoming wireless generation. The degradation of performance due to substrate coupling is a key problem to address for telecommunication circuits, especially for the high throw count switches in RF frontends. In this context, a novel technique for local substrate removal is developed to fabricate membranes of mm-sized RF switch which allows for total etching of silicon handler. RF characterization of membranes reveal a superior linearity performance with lowering of 2nd harmonic by 17.7 dB and improvement in insertion losses by 0.38 dB in comparison with High-Resistivity SOI substrates. This improvement leads to a significant increase in frontend efficiency. These results demonstrate a new route for optimization of circuit performance using post-fabrication substrate processing techniques.