An Electromagnetic Study of Grounded Isolation Trenches at Critical Positions in GaN-on-Si Technology for Integrated Power Electronics

We report computational electromagnetic (EM) investigation into grounded isolation trenches of differing designs and their efficacy in suppressing substrate coupling in GaN-on-Si power integrated circuits (ICs). Compared to previously published works on isolation trench structure, the S-parameter results of our EM investigation implies that the level of substrate coupling can be significantly suppressed by moving a grounded isolation trench filled with high conductivity (σ) material to a critical position which is very close to the interference source (with |S₂₁| ≈ −74 dB for a 100-µm wide grounded isolation trench filled with normal aluminum metal and ≈ 66 dB for even a 1-µm wide trench, both at 100 MHz with a 700-µm lateral separation distance). These results provide helpful guidance for fabrication considerations and the monolithic integration of high-performance power ICs in GaN-on-Si technology.