Circuit partitioning and RF isolation by through-substrate trenches

In this work, theoretical and experimental analysis of RF crosstalk suppression by substrate thinning and trenching is performed. Medici (2D solver) simulation results show that high isolation can be achieved by using high resistivity thinned substrate and through-substrate trenches. Measurements on dedicated G-S-G test structures implemented on thinned Si substrates (thickness 20-100 μm) with and without through-substrate trenches (trench width 5-100 μm) show that isolation between two single-ended capacitive substrate contacts can effectively be controlled by these trenches. While the partial trenches provide additional isolation of ∼10 dB at 1 GHz, the full trenches (forming isolated silicon islands) provide additional isolation of ∼30 dB at 1 GHz.