Field emission mitigation in X-band silicon-etched cavity resonators

An edge-smoothing technique for decreasing field emission and therefore increasing power handling in silicon-based cavity resonators is introduced for the first time in this paper. Specifically, this edge-smoothing process is performed in loaded evanescent-mode resonators by oxidizing the silicon surface before metal coating is applied. This process substantially decreases the cavity-etch-induced edge roughness particularly at the edges of the cavity-loading post where the electric field is the strongest inside the resonant cavity. Experimental results demonstrate that the presented technique results in a 2× power improvement (from 14.7 W to 29.4 W) for a high-quality (Qu = 558) demonstration-vehicle 11.15-GHz resonator with a 15-µm over-the-post air gap. In both the original and improved resonators, an abrupt 10–16 dB increase in loss is observed when gas breakdown inside the resonant cavity occurs. The simple yet effective edge-smoothing process is a critical technology advancement for cavity-based resonators since they are important building blocks in widely-tunable high-Q reconfigurable filters.