Microfabrication of fine-pitch high aspect ratio Faraday cup arrays in silicon

Dense one-dimensional arrays of high aspect ratio Faraday cups have been microfabricated for application as position sensitive charged particle detectors. The method developed to fabricate these Faraday cup arrays utilizes deep reactive ion etching (DRIE) of low resistivity silicon, conformal deposition of an insulator and metal, and a novel method for patterning the cup-to-fanout interconnect to allow for high cup density. Linear arrays of 64 cups have been fabricated with cups ranging in width from 15 to 45 μm. Cup depth-to-width aspect ratios in excess 8:1 can be realized with the method. The minimum spacing between cups demonstrated here was 5 μm. Linear fill factors of the Faraday cups ranged from 50% to 90%, depending on the cup geometry and pitch. The capacitance and leakage current measurements on microfabricated Faraday cups will be discussed along with an electrical model and predictions of the detector performance.