Ultra-Thin 3-D Detector: Charge Collection Characterization and Application for Microdosimetry

An ultra-thin 3-D detector (U3DTHIN) with a 10- μm-thick active region has been proposed to apply for microdosimetry in heavy ion therapy where the ion beam incidence is normal to the detector. The advantage of the detector is that the detector substrate below the silicon-on-insulator layer has been etched away. Extremely small columnar 3-D electrodes allow the detector to be fully depleted at very low biases with a minimum dead region due to their size. In this paper, a charge collection study of the U3DTHIN detector carried out using an ion beam-induced charge collection (IBICC) technique is presented. The IBICC study utilized a microbeam of 5.5 MeV He^{2 +} and 20 MeV ¹²C ions focused to approximately 1- μm diameter. Full charge collection was observed from a bias as low as -10 V. A comparison of the detector response when irradiated from the front and rear side is also presented.