Characterization of AC coupled SOI pixel sensor with pinned depleted diode structure

The experiment of the future electron–positron​ colliders has unprecedented requirements on the vertex resolution, such as around 3μm single point resolution for the inner most detector layer, with fast readout, and very low power-consumption density and material budget. Significant efforts have been put into the development of monolithic silicon pixel sensors, but there have been some challenges to combine all those stringent specifications in a small pixel area. This paper presents a compact prototype pixel sensor fabricated in LAPIS 200 nm SOI process and focuses on the characterization of capacitance of the sensing node with a pinned depleted diode (PDD) structure adopting a novel method of forward bias voltage and AC-coupling on the diode. Three PDD structures with 16 × 20μm2 pixel size were designed and compared using radioactive sources and injected charge. The measurements shows that the designed PDD structure has very low leakage current and around 3.7fF of equivalent input capacitance.