Development of Commercial Grade Silicon Drift Detector with on-Chip JFET: Device Design, Technology & Characterization
Proto-type Silicon Drift Detectors (SDDs) have been realized through a pilot stage fabrication run at the Micro-fabrication facility at Indian Institute of Technology – Bombay (IIT-B). Taking precedence from the fabrication run at IIT-B, commercial grade SDDs with on-chip low noise JFETs are being developed for low energy X-ray spectroscopy and position sensing applications using silicon bipolar technology available with Bharat Electronics Ltd (BEL), Bangalore. This paper presents a detailed illustrative view on the design; fabrication and characterization of the SDDs & in-built JFETs fabricated at BEL. Traditionally, detectors are fabricated over high resistivity silicon substrates whereas JFETs are fabricated over low-resistivity silicon. To design a process for fabrication of both SDD and JFET over high resistivity silicon posed a sufficient technological challenge. Simulations in Technology Computer Aided Design (TCAD) proved helpful in arriving at optimum process parameter values for fabrication of SDDs and on-chip JFETs over the same high resistivity silicon substrate. SDDs & low noise JFETs fabricated at BEL were characterized to extract dc (I-V) performance parameters like total leakage current at anode, transconductance etc. These results formed precursors to fine-tuning the process for the next run aimed at achieving an even lower leakage current level.
