Fabrication of ultra-shallow junction by in situ doped amorphous silicon films and its application in silicon drift detectors

Abstract

In situ doped amorphous silicon film, deposited by plasma enhanced chemical vapor deposition, is employed as a diffusion source to form an ultra-shallow junction and as voltage dividers in silicon drift detectors. By controlling annealing temperature and time, the junction depth can be adjusted precisely, and the shallowest junction depth of 15 nm is achieved. The I–V characteristics of the ultra-shallow junction, fabricated with different annealing temperature, annealing time and doping concentration, are then analyzed, and the reverse leakage current can be reduced to as low as 2 nA cm−2 under a reverse bias of 200 V at room temperature. The doped silicon film is also used to fabricate voltage dividers in silicon drift detectors. The sheet resistance of the silicon film is adjusted by controlling the thickness and annealing conditions, and a high resistance value and small temperature coefficient of the voltage dividers are achieved. Finally, the in situ doped amorphous silicon film is used to fabricate silicon drift detectors and the final energy resolution of 180 eV at 5.9 keV is achieved.