High Efficiency UV Photodiodes Fabricated on p-type Substrate

Newly developed “pure-boron” photodiodes, with high sensitivity and stability in the whole ultraviolet range (UV), are described. The main purpose of this work is to create and characterize a large-area UV photodiode, representing a structure of a pixel in a backside illuminated CMOS image sensor, featuring maximum fill factor and hence sensitivity. The diodes have been processed by the Technology center of DIMES (Delft Institute for Microsystems and Nanoelectronics) on a p-type epitaxial wafer and thus are compatible with standard foundry processing. Care has been taken to keep the electrodes buried as much as possible to limit dark leakage current from interfaces. An electrical and optical characterization has been done by PTB (PhysikalischTechnische Bundesanstalt) using the UV beam lines of the Storage ring facility BESSY in Berlin.