[paper] Embedded CMOS SOI UV Sensors

Michael Yampolsky, Evgeny Pikhay and Yakov Roizin

Embedded UV Sensors in CMOS SOI Technology

Sensors 2022, 22(3), 712;

DOI: 10.3390/s22030712

   
Tower Semiconductor, Migdal Haemek 2310502, Israel

Abstract: We report on ultraviolet (UV) sensors employing high voltage PIN lateral photodiode strings integrated into the production RF SOI (silicon on isolator) CMOS platform. The sensors were optimized for applications that require measurements of short wavelength ultraviolet (UVC) radiation under strong visible and near-infrared lights, such as UV used for sterilization purposes, e.g., COVID-19 disinfection. Responsivity above 0.1 A/W in the UVC range was achieved, and improved blindness to visible and infrared (IR) light demonstrated by implementing back-end dielectric layers transparent to the UV, in combination with differential sensing circuits with polysilicon UV filters. Degradation of the developed sensors under short wavelength UV was investigated and design and operation regimes allowing decreased degradation were discussed. Compared with other embedded solutions, the current design is implemented in a mass-production CMOS SOI technology, without additional masks, and has high sensitivity in UVC.

Fig: (a) A string of PIN photodiodes connected in series by silicide N+, P+, and iSi regions. The diodes are connected by butted silicide. The schematic cross section shows only three connected in series PIN diodes. (b) Cross section of a lateral PIN diode with contacts.