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.
Highlights
UV sensing has been widely researched in view of numerous applications, such as sterilization, flame monitoring, UV spectroscopy, UV cure processes, measuring of solar indexes, UV communications, and so on [1,2,3,4,5,6]
Strings of PIN diodes connected in series with and without UV filters were integrated as elements of RF CMOS mass production process flow without additional masks
Large voltages generated by the strings under UV irradiation and availability of standard elements (MOS transistors, resistors, and capacitors) in the core CMOS platform allow to design UV sensing systems with a small footprint and low cost
Summary
UV sensing has been widely researched in view of numerous applications, such as sterilization, flame monitoring, UV spectroscopy, UV cure processes, measuring of solar indexes, UV communications, and so on [1,2,3,4,5,6]. The reported dose of UV radiation necessary for efficient disinfection is in the range of tens of mJ/(cm2) (or even 3.7 mJ/cm2 [3]), depending on the wavelength of UVB/UVC, properties of surfaces, and different environments [3,4,5]. Sterilization of COVID viruses strongly stimulated the production of germicidal mercury lamps, UVC LEDs, and various UV irradiating systems. Much of the recent innovation in the sterilization field has focused on devices for measuring parameters of UVC/UVB radiation integrated in irradiation setups. It is necessary to guarantee that the processed surfaces receive sufficient doses for sterilization. To guarantee the efficiency of sanitizing, it is necessary to measure the dose of ultraviolet in specific locations and in the presence of intense visible and IR illumination.
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