A Highly Robust Silicon Ultraviolet Selective Radiation Sensor Using Differential Spectral Response Method

Abstract

This paper presents a silicon ultraviolet radiation sensor with over 90% UV internal quantum efficiency (QE) and high selectivity to the UV waveband without using optical filters. The sensor was developed for applications that require UV measurement under strong background visible and near-infrared (NIR) lights, such as solar UV measurement, UV-C monitoring in greenhouses or automated factories, and so on. The developed sensor is composed of monolithically formed silicon photodiodes with different spectral sensitivities: a highly UV responsive photodiode with internal quantum efficiency (QE) of nearly 100% for UV light, and a lowly UV responsive photodiode with UV internal QE lower than 10%. The photodiodes were optimized to match their visible and NIR light responsivity, and the UV signal is extracted from the background radiation by using the differential spectral response method. With this approach, an internal QE of over 90% for UV light was obtained, with a residual internal QE to non-UV light lower than 20% for 400 nm, 5% for 500 nm, 2% for 600 nm and 0.6% to NIR light. The developed sensor showed no responsivity degradation after exposure towards strong UV light. It was confirmed by the simulation results that the residual responsivity is further suppressed by employing an on-chip band-rejection optical layer consisting of several layers of silicon oxide and silicon nitride films.

An Optical Filter-Less CMOS Image Sensor with Differential Spectral Response Pixels for Simultaneous UV-Selective and Visible Imaging

“…However, for 20 nm or less, this comes at a cost of also increasing UV light sensitivity in Pix. B, as shown in our previous work [29]. Therefore, a potential barrier in the depth range of 30 nm to 40 nm was targeted for the sample manufacturing.…”

“…In this work, UV light detection is carried out by leveraging the differential spectral response between pixels with high and low UV sensitivity, as explained in Figure 1. We have previously used this approach to develop a discrete silicon UV radiation sensor by monolithically integrating high and low UV sensitivity photodiodes [28,29]. In this report, the technology was further developed for pinned photodiode with full charge transfer capability, suitable for CIS implementation, and we report an optical filter-less CIS outputting UV-selective and visible light images simultaneously in a single exposure by employing the differential spectral response method.…”

Quantification of UV Light-Induced Spectral Response Degradation of CMOS-Based Photodetectors

“…The junction design is also an important factor, but more likely for degradation effects. Nevertheless, UV light sensing has become in recent years a topic of increasing interest, due to the surge of a plethora of new technological applications, such as sterilization, UV spectroscopy, biological analysis, space imaging, UV-based cure processes, and more [1][2][3][4][5][6][7][8]. Although, there are still a few major challenges in the field of UV light sensing.…”

Embedded UV Sensors in CMOS SOI Technology

“…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 target wavelength for these applications is in UVA (320 nm to 380 nm), UVB (280 nm to 320 nm), and UVC (200 nm to 280 nm) wavelength ranges.…”