A Radiation-Hardened Wide Spectral Response 4T CMOS Image Sensor Pixel Employing a Through-Silicon Via based Photodetector

A novel radiation-hardened 4-transistor (4T) complementary metal-oxide-semiconductor (CMOS) image sensor pixel is proposed, employing a through-silicon-via (TSV) based metal-semiconductor-metal (MSM) photodetector as the photosensitive element. The presented pixel structure is designed and simulated in 0.18 $\mu \mathbf{m}$ CMOS technology. It is shown that deploying the TSV-based MSM photodetector decreases the pixel sensitive area to 3 $\mu \mathbf{m}^{2}$ compared to conventional planar MSM ones, and enhances both the lower and higher wavelengths of the spectral response characteristic of the pixel as well. The designed pixel has a 2.75 $\mu \mathbf{m}$ radius circular structure, the dark current of 77 fA at 1 V reverse bias (at room temperature), a conversion gain of 116 $\mu \mathbf{V.e}^{-1}$, a dynamic range of 58.62 dB, and an approximately linear spectral response in the range of 300 to 800 nm wavelengths of the incident light spectrum. The proposed pixel structure, enabled with a p+ guard ring, also demonstrates insignificant dark current degradation under gamma ray radiation of up to 1 Mrad.