Exploration of Pinned Photodiode Radiation Hardening Solutions Through TCAD Simulations

Abstract

The use of pinned photodiode (PPD) based CMOS image sensors in harsh radiation environment (such as space) is limited by their tolerance to ionizing radiation. Technology computer aided design (TCAD) simulations are performed to reproduce the radiation induced defect and therefore the dark current increase in pinned photodiode pixels up to 1 kGy (i.e. 100 krad) of total ionizing dose (TID). To do so, the TCAD models are calibrated with measurements performed on irradiated pixels. Then, the influence on the PPD radiation hardness of various manufacturing process and pixel design modifications is explored. This works shows that the proposed modification can improve the radiation hardness of pinned photodiode CMOS image sensors against ionizing.

WITHDRAWN: Dark Current in Pinned Photodiode CMOS Image Sensors: A Pre-Fabrication Physics-based Model

“…A conventional 4-T CMOS image sensor pixel (Fig. 1) with doping and dimensions similar as [2], [9] is simulated (mixed-mode) in dark and the electrons collected in the PPD well are measured. The Auger, Band to band, Band-gap narrowing, Temperature and Doping dependent Shockley Read Hall (SRH) models are activated for all simulations.…”

“…The Auger, Band to band, Band-gap narrowing, Temperature and Doping dependent Shockley Read Hall (SRH) models are activated for all simulations. Also, as part of TCAD calibration, the maximum carrier lifetime of minority electrons (τ max ) is selected as 3 × 10 −3 s, with similar values found in the literature [2,7]. This value depends on the minority carrier injection level, energy level of impurity center and temperature [10].…”

“…9). The values of N A , N D , x p1 , x p2 and y j derived for the device in our work (similar as [2,9]) were used (Table 2). For a given T and t int , the values of N I and N D are obtained using ( 5) and ( 18), respectively.…”

“…The dark current of an image sensor, i.e., charge generated in the photo-diode in absence of light, is an important figure of merit that affects the quality (SNR) of a captured image. Dark current temporal noise plays a critical role in lowlight imaging devices like single-photon counting, quanta image sensing and space exploration imagers [1][2][3][4]. Moreover, image sensors used in the nuclear industry and space applications are exposed to high energy particles, increasing the density of defects near photo-diode, thereby increasing the dark current drastically [2][3][4].…”

A Cathodoluminescence Study on the Diffusion Length in AlGaInP/InGaP/AlInP Solar Cell Heterostructures

“…Cross-sectional electron beam induced current (EBIC) and transport imaging in a scanning electron microscope are two techniques applied to measure the minority carrier diffusion length. However, the electric fields and surface recombination are the challenges of the EBIC method [4,5], while a 2D-CCD camera is necessary for the transport imaging technique [6,7]. Cathodoluminescence (CL) has been also applied to measure the minority carrier diffusion length in semiconductors [8].…”