[Paper] A Highly Ultraviolet Light Sensitive and Highly Robust Image Sensor Technology Based on Flattened Si Surface

Abstract

Wavelength [nm]Photon Energy [eV] Depth from Si Surface [nm] Si depth where integrated amount of light decreases to

Si image sensors with wide spectral response and high robustness to ultraviolet light exposure

“…In order to integrate the developed PD technology the image sensor process with various types of active and passive components such as MOS transistors, registers and capacitors, the process flow and conditions regarding to the thermal budget and ion implantations were optimized. For the formation of thin and steep p D layer, process conditions related to the Si surface flatness, ion implantation for PD and activation anneal were tuned; the SiO 2 /Si interface flatness was maintained at the same level as the gate oxide/Si interface, the shallow BF 2 D implantation was carried out through a thin oxide film, and a rapid thermal annealing process equivalent to the activation process of the S/D high concentration region was applied as the dopant activation anneal for the surface high concentration layer of PD [25,26].…”

“…A super high pressure mercury lamp was employed for the UV-light exposure stress. The spectral distribution of the employed UV-light source is shown elsewhere [17]. Fig.…”

“…And its applications to in-pixel buried PDs for emission and absorption PDAs as well as a CMOS image sensor are described. In the next section, the concept and [17,18]. Here, the concentration of neutral region is designed to be high enough to suppress the potential change at the surface due to the generation of fixed charges due to UV-light exposure.…”

“…It is because these image sensors are continuously irradiated by UV-light or sometimes irradiated by strong incident light. For the image sensor development, an improvement of UV-light sensitivity and an improvement of sensitivity robustness to UV-light exposure have been challenges [15,16,17,18]. Fig.…”

“…For this reason, an atomic scale control of the dopant profile of the Si surface region is necessary. It is to form a drift field for photo-generated carriers to be detected [12,17,18]. Also, to increase sensitivity to NIR-light photo-generated carriers generated several tens of micron meters from Si surface must be collected.…”