[Papers] Single Exposure Type Wide Dynamic Range CMOS Image Sensor With Enhanced NIR Sensitivity

In order to respond to increased market demand, we have developed Brillnics H3DR® (Hybrid, High Fidelity, and High Speed Dynamic Range) technology that can achieve the wide dynamic range (WDR) imaging which exceeds 91dB with a single exposure using the standard Back Side Illuminated (BSI) CMOS sensor process 1)-3). In addition to the WDR imaging performance, higher NIR sensitivity for night vision imaging is becoming a crucial performance item, especially in the areas of invehicle / surveillance cameras and emerging sensing applications. To meet and exceed this new demand, we improved the previously reported single exposure type wide dynamic range CIS, and achieved higher NIR sensitivity. The types and characteristics of previously reported major WDR sensors are shown in Table 1. Synthesizing a multiple exposure times in a frame sequential manner 4)-6) and synthesizing a multiple of exposure times in a row sequential manner 7)-9) have been widely used, but those sensors tend to generate motion artifacts and flicker, both caused by time asynchrony. In addition, WDR sensors which have a pair of large and small pixel 10)-11), and a dual pixel sensor for choosing the accumulation time 12)15) has advantage because it keeps the simultaneity of the accumulation times for multiple exposures and can be applicable to small pixels, but the disadvantage is that it reduces the spatial resolution by half. Moreover, the Lateral Overflow Integration Capacitor (LOFIC) sensor 16)-18) can achieve more than 100-dB DR in single exposure, but concern is that it requires unique pixel structure and process technology and complete Abstract In new markets such as in-vehicle cameras, surveillance camera and sensing applications that are rising rapidly in recent years, there is a growing need for better NIR sensing capability for clearer night vision imaging, in addition to wider dynamic range imaging without motion artifacts and higher signal-to-noise (S/N) ratio, especially in low-light situation. We have improved the previously reported single exposure type wide dynamic range CMOS image sensor (CIS), by optimizing the optical structure such as micro lens shape, forming the absorption structure on the Si surface and adding the back side deep trench isolation (BDTI). We achieved high angular response of 91.4%, high Gr/Gb ratio of 98.0% at ±20°, 610nm, and high NIR sensitivity of QE 35.1% at 850nm, 20.5% at 940nm without degrading wide dynamic range performance of 91.3dB and keeping low noise floor of 1.1e-rms.