A 1/2.8-inch 24Mpixel CMOS image sensor with 0.9μm unit pixels separated by full-depth deep-trench isolation

Abstract

CMOS image sensors (CIS) have attracted much attention for the emerging mobile market, and the demand of high-resolution image sensors in mobile applications continues to increase [1-3]. For this reason, pixel pitch has been reduced down to 1.0μσι for mass production. Nevertheless, CISs are continuously scaling down to meet the strong demand for higher-resolution images. However, when the pixel size is reduced down to the sub-micron regime (possibly smaller than the diffraction limit), it is very important to consider photo sensitivity and crosstalk, which determine signal-to-noise ratio (SNR). To minimize degradation of photo sensitivity, back-side illumination (BSI), which collects light at the back side, is widely used instead of front-side illumination. In addition to BSI technology, deep-trench isolation (DTI) has emerged as a leading candidate to suppress crosstalk since it physically isolates the pixel. Previous work shows that partial-depth DTI can be applied in a 1.12μm-pitch pixel [4]. Furthermore, full-depth DTI has been demonstrated in a 1.12μm pixel with 24% larger full-well capacity (FWC), 30% smaller YSNR10, 2.0dB higher SNR, and especially for lower crosstalk (12.5%) compared with a conventional one [5]. In this work, a 24-Mpixel CIS with 0.9μσι unit pixels that takes advantage of full-depth DTI is demonstrated.