The Mass Production of BSI CMOS Image Sensors

Numerous pixel design and process improvements have been driven by the need to maintain or improve image quality at an ever smaller pixel size. A major development in imager technology is the mass production of Backside Illumination (BSI) technology for image sensors at low cost and high yield. The Omnivision-TSMC R&D alliance has been focused on the development of a low cost BSI technology which enables high performance at the 1.4μm pixel node. We report the performance of two BSI products both in mass production, using the same BSI 1.4μm pixel design and process. For the 1.4μm pixel, peak quantum efficiencies of 43.8%, 53.6%, 51.6% has been achieved in the red, green and blue channels respectively, with low crosstalk, excellent Gb/Gr performance, no lag, no FPN, 2.3e total read noise, dark current of 27 e/sec at 50°C, and low white pixel defect density. For 1.75μm pixel products, the baseline BSI process has been re-optimized to achieve peak QE of 53%, 60.2%, and 60.4% in the red, green, and blue channels, respectively. This modified process also meets mass production targets for the three 1.75μm BSI products. Our reliability testing has found no reliability issue associated with OmniBSITM architecture.