Study of Metal Contamination in CMOS Image Sensors by Dark-Current and Deep-Level Transient Spectroscopies

Pixels in complementary metal–oxide–semiconductor (CMOS) image sensors (CISs) are being scaled downward toward 1.0 μm. In this context, improvements in crucial parameters such as dark current per pixel, which suffers from defects incorporated during processing, need to be achieved. Indeed, accidental metallic contamination is a critical issue that induces dark current and reduces yield. In this paper, detection and characterization of gold and tungsten implanted in CISs using dark-current and deep-level transient spectroscopies are reported. Deep levels responsible for dark current are identified, and tungsten is studied for the first time with dark current spectroscopy.