Boosting CMOS Image Sensors: Exploring Silicon Hydride and Hydrocarbon Molecular Ion Implanted in Epitaxial Wafers

This paper presents the effect of SiH_x and C₂H_y mixed molecular ion implantation into an epitaxial layer with low oxygen concentration on the dark current and white spot defects in complementary metal-oxide-semiconductor (CMOS) image sensor pixels. By utilizing a structure where these mixed molecular ions are implanted into the epitaxial layer, we confirmed a 32% reduction in the number of white spot defects and a 13% reduction in dark current compared to epitaxial wafers without implantation in this initial evaluation. These improvements are attributed to three key mechanisms: (1) enhanced gettering capability for metal impurities, (2) effective suppression of oxygen diffusion into the device's active layer, and (3) hydrogen diffusion contributing to the passivation of SiO₂/Si interface defects. Notably, the black dot-like defects and End of Range (EOR) defects formed in the epitaxial layer gettered at lower oxygen concentrations compared to those formed on the Czochralski (CZ) silicon substrate and exhibited higher gettering capacity for Ni. Furthermore, the amount of hydrogen diffusing from EOR defects formed in the epitaxial layer was confirmed to increase.