Effect of Metallic Ion Implantation on Dark Current Distributions of Silicon-Based CMOS Image Sensors

Accidental metallic contamination is known to have a deleterious impact on the dark current characteristics of silicon-based CMOS image sensors (CIS), especially when metallic species are present in the depletion region of the photodiode. Solving a contamination issue requires a clear identification of the contaminant signature on the sensor response. In this study, different metallic species were voluntarily introduced in the photodiode region of Si-based CIS wafers, using ion implantation at relatively low doses. The dark current spectroscopy (DCS) technique is used to quantify the influence of each of these metallic species on the sensor performance. The results presented herein could aid in their identification after accidental contamination in a clean room environment, particularly in the cases of Pd, Mn and Nb, for which the references in the literature are scarce.