Effects of shallow trench isolation on low frequency noise characteristics of source-follower transistors in CMOS image sensors

Abstract

The effects of the shallow trench isolation (STI) edge on low frequency noise characteristics of source-follower (SF) transistors in CMOS image sensors (CIS) were investigated. Random telegraph signal (RTS) noise and 1/f noise were measured in a CIS operating voltage region for a realistic assessment. SF transistor with STI edge in contact with channel shows a lower probability of generating RTS noise but greater RTS amplitude due to the enhanced trap density induced by STI-induced damage. SF MOSFETs without STI exhibit a much lower 1/f noise power spectral density in spite of the greater RTS generation probability, which is due to the decreased trap density. Therefore, SF transistors without STI edge in contact with channel are promising candidates for low noise CIS applications.