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

• The effects of the STI induced damage on LFN of SF transistors were investigated.
• STI process induced damage on the STI edge could contribute to LFN characteristics.
• W STI shows grater RTS noise amplitude while RTS occurrences maintained lower.
• The enhanced multiple RTS event could screen the single event RTS effect in W STI.
• SF transistors without STI are promising candidates for low noise CIS applications.

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.