A low voltage hybrid bulk/SOI CMOS active pixel image sensor

Abstract

A hybrid bulk/silicon-on-insulator (SOI) complementary metal oxide semiconductor (CMOS) active pixel image sensor has been fabricated and studied. The active pixel comprised of reset and source follow transistors on the SOI thin film while the photodiode is fabricated on the SOI handling substrate after removing the buried oxide. The bulk photodiode can be optimized for efficiency with the use of lightly doped SOI substrate without compromising the circuit performance. On the other hand, the elimination of wells on the SOI thin-film allows the use of PMOSFET without increasing the pixel size. The addition of a PMOSFET in the active pixel structure can reduce the minimum operating voltage of the circuit beyond that of conventional designs. With the combination of the high quantum efficiency of bulk photodiode and the low power advantage of SOI technology, the hybrid technology is attractive for scaled low voltage imaging applications.