A novel BEOL transistor (BETr) with InGaZnO embedded in Cu-interconnects for on-chip high voltage I/Os in standard CMOS LSIs

A novel BEOL transistor (BETr) is developed in Cu interconnects with wide band-gap InGaZnO (IGZO) film for on-chip high voltage I/Os in standard CMOS LSIs only by one additional mask. Underlying Cu interconnect and SiN barrier-dielectric on the Cu are utilized as the gate stack in a unique reverse-type thin-film-transistor (TFT) structure. Thickness control of both the IGZO channel and gate SiN is a key to achieve high on-current (I_on) with low leakage (I_off). Ability of high voltage operation (much higher than 3V) with small feature size is expected as an interface bridge for signal conversion between CMOS core-logics with low-voltages and peripheral devices driven with high-voltages.