High on/off-ratio P-type oxide-based transistors integrated onto Cu-interconnects for on-chip high/low voltage-bridging BEOL-CMOS I/Os

A new P-type amorphous SnO thin-film transistor with high I_on/I_off ratio of >10⁴ is developed, for the first time, as a component to complement N-type IGZO transistors for on-chip voltage-bridging BEOL-CMOS I/Os on conventional Si-LSI Cu-interconnects (Fig. 1). Dedicated low-temperature (<;400°C) oxide-semiconductor processes are implemented to overcome several integration challenges (Fig. 2) with only one-mask addition using standard BEOL process tools (Fig. 3). We demonstrate high I_on/I_off ratio of >10⁴ and high-V_d capability (|V_bd|>40V) with gate-to-drain offset structure, showing superior properties over the previously reported values (Table 1). The SnO transistor is suited for the BEOL-CMOS I/O, which gives standard LSIs a special add-on function to control high voltage signals directly in smart society applications.