Overcoming Negative nFET VTH by Defect-Compensated Low-Thermal Budget ITO-IGZO Hetero-Oxide Channel to Achieve Record Mobility and Enhancement-mode Operation

We have successfully demonstrated, low-thermal budget oxide-based FETs with a record I
D,max
of $790\mu\mathrm{A}/\mu\mathrm{m}$ at V
DS
= 1V, an enhancement-mode operation (V
DH
>0), S.S. <90 mV/dec., and DIBL ~20mV/V at an ultra-scaled channel length LCH
CH
of 50 nm. This is enabled by an optimized InSnO
x
-InGaZnO
x
hetero-junction channel to achieve channel defect self-compensation [1]. This approach overcomes the fundamental issue of negative VTH seen in n-type oxide FETs due to donor-type channel oxygen vacancy (Vo) and the limited tunability of gate metal work function. Through our ITO-IGZO channel and defect self-compensation approach, our transistor effective mobility $(\mu_{\text{eff}})$ is boosted to $110\mathrm{~cm}^{2}/\mathrm{V}\cdot\mathrm{s}$ with the channel thickness (TCH) scaled down to 4 nm. This unique T
CH
-independent mobility behavior is not observed for IGZO or ITO mono-channel FETs. With such enhancement, our ITO-IGZO FETs exhibit the best-in-class mobility among oxide-based FETs, and are competitive to unstrained Silicon thin film and SOI FETs, while being compatible with sub- 400 °C back-end-of-line (BEOL) processes.