First Demonstration of Sequential Integration for Stacked Gate-All-Around a-IGZO Nanosheet Transistors with Record Id = 2.05 mA/µm, gm = 1.13 mS/µm and Ultralow SS = 66 mV/dec

In this work, high-performance stacked gate-all-around (GAA) a-IGZO 2-layer nanosheets field-effect transistors (NSFET) has been demonstrated for the first time, with the entire thermal budget below 300°C with back-end-of-line (BEOL) compatibility. The performance of the GAA IGZO nanosheet FETs can be successfully improved for over twice of the single channel. As high-k HfLaO dielectric scales from 10 nm to 4 nm, a short channel 50 nm-long transistor exhibits a record-high g
m
of 1.13 mS/µm at V
ds
=1.5 V and record-high on-state current of 2.05 mA/µm at V
ds
=1 V, the highest among all IGZO-based FETs. Meanwhile, the same short channel transistor achieves ultra-low SS of 66 mV/dec, realizing a record-high quality factor g
m
/SS larger than 10 for the first time among a-IGZO transistors. The GAA NSFETs also show I
off
<10
^-8
µA/µm (measurement limit) and a high on/off ratio > 10
¹¹
despite the 4 nm thin high-k dielectric.