Improved Subthreshold Characteristics by Back-Gate Coupling on Ferroelectric ETSOI FETs

Area of Science:

• Semiconductor device physics
• Materials science

Background:

• Ferroelectric materials offer unique electrical properties for advanced transistors.
• Extremely thin silicon-on-insulator (ETSOI) technology enables miniaturization and improved performance.
• Achieving steep subthreshold swing is crucial for reducing power consumption in electronic devices.

Purpose of the Study:

• To fabricate and characterize extremely thin silicon-on-insulator field-effect transistors (ETSOI FETs) incorporating an ultra-thin ferroelectric layer.
• To investigate the subthreshold characteristics of these devices under double-gate modulation.
• To demonstrate a model for understanding and controlling the subthreshold swing behavior.

Main Methods:

• Fabrication of ETSOI FETs with a 3 nm ferroelectric (FE) hafnium zirconium oxide (Hf_0.5Zr_0.5O₂) layer.
• Extensive investigation of subthreshold characteristics using double-gate modulation.
• Development of an analytical model based on the transient Miller model.

Main Results:

• The minimum subthreshold swing (SS) of a 40 nm ETSOI device was adjustable from 80.8 to 50 mV/dec.
• Demonstrated ultra-steep SS characteristics due to back-gate voltage coupling effects.
• Validated an analytical model for explaining the observed electrical characteristics.

Conclusions:

• The developed FE ETSOI FETs exhibit promising ultra-steep subthreshold swing.
• The devices show feasibility for ultra-low-power applications through dynamic threshold adjustment.
• This research contributes to the advancement of energy-efficient semiconductor devices.