Discrete Ferroelectric Polarization Switching in Nanoscale Oxide-Channel Ferroelectric Field-Effect Transistors

Area of Science:

• Materials Science
• Solid State Physics
• Nanotechnology

Background:

• Ferroelectric materials are crucial for non-volatile memory devices.
• Scaling down ferroelectric field-effect transistors (FeFETs) presents challenges in understanding polarization switching behavior.
• Hafnium-zirconium oxide (HZO) is a promising material for advanced FeFETs.

Purpose of the Study:

• To investigate polarization switching dynamics in scaled HZO FeFETs.
• To understand the impact of channel scaling on memory window (MW) enhancement.
• To probe ferroelectric physics at the nanoscale, down to the ferroelectric (FE) domain level.

Main Methods:

• Fabrication of HZO FeFETs with amorphous indium-tin oxide channels.
• Systematic scaling of channel thickness and length.
• Characterization of polarization switching behavior and memory window.
• Analysis of fatigue effects on device performance.

Main Results:

• Channel thickness scaling, particularly to 2.5 nm, significantly enhances the memory window (MW) up to 2.2 V.
• Discrete ferroelectric polarization switching observed in nanoscale transistors indicates involvement of a few FE domains.
• Estimated ferroelectric domain size in HZO is approximately 40 nm.
• Fatigue experiments show FE domain pinning is a major factor causing negative threshold voltage shift and MW degradation.

Conclusions:

• Channel thickness scaling is an effective strategy for improving MW in HZO FeFETs.
• Nanoscale FeFETs allow observation of discrete FE domain switching, enabling fundamental physics studies.
• FE domain pinning is a critical mechanism limiting the performance and reliability of scaled HZO FeFETs.
• This work provides insights into FE physics at the single domain level, crucial for future device design.