From MFM Capacitors Toward Ferroelectric Transistors: Endurance and Disturb Characteristics of ${\rm HfO}_{2}$-Based FeFET Devices

Abstract

Ferroelectric Si:HfO2 has been investigated starting from metal-ferroelectric-metal (MFM) capacitors over metal-ferroelectric-insulator-semiconductor (MFIS) and finally ferroelectric field-effect-transistor (FeFET) devices. Endurance characteristics and field cycling effects recognized for the material itself are shown to also translate to highly scaled 30-nm FeFET devices. Positive-up negative-down as well as pulsed Id-Vg measurements illustrate how ferroelectric material characteristics of MFM capacitors can also be identified in more complex MFIS and FeFET structures. Antiferroelectric-like characteristics observed for relatively high Si dopant concentration reveal significant trapping superimposed onto the ferroelectric memory window limiting the general program/erase endurance of the devices to 104 cycles. In addition, worst case disturb scenarios for a VDD/2 and VDD/3 scheme are evaluated to prove the viability of one-transistor memory cell concepts. The ability to tailor the ferroelectric properties by appropriate dopant concentration reveals disturb resilience up to 106 disturb cycles while maintaining an ION to IOFF ratio of more than four orders of magnitude.