Modeling and Characterization of Oxide Semiconductor Field-Effect Transistors (OSFETs)
Oxide semiconductors, such as IGZO, ITO, and IWO, are being extensively explored for BEOL memory and logic applications because of their wide-bandgap (> 3eV) allowing ultra-low leakage current (~ 10-18 A/µm) and their ability to be deposited at BEOL-compatible temperature (< 350°C). Achieving good ION and IOFF with logic-compatible supply voltages (~ 1 V) is a critical requirement that the oxide semiconductor field-effect transistors (OSFETs) must meet to be viable for such applications. This requires optimal control of their threshold voltage (VTH) and subthreshold swing (SS), necessitating OSFET models that capture the underlying physics of amorphous OS films, rich in defects and disorder leading to various subgap states.
This project primarily focuses on studying the physics of defect and disorder-limited OSFET operation both through modeling/simulation and experimental characterization methods. These studies would then be transferred to a SPICE-compatible OSFET model that could be used for benchmarking OSFETs for various applications such as the gain-cell memory.
(a) Flowchart Describing the OSFET Model. A 1D Coupled Schrodinger-Poisson Solver Incorporating the Subgap Defect States is Considered.
(b) Model DoS Considered in this Study, including amorphous exponential band tail states, acceptor, and donor Gaussian defect states. EM is the Mobility Edge. The carriers in states above EM are assumed to undergo band-like transport with µ = µBand, whereas those in states below EM are assumed to be trapped with zero mobility.
(c) Model Fit of IDVG Characteristics. (d) Model fit of IDVD Characteristics.