Atomic-layer-deposited HfO2/Al2O3 laminated dielectrics for bendable Si nanomembrane based MOS capacitors

Abstract

Flexible metal-oxide-semiconductor capacitors in a vertical structure using the single-crystalline Si nanomembrane (NM) with a HfO2/Al2O3 bilayer gate stack prepared by atomic layer deposition have been fabricated on plastic substrates by flip-transfer printing of Si NM/Ti/Au based trilayer heterostructures (1.3 cm × 0.9 cm × 360 nm). The electrical properties of the bilayer structure exhibit an excellent improved capacitance-voltage (C-V) frequency dispersion feature associated with an inhibited weak inversion hump and significantly larger accumulation capacitance, thus indicating the effectiveness of the passivation utilizing bilayer high-k dielectrics on a Si NM channel compared with monolayer HfO2. A comprehensive electromechanical characterization has been conducted for HfO2/Al2O3 stacked structures to investigate the effect of bending strain on C-V characteristics, leakage current density, and the associated evolution of interface charges. The presented research will be beneficial to realizing high performance thin-film transistors with lower operating voltage and higher driving current required in emerging flexible and stretchable electronics via optimized design of a nanolaminate gate stack and understanding the impact of mechanical strains on the electrical behavior of such MOS devices.