Fast flexible thin-film transistors with deep submicron channel enabled by nanoimprint lithography

The simplification of fabrication processes that can define very fine patterns for large-area flexible radio-frequency (RF) applications is very desirable because it is generally very challenging to realize submicron scale patterns on flexible substrates. Here we report a generic strategy for fabricating high-performance flexible Si nanomembrane (Si NM)-based RF thin-film transistors (TFTs) with nanoimprint lithography patterned deep-submicron-scale channel lengths which can be easily adapted for large-area and high throughput roll-to-roll manufacturing processes. A unique etched-channel configuration was used to allow for device fabrication compatible with flexible substrates. Optimal device parameters were obtained through device simulation to understand the underlying device physics and to enhance device controllability. Theoretically, the maximum frequency (f_max) of flexible Si NM TFTs can exceed 100 GHz. Experimentally, record breaking 5 GHz and 38 GHz ft and f_max values, respectively, have been successfully demonstrated on plastic substrates.