High-performance flexible BiCMOS electronics based on single-crystal Si nanomembrane

In this work, we have demonstrated for the first time integrated flexible bipolar-complementary metal-oxide-semiconductor (BiCMOS) thin-film transistors (TFTs) based on a transferable single crystalline Si nanomembrane (Si NM) on a single piece of bendable plastic substrate. The n-channel, p-channel metal-oxide semiconductor field-effect transistors (N-MOSFETs & P-MOSFETs), and NPN bipolar junction transistors (BJTs) were realized together on a 340-nm thick Si NM layer with minimized processing complexity at low cost for advanced flexible electronic applications. The fabrication process was simplified by thoughtfully arranging the sequence of necessary ion implantation steps with carefully selected energies, doses and anneal conditions, and by wisely combining some costly processing steps that are otherwise separately needed for all three types of transistors. All types of TFTs demonstrated excellent DC and radio-frequency (RF) characteristics and exhibited stable transconductance and current gain under bending conditions. Overall, Si NM-based flexible BiCMOS TFTs offer great promises for high-performance and multi-functional future flexible electronics applications and is expected to provide a much larger and more versatile platform to address a broader range of applications. Moreover, the flexible BiCMOS process proposed and demonstrated here is compatible with commercial microfabrication technology, making its adaptation to future commercial use straightforward.