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. Electronics: Microfabrication enables integrated silicon-based thin-film transistorsSemiconductor-based thin-film electronics is an emerging field in modern electronics due to the advance in mechanical flexibility, yet the fabrication that is currently relied on the conventional technologies for rigid devices constrain the integration of functional devices on one chip. A team lead by Zhenqiang Ma at University of Wisconsin-Madison developed a single batch processing technique, which allowed them to print multiple transistors on a single piece of plastic substrate. The key step is to selectively dope single crystalline silicon nanomembranes using spatially controllable ion implantation. As a demonstration, integrated bipolar-complementary metal-oxide-semiconductor thin-film transistors with performance comparable to their rigid counterparts are built. The fabrication reported might prove to be an enabling technology for processing a broad range of flexible electronics with potential industrial adaptability.