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

Abstract

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 multifunctional 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.

Dye-sensitized solar cells strike back

“…Hole transporting materials (HTMs) transport charges within the materials themselves, not via movement of ions. 448,449 As such, their mechanism of charge transport is best defined as electronic (or charge) hopping rather than diffusion. Due to the lack of molecular movement, solid-state DSCs (ssDSCs) based on an HTM layer work similarly to liquid DSCs while also maintaining the advantages of a solid-state system.…”

Si nanomebranes: Material properties and applications

“…The thickness of the NM can be precisely controlled and reduced even to ~ 2 nm by repetitive oxidation of the top Si layer followed by HF etching [13,21,29,79]. The fabricated NMs can then be transferred into wide variety of host substrates as per its application requirements [13,21,29,79]. The SEM image in the bottom panel of Fig.…”

“…Various nanomaterials such as nanotubes, nanowires, and two-dimensional (2D) materials have been actively explored for this purpose, because nanomaterials can be chemically synthesized easily on a large scale and exhibit exceptional electrical and optical properties [5, 9, 12-17, 18, 19]. In particular, nanoscale dimension of materials offers great mechanical bendability, which enables the production of flexible and wearable devices with specific functions [1,2,6,9,15,17,[20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38]. Diverse applications, such as wearable tactile sensors, bio-implantable devices and flexible display have been successfully demonstrated [10,18,28,[39][40][41][42][43][44][45][46][47][48][49][50][51].…”

Flexible and Stretchable Microwave Electronics: Past, Present, and Future Perspective

“…[69] Furthermore, high-performance flexible bipolar-CMOS (BiCMOS), with an 8.8 GHz f max for n-type MOSFET (nMOS) and 2.2 GHz f max for p-type MOSFET (pMOS), was demonstrated on transferrable Si NM by employing multiple ion implantations of different doses and energies followed by a single thermal anneal to achieve desired doping profiles for MOSFETs and BJTs. [78] Sandwich-like Si/SiGe/Si NM can be employed to effectively increase electron mobility in TFT channel [73,79] since plastic substrates, unlike a rigid Si wafer, cannot sustain strain in the Si channel. Considering the plasticity properties of many soft flexible substrates under elevated temperatures (e.g., during photoresist baking), projection-like photolithography was employed to circumvent misalignment induced by substrate thermal expansion.…”