Fabrication and characterization of entirely inkjet-printed polysilicon thin film transistors

Abstract In this paper, the fabrication and material innovation involved in the first and only entirely inkjet-printed polysilicon thin film transistors (TFTs) are described. To form TFT layers, five inkjet printing inks were developed with the goal of fabricating TFTs by using purely additive processing without vacuum deposition or conventional lithography. A silicon ink was developed to form both the channels and polysilicon gates, and boron and phosphorus dopant inks were developed for N+ and P+ doping. In addition, a silver nanoparticle (NP) ink was developed to form interconnect traces, and a palladium chloride ink was formulated to create palladium silicide for the ohmic contacts between the source and the drain. The first N-type metal-oxide-semiconductor (MOS) polysilicon TFT was fabricated with a top-gate self-alignment scheme. This exhibited a mobility of approximately 80 cm 2 V s −1 . Next, P-type MOS transistors as well as complementary MOS devices were also successfully fabricated.