In Situ Bipolar Doping via Mechanically Controlled Dipole Under Water

Abstract

Polycrystalline silicon (poly-Si) is essential in integrated circuits and microelectromechanical systems. In addition, poly-Si is gaining attention for next-generation display research with high thermal conductivity, stability, and versatile applications. Conventional fabrication methods for doping patterns involve complex lithography and chemical usage, which have raised environmental concerns. The study of novel methods is necessary for environmental friendliness and a significant simplification of the manufacturing processes. This study introduces a novel bipolar work function control technology utilizing deionized water (DI-W) and nanonewton-scale mechanical force using an atomic force microscope. The method is implemented with a mechanically induced SiO_x layer on poly-Si in DI-W. The induced Si─OH and Si─O bonds decreases the work function, whereas a thicker SiO_x layer with a high oxidation state increases the work function. Based on the magnitude of the applied force (26.73–75.24 nN) and additional DI-W immersion, the induced bond and thickness of the SiO_x layer are controlled. Therefore, bipolar work function control is achieved in the range of −0.25–+0.103 eV. In addition, the electrical characteristics of the fabricated p- and n-type poly-Si diodes are investigated. This method is eco-friendly and enables bipolar doping patterns in a single process with high efficiency.