Porous silicon field emission arrays with built-in spacer

Abstract

In this research, we applied the physical and electrical characteristics of porous silicon to enhance the performance of jield emission devices. The surface of silicon jield emitters have been modified by chemical etching with HF:HN03:H20 solution, and electrochemical etching with HF:ethanol solution. The emitter surface became roughened and had nano-scale fibrils over the emitter surface in both cases. We found PS thin films prepared by chemical etching of Si field emitters also gave similar field enhancement efiects as does electrochemically formed PS. Porous silicon contributed to the increase of the emission current, the reduction of operating voltage, the improvement of the un formity of the emission characteristics between the emitters and the reduction of the probability of emitter failure during operation. I. INTRODUCTION Recent studies on developing field emission devices for practical use have been focused on achieving high emission current at a low voltage [l-31 Emission from field emitters depends on the geometrical shape of the tips, and the surface conditions of the tips, and the cathode materials Porous silicon (PS) can be another field enhancement method due to its nano-scale physical structure [4, 51 PS has been investigated as an insulating material (SOI) in the field of VLSI Since the discovery of visible photoluminescence from PS at room temperature in 1990 by Canham, much attention has been given to the optical properties of PS [6] Particularly, photoluminescence (PL) and electroluminescence (EL) from porous silicon at room temperature have attracted much attention because of their potential application for Si-based opto-electronic devices [7, 81 Thus far, PS thin films have been prepared mainly by electrochemical etching of silicon wafers It has been reported that porous silicon can be formed by either open-circuit etching (i e chemical stain etching), or electrochemical etching of the silicon Beale et al. studied the microstructure and the electrical characteristics of stain etched and electrochemical etched silicon and reported that the two methods produce a porous silicon having similar properties [9] Although electrochemical etching is more widely used to form PS, stain etching is simpler and can give similar advantages such as high emission current at a low operating voltage when it is applied to the field emission devices In this research, chemical etching of Si field emitter arrays (FEAs) was performed to improve the emission properties of a plain Si FEA In addition, a comparison was made with electrochemical etched FEAs 11. FABRICATION