Wang Lianwei

Novel method of separating macroporous arrays from p-type silicon substrate

This paper presents a novel method to fabricate separated macroporous silicon using a single step of photo-assisted electrochemical etching. The method is applied to fabricate silicon microchannel plates in 100 mm p-type silicon wafers, which can be used as electron multipliers and three-dimensional Li-ion microbatteries. Increasing the backside illumination intensity and decreasing the bias simultaneously can generate additional holes during the electrochemical etching which will create lateral etching at the pore tips. In this way the silicon microchannel can be separated from the substrate when the desired depth is reached, then it can be cut into the desired shape by using a laser cutting machine. Also, the mechanism of lateral etching is proposed.

An Array of One-Dimensional Porous Silicon Photonic Crystal Reflector Islands for a Far-Infrared Image Detector

With the aid of photolithography, an array of one-dimensional porous silicon photonic crystal reflector islands for a far infrared image detector ranging from 10 μm to 14 μm is successfully fabricated. Silicon nitride formed by low pressure chemical vapor deposition (LPCVD) was used as the masking layer for the island array formation. After etching, the microstructures were examined by a scanning electron microscope and the optical properties were studied by Fourier transform infrared spectroscopy, the result indicates that the multilayer structure could be obtained in the perpendicular direction via periodically alternative etching current in each pre-pattern. At the same time, the island array has a well-proportioned lateral etching effect, which is very useful for the thermal isolation in lateral orientation of the application in devices. It is concluded that regardless of the absorption of the deposition layer on the substrate, the localized photonic crystalline islands have higher reflectivity. The designed islands structure not only prevents the cracking of the porous silicon layers but is also useful for the application in the cold part for the sensor devices and the interconnection of each pixel.

A Stable Porous Silicon Dielectric Reflector with a Photonic Band Gap Centred at 10μm

By pulsed anodic etching at low temperature, we prepared a porous silicon reflector with a photonic band gap centred in the long-wavelength infrared spectral region (centred at about 12 μm). After proper oxidation process, the stable reflector structure, which can reflect electromagnetic wave from 8μm to 12μm (centred at 10μm) within wide incidence angles (about 50°), is obtained. The wavelength shift of absorption peak of Si-H and Si-O shows the influence of oxidation process and indicates the stability of oxidized porous silicon dielectric reflector, which offers possible applications for the room temperature infrared sensor.

Silicon-on-Insulator Structure Fabricated by Electron Beam Evaporation of Si on Porous Si and Epitaxial Layer Transfer

Epitaxial monocrystalline Si was grown on porous silicon by ultra-high vacuum electron beam evaporation. Results of reflection high-energy electron diffraction, atomic force microscopy, cross-section transmission electron microscopy and Rutherford backscattering spectrometry and channelling (RBS/C) show that the epitaxial layer is of a good quality. Furthermore, silicon-on-insulator materials were successfully produced by bond and etch back of porous silicon. The quality of the silicon-on-insulator samples was investigated by RBS/C and spreading resistance profiling. Experimental results show that both the crystalline quality and electrical quality are good. In addition, the interface between the top Si layer and SiO2 buried layer is very sharp.