Study on Preparation of High Purity Mono-sized Silicon Micro Particles by Pulsated Orifice Ejection Method

Abstract

Preparation of high purity mono-sized silicon particles by Pulsated Orifice Ejection Method (POEM) was investigated. The results of simulation show that a large contact angle between silicon and orifice is necessary for particle formation on processing by POEM. Mono-sized silicon particles can be prepared with quartz orifice and tundish within in a wide variety by POEM. Analyses by Scanning Electron Microscope (SEM) and Orientation Image Microscope (OIM) show that the obtained silicon particles can be divided into two kinds according to their surface morphology and microstructure. One is grape-fruit type silicon particles, which are polycrystalline and consist of many grains mainly in random boundaries, and the other is lemon type, which consists of only two or three grains in twin boundaries with cross-sections sometimes found to be single crystal. Measurements of electrical resistivity on polycrystalline ingots formed in the same conditions as silicon particles show p-type behavior with a room-temperature electrical resistivity in the range 15∼60 Ωcm and carrier concentration less than 2×10¹⁶ cm⁻³ that are suitable for solar cell.