用脉冲电化学法在低HF浓度下制备多孔硅的研究

Preparation of porous silicon etched by pulsed electrochemical method at low HF concentration

用脉冲电化学阳极氧化的方法在 5 %的低HF浓度下获得多孔硅。多孔硅的形成和脉冲电场的施加、去除过程中与电解液 硅半导体体系中物理化学过程的变化有关。在施加电场的间隙 ,由于Si/电解液界面处HF的补充 ,SiO2 的溶解增强 ,使得在低HF浓度下Si的溶解速率比其氧化速率高 ,从而导致多孔硅的形成。同时 ,在高电场作用下 ,由于产生了高浓度的空穴 ,使得氧化层变厚 ,导致在低HF浓度或大电流密度下多孔硅的平均孔径增大。

The preparation of porous silicon at low HF concentration by pulsed electrochemical method was investigated. Porous silicon was obtained at 5% HF concentration which was thought as electropolishing of silicon before. By utilizing pulsed filed, total dissolution rate of Si is higher than that of oxide formation at low HF concentration due to the dissolution rate of SiO 2 is enhanced at electric field off. It results in the formation of porous silicon. Meanwhile, oxide film can become thicker due to high hole density at high electric field. It results in the increasing of average pore size at low HF concentration or high etching current density.