HCl浓度对多孔硅微结构及Si-H键合的影响

Effect of the Concentration of Hydrochloric Acid on the Microstructure and Si-H Bonds in Porous Silicon

采用电化学湿法刻蚀制备了P型多孔硅,通过改变HCl溶液浓度来调整刻蚀液中的氢离子浓度。制备出的多孔硅孔径相同,孔深随着氢离子浓度的提高呈线性增大直至恒定。基于电流突发模型阐述了结构参数的变化:孔径的形成开始于刻蚀的初始阶段,空穴主导了初始阶段的腐蚀,空穴的迁移与消耗过程就是孔径扩张和孔壁形成的过程,该过程与硅片本身的性能密切相关,与氢离子浓度无关,故孔径基本恒定;氢离子浓度的提高加快氢的置换反应直至平衡,从而使反应总速率提高直至恒定,因此孔深先线性增大然后保持恒定;Si-H含量在一定范围内与孔深的变化吻合呈现上升趋势,且键合形式以Si-H2为主。

In order to increase hydrogen ion concentration, hydrochloric acid was added in the etch- ing liquid for the preparation of porous silicon used by electrochemical wet etching. The diameters of pores were constant and the depth linearly increased into constant with the concentration of hydrogen ions. The changes of the diameter and depth of pores were discussed on the basis of current burst mod- el. The apertures formed in the initial stage of etching. In this stage the holes dominated the silicon corro- sion, and the transport and consumption of the holes led to the aperture expansion and the formation of pore walls. The characters of holes were decided by silicon substrates and were not related to the con- centration of hydrogen ions, so the apertures were constant. The increase of hydrogen ion concentration led to the acceleration until constant on the reaction rate of hydrogen displacement, so the system reac- tion rate was accelerated to a constant until it was limited by other reaction. The curve of pore depth - hy- drochloric acid concentration remained constant after a linear increasing. Si-H contents increased with the pore depth in the certain range. Si-H2 bonds dominated in the bondinq type of Si-Hx （x=1, 2, 3）.