Fabrication of nano-porous silicon using alkali etching process

The best conditions for the production of porous silicon (PS) using alkali etching process have been defined and discussed. The surface chemistry of anisotropic etching of n-type Si-wafer is reviewed and the anisotropic chemical etching of silicon in alkaline solution using wetting agents were discussed. The main factors which affect the production of porous silicon from crystalline silicon as a result of anisotropic etching are the concentration of etching solution (KOH) and wetting agent (n-propanol), temperature and time of the etching process. Transformation of crystallographic plane of n-Si (2 1 1) to n-PS (1 0 0) is produced by using {(2  wt%) KOH+(15  vol%) n-propanol} at etching temperature 80 °C and etching time 5 h. These results are confirmed using FTIR which detect the peak at 1015 cm−1. A particle size of 15 nm for porous nano-silicon calculated from the XRD data. Pores of (49–349)  nm in diameter and 25 μm in depth and a pitch of (4.203×10−6–6.92×10−6)  μm per layer are obtained for the same conditions explained above.

► Alkali etching produce NPS. ► Particle size 15, Pore diameter 49nm. ► Transform Si(211) to PS(100).