Patterned Porous Silicon Prepared by Reactive Ion Etching Technique

Abstract

A previous study, porous silicon (PSi) have been fabricated by electrochemical anodization method. The PSi surfaces have an inhomogeneous pores size in the range of 95– 1450 nm. In this study, we have prepared patterned PSi using RIE technique in CF4 gas which is activated by RF plasma. Before the RIE process, the surfaces Si was patterned using the photolithography method. Then, the Si surfaces were etched in various etching time to form patterned PSi. The patterned PSi samples were characterized by SEM, Dektak profilometer, and four-point probe equipment. We found the pore sizes and the pore depths for each the etching time were about 5.30 μm and 12.6 nm; 5.19 μm and 19.6 nm; 4.30 μm and 23.8 nm; 3.40 μm and 28.0 nm for 10 min, 20 min, 30 min, and 40 min, respectively. The pores depths increased with increasing the etching time. Meanwhile, the resistivity of patterned PSi increased with increasing the etching time i.e., 1.14×10-4 Ω.cm, 1.79×10-4 Ω.cm, 2.36×10-4 Ω.cm, and 2.60×10-4 Ω.cm for 10 min, 20 min, 30 min, and 40 min, respectively. This indicated that the pore could be considered as defects or dislocation inside material which resist electrons diffuse toward the electrode.