Open AccessFormation of cross-cutting structures with different porosity on thick silicon wafers
Author(s) -
V. A. Yuzova,
F. F. Merkushev,
Eugene A. Lyaykom
Publication year - 2017
Publication title -
modern electronic materials
Language(s) - English
Resource type - Journals
eISSN - 2452-2449
pISSN - 2452-1779
DOI - 10.1016/j.moem.2017.09.003
Subject(s) - hydrofluoric acid , wafer , materials science , etching (microfabrication) , porous silicon , silicon , layer (electronics) , porosity , mesoporous material , current density , composite material , crystal (programming language) , monocrystalline silicon , chemical engineering , mineralogy , optoelectronics , metallurgy , catalysis , chemistry , organic chemistry , physics , quantum mechanics , engineering , computer science , programming language
Three-layered pass-through structures of two types have been obtained on 500 μm thick single crystal silicon wafers by electrochemical etching in a 48% solution of hydrofluoric acid without using additional single crystal layer removal operations. The first type of the pass-through structures comprises two outermost 220–247.5 μm thick macroporous silicon layers with a pore diameter of 7–10 μm and an intermediate 5–60 μm thick mesoporous silica layer with a pore diameter of 100–150 nm. For the formation of the first type structures we used two-stage etching without cell disassembly:– in a 48% water solution of hydrofluoric acid (H2O: HF = 1: 1 vol.) for 140–180 min with a current density of 40 mA/cm2;– in a 48% water/alcohol solution of hydrofluoric acid (H2O: HF: С2Н5ОН = 1: 1: 1 vol.) for 60–90 min with a current density of 10 mA/cm2.The second type pass-through structures include a macroporous silicon layer with a thickness of 250 μm which interlock in the depth of the silicon wafer to form a cavity with a size of 4–8 μm. For the formation of the second type structures we only used the first one of the abovementioned stages, the etching time being longer, i.e. 210 min. All the etching procedures were carried out in a cooling chamber at 5 °C. The developed technology will provided for easier and more reliable formation of the monolithic structures of membrane-electrode assembly micro fuel cells