Abstract
Macroporous structure of silicon can be obtained with anodization in hydrogen fluoride (HF) solution. The macropore formation in the presence of alcohol was studied. Macroporous layer formation in a low-concentration HF solution is stabilized with the increasing number of carbon in alcohol. The dissolution at the topmost part of the porous layer is observed though the behavior depends upon the type of alcohol. Meanwhile, the total mass loss of dissolved silicon is almost constant. Such dissolution at the top surface occurs only when the concentration of HF is low. Adding organic solvents to the HF solution also leads to the suppression of the pore wall dissolution. The type of alcohol and HF concentration in solution affect the formation of porous silicon.
Highlights
Anodization of silicon in hydrogen fluoride (HF) solution below the critical current density produces a porous silicon layer
Further studies regarding macropores in p-type silicon were performed either in aqueous HF [3] or HF mixed with organic solvents [4]
The stability of porous layers increases with the increasing carbon numbers in the alcohol
Summary
Anodization of silicon in hydrogen fluoride (HF) solution below the critical current density produces a porous silicon layer. The size and shape of the pores are dependent on wafer resistivity, current density, and solution composition. The macroporous structure in n-type silicon substrate was, for the first time, discovered using aqueous HF solution by Theunissen in 1972 [1]. It was in 1994 that Propst and Kohl observed first macropores in p-type silicon [2]. They used anhydrous HF solution with acetonitrile (MeCN) as electrolyte for this macropore formation. Further studies regarding macropores in p-type silicon were performed either in aqueous HF [3] or HF mixed with organic solvents [4]
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