Formation of High Aspect Ratio Macropore Array on p-Type Silicon

Abstract

The fabrication of high aspect ratio macropore arrays on p-type silicon under optimum anodization conditions is demonstrated. The depth of the macropore can reach 400 µm with an aspect ratio of 100. The thickness of the pore wall is 1-2 µm. Presence of cationic surfactant in the electrolyte protects the pore walls and promotes the growth of the unidirectional macropores. The shape of preetched pits is critical for the formation of high aspect ratio macropores on p-type silicon. A self-supported silicon membrane of straight-through macroporous channels has also been obtained.

Advanced In Situ I-V Measurements Used in the Study of Porous Structures Growth on Silicon

“…Macropores were observed from 0.5 to 2 mA/cm 2 with etching time of 320 min; however, it was not possible to get deep and straight macropores unlike the known cases using surfactant or tenside added electrolyte [14]. The nanopores start to grow at 3 mA/cm 2 and their percentage of surface coverage increases up to 15 mA/cm 2 .…”

Self-Adjusting Electrochemical Etching Technique for Producing Nanoporous Silicon Membrane

“…So, pore is difficult to form using this type of dopant [40]. In contrast, the n-type silicon is efficient in collecting minority charge carriers with the help of illumination.…”

“…This is because of the disability of p-type substrate to control the charge carrier collection at the pore tips for anisotropic dissolution of silicon. So, ion can hardly attack the silicon during the pore formation [40]. Besides that, n-type silicon substrate is more efficient to collect the charge carrier with the assistance of photoluminescence to promote columnar pore structure due to the depletion of holes during pore passivity against dissolution [41].…”

“…Normally, alcohol diluents are called as amphiphilic surfactants. The amphiphilic surfactants are hydrocarbon-based surfactants that are absorbed on silicon surface with their non-polar tails attached on hydrophobic silicon surface [40]. The shortest hydrocarbon chain is methanol, which results nearly in well-ordered pore structure.…”

Macroporous Silicon

“…Easy to make; arrays of high aspect ratio can be obtained (Lehmann and Rönnebeck 1999;Chao et al 2000;Chazalviel et al 2002;Urata et al 2012) p-Si (org) Large macropore observed; decisive parameters are electrolyte resistivity, oxidizing power, and "passivation power" (Ponomarev and Lévy-Clément 2000;Christophersen et al 2001;Lust and Lévy-Clément 2002) n + -Si (aqu + oxidant) Small diameter (60-100 nm), highaspect-ratio macropores (Christophersen et al 2000c;Ge et al 2010) …”