Fabrication of antireflective layers on silicon using metal-assisted chemical etching with in situ deposition of silver nanoparticle catalysts

Ag particle-assisted chemical etching of silicon wafers in HF/H2O2 is of interest for its potential to produce antireflective layers for solar cells. In this work, Ag films containing both nanoscale (d<100 nm) and microscale (d<1 μm) particles were deposited through the silver-mirror reaction on planar p-Si(111), planar p-Si(100) and p-Si(100) pre-etched in KOH/isopropanol to produce pyramidal textures. Subsequently, these wafers were subjected to metal-assisted chemical etching (MacEtch) in 1:1:1 (v:v:v) HF(49%):H2O2(30%):EtOH solutions, to produce porous silicon (PSi) containing both micro- and nanoscale roughness features. The resulting surfaces exhibit morphologies that evolve with processing conditions, especially the absence/presence of pyramidal textures and the time the structure is subjected to MacEtch. Under optimal conditions excellent anti-reflection behavior is observed with surface reflectivities being reduced below 10% for either p-Si(100) or p-Si(111) surfaces. For p-Si(100) better results (R∼5%) were obtained for 30 min KOH/isopropanol pre-etch than for either no pre-etch or longer (60 min) pre-etch. The influence of the reductant on Ag particle deposition on p-Si(111) was studied, and MacEtch catalyzed by Ag produced from acetaldehyde reductant produced surfaces with lower reflectivities than those with glucose reductant.