We investigated the effect of etching time on the surface roughness, and electrical and optical properties of ZnO and 2 wt% Al-doped ZnO (AZO) films. The ZnO and AZO films were deposited on glass substrates by RF magnetron sputtering technique. The etching experiment was carried out using a solution of 5% HCl at room temperature. The surface roughness was characterized by Atomic Force Microscopy. The electrical property was measured by Hall measurement system and 4-point probe. The optical property was characterized by UV-vis spectroscopy. After the wet chemical etching, the surface textures were obtained on the surface of the ZnO and AZO films. With the increase of etching time, the surface roughness (RMS) of the films increased and the transmittance of the films was observed to decrease. For the AZO film, a low resistivity of 1.0×10-3 Ω·cm was achieved even after the etching.

Hafnium oxide (HfO2) was very advantageous for substitute material of gate on existing transistor. HfO2 has been widely studied due to high contact with polysilicon and thermal stability and also, it is easily etched by using HF solution. In this study, HfO2 and thermal oxide films were etched by wet etch method using chemical etchant. Etch rate of HfO2 and thermal oxide was linearly increased with increasing concentration of HF and temperature but etch rate of HfO2 was higher than thermal oxide due to H+, F-, and HF2- ions at below 0.5% concentration of HF. And also, etch selectivity was improved by adding Hydrazine as additive.

The present study introduces a novel wet etching technique for nanostructure fabrications which usually requires low surface roughness. Using the current method, acquired profiles were smooth even in the nanoscale, which cannot be easily achieved with conventional wet or dry etching methods. As one of the most popular single crystal silicon etchant, potassium hydroxide (KOH) solution was used as a base solvent and two additives, antimony trioxide (Sb2O3) and ethyl alcohol were employed in. Four experimental parameters, concentrations of KOH, Sb2O3, and ethyl alcohol and temperature were optimized at 60 wt.%, 0.003 wt.%, 10 v/v%, and 23℃, respectively. Effects of additives in KOH solution were investigated on the profiles in both (110) and (111) planes of single crystal silicon wafer. The preliminary results show that additives play a critical role to decrease etch rate significantly down to ~2 nm/min resulting in smooth side wall profiles on (111) plane and enhanced surface roughness.

Sapphire substrate was patterned by a selective chemical wet etching technique, and GaN/InGaN structures were grown on this substrate by MOVPE (Metal Organic Vapor Phase Epitaxy). The surface of grown GaN on patterned sapphire substrate (PSS) has good morphology and uniformity. The patterned sapphire substrate LED showed better light output than conventional LED that improvement 50%. We think these results come from enhancement of internal quantum efficiency by decrease of threading dislocation and increase of light extraction efficiency. Also these LED showed more uniform emission distribution in angle than conventional LED.