A circuit pattern etching of a Silicon-carbide (SiC) surface was conducted with KrF excimer laser irradiation in the presence of HF and H2O2 mixed solutions. SiC have excellent properties of a high hardness, high melting point, wide band gap, high resistance to radiation and chemical stability. This material has come to attract attention as an integrated circuit material for high resistance to environment. However, the material is very difficult in minute processing by the photo-lithography because of its chemical stability. Thus, we developed the new etching method in which a SiC surface was photo-oxidized with H2O or H2O2 by using excimer laser irradiation and was etched by HF water solution. In this experiment, the mixed solution was poured into the thin gap between an Al2O3 glass and the SiC surface with capillary phenomenon. A patterned excimer laser light was, then, irradiated on the SiC surface. The H2O or H2O2 in the reaction solution was photo-dissociated, and the photo-dissociated active oxygen reacted with the SiC. CO2 and SiO2 were formed only on the part exposed by the pattered light forcibly, and an oxidized layer was formed. In this chemical reaction, the CO2 evaporated, and the SiO2 remained on the sample surface. The SiO2 layer was then dissolved by the HF water solution. Thus, etching was conducted by the repetition of the forced oxidization of the SiC and the dissolving of the oxidized layer. In this experiment, the most effective conditions were 20% of H2O2 water solution, 15% HF water solution and 256mJ/cm2 of KrF excimer laser. The etching depth was 80 Å at the laser shot number of 10000. It significantly improved compared with that of using an ArF excimer laser (256mJ/cm2, 193nm), 50 Å.
Humic Acids Aggregates as Microheterogeneus Reaction Media: Alkaline Hydrolysis Reactions
