Laser heat-mode lithography characteristics and mechanism of ZnS-SiO2 thin films

In this work, laser heat-mode lithography characteristics of ZnS-SiO2 composites are investigated by direct laser writing and wet-etching. In order to understand the lithography mechanism, the structural evolution of ZnS-SiO2 film is investigated. Chemically disordered ZnS:O crystalline structures and SiSnO4-n networks were found in the as-deposited sample, while ZnO and SiSn+1O3-n tetrahedral networks were formed after laser writing. Furthermore, the ZnO and SiSn+1O3-n tetrahedrons have higher solubilities in hydrofluoric acid than ZnS:O and SiSnO4-n networks. This leads to superior etching selectivity between laser-written and non-written regions. In addition to this, ZnS-SiO2 patterns can be used as a hard mask for the dry etching process; therefore, transferal of these patterns onto quartz glass is also performed.