Positive and negative etching of As-S thin layers†

The selectivity of the dissolution (SD =νexp)/νunexp) of AsxS100−x thin layers in alkaline solvents is improved by the addition of cation-active surface-active substances (SAS) in the etching solvent. Etching of the layers in aqueous alkaline solvents was positive, i.e. the part of the layer exposed to light dissolved more quickly than the unexposed part. In contrast, dipping layers with x≥40 into CS2 resulted in negative etching in the same aqueous alkaline solvents. Possible mechanisms for the interaction of layers with SAS and CS2 are discussed. On the basis of the results obtained, the As-S layers can be used as positive and negative working resists with submicron resolution.