Effects of a metal layer on selective etching of a Ge5Sb75Te20 phase-change film
Selective etching between an amorphous and a crystalline phase of a Ge5Sb75Te20 alloy film is carried out with an alkaline etching solution of NaOH. The etching selectivity is dependent not only on the concentration of the etching solution but also on the type of metal layer in the film structure. Specifically, Ag and Al metal films for a heat control function during writing in phase change recording show opposite behavior in the selective etching process. Surviving amorphous pits are obtained with the Al metal layer while etched amorphous pits are observed with the Ag metal layer. The etching selectivity of a sample with the survived amorphous pits with Al metal is better than that of the etched amorphous pits with an Ag metal layer.