Fabrication of nano-scale phase change materials using nanoimprint lithography and reactive ion etching process

Phase change random access memory (PRAM) is one of the most promising non-volatile memories due to its ability to store digital data in the form of crystalline and amorphous phases of phase change materials. As a phase change material, Ge₂Sb₂Te₅ (GST225) is usually used, due to its reversible phase transition capability with speeds of less than 100 ns between the crystalline and amorphous phases. In order to fabricate highly integrated PRAM devices, sub micron- to nanometer-sized patterning of GST225 layer must be accomplished. In this study, 70 nm-sized polymer patterns were fabricated using partial filling nanoimprint lithography (NIL) on a GST225 layer, which was deposited by RF sputtering. Then GST225 was etched using Ar/Cl₂ plasma with an ICP etcher. Etch conditions, including Cl ₂ concentration, were optimized to obtain the vertical etch profile of the GST patterns.