Wet Chemical Recess Etching of Ge2Sb2Te5 for 3D PCRAM Memory Applications

Abstract

GeSbTe (GST) compounds have been implemented in Phase Change Random Access Memory (PCRAM) devices. 2D scaling or stacking of PCRAM is limited by cost and therefore the development of 3D architectures is expected. A key requirement for the fabrication of this 3D architecture is the etch-back of the GST. The main objective of this study is to partially recess GST in a controllable way, leaving the surface of the GST smooth after recess. Wet isotropic recess of amorphous and crystalline blanket films as well as patterned samples was explored using commodity chemistries like APM and HPM. Due to some shortcomings of these peroxide-containing solutions, the oxidizing agent was changed from H2O2 to O3. In the ozone-containing solutions the roughness of the GST after etch-back could be controlled as well as the selectivity towards Al2O3, SiO2 and TiN ensured.