Highly Anisotropic and Corrosionless PtMn Etching using Pulse-Time-Modulated Chlorine Plasma

Thin PtMn films have recently been used in magnetic devices such as magnetoresistive random access memories (MRAMs). A general problem with this material is that it is relatively inert during conventional plasma processes, and thus alternative methods such as ion milling, lift-off and electroplating have been employed for pattern transfer. As the density of magnetic memories increases toward the Gbit range, the film must be patterned at sub-micron widths. To achieve this requirement, we propose pulse-time-modulated plasma etching. We found that highly anisotropic PtMn etching could be achieved with smooth and corrosionless sidewalls using pulse-time-modulated (TM) chlorine plasma at a pulse time of 10 to 100μs. We concluded that the incident Cl ^- could enhance the chemical reaction on the PtMn surface.