Etch characteristics of magnetic tunnel junction materials using substrate heating in the pulse-biased inductively coupled plasma

Magnetic tunnel junction (MTJ)-related materials such as CoFeB, MgO, and W were etched in a pulse-biased inductively coupled plasma etch system using a CO/NH₃ gas combination, and the effects of substrate temperature (room temperature ∼200°C) in the pulse-biased condition on the etch characteristics of the MTJ-related material were investigated. The etch selectivity of MTJ materials over W was improved by substrate heating possibly due to the easy removal of the compounds from the etched CoFeB surface during the pulse-on time at the elevated substrate temperature. At high substrate temperature, decreased thickness of etch residue was observed not only on the bottom surface but also on the sidewall surface during the etching, which indirectly indicated the increased volatility of the etch compounds at higher substrate temperature. The etching of CoFeB features masked with W also showed a more anisotropic etch profile by heating the substrate up to 200°C possibly due to the increased the etch selectivity of CoFeB over W and the decreased redeposition of etch products on the sidewall of the CoFeB features.