TaN metal gate damage during high-k (Al2O3) high-temperature etch

TANOS-NAND flash process integration generates various technological difficulties; one of the most relevant is the patterning of TaN metal gates together with Al2O3 high-k dielectrics. BCl3/N-2 based high-temperature plasma etching preferably used for structuring high-k materials reveals severe etch damage effects at the TaN sidewalls. Plasma treatments with different etch gases (BCl3/N-2; O-2/Ar; Cl-2/Ar) were used for detailed analyses of chemical effects on the TaN layer. The damage induced by BCl3/N-2 based plasma was investigated and characterized using blanket wafers. Approaches to overcome this obstacle are proposed.