The effect of SiCl4 additive gas on the Cl-based Al plasma etch procedure

The influences of both SiCl4 additive gas and the magnitude of bias voltage on the anisotropic etch profile of aluminum pattern and the deterioration of photoresist (PR) mask layer have been studied by varying etching conditions. Using Cl2 gas as a primary etchant, the ratio of SiCl4 flow rate to Cl2 and the ion energy bombarded onto the surface were changed systematically. When a small amount of additive gas was added, undercut profile in Al layer was not observed even in the lowest bias voltage measured in this experiment. With the optimized etching condition, the PR deterioration usually reported during metal etching was not observed at all, which allows the complete PR strip without any additional process.