Patent ID: 7972966

Claim:
An etch method comprising: providing a structure including a tungsten (W) portion and a titanium nitride (TiN) portion; applying a first etch gas of sulfur hexafluoride (SF 6 ) and oxygen (O 2 ), in which the ratio of sulfur hexafluoride (SF 6 ) to oxygen (O 2 ) ranges from 1:3.5 to 1:4.5; and applying a second etch gas of nitrogen trifluoride (NF 3 ), helium (He) and chlorine (Cl 2 ), in which the ratio of nitrogen trifluoride (NF 3 ) to chlorine (Cl 2 ) ranges from 1:5 to 2:5 and the ratio of helium (He) to nitrogen trifluoride (NF 3 ) and chlorine (Cl 2 ) ranges from 1:3 to 1:1.