Novel process strategies for strip over tin

Reducing chemistry and process strategies were investigated for strip application with TiN exposed. Base on TiN film loss specification, different chemistries were explored systematically. O₂ rich reducing chemistry greatly reduced the film loss to ~10A with latest thin atomic layer deposition (ALD) TiN, while maintaining high ash rate. Pure reducing chemistry was capable of further reducing the loss down to 6-7 A with reducing N₂ mixture or down to 1-3 A level with a group of proprietary reducing mixtures. Increasing RF power compensated the low ash rate compared to pure H₂ process. One step further, the two processes can be combined to provide additional improvement on productivity. The overall TiN loss is caused by oxidation. Even with pure reducing process, XPS results showed that TiO₂ and TiNxOy are present as the top surface layers. Reducing N₂ mixture had more TiO₂ formed than the new group of mixtures.