A process to reduce the occurrence of metal extrusions in al interconnects

Extrusions are a well-known phenomenon in Al interconnect stacks. We review experimental approaches to mitigate extrusions including depositing a low temperature oxide (LTO) on the film stack, modulation of the metal anneal conditions, and moving the anneal step from post-metal etch to post-metal deposition. After evaluation of the three potential solutions we determined that the movement of the anneal step from post-metal etch to post-metal deposition is the most manufacturable process.