Solid phase replacement process for multilevel high-aspect ratio Al fill applications

We present a high aspect ratio Al fill process using solid phase replacement (SPR). In contrast to earlier work in which polysilicon (poly-Si) was used, B-doped amorphous Si (a-Si:B) is used in this work to ensure application in multilevel Al interconnect schemes. a-Si:B is also effective for rapid replacement. We also report, for the fist time, via chain resistance increase and open failure caused by stress-induced voiding during replacement and show that Ti compound formation at the top of the Al film during the replacement anneal is responsible for this void formation. We further provide evidence that SPR can be used as the fill process for multilevel Al dual damascene interconnects if the anneal time and the Si/Ti volume are optimized and a suitable barrier layer is used