Effect of ammonia plasma pretreatment on silicon-nitride barriers for Cu metallization systems

The barrier properties of plasma-enhanced chemical vapor deposited (PECVD) SiN thin films capped on post chemical mechanical polishing Cu film were in vestigated by various analytical techniques, such as secondary-ion mass spe ctrometry (SIMS), transmission electron microscopy, and atomic force micros copy, focusing on the effect of NH3 plasma pretreatment. SiN films were dep osited at 400 degreesC in a sequential multistage deposition system. Much l ess Cu contamination was detected at the surface of SiN deposited with plas ma pretreatment, compared to that without plasma pretreatment. Also, the am ount of Si diffused into Cu during deposition was found to be significantly reduced after NH3 plasma pretreatment. Similar Cu diffusion behavior was o bserved in SiN films deposited with or without plasma pretreatment, after b eing annealed at 450 degreesC. However, SIMS analysis revealed that Cu diff used faster in SiN deposited with plasma pretreatment than in SiN deposited without plasma pretreatment, after being annealed at 550 degreesC. (C) 200 1 American Vacuum Society.