Effect of idle time on the property of ultra low-k dielectric film

The effect of idle time before process started on the ultra low-k (ULK) film's property (thickness, refractive index, stress) was studied in this paper. The results show that as idle time increase from 0s to 600s, the ULK film's thickness is decreased about 100∼150A while the refractive index has no evident change. As idle time increase from 0s to 420s, the ULK film's stress is decreased about 4∼5Mpa. The thickness decrease mainly comes from the main-deposition stage, slightly come from the initial stage, while the transition stage nearly has no influence on it. The root cause of thickness changes is related to the competitive relationship of film deposition between wafer and chamber body when chamber idle. Base on the experiment results, the automatic process control (APC) system can be introduced to compensate the film thickness loss caused by idle time automatically, thus realize the stability of ULK process.