A Study of Post Process Wafer-Less Chamber Clean Recipe in Lele Process

Study of post process chamber plasm clean in ICP (inductive coupling plasma) chamber has attracted more interest in past decades for by-product peeling defect and first-wafer issue in sub-28nm process. Insufficient post process clean will induce memory effect and impact 1st processed wafer critical dimension (CD). Moreover, rudimental by-product will accumulate on chamber wall and induce peeling defect during process. However, over-clean is another drawback in post clean. Coating layer on ICP chamber, mostly Y2O3, will be damaged by plasma and induce coating peeling in high RF hours. In our paper, in order to balance cleaning efficiency and chamber coating damage, a series of experiments are taken, and optical emission spectrum analysis is applied to evaluate wafer-less auto clean recipe (WAC). As a result, an effective WAC recipe is proposed and inline CD trend and defect performance are considered. Besides, cleaning mechanism of CIP WAC recipe is also investigated in this paper.