Controlling particle contamination during PECVD low-k film processing by optimizing inter- chamber pressure difference

Abstract While current research on particle contamination of wafers is predominantly focused on intrinsic defects formed during the thin-film growth, such as gas-phase reaction nucleation particles, this study addresses the particle contamination from the flow-field effects in the vacuum transmission module (VTM) during the low dielectric constant (low-k) film deposition in plasma-enhanced chemical vapor deposition (PECVD) equipment. We first compared the flow fields in the vacuum process module (VPM) and VTM of PECVD equipment under different transfer pressures (0.2, 0.3, 1, and 2 Torr) by using numerical simulations. Subsequently, we confirmed cross-contamination from VPM to VTM by a cumulative experiment at a lower VTM pressure of 0.2 Torr. The deposits on the surface of both chambers were detected in the cumulative experiment, imaged by scanning electron microscope (SEM), and analysed by energy dispersive X-ray spectrometry (EDX). Both laboratory-controlled tests and fab production-scale validation revealed that the particle counts on the wafers processed with a low-k recipe in the PECVD equipment decrease as VTM transfer pressure increases. This finding eliminated the production particle issue, raising tool uptime by at least 1.5% and boosting wafer yield.