Maintaining a consistent and accurate flow rate of process chemistries is critical to ensuring high yields for plasma-based processes. Small amounts of specialized gases are critical to these plasma-based processes.

For example, the boundary between etch and deposition in high-aspect ratio etches is sometimes very small so that any deviations from these small but critical flow rates can transform the plasma from one regime to the other. The ever-increasing plasma etch requirements continue to demand vertical holes, high selectivity, and adherence to extremely tight critical dimensions. This can only be accomplished by utilizing highly polymerizing gases to etch through high aspect ratio structures of various films. As little as a 1% change in these gas flows will alter the etching process and may create a premature etch-stop condition or produce sub-standard electrical devices due to non-optimal etch profiles. Since industry MFC (Mass Flow Controllers) are all subject to drifting from their set points without continuous and laborious manual calibrations, this precarious condition exists for all critical wafer processing.

Pivotal System's GasFlowMonitor solution provides in situ fault detection for these critical gas flows. The selected gas flows can be tracked and measured in situ for each and every wafer and then compared to fixed control limits. Pivotal's flow measurement is accurate to >99.5%. The customer is then notified when these gases are out of specification so that preventative measures (such as a gas flow calibration procedure or flow set point adjustment) can be taken to ensure the proper flow rates/gas mixtures.

Below are some sample experiments where a fully calibrated MFC was monitored in situ with GasFlowMonitor™ at 3 different flow set points for Nitrogen - 50sccm, 100sccm and 10sccm.

GasFlowMonitor™ Benefits

• Improved bin and line yield - Etching state of the art via and contact patterns or depositing films with highly targeted compositions require balanced process gas flows where minute deviations of process gas flows can lead to significant bin or line yield degradation
• Reduced tool down time and maintenance costs - Time intensive gas calibrations and troubleshooting can be avoided by tracking GasFlowMonitor™ data for each and every wafert