Development of a High-Pressure Compatible Self Plasma-Optical Emission Spectrometer for Real-Time Plasma Process Monitoring

Real-time monitoring of semiconductor processes is a critical task to ensure product yield. Residual gas analysis (RGA) techniques, which collect gases from the exhaust line without modifying the process chamber, have been studied for applications. However, due to the nature of RGA, there is an inevitable delay between the actual process events and the gas measurement. This delay is particularly pronounced in high-pressure exhaust lines, where devices such as Quadruple Mass Spectroscopy (QMS) and Time of Flight-Mass Spectroscopy (TOF-MS) require orifices to operate, further increasing the latency.

In this study, we propose a method to minimize this delay by employing self-plasma optical emission spectroscopy (SP-OES), an optical diagnostic system that generates plasma internally. Unlike conventional configurations that collect light between electrodes, we developed a spherical design that allows direct optical access to the powered electrode, which is more suitable for signal detection under high-pressure conditions. To validate this approach, we performed COMSOL simulations for optical intensity. Furthermore, we experimentally measured the time delay between OES and various residual gas analysis instruments during an actual etching process. The results confirm that SPOES significantly reduces signal delay compared to traditional RGA methods.