Controllable optical emission spectroscopy diagnostic system for analysis of process chemistries

Optical emission spectroscopy (OES) diagnostics have been employed for many years in plasma etch end point detection schemes. Unfortunately some newer process systems have much lower optical emission or limited optical access. To overcome such limitations, an OES diagnostic system making use of variable e-beam has been developed. That system is described and initial experimental results are presented. A strong correlation is observed between the optical emission intensity and e-beam current, a measurable electrical parameter. This correlation offers means to normalize optical signal and to be used as a feedback input to the electronics that control the plasma source. In addition there is a measurable response from the different lines due to energy of the electrons, indicating a new degree of freedom in the diagnostic that can be tapped for more precise analysis of end point.