Electron Beam Excitation Method to Study Gas Phase During Etch Processes

In process optical emission spectroscopy (OES) measurements, excitation mechanisms as dictated by the process plasma can be complex to analyze optical signals quantitatively. Applications of a new electron beam excitation method demonstrate distinct merits for plasma process diagnostics and process control. The electron energy control attribute of the method provides the means to optimize and monitor specific species optical emission in process chemistries to achieve process control such as endpoint. The authors present gas phase results from photoresist ash and SiO2 etch using O-2 and CF4/Ar discharges, respectively. The effluent density variations as measured with the e-beam method during process stages demonstrate process endpoint detection. Simultaneous measurements with FTIR spectroscopy and direct plasma OES is also presented for comparison.