Development of flat cutoff probe for real-time electron density measurement

As the semiconductor process, real-time in-situ plasma diagnostics have received attractive attention because they are expected to perform important functions such as increasing the process yield and abnormality detection. In this study, we developed a bar type flat cutoff probe (BCP) [1-3] embedded in the surface of the chamber wall and electrode to measure electron density during plasma processing. The BCP measures electron density near the plasma-sheath boundary, which is very closely adjacent to the chamber wall or wafer. Also, BCP can measure the electron density in real-time even though various types of wafers are placed on the BCP. In addition, we developed a circuit model of the BCP in which plasma and sheath are considered as coplanar capacitances. The result of the circuit model was verified through both the EM simulation and the experiment.