Plasma enhanced in situ chamber cleaning evaluated by extracted-plasma-parameter analysis

We have demonstrated that high-efficiency in situ chamber cleaning with short gas residence time is possible for SiO₂ etching chambers by use of NF₃ plasma, and that the endpoint determination of the cleaning is possible by monitoring the optical emission intensities of CO or H. Nitrogen trifluoride (NF₃), which has a low N-F bond energy, can generate a plasma with a high density of ions and radicals featuring low kinetic energy. The cleaning efficiency of several halogenated-gas plasmas has been evaluated based on extracted-plasma-parameter analysis. In this analysis important plasma parameters, such as ion energy and ion flux density, can be extracted through a simple rf waveform measurement at the plasma excitation electrode. The accuracy of this technique has been confirmed with a newly developed rf plasma direct probing method and by ion current measurements