In situ chamber cleaning using halogenated-gas plasmas evaluated by plasma-parameter extraction

We have demonstrated that high-efficiency in situ chamber cleaning with high gas flow rate is possible for SiO2 reactive-ion-etching chambers by use of NF3 plasma. The plasma of NF3 gas, which has a low bond energy, can generate a high density of ions and radicals with 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, could be extracted from a simple rf waveform analysis at the excitation electrode. The accuracy of this technique has been confirmed with a newly developed rf-plasma direct probing method. Furthermore, the waveform of the rf-excited plasma potential has been directly measured by the rf-plasma probing method, which has clarified the relationship between the plasma potential and the rf electrode voltage.