Plasma power dissipation at wafer surfaces measured using pulsed photoluminescence spectroscopy

A long-standing problem in plasma processing has been imprecise control and characterization of dissipated power. In particular, the partitioning of energy between gas phase and surface is not easily determined. Yet, for plasma process control and transfer from one reactor to another, it is important to monitor and control energy flux to the wafer. Using pulsed laser photoluminescence spectroscopy, we measure wafer temperatures nonintrusively as a function of time when radio frequency discharges are gated on and off. By so doing, the energy flux to the wafer surface is determined as a function of pressure, power, and frequency. This energy flux is then compared to the total power dissipated, which is calculated from measured current and voltage waveforms. We find that the fractional power dissipated at the wafer surface varies inversely with pressure regardless of applied power and frequency