Real time feedback control of plasma density using a floating probe in semiconductor processing

Real time feedback control of plasma density was developed and carried out in an inductively coupled plasma. This control method uses a floating probe as a sensor because it can measure plasma density in real time without modification of the plasma reactors and it does not perturb the plasma. The results show that through feedback control, plasma density can be maintained constant within a steady state error of less than 0.3% even if there is a sudden pressure disturbance. This feedback control method is expected to improve the repeatability and reliability of plasma reactors.