Plasma Density Enhancement of an Electron Cyclotron Resonance Plasma with Pulse-biased stage

Large-area high-density plasma source is often used to enhance process productivity of large area substrates. Microwave plasma is one of candidates for this purpose. Furthermore, some application requires high-energy ion bombardment to improve film properties. In this study, an electron cyclotron resonance (ECR) plasma, one of high-density microwave plasma sources, in combination with the high voltage pulse power source was investigated. In the experiment, an aluminum chamber was evacuated by a dry pump below 0.1 Pa. Microwave power was introduced to the chamber through a vacuum-sealed quartz plate and quartz guide plates. An array of magnets was placed on the back of each quartz guide plate. Time-dependent plasma density during the pulse-bias application to the ECR plasma was measured by a Langmuir probe. Measured time constant of the density decay during the pulse-off fairly agreed with a simple model considering plasma volume and surface. Time constant of density rise during the pulse-on showed monotonic increase with increasing the pulse voltage. From these values, steady-state plasma densities during pulse-on and -off were evaluated. Plasma density enhancement was also evaluated as a function of secondary electron power injected from the stage. Density enhancement showed strong power dependence and saturation at higher secondary electron powers.