Interpretation of neutral distribution through spatial profile of plasma emission

Abstract

Using a new optical probe technique, plasma emission and its spatial profile are monitored at various gas pressures in electron cyclotron resonance Ar plasma. The emission intensity and its spatial profile strongly depend on the neutral gas pressure. In a spatial plasma emission profile, a hollow profile appears at the chamber center in a specific pressure region. It is suggested that the neutral density depletion at the center is caused by the plasma collisional heating that takes place during ion-neutral charge exchange and ion-neutral elastic collisions.