INTERPRETATION OF NEUTRAL DISTRIBUTION THROUGH SPATIAL PROFILE OF PLASMA EMISSION

Using a new optical probe technique, plasma emission and its spatial p rofile are monitored at various gas pressures in electron cyclotron re sonance Ar plasma. The emission intensity and its spatial profile stro ngly 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 pla ce during ion-neutral charge exchange and ion-neutral elastic collisio ns.