METHOD FOR MEASURING NEGATIVE IONS IN PLASMA, AND PLASMA TREATING METHOD AND APPARATUS

摘要

First, a probe (6) is brought into contact with a plasma of Ar gas to raise its potential over the earth potential. Then a saturation current Ies1 flowing through the probe (6) is measured. Next its potential is lowered below the earth potential to measure its saturation current Iis1. Similarly, currents Ies2 and Iis2 are determined by bringing the probe (6) into contact with a plasma of a mixture gas of Ar gas and a processing gas such as C4F8. The negative ion density in the plasma of the C4f8 gas is determined on the basis of the ratio between Iis1 and Iis2 and the ratio between Ies1 and Ies2.