Characterization and in situ monitoring of a novel compact electron cyclotron resonance plasma source

Abstract

For plasma-assisted processing of future semiconductor devices, a new compact electron cyclotron resonance (ECR) plasma source has been specifically designed. The source is novel in that the magnets required for the production of ECR plasma are movable even in vacuum, and in situ monitoring of the discharge zone is also possible. Typical plasma characteristics were evaluated for nitrogen gas using Langmuir probe diagnostics and ion energy analysis. The measured plasma parameters include electron densities in excess of 1010 cm−3 and low ion energies (<30 eV) with narrow distributions, which can be easily controlled by varying the discharge pressure and downstream position. Moreover, changing the aperture size of the discharge cavity enables one to control the relative ratio of the ionic and atomic species in the plasma. In determining plasma stability, changes in plasma parameters after plasma start-up were investigated. The results show a correlation between changes in the plasma potential and the total plasma optical emission. In situ monitoring of the total plasma emission is suggested as a simple means of providing valuable information in real time about physical plasma parameter changes during processing.