Effects of variously configured magnets on the characteristics of inductively coupled plasmas

Abstract

In this study, the effects of axial electromagnet, variously configured multidipole permanent magnets and their combinations, on the characteristics of a square shaped (210 mm×210 mm) inductively coupled plasma source were investigated using a single electrostatic probe for Ar plasmas. The use of multidipole magnets mainly changed the uniformity of the plasma without changing the ion density of the plasma greatly. An optimized shape of the permanent magnets increased the uniformity of the plasma, and the uniformity of the ion density less than 6.0% could be obtained when measured from the center of the chamber to 10 mm before the chamber wall at 600 W of inductive power and 2 mTorr of operational pressure. The use of axial electromagnet mainly increased the ion density with the decrease of the uniformity, and ion density up to 7.5×1011 cm−3 could be obtained with 25 G at 600 W of inductive power and 5 mTorr of operational pressure. The addition of the optimized multidipole magnet to the axial electromagnet also improved the uniformity, and it showed the lowest electron temperature (3 eV) and plasma potential (34VP). The etch uniformities of polysilicon etched using Cl2 gas showed the similar trends as the uniformities of the ion density measured for variously configured magnets.