Magnetically Enhanced Dual Frequency Reactive Ion Etcher for Dielectric Etching

摘要

A large area high density plasma source with a better radial uniformity was developed for SiO_2 etching applications. Experiments were performed for 200 mm diameter wafers using a parallel plate capacitively coupled plasma excited by 60 MHz rf current. Etching was carried out by applying 1.6 MHz rf power to the lower electrode where a wafer was placed. A point-cusp magnetic field was applied to the upper electrode. The point-cusp magnetic field is generated by arranging 115 permanent magnets on a 266 mm diameter upper electrode with alternate polarity and equal distance. This magnetic field causes no polarization of the plasma due to the ExB drift of electrons where E and B are the dc electric and magnetic field strengths, respectively. Application of point-cusp magnetic fields increases the plasma density by a factor of ～2 and decreases the radial nonuniformity by a factor of > 1.5. The etch rate observed for BPSG is 600 nm/min at 800 W 60 MHz rf power and 1800 W 1.6 MHz rf power. The estimated non-uniformity and the selectivity for photo-resist are +-4 % and 7.5, respectively.