Development of high-density plasma reactor for high-performance processing and future prospects

We have proposed three novel etching techniques, such as (1) pulse-time-modulated plasma; (2) ultrahigh-frequency (UHF) plasma source with a spokewise antenna; and (3) a new radical-injection method with non-perfluorocompound gas chemistries. The pulse-time-modulated plasma makes possible highly selective, high-rate, and charge-build-up-damage-free etching of gate electrodes and Al electrodes. These superior etching characteristics are results of being able to produce, within a few tens of microseconds, a large quantity of negative ions at a low-electron-temperature during the pulsed plasma after-glow. The UHF plasma source with the spokewise antenna can produce uniform (within ±5%), plasma with a density of more than 1011 cm−3 and low temperature of 1.5–2.0 eV in a large-scale plasma source more than 30 cm in diameter. No magnetic field is needed to maintain the high-density plasma. Consequently, the plasma source is fairly simple and lightweight. A new radical-injection method for high-performance SiO2 patterning using non-perfluorocarbon gases (CF3I and C2F4) in high-density plasma have been proposed recently. This method enables polymerization and etching to be controlled independently through the selective generation of CF2 and CF3 radicals. As a result, it can provide both a high etching rate and a high etching selectivity during the formation of high aspect contact-hole (more than 10). The gas chemistries can also suppress charging damage during SiO2 etching by maintaining a low-electron-temperature in the plasma.