Damage-free contact etching using balanced electron drift magnetron etcher

A new plasma source called balanced electron drift (BED) magnetron plasma has been developed for SiO₂ contact/via hole etching. E×B drift of electrons, which is notorious for degrading the uniformity of magnetron plasmas, has been completely balanced by applying appropriate 100 MHz rf power to the upper ring electrode. As a result, charge-up damage free and highly uniform etch rate of ±2.72% profiles were obtained on 200 mm wafer. Micro-loading effect free etching was also achieved by suppressing excess dissociation of C₄F₈. BED magnetron etcher has additional benefit of reducing dopant deactivation in the Si substrate because carbon-rich fluorocarbon film can protect Si surface from high-energy ion bombardment during over-etch period. Also, the addition of Xe has been confirmed to exhibit drastic suppression of the dopant deactivation even at p⁺Si surface, which results in low contact resistance without additional ion implantation after contact etch. BED magnetron etcher using Xe gas can reduce a few tens of process steps after contact etch.