POINT-OF-USE PURIFICATION IN DHF BATHS

Maximizing the purity of dilute hydrofluoric acid (DHF) baths is a pre requisite for maintaining and improving chip yield as linewidths conti nue to shrink. While ultrapure chemicals have reduced ion levels in fr esh DHF baths, exposure to metallics has persisted due to carryover fr om wafers being processed through the bath. A new technology allows co ntinuous, point-of-use purification of DHF solutions for the first tim e. This article describes the design and operation of the new purifica tion system and its components, and explains how the system reduces an d controls metallic ion levels in DHF recirculation baths.