NRD Static Control LLC

Design of a Critical Application Air Ionizer for Semiconductor Manufacturing

As feature sizes on semiconductor devices shrink, the CDM damage threshold drops. For feature sizes below 10 nm, the CDM damage threshold becomes as low as disc drive magnetic recording damage threshold. The goal of this development is to achieve fast decay times at distances <1 meter with greatly reduced swing voltage using α particles instead of corona as an ion source. Also, new cleanliness requirements are more stringent for both front-end and back-end manufacturing. Unlike α, corona ionizers chemically interact with the air and with their own emitters. Alpha ionizers operate at ISO Class 1. Pulsed DC ionization technology reduces recombination and thus allows the ions to travel much further than steady state ionization before recombining, thus neutralizing a larger area. In most instances, long distance results in pulsed ionization with a maximum voltage of such ionizers (typically <150 V) beyond emerging semiconductor industry demands. One of the goals of this study was to find a way to reduce this swing voltage.

This paper presents an advance over the hybrid pulsed alpha design [3] to serve intermediate ionizer to target distances (30-90 cm) with fast discharge (<10 s [2]) and low swings (max offset <±10 V).