A Study on SADP Process Refresh for Patterning Correction

Abstract

SADP/SAQP are important patterning techniques for all the FEOL/BEOL line levels at 7 nm technology node and beyond. Therefore, an accurate CD and profile control of mandrel patterning is the key of a successful SADP/SAQP integration and an incorrect mandrel CD or profile could cause a huge loss due to wafer scrap. In this paper, a novel methodology utilizing multiple etch steps is presented to remove the incorrect patterning stack and to refresh the SADP patterning from the beginning. As a result, the misprocessed wafer could continue the process without loss. Two approaches were discussed in this paper. The results were showing that using dry etch to clear the mandrel stack instead of wet etch then took out the hard-masks and stopping on the IMD is the best way for removing the incorrect patterning stack. This methodology has been tested for up to three passes of refresh to verify the repeatability of both physical and electric data. In addition, a 34 passes prolonged test on the same wafer was conducted over a year showing successful refreshes with consistent physical CD.