Error Factor in Bottom CD Measurement for Contact Hole using CD-SEM

摘要

CD control of hole bottom becomes more difficult with pattern size shrinkage. Since local CD variation of hole patterns is large, CD measurement by CD-SEM is needed for measuring the local CD. Although a technique of observing the hole bottom by CD-SEM has been reported, accuracy of bottom CD measurement is seldom examined. We estimated the tool precision and CD bias required for highly accurate CD control. As a result, the bottom CD measurement repeatability was examined for 0.94nm. Tool precision has sufficient capability for hp45 node. Si transfer process was the technique used for estimating CD bias. CD bias obtained by Si transfer process was constant in the bottom CD range of 45 nm or more. The above result indicates bottom CD measurement using CD-SEM has sufficient capability for measuring bottom CD correctly for hp45 node.