Short loop monitoring of metal stepcoverage by simple electrical measurements

A metal stepcoverage monitoring method using simple electrical measurements has been developed to overcome drawbacks of the standard cross sectioning method. Application on Bicmos and bipolar processes show that (a) stepcoverage related design rules can be easily verified, (b) stepcoverage depends strongly on metal sputter target lifetime making several runs with dummy wafers necessary after metal target change to guarantee good stepcoverage and (c) stepcoverage can vary significantly over the wafer surface demonstrating the importance of metal stepcoverage wafermap data. The effect of metal stepcoverage on electromigration resistance has been found to be very limited. The open failures often did not occur on the steps. The novel method is also well suited for metal stepcoverage control on production wafers and screening of weak parts and for short loop monitoring of metal deposition equipment and dielectric planarization processes.