Application of integrated scatterometry (iODP) to detect and quantify resist profile changes due to resist batch changes in a production environment

Abstract

Scatterometry is currently being used in lithography production as an inline metrology tool to monitor wafer processing and detect excursions. One well-documented excursion is the process variation caused by differences in resist batches. 1 This paper describes the use of Tokyo Electron Limited's integrated Optical Digital Profilometry (iODP TM ) scatterometry system to detect process variations caused by resist batch changes. This system was able to detect a significant shift in resist sidewall angle (SWA) on an incoming resist batch that was undetected by the primary metrology in use at the time, a scanning electron microscope (CD-SEM). This SWA shift correlated to an undesirable shift in post-etch CD created by the new resist batch. Experiments performed in conjunction with the resist supplier confirmed that the normal batch-to-batch variation of a key resist component was enough to produce a change in SWA after processing. This validation led to quality improvement controls by the resist vendor and Qimonda and resulted in the use of iODP as the primary metrology for this process.