A proof of concept of remote contour-based SEM metrology integration in HVM environment

Abstract

The idea to better use the thousands of CD-SEM (critical dimension scanning electron microscope) images that are acquired daily in a fab has been a driver since few years now [1,2]. In previous publications, we advocated for a remote image computing toolbox integration into the wafer fab. Such system would be based on an image computing environment (outside the metrology tools and outside the wafer fab) connected to databases and data-analytic tools so that CD-SEM image information could be enriched by the usage of more complex image treatment tool such as a CNN (convolutional neural network) for qualitative information or image analysis and contour extraction for quantitative and qualitative information. Contour based metrology offers a wide range of “new” measurements capability solutions [2,3,4] which are of interest for the process support (R&D or Production) but also for metrology equipment owners. Expressing the added value of a remote metrology toolbox on top of the existing one from metrology tool themselves is not necessarily an easy task. It is often related to use cases that will really show good return on investment. Many examples of what can be achieved with contour metrology have been published, even with thousands of images computed, but it remains far from being seen as production worthy if not experienced in real time. Based on encouraging preliminary results on valuable data extracted using remote metrology software, a proof-of-concept integration on manufacturing data was put in place in order to gather direct feedback to the fab. This paper will describe how an image computing software has been integrated to the data infrastructure of our wafer fab so that every CD-SEM image is being processed outside the CD-SEM equipment to monitor the image quality on one side (so the CD-SEM tool stability) and perform measurements on the other side. Results extracted from inline contour-based image computing over several months’ worth of data will be presented showing some of the benefits of integrating edge computing solutions in wafer fab production flow.