Model-free and model-based methods for dimensional metrology during the lifetime of a product

Abstract

For future technology nodes, highly accurate dimensional metrology will become more and more important. At this stage, measuring layer thickness in planar test structures or geometrical dimensions in simplified proxy structures may be not sufficient for accurate control of highly sophisticated process steps. Model-based dimensional metrology has the potential to provide critical parameters of interest for process control in high volume manufacturing, while during process and technology development the constrained flexibility of models and the required model-building efforts may be a serious limitation. On the other hand, model-free dimensional metrology may provide sufficient flexibility for process development, while in some cases it may not be production-worthy in high volume manufacturing. This article details advantages and disadvantages of the different methods during the lifetime of a product starting from early development to high-volume production.

Implementation of Electrochemical Methods for Metrology and Analysis of Nano Electronic Structures of Deep Trench DRAM

“…The bottom dimension is obtained by consequent resistor structuring of nitride, amorphous silicon and oxide hardmask opening steps. A direct measurement of this deep trench mask open bottom dimension allows both feed back control of the mask open etch process sequence and feed-forward control of the DT main etch [4]. There is a metrological challenge in analyzing the aspect ratio of the hard mask profile.…”

“…Yet there are three nondestructive analysis techniques such as firstly atom force microscopy (AFM), secondly a model based infrared reflectometry and third a visible light scatterometry used to characterize such structure depth profile, but with major limitations [4].…”

“…However scatterometry is also sensitive to many other details of structure and therefore requires extensive modeling, which is time consuming for use as inline metrology [4].…”