PSM and thin OMOG reticles aerial imaging metrology comparison study
2012
For sub 20nm features, IC (integrated circuits) designs include an increasing number of features approaching the
resolution limits of the scanner compared to the previous generation of IC designs. This trend includes stringent design
rules and complex, ever smaller optical proximity correction (OPC) structures. In this regime, a new type of mask,
known as opaque MoSi on glass (OMOG), has been introduced to overcome the shortcomings of the well-established
phase shift masks (PSM). This paper reviews the fundamental aerial imaging differences between identically designed
PSM and thin OMOG masks. The masks were designed for scanner qualification tests and therefore contain large
selections of 1D and 2D features, including various biases and OPCs. Aerial critical dimension uniformity (CDU)
performance for various features on both masks are reported. Furthermore, special efforts have been made to emphasize
the advantages of aerial imaging metrology versus wafer metrology in terms of shortening scanner qualification cycle
time.
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