Capability assessment and comparison of the Nikon 2i Nikon 3i and IMS-2000 registration measurement devices

摘要

Abstract: A critical product property in the photomask industry is registration. Registration is a measure of how close features placed on the mask actually are relative to where it is desired for them to be located. Of course photomask customers, the integrated circuit (IC) manufacturers, want all features placed exactly where indicated by the circuit design. Consequently, the recent history in the photomask industry has been for specifications on registration to increasingly tighten. Today $POM@.25 $mu@m specifications are commonplace, and many customers are pushing for specifications of half this tolerance as they move into the production of chips of steadily increasing sophistication (eg. 4 and 16 meg devices). As registration specifications increasingly narrow, a serious question facing the photomask industry and their customers is not only whether the presently available lithography tools can conform to the tighter specs, but whether such specs are pushing or beyond present ability to measure registration. The present industry standard for assessing registration is the Ninon 2i; however, there ate two systems which are presently commercially available which claim to be superior to the 2i. One is Ninon's own successor system the Ninon 3i, and the other is the IMS-2000 made by Leitz. This paper discusses the findings of a study conducted by Du Pont Photomask to assess the relative accuracy and repeatability of each of these systems, and evaluates this information against the present trends in industry specifications.!