Optimized inspection of advanced reticles on the TeraScan reticle inspection tool

摘要

Advanced wafer fabs are currently fabricating devices with 90nm and 65nm design rules using 193nm lithography. To meet the challenges at these sub-wavelength technology nodes, mask designers are using a variety of resolution enhancement techniques (RETs) in lithography which require new methods of processing, inspecting and qualifying photomasks. As a result, reticle inspection tools need to be capable of detecting smaller defects on ever tighter critical dimensions and background patterns that are considerably more complicated than before. To meet the challenges of current and future technology nodes, a variety of new inspection modes have been developed on the KLA-Tencor Deep UV TeraScan reticle inspection tool. These new inspection modes include Reflected light (Die-to-Die and Die-to-Database) modes, a Transmitted light Tritone (Die-to-Database) mode for inspecting Embedded Attenuated Phase Shift Masks (EAPSMs) with chrome in the inspection area, as well as a STARlight2 (SL2) mode for contamination detection. The SL2 inspection mode is the natural successor to the STARlight contamination detection algorithm on the previous generation of KLA-Tencor reticle inspection tools. Each of the inspection modes comes with its own set of inspectability and sensitivity capabilities and therefore the selection and/or optimization of a mode can depend upon a number of factors. In this paper we will present the inspection modes that are available on the TeraScan platform and discuss the appropriate use cases for each of the modes, based on reticle type and the intended objectives of the inspection.