Proceedings Article | 2 April 2010
KEYWORDS: Overlay metrology, Critical dimension metrology, Double patterning technology, Semiconducting wafers, Metrology, Lithography, Etching, Optical proximity correction, Scanning electron microscopy, Pattern recognition
Requirements for increasingly integrated metrology solutions continue to drive applications that incorporate process
characterization tools, as well as the ability to improve metrology production capability and cycle time, with a single
application. All of the most critical device layers today, and even non-critical layers, now require optical proximity
correction (OPC), which must be rigorously modeled and calibrated as part of process development and extensively
verified once new product reticles are released using critical dimension-scanning electron microscopy (CD-SEM) tools.
Automatic setup of complex recipes is one of the major trends in CD-SEM applications, which is adding much value to
CD-SEM metrology. In addition, as integrated circuit dimensions and pitches continue to shrink, double patterning (DP)
has become more common. Thus automatic recipe setup has needed to incorporate capabilities to deal simultaneously
with two layers. This has the benefit of allowing the user to measure the two different CD populations and the image
shift in the lithography (i.e., the overlay). Thus automatic recipe creation can be used to characterize the DP pattern for
both CD and overlay.
DesignGauge, the automatic recipe utility for Hitachi CG series CD-SEMs, is not only capable of offline recipe creation,
but also can also directly transfer design-based recipes into standard CD-SEM recipes for use with DP processes. These
recipes can be used for OPC model-building and verification as with previous DesignGauge applications. The software
also provides design template-based recipe setup for production layer recipes, which improves production tool utilization,
as production recipes can thus be written offline for new products, improving first silicon cycle time, engineering time to
generate recipes, and CD-SEM utilization. Another benefit of the application is that recipes are more robust than with
conventional direct image-based pattern recognition. This paper explores the feasibility of matching a two-layer GDS
pattern to features in an image, allowing for the more complex measurements involved in DP characterization.
This work will evaluate DesignGauge with double litho double etch (DLDE DP), including rigorous tests of navigation,
pattern recognition success rates, SEM image placement, throughput of the recipe creation, recipe execution, and verification of proper measurements of the dual CD populations and overlay.
