This paper examines the extendibility of the scatterometry techniques to characterize structures pushing the limits of
current lithographic printing technologies. In particular, we investigate the limits of normal-incidence optical CD (NIOCD)
measurements using the smallest features afforded by the most recent generation of hyper-NA immersion
scanners. Special analysis techniques have also been developed and applied to cases relevant to double exposure and
double patterning lithography. Models were used successfully to decouple CD and overlay values associated with
patterning the first and second set of features on the wafer, using a single scatterometry measurement. These advances
pave the way to the development of full solutions for the general case of double patterning structures with two different
populations of lines or structures.
In addition, the current study focused on seeking a better understanding of the use of scatterometry 3D features
characterization, particularly as it relates to OPC model building and verification. The demonstration of tip-to-tip
measurements on 3D structures is very encouraging as it introduces the advantages of scatterometry, such as reduced
influence of line-edge roughness (LER) and better precision, to the practice of advanced OPC model building.
Applications that require overlay measurement between layers separated by absorbing interlayer films (such as α-
carbon) pose significant challenges for sub-50nm processes. In this paper scatterometry methods are investigated as an
alternative to meet these stringent overlay metrology requirements. In this article, a spectroscopic Diffraction Based
Overlay (DBO) measurement technique is used where registration errors are extracted from specially designed
diffraction targets. DBO measurements are performed on detailed set of wafers with varying α-carbon (ACL)
thicknesses. The correlation in overlay values between wafers with varying ACL thicknesses will be discussed. The total
measurement uncertainty (TMU) requirements for these layers are discussed and the DBO TMU results from sub-50nm
samples are reviewed.
Demanding sub-45 nm node lithographic methodologies such as double patterning (DPT) pose significant challenges for
overlay metrology. In this paper, we investigate scatterometry methods as an alternative approach to meet these stringent
new metrology requirements. We used a spectroscopic diffraction-based overlay (DBO) measurement technique in
which registration errors are extracted from specially designed diffraction targets for double patterning. The results of
overlay measurements are compared to traditional bar-in-bar targets. A comparison between DBO measurements and
CD-SEM measurements is done to show the correlation between the two approaches. We discuss the total measurement
uncertainty (TMU) requirements for sub-45 nm nodes and compare TMU from the different overlay approaches.
This paper discusses the use of scatterometry for scanner focus control in hyper-NA lithography. A variety of techniques
based on phase shift technology have been traditionally used to monitor scanner focus. Recently scatterometry has
offered significant promise as an alternate technique to monitor both focus and dose. In this study, we make careful
comparisons of a Scatterometry-based Focus-Dose Monitoring (SFDM) technique to Phase-grating Focus Monitoring
(PGFM). We discuss the operating principles of these techniques and compare the sensitivity of SFDM to PGFM. In
addition, the variation observed in characterizing intra-field and across-wafer behavior of a hyper-NA immersion
scanner is described when using these different techniques.
Scatterometry techniques are used to characterize the CD uniformity, focus and dose control, as well as the image
contrast of a hyper-NA immersion lithography scanner. Results indicate very good scanner control and stability of these
parameters, as well as good precision and sensitivity of the metrology techniques.