Mr. Farid Askary Profile

Farid Askary

Consultant at MetroBoost

SPIE Involvement:

Author | Instructor

Proceedings Article | 22 August 2001 Paper

Redefining critical in critical dimension metrology

Farid Askary, Neal Sullivan

Proceedings Volume 4344, (2001) https://doi.org/10.1117/12.436721

KEYWORDS: Critical dimension metrology, Metrology, Signal detection, Calibration, Process control, Semiconductor manufacturing, Scanning electron microscopy, Photomasks, Finite element methods, Interfaces

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Critical dimension (CD) metrology as practiced in semiconductor industry displays characteristics not observed in other metrology disciplines. This paper will present some of the unusual aspects of CD metrology and attempt to elucidate the causes for the observed behavior. Through an examination of the characteristics of measurement accuracy, it is possible to observe these situations where CD metrology departs from the ideal. The typical process for achieving accuracy involves the use of certified standards in a well-defined calibration procedure. However, calibrating CD instruments with linewidth standards will not necessarily guarantee sufficient accuracy of subsequent measurements of production samples. This well-known result follows from lack of physical models to relate the detected signal to sample shape in combination with the many-to-one nature of the mathematical mapping that describes the process of obtaining CD from feature shape. Despite this limitation, monitoring tools such as CD-SEM systems have demonstrated to be useful for process control and are extensively used in semiconductor manufacturing. The requisites for a well-behaved measurement process will be described in detail. The unusual characteristics of CD metrology will be identified, as will the underlying reasons for the behavior. These results will be examined in the light of common process control techniques to explain how CD-SEM measurements still add value despite the flaws. In conclusion the role and value of certified standards in feature shape determination will be placed in the context of CD metrology. Reference Measurement Systems in conjunction with calibration standards are recommended to characterize process variations and determine feature shapes across a variety of samples. In order to ensure that the high throughput monitoring metrology tools flag process excursions for not meeting specifications, feature shapes must be quantified with additional metrics besides a single number CD.

Proceedings Article | 2 June 2000 Paper

Importance of measurement accuracy in statistical process control

Farid Askary, Neal Sullivan

Proceedings Volume 3998, (2000) https://doi.org/10.1117/12.386462

KEYWORDS: Scanning electron microscopy, Process control, Critical dimension metrology, Manufacturing, Calibration, Metrology, Photomasks, Systems modeling, Scanning probe microscopes, Semiconducting wafers

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Proceedings Article | 21 May 1996 Paper

Benchmarking multimode CD-SEM metrology to 180 nm

Kevin Monahan, Farid Askary, Richard Elliott, Randy Forcier, Rich Quattrini, Brian Sheumaker, Jason Yee, Herschel Marchman, Robert Bennett, Steven Carlson, Harry Sewell, Diane McCafferty, Javed Sumra, Jane Yan

Proceedings Volume 2725, (1996) https://doi.org/10.1117/12.240105

KEYWORDS: Scanning electron microscopy, Metrology, Semiconducting wafers, Lithography, Reticles, Deep ultraviolet, Atomic force microscopy, Critical dimension metrology, Silicon, Calibration

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Course Instructor

SC108: Fundamentals of Critical Dimension Metrology

Critical Dimension (CD) Metrology involves measurement of planar structures on semiconductor, mask and thin film head substrates. This full day course provides an overview of CD metrology emphasizing Scanning Electron Microscope (SEM) applications for process control and characterization. Metrology specifications and methods for estimating measurement performance for each application are discussed. An overview of image formation in SEM is presented with a discussion of system consequences. Other methods of CD measurement and future trends in CD Metrology are explored.

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