Dr. Keith P. Standiford Profile

Dr. Keith P. Standiford

Director of Engineering at GLOBALFOUNDRIES Inc

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Publications (12)

Proceedings Article | 8 October 2014 Paper

Mask model calibration for MPC applications utilizing shot dose assignment

Ingo Bork, Peter Buck, Sankaranarayanan Paninjath, Kushlendra Mishra, Christian Bürgel, Keith Standiford, Gek Soon Chua

Proceedings Volume 9235, 92350A (2014) https://doi.org/10.1117/12.2069617

KEYWORDS: Calibration, Critical dimension metrology, Scanning electron microscopy, Cadmium, Etching, Error analysis, Visualization, Photomasks, Vestigial sideband modulation, Statistical modeling

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Shrinking feature sizes and the need for tighter CD (Critical Dimension) control require the introduction of new technologies in mask making processes. One of those methods is the dose assignment of individual shots on VSB (Variable Shaped Beam) mask writers to compensate CD non-linearity effects and improve dose edge slope. Using increased dose levels only for most critical features, generally only for the smallest CDs on a mask, the change in mask write time is minimal while the increase in image quality can be significant. However, this technology requires accurate modeling of the mask effects, especially the CD/dose dependencies. This paper describes a mask model calibration flow for Mask Process Correction (MPC) applications with shot dose assignment. The first step in the calibration flow is the selection of appropriate test structures. For this work, a combination of linespace patterns as well as a series of contact patterns are used for calibration. Features sizes vary from 34 nm up to several micrometers in order to capture a wide range of CDs and pattern densities. After mask measurements are completed the results are carefully analyzed and measurements very close to the process window limitation and outliers are removed from the data set. One key finding in this study is that by including patterns exposed at various dose levels the simulated contours of the calibrated model very well match the SEM contours even if the calibration was based entirely on gauge based CD values. In the calibration example shown in this paper, only 1D line and space measurements as well as 1D contact measurements are used for calibration. However, those measurements include patterns exposed at dose levels between 75% and 150% of the nominal dose. The best model achieved in this study uses 2 e-beam kernels and 4 kernels for the simulation of development and etch effects. The model error RMS on a large range of CD down to 34 nm line CD is 0.71 nm. The calibrated model is then used to generate 2D contours for line ends, space ends and contacts and those contours are compared to SEM images. For all patterns, including those very close to the resolution limit, very good contour overlay is achieved. It appears that by including the various dose levels in the calibration a very good separation of the e-beam model components from the etch components is possible and that this also results in very accurate 2D model quality. In conclusion, very accurate mask model calibration is achieved for mask processes using shot dose assignment. Standard test patterns can be used for calibration if they include the dose variations intended for correction.

Proceedings Article | 8 October 2014 Paper

Model-based virtual VSB mask writer verification for efficient mask error checking and optimization prior to MDP

Robert Pack, Keith Standiford, Todd Lukanc, Guo Xiang Ning, Piyush Verma, Fadi Batarseh, Gek Soon Chua, Akira Fujimura, Linyong Pang

Proceedings Volume 9235, 923509 (2014) https://doi.org/10.1117/12.2069613

KEYWORDS: Photomasks, Optical proximity correction, Lithography, Vestigial sideband modulation, Semiconducting wafers, Data modeling, Model-based design, Error analysis, Manufacturing, Critical dimension metrology

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Proceedings Article | 18 March 2014 Paper

EUV OPC modeling and correction requirements

Tamer Coskun, Tom Wallow, Gek Soon Chua, Keith Standiford, Craig Higgins, Yi Zou

Proceedings Volume 9048, 90480W (2014) https://doi.org/10.1117/12.2046341

KEYWORDS: Photomasks, 3D modeling, Optical proximity correction, Data modeling, Extreme ultraviolet, Calibration, Semiconducting wafers, Critical dimension metrology, Extreme ultraviolet lithography, Data processing

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Proceedings Article | 9 September 2013 Paper

A new mask linearity specification for EUV masks based on time dependent dielectric breakdown requirements

Keith Standiford, Christian Bürgel

Proceedings Volume 8880, 88801M (2013) https://doi.org/10.1117/12.2023109

KEYWORDS: Photomasks, Metals, Reliability, Semiconducting wafers, Extreme ultraviolet, Line edge roughness, Dielectric breakdown, Backscatter, Lithography, Back end of line

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Proceedings Article | 9 September 2013 Paper

Entering mask process correction era for EUV mask manufacturing

Christian Bürgel, Keith Standiford, Gek Soon Chua

Proceedings Volume 8880, 888008 (2013) https://doi.org/10.1117/12.2023093

KEYWORDS: Data modeling, Photomasks, Etching, Error analysis, Critical dimension metrology, Inspection, Calibration, Extreme ultraviolet, Statistical modeling, Electronic design automation

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Proceedings Article | 1 April 2013 Paper

Evaluation of methods to improve EUV OPC model accuracy

Tamer Coskun, Chris Clifford, Germain Fenger, Gek Soon Chua, Keith Standiford, Ralph Schlief, Craig Higgins, Yi Zou

Proceedings Volume 8679, 86790V (2013) https://doi.org/10.1117/12.2009281

KEYWORDS: Optical proximity correction, Photomasks, Extreme ultraviolet, Calibration, Extreme ultraviolet lithography, Deep ultraviolet, Lithography, Metrology, Data modeling, Semiconducting wafers

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Proceedings Article | 8 November 2012 Paper

Choosing the data flow paradigm for EUV mask process corrections

Christian Bürgel, Keith Standiford, Gek Chua

Proceedings Volume 8522, 85220Y (2012) https://doi.org/10.1117/12.965225

KEYWORDS: Photomasks, Optical proximity correction, Data modeling, Calibration, Data conversion, Point spread functions, Manufacturing, Extreme ultraviolet, Process modeling, Semiconducting wafers

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Proceedings Article | 23 March 2012 Paper

EUV OPC for the 20-nm node and beyond

Chris Clifford, Yi Zou, Azat Latypov, Oleg Kritsun, Thomas Wallow, Harry Levinson, Fan Jiang, Deniz Civay, Keith Standiford, Ralph Schlief, Lei Sun, Obert Wood, Sudhar Raghunathan, Pawitter Mangat, Hui Peng Koh, Craig Higgins, Jeffrey Schefske, Mandeep Singh

Proceedings Volume 8322, 83221M (2012) https://doi.org/10.1117/12.916171

KEYWORDS: Optical proximity correction, Extreme ultraviolet, Photomasks, Deep ultraviolet, Semiconducting wafers, Extreme ultraviolet lithography, Lithography, Critical dimension metrology, Printing, Monte Carlo methods

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Proceedings Article | 18 March 2009 Open Access

REBL nanowriter: Reflective Electron Beam Lithography

Paul Petric, Chris Bevis, Alan Brodie, Allen Carroll, Anthony Cheung, Luca Grella, Mark McCord, Henry Percy, Keith Standiford, Marek Zywno

Proceedings Volume 7271, 727107 (2009) https://doi.org/10.1117/12.817319

KEYWORDS: Semiconducting wafers, Electron beam lithography, Lithography, Electron beams, Reflectivity, Wafer-level optics, Prisms, Calibration, Electrodes, Mirrors

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Proceedings Article | 27 December 1996 Paper

Comparison of reticle placement performance using two-point and multipoint fitting algorithms

Henry Chris Hamaker, Jerry Martyniuk, Robert Sills, Jeffrey Varner, Keith Standiford

Proceedings Volume 2884, (1996) https://doi.org/10.1117/12.262820

KEYWORDS: Error analysis, Printing, Statistical analysis, Photomasks, Optical alignment, Reticles, Computer simulations, Metrology, Composites, Overlay metrology

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Two of the key performance parameters in the manufacture of photomasks and reticles are composite placement and composite overlay. Multipoint fitting of the placement and overlay errors is typically used in specifying the performance of the printing tool, whereas two-point fitting is more commonly used in the mask-production environment. In this study, Monte Carlo simulation techniques are used to compare the placement results that may be expected using the two methods. Mask yields are evaluated sing the maximum observed error as the primary metric, because this criterion is prevalent in the industry. The influence of several factors is examined, including number of sample points, size of test pattern, and the presence of systematic printing errors. The baseline test case consists of a 7 X 7 grid of points with an extent of 132-nm square with two additional alignment marks separated in the x direction by 144 mm, and random normally distributed errors with standard deviation (sigma) . For this case, the expected maximum error at 95% mask yield from a two-point alignment is approximately 4.5 (sigma) , and (tau) equals 1.3, where (tau) is defined as the ratio of the maximum error for two-point versus multipoint fitting. The expected maximum error depends logarithmically on the number of sample points, and (tau) decreases as the number of points increases. A sinusoidal systematic error in the printing system greatly degrades the yield using two-point alignment but has relatively little effect upon the yield using multipoint alignment. Similarly, an orthogonality mismatch between the printing and metrology tool causes (tau) to increase significantly, whereas a scale mismatch decreases (tau) . It is also demonstrated that the result from two-point alignment has more statistical uncertainty than that from the multipoint methodology, and thus multipoint alignment is more accurate in determining the expected performance of a given printing system from a limited set of sample masks.

Proceedings Article | 19 May 1995 Paper

0.25-um lithography using a 50-kV shaped electron-beam vector scan system

Mark Gesley, Terry Mulera, C. Nurmi, J. Radley, Allan Sagle, Keith Standiford, Zoilo Tan, John Thomas, Lee Veneklasen

Proceedings Volume 2437, (1995) https://doi.org/10.1117/12.209157

KEYWORDS: Electronics, Calibration, Reticles, Lithography, Distortion, Critical dimension metrology, X-rays, Semiconducting wafers, Field programmable gate arrays, Error analysis

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Performance data from a prototype 50 kV shaped electron-beam (e-beam) pattern generator is presented. This technology development is targeted towards 180-130 nm device design rules. It will be able to handle 1X NIST X-ray membranes, glass reduction reticles, and 4- to 8-inch wafers. The prototype system uses a planar stage adapted from the IBM EL-4 design. The electron optics is an 50 kV extension of the AEBLE%+TM) design. Lines and spaces of 0.12 micrometers with < 40 nm corner radius are resolved in 0.4 micrometers thick resist at 50 kV. This evolutionary platform will evolve further to include a new 100 kV column with telecentric deflection and a 21-bit (0.5 mm) major field for improved placement accuracy. A unique immersion shaper, faster data path electronics, and 15-bit (32 micrometers ) minor field deflection electronics will substantially increase the flash rate. To match its much finer address structure, the pattern generator figure word size will increase from 80 to 96 bits. The data path electronics uses field programmable gate array (FPGA) logic allowing writing strategy optimization via software reconfiguration. An advanced stage position control (ASPC) includes three-axis, (lambda) /1024 interferometry and a high bandwidth dynamic corrections processor (DCP). Along with its normal role of coordinate transformation and dynamic correction of deflection distortion, astigmatism, and defocus; the DCP improves accuracy by modifying deflection conditions and focus according to measured substrate height variations. It also enables yaw calibration and correction for Write-on-the Fly^TM motion. The electronics incorporates JTAG components for built-in self- test (BIST), as well as syndrome checking to ensure data integrity. The design includes diagnostic capabilities from offsite as well as from the operator console. A combination of third-party software and an internal job preparation software system is used to fracture patterns. It handles tone reversal, overlap removal, sizing, and proximity correction. Processing of large files in a commercial mask shop environment is made more efficient by retaining hierarchy and using parallel processing and data compression techniques. Large GDSII^TM and MEBES data files can be processed. Data includes timing benchmarks for a 1 Gbit DRAM on both proximity and reduction reticles. The paper presents 50 kV results on silicon and quartz substrates along with examples of overlay to an external grid, field butting, and critical dimension (CD) control data. Selective experiments testing system stability, calibration accuracy, and local correction software implementation on a VAX control computer are also given.

Proceedings Article | 7 December 1994 Paper

Life after the 256-Mb DRAM: e-beam mask makers at the year 2000

Keith Standiford, John Wiesner

Proceedings Volume 2322, (1994) https://doi.org/10.1117/12.195840

KEYWORDS: Photomasks, Semiconducting wafers, Printing, Lithography, Photomask technology, Control systems, X-rays, Electron beam lithography, Deep ultraviolet, Extreme ultraviolet

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