Dr. Gangadhara Raja Muthinti Profile

Dr. Gangadhara Raja Muthinti

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Publications (17)

Proceedings Article | 2 July 2019 Presentation + Paper

Machine learning and hybrid metrology using scatterometry and LE-XRF to detect voids in copper lines

Shay Wolfing, Avron Ger, Kavita Shah, Dexin Kong, Koichi Motoyama, Abraham Arceo de la peña, Huai Huang, Brock Mendoza, Mary Breton, Gangadhara Raja Muthinti, Hosadurga Shobha, John Gaudiello, Aron Cepler, Matthew Sendelbach, Susan Emans, Juntao Li, James Demarest, Gauri Karve, Paul Isbester, Liying Jiang

Proceedings Volume 10959, 109590A (2019) https://doi.org/10.1117/12.2515257

KEYWORDS: Metrology, Machine learning, Scatterometry, Copper

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Proceedings Article | 5 September 2018 Presentation + Paper

In-line characterization of non-selective SiGe nodule defects with scatterometry enabled by machine learning

Dexin Kong, Robin Chao, Mary Breton, Chi-chun Liu, Gangadhara Raja Muthinti, Soon-cheon Seo, Nicolas Loubet, Pietro Montanini, John Gaudiello, Veeraraghavan Basker, Aron Cepler, Susan Ng-Emans, Matthew Sendelbach, Itzik Kaplan, Gilad Barak, Daniel Schmidt, Julien Frougier

Proceedings Volume 10585, 1058510 (2018) https://doi.org/10.1117/12.2297377

KEYWORDS: Scatterometry, Semiconducting wafers, Scanning electron microscopy, Machine learning, Metrology, Data modeling, Scatter measurement, Mathematical modeling, Transmission electron microscopy, Field effect transistors

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As device scaling continues, controlling defect densities on the wafer becomes essential for high volume manufacturing (HVM). One type of defect, the non-selective SiGe nodule, becomes more difficult to control during SiGe epitaxy (EPI) growth for p-type field effect transistor (pFET) source and drain. The process window for SiGe EPI growth with low nodule density becomes extremely tight due to the shrinking of contact poly pitch (CPP). Any tiny process shift or incoming structure shift could introduce a high density of nodules, which could affect device performance and yield. The current defect inspection method has a low throughput, so a fast and quantitative characterization technique is preferred for measuring and monitoring this type of defect. Scatterometry is a fast and non-destructive in-line metrology technique. In this work, novel methods were developed to accurately and comprehensively measure the SiGe nodules with scatterometry information. Top-down critical dimension scanning electron microscopy (CD-SEM) images were collected and analyzed on the same location as scatterometry measurement for calibration. Machine learning (ML) algorithms are used to analyze the correlation between the raw spectra and defect density and area fraction. The analysis showed that the defect density and area fractions can be measured separately by correlating intensity variations. In addition to the defect density and area fraction, we also investigate a novel method – model-based scatterometry hybridized with machine learning capabilities – to quantify the average height of the defects along the sidewall of the gate. Hybridizing the machine learning method with the model-based one could also eliminate the possibility of misinterpreting the defect as some structural parameters. Furthermore, cross-sectional TEM and SEM measurement are used to calibrate the model-based scatterometry results. In this work, the correlation between the SiGe nodule defects and the structural parameters of the device is also studied. The preliminary result shows that there is strong correlation between the defect density and spacer thickness. Correlations between the defect density and the structural parameters provides useful information for process engineers to optimize the EPI growth process. With the advances in the scatterometry-based defect measurement metrology, we demonstrate such fast, quantitative, and comprehensive measurement of SiGe nodule defects can be used to improve the throughput and yield.

Proceedings Article | 19 March 2018 Presentation

Novel hybrid metrology for process integration of gate all around (GAA) devices (Conference Presentation)

Gangadhara Muthinti, Dexin Kong, Susan Ng-Emans, Matthew Sendelbach, Nicolas Loubet, Robinhsinkuo Chao, Abraham Arceo De La Pena, Juntao Li, Brock Mendoza, Veeraraghavan Basker, Tenko Yamashita, John Gaudiello, Aron Cepler, Wei Ti Lee, Gilad Barak

Proceedings Volume 10585, 105850Z (2018) https://doi.org/10.1117/12.2297500

KEYWORDS: Metrology, Gallium arsenide, Etching, Silicon, Measurement devices, Geometrical optics, X-ray fluorescence spectroscopy, Semiconductors, Nanolithography

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Proceedings Article | 12 April 2017 Presentation + Paper

Electrical test prediction using hybrid metrology and machine learning

John Gaudiello, Susan Emans, Michael Shifrin, Yoav Etzioni, Ronen Urenski, Wei Ti Lee, Mary Breton, Robin Chao, Gangadhara Raja Muthinti, Abraham de la Peña, Jacques Simon, Aron Cepler, Matthew Sendelbach

Proceedings Volume 10145, 1014504 (2017) https://doi.org/10.1117/12.2261091

KEYWORDS: Copper, Metrology, Resistance, Machine learning, Metals, Back end of line, Semiconducting wafers, Scatterometry, X-rays, Process control

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Electrical test measurement in the back-end of line (BEOL) is crucial for wafer and die sorting as well as comparing intended process splits. Any in-line, nondestructive technique in the process flow to accurately predict these measurements can significantly improve mean-time-to-detect (MTTD) of defects and improve cycle times for yield and process learning. Measuring after BEOL metallization is commonly done for process control and learning, particularly with scatterometry (also called OCD (Optical Critical Dimension)), which can solve for multiple profile parameters such as metal line height or sidewall angle and does so within patterned regions. This gives scatterometry an advantage over inline microscopy-based techniques, which provide top-down information, since such techniques can be insensitive to sidewall variations hidden under the metal fill of the trench. But when faced with correlation to electrical test measurements that are specific to the BEOL processing, both techniques face the additional challenge of sampling. Microscopy-based techniques are sampling-limited by their small probe size, while scatterometry is traditionally limited (for microprocessors) to scribe targets that mimic device ground rules but are not necessarily designed to be electrically testable. A solution to this sampling challenge lies in a fast reference-based machine learning capability that allows for OCD measurement directly of the electrically-testable structures, even when they are not OCD-compatible. By incorporating such direct OCD measurements, correlation to, and therefore prediction of, resistance of BEOL electrical test structures is significantly improved. Improvements in prediction capability for multiple types of in-die electrically-testable device structures is demonstrated. To further improve the quality of the prediction of the electrical resistance measurements, hybrid metrology using the OCD measurements as well as X-ray metrology (XRF) is used. Hybrid metrology is the practice of combining information from multiple sources in order to enable or improve the measurement of one or more critical parameters. Here, the XRF measurements are used to detect subtle changes in barrier layer composition and thickness that can have second-order effects on the electrical resistance of the test structures. By accounting for such effects with the aid of the X-ray-based measurements, further improvement in the OCD correlation to electrical test measurements is achieved. Using both types of solution incorporation of fast reference-based machine learning on nonOCD-compatible test structures, and hybrid metrology combining OCD with XRF technology improvement in BEOL cycle time learning could be accomplished through improved prediction capability.

Proceedings Article | 31 March 2017 Paper

Materials characterization for process integration of multi-channel gate all around (GAA) devices

Gangadhara Raja Muthinti, Roy Koret, Juntao Li, Tenko Yamashita, Sivananda Kanakasabapathy, Peter Gin, Matthew Sendelbach, Nicolas Loubet, Robin Chao, Abraham de la Peña, Michael Guillorn, John Gaudiello, Aron Cepler, Susan Emans, Shay Wolfling, Avron Ger, Daniel Kandel, Wei Ti Lee, Kevin Matney, Matthew Wormington

Proceedings Volume 10145, 101451U (2017) https://doi.org/10.1117/12.2261377

KEYWORDS: Germanium, Silicon, Diffractive optical elements, Gallium arsenide, Semiconducting wafers, Etching, Solids, X-ray diffraction, X-ray fluorescence spectroscopy, Materials processing

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Proceedings Article | 28 March 2017 Paper

An OCD perspective of line edge and line width roughness metrology

Ravi Bonam, Raja Muthinti, Mary Breton, Chi-Chun Liu, Stuart Sieg, Indira Seshadri, Nicole Saulnier, Jeffrey Shearer, Raghuveer Patlolla, Huai Huang

Proceedings Volume 10145, 1014511 (2017) https://doi.org/10.1117/12.2258196

KEYWORDS: Line width roughness, Metrology, Edge roughness, Optical metrology, Process control, Line edge roughness, Semiconductors, Modeling, Scanning electron microscopy, Critical dimension metrology, Semiconducting wafers, Photomasks, 3D modeling, Extreme ultraviolet, Modulation

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Proceedings Article | 24 March 2017 Paper

Comprehensive analysis of line-edge and line-width roughness for EUV lithography

Ravi Bonam, Chi-Chun Liu, Mary Breton, Stuart Sieg, Indira Seshadri, Nicole Saulnier, Jeffrey Shearer, Raja Muthinti, Raghuveer Patlolla, Huai Huang

Proceedings Volume 10143, 101431A (2017) https://doi.org/10.1117/12.2258194

KEYWORDS: Line width roughness, Edge roughness, Lithography, Extreme ultraviolet lithography, Line edge roughness, Metrology, Photomasks, Semiconducting wafers, Semiconductors, Optical imaging, Photoresist processing, Etching, Extreme ultraviolet, Modulation

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Proceedings Article | 30 March 2016 Paper

Advanced in-line metrology strategy for self-aligned quadruple patterning

Mary Breton, Benoit L'herron, Raja Muthinti, Florence Nelson, Abraham De La Pena, Fee li Le, Eric Miller, Stuart Sieg, James Demarest, Peter Gin, Matthew Wormington, Aron Cepler, Cornel Bozdog, Brock Mendoza, Matthew Sendelbach, Robin Chao, Shay Wolfling, Sivananda Kanakasabapathy, John Gaudiello, Nelson Felix, Tom Cardinal

Proceedings Volume 9778, 977813 (2016) https://doi.org/10.1117/12.2220601

KEYWORDS: Critical dimension metrology, Metrology, Transmission electron microscopy, Optical lithography, Semiconducting wafers, Etching, Process control, Scatterometry, Reactive ion etching, Diffractive optical elements

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Self-Aligned Quadruple Patterning (SAQP) is a promising technique extending the 193-nm lithography to manufacture structures that are 20nm half pitch or smaller. This process adopts multiple sidewall spacer image transfers to split a rather relaxed design into a quarter of its original pitch. Due to the number of multiple process steps required for the pitch splitting in SAQP, the process error propagates through each deposition and etch, and accumulates at the final step into structure variations, such as pitch walk and poor critical dimension uniformity (CDU). They can further affect the downstream processes and lower the yield. The impact of this error propagation becomes significant for advanced technology nodes when the process specifications of device design CD requirements are at nanometer scale. Therefore, semiconductor manufacturing demands strict in-line process control to ensure a high process yield and improved performance, which must rely on precise measurements to enable corrective actions and quick decision making for process development. This work aims to provide a comprehensive metrology solution for SAQP.

During SAQP process development, the challenges in conventional in-line metrology techniques start to surface. For instance, critical-dimension scanning electron microscopy (CDSEM) is commonly the first choice for CD and pitch variation control. However, it is found that the high aspect ratio at mandrel level processes and the trench variations after etch prevent the tool from extracting the true bottom edges of the structure in order to report the position shift. On the other hand, while the complex shape and variations can be captured with scatterometry, or optical CD (OCD), the asymmetric features, such as pitch walk, show low sensitivity with strong correlations in scatterometry. X-ray diffraction (XRD) is known to provide useful direct measurements of the pitch walk in crystalline arrays, yet the data analysis is influenced by the incoming geometry and must be used carefully.

A successful implementation of SAQP process control for yield improvement requires the metrology issues to be addressed. By optimizing the measurement parameters and beam configurations, CDSEM measurements distinguish each of the spaces corresponding to the upstream mandrel processes and report their CDs separately to feed back to the process team for the next development cycle. We also utilize the unique capability in scatterometry to measure the structure details in-line and implement a “predictive” process control, which shows a good correlation between the “predictive” measurement and the cross-sections from our design of experiments (DOE). The ability to measure the pitch walk in scatterometry was also demonstrated. This work also explored the frontier of in-line XRD capability by enabling an automatic RSM fitting on tool to output pitch walk values. With these advances in metrology development, we are able to demonstrate the impacts of in-line monitoring in the SAQP process, to shorten the patterning development learning cycle to improve the yield.

Proceedings Article | 29 March 2016 Paper

Advanced in-line optical metrology of sub-10nm structures for gate all around devices (GAA)

Matthew Sendelbach, Raja Muthinti, Parker Lund, Aron Cepler, John Gaudiello, Oded Cohen, Cornel Bozdog, Mark Klare, Nicolas Loubet, Robin Chao, Michael Guillorn, Nelson Felix, Shay Wolfling, John Ott

Proceedings Volume 9778, 977810 (2016) https://doi.org/10.1117/12.2220379

KEYWORDS: Nanowires, Silicon, Germanium, Metrology, Gallium arsenide, Optical lithography, Scatterometry, Metals, Semiconducting wafers, Multilayers

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SPIE Journal Paper | 3 August 2015 Open Access

Sensitivity analysis and line edge roughness determination of 28-nm pitch silicon fins using Mueller matrix spectroscopic ellipsometry-based optical critical dimension metrology

Dhairya Dixit, Samuel O’Mullane, Sravan Sunkoju, Abhishek Gottipati, Erik Hosler, Vimal Kamineni, Moshe Preil, Nick Keller, Joseph Race, Gangadhara Raja Muthinti, Alain Diebold

JM3, Vol. 14, Issue 03, 031208, (August 2015) https://doi.org/10.1117/12.10.1117/1.JMM.14.3.031208

KEYWORDS: Line edge roughness, Silicon, Scatterometry, Data modeling, Optical components, Scanning electron microscopy, Picosecond phenomena, Chemical elements, Line width roughness, Optical properties

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Proceedings Article | 10 April 2015 Paper

Silicon fin line edge roughness determination and sensitivity analysis by Mueller matrix spectroscopic ellipsometry based scatterometry

Sravan Sunkoju, Dhairya Dixit, Samuel O'Mullane, Erik Hosler, Vimal Kamineni, Moshe Preil, Nick Keller, Joseph Race, Gangadhara Raja Muthinti, Alain Diebold

Proceedings Volume 9424, 94242P (2015) https://doi.org/10.1117/12.2185543

KEYWORDS: Line edge roughness, Silicon, Scatterometry, Data modeling, Optical components, Spatial frequencies, Chemical elements, Optical properties, Inverse optics, Critical dimension metrology

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SPIE Journal Paper | 29 October 2014

Multitechnique metrology methods for evaluating pitch walking in 14 nm and beyond FinFETs

Robin Chao, Kriti Kohli, Yunlin Zhang, Anita Madan, Gangadhara Raja Muthinti, Augustin Hong, David Conklin, Judson Holt, Todd Bailey

JM3, Vol. 13, Issue 04, 041411, (October 2014) https://doi.org/10.1117/12.10.1117/1.JMM.13.4.041411

KEYWORDS: Metrology, Scatterometry, Silicon, Diffraction, X-rays, Data modeling, Semiconducting wafers, X-ray diffraction, 3D modeling

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Proceedings Article | 2 April 2014 Paper

Novel in-line metrology methods for Fin pitch walking monitoring in 14nm node and beyond

Robin Chao, David Conklin, Kriti Kohli, Yunlin Zhang, Anita Madan, G. Raja Muthinti, Augustin Hong, Judson Holt, Todd Bailey

Proceedings Volume 9050, 90501E (2014) https://doi.org/10.1117/12.2057402

KEYWORDS: Scatterometry, Silicon, Metrology, Data modeling, X-ray diffraction, Diffraction, X-rays, Semiconducting wafers, Diffraction gratings, Critical dimension metrology

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Proceedings Article | 18 April 2013 Paper

Fin stress and pitch measurement using X-ray diffraction reciprocal space maps and optical scatterometry

A. Diebold, M. Medikonda, B. Peterson, J. Race, G. Muthinti, V. Kamineni, J. Fronheiser, M. Wormington

Proceedings Volume 8681, 86810I (2013) https://doi.org/10.1117/12.2023081

KEYWORDS: Silicon, Scatterometry, Diffraction, Anisotropy, Germanium, X-ray diffraction, Crystals, Optical properties, Diffraction gratings, Refractive index

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Proceedings Article | 18 April 2013 Paper

Mueller based scatterometry measurement of nanoscale structures with anisotropic in-plane optical properties

Gangadhara Muthinti, Manasa Medikonda, Jody Fronheiser, Vimal Kamineni, Brennan Peterson, Joseph Race, Alain Diebold

Proceedings Volume 8681, 86810M (2013) https://doi.org/10.1117/12.2011649

KEYWORDS: Scatterometry, Optical properties, Silicon, Anisotropy, 3D modeling, Thin films, Scatter measurement, 3D metrology, Spectroscopy

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The uses of strained channel became prevalent at the 65 nm node and have continued to be a large part of logic device performance improvements in every technology generation. These material and integration innovations will continue to be important in sub-22nm devices, and are already being applied in finFET devices where total available in-channel strains are potentially higher. The measurement of structures containing these materials is complicated by the intrinsic correlation of the measured optical thickness and variation of optical properties with strain, as well as the dramatic reduction in total volume of the device. Optical scatterometry has enabled characterization of the feature shape and dimensions of complex 3D structures, including non-planar transistors and memory structures. Ellipsometric methods have been successfully applied to the measurement of thin films of SiGe and related strained structures. A direction for research is validating that the thin film stress results can be extended into the much more physically complex 3D shape. There are clear challenges in this: the stress in a SiGe fin is constrained to match the underlying Si along one axis, but the sides and top are free, leading to very large strain gradients both along the fin width and height. Practical utilization of optical techniques as a development tool is often limited by the complexity of the scatterometry model and setup, and this added material complexity presents a new challenge. In this study, generalized spectroscopic ellipsometric measurements of strained grating was undertaken, in parallel with reference cross sectional and top down SEM data. The measurements were modeled for both anisotropy calculations, as well as full scatterometry calculations, fitting the strain and structure. The degree to which strain and CD can be quickly quantified in an optical model is discussed. Sum decomposition method has been implemented to extract the effective anisotropic coefficients and a discussion on the effect of anisotropy toward modeling is presented. Finally, errors in the scatterometry measurement are analyzed, and the relative strengths and limitations of these optical measurements compared.

SPIE Journal Paper | 27 March 2013

Characterization of e-beam patterned grating structures using Mueller matrix based scatterometry

Gangadhara Raja Muthinti, Brennan Peterson, Ravi Bonam, Alain Diebold

JM3, Vol. 12, Issue 01, 013018, (March 2013) https://doi.org/10.1117/12.10.1117/1.JMM.12.1.013018

KEYWORDS: Scatterometry, Data modeling, Scanning electron microscopy, Electron beam lithography, Metrology, Critical dimension metrology, Spectroscopy, Chemical elements, Optical properties, Diffraction gratings

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Proceedings Article | 5 April 2012 Paper

Investigation of E-beam patterned nanostructures using Mueller Matrix based Scatterometry

Gangadhara Raja Muthinti, Brennan Peterson, Alain Diebold

Proceedings Volume 8324, 83240O (2012) https://doi.org/10.1117/12.916289

KEYWORDS: Scatterometry, Scanning electron microscopy, Data modeling, Metrology, Nanostructures, Spectroscopy, Diffraction, Chemical elements, Critical dimension metrology, Electron beam lithography

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Scatterometry is one of the most useful metrology methods for the characterization and control of critical dimensions (CD) and the detailed topography of periodic structures in microelectronics fabrication processes. Spectroscopic Ellipsometry (SE) and Normal Incidence Reflectometry (NI) based Scatterometry are the most widely used methodologies for metrology of these structures. Evolution of better optical hardware and faster computing capabilities led to the development of Mueller Matrix (MM) based Scatterometry (MMS). In this paper we present the first study of dimensional metrology using full Mueller Matrix (16 element) Scatterometry in the wavelength range of 245nm- 1000nm. Unlike SE and NI, MM data provides complete information about the optical reflection and transmission of polarized light through a sample. MM is a 4x4 transformation matrix (16 elements) describing the change in the intensities of incident polarized light expressed by means of a Stokes Vector. The symmetry properties associated with MM provide an excellent means of measuring and understanding the topography of the periodic nanostructures. Topography here refers to uniformity of the periodic structure. The advantage of MMS over traditional SE Scatterometry is the ability of MMS to measure samples that have anisotropic optical properties and depolarize light. The present study focuses on understanding the precision and accuracy of Mueller based Scatterometry with respect to other methodologies by a systematic approach. Several laterally complex nanoscale structures with dimensions in the order of nanometers were designed and fabricated using a state of the art E-beam pattering tool (VISTEC [R] 300). Later, Spectroscopic Mueller matrix (all 16 elements) and SE data were collected in planar diffraction mode for the samples using J.A. Woollam RC2 [TM] Spectroscopic Ellipsometer. NanoDiffract [TM] (Scatterometry software provided by Nanometrics Inc.) was used to model the nanostructures to precisely calculate the critical dimensions. Complementary techniques like SEM were used to compare the results obtained from Scatterometry. Finally, Mueller and SE based Scatterometry techniques were compared commenting on reliability of MM based Scatterometry.

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