Dr. Malahat A. Tavassoli Profile

Dr. Malahat A. Tavassoli

Area Engineering Manager at Intel Corp

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Author

Publications (20)

Proceedings Article | 12 November 2024 Presentation + Paper

AFM nano-IR for photomask in-line defect characterization

Mitchell First, Elba Gomar-Nadal, Jeff Hsiao, Farhood Rasouli, Malahat Tavassoli, Chunzeng Li, Cassandra Phillips, Jason Osborne, Peter De Wolf

Proceedings Volume 13216, 132160W (2024) https://doi.org/10.1117/12.3037631

KEYWORDS: Atomic force microscopy, FT-IR spectroscopy, Contamination, Plastics, Photomasks, Infrared imaging, Chemical analysis, Equipment, Spectroscopy

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Proceedings Article | 12 January 2024 Presentation + Paper

Mask registration for high-NA EUV lithography

Roman Schmeissner, Susanne Toepfer, Mikhail Poretskiy, Sven Martin, Stephan Zschaeck, Martin Steinhardt, Vivek Mishra, Cindy Zheng, Kowtilya Bijjula, Malahat Tavassoli

Proceedings Volume PC12751, PC1275104 (2024) https://doi.org/10.1117/12.2688259

KEYWORDS: Image registration, Calibration, Extreme ultraviolet, Extreme ultraviolet lithography, Scanners, Overlay metrology, Lithography, Deep ultraviolet, Photomasks, Metrology

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Proceedings Article | 21 November 2023 Presentation + Paper

Development of EUV phase shift mask metrology

Elba Gomar-Nadal, Malahat Tavassoli, Kowtilya Bijjula, Stuart Sherwin, Matt Hettermann, Christian Wilson, Feng Dong, Dave Houser, Alexander Khodarev, Chami Perera, Patrick Naulleau

Proceedings Volume 12751, 127510O (2023) https://doi.org/10.1117/12.2688453

KEYWORDS: Phase shifts, Extreme ultraviolet, Metrology, Reflectance spectroscopy, Reflectometry, Spectroscopy, Signal attenuation, Refractive index, Phase measurement, Thin films

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Proceedings Article | 21 November 2023 Presentation + Paper

Optimizing CD-SEM metrology for anamorphic high-NA EUV photomasks

Deepan Kishore Kumar, Varun Mohan, Hatsey Frezghi, Adam Seeger, Malahat Tavassoli, Masayuki Kuribara, Kiyoshi Oura, Wataru Ito, Soichi Shida, Tatsuro Okawa, Mark Sheppard, Toshimichi Iwai

Proceedings Volume 12751, 127510R (2023) https://doi.org/10.1117/12.2687660

KEYWORDS: Metrology, Extreme ultraviolet, Scanning electron microscopy, Critical dimension metrology, Photomasks, Optical proximity correction, Reticles

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Proceedings Article | 9 September 2013 Paper

Measurement of EUV absorber and resist CD using spectroscopic ellipsometer

Kyung Lee, Malahat Tavassoli, Pei-yang Yan, Guojing Zhang

Proceedings Volume 8880, 88800Q (2013) https://doi.org/10.1117/12.2027231

KEYWORDS: Critical dimension metrology, Extreme ultraviolet, Scanning electron microscopy, Scatterometry, Photomasks, Lithography, Spectroscopy, Metrology, Cadmium, Line edge roughness

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Proceedings Article | 24 March 2009 Paper

Implementation of multiple ROI with single FOV for advanced mask metrology

Kyu-hwa Jeong, Hatsey Frezghi, Malahat Tavassoli, Stephen Kim, Ray Morgan

Proceedings Volume 7272, 72724D (2009) https://doi.org/10.1117/12.826930

KEYWORDS: Scanning electron microscopy, Metrology, Time metrology, Photomasks, Resolution enhancement technologies, Optical proximity correction, Computed tomography, Critical dimension metrology, Cadmium, Control systems

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Proceedings Article | 24 March 2008 Paper

Phase metrology on 45-nm node phase-shift mask structures

Kyung Lee, Malahat Tavassoli, Ute Buttgereit, Dirk Seidel, Robert Birkner, Sascha Perlitz

Proceedings Volume 6922, 69222A (2008) https://doi.org/10.1117/12.772106

KEYWORDS: Photomasks, Metrology, Phase measurement, Phase shifts, Semiconducting wafers, Scanners, Critical dimension metrology, Etching, Cadmium, Resolution enhancement technologies

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Proceedings Article | 31 October 2007 Paper

Laterally resolved off-axis phase measurements on 45-nm node production features using Phame

Ute Buttgereit, Sascha Perlitz, Dirk Seidel, Kyung Lee, Malahat Tavassoli

Proceedings Volume 6730, 67303E (2007) https://doi.org/10.1117/12.746676

KEYWORDS: Diffraction, Phase shifts, Photomasks, Scanners, Phase measurement, Image resolution, Metrology, Printing, Polarization, Semiconducting wafers

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As lithography mask process moves toward 45nm and 32nm node, phase control is becoming more important than ever. To ensure an accurate printing both attenuated and alternating PSMs (Phase Shift Masks) need precise control of phase as a function of both pitch and target sizes. However critical target CDs fall much below conventional phase metrology tools capabilities. Interferometer-based phase shift measurements are limited to large CD targets and require custom designed features in order to function properly, which limits phase measurement. AFM (Atomic Force Microscopy) methods are able to capture small feature sizes but do not consider any diffraction effects which are caused by the topography of the features itself when getting close to the used wavelength. Imaging simulations, both, in a rigorous and a Kirchhoff regime, show the dependency of the phase in the image plane of a microlithography exposure tool on numerical aperture and pitch due to the loss of phase information in the imaging pupil. Additionally, for small features the phase is strongly impacted by polarization and 3D mask effects. For these feature sizes, the image phase does not coincide with the etch depth equivalent phase calculated from the nominal depth and optical constants of the shifter material. Deviations up to 20° have been observed leading to strong variations in the imaging quality and process window variations during scanner printing. Considerations of CD variation between 0 and pi features by simulation show lowest 0/pi CD variation and therefore largest process window if the scanner relevant phase is at 180°. The simulation results illustrate the importance to measure the scanner relevant phase, effective in the image plane of the scanner. Consequently Zeiss, in collaboration with Intel, has developed a laterally resolving Phase Metrology Tool - Phame^® - for in-die phase measurements. The optical metrology tool is able to perform in-die phase measurement on alternating PSM, attenuated PSM and CPL masks down to 120nm half pitch at mask. On-axis measurement results have already been published. In this paper we elaborate on off-axis phase measurement theory and procedure. Furthermore we present first off-axis measurement results over varying features sizes using different illumination conditions.

Proceedings Article | 12 May 2007 Paper

Novel solution for in-die phase control under scanner equivalent optical settings for 45-nm node and below

Sascha Perlitz, Ute Buttgereit, Thomas Scherübl, Dirk Seidel, Kyung M. Lee, Malahat Tavassoli

Proceedings Volume 6607, 66070Z (2007) https://doi.org/10.1117/12.728948

KEYWORDS: Scanners, Photomasks, Phase measurement, Etching, Polarization, Diffraction, Phase shifts, Phase shifting, Metrology, Semiconducting wafers

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As lithography mask process moves toward 45nm and 32nm node, phase control is becoming more important than ever. Both attenuated and alternating Phase Shifting Masks (PSM) need precise control of phase as a function of both pitch and target sizes. However conventional interferometer-based phase shift measurements are limited to large CD targets and require custom designed patterns in order to function properly, which limits phase measurement Zeiss is currently developing an optical phase measurement tool (Phame^TM), providing the capability of extending process control from large CD test features to in-die phase shifting features with high spatial resolution. The necessity of designing this optical metrology tool according to the optical setup of a lithographic exposure tool (scanner) has been researched to be fundamental for the acquisition of phase information generated from features close to the size of the used wavelength. It was found by simulation that the image phase of a scanner depends on polarization and the angle of incidence of the illumination light due to rigorous effects. Additionally, for small features the phase value is strongly influenced by the imaging NA of the scanner due to the loss of phase information in the imaging pupil. Simulations show that the resulting scanner phase in the image plane only coincides with the etch-depth equivalent phase for large test features, exceeding the size of the in-die feature by an order of magnitude. In this paper we introduce the Phame^TM phase metrology tool, which enables the industry to perform in-die phase control for Alternating PSM, Attenuated PSM and CPL masks. The Phame^TM uses a 193nm light source with the optical capability of phase measurement at scanner NA up to the equivalent of a NA1.6 immersion scanner, under varying, scanner relevant angle of incidence for Attenuated PSMs and CPLs, and with the possibility of polarizing the illuminating light. New options for phase shifting mask process control on in-die features will be outlined with first phase measurement results for varying states of polarization.

Proceedings Article | 5 April 2007 Paper

Study of rigorous effects and polarization on phase shifting masks through simulations and in-die phase measurements

Kyung Lee, Malahat Tavassoli, Max Lau, Kiho Baik, Barry Lieberman, Sascha Perlitz, Ute Buttgereit, Thomas Scherübl

Proceedings Volume 6518, 65181Y (2007) https://doi.org/10.1117/12.712908

KEYWORDS: Photomasks, Phase measurement, Scanners, Etching, Semiconducting wafers, Polarization, Phase shifts, Metrology, Near field, Imaging systems

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Proceedings Article | 5 April 2007 Paper

Scatterometry measurement of nested lines, dual space, and rectangular contact CD on phase-shift masks

Kyung Lee, Sanjay Yedur, Sven Henrichs, Malahat Tavassoli, Kiho Baik

Proceedings Volume 6518, 651856 (2007) https://doi.org/10.1117/12.729246

KEYWORDS: Critical dimension metrology, Photomasks, Cadmium, Scatterometry, Scanning electron microscopy, Semiconducting wafers, Scatter measurement, Lithography, Binary data, Metrology

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Proceedings Article | 20 October 2006 Paper

Design-based mask metrology hot spot classification and recipe making through random pattern recognition method

Ying Cui, Kiho Baik, Bob Gleason, Malahat Tavassoli

Proceedings Volume 6349, 63490O (2006) https://doi.org/10.1117/12.690988

KEYWORDS: Metrology, Cadmium, Optical proximity correction, Pattern recognition, Logic, Image classification, Critical dimension metrology, Chromium, Library classification systems, Logic devices

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Proceedings Article | 20 October 2006 Paper

Contact hole CD and profile metrology of binary and phase-shift masks: effect of modeling strategies in application of scatterometery

Kyung-man Lee, Sanjay Yedur, Malahat Tavassoli, Kiho Baik, Milad Tabet

Proceedings Volume 6349, 63490M (2006) https://doi.org/10.1117/12.686305

KEYWORDS: Scanning electron microscopy, Critical dimension metrology, Photomasks, Atomic force microscopy, Binary data, 3D modeling, Cadmium, Metrology, 3D acquisition, 3D metrology

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Scatterometers are widely used for line/space or 2D structure measurements in both wafer and mask industries. This technology is now gaining more acceptance and is being applied 3D structures such as contacts and pads. Contact CDs and trench depth in photomasks are critical monitoring parameters in mask industry and are discussed here. We are reporting contact CDs and profile results measured from targets from Binary, PSM, and Crless plates. The strategies of model creation such as using simple trapezoid versus more advanced shapes affect how well SWA and footings can be measured and reported from these structures. We are reporting CD and profile information obtained with Scatterometer, and then comparing CD SEM, AFM, and cross section SEM. Multiple different modeling configurations were used with different levels of complexity, and we report on optimum modeling strategy to obtain profile information from 3D structures. The relationship between the modeling strategy versus cross correlation between different parameters is discussed. CD linearity, uniformity, and other correlation parameters to the reference CD SEM tool are reported. Target CDs ranged from 60nm up to 600nm. CD uniformity reported from Scatterometry is 20~30% less than that from CD SEMs. This CD uniformity improvement is due to the fact that scatterometer beam samples dozens to hundreds of samples and 'averages' profile parameters, thus eliminating local effect such as line edge roughness. Contact depth are also measured and compared to AFM, in which the bias between the two tools are usually around 3nm or less. In terms of smallest target CD measurable, in this paper we report routine measurement of small contacts with middle CD down to 65nm (bottom CD close to 50nm) with both RP and SE mode. Application of scatterometry method to mask contacts and pads leads to accurate and fast measurement of 3D profiles, and opens up possibility of in-line monitoring of profile information due to the higher runrate compared to traditional metrology tools.

Proceedings Article | 21 June 2006 Paper

CD and profile metrology of embedded phase shift masks using scatterometry

Kyung man Lee, Sanjay Yedur, Dave Hetzer, Malahat Tavassoli, Kiho Baik

Proceedings Volume 6281, 62810Z (2006) https://doi.org/10.1117/12.692699

KEYWORDS: Scanning electron microscopy, Scatterometry, Critical dimension metrology, Photomasks, Etching, Metrology, Phase shifts, Scatter measurement, Phase shifting, Cadmium

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Proceedings Article | 3 May 2006 Paper

Scatterometry based CD and profile metrology of chrome-less masks using optical digital profilometry

Kyung-man Lee, Sanjay Yedur, Wen-hao Cheng, Malahat Tavassoli, Kiho Baik

Proceedings Volume 6283, 628313 (2006) https://doi.org/10.1117/12.681864

KEYWORDS: Scatterometry, Scanning electron microscopy, Photomasks, Atomic force microscopy, Scatter measurement, Critical dimension metrology, Binary data, Cadmium, Quartz, Reflectivity

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Proceedings Article | 24 March 2006 Paper

CD-etch depth measurement from advanced phase-shift masks and wafers using optical scatterometry

Kyung Lee, Sanjay Yedur, Sven Henrichs, Malahat Tavassoli

Proceedings Volume 6152, 61521P (2006) https://doi.org/10.1117/12.655642

KEYWORDS: Scanning electron microscopy, Critical dimension metrology, Scatterometry, Semiconducting wafers, Scatter measurement, Cadmium, Photomasks, Quartz, Atomic force microscopy, Etching

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Proceedings Article | 8 November 2005 Paper

Magnetron reactive sputtering of TaN and TaON films for EUV mask applications

Kyung Lee, Malahat Tavassoli, Alan Stivers, Barry Lieberman

Proceedings Volume 5992, 59922B (2005) https://doi.org/10.1117/12.625006

KEYWORDS: Particles, Inspection, Reflectivity, Extreme ultraviolet, Photomasks, Argon, Optical properties, Sputter deposition, Diffractive optical elements, Surface roughness

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Proceedings Article | 5 November 2005 Paper

CD metrology of binary and phase shift masks using scatterometry

Kyung Lee, Sanjay Yedur, Milad Tabet, Malahat Tavassoli

Proceedings Volume 5992, 59921I (2005) https://doi.org/10.1117/12.631971

KEYWORDS: Critical dimension metrology, Scatterometry, Scanning electron microscopy, Binary data, Quartz, Metrology, Glasses, Calibration, Atomic force microscopy, Phase shifts

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Proceedings Article | 28 August 2003 Paper

SMIF capability at Intel Mask Operation improves yield

Thuc Dam, Matt Pekny, Jim Millino, Gibson Luu, Nitesh Melwani, Aparna Venkatramani, Malahat Tavassoli

Proceedings Volume 5130, (2003) https://doi.org/10.1117/12.504267

KEYWORDS: Reticles, Inspection, Coating, Particles, Yield improvement, Thin film coatings, Photoresist processing, Particle contamination, Etching, Robotics

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Proceedings Article | 25 April 1997 Paper

Small radius bends and large angle splitters in SOI waveguides

James Foresi, Desmond Lim, Ling Liao, Anuradha Agarwal, Lionel Kimerling, M. Tavassoli, M. Cox, Min Cao, Wayne Greene

Proceedings Volume 3007, (1997) https://doi.org/10.1117/12.273843

KEYWORDS: Waveguides, Silicon, Oxides, Crystals, Scattering, Manufacturing, Etching, Doping, Chemical mechanical planarization, Beam propagation method

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