Mr. Michael E. Littau Profile

Michael E. Littau

Research Scientist at Onto Innovation Inc

SPIE Involvement:

Author

Publications (15)

Proceedings Article | 24 March 2006 Paper

Diffraction signature analysis methods for improving scatterometry precision

Mike Littau, Darren Forman, Josh Bruce, Christopher Raymond, Steven Hummel

Proceedings Volume 6152, 615236 (2006) https://doi.org/10.1117/12.656729

KEYWORDS: Diffraction, Polarization, Scatterometry, Critical dimension metrology, Metrology, Analytical research, Measurement devices, Etching, Light scattering, Semiconductors

Read Abstract +

Proceedings Article | 24 March 2006 Paper

Back end of line metrology control applications using scatterometry

Linda Towidjaja, Christopher Raymond, Mike Littau, Darren Forman, Steven Hummel

Proceedings Volume 6152, 61521X (2006) https://doi.org/10.1117/12.656515

KEYWORDS: Scatterometry, Dielectrics, Atomic force microscopy, Etching, Critical dimension metrology, Metals, Semiconducting wafers, Back end of line, Optical properties, Metrology

Read Abstract +

Scatterometry is a novel metrology approach for process control that has recently been gaining more momentum in microlithography applications. The method can simultaneously measure Critical Dimension (CD), Side Wall Angle (SWA), and thickness of more than one layer. It analyzes the scattered and diffracted light from a periodic array of lines or holes that represent the surface structure of the measured sample. Scatterometry provides a non-destructive technique offering high precision and stability along with high tool-uptime performance. As such, it offers an excellent approach for real-time high volume production control with significant advantages as compared to traditional technologies such as CD-SEM and Profilometry. As the structure dimension shrinks considerably, producing high precision results becomes more critical. To date, reports on the deployment of scatterometry in real production environment have focused on Front End of Line (FEOL) applications such as STI and Gate. However, Back End of Line (BEOL) process control has not been widely reported. In this work, we will discuss the results of our study specifically for metal trench and contact layer on both patterned and etched wafers for 65nm technology node. We will also report the comparison between Scatterometry results to Critical Dimension Scanning Electron Microscope (CD-SEM) and Atomic Force Microscope (AFM). Finally we will provide a statistical analysis of our scatterometry results including precision, fleet precision, and TMU analysis. In contrast to the relatively simple stacks that comprise a FEOL structure, BEOL layers are typically complex structures with a large number of underlying layers. Generation of simulated scatterometry signatures that constitute a reference library for complex structures can require long computational times and result in large file sizes. To mitigate the computational overhead, it is necessary to intelligently decide which parameters to fix and which to vary. An additional complication is presented due to similarities in the optical properties of BEOL stack materials, which can introduce potential for parameter cross-correlation in the measurement. We will discuss methodologies for optimally selecting parameters to be fixed or varied to minimize these effects.

Proceedings Article | 24 March 2006 Paper

Dome scatterometry for the measurement of advanced geometry semiconductor devices

Christopher Raymond, Mike Littau, Darren Forman, Steven Hummel

Proceedings Volume 6152, 61521I (2006) https://doi.org/10.1117/12.656466

KEYWORDS: Scatterometry, Domes, Scatter measurement, Silicon, Clouds, Polarization, Diffraction, Atomic force microscopy, Critical dimension metrology, Semiconductors

Read Abstract +

Proceedings Article | 10 May 2005 Paper

Metal etcher qualification using angular scatterometry

Igor Jekauc, Jasen Moffitt, Sushil Shakya, Elizabeth Donohue, Prasad Dasari, Christopher Raymond, Mike Littau

Proceedings Volume 5752, (2005) https://doi.org/10.1117/12.598828

KEYWORDS: Semiconducting wafers, Etching, Metals, Scatterometry, Polymers, Profilometers, Scanning electron microscopy, Critical dimension metrology, Metrology, Tin

Read Abstract +

Proceedings Article | 10 May 2005 Paper

Lithography tool qualification using angular scatterometry

Mike Littau, Christopher Raymond, Prasad Dasari, Jasen Moffitt, Sushil Shakya

Proceedings Volume 5752, (2005) https://doi.org/10.1117/12.600413

KEYWORDS: Lithography, Scatterometry, Semiconducting wafers, Metrology, Optical lithography, Model-based design, Scanners, Process control, Photoresist materials, Diffraction gratings

Read Abstract +

Proceedings Article | 10 May 2005 Paper

Metrology of deep trench etched memory structures using 3D scatterometry

Peter Reinig, Rene Dost, Manfred Moert, Thomas Hingst, Ulrich Mantz, Jasen Moffitt, Sushil Shakya, Christopher Raymond, Mike Littau

Proceedings Volume 5752, (2005) https://doi.org/10.1117/12.599342

KEYWORDS: Scatterometry, Semiconducting wafers, Scanning electron microscopy, 3D modeling, 3D metrology, Metrology, Process control, 3D applications, Scattering, Scatter measurement

Read Abstract +

Proceedings Article | 24 May 2004 Paper

Comparison of solutions to the scatterometry inverse problem

Christopher Raymond, Michael Littau, Andrei Chuprin, Simon Ward

Proceedings Volume 5375, (2004) https://doi.org/10.1117/12.538662

KEYWORDS: Inverse problems, Scatterometry, Light scattering, Remote sensing, Scattering, Optimization (mathematics), Inverse optics, Semiconducting wafers, Critical dimension metrology, Scatter measurement

Read Abstract +

Scatterometry is a novel optical metrology that has received considerable attention in the silicon industry in the past few years. Based on the analysis of light scattered from a periodic sample, scatterometry technology can be thought of as consisting of two parts known as the forward problem and the inverse problem. In the forward problem, a scatterometer “signature” is measured. The signature is simply the measured optical response of the scattering features to some incident illumination, like laser light. In the inverse problem, the signature is analyzed in order to determine the parameters (such as linewidth, thickness, profile, etc) of the scattering features. Typically a rigorous electrodynamic model is used in the solution to the inverse problem, but due to the complexity of the model there is no direct analytic solution. Instead, a variety of numerical methods to solve the inverse problem have been proposed and utilized. The earliest widely used method of solution to the inverse problem involved the generation of a “library” of scatter signatures corresponding to discrete parameter combinations of the structure being measured. Once the library was generated, it was then searched in order to determine the best match to the measured signature. The parameters of the best match were then reported as the parameters of the measured signature. As the technology matured, other methods such as model optimization techniques also emerged. In fact, a variety of alternate techniques have been explored and reported, but a general study comparing the results (and hence the strengths and weaknesses) of the various techniques has yet to be performed. In this research, we shall report results from using several different solutions to the inverse problem on two applications (patterned resist and etched poly). The solution methods shall include the classic library search method as well as three common optimization methods. The results will show that each technique has strengths and weaknesses. For example, the library search methods are generally the most robust but also the most time consuming, and the optimization methods, while fast, are prone to reporting a local but not global minima.

Proceedings Article | 24 May 2004 Paper

Successful application of angular scatterometry to process control in sub-100-nm DRAM device

Jin-ah Kim, Seong-Jin Kim, Soo-Bok Chin, Seok-Hwan Oh, Doo-Hoon Goo, Suk-Joo Lee, Sang-Gyun Woo, Han-Ku Cho, Woo-Sung Han, Joo-Tae Moon, Christopher Raymond, Michael Littau, Byungjoo Youn, Chang-Jin Sohn

Proceedings Volume 5375, (2004) https://doi.org/10.1117/12.536312

KEYWORDS: Scatterometry, Critical dimension metrology, Scanning electron microscopy, Scatter measurement, Metrology, Semiconducting wafers, Light scattering, Process control, Light sources, Time metrology

Read Abstract +

Proceedings Article | 26 June 2003 Paper

Scatterometer-based scanner fingerprinting technique (ScatterLith) and its applications in image field and ACLV analysis

Changan Wang, Gary Zhang, Stephen DeMoor, Mark Boehm, Michael Littau, Christopher Raymond

Proceedings Volume 5040, (2003) https://doi.org/10.1117/12.485434

KEYWORDS: Monochromatic aberrations, Scanners, Critical dimension metrology, Image analysis, Lithography, Image processing, Error analysis, Optical lithography, Manufacturing, Semiconducting wafers

Read Abstract +

The ability to accurately, quickly and automatically fingerprint the lenses of advanced lithography scanners has always been a dream for lithographers. This is truly necessary to understand error sources of ACLV, especially when the optical lithography is pushed into 130 nm regimes and beyond. This dream has become a reality at Texas Instruments with the help of scatterometry. This paper describes the development and characterization of the scatterometer based scanner lens testing technique (ScatterLith) and its application in 193 nm and 248 nm scanner lens fingerprinting. The entire procedure includes a full field exposure through focus in a micro stepping mode, scatterometer measurement of focus matrix, image field analysis and mapping of lens curvature, astigmatism, spherical aberration, line-through pitch analysis and ACLV analysis (i.e. across chip line width variation). ACLV has been directly correlated with image field deviation, lens aberration and illumination source errors. Examples are given to illustrate its applications in accurate focus monitoring with enhanced capability of dynamic image field and lens signature mapping for the latest ArF and KrF scanners used in manufacturing environment for 130nm node and beyond. Analysis of CD variation across a full scanner field is done through a step-by-step image field correction procedure. ACLV contribution of each image field error can be quantified separately. The final across slit CD signature is further analyzed against possible errors from illumination uniformity, illumination pupil fill, and higher order projection lens aberrations. High accuracy and short cycle time make this new technique a very effective tool for in-line real time monitoring and scanner qualification. Its fingerprinting capability also provides lithography engineers a comprehensive understanding of scanner performance for CD control and tool matching. Its extendibility to 90nm and beyond is particularly attractive for future development and manufacturing requirements.

Proceedings Article | 26 June 2003 Paper

Evaluating scanner lens spherical aberration using scatterometer

Changan Wang, Gary Zhang, Colin Tan, Chris Atkinson, Mark Boehm, Jay Brown, David Godfrey, Michael Littau, Christopher Raymond

Proceedings Volume 5040, (2003) https://doi.org/10.1117/12.485437

KEYWORDS: Monochromatic aberrations, Spherical lenses, Scanners, Critical dimension metrology, Optical lithography, Semiconducting wafers, Phase measurement, Scatter measurement, Scanning electron microscopy, Distortion

Read Abstract +

Proceedings Article | 2 June 2003 Paper

Applications of angular scatterometry for the measurement of multiply periodic features

Christopher Raymond, Michael Littau, Byoungjoo Youn, Chang-Jin Sohn, Jin Kim, Young Kang

Proceedings Volume 5038, (2003) https://doi.org/10.1117/12.488116

KEYWORDS: Scatterometry, 3D modeling, Scatter measurement, Scanning electron microscopy, Light scattering, Diffraction, Data modeling, Semiconducting wafers, 3D metrology, Polarization

Read Abstract +

Proceedings Article | 16 July 2002 Paper

Novel implementations of scatterometry for lithography process control

Michael Littau, Christopher Raymond, Christopher Gould, Christy Gambill

Proceedings Volume 4689, (2002) https://doi.org/10.1117/12.473490

KEYWORDS: Lithography, Scatterometry, Diffraction, Diffraction gratings, Semiconducting wafers, Process control, Photoresist materials, Light scattering, Data modeling, Critical dimension metrology

Read Abstract +

Proceedings Article | 22 August 2001 Paper

Gauge control for sub-170-nm DRAM product features

Neal Lafferty, Christopher Gould, Michael Littau, Christopher Raymond

Proceedings Volume 4344, (2001) https://doi.org/10.1117/12.436754

KEYWORDS: Etching, Critical dimension metrology, Semiconducting wafers, Tolerancing, Lithography, Scatter measurement, Scanning electron microscopy, Metrology, Titanium, Diffraction

Read Abstract +

Proceedings Article | 22 August 2001 Paper

Asymmetric line profile measurement using angular scatterometry

Christopher Raymond, Michael Littau, Todd Pitts, Peter Nagy

Proceedings Volume 4344, (2001) https://doi.org/10.1117/12.436769

KEYWORDS: Scatterometry, Scatter measurement, Semiconducting wafers, Light scattering, Diffraction, Diffraction gratings, Photoresist materials, Atomic force microscopy, Metrology, Polarization

Read Abstract +

Proceedings Article | 22 August 2001 Paper

Scatterometry for shallow trench isolation (STI) process metrology

Christopher Raymond, Michael Littau, Richard Markle, Matthew Purdy

Proceedings Volume 4344, (2001) https://doi.org/10.1117/12.436798

KEYWORDS: Semiconducting wafers, Etching, Scatterometry, Scanning electron microscopy, Scatter measurement, Silicon, Atomic force microscopy, Metrology, Light scattering, Diffraction

Read Abstract +

Showing 5 of 15 publications

View contact details

UPDATE YOUR PROFILE

Is this your profile? Update it now.

Sign into your SPIE.org account

Don’t have a profile and want one?

Create an account on SPIE.org

Keywords/Phrases

Search In:

Publication Years