Mr. Robert M. Peters Profile

Robert M. Peters

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Publications (4)

Proceedings Article | 24 March 2006 Paper

Improved profile measurement accuracy via feed-forward spectroscopic ellipsometry

Robert Peters, Suresh Lakkapragada

Proceedings Volume 6152, 61522I (2006) https://doi.org/10.1117/12.656447

KEYWORDS: Critical dimension metrology, Atomic force microscopy, Spectroscopic ellipsometry, Metrology, Lithography, Photoresist materials, Signal processing, Photomasks, Optics manufacturing, Optical testing

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In recent years, optical metrology methods, based on spectroscopic ellipsometry (SE), have gained a strong foothold for use in measuring the 2-dimensional profiles of integrated device features. While optical methods generally provide superior metrology performance compared to other metrology methods, there still remain some challenges to meet precision and accuracy requirements as integrated device geometries continue to shrink at an aggressive rate. Process engineers are employing several new techniques in order to meet device patterning requirements while maintaining manufacturing-worthy process windows. These techniques include thinning the photoresist layers and adding additional underlayer films to act as hard masks for subsequent pattern transfer steps. Thinning the photoresist layer reduces the aspect ratio of patterned grating targets, which, in turn, reduces the signal-to-noise (S/N) ratio of the optical profile measurement. The additional films in the process stack below the gratings increase the number of optical interfaces that must be taken into account when building the optical model for the measurement. The increased complexity of the optical model increases the likelihood that there will be cross-correlation between the underlying films and the grating profile parameters (Critical Dimension or CD, Height, and Sidewall Angle or SWA). The reduction in S/N and increase in cross-correlation often have negative impacts on the precision and overall accuracy of the reported values for the grating profile parameters. In this paper, we will discuss a methodology to overcome the issues described above. The methodology involves performing a standard SE film thickness measurement on an open pad area in close proximity to the grating target of interest. The thickness values are then fed forward to a subsequent SE measurement of the grating target. With the underlayer thickness values fixed based on the film thickness measurement, only the grating profile parameters are solved for during the grating measurement. Decoupling the underlayer film measurement from the grating measurement, greatly reduces, and even eliminates cross-correlation between parameters. Both SE measurements are completed with a total move-acquire-measurement (MAM) time that is <10 seconds per pair, and the resulting values reported for CD, Height, and SWA are more accurate when compared to reference metrology such as Atomic Force Microscopy (AFM). Supporting data will be presented from measurements taken on a 65nm technology node gate lithography process. Using the feed-forward process, the correlation and slope of profile parameters measured via SE compared to AFM measurements is greatly improved. Furthermore, systematic anti-correlation between resist height and SWA that was observed during simultaneous measurement of the film stack and grating is eliminated when the film measurement is decoupled and fed-forward into the grating measurement.

Proceedings Article | 24 May 2004 Paper

Production control of shallow trench isolation (STI) at the 130-nm node using spectroscopic ellipsometry-based profile metrology

Robert Peters, Ray Chiao, Timothy Eckert, Rene Labra, Dario Nappa, Susan Tang, Jarvis Washington

Proceedings Volume 5375, (2004) https://doi.org/10.1117/12.534085

KEYWORDS: Etching, Metrology, Silicon, Critical dimension metrology, Process control, Manufacturing, Profilometers, Transmission electron microscopy, Spectroscopic ellipsometry, Semiconducting wafers

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Shallow Trench Isolation (STI), is a critical process module in the manufacture of advanced CMOS devices. To achieve proper control of the STI process, multiple parameters such as film thickness, etched trench depth, and critical dimension (CD) must be measured with a high degree of precision and accuracy. Historically, these varied parameters were required to be measured independently using different metrology techniques/tools. Film thickness required measurement via reflectometry or ellipsometry, etched trench depth required measurement via profilometer or Atomic Force Microscope (AFM), and CD required measurement via low voltage Scanning Electron Microscope (CD-SEM). This paper will demonstrate the use of Spectroscopic Ellipsometry, via KLA-Tencor’s SpectraCD tool, to simultaneously provide all critical parameters of interest for the STI process, with a single in-line measurement. This metrology technique has been developed and evaluated for process control and product disposition at STI etch, on 130nm generation logic devices manufactured in two Texas Instruments’ fabrication facilities -- the DMOS 5 200mm facility and the DMOS 6 300mm facility. A brief description of the SpectraCD measurement theory and STI profile measurement solution for both dense and isolated structures will be given. Details will be provided on the use of real time regression to accelerate metrology model development. This will be followed by data generated from actual STI production material. Precision-to-tolerance (P/T) ratios well below 0.1 will be demonstrated for all parameters of interest on the STI etch measurements. Measurement matching across multiple SpectraCD tools, well within 130nm node process tolerances, will be demonstrated. Correlation of these measurements to other baseline metrology techniques (profilometer, Spectroscopic Ellipsometer or SE, CD-SEM) will also be presented. Finally, a discussion of the Return-on-Investment (ROI) that may be realized from combining three separate measurements into a single measurement will be provided.

Proceedings Article | 2 June 2003 Paper

Improved gate process control at the 130-nm node using spectroscopic-ellipsometry-based profile metrology

J. Scott Hodges, Yu-Lun Lin, Dale Burrows, Ray Chiao, Robert Peters, Srinivasan Rangarajan, Kamal Bhatia, Suresh Lakkapragada

Proceedings Volume 5038, (2003) https://doi.org/10.1117/12.485002

KEYWORDS: Etching, Metrology, Critical dimension metrology, Transistors, Spectroscopic ellipsometry, Process control, Semiconducting wafers, Oxides, Control systems, Semiconductors

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The ability to control the cross-sectional profile of polysilicon gate structures on semiconductor devices is paramount to maximize product yield and transistor performance. Tighter control of gate profile parameters leads to a tighter distribution of transistor speeds, resulting in more optimized and consistent device performance. Furthermore, the ability to correlate physical in-line profile measurements taken at gate patterning process steps, to back-end-of-line device parametric test results, enables semiconductor manufacturers to minimize the cost per good die produced, by accurately screening out-of-spec product early in the process flow. The significant increase in the number of chips on today's 300mm wafers heightens the importance of obtaining reliable in-line data. In addition, the reduction of design rules to 130nm and below is driving precision requirements on metrology to <1nm, in order to maintain acceptable precision-to-tolerance (P/T) ratios. Historical methods of in-line metrology (Low Voltage Scanning Electron Microscopy, Atomic Force Microscopy, Electrical Critical Dimension Measurement) all face limitations with regards to precision, correlation, or throughput. This paper will demonstrate the use of Spectroscopic Ellipsometry to provide fast, accurate, and precise two-dimensional profile information on polysilicon gate structures. This metrology technique is currently being utilized for in-line process control and product disposition, at the gate lithography and etch process steps, on 130nm generation logic devices manufactured in Texas Instruments' DMOS 6 300mm wafer fabrication facility. A brief description of the measurement theory and gate profile measurement solution for both dense and isolated structures will be given. This will be followed by data generated from DMOS 6 production material. Using Spectroscopic Ellipsometry, precision results of <0.5nm for CD and height, and <0.25 degrees for profile sidewall angle were obtained at both the lithography and etch measurement steps. The use of CD and sidewall angle information in an APC loop to improve control over the gate trim etch process will also be discussed. Data will be presented showing univariate and multivariate correlation of gate etch profile parameters to post-metalization transistor drive current (IDrive) that is equivalent or superior to existing metrology techniques. Finally, examples of where Spectroscopic Ellipsometry has both increased sensitivity and shortened response time to gate etch process excursions will be presented.

Proceedings Article | 2 June 2000 Paper

Overlay metrology productivity and stability enhancements using an offline recipe database manager (RDM)

Stephen DeMoor, Robert Peters, Todd Calvert, Stephanie Hilbun, George Beck, Kristi Bushman, Russell Fields

Proceedings Volume 3998, (2000) https://doi.org/10.1117/12.386456

KEYWORDS: Databases, Overlay metrology, Semiconducting wafers, Manufacturing, Metrology, Pattern recognition, Chlorine, Optics manufacturing, Target recognition, Optical alignment

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