Article

Through-focus scanning-optical-microscope imaging method for nanoscale dimensional analysis

National Institute of Standards and Technology, Gaithersburg, MD 20899, USA.
Optics Letters (Impact Factor: 3.18). 10/2008; 33(17):1990-2. DOI: 10.1364/OL.33.001990
Source: PubMed

ABSTRACT We present a novel optical technique that produces nanometer dimensional measurement sensitivity using a conventional bright-field optical microscope, by analyzing through-focus scanning-optical-microscope images obtained at different focus positions. In principle, this technique can be used to identify which dimension is changing between two nanosized targets and to determine the dimension using a library-matching method. This methodology has potential utility for a wide range of target geometries and application areas, including nanometrology, nanomanufacturing, semiconductor process control, and biotechnology.

Full-text

Available from: Ravikiran Attota, Sep 23, 2014
5 Followers
 · 
252 Views
  • [Show abstract] [Hide abstract]
    ABSTRACT: Measurements of the spatial resolution (resolving power) of an automated interference microscope, based on the Linnik MII-4M microinterferometer, are described. The results obtained are compared with similar values calculated for traditional optical images, described by the Abbe theory. The possibility of overcoming the diffraction limit of resolution using the interference microscope is confirmed.
    Measurement Techniques 08/2013; 56(5):486-491. DOI:10.1007/s11018-013-0232-z · 0.19 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: This paper reports on an investigation to determine whether through-focus scanning optical microscopy (TSOM) is applicable to micrometer-scale through-silicon via (TSV) reveal metrology. TSOM has shown promise as an alternative inspection and dimensional metrology technique for FinFETs and defects. In this paper TSOM measurements were simulated using 546 nm light and applied to copper TSV reveal pillars with height in the 3 μm to 5 μm range and diameter of 5 μm. Simulation results, combined with white light interferometric profilometry, are used in an attempt to correlate TSOM image features to variations in TSV height, diameter, and sidewall angle (SWA). Simulations illustrate the sensitivity of Differential TSOM Images (DTI’s) using the metric of Optical Intensity Range (OIR), for 5 μm diameter and 5 μm height TSV Cu reveal structures, for variation of SWA (Δ = 2°, OIR = 2.35), height (Δ = 20 nm, OIR = 0.28), and diameter (Δ = 40 nm, OIR = 0.57), compared to an OIR noise floor of 0.01. In addition, white light interferometric profilometry reference data is obtained on multiple TSV reveal structures in adjacent die, and averages calculated for each die’s SWA, height, and diameter. TSOM images are obtained on individual TSV’s within each set, with DTI’s obtained by comparing TSV’s from adjacent die. The TSOM DTI’s are compared to average profilometry data from identical die to determine whether there are correlations between DTI and profilometry data. However, with several significant TSV reveal features not accounted for in the simulation model, it is difficult to draw conclusions comparing profilometry measurements to TSOM DTI’s when such features generate strong optical interactions. Thus, even for similar DTI images there are no discernible correlations to SWA, diameter, or height evident in the profilometry data. The use of a more controlled set of test structures may be advantageous in correlating TSOM to optical images.
    SPIE Advanced Lithography; 04/2013
  • [Show abstract] [Hide abstract]
    ABSTRACT: We measure the effective flexure width of a pair of microelectromechanical systems (MEMSs) by measuring their change in comb drive capacitance upon deflection from applied voltage. This effective width is the value that a corresponding model must have in order to match the performance of the true device. Due to process variations, small changes in width from layout have been shown to increase stiffness by as much as 100%. Existing measurement methods can be costly, have unknown accuracy, are not amenable to industrial-scale batch testing, depend on the measurements of additional quantities, and so on. Our electrical probing method appears to address many of these issues. Our method requires an actuating voltage and capacitance sensing of a pair of MEMS that only differ in layout flexure width. We test our method using a low-cost capacitance meter and compare our results against a high-cost scanning electron microscope technique. We achieve nanometer scale uncertainty. [2013-0253]
    Journal of Microelectromechanical Systems 08/2014; 23(4):972-979. DOI:10.1109/JMEMS.2014.2301803 · 1.92 Impact Factor