Fwd: University PhD Dissertation Defense of Bing Dai

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From: Claire Nicholas <claireni@stanford.edu>
Date: Thu, Nov 4, 2010 at 10:29 AM
Subject: Re: University PhD Dissertation Defense of Bing Dai
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Department of Applied Physics

University PhD Dissertation Defense

Keyhole Diffraction Microscopy for Semiconductor Circuit Inspection

Bing Dai

Applied Physics PhD Candidate

Research Advisor: Professor R. Fabian Pease

December 2, 2010 @1:00 P.M.

Location: Allen Building (Formerly CIS-X), Room 101

ABSTRACT

Non-destructive inspection of integrated circuits requires a microscope that features high resolution (<20 nm) and high penetration (>0.07mm of silicon substrate), thus suggesting the use of x-ray microscopy. The advent of intense coherent sources of hard (<1nm wavelength) x-rays has led to the study of x-ray diffraction microscopy in which the image is reconstructed from the far-field diffraction pattern. Because this pattern records only intensity information, additional information, e.g. the phase distribution, is needed for image reconstruction. Here this information is provided by illuminating the sample with a collimated beam of well-defined shape and thus is a form of 'keyhole diffraction microscopy'.  The research featured computer simulations, scaled optical experiments, scaled soft (1.4nm) x-ray experiments and one hard x-ray experiment. The geometry and periodicity of the sample itself were found to affect the reconstruction. Illumination with asymmetric shapes (such as a triangle) sharply bounded gave the best reconstruction.  The results of scaled optical experiment conducted under blind conditions (no a priori knowledge of the sample) suggest that a resolution of 10nm should be readily achievable at an x-ray wavelength of 0.18 nm.