General Colloquium:

February 14 - 4:00pm Phys 223
(Coffee at 3:30p.m. in room 242)

E. Dan Hirleman

William E. and Florence E. Perry Head
School of Mechanical Engineering, Purdue University

CHARACTERIZATION OF NANO/MICROFEATURES ON SURFACES USING LIGHT SCATTERING

Abstract

Nonintrusive optical techniques for accurate sizing of discrete phases (particles, bubbles, cells, organisms) suspended in continuous media have been studied for years and have reached, for some applications, an advanced stage of development. In contrast, a related problem of considerable importance that has received less attention is that of accurate characterization of fine particles or other defects on and under surfaces. This capability is much needed in the fields of semiconductor and integrated circuit fabrication, digital storage media manufacturing, for research on contamination of optical components for both earth- and space-based applications, and for identifying hazardous materials. In this presentation our experimental and theoretical studies of light scattering by features on surfaces relevant to the semiconductor industry will be described. The experimental work involved measurements of angle-resolved light scattering signatures (for 64 scattering angles) from individual particles down to 200 nm in diameter and from ensembles of monodisperse particles down to 60 nm. Our experimental matrix included three angles-of-incidence (30, 45, and 75.3 deg), two wavelengths (632.8 and 488 nm), and a variety of surfaces including bare silicon, a silicon oxide thin film, polysilicon samples with three different roughnesses, and aluminum. Atomic force microscopy (AFM), transmission electron microscopy (TEM), and scanning electron microscopy (SEM) have also been used for independent characterization of the particle and surface topographies. The computational work has involved an approximate model involving modifications of Lorenz-Mie theory (for isolated spheres) to account for the surface effects, and discrete-dipole and finite-element time-domain solutions to Maxwell's equations. Experiments and predictions show good agreement, and the models are being used in predicting the performance of wafer scanners for various experimental conditions and for assisting in the design of future-generation surface defect characterization instruments. Finally, some results for scattering by biological agents and food-borne pathogens will be discussed.

Sponsors: Crane Naval Labs/U.S. Navy, the Semiconductor Research Corporation (SRC), USDA and member companies of the Consortium for Metrology of Semiconductor Nanodefects including ADE Optical Systems, AMD, Applied Materials, Duke Scientific, Hamamatsu/Inspex, Intel, KLA-Tencor, Lawrence Livermore Nat. Lab., SEMATECH, Sumitomo Sitix, and VLSI Standards.

Web site

http://ME.www.ecn.purdue.edu/ME/Fac_Staff/hirleman.whtml