Polarization of Light Scattered by Particles on Silicon Wafers.
Polarization of Light Scattered by Particles on Silicon
Sung, L. P.; Mulholland, G. W.; Germer, T. A.
Surface Characterization for Computer Disks, Wafers, and
Flat Panel Displays. Proceedings. SPIE Proceedings
Series Volume 3619. Society of Photyo-Optical
Instrumentation Engineers (SPIE). January 28, 1999, San
Jose, CA, Society of Photo-Optical Instrumentation
Engineers, Bellingham, WA, 80-89 pp, 1999.
light scattering; particles; silicon; polystyrene
Bidirectional ellipsometry has been developed as a
technique for distinguishing among various scattering
features near surfaces. Employing incident light with
fixed polarization, the technique measures the principal
angle of polarization and the degree of linear
polarization of light scattered into directions out of
the plane of incidence. This technique has been
previously shown to be successful at distinguishing
between subsurface defects and microroughness.
Theoretical models have predicted that the polarization
of light scattered by particles should also be different
than that scattered by subsurface defects and
microroughness. In this paper, experimental results will
be presented which show good agreement with these models
for a range of sizes of polystyrene latex spheres on
silicon wafers. The results demonstrate that the
polarization of light scattered by particles can be used
to determine the size of particulate contaminants on
silicon wafers and other smooth surfaces. The model
calculations, based on different degrees of
approximation, demonstrate that the mean distance of a
particle from the surface is the primary determinant of
the scattered light polarization for small scattering