An optical inspection apparatus and method is provided that utilizes both
linear and nonlinear optical phenomena to detect defects. Embodiments
include irradiating a portion of the surface of an article, such as a
semiconductor device, with a light beam, such as a scanning laser at an
incident wavelength. The light emanating from the irradiated surface
portion is then separated into light at the incident wavelength and light
at one or more predetermined non-incident wavelengths, as by a diffraction
grating, prism or filters. The light at the incident and nonincident
wavelengths is sent to separate detectors, such as photomultipliers (PMT),
which respectively convert the detected linear optical phenomena
(representing, e.g., surface topography) into an electrical signal, and
the detected nonlinear optical phenomena, such as fluorescence, Raman
scattering and/or second harmonic generation, into electrical signals
representing, e.g., chemical composition and material interfaces. The
signal from each detector is sent to a processor, which generates a defect
map based on the information gleaned from both the linear and nonlinear
optical phenomena.
