Grazing Angle Illumination Scattering Apparatus
Original Publication Date: 1987-Aug-01
Included in the Prior Art Database: 2005-Feb-01
Micron size, particulate contamination on patterned semiconductor wafers can be detected by microscopic examination using grazing illumination from more than one source and aspect ratio gradation. In the figure, two lasers, 1 and 2, having different wavelengths, illuminate the area of the wafer 3 under inspection at oblique incidence from nearly opposite directions. The resulting scattered light is magnified and imaged by a microscope objective 4 onto a slit 5 and passes through a dispersive prism 6. This light is then imaged by a lens 7 onto a detector array plane 8 wherein two parallel images of a narrow band of the silicon wafer surface are seen. The intensities of light in these bands correspond to the intensities of the light reflected by one particular area element on the wafer.