Abstract: An apparatus and method are disclosed for detecting the presence of particles on the surface of a material, such as a semiconductor wafer, using the principle of scattered light. Light from a mercury arc lamp is collimated by a Cassegrain mirror collimator. The collimated beam of light is deflected by an annular shaped 45.degree. mirror toward a truncated annular shaped inverted parabolic mirror. Light striking the parabolic mirror is reflected outward in all directions as a converging beam of light toward a ring mirror. Light striking the ring mirror is reflected inward and strikes the surface from all directions at an angle of about 78.degree. to 86.degree. from normal incidence as a small spot.

Abstract: A monochromatic imaging apparatus comprising a pair of similar diffraction gratings, a pair of focusing lenses, a pair of collimating lenses, an entrance slit, an exit slit and an intermediate slit, and means for concurrently moving the two gratings; wherein a polychromatic source image is placed at the entrance slit, and a collimating lens collimates the light rays from the source image and projects the collimated rays onto the first diffraction grating thereby to disperse the rays. The dispersed rays are then focused by the first focusing lens onto the intermediate slit, and then collimated by the second collimating lens onto the second diffraction grating which thereupon recombines the dispersed light. The recombined rays are then focused by the second focusing lens onto the exit slit.

Abstract: A method is disclosed for adjusting a polarizing or interference type video microscope system so as to achieve significant improvement in resolution, contrast, speed of recording, image fidelity and visibility of fine detail, the video microscope system including (1) a polarizing or interference type microscope having an iris diaphragm and a compensator and (2) a video camera having an adjustable gain control circuit and an adjustable DC restoration circuit. The method involves lowering the gain and the clamp level of the DC restoration circuit in the video camera to a minimum, then adjusting the microscope for optimum optical imaging conditions, these conditions including partly closing the iris diaphragm and setting the compensator for .+-. approximately the same bias retardation as the specimin (i.e. .lambda./100-.lambda./50), then opening the diaphragm to the maximal working aperture of the microscope objective and setting the compensator at a bias retardation of around .lambda./9 to .lambda.

Abstract: A video system having a television camera, a digital video signal processor coupled to the output of the television camera and a television monitor coupled to the output of the digital video signal processor is disclosed.

Abstract: A method and apparatus for detecting and measuring the number and sizes of impurities on the surface of a material, such as a semiconductor wafer, wherein high intensity collimated light is directed onto the surface, in the absence of any extraneous light, through a collimating mirror, and employing a point source, whereat the particles will scatter the light, and wherein the surface is viewed by a highly light sensitive TV camera which picks up the scattered light and displays same on a viewing screen. The intensity of scattered light will indicate the size of the particles when compared with a calibrated model. Advantageously, a broad range of light waves is employed and thus enables a range of sizes of particles to be detected by the light scattered thereby. Also, advantageously, with the use of ordinarily available equipment, the system can inspect wafer surfaces for particles having sizes as small as 0.3 microns.