摘要:
Light scattered from illuminated spot on a patterned wafer is first passed through a di-electric filter and then by an optical fiber bundle to a detector. The di-electric filter controls the aperture of the light that is passed to a desired azimuth angle and the optical fiber further limits the aperture.
摘要:
A flaw detector for optically transmissive surfaces having a first light collector above the surface and a second light collector below the surface. A scanning light beam is directed into the first light collector through a beam entrance aperture and only light scattered from the surface is collected. Light specularly reflected from the surface exits the collector through the beam entrance aperture. Similarly, light passing through the surface enters the second collector, but the axial beam component is dumped through an opening in the second collector, while only diffracted light is collected. Preferably, two-stage light collectors are used with the first stage admitting the beam and generating a scattered or diffracted beam component, with the second stage admitting the scattered or diffracted beam component and integrating the component over a collection surface and sampling the integrated portion at a photoelectric detector. An electrical output signal from the detector may be displayed.
摘要:
A test device for calibrating an optical scanner wherein microscopic patterns of light scattering elements simulate the scattering of light from particles or flaws of different sizes. Simulation of different particles sizes is achieved by means of clusters or arrays of these light scattering elements having different areawise densities. Patterns of such clusters or arrays are disposed on a surface with intervening spaces where a random assortment of foreign particles may be expected. In this manner, the foreign particles may be directly compared to a test pattern. The test surface may be a semiconductor wafer having a thin, inert coating with openings therein forming the light scattering elements. The openings may be made by photolithographic techniques, i.e., masking and etching, so that various patterns on a surface may be all created simultaneously by the same process.
摘要:
Flat-field telecentric scan systems, each having a planar scanning reflector situated in a light path and mounted for movement about a scan axis, a concave spherical mirror fixed in a position in the light path an effective focal length away from the scanning reflector to provide a telecentric scan of the light beam, and a lens or mirror with spherical surfaces placed in the light path for providing a flat-field scan. The concave mirror and the additional lens or mirror element may be placed off of the symmetry axis to avoid light obstruction problems provided the tilt of the scanning reflector and the positions and orientations of the concave mirror and additional optical element are selected for a straight-line scan. The additional lens can be either before or after the concave mirror in the light path. It can also be positioned in the path of both light incident on and reflected from the concave mirrors. The lens and concave mirror can be integrally formed by providing a reflective coating on one lens surface. In several embodiments, astigmatism and coma can also be eliminated or minimized.
摘要:
An inspection apparatus for a light diffracting surface employs a planar array of individually addressable light valves for use as a spatial filter in an imaged Fourier plane of a diffraction pattern, with valves having a stripe geometry corresponding to positions of members of the diffraction pattern, blocking light from those members. The remaining valve stripes, i.e. those not blocking light from diffraction order members, are open for transmission of light. Light directed onto the surface, such as a semiconductor wafer, forms elongated curved diffraction orders from repetitive patterns of circuit features. The curved diffraction orders are transformed to linear orders by a Fourier transform lens. The linear diffraction orders from repetitive patterns of circuit features are blocked, while light from non-repetitive features, such as dirt particles or defects is allowed to pass through the light valves to a detector. Patterns of stripes can be recorded corresponding to the repetitive features of different integrated circuits. Different filters may be rapidly switched electronically in synchronization with a beam scanning a patterned surface inspecting different light diffracting patterns in different positions, allowing scattered or diffracted light from non-repetitive features to pass through the filter to a detector. A logical AND combination of two filters may be used so that two regions may be inspected in a single scan of the beam.
摘要:
A two-stage light collector, including a first stage which admits a scanning beam and a second stage which is optically connected to the first stage and has a light detector therein. The first stage has a shape which re-images diffusely scattered radiation from a target on which the radiation impinges. The first stage directs light toward an entrance aperture in the second stage which indirectly reflects light toward the detector associated with the second stage.
摘要:
A scanning laser contaminant and defect detector for reflective surfaces, having a light collector for increasing sensitivity to scattered light. The collector is preferably one quadrant of a spherical shell cradled between V-shaped reflective side walls. The collector has beam entrance and exit ports, as well as a detector port where a light detector resides. The collector is placed in proximity to a surface to be inspected. Light scattered from the test surface is directed to the reflective crown surface, then to the reflective side walls and ultimately to the detector.
摘要:
A controller provides a high voltage to maintain an electro-optic shutter in a transparent condition until a flash of light which would be harmful to personnel is sensed by a phototransistor. The controller then shorts the shutter to ground to minimize light transmission to the user and maintains light transmission at the pre-flash level for a predetermined time to allow the flash to subside. A log converter and differential trigger circuit keep the controller from being triggered by other light flashes which are not dangerous.