Abstract: A system for inspecting and measuring the dimensions of patterned features on lithographic photomasks includes a confocal scanning microscope beneath which is mounted the photomask to be inspected. The photomask is moved to permit the imaging beam from the microscope to record reflectivity information at closely spaced points along a scan line at the metal-substrate interface within the photomask, and the unpatterned side of the mask is positioned facing the microscope so that the imaging beam passes through the transparent substrate material of the mask to the desired measurement plane. An objective lens specially corrected for imaging through transparent materials is used in the optical system, and compensating glass plates may be selectively placed between the objective lens and the photomask when the substrate of the mask is thinner than the thickness of transparent material for which the objective lens was corrected.

Abstract: A scanning confocal optical imaging system is utilized to read or measure data magnetically recorded on a magneto-optic disk. The system includes a laser for producing a linearly polarized beam and a beam splitter for directing the transmitted beam to the disk and for deflecting a portion of the reflected return beam from the disk to a photodetector. A pinhole plate is placed between the beam splitter and the disk for restricting the size of the transmitted and reflected beams, and a polarizer is positioned between the beam splitter and the photodetector to receive the deflected return beam and provide an output that discriminates between the differing directions of rotation of the polarization plane of the transmitted beam by the magnetized area on the disk so that the direction of magnetization of the magnetized area can be read by the photodetector.

Abstract: A system for determining surface profiles of specimens such as semiconductor wafers includes a drive for mounting the wafer for oscillatory movement along a line and an optical imaging system overlying the wafer for focusing a beam on a small sport on the wafer and including a photodetector for detecting the reflected sport from the wafer. The spot is scanned along the line on the wafer while the focal depth of the imaging system is progressively changed while the photodetector and connected digital circuitry generate a plurality of spaced output signals for each scan along the line so that data comprised of a series of spaced signals are provided at a plurality of focus levels extending through the surface profile of the wafer. Computer means are provided for analyzing the data and providing a graphical output of the surface profile.

Abstract: A system for determining surface profiles of specimens such as semiconductor wafers and for making linewidth measurements thereon includes a drive for mounting the wafer for oscillatory movement along a line and an optical imaging system overlying the wafer for focusing a beam on a small spot on the wafer and including a photodetector for detecting the reflected spot from the wafer. The spot is scanned along the line on the wafer while the focal depth of the imaging system is progressively changed while the photodetector and connected digital circuitry generate a plurality of spaced output signals for each scan along the line so that data comprised of a series of spaced signals are provided at a plurality of focus levels extending through the surface profile of the wafer. Computer means are provided for analyzing the data and providing a graphical output of the surface profile from which accurate linewidth measurements are made.

Abstract: A confocal optical imaging system includes a laser for producing a linearly polarized beam which is transmitted through the optical elements of the system, focused on a small spot on the target, and reflected back through the optical elements to a photodetector where the reflectance from the spot is determined. The optical elements include a pinhole plate for restricting the size of the transmitted and reflected beams which plate, along with other of the optical elements, can produce unwanted reflections adding optical noise to the reflected beam from the target. A retardation plate between the pinhole plate and the target alters the polarization of the transmitted beam relative to the reflected beam so that a polarizer will discriminate between the true reflected beam signal and the unwanted reflections to thereby improve the signal-to-noise ratio at the photodetector.

Abstract: A confocal optical imaging system includes a laser for producing a linearly polarized beam which is transmitted through the optical elements of the system, focused on a small spot on the target, and reflected back through the optical elements to a photodetector where the reflectance from the spot is determined. The optical elements include a pinhole plate for restricting the size of the transmitted and reflected beams which plate, along with other of the optical elements, can produce unwanted reflections adding optical noise to the reflected beam from the target. A retardation plate between the pinhole plate and the target alters the polarization of the transmitted beam relative to the reflected beam so that a polarizer will discriminate between the true reflected beam signal and the unwanted reflections to thereby improve the signal-to-noise ratio at the photodete ctor.