Abstract: A profilometer has a constant force mechanism for biasing of the stylus arm. The mechanism has a centrally-aligned configuration of the moving magnet relative to the magnetic coil and also has a magnetic shield isolating these elements from other ferromagnetic materials in the assembly. The moving magnet is made of a material that is hard magnetically and the magnetic shield is made of a series of low hysteresis, high permeability materials. The force thus generated by the stylus biasing device is very linear with the drive current upon the magnetic coil at any particular position of the stylus, thereby allowing for control and predictability of the stylus force upon the surface to be profiled. This predictability is used for dynamic stylus force adjustments during profiling of a specimen. The profilometer is also equipped with a balanced, spring-loaded stylus-stabilizing sensor assembly, task-specific dual-view optics for protection of the delicate stylus assembly, and a temperature drift compensator.

Abstract: An apparatus for both deflecting a beam of light illuminating a spot on a surface and varying the size of the spot, electronically, without changing any system components. The apparatus includes an acousto-optic deflector driven with a linear FM signal produced by a chirp signal generator. The linear FM signal is characterized with a dispersion rate, and the chirp signal generator includes a chirp dispersion selector to vary the dispersion rate. A beam of collimated light passes through the acousto-optic deflector and appropriate focusing optics image the beam onto a spot in a nominal focal plane. The chirp dispersion selector sets the dispersion rate in accord to a nominal rate, resulting in the beam illuminating a spot in the focal plane. Generally, the focal plane coincides with a wafer surface, of the type having periodic and non-periodic features on it. The spot size may be varied from that of a diffraction limited spot to a spot whose maximum size is system dependent.

Abstract: A method and system for spectroscopic ellipsometry employing reflective optics to measure a small region of a sample by reflecting radiation (preferably broadband UV, visible, and near infrared radiation) from the region. The system preferably has an autofocus assembly and a processor programmed to determine from the measurements the thickness and/or complex refractive index of a thin film on the sample. Preferably, only reflective optics are employed along the optical path between the polarizer and analyzer, a sample beam reflects with low incidence angle from each component of the reflective optics, the beam is reflectively focused to a small, compact spot on the sample at a range of high incidence angles, and an incidence angle selection element is provided for selecting for measurement only radiation reflected from the sample at a single, selected angle (or narrow range of angles). The focusing mirror preferably has an elliptical shape,to reduce off-axis aberrations in the focused beam.

Abstract: 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.

Abstract: A method for calibrating an ellipsometer, and an ellipsometer including a processor programmed to control the analyzer, polarizer, and other ellipsometer components, and to process the data measured by the ellipsometer to perform the calibration method automatically. Where the ellipsometer's polarizer rotates and the analyzer remains fixed during measurement, the method determines coarse approximations of values A.sub.0 and P.sub.0, and then processes reflectivity data obtained at two or more analyzer angles to determine refined approximations of the values A.sub.0 and P.sub.0, where P.sub.0 is the angle of the polarizer's optical axis at an initial time, and A.sub.0 is the offset of the actual orientation angle of the analyzer from a nominal analyzer angle. Preferably the ellipsometer is a spectroscopic ellipsometer, the reflectivity data determine a tan.psi. spectrum and a cos.DELTA. spectrum for each of the analyzer angles, and the coarse approximations of A.sub.0 and P.sub.

Abstract: A surface height detection and positioning device for use in a surface inspection system. An incident beam of light impinges obliquely upon the surface, and a position detector is disposed to receive light reflected from the surface. The position detector has a sensitivity characteristic graded along a direction transverse to the surface, so that the output of the position detector is used to determine a height of the surface. The device can be incorporated into a particle detection system that scans patterned wafers with obliquely incident light to search for particles with a particle detector positioned to receive scattered light. In one embodiment, the position detector can have a width that is graded along the direction transverse to the surface, so that a scan line on the surface that is focused upon the position detector crosses the width of that detector in a time that varies as a function of the height of the surface.

Abstract: An apparatus and method for inspecting a substrate, such as a semiconductor wafer, includes crossed cylindrical optical elements that form an elliptical beam that is caused to scan in parallel fashion at an oblique angle to the substrate. Preferably, the smaller dimension of the elliptical beam is perpendicular to the direction of the scan of the beam across the wafer. A reflector converts an angularly varying beam to a telecentrically scanning beam and also provides focusing only in the direction parallel to the telecentric scan. On the other hand, a cylinder lens has a focusing power only in the direction perpendicular to the telecentric scanning.

Abstract: A method and apparatus for performing conductance measurements on a sample using an eddy current probe, without the need for measurement or knowledge of the separation between probe and sample. The probe comprises sense and drive coils mounted in close proximity to each other (or a single coil which functions as both a sense and drive coil), circuitry for producing AC voltage in the drive coil, and a meter for measuring in-phase and quadrature components of induced voltage in the sense coil. Look-up table data can be generated for use in subsequent measurements on samples of unknown conductance by performing eddy current measurements on samples having different known conductances to generate reference lift-off curves, processing the reference lift-off curves to determine a conductance function relating each known conductance to a location along a selected curve, and storing conductance values determined by the conductance function for different points on the selected curve as the look-up table data.

Abstract: The position detector has a sensitivity characteristic graded along a direction transverse to the surface, so that the output of the position detector is used to determine a height of the surface. A surface height detection and positioning device for use in a surface inspection system. An incident beam of light impinges obliquely upon the surface, and a position detector is disposed to receive specularly reflected light, producing a plurality of electrical signals, with a mechanical window, defining an aperture, placed in front of the detector. The aperture's width, along the scan direction, is of sufficient size so as to create a train of signals from each of the plurality of electrical signals, having a frequency equal to the scan frequency. These electrical signals carry information responsive to both the position of reflected beam impinging on the detector and the beam's intensity and are, in turn, related to a height of the surface.

Abstract: An optical surface scanner for semiconductor wafers and like substrates having one channel with a detector receiving collected scattered light and another channel with a detector receiving reflected light. The scattered light signal is indicative of surface haze, particle count and size, while the reflected light signals are indicative of film thickness and/or surface properties as in the case of an opaque or absorbing layer. The latter signal may be used to correct the particle count and size determination and may also be used simultaneously for thin film measurement. The reflectivity or thin film measurement signals may be used to characterize a film layer controller to improve the accuracy of the deposited thickness of the layer.

Abstract: A method of locating particle and defect features on a periodically patterned surface uses multiple threshold intensity levels to identify features in the data stream produced by scanning the surface with a light beam and detecting the light scattered from the surface. High thresholds are assigned to regions of the surface with high background scatter, while low thresholds are assigned to regions of the surface with low background scatter. The scattered light is detected with a wide dynamic range detector producing high resolution 12-bit pixel data capable of resolving the smallest particles and defects of interest in low scatter regions, while avoiding saturation in high scatter regions. Periodic pattern features are removed from the data by mapping features from a plurality of periodically repeating die on the surface to a single die map and looking for overlapping features. Unique, nonoverlapping features are determined to correspond to particles and defects.

Abstract: A stylus profilometer having a counterbalanced stylus with a motion transducer using a vane moving between parallel, spaced-apart, conductive plates which damp the motion of the vane by means of trapped air. The vane forms an electrode with the plates so that the combination is a pair of capacitors in a balanced bridge arrangement. Motion of the stylus causes an unbalance of the bridge indicative of the extent of stylus motion. A lever arm associated with the stylus has a tip influenced by a magnetic field which biases the stylus or controls force on a surface to be measured. The entire assembly has a very low moment of inertia to reduce the effects of vibration on the stylus and thereby increase resolution of the device and reduce damage to the substrate.

Abstract: 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.

Abstract: An apparatus used to inspect patterned wafers and other substrates with periodic features for the presence of particles, defects and other aperiodic features in which a spatial filter placed in the Fourier plane is used in combination with either broadband illumination, angularly diverse illumination or both. In contrast to prior devices that direct light from a single monochromatic source through a pinhole aperture stop, embodiments are describes that illuminate a patterned substrate using (1) a single monochromatic source with a slit-shaped aperture stop for angularly diverse illumination, (2) a single broadband source with a pinhole aperture stop for broadband illumination, (3) a single broadband source with a slit-shaped aperture stop for both broadband and angularly diverse illumination, or (4) multiple sources with an aperture stop for each source for at least angularly diverse illumination.

Abstract: An apparatus and a method for measuring the radius of curvature of a surface using a laser beam with a wavelength selectable from a plurality wavelengths are disclosed. The present invention avoids poor measurement due to destructive interference of the beams reflected at a thin film's upper and lower surfaces. The present invention is applicable to laser reflection stress measurement apparatuses of both scanning and beam-splitting types.

Abstract: A broadband area-division beamsplitter that includes a pair of abutting triangular prisms providing two surfaces that are in optical contact in certain areas and are out of optical contact in other areas. One prism surface is substantially planar while adjoining surface of the other prism has alternating protrusions and depressions. The protrusions contact the substantially planar surface to form an optically continuous medium for light transmission. The depressions do not contact the planar surface forming gaps. The two surfaces are oriented on a diagonal so that light incident through one of the other prism faces is incident on the adjoining surfaces at an angle larger than the critical angle, providing total internal reflection at the out-of-contact gap regions. The protrusions and depressions on the one prism surface may be in the form of a corrugation or a checkerboard or some other patterns. The reticulation size of the pattern may be less than about 10 .mu.

Abstract: A thin film thickness monitor using successive reflection of a polychromatic light beam off of reference thin film of variable optical thickness and a sample thin film whose thickness is to be determined, in which a monochromatic light source is used beforehand to first determine the actual optical thickness of the reference thin film at each relative position of the beam and reference thin film. In one embodiment, the ratio S/R of detected light intensity S from the sample thin film and detected light intensity R from the reference thin film is found for each relative position and the position at which the ratio is a maximum is determined. In another embodiment, this ratio is corrected by a corresponding ratio S.sub.1 /R.sub.1 derived from a bare wafer substrate. The sample can then be located behind additional optical surfaces, such as a vacuum port without causing substantial errors.

Abstract: A surface inspection apparatus having multiple inspection stations to inspect a wafer for a number of characteristics. The wafer is placed on a chuck connected to a rack-and-pinion or equivalent system so that the wafer simultaneously rotates and translates under the fixed position of the inspection stations. A single light source may be used by all stations in turn. One station may be a particle detector with collection optics receiving a small select portion of the light scattered from the wafer surface. A second station may be a roughness detector with a collection system to direct a large portion of scattered light to a detector. A position sensitive detector may be used to determine the slope of the wafer surface at an inspection point when the wafer is not clamped to the chuck, giving a measure of surface deformation. These or other stations are positioned about either of two inspection points at which the beam from the light source may be directed.

Abstract: 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.

Abstract: A particle imager and method for imaging particles on surfaces of substrates. A surface is raster scanned by a collimated light beam and particles on the surface are detected by the scattered light caused by the particles. During a scan path the intensity of the scattered light is measured forming intensity traces and location addresses for the detected particles. Data from each scan path is stored in memory. The imager is pre-calibrated with a test wafer having light scattering marker points spaced at known positions thereon. Scanning the test wafer, a clock measures time elapsed from a start position to each marker point. The corresponding elapsed times and known address locations are stored in memory for reference during data collection.