Abstract: A robot arm in which a hand or end effector placed at the end of, and pivotally joined to first and second pivotally coupled arms is caused to experience linear, straight line motion in response to a single rotary actuator at the far end of the further most arm. A series of belts and pulleys of different sizes coordinate the motion of the two arms and the hand in order to produce straight line or radial motion in response to a single rotary actuator. The robot arm has particular application in semiconductor wafer handling systems in such capacity as transferring wafers between storage cassettes and test platforms and in this application is married to Z and .theta. motion drives.

Abstract: An automatic wafer flatness station is disclosed for obtaining a flatness profile of a semiconductor wafer or other sample from thickness data. The sample to be flatness profiled is supported so that it maintains its natural shape. A processor coupled to a capacitive thickness sensing head and to the support medium is operative to successively position each of a plurality of preselected points of the sample into proximity with the capacitive thickness sensing head for measuring the thickness of the sample at the corresponding point. An analog-to-digital converter converts the thickness measurement into data that is stored in a data table in system memory, the individual addresses of which correspond to the spacial location on the sample of each such preselected point. The processor is operative after the data table is compiled for each sample to compute the flatness profile of one surface therefrom relative to a selectable plane.

Abstract: The present invention discloses means and method for obtaining an increased spacial resolution from a sensor that includes a probe having a characteristic physical dimension that limits its spacial resolution. Such a probe may include a rectangular sensing surface wherein the probe sensitivity increases with surface area while the spacial resolution decreases with increasing surface area. The probe and an object to be measured are controllably moved relatively to each other in such a way as to define preselected increments of relative movement that are selected to be a fraction of the characteristic physical dimension of the probe.

Abstract: The present invention discloses apparatus and method for electronically determining and compensating mechanical fixture induced errors from desired object related information in a measurement system such that data acquisition is obtained with a precision very much better than the manufacturing tolerances of the mechanical fixture. In the preferred embodiment, bow and warp profiles of a semiconductor wafer are obtained with an X, .theta., and Z moveable wafer-receiving chuck that have an accuracy very much better than the mechanical tolerances of the X, .theta., and Z moveable chuck. The system provides for measurement of objectrelated information in plural orientations. Signal processing is disclosed for separating out of the object related information X and .theta. fixture induced error contributions to the data arising from mechanical tolerance of the fixture. Signal processing is disclosed for compensating bow and warp profiles of semiconductor wafers in accordance with the X and .theta.

Abstract: A conductivity-type sensor, typically for use in a wafer sorting system, for detecting the conductivity-type of semiconductor wafers. In measuring conductivity, a two-contact probe is applied to the semiconductor wafer and any static charge which may have been accumulated on the wafer is initially discharged at an accelerated rate. The charge state is measured and an acceptable level of discharge requires repeated indications of discharge below a predetermined level. Discharging and charge measurement is repeated a predetermined number of times as necessary to accomplish discharging or the wafer identified as defective. The conductivity-type of the discharged wafer is read from the rectified polarity of an oscillating signal applied to the contacts. A valid indication of conductivity-type requires two consecutive readings of the same conductivity-type.

Abstract: A conductivity-type sensor, typically for use in a wafer sorting system, for detecting the conductivity-type of semiconductor wafers. In measuring conductivity, a two-contact probe is applied to the semiconductor wafer and any static charge which may have been accumulated on the wafer is initially discharged at an accelerated rate. The charge state is measured and an acceptable level of discharge requires repeated indications of discharge below a predetermined level. Discharging and charge measurement is repeated a predetermined number of times as necessary to accomplish discharging or the wafer identified as defective. The conductivity-type of the discharged wafer is read from the rectified polarity of an oscillating signal applied to the contacts. A valid indication of conductivity-type requires two consecutive readings of the same conductivity-type.

Abstract: An automatic wafer alignment station is disclosed for aligning a wafer having flats about its centroid with the flats oriented in a preselected spatial direction. The wafer is held by a vacuum chuck which is operatively connected to a motor driven carriage for controlled movement about an X axis, to a .theta. actuator carried by the carriage for controlled rotation about the axis of the chuck, and to a Z actuator carried by the carriage for controlled motion about a Z axis. An X capacitive sensor and a Z capacitive sensor are positioned near the wafer. An X processing and Z compensating circuit is responsive to the X and the Z capacitive sensor output signals and provides an electrical signal that has values which exclusively represent the position of the edge of the wafer along the X axis only over a predetermined angular range. Circuit means including an A/D converter and a microprocessor respond to the electrical signal and produce a plurality of corrective signals to the X, Y, and .theta.

Abstract: A self inverting gauging system for such parameters as capacitively sensed distance or inductively sensed resistivity in which the sensor provides an output inversely varying with the dimension of interest. The gauge typically includes a dual slope integrator responsive to a reference value on the up integration and to the sensor output on the down integration. The interval of the down integration necessary to reset the integrator to the original value varies directly, rather than inversely, with the dimension of interest and is typically provided as the digital output indication of a counter. In the application to resistivity gauging, the up integration reference signal is preferably provided by the output of a thickness gauge such that the ultimate counter display represents element resistivity compensated for thickness.

Abstract: A system for reducing higher order nonlinearities in the linearized output of a dimension gauging probe in which the dimension gauging probe provides an output varying inversely with the physical dimension gauged which is in turn linearized to a signal varying proportionally with the physical dimension. Higher order nonlinearities, an error condition, which deviate the correspondence between the gauged dimension and the output from a linear or straight-line function, are reduced by feedback of the linearized output to the probe and, preferably, by feedforward of a portion of the probe output signal to the linearized signal.

Abstract: A self inverting gauging system for such parameters as capacitively sensed distance or inductively sensed resistivity in which the sensor provides an output inversely varying with the dimension of interest. The gauge typically includes a dual slope integrator responsive to a reference value on the up integration and to the sensor output on the down integration. The interval of the down integration necessary to reset the integrator to the original value varies directly, rather than inversely, with the dimension of interest and is typically provided as the digital output indication of a counter. In the application to resistivity gauging, the up integration reference signal is preferably provided by the output of a thickness gauge such that the ultimate counter display represents element resistivity compensated for thickness.

Abstract: A noncontact gauge for edge detecting of semiconductor wafers in a test rig which indexes between circuits in the semiconductor wafer to provide functional tests upon them. The noncontact gauge includes a capacitive probe having an elongated finger that is bent into position a few thousands of an inch above the wafer when positioned for circuit tests in order to detect whether the circuit test system, in indexing from circuit to circuit in the row and column matrix of integrated circuit chips in the wafer, has moved to one edge or the other of the water. The edge detection system operates with conventional wafer test systems which raise and lower the wafer between tests to index from one integrated circuit to the next in the wafer matrix.

Abstract: A system for capacitively gauging distance to an element which is not in a low impedance path to ground. The gauging system operates to provide an indication of distance with the potential on the element at a defined level, typically ground. Several embodiments are presented for making this measurement. A first operates to measure distance at periodic instances when the defined potential exists. A second embodiment uses phase opposite excitation to produce a defined potential at the element either by specific placement of the element or through a feedback control over element potential. The system of the present invention may be adapted for use in capacitive thickness measurement on an ungrounded or highly resistive element.

Abstract: A self-calibration system for use with a dimension-measuring probe. The self-calibration system includes a probe fixture which permits alternative orientation of the probe toward the work piece being gauged, or toward a readily available reference such as free space and a dimension reference typically of virtual infinite size. A closed loop feedback circuit is provided to develop a compensating signal for combination with the probe output to yield a dimension representing signal. The compensating signal is automatically set with the probe oriented toward the reference dimension to cause the dimension representing signal to correspond to a known value. Thereafter, the compensating signal is held constant and gauging of work piece dimensions can continue with system errors eliminated by the compensating signal.