Ade Corporation

Ade Optical Systems Corporation

Noel S Poduje

Robert C Abbe

Roy E Mallory

Roy S Mallory

Neil H Judell

Peter Domenicali

Scott P Keller

Kirk Rodney Johnson

Michael E Fossey

Jaydeep K Sinha

Peter A Harvey

Alexander Belyaev

Randal K Goodall

Richard S Smith

Domenico Tortola

Daniel Klein

An apparatus for measuring semiconductor wafer shape that minimizes wafer distortion. The apparatus includes a plurality of wafer gripping fingers for holding a wafer in a predetermined position during wafer measurement. Each finger includes a groove that contacts the edge of the wafer. The groove and the wafer edge have respective radii of curvature, in which the radius of curvature of the groove is greater than that of the wafer edge. Each finger includes a rigid member having a recess formed in a central location at one end thereof, and a compliant material such as PEEK disposed in the recess in which the groove is formed. The compliant material extends a first distance beyond the rigid member at the central groove location and a second shorter distance beyond the rigid member on each side of the central location. Because the groove areas on each side of the central area are more rigid than the central groove area, the fingers can hold the wafer with a high degree of accuracy while reducing wafer distortion.

Wafer gripping fingers to minimize distortion

Apparatus and methods for calibrating a transducer measurement system having a plurality of subsystems, permitting total system calibration by a few selected adjustments without requiring complete system calibration when a new subsystem is added or a subsystem replaced and without requiring adjustments to be made to each individual subsystem. The measurement system provides a calibrated measurement signal indicative of a characteristic of an object with which the transducer interfaces. Each subsystem is characterized in terms of a minimum number of parameters associated therewith and the parameters are mathematically combined to reflect values of adjustable subsystem or system components. In this manner, variations associated with each separable subsystem from nominal, specified values, are combined and corrected by a single adjustment of a minimum number of selected adjustable components representing the degrees of freedom for errors in the system. In an alternate embodiment, a signal processor is responsive to the subsystem describing parameters for processing a digital replica of a measured signal to provide the calibrated measurement signal.

Apparatus and methods for measurement system calibration

In one aspect, the present invention provides an apparatus for transferring wafers to or from a wafer cassette having a plurality of wafer-receiving slots, wherein the apparatus comprises a wafer paddle which is adapted to be inserted into a wafer cassette alongside a wafer. Edge grippers carried by the wafer paddle releasible grip the wafer by its edges. A first capacitive sensor carried by the wafer paddle is oriented in a first direction for sensing information about a wafer in a wafer receiving slot of the wafer cassette. A second capacitive sensor carried by the wafer paddle is oriented in a direction perpendicular to the first direction for sensing additional proximity information about a wafer in a wafer receiving slot of the cassette. A transport mechanism produces movement of the wafer paddle along at least three axes of movement to permit transferring wafers to or from respective wafer receiving slots of the wafer cassette. In a more specific aspect, the transport mechanism produces movement along five axes: relative translational movement along orthogonal x, y and z axes, rotational movement about a rotational axis, and tilting movement of the wafer paddle about a paddle tilt axis.

Wafer transfer robot

A measurement station which rotates a wafer in a vertical plane and moves a scanning sensor linearly along an axis which is parallel to the wafer rotation plane, thus providing a spiral, or other, scan path across the wafer. The vertical orientation reduces errors from weight induced sagging, especially of large, e.g. 300 mm wafers. The measurement station includes wafer grippers which move in the wafer's plane for securing the wafer in position for rotation. The measurement station also includes master calibration gauges which simplify calibration and obviate the need for calibration test wafers. A technique for reducing vibration and assuring scan repeatability includes coasting of the wafer in rotation and coordinated linear probe motions for scanning. Probe measurement data obtained is digitized early and calibration, demodulation, filtering and other processing is done digitally.

Wafer testing and self-calibration system

A system for semiconductor wafer processing including wafer measurement and characterization having vertical wafer processing apparatus with which only the edge of a wafer is contacted. A wafer processing station is provided having a support bridge to which a rotor subassembly is attached. The rotor subassembly includes a housing and a rotor having a central aperture and a retention mechanism for retaining a wafer in a measurement position. A pair of pivotable probe arms includes one probe arm positioned on either side of the wafer. A sensor provides an image of a wafer prior to its retention by the retention mechanism in the measurement position in order to permit the retention mechanism to avoid any flat on the wafer. Additional sensors eliminate the effect of wobble or vibration of the rotor on wafer measurement results. Artifact removal processors are provided for removing errors in the measured wafer data and a database stores the uncorrupted and corrected data. The system couples with a data network to allow global viewing of wafer processing trouble spots. A correlation of information from actual data and wafer processing simulation is provided for allowing the application of corrective measures before processes deviate beyond control or specification limits.

Wafer handling and processing system

An alignment station for elements such as semiconductor wafers on a robot arm uses a rotating support and edge detector which in combination are operative to place a wafer on the rotating support, detect wafer alignment, move the wafer to bring it into alignment either on the rotating support itself or onto a separate station.

Robot prealigner

An edge detection system for measuring lateral position in the presence of height variations such as found in gauging the edge position of a wafer uses first and second capacitive probes formed of passive elements with the active components kept outside the probe and at a distance that permits a smaller, stabler and more economical probe to be located at the location of the wafer. The probes are instrumented in an electronic circuit having plural operational amplifiers that drive the probes to compensate the edge detection for wafer height effects.

Prealigner probe

A compensated capacitive probe system in which the probe and a guard ring are placed in the feedback path of an operational amplifier. An input signal is applied to the operational amplifier in combination with a portion of the guard signal. The resulting configuration compensates for stray capacitance at a measuring electrode of the probe and for the fact that the operational amplifier is other than mathematically ideal.

A.C. capacitive gauging system

An error compensated thickness measuring system utilizing first and second probes placed on opposite sides of a semiconductor wafer whose thickness is to be measured. The output of the probes is linearized and electronically processed to provide a signal representative of the thickness of the semiconductor wafer. The electronic processing includes an error compensating circuit which removes higher order error in the thickness signal attributable to the wafer being other than precisely centered between the two probes. The error compensating circuitry operates to produce a scaled higher order representation of the displacement of the wafer from the centered condition to combine this with the thickness signal to produce an error compensated signal. The present invention finds particular application in the thickness gauging of semiconductor wafers which represent a substantial impedance to circuit common and in which compensating circuitry is utilized to adjust for or control the potential of the ungrounded object.

Multi-probe grouping system with nonlinear error correction

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. That plane typically maps the other surface of the sample into a plane, for example, simulating the condition where the sample is held in an ideal vacuum chuck for semiconductor processing at which point surface flatness is needed. Other planes may be defined by least squares analysis and 3-point techniques, among others.

Wafer flatness station

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. Data is collected at each of the increments that is representative of a preselected characteristic of the object to be measured with a spacial resolution that is determined by the characteristic probe dimension and the data is digitally filtered to provide processed data representative thereof having a spacial resolution that is determined by the fractional increment of relative motion. In a preferred embodiment, the object measurement system and method of the instant invention has exemplary utility in a wafer profiling station having a capacitive sensor and operable to provide thickness data for regions of the wafer located within one probe-width of its edge. The capacitive sensor includes two capacitive probes each having a generally-rectangular sensing element that is surrounded by a generally-rectangular guard.

Improved spatial resolution measurement system and method

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. contributions fixture induced error are disclosed in order to provide a measurement accuracy not limited by the mechanical tolerances of the X, .theta., and Z moveable wafer after receiving chuck.

Growing community of inventors

Needham Heights, MA, United States of America

Noel S Poduje