Ade Corporation

Kla Tencor Corporation

Ade Technologies

Roy E Mallory

Noel S Poduje

Scott P Keller

Jaydeep K Sinha

Neil Judell

Peter A Harvey

Peter Domenicali

Alexander Belyaev

Stephen MacLeod

Richard S Smith

Richard B Carter

A wafer edge-defect detection system with a probe assembly having one or more capacitive plates conforming in edge shape to an edge shape of a wafer; and processing electronics for electronically driving the one or more capacitive plates and for sensing an electrical signal representing capacitance between each one or more plates and the wafer. Filtering and demodulation techniques enhance the signal to noise ratio.

Wafer edge-defect detection and capacitive probe therefor

An improved non-contact capacitive displacement sensor that may be employed for accurately measuring small distances between the sensor and shaped targets. The non-contact capacitive displacement sensor includes a probe having a sensor element and a guard element. The guard element substantially surrounds the sensor element. At least the sensor element has a shape that substantially matches the shape of a target element.

Shaped non-contact capacitive displacement sensors for measuring shaped targets

A non-contact capacitive displacement measurement gage that provides high accuracy displacement measurements of well-connected targets and poorly-connected targets. The capacitive displacement measurement gage includes a capacitive probe, first and second amplifiers, and a signal generator. The capacitive probe includes a sensor electrode, a guard electrode, and a compensating electrode. The signal generator provides a predetermined voltage signal directly to the sensor electrode, to the guard electrode through the first amplifier having unity gain, and to the compensating electrode through the second amplifier having a predetermined transfer function. The second amplifier assures that substantially zero current is driven into the target element by the probe during gage operation, thereby allowing highly accurate displacement measurements of target elements having unknown or poorly controlled impedance.

Method for high-accuracy non-contact capacitive displacement measurement of poorly connected targets

A method for facilitating field replacement of sensors is presented. The replacement sensor's transfer function need only be measured, not adjusted, and the signal-processing unit's transfer function need only be adjusted, but not measured, to achieve simple field-replacement of sensors. With this method simple calculations and adjustments, typically expedited by means of a computer program, can be made in the field when sensor replacement is required. By way of the presently disclosed method sensor cost and size are not increased since no normalization techniques or components are required.

Method for facilitating the field replacement of sensors

A process for obtaining the periodic component in a data vector of data taken of a sensed property of an element driven by one or more rotary components over several rotations. The procedure comprises first forming the data vector asynchronously with respect to rotation of said one or more rotary components. A series of marker signals representing the rotation of the one or more rotary components is also established. From these the periodic component of data in said data vector is determined as a function of the data in the data vector and the marker signals.

Separation of periodic and non-periodic signal components

A mechanism to provider a bootstrapped power source for a differential operational amplifier includes a three-winding transformer having a first winding disposed between a positive voltage and a plus power input to the amplifier, yielding an initial plus voltage, a second winding disposed between a negative voltage and a minus power input to the amplifier yielding an initial minus voltage, and a third winding disposed between a ground and a plus input to the amplifier providing a feedback path. The differential operational amplifier output is connected to ground. The said amplifier minus input is connect to a signal and when the signal is displaced a first amount from a first voltage, the plus and minus power inputs are displaced approximately the same amount from the initial positive and negative voltages.

Self-bootstrapping transducer interface

A capacitive displacement sensor for measuring thin targets is presented. The plate of the measurement probe is designed to take into account the thin target shape and to provide accurate measurements of the thin target by reducing lateral movement sensitivity of the plate. The probe may also include a guard to reduce capacitive coupling of the plate with other structures which would affect the accuracy of the measurement.

Capacitive displacement sensor for measuring thin targets

A nonlinear current mirror for loop-gain control incorporates a resistor in one section of a current mirror which produces a nonlinear transfer function for the current mirror. When the nonlinear current mirror is included as part of a capacitive displacement gauge the gain of the gauge varies as a function of the input to the current mirror which compensates for the change in gain caused by the probe capacitance. Accordingly, the distance range and/or frequency response of the capacitive displacement gauge is increased.

Nonlinear current mirror for loop-gain control

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

An apparatus for bootstrapping an amplifier of a capacitive displacement transducer. The apparatus replaces a transformer with two capacitors and two resistors configured to provide biased supply voltages to the positive and negative power supply connections of an amplifier configured as a high impedance unity gain buffer in the transducer. The replacement of the transformer with a pair of standard capacitors and resistors provides for similar performance at a reduced size and cost.

Transducer Bootstrapping apparatus

A capacitive gaging system comprising a capacitive displacement sensor and an interface circuit is used to replace a Linear Variable Differential Transducer (LVDT). An output of the capacitive displacement sensor is modified by the interface circuit which provides an output signal or signals representative of different types of LVDT outputs. The capacitive displacement sensor and the interface circuit can then be used to replace the LVDT in an LVDT measurement system. Accordingly, the capacitive displacement sensor and the interface circuit replace the LVDT without replacing the rest of the measurement system.

Method and apparatus for emulation of a linear variable differential

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

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 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. The consecutive readings can be either the first reading of a new wafer identical with the reading of a previous wafer or two consecutive identical readings on the same wafer. Each reading, to be considered an acceptable reading of conductivity-type requires five consecutive, identical conductivity measurements over a predetermined time interval. Failure of such criteria produces a wafer defect indication.

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Bedford, MA, United States of America

Roy E Mallory