Chapman Instruments, Inc.

John E Stephan

Edward J Merritt, Jr

Donald Paul McClimans

Shu W Wang

Dag Lindquist

John A Teleska

Silvio P Marchese-Ragona

Thomas C Bristow

Matthew E Seelig

Robert Bryant

A system for non-contact measurement of thickness of a test object. A laser beam is split into two identical directly opposed input beams. A calibration object of known thickness causes beams to be reflected from sides of the test object. Each reflected beam passes through sensing means including a pinhole aperture and a photodiode sensor. Maximum sensor output defines first and second focal points a known distance apart. The calibration object is removed, and the test object is inserted into the path of the input beams, creating focus position intensity curves for the reflected beams. By determining the deviation, at maximum photodiode output, of the positions of the test object reflecting surfaces from the positions of the calibration object surfaces, the test object thickness can be readily and accurately determined.

Method and apparatus for measuring wafer thickness

A fully automated surface profiling system having a loading chamber and an adjacent measurement chamber containing a phase differential laser optical scanning system and a five-axis positioner having a vacuum chuck for holding and orienting a wafer for surface profile measurement. The positioner can displace a mounted wafer lengthwise and crosswise of the chamber, can rotate the wafer about vertical and horizontal axes through the positioner, and can rotate the wafer about its own axis. Each motion is motor-driven and can be carried out independently of all the others or in compound motion as needed. The positioner can accommodate a series of replaceable chucks for holding wafers of different diameters. The loading chamber has a cassette dock for receiving a cassette containing wafers to be tested, a robotic server, and a prealigner. All operations within the profilometer are controlled by a programmable CPU at a control station. Test results and analysis can be displayed on an onboard monitor or printed out or stored or transmitted. In operation, the robotic server selects a wafer from the cassette, presents the wafer to the prealigner for centering and orientation, and transfers the wafer through a slot into the measurement chamber and installs the wafer on the positioner for measurement. The positioner orients the wafer responsive to program commands from the CPU, and the desired surface profile measurements are made. When all measurements have been completed on a wafer, the robotic server removes the wafer from the positioner, returns it to the cassette, and selects another wafer for testing.

Automated optical surface profile measurement system

Growing community of inventors

Rochester, NY, United States of America

John E Stephan