Abstract: 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.

Abstract: In order to digitize with sufficient resolution an analog signal, which may be generated by a photodetector in a spectrophotometer, an improved analog to digital conversion system is provided having an integrator stage, an analog to digital converter, a microprocessor and interface circuits for providing communication between the microprocessor and a host computer. The integrator may include an operational amplifier with a capacitor in feedback relationship therewith for providing an output which varies linearly as function of time. The microprocessor operates the analog to digital converter to sample the integrator output at successive increments of time which increase in accordance with a binary relationship to an increment corresponding in binary value to the desired upper end of the resolution range. The digitized samples from the analog to digital converter are compared with a predetermined value in the upper end of the amplitude range of the converter.