Abstract: A method and a system for measurement the geometrical parameters of ultra thin wafers with the thickness less than 200 microns. The measurement system comprises two measurement channels and a computer. Each measurement channel comprises a motor-positionable probe further comprising a back pressure probe and a capacitive probe. The capacitive probe is substantially cocentric with the back pressure probe. The air back pressure sensor is used to calibrate the capacitive sensor for a given dielectric permittivity of the conductive target, and the capacitive sensor is used to measure thickness, flatness, bow, and warpage of the ultra-thin electrically conductive target.

Abstract: A non-contact pneumatic-electric dimensional measurement system comprises a stable base on which a semiconductor wafer or workpiece to be measured is placed. A measurement head is held aloft over the wafer or workpiece and base by a rigid support bracket attached to the base. The tip of an air nozzle in the measurement head is directed at the wafer or workpiece and automatically extended to near contact. The nozzle is servo-positioned by an air sensor and motor combination that maintains an air gap between the tip and wafer of about 150 microns with an overall precision of about 3-4 microns. A Heidenhaim linear displacement gauge is attached to the air nozzle and is used to determine the nozzle position to within 0.5 micron. The dimension of the wafer or workpiece is determined to within 0.5 micron by combining the linear displacement gauge reading with an estimate of the air gap derived from a reading of the air nozzle backpressure that has an accuracy of about 0.1 micron.