Ade Corporation

Alexander Belyaev

Noel S Poduje

Roy E Mallory

Jaydeep K Sinha

Peter A Harvey

Peter Domenicali

Richard S Smith

This method removes high frequency noise from shape data, significantly improves metrology system () performance and provides very compact representation of the shape. This model-based method for wafer shape reconstruction from data measured by a dimensional metrology system () is best accomplished using the set of Zernike polynomials (matrix L). The method is based on decomposition of the wafer shape over the complete set of the spatial function. A weighted least squares fit is used to provide the best linear estimates of the decomposition coefficients (Bnk). The method is operable with data that is not taken at regular data points and generates a reduced data field of Zernike coefficients compared to the large size of the original data field.

Specimen topography reconstruction

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

Growing community of inventors

Wayland, MA, United States of America

Alexander Belyaev