Patent ID: 6182510
Filing Date: 2001-02-06
Classification: G01N

Abstract:
An apparatus for determining characteristics of a substrate, comprising:an acquisition and processing module configured to perform a characterization measurement, wherein the acquisition module is configured to (1) inject acoustic waves into the substrate at least one excitation point; and (2) generate a signal set representing a propagation state of the acoustic waves at respective interrogation points on the substrate; and the processing module is configured to (3) compute from the signal set a measurement set related to propagation of the acoustic waves between respective subsets of the interrogation points using a function relating the sets;the processing module being configured to use process functions to compute a respective process measurement set by performing the characterization measurement on the substrate at a respective process time and process location wherein process values of at least one characteristic associated with the substrate are unknown;the processing module being configured to use calibration functions to compute a respective wafer calibration measurement set by performing the characterization measurement on the substrate at a respective calibration time and calibration location wherein calibration values of the at least one characteristic are known; andthe processing module being configured to compute one set of the process values of the at least one characteristic between each respective subset of the interrogation points based on corresponding calibration and process measurement sets using a characterization sensitivity and the calibration values of the at least one characteristic.