Patent ID: 6593738
Filing Date: 2003-07-15
Classification: G01B

Abstract:
An apparatus for measuring thickness and deviations from thickness of a thin conductive film on a substrate, comprising:a rigid frame; support means movably attached to said rigid frame; inductive means rigidly connected to said support means, said inductive means being capable of generating an inductive current in said thin conductive film when located at a distance from said conductive film sufficient for generating said inductive current, said inductive means being precalibrated with respect to a material and thickness of said coating film for predetermined values of said distance so that by measuring electrical characteristics of said inductive means it is possible to match said electrical characteristics with the thickness of said conductive film; and distance stabilization means rigidly connected to said support means and hence to said inductive means, said distance stabilization means being intended for maintaining said predetermined values of said distance constant during measurement of said thickness, said distance stabilization means having an actuating mechanism for moving said support means together with said distance stabilization means and said inductive means with respect to said conductive film; said inductive means comprising an oscillating electric circuit formed by an inductive coil, a capacitor, means for measuring said electrical characteristics, and an alternating current generator; said distance stabilization means comprising an electronic unit and an optical measurement means; said optical measurement unit comprising a microinterferometer for optically measuring deviations of said distance from said predetermined distance and for generating an optical signal; said electronic unit having means for processing said optical signal, means for converting said optical signal into an electrical signal, and means for sending said electrical signal to said actuating mechanism, said electronic unit comprising a double-based photodiode, a differential amplifier connected to said double-based photo-diode, a proportional integral derivation regulator connected to said differential amplifier, and an amplifier connected to said proportional integral derivation regulator and to said actuating mechanism.