Methods for monitoring thickness of a conductive layer

Abstract

Methods and apparatuses for calibrating eddy current sensors. A calibration curve is formed relating thickness of a conductive layer in a magnetic field to a value measured by the eddy current sensors or a value derived from such measurement, such as argument of impedance. The calibration curve may be an analytic function having infinite number terms, such as trigonometric, hyperbolic, and logarithmic, or a continuous plurality of functions, such as lines. High accuracy allows the omission of optical sensors, and use of eddy current sensors for endpoint detection, transition call detection, and closed loop control in which a process parameter is changed based on the measured magnetic flux density change in one or more processing zones.

Dependencies are inferred from the claim text.