Optics: measuring and testing – Dimension – Thickness
Reexamination Certificate
2006-05-23
2006-05-23
Toatley, Jr., Gregory J. (Department: 2877)
Optics: measuring and testing
Dimension
Thickness
C356S364000
Reexamination Certificate
active
07050178
ABSTRACT:
An apparatus for improving the signal to noise ratio of measurements of the thickness of layers in a thin film stack uses a photoacoustic measurement system that includes a time differentiation system for inducing a delay in pump beam pulses. The time differentiation system uses, among other things, a birefringent element and other elements to control the polarization of pump beam pulses. Use of the apparatus involves applying a time varying voltage to an electro-optic modulator driver and setting a time differentiation step; or, in another embodiment, applying a time varying voltage to an electro-optic modulator to induce a fixed time delay delta-t between a vertically polarized pulse and a horizontally polarized pulse. The high frequency operation of the system provides for improved determinations of film thickness.
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Morath Christopher
Stoner Robert J.
Harrington & Smith ,LLP
Rudolph Technologies, Inc.
Stock, Jr. Gordon J.
Toatley , Jr. Gregory J.
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