The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
May. 23, 2006
Filed:
Jul. 12, 2002
Christopher Morath, Morristown, NJ (US);
Robert J. Stoner, Duxbury, MA (US);
Christopher Morath, Morristown, NJ (US);
Robert J. Stoner, Duxbury, MA (US);
Rudolph Technologies, Inc., Flanders, NJ (US);
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.