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Title: Optical method for the determination of stress in thin films

Abstract

A method and optical system is disclosed for measuring an amount of stress in a film layer disposed over a substrate. The method includes steps of: (A) applying a sequence of optical pump pulses to the film layer, individual ones of said optical pump pulses inducing a propagating strain pulse in the film layer, and for each of the optical pump pulses, applying at least one optical probe pulse, the optical probe pulses being applied with different time delays after the application of the corresponding optical probe pulses; (B) detecting variations in an intensity of a reflection of portions of the optical probe pulses, the variations being due at least in part to the propagation of the strain pulse in the film layer; (C) determining, from the detected intensity variations, a sound velocity in the film layer; and (D) calculating, using the determined sound velocity, the amount of stress in the film layer. In one embodiment of this invention the step of detecting measures a period of an oscillation in the intensity of the reflection of portions of the optical probe pulses, while in another embodiment the step of detecting measures a change in intensity of the reflection of portionsmore » of the optical probe pulses and determines a time at which the propagating strain pulse reflects from a boundary of the film layer.« less

Inventors:
 [1]
  1. Barrington, RI
Publication Date:
Research Org.:
Brown Univ., Providence, RI (United States)
OSTI Identifier:
872118
Patent Number(s):
US 5864393
Assignee:
Brown University Research Foundation (Providence, RI)
DOE Contract Number:  
FG02-86ER45267
Resource Type:
Patent
Country of Publication:
United States
Language:
English
Subject:
optical; method; determination; stress; films; disclosed; measuring; amount; film; layer; disposed; substrate; steps; applying; sequence; pump; pulses; individual; ones; inducing; propagating; strain; pulse; probe; applied; time; delays; application; corresponding; detecting; variations; intensity; reflection; portions; due; propagation; determining; detected; sound; velocity; calculating; determined; embodiment; step; measures; period; oscillation; change; determines; reflects; boundary; layer disposed; probe pulse; time delays; optical method; optical pump; intensity variations; pump pulse; time delay; optical probe; film layer; sound velocity; individual ones; responding optical; detecting variations; /356/73/

Citation Formats

Maris, Humphrey J. Optical method for the determination of stress in thin films. United States: N. p., 1999. Web.
Maris, Humphrey J. Optical method for the determination of stress in thin films. United States.
Maris, Humphrey J. 1999. "Optical method for the determination of stress in thin films". United States. https://www.osti.gov/servlets/purl/872118.
@article{osti_872118,
title = {Optical method for the determination of stress in thin films},
author = {Maris, Humphrey J},
abstractNote = {A method and optical system is disclosed for measuring an amount of stress in a film layer disposed over a substrate. The method includes steps of: (A) applying a sequence of optical pump pulses to the film layer, individual ones of said optical pump pulses inducing a propagating strain pulse in the film layer, and for each of the optical pump pulses, applying at least one optical probe pulse, the optical probe pulses being applied with different time delays after the application of the corresponding optical probe pulses; (B) detecting variations in an intensity of a reflection of portions of the optical probe pulses, the variations being due at least in part to the propagation of the strain pulse in the film layer; (C) determining, from the detected intensity variations, a sound velocity in the film layer; and (D) calculating, using the determined sound velocity, the amount of stress in the film layer. In one embodiment of this invention the step of detecting measures a period of an oscillation in the intensity of the reflection of portions of the optical probe pulses, while in another embodiment the step of detecting measures a change in intensity of the reflection of portions of the optical probe pulses and determines a time at which the propagating strain pulse reflects from a boundary of the film layer.},
doi = {},
url = {https://www.osti.gov/biblio/872118}, journal = {},
number = ,
volume = ,
place = {United States},
year = {1999},
month = {1}
}

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