Determination of film thickness and surface profile using reflectometry and spectrally resolved phase shifting interferometry

Article

DOI: 10.1007/s12541-009-0086-0

Cite this article as:
Debnath, S.K., You, J. & Kim, SW. Int. J. Precis. Eng. Manuf. (2009) 10: 5. doi:10.1007/s12541-009-0086-0

Abstract

Surface profiling and film thickness measurement play an important role for inspection in semi conductor industry. White light source had been used as scanning white light interferometry and spectrally resolved white light interferometry for determining surface and film thickness profile. These techniques however failed for thinner film. Recently, reflectometry and spectrally resolved white light interferometry was combined for the same. This technique used Fourier Transform for the calculation of phase in spectral domain with the use of Linnik interferometer. In this method a large amount of carrier offset (carrier fringes) is required to be effective. This carrier fringes in spectrally resolved white light interferometry was achieved by increasing the optical path difference between the test and the reference surface. But, Linnik interferometer cause defocusing problem to create these carrier fringes. We propose in this paper to combine reflectometry and spectrally resolved phase shifting interferometry for measurement of surface and film thickness profile with the use of Michelson objective. Michelson objective will be convenient to implement as compared to the Linnik type and the use of phase shifting interferometry does not necessarily need large number of fringes in the spectral domain.

Keywords

Phase shifting interferometry Reflectometry Spectrally resolved white light interferometry Thin film 

Nomenclature

d

film thickness

N

refractive index of the film

R

reflection coefficient of the surface

r01, r12

Fresnel reflection coefficients

z

profile of the top surface

reflectance

β

phase due to path travel by the light inside the film

λ

wavelength of the light source

σ

wavenumber (= 1/λ)

θ

angle of incidence

ψ

phase due to the multiple reflection of the light source

η(d)

function to be minimized to get correct value of d

ϕ(σ)

Total phase

Copyright information

© Korean Society for Precision Engineering and Springer-Verlag Berlin Heidelberg 2009

Authors and Affiliations

  • Sanjit Kumar Debnath
    • 1
  • Joonho You
    • 2
  • Seung-Woo Kim
    • 1
    • 2
  1. 1.Precision Engineering and Metrology Laboratory, Department of Mechanical EngineeringKAISTDaejeonSouth Korea
  2. 2.KAIST Institute of Optical Science and TechnologyKAISTDaejeonSouth Korea