Open AccessUncertainty improvement of geometrical thickness and refractive index measurement of a silicon wafer using a femtosecond pulse laser
Author(s) -
Saerom Maeng,
Jungjae Park,
O Byungsung,
Jonghan Jin
Publication year - 2012
Publication title -
optics express
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.394
H-Index - 271
ISSN - 1094-4087
DOI - 10.1364/oe.20.012184
Subject(s) - optics , materials science , wafer , refractive index , femtosecond , interferometry , laser , fourier transform , bandwidth (computing) , silicon , optoelectronics , physics , telecommunications , computer science , quantum mechanics
We have proposed a modified method to improve the measurement uncertainty of the geometrical thickness and refractive index of a silicon wafer. Because measurement resolution based on Fourier domain analysis depends on the spectral bandwidth of a light source directly, a femtosecond pulse laser having the broad spectral bandwidth of about 100 nm was adopted as a new light source. A phase detection algorithm in Fourier domain was also modified to minimize the effect related to environmental disturbance. Since the wide spectral bandwidth may cause a dispersion effect in the optical parts of the proposed interferometer, it was considered carefully through numerical simulations. In conclusion, the measurement uncertainty of geometrical thickness was estimated to be 48 nm for a double-polished silicon wafer having the geometrical thickness of 320.7 μm, which was an improvement of about 20 times that obtained by the previous method.