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Sample Setup: Metrology

Overview

A thin film on a substrate can act as an etalon, creating an interference pattern superimposed on the surface reflectivity when viewed in reflection. The spacing of the pattern’s sinusoidal peaks, when combined with the refraction index of the material, can be used to calculate the thickness of the material.

Spectrometer

The USB4000-VIS-NIR (350-1000 nm) is ideal for reflectometry of thin films. The spectrometer is preconfigured with Grating #3, which is blazed at 500 nm; an OFLV-350-1000 Filter to eliminate second- and third-order effects; and a 25 µm slit for optical resolution of ~1.5 nm (FWHM).

Sampling Optics

The R400-7-VIS/NIR Reflection Probe positioned at 90° measures specular reflectance from surfaces such as thin films. An LS-1 Tungsten Halogen Lamp and a STAN-SSH High-reflectivity Specular Reflectance Standard complete the sampling setup.

Measurements

Spectra observed in our operating software reveal oscillations caused by optical interference within the layers of the thin film substrate. Analysis of the wavelength position of the minima or maxima can determine either the thin film’s thickness (with the known refractive index of the film) or its refractive index (with the known film thickness). Keep in mind that the thickness of samples may not be uniform; we recommend measuring several locations on the film.

Ordering Information

Spectrometer Components	Price
USB4000-VIS-NIR General-purpose Spectrometer	$2887
Grating #3, 600 lines per mm, blazed at 500 nm	included
25 µm Slit as entrance aperture	included
DET4-350-1000 Detector with OFLV-350-1000 Order-sorting Filter	included

Sampling Components	Price
LS-1 Tungsten Halogen Light Source	$577
R400-7-VIS-NIR Reflection/Backscattering Probe	$577
RPH-1 Reflection Probe Holder	$104
STAN-SSH High-reflectivity Specular Reflectance Standard	$524
SpectraSuite Spectroscopy Operating Software	$199
ASP Annual Service Package	Call for Price

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