How do you do ellipsometry?
Introduction. Ellipsometry is a technique often used to measure the thickness of a thin film. Generally speaking, the measurement is performed by polarizing an incident light beam, reflecting it off a smooth sample surface at a large oblique angle and then re-polarizing the light beam prior to its intensity measurement …
How does spectroscopic ellipsometry work?
Spectroscopic ellipsometry measures ψ and Δ, both of which describe the output elliptical polarization state after linearly polarized light is reflected obliquely off of a thin film sample. The parameters ψ and Δ are related to the complex Fresnel reflection coefficients according to: ρ = tan ψ eiΔ = rp / rs.
What is Psi and Delta in ellipsometry?
Psi and Delta represent the raw measurement from an ellipsometer. They describe the change in polarization that occurs when the measurement beam interacts with a sample surface. The incident light beam contains electric fields both parallel (p-) and perpendicular (s-) to the plane of incidence.
What is MSE in ellipsometry?
An estimator, like the Mean Squared Error (MSE), is used to quantify the difference between curves.
Is ellipsometry destructive?
Ellipsometry is a very sensitive measurement technique and provides unequaled capabilities for thin film metrology. As an optical technique, spectroscopic ellipsometry is non-destructive and contactless.
Who invented ellipsometry?
Paul Drude
The technique of ellipsometry was invented by Paul Drude in 1887 who used it to determine the dielectric function of various metals and dielectrics. For 75 years following Drude’s pioniering work only a handful of ellipsometric studies were done.
What is complex refractive index?
The complex refractive index m(λ) = mr(λ) + imi(λ), where λ is the free-space wavelength, mr is the real part of the refractive index, and mi is the imaginary part. The real part of a refractive index is the ratio of the free-space speed of light to the phase speed of an electromagnetic wave in the medium.
Which technique gives information about the thickness of film?
Spectroscopic ellipsometry can be used to measure layers in thicknesses ranging from a few nanometers to a few micrometers.
What is critical angle formula?
The critical angle is that of θi which gives a value of 90 degrees. If this information is substituted in the Snell’s Law equation, a generic equation can be obtained to predict the critical angle. The critical angle = the inverse function of the sine (refraction index / incident index).
How do you calculate refractive index?
Refractive index is also equal to the velocity of light c of a given wavelength in empty space divided by its velocity v in a substance, or n = c/v.
How do you measure film thickness?
The thickness of a single-layer film can be measured easily using a spectrophotometer. Note, however, that this is possible only for film thickness in a range of approximately 0.3 to 60 μm, and that the refractive index of the film material is required for measurement.
What is spin coating technique?
Spin coating is a technique used to spread uniform thin films on flat substrates by centrifugal force. The apparatus used for spin coating is called a spin coater, or a spinner. A solution of material is dispensed onto the center of a wafer, which is then rotated at high speed.
What is this tutorial about ellipsometry?
This tutorial provided by the J. A. Woollam is an introduction to ellipsometry for anyone interested in learning more about ellipsometry and its applications. This tutorial is written with the novice in mind, but experienced ellipsometry users will also benefit from the information presented in this discussion.
What is an analyzer in ellipsometry?
In ellipsometry, electromagnetic radiation is emitted by a light source and linearly polarized by a polarizer. It can pass through a compensator (retarder, quarter wave plate) and falls onto the sample. After reflection the radiation passes a second polarizer, which is called analyzer, and falls into the detector.
How is ellipsometry used to measure the optical response?
The measured response depends on optical properties and thickness of individual materials. Thus, ellipsometry is primarily used to determine film thickness and optical constants.
What is an ellipsometer used to measure?
Any ellipsometer will only measure characteristics of the light reflected from or transmitted through the sample. Ellipsometers do not measure film thicknesses or optical functions of materials directly, although these parameters can often be inferred very accurately from the ellipsometry measurements.