How does ellipsometer work?
Ellipsometry measures a change in polarization as light reflects or transmits from a material structure. The polarization change is represented as an amplitude ratio, Ψ, and the phase difference, Δ. The measured response depends on optical properties and thickness of individual materials.
How does ellipsometry measure thickness?
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.
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.
What is N and K in ellipsometry?
The refractive index (n) and extinction coefficient (k) are related to the interaction between a material and incident light, and are associated with refraction and absorption (respectively). They can be considered as the “fingerprint of the material”.
How do you measure refractive index?
A Refractometer is the instrument used to measure refractive index (RI). A refractometer measures the extent to which light is bent when it moves from air into a sample and is typically used to determine the refractive index of a liquid sample.
Who invented ellipsometry?
The technique of ellipsometry was invented by Paul Drude in 1887 who used it to determine the dielectric function of various metals and dielectrics.
What is the symbol of refractive index?
symbol n
Refractive index is usually represented by the symbol n, or sometimes μ .
What is meant by dispersive power?
Definition of dispersive power : the power of a transparent medium to separate different colors of light by refraction as measured by the difference in refractivity for two specified widely differing wavelengths divided by the refractivity at some specified intermediate wavelength.
What is K in ellipsometry?
What is extinction coefficient in ellipsometry?
The extinction coefficient describes the loss of wave energy to the material. It is related to the absorption coefficient, , as: Light loses intensity in an absorbing material according to Beer’s Law: Thus, the extinction coefficient relates how quickly light vanishes in a material.
What is an ellipsometer?
An Ellipsometer at LAAS-CNRS in Toulouse, France. Ellipsometry is an optical technique for investigating the dielectric properties (complex refractive index or dielectric function) of thin films. Ellipsometry measures the change of polarization upon reflection or transmission and compares it to a model.
What is the principle of ellipsometry?
The principle of ellipsometry is simple: The change in the polarization of light reflected from the sample surface is measured by taking the amplitude ratio of two perpendicularly polarized beams. The angle of incidence can be varied.
What determines the polarization change in an ellipsometer?
The exact nature of the polarization change is determined by the sample’s properties (thickness, complex refractive index or dielectric function tensor). Although optical techniques are inherently diffraction-limited, ellipsometry exploits phase information (polarization state), and can achieve sub-nanometer resolution.
Why ellipsometry for microelectronics?
Interest in ellipsometry has grown steadily since the 1960s as it provided the sensitivity necessary to measure nanometer-scale layers used in microelectronics.