548
M. Saini et al.
1.3 Features and Applications of Spectroscopic Ellipsometry
Ellipsometry is a tool for optical measurement using visible/UV/IR polarized light
to probe various physical properties of materials by measuring the change in the
polarization of the reflected or transmitted light [3, 11]. This technique is named
as ellipsometry because an incident plane polarized light gets elliptical polarization
upon reflection. Ellipsometry directly measures the amplitude ratio (ψ) and the phase
difference (Δ) between s- and p-polarized light [3, 11]. In spectroscopic ellipsometry, (ψ, Δ) are measured as a function of wavelength or photon energy. Generally,
an ellipsometry measurement is performed at an angle of light incidence where the
sensitivity of the measurement is observed to be maximum. Ellipsometry can provide
the optical constant, and thin film structures along with very high sensitive measurement of thickness of each and individual layers of specimen [11]. Moreover, real-time
monitoring of growth, itching, or thermal oxidation processes even in solutions can
be characterized using ellipsometry technique. On the other hand, an inherent limitation of ellipsometry is the indirect nature of the characterization method i.e. an
optical model having an initial guess of film thickness and bulk optical constants is
essentially required to investigate the physical properties of a specimen.
1.4 History of Development and Future Aspects
It was Drude, who developed the first ever ellipsometry instrument in 1887 and also
derived the equations of ellipsometry along with the famous Drude model which
is extensively used for expressing the optical properties of metals [3, 12]. Aspnes
et al. have carried out the complete automation of spectroscopic ellipsometry in 1975
[13] as it was very much time consuming due to its manual operation. In 1984, the
first ever real-time monitoring spectroscopic ellipsometry instrument was developed
by Muller and Farmer [14]. Heretofore, there is a continuous improvement in the
spectroscopic ellipsometry instruments, albeit, the errors and ranges of measurement
are highly dependent on the ellipsometry instrument. The knowledge of instrument
and specimen are highly exigent for accurate analysis of ellipsometry data.
Now-a-days, spectroscopic ellipsometry is extensively used in characterizing
plasmonic- and meta-materials besides its rigorous and time-consuming data analysis through fitting optical models [3]. In addition, optically anisotropic specimen
are also being investigated using Mueller matrix approach of ellipsometry which
is adequate to completely describe the optically anisotropic behaviour of a specimen [9, 10]. Ellipsometry instruments and data analysis techniques are getting
matured due to advancement in the technology including the artificial intelligence
and automation. Thus, spectroscopic ellipsometry is becoming popular in the scientific world for precise characterizations of a wide class of materials including metals,
semiconductors, and insulators.
M. Saini et al.
1.3 Features and Applications of Spectroscopic Ellipsometry
Ellipsometry is a tool for optical measurement using visible/UV/IR polarized light
to probe various physical properties of materials by measuring the change in the
polarization of the reflected or transmitted light [3, 11]. This technique is named
as ellipsometry because an incident plane polarized light gets elliptical polarization
upon reflection. Ellipsometry directly measures the amplitude ratio (ψ) and the phase
difference (Δ) between s- and p-polarized light [3, 11]. In spectroscopic ellipsometry, (ψ, Δ) are measured as a function of wavelength or photon energy. Generally,
an ellipsometry measurement is performed at an angle of light incidence where the
sensitivity of the measurement is observed to be maximum. Ellipsometry can provide
the optical constant, and thin film structures along with very high sensitive measurement of thickness of each and individual layers of specimen [11]. Moreover, real-time
monitoring of growth, itching, or thermal oxidation processes even in solutions can
be characterized using ellipsometry technique. On the other hand, an inherent limitation of ellipsometry is the indirect nature of the characterization method i.e. an
optical model having an initial guess of film thickness and bulk optical constants is
essentially required to investigate the physical properties of a specimen.
1.4 History of Development and Future Aspects
It was Drude, who developed the first ever ellipsometry instrument in 1887 and also
derived the equations of ellipsometry along with the famous Drude model which
is extensively used for expressing the optical properties of metals [3, 12]. Aspnes
et al. have carried out the complete automation of spectroscopic ellipsometry in 1975
[13] as it was very much time consuming due to its manual operation. In 1984, the
first ever real-time monitoring spectroscopic ellipsometry instrument was developed
by Muller and Farmer [14]. Heretofore, there is a continuous improvement in the
spectroscopic ellipsometry instruments, albeit, the errors and ranges of measurement
are highly dependent on the ellipsometry instrument. The knowledge of instrument
and specimen are highly exigent for accurate analysis of ellipsometry data.
Now-a-days, spectroscopic ellipsometry is extensively used in characterizing
plasmonic- and meta-materials besides its rigorous and time-consuming data analysis through fitting optical models [3]. In addition, optically anisotropic specimen
are also being investigated using Mueller matrix approach of ellipsometry which
is adequate to completely describe the optically anisotropic behaviour of a specimen [9, 10]. Ellipsometry instruments and data analysis techniques are getting
matured due to advancement in the technology including the artificial intelligence
and automation. Thus, spectroscopic ellipsometry is becoming popular in the scientific world for precise characterizations of a wide class of materials including metals,
semiconductors, and insulators.