In our offeer you can find:
- Imaging ellipsometr EP4
- Ellipsometer SE-2000
- Ellipsometer PUV
- Thin film porosimeter
Ellipsometry, which is an optical technique, measures the change of polarization of light, during passing through a medium. The phase of a polarized light exhibit distortion due to the layer structure during reflection, which enables us to extract material properties of the medium in this structure. It is important to ensure the polarization of incoming light is known, in order to successfully characterize the sample by measuring the polarization of the reflected light. In our case, Semilab uses the so-called rotating compensator technique, which means that the incoming light is first linearly polarized then there is varying phase difference added to the plarized light with a rotating angle. There is another polarizator on the detector side, which measures the actual polarization of the reflected light beam.
This measurement method has many advantages. First of all, it is an optical technique, so it is non contact and non destructive. It measures the layer thickness and optical functions of each layers in a multilayer structure. It has high sensitivity, because it is based on measuring the phase shift of a light beam travelling through a layer structure, and phase angle measurement does not depend on the absolute intensity of light. Using white light sources and monochromators, spectral information can be obtained about the sample.
Ellipsometry measures the ratio of the complex Fresnel reflection coefficients. As this is a complex number, it can be divided to an amplitude term, and a phase shift term, which correspond to the ellipsometric angles, Ψ and Δ. These parameters contains the physical properties of the layer structure, such as the layer thickness and refractive index. As this is a transcendental and highly nonlinear equation, it needs to be solved by numerical methods, on a model-based approach. During this procedure, the layer structure is considered with thickness and optical functions in the model. The relative phase shift is calculated and compared to measured quantities during a numerical regression procedure.
Why use ellipsometry?
Ellipsometry analyzes the change of polarization of light reflected from a sample and yields information about thin film layers that are often even thinner than the wavelength of the probing light itself. The change of amplitude and phase of the p and s components of the light after the reflection from the sample are dependent on film properties like thickness, refractive index, and absorption. Ellipsometry measures the change of the amplitudes and phases with the changing state of rotating polarization components. The measured values are psi and delta. These values need to be put into a computer based model of the sample materials to calculate the thickness, refractive index, absorption, and a variety of sample properties, including morphology, crystal quality, chemical composition, or electrical conductivity. Ellipsometry is an established technology to measure multilayer film thickness, refractive index, and absorption.
Why use imaging ellipsometry?
Imaging ellipsometry combines microscopy and auto nulling ellipsometry The microscopy aspect allows the direct visualization of your sample with an ellipsometric contrast image with a lateral resolution as small as 1 micron. This enables resolving sample areas 1000 times smaller than most micro spot equipped non-imaging spectroscopic ellipsometers. Imaging ellipsometry permits characterization of local sample parameter variation on a microscopic scale. This technology can measure the same ex-situ applications as non-imaging ellipsometers, and many more. It is dedicated to applications where you have lateral structures in the range of 50mm down to 1 micron. This includes patterned samples or where you have tiny samples like tips of a cantilever