Ellipsometry takes advantage of the coherent nature of light to determine thickness of thin films. Light interacts with the various interfaces within the film stack and eventually recombines with the initial surface reflection causing constructive or destructive interference in the detected signal.
The CompleteEASE thickness pre-fit algorithm quickly estimates the film thickness for an unknown layer by leveraging the presence of interference oscillations in the raw measured data. This feature helps to avoid local minima in your fit by providing an automated starting value that is close to the optimized solution.
Global fitting is a feature used to search a defined parameter space for a global minimum. This approach is helpful to avoid local minima that might prevent the correct fit from being obtained. A standard global fit will scan two or more parameters as a grid. Each point gets assigned an MSE value, and the minimum MSE value along with its corresponding parameters is reported at the end.
CompleteEASE also features a randomized global fit algorithm, which will search the parameter space randomly instead of in a grid. The advantage of this method is that an MSE threshold can be set. Once a point below the MSE threshold has been found, the fit is then followed by a standard Levenberg- Marquardt fit. Tests have shown a reduction in global fit time of 5x or better using this feature.
Using the Alternate Models function in CompleteEASE is a huge time saver when testing your films for common complexities. In addition to surface roughness and grading, CompleteEASE can now check for simple anisotropy. CompleteEASE allows you to compare the results from each of these models, see which one CompleteEASE suggests as the best fit, and select which one you want based on the results.
Absorptions in materials can be caused by electronic transitions, lattice vibrations, and free carrier absorptions, among other things. The nature of absorption resonances vary by material and are dependent on a variety of factors. For this reason, mathematical descriptions for absorbing materials are traditionally more complex. CompleteEASE features multiple tools for modeling absorbing films easily and efficiently.
The B-Spline layer was developed in CompleteEASE as an alternative to direct data inversion or oscillator models and has revolutionized optical modeling of semi-absorbing materials. The B-Spline has the following benefits:
+Reduced number of fit parameters
+Complete flexibility in optical constants for any material
+No guesswork about where to place oscillators and what type to choose
The B-Spline is especially useful for describing complex dispersion shapes in a physical manner.
The latest versions of CompleteEASE feature an automated B-Spline feature which enables users to determine the optical properties of semi-absorbing materials with just a few clicks without the need of background information on the material or a reference file.
The General Oscillator layer, or Gen-Osc, was developed to simplify the modeling of material optical constants. The Gen-Osc layer models the dielectric function of a material as a linear summation of wavelength-dependent oscillators.
The oscillators described mathematically in the Gen-Osc layer represent the dipole response of the material and can be used to describe comparable physical parameters, such as band gap.
CompleteEASE provides a convenient Gen-Osc parameterization layer which helps to define the initial starting values of each oscillator in the model. Build your own oscillators using the parameterization window, beginning with a number of built-in functions, including: