VASE to Filmetrics material file conversion

The nanoFAB’s Filmetrics Resist and Dielectric Thickness Mapping System is a convenient tool to measure the thickness and uniformity of unpatterned films on wafers or other planar specimens, due to its location in the cleanroom, lack of any necessary specimen prepartion, non-destructive nature, and quick turnaround. However, a meaningful measurement can only be obtained if the optical constants—the refractive index n and extinction coefficient k as a function of wavelength—used in the reflectance model accurately represent those of the film being measured. While a library of standard materials exists in the Filmetrics software, these may deviate from the optical contants of actual films being used in one’s processing, due to differences in material stoichiometry, morphology, or other reasons.

Accurate optical constants and thickness for one’s films can be measured via variable angle spectroscopic ellipsometry (VASE), using either of the nanoFAB’s J.A. Woollam ellipsometery tools, but this technique is much slower than the Filmetrics, particularly if a uniformity map is desired. A good workflow is therefore to perform VASE on a film, then import the optical constants into the Filmetrics material library, which can then be used to obtain fast, accurate thickness measurements. Unfortunately, the native material file format output by the WVASE32 software cannot directly be read by the version of Filmetrics software available in the cleanroom.

To overcome this problem, the nanoFAB has developed a web app to convert WVASE32 .mat files into the .nnn and .kkk files required by the Filmetrics FILMeasure and FILMapper applications. Use the online form to choose a material category (metal, dielectric, etc.) and upload your .mat file; upon submission, the data is plotted and the converted optical constants (.nnn and .kkk files) are made available for download, and can be added to the Filmetrics material library. The web app is accessible both externally and to networked computers on nanoFAB tools, and the links to the converted files are accessible for at least 24 hours after submission.

We hope that our user community will find this web app helpful, to improve the accuracy and efficiency of thin-film characterization measurements.

For more information, please contact Aaron Hryciw.

Links

• Online VASE to Filmetrics conversion: toolbox.nanofab.ualberta.ca/vase2film