07/31/2018

Measurement of SU-8 photoresist thickness, homogeneity and topography

SU-8 is a high contrast, epoxy based photoresist for microprocessing and other microelectronic applications where a thick, chemically and thermally stable image is required. SU-8 has very high optical transparency over 360 nm, making it ideal for imaging, best for permanent applications where it is exposed, baked and left in place.

Measuring the thickness and homogeneity of SU-8 films, which can be up to several hundred micrometers thick, is a major challenge for most non-contact optical processes.

The FRT MicroProf® with the interferometric sensor CWL FT offers the optimal solution to measure SU-8 photoresist thicknesses.

The CWL FT is based on the spectral evaluation of the superposition of partial waves of a white light source reflected at the interfaces of a transparent layer. At a given layer thickness and refractive index, the intensity of the superimposed partial beams varies with the wavelength. The spectrum then shows a typical interference pattern. From this spectrum and the refractive index of the layer material, the sensor calculates the thickness of transparent layers that are measured at high resolution with vertical resolutions from 10 nm. With the CWL FT the layer thickness can be evaluated at a given position, along a profile or over the entire surface to evaluate its coating homogeneity.

The MicroProf® uses the interferometric sensor for locally resolved, high-precision coating thickness measurements. In a multi-sensor arrangement with the interferometric measuring head and a confocal chromatic distance sensor, the customer has an extremely powerful measuring system for fast, locally resolved layer thickness and topography measurements at. With the MicroProf® a high-resolution 3D measurement of the homogeneity of the photoresist on wafers up to 300 mm can be performed. The complete wafer is measured quickly and non-destructively. The degree of automation ranges from manually operated measuring systems such as the MicroProf® 300, which automatically execute predefined programs, to fully automated wafer handling including automatic pre-alignment and fine alignment in the MicroProf® MHU.

The analysis program FRT Mark III is used for the evaluation of topography data as well as layer thickness measurements in the FRT measuring tools. The results of the 3D mapping include the maximum, minimum and average photoresist thickness.

Whether laboratory, development, quality assurance or production - FRT offers the suitable measuring technology for your application. Do not hesitate to contact us if you have any questions. Our experts will be glad to help you solve your measurement tasks by creating the best possible system configuration for you. In our opinion, a comprehensive solution consists not only of hardware and software development but also of supplementary support and effective technical customer service. FRT provides on-site support through a global network of subsidiaries and distributors. FRT Remote Support enables our experts to support customers worldwide.