In-Situ Film Thickness and Stress Measurement Using Infrared Sensing

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The proposed research project presents a new method for measuring the thickness of thin films. A non-destructive, non-contacting infrared imaging system is synchronized to an AC heat source located within or below the film layer of interest. An AC approach is chosen to exploit differencing schemes that enable high-resolution thickness measurements. The proposed method provides a new tool for measuring the thickness of film coatings with implications in both research and technology. Preliminary experiments have shown that the proposed method is perfectly suitable for measuring film thickness in the range of several microns to millimeters. This proposal aims to extend the method to nanometer thick films by utilizing a radiative heat transfer scheme. The proposed experimental method can be implemented into a production environment for closed-loop feedback control during film deposition. The method is also amenable to quality control in high throughput production environments. As such, the proposed experimental method will significantly improve coating processes and dramatically decrease the time and expense required to improve coating performance and reliability.Using the infrared sensing technology developed in this program, film thickness, integrity and stress can be quantified at any stage of the coating process, both during deposition and/or after manufacture. The ability to monitor film thickness in-situ is a critical need for many applications, as current techniques are based largely on empirical processing studies and post-priori destructive evaluation. Add to that the ability to quantify stress and the method emerges as a significant contribution to the technology of thin film processing and characterization. The proposed method can be used in an enormous range of industrial applications, including (but not limited to): microelectronic fabrication and assembly, MEMS fabrication and performance, thermal barrier coatings used in the energy conversion industry, metallic coatings on glass, and paint or protective coatings in everything from airplanes to cell phones.