SBIR-STTR Award

We propose a phase I feasibility investigation of the merits of a new microwave-based method for near real-time monitoring of thin-film material growth and etching with high spatial resolutions. The method we propose to develop here is based on monitoring the microwave resistivity of the film and the material during its processing (growth or etching) using a spatially confined microwave probe. Material quality, structure, stoichiometry, and impurity content all affect its microwave resistivity and can be detected the probe. Our main objective in this study is to design and develop a prototype probe that can be used in actual deposition chambers to monitor film growth in-situ and in real-time. Such a probe will be invaluable in providing a feedback on the growth conditions to control of the process. Our preliminary studies indicate that the evanescent microwave probe is capable of performing such a task. Furthermore, we will investigate possibility of using multi-frequency probes as a method to investigate hierarchy of properties encountered in multi-layered structures. Depth variation as well as information regarding the gradient of properties will be obtained and monitored to control the deposition process. The proposed work will be performed over a period of 9 months at MICC.

Benefits:
Non-intrusive and non-destructive evaluation of materials as well as process monitoring tools that can operate over a wide range of temperatures and environmental conditions are not readily available. Our proposal addresses this shortcoming. Moreover, the proposed microwave probe can be used to detect cracks and defects in composites and metals of great importance to the airline industry and the Air Force.

Evanescent fields have been extensively used in non-destructive characterization of materials. They provide a means of interaction through an interface and usually yield very high resolutions in excess of the Abbe barrier set by the wavelength. During Phase I of this proposal, we have successfully developed and demonstrated applications of the evanescent microwave probe in thin-film characterization. A first table-top prototype probe is already constructed. We are proposing to extend our studies to develop a second prototype imaging probe capable of operating in a pulsed laser deposition chamber (PLD). This in-situ imaging probe will be used to provide near real-time feedback on the status and the quality of the film growth. More specifically, it will provide information regarding morphology, composition and isotropy of the thin-film. Using parallel probes operating at different frequencies, our imaging tool will provide hyper-spectral information and maps that can be used to adjust the deposition uniformity and composition. The probe's scan rates (up to 2 cm/s), operation temperature (up to 600 degrees C), and resolution (~0.4 um at 1 GHz) will be designed for the PLD environment which is also oxidizing. Working with the researchers at Wright Patterson, we will develop appropriate image analysis and feedback control methods.

Benefits:
EMP has applications in biomedical, polymeric, composite, ceramics, and semiconducting materials. It can be used to detect incipient carries in the tooth enamel and it can be used to non-destructively characterize shallow junctions in ultra large integrated circuits. In polymers it yields information regarding uniformity and conductivity distribution across large areas of interest in light-emitting displays. In multilayer computer printed circuit boards it can be used to check the continuity of buried copper lines.