Fiber-Optic Based Distributed Atomic Absorption Spectroscopy for Film Growth Monitoring

X-ray optical components are required to perform a new level of material characterization at the nanometer scale and are critically needed for the advancement of emerging nanotechnology and other cutting-edge applications. Development of reflective and transmissive X-ray optics, able to reduce the spot size down to a diameter of few nm, is a significant achievement that may spur new frontiers in nanotechnology, metamaterials, biology and medical science and keep the US position of a global leader in cutting edge scientific research and development. However, the manufacturing of multilayer Laue components for X-ray optics by physical vapor deposition (PVD) requires unprecedented precision and accuracy and presents a significant process control challenge. Atomic Absorption Spectroscopy (AAS) is a promising method for accurately determining the deposition rate and composition of the deposited materials. Currently no AAS system provides the accuracy, portability and ease-of-use for adoption in the manufacturing of X-ray optics. Multiple other new-generation thin film technologies require an urgent solution to the same process control challenge. In this SBIR Phase I project AccuStrata will create a novel AAS prototype, installable on a broad variety of PVD systems for manufacturing of X-ray optics, to provide accurate and reliable deposition rate and film composition measurements for dynamic feedback control. The AAS prototype system comprises two major parts – a reconfigurable hardware module located outside the PVD chamber with hallow cathode excitation sources, and a portable fiber-optic-based distributed monitoring frame installed in the area surrounding the deposited substrate inside the deposition chamber. The deposition area is monitored by several beams simultaneously to derive information about the atomic distribution over the entire substrate area for precise deposition rate monitoring. The prefabricated and optically aligned frame structure, installed inside the deposition chamber, eliminates errors associated with window deposition, changes in chamber pressure, and other process factors. The unique shielding design will minimize contamination of the optics resulting in very low long-term drift. During Phase I the prototype system will measure the atomic flux density in a configuration of 3 optical beams near the substrate and provide real-time information about the deposition rate and its fluctuation. The unique fiber optic design provides for superior protection from undesired deposition on the system components and allows easy configurability, facilitating subsequent commercialization in other fields where PVD processes are involved (optics, semiconductor, aerospace, medical, automotive, etc.). Based on its existing software platform, AccuStrata will develop user-friendly software for real-time process analysis, which will further be developed during subsequent Phase II, to create a close-loop in-situ AAS process control system. The system can be easily expanded to more complex beam configurations, such as of 3x3 mesh. It will have the capability to monitor two material concentrations simultaneously and deploy multiple fiber-coupled hollow-cathode light sources as needed for various materials required for manufacturing of X-ray optics.