In-Line Quality and Process Control in Solar and Fuel Cell Manufacturing

The proposed SBIR Phase I program addresses a critical need in solar cell and fuel cell module manufacturing: to inspect in real time the mechanical quality of incoming wafers and finished cells. The objective of the program is to develop a new flaw inspection technology and design a laboratory prototype of an Activation Station (AS) system with follow-up industrial testing with the goal of reducing the cell breakage rate and contribute to improvement of cell process tolerances. Both industry segments represent quickly growing national and world-wide energy markets. To compete with traditional energy sources, both industries are driven by economic reasons to make modules of the highest conversion efficiency and greatest reliability at the lowest production cost. One of the current technological problems that face solar and fuel cell manufacturers is identification and elimination of sources of mechanical defects such as cracks, thermo-elastic stress, and micro-inclusions which lead to the loss of integrity in silicon wafer (solar cell) or ceramic plate (fuel cell) with ultimate in-line breakage of as-grown and processed wafers and cells. The problem is of increased concern in light of the current strategy of reducing cell substrate thickness down to 100 m in the long term, from the current range of 150 to 180 m. It is recognized that development of a methodology for fast in-line flaw detection and process control is required to match a few seconds per wafer throughput rate of typical cell production lines. State-of-the-art solar and fuel cell manufacturing is based on highly automated conveyor belt-type in-line configurations. Each production step requires a real-time feedbackincluding statistical data analysis with linkage to wafer/cell quality. The proposed innovation addresses a common solution for flaw inspection applicable to other high-throughput production. The inspection method is grounded on a novel methodology for advanced crack/flaw inspection using the Activation Station (AS) concept. The AS fundamentally relies on an accurately controlled mechanical strain profile applied to a substrate. Quantitative assessment of the materials elastic response in real time allows fast non-destructive monitoringof the substrates mechanical quality. A statistical analysis is applied to AS data collected in real-time. The primary target will be to search for hidden defects that are not revealed by traditional in-line techniques. When used in high volume production, the AS system will contribute to yield improvement and, as a consequence, energy and cost savings in the manufacturing sector. Development of the AS methodology requires both comprehensive experimental study and supporting computer modeling to justify a prototype development addressed in the proposed project. The project will be supported by analytical equipment including Scanning Acoustic Microscopy, Scanning Electron Microscopy and Focused Ion Beam located at the University of South Florida. Acoustic imaging and computer modeling will be performed by professional consultants.