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

The proposed SBIR Phase IIB project addresses a critical need in solar cells and modules manufacturing: to inspect in real time the mechanical quality of silicon wafers and cells. The overall goal of the entire SBIR project is to transfer the in-line Activation Station (AS) technology from the laboratory level through design, manufacturing and field testing of the AS pre-production prototype. Based on feedback from commercial customers the required improvements in the laboratory AS prototype were identified as keys to commercialize the AS tool. Specific objectives of the Phase IIB include: (1) upgrade the AS tool hardware to improve AS reliability, accuracy and maintenance, (2) upgrade AS tool operational software to allow hand shaking with in-line commercial equipment, (3) improve throughput and insure AS applicability to different shapes and types of silicon substrates, and (4) integrate AS tool in the solar module production line. By completing Phase IIB project the AS technology will progress from the current Technology Readiness Level TRL5 to TRL7. Silicon solar module technology represents a quickly growing national and world- wide energy market. One of the current technological problems that face solar module manufacturers is identification and elimination of sources of mechanical defects such as sub-millimeter length seed cracks which lead to the loss of integrity in a silicon wafer or solar cell and their ultimate in-line breakage. The problem is of increased concern in light of the current strategy of reducing cell substrate thickness down to 100 µm in the long term, from the current range of 150 to 180 µm. The inspection method is grounded on a novel methodology for advanced crack inspection using the AS concept integrated with Resonance Ultrasonic Vibration system. The AS fundamentally relies on an accurately controlled mechanical stress applied to a substrate and measurement of the elastic force response. The research program is based on proven feasibility obtained in Phase I, which established that: (i) the AS method is applicable to both silicon solar and ceramic fuel cells; (ii) the method sensitivity depends on crack location and covers up to 96% of the wafer area supported by computer modeling; (iii) the speed of AS components can be matched to a throughput of production lines. In Phase II, the following tasks were completed: (a) AS tool configuration (system’s component hardware and software) optimized, (b) laboratory AS tool integrated into automatic Resonance Ultrasonic Vibrations system, (c) statistical algorithm for crack inspection developed and implemented in the tool’s software, and (d) the in-line AS prototype tested in solar module and fuel cell production with statistically verified yield improvement.