In-line Crack and Stress Detection in Silicon Solar Cells Using Resonance Ultrasonic Vibrations

Wafer breakage in automated solar cell production lines is a major technical problem and a barrier to further cost reductions in silicon solar module manufacturing. The fragility of silicon wafers is attributed to peripheral and bulk millimeter-length cracks. However, no commercial systems address the critical need for in-line inspection of these cracks. This project will validate the applicability of the Resonance Ultrasonic Vibrations system as a real-time, in-line, manufacturing quality control tool for the fast detection of mechanically unstable silicon solar cells caused by cracks. Phase I confirmed that the Resonance Ultrasonic Vibrations method produced a high 91% crack rejection rate and that the system was capable of matching the 2.0 seconds-per-wafer throughput rate of state-of-the-art solar cell production lines. Phase II is designed to move the technology from the laboratory level to commercial demonstration by developing a system prototype. Specifically, Phase II will (1) specify optimal configurations of the in-line system¿s component hardware and software; (2) develop and justify a system prototype that meets the major specifications for high throughput, high level of stability, reproducibility of data acquisition and analysis, and high sensitivity with respect to crack length and crack location; (3) design a system platform that allows easy integration within and adaptation to various solar cell production lines; and (4) develop a testing protocol. Commercial Applications and Other Benefits as described by the awardee: The silicon-based solar industry, with crystalline silicon as a dominant segment, shows outstanding performance, with approximately 25% yearly growth during recent years. The Resonance Ultrasonic Vibration system should provide a critical quality control tool for this industry, thereby improving productivity, increasing the reliability of products, and reducing manufacturing costs