Wafer testing makes a breakthrough

TIANJIN — Chinese researchers have achieved a breakthrough in micro-LED wafer testing by developing a nondestructive detection method, thereby addressing a longstanding challenge in electroluminescence inspection of micro-LED technology. Micro-LEDs are widely recognized as a fundamental technology for next-generation high-end displays. Achieving near-perfect yields during wafer fabrication is essential to ensure product quality and control repair costs.

Conventional testing approaches face major limitations, with some methods damaging wafer surfaces irreversibly, while others lack precision due to high rates of missed detection and false alarms.

This lack of reliable contact-based, nondestructive testing had been a bottleneck in terms of mass-producing micro-LED applications, particularly for large-area and flexible displays.

A research team led by professor Huang Xian at North China's Tianjin University has addressed this critical gap. Their breakthrough was published recently in the journal Nature Electronics.

The team introduced a flexible three-dimensional probe array capable of adapting to the microscopic contours of micro-LED wafers, applying pressure as low as 0.9 megapascals — comparable to the softness of a gentle breath. This soft-contact approach allows for high-throughput electrical testing without scratching or damaging the wafer surface.

"The contact pressure exerted by our flexible probes is just one ten thousandth that of conventional rigid probes," Huang explained. "This not only preserves the wafer surface but also significantly extends the probe's service life. Even after one million contact cycles, probes retain their original condition."

To support this innovation, the team also developed a custom-designed measurement system that integrates with the flexible probes — enabling precise process control and efficient yield screening in micro-LED manufacturing.

"This breakthrough establishes a new foundation in the field," said Huang. "It closes a major technical gap in micro-LED electroluminescence testing and paves the way for broader applications in advanced wafer inspection and biophotonics."

Currently, this technology is progressing toward commercialization at the Tiankai Higher Education Innovation Park in Tianjin.

Xinhua