Chinese researchers

Xinhua News Agency, Tianjin, June 13 (Reporters Zhang Jianxin and Li Yating) Micro LED is the core component of the next generation of high-end display technology. Wafers equipped with micro LED must achieve a 100% yield, otherwise it will cause huge repair costs for the end product. However, the industry has not found a good method for wafer contact non-destructive testing. Recently, our country’s scientific researchers have filled this technological gap with the method of “conquering hardness with softness”.

Traditional wafer yield inspection methodSome methods are like "stylus engraving jade", which will cause irreversible physical damage to the wafer surface; others can only be "approximately viewed", resulting in a high rate of missed detections and false detections. The technical gap in yield non-destructive testing has seriously hindered the mass production of micro-LED terminal products such as large-area displays and flexible displays.

Recently, the team of Professor Huang Xian of the National Key Laboratory of Precision Testing Technology and Instruments of Tianjin University and the Department of Perceptual Science and Engineering of the School of Precision Instruments broke the bottleneck of micro LED wafer testing and achieved high-throughput non-destructive testing of micro LED wafers. The research results were announced internationally on the 13thPublished in the academic journal "Nature-Electronics".

The picture shows that after the flexible probe contacts the LED wafer, one of the LEDs lights up and emits blue light. (Photo provided by the interviewee)

The research team proposed a detection method based on flexible electronic technology for the first time. The three-dimensional structure of the flexible probe array constructed by this method can adaptively deform the surface topography of the measurement object by virtue of its "softness overcoming rigidity" characteristic, and lightly touches the wafer surface with a "breathing level pressure" of 0.9 MPa.

"The contact pressure of the probe of this technology is only one ten thousandth of that of the traditional rigid probe. It not only does not cause wear on the wafer surface, but also reduces the wear on the probe itself. The probe still looks as good as before after 1 million contact measurements." Huang Xian said.

  In addition, the team also developed a measurement system that matches the three-dimensional flexible probe. Through the collaborative work of probes and detection systems, it provides key tools for efficient process control and quality screening of micro-LED products.

The picture shows the flexible probe in the test system. When the probe contacts the LED wafer, one of the LEDs lights up and emits blue light. The light intensity and wavelength information can be observed through the coaxial light path. (Picture provided by the interviewee)

“We have achieved a breakthrough from zero to one, filling the technical gap in micro-LED electroluminescence detection, and also providing a revolutionary technical solution for other complex wafer detection. With the continuous expansion of the scale of the probe array and detection channels, it may have a wider impact in the fields of wafer-level integrated detection, biophotonics and other fields in the future,” Huang Xian said.

It is reported that this technology has started the productization process in Tiankai Higher Education Science and Innovation Park. In the future, it will provide batch, non-destructive, low-cost testing solutions for the domestic micro-LED industry, and further expand the application fields of flexible electronic technology.