Shanghai University develops new chip bonding technology to enhance Micro LED performance

On December 18th, a research team from Shanghai University recently demonstrated a technology to improve the integration and performance of next-generation Micro LED micro display devices.

It is reported that reducing the LED to a miniature size will bring manufacturing and reliability barriers, with key challenges including integrating Micro LED pixel arrays with silicon control circuits for operating displays.

This integration technology is achieved through the flip chip bonding process, which physically and electronically connects Micro LED chips to the bonding pads on the silicon backplane. However, when the pixel size is reduced to below 50 microns, this adhesive interface is prone to failure due to small defects and mechanical stress.

The manufacturing process of blue light Micro LED using inverted chips. (Source: AIP)

In response to the above issues, the research team at Shanghai University enhanced the flip chip bonding process by using layered gold indium gold (Au/In/Au) metal interlayers instead of traditional pure indium protrusions. The team used flip chip bonding technology to connect Micro LEDs to silicon at a mild temperature of 200 ° C, avoiding damage caused by mismatched heating and cooling, while forming high conductivity bonding.

The research results indicate that compared with pure indium, the gold indium gold (Au/In/Au) multilayer metal interlayer flip chip bonding process reduces resistance by 40%, while also eliminating cracks and gaps on the bonding surface. The shear strength test shows that the mechanical strength of Au/In/Au bonds is more than three times that of the original.

The research team integrated these hierarchical connections into a 15 × In a 30 pixel Micro LED demonstration array, the array has 20 × A 35 micron sized light source. As a result, these panels exhibited high-quality display performance, including low operating voltage and record high

FIB cross-sectional SEM images of indium protrusions (a) and Au/In/Au multilayer films (b),

And SEM images of blue light Micro LED chips after flip chip bonding (c).

(a) 15 × EL image of a 30 pixel blue light Micro LED display. (b) EL image of a blue light Micro LED display screen with the word SHU.