One of the challenges that industries and academic research groups occasionally face is that of transferring semiconductor devices of micrometer-scale from their native substrate to their respective receiving platforms. Now, researchers at the University of Strathclyde have successfully demonstrated a continuous roller printing process for picking up and transferring over 75,000 micrometer-scale semiconductor devices with very high accuracy, in a single roll. With this new method, the team has paved the way to creating a large-scale array of optical components that could be used for rapid manufacturing of micro-LED arrays.
According to the team, their unique printing process based on rollers is a way to tackle the above obstacle, and do so in a scalable manner, all the while meeting the stringent accuracy necessary for such an application. They claim their new roller technology is capable of matching the design of the device layout and has an accuracy of one micron or less. While the setup is inexpensive, it is also simple enough for users to construct it in locations with limited resources.
Large displays are made up of thousands to millions of tiny semiconductor devices. The real challenge was to manipulate these devices, such as taking them from their native substrate and placing them on the target substrate or circuit with high precision. The next hurdle was to inspect these devices, to ascertain their positional accuracy. For mass-manufacturing these displays, it is essential to not only effectively transfer them but also to find a way to look at them to assess their position and to effectively monitor the accuracy and yield.
As to how the transfer process works, the team explained that placing different materials in close proximity or in contact, develop interacting forces between them, generating adhesive forces between different material. The team uses this adhesion to pick up the devices and place them on the target surface. They use optical or adhesive coatings to enhance this adhesion, which makes the process easier.
Right now, the team is working to improve the accuracy of the printing process. At the same time, they are also trying to scale up the number of devices that the operation can transfer at a time. As the process works in terms of accuracy and yield, the team must further improve its scale and accuracy to be commercially viable.
The team is also working on a printing process for active devices. They intend to address individual microelectronic devices that they want to transfer and test such that they do not have any issues from the printing, either in the electrical or optical properties.
One of their biggest challenges is to effectively transfer a three-color display while maintaining good accuracy. The researchers feel their work will have an impact on the market and on the industry in general. By going ahead and overcoming the challenges, the researchers will need to find a method that is to a great extent compatible with the existing industry and manufacturing processes.
Micro-LED displays are making their way into cars for navigation systems, into AR and VR, in gaming monitors, and in the military for training purposes.
