New deep-UV micro-LED array advances maskless photolithography

A team led by Professor Sun Haiding from the University of Science and Technology of China (USTC) has developed a vertically integrated microscale light emitting diode (micro-LED) array and applied it to a deep ultraviolet (DUV) maskless photolithography system. first time. Their research was published in Laser & Photonics Reviews.

Photolithography plays an important role in the production of integrated circuit chips and is one of the major core technologies in the semiconductor and microelectronics industries. Since the 1990s, low-cost, high-resolution maskless photolithography systems have emerged as a hotspot for advanced lithography research. However, patents for this cutting-edge technology are primarily held in Europe, the United States, Japan, and South Korea, creating a major technological barrier.

In this context, Professor Sun’s iGaN team has conducted extensive research on DUV micro-LEDs over the years and innovatively proposed a maskless photolithography system that uses DUV micro-LED arrays as light sources.

They systematically designed and optimized the epitaxial structure, device dimensions, sidewall profile, and geometry of DUV micro-LEDs to improve their power efficiency, modulation bandwidth, and versatility in UV light detection, imaging, and sensing. Significantly improved. Based on this, the team successfully developed an array system based on these DUV micro-LEDs.

In this study, the team further leveraged the advantages of DUV micro-LED’s ultra-small size and ultra-high brightness to propose and fabricate a DUV display integrated chip. They proposed a three-dimensional vertically integrated device architecture in which an AlGaN-based DUV micro-LED array and a zinc oxide (ZnO)-based photodetector (PD) were aligned via a transparent sapphire substrate.

In this architecture, UV photons emitted from a DUV micro-LED array are transmitted through a transparent sapphire substrate and captured by a PD on the backside of the substrate, allowing efficient optical signal transmission.

Additionally, the team developed a self-stabilizing light-emitting system with closed-loop feedback control based on vertically integrated devices. This system can not only monitor the fluctuations in the output light intensity of the micro-LED array, but also provide continuous feedback to ensure stable output power.

Test results showed that the device with the self-stabilizing system maintains high light intensity and long-term stability, while the light intensity of the device without feedback gradually decreases over time.

Using a feedback system, the team successfully demonstrated a DUV micro-LED array with a high pixel density of 564 pixels per inch (PPI) to display sharp patterns on silicon wafers after maskless DUV photolithography and demonstrated its potential at high resolution. Resolution photolithography technology. This is the first demonstration of DUV maskless photolithography based on DUV micro-LED active matrix.

This study develops a new integrated device combining DUV micro-LED arrays and PDs and shows important application prospects in future maskless photolithography systems. It also lays the foundation for the future development of highly integrated and multifunctional 3D optoelectronic integrated systems.

In the next stage, the team will focus on further reducing the size of individual micro-LEDs and PDs, thereby increasing the density and integration of arrays per unit area. It also optimizes the performance of individual devices and uniformity across large wafers, paving the way for higher precision maskless photolithography techniques.