Sandra Kozuch, a PhD student at CEA-Leti, has taken a significant step toward solving a critical bottleneck in micro-LED manufacturing: plasma-induced sidewall damage. At the 71st American Vacuum Society (AVS) conference, her presentation on “CH₄/H₂ etching of N-polar GaN for micro-LED application” earned the Coburn and Winters Student Award for best student presentation. The work introduces a controlled etching mechanism that could preserve the electro-optical performance of micro-LEDs when pixel sizes shrink below 10 µm — a regime where efficiency typically plummets.

Kozuch’s path to this breakthrough began at Polytech Grenoble, specializing in materials science, followed by a work-study stint at STMicroelectronics. Drawn to the intersection of fundamental and applied research, she joined CEA-Leti to focus on gallium nitride etching for next-generation displays and optical communications. Her research zeroes in on a rarely studied area: the physicochemical characterization of pixel sidewalls. Most prior analyses examine the etch bottom, but sidewall degradation is the dominant source of non-radiative recombination as LEDs are miniaturized.

The core of her work explores a CH₄/H₂/Ar plasma chemistry. Kozuch proposed a detailed mechanism: during etching, the plasma forms a polymer layer on the GaN surface. This layer is essential — without it, the process devolves into simple sputtering and the material is not etched effectively. Conversely, if the polymer becomes too thick, it screens the GaN, blocking further etching. By fine-tuning process parameters, her team achieved a balance that minimizes sidewall damage while maintaining a practical etch rate, thereby protecting the electro-optical properties of the pixels.

The implications extend beyond augmented and virtual reality micro-displays. Micro-LEDs are also emerging as a compelling solution for low-power, high-bandwidth fiber-optic data links in high-performance computing, artificial intelligence, and data centers. To bridge the gap between lab-scale insight and industrial viability, Kozuch is collaborating with equipment manufacturer LAM Research through a joint development program. The goal is to translate these etching advances into robust manufacturing processes.

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​​​​Is it possible to etch GaN (gallium nitride) pixels without damaging the sidewalls? This is Sandra Kozuch's goal, a PhD student at CEA-Leti, who has developed advanced etching processes for micro-LED applications intended for augmented reality displays and fiber-optic communications. At the 71st conference of the American Vacuum Society (AVS), Sandra won the award for best student presentation (the Coburn and Winters Student Award), a significant recognition of this breakthrough in etching technology. ​​

Sandra began her academic journey with a preparatory course in mathematics an​d physics before going on to engineering school. She enrolled at Polytech Grenoble in a program specializing in materials science, a field that has long interested her, particularly because of its connection to semiconductors.

Following her work experience at STMicroelectronics, Sandra decided to build on the knowledge she had gained during her work-study program and explore the field of academic research. She then applied to CEA-Leti to pursue a Ph.D., drawn by the opportunity to work at the intersection of fundamental research and industrial applications. Her work on GaN etching for micro-LEDs, presented at the AVS under t​he title “CH4/H2etching of N-polar GaN for micro-LED application," earned her the first student prize.

In her work, Sandra focuses on the physicochemical characterization of pixel sidewalls, a topic that has received little attention in scientific literature. In fact, analyses generally focus on the study of the etch bottom. Her goal is to test a new etching chemistry to limit etch-induced defects in the material at the pixel edges. This would improve the electro-optical properties of GaN micro-LEDs.

A major challenge lies in the miniaturization of LEDs: as their size decreases, electro-optical efficiency declines, becoming critical below 10 µm (microns). Indeed, the impact of micro-LED sidewalls surfaces damaged by plasma etching is no longer negligible and leads to a significant drop in the LED's electro-optical efficiency. Thus, it is essential to develop new etching methods that limit the degradation of micro-LED sidewalls. The chemistry Sandra is studying had already been addressed in the scientific literature, but without any specific mechanism having been proposed.

At the 71st AVS Conference, Sandra proposed a mechanism to explain the etching of GaN using a CH₄/H₂/Ar plasma: this chemical mixture tends to react at the GaN surface to form a polymer layer, the presence of which is essential to the etching process. Without it, the material is simply sputtered, rendering plasma etching ineffective. However, when it becomes too thick, it can also act as an obstacle by screening the GaN to be etched. To control this phenomenon, Sandra's team defined specific parameters that allow the material to be etched while controlling the deposition of a polymer layer on the surface, thereby ensuring a better balance between GaN degradation at the pixel sidewalls and etch rate.

Sandra's work has applications in the field of micro-display technology, such as virtual and augmented reality devices, but that's not all. In fact, micro-LEDs also offer an attractive solution for fiber-optic data transmission in demanding systems, such as high-performance computing, artificial intelligence and data centers.

From an industrial perspective, the main challenge is to develop an etching process that does not damage the material. It is in this context that Sandra ​is collaborating through a joint development program with the equipment manufacturer LAM Research, with the aim of strengthening the link between its research and its practical applications in the semiconductor industry.

Acknowledgements​:S. Ruel, D. Vaufrey, O. Renault

To learn more about the paper:https://doi.org/10.1116/6.0005192

To learn more about the conference:https://avs.org/

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