Display & Semiconductors
We research several industrial applications including quantum dot LED display diode, Cryptotechnology, Battery electrode, Cleaning process for semiconductors, Advanced photo-lithography technology.
Vapor-driven immersion lithography lens stabilizer
Water-based immersion lithography has been introduced for achieving O(10 nm) spatial resolution in the semiconductor industry. The major challenges remaining in immersion lithography are to decrease the tail of the main lens and to prevent residual droplet formation after the main lens while increasing the relative speed of the silicon wafer with respect to the main lens. Here, we propose a novel method to control the shape of the immersion lens by applying Marangoni stress using volatile vapor. Furthermore, we experimentally and theoretically observed that the stability and wafer speed of the immersion lens are increased by the vapor-driven solutal Marangoni effect.
Related publication: J. Ryu, G. Lee, W. Lee, J. Yoon, N. Koo, and H. Kim, "Volatile vapor knife of immersion lithography hood using solutal Marangoni effect," J. Vac. Sci. Technol. B 40(5) (2022) (Selected as Editor's Pick)
Vapor visualization techniques
We measure the vapor distribution of volatile liquid components by detecting a refractive index difference. This method is useful and reliable to understand the material transport in a wide range of research areas. We use this techniques to explore how often flower releases a floral scent (VOC, Volatile organic compounds) and how the droplet evaporates on/under the substrate. For the semi-conductor industry, various chemicals should be used for the manufacturing process. Normally, those are typically very volatile and toxic. Therefore, it is important to control and eliminate those fume for the safety issues. Using this measurement technique, we could provide a new safety guideline. ​
Related publication: M. Kuk, J. Pyeon, H. Kim, "Vapor distribution changes evaporative flux profiles of a sessile droplet," J Colloid Interf. Sci. Accepted. 652, 646-652 (2023)
Coffee-ring-less technology for polygonal quantum dots patterns for display diodes
Currently, quantum dot light-emitting diodes (QD-LEDs) are receiving extensive attention. To maximize their luminous performance, the uniformity of the QD-LEDs is crucial. Although the spontaneously self-induced solutal Marangoni flow of an evaporating binary mixture droplet has been widely investigated and used to suppress coffee-ring patterns in ink-jet printing technology, unfortunately, ring shapes are still present at the edges, and the Marangoni flow generated by the selective evaporation of volatile liquid components cannot be controlled due to its nonlinear instabilities. In this work, polygonal coffee-ring-less QD microarrays are created using two spontaneous and sequential solutal Marangoni flows. During the initial evaporation, internal circulating flows are controlled by polygonal-shaped droplets. After that, sequential interfacial flows are generated by the captured volatile vapors. A theoretical model and scaling analysis are provided to explain the working mechanisms. It is expected that the newly designed printing system can be applied to the mass production of QD-LEDs.
Related publication: J. Pyeon, K. M. Song, Y. Jung, and H. Kim, "Self-induced solutal Marangoni flows realize coffee-ring-less quantum dot microarrays with extensive geometric tunability and scalability," Adv. Sci. 2104519 (2022)