Ajou University, Samsung Electronics develop new material for next-generation semiconductor manufacturing

A joint research team from Ajou University and Samsung Electronics announced Wednesday that it has developed a new material applicable to next-generation semiconductor manufacturing processes.

The material is directly compatible with existing manufacturing processes and is expected to boost productivity while lowering production costs, potentially strengthening the competitiveness of semiconductor materials.

The team, led by Professor Park Seong-jun of Ajou University's departments of electronic engineering and intelligent semiconductor engineering, developed a high-performance photoresist that reduces the EUV exposure dose required to form fine patterns in semiconductor manufacturing while improving durability against etching and pattern retention.

The research, titled "Tin-Coordinated Hybrid Photoresists for Dose-Efficient EUV Lithography," was published in July in the Chemical Engineering Journal, an international academic journal in chemical engineering published by Elsevier.

Ajou University students Lee Seung-hyeon, a fourth-year student in intelligent semiconductor engineering, and Baek Seok-hyeon, an integrated master's-doctoral candidate, along with Lee Hong-jun, a researcher on Samsung Electronics' DS division memory materials technology team, served as co-first authors. Choi Jun-gyu of Ajou University's Institute of Information and Communication Technology, Lee Jeong-hun, a project leader on Samsung Electronics' DS division memory materials technology team who is also a doctoral candidate at Ajou University, and Professor Park co-led the study as co-corresponding authors.

EUV, or extreme ultraviolet, refers to electromagnetic waves with very short wavelengths — shorter than conventional ultraviolet light — used in advanced lithography to etch ultra-fine, high-precision circuits onto semiconductor wafers. Photolithography is the process of transferring a designed circuit onto a wafer and is one of the most critical steps in determining a chip's integration density and performance.

EUV lithography uses extreme ultraviolet light to draw ultra-fine circuits on semiconductor wafers and is a core technology for the mass production of next-generation, high-performance semiconductors. Because it uses light with a wavelength roughly 14 times shorter than that of the widely used argon fluoride (ArF)-based exposure technology, it can produce smaller and more precise semiconductor circuits.

As device integration density increases to improve semiconductor performance, the ability to accurately form and maintain fine patterns at the sub-tens-of-nanometers scale becomes critical. This requires a high-performance photoresist capable of forming sharp patterns with minimal EUV light while withstanding the etching process — in which unwanted material is removed — without pattern collapse.

A photoresist is a light-sensitive material that changes its properties when exposed to light and serves as a key material in semiconductor lithography. The chemically amplified resist (CAR), an organic polymer-based photoresist widely used in conventional semiconductor manufacturing, has shown limitations in EUV lithography, however. EUV processes use very thin photoresist films for patterning, making it difficult to absorb sufficient EUV photons and requiring higher exposure doses, which increases process time and cost. Thin photoresists are also prone to damage during the etching process used to transfer patterns onto the semiconductor substrate, making it difficult to secure adequate etch resistance.

Inorganic metal oxide-based photoresists, by contrast, absorb EUV light well and offer strong etch resistance but present challenges in long-term material stability, storability and compatibility with existing manufacturing processes.

In response, the joint research team developed a hybrid photoresist (HPR) by blending a tin (Sn) precursor into a conventional organic photoresist to combine the strengths of both materials. The team found that in areas exposed to EUV light, the bond between the tin component and the organic photoresist is reinforced, forming a more rigid structure. This structure prevents patterns from disappearing or deforming during development and reduces pattern damage during subsequent etching.

In experiments, the tin-containing HPR showed superior etch resistance compared with conventional organic photoresists. Pattern collapse and deformation caused by external forces were reduced, and the material remained stable after exposure to various solvents used in semiconductor manufacturing.

The HPR can be produced by simply mixing a tin component into an existing photoresist solution, rather than separately synthesizing new polymers or complex metal oxide materials. This allows the material to work with existing solution-based processes without additional synthesis equipment or complex manufacturing steps, and the tin content can be easily adjusted depending on the intended application.

Particularly significant is that the collaboration between Ajou University and Samsung Electronics allowed the team to verify the material's performance under actual EUV process conditions used in semiconductor manufacturing. The team evaluated the HPR's patterning performance in a 12-inch wafer-based EUV process used for mass production. The optimized HPR composition formed patterns of the same size as those produced by conventional organic photoresists while reducing the required EUV exposure dose by approximately 16 to 23 percent, depending on pattern pitch.

Exposure dose is a key factor determining productivity and manufacturing costs in EUV lithography. If the same pattern can be formed with a lower dose, the time required for the patterning process — including the exposure step — is reduced, allowing expensive EUV equipment to be used more efficiently and potentially increasing semiconductor output while lowering production costs. The research is considered a significant advance in next-generation semiconductor materials, as it simultaneously improved fine pattern formation at low exposure doses, post-development pattern retention rate, etch resistance and mechanical stability.