Big Chip News! China Achieves New Breakthrough in Photoresist Technology! How Significant Is This?

    Recently, Professor Peng Hailin's team from Peking University's School of Chemistry and Molecular Engineering, in collaboration with partners, employed cryo-electron tomography to resolve for the first time the microscopic three-dimensional structure, interfacial distribution, and entanglement behavior of photoresist molecules in a liquid-phase environment under in situ conditions. This breakthrough guided the development of an industrial solution capable of significantly reducing photolithography defects.

    Lithography represents the most time-consuming and challenging process in integrated circuit manufacturing, with photoresist serving as the most critical consumable material that profoundly influences the lithography process. With the robust rise of Chinese semiconductor manufacturers and expanding downstream demand, the photoresist market continues to grow. According to a report by Rui Guan Industry Research Institute, China's photoresist market is projected to exceed 11.4 billion yuan in 2024. The domestic substitution process for mid-to-high-end products like KrF photoresists is accelerating, with the market expected to reach 12.3 billion yuan by 2025.

    Major Breakthrough

    According to Science and Technology Daily, lithography technology is one of the core drivers propelling the continuous miniaturization of integrated circuit chip manufacturing processes. Recently, Professor Peng Hailin's team from Peking University's School of Chemistry and Molecular Engineering, in collaboration with partners, utilized cryo-electron tomography (cryo-ET) technology to resolve for the first time the microscopic three-dimensional structure, interfacial distribution, and entanglement behavior of photoresist molecules in a liquid-phase environment under in situ conditions. This breakthrough guided the development of an industrial solution that significantly reduces lithography defects. The related paper was recently published in Nature Communications.

    “Development” is a core step in photolithography, where the exposed regions of photoresist are dissolved by developer solution to precisely transfer circuit patterns onto silicon wafers. Photoresist acts like the ink for etching circuits; its movement within the developer solution directly determines the accuracy and quality of circuit formation, ultimately impacting chip yield. For years, the microscopic behavior of photoresist within developer fluid remained a “black box,” forcing industrial process optimization through trial-and-error—a critical bottleneck hindering yield improvements in advanced 7nm and below processes.

    To tackle this challenge, the research team pioneered the application of cryo-electron tomography in semiconductor science. After standard photolithography exposure on a wafer, they rapidly transferred the developer solution—containing polymerized photoresist—onto an electron microscope grid. Within milliseconds, the sample was cryo-frozen to a glassy state, “freezing” the photoresist's true state within the solution.

    Researchers then tilted the sample in the cryo-EM, capturing a series of two-dimensional projection images at varying angles. Using computer-based three-dimensional reconstruction algorithms, these images were fused into a high-resolution 3D view with sub-5-nanometer resolution. This approach simultaneously addressed three major limitations of traditional techniques: the inability to achieve in-situ, three-dimensional, and high-resolution observation.

    This technique yielded numerous novel discoveries. Professor Gao Yiqin from Peking University's School of Chemistry and Molecular Engineering, one of the paper's corresponding authors, explained that while the industry previously believed dissolved photoresist polymers were primarily dispersed within the liquid, the 3D images revealed they predominantly adsorb at the gas-liquid interface. The team also directly observed for the first time the “coagulation entanglement” of photoresist polymers, which bind via weak forces or hydrophobic interactions. Moreover, polymers adsorbed at the gas-liquid interface are more prone to entanglement, forming aggregated particles with an average size of approximately 30 nanometers. These “aggregated particles” are the root cause of potential defects, as they easily deposit onto intricate circuit patterns, causing circuits that should remain separate to connect.

    The team proposed two practical solutions to control entanglement: appropriately increasing the post-exposure bake temperature to suppress polymer entanglement and reduce large aggregate formation; and optimizing the development process to maintain a continuous liquid film on the wafer surface, enabling it to carry away polymers and prevent deposition. Combining both approaches successfully eliminated pattern defects caused by photoresist residues on 12-inch wafers, reducing defect counts by over 99%.

    How significant is this?

    The implications of this research extend far beyond lithography itself. The power of cryo-electron tomography demonstrated here provides a powerful universal tool for in situ investigation of various chemical reactions occurring in liquid environments—such as catalysis, synthesis, and even biological processes—at the atomic/molecular scale. For the semiconductor industry, precisely understanding the microscopic behavior of polymer materials in liquids will significantly advance defect control and yield improvement in critical advanced manufacturing processes—including lithography, etching, and cleaning—paving the way for next-generation chips with enhanced performance and reliability.

    According to a research report by Shenwan Hongyuan Securities, photolithography is the most time-consuming and technically challenging process in integrated circuit manufacturing, accounting for approximately 50% of the total manufacturing time and about one-third of the production cost. Photoresist, as the most critical consumable in this process, significantly impacts the quality of photolithography.

    During lithography, a layer of photoresist is applied to the silicon wafer. After exposure to ultraviolet light, the photoresist undergoes chemical changes. Following development, the exposed photoresist is removed, transferring the circuit pattern from the mask onto the photoresist. Through subsequent etching, the circuit pattern is then transferred from the photoresist onto the silicon wafer. During etching, the photoresist serves as a protective barrier against corrosion.

    With the advancement of integrated circuits, chip manufacturing feature sizes have become increasingly smaller, placing higher demands on photoresists. Core technical parameters of photoresists include resolution, contrast, and sensitivity. To meet the needs of integrated circuit development, photoresists are evolving toward higher resolution, higher contrast, and higher sensitivity.

    From the demand perspective, photoresists can be categorized into semiconductor photoresists, panel photoresists, and PCB photoresists. Among these, semiconductor photoresists present the highest technical barriers.

    According to a report by global market research firm QYResearch, the photoresist market has long been monopolized by international giants such as Tokyo Ohka Kogyo, Shin-Etsu Chemical, JSR, and Fujifilm. In recent years, driven by multiple factors, China has accelerated its efforts toward semiconductor self-reliance and control, achieving significant technological breakthroughs across multiple segments of the industry chain.

    With the strong rise of Chinese semiconductor manufacturers and expanding downstream demand, photoresist—a critical component of the semiconductor industry—has witnessed substantial growth in scale. According to a report by Rui Guan Industry Research Institute, China's photoresist market reached approximately RMB 10.92 billion in 2023 and is projected to grow to over RMB 11.4 billion in 2024. The domestic substitution process for mid-to-high-end products like KrF photoresist is accelerating, with the market size expected to reach RMB 12.3 billion by 2025.