Photolithography technology is one of the core driving forces behind the continuous miniaturization of integrated circuit chip manufacturing processes.
According to the Science and Technology Daily, recently, Professor Peng Hailin’s team from Peking University’s School of Chemistry and Molecular Engineering, along with collaborators, successfully utilized cryo-electron tomography to analyze the microscopic three-dimensional structure, interfacial distribution, and entanglement behavior of photoresist molecules in a liquid phase environment in situ for the first time. This research guided the development of an industrialization plan that significantly reduces photolithography defects. The related paper was recently published in Nature Communications.
Development is one of the core steps in photolithography, where the developer dissolves the exposed areas of the photoresist, accurately transferring the circuit pattern onto the silicon wafer. The photoresist acts like paint for the circuit, and its movement in the developer directly determines the accuracy and quality of the circuit pattern, thereby affecting chip yield. For a long time, the microscopic behavior of photoresist in the developer has been a “black box,” and process optimization in the industry has relied on trial and error, which has become a key bottleneck limiting yield improvements for advanced processes at 7nm and below.
The Guangming Daily reported that in response to this challenge, the research team took a different approach, being the first to introduce cryo-electron tomography technology into semiconductor research with remarkable results. The researchers ultimately synthesized a microscopic three-dimensional “panoramic photo” with a resolution better than 5nm, overcoming three major pain points of traditional technology that could not achieve in situ, three-dimensional, high-resolution observation.
Gao Yiqin stated that the clear three-dimensional view that emerged for the first time brought a series of disruptive discoveries. The research not only overturned the long-held industry belief that “the polymer is uniformly dispersed after dissolution” but also directly captured the “entanglement” behavior between photoresist polymers in real three-dimensional space for the first time, thereby identifying the root cause of defects in chip patterns—”aggregated particles.” In industrial development, due to the strong hydrophobicity of the photoresist itself, these aggregates can redeposit onto the precise circuit patterns, causing fatal defects such as “bridging.” The research team found that the number of defects on a 12-inch wafer could be as high as 6617, which is unacceptable for large-scale industrial production.
Based on these microscopic findings, the research team proposed two simple and efficient solutions that are compatible with existing semiconductor production lines. “The experimental results are exciting: the pattern defects caused by photoresist residues on the surface of the 12-inch wafer were successfully eliminated, with the number of defects dropping by over 99%, and the solutions demonstrated extremely high reliability and repeatability,” said Wang Hongwei.
“The cryo-electron tomography technology used in this research has application potential that extends far beyond chips and photolithography,” noted Peng Hailin. It provides a powerful tool for probing various liquid-phase interfacial reactions at the atomic/molecular scale (such as catalysis, synthesis, and biological processes). For the semiconductor industry, this successful decoding of the microscopic behavior of polymers in liquids will promote defect control and yield improvement in key processes such as photolithography, etching, and wet cleaning in advanced manufacturing, injecting new momentum into the leapfrog development of chip performance.
Daily Economic News summarized from Science and Technology Daily and Guangming Daily.