Directed Self-Assembly (DSA) has been reported many times in the past decade as a technique for forming fine patterns1- 12. As processes for application to the semiconductor process, the grapho-epitaxy process forms a desired pattern in an isolated area using a physical guide, and the chemical-epitaxy process forms a single pitch over a wide range using a chemical guide are typical. There are many reports regarding the line pattern formation using a lamellar phase to meet the demand for miniaturization from the mass production of semiconductors, and this is partly because the lamellar phase is relatively stable. However, for fine line pattern formation, multiplication techniques such as SADP (self-aligned double patterning) and SAQP (self-aligned quadruple patterning) have matured, and in recent years, the number of cases where EUV (extreme ultra-violet) single exposure is used is increasing. For this reason, DSA is rarely used in mass production of semiconductors. On the other hand, when miniaturizing high-density hole patterns, methods such as multiple exposure and etching, and methods of forming holes by crossing line patterns formed by SADP are relatively expensive. In addition, it is difficult to maintain the uniformity of hole CD (critical dimension) and pitch. In addition, when EUV is applied, it is not easy to suppress defects and form a wide range of patterns due to stochasticity, which has become a problem in recent years. Therefore, the formation of high-density hole patterns using DSA is attracting attention. In DSA, the hole diameter can be controlled by the molecular weight of BCP (block co-polymer), and the pitch tends to be uniform spontaneously. Also, if the chemical-epitaxy process is used, the pattern can be formed over a wide range. However, hole patterns using a cylinder phase tend to have large fluctuations in hole diameter and placement due to the high degree of freedom in placement. It is also important to what extent the established process can be extended to further miniaturization. In this presentation, we report on the hole pattern formation method by the chemo-epitaxy method and efforts to improve the fidelity for application to the semiconductor process.
Direct self-assembly (DSA) can form periodic fine patterns by the repulsive forces between different polymers. As one of the candidates for next-generation lithography, it has been evaluated for semiconductor manufacturing processes for the past 10 years1-11 . Reports of DSA processes using Chemo-epitaxy show many line-and-patterns formed using lamellas and few hole patterns using cylinders. The reason why it is difficult to form a hole pattern is that the direction of line-and-space misalignment is one-dimensional, whereas in the case of a hole, it is two-dimensional, so dislocation defects are likely to occur and process control is difficult. On the other hand, the pitch of hole patterns in semiconductor devices is shrinking year by year, and in the future it may not be possible to form them all at once even with EUV (Extreme ultraviolet) lithography. Therefore, it is expected that there will be an increasing demand for shrinking patterns using DSA additionally. In this presentation, we report on the method of forming a hole pattern by the chemo-epitaxy process and the process condition setting, and discuss the possibility of application to the semiconductor process.
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