Expanding DSA process window with atmospheric control

Abstract

Directed Self Assembly (DSA) is a promising technology for complementary patterning in future nodes. As DSA patterning has continued to evolve there has been many efforts to improve defect performance using hardware, processes, and materials. Traditionally, in PS-b-PMMA block-copolymers (BCP) based patterning schemes, phase separation is achieved using a thermal annealing with controlled temperature and time. In previous work we have expanded our understanding of BCP annealing by demonstrating the ability to improve a process window and fingerprint formation of a lamellar system (31nm pitch BCP) by atmospheric condition control during the thermal anneal, as shown in Figure 1. By reducing the oxygen concentration inside the annealing chamber, we have demonstrated improved densities for fingerprint defects commonly associated with phase separation in BCP systems. Furthermore, by achieving a strong regulation of the concentration at different levels, we have achieved a better understanding of what might be required to fully eliminate these defects for subsequent studies and learning toward device manufacture. By reducing the concentration of oxygen during the thermal anneal process, we have been able to employ noticeably higher annealing temperatures without damaging the BCP films. Ultimately, our goal is to provide an annealing solution that is amenable to high volume manufacturing. In this study, controlled oxygen annealing of a 31nm pitch BCP is evaluated against a known thermal annealing baseline. Oxygen concentration, temperature and time are finely tuned in the study. Finally, polymers with different compositions (ie morphologies: lamellar, PS cylinders, PMMA cylinders) are evaluated, and the correlation between thermal budget and polymer stability is reported.