Novel Spin-on Carbon Hard Mask with Hardening by Ion Implantation

Abstract

In this article, we present a novel high-performance multi-layer resist (MLR) process that uses a spin-on carbon (SOC) hard mask (HM). In the process, a technique involving the implantation of ions into the SOC just after coating was employed. B, P, Ar, and As were implanted in order to compare the degrees of hardening for the same dose amount (1E+15) and equivalent mean projected range Rp (ca. 75 nm); the parameters were controlled by dose energy for each ion. The results indicated that heavier ions with high dose energy showed higher hardening efficiency. The hardening depth in the SOC film approximately corresponded to the mean projected range (Rp). These findings were consistent with the physics of ion implantation, in which elastic and inelastic collisions between ions and target atoms and electrons are considered. As a next step, we attempted to apply this process to form ultra-thin lines using the implantation of Ar ions as an inert species. We confirmed that by using this system, the fundamental lithographic performance obtained was equivalent to that obtained by using the conventional MLR system. Furthermore, excellent etching performance was obtained when the implantation was carried out at higher dose energies. Accordingly, the formation of ultra-thin lines (ca. 25 nm) was successfully achieved by tuning the hardening condition.