To meet Moore’s law, resist resolution improvement has become more and more important. However, it is difficult to improve resist resolution and keep vertical sidewall profile. For example, a high contrast hole resist may cause trench scum, due to very T-top profile. This paper reports several concepts for resist profile tuning without losing performance for lithographic factor , including mask error enhancement factor (MEEF), depth of focus (DOF), and critical dimension uniformity (CDU). To quantitative analysis the resist profile improvement, we define a new factor, Scum fail ratio (F/R%) for new techniques evaluation. The new techniques, including floatable additive, floatable PAG, and new monomer, are discussed. From X-SEM and CD-SEM data, former three concepts could improve resist sidewall profile quantitatively evaluated by Scum fail F/R% and keep lithographic factors. In addition, another key factor, resist residue defect, is also discussed. The high contrast resist with higher receding contact angle (RCA) easily generates more residue defect after development. With the new monomer composition, RCA of Resist E is decreased from 54 to 48 degree after development. Therefore, the residue defect is improved one order.
Unlike optical systems, electron-charging effect is a concern for e-beam lithography. Accumulated charge on the
resist will perturb the route of incident electrons, resulting in pattern distortion or failure. Therefore, reducing charge
accumulation becomes an important topic for high-pattern-density e-beam applications.
In this paper, we used a conductive material as the resist substrate for charging effect evaluation. The e-beam source
from CD-SEM (Critical Dimension SEM) was initially used to conductive performance qualification. When comparing
with non-conductive BARC, we found that the experimental conductive material has an additional 11% to 14%
resist-shrinkage than a non-conducting BARC. However, we cannot repeat this phenomenon in the multiple-e-beam
(MEB) imaging tool. From Monte Carlo simulation, the electrons deeply penetrate through the substrate instead of being
trapped in the resist substrate. It further indicates that although conductive bottom layer can dissipate electron effectively
for surface charging, the film scheme as well as tool grounding are also important for minimizing the charging effect.
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