Study of Pattern Collapse for Freezing Free Litho-Litho-Etch Double Patterning

Abstract

Pattern collapse becomes one of the serious issues for critical patterning process below 45nm half pitch. Many reports have been published in recent days to investigate pattern collapse mechanism. There are factors such as capillary force, hardness, swelling, and pattern profile that can cause pattern collapse.
On the other hand, Litho-Litho-Etch (LLE) without freezing process has been recognized as a promising candidate because of its cost effectiveness among double patterning processes. The materials using 2nd resist formulation is totally different from the one on 1st resist because it is necessary that 2nd resist solution doesn't dissolve 1st resist during 2nd litho process. Therefore, pattern collapse mitigation on freezing free LLE process can pose considerable challenges.
In this report, the improvement of pattern collapse on 2nd resist will be discussed by focusing on the surface free energy and the swelling during its development process.