A study of an acid-induced defect on chemically amplified photoresist applied to sub-30nm NAND flash memory
Yong-Hyun Lim, Jae-Doo Eom, Wooyung Jung, Min‐Sik Jang, Byung-Seok Lee, Jinwoong Kim · Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE · 2011
Recently, we found a peculiar acid induced defect on chemically amplified photo resist applied to sub- 30nm NAND Flash Memory. This defect is like a hole-pattern with about 1um diameter, and induced by diffusion of acid which makes photoresist soluble in developer, even though photoresist is not exposed with KrF. With some experiment results, we found out that HCl gas, by-product of high temperature oxide which is contained inside voids between two gate lines diffuses into photoresist through high temperature oxide from voids, makes photoresist soluble in developer, and eventually creates the hole-type defect on photoresist. To prevent this defect, we can suggest some methods which are substitution of KrF photoresist into I-line photoresist, modification of oxide deposition recipe to suppress by-product, and applying of non-CAR (Chemically Amplification Resist) type KrF photoresist not sensitive to acid.