KrF Photoresist Profile Modulation by NH3 Plasma Treatment for 28 nm SRAM

A novel substrate surface treatment by NH
₃
plasma is introduced in KrF (248 nm) lithography module for 28-nm SRAM with embedded SiGe source/drain. The surface treatment is demonstrated to be able to effectively modulate the photoresist profile from undercut to footing by simply changing the NH
₃
plasma treatment time. It is revealed that the amino related hydrolysis reaction significantly affects the KrF photoresist development.