Substrate Effect on CD Control for Ion Implantation Layer Lithography Beyond 45nm Node

Abstract

Continuous technology-driven scaling has brought ion implantation (IMP) layers to a point, where the achievement of necessary resolution and line width start to meet significant process and material challenges, such as the non-negligible substrate effect. Underlying topography and film stack variation have created severe substrate reflectivity variation that affects critical dimension (CD), CD uniformity, resist profiles, and possibly defectivity, especially, the CD may vary according to different substrate film stacks, such as, trench isolation oxide (blank), and silicon. To minimize such CD offset on topography and blank area, photoresist (PR) thickness optimization in needed in addition to mask size adjustment which may meet some design rule constraints. Besides, in this paper we found that IMP process especially pre-amorphous implantation (PAI) for lightly doped drain (LDD) or source-drain (SD), may introduce one intermediate layer with different n,k that render extra effect on substrate reflectivity which will bring more complexity to photo CD control.