Impact of scanner illumination mode on CD control process margin

Abstract

Conventional and annular illumination modes for a 248 nm DUV scanner will be discussed in this paper for their advantage and drawbacks in critical dimension (CD) control. This includes proximity of line width through pitch size, marginality of resist profile measured as sidewall angle, depth of focus (DOF) in line width variation across field/wafer, and isolated space resolution, supported by SEM and scatterometer [1] metrology. Both illumination modes have been applied in the current technology node with sub-wavelength CD, variable pitch sizes, optical proximity correction (OPC) for resolution enhancement and process control optimization. Each illumination defines process margin in exposure, focus and CD uniformity, to gain capability with improved CD control.