The Method of OPC Correction for Narrow Neck Structures in LDD Layer

Lightly doped drain (LDD) ion implantation is an important process for reducing the hot electron effect. LDD original layout is derived from other original layers through Boolean operations (EB rule). Since it is an EB rule-generated layer, it is easy to have narrow neck structures with dimensions smaller than MRC. In the model-based optical proximity correction process (MBOPC), the movement of the edges of the narrow neck structures is limited, which leads to suboptimal correction results in this region. At the same time, due to the MRC issue in this region, the mask making precision is reduced. In order to solve the above problems, this paper proposes an optical proximity correction method for these narrow neck structures. By removing a rectangular shape from the concave-corner type narrow neck structure with small width and adding a rectangular shape to the convex-corner type narrow neck structure with small space, the initial correction layer is generated before the model correction stage. After that, on the initial correction layer, edge segmentation and model iterative correction are performed to break the limitation of edge movement caused by MRC. By this method, the correction results in the narrow neck structure region are more convergent, and the distances from simulated contour to the gate channel satisfy the process requirement specifications.