Modeling scanner signatures in the context of OPC

Abstract

The requirement for OPC modeling accuracy becomes increasingly stringent as the semiconductor industry enters sub- 0.1um regime. Targeting at capturing the IC pattern printing characteristics through the lithography process, an OPC model is usually in the form of the first principle optical imaging component, refined by some phenomenological components such as resist and etch. The phenomenological components can be adjusted appropriately in order to fit the OPC model to the silicon measurement data. The optical imaging component is the backbone for the OPC model, and it is the key to a stable and physics-centric OPC model. Scanner systematic signatures such as illuminator pupil-fill, illuminator polarization, lens aberration, lens apodization, flare, etc., previously ignored without significant accuracy sacrifice at previous technology nodes, but are playing non-negligible roles at 45nm node and beyond. In order to ensure that the OPC modeling tool can accurately model these important scanner systematic signatures, the core engine (i.e. the optical imaging simulator) of OPC simulator must be able to model these signatures with sufficient accuracy. In this paper, we study the impact on optical proximity effect (OPE) of the aforementioned scanner systematic signatures on several 1D (simple line space, doublet line and doublet space) and 2D (dense line end pullback, isolated line end pullback and T-bar line end pullback) OPC test patterns. We demonstrate that the scanner systematic signatures have significant OPE impact on the level of several nanometers. The predicted OPEs and impact from our OPC simulator matches well with results from an industry standard lithography simulator, and this has laid the foundation of accurate and physics-centric OPC model with the systematic scanner signatures incorporated.