Model-based OPC/DRC considering local flare effects

Abstract

Local flare is caused by scattered light from lens surfaces, and it causes the printed line width to vary or degrades printing accuracy. Consequently, local flare must be taken into account when manufacturing IC devices that use lithography generations of less than 90 nm. In particular, an OPC (Optical Proximity Correction) tool with the ability to compensate local flare effects is required to maintain a high degree of printing accuracy. For model-based OPC to work properly, the predicted line width or shape given by a simulator should show good agreement with experimental results. Local flare intensity is calculated from the optical intensity in the absence of local flare, in order to take diffraction effects into account. An aerial image considering local flare effects is given simply by the sum of optical intensity and local flare intensity. To account for local flare effects in a practical manner, the local flare intensity is converted into a variation in the threshold for OPC/DRC (Design Rules Checking) that predicts the desired shape. This paper describes the impact of local flare, the simulation model including local flare effects, and its results. The simulation results show good agreement with the experimental results, indicating that effective OPC/DRC using this method is possible.