Image fidelity verification: contourIFV

Abstract

The rapidly escalating complexity of resolution enhancement techniques (RET), now commonplace in leading edge lithography, requires accurate verification to avoid yield and performance problems on the patterned wafers. Model-based verification techniques that have been derived from optical proximity correction (OPC) obtain the required checking speed from sparse sampling of the layout at discrete evaluation points along the edges of layout patterns. This sparse sampling allows accurately calibrated models to be used for full chip checking applications. However, there is a demonstrated risk of missing significant patterning errors due to the sparse and edge-centric sampling of the layout. Grid-based simulation approaches which calculate the image on a fine grid over the entire layout space accurately detect patterning problems anywhere in the layout, but can be executed at reasonable runtimes for aerial image models only. The challenge for full-chip model-based verification of RET-enhanced layouts is, therefore, a trade-off between sparse, edge-centric simulation using accurate models versus simulations using approximate models over the entire layout space. This paper presents an approach, termed contourIFV, that has been demonstrated to overcome the aforementioned problems and has been shown to provide significant value in the verification of the RET and OPC prescription.