Full chip compensation for local-flare-induced CD error using OPC/DRC method

Flare has become a significant problem for low K, lithography process.[1] It is generally divided into three parts: long-, local-, short-range. Long-range flare is scattering over a scale of tens of microns, come from reflections within the projection lens. Short-range is scattering over a scale of about 1 micron or less, come from lens aberrations. And local-range flare is scattering over about 1 to 10 microns, comes from inhomogenieties within glass and local pattern density. Especially, local-range flare causes the printed width to vary or degrade printing accuracy. Normally, the local-range flare effect is increase by local pattern density. Therefore the local flare effect can be reduced if the effect of local pattern density within die is compensated effectively. In this paper, we discussed full chip compensation for local flare effect using OPC/DRC method. First of all, we investigated relationship between local flare and pattern density using test pattern and extracted OPC model according to pattern density and also analyzed within chip pattern density distribution using DRC. We separated original layout to OPC target layout according to local pattern density, applied different OPC model to each separated layout. We will show within chip CD variation was improved after local flare effects reduction.