Model-based OPC for node random size contact hole with SRAF

One of the most crucial tasks for under 90nm IC is the small contact holes. Traditional model-based OPC is not effective and doesn't cover the process window regarding side-lobe at all. Although there are some novel approaches which have shown good performances, most of them focus on single size contact hole. Actually, there are much more challenges and difficulties to be implanted them on random size contact holes which have various hole sizes in such high 2-D MEEF condition. In consideration of manufacturability, the combination of off-axis, high NA and sub resolution assist features (SRAFs) is still the better candidate to improve process window of contact hole at 65nm generation. But, even that, the implementation of OPC of this combination still needs new concepts and methodologies involved. The reason is that both of random sizes and arbitrary locations really create a lot of difficulties coming from the conflictive placement of SRAFs and side-lobe for various hole sizes and pitches. Moreover, process window of various pitches are strongly affected by SRAFs rules and side-lobe. Therefore, in order to build a more complete OPC model, the OPC model needs special treatment and procedure together with the consideration of design rule and hybrid OPC handling. This study will depict the whole concept and design avoiding the blocks of model-based OPC treatment and build a working flow for OPC SRAF adding.