Impact of mask error on OPC for 45-nm node

As critical dimensions (CDs) approach (lambda) /two, the use of optical proximity correction (OPC) relies heavily on the ability of the mask vendor to resolve the OPC structures consistently. When an OPC model is generated the reticle and wafer-processing errors are merged, quantified, and fit to a theoretical model. The effectiveness of the OPC model depends greatly on model fit and therefore consistency in the reticle and wafer processing. Variations in either process can 'break' the model resulting in the wrong corrections being applied. Reticle manufacturing variables that effect OPC models are exposure tool resolution, etch process effects, and process push (pre-bias of the fractured data). Most of the errors from these reticle-manufacturing variables are seen during model generation, but there are some regions that are not, and fail to be accounted for such as extremes in the line ends. Since these extreme regions of the mask containing the OPC have a higher mask error enhancement factor (MEEF) than that of the rest of the mask, controlling mask-induced variables is even more important. The phase shift mask (PSM) is one of the most effective approaches to improve ArF lithography performance. MoSi or SiON dry etching technology play an important role to fabricate phase shift masks, such as space bias type Alternating (Alt.) PSM and chrome-less phase shift masks (CPL). The profile of the etched quartz affects the lithography performance. In this paper we evaluate the nominal influences of the MoSi or SiON profiles on pattering and OPC by rigorous electromagnetic field simulations. The influence of the MoSi or SiON profile is investigated by evaluating imaginary masks. In this experiment, we simulated attenuated PSMs with tapered sidewalls, high round and micro-trenches of varying depths. OPC modeling performances of the imaginary masks are measured by the OPC print image CD and model fitting results. I compare the result of print image CD with simulation. I investigate how well the OPC print image CD measurement corresponds to the simulation. Mask CD error and sidewall angle strongly affect the OPC modeling performance. However, micro-trench does not affect the OPC performance. This paper quantifies the effects reticle processing has on the OPC model generation, and also mask CD variations and variable sidewall angles affect the OPC print image CD and OPC model fitting for attenuated PSMs, micro trench depth does not play an important role for OPC print image CD and OPC model fitting.