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Requirements of the e-beam shot quality for mask patterning of the sub-1X device

As the integration node becomes smaller in 193nm ArF immersion optical lithography, the complexity of optical proximity correction (OPC) has been increased continuously. Moreover, pattern design should be changed by more aggressive transformation technique such as inverse lithography technique (ILT). The greater fidelity to the target design on wafers is achieved by the application of these OPC techniques and results in the greater complexity level of the mask patterns. Complicated mask pattern consists of many corners and assist features, which raises the fraction of small shots in e-beam data. To get more accurate mask pattern, the dose stability of small shots becomes more important in a complicated mask pattern. In this paper, we present the evaluation results of the small shot handling capabilities of e-beam machines. According to the results, the information of small shots generated during data fracturing should be considered as a factor that defines the complexity of patterns in e-beam writing. It shows that the small shot printing in e-beam machines need to be improved in order to guarantee mask pattern quality.