Optimization of the Data Preparation for Variable Shaped Beam Mask Writing Machines
As the industry enters the development of the 65nm node the pressure on the data path and tapeout flow is growing. Design complexity and increased deployment of RET result in rapidly growing file sizes, which turned the commodity of mask data preparation into a real bottleneck. Mask manufacturing starting with the 130nm nodes is accompanied by an increasing deployment of variable shaped beam (VSB) mask writing machines. This transition requires the adaptation of the established data preparation path to these circumstances. Historically data has been presented mostly in MEBES or similar intermediate formats to the mask houses. Reformatting these data is a redundant operation, which in addition is not very efficient given the constraints of the intermediate formats. An alternate data preparation flow accommodating the larger files and re-gaining flexibility for TAT and throughput management downstream is suggested. This flow utilizes the hierarchical gds-format as the exchange format in the mask data preparation. The introduction of a hierarchical exchange format enables the transfer of a number of necessary data preparation steps into the hierarchical domain. The paper illustrates the benefit of hierarchical processing based on gds-files with experimental data on file size reduction and TAT improvement for direct format conversions vs. re-fracturing as well as other processing steps.
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