Fabrication Of 5X Reticles Fore 16M DRAMS By Using A Variable-Shaped Electron-Beam System

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Abstract
Recent progress of microfabrication technologies makes it possible to develop 16M DRAMs, the most advanced VLSI devices, by optical lithography using high-performance 5:1 wafer steppers. ior optical lithography, it is very important to fabricate defect-free and accurate reticles with high throughput. Increasing the degree of device integration causes reduction of the pattern dimensions and enlargement of the chip size. This makes the writing time much longer in using the conventional raster-scan electron-beam (EB) system. Moreover, the reticles, which cannot comprise multiple dies under the limitation of the image field of the wafer stepper, must be inspected by the data-comparison method. A software system, that prepare the data for the variable-shaped, vector-scan EB system (JBX-6AIII) efficiently and produce compacted data for the reticle inspection system (KLA-228), has been developed. The variable-shaped EB system has the advantages of a high writing speed and a small address unit size. However, the throughput of the data preparation is very low compared with the raster-scan EB system, because complicated processes such as overlap removal and tone reversal are required. In order to improve the throughput of the data preparation, a hierarchical data format has been introduced into the data-preparation software. The data of 16M DRAMs for the variable-shaped EB system were prepared in 1 hour/layer. To inspect the single-die reticles of 16M DRAMs, a data-comparison inspection system and data conversion software with the capability for data compaction have been used. Defect-free 16M DRAM reticles have been fabricated with a reasonable throughput by these systems.

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