Novel Electron Beam Direct Writing Technique for the Hole Pattern of Quarter-Micron Devices

The electron beam (EB) direct writing technique for the hole pattern of quarter-micron devices was developed. The resist structure used in this technique was EB resist (0.5 µm)/“buffered tungsten (W) layer” (0.05 µm)/SiO 2 /Si substrate. The “buffered W layer” was dry-etched using an EB resist mask, then SiO 2 was dry-etched using the “buffered W layer” as the dry-etching mask. The alignment mark structure was TiN (0.035 µm)/“alignment W layer” (0.085 µm)/Al (0.4 µm) multilayered metallization which was used for metal wiring beneath the SiO 2 layer. The thicknesses of the “alignment W layer” and “buffered W layer” have a strong influence on alignment mark detection and were optimized using computer simulation. Due to this structure and process sequence, high resolution was attained without using a trilayer resist process. In addition to this resist structure, proximity effect correction with data undersizing was applied in order to fabricate patterns as designed.