Step-and-repeat x-ray/photo hybrid lithography for 0.3- mu m MOS devices

X-ray/photo hybrid lithography is proposed as a method for achieving high resolution and high throughput in sub-half-micrometer VLSI fabrication. Distortions and correction techniques are discussed for accurate registration between X-ray and photo levels. Inherent distortions caused by each type of lithography are measured in advance. These distortions are corrected by introducing a linear shrinkage factor into e-beam data preparation for X-ray mask writing. The overlay accuracy between X-ray and photo levels and also between two X-ray levels is less than 0.15 mu m ( sigma ). A three-layer resist system is introduced to fully utilize high-sensitivity and high-resolution features of an X-ray positive resist, FBM-G. An application of hybrid lithography to 0.3- mu m MOS devices is presented.