Maskless lithography using point array technique for fine patterns

We made a steady progress in designing a maskless exposure system using the point array technique. An epoch-making high-resolution maskless lithography system with resolution of less than 1 micron half-pitch has been developed. Exposure results indicated that patterns were resolved up to 0.8 microns half-pitch. Smooth edges of the photoresist for various directions were also confirmed. It is distinctive characteristics of the point array technique. Another merit is coexistence of high resolution and high throughput. 4 inches wafers used in this evaluation were exposed within 30 minutes. Therefore, we consider that tact time of manufacturing a photomask can be shortened drastically. Finally we have challenged to apply an annular stop to our new projection optics system in order to achieve further improvement of optical performance. However, we confirmed that a sidelobe of optical spots, which became stronger by using the annular stop, exerted an undesirable influence upon imaging for fine patterns. Consequently, it became clear that suppressing the sidelobe as well as narrowing the mainlobe of optical spots is important for microlithography using the point array technique.