Pattern Width Homogenization in the Field of Liquid-Crystal-Display Matrix Exposure by Adjusting Each Cell Transmittance

Abstract

Width homogenization of patterns printed by the desktop matrix-exposure system using a commercial liquid-crystal-display projector was investigated. At first, it was thought that the pattern width distribution caused by the dispersion of illumination-light intensity would be easily compensated by adjusting each bright cell transmittance. However, it was fundamentally difficult. Bottom peaks of the image intensity did not reach zero caused by the diffraction and intrinsic transmittance of black cells. For this reason, the bottom peaks also distributed depending on the illumination-light intensity. As a result, image contrast was degraded by reducing the transmittance of bright cells. To print line-and-space (L&S) patterns homogeneously in the exposure field, it was also necessary to increase the transmittance of black cells at places where the illumination-light intensity was low. By this countermeasure, down to 2-pixel L&S patterns were printed almost homogeneously. The width distribution of 4-and 5-pixel L&S patterns was suppressed almost within ±10%.

Two-layer resist process for printing thick patterns by exploiting a maskless projection exposure system using a liquid-crystal-display panel

“…5. [40][41][42] In this system, a commercial LCD projector was diverted and improved by changing the projection lens from the magnification lens to a newly prepared camera lens for macro-photography. In the exposure system, because the pixel size was 7.4 μm, and the black-matrix line width was 1.1μm, the pixel pitch was 8.5 μm.…”

“…For this reason, simple and low-cost maskless lithography systems using digital mirror devices (DMDs) [27][28][29][30][31][32] or liquidcrystal-display (LCD) panels [33][34][35][36][37][38][39][40][41][42] are watched with keen interest. Simple exposure systems using DMDs have already been commercially available for experimental usage from Neoark Corp., Aims System Corp., and others.…”