Multi-Layer Thick Resist Process Using Liquid-Crystal-Display Projection Exposure and Vacuum Treatment Process

Abstract

Thick resist patterning process using liquid-crystal-display (LCD) matrix exposure is demonstrated. Because LCD panels have sufficient contrast between dark and bright cells only for light with wavelengths of longer than 430 nm, resists sensitive to ultra violet (UV) light cannot be directly patterned. For this reason, multi-layer resist structure of OFPR 800/aluminum/SU-8 is developed. After patterning OFPR 800/aluminum using the LCD matrix exposure by light with a central wavelength of 450 nm, patterns are inversely replicated to SU-8 by a flood exposure of UV light. In the initial research stages, a lot of wrinkles and cracks are formed in the aluminum film by the pre-bake process of OFPR 800. However, no-bake vacuum treatment process is contrived, and the defects of SU-8 caused by the excessive exposure through the aluminum cracks are completely prevented. Stable patterning process of thick SU-8 using LCD matrix exposure is certainly established.

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

“…In the past research, three-layer resist structure composed of 1 μm thick OFPR 800 (Tokyo Ohka Kogyo), aluminum film evaporated in nanometer order thick, and 100 μm thick SU-8 was investigated. 38,39) After prebaking the wafer, the positive resist OFPR 800 was patterned at first by exposing using a maskless LCD exposure system. Because all the light rays were stopped by the middle-layer aluminum film, only the OFPR 800 was patterned as assigned on the LCD panel.…”

“…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.…”

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

“…Therefore, maskless lithography systems are preferred, and various exposure systems using liquid-crystal-display (LCD) panels in place of reticles have been proposed [1][2][3][4][5][6][7]. The authors also developed several systems in the past researches [8][9][10][11][12][13][14], and recently, proposed a very low-cost exposure system using a commercial LCD projector as it was [15].…”