High-resolution maskless lithography

An innovative high-resolution maskless lithography system is designed employing a combination of low- and high-numerical-aperture (NA) projection lens systems along with integrated micro-optics, and using Texas Instruments' super video graphic array (SVGA) digital micromirror device (DMD) as the spatial and temporal light modulator. A mercury arc lamp filtered for the G-line (lambda = 435.8 nm) is used as the light source. Exposure experiments are performed using data extraction and transfer software, and synchronous stage control algorithms derived from a point array scrolling technique. Each exposure scan produces a field width (L/S) of approximately 8.47 mm with a field length (longitudinal field) limited only by onboard memory capacity. DMD frame rates of up to 5 kHz (kframes/s), synchronized to the stage motion, are achievable. In this experiment, TSMR-8970XB10 photoresist (PR), diluted to 3.8 cP with PR thinner is prepared. The PR is spin-coated onto a chrome-coated glass substrate to 1.0-mum thickness with 0.1-mum uniformity. A 0.4-mum scan step is used and 27,000 DMD data frames are extracted and transferred to the DMID driver. Results indicate consistent 1.8-mum line space (US) resolved across the entire field width of 8.47 mm. Given optimized exposure and development conditions, 1.5-mum L/S is also observed at certain locations. The potential of this maskless lithography system is substantial; its performance is sufficient for applications in microelectromechanical systems (MEMS), photomasking, high-resolution LCD, high-density printed circuit boards (PCBs), etc. Higher productivity is predicted by a custom Wine (X = 405 nm) lens system designed and used in conjunction with a violet diode laser systems and the development of a real-time driver. (C) 2003 Society of Photo-Optical Instrumentation Engineers.