The Simulation and Inspection for the Starting Phenomenon of Slit Coating Process on Glass Substrate

We developed a two-dimensional Computational Fluid Dynamics (CFD) model of a slit nozzle and coating for photoresist, using the Volume Of Fluid (VOF) to calculate the transient free surface. Parameters studied in simulation, including contact angle, liquid feed rate, slit gap, and coating gap. Simulation results yielded information on operation and buildup conditions, enabling us to examine microscopic fluid flows. Experiments used a slit coater (ITRI) having a slit nozzle 370 mm wide and a 100 µm slit gap, and set on a vertical moving table. A glass substrate was fixed on a horizontal moving table by a vacuum pump. Photoresist is pumped from a tank to the slit nozzle by a plunger. During coating, a CCD camera facing the slit gap imaged coating conditions. Experimental parameters studied included substrate speed, coating gap, and photoresist feed rate. The substrate was operated at 10 to 20 mm/second, the coating gap was set at 100 µm, and the photoresist feed rate was from 0.4 to 0.8 ml. Simulation and experimental results confirmed that CFD simulation was possible in designing the slit nozzle and preverifying coating. Photoresist coating was possible below 1.5 µm thick with 5%uniformity.