Application of a CFD Simulation on Spin Coating Process

In this study, a three-dimensional spin coating model has been built up to simulation the flow formation process of Lagrange droplets in photoresist coating process. Numerical calculation was performed by using the commercial computational fluid dynamics (CFD) package with a Reynolds-averaged N avier-Stokes (RANS) equation solver and a realizable
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- ε two-layer model. The effects of the spin speed, dispensed volume, solvent saturated vapor pressure, initial photoresist viscosity on the film thickness and uniformity have been examined with different spin coating process parameters and material parameters. The initial photoresist viscosity and saturation vapor pressure are important parameters that affect the average film thickness. The spin-coating process of a wetting recipe was simulated using the model and compared with an recipe without wetting. The wetting recipe involves spraying 2.5cc of PGMEA solvent during static conditions, followed by the addition of 1cc of Lagrange photoresist droplets within 4.8 seconds. In contrast, the recipe without wetting injects 2cc of droplets at low speed. At the completion of the entire recipe, the wetting recipe exhibits an improved average film thickness compared to the typical recipe, it shows that wetting recipe can realized the purpose of photoresist reduction.