Influence of Airflow Disturbance on the Uniformity of Spin Coating Film Thickness on Large Area Rectangular Substrates

Spin coating is widely used to form a uniform film on a solid substrate. Airflow disturbance has been considered as one of the most influential factors of film thickness, especially for spin coating on large area noncircular substrates. However, the exact mechanism of airflow disturbance influence, such as air shear force effect or indirect effects on evaporation, so far, remains ambiguous. In this work, the influence mechanism of airflow disturbance on film uniformity on large rectangular substrates is studied. The experiment with airflow disturbance is artificially introduced and contrasts with the common spin coating conditions. Both numerical simulations and experiments show a causal relationship between airflow disturbances and the uniformity of the spin coating film. The film thickness and airflow field results show that the film uniformity is affected by solvent evaporation and air shear force caused by airflow disturbance. Additionally, evaporation inhibition and airflow disturbance results do not support the proposition that air shear forces can affect film uniformity, but that solvent evaporation is the primary factor affecting film thickness uniformity. These conclusions are beneficial to the understanding of the mechanism of airflow disturbance influence on the film thickness uniformity on large rectangular substrates.