Photoresist Spray Coating on Silicon Wafers With Acoustic Resonance Atomization

Aiming at the poor film evenness in conventional ultrasonic spraying coating methods, an acoustic resonance atomization (ARA) is proposed for spray coating on silicon wafers using an in-house experimental prototype. By modulating the acoustic pressure distribution in the optimized acoustic chamber, the ARA can achieve atomized photoresist droplets with $\sim 8.5~\mu $ m in median diameter and concentrated droplet concentration. For mesoscale photoresist droplets, the uniform film of AZ P4620 photoresist is coated on silicon wafers by exploring and optimizing the substrate temperatures and spray velocity. The mechanism of uniform film formation by mesoscale photoresist droplets is explored. Smaller droplets can effectively fill the micro-gaps within the photoresist film layer, forming a dense and uniform film. The experimental results demonstrate that the employed coating process can obtain a controllable photoresist film thickness and evenness index of less than 5% with a high-quality film layer, which provides an alternative technological solution for the spray coating.