Many MEMS devices include deep cavities, tall structures, or non-planar surfaces that challenge traditional spin-coated photoresist. Spray coating solves this problem by distributing photoresist as a fine mist across the wafer surface, allowing the resist to coat sidewalls and recessed structures that spin coating cannot reach effectively. We use spray coat photoresist to achieve conformal coverage on silicon wafers with deep features, trenches, or high-aspect-ratio microstructures. This enables reliable lithography on wafers that already contain etched MEMS features or thick deposited films. Why spray coat exists. On tall topography, spin-coated resist pools at the base and thins at step corners; spray coating lays a uniform resist skin over tops, sidewalls, and recesses. Advantages of Spray-Coated Photoresist - Uniform resist coverage over deep topography - Improved coating on etched trenches and cavities - Reliable lithography on high-aspect-ratio MEMS structures - Reduced resist thinning near step edges - Better pattern fidelity across complex microstructures MEMS Applications for Spray Coat Lithography Engineers typically turn to spray coating in later fabrication steps, when wafers already carry significant surface relief. Typical applications include: - Patterning on deep reactive ion etched (DRIE) silicon structures - Lithography over thick MEMS structural layers - Patterning on wafers with etched cavities or trenches - Microfluidic channel fabrication - Optical MEMS device processing - BioMEMS and lab-on-chip structures
