Spray etching 2 μm features in 304 stainless steel

304 stainless steel samples were patterned with either a photoresist (PR) mask or a silicon nitride (Si3Ni4) mask and then subjected to either wet immersion etching or spray etching techniques with ferric chloride (FeCl3). The silicon nitride mask provides much better adhesion to the stainless steel substrate resulting in less undercut compared to the PR mask. When a silicon nitride mask was subjected to spray etching, better adhesion and less undercut enabled features as small as 1.8 mu m with an etch depth of 5.6 mu m. This is an order of magnitude smaller than current spray etching techniques (20-50 mu m) used in the steel industry. This procedure will allow spray etching features for batch fabrication for a variety of metals including steels, aluminum, nickel-based alloys and copper-based alloys with microscale resolution.