Selective step coverage for micro-fabricated structures

A method for selective coating of micro-fabricated structures within a micro-optical bench device, comprising:

• providing a substrate comprising the micro-fabricated structures;
• providing a shadow mask comprising a top surface, a first bottom surface, and a second bottom surface formed from a recessed portion of the first bottom surface, the shadow mask further comprising a first opening within the top surface and a second opening within the second bottom surface, wherein the second opening is aligned with the first opening and has a second width less than a first width of the first opening, a first overlap between the first opening and the second opening forming a first hole within the shadow mask, wherein the shadow mask further comprises a protection lip along the second bottom surface opposite a first sidewall of the first hole, the protection lip being on only another side of the first hole opposite the first sidewall, the protection lip comprising a lip width corresponding to a difference between the first width of the first opening and the second width of the second opening, the protection lip further comprising a lip thickness corresponding to a difference between a first depth of the first hole extending from the top surface to the second bottom surface and a second depth of the first opening;
• placing the shadow mask on the substrate such that the first bottom surface of the shadow mask is touching the substrate and the second bottom surface of the shadow mask faces the substrate with a gap therebetween;
• sputter depositing a coating material on a first surface of a first micro-fabricated structure of the substrate through the first hole, wherein the first surface is out-of-plane with respect to a plane of the substrate;
• and
• using the protection lip to protect a second surface of a second micro-fabricated structure of the substrate from the coating material during the sputter depositing of the coating material on the first surface of the first micro-fabricated structure, wherein the second surface of the second micro-fabricated structure opposes the first surface of the first micro-fabricated structure on the substrate.