Refractory seed metal for electroplated MEMS structures

A method of creating a micro-electrical-mechanical system (MEMS) device comprising:

• providing a substrate;
• and
• forming a free-standing metal MEMS structure on the substrate, wherein forming the free-standing metal MEMS structure comprises:
• applying a sacrificial release layer on a portion of the substrate;
• applying a layer of seed metal over the substrate and the sacrificial release layer, wherein the seed metal comprises at least one of a refractory metal and a refractory metal alloy;
• applying a photoresist layer on a portion of the layer of seed metal;
• electroplating a metallic material onto the layer of seed metal not covered by the photoresist layer to form a free-standing structure;
• coating at least one additional side of the free-standing structure with a protective layer, the protective layer comprising a material that is resistant to damage or etching during a fabrication processes;
• and
• subsequent to coating at least one additional side of the free-standing structure with a protective layer, removing the photoresist layer, the sacrificial release layer, and a portion of the layer of seed metal not in contact with the free-standing structure, such that the free-standing structure is cantilevered over the substrate;
• wherein a portion of the layer of seed metal in contact with the free-standing structure remains on an underside of the free-standing structure subsequent to the removing of the photoresist layer, the sacrificial release layer, and the portion of the layer of seed metal not in contact with the free-standing structure.

A free-standing and suspended metal micro-electro-mechanical system (MEMS) structure of a MEMS device, wherein the metal MEMS structure is fabricated by:

• applying a sacrificial release layer on a portion of a substrate;
• applying a seed layer of refractory metal over the substrate and the sacrificial release layer;
• applying a photoresist layer on a portion of the seed layer;
• electroplating a metallic material onto the seed layer in an area not covered by the photoresist layer to form a free-standing structure, the free-standing structure being mechanically coupled to and electrically connected with the seed layer;
• and
• removing the photoresist layer, the sacrificial release layer, and a portion of the seed layer such that a layer of refractory metal remains on an underside of the free-standing structure to collectively form a free-standing and suspended metal MEMS structure on the substrate;
• wherein applying the seed layer and electroplating the metallic material further comprises selecting a thickness for each of the seed layer and metallic material to be applied such that a product of a residual stress in the free-standing structure and the thickness of the free-standing structure is greater than three times (3×) that of a product of a residual stress in the seed layer and the thickness of the seed layer.