Thermally assisted magnetic head having an asymmetric plasmon antenna and manufacturing method thereof

A method for manufacturing a thermally assisted magnetic head having a plasmon antenna shaped as a triangular flat plate as viewed from a direction perpendicular to a medium-facing surface, comprising the steps of:

• forming a metal layer to be the plasmon antenna on an insulating layer;
• forming a first mask layer on part of a stacking surface of the metal layer and etching a region of the stacking surface of the metal layer that is not masked by the first mask layer, to form thereby, in the metal layer, a first inclined surface extending from the stacking surface to the insulating layer;
• forming a second mask layer on the first inclined surface and the stacking surface of the metal layer, and etching the second mask layer to remove the second mask layer from the stacking surface of the metal layer, leaving the second mask layer remained on the first inclined surface;
• and
• forming on the metal layer a second inclined surface extending from the first inclined surface to the insulating layer and defining, with the first inclined surface, an interior angle α of a first corner of the plasmon antenna, by further etching the metal layer, using as a mask the second mask layer remained on the first inclined surface, wherein
• the first inclined surface and the stacking surface of the insulating layer define an interior angle β of a second corner of the plasmon antenna;
• the second inclined surface and the stacking surface of the insulating layer define an interior angle γ of a third corner of the plasmon antenna, and
• relationships α<β, α<γ and β≠γ are satisfied.