Method of fabricating reflective mirror by wet-etch using improved mask pattern and reflective mirror fabricated using the same

A process of integrally fabricating by an etching technique an oscillating body having a unitary configuration including both a reflective mirror having a reflective surface, and a plate-shaped spring,

• wherein the reflective mirror is used for optical scan, in a manner that the reflective mirror is angularly oscillated about an oscillation axis parallel to the reflective surface, to thereby vary a direction in which light is reflected from the reflective surface upon entry thereinto,
• wherein the plate-shaped spring is shaped to have a beam structure which extends from the reflective mirror along the oscillation axis and which has a stepped portion,
• wherein the plate-shaped spring is excited by a vibration occurring in at least a portion of the oscillating body, to cause at least a torsional vibration about the oscillation axis, to thereby angularly oscillate the reflective mirror about the oscillation axis by at least the caused torsional vibration, and
• wherein the process comprises:
• a coating step of coating opposite faces of a to-be-processed portion of a plate-shaped etchable material made of a single crystal material, with two etching masks, respectively, wherein the to-be-processed portion is to be processed into the beam structure;
• a mask-pattern forming step of forming a pair of mask patterns on the two etching masks which have been deposited on the opposite faces of the to-be-processed portion, respectively, wherein the pair of mask patterns have respective shapes for forming the beam structure;
• and
• a wet-etching step of, after formation of the pair of mask patterns, wet-etching the etchable material by immersing the etchable material in an etchant.

A method of fabricating by an etching technique a plate-shaped reflective mirror having a reflective surface on which light is incident, the method comprising:

• a coating step of coating at least one of opposite faces of a plate-shaped etchable material made of a single crystal material, with an etching mask;
• a mask-pattern forming step of forming a mask pattern on at least one of opposite faces of the etching mask which has been deposited on the etchable material;
• and
• a wet-etching step of wet-etching the etchable material on which the etching mask has been deposited, by immersing the etchable material in an etchant having a predetermined temperature and a predetermined concentration,
• wherein the mask pattern is generally in the shape of a convex octagon, and
• the mask pattern is shaped to have first sides parallel to a reference line, and second sides perpendicular to the reference line,
• wherein the mask pattern is located relative to the etchable material, such that the first and second sides are each perpendicular to at least one of <110> crystallographic directions of the etchable material on at least one of (100) crystallographic planes of the etchable material, and
• wherein the mask pattern has an outline including a first portion corresponding to at least a separate one of the (100) crystallographic planes, and a second portion corresponding to at least one of (111) crystallographic planes of the etchable material, per each one of four regions into which a surface of the etchable material is separated by two center lines of symmetry orthogonally intersecting at a center point of the mask pattern.