Manufacturing method and optical deflector
A manufacturing method for an optical deflector, in which a piezoelectric film layer having a uniform film thickness is formed on a substrate layer, includes forming a cavity to open to a SiO 2 layer side in a forming region of an outside piezoelectric actuator by etching an SOI wafer from the SiO 2 layer side, covering an exposed surface of the cavity with a SiO 2 layer, and joining the SiO 2 layer of the SOI wafer and a support layer of an SOI wafer to manufacture an SOI wafer in which the cavity is enclosed. Next, after a recess is formed on a back side of the SOI wafer, anisotropic dry etching is carried out from the back side in a depth direction of the recess to remove the SiO 2 layer.
1. A manufacturing method for manufacturing an optical deflector including a mirror part, a movable support part, a fixed support part, first piezoelectric actuators interposed between the mirror part and the movable support part to turn the mirror part reciprocally about a first rotation axis at a resonance frequency, and second piezoelectric actuators interposed between the movable support part and the fixed support part to turn the mirror part reciprocally about a second rotation axis intersecting the first rotation axis at a non-resonant frequency lower than the resonance frequency, the manufacturing method comprising:
a first process in which etching regions and non-etching regions are set on a surface of a first Si wafer on a second SiO2 side, where the first Si wafer has a laminated structure in which a first SiO2 layer, a first Si layer, and a second SiO2 layer are arranged in order in a thickness direction, at least forming regions of the second piezoelectric actuators are included in the etching regions, at least forming regions of the movable support part are included in the non-etching regions, and etching is carried out only on the etching regions of the first Si wafer from the second SiO2 side to form cavities in the first Si layer to open to the second SiO2 side;
a second process of covering an exposed surface of the cavities with a third SiO2 layer;
a third process in which a surface of a second Si wafer on a second Si layer side, where the second Si wafer has a laminated structure of a fourth SiO2 layer and the second Si layer in the thickness direction, is joined to the surface of the first Si wafer on the second SiO2 layer side to form a third Si wafer with the cavities enclosed therein;
a fourth process of laminating a lower electrode layer, a piezoelectric film layer, and an upper electrode layer in order over an entire surface of the third Si wafer on the first SiO2 layer side as a laminated structure layer of piezoelectric actuators;
a fifth process in which anisotropic dry etching is carried out from a surface side of the third Si wafer to a depth of reaching the surface side of the second SiO2 layer to form the first piezoelectric actuators and the second piezoelectric actuators;
a sixth process in which etching is carried out from a back side of the third Si wafer to a depth of reaching a back side of the second SiO2 layer to form, on the back side of the third Si wafer, a recess surrounded by an inner wall of the fixed support part; and
a seventh process in which anisotropic dry etching is carried out from the back side of the third Si wafer in a depth direction of the recess to remove the second SiO2 layer and the third SiO2 layer.
2. The manufacturing method according to claim 1 , wherein a forming region of the mirror part and forming regions of the first piezoelectric actuators are included in the etching regions in the first process.
3. The manufacturing method according to claim 1 , wherein in the first process, a forming region of the mirror part is included in the etching regions, and forming regions of the first piezoelectric actuators are included in the non-etching regions.
4. The manufacturing method according to claim 1 , wherein in the first process, forming regions of the first piezoelectric actuators are included in the etching regions, and a forming region of the mirror part is included in the non-etching regions.
5. The manufacturing method according to claim 1 , wherein a forming region of the mirror part and forming regions of the first piezoelectric actuators are included in the non-etching regions in the first process.
6. The manufacturing method according to claim 5 , wherein the sixth process includes etching, after the fifth process, from the back side of the third Si wafer by excluding at least rib forming regions of the mirror part and the movable support part to form ribs of the second Si layer on back sides of the mirror part and the movable support part.
7. An optical deflector manufactured by the manufacturing method according to claim 1 , the optical deflector including the mirror part, the movable support part, the first piezoelectric actuators, the fixed support part, and the second piezoelectric actuators, and the optical deflector comprising:
the second Si layer, which is formed as a common substrate layer of the mirror part, the movable support part, the first piezoelectric actuators, and the second piezoelectric actuators, and in which the cavities are formed on back sides of at least the second piezoelectric actuators except a back side of at least the movable support part, and
the third SiO2 layer, with which sides of the cavities are covered.