System and method for an optical MEMS transducer
According to an embodiment, an optical MEMS transducer includes a diffraction structure including alternating first reflective elements and openings arranged in a first plane, a reflection structure including second reflective elements and configured to deflect with respect to the diffraction structure, and an optical element configured to direct a first optical signal at the diffraction structure and the reflection structure and to receive a second optical signal from the diffraction structure and the reflection structure. The second reflective elements are arranged in the first plane when the reflection structure is at rest. Other embodiments include corresponding systems and apparatus, each configured to perform various embodiment methods.
1. An optical microelectromechanical systems (MEMS) transducer comprising:
a diffraction structure comprising alternating first reflective elements and openings arranged in a first plane;
a reflection structure comprising second reflective elements and configured to physically deflect with respect to the diffraction structure, wherein the second reflective elements are arranged in the first plane when the reflection structure is at rest; and
an optical element configured to direct a first optical signal at the diffraction structure and the reflection structure and to receive a second optical signal from the diffraction structure and the reflection structure.
2. The optical MEMS transducer of claim 1 , wherein the diffraction structure further comprises:
a ventilated support structure attached to an anchor; and
a diffraction grating supported by the ventilated support structure, the diffraction grating comprising the first reflective elements and the openings.
3. The optical MEMS transducer of claim 1 , wherein the reflection structure further comprises:
a deflectable membrane layer offset from the diffraction structure; and
a plurality of extension structures attached to the deflectable membrane layer, wherein
each extension structure of the plurality of extension structures extends towards an opening of the diffraction structure, and
each of the second reflective elements is attached to an extension structure of the plurality of extension structures inside an opening of the diffraction structure.
4. The optical MEMS transducer of claim 3 , wherein the deflectable membrane layer and the plurality of extension structures are formed of a same fabricated layer disposed in a single fabrication step.
5. The optical MEMS transducer of claim 3 , wherein the deflectable membrane layer further comprises a plurality of openings, each opening of the plurality of openings arranged between two extension structures of the plurality of extension structures.
6. The optical MEMS transducer of claim 1 , further comprising:
a laser configured to transmit a first optical signal at the diffraction structure; and
a photodiode configured to receive a second optical signal from the diffraction structure and the reflection structure.
7. The optical MEMS transducer of claim 1 , further comprising a substrate comprising a cavity extending completely through the substrate from a top surface of the substrate to a bottom surface of the substrate, wherein the diffraction structure and the reflection structure are arranged on the top surface of the substrate above the cavity.
8. An optical microelectromechanical systems (MEMS) transducer comprising:
a rigid backplate comprising a diffraction grating arranged in a first plane;
a deflectable membrane comprising a reflective surface, the reflective surface being arranged in the first plane;
a light emitting element configured to transmit a first optical signal at the diffraction grating; and
an optical detector configured to detect a second optical signal from the diffraction grating and the reflective surface.
9. The optical MEMS transducer of claim 8 , wherein the rigid backplate further comprises a ventilated support structure extending from the diffraction grating to an anchor.
10. The optical MEMS transducer of claim 9 , wherein the ventilated support structure comprises a perforated plate comprising a plurality of perforations.
11. The optical MEMS transducer of claim 9 , wherein the ventilated support structure comprises a plurality of support beams extending radially from the diffraction grating to the anchor.
12. The optical MEMS transducer of claim 8 , wherein the deflectable membrane comprises:
a deflectable membrane layer offset from the rigid backplate;
a plurality of extension structures attached to the deflectable membrane layer, wherein each extension structure of the plurality of extension structures extends towards an opening in the diffraction grating; and
a plurality of reflective elements together comprising the reflective surface, wherein each reflective element of the plurality of reflective elements is attached to an extension structure of the plurality of extension structures inside an opening in the diffraction grating.
13. The optical MEMS transducer of claim 12 , wherein
the plurality of reflective elements comprises a first device layer attached to each extension structure of the plurality of extension structures, and
the first device layer comprises a same layer disposed in a same fabrication step as the rigid backplate.
14. A method of fabricating an optical microelectromechanical systems (MEMS) transducer, the method comprising:
forming a rigid backplate comprising a diffraction grating arranged in a first plane;
forming a deflectable membrane comprising a reflective surface, the reflective surface being arranged in the first plane;
forming a light emitting element configured to transmit a first optical signal at the diffraction grating; and
forming an optical detector configured to detect a second optical signal from the diffraction grating and the reflective surface.
15. The method of claim 14 , wherein:
forming the rigid backplate comprises forming the rigid backplate on a substrate; and
forming the deflectable membrane comprises
forming a plurality of reflective elements in openings in the diffraction grating,
forming a structural material on the rigid backplate,
patterning the structural material to include a plurality of vias extending to the plurality of reflective elements,
forming the deflectable membrane on the structural material, the deflectable membrane being formed over the rigid backplate and attached to the plurality of reflective elements,
removing a backside portion of the substrate, the backside portion extending from a bottom surface of the substrate to a top surface of the substrate beneath the rigid backplate, and
removing a portion of the structural material between the rigid backplate and the deflectable membrane.
16. The method of claim 15 , wherein forming the rigid backplate comprises:
depositing a backplate layer; and
patterning the backplate layer to form a ventilated support structure and the diffraction grating.
17. The method of claim 15 , wherein forming the deflectable membrane comprises:
depositing a membrane layer on the structural material and in the plurality of vias; and
patterning the membrane layer.
18. The method of claim 15 , further comprising forming a plurality of openings in the deflectable membrane, each opening of the plurality of openings being between vias of the plurality of vias.
19. The method of claim 15 , wherein removing the backside portion of the substrate comprises etchings using a Bosch process.
20. The method of claim 15 , wherein the plurality of reflective elements and the rigid backplate are formed of a first fabricated layer formed in a same deposition step.