Micromachined horn
View Patent ↗An acoustic device includes a transducer formed on a first surface of a substrate and an acoustic horn formed in the substrate by a dry-etching process through an opposing second surface of the substrate. The acoustic horn is positioned to amplify sound waves from the transducer and defines a non-linear cross-sectional profile.
1. A method of fabricating an integrated acoustic device, the method comprising:
forming a transducer on a front side of a substrate; and
dry-etching an acoustic horn through a back side of the substrate, a throat of the acoustic horn positioned adjacent to the acoustic transducer, wherein dry-etching the acoustic horn comprises varying a flow ratio of compounds used for etching the substrate to vary a cross-sectional shape of a sidewall of the acoustic horn.
2. A method of fabricating an integrated acoustic device, the method comprising:
forming a transducer on a front side of a substrate; and
dry-etching an acoustic horn through a back side of the substrate, a throat of the acoustic horn positioned adjacent to the acoustic transducer, wherein dry-etching the acoustic horn comprises varying at least one of a time of exposure, a pressure and a concentration of an etching compound used for etching the substrate to vary a cross-sectional shape of a sidewall of the acoustic horn.
3. The method of claim 1 , wherein the dry-etching comprises a deep reactive ion etching (DRIE) etching process.
4. The method of claim 1 , further comprising:
forming a pool of etch resistant material in the front side of the substrate to act as an etch stop for dry-etching the acoustic horn, the transducer being formed on the pool.
5. The method of claim 1 , further comprising:
forming a buried oxide layer on the front side of the substrate as an etch stop for dry-etching the acoustic horn, the transducer being formed on the buried oxide layer.
6. The method of claim 1 , wherein the transducer serves as an etch stop for dry-etching the acoustic horn.
7. The method of claim 1 , wherein dry-etching the acoustic horn further comprises:
dry-etching a first portion of the substrate using a first flow ratio of an etch compound and a polymer depositing compound; and
dry-etching a second portion of the substrate using a second flow ratio of the etch compound and the polymer depositing compound, the second flow ratio causing the sidewalls to be etched more vertically.
8. The method of claim 1 , wherein the cross-sectional shape of the sidewall is substantially exponential.
9. The method of claim 1 , wherein the cross-sectional shape of the sidewall comprises a stepped profile.
10. The method of claim 1 , wherein a shape of a mouth of the acoustic horn comprises one of a circle or an oval.
11. The method of claim 1 , further comprising:
applying a thin film coating on the sidewalls of the acoustic horn.
12. The method of claim 11 , wherein the thin film coating comprises diamond.
13. The method acoustic device of claim 11 , wherein the thin film coating comprises one of silicon nitride and silicon carbide.
14. The method of claim 2 , wherein the cross-sectional shape of the sidewall is substantially exponential.
15. The method of claim 2 , wherein the cross-sectional shape of the sidewall comprises a stepped profile.
16. The method of claim 2 , wherein a shape of a mouth of the acoustic horn comprises one of a circle or an oval.
17. The method of claim 2 , further comprising:
applying a thin film coating on the sidewalls of the acoustic horn.
18. The method of claim 17 , wherein the thin film coating comprises diamond.
19. The method acoustic device of claim 17 , wherein the thin film coating comprises one of silicon nitride and silicon carbide.
20. A method of fabricating an acoustic device, the method comprising:
forming a transducer on a front side of a substrate; and
dry-etching an acoustic horn through a back side of the substrate while varying at least one etch parameter such that the acoustic horn has an asymmetrical cross-sectional profile, a throat of the acoustic horn positioned adjacent to the acoustic transducer.