Etch stop and protection layer for capacitor processing in electroacoustic devices
Electroacoustic devices with a capacitive element and methods for fabricating such electroacoustic devices. An example method includes forming an acoustic device above a first region of a substrate, and forming a capacitive element above a second region of the substrate and adjacent to the acoustic device. The forming of the capacitive element may include forming a protective layer above the substrate where a first portion of the protective layer is above the second region of the substrate and a second portion of the protective layer is above the first region of the substrate, forming a dielectric region above the protective layer, and forming an electrode above the dielectric region. The dielectric region may include a different material than the protective layer.
1. A method for fabricating an electroacoustic device, comprising:
forming an acoustic device above a first region of a substrate; and
forming a capacitive element above a second region of the substrate and adjacent to the acoustic device, wherein forming the capacitive element comprises:
forming a protective layer above the substrate, wherein a first portion of the protective layer is above the second region of the substrate and wherein a second portion of the protective layer is above the first region of the substrate;
forming a dielectric region above the protective layer, the dielectric region comprising a different material than the protective layer; and
forming a first electrode above the dielectric region.
2. The method of claim 1 , wherein the first portion of the protective layer is formed above a second electrode of the capacitive element.
3. The method of claim 1 , further comprising:
forming an insulating layer; and
removing a portion of the insulating layer, wherein a second electrode is formed in an opening from which the portion of the insulating layer was removed, and wherein the protective layer is formed above the second electrode.
4. The method of claim 3 , wherein the insulating layer and the protective layer comprise a same material, and wherein a thickness of the protective layer is greater than a thickness of the insulating layer.
5. The method of claim 1 , wherein forming the dielectric region comprises:
forming the dielectric region above the first region and the second region of the substrate; and
etching a portion of the dielectric region that is above the first region of the substrate.
6. The method of claim 5 , wherein the second portion of the protective layer is formed above the acoustic device, the method further comprising removing the second portion of the protective layer above the acoustic device after the etching of the portion of the dielectric region that is above the first region of the substrate.
7. The method of claim 5 , wherein a third portion of the protective layer is above a third region of the substrate, the third region of the substrate being between the first region and the second region of the substrate.
8. The method of claim 7 , further comprising removing the third portion of the protective layer after etching of a portion of the dielectric region that is above the third region of the substrate.
9. The method of claim 1 , further comprising forming a second electrode of the capacitive element above the second region of the substrate, wherein the first portion of the protective layer is formed above the second electrode of the capacitive element.
10. The method of claim 1 , further comprising:
removing the second portion of the protective layer that is above the first region of the substrate; and
forming an insulating layer above the first region of the substrate after the removing the second portion of the protective layer.
11. The method of claim 10 , wherein the insulating layer is formed prior to forming the acoustic device.
12. The method of claim 11 , wherein forming the acoustic device comprises:
etching one or more portions of the insulating layer to form one or more openings in the insulating layer; and
forming an interdigital transducer (IDT) in the one or more openings.
13. The method of claim 12 , further comprising forming a third electrode above a busbar of the IDT.
14. The method of claim 1 , further comprising forming another acoustic device having a top electrode above the second region of the substrate, wherein the first portion of the protective layer is formed above a second electrode of the capacitive element, and wherein the second electrode of the capacitive element is the top electrode of the other acoustic device.
15. The method of claim 14 , wherein the first portion of the protective layer is formed above the other acoustic device.
16. The method of claim 14 , wherein a portion of the first electrode is formed adjacent to a lateral side of the top electrode.
17. The method of claim 14 , further comprising:
forming another protective layer above the acoustic device and the first electrode; and
trimming a portion of the other protective layer that is above the acoustic device.
18. The method of claim 17 , wherein the other protective layer is formed using a plasma enhanced chemical vapor deposition (PECVD) process.
19. The method of claim 1 , wherein the substrate comprises a piezoelectric substrate.
20. The method of claim 1 , wherein the protective layer comprises an aluminum oxide (Al 2 O 3 ) layer or an aluminum nitride (AlN) layer.
21. The method of claim 1 , wherein the protective layer is formed using an atomic layer deposition (ALD) process.
22. The method of claim 1 , wherein the protective layer comprises an etch stop layer configured to prevent dry etching beneath the etch stop layer.
23. An apparatus for signal processing, comprising:
an acoustic device disposed above a first region of a substrate; and
a capacitive element disposed above a second region of the substrate and adjacent to the acoustic device, wherein the capacitive element comprises:
a first electrode;
a protective layer disposed above the substrate, wherein a first portion of the protective layer is disposed above the second region of the substrate;
a dielectric region disposed above the protective layer and the first electrode, the dielectric region comprising a different material than the protective layer; and
a second electrode disposed above the dielectric region.
24. The apparatus of claim 23 , wherein the first portion of the protective layer is disposed above the first electrode.
25. The apparatus of claim 23 , wherein the acoustic device comprises an interdigital transducer (IDT).
26. The apparatus of claim 25 , wherein a third electrode is disposed above a busbar of the IDT.
27. The apparatus of claim 23 , wherein the substrate comprises a piezoelectric substrate.
28. The apparatus of claim 23 , wherein the protective layer comprises an aluminum oxide (Al 2 O 3 ) layer.
29. The apparatus of claim 23 , wherein the protective layer comprises an aluminum nitride (AlN) layer.
30. The apparatus of claim 23 , wherein the protective layer comprises an etch stop layer configured to prevent dry etching beneath the etch stop layer.