Surface-acoustic-wave (SAW) filter with dielectric material disposed in a piezoelectric layer
An apparatus is disclosed for implementing a surface-acoustic-wave (SAW) filter with dielectric material disposed in a piezoelectric layer. In an example aspect, the apparatus includes a surface-acoustic-wave filter with a piezoelectric layer, an electrode structure, and dielectric material. The piezoelectric layer has at least one channel. The dielectric material is disposed in the at least one channel of the piezoelectric layer and is at least partially covered by the electrode structure.
1. An apparatus comprising:
a surface-acoustic-wave filter comprising:
a piezoelectric layer having a plurality of segmented channels;
an electrode structure comprising multiple fingers; and
dielectric material disposed in each segmented channel of the plurality of segmented channels of the piezoelectric layer, the dielectric material in each segmented channel of the plurality of segmented channels at least partially covered by a corresponding finger of the multiple fingers of the electrode structure, wherein each segmented channel of the plurality of segmented channels extends laterally beyond the corresponding finger of the multiple fingers.
2. The apparatus of claim 1 , wherein:
the electrode structure comprises:
a first busbar and a second busbar;
a first set of fingers of the multiple fingers extending from the first busbar toward the second busbar; and
a second set of fingers of the multiple fingers extending from the second busbar toward the first busbar, wherein the corresponding finger is part of the first set of fingers or the second set of fingers; and
the plurality of segmented channels comprises:
a first plurality of segmented channels that is proximate to ends of fingers associated with the first set of fingers; and
a second plurality of segmented channels that is proximate to ends of fingers associated with the second set of fingers.
3. The apparatus of claim 1 , wherein the plurality of segmented channels have a longitudinal axis that is substantially orthogonal to a longitudinal axis of the corresponding finger.
4. The apparatus of claim 3 , wherein:
the plurality of segmented channels comprises one channel that is proximate to a boundary of an active track region of the surface-acoustic-wave filter; and
the dielectric material disposed in the one channel is at least partially covered by the corresponding finger.
5. The apparatus of claim 1 , wherein the dielectric material in each segmented channel of the plurality of segmented channels is at least partially covered by an end of the corresponding finger of the multiple fingers.
6. The apparatus of claim 5 , wherein:
the plurality of segmented channels comprises a first plurality of segmented channels and a second plurality of segmented channels, wherein the first plurality of segmented channels is approximately parallel to the second plurality of segmented channels and is proximate to a boundary of an active track region of the surface-acoustic-wave filter;
the dielectric material disposed in the first plurality of segmented channels is at least partially covered by the multiple fingers; and
the dielectric material disposed in the second plurality of segmented channels is at least partially covered by the multiple fingers.
7. The apparatus of claim 1 , wherein the surface-acoustic-wave filter comprises a temperature-compensated surface-acoustic-wave filter.
8. The apparatus of claim 1 , wherein the plurality of segmented channels is arranged along an axis associated with a direction of acoustic-wave propagation.
9. The apparatus of claim 1 , wherein longitudinal axes of the plurality of segmented channels are substantially orthogonal to longitudinal axes of the multiple fingers.
10. The apparatus of claim 1 , wherein the dielectric material disposed in each segmented channel of the plurality of segmented channels is fully covered by the corresponding finger of the multiple fingers.
11. The apparatus of claim 1 , wherein a surface of the dielectric material that faces towards the electrode structure is substantially flush with a surface of the piezoelectric layer that faces towards the electrode structure.
12. The apparatus of claim 1 , wherein:
the electrode structure has a pitch; and
a transversal axis of the dielectric material has a width between approximately 30% and 200% of the pitch.
13. The apparatus of claim 1 , wherein a thickness of the dielectric material is between approximately 5% and 100% of a length of two times a pitch of the electrode structure.
14. The apparatus of claim 13 , wherein the thickness of the dielectric material is approximately 50% of the length of two times the pitch of the electrode structure.
15. The apparatus of claim 13 , wherein the thickness of the dielectric material is between approximately 5% and 20% of the length of two times the pitch of the electrode structure.
16. The apparatus of claim 1 , wherein the dielectric material comprises at least one of the following:
tantalum oxide (Ta2O5);
silicon oxide (SiO);
silicon dioxide (SiO2);
silicon nitride (SiN);
hafnium oxide (HfO2);
aluminium oxide (Al2O3);
tungsten trioxide (WO3); or
niobium pentoxide (Nb2O5).
17. The apparatus of claim 1 , wherein:
the surface-acoustic-wave filter comprises multiple cascaded resonators; and
a resonator of the multiple cascaded resonators comprises the piezoelectric layer, the electrode structure, and the dielectric material.
18. The apparatus of claim 1 , wherein:
the surface-acoustic-wave filter comprises a substrate layer;
the substrate layer comprises a compensation layer; and
the piezoelectric layer is disposed between the electrode structure and the compensation layer of the substrate layer.
19. The apparatus of claim 1 , wherein the surface-acoustic-wave filter comprises a thin-film surface-acoustic-wave filter (TFSAW).
20. An apparatus comprising:
a piezoelectric layer configured to propagate an acoustic wave along a first axis, the piezoelectric layer having a plurality of segmented recessed areas with a longitudinal axis that is substantially parallel to the first axis;
an electrode structure comprising multiple fingers; and
dielectric material positioned in the plurality of segmented recessed areas, the dielectric material having at least one surface exposed, the dielectric material in each segmented recessed area at least partially covered by a corresponding finger of the multiple fingers of the electrode structure, wherein each segmented recessed area of the plurality of segmented recessed areas extends laterally beyond the corresponding finger of the multiple fingers.
21. The apparatus of claim 20 , the electrode structure is in contact with the piezoelectric layer and the dielectric material.
22. The apparatus of claim 21 , further comprising:
a surface-acoustic-wave filter comprising the piezoelectric layer, the dielectric material, and the electrode structure.
23. The apparatus of claim 22 , wherein the dielectric material is present within a trap region of the surface-acoustic-wave filter.
24. The apparatus of claim 23 , wherein:
the surface-acoustic-wave filter is configured to generate the acoustic wave such that the acoustic wave has a first velocity within an active track region of the surface-acoustic-wave filter and a second velocity within the trap region; and
the second velocity is lower than the first velocity.