Gradient raised frames n film bulk acoustic resonators
Gradient raised frames in film bulk acoustic resonators. In some embodiments, a film bulk acoustic resonator device can include a substrate, first and second metal layers implemented over the substrate, a piezoelectric layer between the first and second metal layers, and a gradient raised frame implemented relative to one of the first and second metal layers and configured to improve reflection of lateral mode waves and to reduce conversion of main mode waves into lateral mode waves.
1. A film bulk acoustic resonator device comprising:
a substrate;
a first metal layer and a second metal layer implemented over the substrate;
a piezoelectric layer between the first metal layer and the second metal layer, the first metal layer, the second metal layer, and the piezoelectric layer forming an active region; and
a gradient raised frame implemented relative to one of the first and second metal layers and configured to improve reflection of lateral mode waves and to reduce conversion of main mode waves into lateral mode waves, the gradient raised frame including a gradient portion that interfaces with one or more of the first metal layer, the second metal layer, or the piezoelectric layer without passing through the active region.
2. The film bulk acoustic resonator device of claim 1 wherein the second metal layer is above the piezoelectric layer and the first metal layer is below the piezoelectric layer.
3. The film bulk acoustic resonator device of claim 2 wherein the gradient raised frame is implemented above the second metal layer.
4. The film bulk acoustic resonator device of claim 2 wherein the gradient raised frame is implemented below the second metal layer.
5. The film bulk acoustic resonator device of claim 2 wherein the gradient raised frame has an angle relative to a direction parallel to the first and second metal layers and the piezoelectric layer.
6. The film bulk acoustic resonator device of claim 5 wherein the angle is less than 90°.
7. The film bulk acoustic resonator device of claim 2 wherein the gradient raised frame is made of one or more of a heavy material or a low acoustic impedance material.
8. The film bulk acoustic resonator device of claim 2 further comprising a second gradient raised frame implemented relative to one of the first and second metal layers and configured to improve reflection of lateral mode waves and to reduce conversion of main mode waves into lateral mode waves.
9. The film bulk acoustic resonator device of claim 8 wherein the gradient raised frame is implemented above the second metal layer and the second gradient raised frame is implemented below the second metal layer.
10. The film bulk acoustic resonator device of claim 8 wherein the gradient raised frame is implemented above the second metal layer and the second gradient raised frame is implemented above the first metal layer.
11. The film bulk acoustic resonator device of claim 8 wherein the gradient raised frame is implemented below the second metal layer and the second gradient raised frame is implemented below the first metal layer.
12. The film bulk acoustic resonator device of claim 8 wherein the gradient raised frame and the second gradient raised frame have respective angles relative to a direction parallel to the first and second metal layers and the piezoelectric layer.
13. The film bulk acoustic resonator device of claim 12 wherein each of the respective angles is less than 90°.
14. The film bulk acoustic resonator device of claim 8 wherein the gradient raised frame and the second gradient raised frame are made of one or more of a heavy material or a low acoustic impedance material.
15. The film bulk acoustic resonator device of claim 14 wherein the gradient raised frame is made of a heavy material and the second gradient raised frame is made of a low acoustic impedance material.
16. The film bulk acoustic resonator device of claim 2 wherein a passivation layer is implemented above the gradient raised frame.
17. The film bulk acoustic resonator device of claim 16 wherein the passivation layer includes a recessed frame adjacent to an active region.