Slanted apodization for acoustic wave devices

Patent metadata

Field	Value
Publication number	US-11095266-B2
Application number	US-201715728133-A
Country	US
Kind code	B2
Filing date	Oct 9, 2017
Priority date	Oct 7, 2016
Publication date	Aug 17, 2021
Grant date	Aug 17, 2021

Abstract

A device includes a die and an interdigital transducer on the die. The interdigital transducer includes a first bus bar, a second bus bar, and a number of electrode fingers. The first bus bar is parallel to the second bus bar. The electrode fingers are divided into a first set of electrode fingers and a second set of electrode fingers. The first set of electrode fingers extend obliquely from the first bus bar towards the second bus bar. The second set of electrode fingers extend obliquely from the second bus bar towards the first bus bar, and are parallel to and interleaved with the first set of electrode fingers. By providing the electrode fingers oblique to the bus bars, spurious transverse modes may be suppressed while maintaining the quality factor, electromechanical coupling coefficient, and capacitance of the device.

First claim

What is claimed is:

1. A guided surface acoustic wave (SAW) device comprising:
a die comprising a substrate and a piezoelectric layer on the substrate, wherein the piezoelectric layer comprises one of lithium tantalate and lithium niobate and a thickness of the piezoelectric layer is less than two times a wavelength of a primary surface acoustic wave propagated in the piezoelectric layer (λ); and
an interdigital transducer on the die, the interdigital transducer comprising:
a first bus bar;
a second bus bar parallel to the first bus bar; and
a plurality of electrode fingers comprising:
a first set of electrode fingers each extending obliquely from the first bus bar towards the second bus bar; and
a second set of electrode fingers each extending obliquely from the second bus bar towards the first bus bar such that the first set of electrode fingers is parallel to and interleaved with the second set of electrode fingers.

2. The guided SAW device of claim 1 wherein:
an angle between the first set of electrode fingers and a normal to the first bus bar is between 3° and 18°; and
an angle between the second set of electrode fingers and a normal to the second bus bar is between 3° and 18°.

3. The guided SAW device of claim 2 wherein:
the angle between the first set of electrode fingers and the normal to the first bus bar is between 5° and 15°; and
the angle between the second set of electrode fingers and the normal to the second bus bar is between 5° and 15°.

4. The guided SAW device of claim 3 wherein:
the angle between the first set of electrode fingers and the normal to the first bus bar is between 7° and 13′; and
the angle between the second set of electrode fingers and the normal to the second bus bar is between 7° and 13°.

5. The guided SAW device of claim 4 wherein:
the angle between the first set of electrode fingers and the normal to the first bus bar is between 8° and 12°; and
the angle between the second set of electrode fingers and the normal to the second bus bar is between 8° and 12°.

6. The guided SAW device of claim 1 wherein:
an angle between the first set of electrode fingers and a normal to the first bus bar is between −3° and −18°; and
an angle between the second set of electrode fingers and a normal to the second bus bar is between −3° and −18°.

7. The guided SAW device of claim 6 wherein:
the angle between the first set of electrode fingers and the normal to the first bus bar is between −5° and −15°; and
the angle between the second set of electrode fingers and the normal to the second bus bar is between −5° and −15°.

8. The guided SAW device of claim 7 wherein:
the angle between the first set of electrode fingers and the normal to the first bus bar is between −7° and −13°; and
the angle between the second set of electrode fingers and the normal to the second bus bar is between −7° and −13°.

9. The guided SAW device of claim 8 wherein:
the angle between the first set of electrode fingers and the normal to the first bus bar is between −8° and −12°; and
the angle between the second set of electrode fingers and the normal to the second bus bar is between −8° and −12°.

10. The guided SAW device of claim 1 wherein the die further comprises a dielectric layer between the substrate and the piezoelectric layer.

11. The guided SAW device of claim 10 wherein the dielectric layer comprises an oxide.

12. The guided SAW device of claim 1 further comprising a pair of reflectors on the die such that the interdigital transducer is located between the pair of reflectors, wherein each one of the pair of reflectors comprises:
a first reflector bus bar and a second reflector bus bar parallel to the first reflector bus bar; and
a plurality of reflector bars running between the first reflector bus bar and the second reflector bus bar.

13. The guided SAW device of claim 12 wherein, for each one of the pair of reflectors:
the first reflector bus bar is collinear with the first bus bar and the second reflector bus bar is collinear with the second bus bar;
the plurality of reflector bars extend obliquely between the first reflector bus bar and the second reflector bus bar; and
the plurality of reflector bars are parallel to the plurality of electrode fingers.

14. The guided SAW device of claim 13 wherein each one of the pair of reflectors is trapezoidal.

15. The guided SAW device of claim 13 wherein:
a surface of the die on which the interdigital transducer is located is defined by a first pair of parallel die edges and a second pair of parallel die edges perpendicular to the first pair of parallel die edges such that the surface of the die is rectangular;
the first bus bar and the second bus bar are parallel to one of the first pair of parallel die edges and the second pair of parallel die edges; and
the plurality of electrode fingers are oblique to the first pair of parallel die edges and the second pair of parallel die edges.

16. The guided SAW device of claim 15 wherein for each one of the pair of reflectors, one of the first pair of parallel die edges and the second pair of parallel die edges intersect the first reflector bus bar, the second reflector bus bar, and at least one of the plurality of reflector bars such that each one of the pair of reflectors is trapezoidal.

17. The guided SAW device of claim 1 further comprising a plurality of dummy electrodes wherein the plurality of dummy electrodes comprises:
a first set of dummy electrodes each extending obliquely from the first bus bar in an alternating fashion with the first set of electrode fingers towards a corresponding one of the second set of electrode fingers; and
a second set of dummy electrodes each extending obliquely from the second bus bar in an alternating fashion with the second set of electrode fingers towards a corresponding one of the first set of electrode fingers, wherein a length of each one of the first set of dummy electrodes and a length of each one of the second set of dummy electrodes is greater than 1λ.

18. The guided SAW device of claim 17 wherein:
each of the first set of electrode fingers extends between the first bus bar and a first electrode finger termination edge, wherein the first electrode finger termination edge is parallel to the first bus bar such that each one of the first set of electrode fingers is not rectangular; and
each of the second set of electrode fingers extends between the second bus bar and a second electrode finger termination edge, wherein the second electrode finger termination edge is parallel to the second bus bar such that each one of the second set of electrode fingers is not rectangular.

19. The guided SAW device of claim 18 wherein:
each of the first set of dummy electrodes extends between the first bus bar and a first dummy electrode termination edge, wherein the first dummy electrode termination edge is parallel to the first bus bar such that each one of the first set of dummy electrodes is not rectangular; and
each of the second set of dummy electrodes extends between the second bus bar and a second dummy electrode termination edge, wherein the second dummy electrode termination edge is parallel to the second bus bar such that each one of the second set of dummy electrodes is not rectangular.

20. The guided SAW device of claim 1 wherein:
each of the first set of electrode fingers extends between the first bus bar and a first electrode finger termination edge, wherein the first electrode finger termination edge is parallel to t

Assignees

• Qorvo Us Inc

Inventors

• Inoue Shogo
• Solal Marc

Classifications

• H03H9/02574

  of combined substrates, multilayered substrates, piezoelectrical layers on not-piezoelectrical substrate · CPC title

• H03H9/25

  Constructional features of resonators using surface acoustic waves {(devices for manipulating acoustic surface waves in general G10K11/36)} · CPC title

• H03H9/1452

  by finger overlap length, apodisation · CPC title

• H03H9/02992

  Details of bus bars, contact pads or other electrical connections for finger electrodes · CPC title

• H03H9/14558 Primary

  Slanted, tapered or fan shaped transducers (H03H9/14561, H03H9/14564 take precedence) · CPC title