PIEZOELECTRIC LATERALLY VIBRATING RESONATOR STRUCTURE GEOMETRIES FOR SPURIOUS FREQUENCY SUPPRESSION

• US 20130021305A1
• Filed: 07/19/2011
• Published: 01/24/2013
• Est. Priority Date: 07/19/2011
• Status: Active Grant

• Current Assignee: Snaptrack Incorporated (Qualcomm, Inc.)
• Original Assignee: Qualcomm MEMS Technologies Incorporated (Qualcomm, Inc.)
• Inventors: Zuo, Chengjie, Yun, Changhan, Lo, Chi Shun, Kim, Jonghae
• Granted Patent: US 8,816,567 B2
• Time in Patent Office: Days
• US Class Current: 345/204
• CPC Class Codes: H03H 2003/021 the resonators or networks being of the air-gap type
• CPC Class Codes: H03H 3/02 for the manufacture of piezoelectric or electrostrictive resonators or networks H03H3/08 takes precedence
• CPC Class Codes: H03H 9/02055 of the surface including the back surface
• CPC Class Codes: H03H 9/02228 Guided bulk acoustic wave devices or Lamb wave devices having interdigital transducers situated in parallel planes on either side of a piezoelectric layer
• CPC Class Codes: H03H 9/173 Air-gaps
• CPC Class Codes: Y10T 29/42 Piezoelectric device making

Abstract

This disclosure provides implementations of electromechanical systems resonator structures, devices, apparatus, systems, and related processes. In one aspect, a resonator structure includes a first conductive layer of electrodes and a second conductive layer of electrodes. A piezoelectric layer including a piezoelectric material is disposed between the first conductive layer and the second conductive layer. One or more trenches can be formed in the piezoelectric layer on one or both sides in space regions between the electrodes. In some implementations, a process for forming the resonator structure includes removing an exposed portion of the piezoelectric layer to define a trench, for instance, by partial etching or performing an isotropic release etch using a XeF₂ gas or SF₆ plasma. In some other implementations, a portion of a sacrificial layer is removed to define a trench in the piezoelectric layer.

Claims

1. A resonator structure comprising:

a first conductive layer of electrodes disposed along an X axis;

a second conductive layer of electrodes disposed along the X axis and offset from the first conductive layer along a Z axis perpendicular to the X axis; and

a piezoelectric layer including a piezoelectric material, the piezoelectric layer disposed between the first conductive layer and the second conductive layer, the piezoelectric layer having a first side and a second side opposite the first side, the first side proximate the first conductive layer, the second side proximate the second conductive layer;

one or more trenches being formed in the piezoelectric layer on the first side in one or more respective space regions between the electrodes of the first conductive layer.

2. The resonator structure of claim 1, wherein the one or more trenches define elevated regions on the first side of the piezoelectric layer, the elevated regions being aligned with the electrodes of the first conductive layer.

3. The resonator structure of claim 2, wherein the piezoelectric layer has a first height along the Z axis in one of the elevated regions and a second height along the Z axis in one of the space regions, the first height being larger than the second height.

4. The resonator structure of claim 3, wherein the first height and the second height of the piezoelectric layer define a designated height differential.

5. The resonator structure of claim 2, wherein the elevated regions of the piezoelectric layer have planar dimensions along the X and Y axes substantially matching planar dimensions along the X and Y axes of the electrodes of the first conductive layer.

6. The resonator structure of claim 1, wherein the one or more trenches in the piezoelectric material are formed by an etching operation.

7. The resonator structure of claim 1, wherein the one or more further trenches are formed in the piezoelectric layer on the second side in one or more respective space regions between the electrodes of the second conductive layer.

8. The resonator structure of claim 7, wherein the one or more further trenches define elevated regions of the piezoelectric layer on the second side, the one or more further trenches on the second side being aligned with the one or more trenches on the first side of the piezoelectric layer, the elevated regions on the second side being aligned with the elevated regions on the first side of the piezoelectric layer.

9. The resonator structure of claim 8, wherein the piezoelectric layer has a first height along the Z axis in one of the elevated regions and a second height along the Z axis in one of the space regions.

10. The resonator structure of claim 1, wherein the piezoelectric material is selected from the group consisting of:

aluminum nitride, zinc oxide, gallium arsenide, aluminum gallium arsenide, gallium nitride, quartz, zinc-sulfide, cadmium-sulfide, lithium tantalate, lithium niobate, and lead zirconate titanate.

11. The resonator structure of claim 1 further comprising:

one or more tethers coupled to anchor the layers to a supporting apparatus.

12. The resonator structure of claim 1 further comprising:

a display;

a processor configured to communicate with the display, the processor being configured to process image data; and

a memory device configured to communicate with the processor.

13. The structure of claim 12 further comprising:

a driver circuit configured to send at least one signal to the display; and

a controller configured to send at least a portion of the image data to the driver circuit.

15. The structure of claim 12, wherein one or more of the output electrodes are coupled to send the image data to the processor.

16. A process for forming a resonator structure comprising:

depositing a sacrificial layer on a substrate;

forming a lower electrode layer on the sacrificial layer;

depositing a piezoelectric layer on the lower electrode layer;

forming an upper electrode layer on the piezoelectric layer, the upper electrode layer including a space region and an electrode region;

removing an exposed portion of the piezoelectric layer in the space region to define a trench in the piezoelectric layer; and

removing at least a portion of the sacrificial layer to define a cavity such that at least a portion of the lower electrode layer is spaced apart from the substrate.

17. The process of claim 16, wherein removing the exposed portion of the piezoelectric layer includes:

partially etching the exposed portion of the piezoelectric layer to define the trench in the piezoelectric layer.

18. The process of claim 16, wherein the trench defines an elevated region of the piezoelectric layer, the elevated region being aligned with an electrode of the upper conductive layer.

19. The process of claim 18, wherein the piezoelectric layer has a first height in the elevated region and a second height in the space region, the first height being larger than the second height.

20. The process of claim 19, wherein the first height and the second height of the piezoelectric layer define a designated height differential.

21. The process of claim 16, wherein removing the at least a portion of the sacrificial layer includes:

performing an isotropic release etch on the sacrificial layer.

22. The process of claim 21, wherein performing the isotropic release etch on the sacrificial layer includes:

providing at least one of a XeF₂ gas or SF₆ plasma to the sacrificial layer.

23. The process of claim 16, wherein the substrate is formed of an insulating material.

24. The process of claim 16, wherein the substrate is formed of silicon.

25. The process of claim 16, wherein the sacrificial layer includes a material selected from the group consisting of:

molybdenum, germanium, amorphous silicon, and poly-crystalline silicon.

26. The process of claim 16, wherein the sacrificial layer includes a material selected from the group consisting of:

silicon oxynitride and silicon oxide.

27. A process for forming a resonator structure comprising:

depositing a first sacrificial layer on a substrate;

forming a lower electrode layer on the first sacrificial layer, the lower electrode layer including an electrode region and a space region exposing a portion of the first sacrificial layer;

forming a second sacrificial layer on the space region of the lower electrode layer;

depositing a piezoelectric layer on the lower electrode layer and the second sacrificial layer;

forming an upper electrode layer on the piezoelectric layer; and

removing at least a portion the first sacrificial layer and at least a portion of the second sacrificial layer, removal of the portion of the first sacrificial layer defining a cavity such that at least a portion of the lower electrode layer is spaced apart from the substrate, removal of the portion of the second sacrificial layer defining a trench in the piezoelectric layer.

28. The process of claim 27, wherein the trench defines an elevated region of the piezoelectric layer, the elevated region being aligned with an electrode of the upper conductive layer.

29. The process of claim 28, wherein the piezoelectric layer has a first height in the elevated region and a second height in the space region, the first height being larger than the second height.

30. The process of claim 29, wherein the first height and the second height of the piezoelectric layer define a designated height differential.

31. The process of claim 27, wherein removing the at least a portion of the first and second sacrificial layers includes:

performing an isotropic release etch on the sacrificial layers.

32. The process of claim 31, wherein performing the isotropic release etch on the sacrificial layers includes:

providing at least one of a XeF₂ gas or SF₆ plasma to the sacrificial layer.

33. A resonator structure comprising:

first conductive means of electrodes disposed along an X axis;

second conductive means of electrodes disposed along the X axis and offset from the first conductive means along a Z axis perpendicular to the X axis; and

piezoelectric means including a piezoelectric material, the piezoelectric means disposed between the first conductive means and the second conductive means, the piezoelectric means having a first side and a second side opposite the first side, the first side proximate the first conductive means, the second side proximate the second conductive means;

one or more trenches being formed in the piezoelectric means on the first side in one or more respective space regions between the electrodes of the first conductive means.

34. The resonator structure of claim 33, wherein the one or more trenches define elevated regions on the first side of the piezoelectric means, the elevated regions being aligned with the electrodes of the first conductive means.

35. The resonator structure of claim 34, wherein the piezoelectric means has a first height along the Z axis in one of the elevated regions and a second height along the Z axis in one of the space regions, the first height being larger than the second height.