Manufacturing method for flexible PMUT array

1. A method of forming a flexible array of piezoelectric micromechanical ultrasonic transducers, comprising:

providing a carrier configured to support the flexible array of piezoelectric micromechanical ultrasonic transducers (PMUTs);

providing a release layer configured to adhere the flexible array of PMUTs to the carrier;

forming the flexible array of PMUTs over the release layer, comprising

for each PMUT in the flexible array of PMUTs,

laminating a first polymer layer configured to support the PMUT;

depositing a sacrificial material configured to pattern a cavity of the PMUT;

depositing a mechanical layer, wherein the mechanical layer includes a planarization layer configured to provide chemical mechanical planarization to the PMUT, or a mechanical membrane configured to provide stiffness to the PMUT and frequency response adjustment;

depositing a first electrode configured to be coupled to a circuit ground plane;

depositing a piezoelectric layer configured to separate the first electrode and a second electrode;

depositing the second electrode configured to be coupled to a signal; and

creating patterns on the first electrode, the piezoelectric material, and the second electrode configured to route control signals of the PMUT; and

removing the release layer to separate the flexible array of PMUTs from the carrier.

2. The method of claim 1 , further comprising:

depositing a passivation layer configured to encapsulate the first electrode, the piezoelectric layer and the second electrode;

etching contact vias configured to access the first electrode and the second electrode; and

depositing pads and/or a redistribution layer configured to route electrical signals to the first electrode and the second electrode.

3. The method of claim 2 , further comprising:

forming the cavity configured to adjust a frequency response of the PMUT.

4. The method of claim 3 , further comprising:

laminating a second polymer layer configured to encapsulate the first electrode, the piezoelectric layer and the second electrode; and

forming pattern vias configured to support signal access through the redistribution layer.

5. The method of claim 2 , further comprising:

laminating a second polymer layer configured to encapsulate the first electrode, the piezoelectric layer and the second electrode;

forming pattern vias configured to support signal access through the redistribution layer; and

separating the PMUT from the carrier.

6. The method of claim 5 , further comprising:

drilling a release via in the first polymer layer; and

forming the cavity configured to adjust a frequency response of the PMUT by removing the sacrificial material using the release via.

7. The method of claim 6 , further comprising:

laminating a fourth polymer layer configured to enclose the cavity.

8. The method of claim 2 , further comprising:

laminating a second polymer layer configured to encapsulate the first electrode, the piezoelectric layer and the second electrode;

patterning contact vias configured to access the first electrode and the second electrode; and

depositing pads and/or a redistribution layer configured to route electrical signals to the first electrode and the second electrode.

9. The method of claim 8 , further comprising:

forming the cavity configured to adjust a frequency response of the PMUT.

10. The method of claim 8 , further comprising:

laminating a third polymer layer configured to protect the PMUT;

forming pattern vias configured to support signal access through the redistribution layer;

separating the PMUT from the carrier;

drilling a release via in the first polymer layer; and

forming the cavity configured to adjust a frequency response of the PMUT by removing the sacrificial material using the release via.

11. The method of claim 10 , further comprising:

laminating a fourth polymer layer configured to enclose the cavity.

12. The method of claim 9 , further comprising:

laminating a third polymer layer configured to protect the PMUT; and

forming pattern vias configured to support signal access through the redistribution layer.