Ultrasound probe and ultrasound diagnostic apparatus

1. An ultrasound probe comprising a piezoelectric micromachined ultrasound transducer (pMUT) array in which a plurality of pMUTs are arranged, wherein:

the plurality of pMUTs include a plurality of first pMUTs for ultrasound transmission, and a plurality of second pMUTs for ultrasound wave reception, each second pMUT having a structure different from that of each first pMUT;

a substrate on which each of the first pMUTs and second pMUTs are disposed, wherein the substrate includes a thin film part in portions corresponding to the first pMUTs and the substrate does not include the thin film part in portions corresponding to the second pMUTs, wherein the thin film part is thinner than a remainder of the substrate; and

a cell region of each first pMUT and a cell region of each second pMUT are separated from each other in an ultrasound wave radiation plane,

wherein each first pMUT has a diaphragm structure and transmits ultrasound waves by a deflection vibration mode and each second pMUT has a non-diaphragm structure and receives ultrasound waves by a thickness vibration mode.

2. The ultrasound probe according to claim 1 , wherein:

each first pMUT has a structure in which a first lower electrode, a first piezoelectric body and a first upper electrode are sequentially stacked on the substrate;

each second pMUT has a structure in which a second lower electrode, a second piezoelectric body and a second upper electrode are sequentially stacked on the substrate; and

the first piezoelectric body and the second piezoelectric body are formed of respective materials different from each other.

3. The ultrasound probe according to claim 2 , wherein the first piezoelectric body is formed of an inorganic piezoelectric material.

4. The ultrasound probe according to claim 3 , wherein the inorganic piezoelectric material is lead zirconate titanate (PZT).

5. The ultrasound probe according to claim 2 , wherein the second piezoelectric body is formed of an organic piezoelectric material.

6. The ultrasound probe according to claim 5 , wherein the organic piezoelectric material is polyvinylidene fluoride (PVDF) resin.

7. The ultrasound probe according to claim 2 , wherein thickness t of the second piezoelectric body is t≤V/4Fmax, where Fmax represents a maximum frequency in an ultrasound wave frequency band that is used, and V represents a sound velocity in the second piezoelectric body.

8. The ultrasound probe according to claim 1 , wherein:

the diaphragm structure of each first pMUT exhibits the deflection vibration mode in which a vibration plate of the diaphragm structure is caused to deflect in response to expansion and contraction of the vibration plate in an ultrasound frequency band; and

the non-diaphragm structure of each second pMUT does not exhibit the deflection vibration mode in the ultrasound frequency band.

9. The ultrasound probe according to claim 1 , wherein a center-to-center distance L of cells of one of the first pMUTs and one of the second pMUTs adjacent to each other is L≤λc/2, where λc represents a wavelength in a living body with respect to a center frequency Fc of an ultrasound wave frequency band that is used.

10. The ultrasound probe according to claim 1 , wherein:

the plurality of pMUTs are divided into a plurality of channels; and

a number of the plurality of first pMUTs and a number of the plurality of second pMUTs in each channel are different from each other.

11. The ultrasound probe according to claim 1 , wherein the pMUT array includes:

an electronic circuit substrate configured to drive and control a piezoelectric element of each first pMUT and a piezoelectric element of each second pMUT;

a piezoelectric element portion including a piezoelectric element substrate on which the piezoelectric elements are each formed; and

a connector interposed between the electronic circuit substrate and the piezoelectric element substrate,

wherein the electronic circuit substrate and the piezoelectric element substrate are physically and electrically connected with each other by the connector.

12. The ultrasound probe according to claim 1 , wherein: the pMUT array includes an electronic circuit substrate configured to drive and control a piezoelectric element of each first pMUT and a piezoelectric element of each second pMUT;

the piezoelectric elements are formed on the electronic circuit substrate with an insulation layer interposed between the piezoelectric elements and the electronic circuit substrate; and

the electronic circuit substrate and the piezoelectric element are electrically connected with each other by a through electrode provided in the insulation layer.

13. An ultrasound diagnostic apparatus comprising:

the ultrasound probe according to claim 1 ; and

an ultrasound diagnostic apparatus main body to which the ultrasound probe is connected, the ultrasound diagnostic apparatus main body being configured to generate an ultrasound image based on an ultrasound signal from the ultrasound probe.

14. The ultrasound probe according to claim 1 , wherein each first pMUT has a structure in which a first lower electrode, a first piezoelectric body and a first upper electrode are sequentially stacked on the substrate, each second pMUT has a structure in which a second lower electrode, a second piezoelectric body and a second upper electrode are sequentially stacked on the substrate, and wherein the first piezoelectric body of each first pMUT forms the diaphragm structure with the substrate and transmits ultrasound waves by a deflection vibration mode and the second piezoelectric body of each second pMUT forms the non-diaphragm structure with the substrate.

15. The ultrasound probe according to claim 14 , wherein the diaphragm structure of the first PMUT exhibits deflection mode resonance with at least one resonance point in an ultrasound frequency band and the diaphragm structure of the second PMUT exhibits no deflection mode resonance in the ultrasound frequency band.