Micromachined ultrasonic transducer devices having truncated circle shaped cavities
An ultrasonic transducer device is provided. In some embodiments, the ultrasonic transducer device includes a substrate having a membrane support layer formed on a bottom cavity layer, and an opening in the membrane support layer so as to form a transducer cavity. In some embodiments, the opening comprises a truncated circle shape.
1. An ultrasonic transducer device, comprising:
a substrate having a membrane support layer formed on a bottom cavity layer;
an opening in the membrane support layer so as to form a transducer cavity, wherein the opening comprises a squircle shape; and
a plurality of openings in the membrane support layer so as to form a plurality of transducer cavities; wherein:
the transducer cavity is a first transducer cavity, the squircle shape of the first transducer cavity comprises a first linear side corresponding to a location adjacent a second linear side of a squircle shape of a second transducer cavity of the plurality of transducer cavities, and the second transducer cavity is a nearest neighbor of the first transducer cavity; and
the first linear side of the first transducer cavity and the second linear side of the second transducer cavity are shaped so as to double a nearest neighbor distance between the first transducer cavity and the second transducer cavity compared to the nearest neighbor distance if the openings of the first and second transducer cavities comprised circle shapes centered at same locations as the squircle shapes of the first and second transducer cavities and having a same radius of curvature as curved portions of the squircle shapes of the first and second transducer cavities.
2. The device of claim 1 , wherein each of the plurality of transducer cavities has four (4) truncated edges.
3. The device of claim 1 , wherein a distance between the first linear side of the first transducer cavity and the second linear side of the second transducer cavity is 20-30 microns (μm).
4. The device of claim 1 , wherein a minimum distance between any of the plurality of transducer cavities is at least 10 μm.
5. The device of claim 1 , further comprising a transducer membrane bonded to the membrane support layer so as to seal the plurality of transducer cavities.
6. The device of claim 5 , wherein a bond between the transducer membrane and the membrane support layer defines a bonding area, and wherein a percentage of the bonding area normalized to an entire wafer area of the ultrasonic transducer device is at least 50%.
7. The device of claim 5 , wherein the sealed transducer cavities define capacitive micromachined ultrasonic transducers (CMUTs).
8. The device of claim 7 , wherein the membrane support layer comprises SiO 2 .
9. The device of claim 8 , wherein the transducer membrane is flexible.
10. The device of claim 8 , wherein the transducer membrane comprises doped silicon having a dopant concentration of 1×10 18 atoms/cm 3 to 1×10 19 atoms/cm 3 .
11. The device of claim 7 , wherein the bottom cavity layer comprises a layer stack including an SiO 2 layer and an aluminum oxide (Al 2 O 3 ) layer.
12. The device of claim 7 , further comprising a transducer bottom electrode layer disposed beneath the bottom cavity layer.