Electrical contact arrangement for microfabricated ultrasonic transducer
An ultrasound-on-a-chip device has an ultrasonic transducer substrate with plurality of transducer cells, and an electrical substrate. For each transducer cell, one or more conductive bond connections are disposed between the ultrasonic transducer substrate and the electrical substrate. Examples of electrical substrates include CMOS chips, integrated circuits including analog circuits, interposers and printed circuit boards.
1. An apparatus, comprising:
an ultrasound-on-a-chip device having a plurality of ultrasonic transducer cells including first and second ultrasonic transducer cells corresponding to respective first and second cavities of a plurality of cavities of the ultrasound-on-a-chip device; and
for each of the first and second ultrasonic transducer cells of the plurality of ultrasonic transducer cells, multiple conductive connections disposed between a first layer of the ultrasound-on-a-chip device and an integrated circuit, the first layer being between the plurality of cavities and the integrated circuit.
2. The apparatus of claim 1 , wherein the first and second ultrasonic transducer cells are disposed proximate a first side of the first layer and the multiple conductive connections are disposed between a second side of the first layer and the integrated circuit.
3. The apparatus of claim 2 , wherein the multiple conductive connections of the first ultrasonic transducer cell of the plurality of ultrasonic transducer cells are distributed substantially evenly with respect to an area of the first ultrasonic transducer cell.
4. The apparatus of claim 2 , wherein the multiple conductive connections comprise one or more of: thermal compression connections, eutectic connections or silicide connections.
5. The apparatus of claim 2 , wherein the multiple conductive connections of the first and second ultrasonic transducer cells contact a conductive portion of the first layer at a first end thereof, and a metal layer of the integrated circuit at a second end thereof.
6. The apparatus of claim 2 , further comprising a plurality of acoustically inactive regions of the first layer and a respective single conductive connection connected to first and second acoustically inactive regions of the plurality of acoustically inactive regions, the respective single conductive connections disposed between the first layer and the integrated circuit.
7. The apparatus of claim 6 , wherein the first and second acoustically inactive regions of the first layer are disposed between respective adjacent pairs of ultrasonic transducer cells of the plurality of ultrasonic transducer cells.
8. The apparatus of claim 7 , wherein two or more adjacent pairs of ultrasonic transducer cells of the plurality of ultrasonic transducer cells are electrically isolated from one another on a conductive portion of the first layer by isolation trenches formed in the first layer.
9. The apparatus of claim 8 , wherein the isolation trenches form octagonal regions corresponding to individual transducer cells of the plurality of ultrasonic transducer cells.
10. The apparatus of claim 9 , wherein each of the first and second acoustically inactive regions is defined by a border between four adjacent octagonal regions.
11. The apparatus of claim 2 , wherein each conductive connection of the multiple conductive connections of the first and second ultrasonic transducer cells is separated from a nearest neighbor conductive connection by a distance of about 100 microns (μm) or less.
12. The apparatus of claim 1 , wherein the first layer is a first substrate of a composite substrate and the composite substrate further comprises a second substrate that connects to the first substrate to define the plurality of cavities therebetween.
13. The apparatus of claim 12 , further comprising:
a conductive seal ring that surrounds an ultrasonic transducer array defined by the plurality of ultrasonic transducer cells; a plurality of acoustically inactive regions of the composite substrate; and a single conductive connection to each of first and second acoustically inactive regions of the plurality of acoustically inactive regions.
14. The apparatus of claim 13 , wherein the multiple conductive connections comprise one or more of: thermocompression connections, eutectic connections or silicide connections.
15. The apparatus of claim 13 , wherein:
the first substrate of the composite substrate corresponds to a membrane of the ultrasonic transducer array;
the second substrate of the composite substrate is connected to the integrated circuit by the multiple conductive connections; and
the conductive seal ring provides an electrical connection between the first substrate and the integrated circuit, via a portion of the second substrate that is electrically isolated from bottom electrode contacts of the ultrasonic transducer array.
16. The apparatus of claim 15 , wherein the first and second ultrasonic transducer cells are electrically isolated from one another on a conductive portion of a silicon layer of the second substrate by isolation trenches formed in the silicon layer.
17. The apparatus of claim 16 , wherein the isolation trenches form octagonal regions corresponding to the first and second ultrasonic transducer cells.
18. The apparatus of claim 17 , wherein each of the first and second acoustically inactive regions is defined by a border between four adjacent octagonal regions of the octagonal regions.
19. The apparatus of claim 18 , further comprising additional isolation trenches formed on the silicon layer of the second substrate, the additional isolation trenches electrically insulating a portion of the second substrate contacted by the conductive seal ring from the octagonal regions.
20. The apparatus of claim 19 , wherein the multiple conductive connections for each of the first and second ultrasonic transducer cells, the single conductive connection connected to each of the first and second acoustically inactive regions of the composite substrate, and the conductive seal ring contact the conductive portion of the silicon layer of the composite substrate at a first end thereof, and a metal layer of the integrated circuit at a second end thereof.
21. The apparatus of claim 20 , wherein the metal layer of the integrated circuit comprises:
first metal regions to which the multiple conductive connections of the first and second ultrasonic transducers are connected;
second metal regions to which the single conductive connections of the first and second acoustically inactive regions are connected; and
a third metal region to which the conductive seal ring is connected.
22. The apparatus of claim 21 , wherein the first metal regions comprise circular regions having an opening patterned at a center portion thereof.
23. The apparatus of claim 22 , wherein groups of first metal regions are electrically connected together to group the first and second ultrasonic transducer cells as a single functioning ultrasound element.
24. The apparatus of claim 21 , wherein the second metal regions are electrically connected in a grid.
25. The apparatus of claim 12 , wherein each conductive connection of the multiple conductive connections of the first and second ultrasonic transducer cells is separated from a nearest neighbor conductive connection by a distance of about 100 microns (μm) or less.
26. The apparatus of claim 1 , wherein the multiple conductive connections of the first ultrasonic transducer cell comprise three (3) conductive connections.
27. The apparatus of claim 1 , further comprising a probe, wherein the ultrasound-on-a-chip device is disposed within the probe.
28. The apparatus of claim 1 , wherein the multiple conductive connections disposed between the first layer and the integrated circuit include conductive connections for each of the plurality of ultrasonic transducer cells.