CMOS ultrasonic transducers and related apparatus and methods
CMOS Ultrasonic Transducers and processes for making such devices are described. The processes may include forming cavities on a first wafer and bonding the first wafer to a second wafer. The second wafer may be processed to form a membrane for the cavities. Electrical access to the cavities may be provided.
1. A method, comprising:
forming, on a wafer, a complementary metal oxide semiconductor (CMOS) ultrasound transducer (CUT) device having a cavity, a membrane sealing the cavity, and processing circuitry; and
forming an electrical contact on a bottom side of the membrane, the electrical contact physically contacting the bottom side of the membrane and connecting the membrane to the processing circuitry, the bottom side of the membrane proximal the cavity, and wherein the bottom side of the membrane and the electrical contact physically contacting the bottom side of the membrane comprise a same dopant species.
2. The method of claim 1 , wherein the cavity is a first cavity, and wherein the method further comprises forming a plurality of cavities in addition to the first cavity of the CUT device in the wafer and sealing the plurality of cavities with the membrane.
3. The method of claim 1 , wherein the cavity is a first cavity, and wherein the method further comprises forming a plurality of cavities in addition to the first cavity of the CUT device in the wafer and sealing at least two cavities of the plurality of cavities with respective membranes.
4. The method of claim 1 , wherein the electrical contact and the bottom side of the membrane comprise doped silicon.
5. The method of claim 1 , wherein the CUT device lacks metallization on an upper surface of the membrane distal the cavity.
6. The method of claim 1 , wherein the CUT device lacks an electrode on an upper surface of the membrane distal the cavity.
7. The method of claim 1 , wherein the wafer comprises a silicon substrate and wherein the electrical contact contacts the silicon substrate.
8. The method of claim 1 , wherein the electrical contact comprises a trench lined with a conductive material.
9. The method of claim 8 , wherein the conductive material lining the trench is a first conductive material, and wherein the electrical contact further comprises a second conductive material at least partially filling the trench.
10. The method of claim 1 , further comprising forming the electrical contact beneath the bottom side of the membrane.
11. The method of claim 1 , wherein the bottom side of the membrane and the electrical contact physically contacting the bottom side of the membrane are formed from a same material.
12. A method, comprising;
forming, on a wafer, a complementary metal oxide semiconductor (CMOS) ultrasound transducer (CUT) device having a cavity, a membrane sealing the cavity, and processing circuitry; and
forming an electrical contact on a bottom side of the membrane, the electrical contact physically contacting the bottom side of the membrane and connecting the membrane to the processing circuitry, the bottom side of the membrane proximal the cavity, and wherein the bottom side of the membrane and the electrical contact physically contacting the bottom side of the membrane comprise a same material.
13. The method of claim 12 , wherein the cavity is a first cavity, and wherein the method further comprises forming a plurality of cavities in addition to the first cavity of the CUT device in the wafer and sealing the plurality of cavities with the membrane.
14. The method of claim 12 , wherein the cavity is a first cavity, and wherein the method further comprises forming a plurality of cavities in addition to the first cavity of the CUT device in the wafer and sealing at least two cavities of the plurality of cavities with respective membranes.
15. The method of claim 12 , wherein the electrical contact and the bottom side of the membrane comprise doped silicon.
16. The method of claim 12 , wherein the electrical contact and the bottom side of the membrane comprise titanium nitride.
17. The method of claim 12 , wherein the CUT device lacks metallization on an upper surface of the membrane distal the cavity.
18. The method of claim 12 , wherein the CUT device lacks an electrode on an upper surface of the membrane distal the cavity.
19. The method of claim 12 , wherein the wafer comprises a silicon substrate and wherein the electrical contact contacts the silicon substrate.
20. The method of claim 12 , wherein the electrical contact comprises a trench lined with a conductive material.
21. The method of claim 20 , wherein the conductive material lining the trench is a first conductive material, and wherein the electrical contact further comprises a second conductive material at least partially filling the trench.
22. The method of claim 12 , further comprising forming the electrical contact beneath the bottom side of the membrane.
23. An apparatus, comprising:
a plurality of ultrasound elements formed on a support, wherein a first ultrasound element of the plurality of ultrasound elements comprises a first substrate having a plurality of cavities formed therein and at least one membrane overlying the plurality of cavities;
a complementary metal oxide semiconductor (CMOS) circuit formed in the first substrate; and
an electrical contact on the first substrate, the electrical contact disposed beneath a bottom side of the at least one membrane, physically contacting the bottom side of the at least one membrane and connecting the at least one membrane to the CMOS circuit, the bottom side of the at least one membrane being proximate the plurality of cavities, wherein the bottom side of the at least one membrane and the electrical contact physically contacting the bottom side of the at least one membrane comprise a same dopant species.
24. The apparatus of claim 23 , wherein each of the plurality of ultrasound elements is formed by the first substrate having a respective plurality of cavities formed therein with the at least one membrane overlying the respective plurality of cavities.
25. The apparatus of claim 23 , wherein the electrical contact and the bottom side of the at least one membrane comprise doped silicon.
26. The apparatus of claim 23 , wherein the first ultrasonic element lacks metallization on an upper surface of the at least one membrane distal the plurality of cavities.
27. The apparatus of claim 23 , wherein the first ultrasonic element lacks an electrode on an upper surface of the at least one membrane distal the plurality of cavities.
28. The apparatus of claim 23 , wherein the first substrate comprises a silicon substrate, and wherein the electrical contact contacts the silicon substrate.
29. The apparatus of claim 23 , wherein the electrical contact comprises a trench lined with a conductive material.
30. The apparatus of claim 29 , wherein the conductive material lining the trench is a first conductive material, and wherein the electrical contact further comprises a second conductive material at least partially filling the trench.
31. The apparatus of claim 23 , wherein the plurality of cavities is formed above the CMOS circuit on the first substrate.