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 a cavity on a top region of a complementary metal oxide semiconductor (CMOS) substrate, the cavity surrounded by a lip region;
disposing a membrane over the lip region to substantially seal the cavity;
forming a first electrical contact on a top side of the membrane, wherein the top side of the membrane is disposed distal the cavity, and wherein a bottom side of the membrane and the first electrical contact are doped with substantially a same dopant;
forming a second electrical contact on the CMOS substrate; and
connecting the second electrical contact to the first electrical contact.
2. The method of claim 1 , wherein the first electrical contact and the second electrical contact comprise a metal.
3. The method of claim 1 , wherein the first electrical contact and the second electrical contact comprise aluminum.
4. The method of claim 1 , further comprising forming an interface layer between the first electrical contact and the top side of the membrane.
5. The method of claim 1 , wherein the first electrical contact is common to two or more membranes of two or more cavities.
6. The method of claim 1 , wherein forming the second electrical contact comprises etching the CMOS substrate to expose the second electrical contact.
7. The method of claim 1 , further comprising forming a third electrical contact on the CMOS substrate, wherein the third electrical contact is electrically coupled to a substrate electrode disposed on an opposite side of the cavity from the membrane, with the cavity between the substrate electrode and the membrane.
8. The method of claim 1 , wherein the membrane and the first electrical contact are doped with substantially a same dopant.
9. The method of claim 1 , wherein the CMOS substrate comprises processing circuitry configured to:
actuate the membrane to transmit an ultrasound wave; and
detect a received ultrasound wave based on vibration of the membrane.
10. An ultrasound structure, comprising:
a complementary metal-oxide-semiconductor (CMOS) substrate having a cavity formed therein, the cavity surrounded by a lip region;
a membrane disposed over the lip region to substantially seal the cavity;
a first electrical contact on a top side of the membrane, wherein the top side of the membrane is disposed distal to the cavity, and wherein a bottom side of the membrane and the first electrical contact are doped with substantially a same dopant; and
a second electrical contact on the CMOS substrate; wherein
the second electrical contact and the first electrical contact are connected.
11. The ultrasound structure of claim 10 , wherein the first electrical contact and the second electrical contact comprise a metal.
12. The ultrasound structure of claim 10 , wherein the first electrical contact and the second electrical contact comprise aluminum.
13. The ultrasound structure of claim 10 , further comprising an interface layer between the first electrical contact and the top side of the membrane.
14. The ultrasound structure of claim 10 , wherein the first electrical contact is common to two or more membranes of two or more cavities.
15. The ultrasound structure of claim 10 , further comprising a third electrical contact on the CMOS substrate, wherein the third electrical contact is electrically coupled to a substrate electrode disposed on an opposite side of the cavity from the membrane, with the cavity between the substrate electrode and the membrane.
16. The ultrasound structure of claim 10 , wherein the membrane and the first electrical contact are doped with substantially a same dopant.
17. The ultrasound structure of claim 10 , wherein the CMOS substrate comprises processing circuitry configured to:
actuate the membrane to transmit an ultrasound wave; and
detect a received ultrasound wave based on vibration of the membrane.