Capacitive micromachined ultrasonic transducer
The first integrated circuit/transducer device 36 of the handheld probe includes CMOS circuits 110 and cMUT elements 112 . The cMUT elements 112 function to generate an ultrasonic beam, detect an ultrasonic echo, and output electrical signals, while the CMOS circuits 110 function to perform analog or digital operations on the electrical signals generated through operation of the cMUT elements 112 . The manufacturing method for the first integrated circuit/transducer device 36 of the preferred embodiment includes the steps of depositing the lower electrode S 102 ; depositing a sacrificial layer S 104 ; depositing a dielectric layer S 106 ; depositing the upper electrode S 108 ; depositing a protective layer on the upper electrode S 110 ; and removing the sacrificial layer S 112 . In the preferred embodiment, the manufacturing method also includes the step of depositing a sealant layer to seal a cavity between the lower electrode and the upper electrode S 114.
1. A method of producing an integrated circuit/transducer device having a substrate, a complimentary-metal-oxide-semiconductor (CMOS) circuit located over a CMOS circuit region of the substrate, and a capacitive micromachined ultrasonic transducer (cMUT) located over a cMUT region of the substrate, the method comprising:
a) depositing a first layer over both the CMOS circuit region and the cMUT region of the substrate that:
i. forms a layer within the CMOS circuit;
ii. forms a lower electrode within the cMUT element;
b) depositing a dielectric layer over the cMUT region after step a);
c) depositing a sacrificial layer over the cMUT region after step b);
d) depositing a second layer over both the CMOS circuit region and the cMUT region of the substrate that:
i. forms a layer within the CMOS circuit;
ii. forms an upper electrode within the cMUT element;
e) depositing a protective layer over both the CMOS circuit region and the cMUT region after step d);
f) removing the sacrificial layer to form a cavity between the upper electrode and lower electrode of the cMUT after step e); and
g) depositing a sealant layer over the cMUT region to seal the cavity after step f).
2. The method of claim 1 , wherein the lower electrode is a first portion of a capacitor of the cMUT, and the upper electrode is a second portion of the capacitor of the cMUT.
3. The method of claim 1 , wherein the CMOS circuit region is adjacent the cMUT region on the substrate.
4. The method of claim 1 , wherein the first layer forms a transistor gate within the CMOS circuit region.
5. The method of claim 1 , wherein the first layer forms a capacitor plate within the CMOS circuit region.
6. The method of claim 1 , wherein the first layer forms a metallization layer within the CMOS circuit region.
7. The method of claim 1 , wherein the sacrificial layer forms a metal layer within the CMOS circuit region.
8. The method of claim 1 , further comprising thinning the sealant layer after step g).