Monolithic integrated CMUTs fabricated by low-temperature wafer bonding
First Claim
1. A capacitive micromachined ultrasonic transducer (CMUT) array comprising:
- an integrated circuit (IC) substrate including one or more active electrical devices; and
a CMUT membrane layer including membranes for each transducer element of said CMUT array;
wherein said CMUT membrane layer is attached to said IC substrate by a method that includes low-temperature wafer bonding performed after said active electrical devices are present in said substrate.
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Abstract
Low temperature wafer bonding (temperature of 450° C. or less) is employed to fabricate CMUTs on a wafer that already includes active electrical devices. The resulting structures are CMUT arrays integrated with active electronics by a low-temperature wafer bonding process. The use of a low-temperature process preserves the electronics during CMUT fabrication. With this approach, it is not necessary to make compromises in the CMUT or electronics designs, as is typical of the sacrificial release fabrication approach. Various disadvantages of sacrificial release, such as low process control, poor design flexibility, low reproducibility, and reduced performance are avoided with the present approach. With this approach, a CMUT array can be provided with per-cell electrodes connected to the substrate integrated circuitry. This enables complete flexibility in electronically assigning the CMUT cells to CMUT array elements.
93 Citations
20 Claims
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1. A capacitive micromachined ultrasonic transducer (CMUT) array comprising:
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an integrated circuit (IC) substrate including one or more active electrical devices; and a CMUT membrane layer including membranes for each transducer element of said CMUT array; wherein said CMUT membrane layer is attached to said IC substrate by a method that includes low-temperature wafer bonding performed after said active electrical devices are present in said substrate. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A method of making a capacitive micromachined ultrasonic transducer (CMUT) array, the method comprising:
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providing a substrate; fabricating one or more active electrical devices on said substrate to provide an integrated circuit (IC) substrate; providing a CMUT membrane wafer including a CMUT membrane layer; and bonding said CMUT membrane wafer to said IC substrate using a low-temperature wafer bonding process; wherein said CMUT membrane layer includes membranes for each transducer of said CMUT array. - View Dependent Claims (8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20)
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Specification