Ultrasonic transducer array and ultrasonic probe
Capacitors, each of which is electrically connected to a capacitor which is the cell of the CMUT mounted in a chip and is used as a DC block capacitor for protecting an amplifying circuit, are formed as many as plural aligned channels in the chip. The capacitor is an electrostatic capacitance element which is not vibrated acoustically.
1. An ultrasonic transducer array comprising:
a substrate;
a first electrode which is formed above the substrate and extends along an upper surface of the substrate in a first direction;
a second electrode which is formed above the substrate and extends in a second direction orthogonal to the first direction in plan view;
a third electrode which is formed above the substrate under the first electrode and the second electrode and extends in the first direction;
a fourth electrode which is formed above the substrate under the first electrode and the second electrode and extends in the first direction; and
a first gap which is formed between the first electrode and the second electrode in a first area where a part of the first electrode and a part of the second electrode are overlapped with each other in plan view, wherein
the third electrode and the fourth electrode overlapped with each other in plan view configure a first capacitor,
the first electrode, the second electrode, and the first gap overlapped with each other in plan view configure an ultrasonic wave vibrator consisting of a second capacitor, and
a planar shape of each of the first electrode, the second electrode, the third electrode, and the fourth electrode is a rectangle shape.
2. The ultrasonic transducer array according to claim 1 , wherein
the first capacitor is not vibrated acoustically.
3. The ultrasonic transducer array according to claim 1 , further comprising:
a wiring which is arranged in parallel with the second electrode in the first direction and extends in the second direction; and
a resistance element of which one end is connected with the first electrode, and another end is electrically connected to the wiring, wherein
the wiring is electrically connected to a DC power source.
4. The ultrasonic transducer array according to claim 1 , wherein
a part of the first capacitor is overlapped with the first area, and another part of the first capacitor extends in a peripheral area of not being overlapped with the first area in plan view in the first direction.
5. The ultrasonic transducer array according to claim 4 , wherein
a part of the first capacitor is positioned just under a bonding pad formed in the peripheral area.
6. The ultrasonic transducer array according to claim 3 , wherein
the resistance element is integrated with the first electrode and has a cross-sectional area smaller than that of the first electrode.
7. The ultrasonic transducer array according to claim 3 , wherein
the plural first electrodes, the plural third electrodes, the plural fourth electrodes, and the plural resistance elements are arranged in parallel in the second direction, and
each of the plural first electrodes are electrically connected to the wiring through the plural resistance elements.
8. The ultrasonic transducer array according to claim 1 , wherein
the second electrode is electrically connected to a negative terminal of a DC power source,
the third electrode is electrically connected to each of a positive side terminal of the DC power source and the first electrode, and
the fourth electrode is electrically connected to an amplifying circuit.
9. The ultrasonic transducer array according to claim 8 , wherein
the third electrode or the fourth electrode is electrically connected to a driving signal source which supplies a voltage to the second capacitor when ultrasonic waves are oscillated by the ultrasonic wave vibrator.
10. The ultrasonic transducer array according to claim 1 , wherein
the plural first capacitors are formed to be overlapped in a vertical direction, and
the plural first capacitors are connected in parallel with each other.
11. The ultrasonic transducer array according to claim 1 , wherein
a second gap is formed between the third electrode and the fourth electrode.
12. An ultrasonic probe comprising:
the ultrasonic transducer array according to claim 1 .