Thin film transistor and ultrasonic imaging base board

1 . A thin film transistor, comprising:

a substrate, and a first gate, a first gate insulation layer, a first active layer, a second gate insulation layer, and a second gate stacked on a side of the substrate, wherein the first gate is disposed close to the substrate;

wherein an orthographic projection of the first gate on the substrate, an orthographic projection of the second gate on the substrate, and an orthographic projection of the first active layer on the substrate overlap with each other, and the first gate is connected to the second gate;

wherein the first active layer comprises:

a channel region, and a source contact region and a drain contact region located on two sides of the channel region;

wherein the orthographic projection of the first gate on the substrate and the orthographic projection of the second gate on the substrate cover the orthographic projection of the channel region on the substrate; an ion doping concentration of the source contact region and the drain contact region is greater than the ion doping concentration of the channel region;

wherein

the channel region comprises: a first channel region and a second channel region separated from each other in a second direction;

the second gate comprises a first sub-gate and a second sub-gate separated from each other in the second direction;

wherein, in the second direction, the orthographic projection of the first sub-gate on the substrate completely overlaps with the orthographic projection of the first channel region on the substrate, and the orthographic projection of the second sub-gate on the substrate completely overlaps with the orthographic projection of the second channel region on the substrate.

2 . The thin film transistor according to claim 1 , wherein the second gate is connected to the first gate through a via hole penetrating through the first gate insulation layer and the second gate insulation layer.

3 . The thin film transistor according to claim 1 , further comprising:

a third gate disposed on a side of the second gate facing away from the substrate, wherein the third gate is served as a source and a drain of the thin film transistor, and is connected to the first active layer.

4 . The thin film transistor according to claim 3 , wherein

the third gate is connected to the second gate;

the thin film transistor further comprises a transfer metal layer disposed on a side of the third gate facing away from the second gate, and the transfer metal layer is connected to the first gate and the third gate respectively.

5 . The thin film transistor according to claim 4 , further comprising:

a third insulation layer disposed between the second gate and the third gate; and

a fourth insulation layer disposed between the third gate and the transfer metal layer;

wherein the transfer metal layer is connected to the first gate through a via hole penetrating through the fourth insulation layer, the third insulation layer, the second gate insulation layer and the first gate insulation layer;

the transfer metal layer is connected to the third gate through a via hole penetrating through the fourth insulation layer;

the third gate is connected to the second gate through a via hole penetrating through the third insulation layer.

6 . The thin film transistor according to claim 1 , wherein a material of the channel region comprises polysilicon, amorphous silicon, or oxide semiconductor.

7 . A thin film transistor, comprising:

a substrate, and a first gate, a first gate insulation layer, a first active layer, a second gate insulation layer, and a second gate stacked on a side of the substrate, wherein the first gate is disposed close to the substrate;

wherein an orthographic projection of the first gate on the substrate, an orthographic projection of the second gate on the substrate, and an orthographic projection of the first active layer on the substrate overlap with each other, and the first gate is connected to the second gate;

wherein

the first active layer comprises a plurality of sub-regions separated from each other in a first direction;

in the first direction, the orthographic projection of the first gate on the substrate and the orthographic projection of the second gate on the substrate both cover the orthographic projection of the first active layer on the substrate;

a recessed region exists between two adjacent sub-regions, and the second gate is arranged to at least partially fill the recessed region, and the orthographic projection of the second gate on a first plane at least partially covers the orthographic projection of the sub-region on the first plane;

wherein the first plane is perpendicular to the first direction.

8 . An ultrasonic imaging base board, comprising a signal amplification transistor and a conversion transistor connected to the signal amplification transistor, wherein the signal amplification transistor is a thin film transistor comprising a substrate, and a first gate, a first gate insulation layer, a first active layer, a second gate insulation layer, and a second gate stacked on a side of the substrate, wherein the first gate is disposed close to the substrate; an orthographic projection of the first gate on the substrate, an orthographic projection of the second gate on the substrate, and an orthographic projection of the first active layer on the substrate overlap with each other, and the first gate is connected to the second gate;

wherein the ultrasonic imaging base board further comprises:

a piezoelectric conversion unit, configured to convert an ultrasonic pressure signal received by the ultrasonic imaging base board into an electrical signal, and the piezoelectric conversion unit is connected to the conversion transistor.

9 . The ultrasonic imaging base board according to claim 8 , wherein the conversion transistor comprises:

a buffer layer, disposed on a side of the signal amplification transistor;

a second active layer disposed on the buffer layer; and

a connection metal layer disposed between the piezoelectric conversion unit and the second active layer, wherein the connection metal layer is served as the source and drain of the conversion transistor, and is connected to the second active layer.

10 . The ultrasonic imaging base board according to claim 9 , wherein

the signal amplification transistor comprises a transfer metal layer; and

the transfer metal layer and the connection metal layer are arranged in the same layer.

11 . The ultrasonic imaging base board according to claim 8 , wherein the piezoelectric conversion unit comprises:

a first electrode layer disposed on a side of the connection metal layer facing away from the second active layer, and the first electrode layer is connected to the connection metal layer;

a piezoelectric film layer disposed on a side of the first electrode layer facing away from the connection metal layer; and

a second electrode layer disposed on a side of the piezoelectric film layer facing away from the first electrode layer.

12 . The ultrasonic imaging base board according to claim 11 , further comprising:

a fifth insulation layer disposed between the first electrode layer and the connection metal layer, and the first electrode layer is connected to the connection metal layer through a via hole penetrating through the fifth insulation layer.

13 . The ultrasonic imaging base board according to claim 11 , further comprising a second passivation layer disposed between the first electrode layer and the piezoelectric film layer.

14 . An ultrasonic imaging device, comprising the ultrasonic imaging base board according to claim 8 .