Thin film transistor and display substrate, fabrication method thereof, and display device

1. A method for fabricating a display substrate, comprising a method for fabricating a thin film transistor, the method for fabricating the thin film transistor comprising:

providing a substrate;

forming a semiconductor layer over the substrate;

forming a source-drain metal layer over the semiconductor layer;

applying one patterning process to the semiconductor layer and the source-drain metal layer to form an active layer, a source electrode, and a drain electrode;

forming a gate insulating layer and an interlayer insulating layer that cover the active layer, the source electrode, and the drain electrode;

applying a patterning process to the interlayer insulating layer to form a first window in the interlayer insulating layer to expose a portion of the gate insulating layer; and

forming a gate electrode in the first window, an orthogonal projection of the gate electrode on the substrate being in an orthogonal projection of the active layer on the substrate; and

wherein the method for fabricating the display substrate further comprises:

forming a passivation layer over the thin film transistor;

forming a first via hole and a second via hole penetrating through the passivation layer, the interlayer insulating layer, and the gate insulating layer;

forming a transparent conductive layer over the passivation layer and in the first via hole and the second via hole; and

patterning the transparent conductive layer to form a pixel electrode and a first electrode, the pixel electrode being electrically coupled to the drain electrode through the first via hole and the first electrode being electrically coupled to the source electrode through the second via hole.

2. The method according to claim 1 , wherein the method for fabricating the thin film transistor further comprising, before forming the semiconductor layer and the source-drain metal layer:

forming a patterned light-blocking layer over the substrate, the orthogonal projection of a portion of the active layer between the source electrode and the drain electrode on the substrate being in an orthogonal projection of the light-blocking layer on the substrate.

3. The method according to claim 2 , wherein the method for fabricating the thin film transistor further comprising:

forming a buffer layer over the light-blocking layer;

wherein forming the semiconductor layer includes:

forming an amorphous silicon layer over the buffer layer; and

processing the amorphous silicon layer to form a polysilicon layer as the semiconductor layer.

4. The method according to claim 3 , wherein processing the amorphous silicon layer includes:

applying a dehydrogenation process and an excimer laser annealing process to the amorphous silicon layer to form the polysilicon layer as the semiconductor layer.

5. The method according to claim 1 , further comprising, before forming the passivation layer:

forming an organic insulating layer over the thin film transistor;

patterning the organic insulating layer to form a second window, a portion of the second window being directly above at least a portion of a region where the source electrode of the thin film transistor is located and another portion of the second window being directly above at least a portion of a region where the drain electrode of the thin film transistor is located; and

forming a common electrode over the organic insulating layer.

6. A display substrate comprising a thin film transistor, the thin film transistor comprising:

a substrate;

an active layer over the substrate;

a source electrode and a drain electrode over the substrate,

wherein:

the source electrode and the drain electrode are disposed over a surface of the active layer facing away from the substrate, and

orthogonal projections of the source electrode and the drain electrode on the substrate are in an orthogonal projection of the active layer on the substrate;

a gate insulating layer covering the active layer, the source electrode, and the drain electrode;

an interlayer insulating layer over the gate insulating layer, the interlayer insulating layer having a first window exposing a portion of the gate insulating layer; and

a gate electrode in the first window, an orthogonal projection of the gate electrode on the substrate being located in the orthogonal projection of the active layer on the substrate;

wherein the display substrate further comprises:

a passivation layer over the thin film transistor; and

a pixel electrode and a first electrode in a same layer and over the passivation layer, wherein:

the pixel electrode is electrically coupled to the drain electrode through a first via hole penetrating through the passivation layer, the interlayer insulating layer, and the gate insulating layer, and

the first electrode is electrically coupled to the source electrode through a second via hole penetrating through the passivation layer, the interlayer insulating layer, and the gate insulating layer.

7. The display substrate according to claim 6 , further comprising:

an organic insulating layer arranged over the thin film transistor and beneath the passivation layer, the organic insulating layer having a second window including a portion directly above at least a portion of a region where the source electrode of the thin film transisto is located and another portion directly above at least a portion of a region where the drain electrode of the thin film transistor is located; and

a common electrode between the organic insulating layer and the passivation layer.

8. A display device comprising the display substrate according claim 6 .