RELATED APPLICATIONS

The present application is the U.S. national phase entry of PCT/CN2017/115887, with an international filing date of Dec. 13, 2017, which claims the benefit of Chinese Patent Application No. 201710071073.3, filed Feb. 9, 2017, the entire disclosures of which are incorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates to the field of display technologies, and particularly to a thin film transistor and method for fabricating the same, a display substrate, and a display device.

BACKGROUND

An active matrix organic light emitting diode (AMOLED) panel has advantages of a low power consumption, a low fabrication cost, a wide viewing angle, a fast response speed, and thus has gradually replaced the conventional liquid crystal display.

Currently in an AMOLED, an organic light emitting layer is driven by a Drive Thin Film Transistor (DTFT) to emit light. For purpose that the DTFT has a relatively high carrier mobility, a low temperature polycrystalline silicon is generally applied to form an active layer of the DTFT.

In the low temperature polycrystalline silicon film, due to the presence of large amount of grain boundary defect states, the thin film transistor has an unstable threshold voltage and a poor carrier mobility. When the thin film transistor is downscaled, the problem of unstable threshold voltage will become more serious. Currently, a method comprising two steps by using ELA and a CW solid state laser is generally applied to improve the uniformity of a low temperature polycrystalline silicon film, but this causes an increased cost and a complex process, which is not conducive to practical applications.

SUMMARY

In an aspect, embodiments of the present disclosure provide a method for fabricating thin film transistor, the thin film transistor comprises a gate, a source, a drain, and an active layer, a step of forming the active layer comprises:

forming a pattern comprising a thermal insulation layer;

forming a pattern comprising an amorphous silicon layer on the thermal insulation layer, wherein the pattern comprising the amorphous silicon layer comprises a first portion on the thermal insulation layer and a second portion extending beyond the thermal insulation layer; and

treating the pattern comprising the amorphous silicon layer with a laser annealing process to form the active layer from polycrystalline silicon.

In an embodiment, forming the pattern comprising the thermal insulation layer comprises:

preparing a substrate;

depositing a layer of buffer material and a layer of thermal insulation material on the substrate, wherein the buffer material has a thickness smaller than a thickness of the thermal insulation material; and

patterning the layer thermal insulation material to form the pattern comprising the thermal insulation layer.

In an embodiment, forming the pattern comprising the amorphous silicon layer on the pattern comprising the thermal insulation layer comprises:

depositing a layer of amorphous silicon on the substrate on which the pattern comprising the thermal insulation layer has been formed; and

patterning the layer of amorphous silicon to form the pattern comprising the amorphous silicon layer, wherein the amorphous silicon layer has an elongated shape, and comprises a first end portion, a second end portion opposite to the first end portion, and a middle portion between the first end portion and the second end portion, the middle portion is arranged on the thermal insulation layer, and at least one of the first end portion and the second end portion extends beyond the thermal insulation layer.

In an embodiment, both the first end portion and the second end portion extend beyond the thermal insulation layer.

In an embodiment, the first end portion extends beyond the thermal insulation layer by a length of 1-1.5 μm.

In an embodiment, the second end portion extends beyond the thermal insulation layer by a length of 1-1.5 μm.

In an embodiment, the thermal insulation layer has an elongated shape, the thermal insulation layer has a same extending direction as the amorphous silicon layer, and the thermal insulation layer has a width in a direction perpendicular with the extending direction larger than a width of the middle portion in a direction perpendicular with the extending direction.

In an embodiment, the width of the thermal insulation layer in the direction perpendicular with the extending direction is larger than the width of the middle portion in the direction perpendicular with the extending direction by 1-2 μm.

In an embodiment, the buffer material is SiNx, and has a thickness of 50-100 nm.

In an embodiment, the thermal insulation material is SiO2, and has a thickness of 250-350 nm.

In an embodiment, during the laser annealing process, the laser has energy of 350 mJ/cm2-450 mJ/cm2, and has a radiating duration of 7-8 minutes.

In another aspect, embodiments of the present disclosure further provide a thin film transistor, which is fabricated the fabricating method as described above, wherein the thin film transistor comprises an active layer which is formed on a thermal insulation layer from polycrystalline silicon, and the active layer comprises a portion on the thermal insulation layer and a portion extending beyond the thermal insulation layer.

In yet another aspect, embodiments of the present disclosure further provide a display substrate, comprising the thin film transistor as described above.

In yet another aspect, embodiments of the present disclosure further provide a display device, comprising the display substrate as described above.

