Thin-film transistor and thin-film transistor manufacturing method

1. A thin-film transistor comprising:

a substrate;

a gate electrode above the substrate;

a gate insulating layer on the gate electrode;

a semiconductor layer on the gate insulating layer which is located on the gate electrode;

a source electrode above the semiconductor layer;

a drain electrode above the semiconductor layer; and

a barrier layer between the semiconductor layer and the source electrode and between the semiconductor layer and the drain electrode,

wherein each of the source electrode and the drain electrode comprises a metal including copper, and

the barrier layer contains nitrogen and molybdenum and has a density greater than 7.5 g/cm 3 and less than 10.5 g/cm 3 .

2. The thin-film transistor according to claim 1 ,

wherein a composition ratio of nitrogen to molybdenum contained in the barrier layer is greater than 0.9.

3. The thin-film transistor according to claim 2 ,

wherein the barrier layer has a structure including: a plurality of crystal grains comprising Mo 2 N; and nitrogen contained in between the crystal grains.

4. The thin-film transistor according to claim 1 ,

wherein the barrier layer has a thickness of no less than 2 nm and no less than 30 nm.

5. The thin-film transistor according to claim 4 ,

wherein the barrier layer has a thickness of no less than 3 nm and no more than 25 nm.

6. The thin-film transistor according to claim 1 ,

wherein a contact layer is provided between the semiconductor layer and the barrier layer.

7. A thin-film transistor manufacturing method comprising:

preparing a substrate having a semiconductor layer;

forming, above the semiconductor layer, a barrier layer including a molybdenum nitride film; and

forming, on the barrier layer, a source electrode and a drain electrode from a metal including copper,

wherein in the forming of a barrier layer, the substrate and a molybdenum target are placed in a sputtering device and the molybdenum target is sputtered in an unheated state by introducing nitrogen gas and an inert gas, to thereby form the molybdenum nitride film which has a density greater than 7.5 g/cm 3 and less than 10.5 g/cm 3 .

8. The thin-film transistor manufacturing method according to claim 7 ,

wherein the inert gas is argon gas, and

in the forming of a barrier layer, a gas flow rate ratio of the nitrogen gas to the argon gas is set to no less than 1.6 to form the barrier layer.

9. The thin-film transistor manufacturing method according to claim 7 ,

wherein the sputtering in the unheated state in the forming of a barrier layer is performed at room temperature.