Array substrate for a liquid crystal display device having an improved contact property and fabricating method thereof

1. An array substrate for a liquid crystal display device, comprising:

a substrate;

a gate electrode on the substrate;

a gate insulating layer on the gate electrode;

a semiconductor layer on the gate insulating layer;

source and drain electrodes on the semiconductor layer, the source and drain electrodes including a copper layer as an upper layer and a barrier layer as a lower layer;

a first passivation layer on the source and drain electrodes;

a second passivation layer on the first passivation layer, the second passivation layer having a drain contact hole through the first passivation layer, the drain contact hole exposing the barrier layer; and

a pixel electrode connected to the barrier layer through the drain contact hole.

2. The substrate according to claim 1 , wherein the gate electrode has the same material as the source and drain electrodes.

3. The substrate according to claim 2 , further comprising a gate line connected to the gate electrode, a data line crossing the gate line, a gate pad at on end of the gate line and a data pad at one end of the data line.

4. The substrate according to claim 3 , wherein the first and second passivation layers have a gate pad contact hole and a data pad contact hole corresponding to the gate pad and the data pad, the gate pad contact hole and the data pad contact hole exposing the respective barrier layer of the gate pad and data pad.

5. The substrate according to claim 4 , wherein the gate insulating layer is interposed between the gate pad and the first passivation layer.

6. The substrate according to claim 5 , wherein the first and second passivation layer has the gate pad contact hole through the gate insulating layer.

7. The substrate according to claim 1 , wherein the barrier layer includes one of titanium (Ti), molybdenum (Mo), chromium (Cr) and indium (In).

8. The substrate according to claim 1 , wherein the first insulating layer includes an inorganic insulating material.

9. The substrate according to claim 8 , wherein the inorganic insulating material includes one of silicon nitride (SiNx) and silicon oxide (SiO 2 ).

10. The substrate according to claim 1 , wherein the second passivation layer includes an organic insulating material.

11. The substrate according to claim 10 , wherein the organic insulating material has a dielectric constant less than about 3.

12. The substrate according to claim 10 , wherein the organic insulating material is photosensitive.