Fabricating method of thin film transistor

1. A fabricating method of a thin film transistor, comprising:

forming an active layer of polycrystalline silicon;

forming a first insulating layer on the active layer;

forming a gate electrode on the first insulating layer over the active layer;

doping side portions of the active layer with impurities;

applying a small amount of metal to the side portions of the active layer, wherein the small amount of metal is a concentration less than about 1×10 15 /cm 2 ; and

activating the side portions of the active layer such that the small amount of metal is adsorbed into the active layer.

2. The method according to claim 1 , wherein the first insulating layer is one of silicon nitride, silicon oxide and tetra ethyl ortho silicate.

3. The method according to claim 1 , wherein the dopant impurities include one element of Group III.

4. The method according to claim 1 , wherein the dopant impurities include one element of Group V.

5. The method according to claim 1 , wherein the metal in the step of applying a small amount of metal includes one of nickel, lead and cobalt.

6. The method according to claim 1 , wherein activating the side portions of the active layer is performed at a temperature of less than about 500° C.

7. The method according to claim 6 , wherein activating the side portions of the active layer is performed at a temperature between about 350° C. and about 500° C.

8. The method according to claim 1 , wherein the step of applying a small amount of metal to the side portions of the active layer includes one of depositing and sputtering the small amount of metal.

9. The method according to claim 1 , further comprising forming a second insulating layer under the active layer.

10. The method according to claim 1 , wherein the polycrystalline silicon is obtained through depositing amorphous silicon and crystallizing the amorphous silicon.

11. The method according to claim 10 , wherein crystallizing the amorphous silicon is performed by one of a metal induced crystallization method, a field enhanced metal induced crystallization method, a solid phase crystallization method and a laser annealing method.

12. A fabricating method of a thin film transistor, comprising:

forming a first insulating layer on a substrate;

depositing an amorphous silicon layer on the first insulating layer;

crystallizing the amorphous silicon layer to form a polycrystalline silicon layer;

patterning the polycrystalline silicon layer to form an active layer having an island shape;

forming a second insulating layer on a middle portion of the active layer;

forming a gate electrode on the second insulating layer;

doping side portions of the active layer with dopant impurities;

applying a small amount of metal to the side portions of the active layer, wherein the

small amount of metal is a concentration less than about 1×10 15 /cm 2 ;

activating the side portions of the active layer;

forming a third insulating layer on the gate electrode and on the side portions after activating the side portions, wherein the third insulating layer has first and second contact holes respectively exposing the side portions; and

forming source and drain electrodes connected respectively to the side portions through the first and second contact holes.

13. The method according to claim 12 , wherein the first insulating layer is one of silicon nitride, silicon oxide and tetra ethyl ortho silicate.

14. The method according to claim 13 , wherein the second insulating layer is one of silicon nitride, silicon oxide and tetra ethyl ortho silicate.

15. The method according to claim 12 , wherein the dopant impurities include one element of Group III.

16. The method according to claim 12 , wherein the dopant impurities include one element of Group V.

17. The method according to claim 12 , wherein the metal in the step of applying a small amount of metal includes one of nickel, lead and cobalt.

18. The method according to claim 12 , wherein activating the side portions of the active layer is performed at a temperature of less than about 500° C.

19. The method according to claim 18 , wherein activating the side portions of the active layer is performed at a temperature between about 350° C. and about 500° C.

20. The method according to claim 12 , wherein crystallizing the amorphous silicon is performed by one of a metal induced crystallization method, a field enhanced metal induced crystallization method, a solid phase crystallization method and a laser annealing method.

21. The method according to claim 12 , wherein the step of activating the side portions of the active layer includes adsorbing the small amount of metal into the side portions.

22. The method according to claim 12 , wherein the step of applying a small amount of metal to the side portions of the active layer includes one of depositing and sputtering the small amount of metal.

23. A fabricating method of a thin film transistor, comprising:

forming an active layer of polycrystalline silicon;

forming a first insulating layer on the active layer;

forming a gate electrode on the first insulating layer over the active layer;

doping side portions of the active layer with impurities;

applying a small amount of metal to the side portions of the active layer, wherein the small amount of metal is a concentration less than about 1×10 15 /cm 2 ;

activating the side portions of the active layer such that the small amount of metal is adsorbed into the active layer;

forming a second insulating layer on the gate electrode and on the side portions after activating the side portions, wherein the second insulating layer has first and second contact holes respectively exposing the side portions; and

forming source and drain electrodes connected respectively to the side portions through the first and second contact holes.