Thin film transistor, method of fabricating the same, and organic light emitting diode display device having the TFT
A thin film transistor (TFT), a method of fabricating the same, and an organic light emitting diode (OLED) display device having the TFT, the TFT including a substrate, a gate electrode disposed on the substrate, a gate insulating layer disposed on the gate electrode, a semiconductor layer disposed on the gate insulating layer and crystallized using a metal catalyst, and source and drain electrodes disposed on the semiconductor layer and electrically connected to source and drain regions of the semiconductor layer. A second metal is diffused into a surface region of the semiconductor layer, to getter the metal catalyst from a channel region of the semiconductor layer. The second metal can have a lower diffusion coefficient in silicon than the metal catalyst.
1. A thin film transistor (TFT) comprising:
a substrate;
a gate electrode disposed on the substrate;
a gate insulating layer disposed on the gate electrode;
a semiconductor layer disposed on the gate insulating layer and crystallized using a metal catalyst; and
source and drain electrodes disposed on the semiconductor layer and electrically connected to respective source and drain regions of the semiconductor layer,
wherein a second metal, which is different from the metal catalyst, is diffused into a surface region of the semiconductor layer, which faces the source and drain electrodes,
wherein the second metal has a lower diffusion coefficient in the semiconductor layer than the metal catalyst.
2. The TFT according to claim 1 , wherein the diffusion coefficient of the second metal is 1%, or less, than the diffusion coefficient of the metal catalyst.
3. The TFT according to claim 2 , wherein:
the metal catalyst is nickel; and
the second metal has a positive diffusion coefficient that is less than about 10 −7 cm 2 /s.
4. The TFT according to claim 1 , wherein the second metal is selected from the group consisting of Ti, Cr, Mo, W, and an alloy thereof.
5. The TFT according to claim 1 , wherein the semiconductor layer is crystallized using a super grain silicon (SGS) crystallization technique.
6. The TFT according to claim 1 , wherein the source and drain electrodes are formed from a layer formed of one selected from the group consisting of Ti, Cr, Mo, W, and alloy thereof, or a triple layer formed of Ti/Al/Ti or Mo/Al/Mo.
7. The TFT according to claim 1 , wherein the surface region of the semiconductor layer further includes n-type impurities, p-type impurities, and/or defects caused by ion processing or plasma processing.
8. An organic light emitting diode (OLED) display device comprising:
a substrate;
a gate electrode disposed on the substrate;
a gate insulating layer disposed on the gate electrode;
a semiconductor layer disposed on the gate insulating layer and crystallized using a metal catalyst;
source and drain electrodes disposed on the semiconductor layer and electrically connected to respective source and drain regions of the semiconductor layer;
a first electrode electrically connected to one of the source and drain electrodes;
an organic layer disposed on the first electrode, comprising an emission layer (EML); and
a second electrode disposed on the organic layer,
wherein a second metal, which is different from the metal catalyst, is disposed in a surface region of the semiconductor layer, which faces the organic layer, and
wherein the second metal is in the form of a metal silicide.
9. The OLED display device according to claim 8 , wherein the source and drain electrodes are formed of one selected from the group consisting of Ti, Cr, Mo, W, and alloy thereof, or a triple layer formed of Ti/Al/Ti or Mo/Al/Mo.
10. The TFT according to claim 1 , wherein the second metal is in the form of a metal silicide.