Thin film transistor and method for fabricating the same
A thin film transistor that has improved characteristics and uniformity is developed by uniformly controlling low concentration of crystallization catalyst and controlling crystallization position so that no seed exists and no grain boundary exists, or one grain boundary exists in a channel layer of the thin film transistor. The thin film transistor includes a substrate; a semiconductor layer pattern which is formed on the substrate, the semiconductor layer pattern having a channel layer of which no seed exists and no grain boundary exists; a gate insulating film formed on the semiconductor layer pattern; and a gate electrode formed on the gate insulating film. A method for fabricating the thin film transistor includes forming an amorphous silicon layer on a substrate; forming a semiconductor layer pattern having a channel layer in which no seed exists and no grain boundary exists by crystallizing and patterning the amorphous silicon layer; forming a gate insulating film on the semiconductor layer pattern; and forming a gate electrode on the gate insulating film.
1. A method for fabricating a thin film transistor comprising:
forming an amorphous silicon layer on a substrate;
forming a semiconductor layer pattern having a channel layer in which no seed exists and no grain boundary exists by crystallizing and patterning the amorphous silicon layer, the forming a semiconductor layer pattern comprising;
forming a first capping layer on the amorphous silicon layer;
patterning the first capping layer so that a seed is formed in a source region or a drain region of the semiconductor layer pattern;
forming a second capping layer on a top surface of the patterned first capping layer;
forming a metal catalyst layer on the second capping layer;
diffusing a metal catalyst of the metal catalyst layer through the second capping layer into the amorphous silicon layer; and
forming a polycrystalline silicon layer by crystallizing the amorphous silicon layer using the diffused metal catalyst;
forming a gate insulating film on the semiconductor layer pattern; and
forming a gate electrode on the gate insulating film.
2. The method for fabricating the thin film transistor according to claim 1 , wherein the semiconductor layer pattern is formed in such a manner that a width and a length of the semiconductor layer pattern are each shorter than a radius of a grain formed by the seed.
3. The method for fabricating the thin film transistor according to claim 1 , wherein the first capping layer pattern and the second capping layer are each formed of a silicon nitride film or a silicon oxide film.
4. The method for fabricating the thin film transistor according to claim 1 , wherein a thickness of a part of the first capping layer pattern is thicker than that of the second capping layer.
5. The method for fabricating the thin film transistor according to claim 1 , wherein a density of a part the first capping layer pattern is higher than that of the second capping layer.
6. The method for fabricating the thin film transistor according to claim 1 , wherein the second capping layer is also formed on a side surface of the patterned first capping layer as well as on the top surface of the patterned first capping layer.
7. A method for fabricating a thin film transistor comprising:
forming an amorphous silicon layer on a substrate;
forming a semiconductor layer pattern having a channel layer in which no seed exists and no grain boundary exists by crystallizing and patterning the amorphous silicon layer, the forming a semiconductor layer pattern comprising;
forming a first capping layer on the amorphous silicon layer;
patterning the first capping layer so that a seed is formed outside of the channel layer between a source region and a drain region of the semiconductor layer pattern;
forming a second capping layer on a top surface of the patterned first capping layer;
forming a metal catalyst layer on the second capping layer;
diffusing a metal catalyst of the metal catalyst layer through the second capping layer into the amorphous silicon layer; and
forming a polycrystalline silicon layer by crystallizing the amorphous silicon layer using the diffused metal catalyst;
forming a gate insulating film on the semiconductor layer pattern; and
forming a gate electrode on the gate insulating film.
8. The method for fabricating the thin film transistor according to claim 7 , wherein the semiconductor layer pattern is formed in such a manner that a width and a length of the semiconductor layer pattern are each shorter than a diameter of a grain formed by the seed.
9. The method for fabricating the thin film transistor according to claim 7 , wherein the first capping layer pattern and the second capping layer are each formed of a silicon nitride film or a silicon oxide film.
10. The method for fabricating the thin film transistor according to claim 7 , wherein a thickness of a part of the first capping layer pattern is thicker than that of the second capping layer.
11. The method for fabricating the thin film transistor according to claim 7 , wherein a density of a part of the first capping layer pattern is higher than that of the second capping layer.
12. The method for fabricating the thin film transistor according to claim 7 , wherein the second capping layer is also formed on a side surface of the patterned first capping layer as well as on the top surface of the patterned first capping layer.