Transistor and display device
It is an object to manufacture a highly reliable display device using a thin film transistor having favorable electric characteristics and high reliability as a switching element. In a bottom gate thin film transistor including an amorphous oxide semiconductor, an oxide conductive layer having a crystal region is formed between an oxide semiconductor layer which has been dehydrated or dehydrogenated by heat treatment and each of a source electrode layer and a drain electrode layer which are formed using a metal material. Accordingly, contact resistance between the oxide semiconductor layer and each of the source electrode layer and the drain electrode layer can be reduced; thus, a thin film transistor having favorable electric characteristics and a highly reliable display device using the thin film transistor can be provided.
1. A transistor comprising:
a gate electrode layer;
an oxide semiconductor layer adjacent to the gate electrode layer with a gate insulating layer therebetween;
a source electrode layer adjacent to the oxide semiconductor layer with an oxide conductive layer therebetween; and
a drain electrode layer adjacent to the oxide semiconductor layer with the oxide conductive layer therebetween,
wherein the oxide conductive layer includes a microcrystalline region, and
wherein a peak of a desorption constituent, which is derived from moisture, is not shown in a spectrum of the oxide semiconductor layer, which is shown with thermal desorption spectroscopy in a temperature range of greater than or equal to 200° C. and less than or equal to 350° C.
2. The transistor according to claim 1 , wherein the oxide semiconductor layer is amorphous.
3. The transistor according to claim 1 , wherein the source electrode layer and the drain electrode layer are formed using a film including an element selected from Al, Cr, Cu, Ta, Ti, Mo, and W as its main component or an alloy film thereof.
4. The transistor according to claim 1 , further comprising an oxide insulating layer between the oxide semiconductor layer and the oxide conductive layer.
5. The transistor according to claim 4 , wherein the oxide insulating layer is formed by a sputtering method using silicon oxide, silicon nitride oxide, aluminum oxide, or aluminum oxynitride.
6. The transistor according to claim 1 , wherein the oxide conductive layer is formed using one kind selected from indium oxide, an indium oxide-tin oxide alloy, an indium oxide-zinc oxide alloy, zinc oxide, zinc aluminum oxide, zinc aluminum oxynitride, and zinc gallium oxide.
7. A transistor comprising:
a gate electrode layer;
a gate insulating layer over the gate electrode layer;
an oxide semiconductor layer over the gate insulating layer;
an oxide conductive layer over the oxide semiconductor layer;
a source electrode layer over the oxide conductive layer; and
a drain electrode layer over the oxide conductive layer;
wherein the oxide conductive layer includes a microcrystalline region, and
wherein a peak of a desorption constituent, which is derived from moisture, is not shown in a spectrum of the oxide semiconductor layer, which is shown with thermal desorption spectroscopy in a temperature range of greater than or equal to 200° C. and less than or equal to 350° C.
8. The transistor according to claim 7 , wherein the oxide semiconductor layer is amorphous.
9. The transistor according to claim 7 , wherein the source electrode layer and the drain electrode layer are formed using a film including an element selected from Al, Cr, Cu, Ta, Ti, Mo, and W as its main component or an alloy film thereof.
10. The transistor according to claim 7 , further comprising an oxide insulating layer between the oxide semiconductor layer and the oxide conductive layer.
11. The transistor according to claim 10 , wherein the oxide insulating layer is formed by a sputtering method using silicon oxide, silicon nitride oxide, aluminum oxide, or aluminum oxynitride.
12. The transistor according to claim 7 , wherein the oxide conductive layer is formed using one kind selected from indium oxide, an indium oxide-tin oxide alloy, an indium oxide-zinc oxide alloy, zinc oxide, zinc aluminum oxide, zinc aluminum oxynitride, and zinc gallium oxide.
13. A display device comprising:
a pixel portion over a substrate; and
a driver circuit over the substrate and comprising a transistor;
the transistor comprising:
a gate electrode layer;
a gate insulating layer over the gate electrode layer;
an oxide semiconductor layer over the gate insulating layer;
an oxide conductive layer over the oxide semiconductor layer;
a source electrode layer over the oxide conductive layer; and
a drain electrode layer over the oxide conductive layer;
wherein the oxide conductive layer includes a microcrystalline region, and
wherein a peak of a desorption constituent, which is derived from moisture, is not shown in a spectrum of the oxide semiconductor layer, which is shown with thermal desorption spectroscopy in a temperature range of greater than or equal to 200° C. and less than or equal to 350° C.
14. The transistor according to claim 13 , wherein the oxide semiconductor layer is amorphous.
15. The transistor according to claim 13 , wherein the source electrode layer and the drain electrode layer are formed using a film including an element selected from Al, Cr, Cu, Ta, Ti, Mo, and W as its main component or an alloy film thereof.
16. The transistor according to claim 13 , further comprising an oxide insulating layer between the oxide semiconductor layer and the oxide conductive layer.
17. The transistor according to claim 16 , wherein the oxide insulating layer is formed by a sputtering method using silicon oxide, silicon nitride oxide, aluminum oxide, or aluminum oxynitride.
18. The transistor according to claim 13 , wherein the oxide conductive layer is formed using one kind selected from indium oxide, an indium oxide-tin oxide alloy, an indium oxide-zinc oxide alloy, zinc oxide, zinc aluminum oxide, zinc aluminum oxynitride, and zinc gallium oxide.