Transistor having oxide semiconductor layer and display utilizing the same
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;
a gate insulating layer over the gate electrode layer;
an oxide semiconductor layer over the gate insulating layer;
a source electrode layer and a drain electrode layer over the oxide semiconductor layer; and
an oxide insulating layer in contact with the oxide semiconductor layer,
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 comprise 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 , wherein the oxide insulating layer comprises a material selected from the group consisting of silicon oxide, silicon nitride oxide, aluminum oxide, and aluminum oxynitride.
5. The transistor according to claim 1 further comprising a pair of oxide conductive layers partly overlapping with the oxide semiconductor layer over the gate insulating layer,
wherein the pair of oxide conductive layers includes a crystal region.
6. A display device comprising:
a pixel portion and a driver circuit each including a transistor over a substrate, the transistor comprising:
a gate electrode layer over the substrate;
a gate insulating layer over the gate electrode layer;
an oxide semiconductor layer over the gate insulating layer;
a source electrode layer and a drain electrode layer the oxide semiconductor layer; and
an oxide insulating layer in contact with the oxide semiconductor layer,
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.
7. The display device according to claim 6 , wherein the oxide semiconductor layer is amorphous.
8. The display device according to claim 6 , wherein the source electrode layer and the drain electrode layer comprise a film including an element selected from Al, Cr, Cu, Ta, Ti, Mo, and W as its main component or an alloy film thereof.
9. The display device according to claim 6 , wherein the oxide insulating layer comprises a material selected from the group consisting of silicon oxide, silicon nitride oxide, aluminum oxide, and aluminum oxynitride.
10. The transistor according to claim 5 ,
wherein the pair of oxide conductive layers comprises a material selected from the group consisting of 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.
11. The display device according to claim 6 further comprising a pair of oxide conductive layers partly overlapping with the oxide semiconductor layer over the gate insulating layer,
wherein the pair of oxide conductive layers includes a crystal region.
12. The display device according to claim 11 ,
wherein the pair of oxide conductive layers comprises a material selected from the group consisting of 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.