Stability enhancements in metal oxide semiconductor thin film transistors
A plasma hydrogenated region in the dielectric layer of a semiconductor thin film transistor (TFT) structure improves the stability of the TFT. The TFT is a multilayer structure including an electrode, a dielectric layer disposed on the electrode, and a metal oxide semiconductor on the dielectric. Exposure of the dielectric layer to a hydrogen containing plasma prior to deposition of the semiconductor produces a plasma hydrogenated region at the semiconductor-dielectric interface. The plasma hydrogenated region incorporates hydrogen which decreases in concentration from semiconductor/dielectric interface into the bulk of one or both of the dielectric layer and the semiconductor layer.
1. A method of fabricating a multilayer semiconductor structure, comprising:
forming an electrode layer;
forming a dielectric layer proximate to the electrode layer;
after forming the dielectric layer, exposing the dielectric layer to a hydrogen-containing plasma; and
after exposing the dielectric layer to the hydrogen-containing plasma, forming a metal oxide semiconductor layer proximate to the dielectric layer
wherein a hydrogenated region is formed at a semiconductor-dielectric interface of the dielectric layer, the hydrogenated region incorporating hydrogen that decreases in concentration from the semiconductor-dielectric interface into one or both of the dielectric layer and the semiconductor layer.
2. The method of claim 1 , wherein forming the dielectric layer comprises anodizing the electrode layer.
3. The method of claim 1 , wherein the semiconductor layer comprises ZnO and the dielectric layer comprises Al 2 O 3 .
4. The method of claim 1 , wherein forming the electrode layer, forming the dielectric layer, exposing the dielectric layer to the hydrogen-containing plasma, and forming the semiconductor layer are performed in a roll to roll process on a flexible substrate.
5. The method of claim 1 , wherein forming the dielectric layer and forming the semiconductor layer are performed at a temperature of less than 100 C.
6. The method of claim 1 , wherein the hydrogen-containing plasma comprises about 5% hydrogen.
7. The method of claim 1 , wherein the hydrogen-containing plasma comprises deuteruim.
8. The method of claim 1 , wherein exposing the dielectric layer to the hydrogen-containing plasma comprises exposing the dielectric layer to at least about 0.01 Watts/cm 2 for about 3-5 minutes.
9. The method of claim 1 , wherein exposing the dielectric layer to the hydrogen-containing plasma further comprises creating a non-uniform hydrogen concentration profile that decreases from a first level at a first point at a surface of the dielectric layer to a second level at a second point in the dielectric layer farther from the surface.
10. The method of claim 1 , wherein:
forming the multilayer semiconductor structure comprises forming a thin film transistor; and
exposing the dielectric layer to a hydrogen-containing plasma comprises incorporating hydrogen into a hydrogenated region at a surface of the dielectric, the hydrogenated region including the incorporated hydrogen stabilizing a threshold voltage of the transistor.
11. A method of fabricating a multilayer semiconductor structure, comprising:
forming an electrode layer;
forming a dielectric layer proximate to the electrode layer;
after forming the dielectric layer, processing the dielectric layer to create a hydrogenated region at a surface of the dielectric layer, the hydrogenated region having a non-uniform hydrogen profile wherein a concentration of hydrogen decreases from a first point at a surface of the dielectric to a second point within dielectric layer; and
forming a metal oxide semiconductor layer proximate to the dielectric layer.
12. The method of claim 11 , wherein processing the dielectric layer comprises exposing the dielectric layer to a hydrogen-containing plasma after formation of the dielectric.
13. The method of claim 11 , wherein processing the dielectric layer comprises exposing the dielectric layer to a deuterium-containing plasma to create a non-uniform deuterium profile in the dielectric layer wherein a concentration of deuterium decreases from a first point at a surface of the dielectric to a second point within dielectric layer.
14. The method of claim 11 , wherein:
the electrode layer comprises aluminum (Al);
the dielectric comprises aluminum oxide (Al 2 O 3 ); and
the semiconductor comprises zinc oxide (ZnO).
15. The method of claim 11 , wherein processing the dielectric layer comprises increasing a hydrogen concentration at a surface of the dielectric layer, wherein a hydrogen concentration in a bulk of the dielectric layer near an interface between the electrode and the dielectric layer is not substantially increased by the processing.
16. A multilayer semiconductor structure, comprising:
an electrode;
a dielectric layer disposed proximate to the electrode;
a semiconductor layer comprising a metal oxide semiconductor disposed proximate to the dielectric layer; and
a hydrogenated region at a semiconductor-dielectric interface of the dielectric layer, wherein the hydrogenated region incorporates hydrogen that decreases in concentration from the semiconductor-dielectric interface into one or both of the dielectric layer and the semiconductor layer.
17. The semiconductor structure of claim 16 , wherein the hydrogenated region comprises a plasma hydrogenated region.
18. The semiconductor structure of claim 16 , wherein the metal oxide semiconductor comprises ZnO and the dielectric comprises aluminum oxide.
19. The semiconductor structure of claim 16 , wherein the hydrogen incorporated in the hydrogenated region comprises deuterium.
20. The semiconductor structure of claim 16 , further comprising a flexible polymeric substrate, wherein the electrode is disposed on the polymeric substrate.