Method of manufacturing ZnO-based thin film transistor
Provided is a method of manufacturing a ZnO-based thin film transistor (TFT). The method may include forming source and drain electrodes using one or two wet etchings. A tin (Sn) oxide, a fluoride, or a chloride having relatively stable bonding energy against plasma may be included in a channel layer. Because the source and drain electrodes are formed by wet etching, damage to the channel layer and an oxygen vacancy may be prevented or reduced. Because the material having higher bonding energy is distributed in the channel layer, damage to the channel layer occurring when a passivation layer is formed may be prevented or reduced.
1. A method of manufacturing a ZnO-based thin film transistor (TFT, the method comprising:
forming a ZnO-based channel layer on a gate insulating layer;
forming a conductive material layer on the gate insulating layer and the ZnO-based channel layer;
forming a mask layer on the conductive material layer having a pattern corresponding to source and drain electrodes on both sides of the ZnO-based channel layer;
forming the source and drain electrodes by etching the conductive material layer not covered by the mask layer using a wet etchant having a higher selectivity with respect to the conductive material layer than the ZnO-based channel layer; and
forming a passivation layer covering the source and drain electrodes and the ZnO-based channel layer,
wherein the source and drain electrodes are formed by a first etching to remove a portion of the conductive material layer not covered by the mask layer, and a second etching to completely remove the portion of the conductive material layer not covered by the mask layer and over-etch the surface of the ZnO-based channel layer, so that the ZnO-based channel layer includes an over-etched portion between the source electrode and the drain electrode.
2. The method of claim 1 , wherein at least one of a tin (Sn) oxide, a fluoride, and a chloride is further included in the ZnO-based channel layer.
3. The method of claim 2 , wherein the fluoride includes at least one selected from the group consisting of GaF 3 , InF 3 , and ZnF 2 .
4. The method of claim 2 , wherein the chloride includes at least one selected from the group consisting of GaCl 3 , InCl 3 , and ZnCl 2 .
5. The method of claim 1 , wherein the ZnO-based channel layer is formed of gallium-indium-zinc-oxide (GIZO).
6. The method of claim 5 , wherein the ZnO-based channel layer further includes at least one of a tin (Sn) oxide, a fluoride, and a chloride.
7. The method of claim 1 , wherein:
a first etchant for the first etching has a phosphoric acid, a nitric acid, and an acetic acid as main components; and
a second etchant for the second etching has water and a hydrogen peroxide as main components and a trace of hydrogen fluoride (HF).
8. The method of claim 7 , wherein each of the source and drain electrodes is formed of at least one selected from the group consisting of Cu, Mo, Al, Mo/Cu, Mo/Al, Mo/AlNd, Mo/Al/Mo, Mo/AlNd/Mo, Ti/Al, Ti/AlNd, Ti/Al/Ti, and Ti/AlNd/Ti.
9. The method of claim 8 , wherein the conductive material layer includes at least one multi-layer structure including at least one selected from the group consisting of Mo, Ti, Pt, Cu, Al, W, MoW, AlNd, Ni, Ag, Au, IZO, and ITO, or a silicide thereof.
10. The method of claim 8 , further comprising:
injecting active oxygen into a surface of the ZnO-based channel layer, before forming the passivation layer.
11. The method of claim 7 , wherein the conductive material layer includes at least one multi-layer structure including at least one selected from the group consisting of Mo, Ti, Pt, Cu, Al, W, MoW, AlNd, Ni, Ag, Au, IZO, and ITO, or a silicide thereof.
12. The method of claim 7 , further comprising:
injecting active oxygen into a surface of the ZnO-based channel layer, before forming the passivation layer.
13. The method of claim 1 , wherein the conductive material layer includes at least one multi-layer structure including at least one selected from the group consisting of Mo, Ti, Pt, Cu, Al, W, MoW, AlNd, Ni, Ag, Au, IZO, and ITO, or a silicide thereof.
14. The method of claim 1 , further comprising:
injecting active oxygen into a surface of the ZnO-based channel layer, before forming the passivation layer.
15. The method of claim 1 , before forming the ZnO-based channel layer on the gate insulating layer, further comprising:
forming a gate on a substrate; and
forming a gate insulating layer on the gate.