Display device

• US 9,331,100 B2
• Filed: 09/17/2013
• Issued: 05/03/2016
• Est. Priority Date: 09/24/2012
• Status: Active Grant

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: Yamazaki, Shunpei
• Primary Examiner(s): Oh, Jaehwan
• Application Number:
  US14/028,744
• Publication Number:
  US 20140091301A1
• Time in Patent Office: 959 Days
• US Class Current: 1/1
• CPC Class Codes: H01L 27/1225 with semiconductor materials not belonging to the group IV of the periodic table, e.g. InGaZnO
• CPC Class Codes: H01L 29/7869 having a semiconductor body comprising an oxide semiconductor material, e.g. zinc oxide, copper aluminium oxide, cadmium stannate

Abstract

A transistor including an oxide semiconductor layer can have stable electrical characteristics. In addition, a highly reliable display device including the transistor is provided. The display device includes a multi-layer film including an oxide layer and an oxide semiconductor layer; a gate insulating film in contact with the multi-layer film; and a gate electrode overlapping with the multi-layer film with the gate insulating film provided therebetween. The oxide semiconductor layer contains indium, and is in contact with the oxide layer. The oxide layer contains indium, and has a larger energy gap than the oxide semiconductor layer.

Claims

1. A display device comprising:

a multi-layer film including an oxide layer and an oxide semiconductor layer;

a gate insulating film in contact with the multi-layer film; and

a gate electrode overlapping with the multi-layer film with the gate insulating film therebetween,

wherein each of the oxide layer and the oxide semiconductor layer contains indium,

wherein the oxide layer is directly in contact with the gate insulating film,

wherein the oxide semiconductor layer is not directly in contact with the gate insulating film,

wherein the oxide semiconductor layer is in contact with the oxide layer,

wherein a band gap of the oxide layer is larger than a band gap of the oxide semiconductor layer, and

wherein a bottom of a conduction band is gradually decreased from the oxide layer to the oxide semiconductor layer and a top of a valence band is gradually increased from the oxide layer to the oxide semiconductor layer.

2. The display device according to claim 1, wherein a channel is formed in the oxide semiconductor layer.

3. The display device according to claim 1, further comprising a source electrode and a drain electrode, wherein each of the source electrode and the drain electrode is in contact with one of side edges of the oxide semiconductor layer.

4. The display device according to claim 1,

wherein the oxide semiconductor layer includes a crystal part, and

wherein a c-axis of the crystal part is parallel to a normal vector of a surface of the oxide layer.

5. The display device according to claim 1,

wherein each of the oxide semiconductor layer and the oxide layer comprises at least one of indium, zinc, and a metal,

wherein the metal is selected from aluminum, titanium, gallium, yttrium, zirconium, tin, lanthanum, cerium, neodymium, and hafnium, and

wherein an atomic ratio of indium to the metal in the oxide layer is lower than an atomic ratio of indium to the metal in the oxide semiconductor layer.

6. The display device according to claim 1, wherein the oxide semiconductor layer is an In—

Zn oxide, an In—

Ga oxide, or an In—

Ga—

Zn oxide.

7. The display device according to claim 1,

wherein a thickness of the oxide semiconductor layer is greater than or equal to 3 nm and less than or equal to 200 nm, and

wherein a thickness of the oxide layer is greater than or equal to 3 nm and less than or equal to 50 nm.

8. The display device according to claim 1, wherein the thickness of the oxide layer is greater than or equal to 3 nm and less than or equal to 40 nm.

9. The display device according to claim 1, wherein a concentration of silicon in the oxide semiconductor layer is less than 5×

10¹⁸ atoms/cm³.

10. The display device according to claim 1, wherein a concentration of carbon in the oxide semiconductor layer is less than 1×

10¹⁹ atoms/cm³.

11. A display device comprising:

a multi-layer film including an oxide layer and an oxide semiconductor layer;

a gate insulating film in contact with the multi-layer film; and

a gate electrode overlapping with the multi-layer film with the gate insulating film therebetween,

wherein each of the oxide layer and the oxide semiconductor layer contains indium,

wherein the oxide layer is directly in contact with the gate insulating film,

wherein the oxide semiconductor layer is not directly in contact with the gate insulating film,

wherein the oxide semiconductor layer is in contact with the oxide layer,

wherein an energy at a bottom of a conduction band of the oxide layer is closer to a vacuum level than an energy at a bottom of a conduction band of the oxide semiconductor layer, and

wherein a bottom of a conduction band is gradually decreased from the oxide layer to the oxide semiconductor layer and a top of a valence band is gradually increased from the oxide layer to the oxide semiconductor layer.

12. The display device according to claim 11, wherein a gap between the energy at the bottom of the conduction band of the oxide layer and the energy at the bottom of the conduction band of the oxide semiconductor layer is greater than or equal to 0.05 eV and less than or equal to 2 eV.

13. The display device according to claim 11, wherein a channel is formed in the oxide semiconductor layer.

14. The display device according to claim 11, further comprising a source electrode and a drain electrode, wherein each of the source electrode and the drain electrode is in contact with one of side edges of the oxide semiconductor layer.

15. The display device according to claim 11,

wherein the oxide semiconductor layer includes a crystal part, and

wherein a c-axis of the crystal part is parallel to a normal vector of a surface of the oxide layer.

16. The display device according to claim 11,

wherein each of the oxide semiconductor layer and the oxide layer comprises at least one of indium, zinc, and a metal,

wherein the metal is selected from aluminum, titanium, gallium, yttrium, zirconium, tin, lanthanum, cerium, neodymium, and hafnium, and

wherein an atomic ratio of indium to the metal in the oxide layer is lower than an atomic ratio of indium to the metal in the oxide semiconductor layer.

17. The display device according to claim 11, wherein the oxide semiconductor layer is an In—

Zn oxide, an In—

Ga oxide, or an In—

Ga—

Zn oxide.

18. The display device according to claim 11,

wherein a thickness of the oxide semiconductor layer is greater than or equal to 3 nm and less than or equal to 200 nm, and

wherein a thickness of the oxide layer is greater than or equal to 3 nm and less than or equal to 50 nm.

19. The display device according to claim 11, wherein the thickness of the oxide layer is greater than or equal to 3 nm and less than or equal to 40 nm.

20. The display device according to claim 11, wherein a concentration of silicon in the oxide semiconductor layer is less than 5×

10¹⁸ atoms/cm³.

21. The display device according to claim 11, wherein a concentration of carbon in the oxide semiconductor layer is less than 1×

10¹⁹ atoms/cm³.