Semiconductor device including pair of electrodes and oxide semiconductor film with films of low conductivity therebetween

• US 8,772,784 B2
• Filed: 02/21/2013
• Issued: 07/08/2014
• Est. Priority Date: 12/25/2008
• Status: Active Grant

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: Akimoto, Kengo, Tsubuku, Masashi
• Primary Examiner(s): Kraig, William F
• Assistant Examiner(s): Ahmad, Khaja
• Application Number:
  US13/772,692
• Publication Number:
  US 20130175523A1
• Time in Patent Office: 502 Days
• Field of Search: 257/43, 257/59, 257/72, 257/E51.005, 257/E29.117, 257/E21.411, 257/E29.29, 257/E29.293
• US Class Current: 257/72
• CPC Class Codes: H01L 29/66969 of devices having semiconductor bodies not comprising group 14 or group 13/15 materials comprising selenium or tellurium in uncombined form other than as impurities in semiconductor bodies of other materials, comprising cuprous oxide or cuprous iodide H01L21/02365
• CPC Class Codes: H01L 29/78606 with supplementary region or layer in the thin film or in the insulated bulk substrate supporting it for controlling or increasing the safety of the device H01L29/78642, H01L29/78645 take precedence
• CPC Class Codes: H01L 29/78618 characterised by the drain or the source properties, e.g. the doping structure, the composition, the sectional shape or the contact structure silicide contacts, electrodes in general H01L29/458
• CPC Class Codes: H01L 29/7869 having a semiconductor body comprising an oxide semiconductor material, e.g. zinc oxide, copper aluminium oxide, cadmium stannate
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/0002 Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00
• CPC Class Codes: H01L 33/0041 characterised by field-effect operation

Abstract

One of factors that increase the contact resistance at the interface between a first semiconductor layer where a channel is formed and source and drain electrode layers is a film with high electric resistance formed by dust or impurity contamination of a surface of a metal material serving as the source and drain electrode layers. As a solution, a first protective layer and a second protective layer including a second semiconductor having a conductivity that is less than or equal to that of the first semiconductor layer is stacked successively over source and drain electrode layers without exposed to air, the stack of films is used for the source and drain electrode layers.

Claims

1. A semiconductor device comprising:

a first electrode;

a second electrode;

a first semiconductor film over the first electrode;

a second semiconductor film over the second electrode;

an oxide semiconductor film over the first semiconductor film and the second semiconductor film;

an insulating film over the oxide semiconductor film; and

a gate electrode over the insulating film,

wherein the oxide semiconductor film comprises indium and zinc,

wherein the first semiconductor film and the second semiconductor film each have a conductivity less than the oxide semiconductor film,

wherein the first semiconductor film and the second semiconductor film each have smaller thickness than the oxide semiconductor film, and

wherein the oxide semiconductor film comprises sodium at a concentration of 5×

10¹⁸/cm³ or lower.

2. The semiconductor device according to claim 1, wherein the oxide semiconductor film further comprises gallium.

3. The semiconductor device according to claim 1,

wherein the first semiconductor film is a first protective film, and

wherein the second semiconductor film is a second protective film.

4. The semiconductor device according to claim 1, wherein the oxide semiconductor film is in contact with a side surface of the first electrode and a side surface of the second electrode.

5. The semiconductor device according to claim 1, wherein the oxide semiconductor film is in contact with a side surface of the first semiconductor film and a side surface of the second semiconductor film.

6. The semiconductor device according to claim 1, wherein the first semiconductor film and the second semiconductor film each comprise oxide semiconductor.

7. The semiconductor device according to claim 1, wherein the first electrode and the second electrode are over a substrate.

17. The semiconductor device according to claim 1, wherein each of the first semiconductor film and the second semiconductor film comprises indium and zinc.

8. A display device comprising:

a first electrode;

a second electrode;

a first semiconductor film over the first electrode;

a second semiconductor film over the second electrode;

an oxide semiconductor film over the first semiconductor film and the second semiconductor film;

a first insulating film over the oxide semiconductor film;

a gate electrode over the first insulating film;

a second insulating film over the gate electrode; and

a pixel electrode over the second insulating film and electrically connected to the first electrode or the second electrode,

wherein the oxide semiconductor film comprises indium and zinc,

wherein the first semiconductor film and the second semiconductor film each have a conductivity less than the oxide semiconductor film,

wherein the first semiconductor film and the second semiconductor film each have smaller thickness than the oxide semiconductor film, and

wherein the oxide semiconductor film comprises sodium at a concentration of 5×

10¹⁸/cm³ or lower.

9. The display device according to claim 8, wherein the oxide semiconductor film further comprises gallium.

10. The display device according to claim 8,

wherein the first semiconductor film is a first protective film, and

wherein the second semiconductor film is a second protective film.

11. The display device according to claim 8, wherein the oxide semiconductor film is in contact with a side surface of the first electrode and a side surface of the second electrode.

12. The display device according to claim 8, wherein the oxide semiconductor film is in contact with a side surface of the first semiconductor film and a side surface of the second semiconductor film.

13. The display device according to claim 8, wherein the first semiconductor film and the second semiconductor film each comprise oxide semiconductor.

14. The display device according to claim 8, wherein the first electrode and the second electrode are over a substrate.

15. The display device according to claim 8, further comprising a liquid crystal layer over the pixel electrode.

16. The display device according to claim 8, further comprising:

a light-emitting layer over the pixel electrode; and

a third electrode over the light-emitting layer.

18. The display device according to claim 9, wherein each of the first semiconductor film and the second semiconductor film comprises indium and zinc.