SEMICONDUCTOR DEVICE AND METHOD FOR MANUFACTURING THE SAME

• US 20100117078A1
• Filed: 11/09/2009
• Published: 05/13/2010
• Est. Priority Date: 11/13/2008
• Status: Active Grant

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: KUWABARA, Hideaki, AKIMOTO, Kengo, SASAKI, Toshinari
• Granted Patent: US 8,058,647 B2
• Time in Patent Office: Days
• US Class Current: 257/43
• 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 29/04 characterised by their crystalline structure, e.g. polycrystalline, cubic or particular orientation of crystalline planes characterised by physical imperfections H01L29/30
• CPC Class Codes: H01L 29/24 including, apart from doping materials or other impurities, only semiconductor materials not provided for in groups H01L29/16, H01L29/18, H01L29/20, H01L29/22 including organic materials H10K99/00
• CPC Class Codes: H01L 29/458 for thin film silicon, e.g. source or drain electrode
• CPC Class Codes: H01L 29/4908 for thin film semiconductor, e.g. gate of TFT
• 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 29/78696 characterised by the structure of the channel, e.g. multichannel, transverse or longitudinal shape, length or width, doping structure, or the overlap or alignment between the channel and the gate, the source or the drain, or the contacting structure of the channel H01L29/78612 takes precedence; transistors having a drain offset region or a lightly doped drain [LDD] H01L29/78621

Abstract

An object is to increase field effect mobility of a thin film transistor including an oxide semiconductor. Another object is to stabilize electrical characteristics of the thin film transistor. In a thin film transistor including an oxide semiconductor layer, a semiconductor layer or a conductive layer having higher electrical conductivity than the oxide semiconductor is formed over the oxide semiconductor layer, whereby field effect mobility of the thin film transistor can be increased. Further, by forming a semiconductor layer or a conductive layer having higher electrical conductivity than the oxide semiconductor between the oxide semiconductor layer and a protective insulating layer of the thin film transistor, change in composition or deterioration in film quality of the oxide semiconductor layer is prevented, so that electrical characteristics of the thin film transistor can be stabilized.

Claims

1. A semiconductor device comprising:

a gate electrode layer;

a gate insulating layer over the gate electrode layer;

a source electrode layer and a drain electrode layer over the gate insulating layer;

an oxide semiconductor layer over the source electrode layer and the drain electrode layer; and

a semiconductor layer over the oxide semiconductor layer,

wherein the oxide semiconductor layer is in contact with the gate insulating layer and side face portions of the source and drain electrode layers,

wherein electrical conductivity of the semiconductor layer is higher than electrical conductivity of the oxide semiconductor layer, and

wherein the oxide semiconductor layer and the source and drain electrode layers are electrically connected to each other.

2. The semiconductor device according to claim 1, wherein the oxide semiconductor layer includes at least one of indium, gallium, and zinc.

3. The semiconductor device according to claim 1,

wherein the semiconductor layer is an oxide semiconductor layer including at least one of indium, gallium, and zinc, and

wherein the oxide semiconductor layer has a higher oxygen concentration than the semiconductor layer.

4. The semiconductor device according to claim 1,

wherein a carrier concentration of the oxide semiconductor layer is lower than 1×

10¹⁷/cm³.

5. The semiconductor device according to claim 1,

wherein the electrical conductivity of the semiconductor layer is higher than 1.0×

10<sup>−

3</sup> S/cm³.

6. The semiconductor device according to claim 1,

wherein a sodium concentration in the oxide semiconductor layer is equal to or lower than 5×

10¹⁹/cm³.

7. The semiconductor device according to claim 1, wherein the semiconductor device is one selected from the group consisting of a poster, an advertisement, an electronic book, a television set, a digital photo frame, a game machine and a phone.

8. A semiconductor device comprising:

a gate electrode layer;

a gate insulating layer over the gate electrode layer;

a source electrode layer and a drain electrode layer over the gate insulating layer;

a buffer layer having n-type conductivity over the source and drain electrode layers;

an oxide semiconductor layer over the buffer layer; and

a semiconductor layer over the oxide semiconductor layer,

wherein the oxide semiconductor layer is in contact with the gate insulating layer, the buffer layer, and side face portions of the source and drain electrode layers,

wherein electrical conductivity of the semiconductor layer is higher than electrical conductivity of the oxide semiconductor layer,

wherein a carrier concentration of the buffer layer is higher than a carrier concentration of the oxide semiconductor layer, and

wherein the oxide semiconductor layer and top faces of the source and drain electrode layers are electrically connected to each other through the buffer layer.

9. The semiconductor device according to claim 8, wherein the oxide semiconductor layer includes at least one of indium, gallium, and zinc.

10. The semiconductor device according to claim 8,

wherein the semiconductor layer is an oxide semiconductor layer including at least one of indium, gallium, and zinc, and

wherein the oxide semiconductor layer has a higher oxygen concentration than the semiconductor layer.

11. The semiconductor device according to claim 8,

wherein a carrier concentration of the oxide semiconductor layer is lower than 1×

10¹⁷/cm³.

12. The semiconductor device according to claim 8,

wherein the electrical conductivity of the semiconductor layer is higher than 1.0×

10<sup>−

3</sup> S/cm³.

13. The semiconductor device according to claim 8,

wherein a sodium concentration in the oxide semiconductor layer is equal to or lower than 5×

10¹⁹/cm³.

14. The semiconductor device according to claim 8, wherein the carrier concentration of the buffer layer is 1×

10¹⁸/cm³ or higher.

15. The semiconductor device according to claim 8, wherein the semiconductor device is one selected from the group consisting of a poster, an advertisement, an electronic book, a television set, a digital photo frame, a game machine and a phone.

16. A semiconductor device comprising:

a gate electrode layer;

a gate insulating layer over the gate electrode layer;

a source and drain electrode layers over the gate insulating layer;

an oxide semiconductor layer over the source and drain electrode layers;

a semiconductor layer over the oxide semiconductor layer; and

a conductive layer over the semiconductor layer,

wherein the oxide semiconductor layer is in contact with the gate insulating layer and side face portions of the source and drain electrode layers,

wherein electrical conductivity of the semiconductor layer is higher than electrical conductivity of the oxide semiconductor layer,

wherein electrical conductivity of the conductive layer is higher than electrical conductivity of the oxide semiconductor layer and electrical conductivity of the semiconductor layer, and

wherein the oxide semiconductor layer and the source and drain electrode layers are electrically connected to each other.

17. The semiconductor device according to claim 16, wherein the oxide semiconductor layer includes at least one of indium, gallium, and zinc.

18. The semiconductor device according to claim 16,

wherein the semiconductor layer is an oxide semiconductor layer including at least one of indium, gallium, and zinc, and

wherein the oxide semiconductor layer has a higher oxygen concentration than the semiconductor layer.

19. The semiconductor device according to claim 16,

wherein a carrier concentration of the oxide semiconductor layer is lower than 1×

10¹⁷/cm³.

20. The semiconductor device according to claim 16,

wherein the electrical conductivity of the semiconductor layer is higher than 1.0×

10<sup>−

3</sup> S/cm³.

21. The semiconductor device according to claim 16,

wherein a sodium concentration in the oxide semiconductor layer is equal to or lower than 5×

10¹⁹/cm³.

22. The semiconductor device according to claim 16,

wherein the semiconductor layer has a recessed portion provided over part of a region where the oxide semiconductor layer is in contact with the gate insulating layer, and

wherein the conductive layer is formed only over the recessed portion.

23. The semiconductor device according to claim 16, wherein the conductive layer is formed using a metal material such as indium, gallium, or zinc;

an alloy material containing any of the materials as a main component;

or an oxide or a nitride containing any of the metal materials.

24. The semiconductor device according to claim 16, wherein the conductive layer is configured to shield the oxide semiconductor layer from light.

25. The semiconductor device according to claim 16, wherein the semiconductor device is one selected from the group consisting of a poster, an advertisement, an electronic book, a television set, a digital photo frame, a game machine and a phone.

26. A method for manufacturing a semiconductor device comprising the steps of:

forming a gate electrode layer over a substrate;

forming a gate insulating layer over the gate electrode layer;

forming a conductive film over the gate insulating layer;

etching the conductive film to form a source and drain electrode layers;

forming a first oxide semiconductor film over the gate insulating layer and the source and drain electrode layers by a sputtering method;

forming a second oxide semiconductor film over the first oxide semiconductor film by a sputtering method; and

etching the first oxide semiconductor film and the second oxide semiconductor film to form an oxide semiconductor layer and a semiconductor layer,

wherein the oxide semiconductor layer is provided to be in contact with the gate insulating layer and side face portions of the source and drain electrode layers,

wherein the semiconductor layer is provided over the oxide semiconductor layer, and

wherein a proportion of a flow rate of an oxygen gas to the whole film-formation gas for forming the second oxide semiconductor film is made lower than a proportion of a flow rate of an oxygen gas to the whole film-formation gas for forming the first oxide semiconductor film.

27. The method for manufacturing a semiconductor device according to claim 26, wherein the proportion of the flow rate of the oxygen gas for forming the first oxide semiconductor film is 10 vol. % or higher, and the proportion of the flow rate of the oxygen gas for forming the second oxide semiconductor film is lower than 10 vol. %.

28. The method for manufacturing a semiconductor device according to claim 26,

wherein the first oxide semiconductor film is formed in an atmosphere of an argon gas and an oxygen gas, and

wherein the second oxide semiconductor film is formed in an atmosphere of an argon gas.

29. The method for manufacturing a semiconductor device according to claim 26, wherein each of the first oxide semiconductor film and the second oxide semiconductor film includes at least one of indium, gallium, and zinc.

30. The method for manufacturing a semiconductor device according to claim 26, further comprising the steps of forming a conductive layer over the semiconductor layer,

wherein the conductive layer is formed using a metal material such as indium, gallium, or zinc;

an alloy material containing any of the materials as a main component;

or an oxide or a nitride containing any of the metal materials.