Semiconductor device

• US 8,841,662 B2
• Filed: 11/02/2010
• Issued: 09/23/2014
• Est. Priority Date: 11/06/2009
• Status: Active Grant

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: Yamazaki, Shunpei, Hiraishi, Suzunosuke, Akimoto, Kengo, Sakata, Junichiro
• Primary Examiner(s): Mandala, Victor A
• Assistant Examiner(s): JOHNSON, CHRISTOPHER A
• Application Number:
  US12/917,548
• Publication Number:
  US 20110108833A1
• Time in Patent Office: 1,421 Days
• Field of Search: 257/43
• US Class Current: 257/43
• CPC Class Codes: H01L 21/02164 the material being a silicon oxide, e.g. SiO2
• CPC Class Codes: H01L 21/02178 the material containing aluminium, e.g. Al2O3
• CPC Class Codes: H01L 21/02565 Oxide semiconducting materials not being Group 12/16 materials, e.g. ternary compounds
• CPC Class Codes: H01L 21/02631 Physical deposition at reduced pressure, e.g. MBE, sputtering, evaporation
• 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 29/66969 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 29/7869 having a semiconductor body comprising an oxide semiconductor material, e.g. zinc oxide, copper aluminium oxide, cadmium stannate

Abstract

An object is, in a thin film transistor including an oxide semiconductor layer, to reduce contact resistance between the oxide semiconductor layer and source and drain electrode layers electrically connected to the oxide semiconductor layer. The source and drain electrode layers have a stacked-layer structure of two or more layers in which a layer in contact with the oxide semiconductor layer is formed using a metal whose work function is lower than the work function of the oxide semiconductor layer or an alloy containing such a metal. Layers other than the layer in contact with the oxide semiconductor layer of the source and drain electrode layers are formed using an element selected from Al, Cr, Cu, Ta, Ti, Mo, or W, an alloy containing any of these elements as a component, an alloy containing any of these elements in combination, or the like.

Claims

1. A semiconductor device comprising:

an oxide semiconductor layer;

a source electrode layer comprising a first mixed layer, the first mixed layer being in contact with the oxide semiconductor layer; and

a drain electrode layer comprising a second mixed layer, the second mixed layer being in contact with the oxide semiconductor layer,

wherein each of the first mixed layer and the second mixed layer comprises a first metal having a lower work function than the oxide semiconductor layer or an alloy comprising the first metal,

wherein each of the first mixed layer and the second mixed layer comprises a first region and a second region,

wherein the first region is closer to the oxide semiconductor layer than the second region,

wherein each of the first region and the second region comprises the first metal, and

wherein the first region has a larger concentration of the first metal or the alloy than the second region.

2. A semiconductor device according to claim 1, wherein each of the source electrode layer and the drain electrode layer has a stacked-layer structure.

3. The semiconductor device according to claim 1, wherein each of the first mixed layer and the second mixed layer is formed by an MOCVD method.

4. The semiconductor device according to claim 1, wherein the oxide semiconductor layer comprises at least any one of zinc, tin, and gallium.

5. The semiconductor device according to claim 1, wherein the oxide semiconductor layer comprises a depression.

6. A semiconductor device comprising:

an oxide semiconductor layer;

a source electrode layer comprising a first mixed layer, the first mixed layer being in contact with the oxide semiconductor layer; and

a drain electrode layer comprising a second mixed layer, the second mixed layer being in contact with the oxide semiconductor layer,

wherein each of the first mixed layer and the second mixed layer comprises a first metal having a lower work function than the oxide semiconductor layer, or an alloy comprising the first metal,

wherein each of the first mixed layer and the second mixed layer comprises a second metal having high heat resistance,

wherein each of the first mixed layer and the second mixed layer comprises a first region and a second region,

wherein the first region is closer to the oxide semiconductor layer than the second region,

wherein each of the first region and the second region comprises the first metal, and

wherein the first region has a larger concentration of the first metal or the alloy than the second region.

7. The semiconductor device according to claim 6, wherein each of the source electrode layer and the drain electrode layer has a stacked-layer structure.

8. The semiconductor device according to claim 6, wherein each of the first mixed layer and the second mixed layer is formed by an MOCVD method.

9. The semiconductor device according to claim 6, wherein the oxide semiconductor layer comprises at least any one of zinc, tin, and gallium.

10. The semiconductor device according to claim 6, wherein the oxide semiconductor layer comprises a depression.

11. A semiconductor device comprising:

an oxide semiconductor layer;

a source electrode layer comprising a first mixed layer, the first mixed layer being in contact with the oxide semiconductor layer; and

a drain electrode layer comprising a second mixed layer, the second mixed layer being in contact with the oxide semiconductor layer,

wherein each of the first mixed layer and the second mixed layer comprises a first metal having a work function lower than an electron affinity of the oxide semiconductor layer, or an alloy comprising the first metal,

wherein each of the first mixed layer and the second mixed layer comprises a first region and a second region,

wherein the first region is closer to the oxide semiconductor layer than the second region,

wherein each of the first region and the second region comprises the first metal, and

wherein the first region has a larger concentration of the first metal or the alloy than the second region.

12. A semiconductor device according to claim 11, wherein each of the source electrode layer and the drain electrode layer has a stacked-layer structure.

13. The semiconductor device according to claim 11, wherein each of the first mixed layer and the second mixed layer is formed by an MOCVD method.

14. The semiconductor device according to claim 11, wherein the oxide semiconductor layer comprises at least any one of zinc, tin, and gallium.

15. A semiconductor device comprising:

an oxide semiconductor layer;

a source electrode layer comprising a first mixed layer, the first mixed layer being in contact with the oxide semiconductor layer; and

a drain electrode layer comprising a second mixed layer, the second mixed layer being in contact with the oxide semiconductor layer,

wherein each of the first mixed layer and the second mixed layer comprises a first metal having a work function lower than an electron affinity of the oxide semiconductor layer, or an alloy comprising the first metal,

wherein each of the first mixed layer and the second mixed layer further comprises a second first metal having high heat resistance, and

wherein each of the first mixed layer and the second mixed layer comprises a first region and a second region,

wherein the first region is closer to the oxide semiconductor layer than the second region,

wherein each of the first region and the second region comprises the first metal, and

wherein the first region has a larger concentration of the first metal or the alloy than the second region.

16. The semiconductor device according to claim 15, wherein each of the source electrode layer and the drain electrode layer has a stacked-layer structure.

17. The semiconductor device according to claim 15, wherein each of the first mixed layer and the second mixed layer is formed by an MOCVD method.

18. The semiconductor device according to claim 15, wherein the oxide semiconductor layer comprises at least any one of zinc, tin, and gallium.