Semiconductor device and manufacturing method thereof

• US 8,313,980 B2
• Filed: 03/12/2012
• Issued: 11/20/2012
• Est. Priority Date: 10/10/2008
• Status: Active Grant

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: Akimoto, Kengo
• Primary Examiner(s): Smith, Zandra
• Assistant Examiner(s): Anya, Igwe U
• Application Number:
  US13/417,445
• Publication Number:
  US 20120171813A1
• Time in Patent Office: 253 Days
• Field of Search: 438/104, 257/E21.43
• US Class Current: 438/104
• 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 29/45 Ohmic electrodes
• 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 29/7869 having a semiconductor body comprising an oxide semiconductor material, e.g. zinc oxide, copper aluminium oxide, cadmium stannate

Abstract

Electric characteristics and reliability of a thin film transistor are impaired by diffusion of an impurity element into a channel region. The present invention provides a thin film transistor in which aluminum atoms are unlikely to be diffused to an oxide semiconductor layer. A thin film transistor including an oxide semiconductor layer including indium, gallium, and zinc includes source or drain electrode layers in which first conductive layers including aluminum as a main component and second conductive layers including a high-melting-point metal material are stacked. An oxide semiconductor layer 113 is in contact with the second conductive layers and barrier layers including aluminum oxide as a main component, whereby diffusion of aluminum atoms to the oxide semiconductor layer is suppressed.

Claims

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

forming a source electrode layer and a drain electrode layer, each comprising a first conductive layer and a second conductive layer over the first conductive layer;

oxidizing an edge portion of the first conductive layer;

forming an oxide semiconductor layer to be in contact with the edge portion; and

performing a plasma treatment on the oxide semiconductor layer in an atmosphere containing N₂O.

2. The method for manufacturing a semiconductor device according to claim 1, further comprising steps of forming a gate electrode and a gate insulating film before forming the source electrode layer and the drain electrode layer.

3. The method for manufacturing a semiconductor device according to claim 1, wherein the oxide semiconductor layer includes indium, gallium, and zinc.

4. The method for manufacturing a semiconductor device according to claim 1, wherein the first conductive layer includes aluminum.

5. The method for manufacturing a semiconductor device according to claim 1, wherein the second conductive layer includes at least one selected from the group consisting of titanium, tantalum, tungsten, molybdenum, chromium, neodymium, and scandium.

6. The method for manufacturing a semiconductor device according to claim 1, wherein the oxidizing step is one of an oxygen plasma treatment, an ozone treatment using ultraviolet light, and a treatment using hydrogen peroxide.

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

forming a source electrode layer and a drain electrode layer, each comprising a first conductive layer and a second conductive layer over the first conductive layer;

oxidizing an edge portion of the first conductive layer;

forming an oxide semiconductor layer to be in contact with the edge portion;

performing a plasma treatment on the oxide semiconductor layer in an atmosphere containing N₂O; and

forming a protective insulating film over the oxide semiconductor layer.

8. The method for manufacturing a semiconductor device according to claim 7, further comprising steps of forming a gate electrode and a gate insulating film before forming the source electrode layer and the drain electrode layer.

9. The method for manufacturing a semiconductor device according to claim 7, wherein the oxide semiconductor layer includes indium, gallium, and zinc.

10. The method for manufacturing a semiconductor device according to claim 7, wherein the first conductive layer includes aluminum.

11. The method for manufacturing a semiconductor device according to claim 7, wherein the second conductive layer includes at least one selected from the group consisting of titanium, tantalum, tungsten, molybdenum, chromium, neodymium, and scandium.

12. The method for manufacturing a semiconductor device according to claim 7, wherein the oxidizing step is one of an oxygen plasma treatment, an ozone treatment using ultraviolet light, and a treatment using hydrogen peroxide.

13. The method for manufacturing a semiconductor device according to claim 7, wherein the protective insulating film includes at least one of silicon nitride, silicon oxide, and silicon oxynitride.