Semiconductor device and method for manufacturing the same

• US 8,344,387 B2
• Filed: 11/24/2009
• Issued: 01/01/2013
• Est. Priority Date: 11/28/2008
• Status: Active Grant

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: Akimoto, Kengo, Sasaki, Toshinari, Kuwabara, Hideaki
• Primary Examiner(s): GREEN, TELLY D
• Application Number:
  US12/624,888
• Publication Number:
  US 20100133530A1
• Time in Patent Office: 1,134 Days
• Field of Search: 257/9, 257/66, 257/72, 257/E33.019, 257/E21.459, 257/E29.296, 438/104, 438/158
• US Class Current: 257/72
• CPC Class Codes: H01L 21/02554 Oxides
• 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 29/45 Ohmic electrodes
• CPC Class Codes: H01L 29/66742 Thin film unipolar transistors
• 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 29/786 Thin film transistors, i.e. transistors with a channel being at least partly a thin film transistors having only the source or the drain region on an insulator layer H01L29/0653; thin film FinFETs H01L29/785
• 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
• 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, in a thin film transistor in which an oxide semiconductor is used as an active layer, to prevent change in composition, film quality, an interface, or the like of an oxide semiconductor region serving as an active layer, and to stabilize electrical characteristics of the thin film transistor. In a thin film transistor in which a first oxide semiconductor region is used as an active layer, a second oxide semiconductor region having lower electrical conductivity than the first oxide semiconductor region is formed between the first oxide semiconductor region and a protective insulating layer for the thin film transistor, whereby the second oxide semiconductor region serves as a protective layer for the first oxide semiconductor region; thus, change in composition or deterioration in film quality of the first oxide semiconductor region can be prevented, and electrical characteristics of the thin film transistor can be stabilized.

Claims

1. A semiconductor device comprising:

a gate electrode over a substrate;

a gate insulating layer over the gate electrode;

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

a first oxide semiconductor region over the source electrode and the drain electrode; and

a second oxide semiconductor region over the first oxide semiconductor region,

wherein part of the first oxide semiconductor region is in contact with the gate insulating layer and side surface portions of the source electrode and the drain electrode,

wherein an electrical conductivity of the second oxide semiconductor region is lower than an electrical conductivity of the first oxide semiconductor region, and

wherein the first oxide semiconductor region is electrically connected with the source electrode and the drain electrode.

2. The semiconductor device according to claim 1, wherein each of the first oxide semiconductor region and the second oxide semiconductor region contains at least one of indium, gallium, zinc, and tin.

3. The semiconductor device according to claim 1, wherein the first oxide semiconductor region and the second oxide semiconductor region are formed as different oxide semiconductor layers.

4. The semiconductor device according to claim 1, wherein the first oxide semiconductor region and the second oxide semiconductor region are formed in a same oxide semiconductor layer.

5. The semiconductor device according to claim 1, further comprising an oxide film interposed between the part of the first oxide semiconductor region and the side surface portions of the source electrode and the drain electrode.

6. The semiconductor device according to claim 5, wherein the oxide film is formed by a thermal oxidation, an oxygen plasma treatment, or an ozone water treatment.

7. The semiconductor device according to claim 1, further comprising a sidewall insulating layer interposed between the part of the first oxide semiconductor region and the side surface portions of the source electrode and the drain electrode.

8. The semiconductor device according to claim 7, wherein the sidewall insulating layer is formed by using a silicon film, a silicon oxide film, a silicon nitride oxide film, or a silicon oxynitride film.

9. The semiconductor device according to claim 1, wherein the electrical conductivity of the second oxide semiconductor region is 1.0×

10<sup>−

8</sup> S/cm or lower.

10. The semiconductor device according to claim 1, wherein a density of oxygen-hole defects of the second oxide semiconductor region is lower than a density of oxygen-hole defects of the first oxide semiconductor region.

11. 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.

12. A semiconductor device comprising:

a gate electrode over a substrate;

a gate insulating layer over the gate electrode;

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

a first oxide semiconductor layer over the source electrode and the drain electrode; and

an insulating layer interposed between part of the first oxide semiconductor layer and side surface portions of the source electrode and the drain electrode;

a second oxide semiconductor layer over the first oxide semiconductor layer,

wherein the first oxide semiconductor layer is electrically connected with the source electrode and the drain electrode.

13. The semiconductor device according to claim 12, 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.

14. The semiconductor device according to claim 12, wherein each of the first oxide semiconductor layer and the second oxide semiconductor layer contains at least one of indium, gallium, zinc, and tin.

15. The semiconductor device according to claim 12, wherein an electrical conductivity of the second oxide semiconductor layer is 1.0×

10<sup>−

8</sup> S/cm or lower.

16. The semiconductor device according to claim 12, wherein a density of oxygen-hole defects of the second oxide semiconductor layer is lower than a density of oxygen-hole defects of the first oxide semiconductor layer.