THIN FILM TRANSISTOR, METHOD OF PRODUCING THE SAME, ELETCTROOPTIC APPARATUS, AND SENSOR

• US 20100314618A1
• Filed: 06/10/2010
• Published: 12/16/2010
• Est. Priority Date: 06/11/2009
• Status: Active Grant

• Current Assignee: Samsung Display Company Limited (Samsung Electronics Co. Ltd.)
• Original Assignee: Fujifilm Corporation (Fujifilm Holdings Corporation)
• Inventors: Suzuki, Masayuki, Tanaka, Atsushi, Hama, Takeshi
• Granted Patent: US 8,299,461 B2
• Time in Patent Office: Days
• US Class Current: 257/43
• 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 21/02592 amorphous
• CPC Class Codes: H01L 21/02631 Physical deposition at reduced pressure, e.g. MBE, sputtering, evaporation
• 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

A thin film transistor includes: a substrate; and, on the substrate, an oxide semiconductor film which serves as an active layer and contains In, Ga, and Zn, a gate electrode, a gate insulating film, a source electrode, and a drain electrode, wherein, when a molar ratio of In, Ga, and Zn in the oxide semiconductor film is expressed as In:Ga:Zn=(2.0−x):x:y, wherein 0.0<x<2.0 and 0.0<y, the distribution of y in the thickness direction of the oxide semiconductor film is such that the oxide semiconductor film has a region at which a value of y is larger than that at a surface of the oxide semiconductor film at a side closer to the substrate and that at a surface of the oxide semiconductor film at a side farther from the substrate.

Claims

1. A thin film transistor comprising:

a substrate; and

, on the substrate,

an oxide semiconductor film which serves as an active layer and comprises In, Ga, and Zn, a gate electrode, a gate insulating film, a source electrode, and a drain electrode,

wherein, when a molar ratio of In, Ga, and Zn in the oxide semiconductor film is expressed as In;

Ga;

Zn=(2.0−

x);

x;

y, wherein 0.0<

x<

2.0 and 0.0<

y, the distribution of y in the thickness direction of the oxide semiconductor film is such that the oxide semiconductor film has a region in which a value of y is larger than that at a surface of the oxide semiconductor film at a side closer to the substrate and larger than that at a surface of the oxide semiconductor film at a side farther from the substrate.

2. The thin film transistor according to claim 1, wherein an absolute maximum value of y over an entire thickness of the oxide semiconductor film is 1.8 or more.

3. The thin film transistor according to claim 1, wherein an absolute maximum value of y over an entire thickness of the oxide semiconductor film is 5.0 or less.

4. The thin film transistor according to claim 1, wherein a thickness of a region in which the value of y is at least 90% of an absolute maximum value thereof over an entire thickness of the oxide semiconductor film is less than one-third of the entire thickness of the oxide semiconductor film.

5. The thin film transistor according to claim 1, wherein a center of a region in which the value of y is at least 90% of an absolute maximum value thereof over an entire thickness of the oxide semiconductor film is positioned at a side closer to the gate insulating film than the center of the oxide semiconductor layer in a thickness direction thereof.

6. The thin film transistor according to claim 1, wherein a region in which the value of y is at least 90% of an absolute maximum value thereof over an entire thickness of the oxide semiconductor film is included in a region ranging from 1 nm to 30 nm from a surface of the oxide semiconductor film at a side closer to the gate insulating film in a thickness direction of the oxide semiconductor film.

7. The thin film transistor according to claim 1, wherein at least a part of the oxide semiconductor film which includes a region in which the value of y is at least 90% of an absolute maximum value thereof over an entire thickness of the oxide semiconductor film is formed by a series of consecutive film-forming processes during which the semiconductor film is not exposed to the atmosphere.

8. The thin film transistor according to claim 1, wherein at least a part of the oxide semiconductor film which includes a region in which the value of y is at least 90% of an absolute maximum value thereof over an entire thickness of the oxide semiconductor film is amorphous.

9. The thin film transistor according to claim 1, wherein the oxide semiconductor film comprises:

a first region which includes the surface of the oxide semiconductor film at a side closer to the substrate and in which the value of y is from 0.8 to 1.2;

a second region which includes the surface of the oxide semiconductor film at a side farther from the substrate and in which the value of y is from 0.8 to 1.2; and

a third region which includes a region in which y takes an absolute maximum value over an entire thickness of the oxide semiconductor film and in which the value of y is 1.8 or more.

10. The thin film transistor according to claim 9, wherein at least one of a change in the value of y from the first region to the third region and a change in the value of y from the third region to the second region is continuous.

11. The thin film transistor according to claim 1, wherein the thin film transistor is a bottom-gate thin film transistor.

12. A method of producing the thin film transistor of claim 1, the method comprising:

forming at least a part of the oxide semiconductor film which includes a region in which the value of y is at least 90% of an absolute maximum value thereof over an entire thickness of the oxide semiconductor film by a series of consecutive film-forming processes during which the oxide semiconductor film is not exposed to the atmosphere.

13. An electrooptic apparatus comprising the thin film transistor of claim 1.

14. A sensor comprising the thin film transistor of claim 1.