THIN-FILM TRANSISTOR

• US 20140197408A1
• Filed: 08/08/2012
• Published: 07/17/2014
• Est. Priority Date: 08/11/2011
• Status: Active Grant

• Current Assignee: Idemitsu Kosan Company Limited
• Original Assignee: Idemitsu Kosan Company Limited
• Inventors: Tsuruma, Yuki, Ebata, Kazuaki, Tomai, Shigekazu, Matsuzaki, Shigeo
• Granted Patent: US 9,178,076 B2
• Time in Patent Office: Days
• US Class Current: 257/43
• CPC Class Codes: C23C 14/0057 using reactive gases other than O2, H2O, N2, NH3 or CH4
• CPC Class Codes: C23C 14/086 of zinc, germanium, cadmium, indium, tin, thallium or bismuth
• CPC Class Codes: C23C 14/34 Sputtering
• CPC Class Codes: C23C 14/3414 Metallurgical or chemical aspects of target preparation, e.g. casting, powder metallurgy
• CPC Class Codes: H01L 21/02381 Silicon, silicon germanium, germanium
• CPC Class Codes: H01L 21/02488 Insulating materials
• CPC Class Codes: H01L 21/02565 Oxide semiconducting materials not being Group 12/16 materials, e.g. ternary compounds
• CPC Class Codes: H01L 21/02581 Transition metal or rare earth elements
• CPC Class Codes: H01L 21/02631 Physical deposition at reduced pressure, e.g. MBE, sputtering, evaporation
• CPC Class Codes: H01L 21/02667 Crystallisation or recrystallisation of non-monocrystalline semiconductor materials, e.g. regrowth
• 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 29/78693 the semiconducting oxide being amorphous
• 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 (1) includes a source electrode (50), a drain electrode (60), a gate electrode (20), a gate insulating film (30), and a channel layer (40) that is formed of an oxide semiconductor, the channel layer (40) having an average carrier concentration of 1×10¹⁶/cm³ to 5×10¹⁹/cm³, and including a high carrier concentration region (42) that is situated on the side of the gate insulating film (30) and has a carrier concentration higher than the average carrier concentration, and the channel layer (40) having a substantially homogenous composition.

Claims

1. A thin film transistor comprising a source electrode, a drain electrode, a gate electrode, a gate insulating film, and a channel layer that is formed of an oxide semiconductor,

the channel layer having an average carrier concentration of 1×

10¹⁶/cm³ to 5×

10¹⁹/cm³, and comprising a high carrier concentration region that is situated on a side of the gate insulating film and has a carrier concentration higher than the average carrier concentration, and

the channel layer having a substantially homogeneous composition.

2. The thin film transistor according to claim 1,

wherein the channel layer has a thickness of 10 nm or more, and the high carrier concentration region has an average carrier concentration of 1×

10¹⁸/cm³ to 5×

10²¹/cm³.

3. The thin film transistor according to claim 1,

wherein the high carrier concentration region is a region of the channel layer up to a depth of 5 nm from an interface with the gate insulating film.

4. The thin film transistor according to claim 1,

wherein the oxide semiconductor has a crystalline structure.

5. The thin film transistor according to claim 1,

wherein the oxide semiconductor is indium oxide, Ga-doped indium oxide, Al-doped indium oxide, Ga—

Al-doped indium oxide, Zn-doped indium oxide, or Sn-doped indium oxide.

6. The thin film transistor according to claim 5,

wherein the Ga-doped indium oxide has an atomic ratio “

Ga/(Ga+In)”

of 0.007 to 0.207.

7. The thin film transistor according to claim 5, wherein the Al-doped indium oxide has an atomic ratio “

Al/(Al+In)”

of 0.003 to 0.125.

8. The thin film transistor according to claim 1, the thin film transistor having a bottom-gate structure.

9. The thin film transistor according to claim 8, further comprising a protective layer that is formed on the channel layer.

10. The thin film transistor according to claim 9,

wherein the protective layer is an insulating film having oxygen permeability.

11. The thin film transistor according to claim 1, the thin film transistor having a top-gate structure.