Thin film transistor

• US 7,741,643 B2
• Filed: 03/13/2008
• Issued: 06/22/2010
• Est. Priority Date: 03/28/2007
• Status: Expired due to Fees

• Current Assignee: Toppan Printing Co., Ltd. (TOPPAN Holdings, Inc.)
• Original Assignee: Toppan Printing Co., Ltd. (TOPPAN Holdings, Inc.)
• Inventors: Ito, Manabu, Miyazaki, Chihiro
• Primary Examiner(s): Andújar; Leonardo
• Assistant Examiner(s): HARRISTON, WILLIAM A
• Application Number:
  US12/075,873
• Publication Number:
  US 20080237600A1
• Time in Patent Office: 831 Days
• Field of Search: 257/213
• US Class Current: 257/66
• CPC Class Codes: H01L 29/4908 for thin film semiconductor, e.g. gate of TFT
• CPC Class Codes: H01L 29/78609 for preventing leakage current H01L29/78618 takes 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

One embodiment of the present invention is a thin film transistor, including: an insulating substrate; a gate electrode, a gate insulating layer and a semiconductor layer including an oxide, these three elements being formed over the insulating substrate in this order, and the gate insulating layer including: a lower gate insulating layer, the lower gate insulating layer being in contact with the insulating substrate and being an oxide including any one of the elements In, Zn or Ga; and an upper gate insulating layer provided on the lower gate insulating layer, the upper gate insulating layer comprising at least one layer; and a source electrode and a drain electrode formed on the semiconductor layer.

Claims

1. A thin film transistor, comprising:

an insulating substrate;

a gate electrode, a gate insulating layer and a semiconductor layer including an oxide formed over said insulating substrate,

said gate insulating layer further comprising;

a lower gate insulating layer in contact with said insulating substrate and including an oxide having any one of the elements In, Zn or Ga; and

an upper gate insulating layer provided on said lower gate insulating layer, said upper gate insulating layer having at least one layer; and

a source electrode and a drain electrode formed on said semiconductor layer.

3. The thin film transistor according to claim 1, wherein at least one layer of said upper gate insulating layer includes any one of the compounds of silicon oxide, silicon nitride, silicon oxy nitride, aluminium oxide, tantalum oxide, yttria, hafnium oxide, hafnium aluminates, zirconia oxide and titanium oxide.

5. The thin film transistor according to claim 1, wherein at least one layer of said upper gate insulating layer includes any one of the compounds of polyacrylate, polyvinyl alcohol, polystyrene, polyimide, polyester, epoxy, poly vinylphenol and polyvinyl alcohol.

7. The thin film transistor according to claim 1, wherein a film thickness of said lower gate insulating layer is 2 nm-200 nm.

9. The thin film transistor according to claim 1, wherein a resistivity of said lower gate insulating layer is equal to or more than 10¹⁰ Ω

·

cm.

11. The thin film transistor according to claim 1, wherein said insulating substrate is a flexible substrate.

2. A thin film transistor, comprising:

an insulating substrate;

a gate electrode and a gate insulating layer formed over said insulating substrate,

said gate insulating layer comprising;

a lower gate insulating layer in contact with said insulating substrate and including an oxide having any one of the elements In, Zn or Ga; and

an upper gate insulating layer provided on said lower gate insulating layer, said upper gate insulating layer having at least one layer;

a source electrode and a drain electrode formed on said gate insulating layer; and

a semiconductor layer including an oxide, said semiconductor layer being formed at least on said gate insulating layer between said source electrode and said drain electrode.

4. The thin film transistor according to claim 2, wherein at least one layer of said upper gate insulating layer includes any one of the compounds of silicon oxide, silicon nitride, silicon oxy nitride, aluminium oxide, tantalum oxide, yttria, hafnium oxide, hafnium aluminates, zirconia oxide and titanium oxide.

6. The thin film transistor according to claim 2, wherein at least one layer of said upper gate insulating layer includes any one of the compounds of polyacrylate, polyvinyl alcohol, polystyrene, polyimide, polyester, epoxy, poly vinylphenol and polyvinyl alcohol.

8. The thin film transistor according to claim 2, wherein a film thickness of said lower gate insulating layer is 2 nm-200 nm.

10. The thin film transistor according to claim 2, wherein a resistivity of said lower gate insulating layer is equal to or more than 10¹⁰Ω

·

cm.

12. The thin film transistor according to claim 2, wherein said insulating substrate is a flexible substrate.

13. A thin film transistor, comprising:

an insulating substrate;

a gate electrode, a gate insulating layer and a semiconductor layer including an oxide formed over said insulating substrate,

said gate insulating layer further comprising;

a lower gate insulating layer in contact with said insulating substrate and including an oxide having any one of the elements In, Zn or Ga; and

an upper gate insulating layer provided on said lower gate insulating layer, said upper gate insulating layer having at least one layer; and

a source electrode and a drain electrode formed on said semiconductor layer,

wherein at least one layer of said upper gate insulating layer includes any one of the compounds of silicon oxide, silicon nitride, silicon oxy nitride, aluminium oxide, tantalum oxide, yttria, hafnium oxide, hafnium aluminates, zirconia oxide and titanium oxide,

wherein at least one layer of said upper gate insulating layer includes any one of the compounds of polyacrylate, polyvinyl alcohol, polystyrene, polyimide, polyester, epoxy, poly vinylphenol and polyvinyl alcohol,

wherein a film thickness of said lower gate insulating layer is 2 nm-200 nm and said film thickness of said lower gate insulating layer is equal to or less than ⅔

of the total thickness of said gate insulating layer,

wherein a resistivity of said lower gate insulating layer is equal to or more than 10¹⁰ Ω

·

cm, and

wherein said insulating substrate is a flexible substrate.

14. A thin film transistor, comprising:

an insulating substrate;

a gate electrode and a gate insulating layer formed over said insulating substrate,

said gate insulating layer comprising;

a lower gate insulating layer in contact with said insulating substrate and including an oxide having any one of the elements In, Zn or Ga; and

an upper gate insulating layer provided on said lower gate insulating layer, said upper gate insulating layer having at least one layer;

a source electrode and a drain electrode formed on said gate insulating layer; and

a semiconductor layer including an oxide, said semiconductor layer being formed at least on said gate insulating layer between said source electrode and said drain electrode,

wherein at least one layer of said upper gate insulating layer includes any one of the compounds of silicon oxide, silicon nitride, silicon oxy nitride, aluminium oxide, tantalum oxide, yttria, hafnium oxide, hafnium aluminates, zirconia oxide and titanium oxide,

wherein at least one layer of said upper gate insulating layer includes any one of the compounds of polyacrylate, polyvinyl alcohol, polystyrene, polyimide, polyester, epoxy, poly vinylphenol and polyvinyl alcohol,

wherein a film thickness of said lower gate insulating layer is 2 nm-200 nm and said film thickness of said lower gate insulating layer is equal to or less than ⅔

of the total thickness of said gate insulating layer,

wherein a resistivity of said lower gate insulating layer is equal to or more than 10¹⁰ Ω

·

cm, and

wherein said insulating substrate is a flexible substrate.