Metal-Oxide Based Thin-Film Transistors with Fluorinated Active Layer

• US 20130037798A1
• Filed: 08/10/2012
• Published: 02/14/2013
• Est. Priority Date: 08/11/2011
• Status: Active Grant

• Current Assignee: Hong Kong University of Science and Technology
• Original Assignee: Hong Kong University of Science and Technology
• Inventors: WONG, Man, KWOK, Hoi Sing, YE, Zhi
• Granted Patent: US 8,878,176 B2
• Time in Patent Office: Days
• US Class Current: 257/43
• 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

A thin-film transistor with a fluorinated channel and fluorinated source and drain regions and methods of fabrication are provided. The thin-film transistor includes: a substrate; a semiconductor active layer of fluorine-doped metal-oxide formed on the substrate; fluorine-doped source and drain regions disposed adjacent to the semiconductor active layer; a gate electrode disposed over the semiconductor active layer, configured to induce a continuous conduction channel between the source and drain regions; and a gate dielectric material separating the gate electrode and the channel.

Claims

1. A thin-film transistor comprising:

a substrate;

a semiconductor active layer of fluorine-doped metal-oxide formed on the substrate;

fluorine-doped source and drain regions disposed adjacent to the semiconductor active layer;

a gate electrode disposed over the semiconductor active layer, configured to induce a continuous conduction channel between the source and drain regions; and

a gate dielectric material separating the gate electrode and the channel.

2. The thin-film transistor of claim 1, where the volume concentration of fluorine in the channel of the semiconductor active layer is between approximately 10¹⁹ and 4×

10²⁰/cm³.

3. The thin-film transistor of claim 1, where the volume concentration of fluorine in the source and drain regions is greater than or equal to approximately 5×

10²⁰/cm³.

4. The thin-film transistor of claim 1, wherein the material of the source and drain regions is the same metal-oxide semiconductor as the channel.

5. The thin-film transistor of claim 1, wherein the material of the source and drain regions is a metal-oxide semiconductor different from the metal-oxide semiconductor of the channel.

6. The thin-film transistor of claim 1, wherein the thin-film transistor has at least one of the following configurations:

horizontal, vertical, coplanar electrodes, staggered electrodes;

top-gated, bottom-gated, or double-gated.

7. The thin-film transistor of claim 1, wherein the semiconductor active layer is at least one of an oxide of zinc, an oxide of tin, an oxide of copper, an oxide of indium, or an oxide of an alloy comprising at least two or more elements from the group consisting of:

zinc, tin, indium, gallium, aluminum, titanium, silver, and copper.

8. The thin-film transistor of claim 1, wherein the semiconductor active layer is in the amorphous, polycrystalline, or single-crystalline state.

9. The thin-film transistor of claim 1, wherein the thickness of the semiconductor active layer is between approximately 20 nm and 2000 nm.

10. The thin-film transistor of claim 1, wherein the substrate comprises glass, polymer, insulated stainless steel, amorphous silicon, polycrystalline silicon, or single-crystalline silicon containing pre-fabricated conventional integrated circuits.

11. The thin-film transistor of claim 1, wherein the substrate is covered with an electrically insulating layer.

12. The thin-film transistor of claim 1, wherein the gate electrode is made of metal, transparent-conducting oxide, or layer combinations thereof.

13. A method of producing a thin-film transistor, comprising:

forming a metal-oxide semiconductor active island on a substrate;

forming a gate dielectric layer on top of the active island and the substrate;

introducing fluorine into the semiconductor active island through the gate dielectric layer;

forming a gate electrode of the transistor;

introducing impurities including fluorine into source and drain regions and activating the impurities;

forming a second insulating layer;

opening access holes through the gate dielectric layer and the second insulating layer to expose a gate and the source and drain regions of the transistor;

forming a metal layer on top of the second insulating layer; and

patterning the metal layer to form interconnects.

14. The method of claim 13, wherein the step of introducing fluorine uses at least one of ion implantation, ion shower, plasma immersion, sputtering from a metal-oxide pre-mixed with fluorine, evaporation of a metal-oxide charge pre-mixed with fluorine, or chemical synthesis from a metal-oxide precursor pre-mixed with fluorine.

15. The method of claim 13, wherein the temperature of activation of the impurities is between approximately 250°

C. and 550°

C.

16. A method of producing the thin-film transistor, comprising:

forming a semiconductor active island on a substrate;

introducing fluorine into the semiconductor active island;

forming a gate dielectric material on top of active island and the substrate;

forming a gate electrode of the transistor;

introducing impurities including fluorine into the source and drain regions of the transistor and activating the impurities;

forming a second insulating layer;

opening access holes through the gate dielectric material and the second insulating layer to expose a gate and the source and drain regions of the transistor;

forming a metal layer on top of the second insulating layer; and

patterning the metal layer to form interconnects.

17. The method of claim 16, wherein the step of introducing fluorine uses at least one of ion implantation, ion shower, plasma-immersion, sputtering from a metal-oxide pre-mixed with fluorine, evaporation of a metal-oxide charge pre-mixed with fluorine, or chemical synthesis from a metal-oxide precursor pre-mixed with fluorine.

18. The method of claim 16, wherein the temperature of activation of the impurities is between approximately 250°

C. and 550°

C.