Fabrication method of display device

Abstract

Non-uniformity of the sheet resistance associated with ion implantation into a polysilicon semiconductor layer using a ribbon-shaped beam is minimized to prevent variations in the characteristics of fabricated thin film transistors. When the implanted ions are of a first element, a second element that is heavy and has no influence on electric charge is implanted at a critical implantation quantity or more into a dose region of the polysilicon semiconductor layer into which the ions of the first element are implanted.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A through 1K are schematic cross-sectional views illustrating a fabrication process of a thin film transistor substrate according to embodiment 1 of the invention.

FIG. 2 is a diagram for illustrating an actual process of ion implantation for a low-temperature polysilicon semiconductor layer deposited on a large-sized substrate according to embodiment 1 of the invention.

FIGS. 3A through 3D are graphs for illustrating distributions across a substrate of the beam current, of the current density, of the degree of amorphization of the low-temperature polysilicon semiconductor layer, and of the sheet resistance in the low-temperature polysilicon semiconductor layer, in the case of an ion implantation apparatus according to embodiment 1 of the invention.

FIG. 4A is a cross-sectional view of the thin film transistor according to the invention, and FIG. 4B is a top view thereof.

FIG. 5 is a table listing the critical implantation quantities of elements that are implanted in the semiconductor layer in the invention.

FIG. 6 is a diagram for illustrating a process of ion implantation for the low-temperature polysilicon semiconductor layer deposited on a large-sized substrate.

FIGS. 7A through 7D are graphs for illustrating distributions across a substrate of the beam current, of the current density, of the degree of amorphization of the low-temperature polysilicon semiconductor layer, and of the sheet resistance of the polysilicon semiconductor layer, in the case of a beam with an ideal shape.

FIG. 8 is a diagram for illustrating an actual process of ion implantation for a low-temperature polysilicon semiconductor layer deposited on a large-sized substrate.

FIGS. 9A through 9D are graphs for illustrating distributions across a substrate of the beam current, of the current density, of the degree of amorphization of the low-temperature polysilicon semiconductor layer, and of the sheet resistance in the low-temperature polysilicon semiconductor layer, in the case of an actual ion implantation apparatus.

Claims

1. A method of fabricating a display device in which thin film transistors are formed by implanting ions into a polysilicon semiconductor layer deposited on an insulating substrate, the method comprising: implanting, where the ions are of a first element, a second element at a critical implantation quantity or more into a dose region of the polysilicon semiconductor layer in which the ions of the first element is implanted, the second element being heavy and having no influence on electric charge.

2. The method of fabricating a display device according to claim 1, wherein the first element is boron, and the second element is an inert gas that is heavier than the first element.

3. The method of fabricating a display device according to claim 2, wherein the inert gas is one of argon, krypton, and xenon.

4. The method of fabricating a display device according to claim 1, wherein the step of implanting the second element is performed after implanting the first element.

5. The method of fabricating a display device according to claim 1, wherein the step of implanting the second element is performed before implanting the first element.