Thin-film transistor elements and methods of making same

• US 6,566,174 B1
• Filed: 09/06/2000
• Issued: 05/20/2003
• Est. Priority Date: 04/23/1997
• Status: Expired due to Term

• Current Assignee: Gold Charm Limited (Hon Hai Precision Industry Co., Ltd.)
• Original Assignee: NEC Corporation
• Inventors: Takechi, Kazushige, Hirano, Naoto
• Primary Examiner(s): Everhart, Caridad
• Application Number:
  US09/656,370
• Time in Patent Office: 986 Days
• Field of Search: 438/149, 438/161, 438/165, 438/166
• US Class Current: 438/149
• CPC Class Codes: H01L 29/66765 Lateral single gate single channel transistors with inverted structure, i.e. the channel layer is formed after the gate

Abstract

This invention provides an inverted staggered type thin-film transistor element wherein the n-doped amorphous silicon film (14) present in the region where the amorphous silicon film (13) does not overlap with the source-drain electrodes (15) is modified into an insulating film (17) by exposure to a plasma containing ions or radicals of oxygen and/or nitrogen, so that the undesired n-doped amorphous silicon film above a channel region need not be removed and the amorphous silicon film can be made thinner. Moreover, the aperture ratio of a liquid crystal display can be enhanced by utilizing such elements.

Claims

1. A method of making a thin-film transistor element which comprises at least the steps of:

(a) successively forming a gate electrode, a gate insulating film, an amorphous silicon film and an n-doped amorphous silicon film on a transparent insulating substrate;

(b) depositing a metal for use as source-drain electrodes on said n-doped amorphous silicon film and patterning the metal to form source-drain electrodes;

(c) exposing the substrate having said source-drain electrodes formed thereon to a plasma containing ions or radicals of oxygen and/or nitrogen, and thereby modifying said n-doped amorphous silicon film present in the regions where said amorphous silicon film does not overlap with said source-drain electrodes into an insulating film; and

(d) patterning said amorphous silicon film into a desired island-like shape.

2. A method of making a thin-film transistor element which comprises at least the steps of:

(a) successively forming a gate electrode, a gate insulating film, an amorphous silicon film and an n-doped amorphous silicon film on a transparent insulating substrate;

(b) depositing a metal for use as source-drain electrodes on said n-doped amorphous silicon film and patterning the metal to form source-drain electrodes;

(c) exposing the substrate having said source-drain electrodes formed thereon to a plasma containing ions or radicals of oxygen and/or nitrogen, and thereby modifying said n-doped amorphous silicon film present in the regions where said amorphous silicon film does not overlap with said source-drain electrodes into an insulating film;

(d) removing the resulting insulating film by exposure to a solution containing hydrofluoric acid; and

(e) patterning said amorphous silicon film into a desired island-like shape.

3. A method of making a thin-film transistor element which comprises at least the steps of:

(a) successively forming a gate electrode, a gate insulating film, an amorphous silicon film and an n-doped amorphous silicon film on a transparent insulating substrate;

(b) patterning said amorphous silicon film and said n-doped amorphous silicon film into a desired island-like shape;

(c) depositing a metal for use as source-drain electrodes on the resulting island-like amorphous silicon film and n-doped amorphous silicon film and patterning the metal to form source-drain electrodes; and

(d) exposing the substrate having said source-drain electrodes formed thereon to a plasma containing ions or radicals of oxygen and/or nitrogen, and thereby modifying said n-doped amorphous silicon film present in the region where said amorphous silicon film does not overlap with said source-drain electrodes into an insulating film.

4. A method as claimed in claim 3 which, subsequent to step (d), includes the additional step (e) of removing the resulting insulating film by exposure to a solution containing hydrofluoric acid.

5. A method of making a thin-film transistor element which comprises at least the steps of:

(a) successively forming a gate electrode, a gate insulating film, an amorphous silicon film and an n-doped amorphous silicon film on a transparent insulating substrate;

(b) depositing a metal for use as source-drain electrodes on said n-doped amorphous silicon film and patterning the metal to form source-drain electrodes;

(c) etching, in the direction of the depth, a part of said n-doped amorphous silicon film present in the regions where said n-doped amorphous silicon film does not overlap with the source-drain electrodes;

(d) exposing the n-doped amorphous silicon film remaining after the etching step to a plasma containing ions or radicals of oxygen and/or nitrogen, and thereby modifying the remaining n-doped amorphous silicon film into an insulating film; and

(e) patterning said amorphous silicon film into a desired island-like shape.

6. A method of making a thin-film transistor element which comprises at least the steps of:

(a) successively forming a gate electrode, a gate insulating film, an amorphous silicon film and an n-doped amorphous silicon film on a transparent insulating substrate;

(b) depositing a metal for use as source-drain electrodes on said n-doped amorphous silicon film and patterning the metal to form source-drain electrodes;

(c) etching, in the direction of the depth, a part of said n-doped amorphous silicon film present in the regions where said n-doped amorphous silicon film does not overlap with the source-drain electrodes;

(d) exposing the n-doped amorphous silicon film remaining after the etching step to a plasma containing ions or radicals of oxygen and/or nitrogen, and thereby modifying the remaining n-doped amorphous silicon film into an insulating film;

(e) removing the resulting insulating film by exposure to a solution containing hydrofluoric acid; and

(f) patterning said amorphous silicon film into a desired island-like shape.

7. A method of making a thin-film transistor element which comprises at least the steps of:

(a) successively forming a gate electrode, a gate insulating film, an amorphous silicon film and an n-doped amorphous silicon film on a transparent insulating substrate;

(b) patterning said amorphous silicon film and said n-doped amorphous silicon film into a desired island-like shape;

(c) depositing a metal for use as source-drain electrodes on the resulting island-like amorphous silicon film and ndoped amorphous silicon film and patterning the metal to form source-drain electrodes;

(d) etching, in the direction of the depth, a part of said n-doped amorphous silicon film present in the region where said n-doped amorphous silicon film does not overlap with the source-drain electrodes; and

(e) exposing the n-doped amorphous silicon film remaining after the etching step to a plasma containing ions or radicals of oxygen and/or nitrogen, and thereby modifying the remaining n-doped amorphous silicon film into an insulating film.

8. A method as claimed in claim 7 which, subsequent to step (e), includes the additional step of (f) removing the resulting insulating film by exposure to a solution containing hydrofluoric acid.