US 5,668,019 A · Method of fabricating thin film transistor

Abstract

An Si thin film (2) for a channel is formed on an insulating substrate (1), and then a gate insulating film (3) made principally of SiO.sub.2 is formed thereon. On the gate insulating film (3) is formed a gate electrode (4) composed of a Si thin film doped with impurities. The gate electrode (4) is patterned by isotropic etching using a photoresist (11) as a mask, and the gate insulating film (3) is patterned by anisotropic etching using the photoresist (11) as a mask into a configuration wider than the gate electrode (4) to be removed from source/drain regions position. The Si thin film (2) is ion implanted with impurities to form source/drain regions of an offset structure. A thin film transistor having an offset or LDD structure and capable of reducing an off-state drain current is fabricated without the need for increased number of masks and for an accurate photolithography technique, such as in alignment accuracy between masks.

Claims13

Dependent claims

A method of fabricating a thin film transistor, comprising the steps of:

preparing an insulating substrate;
forming a first Si film serving as a channel layer on said insulating substrate;
forming a gate insulating film made principally of SiO.sub.2 on said first Si film;
forming a second Si film doped with an impurity on said gate insulating film;
patterning said second Si film by isotropic etching using a photoresist layer as a mask to form a gate electrode that is narrower than the photoresist layer;
patterning said gate insulating film by anisotropic etching using said photoresist layer as a mask into a configuration that is wider than said gate electrode to form a gate insulating film pattern;
and
ion implanting said first Si film with an impurity using said gate insulating film pattern as a mask to form source/drain regions of an offset structure.

5 more elements

A method of fabricating a thin film transistor, comprising the steps of:

preparing an insulating substrate;
forming a first Si film serving as a channel layer on said insulating substrate;
forming a gate insulating film made principally of SiO.sub.2 on said first Si film;
forming a second Si film doped with an impurity on said gate insulating film;
patterning said second Si film by isotropic etching using a photoresist layer as a mask to form a gate electrode that is narrower than the photoresist layer;
patterning said gate insulating film by anisotropic etching using said photoresist layer as a mask into a configuration that is wider than said gate electrode to form a gate insulating film pattern;
ion implanting said first Si film with first impurities of a conductivity type to a first concentration with an accelerating voltage that is low enough so that said first impurities do not pass through said gate insulting film pattern;
and
ion implanting said first Si film with second impurities of said conductivity type to a second concentration that is less than said first concentration with an accelerating voltage that is high enough so that said second impurities pass through said gate insulating film pattern to form source/drain regions of an LDD structure.

6 more elements

A method of fabricating a thin film transistor, comprising the steps of:

preparing an insulating substrate;
forming a first Si film serving as a channel layer on said insulating substrate;
forming a gate insulating film made principally of SiO.sub.2 on said first Si film;
forming a second Si film doped with an impurity on said gate insulating film;
patterning said second Si film by isotropic etching using a photoresist layer as a mask to form a gate electrode that is narrower than the photoresist layer;
patterning said gate insulating film by anisotropic etching using said photoresist layer as a mask into a configuration that is wider than said gate electrode to form a gate insulating film pattern;
and
ion implanting said first Si film with first impurities of a conductivity type at a high concentration using said gate insulating film pattern as a mask;
etching off said gate insulating film pattern on both ends of said gate electrode;
and
ion implanting said first Si film with second impurities of said conductivity type at a low concentration using said gate electrode and said gate insulating film pattern as a mask to form source/drain regions of an LDD structure.

8 more elements

A method of fabricating a thin film transistor, comprising the steps of:

preparing an insulating substrate;
forming a first Si film serving as a channel layer on said insulating substrate;
forming a gate insulating film made principally of SiO.sub.2 on said first Si film;
forming a second Si film doped with an impurity on said gate insulating film;
patterning said second Si film by isotropic etching using a photoresist layer as a mask to form a gate electrode narrower than said photoresist layer;
ion implanting said first Si film with first impurities of a conductivity type at a high concentration through said gate insulating film using said photoresist layer as a mask;
removing said photoresist layer;
patterning said gate insulating film using said gate electrode as a mask;
and
ion implanting said first Si film with second impurities of said conductivity type at a low concentration using said gate electrode and said gate insulating film as a mask to form source/drain regions of an LDD structure.

7 more elements

Dependencies are inferred from the claim text.

Method of fabricating thin film transistor

Life of this patent

Method of fabricating thin film transistor

Life of this patent

Abstract

Claims13