EP0334052A2
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EP
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Thin film transistor
Assignee: International Business Machines Corp
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Filing: 1989-02-25
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Granted: —
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Expires: 2009-02-25
Abstract
Abstract Thin film field effect transistors are disclosed having direct or near direct contact of the source and drain electrodes to the channel region. Inverted gate (Fig. 3d) and non-inverted gate (Fig. 4e) types are fabricated by forming metallic source and drain electrodes (54′, 56′; 78, 80) within a layer of semiconductor material (46; 68) in contact with the channel region. The electrodes are formed by converting monocrystalline, polycrystalline or amorphous silicon regions to a refractory metal such as tungsten by using a non-self-limiting metal hexafluoride reduction process. The tungsten conversion process is isotropic and provides self-alignment of the source and drain electrodes with the gate in the non-inverted gate TFT. The process is low temperature, allowing the use of amorphous silicon as the semiconductor material. The transistors are especially useful for formation on large glass substrates for fabricating large flat panel displays.
Inventors
- 👤 John Batey
- 👤 Raily V. Joshi
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-03 14:08
CPC Classifications
H; H10; H10D; H10D30/00; H10D30/01; H10D30/021; H10D30/031; H10D30/0312; H10D30/0314; H10D30/0316; H10D30/0321; H10D30/60; H10D30/67; H10D30/6729; H10D30/6737; H10D30/674; H10D30/6741; H10D30/6743; H10D30/6744; H10D30/6746
Claims Analysis
Total Claims: 23
Claim 1
Independent Claim
84 words
A thin film, inverted gate, field effect transistor comprising: a gate electrode layer disposed on a substrate; a first insulator layer disposed on said substrate and said gate electrode; a semiconductor layer disposed on said insulator layer; source and drain electrodes formed within said semiconductor layer of a refractory metal, said source and drain electrodes being spaced apart in the region above said gate electrode; a second insulator layer disposed on said semiconductor layer extending across the region between said source and drain electrodes.
Claim 2
Dependent Claim
84 words
A thin film, inverted gate, field effect transistor comprising: a gate electrode layer disposed on a substrate; a first insulator layer disposed on said substrate and said gate electrode; a semiconductor layer disposed on said insulator layer; source and drain electrodes formed within said semiconductor layer of a refractory metal, said source and drain electrodes being spaced apart in the region above said gate electrode; a second insulator layer disposed on said semiconductor layer extending across the region between said source and drain electrodes.
Claim 3
Dependent Claim
66 words
A thin film field effect transistor comprising: a semiconductor layer disposed on a substrate; a gate insulator layer disposed on said semiconductor layer; a gate electrode layer disposed on said gate insulator layer; and source and drain electrodes formed within said semiconductor layer of a refractory metal, said source and drain electrodes being spaced apart in a portion of the region below said gate insulator layer.
Claim 4
Dependent Claim
66 words
A thin film field effect transistor comprising: a semiconductor layer disposed on a substrate; a gate insulator layer disposed on said semiconductor layer; a gate electrode layer disposed on said gate insulator layer; and source and drain electrodes formed within said semiconductor layer of a refractory metal, said source and drain electrodes being spaced apart in a portion of the region below said gate insulator layer.
Claim 5
Dependent Claim
26 words
The thin film transistor of claim 1 or 2 wherein the semiconductor layer is one of a monocrystalline state, a polycrystalline state or an amorphous state.
Claim 6
Dependent Claim
18 words
The thin film transistor of anyone of the claims 1 to 3 wherein the refractory metal is tungsten.
Claim 7
Dependent Claim
17 words
The thin film transistor of anyone of the claims 1 to 4 wherein the substrate is glass.
Claim 8
Dependent Claim
30 words
The thin film transistor of claim 1 or anyone of the claims 3 to 5 wherein the source and drain electrodes formed within the semiconductor layer contact the insulator layer.
Claim 9
Dependent Claim
40 words
The thin film transistor of claim 1 or anyone of the claims 3 to 5 wherein the source and drain electrodes formed within the semiconductor layer are spaced from said insulator region by a thin layer of said semiconductor layer.
Claim 10
Dependent Claim
37 words
The thin film transistor of claim 1 or anyone of the claims 3 to 7 wherein the spacing between the source and drain electrodes and the insulator layer is in the range between 10 to 50 nm.
Claim 11
Independent Claim
87 words
A method of fabricating a self-aligned thin film field effect transistor comprising the steps of: providing a substrate having a layer of semiconductor material disposed thereon; forming a multilayer gate region on said semiconductor layer thereby defining source and drain regions of said semiconductor layer on either side of said gate region; selectively converting the source and drain regions of said semiconductor material to a refractory metal to form self-aligned source and drain electrodes spaced apart in a portion of the semiconductor material below said gate regions.
Claim 12
Independent Claim
87 words
A method of fabricating a self-aligned thin film field effect transistor comprising the steps of: providing a substrate having a layer of semiconductor material disposed thereon; forming a multilayer gate region on said semiconductor layer thereby defining source and drain regions of said semiconductor layer on either side of said gate region; selectively converting the source and drain regions of said semiconductor material to a refractory metal to form self-aligned source and drain electrodes spaced apart in a portion of the semiconductor material below said gate regions.
Claim 13
Dependent Claim
60 words
The method of claim 9 wherein the multilayer gate region is formed with a first layer of insulator material disposed on said semiconductor layer and a second layer of semiconductor material disposed on said insulator layer, and wherein said second layer of semiconductor material is converted to said refractory metal simultaneously with the conversion of said source and drain regions.
Claim 14
Dependent Claim
58 words
The method of claim 9 or 10 wherein the multilayer gate region is formed with a first layer of insulator material disposed on said semiconductor layer and a second layer of metal disposed on said first layer thereby forming a metal gate, and wherein said metal gate acts as a mask for defining the source and drain regions.
Claim 15
Independent Claim
120 words
A method of fabricating a thin film inverted gate field effect transistor comprising the steps of: providing a substrate having a gate electrode layer disposed thereon and a first insulator layer disposed on said electrode layer and said substrate; depositing a layer of semiconductor material on said insulator layer; depositing a second layer of insulating material on said semiconductor layer and etching source and drain vias in said second insulating layer to expose source and drain regions of said semiconductor layer; selectively converting the semiconductor layer exposed by said vias to a refractory metal to thereby form source and drain electrodes within said semiconductor layer, said source and drain electrodes being spaced apart in the region above said gate electrode.
Claim 16
Independent Claim
120 words
A method of fabricating a thin film inverted gate field effect transistor comprising the steps of: providing a substrate having a gate electrode layer disposed thereon and a first insulator layer disposed on said electrode layer and said substrate; depositing a layer of semiconductor material on said insulator layer; depositing a second layer of insulating material on said semiconductor layer and etching source and drain vias in said second insulating layer to expose source and drain regions of said semiconductor layer; selectively converting the semiconductor layer exposed by said vias to a refractory metal to thereby form source and drain electrodes within said semiconductor layer, said source and drain electrodes being spaced apart in the region above said gate electrode.
Claim 17
Dependent Claim
151 words
A method of claim 12 comprising the steps of: providing a substrate having a gate electrode layer disposed thereon and a first insulator layer disposed on said electrode layer and said substrate; depositing a layer of semiconductor material on said insulator layer; depositing a second layer of insulating material on said semiconductor layer and etching a via in said second insulating layer to expose a region of said semiconductor layer; selectively converting the region of said semiconductor layer exposed by said via to a refractory metal to a depth less than the total thickness thereof; etching the refractory metal to expose a thin layer of semiconductor material and depositing a third layer of insulating material above the gate electrode to define source and drain regions on either side of said third layer; and selectively converting the source and drain regions to a refractory metal to form metallic source and drain electrodes.
Claim 18
Independent Claim
31 words
The method of anyone of the claims 9 to 13 wherein the semiconductor layer is converted to a refractory metal by exposing the semiconductor layer to a refractory metal hexafluoride gas.
Claim 19
Dependent Claim
22 words
The method of claim 14 wherein the metal hexafluoride gas is WF₆ and the source and drain electrodes are converted to W.
Claim 20
Dependent Claim
62 words
The method of claim 14 or 15 wherein the layer of semiconductor material has a thickness greater than the thickness at which the reaction between said semiconductor and said refractory metal hexafluoride is self-limiting and wherein the semiconductor layer is exposed to the metal hexafluoride gas under conditions of flow rate, pressure and temperature sufficient to render said reaction no longer self-limiting.
Claim 21
Independent Claim
36 words
The method of anyone of the claims 12 to 16 wherein the entire thickness of the semiconductor layer is converted to said refractory metal so that said source and drain electrodes contact said first insulating layer.
Claim 22
Dependent Claim
28 words
The method of claim 17 wherein the source and drain electrodes contact channel region within the insulating layer sufficiently to reduce a series resistance therein to near zero.
Claim 23
Independent Claim
40 words
The method of anyone of the claims 12 to 16 wherein less than the entire thickness of the semiconductor layer is converted to said refractory metal so that said source and drain electrodes are spaced from said first insulating layer.
References Cited (Backward Citations)
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