US6787370B2
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Method of forming a weak ferroelectric transistor
Assignee: Micron Technology Inc
•
Filing: 2002-12-16
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Granted: 2004-09-07
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Expires: 2022-12-16
Abstract
Abstract Field effect transistors having a ferroelectric layer overlying a gate insulator layer as well as methods of their formation and use, and devices produced therefrom. Such ferroelectric field effect transistors are suitable for use in memory devices as the polarization of the ferroelectric layer can represent distinct logic states. The polarization of the ferroelectric layer alters the threshold voltage of the field effect transistor thus producing distinctly different conductivity states through the weak ferroelectric transistor at a given gate potential depending upon the polarization. The ferroelectric layer may contain a weak ferroelectric material having spontaneous polarization values in the range of approximately 0.01 μCoulomb/cm 2 to 1 μCoulomb/cm 2 . The ferroelectric layer may contain a doped zinc oxide material doped with lithium and/or magnesium. Such weak ferroelectric materials permit effective transistor operation without the need for a programming conductor interposed between the ferroelectric layer and the gate insulator layer. This is possible because effective programming voltages can be applied across the ferroelectric layer and the gate insulator layer in series without exceeding the breakdown voltage of the gate insulator layer. Furthermore, having a gate insulator layer interposed between a substrate and the ferroelectric material eliminates the undesirable surface interfaces and surface states resulting from a silicon substrate-ferroelectric interface.
Inventors
- 👤 Leonard Forbes
- 👤 Kie Y. Ahn
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 00:58
CPC Classifications
H; H10; H10D; H10D64/00; H10D64/60; H10D64/66; H10D64/68; H10D64/689; H10D30/00; H10D30/60; H10D30/701; H10D64/01; H10D64/031; H10D64/033
Claims Analysis
Total Claims: 35
Claim 1
Independent Claim
135 words
A method of forming a field effect transistor, comprising: forming a gate insulator layer overlying a substrate; forming a ferroelectric layer overlying the gate insulator layer, wherein the ferroelectric layer comprising a weak ferroelectric material having a spontaneous polarization in the range of approximately 0.01 μCoulomb/cm 2 to approximately 1 μCoulomb/cm 2 and wherein the gate insulator layer and the ferroelectric layer each have a thickness and wherein the thickness of the ferroelectric layer is at least 10 times the thickness of the gate insulator layer; forming an upper conductor layer overlying the ferroelectric layer; patterning the gate insulator layer, the ferroelectric layer and the upper conductor layer to define a gate stack structure having sidewalls; forming spacers on the sidewalls of the gate stack structure; and forming source and drain regions in the substrate.
Claim 2
Independent Claim
135 words
A method of forming a field effect transistor, comprising: forming a gate insulator layer overlying a substrate; forming a ferroelectric layer overlying the gate insulator layer, wherein the ferroelectric layer comprising a weak ferroelectric material having a spontaneous polarization in the range of approximately 0.01 μCoulomb/cm 2 to approximately 1 μCoulomb/cm 2 and wherein the gate insulator layer and the ferroelectric layer each have a thickness and wherein the thickness of the ferroelectric layer is at least 10 times the thickness of the gate insulator layer; forming an upper conductor layer overlying the ferroelectric layer; patterning the gate insulator layer, the ferroelectric layer and the upper conductor layer to define a gate stack structure having sidewalls; forming spacers on the sidewalls of the gate stack structure; and forming source and drain regions in the substrate.
Claim 3
Dependent Claim
15 words
The method of claim 1 , wherein the method is performed in the order presented.
Claim 4
Independent Claim
148 words
A method of forming a field effect transistor, comprising: forming a gate insulator layer overlying a substrate; forming a ferroelectric layer overlying the gate insulator layer without a programming conductor interposed between the ferroelectric layer and the gate insulator layer, wherein the ferroelectric layer comprising a weak ferroelectric material having a spontaneous polarization in the range of approximately 0.01 μCoulomb/cm 2 approximately 1 μCoulomb/cm 2 and wherein the gate insulator layer and the ferroelectric layer each have a thickness and wherein the thickness of the ferroelectric layer is at least 10 times the thickness of the gate insulator layer; forming an upper conductor layer overlying the ferroelectric layer; patterning the gate insulator layer, the ferroelectric layer and the upper conductor layer to define a gate stack structure having sidewalls; forming spacers on the sidewalls of the gate stack structure; and forming source and drain regions in the substrate.
Claim 5
Independent Claim
148 words
A method of forming a field effect transistor, comprising: forming a gate insulator layer overlying a substrate; forming a ferroelectric layer overlying the gate insulator layer without a programming conductor interposed between the ferroelectric layer and the gate insulator layer, wherein the ferroelectric layer comprising a weak ferroelectric material having a spontaneous polarization in the range of approximately 0.01 μCoulomb/cm 2 approximately 1 μCoulomb/cm 2 and wherein the gate insulator layer and the ferroelectric layer each have a thickness and wherein the thickness of the ferroelectric layer is at least 10 times the thickness of the gate insulator layer; forming an upper conductor layer overlying the ferroelectric layer; patterning the gate insulator layer, the ferroelectric layer and the upper conductor layer to define a gate stack structure having sidewalls; forming spacers on the sidewalls of the gate stack structure; and forming source and drain regions in the substrate.
Claim 6
Dependent Claim
15 words
The method of claim 3 , wherein the method is performed in the order presented.
Claim 7
Independent Claim
87 words
A method of forming a field effect transistor, comprising: forming a gate insulator layer overlying a substrate; and forming a ferroelectric layer over the gate insulator layer, wherein the ferroelectric layer comprises a doped zinc oxide material having a general formula of Zn x Li 1−x O where x ranges from approximately 0.70 to approximately 0.99, wherein the gate insulator layer and the ferroelectric layer each have a thickness and wherein the thickness of the ferroelectric layer is greater than the thickness of the gate insulator layer.
Claim 8
Independent Claim
87 words
A method of forming a field effect transistor, comprising: forming a gate insulator layer overlying a substrate; and forming a ferroelectric layer over the gate insulator layer, wherein the ferroelectric layer comprises a doped zinc oxide material having a general formula of Zn x Li 1−x O where x ranges from approximately 0.70 to approximately 0.99, wherein the gate insulator layer and the ferroelectric layer each have a thickness and wherein the thickness of the ferroelectric layer is greater than the thickness of the gate insulator layer.
Claim 9
Dependent Claim
15 words
The method of claim 5 , wherein forming the ferroelectric layer comprises jet vapor deposition.
Claim 10
Dependent Claim
19 words
The method of claim 5 , wherein forming the gate insulating layer comprises forming a layer comprising an oxynitride.
Claim 11
Independent Claim
102 words
A method of forming a field effect transistor, comprising: forming a gate insulator layer overlying a substrate; and forming a ferroelectric layer overlying the gate insulator layer and without a programming conductor interposed between the ferroelectric layer and the gate insulator layer, wherein the ferroelectric layer comprises a doped zinc oxide material having a general formula of Zn x Li 1−x O where x ranges from approximately 0.70 to approximately 0.99, wherein the gate insulator layer and the ferroelectric layer each have a thickness and wherein the thickness of the ferroelectric layer is greater than the thickness of the gate insulator layer.
Claim 12
Independent Claim
102 words
A method of forming a field effect transistor, comprising: forming a gate insulator layer overlying a substrate; and forming a ferroelectric layer overlying the gate insulator layer and without a programming conductor interposed between the ferroelectric layer and the gate insulator layer, wherein the ferroelectric layer comprises a doped zinc oxide material having a general formula of Zn x Li 1−x O where x ranges from approximately 0.70 to approximately 0.99, wherein the gate insulator layer and the ferroelectric layer each have a thickness and wherein the thickness of the ferroelectric layer is greater than the thickness of the gate insulator layer.
Claim 13
Dependent Claim
19 words
The method of claim 8 , wherein forming the gate insulating layer comprises forming a layer comprising an oxynitride.
Claim 14
Dependent Claim
24 words
The method of claim 8 , wherein forming the ferroelectric layer comprises sputtering using a target comprising a zinc oxide material having embedded lithium.
Claim 15
Independent Claim
89 words
A method of forming a field effect transistor, comprising: forming a gate insulator layer overlying a substrate; and forming a ferroelectric layer overlying and adjacent the gate insulator layer, wherein the ferroelectric layer comprises a doped zinc oxide material having a general formula of Zn x Mg 1−x O where x ranges from approximately 0.70 to approximately 0.99, wherein the gate insulator layer and the ferroelectric layer each have a thickness and wherein the thickness of the ferroelectric layer is greater than the thickness of the gate insulator layer.
Claim 16
Independent Claim
89 words
A method of forming a field effect transistor, comprising: forming a gate insulator layer overlying a substrate; and forming a ferroelectric layer overlying and adjacent the gate insulator layer, wherein the ferroelectric layer comprises a doped zinc oxide material having a general formula of Zn x Mg 1−x O where x ranges from approximately 0.70 to approximately 0.99, wherein the gate insulator layer and the ferroelectric layer each have a thickness and wherein the thickness of the ferroelectric layer is greater than the thickness of the gate insulator layer.
Claim 17
Dependent Claim
23 words
The method of claim 11 , wherein forming the gate insulating layer comprises forming a layer comprising a silicon nitride or an oxynitride.
Claim 18
Dependent Claim
14 words
The method of claim 11 , wherein forming the ferroelectric layer comprises jet-vapor deposition.
Claim 19
Independent Claim
102 words
A method of forming a field effect transistor, comprising: forming a gate insulator layer overlying a substrate; and forming a ferroelectric layer over the gate insulator layer and without a programming conductor interposed between the ferroelectric layer and the gate insulator layer, wherein the ferroelectric layer comprises a doped zinc oxide material having a general formula of Zn x Mg 1−x O where x ranges from approximately 0.70 to approximately 0.99, wherein the gate insulator layer and the ferroelectric layer each have a thickness and wherein the thickness of the ferroelectric layer is greater than the thickness of the gate insulator layer.
Claim 20
Independent Claim
102 words
A method of forming a field effect transistor, comprising: forming a gate insulator layer overlying a substrate; and forming a ferroelectric layer over the gate insulator layer and without a programming conductor interposed between the ferroelectric layer and the gate insulator layer, wherein the ferroelectric layer comprises a doped zinc oxide material having a general formula of Zn x Mg 1−x O where x ranges from approximately 0.70 to approximately 0.99, wherein the gate insulator layer and the ferroelectric layer each have a thickness and wherein the thickness of the ferroelectric layer is greater than the thickness of the gate insulator layer.
Claim 21
Dependent Claim
24 words
The method of claim 14 , wherein forming the ferroelectric layer comprises sputtering using a target comprising a zinc oxide material having embedded magnesium.
Claim 22
Dependent Claim
15 words
The method of claim 14 , wherein forming the ferroelectric layer comprises jet vapor deposition.
Claim 23
Independent Claim
113 words
A method of forming a field effect transistor, comprising: forming a gate insulator layer overlying a substrate; and forming a ferroelectric layer overlying the gate insulator layer, wherein the ferroelectric layer comprises a doped zinc oxide material having a general formula of Zn x (Li y Mg z )O where x ranges from approximately 0.70 to approximately 0.99, y and z each independently range from approximately 0.00 to approximately 0.30 and the sum of y+z ranges from approximately 0.01 to approximately 0.30, wherein the gate insulator layer and the ferroelectric layer each have a thickness and wherein the thickness of the ferroelectric layer is greater than the thickness of the gate insulator layer.
Claim 24
Independent Claim
113 words
A method of forming a field effect transistor, comprising: forming a gate insulator layer overlying a substrate; and forming a ferroelectric layer overlying the gate insulator layer, wherein the ferroelectric layer comprises a doped zinc oxide material having a general formula of Zn x (Li y Mg z )O where x ranges from approximately 0.70 to approximately 0.99, y and z each independently range from approximately 0.00 to approximately 0.30 and the sum of y+z ranges from approximately 0.01 to approximately 0.30, wherein the gate insulator layer and the ferroelectric layer each have a thickness and wherein the thickness of the ferroelectric layer is greater than the thickness of the gate insulator layer.
Claim 25
Dependent Claim
38 words
The method of claim 17 , wherein the gate insulator layer and the ferroelectric layer each have a thickness and wherein the thickness of the ferroelectric layer is approximately 10 times the thickness of the gate insulator layer.
Claim 26
Dependent Claim
39 words
The method of claim 17 , wherein the gate insulator layer and the ferroelectric layer each have a thickness and wherein the thickness of the ferroelectric layer is at least 5 times the thickness of the gate insulator layer.
Claim 27
Dependent Claim
14 words
The method of claim 17 , wherein forming the ferroelectric layer comprises magnetron sputtering.
Claim 28
Independent Claim
146 words
A method of forming a field effect transistor, comprising: forming a gate insulator layer overlying a substrate; forming a ferroelectric layer overlying the gate insulator layer, wherein the ferroelectric layer comprises a doped zinc oxide material having a general formula of Zn x (Li y Mg z )O where x ranges from approximately 0.70 to approximately 0.99, y and z each independently range from approximately 0.00 to approximately 0.30 and due sum of y+z ranges from approximately 0.01 to approximately 0.30, wherein the gate insulator layer and the ferroelectric layer each have a thickness and wherein the thickness of the ferroelectric layer is greater than the thickness of the gate insulator layer; forming a source region in the substrate; forming a drain region in the substrate and separated from the source region by a channel region; and forming an upper conductor layer overlying the ferroelectric layer.
Claim 29
Independent Claim
146 words
A method of forming a field effect transistor, comprising: forming a gate insulator layer overlying a substrate; forming a ferroelectric layer overlying the gate insulator layer, wherein the ferroelectric layer comprises a doped zinc oxide material having a general formula of Zn x (Li y Mg z )O where x ranges from approximately 0.70 to approximately 0.99, y and z each independently range from approximately 0.00 to approximately 0.30 and due sum of y+z ranges from approximately 0.01 to approximately 0.30, wherein the gate insulator layer and the ferroelectric layer each have a thickness and wherein the thickness of the ferroelectric layer is greater than the thickness of the gate insulator layer; forming a source region in the substrate; forming a drain region in the substrate and separated from the source region by a channel region; and forming an upper conductor layer overlying the ferroelectric layer.
Claim 30
Dependent Claim
15 words
The method of claim 21 , wherein forming the ferroelectric layer comprises jet vapor deposition.
Claim 31
Dependent Claim
20 words
The method of claim 21 , wherein the upper conductor layer comprises a refractory metal suicide overlying a polysilicon layer.
Claim 32
Independent Claim
142 words
A method of forming a field effect transistor comprising: forming a gate insulator layer overlying a substrate; and forming a ferroelectric layer overlying the gate insulator layer and without a programming conductor interposed between the ferroelectric layer and the gate insulator layer, wherein the ferroelectric layer comprises a doped zinc oxide material having a general formula of Zn x (Li y Mg z )O where x ranges from approximately 0.70 to approximately 0.99, y and z each independently range from approximately 0.00 to approximately 0.30 and the sum of y+z ranges from approximately 0.01 to approximately 0.30; and forming an upper conductor layer overlying the ferroelectric layer, wherein the gate insulator layer and the ferroelectric layer each have a thickness and wherein the thickness of the ferroelectric layer is at least 5 times greater than the thickness of the gate insulator layer.
Claim 33
Independent Claim
142 words
A method of forming a field effect transistor comprising: forming a gate insulator layer overlying a substrate; and forming a ferroelectric layer overlying the gate insulator layer and without a programming conductor interposed between the ferroelectric layer and the gate insulator layer, wherein the ferroelectric layer comprises a doped zinc oxide material having a general formula of Zn x (Li y Mg z )O where x ranges from approximately 0.70 to approximately 0.99, y and z each independently range from approximately 0.00 to approximately 0.30 and the sum of y+z ranges from approximately 0.01 to approximately 0.30; and forming an upper conductor layer overlying the ferroelectric layer, wherein the gate insulator layer and the ferroelectric layer each have a thickness and wherein the thickness of the ferroelectric layer is at least 5 times greater than the thickness of the gate insulator layer.
Claim 34
Dependent Claim
15 words
The method of claim 24 , wherein forming the ferroelectric layer comprises jet vapor deposition.
Claim 35
Dependent Claim
20 words
The method of claim 24 , wherein the upper conductor layer comprises a refractory metal silicide overlying a polysilicon layer.
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