Thin-film transistor, method of producing the same, and devices provided with the same
First Claim
1. A thin-film transistor comprising an oxide semiconductor layer, a source electrode, a drain electrode, a gate insulating film and a gate electrode formed on a substrate,wherein the oxide semiconductor layer comprises a first area, a second area and a third area forming a well-type potential in a film-thickness direction, the first area forming a well of the well-type potential and having a first electron affinity, the second area being disposed nearer to the gate electrode than the first area and having a second electron affinity smaller than the first electron affinity, and the third area being disposed farther from the gate electrode than the first area and having a third electron affinity smaller than the first electron affinity,wherein the oxide semiconductor layer is amorphous, andwherein an oxygen deficiency of the third area is greater than an oxygen deficiency of the first area.
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Accused Products
Abstract
A thin-film transistor including an oxide semiconductor layer is disclosed. The oxide semiconductor layer includes a first area, a second area and a third area forming a well-type potential in the film-thickness direction. The first area forms a well of the well-type potential and has a first electron affinity. The second area is disposed nearer to the gate electrode than the first area and has a second electron affinity smaller than the first electron affinity. The third area is disposed farther from the gate electrode than the first area and has a third electron affinity smaller than the first electron affinity. At least an oxygen concentration at the third area is lower than an oxygen concentration at the first area.
179 Citations
26 Claims
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1. A thin-film transistor comprising an oxide semiconductor layer, a source electrode, a drain electrode, a gate insulating film and a gate electrode formed on a substrate,
wherein the oxide semiconductor layer comprises a first area, a second area and a third area forming a well-type potential in a film-thickness direction, the first area forming a well of the well-type potential and having a first electron affinity, the second area being disposed nearer to the gate electrode than the first area and having a second electron affinity smaller than the first electron affinity, and the third area being disposed farther from the gate electrode than the first area and having a third electron affinity smaller than the first electron affinity, wherein the oxide semiconductor layer is amorphous, and wherein an oxygen deficiency of the third area is greater than an oxygen deficiency of the first area.
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4. A thin-film transistor comprising an oxide semiconductor layer, a source electrode, a drain electrode, a gate insulating film and a gate electrode formed on a substrate,
wherein the oxide semiconductor layer comprises a first area, a second area and a third area forming a well-type potential in a film-thickness direction, the first area forming a well of the well-type potential and having a first electron affinity, the second area being disposed nearer to the gate electrode than the first area and having a second electron affinity smaller than the first electron affinity, and the third area being disposed farther from the gate electrode than the first area and having a third electron affinity smaller than the first electron affinity, and wherein at least an oxygen concentration at the third area is lower than an oxygen concentration at the first area, and wherein the second area and the third area have bandgaps larger than a bandgap at the first area.
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8. A thin-film transistor comprising an oxide semiconductor layer, a source electrode, a drain electrode, a gate insulating film and a gate electrode formed on a substrate,
wherein the oxide semiconductor layer comprises a first area, a second area and a third area forming a well-type potential in a film-thickness direction, the first area forming a well of the well-type potential and having a first electron affinity, the second area being disposed nearer to the gate electrode than the first area and having a second electron affinity smaller than the first electron affinity, and the third area being disposed farther from the gate electrode than the first area and having a third electron affinity smaller than the first electron affinity, and wherein at least an oxygen concentration at the third area is lower than an oxygen concentration at the first area, and wherein each area of the oxide semiconductor layer comprises a(In2O3)· - b(Ga2O3)·
c(ZnO), where a≧
0, b≧
0, c≧
0, a+b≠
0, b+c≠
0 and c+a 0, andwherein a value of b/(a+b) at the first area of the oxide semiconductor layer is smaller than values of b/(a+b) at the second area and the third area. - View Dependent Claims (9, 10, 11)
- b(Ga2O3)·
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14. A method of producing a thin-film transistor that comprises an oxide semiconductor layer, a source electrode, a drain electrode, a gate insulating film and a gate electrode formed on a substrate,
wherein the oxide semiconductor layer comprises a first area, a second area and a third area forming a well-type potential in a film-thickness direction, the first area forming a well of the well-type potential and having a first electron affinity, the second area being disposed nearer to the gate electrode than the first area and having a second electron affinity smaller than the first electron affinity, and the third area being disposed farther from the gate electrode than the first area and having a third electron affinity smaller than the first electron affinity, wherein the oxide semiconductor layer is amorphous, and wherein an oxygen deficiency of the third area is greater than an oxygen deficiency of the first area, the method comprising: -
a film formation step of forming the oxide semiconductor layer through sputtering, wherein the oxide semiconductor layer comprises a first area, a second area and a third area forming a well-type potential in a film-thickness direction, the first area forming a well of the well-type potential and having a first electron affinity, the second area being disposed nearer to the gate electrode than the first area and having a second electron affinity smaller than the first electron affinity, and the third area being disposed farther from the gate electrode than the first area and having a third electron affinity smaller than the first electron affinity, wherein the film formation step comprises forming the first area under a first value of oxygen partial pressure/argon partial pressure in a film formation chamber, forming the second area under a second value of oxygen partial pressure/argon partial pressure in the film formation chamber, and forming the third area under a third value of oxygen partial pressure/argon partial pressure in the film formation chamber lower than the first value of oxygen partial pressure/argon partial pressure. - View Dependent Claims (15, 18)
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16. A method of producing a thin-film transistor that comprises an oxide semiconductor layer, a source electrode, a drain electrode, a gate insulating film and a gate electrode formed on a substrate,
wherein the oxide semiconductor layer comprises a first area, a second area and a third area forming a well-type potential in a film-thickness direction, the first area forming a well of the well-type potential and having a first electron affinity, the second area being disposed nearer to the gate electrode than the first area and having a second electron affinity smaller than the first electron affinity, and the third area being disposed farther from the gate electrode than the first area and having a third electron affinity smaller than the first electron affinity, wherein the oxide semiconductor layer is amorphous, and wherein an oxygen deficiency of the third area is greater than an oxygen deficiency of the first area, the method comprising: -
a film formation step of forming the oxide semiconductor layer through sputtering, wherein the oxide semiconductor layer comprises a first area, a second area and a third area forming a well-type potential in a film-thickness direction, the first area forming a well of the well-type potential and having a first electron affinity, the second area being disposed nearer to the gate electrode than the first area and having a second electron affinity smaller than the first electron affinity, and the third area being disposed farther from the gate electrode than the first area and having a third electron affinity smaller than the first electron affinity, wherein the film formation process comprises applying oxygen-containing radicals to a surface on which the first area is formed during and/or after formation of the first area. - View Dependent Claims (19)
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17. A method of producing a thin-film transistor that comprises an oxide semiconductor layer, a source electrode, a drain electrode, a gate insulating film and a gate electrode formed on a substrate,
wherein the oxide semiconductor layer comprises a first area, a second area and a third area forming a well-type potential in a film-thickness direction, the first area forming a well of the well-type potential and having a first electron affinity, the second area being disposed nearer to the gate electrode than the first area and having a second electron affinity smaller than the first electron affinity, and the third area being disposed farther from the gate electrode than the first area and having a third electron affinity smaller than the first electron affinity, wherein the oxide semiconductor layer is amorphous, and wherein an oxygen deficiency of the third area is greater than an oxygen deficiency of the first area, the method comprising: -
a film formation step of forming the oxide semiconductor layer through sputtering, wherein the oxide semiconductor layer comprises a first area, a second area and a third area forming a well-type potential in a film-thickness direction, the first area forming a well of the well-type potential and having a first electron affinity, the second area being disposed nearer to the gate electrode than the first area and having a second electron affinity smaller than the first electron affinity, and the third area being disposed farther from the gate electrode than the first area and having a third electron affinity smaller than the first electron affinity, wherein the film formation process comprises applying ultraviolet light in an ozone atmosphere to a surface on which the first area is formed during and/or after formation of the first area. - View Dependent Claims (20)
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26. A thin-film transistor comprising an oxide semiconductor layer, a source electrode, a drain electrode, a gate insulating film and a gate electrode formed on a substrate,
wherein the oxide semiconductor is an n-type oxide semiconductor, and the oxide semiconductor layer comprises a first area, a second area and a third area forming a well-type potential in a film-thickness direction, the first area forming a well of the well-type potential and having a first electron affinity, the second area being disposed nearer to the gate electrode than the first area and having a second electron affinity smaller than the first electron affinity, and the third area being disposed farther from the gate electrode than the first area and having a third electron affinity smaller than the first electron affinity, wherein the oxide semiconductor layer is amorphous, and wherein at least an oxygen concentration at the third area is lower than an oxygen concentration at the first area.
Specification