THIN FILM TRANSISTOR AND MATRIX DISPLAY DEVICE
First Claim
1. A thin film transistor comprising:
- a semiconductor layer made of ZnO, MgxZn1-xO, CdxZn1-xO or CdO or ZnO, MgxZn1-xO, CdxZn1-xO or CdO that have been doped with (a) an element that can be univalent or (b) Ni; and
a gate insulating film, wherein the gate insulating film includes;
a first insulating film made of a material other than an oxide for constituting an interface in combination with a gate electrode; and
a second insulating film, sandwiched between the first insulating film and the semiconductor layer, that is made of an oxide for constituting interfaces in combination with both the first insulating film and the semiconductor layer.
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Accused Products
Abstract
In a thin film transistor, a gate insulating film having a first insulating film and a second insulating film is formed on a gate electrode, and a semiconductor layer including ZnO etc. is formed on the second insulating film. The first insulating film is formed by using SiNx having a high insulating characteristic, and the second insulating film is formed by using an oxide (for example, SiO2). This structure improves a crystalline characteristic of the semiconductor layer that constitutes an interface in combination with the second insulating film, and decreases a defective level of the interface between the semiconductor layer and the second insulating film. Further, the second insulating film is constituted of the oxide, so that it is possible to restrain a material for the second insulating film from depriving oxygen of the semiconductor layer. This keeps a crystalline characteristic of the semiconductor layer under a preferable condition in the vicinity of the interface between the second insulating film and the semiconductor layer. As a result, it is possible to realize a thin film transistor such that: a leak current level at an OFF area is low, and the mobility is high, and a switching characteristic is preferable. Thus, in the thin film transistor having a transparent semiconductor film, a TFT characteristic is improved.
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Citations
24 Claims
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1. A thin film transistor comprising:
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a semiconductor layer made of ZnO, MgxZn1-xO, CdxZn1-xO or CdO or ZnO, MgxZn1-xO, CdxZn1-xO or CdO that have been doped with (a) an element that can be univalent or (b) Ni; and
a gate insulating film, wherein the gate insulating film includes;
a first insulating film made of a material other than an oxide for constituting an interface in combination with a gate electrode; and
a second insulating film, sandwiched between the first insulating film and the semiconductor layer, that is made of an oxide for constituting interfaces in combination with both the first insulating film and the semiconductor layer. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A thin film transistor comprising:
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a semiconductor layer made of ZnO, MgxZn1-xO, CdxZn1-xO or CdO or ZnO, MgxZn1-xO, CdxZn1-xO or CdO that have been doped with (a) an element that can be univalent or (b) Ni; and
a gate insulating film, wherein the gate insulating film includes;
a first insulating film made of a material other than an oxide for constituting an interface in combination with a gate electrode; and
a second insulating film, sandwiched between the first insulating film and the semiconductor layer, that has an oxide for constituting interfaces in combination with both the first insulating film and the semiconductor layer, the second insulating film being made of KNbO3, KTaO3, BaTiO3, CaSO3, CaZrO3, CdSnO3, SrHfO3, SrSnO3, SrTiO3, YScO3, CaHfO3, MgCeO3, SrCeO3, BaCeO3, SrZrO3, BaZrO3, LiGaO2, mixed crystal (Li1-(x+y)NaxKy)(Ga1-zAlz)O2 of LiGaO2, or a solid solution having at least two of these oxides. - View Dependent Claims (9, 10, 11)
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12. A matrix display device comprising switching elements disposed in a matrix manner, wherein each of the switching elements is constituted of a thin film transistor that includes:
- a semiconductor layer made of ZnO, MgxZn1-xO, CdxZn1-xO or CdO or ZnO, MgxZn1-xO, CdxZn1-xO or CdO that have been doped with (a) an element that can be univalent or (b) Ni; and
a gate insulating film, wherein the gate insulating film has;
a first insulating film made of a material other than an oxide for constituting an interface in combination with a gate electrode; and
a second insulating film, sandwiched between the first insulating film and the semiconductor layer, that is made of an oxide for constituting interfaces in combination with both the first insulating film and the semiconductor layer. - View Dependent Claims (13, 14, 15, 16, 17, 18, 19)
- a semiconductor layer made of ZnO, MgxZn1-xO, CdxZn1-xO or CdO or ZnO, MgxZn1-xO, CdxZn1-xO or CdO that have been doped with (a) an element that can be univalent or (b) Ni; and
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20. A matrix display device comprising switching elements disposed in a matrix manner, wherein
each of the switching elements is constituted of a thin film transistor that includes: - a semiconductor layer made of ZnO, MgxZn1-xO, CdxZn1-xO or CdO or ZnO, MgxZn1-xO, CdxZn1-xO or CdO that have been doped with (a) an element that can be univalent or (b) Ni; and
a gate insulating film, wherein the gate insulating film has;
a first insulating film made of a material other than an oxide for constituting an interface in combination with a gate electrode; and
a second insulating film, sandwiched between the first insulating film and the semiconductor layer, that constitutes interfaces in combination with both the first insulating film and the semiconductor layer, the second insulating film being made of KNbO3, KTaO3, BaTiO3, CaSnO3, CaZrO3, CdSnO3, SrHfO3, SrSnO3, SrTiO3, YScO3, CaHfO3, MgCeO3, SrCeO3, BaCeO3, SrZrO3, BaZrO3, LiGaO2, mixed crystal (Li1-(x+y)NaxKy)(Ga1-zAlz)O2 of LiGaO2, or a solid solution having at least two of these oxides. - View Dependent Claims (21, 22, 23, 24)
- a semiconductor layer made of ZnO, MgxZn1-xO, CdxZn1-xO or CdO or ZnO, MgxZn1-xO, CdxZn1-xO or CdO that have been doped with (a) an element that can be univalent or (b) Ni; and
Specification