Thin film semiconductor device containing polycrystalline Si-Ge alloy and method for producing thereof
First Claim
1. A thin film transistor device comprising:
- (a) an insulator substrate;
(b) a poly-crystalline thin film formed on said insulator substrate; and
(c) a transistor composed of a source, a drain, a channel, and a gate formed on said poly-crystalline thin film, wherein said poly-crystalline thin film in a channel part of said transistor is composed of a silicon-germanium poly-crystalline Si1—
xGex, however, a ratio x of a Ge composition relative to Si is 0<
x<
1, and a ratio x of a Ge composition in the poly-crystalline thin film is larger in a grain boundary than a portion where a Ge composition in an interior grain of crystal becomes the minimum.
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Accused Products
Abstract
The present invention relates to a thin film transistor, in a low-temperature poly-Si thin film becoming an elemental material of the thin film transistor, an object of the invention is to provide the thin film transistor suitable for realizing an image display device having a high performance and a large area at low cost by realizing a poly-crystalline thin film having a crystal structure restraining current scattering in a grain boundary, lessening surface roughness, and capable of realizing high mobility even to a positive hole current.
The object described above is achieved by realizing a TFT with high mobility by restraining a current scattering factor in a grain boundary of crystal with an introduction of Ge into the poly-crystalline Si thin film and with a difference in ratios of Ge compositions between an interior grain of crystal and a grain boundary of crystal resulted from a phase separation involved in crystallization, and by restraining surface roughness using a difference in volumes in a crystal.
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Citations
11 Claims
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1. A thin film transistor device comprising:
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(a) an insulator substrate;
(b) a poly-crystalline thin film formed on said insulator substrate; and
(c) a transistor composed of a source, a drain, a channel, and a gate formed on said poly-crystalline thin film, wherein said poly-crystalline thin film in a channel part of said transistor is composed of a silicon-germanium poly-crystalline Si1—
xGex, however, a ratio x of a Ge composition relative to Si is 0<
x<
1, and a ratio x of a Ge composition in the poly-crystalline thin film is larger in a grain boundary than a portion where a Ge composition in an interior grain of crystal becomes the minimum. - View Dependent Claims (2, 3, 4, 6)
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5. A thin film transistor device comprising:
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(a) an insulator substrate;
(b) a poly-crystalline thin film formed on said insulator substrate; and
(c) a transistor composed of a source, a drain, a channel, and a gate formed on said poly-crystalline thin film, wherein said poly-crystalline thin film in a channel part of said transistor has a {110}-oriented crystal surface and an average lattice constant in a grain boundary is larger than an average lattice constant in an interior grain part of crystal.
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7. A method for producing a thin film transistor device comprising steps of:
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(a) forming an amorphous Si1—
xGex layer of a film thickness of 10-100 nm on an insulator substrate with, however, a ratio x of a Ge composition relative to Si being 0<
x<
1; and
(b) being subjected to a heat treatment for crystallizing the amorphous Si1—
xGex layer by an excimer laser with an energy density of 200-300 mJ/cm2 and the pulse number of 1-50 pieces. - View Dependent Claims (8)
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9. An image display device comprising:
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(a) an image display part;
(b) an image display circuit controlling a display of said image display part and including at least a data driver, a gate driver, and a buffer amplifier; and
(c) a peripheral circuit part positioned in the neighborhood of said image display circuit and controlling said image display circuit, wherein said image display circuit and said peripheral circuit part are integrated on the same substrate as the substrate constituting said image display device, said image display circuit and said peripheral circuit part further comprise an insulator substrate, a poly-crystalline Si1—
xGex thin film formed on said insulator substrate, however, a ratio x of a Ge composition relative to Si is 0<
x<
1, and a circuit part constituted by integrating a plurality of pieces of transistors constituted of sources, drains, channels, and gates formed on said poly-crystalline Si1—
xGex thin film, and said circuit part includes a CMOS type transistor making present as a mixture either one or both of p type transistors or/and n type transistors. - View Dependent Claims (10, 11)
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Specification