Thin film transistor and method for manufacturing the same

摘要

According to one embodiment, a thin film transistor includes a gate electrode, a semiconductor layer, a gate insulating film, and a source electrode and a drain electrode. The semiconductor layer includes an oxide including at least one of gallium and zinc, and indium. The gate insulating film is provided between the gate electrode and the semiconductor layer. The source electrode and a drain electrode are electrically connected to the semiconductor layer and spaced from each other. The semiconductor layer includes a plurality of fine crystallites dispersed three-dimensionally in the semiconductor layer and has periodicity in arrangement of atoms.

主权项

1. A method for manufacturing a thin film transistor including:
a gate electrode; a semiconductor layer provided facing the gate electrode, including an oxide including at least one of gallium and zinc, and indium, and including a plurality of fine crystallites dispersed three-dimensionally and having periodicity in arrangement of atoms; a gate insulating film provided between the gate electrode and the semiconductor layer; and a source electrode and a drain electrode electrically connected to the semiconductor layer and spaced from each other, the method comprising: forming the gate electrode on a major surface of a substrate, forming the gate insulating film made of a silicon oxide film on the gate electrode, forming an oxide film including indium and at least one of gallium and zinc on the gate insulating film, and forming a channel protection layer made of a silicon oxide film on the oxide film so that the oxide film is covered with the channel protection layer to form a stacked film of the gate electrode, the gate insulating film, the oxide film, and the channel protection layer; forming the fine crystallites in the oxide film by heat treatment of the stacked film at 320° C. or more and 380° C. or less in a furnace; and forming the source electrode and the drain electrode so as to be connected to the oxide film, the forming the source electrode and the drain electrode being performed after the forming the fine crystallites, the forming the fine crystallites being performed in a state in which a lower surface of the oxide film is covered with the gate insulating film and an upper surface of the oxide film is covered with the channel protection layer, wherein the fine crystallites are dispersed uniformly in the oxide film, wherein a particle diameter of the fine crystallites is 5 nanometers or less, wherein the oxide film does not include crystallites having a diameter larger than 5 nanometers, wherein the semiconductor layer includes a first region overlapping the gate electrode in a direction perpendicular to the major surface, a second region overlapping the source electrode in the direction, and a third region overlapping the drain electrode in the direction, wherein an average particle diameter of the fine crystallites having the particle diameter of 2 nanometers or more among the plurality of fine crystallites is 3.5 nanometers or less in each of the first, second, and third regions, and wherein oxygen concentrations in the first, second, and third regions are same.