Thin-film transistor, method of producing thin-film transistor, electronic circuit, display, and electronic device

Abstract

Aspects of the invention can provide a thin-film transistor having good transistor characteristics and operable with a low driving voltage, a method of producing such a thin-film transistor, a high-reliability electronic circuit, a display, and an electronic device. In an exemplary thin-film transistor according to the invention, a gate electrode can be formed on a substrate via an underlying layer, and a gate insulating layer can be formed on the substrate such that the gate electrode is covered with the gate insulating layer. A source electrode and a drain electrode are formed on the gate insulating layer such that they are separated from each other by a gap formed just above the gate electrode. An organic semiconductor layer can be formed thereon such that the electrodes are covered with the organic semiconductor layer. A region between the electrodes of the organic semiconductor layer functions as a channel region. A protective layer can be arranged on the organic semiconductor layer. This thin-film transistor is characterized in that the organic semiconductor layer is formed after the gate insulating layer is formed, and the gate insulating layer has the capability of causing the organic semiconductor layer to be aligned.

Description

BACKGROUND OF THE INVENTION [0001] 1. Field of Invention [0002] An aspect of the invention relates to a thin-film transistor, a method of producing a thin-film transistor, an electronic circuit including a thin-film transistor, a display including a thin-film transistor, and an electronic device including a thin-film transistor. [0003] 2. Description of Related Art [0004] In recent years, thin-film transistors using an organic material behaving as a semiconductor in electrical conduction (organic semiconductor material) have been developed. Thin-film transistors of this type have an advantage that a semiconductor layer can be produced by a process using a solution without needing a high-temperature process or a high-vacuum process. The thin-film transistors of this type are also advantageous in that they can be in a thin and light form, they have good flexibility, and they need low material cost. Because of those advantages, they are expected to be used as switching devices in a fle...

AI Technical Summary

Benefits of technology

[0024] In this method of producing a thin-film transistor according to the invention, preferably, the organic semiconductor layer is formed such that the organic semiconductor layer is at least partially in contact with the gate insulating film and such that the organic semiconductor layer is aligned at least in its surface layer facing the gate insulating film. This method according to the invention makes it possible to produce a thin-film transistor capable of operating with a low driving voltage and having good transistor characteristics, in an easy and highly reliable manner.

[0025] Preferably, the method of producing a thin-film transistor according to the invention can further include performing an alignment treatment on a surface, facing the organic semiconductor layer, of the gate insulating layer, and after completion of the step of performing the alignment processing, the step of forming the source region and the drain region is performed such that the source region and the drain region are spaced apart from each other along the direction in which the surface of the gate insulating layer is aligned. This makes it possible to align the gate insulating film in a more reliable fashion. In this method of producing a thin-film transistor, preferably, the alignment treatment is performed by means of rubbing or optical alignment process. This makes it possible to more easily align the gate insulating film.

[0026] Preferably, the method of producing a thin-film transistor according to the invention can further include performing an alignment treatment at least on a surface, facing the organic semiconductor layer, of the gate insulating layer, after the step of forming the source region and the drain region. This makes it possible to impart a high alignment capability to the gate insulating film in a highly reliable fashion.

[0027] In this method of producing ...

Problems solved by technology

However, the carrier mobility of the organic semiconductor layer is generally two or more orders of magnitude smaller than that of semiconductor layers formed of an inorganic material such as silicon, and thus it is very difficult to realize a thin-film transistor using an organic semiconductor layer having high performance and operable with a small driving voltage.

However, sufficient investigation has not been performed on the optimum layer structure, and there is room for improvement in the layer structure.

Besides, if the organic semiconductor layer is exposed to a temperature higher than that temperature, it loses properties of semiconductor.

Another probl...

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