Field effect transistor including .pi.conjugate polymer and liquid crystal display including the field effect transistor

• US 5,892,244 A
• Filed: 04/10/1997
• Issued: 04/06/1999
• Est. Priority Date: 01/10/1989
• Status: Expired due to Fees

• Current Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation), Sumitomo Chemical Company Limited
• Original Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation), Sumitomo Chemical Company Limited
• Inventors: Tanaka, Toshihiko, Fuchigami, Hiroyuki, Tsumura, Akira, Koezuka, Hiroshi, Doi, Syuji
• Primary Examiner(s): CRANE, SARA W
• Application Number:
  US08/835,634
• Time in Patent Office: 726 Days
• Field of Search: 357/8, 357/237, 257/40, 257/72
• US Class Current: 257/40
• CPC Class Codes: G02F 1/133302 Rigid substrates, e.g. inorganic substrates
• CPC Class Codes: G02F 1/1368 in which the switching element is a three-electrode device G02F1/136277 takes precedence
• CPC Class Codes: H10K 10/46 Field-effect transistors, e.g. organic thin-film transistors [OTFT] H10K10/43 takes precedence
• CPC Class Codes: H10K 10/464 Lateral top-gate IGFETs comprising only a single gate
• CPC Class Codes: H10K 10/466 Lateral bottom-gate IGFETs comprising only a single gate
• CPC Class Codes: H10K 10/484 characterised by the channel regions
• CPC Class Codes: H10K 19/10 comprising field-effect transistors
• CPC Class Codes: H10K 71/211 by selective transformation of an existing layer
• CPC Class Codes: H10K 71/30 Doping active layers, e.g. electron transporting layers
• CPC Class Codes: H10K 85/111 comprising aromatic, heteroaromatic, or aryl chains, e.g. polyaniline, polyphenylene or polyphenylene vinylene
• CPC Class Codes: H10K 85/113 Heteroaromatic compounds comprising sulfur or selene, e.g. polythiophene
• CPC Class Codes: H10K 85/114 Poly-phenylenevinylene; Derivatives thereof

Abstract

The present invention relates to a field effect transistor (FET element) in which a π-conjugated polymer film serving as a semiconductor layer is manufactured by first forming a π-conjugated polymer precursor film using a π-conjugated precursor which is soluble in a solvent and then changing the precursor polymer film to the π-conjugated polymer film. A liquid crystal display apparatus uses the FET element as an active drive element. A large number of the FET elements can be manufactured on a large area substrate at the same time at lost cost and operate stably. A large current flow between the source and drain can be significantly modulated by a voltage applied to the gate of the FET element.

Claims

1. A field effect transistor comprising:

a source electrode;

a drain electrode;

a semiconductor layer serving as a current path between said source and drain electrodes and formed of a π

-conjugated polymer which is obtained from a precursor which is soluble in a solvent;

an acid giving film disposed in contact with the semiconductor layer and producing an acid in a reaction in which the π

-conjugated polymer is obtained from said precursor which is soluble in the solvent;

an insulating film disposed on said semiconductor layer; and

a gate electrode disposed on said insulating film opposite from said semiconductor layer for controlling the electrical conductivity of said semiconductor layer in response to a voltage applied to said gate electrode.

2. A field effect transistor in accordance with claim 1, wherein said π

-conjugated polymer which is obtained from a precursor which is soluble in a solvent is represented by the following general formula ##STR16## where R₁ and R₂ are one of --H, alkyl group, and alkoxyl group and n is an integer of at least 10.

3. A field effect transistor in accordance with claim 1, wherein said acid giving film is a π

-conjugated polymer represented by the following general formula ##STR17## where R₆ is one of --H, alkyl group, and alkoxyl group and n is an integer of at least 10.

4. A liquid crystal display apparatus comprising:

a driving part formed of a field effect transistor having;

a source electrode;

a drain electrode;

a semiconductor layer serving as a current path between said source and drain electrodes and formed of a π

-conjugated polymer which is obtained from a precursor which is soluble in a solvent;

an acid giving film disposed in contact with said semiconductor layer and producing an acid in a reaction in which said π

-conjugated polymer is obtained from said precursor which is soluble in the solvent;

an insulating film disposed on said semiconductor layer; and

a gate electrode disposed on said insulating film opposite from said semiconductor layer for controlling the electrical conductivity of said semiconductor layer in response to a voltage applied to said gate electrode; and

a liquid crystal display part connected in series to one of said source electrode and drain electrode and controlled by applying a voltage to said gate electrode.

5. A field effect transistor comprising:

a source electrode;

a drain electrode;

a semiconductor layer serving as a current path between said source and drain electrodes and formed of a π

-conjugated polymer which is obtained from a precursor which is soluble in a solvent, the π

-conjugated polymer having the general formula ##STR18## where R₁ and R₂ are one of --H, alkyl group, and alkoxyl group and n is an integer of at least 10;

an insulating film disposed on said semiconductor layer, the insulating film producing an acid in a reaction in which the π

-conjugated polymer is obtained from said precursor; and

a gate electrode disposed on said insulating film opposite from said semiconductor layer for controlling the electrical conductivity of said semiconductor layer in response to a voltage applied to said gate electrode.