Thin-layer field-effect transistors with MIS structure whose insulator and semiconductor are made of organic materials

• US 5,347,144 A
• Filed: 03/01/1993
• Issued: 09/13/1994
• Est. Priority Date: 07/04/1990
• Status: Expired due to Fees

• Current Assignee: Centre National De La Recherche Scientifique
• Original Assignee: Centre National De La Recherche Scientifique
• Inventors: Horowitz, Gilles, Fichou, Denis, Garnier, Francis
• Primary Examiner(s): Crane, Sara W.
• Application Number:
  US07/966,048
• Time in Patent Office: 561 Days
• Field of Search: 257/40, 257/289, 257/410, 257/347, 257/642
• US Class Current: 257/40
• CPC Class Codes: H01L 29/4908 for thin film semiconductor, e.g. gate of TFT
• CPC Class Codes: H01L 29/51 Insulating materials associated therewith for MIS structures on thin film semiconductor H01L29/4908
• CPC Class Codes: H10K 10/46 Field-effect transistors, e.g. organic thin-film transistors [OTFT] H10K10/43 takes precedence
• 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 85/151 Copolymers
• CPC Class Codes: H10K 85/154 Ladder-type polymers
• CPC Class Codes: H10K 85/615 Polycyclic condensed aromatic hydrocarbons, e.g. anthracene
• CPC Class Codes: H10K 85/649 Aromatic compounds comprising a hetero atom

Abstract

A thin-layer field-effect transistor (TFT) with an MIS structure includes a thin semiconductor layer between a source and a drain. The thin semiconductor layer is in contact with one surface of a thin layer made of insulating material, and in contact by its other surface with a conducting grid. The semiconductor is composed of at least one polyconjugated organic compound with a specific molecular weight. The polyconjugated organic compound or polyconjugated organic compounds contain at least 8 conjugated bonds and have a molecular weight of no greater than approximately 2,000. The thin layer of insulating material is made of an insulating organic polymer having a dielectric constant of at least equal to 5. The transistor is useful as a switching or amplifying element.

Claims

1. A thin-layer field-effect transistor (TFT) with an MIS structure comprising a thin semiconductor layer between a source and a drain, said thin semiconductor layer being in contact with one surface of a thin layer made of insulating material, and said thin insulating layer being in contact by its other surface with a conducting grid, wherein said semiconductor is composed of at least one polyconjugated organic compound which contains at least 8 conjugated bonds and has a molecular weight of no greater than approximately 2,000, and wherein said thin layer of insulating material comprises an insulating organic polymer having a dielectric constant at least equal to 5.

2. A transistor according to claim 1, wherein said insulating polymer has a dielectric constant of at least 6.

3. A transistor according to claim 1, wherein said insulating polymer is polyvinyl alcohol.

4. A transistor according to claim 1, wherein said insulating polymer is cyanoethylpullulane.

5. A transistor according to claim 1, wherein said polyconjugated organic compound has at least 10 conjugated bonds.

6. A transistor according to claim 1, wherein said polyconjugated organic compound contains a sufficient number of conjugated bonds for its mobility under a field effect to be at least equal to 10^-3 cm² V^-1 s^-1.

7. A transistor according to claim 1, wherein said polyconjugated organic compound is at least one member selected from the of:

conjugated oligomers whose units include or are constituted by phenylene groups that may be substituted,

ortho-fused or ortho- and peri-fused aromatic polycyclic hydrocarbons having 4 to 20 fused rings,

polyenes with the formula

space="preserve" listing-type="equation">H--C(T.sub.1)=C(T.sub.2).sub.r --H

wherein T₁ and T₂ independently represent --H or a lower alkyl and r is a whole number which may range from 8 to 50, and

conjugated oligomers whose repeating units contain at least one five-link heterocycle.

8. A transistor according to claim 7, wherein said oligomers containing phenylene units are represented by formula I:

##STR4## wherein R"₁, R"₂, and Z₁ each independently represent --H, Cl, F or a trifluoromethyl group or a nitro group, Y'"'"' represents --C( T₁)=C(T₂)--

--C.tbd.C--

--N(R'"'"')--

--N═

N--

--C(R'"'"')=N--

--N═

C(R'"'"')--,

T₁ and T₂ independently represent --H or a lower alkyl,

R'"'"' represents --H, alkyl, substituted alkyl, aryl, or substituted aryl,

n'"'"' is a number equal to zero or 1,

n'"'"' is a number equal to zero or 1, and

n is a whole number that may range between 3 and 12.

9. A transistor according to the claim 8, wherein Z₁ represents --H.

10. A transistor according to claim 7, wherein said aromatic polycyclic compound is an ortho-fused or ortho- and peri-fused polycyclic compound represented by formula II:

##STR5## corresponding to the molecular formula;

space="preserve" listing-type="equation">C.sub.4t+10 H.sub.2t+8

t being a whole number which can range from 2 to 15.

11. A transistor according to 8, wherein said aromatic heterocycle oligomer is an oligomer with formula:

##STR6## wherein;

X and X'"'"' represent independently O, S, Se, Te, or --N(R)--,

R represents H, alkyl, substituted alkyl, aryl, or substituted aryl;

R₁, R₂, R'"'"'₁, R'"'"'₂, R'"'"'₃, and R"₃ each independently represent --H, Cl, F, --CF₃, --NO₂, --CN, --COOR₃, --N(R₄) (R₅) , alkyl, substituted alkyl, aryl, substituted aryl, alkoxy or polyalkoxy,

R₃ represents an alkyl or substituted alkyl group or a metal,

R₄ represents H or an alkyl or substituted alkyl group,

R₅ represents an alkyl, acyl, or aryl group,

or at least one of the pairs R₁ and R₂ and R'"'"'₁ and R'"'"'₂ together represent a divalent hydrocarbon group which may be unsaturated, interrupted, terminated or a combination thereof by at least one heteroatom,

Y, Y₁, Y₂, and Y₃ independently represent the following groups;

--C(R'"'"')=C(R")--

--C.tbd.C--

--N(R'"'"')--

--N═

N--

--C(R'"'"')═

N----N═

C(R'"'"')--,

R'"'"' and R" independently represent

--H, alkyl, substituted alkyl, aryl, or substituted aryl, a, b, a'"'"', b'"'"' are numbers equal to 0 or 1,

or Y₁ may also represent a cyclic or heterocyclic arylene group, and in this case b=1 and a'"'"'=0,

s and t are whole numbers, including zero, of which at least one is different from zero,

m'"'"' is a whole number equal to at least 1, the numbers s, t, and m'"'"' are such that

m'"'"' (s+t)=m,

m being a whole number between 4 and 24.

12. A transistor according to claim 11, wherein at least one of R'"'"'₃ and R"₃ represents --H.

13. A switching or amplification element comprising a transistor as defined in claim 1.

14. A transistor according to claim 6, wherein said mobility is at least 10^-1 cm² V^-1 s^-1.