JP2006041220A - Organic compound crystal and field effect type transistor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an organic compound crystal, having a more isotropic (two-dimensional) conduction path, that is different from the anisotropic (one-dimensional) conduction path in the inside. <P>SOLUTION: The organic compound crystal is constituted by plurally laminating connection molecules, comprising a first π electronic conjugated-system molecule and a second π electronic conjugated-system molecule which are connected, based on the spiro bond. Each connection molecule has nearly D<SB>2d</SB>symmetric properties. In the organic compound crystal, the first π electronic conjugated-system molecule and the first π electronic conjugated-system molecule, consisting of adjoining connection molecules, are in a laminating condition. Further, the second π electronic conjugated-system molecule and the second π electronic conjugated-system molecule, consisting of adjoining connection molecules, are in a laminated state. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an organic compound crystal composed of connecting molecules formed by connecting two π-electron conjugated molecules, and a field effect transistor in which a channel formation region is composed of such organic compound crystals.

  In recent years, research on organic transistors has been actively conducted, and the performance has reached the level of practical use.

  The interaction between molecules is carried by a π-electron system that extends in a direction perpendicular to the σ bond that forms the skeleton of the molecule. In addition, in order for charge carriers to move freely within the molecule, this π-electron system is conjugated. Thus, it is necessary to spread all over the molecule. That is, carriers in the organic semiconductor crystal move in the crystal via π electron orbits extending in a direction perpendicular to the molecular plane. Therefore, in order to achieve high mobility in an organic semiconductor crystal, it is desirable to adopt a crystal structure in which molecular surfaces of adjacent molecules are arranged so as to overlap in parallel.

  However, many organic semiconductor crystals with high mobility that are currently known have a so-called herringbone structure as shown in a conceptual diagram in FIG. Currently, 2,3,6,7-dibenzoanthracene (also called pentacene), which is a condensed aromatic compound, has been reported to exhibit the best performance as a material (molecule) constituting the channel formation region of an organic transistor. (See, for example, H. Klauk et al., J. Appl. Phys. 92, 5259 (2002)), pentacene molecules have a structure in which a two-dimensional layer having a herringbone structure is laminated in a crystal. (See, for example, RB Champbell et al., Acta Cryst. 14, 705 (1961); D. Homes et al., J. Eur. Chem. 5, 3399 (1999)). As for the electronic state of pentacene, band analysis based on first-principles calculation is performed (see, for example, ML Tiago et al., Phys. Rev. B67, 115212 (2003)). The formation of a dimensional conduction path is supported by the results of band analysis.

  However, in the herringbone structure, the molecular surfaces of adjacent molecules are non-parallel, and at first glance the structure is messy, so the crossing of π electron orbits of adjacent molecules is small, and the π electron orbits of adjacent molecules are small. From the point of view of crossing, the structure is not optimal. Therefore, if the channel formation region of the organic transistor is formed from the material (molecule) forming the herringbone structure, the mobility is limited.

H. Klauk et al., J. Appl. Phys. 92, 5259 (2002) M. L. Tiago et al., Phys. Rev. B67, 115212 (2003) Chemical Society Spring Annual Meeting Proceedings 2F345 “Design and synthesis of new organic donors with orthogonal pi-electron systems via spiro bonds”

On the other hand, there are materials (molecules) having a crystal structure such that BMDT-TTF or the like in which adjacent molecular planes are stacked in parallel with each other (with parallel overlap). FIG. 8 shows a conceptual diagram of the crystal structure of the BMDT-TTF molecule. In such a material, the molecular surfaces of adjacent molecules are stacked in parallel. As shown in the energy band structure of BMDT-TTF in FIG. 9, a relatively wide energy band is formed in the stacking direction (a ^* axis direction), which is an advantageous structure with respect to carrier movement. Yes.

  However, in a molecule having such a planar structure, it is difficult to move the carrier in directions other than the stack axis direction (up and down direction in FIG. 8) due to the property that the planar molecules are stacked in parallel. In other words, a one-dimensional conduction band structure is formed, and the conduction path is anisotropic (one-dimensional). Therefore, when the channel formation region of the field effect transistor is formed from such molecules, the anisotropy of the conduction path must be taken into consideration, which is disadvantageous in configuring the channel formation region. In addition, because of the one-dimensional conduction band structure, there is a problem in that the correlation between charge carriers (for example, Coulomb repulsion between charge carriers) is large and the movement of charge carriers is hindered.

Proceedings of the Spring Annual Meeting of the Chemical Society of Japan held in March 1990 2F345 “Design and Synthesis of New Organic Donor with Orthogonal Pi Electron System by Spiro Coupling” In addition, a compound having a D _2d symmetry in which two equivalent pi-electron systems are connected by a spiro bond is disclosed, but this document does not mention a specific organic compound crystal.

  Accordingly, an object of the present invention is to provide an organic compound crystal having a more isotropic (two-dimensional) conduction path than an anisotropic (one-dimensional) conduction path inside, and the organic compound crystal. An object of the present invention is to provide a field effect transistor having a channel formation region.

In order to achieve the above object, the organic compound crystal of the present invention comprises:
A plurality of connecting molecules formed by connecting a first π-electron conjugated molecule and a second π-electron conjugated molecule based on a spiro bond are stacked organic compound crystals,
In each connecting molecule,
(A) The molecular plane of the first π-electron conjugated molecule and the molecular plane of the second π-electron conjugated molecule are substantially orthogonal,
(B) When it is assumed that the molecular plane of the first π-electron conjugated molecule and the molecular plane of the second π-electron conjugated molecule are in the same plane, if the functional group has a functional group, the functional group is The first π-electron conjugated molecule when it is replaced with an atom, and the second π-electron conjugated molecule when the functional group is replaced with a hydrogen atom when it has a functional group, are the first When rotated 180 degrees around the connection point between the π-electron conjugated molecule and the second π-electron conjugated molecule, they overlap,
In organic compound crystals,
(C) The first π-electron conjugated molecule and the first π-electron conjugated molecule constituting the adjacent connecting molecule are in a stacked state,
(D) The second π-electron conjugated molecule and the second π-electron conjugated molecule constituting the adjacent connecting molecule are in a stacked state.

The field effect transistor of the present invention for achieving the above object is
A field effect transistor having a channel formation region made of an organic compound crystal,
In the organic compound crystal, a plurality of connecting molecules formed by connecting the first π-electron conjugated molecule and the second π-electron conjugated molecule based on a spiro bond are stacked,
In each connecting molecule,
(A) The molecular plane of the first π-electron conjugated molecule and the molecular plane of the second π-electron conjugated molecule are substantially orthogonal,
(B) When it is assumed that the molecular plane of the first π-electron conjugated molecule and the molecular plane of the second π-electron conjugated molecule are in the same plane, if the functional group has a functional group, the functional group is The first π-electron conjugated molecule when it is replaced with an atom, and the second π-electron conjugated molecule when the functional group is replaced with a hydrogen atom when it has a functional group, are the first When rotated 180 degrees around the connection point between the π-electron conjugated molecule and the second π-electron conjugated molecule, they overlap,
In organic compound crystals,
(C) The first π-electron conjugated molecule and the first π-electron conjugated molecule constituting the adjacent connecting molecule are in a stacked state,
(D) The second π-electron conjugated molecule and the second π-electron conjugated molecule constituting the adjacent connecting molecule are in a stacked state.

In the organic compound crystal of the present invention or the field effect transistor of the present invention (hereinafter, these may be collectively referred to simply as the present invention), as shown in FIG. The molecular plane of the molecule (for example, the aromatic ring plane) and the molecular plane of the second π-electron conjugated molecule (for example, the aromatic ring plane) pass through sp ³ orbital atoms or atoms such as silicon or germanium. And substantially orthogonal. Here, “substantially orthogonal” means the molecular plane of the first π-electron conjugated molecule (for example, the aromatic ring plane) and the molecular plane of the second π-electron conjugated molecule (for example, the aromatic ring plane). It means that the angle formed by is 90 degrees ± 10 degrees.

In the present invention,
The first π-electron conjugated molecule and the second π-electron conjugated molecule contain a chalcogen atom as a constituent element,
The distance between chalcogen atoms in the first π-electron conjugated molecule constituting the adjacent connecting molecule is short,
The distance between chalcogen atoms in the second π-electron conjugated molecule constituting the adjacent connecting molecule is short,
A structure having a three-dimensional periodic structure in which first π-electron conjugated molecules in adjacent connecting molecules are connected to each other and second π-electron conjugated molecules in adjacent connecting molecules are connected to each other. It is preferable.

In this case, the van der Waals radius of the chalcogen atom in the first or second π-electron conjugated molecule constituting the connecting molecule is r _1, and the first or second constituting the connecting molecule adjacent to the connecting molecule is used. When the van der Waals radius of the chalcogen atom in the π-electron conjugated molecule is r ₂ , the chalcogen atom (X _i ) in the first or second π-electron conjugated molecule constituting the connecting molecule, and the connecting molecule in the first or second π-electron conjugated chalcogen atoms in molecules constituting the connecting molecules adjacent (X _j), the distance R _ij between at least one pair of chalcogen atoms (X _i, X _j) is
R _ij ≦ (r ₁ + r ₂ ) × 1.1
It is desirable to satisfy

  In the present invention, it can be expected that the interaction between π-electron conjugated molecules increases as the number of chalcogen atoms contained in one π-electron conjugated molecule increases. The ratio of the total chalcogen atom mass to the molecular weight of the molecule is preferably 40% or more, for example.

  In general, a chalcogen atom refers to O (oxygen), S (sulfur), Se (selenium), Te (tellurium), or Po (polonium). In this specification, a chalcogen atom refers to O (oxygen). , S (sulfur), Se (selenium) and Te (tellurium).

In the present invention, when the first or second π-electron conjugated molecule itself is laminated between the first or second π-electron conjugated molecule and the first or second π-electron conjugated molecule, It is preferable that the π-electron orbitals intersect each other by force and that a one-dimensional energy band structure is formed from the crystal structure. Specifically, in the present invention, as a connecting molecule, the following structural formula (1) [wherein R ₁ , R ₂ , R _3, and R ₄ are a hydrogen atom or an alkyl group having 10 or less carbon atoms] Can be exemplified. The alkyl group includes a saturated alkyl group and an unsaturated alkyl group. Here, each of the first or second π electron conjugated molecule is basically composed of a methylenedithio-tetrathiafulvalene (MDT-TTF) molecule.

  Specific examples of the structure of the field effect transistor according to the present invention include the following four types of structures. In the field effect transistor of the present invention, the extended portion of the channel formation region may be referred to as a channel formation region extension.

That is, the field effect transistor having the first structure is a so-called bottom gate / top contact type,
(A) a gate electrode formed on a support;
(B) a gate insulating layer formed on the gate electrode and the support;
(C) a channel formation region formed on the gate insulating layer, a channel formation region extension, and
(D) source / drain electrodes formed on the channel forming region extension part,
It has.

The field effect transistor having the second structure is a so-called bottom gate / bottom contact type,
(A) a gate electrode formed on a support;
(B) a gate insulating layer formed on the gate electrode and the support;
(C) source / drain electrodes formed on the gate insulating layer, and
(D) a channel formation region formed on the portion of the gate insulating layer between the source / drain electrodes;
It has.

Furthermore, the field effect transistor having the third structure is a so-called top gate / top contact type,
(A) a channel formation region formed on the support and a channel formation region extension,
(B) source / drain electrodes formed on the channel forming region extension part;
(C) a gate insulating layer formed on the source / drain electrodes and the channel formation region, and
(D) a gate electrode formed on the gate insulating layer;
It has.

The field effect transistor having the fourth structure is a so-called top gate / bottom contact type,
(A) source / drain electrodes formed on a support;
(B) a channel forming region formed on the portion of the support between the source / drain electrodes;
(C) a gate insulating layer formed on the channel formation region, and
(D) a gate electrode formed on the gate insulating layer;
It has.

  In the field effect transistor of the present invention, as a method for forming a channel formation region made of an organic compound crystal, physical vapor deposition (PVD method) exemplified by vacuum deposition and sputtering; various chemical vapor deposition (CVD method); spin coating method; various printing methods such as screen printing method, ink jet printing method, offset printing method, gravure printing method; air doctor coater method, blade coater method, rod coater method, knife coater method, squeeze coater method , Reverse roll coater method, transfer roll coater method, gravure coater method, kiss coater method, cast coater method, spray coater method, slit orifice coater method, calendar coater method, and any of the spray methods In That.

Further, in the field effect transistor of the present invention, as a material constituting the gate insulating layer, a silicon oxide material, silicon nitride (SiN _Y ), Al ₂ O ₃ , an inorganic exemplified by a metal oxide high dielectric insulating film Not only poly-insulating materials but also polymethyl methacrylate (PMMA), polyvinylphenol (PVP), polyethylene terephthalate (PET), polyoxymethylene (POM), polyvinyl chloride, polyvinylidene fluoride, polysulfone, polycarbonate (PC), polyimide Examples thereof include organic insulating materials, and combinations thereof can also be used. As silicon oxide materials, silicon dioxide (SiO _x ), BPSG, PSG, BSG, AsSG, PbSG, silicon oxynitride (SiON), SOG (spin on glass), low dielectric constant SiO ₂ materials (for example, polyaryl) And ether, cycloperfluorocarbon polymer and benzocyclobutene, cyclic fluororesin, polytetrafluoroethylene, fluorinated aryl ether, fluorinated polyimide, amorphous carbon, and organic SOG).

As a method of forming the gate insulating layer, any one of the above-described various PVD methods; various CVD methods; spin coating methods; various printing methods described above; various coating methods described above; dipping methods; casting methods; Can be mentioned. Alternatively, the gate insulating layer can be formed by oxidizing or nitriding the surface of the gate electrode, or can be obtained by forming an oxide film or a nitride film on the surface of the gate electrode. Examples of a method for oxidizing the surface of the gate electrode include a thermal oxidation method, an oxidation method using O ₂ plasma, and an anodic oxidation method, although depending on the material constituting the gate electrode. Further, as a method of nitriding the surface of the gate electrode, although it depends on the material constituting the gate electrode, a nitriding method using N ₂ plasma can be exemplified. Alternatively, for example, when a gate electrode is made of gold (Au), an insulating material having a functional group capable of forming a chemical bond with the gate electrode, such as a linear hydrocarbon modified at one end with a mercapto group. The gate insulating layer can also be formed on the surface of the gate electrode by covering the surface of the gate electrode with a sex molecule in a self-organizing manner by a method such as immersion.

  Furthermore, in the field effect transistor of the present invention, platinum (Pt), gold (Au), palladium (Pd), chromium (Cr), nickel as materials constituting the gate electrode, the source / drain electrode, and various wirings. (Ni), molybdenum (Mo), niobium (Nb), neodymium (Nd), aluminum (Al), silver (Ag), tantalum (Ta), tungsten (W), copper (Cu), rubidium (Rb), rhodium (Rh), titanium (Ti), indium (In), tin (Sn), etc., or alloys containing these metal elements, conductive particles made of these metals, and conductivity of alloys containing these metals Particle, polysilicon, amorphous silicon, tin oxide, indium oxide, indium-tin oxide (ITO) and include these elements It may be a laminated structure. Furthermore, an organic material such as poly (3,4-ethylenedioxythiophene) / polystyrene sulfonic acid [PEDOT / PSS] can also be used as a material constituting the gate electrode and the source / drain electrode.

  Although the source / drain electrode and gate electrode are formed depending on the materials constituting them, PVD method exemplified by vacuum deposition method and sputtering method; various CVD methods including MOCVD method; spin coating method; Various printing methods using conductive paste and various conductive polymer solutions; various coating methods described above; lift-off method; shadow mask method; plating method such as electrolytic plating method, electroless plating method or a combination thereof; and spraying Any of the methods, or a combination with a patterning technique can be mentioned if necessary. In addition, as the PVD method, (a) various vacuum deposition methods such as electron beam heating method, resistance heating method, flash deposition, (b) plasma deposition method, (c) bipolar sputtering method, direct current sputtering method, direct current magnetron sputtering method Various sputtering methods such as high-frequency sputtering method, magnetron sputtering method, ion beam sputtering method, bias sputtering method, (d) DC (direct current) method, RF method, multi-cathode method, activation reaction method, electric field evaporation method, high-frequency method Various ion plating methods such as an ion plating method and a reactive ion plating method can be given.

  In the field effect transistor of the present invention, as a support, various glass substrates, various glass substrates with an insulating layer formed on the surface, a quartz substrate, a quartz substrate with an insulating layer formed on the surface, and an insulating layer on the surface A silicon substrate formed can be mentioned. Furthermore, as a support, polyethersulfone (PES), polyimide, polycarbonate (PC), polyethylene terephthalate (PET), polymethyl methacrylate (polymethyl methacrylate, PMMA), polyvinyl alcohol (PVA), polyvinylphenol (PVP) And a plastic film, a plastic sheet, and a plastic substrate made of a polymer material exemplified in the above. If a support made of such a flexible polymer material is used, for example, A field effect transistor can be incorporated or integrated into a display device or electronic device having a curved surface. Other examples of the support include a conductive substrate (a substrate made of a metal such as gold or highly oriented graphite). In the present invention, depending on the configuration and structure of the semiconductor device, the semiconductor device is provided on the support member, but this support member can also be made of the above-described materials. An electronic device or a semiconductor device may be sealed with resin.

  When the field effect transistor of the present invention is applied to and used in a display device or various electronic devices, it may be a monolithic integrated circuit in which a number of field effect transistors are integrated on a support, or each field effect transistor may be cut. It may be individualized and used as a discrete part. Further, the field effect transistor may be sealed with resin.

  In the present invention, the first π-electron conjugated molecule and the second π-electron conjugated molecule are made substantially perpendicular to each other with a force much stronger than an intermolecular force such as a covalent bond. When the π-electron conjugated molecules are connected (fixed), the first π-electron conjugated molecules between adjacent connecting molecules are in a stacked state so that the molecular planes are aligned in parallel, and adjacent connecting molecules The second π-electron conjugated molecules between them are stacked so that the molecular planes are aligned in parallel. Therefore, as a result of the formation of a two-dimensional energy band structure in the organic compound crystal, it becomes a material suitable as a material constituting the channel formation region of the field effect transistor, and high mobility can be realized. That is, in the present invention, since the energy band structure is isotropic within the plane including the two stack axes of the organic compound crystal, the channel is made of a material having a conventional one-dimensional energy band structure. The degree of freedom of orientation of the organic compound crystal in the channel formation region is higher than that in the formation region, the handling is easy, and the mobility can be improved.

  Moreover, in the present invention, if a large number of chalcogen atoms having large atomic orbitals are introduced into the π-electron conjugated molecule, for example, compared to an acene hydrocarbon composed of a carbon atom and a hydrogen atom, the π-electron conjugated intermolecular molecule The interaction becomes stronger. That is, the band width is expanded by the overlap of the chalcogen atom orbits, the anisotropy is relaxed, and the charge carrier transport performance in the channel formation region of the field effect transistor can be improved. Furthermore, if the chalcogen atom is positioned so that it can participate in the π-electron conjugated system formed by the molecular skeleton, and the chalcogen atom is positioned as much as possible on the outer periphery of the molecule, that is, the π-electron conjugated system. When arranged on the outer periphery of the molecule, interaction between π-electron conjugated molecules in the lateral direction of the molecular plane between the molecules is also possible. As a result, a two-dimensional conduction path is provided and the conduction bandwidth can be increased. As a result, it can be used as a material constituting an organic active element having high mobility. That is, if an organic compound crystal into which chalcogen atoms are introduced is used as a material constituting the channel formation region, the performance of the organic transistor as a field effect transistor can be further improved.

  Hereinafter, the present invention will be described based on examples with reference to the drawings.

  Example 1 relates to an organic compound crystal and a field effect transistor of the present invention.

  The organic compound crystal of Example 1 is an organic compound crystal in which a plurality of connecting molecules formed by connecting a first π-electron conjugated molecule and a second π-electron conjugated molecule based on a spiro bond are stacked. . In each connecting molecule, the molecular plane of the first π-electron conjugated molecule and the molecular plane of the second π-electron conjugated molecule are substantially orthogonal as shown in FIG. 1 (in Example 1, orthogonal) )is doing. In addition, when it is assumed that the molecular plane of the first π-electron conjugated molecule and the molecular plane of the second π-electron conjugated molecule are in the same plane, when the functional group has a functional group, The first π-electron conjugated system molecule when it is replaced with and the second π-electron conjugated system molecule when the functional group is replaced with a hydrogen atom when it has a functional group are the first π When rotated 180 degrees around the connection point between the electron conjugated molecule and the second π electron conjugated molecule, they overlap.

Here, the first π-electron conjugated molecule and the second π-electron conjugated molecule are derived from a methylenedithio-tetrathiafulvalene (MDT-TTF) molecule represented by the structural formula (2) and the structural formula (2 ′). The connecting molecule has a structure represented by the structural formula (1). However, R ₁ , R ₂ , R ₃ and R ₄ are hydrogen atoms in Example 1. Hereinafter, the connecting molecule represented by the structural formula (1) is referred to as spiro MDT-TTF. Spiro MDT-TTF has D _2d symmetry. In general, it can be said that the connecting molecule constituting the organic compound crystal of the present invention has approximately D _2d symmetry.

  About spiro MDT-TTF, the feasibility of the orthogonal band structure was investigated by calculation simulation. For band analysis, the first principle electronic state calculation program VASP (Vienna Ab-initio Simulation Package) (G. Kresse and J. Furthmuller, Vienna Ab-initio Simulation Package, see at the website, http: // cms. mpi.univie.ac.at/vasp/vasp/vasp.html), and the density functional method (DFT) based on generalized gradient approximation (GGA) was used.

  FIG. 2 shows a crystal structure of an organic compound crystal obtained by performing structure relaxation by electronic state calculation from an appropriate initial structure. That is, in this organic compound crystal, the first π-electron conjugated molecule and the first π-electron conjugated molecule constituting the adjacent connecting molecule are in a stacked state (arranged in parallel to each other), The second π-electron conjugated molecule and the second π-electron conjugated molecule constituting the adjacent connecting molecule are in a stacked state (arranged in parallel to each other).

  FIG. 3 shows the energy band structure along each stack axis direction at this time. Unlike in the case of BMDT-TTF (see FIG. 9), it was confirmed that an isotropic energy band structure was formed in spiro MDT-TTF.

The first π-electron conjugated molecule and the second π-electron conjugated molecule include a chalcogen atom (sulfur atom, S) as a constituent element, and the first π-electron conjugated molecule constituting the adjacent connecting molecule. The distance between the chalcogen atoms in the second π-electron conjugated molecule constituting the adjacent connecting molecule is short, and the first π-electron conjugated molecule in the adjacent connecting molecule is mutually connected. The connected organic compound crystal has a three-dimensional periodic structure in which second π-electron conjugated molecules in adjacent connecting molecules are connected to each other. That is, when the van der Waals radii of chalcogen atoms (sulfur atoms) in the MDT-TTF constituting the spiro MDT-TTF are r ₁ and r ₂ , the first π-electron conjugated molecule constituting the spiro MDT-TTF Alternatively, the chalcogen atom (X _i ) in MDT-TTF corresponding to the second π-electron conjugated molecule and the first π-electron conjugated molecule (or the spir MDT-TTF adjacent to the spiro MDT-TTF) (or in chalcogen atom and (X _j) in MDT-TTF corresponding to the second π-electron conjugated molecules), the distance R _ij between at least one pair of chalcogen atoms (X _i, X _j) is
R _ij ≦ (r ₁ + r ₂ ) × 1.1 = 3.96Å
Is satisfied. Specifically, examples of the value of R _ij include 3.96Å, 3.95Å, and the like. Further, S (sulfur) which is a chalcogen atom is included in the π-electron conjugated system, is conjugated with the π-electron conjugated system, participates in the π-electron conjugated system, or is added to the π-electron conjugated system. It has been captured. Furthermore, in each π-electron conjugated molecule, S (sulfur) that is a chalcogen atom is arranged on the outer periphery of the π-electron conjugated molecule. The ratio of the total chalcogen atom mass to the molecular weight (C ₇ S ₆ H ₄ : 280.47) of the π-electron conjugated molecule (MDT-TTF) is 40% or more (specifically, 68.6%).

The field effect transistor (FET) of Example 1 includes a channel formation region made of the organic compound crystal described above. The field effect transistor of Example 1 is a so-called bottom gate / top contact type thin film transistor (TFT) having the first structure, and a schematic partial sectional view is shown in FIG. ,
(A) a gate electrode 12 formed on the support 11;
(B) a gate insulating layer 13 formed on the gate electrode 12 and the support 11;
(C) a channel formation region 15 and a channel formation region extension 15A formed on the gate insulating layer 13, and
(D) source / drain electrodes 14 formed on the channel forming region extension 15A;
It has.

  Furthermore, an insulating layer (not shown) is formed on the entire surface, and wiring (not shown) connected to the source / drain electrode 14 is formed on the insulating layer.

  The outline of the method for manufacturing the bottom gate / top contact type TFT of Example 1 will be described below.

[Step-100]
First, an organic compound crystal made of spiro MDT-TTF is prepared. Specifically, referring to the literature Y. Misaki et al., Chem. Lett. 729 (1993), compounds 1 and 2 are synthesized as shown in FIG. Next, by reacting compound 2 with tetraiodomethane, an organic compound crystal composed of spiro MDT-TTF represented by compound 3 can be obtained.

[Step-110]
On the other hand, a gate electrode 12 is formed on a support 11 made of a glass substrate having a SiO ₂ layer (not shown) formed on the surface. Specifically, a resist layer (not shown) from which a portion where the gate electrode 12 is to be formed is formed on the support 11 based on a lithography technique. Thereafter, a titanium (Ti) layer (not shown) as an adhesion layer and a gold (Au) layer as a gate electrode 12 are sequentially formed on the entire surface by vacuum deposition, and then the resist layer is removed. To do. Thus, the gate electrode 12 can be obtained based on a so-called lift-off method.

[Step-120]
Next, the gate insulating layer 13 is formed on the support 11 including the gate electrode 12. Specifically, the gate insulating layer 13 made of SiO ₂ is formed on the gate electrode 12 and the support 11 based on the sputtering method. When forming the gate insulating layer 13, by covering a part of the gate electrode 12 with a hard mask, an extraction portion (not shown) of the gate electrode 12 can be formed without a photolithography process.

[Step-130]
Next, a channel formation region 15 and a channel formation region extension portion 15 </ b> A are formed on the gate insulating layer 13. Specifically, the channel forming region 15 and the channel forming region extending portion 15A are formed on the gate insulating layer 13 based on the above-described method for forming a channel forming region made of an organic compound crystal (for example, vacuum deposition method). Can be formed.

[Step-140]
Thereafter, the source / drain electrode 14 is formed on the channel forming region extension portion 15A so as to sandwich the channel forming region 15 (see FIG. 4A). Specifically, a titanium (Ti) layer (not shown) as an adhesion layer and a gold (Au) layer as a source / drain electrode 14 are sequentially formed on the entire surface based on a vacuum deposition method. When the source / drain electrode 14 is formed, the source / drain electrode 14 can be formed without a photolithography process by covering a part of the channel forming region extending portion 15A with a hard mask.

[Step-150]
Finally, an insulating layer (not shown) as a passivation film is formed on the entire surface, an opening is formed in the insulating layer above the source / drain electrode 14, and a wiring material layer is formed on the entire surface including the inside of the opening. By patterning the wiring material layer, the semiconductor device of Example 1 in which the wiring (not shown) connected to the source / drain electrode 14 is formed on the insulating layer can be completed.

The second embodiment is a modification of the first embodiment. The TFT in Example 2 is a so-called bottom gate / bottom contact type, and a schematic partial cross-sectional view is shown in FIG.
(A) a gate electrode 12 formed on the support 11;
(B) a gate insulating layer 13 formed on the gate electrode 12 and the support 11;
(C) a source / drain electrode 14 formed on the gate insulating layer 13, and
(D) a channel forming region 15 formed on the portion of the gate insulating layer 13 between the source / drain electrodes 14;
It has.

  Hereinafter, an outline of a manufacturing method of the bottom gate / bottom contact type TFT of Example 2 will be described.

[Step-200]
First, a spiro MDT-TTF is obtained in the same manner as in [Step-100] of Example 1. Further, after forming the gate electrode 12 on the support 11 in the same manner as in [Step-110] in Example 1, the gate electrode 12 and the support 11 in the same manner as in [Step-120] in Example 1. A gate insulating layer 13 is formed thereon.

[Step-210]
Next, a source / drain electrode 14 made of a gold (Au) layer is formed on the gate insulating layer 13. Specifically, a resist layer from which a portion where the source / drain electrode 14 is to be formed is removed is formed on the gate insulating layer 13 based on the lithography technique. In the same manner as in [Step-110], a titanium (Ti) layer (not shown) as an adhesion layer and gold (Au) as a source / drain electrode 14 are formed on the resist layer and the gate insulating layer 13. The layers are sequentially formed by vacuum deposition, and then the resist layer is removed. Thus, the source / drain electrode 14 can be obtained based on a so-called lift-off method.

[Step-220]
Thereafter, based on the spiro MDT-TTF obtained in [Step-100], on the part of the gate insulating layer 13 between the source / drain electrodes 14 based on the same method as [Step-130] in Example 1. A channel formation region 15 is formed in the step.

[Step-230]
Finally, the same process as [Step-150] of the first embodiment is performed to complete the semiconductor device of the second embodiment.

The third embodiment is also a modification of the first embodiment. The TFT in Example 3 is a so-called top gate / top contact type, and as shown in a schematic partial sectional view in FIG.
(A) a channel forming region 15 and a channel forming region extending portion 15A formed on the support 11;
(B) source / drain electrodes 14 formed on the channel forming region extension 15A;
(C) a gate insulating layer 13 formed on the source / drain electrode 14 and the channel formation region 15, and
(D) a gate electrode 12 formed on the gate insulating layer 13;
It has.

  The outline of the method for manufacturing the top gate / top contact type TFT of Example 3 will be described below.

[Step-300]
First, a spiro MDT-TTF is obtained in the same manner as in [Step-100] of Example 1.

[Step-310]
On the other hand, a channel forming region 15 and a channel forming region are formed on a support 11 made of a glass substrate having a SiO ₂ layer (not shown) formed on the surface, based on the same method as [Step-130] in Example 1. The extending portion 15A is formed.

[Step-320]
Next, the source / drain electrodes 14 are formed on the channel formation region extension 15 </ b> A so as to sandwich the channel formation region 15. Specifically, a titanium (Ti) layer (not shown) as an adhesion layer and a gold (Au) layer as a source / drain electrode 14 are sequentially formed on the entire surface based on a vacuum deposition method. When the source / drain electrode 14 is formed, the source / drain electrode 14 can be formed without a photolithography process by covering a part of the channel forming region extending portion 15A with a hard mask.

[Step-330]
Next, the gate insulating layer 13 is formed on the source / drain electrodes 14 and the channel formation region 15. Specifically, the gate insulating layer 13 can be obtained by depositing PVA on the entire surface by spin coating.

[Step-340]
Thereafter, the gate electrode 12 is formed on the gate insulating layer 13. Specifically, a titanium (Ti) layer (not shown) as an adhesion layer and a gold (Au) layer as a gate electrode 12 are sequentially formed on the entire surface by vacuum evaporation. When the gate electrode 12 is formed, the gate electrode 12 can be formed without a photolithography process by covering a part of the gate insulating layer 13 with a hard mask. Thus, the structure shown in FIG. 5A can be obtained.

[Step-350]
Finally, the same process as [Step-150] in Example 1 is performed to complete the semiconductor device in Example 3.

The fourth embodiment is also a modification of the first embodiment. The TFT in Example 4 is a so-called top gate / bottom contact type, and a schematic partial sectional view is shown in FIG.
(A) source / drain electrodes 14 formed on the support 11;
(B) a channel forming region 15 formed on the portion of the support 11 between the source / drain electrodes 14;
(C) the gate insulating layer 13 formed on the channel formation region 15, and
(D) a gate electrode 12 formed on the gate insulating layer 13;
It has.

  The outline of the method for manufacturing the top gate / bottom contact type TFT of Example 4 will be described below.

[Step-400]
First, the spiro MDT-TTF is obtained in the same manner as in [Step-100] of Example 2.

[Step-410]
On the other hand, source / drain electrodes are formed on a support 11 made of a glass substrate having a SiO ₂ layer (not shown) formed on the surface. Specifically, a titanium (Ti) layer (not shown) as an adhesion layer and a gold (Au) layer as a source / drain electrode 14 are formed on the support 11 based on a vacuum deposition method. When the source / drain electrode 14 is formed, the source / drain electrode 14 can be formed without a photolithography process by covering a part of the support 11 with a hard mask.

[Step-420]
Thereafter, a channel forming region 15 is formed on the support 11 between the source / drain electrodes 14 based on the same method as [Step-130] of the first embodiment. In the fourth embodiment, actually, a channel forming region extending portion 15 </ b> A is formed on the source / drain electrode 14.

[Step-430]
Next, on the source / drain electrode 14 and the channel formation region 15 (actually on the channel formation region 15 and the channel formation region extension 15A), in the same manner as in [Step-330] of Example 3, A gate insulating layer 13 is formed.

[Step-440]
Thereafter, the gate electrode 12 is formed on the gate insulating layer 13 in the same manner as in [Step-340] in Example 3. Thus, the structure shown in FIG. 5B can be obtained.

[Step-450]
Finally, the same process as [Step-150] of the first embodiment is performed to complete the semiconductor device of the fourth embodiment.

  As mentioned above, although this invention was demonstrated based on the preferable Example, this invention is not limited to these Examples. The structure, configuration, and manufacturing conditions of the semiconductor device are examples, and can be changed as appropriate. When the field effect transistor (TFT) obtained by the present invention is applied to and used in a display device or various electronic devices, a monolithic integrated circuit in which a large number of TFTs are integrated on a support or a support member may be used. The TFT may be cut and individualized and used as a discrete component.

FIG. 1 is a diagram schematically showing the structure of an example of a connecting molecule constituting the organic compound crystal of the present invention [see the structural formula (1) for the structural formula]. FIG. 2 is a diagram showing the crystal structure of the organic compound crystal of Example 1 [see the structural formula (1) for the structural formula of the connecting molecule]. FIG. 3 is a diagram showing an energy band structure along each stack axis direction of the organic compound crystal of Example 1 [see the structural formula (1) for the structural formula of the connecting molecule]. FIGS. 4A and 4B are schematic partial cross-sectional views of field effect transistors having first and second structures. 5A and 5B are schematic partial cross-sectional views of a field effect transistor having third and fourth structures. FIG. 6 is a diagram illustrating a synthesis scheme of spiro MDT-TTF. FIG. 7 is a conceptual diagram showing a herringbone structure which is a layered structure of molecules in an organic compound crystal. FIG. 8 is a conceptual diagram showing a stack structure that is a layered structure of molecules in an organic compound crystal. FIG. 9 is a diagram showing an energy band structure of BMDT-TTF.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 ... Support body, 12 ... Gate electrode, 13 ... Gate insulating layer, 14 ... Source / drain electrode, 15 ... Channel formation region, 15A ... Channel formation region extension part

Claims (8)

A plurality of connecting molecules formed by connecting a first π-electron conjugated molecule and a second π-electron conjugated molecule based on a spiro bond are stacked organic compound crystals,
In each connecting molecule,
(A) The molecular plane of the first π-electron conjugated molecule and the molecular plane of the second π-electron conjugated molecule are substantially orthogonal,
(B) When it is assumed that the molecular plane of the first π-electron conjugated molecule and the molecular plane of the second π-electron conjugated molecule are in the same plane, if the functional group has a functional group, the functional group is The first π-electron conjugated molecule when it is replaced with an atom, and the second π-electron conjugated molecule when the functional group is replaced with a hydrogen atom when it has a functional group are the first When rotated 180 degrees around the connection point between the π-electron conjugated molecule and the second π-electron conjugated molecule, they overlap,
In organic compound crystals,
(C) The first π-electron conjugated molecule and the first π-electron conjugated molecule constituting the adjacent connecting molecule are in a stacked state,
(D) An organic compound crystal, wherein the second π-electron conjugated molecule and the second π-electron conjugated molecule constituting the adjacent connecting molecule are in a stacked state. The first π-electron conjugated molecule and the second π-electron conjugated molecule contain a chalcogen atom as a constituent element,
The distance between chalcogen atoms in the first π-electron conjugated molecule constituting the adjacent connecting molecule is short,
The distance between chalcogen atoms in the second π-electron conjugated molecule constituting the adjacent connecting molecule is short,
It has a three-dimensional periodic structure in which the first π-electron conjugated molecules in adjacent connecting molecules are connected to each other, and the second π-electron conjugated molecules in adjacent connecting molecules are connected to each other. The organic compound crystal according to claim 1. The van der Waals radius of the chalcogen atom in the first or second π electron conjugated system molecule constituting the connecting molecule is r _1, and the first or second π electron conjugated system constituting the connecting molecule adjacent to the connecting molecule. When the van der Waals radius of the chalcogen atom in the molecule is r ₂ , the chalcogen atom (X _i ) in the first or second π-electron conjugated molecule constituting the connecting molecule and the connecting molecule adjacent to the connecting molecule are The distance R _ij between at least one set of chalcogen atoms (X _i , X _j ) with the chalcogen atom (X _j ) in the first or second π-electron conjugated molecule constituting
R _ij ≦ (r ₁ + r ₂ ) × 1.1
The organic compound crystal according to claim 2, wherein: The connecting molecule has the following structural formula (1) [wherein R ₁ , R ₂ , R ₃ and R ₄ represent either a hydrogen atom or an alkyl group having 10 or less carbon atoms]. The organic compound crystal according to claim 1.

A field effect transistor having a channel formation region made of an organic compound crystal,
In the organic compound crystal, a plurality of connecting molecules formed by connecting the first π-electron conjugated molecule and the second π-electron conjugated molecule based on a spiro bond are stacked,
In each connecting molecule,
(A) The molecular plane of the first π-electron conjugated molecule and the molecular plane of the second π-electron conjugated molecule are substantially orthogonal,
(B) When it is assumed that the molecular plane of the first π-electron conjugated molecule and the molecular plane of the second π-electron conjugated molecule are in the same plane, if the functional group has a functional group, the functional group is The first π-electron conjugated molecule when it is replaced with an atom, and the second π-electron conjugated molecule when the functional group is replaced with a hydrogen atom when it has a functional group, are the first When rotated 180 degrees around the connection point between the π-electron conjugated molecule and the second π-electron conjugated molecule, they overlap,
In organic compound crystals,
(C) The first π-electron conjugated molecule and the first π-electron conjugated molecule constituting the adjacent connecting molecule are in a stacked state,
(D) A field effect transistor characterized in that the second π-electron conjugated molecule and the second π-electron conjugated molecule constituting the adjacent connecting molecule are in a stacked state. The first π-electron conjugated molecule and the second π-electron conjugated molecule contain a chalcogen atom as a constituent element,
The distance between chalcogen atoms in the first π-electron conjugated molecule constituting the adjacent connecting molecule is short,
The distance between chalcogen atoms in the second π-electron conjugated molecule constituting the adjacent connecting molecule is short,
It has a three-dimensional periodic structure in which the first π-electron conjugated molecules in adjacent connecting molecules are connected to each other, and the second π-electron conjugated molecules in adjacent connecting molecules are connected to each other. The field effect transistor according to claim 5. The van der Waals radius of the chalcogen atom in the first or second π electron conjugated system molecule constituting the connecting molecule is r _1, and the first or second π electron conjugated system constituting the connecting molecule adjacent to the connecting molecule. When the van der Waals radius of the chalcogen atom in the molecule is r ₂ , the chalcogen atom (X _i ) in the first or second π-electron conjugated molecule constituting the connecting molecule and the connecting molecule adjacent to the connecting molecule are The distance R _ij between at least one set of chalcogen atoms (X _i , X _j ) with the chalcogen atom (X _j ) in the first or second π-electron conjugated molecule constituting
R _ij ≦ (r ₁ + r ₂ ) × 1.1
The field effect transistor according to claim 6, wherein: The connecting molecule has the following structural formula (1) [wherein R ₁ , R ₂ , R ₃ and R ₄ represent either a hydrogen atom or an alkyl group having 10 or less carbon atoms]. 6. The field effect transistor according to claim 5, wherein

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