JP2005123354A - Thin film of electron donor acceptor complex and field effect transistor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a field effect transistor having a high operational performance. <P>SOLUTION: The field effect transistor is equipped with (A) a source/drain electrode 14, (B) a channel forming region layer 16 formed between the source electrode 14 and the drain electrode 14, and (C) a gate electrode 12 provided so as to be opposed to the channel forming region layer 16 through the gate insulating film 13. The channel forming region layer 16 is constituted of a separated lamination type electron donor acceptor complex thin film 15 consisting of an electron-donative donor molecular layer and an electron receptive acceptor molecular layer, laminated sequentially in the direction of thickness of the layer 16. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a charge transfer complex thin film and a field effect transistor.

  When manufacturing a semiconductor device from a conventional silicon semiconductor substrate or the like, a photolithography technique and various thin film forming techniques are used. However, these production techniques are complicated, require a long time for manufacturing the semiconductor device, and are a great obstacle to reducing the manufacturing cost of the semiconductor device. Further, the conventional semiconductor device is so-called bulk, and it is difficult to apply it to a field where flexibility and flexibility are required. Furthermore, as symbolized by Moore's Law, the limits of speeding up (accumulation) are becoming visible.

  Research and development of an electronic element that replaces a semiconductor device based on such a conventional silicon semiconductor substrate, such as a field effect transistor (FET), using an electroconductive polymer material has been eagerly advanced. A new field of inexpensive organic electronics is being developed. Field effect transistors which are one field of such organic electronics are known from, for example, Japanese Patent Application Laid-Open Nos. 7-221313 and 7-249775.

JP-A-7-221313 JP-A-7-249775 "Organic Field Effect Transistors", by Yuval Ofir, Vladimir Burtman, and Shlomo Yitzchaik, in The 66th Annual Meeting of the Israel Chemical Society, Tel-Aviv, February 2001, [Search March 17, 2003], Internet <URL : Http://www.weizmann.ac.il/ICS/chemistry66/024Ofir.html> "Organic Quantum-Confined Structures through Molecular Layer Epitaxy", by V. Burtman, A. Zelichenok, and S. Yitzchaik, Angew. Chem. Int. Ed. 38, 2041-2045 (1999)

  Organic electronics is one of the candidates for post-silicon technology, but in reality, very few examples have been realized. In a field effect transistor (FET) using a conventional organic compound in the channel formation region layer, the operation mechanism itself has not yet been able to obtain a unified interpretation, and its characteristics are also an inorganic substance. From the viewpoint of silicon-based materials, the carrier mobility is currently inferior by three orders of magnitude or more.

  An organic FET having a structure in which channel formation region layers and insulating layers made of epitaxially grown organic thin films are alternately stacked has the latest report that the carrier mobility of conventional organic FETs is more than two orders of magnitude due to the quantum confinement effect. ("Organic Field Effect Transistors", by Yuval Ofir, Vladimir Burtman, and Shlomo Yitzchaik, in The 66th Annual Meeting of the Israel Chemical Society, Tel-Aviv, February 2001. (http://www.weizmann.ac.il See /ICS/chemistry66/024Ofir.html). However, the material composing the channel forming region layer reported in this document is only an aromatic fused compound such as polyacene, and the high carrier mobility has not been verified.

  Accordingly, it is an object of the present invention to provide a field effect transistor having high operating performance and a charge transfer complex thin film suitable for constituting a channel formation region layer of the field effect transistor, although not limited thereto. There is to do.

  In order to achieve the above object, the charge transfer complex thin film of the present invention comprises an electron donating donor molecule layer and an electron accepting acceptor molecule layer, which are sequentially laminated. It is a complex thin film.

In addition, the field effect transistor of the present invention for achieving the above object is
(A) source / drain electrodes,
(B) a channel formation region layer formed between the source / drain electrodes, and
(C) a gate electrode provided to face the channel formation region layer with the gate insulating film interposed therebetween,
A field effect transistor comprising:
The channel forming region layer is composed of a separate layered charge transfer complex thin film in which an electron donating donor molecule layer and an electron accepting acceptor molecule layer are sequentially laminated in the thickness direction. And

  In the field effect transistor of the present invention, the donor molecule and the acceptor molecule layer forming the donor molecule layer are generated by generating an electric field in the thickness direction of the channel formation region layer by applying a voltage to the gate electrode. An incomplete charge transfer state can be induced between the acceptor molecules forming the channel and the channel formation region layer can be in a low resistance state.

  Alternatively, in the field effect transistor of the present invention, the second gate electrode facing the gate electrode is provided facing the channel formation region layer with the second gate insulating film interposed therebetween. You can also In such a configuration, the donor molecule layer is formed by generating an electric field in the thickness direction of the channel formation region layer by applying a voltage to the gate electrode and the second gate electrode. An incomplete charge transfer state is induced between the molecule and the acceptor molecule forming the acceptor molecule layer, so that the channel formation region layer can be in a low resistance state. Note that the gate electrode, the second gate electrode, the channel formation region, and the like are arranged in different horizontal planes, and the gate electrode or the second gate electrode is disposed above the channel formation region. The second gate electrode or the gate electrode may be arranged below, and the gate electrode, the second gate electrode, the channel formation region, etc. are arranged in different vertical planes, and the channel The gate electrode or the second gate electrode may be arranged along one vertical plane of the formation region, and the second gate electrode or the gate electrode may be arranged along the other vertical plane of the channel formation region. it can.

  Here, the incomplete charge transfer state means that 0 <ρ <1, preferably 0.5 <ρ <1, where ρ is the charge transfer amount.

  In the charge transfer complex thin film of the present invention or the field effect transistor of the present invention including the above-mentioned preferred forms (hereinafter, these may be collectively referred to as the present invention), the donor molecular layer is The Z direction (thickness direction) is formed from one donor molecule, and it is preferable that only the donor molecule exists in the XY direction, and the acceptor molecule layer also has one acceptor in the Z direction (thickness direction). It is preferably formed of molecules, and only acceptor molecules are present in the XY directions. That is, the donor molecule forming the donor molecule layer is represented by [D], the acceptor molecule forming the acceptor molecule layer is represented by [A], and the donor molecule and the acceptor forming the donor molecule layer. When the chemical bond with the acceptor molecule forming the molecular layer is represented by “=”, in the present invention, “the donor molecular layer and the acceptor molecular layer are sequentially laminated” means “charge transfer complex thin film” However, it is in the state of [A] = [D] in the thickness direction (that is, the donor molecule layer is one layer, the acceptor molecule layer is also one layer, and the donor molecule layer and the acceptor molecule layer are laminated). Or [A] = [D] = [A] (ie, the donor molecule layer is one layer, the acceptor molecule layer is two layers, the acceptor molecule layer, the donor molecule layer). , Or a state in which [D] = [A] = [D] (that is, the donor molecule layer is two layers and the acceptor molecule layer is one layer, A donor molecule layer, an acceptor molecule layer, and a donor molecule layer are sequentially stacked) or [A] = [D] = [A] = [D] (that is, two donor molecule layers) And the acceptor molecule layer is also composed of two layers, and the acceptor molecule layer, the donor molecule layer, the acceptor molecule layer, and the donor molecule layer are sequentially laminated), or [A] = [D] = [A] = [D]... (That is, the donor molecule layer is a multilayer of two or more layers, the acceptor molecule layer is also a multilayer of two or more layers, and the donor molecule layer and the acceptor molecule layer are Means that the total number of layers is 5 or more)Such a state is called a segregated stack. As a concept contrasting with the separated stack type, an alternating stack type (Mixed stack) is known. Here, the alternately stacked charge transfer complex thin film is in a state of [A] = [D] = [A] = [D]... In a single layer, and a large number of such layers are stacked. Refers to a thin film. In the alternately stacked type, a structure in which layers formed only by the same kind of molecules are not stacked.

  In this specification, the donor molecule “composing” the donor molecule layer refers to the donor molecule before reacting with the acceptor molecule or the like, and the acceptor molecule “composing” the acceptor molecule layer reacts with the donor molecule or the like. Refers to the previous acceptor molecule. On the other hand, a donor molecule that “forms” a donor molecule layer is a donor molecule that has reacted with an acceptor molecule or the like, and refers to a donor molecule that has formed a charge transfer complex thin film. The “forming” acceptor molecule is an acceptor molecule after reacting with a donor molecule or the like, and refers to an acceptor molecule in a state of forming a charge transfer complex thin film.

  The charge transfer complex thin film in the present invention can be formed, for example, by molecular epitaxial growth (Molecular Layer Epitaxy, MLE), or by self-assembly by a solution process. The MLE method is described in "Organic Quantum-Confined Structures through Molecular Layer Epitaxy", by V. Burtman, A. Zelichenok, and S. Yitzchaik, Angew. Chem. Int. Ed. 38, 2041-2045 (1999). Details are described. In brief, first, for example, a substrate treated with an OH terminal is reacted with a silane coupling agent to expose an amino group at the terminal. A donor molecule or an acceptor molecule having a functional group that reacts with an amino group, such as a carboxyl group or an acid anhydride group (two water dehydrated from one carboxyl group) is introduced in the gas phase, Only one donor molecule or acceptor molecule is grown on the coupled surface. Since the carboxyl groups or acid anhydride groups do not react with each other, this growth is limited to only one layer. Subsequently, an acceptor molecule or donor molecule having a functional group that reacts with a carboxyl group or an acid anhydride group is introduced in the gas phase, and only one layer on the donor molecule or acceptor molecule that becomes the new base. Grow. By repeating this operation, for example, a charge transfer complex thin film having a structure of [D] = [A] = [D] = [A]... Can be obtained.

In the present invention including the above preferred embodiment, when the ionization potential of the donor molecule constituting the donor molecule layer is I _D and the electron affinity of the acceptor molecule constituting the acceptor molecule layer is E _A , (I _D − E _A ) = 0.3 ± 0.1 (V) is preferably satisfied. By defining the value of (I _D -E _A ) in this way, a neutral-ionic phase transition can be reliably obtained. FIG. 8 shows a combination of a donor molecule constituting the donor molecule layer having such a value of (I _D -E _A ) and an acceptor molecule constituting the acceptor molecule layer. In FIG. 8, the vertical axis represents the electron affinity (unit: volt) of the acceptor molecule, and the horizontal axis represents the ionization potential (unit: volt) of the donor molecule. Moreover, molecular structures, such as a part of various donor molecules shown in FIG. 8, are shown in FIGS. 9 and 10, and molecular structures such as a part of the acceptor molecule are shown in FIGS. 11, 12, and 13. FIG.

In the present invention including the various preferred embodiments described above, a functional group that generates a chemical bond between a donor molecule constituting the donor molecule layer and an acceptor molecule constituting the acceptor molecule layer is provided with a donor molecule layer. It is preferable that the donor molecule and the acceptor molecule constituting the acceptor molecule layer have, and as the functional group, specifically, —NH ₂ , —COOH, —OH, —COCl, —C═O—O -C = O- can be exemplified. Here, as a combination of (functional group possessed by donor molecule constituting donor molecule layer) / (functional group possessed by acceptor molecule constituting acceptor molecule layer), specifically, (—C═O—O—C ═O —) / (— NH ₂ ), (—COOH) / (— NH ₂ ), (—COOH) / (— OH), (—COCl) / (— OH). Alternatively, as a combination of (donor molecule constituting the donor molecule layer) / (acceptor molecule constituting the acceptor molecule layer), a combination having the following structure can be exemplified. Provided that R, R ′ and R ″ are hydrocarbon chains having n = 0 to 10 carbon atoms. In the chain of R, R ′ and R ″ or at the chain end, an ether group, a thioether group or a carbonyl group , May have a thiocarbonyl group, or may have an aromatic substituent such as a phenyl group in this chain or at the chain end. Further, n = 0 represents a state in which the functional group is directly attached to the mother skeleton.

(—R—C═O—O—C═O—R ′) / (— R ″ —NH ₂ )
(-R-COOH) / (- R'-NH 2)
(-R-COOH) / (-R'-OH)
(-R-COCl) / (-R'-OH)

In the present invention including the various preferred embodiments described above, it is necessary to form a charge transfer complex thin film or a channel forming region layer on a substrate. Here, examples of the substrate include SiO ₂ -based materials. Further, it is necessary to chemically bond the substrate and the donor molecule constituting the donor molecule layer, or it is necessary to chemically bond the substrate and the acceptor molecule constituting the acceptor molecule layer. For this purpose, the surface of the substrate is preferably subjected to, for example, silane coupling treatment. Incidentally, in the charge transfer complex thin film of the present invention, if the outermost surface is terminated with an OH group, a silane coupling treatment is possible. The substrate may be composed of any material. In addition to the SiO ₂ -based material, MO _X (where M represents a metal and X> 0, and more specifically, for example, ZrO ₂ , SnO ₂ , In ₂ O ₃ , Nb ₂ O ₅ , ZnO), or organic insulating materials exemplified by polyvinylphenol (PVP) and polyhydroxyalkyl methacrylate. it can. In the field effect transistor of the present invention, a gate insulating film can be used as the substrate.

Here, as the SiO ₂ material, silicon dioxide (SiO ₂ ), BPSG, PSG, BSG, AsSG, PbSG, silicon oxynitride (SiON), SOG (spin on glass), SiO ₂ material having a low dielectric constant (for example, , Polyaryl ether, cycloperfluorocarbon polymer and benzocyclobutene, cyclic fluororesin, polytetrafluoroethylene, fluorinated aryl ether, fluorinated polyimide, amorphous carbon, and organic SOG).

Physical vapor deposition method (PVD method, Physical Vapor Deposition method) exemplified by vacuum deposition method and sputtering method, and various chemical vapor deposition methods (substrates and gate insulating films made of SiO ₂ materials; CVD method, Chemical Vapor Deposition method); spin coating method; printing method such as screen printing method and inkjet printing method; various coating methods described later; dipping method (dipping method); casting method; be able to.

Alternatively, the gate insulating film can be formed by oxidizing 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. Furthermore, 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 film can also be formed on the surface of the gate electrode by covering the surface of the gate electrode with a sex molecule by a method such as an immersion method.

The silane coupling agent can generally be represented by X—Si (OR) ₃ . Here, “X” means a functional group such as a thiol group (mercapto group), amino group, vinyl group, epoxy group, chloro group, methacryl group, and “OR” means a hydrolyzable group (for example, methoxy group). Or ethoxy group). Specific examples of the silane coupling agent include [(R—O) ₃ Si— (CH ₂ ) _n —NH ₂ ] (where R═CH ₃ , C ₂ H _5, etc.).

  Silane coupling treatment methods include exposing the substrate and gate insulating film to silane coupling agent vapor, dipping the silane coupling agent solution (dipping method), and various coating methods using the silane coupling agent solution. The method of apply | coating, and various printing methods and the method of spin-coating a silane coupling agent solution can be mentioned. Here, as a coating 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 Examples thereof include a coater method, a slit orifice coater method, and a calendar coater method.

  As a constituent material of the gate electrode and the source / drain electrode in the field effect transistor of the present invention, gold (Au), platinum (Pt), silver (Ag), palladium (Pd), rubidium (Rb), rhodium (Rh), Various metals such as aluminum (Al), copper (Cu), nickel (Ni), chromium (Cr), tungsten (W), tantalum (Ta), titanium (Ti), indium (In), tin (Sn), etc. In addition, conductive particles made of these metals, or conductive particles made of these metals, or conductive particles made of alloys containing these metals, or a layered structure of layers containing these elements can be used. Furthermore, various conductive polymers such as poly (3,4-ethylenedioxythiophene) / polystyrene sulfonic acid [PEDOT / PSS] can also be exemplified.

  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; Printing methods such as screen printing and ink jet printing methods using conductive paste and various conductive polymer solutions; various coating methods as described above; lift-off method; shadow mask method; plating such as electrolytic plating method, electroless plating method or a combination thereof And any one of spraying methods, or a combination with a patterning technique as 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.

  The following two types of structures can be illustrated as specific structures of the field effect transistor of the present invention.

That is, the field effect transistor having the first structure is a so-called bottom gate type and a top contact type.
(A) a gate electrode formed on a support;
(B) a gate insulating film (corresponding to a substrate) formed on the gate electrode;
(C) a channel forming region layer formed on the gate insulating film and composed of a separate stacked type charge transfer complex thin film; and
(D) source / drain electrodes formed on the charge transfer complex thin film,
It has.

The field effect transistor having the second structure is a so-called top gate type and a top contact type.
(A) a channel-forming region layer formed on a substrate and composed of a separate stacked charge transfer complex thin film;
(B) source / drain electrodes formed on a separate stacked type charge transfer complex thin film,
(C) a gate insulating film formed on the source / drain electrodes and the channel formation region layer, and
(D) a gate electrode formed on the gate insulating film,
It has.

Other examples of the field effect transistor include a bottom gate type bottom contact type field effect transistor and a top gate type bottom contact type field effect transistor. Here, the bottom gate type bottom contact type field effect transistor is
(A) a gate electrode formed on a support;
(B) a gate insulating film (corresponding to a substrate) formed on the gate electrode;
(C) source / drain electrodes formed on the gate insulating film, and
(D) a channel forming region layer formed on at least a gate insulating film and composed of a separate stacked charge transfer complex thin film, and
It has. The top-gate and bottom-contact field effect transistors are
(A) Source / drain electrodes formed on the substrate,
(B) a channel forming region layer formed on at least a substrate and composed of a separate stacked charge transfer complex thin film;
(C) a gate insulating film formed on the source / drain electrodes and the channel formation region layer, and
(D) a gate electrode formed on the gate insulating film,
It has.

  More specifically, the field effect transistor of the present invention is provided on a support or a support member. As the support or support member, various glass substrates or various glass substrates having an insulating layer formed on the surface thereof are used. And a quartz substrate, a quartz substrate with an insulating layer formed on the surface, and a silicon substrate with an insulating layer formed on the surface. Various glass substrates having an insulating layer formed on the surface, a quartz substrate having an insulating layer formed on the surface, or a silicon substrate having an insulating layer formed on the surface can itself constitute a substrate. Furthermore, examples of the support and the support member include a plastic film, a plastic sheet, and a plastic substrate made of a polymer material exemplified by polyethersulfone (PES), polyimide, polycarbonate, and polyethylene terephthalate (PET). If a support or support member 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 shape. It becomes possible. Further, the field effect transistor 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, a monolithic integrated circuit in which a large number of field effect transistors are integrated on a support or a support member may be used. Transistors may be cut and individualized and used as discrete components.

  The charge transfer complex thin film of the present invention is a separate stacked type charge transfer complex thin film in which an electron donating donor molecular layer and an electron accepting acceptor molecular layer are sequentially stacked. The channel forming region layer is composed of a separate stacked charge transfer complex thin film in which an electron donating donor molecular layer and an electron accepting acceptor molecular layer are sequentially stacked in the thickness direction. In the separated-stack type charge transfer complex thin film or channel forming region layer having such a structure, a neutral-ionic phase transition can be caused by applying an electric field in the thickness direction. That is, charge transfer can be caused at the interface between the donor molecular layer and the acceptor molecular layer. The electric field can be generated, for example, by applying a voltage to the gate electrode. As a result, the separated stacked type charge transfer complex thin film or channel formation region layer that was in a high resistance state before applying an electric field is in a low resistance state. Thus, the field effect transistor of the present invention can be turned on / off. In addition, since such a phase transition occurs quickly, the field effect transistor of the present invention has high operating performance.

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

  Example 1 relates to the separated stacked charge-transfer complex thin film and field effect transistor (hereinafter referred to as FET) of the present invention. This separated stacked charge transfer complex thin film is formed by sequentially stacking an electron donating donor molecule layer and an electron accepting acceptor molecule layer. In Example 1, the donor molecule constituting the donor molecule layer (donor molecule before reacting with the acceptor molecule or the like) has the structure of the formula (1) shown in FIG. 1 and acceptor molecules constituting the acceptor molecule layer. (Acceptor molecule before reacting with a donor molecule or the like) has a structure of the formula (2) shown in FIG.

  In the separated stacked charge transfer complex thin film of Example 1, the donor molecule forming the donor molecule layer (the donor molecule after reacting with the acceptor molecule or the like) is represented by [D] to form the acceptor molecule layer. The acceptor molecule (acceptor molecule after reacting with the donor molecule, etc.) is represented by [A], and the chemical bond between the donor molecule forming the donor molecule layer and the acceptor molecule forming the acceptor molecule layer Is represented by “=”, it is in a state of [D] = [A] = [D] = [A] in the thickness direction of the charge transfer complex thin film. That is, there are two donor molecular layers, two acceptor molecular layers, and a total four-layer structure, in which a donor molecular layer, an acceptor molecular layer, a donor molecular layer, and an acceptor molecular layer are sequentially stacked. Have. Moreover, each layer is formed only by the same kind of molecules.

  The FET of Example 1 was provided to face the channel formation region layer with the source / drain electrode 14, the channel formation region layer 16 formed between the source / drain electrodes 14, and the gate insulating film 13 interposed therebetween. A gate electrode 12 is provided. The channel forming region layer 16 is composed of a separate stacked charge transfer complex thin film 15 in which an electron donating donor molecule layer and an electron accepting acceptor molecule layer are sequentially stacked in the thickness direction. Yes. Note that the separation-type charge transfer complex thin film 15 has the above-described structure and configuration.

More specifically, an implementation having the first structure as shown in FIG. 6B is a schematic partial sectional view when the FET is cut along a virtual vertical plane perpendicular to the extending direction of the gate electrode. The FET of Example 1 is a so-called bottom gate type and top contact type thin film transistor (TFT),
(A) a gate electrode 12 formed on a support (more specifically, on a support 11 provided on a support member 10);
(B) a gate insulating film 13 (corresponding to a substrate) formed on the gate electrode 12 and the support 11;
(C) a channel forming region layer 16 formed on the gate insulating film 13 and composed of a separate stacked type charge transfer complex thin film 15, and
(D) a source / drain electrode 14 formed on the charge transfer complex thin film 15;
It has.

In the FET of Example 1, the donor molecule and the acceptor molecule layer forming the donor molecule layer are generated by generating an electric field in the thickness direction of the channel forming region layer 16 by applying a voltage to the gate electrode 12. Induces an incomplete charge transfer state (specifically, the value of ρ is 0.5 <ρ <1 when the amount of charge transfer is ρ). As a result, the channel formation region layer 16 changes from the high resistance state to the low resistance state. More specifically, the resistance value of the channel formation region layer 16 when no voltage is applied to the gate electrode 12 is R ₀ , and the resistance value of the channel formation region layer 16 when a voltage of 10 volts is applied to the gate electrode 12. When R ₁ is set, the value of R ₁ / R ₀ is approximately 10 ⁶ or more.

  Hereinafter, first, a method for forming a separate stacked charge transfer complex thin film of Example 1 will be described with reference to the conceptual diagrams of FIGS. 2A, 2B, 3 and 4. FIG.

[Step-10]
First, the surface of the substrate 1 composed of the SiO ₂ layer is hydrogen-terminated (see FIG. 2A). As a result, the surface of the substrate 1 is terminated with a hydroxyl group. Specific examples of the hydrogen termination method include piranha solution treatment, oxygen plasma treatment, and UV-ozone treatment.

[Step-20]
Next, surface treatment using a silane coupling agent is performed on the SiO ₂ layer as the substrate 1 (see FIG. 2B). Accordingly, when the charge transfer complex thin film is formed in the next step, the charge transfer complex thin film can be self-assembled (epitaxial growth). The silane coupling agent has, for example, the following structural formula (3). Here, R denotes an alkyl group such as CH _3, C ₂ H _5. For example, the substrate 1 is immersed in a dry toluene solution of 3-aminopropyltrimethoxysilane (concentration 3 mmol, temperature 80 to 100 ° C.) for 6 to 10 hours, whereby the alkoxy group of the silane coupling agent and the substrate 1 The hydroxyl group reacts to form a chemical bond, and the surface of the substrate 1 has a structure in which an amino group appears at the terminal. Note that (CH ₂ ) _n in the formula (3) is indicated by “R ₀ ” in the drawing.

(R—O) ₃ Si— (CH ₂ ) _n —NH ₂ (3)

[Step-30]
Thereafter, only one layer of a donor molecular layer or an acceptor molecular layer is epitaxially grown on the surface of the substrate 1 surface-treated with a silane coupling agent based on a chemical reaction. FIG. 3 shows a state in which only one donor molecule layer is epitaxially grown based on the donor molecules constituting the donor molecule layer represented by the formula (1) in FIG. In addition, it is preferable that the donor molecule which comprises the donor molecule layer to laminate | stack has a functional group which reacts with a hydroxyl group, for example, and produces a chemical bond, for example, -COCl, at the both ends of a molecule | numerator. Specifically, a molecular epitaxial growth method (Molecular Layer Epitaxy method) in a gas phase process can be used, and a self-organization method in a liquid phase process can be used. In these methods, the donor molecules or acceptor molecules do not form a bond with each other, and a chemical bond can be formed only between the functional group of the donor molecule and the functional group of the acceptor molecule. Only one layer of donor molecules can be epitaxially grown on the surface of the substrate 1.

  Next, when only one donor molecule layer is epitaxially grown, for example, an acceptor molecule having an hydroxyl group at both ends and constituting an acceptor molecule layer (acceptor molecule shown by the formula (2) in FIG. 1). Based on the above, only one acceptor molecular layer is epitaxially grown on the donor molecular layer. This state is shown in FIG. In the case where only one acceptor molecular layer is epitaxially grown, for example, based on donor molecules that have —COCl at both ends and constitute the donor molecular layer, only one donor molecular layer is formed on the acceptor molecular layer. Epitaxially grow. Specifically, a molecular epitaxial growth method (Molecular Layer Epitaxy method) in a gas phase process can be used, and a self-organization method in a liquid phase process can be used. In these methods, the donor molecules or acceptor molecules do not form a bond with each other, and a chemical bond can be formed only between the functional group of the donor molecule and the functional group of the acceptor molecule. Only one acceptor molecular layer can be epitaxially grown on the donor molecular layer.

  Hereinafter, by sequentially reacting the donor molecule constituting the donor molecule layer and the acceptor molecule constituting the acceptor molecule layer, a desired number of layers (in Example 1, two acceptor molecule layers and two acceptor molecule layers are formed). A separate stacked charge transfer complex thin film having a donor molecular layer) can be formed.

  Hereinafter, with reference to FIGS. 5A to 5D and FIGS. 6A to 6B which are schematic partial cross-sectional views of a support and the like, a method for manufacturing the FET of Example 1 will be described. explain.

[Step-100]
First, a gate electrode is formed on a support. Specifically, a pattern for forming a gate electrode is formed on a support 11 made of polyethersulfone (PES) bonded to a support member 10 made of a silicon substrate based on a resist layer 21 ((A in FIG. 5). )reference).

  Next, a titanium (Ti) layer as an adhesion layer and a gold (Au) layer as a gate electrode 12 are formed on the support 11 and the resist layer 21 by a vacuum deposition method (see FIG. 5B). In the drawings, the adhesion layer is not shown. When vapor deposition is performed, the support member 10 to which the support 11 is bonded is placed on a support holder that can adjust the temperature, and the increase in the support temperature during vapor deposition can be suppressed. Film formation with minimal deformation of the support 11 can be performed.

  Thereafter, the resist layer 21 is removed by a lift-off method, whereby the gate electrode 12 can be obtained (see FIG. 5C).

[Step-110]
Next, a gate insulating film 13 corresponding to a base is formed over the support 11 including the gate electrode 12 (see FIG. 5D). Specifically, the gate insulating film 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 film 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. Further, when the gate insulating film 13 is formed, the support member 10 to which the support 11 is bonded is placed on a support holder whose temperature can be adjusted, and the support temperature during the SiO ₂ film formation is set. Therefore, it is possible to perform film formation with minimal deformation of the support 11.

[Step-120]
Next, a charge transfer complex thin film 15 is formed on the gate insulating film 13 corresponding to the substrate (see FIG. 6A). Specifically, [Step-10] to [Step-30] may be executed.

[Step-130]
Next, a titanium (Ti) layer as an adhesion layer and a gold (Au) layer as a source / drain electrode 14 are formed on the charge transfer complex thin film 15 by a vacuum deposition method (see FIG. 6B). In the drawings, the adhesion layer is not shown. By covering a part of the charge transfer complex thin film 15 with a hard mask, the source / drain electrode 14 can be formed without a photolithography process. When vapor deposition is performed, the support member 10 to which the support 11 is bonded is placed on a support holder that can adjust the temperature, and the increase in the support temperature during vapor deposition can be suppressed. Film formation with minimal deformation of the support 11 can be performed.

[Step-140]
Thereafter, an interlayer insulating layer is formed on the entire surface, and wirings connected to the source / drain electrodes and the gate electrode are formed on the interlayer insulating layer, whereby an FET (more specifically, a TFT) can be completed. .

The second embodiment is a modification of the FET of the first embodiment. The FET of Example 2 has the second structure. That is, as shown in FIG. 7A, which is a schematic partial cross-sectional view when the FET is cut along a virtual vertical plane perpendicular to the extending direction of the gate electrode, the FET of Example 2 is a so-called top gate. Type and top contact type TFT,
(A) a channel forming region layer 16 formed on the substrate 111 and composed of a separate stacked charge transfer complex thin film 15;
(B) a source / drain electrode 14 formed on a separate stacked type charge transfer complex thin film 15;
(C) a gate insulating film 13 formed on the source / drain electrode 14 and the channel formation region layer 16, and
(D) a gate electrode 12 formed on the gate insulating film 13,
It has.

  The FET of the second embodiment is thus different in structure from the FET of the first embodiment, but the materials constituting each component can be the same as the FET of the first embodiment. Therefore, detailed description of the FET of Example 2 is omitted. The outline of the method for manufacturing the FET of Example 2 will be described below.

[Step-200]
First, similarly to [Step-120] of Example 1, to form a charge transfer complex thin film 15 on a substrate 111 made of SiO _2. The base body 111 made of SiO ₂ is formed on the surface of the support member 10 made of a silicon substrate.

[Step-210]
Next, the source / drain electrodes 14 are formed on the charge transfer complex thin film 15 in the same manner as in [Step-130] of Example 1.

[Step-220]
Thereafter, the gate insulating film 13 is formed on the source / drain electrodes 14 and the charge transfer complex thin film 15 in the same manner as in [Step-110] in Example 1.

[Step-230]
Next, the gate electrode 12 is formed on the gate insulating film 13 in the same manner as in [Step-100] in Example 1.

[Step-240]
Thereafter, an interlayer insulating layer 30 made of SiO ₂ is formed on the entire surface, and then an opening is formed in the interlayer insulating layer 30 above the gate electrode 12 and the source / drain electrode 14, and the interlayer insulating layer 30 including the inside of these openings is formed. A wiring material layer is formed thereon, and this wiring material layer is patterned to form a wiring (not shown) connected to the gate electrode 12 and a wiring 31 connected to the source / drain electrode 14. Thus, the FET of Example 2 shown in FIG. 7A can be obtained.

  Example 3 is also a modification of the FET of Example 1. As shown in FIG. 7B, a schematic partial cross-sectional view when the FET is cut along a virtual vertical plane perpendicular to the extending direction of the gate electrode is shown, the FET of Example 3 faces the gate electrode 12. A second gate electrode 41 is provided to face the channel formation region layer 16 with the second gate insulating film 40 interposed therebetween. Note that the gate electrode 12, the second gate electrode 41, the channel formation region 16 and the like are arranged in different horizontal planes, and the second gate electrode 41 is disposed above the channel formation region 16 to form the channel. The gate electrode 12 is arranged below the region 16.

Specifically, the FET of Example 3 is
(A) a gate electrode 12 formed on a support (more specifically, on a support 11 provided on a support member 10);
(B) a gate insulating film 13 (corresponding to a substrate) formed on the gate electrode 12 and the support 11;
(C) a channel forming region layer 16 formed on the gate insulating film 13 and composed of a separate stacked type charge transfer complex thin film 15;
(D) a source / drain electrode 14 formed on the charge transfer complex thin film 15;
(E) a second gate insulating film 40 formed on the source / drain electrode 14 and the channel formation region layer 16, and
(F) a second gate electrode 41 formed on the second gate insulating film 40;
It has.

  Also in the FET of Example 3, an electric field is generated in the thickness direction of the channel formation region layer 16 by applying a voltage to the gate electrode 12 and the second gate electrode 41, thereby forming a donor molecular layer. An incomplete charge transfer state is induced between the molecule and the acceptor molecule forming the acceptor molecule layer, so that the channel forming region layer 16 is brought into a low resistance state.

  The FET of Example 3 is obtained by executing [Step-100] to [Step-130] of Example 1 and then executing [Step-220] to [Step-240] of Example 2. Therefore, detailed description is omitted.

  As mentioned above, although this invention was demonstrated based on the preferable Example, this invention is not limited to these Examples. In Example 1 to Example 3, the donor molecule layer has two layers and the acceptor molecule layer has a four-layer structure. However, the structure of the channel formation region layer in the charge transfer complex thin film or the field effect transistor is as follows. However, the present invention is not limited to this, and it may be a two-layer structure having at least one donor molecule layer and one acceptor molecule layer. The constituent material and manufacturing method of the charge transfer complex thin film, the structure, the constituent material, and the manufacturing method of the field effect transistor are examples, and can be changed as appropriate.

FIG. 1 is a diagram showing the structural formulas of donor molecules constituting the donor molecule layer and acceptor molecules constituting the acceptor molecule layer used in the formation of the separated stacked charge transfer complex thin film of Example 1. 2A and 2B are conceptual diagrams for explaining a process of forming the separated stacked charge transfer complex thin film of Example 1. FIG. FIG. 3 is a conceptual diagram for explaining the step of forming the separated stacked charge transfer complex thin film of Example 1 following FIG. FIG. 4 is a conceptual diagram for explaining the process of forming the separated stacked charge transfer complex thin film of Example 1 following FIG. 3. 5A to 5D are schematic partial cross-sectional views of a support and the like for explaining the method for manufacturing the field-effect transistor of Example 1. FIG. 6A and 6B are schematic partial cross-sectional views of a support and the like for explaining the method for manufacturing the field effect transistor of Example 1 following FIG. 5D. . FIGS. 7A and 7B are schematic partial cross-sectional views of the field effect transistors of Example 2 and Example 3, respectively. FIG. 8 illustrates a combination of a donor molecule constituting the donor molecule layer and an acceptor molecule constituting the acceptor molecule layer satisfying a value of (I _D −E _A ) = 0.3 ± 0.1 (V). It is a graph. FIG. 9 is a diagram showing molecular structures of various donor molecules shown in FIG. FIG. 10 is a diagram showing molecular structures of various donor molecules shown in FIG. FIG. 11 is a diagram showing the molecular structures of the various acceptor molecules shown in FIG. FIG. 12 is a diagram showing the molecular structures of the various acceptor molecules shown in FIG. FIG. 13 is a diagram showing the molecular structures of the various acceptor molecules shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Base | substrate, 10 ... Support member, 11 ... Support body, 111 ... Base | substrate, 12 ... Gate electrode, 13 ... Gate insulating film, 14 ... Source / drain electrode, DESCRIPTION OF SYMBOLS 15 ... Separation | stacking type | mold charge transfer complex thin film, 16 ... Channel formation area layer, 21 ... Resist layer, 30 ... Interlayer insulation layer, 31 ... Wiring, 40 ... 2nd Gate insulating film, 41 ... second gate electrode

Claims (13)

A separated-stacked charge transfer complex thin film comprising an electron-donating donor molecular layer and an electron-accepting acceptor molecular layer sequentially stacked. The charge transfer complex thin film according to claim 1, wherein the donor molecular layer and the acceptor molecular layer are each formed by an epitaxial growth method or a self-organization method. When the ionization potential of the donor molecule constituting the donor molecule layer is I _D and the electron affinity of the acceptor molecule constituting the acceptor molecule layer is E _A , (I _D −E _A ) = 0.3 ± 0.1 (V The charge transfer complex thin film according to claim 1, wherein: The donor molecule constituting the donor molecule layer and the acceptor molecule constituting the acceptor molecule layer have a functional group that causes a chemical bond between the donor molecule constituting the donor molecule layer and the acceptor molecule constituting the acceptor molecule layer. The charge transfer complex thin film according to claim 1, wherein The combination of (functional group possessed by donor molecule constituting donor molecule layer) / (functional group possessed by acceptor molecule constituting acceptor molecule layer) is (-C═O—O—C═O —) / (— NH ₂ ), (—COOH) / (— NH ₂ ), (—COOH) / (— OH), (—COCl) / (— OH), The charge transfer complex thin film according to claim 4 . (A) source / drain electrodes,
(B) a channel formation region layer formed between the source / drain electrodes, and
(C) a gate electrode provided to face the channel formation region layer with the gate insulating film interposed therebetween,
A field effect transistor comprising:
The channel forming region layer is composed of a separate layered charge transfer complex thin film in which an electron donating donor molecule layer and an electron accepting acceptor molecule layer are sequentially laminated in the thickness direction. A field effect transistor. By applying a voltage to the gate electrode, an electric field is generated in the thickness direction of the channel formation region layer, so that a non-adhesion is formed between the donor molecule forming the donor molecule layer and the acceptor molecule forming the acceptor molecule layer. 7. The field effect transistor according to claim 6, wherein a complete charge transfer state is induced, so that the channel forming region layer is brought into a low resistance state. 7. The field effect transistor according to claim 6, wherein a second gate electrode facing the gate electrode is provided facing the channel formation region layer with a second gate insulating film interposed therebetween. . The donor molecule forming the donor molecule layer and the acceptor molecule layer are formed by generating an electric field in the thickness direction of the channel formation region layer by applying a voltage to the gate electrode and the second gate electrode. 9. The field effect transistor according to claim 8, wherein an incomplete charge transfer state is induced between the molecules and the channel forming region layer is brought into a low resistance state. The field effect transistor according to claim 6, wherein the donor molecular layer and the acceptor molecular layer are each formed by an epitaxial growth method or a self-organization method. When the ionization potential of the donor molecule constituting the donor molecule layer is I _D and the electron affinity of the acceptor molecule constituting the acceptor molecule layer is E _A , (I _D −E _A ) = 0.3 ± 0.1 (V The field effect transistor according to claim 6, wherein: The donor molecule constituting the donor molecule layer and the acceptor molecule constituting the acceptor molecule layer have a functional group that causes a chemical bond between the donor molecule constituting the donor molecule layer and the acceptor molecule constituting the acceptor molecule layer. The field effect transistor according to claim 6, wherein The combination of (functional group possessed by donor molecule constituting donor molecule layer) / (functional group possessed by acceptor molecule constituting acceptor molecule layer) is (-C═O—O—C═O —) / (— NH _{2), (- COOH) /} (- NH 2), (- COOH) / (- OH), (- COCl) / (- OH) field effect transistor according to claim 12, characterized in that the .

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