Semiconductor device with layer containing polysiloxane compound Number:7,435,989 from the United States Patent and Trademark Office (PTO) owispatent

Title: Semiconductor device with layer containing polysiloxane compound

Abstract: Provided is a semiconductor device including: a substrate; a layer containing one or more kinds of polymer compounds on the substrate; and an organic semiconductor layer in contact with the layer containing the one or more kinds of polymer compounds, in which at least one kind of the one or more kinds of polymer compounds is a polymer compound having one or more secondary or tertiary aliphatic amino groups, wherein the one or more aliphatic amino groups of the polymer compound having the aliphatic amino groups are bound to at least one of a side chain or a branched chain, and wherein said the layer containing the one or more kinds of polymer compounds contains polysiloxane compounds. With the constitution, a semiconductor device excellent in crystallinity and orientation can be provided.

Patent Number: 7,435,989 Issued on 10/14/2008 to Nakayama,   et al.

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Inventors:	Nakayama; Tomonari (Yokohama, JP), Masumoto; Akane (Yokohama, JP), Go; Shintetsu (Yokohama, JP), Ohnishi; Toshinobu (Yokohama, JP)
Assignee:	Canon Kabushiki Kaisha (Tokyo, JP)
Appl. No.:	11/514,922
Filed:	September 5, 2006

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Foreign Application Priority Data

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Sep 06, 2005 [JP]			2005-258567

Current U.S. Class:	257/40
Current International Class:	H01L 29/08 (20060101); H01L 35/24 (20060101); H01L 51/00 (20060101)
Field of Search:	257/40

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References Cited [Referenced By]

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U.S. Patent Documents

5266222	November 1993	Willis et al.
5324543	June 1994	Ogawa et al.
5659181	August 1997	Bridenbaugh et al.
6617609	September 2003	Kelley et al.
6963080	November 2005	Afzali-Ardakani et al.
7094625	August 2006	Miura et al.
7140321	November 2006	Nakayama et al.
7193237	March 2007	Aramaki et al.
2004/0048188	March 2004	Hatanake et al.
2004/0197699	October 2004	Nakayama et al.
2004/0238816	December 2004	Tano et al.
2005/0001210	January 2005	Lee et al.
2005/0032268	February 2005	Nishikawa et al.
2005/0194588	September 2005	Sasaki et al.
2005/0202348	September 2005	Nakayama et al.
2006/0081880	April 2006	Miyazaki et al.
2006/0113523	June 2006	Kubota et al.
2006/0145141	July 2006	Miura et al.
2006/0214159	September 2006	Nakayama et al.
2007/0012914	January 2007	Miura et al.
2007/0034861	February 2007	Nakamura
2007/0085072	April 2007	Masumoto et al.
2007/0096079	May 2007	Nakayama et al.

Foreign Patent Documents

	5-55568		Mar., 1993		JP
	5-190877		Jul., 1993		JP
	8-264805		Nov., 1996		JP
	2003-304014		Oct., 2003		JP
	2004-6750		Jan., 2004		JP
	2004-253681		Sep., 2004		JP
	2005-32774		Feb., 2005		JP
	2005-509299		Apr., 2005		JP
	WO 2004091001		Oct., 2004		WO
	WO 2005029605		Mar., 2005		WO
	WO 2005086254		Sep., 2005		WO

Other References

T Akiyama, et al., "Synthesis of .pai.-system-expanded compounds using Diels-Alder reactions", Proceedings of the 81st Annual Spring Meeting of the Chemical Society of Japan, 2002, II, p. 990, 2F9-14. (with translation). cited by other . Christos D. Dimitrakopoulos, et al., "Organic Thin Film Transistors for Large Area Electronics", Advanced Materials, vol. 14, No. 2, Jan. 16, 2002, pp. 99-117. cited by other . Kaname Ito, et al., "Oligo(2,6-anthrylene)s: Acene-Oligomer Approach for Organic Field-Effect Transistors", Angew. Chem. Int. Ed., vol. 42, No. 10, 2003, pp. 1159-1162. cited by other.

Primary Examiner: Jackson; Jerome
Assistant Examiner: Ho; Anthony
Attorney, Agent or Firm: Fitzpatrick, Cella, Harper & Scinto

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Claims

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What is claimed is:

1. A semiconductor device comprising: a substrate; a layer containing one or more kinds of polymer compounds on the substrate; and an organic semiconductor layer in contact with the layer containing the one or more kinds of polymer compounds, wherein at least one kind of the one or more kinds of polymer compounds comprises a polymer compound having one or more secondary or tertiary aliphatic amino groups, wherein the one or more aliphatic amino groups is present in at least one of a side chain and a branched chain of the polymer compound having the one or more aliphatic amino groups, wherein the layer containing the one or more kinds of polymer compounds contains polysiloxane compounds, and wherein at least one kind of the polysiloxane compounds comprises a compound having a siloxane structure represented by any one of the following general formula (4), the following general formula (5), and the following general formula (6): ##STR00058## where R.sub.15, R.sub.16, R.sub.19, R.sub.20, R.sub.22, R.sub.25, R.sub.26, and R.sub.28 each in dependently represent a hydrogen atom, a substituted or unsubstituted alkyl group, alkenyl group, or alkynyl group having 1 to 12 carbon atoms, a benzyl group, a phenethyl group, or a styryl group; any one combination of R.sub.15 and R.sub.16, R.sub.19 and R.sub.20, R.sub.19 and R.sub.22, and R.sub.25 and R.sub.26 may bind to each other to form a ring structure; one of R.sub.15 and R.sub.16 represents a substituent except a hydrogen atom; R.sub.17, R.sub.21, R.sub.23, R.sub.27, and R.sub.29 each represent a divalent organic group which has 1 to 12 carbon atoms and which is not directly bound to an aromatic ring; R.sub.18, R.sub.24, and R.sub.30 each represent a hydroxyl group, a substituted or unsubstituted alkyl group, alkenyl group, alkynyl group, or alkoxyl group having 1 to 12 carbon atoms, a benzyl group, a phenethyl group, a styryl group, or a siloxane unit; r, s, and t each represent an integer of 1 or more; and u represents an integer of 2 or more.

2. The semiconductor device according to claim 1, wherein the organic semiconductor layer comprises a low-molecular weight organic semiconductor.

3. The semiconductor device according to claim 1, wherein the organic semiconductor layer comprises one of an acene-based compound or a porphyrin compound.

4. The semiconductor device according to claim 1, wherein a first surface of the layer containing the one or more kinds of polymer compounds is in contact with the organic semiconductor layer, and a second surface of the layer containing the one or more kinds of polymer compounds is in contact with an organic resin layer, said first and second surfaces being opposite to one another.

5. The semiconductor device according to claim 1, wherein the layer containing the one or more kinds of polymer compounds is a crystallization promoting layer.

6. The semiconductor device according to claim 5, wherein the crystallization promoting layer has a function of promoting bonding between crystal grains.

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Description

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BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a semiconductor device having an organic semiconductor.

2. Description of the Related Art

The development of a thin film transistor using an organic semiconductor has gradually become active since the latter half of the 1980s. In addition, the basic performance of a thin film transistor using an organic semiconductor has recently exceeded the basic performance of a thin film transistor using amorphous silicon. An organic material can be easily processed in many cases, and often has a high affinity for a flexible plastic substrate on which a thin film field effect transistor (FET) is formed. Therefore, the organic material is an attractive material for a semiconductor layer in a device requested to have flexibility or a light weight. The following organic semiconductor materials have been heretofore investigated. A first example is an acene-based compound such as pentacene or tetracene disclosed in Japanese Patent Application Laid-Open No. H05-55568. A second example is any one of phthalocyanines each containing lead phthalocyanine disclosed in Japanese Patent Application Laid-Open No. H05-190877. A third example is a low-molecular weight compound such as perylene or a tetracarboxylic acid derivative of perylene. A fourth example is any one of: aromatic oligomers typified by a thiophene hexamer referred to as .alpha.-thienyl or sexithiophene disclosed in Japanese Patent Application Laid-Open No. H08-264805; and polymer compounds such as polythiophene, polythienylenevinylene, and poly-p-phenylenevinylene. It should be noted that most of those materials are described in Advanced Material, 2002, no. 2, p. 99 to 117.

Properties requested for producing a device using any one of those compounds in its semiconductor layer such as non-linear optical property, conductivity, and semiconductivity largely depend on not only the purity of a material for the device but also the crystallinity and orientation of the material. An organic material showing good semiconductor property is generally a compound with an expanded .pi. conjugated system. Meanwhile, a compound with an expanded .pi. conjugated system is generally insoluble or hardly soluble in a solvent. For example, pentacene has high crystallinity and is insoluble in a solvent, so a pentacene thin film is generally formed by employing a vacuum vapor deposition method. As a result, a pentacene thin film showing a high field effect mobility is obtained. However, when the vacuum vapor deposition method is employed, the good processability of an organic material is not sufficiently exerted because of, for example, the large size of an apparatus for the method and a long time period needed for the production of a film.

Meanwhile, there has been also reported an FET using a film obtained by: forming a thin film of a soluble precursor for pentacene through application; and transforming the precursor into pentacene through a heat treatment (see US 2003/0136964 A1).

Further, it has been reported that tetrabenzoporphyrin obtained by heating porphyrin, in which a bulky bicyclo[2.2.2]octadiene skeleton undergoes ring condensation, at 210.degree. C. or higher can be used as an organic semiconductor (speech proceedings II of the 81st spring annual meeting of the Chemical Society of Japan, 2002, p. 990 (2F 9-14), Japanese Patent Application Laid-Open No. 2003-304014, and Japanese Patent Application Laid-Open No. 2004-6750). Although the field effect mobility of an organic semiconductor layer described in any one of those documents is high, the high field effect mobility is realized merely on a silicon substrate or a glass substrate identical to amorphous silicon or the like. Meanwhile, the formation of an organic semiconductor layer stably showing a high mobility even on a resin substrate plays an important role in the realization of a flexible device taking advantage of the characteristics of an organic material.

A known method of forming an organic semiconductor layer stably showing a high mobility is a method involving controlling an interface between a gate insulating layer and the organic semiconductor layer. For example, in Japanese Patent Application Laid-Open No. 2005-32774, the threshold voltage of an organic semiconductor layer to be formed on a gate insulating layer is controlled by causing a silane compound having various substituents to chemically adsorb on the gate insulating layer. In this case, a uniform interface can be formed on an inorganic insulating layer made of SiO.sub.2 or the like, but it has been difficult to cause a silane compound to chemically adsorb to the surface of an organic insulating layer. In addition, Japanese Patent Application Laid-Open No. 2005-509299 discloses a field effect transistor in which a layer composed of polydimethylsiloxane is formed between a gate insulating layer and an organic semiconductor layer. However, no material allowing the formation of a uniform polymer layer on an organic insulating layer and the formation of an organic semiconductor layer on the polymer layer through application has been found. Further investigation into the obtainment of an optimum crystalline orientation with a view to increasing a carrier mobility is probably needed for the obtainment of stable properties of an organic semiconductor even on a flexible substrate.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a semiconductor device having an organic semiconductor layer provided with excellent crystallinity and excellent orientation. It is another object of the present invention to provide a field effect transistor with a high field effect mobility. In addition, according to the present invention, there can be provided a method of producing a semiconductor device with which the above semiconductor device can be obtained through a simple process.

According to one aspect of the present invention, there is provided a semiconductor device including: a substrate; a layer containing one or more kinds of polymer compounds on the substrate; and an organic semiconductor layer in contact with the layer containing the one or more kinds of polymer compounds, in which at least one kind of the one or more kinds of polymer compounds is a polymer compound having one or more secondary or tertiary aliphatic amino groups, wherein the one or more aliphatic amino groups of the polymer compound having the aliphatic amino groups at least one of a side chain and a branched chain, and wherein the layer containing the one or more kinds of polymer compounds contains polysiloxane compounds.

Here, only one kind of a polymer compound may be used, or two or more kinds of polymer compounds may be used as a mixture. In addition, only one kind of the respective polymer compounds may have an aliphatic amino group, or two or more kinds of the polymer compounds may each have an aliphatic amino group. Each of the polymer compounds may have multiple kinds of amino groups in itself. Of course, neither use of a compound having a primary amino group nor use of a compound having no amino group is excluded as long as the requirements described in the scope of claims are satisfied.

Here, the term "polysiloxane compound" refers to a polymer having a siloxane structure (--Si--O--). In addition, the polysiloxane compounds to be used in the present invention each preferably have an organic silane structure. In addition, each of the polysiloxane compounds is preferably a polymer compound having one or more secondary or tertiary aliphatic amino groups. It is needless to say that each of the polysiloxane compounds may be used as a polymer compound except a polymer compound having one or more secondary or tertiary aliphatic amino groups.

In further aspect of the semiconductor device of the present invention, at least one kind of the polysiloxane compounds contains a structure represented by the following general formula (1):

##STR00001##

where R.sub.1 to R.sub.4 each represent a substituted or unsubstituted alkyl group or alkenyl group having 1 to 8 carbon atoms, a substituted or unsubstituted phenyl group, or a siloxane unit; R.sub.1 to R.sub.4 may be identical to or different from one another; and n represents an integer of 1 or more.

The term "substituted or unsubstituted" as used in the specification and the scope of claims means that a hydrogen atom, methyl group, or methylene group in a group or unit of interest may be substituted by any other atom or group. Examples of the other atom or group include a halogen atom, a hydroxyl group, a cyano group, a phenyl group, a nitro group, a mercapto group, and a glycidyl group. When a methyl group or a methylene group is substituted, the number of carbon atoms refers to the number of carbon atoms after the substitution (that is, the actual number of carbon atoms).

In further aspect of the semiconductor device of the present invention, at least one kind of the polysiloxane compounds contains one of a structure represented by the following general formula (2) and a structure represented by the following general formula (3):

##STR00002##

where R.sub.7 to R.sub.10 each represent a substituted or unsubstituted alkyl group or alkenyl group having 1 to 8 carbon atoms, or a substituted or unsubstituted phenyl group; R.sub.7 to R.sub.10 may be identical to or different from each other; m and n each represent an integer of 0 or more; and a sum of m and n represents an integer of 1 or more;

##STR00003##

where R.sub.11 to R.sub.14 each represent a substituted or unsubstituted alkyl group or alkenyl group having 1 to 8 carbon atoms, or a substituted or unsubstituted phenyl group; R.sub.11 to R.sub.14 may be identical to or different from each other; p and q each represent an integer of 0 or more; and a sum of p and q represents an integer of 1 or more.

The term "or" is a concept including the term "and". Therefore, it is needless to, say that the case where at least one kind of the polysiloxane compounds has both the structure represented by the general formula (2) and the structure represented by the general formula (3) is also included in the present invention.

In further aspect of the semiconductor device of the present invention, at least one kind of the polysiloxane compounds contains one or more of siloxane structures represented by the following general formula (4), the following general formula (5), and the following general formula (6):

##STR00004##

where R.sub.15, R.sub.16, R.sub.19, R.sub.20, R.sub.22, R.sub.25, R.sub.26, and R.sub.28 each independently represent a hydrogen atom, a substituted or unsubstituted alkyl group, alkenyl group, or alkynyl group having 1 to 12 carbon atoms, a benzyl group, a phenethyl group, or a styryl group; any one combination of R.sub.15 and R.sub.16, R.sub.19 and R.sub.20, R.sub.19 and R.sub.22, and R.sub.25 and R.sub.26 may bind to each other to form a ring structure; one of R.sub.15 and R.sub.16 represents a substituent except a hydrogen atom; R.sub.17, R.sub.21, R.sub.23, R.sub.27, and R.sub.29 each represent a divalent organic group which has 1 to 12 carbon atoms and which is not directly bound to an aromatic ring; R.sub.18, R.sub.24, and R.sub.30 each represent a hydroxyl group, a substituted or unsubstituted alkyl group, alkenyl group, alkynyl group, or alkoxyl group having 1 to 12 carbon atoms, a benzyl group, a phenethyl group, a styryl group, or a siloxane unit; r, s, and t each represent an integer of 1 or more; and u represents an integer of 2 or more.

In further aspect of the semiconductor device of the present invention, at least one kind of the polysiloxane compounds contains one or more of silsesquioxane structures each containing a skeleton represented by any one of the following general formula (7), the following general formula (8), and the following general formula (9):

##STR00005##

where R.sub.31, R.sub.32, R.sub.34, R.sub.35, R.sub.37, R.sub.39, R.sub.40, and R.sub.42 each independently represent a hydrogen atom, a substituted or unsubstituted alkyl group, alkenyl group, or alkynyl group having 1 to 12 carbon atoms, a benzyl group, a phenethyl group, or a styryl group; any one combination of R.sub.31 and R.sub.32, R.sub.34 and R.sub.35, R.sub.34 and R.sub.37, and R.sub.39 and R.sub.40 may bind to each other to form a ring structure; one of R.sub.31 and R.sub.32 represents a substituent except a hydrogen atom; R.sub.33, R.sub.36, R.sub.38, R.sub.41, and R.sub.43 each represent a divalent organic group which has 1 to 12 carbon atoms and which is not directly bound to an aromatic ring; v, w, and x each represent an integer of 1 or more, and y represents an integer of 2 or more.

In further aspect of the semiconductor device of the present invention, the organic semiconductor layer is composed of a low-molecular weight organic semiconductor.

In further aspect of the semiconductor device of the present invention, the organic semiconductor layer is composed of one of an acene-based compound and a porphyrin compound.

In further aspect of the semiconductor device of the present invention, a surface opposite to a surface of the layer containing the one or more kinds of polymer compounds in contact with the organic semiconductor layer is in contact with an organic resin layer.

An appropriate combination of the foregoing characteristics is also within the scope of the present invention.

Further features of the present invention will become apparent from the following description of exemplary embodiments (with reference to the attached drawings).

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A, 1B and 1C are each a schematic sectional view showing an example of a field effect transistor as a preferred embodiment of the present invention.

DESCRIPTION OF THE EMBODIMENTS

According to the present invention, there can be provided a semiconductor device excellent in crystallinity and orientation.

The present invention is additionally effective when a semiconductor device is a field effect transistor because a semiconductor device having a high field effect mobility can be obtained.

Hereinafter, the present invention will be described in detail by taking a field effect transistor as an example of a semiconductor device. It is needless to say that an effect of the present invention is valid for not only a field effect transistor but also a general semiconductor device. In addition, a numeral provided for a member the description of which is omitted in each figure to which reference is made indicates a member having the same numeral as that provided for a figure to which reference is made in the following description of the present invention.

A field effect transistor according to this embodiment is a device having at least an organic semiconductor, an insulator, and conductors. The insulator is an insulating film (i.e., layer) for covering the conductors serving as electrodes. The organic semiconductor is an organic semiconductor layer that responds to a stimulus (i.e., electric field) generated by the conductor (i.e., electrode). To be specific, the organic semiconductor layer is a layer, the electrical characteristics of which change with an electric field. To be more specific, the organic semiconductor layer is a layer, the conductivity of which, that is, the amount of a current passing through the organic semiconductor layer, changes with a change in electric field.

FIG. 1A is a schematic sectional drawing showing an example of the field effect transistor according to this embodiment. Reference numeral 8 represents a substrate; 1, a gate electrode; 2, a gate insulating layer; 3, a polymer compound-containing layer; 4, a source electrode; 5, a drain electrode; 6, an organic semiconductor layer; and 7, a sealing layer. In the device, the gate electrode 1 is provided on the surface of the substrate 8, the gate insulating layer 2 is provided on the gate electrode 1, the polymer compound-containing layer 3 is provided on the surface of the gate insulating layer 2, and the source electrode 4 and the drain electrode 5 are provided on a surface of the polymer compound-containing layer 3 so as to be separated from each other. In addition, the organic semiconductor layer 6 is provided on the source electrode 4, the drain electrode 5, and the polymer compound-containing layer serving as a separation region between the electrodes, so as to be in contact with both the electrodes 4 and 5. The gate insulating layer 2 is provided to cover the gate electrode 1. Further, the organic semiconductor layer 6 is covered with the sealing layer 7. The substrate 8 and the sealing layer 7 may be interchanged with each other.

In the field effect transistor, when a voltage is applied to the gate electrode, positive or negative charge is induced at a region in the vicinity of an interface between the gate insulating layer and the organic semiconductor layer. (In this way, the region where charge is induced is called channel.) Further, when a voltage is applied between the source electrode and the drain electrode, charge moves between both the electrodes through the channel, thereby generating a current. Therefore, if charge is uniformly generated at the channel when a voltage is applied to the gate electrode, barriers become small and therefore charge can be moved efficiently when a voltage is applied between the source electrode and the drain electrode, thereby making the transistor exhibit a high field effect mobility.

The inventors of the present invention have made extensive studies to find a method of forming an organic semiconductor layer interface which allows charge to be uniformly generated and allows the generated charge to move efficiently. As a result, the inventors have found that, a specific polymer-containing layer 3 is formed so as to be adjacent to the channel (near the interface on the side of the gate insulating layer 2 of the organic semiconductor layer 6 in FIG. 1A), whereby a crystal which is uniform with little defects can be continuously formed at the interface, so a high field effect mobility is exhibited.

A field effect transistor as a preferred embodiment of the present invention includes at least: a substrate; a layer containing one or more kinds of polymer compounds on the substrate; and an organic semiconductor layer in contact with the layer containing the one or more kinds of polymer compounds, in which at least one kind of the one or more kinds of polymer compounds is a polymer compound having one or more secondary or tertiary aliphatic amino groups.

The layer containing the one or more kinds of polymer compounds of the present invention has only to contain a polymer compound having one or more secondary or tertiary aliphatic amino groups, and may contain two or more kinds of polymer compounds as long as the layer maintains sufficient uniformity. Examples of the case where the layer contains two or more kinds of polymer compounds include: the case where the layer simultaneously contains two or more kinds of polymer compounds each having one or more secondary or tertiary aliphatic amino groups; and the case where the layer simultaneously contains one or more kinds of polymer compounds each having one or more secondary or tertiary aliphatic amino groups and one or more kinds of polymer compounds each having none of a secondary aliphatic amino group and a tertiary aliphatic amino group. It is needless to say that the other cases are also within the scope of the present invention.

In the field effect transistor as a preferred embodiment of the present invention, a polymer layer containing a polymer compound having one or more secondary or tertiary aliphatic amino groups (herein after referred to as "A layer") and the organic semiconductor layer (hereinafter referred to as "B layer") are preferably laminated so that the layers are brought into close contact with each other in part, or the entire surface, of the device, that is, the transistor. Here, the term "close contact" refers to a state where the A layer and the B layer are adjacent to each other with no gap at least partially. The crystallization of the B layer is promoted by laminating the A layer so that the A layer is brought into close contact with the B layer, whereby the field effect transistor of the present invention shows a high field effect mobility. Accordingly, the A layer can be generally referred to as a crystallization promoting layer. It should be noted that the term "crystallization promoting layer" as used in the scope of claims and the specification is defined as a layer that not only merely promotes crystallization but also has such crystallization promoting function as described later.

In addition, as described later, the use of a solvent-soluble organic semiconductor material or organic semiconductor precursor enables each of the A layer and the B layer to be produced by using an applying step, so a device can be produced through a simple process.

It should be noted that, according to the present invention, a base structure on which the A layer is formed (the structure is generally a structure composed of a substrate, a gate electrode, and a gate insulating layer. Note that, the gate insulating layer can be omitted in some cases, the structure can be composed only of the substrate depending on a lamination order, or other layers may be formed in the structure) may be referred to as a substrate. In addition, according to the present invention, the term "function of promoting crystallization" refers to a function of promoting stabilization of crystal grains (which may involve the movement and rotation of the crystal grains) and/or bonding between the crystal grains. In addition, according to the present invention, the term "crystallization promoting layer" refers to a layer promoting stabilization of crystal grains (which may involve the movement and rotation of the crystal grains) and/or bonding between the crystal grains.

Hereinafter, the B layer is formed on the A layer. However, the present invention is not limited thereto. It is preferable to form the B layer on the A layer from the viewpoint of imparting an influence of the A layer during the formation of the B layer.

A polymer compound of the present invention has only to have one or more secondary or tertiary aliphatic amino groups. An excessive carrier derived from an impurity and present at an interface between the A layer and a gate insulating layer can be trapped owing to an effect of the basicity of an amino group. As a result, an off-state, current can be suppressed, and an On/Off ratio can be increased. However, a primary aliphatic amino group has high hydrophilicity. Accordingly, when one attempts to obtain the effect, the hydrophobicity of the surface of the A layer is lost, with the result that a promoting, effect on the crystallization of the organic semiconductor layer is lost. On the other hand, a secondary or tertiary aliphatic amino group has high hydrophobicity because a nitrogen atom is substituted by a group except hydrogen such as an alkyl group. Accordingly, amino groups are not unevenly distributed on the surface of the A layer, a reduction in hydrophobicity can be prevented, and an excessive carrier migrating from the interface between the A layer and the gate insulating layer can be trapped in the A layer. As a result, a suppressing effect on an off-state current becomes large. The secondary or tertiary aliphatic amino group described here is a group represented by each of the following formulae where R's each represent an alkyl group, an alkenyl group, an alkynyl group, or a substituent an aromatic ring of which is not directly connected to the nitrogen atom of an amino group such as a benzyl group, a phenethyl group, or a styryl group. More specifically, R's may each represent an arbitrary substituent unless R's are directly connected to any one of a hydrogen atom, an aromatic ring, a carbonyl group, and a sulfonyl group. In addition, R's may bind to each other to form a ring structure, or R's may form a double bond between them to provide an imino group. However, when R's bind to each other to form a ring structure, an aromatic heterocyclic ring such as a pyridine ring, a pyrazine ring, or a triazine ring is excluded. One or more of R's each represent an organic group which is divalent or more, and an amino group is incorporated into the molecular chain of a polymer through the organic group. Suitable examples of the remaining R includes, but not limited to, an alkyl group, an alkenyl group, an alkynyl group, a benzyl group, a phenethyl group, and a styryl group. It should be noted that the basicity constant Kb of an amino group is preferably 1.times.10.sup.-7 to 1.times.10.sup.-2 because the amino group must have some degree of basicity for suppressing an off-state current. Therefore, a polymer compound having one or more secondary or tertiary aliphatic amino groups is used in the A layer of the present invention.

##STR00006##

The number of moles of a secondary or tertiary amino group in 100 g of the polymer compound having an aliphatic amino group of the present invention is preferably of 0.003 or more to 0.4 or less. When the number of moles is less than 0.003, secondary or tertiary amino groups are hardly uniformly present on the surface of the A layer, so the crystal growth of the B layer may be nonuniform. When the number of moles exceeds 0.4, the surface of the A layer is made hydrophilic, so a crystallization promoting effect may be lost.

The polymer compound containing a secondary or tertiary aliphatic amino group may additionally have a primary amino group as long as the compound has one or more secondary or tertiary aliphatic amino groups.

The polymer compound having an aliphatic amino group of the present invention refers to an oligomer or polymer having a number average molecular weight of preferably 200 or more. The number average molecular weight is more preferably 500 or more to 1,000,000 or less. The structure of the oligomer or polymer may be any one of a linear structure, a cyclic structure, a branched structure, a ladder type structure, a crosslinked structure, and a dendrimer structure, and these structures can be arbitrarily combined.

The polymer compound having an aliphatic amino group of the present invention has only to have one or more secondary or tertiary aliphatic amino groups in at least one molecular chain selected from a main chain, a side chain, or a branched chain. Here, the case where the compound has an aliphatic amino group in a branched chain refers to the case where it is hard to determine which chain is a main chain or a side chain such as the case where the polymer compound has a dendritic structure.

Examples of a polymer compound having a secondary or tertiary aliphatic amino group in the main chain include polyalkyleneamines such as polyethylene imine, and copolymers of the polyalkyleneamines. In addition, the main skeleton of a polymer compound having a secondary or tertiary aliphatic amino group in a side chain can be selected from arbitrary skeletons such as polyacrylate, polymethacrylate, polyvinyl ether, polystyrene, polycycloolefin, polyether, polyester, polyallylate, polyamide, polyamideimide, polyimide, polyketone, polysulfone, polyphenylene, polysilicon, polysiloxane, cyclic polysiloxane, and ladder type polysiloxane, and copolymers obtained by combining these skeletons. Examples of the main skeleton of a polymer compound having a secondary or tertiary aliphatic amino group in a branched chain include a polyamideamine dendrimer and hyper-branched polyamide.

It is more preferable that one or more secondary or tertiary aliphatic amino groups be bound to at least one of a side chain and a branched chain. The presence of secondary or tertiary aliphatic amino groups on at least one of a side chain and a branched chain enables amino groups to be uniformly present near the surface of the A layer upon formation of the A layer. As a result, both an excessive carrier derived from an impurity at an interface between the A layer and the B layer and an excessive carrier derived from an impurity and migrating from the gate insulating layer can be efficiently trapped. In addition, at least one of a side chain and a branched chain each having a secondary or tertiary aliphatic amino group exerts an additional promoting effect on crystal growth.

A more preferable example of the polymer compound having an aliphatic amino group of the present invention is a polymer compound having a siloxane skeleton. The polymer compound having a siloxane skeleton is a polymer having a siloxane structure (--Si--O--) and an organic silane structure. That is, a polysiloxane compound may be a copolymer with any other organic polymer or inorganic polymer as long as the compound has those structures. In the case of a copolymer with any other polymer, each of the siloxane structure and the organic silane structure may be present in a main chain, or may be present in aside chain owing to, for example, graft polymerization. The combination of the siloxane structure (--Si--O--) and the organic silane structure can aid the crystallization promoting effect of a secondary or tertiary aliphatic amino group. It should be noted that the organic silane structure is a structure in which Si and C are directly bound to each other.

Potential examples of the structure of the polysiloxane compound to be suitably used in the present invention include various structures such as a straight-chain structure and a cyclic structure. The polysiloxane compound of the present invention more preferably has a highly crosslinked or branched structure. The term "highly crosslinked or branched structure" as used herein includes a network-like structure, a ladder-like structure, a cage-like structure, a star-like structure, and a dendritic structure. There is no need to form the crosslinked or branched structure through a siloxane structure, and a structure in which organic groups such as a vinyl group, an acryloyl group, an epoxy group, and a cinnamoyl group mutually crosslink is also included in the structure. In addition, the structure may include a structure branched through an organic group which is trivalent or more.

In the layer of the polysiloxane compound to be suitably used in the present invention, amino groups can be uniformly distributed in the polysiloxane compound by introducing a secondary or tertiary aliphatic amino group into a highly crosslinked or branched structure at the time of polymerization. Further, unlike a monomolecular layer obtained by causing an active group on the surface of a base material to react with octyltrichlorosilane, hexamethyldisilazane, aminopropyltrialkoxysilane, or the like, the uniform distribution does not depend on the state or shape of the surface of a substrate. As a result, an amorphous layer can be formed on a wide area. Accordingly, the interface between the A layer and the B layer becomes uniform in a wide range comparable to or larger than at least a region in which a channel is formed. In addition, as a result of coupling with an effect of the combination of the siloxane structure and the organic silane structure described above, a continuously uniform crystal having a small number of defects is formed.

The polysiloxane compound to be suitably used for the A layer in the present invention has, for example, a structure represented by the following general formula (1) and its main chain is a siloxane unit and any one of its side chains is a substituent having a hydrogen atom or an organic group such as a carbon atom.

##STR00007##

where R.sub.1 to R.sub.4 each represent a substituted or unsubstituted alkyl group or alkenyl group having 1 to 8 carbon atoms, a substituted or unsubstituted phenyl group, or a siloxane unit; R.sub.1 to R.sub.4 may be identical to or different from each other; n represents an integer of preferably 1 or more, or more preferably 5 or more to 100,000 or less, and it may be impossible to form the A layer which is thin and uniform when n is less than 5 or larger than 100,000.

Each of the substituents R.sub.1 to R.sub.4 may be the siloxane units such as those shown below.

##STR00008##

In the formulae, R's each represent a substituted or unsubstituted alkyl group or alkenyl group having 1 to 8 carbon atoms, a substituted or unsubstituted phenyl group, or a siloxane unit as shown above. R's may be the same functional group or may be different functional groups, respectively.

The shape of the polysiloxane may be of a linear structure, a cyclic structure, a network-like structure, a ladder-like structure, a cage-like structure, or the like, depending on the kinds of substituents in the general formula (1). The polysiloxane to be used in the present invention may be of any of the structures. It is preferable that the shape of the polysiloxane be of the network structure, the ladder-like structure, or the cage-like structure.

Particularly preferable as the polysiloxane compound to be used for the A layer in the present invention is a polysiloxane compound having at least a specific silsesquioxane skeleton represented by the following general formula (2) and/or a specific organosiloxane skeleton represented by the following general formula (3).

##STR00009##

In the formula, R.sub.7 to R.sub.10 each represent a substituted or unsubstituted alkyl group or alkenyl group having 1 to 8 carbon atoms, or a substituted or unsubstituted phenyl group. R.sub.7 to R.sub.10 may be identical to or different from each other. Integers m and n each represent an integer of 0 or more, and the sum of m and n represents an integer of 1 or more. A copolymerization form may be random copolymerization or block copolymerization.

##STR00010##

In the formula, R.sub.11 to R.sub.14 each represent a substituted or unsubstituted alkyl group or alkenyl group having 1 to 8 carbon atoms, or a substituted or unsubstituted phenyl group. R.sub.11 to R.sub.14 may be identical to or different from each other. Integers p and q each represent an integer of 0 or more, and the sum of p and q represents an integer of 1 or more.

The polysiloxane compound may contain one or both of the silsesquioxane skeleton represented by the general formula (2) and the organosiloxane skeleton represented by the general formula (6).

In addition, the substituents R.sub.7 to R.sub.10 and R.sub.11 to R.sub.14 having carbon atoms corresponding to the side chains of the silsesquioxane skeleton and the organosiloxane skeleton each represent a substituted or unsubstituted alkyl group or alkenyl group having 1 to 8 carbon atoms, or a substituted or unsubstituted phenyl group. Those substituents may be the same functional group or may be different functional groups depending on sites. Examples of such a functional group include: an unsubstituted alkyl group such as a methyl group or an ethyl group; an

unsubstituted phenyl group; and a substituted phenyl group such as a dimethylphenyl group or a naphthyl group. The substituents R.sub.7 to R.sub.10 each may contain various atoms such as an oxygen atom, a nitrogen atom, and a metal atom as well as a carbon atom and a hydrogen atom.

The general formula (2) represents a structural formula having a structure in which m silsesquioxane units (hereinafter, referred to as first units) each having the substituents R.sub.7 and R.sub.8 are repeated and a structure in which n silsesquioxane units (hereinafter, referred to as second units) each having the substituents R.sub.9 and R.sub.10 are repeated are connected. It should be noted that integers m and n each represent an integer of 0 or more, and the sum of m and n represents an integer of 1 or more. The formula does not mean that the repeated first units and the repeated second units are separated. Both the units may be separately connected or may be connected while being intermingled at random.

The general formula (3) shows a structural formula in which p repetitive diorganosiloxane units each having the substituents R.sub.11 and R.sub.12 (hereinafter referred to as "first units") and q repetitive diorganosiloxane units each having the substituents R.sub.13 and R.sub.14 (hereinafter referred to as "second units") are connected. It should be noted that p and q each represent an integer of 0 or more and the sum of p and q represents an integer of 1 or more. However, this does not mean that the repetition of the first units and the repetition of the second units are separated from each other. Both units may be connected to each other while being separated from each other, or may be connected to each other while being mixed with each other at random.

In addition, a secondary or tertiary amino group can be introduced into the polysiloxane compound to be used in the present invention when the compound contains at least one of siloxane structures each represented by, for example, the following general formula (4), the following general formula (5), or the following general formula (6):

##STR00011##

where R.sub.15, R.sub.16, R.sub.19, R.sub.20, R.sub.22, R.sub.25, R.sub.26, and R.sub.28 each independently represent a hydrogen atom, a substituted or unsubstituted alkyl group, alkenyl group or alkynyl group having 1 to 12 carbon atoms, a benzyl group, a phenethyl group, or a styryl group; any one combination of R.sub.15 and R.sub.16, R.sub.19 and R.sub.20, R.sub.19 and R.sub.22, and R.sub.25 and R.sub.26 may bind to each other to form a ring structure; one of R.sub.15 and R.sub.16 represents a substituent except a hydrogen atom; R.sub.17, R.sub.21, R.sub.23, R.sub.27, and R.sub.29 each represent a divalent organic group which has 1 to 12 carbon atoms and which is not directly bound to an aromatic ring; R.sub.18, R.sub.24, and R.sub.30 each represent a hydroxyl group, a substituted or unsubstituted alkyl group, alkenyl group, alkynyl group, or alkoxyl group having 1 to 12 carbon atoms, a benzyl group, a phenethyl group, a styryl group, or a siloxane unit; r, s, and t each represent an integer of 1 or more; and u represents an integer of 2 or more.

A polysiloxane compound containing at least one of silsesquioxane structures each represented by the following general formula (7), the following general formula (8), or the following general formula (9) is particularly preferably used in the A layer:

##STR00012##

where R.sub.31, R.sub.32, R.sub.34, R.sub.35, R.sub.37, R.sub.39, R.sub.40, and R.sub.42 each independently represent a hydrogen atom, a substituted or unsubstituted alkyl group, alkenyl group, or alkynyl group having 1 to 12 carbon atoms, a benzyl group, a phenethyl group, or a styryl group; any one combination of R.sub.31 and R.sub.32, R.sub.34 and R.sub.35, R.sub.34 and R.sub.37, and R.sub.39 and R.sub.40 may bind to each other to form a ring structure; one of R.sub.31 and R.sub.32 represents a substituent except a hydrogen atom; R.sub.33, R.sub.36, R.sub.38, R.sub.41, and R.sub.43 each represent a divalent organic group which has 1 to 12 carbon atoms and which is not directly bound to an aromatic ring; v, w, and x each represent an integer of 1 or more; and y represents an integer of 2 or more.

One kind of those polysiloxane compounds can be used alone, or multiple kinds of them can be blended before use. In addition, one polysiloxane compound may have multiple kinds of the above units. In addition, one or more polysiloxane compounds may be blended with any other polymer compound or low-molecular weight compound.

Hereinafter, a method of forming the A layer of the present invention from the above polysiloxane compound will be described.

A preferable example of the A layer in the present invention is a layer mainly containing a polysiloxane compound having at least one of such silsesquioxane skeleton as represented by the general formula (2) and such organosiloxane skeleton as represented by the general formula (3). Examples of a method of forming such layer include a method involving: applying, onto a substrate, a solution containing polyorganosilsesquioxane compounds represented by the following general formula (10) and the following general formula (11) or one of the formulae and/or polyorganosiloxane compounds represented by the following general formula (12) and the following general formula (13) or one of the formulae; and drying the applied film under heat. The examples further include a method involving: applying, onto a substrate, a sol obtained by hydrolyzing a silicon monomer in which the numbers of repetition a, b, c, and d each represent 1 among the compounds represented by the following general formulae (10), (11), (12), and (13); and drying the applied sol under heat.

In the former method involving drying the applied film under heat, the polyorganosilsesquioxane compounds represented by the general formula (10) and the general formula (11) are condensed by a dehydration or dealcoholization reaction to be connected in a ladder fashion. On the other hand, the polyorganosiloxane compounds represented by the following general formula (12) and the following general formula (13) are similarly condensed by a dehydration or dealcoholization reaction to provide an increased molecular weight. At this time, however, the temperature at which the applied film is dried is not so high that organic matter completely disappears. Accordingly, a raw material compound obtains not a complete silica structure but a silsesquioxane skeleton or organosiloxane skeleton as represented by the general formula (2) or (3) in which most part of substituents remain.

The polyorganosilsesquioxane compounds represented by the general formulae (10) and (11) and the polyorganosiloxane compounds represented by the general formulae (12) and (13) may be those commercially available. Those polyorganosilsesquioxane compounds and the polyorganosiloxane compounds may be synthesized via reactions represented by the following reaction formulae (14) and (15).

##STR00013##

The above-mentioned reaction formulae (14) and (15) will be described. A trifunctional organic silicon monomer and/or a bifunctional organic silicon monomer each having an organic group R' are/is hydrolyzed in a solvent such as alcohol to produce a silanol compound. The silicon monomer shown in the above-mentioned reaction formulae is an alkoxide from which R''OH is eliminated by hydrolysis. A chloride of the silicon monomer may also be used, however, in this case, hydrogen chloride is generated as an eliminated component. The silanol compound obtained by hydrolysis is further subjected to dehydration condensation through heating or the like to produce a polyorganosilsesquioxane compound and a polyorganosiloxane compound. Removal of the solvent, a catalyst, and the like leads to the isolation of the polyorganosilsesquioxane compound and the polyorganosiloxane compound as solids. The structures, molecular weights, kinds of terminal groups, and the like of the resultant compounds can be changed by a catalyst, a solvent, a pH, a concentration, and the like employed at the time of the reactions.

##STR00014##

where R.sub.7 and R.sub.8 each represent a substituted or unsubstituted alkyl group or alkenyl group having 1 to 8 carbon atoms, or a substituted or unsubstituted phenyl group; R.sub.7 and R.sub.8 may be identical to or different from each other; R.sub.44 to R.sub.47 each represent an alkyl group having 1 to 4 carbon atoms or a hydrogen atom; and a represents an integer of 1 or more.

##STR00015##

where R.sub.9 and R.sub.10 each represent a substituted or unsubstituted alkyl group or alkenyl group having 1 to 8 carbon atoms, or a substituted or unsubstituted phenyl group; R.sub.9 and R.sub.10 may be identical to or different from each other; R.sub.48 to R.sub.51 each represent an alkyl group having 1 to 4 carbon atoms or a hydrogen atom; and b represents an integer of 1 or more.

##STR00016##

where R.sub.11 and R.sub.12 each represent a substituted or unsubstituted alkyl group or alkenyl group having 1 to 8 carbon atoms, or a substituted or unsubstituted phenyl group; R.sub.11 and R.sub.12 may be identical to or different from each other; R.sub.52 and R.sub.53 each represent an alkyl group having 1 to 4 carbon atoms or a hydrogen atom; and c represents an integer of 1 or more.

##STR00017##

where R.sub.13 and R.sub.14 each represent a substituted or unsubstituted alkyl group or alkenyl group having 1 to 8 carbon atoms, or a substituted or unsubstituted phenyl group; R.sub.13 and R.sub.14 may be identical to or different from each other; R.sub.54 and R.sub.55 each represent an alkyl group having 1 to -4 carbon atoms or a hydrogen atom; and d represents an integer of 1 or more.

The method involving applying a sol obtained by hydrolyzing a silicon monomer onto a substrate and drying the applied sol under heat will be described. The silicon monomer described herein includes the trifunctional silicon monomer shown in the general formulae (16), (17), (18), and (19) and/or the bifunctional silicon monomer shown in the reaction formulae (20) and (21), which are/is stirred in a solvent in the coexistence of water at room temperature or under heat, whereby sol is prepared through hydrolysis and dehydration condensation reactions similar to those in the reaction formulae (14) and (15). Heating of the applied film of the resultant sol leads to condensation of silanol and unreacted alkoxides through a dehydration or dealcoholization reaction. Thus, a dense silsesquioxane or organosiloxane skeleton such as one represented by the general formula (2) or (3) is formed.

##STR00018##

where R.sub.7 to R.sub.10 each represent a substituted or unsubstituted alkyl group or alkenyl group having 1 to 8 carbon atoms, or a substituted or unsubstituted phenyl group; R.sub.7 to R.sub.10 may be identical to or different from each other; and R.sub.56 to R.sub.59 each represent an alkyl group having 1 to 4 carbon atoms or a hydrogen atom.

##STR00019##

where R.sub.11 to R.sub.14 each represent a substituted or unsubstituted alkyl group or alkenyl group having 1 to 8 carbon atoms, or a substituted or unsubstituted phenyl group; R.sub.11 to R.sub.14 may be identical to or different from each other; and R.sub.60 and R.sub.61 each independently represent an alkyl group having 1 to 4 carbon atoms or a hydrogen atom.

Representative examples of a silicon monomer that can be used for preparing a sol include a trifunctional silicon monomer and a bifunctional silicon monomer. Examples of the trifunctional silicon monomer include methyltrimethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, butyltrimethoxysilane, vinyltrimethoxysilane, 3-aminopropyltriethoxysilane, and phenyltrimethoxysilane. Examples of the bifunctional silicon monomer include dimethyldimethoxysilane and diphenyldimethoxysilane.

In addition, a small amount of fluorine-containing silicon monomer such as trifluoropropyltrimethoxysilane, heptadecafluorodecyltrimethoxysilane, or tridecafluorooctyltrimethoxysilane can be added.

Water is preferably added upon preparation of a sol. The pH of a solution changes depending on the concentration of an amino group in the polymer of the present invention and on the addition amount of water, whereby the hydrolysis of a monomer is promoted. The addition amount of water is 0.1 to 20 equivalents with respect to an OR'' group of the monomer in the reaction formula (14) or the reaction formula (15).

In addition, a polyorganosilsesquioxane compound represented by the general formula (10) or the general formula (11), a polyorganosiloxane compound represented by the general formula (12) or the general formula (13), and a silicon monomer in the reaction formula (14) or the reaction formula (15) can be used as a mixture in this case, as in the case of the preparation of a sol, water can be added. The addition amount of water is preferably 0.1 to 20 equivalents with respect to an OR'' group of the monomer.

Further, a tetrafunctional silicon monomer such as tetramethoxysilane or tetraethoxysilane can be used in combination for improving application property or solvent resistance after heating.

A method of introducing a secondary or tertiary amino group into the above polysiloxane compound of which the A layer of the present invention is formed will be described.

The general formulae (4), (5), and (6) each represent a structure in polysiloxane of which the A layer is formed, and the polysiloxane preferably contains at least one of the structures each represented by any one of the general formulae (4), (5), and (6). R.sub.15, R.sub.16, R.sub.19, R.sub.20, R.sub.22, R.sub.25, R.sub.26, and R.sub.28 may represent substituents different from each other, and R.sub.15 and R.sub.16, R