JP2009029746A - Organic materials and semiconductor devices - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a semiconductor device which constitutes a semiconductor layer by using an organic material having high freedom of molecular design and high adaptability to various processes, while exhibiting high carrier mobility. <P>SOLUTION: The semiconductor device has a semiconductor layer constituted by using an organic material comprising a skeleton of structural formula (2). <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an organic material and a semiconductor device including a semiconductor layer made of an organic material, and more particularly to an organic material and a semiconductor device that are highly adaptable to a process.

  In recent years, a semiconductor device including a semiconductor layer made of an organic material has attracted attention. Such a semiconductor device can coat and form a semiconductor layer at a lower temperature than a structure including a semiconductor layer made of an inorganic material. For this reason, it is advantageous for increasing the area, and can be formed on a flexible substrate having no heat resistance such as plastic, and it is expected to reduce the cost as well as increase the number of functions.

Currently, polyacene compounds such as anthracene, naphthacene, and pentacene shown in the following structural formula are widely studied as organic materials constituting the semiconductor layer.

  These acene compounds have high crystallinity because the cohesive force due to the intermolecular interaction utilizing C—H... Π is strong between adjacent molecules. And, in a solid, it is a packing style of a herringbone structure in which molecules are in contact with each other at their faces and sides. As a result, it has been reported that high carrier mobility and excellent semiconductor device characteristics are exhibited (see Non-Patent Document 1 below).

  However, in general, the packing of the herringbone structure is disadvantageous for carrier conduction from the viewpoint of overlapping molecular orbitals, compared to packing of a π stack structure in which molecular surfaces are aligned in parallel. It is said.

  Therefore, by introducing bulky substituents to the pentacene skeleton, a method for packing the pentacene mother skeleton responsible for carrier conduction into a π stack structure as shown in FIG. 6 is proposed to avoid packing of the herringbone structure. (See Patent Document 1 below).

Wei-Qiao Deng and William A. Goddard III, “J. Phys. Chem. B”, 2004 American Chemical Society, Vol. 108, No. 25, 2004, p.8614-8621 US6,690,029 B1

  However, in order to pack the pentacene mother skeleton into a π stack structure, it is necessary to introduce a bulky substituent as described above, and thus the degree of freedom in molecular design is extremely low. For this reason, for example, it was difficult to finely adjust the physical properties according to the process.

  Accordingly, the present invention provides an organic material having a high degree of freedom in molecular design and high adaptability to a process while exhibiting high carrier mobility, and a semiconductor device in which a semiconductor layer is formed using this semiconductor material. Objective.

  The organic material of the present invention for achieving such an object is an organic material represented by the structural formula (1), and is 6,12-Dioxaanthanthrene (6,12-dioxaanthanthrene, so-called perixanthenoxanthene: PXX) is a material in which at least one of positions 2 and 7 is substituted with a substituent other than hydrogen.

ただし、構造式（１）中におけるＲ₁，Ｒ₂の少なくとも一方は水素以外の置換基を示す。

However, at least one of R ₁ and R ₂ in the structural formula (1) represents a substituent other than hydrogen.

The organic semiconductor of the present invention is characterized by including a semiconductor layer formed using an organic material containing a skeleton of the following structural formula (2), that is, perixanthenoxanthene (PXX).

  In the present invention, it is known that perxanthenoxanthene (PXX) contained in the material constituting the semiconductor layer is packed in a π stack structure in a neutral state where no voltage is applied and an ionic state when a voltage is applied. ing. For this reason, it is not necessary to introduce a particularly bulky substituent, and the perixanthenoxanthene (PXX) skeleton can be easily packed in a π stack structure in the semiconductor layer. Therefore, molecular design for stacking the organic material in the semiconductor layer by π is facilitated.

  As described above, according to the present invention, a semiconductor layer having a high carrier mobility is formed by using an organic material having perixanthenoxanthene (PXX) as a packing of a π stack structure. The degree of freedom in molecular design of organic materials can be increased, and process adaptability can be improved. Thereby, it becomes possible to improve the ease of manufacturing a high-performance organic semiconductor device having a high carrier mobility.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

<Organic semiconductor materials>
The organic material of the present invention is a material suitably used as a semiconductor material, and is a perixanthenoxanthene (PXX) derivative represented by the following structural formula (1).

However, at least one of R ₁ and R ₂ represents a substituent other than hydrogen, and one of them may be hydrogen. When both R ₁ and R ₂ are substituents other than hydrogen, R ₁ and R ₂ may be the same or different.

Specific examples when R ₁ and R ₂ are substituents other than hydrogen include alkyl groups (methyl group, ethyl group, propyl group, isopropyl group, tertiary-butyl group, pentyl group, hexyl group, octyl group, Dodecyl group, etc., which may be linear or branched, cycloalkyl group (cyclopentyl group, cyclohexyl group etc.), alkenyl group (vinyl group etc.), alkynyl group (ethynyl group etc.), aryl group (phenyl group, naphthyl) Group), aromatic heterocyclic ring (pyridyl group, thienyl group, furyl group, pyridazinyl group, pyrimidinyl group, pyrazinyl group, triazinyl group, imidazolyl group, pyrazolyl group, thiazolyl group, quinazolinyl group, phthalazinyl group, etc.), heterocyclic group (Pyrrolidyl group, imidazolidyl group, morpholyl group, oxazolidyl group, etc.), alkoxy group (methoxy , Ethoxy group, propyloxy group, pentyloxy group, hexyloxy group, etc.), cycloalkoxy group (cyclopentyloxy group, cyclohexyloxy group, etc.), aryloxy group (phenoxy group, naphthyloxy group, etc.), alkylthio group (methylthio group) , Ethylthio group, propylthio group, pentylthio group, hexylthio group, etc.), cycloalkylthio group (cyclopentylthio group, cyclohexylthio group, etc.), arylthio group (phenylthio group, naphthylthio group, etc.), alkoxycarbonyl group (methyloxycarbonyl group, ethyl) Oxycarbonyl group, butyloxycarbonyl group, octyloxycarbonyl group, etc.), aryloxycarbonyl group (phenyloxycarbonyl group, naphthyloxycarbonyl group, etc.), sulfamoyl group (aminosulfur group) Phonyl group, methylaminosulfonyl group, dimethylaminosulfonyl group, cyclohexylaminosulfonyl group, phenylaminosulfonyl group, naphthylaminosulfonyl group, 2-pyridylaminosulfonyl group, etc.), acyl group (acetyl group, ethylcarbonyl group, propylcarbonyl group, Cyclohexylcarbonyl group, octylcarbonyl group, 2-ethylhexylcarbonyl group, dodecylcarbonyl group, phenylcarbonyl group, naphthylcarbonyl group, pyridylcarbonyl group, etc.), acyloxy group (acetyloxy group, ethylcarbonyloxy group, octylcarbonyloxy group, phenyl) Carbonyloxy group, etc.), amide group (methylcarbonylamino group, ethylcarbonylamino group, dimethylcarbonylamino group, pentylcarbonylamino group, Cyclohexylcarbonylamino group, 2-ethylhexylcarbonylamino group, phenylcarbonylamino group, naphthylcarbonylamino group, etc.), carbamoyl group (aminocarbonyl group, methylaminocarbonyl group, dimethylaminocarbonyl group, cyclohexylaminocarbonyl group, 2-ethylhexyl) Aminocarbonyl group, phenylaminocarbonyl group, naphthylaminocarbonyl group, 2-pyridylaminocarbonyl group, etc.), ureido group (methylureido group, ethylureido group, cyclohexylureido group, dodecylureido group, phenylureido group, naphthylureido group, 2 -Pyridylaminoureido group, etc.), sulfinyl group (methylsulfinyl group, ethylsulfinyl group, butylsulfinyl group, cyclohexylsulfinyl group, -Ethylhexylsulfinyl group, phenylsulfinyl group, naphthylsulfinyl group, 2-pyridylsulfinyl group, etc.), alkylsulfonyl group (methylsulfonyl group, ethylsulfonyl group, butylsulfonyl group, cyclohexylsulfonyl group, 2-ethylhexylsulfonyl group, dodecylsulfonyl group) Etc.), arylsulfonyl group (phenylsulfonyl group, naphthylsulfonyl group, 2-pyridylsulfonyl group, etc.), amino group (amino group, ethylamino group, dimethylamino group, butylamino group, 2-ethylhexylamino group, anilino group, Naphthylamino group, 2-pyridylamino group, etc.), halogen atom (fluorine atom, chlorine atom, bromine atom, iodine atom), fluorinated hydrocarbon group (fluoromethyl group, trifluoromethyl group, pentafluoroethyl) Group, pentafluorophenyl group, etc.), cyano group, nitro group, hydroxy group, mercapto group, silyl group (trimethylsilyl group, triisopropylsilyl group, triphenylsilyl group, phenyldiethylsilyl group, etc.).

  The substituents exemplified above may be further substituted with the above substituents. In addition, a plurality of these substituents may be bonded to each other to form a ring.

In the structural formula (1), particularly preferred examples of R ₁ and R ₂ are a halogen group or an aryl group.

<Semiconductor device>

  FIG. 1 is a cross-sectional view showing an example of a semiconductor device to which the present invention is applied. The semiconductor device shown in this figure is a bottom gate / bottom contact type organic thin film transistor. A gate electrode 3 is patterned on an insulating substrate 1 and a gate insulating film 5 is formed in a state of covering the gate electrode 3. . Then, a source electrode 7s and a drain electrode 7d are formed in a pattern on the gate insulating film 5 so as to sandwich the gate electrode 3, and the source electrode 7s and the drain electrode 7d are formed using an organic material peculiar to the present invention. A semiconductor layer 9 is provided.

  In the semiconductor device having such a configuration, the substrate 1 is made of, for example, a plastic substrate such as polyethylene terephthalate (PET), polyether sulfone (PES), or polyethylene naphthalate (PEN), a glass substrate, or a stainless steel substrate. It is done.

  The gate electrode 3 is made of a metal material such as Al, Cu, Au, Ni, W, Mo, Au, Ag, Ni, Pd, or Cr. Such a gate electrode 3 can be obtained by pattern-etching a metal film formed by sputtering, plating, or vapor deposition using a resist pattern formed by photolithography as a mask. The gate electrode 3 can also be obtained by a printing method such as an ink jet method, a micro contact method, or a screen printing method using a nanoparticle dispersion of Au, Ag, or the like, a metal complex solution, or a conductive molecule solution.

  The gate insulating film 5 is made of an organic insulating material or an inorganic insulating material. In the case of the gate insulating film 5 made of an organic insulating material, for example, an organic insulating film solution in which an organic insulating film material is dissolved in an organic solvent is applied and formed by a method such as spin coating or slit coating.

  The source electrode 7s and the drain electrode 7d are similarly formed using the same metal material as that of the gate electrode 3.

  The semiconductor layer 9 is configured using an organic material including a perixanthenoxanthene (PXX) skeleton. As such an organic material, perixanthenoxanthene (PXX) represented by the following structural formula (2) may be used.

  Further, as the material constituting the semiconductor layer 9, the above-described organic material (PPX derivative) represented by the structural formula (1) may be used.

However, in the case where the organic material constituting the semiconductor layer 9 is a PPX derivative, among the organic materials shown using the structural formula (1), particularly in a state where the semiconductor layer 9 is formed in a film shape, As shown in FIG. 2, the substituents of R ₁ and R ₂ are selected so that the perixanthenoxanthene (PXX) skeleton responsible for carrier conduction is packed into a π stack structure. Particularly preferred examples of R ₁ and R ₂ include a halogen group or an aryl group. In the semiconductor layer 9, any part of molecules packed in the π stack structure may be in a state of being bonded by, for example, heat treatment or light irradiation in a process.

  In the above description, the configuration in which the present invention is applied to a bottom gate / bottom contact type organic thin film transistor has been described. However, the present invention is not limited to this, for example, in FIGS. 3 (1) to 3 (3). The present invention can be applied to the semiconductor device having each structure shown. 3 (1) to 3 (3), the same components as those in FIG.

  That is, the semiconductor device of the present invention can also be applied to a bottom gate / bottom contact type organic thin film transistor as shown in FIG. In the organic thin film transistor shown in this figure, a gate electrode 3, a gate insulating film 5, a semiconductor layer 9, a source electrode 7s and a drain electrode 7d are laminated in this order from the substrate 1 side. And the semiconductor layer 9 is comprised using perixanthenoxanthene (PXX) which is an organic material peculiar to this invention as mentioned above.

  The semiconductor device of the present invention is also applicable to a top gate / bottom contact type organic thin film transistor as shown in FIG. The organic thin film transistor shown in this figure has a source electrode 7s and a drain electrode 7d, a semiconductor layer 9, a gate insulating film 5, and a gate electrode 3 stacked in this order from the substrate 1 side. And the semiconductor layer 9 is comprised using perixanthenoxanthene (PXX) which is an organic material peculiar to this invention as mentioned above.

  Furthermore, the semiconductor device of the present invention can be applied to a top gate / top contact type organic thin film transistor as shown in FIG. The organic thin film transistor shown in this figure has a semiconductor layer 9, a source electrode 7s and a drain electrode 7d, a gate insulating film 5, and a gate electrode 3 stacked in this order from the substrate 1 side. And the semiconductor layer 9 is comprised using perixanthenoxanthene (PXX) which is an organic material peculiar to this invention as mentioned above.

  According to each semiconductor device having the above-described configuration, it is known that the organic material constituting the semiconductor layer 9 is packed in a π stack structure in a neutral state where no voltage is applied and an ionic state when a voltage is applied. Perixanthenoxanthene (PXX).

  As described above, since the semiconductor layer 9 is made of an organic material using perixanthenoxanthene (PXX) originally packed in a π stack structure, it is not necessary to introduce a particularly bulky substituent. Even when the organic material has a high degree of molecular design, the semiconductor layer 9 having good carrier conductivity in which the organic material is packed in a π stack structure can be obtained.

  As a result, the degree of freedom in molecular design of the organic material constituting the semiconductor layer 9 exhibiting high carrier mobility is increased, and process adaptability in forming the semiconductor layer 9 can be improved. As a result, it becomes possible to easily realize a high-performance organic semiconductor device with higher carrier mobility.

  In the above embodiment, the configuration in which the present invention is applied to an organic thin film transistor has been described. However, the present invention is not limited to application to thin film transistors, and can be widely applied to semiconductor devices including a semiconductor layer made of an organic material, and similar effects can be obtained.

<Synthesis Example 1 of Organic Material> Refer to Synthesis Formula (1) 1,1′-bis-2-naphthol (1 equivalent) is dissolved in an aqueous solution of sodium hydroxide (4.5 equivalents), and copper (II) acetate ( 2.8 equivalents) A crude product was obtained by adding aqueous solution and oxidizing in air. The crude product was sublimated under reduced pressure to obtain yellow powdered perixanthenoxanthene (PXX).

It was confirmed by ¹ H-NMR, tof-MS, and X-ray structural analysis that it was the target product.

<Synthesis Example 2 of Organic Material> ... See Synthesis Formula (2) Synthesis Example 1 except that (±) -6,6′-dibromo-1,1′-bis-2-naphthol was used as a starting material. In the same manner, dibromo-PXX (R ₁ = R ₂ = Br) was synthesized.

¹ H-NMR and tof-MS confirmed the desired product.

<Synthesis Example 3 of Organic Material> ... See Synthesis Formula (3) A toluene solution of dibromo-PXX (1 equivalent) and phenylboronic acid pinacol ester (3.5 equivalents) is converted into a catalytic amount of tetrakis (triphenylphosphine) palladium, A crude product of biphenyl-PXX (R ₁ = R ₂ = phenyl group) was obtained by a Suzuki-Miyaura coupling reaction in which it was refluxed in an inert atmosphere in the presence of an aqueous sodium carbonate solution. The desired yellow crystalline powder was obtained by sublimating the crude product under reduced pressure.

It was confirmed by ¹ H-NMR, tof-MS, and X-ray structural analysis that it was the desired product. In the crystal, the diphenyl-PXX molecule formed a column structure (π stack structure) so that the PXX skeletons were stacked in parallel.

<Fabrication of semiconductor device>
With reference to the model diagram of FIG. 4, a semiconductor device was manufactured as follows.

  First, a silicon substrate heavily doped with an n-type dopant is prepared as a substrate 1 that also serves as the gate electrode 3, and an insulating film (thickness: 250 nm) mainly composed of PVP (polyvinylphenol) is formed on this surface by a spin coating method. Thus, a gate insulating film 5 was obtained. A platinum comb-shaped pattern was formed on the gate insulating film 5 made of PVP as the source electrode 7s and the drain electrode 7d. The channel length was 50 μm and the total channel width was 5.6 mm. On the substrate 1 on which the source electrode s and the drain electrode 7d were formed, the synthesized perixanthenoxanthene (PXX) was coated under a high vacuum to form a semiconductor layer 9 having a thickness of 50 nm.

<Measurement of semiconductor characteristics>
FIG. 5 shows the result of measuring the drain current Id with respect to the gate voltage Vg for the semiconductor device manufactured as described above.

As shown in this figure, in the semiconductor device having the semiconductor layer 9 using the perixanthenoxanthene (PXX) characteristic of the present invention, in the on / off operation of the drain electrode current Id by the gate voltage Vg, p-type The characteristics were shown. The hole mobility was 5 × 10 ⁻³ cm ² / Vs, and an on / off ratio of 4 digits or more sufficient for transistor operation was observed.

It is sectional drawing which shows the structural example of the semiconductor device to which this invention is applied. It is a figure which shows an example of the packing state of the organic material in an organic layer. It is sectional drawing which shows the other structural example of the semiconductor device to which this invention is applied. It is a model figure of the semiconductor device produced in the Example. It is a graph which shows the gate voltage-drain electrode current of the semiconductor device produced in the Example. It is a figure which shows an example of packing of (pi) stack structure.

Explanation of symbols

  9 ... Semiconductor layer, 10a, 10b, 10c, 10d ... Semiconductor device (organic thin film transistor)

Claims (6)

An organic material represented by the following structural formula (1).

However, at least one of R ₁ and R ₂ in the structural formula (1) represents a substituent other than hydrogen. The organic material according to claim 1,
An organic material, wherein at least one of R ₁ and R ₂ in the structural formula (1) is independently a halogen group or an aryl group. A semiconductor device comprising a semiconductor layer formed using an organic material containing a skeleton of the following structural formula (2).

The semiconductor device according to claim 3.
The said organic material is following Structural formula (1). The semiconductor device characterized by the above-mentioned.

However, at least one of R ₁ and R ₂ in the structural formula (1) represents a substituent other than hydrogen. The semiconductor device according to claim 3.
In the semiconductor layer, the skeleton of the structural formula (2) is packed with a π stack structure. The semiconductor device according to claim 5.
The said organic material is following Structural formula (1). The semiconductor device characterized by the above-mentioned.

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