JPS6370517A - Formation of electrode - Google Patents

Abstract

PURPOSE:To easily form a highly accurate and fine external electrode by implanting or diffusing a conductive impurity into a desired portion of the conductive layer of an electric element having organic conductive layers, and without degrading the properties of these layers. CONSTITUTION:A conductive impurity 9 is implanted or diffused into a desired region 8 of organic conductive layers or accumulated films 5 of monomolecular films of organic charge transfer complex on a substrate 2. As the conductive impurity to be used, a material having good diffusion properties is preferable, and for instance, metals such as gold, silver, copper, aluminium, chrome, nickel or conductive oxides of various metals are usefull. These conductive impurities are implanted or diffused into the organic conductive layers. As one of the suitable methods for diffusion, there is a vacuum deposition process of metals, and for instance, such metals as mentioned above are vapor-deposited with the evaporation source and the substrate being relatively near in distance. Metal atoms heated at the evaporation time reache the substrate while maintaining a high temperature, and are implanted into the interior of the organic conductive layers 5 thereby forming a conductive region or an electrode 8 in the organic conductive layeres 5.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for forming electrodes of an electric element, and more particularly to a method for easily forming external electrodes on desired portions of an electric element having an organic conductive layer.

(Prior Art) Various electrical elements such as semiconductor elements have been known in the past.
In most cases, inorganic materials are used as materials for the functional parts of these electrical elements. However, as these semiconductor devices are increasingly required to have higher density, higher fineness, and higher integration, the use of conductive organic substances as materials for functional parts of semiconductor devices and the like is being widely considered.

A charge transfer complex is known as a type of conductive organic material, and a method for forming such an organic charge transfer complex as a uniform film on a substrate is the Langmuir method proposed by Langmuir et al.・Prodget method (LB method) is known.

According to this LB method, a monomolecular film of an organic charge transfer complex having a hydrophobic site and a hydrophilic site in one molecule or a cumulative film thereof can be easily formed on a substrate, and By using organic materials that have conductivity as a conductive material, which consists of a monomolecular film or a cumulative film of these conductive organic materials on any substrate? ] A film can be formed.

The organic conductive layer formed in this way has good electrical conductivity in the horizontal direction of the film because the hydrophobic regions with high electrical insulation and the hydrophilic regions with high conductivity overlap in a planar manner. It has the unique property of conductive anisotropy, which shows high insulating properties in the direction perpendicular to the film.

(Problem to be Solved by the Invention) In the various electric devices described above, the method for forming the necessary external electrodes is that when the functional parts of the electric device are made of inorganic materials, these inorganic materials are often Since it has conductivity in all directions, that is, it is an isotropic material, electrodes can be easily formed on its surface. In the case of electrical elements in which the conductive layer is a conductive layer, an insulating layer and a conductive layer overlap vertically, so simply forming a conductive region for an electrode on the surface is not enough to form a layer. Due to the presence of the insulating layer, it is difficult to form an ohmic or Schottky junction, and an effective external electrode cannot be formed.

For example, to form an external electrode, a desired portion of a monomolecular film or its cumulative film is destroyed or peeled off in the vertical direction;
It is necessary to fill it with a conductor. In such a method, since the layer is an organic material and has an extremely fine structure, it is extremely difficult to accurately destroy a monomolecular film or a cumulative film thereof. Therefore, it is not possible to effectively control the parameters such as the distance between the formed electrodes and the area of the electrodes, which greatly affect the physical properties, resulting in the problem that it is not possible to obtain an electrical element of uniform quality. In particular, the higher the density and integration of electrical elements, the more difficult it becomes to perform microfabrication, making it impossible to take advantage of the superior properties of layers consisting of quarter-preformed or stacked films of organic charge transfer complexes. There is a problem.

Therefore, there is a need for a method for easily forming fine external electrodes with a high degree of rust without impairing the characteristics of these layers on electrical elements having functional parts made of conductive organic materials as described above.

(Means for Solving the Problems) As a result of intensive research in response to the above-mentioned demands of the prior art, the present inventor has found that it is possible to easily solve the problem without impairing the density of a conductive layer made of a conductive organic substance or its characteristics. We have discovered a method for forming external electrodes.

That is, the present invention is an electrode forming method characterized by injecting or diffusing a conductive impurity into a desired location of a conductive layer of an electric element having an organic conductive layer.

Next, the present invention will be explained in more detail.

The electric element forming the electrode in the present invention is generally an electric element having a conductive organic layer on any substrate, and the electric element for which the method of the present invention is particularly effective can be formed on any substrate. This is an electric element obtained by forming a quarter-preformed organic charge transfer complex or a cumulative film thereof.

The charge transfer complex used to form the organic conductive layer in the present invention is a compound having a hydrophilic site, a hydrophobic site, and a conductive site within one molecule.

Any of the conventionally known charge transfer complexes having such conditions can be used in the present invention, but a compound suitable for the present invention has a hydrophilic moiety having a quaternary ammonium group and a hydrophobic moiety having an alkyl group or an aryl group. It is a charge transfer complex in which the electroconductive part is a hydrophobic hydrocarbon group such as a group or an alkylaryl group, and the conductive part is a tetracyanoquinodimethane structure.

A preferable compound as the charge transfer complex is the following general formula C.
I).

[A] [TCNQ]nX, (I) For example, the following compounds may be mentioned.

R in the above is a hydrophobic moiety, and is an alkyl group, an aryl group, or an alkylaryl group, and preferably an alkyl group having 5 to 30 carbon atoms. R is a lower alkyl group, n and 9 are 0.1 or 2, m is 0 or 1, and X is various anion groups such as a halogen ion such as a bromine ion or a perchlorate ion. Y
is oxygen or sulfur.

The above compounds may further have a polymerizable group such as a double bond or triple bond in the alkyl group, and 1 on the m ring.
It may have one or more substituents such as an alkyl group, an alkenyl group, a cyano group, an alkoxy group, or a halogen.

Further, TCNQ is suitable for compounds represented by the following formula.

The a Nd position in the above formula may have an arbitrary substituent such as an alkyl group, an alkenyl group, or a halogen atom.

The present inventor has conducted intensive research on charge transfer complexes including the compounds exemplified above, and has found that these charge transfer complexes can be formed as a monomolecular film or a cumulative film thereof on any substrate by a known method. In addition, such a monomolecular film or its cumulative film has high insulating properties in the vertical direction of the film and high conductivity in the horizontal direction of the film, and is extremely It was found that the material exhibits excellent anisotropy in conductivity.

In the present invention, a preferred method for forming a conductive layer on the surface of any substrate using the charge transfer complex is the LB method described above.

In the LB method, for example, in a molecule having a structure having a hydrophilic site and a hydrophobic site in the molecule, such as the above-mentioned charge transfer complex, when the balance between the two (balance of amphiphilicity) is maintained appropriately, This is a method to create a monomolecular film or a cumulative film thereof by utilizing the fact that molecules form a monomolecular layer on the water surface with their hydrophilic groups facing downward.

A monomolecular layer on the water surface has the characteristics of a two-dimensional system, and when the molecules are sparsely dispersed, the area per molecule is A and the surface pressure π
The two-dimensional ideal gas equation, πA:, holds true between T and becomes a "gas film." Here, K is Portzmann's constant and T is absolute temperature. If A is made sufficiently small, the intermolecular interaction will become stronger, resulting in a two-dimensional solid "condensed film" (or solid IIS).A condensed film can be applied to the surface of any object with various materials and shapes, such as glass or resin. This method can be used to form iB molecular films or cumulative films thereof from the charge transfer complex described in No. 111, and the stiffness can be used as a conductive layer for electrical devices.

As a specific manufacturing method, for example, the method shown below can be mentioned.

The desired charge transfer complex is dissolved in a solvent such as chloroform, benzene, acetonitrile, etc. Next, using a suitable apparatus as shown in FIG. 1 of the accompanying drawings, a solution of the charge transfer complex is spread on the aqueous phase 1 to form a charge transfer complex in the form of a film.

Next, a partition plate (or float) 3 is provided to prevent this spread layer from spreading freely on the water phase and spreading too much, and by limiting the spread area, the state of aggregation of the membrane material is controlled, and it is proportional to the state of aggregation. Obtain the surface pressure π. By moving the partition plate 3, the developed area is reduced to control the aggregation state of the membrane material, and the surface pressure P can be gradually increased to set the surface pressure π suitable for membrane production. A monomolecular film of the charge transfer complex is transferred onto the substrate 2 by gently raising or lowering the clean substrate 2 vertically while maintaining this surface pressure. Such a monomolecular film is a film in which molecules are arranged in an orderly manner as schematically shown in FIG. 2a or 2b.

A monomolecular film of the charge transfer complex is manufactured as described above, and by repeating the above steps, a desired number of cumulative films can be formed. To transfer a monolayer of charge transfer complex onto a substrate,
In addition to the vertical dipping method described above, methods such as a horizontal adhesion method and a rotating cylinder method are also possible.

The horizontal deposition method is a method in which a monomolecular film is transferred by bringing the substrate into horizontal contact with the water surface, and the rotating cylinder method is a method in which a cylindrical substrate is rotated above the water surface to transfer the monomolecular film onto the substrate surface. be.

In the vertical immersion method described above, when a substrate with a hydrophilic surface is lifted out of water in a direction across the water surface, a monomolecular film of the charge transfer complex is formed on the substrate with the hydrophilic groups of the charge transfer complex facing the substrate. (Figure 2b). When the substrate is moved up and down as described above, one monomolecular film is stacked on top of the other at each step, forming a cumulative film. Since the direction of the film-forming molecules is reversed during the pulling process and the dipping process, according to this method, between each layer of the monolayer, the hydrophobic groups of the charge transfer complex face each other.
A mold film is formed (FIG. 3a). In contrast, in the horizontal deposition method, a monomolecular film with the hydrophobic groups of the charge transfer complex facing the substrate is formed on the substrate (FIG. 2a). in this way,
Even when monomolecular films are accumulated, there is no change in the direction of the film-forming molecules, and an X-shaped film is formed in which the hydrophobic groups face the substrate in all layers (FIG. 3b). On the other hand, a cumulative film in which the hydrophilic groups in all layers face the substrate side is called a Z-type film (Figure 3c).

The method of transferring the monomolecular film onto the substrate is not limited to the above method, and when using a large-area substrate, a method of extruding the substrate from a roll into an aqueous phase may also be adopted. Further, the directions of the hydrophilic groups and hydrophobic groups described above toward the substrate are in principle, and can be changed by surface treatment of the substrate, etc.

As described above, a conductive layer consisting of a monomolecular film of the charge transfer complex or a cumulative film thereof is formed on the substrate.

In the present invention, a single molecule of the charge transfer complex as described above
Alternatively, the substrate for forming an organic conductive layer consisting of a cumulative film thereof may be made of any material such as metal, glass, ceramics, or plastic materials, and biomaterials with extremely low heat resistance may also be used.

As mentioned above, conductive materials such as metals can also be used.
This is because the monomolecular film or the cumulative film has sufficient insulating properties in the direction perpendicular to the film.

The above-mentioned substrate may have any shape, preferably a flat plate, but is not limited to a flat plate at all. That is, the present invention has the advantage that a film can be formed in accordance with any shape of the surface of the substrate.

The method for forming an electrode on the organic conductive layer formed on the substrate as described above is as shown in FIG. This is a method of forming a conductive region 8 by injecting or diffusing a conductive impurity 9 into a desired region 8 . As the conductive impurity to be used, a conductive material with good diffusivity is preferable.
For example, metals such as gold, silver, copper, aluminum, chromium, and nickel, and conductive oxides of various metals are useful, and methods for pouring or diffusing these conductive impurities into the organic conductive layer include: Although there are various methods, preferred methods include metal vacuum deposition and metal ion implantation.

In the vapor deposition method, for example, a method of vapor depositing the above-mentioned metal while keeping the distance between the vapor deposition source and the substrate relatively close is preferable. By performing evaporation under such conditions, the metal atoms heated during evaporation reach the substrate while maintaining a high temperature, and are injected into the organic conductive layer 5 to form the organic conductive layer 5.
A conductive region or electrode 8 is formed therein. Another vapor deposition method is to heat-treat the metal 10 vacuum-deposited as described above under conditions that do not damage the organic conductive layer, for example, under vacuum at a relatively low temperature, so that the metal of the metal vapor-deposited layer 10 is heated to form the organic conductive layer. 5
This method is to diffuse it into the inside. According to this method, the conductivity between the electrodes is further improved when the vapor deposition layer 10 is formed at a relatively close distance to the vapor deposition source in the above method, and when the vapor deposition layer 10 is formed at a distance from the vapor deposition source, the conductivity between the electrodes is further improved. , something that had almost no conductivity between the electrodes now exhibits high conductivity.

The ion implantation method involves ionizing the target element in a vacuum, electrostatically accelerating the ions to the required energy, and then implanting them into the target (target object). It has the characteristics of being able to implant impurities that cannot be implanted, and also being able to withstand microfabrication.

Furthermore, this method is well established as a semiconductor manufacturing technology, and has high reliability, easy handling of the device, and high productivity. Furthermore, the process itself can be carried out at room temperature, and can be said to be one of the methods extremely suitable for organic materials.

The above-mentioned methods are typical methods, and any method that achieves the same effect as the above can be used in the present invention.

In addition, in the present invention, when the charge transfer complex used has a polymerizable group, after forming the film as described above, the stiff film is polymerized and hardened before or after forming the electrode to increase the film strength. It can also be significantly improved.

(Function/Effect) According to the present invention as described above, when forming an electrode in an organic conductive layer, a heating process at a particularly high temperature is not required. However, any substrate can be used.

Further, unlike the prior art, according to the method of the present invention, there is no need to destroy the organic conductive layer on the substrate when forming the electrode, so it is possible to freely Since electrodes can be easily formed in the region, highly fine processing is possible, and electric elements with excellent electrical properties can be easily provided with good reproducibility.

From the above points, according to the present invention, the electric device produced by the method of the present invention can be highly expected not only as a conventional high-density electric device but also as a bioelectronic device that utilizes living organisms.

Next, the present invention will be explained in more detail with reference to Examples.

Example 1 The above charge transfer complex was dissolved in a mixed solvent of benzene-acetonitrile (volume ratio 1:1) at a concentration of Img/ml, and then the pH was adjusted to 6.8 with lICO3 (:dCl
, was developed on an aqueous phase at a concentration of 4×10-' mol/1 and a water temperature of 17°C.

After removing the solvents acetonitrile and benzene by evaporation,
The surface pressure was increased to 20 dyne/cIm to form a monomolecular film. The surface is subjected to hydrophobic treatment (L) while keeping the surface pressure constant.
A clean glass (30xlO size) coated with three layers of cadmium araxinate (accumulated by method B) was used as a substrate, and the substrate was gently immersed for about 2011II11 at a speed of 15mm/1lin in the transverse direction of the water surface, and then speed 10wn
/min, to accumulate two layers of quarter preform. The above accumulation operation was repeated 10 times to produce a quarter-prepared cumulative film on the substrate.

Next, gold is vacuum evaporated from above the accumulated film using a resistance heating method (film thickness 200 nm).
III11) was formed. In addition, at this time, the distance between the vapor deposition source and the substrate was 10 cm, and the substrate temperature was set to room temperature.

When we measured the current-voltage characteristics between the electrodes for the device created using the above method, a linear relationship was observed at least in the range of 0 to ±1■, indicating that ohmic electrodes were formed. . Also, the conductivity in the in-plane direction of the membrane was calculated from the slope of the straight line in the graph, and it was 0. l 2
It was S/Cot.

On the other hand, gold was vacuum-deposited (film thickness approximately 200n*, room temperature) using the resistance heating method (film thickness approximately 200n*, room temperature) with the distance to the evaporation source set to 40cm on the cumulative film created in exactly the same manner as above. We formed various elements.

Furthermore, when the current-voltage characteristics between the electrodes 11 were measured, it was found that 20
Even when V was applied, only a current of 1×1 O−10 A (noise level of the measurement system) or less flowed, so the space between the electrodes was considered to be an insulator.

The reason why a different result was obtained is that in the former case, gold diffuses into the film during or immediately after deposition, imparting conductivity in the direction perpendicular to the film surface, and creating an ohmic relationship with the conductive region within the film surface. This is thought to be due to the formation of external connection electrodes.

Although this embodiment shows the case where gold diffuses during vapor deposition, it is of course possible to use any impurity other than gold as long as it has a large diffusion constant. However, the applicable materials are greatly influenced by the constituent molecules of the cumulative film, its structure, and film quality.

Example 2 As in Example 1, gold was vacuum-deposited to a thickness of 200 nm (rate: 5 nIl/s) on the cumulative rise of a monomolecular film formed on a substrate in exactly the same manner as in Example 1 (rate: 5 nIl/s), FIG. To form an element like this, the element constants etc. are the same as in Example 1)
.

Furthermore, this was placed in a vacuum electric furnace (2×10 −3 torr or less) and heat treated at 50° C. for 24 hours. After waiting for further cooling and leaving it, the current-voltage characteristics between the gold electrodes were measured and the conductivity was determined to be 0.16 S/c+s, which is 30% more than the 0.12 Sicra without heat treatment. Improvements were made. This is thought to be because gold diffusion was promoted by heat treatment.

Example 3 The same charge transfer complex as in Example 1 was dissolved in a 1:1 (volume ratio) mixed solvent of acetonitrile and benzene at a concentration of IIIIg/ml, and then the pH was adjusted to 6.8 with I+ (:0. The mixture was developed on an aqueous phase with a CdCl2 concentration of 4×10-' mol/4 and a water temperature of 17°C.

After removing the solvents acetonitrile and benzene by evaporation,
The surface pressure was increased to 20 dyne/crrr to form a monomolecular film. l in advance while keeping the surface pressure constant.
Intrinsic (
i type) Using a Si wafer as a substrate, gently move the substrate to 20 mmP at a speed of 15ml1/ff1in in the direction across the water surface.
After being immersed for 1 hour, it was then gently pulled up at a speed of 10 ram/min. The above operation was repeated once again to accumulate a 4-layer monomolecular film.

Of the two samples created as described above, chromium ions were implanted at a rate of 7X10''/crn' over two areas (each 2 x 2 beads in size) with a spacing of 11 on one sample. (acceleration voltage: 30 KeV).

Furthermore, aluminum vapor deposition (resistance heating method) is performed on the sample as a pair of external connection electrodes so as to cover each of the ion-implanted regions. For the other sample, the aluminum electrode was formed as described above without performing ion implantation after film formation.

When 30V was applied between the aluminum electrodes of the two samples obtained as described above, no current exceeding the noise level (10-''A) was observed in the sample without ion implantation. 2 for those with ion implantation
A current of X10-'A flowed. From these results, it was revealed that conductivity in the direction perpendicular to the film surface was obtained by ion-implanting chromium into the monomolecular cumulative film, which has large anisotropy in electrical conductivity.

Examples 4 to 7 In the same manner as in Example 3, monomolecular cumulative films of various charge transfer complexes were created on the respective surfaces of several rows of conductive substrates as shown in Table 1 below, and impurity ions were accelerated. 20K
Gold was implanted in an amount of 8 x 10 I5/am'' at eV.Furthermore, gold was implanted on the implanted area at 15 m by resistance heating.
The film was deposited to a thickness of 0 nm, a voltage was applied between it and a conductive substrate using it as an upper electrode, and the conductivity in the film thickness direction was measured, and the results (A) shown in Table 1 below were obtained.

On the other hand, for comparison, the conductivity was determined in the same manner for the region where ion implantation was not performed. The results (B) are also shown in Table 1.

γ:, 1-=1 Example 4 The proud grandson of the factory worker (2) 1 incl. 81 koji 5-11 ball Polycarbonate with Au vapor deposited Fukotsu-(tom) ridge A 5X10-” B 10-' Example 5 Ruins of Deaf Works (2) 1 incl. 81 items Ag Base ---- Hill ITO substrate Two Earths - Pan-bao A 8X10-2 B 10-7 Example 6 Plate and long moving trace (3) Eno J3U, Rib Au Ship---One ball ITO board Take care! - Pan-covered area B 3xlO-2 Example 7 Namikushoinsha　　(4) 84 kalpa I Ship---One ball ITO board 1” – inscription on the ridge A 6X10-2 B 5X10-' Conductivity A: Method of the present invention (ion implantation) Conductivity B: Comparative example (no ion implantation) The above charge transfer complex has the following structure.

[Brief explanation of the drawing]

FIG. 1 is a diagram schematically showing a method of forming a conductive layer of an electric element of the present invention. FIG. 2 is a schematic diagram of a monomolecular film, and FIG. 3 is a schematic diagram of a cumulative film. FIG. 4 schematically shows the manufacturing process of the electric device of the present invention, and FIG. 5 shows the electric device of the example. 1; aqueous phase 2: substrate 3: float 4: monomolecular film 5; cumulative h1 film 6: hydrophilic site (conductive site) 7; hydrophobic site 8: conductive region 9: conductive impurity 10; young layer 11 Electrode applicant Canon Co., Ltd. 9 Convex τ Figure 1 Figure 2a Figure 2b Figure 3 & Figure 3b

Claims (5)

[Claims] (1) An electrode forming method characterized by injecting or diffusing a conductive impurity into a desired location of a conductive layer of an electric element having an organic conductive layer. (2) The electrode forming method according to claim (1), wherein the organic conductive layer is an anisotropic conductive layer. (3) The organic conductive layer according to claim (1), wherein the organic conductive layer is a monomolecular film of an organic charge transfer complex having a hydrophobic site, a hydrophilic site, and a conductive site in one molecule or a cumulative film thereof. Electrode formation method. (4) The method for forming an electrode according to claim (1), wherein the organic charge transfer complex is a complex of a quaternary ammonium compound and tetracyanoquinodimethane. (5) Claim No. 1 in which the conductive impurity is a metal
) The electrode forming method described in item 1.