JPH03151667A - Switching element and its manufacturing method - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a switching element using an organic thin film, a switching element that is promising as a molecular electronic device to replace current semiconductor electronic devices, and a method for manufacturing the same.

Conventional TechnologyIn recent years, as an alternative to conventional semiconductor electronic devices,
Research and development of molecular electronic devices is becoming more active.

Among these, devices using organic thin films with switching functions can be said to be particularly important elements in the fabrication of logic elements.

Cu/TCN as an organic thin film with switching function
There is a Q (tetracyanoquinodimethane) thin film (US Pat. No. 4,371,883). This organic thin film is about 10'
It is one of the most promising materials, as a switching action occurs when an electric field of V/cm is applied.

This Cu/TCNQ thin film is manufactured as follows. Add C to an acetonitrile solution in which TCNQ is dissolved.
Soak the u-plate for a certain period of time. During immersion, C, which becomes the lower electrode,
On the surface of the u-plate, polycrystalline growth of the Cu/TCNQ complex occurs, resulting in the formation of a Cu/TCNQm film. After forming the organic thin film, an upper electrode made of aluminum or the like is provided. Then, if a voltage is applied between the upper and lower electrodes, a switching operation will occur.

Problems to be Solved by the Invention However, the above-mentioned Cu/TCN Q 1N film has the following problems.

■ The wet method (wet process), which uses a solution of an organic solvent called acetonitrile, is not desirable from the standpoint of work environment safety and health.

■ In the case of the wet method, it is difficult to form a thin film that is homogeneous and has good thickness accuracy. It is difficult to obtain switching elements with good performance.

(2) Furthermore, the wet method, in which a thin organic film is formed that exposes the underlying metal surface, has the problem that it is difficult to integrate or form an array. Particularly when miniaturized, the electrodes are likely to come into contact with each other at the intersections of the upper and lower electrodes, resulting in short circuits.

In other words, it is difficult to manufacture, and furthermore, the resulting structure cannot be said to have sufficient practicality.

In view of the above circumstances, it is an object of the present invention to provide an organic thin film switching element that does not cause problems in the working environment due to organic solvents, has high performance and is easily miniaturized, and a method for manufacturing the same.

Means for Solving the Problems In order to solve the problems, the switching elements according to claims 1 to 5 include an electron-donating organic compound layer or an electron-donating metal layer and an electron-withdrawing organic compound layer between the upper and lower electrodes. The structure includes a laminate in which compound layers are alternately laminated and heat treated.

In addition, in the switching element according to claim 2, each of the upper electrode and the lower electrode includes a plurality of elongated electrodes arranged in parallel, and the elongated electrode forming the upper electrode and the elongated electrode forming the lower electrode. The elongated electrodes are arranged in a crisscross pattern to achieve an integrated (multiple) and array configuration.

In the method for manufacturing a switching element according to claims 6 to 9,
After an electron-donating organic compound layer or an electron-donating metal layer and an electron-withdrawing organic compound layer are alternately deposited on the lower electrode by vacuum evaporation, heat treatment is performed to form a charge transfer complex. Then, the upper electrode is formed.

The electron-donating organic compound in this invention includes aromatic amines, heterocyclic aromatic amines, such as p-
Examples include phenylenediamine, dimethylniline, pyridine, quinoline, acridine, phenazine, and quaternary salts of these compounds, and fulvalene compounds, such as tetrathiofulvalene and tetramethyltetraselenafulvalene, alone or in combination. used in the form

As the electron-donating metal in this invention, alkali metals of Group Ia of the periodic table, such as Na, K, or
No.! B-group metals, such as copper and silver, may be used alone or in combination.

Examples of the electron-withdrawing organic compound in this invention include quinoid-type compounds containing a nitrile group, such as tetracyanoquinodimethane and tetracyanonaphthoquinodimethane, or quinoid-type compounds containing a halogen, such as chloranil and promanil. These can be used alone or in combination.

Function: In the present invention, an organic thin film having a switching function can be formed by a one-line process of vacuum deposition and heat treatment, rather than a conventional wet process, thereby solving problems in the working environment.

In addition, the dry process can easily form a thin film that is homogeneous and has good thickness accuracy, so a device with good performance can be obtained.

Since the organic thin film can be formed on parts other than the lower electrode, contact between the upper and lower electrodes is difficult to occur, and miniaturization is easy.

Embodiments Next, embodiments of the switching element of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows a schematic cross-sectional view showing an embodiment of the switching element of the present invention.

As shown in FIG. 1, in the switching element of the present invention, a charge transfer complex laminate 1 is provided between the lower electrode 12 and the upper electrode 14.
3, and was manufactured as follows.

As shown in FIG. 1, on a substrate 11 on which a lower electrode 12 is formed, an electron-donating organic compound layer or an electron-donating metal layer and an electron-withdrawing organic compound layer are alternately stacked by vacuum evaporation. , Next, heat treatment is performed at an appropriate temperature and for an appropriate time so that a charge transfer complex is formed, and then the laminate 13
An upper electrode 14 can be formed on the surface.

As the substrate 11, an insulating substrate such as a glass substrate or a ceramic substrate is usually used. Examples of the lower electrode 12 include metal layers such as gold, silver, copper, and chromium. A metal plate or silicon substrate that also serves as the lower electrode, or a silicon substrate on which a lower electrode pattern is provided via an insulating layer may be used. As the upper electrode 14, metal layers such as gold, silver, copper, and chromium can also be used.

Usually, only either the electron-donating organic compound layer or the electron-donating metal layer and the electron-withdrawing organic compound layer are laminated, but if the layer structure of the donating layer is Alternatively, the other layer may be formed of an electron-donating metal and used in combination.

Furthermore, although each layer of the electron-donating organic compound layer, electron-donating metal layer, and electron-withdrawing organic compound layer is usually formed of the same compound, layers made of different types of compounds may coexist. You can. The resulting stack of switching elements may have a structure in which layers of charge transfer complexes of different types are stacked. Since various layer configurations are possible and many types of switches with different switch functions can be realized, it is possible to plan a switch series with a wide variety.

The electron donor layer and the electron attractor layer are formed using, for example, the apparatus shown in FIG.

The inside of the vapor deposition apparatus 41 is adjusted to a predetermined degree of vacuum by a vacuum exhaust system 42. The substrate 55 introduced into the device 41 is maintained at an appropriate temperature by the temperature control section 50. Container 43-4
6 contains an electron donating material and an electron attracting material, respectively. For the containers 43 to 46, for example, a crucible is used, but depending on the properties of the material, a Nutsen cell may be used, since it allows vapor deposition in a well-controlled manner under given conditions. Of course, device 4
The number of containers placed in one is not particularly limited. In addition, if it is a low boiling point compound material, it is possible to use the nozzle 52 without putting it in a container.
The vapor may be introduced in a gaseous form while controlling the flow rate from the external sample introduction port 51 for vapor deposition.

In the apparatus shown in FIG. 4, the thickness of the deposited film can be detected using a film thickness meter 49. In addition, a shutter 48 is provided which is linked to the vacuum evacuation system so that deposition is not performed until a desired degree of vacuum is achieved.

Note that the vapor deposition device 41 may be configured to introduce nitrogen gas for pressure adjustment.

The resulting switching element stack 13 may be one in which the reaction has sufficiently progressed and all become charge transfer complexes, as shown in FIG. 10, but a portion remains unreacted, as shown in FIG. In some cases, a charge transfer complex layer 231 and an electron donor layer 232 are used together, or as shown in FIG. It may appear that the layers are within the stack 13.

Further, as shown in FIG. 7, the lower electrode 12 and the upper electrode 1
A plurality of elongated electrodes 12 each having a plurality of long electrodes 12 arranged in parallel.
a..., 14a..., and when the elongated electrodes 12a... for lower electrodes and the elongated electrodes 14a... for upper electrodes are arranged in a crosswise manner, at every intersection 20. This results in an integrated and arrayed structure with independent switching elements, making it more suitable for logic devices.

Example 1 A quartz substrate was used as the substrate, Cu was used as the upper and lower electrodes, Cu was used as the electron-donating metal, and T was used as the electron-withdrawing organic compound.
CNQ was used respectively. Vacuum degree 10-5~10-h
Under Torr, crucible temperature is 1100° for Cu.
For C, TCNQ, crucible temperature 130-200°C
Six layers of Cu and TCNQ were alternately deposited in this order at a temperature of . The total film thickness was approximately 6000, and the weight ratio of Cu and TCNQ was 65:180. The spectral characteristics of the film thus produced were the same as those of TCNQ alone. Subsequently, heat treatment was performed at about 100° C. for 30 minutes under vacuum. This operation turned the membrane green. When we investigated the spectral characteristics of this green organic thin film, we found that they matched those of the TCNQ/Cu complex, as shown in Figure 5, confirming that a charge transfer complex was indeed formed. In addition, the area where the upper and lower electrodes intersect is 1 mm'', and when the electrical characteristics of the film thickness and 6,000 people were investigated, the resistance value in the initial state was approximately 400 Ω, and the resistance value after switching was approximately 950 Ω. It was also formed by a vacuum evaporation method.

Example 2 A switching element was obtained in the same manner as in Example 1, except that the weight ratio of Cu and TCNQ was 65:350. The color of the film after the heat treatment was yellow-green 1 2 . From the measurement results of the spectral characteristics of this yellow-green organic thin film,
It was found that the TCNQ/Cu complex and neutral TCNQ were mixed. It is presumed that a portion of the TCNQ layer remains unreacted.

Example 3 A switching element was obtained in the same manner as in Example 1 using Ag as the electrode, tetrathiofulvalene as the electron-donating organic compound, and chloranil as the electron-withdrawing organic compound.

Example 4 A switching element was obtained in the same manner as in Example 1 using Ag as the electrode, K (potassium) as the electron-donating metal, and TCNQ as the electron-withdrawing organic compound.

Example 5 A switching element was obtained in the same manner as in Example 1, using Ag as the electrode, tetramethylbendine as the electron-donating organic compound, and fluoroTCNQ as the electron-withdrawing organic compound.

Example 6 A switching element was obtained in the same manner as in Example 1 using Ag as the electrode, dihydrodimethylphenazine as the electron-donating organic compound, and tetrafluoroTCNQ as the electron-withdrawing organic compound.

Example 7 A □ switching element was obtained in the same manner as in Example 1 using Ag as the electrode, tetramethylphenylenediamine as the electron-donating organic compound, and TCNQ as the electron-withdrawing organic compound.

When the function of the switching element of Example 1 was measured,
A switching operation was performed as shown in FIG. of course,
The same applies to other switching elements. The switching start voltage Vs was measured for each switching element. The measurement results are shown in Table 1.

3 4 Table 1 Example 8 As a lower electrode on a quartz plate, width 0.2 mm, electrode spacing 0
．． After forming ten Cu electrodes arranged in a 5 mm comb shape using a vapor deposition method, a Cu layer and TCN were formed in the same manner as in Example 1.
After the Q layers were alternately deposited and heat treated, 10 Cr electrodes arranged in a comb-like shape with a width of 0.2 mm and an electrode spacing of 0.5 mm were then used for the upper electrode. A switching element was obtained by forming orthogonal shapes using a vapor deposition method.

This switching element has 10×10=100 independent switching elements. When a voltage was applied to each element individually, each element exhibited normal switching operation as shown in FIG. The switching element of Example 8 is:
By turning specific elements ON or OFF in advance, it can be used as a logic element such as a programmed logic array.

Comparative Example 1 The switching element of Comparative Example 1 has the same upper and lower electrode configuration as Example 8. After forming the lower electrode, it was immersed in an acetonitrile solution containing TCNQ to grow an organic thin film with a thickness of about 2 μm only on the surface of the electrode. Then, an upper electrode was formed by vapor deposition perpendicular to the lower electrode. However, in this switching element, the upper and lower electrodes were short-circuited at 96 locations out of 100 switching elements.

This invention is not limited to the above embodiments. Formation of the vapor-deposited thin film for the electron donor layer and the electron-withdrawing layer is performed under optimal conditions, including the mode of cooling the substrate, depending on the selection of materials and combinations. Further, the heat treatment is also carried out under heating temperature and time conditions that will result in the most appropriate complex formation (easily identified by color change) depending on the selection of material combinations and the like. Electron donor layer/
It goes without saying that the materials and combinations for the electron-withdrawing layer are not limited to the compounds and combinations exemplified above.

Effects of the Invention As described above, the switching elements according to claims 1 to 5 can form an image by a dry process, so there are no problems in the working environment (they are high-performance and easy to miniaturize). It has excellent practicality.

In addition, the switching element according to claim 2 is integrated.
It is designed to be arrayed, making it more practical.

The manufacturing method according to claims 6 to 9 allows the above-mentioned useful switching element to be manufactured easily and safely by a dry process.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view showing the structure of an example of a switching element of the present invention, and FIGS. 2 and 3 are partial cross-sectional views schematically showing the structure of a laminate in other embodiments. FIG. 4 is a schematic explanatory diagram showing the configuration of a vapor deposition apparatus used for manufacturing the switching element of the present invention.
Fig. 5 is a characteristic diagram showing the light absorption characteristics (spectral spectra) of the organic thin film included in the switching element of Example 1, and Fig. 6 shows the resistance value before and after the switching operation of the switching element of Example 1. FIG. 7 is a plan view showing an example of the upper and lower electrodes in the switching element according to the second aspect. 11...Substrate, 12...Lower electrode, 12
a... Long electrode for upper electrode, 13...
Laminated body, 14... Upper electrode, 14a...
Elongated electrode for upper electrode, 231.331... Charge transfer complex layer, 232... Electron donor layer, 33
2... Electron-attracting body layer.

Claims (9)

[Claims] (1) A switching element in which a laminate in which an electron-donating organic compound layer or an electron-donating metal layer and an electron-withdrawing organic compound layer are alternately laminated and heat-treated is provided between the upper and lower electrodes. . (2) Each of the upper electrode and the lower electrode consists of a plurality of long electrodes arranged in parallel, and the long electrodes forming the upper electrode and the long electrodes forming the lower electrode intersect. Switching elements arranged in an array. (3) The switching element according to claim 1 or 2, wherein the electron-donating organic compound is at least one of an aromatic amine, a heterocyclic aromatic amine, and a fullvalene compound. (4) The switching element according to claim 1 or 2, wherein the electron-donating metal is at least one of an alkali metal in group Ia of the periodic table and a metal in group Ib. (5) The switching element according to any one of claims 1 to 4, wherein the electron-withdrawing organic compound is at least one of a quinoid compound containing a nitrile group and a quinoid compound containing a halogen. (6) Electron-donating organic compound layers or electron-donating metal layers and electron-withdrawing organic compound layers are alternately laminated on the lower electrode by vacuum evaporation, and then heated to form a charge transfer complex. A method for manufacturing a switching element, which comprises performing a treatment and then forming an upper electrode. (7) The method for manufacturing a switching element according to claim 6, wherein the electron-donating organic compound is at least one of an aromatic amine, a heterocyclic aromatic amine, and a fullvalene compound. (8) The method for manufacturing a switching element according to claim 6, wherein the electron-donating metal is at least one of an alkali metal in group Ia of the periodic table and a metal in group Ib. (9) The method for manufacturing a switching element according to any one of claims 6 to 8, wherein the electron-withdrawing organic compound is at least one of a quinoid compound containing a nitrile group and a quinoid compound containing a halogen.