Manufacture of diode element

Description: TECHNICAL FIELD [Detailed description of the invention]

【0001】

[Industrial application field]

The present invention relates to a method for manufacturing a diode element using an organic semiconductor thin film.

【0002】

[Conventional technology]

In recent years, high functionality of diode elements has been required, and one of them is the realization of diode elements having a high withstand voltage in the reverse direction. In order to realize such a diode element, a diode element using an organic semiconductor thin film has been proposed. Since diode characteristics cannot be obtained simply by sandwiching both sides of the organic semiconductor thin film with electrodes, diode characteristics are provided by providing an insulating layer on one electrode side to form an asymmetric structure. For example, by using gold for one electrode and aluminum for the other electrode and forming an oxide film on the aluminum electrode, a diode element having an asymmetric structure and a high withstand voltage in the opposite direction was obtained.

【0003】

[Problems to be Solved by the Invention]

However, in the diode element using the conventional organic semiconductor thin film, the thickness of the insulating layer and the thickness of the oxide film of the aluminum electrode cannot be controlled well, so that there is a problem that it is difficult to obtain a product with stable operation. there were.

【0004】

An object of the present invention is to solve such a conventional problem and to provide a method for manufacturing a diode element using an organic semiconductor thin film capable of obtaining a product having stable operation.

【0005】

[Means for solving problems]

In order to achieve the above object, in order to make the organic semiconductor thin film itself have an asymmetric structure in the thickness direction, lead phthalocyanine is vacuum-deposited on an insulating substrate at different substrate temperatures.

【0006】

[Action]

Therefore, according to the present invention, by vacuum-depositing lead phthalocyanine on an insulating substrate at different substrate temperatures, the organic semiconductor thin film itself can have an asymmetric structure in the thickness direction, and the operation is stable in the opposite direction. A diode element having a high withstand voltage can be easily manufactured.

【0007】

[Example]

Hereinafter, examples of the present invention will be described. FIG. 1 shows a cross-sectional configuration of a diode element according to an embodiment of the present invention. In FIG. 1, 1 is an insulating substrate, 2 is a lower electrode provided on a part of the surface thereof, and 3 is a lead phthalocyanine thin film which is an organic semiconductor thin film provided on the insulating substrate 1 so as to cover the lower electrode 2. Reference numeral 4 denotes an upper electrode provided on the lead phthalocyanine thin film 3.

【0008】

As described above, the diode element has a sandwich electrode type structure in which the lead phthalocyanine thin film 3 is sandwiched. The lead phthalocyanine thin film 3 is a thin film formed by a vacuum vapor deposition method, and the crystal on the lower electrode 2 side is composed of a triclinic type crystal 5, and the crystal type on the upper electrode 4 side is composed of a monoclinic type crystal 6. The structure shows the diode characteristics.

【0009】

Using lead phthalocyanine as a raw material, when the vapor deposition source temperature is controlled in the range of 400 to 550 ° C and the vapor deposition rate is vacuum vapor deposition at a constant rate between 0.1 and 20 angstroms / second, the thickness of the thin film is increased. An organic semiconductor thin film having an asymmetric structure consisting of a triclinic type crystal on the back surface side of the film and a monoclinic type crystal on the front surface side of the film can be formed. More specifically, the crystal type of lead phthalocyanine can be controlled by changing the substrate temperature during vapor deposition. When the substrate temperature is room temperature, it becomes a monoclinic type thin film, and when it is about 100 ° C, it becomes a triclinic type thin film. .. That is, first, by keeping the temperature of the insulating substrate 1 at about 100 ° C and depositing lead phthalocyanine, a triclinic type crystal 5 is formed on the lower electrode 2 side, and then the temperature of the insulating substrate 1 is kept at room temperature. By depositing lead phthalocyanine, a monoclinic type crystal 6 is formed on the upper electrode 4 side to form a lead phthalocyanine thin film 3 having an asymmetric structure in the thickness direction of the thin film. When such a lead phthalocyanine thin film 3 is sandwiched between the electrodes 2 and 4 to form a diode element, the state of the barrier at the interface with the electrodes 2 and 4 changes, so that the diode characteristics are exhibited.

【0010】

Hereinafter, the method for manufacturing the diode element in the above embodiment will be described in more detail with reference to FIG. First, as the insulating substrate 1, a quartz glass having a length of 35 mm, a width of 25 mm, and a thickness of 1 mm was ultrasonically cleaned with trichloroethane, acetone, and isopropyl alcohol in this order (step 11). Next, gold was deposited on the surface of the insulating substrate 1 to form the lower electrode 2 with a width of 1 mm and a thickness of 500 angstroms (step 12).

【0011】

Subsequently, a lead phthalocyanine thin film 3 was formed on the electrode forming surface side as follows (step 13). Commercially available lead phthalocyanine as a vapor deposition raw material is repeatedly sublimated and purified three times in a vacuum, placed in a quartz crucible, adjusted in the range of 430 to 440 ° C by resistance heating, and the vapor deposition rate is kept constant at 1 angstrom / sec. A 100 angstrom thick film was formed on the insulated substrate 1 with the substrate temperature kept at 100 ° C. Further, after the substrate temperature was lowered to room temperature in vacuum, a film having a thickness of 1 μm was continuously formed on the insulating substrate 1 at a vapor deposition rate of 1 angstrom / sec.

【0012】

Next, gold was vapor-deposited on the surface of the lead phthalocyanine thin film 3 to form an upper electrode 4 having a width of 1 mm and a thickness of 500 angstroms so as to be orthogonal to the lower electrode 2 (step 14). This element is 10^-5It was left in a torr vacuum vessel for 5 hours to be evacuated (step 15), then taken out of the vacuum vessel, gold wires were joined to both electrodes 2 and 4 with indium, and lead wires were taken out to complete the diode element. (Step 16).

【0013】

In the lead phthalocyanine thin film 3 of the completed diode element, the crystal on the lower electrode 2 side was a triclinic type crystal 6, and the crystal on the upper electrode 4 side was a monoclinic type crystal 5.

【0014】

Next, the operation of the diode element manufactured in this way was investigated using the measurement circuit shown in FIG. In FIG. 3, 7 is a diode element to be measured, 8 is a power source for applying an electric field to the diode element 7, the applied electric field is measured by a voltmeter 9, and the current flowing through the diode element 7 is an ammeter 10. Measured in.

【0015】

First, when an electric field is applied to the diode element before vacuuming in step 15 of FIG. 2 in the direction in which the lower electrode 2 side is positive with respect to the upper electrode 4 side, lead is applied as shown in FIG. A switch operation occurs in which the phthalocyanine thin film 3 changes from a high resistance state to a low resistance state. Next, even if the electric field is reduced, the low resistance state is maintained. However, it can be seen that when an electric field in the opposite direction is applied, almost no current flows and the diode characteristics are exhibited.

【0016】

Subsequently, by vacuuming the diode element in step 15, the switch operation between the high resistance state and the low resistance state becomes small, and the state change is not shown. As a result of investigating the operation of the diode element vacuum-processed in this way using the measurement circuit shown in FIG. 3, as shown in FIG. 5, a diode characteristic with a withstand voltage of 50 V in the reverse direction was shown.

【0017】

As described above, according to the above embodiment, since the lead phthalocyanine thin film was formed as the organic semiconductor thin film by changing the substrate temperature by the vacuum vapor deposition method, the organic semiconductor thin film itself can be easily formed into an asymmetric structure, and the operation is stable. A diode element having a high withstand voltage in the opposite direction can be manufactured extremely easily.

【0018】

[Effect of the invention]

As described above, in the method for manufacturing a diode element according to the present invention, a lead phthalocyanine thin film is formed by changing the substrate temperature by a vacuum vapor deposition method, so that an organic semiconductor thin film having an asymmetric structure in the thickness direction can be easily formed. Therefore, it is possible to easily manufacture a diode element having excellent characteristics with a stable operation and a high withstand voltage in the reverse direction.

[Simple explanation of drawings]

[Figure 1]

Partial sectional view which shows the structure of the diode element in one Example of this invention. [Figure 2]

A flowchart showing an embodiment of a method for manufacturing the diode element. [Fig. 3]

Measurement circuit diagram for investigating the operation of the diode element [Fig. 4]

The figure which shows the applied electric field (voltage)-current characteristic before vacuum processing of the diode element. [Fig. 5]

The figure which shows the applied electric field (voltage)-current characteristic after vacuum processing of the diode element. [Explanation of symbols]

1 Insulated substrate 2 Lower electrode 3 Lead phthalocyanine thin film (organic semiconductor thin film) 4 Top electrode 5 Triclinic type crystals 6 Monoclinic type crystal