JPS59147634A - Formation of insulating film - Google Patents

Abstract

PURPOSE:To form an insulating film consisting of an oxide which has uniform quality and with which dielectric breakdown hardly arises by supplying ionized or activated oxidative gas in an evacuated bell-jar, evaporating an oxide or metal and depositing the same by evaporation on a substrate to be subjected to vapor deposition. CONSTITUTION:A bias voltage is impressed by a power source 6 on a substrate 4 heated to about 150 deg.C by a heater 5 from the rear of said substrate, in a bell- jar 1 the inside of which is evacuated by a vacuum pump. Gaseous O2 13 as oxidative gas is ionized or activated with a gas discharge tube 14 and is supplied through a gas introducing pipe 15. An ITO vapor source 10 is heated to evaporate in this state, and a shutter S4 is opened to deposit ITO by evaporation, thereby forming an ITO transparent electrode on the substrate 4. A Y2O3 insulating film is formed on the substrate 4 from a Y2O3 vapor source 9 by the same operation as mentioned above. A light emitting layer is co-deposited by evaporation by a ZnS vapor source 7 and an Mn vapor source 8 in succession; thereafter an insulating layer is formed by vapor deposition in the same way as mentioned above, and further electrode is formed thereon, whereby an electroluminescence element having the excellent insulating film is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION 1. Industrial Application Field The present invention relates to a method for forming an insulating film.
electroluminescence: hereinafter referred to as E
The present invention relates to a method for forming an insulating film that can be used in light emitting devices such as (referred to as L), solar cells, photosensors, and the like.

2. Prior art The method of converting electric energy into light energy by applying an electric field to a solid film (EL) has been carried out in various ways, and has a wide variety of applications such as displays and EL television receivers. It is being applied to For example, a phosphor thin film has been produced in which Mn is mixed as an actiheter (luminescence center) into ZnS0M1li, which is a U-vt group compound semiconductor. EI uses this phosphor thin film as a light emitter.

Elements have become highly luminous, have a long lifespan, and can be manufactured stably.

However, as a result of studies conducted by the present inventors, it has become clear that the above-mentioned ELJ element has problems arising from the formation method, particularly regarding its insulating film.

Generally, an insulating film (for example, Y2O5) of an IEL element is provided between a substrate and a light emitting layer in order to prevent dielectric breakdown when a voltage is applied. A method is known in which Y2O5 is vaporized by laser beam heating and deposited on a substrate. In addition, RF sputtering method (Ta205, BaTi05, S
There are various methods such as i5N, SiOJ'A formation) or reactive sputtering method (Hf○7, PbTiO film formation). However, all of the known methods have the drawback that the obtained oxide film has an insufficient degree of oxidation and has a stoichiometrically deviated composition, making it susceptible to dielectric breakdown. In addition, when using the sputtering method, after the lower layer is formed by vapor deposition during the manufacturing process of a multilayered element, it may be taken out of the vapor deposition tank and placed in a sputtering device for processing. Since it is exposed to the outside air beforehand, impurities are adsorbed on the surface, causing pinholes. Further, the sputtered film itself cannot be said to be a sufficient film.

3. OBJECTS OF THE INVENTION An object of the present invention is to provide a method capable of forming a homogeneous insulating film with dielectric breakdown and sharp edges.

4. Structure of the invention, that is, the method according to the present invention is to apply a coating material made of an oxide (e.g., Y2O5) or a metal (e.g., Ae) while supplying an ionized or activated oxidizing gas (particularly oxygen). The method is characterized in that it is evaporated and deposited on a substrate to be evaporated, thereby forming an insulating film made of an oxide (for example, Y2O5 or Ae205).

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

First, with reference to FIG. 1, an example of a vacuum evaporation apparatus for forming EL elements by a evaporation method will be described. Inside the metal Pelger 1, the substrate 4 is arranged above, and the Zn is placed below it.
Si source 7, Mn"iM source 8, Y205 evaporation source 9,
ITO (Indium TinOxide) evaporation sources 10 are respectively arranged. SL, 32% S3, and each shutter are different. However, heating means for each evaporation source is omitted from illustration.

Then, while evacuating the inside of the Belshah 1 to 9 x 10 Torr, the substrate 4 is processed to about 150°C with the heater 5. First, the free emission source 9 is heated, and the shack S5
Open the Y2O5 above towards the board 4 and 60 people/mi
It does not fly at a speed of n. At the same time, Herjar
Ionized or activated 02 is supplied from a gas introduction pipe 11 arranged on the side wall of 1. Oxygen 13 is introduced into a gas discharge tube 14 (frequency 13.56 MHz, 300 W) provided in the introduction tube 11, and the oxygen ions or active oxygen are ionized or activated by discharge in the gas discharge tube 14.

In addition, 2 in the figure is a butterfly valve, and 3 is a vacuum valve Y2O.
An insulating film (with a film thickness of, for example, 2,000 layers) consisting of 5 layers can be formed. The thickness of this insulating film is 500 Å or more (preferably 1
500 to 4000 people) is fine, but if it is too thick, please refer to E below.
The threshold voltage of the L element increases, and if it is too thin, dielectric breakdown is likely to occur.This insulating film has excellent properties not found in conventional methods. Y
On the other hand, since the oxygen supplied from the introduction pipe 11 is ionized or activated, the reactivity of the oxygen is high and it efficiently reacts with the evaporated substance.

Therefore, the obtained Y2O5 film is sufficiently oxidized and its composition becomes approximately stoichiometric. The amount of oxygen supplied may be set so that the degree of vacuum in the Pel jar becomes 9 x 10 Torr, but a sufficient degree of oxidation can be obtained if the amount is in the range of 10 to 10 Torr.

The gas discharge tube 14 is preferably constructed as a high-frequency discharge tube, for example as shown in FIGS. 2 and 3.

The high-frequency discharge tube shown in FIG. 2 includes an introduction tube 11 made of glass through which oxygen gas flows, and a cooling jacket tube 33 provided to surround the outer periphery of the oxygen introduction tube 11 (and a cooling water tube 33 through which cooling water 20 flows). ) and discharge electrodes 31 and 32 wound around the outer circumferential surface of the mantle tube 33.

Then, the oxygen gas pressure in the discharge region 36 is 10 Torr.
A discharge is caused between the discharge electrodes 31 and 32 by the voltage from the high frequency power supply 34 while the voltage is maintained below r. Due to dirt, a portion of the oxygen gas is transferred to the discharge area 3.
6 to generate oxygen ions or active oxygen, which are introduced into the Pelger 1 through the inlet 21. The cooling water 20 is allowed to flow through the cooling jacket tube 33 to prevent it from becoming overheated. The discharge electrodes 31 and 32 are link-shaped electrodes, and the distance between the two electrodes is 0.5 to 5.
The inner diameter of each cm is 2 to 10 cmφ or appropriate. In addition, any high frequency can be selected for the high frequency voltage (RF voltage on page 34) applied to the discharge tube, for example, a frequency of 13.56 MHz and an output of 100 W to 2 KW (preferably around 300 W). I can do it. In the high-frequency discharge tube shown in FIG. 3, the discharge electrode 35 consists of a coil-shaped electrode provided on the outer periphery of the cooling jacket tube 33, and the inner diameter of the coil is 2 cmφ to 20 cm.
mφ is appropriate.

In addition, in FIG. 1, the oxygen discharge tube 1 is connected to the exhaust pipe 3.
Gas supply from 4 and waste consumption amount Q in Healthier 1
This is balanced and evacuated to maintain a predetermined oxygen pressure inside the bell shear 1. Reference numeral 6 denotes a power source that applies a bias voltage to a back electrode provided close to or in contact with the substrate 4. A DC voltage in the range of 0 to -1.0 (v) or an AC voltage in the range of 0 to 51 (v) is applied to the rear electrode. It is used to adjust the heating of the substrate 4 to a range of 11 degrees.

FIGS. 4 and 5 show Y2O formed by the method described above,
IE L equipped with a membrane (not represented by 41.44 in the figure)
The element is shown.

The EL element in FIG.
On top of this, a Y2O5 layer 44 with a thickness of 2000 mm to prevent dielectric breakdown, a light emitting layer 371 with a thickness of 5000 mm, and a Y2O5 layer 44 with a thickness of 2000 mm to prevent dielectric breakdown.
205 layers 41 and metal electrodes 42 are sequentially deposited. If the power source 45 is connected between both electrodes 42 and 43 and AC drive is performed, Mn-containing ZnS can be produced relatively stably.
High-intensity yellow-orange light can be obtained from the film 37 with high efficiency, making it suitable for use in long-life displays, etc. Of course, the other elements can be changed to a DC drive system as shown in the structure shown in FIG.

According to the above E■-element, Y2O5t as an insulating film
=44.41 is homogeneous and has a stoichiometric composition as described above, so it is sufficient to prevent dielectric breakdown. Moreover, since the substrate temperature during film formation is low, the film can be formed without being adversely affected by temperature.

For this reason, the Y2O3 layer exhibits sufficient tension and is long.

As the service life is extended, there is no problem even if the thickness is reduced by 11, so the threshold value during driving will decrease. Therefore, this insulating layer satisfactorily satisfies the performance required for an EL element (high dielectric constant and high breakdown voltage).

Next, specific experimental results will be explained.

The dielectric breakdown voltage E (electric field strength) and dielectric constant ε of Y20 JFi formed by the conventional vapor deposition method and Y2O layer formed by the method of the present invention were as follows.

Breakdown electric field (V/cm) Relative permittivity ε Conventional method
3.4 X10 8.5 Invention
5.2
It can be seen that the insulation properties are improved by looking at jψ−. In particular, when used in an EL device, the electric field required for emitting light from the device is 10 oaks (especially I
OV/cm), it is possible that membranes made using the conventional method may be damaged due to fluctuations in power supply voltage, etc., or that the model 1 according to the present invention has a higher withstand voltage. It has become much harder to destroy.

In addition, when we compared the conventional method (deposition of Y2O5 by heating with electronic heat) and the method according to the present invention for the Y2O layer using the AC drive type E2 element with the configuration shown in Fig. 4, we found the following results. ri'iA was applied (however, ri'iJ wave number 5
KIIz).

Threshold voltage (■) Luminance (candela/renal) Conventional method
195 714 Present invention 165
．． 78.2 According to this, E according to the invention
The I7 element has a low threshold voltage and a high luminance of light emission]
I can see that you are doing this. Regarding this luminance, we also measured the change over time, and in the device using the conventional method, the luminance deteriorates over time as shown in Fig. 6, but what about the device according to the present invention? (As shown in Figure 7, it was found that there was almost no change over time.) In addition, in the elements shown in Figures 4 and 5, Y2O
Although it has been described that the five layers 41, 44 are formed by the stem attaching method according to the present invention, it is also possible to continuously form approximately 0 layers of each of the other layers 43, 37, and 42 using the same stem attaching device. That is,
l 10 layer 43 opens the shutter=S11 in FIG.
It is formed by depositing ITO under the introduction of (from). This trot=43 also has a sufficient degree of oxidation like Y2051fi, so it is a conductive film with good transparency. Further, the light emitting layer 37b, the shutter S1,
It is formed by opening S2 to allow Zn, S and Mn vapors to fly out and deposit them together on the substrate. At this time, the basic h'lA degree is preferably 1.00 to 500°C, and the amount of Mn flashing is preferably 0601 to 1% by weight relative to ZnS.

In this way, since each layer is formed successively in the same vapor deposition apparatus, the device creation work is made more efficient, and when the upper layer is formed after the lower layer is formed, it is removed from the apparatus once. This eliminates the problem of surface contamination due to impurities and eliminates the occurrence of pinholes.

Furthermore, the high frequency discharge properties shown in FIGS. 2 and 3 have the following features.

(↓), in the discharge part, the discharge electrodes 31 and 32 are connected to the discharge area 36
It can be installed in a position that does not touch the Therefore, the electrodes 31 and 32 are not bombarded during discharge, and the electrode material does not mix into the waste and contaminate the deposited film.

(2) Since the discharge electrodes 31 and 32 are provided outside the bell shear, in addition to the above problem, the problem of staining of the film 711 due to the electrode material is further resolved, and the film quality can be significantly stabilized. Moreover, the electrodes are not contaminated by the vapor of the vapor deposited material.
No anti-fouling measures are required at all.

(3) In addition, a cooling means for the discharge electrode (in the above example, a water-cooled jacket tube) can be easily provided, and the discharge electrode can also be cooled by air cooling.

(4) In particular, with the well-known RF ion blating method, a discharge tube can produce a sufficient amount of active gas without depending on the degree of vacuum in the Hölscher. By adjusting the amount of sludge introduced and the amount of exhaust without changing the degree of vacuum inside the Hölscher, the sludge and pressure inside the discharge tube can be set, thereby stabilizing the discharge.

Although the present invention has been illustrated above, the above-mentioned example can be further modified based on the technical idea of the present invention.

For example, in addition to the above-mentioned Y2O5, BaTi05, PhTiC) can be used as an evaporation source for forming an insulating film.
, Aez○u, Ta205, HfO2, S
1 02, Ti 02, S town oxides, Y
, Ba, Pb, A6. Ta.

Metals such as Hf, Ti, Sm, etc. can be used. Further, 1. The oxidizing gas is not limited to oxygen, but may be a gas containing oxygen and harmless to the deposited film (for example, air, argon, etc.).

6. Effects of the invention As described above, the present invention deposits oxides or metals while supplying oxidizing scum by ionizing or activating it.
The oxidation reaction progresses sufficiently, and the resulting insulating film has a stoichiometric degree of oxidation. Therefore, an insulating film with improved dielectric strength and improved homogeneity can be obtained.

[Brief explanation of drawings]

The drawings show embodiments of the present invention, in which Fig. 1 is a schematic sectional view of a vapor deposition apparatus, Figs. 2 and 3 are sectional views of two sides of a high-frequency scum discharge tube, and 4. Figure 5 is a cross-sectional view of the two sides of the EL element, Figure 6 is a graph showing the change in luminance over time of a 1=l-element according to the conventional method, and Figure 7 is a graph showing the change in luminance over time of the EL element according to the method of the present invention. It is a graph showing a change in luminance over time. In addition, in the symbols shown in the drawings, 4------1 substrate 7--1 n S evaporation source 3--M n evaporation source 9'---YzO5 evaporation source 1, 0-- --I TO evaporation source 11 --- One waste introduction tube 13 --- Oxidizing gas 14 --- Gas discharge tube 37 --- Light emitting layer 41, 4 4 --- One Dark color Edge layer 42- Electrode 43-'-"'-do VO transparent electrode. Agent: Patent attorney Hiroshi Aisaka (and 1 other person) 4th V 50th

Claims (1)

[Scope of Claims] 1. While supplying an ionized or activated oxidizing gas, a vapor deposition material made of an oxide or metal is evaporated onto a substrate to be deposited, thereby making a vapor deposition material made of an oxide A method for forming an insulating film, the method comprising forming an insulating film. 2. The method according to claim 1, characterized by a high frequency discharge tube for ionizing or activating the oxidizing gas.