JP2640136B2 - Method for manufacturing light emitting layer of thin film EL element - Google Patents

Description

The present invention relates to a method for producing a light emitting layer of a thin film EL device,
More specifically, in the step of forming a light emitting layer using a vacuum film forming method such as a vapor deposition method or a sputtering method, the film forming surface is irradiated with an electron beam to generate cathodoluminescence on the film forming surface. The present invention relates to a method for manufacturing a light emitting layer of a thin film EL device, characterized in that the evaporation amount of an evaporation source is controlled while monitoring the temperature.

[Conventional technology]

Conventionally, as a method for forming a light emitting layer of a thin film EL element, for example, there is Japanese Patent No. 957387.

This method, for example, Mn, Cu, a zinc sulfide based sintered body containing an active substance such as TbF ₃ is irradiated with an electron beam to evaporate,
This is to deposit it on a substrate.

However, in this method, the sintered body does not uniformly evaporate due to an electron beam irradiation method or the like, and the correlation between the concentration of the active substance in the formed thin film and the concentration of the active substance in the sintered body tends to be unstable. There was a disadvantage.

That is, it is known that there is a close correlation between the concentration of the active substance in the zinc sulfide-based thin film used as the light emitting layer of the thin film EL element and the light emission luminance of the thin film EL element. The thin-film EL device in which the light emitting layer is formed by the conventional method having the following drawbacks has a drawback that the light emission luminance level varies.

As a method for improving such a defect, Japanese Patent Application Laid-Open No.
No. 0593 discloses that a base material and an active material are used as separate evaporation sources, and that when the base material and the active material are separately evaporated, the active material is detected after detecting that the base material has been deposited on the substrate. A method of opening a shutter of an evaporation source has been proposed.

[Problems to be solved by the invention]

The method described in Japanese Patent Application Laid-Open No. 61-240593 discloses that the time from the arrival of evaporated particles scattered from an evaporation source to the substrate to the start of deposition is correlated with conditions such as the substrate temperature and the evaporation rate of the evaporation source. Focusing on the fact that there is a relationship, delaying the opening of the shutter of the evaporation source of the active substance, delaying the opening of the shutters of the two evaporation sources at the same time does not solve the problem that a layer of almost only the active substance is initially formed. It is assumed that.

However, since there is no guarantee that the amount of evaporation of the active substance is constant, there is a disadvantage that it is difficult to uniformly deposit the active substance in the base material with good reproducibility.

The present invention solves the drawbacks of the conventional method as described in the above publication, optimally controls the amount of evaporation from each evaporation source, and can produce a high-quality thin-film EL element light-emitting layer with good reproducibility. It is an object of the present invention to provide a method for manufacturing an element light emitting layer.

[Means for solving the problem]

In order to achieve the above object of the present invention, the light emitting layer of the thin film EL element, the base material and the light emitting center of the light emitting layer using a vacuum film forming method,
When the activator is formed by evaporating atoms, molecules or compounds from different evaporation sources, the thin film formed on the substrate is irradiated with an electron beam and the energy is absorbed by the thin film to form a cathode. Luminescence is generated, and the cathodoluminescence is used as a monitor, and by controlling the amount of evaporation of the evaporation source so that the characteristics become optimal, the luminescence center and activator concentration in the thin film are controlled. Things.

[Action]

According to the above method, the energy of the electron beam applied to the thin film being formed is absorbed by the thin film, and the film is activated by the ions and the heating effect at that time. can get.

In general, the light-emitting layer of an EL element emits fluorescence (cathode luminescence) when irradiated with an electron beam. The emission intensity and emission spectrum of the fluorescence change under the influence of the material of the base material and the dopant concentration. Therefore, since the characteristics of the EL element and the characteristics of the cathode luminescence are correlated, each evaporation amount is controlled during the formation of the light emitting layer while monitoring the characteristics of the cathode luminescence so that the optimal EL characteristics can be obtained. By doing so, a light emitting layer of a high quality thin film EL element can be obtained with good reproducibility.

〔Example〕

 One embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a schematic diagram of a thin film forming apparatus, in which 1
Is a vacuum chamber, 2 is a substrate, 3, 4, and 5 are evaporation sources each containing a material in a crucible, 6, 7, and 8 are shutters, 9 is a film thickness monitor, and 1 is a film thickness monitor.
0 is an electron gun, 11 is a spectroscope, and 12 is an SMA (Spectral Multi-Analyzer).

In forming the light emitting layer of the thin film EL element, the evaporation source 3
, Zn in the evaporation source 4, and Mn in the evaporation source 5 are respectively heated, and the evaporation sources 3, 4, and 5 are independently heated.

On the other hand, the substrate 2 housed in the upper part of the vacuum chamber 1 is heated to 200 ° C., and in this state, the shutters 6, 7, 8 provided at the openings of the evaporation sources 3, 4, 5 are opened.

Simultaneously, when the electron gun 10 irradiates the film-forming surface of the substrate 2 with an electron beam, the ZnS: Mn electrons on the film-forming surface transition to an excited state, and emit fluorescence (cathode luminescence) when the electrons are relaxed.

This light emission phenomenon occurs when the energy of the electron beam is absorbed by the film-forming surface, and the film-forming surface is activated by ions or a heating effect by the absorption of this energy.

Cathodoluminescence has the characteristic that the emission spectrum changes according to the properties of the substance irradiated with the electron beam.Therefore, this cathodoluminescence is spectrally separated by the spectroscope 11 and the spectrum is detected by the SMA 12 to obtain. By changing the evaporation temperature of the evaporation sources 3, 4, 5 according to the spectrum obtained,
The evaporation amount of each of the evaporation sources 3, 4, and 5 is controlled so as to obtain the optimum spectrum.

As a result, a light-emitting layer of a high-quality thin-film EL device can be formed with good reproducibility.

Although the present embodiment described the ZnS: Mn-based light-emitting layer, ZnS: Tb, ZnS: Sm and other ZnS-based light-emitting layers, C such as CaS: Eu, etc.
An aS-based light-emitting layer and an SrS-based light-emitting layer such as SrS: Ce can be used as they are.

〔The invention's effect〕

As described in detail above, the present invention irradiates a thin film being formed on a substrate with an electron beam, absorbs the energy of the electron beam into the thin film, monitors cathode luminescence generated at that time, and monitors the characteristics (fluorescence). (Emission spectrum, emission intensity, etc.) by controlling the amount of evaporation from each evaporation source so as to obtain the optimum characteristics, thereby controlling the luminescence center in the thin film and the concentration of the activator. By absorbing energy in the thin film, only the temperature of the film formation surface can be increased without increasing the substrate temperature due to the ion or heating effect.

This makes it possible to produce a high-quality light-emitting layer with good crystallinity with good reproducibility by activating the film-forming surface, and it is not necessary to heat the substrate to a high temperature, so it can be applied to a glass substrate with a low softening temperature. it can.

Further, as described in claim 2, by not only evaporating the base material and the active substance from different evaporation sources, but also evaporating atoms constituting the base material separately from different evaporation sources,
The quality is further improved because tighter control is possible.

[Brief description of the drawings]

The drawing is a schematic view showing one embodiment of a thin film forming apparatus for carrying out the method of the present invention. 1 is a vacuum chamber, 2 is a substrate, 3, 4, and 5 are evaporation sources, 10 is an electron gun, 1
1 is a spectrometer, 12 is SMA.

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor 1200, Manda, Hiratsuka-shi, Kanagawa Pref. Komatsu Ltd. Laboratory (56) References JP-A-63-259067 (JP, A) JP-A-64-83657 (JP) , A) JP-A-63-190238 (JP, A) JP-B-2-20932 (JP, B2)

Claims (2)

(57) [Claims] 1. A method for forming a light emitting layer of a thin film EL device by evaporating atoms, molecules or compounds constituting a base material, a light emission center, and an activator from different evaporation sources using a vacuum film forming method. Then, the thin film formed on the substrate is irradiated with an electron beam, and the energy is absorbed by the thin film to generate cathodoluminescence, and the cathodoluminescence is monitored so that the characteristics become optimal. Controlling the amount of evaporation of the evaporation source to control the emission center and activator concentration in the thin film. 2. The method according to claim 1, wherein atoms constituting a base material of the light emitting layer are separately evaporated from different evaporation sources.