JPH0666153B2 - Method of manufacturing thin film EL device - Google Patents

Description

Description: TECHNICAL FIELD OF THE INVENTION The present invention relates to a method for manufacturing a thin film EL element, and more specifically to a method for manufacturing a thin film EL element which has a wide hysteresis width appearing in luminance vs. voltage characteristics and is stable with time. Regarding the method.

[Technical background of the invention]

In the ZnS: Mn thin film EL element, as shown in FIG. 1, a transparent electrode 2 was laminated on a substrate 1 such as glass, and a ZnS: Mn light emitting layer 4 was formed on the transparent electrode 2 with an insulating film 3 interposed therebetween. Later,
Further, the structure is such that it is sandwiched by the insulating film 3, and a back electrode 5 is further formed on the insulating film 3.

In the case of forming the light emitting layer of the thin film EL element having such a structure, conventionally, the light emitting layer 4 is formed by the vapor deposition method after forming the insulating film 3 on the transparent electrode 2 by the sputtering method, the vapor deposition method or the like. That is, ZnS and metallic manganese or manganese chloride are formed on the insulating film 3 by the action of an electron beam in a vacuum.

The brightness-voltage characteristics of the thin-film EL element having the above-described configuration are
As shown in FIG. 2, the threshold voltage rises sharply,
It saturates at a brightness of several thousand cd / m ² .

However, when the Mn concentration of the light emitting layer 4 is increased, the substrate temperature during the production of the light emitting layer 4 is lowered, and further heat treatment is performed, as shown in FIG. It is known to show different hysteresis phenomena when descending. This characteristic is called the memory phenomenon.

Thus, the thin film EL element exhibiting the hysteresis phenomenon is X
The Y matrix display panel has many advantages such as a simple driving circuit, a large area, easy optical writing, and the like. For this reason, from the end of the 1970s until the beginning of the 1980s, it was actively studied in various places. However, the thin film EL device manufactured by the vapor deposition method as described above has the following two problems.

The saturation brightness and the memory width (voltage width of the hysteresis curve) are in a contradictory relationship. (Marrello et al., IEEE Tr, ED-27 (19
80) P1767, see).

This relationship is shown in FIG. In the figure, the solid line shows the relationship between Mn concentration and brightness, and the broken line shows Mn concentration and memory width / threshold voltage (%).
Shows the relationship with. As is clear from this figure, Mn
The brightness is maximized at a concentration of about 0.3% by weight, while the memory width is maximized at about 1 to 2% by weight. Therefore, when the memory width is increased, the brightness decreases, and when the brightness is increased, the memory width decreases.

Memory width decreases over time (Alt et al., J.Appl.Ph
ys.vol153 (1982) P5186).

This relationship is shown in FIG. As is clear from FIG. 5, the memory width decays in about 100 to 200 hours.

[Outline of Invention]

The present invention has been made in view of the above points, and an object of the present invention is to provide a method of manufacturing a thin film EL element in which the luminance-memory width characteristic and the attenuation of the memory width of the above thin film EL element are improved.

Therefore, according to the method of manufacturing a thin film EL element according to the present invention, a method of manufacturing a thin film EL element having a structure in which a ZnS: Mn light emitting layer is sandwiched with an insulator and having a hysteresis effect on emission luminance vs. applied voltage characteristics is used. , Mn concentration is 0.3 to 1.5% by weight
The ZnS: Mn light emitting layer is 1 to 8 × with one or more selected from the group consisting of dimethyl zinc and diethyl zinc.
10-5 mol / min, 4 to 45 × 10 or more of one or more selected from the group consisting of hydrogen sulfide, dimethyl sulfur and diethyl sulfur
-5 mol / min, and one or more selected from the group consisting of tricarbonylcyclopentadienyl manganese and π-cyclopentadienyl manganese at 0.5 to 2 × 10 −5 mol / min.
It is characterized in that each of them is supplied at a supply rate of minutes and vapor phase growth is performed.

The thin-film EL device manufacturing method according to the present invention is characterized by forming a ZnS: Mn light-emitting layer by an organic vapor deposition method using an organometallic compound, which is different from the conventional vapor deposition method. As is clear from the example, the luminance-memory width characteristic is improved, and the memory width attenuation is also suppressed.

[Specific Description of the Invention]

According to the method of manufacturing a thin film EL device of the present invention, first, an insulating film is formed on a transparent electrode on a substrate such as glass, and then a ZnS: Mn light emitting layer is formed on the insulating film by a metal organic chemical vapor deposition method. Let it form.

The method for forming the transparent electrode and the insulating film on the substrate is
The present invention is not limited thereto, and conventional vapor deposition method, sputtering method, etc. can be effectively used.

The type of the insulating film sandwiching the ZnS: Mn light emitting layer is not limited to the present invention, and for example, conventionally used Sm ₂ O ₃ , Ta ₂ O ₅ , Y ₂ O ₃ , Si ₃ N. It can be ₄ , and so on.

In the present invention, the ZnS: Mn light-emitting layer sandwiched between such insulating films is selected from the group consisting of dimethyl zinc and diethyl zinc, selected from the group consisting of hydrogen sulfide, dimethyl sulfur, and diethyl sulfur. One or more and tricarbonylcyclopentadienyl manganese,
It is produced by vapor phase growth from a source gas containing at least one selected from the group consisting of π-cyclopentadienyl manganese.

It is not clear why the growth of the ZnS: Mn light-emitting layer from such an organometallic compound, unlike the vapor deposition method, improves the luminance vs. memory width characteristics and the characteristics of the memory width with time, but will be described later. As is clear from the examples, the luminance vs. memory width characteristics and the characteristics of the memory width over time are remarkably improved.

The organozinc compound used in the present invention is for constituting ZnS, and together with an organic sulfur compound or hydrogen sulfide described later, forms a ZnS film, and is selected from the group consisting of dimethyl zinc and diethyl zinc. Use one or more of the following:

Further, the organic sulfur compound used in the present invention is Zn in the organic gas phase reaction with the organic zinc compound as described above.
It forms S and uses one or more selected from the group consisting of dimethyl sulfur, diethyl sulfur and hydrogen sulfide.

Mn added as a dopant in the ZnS layer is added as an organic manganese compound in the source gas to form a ZnS: Mn light emitting layer. Such an organic manganese compound is incorporated as a dopant in the ZnS layer in the organic vapor phase growth as described above, and is selected from the group consisting of tricarbonylcyclopentadienyl manganese and π-cyclopentadienyl manganese. Use one or more of the following:

The ZnS: Mn light-emitting layer is grown on the insulating film by organic vapor deposition from such a source gas. At this time, one or more of the organic zinc compounds is 1 × 10 ^-5 × 8 × 10 ^-5 mol / min. It is introduced into the growth system at a flow rate of. If it is less than 1 × 10 ^-5 mol / min, the growth rate will be too slow to be practical, while 8 × 10 ^-5
This is because if the flow rate exceeds mol / min, the film quality of the light emitting layer may deteriorate.

In addition, one or more of organic sulfur compounds and hydrogen sulfide is 4
It is introduced into the growth system at a flow rate of × 10 ^{-5 to} 45 × 10 ^-5 mol / min.
If this flow rate is less than 4 × 10 ^-5 mol / min, the growth rate will be too slow as in the case of the above-mentioned organozinc compound, while if the flow rate exceeds 45 × 10 ^-5 mol / min. This is because the film quality of the light emitting layer may deteriorate.

Furthermore, one or more of the organic manganese compounds is 0.5 × 10 ^−5.
It is introduced into the growth system at a flow rate of ~ 2 x 10 ^-5 mol / min. This is because if the flow rate is less than 0.5 × 10 ⁻⁵ mol / min, the memory may not be displayed, and if it exceeds 2 × 10 ⁻⁵ mol / min, the brightness may be significantly reduced.

The Mn concentration of such a ZnS: Mn light-emitting layer is 0.3 × 1.5% by weight, as will be apparent from Examples described later. 0.3% by weight
If it is less than 1, the memory width becomes too small, while if it exceeds 1.5% by weight, the brightness may be lowered too much.

In the metal organic chemical vapor deposition method as described above, the substrate (substrate and insulating film) temperature is preferably 250 to 350 ° C. If it is lower than 250 ° C, the vapor phase growth rate is insufficient, and if it exceeds 350 ° C, the properties of the light emitting film may deteriorate.

Examples of the present invention will be described below.

Example A thin film EL device having a structure as shown in FIG. 1 was manufactured.

After forming the transparent electrode 2 on the glass substrate 1, an Sm ₂ O ₃ insulating film was formed by vapor deposition. After that, dimethyl zinc, hydrogen sulfide, and further tricarbonylcyclopentadienyl manganese were used to form a ZnS: Mn light emitting layer 4 by metal organic chemical vapor deposition under the following conditions. Then, the insulating film 4 and the A1 back electrode 5 were provided by a usual method to manufacture a thin film EL device.

Condition 1 Flow rate of dimethyl zinc: 2 × 10 ⁻⁵ mol / min Flow rate of H ₂ S: 6.7 × 10 ⁻⁵ mol / min Flow rate of tricarbonylcyclopentadienyl manganese:
1 × 10 ⁻⁵ mol / min Substrate temperature: 300 ° C. Dilute hydrogen flow rate: 2 l / min Substrate temperature: 300 ° C. Growth pressure: 60 torr For comparison, the ZnS: Mn light emitting layer was formed by the conventional EB evaporation method under the following conditions 2. A thin film EL device was manufactured in the same manner as above, except for the above.

Condition 2 Substrate temperature: 180 ° C. Deposition rate: About 1000Å / min Vacuum degree: 3 × 10 ⁻⁶ torr Heat treatment condition: 400 ° C., 1 hour FIG. 6 shows the thin film EL device according to the present invention and the conventional method. 3 shows the Mn luminance dependence of the saturation luminance of the thin film EL device manufactured by. In addition, the memory width
Shows Mn concentration dependence. 6 and 7 in FIG.
Is the thin film EL element according to the present invention, and 7 is the Mn concentration dependence of the thin film EL element manufactured by the conventional method.

As is apparent from FIGS. 6 and 7, the thin film EL element manufactured by the method of the present invention has advantages of higher brightness and wider memory width than the conventional thin film EL element. .

Next, the thin film EL device manufactured by the present invention was
The change with time in the memory width when continuous light emission at m ² was measured. The results are shown in Fig. 8.

As is clear from FIG. 8, in the thin film EL device manufactured according to the present invention, the memory width does not decrease sharply even after a lapse of about 1000 hours, and the temporal variability is greatly improved as compared with the conventional one. I found out.

Incidentally, dimethyl zinc, hydrogen sulfide, tricarbonyl pentadienyl manganese was used in the above examples,
Instead of them, diethyl zinc, dimethyl sulfur,
Similar results were obtained when diethyl sulfur and π-cyclopentadienyl manganese were used.

〔The invention's effect〕

As described above, according to the method for manufacturing a thin film EL element of the present invention, by manufacturing the ZnS: Mn light emitting layer by the metal organic chemical vapor deposition method, it is possible to manufacture a stable thin film EL element having a wide memory width. Has the advantage that

[Brief description of drawings]

FIG. 1 is a sectional view showing the structure of a thin film EL element, FIG. 2 is a diagram showing the luminance-voltage characteristics of a conventional thin film EL element, and FIG. 3 is a luminance-voltage characteristic of a conventional thin film EL element having memory characteristics. FIG. 4 is a diagram showing the luminance and memory width Mn concentration dependence of a conventional thin film EL element, and FIG. 5 is a conventional thin film EL device.
FIG. 6 is a diagram showing the change over time of the memory width of the device, FIG. 6 is a diagram showing the Mn concentration dependence of the brightness of the thin film EL device manufactured according to the present invention, and FIG. 7 is a memory width of the thin film EL device manufactured according to the present invention. FIG. 8 is a graph showing the Mn concentration dependence, and FIG. 8 is a graph showing the change over time in the memory width of the thin film EL device manufactured by the method of the present invention. 1 ... Substrate, 2 ... Transparent electrode, 3 ... Insulating film, 4 ... Zn
S: Mn light emitting layer, 5 ... Back electrode.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Bunjiro Tsujiyama 162 Shirahane, Shirahoji, Tokai-mura, Naka-gun, Ibaraki Prefecture, Nippon Telegraph and Telephone Corporation, Ibaraki Telecommunications Research Institute (56) (JP, A) JP 60-216495 (JP, A) JP 61-256715 (JP, A) JP 60-221988 (JP, A) JP 61-179092 (JP, A)

Claims (1)

[Claims] 1. A method of manufacturing a thin film EL device having a structure in which a ZnS: Mn light emitting layer is sandwiched by an insulator and having a hysteresis effect on emission luminance vs. applied voltage characteristic, wherein the Mn concentration is 0.3 to 1.5.
The ZnS: Mn light-emitting layer, which is contained in a weight percentage of 1, to 1 or more selected from the group consisting of dimethyl zinc and diethyl zinc.
8 × 10 −5 mol / min, 4 to 45 of one or more selected from the group consisting of hydrogen sulfide, dimethyl sulfur and diethyl sulfur
X10-5 mol / min, and 0.5 to 2 x 10-5 m of one or more selected from the group consisting of tricarbonylcyclopentadienyl manganese and π-cyclopentadienyl manganese.
A method for producing a thin film EL element, characterized in that the thin film EL element is produced by vapor-phase growth by supplying each at an ol / min supply rate.