JPH0685352B2 - High frequency sputtering method and thin film EL element manufacturing method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a high frequency sputtering method for a thin film of a kind used for a semiconductor element or the like, and further contains a sulfide such as zinc sulfide, calcium sulfide or strontium sulfide as a main component. And a method for manufacturing a thin film EL device having a phosphor layer.

2. Description of the Related Art Conventionally, vacuum deposition, sputtering, CVD, etc. are well known as methods for producing thin films. Among them, the sputtering method is particularly characterized in that if the target is formed of a desired evaporation material, a high melting point material and a thin film of a multi-component compound that cannot be formed by the vacuum evaporation method can be formed. Also, by introducing a reactive gas during sputtering, a compound thin film of the target substance and the reactive sputtering gas component can be prepared. For these reasons, the sputtering method is one of the thin film forming methods widely used in the field of semiconductors and the like.

The thin film EL element is a light emitting element including a phosphor layer containing sulfide as a main component, and a dielectric layer and an electrode layer sandwiching the phosphor layer. As the phosphor material, ZnS: Mn, ZnS: Tb, F, CaS: Eu,
SrC: Ce, etc. are used, each of yellow-orange, green,
It emits red and blue light. Among them, ZnS: Mn is mainly manufactured by the vacuum deposition method and is put into practical use as an EL display panel, but materials other than ZnS: Mn have not been put into practical use yet, and it is possible to improve the quality by the manufacturing method of seeds. Attempts to increase the brightness have been made. Among them, to date, many of the devices manufactured by the high frequency sputtering method have obtained relatively good characteristics.

However, although the sputtering method has the advantages described above, it has a drawback that the film forming rate is slow. Also, in recent years in the field of semiconductors, elements are becoming finer and multilayer wiring is advancing, and the need for planarization is increasing accordingly. However, in the conventional sputtering method, the evaporation material from the target is anisotropically deposited. Therefore, it has been impossible to realize flatness of the device.

The need for planarization is the same for thin film EL devices. As shown in FIG. 4, the thin film EL element has a first dielectric layer 43, a phosphor layer 44, and a second dielectric layer 45 sequentially formed on a stripe-shaped transparent electrode 42 formed on a substrate 41. Is a transparent electrode on it
A back electrode 46 is formed so as to be orthogonal to 42. At this time, since the transparent electrode 42 is formed on the stripe, a step is formed, so that the back electrode 46 is often disconnected. To prevent this disconnection, measures such as forming a taper on the transparent electrode 42 have been taken, but this is not perfect in terms of reproducibility and the like.

Further, in order to form the phosphor layer, the high frequency sputtering method is often used for the reason described above, but it has a drawback that the film forming speed is slower than that of the vacuum evaporation method. Another disadvantage of the sputtering method is the serious problem that dust such as flakes from the target material adheres to the film-forming surface, causing the film to peel and causing dielectric breakdown when the device emits light. is there.

The present invention aims to solve such problems of the conventional technology.

Means for Solving the Problems The present invention according to claim 1 provides a physical target as a means for increasing the film-forming rate and flattening the element, with respect to the drawbacks of the sputtering method as described above. In addition to the sputtering gas for sputtering, the etching gas capable of chemically etching the target is simultaneously introduced to perform sputtering.

Further, according to the present invention of claim 3, when a phosphor layer containing sulfide as a main component is formed by a high frequency sputtering method, a chlorine gas or a compound gas containing chlorine is added in addition to the sputtering gas. Do the membrane.

Effect According to the high-frequency sputtering method of the present invention, the etching gas introduced into the vacuum apparatus chemically etches the target surface, thereby weakening the bond on the target surface. Since the surface is sputtered by the gas that physically sputters the target in such a state, molecules or atoms on the target surface are easily evaporated and deposited on the substrate, and a high film formation rate is obtained. Furthermore, the etching gas also acts on the thin film deposited on the substrate surface.
That is, the convex portion of the stepped portion of the substrate surface is more easily etched, and in the high frequency sputtering method, the sputtering effect is slightly exerted on the substrate surface, so that the etching effect of the convex portion of the stepped portion is further accelerated. The element can be flattened.

When the above high-frequency sputtering method is used for film formation of the phosphor layer at the time of manufacturing the thin film EL element, the phosphor layer film can be formed at high speed, and the step of the transparent electrode of the base is eliminated so that the back electrode No disconnection occurs. Further, even if dust such as flakes is generated, the flakes are melted and disappear because the target surface is etched by the etching gas. Therefore, it is possible to obtain a good thin film EL device without causing dust such as flakes to adhere to the film-forming surface to cause peeling or to cause dielectric breakdown when the device emits light.

Examples Examples of the present invention will be described below.

FIG. 1 is a structural diagram showing an outline of a sputtering apparatus used for forming a phosphor layer containing sulfide as a main component in the high-frequency sputtering method and the method for manufacturing a thin film EL element of the present invention. A cathode 12 and an anode 13 are arranged in the vacuum container 11. A target 14 is arranged on the cathode 12, and a semiconductor or glass substrate 15 is arranged on the anode 13. A high frequency power supply 17 is connected to the cathode 12 through a matching circuit 16. A plurality of gas introduction ports 20 are attached to the vacuum container 11 via flowmeters 19, respectively, and a plurality of gases can be introduced into the vacuum container 11 while controlling the desired flow rates. Also vacuum container 11
The internal pressure is controlled to a desired pressure by the vacuum exhaust system 18.

Table 1 shows examples of the present invention. Conventionally, when forming the thin films shown in the table by the sputtering method, only the sputtering gas in the table was used. On the other hand, in the present invention, in addition to the above-mentioned sputtering gas, one of the etching gases shown in the table or a mixed gas thereof is simultaneously introduced to perform sputtering. These etching gases are gases that are activated by plasma and can chemically etch the target material. The film formation by sputtering proceeds simultaneously with the etching of the target. That is, the atoms or molecules of the target surface whose binding force is weakened by the etching gas are easily knocked out from the target surface by the sputtering gas and deposited on the substrate surface. Therefore, compared with the conventional method, a high film forming rate can be obtained even when the same high frequency power is applied.

The etching gas also acts on the uneven film deposited on the substrate surface. In the case of the high frequency sputtering method, the substrate surface is slightly affected by sputtering due to the self-bias effect. When the surface of the substrate has irregularities, the convex portion is more susceptible to the action of sputtering, but in the conventional method, it was impossible to flatten the surface of the substrate by only a slight action of sputtering on the surface of the substrate.
However, in the high frequency sputtering method of the present invention,
Since the etching gas that can etch the target material at the same time as the sputtering gas, that is, the gas that can also etch the substrate surface is added, the etching of the convex portion proceeds much faster. As a result, the convex portion on the substrate surface disappears and the substrate surface is flattened.

The flow rate of the etching gas varies depending on the material of the target or the thin film to be formed, but when the etching gas is too much as shown in FIG. 2, the etching effect becomes too large, and conversely the film forming rate is increased. Will fall. Therefore,
It is desirable that the etching gas is approximately 15% or less of the total gas flow rate.

In this embodiment, the case where Al ₂ O ₃ , Si ₃ N ₄ and SiO ₂ shown in Table 1 are formed is described, but the high frequency sputtering method of the present invention is not limited to these thin films. It is obvious that other thin films can be formed in the same manner by appropriately selecting the target material, the generated film, and the etching gas capable of chemically etching the material.

Next, an example in which the above-described high frequency sputtering method is used for forming a light emitting layer of a thin film EL element is shown in FIGS.
Shown according to (c). Striped transparent electrodes 32 as shown in FIG. 3A are formed on a glass substrate 31. A first dielectric layer 33 is formed on the transparent electrode 32. As shown in the figure, since the transparent electrode 32 is formed in a stripe shape, the first dielectric layer 33 also has stripe unevenness. This glass substrate 31 was set in the sputtering device shown in FIG. On the target
A powder obtained by mixing ZnS with 5 wt% of TbF ₃ was firmly spread on a petri dish made of quartz. In the vacuum chamber, Ne and H ₂ S were used as sputtering gas, and CCl was used as etching gas.
₄ Gas is introduced. Gas flow rate is 40SCCM, 4SCCM,
And 4SCCM. The pressure in the vacuum chamber is maintained at 5 × 10 ^-2 Torr and sputtering is performed. The high frequency power was 400W. As shown in FIG. 3B, a ZnS: Tb, F film is formed as a phosphor layer 34 on the first dielectric layer 33, and a portion where the stripe of the transparent electrode 32 is formed (the portion that actually emits light). Was formed to a thickness of 500 nm. As shown in FIG. 3 (b), a flat phosphor layer 34 could be formed by using the above-described high frequency sputtering method of the present invention. The film forming speed was 25 nm / min when the film was formed only with the conventional mixed gas of Ne and H ₂ S, whereas the film forming speed at this time was 40 nm / min, which was 1.5 times or more. In addition, the phosphor layer 34 formed was free of dust such as flakes often seen in the conventional film forming method. Thin film EL device is the third
As shown in FIG. 3C, the second dielectric layer is formed on the phosphor layer 34.
The back electrode 36 is formed so as to be orthogonal to the transparent electrode 32 and the transparent electrode 32, thereby completing the process.

As shown in FIG. 3 (c), when the method for manufacturing a thin film EL element of the present invention is used, the phosphor layer 34 is flattened, so that the back electrode 36 is the same as the conventional thin film shown in FIG. There is no step like the EL element. Therefore, in the thin film EL element manufactured by using the manufacturing method of the present invention, there is no disconnection of the back electrode, and it is possible to obtain a good thin film EL element in which dust such as flakes does not adhere to the phosphor layer. . Further, in the case of a thin film of the phosphor layer, since the high-frequency sputtering method described above is used, it is possible to form a phosphor layer exhibiting good emission characteristics at high speed, and the method for producing a thin film EL element of the present invention The effectiveness has been revealed.

In this embodiment, a mixed gas of Ne and H ₂ S was used as the sputtering gas and CCl ₄ gas was used as the etching gas, but the gas used is not limited to these. For example, as the sputtering gas, an inert gas such as Ar or He or
A mixed gas of H ₂ S and Cl ₂ or
A chlorine gas such as BCl ₃ , ClF, HCl or ClCN, or a compound gas containing chlorine can be used.

Further, in the present embodiment, the case where a ZnS: Tb, F green EL device was manufactured as a thin film EL device was described, but it is clear that the manufacturing method of the present invention is not limited to the material of the phosphor layer, and CaS It can be applied to the production of all EL elements such as: Eu red EL element and SrS: Ce blue EL element that can form a phosphor layer by a sputtering method. In all cases, there is no breakage of the back electrode, there is no dust such as flakes on the phosphor layer, and it is clear that the phosphor layer is formed at high speed.

EFFECTS OF THE INVENTION By using the high frequency sputtering method of the present invention, the film formation rate is high and the film surface can be flattened. Further, according to the present invention, by using the method for manufacturing a thin film EL element, the surface of the phosphor layer can be flattened during the formation of the phosphor layer, so that the breakage of the back electrode can be eliminated. Further, since dust such as flakes is suppressed during the phosphor layer film formation, it is possible to obtain a good thin film EL element without peeling or dielectric breakdown.

[Brief description of drawings]

FIG. 1 shows the high frequency sputtering method and thin film EL of the present invention.
FIG. 2 is a structural diagram showing an outline of a sputtering apparatus used for carrying out the element manufacturing method, FIG. 2 is a graph showing the relationship between the flow rate of the etching gas and the film forming rate, and FIG. 3 is the thin film of the present invention.
FIG. 4 is a cross-sectional view showing a thin film EL element manufactured by the conventional manufacturing method, and FIG. 11 ... Vacuum container, 12 ... Cathode, 13 ... Anode, 14
…… Target, 15 …… Board, 16 …… Matching circuit,
17 …… High frequency power supply, 18 …… Vacuum exhaust system, 19 …… Flowmeter,
20 ... Gas inlet, 31 ... Glass substrate, 32 ... Transparent electrode, 33 ... First dielectric layer, 34 ... Phosphor layer, 35 ... Second
Dielectric layer, 36 ... Back electrode, 41 ... Substrate, 42 ... Transparent electrode, 43 ... First dielectric layer, 44 ... Phosphor layer, 45 ... Second
Dielectric layer, 46 ... Back electrode.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP 63-21787 (JP, A) JP 63-6773 (JP, A) JP 59-119697 (JP, A)

Claims (4)

[Claims] 1. When a gas is introduced into a vacuum chamber to generate plasma and the target is sputtered to deposit a thin film, the target is chemically etched in addition to a sputtering gas that physically sputters the target. A high-frequency sputtering method, characterized in that an effective etching gas is introduced at the same time. 2. When the etching gas capable of chemically etching the target is simultaneously introduced in addition to the sputtering gas for physically sputtering the target, the flow rate of the etching gas is set to 15% of the total gas flow rate. % Or less, The high frequency sputtering method according to claim 1, wherein 3. A method of manufacturing a thin film EL element comprising a phosphor layer formed on a substrate and electrode layers sandwiching the phosphor layer, wherein the phosphor layer containing sulfide as a main component is formed by a high frequency sputtering method. In this case, a chlorine gas or a compound gas containing chlorine is added to the sputtering gas in addition to the sputtering gas. 4. When the phosphor layer containing sulfide as a main component is formed by a high frequency sputtering method, the gas flow rate of chlorine gas or a compound containing chlorine, which is added in addition to the sputtering gas, is set to the total gas flow rate. The method for producing a thin film EL element according to claim 3, wherein the content is 15% or less.