JPH059714A - Electron beam evaporating source - Google Patents

Abstract

PURPOSE:To prevent fracture of a hearth liner due to thermal shock used for an electron beam evaporating source. CONSTITUTION:The vapor source 2 is contained in a plate-like hearth liner 9 disposed on the inside of a crucible 3. This hearth liner 9 consists of a material having high thermal insulation, and its outer diameter is made a little smaller than the inner diameter of the crucible 3. The hearth liner 9 is disposed on the bottom of the crucible 3 with a space 10 provided between the outer surface of the hearth liner 9 and the inner surface of the crucible 3. Or the surface of the hearth liner 9 facing the crucible 3 is made to have a porous layer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electron beam evaporation source used in a vacuum vapor deposition method, an ion plating method or the like, and in particular, a hearth liner is installed inside a water-cooled crucible and a raw material vaporized in the hearth liner. The present invention relates to an electron beam evaporation source adapted to accommodate a.

[0002]

2. Description of the Related Art For example, when manufacturing a semiconductor device,
It is required to form a highly pure thin film. Generally, such thin films are formed by evaporating a solid source in a vacuum using an electron beam evaporation source and depositing it on a substrate. The electron beam evaporation source is one in which a raw material is contained in a water-cooled crucible made of copper called a hearth, and the raw material is directly heated by irradiating the raw material with an electron beam. According to such an electron beam evaporation source, the temperature rise of the crucible is suppressed by water cooling the crucible, so that the crucible material is prevented from being mixed into the thin film to be formed, and a thin film with high purity can be formed. it can.

By the way, in such an electron beam evaporation source, if the raw material is stored in the crucible as it is, the heat of the raw material is taken by the water cooling of the crucible, so that the heat loss increases and the power consumption increases. There is a problem. Further, while the raw material is heated to a temperature higher than the melting point, the crucible can be kept at about 100 ° C. by being water-cooled, so the temperature between the surface portion of the raw material and the temperature of the portion in contact with the crucible However, there is also a problem in that bumping occurs and splash occurs.

Therefore, in order to deal with such a problem, an inner crucible called a hearth liner is installed inside the crucible and the raw material is contained in the hearth liner. The hearth liner is a dish-shaped one having a side wall and a bottom wall formed of a material having a high heat insulating property. When such a hearth liner is used, heat transfer from the raw material to the crucible is reduced, so that heat loss can be reduced and the temperature of the melted raw material can be made uniform.

Conventionally, the hearth liner is made of a homogeneous material and is installed so as to be in close contact with the crucible.

[0006]

However, the hearth liner is required to have heat insulation and heat resistance as well as a material that does not combine with the raw material or vaporize. In addition, it must be capable of holding the dissolved raw material. Therefore, for the hearth liner, graphite, boron nitride, or a special material such as molybdenum, tungsten, or tantalum is used. Such materials are expensive and relatively brittle. On the other hand, since the hearth liner is provided between the evaporation raw material heated to the melting point or higher and the water-cooled crucible, a large temperature gradient is formed between the inner and outer surfaces thereof. For example, when vaporizing silicon, the silicon is heated to about 2000 ° C. Therefore, the temperature of the inner surface of the hearth liner is at that level. On the other hand, the outer surface of the hearth liner is in contact with the crucible, so that the surface is 100
It can be suppressed to about ℃. As a result, a significant temperature difference occurs between the inner and outer surfaces of the hearth liner, and the temperature gradient between them becomes extremely large. And, due to such a large temperature gradient, a very large thermal shock is applied to the hearth liner. In that case, if the hearth liner is in close contact with the inner surface of the crucible, thermal shock may cause cracks to occur at the corners where stress is likely to concentrate. Especially when graphite or boron nitride is used as the material for the hearth liner, such cracks are likely to occur.

When a crack is generated in the hearth liner, the melted raw material contained in the hearth liner flows out through the crack and comes into contact with the surface of the crucible, so that the heat of the raw material is taken by the water-cooled crucible. Become. As a result, the evaporation amount of the raw material is drastically reduced, and the film forming rate is drastically reduced. Therefore, the hearth liner needs to be replaced.

As described above, in the conventional electron beam evaporation source, it is necessary to frequently replace the hearth liner. However, since the hearth liner is made of a special material as described above, it is extremely expensive. Therefore, there is a problem that the cost for forming the thin film becomes very high.

The present invention has been made in view of the above problems, and an object thereof is to obtain an electron beam evaporation source in which the hearth liner is less likely to be damaged by thermal shock.

[0010]

To achieve this object, in the present invention, a layer capable of absorbing thermal shock is provided on the outer surface portion of the hearth liner facing the inner surface of the water cooling crucible. That is, a gap is provided between the outer surface of the hearth liner and the inner surface of the crucible, or the vicinity of the surface of the hearth liner in contact with the crucible is a porous layer.

[0011]

By providing a gap between the outer surface of the hearth liner and the inner surface of the crucible in this way, the temperature gradient generated in the hearth liner is almost eliminated laterally, and only at the bottom wall portion. Therefore, the thermal shock at the corner between the side wall and the bottom wall of the hearth liner where the stress is most concentrated is reduced, and the occurrence of cracks is prevented. Further, if the surface of the hearth liner that contacts the crucible, that is, the vicinity of the outer surface of the hearth liner is a porous layer, the thermal shock is absorbed by the porous layer. Therefore, damage to the hearth liner due to thermal shock is prevented. By forming the dense layer on the inner surface of the hearth liner, it is possible to prevent the melted raw material from soaking into the hearth liner and reacting with the material of the hearth liner. Therefore, the function of the hearth liner is not impaired.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. 1 is a schematic cross-sectional view of the entire structure showing an embodiment of an electron beam evaporation source according to the present invention, and FIG. 2 is an enlarged cross-sectional view of the main part thereof. Further, FIGS. 3 to 5 are enlarged cross-sectional views of a main part showing the different embodiment. In the description of these embodiments, the corresponding parts will be denoted by the same reference numerals and overlapping description will be omitted.

As is apparent from FIG. 1, the electron beam evaporation source 1 is provided with a copper crucible 3 for containing a raw material 2 to be evaporated. A water jacket 4 is provided on the lower surface side of the crucible 3, and the crucible 3 is cooled by cooling water circulating between the water jacket 4 and the outside through a cooling water supply / discharge port 5. There is. The crucible 3 is grounded. A filament 6 is provided on the side of the crucible 3, and a negative potential is applied to the filament 6 by a power supply 7. Furthermore, a magnetic field (not shown) forms a magnetic field perpendicular to the plane of the drawing. Thus, an electron beam 8 is formed by the filament 6, and the electron beam 8 is curved so as to directly hit the evaporation raw material 2 in the crucible 3.

Inside the crucible 3 is a plate-shaped hearth liner 9
Is installed. The hearth liner 9 is made of a dense material such as graphite having a high heat insulating property, and the evaporation raw material 2 is housed in the hearth liner 9. As shown in FIG. 2, the hearth liner 9 has substantially the same shape as the inner surface of the crucible 3, but the outer diameter thereof is slightly smaller than the inner diameter of the crucible 3. The hearth liner 9 is installed on the bottom surface of the crucible 3 so that a small gap 10 is formed between the outer surface of the hearth liner 9 and the inner surface of the crucible 3. The size of the void 10 is 0.
It is set to 1 mm or more and 10 mm or less.

Next, the operation of the electron beam evaporation source 1 thus constructed will be described. When a thin film of aluminum, silicon or the like is to be formed, the electron beam evaporation source 1 is arranged in the lower part of the vacuum chamber. Also,
A substrate is placed in the upper part of the vacuum chamber. Then, the thin film raw material 2 is put into the hearth liner 9, and the hearth liner 9 is placed on the bottom surface of the crucible 3. At this time, a small gap 10 is formed over the entire circumference between the outer surface of the hearth liner 9 and the inner surface of the crucible 3. In this state, apply a negative potential to the filament 6,
Raw material 2 contained in hearth liner 9 inside crucible 3
The electron beam 8 is radiated on the surface. Then, the raw material 2 is heated and its steam is generated. Then, the raw material vapor adheres to the substrate arranged in the upper part of the vacuum chamber.
In this way, a thin film of the raw material 2 is formed on the surface of the substrate.

During this time, the raw material 2 is directly heated by the electron beam 8. Further, since the hearth liner 9 that houses the raw material 2 is formed of a material having a high heat insulating property, the heat of the raw material 2 is rarely released through the hearth liner 9. Moreover, since the side surface of the hearth liner 9 is separated from the crucible 3, the hearth liner 9 is
The heat transfer from the chamber to the crucible 3 is almost exclusively via its bottom surface. Therefore, although the crucible 3 is water-cooled, the heat of the raw material 2 is reduced from being taken by the water cooling of the crucible 3, and the raw material 2 is heated very efficiently.

The raw material 2 in the hearth liner 9 is melted by being heated in this way. However, since the hearth liner 9 is formed of a dense material such as graphite, the melted raw material 2 does not leak or soak into the hearth liner 9. Also,
The raw material 2 does not combine with the material of the hearth liner 9. Therefore, the raw material 2 is reliably held in that state. Since the crucible 3 is water-cooled, copper as the material of the crucible 3 does not evaporate and mix into the vapor of the raw material 2. Further, since the hearth liner 9 is formed of a material that is hard to evaporate, the material of the hearth liner 9 hardly mixes with the raw material vapor. Therefore, the thin film formed by using this electron beam evaporation source 1 has extremely high purity.

By the way, when the raw material 2 contained in the hearth liner 9 is heated and melted, the inner surface of the hearth liner 9 has a temperature similar to that of the melted raw material 2. On the other hand, since the outer surface of the bottom wall of the hearth liner 9 is in contact with the crucible 3, the temperature of that surface is substantially equal to the surface temperature of the crucible 3. Therefore, a large temperature gradient is generated between the inner surface and the outer surface of the hearth liner 9 at the bottom thereof. However, since the outer surface of the side wall of the hearth liner 9 is separated from the inner surface of the crucible 3 and only radiant heat is transmitted between them, a large temperature gradient is formed in the void 10 therebetween. Therefore, there is almost no temperature gradient between the inner and outer surfaces of the side wall of the hearth liner 9. In this way, the temperature gradient generated in the hearth liner 9 is eliminated laterally, leaving only the bottom wall portion. As a result, thermal shock also only occurs along the bottom wall, and the stress concentration at the corner between the side wall and the side wall is reduced.

As described above, in the electron beam evaporation source 1, the thermal shock generated in the hearth liner 9 is absorbed at the side portions thereof, so that cracks or the like are prevented from being generated at the corner portions. Therefore, the hearth liner 9 can be repeatedly used, and the cost for forming a thin film can be reduced.

An experiment was conducted to actually evaporate silicon by an electron beam evaporation source, using a hearth liner that closely adheres to a crucible and a hearth liner having a slightly smaller diameter than the conventional one. The inner diameter of the crucible of the electron beam evaporation source is 6
The power of 0 mm and the electron beam was 2 KW. A graphite hearth liner was used. As a result, when using a hearth liner that closely adheres to the crucible,
Cracks occurred after only three uses, but if a slightly smaller diameter hearth liner was used and a gap was provided between the outer surface of the hearth liner and the inner surface of the crucible, cracks would occur even after 10 uses. It was confirmed that it did not occur.

FIG. 3 shows an embodiment in which the electron beam evaporation source 1 is further improved. In the case of this embodiment, the hearth liner 9 is installed on the bottom surface of the crucible 3 via a thin plate 11 having a heat insulating property. The thin plate 11
Has a thickness of about 0.1 to 10 mm and is made of a material more porous than the hearth liner 9. Other configurations are similar to those of the embodiment shown in FIGS. With this structure, the heat of the raw material 2 is also suppressed from being transferred to the crucible 3 through the bottom wall of the hearth liner 9, so that the heating efficiency of the raw material 2 is further improved. Further, since the thermal shock applied to the hearth liner 9 is absorbed by the porous thin plate 11, the generation of cracks is further prevented.

In the embodiment of FIG. 4, the hearth liner 9
Is installed so as to be in close contact with the inner surface of the crucible 3 as in the conventional case. However, that hearth liner 9
Has a two-layer structure including an inner layer 12 made of a dense material and an outer layer 13 made of a porous material. With such a configuration, the inner surface of the hearth liner 9 becomes dense, so that the melted raw material 2 is also securely held by the hearth liner 9. Since the outer layer 13 is porous, the outer layer 13 can have a large temperature gradient. Therefore, the thermal shock comes to be absorbed by the outer layer 13, and the inner layer 12 is prevented from being cracked or the like.

FIG. 5 shows an embodiment in which the hearth liner 9 is formed of a functionally graded material which continuously changes from dense to porous from the inner surface side to the outer surface side.
Even in such a case, the same effect as that of the embodiment of FIG. 4 can be obtained. Therefore, hearth liner 9
Even if it is installed in close contact with the crucible 3, its hearth liner 9
Is prevented from being damaged by thermal shock.

[0024]

As is apparent from the above description, according to the present invention, a gap is provided between the hearth liner and the crucible, or the surface of the hearth liner that contacts the crucible is made into a porous layer. Therefore, the thermal shock generated in the hearth liner can be absorbed. Therefore, the hearth liner can be repeatedly used, and the cost for forming a thin film can be reduced.

[Brief description of drawings]

FIG. 1 is a schematic vertical sectional view showing an entire structure of an electron beam evaporation source to which the present invention is applied.

FIG. 2 is an enlarged cross-sectional view of the main part of the electron beam evaporation source showing the first embodiment of the present invention.

FIG. 3 is an enlarged sectional view similar to FIG. 2, showing a second embodiment of the present invention.

FIG. 4 is a similar enlarged cross-sectional view showing a third embodiment of the present invention.

FIG. 5 is a similar enlarged sectional view showing a fourth embodiment of the present invention.

[Explanation of symbols]

1 Electron beam evaporation source 2 evaporation raw materials 3 crucible 8 electron beam 9 Hearthliner 10 voids 11 thin plate 12 Inner layer 13 outer layer

Claims (4)

[Claims] 1. An electron beam evaporation source in which a dish-shaped hearth liner is installed between a raw material to be vaporized and a water-cooled crucible containing the raw material, and the raw material is vaporized by irradiating the raw material with an electron beam. In the electron beam evaporation source, an air gap is provided between an outer surface of the hearth liner and an inner surface of the crucible. 2. The electron beam evaporation source according to claim 1, wherein the hearth liner is installed on the bottom surface of the crucible via a thin plate having a heat insulating property. 3. An electron beam evaporation source in which a dish-shaped hearth liner is installed between a raw material to be vaporized and a water-cooled crucible containing the raw material, and the raw material is vaporized by irradiating the raw material with an electron beam. In the electron beam evaporation source, the hearth liner is formed by an inner layer made of a dense material and an outer layer made of a porous material. 4. An electron beam evaporation source in which a dish-shaped hearth liner is installed between a material to be evaporated and a water-cooled crucible containing the material, and the material is evaporated by irradiating the material with an electron beam. In the electron beam evaporation source, the hearth liner is formed of a functionally graded material that continuously changes from dense to porous from the inside to the outside.