JPS59177130A - Vacuum vapor deposition method - Google Patents

Abstract

PURPOSE:To enhance productivity by accelerating the accumulation speed of a thin membrane, in vacuum vapor deposition, by filling the gap between a hearth part and an evaporation material with a heat conductive member having a m.p. lower than that of the evaporation material. CONSTITUTION:In performing vacuum vapor deposition, the gap between an evaporation material 1 such as a silicon ingot and a hearth part 14 is filled with a heat conductive member 4 comprising In or Ga having a m.p. extremely lower than that of the evaporation material 1. A molten liquid part 2 is formed to the upper central part of the evaporation material 1 to perform vapor deposition. In this case, the heat of the solid part of the vapor deposition material is transferred to the hearth part 14 through the heat conductive member 4 to perform heating and vapor deposition. By this method, the accumulation speed of a thin membrane can be accelerated and productivity can be enhanced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to the vapor deposition of high-purity substances, and particularly to molecular beam epitaxy of high-purity, high-melting-point substances.
Beam Epitaxy) also relates to improvements in possible vacuum deposition methods.

[Technical background of the invention]

In recent years, along with the development of vacuum technology, it has become possible to form thin films in an ultra-high vacuum. Thin film formation in an ultra-high vacuum involves heating and evaporating small pieces of metal or non-metal. Examples include vapor deposition, which deposits a thin film on the surface of glass, quartz plates, etc., and molecular beam epitaxy, which heats and evaporates small pieces of metal or non-metal to create particle beams made of neutral molecules to grow crystals. In this specification, these are collectively referred to as vacuum evaporation.

Generally, molecular beam epitaxy is often used in the production of semiconductors, but as is well known, when growing semiconductor crystals, the molecular beam must be kept at a high purity. In addition to using an evaporation material of 100%, the composition of the container containing the molten evaporation material must be such that it is difficult to diffuse into the evaporation material.

However, gallium (Ga), which has a relatively low melting point,
8), to obtain a molecular beam of aluminum (At), use P-B N (Pyroritic-B
A Knudsen cell (Knudsen Cell) based on the OronNtelide method was used. Since this Knudsen cell has low heat resistance, a molecular beam of silicon (Si) (hereinafter also referred to as silicon) with a high melting point is obtained (ζ is a molten liquid part formed in the upper central part of the silicon ingot, and the silicon ingot itself is placed in a crucible). This method is adopted.

To avoid the formation of this melt, for example, an E-gun is used which performs impact heating using an accelerated electron image.

FIG. 1 is a conceptual diagram of a heating system for forming a partial melt in an evaporation material with a high melting point such as silicon, and FIG. 2 is a perspective view showing the configuration of the main parts of an E gun.

Here, the E gun 10 is equipped with a filament 11 that emits an electron beam, a deflection coil 13 that directs the electron beam in an appropriate direction, etc. inside a pedestal 11. A hearth portion 14 to be cooled is provided.

This hearth portion 14 is provided with a recess 15 similar to the bottom shape of a crucible, into which a silicon ingot 1 as a bulk evaporation material is loaded. At this time, the silicon ingot 1 is also made to resemble the bottom shape of the crucible, with the other outer surface as much as possible except for the upper end, and the depression 1
It is made so as to contact the inner surface of 5.

Therefore, the electron beam 16 emitted from the filament 11
is accelerated by an acceleration system (not shown), and at the same time, the electron beam 16 is deflected by the deflection coil I3 so that the electron beam 16 collides intensively with the upper central part of the silicon ingot 1, thereby heating this part. On the other hand, since the lower bottom and side surfaces of the silicon ingot 1 are in contact with the hearth part 14 that is forcibly cooled, the heat from the surface part is removed (that is, the silicon ingot 1 is heated in the upper central part). On the other hand, since it is cooled from the bottom and side surfaces, the inflow heat from the electron beam 16 fit Q t
When the heat 11 absorbed by the hearth portion 14 and the heat 11 are balanced in an appropriate state, the upper central portion of the ingot 1 (the melt portion 2 can be formed).

In this case, since the silicon ingot 1 acts as a crucible, simply by increasing the temperature of the silicon ingot 1, it is possible to form a highly pure thin film that is not affected by the composition of the crucible. .

[Problems with background technology]

In conventional vacuum evaporation methods including molecular beam taxis, the inner surface shape of the general The shapes of the bond 15 and the silicon ingot 1 are determined according to the (or external shape), and if they are in even contact over the entire planned area, at least the upper central part of the silicon ingot 1 The melt portion 2 can be formed in the following manner.

However, since both of these have three-dimensional curved surfaces, it is difficult to achieve reliable surface contact, and the thermal conductivity between them is considerably lower than when flat parts are in contact with each other. Met.

For this reason, as the temperature of the entire ingot rises, the melt spreads and falls from the sides, and as a result, the amount of electricity introduced in the form of electron beams is kept low.

This will be further explained using mathematical formulas.

First, if the amount of heat generated by the collision of the electron beam is Q□, and the amount of heat taken away by the hearth portion is Q2, the following equation holds true.

Q1= 61(Tt Tt) ・・・・・・(1)Q
z = 6t (Tt Ts) (2
) However, 61: Thermal conductivity between the ingot and the hearth part 6, : Thermal conductivity of the ingot T1 : Temperature Tta of the electron beam irradiation part Temperature T of the surface part of the ingot, : Temperature of the hearth part.

Next, when the thermal equilibrium state is established, Q□=Q2 holds, so the above equations (1) and (2) are transformed as follows. Thermal conductivity 6I is smaller than that of the ingot, therefore 6+
<6x, the following equation holds true.

('r, -'rt) □ku1...(4) (Tz Ts) This equation (4) is the temperature difference (T, -T2) of the ingot itself.
This means that the temperature T1 of the electron beam irradiation section must be kept low in order to prevent the melt from spilling or falling.

On the other hand, the evaporation rate from the melt part is determined by the temperature T of the electron beam irradiation part,
The higher the value, the larger the value, and the deposition rate of the thin film can be increased accordingly, but as mentioned above, the temperature T1 of the electron beam irradiation part
Due to this limitation, the deposition rate of the thin film also becomes low, which is the reason why productivity cannot be improved.

Due to the low thermal conductivity between the gold and hearth parts, the temperature of the electron beam irradiation part is limited, which has the disadvantage that the deposition rate of the thin film is kept low.

[Purpose of the invention]

The present invention has been made to eliminate the above-mentioned drawbacks.
The object of the present invention is to provide a vacuum deposition method that can significantly increase the deposition rate of a thin film and thereby improve productivity.

[Summary of the invention]

In order to achieve this object, the present invention charges a lump of evaporative material into the recess of a hearth part to be forcibly cooled, and forms a melt part in the upper central part of the evaporative material exposed from the hearth part. In a vacuum evaporation method in which the gap between the hearth part and the evaporation material is filled with a heat conductive member whose melting point is much lower than that of the evaporation material, the solid state of the evaporation material is It is characterized in that heat from the hearth section is conducted to the hearth section for heating and vapor deposition.

[Embodiments of the invention]

Hereinafter, one embodiment of the present invention will be described with reference to the accompanying drawings.

FIG. 3 is a conceptual diagram of a heating system for implementing the present invention. The same reference numerals as in FIG. 1 indicate the same elements, and the gap between the silicon ingot 1 and the hearth part 14 Gallium has a much lower melting point than gallium (
It differs from FIG. 1 in that it is filled with Ga)4.

Note that gallium (Ga) 4 is filled in the hearth part 14.
When liquefied gallium (Ga) 4 is poured into the recess 15 (into the recess 15) without being forcedly cooled, and the silicon ingot 1 is then loaded into the recess 15, the outer surface of the silicon ingot 1 and the recess 5 are Gallium (Ga) 4 remains in the gap formed between the two surfaces, and the excess gallium (Qa) 4 overflows onto the top surface of the hearth portion 14. This overflowing portion is swept away. ing.

By the way, the advantage of vapor deposition in ultra-high vacuum, including molecular beam evaporation, is that impurities in vacuum, such as oxygen,
The advantage is that it contains extremely little carbon and can deposit highly pure thin films. In this case, while maintaining the high purity of the evaporated material,
The purity of the particle beam must be increased.

In this regard, the melting point of gallium (Ga) is approximately 30,000 yen, and even if it comes into contact with the silicon ingot for a long time, the rate at which it diffuses into the interior of the ingot is extremely small, and therefore the purity of the silicon ingot will not be reduced.

In addition, the temperature and vapor pressure of gallium (Ga) have a relationship as shown in straight line A in Figure 4, and as long as the temperature is kept low, the vapor pressure will be low, and the purity of ultra-high vacuum particle beams will also be maintained. be able to.

Therefore, gallium (Ga) can be a suitable heat conductive material that does not reduce the purity of the evaporation material and the purity of the particle beam. Therefore, the thermal conductivity between the silicon ingot 1 and the hearth portion 14 can be significantly increased.

Examples of vacuum deposition performed using this method will be given below.

First, an E gun 10 with a maximum input of 5 [KSV] is used, a crucible with a volume of 2.6 [: ec] is used as the nose part 14, and the silicon ingot 1 to be loaded therein is used. The purity is 99.9 in the gap between
Fill with 9991 or more gallium (Ga) using the method described above.

Next, when the electron beam 16 emitted from the filament 11 is accelerated with a voltage of approximately 10 [KV] and deflected by 225° by the deflection coil 13, the electron beam 16
The center of the crucible, that is, the upper center of the silicon ingot 1 has been reached.

In this way, the electron beam 16 is not forced to cool down the hearth portion 14.
When irradiation is continued, a melt portion 2 is formed. In this case, in the conventional method, the power that can be introduced in the form of an electron beam, r,
The maximum power that could keep only the upper central part in a melted state was only 005 [:KW], but according to this method, it was 2 [history]
We were able to supply more than enough power.

Furthermore, when comparing the thin film deposition rate assuming that the distance from the evaporation material to the member to be evaporated, that is, the evaporation distance, is 250 [mm], the conventional method was about 50 CA/n+in, but the present method was about 100 CA/n+in. /surface n] was successfully deposited.

During this time, gallium (Ga) 4 is in close contact with the hearth part where copper is used, and gallium (Ga) 4 is in close contact with the hearth part where copper is used.
a) There was no effect of 4, and it is presumed that there was no evaporation.

From the results of this experiment, it can be said that gallium (Ga) 4 is a suitable heat transfer member that can be formed into a thin film under ultra-high vacuum (without any sensitizing effects) and improves thermal conductivity.

In the above example, it is assumed that a semiconductor is manufactured by causing molecular i-ray epitaxy, and a silicon ingot is used as the evaporation material and gallium (
Although the evaporation material is not limited to gallium (Ga), the evaporation material is not limited to gallium (G).
It is also possible to use indium (In) instead of a), and the point is that if it has a much lower melting point than the evaporation material, it can improve the thermal conductivity in the same way as mentioned above, and is easy to handle. It's easy.

Further, in the above embodiment, an E gun is used to form a melt part in the upper central part of the evaporation material (in the present invention, the term is used not only in the upper center but also in the meaning other than the edge part). ,
This heating means can be similarly applied to vapor deposition apparatuses using other heating methods such as laser.

〔Effect of the invention〕

As is clear from the above invention, according to the vacuum evaporation method of the present invention, it is possible to significantly increase the deposition rate of a thin film, thereby achieving the excellent effect of further improving productivity.

[Brief explanation of drawings]

Fig. 1 is a conceptual diagram of a heating system of a vacuum evaporation apparatus using an E gun to explain the conventional vacuum evaporation method, Fig. 2 is a perspective view showing the configuration of the main parts of this E gun, and Fig. 3 4 is a conceptual diagram of a heating thread of an example of a device for carrying out the vacuum evaporation method of the present invention, and FIG. 4 shows the relationship between the temperature and vapor pressure of potassium (Ga') as a heat conductive member used in this heating system. It is a line diagram. 1... Silicon ingot as evaporation material, 2...
- Melt part, 3... Solid part, 4... Gallium as a heat conductive member, 10... E gun, 11... Frame, 12
... filament, 13... deflection coil, 14...
- Hearth part, 15... hollow, 16... pa electron beam. Applicant's agent Kiyoshi Inomata I Prisoner II Moen 2 Figure 1 Kaorugyu 4 M Takaji &('C) -

Claims (1)

[Claims] 1. A lump of evaporation material is loaded into the recess of the hearth part to be forcibly cooled, and a molecular melt part is formed in the upper center of the evaporation material exposed from the hearth part to perform evaporation. In the vacuum evaporation method carried out, the gap between the hearth part and the evaporation material (filling with a heat conductive member whose melting point is much lower than that of the evaporation material,
A vacuum evaporation method characterized in that heating and evaporation are performed by conducting heat of the solid portion of the evaporation material to the hearth portion via the heat conductive member. 2. The vacuum evaporation method according to claim 1, wherein the melt portion is formed by impact heating with an electron beam. 3. The vacuum evaporation method according to claim 1, wherein indium (1n) or gallium (Ga) is used as the heat conductive member.