JPH0230695A - Rotary shaft of vapor-phase growth apparatus - Google Patents

Abstract

PURPOSE:To remarkably decrease the thermal conduction to the lower shaft of a rotary shaft by dividing a susceptor-supporting rotary shaft into upper shaft and lower shaft and narrowing the contacting area of the shafts as far as possible. CONSTITUTION:A rotary shaft fixed to the center of an upper plate of a susceptor 2 is divided into two shafts comprising an upper shaft 4 and a lower shaft 10. The upper shaft 4 to which high-temperature is directly conducted is made of carbon. The lower shaft 10 is made of a metal such as stainless steel having inferior heat-resistance and excellent machinability, mechanical strength and chemical resistance. The lower shaft 10 is rotatably supported by vacuum bearings 21, 22, etc. The outer rings of the bearings are supported by a housing 7 of a rotary mechanism. Since the carbon used as a material for the upper shaft 4 is a soft material, the upper shaft has preferably simple shape. The lower shaft 10 made of metal can be machined to a complicate shape because the material has excellent strength and machinability. A plurality of radially extended attaching branches 8 are attached to the top of the lower shaft 10 as a substitute for a flange.

Description

[Detailed description of the invention] (g) Technical field The present invention relates to a rotating shaft of a vapor phase growth apparatus.

A vapor phase growth apparatus is placed in a chamber and is used to grow a thin film on a crystal substrate heated to an appropriate temperature by flowing a source gas onto the substrate to cause a vapor phase reaction.

There are vertical ones and horizontal ones. This classification is based on the flow of raw material gas.

There are vertical types that allow thin film growth to be performed simultaneously on multiple substrates. This uses a cylindrical substrate support called a susceptor.

The susceptor has a polygonal shape, for example, and a substrate is fixed substantially vertically on each surface.

The susceptor is supported by a rotating shaft and rotates horizontally around the center of the rotating shaft.

(a) Prior art A heater is provided inside the susceptor. This is because the substrate must be heated to a temperature at which crystallization occurs.

Also, the susceptor must rotate. This is because film growth must be uniform not only on a plurality of substrates but also on a single substrate.

The susceptor must be able to withstand heat, so it is made of carbon.

The rotating shaft that supports the seven pigs must be heat resistant. That's not all. Mechanical strength is also essential. It is rotatably supported by bearings,
This is because the gear must also receive rotational force.

Heat-resistant materials include TalWlMo and C.

Using these materials, a rotating shaft can be made from a single piece. However, refractory metals such as TalWlMo2 are expensive. Also, the workability is not good. heavy.

If you want to make it cheaper, it is better to use carbon. Carbon is soft and easy to process. However, since it is a brittle material, it is mechanically weak.

For this reason, it is not possible to make a rotating shaft with a single carbon rod.

Therefore, the present inventors came up with a structure in which the rotating shaft is divided into two shafts, upper and lower, and the upper shaft, which is subject to high heat, is made of carbon, and the lower shaft, which requires mechanical strength, is made of metal such as stainless steel.

Such an upper and lower biaxial structure can satisfy both requirements.

However, even with this vertical two-axis structure, several problems arise because the temperature of the susceptor is high and a large amount of heat is transferred to the rotating shaft.

Even if there is no problem with the shaft itself, the surrounding mechanisms may need to be resolved.

(1) Problems to be Solved by the Invention The heating temperature of the susceptor may exceed 900°C. If the substrate is GaAs, it must be heated to 900° C. or higher. Si
In this case, it may be necessary to raise the temperature to a high temperature.

Due to the high temperature of the susceptor, a large amount of heat flows into the upper axis of the carbon. This heat is transmitted to the lower stainless steel shaft through the shaft joint.

Since the temperature is quite high, the gears and bearings attached to the stainless steel shaft are heated.

(1) Gears and bearings are made of metal. This is a material that is not very heat resistant. This will shorten the life of gears and bearings. It deteriorates due to heat, so it must be repaired frequently.

(2) Also, since metal parts such as gears, bearings, and rotating mechanism housings are strongly heated, gases adsorbed on their surfaces are released. This also causes contamination inside the chamber.

(3) When the stainless steel shaft becomes hot, it expands significantly. Then, the inner ring of the bearing is expanded by the stainless steel shaft. However, the outer ring of the bearing is not heated as much. This is because it is fixed by the rotating mechanism housing and heat can easily escape.

Then, the inner ring of the bearing expands outward. The outer ring does not expand. As a result, the space between the bearings containing the balls becomes narrower. If this happens, the rotation of the bearing will become heavier. In severe cases, the shaft may slip due to the resistance of the bearings.

These drawbacks are caused by the large amount of heat transferred to the lower shaft.

09 Purpose It is an object of the present invention to provide a structure in which a rotating shaft for supporting a susceptor of a vapor phase growth apparatus has a shaft structure divided into upper and lower halves, and can significantly reduce heat transfer to the lower shaft. This is the purpose of

(6) Structure The structure of the present invention is such that the contact area between the stainless steel shaft and the carbon shaft is made as narrow as possible in order to minimize heat conduction in the joint.

The end face of the stainless steel shaft is not a disc-shaped flange, but has multiple branches extending radially.

This branch is for fixing the end face of the stainless steel shaft to the carbon shaft 7 langes with bolts.

Furthermore, the parts other than those to be fixed with bolts are recessed so that they do not come into contact with the end face of the carbon shaft.

Since the contact area is narrow, heat conduction is reduced and heating of the lower shaft is alleviated.

This will be explained using drawings.

FIG. 1 is a schematic overall sectional view of a vapor phase growth apparatus equipped with a rotating shaft according to the present invention. This is a CvD device (Chem
ical'/apor Deposition)
It is sometimes abbreviated as.

The elongated, cylindrical chamber 1 is a vacuum container.

The upper part of the chamber 1 has a hemispherical shape.

A susceptor 2 is provided inside the chamber 1 . This is a polygonal cylindrical body, and a plurality of substrates 3 are attached to the outer surface.

The upper hemisphere of the susceptor 2 is for rectifying the gas flow. This susceptor 2 is sometimes called a barrel type susceptor.

The susceptor 2 is rotatable.

The susceptor 2 is composed of rectangular cylindrical side plates and an upper plate connected to the upper ends of these side plates, and is usually made mainly of carbon.

The upper end of the rotating shaft is fixed to the center of the upper plate of the susceptor 2.

In the present invention, the rotating shaft is divided into two upper and lower shafts. They are an upper shaft 4 and a lower shaft 10.

The upper shaft 4 is made of carbon. This is because it is a part where high heat is directly transmitted. The lower shaft 10 is made of metal such as stainless steel, which has poor heat resistance but excellent workability, mechanical strength, and chemical resistance.

Improvement of the shaft joint 11 that connects the upper and lower shafts,
This is the eye of the present invention.

A carbon resistance heater 5 having a cylindrical shape and having a current path meandering up and down is provided inside the seven pots 2.

The carbon heater 5 is connected to the current input terminal 6 from the outside.
Direct current is supplied.

A source gas introduction pipe 15 is provided in the upper part of the chamber 1 . The source gas is a gas containing constituent elements of the thin film to be grown on the substrate. For example, when growing a GaAs thin film, organic metal gases such as triethyl gallium and trimethyl gallium and arsine are raw material gases, and hydrogen gas is blown into the chamber 1 as a carrier gas.

A gas exhaust pipe 16 is provided on the lower side of the chamber 1 .

A cooling water jacket 17 is provided in the upper half of the chamber 1 .

Now, the lower shaft 10 is rotatably supported by a vacuum bearing 2L 22 or the like. These bearings and their outer rings are supported by the rotating mechanism housing 7.

A bevel gear 9 is fixed to the lower shaft 10.

This is to introduce rotational force. chamber 1
A motor 13 (including a reduction gear) is provided outside the motor.

The rotational force of the motor is transmitted to a horizontal shaft 18 within the chamber by a rotating feedthrough 12 in the wall of the chamber 1 . Horizontal axis 1
The rotational force of 8 rotates the lower shaft 10 by the bevel gear 9.

As already mentioned, if the lower shaft 10 is heated too much, it will damage the gears and bearings, and the clearance of the bearing will become l<l, making it impossible to rotate.

The present invention has a structure in which the connection between the upper and lower shafts at the shaft joint 11 transmits as little heat as possible. Therefore, the contact area is narrowed.

Figure 2 is a partial longitudinal cross-sectional view of the shaft joint, and Figure 3 is a partial longitudinal cross-sectional view of the shaft joint.
FIG.

FIG. 4 is a plan view showing the upper end surface of the lower shaft 10, and FIG. 5 is a perspective view of the vicinity of the upper end of the lower shaft 10.

The lower end of the upper shaft 4 is a regular disc-shaped flange 19. Since carbon is a soft material, its strength may drop significantly if it is processed into a complicated shape. For this reason, it is desirable that the shape be simple.

However, since the lower shaft 10 made of metal has good strength and workability, it can be worked into a complicated shape.

Therefore, the upper end of the lower shaft 10 is not made into a common circular flange.

Instead of a flange, the upper end of the lower shaft 10 is formed with a plurality of radially extending attachment branches 8.

As the number of attachment branches 8, four are illustrated. However, the number is not limited to four, and may be two, three, or five to eight.

The attachment branch 8 is a part for fixing to the upper shaft flange 19 with bolts 14.

For this purpose, the mounting branch 8 is provided with a screw hole 26 .

In order to avoid contact with the end surface of the upper shaft 4, the center portion of the upper end surface of the lower shaft 10 is formed into a wide recess 23.

A hole 25 is further drilled in the center of the recess 23.

A short protrusion 24 is formed at the center of the lower end surface of the upper shaft 4.

The protrusion 24 is inserted into the hole 25. By doing this, the centers of the lower shaft 10 and the upper shaft 4 are aligned.

A bolt 14 is inserted into the hole from the upper side of the upper shaft 7 flange 19 and is threaded into the threaded hole 26 in the mounting branch 8 of the lower shaft. Thereby, the upper shaft 4 is fixed onto the lower shaft 10.

(2) Production The upper and lower shafts are fastened together by bolts 14.

Therefore, when the lower shaft is rotated by the motor 13, the upper shaft also rotates together.

The heat from the heater 5 causes the susceptor 2 to reach a high temperature.

This heat is transferred to the upper shaft 4 and further to the lower shaft 1.
It is transmitted to 0.

However, the contact surface 27 between the lower shaft 10 and the lower end surface of the upper shaft 4 is extremely narrow. This is because most of the upper end surface of the lower shaft 10 is a recess 23, which is non-contact.

Heat transfer is based on three effects: thermal conduction, radiation, and convection.

This is less problematic than convection 1 in a vacuum of 0, I Torr to IQ Torr.

The most important one is heat conduction. This is the manner in which heat is transferred through contact surfaces. In the present invention, the contact surface 27 is extremely narrow. Therefore, heat conduction is extremely low.

In the example of FIGS. 2-5, the contact surface 27 still has some extent.

Therefore, as shown in FIG. 6, it is even more effective to further hollow out the upper end surface of the lower shaft 10, leaving only a very narrow portion around the bolt 14. In other words,
- layer, can suppress heat conduction.

Since heat transfer is proportional to the contact area, it is easy to evaluate how much it has been reduced.

However, since the upper shaft 4 is made of a soft and brittle material, if the contact surface is made too narrow, the load per unit area will increase and there is a risk that the upper shaft will be damaged.

For this reason, there is a limit to the reduction of the contact surface.

Heat radiation is also reduced. When heat is transferred by thermal radiation, from the perspective of the person receiving the heat, it is proportional to the solid angle with respect to the heat source.

In this case, the lower end surface of the upper shaft 7 flange 19 is considered to be the heat source.

Heat from this heat source is equally received by the contact surface 27 of the lower shaft and the recess 23, which is a non-contact surface.

However, there is a space between the mounting branches 8.8. The heat radiated into this space does not become the heat of the lower shaft.

If the upper end surface of the lower shaft also has a wide flange, the radiant heat it receives will be quite large.

However, in the present invention, a plurality of radial attachment branches are provided instead of a wide flange.

That is, in the case of the present invention, the bottom surface of the upper shaft flange is regarded as a heat source, and the solid angle of the end surface of the lower shaft as viewed from the heat source is narrow. Therefore, radiation is also reduced.

The present invention can be applied to growing thin films on one substrate at a time or on many substrates simultaneously. Furthermore, the present invention is applicable not only to barrel-shaped susceptors but also to pancake-shaped susceptors.

In short, the present invention can be applied to any device that rotates a susceptor and heats a substrate supported by the susceptor using heating means provided inside or outside a chamber.

(→Effect The susceptor rotation shaft of the vapor phase growth apparatus is divided into an upper shaft made of carbon and a lower shaft made of metal, and the upper and lower shafts are connected by a shaft joint.In the shaft joint,
Heat conduction and radiation from the upper shaft to the lower shaft are significantly reduced.

The temperature of the lower shaft does not become excessively high.

The deterioration of the bearing gear attached to the lower shaft is delayed. This eliminates the need for frequent inspection and replacement.

The inner ring of the bearing will not expand excessively and become difficult to rotate due to overheating of the lower shaft.

Since the heating of the lower shaft is suppressed, the surface of the lower shaft,
The release of gases adsorbed on gears, bearings, and housing surfaces is reduced, reducing the possibility of contaminating the interior of the chamber.

[Brief explanation of the drawing]

FIG. 1 is an overall vertical sectional view of a vapor phase growth apparatus equipped with a rotating shaft according to the present invention. FIG. 2 is a vertical cross-sectional view of the shaft joint including bolts. FIG. 3 is a vertical cross-sectional view of the shaft joint section taken along a plane making an angle of 45° from the plane containing the bolt. FIG. 4 is a plan view of the upper end surface of the lower shaft. FIG. 5 is a perspective view of the vicinity of the upper end of the lower shaft. FIG. 6 is a partial vertical sectional view of a joint section showing another embodiment. 1... 2... 3... 4... 5... 6...... Chamber susceptor board shaft carbon heater current Introductory terminal 7...Housing 8...Mounting branch 9...Bevel gear 10...Lower shaft 11...Shaft joint 12... ... Rotating feed through 13 ... Motor 14 ... Bolt 15 ... Raw material gas introduction pipe 16 ... Gas exhaust pipe 1γ ... Cooling water jacket 18...Horizontal Shaft 19...Upper shaft flange 21.22...Shaft bearing 23...Four parts 24...Protrusion Bore 25...Hole 26...Thread Hole 27...Contact surface

Claims (1)

[Claims] A chamber 1 that is a vacuum container, a susceptor 2 provided in the chamber 1 and to which a substrate 3 is attached, means for heating the substrate 3, a rotating shaft that rotatably supports the susceptor 2, and a rotating shaft that supports the rotating shaft. The material gas is introduced from one end of the chamber 1, a thin film is grown on the heated substrate 3, and the material gas is grown from the other end of the chamber. In a vapor phase growth apparatus configured to discharge exhaust gas, the rotating shaft includes a first shaft 4 that directly supports the susceptor 2, and a second metal shaft 10 that is provided with a bearing and a rotational drive section. One end of the first shaft 4 becomes a circular flange 19, and one end of the second shaft 10 is formed with a plurality of mounting branches 8 extending radially, and contacts only the vicinity of the screw hole 26 of the mounting branch 8. When the first shaft flange 19 and the mounting branch 8 of the second shaft are fixed with the bolts 14, the upper end surface of the second shaft A rotating shaft for a vapor phase growth apparatus, characterized in that the recessed portion 23 does not come into contact with the first shaft flange.