JP2683580B2 - Conveyance device for heat treatment object to heat treatment furnace and heat treatment method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) The present invention relates to a carrying device and a heat treatment method for carrying in and out an object to be treated in a heat treatment furnace.

(Prior Art) As a transfer device of this type, for example, a device for loading / unloading a semiconductor wafer into / from a process tube, as shown in FIG. 9, a wafer 1 is supported on a boat 2, and this boat 2 is also used as a fork. It is mounted on one end of a so-called transfer arm so that it can be carried in and out of the process tube.

The transfer arm 3 is supported at its other end side by an arm holder 4, and the arm holder 4 is movably fixed to the movable portion 6 along the rails 5, 5 so that the transfer arm 3 can be moved in the longitudinal direction thereof. It is possible to move along.

Further, an end lid 7 having a function of shielding the open end of the process tube is provided on the arm holding tool 4 side of the transfer arm 3, and the end lid 7 is fixed to the arm holding tool 4 by a mounting tool 8. Supported by.

(Problems to be Solved by the Invention) In the conventional transfer apparatus described above, as shown in FIG. 10 (a), even if the boat 2 is completely carried into the process tube 9 by the transfer arm 3, the end lid is Since 7 has not reached the open end of the process tube 9, the open end of the process tube 9 cannot be closed.
The open end of the process tube 9 can be closed by the end lid 7 only when the boat 2 reaches the core of the process tube 9 as shown in FIG.

As described above, in the conventional apparatus, since the end lid 7 is fixed to the transfer arm 3, the fixing position is fixed in order to allow the transfer arm 3 to move the boat 2 to the furnace core. Therefore, the timing of closing the open end of the process tube 9 by the end lid 7 is delayed, and there is no choice but to allow the heat in the process tube 9 to escape until it is closed.

Therefore, an object of the present invention is to solve the above-mentioned conventional problems, and to carry out heat transfer in a process tube to a heat treatment furnace capable of significantly reducing heat escape from a conventional apparatus and a heat treatment apparatus for a heat treatment furnace. To provide a method.

[Structure of the Invention] (Means for Solving the Problems) The object-to-be-processed conveying device for the heat treatment furnace according to the invention as set forth in claim 1 includes a boat for arranging and supporting the objects to be treated in a process tube of the heat treatment furnace. In the transfer device for loading and unloading into and from, a transfer arm that supports and transfers the boat, a tubular member that is provided on the transfer arm at the rear end side of the load of the boat and that surrounds the periphery of the object to be processed, A drive mechanism that drives the transfer arm forward and backward, and is provided movably along the movement path of the transfer arm. When the boat is outside the process tube, a state in which the transfer member is in contact with the rear end side of the transfer of the tubular member. With the transfer arm, and
After closing the open end of the process tube, a blocking plate that allows the transfer arm to move inward of the process tube,
A gas inlet for introducing an inert gas into a region surrounded by the tubular member and the shield plate; and a guide member for guiding the shield plate so as to be movable along the moving direction of the transfer arm. A biasing member that constantly biases the guide member in a direction in which the shield plate abuts the tubular member.

According to a second aspect of the present invention, there is provided an apparatus for transporting an object to be processed with respect to a heat treatment furnace, wherein the boat has an arrangement and supports the elements to be carried in and out of a process tube of the heat treatment furnace. A carry-out arm for carrying in and out into the process tube of the heat treatment furnace, a drive mechanism for driving the transfer arm forward and backward, and a movable mechanism provided along the transfer path of the transfer arm, and the boat outside the process tube. In some cases, a shield plate that moves together with the transfer arm and that allows the transfer arm to move to the back of the process tube after the opening end of the process tube is closed, and a rear end side of the loading port of the boat. A stopper provided on the transfer arm, a guide member for guiding the blocking plate so as to be movable in the same direction as the transfer arm, and the blocking member. Plates, characterized in that it comprises a biasing member for constantly biasing said guide member to the stopper abutting direction.

In the heat treatment method according to the third aspect of the present invention, a boat in which a plurality of objects to be processed are arranged is supported by a tubular member of a transfer arm and surrounds the object to be processed. A heat treatment method of heat-treating a treatment object in a process tube of a heat treatment furnace for heat treatment, wherein the treatment arm heat-treats an object to be treated in a state where the conveyance arm is kept in non-contact with an inner wall of the process tube. A shielding plate provided movably along the movement route is brought into contact with the carrying-in rear end side of the tubular member, and the boat is surrounded by the shielding plate and the tubular member. The tubular member is moved in one direction at the same time, and the shield plate is biased by a biasing member that constantly biases the shield plate in a direction in which the shield plate is in contact with the tubular member. Introduce active gas And the tubular member is inserted into the process tube, and the shielding plate positioned at the carry-in rear end position of the tubular member contacts the open end of the process tube as the tubular member moves. And a step of closing the opening end while urging by the urging member and closing the opening end of the process tube by the shielding plate, Moving independently of each other in the direction to set the object to be processed at a rear processing position in the process tube.

(Operation) The invention according to claim 1 has the following operations and effects.

(A) For example, in the conventional Japanese Patent Laid-Open No. 62-128524, it is necessary to operate the tubular member (conveying arm) and the shield plate by separate drive mechanisms. Even in Japanese Utility Model No. 61-147851, it was necessary to separately arrange the mechanism for closing the shield plate and the mechanism for moving the transfer arm. On the other hand, in the present application, 1
Since the shield plate and the tubular member can be driven by one driving mechanism, the apparatus can be downsized and simplified, and the space of the heat treatment apparatus can be achieved.

(B) Since the shield plate can be moved by the guide member on the movement path of the transfer arm, even when the boat is outside the process tube, the shield plate is provided on the rear end side of the loading of the tubular member surrounding the object to be processed. The object to be processed can be conveyed while being brought into contact with and surrounding the object to be processed. Therefore, the inert gas is inserted into the region surrounded by the shielding plate and the tubular member by the gas introduction port, so that the purging can be performed during the transportation.

Here, unlike the one having a shield plate as in JP-A-62-128524, for example, when performing purging even in a horizontal furnace, the shield plate is pressed by a biasing member to form a tubular member. Enclosement can be ensured by completely abutting. Further, it can be used in a vertical type or in a form in which the object to be processed is inserted from below.

Therefore, before carrying in the object to be processed, the atmosphere around the object to be processed can be surely purged, the atmosphere around the object to be processed can be cleaned in advance, and the inclusion of air or the like into the process tube can be reduced, and the atmosphere in the atmosphere can be reduced. A good heat treatment can be performed by preventing disturbance due to air.

Further, it is possible to prevent the purge gas from leaking from the contact surface between the shield plate and the cylindrical member during the transportation of the object to be treated, so that the purge can be performed more reliably and the atmosphere can be reliably removed to perform a good treatment. It is possible to improve the quality of the processed body and speed up the heat treatment process.

(C) Even after the opening end of the process tube is closed by the shielding plate, the boat can be transported to the furnace core position at the back of the process tube, and even if the opening end is closed immediately after the boat is loaded,
The heat treatment process can continue. As a result, the closing timing of the shielding plate can be implemented earlier than before when the boat is brought in,
When the boat is carried out, the opening and closing timing of the shield plate can be carried out later than before, preventing heat from escaping and speeding up the heat treatment process.
The thermal efficiency can be improved.

According to the invention described in claim 2, the conventional method, for example,
In 57-90935, etc., the transfer arm and the shielding plate had to be operated by separate drive mechanisms. Even in Japanese Utility Model No. 61-147851, it was necessary to separately arrange the mechanism for closing the shield plate and the mechanism for moving the transfer arm. On the other hand, in the present application, since the shield plate and the transfer arm can be moved by one drive mechanism, it is possible to configure a machine that moves the shield plate together with the transfer arm without requiring a plurality of special drive sources.
The size and simplification of the device can be achieved, and the space saving of the heat treatment device can be achieved. Also, since only the transfer arm can be moved in the transfer direction with the shield plate closed during loading / unloading of the boat, heat treatment can be performed while moving to the core position during loading, and the timing of opening the blocking plate must be set before loading / unloading. Can be slower than before. Moreover, since the shield plate is always urged during processing, the shield can be surely shielded, and unlike the one having only the shield plate, the object to be processed is inserted from below the horizontal type, the vertical type or the vertical type. Anything can be applied.

According to the invention described in claim 3, before the object to be processed is carried into the process tube, the atmosphere around the object to be processed can be purged independently of the process tube, and the atmosphere around the object to be processed is preliminarily set. Can be cleaned. Here, even when the tubular member is moving, the shield plate can be reliably brought into contact with the tubular member by the biasing member. Therefore, it is possible to prevent the purge gas from leaking from the contact surface between the shield plate and the cylindrical member during the transportation of the object to be processed, and to perform the purge more reliably. Thereby, entrainment of air or the like into the process tube can be reduced, disturbance due to air in the atmosphere can be prevented, and favorable heat treatment can be performed.

In addition, the closing timing of the shield plate can be performed earlier than in the past to prevent heat escape and speed up the heat treatment process.
It is possible to improve the quality of the object to be processed by reducing the thermal efficiency and reduce the manufacturing cost. Furthermore, the opening / closing timing of the shield plate can be performed later than in the conventional case, and the escape of heat can be reduced, and also from this point, the thermal efficiency can be improved.

(Example) Hereinafter, an example in which the present invention is applied to a heat treatment apparatus for a semiconductor wafer will be described with reference to the drawings.

<First Example> This first example is particularly effective in the case of atom scan (trade name).

In FIG. 1, the transfer arm 10 has one end side formed in a substantially hollow cylindrical shape, and the other end has a small-diameter portion with an arm holder 11.
It is fixed and supported by. As shown in FIG. 2, the tip of the transfer arm 10 has a shape having a hollow cylindrical member 10a and an arc-shaped member 10b which is an example of a half-divided portion formed only by a semicircular portion of the upper region. Has become.

Then, the tip of the arc-shaped member 10b and the hollow cylindrical member 1
In the step portion 10c between the 0a and the arcuate member 10b, locking slits 12 and 13 are formed at two positions, respectively.

The hollow cylindrical member 10a is provided with a gas inlet for introducing an inert gas such as nitrogen gas,
A configuration that enables N2 purging inside this can also be adopted.

As shown in FIG. 2, the boat 20 which can be supported by the arcuate member 10b of the transfer arm 10 has a semicircular shape in the lower region so as to form a hollow cylinder with the arcuate member 10b of the transfer arm 10b. It has an outer shape having a circular arc-shaped member 21, and two support rods (not shown) are stretched over the side plates 21a, 21a at both ends thereof, and the semiconductor wafer 1 is spaced at predetermined intervals on the support rods. A groove for arraying and supporting each is formed. The side plates 21a, 21a of the boat 20 are provided with locking projections 23, 24 which are locked by the locking slits 12, 13 of the transfer arm 10.

Next, a mechanism for driving the transfer arm 10 will be described.
0 so that the first motor 31
Is transmitted to the shaft 33 via the belt 32, and the rotation of the shaft 33 moves the transfer arm 10 along the guide rails 30, 30, and the boat 20 supported on the distal end side of the transfer arm 10 Can be carried in and out of a heat treatment furnace (not shown).

 Next, the configuration of the shielding plate 40 will be described.

The shield plate 40 is formed in a disk shape having a size capable of closing an open end of a process tube (not shown), and has a notch portion 41 through which the transfer arm 10 can be inserted. The shield plate 40 is supported by a movable member 42 which is movable along the guide rails 30, 30. And this moving member
The wire 42 is connected to one end of a wire 43, and the other end of the wire 43 is wound around a winding device 44 which is always biased in the winding direction and can be wound. The winding device 44 is an example of a biasing member, and is fixed to the heat treatment device (not shown).
In this way, the shield plate 40 pulled by the wire 43 is always stopped at the position where it is in contact with one end side of the cylindrical member 10a provided at the tip of the transfer arm 10.

 Next, the operation will be described with reference to FIG.

In step 1, the transfer arm is set, and in step 2, the boat 20 is set on the transfer arm 10. The method of setting the boat 20 will be described later.

In the above-mentioned state, the shield plate 40 comes into contact with one end of the cylindrical member 10a of the transfer arm 10 due to the tension of the wire 43. Also here the cylindrical member
It is also possible to introduce an inert gas such as nitrogen gas into the inside of 10a to prevent disturbance due to air in the atmosphere.

Next, in step 3, the transfer arm 10 is moved to the first motor.
The drive of 31 moves to the process tube 9 side.
Then, since the cylindrical member 10a also moves, the shielding plate 40 that is constantly urged and pressed against the cylindrical member 10a is wound by the winding device 44 by the wire 43. , The transfer arm together with the moving member 42
It moves to the process tube 9 side together with 10.

Then, when the boat 20 is completely carried into the process tube 9, the shield plate 40 that is in contact with the cylindrical member 10a that supports the boat 20 is closed by the open end 9a of the process tube 9.
And the opening end 9a is closed. By this closing drive, it is possible to prevent heat from escaping inside the process tube 9.

After this, since it is necessary to move the transfer arm 10 further, in step 4, the transfer arm 10 continues to move and the boat is moved.
20 is moved to the core of the process tube 9. On this occasion. The shield plate 40 is pulled by the wire 43 and maintains the state of being in contact with the open end of the process tube 9, while the shield plate 40 has the notch 41 for the escape of the transfer arm 10. There is no obstacle to movement.

In the case of atom scan (product name), the heat treatment is executed in the state of step 4, and the boat 20 can be taken out thereafter by reversing the above steps.
Here, when the boat 20 is carried out, the opening end 9a of the process tube 9 can be closed by the shielding plate 40 until the cylindrical member 10a contacts the shielding plate 40, and the cylindrical member 10a is taken out from the process tube 9. Then, the shield plate 40 is returned to the home position together with the transfer arm 10 against the pulling force of the wire 43.

As described above, according to the present embodiment, when the boat 20 is carried in, the timing of closing the opening end 9a of the process tube 9 by the shielding plate 40 can be executed faster than before, while the boat 20 is being carried out. In the case of carrying out from the process tube 9, since the timing of releasing the opening end 9a can be delayed as compared with the conventional case, the escape of heat from the process tube 9 can be significantly reduced as compared with the conventional case.

Next, attachment and detachment of the boat 20 with respect to the carry-out arm 10 will be described. Figure 2 shows the transfer arm.
A method in which only the 10 is driven is shown, and the carry-out arm 10 is moved downward as indicated by an arrow A1, and the transfer arm 10 is moved to a position where the locked projections 23, 34 and the locking slits 12, 13 face each other. Then, it is horizontally moved as shown by arrow A2 to insert the locked projections 23, 24 into the locking slits 12, 13. Then, finally, the boat 20 can be supported by the arcuate member 10b by moving the transfer arm 10 upward as shown by the arrow A3. Removal can be performed by the reverse operation.
The above-described operation can be realized by the relative movement of the boat 20 and the transfer arm 10, and is not limited to the above driving.

The merit that the boat 20 can be attached and detached by the above-described operation is that the conventional boat 100 and the transfer arm 101 shown in FIG.
It can be recognized by comparing with the operation when using. That is, in the case of FIG.
In order to support the above, it is necessary to move the transport 101 in the longitudinal direction at least the length of the boat 100 or more, and in order to secure such a moving stroke, the installation area of the device must be increased. This is disadvantageous because the area cost is high, especially when installed in a clean room. In the case of the present embodiment, a small movement stroke required for engaging the boat 20 and the transfer arm 10 is sufficient, and the installation area can be greatly reduced.

<Second Embodiment> This second embodiment is one in which the present invention is applied to a cantilever type transfer device, and a second embodiment shown in FIG. 4 is different from the first embodiment in that a transfer arm is used. The point is that the fork 10 is used and the boat 50 is mounted on the fork. In this case, since the cylindrical member 10a that fulfills the stopper function of the first embodiment is not provided, the stopper 15 is provided at the position on the trailing end side of the boat 50 for carrying.
It is fixed on 10. Therefore, in the loading operation of FIG. 3 described above, the difference from the first embodiment is that the cylindrical member 10a
It is only that the stopper 15 fulfills the role of (4), and the other points are exactly the same.

<Third Embodiment> This third embodiment is an embodiment in which the present invention is applied to a soft landing type transport device, and is a third embodiment shown in FIG.
The embodiment is different from the second embodiment shown in FIG. 4 in that a function for moving the transfer arm 10 up and down is provided.

That is, the second motor 34 drives the transfer arm 50 in the vertical direction, and the cutout portion formed in the shielding plate 40 to allow the transfer arm 10 to move up and down. Is a cutout portion 41a having a larger cut area than the cutout portion 41 of the second embodiment. The third motor 35
Is a motor used to drive the cam 36 when the horizontality between the transfer arm 10 and the furnace core of the process tube 9 is obtained.

As an operation in the case of this soft landing, after the step 4 in FIG. 3 described above, an operation of placing the boat 50 in the process tube 9 and returning the transfer arm 10 to the home position may be added.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and various modifications can be made within the scope of the gist of the present invention.

The present invention makes it possible to prevent the heat of the process tube 9 from escaping by making the shield plate 40 movable along the movement path of the transfer arm 10. For this purpose, as in the above-described embodiment, The shield plate 40 is always urged toward the rear end side of the boat 20 or 50 for transport, and the transport arm does not need a special drive source.
Although the method of moving together with 10 is excellent in terms of simple structure, the shielding plate 40 may be moved independently by another drive source.

Further, the transport arm 10 and the boat 20 shown in the first embodiment can be modified in various ways.
If the ten modified examples are given, those shown in FIGS. 6A to 6D are conceivable, and a boat corresponding to the carry-out arm 10
Examples of 20 include those shown in FIGS. 7 (a) to 7 (d).

Only the structure different from that of the above embodiment will be described below. The transfer arm 10 shown in FIG. 6 (a) uses the stepped portion 10c side as an engaging table 13a as an engaging member. As shown in FIG. 7A, the boat 20 supported by the transfer arm 10 has a locked projection 24a that is locked to the upper surface of the locking mounting table 13a.

The transfer arm 10 shown in FIG. 6 (b) has locking projections 12a instead of the slits, and the boat 20 supported by this transfer arm 10 is, as shown in FIG. It has a groove 23a to be locked which is locked from the locking projection 12a.

In the transfer arm 10 shown in FIG. 6 (c), the locking member on the tip side is a keyhole 12b, and the locking arm on the stepped portion 10c side projects upward from the tip of the locking table 13a. Forming a vertical piece 13b. On the other hand, the boat 20 supported by the arm 10 has the keyhole as shown in FIG. 7 (c).
It has a locked projection 23 locked to 12b, the locked projection 24a on the other end side, and a vertical piece 24b protruding downward from the tip.

The transfer arm 10 shown in FIG. 6 (b) has the keyhole at one end.
The stepped portion 10c does not require any projection or slit, and the inner surface of the arc is used as the locking member 13c. On the other hand, the boat 20 supported by the transfer arm 10
As shown in FIG. 7 (d), a locked arcuate part having a diameter smaller than that of the arcuate member 21 is provided on the other end side while having a locked projection 23 to be inserted into the keyhole 12b. Has 24c. Further, in the boat 20, the side plate 21b on one end side is formed in a substantially circular shape, and the inflow of air from the open end when the boat 20 is supported by the transfer arm 10 is minimized.

It goes without saying that locking members other than those described above and locked members can be applied, and at least they can be engaged without requiring a movement stroke in the longitudinal direction of the carry-out arm 10,
In addition, any shape can be used as long as it can reliably support a boat and a wafer of considerable weight. Further, in order to supply the inert gas to the wafers on the boat, it is sufficient that the transfer arm 10 is formed in a hollow cylindrical shape. Is possible.

[Effect of the Invention] According to the invention of claim 1, the atmosphere around the object to be processed can be purged before the object to be processed is carried into the process tube, so that the inclusion of air or the like into the process tube is reduced. At the same time, it is possible to prevent disturbance due to air in the atmosphere, perform good heat treatment, improve the quality of the object to be treated, and speed up the heat treatment step. Even after closing the open end of the process tube, the boat can be turned upside down to the core position of the process tube, the opening end can be closed early, and heat escape from the process tube can be significantly reduced. can do.

According to the invention of claim 2, the size and simplification of the apparatus can be achieved, and hence the space saving of the heat treatment apparatus can be achieved.

According to the third aspect of the present invention, since the purging can be performed before the process tube is carried in, the atmosphere around the object to be processed can be cleaned, air and the like can be prevented from being entrained and disturbance, and good heat treatment can be performed. In addition, the closing timing of the shield plate can be performed earlier than in the conventional case, heat can be prevented from escaping, the heat treatment process can be speeded up, the quality of the object to be processed can be improved by improving the thermal efficiency, and the structural cost can be reduced. . Furthermore, the opening / closing timing of the shield plate can be performed later than in the conventional case, and the escape of heat can be reduced, and also from this point, the thermal efficiency can be improved.

[Brief description of the drawings]

1 is a schematic perspective view for explaining a first embodiment of the present invention, FIG. 2 is a schematic perspective view showing details of a transfer arm and a boat of FIG. 1, and FIG. 3 is a view of the apparatus of FIG. FIG. 4 is a schematic perspective view for explaining a boat carrying operation, FIG. 4 is a schematic perspective view for explaining a second embodiment of the present invention, and FIG. 5 is a schematic perspective view for explaining a third embodiment of the present invention. Fig. 6 is a schematic explanatory view for explaining a modified example of the transfer arm of Fig. 1, Fig. 7 is a schematic explanatory view for explaining a modified example of the boat of Fig. 1, and Fig. 8 is an atom. 9 is a schematic perspective view of a conventional transfer arm and boat used for scanning (product name), FIG. 9 is a schematic perspective view for explaining a conventional boat transfer device, and FIG. 10 is a transfer operation of FIG. It is a schematic explanatory drawing for doing. 1 ... Object, 9 ... Process tube, 9a ... Open end, 10 ... Transfer arm, 15 ... Stopper, 20 ... Boat, 40 ... Shielding plate, 42 ... Moving member, 44 ... Energizing member.

Claims (3)

(57) [Claims] 1. A transport device for loading and unloading a boat for arranging and supporting an object to be processed into and out of a process tube of a heat treatment furnace, wherein a transport arm for supporting and transporting the boat, and a transporting rear end side of the boat, Provided on the transfer arm,
A tubular member that surrounds the periphery of the object to be processed, a drive mechanism that drives the transfer arm to move forward and backward, and a movable member that is movable along a movement path of the transfer arm,
When the boat is outside the process tube, the boat moves together with the transfer arm while being in contact with the loading rear end side of the tubular member, and the back of the process tube after the opening end of the process tube is closed. To the transfer arm, a gas inlet for introducing an inert gas into a region surrounded by the tubular member and the shield plate, and the shield plate of the transfer arm. A heat treatment furnace comprising: a guide member that movably guides along a moving direction; and an urging member that constantly urges the guide member in a direction in which the shield plate contacts the tubular member. Conveyance device for objects to be processed. 2. A transport device for loading and unloading a boat for arranging and supporting an object to be processed into and out of a process tube of a heat treatment furnace, wherein the transport arm is for carrying the boat in and out of the process tube of the heat treatment furnace. A drive mechanism for driving the transfer arm forward and backward, and movably provided on the moving path of the transfer arm,
A shield plate that moves integrally with the transfer arm when the boat is outside the process tube, and that allows the transfer arm to move inward of the process tube after closing the open end of the process tube; A stopper provided on the transfer arm at the rear end side of the boat for carrying in; a guide member that guides the shield plate to be movable in the same direction as the transfer arm moves; and the shield plate contacts the stopper. And a biasing member that constantly biases the guide member in a direction. 3. A heat treatment furnace for supporting a boat in which a plurality of objects to be processed are arranged by a cylindrical member of a transfer arm and surrounding the object to be processed, and heat-treating the transfer arm to the object to be processed. A heat treatment method of carrying a heat treatment to an object to be processed in a state where the carrying arm is carried in a process tube and the carrying arm is kept in non-contact with an inner wall of the process tube, wherein the carrying arm is movably provided on a moving path of the carrying arm. The shield plate brought into contact with the carrying-in rear end side of the tubular member, the boat is surrounded by the shield plate and the tubular member, the shield plate and the tubular member in one direction. Simultaneously moving, while biasing the shielding plate by a biasing member that constantly biases the shielding plate in the direction of contacting the tubular member,
A step of introducing an inert gas into the tubular member and purging, and inserting the tubular member into the process tube, and moving the tubular member to position the tubular member at a rear end position of loading. The shielding plate is in contact with the opening end of the process tube, the opening end is closed while being biased by the biasing member, and after closing the opening end of the process tube by the shielding plate A step of independently moving the tubular member in the one direction with respect to the shielding plate to set the object to be processed at a processing position in the interior of the process tube. Heat treatment method.