JPH048911B2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to oxidation of semiconductor wafers, diffusion treatment, single crystal growth by boat method, GaAs epitaxial crystal growth, etc. in various semiconductor and compound semiconductor processes. The present invention relates to a horizontal processing furnace that accommodates a workpiece, and particularly to improvements in a coil heater for semiconductor processing that is wound around the processing furnace.

[Technical background of the invention and its problems] This type of coil heater has a structure in which, for example, a heater wire with a diameter of 6 mm to 12 mm is coated with a heat insulating material and wound in a spiral shape in a fixed direction. Commonly used.

An example of this is shown in FIGS. 7 and 8, in which a horizontal processing furnace 5 in which a work W is accommodated
Coil heater 51 wound in a circular shape around 0
are arranged in the furnace body 52.

As shown in FIG. 8, the coil heater 51 is wound, for example, in the right-handed direction in the direction of the furnace axis X-X', and a predetermined voltage is applied to both ends to bring the required heating temperature to the processing furnace by resistance heating. The configuration is such that it is granted.

When setting the furnace temperature using a coil heater, if you want a long flat zone for uniform heating in the axial direction of the furnace, divide the coil heater into so-called zones, such as 3 zones to 6 zones, and adjust the temperature of each zone. Set them appropriately and combine them to obtain a uniform flat zone. Particularly in this case, both ends of the furnace cool down more easily than the center, so the set temperature of the end zone coil heater is set to a temperature gradient that is slightly higher than the center, resulting in a long, uniform flat zone. Control.

Further, depending on the work to be processed, the temperature of the coil heater may be controlled so that a temperature gradient as shown in FIG. 9 is generated in a part of the zone, for example.

In any case, such coil heaters for semiconductor processes are usually used with some kind of temperature gradient set along the furnace axis direction.

It is desired that temperature control in the axial direction of the furnace be performed with high precision, but on the other hand,
That is, in the radial plane perpendicular to the reactor axis, it is desirable that the temperature be uniform along the transverse direction Y-Y' (FIG. 7) passing through the reactor core P. So-called cross-sectional uniform heating is required.

Particularly in the case of single crystal growth, the quality of the product is greatly affected by the quality of the thermal uniformity.

However, when a spiral coil heater is used, a temperature difference actually occurs before and after the furnace, and a temperature gradient as shown by the broken line Q in FIG. 7, for example, occurs in the transverse direction Y-Y'. There was a problem that cross-sectional heat uniformity could not be obtained. For example, it was found that at a temperature gradient of 1 degree (℃)/cm (at 1250 degrees Celsius), the temperature difference between the front and back of the cross section can reach 1.5 degrees (℃).

To examine the cause of such a temperature difference before and after the cross section, for example, for the right-handed spiral coil heater shown in Figs. 7 and 8, the temperature decreases along the furnace axis direction as shown in Fig. 9. For example, if a slope is set, the cross direction Y-
The upper half 51a (the first
Consider the heating effect contributed by the lower half 51b (FIG. 10a) and the lower half 51b (FIG. 10b) in the transverse direction YY'.

FIGS. 10a and 10b show each heater winding as seen from above, and thus show the upper half 51a of the winding.
The inclination directions of the lower half portion 51b are exactly opposite to each other, and the winding direction of the winding wire is as shown by the solid arrow in the figure.

Since the temperature gradient is set to decrease along the traveling direction of the windings of the coil, the temperature of the coil heater 51 decreases along the furnace axis direction X-X', resulting in almost the same temperature distribution around each winding. It is thought that the area showing , that is, the hot area 53 becomes smaller along the furnace axis direction.

Therefore, in the upper half 51a of the winding, FIG.
It is considered that the temperature on the upper side, ie, the rear side 54 of the furnace, is higher, while for the lower half 51b of the winding, the temperature is conversely higher on the lower side, ie, the front side of the furnace, in FIG.

It is believed that by combining the heating effects of the upper and lower windings, the temperature deviations before and after the furnace are mutually corrected and averaged for each cross section, resulting in cross-sectional uniform heating.

However, in reality, heat always has the property of escaping upward, so the heating effect that contributes to the cross section in the transverse direction Y-Y' is the lower half 51b and the upper half 5.
1a, the ratio is 6:4 to 7:3,
It was observed that the winding portion 51b in the lower half portion was large.

For this reason, the lower half winding portion 5 shown in FIG.
The temperature effect of 1b affects more in the transverse direction Y-Y', and in practice the temperature at the front side 55 of the furnace is higher than at the rear side 54, resulting in a temperature gradient as shown by the dashed line in FIG. I found out.

It is known from experience at manufacturing sites that when a spiral coil heater is used, heat is unevenly distributed between the front and rear of the furnace. body 5
The heat dissipation window 56 in the ceiling of No. 2 is aligned with the vertical axis Z- passing through the core P.
There have been some attempts to offset the position of the solid line along Z' as shown by the chain line, but this has not yet achieved a sufficient effect on heat uniformity.

As mentioned above, in the case of a spiral coil heater, each heater winding does not align with the radial plane perpendicular to the furnace axis, so a temperature difference between the front and rear of the furnace is practically unavoidable. As a solution to this problem, a U-turn type parallel heater, as shown in FIG. 11, has been proposed.

The heater 60 has its respective windings 61 arranged parallel to each other along a radial plane perpendicular to the central axis X-X', and the adjacent windings 61
The structure is such that they are connected in sequence by making a U-turn.

The folded portion 62 of the heater is generally formed integrally into a U-shape by bending as shown in FIG. 12a, or connected by a welded portion 63 as shown in FIG. 12b. In the latter case, bending is difficult and the shape after processing is highly unstable due to spring back, and in the latter case, welding work is troublesome and instability of the welded part is unavoidable. .

Moreover, in any case, in this structure, each winding basically does not form a closed cross section, and a gap 64 is left in the axial direction, resulting in a so-called open-end structure, which is prone to thermal deformation, buckling, etc. This tends to cause instability in shape and defects in strength, which has the problem of impairing the performance and life of the heater.

[Object of the Invention] The present invention has been made in view of the above-mentioned conventional circumstances, and its purpose is to solve the conventional drawbacks, to be easy to manufacture, to have sufficient strength, and to be usable for semiconductor processing. An object of the present invention is to provide a novel coil heater for semiconductor processing, especially in horizontal processing, which can obtain highly accurate cross-sectional heat uniformity.

[Summary of the Invention] In order to achieve the above object of the present invention, the present invention basically provides a coil heater for semiconductor processing that is wound around the processing furnace in a horizontal processing furnace, Parallel portions of each heater winding are spaced parallel to each other along a radial plane perpendicular to the central axis of the heater except for a portion of the angular range; and a parallel portion within the portion of the angular range. Each heater winding is formed with an inclined part bent from one end thereof and extended obliquely with respect to the radial surface, and the extending end of the inclined part of each heater winding is connected to the adjacent heater. The parallel part of the winding is bent and connected to the other end, and the inclined part of each heater winding is positioned along the furnace axis of the processing furnace so as to correspond to the ceiling of the processing furnace. This article proposes a characteristic configuration.

According to the configuration of the above basic invention, each winding of the coil heater is configured as a parallel part along the radial surface for most of its angular range, so that the problems in the conventional spiral coil heater can be solved and the conventional U Unlike turn-type parallel heaters, it maintains a closed cross section, so it exhibits sufficient strength against thermal deformation, etc., and the sloped part can be formed with a simple bending process, so it is easy to manufacture and maintains its shape even after processing. In particular, in the present invention, the inclined part of each heater winding is positioned corresponding to the ceiling part of the horizontal processing furnace which has the least thermal effect on the workpiece, and the inclined part can be maintained as a heating effect. Since the coil heater is not located in the lower half of the furnace, which plays an important role in heating, it is possible to provide a coil heater with excellent cross-sectional heat uniformity.

[Embodiments of the Invention] Hereinafter, embodiments of the present invention will be described with reference to FIGS. 1 to 6 of the drawings.

FIG. 1 shows the basic configuration of a coil heater 1 for semiconductor processing in a horizontal processing furnace as a first embodiment of the present invention.

In the coil heater 1, each of the circular heater windings 2 has a parallel portion 2a that is spaced parallel to each other along a radial plane perpendicular to the central axis X-X' of the coil, and an axis X-X. 1. Adjacent heater windings 2 are connected to each other by this inclined portion 2b and are integrally constructed. The inclined portion 2b is bent from one end 3 of the parallel portion 2a and extends in a state inclined with respect to the radial plane, and the extending end thereof is connected to the other side of the parallel portion 2a of another adjacent heater winding 2. The end portion 4 is bent and connected, and this configuration is repeated for each heater winding 2 in sequence to form a coil heater having a closed cross section.

As shown in FIG.
The heater 1 is wound around the furnace in accordance with It is the composition.

FIG. 2 is a view from the top of the horizontal processing furnace 5, and the inclined portions 2b of each heater winding 2 are inclined with respect to the radial plane and parallel to each other, and interfere with each other. Never. Each inclined portion is positioned so as to correspond to the ceiling portion 5a of the processing furnace 5. That is, as shown in FIG. 3, the inclined part 2b is positioned corresponding to the ceiling part 5a of the furnace 5. The angular range that the inclined portion 2b occupies with respect to the core P is set to a narrow range of approximately 35 degrees to 45 degrees.

Therefore, regarding the cross section of the furnace 5, the inclined portion 2b
is the lower half 7, with the transverse direction Y-Y' as the boundary,
That is, the parallel portion 2a occupies not only the region where the heat influence is large on the workpiece W housed in the furnace 5, but also most of the upper half portion 8 where the influence is less than that region,
Ceiling part 5a that has the least thermal influence on the workpiece W
Since the coil heaters are arranged in accordance with the above, it is possible to significantly improve heat uniformity in the transverse direction within the furnace compared to a spiral coil heater.

In order to manufacture the coil heater 1 having the above configuration, as shown in FIG. The winding 2 of the coil heater 1 is wound along the parallel part 2.
a, and then a pair of pins 11, 1 erected on the outer periphery of the mandrel 10 at intervals in the circumferential direction.
2 as a guide, the coil heater 1 is manufactured by bending at this point to form the inclined portion 2b, and repeating this in sequence as shown by the broken arrow.

Therefore, here, bending is required at the pins 11 and 12, but this bending angle is extremely small compared to conventional U-turn type parallel heaters, and the processing is easy. Since there is little spring back, the stability of the shape is maintained.

For example, as shown in FIG. 5, the pins 11 and 12 are attached by sliding a magnetic plate 14 to a guide rail-shaped holder 13 provided on the inner wall of the mandrel 10. By attracting and receiving the inner end of the pin, the pin 11 is held in a protruding state, and after the processing of the coil heater 1 is completed, the magnetic plate 14 is slid along the rail portion of the holder 13 and pulled out. , 12 inwardly with a hammer or the like as shown by the arrow, the material can be dropped into the mandrel 10 as shown by the chain line. Therefore, the coil heater 1 after processing can be easily removed from the mandrel 10, and the pins 11 and 12 can also be easily set.

A second embodiment of the present invention shown in FIG.
We propose a configuration in which a plurality of long pieces are combined along the X′ direction. The figure is shown as seen from the top surface of the horizontal processing furnace 5, as in FIG.
Three sets of the above-mentioned basic coil heaters 1 equipped with
The heaters 1 are arranged in the direction of the furnace axis X-X', and the end portions of the heaters 1 are integrally connected to each other by the folded portions 15, and the inclination direction of the inclined portions 2b of each adjacent set of coil heaters is as shown in the figure. , are combined alternately in opposite directions.

As mentioned above, each basic type coil heater 1
Since the degree of bending of the inclined portion 2b is small, there is very little instability in the shape due to spring back after processing. However, when a longer coil heater is manufactured, even a slight deformation may occur. It may become larger overall. Therefore, as in the second embodiment, by combining the coil heaters 1 based on the inclined portions 2b in opposite directions, the deformation effect can be canceled out, and as a whole, a more stable integrated coil heater can be obtained. It became possible. This allows for the easy production of longer coil heaters, which are particularly suitable for zoned temperature control.

Although the folded portions 15 connecting each set of coil heaters 1 have a U-turn shape, the number of folded portions 15 is small, so that the problems encountered with conventional U-turn type parallel heaters are solved.

[Effects of the Invention] As described above, in the present invention, each winding of the coil heater has a parallel portion along the radial surface for most of its angular range, so that it is different from the conventional spiral coil heater. Problems can be resolved, and unlike conventional U-turn type parallel heaters,
Since each winding has a closed cross-section, it exhibits sufficient strength against thermal deformation, etc., and its sloping parts require simple bending, so it is easy to manufacture and maintains a stable shape even after processing. In particular, since the inclined part 2b of this coil heater is positioned corresponding to the ceiling of the horizontal processing furnace, the lower half of the cross section of the furnace, which has the greatest thermal effect on the workpiece inside the furnace, is Of course, most of the upper half is occupied by the parallel part of the heater winding, and the inclined part is located in the ceiling where the influence of heat is the least. Therefore, compared to a conventional spiral coil heater, the heat in the front and back of the furnace is reduced. It is possible to provide a coil heater for semiconductor processing that largely eliminates deviation and has high cross-sectional heat uniformity.

[Brief explanation of drawings]

FIG. 1 is an external perspective view showing the basic configuration of a coil heater according to an embodiment of the present invention with lines, and FIG. 2 is a top view showing the arrangement relationship between the coil heater shown in FIG. 1 and a horizontal processing furnace. , Figure 3 is a cross-sectional view of Figure 2,
FIG. 4 is a schematic diagram showing how the coil heater of the present invention is manufactured using a mandrel, FIG. 5 is an enlarged cross-sectional view of the main part of FIG. 4, and FIG. 6 is a diagram of the present invention in which the basic configuration of FIG. A top view showing the second embodiment together with a processing furnace, FIG. 7 is a cross-sectional view of a furnace body equipped with a conventional spiral coil heater, FIG. 8 is a top view of FIG. 7, and FIG. 9 is an inclined view. Figures 10a and 10b are graphs showing the temperature settings of the furnace, respectively, for analyzing and explaining the heat action of the upper and lower halves of the coil heater winding shown in Figure 7. FIG. 11 is a schematic perspective view of a conventional U-turn type parallel heater, and FIGS. 12a and 12b are enlarged views of essential parts showing different shapes of the folded portions of the heater in FIG. 11. 1... Coil heater, 2... Heater winding, 2a
...Parallel part, 2b...Inclination part, 5...Processing furnace, 5
a... Ceiling part, 10... Mandrel.

Claims (1)

[Scope of Claims] 1. A coil heater for semiconductor processing that is wound around the processing furnace in a horizontal processing furnace, wherein the center axis of each heater winding, except for a part of its angular range, parallel parts spaced parallel to each other along a radial plane that is perpendicular to the radial plane; The extending end of the inclined part of each heater winding is bent and connected to the other end of the parallel part of the adjacent heater winding, and each of the above-mentioned 1. A coil heater for semiconductor processing in a horizontal processing furnace, characterized in that an inclined portion of the heater winding is positioned along the furnace axis of the processing furnace so as to correspond to a ceiling portion of the processing furnace. 2. A first coil heater comprising a plurality of heater windings in which the inclined portions of each of the heater windings have the same inclination direction, and a plurality of heater windings in which the inclination direction of the inclined portions is opposite to that of the first coil heater. A coil heater for semiconductor processing in a horizontal processing furnace according to claim 1, wherein the first and second coil heaters are connected at a folded portion. .