JP2756566B2 - Vertical heat treatment equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial application field) The present invention relates to a vertical heat treatment apparatus.

(Prior Art) In a conventional heat treatment apparatus, for example, a low-pressure CVD apparatus, a furnace in which a furnace body for heat treatment is installed in a horizontal direction (ie, a horizontal furnace type) is generally used. However, in recent years, a vertical furnace type heat treatment apparatus having the following advantages has also been used.

The first advantage of the vertical furnace type is that the installation area of the apparatus can be reduced.

A horizontal furnace type heat treatment apparatus naturally requires an installation area proportional to the furnace length. On the other hand, the area required for installing a vertical furnace type heat treatment apparatus is determined by the diameter of the furnace. Since the furnace diameter is generally shorter than the furnace length, the vertical furnace requires a smaller installation area. Moreover, since the heat treatment is performed by continuously aligning the semiconductor wafers in the furnace, the furnace length increases in proportion to the processing capacity, but the furnace diameter does not change even if the processing capacity increases. Thus, the greater the throughput, the greater the advantages of a vertical furnace with respect to installation area.

A second advantage of vertical furnaces is that the supply of process gas into the furnace can take advantage of the convection of gases that occur in the vertical direction.

In both the horizontal furnace type and the vertical furnace type, one of the most important elements in the heat treatment apparatus is to make the temperature distribution in the furnace uniform along the furnace length direction. If the temperature distribution is non-uniform, the quality will vary among the semiconductor wafers processed in the same lot.

(Problems to be Solved by the Invention) In this respect, the vertical furnace type heat treatment apparatus is more disadvantageous than the horizontal furnace type heat treatment apparatus. This is because convection causes heat to move upward, and the temperature rises cumulatively at the furnace top. This accumulation is accompanied by the problem of thermal fatigue of the heater.

For the above reasons, the heat treatment apparatus achieves a uniform temperature distribution in a limited predetermined region in the furnace, and heat-treats the semiconductor wafer only in this region. This is because, at both ends of the furnace, a region having a low temperature is inevitably generated due to the influence of heat radiation to the surroundings, so that it is impossible to make the internal temperature uniform over the entire length of the furnace. Therefore, in order to improve the productivity of the heat treatment apparatus, it is important to increase the ratio of the uniform temperature distribution region. In this regard, the vertical furnace type is more difficult than the horizontal furnace type for the same reason as described above.

As a means for achieving a uniform temperature distribution over a wider area in the furnace in a steady state, in a conventional heat treatment apparatus, a split type heater 2 is provided around a process tube 1 as shown in FIG. Furnace is used. The heater 2 is made of a resistance wire, and is divided into three portions 3a, 3b, 3c by providing terminals T1 to T4 as shown in the drawing. By independently setting the power supply voltage between the terminals T1 and T2, between the terminals T2 and T3, and between the terminals T3 and T4, the current flowing through the resistors 3a, 3b, and 3c can be controlled independently. I have. In this conventional device, the resistors 3a, 3
By making the current flowing through c larger than the current flowing through the resistor 3b at the center, the heater temperature at both ends is increased. As a result, the influence of heat radiation at both ends of the process tube is compensated, so that the area where the temperature distribution is uniform in the central portion is expanded as compared with the case where the resistors 3a, 3b, and 3c all have the same heater temperature.

However, even if the above-described divided heater is used, the efficiency of temperature control at both ends of the process tube is not so high. For this reason, it is difficult to shorten the resistances 3a and 3c to increase the ratio of the region where the temperature distribution is uniform. For example, when the heater temperature of the resistors 3a and 3c is increased and the length thereof is shortened, there is a problem that a non-uniform and abnormal temperature distribution occurs at a boundary between the resistors 3a and 3c.

An object of the present invention is to provide a vertical heat treatment apparatus capable of obtaining a uniform temperature distribution over a wider area in a process tube.

(Means for Solving the Problems) The present invention provides a process tube which is installed substantially vertically and accommodates an object to be processed, and is provided outside the process tube so as to surround an area where the object to be processed is arranged in the process tube. A central heater provided, an upper heater provided above the central heater so as to surround a region including an area above the area where the workpiece is arranged, and the workpiece A lower heater provided below the central heater so as to surround an area including a lower area than the area to be formed, wherein each heater is independently configured, and the upper heater and the lower heater are The central heater is configured to generate a larger amount of heat per unit area than the central heater.
A vertical heat treatment apparatus characterized in that the heat generation amount per unit area on the upper side is smaller than that on the lower side.

(Embodiment) An embodiment in which the apparatus of the present invention is applied to a vertical furnace type heat treatment apparatus will be described below with reference to the drawings.

FIG. 1 shows an embodiment of a heating furnace constituting the heat treatment apparatus of the present invention. In FIG. 1, reference numeral 1 denotes a process tube arranged in a vertical direction. Process tube 1
Is made of quartz glass, silicon carbide, or the like, and has a double tube structure including an outer tube 4a and an inner tube 4b. Supply pipe 23
The processing gas G supplied into the inner tube 4b from the inner tube 4b and the outer tube
Exhausted through the gap between 4a. Process tube 1
Are provided with three independent heaters 6, 8, and 10. The heater 6 is provided at the center of the process tube 1, the heater 8 is provided at the upper end of the process tube 1, and the heater 10 is provided at the lower end of the process tube 1. heater
Reference numerals 6, 8, and 10 each include a coil of a heating resistor, and are connected to independent power supplies 18, 20, and 22, respectively. The heater 6 is composed of one coil, but the heaters 8 and 10 have a two-layer coil structure. That is, the heater 8 includes two coils 8A and 8B, and the heater 10 also includes two coils 10A and 10B.
FIG. 2 shows an equivalent circuit of these heaters 6, 8, and 10. The heater 6 is provided with terminals 12a and 12b.
8 is connected. The coil 8A of the heater 8 is provided with terminals 14a and 14b, and the coil 8B is provided with terminals 14c and 14d. The terminals 14a and 14c are short-circuited, and the terminals 14b and 14d are connected to the power supply 20. Similarly, in the heater 10, of the terminals 16a, 16b, 16c, and 16d provided in the two coils 10A and 10B, the terminals 16a and 16c are short-circuited, and the power supply 22 is connected to the terminals 16b and 16d.
Is connected. As described above, the heaters 6, 8, and 10 generate heat by the current supplied from the independent power supplies 18, 10, and 22,
The process tube 1 is heated.

Heaters 6, 8, 10 for cylindrical process tubes
Are formed in a cylindrical shape, and are installed on the outer peripheral surface of the process tube such that the center thereof coincides with the tube axis of the process tube. The area of the process tube 1 heated by the central heater 6 is an area where a semiconductor wafer to be subjected to a heat treatment is arranged, and is designed so as to achieve a uniform temperature distribution. On the other hand, the upper heater 8 and the lower heater 10 are provided to compensate for the effect of heat radiation at both ends of the process tube and to achieve a uniform temperature distribution over the entire central area. As described above, a general object of the present invention is to reduce the length of the upper heater 8 and the lower heater 10 in the tube axis direction as much as possible.

In the example of FIG. 1, in order to compensate for the influence of heat radiation at both ends in a short heating area, the amount of heat generated per unit area of the upper and lower heaters 8 and 10 is twice that of the central heater 6. Set above. The center heater 6 has a single-layer coil structure, whereas the upper heater 8 and the lower heater
That is why 10 has a two-layer coil structure as described above. Even if the heating values of the heaters 8 and 10 at both ends are increased, an abnormal temperature distribution does not occur in the central area of the process tube. This is because the heaters 8, 10 at both ends and the central heater 6 are completely separated from each other, and no heat conduction occurs. Further, in the example of FIG. 1, heat accumulation in the upper end area due to thermal convection is considered. That is, the heating area by the upper end heater 8 is shorter than the heating area by the lower end heater. The central heater 6
The coil densities of the heat generating resistors constituting the element become coarser as going upward. As a result, heat accumulation in the upper end area is compensated, and a uniform temperature distribution is obtained. Also,
If desired, it is also possible to achieve a temperature distribution with an arbitrary slope.

FIG. 3 is a sectional view more specifically showing a heat treatment apparatus using the heating furnace of FIG. In the figure, reference numeral 21 denotes an outer wall of the heat treatment apparatus. Inside the outer wall 21 is the first
The heating furnace in the figure is installed vertically. On the outside of the heating furnace, at the intervals corresponding to the width of the heaters 8, 6, and 10, holding frames 24, 26,
28 and 30 are provided. Heaters 8, 6, and 10 are provided between these holding frames. The holding frames 24, 26, 28, 30 are made of a heat insulating material, and thereby, heat conduction between the heaters 6, 8, 10 is prevented. Further, the holding frame 30 prevents overheating at the open end of the heat treatment apparatus. Also,
A heat insulating material 32 is filled between each heater and the outer wall 21, and the outer wall 21 is filled.
Is prevented from being heated.

FIG. 4A shows the pitch of the coils constituting the heater 6. FIG. 4B shows the pitch of the coils constituting the heaters 8 and 10. As is apparent from Figure 4A, is made from above the coil pitch of the heater 6 When _{P 1, P 2, P 3} ... P n sequentially, and _{P 1> P 2> P 3} ...> P n. That is, as described above, in order to make the temperature distribution inside the process tube 1 uniform, the pitch is increased in the upper part and smaller in the lower part.

As is clear from FIG. 4B, the inner coils 8A, 10A of the heaters 8, 10 and the outer coils 8B, 10B have the same pitch P. Also, the inner coils 8A, 10A and the outer coils 8B, 10B are arranged so as to be shifted by P / 2.

The width L of each of the coils 6, 8, and 10 is appropriately set according to the length of the process tube 1. As shown, the width of the upper heater 8 is shorter than the width of the lower heater 10. This is to compensate for the heat storage in the upper part due to convection as described above. Further, the wire diameter (d ₂ ) of the heaters 8 and 10 is larger than the wire diameter (d ₁ ) of the heater 6. This makes it possible to increase the amount of heat generated per unit of the heaters 8 and 10 at both ends and to improve the thermal durability of the upper heater 8 exposed to heat accumulation.

As shown in FIG. 3, when performing the heat treatment of the semiconductor wafer using the apparatus of this embodiment, a large number of semiconductor wafers 38 held in the quartz glass boat 36 are housed in the process tube inner tube 4b. . Quartz glass boat
36 is supported by the heat retaining cylinder 40. The heat retaining cylinder 40 has a function of supporting the quartz glass boat and keeping the temperature near the entrance and exit. A rotating mechanism 42 is provided at the lower end of the heat retaining cylinder 40 so that the heat treatment is performed while rotating the semiconductor wafer 38. Further, a lid 44 for closing the entrance is provided to seal the process tube during the heat treatment.

The processing gas G used for the heat treatment is supplied through the supply pipe as described above.
From 23, it is introduced into the inner tube 4b of the process tube. The introduced processing gas is brought into contact with the semiconductor wafer 38 to perform a predetermined heat treatment. At this time, by rotating the semiconductor wafer 38, uniform contact with the processing gas becomes possible. Thereafter, the processing gas is guided to an exhaust unit (not shown) through an opening 46 provided at the top of the inner tube and a gap 34 between the inner tube 4b and the outer tube 4a.

The configuration of the heater in the above embodiment can be variously changed within the scope of the present invention. FIGS. 5A, 5B, 6A, and 6B show examples.

FIG. 5A is a diagram showing a modification of the heater, and FIG. 5B is an equivalent circuit diagram thereof. In this example, the respective coils 8A, 8B are connected to independent power supplies 20A, 20B without short-circuiting the two coils 8A, 8B of the upper heater 8. Similarly, in the lower heater 10, the two coils 10A and 10B are connected to independent power supplies 22A and 22B, respectively. Therefore, including the central heater, five independent drive circuits are formed as a whole. In this modification, the amount of heating by the upper heater 8 and the lower heater 10 can be controlled to a higher range.

FIG. 6A is a diagram showing another modification of the heater, and FIG. 6B is an equivalent circuit diagram thereof. In this example, the configuration of the upper heater 8 and the lower heater 10 is the same as the example of FIGS. 2 and 3, but the configuration of the central heater 6 is different. That is, three heaters 6A, 6B, 6C connected to independent power supplies 18A, 18B, 18C are used as the central heater. That is,
Power supply 18A is connected to terminals 12c and 12d of heater 6A, and power supply 18B
Is connected to terminals 12e and 12f of heater 6B, and power supply 18C is connected to heater
Connected to 6C terminals 12g and 12h. This modification is useful for a heat treatment apparatus having a long process tube.

Further, the heater is not limited to three divisions, but may be divided into plural parts such as five divisions.

Although the above embodiment uses a process tube having a double tube structure, the present invention can be applied to a case where the process tube has a single tube structure.

Further, the wire diameter of the coil in each of the heaters 6, 8, 10 may be equal, and the width of the lower heater 10 may be equal in the upper heater 8.

Next, another embodiment of the present invention will be described with reference to FIG. 7 and FIG.

FIG. 7 shows another embodiment of the heat treatment apparatus according to the present invention, and FIG. 8 shows the lower end portion in detail. In this embodiment, a process tube 1 having a single tube structure is used. The processing gas G is introduced from the top of the process tube 1 and discharged from the exhaust port 50 provided at the lower end. On the side wall of the process tube 1, three independent heaters 6, 8 ', and 10' having the same configuration as in the above-described embodiment are provided. However, the heaters 8 'and 10' at both ends are composed of single-layer coils. The feature of this embodiment is that an independent heater 51 is provided on a lid for closing the entrance at the lower end of the process tube. The lid is an outer cylinder 52 filled with heat insulating material 53 inside.
And an inner cylinder 55 provided with a protection cylinder 56 inside. This structure is described in detail in FIG.

In FIG. 8, the outer cylinder 52 is provided with a flange 54,
The heat insulating material 53 blocks the propagation of heat in the opening direction of the process tube 1. The inner cylinder 55 is installed inside the outer cylinder 52 so as to be able to advance and retreat. That is, the inner cylinder 55 is
Functions as a support member for supporting the quartz glass boat 36 in which is stored. The heater 51, together with the thermocouple thermometer 58,
It is provided further inside a protection tube 56 provided inside the inner tube 55. The protection cylinder 56 shuts off the processing gas G in the process tube 1 and prevents deterioration of the heater due to contact with the gas G. Further, the heater 51 is provided with terminal electrodes 51a and 51b, and these terminal electrodes are connected to a power source (not shown). Reference numeral 60 denotes a support, and a bellows 61 is provided between the support and the outer cylinder flange 54. The support base 60 is a lifting device
62 is fixed to the arm 63. A cooling water passage 64 is provided inside the lower end of the outer wall 21, and sufficient cooling is performed by flowing cooling water through the cooling water passage 64.

In the embodiment of FIGS. 7 and 8, not only the side surface of the process tube 1 but also the inlet / outlet at the bottom of the process tube 1 is heated by the heater 51. Since the entrance / exit portion has the greatest effect of heat radiation, the use of the heater 51 makes it possible to further uniform the temperature distribution in the process tube.

The heater for heating the lower end of the process tube employed in the embodiment shown in FIGS. 7 and 8 can be used alone without being combined with the scope of the present invention. For example, in the embodiment shown in FIGS. 7 and 8, even when the same heater as that of the conventional example shown in FIG. 9 is used for the side wall of the process tube, a certain effect can be obtained by using the heater 51. .

〔The invention's effect〕

According to the present invention, the central heater, the upper heater, and the lower heater are made independent from each other, and the central heater is configured such that the amount of heat generated per unit area on the upper side is smaller than that on the lower side. The heat storage product in the upper end area is compensated, and a uniform temperature distribution is obtained.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a heating furnace of a heat treatment apparatus for explaining one embodiment of the present invention, FIG. 2 is an equivalent circuit diagram of a heater in the heating furnace of FIG. 1, and FIG. 4A and 4B are explanatory views showing the configuration of a heater in the heat treatment apparatus of FIG. 3 in more detail, and FIG. 5A is one of the heaters in the heating furnace of FIG. FIG. 5B is an explanatory diagram showing a modified example, FIG. 5B is an equivalent circuit diagram thereof, FIG. 6A is an explanatory diagram showing another modified example of the heater in the heating furnace of FIG. 1, and FIG. 6B is an equivalent circuit diagram thereof. 7 is an explanatory view of a heating furnace for explaining another embodiment of the present invention, FIG. 8 is an explanatory view showing a part of the heating furnace in FIG. 7, and FIG. It is explanatory drawing which shows typically the heater of the division | segmentation type employ | adopted in the conventional heat processing apparatus. 1 ... process tube, 4a ... outer tube 4b ... inner tube, 6, 8, 10, 51 ... heater 10, 18, 22, ... power supply, 24, 26, 28, 30 ... holding frame 32 ... heat insulating material, 36 ... boat 38 … Wafer, 40… insulated tube

Claims (1)

(57) [Claims] A process tube installed substantially vertically and containing an object to be processed, a central heater provided outside the process tube so as to surround an area in the process tube where the object to be processed is arranged, An upper heater provided above the central heater so as to surround an area including an area above the area where the object is arranged, and an area below the area where the object is arranged And a lower heater provided below the central heater so as to surround an area including: the heaters are independently configured, and the upper heater and the lower heater are unitized as compared with the central heater. The heat generation amount per area is configured to be large, and the central heater is configured so that the heat generation amount per unit area on the upper side is smaller than that on the lower side. Vertical heat treatment apparatus.