JPH04298024A - Vertical type semiconductor diffusion furnace - Google Patents

Abstract

PURPOSE:To prevent disperson of a speed of a temperature descent at wafer cooling of a vertical type semiconductor diffusion furnace formed with a wafer inserting inlet in the lower portion of the furnace. CONSTITUTION:A first invention; a partition pipe 3 is inserted between a heating part 2 and a reacting pipe 5. An airtight plate 8 is provided at a lower end of the partition pipe 3 and closes off between a furnace 1 and the reacting pipe 5. The airtight plate 8 is provided with an intake 3a supplying cooling gas between a heating part 2 and the partition pipe 3 and an outlet 3b discharging the cooling gas between the partition pipe 3 and the reacting pipe 5. A second invention; a cooling pipe 20 of the cooling gas is provided outside a furnace 11, and an upper end of this cooling pipe 20 is connected to an upper portion of a reacting pipe 16 and a lower end of the cooling pipe 20 is connected to a lower end of the reacting pipe 16.

Description

[Detailed description of the invention]

[Object of the invention]

0002

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vertical semiconductor diffusion furnace used in semiconductor heat treatment equipment.

0003

2. Description of the Related Art In the manufacturing process of semiconductor wafers (hereinafter referred to as wafers), vertical semiconductor diffusion furnaces have conventionally been used as heat treatment apparatuses for diffusing impurities or forming oxide films on the surfaces of wafers. In this vertical semiconductor diffusion furnace, the wafer is heated to about 1000°C in order to perform the above-mentioned heat treatment for diffusion and film formation, and after a predetermined period of time,
Forced cooling is performed with an allowable temperature gradient to increase throughput. At this time, the cooling temperature of all wafers must be maintained within an extremely small error range in order to prevent lattice defects due to thermal stress.

[0004] Among such vertical semiconductor diffusion furnaces,
There is one shown in FIG. In the figure, a heating part 22 in which a coiled heating wire is housed is inserted into a furnace body 21 having an inverted U-shape in longitudinal section. A reaction tube 25 made of silicon nitride is coaxially inserted, and as a result, a cylindrical gap 24 is formed between the heating section 22 and the reaction tube 25. A boat 6 (details omitted) is inserted into the reaction tube 25, and several dozen wafers 7 are placed on the boat 6 at equal intervals.

On the other hand, in the lower part of the furnace body 21, there is an intake port 21a.
is 90° as shown in Figure 6(a), which shows the A-A cross-sectional view of the same figure
At the upper part of the furnace body 21, exhaust ports 21b are provided at intervals, as shown in FIG. 2(b). Note that the lower end of the reaction tube 25 is closed with an autocap (not shown).
A support rod (not shown) that supports the boat 6 passes through the center of the autocap in an airtight manner.

In the vertical semiconductor diffusion furnace configured as described above, when cooling the wafer 7, cooling gas (for example, N2 gas) sent from a gas supply device (not shown) reacts with the heating section 22 through the inlet 21a. The cooling gas is sent into the cylindrical gap 24 between the pipe 25, ascends through the gap 24, and is discharged from the exhaust port 21b at the upper end.

A vertical semiconductor diffusion furnace as shown in FIG. 7 is also used. In the figure, a heating section 32 (details omitted) and a reaction tube 35 made of quartz are coaxially inserted in order into a furnace body 31 of a vertical semiconductor diffusion furnace 30, and a boat (not shown) is inserted into the reaction tube 35. Several dozen wafers are placed on it. An autocap 33 is provided at the lower end of the reaction tube 35, an intake port 31a is provided at the bottom of the furnace body 31 on the right side in the figure, and an exhaust port 31b is provided on the left side at the top of the furnace body 31. It is provided.

On the other hand, on the installation surface of the vertical semiconductor diffusion furnace 30, there is a temperature controller 36 that continuously changes the power supplied to the heating section 32 to change the amount of heat generated by the heating section 32, and an air intake port of the furnace body 31. A forced air cooling device 37 to which a blow pipe 37a is connected and discharges a constant amount of cooling gas, and a forced air cooling device 37 that instructs the temperature controller 36 to lower the set temperature at a constant rate during cooling, and simultaneously operates the forced air cooling device 37. A main control device 38 for stopping the engine is installed.

In the vertical semiconductor diffusion furnace configured as described above, when cooling the wafer inside the reaction tube 35, N2 gas is supplied as a cooling gas from the forced air cooling device 37 to the furnace from the air intake port 31a through the blast pipe 37a. The cooling gas is sent into the interior of the body 31, rises between the heating section 32 and the reaction tube 35, and is discharged from the exhaust port 31b.

FIG. 8 shows a conventional vertical semiconductor diffusion furnace in which the cooling gas flow path is different from those in FIGS. 5 and 7. In the figure, a reaction tube 45 coaxially inserted into the heating section 32 inside the furnace body 41 is provided with a supply tube 46 bent in a substantially Z-shape on the left side. is connected to an intake port 45a provided at the center of the upper end of the reaction tube 45, and an exhaust pipe 47 is connected to the lower right side of the reaction tube 45.

Even in the vertical semiconductor diffusion furnace configured in this way, the main controller 38 shown in FIG. 8 controls the temperature controller 36 and forced air cooling device 37 shown in the figure to raise, maintain, and lower the temperature. .

0012

However, in the vertical semiconductor diffusion furnace configured as shown in FIGS. 5 and 7, during cooling, the air inlet 21 at the lower end of the furnace body 21,
The cooling gas sent into the interior from the reaction tubes 25 and 31a is warmed inside and rises, and is discharged from the exhaust ports 21b and 31b at the upper ends, so the temperature of the cooling gas at the lower and upper parts of the reaction tubes 25 and 35 is A difference occurs linearly as shown by the straight line 12 in FIG. Then, the lower portions of the furnace bodies 21, 31 are rapidly cooled, while the upper portions of the furnace bodies 21, 31 are gradually cooled. This also applies to the wafers inside the reaction tubes 25 and 35, and as a result, the oxide film of the wafers may vary, leading to the possibility of producing defective products.

Similarly, the furnace bodies 21, 31 and the reaction tubes 25, 3
5, thermal stress occurs in the lower part due to the difference between the lower part that is rapidly cooled and the upper part that is slowly cooled, and this is repeated every time the wafer is cooled.
There is also a risk that the lifespan of the reaction tubes 25 and 35 will be impaired. This is the same for the vertical semiconductor diffusion furnace shown in FIG.
At this time, the upper wafer, the reaction tube 45 and the furnace body 4
Since the upper part of 1 is rapidly cooled, the reaction tube 45 and the furnace body 4
The upper part of 1 is subjected to heat stress. SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a vertical semiconductor diffusion furnace that can uniformly cool wafers and extend the life of the furnace body, reaction tubes, and the like. [Structure of the invention]

[0014]

[Means and effects for solving the problems] One aspect of the present invention is to provide a vertical semiconductor diffusion furnace in which a heating section and a reaction tube are sequentially inserted into a furnace body having an inverted U-shaped longitudinal section. A partition tube is provided in between, and a sealing plate is provided at the lower end of the partition tube to close the space between the lower end of the furnace body and the lower outer periphery of the reaction tube, and cooling gas is supplied to this sealing plate between the furnace body and the partition tube. By providing an exhaust port for discharging cooling gas between the supply port, the partition tube, and the reaction tube, the difference in cooling rate between the upper and lower parts of the furnace body and reaction tube can be reduced, the cooling rate of the wafers can be made uniform, and the furnace body and This is a vertical semiconductor diffusion furnace that reduces thermal stress on the reaction tube and extends its life.

The second aspect of the present invention is a vertical semiconductor diffusion furnace in which a heating section and a reaction tube are sequentially inserted into a furnace body having an inverted U-shaped longitudinal section, and a gas cooling pipe is provided outside the furnace body. By connecting one side of this gas cooling tube to the top of the reaction tube and the other side to the bottom of the reaction tube, the difference in cooling rate between the top and bottom of the furnace body and reaction tube is reduced, and the wafer This is a vertical semiconductor diffusion furnace that has a uniform cooling rate, reduces thermal stress on the furnace body and reaction tube, and extends its life.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the vertical semiconductor diffusion furnace of the present invention will be described below with reference to the drawings. FIG. 1 is a longitudinal sectional view of a vertical semiconductor diffusion furnace according to the first invention, and FIG. 2 is a bottom view of FIG. 1. 1 and 2, a heating part 2 in which a coiled heating wire is housed is inserted into the inside of a furnace body 1, as in the conventional case, and the shaft of the furnace body 1 into which this heating part 2 is inserted is inserted. A reaction tube 5 is inserted into the core, and inside the reaction tube 5, a wafer (not shown) is placed on a boat 7 whose details are omitted.

On the other hand, a cylindrical partition tube 3 made of quartz is inserted between the heating section 2 and the reaction tube 5, and an annular sealing plate 8 is fixed in advance to the lower end of this partition tube 3. The outer periphery of the sealing plate 8 is in airtight contact with the lower end of the inner periphery of the furnace body 1.
The inner periphery of the reaction tube 5 is in airtight contact with the lower outer periphery of the reaction tube 5. As a result, a cylindrical gap 4A is formed between the heating section 2 and the partition tube 3, and a cylindrical gap 4B is formed between the partition tube 3 and the reaction tube 5, respectively.

Further, as shown in FIG. 2, exhaust ports 3b are provided in the sealing plate 8 between the reaction tube 5 and the partition tube 3 at 90° intervals on the front, rear, left and right sides of the figure. 5 and furnace body 1
In the figure, intake holes 3a are provided at 90° intervals at 45° positions between the two, and these intake holes 3a and exhaust ports 3b have an intake pipe and an exhaust pipe (not shown) that supply cooling gas. each connected.

Now, in the vertical semiconductor diffusion furnace configured as described above, the cooling gas supplied into the furnace body 1 from the intake pipe (not shown) through the intake port 3a is distributed between the heating section 2 and the partition pipe 3. It ascends through the cylindrical gap 4A formed between the partition tube 3, reverses itself at the upper end of the partition tube 3, and descends through the gap 4B formed between the partition tube 3 and the reaction tube 5. At this time, the cooling gas is
While going up the outer periphery of the partition pipe 3, it is gradually cooled down, as shown by the straight line 13 in FIG. The air is cooled down to a temperature of 100.degree. C., and is discharged from an exhaust pipe (not shown) through an exhaust port 3b.

As a result, in the vertical semiconductor diffusion furnace configured in this way, the furnace body is The temperature difference between the upper and lower parts of the furnace body 1 and the reaction tube 5 can be reduced to about half, and the partition pipe 5 can make the upper and lower temperatures almost equal, so the temperature difference between the upper and lower parts of the furnace body 1 and the reaction tube 5 can be reduced. can be reduced. Therefore, not only can thermal stress caused by partial rapid cooling of the furnace body 1 and reaction tube 5 be prevented, but also variations in processing conditions depending on the wafer insertion position can be reduced, and the vertical semiconductor structure has a small temperature gradient and a high cooling effect. It becomes a diffusion furnace.

Next, FIG. 3 shows a vertical sectional view of a vertical semiconductor diffusion furnace according to the second invention. In the figure, on the inner periphery of the furnace body 11 of the vertical semiconductor diffusion furnace 10, there is a heating section 12 (details omitted).
is inserted, a reaction tube 11 is inserted inside this heating section 12, and an autocap 11 is inserted at the lower end of this reaction tube 11.
A is attached.

[0022] On the right side of the furnace body 11, there is an exhaust port 11 at the top.
A is provided with an intake port 11b at the bottom, and these exhaust ports 1
1a, the left ends of L-shaped tubular heat insulation pipes 17A, 17B are connected to the intake port 11b, and these heat insulation pipes 17
A cylindrical heat insulating pipe 19 is connected between the right ends of A and 17B. On the right side of this heat-insulating pipe 19, a small-diameter heat-insulating pipe 19a is provided at the upper part and an intake port 19b is provided at the lower part, and a stop valve 19c is connected to the middle of the heat-insulating pipe 19a. It is connected to the valve control device 9.

On the other hand, on the left side of the reaction tube 16, a gas supply tube 13 bent into an approximately Z-shape is arranged, and the upper end of this gas supply tube 13 is connected to the inlet at the center of the upper end of the reaction tube 16. has been done. Further, at the upper right end of the reaction tube 16, there is an inverted L-shaped conduit 18A that hermetically passes through the exhaust port 11a of the furnace body 11.
Connected to the lower right side of the reaction tube 16 are inverted L-shaped conduits 18B that also airtightly pass through the inlet port 11b of the furnace body 11, and between the right ends of these conduits 18A and 18B is a cylindrical tube with a slightly larger diameter. A cold/heat pipe 20 is connected, and this cold/heat pipe 20
A heat dissipation fin is provided on the outer periphery. Furthermore, the left end of a gas exhaust pipe 14A is connected to the right side of the lower end of the reaction tube 16, and the right end of this gas exhaust pipe 14A is connected to a separate building side exhaust device 15, and the right end of the heat insulating pipe 19a and the building side exhaust are connected. A gas exhaust pipe 14B is also connected to the device 15.

Now, in the vertical semiconductor diffusion furnace configured as described above, when cooling the wafer inside the reaction tube 16, first, the output to the heating section 12 is lowered for a predetermined period of time, and then stopped. Next, while supplying an inert gas (for example, N2 gas) from the gas supply pipe 13 into the reaction tube 16, the stop valve 19c is opened.

Then, the cooling pipe 20 is cooled by the cooling air taken in from the intake port 19b, and the inert gas inside the cooling pipe 20 is rapidly cooled, so that it reacts with the cooling pipe 20 and the conduits 18A and 18B. The flow rate of the inert gas inside the circulation path constituted by the tube 16 increases, and the inside of the reaction tube 16 is rapidly and uniformly cooled.

Next, when taking out the wafer from the reaction tube 16, first close the stop valve 19c and remove the wafer from the reaction tube 16.
After suppressing the flow of inert gas inside, the auto cap 11a is opened and the boat (not shown) is taken out.

In the vertical semiconductor diffusion furnace configured as described above, the inert gas cooled by the cooling tube 20 is refluxed to the lower part of the reaction tube 16, and part of the inert gas warmed in the lower part of the reaction tube 16 is refluxed to the lower part of the reaction tube 16. of the reaction tube 16 flows into the cooling tube 20 from the upper part of the reaction tube 16. As a result, a flow of activated gas inside the reaction tube 16 was caused to flow backwards from bottom to top with respect to the vertical flow supplied from the gas supply tube 13. The difference in temperature between the top and bottom can be reduced, and the difference in temperature between the top and bottom of the furnace body 11 can also be reduced. Therefore, the wafer cooling time is shortened, the variation in cooling temperature depending on the wafer position is reduced, and the furnace body 11
It is also possible to reduce thermal stress on the reaction tube 16.

[0028]

As described above, according to the first invention, in a vertical semiconductor diffusion furnace in which a heating section and a reaction tube are sequentially inserted into a furnace body having an inverted U-shaped longitudinal section, there is a space between the heating section and the reaction tube. A partition tube is provided, and a sealing plate is provided at the lower end of the partition tube to close the space between the lower end of the furnace body and the lower outer circumference of the reaction tube, and this sealing plate has a supply port and a supply port for supplying cooling gas between the furnace body and the partition tube. By providing an outlet for discharging the cooling gas between the partition tube and the reaction tube, the difference in cooling rate between the upper and lower parts of the furnace body and reaction tube is reduced, the wafer cooling rate is made uniform, and the temperature of the furnace body and reaction tube is reduced. A vertical semiconductor diffusion furnace that can reduce thermal stress and extend its life can be obtained.

According to the second invention, in a vertical semiconductor diffusion furnace in which a heating section and a reaction tube are sequentially inserted into a furnace body having an inverted U-shaped longitudinal section, a gas cooling pipe is provided outside the furnace body. One side of this gas cooling tube is connected to the upper part of the reaction tube, and the other side is connected to the lower part of the reaction tube, reducing the difference in cooling rate between the upper and lower parts of the furnace body and reaction tube, and improving the cooling rate of the wafer. It is possible to obtain a vertical semiconductor diffusion furnace that can uniformize the cooling rate, reduce thermal stress on the furnace body and reaction tube, and extend its life.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view showing an embodiment of a vertical semiconductor diffusion furnace of a first invention.

FIG. 2 is a bottom view of FIG. 1.

FIG. 3 is a longitudinal sectional view showing an embodiment of a vertical semiconductor diffusion furnace according to the second invention.

FIG. 4 is a diagram showing the operation of the vertical semiconductor diffusion furnace of the first invention.

FIG. 5 is a longitudinal sectional view showing an example of a conventional vertical semiconductor diffusion furnace.

[Fig. 6] Fig. 6(a) is a sectional view taken along line A-A in Fig. 5, and Fig. 6(b)
is a sectional view taken along line B-B in FIG.

FIG. 7 is a vertical cross-sectional view showing a conventional vertical semiconductor diffusion furnace different from FIG. 5;

FIG. 8 is a vertical cross-sectional view showing a conventional vertical semiconductor diffusion furnace different from FIGS. 5 and 7. FIG.

FIG. 9 is a graph showing the operation of a conventional vertical semiconductor diffusion furnace.

[Explanation of symbols]

1, 11... Furnace body, 2, 12... Heating section, 3... Partition tube, 5,
16... Reaction tube, 6... Boat, 8... Sealing plate, 18A, 18
B...Conduit, 20...Cooling tube.

Claims (2)

[Claims] 1. A vertical semiconductor diffusion furnace in which a heating section and a reaction tube are sequentially inserted into a furnace body having an inverted U-shape in longitudinal section, wherein a partition tube is provided between the heating section and the reaction tube, and the partition tube A sealing plate is provided at the lower end of the furnace body to close the space between the lower end of the furnace body and the lower outer periphery of the reaction tube. A vertical semiconductor diffusion furnace characterized in that an exhaust port is provided for discharging the cooling gas between the reaction tubes. 2. A vertical semiconductor diffusion furnace in which a heating section and a reaction tube are sequentially inserted into a furnace body having an inverted U-shaped vertical cross section, a gas cooling pipe is provided outside the furnace body, and one side of the gas cooling pipe is provided. A vertical semiconductor diffusion furnace characterized in that a gas cooling tube is connected to an upper part of the reaction tube, and the other side of the gas cooling tube is connected to a lower part of the reaction tube.