JPH0613336A - Vertical furnace - Google Patents

Abstract

PURPOSE:To prevent a semiconductor wafer in a vertical furnace from being polluted by entraining less air in the furnace for making thinner a natural oxide film generated by air entrainment and by adopting a heater and a vertically movable mechanism. CONSTITUTION:Vertical furnace of this invention consists of an outer pipe 1, a heater 4 outside the outer pipe 1, an inner tube 6 that can get in and out of the outer pipe 1 with a wafer loading boat 12 housed therein, and a vertically movable mechanism 15 that is installed outside the outer pipe 1 and that can vertically move either the inner pipe 6 alone or together with the wafer loading boat 12.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vertical furnace, and more particularly to a vertical furnace mainly used as a diffusion furnace.

[0002]

2. Description of the Related Art FIG. 3 is a sectional view showing one of conventional examples of a vertical diffusion furnace. In the figure, a is a vertical core tube made of quartz, and a heater b is provided outside the upper half of the tube. c is a process gas inlet formed at a substantially central portion in the vertical direction of the core tube a, d is a process gas exhaust port formed at the center of the head of the core tube a, and e is formed at the lower end of the core tube a. In addition, an inert gas inlet port and f is an inert gas exhaust port.

Reference numeral g denotes a wafer loading boat, h, h, ... Are semiconductor wafers loaded on the wafer loading boat g, and i is a vertical movement mechanism for vertically moving the wafer loading boat g. The conventional vertical diffusion furnace shown in FIG. 3 has a core tube a having a height about twice the height of the wafer board boat g, and the wafer board boat g is located in the lower half of the furnace tube tube a. Then, nitrogen gas N ₂ which is an inert gas is introduced from the inert gas introduction port e to make the inside of the core tube a an inert gas atmosphere and prevent the air from being entrained by the vertical movement mechanism i. The loading boat g is moved upward and positioned in the upper half of the core tube a.

Process gas is supplied from the process gas inlet c to the upper half of the core tube a to diffuse it. Then, when the diffusion is completed, the wafer loading boat g is lowered by the vertical movement mechanism i, the semiconductor wafers h, h, ... Are taken out from the wafer loading boat g in the lower half of the core tube a, and new semiconductor wafers h, h are obtained. , ... Are put in the wafer mounting boat g. That is, the wafers h, h, ... Are exchanged.
Such a vertical diffusion furnace has an advantage that less air is entrained than a horizontal diffusion furnace and the thickness of the natural oxide film is reduced due to the entrainment of air. The reason is that the hotter the gas is, the higher the gas goes, and the lower the temperature of the gas, the more difficult it is to enter the upper part of the vertical diffusion furnace. This is because air from the outside is unlikely to enter the wafer loading boat g that is being diffused.

[0005]

However, the vertical diffusion furnace has less air entrainment than the horizontal diffusion furnace,
Although it has the advantage of reducing the thickness of the natural oxide film due to the entrainment of air, it is inevitable to entrain air even though it is a small amount when loading and unloading the wafer loading boat. It is difficult to completely purge the oxygen gas O ₂ that has entered with the inert gas N ₂ . Therefore, it is difficult to completely prevent the formation of the natural oxide film. Further, the height of the core tube a is as high as about twice the height of the wafer mounting boat g, and the internal volume of the core tube a is extremely wide. Therefore, the amount of the inert gas used for purging the oxygen gas O ₂ is inevitably increased, which causes an increase in manufacturing cost. Then, there is a problem that the inside of the core tube a is contaminated by the heater b, and further, the vertical moving mechanism i in the core tube a can also contaminate it.

The present invention has been made to solve the above problems, and in a vertical furnace, the entrainment of air is reduced to reduce the thickness of the natural oxide film generated by entrainment of air, and a heater is used. , The vertical movement mechanism is intended to prevent the semiconductor wafer in the furnace from being contaminated.

[0007]

A vertical furnace according to a first aspect of the present invention comprises an outer tube, a heater outside the outer tube, and an inner tube that goes in and out of the outer tube. The vertical furnace according to claim 2 is characterized in that a pollution preventing gas for preventing pollution from the outside of the outer tube flows between the outer tube and the inner tube. A vertical furnace according to a third aspect of the present invention is provided with a vertical movement mechanism capable of vertically moving the inner tube and the wafer mounting boat integrally, or vertically moving only the inner tube.

The vertical furnace according to claim 4 is characterized in that the vertical movement mechanism is provided outside the outer tube. The vertical furnace according to claim 5,
A vertically movable arm that can be moved in the vertical direction, an inner tube support portion that is attached to the vertically movable arm and supports an inner tube, and a state that is slidably attached to the inner tube support portion and supports a wafer-loaded boat. And a wafer-carrying boat support that is in a non-supported state, and a vertical movement mechanism.

[0009]

According to the vertical furnace of the first aspect, the wafer loading boat can be placed in the outer tube while being accommodated in the inner tube for heat treatment such as diffusion, and the wafer loading boat is loaded into the outer tube. It is possible to eliminate air entrapment during unloading. The outer tube and the inner tube are interposed between the semiconductor wafer and the heater in the wafer mounting boat during the heat treatment such as diffusion, and the semiconductor wafer is less likely to be contaminated by the heater. According to the vertical furnace of the second aspect, since the pollution preventing gas is supplied between the outer tube and the inner tube, it is possible to more effectively prevent the contaminants from the heater from entering the inner tube side.

According to the vertical furnace of claim 3, by vertically moving the inner tube and the wafer mounting boat integrally, loading and unloading can be performed while the semiconductor wafer in the wafer mounting boat is protected by the inner tube. It is possible to reduce entrapment of air at the time of loading and unloading. Then, the wafer loading boat can be taken out from the inner pipe or inserted into the inner pipe by moving the inner pipe in the state where the wafer loading boat is stored and unloaded from the outer pipe in the upward direction.

According to the vertical furnace of the fourth aspect, the vertical movement mechanism can prevent the semiconductor wafer in the wafer loading boat from being contaminated. According to the vertical furnace of claim 5,
By moving the wafer mounting boat support part attached to the inner pipe supporting part of the vertical movement mechanism to support the wafer mounting boat and moving the inner pipe up and down by the vertical movement mechanism with the wafer mounting boat accommodated therein, The wafer loading boat can be loaded and unloaded from the outer tube while being protected by.
Then, it is possible to load and unload the wafer mounting boat into the inner pipe by moving the inner pipe supporting portion upward with the wafer mounting boat supporting part not supporting the wafer mounting boat. .

[0012]

The vertical furnace of the present invention will be described in detail below with reference to the illustrated embodiments. FIG. 1 is a sectional view showing one embodiment of the vertical furnace of the present invention. In the drawings, reference numeral 1 denotes an outer tube, which is appropriately higher than a wafer loading boat described later, but is not twice as high as a wafer loading boat as in a conventional vertical furnace. 2 is a pollution prevention gas inlet provided in the lower part of the outer tube 1,
HCl which is a pollution prevention gas from the pollution prevention gas inlet 2
Gas or N ₂ gas is supplied. The HCl gas reacts with the metal impurities from the heater, which will be described later, to prevent the metal impurities from entering the inner tube, which will be described later. N ₂
When a gas is used, the gas serves as a carrier that carries metal impurities to the outside and discharges them.

Reference numeral 3 denotes a pollution prevention gas exhaust port formed in the center of the head of the outer tube 1, through which the pollution prevention gas is exhausted.
Reference numeral 4 is a heater provided outside the outer tube 1, and 5 is a tube made of SiC. Reference numeral 6 denotes an inner pipe that can enter and exit the outer pipe 1 from below, and has a double structure in which a partition wall 7 is provided on the inner peripheral side and a gas entrance cavity 8 is formed between the partition wall 7 and the outer wall of the inner pipe. Has become.

A gas inlet 9 is formed in the lower portion of the outer tube 1 and communicates with the gas entrance cavity 8. A gas inlet 10 communicates the gas entrance cavity 8 and the inside of the inner tube 6 at the center of the head of the inner tube 6. The formed gas inlet port 11 is a gas exhaust port formed in the lower portion of the outer pipe 1, and exhausts gas from the inside of the inner pipe 6 to the outside of the inner pipe 6. As described above, the process gas is supplied from the lower portion of the inner pipe 6 through the gas entrance cavity 8 in the upward direction to the inside of the inner pipe 6 in order to sufficiently heat the process gas before entering the inside of the inner pipe 6. is there. 12 is a semiconductor wafer 13, 1
A wafer support boat that mounts 3, ...
Supported by 4.

Reference numeral 15 denotes a vertical movement mechanism, which is provided below the outer tube 1 and outside thereof, and has a screw spindle 16 provided in the vertical direction and a female screw 1 at the base of the vertical movement arm 17.
8 is screwed together. Reference numeral 19 denotes an inner pipe support portion of the vertical movement arm 17, and the inner pipe 6 is supported by the vertical movement arm 17 at the inner pipe support portion 19. Reference numeral 20 denotes a boat support body slidably provided on the inner pipe support portion 19, which supports the boat support portion 14. However, by sliding the boat support portion 14, the boat support portion 14 is supported or not supported. It is possible to put it in a state. In the state shown in FIG. 1, the boat support 20 is in a state of supporting the boat support portion 14.

Next, a method of using the vertical furnace shown in FIG. 1 will be described. First, the wafer mounting boat 12 is released from the inner pipe 6 by moving only the inner pipe 6 upward by the vertical movement mechanism 15 with the boat support 20 of the vertical movement mechanism 15 not supporting the boat support portion 14. . Then, the semiconductor wafers 13, 13, ... Are put in and taken out of the wafer loading boat 12 in the opened state. That is, the semiconductor wafers 13, 13, ...
, 3, ... Are put in the wafer loading boat 12.

Then, the inner tube 6 that has been raised is lowered by the vertical movement mechanism 15 so that the wafer loading boat 12 is completely covered by the inner tube 6, and the boat support 20 is slid. Wafer loading boat 1
The boat supporting portion 14 supporting 2 is brought into a state of supporting.
By supplying the inert gas N ₂ from the gas introduction port 9 of the inner pipe 6 under the state where the wafer mounting boat 12 is completely covered with the inner pipe 6, the inside of the inner pipe 6 containing the wafer mounting boat 12 is The air is replaced with an inert gas N ₂ .

When the gas replacement is completed, the inner tube 6 and the wafer mounting boat 12 are integrally lifted by the vertical movement mechanism 15 and inserted into the outer tube 1. When the inner tube 6 and the wafer mounting boat 12 are integrally housed in the outer tube 1,
A process gas is supplied from the gas inlet 9 into the inner pipe 6 to perform heat treatment such as diffusion. During the time of this treatment, a pollution prevention gas, for example, HCl or an inert gas, which is introduced into the cavity between the outer pipe 1 and the inner pipe 6 from the gas introduction port 2 of the outer pipe 1 and is exhausted from the gas exhaust port. N ₂ is flowing.
Therefore, it is possible to prevent metal impurities from the heater 4 from passing through the outer tube 1 and entering the inner tube 6 to contaminate the surface of the semiconductor wafer 13.

When the heat treatment such as diffusion is completed, the vertical movement mechanism 15
The inner tube 6 and the wafer mounting boat 12 are integrally lowered by the above, and the gas supplied from the gas introduction port 9 of the inner tube 6 is switched from the process gas to the inert gas N ₂ to make the inside of the inner tube 6 an inert gas atmosphere. To do.

When the inner pipe 6 and the wafer mounting boat 12 are completely lowered, the boat support 20 is slid to slide the boat support 1
4 is not supported. In this state, the vertical movement mechanism 15
Only the inner pipe 6 is lifted by the wafer loading boat 12
, And the processed semiconductor wafers 13, 13, ... Are taken out from the wafer mounting boat 12, and new semiconductor wafers 13, 13 ,.

According to the vertical furnace shown in FIG. 1, firstly, the wafer loading boat 12 is placed in the outer tube 1 while the atmosphere inside the inner loading tube 6 containing many wafer loading boats 12 is made to be an inert gas. On the other hand, it is possible to perform loading and unloading, to prevent entrapment of air during loading and unloading, and thus to prevent generation of a natural oxide film. Secondly, the inner tube 6 only needs to have a volume capable of accommodating the wafer mounting boat 12, and the amount of the inert gas required for replacement for preventing the insertion of air may be smaller than in the conventional case. Therefore, the cost can be reduced. Thirdly, the wafer loading boat 1 during the heat treatment such as diffusion.
.. and the heater 4 inside the semiconductor wafer 13, the outer tube 1 and the inner tube 6 are interposed, and a pollution preventing gas is passed between the outer tube 1 and the inner tube 6, so that the semiconductor wafer 13 , 13,
... can be prevented from being contaminated by metallic impurities from the heater 4.

Fourth, the vertical movement mechanism 15 includes the inner pipe 6 and the outer pipe 1.
Since it is located outside the semiconductor wafer, it is possible to prevent the semiconductor wafers 13, 13, ... FIG. 2 is a sectional view showing a modified example 1a of the outer tube of the vertical furnace of the present invention. As shown in FIG. 2, the outer tube 1a may have a double structure to allow the pollution prevention gas to pass through the inside 21 thereof.

[0023]

The vertical furnace according to the first aspect of the present invention comprises an outer tube, a heater outside the outer tube, and an inner tube that goes in and out of the outer tube. Therefore, according to the vertical furnace of claim 1, the wafer-mounted boat can be placed in the outer tube while being accommodated in the inner tube and subjected to heat treatment such as diffusion. When the wafer-mounted boat is loaded into the outer tube, Air entrapment during unloading can be eliminated. The outer tube and the inner tube are interposed between the semiconductor wafer and the heater in the wafer mounting boat during the heat treatment such as diffusion, and the semiconductor wafer is less likely to be contaminated by the heater.

The vertical furnace according to claim 2 is characterized in that a pollution preventing gas for preventing pollution from outside the outer pipe flows between the outer pipe and the inner pipe. Therefore, according to the vertical furnace of claim 2, since the pollution preventing gas is supplied between the outer tube and the inner tube, it is possible to more effectively prevent the contaminants from the heater from entering the inner tube side. it can.

The vertical furnace according to claim 3 is characterized in that it is provided with a vertical movement mechanism capable of vertically moving the inner tube and the wafer-mounting boat as a unit or moving only the inner tube up and down. Is. Therefore, according to the vertical furnace of claim 3, by vertically moving the inner tube and the wafer mounting boat integrally, loading and unloading can be performed while the semiconductor wafer in the wafer mounting boat is protected by the inner tube, Air entrainment during loading and unloading can be reduced. Then, the wafer loading boat is accommodated and the wafer loading boat is unloaded from the outer pipe and is moved upward so that the wafer loading boat can be taken out from the inner pipe and the wafer loading boat can be put into the inner pipe. You can

The vertical furnace according to claim 4 is characterized in that the vertical movement mechanism is provided outside the outer tube. Therefore, according to the vertical furnace of the fourth aspect, the vertical movement mechanism can prevent the semiconductor wafer in the wafer loading boat from being contaminated. The vertical furnace according to claim 5 comprises a vertically movable arm that is vertically movable, an inner pipe support portion that is attached to the vertically movable arm and supports an inner pipe, and is slidably attached to the inner pipe support portion. It is characterized in that the up-and-down movement mechanism has a wafer-loaded boat support that is in a state of supporting the wafer-loaded boat or in a state of not supporting it.

Therefore, according to the vertical furnace of the fifth aspect, the wafer loading boat supporting portion attached to the inner pipe supporting portion is brought into a state of supporting the wafer loading boat so that the wafer loading boat is accommodated in the inner tube. By moving up and down with
The wafer loading boat can be loaded and unloaded from the outer tube while being protected by the inner tube. Then, the wafer mounting boat can be loaded into or unloaded from the inner pipe by moving the inner pipe supporting part up and down with the wafer mounting boat supporting part not supporting the wafer mounting boat.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of a vertical furnace of the present invention.

FIG. 2 is a cross-sectional view showing a modified example of the outer tube of the vertical furnace of the present invention.

FIG. 3 is a cross-sectional view showing a conventional example of a vertical furnace.

[Explanation of symbols]

 1 Outer Pipe 2 Pollution Prevention Gas Inlet 3 Pollution Prevention Gas Exhaust 4 Heater 6 Inner Pipe 9 Gas Inlet 11 Gas Exhaust 12 Wafer Loading Boat 13 Semiconductor Wafer 15 Vertical Movement Mechanism 17 Vertical Movement Arm 19 Inner Pipe Support 20 Boat Support

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[Procedure amendment]

[Submission date] December 29, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] 0002

[Correction method] Change

[Correction content]

[0002]

2. Description of the Related Art FIG. 3 is a sectional view showing one of conventional examples of a vertical diffusion furnace. In the figure, a is a vertical core tube made of quartz, and a heater b is provided outside the upper half of the tube. In addition, a soaking tube 1 made of SiC or the like is provided inside thereof.
Is provided. c is a process gas inlet formed substantially in the center of the core tube a in the vertical direction, and d is the core tube a.
Is a process gas exhaust port formed at 1, e is an inert gas inlet formed at the lower end of the core tube a, and f is an inert gas exhaust port. g is a quartz glass for sealing the core tube a.
It is a chatter.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Name of item to be corrected] 0003

[Correction method] Change

[Correction content]

H is a wafer loading boat, i , i , ... Are semiconductor wafers loaded on the wafer loading boat h , and j is a vertical movement mechanism for moving the wafer loading boat h up and down. The conventional vertical diffusion furnace shown in FIG. 3 has a purge box for the core tube a.
The wafer mounting boat h is positioned in the space k , and nitrogen gas N ₂ which is an inert gas is introduced from the inert gas inlet port e to make the inside of the furnace core tube a an inert gas atmosphere so that air is entrained. The quartz shutter g is opened in the prevented state, and the wafer loading boat h is moved upward by the vertical movement mechanism j to be positioned in the upper half of the reactor core a.

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0004

[Correction method] Change

[Correction content]

Process gas is supplied from the process gas inlet c to the upper half of the core tube a to diffuse it. Then, when the diffusion is completed, the wafer loading boat h is lowered by the vertical movement mechanism j , the semiconductor wafers i 1 , i , ... Are taken out from the wafer loading boat h in the lower half of the core tube a, and new semiconductor wafers i 1 , i , ... are put into the wafer mounting boat h . That is, the wafers i 1 , i 2 , ... Are exchanged.
Such a vertical diffusion furnace has an advantage that less air is entrained than a horizontal diffusion furnace and the thickness of the natural oxide film is reduced due to the entrainment of air. The reason is that the hotter the gas is, the higher the gas goes, and the lower the temperature of the gas, the more difficult it is to enter the upper part of the vertical diffusion furnace. This is because air from the outside is unlikely to enter the wafer loading boat h that is being diffused.

[Procedure amendment 4]

[Document name to be amended] Statement

[Name of item to be corrected] 0005

[Correction method] Change

[Correction content]

[0005]

However, the vertical diffusion furnace has less air entrainment than the horizontal diffusion furnace,
Although it has the advantage of reducing the thickness of the natural oxide film due to the entrainment of air, it is inevitable to entrain air even though it is a small amount when loading and unloading the wafer loading boat. It is difficult to completely purge the oxygen gas O ₂ that has entered with the inert gas N ₂ . Therefore, it is difficult to completely prevent the formation of the natural oxide film. In addition, path
The volume of the storage box k is about twice the volume of the core tube a.
There, very large, the amount of inert gas required for purging of the oxygen gas O ₂ is also inevitably increased, which is a factor of increase manufacturing cost. Then, there is a problem that the core pipe a is contaminated by the heater b, furthermore, the purge
It can also be contaminated by the vertical movement mechanism j in the box k .

[Procedure Amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0012

[Correction method] Change

[Correction content]

[0012]

The vertical furnace of the present invention will be described in detail below with reference to the illustrated embodiments. FIG. 1 is a sectional view showing one embodiment of the vertical furnace of the present invention. In the drawing, 1 is an outer tube, which is appropriately higher than a wafer-loaded boat described later. Reference numeral 2 denotes a pollution prevention gas inlet provided at a lower portion of the outer pipe 1, and HCl gas or N which is a pollution prevention gas is introduced from the pollution prevention gas inlet 2.
₂ Gas is supplied. The HCl gas reacts with the metal impurities from the heater, which will be described later, to prevent the metal impurities from entering the inner tube, which will be described later. When N ₂ gas is used, this gas plays the role of a carrier for carrying and discharging metal impurities to the outside.

[Procedure correction 6]

[Document name to be amended] Statement

[Correction target item name] 0013

[Correction method] Change

[Correction content]

Reference numeral 3 denotes a pollution prevention gas exhaust port formed in the center of the head of the outer tube 1, through which the pollution prevention gas is exhausted.
Reference numeral 4 is a heater provided outside the outer tube 1, and 5 is a soaking tube made of SiC or the like . Reference numeral 6 denotes an inner pipe that can enter and exit the outer pipe 1 from below, and has a double structure in which a partition wall 7 is provided on the inner peripheral side and a gas entrance cavity 8 is formed between the partition wall 7 and the outer wall of the inner pipe. Has become.

[Procedure Amendment 7]

[Document name to be amended] Statement

[Name of item to be corrected] 0025

[Correction method] Change

[Correction content]

The vertical furnace according to claim 3 is characterized in that it is provided with a vertical movement mechanism capable of vertically moving the inner tube and the wafer-mounting boat as a unit or moving only the inner tube up and down. Is. Therefore, according to the vertical furnace of claim 3, by vertically moving the inner tube and the wafer mounting boat integrally, loading and unloading can be performed while the semiconductor wafer in the wafer mounting boat is protected by the inner tube, Air entrainment during loading and unloading can be reduced. Also,
It is possible to prevent contamination from the vertical movement mechanism. Then, the wafer loading boat is accommodated and the wafer loading boat is unloaded from the outer pipe and is moved upward so that the wafer loading boat can be taken out from the inner pipe and the wafer loading boat can be put into the inner pipe. You can

[Procedure Amendment 8]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 3

[Correction method] Change

[Correction content]

[Figure 3]

Claims (5)

[Claims] 1. An outer tube, a heater provided on the outer side of the outer tube, and an inner tube adapted to be able to move in and out of the outer tube with a wafer-loaded boat accommodated therein. Vertical furnace 2. The vertical furnace according to claim 1, wherein a pollution preventing gas for preventing contamination from the outside of the outer tube flows between the outer tube and the inner tube. 3. A vertical movement mechanism according to claim 1, further comprising a vertical movement mechanism capable of vertically moving the inner pipe and the wafer-mounting boat as a unit, or vertically moving only the inner pipe. Type furnace 4. The vertical furnace according to claim 3, wherein the vertical movement mechanism is provided outside the outer tube. 5. A vertically movable arm that is vertically movable, an inner pipe support portion that is attached to the vertically movable arm and supports an inner pipe, and a wafer loading boat that is slidably attached to the inner pipe support portion. 5. The vertical furnace according to claim 3, wherein the vertical movement mechanism has a wafer-carrying boat support that can be supported or unsupported.