JP2000150526A - Heat treatment furnace of wafer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To allow an atmosphere gas to uniformly flow from upper to lower parts inside a reaction tube without generating convection in up and down directions, and to prevent a wafer from being contaminated when the wafer is heat-treated. SOLUTION: In the heat treatment oven where the supply and exhaust vents of an atmosphere gas are provided at the upper and lower parts respectively, of a reaction tube being heated by a heat source, a wafer to be heated is placed on a boat 8 for loading into the reaction tube, and heat treatment is made, the shape of the exhaust vent provided at the lower part of the reaction tube is in a long slit extended in a circumference direction, a back chamber 5 is provided at the outside, and one exhaust vent 6 with a larger opening area than the total area of the above slit opening part is provided in the back chamber 5. In this case, the slit-shaped exhaust vent of the reaction tube may be installed at two places or more in the circumference direction at even intervals.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat treatment furnace in which a wafer made of a semiconductor material such as silicon is heat-treated at a high temperature in an atmosphere gas and the surface thereof is modified to obtain a high-quality wafer. .

[0002]

2. Description of the Related Art Conventionally, an exhaust port of an atmosphere gas of a heat treatment furnace of this kind is provided with a water-cooled stainless steel tube connected to a lower portion of a quartz glass reaction tube so as to extend the reaction tube as disclosed in Japanese Patent No. 2724649. A plurality of openings having a circular cross section were provided on the cylindrical wall surface.

[0003]

In the above conventional heat treatment furnace, the atmosphere gas is supplied from the upper part of the reaction tube during the heat treatment, but generates a convection in the vertical direction inside the reaction tube.
The atmospheric gas comes into contact with a reaction tube, a wafer, a boat supporting the wafer, and the like, and vaporizes impurities and mixes them into the flow. Also, when a stable vortex is generated in the reaction tube, the atmospheric gas containing impurities stays in the reaction tube for a long time, thereby contaminating the wafer and deteriorating the quality.

The present invention recognizes that the cause is that the flow rate of the atmospheric gas is large and uneven in the circumferential direction in the reaction tube because the exhaust port has one or two circular cross-sections. It is intended to improve this. Further, by optimizing the diameter or shape of the cover member at the upper end of the boat on which the wafer is mounted and the diameter of the lower end of the boat in relation to the wafer diameter, the atmospheric gas flowing through the reaction tube passes through the portion. The purpose of the present invention is to prevent eddy currents from being generated when the turbulence occurs.

[0005]

In order to achieve the above object, a heat treatment furnace according to a first aspect of the present invention mounts a cylindrical reaction tube whose longitudinal direction is up and down, and a wafer to be heat treated. It is connected to a boat that is placed inside the reaction tube, a heat source arranged around the reaction tube that gives thermal energy into the reaction tube, and an upper center of the reaction tube that supplies an atmosphere gas for wafer heat treatment into the reaction tube. Supports a gas supply pipe, a circumferentially continuous single slit opened at the bottom of the reaction tube for discharging the atmospheric gas, and the outer wall of the reaction tube located above the slit, and temporarily collects the atmospheric gas discharged from the slit. A back chamber provided to surround the slit, and an exhaust pipe connected to the back chamber for exhausting atmospheric gas from the back chamber to the outside.

[0006] The flow rate of the atmospheric gas inside the reaction tube is
There is a method of uniformly arranging a plurality of exhaust ports in the circumferential direction as in the above-mentioned reference in order to make the openings uniform in the circumferential direction. in this case,
For the following reasons, the effect is small when there are two exhaust ports.
As the wafer diameter increases, the diameter of the reaction tube must be increased, but the exhaust port and the exhaust pipe diameter cannot be increased.Therefore, the ratio of the exhaust port to the inner circumference of the reaction tube decreases, and the uniformity of the flow velocity also decreases. Because you do. The reason why the diameter of the exhaust port and the exhaust pipe cannot be increased is that if the diameter is increased, the outer shape of the heat treatment furnace apparatus is increased in the vertical direction of the reaction tube. This is because the wafer must be loaded at a position higher than the upper end of the exhaust port. In addition, connecting two or more large-diameter and multiple exhaust pipes to the lower part of the reaction tube requires a large space and complicated construction, which also increases the size of the heat treatment furnace and increases the cost. Becomes The first invention is to solve the above-mentioned disadvantage by providing a slit-shaped opening which is continuous in the circumferential direction. With the slit-shaped opening, it is not necessary to enlarge the outer shape of the apparatus in the vertical direction of the reaction tube. However, in order to obtain a uniform exhaust volume at each portion of the slit, the pressure difference before and after the slit must be constant regardless of the location. Therefore, it is necessary to provide a back chamber so that the pressure behind the slit is constant in the back chamber. Further, it is necessary that the cross-sectional area of the discharge port for exhausting the back chamber be larger than the total value of the slit opening areas. As a result, the internal pressure of the back chamber drops below the internal pressure of the reaction tube, and a uniform pressure difference can be generated before and after the slit regardless of the position of the slit. Further, by providing the back chamber, the load applied to the upper and lower portions of the slit can be supported thereby. For this reason, one continuous slit can be formed all around the inner surface of the lower part of the reaction tube. Thereby, a uniform flow velocity can be obtained in the circumferential direction of the reaction tube. In the second invention, since a plurality of slits are provided at equal intervals in the circumferential direction,
The upper and lower connecting portions of the slit remain, and can share and support the load applied to the upper and lower portions of the slit with the back chamber. Therefore, the mechanical strength can be made larger than that of the first invention. In addition, even if the shape of the opening is not a slit, the same effect as in the first aspect can be obtained as long as the back chamber is provided and the total area of the openings is smaller than the area of the outlet passage. For example, it is also possible to arrange a large number of circular openings at a uniform density in the circumferential direction. With this configuration, a uniform flow velocity in the circumferential direction can be obtained even with one exhaust pipe.

[0007] As the diameter of the lower end of the boat becomes larger than the diameter of the wafer, the flow of the atmospheric gas that has descended in the space between the inner wall surface of the reaction tube and the peripheral portion of the wafer is narrowed in the flow path and accompanied by a vortex. become. If this vortex exists stably, the atmospheric gas will stay and the impurity concentration will increase,
Wafer contamination occurs. To prevent this, the diameter of the lower end of the boat needs to be equal to or less than the arithmetic mean value of the inner diameter of the reaction tube and the diameter of the wafer as in the third invention so that the flow path area does not suddenly change here. Most preferably, it is the same diameter as the wafer, but it is difficult due to the structure of the boat. Normally, the boat supports the peripheral portion of the wafer with a rod with a slit, so that the maximum diameter of the rod is larger than the diameter of the wafer.

In order to make the atmosphere gas flow at a uniform flow rate in the inner circumferential direction of the reaction tube, the flow area of the atmosphere gas formed between the inner wall of the reaction tube and the cover member at the upper end of the boat on which the wafer is mounted is reduced. It is effective to form it to 20% or less of the area. For this reason, in the fourth invention, the inner diameter of the reaction tube is 90%.
% Of the cover member having a diameter of at least%, and the annular gas gap formed between the cover member and the inner wall of the reaction tube allows the atmospheric gas to flow uniformly in the circumferential direction. However, if the difference between the diameter of the cover member and the diameter of the wafer is large, a swirl occurs here and the atmospheric gas stays. For this reason, a plurality of holes are opened in the periphery of the cover member at equal intervals in the circumferential direction, and the atmospheric gas flows from both the opening and the annular gap.
If the center of the hole is close to the outer periphery of the wafer, no eddy current is generated.
The diameter of the cover member and the distance between the inner walls of the reaction tube are preferably as small as possible. However, if the diameter is too small, dust is generated due to contact. At present, it is difficult to increase the size to more than 95% from the processing accuracy of this type of equipment.
Atmospheric gas flowing through the hole decreases, and the generation of eddy current cannot be suppressed. Further, the total area of the openings of the holes must be 30% or less of the area of the annular gap, and if it exceeds this, a vortex is generated due to the atmospheric gas passing through the holes. On the other hand, if it is 20% or less, the flow rate of the atmosphere gas passing through the hole is small, and the vortex generated downstream of the annular flow path cannot be suppressed.

Further, if the upper surface of the cover member at the upper end of the boat on which the wafer is mounted is flat, the supplied atmosphere gas changes its traveling direction greatly here. A strong vortex is generated due to a large dead space between the flat cover member and the flat cover member. According to the fifth aspect of the present invention, the provision of the substantially conical cover member allows the supplied atmospheric gas to flow along the conical shape, and suppresses the generation of the vortex by reducing the dead space. You can do it. The material of the conical cover member must be heat-resistant, must not react with the atmosphere in the furnace, and must not contaminate the wafer. Such materials include silicon, quartz glass, silicon carbide, and silicon nitride. Particularly for processing a silicon wafer, high-purity silicon or quartz glass is suitable.

[0010]

Embodiments of the present invention will be described below with reference to the accompanying drawings for understanding the present invention. FIG. 1 is a sectional view of a wafer heat treatment furnace according to a first embodiment of the present invention, in which a quartz glass reaction tube 1 is installed with its longitudinal direction up and down, and a reaction tube A heater 2 as a heat source for heating the inside is provided. The reaction tube 1 is provided at its upper center with a gas supply tube 3 for supplying an atmosphere gas into the inside of the reaction tube, and at a lower portion thereof, a single circumferentially long one for discharging the atmosphere gas is provided. A slit 4 is provided. Also,
Temporarily collect the atmospheric gas discharged from the slit 4,
It has a back chamber 5 provided so as to surround the slit 4, and the back chamber 5 has one outlet 6 having an opening area larger than the total area of the openings of the slit 4.
Is provided. The back chamber 5 also serves to support the reaction tube 1 by connecting the outer wall of the reaction tube 5 located above the slit 4 to the bottom of the reaction tube. In FIG. 1, reference numeral 7 denotes a wafer to be heat-treated, and reference numeral 8 denotes a boat for mounting the wafer.

In the first embodiment of the present invention, when the wafer is placed on the boat 8 and loaded into the reaction tube 1 for heat treatment, the atmosphere gas sent from the gas supply tube 3 is the same as that of the wafer 7. While contacting, it flows down inside the reaction tube 1, and exhaust from the lower part of the reaction tube 1 is made through one long slit 4 continuously provided in the circumferential direction, and surrounds the slit 4 to form a back chamber 5. Is provided in the back chamber 5, and the exhaust port 6 having an area larger than the area of the slit 4 is provided. Further, the exhaust gas is exhausted by the exhaust pipe 20, so that the flowing atmospheric gas generates a vertical convection. No, it is discharged in a smooth flow. Therefore, high quality is achieved without contamination of the wafer 7.

In the wafer heat treatment furnace according to the first embodiment, as a third embodiment, the wafer contamination, the bottom end diameter of the boat, and the inner diameter of the reaction tube were variously varied, and the results of the contamination of the wafer were examined. Are shown in Table 1.

[0013]

[Table 1] That is, according to the third embodiment of the present invention, if the diameter of the lower end portion 13 of the boat is equal to or less than the arithmetic average value of the inner diameter of the reaction tube 1 and the diameter of the wafer 7, no contamination occurs.

FIG. 2 is a sectional view of a main part of a second embodiment of the present invention, in which two slits 4 at the lower portion of the reaction tube 1 are provided at equal intervals in the circumferential direction. Other configurations are the same as those of the first embodiment.

In the second embodiment shown in FIG. 2, the atmospheric gas in the heat treatment reaction tube 1 is exhausted from slits 4 and 4 opened at two places. Since the upper and lower portions of the slit are continuous at two locations, the vertical load can be supported at this portion.

Next, a fourth embodiment of the present invention will be described. FIG. 3 shows a perspective view of the fourth embodiment,
A silicon cover member 9 having a diameter of 92% of the inner diameter of the reaction tube 1 is provided at the upper end of the boat 8, and a plurality of holes 10, 10,.
Are opened at equal intervals.

In the fourth embodiment, after the atmospheric gas is supplied from the gas supply pipe 3, it flows down the gap between the silicon cover member 9 and the reaction pipe 1 and also has holes 10, 10,.
And flow down, so that no vertical convection occurs in the reaction tube 1, and there is no concern that the wafer 7 is contaminated.

Further, a description will be given with reference to FIG. 4 showing a fifth embodiment of the present invention. In the fifth embodiment,
As shown in the sectional view of FIG. 4, a substantially conical quartz glass cover member 11 is provided at the upper end of the boat 8.

In the fifth embodiment, the gas supply pipe 3
Atmosphere gas supplied from above is uniformly distributed in the entire circumferential direction and flows down by the cover member 11 whose upper end has a substantially conical shape, so that there is no generation of vertical convection. Further, since the atmospheric gas flows along the conical surface of the cover member 11, no eddy current is generated.

[0020]

Embodiment 1 FIG. 1 is a sectional view of a wafer heat treatment furnace according to the first invention. As described above, the wafer heat treatment furnace according to the first aspect of the invention uses a reaction tube having an inner diameter of 300 mm, and has one slit 4 formed in the lower part of the reaction tube and continuous in the circumferential direction.
Since the slit width is 1 mm and is formed continuously in the circumferential direction, the slit length is 942 mm. Outlet 6
Is designed to have a diameter of 40 mm, a total opening area of 12.6 cm 2 and a total opening area of the slit 4 of 9.4 cm 2, and the total opening area of the discharge port 6 is larger than the total opening area of the slit 4. This causes a pressure difference between the inside of the reaction tube and the back chamber, as described above, to form a constant differential pressure before and after the slit regardless of the location of the slit, and a constant ambient gas flow rate in the circumferential direction. To get it. If the opening area of the outlet 6 is smaller than the opening area of the slit 4, a pressure difference occurs between the back chamber and the exhaust pipe. For this reason, the flow of the atmospheric gas is concentrated near the outlet, and the uniformity in the circumferential direction is lost. At this time, the boat used for mounting the wafer used disc-shaped silicon of 260 mm at both the upper end and the lower end. The lower end of the boat is fixed on a cylindrical heat insulating block 13 having the same diameter. The specific heat treatment was performed as follows. A silicon wafer 7 cut out from an ingot having a diameter of 200 mm manufactured by the CZ method and processed to a mirror surface is put in a boat 8 for 100 times.
The sheets were placed and loaded in the reaction tube 1, and a heat treatment was performed for one hour at a gas flow rate of 20 / NL and an atmosphere temperature of 1200 ° C. using hydrogen gas as an atmosphere gas. After the heat treatment, all the taken out wafers are replaced with WSA (WAFER SURFAC
E ANALYSIS) was used to measure the degree of contamination of the surface, and it was found that 94% passed the standard judgment value. On the other hand, a silicon wafer cut out from the same ingot and processed to a mirror surface is a conventional heat treatment furnace with no slit or back chamber, and heat-treated under the same conditions. 79% passed. in this way,
According to the wafer heat treatment furnace of the first invention disclosed in this embodiment, it can be seen that the contamination of the processed wafer is reduced.

Embodiment 2 FIG. 2 shows a cross section of a wafer heat treatment furnace according to the second invention. Except for the shape of the slit formed in the lower part of the reaction tube, the configuration is the same as that of the first embodiment. In Example 2, two slits were formed. Each slit width is 1.5mm
The length of one slit is 314 mm. The total opening area of the slit is 9.4 cm2, which is the same as in the first embodiment, and the area of the outlet is 12.6 cm2, which is the same as in the first embodiment. Since the width of the slit is wide and the upper and lower portions of the slit are connected at two places, the mechanical strength is larger than that of the first embodiment, and the production is easy. For this reason, the manufacturing cost of the device is reduced. The uniformity of the flow velocity in the circumferential direction is slightly inferior because the total length of the slit is 2/3 smaller than that in the first embodiment. The same heat treatment as in Example 1 was performed, and the degree of surface contamination was measured. As a result, 91% passed the reference judgment value.

Embodiment 3 Table 1 shows the effects of the third invention. This shows the effect of implementing the third invention in addition to the first invention. In Example 3, the effect was confirmed including a silicon wafer of 150 mm. Of the three test conditions,
B and D do not implement the third invention. As a result of the test conditions of A and C in which the third invention was carried out, the ratio of passing the reference determination value of the degree of contamination was 98%. The result is 94%. The effect of the first invention on a 200 mm silicon wafer was 95% as described above. Therefore, adding the third invention to the first invention makes it possible to reduce the rate of passing the standard determination value of the degree of contamination. Effective to increase. Similarly, it is obvious to those skilled in the art that the present invention is also effective for the second invention.

Embodiment 4 FIG. 3 is a sectional view of a wafer heat treatment furnace according to a fourth invention. The configuration is the same as that of the second embodiment except that a cover member according to the fourth invention is provided at the upper end of the boat. The outer shape of this cover member is 270 mm in diameter,
0%. It has a thickness of 5 mm, 16 holes of 15 mm in diameter, and is opened at equal intervals on a circumference of 210 mm in diameter. The total opening area of the holes corresponds to 21% of the area of the ring-shaped atmosphere gas flow path formed between the inner surface of the reaction tube and the outer periphery of the cover member. When a silicon wafer having a diameter of 200 mm was heat-treated under the same conditions as in Example 2 with the above configuration, the percentage of passing the standard determination value of the degree of contamination was 98%. In Example 2, the effect was 91%, so that the effect of the fourth invention is recognized. The heat treatment was performed by adding the fourth invention to the test condition C of Table 1 in which the third invention was added to the first invention, and the degree of contamination was measured. In this case, the rate of passing the reference determination value was 100%.

Embodiment 5 FIG. 4 is a sectional view of a wafer heat treatment furnace according to a fifth invention. The configuration is the same as that of the fourth embodiment except that a conical cover member is provided at the upper end of the boat instead of the cover member according to the fourth invention. This cover member is made of quartz glass and has a conical shape with a diameter of 260 mm and a height of 65 mm. With the above configuration, a diameter of 200
When the contamination degree was measured by performing a heat treatment on a silicon wafer having a thickness of 2 mm, the ratio of passing the standard determination value was 98%. It can be seen that the fifth invention has the same effect as the fourth invention.

[0025]

As described above in detail, according to the present invention, the atmospheric gas supplied from the supply port is smoothly discharged without generating convection and vortex in the reaction tube, so that there is no contamination of the wafer and a high level. There is an effect that a quality heat-treated wafer can be obtained.

[Brief description of the drawings]

FIG. 1 is a sectional view of a wafer heat treatment furnace according to a first embodiment of the present invention.

FIG. 2 is a sectional view of a main part of a wafer heat treatment furnace according to a second embodiment of the present invention.

FIG. 3 is a perspective view of a wafer heat treatment furnace according to a fourth embodiment of the present invention.

FIG. 4 is a sectional view of a wafer heat treatment furnace according to a fifth embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Quartz glass reaction tube 2 Heater 3 Supply pipe 4 Slit 5 Back chamber 6 Outlet 7 Silicon wafer 8 Boat 9 Silicon cover member 10 Hole 11 Quartz glass cover member 20 Exhaust pipe

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Satoshi Yuzukiwaki 1324-2 Yugahara-cho, Omura-shi, Nagasaki Komatsu Electronic Metals Co., Ltd. Nagasaki Plant (72) Inventor Hiroyuki Matsuyama 1324-2, Yugahara-cho, Omura-shi, Nagasaki Komatsu Electronic Metals Co., Ltd. Nagasaki Factory (72) Inventor Masaaki Sato 1324-2 Yugahara-cho, Omura City, Nagasaki Prefecture Komatsu Electronic Metals Co., Ltd. Nagasaki Factory (72) Inventor Yoichiro Hanada Fukakusa Okameya Fukakusa, Kyoto City, Kyoto Prefecture 127-54, Choshiki-cho (72) Inventor Yoshinobu Hiraishi 1324-2, Ogahara-cho, Omura City, Nagasaki Prefecture Komatsu Electronic Metals Co., Ltd. Nagasaki Plant F-term (reference) 5F045 AD16 AF03 BB14 DP19 DQ05 EB15 EC01 EE20 EF14 EF20 EG08 EK06 EM08 EM09 HA06

Claims (5)

[Claims] 1. A cylindrical reaction tube whose longitudinal direction is the vertical direction, a boat on which a wafer to be heat-treated is placed and loaded inside the reaction tube, and a reaction tube which supplies heat energy to the inside of the reaction tube are arranged around the reaction tube. Heat source, a gas supply pipe connected to the center of the upper part of the reaction tube for supplying an atmosphere gas for wafer heat treatment to the inside of the reaction tube, and a single circumferentially continuous opening at the lower part of the reaction tube for discharging the atmosphere gas. A slit and a back chamber surrounding the slit, which supports the outer wall of the reaction tube located above the slit and temporarily collects an atmosphere gas discharged from the slit, and further exhausts the atmosphere gas from the back chamber to the outside. And an exhaust pipe connected to the back chamber. 2. A cylindrical reaction tube whose longitudinal direction is a vertical direction, a boat on which a wafer to be heat-treated is placed and loaded inside the reaction tube, and a reaction tube which supplies heat energy to the inside of the reaction tube are arranged around the reaction tube. A heat source, a gas supply pipe connected to the center of the upper part of the reaction tube for supplying an atmosphere gas for wafer heat treatment to the inside of the reaction tube, and an equidistant circumferential direction of the reaction tube opened at the lower part of the reaction tube for discharging the atmosphere gas A plurality of slits, a back chamber surrounding the slit, supporting the outer wall of the reaction tube located above the slit, and temporarily collecting the atmospheric gas discharged from the slit,
An exhaust pipe connected to the back chamber for exhausting the atmospheric gas from the back chamber to the outside. 3. The boat according to claim 1, wherein the diameter of the lower end of the boat on which the wafer to be heat-treated is placed is equal to or less than the arithmetic average of the inner diameter of the reaction tube and the diameter of the wafer to be heat-treated. A heat treatment furnace for a wafer according to claim 2. 4. The upper end of the boat is provided with 90
% Of a disk-shaped cover member having a diameter of not less than 95% and not more than 95%. 4. The wafer heat treatment furnace according to claim 1, wherein an opening corresponding to 20% or more and 30% or less of a road area is provided. 5. 5. A substantially conical top member is provided at the upper end of a boat on which a wafer to be heat-treated is placed, and the material of the top member is selected from silicon, quartz glass, silicon carbide, and silicon nitride. The wafer heat treatment furnace according to any one of claims 1 to 3, wherein any one of the materials is used.