JPS6120318A - Vertical diffusion furnace - Google Patents

Abstract

PURPOSE:To obtain a gentle temperature gradient without making the length of a furnace core longer by providing the subfurnace core part which is movable up and down and surrounds a boat part and by inserting it from the opening end of the furnace core part. CONSTITUTION:The crystal tube 11 as a furnace core tube is placed with directing its opening end downward and the sub-crystal tube 15 which is movable up and down in the crystal tube 11 by a driving device 6 is arranged. The sub-crystal tube 15 is heated by the resistance heating heater 12 with being contained in the crystal tube 11. Next, the sub-crystal tube 15 is lowered to the position where it surrounds a boat 13. At this time, the sub-crystal tube 15 is filled with high-purity gas and subsequently the boat 13 is raised to be put in the crystal tube 11, where it is subjected to heat treatment for the predetermined time. When lowering the sub-crystal tube 15, even though it is lowered at a high speed, crystal defects caused by thermal strain are not produced because of low temperature and the temperature distribution shows gentle temperature gradient which is almost same as that in the case the crystal tube 11 is extended.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a vertical diffusion furnace for heat treating semiconductor wafers.

[Technical background of the invention and its problems]

In recent years, semiconductor wafers have become larger in diameter, and wafers of 6 inches or more are also being used. When heat treating a large-diameter I-8, the core tube of the diffusion furnace must also be made thicker. When the core tube becomes thick in this way, in the case of a horizontal diffusion furnace where the core tube is placed on the side, there is a risk that the core tube will deform due to its own weight. In addition, in order to lower the dust level in a horizontal diffusion furnace, a device is required for soft landing of a boat containing semiconductor wafers into the reactor core tube. For this reason, a vertical diffusion furnace, in which the core tube is less deformed by its own weight and does not require a soft landing device, is promising as a furnace for large-diameter semiconductor wafers.

FIG. 12 shows a conventional vertical diffusion furnace. Basically, the structure is a vertical diffusion furnace, and a resistance heater 2, which is a heating section, is provided around a quartz tube 1, which is a furnace core tube.

The boat 3 containing the semiconductor wafers is driven by the drive unit 4 and inserted through the opening at the lower end of the quartz tube 1 .

The quartz tube 1 is heated to 800 to 1000°C by the resistance heater 2.
The center of the quartz tube 1 is heated to a high temperature of ±
Controlled within an error range of 1°C or less. However, once it leaves the opening of the quartz tube 1, the temperature drops rapidly. Such temperature distribution is shown in FIG. 13. The semiconductor wafer is placed in a 1° furnace and the speed at which the boat 3 is inserted must be such that the semiconductor wafer does not warp or crystal defects occur. The larger the diameter of the wafer, the slower the speed needs to be.The wafer is normally placed perpendicular to the direction of movement of the boat, but when it is taken in and out of the furnace, the temperature change around the wafer precedes the change in temperature between the center and the wafer. The larger the diameter of the wafer, the greater the temperature difference between the wafers and the larger the wafer diameter, and the slower the wafer must be taken in and out.

Also, the steeper the temperature gradient, the slower the speed of loading and unloading must be. In order to make the temperature gradient gentler, the length of the quartz tube, which is the furnace core tube, can be made longer.
In a vertical diffusion furnace, the ceiling height of the clean room is limited, so the quartz tube cannot be made very long.

Also, if the length is longer, the distance the boat must travel will be longer, and the time it will take to load and unload the boat will be longer. Also, if the temperature gradient is steep and the insertion speed is slow, the outside air near the opening will affect the
Fluctuations in wafer flat band voltage vFB, etc.
There was a problem that the wafer characteristics changed.

[Purpose of the invention]

The present invention has been made in consideration of the above circumstances, and provides a vertical diffusion furnace that can realize a gentle temperature gradient without increasing the length of the reactor core, and can prevent the occurrence of wafer warping or slipping. The purpose is to

[Summary of the invention]

In order to achieve this invention, the vertical diffusion furnace according to the present invention comprises:
It is characterized by comprising a sub-core part that surrounds the boat part, is inserted from the open end of the core part, and is movable up and down, and an a1 core drive part that drives the sub-core part.

[Embodiments of the invention]

A vertical diffusion furnace according to an embodiment of the present invention is shown in FIG. 1. A quartz tube 11, which is a 1° furnace core tube, is installed with its open end facing downward. A resistance heating motor 12 is provided around this quartz tube 11 . Boat 1 containing many semiconductor wafers
3 is located below the open end of the quartz tube 11. This boat 13 can be moved up and down by a boat drive device 114. A feature of this vertical diffusion furnace is that it is provided with an auxiliary quartz tube 15 that can be moved up and down within the quartz tube 11. This sub-quartz tube 15 can be moved up and down independently of the boat 13 by a sub-quartz tube drive device 16. In this embodiment, the length of the quartz tube 11 and the sub-quartz tube 15 is 600 m, and the length of the boat 13 is 320 a. If the wafers are arranged at a pitch of 4.76am, the maximum
It can be made into 7 sheets.

An example of how to use this vertical diffusion furnace is shown in FIG.

First, the quartz tubes 11 and 12 are heated by the resistance heater 12 at the position where the sub-quartz tube 15 is housed in the quartz tube 11. The semiconductor wafers are stored in the boat 13, and the quartz tube 11
and set it under the opening of the sub-quartz tube 12 (see Fig. 2(a)
)). Next, lower the auxiliary quartz tube 15 to a position surrounding the boat 13 (tl'+2 (b)). At this time, it is possible to fill the inside of the sub-quartz tube 12 with high-purity gas and lower the temperature. Therefore, when lowering the sub-quartz tube 12, even if it is lowered at high speed, crystal defects due to thermal strain will not occur because the temperature is low. This is because the strength of the Naginara wae increases dramatically at low temperatures. Furthermore, the wafer can be held in a high-purity gas atmosphere for a short time.

The temperature distribution in FIG. 2(b) is the same as when the quartz cap 11 is extended, and shows a much gentler temperature gradient in FIG. 3. Next, the boat 13 is gradually raised (FIG. 2 (C)), but because the temperature gradient is gentle, it can be raised relatively quickly. When the boat 13 enters the quartz tube 11, heat treatment is performed there for a predetermined time (second
Figure (d)).

After the heat treatment was completed, the boat 13 was taken out and transferred to the vessel shown in Figure 2 (
Control J may be performed in the order from b) to FIG. 2 (ε1). Even when the boat 13 is lowered, the sub-quartz tube 15 is surrounded, so the temperature changes rapidly, and it is possible to cool the vessel in a high-purity gas atmosphere.

Next, FIG. 4 shows another example of how to use this vertical diffusion furnace. First, at the position where the sub-quartz tube 15 is stored in the quartz tube 11, the resistance heating motor 12 is used to heat the quartz tubes 11 and 12.
heat up. A semiconductor wafer is stored in a boat 13 and set under the openings of the quartz tube 11 and the sub-quartz tube 15 (FIG. 4(a)).

Next, the Dj quartz tube 15 is lowered to a position surrounding the boat 13 (FIG. 4(b)). The temperature distribution at this time is as shown in FIG. Next, the boat 13 is gradually raised, and in this specific example, the auxiliary quartz tube 15 is also raised at the same time (FIG. 4(C)). By raising the sub-quartz tube 15 at the same time, the heat capacity of the bolt 13 is substantially increased, and temperature changes during high-speed movement can be made gentler. When the boat 13 and the first quartz tube 15 enter the quartz tube 11, heat treatment is performed there for a predetermined time (FIG. 4(d)). When the boat 13 is to be taken out after the heat treatment is completed, control is performed in the reverse order from FIG. 4(d) to FIG. 4(a). Note that the moving speed of the sub-quartz tube 15 may be changed depending on the moving speed of the boat 13 and the heat capacities of the sub-quartz tube 15 and the boat 13.

The shape of the auxiliary quartz tube 15 can be various curved shapes.

For example, as shown in FIG. 5, an I-shaped protrusion 17 may be provided inside the sub-quartz tube 15. As a result, the flow of high-purity gas inside the secondary tube 15 becomes smooth. Further, as shown in FIG. 6, a plurality of rings 18 may be provided inside the sub-quartz tube 15. This changes the gas flow to make it uniform. Further, as shown in FIG. 7, the gas flow inside the sub-quartz tube 15 flows along a spiral band 19 in a spiral trajectory, thereby making it possible to equalize the heat and uniformly supply the gas. Furthermore, when two types of gas are used, homogeneous mixing can be quickly achieved. In addition, as shown in Fig. 8, the sub-quartz tube 1
A spiral band 20 may be provided on the outside of 5. Thereby, the gas flow between the sub-quartz tube 15 and the quartz tube 11 can be controlled.

Further, the sub-quartz tube 15 and the boat 13 may be rotated instead of being moved up and down. This further improves uniformity of heat, homogenization of mixed gas, etc.

In addition, the cross-sectional shape of the sub-quartz tube 15 is set to 4 as shown in FIG.
Other shapes such as a square shape may also be used. In addition, instead of a closed rectangular tube, four plates are used to form the sub-core part 1, as shown in Figure 11.
5 may be formed. Even when the cross section is circular, the auxiliary core section 15 may be constructed of two radial members instead of a closed tube, as shown in FIG.

The sub-quartz tube 15 and the quartz tube 11 may be brought into close contact with each other. Further, the sub-quartz tube 15 and the boat 13 may be brought into close contact with each other. Further, if necessary, the sub-quartz tube 15 may be provided with a frontage.

Alternatively, a plurality of sub-quartz tubes may be provided and each may be driven independently. Accurate investigation of heat capacity is possible.

Note that the core and sub-core may be made of a material other than 6-III, such as polycrystalline silicon, to prevent contamination by impurities.

Furthermore, a gas line for introducing high-purity gas may be separately provided in the sub-core.

(Effects of the Invention) As described above, according to the present invention, a gentle temperature gradient can be realized without increasing the length of the reactor core. Therefore, even if the speed of movement of the boat is increased, warping and slipping may occur.

In addition, if the sub-core was swirled with high-purity melon gas, the boat would be immediately moved to I! ! ￥l It is possible to put it in a purity gas atmosphere, and it can receive We'il of outside air (-J).

Furthermore, if you avoid changing the movement of the auxiliary core,
The overall heat capacity can be controlled, and changes in wafer heating can be precisely controlled.

Furthermore, by changing the shape of the auxiliary core, it is possible to control high-purity gas and respond to changes in the shape.

[Brief explanation of drawings]

Figure 1 is a #1 sectional view of a vertical diffusion furnace according to an embodiment of the present invention, Figures 2 and 4 are diagrams showing specific examples of how to use the vertical diffusion furnace, and Figure 3 is a diagram showing a specific example of how to use the vertical diffusion furnace. Graphs showing the temperature distribution of the vertical diffusion furnace, Figures 5, 6, 7, 8, 9, 10, and 11 are for the sub-core of the vertical diffusion furnace, respectively. FIG. 12 is a vertical cross-sectional view of a conventional vertical diffusion furnace, and FIG. 13 is a graph showing the temperature distribution of the vertical diffusion furnace. 1.11...Quartz tube, 2.12...Resistance heater, 3.13...Boat drive IJI device, 15...Station 1
6 quartz tubes, 16... sub-quartz tube drive device. Applicant's representative Kiyoshi Inomata 1st circle 2nd figure 3rd quartz tube equipment (myn) 4th figure 8th figure γ Q-6 Gaffe [! mmJ

Claims (1)

[Scope of Claims] 1. A reactor core with one end open, a heating section for heating the reactor core, a boat section that accommodates semiconductor wafers and is movable up and down, and a boat section that drives the boat up and down at a predetermined speed. a boat driving section; a sub-core section that surrounds the boat section, is inserted into the open end of the core section and is movable up and down; and a sub-core that drives the sub-core section up and down in accordance with the vertical movement of the boat section. Vertical diffusion furnace equipped with a drive unit. 2. The vertical diffusion furnace according to claim 1, wherein the auxiliary core drive section rotationally drives the auxiliary core section. 3. The vertical diffusion furnace according to claim 1 or 2, wherein the boat driving section rotationally drives the boat. 4. A vertical diffusion furnace according to any one of claims 1 to 3, wherein the reactor core is a quartz tube. 5. The vertical diffusion furnace according to any one of claims 1 to 4, wherein the boat part and the auxiliary core part are inserted and taken out from a lower open end of the core part. Vertical diffusion furnace.