JPH04163913A - Vertical type heat treat furnace - Google Patents

Abstract

PURPOSE:To make it possible to perform heat treatment under highly clean atmosphere by performing heat treatment for a semiconductor in a furnace core pipe at the inner side of two core pipes having a double construction thereby prohibiting the entrainment of atmospheric air into the furnace core pipe. CONSTITUTION:Nitrogen is supplied from a gas introducing hole 13 to a furnace core pipe 11. The introduced nitrogen moves through the inside of the pipe 11 and is released from an opening 11a at the lower end of the pipe 11. On the other hand, when nitrogen is introduced from a gas introducing hole 14 to a furnace core pipe 12, the nitrogen passes through the space between pipe 11 and pipe 12 and becomes confluent at the opening 11a at the lower end of the pipe 11 and then ejected to the outside of furnace. By this flow, the entrainment of atmospheric air to the inside of the pipe 11 can be prevented. Thus, heat treatment can be performed under highly clean atmosphere, the production process can be cleaned, process can be stabilized and the production cost can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a vertical heat treatment furnace, and more particularly to a highly clean vertical heat treatment furnace that does not involve air when carrying in semiconductor substrates.

[Prior Art] Conventionally, in this type of vertical heat treatment furnace, the furnace core tube 31 has a single-tube structure, as shown in FIG. In addition, 32 is a heater, 3
3 is a boat, 34 is a semiconductor substrate, and 35 is a gas inlet.

The semiconductor substrate 34 is installed on the boat 33 and
It is conveyed to the inside of the furnace core tube 31 together with the furnace core tube 31.

At this time, heat treatment gas is introduced from the gas inlet 35, the inside of the furnace core tube 31 is filled with the heat treatment gas, and the gas is discharged from the lower end of the furnace core tube 31. At the same time, the furnace core tube 31 was maintained at a high temperature of usually 800° C. to 1000° C. by a heater 32, and heat treatment was performed.

[Problem to be solved by the invention] In the conventional vertical heat treatment furnace described above, the furnace core tube has a monocylindrical structure, so gas is introduced from the upper part of the furnace core tube to fill the inside of the furnace core tube with gas. Even if the overflow gas is allowed to flow, it will quickly diffuse, and the gas concentration outside the furnace core tube will be extremely low even in the vicinity of the furnace core tube. Therefore, when the semiconductor substrate is carried into the furnace core tube, the atmosphere is drawn in, so there is a problem that the atmosphere gets mixed into the furnace core tube. Since the atmosphere contains approximately 20% oxygen and the furnace core tube is at a high temperature, when the atmosphere is drawn into the furnace core tube, the semiconductor substrate carried into the furnace core tube is quickly oxidized by oxygen. Put it away. This causes a decrease in device reliability and a decrease in product yield for processes that do not require an oxidizing atmosphere, such as impurity activation heat treatment after ion implantation or post-silicide film formation heat treatment. In the former case, a silicon oxide film is formed on the surface of the semiconductor substrate, and in the latter case, the silicide film is peeled off.

SUMMARY OF THE INVENTION An object of the present invention is to provide a vertical heat treatment furnace that prevents atmospheric air from being drawn in when semiconductor substrates are transported.

[Means to solve the problem]

In order to achieve the above object, the vertical heat treatment furnace according to the present invention is a vertical heat treatment furnace having a first furnace core tube and a second furnace core tube, the two furnace core tubes having: The first furnace core tube is placed on the inside and the second furnace core tube is placed on the outside, resulting in a dual structure of inside and outside. The first furnace core tube is used for heat treatment of semiconductor substrates. be.

The second furnace core tube is longer than the first furnace core tube, protrudes from the end opening of the first furnace core tube in the tube axis direction, and extends beyond the end opening of the first furnace core tube. The second furnace core tube has a reduced inner diameter on the end opening side of the first furnace core tube, and the first furnace core tube and the second furnace core tube, and within the first furnace core tube,
The inert fluid is made to flow, join together at the end opening side of the first furnace core tube, and be discharged outside the furnace.

[Function] By flowing inert gas into each of the two furnace core tubes that have a double inner and outer tube structure and merging them at the lower end opening of the furnace core tube and discharging them outside the furnace, atmospheric air can be released into the furnace core tube. Prevent entanglement.

〔Example〕

Hereinafter, the present invention will be explained with reference to the drawings.

(Example 1) FIG. 1 is a sectional view showing Example 1 of the present invention.

In the figure, 11 is a first furnace core tube, and 12 is a second furnace core tube, which are arranged in double layers, inside and outside. In addition, the inner furnace core tube 11 is set shorter than the outer furnace core tube 12,
The lower end of the outer furnace core tube 12 projects downward from the lower end opening 11a of the inner furnace core tube 11 and wraps around it.

Further, 13 is a first gas inlet, 14 is a second gas inlet, 15 is a heater, 16 is a boat, and 17 is a semiconductor substrate. In this example, heat treatment in a nitrogen atmosphere will be described. Inject nitrogen from the first gas inlet 13 to the first furnace core tube l.
Introduce into l. The introduced nitrogen advances inside the first furnace core tube 11 and is released from the lower end opening of the first furnace core tube 11. - side, from the second gas inlet 14 to the second furnace core tube 1
When nitrogen is introduced into the furnace core tube 2, the nitrogen passes between the first furnace core tube 11 and the second furnace core tube 12, reaches the lower end of the first furnace core tube 11, and enters the shutter core tube 11. Nitrogen in the furnace tube 11 joins together at the lower end opening side and is discharged outside the furnace, and this flow prevents atmospheric air from being drawn into the furnace core tube 11.

FIG. 2 is a diagram showing the effects of the present invention. That is, it shows the relationship between the distance from the lower end opening of the furnace core tube at the time of carrying in the semiconductor substrate and the oxygen concentration within the furnace core tube at that distance. The dotted line is for the vertical furnace tube of the prior art, and the solid line is for the vertical furnace tube of the present invention.

In addition, in the case of the vertical furnace core tube of the present invention, the distance is the distance from the lower end opening of the furnace core tube 11 in FIG. In the case of the conventional vertical furnace core tube, the oxygen concentration at the lower end opening is extremely high and the temperature is high, so that the surface of the semiconductor substrate is oxidized during the loading process.

On the other hand, the furnace core tube of the present invention has a low oxygen concentration throughout the entire interior of the furnace, allowing highly clean heat treatment.

(Example 2) FIG. 3 is a sectional view showing a second embodiment of the present invention.

In the figure, 21 is a first furnace core tube, 22 is a second furnace core tube, 23 is a first gas inlet, 24 is a second gas inlet,
25 is a heater, 26 is a boat, and 27 is a semiconductor substrate. In this embodiment, the inner diameter of the lower end of the second furnace core tube 22 is reduced. The other configurations are the same as in the first embodiment.

According to this embodiment, since the inner diameter of the lower end portion of the second furnace core tube 22, that is, the lower end opening 21a side of the first furnace core tube 21 is reduced, the inner diameter of the inner and outer furnace core tubes 21 at this portion is reduced. .22 becomes narrower, so the amount of nitrogen introduced from the second gas inlet 24 can be reduced, and the same effect as in the first embodiment can be obtained. This means that as the diameter of the semiconductor substrate 27 increases, the size of the vertical heat treatment furnace used also increases, but the amount of nitrogen used at this time can be saved, so manufacturing costs can be reduced. There are advantages.

[Effects of the Invention] As explained above, the present invention is a vertical heat treatment furnace having a second furnace core tube inside the first furnace core tube, and the first furnace core tube is connected to the second furnace core tube. The length is longer, and inert gas is passed between the first furnace core tube and the second furnace core tube, and after merging at the lower end of the second furnace core tube, it is discharged from the first furnace core tube. With this structure, it is possible to completely eliminate atmospheric air that is drawn into the furnace core tube when the semiconductor substrate is carried into the furnace core tube. This allows heat treatment to be performed in a highly clean atmosphere, making the manufacturing process cleaner and, as a result, more stable.

This has the effect of reducing manufacturing costs and improving the reliability of semiconductor devices.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing Embodiment 1 of the present invention, and FIG.
A diagram comparing the in-furnace oxygen concentration at the time of loading semiconductor substrates between a vertical heat treatment furnace of the present invention and a conventional heat treatment furnace. FIG. 3 is a cross-sectional view showing Example 2 of the present invention, and FIG. 4 is a conventional heat treatment furnace. FIG. 2 is a cross-sectional view showing an example vertical heat treatment furnace. 11.21...First furnace core tube 12.22...Second furnace core tube 13.23...First gas inlet 14.24...Second gas inlet 15. 25...Heater 16,26...Boat 17.27...Semiconductor substrate

Claims (1)

[Scope of Claims] (1) A vertical heat treatment furnace having a first furnace core tube and a second furnace core tube, wherein the two furnace core tubes have the first furnace core tube on the inside. , a vertical heat treatment method characterized in that a second furnace core tube is placed on the outside and is combined into an inside and outside double structure, and the first furnace core tube is for heat-treating a semiconductor substrate. Furnace. (2) The second furnace core tube is longer than the first furnace core tube, protrudes in the tube axis direction from the end opening of the first furnace core tube, and the second furnace core tube is longer than the first furnace core tube, and extends from the end opening of the first furnace core tube. The vertical heat treatment furnace according to claim 1, wherein the vertical heat treatment furnace surrounds the periphery of the furnace. (3) Claims (1) and (2) characterized in that the second furnace core tube has a reduced inner diameter on the end opening side of the first furnace core tube. Vertical heat treatment furnace as described in section. (4) An inert fluid is caused to flow between the first furnace core tube and the second furnace core tube and within the first furnace core tube, and to the end opening side of the first furnace core tube. Claims (1) and (1) are characterized in that they are combined and discharged outside the furnace.
The vertical heat treatment furnace described in item 2) and item (3).