JPH0120640Y2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field The present invention relates to a heating device for an electric furnace, and is particularly suitable for application to, for example, a heating device for a diffusion furnace for semiconductor wafers.

BACKGROUND TECHNOLOGY An electric furnace such as a diffusion furnace is usually equipped with a heat treatment tube made of quartz glass or the like, and semiconductor wafers to be processed are loaded on a predetermined wafer board and placed at a predetermined position inside the processing tube. be done. The heat treatment tube is surrounded by a heat insulation layer made of a predetermined heat insulating material, and a heating means is provided between the heat treatment tube and the heat insulation layer. As the heating means, a resistance heating wire such as a nichrome wire coiled around the heat treatment tube is usually used.

Among such electric furnaces, especially in semiconductor wafer diffusion furnaces, the temperature distribution within the heat treatment tube is an extremely important factor. In other words, the temperature distribution is uniform even inside the heat treatment tube (for example, if the furnace length is 600~
(at 1000mm, within 1200℃±0.25℃), otherwise the heat treatment of the semiconductor wafers stacked on the wafer board will not be uniform. This is a very important problem for semiconductor devices that cannot tolerate even subtle errors. Therefore, various efforts have been made to make the temperature distribution within the heat treatment tube as uniform as possible.

Problems to be Solved by the Invention When the length of the electric furnace as described above becomes long, for example, 1 to 2.5 m, it becomes difficult to heat the entire furnace with one resistance heating wire. Therefore, the heating means is substantially divided into several blocks along the furnace axis, and a drive current is supplied to the resistance heating wire of each block to heat it. in this case,
The lead terminal must be pulled out from the resistance heating wire midway through the electric furnace. Conventionally, this lead terminal was brought out through an adiabatic furnace over the shortest distance. However, when the lead terminal is pulled out in this way, heat escapes to the outside of the furnace through this lead terminal, and as a result, a valley in the temperature distribution occurs near this part, as will be described later in connection with Figure 3. was formed, and a uniform distribution could not be obtained.

Means for Solving the Problems The present invention has been made in view of the above-mentioned problems, and includes a heat insulating layer disposed surrounding a heat treatment tube of an electric furnace, and an inner surface of the heat treatment tube in an electric furnace. an electric heating means arranged around the tube; and at least one electric heating means connected through the insulation layer to the electric heating means.
In the heating device for an electric furnace, the lead terminals are arranged in a crank shape inside the heat insulating layer. By bending the lead terminal, the position where the lead terminal is drawn into the heat-insulating layer and the position where it is pulled out from the heat-insulating layer are offset from each other in the direction along the longitudinal axis of the heat treatment tube.

Embodiment Hereinafter, an embodiment in which the present invention is applied to a heating device for a vertical diffusion furnace for semiconductor wafers will be described with reference to the drawings.

As shown in FIG. 1, the diffusion furnace includes a processing tube 1 made of quartz glass whose longitudinal axis is arranged in a substantially vertical direction. The upper end of the processing tube 1 is wide open as shown in the figure, and a wafer boat loaded with semiconductor wafers such as silicon is inserted through the upper opening and suspended at a predetermined position within the processing tube 1. During heat treatment, this upper opening is closed with a predetermined lid.

The processing tube 1 is surrounded by a heat insulating layer 2 made of a fibrous heat insulating material containing, for example, about 52 to 62% alumina and the remainder being SiO ₂ . A resistance heating wire 3 (for example, Kanthal A-1: trade name) is held in a coil shape on the inner surface of this heat insulating layer 2.

The resistance heating wire 3 extends along the longitudinal axis of the processing tube 1.
It is divided into two blocks, and lead terminals 4, 5, 6, and 7 are connected to both upper and lower ends and two middle parts, respectively.

Lead terminals 6 and 7 connected to the intermediate portion of the resistance heating wire 3 are bent into a crank shape inside the heat insulating layer 2, as shown. For example, the lead terminal 6 is constructed by bending a metal plate into a crank-shaped cross section, as shown in an enlarged view in FIG.
One end thereof is welded to the resistance heating wire 3. The other end of the lead terminal 6 is bolted to an external conducting wire 8. A heat dissipation block may be interposed between the lead terminal 6 and the external conducting wire 8 to prevent the external conducting wire 8 from being oxidized due to heat transmitted through the lead terminal.

Conventionally, the lead terminal was pulled out straight from the connection position with the resistance heating wire, as shown by the imaginary line in FIG. Therefore, as shown by broken lines in FIG. 3, valleys were formed in the temperature distribution at positions slightly inside the lead terminal positions BA and B. The reason why the temperature is higher at both ends of the graph is to compensate for the temperature drop near the furnace mouth.

On the other hand, as in this example, the lead terminals 6 and 7 are each bent into a crank shape, and the lead terminals 6 and 7 are pulled out to the position where the lead terminals 6 and 7 are drawn into the heat insulating layer 2, i.e., When each lead terminal 6 or 7 is deviated from the connection position of the resistance heating wire 3 in the furnace length direction, no valley is formed in the temperature distribution and a substantially uniform temperature distribution ( For example, 1200℃±0.25℃~1200℃±0.1℃)
was gotten.

The preferred deflection distance, i.e. the vertical distance l between the extraction position of the terminal and the connection position to the resistance heating wire, is:
For example, when the thickness of the heat insulating layer is about 30 to 80 mm, the coil diameter of the resistance heating wire 3 is about 80 to 300 mm, and the coil pitch is about 14 mm, the thickness is about 30 to 200 mm, more preferably about 50 to 150 mm. Ta.

Note that each lead terminal does not need to be bent at right angles as in this example, and various other shapes can be used.

In addition, if the heat insulation layer 2 is thin, for example, about 30 mm,
As shown in FIG. 4, an auxiliary heat insulating layer 12 may be provided on the outer periphery of this heat insulating layer 2, and the lead terminals 6 and 7 may be bent inside this auxiliary heat insulating layer 12. Such a configuration is convenient because a conventional heating device can be used as is.

Although an embodiment in which the present invention is applied to a heating device for a vertical diffusion furnace for semiconductor wafers has been described above, the present invention can be applied to heating devices for a horizontal diffusion furnace and various other electric furnaces.

Effects of the Invention As explained above, in the present invention, the lead terminals are drawn out from the side of the heat insulating layer to the outside, and the lead terminals are connected to the heat insulating layer from the connection position to electric heating means such as resistance heating wires. The retracting positions are offset from each other in the furnace length direction, that is, in the longitudinal direction of the heat treatment tube of the electric furnace. Therefore, it is possible to effectively prevent the heat inside the furnace from escaping to the outside through the lead terminals. As a result, the temperature inside the furnace does not drop locally, and a substantially uniform temperature distribution can be obtained throughout the inside of the furnace.

[Brief explanation of the drawing]

The drawings show an embodiment in which the present invention is applied to a vertical diffusion furnace for semiconductor wafers. Figure 1 is a schematic vertical cross-sectional view of the diffusion furnace, and Figure 2 is an enlarged vertical cross-section of the lead terminal part. 3 is a graph showing the temperature distribution in the furnace, and FIG. 4 is a partially enlarged vertical sectional view showing a modification of the diffusion furnace. In addition, in the symbols used in the drawings, 1...processing tube, 2...insulating layer, 3...resistance heating wire, 6, 7...
...It is a lead terminal.

Claims (1)

[Claims for Utility Model Registration] A heat insulating layer disposed surrounding a heat treatment tube of an electric furnace, an electric heating means disposed on the inner surface of this heat insulating layer and around the heat treatment tube, and a heat insulating layer that passes through the heat treatment tube. and at least one lead terminal connected to the electric heating means, the heating device for an electric furnace configured such that the lead terminal is drawn out from a side surface of the heat insulating layer, the lead terminal is bent inside the heat-insulating layer, and a position where the lead terminal is drawn into the heat-insulating layer and a position where the lead terminal is pulled out from the heat-treating layer are offset from each other in a direction along the longitudinal axis of the heat treatment tube. A heating device for an electric furnace.