JPS62182199A - Diffusion furnace - Google Patents

Abstract

PURPOSE:To uniformize temperature distribution in a furnace core tube and obtain a treating material having uniform properties or thickness throughout the whole material, by attaching a spiral gas-flow guide plate to the inner circumference of the furnace core tube. CONSTITUTION:A diffusion board 7 holding a number of wafers 8, etc., is inserted into a furnace core tube 2 heated with a heater 3, the furnace opening 4 is closed with a cap 9 and the wafers 8 are maintained at a specific temperature. A gas containing impurities, etc., is introduced into the core tube 2 through a gas-inlet port 5 attached to the innermost part 2a of the tube 2. The introduced gas is spirally guided with a flow-guide plate 10 to form a gyrating gas flow. The gas is heated also from the outside of the heater 3 to generate convection flow in the gas. The gas is agitated by convection as well as gyrating flow to uniformize the temperature distribution in the tube. The gas is diffused to an deposited on a surface of the wafer 8 in this gas atmosphere.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a diffusion furnace used to form an oxide film on a wafer made of silicon or the like, or to perform impurity diffusion or annealing treatment.

<Prior art> A conventional diffusion furnace generally has the following structure, as shown in the cross-sectional view of FIG.
It has a structure in which a heater 2° is placed near the outer periphery of a 1° cylindrical furnace tube made of quartz.

In this diffusion furnace, first, a diffusion boat 4° on which a large number of wafers 3°, etc. are placed is operated at a predetermined position within a furnace tube 1° which is heated to a predetermined temperature by a heater 2°. After inserting with a jig, the furnace opening of the furnace tube 1° is closed with a cap 5.
The furnace tube is closed at 1° and the wafer 3° inside the furnace tube 1° is kept at a predetermined temperature. And the furnace tube l. A gas containing impurities, which is supplied from a gas supply port 6° formed in the inner inner wall of the wafer 3, is applied to the surface of the wafer 3°, thereby performing the required diffusion or growth of an oxide film.

<Problem to be solved by the invention> By the way, in the above-mentioned diffusion furnace, the gas injected into the furnace core tube 1° is heated from the outside by the heater 2°.
Furnace tube l. The gas near the inner peripheral surface of the tube is heated to a higher temperature faster than the gas located in the center, causing convection.

In that case, in a conventional diffusion furnace, the inner surface of the 1° furnace tube is
Since it is formed with a smooth circumferential surface without any protrusions, gas flows upward from the bottom of the core tube 1° to the neck along the inner circumferential surface of the tube, as shown by the arrowhead in the explanatory diagram of FIG. , follows a path that flows from the top to the left and right center position of 1° of the reactor core tube and returns to the bottom. Therefore, between the upper half region along the inner circumferential surface of the furnace core tube 1o and the region including the center and bottom 1. : A temperature difference occurs, and the temperature distribution inside the core tube IO becomes uneven. As a result, the characteristics of each part of the wafer subjected to the diffusion process may differ, and the thickness of the oxide film may vary.

The present invention has been made in view of the two problems, and aims to equalize the temperature distribution within the reactor core tube into which gas is injected, and to make the characteristics of the object to be processed constant in each part.

Means for Solving the Problems> In order to achieve the above object, the present invention configures a diffusion furnace by attaching a spiral airflow guide plate to the inner peripheral surface of the furnace core tube.

<Operation> According to the above configuration, the gas injected into the reactor core tube is forced to flow in a spiral manner by the airflow guide plate, and the gas is agitated by the stirring effect of this swirling flow. is,
As a result, the temperature distribution within the tube is made uniform.

<Example> Hereinafter, the present invention will be described in detail based on an example shown in the drawings.

FIGS. 1 and 2 show an embodiment of the present invention, with FIG. 1 being a sectional view and FIG. 2 being a perspective view showing a main part cut away. In these figures, reference numeral 1 denotes a furnace body of a diffusion furnace, 2 a furnace core tube passing through the furnace body, and 3 a heater disposed near the outer periphery of the furnace core tube 2. The furnace core tube 2 has a furnace opening 4 at one end,
It is a cylindrical tube made of quartz whose other end is closed by an inner inner wall 2a, and gas containing impurities is supplied into the tube from a gas supply port 5 formed on the inner inner wall 2a, and a gas containing impurities is formed on the outer peripheral wall 2b. The air is discharged to the outside from an exhaust duct 6.

Further, reference numeral 7 indicates a diffusion boat, and 8 indicates wafers placed on the diffusion boat 7 at intervals.

The diffusion boat 7 is connected to the reactor core tube 2 by an operation jig (not shown).
It is inserted and placed at a predetermined position in the soaking area. 9 is a cap of the furnace core tube 2.

There is a spiral airflow guide plate on the inner peripheral surface of the furnace core tube 2! 0 is set. The air flow guide plate 10 is a spirally continuous quartz band plate having a constant narrow width, and its outer peripheral edge is fixed to the inner peripheral surface of the furnace tube 2 over its entire length. In this embodiment, the airflow guide plate 10 is provided inside the reactor core tube 2 at the innermost side of the installation position of the diffusion boat 7, but the airflow guide plate 10 may be provided over the entire length of the reactor core tube 2. The mounting location of the airflow guide plate 10 is not limited to the mounting location in the illustrated embodiment.

In the above configuration, when performing a diffusion process on wafers 8, first, a large number of wafers 8. After the diffusion boat 7 on which the... is placed is inserted using an operating jig, the furnace port 4 of the furnace tube 2 is closed with a cap 9, and the wafers 8 in the furnace tube 2 are maintained at a predetermined temperature. On the other hand, the furnace core tube 2
A gas containing impurities is injected and supplied into the interior from a gas supply port 5 formed in the inner back wall 2a. This gas is
It adheres to the surface of the wafer 8 that has been heated to a predetermined temperature, thereby performing the required diffusion.

In this case, since there is an airflow guide plate IO on the inner peripheral surface of the furnace core tube 2, the gas injected into the furnace core tube 2 is passed through the airflow guide plate IO as shown by arrow A in the explanatory diagram of FIG. It is guided in a spiral and is forced to turn in one direction, either toward the cloth waste or counterclockwise. The gas also causes convection due to the heating from the outside of the heater 3, but the gas is forced to flow in a spiral manner against this convection, so it is agitated by the convection and the swirling flow, and as a result, Temperature distribution inside the tube becomes uniform. Since the wafer 8 comes into contact with the gas in this gas atmosphere with a uniform temperature distribution, each part of the wafer 8 has constant characteristics.

Note that the present invention can also be applied to a diffusion furnace for growing an oxide film.

<Effects of the Invention> As described above, according to the present invention, the gas injected into the reactor core tube flows in a spiral manner by the airflow guide plate, and the temperature distribution in the tube is improved by the stirring effect of this swirling flow. As a result, local variations in the properties of the object to be processed are eliminated, and the object to be processed has constant characteristics or film thickness in each part.

[Brief explanation of drawings]

Figures 1 to 3 relate to an embodiment of the present invention, in which Figure 1 is a sectional view of a diffusion furnace, Figure 2 is a perspective view showing its main parts broken away, and Figure 3 shows its operating state. FIG. 4 and 5 relate to a conventional example, with FIG. 4 being a sectional view and FIG. 5 being an explanatory view showing the operating state. 1... Furnace body, 2... Furnace tube, 3... Heater, 5...
...Gas supply port, 7.Diffusion boat, 8.Wafer,
lO...Airflow guide plate.

Claims (1)

[Claims] (1) A diffusion furnace characterized in that a spiral airflow guide plate is attached to the inner circumferential surface of the furnace core tube.