JPS582357B2 - heat treatment equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a heat treatment apparatus used in manufacturing methods that require high temperature heat treatment such as oxidation or impurity diffusion.

The method for manufacturing a semiconductor device will be described below as an example.

FIG. 1 shows a cross section of a heat treatment furnace as an example of a conventional heat treatment apparatus.

In this figure, 1 is a heat treatment furnace tube, 2 is an insertion port for wafers to be heat treated, 3 is a lid for opening and closing the insertion port 2, and 4 is a lid for opening and closing the insertion port 2.
is a heater that heats the heat treatment furnace tube 1.

Such devices have conventionally been widely used in high-temperature heat treatments such as oxidation processes and impurity diffusion processes in the manufacture of semiconductor devices.

In performing the heat treatment, the lid 3 is removed and the wafer is taken in and taken out, and the insertion speed and withdrawal speed at this time are extremely important as they influence the characteristics of the semiconductor device to be manufactured.

In other words, if the insertion and withdrawal speeds are fast,
Strain occurs in the wafer, often resulting in an increase in the reverse saturation current of the pn junction, or in bipolar transistors, deterioration of characteristics such as a decrease in hFE and a decrease in yield.

Further, when the insertion speed and withdrawal speed are slow, different problems arise than when the speed is fast as described above.

FIG. 2a is a temperature distribution diagram near the insertion port 2 of the heat treatment furnace tube 1 in the heat treatment furnace mentioned above, and FIG. 2b is a diagram showing the state of intrusion of external air. The horizontal axes in Figure 2b correspond.

When the lid body 3 is removed, the external air flows into the heat treatment furnace tube 1.
It has penetrated 50 to 70 cm into the interior through the insertion port 2 and even reached a part of the soaking zone.

When the wafer is inserted at a slow speed, the temperature of the wafer is raised in the outside air, and the wafer is unnecessarily oxidized by oxygen and water vapor in the outside air.

Therefore, in a heat treatment process aimed at forming an oxide film, the formed oxide film becomes non-uniform, and in a heat treatment process aimed at impurity diffusion, the diffused impurities become non-uniform.

In addition, if the wafer withdrawal speed is slow, it is equivalent to performing low-temperature heat treatment in an oxygen atmosphere in the outside air, and at the same time, unnecessary oxidation occurs, and at the same time, oxidation occurs at the interface between the silicon and silicon oxide films. This will increase the surface state density.

Particularly in a MOS field effect transistor, this surface state density directly affects the threshold voltage, and this state is shown in FIG.

That is, in FIG. 3, a indicates the wafer withdrawal speed of 60c.
The distribution of the threshold voltage in the case of m/sec is shown, and b also shows the distribution of the threshold voltage in the case of 0.1 cm/sec.

Therefore, in case a above, since the wafer is cooled relatively rapidly, the number of surface state densities is small, and
There is little variation.

In case b, since the wafer is gradually cooled, the number of surface state densities increases due to the influence of oxygen in the outside air, and
There is a lot of variation.

From these facts, it can be seen that the insertion and withdrawal speeds during heat treatment in the manufacture of semiconductor devices need to be performed at low speeds while preventing outside air from entering the high temperature section.

By the way, a method shown in FIG. 4 can be considered as a method of preventing the intrusion of outside air.

In this method, an inert gas (nitrogen, argon, etc.) outlet 5 is provided near the insertion port 2 of the heat treatment furnace tube 1, and the inert gas is blown out from the inert gas outlet 5 during insertion and withdrawal. , the outside air is shielded by creating a gas curtain 6.

However, in this method, since the inert gas outlet 5 is attached to the heat treatment furnace tube 1, there is a problem that the inert gas outlet 5 is often damaged when the heat treatment furnace tube 1 is removed and cleaned. .

This invention was made to solve the above-mentioned inconveniences, and one embodiment thereof is shown in FIG.

In this figure, 7 is a purge pipe that is attached to the heat treatment furnace tube 1 by a method such as fitting it together, and an inert gas outlet 5 is provided in a part of this purge pipe 7, and inert gas is blown out from this part. It is configured like this.

With this configuration, the purge tube 7 can be removed when the heat treatment furnace tube 1 is removed or cleaned, and the inert gas outlet 5 can be prevented from being damaged.

In addition, by providing a plurality of inert gas outlet ports 5,
Needless to say, the intrusion of outside air can be more completely prevented.

Further, the other end of the purge pipe 7 may be fitted with a lid 3 as shown in FIG. 2 by rubbing or the like.

As explained above, in this invention, a purge pipe is provided at the outlet of the heat treatment furnace tube, and the inert gas is made to flow out from the purge pipe to create a gas curtain.This prevents outside air from entering the heat treatment furnace tube when wafers are taken in and out. less to do.

Furthermore, since the inert gas outlet is provided in the purge tube, there is an advantage that the inert gas outlet will not be damaged even when the heat treatment furnace tube is removed.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view of a conventional heat treatment furnace, Figures 2a and b are characteristic diagrams showing the temperature distribution inside the heat treatment furnace and the state of intrusion of outside air, and Figure 3 is when the wafer withdrawal speed is fast and slow. FIG. 4 is a sectional view showing a conventional method for preventing the intrusion of outside air, and FIG. 5 is a sectional view showing an embodiment of the present invention. In the figure, 1 is a heat treatment furnace tube, 2 is an insertion port, 3 is a lid, 4 is a heater, 5 is an inert gas outlet, 6 is a gas curtain, and 7 is a purge pipe. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Claims] 1. A heat treatment apparatus characterized in that a purge pipe having an inert gas outlet for creating a gas curtain is attached to the outlet of a heat treatment furnace tube.