JPH03185719A - Diffusion furnace - Google Patents

Abstract

PURPOSE:To prevent entry of oxygen into a reaction quartz tube and enable a stable semiconductor wafer processing wherein the wafer is not subjected to high temperature oxygen when it goes in and out of a furnace by placing at the reaction quartz tube and its port to the furnace a separate additional quartz tube with the same shape. CONSTITUTION:A cylindrical additional quartz tube 11 in contact with an inlet of a cylindrical reaction quartz tube 1 having a diameter equal to that of the reaction quartz tube 1 and length of 3 to 5 times the diameter is provided. In this case, the additional quartz tube 11 placed at the inlet of the reaction quartz tube shifts the position of oxygen entry to the right in the figure by its length and a temperature in the oxygen entry part is sufficiently low so that a wafer is not subjected to high temperature oxygen when it goes in and out of a furnace. Thus stable semiconductor wafer processing is possible.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to semiconductor manufacturing equipment, and particularly to the structure of a diffusion furnace.

[Conventional technology]

FIG. 3 is a schematic cross-sectional view of a conventional diffusion furnace.

Conventionally, this type of diffusion furnace includes a reaction quartz tube 1 for storing a semiconductor wafer 6 placed in a quartz port 5, and a heating tube located around the outer periphery of the reaction quartz tube 1, as shown in FIG. , a scavenger 4 provided at the opening at one end of the reaction quartz tube l, a saucer 7 provided adjacent to this opening, and a gas inlet provided at the other end of the reaction quartz tube 1. It consists of a mouth 2. Next, to explain the case of diffusing impurities into a semiconductor wafer, the semiconductor wafer 6 is placed in the quartz port 5, placed in the reaction quartz tube 1, and
This is done by treating glass at a predetermined temperature. At this time, N2 gas is flowed into the reaction quartz tube from the gas introduction tube 2,
This prevents air from entering the reaction quartz tube from the furnace opening 3A.

[Problem to be solved by the invention]

However, in the conventional diffusion furnace described above, the distance that air goes around from the furnace opening 3A to the reaction quartz tube 1 is usually about three times the diameter of the reaction quartz tube. In recent years, as wafers have become larger in diameter, this distance has also tended to become larger. At this time, the problem is the oxygen in the surrounding air, and the longer the distance of the surrounding air, the more oxygen will be present in the higher temperature parts of the reaction quartz tube.

When the quartz port is exposed to the furnace, the wafer is exposed to this high temperature oxygen. Therefore, the wafer 71 will be oxidized. Therefore, it becomes a problem in the case of a process in which it is desired to avoid oxidizing the waeno at all (even if only slightly). Further, for example, when controlling a thin and precise film thickness in a gate oxidation process, etc., it becomes a factor of variation. For example, if the furnace core tube diameter is 20 cm, the distance for oxygen to go around is approximately 60 cm.
m, and in a furnace used at 1000°C, the temperature at that point will be 500°C or higher, and Waeno 1 will be exposed to oxygen at 500°C or higher for every 4 people at the port.

An object of the present invention is to provide a diffusion furnace that solves this problem.

[Means to solve the problem]

The diffusion furnace of the present invention includes a cylindrical attached quartz tube that is in contact with the inlet of the cylindrical quartz tube for reaction, has the same diameter as the quartz tube for reaction, and has a length of 3 to 5 times the diameter. It consists of a tube.

〔Example〕 Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a schematic sectional view of a diffusion furnace showing an embodiment of the present invention. This diffusion furnace is provided with an accessory quartz tube 11 in contact with the scavenger 4. Other than that, it is the same as the conventional example. The diameter of this accessory quartz tube 11 is the same as that of the reaction quartz tube, for example, its diameter is 20 cm, and its length is 80 cm, which is four times as long. Further, this accessory quartz tube 11 has the function of an exhaust port 12 to the scavenger 4.

Let us now consider the circulation of air (that is, oxygen) in this diffusion furnace. In the case of this embodiment, the air inlet is considered to be the end 1A of the attached quartz tube 11, so
The oxygen wrap-around length is IB at 60 cm from LA. Since this point is inside the attached quartz tube 11, the temperature is close to room temperature, and unlike the conventional method, the number of people is 4.
It can be seen that the wafer is not exposed to high temperature oxygen at this time.

That is, the attached quartz tube 11 installed at the reactor quartz tube furnace mouth
However, since the oxygen wrapping position has been shifted to the right by that length, and the temperature of the oxygen wrapping portion has become sufficiently low, it can be seen that the problem at input/output 4 does not occur.

FIG. 2 is a schematic sectional view of a diffusion furnace showing another embodiment of the present invention. This diffusion furnace has N in the center of the attached quartz tube 11.
Two gas inlets 21 are provided. In the case of this embodiment, the effect of preventing oxygen leakage is greater than in the previous embodiment, and the oxygen leakage length is approximately 20 cm from the air circulation inlet 2B. The temperature in this part is lower than in the previous embodiment, almost at room temperature.

Furthermore, although the present invention has been described with reference to a diffusion furnace, HotWal
It can be easily inferred that this method can also be applied to an L type low pressure CVD furnace.

〔Effect of the invention〕

As explained above, in the present invention, by installing a separate quartz tube for reaction and an attached quartz tube of the same shape (it is better if there is an N2 gas inlet) at the mouth of the quartz tube for reaction, This has the effect of providing a diffusion furnace that can prevent oxygen from leaking into the tube, thereby enabling stable semiconductor wafer processing in which wafers are not exposed to high-temperature oxygen when people are out at 4 o'clock.

[Brief explanation of drawings]

FIG. 1 is a schematic sectional view of a diffusion furnace showing one embodiment of the present invention;
FIG. 2 is a schematic sectional view of a diffusion furnace showing another embodiment of the present invention, and FIG. 3 is a schematic sectional view of a diffusion furnace showing a conventional example. 1...Quartz tube for reaction, 2...Gas introduction part, 3...Heater, 4...Scavenger, 5...Quartz hoard , 6...Semiconductor wafer 7...Saucer, 11...Quartz tube for attachment, 12.Block/scavenger opening, 21...
...Introduction port.

Claims (1)

[Claims] It is characterized by comprising a cylindrical attached quartz tube that is in contact with the inlet of the cylindrical reaction quartz tube, has the same diameter as the reaction quartz tube, and has a length 3 to 5 times the diameter. diffusion furnace.