JPH01205425A - Oxidation furnace - Google Patents

Abstract

PURPOSE:To facilitate control for equalizing temperature distribution within a process tube and to improve uniformities of temperature distribution and gaseous flow within the process tube, by introducing hydrogen and oxygen gases into a combustion chamber of an external combustion apparatus while the combustion chamber or a gas inlet path is heated externally. CONSTITUTION:Oxygen and hydrogen gases are heated in inlet tubes to a temperature higher than an ignition point so that they are given an energy required for combustion. As soon as the hydrogen gas is fed in jet into a combustion chamber 50 through a tip nozzle 33 of a hydrogen inlet tube 30, the hydrogen gas comes into contact with oxygen gas to cause ignition. Thus, combustion is started. This combustion of the hydrogen and oxygen gases produces water vapor, which is fed into a process tube 1 via a supply tube 60 and a gas inlet port 2 and contributes to oxidation of a semiconductor wafer 8. Since the water vapor is obtained by combustion of hydrogen and oxygen gases within an external combustion apparatus 10, the process tube 1 is not be affected in any way by heat generated by the combustion. Accordingly, control for equalizing temperature distribution within the process tube 1 can be facilitated, while flow of wet gas also can be made uniform. As a result, uniform temperature can be ensured for a longer range and an oxide film having uniform thickness can be obtained. Thus, the yield of the semiconductor wafer 8 can be improved substantially.

Description

DETAILED DESCRIPTION OF THE INVENTION OBJECTS OF THE INVENTION (Industrial Field of Application) The present invention relates to an oxidation furnace for forming an oxide film on an object to be processed such as a semiconductor wafer.

(Prior art) As a conventional oxidation furnace of this type, for example, the
2 and Japanese Patent Publication No. 62-6342.

In both of these systems, a heating means for heating the wafer and a heating means for generating steam are placed around the process tube for oxidizing semiconductor wafers, and the inside of the process tube is divided into a combustion area for generating steam and an oxide film forming area. It is also used for both.

On the other hand, in JP-A-55-90405, an external combustion device for generating steam is arranged separately from the process tube, and hydrogen gas is brought into contact with a heat source at a temperature above its ignition point together with oxygen gas in this combustion chamber. , oxygen gas, and hydrogen gas are combusted and combined to obtain water vapor, which is then supplied into the process tube.

(Problems to be Solved by the Invention) In a device in which the inside of the process tube is also used as a combustion region for steam generation, the oxide film formation region in the process tube is affected by the heat of the combustion region, and the oxide film The temperature distribution in the formation region and the flow of wet gas were not uniform, and in particular, the film thickness of the wafer near the flame in the combustion region was not uniform, resulting in poor yield.

On the other hand, according to Japanese Unexamined Patent Publication No. 55-90405, water vapor is generated by an external combustion device separate from the process tube, so the above-mentioned problem can be solved.

However, in the above device, the hydrogen gas introduction pipe is inserted into the combustion chamber for a long time, and in order to prevent combustion accidents caused by non-combustion of hydrogen gas, hydrogen gas and oxygen gas are combusted and combined near the wall of the combustion chamber. There is.

Therefore, when the area near the wall is heated and loses clarity, meaning it loses its transparency, molecules in the quartz constituting the combustion chamber or impurities scatter into the combustion chamber and adhere to the water vapor, and these impurities enter the process tube along with the water vapor. There was a problem in that the semiconductor wafers supplied to the factory were defective.

Further, since it is necessary to arrange a heat source at the tip side of the hydrogen gas gas tube inserted for a long time into the combustion chamber, there are problems in that the structure is complicated, manufacturing is difficult, and the cost is high.

Furthermore, in addition to the above examples, there are also some that use a condensing lens as a heat source on the tip side of the hydrogen gas introduction pipe, and in both cases, the combustion position of hydrogen gas is fixed and it is easy to change the combustion position freely. There is a problem that it is not possible to select the amount of hydrogen gas or oxygen gas depending on the type of process (especially the type of degree of oxidation). In this case, since the size of the flame is different, in order to prevent the above-mentioned devitrification, it is preferable to be able to freely select the combustion position of the hydrogen gas, and this selection has been extremely difficult with conventional devices.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to solve the above-mentioned conventional problems, and to facilitate uniform control of temperature distribution within the process tube by arranging an external combustion device for generating steam outside the process tube. By improving the uniformity of temperature distribution and gas flow inside the tube, a long soaking length can be ensured, and impurities are not generated when steam is generated, making it possible to perform oxidation treatment with a high yield, and the configuration is simple. Our goal is to provide a low-cost oxidation furnace.

"Structure of the Invention" (Means for Solving Problems) The present invention performs oxidation treatment by supplying steam generated by combustion and combination of hydrogen gas and oxygen gas in an external combustion device into a process tube. Preferably, the combustion chamber or the gas introduction path of the external combustion device is configured to allow the hydrogen gas and oxygen gas to flow into the combustion chamber while heating the external combustion device. The external combustion device includes an introduction pipe for introducing oxygen gas and hydrogen gas independently, and a heating device that is placed around one or both of the introduction pipes and heats the gas in the introduction pipe to a temperature above the ignition point. and oxygen gas, at least one of which is heated.

The method may be configured to include a combustion chamber that introduces hydrogen gas and brings it into contact with each other to combust and combine them to produce urine vapor, and a supply pipe that supplies this vapor to the gas inlet of the process tube. can.

(Function) One or both of hydrogen gas and oxygen gas is heated to a temperature equal to or higher than the ignition point temperature of the gas at the introduction pipe section which is in the middle of the path for introducing and mixing hydrogen gas and oxygen gas into the combustion chamber.

If both of the above gases are introduced into the combustion chamber in this state, the two gases will come into contact and mix, resulting in combustible combination and generation of water vapor. Steam can be similarly generated by introducing both of the above gases into the tank. In this way, the present invention does not have a heat source inside the combustion chamber, and only heats the combustion chamber or the gas introduction path from the outside before introducing gas into the combustion chamber.
Since combustion can be carried out within the combustion chamber, the structure can be simplified and the cost of the device can be reduced. Moreover, since a heat source is not required on the discharge end side of the gas introduction pipe, it becomes easy to freely select the position of the discharge end of the gas introduction pipe. .

It is also separate from the process tube that performs the oxidation treatment (
Since this external combustion device is provided, the influence of heat from this external combustion device on the process tube is reduced, and it is easier to control the uniformity of heat in the oxide film forming area within the process tube, which improves the uniformity of the flow of wet gas. Since uniformity can be ensured, a long uniformity can be ensured, and an oxidation furnace with a high yield can be provided.

(Example) Hereinafter, an example in which the present invention is applied to a high-pressure oxidation furnace for semiconductor wafers will be specifically described with reference to the drawings. .

First, the overall structure of the high-pressure oxidation furnace will be explained with reference to FIG. A heater 3 placed around this. A cap 72 that seals the open end of the tube during processing
and external combustion equipment 10, etc. are arranged.

, and the connection between the supply pipe 60 of [C2 said external combustion device]-〇 and the gas introduction 1-12 of [Bus.
It uses the hole join method, in which quartz tubes are rubbed together. .

By using the pole join I''fM configuration, the distance between the external combustion device 10 and the process tube can be shortened, and water vapor condensation can be prevented without the need for a tape heater or the like.

In addition, if there is a concern that the heat effect of the external combustion device 10 may be affected by the heat effect on the joints arranged at a short distance in this way, it is necessary to install a hole joint at a distance that will not have any adverse effects, or to install a flame shield on the supply pipe 60 side. You may also form a partition plate for use. Also,
The connection between the gas introduction system 2 and the supply pipe 60 is not limited to the above-mentioned pole joint 1 to force type. A pressure control system in the tank 70, a cooling system for the tank 70, etc. are provided, and the flow meter 1 pressure cage P-
I゛, flow controller MFC1 check valve CV, 21 dollar half MV, square valve 13V, safety valve knife? ■It is composed of etc. Also, a mixing tank trap 74 is used to balance the pressure difference between the tank 70 and the process tube 1.
゜Cooling refill to drain the cooling water in tank 70→
) Web I to wrap 76, etc. are provided.

The pressure inside the tank 70 will be increased to about 10 atmospheres, and a safety valve RV and a pressure gauge F3 are provided to prevent an explosion inside the tank 70.

Semiconductor wafers 8 mounted on the boat 4 at predetermined intervals are placed in the process tube 1 placed in a tank 70 maintained at high pressure, and a water vapor atmosphere is created in the process tube 1. In addition, heater 3
By heating the wafer 8, an oxide film is formed on the surface of the wafer 8.

Such a high-pressure oxidation furnace has the advantage that the oxidation temperature can be lowered and the oxidation time can be shortened compared to the case where the same film thickness is obtained by normal pressure oxidation.

The apparatus of this embodiment has an external combustion device] separately from the process tube. This external combustion device N10 is arranged in a tank 70 in which the process tube 1 is arranged.

The external combustion device TO burns oxygen gas and hydrogen gas to generate water vapor, and supplies this water vapor to the gas inlet 2 of the process tube 1. .

This external combustion device 10 has the following configuration.

Zunawaji has an introduction pipe 20.30 for introducing oxygen gas and hydrogen gas independently, and is arranged around this introduction pipe 20.30 to heat the gas in the introduction pipe 20.30 to a temperature above the ignition point. heating means 40 for heating up to
The combustion chamber 50 is connected to the combustion chamber 50 and generates water vapor by combustion and combining oxygen gas and hydrogen gas, and the supply pipe 60 supplies the water vapor to the gas inlet 2 of the process tube.

The introduction pipes 20 and 30 are configured as coaxial double pipes, and in this embodiment, the hydrogen gas introduction pipe 30 is disposed inside the oxygen gas introduction pipe 20.

Note that the oxygen gas introduction pipe 20 is constructed integrally with the combustion chamber 50, and is constructed of quartz glass in this embodiment. Further, the hydrogen gas introduction pipe 30 disposed within the oxygen gas introduction pipe 20 is supported by a tube connector 34 so that the nozzle 33 provided at its tip is disposed within the combustion chamber, as shown in FIG. ing.

The hydrogen gas introduction pipe 30 includes a vertical pipe 32 for introducing hydrogen gas at one end of a horizontal pipe 31, and the nozzle 33 is formed at the other end.

As shown in the figure, the nozzle 33 is formed obliquely downward and inclined at an angle fS with respect to the horizontal, for example, at an angle of 5 degrees.

Next, the combustion chamber 50 is integrally formed of quartz glass.
, the oxygen gas introduction pipe 20 and the supply pipe 60 will be explained. .

The oxygen gas introduction pipe 20 is connected to the connecting end 2 of the horizontal pipe 21]
, a communicates with the combustion chamber 50, and a vertical pipe 22 is disposed at the other end, through which oxygen gas can be introduced.

Further, the combustion chamber 50 having the oxygen gas introduction pipe 20 at one end of a hollow cylindrical shape has a structure in which the supply pipe 60 is connected to the other end.

The supply pipe 60 is formed in such a shape that one end thereof can be ball-jointed with the gas inlet 2.

Note that the supply pipe 60 is arranged on the circumferential surface of the combustion chamber 50, and the introduction pipe 2
It is also possible to have a configuration in which it is not provided at one end opposite to the 0.30 connection end. In this case, the device can be made smaller, and
Compared to the case where the flame is provided at the opposite end of the hydrogen gas introduction pipe 30, it is possible to prevent the flame from directly entering the supply pipe 60, and the thermal influence on the outside of the external combustion device 10 can be reduced.

Next, the heating means 40 arranged around the oxygen gas introduction pipe 20 and the hydrogen gas introduction pipe 30 that constitute a double pipe will be explained.
As shown in FIG. Supported to open and close freely.

Further, an R-type thermocouple 45 is disposed at the edge of the half-split type heaters 41 and 42 for temperature detection, and this thermocouple 45
By detecting the temperature at , the temperature is constantly controlled at, for example, about 850°C.

A support body for supporting the combustion chamber 5o is provided adjacent to the heating means 40. This support body is formed from a lower support body 55°56 which is divided into upper and lower halves,
In order to make the inside of each support body 55, 56 a cooling part for preventing heat release from the combustion chamber 50, cooling water inlets 55a, 56a and cooling water outlets 55b, 56 for circulating cooling water are provided.
b is provided. Note that the cooling water outlet 55 b of the lower support 55 and the cooling water inlet D 56 a of the upper support 56 are connected by an SUS flexible tube 58 . Furthermore, cutouts 55. c, 56c are formed, and notches 55c, 56c are formed.
A flame detector 57 for detecting flame within the combustion chamber 50 is disposed through the combustion chamber 50.

When an abnormal flame is detected by this detector 57,
The alarm signal is fed back to the system controller.Next, the operation will be explained.

[External Combustion Device] 0 employs the previously proposed heat carrying method (Japanese Patent Application No. 62-43751).

That is, for example, 50% of oxygen gas is introduced into the oxygen gas introduction pipe 20.
! On the other hand, hydrogen gas H2 is supplied to the hydrogen gas introduction pipe 30 at a rate of 4.8i77 minutes. .

Note that hydrogen gas is required for combustion to generate water vapor.

Although the ratio of oxygen gas is a predetermined ratio, the reason why a large amount of oxygen gas is supplied as described above is that the oxygen gas that is not used for combustion is used as a carrier when supplying water vapor to the process tube 1-. It is. It goes without saying that this oxygen gas is also used to form an oxide film.

Here, the oxygen gas introduction pipe 20. Oxygen gas and hydrogen gas supplied through the hydrogen gas introduction pipe 30 are heated by the heating means 40.
For example, hydrogen gas is heated to a temperature above its ignition point, providing the energy necessary for combustion.

Then, at the moment when hydrogen gas is released from the tip nozzle 33 of the hydrogen gas introduction pipe 30 into the combustion chamber 50, it comes into contact with the hydrogen gas or oxygen gas, ignites, and starts combustion.
・Konaru.

According to experiments, the temperature of the heating means 40 is about 750.
In the case of °C, hydrogen gas will not ignite even if the temperature is near the tip nozzle 33 of the hydrogen gas pipe 30 or at a temperature lower than the ignition point temperature of hydrogen gas, for example 382 °C.
This experiment shows that even if the temperature at the combustion position is lower than the ignition point of hydrogen gas, the hydrogen gas will not ignite if the temperature is around 730℃. If it is heated above its ignition point, it will ignite.

It goes without saying that since there is no oxygen gas or air in the middle of the path of the hydrogen gas introduction pipe 20, there is no risk of hydrogen gas igniting in the middle of the introduction pipe. When it burns, steam is generated, and this steam is passed through the supply pipe 60° gas introduction n 2
It enters the process tube 1 through the wafer and contributes to the oxidation of a semiconductor wafer (not shown).

Here, either a flame is generated in the combustion chamber 50 due to the above-mentioned combustion, or by tilting the nozzle 33 of the hydrogen gas introduction pipe 30 diagonally downward with respect to the horizontal direction, the flame tends to move upward directly into the combustion chamber. Since there is no contact with the top surface of 50,
It is possible to prevent devitrification reduction in which the combustion chamber 50 made of quartz becomes opaque, and at this time, it is possible to prevent quartz from adhering to water vapor as an impurity7.
Since such impurities are not supplied into the process tube, the yield of semiconductor wafers can be improved.

In this embodiment, the external combustion device 50 generates hydrogen gas.

Since water vapor is obtained by burning oxygen gas, the heat generated during combustion can be prevented from having an adverse effect on the process tube. Therefore, the temperature inside the process tube 1 can be easily controlled to be uniform, and the flow of gas from the web 1 to the web 1 is also made uniform, ensuring a long soaking length. , the yield of semiconductor wafers 8 can be improved.

In the embodiment described above, the reason why the external combustion device 10 is also placed inside the tank 70 is that the pressure inside the tank is maintained at a predetermined value. It is not necessary to apply a special supply pressure to supply water vapor, and if the external combustion device]○ is placed outside the tank 70, the difference will be caused by the need to apply pressure for supply and the configuration will be complicated. This is to become.

Note that the present invention is not limited to the above embodiments,
Various modifications are possible within the scope of the invention.

For example, hydrogen gas introduction pipe 30. The oxygen gas introduction pipe 20 does not necessarily need to be constructed as a coaxial double pipe, and may be constructed so as to be connected to the combustion chamber 50 separately.

In this case, the heating means 40 may be provided separately in each introduction pipe, or may be provided in either one of the hydrogen gas introduction pipe 30 or the oxygen gas introduction pipe 20. Also, depending on the degree of oxidation, the flow rates of oxygen gas and hydrogen gas can be adjusted according to the flow rate of the flow rate controller MFC.
, the size of the flame inside the combustion chamber 50 changes, so the hydrogen gas intake pipe 30 or the oxygen gas introduction pipe 20 is connected to the combustion chamber 50 so that the flame does not come into contact with the wall surface of the combustion chamber 50. It is also possible to have a structure in which the discharge position can be easily changed. In this case, unlike conventional devices, the structure does not require a heat source at the tip of the introduction tube, so it is easy to implement.

"Effects of the Invention" As explained above, according to the present invention, since the external combustion device for generating steam is disposed outside the process tube, it becomes easy to uniformly control the temperature distribution inside the process tube. The gas flow can be made uniform, and the yield of objects to be processed during oxidation treatment can be improved.

Furthermore, since there is no need to dispose any heat source within the external combustion chamber, the structure of the external combustion device is simplified, and the structure of the entire oxidation furnace is simplified, thereby reducing costs. .

In addition, since there is no need to provide a heat source at the tip of the hydrogen or oxygen introduction tube, it is easy to freely select the tip position of the introduction tube. It is possible to easily prevent the devitrification phenomenon that occurs when the flame comes into contact with the wall surface of the room, and it is possible to prevent impurities from flowing into the process tube, thereby contributing to an improvement in the yield of objects to be processed.

[Brief explanation of the drawing]

FIG. 1 is a schematic explanatory diagram showing the overall configuration of a high-pressure oxidation furnace according to an embodiment of the present invention, FIG. 2 is an exploded perspective view of an external combustion device applied to the high-pressure oxidation furnace of FIGS. 1-3, and FIG. is a front view of the external combustion device shown in Fig. 2, 1... process tube, 2... gas introduced 1.8... object to be processed,] 0...
External combustion device, 20... Oxygen gas introduction pipe, 30... Hydrogen gas introduction pipe, 40... Heating means, 41.42... Split type heater,
50... Combustion chamber, 60... Supply pipe, 70... High pressure container. Agent Patent attorney Inoue - (1 other person) -20=

Claims (1)

[Claims] An oxidation treatment is performed by supplying water vapor generated by combustion and combination of hydrogen gas and oxygen gas in an external combustion device into a process tube, wherein the combustion chamber of the external combustion device or the gas An oxidation furnace characterized in that the hydrogen gas and oxygen gas are allowed to flow into the combustion chamber while the introduction path is heated from the outside.