JP2678184B2 - Oxidation furnace - Google Patents

Description

Description: [Object of the Invention] (Field of Industrial 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, Japanese Patent Publication No.
And those disclosed in Japanese Examined Patent Publication No. 62-6342.

In all of these, a heating means for heating a wafer and a heating means for generating steam are arranged around a process tube for oxidizing a semiconductor wafer, and a combustion area for generating steam and an oxide film forming area are provided in the process tube. It is also used for.

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

(Problems to be Solved by the Invention) In the case where the inside of the process tube is also used as the combustion region for generating steam, the oxide film forming region in the process tube is affected by the heat of the combustion region, and the oxide film is formed. The temperature distribution in the formation area and the flow of wet gas are not uniform,
In particular, the wafer near the flame in the burning region had a non-uniform film thickness and the yield was poor.

On the other hand, in the case where the external combustion device is provided, since the steam is generated by the external combustion device which is separate from the process tube, the above-mentioned problem can be solved.

Further, for example, as in the device shown in FIG. 3 of JP-A-62-45128, pipes for introducing hydrogen gas and oxygen gas are provided in the combustion chamber of the external combustion device, and a heater is provided for only one of the pipes. There is something.

However, in the above apparatus, since only one of the two gases can be heated, the other gas that is not heated becomes inactive and the combustion reaction becomes insufficient.

Furthermore, in order to be able to heat both gases, Japanese Patent Laid-Open No. 55-
No. 90405, FIG. 1 of JP-A No. 62-185329, No. 1 of JP-A No. 60-186023, and No. 1 of JP-A No. 62-45182.
In the apparatus shown in the figure, a heater or the like is provided in the combustion chamber of the external combustion device, while a hydrogen gas introduction pipe, for example, is inserted long into the combustion chamber provided with the heater.

However, in the case of combusting each gas in a combustion chamber equipped with a heater, the insertion tip end region of the gas introduction pipe inserted into the combustion chamber is heated, but the insertion base end portion is not sufficiently heated and the combustion reaction There was a problem that was insufficient.

Further, in the case of combusting each gas in a combustion chamber equipped with a heater, even in the device disclosed in, for example, JP-A-61-91934, each gas is heated and combusted only after being introduced into the combustion chamber. Therefore, there is a problem that the combustion reaction becomes insufficient even in this case.

Further, in the case where the above-mentioned introduction pipe is inserted long, the hydrogen gas introduction pipe is inserted long into the combustion chamber equipped with the heater, and in order to prevent an explosion accident caused by non-combustion of hydrogen gas, hydrogen gas and oxygen gas are burned. Combustion compounded near the wall of the chamber.

Therefore, the vicinity of the wall surface is heated and devitrification, that is, the transparency is lost, and the molecules in the quartz constituting the combustion chamber are scattered as impurities in the combustion chamber and adhere to the steam, and the impurities are supplied into the process tube together with the steam. Therefore, there is a problem that the semiconductor wafer becomes defective.

In addition, since it is necessary to dispose the heat source on the tip side of the hydrogen gas introduction pipe long inserted in the combustion chamber as described above, there is a problem that the configuration becomes complicated, the manufacturing becomes difficult, and the cost becomes high.

Furthermore, in addition to the above example, there is also one that employs a condenser lens as a heat source on the tip side of the hydrogen gas introduction pipe, but in both cases, the combustion position of hydrogen gas is fixed, and the combustion position can be easily set freely. There is a problem that you cannot select. That is, depending on the type of process (particularly, the type of degree of oxidation), there is a method in which the amount of hydrogen gas and oxygen gas is variable by an external flow rate controller. In this case,
Since the sizes of the flames are different, it is preferable to freely select the combustion position of the hydrogen gas in order to prevent the devitrification, and it has been extremely difficult for the conventional device to select this position.

Therefore, an object of the present invention is to solve the above-mentioned conventional problems, and to activate both of hydrogen gas and oxygen gas by heating them, but to explode due to non-combustion of hydrogen gas. An object of the present invention is to provide an oxidation furnace which can prevent an accident, can be accurately combusted in the combustion apparatus, and has a simple structure and low cost.

Further, another object of the present invention is to make the combustion position freely changeable, so that impurities are not generated when steam is generated, an oxidation process with high yield can be executed, and moreover, the temperature distribution in the process tube can be improved. An object of the present invention is to provide an oxidation furnace that facilitates uniform control and increases the temperature distribution in the process tube and the uniformity of gas flow to ensure a long soaking length.

[Structure of the Invention] (Means for Solving Problems) An oxidizing furnace according to the invention of claim 1 is an external combustion device for combusting and combining hydrogen gas and oxygen gas to generate steam, and the external device. The external combustion device has a process tube that supplies the water vapor of the combustion device to oxidize the object to be processed, and a first heating unit that heats the object to be processed, and the external combustion device includes the hydrogen gas and the oxygen gas. And a combustion chamber for burning the hydrogen gas and the oxygen gas into the combustion chamber independently of each other, and the discharge end of the inner pipe is burned more than the discharge end of the outer pipe. It is characterized in that it has a gas introducing pipe of a double pipe structure protruding into the room, and a second heating means arranged around the gas introducing pipe and heating both gases in the pipe.

According to a second aspect of the present invention, in the oxidizing furnace according to the first aspect, the discharge end of the inner pipe is inclined downward.

An oxidizing furnace according to a third aspect of the present invention is the oxidizing furnace according to the first or second aspect, wherein the second heating means is a heater wire divided into two parts on both sides of the gas introducing pipe, and each of the heaters. And a pair of openable and closable housings that respectively support the wires.

The oxidation furnace according to the invention described in claim 4 is any one of claims 1 to 3.
In any one of the above, a flow rate controller that is connected to the gas introduction pipe and controls each flow rate of the hydrogen gas and oxygen gas supplied into the combustion chamber is provided, and the combustion is performed by changing each flow rate of the flow rate controller. The feature is that the combustion position is changed indoors.

(Operation) According to the invention described in claim 1, the following operation effects are obtained.

(A) The process temperature in the process tube and the temperature for heating the hydrogen gas and the oxygen gas can be independently controlled by the first and second heating means.

Moreover, by heating the gas introducing pipe for introducing both hydrogen and oxygen gas into the combustion chamber by the second heating means, the two gases do not come into contact with each other in the middle of the gas introducing pipe and both gases are combusted without fail. Burn in contact with the room. At this time, if oxygen gas is supplied to the outer pipe and hydrogen gas is supplied to the inner pipe, the discharge end of the inner pipe from which the hydrogen gas is discharged protrudes toward the combustion chamber side. Both gases come into contact with each other in the room and a combustion reaction occurs to generate steam. In this way, since the inner tube projects more than the outer tube,
Even if the combustion chamber itself is not directly heated, ignition can be performed from the discharge end of the inner pipe as soon as gas is supplied to the combustion chamber.

Even in the double pipe structure, when the outer pipe projects from the inner pipe as in the conventional case, when oxygen gas is supplied to the outer pipe and hydrogen gas is supplied to the inner pipe, combustion is performed in the outer pipe having a considerably small cross-sectional area. In addition, the flame may come into contact with the outer tube to deposit impurities resulting from the devitrification phenomenon, resulting in defective wafers or damage to the outer tube due to a rapid combustion reaction in a narrow outer tube. According to the first aspect of the present invention, since the inner pipe projects from the outer pipe, such precipitation of impurities and damage to the outer pipe can be prevented.

(B) Oxygen and hydrogen gas can be supplied to the combustion chamber in a heated state by the gas introduction pipe with a double pipe structure, so when supplying each gas to the combustion chamber in a state where only hydrogen gas is heated. Compared with, both gases are heated and both gases are activated, the reaction rate is improved, the combustion reaction is sufficiently performed, the ignition combustion becomes smooth and easy, and the combustion is surely caused, and the combustion efficiency is improved. improves.

(C) By providing the second heating means on the gas introduction pipe side of the double pipe structure, both gases are heated at the same time.
It is not necessary to dispose the heating means for each gas introduction pipe, the structure of the entire apparatus is simplified, and the apparatus can be downsized and the manufacturing cost can be reduced.

According to the second aspect of the present invention, when hydrogen gas is supplied to the inner pipe, the discharge end from which hydrogen gas is discharged protrudes toward the combustion chamber side. Occurs. A flame is generated in the combustion chamber due to this combustion, but the discharge end of the inner pipe to which hydrogen gas is supplied is inclined downward, so that the flame that tends to move upward may directly contact the wall surface of the combustion chamber. Since the property can be reduced, the devitrification phenomenon can be prevented, and at this time, impurities can be prevented from adhering to water vapor. This prevents impurities from being supplied into the process tube, so that the yield of the object to be processed can be improved.

According to the invention of claim 3, the second heating means comprises:
By having a case that can be opened and closed, during maintenance,
Since it is only necessary to open the casing, maintenance of the heater wire and the like becomes easy. Further, when cooling the gas introduction pipe, it is possible to rapidly cool it by opening it.

According to the invention described in claim 4, when the flow rates of the oxygen gas and the hydrogen gas are changed by the flow rate control depending on the degree of oxidation, the size of the flame and the combustion position in the combustion chamber are changed, so that the gas is discharged from the gas introduction pipe. The discharge position of the generated gas can be changed and the flame can be easily controlled so as not to contact the wall surface of the combustion chamber.

(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 described with reference to FIG.

Inside the tank 70, which is a high-pressure container, the process tube 1,
A heater 3 arranged around this, a cap 72 for sealing the open end of the process tube 1 during the process, an external combustion device 10 and the like are arranged. Then, the external combustion device 10
The supply pipe 60 and the gas inlet 2 of the process tube 1 are connected by a ball joint method in which quartz tubes are slid together.

With the ball joint structure, the distance between the external combustion device 10 and the process tube 1 can be shortened, and the condensation of water vapor can be prevented without using a tape heater or the like. When the distance is shortened in this way, the external combustion device
Although there is a concern about the heat effect of 10, the ball joint may be provided at a distance that does not have an adverse effect, or a partition plate for flame blocking may be formed on the supply pipe 60 side. Also, gas inlet 2
The connection between the supply pipe 60 and the supply pipe 60 is not limited to the ball joint method.

A supply system for supplying oxygen and hydrogen to the external combustion device 10, a pressure control system in the tank 70, a cooling system for the tank 70, etc. are provided, and a flow meter F, a pressure gauge PT, a flow controller. It consists of MFC, check valve CV, needle valve MV, three-way valve BV, safety valve RV, etc. Also,
A mixing trap 74 for balancing the pressure difference between the tank 70 and the process tube 1, a cooling reserve trap 76 for trapping the cooling water of the tank 70, and the like are provided.

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

Then, in the process tube 1 arranged in the tank 70 maintained at a high pressure, the semiconductor wafers 8 mounted on the boat 4 at predetermined intervals are arranged, and the inside of the process tube 1 is made to have a water vapor atmosphere. At the same time, by heating with the heater 3 as the first heating means, an oxide film is formed on the surface of the wafer 8.

In such a high-pressure oxidation furnace, there is an advantage that the oxidation temperature can be lowered and the oxidation time can be shortened as compared with the case where the same film thickness is obtained by the atmospheric pressure oxidation.

The apparatus of this embodiment has an external combustion device 10 separately from the process tube 1. The external combustion device 10 is arranged in a tank 70 in which the process tube 1 is arranged.

The external combustion device 10 burns oxygen gas and hydrogen gas to generate steam, and supplies the steam to the gas inlet 2 of the process tube 1.

 The external combustion device 10 has the following configuration.

That is, the introduction pipes 20 and 30 for independently introducing oxygen gas and hydrogen gas, and the introduction pipes 20 and 30 are arranged around the introduction pipes 20 and 30 to heat the gas in the introduction pipes 20 and 30 to a temperature equal to or higher than the ignition point. Heating means 40 as a second heating means, and the introduction pipe
It has a combustion chamber 50 connected to 20, 30 and combusting and combining oxygen gas and hydrogen gas to generate steam, and a supply pipe 60 for supplying this steam to the gas inlet 2 of the process tube.

The introduction pipes 20 and 30 are configured as coaxial double pipes,
In this embodiment, a hydrogen gas introduction pipe is provided inside the oxygen gas introduction pipe 20.
30 is arranged.

The oxygen gas introducing pipe 20 is integrally formed with the combustion chamber 50, and is made of quartz glass in this embodiment.
Further, a hydrogen gas introduction pipe arranged in the oxygen gas introduction pipe 20.
No. 30 is a nozzle provided at the tip of the nozzle as shown in FIG.
Tube connector 34 so that 33 is placed in the combustion chamber
Supported by

The hydrogen gas introducing pipe 30 is provided with 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 at an angle inclined obliquely downward with respect to the horizontal, for example, an angle inclined at 5 degrees.

Next, the combustion chamber 5 integrally formed of quartz glass
The 0, oxygen gas introduction pipe 20 and supply pipe 60 will be described.

The oxygen gas introducing pipe 20 is connected to the combustion chamber 50 at the connecting end 21a of the horizontal pipe 21, and a vertical pipe 22 is arranged at the other end side, and the vertical pipe 22 can introduce oxygen gas. There is.

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

One end of the supply pipe 60 is formed into a shape that can be ball-joined with the gas introduction port 2.

The supply pipe 60 is arranged around the combustion chamber 50, and the introduction pipes 20, 3
It may be configured such that it is not provided at one end on the side opposite to the connection end of 0. In this case, the device is downsized, and the flame is directly supplied to the pipe as compared with the case where the device is provided at the opposite end of the hydrogen gas introduction pipe 30.
It is possible to prevent the heat from invading the inside of the external combustion device 60 and reduce the thermal influence on the outside of the external combustion device 10.

Next, the heating means 40 arranged around the oxygen gas introduction pipe 20 and the hydrogen gas introduction pipe 30 which form a double pipe will be described. This heating means 40 includes half heaters 41 and 42 as the two heaters. The casings 43 and 44, which are arranged above and below the heavy pipe and respectively support the half heaters 41 and 42, are openably and closably supported via hinges as shown in FIG. There is.

Further, an R type thermocouple 45 is arranged to detect the temperature of the half-divided heaters 41, 42, and the temperature is detected by the thermocouple 45 so that the temperature is controlled at about 850 ° C. at all times. Has become.

Adjacent to the heating means 40, a support for supporting the combustion chamber 50 is provided. This support is 2 up and down
Cooling water for circulating the cooling water, which is formed from the divided lower and upper supports 55, 56 and uses the inside of each of the supports 55, 56 as a cooling unit for preventing heat release of the combustion chamber 50. Inlet 55a, 56
a and cooling water outlets 55b and 56b are provided. The cooling water outlet 55b of the lower support 55 and the cooling water inlet 56a of the upper support 56 are connected by a SUS flexible tube 58. Further, notches 55c, 56c are formed on the side surfaces of the respective supports 55, 56, and a flame detector 57 for detecting the flame in the combustion chamber 50 is arranged through the notches 55c, 56c. There is.

If an abnormal flame is detected by this detector 57,
The alarm signal is fed back to the system controller.

 Next, the operation will be described.

The external combustion device 10 employs the previously proposed heat carrying method (Japanese Patent Laid-Open No. 62-43751).

That is, the oxygen gas is introduced into the oxygen gas introducing pipe 20, for example, 5
/ Min while supplying hydrogen gas to the hydrogen gas inlet pipe 30
Supply H2 at 4.8 / min. The ratio of hydrogen gas and oxygen gas required for combustion to generate water vapor is a predetermined ratio, but the reason for supplying a large amount of oxygen gas as described above is as follows.
Oxygen gas that is not burnt is used as the process tube 1
This is because it is used as a carrier when water vapor is supplied to. Needless to say, this oxygen gas is also used for forming an oxide film.

Here, the oxygen gas and hydrogen gas supplied through the oxygen gas introduction pipe 20 and the hydrogen gas introduction pipe 30 are heated by the heating means 40 to, for example, a temperature equal to or higher than the ignition point of the hydrogen gas, and the energy required for combustion is Given.

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

Here, according to the experiment, the temperature of the heating means 40 is about 750 ° C.
In the case of, the temperature in the vicinity of the tip nozzle 33 of the hydrogen gas introduction pipe 30 is lower than the ignition point temperature of hydrogen gas, for example, 382 ° C.
However, the hydrogen gas ignited, but the temperature of the heating means 40 was 730 ° C.
No ignition occurred in the vicinity.

This experiment shows that even if the temperature at the combustion position is lower than the ignition point of hydrogen gas, when the hydrogen gas passes through the hydrogen gas introducing pipe 30, it is ignited if it is heated above the ignition point.

Needless to say, since there is no oxygen gas or air in the path of the hydrogen gas introduction pipe 20, there is no risk of ignition of hydrogen gas in the middle of the introduction pipe.

When hydrogen gas and oxygen gas are burned in this way, water vapor is generated, and this water vapor enters the process tube 1 through the supply pipe 60 and the gas introduction port 2 and contributes to the oxidation of a semiconductor wafer (not shown). .

Here, a flame is generated in the combustion chamber 50 by the above combustion, but by inclining the nozzle 33 of the hydrogen gas introduction pipe 30 obliquely downward with respect to the horizontal, the flame that tends to go upward is directly generated in the combustion chamber. Since it does not come into contact with the upper surface of 50, it is possible to prevent devitrification reduction that makes the combustion chamber 50 made of quartz opaque, and at this time, it is possible to prevent quartz from adhering to water vapor as an impurity. . Therefore, since such impurities are not supplied into the process tube 1, the yield of semiconductor wafers can be improved.

In this embodiment, since the external combustion device 50 burns hydrogen gas and oxygen gas to obtain steam, it is possible to prevent the heat generated during the burning from adversely affecting the process tube 1. Therefore, the temperature inside the process tube 1 can be easily controlled to be uniform, and the flow of the wet gas is also uniformed, so that the soaking length can be ensured to be long, the thickness of the oxide film can be uniformized, and the yield of the semiconductor wafer 8 can be improved. Can be improved.

Further, in the above-described embodiment, the reason why the external combustion device 10 is also arranged in the tank 70 is that the pressure in the tank is kept at a predetermined value, so that the external combustion device 10 causes water vapor to enter the process tube 1. It is not necessary to apply a special supply pressure to supply the external combustion device 10 to the tank.
This is because if it is arranged outside 70, the structure becomes complicated, such as the pressure for supply is applied.

It should be noted that the present invention is not limited to the above embodiment, and various modifications can be made within the scope of the present invention.

For example, the hydrogen gas introduction pipe 30, the oxygen gas introduction pipe 20,
It is not always necessary to form the coaxial double tube, and they may be separately connected to the combustion chamber 50.

In this case, the heating means 40 may be separately provided 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. When the flow rate of oxygen gas or hydrogen gas is changed by the flow rate controller MFC depending on the degree of oxidation, the combustion chamber 50
Since the size of the flame inside changes, the discharge position of the hydrogen gas introduction pipe 30 or the oxygen gas introduction pipe 20 with respect to the combustion chamber 50 can be easily changed so that this flame does not contact the wall surface of the combustion chamber 50. You can also do it. In this case, unlike the conventional device, since it does not require a heat source at the tip of the introduction tube,
The realization becomes easy.

According to the invention described in claim 1, the process temperature and the temperature for heating the hydrogen gas and the oxygen gas can be independently controlled,
Moreover, since the inner pipe projects beyond the outer pipe, it is possible to ignite from the discharge end of the pipe as soon as gas is supplied to the combustion chamber, without directly heating the combustion chamber itself. In addition, precipitation of impurities and damage to the outer tube can be prevented. In addition, the gas introduction pipe having the double-pipe structure activates both gases, improves the reaction rate, sufficiently performs the combustion reaction, and improves the combustion efficiency.

According to the invention described in claim 2, since the discharge end of the inner pipe is inclined downward, the possibility that the flame due to combustion directly contacts the wall surface of the combustion chamber is reduced, and the devitrification phenomenon is prevented. Since the impurities do not adhere to the water vapor, the yield of the object to be processed can be improved.

According to the third aspect of the present invention, the heating means is constituted by a housing that can be opened and closed, which facilitates maintenance.

According to the invention described in claim 4, since the flow rate of the oxygen gas and the hydrogen gas can be changed by the flow rate control to easily change the combustion position and the size of the flame in the combustion chamber, this flame is formed on the wall surface of the combustion chamber. It can prevent contact.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic explanatory view showing the overall configuration of a high pressure oxidation furnace according to an embodiment of the present invention, and FIG. 2 is an exploded view of an external combustion device applied to the high pressure oxidation furnace of FIG. Fig. 3 is a front view of the external combustion device of Fig. 2, 1 ... Process tube, 2 ... Gas inlet port, 8 ... Object to be processed, 10 ... External combustion device, 20 ... Oxygen gas Introducing pipe, 30 …… Hydrogen gas introducing pipe, 40 …… Heating means, 41, 42 …… Split heater, 50 …… Combustion chamber, 60 …… Supply pipe, 70 …… High pressure vessel.

Claims (4)

(57) [Claims] 1. An external combustor for combusting a hydrogen gas and an oxygen gas to generate steam, a process tube for supplying the steam of the external combustor to oxidize an object to be processed, and the object to be processed. A first heating means for heating the body; and the external combustion device, wherein the external combustion device independently burns the hydrogen gas and the oxygen gas in the combustion chamber that burns the hydrogen gas and the oxygen gas, respectively. A gas introduction pipe having a double-tube structure, which is composed of an inner pipe and an outer pipe to be introduced, and has a discharge end of the inner pipe protruding into the combustion chamber more than a discharge end of the outer pipe, and is arranged around the gas introduction pipe. And a second heating means for heating both gases in the tube. 2. The oxidizing furnace according to claim 1, wherein the discharge end of the inner pipe is inclined downward. 3. The heater according to claim 1, wherein the second heating means supports the heater wire divided into two parts on both sides of the gas introducing pipe, and supports the heater wire. And a pair of housings that can be opened and closed. 4. A flow rate controller according to any one of claims 1 to 3, which is connected to the gas introduction pipe and which controls each flow rate of the hydrogen gas and the oxygen gas supplied into the combustion chamber. And a combustion position in the combustion chamber is changed by changing each flow rate of the flow rate controller.