JP3242244B2 - Oxidation treatment apparatus and oxidation treatment method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an oxidation treatment apparatus and an oxidation treatment method.

[0002]

2. Description of the Related Art In the manufacture of semiconductor devices, for example, there is an oxidation treatment step of forming an oxide film on the surface of a semiconductor wafer. As one method of the oxidation treatment, a semiconductor wafer is steamed at a high temperature in a processing furnace. And oxidizing (wet oxidizing) by contacting with a gas. In order to perform such an oxidation treatment, for example, Japanese Patent Publication No. 63-605
No. 28, JP-A-63-210501, etc., react hydrogen gas with oxygen gas (combustion).
There is known a method in which a combustion device for generating steam is provided outside the processing furnace independently, and steam generated by the combustion device is supplied to the processing furnace through a steam supply pipe.

According to this method, unlike the method in which hydrogen gas and oxygen gas are burned in a processing furnace to generate steam, the heating state in the processing furnace can be controlled separately from the operating state of the combustion device. Therefore, it is possible to perform the oxidation treatment on the semiconductor wafer in the processing furnace with high reliability, safety and reproducibility.

[0004]

In such an oxidation treatment, how to improve the quality of the oxide film is an important issue, and it is necessary to select combustion conditions of a combustion apparatus, temperature conditions of a processing furnace, and the like. The film quality has been improved. However, in the current configuration of the oxidation treatment apparatus, the conditions to be selected are limited, and there are some which are close to the limit in improving the film quality. Therefore, attention has been paid to the fact that low-pressure CVD has been successful in improving the film quality by a film forming process under reduced pressure, and a similar idea has been proposed in which the oxidation process is performed under reduced pressure.

[0005] However, if the oxidation treatment in the processing furnace is performed under reduced pressure, the reaction (combustion) between hydrogen gas and oxygen gas in the combustion device becomes unstable, and it becomes difficult to supply steam stably. In addition, there is a problem that the danger of explosion due to hydrogen gas is increased, and it has been difficult to realize wet oxidation treatment under reduced pressure.

[0006] The present invention has been made in view of such circumstances, and has as its object to provide an oxidation treatment apparatus and an oxidation treatment method that enable wet oxidation treatment under reduced pressure.

[0007]

According to a first aspect of the present invention, there is provided an oxidation treatment apparatus for oxidizing an object to be processed at a high temperature, and a decompression means for depressurizing the treatment furnace. A combustion device provided outside the processing furnace for burning hydrogen gas and oxygen gas to generate steam, a steam supply line connecting the combustion device to the processing furnace, and a steam supply line connected to the steam supply line. It is characterized in that a throttle portion for generating a pressure difference between the combustion device side and the processing furnace side is provided.

Further, the oxidation treatment apparatus according to the second aspect of the present invention is based on the premise of the first aspect, wherein the throttle portion is provided in multiple stages along the steam supply pipe.

Further, the oxidation treatment apparatus according to a third aspect of the present invention is based on the premise of the first or second aspect, wherein a heating section for heating the steam immediately after passing through the throttle section is provided in the steam supply pipe line. It is characterized by being provided.

Further, in the oxidation treatment method according to the present invention, preferably, a step of reacting hydrogen gas and oxygen gas to generate steam, and the reduced pressure is directly applied to the reaction in a processing furnace in which the steam is reduced in pressure. The method is characterized by comprising a step of supplying in a pressure-blocked state so as not to act, and a step of oxidizing by bringing the object into contact with the steam while heating the object in the depressurized processing furnace.

[0011]

According to the first aspect of the present invention, since the steam supply pipe connecting the combustion device and the processing furnace is provided with the throttle portion for generating a pressure difference between the combustion device side and the processing furnace side, the processing furnace By reducing the pressure, the effect of the reduced pressure on the combustion device is reduced or eliminated, and stable combustion in the combustion device becomes possible. As a result, the supply of water vapor can be stabilized and the safety can be improved. Therefore, wet oxidation can be performed under reduced pressure, and the quality of the oxide film can be improved.

According to the second aspect of the present invention, a large pressure difference is caused by a multistage throttle portion so that the pressure on the combustion device side is close to normal pressure and the pressure on the processing furnace side is sufficiently low without a sudden pressure change. And further stabilization of combustion and further improvement of film quality can be achieved.

According to the third aspect of the present invention, since the steam immediately after passing through the throttle section is heated by the heating section, dew condensation of the steam due to the pressure change is prevented, and the film quality can be further improved.

According to the fourth aspect of the present invention, since the wet oxidation of the object to be processed is performed under reduced pressure, the oxidation rate is reduced and the thickness of the oxide film formed on the object to be processed can be easily controlled. And the film quality can be improved and an extremely thin film can be formed.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to the accompanying drawings.

In FIG. 1 showing the overall structure of an oxidation treatment apparatus, reference numeral 1 denotes a semiconductor wafer W to be processed, for example, 850.
This processing furnace 1 is a vertical processing furnace for performing an oxidation treatment at a high temperature of about ° C. The processing furnace 1 includes a vertically long cylindrical heat-resistant, for example, quartz-made reaction tube 2 having an open lower end. The reaction tube 2 becomes a highly airtight container when the lower end opening is closed by the lid 3. A lid 3 for opening and closing the lower end opening is disposed below the reaction tube 2. On the lid 3, a large number of semiconductor wafers W are vertically spaced in multiple stages (for example, 150). The wafer boat 4 is supported via a heat retaining cylinder 5.

The lid 3 is connected to an elevating mechanism 6 for carrying the wafer boat 4 in and out of the reaction tube 2 and opening and closing the lid 3. A heater 7 for heating the inside of the reaction tube 2 to a desired temperature, for example, about 800 to 1000 ° C., is provided around the reaction tube 2, and an outer shell 9 is further provided on the outer periphery thereof through a heat insulating material 8.

A steam introduction pipe 10 is integrally provided on one side (lower side wall) of the reaction tube 2, and the base side of the steam introduction pipe 10 is integrally formed with the tube wall of the reaction tube 2 to rise upward. After being guided, it is opened toward the water vapor introduction port 11 formed in a concave shape at the upper end portion in the reaction tube 2. An exhaust pipe 12 is integrally provided on the other side (lower side wall) of the reaction tube 2, and the exhaust pipe 12 is provided with a pressure reducing pump 13 as a pressure reducing means for reducing the pressure inside the reaction tube 2. 14 is airtightly connected via a flange joint 16 provided with a double O-ring 15.

An opening / closing valve 17 composed of, for example, an angle valve is interposed in the pressure reducing pipe 14 and a bypass pipe 18 for bypassing the opening / closing valve 17 is connected.
An opening / closing valve 19 composed of, for example, an air operated valve and a pressure control valve 20 composed of, for example, a piezo valve are interposed therebetween. A predetermined pressure, for example, 300 to 5
When the pressure is reduced to about 00 Torr, the pressure is first detected by a pressure sensor 21 provided in
The on-off valve 17 is opened to reduce the pressure to a predetermined pressure. Thereafter, the on-off valve 17 of the pressure reducing pipe 14 is closed and the on-off valve 19 of the bypass pipe 18 is opened to maintain the predetermined pressure by the pressure control valve 20. To be controlled by the controller 22. The downstream side of the pressure reducing pipe 14 is connected to a factory exhaust duct (not shown).

On the other hand, a combustion (reaction) device 23 for burning (reacting) hydrogen gas and oxygen gas to generate steam is connected to a steam introduction tube 10 of the reaction tube 2 via a steam supply line 24. I have. As shown in FIG. 3, the combustion device 23 includes a vertically long cylindrical heat-resistant combustion vessel 25 made of, for example, quartz, and the bottom of the combustion vessel 25 is made of quartz that extends integrally below the combustion vessel 25. A gas introduction pipe 26 is provided. The gas introduction pipe 26 has a double pipe structure, and has a hydrogen gas introduction pipe 27 at the center and an oxygen gas introduction pipe 28 at the outer periphery. Central hydrogen gas inlet pipe 27
Has a connection port 27a projecting downward through the closed lower end portion of the outer oxygen gas introduction pipe 28, and the outer oxygen gas introduction pipe 28 has a connection port 28 projecting outward from one side from the lower side.
a.

As shown in FIG. 1, a switching valve 29 and a flow control mechanism 3 are connected to a connection port 27a of the hydrogen gas introduction pipe 27.
In addition, a hydrogen gas source 31 is connected via a valve 0 and a nitrogen gas source 33 is connected via a pipe branched from a switching valve 29 and a flow control mechanism 32. An oxygen gas source 35 is connected to a connection port 28 a of the oxygen gas introduction pipe 28 via a flow rate control mechanism 34.

As shown in FIG. 3, a flat circular recess 36 is integrally formed at the center of the bottom in the combustion vessel 25, and the upper end of the oxygen gas introducing pipe 28 is connected to the bottom of the recess 36. . A quartz diffusion plate 37 of an appropriate width and an annular shape is formed integrally with the recess 36 at a substantially middle portion in the depth direction like a horizontal partition wall. The upper end of 27 is provided continuously.

At a position slightly lower than the diffusion plate 37 of the hydrogen gas introduction pipe 27, a hydrogen gas ejection nozzle 38 having a small diameter and also serving to prevent backflow of oxygen gas is integrally formed. An annular space 39 formed below the diffusion plate 37 in the recess 36 communicates with the oxygen gas introduction pipe 28, and the oxygen gas is diffused from the annular space 39 into the combustion vessel 25 and blows out. 37 is provided with a plurality of small-diameter oxygen gas ejection nozzles 40 that are widely dispersed.

A gas heater 41 is provided around the gas inlet pipe 26 having the double pipe structure. The gas heating heater 41 heats the hydrogen gas and the oxygen gas that are conducted to the hydrogen gas introduction pipe 27 and the oxygen gas introduction pipe 28 to a temperature equal to or higher than the auto-ignition temperature, and the heated hydrogen gas and the oxygen gas are supplied to the hydrogen gas ejection nozzle. 38 and oxygen gas jet nozzle 4
By spraying from 0 into the combustion vessel 25 and mixing, the flame F is raised and burned. This combustion produces steam. A heat insulating material 42 is interposed between the gas heating heater 41 and the bottom of the combustion vessel 25, and a cooling mechanism 43 composed of, for example, a water-cooled jacket for cooling this to about 500 ° C. is provided around the combustion vessel 25. It is arranged. At the top of the combustion vessel 25, a steam supply pipe 24 made of quartz is integrally formed so as to protrude, and this steam supply pipe 24 is connected to the steam introduction pipe 10 of the reaction tube 2 as shown in FIG. Joint 4 with O-ring 44 interposed
5 is hermetically connected.

In the steam supply line 24,
As shown in FIG. 2, an orifice 46, for example, a quartz orifice 46 for producing a pressure difference (P1-P2) is integrally provided between the combustion device 23 and the processing furnace 1 side. This orifice 46
By selecting the size and thickness of the bore with respect to the inner diameter of the steam supply pipe 24, for example, the pressure P2 on the processing furnace 1 side is about 300 to 500 Torr and the pressure P1 on the combustion apparatus 23 side is about 600 Torr. It is composed of As shown in FIG. 1, the steam immediately after passing through the orifice 46 is, for example, 2
Steam heater 4 which is a heating unit for heating to about 00 ° C.
7 is provided to prevent the dew condensation of water vapor caused by a pressure change (adiabatic expansion) accompanying the passage of the orifice 46.

Next, the operation of the oxidation treatment apparatus having the above configuration will be described. First, the combustion vessel 2 is supplied from the nitrogen gas source 33.
5 and the processing furnace 1 through a steam supply line 24.
The inside of the reaction tube 2 is replaced with nitrogen gas by evacuating the inside of the reaction tube 2 through the decompression tube 14 and the decompression pump 13 while supplying the semiconductor wafer W to the semiconductor wafer W. Is loaded into the reaction tube 2 together with the heat retaining tube 5. Next, the reaction tube 2 is controlled by the pressure control by the controller 22 while the supply of the nitrogen gas is continued.
After the pressure in the inside is reduced to a predetermined pressure, for example, 400 Torr, the nitrogen gas source 33 is switched to the oxygen gas source 35 while maintaining this pressure.
And the inside of the reaction tube 2 is replaced with oxygen gas.

Next, while maintaining the pressure, the flow rate ratio of hydrogen gas to hydrogen gas from the hydrogen gas source 31 is, for example, 1: 1.
The hydrogen gas and the oxygen gas are heated by, for example, about 850 ° C. by the gas heating heater 41 and burned in the combustion vessel 25 to generate steam. The semiconductor wafer W is subjected to a required wet oxidation treatment by supplying it into the reaction tube 2 maintained at a reduced pressure of 400 Torr and at a predetermined temperature of, for example, 850 ° C. The hydrogen gas and the oxygen gas supplied into the combustion vessel 25 burn at a ratio of about 2 to 1 according to the stoichiometry. Therefore, although the oxygen gas is slightly excessively supplied, the excess oxygen gas acts as a carrier gas for water vapor and contributes to the oxidation treatment in the reaction tube 2.

When the wet oxidation treatment is to be performed under reduced pressure, a reduced pressure acts on the combustion device 23 from the reaction tube 2 maintained at a reduced pressure via the steam supply line 24, and the stable combustion in the combustion device 23 is performed. Combustion may be hindered. Therefore, an orifice 46 for generating a pressure difference between the combustion device 23 and the processing furnace 1 is provided in the steam supply line 24 connecting the combustion device 23 and the reaction tube 2 of the processing furnace 1. The orifice 46 buffers or cuts off the reduced pressure that is going to act directly on the combustion device 23 from the second through the steam supply line 24, so that stable combustion in the combustion device 23 is ensured. As a result, the supply of steam can be stabilized and safety can be improved.
Wet oxidation treatment under reduced pressure is possible, and the quality of the oxide film can be improved.

That is, as this oxidation treatment method, a step of reacting hydrogen gas and oxygen gas to generate steam, and the step of reducing the steam directly into the reaction tube 2 of the processing furnace 1 in which the steam is reduced, are directly applied to the reaction. Supplying the semiconductor wafer W as an object to be processed in the reaction tube 2 of the decompressed processing furnace 1 while heating the semiconductor wafer W in contact with the water vapor so as to perform an oxidation treatment And

Therefore, since the wet oxidation treatment of the semiconductor wafer W is performed under reduced pressure, the oxidation rate is slowed down, the control of the thickness of the oxide film formed on the semiconductor wafer W becomes easy, and the film quality is improved. In addition, it becomes easy to form an extremely thin film (for example, about 50 Å). Further, since the steam immediately after passing through the orifice 46 is heated by the steam heater 47, dew condensation of the steam due to the pressure change is prevented, and the film quality can be further improved.

Further, in the combustion device 23, the oxygen gas ejecting nozzle 40 projects above the tip of the central hydrogen gas ejecting nozzle 38 and is released far away to the periphery and is widely dispersed. The gas is diffused and ejected in a wide range around the gas, and the flame F becomes thicker in the radial direction and shorter in the height direction in the combustion vessel 25, so that the gas is efficiently burned. Therefore, even if the pressure is somewhat reduced in the combustion vessel 25 through the steam supply pipe 24, the flame F is not elongated and the combustion is not unstable.

After the oxidation treatment is completed in this way,
In the reverse procedure, the supply of hydrogen gas was stopped, the replacement with oxygen gas in the processing furnace and the replacement with nitrogen gas were sequentially performed, and the decompression pump 13 was stopped to return the inside of the reaction tube 2 to normal pressure. The semiconductor wafer W may be unloaded from the inside of the reaction tube 2 by the elevating mechanism 6 together with the wafer boat 4 and the heat retaining cylinder 5.

FIG. 4 shows a modification of the throttle provided in the steam supply line 24. A quartz orifice 4 is provided at an appropriate interval along the longitudinal direction of the steam supply pipe 24.
6 are provided in multiple stages (four stages in the illustrated example) and integrally, and the steam supply line 2 is provided so as to cover the entire orifice 46.
4, a steam heater 47 is provided. According to the multi-stage orifice 46, the steam supply pipe 24
By selecting the size and thickness of each orifice 46 with respect to the inner diameter of the orifice 46, the distance between the orifices 46, and the like, the combustion device 23 side is set to a pressure P1 close to normal pressure and the processing furnace 1 side is set to a sufficiently low pressure P2. A large pressure difference (P1-P2) can be generated without a sudden change in pressure, so that combustion can be further stabilized and film quality can be further improved.

FIG. 5 shows another modification of the throttle provided in the steam supply pipe 24. A convergent divergent nozzle 48 made of quartz is integrally provided as a throttle in the steam supply pipe 24, and a steam heater 4 is provided around the steam supply pipe 24 so as to cover the entire convergent divergent nozzle 48.
7 are provided. According to this tapered divergent nozzle 48, the pressure of the combustion device 23 side is close to the normal pressure similarly to the multistage orifice 46 by selecting the size and length of the diameter of the tapered divergent nozzle 48 with respect to the inner diameter of the steam supply pipe 24. A large pressure difference (P1−P2) can be generated without causing a rapid pressure change so as to set P1 and the processing furnace 1 side to a sufficiently low pressure P2, further stabilizing combustion and further improving film quality. Can be improved.

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, a so-called in-pipe orifice is illustrated as the throttle section in the embodiment of FIGS. 2 and 4, but a so-called in-pipe nozzle may be used. Further, the constricted portion may be formed over the entirety of the steam supply line 24, that is, the steam supply line 24 may be formed of a thin tube. In this case, an in-pipe orifice and an in-pipe nozzle become unnecessary. .

The processing furnace 1 is exemplified by a vertical furnace, but may be a horizontal furnace. As the object to be processed, a semiconductor wafer W is exemplified, but for example, an LCD
And so on. Further, since the oxidation treatment apparatus of the embodiment has the high-temperature treatment furnace 1 and the decompression means (decompression pump 13), it is used as a decompression CVD apparatus by connecting a treatment gas supply source instead of the combustion device 23. It is also possible.

[0037]

In summary, according to the present invention, the following excellent effects can be obtained.

(1) According to the first aspect of the present invention, since the steam supply pipe connecting the combustion device and the processing furnace is provided with the throttle portion for generating a pressure difference between the combustion device and the processing furnace. By reducing the pressure in the processing furnace, the effect of the reduced pressure on the combustion device is reduced or eliminated, and stable combustion in the combustion device becomes possible. As a result, the supply of water vapor can be stabilized and the safety can be improved. Therefore, wet oxidation can be performed under reduced pressure, and the quality of the oxide film can be improved.

(2) According to the second aspect of the present invention, a large pressure difference is caused by a rapid pressure change so that the combustion device side is brought to a pressure close to normal pressure and the processing furnace side is brought to a sufficiently low pressure by the multistage throttle portion. Can be generated without causing the combustion, and the combustion can be further stabilized and the film quality can be further improved.

(3) According to the third aspect of the present invention, since the steam immediately after passing through the narrowing section is heated by the heating section, dew condensation of the steam due to the pressure change is prevented, and the film quality can be further improved. .

(4) According to the fourth aspect of the present invention, since the wet oxidation of the object to be processed is performed under reduced pressure, the oxidation rate is reduced and the thickness of the oxide film formed on the object to be processed is reduced. Control becomes easy, and film quality can be improved and an extremely thin film can be formed.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of an oxidation treatment apparatus showing one embodiment of the present invention.

FIG. 2 is an enlarged cross-sectional view of a throttle unit.

FIG. 3 is an enlarged sectional view of the combustion device.

FIG. 4 is a cross-sectional view illustrating a modified example of a throttle unit.

FIG. 5 is a cross-sectional view showing another modification of the throttle unit.

[Explanation of symbols]

 W Semiconductor wafer (object to be processed) 1 Processing furnace 2 Reaction tube 13 Decompression pump (decompression means) 14 Decompression tube 23 Combustion device 24 Steam supply line 46 Orifice (throttle portion) 47 Steam heater (heating portion) 48 Tapered divergent nozzle (Aperture section)

Claims (4)

(57) [Claims] 1. A processing furnace for oxidizing an object to be processed at a high temperature, a pressure reducing means for reducing the pressure of the processing furnace, and a combustion provided outside the processing furnace for burning hydrogen gas and oxygen gas to generate steam. An apparatus, a steam supply pipe connecting the combustion apparatus and the processing furnace, and a throttle provided in the steam supply pipe to generate a pressure difference between the combustion apparatus side and the processing furnace side. Oxidation treatment equipment. 2. The oxidation treatment apparatus according to claim 1, wherein the throttle portion is provided in multiple stages along the steam supply pipe. 3. The oxidation treatment apparatus according to claim 1, wherein a heating section for heating steam immediately after passing through the throttle section is provided around the steam supply pipe. 4. A step of reacting a hydrogen gas and an oxygen gas to generate steam, and supplying the steam into a reduced-pressure processing furnace in a pressure-blocked manner so that the reduced pressure does not directly affect the reaction. An oxidation treatment method, comprising: a step of heating an object to be processed in a reduced-pressure processing furnace and contacting the object with the steam to perform an oxidation treatment.