JP2000049152A - Wet oxidation equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an oxide film thickness and growth rate while maintaining high quality of an oxide film by using an inert gas used to suppress oxide film formation in a conventional wet oxidation apparatus. To provide a wet oxidizer capable of controlling the temperature. SOLUTION: The wet oxidation apparatus of the present invention uses a gas injected through a first gas inlet and a second gas inlet to form an oxide film on a wafer loaded therein, and an outlet thereof. A combustor connected to a first gas inlet of the reaction furnace, and combusting a gas injected through the first inlet and the second inlet to discharge the gas into the first gas inlet of the reaction furnace; A hydrogen gas supply pipe for supplying hydrogen gas to the combustor, an oxygen gas supply pipe for supplying oxygen gas to the combustor, a first inert gas supply pipe for supplying inert gas to the combustor, and a reaction furnace. A second inert gas supply pipe for supplying an inert gas.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for forming an oxide film on a semiconductor substrate or a wafer, and more particularly, to a method of performing wet oxidation while injecting an inert gas into a reaction furnace to thereby obtain a thick oxide film. The present invention relates to a wet oxidizer capable of adjusting the length and growth time.

[0002]

2. Description of the Related Art As semiconductor devices have become more highly integrated, the size of elements constituting the semiconductor devices has been miniaturized, which has further complicated the wafer manufacturing process. In particular, while the diameter of a reaction furnace for forming an oxide film on a wafer is increasing as the diameter of the wafer is increased, the oxide film grown in the reaction furnace is required to be thinner and higher in quality.

In the semiconductor industry, silicon dioxide (S
iO ₂ ) films (hereinafter referred to as oxide films) are used for a wide variety of applications. For example, an oxide film is used as a field oxide film for electrically insulating each element,
It is used as a gate oxide film of an element or as a passivation layer that insulates metal wiring and protects a semiconductor device from an external environment.

As a method of forming an oxide film, there are a dry oxidation method using oxygen and a wet oxidation method using steam as an oxidizing agent. Among them, the wet oxidation method is mainly used for forming a thick oxide film because the growth rate of the oxide film is high. However, recently, the wet oxidation method has a thickness of about 30 mm.
It is also used to form a thin oxide film of 0 ° or less.
This is because the wet oxidation method has a higher growth rate of the oxide film than the dry oxidation method, and a high-quality oxide film can be obtained.

A method and a feature of forming an oxide film by a wet oxidation method are described in, for example, Silicon Processing For The VLSI Era,
Volume 1, U.S. Pat.No. 5,524,834 and U.S. Pat.
No. 6,086,045. A conventional wet oxidizer will be described with reference to FIG. FIG. 1 is a schematic view of a reaction furnace (oxidizing furnace) used in a conventional wet oxidation process. FIG.
As shown in FIG. 2, a wafer loading section 80 on which wafers (not shown) for carrying out the oxidation process are loaded is located in the reaction furnace 100. A gas inlet 70 is formed in the upper part of the reaction furnace 100, and a gas outlet 90 for discharging used gas is formed in a lower part. The gas inlet 70 is connected to the combustor 50 via a pipe 60.

The gas supply pipe for supplying gas to the reaction furnace 100 will be described in detail. Nitrogen gas, oxygen gas, hydrogen gas and hydrogen chloride gas are supplied through the supply pipe 10,
It is supplied to the reactor 100 via 12, 14, and 16. In addition, each of these supply pipes is provided with a reaction furnace 10.
A mass flow controller (MFC) 40 for adjusting the amount of gas supplied to the chamber and a valve 30 for shutting off the gas flow are mounted.

Among the supplied gases, oxygen gas and hydrogen gas are involved in the formation of an oxide film, and hydrogen chloride gas is a cation (N) existing in the oxide film of the wafer.
a ⁺ , K ⁺ ) in the form of NaCl, KCl, etc.
This is for improving the quality of the oxide film by preventing cations from bonding with other ions in the oxide film. Nitrogen gas is a gas that suppresses the reaction between oxygen and hydrogen and hinders the formation of an oxide film. This will be further described later.

[0008] Oxygen, hydrogen, and hydrogen chloride gas for forming an oxide film are supplied through supply pipes 12, 14, and 16, and the gas that has passed through each MFC 40 and valve 30 is
It is introduced into the reaction furnace 100 via the combustor 50 and the supply pipe 60. Of these gases, oxygen gas and hydrogen chloride gas pass through the valve 30 and are combined in one pipe 20 and introduced into the combustor 50, and hydrogen gas is separately supplied to the combustor 50 through the pipe 22. Will be introduced. At this time, M
The FC 40 controls the amount of gas required for an oxidation reaction to form an oxide film, and the valve 30 shuts off gas supply as needed.

In a standby state before an oxide film is formed, when a wafer held by the wafer loading unit 80 is loaded into the reaction furnace 100, only nitrogen gas flows into the reaction furnace 100 via the pipe 10. The internal temperature of the reactor 100 is
It is maintained at about 600-650 ° C. Also, while maintaining a constant temperature for about 5 minutes by a heater (not shown) installed in the reaction furnace (initial thermal stabilization step), nitrogen gas is continuously flowed into the reaction furnace. Here, the nitrogen gas is
Since it is an inert gas, it serves to prevent an oxide film from being formed on the wafer.

Next, while shutting off nitrogen gas and introducing oxygen gas into the reactor, the temperature of the reactor is raised to about 850 ° C.-10
Raise to 00 ° C. As a result, oxygen reacts with the silicon surface of the wafer in the reaction furnace, and an initial oxide film is formed on the wafer. When the internal temperature of the reactor reaches a predetermined temperature, a temperature stabilization step is performed. This predetermined temperature depends on the oxidation process conditions, but is about 850.
C.-has a temperature range of about 1000C. As described above, when the internal temperature of the reactor is stabilized, hydrogen and oxygen gas are simultaneously introduced into the reactor to perform a wet oxidation step of growing a wet oxide film. At this time, oxygen and hydrogen gas are
The two react with each other in the combustor 50 and are supplied to the reaction furnace 100 in a water vapor state.

After the completion of the wet oxidation step, a late temperature stabilization step is performed while only nitrogen gas is again introduced into the reactor. Next, the temperature of the reactor is lowered, and the wafer is unloaded from the reactor.

According to the above-mentioned conventional wet oxidation apparatus, in order to perform wet oxidation in a reaction furnace, oxygen gas and hydrogen gas are thermally reacted in a combustor, and steam generated by this thermal reaction is injected into the reaction furnace. , An oxide film is formed on a silicon wafer. However, in the conventional oxidizing apparatus, the role of nitrogen is to prevent oxygen and hydrogen from reacting with each other before and after forming the oxide film to form an oxide film. Nitrogen has a characteristic of suppressing a combustion reaction between oxygen and hydrogen in a combustor.

However, in the conventional wet oxidation apparatus, there is a limit in reducing the thickness of the oxide film. In particular, in order to maintain the high quality of the oxide film, the wet oxidation method is more advantageous than the dry oxidation method, but it is difficult to control the thickness of the oxide film. There was a need for a compromise between

[0014]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to maintain the high quality of an oxide film by using an inert gas used to suppress the formation of an oxide film in a conventional wet oxidation apparatus. Another object of the present invention is to provide a wet oxidizer capable of controlling the thickness and growth rate of an oxide film.

[0015]

According to a first aspect of the present invention, there is provided a wet oxidizing apparatus comprising:
A reaction furnace having a first gas inlet and a second gas inlet, and using a gas injected through the first gas inlet and the second gas inlet to form an oxide film on a wafer loaded therein; It has a first inlet and a second inlet, the outlet of which is connected to the first gas inlet of the reactor, and burns and reacts the gas injected through the first inlet and the second inlet. A combustor discharging to a first gas inlet of the reactor;
A hydrogen gas supply pipe connected to the first inlet of the combustor and supplying hydrogen gas to the combustor; an oxygen gas supply pipe connected to the second inlet of the combustor and supplying oxygen gas to the combustor; A first inert gas supply pipe connected to the second inlet of the combustor and supplying an inert gas to the combustor;
A second inert gas supply pipe connected to the gas inlet and supplying an inert gas to the reaction furnace.

According to the wet oxidizing device of the present invention, the inert gas passing through the first and second inert gas supply pipes is a group consisting of nitrogen, argon, helium gas and a mixed gas thereof. Is chosen from

According to the wet oxidizer of the present invention, the flow of the hydrogen gas flowing out of the hydrogen gas supply pipe is regulated by the first fluid mass controller (MFC) and the first valve, and the oxygen gas supply is performed. The flow of oxygen gas flowing out of the pipe is regulated by the second MFC and the second valve, and the flow of first inert gas flowing out of the first inert gas supply pipe is regulated by the third MFC and the third valve, and the flow of the second inert gas is controlled by the third MFC and the third valve. The flow of the second inert gas flowing out of the active gas supply pipe is the fourth MF
Regulated by C and the fourth valve.

According to a fourth aspect of the present invention, the wet oxidizer further comprises a hydrogen chloride gas supply pipe connected to the second inlet of the combustor and supplying hydrogen chloride gas to the combustor. According to the wet oxidation apparatus of the present invention, the flow of the hydrogen chloride gas flowing out of the hydrogen chloride gas supply pipe is regulated by the fifth MFC and the fifth valve.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings. FIG. 2 is a schematic view showing the piping of the wet oxidation apparatus according to the present invention, and FIG. 3 is a plan view and a front view showing the reaction furnace of FIG.

As shown in FIGS. 2 and 3, the wet oxidizer according to the present invention has a first gas inlet 72 and a second gas inlet 75, and is provided through the first gas inlet 72 and the second gas inlet 75. A reaction furnace 102 for forming an oxide film on a wafer loaded therein using a gas to be injected, a first injection port 27 and a second injection port 26, and a first injection port 2
And a pipe connected to the first inlet 27 of the combustor 52 by causing a combustion reaction of the gas injected through the second inlet 7 and the second inlet 26 and discharging the gas to the first gas inlet 72 of the reactor. Wherein the first fluid mass controller (mass flow controll)
er; MFC) The gas flow is regulated by the 42 d and the first valve 32 d, and the hydrogen gas supply pipe 14 supplies hydrogen gas to the combustor 52, and the pipe is connected to the second inlet 26 of the combustor 52. And the second MFC 42b and the second valve 32b
The flow of the gas is adjusted by the oxygen gas supply pipe 12 for supplying oxygen gas to the combustor 52, and the pipe connected to the second inlet 26 of the combustor. The gas is supplied by the third MFC 42a and the third valve 32a. And a pipe connected to a first inert gas supply pipe 10 for supplying an inert gas (for example, nitrogen gas) to the combustor and a second gas inlet 75 of the reaction furnace. And the fourth valve 32
e, a gas flow is adjusted by e, a second inert gas supply pipe 11 for supplying an inert gas (for example, nitrogen gas) to the reaction furnace, and a pipe connected to the second inlet 26 of the combustor. , A fifth MFC 42c and a fifth valve 32c, the flow of gas being adjusted, and a hydrogen chloride gas supply pipe 16 for supplying hydrogen chloride gas to the combustor.

Reference numeral 25 denotes a passage through which oxygen, hydrogen chloride, and nitrogen gas are put together and enters the second inlet 26 of the combustor 52. Reference numerals 62 and 65 denote the first gas inlet 72 and the second gas inlet 72, respectively. The gas flowing into the gas inlet 75 is the reactor 1
Reference numeral 82 denotes a wafer loading portion on which wafers are loaded, and reference numeral 92 denotes a gas outlet for discharging gas generated or reacted after the reaction in the reaction furnace.

Regarding the gas flow in the apparatus shown in FIG. 2, nitrogen, oxygen and hydrogen chloride gas
After passing through 2a, 42b, 42c and valves 32a, 32b, 32c, they are put together in one pipe 25 and
, And only hydrogen gas is separately introduced into the first inlet 27 of the combustor 52 via the pipe 27. And, as shown in FIG.
Direct reactor 1 via separate MFC 42e and valve 32e
02 is injected into the second gas inlet 75. Hereinafter, the nitrogen gas passing through the combustor 52 is referred to as a first nitrogen gas, and the nitrogen gas directly supplied to the reactor 102 is referred to as a second nitrogen gas.

The operation of the wet oxidation apparatus according to the present invention will be described. First, the wafer for forming the oxide film is
The reactor 102 is loaded. Then, a first temperature stabilization phase begins. In the first temperature stabilization step, the first nitrogen gas and a small amount of oxygen gas are introduced into the reactor for about 5 to 7 times.
The temperature is adjusted to a constant value while flowing for minutes. At this time, the role of nitrogen is the same as that of a conventional wet oxidizer.

After the first temperature stabilization step, when the initial temperature inside the reaction furnace is stabilized, a heater coil (not shown) around the reaction furnace is heated to perform a temperature raising step. In this temperature raising phase, the temperature of the reactor is reduced to about 8
The same amount of the first nitrogen gas and the oxygen gas used in the first temperature stabilization step are flowed into the reaction furnace 102 while increasing the temperature to 00-900 ° C. This temperature raising step is performed for about 20 to about 30 minutes. During the temperature rising phase, the surface of the wafer loaded inside the reaction furnace reacts with a small amount of oxygen gas contained in nitrogen gas to form an oxide film having a thickness of about 5 to 30 mm on the wafer. You. The inside of the reactor is maintained at a normal pressure atmosphere while the nitrogen gas and the oxygen gas flow.

After the completion of the temperature raising step, a second temperature stabilization step is performed. The second temperature stabilization step comprises a first nitrogen,
While the second nitrogen and oxygen gases are flowing into the reaction furnace 102 through the pipes 62 and 65, the temperature of the reaction furnace is maintained at a constant temperature required for the wet oxidation process. The primary nitrogen, secondary nitrogen and oxygen gas have the same conditions as those used in the temperature raising stage. This step is performed for about 7 to 9 minutes.

The second temperature stabilization step is performed to maintain the temperature of the reactor constant before performing the wet oxidation step. Therefore, the temperature of the reactor, which has been increased in the temperature increasing step, is stably maintained in the second temperature stabilizing step. If the wet oxidation is performed with the temperature of the reaction furnace being unstable, it is difficult to control the growth rate and quality of the oxide film grown on the wafer.

After the second temperature stabilization step, a wet oxidation step is performed. The wet oxidation step includes a first combustion process and a second combustion process. In the first combustion step, the first
The flow of nitrogen gas is interrupted and about 5 L / min to 10 L / m
The second nitrogen gas in is caused to flow into the reaction furnace 102 via the pipe 65, and about 3 L / min of oxygen gas is caused to flow into the reaction furnace 102 via the pipe 62. The first combustion step is performed for about 1 to 2 minutes, and the partial pressure of oxygen gas is increased inside the reaction furnace, so that an oxide film is actively formed.

In the second combustion step, about 3 L / min of hydrogen gas flows under the same conditions as in the first combustion step. The oxygen gas and the hydrogen gas are mixed in the combustor 52, and the heat applied to the combustor 52 causes a chemical reaction between the oxygen and the hydrogen to form water vapor (H ₂ O). The second combustion process is performed for about one minute, and serves to form initial steam for forming a wet oxide film.

As described above, the operation of the wet oxidizer according to the present invention is different from that of the conventional wet oxidizer. During the formation of the oxide film, the thickness of the formed oxide film can be reduced by appropriately delaying the formation time of the oxide film by adding nitrogen gas together with oxygen and hydrogen gases.

Subsequently, the wet oxidation step is performed for about 20 minutes to about 3 minutes.
Performed at constant temperature for 0 minutes. The amount of the second nitrogen gas introduced at this stage can be selected in a wide range depending on the temperature and time of the wet oxidation process, the desired thickness of the oxide film, and the like. For example, a person having ordinary skill in the art can obtain a uniform oxide film and a desired thickness by varying the wet oxidation temperature and the amount of the second inert gas. It will be appreciated that the amount of secondary nitrogen gas can be easily selected by reference to the data.

To give a specific example, about 2.5-10 L
/ Min of the second nitrogen gas, about 2-5 L / min of the oxygen gas and about 3-7.5 L / min of the hydrogen gas are supplied to pipes 62 and 65, respectively.
Through the reactor 102. At this time, the first
Nitrogen gas does not enter the combustor and does not interfere with the reaction between oxygen and hydrogen. The steam and the second nitrogen gas generated in the combustor 52 are mixed at the head of the reaction
02.

At this time, the second nitrogen gas, which is an inert gas, does not participate in the formation of the oxide film. Rather, it serves to keep the partial pressure inside the reactor constant and slow down the growth rate of the oxide film. This means that the thickness of the oxide film can be easily adjusted. Here, as a means for maintaining a constant partial pressure inside the reactor, not only nitrogen gas but also an inert gas such as argon and helium can be used, or nitrogen, argon, helium, etc. are mixed. The used gas can also be used.

After the wet oxidation step, the supply of oxygen gas and hydrogen gas is interrupted, and the third temperature stabilization step is performed while the first and second nitrogen gases are flowing into the reactor. The third temperature stabilization step is a heat treatment step for physically stabilizing the wet oxide film grown on the wafer, and is performed for about 10 minutes at the same temperature condition as the wet oxidation step. During the third temperature stabilization step, about 10 L / min of the first nitrogen gas and about 5 L / min.
L / min of second nitrogen gas is introduced into the reactor.

Next, a temperature lowering step is performed for about 40 to 60 minutes to lower the temperature of the reactor to about 650 ° C. Then, an unloading step of unloading the wafer on which the oxide film is formed from the reaction furnace is performed. In the temperature lowering step and the unloading step, the first nitrogen gas and the second nitrogen gas are introduced into the reactor in the same amount as in the third temperature stabilizing step.

[0035]

As described above, according to the wet oxidizer of the present invention, the inert gas used for suppressing the reaction between oxygen and hydrogen in the conventional wet oxidizer participates in the process of forming the oxide film. By doing so, the growth rate of the wet oxide film can be delayed. Therefore, the film thickness can be reduced while maintaining the high quality of the wet oxide film.

[Brief description of the drawings]

FIG. 1 is a schematic view showing a pipe of a conventional wet oxidation apparatus.

FIG. 2 is a schematic diagram showing piping of a wet oxidation apparatus according to the present invention.

FIG. 3 is a plan view and a front view showing the reaction furnace of FIG. 2;

[Explanation of symbols]

Reference Signs List 10 first inert gas supply pipe 11 second inert gas supply pipe 12 oxygen gas supply pipe 14 hydrogen gas supply pipe 16 hydrogen chloride gas supply pipe 26 second inlet 27 first inlet 32a, 32b, 32c, 32d, 32e Valve 42a, 42b, 42c, 42d, 42e Fluid Mass Controller (MFC) 52 Combustor 72 First Gas Inlet 75 Second Gas Inlet 102 Reactor

Claims (5)

[Claims] 1. An oxide film having a first gas inlet and a second gas inlet, wherein an oxide film is formed on a wafer loaded therein using a gas injected through the first gas inlet and the second gas inlet. A reaction furnace to be formed, having a first inlet and a second inlet, the outlet of which is connected to a first gas inlet of the reactor, and via the first inlet and the second inlet. A combustor for causing a combustion reaction of the injected gas and discharging the gas to the first gas inlet of the reaction furnace; and hydrogen connected to the first injection port of the combustor and supplying hydrogen gas to the combustor. A gas supply pipe, an oxygen gas supply pipe connected to the second inlet of the combustor, for supplying oxygen gas to the combustor, and an oxygen gas supply pipe connected to the second inlet of the combustor, A first inert gas supply pipe for supplying an inert gas, Serial connected to the second gas inlet of the reactor, the wet oxidation apparatus characterized by comprising a second inert gas supply pipe for supplying inert gas into the reaction furnace. 2. An inert gas passing through the first and second inert gas supply pipes is selected from the group consisting of nitrogen, argon, helium gas, and a mixed gas thereof. Item 2. A wet oxidation apparatus according to Item 1. 3. The flow of hydrogen gas flowing out of the hydrogen gas supply pipe is controlled by a first fluid mass controller (mass flow controller).
ller; MFC) and the flow of oxygen gas flowing out of the oxygen gas supply pipe regulated by the first valve and regulated by the second fluid mass regulator and the second valve, and flowing out of the first inert gas supply pipe. 1 The flow of the inert gas is the third
The flow of the second inert gas adjusted by the fluid mass adjuster and the third valve and flowing out of the second inert gas supply pipe is adjusted by the fourth fluid mass adjuster and the fourth valve. The wet oxidizer according to claim 1. 4. The wet oxidizer according to claim 1, further comprising a hydrogen chloride gas supply pipe connected to the second inlet of the combustor and supplying hydrogen chloride gas to the combustor. . 5. The wet oxidizer according to claim 4, wherein the flow of the hydrogen chloride gas flowing from the hydrogen chloride gas supply pipe is adjusted by a fifth fluid mass controller and a fifth valve.