JPH11135492A - Method and device for forming silicon oxide film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method whereby generation of roughness in a surface of a silicon layer during formation of a silicon oxide film is prevented and a silicon oxide film which is excellent in property is formed without a dry oxide film in a surface of a silicon layer. SOLUTION: In a formation method of a silicon oxide film, a treatment chamber 10, a substrate carrying in/out part 25 provided to the treatment chamber 10, and a silicon oxide formation device with first and second wet gas generation devices 30B, 30A, are used. The method comprises process of (A) when a substrate 40 is carried into the treatment chamber 10 through the substrate carrying in/out part 25, wet gas is introduced to the substrate carrying in/out part 25, and a silicon oxide film is formed in a surface of a silicon layer by forming wet gas atmosphere of a temperature whereat silicon atom is not liberated from a surface of a silicon layer in the substrate carrying in/out part 25; and process of (B) where a silicon oxide film is further formed in a surface of a silicon layer by introducing wet gas to the treatment chamber 10 after the substrate 40 is carried inside the treatment chamber 10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a silicon oxide film in the manufacture of a semiconductor device and a silicon oxide film forming apparatus suitable for implementing the method for forming a silicon oxide film.

[0002]

2. Description of the Related Art For example, in manufacturing a MOS type semiconductor device, it is necessary to form a gate oxide film made of a silicon oxide film on the surface of a silicon semiconductor substrate. Also, in manufacturing a thin film transistor (TFT), it is necessary to form a gate oxide film made of a silicon oxide film on the surface of a silicon layer provided on an insulating substrate. It is not an exaggeration to say that such a silicon oxide film is responsible for the reliability of the semiconductor device. Therefore, a silicon oxide film is always required to have high dielectric breakdown voltage and long-term reliability.

[0003] For example, in the case of manufacturing a MOS type semiconductor device, conventionally, NH ₄ OH /
The surface of the silicon semiconductor substrate is cleaned by RCA cleaning in which the surface is washed with an H ₂ O ₂ aqueous solution and further washed with an HCl / H ₂ O ₂ aqueous solution, and fine particles and metal impurities are removed from the surface. When the RCA cleaning is performed, the surface of the silicon semiconductor substrate reacts with the cleaning liquid to form a silicon oxide film having a thickness of about 0.5 to 1 nm (hereinafter, such a silicon oxide film is simply referred to as an oxide film). The thickness of such an oxide film is not uniform, and the cleaning liquid component remains in the oxide film. Therefore, the silicon semiconductor substrate is immersed in a hydrofluoric acid aqueous solution to remove such an oxide film, and further, a chemical component is removed with pure water. Thereby, it is possible to obtain a surface of the silicon semiconductor substrate that is mostly terminated with hydrogen and extremely partially terminated with fluorine. In this specification, obtaining a surface of a silicon semiconductor substrate that is mostly terminated with hydrogen and a very small portion is terminated with fluorine is referred to as exposing the surface of the silicon semiconductor substrate in this specification. I do. Thereafter, the silicon semiconductor substrate is carried into a processing chamber (oxidizing furnace) of the silicon oxide film forming apparatus, and a silicon oxide film is formed on the surface of the silicon semiconductor substrate.

[0004] As the silicon oxide film forming apparatus, as the gate oxide film becomes thinner and the substrate becomes larger in diameter, a quartz-type processing chamber (oxidizing furnace) is held horizontally and a vertical method is held vertically. Are shifting to silicon oxide film forming apparatuses. This is because the vertical type silicon oxide film forming apparatus is easier to cope with the enlargement of the substrate diameter than the horizontal type silicon oxide film forming apparatus, and also when the silicon semiconductor substrate is carried into the processing chamber. This is because a silicon oxide film generated by entrainment in the atmosphere (hereinafter, such a silicon oxide film is referred to as a natural oxide film) can be reduced.
However, even when a vertical silicon oxide film forming apparatus is used, a natural oxide film having a thickness of about 2 nm is formed on the surface of the silicon semiconductor substrate. The natural oxide film contains a large amount of impurities in the atmosphere, and the existence of the natural oxide film cannot be ignored in thinning the gate oxide film. Therefore, (1) a method in which a large amount of nitrogen gas is caused to flow into a purge chamber provided in a silicon oxide film forming apparatus to form a nitrogen gas atmosphere (nitrogen gas purge method), and (2) once the purge chamber is evacuated, A method has been proposed in which a purge chamber is replaced with nitrogen gas or the like to remove the atmosphere (vacuum load lock method) or the like, and the formation of a natural oxide film is suppressed as much as possible.

[0005] Then, the silicon semiconductor substrate is carried into the processing chamber (oxidizing furnace) with the processing chamber (oxidizing furnace) in an inert gas atmosphere, and then the processing chamber (oxidizing furnace) is oxidized. The gate oxide film is formed by switching and heat-treating the silicon semiconductor substrate. A method of thermally oxidizing the surface of a silicon semiconductor substrate by introducing high-purity water vapor into a processing chamber maintained at a high temperature (wet oxidation method) is used for forming a gate oxide film. A gate oxide film with higher electrical reliability can be formed than a method of oxidizing the surface of a silicon semiconductor substrate with oxygen gas (dry oxidation method). As one of the wet oxidation methods, there is a pyrogenic oxidation method (also referred to as a hydrogen combustion oxidation method) using water vapor generated by mixing hydrogen gas with oxygen gas at a high temperature and burning the mixture. Usually, in this pyrogenic oxidation method, the pyrogen oxidation method is provided outside a processing chamber (oxidizing furnace), and
Oxygen gas is supplied into the combustion chamber maintained at 0 to 900 ° C., and then hydrogen gas is supplied into the combustion chamber to burn the hydrogen gas at a high temperature. The water vapor thus obtained is used as an oxidizing species.

FIG. 9 is a schematic cross-sectional view of a conventional silicon oxide film forming apparatus for forming a silicon oxide film by a pyrogenic oxidation method. The vertical type silicon oxide film forming apparatus includes a processing chamber 10 having a double tube structure made of quartz and held in a vertical direction, a gas introduction unit 12 for introducing water vapor or the like into the processing chamber 10, and a processing chamber. A gas exhaust unit 13 for exhausting gas from the heater 10, a heater 14 for maintaining the inside of the processing chamber 10 at a predetermined atmospheric temperature through a cylindrical heat equalizing pipe 16 made of SiC, a purge chamber 20, and a purge chamber 2.
A gas introduction unit 21 for introducing nitrogen gas into the gas chamber 0, a gas exhaust unit 22 for exhausting gas from the purge chamber 20, a shutter 15 for separating the processing chamber 10 from the purge chamber 20, and a silicon semiconductor substrate. It comprises an elevator mechanism 23 for carrying in and out. Elevator mechanism 2
A quartz boat 24 for mounting a silicon semiconductor substrate is attached to 3. Further, the hydrogen gas and the oxygen gas supplied to the combustion chamber 30 via the pipes 31 and 32 are mixed at a high temperature in the combustion chamber 30, and the hydrogen gas is burned to generate steam. The water vapor is introduced into the processing chamber 10 through the pipe 33, the gas flow path 11, and the gas introduction unit 12. The gas flow path 11 corresponds to a space between the inner wall and the outer wall of the processing chamber 10 having a double pipe structure.

FIGS. 9 and 10 show an outline of a conventional silicon oxide film forming method based on a pyrogenic oxidation method using the vertical type silicon oxide film forming apparatus shown in FIG.
This will be described below with reference to FIGS.

[Step-10] Nitrogen gas is introduced into the processing chamber 10 through the pipe 32, the combustion chamber 30, the pipe 33, the gas flow path 11 and the gas introduction unit 12, and the inside of the processing chamber 10 is set to a nitrogen gas atmosphere. Further, the atmosphere temperature in the processing chamber 10 is maintained at 700 to 800 ° C. by the heater 14 via the soaking tube 16. In this state, the shutter 15 is closed (see FIG. 10A). The purge chamber 20 is open to the atmosphere.

[Step-20] Then, the silicon semiconductor substrate 40 is carried into the purge chamber 20, and the silicon semiconductor substrate 40 is placed on the quartz boat 24. After the loading of the silicon semiconductor substrate 40 into the purge chamber 20 is completed, a door (not shown) is closed, nitrogen gas is introduced into the purge chamber 20 from the gas introduction unit 21, discharged from the gas exhaust unit 22, and the inside of the purge chamber 20 is purged. A nitrogen gas atmosphere is used (see FIG. 10B).

[Step-30] When the inside of the purge chamber 20 becomes a sufficient nitrogen gas atmosphere, the shutter 15 is opened (see FIG. 11B), the elevator mechanism 23 is operated, and the quartz boat 24 is raised. The silicon semiconductor substrate 4
0 is carried into the processing chamber 10 (see FIG. 12A).
After the elevator mechanism 23 reaches the highest position, the shutter 15 is closed.

If the processing chamber 10 is left in a nitrogen gas atmosphere before the shutter 15 is opened, the following problems occur. That is, when the silicon semiconductor substrate whose surface is exposed with the hydrofluoric acid aqueous solution is carried into a high-temperature nitrogen gas atmosphere, the surface of the silicon semiconductor substrate 40 becomes rough. This phenomenon occurs because part of the Si—H bond and part of the Si—F bond formed on the surface of the silicon semiconductor substrate 40 by the cleaning with the hydrofluoric acid aqueous solution are lost due to thermal desorption of hydrogen or fluorine. This is considered to be caused by an etching phenomenon occurring on the surface of the silicon semiconductor substrate 40. For example, when the temperature of a silicon semiconductor substrate is raised to 600 ° C. or more in argon gas, severe irregularities may occur on the surface of the silicon semiconductor substrate, as described in Baifukan, Tadahiro Omi, “Ultra Clean ULSI Technology”, page 21. Have been. In order to suppress such a phenomenon, the shutter 15
Before opening the chamber, for example, a nitrogen gas containing about 0.5% by volume of oxygen gas is introduced into the processing chamber 10 from the gas introduction unit 12, and about 0.5% by volume of oxygen gas is A nitrogen gas atmosphere is used (see FIG. 11A).

[Step-40] Thereafter, the atmosphere temperature in the processing chamber 10 is set to 800 to 900 ° C. And piping 3
Oxygen gas and hydrogen gas are supplied into the combustion chamber 30 via the first and 32, and the water vapor generated by mixing and burning the hydrogen gas and the oxygen gas at a high temperature in the combustion chamber 30 is
The gas is introduced into the processing chamber 10 through the pipe 33, the gas flow path 11, and the gas introduction unit 12, and is exhausted from the gas exhaust unit 13 (FIG. 1).
2 (B)). Thus, a silicon oxide film is formed on the surface of the silicon semiconductor substrate 40. Here, in order to prevent the detonation reaction from occurring due to the incompletely burned hydrogen gas flowing into the processing chamber 10 before the steam is introduced into the processing chamber 10, the combustion chamber 30
Before supplying hydrogen gas to the combustion chamber 3 through the pipe 31
0 is supplied with oxygen gas. The temperature in the combustion chamber 30 is
For example, 700-900 ° C by a heater (not shown)
To hold.

[0013]

Before the shutter 15 is opened, a nitrogen gas containing about 0.5% by volume of oxygen gas is introduced into the processing chamber 10 from the gas introducing section 12, and the processing chamber 10 is opened.
By setting the inside of the inside to a nitrogen gas atmosphere containing about 0.5% by volume of oxygen gas (see FIG. 11A), a phenomenon in which unevenness is formed on the surface of the silicon semiconductor substrate can be suppressed. Alternatively, "Ultra Clean ULSI Technology", published by Baifukan and written by Tadahiro Omi, page 21, states that a hydrogen-terminated silicon semiconductor substrate is subjected to dry oxidation at 300 ° C. where terminal hydrogen is stably present and formed by this method. It has been reported that the problem of forming irregularities on the surface of a silicon semiconductor substrate can be avoided by using the formed silicon oxide film as a protective film.

However, since nitrogen gas containing oxygen gas is introduced into the processing chamber 10 in order to suppress the phenomenon that unevenness is formed on the surface of the silicon semiconductor substrate, the silicon carried into the processing chamber 10 is not introduced. A silicon oxide film is formed on the surface of the semiconductor substrate. Such a silicon oxide film is essentially a silicon oxide film formed by so-called dry oxidation (called a dry oxide film), and a silicon oxide film formed by a wet oxidation method (called a wet oxide film). Inferior in characteristics. For example, the inside of the processing chamber 10 is maintained at 800 ° C., and a silicon semiconductor substrate is placed in the processing chamber 10 while a nitrogen gas containing 0.5% by volume of oxygen gas is introduced into the processing chamber 10 from the gas introduction unit 12. Then, a dry oxide film of 2 nm or more is formed on the surface of the silicon semiconductor substrate. In a semiconductor device having a gate length of 0.18 to 0.13 μm, it is expected that a gate oxide film having a thickness of 4 to 3 nm will be used. Thus, for example, when an attempt is made to form a gate oxide film having a thickness of 4 nm, 50% or more of the thickness is occupied by the dry oxide film.

A means for solving such a problem is disclosed in Japanese Patent Application Laid-Open No. 6-291112. That is, this patent discloses a technique in which a silicon semiconductor substrate is washed with an aqueous solution of hydrofluoric acid, and then the silicon semiconductor substrate is immersed in a hydrogen peroxide solution to form a silicon oxide film as a protective film on the surface of the silicon semiconductor substrate. It is disclosed in the publication. However, in this method, it is difficult to form a uniform silicon oxide film on the surface of the silicon semiconductor substrate with good reproducibility by controlling the concentration of hydrogen peroxide solution or the like. There is also a problem that impurities in the hydrogen peroxide solution are taken into the silicon oxide film.

A method of forming a silicon oxide film having excellent long-term stability, high withstand voltage and a small thickness is described in, for example,
It is disclosed in JP-A-6-318588. In this method, an ultrathin thermal oxide film is formed on the surface of a silicon semiconductor by a thermal oxidation method, and then a silicon oxide film is deposited on the ultrathin thermal oxide film by a vapor deposition method (CVD method). Heat treatment in an oxidizing atmosphere. In this method, since a silicon oxide film is deposited by a vapor phase growth method (CVD method), there is a problem that a process of forming the silicon oxide film is complicated.

The above problem occurs not only on the surface of a silicon semiconductor substrate but also on the surface of a silicon layer provided on an insulating substrate or an insulating layer.

Accordingly, it is an object of the present invention to prevent the surface of the silicon layer from being roughened (irregular) when forming a silicon oxide film on the surface of the silicon layer, and to dry oxidize the surface of the silicon layer. A silicon oxide film with excellent characteristics can be formed without forming a film, and
A method for forming a silicon oxide film in which the time for forming a silicon oxide film is not prolonged to the left as compared with a conventional method for forming a silicon oxide film, and a silicon oxide film suitable for performing such a method for forming a silicon oxide film An object of the present invention is to provide a forming apparatus.

[0019]

According to the present invention, there is provided an apparatus for forming a silicon oxide film, comprising: (a) a processing chamber for forming a silicon oxide film on a surface of a silicon layer;
(B) a substrate loading / unloading section provided in the processing chamber for loading / unloading a substrate having a silicon layer into / from the processing chamber; and (c) a wet gas connected to the substrate loading / unloading section. A first wet gas generator for producing an atmosphere, and (d)
A second wet gas generator connected to the processing chamber and configured to bring the processing chamber into a wet gas atmosphere.

In the processing chamber of the silicon oxide film forming apparatus of the present invention, the silicon oxide film is formed on the surface of the silicon layer on each substrate while each substrate is held horizontally and a plurality of substrates are arranged vertically. Is preferably formed. The substrate loading / unloading section is provided at a lower portion of the processing chamber. The substrate is moved in the vertical direction, and is loaded / unloaded into the processing chamber via the substrate loading / unloading section.
It is preferable to provide a wet gas introduction unit connected to the wet gas generation device of the above, and a wet gas exhaust unit substantially opposed to the wet gas introduction unit in the horizontal direction. Further, an inert gas introduction section and an inert gas exhaust section are provided in the substrate carry-in / out section, and the inert gas introduction section is provided above and below the wet gas introduction section. It is preferable that the exhaust unit is disposed substantially facing the inert gas introduction unit in the horizontal direction. With such a structure, the flow of the wet gas in the horizontal direction in the substrate loading / unloading section is sandwiched between the flows of the inert gas in the horizontal direction, and the in-plane film thickness uniformity of the silicon oxide film in the silicon layer is improved. The uniformity of the inter-plane film thickness can be improved, and the wet gas can be prevented from flowing out of the region other than the substrate loading / unloading section in the first silicon oxide film forming step.

In the processing chamber of the silicon oxide film forming apparatus according to the present invention, when the substrate is carried into the processing chamber via the substrate carrying-in / out portion, the wet gas generated by the first wet gas generator is used for the substrate. It is preferable that the substrate is brought into and taken out of the loading / unloading section and the base loading / unloading section is set in a wet gas atmosphere, and a silicon oxide film is formed on the surface of the silicon layer. In this case, it is desirable that the temperature of the wet gas atmosphere in the substrate carry-in / out portion be a temperature at which silicon atoms do not desorb from the surface of the silicon layer.

In order to achieve the above object, the method for forming a silicon oxide film according to the present invention comprises: (a) a treatment chamber for forming a silicon oxide film on the surface of a silicon layer; and (b) a substrate having a silicon layer. A substrate loading / unloading section provided in the processing chamber for loading and unloading the substrate into and out of the processing chamber; and (c) a first wet process connected to the substrate loading / unloading section for setting the substrate loading / unloading section to a wet gas atmosphere. Formation of a silicon oxide film using a silicon oxide film forming apparatus provided with a gas generator and (d) a second wet gas generator connected to the processing chamber and having a wet gas atmosphere in the processing chamber. (A) when a substrate is carried into a processing chamber via a substrate carry-in / out section, a wet gas generated by the first wet gas generator is introduced into the substrate carry-in / out section to carry in / out the substrate. Part is a wet gas atmosphere, and
A first silicon oxide film forming step of forming a silicon oxide film on the surface of the silicon layer while keeping the temperature of the wet gas atmosphere at a temperature at which silicon atoms do not desorb from the surface of the silicon layer; and (B) treating the substrate After being carried into the room, the wet gas generated by the second wet gas generator is introduced into the processing chamber to make the processing chamber a wet gas atmosphere, thereby further forming a silicon oxide film on the surface of the silicon layer. 2) forming a silicon oxide film.

In the method of forming a silicon oxide film according to the present invention, the ambient temperature at which silicon atoms do not desorb from the surface of the silicon layer is a temperature at which the bond between the atoms terminating the silicon layer surface and the silicon atoms is not broken. Is preferred. Further, the temperature at which silicon atoms do not desorb from the surface of the silicon layer is preferably a temperature at which Si—H bonds on the surface of the silicon layer are not broken or a temperature at which Si—F bonds on the surface of the silicon layer are not broken. When a silicon semiconductor substrate having a (100) plane orientation is used as the base having the silicon layer, most of the hydrogen atoms on the surface of the silicon semiconductor substrate are bonded one by one to two bonds of silicon atoms, It has a terminal structure of H-Si-H. However, a portion where the surface state of the silicon semiconductor substrate is broken (for example, a step formation portion) has a terminal structure in which a hydrogen atom is bonded to only one bond of a silicon atom, or a three-bonded silicon atom. There is a terminal structure in which a hydrogen atom is bonded to each of the hands.
Usually, the remaining bonds of silicon atoms are bonded to silicon atoms inside the crystal. In the present specification, "Si-
The term "H bond" refers to a terminal structure in which a hydrogen atom is bonded to each of two bonds of a silicon atom, a terminal structure in which a hydrogen atom is bonded to only one bond of a silicon atom, or And all the terminal structures in which a hydrogen atom is bonded to each of three bonding hands of a silicon atom. The temperature of the wet gas atmosphere in the first silicon oxide film forming step is more specifically a temperature at which the wet gas does not condense on the silicon layer, preferably 150 ° C.
On the other hand, on the other hand, the temperature is preferably 500 ° C. or less, preferably 450 ° C. or less, more preferably 400 ° C. or less, and still more preferably 350 ° C. or less from the viewpoint of throughput.

In the method for forming a silicon oxide film according to the present invention, the ambient temperature in the second silicon oxide film forming step is preferably higher than the ambient temperature in the first silicon oxide film forming step. The ambient temperature in the second silicon oxide film forming step is 600 to 1200 ° C.
Preferably 700-1000 ° C., more preferably 7
It is desirable that the temperature be 50 to 900 ° C., but it is not limited to such a value.

Further, the method of generating a wet gas in the first wet gas generator and / or the second wet gas generator is as follows.
At least one of a hydrogen gas combustion method (pyrogenic method), a method of producing steam by heating pure water, and a method of producing steam by bubbling heated pure water with oxygen gas or an inert gas. It is preferred that Since the silicon oxide film is formed by an oxidation method using a wet gas, excellent time-dependent dielectric breakdown (TDD)
B) A silicon oxide film having characteristics can be obtained.
Note that the same wet gas generation method or different wet gas generation methods may be used in the first silicon oxide film forming step and the second silicon oxide film forming step. A first silicon oxide film forming step, a second silicon oxide film forming step, or a first silicon oxide film forming step and a second silicon oxide film forming step;
The wet gas in the step of forming a silicon oxide film may be diluted with an inert gas such as a nitrogen gas, an argon gas, and a helium gas. As a result, rapid oxidation on the surface of the silicon layer can be suppressed, and the uniformity of the in-plane film thickness and the inter-plane film thickness can be improved.

The halogen gas is contained in the wet gas in the first silicon oxide film forming step, the second silicon oxide film forming step, or the first silicon oxide film forming step and the second silicon oxide film forming step. May be. As a result, a silicon oxide film having excellent time zero dielectric breakdown (TZDB) characteristics and temporal dielectric breakdown (TDDB) characteristics can be obtained. Examples of the halogen element include chlorine, bromine, and fluorine, and among them, chlorine is preferable. Examples of the form of the halogen element contained in the wet gas include hydrogen chloride (HCl), CCl ₄ ,
It can be exemplified _{C 2 HCl 3, Cl 2,} HBr, NF 3. The content of the halogen element in the wet gas is 0.001 to 10% by volume, preferably 0.005 to 10% by volume, more preferably 0.1 to 10% by volume, based on the form of the molecule or the compound.
02 to 10% by volume. For example, when using hydrogen chloride gas, the content of hydrogen chloride gas in the wet gas is 0.02 to 1
Desirably, it is 0% by volume. By setting the atmosphere in the second silicon oxide film forming step to a wet gas atmosphere containing a halogen element, the characteristics of the silicon oxide film formed in the first silicon oxide film forming step can be further improved. Can be planned. That is, a silicon dangling bond (Si.) Or SiOH, which is a defect that can occur in the first silicon oxide film forming step, reacts with a halogen element in the second silicon oxide film forming step, and the silicon dangling bond terminates or As a result of the dehydration reaction, these defects, which are reliability deterioration factors, are eliminated.
In particular, elimination of these defects is effective for the initial silicon oxide film formed in the first silicon oxide film forming step.

In order to further improve the characteristics of the formed silicon oxide film, in the method of forming a silicon oxide film according to the present invention, after the completion of the second silicon oxide film forming step, the formed silicon oxide film is subjected to a heat treatment. Is preferably applied.

In this case, it is desirable that the atmosphere for the heat treatment be an inert gas atmosphere containing a halogen element.
By heat-treating the silicon oxide film in an inert gas atmosphere containing a halogen element, the termination of a silicon dangling bond (eg, Si. + Cl → SiCl) at the interface between the silicon oxide film and the silicon layer and the dehydration effect (SiOH + HCl) (→ SiCl + H ₂ O), a factor that lowers the reliability of the silicon oxide film is more reliably eliminated, and a silicon oxide film having excellent time-zero dielectric breakdown (TZDB) characteristics and time-dependent dielectric breakdown (TDDB) characteristics can be obtained. . Examples of the inert gas in the heat treatment include a nitrogen gas, an argon gas, and a helium gas. In addition, examples of the halogen element include chlorine, bromine, and fluorine, and among them, chlorine is preferable. Examples of the form of the halogen element contained in the inert gas include hydrogen chloride (HCl), CCl ₄ ,
It can be exemplified _{C 2 HCl 3, Cl 2,} HBr, NF 3. The content of the halogen element in the inert gas is 0.001 to 10% by volume, based on the form of the molecule or compound,
Preferably it is 0.005 to 10% by volume, more preferably 0.02 to 10% by volume. For example, when using hydrogen chloride gas, the hydrogen chloride gas content in the inert gas is 0.0
It is desirably 2 to 10% by volume.

In the method of forming a silicon oxide film of the present invention, the heat treatment may be a single-wafer treatment.
Preferably, the furnace annealing process is performed in the processing chamber of the silicon oxide film forming apparatus of the present invention. The temperature of the heat treatment is 700 to 1200 ° C, preferably 700 to 100 ° C.
0 ° C, more preferably 700 to 950 ° C. When the heat treatment is furnace annealing, the heat treatment time is 5 to 60 minutes, preferably 10 to 40 minutes, and more preferably 20 to 30 minutes. On the other hand, when the heat treatment is a single-wafer treatment, the heat treatment time is preferably 1 to 10 minutes. In the case of single-wafer processing, it is necessary to use a heat treatment apparatus different from the silicon oxide film forming apparatus of the present invention.

In the method of forming a silicon oxide film according to the present invention, it is desirable that the temperature of the atmosphere when the formed silicon oxide film is subjected to the heat treatment be higher than the temperature of the atmosphere in the second silicon oxide film forming step. In this case, after the completion of the second silicon oxide film forming step, the atmosphere may be switched to an inert gas atmosphere, and then the temperature may be increased to an ambient temperature for performing a heat treatment. After switching to the active gas atmosphere, it is preferable to raise the temperature to the ambient temperature for performing the heat treatment. Here, examples of the inert gas include a nitrogen gas, an argon gas, and a helium gas. Examples of the form of the halogen element contained in the inert gas include hydrogen chloride (HCl), CCl ₄ , C ₂ HCl ₃ , Cl ₂ , HBr, and N.
F ₃ can be mentioned. The content of the halogen element in the inert gas is based on the form of the molecule or compound,
0.001 to 10% by volume, preferably 0.005 to 10%
%, More preferably 0.02 to 10% by volume.
For example, when using hydrogen chloride gas, the content of hydrogen chloride gas in the inert gas is preferably 0.02 to 10% by volume.

The heat treatment may be performed in a state where the atmosphere of an inert gas containing a halogen element is reduced in pressure from the atmospheric pressure.

After the heat treatment, the silicon oxide film may be nitrided. In this case, the nitriding treatment is performed with N ₂ O gas, NO
It is desirable to carry out in an atmosphere of gas and NO ₂ gas, and it is particularly desirable to carry out in an atmosphere of N ₂ O gas. Alternatively, it is preferable to perform the nitriding treatment in an atmosphere of NH ₃ gas, N ₂ H ₄ , and hydrazine derivative, and then perform the annealing treatment in an atmosphere of N ₂ O gas and O ₂ . 700 nitriding
It is preferable that the heating be performed at a temperature of from 1200 to 1200 ° C., preferably from 800 to 1150 ° C., more preferably from 900 to 1100 ° C. In this case, it is preferable to heat the silicon layer by infrared irradiation and furnace annealing.

Alternatively, the atmosphere for the heat treatment may be a nitrogen-based gas atmosphere. Here, as nitrogen-based gas,
Examples include N ₂ , NH ₃ , N ₂ O, NO ₂ , and NO.

In the method of forming a silicon oxide film according to the present invention, the final silicon oxide film after the second silicon oxide film forming step has a predetermined thickness required for a semiconductor device. Good. On the other hand, the thickness of the silicon oxide film after the first silicon oxide film forming step is preferably as thin as possible. However, the plane orientation of the silicon semiconductor substrate currently used in the manufacture of semiconductor devices is almost (100), and no matter how the surface of the silicon semiconductor substrate is smoothed, the surface of the silicon semiconductor substrate must be (100). A step called a step is formed. This step is usually for one layer of silicon atoms, but in some cases, a step for two to three layers may be formed. Therefore, the thickness of the silicon oxide film after the first silicon oxide film forming step is 0.8 nm or more, for example, 0.8 to 1.2 n when a (100) silicon semiconductor substrate is used as the silicon layer.
m is preferable, but the value is not limited to such a value.

In the method for forming a silicon oxide film according to the present invention, in the first silicon oxide film forming step, the atmosphere before the formation of the silicon oxide film is changed to the silicon oxide before the formation of the silicon oxide film based on the wet gas. In order to suppress the formation of a film, an inert gas atmosphere such as a nitrogen gas, an argon gas, or a helium gas, or a reduced-pressure atmosphere is preferable.

Normally, before forming a silicon oxide film on a silicon layer, the silicon layer is washed with an NH ₄ OH / H ₂ O ₂ aqueous solution, and
The surface of the silicon layer is cleaned by RCA cleaning in which the silicon layer is cleaned with a 1 / H ₂ O ₂ aqueous solution, fine particles and metal impurities are removed from the surface, and then the silicon layer is immersed in a hydrofluoric acid aqueous solution. However, when the silicon layer is subsequently exposed to the air, the surface of the silicon layer is contaminated, and moisture and organic substances adhere to the surface of the silicon layer, or Si atoms on the surface of the silicon layer combine with hydroxyl groups (OH). (For example, see the document “Highly-reliable Gate Oxide Formation f
or Giga-ScaleLSIs by using Closed Wet Cleaning Sys
tem and Wet Oxidation with Ultra-Dry Unloading ",
J. Yugami, et al., International Rlectron Device M
eeting Technical Digest 95, pp 855-858). In such a case, when the formation of the silicon oxide film is started as it is, moisture, an organic substance, or Si-OH is taken into the formed silicon oxide film, and the characteristics of the formed silicon oxide film deteriorate or It can cause the generation of defective portions. Note that the defect portion is a portion of a silicon oxide film including a defect such as a silicon dangling bond (Si.) Or a Si-H bond, or a Si-O-
Si bond is compressed by stress or Si-OS
Si-O in which the angle of the i-bond is thick or different from the angle of the Si-O-Si bond in the bulk silicon oxide film
-Means a portion of the silicon oxide film including the Si bond. Therefore, in order to avoid such problems,
The method for forming a silicon oxide film of the present invention includes a step of cleaning the surface of the silicon layer before the first silicon oxide film forming step, without exposing the silicon layer after the surface cleaning to the atmosphere (ie, for example, First from silicon layer surface cleaning
The atmosphere up to the start of the silicon oxide film formation step is an inert gas atmosphere or a vacuum atmosphere), and the first silicon oxide film formation step is preferably performed. As a result, a silicon oxide film can be formed on a silicon layer having a surface that is mostly terminated with hydrogen and a very small portion is terminated with fluorine, and the characteristics of the formed silicon oxide film are deteriorated or defects are generated. Can be prevented.

In the method of forming a silicon oxide film according to the present invention, the term “silicon layer” refers to not only a substrate itself such as a silicon semiconductor substrate but also an epitaxial silicon layer formed on the substrate (epitaxial layer formed by a selective epitaxial growth method). Silicon layer), polysilicon layer,
Alternatively, a silicon oxide film such as an amorphous silicon layer, a silicon layer in an SOI structure manufactured based on a so-called bonding method or a SIMOX method, and further a semiconductor element or a component of a semiconductor element formed on a substrate or these layers. It means a silicon layer (base) to be formed. The method of manufacturing the silicon semiconductor substrate is CZ method, MCZ method, DLC
Any method such as the Z method and the FZ method may be used, or a method in which crystal defects are removed by high-temperature hydrogen annealing beforehand may be used.

The method of forming a silicon oxide film of the present invention includes, for example, forming a gate oxide film of a MOS transistor, forming an interlayer insulating film and an element isolation region, forming a gate oxide film of a top gate or bottom gate thin film transistor, and flash memory. For example, the present invention can be applied to formation of a silicon oxide film in various semiconductor devices, such as formation of a tunnel oxide film.

In the present invention, a silicon oxide film is formed on the surface of the silicon layer when the substrate is loaded into the processing chamber via the substrate loading / unloading section, that is, during the loading of the substrate into the processing chamber. Since the silicon oxide film is formed on the surface of the silicon layer in a relatively low-temperature wet gas atmosphere, the time required for forming the entire silicon oxide film can be prolonged as compared to the conventional silicon oxide film forming method. Absent.

In a state where the atmosphere is maintained at a temperature at which silicon atoms do not desorb from the surface of the silicon layer, the formation of a silicon oxide film on the surface of the silicon layer is started by an oxidation method using a wet gas. By setting the ambient temperature at the start of the formation of the silicon oxide film to such a temperature, it is possible to prevent the surface of the silicon layer from being uneven (rough). The oxidation of silicon atoms starts from the silicon atoms inside one layer, not from the outermost surface of the silicon layer. That is, it starts with a so-called back bond. Accordingly, since the smoothness of the interface between the silicon layer and the silicon oxide film is maintained at the atomic level, the characteristics of the silicon oxide film finally formed are excellent. Further, since the second silicon oxide film forming step is started with the silicon oxide film formed, the temperature rises from the ambient temperature in the first silicon oxide film forming step to the ambient temperature in the second silicon oxide film forming step. Irregularities (roughness) on the surface of the silicon layer can be prevented even when heated. In addition, since the silicon oxide film is formed on the surface of the silicon layer by an oxidation method using a wet gas, the silicon oxide film finally formed does not include a dry oxide film, and a silicon oxide film having excellent characteristics is formed. Can be formed.

After the silicon semiconductor substrate is loaded into the processing chamber, the first silicon oxide film forming step and the second silicon oxide film forming step may be performed.゜ C to 800 ゜ C
And a time for forcibly lowering the ambient temperature in the processing chamber from, for example, 800 ° C. to 350 ° C. by air cooling or the like, and such a method requires a conventional silicon oxide film. The time required for the entire formation of the silicon oxide film is 1.5 to 2 times as long as the formation method. In addition, deterioration of the heater, quartz parts, heat insulating material, and the like is likely to occur due to repetition of low temperature to high temperature to low temperature.

[0042]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described based on embodiments with reference to the drawings.

(Example 1) FIG. 1 is a schematic sectional view of a vertical type silicon oxide film forming apparatus according to the present invention. In this silicon oxide film forming apparatus, a silicon oxide film is formed by a pyrogenic oxidation method. The silicon oxide film forming apparatus shown in FIG. 1 includes a processing chamber 10 having a double tube structure made of quartz and held in a vertical direction, and a gas introduction unit 12 for introducing a wet gas or an inert gas into the processing chamber 10. A gas exhaust unit 13 for exhausting gas from the processing chamber 10, a heater 14 for maintaining the inside of the processing chamber 10 at a predetermined atmospheric temperature via a cylindrical soaking tube 16 made of SiC, and a purge chamber 2.
0, a gas introduction unit 21 for introducing nitrogen gas into the purge chamber 20, a gas exhaust unit 22 for exhausting gas from the purge chamber 20, a shutter 15 for separating the processing chamber 10 from the purge chamber 20, and a silicon layer. And an elevator mechanism 23 for carrying in and out the substrate having the above. A quartz boat 24 for mounting a substrate having a silicon layer is attached to the elevator mechanism 23. In the processing chamber 10, a silicon oxide film is formed on the surface of the silicon layer. In the processing chamber 10, a silicon oxide film is formed on the surface of the silicon layer in each substrate while each substrate is held horizontally and a plurality of substrates are arranged in a vertical manner.

A substrate loading / unloading section 25 is provided below the processing chamber 10 to transport a substrate having a silicon layer into and out of the processing chamber 10. The substrate carrying-in / out section 25 is provided with a wet gas introduction section 26 and a wet gas exhaust section 27 substantially opposed to the wet gas introduction section 26 in the horizontal direction.
FIG. 2 is a conceptual diagram when a portion including the wet gas introduction section 26 and the wet gas exhaust section 27 of the substrate carrying-in / out section 25 is cut along a horizontal plane. The substrate carrying-in / out section 25 further includes inert gas introduction sections 28A and 28B and an inert gas exhaust section 29.
A, 29B are provided. Inert gas introduction part 28A
The inert gas introduction part 28B is provided above and below the wet gas introduction part 26, respectively. The inert gas exhaust sections 29A and 29B are connected to these inert gas introduction sections 2A and 2B.
8A and 28B, and are disposed substantially in the horizontal direction.

This silicon oxide film forming apparatus further comprises:
The processing chamber 1 is connected to the processing chamber 10, which is connected to the substrate loading / unloading section 25, and is connected to the processing chamber 10, which is a first wet gas generator for setting the substrate loading / unloading section 25 to a wet gas atmosphere.
A combustion chamber 30A, which is a second wet gas generator for providing a wet gas atmosphere inside 0, is provided. Piping 32A
The hydrogen gas supplied to the combustion chamber 30A through the
By mixing and burning the oxygen gas supplied to the combustion chamber 30A via A at a high temperature in the combustion chamber 30A,
Generates steam. The water vapor is introduced into the processing chamber 10 via the pipe 33A, the gas passage 11, and the gas introduction unit 12. The gas flow path 11 corresponds to a space between the inner wall and the outer wall of the processing chamber 10 having a double pipe structure. Alternatively, the hydrogen gas supplied to the combustion chamber 30B via the pipe 32B is mixed with the oxygen gas supplied to the combustion chamber 30B via the pipe 31B at a high temperature in the combustion chamber 30B, and the mixture is burned. Is generated. Such steam is
The gas is introduced into the substrate carrying-in / out section 25 through the pipe 33 </ b> B and the wet gas introduction section 26, and is exhausted from the wet gas exhaust section 27. The temperature in the combustion chambers 30A and 30B is maintained at 700 to 900 ° C. by, for example, a heater (not shown). In the silicon oxide film forming apparatus shown in FIG.
Although the first wet gas generator and the second wet gas generator are separate combustion chambers 30A and 30B, they may be one common combustion chamber.

In the method of forming a silicon oxide film according to the first embodiment, the silicon oxide film forming apparatus shown in FIG.
The first silicon oxide film forming step and the second silicon oxide film forming step were performed in the processing chamber 10. In Example 1, the silicon semiconductor substrate 40 was used as a base having a silicon layer. The formed silicon oxide film functions as a gate oxide film. In Example 1, a pyrogenic oxidation method was employed as an oxidation method using a wet gas in the first silicon oxide film forming step and the second silicon oxide film forming step. Further, after the completion of the second silicon oxide film forming step, the formed silicon oxide film is subjected to heat treatment (furnace annealing treatment) in an inert gas atmosphere containing a halogen element (a nitrogen gas atmosphere containing hydrogen chloride). ). Hereinafter, a method for forming a silicon oxide film according to the first embodiment will be described with reference to FIGS. 1, 3 to 5, and 6. 3 to 5 and FIG. 8 to be described later, the diagram on the left is a conceptual diagram of the processing chamber 10 and the like, and the graph on the right is a temperature distribution in the processing chamber 10, the substrate loading / unloading section 25, and the purge chamber 20. FIG.

[Step-100] First, an N-type silicon wafer doped with phosphorus and having a diameter of 8 inches (made by the CZ method)
LOC is formed on a silicon semiconductor substrate 40 by a known method.
An element isolation region 41 having an OS structure was formed, and then well ion implantation, channel stop ion implantation, and threshold adjustment ion implantation were performed. Note that the element isolation region may have a trench structure or a combination of a LOCOS structure and a trench structure. Thereafter, fine particles and metal impurities on the surface of the silicon semiconductor substrate 40 are removed by RCA cleaning, and then the surface of the silicon semiconductor substrate 40 is cleaned with a 0.1% hydrofluoric acid aqueous solution to expose the surface of the silicon semiconductor substrate 40. (See FIG. 6A). The surface of the silicon semiconductor substrate 40 is mostly terminated with hydrogen, and a very small portion is terminated with fluorine.

[Step-110] Next, the silicon semiconductor substrate 40 was loaded into the purge chamber 20 of the silicon oxide film forming apparatus shown in FIG. After the loading of the silicon semiconductor substrate 40 into the purge chamber 20 is completed, a door (not shown) is closed, nitrogen gas is introduced into the purge chamber 20 from the gas introduction unit 21, discharged from the gas exhaust unit 22, and discharged from the purge chamber 20. The inside was set to a nitrogen gas atmosphere. On the other hand, nitrogen gas is introduced into the processing chamber 10 from the gas introduction unit 12 and exhausted from the gas exhaust unit 13.
The inside is made an inert gas atmosphere such as a nitrogen gas atmosphere (a reduced pressure atmosphere may be used), and the heater 14 is connected via a soaking tube 16.
As a result, the ambient temperature in the processing chamber 10 was maintained at 800 ° C. In this state, the shutter 15 is closed. Further, the combustion chamber 30 is connected via the pipes 31B and 32B.
The hydrogen gas supplied to B is mixed with oxygen gas at a high temperature in the combustion chamber 30B and burned to generate steam, and the steam is supplied to the pipe 33B and the wet gas introduction unit 26.
, And introduced into the substrate carrying-in / out section 25, and exhausted from the wet gas exhaust section 27. Further, an inert gas (a nitrogen gas is used in the first embodiment) is supplied to the inert gas introduction portions 28A and 28A.
8B, the gas was introduced into the substrate loading / unloading section 25, and exhausted from the inert gas exhaust sections 29A, 29B. And these states were held as schematically shown in FIG.

[Step-120] The oxygen gas concentration in the purge chamber 20 is monitored.
m, it is determined that the inside of the purge chamber 20 has become a sufficient nitrogen gas atmosphere. After that, shutter 15
Is opened, and the elevator mechanism 23 is operated to operate the quartz boat 2
4 at a rising speed of 5 cm / min.
The silicon semiconductor substrate 40 serving as a base is carried into the processing chamber 10 via 5. At this time, the wet gas generated in the combustion chamber 30B, which is the first wet gas generator, is continuously introduced into the substrate loading / unloading section 25, and the substrate loading / unloading section 25 is set to a wet gas atmosphere, whereby the surface of the silicon layer is exposed. Then, a silicon oxide film was formed. That is, while maintaining the ambient temperature at a temperature at which silicon atoms do not desorb from the surface of the silicon layer (the silicon semiconductor substrate 40 in the first embodiment) (specifically, in the first embodiment, the ambient temperature is set to 150 ° C.). ~ 3
(Set at 50 ° C.) and a first silicon oxide film forming step of forming a silicon oxide film 42 on the surface of the silicon layer by an oxidation method using a wet gas was performed. This state is schematically shown in FIG. The temperature of the wet gas when the silicon semiconductor substrate 40 starts to come into contact with the wet gas in the substrate loading / unloading section 25 is about 150 ° C.
0 is about 350 ° C. when the wet gas does not come into contact with the wet gas in the substrate loading / unloading section 25, and the ambient temperature when the silicon semiconductor substrate 40 exits the substrate loading / unloading section 25 is about 400 ° C. As described above, the temperatures of the wet gas and the inert gas were controlled by a heater (not shown). In Example 1, the time during which one silicon semiconductor substrate 40 was in contact with the wet gas in the substrate loading / unloading section 25 was set to 4 minutes. Thus, when the first silicon oxide film forming step is completed, that is, when the silicon semiconductor substrate 40 is
At the point when it stops contacting the wet gas in 5,
A silicon oxide film having a thickness of 1 nm was formed on the surface of the silicon layer (the silicon semiconductor substrate 40 in Example 1) (see FIG. 6B). The thickness of this silicon oxide film is S
This is a thickness corresponding to several molecular layers of iO ₂ , and is sufficient to function as a protective film even in consideration of steps on the surface of the silicon semiconductor substrate. The wet gas may be diluted with, for example, nitrogen gas. As a result, more excellent controllability of the thickness of the silicon oxide film can be obtained.

[Step-130] The raising of the quartz boat 24 was continued, and all the silicon semiconductor substrates 40 were finally stored in the upper part of the processing chamber 10. After the elevator mechanism 23 reached the highest position, the shutter 15 was closed. As a result, communication between the processing chamber 10 and the purge chamber 20 is stopped. The ambient temperature in the processing chamber 10 is maintained at 800 ° C. by the heater 14,
Since a silicon oxide film that also functions as a protective film is already formed on the surface of the substrate 0, it is possible to suppress the occurrence of roughness on the surface of the silicon semiconductor substrate 40.

[Step-140] Thereafter, the introduction of the inert gas (nitrogen gas) into the processing chamber 10 was stopped. Further, the introduction of the wet gas into the substrate carrying-in / out section 25 is stopped, and the piping 3 is stopped.
3B, an inert gas (for example, nitrogen gas) was introduced into the substrate carrying-in / out section 25 through the wet gas introduction section 26, and the gas was continuously exhausted from the wet gas exhaust section 27. Then, after the ambient temperature in the processing chamber 10 is stabilized to a temperature higher than the ambient temperature in the first silicon oxide film forming step (800 ° C. in the first embodiment), the combustion in the second wet gas generator is performed. The wet gas generated in the chamber 30A was introduced into the processing chamber 10. That is, the hydrogen gas and the oxygen gas supplied to the combustion chamber 30A through the pipes 31A and 32A are mixed at a high temperature in the combustion chamber 30A, and the steam generated by burning the hydrogen gas (by a parogenic method). Generated steam)
Was introduced into the processing chamber 10 via the pipe 33A, the gas flow path 11, and the gas introduction unit 12 (see FIG. 5). Thus,
By setting the processing chamber 10 to a wet gas atmosphere at a temperature of 800 ° C., the silicon semiconductor substrate 40 as a silicon layer is formed.
A silicon oxide film having a total thickness of 4.0 nm was formed on the surface (see FIG. 6C). The wet gas may be diluted with, for example, nitrogen gas. As a result, more excellent controllability of the thickness of the silicon oxide film can be obtained.

As described above, the formation of the silicon oxide film 42 on the surface of the silicon semiconductor substrate 40 is completed.
Thereafter, the interior of the processing chamber 10 is set to an inert gas atmosphere such as nitrogen gas, the shutter 15 is opened, the elevator mechanism 23 is operated, the quartz boat 24 is lowered, and the shutter 15 is closed. Semiconductor substrate 40
However, if it is intended to form a silicon oxide film having higher characteristics, it is preferable to perform a heat treatment described below on the silicon oxide film.

[Step-150] That is, after that, the processing chamber 1
The introduction of the wet gas to 0 was stopped, and the temperature of the atmosphere in the processing chamber 10 was raised to 850 ° C. by the heater 14 while introducing the nitrogen gas into the processing chamber 10 from the gas introduction unit 12.
Next, nitrogen gas containing 0.1% by volume of hydrogen chloride was introduced into the processing chamber 10 from the gas introduction unit 12, and heat treatment was performed for 30 minutes (see FIG. 6D).

[Step-160] With the above, the formation of the silicon oxide film 42 on the surface of the silicon semiconductor substrate 40 is completed. Thereafter, the processing chamber 10 was set to a nitrogen gas atmosphere, the shutter 15 was opened, the elevator mechanism 23 was operated, the quartz boat 24 was lowered, the shutter 15 was closed, and the silicon semiconductor substrate 40 was unloaded from the purge chamber 20.

(Embodiment 2) Embodiment 2 is a modification of Embodiment 1. Example 2 is different from Example 1 in that the wet gas in the first silicon oxide film forming step and the second silicon oxide film forming step contains a halogen element (specifically, chlorine). It is in. Note that chlorine is in the form of hydrogen chloride, and the concentration of hydrogen chloride contained in the wet gas was 0.1% by volume. More specifically, in the same step as [Step-130] of Example 1, the concentration was 0.1% by volume.
The first silicon oxide film forming step was performed using a wet gas containing hydrogen chloride. Further, [Step-
140], a second silicon oxide film forming step was performed using a wet gas containing 0.1% by volume of hydrogen chloride. Except for the above, a silicon oxide film was formed in the same manner as in Example 1.

(Embodiment 3) Embodiment 3 is also a modification of Embodiment 1. Example 3 is different from Example 1 in that after completion of the second silicon oxide film forming step, the atmosphere is switched to an inert gas atmosphere containing a halogen element, and then the temperature is raised to an ambient temperature for performing heat treatment. It is in a warm spot. Specifically, in the same step as [Step-150] in Example 1, after the introduction of the wet gas into the processing chamber 10 is stopped, an inert gas containing 0.1% by volume of hydrogen chloride ( While introducing (nitrogen gas) from the gas introduction unit 12 into the processing chamber 10,
The temperature of the atmosphere in the processing chamber 10 was raised to 850 ° C. by the heater 14. Next, nitrogen gas containing 0.1% by volume of hydrogen chloride was continuously introduced into the processing chamber 10 from the gas introduction unit 12, and heat treatment was performed for 30 minutes. Except for the above points,
A silicon oxide film was formed in the same manner as in Example 1.

Although the present invention has been described based on the preferred embodiments, the present invention is not limited to these embodiments. The various conditions and the structure of the silicon oxide film forming apparatus described in the embodiments are merely examples, and can be changed as appropriate. The method for generating a wet gas in the first and / or the second wet gas generator includes not only a hydrogen gas combustion method but also a method of generating water vapor by heating pure water, and a method of generating oxygen gas or non-oxygen gas. A method in which steam is generated by bubbling heated pure water with an active gas, or a method using these oxidation methods in combination can be employed.
An oxidation method in a first silicon oxide film forming step;
An oxidation method different from the oxidation method in the method of forming a silicon oxide film described above may be used.

FIG. 7 is a schematic sectional view of a modified example of the silicon oxide film forming apparatus of the present invention. Unlike the silicon oxide film forming apparatus shown in FIG. 1, in the silicon oxide film forming apparatus shown in FIG. 7, an inert gas introduction section and an inert gas exhaust section are not provided in the substrate carry-in / out section. Other structures can be the same as those of the silicon oxide film forming apparatus shown in FIG. 1, and therefore, detailed description is omitted.

In the silicon oxide film forming apparatus shown in FIG. 7, the steam generated in the combustion chamber 30B, which is the first wet gas generator, is introduced from the wet gas introducing section 26 into the substrate carrying-in / out section 25, The gas is exhausted from a wet gas exhaust unit 27 which is substantially opposed to the wet gas introduction unit 26 in the horizontal direction.
FIG. 8 shows a state of a first silicon oxide film forming step, which is the same as [Step-120] of the first embodiment, when a silicon oxide film is formed using this silicon oxide film forming apparatus.
Is shown schematically in FIG. The flow of the wet gas introduced into the substrate carrying-in / out section 25 from the wet gas introduction section 26 is controlled by the gas introduction section 12.
Of the inert gas introduced into the processing chamber 10 from the gas exhaust unit 13 and exhausted from the gas exhaust unit 13, and the flow of the inert gas introduced into the purge chamber 20 from the gas introducing unit 21 and exhausted from the gas exhaust unit 22. , Generally controlled.

In the embodiment, the silicon oxide film is formed exclusively on the surface of the silicon semiconductor substrate, but the silicon oxide film is formed on the epitaxial silicon layer formed on the insulating layer formed on the substrate. An epitaxial silicon layer formed on a silicon semiconductor substrate surface by a selective epitaxial growth method in a semiconductor device manufacturing process, a polysilicon layer formed on an insulating layer formed on the substrate, or A silicon oxide film can be formed on the surface of the amorphous silicon layer or the like.
Alternatively, a silicon oxide film may be formed on the surface of a silicon layer in an SOI structure, or a silicon element may be formed on a substrate on which a semiconductor element or a component of the semiconductor element is formed, or on a surface of a silicon layer formed thereon. An oxide film may be formed. Furthermore, a silicon oxide film may be formed on a surface of a silicon element formed on a substrate on which a semiconductor element or a component of the semiconductor element is formed, or a base insulating layer formed on the substrate. The heat treatment after the formation of the silicon oxide film is not essential and can be omitted in some cases.

In the embodiment, after cleaning the surface of the silicon semiconductor substrate 40 with a 0.1% aqueous hydrofluoric acid solution, the silicon semiconductor substrate 40 is carried into the silicon oxide film forming apparatus. The atmosphere from the surface cleaning to the transfer to the silicon oxide film forming apparatus may be an inert gas (for example, nitrogen gas) atmosphere. still,
Such an atmosphere may be, for example, an inert gas atmosphere in a silicon semiconductor substrate surface cleaning apparatus and a silicon oxide film forming apparatus in which the silicon semiconductor substrate 40 is placed in a transport box filled with an inert gas. From the surface cleaning device for the silicon semiconductor substrate to the silicon oxide film forming device using a method for carrying the substrate into the purge chamber 20 and a cluster tool device including a surface cleaning device, a silicon oxide film forming device, a transport path, a loader and an unloader. This can be achieved by a method in which the purging chamber 20 is connected to the purge chamber 20 by a transfer path, and the atmosphere of the surface cleaning apparatus and the transfer path is set to an inert gas atmosphere.

Alternatively, instead of cleaning the surface of the silicon semiconductor substrate 40 with a 0.1% hydrofluoric acid aqueous solution, a gas phase cleaning method using anhydrous hydrogen fluoride gas is performed under the conditions shown in Table 1. The surface of the silicon semiconductor substrate 40 may be cleaned. Note that methanol is added to prevent generation of particles. Alternatively, the surface of the silicon semiconductor substrate 40 may be cleaned by a gas phase cleaning method using hydrogen chloride gas under the conditions exemplified in Table 2.
Before the surface cleaning of the silicon semiconductor substrate 40 is started or after the surface cleaning is completed, the atmosphere in the surface cleaning apparatus or the atmosphere in the transfer path may be an inert gas atmosphere,
For example, a vacuum atmosphere of about 1.3 × 10 ⁻¹ Pa (10 ⁻³ Torr) may be used. When the atmosphere in the transfer path or the like is a vacuum atmosphere, the atmosphere in the purge chamber 20 of the silicon oxide film forming apparatus when the silicon semiconductor substrate is carried in is, for example, 1.3 × 10 ⁻¹ Pa (10 ^−3). A vacuum atmosphere of about Torr may be set, and after the loading of the silicon semiconductor substrate is completed, the atmosphere of the purge chamber 20 may be an inert gas (for example, nitrogen gas) atmosphere at atmospheric pressure. As a result, the surface of the silicon layer terminated with hydrogen or fluorine before the formation of the silicon oxide film can be kept in a state free of contamination and the like, and as a result, moisture, organic substances, or Si
It is possible to effectively prevent the characteristics of the formed silicon oxide film from deteriorating or generating a defective portion due to the incorporation of -OH.

[0063]

[Table 1] Anhydrous hydrogen fluoride gas: 300 sccm Methanol vapor: 80 sccm Nitrogen gas: 1000 sccm Pressure: 0.3 Pa Temperature: 60 ° C

[0064]

[Table 2] Hydrogen chloride gas / nitrogen gas: 1% by volume Temperature: 800 ° C

[0065]

According to the present invention, a silicon oxide film is formed on the surface of a silicon layer when a substrate is carried into a processing chamber via a substrate carrying-in / out portion, and therefore, compared with a conventional silicon oxide film forming method. However, the time required for the entire formation of the silicon oxide film is not prolonged to the left. In the method for forming a silicon oxide film of the present invention, the formation of the silicon oxide film on the surface of the silicon layer is started at an ambient temperature at which silicon atoms are not desorbed from the surface of the silicon layer. (Roughness) can be prevented. Further, since the second silicon oxide film forming step is started with the silicon oxide film formed, the temperature rises from the ambient temperature in the first silicon oxide film forming step to the ambient temperature in the second silicon oxide film forming step. Even when warm,
Irregularities (roughness) can be prevented from being generated on the surface of the silicon layer. In addition, the finally formed silicon oxide film does not include a dry oxide film having low reliability, and a silicon oxide film having excellent characteristics can be formed. Therefore, a decrease in channel mobility can be prevented, the drive current of the MOS transistor element hardly deteriorates, and the occurrence of a stress leak phenomenon that causes deterioration of data retention characteristics in a flash memory or the like can be suppressed.
It is possible to form a very thin, for example, gate oxide film having excellent long-term reliability.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a vertical type silicon oxide film forming apparatus of the present invention.

FIG. 2 is a conceptual diagram when a substrate loading / unloading section is cut along a horizontal plane.

FIG. 3 is a conceptual diagram of a silicon oxide film forming apparatus and the like for describing a method of forming a silicon oxide film according to a first embodiment.

FIG. 4 is a conceptual diagram of a silicon oxide film forming apparatus and the like for explaining a method of forming a silicon oxide film according to the first embodiment, following FIG. 3;

FIG. 5 is a conceptual diagram of a silicon oxide film forming apparatus and the like for explaining a method of forming a silicon oxide film according to the first embodiment, following FIG. 4;

FIG. 6 is a schematic partial cross-sectional view of a silicon semiconductor substrate and the like for describing a method of forming a silicon oxide film of Example 1.

FIG. 7 is a schematic sectional view of a modification of the vertical type silicon oxide film forming apparatus of the present invention.

FIG. 8 is a conceptual diagram showing a first silicon oxide film forming step in a modification of the vertical type silicon oxide film forming apparatus of the present invention shown in FIG. 7;

FIG. 9 is a schematic sectional view of a conventional vertical type silicon oxide film forming apparatus (thermal oxidation furnace).

FIG. 10 is a conceptual diagram of a silicon oxide film forming apparatus and the like for describing a conventional silicon oxide film forming method.

FIG. 11 is a conceptual diagram of a silicon oxide film forming apparatus and the like for explaining a conventional method of forming a silicon oxide film, following FIG.

FIG. 12 is a conceptual diagram of a silicon oxide film forming apparatus and the like for explaining a conventional method of forming a silicon oxide film, following FIG. 11;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 ... Processing chamber, 11 ... Gas flow path, 12 ... Gas introduction part, 13 ... Gas exhaust part, 14 ... Heater,
15 ... shutter, 16 ... heat equalizing tube, 20 ...
Purge chamber, 21: gas introduction unit, 22: gas exhaust unit, 23: elevator mechanism, 24: quartz boat, 25: substrate loading / unloading unit, 26: wet gas introduction unit , 27 ... wet gas exhaust unit, 28A, 28B ...
Inert gas introduction part, 29A, 29B ... inert gas exhaust part, 30A, 30B ... combustion chamber, 31A, 31B,
32A, 32B, 33A, 33B ... piping, 40 ...
.Silicon semiconductor substrate, 41... Element isolation region, 42
... Silicon oxide film

Claims (28)

[Claims] 1. A processing chamber for forming a silicon oxide film on the surface of a silicon layer. 2. A processing chamber for loading and unloading a substrate having a silicon layer into and from the processing chamber. (C) a first wet gas generating device connected to the substrate carry-in / out portion for setting the substrate carry-in / out portion to a wet gas atmosphere; and (d) a processing chamber connected to the processing chamber. A silicon oxide film forming apparatus, comprising: a second wet gas generator for making a room a wet gas atmosphere. 2. In a processing chamber, each substrate is held horizontally,
In addition, a silicon oxide film is formed on the surface of the silicon layer in each substrate in a state where a plurality of substrates are arranged in a vertical manner, and the substrate loading / unloading section is provided at a lower portion of the processing chamber, and the substrate moves vertically. The substrate is carried into and out of the processing chamber via the substrate carrying-in / out part. The substrate carrying-in / out part has a wet gas introduction part connected to the first wet gas generating device, and a horizontal direction with the wet gas introduction part. 2. The silicon oxide film forming apparatus according to claim 1, further comprising a wet gas exhaust unit substantially facing the gas exhaust unit. 3. An inert gas introduction section and an inert gas exhaust section are further provided in the substrate carry-in / out section, and the inert gas introduction section is provided above and below the wet gas introduction section. 3. The silicon oxide film forming apparatus according to claim 2, wherein the inert gas exhaust unit is disposed substantially facing the inert gas introduction unit in a horizontal direction. 4. When the substrate is carried into the processing chamber via the substrate carrying-in / out section, the wet gas generated by the first wet gas generating device is introduced into the substrate carrying-in / out section, and the substrate carrying-in / out section is moved. 3. The silicon oxide film forming apparatus according to claim 2, wherein a wet gas atmosphere is used, and a silicon oxide film is formed on a surface of the silicon layer. 5. The silicon oxide film forming apparatus according to claim 4, wherein the temperature of the wet gas atmosphere in the substrate loading / unloading section is a temperature at which silicon atoms do not desorb from the surface of the silicon layer. 6. A processing chamber for forming a silicon oxide film on the surface of a silicon layer. 2. A processing chamber for loading and unloading a substrate having a silicon layer into and from the processing chamber. (C) a first wet gas generating device connected to the substrate carry-in / out portion for setting the substrate carry-in / out portion to a wet gas atmosphere; and (d) a processing chamber connected to the processing chamber. A method for forming a silicon oxide film using a silicon oxide film forming apparatus comprising: a second wet gas generating device for setting a room to a wet gas atmosphere, wherein (A) processing is performed via a substrate carrying-in / out portion. When the substrate is loaded into the chamber, the wet gas generated by the first wet gas generator is introduced into the substrate loading / unloading section to set the substrate loading / unloading section to a wet gas atmosphere, and the temperature of the wet gas atmosphere is changed to a silicon layer. Temperature at which silicon atoms do not desorb from the surface of A first silicon oxide film forming step of forming a silicon oxide film on the surface of the silicon layer in the state; and (B) transporting the substrate into the processing chamber, and then discharging the wet gas generated by the second wet gas generator. Forming a silicon oxide film on the surface of the silicon layer by introducing the processing chamber into a wet gas atmosphere by introducing the silicon oxide film into the processing chamber. Method. 7. An atmosphere temperature at which silicon atoms are not desorbed from the surface of the silicon layer is a temperature at which a bond between the atoms terminating the silicon layer surface and the silicon atoms is not broken. The method for forming a silicon oxide film according to the above. 8. The silicon oxide film according to claim 7, wherein the ambient temperature at which silicon atoms do not desorb from the surface of the silicon layer is a temperature at which Si—H bonds on the surface of the silicon layer are not broken. Forming method. 9. The silicon oxide film according to claim 7, wherein the ambient temperature at which silicon atoms do not desorb from the surface of the silicon layer is a temperature at which Si—F bonds on the surface of the silicon layer are not broken. Forming method. 10. The method for forming a silicon oxide film according to claim 6, wherein the ambient temperature in the second silicon oxide film forming step is higher than the ambient temperature in the first silicon oxide film forming step. 11. The first wet gas generator and / or the second wet gas generator.
The method of generating a wet gas in the wet gas generator of the present invention is a hydrogen gas combustion method, a method of generating steam by heating pure water, and a method of generating steam by bubbling heated pure water with an oxygen gas or an inert gas. 7. The method for forming a silicon oxide film according to claim 6, wherein the method is at least one of the methods. 12. A halogen element is contained in a wet gas in the first silicon oxide film forming step, the second silicon oxide film forming step, or the first silicon oxide film forming step and the second silicon oxide film forming step. The method for forming a silicon oxide film according to claim 6, wherein the silicon oxide film is contained. 13. The method for forming a silicon oxide film according to claim 12, wherein the halogen element is chlorine. 14. The silicon oxide film according to claim 13, wherein chlorine is in the form of hydrogen chloride, and the concentration of hydrogen chloride contained in the wet gas is 0.02 to 10% by volume. Forming method. 15. The wet gas in the first silicon oxide film forming step, the second silicon oxide film forming step, or the first silicon oxide film forming step and the second silicon oxide film forming step is an inert gas. The method for forming a silicon oxide film according to claim 6, wherein the silicon oxide film is diluted. 16. The method for forming a silicon oxide film according to claim 6, wherein a heat treatment is performed on the formed silicon oxide film after the completion of the second silicon oxide film forming step. 17. An atmosphere for the heat treatment is an inert gas atmosphere containing a halogen element.
7. The method for forming a silicon oxide film according to 6. 18. The method according to claim 17, wherein the halogen element is chlorine. 19. The silicon oxide film according to claim 18, wherein chlorine is in the form of hydrogen chloride, and the concentration of hydrogen chloride contained in the inert gas is 0.02 to 10% by volume. Formation method. 20. The method according to claim 16, wherein the heat treatment is performed at a temperature of 700 to 950 ° C. 21. The method for forming a silicon oxide film according to claim 20, wherein the heat treatment is performed in a processing chamber. 22. The silicon oxide film according to claim 16, wherein an ambient temperature at the time of performing a heat treatment on the formed silicon oxide film is higher than an ambient temperature in the second silicon oxide film forming step. Forming method. 23. After the completion of the second silicon oxide film forming step, the atmosphere is switched to an inert gas atmosphere containing a halogen element, and then the temperature is increased to an ambient temperature for performing a heat treatment. Item 23. The method for forming a silicon oxide film according to Item 22. 24. The method according to claim 23, wherein the halogen element is chlorine. 25. The silicon oxide film according to claim 24, wherein the chlorine is in the form of hydrogen chloride, and the concentration of hydrogen chloride contained in the inert gas is 0.02 to 10% by volume. Formation method. 26. An atmosphere before forming a silicon oxide film is an inert gas atmosphere.
3. The method for forming a silicon oxide film according to item 1. 27. The method according to claim 27, further comprising the step of cleaning the surface of the silicon layer before forming the silicon oxide film, wherein the silicon oxide film is formed without exposing the silicon layer after the surface cleaning to the atmosphere. Item 7. A method for forming a silicon oxide film according to Item 6. 28. The method according to claim 6, wherein the silicon layer comprises an epitaxial silicon layer formed on the substrate.