JPH11162970A - Method of formation of oxide film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent occurrence of explosive gas reaction caused by hydrogen of incomplete combustion, by introducing inert gas including hydrogen gas and oxidative gas into a steam generator so as to generate steam, and oxidating the surface of a semiconductor by the steam so as to form an oxide film. SOLUTION: A plurality of silicon semiconductor substrates are carried into a board carrying-in/out part 20, and are placed on a quartz board 24, and nitrogen gas is introduced from a gas introduction part 21 into the board carrying-in/out part 20 so as to put the inside of the board carrying-in/out part 20 in nitrogen gas atmosphere. Then, a shutter 15 is opened, and the quartz board 24 is lifted by an elevator mechanism 23, and it is carried in a processing room 10. Next, oxygen gas is supplied from a pipe 33 while supplying hydrogen gas and nitrogen gas from pipes 32 and 34 into a steam generator 30, and the steam generated by the reaction between the oxygen gas and the hydrogen gas is introduced into a processing room 10 so as to oxidate the surface of a silicon semiconductor substrate 40 and form an oxide film.

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 an oxide film in the manufacture of a semiconductor device, for example.

[0002]

2. Description of the Related Art For example, M based on a silicon semiconductor substrate
In the manufacture of an OS 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.

For example, based on a silicon semiconductor substrate, an MO
Conventionally, when manufacturing an S-type semiconductor device, before forming a gate oxide film, a silicon semiconductor is washed by an RCA cleaning method of washing with an NH ₄ OH / H ₂ O ₂ aqueous solution and further washing with an HCl / H ₂ O ₂ aqueous solution. The surface of the substrate is cleaned to remove fine particles and metal impurities from the surface. By the way, when the RCA cleaning is performed, the surface of the silicon semiconductor substrate reacts with the cleaning liquid,
A silicon oxide film having a thickness of about 0.5 to 1 nm is formed. The thickness of such a silicon oxide film is not uniform, and a cleaning liquid component remains in the silicon oxide film. Therefore, the silicon semiconductor substrate is immersed in a hydrofluoric acid aqueous solution to remove the silicon oxide film, and further, the 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 of flowing a large amount of nitrogen gas into the substrate loading / unloading section provided in the silicon oxide film forming apparatus to form a nitrogen gas atmosphere (nitrogen gas purge method), (2)
Once the inside of the substrate loading / unloading section is evacuated, a method of replacing the inside of the substrate loading / unloading section with nitrogen gas or the like to eliminate the atmosphere (vacuum load lock method) or the like is adopted, and the formation of a natural oxide film is suppressed as much as possible. A method has been proposed.

[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. 17 is a conceptual diagram of a vertical type 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 furnace 10, a heater 14 for maintaining the inside of the processing chamber 10 at a predetermined atmospheric temperature through a cylindrical heat equalizing tube 16 made of SiC, a substrate loading / unloading unit 20, a substrate Gas introduction unit 21 for introducing nitrogen gas into carry-in / out unit 20
And a gas exhaust unit 2 for exhausting gas from the substrate loading / unloading unit 20
2, a shutter 15 for separating the processing chamber 10 from the substrate loading / unloading section 20, and an elevator mechanism 23 for transporting the silicon semiconductor substrate into and out of the processing chamber 10.
A quartz boat 24 for mounting a silicon semiconductor substrate is attached to the elevator mechanism 23. Also,
Hydrogen gas supplied to the combustion chamber 100 is mixed with oxygen gas at a high temperature in the combustion chamber 100 and burned to generate steam. The water vapor is supplied to the pipe 31,
The gas is introduced into the processing chamber 10 through 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.

[0007] 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. 17 will be described with reference to FIGS. 17 and 18 to 21. This will be described below.

[Step-10] piping 33, combustion chamber 100,
Nitrogen gas is introduced into the processing chamber 10 through the pipe 31, 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. Is maintained at 700 to 800 ° C. In this state, the shutter 15 is closed (see FIG. 18A). Substrate loading / unloading section 20
Is open to the atmosphere.

[Step-20] The substrate loading / unloading section 20
Then, the silicon semiconductor substrate 40 is carried in, and the silicon semiconductor substrate 40 is placed on the quartz boat 24. Substrate loading / unloading section 20
After the loading of the silicon semiconductor substrate 40 into the substrate is completed, a door (not shown) is closed, nitrogen gas is introduced from the gas introduction unit 21 into the substrate loading / unloading unit 20, discharged from the gas exhaust unit 22, and discharged into the substrate loading / unloading unit 20. In a nitrogen gas atmosphere (see FIG. 18B).

[Step-30] When the inside of the substrate loading / unloading section 20 has a sufficient nitrogen gas atmosphere, the shutter 15 is opened (see FIG. 19B), the elevator mechanism 23 is operated, and the quartz boat 24 is operated. And the silicon semiconductor substrate 40 is carried into the processing chamber 10 (see FIG. 20A). When the elevator mechanism 23 reaches the highest position,
The base of the quartz boat 24 prevents communication between the processing chamber 10 and the substrate loading / unloading section 20.

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 by cleaning with a hydrofluoric acid aqueous solution and pure water 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 washing with the hydrofluoric acid aqueous solution and the pure water are heated and desorbed by hydrogen and fluorine. It is considered that the loss is caused by separation and that the etching phenomenon occurs 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 an argon gas, severe irregularities may occur on the surface of the silicon semiconductor substrate.
It is described in page 21 of "Ultra Clean ULSI Technology" by Tadahiro Omi, published by Baifukan. In order to suppress such a phenomenon, before opening the shutter 15, for example,
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 the inside of the processing chamber 10 is made into a nitrogen gas atmosphere containing about 0.5% by volume of oxygen gas. (See FIG. 19A).

[Step-40] Thereafter, the atmosphere temperature in the processing chamber 10 is set to 800 to 900 ° C. And piping 3
Hydrogen gas and oxygen gas are supplied from 2, 33 into the combustion chamber 100, and the hydrogen gas is mixed with the oxygen gas at a high temperature in the combustion chamber 100, and the steam generated by burning is mixed with hydrogen gas.
The gas is introduced into the processing chamber 10 through the pipe 31, the gas flow path 11, and the gas introduction unit 12, and is exhausted from the gas exhaust unit 13 (FIG. 2).
1). The temperature in the combustion chamber 100 is maintained at 700 to 900 ° C. by, for example, a heater (not shown).
Thus, a silicon oxide film is formed on the surface of the silicon semiconductor substrate 40.

It is to be noted that the incompletely burned hydrogen gas may flow into the processing chamber 10 and flow out of the system before the steam is introduced into the processing chamber 10, thereby causing a detonation reaction. . In order to prevent such a detonation reaction, oxygen gas is supplied from the pipe 33 to the combustion chamber 100 before hydrogen gas is supplied from the pipe 32 to the combustion chamber 100 (FIG. 20B). reference). As a result, oxygen gas flows into the processing chamber 10 through the pipe 31, the gas flow path 11, and the gas introduction unit 12.

[0014]

However, as a result of supplying oxygen gas from the pipe 33 to the combustion chamber 100 in order to prevent such a detonation reaction from the incompletely burned hydrogen gas, the pipe 31, Oxygen gas flows into the processing chamber 10 through the gas flow path 11 and the gas introduction unit 12, and a silicon oxide film (hereinafter, referred to as a dry oxide film) is formed on the surface of the silicon semiconductor substrate 40 by the dry oxygen gas. I will. As the thickness of the gate oxide film is reduced, the proportion of the dry oxide film is increasing and cannot be ignored.

In the pyrogenic oxidation method, hydrogen gas sufficiently diluted with an inert gas is supplied from a pipe 32 to a combustion chamber 1.
After supplying oxygen gas to the combustion chamber 100 from the pipe 33 to generate steam in the combustion chamber 100,
Oxygen gas does not flow into the processing chamber 10 and formation of a dry oxide film can be suppressed. Here, sufficiently diluting the hydrogen gas with the inert gas means that the concentration of the hydrogen gas is set to a concentration equal to or lower than the combustion range in air or oxygen gas.

However, such a method has a problem that it is difficult to stably burn the hydrogen gas in the combustion chamber 100 as a result of the hydrogen gas concentration being too low.

When a thin silicon oxide film is to be formed, the oxidation rate is higher in the humidification oxidation method than in the dry oxidation method. . However,
There is a problem that shortening the oxidation time hinders uniformization of the thickness of the silicon oxide film. Therefore, when a thin silicon oxide film is formed by using the humidifying oxidation method, the oxidation rate must be suppressed by another method.

As a method for suppressing the oxidation rate, there is a method in which steam is generated under reduced pressure and a silicon oxide film is formed under reduced pressure. As described above, when the silicon oxide film is formed under reduced pressure, the supply rate of the oxidizing species is small, so that the oxidation rate can be suppressed. However, in the method of generating steam under such reduced pressure, the operation of the combustion chamber 100 for generating steam is not stable. That is, it is difficult to stably burn hydrogen gas under reduced pressure, and as a result, there is a problem that it is difficult to stably form a thin silicon oxide film while suppressing the oxidation rate.

Accordingly, it is an object of the present invention to reliably prevent a detonation reaction from occurring due to incompletely burned hydrogen gas, and to form an oxide film in a stable state.
An object of the present invention is to provide a method for forming an oxide film which can be performed in a state where the oxidation rate is controlled and suppressed.

[0020]

To achieve the above object, the method of forming an oxide film according to the present invention comprises: (a) introducing an inert gas containing hydrogen gas into a steam generator;
(B) Thereafter, an oxidizing gas is introduced into the water vapor generator, and the surface of the semiconductor layer is oxidized by water vapor generated by a reaction between the hydrogen gas and the oxidizing gas in the water vapor generator. Forming an oxide film on the surface. Incidentally, the oxide film in the present invention includes a nitrided oxide film.

In the method for forming an oxide film according to the present invention, the reaction between the hydrogen gas and the oxidizing gas in the water vapor generator is, for example, a Ni-based catalyst such as NiO, a Pt-based catalyst such as Pt or PtO ₂ , Pd or PdO. Pd-based catalyst and the like, Ir-based catalyst, Ru and Ru-based catalyst RuO _2, etc., Ag-based catalyst such as Ag or Ag ₂ O, Au-based catalysts, Cu catalysts, such as CuO, Mn-based catalysts such as MnO _2, A reaction based on catalytic action using a Co-based catalyst such as Co ₃ O ₄ can be achieved. Such an embodiment is hereinafter referred to as an oxide film forming method according to the first embodiment of the present invention.

Alternatively, the reaction between the hydrogen gas and the oxidizing gas in the steam generator in the method for forming an oxide film of the present invention may be a reaction based on irradiation of the hydrogen gas and the oxidizing gas with electromagnetic waves. it can. In addition, such a form,
Hereinafter, a method for forming an oxide film according to the second embodiment of the present invention will be referred to as a method. In this case, as the electromagnetic wave, for example, a frequency of 2.45 G
Hz microwaves can be used.

In the method of forming an oxide film according to the present invention, the hydrogen gas concentration in the step (a) is not more than a combustion range in air or oxygen gas (a mixed gas of air and hydrogen gas or an oxygen gas and hydrogen gas). When the mixed gas with the gas is ignited, it is desirable that the temperature of the mixed gas is a hydrogen gas concentration at which the spontaneous ignition temperature cannot be maintained and combustion does not occur. Specifically, depending on the oxidizing gas used, the concentration of the hydrogen gas is set to be equal to or less than the combustion range in air (4.0% by volume or less in terms of volume% with air), or It is desirable to set the concentration so as to be below the combustion range in oxygen (4.5% by volume or less when expressed in terms of volume% with oxygen).

Examples of the inert gas containing hydrogen gas include nitrogen, argon, helium, neon, krypton, and xenon.

The oxidizing gas used in the method of forming an oxide film according to the present invention may be an oxygen gas or a nitrogen oxide-based gas (eg, NO gas, N ₂ O gas, NO ₂ ). In the case where oxygen gas is used as the oxidizing gas, the oxide film is formed using an oxide of an element mainly forming the semiconductor layer. For example, when the element mainly constituting the semiconductor layer is Si, the composition of the oxide film is SiO ₂ . On the other hand, when NO gas, N ₂ O gas, or NO ₂ is used as the oxidizing gas, the oxide film is formed of a nitride oxide of an element mainly constituting the semiconductor layer. For example, the element mainly constituting the semiconductor layer is S
In the case of i, the composition of the oxide film is SiO _X N _Y. In some cases, the oxidizing gas may be diluted with an inert gas such as nitrogen, argon, helium, neon, krypton, or xenon.

According to the present invention, in order to avoid the occurrence of a phenomenon in which the surface of a silicon semiconductor substrate is roughened (irregular) as a result of setting the atmosphere before forming a silicon oxide film based on the humidifying oxidation method to a high-temperature nitrogen gas atmosphere. In the method (2), it is preferable that in the step (b), the formation of the oxide film is started in a state where the atmosphere temperature is maintained at a temperature at which atoms mainly constituting the semiconductor layer do not desorb from the surface of the semiconductor layer. still,
The temperature at which atoms mainly constituting the semiconductor layer do not desorb from the surface of the semiconductor layer is preferably a temperature at which bonds between atoms terminating the surface of the semiconductor layer and atoms mainly constituting the semiconductor layer are not broken. . The atoms mainly constituting the semiconductor layer are S
i, that is, the semiconductor layer is a silicon semiconductor substrate,
When a single-crystal silicon layer, a polysilicon layer or an amorphous silicon layer is used, the temperature at which atoms mainly constituting the semiconductor layer do not desorb from the surface of the semiconductor layer is
It is desirable that the temperature be a temperature at which the Si—H bond on the surface of the semiconductor layer is not broken, or a temperature at which the Si—F bond on the surface of the semiconductor layer is not broken. When a silicon semiconductor substrate having a plane orientation of (100) is used as a semiconductor 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.
-Si-H has a terminal structure. 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. The expression “Si—H bond” in this specification refers to a terminal structure in which a hydrogen atom is bonded to each of two silicon atoms, and a hydrogen atom is bonded to only one silicon atom. The terminating structure in a state in which a hydrogen atom is bonded to each of the three bonding atoms of a silicon atom, or the terminating structure in a state in which a hydrogen atom is bonded to each of three bonding hands of a silicon atom is included. The temperature at which the formation of an oxide film on the surface of the semiconductor layer is started is more specifically at a temperature at which water vapor does not condense on the semiconductor layer, preferably 2 ° C.
It is desirable that the temperature be not less than 00 ° C, more preferably not less than 300 ° C, from the viewpoint of throughput.

In the method of the present invention, in step (b), the temperature of the semiconductor layer when the formation of the oxide film is completed may be higher than the temperature of the semiconductor layer when the formation of the oxide film is started. Good. In this case, when the formation of the oxide film is completed, the temperature of the semiconductor layer is 600 to 1200 ° C., preferably 700 to 1000 ° C., and more preferably 750.
Although it is desirable that the temperature is in the range of 900 ° C. to 900 ° C., it is not limited to such a value. The temperature may be raised stepwise (stepwise) or continuously.

When the temperature is raised stepwise, an oxide film is formed on the surface of the semiconductor layer at a temperature at which atoms mainly constituting the semiconductor layer do not desorb from the surface of the semiconductor layer, and then a predetermined period of time. A first oxide film forming step of forming an oxide film while holding the semiconductor layer within a temperature range in which atoms mainly constituting the semiconductor layer do not desorb from the surface of the semiconductor layer; It is preferable to include a second oxide film forming step of further forming an oxide film at a temperature higher than a temperature range in which the atoms constituting the oxide film do not desorb to a desired thickness. Second
The oxide film forming temperature in the oxide film forming step of
It is desirable that the temperature is in the range of from 700 to 1200 ° C, preferably from 700 to 1000 ° C, and more preferably from 750 to 900 ° C. Note that the upper limit of the semiconductor layer holding temperature range in the first oxide film forming step is 500 ° C., preferably 450 ° C. or less, and more preferably 400 ° C. The final thickness of the oxide film after the second oxide film forming step may be a predetermined thickness required for the semiconductor element. On the other hand, the thickness of the oxide film after the first oxide film forming step is preferably as thin as possible. However, the plane orientation of a silicon semiconductor substrate currently used for manufacturing a semiconductor device is almost (100) in most cases, and no matter how smooth the surface of the silicon semiconductor substrate is (10).
0) A step called a step is always formed on the surface of silicon. 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 oxide film after the first oxide film forming step is preferably 1 nm or more when a (100) silicon semiconductor substrate is used as the semiconductor layer, but is not limited thereto.

A temperature raising step may be included between the first oxide film forming step and the second oxide film forming step. In this case, it is desirable that the atmosphere in the temperature raising step be an inert gas atmosphere or a reduced pressure atmosphere, or an oxidizing atmosphere containing water vapor. Here, examples of the inert gas include a nitrogen gas, an argon gas, and a helium gas. Incidentally, the inert gas or the gas containing water vapor in the atmosphere in the temperature raising step may contain a halogen element. Thereby, the characteristics of the oxide film formed in the first oxide film forming step can be further improved. That is, when the atoms mainly constituting the semiconductor layer are Si, silicon dangling bonds (Si.) And SiOH, which are defects that can be generated in the first oxide film forming step, react with the halogen element in the temperature increasing step and silicon As a result of termination of dangling bonds or dehydration reaction,
These defects, which are reliability deterioration factors, are eliminated. In particular, the elimination of these defects is effective for the initial silicon oxide film formed in the first oxide film forming step. 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 or the gas containing water vapor include hydrogen chloride (H
Cl), CCl ₄ , C ₂ HCl ₃ , Cl ₂ , HBr, NF ₃
Can be mentioned. The content of the halogen element in the gas containing an inert gas or water vapor is 0.001 to 10% by volume, preferably 0.005 to 10% by volume, more preferably 0.02 to 10% by volume, based on the form of the molecule or the compound. ~
10% by volume. For example, when using hydrogen chloride gas,
The hydrogen chloride gas content in the gas containing an inert gas or water vapor is desirably 0.02 to 10% by volume.
Note that the atmosphere in the temperature raising step may be an atmosphere containing steam diluted with an inert gas.

In the method of forming an oxide film according to the present invention, a halogen element may be contained in a gas atmosphere containing water vapor during the formation of the oxide film. As a result, an oxide film having excellent time-zero dielectric breakdown (TZDB) characteristics and temporal dielectric breakdown (TDDB) characteristics can be obtained. In addition, as the halogen element, chlorine, bromine and fluorine can be exemplified.
Of these, chlorine is preferred. As the form of the halogen element contained in the gas containing water vapor, for example,
Hydrogen chloride (HCl), CCl ₄ , C ₂ HCl ₃ , Cl ₂ , H
Br and NF ₃ can be mentioned. The content of the halogen element in the gas containing water vapor is 0.001 to 10% by volume, preferably 0.1 to 10% by volume, based on the form of the molecule or the compound.
005 to 10% by volume, more preferably 0.02 to 10% by volume. For example, when using hydrogen chloride gas, the content of hydrogen chloride gas in the gas containing water vapor is desirably 0.02 to 10% by volume.

In order to further improve the characteristics of the formed oxide film, in the method of the present invention, it is preferable to perform a heat treatment on the formed oxide film after the completion of the step (b).

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 oxide film in an inert gas atmosphere containing a halogen element, time-zero dielectric breakdown (TZD)
B) An oxide film having excellent 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. Also, as a halogen element, chlorine,
Bromine and fluorine can be mentioned, and among them, chlorine is desirable. Examples of the form of the halogen element contained in the inert gas include hydrogen chloride (HCl),
Examples include CCl ₄ , C ₂ HCl ₃ , Cl ₂ , HBr, and NF ₃ . The content of the halogen element in the inert gas ranges from 0.001 to 0.001 based on the form of the molecule or compound.
It is 10% by volume, preferably 0.005 to 10% by volume, and 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 temperature of the heat treatment is 700 to 1200 ° C.
Preferably 700-1000 ° C., more preferably 70
0 to 950 ° C. In addition, the time of the heat treatment is preferably 1 to 10 minutes when performing the single-wafer processing, and 5 to 60 minutes, preferably 10 to 4 when performing the batch processing.
It is desirable to set it to 0 minutes, more preferably 20 to 30 minutes.

When heat treatment is performed in the method of forming an oxide film according to the present invention, it is preferable that the temperature of the atmosphere when the heat treatment is performed on the formed oxide film is higher than the temperature when the formation of the oxide film is completed. In this case, after the formation of the oxide film is completed, the atmosphere in the processing chamber is switched to an inert gas atmosphere, and then the temperature may be increased to the ambient temperature for performing the 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 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), CC
_{l 4, C 2 HCl 3,} Cl 2, HBr, may be mentioned NF _3. The content of the halogen element in the inert gas is 0.001 to 10% by volume, preferably 0.005 to 10% by volume, more preferably 0.02 to 10% by volume, based on the form of the molecule or compound. is there. 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.

In the method of forming an oxide film according to the present invention, after the heat treatment, the silicon oxide film may be nitrided. In this case, the nitriding treatment is preferably performed in an N ₂ O gas, NO gas, or NO ₂ gas atmosphere, and particularly preferably in an N ₂ O gas atmosphere. Alternatively, the nitriding treatment is performed using NH.
It is preferable to perform annealing in an atmosphere of _three gases, N ₂ H ₄ , and a hydrazine derivative, and then perform annealing in an atmosphere of N ₂ O and O ₂ . 700 to 1200 ° C., preferably 800 to 1150 ° C., more preferably 90 ° C.
The heating is preferably performed at a temperature of 0 to 1100 ° C. In this case, it is preferable that the silicon layer be heated by infrared irradiation and furnace annealing. Alternatively, the atmosphere for the heat treatment may be a nitrogen-based gas atmosphere. Here, N ₂ , NH ₃ , N ₂ O, NO ₂ , and NO can be exemplified as the nitrogen-based gas.

Normally, before forming a silicon oxide film on the surface of a silicon semiconductor substrate, RC is used to wash with an NH ₄ OH / H ₂ O ₂ aqueous solution and then with an HCl / H ₂ O ₂ aqueous solution.
After cleaning the surface of the silicon semiconductor substrate by A cleaning and removing fine particles and metal impurities from the surface, the silicon semiconductor substrate is cleaned with a hydrofluoric acid aqueous solution and pure water. However, when the silicon semiconductor substrate is subsequently exposed to the air, the surface of the silicon semiconductor substrate is contaminated, moisture and organic substances adhere to the surface of the silicon semiconductor substrate, or Si atoms on the surface of the silicon semiconductor substrate become hydroxyl groups ( O
H) (see, for example, the document "Highly-relia"
ble Gate Oxide Formation for Giga-Scale LSIs by us
ing Closed Wet Cleaning System and Wet Oxidation w
ith Ultra-Dry Unloading ", J. Yugami, et al., Inter
national Electron Device MeetingTechnical Digest 9
5, see pp 855-858). In such a case, when the formation of the oxide film is started as it is, moisture or an organic substance or, for example, Si-OH is contained in the formed silicon oxide film.
Is taken in, which may cause deterioration of the characteristics of the formed silicon oxide film or generation of a defective portion. In addition, a defect part is a silicon dangling bond (Si.) Or Si-
A portion of the silicon oxide film containing defects such as H bonds,
Alternatively, a Si-O-Si bond in which the Si-O-Si bond is compressed by stress or the angle of the Si-O-Si bond is different from the angle of the Si-O-Si bond in the thick or bulk silicon oxide film Means the portion of the silicon oxide film containing. Therefore, in order to avoid the occurrence of such a problem, the method of the present invention includes a step of cleaning the surface of the semiconductor layer before forming the oxide film, and exposing the semiconductor layer after the surface cleaning to the atmosphere. The formation of the oxide film is preferably performed without using an inert gas atmosphere or a vacuum atmosphere from the cleaning of the surface of the semiconductor layer to the start of the oxide film formation step. Thus, for example, when a silicon semiconductor substrate is used as a semiconductor layer, a silicon oxide film can be formed on the surface of a silicon semiconductor substrate having a surface that is mostly terminated with hydrogen and a portion of which is extremely terminated with fluorine, It is possible to prevent the characteristics of the formed silicon oxide film from deteriorating or the occurrence of defective portions.

As the semiconductor layer, not only a silicon semiconductor substrate such as a silicon single crystal wafer, but also an epitaxial silicon layer, a polysilicon layer, or an amorphous silicon layer on a semiconductor substrate, and a silicon semiconductor substrate or a semiconductor element Means an underlayer on which an oxide film is to be formed. Forming an oxide film on a semiconductor layer includes not only forming an oxide film on a semiconductor layer formed on or above a semiconductor substrate or the like, but also forming an oxide film on the surface of the semiconductor substrate. Incidentally, the silicon single crystal wafer can be obtained by the CZ method, the MCZ method, the DLCZ method, and the FZ method.
The wafer may be manufactured by any method such as the Z method, or may be subjected to hydrogen annealing in advance. Further, the semiconductor layer may be made of Si-Ge.

The method for forming an oxide film according to the present invention is, for example, an MO method.
The formation of oxide films in various semiconductor devices, such as the formation of gate oxide films for S-type transistors, the formation of interlayer insulating films and element isolation regions, the formation of gate oxide films for top gate or bottom gate thin film transistors, and the formation of tunnel oxide films for flash memories. Can be applied to forming.

In the method for forming an oxide film according to the second aspect of the present invention, in the oxygen plasma generated by microwave discharge, the ground state O ₂ (X ³ Σg ⁻ ) is changed to the excited state O ₂ ( a ^3? uj ⁺⁾ or O ₂ (B ^{3 Σu -)} to be excited, respectively, to dissociate the oxygen atom by the following equation.

[0040]

Embedded image O ₂ (X ³ -g ⁻ ) + e → O ₂ (A ^{3 +} u ⁺ ) + e Formula (1-1) O ₂ (A ³ Σu ⁺ ) + e → O ( ³ P) + O ( ³ P) + e Formula (1-2) O ₂ (X ³ Σg ⁻ ) + e → O ₂ (B ³ Σu ⁻ ) + e Formula (1-3) O ₂ (B ³ Σu ⁻ ) + e → O ( ^{3 P) + O (1 D} ) + e equation (1-4)

Therefore, excited oxygen molecules and oxygen atoms are present in the oxygen plasma, and these become reactive species. When hydrogen H ₂ is introduced here, the following plasma is generated.

[0042]

H ₂ + e → 2H Formula (2)

In the oxygen plasma, for example, the formula (1)
The oxygen plasma generated in -2) reacts with the hydrogen plasma generated in equation (2) to generate water vapor. Then, the surface of the heated semiconductor layer is oxidized by the water vapor, and an oxide film is formed on the surface of the semiconductor layer.

[0044]

Embedded image 2H + O ( ³ P) → H ₂ O Formula (3)

In the method of forming an oxide film according to the present invention, since the inert gas containing hydrogen gas is introduced into the steam generator before introducing the oxidizing gas into the steam generator, the semiconductor layer is brought into contact with the oxidizing gas. Therefore, formation of a dry oxide film on the surface of the semiconductor layer can be reliably prevented. In addition, since the oxide film is formed by an oxidation method using water vapor, an oxide film having excellent time-dependent dielectric breakdown (TDDB) characteristics can be obtained.

In the method for forming an oxide film according to the first aspect of the present invention, since the hydrogen gas and the oxidizing gas are reacted based on the catalytic action to generate steam, the steam is generated even if the hydrogen gas concentration is sufficiently low. Can be generated. Also, in the method for forming an oxide film according to the second aspect of the present invention, since the water vapor is generated based on the reaction between the oxygen plasma and the hydrogen plasma, the water vapor is generated even if the hydrogen gas concentration is sufficiently low. Can be. Therefore, not only can the detonation reaction caused by the hydrogen gas be prevented, but also the formation of the oxide film can be stably performed.
In addition, the oxidation can be performed in a state where the oxidation rate is controlled and suppressed.

[0047]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings based on embodiments of the invention (hereinafter abbreviated as embodiments).

(Embodiment 1) Embodiment 1 relates to a method for forming an oxide film according to the first aspect of the present invention. That is,
The method of forming an oxide film according to the first embodiment includes (a) a step of introducing an inert gas containing hydrogen gas into a steam generator, and (b) thereafter, introducing an oxidizing gas into the steam generator to generate steam. A process of oxidizing the surface of the semiconductor layer with water vapor generated by a reaction between the hydrogen gas and the oxidizing gas in the device, thereby forming an oxide film on the surface of the semiconductor layer. The reaction with the oxidizing gas was defined as a reaction based on a catalytic action. Note that oxygen gas is used as the oxidizing gas. The semiconductor layer is composed of the silicon semiconductor substrate itself. The formed oxide film functions as a gate oxide film.

FIG. 1 is a schematic sectional view of an oxide film forming apparatus suitable for carrying out the method for forming an oxide film according to the first embodiment. This oxide film forming apparatus has substantially the same structure as the conventional vertical silicon oxide film forming apparatus shown in FIG. However, a steam generator 30 is provided instead of the combustion chamber 100. The inside of the steam generator 30 is filled with a Ni-based catalyst (not shown).
The i-based catalyst is heated to a desired temperature by a heater (not shown) disposed inside the steam generator 30. Hydrogen gas, oxygen gas, and inert gas (in the first embodiment, nitrogen gas) are supplied to the steam generator 30 from each of the pipes 32, 33, and 34.

Hereinafter, the method of forming an oxide film according to the first embodiment will be described with reference to FIG. 2 which is a schematic partial cross-sectional view of a silicon semiconductor substrate and the like, and FIGS.
With reference to FIG.

[Step-100] First, an N-type silicon wafer of 8 inches in diameter doped with phosphorus (prepared by CZ method)
LOC is formed on a silicon semiconductor substrate 40 by a known method.
An element isolation region 41 having an OS structure is formed, and then well ion implantation, channel stop ion implantation, and threshold adjustment ion implantation are 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% aqueous hydrofluoric acid solution and pure water. The surface is exposed (see FIG. 2A). 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, a plurality of silicon semiconductor substrates 40 are loaded into the substrate loading / unloading section 20 of the oxide film forming apparatus shown in FIG.
(See FIG. 3A). In addition, nitrogen gas is introduced into the processing chamber 10 from the gas introduction unit 12, the inside of the processing chamber 10 is set to an inert gas atmosphere such as nitrogen gas, and the atmosphere At 800 ° C. In this state, the shutter 15 is closed.

[Step-120] Then, the substrate loading / unloading section 2
0, the door (not shown) is closed, and the gas introduction unit 21 is inserted into the substrate carry-in / out unit 20.
, And exhausted from the gas exhaust unit 22 to make the inside of the substrate loading / unloading unit 20 a nitrogen gas atmosphere. The oxygen gas concentration in the substrate loading / unloading section 20 is monitored, and if the oxygen gas concentration becomes, for example, 100 ppm or less, it is determined that the inside of the substrate loading / unloading section 20 has a sufficient nitrogen gas atmosphere. Thereafter, the shutter 15 is opened (see FIG. 3B), and the elevator mechanism 23 is operated to operate the quartz boat 24.
Is raised (rising speed: 250 mm / min), and the silicon semiconductor substrate 40 is carried into the processing chamber 10 having a double-tube structure made of quartz (see FIG. 4A). When the elevator mechanism 23 reaches the highest position, the base of the quartz boat 24 stops communication between the processing chamber 10 and the substrate loading / unloading section 20.

[Step-130] Next, hydrogen gas (flow rate: 0.2 SL) is supplied from the pipes 32 and 34 to the steam generator 30.
M) and nitrogen gas (flow rate: 10 SLM) are supplied (see FIG. 4B). These gases are supplied to the steam generator 3
0, the gas flows into the processing chamber 10 via the pipe 31, the gas flow path 11, and the gas introduction unit 12, and is discharged from the gas exhaust unit 13 to the outside of the system. Since the concentration of the hydrogen gas in the mixed gas of the hydrogen gas and the nitrogen gas is 2% by volume, it is possible to reliably prevent the detonation reaction from occurring. Further, since there is no oxygen gas which is an oxidizing gas, it is possible to reliably prevent a dry oxide film from being formed on the surface of the semiconductor layer (the silicon semiconductor substrate 40 in the first embodiment).

[Step-140] When the atmosphere in the processing chamber 10 becomes a mixed gas atmosphere of hydrogen gas and nitrogen gas, hydrogen gas (flow rate: 0.2 SLM) is supplied from the pipes 32 and 34 to the steam generator 30. ) And nitrogen gas (flow rate: 10S)
While continuously supplying LM), oxygen gas (flow rate: 10 SLM) is supplied from the pipe 33 to the steam generator 30.
The catalyst filled in the steam generator 30 is previously heated to a predetermined temperature by a heater (not shown). As a result, the hydrogen gas reacts with the oxygen gas, which is an oxidizing gas, in the steam generator 30 to generate steam. This water vapor is introduced into the processing chamber 10 via the pipe 31, the gas flow path 11 and the gas introduction unit 12, and the surface of the silicon semiconductor substrate 40, which is a semiconductor layer, is oxidized. In the embodiment 1, SiO
₂ film) is formed (see FIGS. 5 and 2B).

[Step-150] When an oxide film having a desired thickness is formed, supply of hydrogen gas and oxygen gas to the steam generator 30 is stopped. Then, the inside of the processing chamber 10 is set to an inert gas atmosphere such as a nitrogen gas,
Is operated to lower the quartz boat 24, and then a door (not shown) is opened to carry out the silicon semiconductor substrate 40.

[Step-160] Thereafter, a polysilicon layer containing no impurities is formed on the entire surface by a CVD method.
Next, the polysilicon layer is patterned based on a photolithography technique and a dry etching technique. Then, impurities are implanted into the polysilicon layer and the silicon semiconductor substrate 40 by an ion implantation method. Thus, the gate electrode 43 can be formed on the silicon oxide film 42, which is the gate oxide film, and at the same time, the LDD structure can be formed (see FIG. 4C).

[Step-170] Next, an insulating film is formed on the entire surface, and the insulating film is etched by an anisotropic dry etching technique to form sidewalls 44 on the side walls of the gate electrode 43. Next, in order to form the source / drain regions 45, impurities are implanted into the silicon semiconductor substrate 40 by an ion implantation method, and then activation heat treatment of the implanted impurities is performed. After that, an insulating layer 46 is formed on the entire surface by CV.
An opening is provided in the insulating layer 46 above the source / drain region 45, and a wiring material layer is formed on the insulating layer 46 including the inside of the opening by a sputtering method. Is patterned to form a wiring 47, and a MOS FET whose schematic partial cross-sectional view is shown in FIG. 2D can be obtained.

(Embodiment 2) Embodiment 2 is a modification of the method for forming an oxide film of Embodiment 1. Embodiment 2
In the step of forming an oxide film, while maintaining the ambient temperature at a temperature at which atoms (Si in Embodiment 2) mainly constituting the semiconductor layer do not desorb from the surface of the semiconductor layer, Start forming. The temperature at which atoms mainly constituting the semiconductor layer do not desorb from the surface of the semiconductor layer is a temperature at which bonds between atoms terminating the surface of the semiconductor layer and atoms mainly constituting the semiconductor layer are not broken, More specifically, it is a temperature at which the Si—H bond on the surface of the semiconductor layer is not broken.

Further, in Embodiment 2, after an oxide film is formed on the surface of the semiconductor layer at a temperature at which atoms mainly constituting the semiconductor layer do not desorb from the surface of the semiconductor layer,
A first oxide film forming step of forming an oxide film by holding the semiconductor layer within a temperature range in which atoms mainly constituting the semiconductor layer do not desorb from the surface of the semiconductor layer for a predetermined period; A second oxide film forming step of further forming an oxide film at a temperature higher than a temperature range in which atoms mainly constituting the layer do not desorb until a desired thickness is obtained.

Also in the second embodiment, the semiconductor layer is formed of the silicon semiconductor substrate 40. Further, the first oxide film forming step and the second oxide film forming step are performed in the processing chamber 10 using the oxide film forming apparatus shown in FIG. Further, the first oxide film forming step and the second oxide film forming step are performed by a batch method.

Hereinafter, a method for forming a silicon oxide film according to the second embodiment will be described with reference to FIGS. FIG. 6A schematically shows an ambient temperature profile in the second embodiment. In FIG. 6, the lower limit of the ambient temperature at the time of initiating the formation of the oxide film on the surface of the semiconductor layer shown in T _1, ambient temperature atom which mainly constitute the semiconductor layer from the surface of the semiconductor layer is not eliminated shows the upper limit value T _2. Also,
The ambient temperature of the second oxide film formation step shown in T _3, indicating the ambient temperature in the heat treatment at T _4. Furthermore,
In FIG. 6, a solid line indicates a state in which an oxide film is formed, and a dashed line indicates a process in which the ambient temperature is raised to the ambient temperature at which the formation of the oxide film on the surface of the semiconductor layer is started,
After the formation of the oxide film is completed, a process of lowering the ambient temperature to room temperature is shown, and a double line represents a heat treatment process. In the figure, "R
"T" means room temperature (normal temperature).

[Step-200] First, after a device isolation region and the like are formed in a silicon semiconductor substrate in the same manner as in the first embodiment, fine particles and metal impurities on the surface of the silicon semiconductor substrate are removed by RCA cleaning. Then, the surface of the silicon semiconductor substrate is washed with a 0.1% aqueous hydrofluoric acid solution and pure water to expose the surface of the silicon semiconductor substrate.

[Step-210] Next, a plurality of silicon semiconductor substrates 40 are loaded into the substrate loading / unloading section 20 of the oxide film forming apparatus shown in FIG.
(See FIG. 7A). Note that nitrogen gas is introduced from the gas introduction unit 12 into the processing chamber 10, the inside of the processing chamber 10 is set to an inert gas atmosphere such as nitrogen gas, and the temperature of the atmosphere inside the processing chamber 10 is controlled by the heater 14 through the soaking tube 16. At 400 ° C. In this state, the shutter 15 is closed.

[Step-220] Then, the substrate loading / unloading section 2
0, the door (not shown) is closed, and the gas introduction unit 21 is inserted into the substrate carry-in / out unit 20.
The nitrogen gas was introduced from the gas exhaust unit 22 and exhausted from the gas exhaust unit 22, and the inside of the substrate loading / unloading unit 20 was set to a nitrogen gas atmosphere. The oxygen gas concentration in the substrate loading / unloading section 20 is monitored, and if the oxygen gas concentration becomes, for example, 100 ppm or less, it is determined that the inside of the substrate loading / unloading section 20 has a sufficient nitrogen gas atmosphere. Thereafter, the shutter 15 is opened (see FIG. 7B), the elevator mechanism 23 is operated, and the quartz boat 24 is opened.
Is raised (rising speed: 250 mm / min), and the silicon semiconductor substrate 40 is carried into the processing chamber 10 having a double tube structure made of quartz (see FIG. 8A). Since the ambient temperature in the processing chamber 10 is maintained at 400 ° C. by the heater 14, that is, the ambient temperature is maintained at a temperature at which atoms mainly constituting the semiconductor layer do not desorb from the surface of the semiconductor layer. In addition, generation of roughness on the surface of the semiconductor layer (the silicon semiconductor substrate 40 in the second embodiment) can be suppressed.

[Step-230] Next, similarly to [Step-130] of the first embodiment, hydrogen gas (flow rate: 0.2 SLM) and nitrogen gas (flow rate: 10 SLM) are supplied from the pipes 32 and 34 to the steam generator 30. (FIG. 8B)
reference). These gases are supplied to the steam generator 30, the pipe 3
1. The gas flows into the processing chamber 10 via the gas flow path 11 and the gas introduction unit 12, and is discharged from the gas exhaust unit 13 to the outside of the system. Since the concentration of the hydrogen gas in the mixed gas of the hydrogen gas and the nitrogen gas is 2% by volume, it is possible to reliably prevent the detonation reaction from occurring. Further, since there is no oxygen gas which is an oxidizing gas, it is possible to reliably prevent a dry oxide film from being formed on the surface of the semiconductor layer.

[Step-240] Next, formation of an oxide film is started while maintaining the ambient temperature at a temperature at which atoms mainly constituting the semiconductor layer do not desorb from the surface of the semiconductor layer. Then, a first oxide film forming step of forming an oxide film while holding the semiconductor layer in a temperature range in which atoms (Si in Embodiment 2) mainly constituting the semiconductor layer do not desorb from the surface of the semiconductor layer is performed. Execute. That is, as in [Step-140] of the first embodiment, when the atmosphere in the processing chamber 10 is sufficiently a mixed gas atmosphere of hydrogen gas and nitrogen gas, the pipes 32 and 34 are connected to the steam generator 30 through the pipes 32 and 34. Hydrogen gas (flow rate: 0.2 SLM) and nitrogen gas (flow rate: 10 SLM)
While supplying oxygen gas (flow rate: 10 SLM) from the pipe 33 to the steam generator 30. Thus, the hydrogen gas and the oxidizing gas react in the steam generator 30 to generate steam. This water vapor is supplied to the pipe 3
1. The silicon semiconductor substrate 4 which flows into the processing chamber 10 via the gas flow path 11 and the gas introduction unit 12 and is a semiconductor layer
0 is oxidized, and an oxide film (SiO ₂ film in the _second embodiment) is formed on the surface of the semiconductor layer (see FIG. 9A). The temperature of the atmosphere in the processing chamber 10 is kept at 400 ° C. by the heater 14 through the soaking tube 16. In this [Step-240], a silicon oxide film having a thickness of 1.2 nm is formed on the surface of the silicon semiconductor substrate 40. The thickness of the silicon oxide film is a thickness corresponding to several molecular layers of SiO ₂ , and is a thickness sufficient to function as a protective film even in consideration of steps on the surface of the silicon semiconductor substrate.

[Step-250] Thereafter, the supply of hydrogen gas and oxygen gas to the steam generator 30 is stopped, and an inert gas (nitrogen gas) is supplied to the pipe 34, the steam generator 30,
The processing chamber 1 of the oxide film forming apparatus is introduced into the processing chamber 10 through the pipe 31, the gas flow path 11, and the gas introduction unit 12.
The ambient temperature within 0 is raised to 800 ° C. by the heater 14 through the soaking tube 16 (see FIG. 9B).
The heating rate was 10 ° C./min. [Step-240]
Since an oxide film that also functions as a protective film has already been formed on the surface of the semiconductor layer, no roughness occurs on the surface of the semiconductor layer (silicon semiconductor substrate 40) in this [Step-250]. .

[Step-260] The temperature of the atmosphere in the processing chamber 10 is raised to a temperature (800 ° C. in Embodiment 2) higher than the temperature range in which atoms mainly constituting the semiconductor layer do not desorb from the surface of the semiconductor layer. Is reached, a second oxide film forming step of further forming an oxide film until a desired thickness is performed while maintaining the atmosphere at this temperature. In particular,
Again, similarly to [Step-230], the steam generator 30
Hydrogen gas from pipes 32 and 34 (flow rate: 0.2 SLM)
And nitrogen gas (flow rate: 10 SLM), and the processing chamber 1
The atmosphere of 0 is a mixed gas atmosphere of hydrogen gas and nitrogen gas (see FIG. 10A). Since the concentration of the hydrogen gas in the mixed gas of the hydrogen gas and the nitrogen gas is 2% by volume, it is possible to reliably prevent the detonation reaction from occurring.
After that, the hydrogen gas (flow rate: 0.2 SLM) and the nitrogen gas (flow rate: 10
While continuing to supply SLM), oxygen gas (flow rate: 10 SLM) is supplied from the pipe 33 to the steam generator 30.
As a result, the generated water vapor flows into the processing chamber 10 via the pipe 31, the gas flow path 11, and the gas introduction unit 12, and the surface of the silicon semiconductor substrate 40, which is a semiconductor layer, is further oxidized. Then, an oxide film having a desired thickness (a SiO ₂ film having a total thickness of 4.0 nm in the _second embodiment) is formed (see FIG. 10B). The ambient temperature at the time when the formation of the oxide film having the desired thickness is completed (Embodiment 2)
Is higher than the ambient temperature at which the formation of the oxide film on the surface of the semiconductor layer is started (400 ° C. in Embodiment 2).

As described above, the formation of the silicon oxide film on the surface of the silicon semiconductor substrate 40 is completed. Then, the door (not shown) is opened, and the silicon semiconductor substrate 40 is carried out.

In [Step-250], the processing chamber 10
The temperature of the atmosphere in the processing chamber 10 of the oxide film forming apparatus may be raised to 800 ° C. by the heater 14 via the soaking tube 16 without stopping the supply of steam to the apparatus.

In [Step-260], since an oxide film has already been formed on the surface of the semiconductor layer, a dry oxide film is formed even when oxygen gas, which is an oxidizing gas, comes into contact with the semiconductor layer. Nothing. Therefore, instead of setting the atmosphere of the processing chamber 10 to a mixed gas atmosphere of hydrogen gas and nitrogen gas, while continuously supplying nitrogen gas (flow rate: 10 SLM) from the pipe 34 to the steam generator 30, An oxygen gas (flow rate: 10 SLM) may be supplied from 33, and then a hydrogen gas (flow rate: 10 SLM) may be supplied from the pipe 32 to the steam generator 30 to generate steam. Alternatively, an oxide film may be further formed based on a conventional pyrogenic oxidation method.

(Embodiment 3) Embodiment 3 is a modification of the oxide film forming method of Embodiment 2. In the third embodiment, following [Step-260] of the second embodiment, an inert gas atmosphere containing a halogen element (a nitrogen gas atmosphere containing hydrogen chloride) is applied to the formed oxide film.
Heat treatment (furnace annealing) is performed in the inside. by this,
An oxide film having excellent time zero dielectric breakdown (TZDB) characteristics and temporal dielectric breakdown (TDDB) characteristics can be obtained.

Specifically, [Step-26] of Embodiment 2
0], the supply of the hydrogen gas and the oxygen gas to the steam generator 30 is stopped, and the inert gas (nitrogen gas) is supplied to the pipe 34, the steam generator 30, the pipe 31, the gas flow path 11
The temperature of the atmosphere in the processing chamber 10 of the oxide film forming apparatus is raised to 850 ° C. by the heater 14 while the gas is introduced into the processing chamber 10 through the gas inlet 12. Thereafter, a nitrogen gas containing 0.1% by volume of hydrogen chloride is introduced into the processing chamber 10 from the gas introduction unit 12, and heat treatment is performed for 30 minutes. As described above, the formation of the silicon oxide film on the surface of the silicon semiconductor substrate 40 is completed. Thereafter, the inside of the processing chamber 10 is set to an inert gas atmosphere such as a nitrogen gas, and the elevator mechanism 23 is operated to lower the quartz boat 24. And then
The door (not shown) is opened, and the silicon semiconductor substrate 40 is carried out. The ambient temperature profile in the third embodiment is schematically shown in FIG.

(Embodiment 4) Embodiment 4 relates to a method for forming an oxide film according to the second aspect of the present invention. That is,
The method for forming an oxide film according to the fourth embodiment includes (a) a step of introducing an inert gas containing hydrogen gas into a steam generator, and (b) thereafter, introducing an oxidizing gas into the steam generator to generate steam. A process of oxidizing the surface of the semiconductor layer with water vapor generated by a reaction between the hydrogen gas and the oxidizing gas in the device, thereby forming an oxide film on the surface of the semiconductor layer. The reaction with the oxidizing gas was a reaction based on irradiation of the hydrogen gas and the oxidizing gas with electromagnetic waves. Here, the electromagnetic wave is a microwave of 2.45 GHz, and oxygen gas is used as the oxidizing gas. The semiconductor layer is composed of the silicon semiconductor substrate itself. The formed oxide film functions as a gate oxide film.

FIG. 13 is a conceptual diagram of an apparatus suitable for implementing the method of forming an oxide film according to the fourth embodiment. This apparatus includes a processing chamber 60 and a steam generator 70. The water vapor generator 70 includes a water vapor generation chamber 71 made of quartz, a microwave waveguide 72, and a magnetron 73 attached to the microwave waveguide 72. In the magnetron 73, a microwave having a frequency of 2.45 GHz is generated. The microwave is introduced into the water vapor generation chamber 71 via the microwave waveguide 72. Hydrogen gas and oxygen gas are introduced into the steam generation chamber 71 via pipes 74 and 75. Microwave (electromagnetic wave) for hydrogen gas and oxygen gas introduced into steam generation chamber 71
Is irradiated. Accordingly, Equations (1-1) to (1-
4) and the reaction shown in equation (2) proceed, oxygen plasma and hydrogen plasma are generated, and as a result of the reaction shown in equation (3), water vapor is generated. A heater 77 is provided outside the steam generation chamber 71, and the inside of the steam generation chamber 71 is maintained at a desired temperature (for example, 200 to 300 ° C.). The water vapor generated in the water vapor generation chamber 71 is supplied to the pipe 7
8 and is introduced into the processing chamber 60. A heater 79 is provided outside the pipe 78 in order to prevent condensation of water vapor in the pipe 78.
It is preferable to keep at ゜ C. Further, a pipe 76 for introducing an inert gas (for example, nitrogen gas) into the steam generation chamber 71 is provided in the steam generation chamber 71.

The processing chamber 60 is provided with a quartz boat 61 and a heater 62 composed of a heating lamp, so that the atmospheric temperature in the processing chamber 60 can be set to a desired temperature. The water vapor and the gas in the processing chamber 60 are exhausted by the gas exhaust unit 63.
From the system.

Hereinafter, a method of forming an oxide film according to the fourth embodiment using the oxide film forming apparatus shown in FIG. 13 will be described.

[Step-400] First, an element isolation region and the like are formed in a silicon semiconductor substrate in the same manner as in the first embodiment, and then fine particles and metal impurities on the surface of the silicon semiconductor substrate are removed by RCA cleaning. Then, the surface of the silicon semiconductor substrate is washed with a 0.1% aqueous hydrofluoric acid solution and pure water to expose the surface of the silicon semiconductor substrate.

[Step-410] Next, the plurality of silicon semiconductor substrates 40 are carried into the processing chamber 60 of the oxide film forming apparatus shown in FIG. It should be noted that nitrogen gas is introduced into the processing chamber 60 via pipes 76 and 78, the inside of the processing chamber 10 is set to an inert gas atmosphere such as nitrogen gas, and the temperature of the atmosphere in the processing chamber 60 is previously set to 800 by the heater 62. Keep at ゜ C.

[Step-420] Next, the steam generation chamber 7
1, a hydrogen gas (flow rate: 0.2 SLM) is supplied from a pipe 74, and a nitrogen gas (flow rate: 10 SLM) is supplied from a pipe 76. These gases are supplied to the processing chamber 6 via a pipe 78.
0, and is discharged out of the system from the gas exhaust unit 63.
The hydrogen gas concentration in the mixed gas of hydrogen gas and nitrogen gas is 2
Due to the volume%, it is possible to reliably prevent the detonation reaction from occurring. Further, since oxygen gas, which is an oxidizing gas, does not exist, it is possible to reliably prevent a dry oxide film from being formed on the surface of the semiconductor layer (the silicon semiconductor substrate 40 also in the fourth embodiment).

[Step-430] When the atmosphere in the processing chamber 60 becomes a mixed gas atmosphere of hydrogen gas and nitrogen gas, hydrogen gas (flow rate: 0.2 SLM) is supplied from the pipes 74 and 76 to the steam generating chamber 71. ) And nitrogen gas (flow rate: 10SL)
While continuing to supply M), pipe 75
Supplies oxygen gas (flow rate: 10 SLM). At the same time, microwave power is supplied to the magnetron 73, and the microwave of 2.45 GHz generated by the magnetron 73 is introduced into the steam generation chamber 71 through the microwave waveguide 72. By this, that is, by irradiating the hydrogen gas and the oxidizing gas (oxygen gas in the fourth embodiment) with an electromagnetic wave, the reactions of the above formulas (1-1) to (1-4) and the formula (2) ), The reaction of the formula (3) occurs, and steam is generated. The generated steam passes through the processing chamber 6 via the pipe 78.
When the temperature reaches 0, the surface of the semiconductor layer (specifically, the silicon semiconductor substrate 40) heated by the heater 62 is oxidized. Thus, an oxide film (SiO ₂ film in the fourth embodiment) can be formed on the surface of the semiconductor layer. Table 1 shows the conditions for forming the oxide film.

[0083]

[Table 1] Microwave power: 10 kW Microwave frequency: 2.45 GHz Oxygen gas flow rate: 10 SLM Hydrogen gas flow rate: 0.2 SLM Nitrogen gas flow rate: 10 SLM

[Step-440] When an oxide film having a desired thickness is formed, supply of hydrogen gas and oxygen gas to the steam generation chamber 71 is stopped. Then, after the inside of the processing chamber 60 is set to an inert gas atmosphere such as a nitrogen gas, a door (not shown) is opened, and the silicon semiconductor substrate 40 is carried out.

(Embodiment 5) Embodiment 5 is a modification of the method for forming an oxide film of Embodiment 4. Embodiment 5
In the step of forming an oxide film, while maintaining the ambient temperature at a temperature at which atoms (Si in Embodiment 5) mainly constituting the semiconductor layer do not desorb from the surface of the semiconductor layer, Start forming. The temperature at which atoms mainly constituting the semiconductor layer do not desorb from the surface of the semiconductor layer is a temperature at which bonds between atoms terminating the surface of the semiconductor layer and atoms mainly constituting the semiconductor layer are not broken, More specifically, it is a temperature at which the Si—H bond on the surface of the semiconductor layer is not broken.

Further, in the fifth embodiment, after an oxide film is formed on the surface of the semiconductor layer at a temperature at which atoms mainly constituting the semiconductor layer do not desorb from the surface of the semiconductor layer,
A first oxide film forming step of forming an oxide film by holding the semiconductor layer within a temperature range in which atoms mainly constituting the semiconductor layer do not desorb from the surface of the semiconductor layer for a predetermined period; A second oxide film forming step of further forming an oxide film at a temperature higher than a temperature range in which atoms mainly constituting the layer do not desorb until a desired thickness is obtained.

Also in the fifth embodiment, the semiconductor layer is formed of the silicon semiconductor substrate 40. Further, the first oxide film forming step and the second oxide film forming step are performed in the processing chamber 60 using the oxide film forming apparatus shown in FIG. Further, the first oxide film forming step and the second oxide film forming step are performed by a batch method.

Hereinafter, a method for forming a silicon oxide film according to the fifth embodiment will be described. Note that the ambient temperature profile in the fifth embodiment is the same as that in FIG.

[Step-500] First, after an element isolation region and the like are formed in a silicon semiconductor substrate in the same manner as in the first embodiment, fine particles and metal impurities on the surface of the silicon semiconductor substrate are removed by RCA cleaning. Then, the surface of the silicon semiconductor substrate is washed with a 0.1% aqueous hydrofluoric acid solution and pure water to expose the surface of the silicon semiconductor substrate.

[Step-510] Next, the plurality of silicon semiconductor substrates 40 are loaded into the processing chamber 60 shown in FIG. It should be noted that nitrogen gas is introduced into the processing chamber 60 from the pipe 76, the inside of the processing chamber 60 is set to an inert gas atmosphere such as nitrogen gas, and
2, the atmosphere temperature in the processing chamber 60 is maintained at 400 ° C.

[Step-520] After the loading of the silicon semiconductor substrate 40 into the processing chamber 60 is completed, a door (not shown) is closed. The atmosphere temperature in the processing chamber 60 is controlled by the heater 62.
Is maintained at 400 ° C., that is, since the ambient temperature is maintained at a temperature at which atoms mainly constituting the semiconductor layer do not desorb from the surface of the semiconductor layer, the semiconductor layer (in the fifth embodiment, The generation of roughness on the surface of the silicon semiconductor substrate 40) can be suppressed.

[Step-530] Next, as in [Step-420] of the fourth embodiment, the pipe 7 is connected to the steam generation chamber 71.
A hydrogen gas (flow rate: 0.2 SLM) is supplied from 4 and a nitrogen gas (flow rate: 10 SLM) is supplied from the pipe 76. These gases flow into the processing chamber 60 via the pipe 78 and are discharged from the gas exhaust unit 63 to the outside of the system. Since the concentration of the hydrogen gas in the mixed gas of the hydrogen gas and the nitrogen gas is 2% by volume, it is possible to reliably prevent the detonation reaction from occurring. Further, since oxygen gas, which is an oxidizing gas, does not exist, it is possible to reliably prevent a dry oxide film from being formed on the surface of the semiconductor layer (the silicon semiconductor substrate 40 also in the fifth embodiment).

[Step-540] Next, formation of an oxide film is started while maintaining the ambient temperature at a temperature at which atoms mainly constituting the semiconductor layer do not desorb from the surface of the semiconductor layer. Then, a first oxide film forming step of forming the oxide film while holding the semiconductor layer in a temperature range in which atoms (Si in Embodiment 5) mainly constituting the semiconductor layer do not desorb from the surface of the semiconductor layer is performed. Execute. That is, similarly to [Step-430] of the fourth embodiment, if the atmosphere in the processing chamber 60 becomes a mixed gas atmosphere of hydrogen gas and nitrogen gas, the pipes 74 and 76 are transferred to the steam generating chamber 71 from the pipes 74 and 76. Hydrogen gas (flow rate:
While continuously supplying 0.2 SLM) and nitrogen gas (flow rate: 10 SLM), oxygen gas (flow rate: 10 SLM) is supplied from the pipe 75 to the steam generation chamber 71. At the same time, microwave power is supplied to the magnetron 73 and the magnetron 7
The microwave of 2.45 GHz generated in Step 3 is introduced into the steam generating chamber 71 through the microwave waveguide 72. Thus, that is, by irradiating the hydrogen gas and the oxidizing gas (the oxygen gas in the fifth embodiment also) with the electromagnetic waves, water vapor is generated. The generated steam reaches the processing chamber 60 via the pipe 78, and is heated by the heater 62 in the semiconductor layer (specifically, the silicon semiconductor substrate 40).
Is oxidized. Thus, an oxide film (SiO ₂ film in the fifth embodiment) can be formed on the surface of the semiconductor layer. The conditions for forming the oxide film may be the same as the conditions exemplified in Table 1. The processing chamber 6 is controlled by the heater 62.
The atmosphere temperature in 0 is kept at 400 ° C. In this step, a silicon oxide film having a thickness of 1.2 nm is formed on the surface of the silicon semiconductor substrate 40. The thickness of the silicon oxide film is a thickness corresponding to several molecular layers of SiO ₂ , and is a thickness sufficient to function as a protective film even in consideration of steps on the surface of the silicon semiconductor substrate.

[Step-550] Then, the steam generating chamber 7
1 and the supply of hydrogen gas and oxygen gas to the processing chamber 60 is stopped.
The temperature of the atmosphere in the processing chamber 60 of the oxide film forming apparatus is raised to 800 ° C. The heating rate is 10 ° C./min. [Step-54
0], since an oxide film that also functions as a protective film has already been formed on the surface of the semiconductor layer, this [Step-550]
In this case, the surface of the semiconductor layer (silicon semiconductor substrate 40) is not roughened.

[Step-560] The temperature of the atmosphere in the processing chamber 60 is raised to a temperature (800 ° C. in Embodiment 5) higher than the temperature range in which atoms mainly constituting the semiconductor layer do not desorb from the surface of the semiconductor layer. Is reached, a second oxide film forming step of further forming an oxide film until a desired thickness is performed while maintaining the atmosphere at this temperature. In particular,
Again, in the same manner as in [Step-540], hydrogen gas (flow rate: 0.2 SLM) and nitrogen gas (flow rate: 10 SLM) are supplied to the steam generation chamber 71 from the pipes 74 and 76, and the processing chamber 60 is supplied.
Is a mixed gas atmosphere of hydrogen gas and nitrogen gas. Since the concentration of the hydrogen gas in the mixed gas of the hydrogen gas and the nitrogen gas is 2% by volume, it is possible to reliably prevent the detonation reaction from occurring. Then, the steam generation chamber 71
Gas from pipes 74 and 76 (flow rate: 0.2 SLM)
And oxygen gas (flow rate: 10 SLM) from the pipe 75 to the steam generation chamber 71 while continuously supplying nitrogen gas (flow rate: 10 SLM).
10 SLM). As a result, the generated steam flows into the processing chamber 60 via the pipe 78, and the surface of the silicon semiconductor substrate 40 as the semiconductor layer is further oxidized, so that an oxide film having a desired thickness is formed on the surface of the semiconductor layer. Form 5
A SiO ₂ film with a total thickness of 4.0 nm is formed. The ambient temperature at which the formation of the oxide film having a desired thickness is completed (800 ° C. in Embodiment 5) is the ambient temperature at which the formation of the oxide film on the surface of the semiconductor layer is started. In the embodiment 5, the temperature is higher than 400 ° C.).

As described above, the formation of the silicon oxide film on the surface of the silicon semiconductor substrate 40 is completed. Thereafter, the inside of the processing chamber 60 is set to an inert gas atmosphere such as nitrogen gas, and then the door (not shown) is opened to open the silicon semiconductor film. The substrate 40 is unloaded.

In [Step-550], the processing chamber 60
The temperature of the atmosphere in the processing chamber 60 of the oxide film forming apparatus is adjusted to 8
The temperature may be raised to 00 ° C.

In [Step-560], since an oxide film is already formed on the surface of the semiconductor layer, a dry oxide film is formed even when oxygen gas, which is an oxidizing gas, comes into contact with the semiconductor layer. Nothing. Therefore, instead of setting the atmosphere of the processing chamber 60 to a mixed gas atmosphere of hydrogen gas and nitrogen gas, the nitrogen gas (flow rate: 10 SLM) is continuously supplied from the pipe 76 to the steam generation chamber 71,
1 may be supplied with an oxygen gas (flow rate: 10 SLM) from a pipe 75, and then a hydrogen gas (flow rate: 10 SLM) may be supplied from a pipe 74 to the steam generation chamber 71 to generate steam. Alternatively, an oxide film may be further formed based on a conventional pyrogenic oxidation method.

(Embodiment 6) Embodiment 6 is a modification of the oxide film forming method of Embodiment 5. In the sixth embodiment, following [Step-560] of the fifth embodiment, an inert gas atmosphere containing a halogen element (a nitrogen gas atmosphere containing hydrogen chloride) is applied to the formed oxide film.
Heat treatment (furnace annealing) is performed in the inside. by this,
An oxide film having excellent time zero dielectric breakdown (TZDB) characteristics and temporal dielectric breakdown (TDDB) characteristics can be obtained.

Specifically, [Step-56] of Embodiment 5
0], the supply of hydrogen gas and oxygen gas to the water vapor generation chamber 71 is stopped, and an oxide film is formed while introducing an inert gas (nitrogen gas) from the pipes 76 and 78 into the processing chamber 60. The ambient temperature of the processing chamber 60 of the apparatus is raised to 850 ° C. by the heater 62. Then, hydrogen chloride was added to 0.1.
A nitrogen gas containing 1% by volume is introduced into the processing chamber 60 from the pipes 76 and 78, and heat treatment is performed for 30 minutes. As described above, the formation of the silicon oxide film on the surface of the silicon semiconductor substrate 40 is completed. Thereafter, the inside of the processing chamber 60 is set to an inert gas atmosphere such as a nitrogen gas. Take it out. The ambient temperature profile in the sixth embodiment may be the same as that shown in FIG.

(Embodiment 7) Embodiment 7 is a modification of Embodiments 5 and 6. FIG. 14 is a conceptual diagram of an oxide film forming apparatus suitable for carrying out the oxide film forming method of the seventh embodiment. This oxide film forming apparatus differs from the apparatus shown in FIG. 13 in that it has a structure in which a steam generator and a processing chamber are integrated. This oxide film forming apparatus includes a processing chamber 80, a stage 81 on which a semiconductor layer (the silicon semiconductor substrate 40 also in the seventh embodiment) is mounted,
A magnet 83 provided outside the processing chamber 80;
And a gas introduction section 86, 87 disposed at the top of the processing chamber 80. The processing chamber 80 has a plasma generation area 80A.
And a reaction region 80B. Further, a lamp serving as a heating unit 82 for heating the silicon semiconductor substrate 40 is housed in the stage 81. A magnetron 85 is attached to the microwave waveguide 84, and a microwave of 2.45 GHz is generated by the magnetron 85, and the microwave is introduced into the plasma generation region 80 A of the processing chamber 80 through the microwave waveguide 84. . The water vapor generator includes a plasma generation region 80A, a microwave waveguide 84, and a magnetron 85. Further, hydrogen gas and oxygen gas are introduced into the processing chamber 10 from each of the gas introduction sections 86 and 87. In addition, an inert gas (for example, nitrogen gas) is introduced into the processing chamber 80 from a gas introduction unit 88 provided on a side surface of the processing chamber 80. Various gases introduced into the processing chamber 80 are exhausted out of the system from a gas exhaust unit 89 provided at a lower part of the processing chamber 80. The oxide film forming apparatus shown in FIG. 14 is an apparatus suitable for a method of forming an oxide film by a single wafer method. For example, one silicon semiconductor substrate 40 is placed on the stage 81.

In the seventh embodiment, a silicon semiconductor substrate was used as a semiconductor layer. The method for forming an oxide film according to the seventh embodiment using the oxide film forming apparatus shown in FIG. 14 will be described below.

[Step-700] First, after a device isolation region and the like are formed in a silicon semiconductor substrate in the same manner as in the first embodiment, fine particles and metal impurities on the surface of the silicon semiconductor substrate are removed by RCA cleaning. Then, the surface of the silicon semiconductor substrate is washed with a 0.1% aqueous hydrofluoric acid solution and pure water to expose the surface of the silicon semiconductor substrate.

[Step-710] Next, the silicon semiconductor substrate 40 is loaded into the oxide film forming apparatus shown in FIG. (Eg, nitrogen gas) is introduced into the processing chamber 80. Then, the silicon semiconductor substrate 40 is heated to 400 ° C. by the heating means 82. At this temperature, the Si—H bond on the surface of the semiconductor layer is not broken. Therefore, no unevenness (roughness) occurs on the surface of the semiconductor layer (the silicon semiconductor substrate 40 in the seventh embodiment).

[Step-720] Then, while introducing an inert gas (for example, nitrogen gas, flow rate of 10 SLM) as a diluting gas into the processing chamber 80 from the gas introducing section 88, the gas from the gas introducing section 86 to the inside of the processing chamber 80 is changed. Is introduced with a hydrogen gas at a flow rate of 0.2 SLM. As a result, the concentration of hydrogen gas in the processing chamber 80 before the generation of water vapor becomes a sufficiently low value, and it is possible to reliably prevent a detonation reaction from occurring, and to surely prevent the formation of a dry oxide film. be able to.

[Step-730] After the atmosphere in the processing chamber 80 becomes a mixed gas atmosphere of hydrogen gas and an inert gas, the inert gas processing chamber 80
Oxygen gas, for example, with a flow rate of 10 SLM is introduced into the processing chamber 80 from the gas introduction part 87 while continuing the introduction into the inside and the introduction of the hydrogen gas from the gas introduction part 86 into the processing chamber 80. At the same time, microwave power is supplied to the magnetron 85, and the microwave of 2.45 GHz generated by the magnetron 85 is introduced into the plasma generation region 80 </ b> A of the processing chamber 80 via the microwave waveguide 84. Thus, that is, by irradiating the hydrogen gas and the oxidizing gas with electromagnetic waves, the reactions of the above-described equations (1-1) to (1-4) and the reactions of the above-described equations (2) and (3) occur. Generates water vapor.
The generated steam reaches the reaction region 80B located below the processing chamber 80, and the surface of the semiconductor layer (specifically, the silicon semiconductor substrate 40) heated by the heating unit 82 is oxidized. Thus, an oxide film (a silicon oxide film in Embodiment 7) can be formed on the surface of the semiconductor layer. The conditions for forming the oxide film may be the same as those in Table 1.
In this step, an oxide film having a thickness of 1 nm is formed.

[Step-740] Then, the magnetron 8
The supply of the microwave power to the processing chamber 5 and the introduction of the hydrogen gas and the oxygen gas into the processing chamber 80 are stopped. To raise the temperature of the silicon semiconductor substrate to 800 ° C. Since an oxide film has already been formed on the surface of the semiconductor layer, no irregularities (roughness) occur on the surface of the semiconductor layer in this temperature raising step. Next, hydrogen gas and oxygen gas are again introduced into the processing chamber 80 from the gas introduction unit 86 and the gas introduction unit 87. At the same time, the microwave power is again supplied to the magnetron 85, and the microwave of 2.45 GHz generated by the magnetron 85 is supplied to the plasma generation region 80 A of the processing chamber 80 through the microwave waveguide 84.
To be introduced. Thus, that is, by irradiating the hydrogen gas and the oxygen gas with electromagnetic waves, the above-mentioned formula (1-
The reactions 1) to (1-4) and the reactions of the formulas (2) and (3) occur, and steam is generated. The generated water vapor reaches the reaction region 80B located below the processing chamber 80, and further oxidizes the surface of the semiconductor layer (specifically, a silicon semiconductor substrate) heated by the heating means 82. Thus, an oxide film (SiO ₂ film in the seventh embodiment) having a total thickness of 4 nm is formed on the surface of the semiconductor layer. Table 2 below shows the conditions for forming the oxide film.

[0108]

[Table 2] Microwave power: 10 kW Microwave frequency: 2.45 GHz Oxygen gas flow rate: 10 SLM Hydrogen gas flow rate: 0.2 SLM Inert gas flow rate: 10 SLM Substrate temperature: 800 ° C.

Thereafter, the semiconductor layer may be carried out of the processing chamber 80 of the oxide film forming apparatus. However, when the formation of an oxide film having higher characteristics is intended, the heat treatment described below is applied to the oxide film. Is preferred. That is, [Step-74
0], the supply of the microwave power to the magnetron 85 and the introduction of the hydrogen gas and the oxygen gas into the processing chamber 80 are stopped.
While continuing the introduction into the inside, the temperature of the silicon semiconductor substrate is raised to 850 ° C. by the heating means 82. Next, nitrogen gas containing 0.1% by volume of hydrogen chloride gas is introduced into the processing chamber 80 from the gas introduction unit 88, and heat treatment is performed for 5 minutes. As a result, an oxide film having excellent time-zero dielectric breakdown (TZDB) characteristics and temporal dielectric breakdown (TDDB) characteristics can be obtained.

The present invention has been described based on the embodiments of the present invention, but the present invention is not limited to these embodiments. The oxide film forming apparatus described in the embodiment of the invention is an example, and the design can be changed as appropriate. Further, the conditions for generating and oxidizing water vapor described in the embodiment of the invention are also examples, and can be appropriately changed as necessary.

FIGS. 11 and 12 show modifications of an oxide film forming apparatus suitable for carrying out the oxide film forming method according to the first embodiment of the present invention. The oxide film forming apparatus shown in FIG.
0, and a resistance heater 51 as a heating unit for heating the semiconductor layer. The processing chamber 50 is formed of a quartz furnace tube, and a semiconductor layer (specifically, for example, a silicon semiconductor substrate) is formed therein to form an oxide film on the semiconductor layer.
To store. The resistance heater 51 serving as a heating unit is provided outside the processing chamber 50 and is provided substantially in parallel with the surface of the semiconductor layer. The semiconductor layer (for example, the silicon semiconductor substrate 40) is placed on the wafer table 52, and is supplied through a gate valve 53 provided at one end of the processing chamber 50.
It is carried into and out of the processing chamber 50. In the oxide film forming apparatus, a gas introduction unit 54 for introducing steam or the like into the processing chamber 50 is provided.
And a gas exhaust unit 55 for exhausting gas from the processing chamber 50. The oxide film forming apparatus shown in FIG.
This is an apparatus suitable for a method of forming an oxide film by a single-wafer method. For example, one silicon semiconductor substrate 40 is placed on a wafer table 52. The temperature of the semiconductor layer (specifically, for example, a silicon semiconductor substrate) can be measured by a thermocouple (not shown). Note that the surface of the semiconductor layer is oxidized by water vapor generated by reacting a hydrogen gas and an oxidizing gas with a water vapor generator having a structure similar to that of Embodiment 1, thereby forming an oxide film on the surface of the semiconductor layer. I do. The illustration of the steam generator and the piping connecting the steam generator and the gas introduction unit 54 are omitted.

Alternatively, a horizontal type oxide film forming apparatus of the type schematically shown in FIG. 12 can be used. In the horizontal type oxide film forming apparatus shown in FIG.
The heating means includes a plurality of lamps 51A that emit infrared light or visible light. The temperature of the silicon semiconductor substrate is measured by a pyrometer (not shown).
Other structures can be basically the same as those of the oxide film forming apparatus shown in FIG. 11, and a detailed description thereof will be omitted. The method of forming the oxide film using the oxide film forming apparatus shown in FIG. 11 or FIG. Since the method can be the same as the method for forming an oxide film described above, detailed description is omitted.

FIG. 15 shows a modification of the oxide film forming apparatus suitable for carrying out the oxide film forming method according to the second aspect of the present invention. This oxide film forming apparatus is different from the apparatus shown in FIG. 13 in that a heater 62 is provided inside the processing chamber 60 instead of the heater 62 provided outside the processing chamber 60. On the point. The oxide film forming apparatus shown in FIG.
This is an apparatus suitable for a method of forming an oxide film by a single-wafer method. For example, one silicon semiconductor substrate 40 is mounted on the substrate mounting table 64. Other structures are the same as those of the device shown in FIG. The method for forming the oxide film using the oxide film forming apparatus shown in FIG. Since the method can be the same as the method for forming the film, detailed description is omitted.

In the third, sixth, or seventh embodiment, the temperature of the semiconductor layer is increased to 850 ° C. by a heating means while an inert gas (eg, nitrogen gas) is introduced into the processing chamber from a gas inlet or a pipe. C, but instead, an inert gas (for example, nitrogen gas) containing, for example, 0.1% by volume of hydrogen chloride gas is introduced into the processing chamber from a gas introduction part or a pipe, and the temperature of the semiconductor layer is reduced. The temperature may be raised to 850 ° C. by a heating means.

In the embodiment of the present invention, a silicon oxide film is formed exclusively on the surface of a silicon semiconductor substrate. However, based on the oxide film forming method of the present invention, a silicon An oxide film can be formed, or a silicon oxide film can be formed on a surface of a polysilicon layer or an amorphous silicon layer formed on an insulating layer formed on a substrate. 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.

Alternatively, in the embodiment of the invention, after the surface of the semiconductor layer is cleaned with a 0.1% aqueous solution of hydrofluoric acid and pure water, the semiconductor layer is carried into the oxide film forming apparatus. The atmosphere from the surface cleaning to the transfer to the oxide film forming apparatus may be an inert gas (eg, nitrogen gas) atmosphere. In addition, such an atmosphere is, for example, an atmosphere of a semiconductor layer surface cleaning apparatus is an inert gas atmosphere, and a semiconductor layer (for example, a silicon semiconductor substrate) is placed in a transport box filled with an inert gas. As shown in the schematic diagram in FIG. 16, a method for carrying in the oxide film forming apparatus, a surface cleaning apparatus, an oxide film forming apparatus, a transport path, a cluster tool apparatus including a loader and an unloader, This can be achieved by a method in which the surface of the surface cleaning device, the transfer path, and the processing chamber of the oxide film forming apparatus are set to an inert gas atmosphere by connecting the oxide film forming apparatus to the oxide film forming apparatus.

Alternatively, instead of cleaning the surface of the semiconductor layer with a 0.1% aqueous hydrofluoric acid solution and pure water, a gas phase cleaning method using anhydrous hydrogen fluoride gas under the conditions shown in Table 3 is used. May be used to clean the surface of the semiconductor layer.
Note that methanol is added to prevent generation of particles. Alternatively, the surface of the semiconductor layer may be cleaned by a gas phase cleaning method using hydrogen chloride gas under the conditions shown in Table 4. Note that the atmosphere in the surface cleaning device or the atmosphere in the transfer path before the start of surface cleaning of the semiconductor layer or after completion of the surface cleaning 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 substrate loading / unloading portion or the processing chamber of the oxide film forming apparatus when loading the semiconductor layer is set to, for example, 1.3 × 10 ⁻¹ Pa (10 A vacuum atmosphere of about ^-3 Torr may be used, and after the loading of the semiconductor layer is completed, the atmosphere of the substrate loading / unloading section or the processing chamber may be an inert gas (eg, nitrogen gas) atmosphere.

[0118]

[Table 3] Anhydrous hydrogen fluoride gas: 300 SCCM Methanol vapor: 80 SCCM Nitrogen gas: 1000 SCCM Pressure: 0.3 Pa Temperature: 60 ° C

[0119]

[Table 4] Hydrogen chloride gas / nitrogen gas: 1% by volume Temperature: 800 ° C

By employing these methods, it is possible to keep the surface of the semiconductor layer free from contamination or the like before forming the oxide film. It is possible to effectively prevent Si-OH from being taken in and lowering the characteristics of the formed oxide film or generating a defective portion.

[0121]

According to the method for forming an oxide film of the present invention,
Since the semiconductor layer does not come into contact with the oxidizing gas before forming the oxide film, formation of a dry oxide film on the surface of the semiconductor layer can be reliably prevented. In addition, since the oxide film is formed by an oxidation method using water vapor, an oxide film having excellent time-dependent dielectric breakdown (TDDB) characteristics can be obtained. In addition, hydrogen gas and oxidizing gas are reacted based on catalytic action to generate steam, or
For example, if water vapor is generated based on the reaction between oxygen plasma and hydrogen plasma, water vapor can be generated even if the hydrogen gas concentration is sufficiently low. As a result, the detonation reaction due to hydrogen gas is reliably prevented. In addition to this, it is possible to perform the formation of the oxide film in a stable state and with the oxidation rate controlled / suppressed, so that an extremely thin oxide film can be formed.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of an oxide film forming apparatus suitable for performing an oxide film forming method according to a first embodiment of the present invention.

FIG. 2 is a schematic partial cross-sectional view of a silicon semiconductor substrate or the like for describing a method of forming an oxide film according to the first embodiment of the present invention.

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

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

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

FIG. 6 shows Embodiment 2 and Embodiment 5 of the present invention;
17 is an atmosphere temperature profile according to Embodiment 3 and Embodiment 6 of the present invention.

FIG. 7 is a conceptual diagram of an oxide film forming apparatus and the like for describing a method of forming an oxide film according to a second embodiment of the present invention.

8 is a conceptual diagram of an oxide film forming apparatus and the like for describing a method of forming an oxide film according to a second embodiment of the present invention, following FIG. 7;

FIG. 9 is a conceptual diagram of an oxide film forming apparatus and the like for describing a method of forming an oxide film according to a second embodiment of the present invention, following FIG. 8;

FIG. 10 is a conceptual diagram of an oxide film forming apparatus and the like for describing a method of forming an oxide film according to the second embodiment of the present invention, following FIG. 9;

FIG. 11 is a schematic sectional view of a modification of the oxide film forming apparatus suitable for performing the method of forming an oxide film according to the first embodiment of the present invention.

FIG. 12 is a schematic sectional view of a modification of the oxide film forming apparatus suitable for performing the method of forming an oxide film according to the first embodiment of the present invention.

FIG. 13 is a schematic cross-sectional view of a modification of the oxide film forming apparatus suitable for performing the method of forming an oxide film according to the second embodiment of the present invention.

FIG. 14 is a schematic cross-sectional view of a modification of the oxide film forming apparatus suitable for performing the method of forming an oxide film according to the second aspect of the present invention.

FIG. 15 is a schematic cross-sectional view of a modification of the oxide film forming apparatus suitable for performing the method of forming an oxide film according to the second embodiment of the present invention.

FIG. 16 is a schematic view of a cluster tool device.

FIG. 17 is a schematic sectional view of a conventional vertical type silicon oxide film forming apparatus (thermal oxidation furnace).

FIG. 18 is a schematic sectional view of a silicon oxide film forming apparatus and the like for explaining a conventional method of forming a silicon oxide film.

FIG. 19 is a schematic cross-sectional view of a silicon oxide film forming apparatus and the like for describing a conventional method of forming a silicon oxide film, following FIG. 18;

FIG. 20 is a schematic cross-sectional view of a silicon oxide film forming apparatus and the like for explaining a conventional method of forming a silicon oxide film, following FIG. 19;

FIG. 21 is a schematic sectional view of a silicon oxide film forming apparatus and the like for explaining a conventional method of forming a silicon oxide film, following FIG. 20;

[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 ...
Substrate loading / unloading section, 21: gas introduction section, 22: gas exhaust section, 23: elevator mechanism, 24: quartz boat, 30: steam generator, 31, 32, 33,
34 ... piping, 31, 131 ... piping, 40 ...
Silicon semiconductor substrate, 41 ... element isolation region, 42
..Oxide film, 43 gate electrode, 50 processing chamber, 51 resistance heater, 51A lamp
52: wafer stage, 53: gate valve, 54
..Gas introduction part, 55 gas exhaust part, 60 processing chamber, 61 quartz boat, 62 heater, 63
... Gas exhaust part, 70 ... Steam generator, 71
..Steam generating chamber, 72... Microwave waveguide, 73
... magnetron, 74, 75, 76, 78 ... piping, 77, 79 ... heater, 80 ... processing chamber, 80
A: Plasma generation area, 80B: Reaction area, 8
DESCRIPTION OF SYMBOLS 1 ... Stage, 82 ... Heating means, 83 ... Magnet, 84 ... Microwave waveguide, 85 ... Magnetron, 86, 87, 88 ... Gas introduction part, 89 ...
Gas exhaust section

Claims (17)

[Claims] (1) a step of introducing an inert gas containing hydrogen gas into a steam generator; and (b) then introducing an oxidizing gas into the steam generator, and introducing hydrogen gas in the steam generator. A process of oxidizing a surface of the semiconductor layer with water vapor generated by a reaction between a gas and an oxidizing gas, thereby forming an oxide film on the surface of the semiconductor layer. 2. The method according to claim 1, wherein the reaction between the hydrogen gas and the oxidizing gas in the steam generator is a reaction based on a catalytic action. 3. The method according to claim 1, wherein the reaction between the hydrogen gas and the oxidizing gas in the steam generator is a reaction based on irradiation of the hydrogen gas and the oxidizing gas with electromagnetic waves. A method for forming an oxide film. 4. The method according to claim 3, wherein the electromagnetic wave is a microwave. 5. The method according to claim 1, wherein the hydrogen gas concentration in the step (a) is lower than a combustion range in air or oxygen gas. 6. The oxidizing gas is oxygen gas, NO gas or N gas.
_{2. The} method for forming an oxide film according to claim 1, wherein the gas is ₂ O gas. 7. The method according to claim 1, wherein in the step (b), the formation of the oxide film is started in a state where the atmosphere temperature is kept at a temperature at which atoms mainly constituting the semiconductor layer do not desorb from the surface of the semiconductor layer. The method for forming an oxide film according to claim 1. 8. The temperature at which atoms mainly constituting the semiconductor layer do not desorb from the surface of the semiconductor layer is the temperature at which bonds between atoms terminating the surface of the semiconductor layer and atoms mainly constituting the semiconductor layer are not broken. The method for forming an oxide film according to claim 7, wherein: 9. The method according to claim 8, wherein atoms mainly constituting the semiconductor layer are Si. 10. The temperature at which atoms mainly constituting the semiconductor layer do not desorb from the surface of the semiconductor layer depends on the Si—H on the surface of the semiconductor layer.
The method for forming an oxide film according to claim 9, wherein the temperature is a temperature at which the bond is not broken. 11. The temperature at which atoms mainly constituting the semiconductor layer do not desorb from the surface of the semiconductor layer depends on the Si-F on the surface of the semiconductor layer.
The method for forming an oxide film according to claim 9, wherein the temperature is a temperature at which the bond is not broken. 12. The method according to claim 1, wherein in the step (b), the temperature of the semiconductor layer when the formation of the oxide film is completed is higher than the temperature of the semiconductor layer when the formation of the oxide film is started. 8. The method for forming an oxide film according to 7. 13. The method according to claim 1, wherein after the step (b) is completed, the formed oxide film is subjected to a heat treatment. 14. The heat treatment atmosphere is an inert gas atmosphere containing a halogen element.
4. The method for forming an oxide film according to 3. 15. The method for forming an oxide film according to claim 14, wherein the halogen element is chlorine. 16. The oxide film according to claim 15, 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. Forming method. 17. The method according to claim 13, wherein the heat treatment is performed at a temperature of 700 to 950 ° C.