JPH11162971A - Formation method for oxide film, and manufacture of p-type semiconductor element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a thin oxide film stably by humidifying oxidation method, by forming an oxide film on the surface of a semiconductor layer using steam produced by applying electromagnetic waves to hydrogen gas and oxygen gas, and further, nitriding the surface of the oxide film by nitrogen molecules in excitation state produced from nitrogen gas. SOLUTION: Hydrogen gas and oxygen gas are introduced into a processing chamber 10 from gas introduction parts 16A and 16B. Steam is produced by applying electromagnetic waves to hydrogen gas and oxygen gas. The produced steam reaches a reaction region 10B positioned under a processing chamber 10, and the surface of a semiconductor layer 20 heated by a heating means 12 is oxidized. That is, an oxide film can be made on the surface of the semiconductor layer 20. Then, nitrogenous gas is introduced into the processing chamber 10 from a gas introduction part 16C. Nitrogen molecules or nitrogen atoms ions in excitation state produced by applying electromagnetic waves to the nitrogenous gas reach the reaction region 10B positioned under the processing chamber 10, and the surface of the oxide film is nitrided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for forming an oxide film and a method for manufacturing a p-type semiconductor device, and more particularly to a method for forming an oxide film having a nitrided surface and a method for forming such an oxide film as a gate oxide film. The present invention relates to a method for manufacturing a p-type semiconductor device applied to the formation of a semiconductor device.

[0002]

2. Description of the Related Art For example, in manufacturing a MOS type semiconductor device based on a silicon semiconductor substrate, it is necessary to form a gate oxide film made of a silicon oxide film on the surface of the silicon semiconductor substrate. Also, thin film transistors (TFTs)
It is also 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.

With the increase in the degree of integration of semiconductor devices, the thickness of the gate oxide film of a MOS type semiconductor device is also becoming thinner, and the thickness of the gate oxide film in a semiconductor device having a gate length of 0.1 μm is expected to be about 3 nm. ing. Methods of forming silicon oxide films are broadly classified into two methods: a dry oxidation method using dry oxygen as an oxidizing species and a humidifying oxidation method using steam as an oxidizing species. The dry oxidation method is a method for forming a silicon oxide film on the surface of a silicon semiconductor substrate by supplying sufficiently dried oxygen to a heated silicon semiconductor substrate. The humidification oxidation method is a method in which a silicon oxide film is formed on the surface of a silicon semiconductor substrate by supplying a high-temperature carrier gas containing water vapor to the silicon semiconductor substrate. In general, a silicon oxide film formed by a humidification oxidation method has higher reliability than a silicon oxide film formed by a dry oxidation method.

[0004] A kind of humidification oxidation method is a pyrogenic oxidation method. This method is a method in which pure hydrogen gas is burned to generate steam in order to increase the reproducibility of the humidification oxidation method and eliminate the need for controlling the amount of water. According to this pyrogenic method, since steam can be generated most stably, a uniform silicon oxide film can be formed.
In addition, since a gas is used as a raw material for generating steam, there is an advantage that impurities can be easily controlled.

In recent years, in CMOS transistors,
For the purpose of reducing power consumption, lowering the voltage has been attempted. For this reason, a sufficiently low and symmetric threshold voltage is required for the PMOS semiconductor device and the NMOS semiconductor device.
In order to cope with such a demand, in a PMOS semiconductor device, a gate electrode made of a polysilicon layer containing a p-type impurity is replaced with a gate electrode made of a polysilicon layer containing an n-type impurity. Is used. However, boron atoms (B), which are usually used p-type impurities, easily pass through the gate oxide film from the gate electrode to the silicon semiconductor substrate by various heat treatments in the semiconductor device manufacturing process after the formation of the gate electrode. , The threshold voltage of the PMOS semiconductor element is varied. Such a phenomenon becomes more conspicuous when the gate oxide film is made thinner to reduce the voltage.

[0006]

When an attempt is made to form a thin silicon oxide film, the humidification oxidation method has a higher oxidation rate than the dry oxidation method. For example, the oxidation temperature is reduced and the oxidation time is shortened. Must. However, there is a problem that shortening the oxidation time prevents 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 hydrogen gas combustion device 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.

Further, in order to suppress the fluctuation of the threshold voltage of the PMOS semiconductor element caused by the diffusion of the boron atoms (B) into the silicon semiconductor substrate, a method of introducing nitrogen atoms into the gate oxide film has been attempted. Therefore, the effect of suppressing the diffusion of boron atoms has been confirmed. As a method for introducing nitrogen atoms into a gate oxide film, for example, a so-called plasma nitridation method in which a nitrogen plasma is generated by performing a discharge in a nitrogen gas atmosphere is described in the document "Ultrathin nitrogen-profile".
engineered gate dielectric filmes ", SVHattangad
y, et al., 1996, known from IEDM. In the plasma nitridation method described in this document, since only the surface of the gate oxide film is nitrided, nitrogen enters the silicon semiconductor substrate as in the case of introducing nitrogen atoms into the gate oxide film by the thermal nitridation method. As a result, there is no adverse effect on semiconductor element characteristics such as a reduction in current driving capability.

However, in the plasma nitriding method described in this document, since the silicon oxide film is formed based on the thermal oxidation method, the formation of the silicon oxide film and the plasma nitridation of the silicon oxide film are performed by different apparatuses. In addition, it is necessary to perform the process in two steps. That is, there is a problem that the number of manufacturing steps of the semiconductor device is increased and a manufacturing time of the semiconductor device is prolonged, or a problem that two types of devices, an oxidizing device and a plasma nitriding device, are required.

Accordingly, an object of the present invention is to form a thin oxide film stably by a humidifying oxidation method.
For forming an oxide film capable of reliably suppressing the diffusion of boron atoms in forming a gate electrode of a p-type semiconductor device, and a method for manufacturing a p-type semiconductor device in which such an oxide film formation method is applied to the formation of a gate oxide film Is to provide. It is a further object of the present invention to provide a method for forming an oxide film capable of nitriding only the surface of the oxide film in one apparatus, and a p-type semiconductor in which such a method for forming an oxide film is applied to the formation of a gate oxide film. An object of the present invention is to provide a device manufacturing method.

[0011]

In order to achieve the above object, the method of forming an oxide film according to the present invention comprises the steps of (a) irradiating a hydrogen gas and an oxygen gas with electromagnetic waves to generate water vapor, A step of oxidizing the surface of the semiconductor layer by using the semiconductor layer to form an oxide film on the surface of the semiconductor layer, and (b) using an excited state of nitrogen molecules or nitrogen molecule ions generated by irradiating a nitrogen-based gas with electromagnetic waves. Nitriding the surface of the oxide film.

In order to achieve the above object, a method of manufacturing a p-type semiconductor device according to the present invention comprises: (A) forming a gate oxide film on a surface of a semiconductor layer; and (B) forming a gate oxide film on the gate oxide film. Forming a gate electrode made of a silicon layer containing a p-type impurity, wherein the step (A) comprises: (i) irradiating a hydrogen gas and an oxygen gas with an electromagnetic wave. A step of oxidizing the surface of the semiconductor layer using the water vapor to form an oxide film on the surface of the semiconductor layer; and (b) exciting the nitrogen-based gas by irradiating it with electromagnetic waves. Nitriding the surface of the oxide film with nitrogen molecules or nitrogen molecule ions in a state, thereby forming a gate oxide film.

In the method of manufacturing a p-type semiconductor device according to the present invention, the formation of a gate electrode made of a silicon layer containing a p-type impurity (for example, a polysilicon layer or an amorphous silicon layer) is performed, for example, using a p-type impurity (for example, boron). ), A method of patterning the silicon layer after forming the silicon layer based on the CVD method, and a method of ion-implanting a p-type impurity (for example, boron or BF ₂ ) by forming a silicon layer containing no impurities by the CVD method. And then patterning the silicon layer. A silicon layer containing no impurities is formed by a CVD method, followed by patterning, and then a p-type impurity (for example, boron or BF ₂ ) is ion-implanted. And a method of injecting into a silicon layer. In the step (B), after forming a silicon layer containing a p-type impurity, a silicide layer is formed on the silicon layer, and then the silicide layer and the silicon layer are patterned to form a gate electrode having a polycide structure. May be formed.

In the method of forming an oxide film or the method of manufacturing a p-type semiconductor device of the present invention (hereinafter, these may be collectively simply referred to as the method of the present invention), for example, a frequency of 2.45 GHz is used as an electromagnetic wave. Can be used. In a state in which water vapor generated based on hydrogen gas and oxygen gas is diluted with an inert gas such as nitrogen, argon, helium, neon, krypton, or xenon, or using these inert gases as a carrier gas, An oxide film may be formed on the surface of the layer.

In the present invention, as the nitrogen-based gas to be irradiated with the electromagnetic wave, NO, in addition to nitrogen gas (N ₂ gas),
Gases that are compounds of a nitrogen atom and an oxygen atom, such as N ₂ O and NO ₂ , can be exemplified.

In the method of the present invention, the steps (a) and (b) are performed in the same processing chamber, which simplifies the structure of the apparatus or shortens the time for forming an oxide film or a gate oxide film. Is preferred.

In the case of manufacturing a MOS type semiconductor device based on a silicon semiconductor substrate, conventionally, before forming a gate oxide film, the substrate is washed with an aqueous solution of NH ₄ OH / H ₂ O ₂ and further washed with HCl.
The surface of the silicon semiconductor substrate is cleaned by RCA cleaning of cleaning with an aqueous solution of / H ₂ O ₂ 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 to form a silicon oxide film having a thickness of about 0.5 to 1 nm. The thickness of such a silicon oxide film is not uniform, and a cleaning solution 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, a silicon oxide film is formed on the surface of the silicon semiconductor substrate.

If the atmosphere before forming the silicon oxide film based on the humidifying oxidation method is a high-temperature nitrogen gas atmosphere, the surface of the silicon semiconductor substrate becomes rough (unevenness). Such a phenomenon occurs when a part of the Si—H bond or a part of the Si—F bond formed on the surface of the silicon semiconductor substrate by washing with the hydrofluoric acid aqueous solution and the pure water,
It is considered that hydrogen and fluorine are lost due to thermal desorption, resulting in an etching phenomenon on the surface of the silicon semiconductor substrate. For example, when the temperature of a silicon semiconductor substrate is raised to 600 ° C. or more in argon gas, severe irregularities may occur on the surface of the silicon semiconductor substrate, as described in Baifukan, Tadahiro Omi, “Ultra Clean ULSI Technology”, page 21. Have been.

Therefore, in order to avoid the occurrence of such a phenomenon that the surface of the semiconductor layer is roughened (irregularities), in the method of the present invention, in the step (a), the surface of the semiconductor layer is removed from the surface of the semiconductor layer. It is preferable to start formation of an oxide film on the surface of the semiconductor layer in a state where the semiconductor layer is held at a temperature at which atoms mainly constituting the semiconductor layer do not desorb. 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. Is desirable. When the atoms mainly constituting the semiconductor layer are Si, that is, when the semiconductor layer is composed of a silicon semiconductor substrate, a single crystal silicon layer, a polysilicon layer, or an amorphous silicon layer, the semiconductor layer is removed from the surface of the semiconductor layer. It is desirable that the temperature at which the main constituent atoms do not desorb 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 hydrogen atoms on the surface of the silicon semiconductor substrate are 2% of silicon atoms.
One to each of the two bonds, HS
It has an iH termination structure. However, a portion where the surface state of the silicon semiconductor substrate is broken (for example, a step forming portion)
Has a terminal structure in which a hydrogen atom is bonded to only one bond of a silicon atom, or a terminal structure in which a hydrogen atom is bonded to each of three bonds of a silicon atom. 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 the oxide film on the surface of the semiconductor layer is started is more specifically a temperature at which water vapor does not condense on the semiconductor layer, preferably 200 ° C.
It is desirable that the temperature be at least ゜ C, more preferably at least 300 ゜ C, from the viewpoint of throughput.

In the method of the present invention, in the step (a), 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 the present invention, the gas atmosphere containing water vapor during the formation of the oxide film may contain a halogen element. As a result, the time zero breakdown (TZD)
B) An oxide film having excellent characteristics and time-dependent dielectric breakdown (TDDB) characteristics can be obtained. In addition, as the halogen element, chlorine, bromine and fluorine can be mentioned, and among them, chlorine is preferable. Examples of the form of the halogen element contained in the gas containing water vapor include hydrogen chloride (HCl), CCl ₄ , C ₂ HCl ₃ , Cl ₂ , HBr, and N.
F ₃ can be mentioned. The content of the halogen element in the gas containing water vapor is 0.001 to 10% by volume, preferably 0.005 to 10% by volume, based on the form of the molecule or the compound.
It is 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 between the steps (a) and (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.

In the method of the present invention, it is preferable to perform the heat treatment in the same processing chamber. The heat treatment temperature is 7
The temperature is from 00 to 1200 ° C, preferably from 700 to 1000 ° C, and more preferably from 700 to 950 ° C. Also,
The time of the heat treatment is preferably 1 to 10 minutes when performing the single-wafer processing, and 5 to 60 minutes when performing the batch processing.
Minutes, preferably 10 to 40 minutes, more preferably 20 to 3 minutes.
Desirably, it is 0 minutes.

When heat treatment is performed in the method of the present invention,
It is desirable 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, for example, hydrogen chloride (HCl), CCl ₄ , C ₂ H
Cl ₃ , Cl ₂ , HBr and NF ₃ can be mentioned.
The content of the halogen element in the inert gas is from 0.001 to 10% by volume, preferably from 0.005 to 10% by volume, more preferably from 0.0 to 10% by volume, based on the form of the molecule or the compound.
It is 2 to 10% by volume. For example, when using hydrogen chloride gas, the content of hydrogen chloride gas in the inert gas is 0.02 to 1
Desirably, it is 0% by volume.

Normally, before a silicon oxide film is formed on the surface of a silicon semiconductor substrate, the substrate is washed with an aqueous solution of NH ₄ OH / H ₂ O ₂ and further washed with an aqueous solution of HCl / H ₂ O _2.
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 Meeting Technical Digest
95, pp 855-858). In such a case, if the formation of the oxide film is started as it is, moisture or an organic substance or, for example, Si—O
H is taken in and may cause deterioration of characteristics of the formed silicon oxide film or generation of a defective portion. In addition, a defect part is a silicon dangling bond (Si
-Si bond containing a defect such as -H bond, or Si-O-Si bond is compressed by stress or Si-O-Si bond has a thick angle or Si-O in a bulk silicon oxide film. −Si bond means a portion of the silicon oxide film including a Si—O—Si bond that is different from the angle. 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,
The formation of the oxide film is performed without exposing the semiconductor layer after the surface cleaning to the atmosphere (that is, the atmosphere from the cleaning of the semiconductor layer surface to the start of the oxide film forming step is an inert gas atmosphere or a vacuum atmosphere). Is preferred. 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.

In the formation of an oxide film, hydrogen gas and oxygen gas are introduced into the processing chamber. At this time, it is required that hydrogen gas flows into the processing chamber and flows out of the system, thereby causing a detonation reaction. To prevent this, it is preferable to introduce oxygen gas before introducing hydrogen gas into the treatment chamber. However, there is a possibility that an oxide film is formed in the semiconductor layer by introduction of oxygen gas into the treatment chamber. Such an oxide film is a dry oxide film and has inferior characteristics to an oxide film formed by a humidification oxidation method. In order to reliably prevent the formation of such a dry oxide film, for example, a hydrogen gas diluted with an inert gas such as a nitrogen gas is first introduced into a processing chamber before the formation of an oxide film, and then the processing is performed. What is necessary is just to introduce oxygen gas into a room. However, in this case, in order to surely prevent the occurrence of a detonation reaction, the concentration of the hydrogen gas should be set so that the hydrogen gas does not react with the oxygen gas and burn, specifically, in air. Below the detonation range (18.3% by volume or less when expressed in terms of volume with air), preferably below the combustion range in air (less than 4.0% by volume when expressed in volume% with air) ) Or below the detonation range in oxygen (less than 15.0% by volume when expressed in terms of volume% with oxygen), preferably below the combustion range in oxygen (expressed as volume% with oxygen) In this case, the concentration is desirably set to be 4.5% by volume or less.

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 of 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 oxygen plasma generated by the microwave discharge, the ground state O ₂ (X ³ Σg ⁻ ) is excited by the collision of electrons with the excited state O ₂ (A ³ Σu ⁺ ) or O ₂ (B ³ Σ).
u ^-) to be excited, respectively, to dissociate the oxygen atom by the following equation.

[0033]

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.

[0035]

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.

[0037]

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

In the method of the present invention, steam is generated based on such a reaction between oxygen plasma and hydrogen plasma, so that steam can be easily and reliably generated even under reduced pressure, for example. With the oxidation rate controlled, a thin oxide film can be formed by the humidification oxidation method.

On the other hand, when a nitrogen (N ₂ ) gas is used as the nitrogen-based gas, the nitrogen N ₂ is excited in the microwave plasma by the following formula, for example. That is, electrons existing in the plasma are excited, and the excited nitrogen molecules and nitrogen molecule ions are generated by the inelastic collision of the electrons with the nitrogen molecules. These excited nitrogen molecules and nitrogen molecule ions bond oxygen atoms with atoms mainly constituting the semiconductor layer on the surface of the oxide film (for example, when the atoms mainly constituting the semiconductor layer are Si, Si—O The bond is cut to form a nitrided oxide (eg, a Si—O—N bond), and the surface of the oxide film is nitrided. The composition of the surface of the oxide film is represented by SiO _X N _Y when the atoms mainly constituting the semiconductor layer are Si.

[0040]

Embedded image N ₂ (X ¹ Σg) + e → N ₂ (A ³ Σu ⁺ ) + e Formula (4-1) N ₂ (N ¹ Σg) + e → N ₂ (C ³ Πu) + e Formula (4-2) N ₂ (C ³ Πu) + e → N ₂ (B ³ Πg) + hv Formula (4-3) N ₂ (B ³ Πg) + e → N ₂ (A ³ Σu ⁺ ) + hv Formula (4-4)

In the method of the present invention, an oxide film or a gate oxide film is formed by irradiating a hydrogen gas, an oxygen gas, and a nitrogen-based gas with electromagnetic waves. Thus, an oxide film or a gate oxide film can be formed, and the device configuration for forming the oxide film or the gate oxide film can be simplified. In addition, since the steam is generated by irradiating the hydrogen gas and the oxygen gas with the electromagnetic wave, the steam is easily and reliably generated in a state where the oxidation rate is suppressed and controlled, that is, for example, even under reduced pressure. This makes it possible to form a thin oxide film by the humidifying oxidation method. 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.

Since only the surface of the oxide film is nitrided,
Unlike the introduction of nitrogen atoms into a gate oxide film by a thermal nitridation method, there is no adverse effect on semiconductor device characteristics such as a reduction in current driving capability due to the intrusion of nitrogen into a silicon semiconductor substrate. Further, since the oxide film is nitrided, boron atoms pass through the gate oxide film and reach the silicon semiconductor substrate by various heat treatments in a semiconductor device manufacturing process after the formation of the gate electrode, and the threshold voltage of the PMOS semiconductor element is reduced. A phenomenon such as fluctuation can be reliably avoided.

[0043]

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

(Embodiment 1) FIG. 1 shows a conceptual diagram of a single wafer type oxide film forming apparatus suitable for carrying out the method of the present invention. This oxide film forming apparatus includes a processing chamber 10 and a semiconductor layer (Example 1).
, A stage 11 on which a silicon semiconductor substrate 20) is mounted, a magnet 13 disposed outside the processing chamber 10,
Microwave waveguide 1 mounted on top of processing chamber 10
4 and a gas inlet 16 disposed at the top of the processing chamber 10.
A, 16B and 16C. Processing room 10
Is composed of a plasma generation region 10A and a reaction region 10B. Further, a lamp as heating means 12 for heating silicon semiconductor substrate 20 is housed in stage 11. A magnetron 15 is attached to the microwave waveguide 14, and 2.
A microwave of 45 GHz is generated, and the microwave is introduced into the plasma generation region 10A of the processing chamber 10 via the microwave waveguide 14. Further, hydrogen gas, oxygen gas, and nitrogen gas are introduced into the processing chamber 10 from each of the gas introduction units 16A, 16B, and 16C. In addition, an inert gas (for example, nitrogen gas) is introduced into the processing chamber 10 from a gas introduction unit 17 provided on a side surface of the processing chamber 10.
Various gases introduced into the processing chamber 10 are exhausted out of the system from a gas exhaust unit 18 provided in a lower part of the processing chamber 10.

In Example 1, a silicon semiconductor substrate was used as a semiconductor layer. In the first embodiment,
After the 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, the oxide film is formed from the surface of the semiconductor layer for a predetermined period. A first oxide film forming step of forming an oxide film while maintaining the semiconductor layer in a temperature range in which atoms mainly constituting the layer do not desorb, and removing atoms mainly forming the semiconductor layer from the surface of the semiconductor layer. A second oxide film forming step of further forming an oxide film at a temperature higher than the non-existent temperature range until a desired thickness is obtained. The method of forming an oxide film and the method of manufacturing a p-type semiconductor device of the present invention using the oxide film forming apparatus shown in FIG. 1 will be described below with reference to FIG. It will be described with reference to FIG.

[Step-100] First, an N-type silicon wafer doped with phosphorus and having a diameter of 8 inches (prepared by the CZ method)
LOC is formed on the silicon semiconductor substrate 20 by a known method.
An element isolation region 21 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 20 are removed by RCA cleaning, and then the surface of the silicon semiconductor substrate 20 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 20 is mostly terminated with hydrogen, and a very small part is terminated with fluorine.

[Step-110] Next, the silicon semiconductor substrate 20 is loaded into the oxide film forming apparatus shown in FIG.
From 7, an inert gas (for example, nitrogen gas) is introduced into the processing chamber 10. Then, the silicon semiconductor substrate 20 is heated to 300 ° C. by the heating means 12. At this temperature, the Si—H bond on the surface of the semiconductor layer is not broken.
Therefore, no irregularities (roughness) are generated on the surface of the semiconductor layer (the silicon semiconductor substrate in the first embodiment).

[Step-120] Then, while introducing an inert gas (for example, nitrogen gas) as a diluting gas into the processing chamber 10 from the gas introducing section 17, the gas is introduced from the gas introducing section 16A and the gas introducing section 16B to the processing chamber. Hydrogen gas and oxygen gas are introduced into 10. At the same time, microwave power is supplied to the magnetron 15 and the 2.4 generated by the magnetron 15 is generated.
A microwave of 5 GHz is introduced into the plasma generation region 10A of the processing chamber 10 via the microwave waveguide 14. Thus, that is, by irradiating the hydrogen gas and the oxygen gas with the electromagnetic waves, the reactions of the above-described equations (1-1) to (1-4) and the reactions of the equations (2) and (3) occur. Water vapor is generated. The generated steam reaches the reaction region 10B located below the processing chamber 10 and is heated by the heating means 12 in the semiconductor layer (specifically, the silicon semiconductor substrate 20).
Is oxidized. Thus, an oxide film (a silicon oxide film in Example 1) can be formed on the surface of the semiconductor layer. Table 1 shows the conditions for forming the oxide film. In the first oxide film forming step, a thickness of 1 n
An oxide film of m is formed.

[0049]

[Table 1] 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: 300 ° C.

[Step-130] Then, the magnetron 1
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 10 are stopped, and the introduction of the inert gas from the gas inlet 17 into the processing chamber 10 is continued. To raise the temperature of the silicon semiconductor substrate to 800 ° C. Since an oxide film is already formed on the surface of the semiconductor layer, the semiconductor layer (Example 1)
(Silicon semiconductor substrate) has irregularities (roughness) on the surface
Does not occur. Then, again, the gas introduction unit 16A
And, a hydrogen gas and an oxygen gas are introduced into the processing chamber 10 from the gas introduction unit 16B. At the same time, magnetron 15
Is supplied with microwave power, and the microwave of 2.45 GHz generated by the magnetron 15 is supplied to the microwave waveguide 1.
4 and is introduced into the plasma generation region 10 </ b> A of the processing chamber 10. Thus, that is, by irradiating the hydrogen gas and the oxygen gas with electromagnetic waves,
The reaction of (1-4) and the reactions of formulas (2) and (3) occur, and steam is generated. The generated steam reaches the reaction region 10B located below the processing chamber 10 and is heated by the heating means 12B.
Then, the surface of the semiconductor layer (specifically, the silicon semiconductor substrate) heated is further oxidized. Thus, an oxide film (a silicon oxide film in Example 1) having a total thickness of 4 nm is formed on the surface of the semiconductor layer. Table 2 below shows conditions for forming an oxide film in the second oxide film forming step.

[0051]

[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.

[Step-140] After the formation of the oxide film is completed, supply of microwave power to the magnetron 15 and the processing chamber 10
The introduction of hydrogen gas and oxygen gas into the semiconductor substrate is stopped, and the silicon semiconductor substrate 20 is cooled to room temperature. Next, the introduction of the inert gas from the gas introduction unit 17 into the processing chamber 10 is stopped. Thereafter, a nitrogen gas, which is a nitrogen-based gas, is introduced into the processing chamber 10 from the gas introduction unit 16C. At the same time, microwave power is supplied to the magnetron 15 and the microwave of 2.45 GHz generated by the magnetron 15 is passed through the microwave waveguide 14 to the plasma generation region 10A of the processing chamber 10.
To be introduced. Thus, that is, by irradiating the nitrogen gas with an electromagnetic wave, the above equations (4-1) to (4-4) are obtained.
In the reaction region 10B in which the excited state nitrogen molecule or nitrogen molecule ion generated by the
And the surface of the oxide film (specifically, the silicon oxide film) is nitrided. Thus, the oxide film 22 whose surface is nitrided
(In the first embodiment, a silicon oxide film, which corresponds to a gate oxide film) can be formed on the surface of the semiconductor layer. This state is schematically shown in FIG. In the drawing, the illustration of the nitrided portion of the oxide film is omitted.
Table 3 shows the conditions of nitriding. The reason for setting the temperature of the silicon semiconductor substrate to room temperature is to suppress diffusion of nitrogen atoms into the silicon semiconductor substrate in the nitriding treatment.

[0053]

[Table 3] Microwave power: 1 kW Microwave frequency: 2.45 GHz Nitrogen gas flow rate: 0.4 SLM Pressure: 0.16 Pa Substrate temperature: room temperature (25 ° C.)

[Step-150] Thereafter, the semiconductor layer is unloaded from the oxide film forming apparatus, and then the semiconductor layer is loaded into a known CVD apparatus. Then, a silicon layer containing no impurities (a polysilicon layer in the first embodiment) is formed on the entire surface by a CVD method. Next, the silicon layer is patterned based on a photolithography technique and a dry etching technique. Then, boron ions are implanted into the silicon layer and the silicon semiconductor substrate by an ion implantation method. As a result, the gate electrode 2 made of a silicon layer containing a p-type impurity (specifically, a polysilicon layer) is formed on the gate oxide film.
3 can be formed, and at the same time, an LDD structure can be formed (see FIG. 2C).

[Step-160] Next, an insulating film is formed on the entire surface, and the insulating film is etched by an anisotropic dry etching technique to form a sidewall 24 on the side wall of the gate electrode 23. Next, in order to form the source / drain regions 25, boron ions are implanted into the silicon semiconductor substrate by an ion implantation method, and then activation heat treatment of the ion-implanted impurities is performed. Then, an insulating layer 26 is
An opening is provided in the insulating layer 26 above the source / drain region 25, and a wiring material layer is formed on the insulating layer 26 including the inside of the opening by a sputtering method. Is patterned to form a wiring 27, and a p-type semiconductor element 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 and the method for manufacturing a p-type semiconductor device of Embodiment 1. Example 2 differs from Example 1 in that a heat treatment is performed on the formed oxide film between the step of forming an oxide film on the surface of the semiconductor layer and the step of nitriding the surface of the oxide film. is there. Hereinafter, a method for forming an oxide film and a method for manufacturing a p-type semiconductor device according to the second embodiment will be described. Incidentally, the oxide film forming apparatus shown in FIG.

[Step-200] [Step-10] of Example 1
0] to [Step-130], an oxide film having a total thickness of 4 nm (the silicon oxide film in the second embodiment) is formed on the surface of the semiconductor layer (the silicon semiconductor substrate in the second embodiment). Form.

[Step-210] Then, the magnetron 1
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 10 are stopped, and the introduction of the inert gas from the gas inlet 17 into the processing chamber 10 is continued. To raise the temperature of the silicon semiconductor substrate to 850 ° C. Next, nitrogen gas containing 0.1% by volume of hydrogen chloride gas is introduced into the processing chamber 10 from the gas introduction unit 17 and heat treatment is performed for 5 minutes. As a result, time-zero dielectric breakdown (TZDB) characteristics and time-dependent dielectric breakdown (TDD)
B) An oxide film having excellent characteristics can be obtained.

[Step-220] Thereafter, the gas introduction unit 17
The introduction of nitrogen gas containing 0.1% by volume of hydrogen chloride gas into the processing chamber 10 is stopped, and an inert gas (for example, nitrogen gas) is introduced into the processing chamber 10 from the gas introduction unit 17. Then, after the silicon semiconductor substrate is cooled to room temperature, the same steps as [Step-140] to [Step-160] of the first embodiment are performed, whereby a p-type semiconductor element can be obtained.

Although the present invention has been described based on the preferred embodiments, the present invention is not limited to these embodiments. The various conditions and the structure of the oxide film forming apparatus described in the embodiments are merely examples, and can be appropriately changed.

For example, in [Step-130] of the first embodiment, the supply of the microwave power to the magnetron 15 and the introduction of the hydrogen gas and the oxygen gas into the processing chamber 10 are not interrupted by the heating means 12 without stopping the silicon semiconductor substrate. To 80
The temperature may be raised to 0 ° C. Further, [Step-
210], the temperature of the silicon semiconductor substrate was raised to 850 ° C. by a heating means while introducing an inert gas (for example, nitrogen gas) from the gas introduction unit 17 into the processing chamber 10. The temperature of the silicon semiconductor substrate was raised to 850 ° C. by a heating unit while introducing an inert gas (for example, nitrogen gas) containing 0.1% by volume of hydrogen gas into the processing chamber 10 from the gas introduction unit 17. Is also good. Further, the atmosphere in each of the first oxide film forming step, the temperature raising step, and the second oxide film forming step may include, for example, a hydrogen chloride gas.

In the embodiment, the silicon oxide film is formed exclusively on the surface of the silicon semiconductor substrate. However, the silicon oxide film is formed on the epitaxial silicon layer formed on the substrate based on the oxide film forming method of the present invention. It can be formed, or a silicon oxide film can be formed on the 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. The formation of the oxide film including the nitriding treatment can be performed not only in a single wafer process but also in a batch process in which a plurality of semiconductor layers are simultaneously processed.

Alternatively, in the example, after the surface of the semiconductor layer was washed with a 0.1% aqueous solution of hydrofluoric acid and pure water, the semiconductor layer was carried into the oxide film forming apparatus. The atmosphere before the transfer to the oxide film forming apparatus may be an inert gas (for example, nitrogen gas) atmosphere. Note that such an atmosphere may be, for example, an atmosphere of a semiconductor layer surface cleaning apparatus set to an inert gas atmosphere, and a semiconductor layer (for example, a silicon semiconductor substrate) placed in a transport box filled with an inert gas. As shown in the schematic diagram in FIG. 3, a method for loading the wafer into the oxide film forming apparatus, and a cluster tool apparatus including a surface cleaning apparatus, an oxide film forming apparatus, a transport path, a loader, and an unloader. This can be achieved by a method in which the path to the oxide film forming apparatus is connected by a transfer path, and the atmosphere in the surface cleaning apparatus, the transfer path, and the processing chamber of the oxide film forming apparatus is an inert gas atmosphere.

Alternatively, instead of cleaning the surface of the semiconductor layer with a 0.1% hydrofluoric acid aqueous solution and pure water, a gas phase cleaning method using anhydrous hydrogen fluoride gas under the conditions shown in Table 4 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 vapor phase cleaning method using hydrogen chloride gas under the conditions exemplified in Table 5. 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. If the atmosphere in the transfer path or the like is a vacuum atmosphere, the atmosphere in the processing chamber 10 of the oxide film forming apparatus when the semiconductor layer is carried in is set to, for example, 1.3 × 10 ^-1 Pa.
A vacuum atmosphere of about (10 ⁻³ Torr) may be set, and after the transfer of the semiconductor layer is completed, the atmosphere of the processing chamber 10 may be set to an inert gas (eg, nitrogen gas) atmosphere.

[0065]

[Table 4] Anhydrous hydrogen fluoride gas: 300 SCCM Methanol vapor: 80 SCCM Nitrogen gas: 1000 SCCM Pressure: 0.3 Pa Temperature: 60 ° C

[0066]

[Table 5] 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. As a result, the formed oxide film contains moisture, organic substances, It is possible to effectively prevent Si-OH from being taken in, thereby lowering the characteristics of the formed oxide film or generating a defective portion.

As described above, in forming an oxide film, hydrogen gas and oxygen gas are introduced into the processing chamber 10, and at this time, the hydrogen gas flows into the processing chamber 10 and flows out of the system. For example, in order to prevent a detonation reaction from occurring and prevent a dry oxide film from being formed on the semiconductor layer, for example, [Step-12] of Example 1
0], while introducing an inert gas (for example, nitrogen gas) as a diluting gas at a flow rate of 10 SLM from the gas introducing unit 17 into the processing chamber 10, a flow rate of 0.2 SLM from the gas introducing unit 16 A into the processing chamber 10. Of hydrogen gas,
Then, for example, oxygen gas at a flow rate of 10 SLM may be introduced into the processing chamber 10 from the gas introduction unit 16B. Next, microwave power is supplied to the magnetron 15, and the microwave of 2.45 GHz generated by the magnetron 15 is introduced into the plasma generation region 10A of the processing chamber 10 via the microwave waveguide 14. By such operation,
The hydrogen gas concentration in the processing chamber 10 before the generation of water vapor has a sufficiently low value, so that it is possible to reliably prevent the detonation reaction from occurring, and also to surely prevent the formation of a dry oxide film. .

[0069]

According to the present invention, an oxide film or a gate oxide film can be formed essentially in one oxide film forming apparatus, and one apparatus for forming an oxide film or a gate oxide film is used. And the configuration of the apparatus can be simplified. In addition, it is possible to easily and surely generate water vapor in a state where the oxidation rate is suppressed and controlled, and a thin oxide film can be formed by the humidification oxidation method. 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, since only the surface of the oxide film is nitrided, there is no adverse effect on the characteristics of the semiconductor device such as a reduction in current driving capability. Further, since the oxide film is nitrided, the p-type impurity reaches the semiconductor layer through the gate oxide film by various heat treatments in a semiconductor device manufacturing process after the formation of the gate electrode, for example, so that the threshold voltage of the PMOS semiconductor element is reduced. A phenomenon such as fluctuation can be reliably avoided.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram of an oxide film forming apparatus suitable for carrying out a method of the present invention.

FIG. 2 is a schematic partial cross-sectional view of a silicon semiconductor substrate and the like for describing a method of forming an oxide film of Example 1.

FIG. 3 is a schematic view of a cluster tool device.

[Explanation of symbols]

10 processing chamber, 10A plasma generation area, 1
OB: reaction area, 11: stage, 12:
Heating means, 13: magnet, 14: microwave waveguide, 15: magnetron, 16A, 16B, 16
C, 17: gas introduction section, 18: gas exhaust section, 2
0: silicon semiconductor substrate, 21: element isolation region, 22: oxide film (gate oxide film), 23: gate electrode, 24: sidewall, 25: source / drain region , 26 ... insulating layer, 27 ... wiring

Claims (28)

[Claims] (A) irradiating a hydrogen gas and an oxygen gas with electromagnetic waves to generate water vapor, and using the water vapor to oxidize the surface of the semiconductor layer, thereby forming an oxide film on the surface of the semiconductor layer; And (b) nitriding the surface of the oxide film with excited nitrogen molecules or nitrogen molecule ions generated by irradiating the nitrogen-based gas with electromagnetic waves. . 2. The method according to claim 1, wherein the electromagnetic waves are microwaves. 3. The method according to claim 1, wherein the steps (a) and (b) are performed in the same processing chamber. 4. The method according to claim 1, wherein in the step (a), formation of the oxide film is started while the semiconductor layer is maintained 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. 5. 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 at 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 4, wherein: 6. The method according to claim 5, wherein atoms mainly constituting the semiconductor layer are Si. 7. 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 Si—H bonds on the surface of the semiconductor layer are not broken.
3. The method for forming an oxide film according to item 1. 8. 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 Si—F bonds on the surface of the semiconductor layer are not broken.
3. The method for forming an oxide film according to item 1. 9. The process according to claim 1, wherein 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. 5. The method for forming an oxide film according to 4. 10. The method for forming an oxide film according to claim 1, wherein a heat treatment is applied to the formed oxide film between the steps (a) and (b). 11. The heat treatment atmosphere is an inert gas atmosphere containing a halogen element.
0. The method for forming an oxide film according to item 0. 12. The method for forming an oxide film according to claim 11, wherein the halogen element is chlorine. 13. The oxide film according to claim 12, 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. 14. The method according to claim 10, wherein the heat treatment is performed at a temperature of 700 to 950 ° C. 15. A method comprising the steps of: (A) forming a gate oxide film on the surface of a semiconductor layer; and (B) forming a gate electrode made of a silicon layer containing a p-type impurity on the gate oxide film. A method for manufacturing a semiconductor device, comprising: (a) irradiating a hydrogen gas and an oxygen gas with electromagnetic waves to generate water vapor, and oxidizing the surface of the semiconductor layer using the water vapor; Forming an oxide film on the surface of the semiconductor layer by (b) nitriding the surface of the oxide film with nitrogen molecules or nitrogen molecule ions in an excited state generated by irradiating a nitrogen-based gas with electromagnetic waves; Forming a gate oxide film. 16. The method according to claim 15, wherein the electromagnetic wave is a microwave. 17. The method according to claim 15, wherein the steps (a) and (b) are performed in the same processing chamber. 18. The method according to claim 18, wherein in the step (a), formation of the oxide film is started while the semiconductor layer 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 manufacturing a p-type semiconductor device according to claim 15, wherein 19. 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 according to claim 18, wherein: 20. The method according to claim 19, wherein atoms mainly constituting the semiconductor layer are Si. 21. 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 according to claim 20, wherein the temperature is a temperature at which the bond is not broken. 22. 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 according to claim 20, wherein the temperature is a temperature at which the bond is not broken. 23. The method according to claim 18, wherein in the step (a), the temperature of the semiconductor layer when the formation of the oxide film is completed is higher than the ambient temperature when the formation of the oxide film is started. A manufacturing method of the p-type semiconductor device according to the above. 24. The method according to claim 15, wherein the formed oxide film is subjected to a heat treatment between the steps (a) and (b).
3. The method for manufacturing a p-type semiconductor device according to item 1. 25. The heat treatment atmosphere is an inert gas atmosphere containing a halogen element.
5. The method for manufacturing a p-type semiconductor device according to item 4. 26. The method according to claim 25, wherein the halogen element is chlorine. 27. The p-type semiconductor according to claim 26, wherein chlorine is in the form of hydrogen chloride, and the concentration of hydrogen chloride contained in the inert gas is 0.02 to 10% by volume. Device manufacturing method. 28. The method according to claim 24, wherein the heat treatment is performed at a temperature of 700 to 950 ° C.