JP2000216154A - Forming method of oxide film and manufacture of p-type semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable a thin oxide film to be stably formed and to restrain boron from being diffused from a gate electrode included in a P-type semiconductor device, by a method wherein the surface of a semiconductor layer is oxidized by steam generated by irradiating hydrogen and oxygen with electromagnetic waves, the surface of the oxide film is nitrided by irradiating nitrogen with electromagnetic waves, and the oxide film is thermally treated. SOLUTION: Hydrogen and oxygen are introduced into a processing chamber 10, microwaves generated by a magnetron 15 are introduced into the plasma generating region 10A of the processing chamber 10 to generate steam, and the surface of a silicon semiconductor substrate 20 is oxidized by the water vapor. Thereafter, nitrogen is introduced into the processing chamber 10, microwaves generated by the magnetron 15 are introduced into the plasma generating region 10A of the processing chamber 10, nitrogen molecules and nitrogen molecule ions excited by irradiation with electromagnetic waves are guided to a reaction region 10B, and the oxide film whose surface is nitrided is formed on the surface of a semiconductor layer. Then, nitrogen is continuously introduced into the processing chamber 10, and the silicon semiconductor substrate 20 is thermally treated at a temperature of, for instance, 850 deg.C.

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 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 by gate oxidation. The present invention relates to a method for manufacturing a p-type semiconductor device applied to formation of a film, and more specifically, to a method for manufacturing a p-channel type MOSFET in a CMOSFET having a dual gate structure.

[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 humidifying oxidation method is a method of forming a silicon oxide film on the surface of a silicon semiconductor substrate in a high-temperature oxidizing atmosphere containing water vapor. 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. The CMOSF having such a structure
ET is called a CMOSFET having a dual gate structure. 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. In some cases, the threshold voltage of the PMOS semiconductor element is changed.

[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 increases and a manufacturing time of the semiconductor device is prolonged, or a problem that two types of devices, an oxidation device and a plasma nitriding device, are required.

If the surface of the oxide film is nitrided by nitrogen molecules or nitrogen molecule ions in an excited state, a defect may be generated in the oxide film, and such a defect may need to be recovered or removed by some means. .

Therefore, an object of the present invention is to form a thin oxide film stably by a humidifying oxidation method.
And a method for forming an oxide film having high reliability, which makes it possible to reliably suppress the diffusion of boron atoms from a gate electrode constituting a semiconductor device, and a method for forming such an oxide film. It is another object of the present invention to provide a method for manufacturing a p-type semiconductor device applied to a semiconductor device. Still another object of the present invention is to provide a method for forming an oxide film capable of nitriding only the surface of the oxide film with a single apparatus, and a p-type method in which the method for forming an oxide film is applied to the formation of a gate oxide film. Method of manufacturing semiconductor device, more specifically, p-channel MOSFET in CMOSFET having dual gate structure
It is to provide a manufacturing method of.

[0012]

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) exciting nitrogen molecules, nitrogen molecule ions generated by irradiating a nitrogen-based gas with electromagnetic waves; Nitriding the surface of the oxide film with nitrogen atoms or nitrogen atom ions,
(C) heat-treating the oxide film whose surface has been nitrided.

In order to achieve the above object, a method of manufacturing a p-type semiconductor device according to the present invention comprises the steps of (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. A step of nitriding the surface of the oxide film with nitrogen molecules, nitrogen molecule ions, nitrogen atoms or nitrogen atom ions in a state to form a gate oxide film, and (c) heat treating the gate oxide film. Specially To.

The method of forming an oxide film according to the present invention or p.
In the method for manufacturing a semiconductor device, "nitriding the surface of an oxide film with nitrogen molecules, nitrogen molecule ions, nitrogen atoms or nitrogen atom ions" means at least nitrogen atoms, nitrogen molecule ions, nitrogen atoms or nitrogen atom ions. It means that the surface of the oxide film is nitrided by any of them.
That is, more specifically, the surface of the oxide film is nitrided by one, two, three, or four of nitrogen molecule, nitrogen molecule ion, nitrogen atom, and nitrogen atom ion. Means to do.

In the method for manufacturing a p-type semiconductor device according to the present invention,
A silicon layer containing a p-type impurity (eg, polysilicon
Gate electrode consisting of a silicon layer and an amorphous silicon layer).
As a formation method, for example, a p-type impurity (for example, boro
After forming a silicon layer containing
The method of patterning such a silicon layer,
P-type impurities after forming a silicon layer by CVD
Object (for example, boron or BF _Two) By ion implantation
The silicon layer and then pattern the silicon layer
Method, a silicon layer containing no impurities is formed by the CVD method.
Patterning, and then p-type impurities (eg,
If boron or BF_Two) Is injected into the silicon layer by ion implantation.
Can be mentioned. In step (B),
After forming a silicon layer containing a p-type impurity,
Form a silicide layer on the silicon layer, and then
By patterning the
To form a gate electrode having a polycide structure.
No. Alternatively, in the step (B), a p-type impurity is contained.
After forming a silicon layer, a tongue is
A refractory metal material layer such as stainless steel is formed. In addition, silicon
Reaction to prevent the reaction between the layer and the refractory metal layer
As a barrier film, a refractory metal nitride (eg,
(WN), and a refractory metal material layer is formed thereon.
Preferably. Next, the refractory metal material layer and the silicon
Has a two-layer structure by patterning the con-layer
May be formed.

In the method of forming an oxide film or the method of manufacturing a p-type semiconductor device according to 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. Examples of the nitrogen-based gas to be irradiated with an electromagnetic wave include a gas that is a compound of a nitrogen atom and an oxygen atom, such as NO, N ₂ O, and NO ₂ , in addition to nitrogen gas (N ₂ gas). .

In the method of the present invention, the steps (a) and (b) may be performed in the same processing chamber, or alternatively, the steps (a), (b) and (c) may be performed in the same processing chamber. It is preferable to perform the treatment indoors from the viewpoint of simplifying the structure of the device or reducing the time required for forming an oxide film or a gate oxide film.

In the present invention, it is desirable that the atmosphere for the heat treatment be an inert gas atmosphere. Examples of the inert gas in the heat treatment include a nitrogen gas, an argon gas, and a helium gas. The heat treatment temperature is 700
~ 1200 ° C, preferably 700-1000 ° C, more preferably 700-950 ° C. Further, 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 40 minutes, more preferably 20 to 30 when performing the batch processing. Minutes. It is desirable that the temperature of the atmosphere during the heat treatment be higher than the temperature when the nitriding of the oxide film is completed. When the step (b) and the step (c) are performed in the same processing chamber, after the completion of the step (b), the atmosphere in the processing chamber is switched to an inert gas atmosphere, and the temperature is raised to an ambient temperature for performing heat treatment. Is preferred.

The atmosphere for the heat treatment may be an inert gas atmosphere containing a halogen element. Also in this case, examples of the inert gas in the heat treatment include a nitrogen gas, an argon gas, and a helium gas. In addition, examples of the halogen element include chlorine, bromine, and fluorine, and among them, chlorine is preferable. As the form of the halogen element contained in the inert gas, for example, hydrogen chloride (HCl), CCl ₄ , C ₂ HCl ₃ , C ₂
l _2, HBr, mention may be made of the NF _3. The content of the halogen element in the inert gas 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 inert gas is preferably 0.02 to 10% by volume.

Normally, before a silicon oxide film is formed on the surface of a silicon semiconductor substrate, the substrate is washed with an NH ₄ OH / H ₂ O ₂ aqueous solution, and further washed 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 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 present invention includes a step of cleaning the surface of the semiconductor layer before forming the oxide film, and without exposing the semiconductor layer after the surface cleaning to the atmosphere ( That is, for example,
The atmosphere from the cleaning of the semiconductor layer surface to the start of the oxide film formation step is an inert gas atmosphere or a vacuum atmosphere), and the oxide film is preferably formed. by this,
For example, when a silicon semiconductor substrate is used as a semiconductor layer, a silicon oxide film can be formed and formed on a surface of a silicon semiconductor substrate having a surface which is mostly terminated with hydrogen and a portion of which is extremely terminated with fluorine. It is possible to prevent the characteristics of the silicon oxide film from deteriorating or the occurrence of defective portions.

In the formation of the oxide film, hydrogen gas and oxygen gas are introduced into the processing chamber. At this time, it is required that the hydrogen gas flows into the processing chamber and flows out of the system to cause 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 formed on the semiconductor substrate, and further, a silicon semiconductor substrate or any of these layers Means a base on which an oxide film is to be formed, such as a substrate on which a semiconductor element is 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.
In addition, the silicon single crystal wafer is used for CZ method, MCZ method, DL
The wafer may be manufactured by any method such as the CZ method and the FZ method, or may be one to which hydrogen annealing has been applied 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 oxygen plasma generated by the microwave discharge, the ground state O ₂ (X ³ Σg ⁻ ) is excited by electrons and the excited state is 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.

O ₂ (X ³ Σg ⁻ ) + e → O ₂ (A ³ Σu ⁺ ) + 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 Formula (1-4)

Accordingly, 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 by microwave discharge.

H ₂ + e → 2H Formula (2)

Then, of 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.

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 nitrogen molecules, nitrogen molecule ions, nitrogen atoms, and nitrogen atom ions excited by the inelastic collision of the electrons with the nitrogen molecules are generated. These excited nitrogen molecules, nitrogen molecule ions, nitrogen atoms, and nitrogen atom ions form bonds between atoms mainly constituting the semiconductor layer on the surface of the oxide film and oxygen atoms (for example, atoms mainly constituting the semiconductor layer are In the case of Si, a Si—O 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.

N ₂ (X ¹ Σg) + e → N ₂ (A ³ Σu ⁺ ) + e Equation (4-1) N ₂ (N ¹ Σg) + e → N ₂ (C ³ Πu) + e Equation ( 4-2) N ₂ (C ³ Πu) + e → N ₂ (B ³ Πg) + hv Equation (4-3) N ₂ (B ³ Πg) + e → N ₂ (A ³ Σu ⁺ ) + hv Equation (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 an electromagnetic wave. 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.

In addition, after nitriding the surface of the oxide film, the oxide film or the gate oxide film whose surface has been nitrided is subjected to a heat treatment, so that the oxide film is excited by nitrogen molecules, nitrogen molecule ions, nitrogen atoms, and nitrogen atom ions in an excited state. It is possible to recover or remove defects in the oxide film generated when the surface is nitrided. If the steps (a), (b) and (c) are performed in the same processing chamber, the structure of an apparatus for forming an oxide film or a gate oxide film can be further simplified.

[0036]

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 the semiconductor layer, and nitrogen (N ₂ ) gas was used as the nitrogen-based gas. Further, the oxidation step, the nitridation step, and the heat treatment step were performed in the same processing chamber. Hereinafter, a method for forming an oxide film according to the present invention using the oxide film forming apparatus shown in FIG. 1 and a p-type semiconductor device (specifically, a p-channel type MOSF in a CMOSFET having a dual gate structure)
Hereinafter, the method of manufacturing ET) will be described with reference to FIG. 2 which is a schematic partial cross-sectional view of the silicon semiconductor substrate 20 and the like.

[Step-100] First, a silicon semiconductor substrate 20 which is a boron-doped P-type silicon wafer having a diameter of 8 inches (made by the CZ method) is placed on a silicon semiconductor substrate 20 by a known method.
An element isolation region 21 having an OCOS 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. Exposing the surface (Fig. 2
(A)).

[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 800 ° C. by the heating means 12. After that, while introducing an inert gas (for example, nitrogen gas) as a diluting gas from the gas introduction unit 17 into the processing chamber 10, the gas introduction unit 16.
Hydrogen gas and oxygen gas are introduced into the processing chamber 10 from A and the gas introduction unit 16B. 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 introduced into the plasma generation region 10 </ b> A of the processing chamber 10 via the microwave waveguide 14. By this, that is, by irradiating the hydrogen gas and the oxygen gas with electromagnetic waves, the above-mentioned formulas (1-1) to (1)
-4) and the reactions of formulas (2) and (3) occur.
Water vapor is generated. The generated steam reaches the reaction region 10B located below the processing chamber 10, and the surface of the semiconductor layer (specifically, the silicon semiconductor substrate 20) heated by the heating unit 12 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 below shows the conditions for forming the oxide film.
An example is shown below.

[Table 1] Microwave power: 10 kW Microwave frequency: 2.45 GHz Oxygen gas flow rate: 10 SLM Hydrogen gas flow rate: 0.2 SLM Substrate temperature: 800 ° C.

[Step-120] 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 the hydrogen gas and the oxygen gas into the processing chamber 10 is stopped, and the silicon semiconductor substrate 20 is cooled to room temperature while the inert gas is introduced into the processing chamber 10 from the gas introduction unit 17. Next, the introduction of the inert gas from the gas introduction unit 17 into the processing chamber 10 is stopped. After that, the processing chamber 10
Then, nitrogen gas, which is a nitrogen-based gas, is introduced. 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 introduced into the plasma generation region 10 </ b> A of the processing chamber 10 via the microwave waveguide 14. Thus, that is, by irradiating the nitrogen gas with an electromagnetic wave, the above-described formulas (4-1) to (4-1) are applied.
Excited nitrogen molecules, nitrogen molecular ions, and the like generated in the reaction of (4-4) reach the reaction region 10B located below the processing chamber 10 and are oxidized (specifically, silicon oxide).
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.
Here, illustration of a nitrided portion of the oxide film is omitted in the figure. The nitriding conditions are shown in Table 2 below. still,
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 during the nitriding treatment.

[Table 2] 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-130] After the completion of the nitriding treatment, the supply of the microwave power to the magnetron 15 is stopped, and while the introduction of the nitrogen gas into the processing chamber 10 is continued, the silicon semiconductor substrate 20 is heated to 850 ° C. Raise the temperature. Then, after performing the heat treatment under the conditions exemplified in Table 3 below, the processing chamber 10
The silicon semiconductor substrate 20 is cooled to room temperature while continuously introducing nitrogen gas into the silicon semiconductor substrate 20.

[Table 3] Nitrogen gas flow rate: 4 SLM Substrate temperature: 850 ° C

[Step-140] Thereafter, the semiconductor layer is unloaded from the oxide film forming apparatus, and then the semiconductor layer (specifically, the silicon semiconductor substrate 20) is loaded into a known CVD apparatus. Then, a silicon layer containing no impurity (a polysilicon layer in the first embodiment) is formed on the entire surface by the CVD method. Next, based on a known lithography technique and ion implantation technique, boron is introduced into a gate electrode for a p-channel MOSFET and phosphorus is introduced into a gate electrode for an n-channel MOSFET, and then the silicon layer is patterned. As a result, a gate electrode 23 made of a silicon layer (specifically, a polysilicon layer) containing a p-type impurity for a p-channel MOSFET can be formed on the gate insulating film (FIG. 2C).
reference). At the same time, an n-channel type MO is formed on the gate insulating film.
The gate electrode 23 made of a silicon layer (specifically, a polysilicon layer) containing an n-type impurity for the SFET can be formed.

[Step-150] Thereafter, an LDD region is formed using a known technique, an insulating film is formed on the entire surface, and the insulating film is etched based on an anisotropic dry etching technique to form a gate electrode. Side wall 2 on the side wall of 23
4 is formed. Next, in order to form the source / drain regions 25, boron is applied to the region of the silicon semiconductor substrate where the p-channel MOSFET is to be formed, based on the known lithography technique and ion implantation technique, and n-channel M
After phosphorus is introduced into the region of the silicon semiconductor substrate where the OSFET is to be formed, heat treatment for activating the implanted impurities is performed. Thereafter, an insulating layer 26 is formed on the entire surface by CV.
An opening is formed in the insulating layer 26 above the source / drain region 25 by a method D, and a wiring material layer is formed on the insulating layer 26 including the inside of the opening by a sputtering method. The wiring 27 is formed by patterning, and a p-type semiconductor element (more specifically, a p-channel MOSFET in a CMOSFET having a dual gate structure) whose schematic partial cross-sectional view is shown in FIG. Obtainable.

After [Step-120] is completed, the semiconductor layer may be carried out of the oxide film forming apparatus, and then may be carried into a heat treatment apparatus shown in a schematic view in FIG. 3 for heat treatment. . The batch type heat treatment apparatus of the vertical type includes a processing chamber 30 having a double tube structure made of quartz and held vertically.
Gas introduction unit 3 for introducing an inert gas into the processing chamber 30
2 and a gas exhaust unit 33 for exhausting gas from the processing chamber 30
And a heater 34 for maintaining the inside of the processing chamber 30 at a predetermined ambient temperature via a cylindrical heat equalizing tube 36 made of SiC.
, Substrate loading / unloading section 40, processing chamber 30 and substrate loading / unloading section 4
The shutter comprises a shutter 35 for partitioning the silicon semiconductor substrate from the inside of the processing chamber 30, and an elevator mechanism 41 for carrying the silicon semiconductor substrate into and out of the processing chamber 30. A quartz boat 42 for mounting a silicon semiconductor substrate is attached to the elevator mechanism 41. In addition, the inert gas is supplied to the pipe 31 and the gas passage 3.
The gas is introduced into the processing chamber 30 through the gas inlet 1 and the gas inlet 32. The gas flow path 31 corresponds to a space between an inner wall and an outer wall of the processing chamber 30 having a double pipe structure.

When performing the heat treatment, the plurality of silicon semiconductor substrates 20 are loaded into the substrate loading / unloading section 40 and placed on the quartz boat 42, and then the elevator mechanism 41 is operated to move the quartz boat 42 into the processing chamber. After being carried into the shutter 30, the shutter 35 is closed. And, the pipe 31, the gas flow path 31
The heater 34 is operated while the inert gas is being introduced into the processing chamber 30 through the gas introduction unit 32 to raise the temperature of the processing chamber 30 to a desired temperature, thereby performing heat treatment. After the completion of the heat treatment, the operation of the heater 34 is stopped, the temperature in the processing chamber 30 is lowered to room temperature, the shutter 35 is opened, and the elevator mechanism 41 is opened.
Is operated to carry out the quartz boat 42 into the processing chamber 30,
Furthermore, the silicon semiconductor substrate may be unloaded from the quartz boat 42 and [Step-140] and subsequent steps may be executed.

Embodiment 2 Embodiment 2 is a modification of the method of forming an oxide film and the method of manufacturing a p-type semiconductor device (specifically, a p-channel MOSFET in a CMOSFET having a dual gate structure) of Embodiment 1. It is. Example 2
The difference from Example 1 is that the semiconductor layer surface is cleaned before the oxide film is formed, and then the semiconductor layer is not exposed to the atmosphere (that is, for example, the cleaning of the semiconductor layer surface and the start of the oxide film forming step). The atmosphere up to the above is an inert gas atmosphere or a vacuum atmosphere), and an oxide film is formed.

That is, after cleaning the surface of the semiconductor layer with a 0.1% aqueous solution of hydrofluoric acid and pure water in Example 1, the semiconductor layer was carried into an oxide film forming apparatus. On the other hand, in the second embodiment, the atmosphere from the surface cleaning of the semiconductor layer to the transfer to the oxide film forming apparatus is an inert gas (for example, nitrogen gas) atmosphere. To this end, as shown in the schematic diagram of FIG. 4, a surface cleaning device, an oxide film forming device, a transport path, a cluster tool device including a loader and an unloader are used, and the process from the surface cleaning device to the oxide film forming device is performed. This can be achieved by a method in which the atmosphere in the processing chamber of the surface cleaning apparatus, the transport path, and the oxide film forming apparatus is set to an inert gas atmosphere. The atmosphere in the surface cleaning apparatus and the atmosphere in the transfer path before starting the surface cleaning of the semiconductor layer or after the surface cleaning is completed may be an inert gas atmosphere, for example, 1.3 × 10 ⁻¹ Pa (10 ^-3 To
It may be a vacuum atmosphere of about rr). When 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 (10 ^-3 Torr). The atmosphere in the processing chamber 10 may be an inert gas (eg, nitrogen gas) atmosphere after the loading of the semiconductor layer is completed.
Alternatively, such an atmosphere is, for example, an atmosphere of an apparatus for cleaning a surface of a semiconductor layer being an inert gas atmosphere, and
This can also be achieved by a method in which a semiconductor layer (for example, a silicon semiconductor substrate) is placed in a transport box filled with an inert gas and is loaded into an oxide film forming apparatus.

In Example 2, instead of cleaning the surface of the semiconductor layer with a 0.1% hydrofluoric acid aqueous solution and pure water, an anhydrous hydrogen fluoride gas was used under the conditions shown in Table 3. The surface of the semiconductor layer was cleaned by a phase cleaning method. Note that methanol is added to prevent generation of particles. In some cases, under the conditions exemplified in Table 4,
The surface of the semiconductor layer may be cleaned by a gas phase cleaning method using hydrogen chloride gas.

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

[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. 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. Further, by using the cluster tool device, the device installation area can be reduced.

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.

In the embodiments, 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 the 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 the 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, two processing chambers 10 may be prepared, an oxide film may be formed on the surface of the semiconductor layer in one processing chamber 10, the surface of the oxide film may be nitrided in the other processing chamber 10, and heat treatment may be performed. .

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. .

[0059]

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. In addition, since the heat treatment is performed after the nitriding treatment, defects of the oxide film caused by the nitriding treatment can be recovered or removed, and a highly reliable oxide film or gate oxide film can be obtained.

[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 diagram of a heat treatment apparatus.

FIG. 4 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

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01L 21/336 H01L 29/80 W 29/80 F term (Reference) 5F040 DA00 DA06 DB03 DC01 EB12 EC07 ED01 ED05 EF02 EH05 EK01 EK05 FC00 FC05 5F058 BA20 BD01 BD04 BD10 BF55 BF63 BF72 BF74 BH01 BH04 BJ01 BJ10 5F110 AA08 AA14 AA16 BB04 CC02 EE09 EE28 EE32 FF02 FF04 FF09 FF31 FF36 GG02 GG12 GG12 GG12 GG36

Claims (10)

[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; (B) nitriding the surface of the oxide film with excited nitrogen molecules, nitrogen molecule ions, nitrogen atoms or nitrogen atom ions generated by irradiating a nitrogen-based gas with electromagnetic waves; Heat treating the nitrided oxide film. 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 the steps (a), (b) and (c) are performed in the same processing chamber. 5. The method according to claim 1, wherein the heat treatment is performed at a temperature of 700 to 950 ° C. 6. A method comprising: (A) forming a gate oxide film on a 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) irradiating the nitrogen-based gas with an electromagnetic wave to produce an excited state of nitrogen molecules, nitrogen molecule ions, nitrogen atoms, or nitrogen atom ions. Nitriding the surface,
A method for manufacturing a p-type semiconductor device, comprising: forming a gate oxide film; and (c) heat-treating the gate oxide film. 7. The method according to claim 6, wherein the electromagnetic wave is a microwave. 8. The method according to claim 6, wherein the steps (a) and (b) are performed in the same processing chamber. 9. The method according to claim 6, wherein the steps (a), (b) and (c) are performed in the same processing chamber. 10. The method according to claim 6, wherein the heat treatment is performed at a temperature of 700 to 950 ° C.