JP2000332005A - Plasma nitriding apparatus, formation of insulating film, and manufacture of p-type semiconductor element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a plasma nitriding apparatus capable of controlling plasma density and controlling the energy of reactant kinds entering a semiconductor substrate independently, and capable of introducing nitrogen having a concentration as high as possible only into the surface of an insulating film. SOLUTION: A plasma nitriding apparatus for nitriding the surface of an oxide film comprises (A) a plasma-forming region 10A for forming nitrogen molecules or nitrogen molecule ions in excited states by having the nitrogen- family gas irradiated with electromagnetic waves and (B) a treatment chamber 10 having a plasma nitriding region 10B. A first electrode 20, to which a potential equal to or negative than the potential of the plasma forming region 10A, is applied and a second electrode 21 to which a potential positive than the potential of the first electrode 20 is applied, from the plasma forming region 10A side, are provided in the plasma nitriding region 10B.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a plasma nitriding apparatus, a method for forming an insulating film and a method for manufacturing a p-type semiconductor device using the plasma nitriding apparatus, and more particularly, to a method for manufacturing a p-type semiconductor device.
The present invention relates to a method for forming an insulating film having a nitrided surface and a method for manufacturing a p-type semiconductor device in which the method for forming an insulating film is applied to forming a gate insulating film.

[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 2 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. 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. , 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]

In order to suppress the fluctuation of the threshold voltage of the PMOS semiconductor device caused by the diffusion of boron atoms into the silicon semiconductor substrate, a method for 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 of generating nitrogen plasma by performing discharge in a nitrogen gas atmosphere is described in the literature "Ultrathin nitrogen".
-profile engineered gate dielectric filmes ", SV
Known from Hattangady, et al., 1996, 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, it is not possible to independently control the plasma density and the energy of the reactive species entering the semiconductor substrate. Therefore, control of the nitrogen concentration in the insulating film and control of the nitrogen concentration profile cannot be performed simultaneously,
It is difficult to introduce as high a concentration of nitrogen as possible into only the surface of the insulating film.

Accordingly, an object of the present invention is to make it possible to independently control the plasma density and the energy of the reactive species entering the semiconductor layer on the surface of the substrate, so that the surface of the semiconductor layer has a concentration as high as possible. It is an object of the present invention to provide a plasma nitriding apparatus capable of introducing nitrogen, a method for forming an insulating film using the plasma nitriding apparatus, and a method for manufacturing a p-type semiconductor device.

[0009]

In order to achieve the above object, the plasma nitriding apparatus of the present invention comprises: (A) irradiating a nitrogen-based gas with an electromagnetic wave to thereby produce excited nitrogen molecules, nitrogen molecule ions, A plasma nitriding apparatus for nitriding the surface of an oxide film, comprising: a processing chamber having a plasma generation region for generating nitrogen atoms or nitrogen atom ions; and (B) a plasma nitriding region. In the region, a first electrode to which a potential equal to or higher than the plasma generation region is applied and a second electrode to which a more positive potential is applied than the first electrode are applied from the plasma generation region side. , Are provided.

In order to achieve the above object, the method of forming an insulating film according to the present invention comprises the steps of: (A) irradiating a nitrogen-based gas with an electromagnetic wave to produce nitrogen molecules in an excited state;
A processing chamber having a plasma generation region for generating nitrogen atoms or nitrogen atom ions, and (B) a plasma nitridation treatment region is provided. A first electrode to which a negative potential is applied more than the plasma generation region;
And a second electrode to which a more positive potential is applied than the first electrode,
(A) using a plasma nitriding apparatus equipped with
A step of forming an oxide film by oxidizing a semiconductor layer on the surface of the substrate, and (b) placing the substrate in a plasma nitridation region of a plasma nitridation apparatus, and generating excited state nitrogen molecules and nitrogen generated in a plasma generation region. Performing a nitriding treatment on the surface of the oxide film using molecular ions, nitrogen atoms or nitrogen atom ions.

In order to achieve the above object, a method for manufacturing a p-type semiconductor device according to the present invention comprises the steps of (a) forming a gate insulating film on the surface of a semiconductor layer; and (b) forming p-type semiconductor on the gate insulating film. Forming a gate electrode made of a silicon layer containing a p-type impurity, the method comprising the steps of:
The step (a) includes (a) a step of forming an oxide film by oxidizing a semiconductor layer on the substrate surface, and (b) (A) irradiating a nitrogen-based gas with an electromagnetic wave to produce excited nitrogen molecules. A processing chamber having a plasma generation region for generating nitrogen molecular ions, nitrogen atoms or nitrogen atom ions, and (B) a plasma nitriding region is provided. Using a plasma nitriding apparatus provided with a first electrode to which an equal potential or a more negative potential than the plasma generation region is applied, and a second electrode to which a more positive potential than the first electrode is applied. The substrate is placed in the plasma nitridation region of the plasma nitridation apparatus, and the excited state of nitrogen molecules, nitrogen molecule ions, nitrogen atoms or nitrogen atoms generated in the plasma generation region. Using down, characterized in that it comprises the step, performing a nitriding treatment on the surface of the oxide film.

According to the plasma nitriding apparatus, the method for forming an insulating film, or the method for manufacturing a p-type semiconductor device of the present invention,
In some cases, these may be collectively referred to as the present invention. By applying a negative potential to the first electrode from the plasma generation region, plasma (specifically, nitrogen molecules, nitrogen By drawing molecular ions, nitrogen atoms, or nitrogen atom ions into the plasma nitriding region and applying a positive potential to the second electrode more than the first electrode, the plasma (specifically, the plasma) drawn from the plasma generation region , Nitrogen molecule, nitrogen molecule ion, nitrogen atom or nitrogen atom ion). Since the potential of the first electrode and the second electrode depends on the plasma nitriding apparatus, plasma generation conditions, and the like, the insulating film is formed under various conditions. The potential to be applied to the first electrode and the second electrode may be determined based on the nitrogen concentration and the nitrogen concentration profile. As the electromagnetic wave, a microwave of 1 GHz to 100 GHz, for example, a microwave of a frequency of 2.45 GHz can be used.

In the method of forming an insulating film or the method of manufacturing a p-type semiconductor device according to the present invention, dry oxygen gas and water vapor are mentioned as oxidizing species for oxidizing the semiconductor layer on the substrate surface in the step (a). be able to. As a method for generating water vapor, a method of burning oxygen gas and hydrogen gas (pyrogenic method), a method of heating pure water, a method of bubbling heated pure water with an oxygen gas or an inert gas, a catalyst (for example, NiO Ni-based catalyst and the like, Pt-based catalyst ₂ such as Pt or PtO, Pd and Pd-based catalyst such as PdO, Ir-based catalyst, Ru and Ru-based catalyst RuO _2, etc., Ag-based catalyst such as Ag or Ag ₂ O, Au-based catalyst, Cu
Cu based catalyst such as O, Mn based catalyst such as MnO ₂ , Co ₃ O ₄
And the like, a method of reacting a hydrogen gas and an oxidizing gas based on a catalytic action using a Co-based catalyst such as
A method of irradiating a hydrogen gas and an oxygen gas with an electromagnetic wave of 1 GHz to 100 GHz (for example, a microwave having a frequency of 2.45 GHz) (hereinafter, referred to as a plasma oxidation method for convenience);
That is, after the substrate is carried into the plasma nitriding region of the plasma nitriding device, water vapor is generated in the plasma generation region by irradiating the hydrogen gas and the oxygen gas with electromagnetic waves, and the semiconductor layer on the substrate surface is formed using the water vapor. It is desirable to adopt a method of oxidizing the acid. By employing such a plasma oxidation method, it is possible to form an oxide film on the semiconductor layer on the substrate surface and to nitride the surface of the oxide film with one device, thereby simplifying the device configuration. And it is preferable in terms of shortening the time for forming the insulating film and the gate insulating film. When the plasma oxidation method is used, 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 these inert gases are used. May be used as a carrier gas to form an oxide film on the surface of the semiconductor layer. Note that an oxide film can also be formed by a method using these methods for generating steam in combination. A method for forming an oxide film on the surface of the semiconductor layer based on the method for generating water vapor may be collectively referred to as a humidification oxidation method.

In the step (b) of the method of manufacturing a p-type semiconductor device according to the present invention, as a method of forming a gate electrode made of a silicon layer containing a p-type impurity (for example, a polysilicon layer or an amorphous silicon layer), for example, Forming a silicon layer containing a p-type impurity (for example, boron) based on the CVD method, and then patterning the silicon layer. Forming a silicon layer containing no impurity by the CVD method, and then forming a p-type impurity (for example, boron or BF) ₂ ) is implanted into the silicon layer by an ion implantation method, and then the silicon layer is patterned.
After being formed by the VD method, patterning is performed.
A method of implanting a p-type impurity (for example, boron or BF ₂ ) into a silicon layer by an ion implantation method can be given.
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. After forming a silicon layer containing a p-type impurity, a refractory metal layer such as tungsten is formed on the silicon layer, and then the refractory metal layer and the silicon layer are patterned. Alternatively, a gate electrode having a polymetal structure may be formed.

In the present invention, as a nitrogen-based gas to be irradiated with electromagnetic waves, in addition to nitrogen gas (N ₂ gas), NO, N
Gases that are compounds of a nitrogen atom and an oxygen atom, such as ₂ O and NO ₂ , can be exemplified. That is, the nitrogen-based gas is replaced with N ₂ ,
At least one gas selected from the group consisting of NO, N ₂ O and NO ₂ can be used. Nitrogen gas is
A mixture of at least two of these gases may be used.

In the method of the present invention, after the nitriding treatment is performed on the surface of the oxide film in the step (b), a heat treatment is performed on the obtained insulating film so as to reduce the damage caused on the insulating film. Is preferred. The heat treatment is desirably performed in an atmosphere of an inert gas such as nitrogen gas.
00 ° C to 1200 ° C, and the heat treatment time may be 10 seconds to 1 hour.

When a MOS type semiconductor device is manufactured on the basis of a silicon semiconductor substrate, conventionally, before forming a gate insulating film, it is washed with an aqueous solution of NH ₄ OH / H ₂ O ₂ and further added 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, an insulating film is formed on the surface of the silicon semiconductor substrate.

By the way, 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 may become rough (unevenness). Such a phenomenon occurs because 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 pure water increases hydrogen or fluorine. It is thought to be lost due to thermal desorption and caused by an etching phenomenon occurring 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 an argon gas, severe irregularities may occur on the surface of the silicon semiconductor substrate.
It is described in page 21 of "Ultra Clean ULSI Technology" by Tadahiro Omi, published by Baifukan.

In the step (a), formation of an oxide film on the surface of the semiconductor layer is started while maintaining the semiconductor layer at a temperature at which atoms mainly constituting the semiconductor layer do not desorb from the surface of the semiconductor layer. Thus, it is possible to avoid such a phenomenon that the surface of the semiconductor layer is roughened (irregular). 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 bonded one by one to two bonds of silicon atoms. It has a -H termination structure. However, a portion where the surface state of the silicon semiconductor substrate is broken (for example, a step formation portion) has a terminal structure in which a hydrogen atom is bonded to only one bond of a silicon atom, or a three-bonded silicon atom. There is a terminal structure in which a hydrogen atom is bonded to each of the hands. Usually, the remaining bonds of silicon atoms are bonded to silicon atoms inside the crystal. The expression “Si—H bond” in this specification refers to a terminal structure in which a hydrogen atom is bonded to each of two silicon atoms, and a hydrogen atom is bonded to only one silicon atom. The terminating structure in a state in which a hydrogen atom is bonded to each of the three bonding atoms of a silicon atom, or the terminating structure in a state where a hydrogen atom is bonded to each of three bonding hands of a silicon atom is included. The temperature at which the formation of an oxide film on the surface of the semiconductor layer starts is
More specifically, the temperature is higher than the temperature at which water vapor does not condense on the semiconductor layer, preferably 200 ° C. or higher, more preferably 30 ° C.
It is desirable that the temperature be 0 ° C. or more from the viewpoint of throughput.

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. In this case, the temperature of the semiconductor layer when the formation of the oxide film is completed is
600 to 1200 ° C, preferably 700 to 100
It is desirable that the temperature is 0 ° C, more preferably 750 to 900 ° C, but 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. The upper limit of the semiconductor layer holding temperature range in the first oxide film forming step may be 500 ° C., preferably 450 ° C., 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 the silicon semiconductor substrate currently used in the manufacture of semiconductor devices is almost (100), and no matter how the surface of the silicon semiconductor substrate is smoothed, the surface of the silicon semiconductor substrate must be (100). A step called a step is formed. This step is usually for one layer of silicon atoms,
In some cases, a step of 2 to 3 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, eliminating these defects is effective for the initial 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 (HCl), C
Cl ₄ , C ₂ HCl ₃ , Cl ₂ , HBr and 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 0.001% by volume, based on the form of the molecule or the compound.
5 to 10% by volume, more preferably 0.02 to 10% by volume
It is. For example, when hydrogen chloride gas is used, the content of hydrogen chloride gas in an inert gas or a gas containing water vapor is preferably 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, a halogen element may be contained in an oxidizing atmosphere containing water vapor during formation of the oxide film. 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, the formed oxide film may be subjected to a heat treatment between the steps (a) and (b). .

In this case, it is desirable that the atmosphere of the heat treatment be an inert gas atmosphere containing a halogen element. By performing heat treatment on the oxide film in an atmosphere of an inert gas containing a halogen element, an oxide film having excellent time-zero dielectric breakdown (TZDB) characteristics and temporal dielectric breakdown (TDDB) characteristics can be obtained. Examples of the inert gas in the heat treatment include a nitrogen gas, an argon gas, and a helium gas. In addition, examples of the halogen element include chlorine, bromine, and fluorine, and among them, chlorine is preferable. Examples of the form of the halogen element contained in the inert gas include hydrogen chloride (HCl), CCl ₄ , C ₂ HCl ₃ , Cl ₂ , HBr, and N.
F ₃ can be mentioned. The content of the halogen element in the inert gas is based on the form of the molecule or compound,
0.001 to 10% by volume, preferably 0.005 to 10%
%, More preferably 0.02 to 10% by volume.
For example, when using hydrogen chloride gas, the content of hydrogen chloride gas in the inert gas is preferably 0.02 to 10% by volume.

It is preferable that the heat treatment be performed in the same processing chamber. The temperature of the heat treatment is 700-1200 ° C.
Preferably 700-1000 ° C., more preferably 70
0 to 950 ° C. Further, the time of the heat treatment is preferably set to 1 to 10 minutes when performing the single-wafer treatment,
When performed in a batch system, 5 to 60 minutes, preferably 10 to
It is desirable to set it to 40 minutes, more preferably 20 to 30 minutes.

In the case of performing the heat treatment, it is preferable that the temperature of the atmosphere when the heat treatment is performed on the formed oxide film is higher than the temperature when the formation of the oxide film is completed. In this case, after the formation of the oxide film is completed, the atmosphere in the processing chamber is switched to an inert gas atmosphere, and then the temperature may be increased to an ambient temperature for performing heat treatment, or the atmosphere may include a halogen element. After switching to the inert gas atmosphere, the temperature may be raised to the ambient temperature for performing the heat treatment. Here, examples of the inert gas include a nitrogen gas, an argon gas, and a helium gas. Examples of the halogen element include chlorine, bromine, and fluorine, and among them, chlorine is preferable. Examples of the form of the halogen element contained in the inert gas include hydrogen chloride (HCl), CCl ₄ , C ₂ HCl ₃ , Cl ₂ , and HB.
r and NF ₃ . The content of the halogen element in the inert gas is 0.001 to 10% by volume, preferably 0.005 to 10% by volume, based on the form of the molecule or 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 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 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. Accordingly, for example, when a silicon semiconductor substrate is used as a semiconductor layer, an oxide film can be formed on the surface of a silicon semiconductor substrate having a surface which is mostly terminated with hydrogen and a part of which is terminated with fluorine, and formed. It is possible to prevent the characteristics of the oxide film from deteriorating or the occurrence of defective portions.

When the plasma oxidation method is employed for forming the oxide film, for example, hydrogen gas and oxygen gas are introduced into the processing chamber. At this time, hydrogen gas flows into the processing chamber,
It is desirable to introduce oxygen gas before introducing hydrogen gas into the processing chamber in order to prevent a detonation reaction from occurring by flowing out of the system. 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,
The properties are inferior to those of the oxide film formed by the humidifying 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 of (18.3% by volume with air)
% By volume), preferably below the combustion range in air (less than 4.0% by volume when expressed in terms of volume% with air) or below the detonation range in oxygen (% by volume with oxygen) , 15.0% by volume or less, preferably below the combustion range in oxygen (4.5% by volume with oxygen).
(% 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 insulating film is to be formed. When a silicon semiconductor substrate is used as the semiconductor layer, the substrate is the silicon semiconductor substrate itself. Forming an insulating film on a semiconductor layer includes not only forming an insulating film on a semiconductor layer formed on or above a semiconductor substrate or the like, but also forming an insulating film on the surface of a semiconductor substrate. Incidentally, the silicon single crystal wafer may be a wafer produced by any method such as a CZ method, an MCZ method, a DLCZ method, an FZ method, or a wafer to which hydrogen annealing has been added in advance. Further, the semiconductor layer may be made of Si-Ge.

The method of forming an insulating film according to the present invention is, for example, an MO method.
For example, formation of a gate insulating film, an interlayer insulating film and an element isolation region of an S-type transistor, formation of a gate insulating film of a top gate or bottom gate thin film transistor, formation of a tunnel insulating film of a flash memory, etc. Can be applied to forming.

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.

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

When the plasma oxidation method is employed, in the oxygen plasma generated by 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 (A ³ Σu ⁺ ). It is excited by O ₂ (B ³ Σu ⁻ ) and dissociates into oxygen atoms as shown in the following formulas.

O ₂ (X ³ Σg ⁻ ) + e → O ₂ (A ³ Σu ⁺ ) + e Formula (2-1) O ₂ (A ³ Σu ⁺ ) + e → O ( ³ P) + O ( ³ P) ) + E Formula (2-2) O ₂ (X ³ Σg ⁻ ) + e → O ₂ (B ³ Σu ⁻ ) + e Formula (2-3) O ₂ (B ³ Σu ⁻ ) + e → O ( ³ P) + O ( ¹ D) + e Equation (2-4)

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.

H ₂ + e → 2H Formula (3)

Then, of the oxygen plasma, for example, the formula (2)
The oxygen plasma generated in -2) and the hydrogen plasma generated in equation (3) react 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 (4)

In the plasma nitriding apparatus of the present invention, since the first electrode is provided, the plasma can be efficiently extracted from the plasma generation area to the plasma nitriding area, and the second electrode is provided. Therefore, the plasma extracted from the plasma generation region can be made to collide with the surface of the oxide film in a decelerated state.
Therefore, it is possible to independently control the plasma density and the energy of the reactive species entering the oxide film.

Further, it is not necessary to perform a nitriding treatment at a high temperature as in the thermal nitridation method. For example, a nitridation treatment for nitriding the surface of an oxide film at room temperature can be performed. There is no adverse effect on the characteristics of the semiconductor element such as a problem that occurs in the case of introduction into the film, that is, a decrease in current driving capability due to nitrogen intrusion into the silicon semiconductor substrate. Further, since the oxide film is nitrided, for example, boron atoms contained in the gate electrode pass through the gate insulating film to the silicon semiconductor substrate by various heat treatments in a semiconductor device manufacturing process after the gate electrode is formed, and the p-type The phenomenon that the threshold voltage of the semiconductor element fluctuates can be reliably avoided.

When the plasma oxidation method is employed, an insulating film or a gate insulating film is formed by irradiating a hydrogen gas, an oxygen gas, and a nitrogen-based gas with an electromagnetic wave. An insulating film or a gate insulating film can be formed in a processing apparatus, and a device configuration for forming the insulating film or the gate insulating film can be simplified. In addition, if the steam is generated by irradiating the hydrogen gas and the oxygen gas with an electromagnetic wave, the oxidation rate is suppressed and controlled, that is,
For example, even under a reduced pressure, water vapor can be easily and reliably generated, and a thin oxide film can be formed by a humidification oxidation method in a state where the oxidation rate is controlled. 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.

[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 plasma nitriding apparatus of the present invention. The plasma nitriding apparatus includes a processing chamber 10 and a stage 11 on which a semiconductor layer (a silicon semiconductor substrate 30 in the first embodiment) is mounted.
A magnet 13 disposed outside the processing chamber 10, a microwave waveguide 14 attached to the top of the processing chamber 10,
Gas inlets 16A, 16 provided at the top of the processing chamber 10
B, 16C. The processing chamber 10 includes a plasma generation region 10A and a plasma nitriding region 10B, and the stage 11 is disposed in the plasma nitriding region 10B. The silicon semiconductor substrate 30
A lamp, which is a heating means 12 for heating the lamp, is housed in the stage 11. A magnetron 15 is attached to the microwave waveguide 14, and the microwaves of 1 GHz to 100 GHz (for example,
(A microwave of 2.45 GHz) is generated, and the microwave is transmitted through the microwave waveguide 14 to the processing chamber 10.
To the plasma generation region 10A. Further, the processing chamber 1 is supplied from each of the gas introduction sections 16A, 16B, and 16C.
A hydrogen gas, an oxygen gas, and a nitrogen gas are introduced into 0. 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 the plasma generation region 10A, an electromagnetic wave of 1 GHz to 100 GHz (for example,
By irradiation with a microwave of 2.45 GHz), excited nitrogen molecules, nitrogen molecule ions, nitrogen atoms, or nitrogen atom ions are generated. In the plasma nitriding region 10B, the surface of the oxide film formed on the semiconductor layer on the substrate surface is nitrided.

The first electrode 20 and the first electrode 20 to which the same potential as the plasma generation region 10A or a negative potential is applied from the plasma generation region 10A are applied to the plasma nitridation region 10B from the plasma generation region 10A side. A second electrode 21 to which a more positive potential is applied is provided. The first electrode 20 and the second electrode 21 may have, for example, a ring-like electrode or a structure in which a plurality of electrode plates are juxtaposed. Note that the first electrode 20 functions as an extraction electrode, and the second electrode 21 functions as a deceleration electrode.

In Example 1, a silicon semiconductor substrate was used as the semiconductor layer. In the first embodiment,
The plasma oxidation method was adopted. The method of forming an insulating film and the method of manufacturing a p-type semiconductor device of the present invention using the plasma nitriding apparatus shown in FIG. 1 (more specifically, a p-channel type MO in a CMOSFET having a dual gate structure).
SFET) will be described below with reference to FIG. 2 which is a schematic partial cross-sectional view of the silicon semiconductor substrate 30 and the like.

[Step-100] First, an N-type silicon wafer of 8 inches in diameter doped with phosphorus (prepared by CZ method)
LOC is formed on the silicon semiconductor substrate 30 by a known method.
An element isolation region 31 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 30 are removed by RCA cleaning, and then the surface of the silicon semiconductor substrate 30 is cleaned with a 0.1% aqueous solution of hydrofluoric acid and pure water. The surface is exposed (see FIG. 2A). Most of the surface of the silicon semiconductor substrate 30 is terminated with hydrogen, and a very small portion is terminated with fluorine.

[Step-110] Next, the silicon semiconductor substrate 30 is carried into the plasma nitriding apparatus shown in FIG. 1 from a door (not shown), and is placed on the stage 11. (For example, nitrogen gas)
Introduce into 0. Then, the silicon semiconductor substrate 30 is heated to 800 ° C. by the heating means 12.

[Step-120] Thereafter, introduction of an inert gas (for example, nitrogen gas) as a diluting gas into the processing chamber 10 is interrupted, and the gas introduction section 16A and the gas introduction section 16B are stopped.
Then, hydrogen gas and oxygen gas are introduced into the processing chamber 10.
At the same time, microwave power is supplied to the magnetron 15,
1GHz to 100GH generated by magnetron 15
A microwave of z (for example, a microwave of 2.45 GHz) is introduced into the plasma generation region 10A of the processing chamber 10 via the microwave waveguide 14. This means that
By irradiating the hydrogen gas and the oxygen gas with electromagnetic waves, the reactions of the above-described equations (2-1) to (2-4), and the reactions of the equations (3) and (4) occur, and water vapor is generated. The generated water vapor reaches the plasma nitridation processing 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 30).
Is oxidized. Thus, an oxide film having a thickness of 2 nm (a silicon oxide film in Example 1) is formed on the surface of the semiconductor layer.
Can be formed. Table 1 shows the conditions for forming the oxide film. In this step, the first electrode 2
0 and the second electrode 21 are not operated.

[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-130] 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 chamber is stopped, and the silicon semiconductor substrate 30 is cooled to room temperature while introducing an inert gas from the gas introduction unit 17 into the processing chamber 10. Next, the introduction of the inert gas from the gas introduction unit 17 into the processing chamber 10 is interrupted. 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 microwaves of 1 GHz to 100 GHz (for example, microwaves of 2.45 GHz) generated by the magnetron 15 are generated in the processing chamber 10 through the microwave waveguide 14. The first electrode 20 and the second electrode 21 are introduced into the region 10A.
Activate Thus, that is, by irradiating the nitrogen gas with an electromagnetic wave, the above-described equations (1-1) to (1-
Excited nitrogen molecules, nitrogen molecule ions, nitrogen atoms or nitrogen atom ions generated in the plasma generation region 10A based on the reaction 4) are applied to the first electrode 20 in the plasma nitridation region 10B located below the processing chamber 10. Pulled out by the action of. By the operation of the second electrode 21, the plasma extracted from the plasma generation region 10A collides with the surface of the oxide film in a decelerated state, and the surface of the oxide film (specifically, the silicon oxide film) is nitrided. The first
Non-ionized nitrogen molecules and nitrogen atoms which are not affected by the electrode 20 and the second electrode 21 similarly reach the plasma nitriding region 10B, and the surface of the oxide film is nitrided. Thus, the insulating film 32 whose surface is nitrided (in the first embodiment, a silicon oxynitride film, which corresponds to a gate insulating 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. The nitriding conditions are shown in Table 2 below. The silicon semiconductor substrate 3
The reason why the temperature of 0 is set to room temperature is to suppress diffusion of nitrogen atoms into the silicon semiconductor substrate 30 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.) Potential of first electrode: plasma generation area 10 A For-
200 volts potential of the second electrode: +200 volts with respect to the first electrode

[Step-140] Thereafter, the gas introduction unit 16
While the introduction of nitrogen gas from C into the processing chamber 10 is stopped, and the inert gas is introduced into the processing chamber 10 from the gas introduction unit 17, the silicon semiconductor substrate 30 is
Raise the temperature to 50 ° C. And the silicon semiconductor substrate 3
When the temperature of 0 reaches 850 ° C. and the temperature is stabilized, heat treatment is performed at a nitrogen gas flow rate of 4 SLM for 5 minutes. By this heat treatment, damage caused on the insulating film can be reduced.

[Step-150] Thereafter, the silicon semiconductor substrate 30 is cooled to room temperature, the silicon semiconductor substrate 30 is unloaded from the plasma nitriding apparatus, and then a known CV
The silicon semiconductor substrate 30 is carried into the D device. And
A silicon layer containing no impurities (a polysilicon layer in the second embodiment) is formed on the entire surface by a CVD method. Next, based on a known lithography technique and an ion implantation technique, a gate electrode 33 for a p-channel MOSFET is formed.
After introducing boron into the gate electrode for the n-channel MOSFET and introducing boron, respectively, the silicon layer is patterned. Thus, a gate electrode 33 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. In addition, a gate electrode made of a silicon layer containing an n-type impurity (specifically, a polysilicon layer) for an n-channel MOSFET can be formed on the gate insulating film. After that, an LDD region is formed by using a known technique (see FIG. 2C).

[Step-160] Next, an insulating material layer is formed on the entire surface, and the insulating material layer is etched by an anisotropic dry etching technique to form sidewalls 34 on the side walls of the gate electrode. Next, the source / drain region 3
In order to form 5, boron is applied to the region of the silicon semiconductor substrate where the p-channel MOSFET is to be formed, and phosphorus is added to the region of the silicon semiconductor substrate where the n-channel MOSFET is to be formed, based on known lithography and ion implantation techniques. Are respectively introduced, and an activation heat treatment of the ion-implanted impurities is performed. Thereafter, an interlayer insulating layer 36 is formed on the entire surface by the CVD method, an opening is provided in the interlayer insulating layer 36 above the source / drain region, and a wiring material layer is sputtered on the interlayer insulating layer 36 including the inside of the opening. The wiring 37 is formed by patterning the wiring material layer, and a p-type semiconductor device (more specifically, a dual gate structure) whose schematic partial cross-sectional view is shown in FIG. -Channel type MO in CMOSFET having
SFET).

(Embodiment 2) Embodiment 2 is a modification of Embodiment 1. In the first embodiment, the silicon semiconductor substrate 30
Although the oxide film was formed by the plasma oxidation method while being heated to 00 ° C., in Example 2, two-stage oxidation is performed based on the plasma oxidation method. That is, after the formation of the oxide film is started at a temperature at which atoms mainly constituting the semiconductor layer do not desorb from the surface of the semiconductor layer, the formation of the oxide film is started for a predetermined period. A first oxide film forming step of forming an oxide film while holding the semiconductor layer in a temperature range in which atoms mainly constituting the semiconductor layer do not desorb from the semiconductor layer, and atoms mainly constituting 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 a temperature range at which no desorption occurs until a desired thickness is obtained.
The plasma nitriding apparatus shown in FIG. 1 is also used in the second embodiment.

[Step-200] First, the same step as [Step-100] of the first embodiment is performed.

[Step-210] Next, the silicon semiconductor substrate 30 is carried into the plasma nitriding apparatus shown in FIG. 1 from a door (not shown), and is placed on the stage 11. (For example, nitrogen gas)
Introduce into 0. Then, the silicon semiconductor substrate 30 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 second embodiment).

[Step-220] 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 16 A and the gas introducing section 16 B into the processing chamber. Hydrogen gas and oxygen gas are introduced into 10. At the same time, microwave power is supplied to the magnetron 15 to generate 1 GH generated by the magnetron 15.
microwave of z to 100 GHz (for example, 2.45 G
(Microwave of 1 Hz) is introduced into the plasma generation region 10A of the processing chamber 10 through the microwave waveguide 14. Thereby, steam is generated. The generated steam is in processing chamber 1
The surface of the semiconductor layer (specifically, the silicon semiconductor substrate 30) that reaches the plasma nitridation processing region 10 </ b> B below 0 and is heated by the heating unit 12 is oxidized. Thus, an oxide film (a silicon oxide film in Example 2) can be formed on the surface of the semiconductor layer. Table 3 below shows conditions for forming the oxide film. In this first oxide film forming step, an oxide film having a thickness of 1 nm is formed. still,
In this step, the first electrode 20 and the second electrode 21 are not operated.

[Table 3] 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-230] 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 interrupted, and the introduction of the inert gas from the gas inlet 17 into the processing chamber 10 is continued. The silicon semiconductor substrate 30 at 800 ° C.
Heat up to Since an oxide film has already been formed on the surface of the semiconductor layer, no irregularities (roughness) occur on the surface of the semiconductor layer (the silicon semiconductor substrate 30 in the second embodiment) in this temperature raising step. Next, hydrogen gas and oxygen gas are again introduced into the processing chamber 10 from the gas introduction unit 16A and the gas introduction unit 16B. At the same time, the microwave power is again supplied to the magnetron 15 so that the magnetron 15
The microwave of 1 GHz to 100 GHz (for example, the microwave of 2.45 GHz) generated by the above-described process is supplied to the plasma generation region 10 of the processing chamber 10 through the microwave waveguide 14.
Introduce to A. Thereby, steam is generated. The generated water vapor reaches the plasma nitriding region 10B located below the processing chamber 10, and further oxidizes the surface of the semiconductor layer (specifically, the silicon semiconductor substrate 30) heated by the heating unit 12. Thus, an oxide film having a total thickness of 4 nm (a silicon oxide film in Example 2) is formed on the surface of the semiconductor layer.
To form Table 4 shows the conditions for forming the oxide film in the second oxide film forming step. In this step, the first electrode 20 and the second electrode 21 are not operated.

[Table 4] 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-240] After that, by performing [Step-130] to [Step-160] of the first embodiment, a p-type semiconductor device can be obtained.

Example 3 Example 3 is a modification of the method of forming an insulating film and the method of manufacturing a p-type semiconductor device of Example 1. Example 3 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. It is in. Hereinafter, a method for forming an insulating film and a method for manufacturing a p-type semiconductor device according to the third embodiment will be described. In the third embodiment, the plasma nitriding apparatus shown in FIG. 1 is used.

[Step-300] [Step-10] of Example 1
0] to [Step-120], an oxide film having a thickness of 2 nm (a silicon oxide film in the third embodiment) is formed on the surface of the semiconductor layer (the silicon semiconductor substrate 30 in the third embodiment). To form

[Step-310] 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.
As a result, the temperature of the silicon semiconductor substrate 30 is raised to 850 ° C. Next, nitrogen gas containing 0.1% by volume of hydrogen chloride gas was introduced into the processing chamber 10 from the gas introduction unit 17,
Heat treatment for minutes. As a result, an oxide film having excellent time-zero dielectric breakdown (TZDB) characteristics and temporal dielectric breakdown (TDDB) characteristics can be obtained.

[Step-320] Then, 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 cooling the silicon semiconductor substrate 30 to room temperature,
By performing the same steps as [Step-130] to [Step-160] in Example 1, a p-type semiconductor element can be obtained. Note that the heat treatment of the third embodiment is the same as that of the second embodiment.
It may be added to the oxide film forming step of the stage.

(Embodiment 4) Embodiment 4 is also a modification of Embodiment 1. Embodiment 4 is different from Embodiment 1 in that a pyrogenic oxidation method is used for forming an oxide film.

FIG. 3 is a conceptual diagram of a vertical type oxide film forming apparatus for forming a silicon oxide film based on a pyrogenic oxidation method. This vertical type oxide film forming apparatus
Oxidation furnace 40 of double tube structure made of quartz held vertically
(Corresponding to a processing chamber) and the wet gas and / or
A gas introduction unit 42 for introducing a gas, a gas exhaust unit 43 for exhausting a wet gas and / or gas from the oxidation furnace 40,
A heater 44 for maintaining the inside of the oxidation furnace 40 at a predetermined atmospheric temperature via a cylindrical soaking tube 46 made of iC, a substrate carrying-in / out part 50, and an inert gas such as a nitrogen gas are introduced into the substrate carrying-in / out part 50. A gas inlet 51 for exhausting the gas, a gas exhaust unit 52 for exhausting gas from the substrate carry-in / out unit 50, a shutter 45 separating the oxidation furnace 40 and the substrate carry-in / out unit 50,
An elevator mechanism 53 is provided to carry the silicon semiconductor substrate 30 into and out of the oxidation furnace 40. A quartz boat 54 for mounting the silicon semiconductor substrate 30 is attached to the elevator mechanism 53. In addition, the hydrogen gas supplied to the combustion chamber 60 is
A wet gas is generated by mixing and burning at a high temperature in the furnace. The wet gas is introduced into the oxidation furnace 40 via the pipe 61, the gas flow path 41, and the gas introduction unit 42. The gas flow path 41 is provided in the oxidation furnace 40 having a double pipe structure.
Corresponds to the space between the inner wall and the outer wall.

An outline of a method for forming an oxide film based on a pyrogenic oxidation method using the vertical type oxide film forming apparatus shown in FIG. 3 will be described below.

[Step-400] First, the same step as [Step-100] of the first embodiment is performed.

[Step-410] The pipe 62, the combustion chamber 60,
Nitrogen gas is introduced into the oxidizing furnace 40 through the pipe 61, the gas flow path 41 and the gas introducing section 42, the inside of the oxidizing furnace 40 is set to a nitrogen gas atmosphere, and the heater 44 is heated by the heater 44 through the soaking pipe 46. The ambient temperature is maintained at around 700 ° C. In this state, the shutter 45 is closed. The substrate loading / unloading section 50 is open to the atmosphere.
Then, the silicon semiconductor substrate 30 is loaded into the substrate loading / unloading section 50, and the silicon semiconductor substrate 30 is placed on the quartz boat 54. Silicon semiconductor substrate 30 to substrate carrying-in / out section 50
Is completed, the door (not shown) is closed, a nitrogen gas is introduced into the substrate carrying-in / out section 50 from the gas introduction section 51, and the gas is exhausted from the gas exhausting section 52, and the inside of the substrate carrying-in / out section 50 is set to a nitrogen gas atmosphere.

[Step-420] When the inside of the substrate loading / unloading section 50 has a sufficient nitrogen gas atmosphere, the shutter 45 is opened and the elevator mechanism 53 is operated to activate the quartz boat 54.
And the silicon semiconductor substrate 30 is carried into the oxidation furnace 40. When the elevator mechanism 53 reaches the highest position, the base of the quartz boat 54 stops communication between the oxidation furnace 40 and the substrate loading / unloading section 50.

[Step-430] Thereafter, the ambient temperature of the oxidation furnace 40 in a nitrogen gas atmosphere is raised to 800 to 900 ° C. Then, the combustion chamber 60 is connected through the pipes 62 and 63.
An oxygen gas and a hydrogen gas are supplied into the inside, and the wet gas generated by mixing and burning the hydrogen gas and the oxygen gas at a high temperature in the combustion chamber 60 is supplied to a pipe 61, a gas passage 41 and a gas introduction section 42. The gas is introduced into the oxidation furnace 40 via the gas exhaust unit 43 and exhausted from the gas exhaust unit 43. As a result, an oxide film is formed on the surface of the silicon semiconductor substrate 30. The combustion chamber 60
The internal temperature is increased by, for example, 700 heaters (not shown).
Keep at ~ 900 ° C.

[Step-440] After an oxide film having a desired thickness is formed, supply of oxygen gas and hydrogen gas into the combustion chamber 60 is stopped, and then inert gas such as nitrogen gas is introduced into the oxidation furnace 40. While introducing the gas, the ambient temperature of the oxidation
The temperature is lowered to about 0 ° C., then the elevator mechanism 53 is operated to lower the quartz boat 54, and then the silicon semiconductor substrate 30 is unloaded from the substrate loading / unloading section 50.

[Step-450] After that, by performing [Step-130] to [Step-160] of the first embodiment, a p-type semiconductor element can be obtained. Example 4
The two-stage oxide film forming process described in the second embodiment may be executed based on the pyrogenic oxidation method described above, or the heat treatment described in the third embodiment may be added.

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 structures of the plasma nitriding apparatus and the oxide film forming apparatus described in the embodiments are merely examples, and can be appropriately changed. Depending on the plasma nitriding apparatus and / or the plasma nitriding conditions, the first electrode may be omitted in some cases as long as the plasma can be reliably drawn from the plasma generating region to the plasma nitriding region.

For example, in [Step-230] of the second 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. 30 may be heated to 800 ° C. Further, in [Step-310] of Example 3, an inert gas (for example, nitrogen gas)
Is introduced into the processing chamber 10 from the gas introduction part 17 and the temperature of the silicon semiconductor substrate 30 is raised to 850 ° C. by a heating means.
Temperature, but instead, an inert gas (for example, nitrogen gas) containing, for example, 0.1% by volume of hydrogen chloride gas is introduced into the processing chamber 10 from the gas introduction unit 17 while the silicon semiconductor substrate 30 850 ° C by heating means
Temperature may be increased. Further, a first oxide film forming step,
The atmosphere in each of the temperature raising step and the second oxide film forming step may include, for example, a hydrogen chloride gas.

In the embodiments, the insulating film is formed exclusively on the surface of the silicon semiconductor substrate. However, the insulating film is formed on the epitaxial silicon layer formed on the substrate based on the insulating film forming method of the present invention. Alternatively, an insulating 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, an insulating film may be formed on the surface of the silicon layer in the SOI structure, or the insulating film may be formed on the surface of the semiconductor element or the substrate on which the components of the semiconductor element are formed, or the surface of the silicon layer formed thereon. May be formed. Further, an insulating film may be formed on a surface of a substrate on which a semiconductor element or a component of the semiconductor element is formed, or a silicon layer formed on a base insulating layer formed on the substrate. The formation of the oxide film and / or the nitridation treatment of the surface of the oxide film 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 embodiment, after the surface of the semiconductor layer is cleaned with a 0.1% aqueous solution of hydrofluoric acid and pure water, the semiconductor layer is treated with a plasma nitriding apparatus or an oxide film forming apparatus (hereinafter referred to as these apparatuses). Are collectively referred to as a plasma processing apparatus or the like), but the atmosphere from the surface cleaning of the semiconductor layer to the transfer to the plasma nitriding apparatus or the like 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 of FIG. 4, a method of carrying in a plasma nitriding apparatus or the like, and a surface cleaning apparatus, a plasma nitriding apparatus, or the like, a surface cleaning using a cluster tool device including a transport path, a loader, and an unloader. This can be achieved by a method in which the apparatus is connected to the plasma nitriding apparatus and the like by a transport path, and the atmosphere of the surface cleaning apparatus, the transport path, the plasma nitriding apparatus and the like is an inert gas atmosphere.

Alternatively, instead of cleaning the surface of the semiconductor layer with a 0.1% aqueous hydrofluoric acid solution and pure water, a gas phase cleaning method using anhydrous hydrogen fluoride gas under the conditions shown in Table 5 is used. May be used to clean the surface of the semiconductor layer.
Note that methanol is added to prevent generation of particles. Alternatively, the surface of the semiconductor layer may be cleaned by a gas phase cleaning method using hydrogen chloride gas under the conditions shown in Table 6. Note that the atmosphere in the surface cleaning device or the atmosphere in the transfer path before the start of surface cleaning of the semiconductor layer or after completion of the surface cleaning may be an inert gas atmosphere,
For example, a vacuum atmosphere of about 1.3 × 10 ⁻¹ Pa (10 ⁻³ Torr) may be used. When the atmosphere in the transfer path or the like is a vacuum atmosphere, the atmosphere of the plasma nitriding apparatus or the like when loading the semiconductor layer is set to, for example, 1.3 × 10 ⁻¹ Pa (1
A vacuum atmosphere of about 0 ⁻³ Torr may be set, and after the semiconductor layer is completely loaded, the atmosphere of the plasma nitriding apparatus or the like may be an inert gas (eg, nitrogen gas) atmosphere.

[Table 5] Anhydrous hydrogen fluoride gas: 300 SCCM Methanol vapor: 80 SCCM Nitrogen gas: 1000 SCCM Pressure: 0.3 Pa Temperature: 60 ° C.

[Table 6] 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, or, for example, 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, when the plasma oxidation method is employed, when forming an oxide film, hydrogen gas and oxygen gas are introduced into the processing chamber 10. In order to prevent a detonation reaction from being caused by flowing in and flowing out of the system, and to prevent a dry oxide film from being formed on the semiconductor layer, for example, [Step- 120], while introducing an inert gas (for example, nitrogen gas) as a diluting gas at a flow rate of 10 SLM from the gas introduction unit 17 into the processing chamber 10, the flow rate of the inert gas (eg, nitrogen gas) from the gas introduction unit 16 </ b> A into the processing chamber 10 is reduced to 0.1.
2 SLM of hydrogen gas is introduced, and then, for example, the introduction of oxygen gas at a flow rate of 10 SLM into the processing chamber 10 from, for example, the gas introduction unit 16B is started, and the inert gas processing chamber 1 for dilution
What is necessary is just to stop the introduction into 0. 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 10 </ b> A of the processing chamber 10 through the microwave waveguide 14. By such an operation, the concentration of hydrogen gas in the processing chamber 10 before the generation of steam becomes a sufficiently low value, and it is possible to reliably prevent the detonation reaction from occurring, and furthermore, to surely form the dry oxide film. Can be prevented.

[0087]

According to the present invention, by operating the first electrode and the second electrode, it is possible to independently control the plasma density and control the energy of the reactive species entering the oxide film, and the Nitrogen molecules, nitrogen molecule ions, nitrogen atoms, or nitrogen atom ions can be introduced shallowly into the oxide film so that the surface of the film is nitrided. Since the surface of the oxide film is nitrided, there is no adverse effect on the characteristics of the semiconductor element such as a decrease in current driving capability. Further, since the oxide film is nitrided, p-type impurities contained in the gate electrode reach the semiconductor layer through the gate insulating film by various heat treatments in a semiconductor device manufacturing process after the formation of the gate electrode, for example. The phenomenon that the threshold voltage of the element fluctuates can be reliably avoided.

When an oxide film is formed based on water vapor generated by a method of irradiating a hydrogen gas and an oxygen gas with an electromagnetic wave, an insulating film or a gate insulating film is formed essentially in one plasma nitriding apparatus. It is possible to use only one device for forming the insulating film or the gate insulating film, and the configuration of the device can be simplified. Further, 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.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram of a plasma nitriding 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 insulating film of Example 1.

FIG. 3 is a conceptual diagram of a vertical type oxide film forming apparatus for forming an oxide film based on a pyrogenic oxidation method.

FIG. 4 is a schematic view of a cluster tool device.

[Explanation of symbols]

10 processing chamber, 10A plasma generation area, 1
0B: Plasma nitriding region, 11: Stage, 12: Heating means, 13: Magnet, 14 ...
Microwave waveguide, 15 ... magnetron, 16A,
16B, 16C, 17 ... gas introduction part, 18 ... gas exhaust part, 20 ... first electrode, 21 ... second electrode,
Reference Signs List 30 silicon semiconductor substrate 31 element isolation region 32 insulating film (gate insulating film) 33 gate electrode 34 side wall 35 source / drain region , 36 ... interlayer insulating layer, 37 ...
wiring

 ──────────────────────────────────────────────────続 き Continued from the front page F term (reference) BC11 BD01 BD03 BD04 BD09 BD10 BD15 BE03 BF51 BF52 BF53 BF55 BF56 BF63 BF72 BF73 BF74 BH01 BJ01

Claims (11)

[Claims] (A) a plasma generation region for generating nitrogen molecules, nitrogen molecule ions, nitrogen atoms or nitrogen atom ions in an excited state by irradiating a nitrogen-based gas with an electromagnetic wave; and (B) plasma nitriding treatment. A processing chamber having an area,
A plasma nitriding apparatus for nitriding a surface of an oxide film, wherein a potential equal to or lower than the plasma generation region is applied to the plasma nitridation region from the plasma generation region side. A plasma nitriding apparatus, comprising: one electrode; and a second electrode to which a potential more positive than the first electrode is applied. 2. Applying a negative potential to the first electrode from the plasma generation region to draw plasma from the plasma generation region to the plasma nitriding region, and applying a second electrode to the second electrode with a positive potential than the first electrode. 2. The plasma nitriding apparatus according to claim 1, wherein the speed of the plasma extracted from the plasma generation region is reduced by applying the pressure. 3. The plasma nitriding apparatus according to claim 1, wherein the electromagnetic wave is a microwave. 4. A plasma generating region for generating nitrogen molecules, nitrogen molecular ions, nitrogen atoms or nitrogen atom ions in an excited state by irradiating a nitrogen-based gas with an electromagnetic wave, and (B) a plasma nitriding treatment. A first electrode to which a potential equal to or higher than the plasma generation region is applied to the plasma nitridation region from the plasma generation region side, and a first electrode; A method of forming an insulating film using a plasma nitriding apparatus provided with a second electrode to which a more positive potential is applied, comprising: (a) oxidizing a semiconductor layer on a substrate surface by oxidizing the oxide film; And (b) placing a substrate in a plasma nitridation region of a plasma nitridation apparatus, and generating excited nitrogen molecules and nitrogen molecule ions in a plasma generation region. Using a nitrogen atom or a nitrogen atom ions, the method of forming the insulating film, which comprises the step, performing a nitriding treatment on the surface of the oxide film. 5. Applying a negative potential to the first electrode from the plasma generation region to draw plasma from the plasma generation region to the plasma nitriding region, and applying a second electrode to the second electrode with a more positive potential than the first electrode. 5. The method according to claim 4, wherein by applying a voltage, the plasma extracted from the plasma generation region is made to collide with the oxide film in a decelerated state. 6. In the step (a), after the substrate is carried into a plasma nitriding region of a plasma nitriding device, hydrogen gas and oxygen gas are irradiated with electromagnetic waves to generate water vapor in a plasma generating region. 5. The method for forming an insulating film according to claim 4, comprising a step of oxidizing a semiconductor layer on a substrate surface using said water vapor. 7. The method according to claim 4, wherein the electromagnetic wave is a microwave. 8. A method comprising: (a) forming a gate insulating 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 insulating film. A method for manufacturing a semiconductor device, comprising: (a) forming an oxide film by oxidizing a semiconductor layer on a substrate surface; and (b) irradiating a nitrogen-based gas with electromagnetic waves. A plasma generating region for generating excited state nitrogen molecules, nitrogen molecule ions, nitrogen atoms or nitrogen atom ions,
And (B) a processing chamber having a plasma nitriding region, wherein the plasma nitriding region has a potential equal to or higher than the plasma generating region from the plasma generating region. Using a plasma nitriding apparatus provided with one electrode and a second electrode to which a positive potential is applied more than the first electrode, a substrate is placed in a plasma nitriding region of the plasma nitriding apparatus, Performing a nitriding treatment on the surface of the oxide film using nitrogen molecules, nitrogen molecule ions, nitrogen atoms or nitrogen atom ions in an excited state generated in the generation region. Production method. 9. Applying a negative potential to the first electrode from the plasma generation region to draw plasma from the plasma generation region to the plasma nitriding region, and applying a second electrode to the second electrode at a more positive potential than the first electrode. The method of manufacturing a p-type semiconductor device according to claim 8, wherein by applying a voltage, the plasma extracted from the plasma generation region is made to collide with the oxide film in a decelerated state. 10. In the step (a), after carrying the substrate into the plasma nitriding region of the plasma nitriding device, the substrate is irradiated with electromagnetic waves to hydrogen gas and oxygen gas to generate water vapor in the plasma generating region. 9. The method for manufacturing a p-type semiconductor device according to claim 8, comprising a step of oxidizing a semiconductor layer on a substrate surface using said water vapor. 11. The method according to claim 8, wherein the electromagnetic wave is a microwave.