JP4403321B2 - Method for forming oxide film and method for manufacturing p-type semiconductor element - Google Patents

Description

[0001]
BACKGROUND 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 specifically, a method for forming an oxide film having a nitrided surface, and a method for applying such a method for forming an oxide film to the formation of a gate oxide film. More specifically, the present invention relates to a method for manufacturing a p-channel MOSFET in a CMOSFET having a dual gate structure.
[0002]
[Prior art]
For example, in the manufacture of 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 in manufacturing a thin film transistor (TFT), it is necessary to form a gate oxide film made of a silicon oxide film on the surface of a silicon layer provided on an insulating substrate. It is no exaggeration to say that such a silicon oxide film is responsible for the reliability of the semiconductor device. Accordingly, the silicon oxide film is always required to have high breakdown voltage and long-term reliability.
[0003]
Along with the high integration of semiconductor devices, the gate oxide film of MOS type semiconductor devices is also becoming thinner, and the thickness of the gate oxide film in a semiconductor device having a gate length of 0.1 μm generation is expected to be about 3 nm. Silicon oxide film formation methods can be broadly classified into two methods: a dry oxidation method using dry oxygen as an oxidizing species, and a humidified oxidation method using water vapor as an oxidizing species. The dry oxidation method is a method of 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 humidified 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 humidified oxidation method is more reliable than a silicon oxide film formed by a dry oxidation method.
[0004]
One type of humidification oxidation method is a pyrogenic oxidation method. This method is a method of generating water vapor by burning pure hydrogen gas in order to improve the reproducibility of the humidification oxidation method and eliminate the need for water amount management. Since this pyrogenic method can generate water vapor most stably, a uniform silicon oxide film can be formed. Further, since gas is used as a raw material for generating water vapor, there is an advantage that impurities can be easily controlled.
[0005]
In recent years, CMOS transistors have been reduced in voltage to reduce power consumption. For this reason, sufficiently low and symmetrical threshold voltages are required for PMOS and NMOS semiconductor devices. . In order to cope with such a demand, in the PMOS semiconductor device, instead of the conventional gate electrode composed of the polysilicon layer containing n-type impurities, the gate electrode composed of the polysilicon layer containing p-type impurities. Is being used. A CMOSFET having such a structure is called a CMOSFET having a dual gate structure. However, boron atoms (B), which are commonly used p-type impurities, easily pass through the gate oxide film from the gate electrode and reach the silicon semiconductor substrate by various heat treatments in the semiconductor device manufacturing process after forming the gate electrode. The threshold voltage of the PMOS semiconductor device may be varied.
[0006]
[Problems to be solved by the invention]
When a thin silicon oxide film is to be formed, the humidification oxidation method has a higher oxidation rate than the dry oxidation method. For example, the oxidation temperature must be lowered and the oxidation time must be shortened. However, the shortening of the oxidation time has a problem that the uniformity of the thickness of the silicon oxide film is hindered. Therefore, when the thin silicon oxide film is formed by employing the humidified oxidation method, the oxidation rate must be suppressed by another method.
[0007]
As a method for suppressing the oxidation rate, there is a method in which water vapor is generated under reduced pressure and a silicon oxide film is formed under reduced pressure. In this way, if the silicon oxide film is formed under reduced pressure, the amount of oxidizing species supplied is small, so that the oxidation rate can be suppressed. However, in the method of generating water vapor under such reduced pressure, the operation of the hydrogen gas combustion apparatus for generating water vapor is not stable. That is, it is difficult to stably burn hydrogen gas under reduced pressure, and as a result, it is difficult to stably form a thin silicon oxide film while suppressing the oxidation rate.
[0008]
In order to suppress fluctuations in the threshold voltage of the PMOS semiconductor element due to 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. The effect of suppressing boron atom diffusion has also been confirmed. As a method for introducing nitrogen atoms into the gate oxide film, for example, a so-called plasma nitridation method in which nitrogen plasma is generated by performing discharge in a nitrogen gas atmosphere is described in the literature "Ultrathin nitrogen-profile engineered gate dielectric filmes", SV Hattangady , et al., 1996, known from IEDM. In the plasma nitriding method described in this document, since only the surface of the gate oxide film is nitrided, nitrogen penetrates into the silicon semiconductor substrate as in the introduction of nitrogen atoms into the gate oxide film by thermal nitriding. Therefore, there is no adverse effect on the semiconductor element characteristics such as a decrease in current driving capability.
[0009]
However, in the plasma nitridation 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 with different apparatuses. It is necessary to carry out the process. That is, there are problems that the manufacturing process of the semiconductor device is increased and the manufacturing time of the semiconductor device is extended, or that two types of devices, an oxidizer and a plasma nitridation device, are required.
[0010]
Further, when the surface of the oxide film is nitrided by excited nitrogen molecules or nitrogen molecular ions, there is a possibility that defects are generated in the oxide film, and such defects may have to be recovered or removed by some means.
[0011]
Accordingly, an object of the present invention is to stably form a thin oxide film by a humidified oxidation method, and to reliably suppress the diffusion of boron atoms from the gate electrode constituting the p-type semiconductor element. An object of the present invention is to provide a method for forming an oxide film having high reliability and a method for manufacturing a p-type semiconductor element in which the method for forming an oxide film is applied to the formation of a gate oxide film. Furthermore, an object of the present invention is to form an oxide film that can nitride only the surface of the oxide film with one apparatus, and a p-type in which such an oxide film formation method is applied to the formation of a gate oxide film. An object of the present invention is to provide a method for manufacturing a semiconductor device, more specifically, a method for manufacturing a p-channel MOSFET in a CMOSFET having a dual gate structure.
[0012]
[Means for Solving the Problems]
In order to achieve the above object, the method for forming an oxide film of the present invention comprises:
(A) a step of generating water vapor by irradiating electromagnetic waves to hydrogen gas and oxygen gas, oxidizing the surface of the semiconductor layer using the water vapor, and forming an oxide film on the surface of the semiconductor layer;
(B) nitriding the surface of the oxide film with excited nitrogen molecules, nitrogen molecular ions, nitrogen atoms or nitrogen atom ions generated by irradiating a nitrogen-based gas with electromagnetic waves;
(C) a step of heat-treating the oxide film having a nitrided surface;
It is characterized by comprising.
[0013]
Moreover, the manufacturing method of the p-type semiconductor element of this invention for achieving said objective is as follows.
(A) forming a gate oxide film on the surface of the semiconductor layer;
(B) forming a gate electrode made of a silicon layer containing a p-type impurity on the gate oxide film;
A method of manufacturing a p-type semiconductor device comprising:
Step (A)
(A) a step of generating water vapor by irradiating electromagnetic waves to hydrogen gas and oxygen gas, oxidizing the surface of the semiconductor layer using the water vapor, and forming an oxide film on the surface of the semiconductor layer;
(B) A step of nitriding the surface of the oxide film with excited nitrogen molecules, nitrogen molecular ions, nitrogen atoms or nitrogen atom ions generated by irradiating a nitrogen-based gas with electromagnetic waves, thereby forming a gate oxide film When,
(C) a step of heat-treating the gate oxide film;
It is characterized by comprising.
[0014]
In the method for forming an oxide film or the method for manufacturing a p-type semiconductor element of the present invention, “nitriding the surface of the oxide film with nitrogen molecules, nitrogen molecular ions, nitrogen atoms or nitrogen atom ions” means at least nitrogen molecules. It means that the surface of the oxide film is nitrided with nitrogen molecular ions, nitrogen atoms or nitrogen atom ions. That is, more specifically, the surface of the oxide film is nitrided by any one, two, three, or four of nitrogen molecules, nitrogen molecular ions, nitrogen atoms and nitrogen atom ions. It means to do.
[0015]
In the method for manufacturing a p-type semiconductor element of the present invention, for example, a p-type impurity (for example, boron) is used as a method for forming a gate electrode made of a silicon layer containing a p-type impurity (for example, a polysilicon layer or an amorphous silicon layer). A method of patterning the silicon layer after forming the silicon layer containing the CVD method based on the CVD method, and a p-type impurity (for example, boron or BF) after forming the silicon layer not containing the impurity by the CVD method. ₂ ) Is implanted into the silicon layer by ion implantation, followed by patterning the silicon layer, patterning after forming a silicon layer not containing impurities by CVD, and then p-type impurities (for example, boron or BF). ₂ ) May be implanted into the silicon layer by ion implantation. In the step (B), after forming a silicon layer containing a p-type impurity, a silicide layer is formed on the silicon layer, and then the silicide layer and the silicon layer are patterned to form a gate electrode having a polycide structure. May be formed. Alternatively, in step (B), after forming a silicon layer containing p-type impurities, a refractory metal material layer such as tungsten is formed on the silicon layer. As a reaction preventing film for preventing the reaction between the silicon layer and the refractory metal material layer, a refractory metal nitride (for example, WN) is formed on the silicon layer, and the refractory metal material layer is formed thereon. It is preferable to form. Next, a gate electrode having a two-layer structure may be formed by patterning the refractory metal material layer and the silicon layer.
[0016]
In the method for forming an oxide film or the method for manufacturing a p-type semiconductor element of the present invention (hereinafter, these may be collectively referred to simply as the method of the present invention), for example, microwaves having a frequency of 2.45 GHz are used as electromagnetic waves. Can be used. In a state where 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 carrier gases, a semiconductor An oxide film may be formed on the surface of the layer. In addition, nitrogen gas (N ₂ Gas), NO, N ₂ O, NO ₂ Examples thereof include a gas that is a compound of a nitrogen atom and an oxygen atom.
[0017]
In the method of the present invention, the step (a) and the step (b) are performed in the same processing chamber, or the step (a), the step (b) and the step (c) are performed in the same processing chamber. This is preferable from the viewpoint of simplifying the device configuration or shortening the formation time of the oxide film and the gate oxide film.
[0018]
In the present invention, it is desirable that the heat treatment atmosphere be an inert gas atmosphere. Examples of the inert gas in the heat treatment include nitrogen gas, argon gas, and helium gas. The heat treatment temperature is 700 to 1200 ° C, preferably 700 to 1000 ° C, more preferably 700 to 950 ° C. In addition, the heat treatment time is preferably 1 to 10 minutes in the case of single wafer processing, 5 to 60 minutes, preferably 10 to 40 minutes, more preferably 20 to 30 in the batch mode. It is desirable to use minutes. Note that it is desirable that the atmospheric temperature during the heat treatment be higher than the temperature when the nitridation of the oxide film is completed. In addition, when the process (b) and the process (c) are performed in the same processing chamber, after the completion of the process (b), the atmosphere in the processing chamber is switched to an inert gas atmosphere, and the temperature is increased to an atmospheric temperature for performing the heat treatment. It is preferable to do.
[0019]
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 nitrogen gas, argon gas, and helium gas. Further, examples of the halogen element include chlorine, bromine, and fluorine. Among them, chlorine is desirable. Examples of the form of the halogen element contained in the inert gas include hydrogen chloride (HCl) and CCl. _Four , C ₂ HCl _Three , Cl ₂ , HBr, NF _Three Can be mentioned. The halogen element content in the inert gas is 0.001 to 10% by volume, preferably 0.005 to 10% by volume, more preferably 0.02 to 10% by volume, based on the form of the molecule or compound. is there. For example, when hydrogen chloride gas is used, the hydrogen chloride gas content in the inert gas is preferably 0.02 to 10% by volume.
[0020]
Usually, before forming a silicon oxide film on the surface of a silicon semiconductor substrate, NH _Four OH / H ₂ O ₂ Wash with aqueous solution and further HCl / H ₂ O ₂ The surface of the silicon semiconductor substrate is cleaned by RCA cleaning, which is performed by cleaning with an aqueous solution. After removing fine particles and metal impurities from the surface, the silicon semiconductor substrate is cleaned with an aqueous hydrofluoric acid solution and pure water. However, after that, when the silicon semiconductor substrate is exposed to the atmosphere, the surface of the silicon semiconductor substrate is contaminated, moisture or organic matter adheres to the surface of the silicon semiconductor substrate, or Si atoms on the surface of the silicon semiconductor substrate become hydroxyl groups ( OH) (for example, “Highly-reliable Gate Oxide Formation for Giga-Scale LSIs by using Closed Wet Cleaning System and Wet Oxidation with Ultra-Dry Unloading”, J. Yugami, et al., International Electron (See Device Meeting Technical Digest 95, pp 855-858). In such a case, when the formation of the oxide film is started as it is, moisture, organic matter, or, for example, Si—OH is taken into the formed silicon oxide film, and the characteristic of the formed silicon oxide film is reduced. It may cause a defective part. The defect portion is a portion of a silicon oxide film including defects such as silicon dangling bonds (Si.) And Si—H bonds, or Si—O—Si bonds are compressed by stress or Si—O—. It means a portion of a silicon oxide film containing Si—O—Si bonds in which the Si bond angle is thick or different from the Si—O—Si bond angle in the bulk silicon oxide film. 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 the formation of the oxide film without exposing the semiconductor layer after the surface cleaning to the atmosphere ( That is, for example, the atmosphere from the cleaning of the surface of the semiconductor layer to the start of the oxide film forming process is preferably an inert gas atmosphere or a vacuum atmosphere), and the oxide film is preferably formed. Thus, for example, when a silicon semiconductor substrate is used as the semiconductor layer, a silicon oxide film can be formed on the surface of the silicon semiconductor substrate having a surface that is mostly terminated with hydrogen and a pole portion is terminated with fluorine. It is possible to prevent deterioration of characteristics of the formed silicon oxide film or generation of defective portions.
[0021]
In the formation of the oxide film, hydrogen gas and oxygen gas are introduced into the processing chamber. At this time, in order to prevent the squeal gas reaction from occurring due to the hydrogen gas flowing into the processing chamber and flowing out of the system. In addition, it is desirable to introduce oxygen gas before introducing hydrogen gas into the processing chamber. However, there is a possibility that an oxide film is formed in the semiconductor layer by introducing oxygen gas into the processing chamber. Such an oxide film is a dry oxide film and is inferior in characteristics to an oxide film formed by a humidified oxidation method. In order to reliably prevent the formation of such a dry oxide film, for example, hydrogen gas diluted with an inert gas such as nitrogen gas is first introduced into the processing chamber before starting the formation of the oxide film, and then the processing is performed. Oxygen gas may be introduced into the room. However, in this case, in order to surely prevent the occurrence of the squeal gas reaction, the concentration of hydrogen gas is set to a concentration at which hydrogen gas does not react with oxygen gas and burn, specifically, in the air. Detonation range (18.3% or less when expressed in volume% with air), preferably below the combustion range in air (4.0% or less when expressed with volume% with air) ) Or less than the detonation range in oxygen (when expressed in volume% with oxygen, 15.0 volume% or less), preferably less than the combustion range in oxygen (expressed in volume% with oxygen) In such a case, the concentration is preferably 4.5% by volume or less.
[0022]
As a 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 and a semiconductor element on these layers Means a base on which an oxide film is to be formed. Forming an oxide film on a semiconductor layer includes not only forming an oxide film on a semiconductor layer formed on or above a semiconductor substrate or the like, but also forming an oxide film on the surface of the semiconductor substrate. The silicon single crystal wafer may be a wafer produced by any method such as CZ method, MCZ method, DLCZ method, FZ method, etc., or may be pre-hydrogenated. The semiconductor layer may be made of Si—Ge.
[0023]
The oxide film forming method of the present invention includes, for example, gate oxide films of MOS transistors, formation of interlayer insulating films and element isolation regions, formation of gate oxide films of top gate type or bottom gate type thin film transistors, and tunnel oxide films of flash memories. The present invention can be applied to the formation of oxide films in various semiconductor devices.
[0024]
In the oxygen plasma generated by microwave discharge, the ground state O ₂ (X ^Three Σg ^- ) Is the excited state O due to the collision of electrons. ₂ (A ^Three Σu ⁺ ) Or O ₂ (B ^Three Σu ^- ) And dissociate into oxygen atoms as shown in the following equations.
[0025]
O ₂ (X ^Three Σg ^- ) + E → O ₂ (A ^Three Σu ⁺ ) + E Formula (1-1)
O ₂ (A ^Three Σu ⁺ ) + E → O ( ^Three P) + O ( ^Three P) + e Formula (1-2)
O ₂ (X ^Three Σg ^- ) + E → O ₂ (B ^Three Σu ^- ) + E Formula (1-3)
O ₂ (B ^Three Σu ^- ) + E → O ( ^Three P) + O ( ¹ D) + e Formula (1-4)
[0026]
Accordingly, excited oxygen molecules and oxygen atoms exist in the oxygen plasma, and these become reactive species. Hydrogen H here ₂ Is introduced, the following plasma is generated by microwave discharge.
[0027]
H ₂ + E → 2H Formula (2)
[0028]
In the oxygen plasma, for example, the oxygen plasma generated by the equation (1-2) and the hydrogen plasma generated by the equation (2) 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.
[0029]
2H + O ( ^Three P) → H ₂ O Formula (3)
[0030]
In the method of the present invention, since water vapor is generated based on such a reaction between oxygen plasma and hydrogen plasma, for example, water vapor can be generated easily and reliably even under reduced pressure, and the oxidation rate is reduced. A thin oxide film can be formed by a humidified oxidation method in a controlled state.
[0031]
On the other hand, nitrogen (N ₂ ) Nitrogen N when using gas ₂ Is excited in a microwave plasma, for example, as in the following equation. That is, electrons existing in the plasma are excited, and nitrogen molecules, nitrogen molecular ions, nitrogen atoms, and nitrogen atom ions excited by inelastic collisions with the nitrogen molecules are generated. These excited nitrogen molecules, nitrogen molecular ions, nitrogen atoms, nitrogen atom ions are bonds between oxygen atoms and atoms that mainly constitute the semiconductor layer on the surface of the oxide film (for example, atoms that mainly constitute the semiconductor layer In the case of Si, the Si—O bond is cut to form a nitrided oxide (for example, Si—O—N bond), and the surface of the oxide film is nitrided. The composition of the surface of the oxide film is such that when the atoms mainly constituting the semiconductor layer are Si, SiO _X N _Y It is represented by
[0032]
N ₂ (X ¹ Σg) + e → N ₂ (A ^Three Σu ⁺ ) + E Formula (4-1)
N ₂ (N ¹ Σg) + e → N ₂ (C ^Three Πu) + e Formula (4-2)
N ₂ (C ^Three Πu) + e → N ₂ (B ^Three Πg) + hν formula (4-3)
N ₂ (B ^Three Πg) + e → N ₂ (A ^Three Σu ⁺ ) + Hν formula (4-4)
[0033]
In the method of the present invention, an oxide film or a gate oxide film is formed on the basis of irradiating electromagnetic waves to hydrogen gas, oxygen gas, and nitrogen-based gas. Therefore, an oxide film is essentially formed in one oxide film forming apparatus. Alternatively, the gate oxide film can be formed, and the device configuration for forming the oxide film or the gate oxide film can be simplified. Further, since water vapor is generated by irradiating hydrogen gas and oxygen gas with electromagnetic waves, water vapor is easily and reliably generated even in a state where the oxidation rate is suppressed and controlled, that is, for example, under reduced pressure. And a thin oxide film can be formed by a humidified oxidation method. In addition, since the oxide film is formed by an oxidation method using water vapor, an oxide film having excellent dielectric breakdown (TDDB) characteristics can be obtained.
[0034]
In addition, since only the surface of the oxide film is nitrided, semiconductor element characteristics such as a decrease in current drive capability due to nitrogen intrusion into the silicon semiconductor substrate, such as introduction of nitrogen atoms into the gate oxide film by thermal nitridation There is no adverse effect on. Furthermore, since the oxide film is nitrided, for example, boron atoms pass through the gate oxide film and reach the silicon semiconductor substrate by various heat treatments in the semiconductor device manufacturing process after forming the gate electrode, and the threshold voltage of the PMOS semiconductor element is increased. It is possible to reliably avoid the phenomenon of fluctuation.
[0035]
In addition, after nitriding the surface of the oxide film, the oxide film or gate oxide film having a nitrided surface is heat-treated, so that the surface of the oxide film is nitrided by excited nitrogen molecules, nitrogen molecular ions, nitrogen atoms, or nitrogen atom ions. It is possible to recover or remove the defects of the oxide film generated during the process. Note that if step (a), step (b), and step (c) are performed in the same processing chamber, the apparatus configuration for forming the oxide film or the gate oxide film can be further simplified.
[0036]
【Example】
Hereinafter, the present invention will be described based on examples with reference to the drawings.
[0037]
Example 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. The oxide film forming apparatus includes a processing chamber 10, a stage 11 on which a semiconductor layer (a silicon semiconductor substrate 20 in the first embodiment) is placed, a magnet 13 disposed outside the processing chamber 10, and the processing chamber 10. A microwave waveguide 14 attached to the top of the processing chamber 10 and gas introducing portions 16A, 16B, 16C disposed on the top of the processing chamber 10. The processing chamber 10 includes a plasma generation region 10A and a reaction region 10B. In addition, a lamp which is a heating means 12 for heating the silicon semiconductor substrate 20 is housed in the stage 11. A magnetron 15 is attached to the microwave waveguide 14, and a microwave of 2.45 GHz is generated by the magnetron 15, and the microwave is introduced into the plasma generation region 10 </ b> A of the processing chamber 10 through the microwave waveguide 14. The Furthermore, hydrogen gas, oxygen gas, and nitrogen gas are introduced into the processing chamber 10 from each of the gas introduction portions 16A, 16B, and 16C. Further, an inert gas (for example, nitrogen gas) is introduced into the processing chamber 10 from the gas introduction part 17 disposed on the 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 the lower portion of the processing chamber 10.
[0038]
In Example 1, a silicon semiconductor substrate is used as the semiconductor layer, and nitrogen (N ₂ ) Gas was used. Further, the oxidation process, the nitriding process, and the heat treatment process 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 method for manufacturing a p-type semiconductor element (specifically, a p-channel MOSFET in a CMOSFET having a dual gate structure) will be described. Hereinafter, description will be given with reference to FIG. 2 which is a schematic partial sectional view of the silicon semiconductor substrate 20 and the like.
[0039]
[Step-100]
First, an element isolation region 21 having a LOCOS structure is formed by a known method on a silicon semiconductor substrate 20 which is a P-type silicon wafer (manufactured by the CZ method) having a diameter of 8 inches doped with boron, and then well ion implantation, Channel stop ion implantation and threshold adjustment ion implantation are performed. 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% hydrofluoric acid aqueous solution and pure water. The surface is exposed (see FIG. 2A).
[0040]
[Step-110]
Next, after the silicon semiconductor substrate 20 is carried into the oxide film forming apparatus shown in FIG. 1 from a door (not shown) and placed on the stage 11, an inert gas (for example, nitrogen gas) is supplied from the gas introduction unit 17 to the processing chamber. 10 is introduced. Then, the silicon semiconductor substrate 20 is heated to 800 ° C. by the heating means 12. Thereafter, hydrogen gas and oxygen gas are introduced into the processing chamber 10 from the gas introducing portion 16A and the gas introducing portion 16B while introducing an inert gas (for example, nitrogen gas) as a dilution gas from the gas introducing portion 17 into the processing chamber 10. Is introduced. At the same time, microwave power is supplied to the magnetron 15, and the 2.45 GHz microwave 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. Thus, that is, by irradiating the hydrogen gas and the oxygen gas with electromagnetic waves, the reactions of the above formulas (1-1) to (1-4) and the reactions of the formulas (2) and (3) occur. Water vapor is generated. The generated water vapor 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 means 12 is oxidized. Thus, an oxide film (a silicon oxide film in the first embodiment) can be formed on the surface of the semiconductor layer. The formation conditions of the oxide film are illustrated in Table 1 below.
[0041]
[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
[0042]
[Step-120]
After the formation of the oxide film is completed, the supply of microwave power to the magnetron 15 and the introduction of hydrogen gas and oxygen gas into the processing chamber 10 are stopped, and an inert gas is introduced into the processing chamber 10 from the gas introduction unit 17. Then, the silicon semiconductor substrate 20 is cooled to room temperature. Next, the introduction of the inert gas from the gas introduction unit 17 into the processing chamber 10 is stopped. Thereafter, nitrogen gas, which is a nitrogen-based gas, is introduced from the gas introduction unit 16 </ b> C into the processing chamber 10. At the same time, microwave power is supplied to the magnetron 15, and the 2.45 GHz microwave 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. Thus, that is, excited nitrogen molecules and nitrogen molecular ions generated in the reactions of the above-described formulas (4-1) to (4-4) by irradiating electromagnetic waves to nitrogen gas are below the processing chamber 10. Reaches the reaction region 10B located in the region, and the surface of the oxide film (specifically, the silicon oxide film) is nitrided. In this way, the oxide film 22 having a nitrided surface (in the first embodiment, a silicon oxide film and corresponding to a gate oxide film) can be formed on the surface of the semiconductor layer. This state is schematically shown in FIG. Here, the illustration of the nitrided portion of the oxide film is omitted in the figure. The nitriding conditions are illustrated in Table 2 below. The reason why the temperature of the silicon semiconductor substrate is set to room temperature is to suppress diffusion of nitrogen atoms into the silicon semiconductor substrate during nitriding.
[0043]
[Table 2]
Microwave power: 1kW
Microwave frequency: 2.45 GHz
Nitrogen gas flow rate: 0.4 SLM
Pressure: 0.16 Pa
Substrate temperature: Room temperature (25 ° C)
[0044]
[Step-130]
After completion of the nitriding process, the supply of microwave power to the magnetron 15 is stopped, and the silicon semiconductor substrate 20 is heated to 850 ° C. while continuing to introduce nitrogen gas into the processing chamber 10. Then, after performing heat treatment under the conditions illustrated in Table 3 below, the silicon semiconductor substrate 20 is cooled to room temperature while continuing to introduce nitrogen gas into the processing chamber 10.
[0045]
[Table 3]
Nitrogen gas flow rate: 4SLM
Substrate temperature: 850 ° C
[0046]
[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 impurities (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 the gate electrode for the p-channel MOSFET and phosphorus is introduced into the gate electrode for the 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 the p-channel MOSFET can be formed on the gate insulating film (FIG. 2C). reference). In addition, a gate electrode 23 made of a silicon layer (specifically, a polysilicon layer) containing an n-type impurity for an n-channel MOSFET can be formed on the gate insulating film.
[0047]
[Step-150]
Thereafter, an LDD region is formed using a known technique, an insulating film is then formed on the entire surface, and the insulating film is etched based on an anisotropic dry etching technique, and a sidewall 24 is formed on the side wall of the gate electrode 23. Form. Next, in order to form the source / drain region 25, boron is formed in the region of the silicon semiconductor substrate on which the p-channel MOSFET is to be formed, and silicon on which the n-channel MOSFET is to be formed, based on a known lithography technique and ion implantation technique After introducing phosphorus into each region of the semiconductor substrate, activation heat treatment is performed on the implanted impurities. Thereafter, an insulating layer 26 is formed on the entire surface by a CVD method, an opening is provided in the insulating layer 26 above the source / drain region 25, and a wiring material layer is formed on the insulating layer 26 including the opening by a sputtering method. The wiring 27 is formed by patterning the wiring material layer, and a p-type semiconductor element (more specifically, having a dual gate structure) shown in a schematic partial sectional view in FIG. A p-channel MOSFET in a CMOSFET) can be obtained.
[0048]
Note that after completing [Step-120], the semiconductor layer may be unloaded from the oxide film forming apparatus, and then the semiconductor layer may be loaded into a heat treatment apparatus schematically shown in FIG. This vertical batch-type heat treatment apparatus includes a quartz double tube structure processing chamber 30 held in a vertical direction, a gas introduction section 32 for introducing an inert gas into the processing chamber 30, a processing A gas exhaust unit 33 for exhausting gas from the chamber 30, a heater 34 for maintaining the inside of the processing chamber 30 at a predetermined atmospheric temperature via a cylindrical soaking tube 36 made of SiC, a substrate carry-in / out unit 40, The shutter 35 partitions the processing chamber 30 and the substrate loading / unloading section 40 and an elevator mechanism 41 for loading and unloading the silicon semiconductor substrate into and out of the processing chamber 30. A quartz boat 42 for mounting the silicon semiconductor substrate is attached to the elevator mechanism 41. The inert gas is introduced into the processing chamber 30 through the pipe 31, the gas flow path 31, and the gas introduction part 32. The gas flow path 31 corresponds to a space between the inner wall and the outer wall of the processing chamber 30 having a double tube structure.
[0049]
When performing heat treatment, a 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 place the quartz boat 42 in the processing chamber 30. After carrying in, the shutter 35 is closed. Then, while introducing an inert gas into the processing chamber 30 through the pipe 31, the gas flow path 31 and the gas introduction part 32, the heater 34 is operated to raise the temperature in the processing chamber 30 to a desired temperature, and heat treatment is performed. I do. After the heat treatment is completed, 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, the elevator mechanism 41 is operated, and the quartz boat 42 is carried out into the processing chamber 30. The silicon semiconductor substrate may be unloaded from the boat 42 and [Step-140] and subsequent steps may be executed.
[0050]
(Example 2)
Example 2 is a modification of the method for forming an oxide film and a method for manufacturing a p-type semiconductor element (specifically, a p-channel type MOSFET in a CMOSFET having a dual gate structure) in Example 1. The second embodiment is different from the first embodiment in that the surface of the semiconductor layer is cleaned before the formation of the oxide film, and then the semiconductor layer is not exposed to the atmosphere (that is, the oxide film is formed from the cleaning of the surface of the semiconductor layer, for example). The atmosphere until the start of the process is an inert gas atmosphere or a vacuum atmosphere), and the oxide film is formed.
[0051]
That is, after cleaning the surface of the semiconductor layer with 0.1% hydrofluoric acid aqueous solution and pure water in Example 1, the semiconductor layer was carried into the oxide film forming apparatus. On the other hand, in Example 2, the atmosphere from cleaning the surface of the semiconductor layer to carrying it into the oxide film forming apparatus is an inert gas (for example, nitrogen gas) atmosphere. For this purpose, as shown in the schematic diagram of FIG. 4, a cluster tool device composed of a surface cleaning device, an oxide film forming device, a conveyance path, a loader and an unloader is used, and from the surface cleaning device to the oxide film forming device. It can be achieved by a method in which the atmosphere in the processing chamber of the surface cleaning apparatus, the conveyance path, and the oxide film forming apparatus is made an inert gas atmosphere. The atmosphere in the surface cleaning apparatus and the atmosphere in the transport path before the start of the surface cleaning of the semiconductor layer or after the completion of the surface cleaning may be an inert gas atmosphere, for example, 1.3 × 10. ^-1 Pa (10 ^-3 A vacuum atmosphere of about Torr) may be used. 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, for example, 1.3 × 10. ^-1 Pa (10 ^-3 (Torr) degree vacuum atmosphere, and after the semiconductor layer is completely loaded, the atmosphere in the processing chamber 10 may be an inert gas (for example, nitrogen gas) atmosphere. Alternatively, for example, the atmosphere of the semiconductor layer surface cleaning apparatus is an inert gas atmosphere, and the semiconductor layer (for example, a silicon semiconductor substrate) is placed in a transport box filled with the inert gas. It can also be achieved by a method of carrying it into the oxide film forming apparatus.
[0052]
In Example 2, instead of performing surface cleaning of the semiconductor layer with a 0.1% hydrofluoric acid aqueous solution and pure water, a vapor phase cleaning method using anhydrous hydrogen fluoride gas under the conditions illustrated in Table 3 Then, the surface of the semiconductor layer was cleaned. Note that methanol is added to prevent the generation of particles. In some cases, the surface of the semiconductor layer may be cleaned by a vapor phase cleaning method using hydrogen chloride gas under the conditions exemplified in Table 4.
[0053]
[Table 3]
Anhydrous hydrogen fluoride gas: 300 SCCM
Methanol vapor: 80 SCCM
Nitrogen gas: 1000 SCCM
Pressure: 0.3 Pa
Temperature: 60 ° C
[0054]
[Table 4]
Hydrogen chloride gas / nitrogen gas: 1% by volume
Temperature: 800 ° C
[0055]
By adopting these methods, the surface of the semiconductor layer can be kept free from contamination before the oxide film is formed. As a result, moisture, organic matter, or, for example, Si—OH is contained in the formed oxide film. As a result, it is possible to effectively prevent deterioration of the characteristics of the formed oxide film or generation of a defective portion. Furthermore, by using a cluster tool device, the device installation area can be reduced.
[0056]
As mentioned above, although this invention was demonstrated based on the preferable Example, this invention is not limited to these Examples. The various conditions described in the embodiments and the structure of the oxide film forming apparatus are examples and can be changed as appropriate.
[0057]
In the embodiment, a silicon oxide film is formed exclusively on the surface of a silicon semiconductor substrate. However, based on the method for forming an oxide film of the present invention, a silicon oxide film is formed on an epitaxial silicon layer formed on the substrate. Alternatively, 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 the substrate. Alternatively, a silicon oxide film may be formed on the surface of the silicon layer in the SOI structure, or silicon on the surface of the substrate on which the semiconductor element or the component of the semiconductor element is formed, or the 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. Formation of an oxide film including nitriding treatment can be performed not only by a single wafer method but also by a batch method in which a plurality of semiconductor layers are processed simultaneously. 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. .
[0058]
As described above, in forming the oxide film, hydrogen gas and oxygen gas are introduced into the processing chamber 10. At this time, hydrogen gas flows into the processing chamber 10 and flows out of the system. In order to prevent the occurrence of a blast reaction and to prevent the formation of a dry oxide film in the semiconductor layer, for example, in [Step-120] of Example 1, the treatment is performed from the gas introduction unit 17. While introducing an inert gas (for example, nitrogen gas) as a dilution gas having a flow rate of 10 SLM into the chamber 10, for example, hydrogen gas having a flow rate of 0.2 SLM is introduced into the processing chamber 10 from the gas introduction unit 16 </ b> A. What is necessary is just to introduce | transduce oxygen gas of the flow volume of 10 SLM, for example in the process chamber 10 from the gas introduction part 16B. Next, microwave power is supplied to the magnetron 15, and the 2.45 GHz microwave 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 hydrogen gas concentration in the processing chamber 10 before the generation of water vapor becomes a sufficiently low value, and it is possible to reliably prevent the squeal gas reaction from occurring, and to ensure the formation of the dry oxide film. Can be prevented.
[0059]
【The invention's effect】
In the present invention, an oxide film or a gate oxide film can be formed essentially in one oxide film forming apparatus, and only one apparatus for forming an oxide film or a gate oxide film is required. The configuration can be simplified. Further, it becomes possible to easily and reliably generate water vapor in a state where the oxidation rate is suppressed and controlled, and a thin oxide film can be formed by a humidified oxidation method. In addition, since the oxide film is formed by an oxidation method using water vapor, an oxide film having excellent 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 semiconductor element characteristics such as a decrease in current driving capability. Furthermore, since the oxide film is nitrided, for example, the p-type impurity reaches the semiconductor layer through the gate oxide film by various heat treatments in the semiconductor device manufacturing process after forming the gate electrode. It is possible to reliably avoid the phenomenon of fluctuation. In addition, since heat treatment is performed after the nitriding treatment, defects in the oxide film generated 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 the method of the present invention.
2 is a schematic partial cross-sectional view of a silicon semiconductor substrate and the like for explaining a method of forming an oxide film of Example 1. FIG.
FIG. 3 is a schematic view of a heat treatment apparatus.
FIG. 4 is a schematic diagram of a cluster tool device.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... Processing chamber, 10A ... Plasma generation area, 10B ... Reaction area, 11 ... Stage, 12 ... Heating means, 13 ... Magnet, 14 ... Microwave waveguide, DESCRIPTION OF SYMBOLS 15 ... Magnetron, 16A, 16B, 16C, 17 ... Gas introduction part, 18 ... Gas exhaust part, 20 ... Silicon semiconductor substrate, 21 ... Element isolation region, 22 ... Oxide film (Gate oxide film), 23 ... gate electrode, 24 ... side wall, 25 ... source / drain region, 26 ... insulating layer, 27 ... wiring

Claims (8)

(A) a step of generating water vapor by irradiating electromagnetic waves to hydrogen gas and oxygen gas, oxidizing the surface of the semiconductor layer using the water vapor, and forming an oxide film on the surface of the semiconductor layer;
(B) nitriding the surface of the oxide film with excited nitrogen molecules, nitrogen molecular ions, nitrogen atoms or nitrogen atom ions generated by irradiating a nitrogen-based gas with electromagnetic waves;
(C) a step of heat-treating the oxide film having a nitrided surface;
Ri consists of,
A method for forming an oxide film, wherein the step (a) and the step (b) are performed in the same processing chamber.   2. The method for forming an oxide film according to claim 1, wherein the electromagnetic wave is a microwave.   2. The method for forming an oxide film according to claim 1, wherein the step (a), the step (b), and the step (c) are performed in the same processing chamber.   The method of forming an oxide film according to claim 1, wherein the heat treatment is performed at a temperature of 700 to 950 ° C. (A) forming a gate oxide film on the surface of the semiconductor layer;
(B) forming a gate electrode made of a silicon layer containing a p-type impurity on the gate oxide film;
A method of manufacturing a p-type semiconductor device comprising:
Step (A)
(A) a step of generating water vapor by irradiating electromagnetic waves to hydrogen gas and oxygen gas, oxidizing the surface of the semiconductor layer using the water vapor, and forming an oxide film on the surface of the semiconductor layer;
(B) A step of nitriding the surface of the oxide film with excited nitrogen molecules, nitrogen molecular ions, nitrogen atoms or nitrogen atom ions generated by irradiating a nitrogen-based gas with electromagnetic waves, thereby forming a gate oxide film When,
(C) a step of heat-treating the gate oxide film;
Ri consists of,
A method of manufacturing a p-type semiconductor element, wherein the step (a) and the step (b) are performed in the same processing chamber. The method of manufacturing a p-type semiconductor element according to claim 5 , wherein the electromagnetic wave is a microwave. 6. The method of manufacturing a p-type semiconductor element according to claim 5 , wherein the step (a), the step (b), and the step (c) are performed in the same processing chamber. The method of manufacturing a p-type semiconductor device according to claim 5 , wherein the heat treatment is performed at a temperature of 700 to 950 ° C.

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