JP2004266263A - Method for manufacturing semiconductor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent the formation of an interface which acts as a low dielectric layer and to obtain an insulating metal oxide film having a stoichiometric composition. <P>SOLUTION: A metal film 12 is deposited on a silicon substrate 1 under a non-oxidative atmosphere. Subsequently, the metal film 12 is oxidized with an oxygen radical 13 to form a metal oxide film 2 which acts as a gate insulation film. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

  The present invention relates to a method for manufacturing a semiconductor device having a gate insulating film made of a high dielectric material.

2. Description of the Related Art MOSFETs have been miniaturized along with recent technological developments for high integration and high speed in semiconductor devices. As the thickness of the gate insulating film is reduced with miniaturization, problems such as an increase in gate leak current due to a tunnel current become apparent. In order to suppress this problem, a thin oxide film (SiO ₂ film) is formed by using a metal oxide such as hafnium oxide (HfO ₂ ) or zirconium oxide (ZrO ₂ ), that is, a high dielectric constant material for the gate insulating film. A method of increasing the physical film thickness while realizing the equivalent film thickness EOT (Equivalent Oxide Thickness) has been studied. For example, Non-Patent Document 1 discloses a method using ZrO ₂ for a gate insulating film.
Yamaguchi, Satake, Chokai, Extended Abstracts of the 2000 International Conference on Solid State Devices and Materials, Japan, August 29, 2000, pp.228-229

However, it has been reported that in a gate insulating film using a metal oxide such as ZrO ₂ , an interface layer (for example, a silicate layer) is formed between the surface of a silicon substrate and a high-dielectric-constant gate insulating film. . Since the interface layer has a smaller dielectric constant than a metal oxide serving as a high dielectric constant material, the presence of the interface layer lowers the effective dielectric constant of the gate insulating film.

  As means for improving the effective dielectric constant and heat resistance of a gate insulating film made of a high dielectric material, a composite film using various metal oxide films and a gradient composition film have been proposed. However, due to interdiffusion at the time of deposition or oxidation of these metal oxide films, a film as designed is not necessarily obtained with respect to the thickness of the interface layer and the composition distribution in the thickness direction of the composite film and the like.

  In view of the above, it is a first object of the present invention to suppress formation of an interface layer serving as a low dielectric constant layer, to obtain an insulating metal oxide film having a stoichiometric composition, A second object is to obtain a composite metal oxide film having an interface layer thickness and a composition.

  In order to achieve each of the above objects, a method of manufacturing a semiconductor device according to the present invention includes the steps of: depositing a metal film on a silicon region in a non-oxidizing atmosphere; and oxidizing the metal film using oxygen radicals. Forming a metal oxide film to be a gate insulating film.

  According to the method for manufacturing a semiconductor device of the present invention, after previously depositing a metal to be a material for a high-k gate insulating film, an oxygen radical is used as an oxidizing species of the metal. Oxygen can be supplied to the metal in a highly oxidizing atmosphere. Therefore, the metal film can be oxidized while minimizing the oxidation of the silicon region such as the silicon substrate, so that the formation of the low dielectric constant interface layer can be suppressed, whereby the insulating metal oxide having the stoichiometric composition can be suppressed. A film, that is, a high-k gate insulating film can be formed.

  Further, according to the method of manufacturing a semiconductor device of the present invention, since the step of depositing the metal film and the step of oxidizing the metal film are separated from each other, the film deposition mechanism is not required as in the conventional step of forming a metal oxide film under a high temperature atmosphere. The oxidation process is not limited. Further, the oxidation process of the metal film is a relatively low-temperature process utilizing the reactivity of oxygen radicals. Therefore, even when depositing or oxidizing a composite film, a gradient composition film, or the like, it is possible to prevent interdiffusion between film constituent atoms and between the film constituent atoms and silicon atoms in the silicon region, A composite metal oxide film (or a gradient composition film) having a desired interface layer thickness and composition can be obtained.

  In the present application, the non-oxidizing atmosphere means an atmosphere that does not substantially contain oxygen (oxidizing species).

  In the method for manufacturing a semiconductor device of the present invention, oxygen radicals may be supplied by a plasma generator using an oxygen-containing gas or may be supplied by an ozone generator. When the latter ozone generator is used, oxygen radicals are supplied by the decomposition of the ozone generated from the ozone generator into oxygen radicals and oxygen molecules on the surface of the silicon region.

  In the method of manufacturing a semiconductor device according to the present invention, it is preferable that a region for oxidizing the metal film and a region for generating oxygen radicals are substantially separated.

  This can prevent oxygen ions generated together with oxygen radicals in, for example, remote plasma oxidation from entering a region where the metal film is oxidized.

  In the method of manufacturing a semiconductor device according to the present invention, it is preferable that the oxidation of the metal film is performed on a sample holder that is electrically kept at a floating potential.

  This can prevent or suppress oxygen ions from oxidizing the metal film in plasma oxidation or the like.

  In the method for manufacturing a semiconductor device of the present invention, the lower limit of the temperature at which the metal film is oxidized may be the lowest temperature at which the metal film can be oxidized by oxygen radicals. Specifically, the lower limit of the temperature at which a metal film such as an Hf film is oxidized is about 300 ° C.

  In the method for manufacturing a semiconductor device of the present invention, the upper limit of the temperature at which the metal film is oxidized may be the lowest temperature at which the oxidation of the metal film proceeds by oxygen atoms or oxygen molecules. Specifically, the upper limit of the temperature at which the metal film is oxidized is about 500 ° C.

  In the method for manufacturing a semiconductor device of the present invention, when oxidizing a metal film, by controlling the number of oxygen radicals flying to the metal film, or controlling the processing time or processing temperature by oxygen radicals, the metal oxide film and the silicon region The thickness of the interface layer formed at the interface may be controlled.

  This can improve the reliability of the gate insulating film or the carrier mobility.

  In the method of manufacturing a semiconductor device according to the present invention, the temperature of the silicon region when depositing the metal film is set to less than 300 ° C., and the energy per metal particle when the metal particles serving as the metal film fly into the silicon region. Is preferably 1 eV or less.

  This can prevent an interface layer from being formed between the silicon region and the metal film, and prevent damage to the silicon region due to implantation of metal particles.

  In the method of manufacturing a semiconductor device according to the present invention, when depositing a metal film, the thickness of the metal film is set such that the thickness of the metal oxide film formed by oxidizing the metal film is less than 3 nm. The effects of the invention are remarkably obtained.

  In the method of manufacturing a semiconductor device according to the present invention, when depositing a metal film, if the thickness of the metal film is set to less than 1.9 nm, the above-described effects of the present invention can be remarkably obtained.

  In the method for manufacturing a semiconductor device according to the present invention, when the element constituting the metal film is selected from the group consisting of hafnium, zirconium, titanium, tantalum, aluminum and silicon, the dielectric constant of the gate insulating film is reliably high. Become. In this case, when two or more elements constituting the metal film are selected from the above group, the gate insulating film can have improved heat resistance as well as dielectric constant. Further, the composition ratio of two or more elements selected from the above group in the metal film may be changed along the thickness direction of the metal film.

  In the method of manufacturing a semiconductor device of the present invention, when a metal nitride film is deposited on a silicon region instead of a metal film, the gate insulating film can have improved dielectric constant and heat resistance.

  In the method for manufacturing a semiconductor device of the present invention, when heat treatment is performed on the gate insulating film after forming the gate insulating film, the film quality of the gate insulating film can be improved. At this time, if the heat treatment is performed in an atmosphere that does not substantially contain oxygen, for example, an atmosphere made of an inert gas or a vacuum atmosphere, supply of oxygen to the interface layer can be prevented, thereby increasing the growth of the interface layer. Can be suppressed.

  In order to achieve each of the above objects, another method of manufacturing a semiconductor device according to the present invention includes the steps of: depositing a metal film on a silicon region in a non-oxidizing atmosphere; and oxidizing the metal film. Forming a metal oxide film serving as a gate insulating film by oxidizing the metal film using radicals that can be formed.

According to another method of manufacturing a semiconductor device according to the present invention, after a metal serving as a material for a high-k gate insulating film is previously deposited, the metal film is oxidized (or oxynitrided) to oxidize (oxidize) the metal. Nitrogen may be used), for example, oxygen radicals, NO radicals, N ₂ O radicals, or the like are used. By appropriately setting the treatment temperature, oxygen is supplied to the metal in a highly controllable oxidizing atmosphere. can do. Therefore, the metal film can be oxidized while minimizing the oxidation of the silicon region such as the silicon substrate, so that the formation of the low dielectric constant interface layer can be suppressed, whereby the insulating metal oxide having the stoichiometric composition can be suppressed. A film, that is, a high-k gate insulating film can be formed.

  Further, according to the method of manufacturing a semiconductor device of the present invention, since the step of depositing the metal film and the step of oxidizing the metal film are separated from each other, the film deposition mechanism is not required as in the conventional step of forming a metal oxide film under a high temperature atmosphere. The oxidation process is not limited. Further, the oxidation step of the metal film is a relatively low-temperature process utilizing the reactivity of radicals serving as oxidizing species. Therefore, even when depositing or oxidizing a composite film, a gradient composition film, or the like, it is possible to prevent interdiffusion between film constituent atoms and between the film constituent atoms and silicon atoms in the silicon region, A composite metal oxide film having a desired interface layer thickness and composition can be obtained.

  According to the present invention, the metal film can be oxidized while suppressing the oxidation of the silicon region as much as possible, so that the high-k gate insulating film can be formed while suppressing the formation of the low dielectric constant interface layer. Further, according to the present invention, since the deposition process of the metal film and the oxidation process of the metal film are separated and a relatively low-temperature oxidation process utilizing the reactivity of oxygen radicals is performed, a composite film, a gradient composition film, etc. Since interdiffusion can be prevented even during deposition or oxidation, a gate insulating film made of a composite metal oxide film having a desired interface layer thickness and composition can be realized.

(Comparative example)
Hereinafter, as a comparative example with respect to each embodiment of the present invention, a conventional method for forming a high dielectric constant gate insulating film made of a metal oxide will be described with reference to the drawings.

  FIG. 1 is a cross-sectional view showing one step of a method for forming a high dielectric constant gate insulating film according to a comparative example.

As shown in FIG. 1, first, a p-type silicon substrate 1 is introduced into a chamber of a film forming apparatus. Here, an apparatus based on a DC sputtering method is used as a film forming apparatus. Subsequently, a metal oxide film 2 is formed directly on the silicon substrate 1. As the metal oxide film 2, a metal oxide film made of hafnium oxide (HfO ₂ ) is formed.

In the formation of the metal oxide film 2 by sputtering, hafnium (Hf) metal is used as a target and discharge is caused inside the chamber by applying a DC voltage using an atmosphere composed of a mixed gas of Ar gas and O ₂ gas. . Thus, the metal oxide film 2 made of the HfO ₂ film is formed by the reactive sputtering. At this time, an HfO ₂ thin film of about 3 to 10 nm can be obtained by controlling the sputtering time.

However, in the step of forming the metal oxide film 2, as shown in FIG. 1 or 2 (a), the diffusion of silicon from the silicon substrate 1 and the diffusion of oxygen from the atmosphere cause An interface layer 3 of about 3 nm is formed between the film 2 and the HfO ₂ film. This interface layer 3 is considered to be a silicon oxide film-rich silicate layer.

  After that, for example, a tungsten (W) film is deposited on the metal oxide film 2 by a sputtering method, and then the W film is processed into the gate electrode 4 by a known lithography technique and a dry etching technique. Thereby, a capacitor structure can be obtained.

The capacitor characteristics (the relationship between the high-k film physical film thickness and the equivalent oxide film thickness) of a metal oxide thin film (high-k gate insulating film) having a thickness of 1.3 to 10 nm manufactured using this comparative example are shown. This is shown in the graph of FIG. In FIG. 3, the horizontal axis represents the physical thickness t _phy (nm) of the deposited high-k film, and the vertical axis represents the equivalent oxide thickness EOT (nm) obtained by CV measurement. Here, the slope in the graph of FIG. 3 corresponds to the reciprocal of the relative dielectric constant k of the high-k film. Therefore, it can be seen from FIG. 3A that k = 30. The intercept (y-intercept) of about 1.5 nm obtained by extrapolating the line shown in FIG. 3A to the vertical axis corresponds to the EOT value of the interface layer. That is, in consideration of the fact that the physical thickness of the interface layer is about 3 nm in this comparative example, it is understood that the relative dielectric constant of the interface layer is about 8 which is about twice that of the silicon oxide film. However, since the expected EOT value at the time of introducing the high-k gate insulating film is considered to be less than about 1.3 nm, it is necessary to minimize the formation of such an interface layer having a large EOT value.

  The reason why the thick interface layer is formed in the method of forming the gate insulating film of this comparative example is considered as follows. That is, since the reactivity of oxygen ions and oxygen atoms in the atmosphere gas is high, the surface of the silicon substrate is easily oxidized in the initial stage of deposition of the metal oxide film.

(1st Embodiment)
Hereinafter, a method for manufacturing a semiconductor device according to the first embodiment of the present invention, specifically, a method for forming a high dielectric constant gate insulating film made of a metal oxide will be described.

  FIGS. 4A to 4C show a method of forming a high dielectric constant gate insulating film according to the first embodiment, more specifically, a method of forming a gate insulating film made of a metal oxide film by oxidizing a metal film. It is sectional drawing which shows each process.

  First, the natural oxide film on the surface of the p-type silicon substrate 1 is removed with a hydrofluoric acid aqueous solution, thereby exposing a clean silicon surface. At this time, after cleaning the surface of the silicon substrate 1, the surface may be nitrided as necessary. Subsequently, the silicon substrate 1 is introduced into a chamber of a film forming apparatus (not shown). Here, as a film forming apparatus, an apparatus based on a PVD (physical vapor deposition) method, for example, a DC sputtering method is used. Specifically, as shown in FIG. 4A, a metal atom (for example, Hf atom) 11 is blown toward the silicon substrate 1 by a direct current sputtering method, and thereby a metal film (for example, Hf atom) is directly formed on the silicon substrate 1. For example, an Hf film 12 is formed. When a hafnium (Hf) metal film is formed as the metal film 12, for example, a hafnium metal is used as the target 10 and a non-oxidizing atmosphere is used to generate a discharge by applying a DC voltage inside the chamber. By doing so, an Hf metal film is formed by reactive sputtering. The non-oxidizing atmosphere used here, for example, an atmosphere composed of argon (Ar) gas as shown in FIG. 4A, does not substantially contain oxygen (oxidizing species). Further, by controlling the sputtering time, an Hf thin film (metal film 12) having a desired thickness can be obtained. Further, when the Hf thin film is formed at a substrate temperature equal to or lower than the crystallization temperature (about 600 ° C.), the Hf thin film becomes amorphous, and no columnar structure is observed in the sectional structure.

  In the deposition of the Hf film as the metal film 12, the temperature of the silicon substrate 1 and the energy of metal atoms are reduced in order to suppress the formation of a mixing layer at the interface between the Hf film and the silicon substrate 1 and the subsequent oxidation. I do. Specifically, it is desirable that the temperature of the silicon substrate 1 be lower than 300 ° C. Thus, the thickness of the mixing layer can be reduced, so that the interface layer generated by oxidizing the mixing layer can be reduced. When depositing an Hf film, the energy (particle energy) per metal atom (Hf atom) 11 flying on the silicon substrate 1 is small (specifically, it is 1 eV or less). More desirable. Thereby, damage to the silicon region due to the implantation of the metal particles can be prevented.

  Although the particle energy is basically large in the sputtering method used in the present embodiment, the particle energy can be reduced to about 1 eV by selecting a low vacuum region of about 400 Pa as an operating pressure (pressure inside the chamber). Can be suppressed. In this embodiment, the sputtering method is used. However, in order to reduce the particle energy, it is possible to realize the particle energy of about the heat energy. The vacuum evaporation method, the electron beam evaporation method, the laser evaporation method, or the CVD (chemical vapor) method. deposition) method can also be used.

Next, as shown in FIG. 4B, the surface of the metal film 12 made of Hf is exposed to an atmosphere mainly containing oxygen radicals 13 as oxidizing species. At this time, the atmosphere contains a considerable number of unactivated oxygen atoms (or oxygen molecules) 14. By oxidizing the metal film 12 in such an atmosphere, a metal oxide film (specifically, an HfO ₂ film) 2 having a stoichiometric composition becomes a gate insulating film from the metal film 12. It is formed. At this time, an interface layer 3 is formed between the silicon substrate 1 and the HfO ₂ film as the metal oxide film 2. The interface layer 3 is a silicon oxide film formed by oxidizing the surface of the silicon substrate 1, or a silicate containing a very small amount of Hf.

  Note that a plasma generator or an ozone generator can be used as a generator of the oxygen radicals 13. In the present embodiment, a remote plasma processing apparatus as shown in FIG. 5 can be used. Hereinafter, the oxidation treatment of the metal film surface by this apparatus will be described.

First, as shown in FIG. 5, a silicon substrate (silicon wafer) 1 is introduced into a chamber 51 of a remote plasma processing apparatus 50, and is placed on a substrate holder 52. Next, a gas containing oxygen, for example, an O ₂ gas or an N ₂ O gas is introduced from a cylinder 54 into a radical generation chamber 53 provided above the chamber 51, and RF power is applied to generate radicals. A plasma 55 containing oxygen is generated in the chamber 53. Note that a high-frequency power supply 56 is connected to the radical generation chamber 53 via a matcher 57 for applying RF power. The chamber 51 and the radical generation chamber 53 are connected by a plurality of connection holes.

  At the time of generation of the plasma 55, it is necessary to confine spatially or electrically oxygen ions in the radical generation chamber 53 so that the silicon wafer 1 is not directly exposed to the plasma 55 in the radical generation chamber 53. It is. Therefore, in the present embodiment, the silicon wafer 1 is prevented from being directly exposed to the plasma 55 by maintaining the substrate holder 52 at the floating potential without applying the bias power. As a result, the oxidizing species reaching the silicon wafer 1 can be changed to oxygen atoms (molecules) 14 and oxygen radicals 13 instead of oxygen ions. As a specific method of realizing the radical generation chamber 53, an ozone generator can be used in addition to various plasma generators. When the latter ozone generator is used, ozone generated from the ozone generator is decomposed into oxygen radicals and oxygen molecules on the surface of the silicon region, so that oxygen radicals are supplied.

As described above, for example, the Hf metal film is oxidized using a remote plasma processing apparatus or an ozone generator using a gas containing O ₂ or N ₂ O, so that the Hf metal film is mainly treated. Oxidation treatment using oxygen radicals can be performed. Oxygen radicals have higher chemical reactivity than oxygen atoms (molecules), but have lower kinetic energy to enter the metal film than oxygen ions.

Now, in order to obtain a HfO ₂ film which is a metal oxide film by oxidizing the Hf metal film using oxygen atoms (molecules), a heat treatment in an oxidizing atmosphere of several hundred ° C. or more is required. However, in this case, supply of oxygen not only to the Hf metal film but also to the silicon substrate surface is unavoidable, so that an interface layer having a low dielectric constant is formed between the silicon substrate and the Hf metal film. When such an interface layer is formed, the dielectric constant of the entire high-k gate insulating film decreases as shown in FIG. 3A (that is, EOT increases). In addition, as a result of crystallization of the metal oxide film at the same time as oxidation of the metal film due to the high-temperature heat treatment, the degree of leakage current via the crystal grain boundaries becomes serious.

  On the other hand, when oxygen ions are used, the metal film can be oxidized even when the processing temperature of the silicon substrate is about 300 ° C. or less. Thus, crystallization of the metal oxide film can be suppressed. Further, by controlling the energy of oxygen ions, it is possible to suppress and control the formation of the interface layer. However, if the thickness of the metal film to be oxidized becomes about 1 nm, or if the thickness of the oxidized metal oxide film becomes 3 nm or less, it is not impossible in principle. In addition, since it becomes difficult to completely control low energy ions corresponding to an extremely thin film thickness, it becomes difficult to suppress the formation of an interface layer.

  On the other hand, when oxygen radicals are used, a process window different from oxygen atoms (molecules) and oxygen ions exists by using both the chemical reactivity and the thermal diffusion effect at a relatively low temperature. Hereinafter, this will be described with reference to FIGS. 6 and 7.

The graph in FIG. 6A shows the dependence of the rate of increase in the thickness of the Hf metal film after oxidation on the processing temperature when the oxidation treatment of the Hf metal film is performed for a certain period of time (120 seconds) using oxygen radicals. Is shown. For reference, the graph of FIG. 6B shows the Hf metal film after the oxidation of the Hf metal film in the case where the oxidation treatment was performed on the Hf metal film using oxygen atoms (oxygen molecules) for a certain period of time (120 seconds). This shows the dependence of the film thickness increase rate on the processing temperature. Here, the film thickness increase rate is a ratio t / t ₀ of the thickness t of the Hf metal film (Hf oxide film) after oxidation to the thickness t ₀ of the Hf metal film before oxidation. When the Hf metal film is oxidized to form a HfO ₂ film having a stoichiometric composition, t / t ₀ is about 1.6. Therefore, if the thickness of the Hf metal film is increased to an extent that t / t ₀ exceeds 1.6 due to oxidation of the Hf metal film, it can be considered that an interface layer has been formed.

  As can be seen from FIG. 6, when the temperature of the oxidation treatment using oxygen radicals is as low as about 300 ° C., as in the case where oxygen atoms (oxygen molecules) are used, an increase in the film thickness indicating oxidation of the Hf metal film. Can not be seen. Conversely, when the temperature of the oxidation treatment using oxygen radicals is as high as about 500 ° C., the oxidation reaction is completely controlled by thermal diffusion, as in the case of using oxygen atoms (oxygen molecules). Interfacial layer formation cannot be avoided. That is, the advantage of using oxygen radicals is found in the intermediate temperature range (300 to 500 ° C.) between these temperatures. In other words, when oxygen atoms (oxygen molecules) are used in this temperature range, no oxidation reaction of the Hf metal film is observed, whereas when oxygen radicals are used in this temperature range, the Hf metal film is not oxidized. An increase in the film thickness due to the oxidation reaction is observed. In this case, it is considered that the chemical reaction of oxygen radicals and the thermal diffusion effect due to the heating of the substrate were combined, and a unique oxidation reaction mechanism worked.

FIG. 7 shows the respective oxide film equivalent film thickness EOT and leak current density Jg of a HfO ₂ film obtained by performing an oxidation treatment at 400 ° C. using oxygen radicals on a 3 nm-thick Hf metal film. This shows the dependence on the processing time (irradiation time of oxygen radicals). Here, since the oxidation of the metal film depends not only on the supply amount of oxygen radicals but also on the thermal diffusion phenomenon, the metal film is completely oxidized and has a stable composition (stoichiometric composition). Until the film is formed, as shown in FIG. 7, a certain processing time is required according to the thickness of the metal film, the oxidation temperature and the like.

  As described above, in the oxidation of a metal film using oxygen radicals, oxygen atoms (oxygen molecules) and oxygen ions are used because the chemical reactivity of oxygen radicals and the thermal diffusion effect at a relatively low temperature can be used together. It can have a different process window than the oxidation of the metal film.

Further, in the oxidation treatment method using oxygen radicals of this embodiment, the thickness of the metal oxide film (specifically, the HfO ₂ film) is 3 nm because the formation of the interface layer has a serious effect on the oxide film equivalent thickness EOT. In the region where the thickness is less than 1.9 nm, in other words, in the region where the thickness of the metal film before the oxidation treatment is less than 1.9 nm, there is a particular advantage over the prior art such as the comparative example.

  Further, also in the present embodiment, in order to prevent the supply of oxygen to the interface layer 3 formed between the silicon substrate 1 and the Hf metal film 12 while oxidizing the Hf metal film 12, the Hf metal to be oxidized is used. It is necessary to control the processing time according to the film thickness of the film 12, the processing temperature, and the like. Here, a metal oxide film (high-k) manufactured by performing a uniform oxidation treatment on the Hf metal film having various thicknesses (1 to 6 nm) based on the present embodiment at a processing temperature of 400 ° C. and a processing time of 120 sec. The characteristics of the capacitor (the relationship between the high-k film physical film thickness and the equivalent oxide film thickness EOT) in the gate insulating film) are shown in the graph of FIG.

In the present embodiment, after the oxidation treatment of the metal film 12 shown in FIG. 4B, that is, the step of forming the metal oxide film 2 serving as the high-k gate insulating film, the electrical characteristics of the metal oxide film 2 are changed. In order to sufficiently improve the film quality, as shown in FIG. 4C, annealing after the oxidation treatment is performed as a post-processing step. Specifically, in order to improve the non-equilibrium in the oxidation treatment, that is, to improve the bonding property and uniformity between oxygen atoms and Hf metal atoms, annealing after the oxidation treatment is performed as a post-treatment step. At this time, the heat treatment is performed in an atmosphere containing substantially no oxygen (oxidizing species), for example, in an atmosphere of nitrogen (N ₂ ) as shown in FIG. 4C, or in an atmosphere of an inert gas such as argon. By doing so, it is possible to avoid supply of oxygen to the interface layer 3 and thereby suppress an increase in the thickness of the interface layer 3. Further, a vacuum atmosphere may be used as the atmosphere that does not substantially contain oxygen.

  As described above, according to this embodiment, after the metal (Hf metal) serving as the material of the high-k gate insulating film is deposited in advance, and the oxygen radical 13 is used as the oxidizing species of the metal, the processing temperature is appropriately set. , Oxygen can be supplied to the metal in an oxidizing atmosphere with high controllability. Therefore, since the metal film 12 can be oxidized while suppressing the oxidation of the silicon substrate 1 as much as possible, the formation of the interface layer 3 having a low dielectric constant can be suppressed, whereby the insulating metal having a stoichiometric composition can be suppressed. The oxide film 2, that is, a high-k gate insulating film can be formed.

Specifically, when the HfO ₂ film (metal oxide film 2) is formed by sputtering in an oxidizing atmosphere at a temperature of several hundred degrees Celsius or more in the comparative example, as shown in FIG. On the other hand, in the present embodiment, as shown in FIG. 2B, the thickness of the interface layer 3 is reduced, and as a result, excellent electrical characteristics as shown in FIG. 3B are obtained. be able to. Specifically, from FIG. 3B, the contribution of the interface layer to EOT in this embodiment using oxygen radicals is about 0.4 nm, which is suppressed by about 1 nm as compared with the comparative example. You can see that.

  As described above, in the present embodiment, the details such as the degree of optimization are unknown, but a unique oxidation reaction mechanism works due to the combination of the chemical reactivity of oxygen radicals and the heat diffusion effect by substrate heating. It is considered that the formation of the interface layer can be suppressed to the maximum. Further, in the oxidation treatment method using oxygen radicals of the present embodiment, in the region where the thickness of the metal oxide film is less than 3 nm, that is, before the oxidation treatment, the formation of the interface layer seriously affects the equivalent oxide thickness EOT. In the region where the thickness of the metal film is less than 1.9 nm, it is particularly superior to the prior art such as the comparative example.

  In addition, the oxidation treatment using oxygen radicals of the present embodiment is not directly affected by plasma distribution or the like in terms of film uniformity as compared with the oxidation treatment using oxygen ions (for example, oxygen ions And is not affected by ion bombardment in terms of film quality.

  Further, according to the present embodiment, since the deposition process of the metal film 12 and the oxidation process of the metal film 12 are separated, the oxidation process is not included in the film deposition mechanism as in the conventional metal oxide film formation process under a high temperature atmosphere. There is no limit. Further, the step of oxidizing the metal film 12 is a relatively low temperature process utilizing the reactivity of the oxygen radicals 13. Therefore, even when depositing or oxidizing a composite film or a gradient composition film, etc., it is possible to prevent interdiffusion between film constituent atoms and between the film constituent atoms and silicon atoms in the silicon substrate. A composite metal oxide film having a desired interface layer thickness and composition can be obtained.

  In the first embodiment, the silicon region where the higk-k gate insulating film is formed is not limited to the silicon substrate 1 and may be a silicon film or a substrate or a film mainly made of silicon. Is also good.

  Further, in the first embodiment, the metal film 12 made of Hf is formed directly on the surface of the silicon substrate 1. Alternatively, the metal film 12 may be formed on the surface of the silicon substrate 1 before forming the metal film 12. A nitriding treatment (pretreatment) may be performed. Thereby, the formation of the interface layer can be further suppressed.

  In the first embodiment, the material of the metal film 12 has been described using Hf as an example. However, the material is not limited to Hf, and may be zirconium, titanium, tantalum, aluminum, or another metal (for example, La or the like selected from the group of rare earth metals). ) May be used. By doing so, the dielectric constant of the metal oxide film (that is, the high-k gate insulating film) formed by oxidizing the metal film increases. Further, as an element constituting the metal film 12, two or more elements are selected from hafnium, zirconium, titanium, tantalum, aluminum and other metals (for example, La selected from the group of rare earth metals) and silicon. Is also good. This makes it possible to improve the heat resistance as well as the dielectric constant of the high-k gate insulating film. At this time, the composition ratio of the selected two or more elements in the metal film may be changed along the thickness direction of the metal film.

  In the first embodiment, the lower limit of the temperature at which the metal film 12 is oxidized may be the lowest temperature at which the metal film 12 can be oxidized by the oxygen radicals 13. Specifically, when the metal film 12 is Hf metal or the like, the lower limit of the temperature is 300 ° C.

  In the first embodiment, the upper limit of the temperature at which the metal film 12 is oxidized may be the lowest temperature at which the oxidation of the metal film 12 proceeds by oxygen atoms or oxygen molecules. Specifically, when the metal film 12 is Hf metal or the like, the upper limit of the temperature is 500 ° C.

In the first embodiment, an oxygen radical is used as a radical serving as an oxidizing species of the metal film 12, but another radical such as a NO radical or an N ₂ O radical may be used instead.

  In the first embodiment, after the step of forming the metal oxide film 2 shown in FIG. 4B, another metal film is formed on the metal oxide film 2 in an atmosphere containing substantially no oxygen. The method may include a step of depositing and a step of forming another metal oxide film to be a gate insulating film by oxidizing the other metal film in an atmosphere containing oxygen. In other words, the deposition of the thin metal film and the oxidation of the metal film may be repeatedly performed. In this case, since the metal film is completely oxidized, it becomes easy to obtain a metal oxide film having a stoichiometric composition.

  In the first embodiment, the metal oxide film 2, that is, the gate insulating film has been described as an example of the application of the high-k film. Needless to say, it may be used for

(Second embodiment)
Hereinafter, a method for manufacturing a semiconductor device according to the second embodiment of the present invention, specifically, a method for forming a high dielectric constant gate insulating film made of a metal oxide will be described. The feature of the present embodiment is that an oxynitride film of various metals, which has been proposed as a means for improving the heat resistance in addition to the effective dielectric constant, is used for the high dielectric material constituting the gate insulating film. . Specifically, a method for obtaining a high dielectric material, that is, a metal oxynitride film for a gate insulating film by performing an oxidation treatment on a metal nitride film using oxygen radicals will be described.

  FIGS. 8A to 8C are cross-sectional views showing each step of a method for forming a high dielectric constant gate insulating film according to the second embodiment.

First, the natural oxide film on the surface of the p-type silicon substrate 1 is removed with a hydrofluoric acid aqueous solution, thereby exposing a clean silicon surface. At this time, after cleaning the surface of the silicon substrate 1, the surface may be nitrided as necessary. Subsequently, the silicon substrate 1 is introduced into a chamber of a film forming apparatus (not shown). Here, an apparatus based on a PVD method, for example, a DC sputtering method is used as a film forming apparatus. Specifically, as shown in FIG. 8A, metal atoms (for example, Hf atoms) 11 and nitrogen atoms 16 are blown toward the silicon substrate 1 by a direct current sputtering method, and thereby, are directly formed on the silicon substrate 1. Then, a metal nitride film (for example, a HfN (hafnium nitride) film) 17 is formed. When, for example, an HfN metal nitride film is formed as the metal nitride film 17, inside the chamber, a hafnium metal is used as the target 10 and a non-oxidizing atmosphere composed of Ar gas and nitrogen (N ₂ ) gas (FIG. 8A). ) To generate a discharge when a DC voltage is applied. By doing so, an HfN metal nitride film is formed by reactive sputtering.

  That is, the present embodiment is different from the first embodiment (see FIGS. 4A to 4C) in that an HfN metal nitride film 17 is formed on the silicon substrate 1 instead of the Hf metal film 12. That is the point.

  Next, as shown in FIG. 8B, the surface of the metal nitride film 17 made of HfN is exposed to an atmosphere mainly containing oxygen radicals 13 as oxidizing species. At this time, the atmosphere contains a considerable number of unactivated oxygen atoms (or oxygen molecules) 14. By oxidizing the metal nitride film 17 in such an atmosphere, a metal oxynitride film (specifically, an HfON film) 18 serving as a gate insulating film is formed from the metal nitride film 17. At this time, the interface layer 3 is formed between the silicon substrate 1 and the HfON film which is the metal oxynitride film 18. The interface layer 3 is a silicon oxide film formed by oxidizing the surface of the silicon substrate 1 or a silicate containing very small amounts of Hf and N.

In this embodiment, a remote plasma processing apparatus as shown in FIG. 5 is used as the oxygen radical 13 generator, as in the first embodiment. Specifically, the silicon substrate (silicon wafer) 1 is introduced into the chamber 51 of the remote plasma processing apparatus 50, and is set on the substrate holder 52. Next, a gas containing oxygen, for example, an O ₂ gas or an N ₂ O gas is introduced from a cylinder 54 into a radical generation chamber 53 provided above the chamber 51, and RF power is applied to generate radicals. A plasma 55 containing oxygen is generated in the chamber 53. Here, by keeping the substrate holder 52 at the floating potential, the oxidizing species reaching the silicon wafer 1 can be oxygen atoms (molecules) 14 and oxygen radicals 13 excluding oxygen ions. By maintaining the substrate temperature at 400 ° C., the oxidation treatment mainly by oxygen radicals can be performed on the metal nitride film 17 made of HfN. That is, the HfON metal oxynitride film 18 can be formed by injecting oxygen into the HfN metal nitride film 17.

  Next, after the HfON metal oxynitride film 18, that is, the high-k gate insulating film, is formed, as shown in FIG. Heat treatment is performed as a processing step. In the heat treatment after the formation of the HfON film, in an atmosphere containing substantially no oxygen (oxidizing species), for example, in an atmosphere of nitrogen as shown in FIG. 8C, or in an atmosphere of an inert gas such as argon. By performing the heat treatment in, the supply of oxygen to the interface layer 3 can be avoided, and thereby the increase in the thickness of the interface layer 3 can be suppressed. By this heat treatment, oxygen can be evenly distributed in the HfN metal nitride film to which oxygen has been supplied, whereby the composition of the HfON metal oxynitride film 18 can be made stoichiometric.

  As described above, according to the present embodiment, after the metal nitride (HfN) serving as the material of the high-k gate insulating film is previously deposited, and the oxygen radical 13 is used as the oxidizing species of the metal nitride, the processing temperature is reduced. With appropriate settings, oxygen can be supplied to the metal nitride in an oxidizing atmosphere with high controllability. Therefore, the metal nitride film 17 can be oxidized while suppressing the oxidation of the silicon substrate 1 as much as possible, so that the formation of the interface layer 3 having a low dielectric constant can be suppressed. The metal oxynitride film 18, that is, the high-k gate insulating film can be formed.

  In addition, the oxidation treatment using oxygen radicals of the present embodiment is not directly affected by plasma distribution or the like in terms of film uniformity as compared with the oxidation treatment using oxygen ions (for example, oxygen ions And is not affected by ion bombardment in terms of film quality.

  Further, according to the present embodiment, since the deposition process of the metal nitride film 17 and the oxidation process of the metal nitride film 17 are separated, the oxidation process is performed by the film deposition mechanism as in the conventional metal oxide film formation process under a high temperature atmosphere. The process is not limited. Further, the oxidation step of the metal nitride film 17 is a relatively low temperature process utilizing the reactivity of the oxygen radicals 13. Therefore, even when depositing or oxidizing a composite film or a gradient composition film, etc., it is possible to prevent interdiffusion between film constituent atoms and between the film constituent atoms and silicon atoms in the silicon substrate. A composite metal oxynitride film having a desired interface layer thickness and composition can be obtained.

  Further, according to the present embodiment, instead of forming the metal oxide film 2 serving as the gate insulating film by oxidizing the metal film 12 as in the first embodiment, the metal nitride film 17 is oxidized to form the gate insulating film. A metal oxynitride film 18 serving as a film is formed. For this reason, in the gate insulating film, the heat resistance as well as the dielectric constant can be improved.

  In the second embodiment, the silicon region where the higk-k gate insulating film is formed is not limited to the silicon substrate 1 and may be a silicon film or a substrate or film mainly made of silicon. Is also good.

  Further, in the second embodiment, the metal nitride film 17 made of HfN is formed directly on the surface of the silicon substrate 1, but instead, the metal nitride film 17 is formed on the surface of the silicon substrate 1 before the metal nitride film 17 is formed. On the other hand, a nitriding treatment (pretreatment) may be performed. Thereby, the formation of the interface layer can be further suppressed.

  Further, in the second embodiment, the description has been given by taking the nitride of Hf as an example of the material of the metal nitride film 17. However, the material is not limited thereto, and zirconium, titanium, tantalum, aluminum or other metals (for example, from the group of rare earth metals). A nitride of selected La or the like may be used. By doing so, the dielectric constant of the metal oxynitride film (that is, the high-k gate insulating film) formed by oxidizing the metal nitride film increases. Further, as the elements (other than nitrogen) constituting the metal nitride film 17, two or more kinds of hafnium, zirconium, titanium, tantalum, aluminum and other metals (for example, La selected from the group of rare earth metals) and silicon are used. Elements may be selected. By doing so, the heat resistance as well as the dielectric constant of the high-k gate insulating film can be further improved. At this time, the composition ratio of the selected two or more elements in the metal nitride film may be changed along the thickness direction of the metal nitride film.

  In the second embodiment, the lower limit of the temperature at which the metal nitride film 17 is oxidized may be the lowest temperature at which the metal nitride film 17 can be oxidized by the oxygen radicals 13 (for example, 300 ° C.).

  In the second embodiment, the upper limit of the temperature at which the metal nitride film 17 is oxidized may be the lowest temperature (for example, 500 ° C.) at which the oxidation of the metal nitride film 17 proceeds by oxygen atoms or oxygen molecules. .

Further, in the second embodiment, oxygen radicals are used as radicals that become oxidizing species of the metal nitride film 17, but other radicals such as NO radicals or N ₂ O radicals may be used instead.

  In the second embodiment, after the step of forming the metal oxynitride film 18 shown in FIG. 8B, another metal is deposited on the metal oxynitride film 18 in an atmosphere substantially free of oxygen. A step of depositing a nitride film (may be a metal film; the same applies hereinafter) and a step of forming another metal oxynitride film to be a gate insulating film by oxidizing the other metal nitride film in an atmosphere containing oxygen May be provided. In other words, the deposition of the thin metal nitride film and the oxidation of the metal nitride film may be repeatedly performed. In this case, since the metal nitride film is completely oxidized, it becomes easy to obtain a metal oxynitride film having a stoichiometric composition.

  In the second embodiment, the metal oxynitride film 18, that is, the gate insulating film has been described as an example of the use of the high-k film. Needless to say, it may be used for a film.

(Third embodiment)
Hereinafter, a method for manufacturing a semiconductor device according to the third embodiment of the present invention, specifically, a method for forming a high dielectric constant gate insulating film made of a metal oxide will be described. The feature of this embodiment is that a composite metal oxide made of various high dielectric materials has been proposed as a means for improving the effective dielectric constant and the heat resistance of the high dielectric material constituting the gate insulating film. The use of a membrane. Specifically, a method for obtaining a high dielectric material, that is, a composite metal oxide film for a gate insulating film by performing an oxidation treatment on the composite metal film using oxygen radicals will be described.

  FIGS. 9A to 9C are cross-sectional views illustrating respective steps of a method for forming a high dielectric constant gate insulating film according to the third embodiment.

  First, the natural oxide film on the surface of the p-type silicon substrate 1 is removed with a hydrofluoric acid aqueous solution, thereby exposing a clean silicon surface. At this time, after cleaning the surface of the silicon substrate 1, the surface may be nitrided as necessary. Subsequently, the silicon substrate 1 is introduced into a chamber of a film forming apparatus (not shown). Here, an apparatus based on a PVD method, for example, a co-sputtering method is used as a film forming apparatus. Specifically, as shown in FIG. 9A, metal atoms (for example, Hf atoms) 11 and additional atoms 20 (for example, silicon (Si) or aluminum (Al) are formed by a co-sputtering method using a plurality of targets 10 and 19. )) Simultaneously or alternately toward the silicon substrate 1, whereby a composite metal film having a desired composition (for example, an HfSi composite metal film of Hf and Si, or Hf and Al) is directly formed on the silicon substrate 1. HfAl composite metal film) 21 is formed. When, for example, an HfSi composite metal film is formed as the composite metal film 21, a target 10 made of hafnium metal and another target 19 made of silicon as an additive element are each placed in a non-oxidizing atmosphere made of Ar gas inside the chamber. (See FIG. 9 (a).) The discharge is caused by the application of a DC voltage. By doing so, an HfSi composite metal film is formed by reactive sputtering.

  In the step shown in FIG. 9A, the input power to each of the targets 10 and 19 and the discharge time are modulated, so that, in addition to the composite composition, the gradient composition (the composition ratio of each element in the metal film is reduced). A composite metal film (eg, HfSi or HfAl) having a composition that changes along the thickness direction can be obtained.

  In the step shown in FIG. 9A, an alloy target (for example, a target made of HfSi or HfAl) may be used instead of the targets 10 and 19.

  As described above, the present embodiment is different from the first embodiment (see FIGS. 4A to 4C) in that, instead of the Hf metal film 12 on the silicon substrate 1, for example, HfSi or HfAl This is the point that the composite metal film 21 made of the metal is formed.

Next, as shown in FIG. 9B, the surface of the composite metal film 21 made of HfSi or HfAl is exposed to an atmosphere mainly containing oxygen radicals 13 as oxidizing species. At this time, the atmosphere contains a considerable number of unactivated oxygen atoms (or oxygen molecules) 14. By performing an oxidation treatment on the composite metal film 21 in such an atmosphere, a composite metal oxide film (specifically, an HfSiO ₂ film or an HfAlO ₂ film) 22 serving as a gate insulating film is formed from the composite metal film 21. It is formed. At this time, the interface layer 3 is formed between the silicon substrate 1 and the composite metal oxide film 22. The interface layer 3 is a silicon oxide film formed by oxidizing the surface of the silicon substrate 1.

In this embodiment, a remote plasma processing apparatus as shown in FIG. 5 is used as the oxygen radical 13 generator, as in the first embodiment. Specifically, the silicon substrate (silicon wafer) 1 is introduced into the chamber 51 of the remote plasma processing apparatus 50, and is set on the substrate holder 52. Next, a gas containing oxygen, for example, an O ₂ gas or an N ₂ O gas is introduced from a cylinder 54 into a radical generation chamber 53 provided above the chamber 51, and RF power is applied to generate radicals. A plasma 55 containing oxygen is generated in the chamber 53. Here, by keeping the substrate holder 52 at the floating potential, the oxidizing species reaching the silicon wafer 1 can be oxygen atoms (molecules) 14 and oxygen radicals 13 excluding oxygen ions. Further, by maintaining the substrate temperature at 400 ° C., the oxidation treatment mainly by oxygen radicals can be performed on the composite metal film 21 made of HfSi or HfAl. That is, by injecting oxygen into the composite metal film 21, a composite metal oxide film 22 such as an HfSiO ₂ film or an HfAlO ₂ film can be formed.

  Next, after forming the composite metal oxide film 22, that is, the high-k gate insulating film, in order to sufficiently improve the film quality such as the electrical characteristics of the composite metal oxide film 22, as shown in FIG. Heat treatment is performed as a process. In the heat treatment after the formation of the composite metal oxide film 22, an atmosphere substantially free of oxygen (oxidizing species), for example, an atmosphere of nitrogen as shown in FIG. 9C, or an inert gas such as argon By performing the heat treatment in an atmosphere consisting of, supply of oxygen to the interface layer 3 can be avoided, thereby suppressing an increase in the thickness of the interface layer 3. By this heat treatment, oxygen can be evenly distributed in the composite metal film to which oxygen has been supplied, whereby the composition of the composite metal oxide film 22 can be made stoichiometric.

  As described above, according to the present embodiment, after the composite metal (HfSi or HfAl) serving as the material of the high-k gate insulating film is previously deposited, the oxygen radical 13 is used as the oxidizing species of the composite metal. By setting the temperature appropriately, oxygen can be supplied to the composite metal in an oxidizing atmosphere with high controllability. Accordingly, the composite metal film 21 can be oxidized while suppressing the oxidation of the silicon substrate 1 as much as possible, so that the formation of the interface layer 3 having a low dielectric constant can be suppressed. The composite metal oxide film 22, that is, the high-k gate insulating film can be formed.

  In addition, the oxidation treatment using oxygen radicals of the present embodiment is not directly affected by plasma distribution or the like in terms of film uniformity as compared with the oxidation treatment using oxygen ions (for example, oxygen ions And is not affected by ion bombardment in terms of film quality.

  Furthermore, a composite film using various metal oxide films, which has been conventionally proposed as a means for improving heat resistance in addition to an effective dielectric constant, for a high dielectric material constituting a gate insulating film, When a gradient composition film was used, a film as designed was not always obtained due to mutual diffusion during deposition or oxidation of these metal oxide films.

  On the other hand, according to the present embodiment, the step of depositing the composite metal film 21 and the step of oxidizing the composite metal film 21 are separated, so that the film deposition mechanism is different from the conventional step of forming a metal oxide film in a high-temperature atmosphere. The oxidation process is not limited. Further, the step of oxidizing the composite metal film 21 is a relatively low temperature process utilizing the reactivity of the oxygen radicals 13. Therefore, even when depositing or oxidizing the composite metal film 21 (or the gradient composition film), mutual diffusion between film constituting atoms and between the film constituting atoms and silicon atoms in the silicon substrate are prevented. Therefore, a composite metal oxide film 22 having a desired interface layer thickness and composition can be obtained.

  Further, according to the present embodiment, instead of oxidizing the metal film 12 to form the metal oxide film 2 serving as the gate insulating film as in the first embodiment, the composite metal film 21 is oxidized to form the gate insulating film. A composite metal oxide film 22 serving as a film is formed. For this reason, in the gate insulating film, the heat resistance as well as the dielectric constant can be improved.

  In the third embodiment, the silicon region where the higk-k gate insulating film is formed is not limited to the silicon substrate 1 and may be a silicon film or a substrate or film mainly made of silicon. Is also good.

  Further, in the third embodiment, the composite metal film 21 made of HfSi or HfAl is formed directly on the surface of the silicon substrate 1, but instead of this, the silicon substrate 1 is formed before the composite metal film 21 is formed. The surface may be subjected to a nitriding treatment (pretreatment). Thereby, the formation of the interface layer can be further suppressed.

  Further, in the third embodiment, HfSi or HfAl has been described as an example of the material of the composite metal film 21, but the material is not limited thereto, and zirconium, titanium, tantalum, aluminum, and other elements constituting the composite metal film 21 may be used. (For example, La selected from the group of rare earth metals) and silicon, two or more elements may be selected. Also, at the time of depositing the composite metal film 21, a composite metal nitride film is formed by introducing nitrogen into the atmosphere as in the second embodiment, and the composite metal oxynitride film is formed by oxidizing it. May be.

  In the third embodiment, the lower limit of the temperature at which the composite metal film 21 is oxidized may be the lowest temperature (for example, 300 ° C.) at which the composite metal film 21 can be oxidized by the oxygen radicals 13.

  In the third embodiment, the upper limit of the temperature at which the composite metal film 21 is oxidized may be the lowest temperature at which the oxidation of the composite metal film 21 proceeds by oxygen atoms or oxygen molecules (for example, 500 ° C.). .

Further, in the third embodiment, an oxygen radical is used as a radical serving as an oxidizing species of the composite metal film 21, but another radical such as a NO radical or an N ₂ O radical may be used instead.

  Further, in the third embodiment, after the step of forming the composite metal oxide film 22 shown in FIG. 9B, another composite metal oxide film 22 is formed on the composite metal oxide film 22 in an atmosphere substantially free of oxygen. A step of depositing a composite metal film (may be a metal film; the same applies hereinafter) and oxidizing the other composite metal film in an atmosphere containing oxygen to form another composite metal oxide film serving as a gate insulating film And a step. In other words, the deposition of the thin composite metal film and the oxidation of the composite metal film may be repeatedly performed. In this case, since the composite metal film is completely oxidized, it becomes easy to obtain a composite metal oxide film having a stoichiometric composition.

  In the third embodiment, the composite metal oxide film 22, that is, the gate insulating film has been described as an example of the application of the high-k film. Needless to say, it may be used for a film.

  By the way, in each embodiment of the present invention, in consideration of the influence on the reliability of the gate insulating film and the carrier mobility, the thinner the interface layer, the better. That is, it is important to control the thickness of the interface layer to a desired value. For this purpose, in each embodiment of the present invention, the number of oxygen radicals flying to the metal film (or the metal nitride film or the composite metal film), or the processing time or the processing temperature by the oxygen radicals, is controlled, so that the metal oxide film is formed. (Or a metal oxynitride film or a composite metal oxide film) and the thickness of the interface layer formed at the interface between the silicon substrate and the silicon substrate.

  As described above, the present invention relates to a method for forming a high dielectric constant film, and is particularly useful when applied to a method for manufacturing an electronic device having a gate insulating film.

FIG. 5 is a cross-sectional view showing one step of a method for forming a high-k gate insulating film according to a comparative example. (A) is a figure which shows a mode that the thick interface layer was formed in the formation method of the high dielectric constant gate insulating film according to the comparative example, and (b) is a high dielectric constant gate according to the first embodiment of the present invention. FIG. 4 is a diagram illustrating a state in which a thin interface layer is formed in a method for forming an insulating film. FIG. 4 is a diagram illustrating capacitor characteristics of a gate insulating film manufactured based on each of the methods for forming a high dielectric constant gate insulating film according to the first embodiment of the present invention and a comparative example. FIGS. 3A to 3C are cross-sectional views illustrating respective steps of a method for forming a high dielectric constant gate insulating film according to the first embodiment of the present invention. FIG. 2 is a configuration diagram of a remote plasma processing apparatus used in a method of forming a high dielectric constant gate insulating film according to first, second, and third embodiments of the present invention. FIG. 4 is a diagram showing the dependence of the rate of increase in film thickness of the Hf metal film after oxidation on the processing temperature in the method for forming a high dielectric constant gate insulating film according to the first embodiment of the present invention. In the HfO ₂ film obtained by oxidizing a 3 nm-thick Hf metal film using oxygen radicals at 400 ° C., the respective processing time (oxygen equivalent film thickness EOT and leakage current density Jg) FIG. 4 is a diagram showing dependence on radical irradiation time). (A)-(c) is sectional drawing which shows each process of the formation method of the high dielectric constant gate insulating film which concerns on 2nd Embodiment of this invention. (A)-(c) is sectional drawing which shows each process of the formation method of the high dielectric constant gate insulating film which concerns on 3rd Embodiment of this invention.

Explanation of reference numerals

1 silicon substrate 2 metal oxide film (high-k layer)
Reference Signs List 3 interface layer 4 gate electrode 10 target 11 metal atom 12 metal film 13 oxygen radical 14 oxygen atom (molecule)
Reference Signs List 16 nitrogen atom 17 metal nitride film 18 metal oxynitride film 19 other target 20 additional atom 21 composite metal film 22 composite metal oxide film 50 remote plasma processing apparatus 51 chamber 52 substrate holder 53 radical generation chamber 54 cylinder 55 plasma 56 high frequency power supply 57 Matcher

Claims (21)

Depositing a metal film on the silicon region in a non-oxidizing atmosphere;
Forming a metal oxide film serving as a gate insulating film by oxidizing the metal film using oxygen radicals.   The method according to claim 1, wherein the oxygen radical is supplied by a plasma generator using a gas containing oxygen.   The method according to claim 1, wherein the oxygen radical is supplied by an ozone generator.   2. The method according to claim 1, wherein a region where the metal film is oxidized and a region where the oxygen radical is generated are substantially separated.   2. The method according to claim 1, wherein the oxidation of the metal film is performed on a sample holder electrically kept at a floating potential.   2. The method according to claim 1, wherein a lower limit of a temperature at which the metal film is oxidized is a minimum temperature at which the metal film can be oxidized by the oxygen radical.   2. The method according to claim 1, wherein a lower limit of a temperature at which the metal film is oxidized is 300 ° C. 3.   2. The method according to claim 1, wherein the upper limit of the temperature at which the metal film is oxidized is a minimum temperature at which oxidation of the metal film proceeds by oxygen atoms or oxygen molecules. 3.   The method according to claim 1, wherein an upper limit of a temperature at which the metal film is oxidized is 500 ° C.   When the metal film is oxidized, the number of the oxygen radicals flying to the metal film, or the processing time or the processing temperature by the oxygen radical, is controlled to form an interface between the metal oxide film and the silicon region. 2. The method according to claim 1, wherein the thickness of the interface layer is controlled.   The temperature of the silicon region when depositing the metal film is set to less than 300 ° C., and the energy per metal particle when the metal particles serving as the metal film fly to the silicon region is set to 1 eV or less. 2. The method for manufacturing a semiconductor device according to claim 1, wherein:   The film thickness of the metal film is set such that the thickness of the metal oxide film formed by oxidizing the metal film is less than 3 nm when depositing the metal film. Of manufacturing a semiconductor device.   2. The method according to claim 1, wherein when depositing the metal film, the thickness of the metal film is set to less than 1.9 nm.   2. The method according to claim 1, wherein an element forming the metal film is selected from a group consisting of hafnium, zirconium, titanium, tantalum, aluminum, and silicon.   The method according to claim 14, wherein two or more elements constituting the metal film are selected from the group.   17. The semiconductor device according to claim 15, wherein a composition ratio of two or more elements selected from the group in the metal film is changed along a thickness direction of the metal film. Method.   2. The method according to claim 1, wherein a metal nitride film is deposited on the silicon region instead of the metal film.   2. The method according to claim 1, wherein a heat treatment is performed on the gate insulating film after forming the gate insulating film.   19. The method according to claim 18, wherein the heat treatment is performed in an atmosphere containing substantially no oxygen.   20. The method according to claim 19, wherein the atmosphere is made of an inert gas or a vacuum. Depositing a metal film on the silicon region in a non-oxidizing atmosphere;
Forming a metal oxide film serving as a gate insulating film by oxidizing the metal film using radicals capable of oxidizing the metal film.

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