JP2007073726A - Semiconductor device and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a semiconductor device where electrode oxidation in a gate electrode interface is suppressed, effectual work function deterioration of a gate electrode is suppressed, and threshold voltage Vt is reduced. <P>SOLUTION: An oxygen concentration adjusting thin film 4 is formed between a gate insulating film 3A and a gate electrode 6. Thus, there is provided a MIS transistor wherein electrode oxidation is suppressed in the gate electrode interface, effectual work function deterioration in the gate electrode does not occur, and threshold voltage Vt is reduced, by absorbing diffusion oxygen in the oxygen concentration adjusting thin film 4. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a semiconductor device including a transistor, and more particularly to a semiconductor device including a field effect transistor (FET) having a gate insulating film made of a high dielectric constant oxide.

  Conventionally, a field effect transistor (MISFET) having a MIS (metal-insulator-semiconductor) structure is used as a field effect transistor. In this technical field, high-speed operation and low power consumption are required. For example, in order to realize a higher speed, the drive current is increased by increasing the gate capacitance of the MISFET. With the miniaturization of the MISFET, the conventional gate insulating film has been extremely thinned, and its film thickness is about 1.5 nm or less.

  However, when the gate insulating film is thinned to 2 nm or less, the electron permeability increases dramatically, and an excessive tunnel leakage current flows between the gate electrode and the silicon substrate. As a result, even if high-speed operation can be realized, it is difficult to reduce power consumption. Further, if the leakage current increases, the original operation of the capacitor for accumulating charges becomes difficult, and no on-current is generated.

Therefore, recently, in order to overcome the physical property limit, it is expected that a material having a dielectric constant higher than that of the silicon oxide film is used as the gate insulating film. Attempts were made to achieve the same capacitance value as that of silicon oxide film with a thicker physical film thickness and not only to suppress leakage current as much as possible, but also to obtain larger on-current by obtaining a large gate insulating film capacitance. (For example, refer nonpatent literature 1).
Journal of Applied Physics vol.89, 5243 (2001)

  However, when a gate dielectric film having a high dielectric constant (high-k) is used, if the electrode is not limited to polysilicon but metal silicide or metal is used, the following new problem occurs in the heat treatment process for forming the gate electrode. It has become apparent. That is, since oxygen is thermally diffused from directly under the gate electrode to the gate electrode side and the gate electrode is oxidized, the effective work function of the gate electrode is deteriorated and the threshold voltage Vt is increased.

  The present invention was created in view of such circumstances, and an object thereof is to provide a semiconductor device including a MIS transistor with a reduced threshold voltage Vt.

  A semiconductor device according to the present invention includes a MIS transistor having a gate electrode through a gate insulating film on a semiconductor substrate on which a source and a drain are formed, and a thin film containing an oxygen concentration adjusting substance directly below the gate electrode. According to this, oxygen diffusion to the gate electrode can be prevented from being absorbed by the oxygen concentration adjusting thin film by the oxygen concentration adjustment thin film being absorbed from directly under the gate electrode.

  That is, even if the gate insulating film is made of a material having a high dielectric constant in order to secure an on-current, an oxygen concentration adjusting substance exists immediately under the gate electrode in the heat treatment process for forming the gate electrode of the MIS transistor. Oxygen diffused from oxygen can be absorbed to prevent oxygen diffusion to the gate electrode, thereby suppressing an increase in threshold voltage Vt.

  Here, as a configuration of the oxygen concentration adjusting substance, there is an aspect in which it exists in a layered manner between the gate insulating film and the gate electrode. In this case, the diffusion of oxygen from directly under the gate electrode to the gate electrode is suppressed to prevent the deterioration of the effective work function of the gate electrode. Therefore, the threshold voltage Vt can be effectively reduced.

  Furthermore, as a configuration of the oxygen concentration adjusting substance, there is an aspect in which it is inherent in the gate insulating film. In this case, the interface area between the oxygen concentration adjusting substance and the gate insulating film is further increased, so that oxygen defects in the gate insulating film are effectively prevented, so that the diffusion of oxygen from directly under the gate electrode to the gate electrode is effectively suppressed. In addition, since the effective work function of the gate electrode is prevented from being deteriorated and the oxygen defect in the gate insulating film is suppressed, the lowering of the dielectric constant and the increase of the leakage current can be prevented. Can be reduced.

  However, there is a tendency that the charge conducts through the grain boundary between the oxygen concentration adjusting substance and the gate insulating film and the leakage current increases. By further reducing and dispersing the oxygen concentration adjusting substance, the interface area between the oxygen concentration adjusting substance and the gate insulating film can be increased. In order to prevent oxygen defects in the gate insulating film more effectively, the diffusion of oxygen from directly under the gate electrode to the gate electrode is suppressed to prevent deterioration of the effective work function of the gate electrode and the oxygen in the gate insulating film. By suppressing defects, it is possible to prevent a decrease in dielectric constant and an increase in leakage current, so that the threshold voltage Vt can be reduced. In addition, since the oxygen concentration adjusting substance is uniformly dispersed, a leak path is not formed, and a reduction effect of the threshold voltage Vt is strongly expected.

  Further, the oxygen concentration adjusting substance is configured such that a thin film containing the oxygen concentration adjusting substance is mixed with the gate insulating film, the oxygen concentration adjusting substance exists between the gate insulating film and the gate electrode, and There is a mode of being inherent in In this case, the interface area between the oxygen concentration adjusting substance and the gate insulating film can be increased. In order to more effectively prevent oxygen vacancies in the gate insulating film, the diffusion of oxygen from directly under the gate electrode to the gate electrode is suppressed to prevent deterioration of the effective work function of the gate electrode, and in the gate insulating film. By suppressing the oxygen defects, it is possible to prevent a decrease in dielectric constant and an increase in leakage current, so that the threshold voltage Vt can be reduced.

Here, as the oxygen concentration adjusting substance, a substance including at least one or more polyvalent metal oxide MO ₂ or the like in at least one or more tetravalent and stable metal oxide AO ₂ is used. Is preferred. The multivalent metal M is any one of Ce, Yb, and Mn, and the tetravalent metal element A is any one of Zr, Hf, C, Si, Ge, Sn, and Pb.

In this case, the binding state and coordination number of the polyvalent metal M in the oxygen concentration adjusting substance are changed, and the oxygen storage capacity (OSC) characteristic of storing oxygen in an oxidizing atmosphere is obtained. Since the oxygen concentration adjusting substance itself often has a higher dielectric constant than SiO ₂ , the threshold voltage Vt can be reduced.

  In particular, by setting the M composition to 0.1 <x <0.8, high OSC characteristics can be obtained, and oxygen defects immediately below the gate electrode are further suppressed, so that the dielectric constant is decreased and the leakage current is increased. The threshold voltage Vt can be reduced.

  The method for manufacturing a semiconductor device according to the present invention includes a first step of forming a gate insulating film having a high dielectric constant on a semiconductor substrate, and a second step of forming a thin film containing an oxygen concentration adjusting substance on the gate insulating film. And a third step of forming a gate electrode on the oxygen concentration adjusting substance.

  As a result, a semiconductor device in which a thin film containing an oxygen concentration adjusting substance exists in a layered manner between the gate insulating film and the gate electrode can be manufactured, and a function of suppressing oxygen diffusion to the gate electrode and an increase in threshold voltage can be realized.

A method for manufacturing a semiconductor device according to the present invention includes a first step of forming a gate insulating film having a high dielectric constant on a semiconductor substrate,
A second step of forming a thin film containing an oxygen concentration adjusting material on the gate insulating film; a third step of forming a gate electrode on the oxygen concentration adjusting material; and the first step, In the second step, these steps are repeated a plurality of times.

  As a result, a repeated multilayer film of a gate insulating film and a thin film containing an oxygen concentration adjusting substance can be formed, and the contact surface area of both films can be increased. Can do.

  In the above, it is preferable that the second step includes a step of applying or depositing a material containing the oxygen concentration adjusting substance and a step of annealing.

  The method for manufacturing a semiconductor device according to the present invention includes a first step of forming a gate insulating film having a high dielectric constant on a semiconductor substrate in a state where an oxygen concentration adjusting material is dispersed therein, and the oxygen concentration adjustment. And a second step of forming a gate electrode on the gate insulating film in which the substance is dispersed internally.

  In this case, since the interface area between the oxygen concentration adjusting substance and the gate insulating film is increased by the diffusion of the oxygen concentration adjusting substance in the gate insulating film, the function of suppressing the oxygen diffusion to the gate electrode and the increase in threshold voltage is further enhanced. Can do.

A method for manufacturing a semiconductor device according to the present invention includes a first step of forming a gate insulating film having a high dielectric constant on a semiconductor substrate,
A second step of forming a thin film containing an oxygen concentration adjusting material on the gate insulating film; a third step of forming a gate electrode on the oxygen concentration adjusting material; and annealing to adjust the oxygen concentration. And a fourth step of forming a mixing layer by diffusing constituent materials of both at the interface between the thin film containing the substance and the gate insulating film.

  In this case, since the interface area between the oxygen concentration adjusting substance and the gate insulating film is increased by forming the mixing layer, the function of suppressing oxygen diffusion to the gate electrode and the threshold voltage rise can be further enhanced.

  According to the present invention, even if the gate insulating film is made of a material having a high dielectric constant in order to secure an on-current, the diffusion of oxygen to the gate electrode in the manufacturing process is suppressed, and the effective work function of the gate electrode is reduced. By suppressing the deterioration, the threshold voltage Vt can be lowered, and as a result, both the demand for high speed operation and low power consumption can be satisfied.

  Embodiments of a semiconductor device according to the present invention will be described below in detail with reference to the drawings.

(Embodiment 1)
The first embodiment of the present invention relates to a semiconductor device provided with a P-type MIS (Metal Insulator Semiconductor) transistor.

<Configuration of FET>
FIG. 1A is a diagram showing a cross-sectional configuration of the P-channel MIS transistor in the first embodiment of the present invention. Reference numeral 1 denotes an N-type silicon substrate, 3A denotes a gate insulating film, 4 denotes an oxygen concentration adjusting thin film, and 5 denotes an element isolation insulating film. The structure and manufacturing method of the gate insulating film 3A and the oxygen concentration adjusting thin film 4 will be described later. 6 is a gate electrode made of polysilicon, 7 is a side wall of an insulating film (for example, a CVD silicon nitride film) formed on the side wall of the gate electrode 6, and 8 is a diffusion layer (source / drain region) into which a P-type impurity is introduced. ).

<Configuration and fabrication of gate insulating film>
In order to manufacture the MIS transistor shown in FIG. 1A, the N-type silicon substrate 1 is carried into the chamber, and a target made of, for example, Hf (hafnium) metal is prepared in the chamber, and then the chamber is formed. Ar gas is introduced into the inside. Thereby, the inside of the chamber becomes a non-oxidizing atmosphere. Thereafter, discharge is caused by applying a voltage in the chamber. In this way, Hf atoms fly from the target made of Hf metal toward the silicon substrate 1 by the sputtering effect, and the metal film 2 made of Hf metal (see FIG. 1B) is deposited on the silicon substrate 1. The

Next, by oxidizing the metal film 2 in an oxidizing atmosphere, a metal oxide film 3 made of HfO ₂ is formed as shown in FIG. Specifically, it is as follows. That is, the silicon substrate on which the metal film 2 is deposited is carried into the plasma processing chamber of the plasma processing apparatus, and the substrate is placed on the lower electrode. Subsequently, after introducing O ₂ gas into the plasma processing chamber, RF power is applied to an RF (Radio Frequency) electrode of the plasma processing apparatus to generate plasma composed of O ₂ gas. This creates an oxidizing atmosphere in the chamber. Subsequently, when power is applied to the lower electrode on which the substrate is placed, oxidizing species such as oxygen atoms and oxygen ions containing radicals fly toward the metal film 2. Here, it is possible to control the energy given to the oxygen atoms or oxygen ions and to control the dose amount of the oxygen atoms or oxygen ions. For example, when the inside of the chamber is brought to a floating potential without applying RF power to the lower electrode, most of the oxidized species injected into the metal film 2 are oxygen atoms. In addition, when RF power is applied to the lower electrode, oxygen ions among the oxidizing species are implanted into the metal film 2 by the self-bias voltage. That is, the Hf metal film 2, that is, the Hf metal film is subjected to plasma treatment using O ₂ gas, thereby controlling the implantation depth and implantation amount of oxygen ions or oxygen atoms into the Hf metal film. Can be oxidized. By this oxidation treatment, the metal film 2 made of Hf is oxidized to become a metal oxide film 3 made of HfO _2, and the metal oxide film 3 having this stoichiometric composition ratio is used as the gate insulating film 3A of the transistor.

In the metal oxide film 3 formed in a non-equilibrium state, the bonding state between oxygen atoms and metal atoms (Hf atoms) is insufficient, and the uniformity of the oxygen concentration distribution is insufficient, so that sufficient electrical characteristics can be obtained. Not shown. Therefore, in order to obtain the metal oxide film 3 having sufficient electrical characteristics, the substrate 1 on which the metal oxide film 3 is formed is heated as a post-treatment of the oxidation process of the metal film 2. Specifically, the substrate 1 is carried into the chamber and N ₂ gas is introduced into the chamber. Thereby, the inside of the chamber becomes a non-oxidizing atmosphere. Thereafter, an annealing process is performed by heating the substrate 1.

<Configuration of oxygen concentration adjusting thin film>
Next, an oxygen concentration adjusting thin film 4 and a gate electrode 6 are formed on the substrate 1 via a gate insulating film 3A made of a metal oxide film 3. Here, the oxygen concentration adjusting thin film 4 is formed in a layered form directly on the gate insulating film 3A. An oxygen concentration adjusting thin film 4 is formed on the gate insulating film 3A by sputtering, and the gate insulating film 3A is capped so that the gate insulating film 3A does not contact the gate electrode 6 in the film thickness direction. Thereby, the oxygen concentration adjusting thin film 4 does not allow diffusion oxygen to reach the gate electrode 6, and deterioration of the effective work function of the gate electrode 6 can be prevented. Furthermore, by suppressing oxygen defects in the gate insulating film 3A, it is possible to prevent a decrease in dielectric constant and an increase in leakage current.

  FIG. 2A shows the gate insulating film 3A, the oxygen concentration adjusting thin film 4 and the gate electrode 6 extracted from FIG. Instead of the configuration of the layered oxygen concentration adjusting thin film 4, a configuration as shown in FIG. In the case of FIG. 2B, although the total film thickness of each does not change, the gate insulating film 3A and the oxygen concentration adjusting thin film 4 are laminated by alternately repeating sputtering. Thereby, the gate insulating film 3A does not contact the gate electrode 6 in the film thickness direction, and the contact area between the gate insulating film 3A and the oxygen concentration adjusting thin film 4 is further increased. Since oxygen is trapped in the gate insulating film 3A in the two upper and lower portions separated by the oxygen concentration adjusting thin film 4, the oxygen trapping effect is enhanced and deterioration of the effective work function of the gate electrode 6 can be prevented. . Furthermore, by suppressing oxygen defects in the gate insulating film 3A, it is possible to prevent a decrease in dielectric constant and an increase in leakage current. Further, the effect of reducing the threshold voltage Vt is expected to be strong.

The oxygen concentration adjusting thin film 4 is made of a material represented by A _1-x M _x O ₂ (A: tetravalent metal element, M: polyvalent metal). Here, x is a real number less than 1. For example, a substance composed of ZrO ₂ and CeO ₂ is a substance that easily absorbs oxygen in an oxidizing atmosphere. Moreover, these substances have a dielectric constant larger than that of SiO ₂ and HfO ₂ .

  It is assumed that an element isolation insulating film 5 having an STI (Shallow trench isolation) structure, for example, is formed on the substrate 1.

  Next, after forming a sidewall 7 of an insulating film on the side surface of the gate electrode 6, an impurity diffusion layer 8 to be a source region and a drain region is formed on the surface portion of the substrate 1. Thereafter, an interlayer insulating film is formed on the substrate 1 including the gate electrode 6 and the like. Further, an N-type MIS transistor is completed by forming a wiring including a plug portion connected to the impurity diffusion layer 8 on the interlayer insulating film.

<Types of oxygen concentration adjusting substances>
A _1-x M _x O oxygen concentration adjusting substance is represented by _2, the stable in the oxide AO ₂ metal in at least one or more tetravalent oxide of at least one polyvalent metal MO ₂ It is a substance containing etc. The coordination state of oxygen with respect to M ions and the valence of M ions change due to changes in the lattice state of AO ₂ and MO ₂ depending on the degree of the correlation effect of mixing and solid solution. As a result, the oxygen storage capacity (OSC) characteristics for storing oxygen in the oxidizing atmosphere of MO ₂ greatly increase the characteristics of the single bulk. Furthermore, the oxygen concentration adjusting substance itself has a higher dielectric constant than SiO ₂ .

<Composition of oxygen concentration adjusting substance>
As the composition of the oxygen concentration adjusting substance A _1-x M _x O ₂ , the tetravalent metal element A is Zr, Hf, C, Si, which is tetravalent and has a stable valence among the elements of groups 4A and 4B. , Ge, Sn, Pb. This is because since the ionic bondability with oxygen is small and the covalent bondability is large, valence fluctuation hardly occurs and the lattice stability is high. The multivalent metal M is preferably made of Ce, Yb, Mn. This is because it has the property of easily changing the valence of ions depending on the coordination state of oxygen and the property of a high relative dielectric constant. In addition, regarding the selection of each element of A and M, at least one element may be selected from the above, and it is only necessary to obtain an oxygen storage capacity (OSC) characteristic for storing oxygen in a desired oxidizing atmosphere.

<Composition ratio of oxygen concentration adjusting substance>
As AO ₂ shows the case of a mixture of CeO ₂ as an example of ZrO _2, MO _2. CeO ₂ has an oxygen storage capacity (OSC) for storing oxygen in an oxidizing atmosphere, and is used as a co-catalyst that can obtain a stable purification activity even if the oxygen concentration in the exhaust gas varies. However, it is said that the OSC tends to decrease due to the crystal growth of CeO ₂ through a high temperature process. Therefore, zirconia (ZrO ₂ ) is added to CeO ₂ in order to suppress the crystal growth of CeO ₂ and maintain a high OSC. In addition, it is said that a composite oxide or a solid solution of CeO ₂ and ZrO ₂ at least partially shows OSC, and by adding ZrO ₂ , heat resistance is improved, and OSC after high temperature durability is obtained. Remains. As a result of investigating the Ce composition dependency of the OSC characteristics, as shown in FIG. 3, it was found that the OSC characteristics were exhibited when 0.1 <X <0.8, and particularly when Ce was 0.4. . In this case, since oxygen can be efficiently captured, it is desirable to produce the oxygen concentration adjusting thin film 4 within this composition ratio.

<Production of oxygen concentration adjusting substance>
Here, a case where a mixture of ZrO ₂ as AO _{2 and} CeO ₂ as MO ₂ in the production of the oxygen concentration adjusting thin film 4 is shown as an example. It contains a Zr compound and Ce compound that decomposes by heating and an organic substance, forms a solution in which the Zr compound and Ce compound are dissolved at least at the time of heating, and at least a part of the organic substance is liquid after a part of the Zr compound and Ce compound decomposes The mixture is adjusted. In the decomposition step, the mixture is heated to decompose the mixture to form a uniform precursor. Since a uniform solution is formed at least when the mixture is heated, Zr ions and Ce ions are uniformly mixed. Although the mixture is decomposed by further heating, since at least a part of the organic substance is liquid after decomposition of at least a part of the Zr compound and the Ce compound, the Zr ion and the Ce ion are uniformly distributed in the liquid organic substance at the atomic level. A mixed state can be maintained. As a result, a precursor in which Zr ions and Ce ions are uniformly mixed is formed. By coating this precursor on the gate insulating film 3A and oxidizing it, the oxygen concentration adjusting thin film 4 can be formed. The manufacturing method is not limited to the above, and the film may be formed by a CVD method using the precursor, or may be formed by a co-sputtering method or a molecular beam epitaxy method.

<Comparative example 1>
In contrast to the MIS transistor shown in FIG. 1A shown in the first embodiment, a MIS transistor having a structure without the oxygen concentration adjusting thin film 4 as shown in FIG. 10 was fabricated. As the gate insulating film 3A, an SiO ₂ film formed using ALD was used. The result of the capacitor (CV) characteristics with this structure is shown by curve A in FIG. The vertical axis represents capacitance C, and the horizontal axis represents gate voltage Vg.

<Comparative example 2>
In contrast to the MIS transistor shown in FIG. 1A shown in the first embodiment, a MIS transistor having a structure without the oxygen concentration adjusting thin film 4 as shown in FIG. 10 was fabricated. As the gate insulating film 3A, an HfO ₂ film formed using ALD was used. The result of the capacitor (C-V) characteristics with this structure is shown by curve B in FIG.

<effect>
As shown in Comparative Example 1 and Comparative Example 2, in the case of FIG. 5A in which the oxygen concentration adjusting thin film 4 is not provided between the gate insulating film 3A and the gate electrode 6, the gate electrode 6 is formed by a heat treatment process after the gate electrode is manufactured. Oxygen was diffusing.

On the other hand, according to the present embodiment, in the case of the configuration of FIG. 2A, the capacitor (C-V) characteristic indicated by the curve C in FIG. The capacitor (CV) characteristic shown by the curve D in FIG. 4 was obtained. Since diffused oxygen is absorbed by the oxygen concentration adjusting thin film 4 as shown in FIG. 5B, electrode oxidation at the gate electrode interface can be suppressed and deterioration of the effective work function of the gate electrode 6 can be prevented. Further, the oxygen concentration adjusting substance itself has a higher dielectric constant than SiO ₂ . That is, the flat band voltage (Vfb) approaches the value of the curve A of the comparative example 1 (SiO ₂ film) as compared with the curve B of the comparative example 2 (HfO ₂ film), and the threshold voltage Vt can be lowered. did it. Even though the volume ratio of the gate insulating film 3A and the oxygen concentration adjusting thin film 4 is the same, the contact surface area is large, so that the absorption efficiency of diffused oxygen is higher, and the curve D has a lower threshold voltage Vt than the curve C. .

(Embodiment 2)
The semiconductor device according to the second embodiment of the present invention has a configuration in which oxygen concentration adjusting particles are dispersed inside the gate insulating film. Hereinafter, the case where a semiconductor device provided with a P-type MIS transistor is formed will be described as an example, and the difference from the first embodiment will be mainly described.

<Configuration of oxygen concentration adjusting thin film>
As shown in FIG. 6A, when forming the gate insulating film 3A, the oxygen concentration adjusting particles 4A are formed at the same time so that the oxygen concentration adjusting particles 4A are dispersed inside the gate insulating film 3A. To do. Specifically, a CVD (Chemical Vapor Deposition) method using as a source a colloidal precursor of ZrO ₂ —CeO ₂ polymerized and grown to a particle shape produced by the manufacturing method shown in Embodiment 1, and an organic precursor containing Hf metal. It can form by forming into a film.

Further, as shown in FIG. 6B, the oxygen concentration adjusting solid solution 4B is formed simultaneously with the formation of the gate insulating film 3A, and the oxygen concentration adjusting solid solution 4B is uniformly dispersed in the gate insulating film 3A. Like that. Specifically, a film is formed by a CVD method using a nano-order fine particle-shaped ZrO ₂ —CeO ₂ colloid precursor and an organic precursor containing Hf metal produced by the manufacturing method shown in the first embodiment as a source. Can be formed. Moreover, it can form by performing CVD method based on the organic substance source containing Zr, Ce, and Hf.

  Other than that, a semiconductor device was manufactured with the same structure as in the first embodiment.

<effect>
In the configuration of FIG. 6A, the result is as shown by the curve E in FIG. Although deterioration due to leaks in which the oxygen concentration adjusting particles 4A pass through each other is observed, the contact surface area between the oxygen concentration adjusting particles 4A and the gate insulating film 3A is increased, so that the flat band voltage (Vfb) is compared with Comparative Example 2 (HfO ₂ Film) was improved from curve B, and a result approaching curve A of Comparative Example 1 (SiO ₂ film) was seen, and the threshold voltage Vt could be reduced.

In the configuration of FIG. 6B, the result is as shown by the curve F in FIG. Since the contact surface area between the oxygen concentration adjusting particles 4A and the gate insulating film 3A is larger than that in the configuration of FIG. 6A, the flat band voltage (Vfb) is obtained from the curve B of Comparative Example 2 (HfO ₂ film). Improvement was seen, and a result approaching the curve A of Comparative Example 1 (SiO ₂ film) was seen, and the threshold voltage Vt could be efficiently reduced. In addition, as compared with E, the effect of reducing the leakage current with a smaller amount of grain boundary connection was also shown.

(Embodiment 3)
The semiconductor device according to Embodiment 3 of the present invention has a configuration in which oxygen concentration adjusting particles are dispersed inside the gate insulating film. Hereinafter, the case where a semiconductor device provided with a P-type MIS transistor is formed will be described as an example, and the difference from the first embodiment will be mainly described.

<Configuration of oxygen concentration adjusting thin film>
As shown in FIG. 1, an oxygen concentration adjusting thin film 4 and a gate electrode 6 are formed on a semiconductor substrate 1 via a gate insulating film 3A made of a metal oxide film 3. Here, the oxygen concentration adjusting thin film 4 is formed in a layered form directly on the gate insulating film 3A. An oxygen concentration adjusting thin film 4 is formed on the gate insulating film 3A by ALD, and as shown in FIG. 8A, the gate insulating film 3A is capped so as to be separated from the gate electrode 6. Thereafter, the structure shown in FIG. 8B is obtained by annealing in an oxygen atmosphere. Specifically, each metal element is diffused and mixed at the interface between the oxygen concentration adjusting thin film 4 and the gate insulating film 3A by annealing at 600 ° C. for 10 minutes in an oxygen atmosphere. Reference numeral 10 denotes a mixing layer. The oxygen concentration adjusting thin film 4 does not allow diffusion oxygen to reach the gate electrode 6, prevents deterioration of the effective work function of the gate electrode 6, suppresses oxygen defects in the gate insulating film 3 A, and further mixes the mixing layer at the interface. The threshold voltage Vt can be efficiently reduced by the high dielectric constant characteristic of 10.

  Other than that, a semiconductor device was manufactured with the same structure as in the first embodiment.

<effect>
In the configuration of FIG. 8B, the result is as shown by the curve G in FIG. Although the deterioration due to the leak that passes the composition fluctuation of the oxygen concentration adjusting thin film 4 in the mixing region is observed, the flat band voltage (Vfb) is improved from the curve B of Comparative Example 2 (HfO ₂ film). example 1 results approaching the curve a (SiO ₂ film) was observed, it was possible to reduce the threshold voltage Vt.

In the above first to third embodiments, the case where the oxygen concentration adjusting substance is ZrO ₂ —CeO ₂ has been described, but the tetravalent metal element A is a tetravalent element among the elements of Group 4A and Group 4B. Any number may be used as long as the number is stable from Zr, Hf, C, Si, Ge, Sn, and Pb. In particular, in the case of Zr and Hf, they may be the same as the constituent elements of the gate insulating film 3A that is often used, and the interface characteristics between the oxygen concentration adjusting substance and the gate insulating film are excellent, and are particularly useful.

  In each of the above embodiments, a P-type MISFET has been described. Originally, characteristic deterioration was observed in the P-type MISFET as compared with the N-type MISFET, so that the improvement effect in this case is very large and remarkable. Also in the N-type MISFET, the improvement effect by the means of the present case is an effective means without changing.

<Production method>
(Method for Manufacturing Semiconductor Device of First Embodiment)
For A _1-x M x O ₂ oxygen concentration adjustment film 4 describes the case of _{Zr 1-x Ce x O 2} .

After the metal oxide film 3 is formed, a solution containing a Zr compound and a Ce compound and an organic substance that are decomposed by heating, and at least the Zr compound and the Ce compound are dissolved during heating is formed. Then, after a part of the Zr compound and the Ce compound is decomposed, a mixture in which at least a part of the organic substance is liquid is prepared. In the decomposition step, the mixture is heated to decompose the mixture to form a uniform precursor. Since a uniform solution is formed at least when the mixture is heated, Zr ions and Ce ions are uniformly mixed. The mixture is decomposed by further heating. After at least a part of the Zr compound and the Ce compound is decomposed, at least a part of the organic substance is liquid, so that the Zr ion and Ce ion are uniform in the liquid organic substance at the atomic level. The mixed state can be maintained. Thereby, a precursor in which Zr ions and Ce ions are uniformly mixed can be formed. The precursor is applied on the gate insulating film 3A and oxidized to form the oxygen concentration adjusting thin film 4. Thereafter, a gate electrode 6 made of polysilicon is deposited.
Alternatively, as another example, after forming the metal oxide film 3, sputtering is performed on the target obtained by sintering the precursor, and a thin film having a target composition is deposited and reacted on the metal oxide film 3. Examples include RF power 200 W, substrate target distance 80 mm, sputtering gas ratio Ar: O ₂ = 4: 1, sputtering pressure 10 mTorr, and film formation at room temperature. Thereafter, an annealing process is performed at 450 ° C. for 15 seconds in an oxygen atmosphere to form the oxygen concentration adjusting thin film 4. Thereafter, a gate electrode made of polysilicon is deposited.

(Method for Manufacturing Semiconductor Device of Second Embodiment)
After forming the metal oxide film 3, by forming a nano-order fine particle-shaped Zr alkoxide and Ce alkoxide precursor prepared by a sol-gel method and an alkoxide precursor containing Hf metal as a source, a film is formed by a CVD method. An oxygen concentration adjusting thin film 4 is formed. Further, the oxygen concentration adjusting thin film 4 is formed by performing a CVD method based on an organic source containing Zr, Ce and Hf. Thereafter, a gate electrode 6 made of polysilicon is deposited.

(Method for Manufacturing Semiconductor Device of Embodiment 3)
After the metal oxide film 3 is formed, it is deposited by ALD, and as shown in FIG. 8A, the gate insulating film 3A is capped so as to be separated from the gate electrode 6. Thereafter, the structure shown in FIG. 8B is obtained by annealing in an oxygen atmosphere. Specifically, each metal element is diffused and mixed at the interface between the oxygen concentration adjusting thin film 4 and the gate insulating film 3A by annealing at 600 ° C. for 10 minutes in an oxygen atmosphere.

There are also the following methods for producing the mixing layer. A solution consisting of Zr alkoxides and Ce alkoxide using a sol-gel method of reacting applied, further the heating temperature by the 450 ° C. to form a Zr _1-x Ce _x O ₂ on the fiber. Thereafter, the mixing layer 10 is formed by further depositing the gate insulating film 3A. Thereafter, a gate electrode 6 made of polysilicon is deposited.

  As described above, the present invention is useful in suppressing the diffusion of oxygen to the gate electrode and lowering the threshold voltage Vt in the MIS transistor.

(A) Cross-sectional view of MIS transistor in Embodiment 1 of the present invention, (b) Fabrication diagram of gate oxide film Sectional drawing which showed the structure of the oxygen concentration adjustment thin film in Embodiment 1 of this invention It shows the composition dependency of OSC characteristics of the oxygen concentration adjustment film Zr _1-x Ce _x O ₂ in the first embodiment of the present invention The figure which showed the capacitor (CV) characteristic in Embodiment 1 of this invention and a comparative example Sectional drawing of the MIS transistor which showed the presence or absence of oxygen diffusion which is the effect in Embodiment 1 of this invention Sectional drawing which showed the structure of the oxygen concentration adjustment thin film in Embodiment 2 of this invention The figure which showed the capacitor (CV) characteristic in Embodiment 2 and a comparative example of this invention Sectional drawing which showed the structure of the oxygen concentration adjustment thin film in Embodiment 3 of this invention The figure which showed the capacitor (CV) characteristic in Embodiment 3 of this invention and a comparative example Cross-sectional view of MIS transistor of comparative example

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 N type silicon substrate 2 Metal film 3 Metal oxide film 3A Gate insulating film 4 Oxygen concentration adjusting thin film 4A Oxygen concentration adjusting particle 4B Oxygen concentration adjusting solid solution 5 Element isolation insulating film 6 Gate electrode 7 Side wall 8 Impurity diffusion layer 9 Thermal oxide SiO ₂ membranes 10 mixing layers

Claims (12)

  A semiconductor device comprising a MIS transistor having a gate electrode through a gate insulating film on a semiconductor substrate on which a source and a drain are formed, and a thin film containing an oxygen concentration adjusting substance directly under the gate electrode.   The semiconductor device according to claim 1, wherein the oxygen concentration adjusting substance is present in a layered manner between the gate insulating film and the gate electrode.   The semiconductor device according to claim 1, wherein the oxygen concentration adjusting substance is inherent in the gate insulating film.   2. The semiconductor device according to claim 1, wherein the thin film containing the oxygen concentration adjusting substance is present between the gate insulating film and the gate electrode, and the oxygen concentration adjusting substance is mixed and contained in the gate insulating film. The oxygen concentration adjusting substance is A _1-x M _x O ₂ (A: a tetravalent metal element, M: a polyvalent metal), and the bonding state or coordination number of oxygen due to fluctuations in the valence of M ions The semiconductor device according to claim 1, wherein the semiconductor device is made of a material that changes.   The multivalent metal M is any one of Ce, Yb, and Mn, and the tetravalent metal element A is any one of Zr, Hf, C, Si, Ge, Sn, and Pb. Semiconductor device. The composition of M ions of the A _1-x M _x O ₂ (A: tetravalent metal element, M: multivalent metal) is 0.1 <X <0.8. Semiconductor device. A first step of forming a high dielectric constant gate insulating film on a semiconductor substrate;
A second step of forming a thin film containing an oxygen concentration adjusting material on the gate insulating film;
And a third step of forming a gate electrode on the oxygen concentration adjusting material. A first step of forming a high dielectric constant gate insulating film on a semiconductor substrate;
A second step of forming a thin film containing an oxygen concentration adjusting material on the gate insulating film;
A third step of forming a gate electrode on the oxygen concentration adjusting material,
The first step and the second step are a method for manufacturing a semiconductor device in which these steps are repeated a plurality of times.   10. The method of manufacturing a semiconductor device according to claim 8, wherein the second step includes a step of applying or depositing a material containing the oxygen concentration adjusting substance and a step of annealing. A first step of forming a high dielectric constant gate insulating film on a semiconductor substrate in a state where an oxygen concentration adjusting substance is dispersed therein;
And a second step of forming a gate electrode on the gate insulating film in which the oxygen concentration adjusting substance is dispersed internally. A first step of forming a high dielectric constant gate insulating film on a semiconductor substrate;
A second step of forming a thin film containing an oxygen concentration adjusting material on the gate insulating film;
A third step of forming a gate electrode on the oxygen concentration adjusting material;
And a fourth step of forming a mixing layer by diffusing constituent materials of both at the interface between the thin film containing the oxygen concentration adjusting substance and the gate insulating film by annealing.

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