JP5284335B2 - Semiconductor device - Google Patents

Description

  The present invention relates to a semiconductor device.

In MOS transistors, there is a problem that leakage current between a gate and a substrate increases due to a direct tunneling phenomenon in a carrier film. In order to avoid such a tunneling phenomenon, it has been proposed to form a gate insulating film using a material whose dielectric constant is significantly higher than that of SiO ₂ . Specifically, it is a metal oxide film having a high dielectric constant such as an oxide of a high dielectric constant metal such as ZrO ₂ or HfO ₂ , or a compound of the compound with SiO ₂ so-called silicate. Furthermore, the silicate containing nitrogen can maintain an amorphous state even at 1000 ° C., and the relative dielectric constant is as high as about 20. In addition, since diffusion of impurities such as boron in the film is small, application to a CMOS process requiring heat resistance is expected.

  However, when a gate electrode made of polycrystalline Si and a gate insulating film made of a metal oxide such as Hf or Zr are combined, the threshold value varies. This variation is very large, and it is difficult to make adjustment by adjusting the impurity concentration of the substrate portion as is normally done. Such a phenomenon has been confirmed to occur not only in the case of a pure semiconductor gate electrode such as Si or Ge but also in a metal silicide or metal germanide.

Therefore, a method of suppressing variation in threshold value by adding an additive element having a large valence of 1 to an N-MIS transistor and adding an additive element having a small valence of 1 to a P-MIS transistor and changing the charge state Has been proposed (see, for example, Patent Document 1).
JP 2002-280461 A

  However, adding different additive elements between the N-MIS transistor and the P-MIS transistor leads to complication of the manufacturing process and increases the manufacturing cost as a whole.

  In order to keep the threshold value low, an additive element having a concentration as high as 10 at (atomic)% must be added. If the concentration of the additive element becomes high, the characteristics of the additive element itself cannot be ignored. For example, excessive additive elements lead to a decrease in dielectric constant. In addition, since there are a large number of fixed charges in the insulating film due to excessive additive elements, electrons or holes serving as carriers of the transistor are scattered by the fixed charges in the insulating film, and electron mobility or hole This leads to a decrease in mobility. Thus, when a high concentration additive element is introduced into the gate insulating film made of a metal oxide, there is a problem that the dielectric constant is lowered and the mobility of electrons or holes is lowered, resulting in deterioration of characteristics.

  The present invention has been made in consideration of the above circumstances, and an object of the present invention is to provide a semiconductor device capable of preventing deterioration of element characteristics as much as possible.

  A semiconductor device according to a first aspect of the present invention includes a semiconductor substrate, a gate insulating film provided on the semiconductor substrate, a first gate electrode provided on the gate insulating film, and the first gate electrode. An interelectrode insulating film containing metal and oxygen, a second gate electrode provided on the interelectrode insulating film, and a source / source provided on the semiconductor substrate on both sides of the first and second gate electrodes. The inter-electrode insulating film includes at least one additive element selected from phosphorus, arsenic, antimony, and bismuth, and the content thereof is not less than 0.1 at% and not more than 3 at% It is characterized by.

  A semiconductor device according to a second aspect of the present invention includes a semiconductor substrate, a gate insulating film provided on the semiconductor substrate, a first gate electrode provided on the gate insulating film, and the first gate. An interelectrode insulating film containing metal and oxygen provided on the electrode; a second gate electrode provided on the interelectrode insulating film; and provided on the semiconductor substrate on both sides of the first and second gate electrodes. The inter-electrode insulating film includes at least one additive element selected from sulfur, selenium, and tellurium, and the content thereof is 0.003 at% or more and 3 at% or less. It is characterized by.

  According to the present invention, deterioration of element characteristics can be prevented as much as possible.

  Embodiments of the present invention will be described below with reference to the drawings.

(First embodiment)
The semiconductor device according to the first embodiment of the present invention includes a gate insulating film made of a high dielectric material provided on a semiconductor substrate, a gate electrode provided on the gate insulating film, and the semiconductor substrate on both sides of the gate electrode. It has a MIS transistor having a provided source / drain region. The gate insulating film includes metal and oxygen, and includes at least one element selected from Group 5, Group 6, Group 15 and Group 16 having a concentration of 3 at (atomic)% or less as an additive element. . In the following description, hafnium (Hf) is used as the metal contained in the gate insulating film, and antimony (Sb) is used as the additive element.

  The metal and oxygen constituting the gate insulating film of the semiconductor device according to the present embodiment combine to form a metal oxide in the gate insulating film as schematically shown in FIG. As shown in FIG. 1, Sb as an additive element is substituted for Hf and oxygen and contained in the gate insulating film.

In the metal oxide as the high dielectric, oxygen vacancies are formed in a large amount not only immediately after film formation, but also in a gate electrode formation process or a heat treatment process corresponding to activation. The amount depends on the film formation condition of the gate insulating film, the formation condition of the gate electrode made of semiconductor, or the heat treatment condition corresponding to the activation, but reaches 0.1 at% when the amount of defects is large.
However, desorption of oxygen from the gate insulating film can be suppressed by adding Sb as an additive element. As shown in FIG. 1, Sb added as an additional element may be substituted with Hf or with oxygen. In any case, the added Sb forms a strong bond with oxygen in the insulating film, stabilizes it, and has an effect of suppressing desorption of oxygen.

  FIG. 2 is a spectrum measured by XPS (X-ray Photoelectron Spectroscopy) showing the binding state of Sb added in the present embodiment and the comparative example. In this embodiment, Sb added was approximately 1.0 at%, and Sb added in the comparative example was approximately 3.1 at%. In this embodiment and the comparative example, it is understood that Sb is mainly bonded to oxygen and is substituted for Hf. In FIG. 2, the Hf-Sb bond is not detected, because the oxygen deficiency is at most 0.1 at%, and the Hf-Sb bond is less than the amount detectable by XPS. The bonding state of these trace elements can be evaluated by EELS (Electron Energy Loss Spectroscopy). EELS is excellent for the analysis of elements with small atomic numbers. Therefore, it is preferable to use EELS when evaluating phosphorus, arsenic, antimony, bismuth and the like.

The point of concern due to the excessive addition of Sb is a decrease in leakage current due to a decrease in dielectric constant. Since the dielectric constant of HfO ₂ is about 20 and the dielectric constant of Sb ₂ O ₃ is about 8, an excessive addition of Sb may cause an increase in leakage current due to a decrease in dielectric constant.

  FIG. 3 shows changes in gate leakage current depending on the addition concentration of Sb in this embodiment and Comparative Examples 1 and 2. In the case of the present embodiment in which Sb was added at 1.0 at%, the gate leakage current was greatly reduced as compared with the case of Comparative Example 1 in which Sb was not added. This effect is an effect that the oxygen deficient sites in the high dielectric insulating film are compensated more than the decrease in the dielectric constant due to the addition of Sb, and the trap sites of electrons and holes are reduced. However, in the case of Comparative Example 2 in which 3.1 at% of Sb was added, the gate leakage current slightly increased compared to the case of the present embodiment in which 1.0 at% of Sb was added. As described above, this is considered to be an increase in leakage current due to a decrease in dielectric constant due to excessive addition of Sb.

  Similar to the semiconductor device of this embodiment, FIG. 4 shows capacitance-voltage characteristics of an N-type silicon gate-MOS capacitor to which Sb is added at 1.0 at% and a P-type silicon gate-MOS capacitor. As shown in FIG. 4, as in this embodiment, the difference in flat band voltage between the N-type silicon gate-MOS capacitor to which Sb is added at 1.0 at% and the P-type silicon gate-MOS capacitor is about 0.7V. The threshold can be adjusted by implanting ions into the channel region, and the fluctuation of the flat band voltage is suppressed to a practical level as a MISFET. As a result, a semiconductor device including a MIS transistor capable of normal operation is obtained.

  On the other hand, as shown in FIG. 5, in the conventional case where Sb is not added (Sb = 0%), the difference in flat band voltage between the N-type silicon gate-MOS capacitor and the P-type silicon gate-MOS capacitor is Since it is only about 0.3 V, it is difficult to adjust the threshold by ion implantation into the channel region, and it cannot be used as a MISFET.

  Further, as shown in FIG. 6, in the case of the comparative example in which Sat is added at 3.1 at%, the difference in flat band voltage is 0.6 V, which is sufficient. However, the capacitance decreases due to the decrease in dielectric constant, and Sb itself A flat band shift in the negative direction due to an increase in the fixed charge formed is observed.

  According to the above explanation and the knowledge of the present inventors, it is desirable that the amount of the additive element be 0.003 at% or more and 3 at% or less. Further, if the additive element is reduced to 3 at% or less, a decrease in electron mobility or hole mobility due to scattering of electrons or holes serving as transistor carriers due to an increase in the fixed charge amount can be suppressed to a negligible level.

  As described above, according to this embodiment, it is possible to avoid fluctuations in the threshold and to prevent deterioration of characteristics as much as possible.

  In this embodiment, the same additive element can be added to the N-MIS transistor and the P-MIS transistor, so that the manufacturing process can be prevented from becoming complicated, and the manufacturing cost can be increased. Can be suppressed.

(Second Embodiment)
Next, FIG. 7 shows a semiconductor device according to the second embodiment of the present invention. FIG. 7 is a cross-sectional view of the semiconductor device according to the present embodiment. The semiconductor device according to the present embodiment includes a MIS transistor, and the gate insulating film of the MIS transistor has the same configuration as the gate insulating film of the semiconductor device of the first embodiment. As shown in FIG. 7, a silicon thermal oxide film 22 for element isolation is formed on a p-type silicon substrate 21. On the surface of the silicon substrate, a shallow diffusion layer 30a and a deep diffusion layer 30b, which become n-type source and drain by ion implantation of arsenic, are formed. A gate insulating film 24 made of HfSiSbOx is formed on the surface of the silicon substrate 21. Further, a gate electrode 26 made of polycrystalline silicon is formed on the gate insulating film 24. A side wall 28 made of, for example, a silicon oxide film is formed on the side of the gate electrode 26. A NiSi layer 26 is formed on the deep diffusion layer 27b of the source / drain. The MIS transistor of this embodiment configured as described above is covered with an interlayer insulating film 34.

  Next, the manufacturing process of the semiconductor device according to the present embodiment will be explained with reference to FIGS. 8A to 10C are cross-sectional views illustrating the manufacturing steps of the semiconductor device according to the present embodiment.

  First, the element isolation region 22 is formed in the semiconductor substrate 21. Here, a p-type silicon substrate 21 was used as the semiconductor substrate, and the element isolation region 22 was formed by a well-known method. That is, first, a trench for STI (Shallow Trench Isolation) (for example, a depth of about 0.4 μm) was provided on the substrate 21, and a silicon oxide film was deposited on the entire surface by a CVD (Chemical Vapor Deposition) method. Subsequently, CMP (Chemo-Mechanical Polish) was performed to fill the trench with a silicon oxide film, thereby obtaining an element isolation region 22 as shown in FIG.

Next, after ion implantation of boron (B) for threshold adjustment was performed in a region where an element was to be formed, HfSiSbOx as an insulating film 24 was formed by sputtering as shown in FIG. 8B. The ratio of Hf to the sum of Hf and Si in the insulating film 24 (Hf / (Hf + Si) is controlled by using three targets, an Hf target and an Si target, and an Sb target used as an impurity to be added and controlling the applied power ratio. ) And the amount of impurity Sb contained in the insulating film 24 was controlled. In this embodiment, the ratio Hf / (Hf + Si) is 0.5, but can be any value within the range of 0.3 to 1.0. Moreover, although the amount of Sb is 1.0 at%, as described in the first embodiment, it can be set to any value within the range of 0.003 at% to 3 at%. Note that the amount of the impurity Sb was evaluated using XPS.
Further, the dielectric film may be an oxynitride film or a nitride film containing nitrogen by controlling the amounts of nitrogen and oxygen mixed in the atmosphere during sputtering. The substrate temperature at the time of film formation can be arbitrarily set, but in this embodiment, it was performed at room temperature. The thickness of the insulating film 24 can be determined as appropriate within a range of 2 nm to 5 nm, but in this embodiment, it is 4 nm.

Next, a polycrystalline silicon film to be the semiconductor gate electrode 26 was deposited on the gate insulating film 24 by CVD in an atmosphere containing Si ₂ H ₆ gas or SiH ₄ gas as shown in FIG.

  Next, a resist pattern 40 is formed on the polycrystalline silicon film, and by using this resist pattern 40 as a mask, the polycrystalline silicon film is patterned by reactive ion etching using CFx gas. A gate electrode 26 was formed as shown in a). Subsequently, the insulating film 24 is etched with an aqueous hydrofluoric acid solution with the resist pattern 40 left, to form a gate insulating film 24 as shown in FIG. 9B. At this time, the surface of the substrate 21 is exposed on both sides of the gate insulating film 24.

Thereafter, as shown in FIG. 9C, arsenic (As) is ion-implanted into the exposed substrate 21 to form a shallow impurity region 30a. The ion implantation conditions at this time were an acceleration voltage of 200 eV and a dose of about 1 × 10 ¹⁵ cm ⁻² .

Next, after removing the resist pattern 40, SiO ₂ or SiN is deposited on the entire surface by a CVD method or the like, and is etched on the entire surface using anisotropic etching, as shown in FIG. A gate sidewall 28 was left on the side surface of the electrode 26 with a thickness of 10 nm.

Using the gate sidewall 28 and the gate electrode 26 as a mask, arsenic is ion-implanted into the substrate 21 under the conditions of an acceleration voltage of 10 keV and a dose of 1 × 10 ¹⁵ cm ⁻² , as shown in FIG. A deep impurity region 30b was formed. Subsequently, heat treatment was performed at a temperature of 600 ° C. or higher to activate the impurities, and the extension layer 30a and the source / drain regions 30b were formed. In order to activate the impurities, it is preferable to perform a high-temperature treatment for a short time of about 10 seconds at a temperature of about 1000 ° C.

  Next, a Ni film is formed on the entire surface, and heat treatment is performed at a temperature of about 400 ° C. to react the exposed silicon and Ni. Then, unreacted Ni is removed by a mixed liquid of sulfuric acid and hydrogen peroxide solution. It was removed by etching. Thereby, as shown in FIG. 10C, a Ni silicide (NiSi) layer 32 is formed on the source / drain region 30b. At this time, a Ni silicide layer is also formed on the upper surface of the gate electrode 26 made of polycrystalline silicon (not shown). Thereafter, a silicon oxide film was deposited on the entire surface by a CVD method to form an interlayer insulating film 34 shown in FIG.

Although not shown in the drawing, a MOS structure up to the first layer wiring is obtained thereafter by manufacturing by a well-known method. For example, a contact hole leading to the NiSi layer 32 is opened in the interlayer insulating film 34, TiN as a barrier metal is deposited by CVD on the bottom surface of the contact hole, W is deposited as a plug material on the entire surface, and the contact hole is formed. Embed.
Thereafter, the entire surface is planarized by CMP, an Al—Cu film is subsequently deposited as a wiring material, and the Al—Cu film is patterned by photolithography to obtain a MOS structure up to the first layer wiring.

  Similarly to the first embodiment, the semiconductor device of the present embodiment can avoid fluctuations in threshold and can prevent deterioration of characteristics as much as possible.

  Further, similarly to the first embodiment, the same additive element can be added to the N-MIS transistor and the P-MIS transistor, so that the manufacturing process can be prevented from becoming complicated, and the manufacturing cost increases. Can be suppressed.

(Third embodiment)
Next, a semiconductor device according to a third embodiment of the present invention is shown in FIG. FIG. 11 is a sectional view of the semiconductor device according to the present embodiment. The semiconductor device of this embodiment has a configuration in which the gate electrode 26 made of polysilicon in the semiconductor device according to the second embodiment shown in FIG. 7 is replaced with a gate electrode 27 made of a metal semiconductor compound, for example, Ni silicide (NiSi). ing.

  Next, the manufacturing process of the semiconductor device of this embodiment will be described with reference to FIG. FIG. 12 is a cross-sectional view showing the manufacturing process of the semiconductor device of this embodiment.

  First, the processes up to the step of forming the interlayer insulating film 34 are formed in the same manner as in the second embodiment described above. Thereafter, as shown in FIG. 12, a Ni film 29 is deposited on the entire surface, and heat treatment is performed at a temperature of about 400 ° C. to react all the silicon in the polycrystalline silicon film 26 with Ni, thereby forming Ni silicide. Since the heat treatment temperature is as low as about 400 ° C., the profiles of the extension layer 30a and the source / drain region 30b do not change. In the polycrystalline silicon film 26, phosphorus (P), arsenic (As), antimony (Sb), or boron (B) may be introduced in advance. After the reaction, unreacted Ni is removed using a mixed solution of sulfuric acid and hydrogen peroxide solution to form a gate electrode 27 made of NiSi as shown in FIG.

Although not shown in the drawing, a MOS structure up to the first layer wiring is obtained thereafter by manufacturing by a well-known method. For example, a contact hole leading to the NiSi layer 32 is opened in the interlayer insulating film 34, TiN as a barrier metal is deposited by CVD on the bottom surface of the contact hole, W is deposited as a plug material on the entire surface, and the contact hole is formed. Embed.
Thereafter, the entire surface is planarized by CMP, an Al—Cu film is subsequently deposited as a wiring material, and the Al—Cu film is patterned by photolithography to obtain a MOS structure up to the first layer wiring.

  Similarly to the first embodiment, the semiconductor device of the present embodiment can avoid fluctuations in threshold and can prevent deterioration of characteristics as much as possible.

  Further, similarly to the first embodiment, the same additive element can be added to the N-MIS transistor and the P-MIS transistor, so that the manufacturing process can be prevented from becoming complicated, and the manufacturing cost increases. Can be suppressed.

(Fourth embodiment)
Next, FIG. 10 shows a semiconductor device according to the fourth embodiment of the present invention. The semiconductor device of this embodiment is the same as the semiconductor device of the second embodiment shown in FIG. 7 except that the gate insulating film 24 includes an insulating film 24a made of HfSiSbOx, an insulating film 24b made of HfSiOx, and an insulating film 24c made of HfSiSbOx. The structure is replaced with a gate insulating film 24 having a three-layer structure.

  Next, a method for manufacturing the semiconductor device of this embodiment will be described with reference to FIGS. 14 (a) to 16 (c). FIG. 14A to FIG. 16C are cross-sectional views showing the manufacturing process of the semiconductor device of this embodiment.

  First, the element isolation region 22 is provided in the semiconductor substrate 21. Here, a p-type Si substrate was used as the semiconductor substrate, and the element isolation region 22 was formed by a well-known method. That is, first, an STI trench (for example, a depth of about 0.4 μm) was provided on the substrate 21, and a silicon oxide film was deposited on the entire surface by CVD. Subsequently, CMP was performed to fill the trench with a silicon oxide film, thereby obtaining an element isolation region 22 as shown in FIG.

  Subsequently, after ion implantation of B for threshold adjustment in a region where an element is to be formed, HfSiSbOx as an insulating film 24a was formed by sputtering as shown in FIG. 14B. Using three targets, an Hf target and an Si target, and an Sb target used as an impurity to be added, the ratio of Hf to Si in the insulating film 24a (Hf / (Hf + Si)) and insulation are controlled by controlling the applied power ratio. The amount of impurity Sb contained in the film 24a was controlled. In this embodiment, the ratio Hf / (Hf + Si) is 0.5, but can be any value within the range of 0.3 to 1.0. Moreover, although the amount of Sb is 1.0 at%, it can be set to any value within the range of 0.003 at% to 3 at%. Note that the amount of the impurity Sb was evaluated using XPS. Further, the insulating film 24a may be an oxynitride film or a nitride film containing nitrogen by controlling the amounts of nitrogen and oxygen mixed in the atmosphere during sputtering. The substrate temperature at the time of film formation can be arbitrarily set, but in this embodiment, it was performed at room temperature. The film thickness of the insulating film 24a made of HfSiSbOx can be determined as appropriate within a range of 0.5 nm to 1.5 nm, and is set to 1 nm in this embodiment.

  Next, the power applied to the Sb target was set to 0, and the insulating film 24b made of HfSiOx was formed so as not to cause sputtering from the Sb target. The thickness of the insulating film 24b made of HfSiOx can be appropriately determined within a range of 1 nm to 3 nm, and in this embodiment, it is 2 nm.

  Subsequently, an insulating film 24c made of HfSiSbOx was formed on the insulating film 24b by a sputtering method in the same manner as the method for depositing the insulating film 24a. In this embodiment, the ratio Hf / (Hf + Si) is 0.5, but can be any value within the range of 0.3 to 1.0. The amount of Sb is 1.0 at%, but can be any value within the range of 0.003 at% to 3 at%. Of course, as long as the amount of Sb in the insulating film 24c made of HfSiSbOx is in the range of 0.003 at% to 3 at%, the contents of the lower film 24a made of HfSiSbOx and Sb may be different.

The deposition method of the gate insulating film 24 is not limited to the above method. For example, when depositing by the CVD method, insulating films 24a and 24c made of HfSiSbOx are formed by flowing a gas such as SbCl ₃ which is a source gas of an additive element only when depositing the insulating film 24a and the insulating film 24c. Also good.

Next, as shown in FIG. 14C, a polycrystalline silicon film to be the semiconductor gate electrode 26 was deposited on the gate insulating film 24 by CVD in an atmosphere containing Si ₂ H ₆ or SiH ₄ .

  Next, a resist pattern 40 is formed on the polycrystalline silicon film, and by using this resist pattern 40 as a mask, the polycrystalline silicon film is patterned by reactive ion etching using CFx gas. A gate electrode 26 was formed as shown in a). Subsequently, with the resist pattern 40 left, the insulating film 24 is etched with a hydrofluoric acid aqueous solution and processed as shown in FIG. 15B to form three layers of insulating films 24a, 24b, and 24c. A gate insulating film 24 having a structure was obtained. At this time, the surface of the semiconductor substrate 21 on both sides of the gate insulating film 24 is exposed.

Next, as shown in FIG. 15C, arsenic ions were implanted into the exposed substrate 21 to form a shallow impurity region 30a. The ion implantation conditions at this time were an acceleration voltage of 200 eV and a dose of about 1 × 10 ¹⁵ cm ⁻² .

Subsequently, after removing the resist pattern 40, SiO ₂ or SiN is deposited on the entire surface by a CVD method or the like, and is etched on the entire surface, so that a 10 nm thickness is formed on the side surface of the gate electrode 26 as shown in FIG. The gate side wall 28 was left with a film thickness.

Using the gate sidewall 28 and the gate electrode 26 as a mask, arsenic is ion-implanted into the substrate 21 under the conditions of an acceleration voltage of 10 keV and a dose of 1 × 10 ¹⁵ cm ⁻² , for example, as shown in FIG. Impurity region 30b was formed. Subsequently, the impurity implanted by heat treatment at a temperature of 600 ° C. or higher was activated, and the extension layer 30a and the source / drain regions 30b were formed. In order to activate the impurities, it is preferable to perform a high-temperature treatment for a short time of about 10 seconds at a temperature of about 1000 ° C.

  Next, after forming a Ni film on the entire surface and performing a heat treatment at a temperature of about 400 ° C., unreacted Ni is removed by etching with a mixed liquid of sulfuric acid and hydrogen peroxide solution, whereby FIG. ), A Ni silicide (NiSi) layer 32 was formed on the source / drain region 30b. At this time, a Ni silicide layer is also formed on the upper surface of the gate electrode 26 made of polycrystalline silicon (not shown). Thereafter, a silicon oxide film was deposited on the entire surface by a CVD method to form an interlayer insulating film 34 shown in FIG.

Although not shown in the drawing, a MOS structure up to the first layer wiring is obtained thereafter by manufacturing by a well-known method. For example, a contact hole leading to the NiSi layer 32 is opened in the interlayer insulating film 34, TiN as a barrier metal is deposited by CVD on the bottom surface of the contact hole, W is deposited as a plug material on the entire surface, and the contact hole is formed. Embed.
Thereafter, the entire surface is planarized by CMP, an Al—Cu film is subsequently deposited as a wiring material, and the Al—Cu film is patterned by photolithography to obtain a MOS structure up to the first layer wiring.

  Similarly to the first embodiment, the semiconductor device of the present embodiment can avoid fluctuations in threshold and can prevent deterioration of characteristics as much as possible.

  Further, similarly to the first embodiment, the same additive element can be added to the N-MIS transistor and the P-MIS transistor, so that the manufacturing process can be prevented from becoming complicated, and the manufacturing cost increases. Can be suppressed.

  Note that the gate insulating film 24 does not have to be three layers as in this embodiment, and it is sufficient that the concentration of the additive element is high at the interface with the semiconductor substrate or the interface with the gate electrode. For example, as shown in FIG. 17, the concentration of the additive element of the gate insulating film 24 made of a high dielectric metal oxide film to which the additive element is added is such that the concentration between the gate insulating film central portion and the interface with the gate electrode and the semiconductor substrate You may comprise so that it may each increase toward an interface. Further, the gate insulating film may be configured to increase from the center of the gate insulating film toward at least one of the interface with the gate electrode and the interface with the semiconductor substrate. In FIG. 17, the concentration of the additive element increases linearly from the center of the gate insulating film toward the interface with the gate electrode and the interface with the semiconductor substrate, but may be configured to increase stepwise. . Further, the additive element may be formed so that the concentration of the additive element increases stepwise, and then the additive element may be diffused toward the central portion of the gate insulating film by performing heat treatment at a temperature of about 600 ° C.

  As in this embodiment, by configuring the concentration of the additive element to be high at the interface with the gate electrode or the interface with the semiconductor substrate, oxygen vacancies that are likely to form near the electrode or the semiconductor substrate are effectively compensated. In addition, the increase in gate leakage current and the increase in fixed charge can be reduced.

  Various modifications can be made to the above-described second to fourth embodiments. Although description has been made using antimony (Sb) as the additive element, phosphorus (P), arsenic (As), or bismuth (Bi), which are the same group 15 elements as Sb, may be used as the additive element. Further, sulfur (S), selenium (Se), and tellurium (Te) which are group 16 elements may be used. Vanadium (V), niobium (Nb), and tantalum (Ta) which are group 5 elements may be used. Further, chromium (Cr), molybdenum (Mo), or tungsten (W) which are group 6 elements may be used. When any of Sb, P, As, and Bi is used as the additive element, oxygen vacancies formed in the gate electrode formation process or the activation heat treatment process are diffused in the gate insulating film. In order to compensate effectively by doing, it is preferable that it is 0.1 at% or more and 3 at% or less. In addition, when any of S, Se, Te, V, Nb, Ta, Cr, Mo, and W is used as the additive element, oxygen formed in the gate electrode formation process or the heat treatment process corresponding to activation is used. In order to compensate for the deficiency, it is preferably 0.003 at% or more and 3 at% or less. Note that the additive element need not be one kind, and a plurality of additive elements may be added simultaneously. However, as described in the first embodiment, the total concentration of the additive elements is desirably 3 at% or less.

As the silicide layer 32 formed on the source / drain region 30b, CoSi ₂ or TiSi ₂ can be used instead of NiSi.

Further, SiGe may be used as the gate electrode. SiGe, for example a gas SiH ₄ or Si ₂ H _6, can be formed by mixing a gas containing Ge such as Ge ₂ H _6. Silicide and / or germanide may be used as the gate electrode. In this case, examples of the silicide include WSi ₂ , NiSi, CoSi ₂ , PtSi, and MoSi ₂ . The _{germanide, WGe 2, NiGe, NiGe 2} , CoGe 2, PtGe, and the like moge ₂ and the like. Alternatively, a lanthanoid metal silicide or germanide may be used.

As the gate insulating film 24, a film made of HfO ₂ or a mixed film of HfO ₂ and aluminum oxide can be used, a film made of ZrO ₂ or a mixed film of ZrO ₂ and silicon oxide, A mixed film of ZrO ₂ and Al ₂ O ₃ may be used. Further, a mixed film of an oxide film or a TiO ₂ and silicon comprising a TiO _2, or a mixed film of TiO ₂ and Al ₂ O _3. Further, it may be an oxide of a lanthanoid metal typified by La ₂ O ₃ or a mixture of this oxide and SiO ₂ . A mixture of an oxide of a lanthanoid metal such as La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu and Al ₂ O ₃ may be used.

For the formation of the gate insulating film 24, MOCVD, halide CVD, or atomic layer deposition may be used. It is desirable to nitride the gate insulating film because it causes phase separation and crystallization of the film due to heat treatment such as electrode activation, leading to an increase in leakage current. For example, in an atmosphere containing NH ₃ It can be nitrided by CVD. Alternatively, an atmosphere containing N, for example, Hf in the case of Hf, can be performed by CVD using Hf (N (C ₂ H ₅ ) ₂ ) ₄ . When the metal in the metal oxide is changed, a precursor containing nitrogen may be selected as a precursor containing the metal. Further, nitrogen activated by plasma can be contained in the atmosphere. Or you may expose to N plasma after film-forming. At this time, the additive element may be added by selecting and simultaneously introducing a source gas corresponding to the additive element such as SbCl ₃ . In addition to the above-described film forming method, the additive element can be added by ion-implanting the additive element after depositing the gate insulating film.

  In order to prevent oxygen (O) from escaping to the gate electrode side, an insulating film 25 made of Si oxide or Si oxynitride is provided between the gate insulating film 24 and the gate electrode 26 as shown in FIG. May be provided. However, in order to prevent an increase in leakage current due to a decrease in dielectric constant, the film thickness of the insulating film 25 is desirably 2 nm or less.

  In order to prevent oxygen (O) from escaping to the semiconductor substrate side, an insulating film made of Si oxide or Si oxynitride is formed between the gate insulating film 24 and the semiconductor substrate 21 as shown in FIG. 23 may be provided. However, in order to prevent an increase in leakage current due to a decrease in dielectric constant, the film thickness of the insulating film 23 is desirably 2 nm or less.

  In the second to fourth embodiments, the MIS transistor formed directly on the Si substrate has been described as an example. However, the present invention is not limited to such a structure. The present invention can also be applied to an SOI (Silicon ON Insulator) structure, a vertical MIS transistor that allows current to flow in the direction perpendicular to the substrate, and a vertical MIS transistor that allows current to flow to the side surface of the Si pillar.

  Furthermore, the same effect can be obtained when Ge, SiGe, strained Si, or strained Ge is used as the substrate instead of silicon as the semiconductor substrate.

(Fifth embodiment)
Next, a semiconductor device according to a fifth embodiment of the present invention will be described with reference to FIGS.

  The semiconductor device of this embodiment is a non-volatile semiconductor memory device, and FIG. A silicon thermal oxide film 52 for element isolation is provided on the p-type silicon substrate 51. In the silicon substrate 51, a shallow diffusion layer 58a and a deep diffusion layer 58b to be n-type source and drain are formed by arsenic ion implantation. On the surface of the silicon substrate 51, a tunnel oxide film 53 made of oxynitride containing silicon, oxygen, and nitrogen as main components is provided as a tunnel oxide film. On the tunnel oxide film 53, a floating gate electrode 54a made of polycrystalline silicon is provided. Further, an interelectrode insulating film 55 made of hafnium oxide (HfSiSbOx) having a film thickness of 15 nm is provided on the floating gate electrode 54a. Further, a control gate electrode 54 b made of polycrystalline silicon is provided on the interelectrode insulating film 55. The floating gate electrode 54a, the interelectrode insulating film 55, and the control gate electrode 54b constitute a gate portion 56. An insulating film 57 made of silicon oxide is provided on the side and upper surface of the gate portion 56 made of the floating gate electrode 54a, the interelectrode insulating film 55, and the control gate electrode 54b. The insulating film 57 and the source / drain regions 58b are covered with an interlayer insulating film 59 made of silicon oxide. The interlayer insulating film 59 is provided with openings (not shown) for making contact with the source and drain regions 58b and the control gate electrode 54b, and an electrode made of Al so as to fill these openings. (Not shown) is provided.

  Next, the method for fabricating the nonvolatile semiconductor memory device according to the present embodiment will be explained with reference to FIGS.

  First, as shown in FIG. 21A, an element isolation region 52 is provided in a semiconductor substrate 51. Here, a p-type Si substrate was used as the semiconductor substrate 51, and the element isolation region 52 was formed by a well-known method. That is, first, an STI trench (for example, a depth of about 0.4 μm) was provided on the substrate 51, and a silicon oxide film was deposited on the entire surface by CVD. Subsequently, CMP was performed to fill a silicon oxide film in the trench, and an element isolation region 52 was obtained as shown in FIG.

Next, as shown in FIG. 21B, a silicon oxide film having a thickness of 7 nm is formed by, for example, thermal oxidation with dry oxygen, and the silicon oxide film is exposed to, for example, an ammonia (NH ₃ ) gas atmosphere to form nitrogen atoms. A tunnel oxide film (gate insulating film) 53 made of oxynitride into which is introduced is formed.

  Subsequently, as shown in FIG. 21C, an n-type polycrystalline silicon film 54a having a thickness of 200 nm and doped with phosphorus is deposited on the tunnel oxide film 53.

  Next, as shown in FIG. 22A, an interelectrode insulating film 55 made of hafnium oxide (HfSiSbOx) to which antimony (Sb) is added as an impurity having a thickness of 15 nm, for example, is sputtered on the polycrystalline silicon film 54a. The film was formed by the method. The interelectrode insulating film 55 made of HfSiSbOx is formed by using three targets, that is, an Hf target, an Si target, and an Sb target used as an impurity to be added, and the applied power ratio is controlled to make the interelectrode insulating film 55 made of HfSiSbOx. This was performed by controlling the ratio of Hf to the sum of Hf and Si (Hf / (Hf + Si)) and the amount of impurity Sb contained in the HfSiSbOx film. In this embodiment, the ratio Hf / (Hf + Si) is 0.5, but can be any value within the range of 0.3 to 1.0. Moreover, although the amount of Sb is 1.0 at percent, it can be any value within the range of 0.003 at% to 3 at%.

Subsequently, heat treatment is performed using dry oxygen at a temperature of 650 ° C. as shown in FIG.
Atomic oxygen introduced at this time repairs defects such as oxygen vacancies and helps efficiently introduce Sb atoms that were not introduced when deposited by sputtering into oxygen vacancy sites or hafnium vacancy sites. .

  Next, as shown in FIG. 22C, an n-type polycrystalline silicon 54b doped with phosphorus having a thickness of 200 nm is deposited on the interelectrode insulating film 55.

  Next, as shown in FIG. 23A, a resist pattern 60 is formed on the n-type polycrystalline silicon 54b, and using the resist pattern 60 as a mask, the polycrystalline silicon film 54b, the interelectrode insulating film 55, the polycrystalline The silicon film 54a and the tunnel oxide film 53 are patterned by a reactive ion etching method to form the gate portion 56 and the gate insulating film 53. At this time, the surface of the semiconductor substrate 51 is exposed on both sides of the gate portion 56.

Further, as shown in FIG. 23B, arsenic ions are implanted into the exposed element region of the substrate 51 to form a shallow impurity region 58a. The implantation conditions at this time were 200 eV and a dose of about 1 × 10 ¹⁵ cm ⁻² . Thereafter, the resist pattern is removed.

  Next, as shown in FIG. 24A, heat treatment is performed in an oxidizing atmosphere for the purpose of recovery of processing damage and the like, and a post-oxide film 57 of about 3 nm is formed so as to cover the side surface and upper surface of the gate portion 56. .

Next, as shown in FIG. 24B, for example, phosphorus is ion-implanted over the entire surface with a dose of 3 × 10 ¹⁵ cm ⁻² . The implanted phosphorus ions are distributed inside the silicon substrate 51 around the peak depth depending on the acceleration energy. Thereafter, for example, heat treatment is performed at 1000 ° C. for 20 seconds to diffuse and activate phosphorus in the silicon substrate 51 to form a diffusion layer 59b to be a source / drain region. Thereafter, a silicon oxide film having a thickness of 300 nm is deposited on the entire surface by a CVD method to form an interlayer insulating film 58 shown in FIG.

  Although not shown in the drawing, a MOS structure up to the first layer wiring is obtained thereafter by manufacturing by a well-known method. For example, a contact hole leading to the source / drain region 57b is opened in the interlayer insulating film 58, TiN as a barrier metal is deposited by CVD on the bottom surface of the contact hole, W is deposited as a plug material on the entire surface, and then contact is made. Embed the hole. Thereafter, the entire surface is planarized by CMP, an Al—Cu film is subsequently deposited as a wiring material, and the Al—Cu film is patterned by photolithography to obtain a MOS structure up to the first layer wiring.

  According to this embodiment, the interelectrode insulating film 55 between the floating gate electrode 54a and the control gate electrode 54b is made of a material in which 1% of antimony is added to hafnium oxide, thereby compensating for defects such as oxygen vacancies. Thus, a nonvolatile semiconductor memory device with low leakage current can be realized.

  As described above, according to the present embodiment, deterioration of element characteristics can be prevented as much as possible.

  Various modifications can be made to this embodiment. Although description has been given using Sb as the additive element, phosphorus, arsenic, or bismuth, which is the same group 15 element as Sb, may be used as the additive element. Further, sulfur, selenium and tellurium which are group 16 elements may be used. Vanadium, niobium, and tantalum, which are Group 5 elements, may be used. Further, a group 6 element such as chromium, molybdenum, or tungsten may be used. When any one of Sb, P, As, and Bi is used as the additive element, the oxygen formed in the gate electrode formation step or the heat treatment step corresponding to the activation effectively by diffusing in the gate insulating film. In order to compensate for deficiency, it is preferably 0.1 at% or more and 3 at% or less. In addition, when any of S, Se, Te, V, Nb, Ta, Cr, Mo, and W is used as the additive element, oxygen formed in the gate electrode formation process or the heat treatment process corresponding to activation is used. In order to compensate for the deficiency, it is preferably 0.003 at% or more and 3 at% or less. Note that the additive element need not be one kind, and a plurality of additive elements may be added simultaneously. However, as described in the first embodiment, the total concentration of the additive elements is desirably 3 at% or less.

Further, SiGe may be used as the gate electrode as the floating gate electrode 54a and the control gate electrode 54b. SiGe, for example a gas SiH ₄ or Si ₂ H _6, can be formed by mixing a gas containing Ge such as Ge ₂ H _6. Silicide and / or germanide may be used as the floating gate electrode 54a and the control gate electrode 54b. Examples of the silicide include WSi ₂ , NiSi, CoSi ₂ , PtSi, and MoSi ₂ . The _{germanide, WGe 2, NiGe, NiGe 2} , CoGe 2, PtGe, and the like moge ₂ and the like. Alternatively, a lanthanoid metal silicide or germanide may be used.

As the interelectrode insulating film 55, an HfO ₂ film, a mixture of HfO ₂ and aluminum oxide, ZrO ₂ , a mixture of ZrO ₂ and silicon oxide, or ZrO ₂ and Al ₂ can also be used. A mixture with O ₃ may also be used. TiO ₂ , a mixture of TiO ₂ and silicon oxide, or a mixture of TiO ₂ and Al ₂ O ₃ may be used. It may be an oxide of a lanthanoid metal typified by La ₂ O ₃ or a mixture of this oxide and SiO ₂ . Even an oxide of a lanthanoid metal such as La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu, or a mixture of this oxide and Al ₂ O ₃ Good.

For forming the interelectrode insulating film 55, MOCVD, halide CVD, or atomic layer deposition may be used. The insulating film 55 is preferably nitrided, for example, in an atmosphere containing NH ₃ , because the film undergoes phase separation or crystallization due to heat treatment such as electrode activation, leading to an increase in leakage current. It can be nitrided by CVD. Alternatively, an atmosphere containing N, for example, Hf in the case of Hf, can be performed by CVD using Hf (N (C ₂ H ₅ ) ₂ ) ₄ . When the metal in the metal oxide is changed, a precursor containing nitrogen may be selected as a precursor containing the metal. Further, nitrogen activated by plasma can be contained in the atmosphere. Or you may expose to N plasma after film-forming.
At this time, the additive element may be added by selecting and simultaneously introducing a source gas corresponding to the additive element such as SbCl ₃ . In addition to the above-described film forming method, the additive element can be added by ion-implanting the additive element after depositing the gate insulating film.

  Similarly to the case described with reference to FIG. 18, a Si oxide film or a Si oxynitride film may be included between the interelectrode insulating film 55, the floating gate electrode 54a, and the control gate electrode 54b. However, in order to prevent an increase in leakage current due to a decrease in dielectric constant, the thickness of the Si oxide film or Si oxynitride film is desirably 2 nm or less.

  Further, even when Ge, SiGe, strained Si, or strained Ge is used as the semiconductor substrate 51, the nonvolatile semiconductor memory device can be manufactured as in the fifth embodiment, and the same effect can be obtained.

  As described above, according to each embodiment of the present invention, it is possible to prevent deterioration of element characteristics as much as possible.

FIG. 3 is a schematic diagram showing a bonding state in a metal oxide film constituting the gate insulating film of the semiconductor device according to the first embodiment of the present invention. The spectrum measured by XPS showing the coupling | bonding state of Sb added to the gate insulating film of the semiconductor device by 1st Embodiment and comparative example of this invention. 6 shows gate leakage current characteristics of the semiconductor device according to the first embodiment of the present invention and a comparative example. The figure which shows the capacity-voltage characteristic of the semiconductor device by 1st Embodiment of this invention. FIG. 10 is a graph showing capacitance-voltage characteristics of a conventional semiconductor device. FIG. 11 is a graph showing capacitance-voltage characteristics of a semiconductor device according to a comparative example. Sectional drawing which shows the semiconductor device by 2nd Embodiment of this invention. Sectional drawing which shows the manufacturing process of the semiconductor device by 2nd Embodiment of this invention. Sectional drawing which shows the manufacturing process of the semiconductor device by 2nd Embodiment of this invention. Sectional drawing which shows the manufacturing process of the semiconductor device by 2nd Embodiment of this invention. Sectional drawing which shows the semiconductor device by 3rd Embodiment of this invention. Sectional drawing which shows the manufacturing process of the semiconductor device by 3rd Embodiment of this invention. Sectional drawing which shows the semiconductor device by 4th Embodiment of this invention. Sectional drawing which shows the manufacturing process of the semiconductor device by 4th Embodiment of this invention. Sectional drawing which shows the manufacturing process of the semiconductor device by 4th Embodiment of this invention. Sectional drawing which shows the manufacturing process of the semiconductor device by 4th Embodiment of this invention. Sectional drawing which shows the manufacturing process of the semiconductor device by the modification of 4th Embodiment of this invention. Sectional drawing of the semiconductor device by the modification of 1st thru | or 4th Embodiment of this invention. Sectional drawing of the semiconductor device by the modification of 1st thru | or 4th Embodiment of this invention. Sectional drawing of the semiconductor device by the modification of 5th Embodiment of this invention. Sectional drawing which shows the manufacturing process of the semiconductor device by 5th Embodiment of this invention. Sectional drawing which shows the manufacturing process of the semiconductor device by 5th Embodiment of this invention. Sectional drawing which shows the manufacturing process of the semiconductor device by 5th Embodiment of this invention. Sectional drawing which shows the manufacturing process of the semiconductor device by 5th Embodiment of this invention.

21 Semiconductor substrate 22 Element isolation region 24 Gate insulating film 24a Insulating film 24b Insulating film 24c Insulating film 26 Gate electrode 28 Side wall 30a Extension layer 30b Source / drain region 32 Silicide layer 34 Interlayer insulating film

Claims (5)

A semiconductor substrate;
A gate insulating film provided on the semiconductor substrate;
A first gate electrode provided on the gate insulating film;
An interelectrode insulating film including a metal and oxygen provided on the first gate electrode;
A second gate electrode provided on the interelectrode insulating film;
Source / drain regions provided in the semiconductor substrate on both sides of the first and second gate electrodes;
With
The inter-electrode insulating film contains at least one additive element selected from phosphorus, arsenic, antimony, and bismuth, and the content thereof is 0.1 at% or more and 3 at% or less. A semiconductor substrate;
A gate insulating film provided on the semiconductor substrate;
A first gate electrode provided on the gate insulating film;
An interelectrode insulating film including a metal and oxygen provided on the first gate electrode;
A second gate electrode provided on the interelectrode insulating film;
Source / drain regions provided in the semiconductor substrate on both sides of the first and second gate electrodes;
With
The interelectrode insulating film contains at least one additive element selected from sulfur, selenium, and tellurium, and the content thereof is 0.003 at% or more and 3 at% or less.   3. The semiconductor device according to claim 1, wherein the interelectrode insulating film includes a bond between the metal element and the additive element or a bond between the oxygen and the additive element.   An insulating film made of Si oxide or Si oxynitride is provided between the interelectrode insulating film and the first gate electrode and between the interelectrode insulating film and the second gate electrode. The semiconductor device according to claim 1, wherein: It said metals, Hf, Zr, semiconductor device according to any one of claims 1 to 4, characterized in that at least one element selected from the group consisting of Ti and lanthanoid elements.

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