Semiconductor device and method for manufacturing the same

Abstract

To suppress increase in contact resistance.SOLUTION: There is provided a semiconductor device including: a ferroelectric capacitor including a first electrode, a ferroelectric film provided on the first electrode, and a second electrode provided on the ferroelectric film; an oxidation suppression film provided in contact with a top surface of the second electrode; and a conductive plug including an adhesion film that penetrates through the oxidation suppression film and that is in contact with the oxidation suppression film and the second electrode, and a conductive film on the adhesion film. The second electrode includes a first metal element, the adhesion film includes a second metal element, and the oxidation suppression film includes an oxide film, a nitride film, or an iridium nitride film of a third metal element that has a higher ionization tendency than the first metal element and the second metal element.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a semiconductor device and a method for manufacturing the semiconductor device. [Background technology]

[0002] Ferroelectric random access memories (FeRAMs) are known that store data in ferroelectric capacitors by utilizing polarization reversal of ferroelectrics. The ferroelectric capacitors include a lower electrode, a ferroelectric film provided on the lower electrode, and an upper electrode provided on the ferroelectric film. A conductive plug is formed on the upper electrode, connecting to the upper electrode.

[0003] The characteristics of a ferroelectric film deteriorate when it is reduced by hydrogen generated during the manufacturing process of FeRAM. Therefore, a method for suppressing the penetration of hydrogen into the ferroelectric film has been proposed (for example, Patent Document 1). Furthermore, a ferroelectric capacitor is formed by patterning it into a desired shape using etching or the like, and a recovery annealing process (heat treatment) is performed in an oxygen atmosphere to repair process damage. This recovery annealing process forms an oxide layer on the top surface of the upper electrode, and this oxide layer can increase the contact resistance between the conductive plug and the upper electrode. Therefore, a method for suppressing the increase in contact resistance has been proposed (for example, Patent Document 2). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-188243 [Patent Document 2] Japanese Patent Application Laid-Open No. 2001-127264 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the method described in Patent Document 2 leaves room for improvement in terms of suppressing an increase in contact resistance between the conductive plug and the upper electrode.

[0006] In one aspect, an object is to suppress an increase in contact resistance. [Means for solving the problem]

[0007] In one aspect, a semiconductor device includes a ferroelectric capacitor having a first electrode, a ferroelectric film provided on the first electrode, and a second electrode provided on the ferroelectric film, an oxidation inhibitor film provided in contact with the upper surface of the second electrode, and a conductive plug penetrating the oxidation inhibitor film and including an adhesion film in contact with the oxidation inhibitor film and the second electrode and a conductive film on the adhesion film, wherein the second electrode includes a first metal element, the adhesion film includes a second metal element, and the oxidation inhibitor film includes an oxide film or nitride film of a third metal element having a greater ionization tendency than the first metal element and the second metal element, or an iridium nitride film.

[0008] In one aspect, a method for manufacturing a semiconductor device includes the steps of: forming a film that will become a first electrode; forming a ferroelectric film on the film that will become the first electrode; forming a film that will become a second electrode on the ferroelectric film; forming an oxidation inhibitor film that contacts the upper surface of the film that will become the second electrode; patterning the film that will become the first electrode, the ferroelectric film, the film that will become the second electrode, and the oxidation inhibitor film to form a ferroelectric capacitor having the first electrode, the ferroelectric film, and the second electrode; performing a heat treatment on the ferroelectric capacitor in an oxygen atmosphere; and, after the heat treatment, forming a conductive plug that penetrates the oxidation inhibitor film and includes an adhesion film that contacts the oxidation inhibitor film and the second electrode and a conductive film on the adhesion film, wherein the second electrode contains a first metal element, the adhesion film contains a second metal element, and the oxidation inhibitor film includes an oxide film or nitride film of a third metal element that has a greater ionization tendency than the first metal element and the second metal element, or an iridium nitride film. [Effects of the Invention]

[0009] As one aspect, an increase in contact resistance can be suppressed. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a cross-sectional view of a semiconductor device according to a first embodiment. [Figure 2] 2(a) to 2(c) are cross-sectional views (part 1) illustrating a method for manufacturing a semiconductor device according to the first embodiment. [Figure 3] 3(a) and 3(b) are cross-sectional views (part 2) illustrating the method for manufacturing the semiconductor device according to the first embodiment. [Figure 4] 4(a) and 4(b) are cross-sectional views (part 3) illustrating the method for manufacturing the semiconductor device according to the first embodiment. [Figure 5] 5(a) and 5(b) are cross-sectional views (part 1) showing a method for manufacturing a semiconductor device according to a comparative example. [Figure 6] 6(a) and 6(b) are cross-sectional views (part 2) showing a method for manufacturing a semiconductor device according to a comparative example. [Figure 7] FIG. 7 shows the results of an oxidation investigation carried out on Samples 1 and 2. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments of the present invention will be described with reference to the drawings. [Example]

[0012] FIG. 1 is a cross-sectional view of a semiconductor device 100 according to a first embodiment. As shown in FIG. 1, the semiconductor device 100 is formed on a semiconductor substrate 10, which is, for example, a P-type silicon substrate. An element isolation region 12 made of an insulator such as silicon oxide (SiO2) is formed in a surface layer portion of the semiconductor substrate 10, and defines a region in which a transistor Ta is formed. Also, a source region S and a drain region D of the transistor Ta are formed in the surface layer portion of the semiconductor substrate 10. The source region S and the drain region D are made of, for example, an N-type semiconductor.

[0013] A gate electrode G is provided on a semiconductor substrate 10 via a gate insulating film 14. The gate insulating film 14 is made of, for example, SiO2, and the gate electrode G is made of, for example, polysilicon. The gate electrode G functions as a word line. Sidewalls 16 made of an insulator such as SiO2 are provided on the sides of the gate electrode G. Silicide layers 18 are provided on the surfaces of the source region S, the drain region D, and the gate electrode G to reduce contact resistance. The transistor Ta is a field-effect transistor.

[0014] A cover film 20, an interlayer insulating film 22, an etch stopper film 24, an interlayer insulating film 26, an oxidation prevention film 28, and a buffer film 30 are stacked in this order on the transistor Ta. The cover film 20 is approximately 50 nm to 100 nm thick and is made of an insulator such as silicon nitride (SiN). The interlayer insulating film 22 is approximately 300 nm to 400 nm thick and is made of SiO2 or the like. The etch stopper film 24 is approximately 20 nm to 50 nm thick and is made of an insulator such as SiN. The interlayer insulating film 26 is approximately 200 nm to 300 nm thick and is made of SiO2 or the like. The oxidation prevention film 28 is approximately 50 nm to 150 nm thick and is made of an insulator such as SiN. The buffer film 30 is approximately 200 nm to 300 nm thick and is made of an insulator such as SiO2.

[0015] Conductive plugs 32, 34 penetrate the interlayer insulating film 22 and the cover film 20 and are connected to the source region S and the drain region D, respectively. The conductive plugs 32, 34 are made of a conductor such as tungsten (W). A wiring 38 that functions as a bit line is provided, penetrating the interlayer insulating film 26 and the etch stopper film 24. The wiring 38 is electrically connected to the drain region D of the transistor Ta via the conductive plug 34. The wiring 38 is made of a conductor such as W. A conductive plug 36 is provided, penetrating the buffer film 30, the oxidation suppression film 28, the interlayer insulating film 26, and the etch stopper film 24, and is connected to the conductive plug 32. The conductive plug 36 is made of a conductor such as W.

[0016] A ferroelectric capacitor Ca is provided on the buffer film 30. The ferroelectric capacitor Ca has a laminated structure in which a lower electrode 40, a ferroelectric film 42, and an upper electrode 44 are laminated. The lower electrode 40 is electrically connected to the source region S of the transistor Ta via conductive plugs 36 and 32.

[0017] The lower electrode 40 has an adhesive film 46, an oxygen barrier conductive film 48, and an electrode film 50 stacked in this order. The adhesive film 46 has a thickness of about 1 nm to 10 nm and is made of a conductor such as titanium nitride (TiN). The adhesive film 46 functions to improve adhesion between the conductive plug 36 and the oxygen barrier conductive film 48. The oxygen barrier conductive film 48 has a thickness of about 50 nm to 100 nm and is a film with low oxygen permeability, and functions to suppress oxygen diffusion into the conductive plug 36. The oxygen barrier conductive film 48 has lower oxygen permeability than the adhesive film 46 and the electrode film 50. The oxygen barrier conductive film 48 is made of, for example, titanium aluminum nitride (TiAlN), titanium aluminum oxynitride (TiAlON), titanium silicon nitride (TiSiN), tantalum aluminum nitride (TaAlN), tantalum aluminum oxynitride (TaAlON), or tantalum silicon nitride (TaSiN). The electrode film 50 has a thickness of about 10 nm to 100 nm, and is made of a conductor such as iridium (Ir).

[0018] The ferroelectric film 42 is formed containing a ferroelectric oxide having a perovskite crystal structure, such as PZT (Pb(Zr,Ti)O3) or SBT (SrBi2Ta2O9), etc. The thickness of the ferroelectric film 42 is about 50 nm to 150 nm.

[0019] The upper electrode 44 is formed to contain a first metal element. In Example 1, the first metal element is iridium (Ir). The upper electrode 44 is formed by laminating an electrode film 52 and an electrode film 54 in this order. For example, the electrode film 52 has a thickness of about 100 nm to 200 nm and is made of iridium oxide (IrO2). The electrode film 54 is provided to reduce contact resistance, has a thickness of 50 nm to 150 nm, and is made of iridium (Ir).

[0020] An oxidation suppression film 56, which is an insulating film, is provided in contact with the upper surface of the electrode film 54 of the upper electrode 44. The oxidation suppression film 56 includes an oxide film or a nitride film of a third metal element. The third metal element is a metal having a higher ionization tendency than the first metal element included in the upper electrode 44 and the second metal element included in the adhesive film 66 of the conductive plug 64, which will be described later. In the first embodiment, the third metal element is aluminum (Al). For example, the oxidation suppression film 56 is an aluminum oxide (Al) film having a thickness of about 50 nm to 100 nm. x O y ) film or aluminum nitride (Al x N y ) membrane.

[0021] The side surfaces of the lower electrode 40, the ferroelectric film 42, the upper electrode 44, and the oxidation prevention film 56 are continuous and do not have discontinuous protruding portions. The widths of the lower electrode 40, the ferroelectric film 42, the upper electrode 44, and the oxidation prevention film 56 may be gradually narrowed from the lower electrode 40 toward the oxidation prevention film 56, or may be substantially the same width.

[0022] A protective film 58 is provided to cover the ferroelectric capacitor Ca and the oxidation prevention film 56. The protective film 58 has a thickness of about 20 nm to 70 nm and is made of aluminum oxide (Al x Oy ), magnesium oxide (Mg x O y ), aluminum nitride (Al x N y ), or magnesium nitride (Mg x N y The protective film 58 has the function of preventing hydrogen and moisture from penetrating into the ferroelectric capacitor Ca.

[0023] The oxidation prevention film 56 and the protective film 58 are made of the same material (e.g., Al x O y ), or may be made of a different material (for example, the oxidation prevention film 56 may be made of Al x O y The protective film 58 is Mg x O y The same material means that the constituent elements are the same, but the composition ratio may be different. x O y ), the Al on the top surface of the upper electrode 44 x O y The thickness of the Al on the side of the ferroelectric capacitor Ca x O y For example, the thickness of the Al x O y The thickness of the Al on the side of the ferroelectric capacitor Ca x O y The thickness may be 1.5 times or more, 2.0 times or more, or 2.5 times or more of the thickness of the substrate.

[0024] An interlayer insulating film 60 made of SiO2 or the like is provided on the protective film 58. The thickness of the interlayer insulating film 60 is approximately 1000 nm to 1800 nm. A conductive plug 64 is provided penetrating the interlayer insulating film 60, the protective film 58, and the oxidation prevention film 56. The conductive plug 64 is connected to the upper electrode 44 of the ferroelectric capacitor Ca. The conductive plug 64 includes an adhesive film 66 in contact with the interlayer insulating film 60, the protective film 58, the oxidation prevention film 56, and the electrode film 54 of the upper electrode 44, and a conductive film 68 provided on the adhesive film 66. The adhesive film 66 functions to improve adhesion between the conductive film 68 and the interlayer insulating film 60, the protective film 58, the oxidation prevention film 56, and the electrode film 54 of the upper electrode 44. The adhesive film 66 is formed to contain a second metal element. The second metal element is a metal having a lower ionization tendency than the third metal element (Al) contained in the oxidation prevention film 56. In Example 1, the second metal element is titanium (Ti). For example, the adhesion film 66 has a thickness of about 2 nm to 10 nm and is formed of titanium (Ti), titanium nitride (TiN), or a laminate of Ti and TiN. The conductive film 68 is formed of, for example, tungsten (W).

[0025] An interconnection 70 functioning as a plate line is provided on the interlayer insulating film 60. The interconnection 70 has a layered structure in which a barrier film 72, an interconnection film 74, and a barrier film 76 are stacked. The barrier films 72 and 76 are made of, for example, Ti or TiN. The interconnection film 74 is made of a conductor such as an aluminum-copper alloy. The interconnection 70 is electrically connected to the upper electrode 44 of the ferroelectric capacitor Ca via a conductive plug 64.

[0026] [Manufacturing method] 2(a) to 4(b) are cross-sectional views showing a manufacturing method of the semiconductor device 100 according to the first embodiment. FIG. 4(b) is an enlarged view of region A in FIG. 4(a). As shown in FIG. 2(a), an isolation region 12 is formed in a surface layer of a semiconductor substrate 10, which is, for example, a P-type silicon substrate, using shallow trench isolation (STI) technology. Next, a SiO2 film for forming a gate insulating film 14 is formed on the surface of the semiconductor substrate 10 using thermal oxidation, and then a polysilicon film for forming a gate electrode G is deposited using chemical vapor deposition (CVD). Thereafter, the SiO2 film and polysilicon film are patterned using photolithography and etching to form the gate insulating film 14 and the gate electrode G.

[0027] Next, an insulating film such as SiO2 is formed using a CVD method to cover the gate electrode G, and then the insulating film is etched back to form sidewalls 16 that cover the side surfaces of the gate electrode G. Next, using the gate electrode G and the sidewalls 16 as a mask, ion implantation is performed to form the source region S and the drain region D. After that, heat treatment is performed to activate the N-type impurity diffusion regions that constitute the source region S and the drain region D. Next, a salicide process is used to form silicide layers 18 on the surfaces of the source region S, the drain region D, and the gate electrode G to reduce contact resistance. This completes the formation of the transistor Ta on the semiconductor substrate 10.

[0028] As shown in FIG. 2(b), a cover film 20 is formed by depositing an insulating film such as SiN on the surface of the transistor Ta using the CVD method. Next, an interlayer insulating film 22 such as SiO2 is formed on the cover film 20 using the CVD method, and the surface of the interlayer insulating film 22 is then planarized using the CMP (chemical mechanical polishing) method. Next, contact holes reaching the source region S and the drain region D are formed in the interlayer insulating film 22 and the cover film 20 using the photolithography method and the etching method. Next, an adhesive film such as Ti is formed on the side and bottom of the contact holes using the sputtering method or the CVD method, and the contact holes are then filled with a conductive film such as W using the CVD method. Next, the excess adhesive film and conductive film deposited on the interlayer insulating film 22 are removed using the CMP method, thereby forming conductive plugs 32 and 34.

[0029] As shown in FIG. 2(c), an insulating film such as SiN is deposited on the interlayer insulating film 22 using the CVD method to form an etch stopper film 24. Next, an interlayer insulating film 26 such as SiO2 is formed on the etch stopper film 24 using the CVD method. Next, a linear trench is formed in the interlayer insulating film 26 and the etch stopper film 24 in a region where the wiring 38 will be formed using photolithography and etching. Next, an adhesive film such as Ti is formed on the side and bottom of the linear trench using the sputtering method or the CVD method, and then a conductive film such as W is filled into the linear trench using the CVD method. Next, the excess adhesive film and conductive film deposited on the interlayer insulating film 26 are removed using the CMP method to form the wiring 38.

[0030] Next, an insulating film such as SiN is deposited on the interlayer insulating film 26 using the CVD method to form an oxidation prevention film 28. Next, an insulating film such as SiO2 is deposited on the oxidation prevention film 28 using the CVD method to form a buffer film 30. Next, photolithography and etching are used to form contact holes that penetrate the buffer film 30, the oxidation prevention film 28, the interlayer insulating film 26, and the etch stopper film 24 and reach the conductive plug 32. Next, an adhesion film such as Ti is formed on the side and bottom surfaces of the contact hole using the sputtering method or the CVD method, and then the contact hole is filled with a conductive film such as W using the CVD method. Next, excess adhesion film and conductive film deposited on the buffer film 30 are removed using the CMP method to form a conductive plug 36. The conductive plug 36 is connected to the conductive plug 32.

[0031] As shown in FIG. 3( a), an adhesion film 46 made of, for example, TiN is formed on the buffer film 30 by PVD (Physical Vapor Deposition). An oxygen barrier conductive film 48 made of, for example, TiAlN is formed on the adhesion film 46 by PVD. An electrode film 50 made of, for example, Ir is formed on the oxygen barrier conductive film 48 by PVD. A ferroelectric film 42 made of, for example, PZT is formed on the electrode film 50 by PVD or CVD. Thereafter, the ferroelectric film 42 is subjected to a rapid thermal treatment, which is a heat treatment in an oxygen atmosphere. This causes desorption and oxidation of excess elements in the ferroelectric film 42, completing the crystallization of the ferroelectric film 42. Next, an electrode film 52 made of, for example, IrO2 is formed on the ferroelectric film 42 by PVD. An electrode film 54 made of, for example, Ir is formed on the electrode film 52 by PVD. A ferroelectric film 54 made of, for example, Al is sputtered on the electrode film 54. x O y or Al x N y An oxidation prevention film 56 made of the following is formed.

[0032] 3(b), photolithography and etching are used to pattern the oxidation suppression film 56, the electrode film 54, the electrode film 52, the ferroelectric film 42, the electrode film 50, the oxygen barrier conductive film 48, and the adhesive film 46. This forms a ferroelectric capacitor Ca having a lower electrode 40 including the adhesive film 46, the oxygen barrier conductive film 48, and the electrode film 50, and an upper electrode 44 including the ferroelectric film 42, the electrode film 52, and the electrode film 54. After the ferroelectric capacitor Ca is formed, recovery annealing, which is a heat treatment in an oxygen atmosphere, is performed on the ferroelectric capacitor Ca to remove process damage such as etching.

[0033] As shown in FIGS. 4(a) and 4(b), a CVD method or a PVD method is used to deposit, for example, Al so as to cover the ferroelectric capacitor Ca and the oxidation prevention film 56. x O y , Mg x O y , Al x N y , or Mg x N y A protective film 58 made of TiN or TiN is formed. An interlayer insulating film 60 mainly containing SiO2 is formed on the protective film 58 using a CVD method. The surface of the interlayer insulating film 60 is then planarized using a CMP method. Next, photolithography and etching are used to form contact holes that penetrate the interlayer insulating film 60, the protective film 58, and the oxidation suppression film 56 and reach the upper electrode 44 of the ferroelectric capacitor Ca. Next, an adhesion film 66 made of, for example, Ti, TiN, or a laminate of Ti and TiN is formed on the side and bottom surfaces of the contact holes using a sputtering method. Thereafter, a conductive film 68 made of W or the like is filled into the contact holes using a CVD method. Next, CMP is used to remove excess adhesion film 66 and conductive film 68 deposited on the interlayer insulating film 60, thereby forming conductive plugs 64.

[0034] 1, a barrier film 72, a wiring film 74, and a barrier film 76 are laminated on the surface of the interlayer insulating film 60. Next, the laminated film is patterned using photolithography and etching to form the wiring 70. The wiring 70 is electrically connected to the upper electrode 44 of the ferroelectric capacitor Ca via the conductive plug 64. Through the above steps, the semiconductor device 100 of Example 1 is formed.

[0035] [Comparative Example] The semiconductor device according to the comparative example differs from the semiconductor device 100 of the first embodiment in that no oxidation prevention film is provided on the top surface of the upper electrode 44. The other configurations are the same as those of the semiconductor device 100 of the first embodiment.

[0036] 5(a) to 6(b) are cross-sectional views showing a semiconductor device manufacturing method according to a comparative example. FIG. 6(b) is an enlarged view of region A in FIG. 6(a). First, the same manufacturing process as that shown in FIGS. 2(a) to 2(c) of Example 1 is performed. Then, as shown in FIG. 5(a), an adhesion film 46 made of TiN, an oxygen barrier conductive film 48 made of TiAlN, an electrode film 50 made of Ir, and a ferroelectric film 42 made of PZT are formed on the buffer film 30. Then, the ferroelectric film 42 is subjected to a rapid thermal treatment, which is a heat treatment in an oxygen atmosphere. Next, an electrode film 52 made of IrO2 and an electrode film 54 made of Ir are formed on the ferroelectric film 42.

[0037] As shown in FIG. 5(b), the electrode film 54, the electrode film 52, the ferroelectric film 42, the electrode film 50, the oxygen barrier conductive film 48, and the adhesive film 46 are patterned using photolithography and etching. As a result, a ferroelectric capacitor Ca is formed, which has a lower electrode 40 including the adhesive film 46, the oxygen barrier conductive film 48, and the electrode film 50, and an upper electrode 44 including the ferroelectric film 42, the electrode film 52, and the electrode film 54. After the ferroelectric capacitor Ca is formed, in order to remove process damage such as etching, the ferroelectric capacitor Ca is subjected to a recovery annealing treatment, which is a heat treatment in an oxygen atmosphere. In this recovery annealing treatment, the upper surface of the electrode film 54 is exposed to the oxygen atmosphere, and an oxide layer 55 is formed on the upper surface of the electrode film 54. The oxide layer 55 is made of, for example, iridium oxide (IrO x ) layer.

[0038] As shown in FIGS. 6(a) and 6(b), a protective film 58 is formed to cover the ferroelectric capacitor Ca. An interlayer insulating film 60 is formed on the protective film 58. Next, photolithography and etching are used to form contact holes that penetrate the interlayer insulating film 60 and the protective film 58 and reach the upper electrodes 44 of the ferroelectric capacitors Ca. Next, an adhesion film 66 made of Ti, TiN, or a laminate of Ti and TiN is formed on the side and bottom surfaces of the contact holes using a sputtering method. Thereafter, a conductive film 68 made of W or the like is filled into the contact holes using a CVD method. Next, CMP is used to remove excess adhesion film 66 and conductive film 68 deposited on the interlayer insulating film 60, thereby forming conductive plugs 64.

[0039] Since an oxide layer 55 is formed on the upper surface of the electrode film 54 by oxidizing the electrode film 54, the adhesive film 66 of the conductive plug 64 is formed in contact with the oxide layer 55. The adhesive film 66 is formed of Ti, TiN, or a laminate of Ti and TiN, and the electrode film 54 is formed of Ir. Since Ti has a higher ionization tendency than Ir, the temperature rise in the manufacturing process of the adhesive film 66 and the conductive film 68 makes it easier for oxygen contained in the oxide layer 55 to diffuse into the adhesive film 66 in a solid phase. When oxygen diffuses into the adhesive film 66, an oxide of Ti (second metal element) contained in the adhesive film 66 (TiO X An insulating layer 65 made of SiO 2 or oxynitride (TiON) may be partially formed between the conductive plug 64 and the electrode film 54. For example, when the conductive film 68 is formed using a CVD method, the temperature rises to about 400° C., which makes it easier for oxygen contained in the oxide layer 55 to diffuse into the adhesion film 66 in a solid phase.

[0040] Thereafter, although not shown, similarly to the semiconductor device 100 of the first embodiment, a barrier film 72, a wiring film 74, and a wiring 70 including a barrier film 76 are formed on the surface of the interlayer insulating film 60.

[0041] In the comparative example, an oxide layer 55 is formed on the upper surface of the electrode film 54 of the upper electrode 44 by a recovery annealing process after the ferroelectric capacitor Ca is formed. Therefore, the temperature rise when forming the conductive plug 64 in contact with the electrode film 54 causes oxygen in the oxide layer 55 to diffuse into the adhesive film 66 of the conductive plug 64 in a solid phase. As a result, the oxide (TiO X ) or oxynitride (TiON), an insulating layer 65 is formed. The insulating layer 65 is partially formed between the conductive plug 64 and the electrode film 54, which increases the contact resistance between the conductive plug 64 and the upper electrode 44. In addition, the variation in the contact resistance between the conductive plug 64 and the upper electrode 44 increases among a plurality of semiconductor devices.

[0042] Even if the contact hole for forming the conductive plug 64 is formed by etching deeply enough to remove the oxide layer 55, the adhesive film 66 is formed in contact with the side surface of the oxide layer 55. Therefore, even in this case, oxygen in the oxide layer 55 diffuses into the adhesive film 66 in a solid phase, and the oxide of Ti (second metal element) contained in the adhesive film 66 (TiO X ) or oxynitride (TiON) may form an insulating layer 65.

[0043] In contrast, in Example 1, as shown in FIGS. 3( a) and 3(b), an oxidation inhibitor film 56 is formed in contact with the upper surface of the electrode film 54 of the upper electrode 44 before performing a recovery annealing treatment (heat treatment) on the ferroelectric capacitor Ca. Therefore, even when a recovery annealing treatment is performed on the ferroelectric capacitor Ca, oxidation of the upper surface of the electrode film 54 is suppressed. The oxidation inhibitor film 56 is an oxide film or nitride film of Al (a third metal element) which has a higher ionization tendency than Ir (a first metal element) contained in the electrode film 54. Oxidation of a film containing a metal element with a higher ionization tendency progresses more easily than a film containing a metal element with a lower ionization tendency. Therefore, even if the oxidation inhibitor film 56 is not a dense film and oxygen penetrates into the interior during the recovery annealing treatment, the oxygen is easily taken in by the oxidation inhibitor film 56 containing Al which has a higher ionization tendency, and thus the oxygen is suppressed from reaching the electrode film 54. Therefore, oxidation of the upper surface of the electrode film 54 is effectively suppressed.

[0044] 4(b), the formation of an insulating layer made of an oxide or oxynitride of Ti (second metal element) contained in the adhesion film 66 between the conductive plug 64 and the electrode film 54 is suppressed. Therefore, an increase in contact resistance between the conductive plug 64 and the upper electrode 44 and variations in contact resistance among a plurality of semiconductor devices 100 can be suppressed.

[0045] As shown in FIG. 4(b), the adhesion film 66 of the conductive plug 64 is formed in contact with the side surface of the oxidation inhibitor film 56. The oxidation inhibitor film 56 is an oxide film or nitride film of Al (third metal element) which has a higher ionization tendency than Ti (second metal element) contained in the adhesion film 66. For this reason, oxygen contained in the oxidation inhibitor film 56 is less likely to diffuse into the adhesion film 66 which contains Ti which has a lower ionization tendency. Therefore, even if the adhesion film 66 is formed in contact with the oxidation inhibitor film 56, the formation of an insulating film made of an oxide or oxynitride of Ti (second metal element) contained in the adhesion film 66 is suppressed.

[0046] As described above, according to the first embodiment, the oxidation prevention film 56 is provided in contact with the upper surface of the upper electrode 44 of the ferroelectric capacitor Ca. A conductive plug 64 is provided, which penetrates the oxidation prevention film 56 and includes an adhesive film 66 in contact with the oxidation prevention film 56 and the upper electrode 44, and a conductive film 68 on the adhesive film 66. The oxidation prevention film 56 is an oxide film (Al x O y ) or nitride film (Al x N y ) is included. As a result, as described above, the formation of an insulating film made of an oxide or oxynitride of Ti (second metal element) contained in the adhesion film 66 between the conductive plug 64 and the upper electrode 44 is suppressed. Therefore, an increase in contact resistance between the conductive plug 64 and the upper electrode 44 and variations in contact resistance among a plurality of semiconductor devices 100 can be suppressed.

[0047] In addition, in Example 1, the upper electrode 44 contains iridium (Ir). Ir is advantageous in that it remains conductive even when oxidized, and its catalytic action is relatively weak, so the characteristics of the ferroelectric film 42 are less likely to deteriorate. In addition, oxygen is supplied from iridium oxide to the ferroelectric film 42, so deterioration of the characteristics of the ferroelectric capacitor Ca can be suppressed. The adhesion film 66 contains titanium (Ti). This can improve the adhesion between the conductive film 68 and the upper electrode 44 and the oxidation prevention film 56.

[0048] In the first embodiment, the oxidation prevention film 56 is an aluminum (Al) oxide film (Al x O y ) or nitride film (Al x N y ). This makes it possible to suppress the formation of an insulating film made of an oxide or oxynitride of Ti (second metal element) contained in the adhesion film 66 between the conductive plug 64 and the upper electrode 44, and also to suppress the penetration of hydrogen and the like into the ferroelectric capacitor Ca. The oxidation suppression film 56 is an oxide film of aluminum (Al) (Al x O y ) or nitride film (Al x N y ) instead of magnesium (Mg) oxide film (Mg x O y ) or nitride film (Mg x N y ) may be included. Even in this case, it is possible to suppress the formation of an insulating film made of an oxide or oxynitride of Ti (second metal element) contained in the adhesion film 66 between the conductive plug 64 and the upper electrode 44, and also to suppress the penetration of hydrogen and the like into the ferroelectric capacitor Ca. The oxidation suppression film 56 is preferably made of Al x O y , Al x N y , Mg x O y , and Mg x N y The film may be a laminated film of at least two of the above layers.

[0049] In the first embodiment, the oxidation prevention film 56 and the protective film 58 are made of the same material (for example, Al x O y In this case, the Al on the top surface of the ferroelectric capacitor Ca may be x O y The thickness of the Al on the side of the ferroelectric capacitor Ca x O y In this way, the thickness of the Al on the top surface of the ferroelectric capacitor Ca becomes thicker than that of the Al x O yBy increasing the thickness of the ferroelectric capacitor Ca, it is possible to effectively prevent hydrogen and the like from entering the ferroelectric capacitor Ca.

[0050] In the first embodiment, the oxidation prevention film 56 and the protective film 58 are made of different materials (for example, the oxidation prevention film 56 is made of Al). x O y The protective film 58 is Al x N y or Mg x O y In this case, the options for selecting the materials for the oxidation prevention film 56 and the protective film 58 are broadened.

[0051] In the first embodiment, the upper electrode 44 is formed containing Ir, but the present invention is not limited to this and may be formed containing platinum (Pt), for example. The adhesion film 66 is formed containing Ti, but may be formed of other materials as long as they can function as an adhesive, for example, chromium (Cr). The oxidation prevention film 56 may be formed containing an oxide or nitride film of a third metal element having a higher ionization tendency than the first metal element contained in the upper electrode 44 and the second metal element contained in the adhesion film 66, and may be formed of a material other than an oxide or nitride film of Al or Mg. [Example]

[0052] In the semiconductor device according to the second embodiment, the oxidation prevention film 56 is made of iridium nitride (IrN x The semiconductor device according to the second embodiment differs from the semiconductor device 100 of the first embodiment in that an IrN film is used as the oxidation prevention film 56. The other configurations are the same as those of the first embodiment, so illustrations and explanations thereof will be omitted. x Except for the film formation, the method is the same as the method for manufacturing the semiconductor device 100 according to the first embodiment shown in FIGS. 2(a) to 4(b).

[0053] where IrN x The following describes an experiment to evaluate the oxidation characteristics of the film and Ir film. The following samples 1 and 2 were used in the experiment. Sample 1: A 5-nm thick iridium nitride (IrN) film was formed on a magnesium oxide (MgO) substrate with a titanium (Ti) film as an adhesive film. x ) forming a film Sample 2: A 5-nm-thick iridium (Ir) film was formed on a magnesium oxide (MgO) substrate via a titanium (Ti) film as an adhesive film. The above samples 1 and 2 were left for 3 minutes in an atmosphere of 10% oxygen and argon at a temperature of 400°C and a pressure of 1 Torr, and the Ir film and IrN x The amount of oxidation of the Ir film and IrN film was investigated. x The amount of oxidation of the film was investigated, and the temperature was further increased to 600°C and left for 3 minutes. x The amount of oxidation of the film was investigated using X-ray photoelectron spectroscopy (XPS).

[0054] FIG. 7 shows the results of the oxidation investigation carried out on Samples 1 and 2. The horizontal axis of FIG. 7 represents the temperature, and the vertical axis represents the IrN x As shown in Figure 7, the volume ratio of the IrO2 film to the IrN film and the IrO2 film is x It can be seen that the IrN film is less susceptible to oxidation than the Ir film. x It can be said that the membrane has a high effect of suppressing oxygen diffusion.

[0055] Therefore, in Example 2, the oxidation prevention film 56 is made of iridium nitride (IrN x) film is used. As a result, even if recovery annealing is performed on the ferroelectric capacitor Ca, the oxidation prevention film 56 has a high effect of suppressing oxygen diffusion, and therefore oxygen is prevented from reaching the electrode film 54. Therefore, the upper surface of the electrode film 54 is prevented from being oxidized, and as a result, an insulating layer made of an oxide or oxynitride of Ti (second metal element) contained in the adhesion film 66 is prevented from being formed between the conductive plug 64 and the electrode film 54. This makes it possible to suppress an increase in contact resistance between the conductive plug 64 and the upper electrode 44 and variations in contact resistance between a plurality of semiconductor devices. Furthermore, the adhesion film 66 is formed in contact with the side surface of the oxidation prevention film 56, and the oxidation prevention film 56 is made of iridium nitride (IrN x ) film, the diffusion of oxygen from the oxidation-prevention film 56 to the adhesion film 66 is suppressed. Therefore, in this respect, the formation of an insulating film made of an oxide or oxynitride of Ti (second metal element) contained in the adhesion film 66 is suppressed.

[0056] In the second embodiment, as in the first embodiment, the upper electrode 44 is not limited to being formed containing Ir, but may be formed containing, for example, platinum (Pt), etc. The adhesion film 66 is not limited to being formed containing Ti, but may be formed containing, for example, chromium (Cr), etc.

[0057] Although the embodiments of the present invention have been described in detail above, the present invention is not limited to such specific embodiments, and various modifications and variations are possible within the scope of the gist of the present invention as defined in the claims. [Explanation of symbols]

[0058] 10. Semiconductor substrate 40 Lower electrode (1st electrode) 42 Ferroelectric film 44 Upper electrode (second electrode) 46 Adhesion Film 48 Oxygen barrier conductive film 50, 52, 54 electrode membrane 56 Oxidation inhibitor film 58 Protective film 60 Interlayer insulating film 64 Conductive plug 65 Insulating layer 66 Adhesion Film 68 Conductive Film 100 Semiconductor device Ca ferroelectric capacitor G gate electrode S source region D drain region Ta transistor

Claims

1. a ferroelectric capacitor having a first electrode, a ferroelectric film provided on the first electrode, and a second electrode provided on the ferroelectric film; an oxidation prevention film provided in contact with an upper surface of the second electrode; a conductive plug that penetrates the oxidation suppression film and is in contact with the oxidation suppression film and the second electrode, and that includes an adhesive film and a conductive film on the adhesive film; The oxidation inhibitor film is an iridium nitride film.

2. a ferroelectric capacitor having a first electrode, a ferroelectric film provided on the first electrode, and a second electrode provided on the ferroelectric film; an oxidation prevention film provided in contact with an upper surface of the second electrode; a conductive plug that penetrates the oxidation suppression film and is in contact with the oxidation suppression film and the second electrode, and that includes an adhesive film and a conductive film on the adhesive film; the second electrode includes a first metal element; the adhesion film contains a second metal element, the oxidation suppression film is an insulating film including a nitride film of a third metal element having a higher ionization tendency than the first metal element and the second metal element.

3. The semiconductor device according to claim 2 , wherein said third metal element is aluminum.

4. the second electrode includes iridium; The semiconductor device according to claim 1 , wherein the adhesive film contains titanium.

5. a protective film covering the ferroelectric capacitor and the oxidation suppression film, the oxidation suppression film and the protective film are oxide films or nitride films formed of the same material; 4. The semiconductor device according to claim 2, wherein the thickness of said oxide film or said nitride film on the top surface of said ferroelectric capacitor is greater than the thickness of said oxide film or said nitride film on the side surface of said ferroelectric capacitor.

6. a protective film covering the ferroelectric capacitor and the oxidation suppression film, 3. The semiconductor device according to claim 2, wherein said oxidation suppression film and said protection film are oxide films or nitride films made of different materials.

7. forming a film to be a first electrode; forming a ferroelectric film on the film that will become the first electrode; forming a film to be a second electrode on the ferroelectric film; forming an oxidation prevention film in contact with an upper surface of the film that will become the second electrode; a step of patterning the film to be the first electrode, the ferroelectric film, the film to be the second electrode, and the oxidation suppression film to form a ferroelectric capacitor having the first electrode, the ferroelectric film, and the second electrode; a step of subjecting the ferroelectric capacitor to a heat treatment in an oxygen atmosphere; and after the heat treatment, forming a conductive plug that penetrates the oxidation suppression film and is in contact with the oxidation suppression film and the second electrode, and that includes an adhesive film and a conductive film on the adhesive film, The method for manufacturing a semiconductor device, wherein the oxidation inhibitor film is an iridium nitride film.

8. forming a film to be a first electrode; forming a ferroelectric film on the film that will become the first electrode; forming a film to be a second electrode on the ferroelectric film; forming an oxidation prevention film in contact with an upper surface of the film that will become the second electrode; a step of patterning the film to be the first electrode, the ferroelectric film, the film to be the second electrode, and the oxidation suppression film to form a ferroelectric capacitor having the first electrode, the ferroelectric film, and the second electrode; a step of subjecting the ferroelectric capacitor to a heat treatment in an oxygen atmosphere; and after the heat treatment, forming a conductive plug that penetrates the oxidation suppression film and is in contact with the oxidation suppression film and the second electrode, and that includes an adhesive film and a conductive film on the adhesive film, A method for manufacturing a semiconductor device, wherein the second electrode contains a first metal element, the adhesion film contains a second metal element, and the oxidation inhibition film contains a nitride film of a third metal element having a greater ionization tendency than the first metal element and the second metal element.

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