Film forming method, film forming apparatus, and semiconductor device

Abstract

To provide a film deposition method for depositing a metal oxide film having a high dielectric constant, a film deposition apparatus, and a semiconductor device.SOLUTION: The film forming apparatus includes a film forming unit configured to form a metal oxide film, and a doping unit configured to the metal oxide film with a dopant such that an energy difference obtained by subtracting an energy at which a crystal structure of the metal oxide film becomes monoclinic from an energy at which the crystal structure of the metal oxide film becomes tetragonal is lower than an energy difference in the metal oxide film in an undoped state.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present disclosure relates to a film forming method, a film forming apparatus, and a semiconductor device. [Background technology]

[0002] Patent Document 1 listed below discloses a "method for forming a metal oxide film, comprising the steps of: adsorbing an inhibitor containing a heterocyclic compound excluding alcohols and amines into recesses formed in a substrate; supplying a precursor gas containing a metal complex to the recesses to which the inhibitor has been adsorbed, thereby forming a precursor layer on the substrate; and supplying an oxidizing gas to the recesses in which the precursor layer has been formed, thereby oxidizing the precursor layer to form a metal oxide layer." [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-52034 Summary of the Invention [Problem to be solved by the invention]

[0004] The present disclosure provides techniques for depositing high dielectric constant metal oxide films. [Means for solving the problem]

[0005] A film forming method according to one embodiment of the present disclosure includes steps a) and b). Step a) is forming a metal oxide film. Step b) is doping the metal oxide film with a dopant such that the energy difference, obtained by subtracting the energy at which the crystal structure of the metal oxide film becomes monoclinic from the energy at which the crystal structure of the metal oxide film becomes tetragonal, is lower than the energy difference in an undoped metal oxide film. [Effects of the Invention]

[0006] According to the present disclosure, a metal oxide film with a high dielectric constant can be formed. [Brief explanation of the drawings]

[0007] [Figure 1A] FIG. 1A is a diagram showing the relationship between the energy difference for each dopant and the crystal volume for ZrO2. [Figure 1B] FIG. 1B shows the relationship between the energy difference for each dopant and the crystal volume for HfO2. [Figure 2A] FIG. 2A is a diagram illustrating the ion implantation method. [Figure 2B] FIG. 2B is a diagram illustrating the gas cluster ion beam method. [Figure 2C] FIG. 2C is a diagram illustrating the nanolaminate method. [Figure 2D] FIG. 2D is a diagram illustrating the dopant solution immersion method. [Figure 2E] FIG. 2E is a diagram illustrating the thermal diffusion doping method. [Figure 2F] FIG. 2F is a diagram illustrating the laser doping method. [Figure 2G] FIG. 2G is a diagram illustrating the flash lamp method. [Figure 2H] FIG. 2H is a diagram illustrating the deposited film method. [Figure 3] FIG. 3 is a diagram showing an example of a process flow of the film forming method according to the embodiment. [Figure 4] FIG. 4 is a diagram showing an example of the flow of the initial process in the film forming method according to the embodiment. [Figure 5] FIG. 5 is a block diagram schematically illustrating an example of the configuration of a film forming apparatus according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, embodiments of a film formation method, a film formation apparatus, and a semiconductor device disclosed in the present application will be described in detail with reference to the drawings. Note that the disclosed film formation method, film formation apparatus, and semiconductor device are not limited to the embodiments.

[0009] Metal oxide films have traditionally been used as dielectric films or insulating films in semiconductor devices. For example, in dynamic random access memories (DRAMs), metal oxide films made of metal oxides such as ZrO2 (zirconium oxide) and HfO2 (hafnium oxide) are used as capacitor materials.

[0010] Meanwhile, metal oxide films with higher dielectric constants are required to suppress leakage currents associated with the miniaturization of semiconductor devices, and therefore, a technology for forming metal oxide films with high dielectric constants is desired.

[0011] (Embodiment) [Dopant] An embodiment will be described. First, the relationship between the crystal structure of a metal oxide and its dielectric constant will be described. In the following, ZrO2 and HfO2 will be used as examples of metal oxides.

[0012] At room temperature, ZrO2 and HfO2 have a stable monoclinic crystal structure. Room temperature refers to the standard indoor temperature, for example, 10 to 30°C. However, at temperatures exceeding 1000°C, ZrO2 and HfO2 change to a tetragonal crystal structure, increasing their dielectric constant, but they are not stable at room temperature.

[0013] Therefore, the present inventors have identified a dopant that can be doped into ZrO2 or HfO2 to stabilize the tetragonal crystal structure at room temperature using the following method.

[0014] First, for each dopant considered as a candidate for doping into ZrO2 and HfO2, various crystal structures were constructed using software, and structural optimization was performed to search for stable crystal structures. Examples of software for constructing crystal structures include VESTA (Molecular Structure Drawing Program). Then, for each dopant, the energies at which the crystal structure becomes tetragonal and the energies at which the crystal structure becomes monoclinic were calculated using electronic structure calculation software. Examples of electronic structure calculation software include software using plane wave basis functions, such as VASP (Vienna Ab initio Simulation Package), CASTEP, Quantum Espresso, pwscf, PHASE, OpenMX, STATE-SENRI, QMA, ABINIT, WIEN2k, PARATEC, DMOL3, QMAS, Osaka2k, STATE, Qbox, FPSEID, CP2K, JDFTx, and xTAPP. The energy at which the crystal structure becomes tetragonal and the energy at which the crystal structure becomes monoclinic were calculated by adding the electron energy and lattice energy of the crystal structure, respectively. Then, for each dopant, the energy difference was calculated by subtracting the energy at which the crystal structure becomes monoclinic from the energy at which the crystal structure becomes tetragonal.

[0015] Figure 1A shows the relationship between the energy difference for each dopant and the crystal volume for ZrO2. Figure 1B shows the relationship between the energy difference for each dopant and the crystal volume for HfO2. The vertical axis of Figures 1A and 1B shows the energy difference ΔE obtained by subtracting the energy at which the crystal structure becomes monoclinic from the energy at which the crystal structure becomes tetragonal. t-m The horizontal axis is the volume of the crystal in tetragonal form, V t [Å 3 ].

[0016] Figure 1A shows the composition formula of ZrO2 for each dopant at a position corresponding to the energy difference and crystal volume. The dotted line "III-VII" indicates the relationship between the energy difference and crystal volume when the dopant is a compound of a group III element and a group VII element. The dotted line "II" indicates the relationship between the energy difference and crystal volume when the dopant is a group II element. The dotted line "III" indicates the relationship between the energy difference and crystal volume when the dopant is a group III element. The dotted line "II-S" indicates the relationship between the energy difference and crystal volume when the dopant is a compound of a group II element and sulfur. Figure 1A also shows the relationship between the energy difference and crystal volume when the dopant is, for example, a group IV element such as "Si" or "Ge," or a compound of a group III element and a group V element such as "AlP," "AlAs," "GaP," or "GaAs."

[0017] Group II elements are elements in Group 2 (Group IIA in the old IUPAC (International Union of Pure and Applied Chemistry) nomenclature) and Group 12 (Group II-B in the old IUPAC nomenclature) of the periodic table. Group III elements are elements in Group 3 (Group IIIA in the old IUPAC nomenclature) and Group 13 (Group IIIB in the old IUPAC nomenclature) of the periodic table. Group VII elements are elements in Group 7 (Group VIIA in the old IUPAC nomenclature) and Group 17 (Group VIIB in the old IUPAC nomenclature) of the periodic table. Group IV elements are elements in Group 4 (Group IVA in the old IUPAC nomenclature) and Group 14 (Group IVB in the old IUPAC nomenclature) of the periodic table. Group V elements are elements in Group 5 (Group VA in the old IUPAC nomenclature) and Group 15 (Group VB in the old IUPAC nomenclature) of the periodic table.

[0018] In Figure 1A, the energy difference and crystal volume of undoped ZrO2 are shown as "UND." The numbers attached to the elements "Ce" and "Ge," such as "Ce2" and "Ge3," indicate the number of dopant atoms in a 2x2x2 cell. Note that sulfur (S) alone is excluded from the list of dopants that increase the dielectric constant for the following reasons: Because sulfur is hexavalent when substituted at the cation site, charge compensation by a +2valent metal is required for Zr and Hf (tetravalent), and so doping with S alone does not meet the compensation conditions. On the other hand, doping (-2valent) at the anion site (instead of O) results in the structure itself collapsing from a tetragonal crystal, destabilizing the structure.

[0019] Figure 1B shows the composition formula of HfO2 for each dopant at a position corresponding to the energy difference and crystal volume. The dotted line "II" indicates the relationship between the energy difference and crystal volume when the dopant is a Group II element. The dotted line "III" indicates the relationship between the energy difference and crystal volume when the dopant is a Group III element. The dotted line "II-S" indicates the relationship between the energy difference and crystal volume when the dopant is a compound of Group II element and sulfur. Figure 1B also shows the relationship between the energy difference and crystal volume when the dopant is, for example, a Group IV element such as "Si" or "Ge," or a compound of Group III and Group V elements such as "AlP," "AlAs," "GaP," or "GaAs."

[0020] In addition, in FIG. 1B, the energy difference and crystal volume of undoped HfO2 are shown as "UND".

[0021] Figures 1A and 1B show the relationship between energy difference and crystal volume when constructing crystal structures ideally doped with dopants. For example, Si2 and Ge2 are doped with approximately 6% Si2 or Ge2. Si3 and Ge3 are doped with approximately 6% Si3 or Ge3. ZnS is doped with approximately 3% Zn and approximately 3% S.

[0022] The energy difference on the vertical axis in Figures 1A and 1B corresponds to the stability of the tetragonal crystal structure when doped. The smaller the energy difference, the more likely the crystal structure is to be stable in a tetragonal state when doped, and the higher the dielectric constant. In particular, dopants with an energy difference of zero or less tend to stabilize the crystal structure in a tetragonal state even at room temperature.

[0023] When ZrO2 is doped with a dopant whose energy difference is smaller than the UND shown in Figure 1A, the crystal structure becomes more stable in a tetragonal state than in the undoped state, resulting in a higher dielectric constant. For example, when ZrO2 is doped with a compound of group III and group VII elements (excluding GaI), a group II element, a group III element, a compound of group II elements and sulfur, a group IV element, or a compound of group III elements and group V elements, the crystal structure becomes more stable in a tetragonal state and the dielectric constant becomes higher. In particular, when ZrO2 is doped with a group IV element such as Si or Ge, a compound of group III and group V elements, or a compound of group II elements and sulfur, the crystal structure becomes more stable in a tetragonal state even at room temperature, resulting in a higher dielectric constant. For example, the dielectric constant of ZrO2 increases when it is doped with any of Si, Ge, ZnS, MgS, CaS, SrS, BaS, AlP, AlAs, GaP, and GaAs, and the dielectric constant is highest when it is doped with ZnS.

[0024] When HfO2 is doped with a dopant with an energy difference smaller than the UND shown in Figure 1B, the crystal structure becomes more stable in a tetragonal state than in the undoped state, resulting in a higher dielectric constant. For example, when HfO2 is doped with a group II element, a group III element, a compound of group II elements and sulfur, a group IV element, or a compound of group III elements and group V elements, the crystal structure becomes more stable in a tetragonal state and the dielectric constant becomes higher. In particular, when HfO2 is doped with a group IV element such as Si or Ge, a compound of group III elements and group V elements, or a compound of group II elements and sulfur, the crystal structure becomes more stable in a tetragonal state even at room temperature, resulting in a higher dielectric constant. For example, when HfO2 is doped with any of Si, Ge, SrS, ZnS, MgS, CaS, BaS, AlP, AlAs, GaP, or GaAs, the dielectric constant becomes higher, and when doped with ZnS, the dielectric constant becomes the highest.

[0025] In Figures 1A and 1B, ZrO2 and HfO2 are used as examples of metal oxides, and dopants that increase the dielectric constant when doped are shown. However, metal oxides such as ZrO 2、 The metal oxide is not limited to HfO2. The metal oxide may be, for example, another metal oxide such as magnesium oxide or aluminum oxide. For other metal oxides, a similar method can be used to identify a dopant that stabilizes the tetragonal crystal structure, thereby identifying a dopant that increases the dielectric constant when doped. For example, for each dopant considered as a candidate for doping with other metal oxides, the energy at which the crystal structure becomes tetragonal and the energy at which the crystal structure becomes monoclinic are calculated. Then, for each dopant, the energy difference is calculated by subtracting the energy at which the crystal structure becomes monoclinic from the energy at which the crystal structure becomes tetragonal. Then, by identifying a dopant whose energy difference is smaller than the energy difference of the undoped metal oxide, a dopant that increases the dielectric constant when doped can be identified.

[0026] In the film formation method according to this embodiment, a metal oxide film is formed. For example, a ZrO2 or HfO2 film is formed. Examples of techniques for forming the metal oxide film include ALD (Atomic Layer Deposition), PVD (Physical Vapor Deposition), and CVD (Chemical Vapor Deposition).

[0027] In the film formation method according to the present embodiment, the metal oxide film is doped with a dopant that, when doped into the metal oxide film, reduces the energy difference, obtained by subtracting the energy at which the crystal structure of the metal oxide film becomes tetragonal from the energy at which the crystal structure becomes monoclinic, compared to the energy difference in the undoped metal oxide film. By doping the metal oxide film with such a dopant, the crystal structure of the metal oxide film can be more easily stabilized in a tetragonal state, and a metal oxide film with a high dielectric constant can be formed.

[0028] Examples of methods for doping with a dopant include ion implantation, gas cluster ion beam, nanolaminate, dopant solution immersion, thermal diffusion doping, laser doping, flash lamp doping, and deposited film method.

[0029] 2A is a diagram illustrating the ion implantation method. In the ion implantation method, a substrate W, such as a semiconductor wafer having a metal oxide film formed thereon, is placed on a stage 30. In the ion implantation method, ions of the target impurity are generated by an ion source 31, and an acceleration unit (not shown) applies an electromagnetic field to the ions to accelerate them into an ion beam 32, which is then focused by an electrostatic lens (not shown). In the ion implantation method, an AC voltage is applied laterally to the ion beam 32 to vibrate the ion beam 32 laterally, and the ions are irradiated onto the metal oxide film of the substrate W through small holes 34, thereby implanting the impurity ions into the metal oxide film.

[0030] FIG. 2B is a diagram illustrating the gas cluster ion beam method. In the gas cluster ion beam method, a substrate W on which a metal oxide film has been formed is fixed to a stage 40. In the gas cluster ion beam method, gas atoms of the target impurity are supplied to a nozzle 42 via a pipe 41, and a gas flow is ejected from the nozzle 42. In the gas cluster ion beam method, the pressure of the gas ejected from the nozzle 42 is controlled to eject gas clusters composed of hundreds to thousands of impurity gas atoms bonded together by van der Waals forces or the like from the nozzle 42. In the gas cluster ion beam method, the ejected gas clusters are ionized by an ionizer 43, and an electromagnetic field is applied by an accelerator 44 to accelerate the gas clusters into a gas cluster ion beam. In the gas cluster ion beam method, the gas cluster ion beam is passed through a magnetic field generated by a magnet 45, allowing particles of the target mass to pass through, and the gas cluster ion beam is neutralized by a neutralizer 46. In the gas cluster ion beam method, the diameter of the neutralized gas clusters is adjusted by the aperture 47, and the gas clusters that have passed through the aperture 47 are irradiated onto the metal oxide film of the substrate W, thereby implanting impurities into the metal oxide film.

[0031] FIG. 2C is a diagram illustrating the nanolaminate method. In the nanolaminate method, metal oxide films 51 and dopant films 52 are alternately laminated depending on the ratio of the dopants to be doped. Each layer may be formed by either ALD or PVD, or ALD and PVD may be switched for each layer. For example, if HfO2 and ZrO2 are formed as metal oxide film 51 and doped with ZnS, the film is formed in the following order: HfO2 → ZrO2 → ZnS → HfO2 → ZrO2 → ZnS → ... until the desired film thickness is reached.

[0032] Here, an example of a precursor used when forming a dopant film by ALD will be described.

[0033] When forming a HfO2 film, the precursor of Hf is, for example, HyALD (tri(dimethylamino)cyclopentadienylhafnium:C 11 H23 Examples include N3Hf, HOC (cyclopentadienyltris(dimethylamido)hafnium: HfCp(NMe2)3), TDMAH (tetrakis(dimethylamino)hafnium: Hf[N(CH3)2]4), and TEMAH (tetrakis(N-ethylmethylamino)hafnium). For example, the molecular structure of HyALD is represented as shown in (1) below. The molecular structure of HOC is represented as shown in (2) below. The molecular structure of TDMAH is represented as shown in (3) below. The molecular structure of TEMAH is represented as shown in (4) below.

[0034] [ka]

[0035] Furthermore, when depositing a ZrO2 film, examples of Zr precursors include ZyALD (tri(dimethylamino)cyclopentadienylzirconium: (C5H5)Zr[N(CH3)2]3), ZAC (cyclopentadienyltris(dimethylamido)zirconium: ZrCp(NMe2)3), TEMAZ (tetrakis(N-ethylmethylamino)zirconium), and TDMAZ (tetrakis(dimethylamino)zirconium: [(CH3)2N]4Zr). For example, the molecular structure of ZyALD is expressed as shown in (5) below. The molecular structure of TEMAZ is expressed as shown in (6) below.

[0036] [ka]

[0037] Furthermore, when forming a film of a dopant containing Zn, examples of Zn precursors include Zn, Zn(DMP)2, Zn(eeki)2, Zn(OAc)2, Zn(thd)2, Zn[N(SiMe3)2]2, ZnCl2, ZnEt2, ZnI2, ZnMe(OiPr), and ZnMe2.

[0038] Furthermore, when forming a film of a dopant containing Sr, an example of the precursor of Sr is Sr(iPr3Cp)2. When forming a film of a dopant containing Mg, an example of the precursor of Mg is Mg(EtCp)2, Mg(Cp)2, or Mg(MeCp)2. When forming a film of a dopant containing Ce, an example of the precursor of Ce is Ce(iPrCp)3. When forming a film of a dopant containing Sn, an example of the precursor of Sn is TDMASn. When forming a film of a dopant containing Y, an example of the precursor of Y is Y(EtCp)3. When forming a film of a dopant containing La, an example of the precursor of La is La(iPrCp)3. When forming a film of a dopant containing Ge, examples of the precursor of Ge include Ge(N(Me)2)4 and Ge(OnBu)4. When forming a film of a dopant containing Si, examples of the precursor of Si include 3DMAS (Tris(dimethylamino)silane) and BTBAS (Bistertiarybutylaminosilane).

[0039] The precursors described above are merely examples, and the present invention is not limited to these. Any precursor may be used as long as it can form the respective films.

[0040] 2D is a diagram illustrating a dopant solution immersion method, in which a metal oxide film 61 formed on a substrate W is immersed in a dopant solution 62 containing a dopant, and the dopant is implanted into the metal oxide film 61.

[0041] 2E is a diagram illustrating the thermal diffusion doping method, in which a substrate W having a metal oxide film formed thereon is placed in a chamber 71, and while the substrate W is heated by a heat source 72 such as a heater provided in the chamber 71, a dopant gas containing a dopant is flowed into the chamber 71 to inject the dopant into the metal oxide film on the substrate W.

[0042] 2F is a diagram illustrating the laser doping method. In the laser doping method, a substrate W on which a metal oxide film has been formed is placed on a stage 82 in a chamber 81. A transmission window 83 that transmits laser light is provided above the stage 82 in the chamber 81. In the laser doping method, a dopant gas containing a dopant is flowed into the chamber 81 while irradiating the substrate W with laser light 84 through the transmission window 83, thereby injecting the dopant into the metal oxide film of the substrate W.

[0043] FIG. 2G is a diagram illustrating the flash lamp method. In the flash lamp method, a substrate W having a metal oxide film formed thereon is placed on a stage 92 in a chamber 91. A heater 93 is provided on the stage 92. The chamber 91 has a transmissive section 94 formed entirely above the stage 92 using a light-transmitting material. A flash lamp 95 is provided above the chamber 91. A light-reflecting reflector 96 is provided above the flash lamp 95 to cover the flash lamp 95. The reflector 96 reflects light emitted upward from the flash lamp 95 downward and guides it to the substrate W. In the flash lamp method, the substrate W is heated by the heater 93, a dopant gas containing a dopant is flowed into the chamber 91, and the flash lamp 95 is turned on to implant the dopant into the metal oxide film on the substrate W.

[0044] 2H is a diagram illustrating the deposition film method. In the deposition film method, a sacrificial film 99 containing a dopant is formed on the upper surface of the substrate W on which a metal oxide film has been formed, and then the dopant in the sacrificial film 99 is diffused by heating, thereby implanting the dopant into the metal oxide film of the substrate W. After implanting the dopant, the sacrificial film 99 is removed by etching or the like.

[0045] In the film formation method according to this embodiment, a metal oxide film having a desired thickness may be formed by ALD, PVD, or CVD, and then the metal oxide film may be doped with a dopant. Alternatively, in the film formation method according to this embodiment, a metal oxide film may be formed to a desired thickness by alternately repeating the formation of a metal oxide film by ALD, PVD, or CVD and the doping of the metal oxide film with a dopant. The metal oxide film can be doped with a dopant in any of the above-mentioned ion implantation method, gas cluster ion beam method, dopant solution immersion method, thermal diffusion doping method, laser doping method, flash lamp method, and deposited film method.

[0046] [Film forming method] Next, an example of a specific flow for forming a metal oxide film using the film formation method according to the embodiment will be described. The following describes an example in which a ZrO2 film, a HfO2 film, or a mixed film of ZrO2 and HfO2 is formed as a metal oxide film in one chamber by the nanolaminate method while doping with ZrS. FIG. 3 is a diagram showing an example of a process flow for the film formation method according to the embodiment. A substrate W to be formed on is placed in the chamber, and the chamber is depressurized to a predetermined vacuum level, and then the process shown in FIG. 3 is carried out.

[0047] In step S10, gases used to deposit one or both of Zr and Hf are supplied to the chamber. For example, when depositing a ZrO2 film, TDMAZ is supplied. When depositing a HfO2 film, TDMAH is supplied. When depositing a mixed film of ZrO2 and HfO2, TDMAZ and TDMAH are supplied.

[0048] In step S11, a purge gas is introduced to evacuate the chamber. Step S11 may be omitted. Alternatively, in step S11, a plasma may be generated while an oxidizing gas is introduced, similar to step S14 described later, to deposit a film of ZrO2, HfO2, or both.

[0049] In step S12, a Zn precursor, for example, any one of Zn(DMP)2, ZnEt2, and ZnMe2, is supplied to the chamber. In step S13, a purge gas is introduced to evacuate the chamber.

[0050] In step S14, a plasma is generated while an oxidizing gas such as O3 gas or O2 is flowing to oxidize Zr, Hf, and Zn, forming a film of ZrO2, HfO2, or both, and also oxidizing the Zn precursor to produce ZnO. In step S15, a purge gas is flowed to evacuate the chamber. Note that step S15 may be omitted.

[0051] In step S16, sulfur oxide (SO) gas such as SO gas is supplied to the chamber. In step S17, H2O is supplied to the chamber to generate sulfuric acid through the reaction SO3 + H2O → H2SO4, and the sulfuric acid is reacted with ZrO to dope ZrS. In step S18, a purge gas is introduced to evacuate the chamber.

[0052] In the film formation method shown in FIG. 3, steps S10 to S18 are repeated until a target film thickness is reached, thereby forming a metal oxide film of ZrS-doped ZrO2, HfO2, or both.

[0053] 3, the film formation method is described as repeating steps S10 to S17 until the target film thickness is reached, but the present invention is not limited to this. Steps S10 and S14 may be performed first to form a metal oxide film of one or both of ZrO2 and HfO2 to the target film thickness, and then steps S12 to S17 may be performed to dope ZrS.

[0054] In order to more stably form a metal oxide film having a tetragonal crystal structure, the film formation method according to the embodiment may perform the following initial treatment before forming the metal oxide film. Figure 4 is a diagram showing an example of the flow of the initial treatment in the film formation method according to the embodiment.

[0055] A thin film 20 of either or both ZrO2 and HfO2 is formed on a substrate W (FIG. 4(1)). FIG. 4(1) shows the state in which the thin film 20 of ZrO2 has been formed on the substrate W. The crystal structure of the ZrO2 in the thin film 20 is monoclinic. "ZrO2(m)" indicates that the crystal structure of ZrO2 is monoclinic.

[0056] The ZrO2 or HfO2 thin film 20 is treated with sulfuric acid or phosphoric acid, and the surface is coated with SO4 2- PO4 3- ions are carried (FIG. 4(2)). FIG. 4(2) shows that the ZrO2(m) of the thin film 20 has been treated with sulfuric acid. Note that FIG. 4(2) shows an example in which the ZrO2 or HfO2 of the thin film 20 is treated with sulfuric acid or phosphoric acid, but the present invention is not limited to this. In FIG. 4(2), the ZrO2 or HfO2 of the thin film 20 may be treated with any one of the chemical solutions of sulfuric acid, phosphoric acid, hydrogen peroxide, dilute hydrofluoric acid, hydrochloric acid, and ammonia, or a mixture of two or more of these chemical solutions.

[0057] The processed substrate W is baked at 500°C or higher (Figure 4(3)). By baking, the crystal structure of ZrO2 and HfO2 in the thin film 20 becomes tetragonal. In Figure 4(3), the crystal structure of ZrO2 in the sulfuric acid-treated thin film 20 becomes tetragonal. "ZrO2(t)" indicates that the crystal structure of ZrO2 is tetragonal.

[0058] The sulfuric acid and phosphoric acid remaining on the surface of the substrate W are removed by washing and drying (FIG. 4(4)). ZrO2 or HfO2 with a tetragonal crystal structure is formed on the thin film 20 as a template. In FIG. 4(4), ZrO2 with a tetragonal crystal structure is formed on the thin film 20.

[0059] On the thin film 20 having a tetragonal crystal structure, a film 21 of one or both of ZrO2 and HfO2 is formed in the same manner as the thin film 20 by the film formation method according to the embodiment (FIG. 4(5)). In FIG. 4(5), a film 21 of ZrO2 having a tetragonal crystal structure is further formed on the thin film 20 having a tetragonal crystal structure. In this way, by forming the film 21 on the thin film 20 having a tetragonal crystal structure, the film 21 having a tetragonal crystal structure can be stably formed.

[0060] Note that the process of Figure 4(4) is not essential and may be omitted. Figure 4(5)' shows a case where Figure 4(4) is omitted and a film 21 of one or both of ZrO2 and HfO2 is formed on a thin film 20 on which sulfuric acid and phosphoric acid remain, similar to the thin film 20, by the film formation method of the embodiment. In Figure 4(5)', a film 21 of ZrO2 with a tetragonal crystal structure is further formed on the thin film 20 of ZrO2 on which sulfuric acid and phosphoric acid remain. Even in this case, the film 21 with a tetragonal crystal structure can be stably formed.

[0061] By performing the initial process of forming the thin film 20 having a tetragonal crystal structure on the substrate W in this manner, the thin film 20 or film 21 of metal oxide having a tetragonal crystal structure can be stably formed from the vicinity of the interface with the substrate W.

[0062] [Configuration of Film Forming Apparatus 10] Next, an example of a film formation apparatus 10 for performing film formation by the film formation method according to the embodiment will be described. Fig. 5 is a block diagram showing a schematic configuration of the film formation apparatus 10 according to the embodiment. The film formation apparatus 10 has a film formation section 11 and a doping section 12.

[0063] The film forming unit 11 is a unit that forms a metal oxide film. The film forming unit 11 has a chamber and is configured to be able to form a metal oxide film in the chamber by any one of ALD, PVD, and CVD. For example, the film forming unit 11 can be configured using a film forming apparatus or the like that can perform any one of ALD, PVD, and CVD film formation processes.

[0064] The doping section 12 is configured to dope the metal oxide film with a dopant that, when doped into the metal oxide film, reduces the energy difference, obtained by subtracting the energy at which the crystal structure of the metal oxide film becomes monoclinic from the energy at which the crystal structure of the metal oxide film becomes tetragonal, to be lower than the energy difference in the undoped metal oxide film.

[0065] The doping unit 12 may be provided in the chamber of the film formation unit 11, or in a chamber separate from the chamber of the film formation unit 11. When the doping unit 12 performs doping by ion implantation and the film formation unit 11 forms a metal oxide film by ALD or PVD, the doping unit 12 is provided in a chamber separate from the chamber of the film formation unit 11. On the other hand, when the doping unit 12 performs doping by ion implantation and the film formation unit 11 forms a metal oxide film by PVD, the doping unit 12 may be provided in the chamber of the film formation unit 11, or in a separate chamber. When the doping unit 12 performs doping by any of a gas cluster ion beam method, a dopant solution immersion method, a thermal diffusion doping method, a laser doping method, a flash lamp method, and a deposited film method, the doping unit 12 is provided in a chamber separate from the chamber of the film formation unit 11. When the doping unit 12 performs doping by the nanolaminate method, the doping unit 12 is provided in the chamber of the film forming unit 11 .

[0066] When the film formation unit 11 and the doping unit 12 are configured as separate chambers, the film formation apparatus 10 is provided with a transport mechanism such as a transport arm for transporting the substrate W. When a metal oxide film is formed, the film formation apparatus 10 transports the substrate W to the film formation unit 11 by the transport mechanism, and when doping with a dopant, the transport mechanism transports the substrate W to the doping unit 12.

[0067] When a metal oxide film having a desired thickness is formed and then doped with a dopant, the film forming apparatus 10 forms a metal oxide film having a desired thickness in the film forming section 11, and then dopes the metal oxide film with a dopant in the doping section 12.

[0068] On the other hand, when a metal oxide film is formed by alternately repeating film formation and doping, the film formation apparatus 10 alternately repeats the formation of a metal oxide film in the film formation section 11 and the doping of a dopant into the metal oxide film in the doping section 12 to form a metal oxide film to the desired thickness.

[0069] The film formation apparatus 10 forms a metal oxide film on the substrate W by the film formation method according to the present embodiment. For example, the film formation apparatus 10 forms a metal oxide film as a dielectric film or an insulating film of a semiconductor device to be manufactured on the substrate W by the film formation method according to the present embodiment. For example, the film formation apparatus 10 forms a metal oxide film as a dielectric film or a gate insulating film of a capacitor of the semiconductor device by the film formation method according to the present embodiment. In this way, the film formation apparatus 10 can form a metal oxide film with a high dielectric constant. By being able to form a metal oxide film with a high dielectric constant as a dielectric film or an insulating film of a semiconductor device in this way, leakage current in the metal oxide film can be suppressed even when the semiconductor device is miniaturized.

[0070] [effect] The above describes the embodiments. As described above, the film formation method according to the embodiments includes step a) (e.g., steps S10, S12, and S14) and step b) (e.g., steps S13 to S17). In step a), a metal oxide film is formed. In step b), the metal oxide film is doped with a dopant such that the energy difference, obtained by subtracting the energy at which the crystal structure of the metal oxide film becomes monoclinic from the energy at which the crystal structure of the metal oxide film becomes tetragonal, is lower than the energy difference in an undoped metal oxide film. As a result, the film formation method according to the embodiments can form a metal oxide film with a high dielectric constant.

[0071] The dopant is a material that, when doped into a metal oxide film, causes the energy difference, obtained by subtracting the energy at which the crystal structure of the metal oxide film becomes monoclinic from the energy at which the crystal structure of the metal oxide film becomes tetragonal, to be equal to or less than 0. As a result, the film deposition method according to the embodiment can stably deposit a metal oxide film with a high dielectric constant.

[0072] The metal oxide film is a ZrO2 film. The dopant is any one of a compound of a Group III element and a Group VII element excluding GaI, a Group II element, a Group III element, a compound of a Group II element and sulfur, and a Group IV element, or a compound of a Group III element and a Group V element. This allows the film deposition method according to the embodiment to deposit a ZrO2 film with a high dielectric constant. The dopant is any one of Si, Ge, ZnS, MgS, CaS, SrS, BaS, AlP, AlAs, GaP, and GaAs. This allows the film deposition method according to the embodiment to stably deposit a ZrO2 film with a higher dielectric constant.

[0073] The metal oxide film is a HfO2 film. The dopant is any one of a group II element, a group III element, a compound of a group II element and sulfur, a group IV element, and a compound of a group III element and a group V element. This allows the film deposition method according to the embodiment to deposit a HfO2 film with a high dielectric constant. The dopant is any one of Si, Ge, SrS, ZnS, MgS, CaS, BaS, AlP, AlAs, GaP, and GaAs. This allows the film deposition method according to the embodiment to stably deposit a HfO2 film with a higher dielectric constant.

[0074] In step b), the dopant is doped into the metal oxide film by any one of ion implantation, gas cluster ion beam, nanolaminate, dopant solution immersion, thermal diffusion doping, laser doping, flash lamp doping, and deposited film deposition. This allows the film forming method according to the embodiment to dope the dopant into the metal oxide film.

[0075] The metal oxide film is a ZrO2 film, a HfO2 film, or a mixed film of ZrO2 and HfO2. The film forming method according to the embodiment further includes step c), which is a step performed before step a). Step c) includes forming a thin film 20 of one or both of ZrO2 and HfO2, treating the surface of the thin film 20 with any one of sulfuric acid, phosphoric acid, hydrogen peroxide, dilute hydrofluoric acid, hydrochloric acid, and ammonia, or a mixture of two or more of these chemicals, and then baking the thin film. In step c), after baking, the surface is further cleaned and dried to remove any remaining chemical or mixture from the surface. As a result, the film forming method according to the embodiment can stably form a ZrO2 film, HfO2 film, or mixed film of ZrO2 and HfO2 with a tetragonal crystal structure on the thin film 20 in step a).

[0076] It should be noted that the disclosed embodiments are illustrative in all respects and should not be considered limiting. Indeed, the above-described embodiments may be embodied in various forms. Furthermore, the above-described embodiments may be omitted, substituted, or modified in various forms without departing from the scope and spirit of the appended claims.

[0077] Furthermore, the following supplementary notes are disclosed regarding the above-described embodiment.

[0078] (Appendix 1) a) forming a metal oxide film; b) doping the metal oxide film with a dopant such that an energy difference, obtained by subtracting an energy at which the crystal structure of the metal oxide film becomes monoclinic from an energy at which the crystal structure of the metal oxide film becomes tetragonal, is lower than the energy difference in the undoped metal oxide film; A film forming method comprising:

[0079] (Appendix 2) The dopant is a material that, when doped into the metal oxide film, causes an energy difference of zero or less, obtained by subtracting the energy at which the crystal structure of the metal oxide film becomes monoclinic from the energy at which the crystal structure of the metal oxide film becomes tetragonal. 2. The film forming method according to claim 1.

[0080] (Appendix 3) the metal oxide film is a ZrO2 film, The dopant is any one of a compound of a group III element and a group VII element except GaI, a group II element, a group III element, a compound of a group II element and sulfur, a group IV element, and a compound of a group III element and a group V element. 3. The film forming method according to claim 1 or 2.

[0081] (Appendix 4) The dopant is any one of Si, Ge, ZnS, MgS, CaS, SrS, BaS, AlP, AlAs, GaP, and GaAs. 4. The film forming method according to claim 3.

[0082] (Appendix 5) the metal oxide film is a HfO2 film, The dopant is any one of a group II element, a group III element, a compound of a group II element and sulfur, a group IV element, and a compound of a group III element and a group V element. 3. The film forming method according to claim 1 or 2.

[0083] (Appendix 6) The dopant is any one of Si, Ge, SrS, ZnS, MgS, CaS, BaS, AlP, AlAs, GaP, and GaAs. 6. The film forming method according to claim 5.

[0084] (Appendix 7) In the step b), the dopant is doped into the metal oxide film by any one of ion implantation, gas cluster ion beam, nanolaminate, dopant solution immersion, thermal diffusion doping, laser doping, flash lamp doping, and deposited film method. 7. A film forming method according to any one of claims 1 to 6.

[0085] (Appendix 8) the metal oxide film is a ZrO2 film, a HfO2 film, or a mixed film of ZrO2 and HfO2, c) A process carried out before the process a) further includes a process of forming a thin film of one or both of ZrO2 and HfO2, treating the surface of the thin film with any one of sulfuric acid, phosphoric acid, hydrogen peroxide solution, dilute hydrofluoric acid, hydrochloric acid, and ammonia, or a mixture of any two or more chemicals, and then baking the thin film. 8. A film forming method according to any one of claims 1 to 7.

[0086] (Appendix 9) In the step c), after the baking, the surface is washed and dried to further remove the chemical solution or the mixture remaining on the surface. 9. The film forming method according to claim 8.

[0087] (Appendix 10) a film forming unit configured to form a metal oxide film; a doping unit configured to dope the metal oxide film with a dopant that is doped into the metal oxide film such that an energy difference, obtained by subtracting an energy at which the crystal structure of the metal oxide film becomes monoclinic from an energy at which the crystal structure of the metal oxide film becomes tetragonal, is lower than the energy difference in the metal oxide film in an undoped state; A film forming apparatus having the above structure.

[0088] (Appendix 11) A semiconductor device having a metal oxide film, The metal oxide film is doped with a dopant that is doped into the metal oxide film, and the energy difference obtained by subtracting the energy at which the crystal structure of the metal oxide film becomes monoclinic from the energy at which the crystal structure of the metal oxide film becomes tetragonal by doping the metal oxide film is lower than the energy difference in the metal oxide film in an undoped state. Semiconductor device. [Explanation of symbols]

[0089] 10 Film deposition equipment 11 Film forming section 12 Dope Section 20 Thin Films 21 Membrane 30 stages 31 Ion Source 32 Ion beam 33 small hole 40 stages 41 Piping 42 nozzles 43 Ionizer 44 Acceleration section 45 Magnet 46 Neutralization Department 47 Aperture 51 Metal oxide film 52 membrane 61 Metal oxide film 62 Dopant Solution 71 Chamber 72 Heat source 81 Chamber 82 Stages 83 Transparent window 84 Laser light 91 Chamber 92 Stages 93 Heater 94 Transparent part 95 Flash Lamp 96 Reflector 99 Sacrificial Film W substrate

Claims

1. a) forming a metal oxide film; b) doping the metal oxide film with a dopant such that an energy difference, obtained by subtracting an energy at which the crystal structure of the metal oxide film becomes monoclinic from an energy at which the crystal structure of the metal oxide film becomes tetragonal, is lower than the energy difference in the undoped metal oxide film; A film forming method comprising:

2. The dopant is a material that, when doped into the metal oxide film, causes an energy difference of zero or less, obtained by subtracting the energy at which the crystal structure of the metal oxide film becomes monoclinic from the energy at which the crystal structure of the metal oxide film becomes tetragonal. The film forming method according to claim 1 .

3. The metal oxide film is ZrO ２ is a membrane, The dopant is any one of a compound of a group III element (excluding GaI) and a group VII element, a group II element, a group III element, a compound of a group II element and sulfur, a group IV element, or a compound of a group III element and a group V element. The film forming method according to claim 1 .

4. The dopant is any one of Si, Ge, ZnS, MgS, CaS, SrS, BaS, AlP, AlAs, GaP, and GaAs. The film forming method according to claim 3 .

5. The metal oxide film is HfO ２ is a membrane, The dopant is any one of a group II element, a group III element, a compound of a group II element and sulfur, a group IV element, and a compound of a group III element and a group V element. The film forming method according to claim 1 .

6. The dopant is any one of Si, Ge, SrS, ZnS, MgS, CaS, BaS, AlP, AlAs, GaP, and GaAs. The film forming method according to claim 5 .

7. In the step b), the dopant is doped into the metal oxide film by any one of ion implantation, gas cluster ion beam, nanolaminate, dopant solution immersion, thermal diffusion doping, laser doping, flash lamp doping, and deposited film method. The film forming method according to claim 1 .

8. The metal oxide film is ZrO ２ membrane, HfO ２ film, or ZrO ２ and HfO ２ It is a mixed film of c) a step carried out before step a), comprising: ２ , HfO ２ and further comprising a step of forming a thin film by one or both of the above, treating the surface of the thin film with sulfuric acid or phosphoric acid, and then baking the film. The film forming method according to claim 1 .

9. In the step c), after the firing, the surface is washed and dried to further remove sulfuric acid or phosphoric acid remaining on the surface. The film forming method according to claim 8 .

10. a film forming unit configured to form a metal oxide film; a doping unit configured to dope the metal oxide film with a dopant that is doped into the metal oxide film such that an energy difference, obtained by subtracting an energy at which the crystal structure of the metal oxide film becomes monoclinic from an energy at which the crystal structure of the metal oxide film becomes tetragonal, is lower than the energy difference in the metal oxide film in an undoped state; A film forming apparatus having the above structure.

11. A semiconductor device having a metal oxide film, The metal oxide film is doped with a dopant that is doped into the metal oxide film, and the energy difference obtained by subtracting the energy at which the crystal structure of the metal oxide film becomes monoclinic from the energy at which the crystal structure of the metal oxide film becomes tetragonal by doping the metal oxide film is lower than the energy difference in the metal oxide film in an undoped state. Semiconductor device.

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