METHOD FOR SELECTIVELY FORMING Ru THIN FILM

Abstract

This method for forming an Ru thin film by a chemical vapor deposition method according to the present invention uses, as a raw material precursor, an Ru complex with a substrate selectivity s represented by the formula satisfies s > 0. Consequently, an Ru thin film is selectively formed in a first region composed of a metal M on a substrate. At this time, formation of the Ru thin film is suppressed in a second region composed of a compound C which is any of an oxide, a carbide, a nitride, a silicide, an oxycarbide, and an oxynitride on the substrate. T1: Film thickness (T1 > 0 nm) obtained when an Ru thin film is formed using metal M as the substrate, for an arbitrary film forming time at a film forming temperature of 200°C or lower. T2: Film thickness (T2 ≥ 0 nm) obtained when an Ru thin film is formed using a compound C as the substrate under the same conditions as those used when the metal M is used as the substrate.

Description

Method for selectively forming Ru thin film

[0001] The present invention relates to a method for selectively depositing a Ru thin film by chemical vapor deposition in order to preferentially deposit a Ru thin film in a predetermined region when manufacturing wiring substrates for semiconductor devices and the like.

[0002] Thin films made of Ru (ruthenium) or Ru compounds (hereinafter referred to as Ru thin films or simply thin films) are expected to be used as wiring and electrode materials for various semiconductor devices. In particular, the importance of Ru has become more pronounced in recent years due to the miniaturization of wiring in response to the ultra-miniaturization of semiconductor devices and the like. Currently, Cu is the mainstream wiring material for semiconductor devices. However, future semiconductor devices are planned to have wiring widths on the 10 nm level, which is smaller than the mean free path of Cu electrons (approximately 38.7 nm). When a Cu thin film is applied to such fine wiring, the resistance coefficient due to surface scattering and grain boundary scattering, which is proportional to the mean free path, increases, resulting in an increase in the resistance value (specific resistance) of the wiring. In contrast, the mean free path of Ru electrons is much shorter than that of Cu (10.8 nm), which has the advantage of suppressing the aforementioned increase in specific resistance. Furthermore, Ru has a melting point of 2250° C., which is higher than that of Cu (1085° C.), and therefore has good electromigration resistance. Due to these advantages, the use of Ru as a wiring material is becoming more widespread.

[0003] As mentioned above, Cu wiring is currently the mainstream for wiring in semiconductor devices, etc., but methods have been proposed for forming protective and covering films of other metals on Cu wiring for the purpose of improving reliability and bottom-up. Ru thin films are effective not only as wiring and electrode materials but also as protective and covering films for Cu wiring and the like.

[0004] Chemical vapor deposition methods such as CVD (chemical vapor deposition) and ALD (atomic layer deposition) are used as manufacturing processes for Ru thin films. In forming a Ru thin film using chemical vapor deposition, a source gas is generated from a Ru complex, which serves as a precursor (thin film raw material). The source gas is introduced onto the surface of the substrate on which the film is to be formed, and energy such as heating is applied to decompose the Ru complex, causing Ru to precipitate and deposit, resulting in a Ru thin film. To promote Ru deposition, an oxidizing gas such as oxygen or a reducing gas such as hydrogen is typically introduced as a reactive gas depending on the structure of the Ru complex. The applicant of the present application has previously developed and disclosed various Ru complexes that serve as precursors (Patent Documents 1 to 3).

[0005] In the manufacture of wiring and electrodes for semiconductor devices, etc., it is necessary to form a thin film in a specific region on the surface of a substrate. Photolithography has long been widely used as a technique for partially depositing a thin film for such purposes. For the partial deposition of Ru thin films, the application of chemical vapor deposition using photolithography has been widely known.

[0006] However, in the case of next-generation semiconductor devices, further miniaturization is increasingly forcing the adoption of multi-patterning techniques. Film formation by photolithography requires numerous steps, such as patterning and exposure treatments using resist or the like before film formation, and removal of resist or the like after film formation. Therefore, photolithography is expected to significantly increase the cost of manufacturing semiconductor devices that employ multi-patterning.

[0007] Area selective deposition (ASD) has attracted attention as one of the means to address this issue. ASD is a deposition process that utilizes the chemical or physical properties of the substrate surface and the deposition source to deposit a desired thin film in a controlled manner in a specific area, while simultaneously avoiding deposition in other areas adjacent to the specific area. ASD is expected to become an important deposition process in the future because it can selectively deposit a thin film with fewer steps than conventional photolithography.

[0008] There have also been several reports on selective deposition of Ru films using ASD. One specific method involves applying an inhibitor treatment to the surface of a substrate in areas where the Ru thin film is not desired to grow. For example, Patent Document 4 proposes a method for achieving area-selective chemical vapor deposition by exposing the substrate to an additive such as silylamine, selectively forming a surfactant layer on the surface of the dielectric material of the substrate, and then depositing a Ru thin film, thereby selectively depositing the Ru film on the conductive material of the substrate.

[0009] Furthermore, Patent Document 5 discloses a method utilizing the selectivity of Ru complexes under a predetermined reaction atmosphere. Specifically, utilizing the fact that a specific Ru complex selectively deposits on the surface of a conductive material such as a metal in a reducing gas, the method performs initial deposition on the surface of the conductive material in an oxygen-free atmosphere using a reducing gas, and then introduces oxygen into the atmosphere to promote Ru deposition. Furthermore, Non-Patent Document 1, which is a process similar to this technique, performs initial deposition in a reducing atmosphere such as hydrogen, and then introduces hydrogen to promote Ru deposition, thereby achieving area-selective chemical vapor deposition.

[0010] Patent No. 7372353 Publication Patent No. 4746141 Publication Patent No. 7148377 Publication Special Publication No. 2023-516857 Publication Patent No. 7361771 Publication

[0011] Junling Lu, Ke-Bin Low, Yu Lei, Joseph A. Libera, Alan Nicholls,Peter C. Stair, Jeffrey W. Elam, Toward atomically-precise synthesis of supported bimetallic nanoparticles using atomic layer deposition, Nat. Commun. 2014, 5, 1-9.

[0012] However, while the method of applying an inhibition treatment to regions where the Ru thin film growth is not desired, as in Patent Document 4, enables selective film formation, it also raises other problems. There are concerns that the additives used in the inhibition treatment, such as amines and oxidizing substances, may oxidize or contaminate the substrate upon contact with and reaction with the substrate. This oxidation and contamination of the substrate is particularly likely to occur in the early stages of film formation. Furthermore, damage to the substrate due to oxidation or contamination can significantly increase the substrate's resistance. Even if an additive has little effect on the substrate, if it remains on the substrate, it may itself increase the resistance. Furthermore, even if the additive is removed after the Ru thin film is formed, there is a possibility that the substrate may be damaged during this process. The additive removal process increases the number of steps and requires additional equipment, making it an inefficient process.

[0013] Furthermore, in processes such as those described in Patent Document 5, in which the reaction atmosphere is changed for each film formation stage, switching of the reaction gas is necessary, which poses problems in terms of process management and safety management. Hydrogen and oxygen are explosive and flammable gases, and in particular, the minimum ignition energy of hydrogen in oxygen gas (and oxygen in hydrogen gas) is lower than the ignition energy of hydrogen in air. Using both hydrogen and oxygen, as in the above-mentioned prior art, raises safety concerns. Furthermore, there is a risk of reduced productivity due to the need for additional equipment to ensure safety.

[0014] The present invention has been made in light of the above background, and provides a method for selectively depositing a Ru thin film by chemical vapor deposition based on a different concept from conventional methods. To this end, the present invention provides a deposition process that is free from the risk of substrate damage caused by an inhibiting treatment for selective deposition, and that furthermore, enables a clearer distinction than conventional methods to be made between the presence or absence of deposition in the selected and non-selective regions.

[0015] In order to solve the above-mentioned problems, the present inventors first reexamined the properties of the Ru complexes used as chemical vapor deposition raw materials that the applicant had previously developed, and found that, when a certain Ru complex is used at a low film formation temperature (200°C or lower), the thickness of the Ru thin film formed on the surface of a substrate made of a metal such as Cu is relatively large, but when the substrate surface is made of a compound such as an oxide, the thickness of the Ru thin film formed under the same conditions is extremely small.

[0016] FIG. 1 illustrates the difference in film thickness change depending on the substrate. In the chemical vapor deposition process for forming a Ru thin film, nucleation is required as an initial step, and the generated nuclei act as starting points for Ru precipitation and deposition to form a thin film. The difference in film thickness caused by differences in substrate material shown in FIG. 1 is thought to be due to a delay in nucleation (nucleation delay). Ru complexes that can exhibit such nucleation delay based on the substrate material can form Ru thin films with substrate selectivity. In other words, the Ru complex itself can be said to have substrate selectivity. The inventors conceived the present invention by embodying the substrate selectivity of the Ru complex as a substrate selectivity, making this a characteristic of the Ru complex, and conceiving that the above-mentioned problem can be solved by chemical vapor deposition using a Ru complex with a predetermined substrate selectivity.

[0017] That is, the present invention provides a selective film formation method for preferentially forming a Ru thin film made of Ru or a Ru compound by chemical vapor deposition on a substrate having a first region whose surface is made of a metal M and a second region whose surface is made of a compound C selected from oxide, carbide, nitride, silicide, oxycarbide, and oxynitride, the first region, the chemical vapor deposition comprising a step of transporting a source gas generated from a Ru complex onto the substrate and heating it, the Ru complex having a substrate selectivity s represented by the following formula, wherein the substrate selectivity s is greater than 0:

[0018] T １ : The thickness of a Ru thin film formed on a metal M substrate at a film formation temperature of 200°C or less for an arbitrary film formation time, T １ >0 nm. ２: the film thickness when a Ru thin film is formed using compound C as a substrate under the same conditions as when the metal M is used as a substrate, and T ２ ≧0 nm.

[0019] As described above, in the method for selectively depositing a Ru thin film according to the present invention, the substrate on which the film is to be deposited is divided into a first region and a second region, and the Ru thin film is preferentially deposited on the first region. In the present invention, the Ru complex used in the film deposition process by chemical vapor deposition has a substrate selectivity, as defined above, of greater than 0. Other factors are the same as in a conventional method for depositing a Ru thin film by chemical vapor deposition. The present invention will be described in more detail below.

[0020] A. Substrate The substrate in the present invention is divided into a first region and a second region. The first region is made of a metal M, the surface of which is a conductive material. Specifically, the metal M may be at least one of Cu, Al, W, Si, Ti, Ta, Mo, Ru, Pt, Ir, Rh, Pd, Au, Ag, Hf, Co, Zr, Cr, Ge, In, Ga, As, Fe, and Ni. Multiple first regions may be set on the substrate. Furthermore, when multiple first regions are set, two or more metals may be selected from the specific examples of the metal M, and different metals M may be applied to each first region.

[0021] The surface of the second region is made of a compound C, which is any one of oxide, carbide, nitride, silicide, carbide oxide, and nitride oxide. The compound C is often made of an insulating material (dielectric material). The compound C that becomes the second region is often an oxide, carbide, nitride, silicide, carbide oxide, and nitride oxide of a metal. The metal in this case may be the metal M described above. Specific materials for the compound C include CuO, Cu ２ O.W. ２ O ３ , W.O. ２ , W.O. ３ , SiO, SiO ２ , SiCOH, SiOC, SiON, Cu ３ N, SiN, Si ３ N ４ , TiN, Ti ２ N, TaN, MoN, Mo ２N, Mo ３ N ２ , Mn ３ N ２ , Mn ２ N, WN, W ２ N., W.N. ２ , W ３ N ４ , ZrN, CrN, Cr ２ N, TiSi ２ , MoSi ２ , TaSi ２ , WSi ２ , ZrSi ２ , CrSi ２ , NiSi ２ , PtSi ２ , CoSi ２ As with the first region, the second region may be set at a plurality of locations on the substrate. Alternatively, two or more types of compound C may be set in a plurality of second regions set on the substrate, and different compounds C may be applied to the respective second regions.

[0022] The first and second regions may be integrated with the substrate, or may be formed as a thin film on the substrate. For example, the substrate may be made of the material of the second region, and a thin film of metal M may be formed on the substrate to form the first region. Alternatively, the substrate may be made of a material different from both metal M and compound C, and thin films of the materials of the first and second regions may be formed on the substrate. In such cases, the material of the substrate is not limited, and may be a substrate such as a Si wafer that is often used in semiconductor devices, or may be a material other than the metals and compounds listed above, or may be a resin, plastic, etc.

[0023] Furthermore, there are no particular limitations on the shapes of the first and second regions. The first and second regions may be substantially flush with the surface of the substrate. A groove (trench) may be formed in the substrate, and its bottom or inner wall surface may serve as the first or second region. There are no particular limitations on the dimensions of the substrate and the first and second regions.

[0024] B. Ru Complex In the present invention, a Ru complex having the substrate selectivity s defined above as s>0 is used when forming a film by chemical vapor deposition.

[0025] B-1 Substrate selectivity of Ru complex In the present invention, the substrate selectivity s of the Ru complex is the thickness T of the Ru complex on each substrate when a Ru thin film is formed using a metal M and a compound C as substrates at a film formation temperature of 200° C. or less. １ , T ２ In this calculation, the film formation temperature was set to 200°C or less because the substrate selectivity of the Ru complex discovered in the present invention is manifested in this temperature range. This temperature range is also useful in light of the recent demand for lower temperature processes in the field of mounting semiconductor devices and the like.

[0026]

[0027] In calculating the substrate selectivity s of various Ru complexes, a substrate having a first region and a second region on which a Ru thin film is actually formed may be used. Alternatively, a preliminary film formation test may be performed in advance using the metal M (first region) and the compound C (second region) that are set in the substrate on which a Ru thin film is actually formed.

[0028] When calculating the substrate selectivity s by conducting a preliminary film formation test, the film formation temperature in the film formation test is set to 200°C or lower. The higher the film formation temperature, the more the nucleation of ruthenium is promoted, making it difficult to confirm the difference from Ru complexes, which are prone to nucleation delay. Therefore, the film formation temperature can be set lower, and may be set to 180°C or lower. However, at a film formation temperature below 120°C, the precipitation of a Ru thin film also on the metal M becomes difficult, making it difficult to calculate the substrate selectivity s. Therefore, it is preferable that the film formation temperature be 120°C or higher.

[0029] In the present invention, a Ru complex having a substrate selectivity s of s>0 is used as a raw material for film formation by chemical vapor deposition. １ >0 is T ２ ≧0 and T １ >T ２ This means that the Ru complex that can become T １ rises, but T ２ is due to the nucleation delay. １ In order to obtain an appropriate substrate selectivity s, T１ It is not advisable to calculate the substrate selectivity s when T １ In the present invention, it is preferable to use the value calculated when the substrate selectivity s is in the range of 2 nm to 6 nm as the value of the Ru complex. In addition, in the present invention, it is preferable to use a Ru complex whose substrate selectivity s calculated in this range is 0.2 to 1.0.

[0030] In the preliminary film formation test for calculating the substrate selectivity s, the film formation conditions other than the film formation temperature were T １ is within the above-mentioned preferred range. The film formation pressure is preferably 40 torr or more and 80 torr or less. Furthermore, supplying a reactive gas for Ru film formation is preferred, and it is preferred to supply a reactive gas corresponding to the Ru complex to be used at a flow rate of 30 sccm or more and 200 sccm or less.

[0031] B-2 Specific Structure of Ru Complex In the present invention, examples of Ru complexes having a suitable substrate selectivity s (s>0) for the above-described metal M include Ru complexes having a trimethylenemethane ligand, a carbonyl ligand, an isocyanide ligand, a pyridine ligand, an amine ligand, an imidazole ligand, a pyridazine ligand, a pyrimidine ligand, a pyrazine ligand, or a benzene ligand as the ligand. Substituents may be introduced into these ligands. Specific examples include Ru complex I, Ru complex II, Ru complex III, Ru complex IV, and Ru complex V shown in (1) to (5) below. These Ru complexes are described in the above-mentioned Patent Documents 1 to 3.

[0032] (1) Ru complex I (In the formula, the ligand L １ is a linear or branched chain hydrocarbon group or a cyclic hydrocarbon group having from 2 to 13 carbon atoms. The ligand X is any one of a carbonyl ligand, an isocyanide ligand, a pyridine ligand, an amine ligand, an imidazole ligand, a pyridazine ligand, a pyrimidine ligand, and a pyrazine ligand.

[0033] Specific examples of precursors formed from this Ru complex I include (η ４-methylene-1,3-propanediyl)tricarbonylruthenium, or (η ４ Examples of suitable ruthenium compounds include (η4-methylene-1,3-propanediyl)tricarbonylruthenium (where L1 is a trimethylenemethane ligand and X is a carbonyl ligand). Another example is [(η4-methylene-1,3-propanediyl)-ruthenium-dicarbonyl-(2-isocyano-2-methylpropane)] shown in Chemical Formula 4.

[0034]

[0035]

[0036]

[0037] (2) Ru complex II (In the formula, R １ , R ２ may be the same or different, and each is either a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.

[0038] A specific example of the precursor composed of this Ru complex II is dicarbonyl-bis(5-methyl-2,4-hexanediketonato)ruthenium(II) of the following formula:

[0039]

[0040] (3) Ru complex III (In the formula, the ligand L ２ is shown in the following formula (L ２ -1) or (L ２ -2) and is a ligand containing one nitrogen atom.

[0041] (where * denotes the position of the atom bridging and coordinating to ruthenium. R ３ ~R １０ may be the same or different, and each is either a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.

[0042] A specific example of the precursor composed of this Ru complex III is hexacarbonyl [μ-[(1,2-η)-3-methyl-N-(1-methylpropyl)-1-butene-1-aminato-κC] of the following formula: ２ , κN １ : κN １ ]]diruthenium (Ru-Ru).

[0043]

[0044] (4) Ru complex IV (Ligand L coordinated to ruthenium ３ and ligand L ４ is expressed by the following formula:

[0045] (ligand L ３ , L ４ The substituent R １１ ~R ２２ are each independently a hydrogen atom or a linear or branched alkyl group having 1 to 4 carbon atoms.

[0046] Specific examples of precursors composed of this Ru complex IV include benzene(methylene-1,3-propanediyl)ruthenium and (methylene-1,3-propanediyl)[1-methyl-4-(1-methylethyl)benzene]ruthenium of the following formulas.

[0047]

[0048] (5) Ru complex V

[0049] C. Film Formation Conditions for the Selective Film Formation Method of the Present Invention The selective film formation method of the present invention utilizes the substrate selectivity of the precursor Ru complex at relatively low temperatures, and preferentially forms a Ru thin film in a first region where the metal M is present on the surface in a single process. Therefore, the present invention does not require switching of the reaction atmosphere during film formation, as in the prior art (Patent Document 5, Non-Patent Document 1). Furthermore, additional processes such as the inhibition treatment of Patent Document 4 are also unnecessary. Note that a single process refers to a process until a Ru thin film of a desired thickness is formed in the first region. In the case of a CVD method, this refers to a single film formation process, and in the case of an ALD method in which atomic layer-level film formation is performed in multiple cycles, this refers to a process until the completion of the multiple cycles. Furthermore, preferentially forming a Ru thin film in the first region means that the thickness of the Ru thin film in the first region is clearly greater than the thickness of the Ru thin film in the second region. It is preferable that no Ru thin film is formed in the second region (thickness 0 nm), but formation of an extremely thin Ru thin film is acceptable. The thickness of the Ru thin film in the second region is preferably 4 nm or less, more preferably 3 nm or less, and particularly preferably 2 nm or less. The film formation conditions in the method for selectively forming a Ru thin film according to the present invention are basically the same as those in conventional chemical vapor deposition methods.

[0050] C-1 Generation of Source Gas The source gas used in the chemical vapor deposition method is preferably generated by heating and vaporizing a Ru complex precursor. The source heating temperature is appropriately set depending on the melting point and vapor pressure of the Ru complex. For the Ru complexes I to V described above, the source heating temperature is set in the range of 10°C to 140°C.

[0051] The generated raw material gas is transported to the substrate (reaction vessel) together with a carrier gas. An inert gas (e.g., Ar) commonly used in chemical vapor deposition is also used as the carrier gas. The flow rate of the carrier gas is appropriately set depending on the vapor pressure and reactivity of the Ru complex. If the flow rate is too low, the Ru complex cannot be stably supplied, whereas if the flow rate is too high, the partial pressure of the Ru complex decreases, preventing it from being sufficiently decomposed. Therefore, the flow rate is preferably set to 5 sccm or more and 200 sccm or less.

[0052] C-2 Reactant Gas In chemical vapor deposition, a reactant gas is typically transported onto the substrate together with the source gas to promote the decomposition of the Ru complex and achieve a suitable film formation rate. The reactant gas may be an oxidizing gas such as oxygen or ozone, or a non-oxidizing gas such as hydrogen, water vapor, ammonia, an amine compound, or a hydrazine derivative. The reactant gas is selected depending on the decomposition characteristics of the Ru complex. For example, both oxidizing and non-oxidizing gases can be used for the Ru complexes I to V described above. The flow rate of the reactant gas is appropriately set depending on the reactivity of the Ru complex, and the flow rate is preferably 5 sccm or more and 200 sccm or less.

[0053] C-3 Film Formation Conditions The film formation temperature for the Ru thin film in the present invention is 200°C or lower. This is to allow the Ru complex, which is the precursor, to exhibit substrate selectivity. In addition, in order to more effectively utilize the substrate selectivity, the film formation temperature is preferably 120°C or higher and 180°C or lower. The film formation temperature refers to the surface temperature of the substrate, and is usually adjusted by the heating temperature of the substrate. Furthermore, the film formation pressure, which is a film formation condition other than the film formation temperature, is the same as the pressure used in ordinary chemical vapor deposition. This pressure is set appropriately depending on the vapor pressure and reactivity of the Ru complex, and is preferably 1 torr or higher and 100 torr or lower.

[0054] Under the above film formation conditions, a Ru thin film is preferentially formed on the surface of the metal M in the first region. The film thickness of the Ru thin film in the first region can be set according to the film formation time and is not particularly limited. However, as the film formation time increases, the formation of the Ru thin film also progresses in the second region. The film thickness of the Ru thin film in the first region is preferably 2 nm or more and 10 nm or less.

[0055] After forming a Ru thin film on a substrate having a first region and a second region as film formation targets by the process described above, the substrate selectivity s may be confirmed and calculated from the film thickness in each region. When the substrate selectivity calculated in this actual film formation process is referred to as the effective substrate selectivity (s'), it is preferable that the effective substrate selectivity s' approximates the substrate selectivity (s) obtained from the preliminary film formation test described above.

[0056] As described above, the present invention is a method for forming a Ru thin film by chemical vapor deposition, which applies a substrate having both a metal and a compound on its surface, and preferentially and selectively forms a Ru thin film on the metal surface. The present invention utilizes the substrate selectivity of the Ru complex precursor to selectively form the Ru thin film. This simplifies the Ru thin film formation process.

[0057] FIG. 1 is a diagram illustrating the difference in film thickness change depending on the substrate material for the Ru complex applied in the present invention. FIG. 2 is a diagram illustrating the outline of the configuration of the film formation apparatus used in this embodiment. FIG. 3 is a graph showing the change in film thickness of the Ru thin film on each substrate for various Ru complexes in the preliminary film formation test of the first embodiment. FIG. 4 is a graph showing the transition of the substrate selectivity for various Ru complexes with respect to the substrate material in the preliminary film formation test of the first embodiment. Photographs showing the film formation state on each substrate by complex I in the preliminary film formation test of the first embodiment. FIG. 5 is a diagram showing the appearance of a substrate having a first region and a second region used in the second embodiment. 6 is a cross-sectional SEM photograph of the first region and the second region after the Ru thin film has been formed in the film formation test of the second embodiment.

[0058] First Embodiment: Hereinafter, an embodiment of the present invention will be described. In this embodiment, in order to calculate the substrate selectivity of various Ru complexes, a preliminary film formation test was carried out using a single substrate consisting of metal M and compound C as the film formation target. The Ru complexes investigated in this embodiment are three types: (η4-methylene-1,3-propanediyl)tricarbonylruthenium of Chemical Formula 3, which is Ru complex I; dicarbonyl-bis(5-methyl-2,4-hexanediketonato)ruthenium(II) of Chemical Formula 6, which is Ru complex II; and benzene(methylene-1,3-propanediyl)ruthenium of Chemical Formula 12, which is Ru complex IV.

[0059] In this embodiment, a substrate is prepared by forming a thin film of Cu (20 mm square, 80 nm thick) as a metal M on a Si wafer (40 mm square, 1 mm thick) by sputtering, and the same Si wafer is coated with an oxide (compound C) of SiO ２Three types of substrates were prepared: a substrate on which a thin film of TiN (dimensions: 20 mm square, thickness: 100 nm) was formed; and a substrate on which a thin film of TiN (dimensions: 20 mm square, thickness: 20 nm) which is a nitride (compound C) was formed on the same Si wafer, and the film formation characteristics of each were examined.

[0060] In the film formation test, a CVD film formation apparatus having the configuration shown in Fig. 2 was used as the film formation apparatus. In the film formation test, each substrate was set in the reactor of the CVD film formation apparatus shown in Fig. 2, and then a Ru complex was sealed in a source container, and the Ru complex was heated to generate a source gas, which was then introduced into the reactor together with a carrier gas and a reactive gas to form a Ru thin film. The film formation conditions in this embodiment are as follows:

[0061]

[0062] After the film formation test, the thickness of the Ru thin film was measured for each substrate by X-ray fluorescence analysis (XRF). １ ) and compound C (SiO ２ , TiN) ２ ) was used to calculate the substrate selectivity s for the metal M. The results are shown in Table 2. Also, the film formation time and the thickness T of the Ru thin film for each Ru complex and each substrate were plotted based on Table 2. １ , T ２ The graph showing the relationship between the thickness of each Ru complex on the metal M (Cu) (T １ 4 shows a graph illustrating the change in substrate selectivity s due to the change in . As an example of the results of this embodiment, planar SEM images of the surfaces of the substrates when the film formation time was set to 30 minutes and 60 minutes using Ru complex I are shown.

[0063]

[0064] From Table 2 and FIG. 3, it can be seen that, for each of the Ru complexes investigated in this embodiment, at a film formation temperature of 180° C. or less, the formation of a Ru thin film begins immediately on the Cu substrate, which is the metal M, and the film thickness T １ On the other hand, compound C, SiO ２In the case of the substrate and the TiN substrate, the film formation is delayed due to the delayed nucleation. １ , T ２ The substrate selectivity s of the Ru complex relative to the metal M (Cu) calculated from the above formula is s>0.

[0065] Furthermore, referring to FIG. 4, the substrate selectivity s of the Ru complex to the metal M (Cu) increases with increasing film formation time (thickness T １ This is because, although nucleation delay occurs in compound C, it does not mean that a Ru thin film is not formed, but rather the Ru thin film grows after nucleation. For this reason, when obtaining the substrate selectivity s of the Ru complex in a preliminary test, it is necessary to consider the thickness T １ It is preferable to calculate in a range where the thickness is 6 nm or less.

[0066] Considering the substrate selectivity s for each Ru complex, Ru complex I (η4-methylene-1,3-propanediyl)tricarbonyl ruthenium has a SiO ２ and TiN. １ Dicarbonyl-bis(5-methyl-2,4-hexanediketonato)ruthenium(II) of Ru complex II can maintain high substrate selectivity for TiN, but SiO ２ For the film thickness T １ The benzene(methylene-1,3-propanediyl)ruthenium of Ru complex IV has a tendency to decrease due to the increase in SiO ２ The substrate selectivity for both TiN and TiN is １ From the viewpoint of substrate selectivity, Ru complex I and Ru complex II are particularly suitable Ru complexes. This is because they contain a carbonyl ligand. The carbonyl ligand has an appropriate bonding strength with Ru, and while the Ru complex is moderately stable, it decomposes relatively easily when heated.

[0067] Second Embodiment: In this embodiment, based on the results of the first embodiment, a substrate having a first region and a second region was prepared as a film formation target, and it was confirmed whether or not selective film formation was possible using each Ru complex.

[0068] 6 shows the appearance of the substrate used in this embodiment. This substrate was prepared by forming a Cu thin film (20 mm square, 80 nm thick) and a TiN thin film (20 mm square, 80 nm thick) on a Si wafer (40 mm square, 1 mm thick) by sputtering, and then forming a first region (Cu) and a second region (SiO ２ , TiN) was formed.

[0069] The Ru complexes investigated in this embodiment are (η4-methylene-1,3-propanediyl)tricarbonyl ruthenium (Ru complex I), dicarbonyl-bis(5-methyl-2,4-hexanediketonato)ruthenium(II) (Ru complex II), and benzene(methylene-1,3-propanediyl)ruthenium (Ru complex IV), as in the first embodiment. In this embodiment, for each Ru complex, the film formation conditions, such as the film formation temperature and film formation pressure, were changed and the conditions were set so that a Ru thin film of 6 nm was formed on the first region (Cu film). The film formation process was the same as in the first embodiment. After the film formation, the first region (Cu film) and the second region (SiO ２ The thickness of the Ru thin film in each of the TiN films was measured, and the effective substrate selectivity s' was calculated. The results of the above investigation are shown in Table 3.

[0070]

[0071] From Table 3, it can be seen that by applying each Ru complex, even in a substrate in which the first and second regions are actually divided and set, a Ru thin film is preferentially formed on the surface of Cu (metal M), which is the first region. Figure 7 shows cross-sectional SEM images of the first and second regions after film formation using Ru complex I.

[0072] The effective substrate selectivity s' in this embodiment is in good agreement with the substrate selectivity s (value for Cu film thickness of 6 nm) calculated in the first embodiment. Therefore, it was confirmed that application of the Ru complex having a predetermined substrate selectivity s according to the present invention enables preferential formation of a Ru thin film on the first region whose surface is composed of metal M.

[0073] The present invention is a film formation process that enables selective formation of Ru thin films by utilizing the properties of a specific Ru complex at relatively low temperatures. The selective Ru thin film formation method of the present invention enables selective formation of Ru thin films in a single step without inhibiting treatment of areas where film formation is to be avoided or adjusting the reaction atmosphere during film formation. The present invention is useful for forming electrodes and wiring in various semiconductor devices, etc., and for bottom-up coating of metal films on substrates. In particular, the present invention is useful for miniaturization and multi-patterning technologies in next-generation semiconductor devices that are being planned in recent years.

Claims

1. A selective film formation method for preferentially forming a Ru thin film made of Ru or a Ru compound by chemical vapor deposition on a substrate having a first region whose surface is made of a metal M and a second region whose surface is made of a compound C selected from oxide, carbide, nitride, silicide, oxycarbide, and oxynitride, the first region, wherein the chemical vapor deposition method includes a step of transporting a source gas generated from a Ru complex onto the substrate and heating it, the Ru complex having a substrate selectivity s expressed by the following formula, wherein the substrate selectivity s is greater than 0: T １ : The thickness of a Ru thin film formed on a metal M substrate at a film formation temperature of 200°C or less for an arbitrary film formation time, T １ >0 nm. ２ : the film thickness when a Ru thin film is formed using compound C as a substrate under the same conditions as when the metal M is used as a substrate, and T ２ ≧0 nm.

2. The method for selectively forming a Ru thin film according to claim 1, wherein the Ru complex is a Ru complex containing a carbonyl ligand as a ligand.

3. A method for selectively depositing a Ru thin film according to claim 1 or claim 2, wherein the metal M is at least one of Cu, Al, W, Si, Ti, Ta, Mo, Ru, Pt, Ir, Rh, Pd, Au, Ag, Hf, Co, Zr, Cr, Ge, In, Ga, As, Fe, and Ni.

4. A method for selectively depositing a Ru thin film according to claim 1 or 2, wherein compound C is at least one of oxide, carbide, nitride, silicide, oxycarbide, and oxynitride of metal M.

5. Ru complexes are １ 3. The method for selectively depositing a Ru thin film according to claim 1, wherein the substrate selectivity s is s≧0.2 within a range of 2 nm to 6 nm.

6. The method for selectively forming a Ru thin film according to claim 1 or 2, wherein the Ru complex is any one of (1) Ru complex I, (2) Ru complex II, (3) Ru complex III, (4) Ru complex IV, and (5) Ru complex V, represented by the following formula: (1) Ru complex I (In the formula, the ligand L １ is a linear or branched chain hydrocarbon group or a cyclic hydrocarbon group having 2 to 13 carbon atoms. Ligand X is any one of a carbonyl ligand, an isocyanide ligand, a pyridine ligand, an amine ligand, an imidazole ligand, a pyridazine ligand, a pyrimidine ligand, and a pyrazine ligand. (2) Ru Complex II (In the formula, R １ , R ２ may be the same or different, and each represents one of a hydrogen atom and an alkyl group having 1 to 4 carbon atoms. (3) Ru Complex III (In the formula, the ligand L ２ is shown in the following formula (L ２ -1) or (L ２ -2) and is a ligand containing one nitrogen atom. (where * denotes the position of the atom bridging and coordinating to ruthenium. R ３ ~R １０ may be the same or different, and each represents one of a hydrogen atom and an alkyl group having 1 to 4 carbon atoms. (4) Ru Complex IV (Ligand L coordinated to ruthenium ３ and ligand L ４ is expressed by the following formula: (ligand L ３ , L ４ The substituent R １１ ~R ２２ are each independently a hydrogen atom or a linear or branched alkyl group having 1 to 4 carbon atoms. (5) Ru Complex V

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