Selective deposition method for Ru thin films

Abstract

To provide a method of selectively depositing a film in a desired region on a substrate without switching an inhibition treatment or a reactive gas.SOLUTION: A Ru thin film is selectively deposited on a first region composed of a metal M on a substrate using a Ru chelate with a substrate selectivity of S>0 shown by an equation below as a precursor. A film deposition of the Ru thin film is suppressed in a second region that is composed of either of an oxide, a carbide, a nitride, a silicide, an oxycarbide, or an oxynitride on the substrate. T1: a thickness of the Ru thin film deposited for an arbitrary time at a film deposition temperature of 200°C or less on a metal M as a base material (T1>0 nm). T2: a film thickness when the Ru thin film is deposited on a compound C as the base material under a same condition as that for the metal M as the base material (T2≥0 nm).SELECTED DRAWING: Figure 3

Description

[Technical Field]

[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. [Background technology]

[0002] Thin films composed 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 increasingly apparent due to the recent trend toward miniaturization of wiring in response to the ultra-miniaturization of semiconductor devices. Currently, Cu is the mainstream wiring material for semiconductor devices. However, future semiconductor device developments are expected to achieve wiring widths on the 10-nm level, which is smaller than the mean free path of Cu electrons (approximately 38.7 nm). The application of Cu thin films to such fine wiring increases the resistance coefficient due to surface scattering and grain boundary scattering, which are proportional to the mean free path, 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), thereby offering the advantage of suppressing the aforementioned increase in specific resistance. Furthermore, Ru's melting point of 2250°C, higher than that of Cu (1085°C), also provides 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, but methods have been proposed for forming protective and coating films of other metals on Cu wiring to improve reliability and for bottom-up applications. Ru thin films are effective not only as wiring and electrode materials, but also as protective and coating films for Cu and other wiring.

[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 the formation of Ru thin films by 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 thin films in specific regions on the surface of a substrate. Photolithography has long been widely used as a technique for partially depositing thin films for such applications. For the partial deposition of Ru thin films, the application of chemical vapor deposition using photolithography has also 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) is attracting 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 can selectively deposit thin films with fewer steps than conventional photolithography, and is therefore expected to become an important deposition process in the future.

[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 you do not want the Ru thin film 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] Patent Document 5 discloses a method that utilizes the selectivity of Ru complexes under a specific reaction atmosphere. Specifically, by 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 method, 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. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] Patent No. 7372353 [Patent Document 2] Patent No. 4746141 [Patent Document 3] Patent No. 7148377 [Patent Document 4] Special Publication No. 2023-516857 [Patent Document 5] Patent No. 7361771 [Non-patent literature]

[0011] [Non-Patent Document 1] Junling Lu, Ke-BinLow, 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. Summary of the Invention [Problem to be solved by the invention]

[0012] However, while the method of applying an inhibitor 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 inhibitor treatment, such as amines and oxidizing substances, may oxidize or contaminate the substrate upon contact 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, where the reaction atmosphere is changed for each film formation stage, switching of the reaction gas is necessary, which poses problems in terms of process control 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, the need for additional equipment to ensure safety may result in reduced productivity.

[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, can clearly distinguish between the presence or absence of deposition in the selected and non-selective regions. [Means for solving the problem]

[0015] In order to solve the above 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. As a result, they 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 film is formed on the surface of a substrate made of a compound such as an oxide, the thickness of the Ru thin film is extremely small, even when the film is formed under the same conditions.

[0016] FIG. 1 is a diagram illustrating the difference in film thickness change depending on the substrate, as described above. 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, as 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, it can be said that the Ru complex itself has substrate selectivity. The inventors conceived the present invention by embodying the substrate selectivity of the above-mentioned Ru complex as a substrate selectivity, making this a characteristic of the Ru complex, and conceiving that the above-mentioned problems 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 that is any one of oxide, carbide, nitride, silicide, oxycarbide, and oxynitride, the first region being the first region, the chemical vapor deposition method 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]

number

[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 deposited preferentially 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 greater than 0, as defined above. Other factors are the same as in the method for depositing a Ru thin film by a conventional chemical vapor deposition method. The present invention will be described in more detail below.

[0020] A Base material The substrate in the present invention is divided into a first region and a second region. The first region has a surface made of a metal M, which is a conductive material. Specifically, the metal M can 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. A plurality of first regions may be set on the substrate. Furthermore, when a plurality of 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, oxycarbide, and oxynitride. The compound C is often made of an insulating material (dielectric material). The compound C that becomes the second region is often a metal oxide, carbide, nitride, silicide, oxycarbide, and oxynitride. The metal in this case may be the metal M described above. Specific examples of the compound C include at least one of CuO, Cu2O, W2O3, WO2, WO3, SiO, SiO2, SiCOH, SiOC, SiON, Cu3N, SiN, Si3N4, TiN, Ti2N, TaN, MoN, Mo2N, Mo3N2, Mn3N2, Mn2N, WN, W2N, WN2, W3N4, ZrN, CrN, Cr2N, TiSi2, MoSi2, TaSi2, WSi2, ZrSi2, CrSi2, NiSi2, PtSi2, and CoSi2. Similar to the first region, the second region may be formed in multiple locations on the substrate. Alternatively, two or more types of compound C may be formed in multiple second regions formed on the substrate, with different compounds C applied to each second region.

[0022] The first and second regions may be integrated with the substrate or 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 commonly 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, when forming a film by chemical vapor deposition, a Ru complex having the substrate selectivity s defined above as s>0 is used.

[0025] B-1 Substrate selectivity of Ru complexes In the present invention, the substrate selectivity s of a Ru complex is calculated from the film thicknesses T1 and T2 on the respective substrates 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. In this calculation, the film formation temperature is set to 200°C or less because the substrate selectivity of the Ru complex discovered in the present invention is expressed within this temperature range. Furthermore, this temperature range is useful in light of the recent demand for lower temperature processes in the field of mounting semiconductor devices and the like.

[0026]

number

[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) 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 with 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 film formation temperatures below 120°C, the precipitation of a Ru thin film on the metal M also becomes difficult, making it difficult to calculate the substrate selectivity s. Therefore, it is preferable to set the film formation temperature to 120°C or higher.

[0029] In the present invention, a Ru complex with a substrate selectivity s > 0 is used as a raw material for film formation by chemical vapor deposition. Referring to Figure 1 and Equation 2, this means applying a Ru complex that satisfies T1 > 0, T2 ≥ 0, and T1 > T2. In this case, T1 increases with increasing film formation time, but T2 increases later than T1 due to delayed nucleation. To obtain an appropriate substrate selectivity s, it is not desirable to calculate T1 when it becomes excessively large. It is preferable to use the substrate selectivity s calculated for the Ru complex when T1 is in the range of 2 nm to 6 nm. In the present invention, it is preferable to use a Ru complex with a substrate selectivity s of 0.2 to 1.0 calculated within this range.

[0030] In the preliminary film formation test for calculating the substrate selectivity s, the film formation conditions other than the film formation temperature are such that the film formation time T1 falls 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 preferable 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-mentioned 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. 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 [ka] (In the formula, the ligand L1 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] A specific example of the precursor composed of this Ru complex I is (η 4 -methylene-1,3-propanediyl)tricarbonylruthenium, or (η 4 (η4-methylene-1,3-propanediyl)-ruthenium-dicarbonyl-(2-isocyano-2-methylpropane) (L1: trimethylenemethane-based ligand, X: carbonyl ligand). Also included is [(η4-methylene-1,3-propanediyl)-ruthenium-dicarbonyl-(2-isocyano-2-methylpropane)] of Chemical Formula 4.

[0034] [ka]

[0035] [ka]

[0036] [ka]

[0037] (2) Ru Complex II [ka] (In the formula, R1 and R2 may be the same or different and each represents one of a hydrogen atom and 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] [ka]

[0040] (3) Ru complex III [ka] (In the formula, the ligand L2 is a ligand represented by either (L2-1) or (L2-2) shown in the following formula, and is a ligand containing one nitrogen atom.)

[0041] [ka] (In the formula, * indicates the position of the atom bridging and coordinating to ruthenium. R3 to 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) is an example.

[0043] [ka]

[0044] (4) Ru complex IV [ka] (The ligands L3 and L4 coordinated to ruthenium are represented by the following formulas:

[0045] [ka] (Substituent R of ligands L3 and L4 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] [ka]

[0048] (5) Ru complex V [ka]

[0049] C. Film formation conditions in the selective film formation method of the present invention The method for selectively depositing a Ru thin film according to the present invention utilizes the substrate selectivity of the Ru complex precursor at relatively low temperatures. The Ru thin film is preferentially deposited in a single process on the first region where the metal M is present on the surface. Therefore, unlike the prior art (Patent Document 5 and Non-Patent Document 1), the present invention does not require switching of the reaction atmosphere during deposition. Furthermore, additional processes such as the inhibition treatment described in Patent Document 4 are also unnecessary. Note that a single process refers to the process required to deposit a Ru thin film of a desired thickness in the first region. In the case of a CVD method, this refers to a single deposition process, while in the case of an ALD method, which involves multiple cycles of atomic layer-level deposition, this refers to the process required to complete the multiple cycles. Furthermore, preferentially depositing 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 (0 nm thick) is deposited in the second region, but the deposition 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 selective Ru thin film formation method according to the present invention are basically the same as those in conventional chemical vapor deposition methods.

[0050] C-1 Generation of raw 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. The carrier gas is also an inert gas (e.g., Ar) that is commonly used in chemical vapor deposition. The flow rate of the carrier gas is set appropriately depending on the vapor pressure and reactivity of the Ru complex. If the flow rate is too low, the Ru complex cannot be supplied stably, and if the flow rate is too high, the partial pressure of the Ru complex drops, preventing it from being fully decomposed. Therefore, the flow rate is preferably set to 5 sccm or more and 200 sccm or less.

[0052] C-2 Reactive gas In chemical vapor deposition, a reactive gas is usually 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 reactive 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 reactive 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 reactive gas is appropriately set depending on the reactivity of the Ru complex, and 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 set to 200°C or lower. This is to allow the Ru complex precursor to exhibit substrate selectivity. Furthermore, to more effectively utilize 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. Regarding the film formation pressure, which is another film formation condition besides the film formation temperature, the pressure used in ordinary chemical vapor deposition is applied. 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 above-mentioned preliminary film formation test. [Effects of the Invention]

[0056] As explained above, the present invention relates to a method for forming a Ru thin film by chemical vapor deposition, which involves applying a substrate having both a metal and a compound on its surface, and for preferentially and selectively forming 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. [Brief explanation of the drawings]

[0057] [Figure 1] FIG. 2 is a diagram illustrating the difference in film thickness change depending on the substrate material of the Ru complex applied in the present invention. [Figure 2] FIG. 2 is a diagram illustrating the outline of the configuration of a film forming apparatus used in this embodiment. [Figure 3] 4 is a graph showing the change in thickness of a Ru thin film on each substrate using various Ru complexes in a preliminary film formation test of the first embodiment. [Figure 4] 4 is a graph showing the transition of substrate selectivity for various Ru complexes relative to substrate materials in a preliminary film-forming test of the first embodiment. [Figure 5] Photographs showing the state of film formation on each substrate using Complex I in a preliminary film formation test of the first embodiment. [Figure 6] FIG. 10 is a diagram showing the appearance of a substrate having a first region and a second region used in the second embodiment. [Figure 7] 10 is a cross-sectional SEM photograph of the first region and the second region after a Ru thin film is formed in a 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), which is Ru complex II, which is Chemical Formula 6; and benzene(methylene-1,3-propanediyl)ruthenium, which is Ru complex IV, which is Chemical Formula 12.

[0059] In this embodiment, three types of substrates were prepared: a substrate in which a thin film of Cu (20 mm square, 80 nm thick), which is metal M, was formed on a Si wafer (40 mm square, 1 mm thick) by sputtering; a substrate in which a thin film of SiO2 (20 mm square, 100 nm thick), which is oxide (compound C), was formed on the same Si wafer; and a substrate in which a thin film of TiN (20 mm square, 20 nm thick), which is nitride (compound C), was formed on the same Si wafer, and the film formation characteristics were examined for each.

[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] [Table 1]

[0062] After the film formation test, the thickness of the Ru thin film was measured for each substrate by X-ray fluorescence spectroscopy (XRF). The substrate selectivity s for metal M was calculated from the thickness (T1) of the Ru thin film relative to metal M (Cu) and the thickness (T2) of the Ru thin film relative to compound C (SiO2, TiN). The results are shown in Table 2. FIG. 3 shows a graph plotted based on Table 2, illustrating the relationship between the film formation time and the Ru thin film thicknesses T1 and T2 for each Ru complex and each substrate. FIG. 4 shows a graph illustrating the change in substrate selectivity s with the change in film thickness (T1) on metal M (Cu) for each Ru complex. As an example of the results of this embodiment, planar SEM images of the surface of each substrate are shown when the film formation time was 30 minutes and 60 minutes using Ru complex I.

[0063] [Table 2]

[0064] 3, for each of the Ru complexes investigated in this embodiment, at a film formation temperature of 180°C or less, Ru thin film formation begins immediately on a Cu substrate (metal M), and the film thickness T1 increases as the film formation time increases. On the other hand, for the SiO2 and TiN substrates (compound C), film formation is delayed due to delayed nucleation. Furthermore, the substrate selectivity s of the Ru complex relative to the metal M (Cu), calculated from the film thicknesses (T1, T2) of the Ru thin film on each substrate, is s>0.

[0065] Furthermore, referring to Figure 4, the substrate selectivity s of the Ru complex relative to the metal M (Cu) tends to decrease with increasing film formation time (increasing thickness T1 of the Ru thin film). This is because although nucleation delay occurs in compound C, it does not mean that the 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 through a preliminary test, it is preferable to calculate it within a range where the thickness T1 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 exhibits high substrate selectivity for both SiO2 and TiN, regardless of the film thickness (T1). Ru complex II (dicarbonyl-bis(5-methyl-2,4-hexanediketonato)ruthenium(II)) maintains high substrate selectivity for TiN, but its substrate selectivity for SiO2 tends to decrease with increasing film thickness (T1). Ru complex IV (benzene(methylene-1,3-propanediyl)ruthenium) exhibits substrate selectivity that depends on the film thickness (T1) for both SiO2 and TiN. From these results, Ru complex I and Ru complex II are particularly suitable Ru complexes in terms of substrate selectivity, which is attributed to the presence of carbonyl ligands. Carbonyl ligands have an appropriate bonding strength with Ru, and while they are moderately stable in the Ru complex state, they decompose relatively easily under heat.

[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] Fig. 6 shows the appearance of the substrate used in this embodiment. This substrate was fabricated by depositing 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, thereby forming a first region (Cu) and a second region (SiO, TiN).

[0069] The Ru complexes investigated in this embodiment were (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 varied to form a 6-nm Ru thin film on the first region (Cu film). The film formation process was the same as in the first embodiment. After film formation, the film thicknesses of the Ru thin films in the first region (Cu film) and the second region (SiO2 film and TiN film) were measured, and the effective substrate selectivity s' was calculated. The results of the above investigation are shown in Table 3.

[0070] [Table 3]

[0071] Table 3 shows that by applying each Ru complex, even in a substrate in which the first and second regions are actually separated, 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. [Industrial Applicability]

[0073] The present invention is a film formation process that enables selective deposition of Ru thin films by utilizing the properties of a specific Ru complex at relatively low temperatures. The selective Ru thin film deposition method of the present invention enables selective deposition of Ru thin films in a single step without inhibiting areas where deposition is to be avoided or adjusting the reaction atmosphere during deposition. 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 for 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 method comprising: The chemical vapor deposition method includes a step of transporting a source gas generated from a Ru complex onto the substrate and heating the source gas, The Ru complex has a substrate selectivity s represented by the following formula: s>0, The Ru complex is any one of (i) Ru complex I, (ii) Ru complex II, and (iii) Ru complex IV represented by the following formula: A method for selectively depositing a Ru thin film, characterized in that the Ru thin film is deposited at a deposition temperature of 200° C. or less. [Equation 1] 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. T 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. (i) Ru complex I 【number】 (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, and the ligand X is a carbonyl ligand.) (ii) Ru complex II 【number】 (In the formula, R 1 and 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.) (iii) Ru complex IV 【number】 (The ligands L 3 and L 4 coordinated to ruthenium are represented by the following formulae: 【number】 (The substituents R 11 to R 22 of the ligands L 3 and L 4 are each independently a hydrogen atom or a linear or branched alkyl group having from 1 to 4 carbon atoms.)

2. 2. The method for selectively depositing a Ru thin film according to claim 1, 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.

3. 3. The method for selectively depositing a Ru thin film according to claim 1, wherein the compound C is at least one of an oxide, a carbide, a nitride, a silicide, an oxycarbide, and an oxynitride of the metal M.

4. The Ru complex is 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.

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