Method of selective film formation of ru thin films

Abstract

In the method for forming a Ru thin film using chemical vapor deposition of the present invention, a Ru complex with a substrate selectivity s of s > 0, as shown in the following formula, is used as the raw material precursor. This allows for selective formation of a Ru thin film in a first region on a substrate composed of metal M. At this time, the formation of a Ru thin film in a second region on the substrate composed of compound C, which is any one of oxide, carbide, nitride, silicate, carbide oxide, and nitride oxide, is suppressed. T1: Film thickness when the Ru thin film is formed using metal M as the substrate, at a film formation temperature below 200°C, and for any film formation time (T1 > 0 nm). T2: Film thickness when the Ru thin film is formed using compound C as the substrate under the same conditions as when the aforementioned metal M is used as the substrate (T2 ≥ 0 nm).

Description

Technical Field

[0001] The present invention relates to a selective film formation method for Ru thin films, which involves preferentially forming Ru thin films in designated areas by chemical vapor deposition when manufacturing wiring substrates for semiconductor devices, etc. Prior 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 prominent in the context of wiring miniaturization in response to the recent trend of ultra-miniaturization of semiconductor devices. Cu has become the mainstream wiring material for semiconductor devices. However, there are plans to develop semiconductor devices with wiring widths on the order of 10 nm, which is smaller than the mean free radius of electrons in Cu (approximately 38.7 nm). When Cu thin films are used for such fine wiring, the drag coefficient caused by surface scattering and grain boundary scattering, which are proportional to the mean free radius, increases, and the resistivity (specific resistance) of the wiring rises. In contrast, the mean free radius of electrons in Ru is much shorter than that of Cu (10.8 nm), and Ru has the advantage of suppressing the aforementioned increase in specific resistance. Furthermore, because Ru has a high melting point of 2250℃, which is higher than that of Cu (1085℃), it also exhibits good electromigration resistance. Due to these advantages, Ru is increasingly being widely used as a wiring material.

[0003] Furthermore, as mentioned above, Cu wiring is currently the mainstream material for wiring in semiconductor devices. To improve reliability or for bottom-up design, methods have been proposed to form protective films or coatings of other metals on Cu wiring. In addition to wiring and electrode materials, Ru thin films can also be effective as protective films or coatings for wiring of Cu and other materials.

[0004] As a manufacturing process for Ru thin films, chemical vapor deposition (CVD) and atomic layer evaporation (ALD) methods are commonly used. In chemical vapor deposition, Ru thin films are formed by generating a raw material gas from Ru complexes (the precursor of the film material). This raw material gas is introduced onto the surface of the substrate to which the film is to be formed. Energy, such as heating, is applied to decompose the Ru complexes, causing Ru to precipitate and deposit, thus forming a Ru thin film. To promote Ru precipitation, oxidizing gases such as oxygen or reducing gases such as hydrogen are typically introduced as reactant gases, depending on the composition of the Ru complexes. The applicant has developed and disclosed various Ru complexes as precursors (Patent Documents 1-3).

[0005] However, in the manufacture of wiring and electrodes for semiconductor devices, it is necessary to form thin films in specific areas on the surface of a substrate. Photolithography has been widely used since ancient times as a technique for partially forming thin films for this purpose. Chemical vapor deposition, which utilizes photolithography, is now widely known to be suitable for partially forming thin films.

[0006] However, in next-generation semiconductor devices, the need for multiple patterning techniques is increasing due to the need for further miniaturization. Film deposition using photolithography requires multiple steps, including patterning and exposure processing with resists before deposition, and resist removal after deposition. Therefore, it is predicted that photolithography will significantly increase the cost of manufacturing semiconductor devices employing the aforementioned multiple patterning techniques.

[0007] As one of the methods to address this issue, Area Selective Deposition (ASD) has attracted attention. ASD refers to a film deposition process that utilizes the chemical or physical properties of the substrate surface and the vapor deposition source to control the formation of the desired thin film within a specific area, while simultaneously avoiding film deposition in other areas adjacent to the specific area. Because ASD can selectively form thin films with fewer steps compared to conventional photolithography, it is expected to become an important film deposition process in the future.

[0008] Several case reports have also been presented regarding the selective deposition of Ru films applicable to ASD. Specific methods include processes that apply a barrier treatment to the surface of the substrate in areas where Ru film growth is undesirable. For example, Patent Document 4 proposes a method for achieving region-selective chemical vapor deposition by exposing the substrate to additives such as silicone amines, selectively generating an surfactant layer on the surface of the substrate's dielectric material, and then depositing a 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 specified reaction environment. Specifically, a specific Ru complex is selectively deposited on the surface of a conductive material such as a metal in a reducing gas environment. Initial deposition is performed on the conductive material surface in an environment using a reducing gas and without oxygen, followed by the introduction of oxygen into the environment to promote Ru deposition. Further, as a process similar to this method, Non-Patent Document 1 performs initial deposition in a reducing environment such as hydrogen, followed by the introduction of hydrogen to promote Ru deposition, thereby achieving regionally selective chemical vapor deposition. [Previous Technical Documents] [Patent Literature]

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

[0011] [Non-Patent Literature 1] 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. Summary of the Invention

[0012] [The problem that the invention aims to solve] However, while the method of applying a barrier treatment to areas where Ru film growth does not occur, as described in Patent Document 4 above, enables selective film formation, it still presents other problems. There are concerns that the amines or oxidizing substances in the additives used in the barrier treatment may cause substrate oxidation or contamination upon contact and reaction with the substrate. This oxidation and contamination is particularly likely to occur in the early stages of film formation. Furthermore, substrate damage caused by oxidation or contamination may significantly increase the substrate's resistivity. Even additives with minimal impact on the substrate may still increase resistivity if they remain on the substrate. Moreover, even if the additives are removed after Ru film formation, there is still a possibility of damaging the substrate at that time. The removal of additives necessitates increasing the number of steps or adding equipment, making it a potentially inefficient process.

[0013] Furthermore, as in Patent Document 5, processes requiring changes to the reaction environment at each film-forming stage necessitate switching the reaction gas, which presents obstacles in terms of process management and safety. Hydrogen and oxygen are explosive and flammable gases, especially since the minimum ignition energy of hydrogen in oxygen (and oxygen in hydrogen) is lower than that of hydrogen in air. As described in the prior art, the use of both hydrogen and oxygen raises safety concerns. Moreover, the necessity of additional equipment to ensure safety raises concerns about reduced productivity.

[0014] This invention was made based on the background described above, and provides a method based on a different idea than those previously proposed, which allows for the selective deposition of Ru films using chemical vapor deposition. To this end, this invention provides a film deposition process that avoids concerns about substrate damage caused by the hindering processes used in selective film deposition, and can more clearly distinguish the presence or absence of film deposition relative to selected and unselected areas than before. [Methods used to solve problems]

[0015] In order to solve the above-mentioned problems, the inventors first reviewed the characteristics of Ru complexes used in chemical vapor deposition materials developed to date. The results showed that even when the film-forming temperature was set to a low level (below 200°C), the thickness of the Ru film on a substrate composed of metals such as Cu was relatively large. However, on a substrate composed of compounds such as oxides, even under the same conditions, the thickness of the Ru film was extremely small.

[0016] Figure 1 illustrates the difference in film thickness formed from the substrates described above. In the chemical vapor deposition process of Ru thin films, nucleation is necessary as an initial stage. The generated nuclei become the starting point for Ru precipitation and deposition to form a thin film. The difference in film thickness caused by the difference in substrate material shown in Figure 1 is considered to be due to the delay in nucleation (nucleation delay). This Ru complex system, which exhibits a nucleation delay based on the substrate material, can form Ru thin films with substrate selectivity. That is, the Ru complex itself can be said to have substrate selectivity. The inventors have concretized the substrate selectivity of the Ru complex as a substrate selectivity rate, and regarded this as a characteristic of the Ru complex. By using a Ru complex with a specified substrate selectivity rate for chemical vapor deposition, the above-mentioned problem can be solved, and thus the present invention was conceived.

[0017] That is, the present invention is a selective film-forming method for Ru thin films, which involves selectively forming a Ru thin film composed of Ru or Ru compounds on the first region of a substrate having a first region and a second region by chemical vapor deposition. The first region has a surface composed of metal M, and the second region has a surface composed of any compound C, such as oxide, carbide, nitride, silicate, carbide oxide, and nitride oxide. The aforementioned chemical vapor deposition method includes the step of conveying a raw material gas generated from a Ru complex onto the aforementioned substrate and simultaneously heating it. The aforementioned Ru complex has a substrate selectivity s as shown in the following formula, and the aforementioned substrate selectivity s>0.

[0018] T1: The thickness of the Ru film when the metal M is used as the substrate, the film formation temperature is below 200℃, and the film formation time is arbitrary, T1>0nm. T2: The film thickness when Ru film is formed using compound C as substrate under the same conditions as when metal M is used as substrate, T2 ≧ 0 nm.

[0019] As described above, in the selective film formation method for Ru thin films of the present invention, the substrate to which the film is to be formed is divided into a first region and a second region, and the Ru thin film is preferentially formed on the first region. Furthermore, in the present invention, substrates with a selectivity exceeding 0 as defined above are used as Ru composites in the film formation step using chemical vapor deposition. Other than these, the process is the same as the conventional method for forming Ru thin films using chemical vapor deposition. The present invention will now be described in more detail.

[0020] A substrate The substrate of this invention is divided into a first region and a second region. The first region is composed of a conductive metal M on its surface. Specifically, the metal M can be at least any 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 can also be formed on the substrate. Furthermore, when a plurality of first regions are formed, two or more metals can be selected from the aforementioned specific examples of metal M, and different metals M can be applied to individual first regions.

[0021] The second region is composed of a compound C consisting of oxides, carbides, nitrides, silicates, carbide oxides, and nitride oxides. Compound C is often composed of an insulating material (dielectric material). Furthermore, the compound C in the second region is often an oxide, carbide, nitride, silicate, carbide oxide, or nitride oxide of a metal. The metal in this case can also be one of the aforementioned metals M. Specific materials for compound C may 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, a plurality of second regions may be formed on the substrate. Furthermore, two or more types of compound C may be used for the plurality of second regions formed on the substrate, and different compounds C may be applied to individual second regions.

[0022] The first and second regions can be integral with the substrate or formed as thin films on the substrate. For example, the substrate can be made of the material of the second region, and a thin film of metal M can be formed thereon to form the first region. Alternatively, the substrate can be made of a different material from both metal M and compound C, and thin films of separate materials for the first and second regions can be formed thereon. In this case, the material of the substrate is not limited; it can be a substrate such as a Si wafer commonly used in semiconductor devices, a material other than the metals and compounds mentioned above, or a resin or gum.

[0023] Furthermore, the shapes of Region 1 and Region 2 are not particularly limited. Region 1 and Region 2 may also be located on a plane roughly parallel to the surface of the substrate. A trench may be formed on the substrate, and its bottom or inner wall surface may also constitute Region 1 or Region 2. Moreover, there are no restrictions on the dimensions of the substrate and Regions 1 and 2.

[0024] B Ru complex In this invention, when forming a film using chemical vapor deposition, the substrate selectivity s defined above is for Ru complexes with s>0.

[0025] B-1 Ru miscible substrate selectivity In this invention, the substrate selectivity s of the Ru complex refers to the film thickness T1 and T2 of individual substrates when a Ru thin film is formed using metal M and compound C as substrates at a film-forming temperature below 200°C. The reason for setting the film-forming temperature to below 200°C is that the substrate selectivity of the Ru complex discovered in this invention is exhibited within this temperature range. Furthermore, this is also a useful temperature range considering the recent demand for lower-temperature processes in the semiconductor device and other assembly fields.

[0026]

[0027] In calculating the substrate selectivity s of various Ru complexes, substrates that actually have a first region and a second region for Ru film formation can also be used. Furthermore, preliminary film formation tests can be conducted using metal M (first region) and compound C (second region) as substrates, respectively, where metal M (first region) and compound C (second region) are set as substrates that actually form the Ru film.

[0028] In the preliminary film-forming test to calculate the substrate selectivity s, the film-forming temperature in this test is set to below 200°C. The higher the film-forming temperature, the more difficult it becomes to confirm the difference between Ru complexes, which are prone to delayed nucleation, as ruthenium nucleation is promoted. Therefore, the film-forming temperature can be set to a lower temperature, even below 180°C. However, at film-forming temperatures below 120°C, even for metallic M, Ru film precipitation becomes difficult, making it difficult to calculate the substrate selectivity s. Therefore, a film-forming temperature of 120°C or higher is preferred.

[0029] Furthermore, in this invention, Ru complexes with a substrate selectivity s of s > 0 are used as the film-forming material for chemical vapor deposition. Referring to formulas 1 and 2, this means that Ru complexes with T1 > 0 and T2 ≥ 0, and T1 > T2, are applicable. In this case, T1 increases with increasing film formation time, but the increase in T2 is slower than that of T1 due to delayed nucleation. To obtain a suitable substrate selectivity s, calculations performed when T1 has become excessively large are undesirable. The substrate selectivity s is preferably calculated when T1 is in the range of 2 nm to 6 nm for the Ru complex. Moreover, in this invention, Ru complexes with a substrate selectivity s of 0.2 to 1.0 calculated within this range are preferred.

[0030] Furthermore, in the preliminary film-forming test used to calculate the substrate selectivity s, regarding film-forming conditions other than the film-forming temperature, it is acceptable as long as the film-forming time makes T1 fall within the aforementioned suitable range. Also, the film-forming pressure is preferably between 40 torr and 80 torr. Moreover, in Ru film formation, it is preferable to supply a reactive gas, preferably at a flow rate of 30 sccm to 200 sccm for the reactive gas corresponding to the applicable Ru complex.

[0031] The specific composition of B-2 Ru complex In this invention, Ru complexes having a suitable substrate selectivity s (s>0) relative to the aforementioned metal M can be exemplified by Ru complexes having trimethylenemethane ligands, carbonyl ligands, isonitrile ligands, pyridine ligands, amine ligands, imidazole ligands, pyrimidine ligands, pyridine ligands, and benzene ligands as ligands. Substituents may also be introduced into these ligands. Specifically, Ru complexes I, II, III, IV, and V, as described in (1) to (5) below, can be cited. These Ru complexes are described in Patent Documents 1 to 3.

[0032] (1) Ru complex I (In the formula, ligand L1 is a straight-chain or branched chain hydrocarbon group or a cyclic hydrocarbon group with 2 to 13 carbon atoms. Also, ligand X is any one of a carbonyl ligand, isonitrile ligand, pyridine ligand, amine ligand, imidazole ligand, pyrazine ligand, pyrimidine ligand, or pyrazine ligand.)

[0033] Specific examples of precursors composed of Ru complex I include (η4-methylene-1,3-propanediyl)ruthenium tricarbonylide as described in Compound 2, or (η4-2-propylene-1-yl,3-propanediyl)ruthenium tricarbonylide as described in Compound 3 (L1: trimethylenemethane ligand, X: carbonyl ligand). Also, [(η4-methylene-1,3-propanediyl)-ruthenium-dicarbonyl-(2-isocyano-2-methylpropane)] as described in Compound 4.

[0034]

[0035]

[0036]

[0037] (2) Ru complex II (In the formula, R1 and R2 can be the same or different from each other, and can be either hydrogen atoms or alkyl groups with 1 to 4 carbon atoms.)

[0038] As a specific example of a precursor composed of Ru complex II, dicarbonyl-bis(5-methyl-2,4-hexanedione)ruthenium(II) with the following formula can be cited.

[0039]

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

[0041] , (In the formula, * represents the position of the atom that is bridged with ruthenium. R3 to R10 can be the same or different from each other, and can be any one of a hydrogen atom or an alkyl group with 1 to 4 carbon atoms.)

[0042] As a specific example of a precursor composed of Ru complex III, one can cite hexacarbonyl[μ-[(1,2-η)-3-methyl-N-(1-methylpropyl)-1-buten-1-amino-κC2,κN1:κN1]] ruthenium (Ru-Ru) as follows.

[0043]

[0044] (4) Ru complex IV (The ruthenium-coordinated ligands L3 and L4 are as shown in the following formula.)

[0045] (The substituents R11 to R22 of ligands L3 and L4 are each independently a hydrogen atom or a straight-chain or branched alkyl group having 1 to 4 carbon atoms.)

[0046] As a specific example of a precursor composed of the Ru complex IV, examples include benzene(methylene-1,3-propanediyl)ruthenium or (methylene-1,3-propanediyl)[1-methyl-4-(1-methylethyl)benzene]ruthenium as follows.

[0047]

[0048] (5) Ru complex V

[0049] C. Film-forming conditions of the selective film-forming method of the present invention The selective film formation method for Ru thin films of the present invention utilizes the substrate selectivity of the Ru complex in a relatively low temperature region to preferentially form a Ru thin film in a first region having a metal M on the surface in a single step. Therefore, in the present invention, it is not necessary to switch the reaction environment during film formation as in the prior art (Patent Document 5, Non-Patent Document 1). Furthermore, additional steps such as the obstacle treatment in Patent Document 4 are not required. Moreover, "single step" means the step until a Ru thin film of the desired thickness is formed in the first region; in the CVD method, it means one film formation step; in the ALD method, which forms films at the atomic layer level through multiple cycles, it means the step until the aforementioned multiple cycles are completed. Furthermore, preferentially forming the Ru thin film in the first region means creating a state where the thickness of the Ru thin film in the first region is significantly greater than the thickness of the Ru thin film in the second region. In the second region, it is preferable that the Ru thin film is not formed at all (film thickness 0 nm), but the formation of extremely thin Ru thin films is permissible. The Ru thin film in the second region is preferably 4 nm or less, more preferably 3 nm or less, and especially preferably 2 nm or less. Furthermore, the film formation conditions in the selective film formation method for Ru thin films of the present invention are basically applicable to the film formation conditions in conventional chemical vapor deposition methods.

[0050] C-1 Generation of feedstock gas It is preferable to supply a raw material gas system to the chemical vapor deposition process by vaporizing a Ru complex as a precursor. The heating temperature of this raw material is appropriately set according to the melting point and vapor pressure of the Ru complex. For the aforementioned Ru complexes I to Ru complexes V, the heating temperature of the raw material is set in the range of 10°C to 140°C.

[0051] The generated feed gas system, along with the carrier gas, is transported to the substrate (reaction vessel). The carrier gas is also an inert gas (such as Ar) commonly used in chemical vapor deposition. The flow rate of the carrier gas is appropriately set according to the vapor pressure or reactivity of the Ru complex. If it is too low, the Ru complex cannot be stably supplied; if it is too high, the partial pressure of the Ru complex will decrease and it will not decompose sufficiently. Therefore, the flow rate is preferably between 5 sccm and 200 sccm.

[0052] C-2 Reaction Gas In chemical vapor deposition, to promote the decomposition of Ru complexes and achieve a suitable film formation rate, the reactant gas and the feed gas are usually supplied together to the substrate. The reactant gas can be an oxidizing gas such as oxygen or ozone, or a non-oxidizing gas such as hydrogen, water vapor, ammonia, amine compounds, or hydride derivatives. The reactant gas system is selected according to the decomposition characteristics of the Ru complexes. 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 according to the reactivity of the Ru complexes, and a flow rate of 5 sccm to 200 sccm is preferred.

[0053] C-3 Film Formation Conditions The film-forming temperature of the Ru thin film in this invention is set to below 200°C. This is to allow the Ru complex to exhibit substrate selectivity. Furthermore, while making more efficient use of substrate selectivity, the film-forming temperature is preferably between 120°C and 180°C. Moreover, the film-forming temperature refers to the surface temperature of the substrate, which is usually adjusted by heating the substrate. Regarding the film-forming pressure other than the film-forming temperature, the pressure of a conventional chemical vapor deposition method is applied. This pressure is appropriately set according to the vapor pressure or reactivity of the Ru complex, preferably between 1 torr and 100 torr.

[0054] Under the above film formation conditions, a Ru film will preferentially form on the metal M surface in region 1. The thickness of the Ru film in region 1 can be set according to the film formation time and is not particularly limited. However, if the film formation time is increased, a Ru film will also form in region 2. The thickness of the Ru film in region 1 is preferably between 2 nm and 10 nm.

[0055] Furthermore, after forming a Ru film on the substrate having the film-forming object, namely the first region and the second region, by means of the steps described above, the substrate selectivity s can be reliably calculated from the film thickness of each region. When the substrate selectivity calculated by this actual film-forming step is taken as the effective substrate selectivity (s'), the effective substrate selectivity s' is preferably approximately the same as the substrate selectivity (s) obtained from the above-described preliminary film-forming test. [Invention Effects]

[0056] As explained above, this invention is a method for selectively and preferentially forming a Ru thin film on a metal surface in the formation of a Ru thin film by chemical vapor deposition on a substrate having both a metal and a compound on its surface. This invention utilizes the selectivity of the Ru complex substrate as a precursor for selective Ru film formation. This simplifies the Ru thin film formation process. Simple Explanation of the Diagram

[0057] [Figure 1] is a diagram illustrating the difference in film thickness of the Ru complex to which this invention is applicable due to different substrate materials. [Figure 2] is a diagram illustrating the general structure of the film-forming apparatus used in this embodiment. [Figure 3] shows the film thickness variation of various Ru complexes on various substrates in the preliminary film formation test of the first embodiment. [Figure 4] shows the change in substrate selectivity of various Ru complexes to substrate material in the preparatory film-forming test of the first embodiment. [Figure 5] shows photographs of the film formation state on various substrates obtained from complex I during a preliminary film formation test of the first embodiment. [Figure 6] shows the appearance of the substrate having the first region and the second region used in the second embodiment. [Figure 7] Cross-sectional SEM images of the first and second regions of the Ru film after film formation in the film formation test of the second embodiment. Implementation

[0058] First Embodiment: Hereinafter, embodiments of the present invention will be described. In this embodiment, in order to calculate the substrate selectivity of various Ru complexes, a preliminary film-forming test was conducted using a single substrate composed of metal M and compound C as the film-forming object. The Ru complexes examined in this embodiment are the three types described above: Ru complex I, ruthenium tricarbonyl 3-(n4-methylene-1,3-propanediyl)tricarbonyl; Ru complex II, ruthenium dicarbonyl-bis(5-methyl-2,4-hexanedione)ruthenium (II), and Ru complex IV, ruthenium benzene(methylene-1,3-propanediyl)ruthenium.

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

[0060] In the film formation test, the film formation apparatus used was the CVD film formation apparatus shown in Figure 2. The film formation test involved placing various substrates inside the reactor of the CVD film formation apparatus shown in Figure 2, sealing the Ru complex into a raw material container, heating the Ru complex to generate a raw material gas, and then introducing the carrier gas and reactant gas together into the reactor to form a Ru thin film. The film formation conditions in this embodiment are described below.

[0061]

[0062] After the film deposition test, the film thickness of the Ru film was measured using X-ray fluorescence (XRF) analysis on each substrate. Then, the substrate selectivity s relative to metal M was calculated from the film thickness (T1) of the Ru film relative to metal M (Cu) and the film thickness (T2) of the Ru film relative to compound C (SiO2, TiN). The results are shown in Table 2. Furthermore, Figure 3 shows the relationship between the film deposition time of each Ru complex and each substrate and the film thicknesses T1 and T2 of the Ru film, plotted based on Table 2. Figure 4 shows the change in substrate selectivity s caused by the change in the film thickness (T1) of each Ru complex on metal M (Cu). As an example of the results of this embodiment, planar SEM images of the surface of each substrate with Ru complex I and film deposition times set to 30 min and 60 min are shown.

[0063]

[0064] Table 2 and Figure 3 show that, in this embodiment, the Ru complexes examined at film-forming temperatures below 180°C begin forming Ru films on the Cu substrate of metal M immediately after the formation process begins, and the film thickness T1 increases with increasing film-forming time. On the other hand, slow film formation occurs on the SiO2 and TiN substrates of compound C due to delayed nucleation. Furthermore, the substrate selectivity s of the Ru complexes for metal M (Cu), calculated from the film thicknesses (T1, T2) of the Ru films on each substrate, is s>0.

[0065] Furthermore, referring to Figure 4, the substrate selectivity s of the Ru complex for metal M (Cu) tends to decrease with increasing film formation time (increase in the film thickness T1 of the Ru film). This is because although nucleation is delayed in compound C, it does not mean that the Ru film has not formed, but rather that the Ru film grows after nucleation. Due to this, when obtaining the substrate selectivity s of the Ru complex through preliminary experiments, it is preferable to calculate it within a range where the film thickness T1 is below 6 nm.

[0066] When examining the substrate selectivity *s* of various Ru complexes, Ru complex I, (η4-methylene-1,3-propanediyl)tricarbonylruthenium, exhibits high substrate selectivity relative to both SiO2 and TiN, regardless of film thickness *T1*. Ru complex II, dicarbonyl-bis(5-methyl-2,4-hexanedione)ruthenium(II), maintains high substrate selectivity relative to TiN, but its selectivity relative to SiO2 tends to decrease with increasing film thickness *T1*. Ru complex IV, benzene(methylene-1,3-propanediyl)ruthenium, shows substrate selectivity relative to both SiO2 and TiN that depends on film thickness *T1*. Due to these factors, from the viewpoint of substrate selectivity, Ru complexes I and II can be considered particularly suitable Ru complexes, as they possess carbonyl ligands. This is believed to be due to the carbonyl ligand having a moderate binding force to Ru, exhibiting moderate stability in the Ru complex state, and being relatively easy to decompose under heating.

[0067] Second embodiment: This embodiment is based on the results of the first embodiment described above, and prepares a substrate having a first region and a second region as the film-forming object, and confirms the feasibility of selective film formation using each Ru complex.

[0068] Figure 6 shows the appearance of the substrate used in this embodiment. The substrate is formed by sputtering a Cu thin film (20mm square, 80nm thick) and a TiN thin film (20mm square, 80nm thick) on a Si wafer (size: 40mm square, thickness: 1mm) to form the first region (Cu) and the second region (SiO2, TiN).

[0069] The Ru complexes examined in this embodiment are the same as those in the first embodiment: n-4-methylene-1,3-propanediyl)ruthenium tricarbonyl (Ru complex I), dicarbonyl-bis(5-methyl-2,4-hexanedione)ruthenium (II) (Ru complex II), and benzene(methylene-1,3-propanediyl)ruthenium (Ru complex IV). In this embodiment, for each Ru complex, the film-forming conditions, such as film-forming temperature and film-forming pressure, were varied, and the conditions were set so that the Ru film formed on the first region (Cu film) would be 6 nm thick. The film-forming steps were the same as in the first embodiment. After film formation, the film thickness of the Ru film on the first region (Cu film) and the second region (SiO2 film and TiN film) was measured, and the effective substrate selectivity s´ was calculated. The results of the above examination are shown in Table 3.

[0070]

[0071] As shown in Table 3, by applying various Ru complexes, even on substrates that are actually distinguished and designated as Region 1 and Region 2, Ru films will preferentially form on the Cu (metal M) surface of Region 1. Figure 7 shows cross-sectional SEM images of Region 1 and Region 2 after film formation by Ru complex I.

[0072] Furthermore, the effective substrate selectivity s´ in this embodiment is in good agreement with the substrate selectivity s (for Cu, the value is 6 nm for film thickness) calculated in the first embodiment. Therefore, it has been confirmed that by using the Ru composite with the specified substrate selectivity s obtained by the present invention, Ru thin film can be preferentially formed on the first region whose surface is composed of metal M. [Industrial Applicability]

[0073] This invention utilizes the characteristics of a relatively low-temperature region of a specific Ru complex to create a selective Ru thin film deposition process. This selective Ru thin film deposition method allows for the selective deposition of Ru thin films in a single step, without requiring obstruction treatment of areas to be avoided for film deposition or adjustment of the reaction environment during film deposition. This invention is applicable to the formation of electrodes and wiring in various semiconductor devices, or to the bottom-up design and coating of metal films on substrates. In particular, this invention has applications in the miniaturization or multi-patterning technology of next-generation semiconductor devices planned in recent years.

[0074] 1: Heater 2:Substrate 3: Reactor 4: Spray head 5: Carrier gases such as nitrogen 6: Raw material containers 7: Reactive gases such as hydrogen 8: Mass flow controller 9: Pump 10: Valve

Claims

1. A selective film-forming method for Ru thin films, comprising selectively forming a Ru thin film composed of Ru or a Ru compound on a substrate having a first region and a second region by means of chemical vapor deposition, wherein the first region is composed of a metal M on its surface, and the second region is composed of a compound C of any one of oxide, carbide, nitride, silicate, carbide oxide, and nitride oxide, wherein the chemical vapor deposition method includes a step of conveying a raw material gas generated by the Ru complex onto the substrate and heating it together, wherein the Ru complex has a substrate selectivity s as shown in the following formula, and the substrate selectivity s > 0; T1: the film thickness when the Ru thin film is formed at a film-forming temperature of 200°C or below and at any film-forming time, with T1 > 0 nm; T2: The film thickness when Ru film is formed under the same conditions as when metal M is used as the substrate, with compound C as the substrate, T2 ≧ 0 nm.

2. The selective film-forming method of Ru thin film as claimed in claim 1, wherein the Ru complex is a Ru complex containing carbonyl ligands as ligands.

3. A selective film-forming method for Ru thin films as claimed in claim 1 or claim 2, wherein the metal M is at least any 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 selective film-forming method for Ru thin films as claimed in claim 1 or claim 2, wherein compound C is at least one of an oxide, carbide, nitride, silicate, carbide oxide, and nitride oxide of metal M.

5. A selective film-forming method for Ru thin films as described in claim 1 or claim 2, wherein the Ru complex system T1 is in the range of 2 nm to 6 nm and the substrate selectivity s is s ≥ 0.

2.

6. A selective film-forming method for Ru thin films as claimed in claim 1 or claim 2, wherein the Ru complex is any one of the following formulas: (1) Ru complex I, (2) Ru complex II, (3) Ru complex III, (4) Ru complex IV, (5) Ru complex V; (1) Ru complex I: In the formula, ligand L1 is a straight-chain or branched chain hydrocarbon group or cyclic hydrocarbon group with 2 to 13 carbon atoms; and ligand X is any one of a carbonyl ligand or an isonitrile ligand, a pyridine ligand, an amine ligand, an imidazole ligand, a pyrimidine ligand, or a pyridine ligand; (2) Ru complex II: In the formula, R1 and R2 may be the same or different from each other, and are either hydrogen atoms or alkyl groups with 1 to 4 carbon atoms; (3) Ru complex III In the formula, ligand L2 is the ligand shown in either (L2-1) or (L2-2) as shown below, and is a ligand containing 1 nitrogen atom; , In the formula, * is the position of the ruthenium-bridged and coordinated atom, R3~R10 can be the same or different from each other, and are either hydrogen atoms or alkyl groups with 1 to 4 carbons respectively; (4) The ruthenium-coordinated ligands L3 and L4 of Ru complex IV are shown in the formula below; The substituents R11~R22 of ligands L3 and L4 are independently hydrogen atoms or straight-chain or branched alkyl groups with 1 to 4 carbons respectively; (5) Ru complex V.

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