Method of filling a metal and substrate processing apparatus

Abstract

A semiconductor wafer is formed with a metal-containing film to suppress shape defects of a metal wiring formed in a recess and reduce the resistivity of the wiring. A method of the present disclosure for embedding metal in a recess formed in a substrate includes the following steps: forming a metal nitride film on a substrate on which the recess is formed to embed metal nitride in the recess; and then forming a metal film of a metal contained in the metal nitride on the upper surface side of the metal nitride film, by diffusing nitrogen atoms from the metal nitride film side to the metal film side to set a state in which the metal with a reduced nitrogen content is embedded in the recess.

Description

Technical Field

[0001] This disclosure relates to a method for burying metal and a substrate processing apparatus. Background Technology

[0002] In semiconductor devices, the wiring that forms circuits is formed by depositing metal films on semiconductor wafers (hereinafter referred to as wafers) with recesses using methods such as chemical vapor deposition (CVD) and atomic layer deposition (ALD). On the other hand, with the further development of higher integration in semiconductor devices, wiring is becoming increasingly thinner and the spacing between wiring lines is narrower, thus increasing the difficulty of fabrication. Furthermore, since thinner wiring results in higher resistance, the use of metal materials with low resistivity is being investigated.

[0003] For example, Patent Document 1 describes a memory array for a semiconductor memory device. The memory cell array is composed of a stack of multiple layers, including a metal layer, an intermediate layer, and an insulating layer, which serve as control electrodes. It is also described that the metal layer is a molybdenum layer with low resistance, serving as the control electrode.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2016-201407 Summary of the Invention

[0007] The problem the invention aims to solve

[0008] This disclosure provides a technique for forming a metal-containing film on a semiconductor wafer to suppress shape defects in metal wiring formed in recesses and reduce the resistivity of the wiring.

[0009] Solution for solving the problem

[0010] The method disclosed herein is used to fill metal into recesses formed in a substrate, the method comprising the following steps:

[0011] A metal nitride film is formed on a substrate having the recess to fill the recess with metal nitride; and

[0012] Next, a metal film containing the metal contained in the metal nitride is formed on the upper surface side of the metal nitride film, and the state in which the metal with a reduced nitrogen content is buried in the recess is achieved by allowing nitrogen atoms to diffuse from the metal nitride film side to the metal film side.

[0013] The effects of the invention

[0014] According to this disclosure, it is possible to form a metal-containing film on a semiconductor wafer to suppress shape defects in metal wiring formed in recesses and reduce the resistivity of the wiring. Attached Figure Description

[0015] Figure 1A This is an SEM image showing the surface layer of the wafer that is being processed.

[0016] Figure 1B This is a SEM image showing the surface layer of a wafer with a metal film formed by a comparative method.

[0017] Figure 2A This is a first longitudinal sectional side view of the wafer involved in the processing of the implementation method.

[0018] Figure 2B This is a second longitudinal sectional side view of the wafer involved in the processing of the implementation method.

[0019] Figure 2C This is a third longitudinal sectional side view of the wafer involved in the processing of the implementation method.

[0020] Figure 2D This is a fourth longitudinal sectional side view of the wafer involved in the processing of the implementation method.

[0021] Figure 2E This is a fifth longitudinal sectional side view of the wafer involved in the processing of the implementation method.

[0022] Figure 2F This is a sixth longitudinal sectional side view of the wafer involved in the processing of the implementation method.

[0023] Figure 3 This is a top view of the substrate processing apparatus according to the embodiment.

[0024] Figure 4 This is a longitudinal sectional side view showing the processing module of the substrate processing apparatus.

[0025] Figure 5A This is the first graph showing the experimental results of Experiment 1.

[0026] Figure 5B This is the second graph showing the experimental results of Experiment 1.

[0027] Figure 5C This is the third graph showing the experimental results of Experiment 1.

[0028] Figure 5D This is the fourth graph showing the experimental results of Experiment 1.

[0029] Figure 6 This is the sixth graph showing the experimental results of Experiment 1.

[0030] Figure 7A This is the first SEM image showing the experimental results of Experiment 2.

[0031] Figure 7B This is the second SEM image showing the experimental results of Experiment 2.

[0032] Figure 7C This is the third SEM image showing the experimental results of Experiment 2.

[0033] Figure 8A This is the first SEM image showing the experimental results of the reference example.

[0034] Figure 8B This is a second SEM image showing the experimental results of a reference example. Detailed Implementation

[0035] Regarding the method for filling metal into the recesses of a wafer W, which serves as a substrate, as disclosed herein (hereinafter referred to as the metal filling method), the following embodiments will be described based on a processing example of forming wiring metal constituting buried word line structures (bWL) of DRAM on a wafer W made of a Si (silicon) substrate. First, using Figure 1A To illustrate the structure of the wafer W, which is the object of processing. Figure 1A This is an SEM image showing a cross-section of the surface layer of the wafer W, which is the object of processing.

[0036] Regarding the detailed shape, in Figure 2A As explained below, the surface layer of the wafer W is, for example, composed of a Si layer 10 on the surface of the wafer W and a SiOx film (silicon oxide film) 10a formed on the Si layer 10, wherein the SiOx film 10a is formed as an interlayer insulating layer. A cross-sectional schematic diagram of this surface layer is shown below. Figure 2A As shown, multiple uneven shapes formed by etching are arranged on the surface of the Si layer 10, and these uneven surfaces are covered by a SiOx film 10a. The SiOx film 10a is relatively thick at the upper end of the sidewall 14, for example, about 60 nm, and thinner in other parts, for example, about 1 nm to 3 nm. The surface portion of the wafer W composed of the Si layer 10 and the SiOx film 10a includes a recess 11 and sidewalls 14 forming both sides of the recess 11.

[0037] These recesses 11 are elongated grooves extending in a direction perpendicular to the paper surface and opening toward the upper surface. For example... Figure 1AAs shown, multiple recesses 11 are arranged at intervals of approximately 20 nm to 50 nm, forming relatively deep and narrow grooves. Furthermore, each recess has an opening width of approximately 10 nm to 20 nm and a depth of approximately 100 nm to 250 nm. The width of the recess 11 is narrowest at its lower end and widens upwards, reaching its widest point at the opening. The width of the sidewalls 14 constituting the two sides of the recess 11 is widest at its lower end and narrows upwards, reaching its narrowest point at its front end.

[0038] As such, the sidewall 14 is long and narrow from the base to the top, making it a shape that is easily flexible. In this embodiment, a metal film 12 is formed within the recess 11 formed by such sidewall 14 to form a wiring metal 13 with relatively low resistivity. In this example, the aim is to form a metal wiring with a resistivity equal to or higher than that of conventionally used TiN (titanium nitride), as described in the embodiments described later. From this point of view, Mo (molybdenum) is considered as a wiring material capable of achieving a resistivity lower than that of TiN.

[0039] Before describing the metal landfill method of this disclosure, hereby, using Figure 1B This describes a method for comparing the metal landfill method disclosed herein with the method of comparison. Figure 1B This is a SEM image showing the surface layer of a wafer W to which a metal film 12M is formed by a comparative method. Furthermore, this metal film 12M is formed with a thickness of 10 nm when the film is deposited on a flat wafer W. Hereinafter, even when the film is deposited on a wafer W with recesses 11, it will sometimes be simply referred to as a film with a thickness of 10 nm.

[0040] The 12M metal membrane is composed of Mo (molybdenum). In the comparative metal landfill methods, specifically... Figure 1A The wafer W shown, containing the above-described structure, is formed with a metal film 12M by using the ALD method for isotropic deposition to completely fill the recess 11. At this time, the thickness of the metal film 12M formed on the sidewall 14 of the recess 11 gradually increases along the surface of the sidewall 14. Therefore, the metal films 12M formed on the opposing sidewalls 14 gradually approach each other as the thickness increases.

[0041] Here, the opposing metal films 12M within the recess 11 have a thickness of approximately 10 nm. When their gap narrows, as... Figure 1BAs shown, it is confirmed that the two sidewalls 14 constituting the recess 11 bend towards the center of the recess 11 in a mutually attractive manner, narrowing the opening width of the recess 11. This phenomenon is believed to be caused by the mutual attraction between the metal films 12M grown along the sidewalls 14 through van der Waals forces. On the other hand, as described above, when the sidewalls 14 bend towards the center of the recess 11 and the opening width narrows, in adjacent recesses 11, the sidewalls 14 flex outwards, widening the opening width. This phenomenon occurs along the extension direction of the groove formed by the recesses 11 and is therefore also referred to as line bending.

[0042] exist Figure 1B In the example shown, the recesses 11 with narrower openings and those with wider openings are arranged in a roughly alternating configuration. In these deformed recesses 11, when the metal film 12M is deposited until the recess 11 is completely filled, the wiring metal within the recess 11 also forms both narrow and wide wiring metal, resulting in poor shape. As described above, the metal-filling method of this comparative approach, which fills the trench formed by the recesses 11 with Mo, can reduce the resistivity of the wiring metal compared to TiN, but it is known that it may lead to poor shape.

[0043] Below, several comparative methods studied outside of this will be briefly described. To suppress shape defects caused by the 12M metal film in the comparative methods, embodiments as described later can be considered ( Figure 7A This is an example of a method for forming a metal nitride film with a van der Waals force weaker than that of a metal film. The metal nitride film consists of Mo and N (nitrogen) as constituent elements, but does not contain other elements; specifically, it is composed of Mo₂N (molybdenum nitride).

[0044] Compared to metal films, metal nitride films exhibit weaker van der Waals forces. Therefore, even when the film is deposited on the inner surface of the recess 11, the bending force on the opposing sidewalls 14 is small, which can suppress deviations in the width of the wiring metal. However, the resistivity of metal nitride films is higher than that of metal films, specifically, about 100 times higher. Therefore, when using extremely narrow wiring metal as in this embodiment, it results in high resistance.

[0045] Therefore, in order to eliminate the high resistivity state, multiple annealing processes were investigated after the formation of the metal nitride film to release nitrogen from the metal nitride film. However, as described in the reference example below ( Figure 8A , Figure 8B As shown in the figure, the nitride metal film shrinks significantly and suffers structural damage after annealing. As described above, even multiple annealing treatments of the metal nitride film cannot solve the problem of this disclosure.

[0046] In addition, as another method, forming a metal film after forming a metal nitride film was also investigated. It is considered that by providing a metal nitride film on the surface of the sidewall 14, which is thin in the width direction and long in the depth direction, the sidewall 14 is strengthened and becomes less prone to bending. Furthermore, it is intended to suppress the resistivity of the wiring metal itself by forming a metal film on the metal nitride film. However, since the van der Waals forces of the opposing metal films within the recess 11 are relatively high, the sidewalls 14 still bend in a mutually attractive manner, and the shape defects of the wiring metal caused by the metal nitride film and the metal film cannot be suppressed.

[0047] As described above, after studying various comparison methods, the solution of this embodiment was found to resolve the shape defects and reduced resistivity of the wiring metal 13. Hereinafter, using... Figures 2A-2F The wiring method in this embodiment will be explained. Figures 2A-2F This is an enlarged cross-sectional view showing the recess 11 and the two sidewalls 14 constituting the recess 11. (See attached image.) Figure 2D As shown, the metal film 12 formed in this embodiment consists of a lower metal film 12a, a metal nitride film 12b, and an upper metal film 12c. In the following text, the lower metal film 12a and the upper metal film 12c are sometimes referred to as metal films 12a and 12c, and sometimes the lower metal film 12a, the metal nitride film 12b, and the upper metal film 12c are simply referred to as films 12a, 12b, and 12c.

[0048] In the processing of this embodiment, the metal film 12a is pressed down ( Figure 2A ), metal nitride film 12b ( Figure 2B , Figure 2C ), upper metal film 12c ( Figure 2D The order of ) is Figure 1A After the wafer W shown is formed with each film, it undergoes an annealing process. Figure 2E ) to form wiring metal 13 ( Figure 2F ).

[0049] The lower metal film 12a, like the metal film 12M in the comparative embodiment, is composed of Mo, and does not contain N (nitrogen) or other metals as constituent elements. Furthermore, as... Figure 2A As shown, the lower metal film 12a is formed on the surface of the wafer W before processing, for example, by the ALD method, similar to the comparative method. At this time, the film is formed to a relatively thin thickness, such that the sidewalls 14 will not bend as in the comparative method described above. Specifically, the thickness of the lower metal film 12a is preferably about 2 nm to 3 nm, and can also be about 7.5 nm if a thicker layer is desired. The thickness of the lower metal film 12a that prevents the sidewalls 14 from bending can be determined in advance through preliminary experiments.

[0050] like Figure 2AAs shown, the lower metal film 12a formed under this film thickness condition is formed with a substantially uniform film thickness on the surface of the SiOx film 10a, specifically on the inner surface of the recess 11 and on the surface of the SiOx film 10a excluding the recess 11. Regarding the thinner lower metal film 12a, the van der Waals forces acting between the opposing films 12a are small, which can suppress the deflection of the sidewall 14. On the other hand, by providing the lower metal film 12a with relatively low resistivity in contact with the SiOx films 10a constituting the side and bottom surfaces of the recess 11, the resistivity of the wiring metal 13 can be reduced. Figure 2F The resistance value of the interface region between the SiOx film 10a and the SiOx film 10a.

[0051] In Figure 1A When the wafer W is heated to, for example, 580°C, a molybdenum-containing gas and a reducing gas are alternately supplied to the wafer W as raw material gases via a purge gas supply to form a lower metal film 12a. The molybdenum-containing gas is, for example, MoO2Cl2 (molybdenum dichlorodioxide) gas, the reducing gas is, for example, H2 gas, and the purge gas is, for example, an inactive gas such as Ar (argon). These molybdenum-containing gas, reducing gas, and purge gas do not contain nitrogen as constituent elements.

[0052] Next, as Figure 2B As shown, for example, a metal nitride film 12b is formed on the surface of the lower metal film 12a using the ALD method. The metal nitride film 12b comprises Mo and N, but no other elements; specifically, it is composed of Mo₂N (molybdenum nitride). Compared to Mo, Mo₂N constituting the metal nitride film 12b has higher resistivity and weaker van der Waals forces. Therefore, even though the metal nitride film 12b is formed on the inner surface of the recess 11, it is possible to suppress the bending of the opposing sidewalls 14 across the recess 11 in a mutually attractive manner.

[0053] As the thickness of the metal nitride film 12b on the lower metal film 12a increases, the metal nitride is gradually embedded into the recess 11, eventually completely filling the recess 11. Figure 2C The longitudinal cross-sectional shape of the metal nitride film 12b filling the recess 11 is a wedge shape that narrows as it goes downward.

[0054] Completely filling the recess 11 with the metal nitride film 12b means that the metal nitride film 12b substantially fills the internal space of the recess 11, but it can also mean that the upper part of the internal space of the recess 11 is slightly empty after the metal nitride film 12b is formed. When the recess 11 is completely filled with the metal nitride film 12b, the film formation of the metal nitride film 12b is completed.

[0055] Regarding the formation of metal nitride film 12b, for example by the ALD method... Figure 1AThe wafer W shown is heated to, for example, 400°C, and alternately supplied with a molybdenum-containing gas and a nitrogen-containing gas as raw materials via a purge gas supply. The molybdenum-containing gas is, for example, MoO2Cl2 gas, and the nitrogen-containing gas is, for example, NH3 (ammonia) gas. Alternatively, the nitrogen-containing gas can be N2 (nitrogen) gas. The purge gas is, for example, an inert gas such as Ar (argon). Both the molybdenum-containing gas and the purge gas may contain nitrogen as components; when a nitrogen-containing purge gas is supplied, the supply of the nitrogen-containing gas described above may sometimes be omitted.

[0056] Next, as Figure 2D As shown, an upper metal film 12c is formed on the surface of a metal nitride film 12b using the ALD method to achieve a substantially uniform thickness. However, the upper metal film 12c can also be formed using other anisotropic film-forming methods. Like the lower metal film 12a, the upper metal film 12c contains Mo as a constituent element but does not contain nitrogen or other metals. Since the upper metal film 12c is disposed on the surface of the metal nitride film 12b, its thickness does not need to be limited as in the case of the lower metal film 12a. The lower metal film 12a is preferably formed to a thickness sufficient to allow for the release of nitrogen atoms from the metal nitride film 12b, as described later. Specifically, the thickness of the upper metal film 12c is preferably, for example, around 10 nm to 30 nm. However, as long as nitrogen atoms can be released from the metal nitride film 12b, its thickness can be the same as that of the lower metal film 12a.

[0057] The lower and upper surfaces of the metal nitride film 12b, disposed between the upper metal film 12c and the lower metal film 12a, are in contact with the upper metal film 12c and the lower metal film 12a, where the nitrogen concentration is lower than that of the metal nitride film 12b. Therefore, nitrogen within the metal nitride film 12b diffuses to the metal films 12a and 12c through the interface regions between the metal films 12a and 12c and the metal nitride film 12b. Figure 2E (Solid arrow). Moreover, in the upper metal film 12c, which is in contact with a clean, depressurized atmosphere or atmospheric atmosphere, when the concentration of diffused nitrogen increases to a certain extent, nitrogen may be released from its surface, for example. In order to ensure that such a phenomenon occurs sufficiently throughout the entire region containing the metal film 12, the wafer W on which the upper metal film 12c is formed is subjected to an annealing treatment.

[0058] In the annealing process, the wafer W, placed under a reduced pressure atmosphere, is heated to, for example, 580 degrees Celsius, and a reducing gas is supplied. The reducing gas, for example, is H2 (hydrogen) gas, which can suppress the oxidation of the metal film 12. Such an annealing process allows nitrogen to diffuse out from the entire region of the metal nitride film 12b disposed in the recess 11 with a large depth-to-width ratio, including the deep portion, thereby equalizing the nitrogen concentration in the entire region of the metal film 12, including the deep portion. In addition, the annealing process promotes the release of nitrogen from the surface of the upper metal film 12c. In this nitrogen release, in addition to the direct release of nitrogen atoms from the surface of the upper metal film 12c, for example, a reaction product (nitrogen compound) of oxygen and nitrogen contained in the film, originating from the reducing gas, a molybdenum-containing gas as a raw material, is also released.

[0059] Through this release, nitrogen continuously diffuses from the side of the metal nitride film 12b, where the nitrogen concentration is relatively high, to the upper metal film 12c, where the nitrogen concentration is relatively low. As a result, the nitrogen concentration within the metal nitride film 12b gradually decreases. In the lower metal film 12a, which is in contact with the metal nitride film 12b, the nitrogen concentration also temporarily increases due to diffusion from the metal nitride film 12b, but then the direction of nitrogen diffusion changes towards the side of the metal nitride film 12b where the nitrogen concentration is decreasing, and it is assumed that the nitrogen concentration will decrease again.

[0060] By annealing the wafer W on which the upper metal film 12c is formed as described above, the nitrogen content can be reduced, thereby forming a wiring metal 13 with low resistivity. In this example, the wiring metal 13 is composed of a lower metal film 12a and a metal nitride film 12b, but it is also possible to fill the upper region of the recess 11 with the upper metal film 12c, so that, for example, the upper central side of the wiring metal 13 is composed of the upper metal film 12c. In addition, the unwanted upper metal film 12c can be removed by etching or the like. According to the method of this embodiment as described above, after filling the recess 11 with the metal nitride film 12b, which has relatively small van der Waals forces, the upper metal film 12c is formed on the metal nitride film 12b and removed by nitrogen diffusion. As a result, the resistivity of the wiring metal 13 can be reduced, and a wiring metal 13 with a uniform width and good shape can be formed.

[0061] Reference Figure 3The substrate processing apparatus 1, capable of performing the aforementioned series of processes, is illustrated by a top view. The substrate processing apparatus 1 is, for example, a vacuum processing apparatus configured as a multi-chamber system. Furthermore, the substrate processing apparatus 1 includes an atmospheric pressure transport chamber 22, for example, an atmospheric pressure atmosphere. A loading port 21 is provided near the front of the atmospheric pressure transport chamber 22 for transferring wafer W between itself and a transport container C containing wafer W. An opening / closing door 27, which opens during the loading and unloading of wafer W between itself and the transport container C, is provided on the front wall of the atmospheric pressure transport chamber 22. Additionally, a transport arm 25 for transporting wafer W is provided inside the atmospheric pressure transport chamber 22. Furthermore, when viewing the atmospheric pressure transport chamber 22 from the loading port 21 side, an alignment chamber 26 for adjusting the orientation and eccentricity of wafer W is provided on the left side wall of the atmospheric pressure transport chamber 22.

[0062] Two loading interlock vacuum chambers 23, arranged horizontally, are connected to the wall opposite to the loading port 21 in the atmospheric pressure transfer chamber 22. Each loading interlock vacuum chamber 23 has the function of switching its internal atmosphere between atmospheric pressure and vacuum while housing the wafer W. When viewed from the atmospheric pressure transfer chamber 22, a vacuum transfer chamber 24 is arranged inside these loading interlock vacuum chambers 23. Each loading interlock vacuum chamber 23 is connected to the atmospheric pressure transfer chamber 22 and the vacuum transfer chamber 24 via a gate valve 29.

[0063] An exhaust mechanism (not shown) is connected to the vacuum transfer chamber 24. The interior space of the vacuum transfer chamber 24 is a vacuum atmosphere, and a transfer arm 28 is installed in this interior space. Processing modules 101-104 are connected to the side walls of the vacuum transfer chamber 24 in a clockwise order. Processing module 101 is configured to form a lower metal film 12a, processing module 102 is configured to form a metal nitride film 12b, and processing module 103 is configured to form an upper metal film 12c. Processing module 102 is equivalent to a metal nitride film forming module, and processing module 103 is equivalent to a metal film forming module. The transfer of wafers W between processing modules 101-104 and each interlocked vacuum chamber 23 is performed by the transfer arm 28.

[0064] Each processing module 101-104 includes a processing container 51 that is vented by creating an internal vacuum atmosphere, and a substrate mounting stage 55 disposed within the processing container 51 and arranged to hold a wafer W. Figure 4 Each process is carried out within the processing container 51.

[0065] The substrate processing apparatus 1 includes a control unit 20, which functions as a computer and contains a program. The program contains instructions (steps) for performing the described wafer W processing and wafer W transport processes. This program is stored in a storage medium such as an optical disc, hard disk, DVD, or non-volatile memory, and is read from the storage medium and installed in the control unit 20.

[0066] The control unit 20 outputs control signals to each part of the substrate processing apparatus 1 through this program to control the operation of each part. Specifically, it controls the operation of the processing modules 101-104, the opening and closing of each gate valve 29, the operation of the conveying arm 25, the operation of the conveying arm 28, the operation of the exhaust mechanism, and the switching of pressure in the loading interlock vacuum chamber 23.

[0067] Regarding the transport path of the wafer W in the substrate processing apparatus 1, the wafer W is first transported in the following order: transport container C → loading port 21 → atmospheric pressure transport chamber 22 → loading interlock vacuum chamber 23 → vacuum transport chamber 24 → processing module 101. Furthermore, the wafer W for which a lower metal film 12a has been formed by processing module 101 is transported in the following order: processing module 101 → vacuum transport chamber 24 → processing module 102. The wafer W for which a metal nitride film 12b has been formed by processing module 102 is transported in the following order: processing module 102 → vacuum transport chamber 24 → processing module 103.

[0068] Furthermore, the wafer W, on which the upper metal film 12c has been formed by the processing module 103, is transported in the order of processing module 103 → vacuum transfer chamber 24 → processing module 104. The wafer W, which has undergone annealing treatment by the processing module 104, is transported in the order of processing module 104 → vacuum transfer chamber 24 → loading interlock vacuum chamber 23 → atmospheric pressure transfer chamber 22, and then returned to the transfer container C.

[0069] Next, taking processing modules 101-104 as examples, using... Figure 4 The longitudinal sectional side view illustrates an example of the structure of the processing module 101. The processing container 51 of the processing module 101 is, for example, made of aluminum. A wafer W transfer port is formed on the side wall of the processing container 51, and a gate valve G1 is provided to open and close the transfer port. An annular exhaust pipe 52, for example, with a rectangular cross-section, is disposed on the upper part of the side wall of the processing container 51. A slit 52a is provided along the inner circumferential surface of the exhaust pipe 52, and an exhaust port 52b is formed on the outer wall of the exhaust pipe 52. A top wall 54 is provided on the upper surface of the exhaust pipe 52 to close the upper opening of the processing container 51 by means of an insulating member 53, and the exhaust pipe 52 and the insulating member 53 are hermetically sealed by a sealing ring.

[0070] Inside the processing container 51 is a substrate mounting stage 55 for horizontally supporting the wafer W. This substrate mounting stage 55 is formed into a circular plate shape from a ceramic material such as aluminum nitride (AlN) or a metallic material such as an aluminum or nickel alloy. In this example, a heater 56A for heating the wafer W is embedded in the substrate mounting stage 55. The heater 56A heats the wafer W to, for example, the film-forming temperature described above. The outer peripheral region and sides of the upper surface of the substrate mounting stage 55 are covered by a cover member formed of a ceramic material such as alumina.

[0071] The substrate mounting stage 55 is connected to a lifting mechanism 57 disposed below the processing container 51 via a support member, configured to... Figure 4 The processing position, indicated by the solid line, moves freely between the junction point of the processing location and the wafer W, indicated by the dashed line below it. Figure 4 In the diagram, denoted by 52c, it refers to a dividing member used to divide the interior of the processing container 51 vertically together with the substrate mounting stage 55 that has risen to the processing position. On the lower side of the substrate mounting stage 55 within the processing container 51, three (only two shown) support pins 58 are provided, which can be freely raised and lowered by a lifting mechanism located below the processing container 51. The support pins 58 are configured to pass through through holes in the substrate mounting stage 55 located at the junction position and protrude and retract relative to the upper surface of the substrate mounting stage 55, for use in... Figure 3 The conveying arm 28 of the vacuum conveying chamber 24 shown in the figure connects the wafer W to the substrate mounting stage 55. The mark 59 in the figure refers to the bellows that separates the atmosphere inside the processing container 51 from the outside air and expands and contracts with the lifting and lowering movements of the substrate mounting stage 55 and the support pin 58.

[0072] A spray head 61 for supplying various gases into the processing container 51 in a spray-like manner is provided in the processing container 51 facing the substrate mounting stage 55. The spray head 61 includes a main body fixed to the top wall 54 of the processing container 51 and a spray plate 62 connected below the main body, the interior of which forms a gas diffusion space 63. A downwardly protruding annular protrusion is formed on the periphery of the spray plate 62, and a gas ejection hole 64 is formed on the flat surface inside the annular protrusion. A gas supply mechanism 6A is connected to the top wall 54 and the main body of the spray head 61.

[0073] The gas supply mechanism 6A includes a raw material gas supply section 71A configured to supply raw material gas to the processing container 51 and a reducing gas supply section 72A configured to supply reducing gas. Furthermore, the gas supply mechanism 6A includes two purge gas supply sections 73A configured to supply purge gas. The raw material gas supply section 71A includes a raw material gas supply source 74A and a supply path 75A. In the supply path 75A, a flow adjustment section M1A, a storage tank T1A, and a valve V1A are provided from the upstream side.

[0074] The reducing gas supply unit 72A includes a reducing gas supply source 76A and a supply path 77A. In the supply path 77A, a flow adjustment unit M2A, a storage tank T2A, and a valve V2A are respectively provided from the upstream side. Each purge gas supply unit 73A includes a purge gas supply source 78A and a supply path 79A. A flow path adjustment unit M3A and a valve V3A are provided in each supply path 79A. One purge gas supply unit 73A's supply path 79A is connected to the raw material gas supply path 75A to purge the raw material gas, and the other purge gas supply unit 73A's supply path 79A is connected to the reducing gas supply path 77A to purge the reducing gas. As described above, the raw material gas supply unit 71A, the reducing gas supply unit 72A, and the purge gas supply unit 73A are configured to supply the raw material gas, reducing gas, and purge gas separately to the processing container 51.

[0075] The processing container 51 is connected to the vacuum exhaust path 66 via the exhaust port 52b. A vacuum exhaust section 67, for example a vacuum pump, is provided on the downstream side of the vacuum exhaust path 66. The vacuum exhaust section 67 is configured to perform vacuum exhaust of the gas inside the processing container 51. A pressure regulating valve, such as an APC valve (not shown), is provided between the vacuum exhaust path 66 and the processing container 51 and the vacuum exhaust section 67.

[0076] Other processing modules 102-104 have a structure substantially the same as that of processing module 101, and the differences from processing module 101 will be briefly explained. In processing module 102, which forms the metal nitride film 12b, instead of Figure 4 The reducing gas supply unit 72A becomes a nitrogen-containing gas supply unit, and the supply source 76A becomes a nitrogen-containing gas supply source. The raw material gas supply unit 71A may not be provided in the processing module 104 for annealing.

[0077] Using a substrate processing apparatus 1 having the structure described above. Figure 3 , Figure 4 and representing membrane changes Figures 2A-2F To illustrate the actions performed on wafer W using device 1. First, when the conveyor arm 28 moves from... Figure 3 When the load-interlocking vacuum chamber 23 receives the wafer W, which is to be processed, it moves the wafer W to the processing module 101 located on the near left side. Then, it opens... Figure 4 The gate valve G1 of the processing module 101 shown uses the transfer arm 28 to allow the wafer W to enter the processing container 51 from the transfer inlet. Furthermore, the support pin 58 is used to transfer the wafer W from the transfer arm 28 to the substrate mounting stage 55, causing the transfer arm 28 to exit the processing container 51 and close the gate valve G1.

[0078] As described above, a lower metal film 12a is formed in the processing module 101. Based on the process for forming the lower metal film 12a with a predetermined film thickness, the pressure inside the processing container 51 and the temperature of the wafer W are adjusted, and the raw material gas, reducing gas, and purge gas are repeatedly supplied to the processing container 51 in a predetermined order. Thus, the lower metal film 12a is formed with a predetermined film thickness while suppressing the bending of the sidewall 14. Figure 2A (The process of forming the basement membrane).

[0079] Furthermore, the wafer W, after the deposition of the lower metal film 12a is completed, is removed from the processing module 101 in the reverse order of its loading and transported toward the processing module 102. Then, it is loaded into the processing module 102 in the same order as when it was loaded into the processing module 101 to form the metal nitride film 12b. Based on the process for forming the film in a manner that fills the recess 11, the pressure inside the processing container 51 and the temperature of the wafer W are adjusted, and the raw material gas, nitrogen-containing gas, and purge gas are repeatedly supplied to the processing container 51 in a predetermined order. Thus, the metal nitride film 12b is formed to the extent that the recess 11 is completely filled while suppressing the bending of the sidewall 14. Figure 2B , Figure 2C (The process of filling the recess 11 with metal nitride).

[0080] Next, the wafer W, after the metal nitride film 12b has been deposited, is sent from processing module 102 through the same process as processing module 101 and transferred to processing module 103 for the deposition of the upper metal film 12c. Based on the process for depositing film to a predetermined thickness, the pressure inside processing container 51 and the temperature of wafer W are adjusted, and the raw material gas, reducing gas, and purge gas are repeatedly supplied to processing container 51 in a predetermined order. Thus, an upper metal film 12c of a predetermined thickness is formed.

[0081] Then, the wafer W, with the upper metal film 12c already formed, is similarly removed from processing module 103 and moved into processing module 104 for annealing. The pressure inside processing container 51 and the temperature of wafer W are adjusted based on the process for forming the fully nitrogen-free wiring metal 13, and reducing gas and purging gas are supplied simultaneously (for example, a hydrogen supply process) for a predetermined time, such as 3 to 8 hours. This allows for sufficient diffusion and release of nitrogen throughout the entire area, thereby more reliably removing nitrogen from the entire area containing the metal film 12. Figure 2E Furthermore, when a wiring metal 13 with reduced resistivity is formed ( Figure 2F Annealing is completed (the process of allowing nitrogen atoms to diffuse into the recess 11 to achieve a state in which the nitrogen content of the metal has decreased).

[0082] The wafer W, with wiring metal 13 formed by annealing, is transported into the loading interlock vacuum chamber 23 and then returned to the transport container C via the loading port 21. As explained above, the substrate processing apparatus 1 and metal embedding method of this disclosure can form wiring metal 13 with reduced resistivity and good shape.

[0083] Furthermore, the annealing process, which requires several hours of processing time, is not limited to being performed by a single-wafer processing module 104. For example, after the upper metal film 12c is formed in the processing module (metal film formation module) 103, the wafer W is returned to the transport container C, and the processing in the substrate processing apparatus 1 is completed. Then, for example, in a batch annealing apparatus, multiple wafers W can be annealed together.

[0084] Furthermore, the substrate processing apparatus 1 is not limited to having individual processing modules 101-103. For example, the substrate processing apparatus 1 may also be configured as a batch heat treatment module that continuously performs film deposition and annealing processes. In this case, after multiple wafers W are loaded into the batch heat treatment module before film deposition, the gas supplied to the heat treatment module is switched sequentially to perform film deposition of the lower metal film 12a → the metal nitride film 12b → the upper metal film 12c. Then, the gas supplied to the heat treatment module is switched to a reducing gas (H2 gas) to perform the annealing process.

[0085] (Modified Example)

[0086] As shown in the above embodiments, when the lower metal film 12a and the metal nitride film 12b are formed by different processing modules 101 and 102, it is not necessary to adjust the pressure and temperature based on each film formation process each time, which can improve the efficiency of film formation and is therefore preferred. However, it is not limited to this, and the lower metal film 12a and the metal nitride film 12b can also be formed by either processing module 101 or processing module 102. In this case, the area occupied by the substrate processing apparatus 1 can be reduced. Moreover, for example, when the films 12a and 12b are formed by a common processing module 101, the nitrogen-containing gas supply section described above can be provided in the gas supply mechanism 6A. Furthermore, by also forming the metal film 12c in the processing module 101, all films 12a to 12c can be formed by processing module 101 alone, and annealing can also be performed.

[0087] In the embodiments of this disclosure, the lower metal films 12a to 12c are preferably formed in an isotropic manner. However, as shown in this example, if the side shape of the recess 11 is not orthogonal to the surface but is an inclined surface that widens as it goes upward, the film can also be formed by a film forming method such as anisotropic CVD.

[0088] The annealing process performed in this embodiment is not limited to the process described above, and the process can be appropriately modified according to the composition, shape, and thickness of the metal film 12. Furthermore, this annealing process is not essential in the method disclosed herein, and other means can be used. As an example of other means, the wafer W can be heat-treated under a reduced pressure atmosphere without a reducing gas supply. As another example, the wafer W can be heat-treated under an atmospheric atmosphere without a reducing gas supply. Heat treatment is effective for nitrogen diffusion and removal in the metal film 12, and experiments have shown that the temperature of the wafer W can be higher than 580°C and lower than 850°C. However, it is not limited to this temperature range; even if it deviates from this temperature range to some extent, it is highly likely that it can be achieved, and it is believed that temperatures of around 550°C to 900°C can be reached.

[0089] Regarding the recess 11 in the embodiments of this disclosure, a groove shape is not a necessary condition. The metal-filling method of this disclosure is also useful, for example, for setting wiring metal in through holes. In particular, for very fine and long through holes, where the sidewalls constituting the through hole are thin, the method of this disclosure can form wiring metal with reduced resistivity in a good shape.

[0090] Regarding the metal-containing film 12 in the embodiments of this disclosure, the example shown is that it contains Mo as a metal, but it is not limited thereto. It may also be composed of other metals with relatively low resistivity, such as Al (aluminum), Cu (copper), W (tungsten), Ti (titanium), Ag (silver), or alloys thereof. In this case, the lower metal film 12a and the upper metal film 12c do not contain nitrogen as constituent elements.

[0091] In the embodiments of this disclosure, the lower metal film 12a is formed to achieve low resistance of the wiring metal 13, but this is not a necessary condition, and the lower metal film 12a may not be formed. The metal nitride film 12b is formed in such a way that it fills the recess 11, but this is not a necessary condition, and the upper space in the recess 11 may not be filled, but the upper metal film 12c may be placed in the upper space. In this case, it is sufficient to form a metal nitride film 12b with a sufficient film thickness so that the sidewall 14 will not bend due to the van der Waals force of the upper metal film 12c during film formation.

[0092] Furthermore, in order to efficiently diffuse nitrogen from the metal nitride film 12b, the upper metal film 12c is formed to cover the entire surface area of ​​the metal nitride film 12b. However, this is only a preferred method of covering the entire surface area of ​​the metal nitride film 12b as extensively as possible, and does not preclude the possibility of covering only a portion of the surface of the metal nitride film 12b. To allow nitrogen from the metal nitride film 12b disposed within the recess 11 to diffuse and release upwards, the upper metal film 12c may, for example, be formed to cover only the opening area of ​​the recess 11.

[0093] Furthermore, the embodiments disclosed herein should be considered illustrative in all respects and not restrictive. The above embodiments may also be omitted, substituted, modified, and combined in various ways without departing from the appended claims and their spirit.

[0094] Example

[0095] (Experiment 1)

[0096] Regarding wafers with metal films deposited on metal nitride films, the nitrogen removal effect of the metal nitride films was confirmed. Specifically, metal films with different thicknesses were formed on metal nitride films deposited on the surface of bare wafers, and differences in nitrogen removal effects were confirmed.

[0097] A. Experimental conditions

[0098] Four unpatterned, flat, bare wafers were prepared. On the surface of each wafer, which served as a SiO2 film, a Mo nitride film composed of Mo2N and Mo films of varying thicknesses were formed, similar to the previous embodiment. The Mo nitride film had a thickness of 15 nm, and the Mo films had thicknesses of 0 nm (no Mo film), 5 nm, 10 nm, and 20 nm. These wafers were not annealed but instead subjected to heat treatment under reduced pressure and the same conditions to a degree sufficient for nitrogen diffusion and removal. The surface regions of each wafer after this heat treatment were analyzed using X-ray photoelectron spectroscopy (XPS), and the sheet resistance was measured.

[0099] B. Experimental Results

[0100] (1) Composition analysis results

[0101] Figures 5A-5D The results of compositional analysis of the surface regions of each wafer to which the Mo film is formed are shown. Specifically, the atomic percentage (At%) at a depth relative to the upper surface of each wafer is shown, excluding Si (silicon) atoms. Figure 5AThe compositional analysis results of a wafer without a Mo film are shown. The boundary line is shown at a location corresponding to the interface between the Mo nitride film and the SiO2 film. The region shallower than this interface corresponds to the Mo nitride film, and the region deeper corresponds to the SiO2 film.

[0102] In the Mo nitride film sufficiently far from the interface, the proportions of Mo atoms and N atoms are slightly higher than approximately 50% and 40%, respectively, while the proportion of O (oxygen) atoms is around 5%. These proportions remain roughly constant relative to depth. Furthermore, it is presumed that the O atoms in this region originate from the aforementioned feed gas.

[0103] The region encompassing both shallow and deep areas, including the previously described interface, is the interface region between the Mo nitride film and the SiO2 film. In this interface region, the number of atoms other than O atoms decreases sharply towards the SiO2 film, while the number of O atoms increases. Furthermore, in the SiO2 film sufficiently far from the interface, Mo atoms converge to below 10%, N atoms converge to approximately 0%, and O atoms converge to approximately 65%.

[0104] Figure 5B The figure shows the compositional analysis results of a wafer with a 5 nm Mo film. According to the figure, in the Mo nitride film and the Mo film, which are sufficiently far from the interface with the SiO2 film, the proportions of Mo, N, and O atoms are approximately constant relative to depth. Based on this, it can be determined that N atoms are sufficiently diffused in the Mo nitride film and the Mo film. Furthermore, the details of the concentration of each atom are as follows: the proportion of O atoms... Figure 5A Compared to slight increases of 1% and 2%, the proportion of Mo atoms rose to approximately 65%, while the proportion of N atoms decreased to less than 30%.

[0105] To examine the proportion of N atoms in this experiment, a rough proportion was calculated as a reference value under the following conditions: N atoms in the Mo nitride film are fully diffused into Mo films with a thickness of 1 / 3 of the Mo nitride film thickness, and the proportion of N atoms is homogeneous in these films. Specifically, according to Figure 5A The proportion of N atoms, for example, 42% in a Mo nitride film with a thickness of 1, is calculated as a reference value in a Mo nitride film with a thickness of 1 + 1 / 3 and after diffusion and homogenization. Assuming the number of N atoms remains unchanged before and after diffusion, the relationship 4 / 3 × (reference value) = 1 × 42 holds. Based on this relationship, the reference value for the proportion of N atoms after homogenization is 31.5%. In contrast, according to... Figure 5B The proportion of N atoms decreased to less than 30% as previously stated, therefore it is speculated that in this experimental result, N atoms were released from the Mo film, and the number of N atoms decreased.

[0106] Figure 5C It shows the formation of Figure 5BThe figure presents the compositional analysis results of a 10 nm thick Mo film wafer, twice the thickness of the SiO2 film. In this figure, the concentration gradient of each atom relative to depth is identified in the Mo nitride and Mo films, excluding the interface region with the SiO2 film. At depths comparable to the Mo film, particularly at the surface, the proportion of Mo atoms is as high as over 95%, decreasing with increasing depth relative to the Mo film. The proportion of N atoms in the Mo film is less than about 5%, increasing with increasing depth relative to the interface region between the Mo and Mo nitride films, reaching approximately 15% at the middle depth of the Mo nitride film.

[0107] and Figure 5B Similarly, the reference value for the proportion of N atoms in the Mo film after sufficient diffusion into a Mo film with a thickness of 2 / 3 of the Mo nitride film and homogenization in these films was calculated. If the proportion of N atoms in a 1-thickness Mo nitride film is 42%, and this is diffused and homogenized in a 1+2 / 3 thickness Mo nitride film and the Mo film, then the relationship 5 / 3 × (reference value) = 1 × 42 holds. Thus, the reference value for the proportion of homogenized N atoms is 25.2%. In contrast, the proportion of N atoms in this compositional analysis is significantly lower than this reference value at any depth, as mentioned above. Therefore, based on this compositional analysis, it is believed that doubling the thickness of the Mo film increases the amount of N atoms released from the Mo film. Furthermore, the proportion of O atoms in the Mo film, especially at the surface, is 0%, and increases with depth relative to the surface. It can be inferred that oxygen is released along with nitrogen in the Mo film.

[0108] Figure 5D It shows the formation of Figure 5B The compositional analysis results are shown for a wafer with a Mo film thickness of 4 times, or 20 nm. According to the figure, in regions shallower than the middle depth of the Mo nitride film, the proportion of Mo atoms is 100%, while the proportions of N atoms and O atoms are 0%. Similarly, if the 42% N atom proportion in a 1-thickness Mo nitride film diffuses and homogenizes in a 1+4 / 3 thickness Mo nitride film and a Mo film, then the relationship 7 / 3 × (reference value) = 1 × 42 holds true. The reference value for the homogenized N atom proportion obtained from this is 18%, while the proportion of N atoms in this compositional analysis result is 0% at any depth. Thus, by making the Mo film 4 times thicker than the Mo nitride film, the amount of N atoms released from the Mo film is further increased, and it is possible to virtually remove all N atoms, making the Mo nitride film essentially a Mo film.

[0109] (2) Thin film resistance measurement results

[0110] Figure 6This is a graph showing the sheet resistance of each wafer with Mo films of different thicknesses. In this graph, as a reference for comparison, the sheet resistance of bare wafers with Mo films of varying thicknesses, Mo nitride films, and TiN (titanium nitride) films with resistivity of, for example, 50 μΩcm and a thickness of 20 nm are also shown.

[0111] As shown in the figure, the sheet resistance of the 5nm thick Mo film and the 15nm thick Mo nitride film are approximately the midpoint between the sheet resistance of the Mo nitride film and the Mo film, respectively. The resistivity of both the Mo film and the Mo nitride film is also approximately the midpoint between the resistivity of the Mo nitride film and the Mo film. The sheet resistance of the 10nm thick Mo film and the 15nm thick Mo nitride film is close to that of the TiN film, and their resistivity is comparable to that of the TiN film. The sheet resistance of the 20nm thick Mo film and the 15nm thick Mo nitride film decreases to the level of the Mo film's sheet resistance, and their resistivity decreases to the level of the Mo film's resistivity. These sheet resistance measurements confirm that the Mo film removes nitrogen from the Mo nitride film, thus reducing its resistivity. Furthermore, it confirms that increasing the thickness of the Mo film effectively removes nitrogen, achieving sheet resistance and resistivity comparable to those of the Mo film.

[0112] (Experiment 2)

[0113] In a wafer with multiple recesses formed on the surface of a SiO2 film, resistivity and shape changes were confirmed for unformed films, Mo films, Mo nitride films, mixed films of Mo and nitride films, and the mixed film after annealing.

[0114] A. Experimental conditions

[0115] Five wafers with multiple recesses, similar to those in the embodiment, were prepared. One wafer was left uncoated, while the other two wafers were coated with a Mo film and a Mo nitride film, respectively, using a film-forming process with a thickness of 20 nm. Furthermore, a mixed film was formed on the remaining two wafers. This mixed film was formed by forming a 7.5 nm thick Mo film, a 15 nm thick Mo nitride film, and another 15 nm thick Mo film, according to the film-forming process. One of the wafers was subjected to the annealing treatment (580°C, 3 hours) illustrated in the embodiment.

[0116] The film deposition portions of each wafer were imaged using a scanning electron microscope (SEM) to confirm shape changes and measure resistivity. Furthermore, resistivity was measured using films deposited on flat wafers without recesses using the same deposition process.

[0117] B. Experimental Results

[0118] (1) Shape change

[0119] Figures 7A-7C SEM images of Mo nitride films, unannealed hybrid films, and annealed hybrid films are shown. SEM images of unformed Mo films are omitted. The width of the recesses was measured based on the captured SEM images, and the bending displacement, representing the degree of sidewall curvature, was calculated. Regarding the width of the recesses, due to the sidewall curvature, narrow and wide widths alternate. Therefore, the bending displacement was obtained by measuring the width of each recess individually and calculating the difference between the average of the wide widths and the average of the narrow widths.

[0120] Regarding the bending displacement, it is 7.5 nm in the uncoated case, 31.1 nm in the Mo film case, 4.32 nm in the Mo nitride film case, 11.2 nm in the unannealed hybrid film, and 10.0 nm in the annealed hybrid film. Therefore, the bending displacement of both hybrid films is significantly lower than that of the Mo film, approaching the bending displacement of the uncoated case. Furthermore, the bending displacement of the annealed hybrid film is slightly smaller than that of the unannealed hybrid film, thus it is considered that a good shape was obtained through annealing.

[0121] like Figure 7B , Figure 7C As shown in the grayscale images, in the unannealed mixed film, each film can be identified by the depth of grayscale. The annealed mixed film shows no variation in grayscale depth, becoming a uniform film. This confirms that through annealing, nitrogen diffuses sufficiently within the mixed film, resulting in a mixed film with uniform nitrogen content. On the other hand, according to... Figure 7B By performing film formation according to the process described above, a light-gray Mo film covers the sidewalls and is formed thinly, and a dark-gray Mo nitride film is formed by covering this Mo film, completely filling the recess. Moreover, the light-colored Mo film uniformly covering the surface of the Mo nitride film is formed thicker than the Mo nitride film at the front end of the sidewall, which is believed to be because Mo film formation occurs in the interface region between the Mo nitride film and the Mo film due to nitrogen diffusion.

[0122] (2) Resistivity

[0123] The resistivity of each wafer after film deposition on other flat wafers using the same process was measured, and the resistivity was calculated based on this resistivity and the resistivity of the wafer before film deposition. The resistivity of the Mo film with a thickness of 20.5 nm was 14 μΩcm, and the resistivity of the Mo nitride film with a thickness of 14 nm was 1294 μΩcm. The resistivity of the unannealed hybrid film with a thickness of 24.1 nm was 15 μΩcm, and the resistivity of the annealed hybrid film with a thickness of 28.8 nm was 14 μΩcm. Regardless of whether annealing was performed, the resistivity was the same as that of the Mo film. Moreover, the resistivity of the annealed hybrid film was lower than that of the unannealed hybrid film.

[0124] (Example for reference)

[0125] Without a Mo film, experiments were conducted to confirm whether nitrogen in the Mo nitride film could be released and removed by annealing. In this experiment, after forming a Mo nitride film with a thickness of 15 nm on a wafer with multiple recesses formed in the same manner as in the comparison, the same annealing process as in Experiment 2 was performed, and the locations were confirmed by SEM.

[0126] Figure 8A This is an SEM image of the surface of the wafer. Figure 8B This is a SEM image of the side of the wafer. Voids resembling fractures were identified in certain locations within the annealed Mo nitride film. This is believed to be due to the increased density difference between the Mo nitride film and the sidewalls caused by the annealing process, leading to shrinkage and peeling of the Mo nitride film relative to the sidewalls, resulting in fractures. Furthermore, stress was observed between the sidewalls and the shrinking Mo nitride film on the side of the Mo nitride film, causing structural collapse.

[0127] The resistivity of the annealed Mo nitride film was also confirmed. Specifically, the sheet resistance was measured for annealed Mo nitride films obtained by performing the same film deposition process and annealing on a flat wafer plane. Thus, the annealed Mo nitride film represents an intermediate level of sheet resistance and resistivity between Mo nitride films and Mo films.

[0128] As mentioned above, even annealing the Mo nitride film not covered by the Mo film cannot simultaneously satisfy both the suppression of shape defects and the reduction of resistivity. In contrast, if a Mo nitride film covered by a Mo film is formed as in this example, both aspects can be satisfied, and it has been confirmed that annealing further enhances this effect. Furthermore, no structural collapse was observed in the annealed hybrid film, presumably because Mo atoms from the Mo film, which has a higher film density than the Mo nitride film, entered the Mo nitride film, thereby suppressing shrinkage. As stated above, it can be considered that the metal embedding method in this example can form wiring metal capable of suppressing shape defects and reducing resistivity.

[0129] Explanation of reference numerals in the attached figures

[0130] W: Wafer; 12b: Metal nitride film; 12c: Top metal film; 11: Recess; 13: Wiring metal.

Claims

1. A method for filling a recess formed in a substrate with metal, the method comprising the following steps: A metal nitride film is formed on a substrate having the recess to fill the recess with metal nitride; and Next, a metal film containing the metal contained in the metal nitride is formed on the upper surface side of the metal nitride film, and the state in which the metal with a reduced nitrogen content is buried in the recess is achieved by allowing nitrogen atoms to diffuse from the metal nitride film side to the metal film side.

2. The method according to claim 1, wherein, The process of setting the landfill to a state in which the nitrogen content of the metal has decreased includes the following steps: heating at a temperature in the range of 550°C to 900°C under a reduced pressure atmosphere.

3. The method according to claim 2, wherein, The heating process includes the process of supplying hydrogen gas.

4. The method according to claim 1, wherein, The process includes forming a base film of the metal within the recess before the process of filling the recess with metal nitride.

5. The method according to claim 1, wherein, In the process of filling the recess with metal nitride, the metal nitride film is formed by filling the entire recess with the metal nitride.

6. The method according to claim 1, wherein, The metal constituting the metal nitride film and the metal film is molybdenum.

7. The method according to claim 1, wherein, The recesses are arranged in a plurality of directions along the surface of the substrate, and each of the recesses extends on the surface of the substrate in a direction intersecting the aforementioned direction.

8. The method according to claim 1, wherein, The resistivity of metals with reduced nitrogen content is in the range of 10 μΩcm to 50 μΩcm.

9. A substrate processing apparatus for filling a recess formed in a substrate with metal, the substrate processing apparatus comprising: A metal nitride film forming module is used to form a metal nitride film on a substrate having the recesses, thereby filling the recesses with metal nitride; and A metal film forming module is used to form a metal film of the metal contained in the metal nitride on the upper surface side of the metal nitride film, and to set the state in which the metal with a reduced nitrogen content is buried in the recess by allowing nitrogen atoms to diffuse from the metal nitride film side to the metal film side.

Images