Method for filling metal and substrate processing device

Abstract

The present invention inhibits a metal wiring line, which is formed in recesses by depositing a metal-containing film on a semiconductor wafer, from suffering shape failures and also reduces the resistivity of the wiring line. This method is for filling a metal into recesses formed in a substrate, and includes: a step in which a metal nitride film is formed on the substrate having the recesses formed therein to fill the metal nitride into the recesses; and a step in which a film of a metal contained in the metal nitride is subsequently formed on the upper surface of the metal nitride film and nitrogen atoms are caused to diffuse from the metal nitride film to the metal film, thereby making the recesses filled with the metal having a reduced nitrogen content.

Description

METAL EMBEDDING METHOD AND SUBSTRATE PROCESSING APPARATUS

[0001] The present disclosure relates to a method for embedding metal and a substrate processing apparatus.

[0002] In semiconductor devices, wiring that constitutes circuits is formed by depositing a metal film on a semiconductor wafer (hereinafter referred to as "wafer") with a recessed portion, for example, by chemical vapor deposition (CVD) or atomic layer deposition (ALD). Meanwhile, as semiconductor devices become increasingly highly integrated, the difficulty of forming wiring is increasing due to the trend toward thinner lines and narrower spacing between wires. Furthermore, because thinner wiring increases resistance, the use of metal materials with low resistivity is being considered.

[0003] For example, Patent Document 1 describes a memory array of a semiconductor memory device. The memory cell array is composed of a laminated body in which a metal layer serving as a control electrode, an intermediate layer, and an insulating layer are stacked. The document describes that the metal layer is a molybdenum layer with low resistance that serves as a control electrode.

[0004] Japanese Patent Application Laid-Open No. 2016-201407

[0005] The present disclosure provides a technique for suppressing shape defects in metal wiring formed in recesses by depositing a metal-containing film on a semiconductor wafer, and reducing the resistivity of the wiring.

[0006] The method disclosed herein is a method for embedding a metal in a recess formed in a substrate, and includes the steps of: forming a metal nitride film on the substrate in which the recess is formed, and embedding the metal nitride in the recess; and subsequently forming a metal film of a metal contained in the metal nitride on the upper surface side of the metal nitride film, and diffusing nitrogen atoms from the metal nitride film side to the metal film side, thereby embedding the metal with a reduced nitrogen content in the recess.

[0007] According to the present disclosure, it is possible to suppress shape defects in metal wiring formed in recesses by forming a metal-containing film on a semiconductor wafer, and to reduce the resistivity of the wiring.

[0008] 1 is a SEM image showing a surface layer of a wafer to be processed; FIG. 2 is a SEM image showing a surface layer of a wafer on which a metal film has been formed by a method of a comparative embodiment; FIG. 3 is a first longitudinal sectional side view of a wafer involved in processing according to an embodiment; FIG. 4 is a second longitudinal sectional side view of a wafer involved in processing according to an embodiment; FIG. 5 is a third longitudinal sectional side view of a wafer involved in processing according to an embodiment; FIG. 6 is a sixth longitudinal sectional side view of a wafer involved in processing according to an embodiment; FIG. 7 is a plan view of a substrate processing apparatus according to an embodiment; FIG. 8 is a longitudinal sectional side view showing a processing module of the substrate processing apparatus; FIG. 9 is a first graph showing test results of Experiment 1; FIG. 10 is a second graph showing test results of Experiment 1; FIG. 11 is a third graph showing test results of Experiment 1; FIG. 12 is a fourth graph showing test results of Experiment 1; FIG. 13 is a sixth graph showing test results of Experiment 1; FIG. 14 is a first SEM image showing test results of Experiment 2; FIG. 15 is a second SEM image showing test results of Experiment 2; and FIG. 16 is a third SEM image showing test results of Experiment 2. 10A and 10B are first and second SEM images showing test results of a reference example, respectively;

[0009] In the following embodiment, a method for filling recesses of a wafer W (hereinafter referred to as a metal filling method) according to the present disclosure will be described based on a processing example in which metal wiring constituting buried word line structures (bWL) of a DRAM is formed on a wafer W made of a Si (silicon) substrate. First, the configuration of the wafer W to be processed will be described with reference to FIG. 1A. FIG. 1A is an SEM image showing a cross section of a surface layer of the wafer W to be processed.

[0010] Although the detailed shape will be described with reference to FIG. 2A and other figures, the surface layer portion of the wafer W is composed of, for example, 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, with the SiOx film 10a serving as an interlayer insulating layer. As shown in FIG. 2A , which is a schematic cross-sectional view of the surface layer portion, the surface of the Si layer 10 has an array of multiple uneven shapes formed by etching, and these uneven surfaces are covered with the SiOx film 10a. The thickness of the SiOx film 10a is relatively thick, for example, about 60 nm, at the upper end of the sidewall 14, and is relatively thin, about 1 to 3 nm, in other portions. The surface layer portion of the wafer W composed of the Si layer 10 and the SiOx film 10a in this manner includes the recess 11 and the sidewalls 14 on both sides that define the recess 11.

[0011] Each of these recesses 11 is a vertically elongated trench that extends in a direction perpendicular to the paper surface and opens toward the upper surface. As shown in FIG. 1A, the recesses 11 are arranged at intervals of, for example, about 20 to 50 nm, and each recess is a relatively deep and narrow groove. The recesses are formed with an opening width of about 10 to 20 nm and a depth of about 100 to 250 nm. The width of the recess 11 is narrowest at the bottom end, widens toward the top, and is widest at the opening. The width of the sidewalls 14 on both sides that make up the recess 11 is widest at the bottom end, narrows toward the top, and is narrowest at the tip.

[0012] As described above, the sidewalls 14 have a long dimension from the base end to the top end and a thin width, resulting in a shape that is easily bent. In this embodiment, a metal-containing film (metal film) 12 is formed in the recess 11 formed by such sidewalls 14 to form a wiring metal (metal) 13 having a relatively low resistivity. In this example, the objective is to form a metal wiring having a resistivity equal to or higher than that of conventionally used TiN (titanium nitride), as described in the examples below. From this perspective, attention was focused on Mo (molybdenum) as a wiring material that can achieve a resistivity lower than that of TiN.

[0013] Before describing the metal filling method of the present disclosure, a comparative method to be compared with the metal filling method of the present disclosure will be described with reference to FIG. 1B . FIG. 1B is an SEM image showing the surface layer of a wafer W on which a metal film 12M has been formed by the comparative method. Note that the metal film 12M was formed under conditions that would result in a film thickness of 10 nm when formed on a flat wafer W. Hereinafter, even when a film is formed on a wafer W having a recess 11 formed therein, it may be simply referred to as a film having a film thickness of 10 nm.

[0014] The metal film 12M is made of Mo (molybdenum). In the comparative metal filling method, the metal film 12M is formed on the wafer W including the structure shown in FIG. 1A using an ALD method for isotropic film formation so as to completely fill the entire recess 11. At this time, the thickness of the metal film 12M formed on the sidewall 14 of the recess 11 increases along the surface of the sidewall 14. Therefore, the metal films 12M formed on opposing sidewall 14 surfaces become closer as their thickness increases.

[0015] Here, it has been confirmed that when the opposing metal films 12M in the recess 11 reach a thickness of, for example, about 10 nm and the gap between them narrows, as shown in FIG. 1B , the two sidewalls 14 constituting the recess 11 bend toward the center of the recess 11 as if they are attracted to each other, thereby narrowing the opening width of the recess 11. This phenomenon is thought to be caused by the metal films 12M growing along the sidewalls 14 being attracted to each other by van der Waals forces. On the other hand, as described above, when the sidewalls 14 bend toward the center of the recess 11 and the opening width narrows, the sidewalls 14 of the recess 11 adjacent to the relevant recess 11 bend outward, thereby widening the opening width. This phenomenon is also called line bending because it occurs along the extension direction of the trench formed by the recess 11.

[0016] 1B, recesses 11 with narrower opening widths and recesses 11 with wider opening widths are arranged roughly alternately. If a metal film 12M is formed in such a deformed recess 11 until the entire recess 11 is filled, the wiring metal in the recess 11 will have both narrow and wide wiring widths, resulting in a defective shape. As described above, it was found that the metal filling method of this comparative example, in which metal Mo is filled in the trench formed by the recess 11, can reduce the resistivity of the wiring metal compared to TiN, but may result in a defective shape.

[0017] Below, we will briefly describe several other comparative embodiments that were investigated. In order to suppress the shape defects caused by the metal film 12M in the comparative embodiments, a method of forming a metal nitride film, which has weaker van der Waals forces than a metal film, as in the example described later (FIG. 7A) can be considered. The metal nitride film contains Mo and N (nitrogen) as components and does not contain other elements, specifically Mo. ２ It is composed of N (molybdenum nitride).

[0018] Since the van der Waals force of a metal nitride film is weaker than that of a metal film, even when the metal nitride film is formed on the inner surface of the recess 11, it exerts little force to bend the opposing sidewall 14, thereby suppressing variations in the width of the wiring metal. However, since the metal nitride film has a higher resistivity than a metal film, specifically about 100 times that of a metal film, when the metal nitride film is formed into an extremely narrow wiring metal as in this embodiment, the resistance becomes high.

[0019] Therefore, in order to resolve the high resistivity, we investigated the possibility of performing multiple annealing processes after forming a metal nitride film to release nitrogen from the metal nitride film. However, as shown in the reference examples (FIGS. 8A and 8B) described below, the metal nitride film after the annealing process significantly shrunk and suffered structural damage. As described above, performing multiple annealing processes on the metal nitride film did not solve the problem of the present disclosure.

[0020] As another approach, we also considered depositing a metal film after depositing a metal nitride film. We assumed that 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, would reinforce the sidewall 14 and make it less likely to bend. We then attempted to suppress the resistivity of the wiring metal itself by depositing a metal film on the metal nitride film. However, because the van der Waals forces between the opposing metal films in the recess 11 are relatively strong, the sidewalls 14 still bend as if attracting each other, and we were unable to suppress the shape defects of the wiring metal due to the metal nitride film and the metal film.

[0021] As described above, after examining various comparative examples, the process of this embodiment was found to be able to resolve the problems of poor shape and reduced resistivity of the wiring metal 13. The wiring technique of this embodiment will be described below with reference to FIGS. 2A to 2F. FIGS. 2A to 2F are enlarged cross-sectional views showing the recess 11 and the two sidewalls 14 that form the recess 11. As shown in FIG. 2D, the metal-containing film 12 formed in this embodiment includes a lower metal film 12a, a metal nitride film 12b, and an upper metal film 12c. Hereinafter, the lower metal film 12a and the upper metal film 12c may be referred to as metal films 12a and 12c, and the lower metal film 12a, the metal nitride film 12b, and the upper metal film 12c may be simply referred to as films 12a, 12b, and 12c.

[0022] In this embodiment, the process involves depositing a lower metal film 12a (FIG. 2A), a metal nitride film 12b (FIGS. 2B and 2C), and an upper metal film 12c (FIG. 2D) in this order on the wafer W shown in FIG. 1A, and then performing an annealing process (FIG. 2E) to form the wiring metal 13 (FIG. 2F).

[0023] Like the metal film 12M of the comparative embodiment, the lower metal film 12a is composed of Mo and does not contain N (nitrogen) or other metals as constituent elements. As shown in FIG. 2A , the lower metal film 12a is formed on the surface of the wafer W before processing, for example, by ALD, as in the comparative embodiment. As in the comparative embodiment described above, the lower metal film 12a is formed to a thickness that does not cause bending of the sidewall 14, i.e., a relatively thin thickness. Specifically, the thickness of the lower metal film 12a is preferably, for example, about 2 to 3 nm, and may be about 7.5 nm if formed thicker. The thickness of the lower metal film 12a that does not cause bending of the sidewall 14 can be determined in advance by preliminary testing or the like.

[0024] 2A, the lower metal film 12a formed under these film thickness conditions is formed with a substantially uniform 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 other than the recess 11. The thin lower metal film 12a has a small van der Waals force acting between the opposing films 12a, suppressing bending of the sidewall 14. On the other hand, by providing the lower metal film 12a with a relatively low resistivity so as to be in contact with the SiOx film 10a that forms the side and bottom surfaces of the recess 11, the resistance value of the interface region between the wiring metal 13 (FIG. 2F) and the SiOx film 10a can be reduced.

[0025] The lower metal film 12a is formed by alternately supplying a molybdenum-containing gas and a reducing gas, which are raw material gases, to the wafer W via a purge gas, while the wafer W is heated to a temperature of, for example, 580° C. as shown in FIG. 1A. The molybdenum-containing gas is, for example, MoO ２ Cl ２ (molybdenum dioxide dichloride) gas, and the reducing gas is, for example, H ２ The molybdenum-containing gas, the reducing gas, and the purge gas are inert gases such as Ar (argon) gas, etc. The molybdenum-containing gas, the reducing gas, and the purge gas do not contain nitrogen as a component.

[0026] 2B, a metal nitride film 12b is formed on the surface of the lower metal film 12a by, for example, the ALD method. The metal nitride film 12b contains Mo and N as components and does not contain any other elements. Specifically, Mo ２The metal nitride film 12b is made of Mo (molybdenum nitride). ２ N has a higher resistivity and a weaker van der Waals force than Mo. Therefore, even if the metal nitride film 12b is formed on the inner surface of the recess 11, the side walls 14 facing each other across the recess 11 can be prevented from bending as if they are attracting each other.

[0027] As the thickness of the metal nitride film 12b on the lower metal film 12a increases, the metal nitride gradually fills the recess 11, eventually completely filling the recess 11 (FIG. 2C). The vertical cross section of the metal nitride film 12b that has completely filled the recess 11 has a wedge shape that narrows downward.

[0028] Filling the entire recess 11 with the metal nitride film 12b means that the internal space of the recess 11 is almost completely filled with the metal nitride film 12b, but it is also acceptable for the upper portion of the internal space of the recess 11 to remain slightly after the formation of the metal nitride film 12b. When the entire recess 11 is completely filled with the metal nitride film 12b, the formation of the metal nitride film 12b is completed.

[0029] The metal nitride film 12b is formed by, for example, ALD, by alternately supplying source gases, molybdenum-containing gas and nitrogen-containing gas, to the wafer W via a purge gas supply, while the wafer W shown in FIG. 1A is heated to, for example, 400° C. The molybdenum-containing gas is, for example, MoO ２ Cl ２ The nitrogen-containing gas is, for example, NH ３ (ammonia) gas. The nitrogen-containing gas is N ２ The purge gas may be, for example, an inert gas such as Ar (argon) gas. The molybdenum-containing gas and the purge gas may contain nitrogen as a component, and when a purge gas containing nitrogen is supplied, it may not be necessary to supply the nitrogen-containing gas described above.

[0030] Next, as shown in FIG. 2D , an upper metal film 12c is formed on the surface of the metal nitride film 12b by ALD to a generally uniform thickness. In this case, the upper metal film 12c may be formed by other anisotropic film formation methods. Like the lower metal film 12a, the upper metal film 12c contains Mo as a component but does not contain nitrogen or other metals. Because the upper metal film 12c is formed on the surface of the metal nitride film 12b, there is no need to limit its thickness, as there is for the lower metal film 12a. The lower metal film 12a is preferably formed to a thickness sufficient to perform the process of releasing nitrogen atoms from the metal nitride film 12b, which will be described later. Specifically, the thickness of the upper metal film 12c is preferably approximately 10 to 30 nm. However, the thickness of the upper metal film 12c may be approximately the same as that of the lower metal film 12a, as long as nitrogen atoms can be released from the metal nitride film 12b.

[0031] The metal nitride film 12b, located between the upper and lower metal films 12a and 12c, has its lower and upper surfaces in contact with the upper and lower metal films 12a and 12b, which have a lower nitrogen concentration than the metal nitride film 12b. Therefore, nitrogen in the metal nitride film 12b diffuses into the metal films 12a and 12c through the interface regions between the metal films 12a and 12c and the metal nitride film 12b (solid arrows in FIG. 2E). When the concentration of the diffused nitrogen in the upper metal film 12c, which is in contact with an atmosphere such as a clean reduced-pressure atmosphere or air, increases to a certain level, nitrogen is released from the surface. To ensure this phenomenon occurs throughout the entire metal-containing film 12, the wafer W on which the upper metal film 12c is formed is subjected to an annealing process.

[0032] In the annealing process, the wafer W placed in a reduced pressure atmosphere is heated to, for example, 580° C., and a reducing gas is supplied. The reducing gas is, for example, H ２The annealing treatment is a hydrogen (H2) gas, which can suppress oxidation of the metal-containing film 12. Such an annealing treatment diffuses nitrogen from the entire area, including the deep portion, of the metal nitride film 12b provided in the recess 11 having a relatively large aspect ratio, thereby balancing the nitrogen concentration throughout the entire area, including the deep portion, of the metal-containing film 12. The annealing treatment also promotes the release of nitrogen from the surface of the upper metal film 12c. In this nitrogen release, not only nitrogen atoms are directly released from the surface of the upper metal film 12c, but also reaction products (nitrogen compounds) of nitrogen and oxygen contained in the film originating from, for example, a reducing gas or a molybdenum-containing gas as a raw material are released.

[0033] Due to this release, nitrogen continuously diffuses from the metal nitride film 12b, which has a relatively high nitrogen concentration, into the upper metal film 12c, which has a relatively low nitrogen concentration. As a result, the nitrogen concentration in the metal nitride film 12b decreases. The nitrogen concentration in the lower metal film 12a, which is in contact with the metal nitride film 12b, also temporarily increases due to diffusion from the metal nitride film 12b. However, it is thought that the direction of nitrogen diffusion then changes toward the metal nitride film 12b, where the nitrogen concentration is decreasing, and the nitrogen concentration decreases again.

[0034] By annealing the wafer W on which the upper metal film 12c has been formed as described above, the nitrogen content can be reduced, resulting in the formation of a metal wiring 13 with low resistivity. In this example, the metal wiring 13 is composed of the lower metal film 12a and the metal nitride film 12b. However, the upper metal film 12c may be embedded in the upper region of the recess 11, so that, for example, the upper central portion of the upper metal film 12c is formed. Furthermore, unnecessary upper metal film 12c may be removed by etching or the like. According to the method of this embodiment described above, after filling the recess 11 with the metal nitride film 12b, which has relatively low van der Waals forces, the upper metal film 12c is formed on the metal nitride film 12b, and nitrogen is diffused and removed. This reduces the resistivity of the metal wiring 13 and allows the formation of a metal wiring 13 with a uniform width and a good shape.

[0035] A substrate processing apparatus 1 capable of carrying out the above series of processes will be described with reference to the plan view of FIG. 3 . The substrate processing apparatus 1 is configured, for example, as a multi-chamber vacuum processing apparatus. The substrate processing apparatus 1 includes an atmospheric pressure transfer chamber 22, which is maintained under atmospheric pressure. A load port 21 is provided in front of the atmospheric pressure transfer chamber 22 for transferring a wafer W to and from a transfer container C containing a wafer W. A door 27 is provided on the front wall of the atmospheric pressure transfer chamber 22, and is opened when transferring a wafer W to and from the transfer container C. A transfer arm 25 for transferring the wafer W is also provided within the atmospheric pressure transfer chamber 22. Furthermore, an alignment chamber 26 for adjusting the orientation and eccentricity of the wafer W is provided on the left wall of the atmospheric pressure transfer chamber 22, as viewed from the load port 21 side of the atmospheric pressure transfer chamber 22.

[0036] Two load lock chambers 23, arranged side by side, are connected to the wall of the atmospheric pressure transfer chamber 22 opposite the load port 21. The load lock chambers 23 have the function of switching the internal atmosphere between an atmospheric pressure atmosphere and a vacuum atmosphere while accommodating a wafer W. As viewed from the atmospheric pressure transfer chamber 22, a vacuum transfer chamber 24 is disposed at the rear of these load lock chambers 23. The atmospheric pressure transfer chamber 22 and the vacuum transfer chamber 24 are connected to each load lock chamber 23 via a gate valve 29.

[0037] An exhaust mechanism (not shown) is connected to the vacuum transfer chamber 24, and its internal space is kept under vacuum. A transfer arm 28 is provided in this internal space. Process modules 101 to 104 are connected to the sidewall of the vacuum transfer chamber 24, lined up in this order clockwise. Process module 101 is configured to deposit a lower metal film 12a, process module 102 is configured to deposit a metal nitride film 12b, and process module 103 is configured to deposit an upper metal film 12c. Process module 102 corresponds to a metal nitride film deposition module, and process module 103 corresponds to a metal film deposition module. Transfer of wafers W between the process modules 101 to 104 and each load lock chamber 23 is performed by the transfer arm 28.

[0038] Each of the processing modules 101 to 104 includes a processing vessel 51 that is evacuated to create a vacuum atmosphere inside, and a substrate mounting table 55 (FIG. 4) that is provided within the processing vessel 51 and on which a wafer W is placed, and each processing is performed within the processing vessel 51.

[0039] The substrate processing apparatus 1 includes a control unit 20, which is a computer, and the control unit 20 includes a program. The program includes instructions (steps) for carrying out the above-described processing of the wafer W and the transport process of the wafer W. The program is stored in a storage medium, such as a compact disc, a hard disk, a DVD, or a nonvolatile memory, and is read from the storage medium and installed in the control unit 20.

[0040] The control unit 20 uses the program to output control signals to each part of the substrate processing apparatus 1, thereby controlling the operation of each part. Specifically, the control unit 20 controls operations such as the operation of the processing modules 101 to 104, the opening and closing of each gate valve 29, the operation of the transfer arm 25, the operation of the transfer arm 28, the operation of the exhaust mechanism, and the switching of the pressure in the load lock chamber 23.

[0041] Regarding the transfer path of the wafer W in the substrate processing apparatus 1, the wafer W is first transferred in the following order: transfer container C → load port 21 → atmospheric pressure transfer chamber 22 → load lock chamber 23 → vacuum transfer chamber 24 → processing module 101. Then, the wafer W on which the lower metal film 12a has been formed in the processing module 101 is transferred in the following order: processing module 101 → vacuum transfer chamber 24 → processing module 102. The wafer W on which the metal nitride film 12b has been formed in the processing module 102 is transferred in the following order: processing module 102 → vacuum transfer chamber 24 → processing module 103.

[0042] The wafer W on which the upper metal film 12c has been formed in the processing module 103 is transferred in the order of processing module 103 → vacuum transfer chamber 24 → processing module 104. The wafer W that has been annealed in the processing module 104 is transferred in the order of processing module 104 → vacuum transfer chamber 24 → load lock chamber 23 → atmospheric pressure transfer chamber 22, and then returned to the transfer container C.

[0043] Next, an example configuration of the process module 101 will be described, taking the process modules 101-104 as a representative, with reference to the longitudinal side view of FIG. 4 . The process vessel 51 of the process module 101 is made of, for example, aluminum. A transfer port for the wafer W is formed in the sidewall of the process vessel 51, and a gate valve G1 for opening and closing the transfer port is provided. An exhaust duct 52, which is shaped like a ring and has a rectangular cross section, is disposed in the upper part of the sidewall of the process vessel 51. A slit 52a is formed along the inner periphery of the exhaust duct 52, and an exhaust port 52b is formed in the outer wall of the exhaust duct 52. A ceiling wall 54 is provided on the upper surface of the exhaust duct 52 to close the upper opening of the process vessel 51 via an insulating member 53, and the space between the exhaust duct 52 and the insulating member 53 is airtightly sealed with a seal ring.

[0044] A substrate mounting table 55 for horizontally supporting a wafer W is provided inside the processing vessel 51. The substrate mounting table 55 is formed in a disk shape from a ceramic material such as aluminum nitride (AlN) or a metal 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 table 55, and the heater 56A heats the wafer W, for example, to the aforementioned film formation temperature. The outer peripheral region and side surfaces of the upper surface of the substrate mounting table 55 are covered with a cover member made of ceramic such as alumina.

[0045] The substrate mounting table 55 is connected via a support member to an elevating mechanism 57 provided below the processing vessel 51 and is configured to be freely raised and lowered between a processing position indicated by a solid line in FIG. 4 and a wafer W transfer position indicated by a dashed line below the processing position indicated by a solid line in FIG. 4 . In FIG. 4 , reference numeral 52c denotes a partition member that, together with the substrate mounting table 55 raised to the processing position, divides the interior of the processing vessel 51 into upper and lower sections. Three support pins 58 (only two are shown) are provided below the substrate mounting table 55 in the processing vessel 51 so as to be freely raised and lowered by an elevating mechanism provided below the processing vessel 51. The support pins 58 are inserted into through holes in the substrate mounting table 55 at the transfer position and are configured to be able to protrude and retract relative to the upper surface of the substrate mounting table 55. These support pins 58 are used to transfer the wafer W between the transfer arm 28 of the vacuum transfer chamber 24 shown in FIG. 3 and the substrate mounting table 55. Reference numeral 59 in the figure denotes a bellows that separates the atmosphere inside the processing vessel 51 from the outside air and expands and contracts in accordance with the vertical movements of the substrate mounting table 55 and the support pins 58, respectively.

[0046] A shower head 61 for supplying various gases into the processing vessel 51 in a shower-like manner is provided in the processing vessel 51, facing the substrate mounting table 55. The shower head 61 includes a main body fixed to the ceiling wall 54 of the processing vessel 51 and a shower plate 62 connected below the main body, and the interior thereof forms a gas diffusion space 63. A circular protrusion that protrudes downward is formed on the periphery of the shower plate 62, and gas discharge holes 64 are formed on the flat surface inside the circular protrusion. A gas supply mechanism 6A is connected to the ceiling wall 54 and the main body of the shower head 61.

[0047] The gas supply mechanism 6A includes a source gas supply unit 71A configured to supply a source gas to the processing vessel 51, and a reducing gas supply unit 72A configured to supply a reducing gas. The gas supply mechanism 6A further includes two purge gas supply units 73A configured to supply a purge gas. The source gas supply unit 71A includes a source gas supply source 74A and a supply path 75A. The supply path 75A is provided with, from the upstream side, a flow rate adjustment unit M1A, a storage tank T1A, and a valve V1A.

[0048] The reducing gas supply unit 72A includes a reducing gas supply source 76A and a supply path 77A, and the supply path 77A is provided with, from upstream to downstream, a flow rate adjuster M2A, a storage tank T2A, and a valve V2A. Each purge gas supply unit 73A includes a purge gas supply source 78A and a supply path 79A, and each supply path 79A is provided with a flow path adjuster M3A and a valve V3A. The supply path 79A of one purge gas supply unit 73A is connected to the source gas supply path 75A to purge the source gas, and the supply path 79A of the other purge gas supply unit 73A is connected to the reducing gas supply path 77A to purge the reducing gas. As described above, the source gas supply unit 71A, the reducing gas supply unit 72A, and the purge gas supply unit 73A are configured to individually supply the source gas, the reducing gas, and the purge gas into the processing vessel 51, respectively.

[0049] The processing vessel 51 is connected to a vacuum exhaust line 66 via the exhaust port 52b, and a vacuum exhaust unit 67, such as a vacuum pump, is provided downstream of the vacuum exhaust line 66 and configured to evacuate the gas inside the processing vessel 51. A pressure control valve, such as an APC valve (not shown), is provided in the vacuum exhaust line 66 between the processing vessel 51 and the vacuum exhaust unit 67.

[0050] The other process modules 102 to 104 have substantially the same configuration as the process module 101 described above, but differences from the process module 101 will be briefly described below. The process module 102 that forms the metal nitride film 12b has a nitrogen-containing gas supply unit instead of the reducing gas supply unit 72A in Figure 4, and the supply source 76A becomes a nitrogen-containing gas supply source. The process module 104 that performs the annealing process does not need to be provided with the raw material gas supply unit 71A.

[0051] 3 and 4, which show the substrate processing apparatus 1, and FIGS. 2A to 2F, which show film changes, an operation of performing a series of processes on a wafer W will be described. First, the transfer arm 28 receives the wafer W to be processed from the load lock chamber 23 shown in FIG. 3, and transfers the wafer W to the processing module 101 located on the front left. Thereafter, the gate valve G1 of the processing module 101 shown in FIG. 4 is opened, and the transfer arm 28 advances the wafer W through the loading port into the processing vessel 51. The wafer W is then transferred from the transfer arm 28 to the substrate mounting table 55 using the support pins 58, and the transfer arm 28 is then withdrawn from the processing vessel 51, and the gate valve G1 is closed.

[0052] As described above, the lower metal film 12a is formed in the processing module 101. Based on a recipe for forming the lower metal film 12a to a predetermined thickness, the pressure in the processing vessel 51 and the temperature of the wafer W are adjusted, and a source gas, a reducing gas, and a purge gas are repeatedly supplied to the processing vessel 51 in a predetermined order. This allows the lower metal film 12a to be formed to a predetermined thickness while suppressing bending of the sidewall 14 ( FIG. 2A ) (step of forming a base film).

[0053] Then, the wafer W on which the lower metal film 12a has been formed is unloaded from the processing module 101 in the reverse order of the loading procedure, and transferred toward the processing module 102. Thereafter, the wafer W is loaded into the processing module 102 in the same order as the loading procedure into the processing module 101, and a metal nitride film 12b is formed. Based on a recipe for film formation so as to completely fill the recess 11, the pressure in the processing vessel 51 and the temperature of the wafer W are adjusted, and the source gas, nitrogen-containing gas, and purge gas are repeatedly supplied to the processing vessel 51 in a predetermined order. In this way, the metal nitride film 12b is formed to completely fill the entire recess 11 while suppressing bending of the sidewall 14 ( FIGS. 2B and 2C ) (a process of filling the recess 11 with metal nitride).

[0054] Next, the wafer W on which the metal nitride film 12b has been formed is transferred from the process module 102 in the same procedure as in the process module 101, and transferred into the process module 103, where the upper metal film 12c is formed. The pressure in the process vessel 51 and the temperature of the wafer W are adjusted based on a preset recipe for forming a film with a predetermined thickness, and the source gas, reducing gas, and purge gas are repeatedly supplied to the process vessel 51 in a predetermined order. In this way, the upper metal film 12c with a predetermined thickness is formed.

[0055] After that, the wafer W on which the upper metal film 12c has been formed is similarly unloaded from the processing module 103 and loaded into the processing module 104 for annealing. The pressure in the processing chamber 51 and the temperature of the wafer W are adjusted based on a recipe for forming the wiring metal 13 from which nitrogen has been sufficiently removed, and a reducing gas and a purge gas are simultaneously supplied for a predetermined time, such as 3 to 8 hours (a hydrogen gas supply step). This allows nitrogen to be sufficiently diffused and released throughout the entire region, ensuring that nitrogen is more reliably removed from the entire metal-containing film 12 ( FIG. 2E ). Once the wiring metal 13 with reduced resistivity is formed ( FIG. 2F ), the annealing step is completed (a step of diffusing nitrogen atoms to fill the recesses 11 with a metal having a reduced nitrogen content).

[0056] The wafer W on which the metal wiring 13 has been formed by the annealing process is loaded into the load lock chamber 23 and then returned to the transfer container C via the load port 21. As described above, the substrate processing apparatus 1 and metal filling method according to the present disclosure can reduce the resistivity and form the metal wiring 13 with a good shape.

[0057] The annealing process, which requires a processing time of several hours, is not limited to being performed in the single-wafer processing module 104. For example, after the upper metal film 12c is formed in the processing module (metal film deposition module) 103, the wafer W is returned to the transfer container C, and the processing in the substrate processing apparatus 1 is completed. After that, a large number of wafers W may be annealed at once in, for example, a batch-type annealing apparatus.

[0058] Furthermore, the substrate processing apparatus 1 is not limited to being equipped with the single-wafer processing modules 101 to 103. For example, the substrate processing apparatus 1 may be configured with a batch-type heat treatment module that performs film formation and annealing in succession. In this case, after a large number of wafers W before film formation are loaded into the batch-type heat treatment module, the gases supplied to the heat treatment module are switched sequentially to form the lower metal film 12a, the metal nitride film 12b, and the upper metal film 12c in this order. Thereafter, the gas supplied to the heat treatment module is switched to a reducing gas (H ２ The gas is then switched to the annealing gas.

[0059] (Modification) As shown in the above-described embodiment, forming the lower metal film 12a and the metal nitride film 12b in different process modules 101 and 102 is preferable because it eliminates the need to adjust the pressure and temperature based on the recipe for each film formation process, thereby improving film formation efficiency. However, this is not limited to this. The lower metal film 12a and the metal nitride film 12b may be formed in either the process module 101 or the process module 102, which reduces the footprint of the substrate processing apparatus 1. For example, if the films 12a and 12b are formed in a common process module 101, the gas supply mechanism 6A may be provided with the nitrogen-containing gas supply unit described above. Furthermore, by forming the metal film 12c in the process module 101, all of the films 12a to 12c may be formed in the process module 101 alone, and annealing may also be performed.

[0060] In the embodiment of the present disclosure, it is preferable that the lower metal films 12a to 12c are formed isotropically; however, if the side shape of the recess 11 is not perpendicular to the surface but is an inclined surface that widens upward as it extends upward, as shown in this example, the films can also be formed by an anisotropic film formation method such as a CVD method.

[0061] The annealing process performed in this embodiment is not limited to the process recipe described above, and the process recipe is appropriately modified depending on the composition, shape, and thickness of the metal-containing film 12. Furthermore, the annealing process is not essential to the method disclosed herein, and other means may be used. An example of such other means may be heat treatment of the wafer W in a reduced pressure atmosphere without supplying a reducing gas. Another example may be heat treatment of the wafer W in an air atmosphere without supplying a reducing gas. It has been found through experiments and the like that heat treatment is effective for diffusing and removing nitrogen in the metal-containing film 12, and that the temperature of the wafer W may be higher than 580°C and lower than or equal to 850°C. However, the temperature range is not limited to this range, and it is highly likely that the process can be achieved even if the temperature is somewhat outside this range, and it is believed that temperatures ranging from about 550°C to 900°C are possible.

[0062] The recess 11 in the embodiment of the present disclosure does not necessarily have to be a trench. The metal filling method of the present disclosure is also useful, for example, when providing wiring metal in a via. In particular, when the via is extremely thin and long and the sidewalls that make up the via are thin, the method of the present disclosure can form wiring metal with reduced resistivity and a good shape.

[0063] In the embodiment of the present disclosure, the metal-containing film 12 contains Mo as the metal, but is not limited thereto and may be composed of other metals with relatively low resistivity, such as aluminum (Al), copper (Cu), tungsten (W), titanium (Ti), silver (Ag), or alloys thereof. In this case, the lower metal film 12 a and the upper metal film 12 c do not contain nitrogen as a constituent element.

[0064] In the embodiment of the present disclosure, the lower metal film 12a is formed to reduce the resistance of the wiring metal 13, but this is not an essential condition, and the lower metal film 12a may not be formed. The metal nitride film 12b is formed so as to completely fill the recess 11, but this is not an essential condition, and the upper metal film 12c may be provided in the upper space within the recess 11 without completely filling the upper space. In this case, the metal nitride film 12b should be formed to a thickness sufficient to prevent the sidewall 14 from bending due to the van der Waals force of the upper metal film 12c during film formation.

[0065] The upper metal film 12c is formed to cover the entire surface of the metal nitride film 12b in order to efficiently diffuse nitrogen from the metal nitride film 12b, but this does not exclude the case where the upper metal film 12c covers only a portion of the surface of the metal nitride film 12b, although it is preferable to cover the entire surface of the metal nitride film 12b as widely as possible. The upper metal film 12c may be formed to cover only the opening region of the recess 11, for example, in order to diffuse and release nitrogen from the metal nitride film 12b arranged in the recess 11 upward.

[0066] It should be noted that the embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive, and various omissions, substitutions, modifications, and combinations may be made to the above-described embodiments without departing from the scope and spirit of the appended claims.

[0067] (Experiment 1) The nitrogen removal effect of the metal nitride film was confirmed for wafers with a metal film formed on the metal nitride film. Specifically, metal films with different thicknesses were formed on the metal nitride film on the surface of a bare wafer, and the difference in nitrogen removal effect was confirmed. A. Experimental conditions Four flat bare wafers with no patterning were prepared. The wafers were made of SiO ２ On the surface layer, which is a film, Mo ２The wafers were fabricated by depositing a Mo nitride film composed of N on top of which Mo films of different thicknesses were formed. The Mo nitride film was 15 nm thick, and the Mo films were 0 nm (no Mo film formed), 5 nm, 10 nm, and 20 nm thick. These wafers were not annealed, but instead were subjected to a heat treatment under the same conditions in a reduced pressure atmosphere to a degree sufficient to diffuse and remove nitrogen. After the heat treatment, the surface region of each wafer was subjected to composition analysis using X-ray photoelectron spectroscopy (XPS), and the sheet resistance was measured.

[0068] B. Experimental Results (1) Composition Analysis Results Figures 5A to 5D show the composition analysis results of the surface region of each wafer on which a Mo film was formed. Specifically, they show the atomic percentage (At%) at the depth relative to the top surface of each wafer, and the atomic percentage excludes Si (silicon) atoms. Figure 5A shows the composition analysis results of a wafer on which no Mo film was formed. The Mo nitride film and SiO ２ The boundary line is shown at the position corresponding to the interface with the film. The region shallower than the interface is the Mo nitride film, and the deeper region is the SiO ２ It corresponds to a membrane.

[0069] In the Mo nitride film far enough from the interface, the proportions of Mo atoms and N atoms were approximately 50% and slightly higher than 40%, respectively, and the proportion of O (oxygen) atoms was around 5%, and these proportions were roughly constant with depth. The O atoms in this region were presumed to be derived from the source gas mentioned above.

[0070] The region including the relatively shallow region and the deep region including the interface described above is the region between the Mo nitride film and the SiO ２ The interface region is an interface region with the film. ２ As the film is approached, atoms other than O atoms rapidly decrease, while O atoms increase. ２ In the film, the Mo atoms were found to be 10% or less, the N atoms were found to be almost zero, and the O atoms were found to be about 65%.

[0071] FIG. 5B shows the composition analysis results of a wafer on which a 5 nm Mo film was formed. ２In the Mo nitride film and Mo film far enough away from the interface with the film, the proportions of Mo atoms, N atoms, and O atoms were roughly constant with depth. From this, it was determined that N atoms were sufficiently diffused in the Mo nitride film and Mo film. The details of the concentration of each atom showed that the proportion of O atoms increased slightly by 1-2% compared to Figure 5A, the proportion of Mo atoms increased to about 65%, and the proportion of N atoms decreased to just under 30%.

[0072] To consider the N atom ratio in this test, we simply calculated the approximate ratio as a reference value when N atoms in the Mo nitride film sufficiently diffused into a Mo film having a thickness 1 / 3 of the Mo nitride film, resulting in a uniform N atom ratio in these films. Specifically, based on FIG. 5A , the ratio of N atoms, for example, 42% in the Mo nitride film corresponding to a thickness of 1, was calculated as the reference value for the ratio of N atoms diffused and uniformed in the Mo nitride film and the Mo film having a thickness of 1 + 1 / 3. 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 uniform N atom ratio was 31.5%. In contrast, as shown in FIG. 5B , the N atom ratio was low (just under 30%), as previously described. Therefore, it is inferred that N atoms were released from the Mo film, resulting in a decrease in the number of N atoms in this test.

[0073] 5C shows the composition analysis results of a wafer on which a 10 nm Mo film, which is twice the film thickness in FIG. 5B, is formed. ２ A concentration gradient of each atom with respect to depth was confirmed in the Mo nitride film and Mo film other than the interface region with the film. At the depth corresponding to the Mo film, the proportion of Mo atoms was high, exceeding 95%, especially in the surface region, and decreased with increasing depth from the Mo film. The proportion of N atoms was slightly less than 5% in the Mo film, and increased with increasing depth from the interface region between the Mo film and the Mo nitride film, reaching approximately 15% at an intermediate depth in the Mo nitride film.

[0074] As in Figure 5B, the N atoms in the Mo film were sufficiently diffused into a Mo film having a thickness 2 / 3 of the Mo nitride film, and the reference value of the N atom ratio homogenized in these films was calculated. If the N atom ratio in the Mo nitride film with a thickness of 1 (42%) is assumed to have diffused and homogenized in the Mo nitride film and the Mo film with a thickness of 1 + 2 / 3, the relationship 5 / 3 × (reference value) = 1 × 42 holds. While the reference value for the homogenized N atom ratio is 25.2%, the N atom ratio in the composition analysis results was significantly lower than this reference value at all depths, as previously described. Therefore, the composition analysis results suggest that doubling the thickness of the Mo film increased the amount of N atoms released from the Mo film. The O atom ratio was zero, especially at the surface of the Mo film, and increased with increasing depth from the surface. This is thought to be due to oxygen being released along with nitrogen being released from the Mo film.

[0075] Figure 5D shows the composition analysis results for a wafer with a 20-nm Mo film, four times thicker than that shown in Figure 5B. According to this figure, in the region shallower than the intermediate depth of the Mo nitride film, the proportion of Mo atoms was 100%, and the proportions of N and O atoms were zero. As described above, if N atoms, which accounted for 42% in the Mo nitride film with a thickness of 1, were diffused and homogenized in the Mo nitride film with a thickness of 1 + 4 / 3 and the Mo film, the relationship 7 / 3 × (reference value) = 1 × 42 holds. The reference value for the homogenized proportion of N atoms based on this would be 18%, but the proportion of N atoms in this composition analysis was zero at all depths. Thus, by making the Mo film four times thicker than the Mo nitride film, the amount of N atoms released from the Mo film was further increased, and almost all N atoms were removed, essentially converting the Mo nitride film into a Mo film.

[0076] (2) Sheet Resistance Measurement Results Figure 6 is a graph showing the sheet resistance of each wafer on which the Mo film with the different thicknesses is formed. In the same figure, as a reference for comparison, the sheet resistance of each wafer is measured using SiO ２ The sheet resistance of bare wafers on which Mo films and Mo nitride films of varying thicknesses are provided are also shown, along with the sheet resistance of TiN (titanium nitride) having a resistivity of, for example, 50 μΩcm and a thickness of 20 nm.

[0077] From the figure, the sheet resistance of a 5-nm-thick Mo film and a 15-nm-thick Mo nitride film was approximately intermediate between the sheet resistance of the Mo nitride film and the Mo film, and the resistivity of the Mo film and the Mo nitride film was approximately intermediate between the sheet resistance of the Mo nitride film and the Mo film. The sheet resistance of a 10-nm-thick Mo film and a 15-nm-thick Mo nitride film was close to the sheet resistance of a TiN film, and the resistivity of the Mo film and the Mo nitride film was approximately the same as the TiN film. The sheet resistance of a 20-nm-thick Mo film and a 15-nm-thick Mo nitride film was reduced to approximately the sheet resistance of the Mo film, and the resistivity of the Mo film and the Mo nitride film was reduced to approximately the same as the Mo film. These sheet resistance measurements also confirmed that the Mo film removes nitrogen from the Mo nitride film, thereby reducing its resistivity. It was also confirmed that increasing the thickness of the Mo film effectively removes nitrogen and makes it possible to achieve sheet resistance and resistivity comparable to those of the Mo film.

[0078] (Experiment 2) SiO ２ For wafers with multiple recesses formed on the film surface, the resistivity and shape change were confirmed for each of the following: an unformed film, a Mo film, a Mo nitride film, a mixed film of a Mo film and a nitride film, and the mixed film after annealing. A. Experimental Conditions Five wafers with multiple recesses similar to those in the embodiment were prepared. One of them was unformed, and two were formed using a recipe for depositing a Mo film and a Mo nitride film to thicknesses of 20 nm, respectively. The remaining two were formed with a mixed film. The mixed film was formed using a recipe for depositing a 7.5 nm thick Mo film, a 15 nm thick Mo nitride film, and a 15 nm thick Mo film, in that order. One of the wafers was subjected to the annealing treatment (580°C, 3 hours) exemplified in the embodiment. The film-formed portions of each of the wafers were imaged using a scanning electron microscope (SEM) to confirm shape changes and measure resistivity. The resistivity was measured using a film formed on a flat wafer with no recesses using the same film formation recipe.

[0079] B. Experimental Results (1) Shape Change Figures 7A to 7C show SEM images of the Mo nitride film, the mixed film without annealing treatment, and the mixed film with annealing treatment; SEM images of the unformed film and the Mo film are not shown. The width of the recesses was measured from the captured SEM images, and the bending displacement, which indicates the degree of bending of the sidewalls, was calculated. The width of the recesses alternates between narrow and wide widths due to the bending of the sidewalls. Therefore, the bending displacement was calculated by measuring the width of each recess and calculating the difference between the average wide width and the average narrow width.

[0080] The bending displacement was 7.5 nm for the unformed film, 31.1 nm for the Mo film, 4.32 nm for the Mo nitride film, 11.2 nm for the unannealed mixed film, and 10.0 nm for the annealed mixed film. The bending displacements of the two mixed films were significantly reduced compared to that of the Mo film, approaching that of the unformed film. Furthermore, since the bending displacement of the annealed mixed film was slightly smaller than that of the unannealed mixed film, it was thought that a good shape was obtained by the annealing treatment.

[0081] As shown in the grayscale images in Figures 7B and 7C, the unannealed mixed film shows the gray scale variations of each film. The annealed mixed film shows a uniform film with no gray scale variations. This confirms that the annealing treatment sufficiently diffuses nitrogen within the mixed film, resulting in a mixed film with a uniform nitrogen content. On the other hand, Figure 7B shows that the film formation using the above recipe results in a thin, light-gray Mo film covering the sidewalls, followed by a dark-gray Mo nitride film covering the Mo film, completely filling the recess. The light Mo film uniformly covering the surface of the Mo nitride film is thicker than the Mo nitride film on the top of the sidewalls. This is thought to be due to nitrogen diffusion, which causes the interface between the Mo nitride film and the Mo film to become a Mo film.

[0082] (2) Resistivity The resistance of each wafer was measured using a similar recipe on a separate wafer with a flat surface, and the resistivity was calculated from the measured resistance and the resistivity of the wafer before film formation. The resistivity of a Mo film with a film thickness of 20.5 nm was 14 μΩcm, and the resistivity of a Mo nitride film with a film thickness of 14 nm was 1294 μΩcm. The resistivity of a non-annealed mixed film with a film thickness of 24.1 nm was 15 μΩcm, and the resistivity of an annealed mixed film with a film thickness of 28.8 nm was 14 μΩcm, resulting in resistivity comparable to that of a Mo film regardless of whether annealing was performed. The resistivity of the annealed mixed film was lower than that of the non-annealed mixed film.

[0083] (Reference Example) An experiment was conducted to confirm whether nitrogen in a Mo nitride film can be released and removed by annealing without providing a Mo film. In this experiment, a recipe for forming a 15 nm thick Mo nitride film was used on a wafer with multiple recesses similar to those in the comparative example, and then the same annealing treatment as in Experiment 2 was performed, and each portion was examined using an SEM.

[0084] Figure 8A is an SEM image of the surface of the wafer, and Figure 8B is an SEM image of the side of the wafer. Cracks were observed in places on the flat surface of the annealed Mo nitride film. This is thought to be because the annealing treatment increased the difference in film density between the Mo nitride film and the sidewall, causing the Mo nitride film to shrink and peel off from the sidewall, resulting in fractures. It was also confirmed that stress was generated in the sidewall between the shrunk Mo nitride film and the sidewall, causing structural collapse.

[0085] The resistance of the annealed Mo nitride film was also confirmed. Specifically, the sheet resistance of the annealed Mo nitride film, which was formed on the flat surface of a flat wafer using the same film formation recipe and annealing process, was measured. The results showed that the annealed Mo nitride film had sheet resistance and resistivity that were intermediate between those of the Mo nitride film and the Mo film.

[0086] As described above, even when annealing a Mo nitride film that is not covered with a Mo film, it was not possible to suppress shape defects and reduce resistivity. In contrast, forming a Mo nitride film covered with a Mo film as in this example can satisfy these requirements, and it was confirmed that the annealing treatment can further improve these effects. Furthermore, it is presumed that the reason why structural collapse was not observed in the annealed mixed film is because Mo atoms in the Mo film, which has a higher film density than the Mo nitride film, penetrate into the Mo nitride film and suppress shrinkage. As described above, it is believed that the metal filling method of this example can form a wiring metal that can suppress shape defects and reduce resistivity.

[0087] W wafer 12b metal nitride film 12c upper metal film 11 recess 13 wiring metal

Claims

1. A method for filling recesses formed in a substrate with a metal, comprising the steps of: forming a metal nitride film on the substrate having the recesses formed therein, and filling the recesses with the metal nitride; and then forming a metal film of a metal contained in the metal nitride on the upper surface of the metal nitride film, and diffusing nitrogen atoms from the metal nitride film side to the metal film side, thereby filling the recesses with the metal having a reduced nitrogen content.

2. The method of claim 1, wherein the step of embedding the reduced nitrogen content metal comprises heating at a temperature in the range of 550-900°C under a reduced pressure atmosphere.

3. The method of claim 2, wherein the heating step includes the step of supplying hydrogen gas.

4. The method according to claim 1, further comprising the step of forming an underlayer of the metal in the recess before carrying out the step of filling the recess with metal nitride.

5. The method according to claim 1, wherein in the step of filling the recess with metal nitride, the metal nitride film is formed so that the metal nitride fills the entire recess.

6. The method of claim 1, wherein the metal comprising the metal nitride film and the metal film is molybdenum.

7. The method according to claim 1, wherein the recesses are formed in a plurality of rows along a direction along the surface of the substrate, and each recess is provided so as to extend along a direction intersecting the one direction on the surface of the substrate.

8. The method of claim 1, wherein the metal with reduced nitrogen content has a resistivity in the range of 10 to 50 μΩcm.

9. A substrate processing apparatus for filling recesses formed in a substrate with metal, comprising: a metal nitride film deposition module for forming a metal nitride film on the substrate having the recesses formed therein and filling the recesses with the metal nitride; and a metal film deposition module for forming a metal film of a metal contained in the metal nitride on an upper surface of the metal nitride film and diffusing nitrogen atoms from the metal nitride film side to the metal film side, thereby filling the recesses with the metal having a reduced nitrogen content.

Images