Substrate treatment method and substrate treatment system

Abstract

A substrate treatment method according to the present invention comprises: forming a metal film on a substrate by electroless plating; irradiating the surface of the substrate on which the metal film is formed, with a gas cluster ion beam generated by ionizing and accelerating clusters of atoms or molecules of an inert gas; and subjecting the substrate to a reduction annealing treatment after the substrate is irradiated with the gas cluster ion beam.

Description

Substrate processing method and substrate processing system

[0001] The present disclosure relates to a substrate processing method and a substrate processing system.

[0002] Patent Document 1 describes that when forming buried multilayer wiring, in a via formed in an insulating film provided on the wiring, a film containing Cu, Co, Ni or Ru is formed by electroless plating from the bottom surface where the wiring is exposed, using the exposed wiring as a catalyst.

[0003] International Publication No. 2019 / 151078

[0004] The present disclosure provides a substrate processing method and a substrate processing system that can form a sound, low-resistance metal film using electroless plating.

[0005] A substrate processing method according to one aspect of the present disclosure includes forming a metal film on a substrate by electroless plating, irradiating a surface of the substrate on which the metal film has been formed with a gas cluster ion beam formed by ionizing and accelerating clusters of atoms or molecules of an inert gas, and performing a reduction annealing process on the substrate after irradiating the surface with the gas cluster ion beam.

[0006] According to the present disclosure, a substrate processing method and a substrate processing system are provided that are capable of forming a sound, low-resistance metal film using electroless plating.

[0007] 1 is a schematic diagram showing a state in which cracks occur when reduction annealing is performed after a Ru film is formed as a metal film by electroless plating. FIG. 2 is a flowchart showing a substrate processing method according to an embodiment. FIG. 3 is a cross-sectional view showing an example of the structure of a substrate to which a substrate processing method according to an embodiment is applied. FIG. 4 is a cross-sectional view showing a state in which a Ru film is embedded as a metal film by electroless plating in a via formed in the substrate of FIG. 3. ２6 is a TEM photograph of a Ru film when irradiated with GCIB from a gas at an acceleration voltage of 20 kV. FIG. 7 is a block diagram showing a substrate processing system for carrying out a substrate processing method according to an embodiment. FIG. 8 is a cross-sectional view showing an example of an electroless plating apparatus included in the substrate processing system of FIG. 6. FIG. 9 is a cross-sectional view showing an example of a GCIB irradiation apparatus included in the substrate processing system of FIG. 6. FIG. 10 is a cross-sectional view showing an example of a reduction annealing treatment apparatus included in the substrate processing system of FIG.

[0008] Hereinafter, embodiments will be described with reference to the accompanying drawings.

[0009] <Background> First, the background will be explained. Patent Document 1 discloses the formation of a film containing Cu, Co, Ni, or Ru in a via by electroless plating. Among these, Ru is attracting attention as a next-generation wiring material. Mo is also attracting attention as a next-generation wiring material. However, when a metal film is formed by electroless plating, oxidation is observed on the film surface and within the film in the as-deposited state. Furthermore, metal films formed by electroless plating are often not sufficiently crystallized in the as-deposited state, with minute grain sizes and a state close to amorphous. For this reason, the resistance of the metal film is high in the as-deposited state.

[0010] To solve this problem, it is conceivable to form a metal film by electroless plating and then subject the metal film to reduction annealing treatment to decompose the oxide and promote crystallization.

[0011] However, when a metal film is subjected to reduction annealing to promote crystallization, the adhesion between the crystal grains is reduced due to the removal of oxygen from the oxides present between the crystal grains. In this state, crystal growth from an amorphous state causes significant volume shrinkage, which generates tensile stress between the crystal grains, potentially leading to cracks between the crystal grains depending on the metal. Ru films are particularly susceptible to oxidation and are hard, making them prone to cracking between the crystal grains. Figure 1 is a schematic diagram showing the state of a Ru film formed as a metal film by electroless plating and then subjected to reduction annealing. As shown in Figure 1, cracks C are observed along the grain boundaries in the Ru film.

[0012] Therefore, in one embodiment, as a post-treatment after forming a metal film by electroless plating, Ar gas or N ２ The method involves irradiating a substrate on which a metal film has been formed by electroless plating with a gas cluster ion beam generated by ionizing and accelerating clusters of atoms or molecules of an inert gas, such as a gaseous oxide, followed by reduction annealing. By irradiating a substrate on which a metal film has been formed by electroless plating with a gas cluster ion beam generated by an inert gas, a crystalline surface-modified layer with a low oxygen concentration and rich in metal is formed on the surface of the metal film. Then, by performing reduction annealing on the surface of such a crystallized surface-modified layer, crystals in the oxygen-poor surface-modified layer act as starting points for crystal growth. This reduces oxides between crystal grains, suppresses the loss of adhesion between crystal grains due to oxygen detachment, and also suppresses tensile stress between crystal grains. This suppresses cracking at the crystal grain boundaries, resulting in the formation of a sound, low-resistance metal film.

[0013] <Substrate Processing Method> Next, a substrate processing method according to one embodiment will be described in more detail. Fig. 2 is a flowchart showing the substrate processing method according to one embodiment. The substrate processing method of this embodiment includes a step of forming a metal film on a substrate by electroless plating (step ST1), a step of irradiating the surface of the substrate after the metal film has been formed with a gas cluster ion beam of inert gas atoms or molecules (step ST2), and a step of performing a reduction annealing treatment on the substrate after step ST2 (step ST3).

[0014] In step ST1, the substrate is not particularly limited, but a semiconductor substrate (semiconductor wafer) having a semiconductor base such as silicon can be used. For example, a substrate having a structure as shown in FIG. 3 may be used. The substrate W in FIG. 3 has a structure 110 provided on a Si base (not shown). The structure 110 has a lower wiring 101 and an insulating film 102 formed on the lower wiring 101, and a fine via 103 is formed in the insulating film 102. The lower wiring 101 is exposed at the bottom of the via 103. The insulating film 102 has a lower nitride film 102a and an upper oxide film 102b. Cu or Ru can be suitably used for the lower wiring 101. Alternatively, Ni or Co can be used.

[0015] The electroless plating process in step ST1 is performed by applying a chemical solution (plating solution) for electroless plating onto the substrate and then heating the substrate. The heating temperature is preferably 60 to 70° C. After heating, the substrate is subjected to a drying process.

[0016] The metal film formed by electroless plating is not particularly limited, but when the substrate has the structure shown in Fig. 3, electroless plating is performed to embed a metal film 105 as a wiring layer in the via 103, as shown in Fig. 4. The metal film 105 may be a Ru film, in which case the Ru film grows bottom-up from the bottom of the via 103 using the lower wiring 101 exposed at the bottom of the via 103 as a catalyst. The metal film 105 used for embedding may also be a Mo film.

[0017] The structure of the substrate is not limited to that shown in Fig. 3, and the metal film is not limited to a Ru film or a Mo film. The metal constituting the metal film may be any metal that can be formed as a wiring layer by electroless plating.

[0018] In step ST2, the gas cluster ion beam (GCIB) is formed by adiabatically expanding a gas, generating clusters in which several to tens of thousands of atoms or molecules of the gas aggregate due to van der Waals forces, and ionizing and accelerating the clusters.

[0019] In this embodiment, an inert gas is used as the gas for generating the GCIB in step ST2. The inert gas is Ar gas and N ２ The gas may be at least one of:

[0020] The GCIB generated by ionizing and accelerating clusters of atoms or molecules of an inert gas has high energy, and when this beam is irradiated onto the metal film on the substrate surface, the irradiated portion is modified into a metal-rich crystalline layer with a low oxygen concentration by the energy generated when the GCIB collides. In other words, a surface-modified layer is formed on the surface of the metal film by the energy of the GCIB. The thickness of the surface-modified layer is, for example, about 10 to 20 nm.

[0021] FIG. 5 shows the results of the electroless plating of Ru films. ２ 5 is a TEM photograph of a Ru film when irradiated with a gas GCIB at an acceleration voltage of 20 kV. From Fig. 5, it can be seen that a crystalline surface-modified layer is formed on the surface of the Ru film in a nearly amorphous state.

[0022] Ar gas and N are used as inert gases to form GCIB. ２ When comparing gases, Ar gas tends to have a greater modification effect, while N ２ Therefore, in step ST2, Ar gas and N gas are used as the inert gas. ２ When both gases are used, the GCIB generated by Ar gas is first irradiated, and then N ２ A sequential mode may be used in which GCIB generated by Ar gas is irradiated first, and then a process that emphasizes modification is performed by GCIB irradiation of Ar gas, and then a process that emphasizes modification by N gas is performed. ２ By irradiating the gas with GCIB, it is possible to perform a treatment that emphasizes surface smoothness.

[0023] When the inert gas is Ar gas, a good crack suppression effect can be obtained by setting the acceleration voltage to 17 kV or more. ２In the case of gas, a good crack suppression effect can be obtained by setting the acceleration voltage to 13 kV or more. The higher the acceleration voltage, the higher the GCIB irradiation energy and the thicker the surface modification layer tends to be. However, if the acceleration voltage is too high, the effect saturates and sputtering may occur, which may have a negative impact on the surroundings during device formation. From this perspective, Ar gas and N ２ The acceleration voltage for both gases is preferably 25 kV or less.

[0024] The step of subjecting the substrate to reduction annealing in step ST3 is a step of reducing the oxidized portions of the metal film and promoting crystallization of the metal film to reduce the resistance of the metal film.

[0025] The reduction annealing treatment may be a thermal annealing treatment or a plasma annealing treatment. The thermal annealing treatment is an annealing treatment in which the substrate is heated while supplying a reducing gas, and may be a normal pressure treatment. The plasma annealing treatment is an annealing treatment in which a gas containing H element, for example, H ２ Gas alone or H ２ This is a vacuum process in which the substrate is annealed using plasma of gas and inert gas.

[0026] When the reduction annealing is a thermal annealing, the substrate temperature may be 200 to 430° C., for example, 400° C. The reduction gas may be a forming gas, H ２ Gases such as forming gas and formic acid can be used. ２ Gas and N ２ It is a mixture of gases, H ２ The gas content can be 5.7% or less of the explosion limit, e.g., 4%. The duration of the thermal annealing treatment depends on the thickness of the metal film, but may be about 5 to 120 minutes. The thermal annealing treatment is performed under atmospheric pressure, but it is preferable to use a sealed device so that the gas composition can be maintained.

[0027] When the reduction annealing is a plasma annealing, the treatment is performed in a vacuum atmosphere. The pressure may be in the range of 100 mTorr to 2 Torr (13.3 to 266.6 Pa). The substrate temperature may be in the range of 200 to 430°C, preferably 350 to 400°C. The plasma used in this treatment is not particularly limited, and various plasmas such as capacitively coupled plasma, inductively coupled plasma, and microwave plasma can be used.

[0028] As described above, in this embodiment, the metal film formed by electroless plating is subjected to GCIB irradiation with atoms or molecules of an inert gas in step ST2, and then subjected to reduction annealing treatment in step ST3, thereby suppressing the occurrence of cracks in the metal film.

[0029] In other words, the irradiation of the gas cluster ion beam with atoms or molecules of an inert gas in step ST2 forms a crystalline surface-modified layer with a low oxygen concentration and rich in metal on the surface of the metal film, and then the reduction annealing treatment in step ST3 causes crystal growth to originate from the crystals in the oxygen-poor surface layer. This prevents the deterioration of adhesion between crystal grains due to oxygen detachment from oxides between the crystal grains during crystal growth. Furthermore, since the origin of crystal growth is the crystals in the surface-modified layer, no significant volume shrinkage occurs and tensile stress between the crystal grains is also suppressed. This prevents cracks at the crystal grain boundaries, resulting in the formation of a sound, low-resistance metal film.

[0030] In particular, since Ru films are expected to be a next-generation wiring material and are prone to cracking due to reduction annealing after electroless plating, the method of this embodiment is effective. For example, when a substrate having a structure in which fine vias 103 are formed, as shown in FIG. 3 , is used and a Ru film is embedded as a wiring layer as the metal film 105 in the vias 103, void-free embedding is difficult using conventional CVD or PVD. However, void-free embedding can be achieved by using electroless plating as in this embodiment. That is, when embedding the Ru film using electroless plating, Ru selectively grows from the lower-layer wiring 101 using the lower-layer wiring 101 exposed at the bottom of the via 103 as a catalyst, and is embedded by bottom-up growth, so that void-free embedding is possible even in fine vias. Furthermore, the temperature during film formation is low, at less than 100° C. Furthermore, in this embodiment, as described above, a low-resistance Ru film can be obtained by electroless plating without generating cracks, thereby effectively utilizing the advantages of embedding Ru in such vias by electroless plating. Furthermore, like the Ru film, a Mo film, which is expected to be a next-generation wiring, may be used as the metal film 105. Like the Ru film, the Mo film is a hard metal film and is prone to cracking during reduction annealing, but this embodiment suppresses cracking at the grain boundaries, thereby enabling a reduction in resistance.

[0031] This embodiment is applicable not only to the case where selective growth is performed from the lower layer wiring exposed at the bottom of the via as shown in FIG. 3, and is not limited to a Ru film or a Mo film, but may also be a film of another metal that can be formed by electroless plating.

[0032] <Substrate Processing System> Next, a substrate processing system for carrying out the above-described substrate processing method will be described. Fig. 6 is a block diagram showing a substrate processing system for carrying out the substrate processing method of one embodiment. Here, the case where a Ru film is used as the metal film will be described as an example.

[0033] The substrate processing system 200 includes an electroless plating apparatus 300, a GCIB irradiation apparatus 400, and a reduction annealing treatment apparatus 500. Substrates are transported between the electroless plating apparatus 300 and the GCIB irradiation apparatus 400, and between the GCIB irradiation apparatus 400 and the reduction annealing treatment apparatus 500, by substrate transport mechanisms 600 and 700, respectively. The substrate processing system 200 also includes a control unit 800 for controlling the electroless plating apparatus 300, the GCIB irradiation apparatus 400, the reduction annealing treatment apparatus 500, and the substrate transport mechanisms 600 and 700. Each of these will be described individually below.

[0034] Electroless Plating Apparatus FIG. 7 is a cross-sectional view showing an example of an electroless plating apparatus 300. The electroless plating apparatus 300 forms a Ru film as a metal film by electroless plating, and as shown in FIG. 7, includes a chamber 51, a substrate holding unit 52, and a plating solution supply unit 53. The substrate holding unit 52 is disposed within the chamber 51 and has a chuck member 521 that vacuum-sucks the lower surface (rear surface) of the substrate W, thereby holding the substrate W horizontally. The substrate holding unit 52 may be a mechanical chuck. The plating solution supply unit 53 supplies plating solution L1 to the upper surface (processing surface) of the substrate W held by the substrate holding unit 52.

[0035] A rotary motor 523 is connected to the substrate holder 52 via a rotary shaft 522. When the rotary motor 523 is driven, the substrate holder 52 rotates together with the substrate W. The rotary motor 523 is supported by a base 524 fixed to the chamber 51.

[0036] The plating solution supply unit 53 has a plating solution nozzle 531 that discharges the plating solution L1 onto the substrate W held by the substrate holder 52, and a plating solution supply source 532 that supplies the plating solution L1 to the plating solution nozzle 531. The plating solution supply source 532 supplies the plating solution L1, the temperature of which has been adjusted to a predetermined temperature, to the plating solution nozzle 531. The plating solution nozzle 531 is held by a nozzle arm 56 and configured to be movable.

[0037] The plating solution L1 is, for example, a plating solution for autocatalytic (reducing) electroless plating, and contains Ru ions and a reducing agent such as hypophosphorous acid, dimethylamine borane, or hydrazine. The plating solution L1 may also contain appropriate additives. The plating solution L1 is discharged from the plating solution nozzle 531, thereby coating the upper surface of the substrate W with a Ru film.

[0038] The electroless plating apparatus 300 further includes other processing liquid supply units, namely, a cleaning liquid supply unit 54 that supplies cleaning liquid L2 to the upper surface of the substrate W held by the substrate holding unit 52, and a rinsing liquid supply unit 55 that supplies rinsing liquid L3 to the upper surface of the substrate W.

[0039] The cleaning liquid supply unit 54 has a cleaning liquid nozzle 541 that discharges the cleaning liquid L2 onto the substrate W held by the substrate holder 52, and a cleaning liquid supply source 542 that supplies the cleaning liquid L2 to the cleaning liquid nozzle 541. For example, an organic acid or dilute hydrofluoric acid (DHF) can be used as the cleaning liquid L2. The cleaning liquid nozzle 541 is held by a nozzle arm 56 and is movable together with the plating liquid nozzle 531.

[0040] The rinse liquid supply unit 55 has a rinse liquid nozzle 551 that discharges rinse liquid L3 onto the substrate W held by the substrate holder 52, and a rinse liquid supply source 552 that supplies rinse liquid L3 to the rinse liquid nozzle 551. The rinse liquid nozzle 551 is held by a nozzle arm 56 and is movable together with the plating liquid nozzle 531 and the cleaning liquid nozzle 541. As the rinse liquid L3, for example, pure water can be used.

[0041] The nozzle arm 56 holding the plating solution nozzle 531, the cleaning solution nozzle 541, and the rinsing solution nozzle 551 is configured to be moved horizontally and vertically by a nozzle moving mechanism (not shown), and the nozzle arm 56 is movable between a discharge position where the plating solution L1, the cleaning solution L2, or the rinsing solution L3 is discharged onto the substrate W, and a retracted position where the nozzle arm 56 is retracted from the discharge position. The discharge position is a position where the liquid can be supplied to any position on the top surface of the substrate W, for example, a position where the liquid can be supplied to the center of the substrate W. The retracted position is a position outside the substrate W.

[0042] A cup 571 is provided around the substrate holder 52. The cup 571 is formed in a ring shape and receives liquid splashed from the substrate W when the substrate W rotates, and guides the liquid to a drain duct 581, which will be described later. An atmosphere blocking cover 572 is provided on the outer periphery of the cup 571 to prevent the atmosphere around the substrate W from diffusing into the chamber 51. The atmosphere blocking cover 572 is formed in a cylindrical shape that extends in the vertical direction and is open at the top. A lid 6, which will be described later, can be inserted into the atmosphere blocking cover 572 from above.

[0043] A drain duct 581 is provided below the cup 571. The drain duct 581 is formed in a ring shape, and receives and discharges the liquid that has been received by the cup 571 and has descended, as well as the processing liquid that has descended directly from around the substrate W. An inner cover 582 is provided on the inner periphery of the drain duct 581.

[0044] The upper surface of the substrate W held by the substrate holder 52 is covered by a lid 6. The lid 6 has a ceiling portion 61 extending horizontally and a side wall portion 62 extending downward from the ceiling portion 61. When the lid 6 is positioned at a lower position (i.e., a processing position) described below, the ceiling portion 61 faces the substrate W above the substrate W held by the substrate holder 52 at a relatively small distance.

[0045] The ceiling portion 61 includes a first ceiling plate 611 and a second ceiling plate 612 disposed on the first ceiling plate 611. The first ceiling plate 611 and the second ceiling plate 612 are disposed so as to sandwich the heater 63. A seal ring 613 is disposed between the first ceiling plate 611 and the second ceiling plate 612 on the outer periphery of the heater 63. This seal ring 613 seals the heater 63 and prevents the heater 63 from coming into contact with solutions such as the plating solution L1. The first ceiling plate 611 and the second ceiling plate 612 may be formed from a material that is suitable for corrosion resistance against solutions such as the plating solution L1, such as an aluminum alloy. To further enhance corrosion resistance, the first ceiling plate 611, the second ceiling plate 612, and the side wall portion 62 may be coated with Teflon (registered trademark).

[0046] A lid moving mechanism 7 is connected to the lid 6 via a lid arm 71. The lid moving mechanism 7 has a swing motor 72 that moves the lid 6 horizontally and a cylinder 73 that moves the lid 6 up and down. The swing motor 72 is attached to a support plate 74 that is provided so as to be movable up and down relative to the cylinder 73.

[0047] The swing motor 72 of the lid moving mechanism 7 moves the lid 6 between an upper position (position indicated by a two-dot chain line in FIG. 6 ) located above the substrate W held by the substrate holder 52, and a retracted position (not shown) retracted from the upper position. The retracted position is a position outside the substrate W in the chamber 51. The rotation axis of the swing motor 72 extends in the vertical direction, and the lid 6 can swing horizontally between the upper position and the retracted position.

[0048] The cylinder 73 of the lid moving mechanism 7 moves the lid 6 between a lower position (shown by a solid line in FIG. 6 ), which is a processing position, and an upper position, thereby adjusting the distance between the substrate W, on whose upper surface the plating solution L1 is poured, and the first ceiling plate 611 of the ceiling section 61. When the lid 6 is disposed in the lower position, the first ceiling plate 611 is close to the substrate W.

[0049] When the lid 6 is positioned at the lower position, the plating solution L1 on the substrate W is heated by the heater 63.

[0050] The side wall portion 62 of the lid body 6 extends downward from the peripheral portion of the first ceiling plate 611 of the ceiling portion 61, and is positioned on the outer periphery of the substrate W when the lid body 6 is positioned in a lower position to heat the plating solution L1 on the substrate W.

[0051] The ceiling 61 and side wall 62 of the lid 6 are covered by a lid cover 64. This lid cover 64 is placed on a second ceiling plate 612 of the lid 6 via a plurality of supports 65. In order to prevent heat from escaping from inside the lid 6 to the surroundings, the lid cover 64 is preferably made of a material having higher thermal insulation properties than the ceiling 61 and side wall 62, such as a resin material.

[0052] A fan filter unit 59 is provided at the top of the chamber 51 to supply clean air around the lid 6. The fan filter unit 59 supplies air into the chamber 51 (particularly into the atmosphere blocking cover 572). The supplied air flows toward an exhaust pipe 81, which will be described later. A downflow, in which this air flows downward, is formed around the lid 6, and gas vaporized from the processing liquid, such as the plating liquid L1, flows toward the exhaust pipe 81 by this downflow. This prevents gas vaporized from the processing liquid from rising and diffusing within the chamber 51.

[0053] The gas supplied from the fan filter unit 59 is exhausted by the exhaust mechanism 8. This exhaust mechanism 8 has two exhaust pipes 81 provided below the cup 571 and an exhaust duct 82 provided below the drain duct 581. The two exhaust pipes 81 penetrate the bottom of the drain duct 581 and are each connected to the exhaust duct 82. The exhaust duct 82 is formed in a substantially semicircular ring shape when viewed from above. One exhaust duct 82 is provided below the drain duct 581, and two exhaust pipes 81 are connected to this exhaust duct 82.

[0054] In the electroless plating apparatus 300 configured in this manner, first, clean air is supplied into the chamber 51 from the fan filter unit 59, and the substrate W is loaded into the electroless plating apparatus 300 and held horizontally by the substrate holding portion 52.

[0055] Next, a cleaning process is performed on the substrate W held by the substrate holder 52. In this cleaning process, the rotation motor 523 rotates the substrate W at a predetermined rotation speed, the nozzle arm 56 moves from the retracted position to the discharge position, and the cleaning liquid L2 is supplied from the cleaning liquid nozzle 541 to the upper surface of the rotating substrate W. This cleans the surface of the substrate W and removes any attached matter. The cleaning liquid L2 supplied to the substrate W is discharged into the drain duct 581.

[0056] Next, a rinse process is performed on the substrate W. In this rinse process, a rinse liquid L3 is supplied from the rinse liquid nozzle 551 to the rotating substrate W to rinse the surface of the substrate W. This washes away the cleaning liquid L2 remaining on the substrate W. The rinse liquid L3 supplied to the substrate W is discharged into the drain duct 581.

[0057] Next, plating solution L1 is supplied to the upper surface of the substrate W held by the substrate holder 52, forming a puddle of plating solution L1 on the upper surface of the substrate W. To form a puddle on the upper surface of the substrate W, the plating solution nozzle 531 first ejects plating solution L1 onto the upper surface of the substrate W while the substrate W is rotated at a speed slower than that used during the rinsing process. Surface tension causes the plating solution L1 to remain on the upper surface, forming a layer of plating solution L1 known as a puddle. A portion of the plating solution L1 flows out from the upper surface and is discharged through the drain duct 581. After a predetermined amount of plating solution L1 has been ejected from the plating solution nozzle 531, ejection of plating solution L1 is stopped. The nozzle arm 56 is then retracted to the retracted position. By forming a puddle while rotating the substrate W in this manner, a uniform plating film can be achieved. Alternatively, the rotation of the substrate W may be stopped to increase the amount of plating solution L1 applied.

[0058] Next, a process is performed to heat the plating solution L1 provided on the substrate W. This plating solution heating process includes the steps of covering the substrate W with the lid 6, supplying an inert gas, placing the lid 6 at a lower processing position to actually heat the plating solution L1, and retracting the lid 6 from above the substrate W. During the process of heating the plating solution L1, it is preferable that the rotation speed of the substrate W (including when stopped) be maintained in the same manner as when the plating solution was provided.

[0059] The operation of supplying inert gas is to supply inert gas into the space between the substrate W held by the substrate holder 52 and the lid body 6 located at a lower position, thereby performing plating processing on the upper surface of the substrate W while maintaining a low-oxygen atmosphere around the substrate W.

[0060] When the temperature of plating solution L1 is actually raised to a temperature at which the components in plating solution L1 precipitate, the components of plating solution L1 precipitate and form and grow a plating film (Ru film) on the upper surface of substrate W. This heating operation is carried out for a time required to obtain a plating film of a desired thickness, while maintaining the temperature of plating solution L1 at a temperature at which the plating film precipitates, for example, 50 to 85°C.

[0061] Next, the substrate W is rinsed. In this rinse, the rotation speed of the substrate W is first increased to be higher than the rotation speed during the plating (puddle formation and heating) process, and the substrate W is rotated at, for example, the same rotation speed as that used in the substrate rinsing process before the plating process. Next, the rinse liquid nozzle 551 is moved from the retracted position to the discharge position. Next, rinse liquid L3 is supplied from the rinse liquid nozzle 551 to the rotating substrate W to wash away the plating liquid L1 remaining on the substrate W.

[0062] Next, a drying process is performed on the substrate W. In this drying process, the substrate W is rotated at high speed to shake off the rinse liquid L3 remaining on the substrate W and dry it. This results in a substrate having a Ru film, which is an electroless plating film in a dried state. In this case, N ２ An inert gas, such as a gas, may be blown onto the substrate W to facilitate drying.

[0063] Thereafter, the substrate W is removed from the substrate holder 52 and carried out of the electroless plating apparatus 300 .

[0064] In practice, a plurality of electroless plating apparatuses 300 are arranged as a unit. That is, for example, a plurality of electroless plating apparatuses 300, a loading / unloading station for loading and unloading substrates W, and a transport mechanism are unitized, and a substrate is transported by the transport mechanism from a substrate storage container for storing a plurality of substrates arranged in the loading / unloading station to one of the electroless plating apparatuses 300, and the substrate is processed by that electroless plating apparatus 300.

[0065] 8 is a cross-sectional view showing an example of a GCIB irradiation apparatus 400. The GCIB irradiation apparatus 400 irradiates a substrate W on which a Ru film has been formed by electroless plating with GCIB produced by inert gas atoms or molecules, thereby forming a surface modified layer by GCIB on the surface of the Ru film.

[0066] The GCIB irradiation device 400 contains an inert gas, such as Ar gas or N ２ The chamber has a source chamber 202 in which a gas is injected to form a cluster flow, and a target chamber 203 in which the cluster flow formed in the source chamber 202 is converted into a cluster beam and irradiated onto a target substrate S. The source chamber 202 and the target chamber 203 are separated by a partition wall 204.

[0067] A nozzle 205 is provided in the source chamber 202 for injecting an inert gas flow and forming the inert gas into clusters. A nozzle pipe 206 is connected to the nozzle 205, and an inert gas is supplied to the nozzle pipe 206 from a gas source (not shown) outside the source chamber 202. The pressure of the inert gas injected from the nozzle 205 is controlled by a regulator (not shown), and the inert gas in this jet undergoes adiabatic expansion, and its atoms or molecules (atoms of Ar gas or N ２ The gas molecules aggregate into clusters of several to tens of thousands due to van der Waals forces, forming a cluster flow.

[0068] A skimmer 207 is provided in the source chamber 202, facing the nozzle 205. The skimmer 207 is provided on the partition wall 204 so as to protrude toward the nozzle 205, and has an aperture through which the cluster flow ejected from the nozzle 205 passes, thereby preventing shock waves.

[0069] A cluster flow is introduced into the target chamber 203 through an aperture in the skimmer 207, and an ionizer 211 consisting of a plurality of annular electrodes is arranged along the cluster flow, where the cluster flow is ionized. An accelerator 212 is provided downstream of the ionizer 211 to apply an acceleration voltage (bias voltage) and accelerate the ionized cluster flow. Therefore, the cluster flow is ionized by the ionizer 211 and accelerated by the accelerator 212 to become a GCIB.

[0070] A first aperture 213, a permanent magnet 214, and a second aperture 215 are provided downstream of the accelerator 212. The diameter of the GCIB is adjusted by the first aperture 213 and the second aperture 215, and the trajectory of small mass particles, such as monomer ions and small mass cluster particles, is bent by the permanent magnet 214, so that a GCIB of an appropriate size passes through the second aperture 215.

[0071] The GCIB is formed by the nozzle 205, the nozzle pipe 206, the skimmer 207, the ionizer 211, the accelerator 212, the first aperture 213, the permanent magnet 214, the second aperture 215, and the like.

[0072] An XY stage 220 is disposed downstream of the second aperture 215. The XY stage 220 holds a substrate W having a Ru film formed on its surface as a metal film, and scans the substrate W two-dimensionally. The substrate W is loaded and unloaded through a loading / unloading port (not shown) provided in the target chamber 203, and the loading / unloading port can be opened and closed by a gate valve (not shown). The substrate W used in this case may be, for example, a semiconductor substrate (semiconductor wafer) having a structure as shown in FIG. 4, but is not limited to this.

[0073] The source chamber 202 and the target chamber 203 are provided with vacuum pumps 221 and 222, respectively, which draw a vacuum so that the insides of the source chamber 202 and the target chamber 203 are brought into a predetermined reduced pressure (vacuum) state.

[0074] The pressure in the substrate placement area of ​​the target chamber 203 is measured by a pressure gauge 234, and is controlled by an automatic pressure control valve (not shown) connected to the vacuum pump 222 so that the pressure on the pressure gauge 234 becomes a predetermined value.

[0075] In the GCIB irradiation apparatus 400 configured as described above, first, the gate valve (not shown) of the target chamber 203 is opened, and the substrate W is loaded through a loading / unloading port (not shown) and held on the XY stage 220. In this state, the source chamber 202 and the target chamber 203 are evacuated to a high vacuum by the vacuum pumps 221 and 222.

[0076] Then, an inert gas is injected from a nozzle 205 in the source chamber 202 to form a cluster flow. The cluster flow is ionized by an ionizer 211 and accelerated by an accelerator 212 to form a GCIB, which is irradiated onto a substrate W supported by an XY table 220. At this time, the substrate W is scanned by the XY table 220, whereby the GCIB is scanned over the substrate W.

[0077] To form the GCIB, a cluster flow supplied from the source chamber 202 to the target chamber 203 is ionized by an ionizer 211 and accelerated by an accelerator 212. The accelerator 212 applies an acceleration voltage (bias voltage) to accelerate the ionized clusters; the higher the acceleration voltage, the more the GCIB is accelerated. The GCIB formed in this manner is passed through first and second apertures 213 and 215 to adjust the beam diameter, and a permanent magnet 214 deflects small particles from the beam path, thereby appropriately controlling the size of the clusters. The GCIB, whose beam diameter and cluster size are controlled in this manner, is irradiated onto the substrate W.

[0078] In this way, when the substrate W is irradiated with GCIB from an inert gas, the GCIB collides with the Ru film, which is a metal film formed on the surface of the substrate, and the GCIB collides with the collidered portion to form a crystalline layer that is low in oxygen concentration and rich in Ru due to the energy of the collision. That is, a crystalline surface-modified layer that is low in oxygen concentration and rich in Ru is formed on the surface of the Ru film, which is a metal film. The acceleration voltage of the GCIB at this time is preferably 17 kV or more when the inert gas is Ar gas, and is preferably 17 kV or more when the inert gas is N ２ In the case of gas, an acceleration voltage of 13 kV or more is preferable. A higher acceleration voltage allows a thicker surface modification layer to be formed, but if the acceleration voltage is too high, the effect will saturate and the sputtering effect will increase, so an acceleration voltage of 25 kV or less is preferable.

[0079] 9 is a cross-sectional view showing an example of a reduction annealing treatment apparatus 500. The reduction annealing treatment apparatus 500 includes a treatment vessel 310, a heating plate 320, and a gas supply unit 330.

[0080] The processing vessel 310 is a cylindrical metal vessel with a substantially sealed structure, and its interior is maintained at atmospheric pressure. A heating plate 320 is provided at the center of the bottom of the processing vessel 310. A loading / unloading port 311 for loading and unloading the substrate W is formed in the sidewall of the processing vessel 310, and the loading / unloading port 311 is opened and closed by a shutter 312. A gas inlet 313 for introducing a reducing gas is formed in the center of the ceiling wall of the processing vessel 310, and a plurality of exhaust ports 314 are formed outside the heating plate 320 in the bottom wall.

[0081] The heating plate 320 is made of metal and heats the substrate W placed on its upper surface, and has a heater 321 embedded inside. The heater 321 heats the heating plate 320 so that the temperature of the substrate W placed on it reaches 200 to 430°C, for example, 400°C.

[0082] The gas supply unit 330 supplies a reducing gas into the processing vessel 310 through a pipe 331 and a gas inlet 313. The reducing gas may be a forming gas, H ２ Gas, formic acid, etc. can be used.

[0083] In the reduction annealing treatment apparatus 500 configured as described above, first, the substrate W that has been treated by the GCIB irradiation device 400 is carried into the treatment vessel 310 by a transfer mechanism (not shown) and placed on the heating plate 320. At this time, the temperature of the heating plate 320 is controlled by the heater 321 so that the temperature of the placed substrate W is 200 to 430°C, for example, 400°C.

[0084] Next, a reducing gas is supplied from the gas supply unit 330 into the processing vessel 310, and a reduction annealing process is performed on the substrate W on the heating plate 320. This reduces the oxidized portions of the Ru film and promotes crystallization of the Ru film, thereby reducing the resistance of the Ru film. The processing time at this time may be approximately 5 to 120 minutes.

[0085] After the supply of the reducing gas for a predetermined time, the supply of the reducing gas is stopped, and the substrate on the heating plate 320 is carried out from the processing chamber 310 by a transfer mechanism (not shown).

[0086] In practice, the reduction annealing treatment apparatus 500 is incorporated into a system configured such that substrates are transported to the reduction annealing treatment apparatus 500 from a substrate storage container arranged in a carry-in / out station by a transport mechanism.

[0087] In the above example, the reduction annealing treatment apparatus 500 is described as one that performs thermal annealing at normal pressure while supplying a reducing gas, but a reduction annealing treatment apparatus 500 that performs plasma annealing of a substrate using plasma of a gas containing hydrogen elements may also be used. In an apparatus for performing such plasma annealing, a substrate is placed on a substrate placement table in a processing chamber, the processing chamber is brought into a reduced pressure (vacuum) state, and a gas containing hydrogen elements, such as H, is supplied from a gas supply unit. ２ Gas or H ２ A plasma generating device may be used which supplies a gas and an inert gas and forms a high frequency electric field between the substrate stage and the upper electrode to generate plasma.

[0088] When performing atmospheric pressure processing using the reduction annealing processing apparatus 500 that performs thermal annealing, it is necessary to return the pressure to atmospheric pressure after the processing performed in vacuum by the GCIB irradiation apparatus 400. In contrast, when the reduction annealing processing is plasma annealing, the GCIB irradiation processing and hydrogen plasma processing can be performed in-situ, which is efficient.

[0089] [Substrate Transport Mechanism] The substrate transport mechanisms 600 and 700 transport substrates stored in a substrate storage container between the electroless plating apparatus 300 and the GCIB irradiation apparatus 400, and between the GCIB irradiation apparatus 400 and the reduction annealing treatment apparatus 500, respectively. The substrate transport mechanisms 600 and 700 preferably transport the substrates while the substrate storage container is maintained in a non-oxidizing atmosphere such as an inert atmosphere or a reducing atmosphere, so as to suppress oxidation of the Ru film formed by electroless plating.

[0090] [Controller] The controller 800 controls each component of the substrate processing system 200, i.e., the electroless plating apparatus 300, the GCIB irradiation apparatus 400, the reduction annealing treatment apparatus 500, and the substrate transport mechanisms 600 and 700. The controller 800 includes a main controller having a CPU (computer), an input device, an output device, a display device, and a storage device. The main controller of the controller 800 causes the substrate processing system 200 to perform a desired operation based on a processing recipe stored in, for example, a storage medium built into the storage device or a storage medium set in the storage device.

[0091] In the substrate processing system 200, the electroless plating apparatus 300, the GCIB irradiation apparatus 400, and the reduction annealing treatment apparatus 500 configured as described above are operated as described above under the control of the control unit 800, thereby realizing one embodiment of the substrate processing method.

[0092] <Experimental Example> Next, an experimental example will be described. Here, a Ru film was formed as a metal film by electroless plating, and then a process of irradiating the Ru film with GCIB under various conditions was carried out. After that, a reduction annealing process was carried out on the sample. The film state and resistivity were evaluated. The reduction annealing process was carried out using forming gas (H ２The GCIB irradiation process was carried out using an inert gas such as Ar gas or N ２ In the case of Ar gas, the acceleration voltage was changed to 9 kV, 13 kV, 17 kV, 20 kV, 25 kV, and 30 kV. ２ In the case of gas, the acceleration voltage was varied between 5 kV, 13 kV, 17 kV, 20 kV, 25 kV, and 30 kV. For comparison, the state and resistivity of the film were also evaluated for a sample in which a Ru film was formed by electroless plating and then subjected to reduction annealing under the same conditions without the GCIB irradiation step.

[0093] As a result, the resistivity of the comparative sample not subjected to the GCIB irradiation step was 18.5 μΩcm, and cracks were observed in the film. In contrast, when the reduction annealing treatment was performed after the GCIB irradiation step using Ar gas, and when the N ２ When the reduction annealing treatment was carried out after the step of irradiating the GCIB with gas, the resistivity and the presence or absence of cracks in the film were as shown in Tables 1 and 2, respectively.

[0094]

[0095]

[0096] That is, when the reduction annealing treatment was performed after the step of irradiating GCIB with Ar gas, as shown in Table 1, an improvement in resistivity was observed at acceleration voltages of 9 kV and 13 kV, but some cracks remained in the film. At acceleration voltages of 17 to 25 kV, the resistivity was lower than that of the comparative sample, and no cracks were observed in the film. At an acceleration voltage of 30 kV, the resistivity was similar to that of the comparative sample, but no cracks were observed in the film. ２ When reduction annealing was performed after the step of irradiating GCIB gas, no improvement in resistivity was observed at an acceleration voltage of 5 kV, and cracking in the film was hardly improved, as shown in Table 2. At acceleration voltages of 13 to 25 kV, the resistivity improved in many samples, and no cracking in the film was observed. Even at an acceleration voltage of 30 kV, the resistivity was 16.6 μΩcm, and no cracking in the film was observed, but the effect tended to saturate.

[0097] Although the embodiments have been described above, the disclosed embodiments should be considered to be illustrative and not restrictive in all respects. The above-described embodiments may be omitted, substituted, or modified in various ways without departing from the scope and spirit of the appended claims.

[0098] For example, the electroless plating apparatus of the above embodiment is merely an example, and apparatuses of various other configurations can be used. Furthermore, the GCIB irradiation apparatus is also merely an example, and the apparatus configuration is not limited as long as it can generate, ionize, and accelerate clusters of inert gas atoms or molecules and irradiate the GCIB onto a substrate. Furthermore, the reduction annealing treatment apparatus of the above embodiment is also merely an example, and the apparatus configuration is not limited as long as it can perform thermal annealing treatment or plasma annealing treatment.

[0099] Furthermore, in the above embodiment, an example has been given of a case in which a Ru film is formed as a metal film on the substrate of FIG. 3 and selectively grown bottom-up from the lower wiring at the bottom of the via, but the structure of the substrate is not limited to that of FIG. 3, and the metal constituting the metal film may be any metal that can be formed as a wiring layer by electroless plating.

[0100] Furthermore, although the case where a semiconductor substrate (semiconductor wafer) having a semiconductor base is used as the substrate has been described, the substrate is not limited to a semiconductor wafer and may be other substrates such as an FPD (flat panel display) substrate or a ceramic substrate.

[0101] 101; lower layer wiring, 102; insulating film, 102a; nitride film, 102b; oxide film, 103; via, 105; metal film (Ru film), 110; structural unit, 200; substrate processing system, 300; electroless plating apparatus, 400; GCIB irradiation apparatus, 500; reduction annealing treatment apparatus, 600, 700; substrate transport mechanism, 800; control unit, W; substrate

Claims

1. Forming a metal film on a substrate by electroless plating; irradiating the surface of the substrate on which the metal film is formed with a gas cluster ion beam generated by ionizing and accelerating clusters of atoms or molecules of an inert gas; and performing a reduction annealing treatment on the substrate after irradiating the gas cluster ion beam. A substrate processing method comprising the above steps.

2. The substrate processing method according to claim 1, wherein when the gas cluster ion beam is irradiated onto the surface of the metal film, a crystalline surface modification layer with a low oxygen concentration and rich in metal is formed on the surface of the metal film.

3. The substrate processing method according to claim 1 or 2, wherein the metal film is a Ru film or a Mo film.

4. The substrate has an underlying wiring, an insulating film formed on the underlying wiring, and a via provided in the insulating film such that the underlying wiring is exposed at the bottom surface. The metal film is embedded in the via. The substrate processing method according to claim 1 or 2.

5. The metal film is a Ru film, and the Ru film grows bottom-up in the via from the underlying wiring using the underlying wiring as a catalyst. The substrate processing method according to claim 4.

6. Irradiating the gas cluster ion beam uses at least one of Ar gas and N ２ gas as an inert gas, and the substrate processing method according to claim 1 or claim 2.

7. The inert gas is an Ar gas, and the acceleration voltage when generating the gas cluster ion beam is 17 kV or more. The substrate processing method according to claim 6.

8. The inert gas is N ２ gas, and the acceleration voltage when generating the gas cluster ion beam is 13 kV or more. The substrate processing method according to claim 6.

9. Irradiating the gas cluster ion beam includes first irradiating the gas cluster ion beam using Ar gas as an inert gas, and then irradiating the gas cluster ion beam using N ２ gas as an inert gas. The substrate processing method according to claim 6.

10. Forming the metal film by electroless plating includes applying an electroless plating solution on the substrate, heating the substrate to deposit a plating film to form the metal film, and drying the substrate. The substrate processing method according to claim 1 or 2.

11. Performing the reduction annealing treatment on the substrate is carried out by heating and annealing the substrate at normal pressure while supplying a reducing gas. The substrate processing method according to claim 1 or 2.

12. Performing the reduction annealing treatment on the substrate is carried out by plasma annealing the substrate with a plasma of a gas containing a hydrogen element. The substrate processing method according to claim 1 or 2.

13. A substrate processing system comprising: an electroless plating apparatus for forming a metal film on a substrate by electroless plating; a gas cluster ion beam irradiation apparatus for irradiating a surface of the substrate on which the metal film is formed by the electroless plating apparatus with a gas cluster ion beam formed by ionizing and accelerating clusters of atoms or molecules of an inert gas; and a reduction annealing apparatus for subjecting the substrate irradiated with the gas cluster ion beam by the gas cluster ion beam irradiation apparatus to a reduction annealing treatment.

14. The gas cluster ion beam irradiation apparatus forms a crystalline surface modification layer that is metal-rich with a low oxygen concentration on the surface of the metal film by irradiating the surface of the metal film with the gas cluster ion beam. The substrate processing system according to claim 13.

15. The gas cluster ion beam irradiation device uses at least one of Ar gas and N ２ gas as an inert gas when generating the gas cluster ion beam, and the substrate processing system according to claim 13 or claim 14.

16. The inert gas is an Ar gas, and the acceleration voltage when generating the gas cluster ion beam is 17 kV or more. The substrate processing system according to claim 15.

17. The inert gas is N ２ gas, and the acceleration voltage when generating the gas cluster ion beam is 13 kV or more. The substrate processing system according to claim 15.

18. The reduction annealing apparatus is an apparatus for heating and annealing the substrate at normal pressure while supplying a reducing gas. The substrate processing system according to claim 13 or claim 14.

19. The reduction annealing apparatus is a plasma annealing apparatus for processing the substrate with a plasma of a gas containing a hydrogen element. The substrate processing system according to claim 13 or claim 14.

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