Substrate processing method and substrate processing system

Abstract

To provide a substrate processing method and substrate processing system, capable of forming a metal film sound and having low resistance using electroless plating.SOLUTION: A substrate processing method comprises steps of: forming a metal film on a substrate by electroless plating; irradiating the surface of the substrate including the metal film with a gas cluster ion beam generated by ionizing and accelerating the cluster of atoms or molecules of inactive gas; and reducing and annealing the substrate.SELECTED DRAWING: Figure 2

Description

Technical Field

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

Background Art

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

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The present disclosure provides a substrate processing method and a substrate processing system capable of forming a sound and low-resistance metal film using electroless plating.

Means for Solving the Problems

[0005] A substrate processing method according to an aspect of the present disclosure includes a step of forming a metal film by electroless plating on a substrate, a step of irradiating a 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 a step of performing a reduction annealing treatment on the substrate after the step of irradiating the gas cluster ion beam.

Effects of the Invention

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

Brief Description of the Drawings

[0007]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Embodiments for Carrying Out the Invention

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

[0009] <Background> First, the background will be described. Patent Document 1 mentioned above describes forming a film containing Cu, Co, Ni, or Ru by electroless plating in a via. Among these, Ru has attracted attention as a next-generation wiring material. Also, Mo has been attracting attention as a next-generation wiring material. However, when forming a metal film by electroless plating, oxidation can be seen on the film surface and in the film in the as-depo state. Also, the metal film formed by electroless plating is often not sufficiently crystallized in the as-depo state, the grain size is very small, and it is in a state close to amorphous. For this reason, the resistance of the film is high in the state where the metal film is formed (as-depo).

[0010] For this reason, after forming a metal film by electroless plating, it is conceivable to perform a reduction annealing treatment on the metal film to decompose the oxide and promote crystallization.

[0011] However, when promoting crystallization by performing a reduction annealing treatment on the metal film, the adhesion between the crystal grains decreases due to the release of oxygen of the oxide existing between the crystal grains. In this state, a large volume shrinkage occurs due to crystal growth from the amorphous state, and a tensile stress is generated between the crystal grains, and cracks may occur between the crystal grains depending on the metal. In particular, since the Ru film is easily oxidized and hard, such cracks between the crystal grains are likely to occur. FIG. 1 is a schematic diagram showing the state of the film when a Ru film is formed as a metal film by electroless plating and then subjected to a reduction annealing treatment. As shown in FIG. 1, it can be seen that cracks C have occurred along the crystal grain boundaries in the Ru film.

[0012] Therefore, in one embodiment, as a post-treatment after forming a metal film by electroless plating, clusters of atoms or molecules of an inert gas such as Ar gas or N2 gas are ionized on the surface of the substrate, accelerated, and the resulting gas cluster ion beam is irradiated, followed by a reduction annealing treatment. By irradiating the substrate on which the metal film is formed by electroless plating with the gas cluster ion beam of the inert gas as described above, a crystalline surface modification layer with a low oxygen concentration and rich in metal is formed on the surface of the metal film. Then, by performing a reduction annealing treatment in a state where such a crystallized surface modification layer is formed, crystal growth starts from the crystals of the surface modification layer with less oxygen, so there is less oxide between the crystal grains, suppression of a decrease in the adhesion of the crystal grains due to oxygen desorption, and suppression of the tensile stress between the crystal grains. For this reason, cracks at the grain boundaries are suppressed, and a sound and low-resistance metal film can be formed.

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

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

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

[0016] The metal film formed by electroless plating is not particularly limited. However, when the substrate has the structure shown in FIG. 3, as shown in FIG. 4, by performing an electroless plating process, a metal film 105 is embedded in the via 103 as a wiring layer. When the metal film 105 is a Ru film, the Ru film grows bottom-up from the bottom surface of the via 103 using the lower layer wiring 101 exposed at the bottom surface of the via 103 as a catalyst. The metal film 105 may be a Mo film.

[0017] The structure of the substrate is not limited to that of 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 formed as a wiring layer by electroless plating.

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

[0019] In this embodiment, an inert gas is used as the gas for generating the GCIB in step ST2. The inert gas may be at least one of Ar gas and N2 gas.

[0020] The GCIB generated by ionizing and accelerating clusters of atoms or molecules of the inert gas has high energy. When this 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 due to the energy at the time of the GCIB collision. That is, a surface modification layer is formed on the surface of the metal film by the energy of the GCIB. The thickness of the surface modification layer is, for example, about 10 to 20 nm.

[0021] FIG. 5 is a TEM photograph of the Ru film when the GCIB by N2 gas is irradiated onto the Ru film formed by electroless plating at an acceleration voltage of 20 kV. From FIG. 5, it is confirmed that a crystalline surface modification layer is formed on the surface of the Ru film in a substantially amorphous state.

[0022] When comparing Ar gas and N2 gas as the inert gas for forming the GCIB, Ar gas tends to have a greater modification effect, and N2 gas tends to have higher surface smoothness. Therefore, in step ST2, as an embodiment of using both Ar gas and N2 gas as the inert gas, a sequential mode such as irradiating the GCIB first generated by Ar gas and then irradiating the GCIB generated by N2 gas may be used. Thereby, a process emphasizing the modifiability can be performed first by irradiating the GCIB of Ar gas, and then a process emphasizing the surface smoothness can be performed by irradiating the GCIB of N2 gas.

[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 higher. Also, when the gas is N2 gas, a good crack suppression effect can be obtained by setting the acceleration voltage to 13 kV or higher. The higher the acceleration voltage, the higher the irradiation energy of the GCIB, and the surface modification layer tends to be thicker. However, if the acceleration voltage is too high, the effect saturates, and sputtering may occur, which may adversely affect the surroundings during device formation. From such a perspective, it is preferable that the acceleration voltage is 25 kV or lower for both Ar gas and N2 gas.

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

[0025] The reduction annealing treatment may be a heat annealing treatment or a plasma annealing treatment. The heat annealing treatment is an annealing treatment in which the substrate is heated while supplying a reducing gas, and it may be an atmospheric pressure treatment. The plasma annealing treatment is one in which the substrate is annealed by a gas containing H element, for example, H2 gas alone or a plasma of H2 gas + inert gas, and it is a vacuum treatment.

[0026] When the reduction annealing treatment is a heat annealing treatment, the substrate temperature may be 200 to 430 °C, for example, 400 °C. Examples of the reducing gas include forming gas, H2 gas, formic acid, etc., and at least one of these can be preferably used. Forming gas is a mixed gas of H2 gas and N2 gas, and one in which H2 gas is 5.7% or less of the explosion limit, for example, 4%, can be used. The time of the heat annealing treatment depends on the thickness of the metal film, but it may be about 5 to 120 minutes. Although the heat annealing treatment is an atmospheric pressure treatment, it is preferably performed using a device with a sealed structure so that the gas composition can be maintained.

[0027] When the reduction annealing treatment is a plasma annealing treatment, the treatment is performed in a vacuum atmosphere. The pressure at that time may be in the range of 100 mTorr to 2 Torr (13.3 to 266.6 Pa). Also, the substrate temperature may be in the range of 200 to 430°C, and the range of 350 to 400°C is preferable. The plasma at this time 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 the present embodiment, after irradiating the metal film formed by electroless plating with the gas cluster ion beam by the atoms or molecules of the inert gas in step ST2, by performing the reduction annealing treatment in step ST3, the generation of cracks in the metal film is suppressed.

[0029] That is, by irradiating the gas cluster ion beam with the atoms or molecules of the inert gas in step ST2, a crystalline surface modification layer rich in metal with a low oxygen concentration is formed on the surface of the metal film, and then by performing the reduction annealing treatment in step ST3, crystal growth starts from the crystals in the surface layer with less oxygen. As a result, the decrease in the adhesion of crystal grains due to the release of oxygen from the oxides between crystal grains during crystal growth is suppressed, and since the starting point of crystal growth is the crystal of the surface modification layer, the tensile stress between crystal grains is also suppressed. Therefore, cracks at the grain boundaries are suppressed, and a sound and low-resistance metal film can be formed.

[0030] In particular, the Ru film is expected as a next-generation wiring material, and since cracks are likely to occur due to the reduction annealing treatment after electroless plating, the method of this embodiment is effective. For example, when using, as a substrate, one having a structure in which fine vias 103 as shown in FIG. 3 are formed, and embedding a Ru film as a metal film 105 in the vias 103 as a wiring layer, it is difficult to achieve voidless embedding with conventional CVD or PVD. However, by using electroless plating as in this embodiment, voidless embedding can be achieved. That is, in the case of electroless plating, Ru selectively grows from the underlying wiring 101 exposed on the bottom surface of the via 103 using the underlying wiring 101 as a catalyst, and is embedded by bottom-up growth, enabling voidless embedding even in fine vias. Also, the temperature during film formation is as low as less than 100°C. And in this embodiment, as described above, since a low-resistance Ru film can be obtained without generating cracks by electroless plating, the advantages when embedding Ru in such vias by electroless plating can be effectively exerted. Also, as the metal film 105, a Mo film, which is also expected as a next-generation wiring like the Ru film, may be used. The Mo film is also a hard metal film like the Ru film and is prone to cracking during the reduction annealing treatment. However, with this embodiment, cracks at the grain boundaries can be suppressed and the resistance can be reduced.

[0031] This embodiment is applicable not only when selectively growing from the underlying wiring exposed at the bottom of the via as shown in FIG. 3, and not only to Ru films and Mo films, but also to films of other metals that can be formed by electroless plating.

[0032] <Substrate processing system> Next, a substrate processing system for implementing the above substrate processing method will be described. FIG. 6 is a block diagram showing a substrate processing system for implementing the substrate processing method of an 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 apparatus 500. The transfer of the substrate between the electroless plating apparatus 300 and the GCIB irradiation apparatus 400, and the transfer of the substrate between the GCIB irradiation apparatus 400 and the reduction annealing apparatus 500 are respectively performed by substrate transfer mechanisms 600 and 700. Further, the substrate processing system 200 includes a control unit 800 for controlling the electroless plating apparatus 300, the GCIB irradiation apparatus 400, the reduction annealing apparatus 500, and the substrate transfer mechanisms 600 and 700. These will be described individually below.

[0034] [Electroless Plating Apparatus] FIG. 7 is a cross-sectional view showing an example of the 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 in the chamber 51 and has a chuck member 521 that vacuum-sucks the lower surface (back surface) of the substrate W, and horizontally holds the substrate W. The substrate holding unit 52 may be a mechanical chuck. The plating solution supply unit 53 supplies a plating solution L1 to the upper surface (processing surface) of the substrate W held by the substrate holding unit 52.

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

[0036] The plating solution supply unit 53 includes a plating solution nozzle 531 that discharges the plating solution L1 onto the substrate W held by the substrate holding unit 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, which is temperature-controlled to a predetermined temperature, to the plating solution nozzle 531. The plating solution nozzle 531 is held by a nozzle arm 56 and is configured to be movable.

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

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

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

[0040] The rinse liquid supply unit 55 includes a rinse liquid nozzle 551 that discharges the rinse liquid L3 onto the substrate W held by the substrate holding unit 52, and a rinse liquid supply source 552 that supplies the rinse liquid L3 to the rinse liquid nozzle 551. The rinse liquid nozzle 551 is held by the nozzle arm 56 and is movable together with the plating solution 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 that holds the plating liquid nozzle 531, the cleaning liquid nozzle 541, and the rinse liquid nozzle 551 is configured to be moved in the horizontal and vertical directions by a nozzle movement mechanism (not shown). The nozzle arm 56 is movable between a discharge position where the plating liquid L1, the cleaning liquid L2, or the rinse liquid L3 is discharged onto the substrate W and a retracted position where it is retracted from the discharge position. The discharge position is a position where the liquid can be supplied to any position on the upper surface of the substrate W. For example, it is 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 holding portion 52. This cup 571 is formed in a ring shape and receives the liquid scattered from the substrate W during the rotation of the substrate W and guides it to a drain duct 581 described later. An atmosphere shielding cover 572 is provided on the outer peripheral side of the cup 571 to suppress the diffusion of the atmosphere around the substrate W into the chamber 51. This atmosphere shielding cover 572 is formed in a cylindrical shape so as to extend in the vertical direction and has an open upper end. A lid body 6 described later can be inserted into the atmosphere shielding cover 572 from above.

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

[0044] The upper surface of the substrate W held by the substrate holding portion 52 is covered by a lid body 6. The lid body 6 has a ceiling portion 61 extending in the horizontal direction and a side wall portion 62 extending downward from the ceiling portion 61. The ceiling portion 61 faces the substrate W above the substrate W held by the substrate holding portion 52 at a relatively small interval when the lid body 6 is in a lower position (i.e., the processing position) described later.

[0045] The ceiling part 61 includes a first ceiling plate 611 and a second ceiling plate 612 provided on the first ceiling plate 611. The first ceiling plate 611 and the second ceiling plate 612 are provided so as to sandwich the heater 63. A seal ring 613 is provided on the outer peripheral side of the heater 63 between the first ceiling plate 611 and the second ceiling plate 612, and the heater 63 is sealed by this seal ring 613 so that the heater 63 does not come into contact with a liquid such as the plating liquid L1. The first ceiling plate 611 and the second ceiling plate 612 may be formed of a material suitable for having corrosion resistance against a liquid such as the plating liquid L1, for example, an aluminum alloy. Further, in order to enhance the corrosion resistance, the first ceiling plate 611, the second ceiling plate 612, and the side wall part 62 may be coated with Teflon (registered trademark).

[0046] A lid body moving mechanism 7 is connected to the lid body 6 via a lid body arm 71. The lid body moving mechanism 7 has a turning motor 72 that moves the lid body 6 in the horizontal direction and a cylinder 73 that moves the lid body 6 in the vertical direction. The turning motor 72 is attached to a support plate 74 that is movably provided in the vertical direction with respect to the cylinder 73.

[0047] The turning motor 72 of the lid body moving mechanism 7 moves the lid body 6 between an upper position disposed above the substrate W held by the substrate holding part 52 and a retracted position retracted from the upper position. The retracted position is a position outside the substrate W in the chamber 51. The rotation axis of the turning motor 72 extends in the vertical direction, and the lid body 6 is capable of turning and moving in the horizontal direction between the upper position and the retracted position.

[0048] The cylinder 73 of the lid body moving mechanism 7 moves the lid body 6 between a lower position (the position shown by the solid line in FIG. 6) and an upper position (the position shown by the two-dot chain line in FIG. 6) to adjust the distance between the substrate W with the plating liquid L1 filled on the upper surface and the first ceiling plate 611 of the ceiling part 61. When the lid body 6 is disposed at the lower position, the first ceiling plate 611 approaches the substrate W.

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

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

[0051] The ceiling portion 61 and the side wall portion 62 of the lid 6 are covered by the lid cover 64. This lid cover 64 is placed on the second ceiling plate 612 of the lid 6 via a plurality of support portions 65. The lid cover 64 is preferably formed of a material having higher heat insulation than the ceiling portion 61 and the side wall portion 62, for example, a resin material, in order to suppress the escape of heat inside the lid 6 to the surroundings.

[0052] At the upper part of the chamber 51, a fan filter unit 59 for supplying clean air around the lid 6 is provided. The fan filter unit 59 supplies air into the chamber 51 (particularly, inside the atmosphere shielding cover 572). The supplied air flows toward the exhaust pipe 81 described later. A downflow in which this air flows downward is formed around the lid 6, and the gas vaporized from the processing liquid such as the plating solution L1 flows toward the exhaust pipe 81 by this downflow. Thereby, it is possible to prevent the gas vaporized from the processing liquid from rising and diffusing into the chamber 51.

[0053] The gas supplied from the fan filter unit 59 described above is discharged by the exhaust mechanism 8. This exhaust mechanism 8 includes 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 communicate with the exhaust duct 82 respectively. The exhaust duct 82 is formed in a substantially semi-circular ring shape when viewed from above. One exhaust duct 82 is provided below the drain duct 581, and the two exhaust pipes 81 communicate with this exhaust duct 82.

[0054] In the electroless plating apparatus 300 configured as described above, first, with clean air being supplied into the chamber 51 from the fan filter unit 59, the substrate W is carried into the electroless plating apparatus 300 and horizontally held by the substrate holding unit 52.

[0055] Next, a cleaning process of the substrate W held by the substrate holding unit 52 is performed. In this cleaning process, the substrate W is rotated at a predetermined rotational speed by the rotation motor 523, the nozzle arm 56 is moved from the retracted position to the discharge position, and the cleaning liquid L2 is supplied from the cleaning liquid nozzle 541 onto the upper surface of the rotating substrate W. Thereby, the surface of the substrate W is cleaned and deposits and the like are removed. The cleaning liquid L2 supplied to the substrate W is discharged to the drain duct 581.

[0056] Subsequently, a rinsing process of the substrate W is performed. In this rinsing process, the rinsing liquid L3 is supplied from the rinsing liquid nozzle 551 to the rotating substrate W to perform a rinsing process on the surface of the substrate W. Thereby, the cleaning liquid L2 remaining on the substrate W is washed away. The rinsing liquid L3 supplied to the substrate W is discharged to the drain duct 581.

[0057] Next, the plating liquid L1 is supplied onto the upper surface of the substrate W held by the substrate holding unit 52 to form a paddle of the plating liquid L1 on the upper surface of the substrate W. When forming the paddle on the upper surface of the substrate W, first, with the substrate W being rotated at a rotational speed lower than that during the rinsing process, the plating liquid L1 is discharged from the plating liquid nozzle 531 onto the upper surface of the substrate W. This plating liquid L1 stays on the upper surface due to surface tension, and a so-called paddle, which is a layer of the plating liquid L1, is formed. A part of the plating liquid L1 flows out from the upper surface and is discharged through the drain duct 581. After discharging a predetermined amount of the plating liquid L1 from the plating liquid nozzle 531, the discharge of the plating liquid L1 is stopped. Then, the nozzle arm 56 is retracted to the retracted position. By performing paddle formation while rotating the substrate W in this way, the plating film can be made uniform. Note that the rotation of the substrate W may be stopped and the amount of the plating liquid L1 charged may be increased.

[0058] Next, a process of heating the plating solution L1 mounted on the substrate W is performed. This plating solution heating process includes an operation of covering the substrate W with the lid 6, an operation of supplying an inert gas, an operation of actually heating the plating solution L1 with the lid 6 disposed at a lower position, and an operation of retracting the lid 6 from above the substrate W. Note that it is preferable that the rotation speed of the substrate W (including the case of stopping) is maintained in the same manner as in the case of mounting the plating solution even during the process of heating the plating solution L1.

[0059] The operation of supplying the inert gas is for supplying the inert gas into the space between the substrate W held by the substrate holding portion 52 and the lid 6 disposed at a lower position, and performing the plating process on the upper surface of the substrate W while maintaining the periphery of the substrate W in a low-oxygen atmosphere.

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

[0061] Next, a rinsing process of the substrate W is performed. In this rinsing process, first, the rotation speed of the substrate W is increased from the rotation speed during the plating process (paddle formation and heating), and the substrate W is rotated, for example, at the same rotation speed as the substrate rinsing process before the plating process. Subsequently, the rinse liquid nozzle 551 is moved from the retracted position to the discharge position. Next, the rinse liquid L3 is supplied from the rinse liquid nozzle 551 to the rotating substrate W to wash away the plating solution L1 remaining on the substrate W.

[0062] Subsequently, a drying process of the substrate W is performed. In this drying process, the substrate W is rotated at a high speed to shake off and dry the rinse liquid L3 remaining on the substrate W. Thereby, a substrate having a Ru film which is an electroless plating film in a dried state is obtained. In this case, an inert gas such as N2 gas may be blown onto the substrate W to promote drying.

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

[0064] In fact, a plurality of electroless plating apparatuses 300 are arranged and unitized, and are arranged at the loading / unloading station. The substrate is conveyed from a substrate storage container that stores a plurality of substrates to any one of the electroless plating apparatuses 300 by a conveying mechanism for processing.

[0065] [GCIB Irradiation Apparatus] FIG. 8 is a cross-sectional view showing an example of the GCIB irradiation apparatus 400. The GCIB irradiation apparatus 400 irradiates a substrate W on which a Ru film is formed by electroless plating with GCIB by inert gas atoms or molecules to form a surface modification layer by GCIB on the surface of the Ru film.

[0066] This GCIB irradiation apparatus 400 includes a source chamber 202 in which an inert gas, which is a source gas, for example, Ar gas or N2 gas is jetted to form a cluster flow, and a target chamber 203 that irradiates the cluster flow formed in the source chamber 202 as a cluster beam onto a substrate S that is a target. The source chamber 202 and the target chamber 203 are partitioned by a partition wall 204.

[0067] In the source chamber 202, a nozzle 205 for jetting an inert gas flow and clustering it is provided. A nozzle pipe 206 is connected to the nozzle 205, and an inert gas is supplied from a gas source (not shown) outside the source chamber 202 to the nozzle pipe 206. The pressure of the inert gas jetted from the nozzle 205 is controlled by a regulator (not shown), and the inert gas in this jet stream adiabatically expands, and its atoms or molecules (atoms of Ar gas or molecules of N2 gas) aggregate from several to tens of thousands by van der Waals forces to form a cluster, and a cluster flow is formed.

[0068] In addition, a skimmer 207 is provided in the source chamber 202 so as to face the nozzle 205. The skimmer 207 is provided on the partition wall 204 so as to protrude toward the nozzle 205 side, has an aperture through which the cluster flow ejected from the nozzle 205 passes, and is configured to prevent shock waves.

[0069] In the target chamber 203, the cluster flow is introduced through the aperture of the skimmer 207, and along the cluster flow, an ionizer 211 composed of a plurality of annular electrodes is arranged, where the cluster flow is ionized. Downstream of the ionizer 211, an accelerator 212 for applying an acceleration voltage (bias voltage) to accelerate the ionized cluster flow is provided. Therefore, the cluster flow is ionized by the ionizer 211 and accelerated by the accelerator 212 to become a GCIB.

[0070] Downstream of the accelerator 212, a first aperture 213, a permanent magnet 214, and a second aperture 215 are provided. The first aperture 213 and the second aperture 215 adjust the diameter of the GCIB, and the permanent magnet 214 bends the trajectories of particles with small mass, such as monomer ions and cluster particles with small mass, so that a GCIB with an appropriate size passes through the second aperture 215.

[0071] A 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, etc.

[0072] On the downstream side of the second aperture 215, an X-Y stage 220 is disposed which holds a substrate W having a Ru film formed as a metal film on its surface and two-dimensionally scans the substrate W. The substrate W is adapted to be carried in and out from a carry-in / carry-out port (not shown) provided in the target chamber 203, and the carry-in / carry-out port can be opened and closed by a gate valve (not shown). As the substrate W used at this time, for example, a semiconductor substrate (semiconductor wafer) having a structure as shown in FIG. 4 can be mentioned, but it is not limited thereto.

[0073] A vacuum pump 221 and 222 are provided in the source chamber 202 and the target chamber 203, respectively. By evacuating by these, the inside of the source chamber 202 and the target chamber 203 is 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 of 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, the substrate W is carried in from the carry-in / carry-out port (not shown), and is held by the X-Y stage 220. In this state, the source chamber 202 and the target chamber 203 are evacuated by the vacuum pumps 221 and 222 to a high vacuum degree.

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

[0077] When forming the GCIB, the cluster stream supplied from the source chamber 202 to the target chamber 203 is ionized by the ionizer 211 and accelerated by the accelerator 212. The accelerator 212 applies an acceleration voltage (bias voltage) to accelerate the ionized cluster, and the higher the acceleration voltage, the more the GCIB is accelerated. The GCIB thus formed is passed through the first and second apertures 213, 215 to adjust the beam diameter, and the permanent magnet 214 removes particles with a small mass from the beam path, appropriately controlling the size of the cluster. The GCIB with the beam diameter and cluster size thus controlled is irradiated onto the substrate W.

[0078] In this way, when the GCIB formed by the inert gas irradiates the substrate W, the GCIB collides with the Ru film which is a metal film formed on the substrate surface, and the collided portion is modified into a crystalline layer with a low oxygen concentration and rich in Ru by the energy at the time of the collision. That is, a crystalline surface modification layer with a low oxygen concentration and rich in Ru is formed on the surface of the Ru film which is a metal film. At this time, the acceleration voltage of the GCIB is preferably 17 kV or more when the inert gas is Ar gas, and preferably 13 kV or more when the inert gas is N2 gas. A higher acceleration voltage can form a thicker surface modification layer, but if the acceleration voltage is too high, the effect will saturate and the sputtering effect will increase. Therefore, the acceleration voltage is preferably 25 kV or less.

[0079] [Reduction Annealing Treatment Apparatus] FIG. 9 is a cross-sectional view showing an example of the reduction annealing treatment apparatus 500. The reduction annealing treatment apparatus 500 includes a processing container 310, a heating plate 320, and a gas supply unit 330.

[0080] The processing container 310 is a metal container with a substantially airtight cylindrical shape, and the inside is maintained at normal pressure. A heating plate 320 is provided at the center of the bottom inside the processing container 310. A carry-in / outlet 311 for carrying the substrate W in and out is formed on the side wall of the processing container 310, and the carry-in / outlet 311 is opened and closed by a shutter 312. Further, a gas inlet 313 for introducing a reducing gas is formed at the center of the top wall of the processing container 310, and a plurality of exhaust ports 314 are formed outside the heating plate 320 on the bottom wall.

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

[0082] The gas supply unit 330 supplies a reducing gas into the processing container 310 through the pipe 331 and the gas inlet 313. As the reducing gas, forming gas, H2 gas, formic acid, etc. can be used.

[0083] In the reduction annealing processing apparatus 500 configured as described above, first, a substrate W after being processed by the GCIB irradiation apparatus 400 is carried into the processing container 310 by a transport 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 becomes 200 to 430 ° C, for example, 400 ° C.

[0084] Next, a reducing gas is supplied from the gas supply unit 330 into the processing container 310, and a reduction annealing process is performed on the substrate W on the heating plate 320. Thereby, the oxidized portion of the Ru film is reduced, the crystallization of the Ru film is promoted, and the Ru film is made to have a lower resistance. The processing time at this time may be about 5 to 120 minutes.

[0085] After supplying 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 container 310 by a transport mechanism (not shown).

[0086] Note that the reduction annealing processing apparatus 500 is actually incorporated into a system configured such that a substrate is conveyed from a substrate storage container disposed at the loading / unloading station to the reduction annealing processing apparatus 500 by a conveyance mechanism.

[0087] Note that in the above example, the reduction annealing processing apparatus 500 that performs heating annealing at normal pressure while supplying a reducing gas has been described. However, as the reduction annealing processing apparatus 500, an apparatus that performs plasma annealing of a substrate with a gas plasma containing a hydrogen element may also be used. As an apparatus that performs such plasma annealing, a substrate is placed on a substrate mounting table in a processing container, the inside of the processing container is set to a reduced pressure (vacuum) state, and a gas containing a hydrogen element such as H2 gas or H2 gas + inert gas is supplied from a gas supply unit, and a high-frequency electric field is formed between the substrate mounting table and an upper electrode to generate plasma.

[0088] When performing normal pressure processing using the reduction annealing processing apparatus 500 that performs heating annealing, it is necessary to return from the processing by the GCIB irradiation apparatus 400 performed in a vacuum to normal pressure. On the other hand, since the reduction annealing process is a vacuum process in the case of plasma annealing, the GCIB irradiation process and the hydrogen plasma process can be performed in-situ, which is efficient.

[0089] [Substrate Conveyance Mechanism] The substrate conveyance mechanisms 600 and 700 each convey a substrate in a state where a plurality of substrates are 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 processing apparatus 500. The substrate conveyance mechanisms 600 and 700 preferably convey the substrate storage container while maintaining it 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] [Control Unit] The control unit 800 controls each component of the substrate processing system 200, namely, the electroless plating apparatus 300, the GCIB irradiation apparatus 400, the reduction annealing apparatus 500, and the substrate transfer mechanisms 600 and 700. The control unit 800 includes a main control unit having a CPU (computer), an input device, an output device, a display device, and a storage device. The main control unit of the control unit 800 causes the substrate processing system 200 to execute a desired operation based on, for example, a processing recipe stored in a storage medium built into the storage device or a storage medium set in the storage device.

[0091] In the substrate processing system 200, under the control of the control unit 800, by operating the electroless plating apparatus 300, the GCIB irradiation apparatus 400, and the reduction annealing apparatus 500 configured as described above as described above, a substrate processing method according to an embodiment can be realized.

[0092] <Experimental Example> Next, experimental examples will be described. Here, after forming a Ru film as a metal film by electroless plating, a sample that was subjected to reduction annealing after performing a step of irradiating GCIB under various conditions was evaluated for the film state and resistivity. The reduction annealing treatment was performed at 400 ° C. for 10 minutes using forming gas (H2 gas concentration 4%). In the step of irradiating GCIB, Ar gas or N2 gas was used as the inert gas. 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. In the case of N2 gas, the acceleration voltage was changed to 5 kV, 13 kV, 17 kV, 20 kV, 25 kV, and 30 kV. For comparison, the film state and resistivity were also evaluated for a sample that was subjected to reduction annealing under the same conditions without performing the step of irradiating GCIB after forming a Ru film by electroless plating.

[0093] As a result, for the comparative sample without the step of irradiating with GCIB, the resistivity was 18.5 μΩcm, and cracks were observed in the film. On the other hand, when the reduction annealing treatment was performed after the step of irradiating with GCIB using Ar gas, and when the reduction annealing treatment was performed after the step of irradiating with GCIB using N2 gas, the resistivity and the presence or absence of cracks in the film were as shown in Table 1 and Table 2, respectively.

[0094]

Table 1

[0095]

Table 2

[0096] That is, when the reduction annealing treatment was performed after the step of irradiating with GCIB using Ar gas, as shown in Table 1, when the acceleration voltage was 9 kV and 13 kV, an improvement in resistivity was observed, but some cracks remained in the film. When the acceleration voltage was 17 to 25 kV, the resistivity was lower than that of the comparative sample, and no cracks were observed in the film. When the acceleration voltage was 30 kV, the resistivity was comparable to that of the comparative sample, but no cracks were observed in the film. Also, when the reduction annealing treatment was performed after the step of irradiating with GCIB using N2 gas, as shown in Table 2, when the acceleration voltage was 5 kV, no improvement in resistivity was observed, and almost no improvement in cracks in the film was observed. When the acceleration voltage was 13 to 25 kV, the resistivity was improved in many samples, and no cracks were observed in the film. Even when the acceleration voltage was 30 kV, the resistivity was 16.6 μΩcm, and no cracks were observed in the film, but a tendency of saturation of the effect was observed.

[0097] <Other applications> As described above, the embodiments have been described. However, the embodiments disclosed this time should be considered as illustrative in all respects and not restrictive. The above embodiments may be omitted, substituted, or changed in various forms without departing from the scope and gist of the appended claims.

[0098] For example, the electroless plating apparatus of the above embodiment is merely an example, and apparatuses with various other configurations can be used. Also, the GCIB irradiation apparatus is 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 to irradiate the substrate with GCIB. Further, the reduction annealing apparatus of the above embodiment is merely an example, and the apparatus form is not limited as long as it can perform heat annealing treatment or plasma annealing treatment.

[0099] Furthermore, in the above embodiment, the case where an Ru film is formed as a metal film on the substrate of FIG. 3 and bottom-up growth is selectively performed from the lower layer wiring at the bottom of the via is illustrated. However, the structure of the substrate is not limited to that of FIG. 3, and the metal constituting the metal film may be any metal formed as a wiring layer by electroless plating.

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

Explanation of Reference Numerals

[0101] 101; Lower layer wiring 102; Insulating film 102a; Nitride film 102b; Oxide film 103; Via 105; Metal film (Ru film) 110; Structural part 200; Substrate processing system 300; Electroless plating apparatus 400; GCIB irradiation apparatus 500; Reduction annealing apparatus 600, 700; Substrate transfer mechanism 800; Control unit W; Substrate

Claims

1. A step of forming a metal film on a substrate by electroless plating; A step of irradiating a 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; A step of subjecting the substrate to a reduction annealing treatment after the step of irradiating the gas cluster ion beam; A substrate processing method comprising:

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 that is metal-rich with a low oxygen concentration 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 so that the underlying wiring is exposed on a bottom surface. The substrate processing method according to claim 1 or 2, wherein the metal film is embedded in the via.

5. The substrate processing method according to claim 4, wherein 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.

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

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

10. The step of 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 be the metal film, and drying the substrate. The substrate processing method according to claim 1 or 2.

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

14. The gas cluster ion beam irradiation device irradiates the surface of the metal film with the gas cluster ion beam, so that a crystalline surface modification layer with a low oxygen concentration and rich in metal is formed on the surface of the metal film. 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 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 treatment device is a device that heats and anneals 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 treatment device is a plasma annealing device that processes 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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