Plating method

Abstract

Provided is a technique capable of uniformizing the height of bumps.　The present invention provides a plating method using a plating apparatus 1000 including a plating tank 10, a substrate holder 30, a power supply 80, and a stirring mechanism 60, the method including: controlling the power supply so that a positive direction current for depositing a metal on a substrate Wf from a plating liquid and a reverse current pulse, which is a pulsed current flowing in a direction opposite from the positive direction current, are supplied to the substrate and an anode 11 a plurality of times during the execution of plating processing for plating the substrate; acquiring a substrate voltage fluctuation width after the reverse current pulse is supplied during the execution of the plating processing; and executing control for changing the stirring strength of the stirring mechanism according to the acquired fluctuation width.

Description

Plating Method

[0001] The present invention relates to a plating method.

[0002] Conventionally, plating methods for plating a substrate have been known (see, for example, Patent Documents 1, 2, and 3). A plating apparatus used in such a plating method includes, for example, a plating tank that stores a plating solution and in which an anode is disposed, a substrate holder that holds a substrate serving as a cathode facing the anode, a power source configured to supply current to the substrate and the anode, and an agitation mechanism configured to agitate the plating solution. Furthermore, in such conventional plating apparatuses, the plating solution in the plating tank contains an accelerator to accelerate plating.

[0003] Patent Documents 2 and 3 also disclose a technique for forming bumps by depositing metal on a substrate by plating, and a technique for controlling a power supply so that forward current and reverse current pulses are supplied to the substrate and the anode.

[0004] Japanese Patent No. 7079388 Japanese Patent No. 7357824 Japanese Patent Laid-Open No. 2006-131926

[0005] In recent years, there has been a demand for uniform height of bumps formed on a substrate by plating, and in this respect, there is room for improvement in conventional techniques.

[0006] The present invention has been made in view of the above, and one of its objects is to provide a technique that can make the height of bumps uniform.

[0007] (Aspect 1) In order to achieve the above object, a plating method according to one aspect of the present invention is a plating method using a plating apparatus including: a plating tank that stores a plating solution containing an accelerator that accelerates plating and in which an anode is disposed; a substrate holder configured to hold a substrate as a cathode so as to face the anode; a power source configured to supply current to the substrate and the anode; and a stirring mechanism configured to stir the plating solution, wherein, during a plating process for plating the substrate, a forward current for depositing metal from the plating solution onto the substrate and a reverse current for depositing metal from the plating solution onto the substrate are applied. The plating method includes controlling the power supply so that a reverse current pulse, which is a current flowing in pulses, is supplied to the substrate and the anode multiple times, and acquiring a fluctuation range of the voltage of the substrate after the reverse current pulse is supplied during the plating process, and executing control to change the stirring strength of the stirring mechanism in accordance with the acquired fluctuation range, wherein the fluctuation range is the difference between the voltage immediately before the reverse current pulse is supplied and the minimum value of the voltage that occurs after the reverse current pulse is supplied, or the difference between the minimum value and the maximum value of the voltage that occurs after the minimum value has occurred.

[0008] According to this aspect, the fluctuation width of the voltage after the reverse current pulse is supplied can be kept within a predetermined range, thereby making it possible to uniformize the height of the bumps formed by the metal deposited on the substrate.

[0009] (Aspect 2) In the aspect 1, the stirring mechanism may include a paddle disposed between the substrate and the anode and configured to stir the plating solution.

[0010] (Aspect 3) In the aspect 1, the stirring mechanism may include a rotation mechanism configured to rotate the substrate holder to stir the plating solution.

[0011] (Aspect 4) In the above aspect 1, the stirring mechanism may include a plating solution flow mechanism configured to flow the plating solution in the plating tank, thereby stirring the plating solution.

[0012] (Aspect 5) In any one of Aspects 1 to 4 above, the fluctuation range of the voltage of the substrate after the reverse current pulse is supplied may include a fluctuation range of the voltage between the substrate and the anode after the reverse current pulse is supplied, or a fluctuation range of the voltage between the substrate and a reference electrode disposed in the plating tank after the reverse current pulse is supplied.

[0013] (Aspect 6) In order to achieve the above object, a plating method according to one aspect of the present invention is a plating method using a plating apparatus including: a plating tank that stores a plating solution containing an accelerator for accelerating plating and in which an anode is disposed; a substrate holder configured to hold a substrate as a cathode facing the anode; a power source configured to supply current to the substrate and the anode; and a stirring mechanism configured to stir the plating solution, wherein, before a plating process is performed on the substrate, a reverse current pulse, which is a current flowing in a pulsed manner in a direction opposite to a forward current for depositing metal from the plating solution on the substrate, is supplied to the substrate and the anode. and determining in advance a control map of the stirring intensity of the stirring mechanism so that a fluctuation range of the voltage of the substrate after the reverse current pulse is supplied falls within a predetermined range; and controlling the power supply during the plating process so that the forward current and the reverse current pulse are supplied to the substrate and the anode multiple times while controlling the stirring intensity of the stirring mechanism based on the control map determined in advance, wherein the fluctuation range is the difference between the voltage immediately before the reverse current pulse is supplied and a minimum value of the voltage that occurs after the reverse current pulse is supplied, or the difference between the minimum value and a maximum value of the voltage that occurs after the minimum value has occurred.

[0014] According to this aspect, the fluctuation width of the voltage after the reverse current pulse is supplied can be kept within a predetermined range, thereby making it possible to uniformize the height of the bumps formed by the metal deposited on the substrate by plating.

[0015] FIG. 6A is a perspective view showing the overall configuration of a plating apparatus according to an embodiment. FIG. 6B is a schematic view showing a state in which a substrate according to an embodiment is immersed in a plating solution. FIG. 6C is a schematic view showing a paddle according to an embodiment. FIG. 6A is a schematic view showing a surface configuration of a substrate according to an embodiment. FIG. 6B is a schematic view showing an example of an opening pattern of a photoresist layer according to an embodiment. FIG. 6C is a graph showing an example of measuring the height of bumps in each pattern region when multiple bumps are formed on a substrate having a photoresist layer as exemplified in FIG. 6B. FIG. 8A and FIG. 8B are diagrams for explaining the voltage fluctuation range. FIG. 8B is an example of a flowchart showing a plating method according to an embodiment. FIG. 10A and FIG. 10B are graphs showing experimental results using a substrate with bump pattern 1. FIG. 11A and FIG. 11B are graphs showing experimental results using a substrate with bump pattern 2. FIG. 11C is an example of a flowchart showing a plating method according to an embodiment.

[0016] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the drawings are diagrammatically illustrated to facilitate understanding of the characteristics of the components, and the dimensional ratios of the components may not be the same as those in reality. In addition, some of the drawings show an X-Y-Z Cartesian coordinate system for reference. In these Cartesian coordinate systems, the Z direction corresponds to the upward direction, and the -Z direction corresponds to the downward direction (the direction in which gravity acts).

[0017] (Embodiment 1) Fig. 1 is a perspective view showing the overall configuration of a plating apparatus 1000 according to an embodiment. Fig. 2 is a plan view (top view) showing the overall configuration of the plating apparatus 1000 according to an embodiment. As shown in Figs. 1 and 2, the plating apparatus 1000 includes a load port 100, a transfer robot 110, an aligner 120, a pre-wet module 200, a pre-soak module 300, a plating module 400, a cleaning module 500, a spin rinse dryer 600, a transfer device 700, and a control module 800.

[0018] The load port 100 is a module for loading substrates stored in a cassette such as a FOUP (not shown) into the plating apparatus 1000 and unloading substrates from the plating apparatus 1000 to the cassette. In this embodiment, four load ports 100 are arranged horizontally, but the number and arrangement of the load ports 100 are optional. The transfer robot 110 is a robot for transporting substrates, and is configured to transfer substrates between the load port 100, the aligner 120, the pre-wet module 200, and the spin rinse dryer 600. When transferring substrates between the transfer robot 110 and the transfer device 700, the transfer robot 110 and the transfer device 700 can transfer the substrates via a temporary stage (not shown).

[0019] The aligner 120 is a module for aligning the positions of the substrate's orientation flat, notch, and the like in a predetermined direction. In this embodiment, two aligners 120 are arranged horizontally, but the number and arrangement of the aligners 120 are optional. The prewet module 200 wets the surface of the substrate to be plated with a treatment liquid such as pure water or degassed water before plating, thereby replacing air within a pattern formed on the substrate surface with the treatment liquid. The prewet module 200 is configured to perform a prewet process that replaces the treatment liquid within the pattern with a plating liquid during plating, thereby making it easier to supply the plating liquid within the pattern. In this embodiment, two prewet modules 200 are arranged vertically, but the number and arrangement of the prewet modules 200 are optional.

[0020] The presoak module 300 is configured to perform a presoak process, which involves etching away, for example, an oxide film with high electrical resistance present on the surface of a seed layer formed on the surface of a substrate to be plated before plating, using a treatment solution such as sulfuric acid or hydrochloric acid to clean or activate the surface of the substrate to be plated. In this embodiment, two presoak modules 300 are arranged vertically, but the number and arrangement of the presoak modules 300 are optional. The plating module 400 applies plating to the substrate. In this embodiment, two sets of 12 plating modules 400 are arranged vertically, three vertically and four horizontally, for a total of 24 plating modules 400, but the number and arrangement of the plating modules 400 are optional.

[0021] The cleaning module 500 is configured to perform a cleaning process on the substrate to remove plating solution and the like remaining on the substrate after plating. In this embodiment, two cleaning modules 500 are arranged vertically, but the number and arrangement of the cleaning modules 500 are optional. The spin rinse dryer 600 is a module for drying the substrate after cleaning by rotating it at high speed. In this embodiment, two spin rinse dryers 600 are arranged vertically, but the number and arrangement of the spin rinse dryers 600 are optional. The transport device 700 is a device for transporting substrates between multiple modules within the plating apparatus 1000. The control module 800 is configured to control the multiple modules of the plating apparatus 1000 and can be configured, for example, as a general computer or a dedicated computer equipped with an input / output interface with an operator.

[0022] An example of a series of plating processes performed by the plating apparatus 1000 will be described. First, a substrate stored in a cassette is loaded into the load port 100. Next, the transfer robot 110 removes the substrate from the cassette in the load port 100 and transfers the substrate to the aligner 120. The aligner 120 aligns the positions of the orientation flat, notch, and the like of the substrate to a predetermined direction. The transfer robot 110 delivers the substrate, whose direction has been aligned by the aligner 120, to the pre-wet module 200.

[0023] The pre-wet module 200 performs a pre-wet process on the substrate. The transport device 700 transports the substrate that has been subjected to the pre-wet process to the pre-soak module 300. The pre-soak module 300 performs a pre-soak process on the substrate. The transport device 700 transports the substrate that has been subjected to the pre-soak process to the plating module 400. The plating module 400 platings the substrate.

[0024] The transfer device 700 transfers the substrate after plating to the cleaning module 500. The cleaning module 500 performs a cleaning process on the substrate. The transfer device 700 transfers the substrate after cleaning to the spin rinse dryer 600. The spin rinse dryer 600 dries the substrate. The transfer robot 110 receives the substrate from the spin rinse dryer 600 and transfers the dried substrate to a cassette on the load port 100. Finally, the cassette containing the substrate is removed from the load port 100.

[0025] It should be noted that the configuration of the plating apparatus 1000 described in FIGS. 1 and 2 is merely an example, and the configuration of the plating apparatus 1000 is not limited to the configurations shown in FIGS.

[0026] Next, a description will be given of the plating module 400. Since the multiple plating modules 400 included in the plating apparatus 1000 according to this embodiment have the same configuration, only one plating module 400 will be described.

[0027] Fig. 3 is a schematic diagram showing the configuration of the plating module 400 in the plating apparatus 1000. Specifically, Fig. 3 schematically shows the plating module 400 in a state before the substrate Wf is immersed in the plating solution Ps. Fig. 4 is a schematic diagram showing the state after the substrate Wf is immersed in the plating solution Ps.

[0028] 3 and 4 is, for example, a plating apparatus (a so-called cup-type plating apparatus) in which the substrate Wf is immersed in the plating solution Ps with its surface oriented horizontally. However, the configuration of the plating apparatus 1000 is not limited to this, and may be, for example, a plating apparatus in which the substrate Wf is immersed in the plating solution Ps with its surface oriented non-horizontally (for example, vertically relative to the ground).

[0029] 3 and 4, a plating module 400 of a plating apparatus 1000 includes a plating tank 10, an overflow tank 20, a substrate holder 30, and a paddle 70 as an example of an agitation mechanism 60. As shown in FIG. 3, the plating module 400 also includes a rotation mechanism 40, a tilting mechanism 45, and an elevation mechanism 50. As shown in FIG. 3, the plating module 400 also includes sensors 130. As shown in FIG. 4, the plating module 400 also includes a power supply 80 and a plating solution flow mechanism 90.

[0030] The plating tank 10 according to this embodiment is a bottomed container with an opening at the top. Specifically, the plating tank 10 has a bottom wall 10a and an outer peripheral wall 10b extending upward from the outer periphery of the bottom wall 10a, with the upper portion of the outer peripheral wall 10b being open. The shape of the outer peripheral wall 10b of the plating tank 10 is not particularly limited, but the outer peripheral wall 10b according to this embodiment has a cylindrical shape, for example. A plating solution Ps is stored inside the plating tank 10.

[0031] The plating solution Ps may be any solution containing ions of the metal elements that make up the plating film, and specific examples thereof are not particularly limited. In this embodiment, copper plating is used as an example of plating, and a copper sulfate solution is used as an example of plating solution Ps. The plating solution Ps may also contain certain additives.

[0032] The plating solution Ps may contain, for example, an accelerator that accelerates plating (specifically, an accelerator that accelerates the formation of a plating film). For example, SPS (bis(3-sulfopropyl)disulfide) or the like may be used as the accelerator.

[0033] An anode 11 is disposed inside the plating tank 10. The specific type of the anode 11 is not particularly limited, and may be an insoluble anode or a soluble anode. In the present embodiment, an insoluble anode is used as an example of the anode 11. The specific type of the insoluble anode is not particularly limited, and platinum, iridium oxide, or the like may be used.

[0034] As illustrated in Figures 3 and 4, an ion resistor 12 may be disposed above the anode 11 inside the plating tank 10. Specifically, as illustrated in the partially enlarged view of Figure 4, the ion resistor 12 is configured as a porous plate member having a plurality of holes 12a (pores). The holes 12a are provided so as to connect the lower surface and the upper surface of the ion resistor 12.

[0035] The ion resistor 12 is provided to homogenize the electric field formed between the anode 11 and the substrate Wf serving as the cathode. By disposing the ion resistor 12 in the plating tank 10 as in this embodiment, it is possible to easily homogenize the thickness of the plating film (plating layer) formed on the substrate Wf.

[0036] As illustrated in Figures 3 and 4, a membrane 16 may be disposed inside the plating tank 10 above the anode 11 and below the ionic resistor 12. In this case, the membrane 16 divides the interior of the plating tank 10 into an anode chamber 17a below the membrane 16 and a cathode chamber 17b above the membrane 16. The anode 11 is disposed in the anode chamber 17a, and the ionic resistor 12 and the substrate Wf are disposed in the cathode chamber 17b. The membrane 16 is configured to allow ionic species, including metal ions, contained in the plating solution Ps to pass through the membrane 16 while inhibiting non-ionic plating additives contained in the plating solution Ps from passing through the membrane 16. For example, an ion exchange membrane can be used as such a membrane 16.

[0037] 4, the plating solution flow mechanism 90 is configured to flow the plating solution Ps in the plating tank 10. The flow of the plating solution Ps in the plating tank 10 causes the plating solution Ps in the plating tank 10 to be agitated. The plating solution flow mechanism 90 according to this embodiment includes, for example, a first flow mechanism 91a and a second flow mechanism 91b.

[0038] The first flow mechanism 91a is a mechanism for causing the plating solution Ps in the anode chamber 17a to flow. The second flow mechanism 91b is a mechanism for causing the plating solution Ps in the cathode chamber 17b to flow. The first flow mechanism 91a is connected to the anode chamber 17a via a pipe 92a. The second flow mechanism 91b is connected to the cathode chamber 17b via a pipe 92b. The first flow mechanism 91a and the second flow mechanism 91b each include a pump or the like for pressure-feeding the plating solution Ps.

[0039] 3 and 4, the plating tank 10 is provided with a supply port for supplying the plating solution Ps to the plating tank 10. Specifically, the outer peripheral wall 10b of the plating tank 10 according to this embodiment is provided with a first supply port 13a for supplying the plating solution Ps to the anode chamber 17a and a second supply port 13b for supplying the plating solution Ps to the cathode chamber 17b. The plating solution Ps discharged from the first discharge port 14a is pressure-fed by the first flow mechanism 91a and is again supplied to the anode chamber 17a from the first supply port 13a.

[0040] The overflow tank 20 is a bottomed container disposed outside the plating tank 10. The overflow tank 20 is provided to temporarily store the plating solution Ps that has exceeded the upper end of the outer wall 10b of the plating tank 10 (i.e., the plating solution Ps that has overflowed from the plating tank 10). The plating solution Ps stored in the overflow tank 20 is discharged from the second outlet 14b, then pressure-fed by the second flow mechanism 91b, and again supplied to the cathode chamber 17b from the second supply port 13b.

[0041] The substrate holder 30 holds the substrate Wf as a cathode so that the surface Wfa to be plated of the substrate Wf faces the anode 11. In this embodiment, the surface Wfa to be plated of the substrate Wf is specifically provided on the surface (lower surface) facing downward of the substrate Wf.

[0042] The substrate holder 30 is connected to a rotation mechanism 40. The rotation mechanism 40 is a mechanism for rotating the substrate holder 30. "R1" illustrated in FIG. 3 is an example of the rotation direction of the substrate holder 30. A known rotation motor or the like can be used as the rotation mechanism 40. The tilt mechanism 45 is a mechanism for tilting the rotation mechanism 40 and the substrate holder 30. The lifting mechanism 50 is supported by a support shaft 51 extending in the vertical direction. The lifting mechanism 50 is a mechanism for raising and lowering the substrate holder 30, the rotation mechanism 40, and the tilting mechanism 45 in the vertical direction. A known lifting mechanism such as a linear actuator can be used as the lifting mechanism 50.

[0043] The control module 800 includes a microcomputer, which includes a processor 801, a storage device 802 as a non-transitory storage medium, etc. The control module 800 controls the operation of the plating module 400 by operating the processor 801 based on instructions from a program stored in the storage device 802.

[0044] 3, the sensors 130 detect various types of information used for various controls of the control module 800 and transmit the detection results to the control module 800. The sensors 130 include, for example, a current sensor that detects the current value (A) between the anode 11 and the substrate Wf.

[0045] The sensors 130 also include a voltage sensor that detects the voltage value (V) of the substrate Wf. The voltage sensor according to this embodiment is also configured to detect the "fluctuation range (Wd) of the voltage of the substrate Wf," which will be described later.

[0046] The voltage sensor may detect the voltage value between the substrate Wf and the anode 11, or may detect the "voltage fluctuation range (Wd) between the substrate Wf and the anode 11." Alternatively, the voltage sensor may detect the voltage value between the substrate Wf and the reference electrode 18 (illustrated in FIG. 4 ), or may detect the "voltage fluctuation range (Wd) between the substrate Wf and the reference electrode 18." The reference electrode 18 is disposed inside the plating tank 10 and is used as a reference electrode instead of the anode 11 when detecting the voltage or voltage fluctuation range. The specific location of the reference electrode 18 inside the plating tank 10 is not particularly limited, but in the present embodiment, as an example, it is disposed near the anode 11 of the plating tank 10 (on the bottom wall 10 a in the present embodiment).

[0047] The sensors 130 also include a speed sensor for detecting the movement speed (rpm or m / sec) of the paddle 70. The sensors 130 also include a rotation speed sensor for detecting the rotation speed (rpm) of the substrate holder 30. The sensors 130 also include a flow rate sensor for detecting the flow rate (m / sec) of the plating solution Ps in the plating tank 10. Specifically, the flow rate sensors include a flow rate sensor for detecting the flow rate of the plating solution Ps in the anode chamber 17a and a flow rate sensor for detecting the flow rate of the plating solution Ps in the cathode chamber 17b.

[0048] 4, the power supply 80 is electrically connected to the substrate Wf and the anode 11, and is configured to supply current between the substrate Wf and the anode 11. The operation of the power supply 80 is controlled by a control module 800.

[0049] The control module 800 of this embodiment controls the power supply 80 so that, at least during the "plating process" in which plating is performed on the substrate Wf, a "forward current" for depositing metal from the plating solution Ps onto the substrate Wf and a "reverse current pulse," which is a current flowing in pulses in the opposite direction to the forward current, are supplied to the substrate Wf and the anode 11.

[0050] Specifically, the control module 800 controls the power supply 80 so that, for example, a forward current is supplied and then a reverse current pulse is supplied. More specifically, the control module 800 according to the present embodiment controls the power supply 80 so that, for example, a forward current and a reverse current pulse are alternately supplied.

[0051] 5 is a schematic plan view of the paddle 70. Referring to FIGS. 3, 4, and 5, the paddle 70 is disposed between the substrate Wf and the anode 11 (specifically, in the present embodiment, as an example, between the substrate Wf and the ion resistor 12). The paddle 70 is driven by a driving device 77 that receives instructions from a control module 800. Driving the paddle 70 agitates the plating solution Ps in the plating tank 10.

[0052] The paddle 70 according to the present embodiment is, for example, driven alternately in a "first direction (in the present embodiment, the X direction as an example)" parallel to the substrate Wf and a "second direction (in the present embodiment, the −X direction as an example)" opposite to the first direction. That is, the paddle 70 according to the present embodiment moves back and forth in the X-axis direction as an example.

[0053] 5, the paddle 70 according to this embodiment includes, as an example, a plurality of stirring members 71a extending in a direction (the direction of the Y axis) perpendicular to the first and second directions of the paddle 70. A gap is provided between adjacent stirring members 71a. One end of each of the stirring members 71a is connected to a connecting member 72a, and the other end is connected to a connecting member 72b.

[0054] However, the configuration of the paddle 70 is not limited to this, and various known paddles such as those exemplified in Patent Document 1 can be used.

[0055] The paddle 70 only needs to be disposed inside the plating tank 10 at least when stirring the plating solution Ps, and does not need to be disposed inside the plating tank 10 all the time. For example, when the driving of the paddle 70 is stopped and the plating solution Ps is not stirred by the paddle 70, the paddle 70 may not be disposed inside the plating tank 10.

[0056] Note that "the moving speed of the paddle 70 is N (rpm)" specifically means that the paddle 70 makes one reciprocating movement (i.e., the paddle 70 starts from a predetermined position, moves, for example, in a first direction, then moves in a second direction, moves in the first direction again, and returns to the predetermined position) N times per minute. The faster the moving speed of the paddle 70, the stronger the stirring strength of the plating solution Ps by the paddle 70. In other words, the moving speed of the paddle 70 is an example of the "stirring strength of the plating solution Ps."

[0057] Fig. 6A is a schematic diagram for explaining the surface structure of the substrate Wf. Specifically, Fig. 6A is a schematic cross-sectional view showing bumps 143 formed on the substrate Wf by plating. Specifically, the bumps 143 are formed from a metal (e.g., Cu) deposited on the substrate Wf.

[0058] As illustrated in Fig. 6(A), a thin metal seed layer 140 is provided in advance on the entire surface of the substrate Wf according to this embodiment. During plating, power is supplied to the surface of the substrate Wf via this seed layer 140. A photoresist layer 141 is provided on the surface of the seed layer 140 opposite the substrate Wf side. The photoresist layer 141 has openings 142 in areas where bumps 143 are to be formed. Note that "φ" illustrated in Fig. 6(A) is the diameter (μm) of the openings 142 in the photoresist layer 141, and "BH" is the height (μm) of the bumps 143.

[0059] 6B is a schematic diagram showing an example of an opening pattern in the photoresist layer 141. Nos. 1 and 2 in FIG. 6B show examples in which the diameter φ of the openings 142 is relatively small (for example, 30 μm), while Nos. 3 and 4 show examples in which the diameter φ of the openings 142 is relatively large (for example, 75 μm). Comparing Nos. 1 and 2, the openings 142 are arranged at a higher density in No. 1 than in No. 2. Comparing Nos. 3 and 4, the openings 142 are arranged at a higher density in No. 3 than in No. 4.

[0060] The substrate Wf provided with the photoresist layer 141 as described above is held by the substrate holder 30 and immersed in the plating solution Ps in the plating tank 10 to perform the plating process. During the plating process, the surface of the substrate Wf, except for the openings 142 in the photoresist layer 141, is shielded from the plating solution Ps by the photoresist layer 141. As a result, a plating film grows only in the openings 142 in the photoresist layer 141, thereby forming bumps 143 on the substrate Wf. Note that the photoresist layer 141 may be removed after the plating process.

[0061] Fig. 7 is a graph showing an example of measuring the height (BH) of the bumps 143 in each pattern region when multiple bumps 143 are formed on a substrate Wf having a photoresist layer 141 as exemplified in Fig. 6(B). On the vertical axis of Fig. 7, the height (BH) of each bump 143 corresponding to each of pattern regions P1, P2, P3, and P4 in Fig. 6(B) specifically indicates the average value of the heights of the multiple bumps 143 included in that pattern region.

[0062] The graph on the left of Figure 7 shows the measurement results when a forward current was supplied throughout the entire plating process to form bump 143, and the graph on the right of Figure 7 shows the measurement results when a reverse current pulse was supplied once during the plating process to form bump 143.

[0063] 7, among all the pattern regions, the height (BH) of the bump 143 in pattern region P1 is the smallest, and the height (BH) of the bump 143 in pattern region P4 is the largest. This is because the smaller the diameter φ of the openings 142 and the higher the arrangement density of the openings 142, the more difficult it becomes for metal ions to be sufficiently replenished into the openings 142, resulting in a lower formation rate of the plating film. Here, the difference between the maximum and minimum heights (BH) of the bumps 143 is defined as the "bump height variation (ΔBH)."

[0064] 7, it can be seen that when a reverse current pulse is supplied during the plating process (the graph on the right in FIG. 7), the bump height variation (ΔBH) is smaller than when a reverse current pulse is not supplied (the graph on the left in FIG. 7). Thus, by supplying a reverse current pulse, it is possible to make the height of the bumps 143 uniform.

[0065] 8A and 8B are diagrams illustrating the voltage fluctuation width (Wd). The horizontal axis of each of FIGS. 8A and 8B represents time, and the vertical axis represents the voltage of the substrate Wf during plating (specifically, the voltage between the substrate Wf and the anode 11). As illustrated in FIGS. 8A and 8B, when a reverse current pulse is supplied after a forward current is supplied during plating, the voltage drops, resulting in a minimum voltage value. This is thought to be due to the accelerator contained in the plating solution Ps being re-adsorbed onto the substrate Wf by the reverse current pulse, resulting in a voltage drop and a minimum voltage value.

[0066] Here, the difference between the voltage immediately before the reverse current pulse is supplied and the minimum value is referred to as the "fluctuation width (Wd)" (FIG. 8A). Alternatively, the difference between the minimum value and the maximum value that occurs after this minimum value may be used as the "fluctuation width (Wd)" (FIG. 8B).

[0067] Even when a constant reverse current pulse is supplied, the fluctuation width (Wd) may change over plating time. Specifically, even when a constant reverse current pulse is supplied, the fluctuation width (Wd) may decrease over plating time (see FIGS. 10A and 11A, described later). In such cases, the fluctuation width (Wd) may not fall within a predetermined range, potentially resulting in insufficient uniformity of bump height. Furthermore, the amount of change in the fluctuation width (Wd) can be kept within a predetermined range by changing the stirring intensity. Therefore, in this embodiment, the control described below in FIG. 9 is performed.

[0068] 9 is an example of a flowchart for explaining the plating method according to this embodiment (Embodiment 1). First, the control module 800 executes a "power supply control process" (step S10) to control the power supply 80 so that forward current and reverse current pulses are supplied multiple times to the substrate Wf and the anode 11 placed in the plating solution Ps during the plating process. Specifically, in step S10, the control module 800 according to this embodiment, for example, causes the power supply 80 to alternately supply forward current and reverse current pulses multiple times.

[0069] In step S10, the control module 800 according to this embodiment supplies, as an example, a constant value of forward current and a constant value of reverse current pulses.

[0070] The supply time of the forward current is not particularly limited, but may be a length that occupies the majority of the total time during which the plating process is performed. In the present embodiment, the value of the forward current is a constant value, but this is not limited thereto and may vary over time. The specific value of the period during which the reverse current pulse is supplied is not particularly limited, but may be, for example, about 0.1 seconds to several seconds. The magnitude of the reverse current pulse is not particularly limited, but it is preferable to set it to a value that allows sufficient desorption of the accelerator.

[0071] Furthermore, as exemplified in the aforementioned Patent Document 2, after the supply of the reverse current pulse, a "rest period" may be provided in which the value of the supply current from the power supply 80 (current output of the power supply 80) is set to zero. In this case, after the lapse of this rest period, a forward current is supplied again. Note that the specific value of the length of the "rest period" is not particularly limited, but may be, for example, a value of about 0.1 seconds to several seconds.

[0072] In step S20, the control module 800 executes the "agitation intensity control process" during the execution of the plating process. Specifically, the control module 800 according to the present embodiment executes the "agitation intensity control process" during the execution of the power supply control process according to step S10 during the execution of the plating process.

[0073] More specifically, in the stirring intensity control process in step S20, the control module 800 acquires the fluctuation width (Wd) of the voltage of the substrate Wf after the reverse current pulse is supplied, and then executes control to change the stirring intensity of the stirring mechanism 60 in accordance with the fluctuation width (Wd) of the voltage so that the acquired fluctuation width (Wd) falls within a predetermined range.

[0074] As a specific example of the "fluctuation width (Wd) of the voltage of the substrate Wf after the reverse current pulse is supplied," the "fluctuation width (Wd) of the voltage between the substrate Wf and the anode 11 after the reverse current pulse is supplied" may be used. Alternatively, the "fluctuation width (Wd) of the voltage between the substrate Wf and the reference electrode 18 after the reverse current pulse is supplied" may be used. In the following description of this embodiment, the "fluctuation width (Wd) of the voltage between the substrate Wf and the anode 11 after the reverse current pulse is supplied" is used as a specific example of the "fluctuation width (Wd) of the voltage of the substrate Wf after the reverse current pulse is supplied."

[0075] Specifically, a control map (data map) that defines the relationship between the fluctuation range (Wd) of the voltage between the substrate Wf and the anode 11 after a reverse current pulse is supplied and the stirring intensity (for example, the movement speed of the paddle 70) is stored (set) in advance in, for example, the storage device 802 of the control module 800 according to this embodiment. This control map defines the relationship between the fluctuation range (Wd) of the voltage and the stirring intensity so that, when the stirring intensity is controlled based on this control map, the fluctuation range (Wd) of the voltage falls within a predetermined range. This control map may be obtained in advance, for example, by conducting experiments or the like, and stored in the storage device 802.

[0076] As an example, this control map defines the relationship between the voltage fluctuation range (Wd) and the stirring intensity so that the smaller the voltage fluctuation range (Wd), the smaller the stirring intensity (e.g., the slower the movement speed of the paddle 70).

[0077] In step S20, the control module 800 acquires the fluctuation width (Wd) of the voltage between the substrate Wf and the anode 11 after the reverse current pulse is supplied based on the detection results of the sensors 130 (e.g., voltage sensors). Then, the control module 800 extracts the stirring intensity corresponding to the acquired fluctuation width of the voltage from the control map, and controls the stirring mechanism 60 (e.g., the paddle 70) so as to obtain the extracted stirring intensity. This makes it possible to keep the actual fluctuation width (Wd) within a predetermined range.

[0078] Note that "keeping the voltage fluctuation range (Wd) within a predetermined range" specifically means keeping the voltage fluctuation range (Wd) within a range equal to or greater than a "predetermined lower limit value" and equal to or less than a "predetermined upper limit value." In other words, "keeping the voltage fluctuation range (Wd) within a predetermined range" means preventing the voltage fluctuation range (Wd) from becoming too small below the lower limit value, and preventing it from becoming too large above the upper limit value.

[0079] When changing the stirring intensity of the stirring mechanism 60, the control module 800 may change the stirring intensity of the stirring mechanism 60 stepwise as the plating process progresses, or may change the stirring intensity continuously.

[0080] As a specific example, the control module 800 may gradually slow the movement speed of the paddle 70 over time, for example, to 150 rpm, 135 rpm, and 100 rpm (see FIG. 10B , described later). Alternatively, the control module 800 may continuously slow the movement speed of the paddle 70 over time, for example, to 150 rpm, 149 rpm, 148 rpm, ..., and 100 rpm.

[0081] Note that the specific value of the predetermined range of the voltage fluctuation width (Wd) in step S20 is not particularly limited, but the smaller the change in this fluctuation width (Wd) (change over time), the more uniform the height of the bumps 143. Based on this viewpoint, an appropriate value of the predetermined range may be determined in advance by experiment or the like and stored in the storage device 802.

[0082] As a specific example, a numerical range of the voltage fluctuation width (Wd) may be determined by experiment or the like so that the uniformity of the bump height (specifically, the difference between the maximum and minimum heights of the bumps 143 within one die) is, for example, 5.0 μm or less within the predetermined range of the voltage fluctuation width (Wd). In this case, the uniformity of the bump height can be kept to 5.0 μm or less.

[0083] Alternatively, the predetermined range of the voltage fluctuation width (Wd) may be determined based on the voltage fluctuation width when the reverse current pulse is first supplied during plating processing. Specifically, in this case, the predetermined range of the voltage fluctuation width (Wd) may be, for example, 10% to 100% of the voltage fluctuation width when the reverse current pulse is first supplied (note that this specific percentage value may be set appropriately).

[0084] According to the present embodiment as described above, the fluctuation width of the voltage after the reverse current pulse is supplied can be kept within a predetermined range, thereby making it possible to uniformize the height of the bumps 143 formed by the metal deposited on the substrate Wf.

[0085] (First Modification of First Embodiment) In the above-described embodiment, the paddle 70 is used as the stirring mechanism 60, but the present invention is not limited to this configuration. The stirring mechanism 60 may be at least one selected from the paddle 70, the rotation mechanism 40 that rotates the substrate holder 30, and the plating solution flow mechanism 90.

[0086] When the rotation mechanism 40 is used as the stirring mechanism 60, the control module 800 may use the rotation speed (rpm) of the substrate holder 30 as the stirring intensity used in step S20. Specifically, in this case, the control module 800 controls the rotation mechanism 40 in accordance with the voltage fluctuation range in step S20, thereby controlling the rotation speed of the substrate holder 30 in accordance with the voltage fluctuation range.

[0087] Alternatively, when the plating solution flow mechanism 90 is used as the stirring mechanism 60, the control module 800 may use the flow rate (m / sec) of the plating solution Ps in the plating tank 10 as the stirring intensity used in step S20. Specifically, in this case, the control module 800 controls the plating solution flow mechanism 90 in accordance with the fluctuation range of the voltage in step S20, thereby controlling the flow rate of the plating solution Ps in accordance with the fluctuation range of the voltage.

[0088] (Example) An experiment was conducted to confirm the effects of the above-described embodiment. Specifically, a substrate Wf was prepared having a "bump pattern 1" in which bumps 143 with an opening ratio in the range of 5% to 40% were mixed as the arrangement pattern of the bumps 143 (hereinafter referred to as the "bump pattern"), and a substrate Wf having a "bump pattern 2" in which bumps 143 with an opening ratio in the range of 15% to 40% were mixed. Then, plating was performed using these substrates Wf. Table 1 shown below is a table for explaining the results of this experiment.

[0089]

[0090] 10A and 10B are graphs showing experimental results using a substrate Wf with a bump pattern 1. Specifically, Fig. 10A shows the change in voltage between the substrate Wf and the anode 11 when a current is supplied to the substrate Wf and the anode 11 at a constant stirring intensity using the substrate Wf with the bump pattern 1. Fig. 10B shows the change in voltage between the substrate Wf and the anode 11 when a current is supplied to the substrate Wf and the anode 11 with the substrate Wf with the bump pattern 1 and the stirring intensity is controlled in accordance with the voltage fluctuation range so that the voltage fluctuation range falls within a predetermined range, as in the above-described embodiment.

[0091] 11A and 11B are graphs showing experimental results using a substrate Wf with a bump pattern 2. Specifically, Fig. 11A shows the change in voltage between the substrate Wf and the anode 11 when a current is supplied to the substrate Wf and the anode 11 at a constant stirring intensity using a substrate Wf with a bump pattern 2. Fig. 11B shows the change in voltage between the substrate Wf and the anode 11 when a current is supplied to the substrate Wf and the anode 11 with a substrate Wf with a bump pattern 2 and the stirring intensity is controlled in accordance with the voltage fluctuation range so that the voltage fluctuation range falls within a predetermined range, as in the above-described embodiment.

[0092] More specifically, in Fig. 10A, a plating process was performed using a substrate Wf with bump pattern 1 at a constant stirring intensity (the paddle 70 moving speed was constant at 150 rpm) until the plating film thickness reached 40 μm. As a result, as shown in Fig. 10A, the voltage fluctuation range decreased over time. In this case, as shown in Table 1, the uniformity of the bump height (the difference between the maximum and minimum heights of the bumps 143) was 8.5 μm.

[0093] On the other hand, in FIG. 10(B), a plating process was performed using a substrate Wf with bump pattern 1 while controlling the stirring intensity according to the voltage fluctuation range. Specifically, in FIG. 10(B), a plating process was performed using a substrate Wf with bump pattern 1, controlling the stirring intensity of the paddle 70 so that the voltage fluctuation range was within a range of 10% to 150% of the voltage fluctuation range (Wd1) when the reverse current pulse was first applied, until the plating film thickness reached 40 μm. More specifically, the plating process was performed while changing the movement speed of the paddle 70 from 150 rpm, 135 rpm, to 100 rpm as the voltage fluctuation range decreased. As a result, as shown in Table 1, the bump height uniformity was 4.6 μm. In this case, a value of 46% was obtained as the improvement rate of the bump height uniformity.

[0094] 11A, a plating process was performed using a substrate Wf with a bump pattern 2 at a constant stirring intensity (the moving speed of the paddle 70 was constant at 50 rpm) until the thickness of the plated film reached 40 μm. As a result, as shown in Table 1, the uniformity of the bump height was 5.2 μm.

[0095] On the other hand, in FIG. 11B , a plating process was performed using a substrate Wf with a bump pattern 2 while controlling the stirring intensity according to the voltage fluctuation range. Specifically, in FIG. 11B , a plating process was performed using a substrate Wf with a bump pattern 2, controlling the stirring intensity of the paddle 70 so that the voltage fluctuation range was within a range of 10% to 150% of the voltage fluctuation range (Wd1) when the reverse current pulse was first applied, until the plating film thickness reached 40 μm. More specifically, the plating process was performed while changing the movement speed of the paddle 70 from 70 rpm, 50 rpm, to 30 rpm as the voltage fluctuation range decreased. As a result, as shown in Table 1, the bump height uniformity was 4.4 μm. In this case, a value of 15% was obtained as the improvement rate of the bump height uniformity.

[0096] As described above, it was confirmed that in both bump pattern 1 and bump pattern 2, the uniformity of the bump height can be improved by controlling the stirring intensity according to the voltage fluctuation range, that is, the height of bump 143 can be made uniform.

[0097] As mentioned above, when the rotation speed of the substrate holder 30 was controlled in accordance with the voltage fluctuation range, or when the flow rate of the plating solution Ps was controlled in accordance with the voltage fluctuation range, experiments similar to the above-mentioned case (when the movement speed of the paddle 70 was controlled in accordance with the voltage fluctuation range) were conducted using bump pattern 1 and bump pattern 2. As a result, when the rotation speed of the substrate holder 30 was controlled in accordance with the voltage fluctuation range, or when the flow rate of the plating solution Ps was controlled in accordance with the voltage fluctuation range, good values ​​of uniformity in bump height were obtained, similar to the above-mentioned case.

[0098] Next, a second embodiment of the present invention will be described. The plating method according to this embodiment differs from the plating method according to the first embodiment in that the flowchart shown in Fig. 12, which will be described later, is executed instead of the flowchart shown in Fig. 9. The hardware configuration of the plating apparatus used in the plating method according to this embodiment is the same as that of the plating apparatus according to the first embodiment described with reference to Figs. 1 to 8, and therefore Figs. 1 to 8 also apply to this embodiment.

[0099] 12 is an example of a flowchart for explaining the plating method according to the present embodiment (Embodiment 2). Note that step S100 in FIG. 12 is executed "before the plating process is performed" (i.e., executed in advance). On the other hand, step S110 is executed "during the plating process."

[0100] In step S100, the user supplies a reverse current pulse from the power supply 80 to the substrate Wf and the anode 11, and determines a control map for the stirring intensity of the stirring mechanism 60 so that the fluctuation range (Wd) of the voltage of the substrate Wf after the reverse current pulse is supplied falls within a specified range.

[0101] As a specific example of the "fluctuation width (Wd) of the voltage of the substrate Wf after the reverse current pulse is supplied," the "fluctuation width (Wd) of the voltage between the substrate Wf and the anode 11 after the reverse current pulse is supplied" may be used. Alternatively, the "fluctuation width (Wd) of the voltage between the substrate Wf and the reference electrode 18 after the reverse current pulse is supplied" may be used.

[0102] The substrate Wf used in step S100 is different from the substrate Wf used in step S110, which will be described later. That is, the substrate Wf used in step S100 is a "dummy substrate for experiment."

[0103] Specifically, in step S100, the user experimentally determines the stirring strength of stirring mechanism 60 such that the voltage fluctuation width (Wd) falls within a predetermined range, as described above with reference to Figures 10(B) and 11(B). Then, the determined stirring strength of stirring mechanism 60 is stored in advance in storage device 802 of control module 800 as an "agitation strength control map."

[0104] That is, this stirring intensity control map defines the stirring intensity of the stirring mechanism 60 in relation to time (elapsed time of plating process) so that the voltage fluctuation width (Wd) falls within a predetermined range.

[0105] As a specific example, the stirring intensity defined in this control map changes over time. For example, the stirring intensity in this control map changes over time, for example, from the start of the plating process until a first time elapses, the stirring intensity is a "first value (e.g., 150 rpm)," from the first time until a second time elapses, the stirring intensity is a "second value (e.g., 135 rpm)," and from the second time until a third time elapses, the stirring intensity is a "third value (e.g., 100 rpm)."

[0106] Next, in step S110, which is executed when the plating process is performed, the control module 800 controls the stirring intensity of the stirring mechanism 60 based on the stirring intensity control map previously obtained in step S100, while controlling the power supply 80 so that forward current and reverse current pulses are supplied to the substrate Wf and the anode 11 multiple times.

[0107] By executing step S110, as described above with reference to Figures 10(B) and 11(B), the plating process can be performed by supplying forward current and reverse current pulses multiple times while changing the stirring intensity over time (for example, while changing the rotation speed of the paddle 70 from 150 rpm to 135 rpm to 100 rpm, or, for example, from 70 rpm to 50 rpm to 30 rpm).

[0108] In the present embodiment as described above, the fluctuation width of the voltage after the reverse current pulse is supplied can be kept within a predetermined range, thereby making it possible to uniformize the height of the bumps 143 formed by the metal deposited on the substrate Wf.

[0109] Although the embodiments and modifications of the present invention have been described in detail above, the present invention is not limited to such specific embodiments and modifications, and various further modifications and changes are possible within the scope of the present invention as defined in the claims.

[0110] REFERENCE SIGNS LIST 10 Plating tank 11 Anode 18 Reference electrode 30 Substrate holder 40 Rotation mechanism 60 Stirring mechanism 70 Paddle 80 Power supply 90 Plating solution flow mechanism 1000 Plating device Ps Plating solution Wf Substrate

Claims

1. A plating method using a plating apparatus comprising: a plating tank in which a plating solution containing an accelerator for accelerating plating is stored and in which an anode is disposed; a substrate holder configured to hold a substrate as a cathode facing the anode; a power source configured to supply current to the substrate and the anode; and a stirring mechanism configured to stir the plating solution, the method comprising: controlling the power source so that, during a plating process for plating the substrate, a forward current for depositing metal from the plating solution onto the substrate and a reverse current pulse, which is a current flowing in pulses in the opposite direction to the forward current, are supplied to the substrate and the anode multiple times; and acquiring, during the plating process, a fluctuation range of the voltage of the substrate after the reverse current pulse is supplied, and controlling the stirring strength of the stirring mechanism in accordance with the acquired fluctuation range. The plating method, wherein the fluctuation range is a difference between the voltage immediately before the reverse current pulse is supplied and a minimum value of the voltage that occurs after the reverse current pulse is supplied, or a difference between the minimum value and a maximum value of the voltage that occurs after the minimum value occurs.

2. The plating method of claim 1, wherein the stirring mechanism includes a paddle positioned between the substrate and the anode and configured to stir the plating solution.

3. The plating method according to claim 1, wherein the stirring mechanism includes a rotation mechanism configured to rotate the substrate holder to stir the plating solution.

4. The plating method according to claim 1, wherein the stirring mechanism includes a plating solution flow mechanism configured to stir the plating solution by causing the plating solution in the plating tank to flow.

5. The plating method according to claim 1, wherein the fluctuation range of the voltage of the substrate after the reverse current pulse is supplied includes the fluctuation range of the voltage between the substrate and the anode after the reverse current pulse is supplied, or the fluctuation range of the voltage between the substrate and a reference electrode disposed in the plating tank after the reverse current pulse is supplied.

6. A plating method using a plating apparatus comprising: a plating tank containing a plating solution containing an accelerator for accelerating plating and in which an anode is disposed; a substrate holder configured to hold a substrate as a cathode facing the anode; a power source configured to supply current to the substrate and the anode; and a stirring mechanism configured to stir the plating solution, the method comprising: controlling the power source, before performing a plating process to plate the substrate, so that a reverse current pulse, which is a current flowing in a pulsed manner in the opposite direction to a forward current for depositing metal from the plating solution on the substrate, is supplied to the substrate and the anode; and determining in advance a control map of the stirring strength of the stirring mechanism such that the fluctuation width of the voltage of the substrate after the reverse current pulse is supplied falls within a predetermined range; and controlling the power source during the plating process so that the forward current and the reverse current pulse are supplied to the substrate and the anode multiple times while controlling the stirring strength of the stirring mechanism based on the control map determined in advance. The plating method, wherein the fluctuation range is a difference between the voltage immediately before the reverse current pulse is supplied and a minimum value of the voltage that occurs after the reverse current pulse is supplied, or a difference between the minimum value and a maximum value of the voltage that occurs after the minimum value occurs.

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