Plating method

Abstract

A technique capable of equalizing the height of bumps is provided. The plating method includes: obtaining the opening density change direction (Dr2); holding a substrate (Wf) for which the opening density change direction has been obtained on a substrate holder (30); immersing the substrate held on the substrate holder in the interior of a plating solution (Ps) so as to face an anode; performing a first plating process in which, while rotating the substrate holder and stirring the plating solution by a stirring mechanism (60), a positive current is supplied from a power supply (80); performing a second plating process in which, in a state where the opening density change direction is not parallel to the flow direction (Dr1) of the plating solution stirred by the stirring mechanism and with the rotation of the substrate holder stopped, a reverse current pulse is supplied from the power supply while stirring the plating solution by the stirring mechanism; and performing the above-described first plating process again.

Description

Technical Field

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

[0002] Conventionally, a plating method for plating a substrate has been known (for example, refer to Patent Documents 1, 2, and 3). A plating apparatus used in such a plating method includes, for example: a plating bath that stores a plating solution and is provided with an anode; a substrate holder that holds the substrate as a cathode so as to face the anode; a power supply configured to supply current between the substrate and the anode; and a stirring mechanism configured to stir the plating solution (for example, refer to Patent Documents 1 and 2).

[0003] In addition, Patent Documents 2 and 3 also disclose a technique of forming bumps by plating metal onto a substrate. Further, Patent Documents 2 and 3 also disclose the following technique: in a plating method using a plating solution containing an accelerator for promoting plating, the power supply is controlled to supply a forward current and a reverse current pulse to the substrate and the anode.

[0004] Patent Document 1: Japanese Patent No. 7079388

[0005] Patent Document 2: Japanese Patent No. 7357824

[0006] Patent Document 3: Japanese Unexamined Patent Application Publication No. 2006 - 131926

[0007] In recent years, there has been a demand for making the height of bumps formed on a substrate by plating uniform. In this regard, there is room for improvement in the prior art. Summary of the Invention

[0008] The present invention has been made in view of the above circumstances, and one of its objects is to provide a technique capable of achieving uniform height of bumps.

[0009] (Aspect 1)

[0010] To achieve the above object, a plating method according to one embodiment of the present invention includes: obtaining the direction of change in the opening density of a photoresist layer provided on a substrate, i.e., the opening density change direction; holding the substrate having obtained the opening density change direction on a substrate holder; immersing the substrate held on the substrate holder in the interior of a plating solution in a plating bath in a manner opposite to an anode, the plating bath storing the plating solution containing an accelerator for promoting plating and having the anode disposed therein; performing a first plating process in which, while rotating the substrate holder and stirring the plating solution by a stirring mechanism, a power supply configured to supply a current between the substrate and the anode supplies a forward current for depositing a metal from the plating solution onto the substrate; performing a second plating process in which, in a state where the opening density change direction is not parallel to the flow direction of the plating solution stirred by the stirring mechanism and with the rotation of the substrate holder stopped, while stirring the plating solution by the stirring mechanism, the power supply supplies a current flowing in a pulsed manner in a direction opposite to the forward current, i.e., a reverse current pulse; and performing the first plating process again.

[0011] According to this embodiment, it is possible to achieve the uniformization of the height of bumps formed of the metal deposited on the substrate.

[0012] (Embodiment 2)

[0013] In the above Embodiment 1, in the second plating process, the opening density change direction may be perpendicular to the flow direction of the plating solution stirred by the stirring mechanism.

[0014] (Embodiment 3)

[0015] Based on the above Embodiment 1 or Embodiment 2, the stirring mechanism may include blades configured to stir the plating solution in the plating bath by reciprocating movement, and the direction of reciprocating movement of the blades may be used as the flow direction of the plating solution stirred by the stirring mechanism in the second plating process. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 FIG. is a perspective view showing the overall structure of a plating apparatus according to an embodiment.

[0017] Figure 2 FIG. is a top view showing the overall structure of a plating apparatus according to an embodiment.

[0018] Figure 3 FIG. is a schematic diagram showing the structure of a plating module according to an embodiment.

[0019] Figure 4 FIG. is a schematic diagram showing a state where a substrate according to an embodiment is immersed in a plating solution.

[0020] Figure 5 It is a schematic top view of the blade of the embodiment.

[0021] Figure 6 (A) thereof is a schematic diagram for explaining the surface structure of the substrate of the embodiment. Figure 6 (B) thereof is a schematic diagram showing an example of the opening pattern of the photoresist layer of the embodiment.

[0022] Figure 7 (A) of Figure 7 (B) of

[0023] Figure 8 It shows when Figure 6 (B) exemplified has a plurality of bumps formed on the substrate of the photoresist layer, it is a chart showing an example of the height of the bumps measured in each pattern area.

[0024] Figure 9 It is an example of a flowchart for explaining the plating method of the embodiment.

[0025] Figure 10 It is a schematic top view for explaining the direction of change in the opening density of the substrate of the embodiment.

[0026] Figure 11 (A) of Figure 11 (B) of Detailed Embodiments

[0027] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In addition, the drawings are schematically illustrated for facilitating the understanding of the features of the constituent elements, and the dimensional ratios and the like of each constituent element are not limited to the same as the actual situation. In addition, in some of the drawings, for reference, an orthogonal coordinate of X–Y–Z is illustrated. The Z direction in this orthogonal coordinate corresponds to the upper side, and the –Z direction corresponds to the lower side (the direction of the action of gravity).

[0028] Figure 1 It is a perspective view showing the overall structure of the plating apparatus 1000 of the embodiment. Figure 2 It is a top view (plan view) showing the overall structure of the plating apparatus 1000 of the embodiment. As Figure 1 and Figure 2As shown in the figure, the plating apparatus 1000 includes: a loading port 100, a transfer robot 110, an aligner 120, a pre-wetting module 200, a pre-dipping module 300, a plating module 400, a cleaning module 500, a spin dryer 600, a transfer device 700, and a control module 800.

[0029] The loading port 100 is a module for loading a substrate accommodated in a cassette such as a FOUP (not shown) into the plating apparatus 1000 or unloading the substrate from the plating apparatus 1000 to the cassette. In the present embodiment, four loading ports 100 are arranged and configured in the horizontal direction, but the number and configuration of the loading ports 100 are arbitrary. The transfer robot 110 is a robot for transferring the substrate, and is configured to transfer the substrate between the loading port 100, the aligner 120, the pre-wetting module 200, and the spin dryer 600. When transferring the substrate between the transfer robot 110 and the transfer device 700, the transfer robot 110 and the transfer device 700 can transfer the substrate via a temporary stage (not shown).

[0030] The aligner 120 is a module for aligning the positioning plane, notch, etc. of the substrate in a specified direction. In the present embodiment, two aligners 120 are arranged and configured in the horizontal direction, but the number and configuration of the aligners 120 are arbitrary. The pre-wetting module 200 replaces the air inside the pattern formed on the surface of the substrate with a treatment liquid by wetting the surface to be plated of the substrate before the plating treatment with a treatment liquid such as pure water or degassed water. The pre-wetting module 200 is configured to perform a pre-wetting treatment, which is a treatment that makes it easy to supply the plating liquid into the pattern by replacing the treatment liquid inside the pattern with the plating liquid during plating. In the present embodiment, two pre-wetting modules 200 are arranged and configured in the vertical direction, but the number and configuration of the pre-wetting modules 200 are arbitrary.

[0031] The pre-dipping module 300 is configured to perform a pre-dipping treatment, which is a treatment for etching and removing a resistive oxide film such as on the surface of the seed layer formed on the surface to be plated of the substrate before the plating treatment with a treatment liquid such as sulfuric acid or hydrochloric acid to clean or activate the surface of the plating substrate. In the present embodiment, two pre-dipping modules 300 are arranged and configured in the vertical direction, but the number and configuration of the pre-dipping modules 300 are arbitrary. The plating module 400 performs plating on the substrate. In the present embodiment, there are two sets of twelve plating modules 400 arranged in three in the vertical direction and four in the horizontal direction, with a total of twenty-four plating modules 400 provided, but the number and configuration of the plating modules 400 are arbitrary.

[0032] The cleaning module 500 is configured to perform a cleaning process on the substrate in order to remove plating solution and the like remaining on the substrate after the plating process. In the present embodiment, two cleaning modules 500 are arranged and configured in the vertical direction, but the number and configuration of the cleaning modules 500 are arbitrary. The spin dryer 600 is a module for drying the substrate by rotating it at high speed after the cleaning process. In the present embodiment, two spin dryers 600 are arranged and configured in the vertical direction, but the number and configuration of the spin dryers 600 are arbitrary. The conveying device 700 is a device for conveying the substrate between multiple modules in the plating apparatus 1000. The control module 800 is configured to control multiple modules of the plating apparatus 1000 and can be constituted by, for example, a general computer or a dedicated computer having an input / output interface with the operator.

[0033] An example of a series of plating processes performed by the plating apparatus 1000 will be described. First, the substrate stored in the cassette is carried into the loading port 100. Next, the transfer robot 110 takes out the substrate from the cassette at the loading port 100 and conveys the substrate to the aligner 120. The aligner 120 aligns the positioning plane, notch, and other positions of the substrate in a specified direction. The transfer robot 110 transfers the substrate whose direction has been aligned by the aligner 120 to the pre-wetting module 200.

[0034] The pre-wetting module 200 performs a pre-wetting process on the substrate. The conveying device 700 conveys the substrate that has been subjected to the pre-wetting process to the pre-dipping module 300. The pre-dipping module 300 performs a pre-dipping process on the substrate. The conveying device 700 conveys the substrate that has been subjected to the pre-dipping process to the plating module 400. The plating module 400 performs plating on the substrate.

[0035] The conveying device 700 conveys the substrate that has been subjected to the plating process to the cleaning module 500. The cleaning module 500 performs a cleaning process on the substrate. The conveying device 700 conveys the substrate that has been subjected to the cleaning process to the spin dryer 600. The spin dryer 600 performs a drying process on the substrate. The transfer robot 110 receives the substrate from the spin dryer 600 and conveys the substrate that has been subjected to the drying process to the cassette at the loading port 100. Finally, the cassette containing the substrate is taken out from the loading port 100.

[0036] In addition, Figure 1 , Figure 2 the structure of the plating apparatus 1000 described in Figure 1 , Figure 2 is merely an example, and the structure of the plating apparatus 1000 is not limited to the

[0037] structure. Next, the plating module 400 will be described. In addition, the multiple plating modules 400 included in the plating apparatus 1000 of the present embodiment have the same structure, so one plating module 400 will be described.

[0038] Figure 3 is a schematic diagram showing the structure of the plating module 400 in the plating apparatus 1000. Specifically, Figure 3 schematically illustrates the plating module 400 in a state before the substrate Wf is immersed in the plating solution Ps. Figure 4 is a schematic diagram showing the state in which the substrate Wf is immersed in the plating solution Ps.

[0039] As an example, Figure 3 and Figure 4 the illustrated plating apparatus 1000 is a type of plating apparatus (so-called cup type plating apparatus) that immerses the substrate Wf in the plating solution Ps in a state where the plane direction of the substrate Wf is horizontal. However, the structure of the plating apparatus 1000 is not limited thereto. For example, it may also be a type of plating apparatus that immerses the substrate Wf in the plating solution Ps in a state where the plane direction of the substrate Wf is non-horizontal (as an example, a direction perpendicular to the ground).

[0040] Figure 3 and Figure 4 the plating module 400 of the illustrated plating apparatus 1000 includes: a plating tank 10, an overflow tank 20, a substrate holder 30, and a paddle 70 as an example of the stirring mechanism 60. In addition, as Figure 3 illustrated, the plating module 400 includes a rotation mechanism 40, an inclination mechanism 45, and a lifting mechanism 50. In addition, as Figure 3 illustrated, the plating module 400 includes sensors 130. In addition, as Figure 4 illustrated, the plating module 400 includes a power supply 80 and a plating solution flow mechanism 90.

[0041] The plating tank 10 of the present embodiment is composed of a bottomed container having 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 peripheral edge of the bottom wall 10a, and the upper part of the outer peripheral wall 10b is open. In addition, the shape of the outer peripheral wall 10b of the plating tank 10 is not particularly limited, but in the present embodiment, the outer peripheral wall 10b has a cylindrical shape as an example. The plating solution Ps is stored inside the plating tank 10.

[0042] As the plating solution Ps, any solution containing ions of metal elements constituting the plating film may be used, and its specific example is not particularly limited. In the present embodiment, as an example of the plating process, copper plating is used, and as an example of the plating solution Ps, a copper sulfate solution is used. In addition, the plating solution Ps may also contain a prescribed additive.

[0043] As an additive contained in the plating solution Ps, for example, an accelerator that promotes plating (specifically, an accelerator that promotes the formation of a plating film) can be used. As such an accelerator, for example, SPS (bis(3-sulfopropyl) disulfide) or the like can be used.

[0044] An anode 11 is disposed inside the plating tank 10. The specific type of the anode 11 is not particularly limited and can be an insoluble anode or a soluble anode. In the present embodiment, as an example of the anode 11, an insoluble anode is used. The specific type of the insoluble anode is not particularly limited, and platinum, iridium oxide, or the like can be used.

[0045] As Figure 3 , Figure 4 As exemplified, an ion resistor 12 can also be disposed inside the plating tank 10 above the anode 11. Specifically, as exemplified by the partial enlarged view of Figure 4 , the ion resistor 12 is composed of a porous plate member having a plurality of holes 12a (fine holes). The holes 12a are provided to communicate the lower surface and the upper surface of the ion resistor 12.

[0046] The ion resistor 12 is provided to achieve the uniformization of the electric field formed between the anode 11 and the substrate Wf as the cathode. As in the present embodiment, by disposing the ion resistor 12 in the plating tank 10, the uniformization of the film thickness of the plating film (plating layer) formed on the substrate Wf can be easily achieved.

[0047] As Figure 3 , Figure 4 As exemplified, a film 16 can also be disposed inside the plating tank 10 at a position above the anode 11 and below the ion resistor 12. In this case, the inside of the plating tank 10 is divided by the film 16 into an anode chamber 17a below the film 16 and a cathode chamber 17b above the film 16. The anode 11 is disposed in the anode chamber 17a, and the ion resistor 12 and the substrate Wf are disposed in the cathode chamber 17b. The film 16 is configured to allow ion species containing metal ions contained in the plating solution Ps to pass through the film 16 and to inhibit non-ionic plating additives contained in the plating solution Ps from passing through the film 16. As such a film 16, for example, an ion exchange membrane can be used.

[0048] As Figure 4 As exemplified, the plating solution flow mechanism 90 is configured to cause the plating solution Ps in the plating tank 10 to flow. The plating solution flow mechanism 90 of the present embodiment includes, as an example, a first flow mechanism 91a and a second flow mechanism 91b.

[0049] The first fluid mechanism 91a is a mechanism for causing the plating solution Ps in the anode chamber 17a to flow. The second fluid mechanism 91b is a mechanism for causing the plating solution Ps in the cathode chamber 17b to flow. The first fluid mechanism 91a communicates with the anode chamber 17a via a pipe 92a. The second fluid mechanism 91b communicates with the cathode chamber 17b via a pipe 92b. In addition, the first fluid mechanism 91a and the second fluid mechanism 91b each include a pump or the like for pumping the plating solution Ps.

[0050] Refer to Figure 3 and Figure 4 , a supply port for supplying the plating solution Ps to the plating tank 10 is provided in the plating tank 10. Specifically, 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 are provided on the outer peripheral wall 10b of the plating tank 10 in the present embodiment. The plating solution Ps discharged from the first discharge port 14a is pumped by the first fluid mechanism 91a and is supplied again to the anode chamber 17a from the first supply port 13a.

[0051] The overflow tank 20 is constituted by a bottomed container disposed outside the plating tank 10. The overflow tank 20 is provided for temporarily storing the plating solution Ps that exceeds the upper end of the outer peripheral wall 10b of the plating tank 10 (i.e., the plating solution Ps that overflows from the plating tank 10). The plating solution Ps stored in the overflow tank 20 is pumped by the second fluid mechanism 91b after being discharged from the second discharge port 14b and is supplied again to the cathode chamber 17b from the second supply port 13b.

[0052] The substrate holder 30 holds the substrate Wf as a cathode such that the plated surface Wfa of the substrate Wf faces the anode 11. In the present embodiment, the plated surface Wfa of the substrate Wf is specifically provided on the surface (lower surface) of the substrate Wf facing the lower side.

[0053] The substrate holder 30 is connected to a rotation mechanism 40. The rotation mechanism 40 is a mechanism for rotating the substrate holder 30. Figure 3 The illustrated "R1" is an example of the rotation direction of the substrate holder 30. As the rotation mechanism 40, a known rotation motor or the like can be used. The tilting 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 lifting and lowering the substrate holder 30, the rotation mechanism 40, and the tilting mechanism 45 in the vertical direction. As the lifting mechanism 50, a known lifting mechanism such as a direct-acting actuator can be used.

[0054] The control module 800 includes a microcomputer, which includes a processor 801, a storage device 802 serving as a non-transitory storage medium, etc. The control module 800 controls the operation of the plating module 400 by operating through the processor 801 based on the instructions of the program stored in the storage device 802.

[0055] Refer to Figure 3 , the sensors 130 detect various information 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, and a voltage sensor that detects the voltage value (V) between the anode 11 and the substrate Wf.

[0056] In addition, the sensors 130 include a speed sensor for detecting the moving speed (rpm or m / sec) of the paddle 70. In addition, the sensors 130 include a rotational speed sensor for detecting the rotational speed (rpm) of the substrate holder 30. In addition, the sensors 130 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 sensor includes 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.

[0057] In addition, the sensors 130 include an angle sensor for detecting the rotational angle of the substrate holder 30. The control module 800 can obtain the rotational angle (rotational position) of the substrate holder 30 by acquiring the detection result of the angle sensor, and thus can also obtain the rotational angle (rotational position) of the substrate Wf held by the substrate holder 30.

[0058] As Figure 4 illustrated, 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 the control module 800.

[0059] During the "plating process" of plating the substrate Wf, the control module 800 of the present embodiment controls the power supply 80 in such a way as to supply a "forward current" for depositing metal from the plating solution Ps onto the substrate Wf and a current flowing in a pulsed manner in the direction opposite to the forward current, that is, a "reverse current pulse".

[0060] Figure 5 is a schematic top view of the paddle 70. Refer to Figure 3 , Figure 4 and Figure 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 has received an instruction from the control module 800. The paddle 70 is driven to stir the plating solution Ps in the plating tank 10.

[0061] As an example, the paddle 70 of the present embodiment is alternately driven along a "first direction (in the present embodiment, as an example, the X direction) parallel to the substrate Wf" and a "second direction (in the present embodiment, as an example, the -X direction) opposite to the first direction". That is, as an example, the paddle 70 of the present embodiment reciprocates in the direction of the X-axis.

[0062] As Figure 5 illustrated, as an example, the paddle 70 of the present embodiment has a plurality of stirring members 71a extending in a direction (the direction of the Y-axis) perpendicular to the first direction and the second direction of the paddle 70. A gap is provided between adjacent stirring members 71a. One end of the plurality of stirring members 71a is connected to the connecting member 72a, and the other end is connected to the connecting member 72b.

[0063] However, the structure of the paddle 70 is not limited thereto. For example, various known paddles such as those illustrated in Patent Document 1 can be used.

[0064] In addition, 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 always disposed inside the plating tank 10. For example, when the driving of the paddle 70 is stopped and the paddle 70 does not stir the plating solution Ps, the paddle 70 can also be configured not to be disposed inside the plating tank 10.

[0065] In addition, "the moving speed of the paddle 70 is N (rpm)" specifically means that the paddle 70 reciprocates N times in one minute (that is, the paddle 70 moves from a specified position, for example, moves in the first direction, then moves in the second direction, and then moves in the first direction again and returns to the specified position). The faster the moving speed of the paddle 70, the stronger the stirring intensity of the paddle 70 on the plating solution Ps. That is, the moving speed of the paddle 70 is an example of "the stirring intensity of the plating solution Ps".

[0066] Figure 6 (A) is a schematic diagram for explaining the surface structure of the substrate Wf. Specifically, in Figure 6 (A), a case where bumps 143 are formed on the substrate Wf by plating treatment is schematically shown in a cross-sectional view. In addition, the bumps 143 are specifically formed of a metal (such as Cu) deposited on the substrate Wf.

[0067] As Figure 6As exemplified in (A) thereof, a thin metal seed layer 140 is provided in advance as an example on the entire surface of the substrate Wf in the present embodiment. During the plating process, power is supplied to the surface of the substrate Wf via the seed layer 140. A photoresist layer 141 is provided on the surface of the seed layer 140 on the side opposite to the substrate Wf side. The photoresist layer 141 has an opening 142 at a portion where the bump 143 should be formed. In addition, Figure 6 "φ" exemplified in (A) thereof is the diameter (μm) of the opening 142 of the photoresist layer 141, and "BH" is the height (μm) of the bump 143.

[0068] Figure 6 (B) thereof is a schematic diagram showing an example of the opening pattern of the photoresist layer 141. In Figure 6 No1 and No2 in (B) thereof, examples where the diameter φ of the opening 142 is relatively small (for example, 30 μm) are illustrated, and No3 and No4 illustrate examples where the diameter φ of the opening 142 is relatively large (for example, 75 μm). If No1 is compared with No2, No1 has the openings 142 arranged at a higher density than No2. If No3 is compared with No4, No3 has the openings 142 arranged at a higher density than No4.

[0069] 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 for plating treatment. During the execution of the plating treatment, the portion of the surface of the substrate Wf other than the opening 142 of the photoresist layer 141 is shielded from the plating solution Ps by the photoresist layer 141. As a result, the plating film grows only at the portion of the opening 142 of the photoresist layer 141, and thus the bump 143 is formed on the substrate Wf. In addition, the photoresist layer 141 can be removed after the plating treatment.

[0070] Figure 7 (A) thereof and Figure 7 (B) thereof are diagrams for explaining an example of the time waveform of the current output from the power supply 80 in the present embodiment and supplied to the anode 11 and the substrate Wf. As exemplified in Figure 7 (A) thereof and Figure 7 (B) thereof, the power supply 80 receives an instruction from the control module 800 and supplies a forward current during the first period T1. "Forward" is the direction in which the current flows from the anode 11 toward the substrate Wf in the plating solution Ps. Therefore, during the first period T1, metal ions in the plating solution Ps are reduced on the plated surface Wfa of the substrate Wf, and thus metal (bump 143) is deposited on the plated surface Wfa to form a plating film.

[0071] For the actual growth of the coating film, the length of the first period T1 may also be a time that occupies most of the entire time for the plating process. In other words, the sum of the lengths of the subsequent second period T2 and third period T3 may also be negligible compared to the length of the first period T1. The magnitude of the forward current may be, for example, a constant current value throughout the first period T1. Alternatively, the current value of the forward current may also be controlled to vary with time.

[0072] During the second period T2 set in the middle of the first period T1, the power supply 80 receives an instruction from the control module 800 and supplies a current in the direction opposite to the above-mentioned forward current, that is, a reverse current pulse. For example, the length of the second period T2, that is, the pulse width of the reverse current pulse, may also be about 0.1 second to several seconds. During the second period T2, contrary to the reduction reaction of metal ions in the first period T1, a part of the metal in the coating film formed on the substrate Wf in the first period T1 is redissolved in the plating solution Ps, and the accelerator (one of the additives contained in the plating solution Ps) attached to the outermost surface of the coating film during the reduction reaction detaches from the coating film surface. In addition, the current value of the reverse current pulse is preferably set to a value that allows the accelerator to detach sufficiently.

[0073] As Figure 7 illustrated in (B) of, the power supply 80 may also stop current supply during the third period T3 following the second period T2. That is, during the third period T3, the current does not flow in the forward or reverse direction in the plating solution Ps. Similar to the second period T2, the length of the third period T3 is a time of a very short length compared to the first period T1 and may be, for example, about 0.1 second to several seconds. During the third period T3, the accelerator that has detached from the coating film surface diffuses in the plating solution Ps.

[0074] After the second period T2 or the third period T3, the power supply 80 supplies the forward current again. The forward current continues until the end of the specified plating process time, for example, until the film thickness of the formed coating film reaches the specified target film thickness.

[0075] Figure 8 is a diagram showing an example of measuring the height (BH) of the bumps 143 in each pattern region when a plurality of bumps 143 are formed on the substrate Wf having the Figure 6 photoresist layer 141 illustrated in (B) of. In the Figure 8 vertical axis, the height (BH) of each bump 143 corresponding to each pattern region P1, P2, P3, P4 in (B) of Figure 6 specifically shows the average value of the heights of the plurality of bumps 143 included in the pattern region.

[0076] Figure 8The graph on the left shows the measurement results of the case where a positive current is supplied throughout the plating process to form the bump 143. Figure 8 The graph on the right shows the measurement results of the case where a reverse current pulse is supplied once during the plating process to form the bump 143.

[0077] According to Figure 8 it can be seen that in all the pattern areas, the height (BH) of the bump 143 in the pattern area P1 is the lowest, and the height (BH) of the bump 143 in the pattern area P4 is the highest. This is because the smaller the diameter φ of the opening 142 and the higher the arrangement density of the openings 142, the more difficult it is for metal ions to be sufficiently replenished into the openings 142, and thus the formation rate of the plating film becomes lower. Here, the difference between the maximum value and the minimum value of the height (BH) of the bump 143 is defined as the "bump height deviation (ΔBH)".

[0078] According to Figure 8 it can be seen that in the case where a reverse current pulse is supplied during the plating process ( Figure 8 the graph on the right), compared with the case where no reverse current pulse is supplied ( Figure 8 the graph on the left), the bump height deviation (ΔBH) is smaller. In this way, by supplying a reverse current pulse, it is possible to achieve the uniformity of the height of the bump 143.

[0079] Figure 10 is a schematic top view for explaining the direction of the change in the opening density of the photoresist layer 141 provided on the substrate Wf, that is, the "opening density change direction (Dr2)". As an example, in Figure 10 the openings 142 of the photoresist layer 141 include a "region Ar1 (i.e., a region with a "sparse" opening density) where the opening density is lower than a specified value, and a "region Ar2 (i.e., a region with a "dense" opening density)" where the opening density is higher than that of the region Ar1. In this case, the opening density change direction (Dr2) is the direction from the region Ar1 to the region Ar2 (or, the direction from the region Ar2 to the region Ar1).

[0080] Here, through the research of the inventors, it is known that when a reverse current pulse is supplied, the degree of uniformity of the height of the bump 143 varies according to the angle (α1) formed by the "opening density change direction (Dr2)" and the flow direction (Dr1) of the plating solution Ps during stirring (for the detailed content, refer to the description of the experimental results explained in Figure 11 ). Therefore, in the present embodiment, in order to effectively achieve the uniformity of the height of the bump 143, the plating method described in the following Figure 9 is performed.

[0081] Figure 9This is an example of a flowchart for explaining the plating method of the present embodiment. First, the user (operator) obtains the direction of the change in the opening density of the photoresist layer 141 provided on the substrate Wf, that is, the "direction of change in opening density (Dr2)" (step S10).

[0082] In addition, when the user obtains the direction of change in opening density (Dr2), for example, when information related to the opening density is described in the specification of the substrate Wf or the like, the user can also obtain the direction of change in opening density (Dr2) based on the specification or the like. Alternatively, the user can also observe the substrate Wf visually, using a microscope, etc., thereby obtaining (i.e., measuring) the direction of change in opening density (Dr2).

[0083] After step S10, the user or the control module 800 holds the substrate Wf for which the direction of change in opening density (Dr2) has been obtained on the substrate holder 30 (step S20).

[0084] In addition, the substrate Wf is held on the substrate holder 30, for example, in such a manner that the positioning plane provided on the substrate Wf faces a specified direction of the substrate holder 30. That is, the substrate Wf is held on the substrate holder 30 in such a manner that the orientation (direction of the positioning plane) of the substrate Wf can be grasped. Therefore, in the state where the substrate Wf is held on the substrate holder 30, the control module 800 can grasp in which direction the direction of change in opening density (Dr2) of the substrate Wf is oriented.

[0085] Next, the control module 800 immerses the substrate Wf held on the substrate holder 30 into the plating solution Ps inside the plating tank 10 so as to face the anode 11 (step S30).

[0086] Next, the control module 800 performs a first plating process (step S40). Specifically, in step S40, the control module 800 performs stirring of the plating solution Ps using the stirring mechanism 60 (as an example, the paddle 70), and rotation of the substrate holder 30 using the rotation mechanism 40, and causes the power supply 80 to supply a positive current for a specified time. Thereby, a plating film (specifically, the bump 143) is formed on the substrate Wf.

[0087] Next, the control module 800 performs a second plating process (step S50). Specifically, in step S50, the control module 800 supplies a reverse current pulse while stirring the plating solution Ps by the stirring mechanism 60 in a state where the direction of change in opening density (Dr2) is not parallel to the flow direction (Dr1) of the plating solution Ps stirred by the stirring mechanism 60 and in a state where the rotation of the substrate holder 30 is stopped.

[0088] In addition, the "direction of change in opening density (Dr2)" is not parallel to the "flow direction of the plating solution Ps (Dr1)", which means that the "direction of change in opening density (Dr2)" and the "flow direction of the plating solution Ps (Dr1)" are neither the same direction nor the opposite direction.

[0089] Specifically, referring to Figure 10 , the control module 800 of the present embodiment stops the rotation of the substrate holder 30 at an angle (α1) formed by the direction of change in opening density (Dr2) and the flow direction of the plating solution Ps (Dr1) that is greater than 0 degrees and less than 180 degrees.

[0090] In Figure 10 , as an example, the rotation of the substrate holder 30 is stopped in such a way that the direction of change in opening density (Dr2) is perpendicular to the flow direction of the plating solution Ps (Dr1) (α1 is 90 degrees). While the rotation of the substrate holder 30 is stopped in this way, the control module 800 supplies a reverse current pulse from the power supply 80 while stirring the plating solution Ps by the stirring mechanism 60.

[0091] In addition, in the present embodiment, the "flow direction of the plating solution Ps stirred by the stirring mechanism 60 (Dr1)" is specifically the same as the "direction of reciprocating movement of the blade 70 (Dr1)". Therefore, the "direction of reciprocating movement of the blade 70 (Dr1)" can also be used as the "flow direction of the plating solution Ps stirred by the stirring mechanism 60 (Dr1)".

[0092] That is, in this case, in step S50, the control module 800 only needs to supply a reverse current pulse from the power supply 80 while stirring the plating solution Ps by the stirring mechanism 60 in a state where the direction of change in opening density (Dr2) is not parallel to the direction of reciprocating movement of the blade 70 (Dr1) and in a state where the rotation of the substrate holder 30 is stopped.

[0093] Referring to Figure 9 , after step S50, the control module 800 executes the first plating process again (step S60).

[0094] In addition, the control module 800 can also repeatedly execute Figure 9 steps S40, S50, and S60.

[0095] Figure 11 (A) of Figure 11 and Figure 11 (A) of Figure 11The vertical axis of (B) shows the uniformity within the bare chip (the difference between the maximum and minimum heights of the bumps 143).

[0096] Specifically, Figure 11 (A) shows the results of experiments conducted using a substrate Wf with a relatively large deviation in the opening rate of the bumps 143 (substrate Wf with an 8-fold difference in the opening rate within the bare chip). Additionally, Figure 11 (B) shows the results of experiments conducted using a substrate Wf with a relatively small deviation in the opening rate of the bumps 143 (substrate Wf with a 3-fold difference in the opening rate within the bare chip).

[0097] Figure 11 (A), Sample No1 is the experimental result when only the first plating treatment is performed (i.e., when only a forward current is supplied). Sample No2 is the experimental result when the plating method of the present embodiment ( Figure 9 ) is used. Specifically, in Sample No2, in the second plating treatment of step S50, 90 degrees is used as the formed angle (α1). Sample No3 is the experimental result when Figure 9 the steps S10 to S60 of the flowchart are executed, but in the second plating treatment of step S50, zero degrees (or 180 degrees) is used as the formed angle (α1). That is, Sample No2 is an example, and Sample No1 and Sample No3 are comparative examples.

[0098] Comparing Sample No1 with Sample No2 and Sample No3, it can be seen that by supplying a reverse current pulse during the plating treatment, the value of the uniformity within the bare chip can be reduced (i.e., it can be seen that the height uniformity of the bumps 143 can be achieved). Additionally, comparing Sample No2 with Sample No3, it can be seen that the value of the uniformity within the bare chip varies according to the value of the angle (α1) formed during the execution of the second plating treatment.

[0099] Moreover, comparing Sample No2 with Sample No3, it can be seen that the value of the uniformity within the bare chip of Sample No2 is lower than that of Sample No3. From this, it can be known that when, as in Sample No2, the rotation of the substrate holder 30 is stopped in a state where the opening density change direction (Dr2) is not parallel to the flow direction (Dr1) of the plating solution Ps during stirring in the second plating treatment, compared with the case where, as in Sample No3, the rotation of the substrate holder 30 is stopped in a state where the opening density change direction (Dr2) is parallel to the flow direction (Dr1) of the plating solution Ps during stirring, the value of the uniformity within the bare chip can be reduced.

[0100] This is considered to be the case where, during the second plating process, the direction of change in the opening density (Dr2) is not parallel to the flow direction (Dr1) of the plating solution Ps during agitation, compared to the case where it is not. In this situation, the plating solution Ps present on the surface of the substrate Wf (i.e., the surface of the plating film) can be agitated more uniformly over the entire surface of the substrate Wf, and thus the detachment of the promoter from the surface of the plating film can be carried out uniformly and effectively. As a result, the value of the uniformity within the bare chip becomes smaller.

[0101] Figure 11 The sample No. 4 in (B) is the experimental result in the case where only the first plating process is performed (i.e., only a forward current is supplied). The sample No. 5 is the experimental result in the case where the plating method of the present embodiment ( Figure 9 ) is performed. Specifically, in the sample No. 5, in the second plating process of step S50, 90 degrees is used as the formed angle (α1). The sample No. 6 is the experimental result in the case where the steps S10 to S60 of the Figure 9 flow chart are performed, but 0 degrees (or 180 degrees) is used as the formed angle (α1) in the second plating process of step S50. That is, the sample No. 5 is an example, and the sample No. 4 and the sample No. 6 are comparative examples.

[0102] Comparing the sample No. 4 with the sample No. 5 and the sample No. 6, it can be seen that by supplying a reverse current pulse during the plating process, the value of the uniformity within the bare chip can be reduced. In addition, comparing the sample No. 5 with the sample No. 6, it can be seen that the value of the uniformity within the bare chip varies according to the value of the angle (α1) formed during the execution of the second plating process.

[0103] Moreover, comparing the sample No. 5 with the sample No. 6, it can be seen that in the case where, as in the sample No. 5, during the second plating process, the rotation of the substrate holder 30 is stopped in a state where the direction of change in the opening density (Dr2) is not parallel to the flow direction (Dr1) of the plating solution Ps during agitation, compared to the case where, as in the sample No. 6, the rotation of the substrate holder 30 is stopped in a state where the direction of change in the opening density (Dr2) is parallel to the flow direction (Dr1) of the plating solution Ps during agitation, the value of the uniformity within the bare chip can be reduced.

[0104] As described above, it can be seen that the uniformity within the bare chip varies according to the value of the angle (α1) formed during the execution of the second plating process, that is, the degree of uniformity of the height of the bumps 143 changes.

[0105] In addition, in the present embodiment, as an example of the angle (α1) formed during the execution of the second plating treatment, 90 degrees is used, but it is not limited thereto. As long as the formed angle (α1) is within the range of greater than 0 degrees and less than 180 degrees, it is not particularly limited. Regarding the formed angle (α1), a value that can best achieve the uniformity of the height of the bump 143 is obtained through experiments in advance, and the obtained value may be set as the formed angle (α1).

[0106] After investigating the relationship between the formed angle (α1) and the uniformity of the height of the bump 143, it is found that there is a tendency that the closer the value of the formed angle (α1) is to 90 degrees, the more uniform the height of the bump 143 becomes. Therefore, from the perspective of achieving the uniformity of the height of the bump 143, the formed angle (α1) is preferably a value selected from the range of 40 degrees or more and 135 degrees or less, more preferably a value selected from the range of 80 degrees or more and 100 degrees or less, and further preferably 90 degrees.

[0107] According to the present embodiment described above, the uniformity of the height of the bump 143 can be achieved.

[0108] As described above, the embodiments and modification examples of the present invention have been described in detail, but the present invention is not limited to the specific embodiments and modification examples, and various further deformations and changes can be made within the scope of the present invention described in the claims.

[0109] Description of Reference Numerals

[0110] 10... plating tank; 11... anode; 30... substrate holder; 60... stirring mechanism; 70... paddle;

[0111] 80... power supply; 141... photoresist layer; 142... opening; Ps... plating solution; Wf... substrate;

[0112] Dr1... flow direction of the plating solution stirred by the stirring mechanism; Dr2... opening density change direction.

Claims

1. A plating method, characterized in that, Comprising: Obtaining the direction of the change in the opening density of the photoresist layer provided on the substrate, i.e., the opening density change direction; Holding the substrate on which the opening density change direction has been obtained on a substrate holder; Immersing the substrate held on the substrate holder in the interior of the plating solution in a plating bath in a manner facing the anode, the plating bath storing the plating solution containing a promoter for promoting plating and being provided with the anode; Performing a first plating process in which, while rotating the substrate holder and stirring the plating solution by a stirring mechanism, a power supply configured to supply a current between the substrate and the anode supplies a forward current for depositing metal from the plating solution onto the substrate; Performing a second plating process in which, in a state where the opening density change direction is not parallel to the flow direction of the plating solution stirred by the stirring mechanism and with the rotation of the substrate holder stopped, while stirring the plating solution by the stirring mechanism, the power supply supplies a current flowing in a pulsed manner in a direction opposite to the forward current, i.e., a reverse current pulse; And Performing the first plating process again.

2. The plating method according to claim 1, wherein In the second plating process, the opening density change direction is perpendicular to the flow direction of the plating solution stirred by the stirring mechanism.

3. The plating method according to claim 1, wherein The stirring mechanism includes blades configured to stir the plating solution in the plating bath by reciprocating movement, As the flow direction of the plating solution stirred by the stirring mechanism in the second plating process, the direction of the reciprocating movement of the blades is used.

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