Plating method

Abstract

Provided is a technique capable of achieving uniformization of the height of a bump. The plating method comprises the following steps: acquiring an opening density change direction (Dr2); holding the substrate (Wf) on a substrate holder (30), the opening density of the substrate (Wf) having been changed; immersing the substrate held by the substrate holder in the plating solution (Ps) so as to face the anode; performing a first plating process in which a forward current is supplied to a power source (80) while the substrate holder is rotated and the plating solution is stirred by a stirring mechanism (60); performing a second plating process in which a reverse current pulse is supplied by the power source while stirring the plating solution by the stirring mechanism in a state in which the opening density change direction is not parallel to the flow direction (Dr1) of the plating solution stirred by the stirring mechanism and in a state in which the rotation of the substrate holder is stopped; and performing the first plating treatment again.

Description

Technical Field

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

[0002] Conventionally, there is a known plating method for plating a substrate (for example, see Patent Documents 1, 2, and 3). A plating device used in such a plating method includes, for example, a plating tank storing a plating solution and provided with an anode; a substrate holder holding the substrate as a cathode facing 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, see Patent Documents 1 and 2).

[0003] In addition, the technology of forming bumps by depositing metal on the substrate by plating is also disclosed in Patent Documents 2 and 3. In addition, the following technology is also disclosed in Patent Documents 2 and 3: in a plating method using a plating solution containing an accelerator that promotes plating, a power supply is controlled in a manner that forward current and reverse current pulses are supplied 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 Patent Application Laid-Open No. 2006-131926

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

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

[0009] (Method 1)

[0010] In order to achieve the above-mentioned purpose, a plating method according to one embodiment of the present invention comprises: obtaining a direction in which the opening density of a photoresist layer provided on a substrate changes, that is, a direction in which the opening density changes; holding the substrate having the above-mentioned opening density change direction obtained on a substrate holder; immersing the substrate held on the substrate holder in a plating solution in a plating tank in a manner opposite to an anode, wherein the plating tank stores the plating solution containing an accelerator for promoting plating and is provided with the anode; performing a first plating process, in which the substrate holder is rotated and the plating solution is stirred by a stirring mechanism. liquid, while causing a power supply configured to supply current between the substrate and the anode to supply a forward current for causing the metal to precipitate from the plating liquid to the substrate; performing a second plating process, in which, in the second plating process, in a state in which the opening density change direction is not parallel to the flow direction of the plating liquid stirred by the stirring mechanism and in a state in which the rotation of the substrate holder is stopped, the plating liquid is stirred by the stirring mechanism while causing the power supply to supply a current flowing in a pulsed state in the direction opposite to the forward current, i.e., a reverse current pulse; and performing the first plating process again.

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

[0012] (Method 2)

[0013] In the above-mentioned aspect 1, in the above-mentioned second plating process, the direction in which the opening density changes may be perpendicular to the flow direction of the above-mentioned plating solution stirred by the above-mentioned stirring mechanism.

[0014] (Method 3)

[0015] Based on the above-mentioned method 1 or method 2, the above-mentioned stirring mechanism may also include a paddle configured to stir the above-mentioned plating liquid in the above-mentioned plating tank by reciprocating movement, and the direction of the reciprocating movement of the above-mentioned paddle is used as the flow direction of the above-mentioned plating liquid stirred by the above-mentioned stirring mechanism in the above-mentioned second plating treatment. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0017] Figure 2 It is a plan view showing the overall structure of the plating apparatus according to the embodiment.

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

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

[0020] Figure 5 is a schematic top view of a blade according to an embodiment.

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

[0022] Figure 7 (A) and Figure 7 (B) is a diagram for explaining an example of a time waveform of a current supplied from the power supply to the anode and the substrate according to the embodiment.

[0023] Figure 8 It means that in Figure 6 (B) is a graph showing an example of measuring the height of the bumps in each pattern region when a plurality of bumps are formed on the substrate of the photoresist layer exemplified.

[0024] Fig. 9 This is an example of a flowchart for explaining the plating method according to the embodiment.

[0025] Fig.10 This is a schematic plan view for explaining the direction in which the opening density of the substrate changes according to the embodiment.

[0026] Fig.11 (A) and Fig.11 (B) is a diagram for explaining that the degree of uniformity of the bump height changes depending on the angle formed by the direction of change in the opening density of the substrate and the flow direction of the plating solution during stirring. DETAILED DESCRIPTION

[0027] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In addition, the accompanying drawings are schematically illustrated to facilitate understanding of the features of the constituent elements, and the size ratios of the constituent elements are not limited to the same as the actual situation. In addition, in some drawings, X-Y-Z orthogonal coordinates are illustrated for reference. The Z direction in the orthogonal coordinates corresponds to the top, and the -Z direction corresponds to the bottom (the direction in which gravity acts).

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

[0029] The loading port 100 is a module for carrying a substrate contained in a box such as a FOUP (not shown) into the plating device 1000, or carrying a substrate out of the plating device 1000 to a box. In the present embodiment, four loading ports 100 are arranged in a horizontal direction, but the number and arrangement of the loading ports 100 are arbitrary. The conveying robot 110 is a robot for conveying substrates, and is configured to transfer substrates between the loading port 100, the aligner 120, the pre-wetting module 200, and the spin dryer 600. When the substrate is transferred between the conveying robot 110 and the conveying device 700, the conveying robot 110 and the conveying device 700 can transfer the substrate via a temporary table (not shown).

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

[0031] The prepreg module 300 is configured to perform a prepreg treatment, which is a treatment for cleaning or activating the surface of the plated substrate by etching away a high-resistance oxide film such as a seed layer surface formed on the plated surface of the substrate before the plating treatment with a treatment solution such as sulfuric acid or hydrochloric acid. In the present embodiment, two prepreg modules 300 are arranged in the vertical direction, but the number and configuration of the prepreg modules 300 are arbitrary. The plating module 400 plates the substrate. In the present embodiment, there are two groups of 12 plating modules 400, which are arranged in the vertical direction with 3 units and arranged in the horizontal direction with 4 units, and a total of 24 plating modules 400 are provided, but the number and configuration of the plating modules 400 are arbitrary.

[0032] The cleaning module 500 is configured to perform cleaning on the substrate in order to remove the plating liquid etc. remaining in the substrate after the plating treatment. In the present embodiment, two cleaning modules 500 are arranged in the vertical direction, but the number and configuration of the cleaning modules 500 are arbitrary. The spin dryer 600 is a module for rotating the substrate after the cleaning treatment at high speed for drying. In the present embodiment, two spin dryers 600 are arranged 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 substrates between multiple modules in the plating device 1000. The control module 800 is configured to control multiple modules of the plating device 1000, and can be composed of a common computer or a special computer having an input and output interface with an operator, for example.

[0033] An example of a series of plating processes performed by the plating device 1000 is described. First, the substrate stored in the box is carried into the loading port 100. Then, the conveying robot 110 takes out the substrate from the box of the loading port 100 and conveys the substrate to the aligner 120. The aligner 120 aligns the positioning plane, the notch, etc. of the substrate in a predetermined direction. The conveying robot 110 delivers the substrate aligned by the aligner 120 to the pre-wetting module 200.

[0034] The prewetting module 200 performs a prewetting process on the substrate. The conveying device 700 conveys the substrate subjected to the prewetting process to the prepreg module 300. The prepreg module 300 performs a prepreg process on the substrate. The conveying device 700 conveys the substrate subjected to the prepreg process to the plating module 400. The plating module 400 performs plating on the substrate.

[0035] The conveying device 700 conveys the substrate 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 subjected to the cleaning process to the spin dryer 600. The spin dryer 600 performs a drying process on the substrate. The conveying robot 110 receives the substrate from the spin dryer 600 and conveys the substrate subjected to the drying process to the box of the loading port 100. Finally, the box containing the substrate is unloaded from the loading port 100.

[0036] also, Figure 1 , Figure 2 The structure of the plating device 1000 described in the above is merely an example, and the structure of the plating device 1000 is not limited to Figure 1 , Figure 2 structure.

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

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

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

[0040] Figure 3 and Figure 4 The plating module 400 of the illustrated plating device 1000 includes a plating tank 10, an overflow tank 20, a substrate holder 30, and a paddle 70 as an example of a stirring mechanism 60. Figure 3 As shown in the example, the plating module 400 includes a rotating mechanism 40, a tilting mechanism 45, and a lifting mechanism 50. Figure 3 As shown in the example, the plating module 400 includes sensors 130. Figure 4 As illustrated, the plating module 400 includes a power source 80 and a plating solution flow mechanism 90 .

[0041] The plating tank 10 of the present embodiment is composed of 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 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 the outer peripheral wall 10b of the present embodiment has a cylindrical shape as an example. The plating solution Ps is stored inside the plating tank 10.

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

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

[0045] like Figure 3 , Figure 4 As shown in the example, the ion resistor 12 may be arranged above the anode 11 in the plating tank 10. Figure 4 As shown in the partially enlarged view of FIG. 1 , the ion resistor 12 is composed of a porous plate member having a plurality of holes 12 a (fine pores). The holes 12 a are provided so as to connect the lower surface and the upper surface of the ion resistor 12 .

[0046] The ionic resistor 12 is provided to achieve uniformity of the electric field formed between the anode 11 and the substrate Wf as the cathode. By configuring the ionic resistor 12 in the plating tank 10 as in the present embodiment, the thickness of the plated film (plating layer) formed on the substrate Wf can be easily uniformed.

[0047] like Figure 3 , Figure 4 As shown in the example, the membrane 16 can also be arranged 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 into an anode chamber 17a below the membrane 16 and a cathode chamber 17b above the membrane 16 by the membrane 16. The anode 11 is arranged in the anode chamber 17a, and the ion resistor 12 and the substrate Wf are arranged in the cathode chamber 17b. The membrane 16 is configured to allow ion species containing metal ions contained in the plating solution Ps to pass through the membrane 16, and to inhibit non-ionic plating additives contained in the plating solution Ps from passing through the membrane 16. As such a membrane 16, for example, an ion exchange membrane can be used.

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

[0049] The first flow mechanism 91a is a mechanism for flowing the plating solution Ps in the anode chamber 17a. The second flow mechanism 91b is a mechanism for flowing the plating solution Ps in the cathode chamber 17b. The first flow mechanism 91a is connected to the anode chamber 17a via the pipe 92a. The second flow mechanism 91b is connected to the cathode chamber 17b via the pipe 92b. In addition, the first flow mechanism 91a and the second flow mechanism 91b are respectively equipped with a pump for pressurizing the plating solution Ps.

[0050] Reference Figure 3 and Figure 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 of the present 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 supplied to the anode chamber 17a from the first supply port 13a again.

[0051] The overflow tank 20 is composed of a bottomed container arranged outside the plating tank 10. The overflow tank 20 is provided to temporarily store 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 overflowing from the plating tank 10). The plating solution Ps stored in the overflow tank 20 is discharged from the second discharge port 14b, and then is pressure-fed by the second flow mechanism 91b and supplied to the cathode chamber 17b again from the second supply port 13b.

[0052] The substrate holder 30 holds the substrate Wf serving as a cathode so 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 downwardly facing surface (lower surface) of the substrate Wf.

[0053] The substrate holder 30 is connected to the rotating mechanism 40 . The rotating 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 rotating mechanism 40, a known rotating motor or the like can be used. The tilting mechanism 45 is a mechanism for tilting the rotating mechanism 40 and the substrate holder 30. The lifting mechanism 50 is supported by a support shaft 51 extending in the up-down direction. The lifting mechanism 50 is a mechanism for lifting and lowering the substrate holder 30, the rotating mechanism 40, and the tilting mechanism 45 in the up-down 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 including 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 of a program stored in the storage device 802 .

[0055] Reference Figure 3 The sensor class 130 detects various information used for various controls of the control module 800 and transmits the detection results to the control module 800. The sensor class 130 includes, for example, a current sensor for detecting a current value (A) between the anode 11 and the substrate Wf, and a voltage sensor for detecting a voltage value (V) between the anode 11 and the substrate Wf.

[0056] In addition, the sensor class 130 includes a speed sensor for detecting the moving speed (rpm, or m / sec) of the paddle 70. In addition, the sensor class 130 includes a rotation speed sensor for detecting the rotation speed (rpm) of the substrate holder 30. In addition, the sensor class 130 includes 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 sensor class 130 includes an angle sensor for detecting the rotation angle of the substrate holder 30. The control module 800 can obtain the rotation angle (rotation position) of the substrate holder 30 by acquiring the detection result of the angle sensor, thereby also obtaining the rotation angle (rotation position) of the substrate Wf held by the substrate holder 30.

[0058] like Figure 4 As illustrated, the power source 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 source 80 is controlled by a control module 800.

[0059] The control module 800 of this embodiment controls the power supply 80 in a manner that supplies a "forward current" for causing metal to precipitate from the plating liquid Ps onto the substrate Wf, and a current that flows in a pulsed manner in the opposite direction to the forward current, i.e., a "reverse current pulse", when performing a "plating treatment" on the substrate Wf.

[0060] Figure 5 is a schematic top view of the blade 70. Figure 3 , Figure 4 and Figure 5The paddle 70 is disposed between the substrate Wf and the anode 11 (specifically, in the present embodiment, between the substrate Wf and the ion resistor 12 as an example). The paddle 70 is driven by the driving device 77 which receives the instruction of the control module 800. The paddle 70 is driven to stir the plating solution Ps in the plating tank 10.

[0061] The paddle 70 of the present embodiment is driven alternately in 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, as an example. That is, the paddle 70 of the present embodiment reciprocates in the direction of the X axis, as an example.

[0062] like Figure 5 As illustrated, the paddle 70 of this embodiment has, as an example, 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, and various known paddles as exemplified in Patent Document 1, for example, may be used.

[0064] In addition, the paddle 70 only needs to be arranged inside the plating tank 10 at least when stirring the plating solution Ps, and does not need to be always arranged inside the plating tank 10. 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 can also be configured not to be arranged 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 once N times within 1 minute (that is, the paddle 70 moves from a predetermined position, for example, in a first direction, then moves in a second direction, and then moves in the first direction again to return to the predetermined position). The faster the moving speed of the paddle 70, the stronger the stirring intensity of the plating solution Ps by the paddle 70. 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, Figure 6 In (A), a schematic cross-sectional view shows a state where bumps 143 are formed on the substrate Wf by plating. Specifically, the bumps 143 are formed of a metal (eg, Cu) deposited on the substrate Wf.

[0067] like Figure 6As shown in (A), a thin metal seed layer 140 is pre-set on the entire surface of the substrate Wf in this embodiment as an example. During the plating process, power is supplied to the surface of the substrate Wf through 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 in the portion where the bump 143 is to be formed. In addition, Figure 6 “φ” illustrated in (A) 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) is a schematic diagram showing an example of an opening pattern of the photoresist layer 141. Figure 6 In (B), No. 1 and No. 2 are shown in the figure, the case where the diameter φ of the opening 142 is relatively small (as an example, 30 μm), and No. 3 and No. 4 are shown in the figure, the case where the diameter φ of the opening 142 is relatively large (as an example, 75 μm). If No. 1 is compared with No. 2, No. 1 has the openings 142 arranged at a higher density than No. 2. If No. 3 is compared with No. 4, No. 3 has the openings 142 arranged at a higher density than No. 4.

[0069] The substrate Wf provided with the above-mentioned photoresist layer 141 is held by the substrate holder 30 and immersed in the plating solution Ps of 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 plated film grows only on the portion of the opening 142 of the photoresist layer 141, thereby forming a bump 143 on the substrate Wf. In addition, the photoresist layer 141 may be removed after the plating treatment.

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

[0071] In order to actually grow the plated film, the length of the first period T1 may also be a time that occupies most of the total time for the plating process. In other words, compared with the length of the first period T1, the sum of the lengths of the second period T2 and the third period T3 described later may also be negligible. The magnitude of the forward current may, for example, be a current value that is constant throughout the first period T1. Alternatively, the current value of the forward current may also be controlled to vary with time.

[0072] In the second period T2 provided in the middle of the first period T1, the power supply 80 receives the instruction of the control module 800 and supplies a current in the opposite direction to the above-mentioned forward current, i.e., a reverse current pulse. For example, the length of the second period T2, i.e., the pulse width of the reverse current pulse, may also be about 0.1 seconds to several seconds. In the second period T2, in contrast to the reduction reaction of the metal ions in the first period T1, the metal of a part of the plated film formed on the substrate Wf in the first period T1 is dissolved again 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 plated film in the reduction reaction is detached from the surface of the plated film. In addition, the current value of the reverse current pulse is preferably set to a value that fully performs the detachment of the accelerator.

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

[0074] After the second period T2 or the third period T3, the power source 80 supplies the forward current again. The forward current continues until the predetermined plating treatment time ends, for example, until the film thickness of the formed plated film reaches a predetermined target film thickness.

[0075] Figure 8 It means that in Figure 6 This is a graph 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 of the photoresist layer 141 illustrated in (B). Figure 8 In the vertical axis, Figure 6 The height (BH) of each bump 143 corresponding to each pattern area P1, P2, P3, P4 in (B) specifically shows the average value of the heights of the plurality of bumps 143 included in the pattern area.

[0076] Figure 8The graph on the left shows the measurement results of the case where the bump 143 is formed by supplying a forward current during the entire plating process. Figure 8 The graph on the right shows the measurement results when the bump 143 is formed by supplying a reverse current pulse once during the plating process.

[0077] according to Figure 8 It can be seen that among all 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 configuration density of the opening 142, the more difficult it is for the metal ions to fully replenish the opening 142, and thus the formation rate of the plated film becomes lower. Here, the difference between the maximum and minimum values ​​of the height (BH) of the bump 143 is defined as "bump height deviation (ΔBH)".

[0078] according to Figure 8 It can be seen that when a reverse current pulse is supplied during the plating process ( Figure 8 The graph on the right) is compared with the case where no reverse current pulse is supplied ( Figure 8 In comparison with the graph on the left side, the bump height variation (ΔBH) is smaller. In this way, by supplying the reverse current pulse, the height of the bump 143 can be made uniform.

[0079] Fig.10 1 is a schematic top view for explaining the direction in which the opening density of the photoresist layer 141 provided on the substrate Wf changes, that is, the "opening density change direction (Dr2)". Fig.10 In the embodiment, the opening 142 of the photoresist layer 141 includes a “region Ar1” (i.e., a region with “sparse” opening density)” having an opening density lower than a specified value, and a “region Ar2” (i.e., a region with “dense” opening density) having an opening density higher than that of the region Ar1. In this case, the direction of change of the opening density (Dr2) is the direction from the region Ar1 toward the region Ar2 (or, the direction from the region Ar2 toward the region Ar1).

[0080] Here, the inventors' research has revealed that when a reverse current pulse is supplied, the degree of uniformity of the height of the bump 143 changes 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 (the details of which are described later). Fig.11 Therefore, in this embodiment, in order to effectively achieve uniform height of bump 143, the following steps are performed: Fig. 9 The plating method described in .

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

[0082] Furthermore, when the user acquires the opening density change direction (Dr2), for example, if information related to the opening density is recorded in the specification of the substrate Wf, the user may acquire the opening density change direction (Dr2) based on the specification. Alternatively, the user may observe the substrate Wf visually or using a microscope to acquire (i.e., measure) the opening density change direction (Dr2).

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

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

[0085] Next, the control module 800 immerses the substrate Wf held by the substrate holder 30 in the plating solution Ps of the plating tub 10 so as to face the anode 11 (step S30 ).

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

[0087] Next, the control module 800 performs the second plating process (step S50). Specifically, in step S50, the control module 800 causes the power supply 80 to supply a reverse current pulse while stirring the plating solution Ps by the stirring mechanism 60, while the opening density change direction (Dr2) is not parallel to the flow direction (Dr1) of the plating solution Ps stirred by the stirring mechanism 60 and the rotation of the substrate holder 30 is stopped.

[0088] In addition, the "opening density change direction (Dr2)" and the "flow direction of the plating liquid Ps (Dr1)" are not parallel. In other words, the "opening density change direction (Dr2)" and the "flow direction of the plating liquid Ps (Dr1)" are not the same direction nor the opposite direction.

[0089] Specifically, refer to Fig.10 The control module 800 of this embodiment stops the rotation of the substrate holder 30 when the angle (α1) formed by the opening density change direction (Dr2) and the flow direction (Dr1) of the plating solution Ps is greater than 0 degrees and less than 180 degrees.

[0090] exist Fig.10 As an example, the rotation of the substrate holder 30 is stopped in such a manner that the opening density change direction (Dr2) is perpendicular to the flow direction (Dr1) of the plating solution Ps (α1 is 90 degrees). In this manner, the control module 800 stops the rotation of the substrate holder 30, while stirring the plating solution Ps through the stirring mechanism 60, and at the same time, causes the power supply 80 to supply a reverse current pulse.

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

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

[0093] Reference Fig. 9 , after step S50, the control module 800 performs the first plating process again (step S60).

[0094] In addition, the control module 800 can also repeatedly execute multiple Fig. 9 Step S40, step S50, and step S60.

[0095] Fig.11 (A) and Fig.11 (B) is a diagram for explaining that the degree of uniformity of the height of the bumps 143 changes 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. Fig.11 (A) and Fig.11The vertical axis of (B) shows the uniformity within the bare chip (the difference between the maximum value and the minimum value of the height of the bump 143 ).

[0096] Specifically, Fig.11 (A) shows the results of an experiment using a substrate Wf with a relatively large degree of deviation in the aperture ratio of the bump 143 (a substrate Wf with an aperture ratio difference of 8 times in the bare chip). Fig.11 (B) shows the result of an experiment using a substrate Wf in which the degree of variation in the aperture ratio of the bumps 143 is relatively small (a substrate Wf in which the difference in the aperture ratio within the bare chip is three times).

[0097] Fig.11 Sample No. 1 of (A) is the experimental result when only the first plating process is performed (that is, when only the forward current is supplied). Sample No. 2 is the experimental result when the plating method of this embodiment ( Fig. 9 Specifically, in sample No2, in the second plating process of step S50, 90 degrees is used as the angle (α1). Sample No3 is performed Fig. 9 The experimental results are as follows: Steps S10 to S60 of the flowchart of FIG. 5 , but in the second plating process of step S50 , zero degree (or 180 degrees) is used as the angle (α1). That is, sample No. 2 is an embodiment, and samples No. 1 and No. 3 are comparative examples.

[0098] Comparing sample No. 1 with sample No. 2 and sample No. 3, it can be seen that the uniformity value within the bare chip can be reduced by supplying a reverse current pulse during the plating process (that is, it can be seen that the height of the bump 143 can be made uniform). In addition, comparing sample No. 2 with sample No. 3, it can be seen that the uniformity value within the bare chip changes according to the value of the angle (α1) formed when the second plating process is performed.

[0099] Moreover, by comparing sample No. 2 with sample No. 3, it can be seen that the value of the uniformity within the bare chip of sample No. 2 is lower than that of sample No. 3. Therefore, it can be seen that when 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 during the second plating process as in sample No. 2, the value of the uniformity within the bare chip can be reduced compared to the case where 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 as in sample No. 3.

[0100] This is considered to be because, during the second plating treatment, the opening density change direction (Dr2) is not parallel to the flow direction (Dr1) of the plating liquid Ps during stirring, compared to a case where this is not the case, the plating liquid Ps present on the surface of the substrate Wf (i.e., the surface of the plating film) can be more evenly stirred over the entire surface of the substrate Wf, thereby enabling the promoter to be evenly and effectively separated from the surface of the plating film, resulting in a smaller value of uniformity within the bare chip.

[0101] Fig.11 Sample No. 4 of (B) is the experimental result when only the first plating process is performed (that is, when only the forward current is supplied). Sample No. 5 is the experimental result when the plating method of this embodiment is performed ( Fig. 9 Specifically, in sample No. 5, in the second plating process of step S50, 90 degrees is used as the angle (α1). Sample No. 6 is performed Fig. 9 The experimental results are as follows: Steps S10 to S60 of the flowchart of FIG. 5 , but in the second plating process of step S50 , zero degree (or 180 degrees) is used as the angle (α1). That is, sample No. 5 is an example, and samples No. 4 and No. 6 are comparative examples.

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

[0103] Moreover, by comparing sample No. 5 with sample No. 6, it can be seen that when 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 liquid Ps during stirring during the second plating treatment as in sample No. 5, the value of uniformity within the bare chip can be reduced compared with the case where 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 liquid Ps during stirring as in sample No. 6.

[0104] As described above, it is known that the uniformity within the bare chip changes depending on the value of the angle (α1) formed when the second plating process is performed, that is, the degree of uniformity of the height of the bump 143 changes.

[0105] In addition, in this embodiment, 90 degrees is used as an example of the angle (α1) formed when the second plating process is performed, but it is not limited to this. As long as the angle (α1) is greater than 0 degrees and less than 180 degrees, it is not particularly limited. Regarding the angle (α1), the value that can best achieve uniformity of the height of the bump 143 can be obtained in advance through experiments, and the obtained value can be set as the angle (α1).

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

[0107] According to the present embodiment described above, the height of the bumps 143 can be made uniform.

[0108] As mentioned above, although embodiment and modification of this invention are described in detail, this invention is not limited to this specific embodiment and modification, and various modifications and changes are possible within the scope of this invention described in the claims.

[0109] Description of Reference Numerals

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

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

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

Claims

1. A plating method, characterized in that: include: Obtaining a direction in which the opening density of the photoresist layer disposed on the substrate changes, that is, a direction in which the opening density changes; Keeping the substrate having the opening density change direction obtained on a substrate support; The substrate held by the substrate holder is immersed in a plating solution of a plating tank so as to face an anode. The plating tank stores the plating solution containing an accelerator for promoting plating and is provided with the anode. performing a first plating process, in which a power source configured to supply current between the substrate and the anode supplies a forward current for depositing metal from the plating solution onto the substrate while rotating the substrate holder and stirring the plating solution by a stirring mechanism; performing a second plating process, in which, in a state in which the opening density change direction is not parallel to the flow direction of the plating solution stirred by the stirring mechanism and in a state in which the rotation of the substrate holder is stopped, the plating solution is stirred by the stirring mechanism while 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; as well as The first plating process is performed again.

2. The plating method according to claim 1, characterized in that In the second plating process, the opening density changing direction is perpendicular to a flow direction of the plating solution stirred by the stirring mechanism.

3. The plating method according to claim 1, characterized in that The stirring mechanism includes a paddle configured to stir the plating solution in the plating tank by reciprocating movement. As the flow direction of the plating solution stirred by the stirring mechanism in the second plating process, the direction in which the paddle moves back and forth is used.

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