Plating device and plating method

Abstract

A plurality of bumps are formed on a substrate at a uniform height. A plating device for forming bumps on a substrate is provided. The plating device comprises: a substrate holder configured to hold the substrate; a plating tank configured to contain a plating solution together with the substrate holder; an anode arranged in the plating tank in a manner opposite to the substrate held on the substrate holder; a power supply configured to supply current between the substrate and the anode; and a control unit configured to output a current having the following periods from the power supply: a first period for supplying a forward current for causing metal to precipitate from the plating solution on the substrate, a second period for supplying at least one reverse current pulse flowing in a direction opposite to the forward current, and a third period for stopping the current supply in the middle of transitioning from the reverse current pulse to the forward current.

Description

Technical Field

[0001] The present invention relates to a plating device and a plating method, and in particular to a plating device and a plating method for forming a bump on a substrate. Background Art

[0002] A metal plating film such as Cu is formed on the surface of a semiconductor device or electronic component substrate. For example, a substrate to be plated is often held on a substrate holder, and the substrate holder and the substrate are immersed in a plating tank containing a plating solution for electroplating. The substrate holder holds the substrate in a manner that exposes the plated surface of the substrate. In the plating solution, an anode is arranged in a manner corresponding to the exposed surface of the substrate, and a voltage is applied between the substrate and the anode, so that an electroplated film can be formed on the exposed surface of the substrate.

[0003] For example, a photoresist layer having a plurality of openings is disposed on the surface of the substrate. By plating the substrate with the photoresist layer, bumps can be formed in the openings.

[0004] Patent Document 1: Japanese Patent Application Publication No. 2006-131926

[0005] Patent Document 2: Japanese Patent Application Publication No. 2011-026708

[0006] It is required to form a plurality of bumps with uniform height on a substrate.

[0007] Patent document 1 discloses that bumps are formed by plating by alternately supplying positive current pulses and negative current pulses, but does not disclose a method for forming multiple bumps with uniform height. Patent document 2 discloses that bumps are formed on a substrate using positive voltage pulses and reverse voltage pulses. In addition, a period in which the voltage is zero is provided between the positive voltage and the negative voltage (Figures 16 to 18). However, since the voltage is controlled instead of the current, the current actually flowing in the plating solution changes with time, that is, with the growth of the plated film, and therefore the effect of the present invention described later cannot be stably produced (see Fig. 9 In addition, even if the applied voltage is zero, there is still a situation where current flows in the plating solution, so the effect of the present invention described later cannot be fully exerted (refer to Fig. 9 The density difference of the formation promoter molecules is explained). Summary of the invention

[0008] According to one embodiment, a plating device is provided for forming a bump on a substrate, wherein the device comprises: a substrate holder configured to hold the substrate; a plating tank configured to accommodate a plating solution together with the substrate holder; an anode configured in the plating tank to be opposite to the substrate held on the substrate holder; a power supply configured to supply current between the substrate and the anode; and a control unit configured to output from the power supply a current having the following periods: a first period for supplying a forward current for causing metal to precipitate from the plating solution on the substrate, a second period for supplying at least one reverse current pulse flowing in a direction opposite to the forward current, and a third period for stopping the current supply in the middle of transitioning from the reverse current pulse to the forward current.

[0009] In addition, according to one embodiment, a plating method is provided, which is used to form a bump on a substrate, comprising supplying a current having the following periods between the above-mentioned substrate and an anode arranged in the plating tank: a first period of supplying a forward current for causing metal to precipitate from the plating liquid in the above-mentioned plating tank on the above-mentioned substrate, a second period of supplying at least one reverse current pulse flowing in a direction opposite to the above-mentioned forward current, and a third period of stopping the current supply in the middle of the transition from the above-mentioned reverse current pulse to the above-mentioned forward current. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 It is an overall configuration diagram of a plating device according to one embodiment of the present invention.

[0011] Figure 2 This is a schematic side cross-sectional view of a plating module according to one embodiment of the present invention.

[0012] Figure 3 It is a schematic diagram which shows the bump formed using the plating apparatus which is one embodiment of this invention.

[0013] Figure 4 This is a graph showing a time waveform of a plating current output from a power supply in a plating apparatus according to an embodiment of the present invention.

[0014] Figure 5 It means Figure 4 Graph of the time waveforms of different plating currents.

[0015] Figure 6 It is a schematic diagram showing an opening pattern of a photoresist layer used to form a plurality of bumps.

[0016] Figure 7 is used Figure 6 An example of measuring the bump height BH when a plurality of bumps are formed on a photoresist layer.

[0017] Figure 8 This is a graph showing bump height deviation ΔBH under various conditions when bumps are formed by changing the plating current conditions.

[0018] Fig. 9 This is a conceptual diagram for explaining the principle of improving the uniformity of the heights of the plurality of bumps.

[0019] Fig.10 This is a graph comparing the bump height deviation ΔBH when the stirring of the plating solution is stopped in the third period T3 and when the stirring is not stopped.

[0020] Fig.11 This is a graph showing a time waveform of a plating current output from a power supply in a plating apparatus according to an embodiment of the present invention. DETAILED DESCRIPTION

[0021] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In the drawings described below, the same or corresponding components are denoted by the same reference numerals and duplicate descriptions are omitted.

[0022] Figure 1 FIG. 1 is an overall configuration diagram of a plating device 10 according to an embodiment of the present invention. Figure 1 As shown, the plating device 10 has two cassette worktables 102, an aligner 104 for aligning the position of the positioning plane, notch, etc. of the substrate in a predetermined direction, and a spin dryer 106 for rotating the substrate after the plating process at high speed to dry it. The cassette worktable 102 carries a cassette 100 containing substrates such as semiconductor wafers. A loading / unloading station 120 is provided near the spin dryer 106, and the loading / unloading station 120 carries the substrate holder 30 to load and unload the substrate. A conveying robot 122 is arranged in the center of these units 100, 104, 106, and 120, and the conveying robot 122 conveys the substrate between these units.

[0023] The loading / unloading station 120 includes a flat plate-shaped loading plate 152 that is freely slidable laterally along the guide rails 150. Two substrate holders 30 are placed side by side on the loading plate 152 in a horizontal state, and after a substrate is transferred between one substrate holder 30 and the transfer robot 122, the loading plate 152 slides laterally to transfer a substrate between the other substrate holder 30 and the transfer robot 122.

[0024] The plating device 10 further includes a storage tank 124, a pre-wetting module 126, a pre-preg module 128, a first rinsing module 130a, an air blowing module 132, a second rinsing module 130b and a plating module 110. In the storage tank 124, the substrate holder 30 is stored and temporarily placed. In the pre-wetting module 126, the substrate is immersed in pure water. In the pre-preg module 128, the oxide film on the surface of the conductive layer such as the seed layer formed on the surface of the substrate is etched and removed. In the first rinsing module 130a, the pre-preg substrate is cleaned together with the substrate holder 30 by a cleaning liquid (pure water, etc.). In the air blowing module 132, the liquid removal of the cleaned substrate is performed. In the second rinsing module 130b, the plated substrate is cleaned together with the substrate holder 30 by a cleaning liquid. The loading / unloading station 120 , the stocker 124 , the pre-wetting module 126 , the pre-preg module 128 , the first rinsing module 130 a , the blowing module 132 , the second rinsing module 130 b , and the plating module 110 are sequentially arranged.

[0025] The plating module 110 is configured to accommodate a plurality of plating tanks 114 inside an overflow tank 136, for example. Figure 1 In the example of FIG. 1 , the plating module 110 has eight plating tanks 114. Each plating tank 114 is configured to accommodate one substrate therein, immerse the substrate in a plating solution held therein, and perform plating such as copper plating on the surface of the substrate.

[0026] The plating device 10 has, for example, a conveying device 140 using a linear motor method, and the conveying device 140 is located on the side of the above-mentioned devices, and conveys the substrate holder 30 together with the substrate between the above-mentioned devices. The conveying device 140 has a first conveying device 142 and a second conveying device 144. The first conveying device 142 is configured to convey the substrate between the loading / unloading station 120, the storage container 124, the pre-wetting module 126, the pre-preg module 128, the first rinsing module 130a, and the blowing module 132. The second conveying device 144 is configured to convey the substrate between the first rinsing module 130a, the second rinsing module 130b, the blowing module 132, and the plating module 110. The plating device 10 may also only have the first conveying device 142, but not the second conveying device 144.

[0027] A paddle driving unit 160 and a paddle follower 162 are disposed on both sides of the overflow tank 136 . The paddle driving unit 160 and the paddle follower 162 drive a paddle as a stirring rod located inside each plating tank 114 and stirring the plating liquid in the plating tank 114 .

[0028] An example of a series of plating processes performed by the plating device 10 is described. First, a substrate is taken out from the box 100 mounted on the box worktable 102 by the conveying robot 122, and the substrate is conveyed to the aligner 104. The aligner 104 aligns the positions of the positioning plane, the notch, etc. in a predetermined direction. The conveying robot 122 conveys the substrate aligned by the aligner 104 to the loading / unloading station 120.

[0029] In the loading / unloading station 120, two substrate holders 30 stored in the stocker 124 are simultaneously held by the first conveying device 142 of the conveying device 140 and conveyed to the loading / unloading station 120. Then, the two substrate holders 30 are simultaneously horizontally placed on the placement plate 152 of the loading / unloading station 120. In this state, the conveying robot 122 conveys the substrate to each substrate holder 30, and the substrate holder 30 holds the conveyed substrate.

[0030] Next, two substrate holders 30 holding the substrates are simultaneously held by the first conveyor device 142 of the conveyor device 140 and stored in the pre-wet module 126. Next, the substrate holder 30 holding the substrate processed by the pre-wet module 126 is conveyed to the pre-preg module 128 by the first conveyor device 142, and the oxide film on the substrate is etched by the pre-preg module 128. Next, the substrate holder 30 holding the substrate is conveyed to the first rinse module 130a, and the surface of the substrate is rinsed with pure water stored in the first rinse module 130a.

[0031] The substrate holder 30 holding the substrate after the water washing is transported from the first rinsing module 130a to the plating module 110 by the second conveying device 144, and is stored in the plating tank 114 filled with the plating solution. The second conveying device 144 repeats the above steps in sequence, and the substrate holder 30 holding the substrate is stored in each plating tank 114 of the plating module 110 in sequence.

[0032] In each plating tank 114 , a plating current is supplied between an anode (not shown) in the plating tank 114 and the substrate, and the paddle driving unit 160 and the paddle follower 162 reciprocate the paddle parallel to the surface of the substrate, thereby plating the surface of the substrate.

[0033] After the plating is completed, the second conveying device 144 simultaneously holds two substrate holders 30 holding the plated substrates and conveys them to the second rinsing module 130b, where they are immersed in the pure water contained in the second rinsing module 130b to clean the surface of the substrates with pure water. Next, the second conveying device 144 conveys the substrate holder 30 to the air blowing module 132, where water droplets attached to the substrate holder 30 are removed by blowing air. Thereafter, the first conveying device 142 conveys the substrate holder 30 to the loading / unloading station 120.

[0034] In the loading / unloading station 120, the processed substrate is taken out from the substrate holder 30 by the conveying robot 122 and conveyed to the spin dryer 106. The spin dryer 106 spins the substrate after the plating process at high speed to dry it. The dried substrate is returned to the box 100 by the conveying robot 122.

[0035] Figure 2 1 is a schematic side sectional view of the above-mentioned plating module 110. As shown in the figure, the plating module 110 has: an anode support 220, which is configured to hold an anode 221; a substrate support 30, which is configured to hold a substrate W; a plating tank 114, which accommodates a plating solution Q containing an additive; and an overflow tank 136, which receives the plating solution Q overflowing from the plating tank 114 and discharges it. The plating tank 114 and the overflow tank 136 are separated by a partition wall 255. The anode support 220 and the substrate support 30 are accommodated in the interior of the plating tank 114. As described above, the substrate support 30 holding the substrate W is conveyed by the second conveying device 144 (refer to Figure 1 ) is transported and received in the plating tank 114.

[0036] In addition, Figure 2 Only one plating tank 114 is shown in FIG. 1 , but as described above, the plating module 110 may include multiple Figure 2 The structure shown is the same as the plating tank 114.

[0037] The anode 221 is electrically connected to the positive terminal 271 of the power supply 270 via the electrical terminal 223 provided on the anode holder 220. The substrate W is electrically connected to the negative terminal 272 of the power supply 270 via the electrical contact 242 in contact with the peripheral portion of the substrate W and the electrical terminal 243 provided on the substrate holder 30. The power supply 270 is configured to supply a plating current between the anode 221 connected to the positive terminal 271 and the substrate W connected to the negative terminal 272, and to measure an applied voltage between the positive terminal 271 and the negative terminal 272.

[0038] In addition, the power supply 270 is connected to a control controller 260 for controlling the operation of the power supply 270, and the control controller 260 is connected to a computer 265. The computer 265 provides a user interface for the operator of the plating device 10. The operator of the plating device 10 can input various setting information related to the plating process via the computer 265. The setting information includes, for example, a set value of the plating current output by the power supply 270. The control controller 260 operates the power supply 270 according to the set value of the plating current input by the operator. The control controller 260 also provides the computer 265 with status information based on information on the applied voltage between the terminals 271 and 272 measured in the power supply 270. The operator of the plating device 10 can receive the status information via the computer 265. The control controller 260 can also be configured to control the operation of each part other than the power supply 270 in the plating module 110 or each unit other than the plating module 110 in the plating device 10, and provide various status information related to these operations to the computer 265.

[0039] The anode holder 220 holding the anode 221 and the substrate holder 30 holding the substrate W are immersed in the plating solution Q in the plating tank 114, and are arranged opposite to each other in such a manner that the anode 221 is substantially parallel to the plated surface W1 of the substrate W. The anode 221 and the substrate W are supplied with a plating current from the power supply 270 while being immersed in the plating solution Q in the plating tank 114. As a result, the metal ions in the plating solution Q are reduced on the plated surface W1 of the substrate W, and a film is formed on the plated surface W1.

[0040] The anode support 220 has an anode shield 225 for adjusting the electric field between the anode 221 and the substrate W. The anode shield 225 is, for example, a substantially plate-shaped member made of a dielectric material, and is disposed on the front surface of the anode support 220 (the surface on the side opposite to the substrate support 30). That is, the anode shield 225 is disposed between the anode 221 and the substrate support 30. The anode shield 225 has a first opening 225a in a substantially central portion, and the first opening 225a is for the current flowing between the anode 221 and the substrate W to pass through. The diameter of the opening 225a is preferably smaller than the diameter of the anode 221. The anode shield 225 may also be configured to be able to adjust the diameter of the opening 225a.

[0041] The plating module 110 further includes an adjustment plate 230 for adjusting the electric field between the anode 221 and the substrate W. The adjustment plate 230 is, for example, a substantially plate-shaped member made of a dielectric material, and is disposed between the anode shield 225 and the substrate holder 30 (substrate W). The adjustment plate 230 includes a second opening 230a through which the current flowing between the anode 221 and the substrate W passes. The diameter of the opening 230a is preferably smaller than the diameter of the substrate W. The adjustment plate 230 may also be configured to be able to adjust the diameter of the opening 230a.

[0042] A paddle 235 is provided between the adjustment plate 230 and the substrate holder 30, and the paddle 235 is used to stir the plating liquid Q near the plated surface W1 of the substrate W. The paddle 235 is a substantially rod-shaped member, and is provided in the plating tank 114 in a manner facing the vertical direction. One end of the paddle 235 is fixed to a paddle driving device 236. The operation of the paddle driving device 236 is controlled by a control controller 260, and the paddle 235 is horizontally moved along the plated surface W1 of the substrate W by the paddle driving device 236. Thus, the plating liquid Q is stirred.

[0043] The plating tank 114 has a plating solution supply port 256 for supplying the plating solution Q into the tank. The overflow tank 136 has a plating solution discharge port 257 for discharging the plating solution Q overflowing from the plating tank 114. The plating solution supply port 256 is arranged at the bottom of the plating tank 114, and the plating solution discharge port 257 is arranged at the bottom of the overflow tank 136.

[0044] When the plating solution Q is supplied to the plating tank 114 from the plating solution supply port 256, the plating solution Q overflows from the plating tank 114, passes over the partition wall 255, and flows into the overflow tank 136. The plating solution Q flowing into the overflow tank 136 is discharged from the plating solution discharge port 257, and impurities are removed by a filter or the like of the plating solution circulation device 258. The plating solution Q from which impurities have been removed is supplied to the plating tank 114 via the plating solution supply port 256 by the plating solution circulation device 258.

[0045] Figure 3Schematic diagram showing a bump formed on a substrate W by plating the surface of the substrate W using a plating device 10 according to an embodiment of the present invention. A thin seed layer 301 of metal is pre-formed on the entire surface of the substrate W, and power is supplied to the surface of the substrate W via the seed layer 301 during plating. A photoresist layer 302 is formed on the seed layer 301, and the photoresist layer 302 has an opening 302a at a portion where the bump is to be formed. The substrate W on which the photoresist layer 302 is formed is held by a substrate holder 30 and immersed in a plating solution Q in a plating tank 114 for plating. During plating, portions of the surface of the substrate W other than the opening 302a of the photoresist layer 302 are shielded from the plating solution Q by the photoresist layer 302. As a result, the plated film grows only on the bottom surface of the opening 302a of the photoresist layer 302, thereby forming a bump 303 on the substrate W. In addition, the photoresist layer 302 is removed after the plating process (refer to Figure 3 right).

[0046] A plurality of such bumps 303 are formed on a substrate W using a photoresist layer 302 having a predetermined opening pattern. Depending on the size of the openings (i.e., the opening diameter) and the density of the openings (i.e., the number of openings per unit area), the height (thickness) of the bumps 303 formed in each opening may vary even on the same substrate W. Therefore, it is required to form a plurality of bumps 303 on a substrate W with a uniform height.

[0047] Figure 4 1 is a graph showing a time waveform of a plating current output from the power supply 270 and flowing between the anode 221 and the substrate W in the plating device 10 according to one embodiment of the present invention. Figure 4 As shown, the power supply 270 outputs a forward current in the first period T1. "Forward" refers to the direction in which the current flows from the anode 221 toward the substrate W in the plating solution Q. Therefore, in the first period T1, the metal ions in the plating solution Q are reduced on the plated surface W1 of the substrate W, thereby precipitating the metal on the plated surface W1 (i.e., forming a plating film). The length of the first period T1 can be a time that accounts for most of the total time for the plating process so that the plating film actually grows. 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 can be a negligible degree. The magnitude of the forward current can be, for example, a current value I1 that is constant throughout the entire first period T1. Alternatively, the current value I1 of the forward current can also be controlled to change over time.

[0048] In the second period T2 provided in the middle of the first period T1, the power supply 270 outputs a current in the opposite direction to the forward current described above. The current continues to have a current value I2 having a different sign from I1 during the second period T2. The length of the second period T2 is a time period that is extremely short compared to the first period T1. Therefore, the current in the second period T2 is pulse-shaped, and hereinafter referred to as a "reverse current pulse" in this specification. For example, the length of the second period T2, that is, the pulse width of the reverse current pulse, can be about 0.1 seconds to several seconds. In the second period T2, contrary to the reduction reaction of the metal ions in the first period T1, the metal of a part of the plating film formed on the plated surface W1 in the first period T1 is dissolved again in the plating solution Q, and the accelerator (one of the additives contained in the plating solution Q) attached to the outermost surface of the plating film in the reduction reaction is desorbed from the surface of the plating film. The details will be described later.

[0049] In addition, the current value I2 of the reverse current pulse is preferably set to a value that sufficiently desorbs the accelerator. In addition, when the current value I2 is set equal to the current value I1, a combination of a power supply with a single polarity output and a polarity reversal switch capable of reversing the polarity of the output of the power supply may be used instead of the power supply 270 with positive and negative polarities as described above.

[0050] In addition, in the third period T3 following the second period T2, the power supply 270 stops outputting current. That is, in the third period T3, the current does not flow in the plating solution Q in the forward direction or in the reverse direction. As in the second period T2, the length of the third period T3 is a time that is extremely short compared to the first period T1, for example, it can be about 0.1 seconds to several seconds. The details are still described later, but in the third period T3, the accelerator desorbed from the surface of the plated film diffuses in the plating solution Q.

[0051] After the third period T3, the power source 270 again outputs the forward current (current value I1). 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.

[0052] Like this, in Figure 4 In the embodiment shown, the power supply 270 supplies a reverse current pulse in the middle of the first period T1 of outputting the forward current, and stops the current in a short period of time shortly after the reverse current pulse. The time position of the reverse current pulse (and the subsequent current stop) in the entire first period T1 is not particularly limited, but from the perspective of uniformizing the height of the plurality of bumps 303 formed on the substrate W, the reverse current pulse is preferably started in the first half of the entire period of the plating process (the reason will be described later).

[0053] Figure 5 It means Figure 4 Graph of the time waveforms of different plating currents. Figure 5 The graph on the left side shows that the forward current is continuously supplied throughout the entire period (period T1) during which the plating process is performed. Figure 5 The graph on the right side shows that one reverse current pulse is supplied (period T2) during the plating process period T1, but the current is not stopped.

[0054] Next, experimental results regarding the uniformity of the heights of the plurality of bumps 303 formed on the substrate W will be described. Figure 6 3 is a schematic diagram showing the opening pattern of the photoresist layer 302 used in this experiment to form a plurality of bumps 303. Figure 6 In the opening pattern shown, in the pattern area P1, the opening diameter (Refer to Figure 3 ) small openings 302a are arranged at a high density, and in the pattern area P2, the opening diameter The small openings 302a are arranged at a low density (i.e., sparsely), and in the pattern area P3, the opening diameter is The large openings 302a are arranged at a high density. In the pattern area P4, the opening diameter is The large openings 302a are arranged at a low density.

[0055] Figure 7 is used Figure 6 When a plurality of bumps 303 are formed on a substrate W by the photoresist layer 302 shown in FIG. 1 , the height BH of the bumps 303 in each pattern region is measured (see FIG. 1 ). Figure 3 ). Figure 7 In FIG. 1 , each bump height BH corresponding to each pattern region P1 , P2 , P3 , and P4 represents a value obtained by measuring the heights of a plurality of bumps 303 included in the pattern region and averaging the measured heights. Figure 7 The diagram on the left shows Figure 5 As shown in the left graph, the forward current is supplied throughout the entire plating process to form the bump 303. Figure 7 The diagram on the right shows Figure 5 As shown in the right graph, this is a measurement result when a single reverse current pulse is supplied during the plating process to form the bump 303 .

[0056] like Figure 7As shown in FIG. 1 , it can be seen that the height BH of the bump 303 formed on the substrate W is different for each pattern area even within the same substrate. Among the entire pattern area, the bump height BH of the pattern area P1 is the lowest, and the bump height BH of the pattern area P4 is the highest. This is because the smaller the diameter φ of the opening 302a and the higher the configuration density of the opening 302a, the less likely it is that the metal ions will be fully replenished in the opening 302a, and thus the formation rate of the plated film is lower. Here, as Figure 7 As described in , the difference between the maximum and minimum values ​​of the bump height BH in the substrate is defined as the bump height deviation ΔBH. Figure 7 It can be seen that when a reverse current pulse is supplied during the plating process ( Figure 7 The graph on the right) is compared with the case where no reverse current pulse is supplied ( Figure 7 Compared with the graph on the left), the bump height deviation ΔBH is smaller.

[0057] Figure 8 : is a graph showing the bump height deviation ΔBH under various conditions when the bumps 303 are formed on the substrate W by variously changing the plating current conditions. The plating current under condition 1 is Figure 5 The plating current shown in the graph on the left (i.e., the forward current is supplied throughout the entire plating process) is Figure 5 The plating current shown in the graph on the right (i.e., a forward current and a reverse current pulse are supplied during the plating process) is the same as the bump height deviation ΔBH corresponding to the above two conditions. Figure 7 The bump height deviation ΔBH shown in the graph of is the same.

[0058] exist Figure 8 The plating currents for conditions 3 to 6 are Figure 4 That is, in conditions 3 to 6, a reverse current pulse is supplied in the middle of the forward current and the current is stopped for a short time following the reverse current pulse to form the bump 303. Figure 8 As shown, by forming the bumps 303 using such a plating current, the bump height deviation ΔBH can be further reduced, specifically, further reduced compared to the case of using the plating current of condition 2. That is, a plurality of bumps 303 of various diameters and arrangement densities can be formed on the substrate W with more uniform heights.

[0059] Fig. 9 is to use Figure 4 As described above, in the plated surface of the substrate W, in the places where the diameter of the openings 302a of the photoresist layer 302 is large and the arrangement density of the openings 302a is low (for example, Figure 6The formation rate of the plated film is higher than that of the pattern area P4 (e.g., the pattern area P1) where the forward current is not supplied. Therefore, in the period before the second period T2 where the reverse current pulse is supplied in the first period T1 where the forward current is supplied, the plated film thickness of the area where the opening diameter is large and / or the opening density is low is thicker than that of the area where the opening diameter is small and / or the opening density is high ( Fig. 9 stage (A)).

[0060] Here, the plating solution Q contains, as one of the additives, an accelerator (e.g., SPS (bis(3-sulfopropyl) disulfide) etc.) that has the function of promoting the formation of the plated film. Such accelerator molecules are concentrated and adsorbed on the surface of the plated film at a constant density wherever they are, promoting the reduction reaction of the metal ions. During the second period T2 during which the reverse current pulse is supplied, the accelerator molecules are desorbed from the surface of the plated film and diffuse inside and near the opening 302a. At this time, since the accelerator molecules are originally concentrated and adsorbed on the surface of the plated film at a constant density, the local concentration of the accelerator molecules desorbed from the surface of the plated film inside each opening 302a is constant ( Fig. 9 stage (B)).

[0061] However, in the place with high opening density, there are also desorbed promoter molecules in the adjacent opening 302a, so the concentration gradient of promoter molecules near the above-mentioned multiple openings 302a is small. Therefore, there are relatively few molecules among these promoter molecules that leave the opening 302 and diffuse to a farther distance, and most promoter molecules are retained near the opening 302a. In contrast, in the place with low opening density, the influence from the adjacent opening 302a is small, so the concentration gradient of promoter molecules near the multiple openings 302a is large. Therefore, most of the promoter molecules desorbed from the plated film diffuse to a distance, and there are few promoter molecules remaining near the opening 302a. As a result, during the third period T3 when the current does not flow in the plating solution Q, near the opening 302a located at the place with high opening density, the average concentration of promoter molecules becomes higher than that near the opening 302a located at the place with low opening density. That is, according to the difference in opening density, the average concentration of promoter molecules produces differences. In addition, the difference in the size of the opening 302a also creates a similar difference in the concentration of the promoter molecules (if the opening diameter is large, the promoter molecules are more likely to diffuse outside the opening 302a, so the concentration of the promoter molecules becomes low near the opening 302a with a large diameter).

[0062] As described above, the concentration of the promoter molecules near the opening 302a is different according to the structure (i.e., diameter and arrangement density) of the opening 302a forming the plated film, so when the forward current is supplied again after the third period T3, the amount of promoter molecules adsorbed again on the surface of the plated film in the opening 302a is different depending on the location. Specifically, in a location with a large opening diameter and / or a low opening density, the amount of promoter molecules adsorbed again is relatively small, and in a location with a small opening diameter and / or a high opening density, the amount of promoter molecules adsorbed again is relatively large ( Fig. 9 stage (C)).

[0063] Furthermore, as described above, the desorption of the accelerator occurs in the same manner (stage (B)). Therefore, if the process from desorption to re-adsorption is considered as a whole, the density (or amount) of the accelerator molecules that are re-adsorbed and present on the surface of the plated film is relatively small in the openings 302a arranged at a location with a large opening diameter and / or a low opening density, and is relatively large in the openings 302a arranged at a location with a small opening diameter and / or a high opening density. Fig. 9 Therefore, on the surface of the plated film located in a place where the opening diameter is small and / or the opening density is high, the effect of the accelerator becomes greater than that in a place where the opening diameter is large and / or the opening density is low, and the plating rate increases. As a result, the film thickness difference of the initially existing plated film caused by the location (refer to stage (A)) is compensated, and as a result, the film thickness of the plated film (i.e., the bump 303) formed in the opening 302a is uniformed regardless of the difference in the structure of the opening 302a ( Fig. 9 stage (E)).

[0064] According to the above description, it can be understood that in order to make the height of the bump 303 uniform, it is important to make the promoter molecules adsorbed again after desorption have density differences according to the location. And the density difference is caused by the fact that the degree of diffusion of the desorbed promoter molecules from the plating film to the distance in the second period T2 and the third period T3 is different according to the location (i.e., the size and configuration density of the opening 302a). Therefore, when the paddle 235 is always stirring the plating liquid Q (also in the second and third periods), the diffusion of the promoter molecules is uniformed due to the stirring, so that the density difference of the promoter molecules adsorbed again according to the location is weakened. Therefore, in order to further improve the uniformity of the height of the bump 303, it is preferred to stop the stirring of the plating liquid Q by the paddle 235 in the third period T3, or to reduce the stirring intensity in both the second period T2 and the third period T3.

[0065] Fig.10The graph compares the bump height deviation ΔBH when the paddle 235 stops stirring the plating solution Q in the third period T3 and when the paddle 235 does not stop stirring the plating solution Q. The graph shows that stopping stirring the plating solution Q has a greater effect on reducing the bump height deviation ΔBH.

[0066] In addition, as described above, by causing the desorption and re-adsorption of the promoter molecules, the plating rate after re-adsorption has a distribution opposite to that before desorption, but sufficiently extending the plating time at the plating rate after re-adsorption is effective in making the film thickness of the plated film (bump 303) uniform. Therefore, the supply of the reverse current pulse and the subsequent stop of the current are preferably started in the first half of the entire period of the plating process.

[0067] In the above Figure 4 In the embodiment shown, the reverse current pulse is supplied and the current is stopped only once in the middle of the first period T1, but the number of times may be multiple. As mentioned above, the density of the promoter molecules adsorbed again on the surface of the plated film varies depending on the location ( Fig. 9 However, after a period of time after the forward current is supplied after the third period T3, the number of promoter molecules adsorbed again gradually increases, so that the density of promoter molecules present on the surface of the plated film gradually becomes saturated and becomes the same regardless of the location. Therefore, by supplying multiple reverse current pulses and stopping the current, the desorption and re-adsorption of promoter molecules are repeated, and a density difference of promoter molecules can be generated each time they are re-adsorbed. As a result, the film thickness of the plated film (i.e., bump 303) can be made more uniform.

[0068] Fig.11 2 is a graph showing the time waveform of the plating current and the output voltage of the power supply 270 corresponding to the plating current in an embodiment in which the supply of reverse current pulses and the stop of the current are performed multiple times. Figure 4 and Fig.11 In the embodiment of the present invention, the power supply 270 is controlled by the control controller 260 so as to output the set (e.g., constant) current values ​​I1 and I2. Fig.11 As shown, the output voltage of the power supply 270 needs a certain rise time to return to the voltage V1 corresponding to the forward current I1 after the reverse current pulse and the current stop. This temporal change of the output voltage is caused by the change in the adsorption state of the additives (accelerators and inhibitors) on the surface of the plated film, so that the resistance (polarization resistance) of the surface of the cathode, that is, the surface of the plated film, changes.

[0069] Specifically, Fig.11As shown in FIG. 1 , the output voltage changes from V1 to V0 by applying the reverse current pulse, and then temporarily returns to V1 shortly after applying the forward current I1 (in addition, this voltage change is Fig.11 (It is produced in a very short time under the time scale of , so it is drawn with a thin vertical line in the figure). At this moment, that is, shortly after the application of the forward current I1, the promoter is hardly adsorbed on the surface of the plated film, and the adsorption of the promoter gradually proceeds from this state. Therefore, the resistance gradually decreases, and thus, the output voltage decreases toward V2. Afterwards, on the basis of the promoter, the inhibitor also begins to be adsorbed, and the inhibitor's inhibitory effect on the formation of the plated film becomes stronger. As a result, the output voltage turns from decreasing to increasing with V2 as the extreme value, and gradually increases toward V1. In this process, the promoter also continues to be adsorbed and concentrated, and soon the effects of the promoter and the inhibitor reach a state of equilibrium, and the output voltage stabilizes at V1. That is, the accumulation of the promoter on the surface of the plated film is saturated to a certain constant amount.

[0070] Here, the accumulation amount of the accelerator is saturated, which means that the density of the accelerator molecules present on the surface of the plated film is the same regardless of the location. Fig. 9 It can be understood from the relevant description that if the promoter is desorbed when the saturation or near-saturation state is reached, the density difference generated by the field when the promoter molecules are adsorbed again will be the largest. Fig.11 As in the embodiment of the present invention, when applying a plurality of reverse current pulses, it is preferred that the next reverse current pulse be applied after the output voltage V of the power supply 270 returns to a value sufficiently close to the original voltage V1 (eg, 90% of the original voltage V1).

[0071] The embodiments of the present invention are described above based on several examples, but the embodiments of the invention described above are used to facilitate understanding of the present invention and do not limit the present invention. The present invention can be changed and improved without departing from its main purpose, and the present invention certainly includes its equivalents. In addition, within the scope of at least a part of the above-mentioned problems that can be solved or within the scope of at least a part of the effects that can be achieved, any combination or omission of the constituent elements described in the claims and the specification can be performed.

Claims

1. A plating device for forming a bump on a substrate, the plating device comprising: a substrate holder configured to hold the substrate; a plating tank configured to contain a plating solution together with the substrate support; an anode, the anode being arranged in the plating tank so as to face the substrate held by the substrate holder; a power source configured to supply current between the substrate and the anode; a paddle blade, the paddle blade being used to stir the plating solution in the plating tank; and Control Department, The control unit is configured to output a current having the following periods from the power supply: a first period for supplying a forward current for depositing metal from the plating solution on the substrate, a second period for supplying at least one reverse current pulse flowing in a direction opposite to the forward current, and a third period for stopping the current supply in the middle of transitioning from the reverse current pulse to the forward current. The control unit is further configured to reduce the stirring intensity of the paddle or stop the stirring at least during the third period. The plating solution is stirred at a first intensity during the first period, and the plating solution is stirred at a second intensity weaker than the first intensity during at least the third period of the second period and the third period, or the stirring is stopped.

2. The plating device according to claim 1, characterized in that: The control unit is configured to reduce the stirring intensity of the paddle or stop the stirring between the second period and the third period.

3. The plating device according to claim 1 or 2, characterized in that: The control unit is configured to output a current having a plurality of sets of the second period and the third period from the power supply.

4. The plating device according to claim 3, characterized in that: The control unit is configured to supply the reverse current pulse after the output voltage of the power supply in the first period becomes 90% or more of the output voltage of the power supply after stabilization in the first period.

5. The plating device according to claim 1, characterized in that: The substrate includes a metal seed layer and a shielding film shielding the metal seed layer from the plating solution in a portion other than a bump to be formed.

6. The plating device according to claim 5, characterized in that: The shielding film has a pattern corresponding to a plurality of bumps having different diameters.

7. The plating device according to claim 5, characterized in that: The mask film has a pattern in which a plurality of bumps to be formed are arranged at different densities.

8. A plating method for forming a bump on a substrate having a plurality of different pattern areas, the plating method comprising: Supplying a current having the following periods between the substrate having the plurality of different pattern areas arranged in the plating tank and the anode: a first period of supplying a forward current for causing metal to precipitate on the substrate from a plating solution containing an accelerator in the plating tank; and a second period of supplying at least one reverse current pulse flowing in a direction opposite to the forward current for desorbing the accelerator attached to the surface of the metal precipitated during the first period; and a third period in which the current supply is stopped during the transition from the reverse current pulse to the forward current in order to make the concentration of the desorbed accelerator in the plating solution form a concentration difference corresponding to the structure of each of the pattern regions, The plating solution is stirred at a first intensity during the first period, and the plating solution is stirred at a second intensity weaker than the first intensity during at least the third period of the second period and the third period, or the stirring is stopped.

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