US20240183057A1

US20240183057A1 - Plating apparatus

Info

Publication number: US20240183057A1
Application number: US17/797,030
Authority: US
Inventors: Shigeyuki NAKAHAMA; Mizuki Nagai
Original assignee: Ebara Corp
Current assignee: Ebara Corp
Priority date: 2021-09-28
Filing date: 2021-09-28
Publication date: 2024-06-06
Also published as: WO2023053182A1; CN115135814A; CN115135814B; JPWO2023053182A1; KR102494899B1; JP7090834B1

Abstract

Provided is a technique that allows ensuring an in-plane uniformity of film thickness of a substrate.A plating apparatus 1 includes auxiliary anodes 60a, 606, 60c, 60d. End portion proximal regions in an extending direction of the auxiliary anode are covered by resistive elements 65 having electrical conduction rates larger than zero, and the electrical conduction rates are lower than an electrical conduction rate of a plating solution. A region closer to a center than the end portion proximal regions of the auxiliary anode is not covered by the resistive element, and a surface of the region closer to the center than the end portion proximal regions of the auxiliary anode is exposed.

Description

TECHNICAL FIELD

The present invention relates to a plating apparatus.

BACKGROUND ART

Conventionally, there has been known a plating apparatus that performs a plating process on a substrate that includes a plating tank accumulating a plating solution and is provided with an anode, a substrate holder that holds a substrate as a cathode such that the substrate is opposed to the anode, and auxiliary anodes (auxiliary electrodes) arranged in a portion between the substrate and the anode inside the plating tank (see, for example, PTL 1). Specifically, the substrate used in the plating apparatus illustrated in PTL 1 is a polygonal substrate having a plurality of sides, and is power-fed electricity from the respective sides of the substrate. The auxiliary anodes extend in extending directions of the sides of the substrate.

CITATION LIST

Patent Literature

PTL 1: Japanese Unexamined Patent Application Publication No. 2021-11624

SUMMARY OF INVENTION

Technical Problem

In a conventional plating apparatus as described above, amounts of current supplied from end portion proximal regions of the auxiliary anodes to end portion proximal regions of the substrate (that is, “corner portions” of the polygonal substrate) may possibly increase excessively. In this case, film thicknesses of the corner portions of the substrate may possibly increase compared with film thicknesses of other portions of the substrate, and an in-plane uniformity of film thickness of the substrate may possibly deteriorate.
Therefore, to deal with the above-described problem, covering the end portion proximal regions of the auxiliary anodes with current-shielding masks may be considered. Specifically, the current-shielding mask is configured of an insulator, and has a current shielding property. However, when using such current-shielding mask, this time, the amounts of current supplied to the corner portions of the substrate may possibly decrease excessively. In this case, the film thicknesses of the corner portions of the substrate decrease compared with the film thicknesses of the other portions of the substrate, and it becomes difficult to sufficiently ensure the in-plane uniformity of film thickness of the substrate.
As above, the conventional plating apparatus has a room for improvement in ensuring the in-plane uniformity of film thickness of the substrate.
The present invention has been made in view of the above, and one of the objects of the present invention is to provide a technique that can ensure an in-plane uniformity of film thickness of a substrate.

Solution to Problem

(Aspect 1) To achieve the above-described object, a plating apparatus according to one aspect of the present invention includes a plating tank, a substrate holder, an intermediate mask, and an auxiliary anode. The plating tank is configured to accumulate a plating solution and is provided with an anode. The substrate holder is configured to hold a substrate as a cathode such that the substrate is opposed to the anode. The substrate is a polygonal substrate having a plurality of sides. The intermediate mask is arranged between the anode and the substrate inside the plating tank. The intermediate mask is provided with a hole that allows a current flowing between the anode and the substrate to pass therethrough. The hole of the intermediate mask is a polygonal hole having a plurality of sides corresponding to the respective plurality of sides of the substrate. The auxiliary anode is arranged between the substrate and the intermediate mask so as to correspond to at least one side of the hole of the intermediate mask. The auxiliary anode extends in an extending direction of the side of the hole of the intermediate mask. End portion proximal regions of the auxiliary anode from both end portions in an extending direction of the auxiliary anode toward a center are covered by resistive elements having electrical conduction rates larger than zero, the electrical conduction rates are lower than an electrical conduction rate of the plating solution, a region closer to the center than the end portion proximal regions of the auxiliary anode is not covered by the resistive element, and a surface of the region closer to the center than the end portion proximal regions of the auxiliary anode is exposed.
With this aspect, since the end portion proximal regions of the auxiliary anode are covered by the resistive elements as described above, amounts of current flowing from the end portion proximal regions of the auxiliary anode toward end portion proximal regions of the sides of the substrate (that is, “corner portions” of the polygonal substrate) can be suppressed. Therefore, increases of film thicknesses of the corner portions of the substrate compared with film thicknesses of other portions of the substrate can be suppressed. Since the resistive element has a high electrical conduction rate compared with the current-shielding mask constituted of an insulator, as for example, in the case where the end portion proximal regions of the auxiliary anode are covered by the current-shielding masks, decreases of the film thicknesses of the corner portions of the substrate compared with the film thicknesses of the other portions of the substrate can be suppressed. Accordingly, with this aspect, an in-plane uniformity of film thickness of the substrate can be ensured.
(Aspect 2) In the aspect 1 described above, the electrical conduction rates of the resistive elements may decrease along from a central side toward end portion sides in the extending direction of the auxiliary anode covered by the resistive elements.
With this aspect, the in-plane uniformity of film thickness of the substrate can be effectively ensured.
(Aspect 3) In the aspect 1 or 2 described above, the resistive element may have a plurality of holes, and the electrical conduction rates of the resistive elements may decrease along from the central side toward the end portion sides by a density of the holes of the resistive element decreasing along from the central side toward the end portion sides.
Since the density of the holes of the resistive element can be easily adjusted, with this aspect, the electrical conduction rate of the resistive element can be easily decreased along from the central side toward the end portion sides.
(Aspect 4) In any one of the aspects 1 to 3, lengths in the extending direction of the auxiliary anode of the end portion proximal regions of the auxiliary anode may be a length of 10% or less of a total length of the auxiliary anode.
(Aspect 5) In any one of the aspects 1 to 4, the plating apparatus may include a housing portion configured to house the auxiliary anode inside the housing portion. The housing portion may be provided with an opening opened so as to face the substrate. The opening may be closed by a membrane configured to allow metal ions included in the plating solution to pass through the membrane and inhibit oxygen generated from surfaces of the auxiliary anode from passing through the membrane.
With this aspect, even in a hypothetical case where oxygen generates from the surfaces of the auxiliary anode in the plating process, an invasion of the generated oxygen into the plating solution outside the housing portion can be suppressed. Therefore, a deterioration of a plating quality of the substrate caused by the oxygen having invaded the plating solution outside the housing portion can be suppressed.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is an entire layout drawing of a plating apparatus according to an embodiment.

FIG. 2 is a schematic cross-sectional view illustrating a peripheral configuration of one plating tank in the plating apparatus according to the embodiment.

FIG. 3 is a schematic front view of a substrate according to the embodiment.

FIG. 4 is a schematic diagram for describing a configuration of a contact member according to the embodiment.

FIG. 5 is a schematic front view of a plurality of auxiliary anodes according to the embodiment.

FIG. 6 is an enlarged schematic diagram illustrating one auxiliary anode according to the embodiment.

FIG. 7 is a schematic perspective view of a peripheral configuration of an intermediate mask according to the embodiment.

FIG. 8 is a chart indicating experimental results of a plating apparatus according to a working example.

FIG. 9 is a chart indicating experimental results of a plating apparatus according to Comparative Example 1.

FIG. 10 is a chart indicating experimental results of a plating apparatus according to Comparative Example 2.

DESCRIPTION OF EMBODIMENTS

The following describes an embodiment of the present invention with reference to the drawings. Note that the drawings are schematically illustrated to facilitate understanding of features of the embodiment, and dimensional proportions and the like of each constituent element are not necessarily the same as the actual ones. In some drawings, orthogonal coordinates of X-Y-Z are illustrated for reference. Of the orthogonal coordinates, the Z-direction corresponds to an upper side, and the −Z-direction corresponds to a lower side (the direction in which gravity acts).
FIG. 1 is an entire layout drawing of a plating apparatus 1 according to this embodiment. As illustrated in FIG. 1 , the plating apparatus 1 according to this embodiment includes two cassette tables 102, an aligner 104 that adjusts a position of an orientation flat, a notch, and the like of a substrate Wf in a predetermined direction, and a spin rinse dryer 106 that rotates the substrate Wf after a plating process at high speed and dries the substrate Wf. On the cassette table 102, a cassette 100 that stores the substrate Wf such as a semiconductor wafer is mounted. Near the spin rinse dryer 106, a load/unload station 120 on which a substrate holder 20 is placed to perform attach and remove of the substrate Wf is disposed. A transfer robot 122 is a robot for transferring the substrate Wf between the cassette 100, the aligner 104, the spin rinse dryer 106, and the load/unload station 120.
The load/unload station 120 includes a flat plate-shaped placing plate 152 that is slidable in a lateral direction along a rail 150. Two substrate holders 20 are placed in parallel in a horizontal state on the placing plate 152. After a delivery and receipt of a substrate Wf has been performed between one of the substrate holders 20 and the transfer robot 122, the placing plate 152 is slid in the lateral direction, and a delivery and receipt of another substrate Wf is performed between the other substrate holder 20 and the transfer robot 122.
In addition, the plating apparatus 1 includes a stocker 124, a pre-wet module 126, a pre-soak module 128, a first rinse module 130 a, a blow module 132, a second rinse module 130 b, a plating module 110, a transfer device 140, and a control module 170. In the stocker 124, storage and temporarily placement of the substrate holders 20 are performed. In the pre-wet module 126, the substrates Wf are immersed in pure water. In the pre-soak module 128, oxidized films on surfaces of conductive layers of seed layers and the like formed on surfaces of the substrates Wf are removed by etching. In the first rinse module 130 a, the substrates Wf after being pre-soaked are cleaned by a cleaning liquid (such as pure water) together with the substrate holders 20. In the blow module 132, a liquid draining of the substrates Wf after being cleaned is performed. In the second rinse module 130 b, the substrates Wf after the plating process are cleaned by the cleaning liquid together with the substrate holders 20.
The plating module 110 is configured, for example, so as to house a plurality of plating tanks 10 inside an overflow tank 136. Each plating tank 10 houses one substrate Wf inside, and is configured to immerse the substrate Wf in a plating solution held inside to perform a copper plating and the like on a surface of the substrate Wf.
The transfer device 140 is a transfer device that employs, for example, a linear motor system, and transfers the substrate holders 20 between respective devices of the plating apparatus 1 together with the substrates Wf. The transfer device 140 according to this embodiment includes, for example, a first transfer device 142 and a second transfer device 144. The first transfer device 142 transfers the substrates Wf between the load/unload station 120, the stocker 124, the pre-wet module 126, the pre-soak module 128, the first rinse module 130 a, and the blow module 132. The second transfer device 144 transfers the substrates Wf between the first rinse module 130 a, the second rinse module 130 b, the blow module 132, and the plating module 110. Note that the plating apparatus 1 need not include the second transfer device 144, and may include the first transfer device 142 alone.
On both sides of the overflow tank 136, a paddle driving portion 160 and a paddle driven portion 162 that drive a paddle that is positioned inside each plating tank 10 and stirs the plating solution in the plating tank 10 are arranged.
The control module 170 is configured to control an operation of the plating apparatus 1. Specifically, the control module 170 according to this embodiment includes a microcomputer. The microcomputer includes a Central Processing Unit (CPU) 171 as a processor, a storage device 172 as a non-transitory storage medium, and the like. The control module 170 controls a controlled device of the plating apparatus 1 by the CPU 171 operating according to commands of a program stored in the storage device 172.
One example of a sequence of a plating process according to the plating apparatus 1 will be described. First, the transfer robot 122 grips one substrate Wf from the cassette 100 mounted to the cassette table 102 and transfers the substrate Wf to the aligner 104. The aligner 104 adjusts a position of an orientation flat, a notch, and the like in a predetermined direction. The substrate Wf whose position has been adjusted in the predetermined direction is transferred to the load/unload station 120 by the transfer robot 122.
In the load/unload station 120, the two substrate holders 20 housed in the stocker 124 are simultaneously griped by the first transfer device 142 of the transfer device 140, and transferred to the load/unload station 120. Subsequently, the two substrate holders 20 are simultaneously placed horizontally on the placing plate 152 of the load/unload station 120. In this state, the transfer robot 122 transfers the substrates Wf to the respective substrate holders 20, and the transferred substrates Wf are held by the substrate holders 20.
Next, the two substrate holders 20 holding the substrates Wf are simultaneously griped by the first transfer device 142 of the transfer device 140, and housed in the pre-wet module 126. Next, the substrate holders 20 holding the substrates Wf processed in the pre-wet module 126 are transferred to the pre-soak module 128 by the first transfer device 142, and the oxidized film on the substrate Wf is etched by the pre-soak module 128. Subsequently, the substrate holders 20 holding the substrates Wf are transferred to the first rinse module 130 a, and the surfaces of the substrates Wf are water-cleaned with pure water housed in the first rinse module 130 a.
The substrate holders 20 holding the substrates Wf after being water-cleaned are transferred from the first rinse module 130 a to the plating module 110 by the second transfer device 144, and are housed in the plating tanks 10. The second transfer device 144 repeatedly performs the above-described process, and sequentially houses the substrate holders 20 holding the substrates Wf into the respective plating tanks 10 of the plating module 110.
In each plating tank 10, a plating voltage is applied between an anode and the substrate Wf in the plating tank 10, and a plating process is performed on the surface of the substrate Wf. In the plating process, the plating solution in the plating tank 10 may be stirred by the paddle being driven by the paddle driving portion 160 and the paddle driven portion 162. However, the configuration of the plating apparatus 1 is not limited to this, and for example, the plating apparatus 1 may have a configuration without the paddle, the paddle driving portion 160, or the paddle driven portion 162.
After the plating process is performed, the two substrate holders 20 holding the substrates Wf after the plating process are simultaneously griped by the second transfer device 144, transferred to the second rinse module 130 b, and immersed in pure water housed in the second rinse module 130 b to clean the surfaces of the substrates Wf with the pure water. Next, the substrate holders 20 are transferred to a blow module 132 by the second transfer device 144, and water droplets attached to the substrate holders 20 are removed by air spray and the like. Afterwards, the substrate holders 20 are transferred to the load/unload station 120 by the first transfer device 142.
In the load/unload station 120, the substrates Wf after being processed are griped by the transfer robot 122 from the substrate holders 20, and transferred to the spin rinse dryer 106. The spin rinse dryer 106 rotates the substrates Wf after the plating process at high speed and dries the substrates Wf. The dried substrates Wf are returned to the cassette 100 by the transfer robot 122
Note that, the configuration of the plating apparatus 1 described in the above FIG. 1 is merely an example, and the configuration of the plating apparatus 1 is not limited to the configuration in FIG. 1 .
Subsequently, details of a peripheral configuration of the plating tank 10 in the plating apparatus 1 will be described. Since the plurality of plating tanks 10 according to this embodiment have the identical configuration, the peripheral configuration of one plating tank 10 will be described.
FIG. 2 is a schematic cross-sectional view illustrating the peripheral configuration of one plating tank 10 in the plating apparatus 1 according to this embodiment. FIG. 2 schematically illustrates the peripheral configuration of the plating tank 10 while the plating process is performed on the substrate Wf. The plating apparatus 1 illustrated in FIG. 2 is, for example, a type of plating apparatus (that is, a dip type plating apparatus) that sets a surface direction (a direction along the surface) of the substrate Wf in the vertical direction and immerses the substrate Wf in a plating solution Ps.
However, a specific example of the plating apparatus 1 is not limited to this. Another example of the plating apparatus 1 may be a type of plating apparatus (that is, a cup type plating apparatus) that sets the surface direction of the substrate Wf in a horizontal direction and immerses the substrate Wf in the plating solution Ps.
As illustrated in FIG. 2 , the plating tank 10 according to this embodiment is configured of a container with a bottom and having an opening in an upper portion. Inside the plating tank 10, the plating solution Ps is accumulated. It is only necessary for the plating solution Ps to be a solution including ions of a metallic element for constituting a plating film, and a specific example of the plating solution Ps is not particularly limited. In this embodiment, a copper plating process is used as an example of the plating process, and a copper sulfate solution is used as an example of the plating solution Ps.
The plating apparatus 1 includes an anode 30, an anode box 40, a membrane 50 and an anode mask 45. The anode box 40 is arranged inside the plating tank 10. The anode box 40 is a member (housing member) for internally housing the anode 30. The anode 30 according to this embodiment is arranged inside the anode box 40. In a portion opposed to the substrate Wf of the anode box 40, an opening 40 a is provided. The membrane 50 is disposed so as to obstruct the opening 40 a. Inside the anode box 40, the plating solution Ps is accumulated.
The anode 30 is electrically connected to a positive electrode (positive pole) of a power source (not illustrated). A specific type of the anode 30 is not particularly limited, and it may be an insoluble anode or may be a soluble anode. In this embodiment, an insoluble anode is used as an example of the anode 30. A specific type of the insoluble anode is not particularly limited, and platinum, iridium oxide, and the like can be used.
The membrane 50 is constituted of a membrane that allows metal ions (such as copper ions in the copper sulfate) included in the plating solution Ps to pass through the membrane and inhibit oxygen generated from the surface of the anode 30 from passing through the membrane. As the membrane 50, a neutral membrane can be used as an example.
According to this embodiment, the anode 30 is housed inside the anode box 40 as described above, and the opening 40 a of the anode box 40 is closed by the membrane 50. Thus, even in a hypothetical case where oxygen generates from the surface of the anode 30 in the plating process, an invasion of the generated oxygen into the plating solution Ps outside the anode box 40 can be suppressed. Therefore, a deterioration of a plating quality of the substrate Wf caused by the oxygen having invaded the plating solution Ps outside the anode box 40 can be suppressed.
The anode mask 45 is arranged between the anode 30 and the substrate Wf. The anode mask 45 according to this embodiment is arranged inside the anode box 40. In the center of the anode mask 45, a hole 45 a that allows electricity flowing between the anode 30 and the substrate Wf to pass through is provided.
Note that the anode box 40, the membrane 50, and the anode mask 45 are not essential configurations in this embodiment. The plating apparatus 1 need not include these configurations.
The substrate holder 20 is a member for holding the substrate Wf as the cathode. Specifically, the substrate holder 20 holds the substrate Wf such that a surface of the substrate Wf is opposed to the anode 30 in the plating process of the substrate Wf. More specifically, the substrate holder 20 according to this embodiment holds the substrate Wf such that a surface direction of the substrate Wf is set in the vertical direction. By the plating process, a plating film is formed on a surface to be plated (a surface opposed to the anode 30) of the substrate Wf.
FIG. 3 is a schematic front view of the substrate Wf. Specifically, FIG. 3 illustrates a state where the substrate Wf is viewed from the normal direction of the surface to be plated of the substrate Wf. The substrate Wf according to this embodiment is a polygonal substrate having a plurality of sides. The number of sides of the substrate Wf is not particularly limited, and it may be three, four, five, or more. The number of sides of the substrate Wf according to this embodiment is four, as an example. That is, the substrate Wf according to this embodiment is a rectangular-shaped polygonal substrate having a side 90 a, a side 90 b, a side 90 c, and a side 90 d. The side 90 a and the side 90 b are opposed to one another, and the side 90 c and the side 90 d are opposed to one another.
As an example, lengths of the respective sides of the substrate Wf according to this embodiment are equal to one another. That is, the substrate Wf according to this embodiment has a square shape in front view. However, the configuration of the substrate Wf is not limited to this, and for example, the lengths of the respective sides of the substrate Wf may be different from one another.
In this embodiment, electricity that is power-fed to the substrate Wf is supplied from the respective sides of the substrate Wf. Specifically, the substrate Wf according to this embodiment is power-fed electricity from the respective sides of the substrate Wf via contact members 80 described later. However, it is not limited to this configuration, and for example, the electricity power fed to the substrate Wf can be power-fed from two sides opposed to one another of the substrate Wf.
FIG. 4 is a schematic diagram for describing a configuration of the contact members 80. The contact members 80 are arranged in the substrate holder 20. The contact members 80 are electrically connected to a negative electrode (negative pole) of the power source via a busbar 82 as an electrical wiring. With reference to an enlarged view of the portion A1 in FIG. 4 , the contact member 80 includes a plurality of contact pins 81. The contact pins 81 power-feed electricity to each of the sides (sides 90 a to 90 d) of the substrate Wf by contacting each of the sides of the substrate Wf.
With reference to FIG. 2 again, the plating apparatus 1 according to this embodiment includes at least one auxiliary anode. That is, the plating apparatus 1 may include one auxiliary anode, and may include a plurality of auxiliary anodes. The plating apparatus 1 according to this embodiment, as one example, includes a plurality of auxiliary anodes (auxiliary anodes 60 a to 60 d). The plurality of auxiliary anodes are arranged in a portion between the anode 30 and the substrate Wf inside the plating tank 10, and specifically, arranged in a portion between the substrate Wf and an intermediate mask 70 described later. The auxiliary anode according to this embodiment is housed inside a housing portion 71 described later. The plurality of auxiliary anodes are electrically connected to the positive electrode of the power source similarly to the anode 30.
A specific type of the auxiliary anode is not particularly limited, and it may be an insoluble anode or a soluble anode. In this embodiment, an insoluble anode is used as an example of the auxiliary anode. A specific type of the insoluble anode is not particularly limited, and platinum, iridium oxide, and the like can be used.
FIG. 5 is a schematic front view of the plurality of auxiliary anodes. Specifically, FIG. 5 schematically illustrates a state where the plurality of auxiliary anodes are viewed from the normal direction of the surface to be plated of the substrate Wf. In FIG. 5 , for reference, the substrate Wf is also indicated by two-dot chain lines. The number of the auxiliary anodes corresponds to the number of sides of the substrate Wf, and also corresponds to the number of sides of a hole 70 a described later of the intermediate mask 70.
Specifically, the number of auxiliary anodes according to this embodiment is four as an example. That is, the plurality of auxiliary anodes according to this embodiment are constituted of an auxiliary anode 60 a, an auxiliary anode 60 b, an auxiliary anode 60 c, and an auxiliary anode 60 d. As illustrated in FIG. 5 , the respective auxiliary anodes are arranged so as to be positioned at a proximity of the respective sides of the substrate Wf when viewed from the normal direction of the surface to be plated of the substrate Wf.
The respective auxiliary anodes are arranged so as to correspond to the respective sides of the hole 70 a described later of the intermediate mask 70, and extend in extending directions of the sides of the hole 70 a (as for sides of the hole 70 a, see FIG. 7 described later). Specifically, the auxiliary anode 60 a corresponds to a side 72 a of the hole 70 a, and extends in an extending direction (Y-direction) of the side 72 a. The auxiliary anode 60 b corresponds to a side 72 b of the hole 70 a, and extends in an extending direction (Y-direction) of the side 72 b. The auxiliary anode 60 c corresponds to a side 72 c of the hole 70 a, and extends in an extending direction (Z-direction) of the side 72 c. The auxiliary anode 60 d corresponds to a side 72 d of the hole 70 a, and extends in an extending direction (Z-direction) of the side 72 d.
The respective auxiliary anodes according to this embodiment are arranged so as to correspond to the respective sides of the substrate Wf, and extend in the extending directions of the respective sides of the substrate Wf. Specifically, the auxiliary anode 60 a corresponds to the side 90 a of the substrate Wf, and extends in the extending direction (Y-direction) of the side 90 a. The auxiliary anode 60 b corresponds to the side 90 b, and extends in the extending direction (Y-direction) of the side 90 b. The auxiliary anode 60 c corresponds to the side 90 c, and extends in the extending direction (Z-direction) of the side 90 c. The auxiliary anode 60 d corresponds to the side 90 d, and extends in the extending direction (Z-direction) of the side 90 d.
Power feeding to the plurality of auxiliary anodes may be performed simultaneously or performed individually. Among the plurality of auxiliary anodes, the power feeding may be performed in each pair of auxiliary anodes that are opposed to one another and extends in parallel with one another. As described above, while the auxiliary anodes according to this embodiment are arranged so as to correspond to the respective sides of the substrate Wf, it is not limited to this configuration. The auxiliary anodes may be arranged so as to correspond to only one side, or only two opposing sides of the substrate Wf.
With reference to FIG. 2 again, the plating apparatus 1 includes the intermediate mask 70 and a membrane 51. FIG. 7 is a schematic perspective view of a peripheral configuration of the intermediate mask 70. With reference to FIG. 2 and FIG. 7 , the intermediate mask 70 is arranged between the anode 30 and the substrate Wf. Specifically, the intermediate mask 70 according to this embodiment is arranged between the anode box 40 and the substrate Wf. In the center of the intermediate mask 70, the hole 70 a that allows electricity flowing between the anode 30 and the substrate Wf to pass through is provided.
The hole 70 a of the intermediate mask 70 is a polygonal hole, and has a plurality of sides ( sides 72 a, 72 b, 72 c, 72 d) corresponding to the respective plurality of sides of the substrate Wf. Specifically, the side 72 a corresponds to the side 90 a of the substrate Wf, the side 72 b corresponds to the side 90 b of the substrate Wf, the side 72 c corresponds to the side 90 c of the substrate Wf, and the side 72 d corresponds to the side 90 d of the substrate Wf. The side 72 a extends in the extending direction of the side 90 a, the side 72 b extends in the extending direction of the side 90 b, the side 72 c extends in the extending direction of the side 90 c, and the side 72 d extends in the extending direction of the side 90 d.
On a surface opposed to the substrate Wf of the intermediate mask 70 according to this embodiment, the housing portion 71 for housing the auxiliary anodes 60 a, 60 b, 60 c, 60 d is disposed. The housing portion 71 is provided with an opening 71 a that is opened so as to face the substrate Wf.
The membrane 51 obstructs the opening 71 a of the housing portion 71. Inside the housing portion 71, the plating solution Ps is accumulated. As the membrane 51, one similar to the above-described membrane 50 can be used. That is, the membrane 51 according to this embodiment is constituted of a membrane that allows metal ions (such as copper ions in the copper sulfate) included in the plating solution Ps to pass through the membrane and inhibit the oxygen generated from the surfaces of the auxiliary anode from passing through the membrane. As the membrane 51, a neutral membrane can be used as an example.
According to this embodiment, since the auxiliary anode is housed in the housing portion 71 as described above, and the opening 71 a of the housing portion 71 is closed by the membrane 51, even in a hypothetical case where oxygen generates from the surfaces of the auxiliary anode in the plating process, an invasion of the generated oxygen into the plating solution Ps outside the housing portion 71 can be suppressed. Therefore, a deterioration of the plating quality of the substrate Wf caused by the oxygen having invaded the plating solution Ps outside the housing portion 71 can be suppressed.
FIG. 6 is an enlarged schematic diagram illustrating one auxiliary anode among the plurality of auxiliary anodes (specifically, the auxiliary anode 60 a). As illustrated in FIG. 5 and FIG. 6 , regions from both end portions in the extending direction of the auxiliary anode toward the center (referred to as “end portion proximal regions R1”) of each auxiliary anode are covered by resistive elements 65. On the other hand, a region closer to the center than the end portion proximal regions R1 (referred to as a “non-end portion region R2”) of each auxiliary anode is not covered by the resistive elements 65, and a surface of the region closer to the center than the end portion proximal regions of the auxiliary anode is exposed. That is, each auxiliary anode has the regions covered by the resistive elements 65 (end portion proximal regions R1) and the region not covered by the resistive element 65 (non-end portion region R2).
In this embodiment, lengths of the end portion proximal regions R1 of the auxiliary anode (a length when measured in the extending direction of the auxiliary anode) are, for example, a length of 10% or less of a total length DI of the auxiliary anode. Moreover, in this embodiment, a length of the end portion proximal region R1 closer to a peripheral side than the center of the auxiliary anode and a length of the end portion proximal region R1 on the other side are the same, but it is not limited to this. The length of the end portion proximal region R1 closer to the peripheral side than the center of the auxiliary anode and the length of the end portion proximal region R1 on the other side may be different from one another.
The resistive element 65 covers not only outer peripheral side surfaces extending in the extending direction of the auxiliary anode among the end portion proximal regions R1 of the auxiliary anode (such as, in FIG. 6 , an outer peripheral side surface extending in the Y-direction), but also end surfaces in the extending direction of the auxiliary anode (such as, in FIG. 6 , the end surfaces facing the Y-direction and the −Y-direction of the auxiliary anode 60 a).
The resistive element 65 has an electrical conduction rate larger than zero, and has the electrical conduction rate lower than an electrical conduction rate of the plating solution Ps.
With reference to an enlarged view of the part B1 and an enlarged view of the part B2 in FIG. 6 , the resistive elements 65 according to this embodiment are configured to have electrical conduction rates that decrease along from a central side toward end portion sides in the extending direction of the auxiliary anode covered by the resistive elements 65.
As a specific example of the above-described configuration, the resistive element 65 according to this embodiment is constituted of a member provided with a plurality of holes 66 (that is, a “porous member”). Specifically, the resistive element 65 according to this embodiment is configured of a porous member constituted of an insulator provided with the plurality of holes 66. The plurality of holes 66 are disposed so as to penetrate the insulator. As the insulator, a resin, such as polyetheretherketone and polyvinyl chloride, can be used. Electricity can flow passing through the holes 66 of the resistive element 65. Accordingly, the resistive element 65 has an electrical conduction rate larger than zero.
The resistive elements 65 are configured such that densities of the holes 66 (a volume of the holes 66 per unit volume of the resistive element 65) in the resistive element 65 decrease along from the central side toward the end portion sides in the extending direction of the auxiliary anode. Since the density of the holes 66 of the resistive element 65 can be easily adjusted, this configuration can allow the electrical conduction rate of the resistive element 65 to be easily decreased along from the central side toward the end portion side.
In this embodiment as described above, since the end portion proximal regions R1 in the extending direction of the auxiliary anode are covered by the resistive elements 65 described above, amounts of current flowing from the end portion proximal regions R1 of the auxiliary anode toward the end portion proximal regions of the sides of the substrate Wf (that is, “corner portions 91” of the polygonal substrate Wf) can be suppressed. Therefore, increases of film thicknesses of the corner portions 91 of the substrate Wf compared with film thicknesses of other portions of the substrate Wf can be suppressed. Since the resistive element 65 has a high electrical conduction rate compared with the current-shielding mask, as in the case where the end portion proximal regions R1 of the auxiliary anode are covered by the current-shielding masks, decreases of the film thicknesses of the corner portions 91 of the substrate Wf compared with the film thicknesses of the other portions of the substrate Wf can be suppressed. Accordingly, with this aspect, an in-plane uniformity of film thickness of the substrate Wf can be achieved.
Moreover, with this embodiment, since the electrical conduction rates of the resistive elements 65 decrease along from the central side toward the end portion sides in the extending direction of the auxiliary anode covered by the resistive elements 65, the in-plane uniformity of film thickness of the substrate Wf can be achieved effectively.
Although the embodiments and modifications of the present invention have been described in detail above, the present invention is not limited to such specific embodiments or modifications, and further various kinds of variants and modifications are possible within the scope of the gist of the present invention described in the claims.

Examples

The following describes a working example of the present invention together with comparative examples. However, the present invention is not limited to the working example described below.
FIG. 8 is a chart indicating experimental results of the plating apparatus 1 according to the working example. FIG. 9 is a chart indicating experimental results of a plating apparatus according to Comparative Example 1. FIG. 10 is a chart indicating experimental results of a plating apparatus according to Comparative Example 2. The horizontal axes in FIG. 8 . FIG. 9 , and FIG. 10 indicate a distance (mum) from the center of the sides of the substrate Wf, and the vertical axes indicate a film thickness (μm) of the plating film of the substrate Wf. The measurement area of the film thickness is an area indicated by “E1” in FIG. 3 described above (proximal area of the side 90 a).
The substrate Wf of the plating apparatus 1 used in the measurement of FIG. 8 is a polygonal substrate Wf described in FIG. 3 and the like (specifically, a square substrate in front view). Each side of the substrate Wf has a length of 600 mm. The total length DI in the extending direction of the auxiliary anode used in the measurement is 510 mm, the length of the end portion proximal region R1 of the auxiliary anode is 30 mm, and the length of the non-end portion region R2 of the auxiliary anode is 450 mm.
However, as the resistive element 65 used in the measurement of FIG. 8 , not one having an electrical conduction rate changed in the extending direction of the auxiliary anode as described in FIG. 6 , but instead, one having an electrical conduction rate that was uniform from the central side toward the end portion sides in the extending direction of the auxiliary anode was used. Using the plating apparatus 1, a plating process was performed on the substrate Wf, and the film thickness of the substrate Wf was measured.
Meanwhile, the plating apparatus according to Comparative Example 1 indicated in FIG. 9 is unlike the plating apparatus 1 according to the working example in that the resistive element 65, the current-shielding mask, and the like are not disposed in the auxiliary anode. The plating apparatus according to Comparative Example 2 indicated in FIG. 10 is unlike the plating apparatus 1 according to the working example in that the current-shielding mask instead of the resistive element 65 is arranged in the auxiliary anode. The current-shielding mask is configured of an insulator. As the insulator, polyetheretherketone was used.
As understood from the part C1 and the part C2 in FIG. 9 , in the plating apparatus according to comparative example 1, the film thicknesses of the end portion proximal regions of the side of the substrate (that is, the “corner portions”) have increased compared with the film thickness of the center portion of the side of the substrate. This may be construed that the amounts of current supplied from the end portion proximal regions of each of the auxiliary anodes to the corner portions of the substrates increased excessively, thus resulting in increases of the film thicknesses of the corner portions of the substrate compared with the film thicknesses of the other portions of the substrate.
Meanwhile, in the plating apparatus according to Comparative Example 2 in FIG. 10 , as understood from the part C1 and the part C2 in FIG. 10 , the film thicknesses of the corner portions of the substrate have decreased compared with the film thickness of the center portion of the side of the substrate. This may be considered to be caused by currents flowing from the end portion proximal regions of the auxiliary anode to the corner portions of the substrate being shielded by the current-shielding mask.
As understood from the part C3 and the part C4 in FIG. 10 , in the plating apparatus according to Comparative Example 2, it can be construed that the film thicknesses have increased more in the end portion proximal regions of the central side portion (proximal regions having a −200 mm or 200 mm distance from the center) than the corner portions of the substrate. This may be considered to be caused by the current shielded by the current-shielding mask concentrating in this portion. The in-plane uniformity of film thickness of the substrate Wf using the plating apparatus according to Comparative Example 2 is 7% measured according to “Range/2Ave (that is, (maximum value−minimum value of film thickness)/(average value of film thickness×2)).”
In contrast to this, according to the working example indicated in FIG. 8 , any increase of the film thickness in the part C1 or the part C2 as in Comparative Example 1 is not observed, and any decrease of the film thickness in the part C1 or the part C2 as in Comparative Example 2 is not recognized. Further, any increase in the film thickness in the part C3 or the part C4 as in Comparative Example 2 is not recognized. As a result, according to the working example, it can be understood that a uniform film thickness is obtained from the center of the sides to the corner portions 91 of the substrate Wf. The in-plane uniformity of film thickness of the substrate Wf using the plating apparatus 1 according to this working example is 2% measured according to “Range/2Ave.” Thus, with this working example, the in-plane uniformity of film thickness of the substrate Wf can be achieved.

REFERENCE SIGNS LIST

- 1 . . . plating apparatus
- 10 . . . plating tank
- 20 . . . substrate holder
- 30 . . . anode
- 51 . . . membrane
- 60 a, 60 b. 60 c, 60 d . . . auxiliary anode
- 65 . . . resistive element
- 66 . . . hole
- 70 . . . intermediate mask
- 70 a . . . hole
- 71 . . . housing portion
- 71 a . . . opening
- 72 a, 72 b, 72 c, 72 d . . . side
- Ps . . . plating solution
- Wf . . . substrate
- 90 a, 90 b, 90 c, 90 d . . . side of substrate

Claims

1. A plating apparatus comprising:

a plating tank configured to accumulate a plating solution and provided with an anode;

a substrate holder configured to hold a substrate as a cathode such that the substrate is opposed to the anode, the substrate being a polygonal substrate having a plurality of sides;

an intermediate mask arranged between the anode and the substrate inside the plating tank, the intermediate mask being provided with a hole that allows a current flowing between the anode and the substrate to pass therethrough; and

an auxiliary anode, wherein

the hole of the intermediate mask is a polygonal hole having a plurality of sides corresponding to the respective plurality of sides of the substrate,

the auxiliary anode is arranged between the substrate and the intermediate mask so as to correspond to at least one side of the hole of the intermediate mask, and the auxiliary anode extends in an extending direction of the side of the hole of the intermediate mask, and

end portion proximal regions of the auxiliary anode from both end portions in an extending direction of the auxiliary anode toward a center are covered by resistive elements having electrical conduction rates larger than zero, the electrical conduction rates are lower than an electrical conduction rate of the plating solution, a region closer to the center than the end portion proximal regions of the auxiliary anode is not covered by the resistive element, and a surface of the region closer to the center than the end portion proximal regions of the auxiliary anode is exposed.

2. The plating apparatus according to claim 1, wherein

the electrical conduction rates of the resistive elements decrease along from a central side toward end portion sides in the extending direction of the auxiliary anode covered by the resistive elements.

3. The plating apparatus according to claim 1, wherein

the resistive element has a plurality of holes, and

the electrical conduction rates of the resistive elements decrease along from the central side toward the end portion sides by a density of the holes of the resistive element decreasing along from the central side toward the end portion sides.

4. The plating apparatus according to any one of claim 1, wherein

lengths in the extending direction of the auxiliary anode of the end portion proximal regions of the auxiliary anode are a length of 10% or less of a total length of the auxiliary anode.

5. The plating apparatus according to any one of claim 1, wherein

the plating apparatus includes a housing portion configured to house the auxiliary anode inside the housing portion,

the housing portion is provided with an opening opened so as to face the substrate, and

the opening is closed by a membrane configured to allow metal ions included in the plating solution to pass through the membrane and inhibit oxygen generated from surfaces of the auxiliary anode from passing through the membrane.