Plating apparatus and method of cleaning substrate holder

A plating apparatus includes: a plating bath configured to store a plating solution therein; a substrate transport device configured to remove a substrate before plating from a substrate cassette and return the substrate after plating to the substrate cassette; a substrate holder configured to detachably hold the substrate with a sealing member sealing a peripheral portion of the substrate and immerse the substrate in the plating solution in the plating bath; a dummy substrate arranged in a position accessible by the substrate transport device; and a substrate holder cleaning bath configured to immerse the substrate holder in a cleaning liquid to clean the substrate holder when holding the dummy substrate with the sealing member sealing a peripheral portion of the dummy substrate.

CROSS REFERENCE TO RELATED APPLICATION

This application claims priority to Japanese Patent Application No. 2012-159205, filed Jul. 18, 2012, the entire content of which is hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a plating apparatus and a method of cleaning a substrate holder, and more particularly to a dip-type plating apparatus in which a substrate, such as a semiconductor wafer, held by a substrate holder is immersed in a plating solution to form e.g., connecting bumps or interconnects on a surface of the substrate, and to a method for cleaning a substrate holder for use in such a plating apparatus.

2. Description of the Related Art

Electroplating is widely used to form connecting bumps at predetermined positions on a surface of a substrate, such as a semiconductor wafer. As shown inFIGS. 1 and 2, a substrate W is prepared with a seed layer200formed as a feeding layer on the substrate surface, a resist202coating the surface of the seed layer200, and openings202aformed at predetermined positions in the resist202. While sealing a peripheral portion of the surface of the substrate W with a sealing member204mounted to a substrate holder, a plating area A of the substrate surface, surrounded by the sealing member204, is brought into contact with a plating solution. A metal206, which is used as bumps, is formed by plating on exposed surfaces of the seed layer200, lying inside the resist openings202ain the plating area A.

When the peripheral portion of the surface of the substrate W is sealed with the sealing member204of the substrate holder in this manner, the sealing member204may bridge over those resist openings202which lie in the peripheral portion of the surface of the substrate W. This would generally be unavoidable because of the necessity for securing the largest possible effective surface area of the substrate W. When the metal206is formed in the openings202aover which the sealing member204bridges, the metal206may be deposited abnormally and reach a top surface of the resist202, resulting in adhesion of an over-deposited metal207to the sealing member204. The metal207adhering to the sealing member204grows every time plating of a substrate is performed.

If the substrate holder is used continuously with the metal207left on the sealing member204, there will be a deficiency of a thickness or poor in-plane uniformity of a metal film formed on a substrate surface. Furthermore, leakage of a plating solution can occur when the plating area A of the substrate surface, surrounded by the sealing member204, is immersed in the plating solution. It is therefore necessary to clean the substrate holder, periodically or as needed, to remove the metal207from the sealing member204.

When the substrate holder is used in plating of a substrate having no resist film formed on the substrate surface, the seed layer200directly contacts the sealing member204of the substrate holder. Therefore, the metal207, abnormally deposited on the substrate surface, may adhere to the sealing member204.

In common practice, therefore, during maintenance work of the substrate holder, the substrate holder is cleaned manually, or with a cleaning liquid (chemical liquid) capable of dissolving the metal207. Upon the maintenance work, in general, the substrate holder is removed from the plating apparatus and cleaning of the substrate holder and periodic replacement of parts are carried out.

A cleaning apparatus for automatically cleaning a suspended jig has been proposed. The cleaning apparatus includes a film-removing solution bath, a water bath, an acid cleaning bath, etc. arranged in this order in a space in which the suspended jig is transported by a transport means (see Japanese Laid-Open Utility Model Publication No. 58-92374). A cleaning apparatus has been proposed which, instead of a common dip or immersion method, employs a jet method in which a cleaning liquid is jetted toward a cleaning object (see Japanese Laid-Open Utility Model Publication No. 61-159083). A workpiece transport system has been proposed which allows a pallet, holding workpieces, to pass through a water-cleaning section, and then immerses the pallet in a pool of water and stores the pallet therein so as to prevent drying and oxidation of the workpieces (see Japanese Laid-Open Patent Publication No. 63-166990). A liquid processing apparatus has been proposed in which a substrate holder, holding a substrate, is moved from a processing bath to a cleaning section, where the substrate holder is cleaned together with the processing surface of the substrate (see Japanese Laid-Open Patent Publication No. 2002-249896).

The applicant has proposed a plating apparatus having a substrate holder cleaning section for cleaning a substrate holder in an open state, not holding a substrate. The plating apparatus can automatically clean the substrate holder without removing it from the plating apparatus (see Japanese Laid-Open Patent Publication No. 2008-45179).

An operation of the plating apparatus needs to be stopped in order to remove the substrate holder from the apparatus and clean the substrate holder. Even if a spare substrate holder is provided, the plating apparatus needs to be stopped at least during replacement of the substrate holder, resulting in a lowered productivity of the plating apparatus. In addition, it is laborious to remove the substrate holder from the plating apparatus.

The above-mentioned patent documents are not directed to a technique for automatically cleaning a substrate holder when it is stored in a plating apparatus, i.e. without taking the substrate holder out of the plating apparatus.

When a substrate holder in an open state, not holding a substrate, is cleaned as described in the Japanese Laid-Open Patent Publication No. 2008-45179, an electrical contact which is kept in contact with a seed layer of a substrate to feed electricity to the seed layer, will become wet with a cleaning liquid. If an electrical contact in a wet state comes into contact with a seed layer of a substrate, the seed layer may dissolve at its contact portion with the electrical contact, leading to a decrease in the electrical conduction between the electrical contact and the seed layer. An electrical contact must therefore be in a dry state upon contact with a seed layer. Thus, a substrate holder with an electrical contact in a wet state cannot be used until the electrical contact becomes dry. It is generally quite difficult to dry the electrical contact, located inside the substrate holder, in a short time.

In a case of using a plating apparatus which is configured to perform multi-layer composite plating on a surface of a substrate held by the substrate holder, a metal207(seeFIG. 2), composed of different types of metals, may be abnormally deposited on the sealing member of the substrate holder. In most cases, no common cleaning liquid can effectively dissolve and remove the metal207composed of different types of metals. Therefore, different types of cleaning liquids should be used to clean the substrate holder. However, a plurality of cleaning baths for the different types of cleaning liquids should be provided for removing the different types of metals abnormally deposited on the sealing member of the substrate holder, thus considerably increasing a footprint of the plating apparatus.

SUMMARY OF THE INVENTION

The present invention has been made in view of the above situation. It is therefore an object of the present invention to provide a plating apparatus capable of cleaning a substrate holder with a cleaning liquid while keeping the plating apparatus in operation without removing the substrate holder from the plating apparatus and without wetting an electrical contact of the substrate holder with the cleaning liquid, and to provide a method for cleaning the substrate holder.

In order to achieve the object, the present invention provides a plating apparatus including: a plating bath configured to store a plating solution therein; a substrate transport device configured to remove a substrate before plating from a substrate cassette and return the substrate after plating to the substrate cassette; a substrate holder configured to detachably hold the substrate with a sealing member sealing a peripheral portion of the substrate and immerse the substrate in the plating solution in the plating bath; a dummy substrate arranged in a position accessible by the substrate transport device; and a substrate holder cleaning bath configured to immerse the substrate holder in a cleaning liquid to clean the substrate holder when holding the dummy substrate with the sealing member sealing a peripheral portion of the dummy substrate.

By thus cleaning the substrate holder with the cleaning liquid that has been supplied into the cleaning bath, a metal adhering to the sealing member of the substrate holder can be removed without stopping the operation of the plating apparatus and without removing the substrate holder from the apparatus. Furthermore, by cleaning the substrate holder holding the dummy substrate while sealing the peripheral portion of the dummy substrate with the sealing member, the substrate holder can be cleaned with the cleaning liquid while preventing an electrical contact(s), provided in the substrate holder, from becoming wet with the cleaning liquid.

In a preferred embodiment of the present invention, the substrate holder cleaning bath is configured to individually supply different types of cleaning liquids and a rinsing liquid into the substrate holder cleaning bath.

When different types of metals, e.g. a first metal and a second metal, are attached to the sealing member of the substrate holder, the substrate holder can be cleaned in the following manner. A first cleaning liquid, which is capable of dissolving the first metal, is supplied into the substrate holder cleaning bath to clean the substrate holder, followed by rinsing of the substrate holder with a rinsing liquid, and thereafter a second cleaning liquid, which is capable of dissolving the second metal, is supplied into the substrate holder cleaning bath to clean the substrate holder, followed by rinsing of the substrate holder with a rinsing liquid. Thus, the substrate holder cleaning bath can effectively dissolve and remove different types of metals, adhering to the sealing member of the substrate holder, without incurring an increase in a footprint of the plating apparatus.

In a preferred embodiment of the present invention, the substrate holder cleaning bath serves as a storage bath for storing the substrate holder therein.

The use of such substrate holder cleaning bath can avoid an increase in the footprint of the plating apparatus.

In a preferred embodiment of the present invention, the substrate holder is one of a plurality of substrate holders, the plating bath is operable to plate substrates with use of a part of the plurality of substrate holders, and the substrate holder cleaning bath is operable to clean other part of the plurality of substrate holders.

In a preferred embodiment of the present invention, the dummy substrate is stored in a substrate cassette which is arranged in a position accessible by the substrate transport device.

With this structure, it is not necessary to provide the dummy substrate in the plating apparatus, and the dummy substrate can be carried into the plating apparatus just before its use for cleaning of the substrate holder.

The present invention also provides a method of cleaning a substrate holder including: suspending a substrate holder in a substrate holder cleaning bath, the substrate holder holding a dummy substrate with a sealing member sealing a peripheral portion of the dummy substrate; and supplying a cleaning liquid into the substrate holder cleaning bath until the substrate holder is immersed in the cleaning liquid to clean the substrate holder.

In a preferred embodiment of the present invention, different types of cleaning liquids and a rinsing liquid are individually and sequentially supplied into the substrate holder cleaning bath to clean the substrate holder sequentially with the cleaning liquids.

According to the present invention, the substrate holder can be cleaned with the cleaning liquid while keeping the plating apparatus in operation, without removing the substrate holder from the apparatus and without wetting an electrical contact, provided in the substrate holder, with the cleaning liquid. It therefore becomes possible to prevent a decrease in the throughput of the plating apparatus due to cleaning of substrate holders.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of the present invention will now be described in detail with reference to the drawings. The following description illustrates an exemplary case where bumps of a Cu—Ni—SnAg alloy are formed at predetermined positions on a surface of a substrate, such as a semiconductor wafer, by sequentially carrying out copper plating, nickel plating, and Sn—Ag alloy plating on the substrate surface. It is noted that the present invention is not limited to the use of such plating metals.

FIG. 3shows an overall layout plan of a plating apparatus according to an embodiment of the present invention. As shown inFIG. 3, the plating apparatus includes two cassette tables12on which substrate cassettes10, each storing substrates W, such as semiconductor wafers, are placed, an aligner14for aligning an orientation flat or a notch of a substrate W in a predetermined direction, and a spin drier16for drying the substrate W after plating by rotating it at a high speed. Near these units is provided a substrate loading unit20for placing a substrate holder18thereon and loading the substrate W into the substrate holder18and removing the substrate W from the substrate holder18. Further, in the center of these units is disposed a substrate transport device22constituted by a transport robot for transporting the substrate W between these units.

A dummy substrate cassette24in which dummy substrates DW are stored is disposed adjacent to the substrate transport device22so that the substrate transport device22is accessible to the dummy substrates DW stored in the dummy substrate cassette24. A dummy substrate DW is a non-patterned substrate having the same shape as the substrate W, and may be a bare silicon substrate or a substrate having a silicon oxide layer formed on its surface. As with the substrate W, the dummy substrate DW is attached to and removed from the substrate holder18by the substrate loading unit20. The number of dummy substrates DW is larger than the number of substrate holders18to be cleaned at a time.

The plating apparatus further includes a first substrate holder cleaning bath26aand a second substrate holder cleaning bath26b, each of which serves not only as a cleaning bath but also as a storage bath for storing and temporarily storing substrate holders18therein, a pre-wetting bath28for immersing a substrate in pure water to enhance hydrophilicity of the surface of the substrate, a pretreatment bath30for carrying out a pre-plating treatment of the surface of the substrate, a pretreatment solution water-cleaning bath32for removing a pretreatment solution adhering to the substrate and the substrate holder18, a Cu plating bath34afor holding a Cu plating solution therein and carrying out electroplating of the surface of the substrate to form a Cu film on the substrate surface, a first water-cleaning bath36afor removing the Cu plating solution adhering to the substrate and the substrate holder18, an Ni plating bath34bfor holding an Ni plating solution therein and carrying out electroplating of the surface of the substrate to form an Ni film on the surface of the Cu film, a second water-cleaning bath36bfor removing the Ni plating solution adhering to the substrate and the substrate holder18, a blow bath38for cleaning the substrate surface with pure water and then removing the pure water from the surface (by air blowing), an Sn—Ag alloy plating bath34cfor holding an Sn—Ag alloy plating solution therein and carrying out electroplating of the surface of the substrate to form an Sn—Ag alloy film on the surface of the Ni film, and a third water-cleaning bath36cfor removing the Sn—Ag alloy plating solution adhering to the substrate and the substrate holder18. These baths are arranged in this order starting from the one nearest to the substrate loading unit20.

A cleaning liquid, which is capable of dissolving a metal207(seeFIG. 2) adhering to a sealing member, is supplied into the pretreatment bath30. An aqueous solution of sulfuric acid and hydrogen peroxide may be used as the cleaning liquid in order to dissolve copper. An aqueous solution of sodium hydroxide may be used as the cleaning liquid in order to dissolve nickel. A 30-50 wt % aqueous solution of nitric acid or an aqueous solution of methanesulfonic acid may be used as the cleaning liquid in order to dissolve the Sn—Ag alloy. The pretreatment solution water-cleaning bath32is provided with a blowing mechanism for blowing air toward the substrate holder18, holding a substrate after water cleaning, while moving the substrate holder18upward, to remove pure water adhering to the substrate and the substrate holder18. In this embodiment a large number of Sn—Ag alloy plating baths34care provided so as to increase an operating rate.

Located lateral to the above baths, there is provided a substrate holder transport device40, driven e.g., by a linear motor, for transporting the substrate holder18, together with a substrate, between the baths. The substrate holder transport device40has a first transporter42for transporting a substrate between the substrate loading unit20and the substrate holder cleaning baths26aand26b, and a second transporter44for transporting the substrate between the substrate holder cleaning baths26aand26b, the pre-wetting bath28, the pretreatment bath30, the water-cleaning baths32,36a,36b, and36c, the plating baths34a,34b, and34c, and the blow bath38. The substrate holder transport device40may be provided with only the first transporter42without being provided with the second transporter44.

Paddle driving devices46are provided each for driving a paddle (not shown) disposed in each of the plating baths34a,34b, and34cas an agitator for agitating a plating solution. The paddle driving devices46are located at the opposite side of the substrate holder transport device40.

The substrate loading unit20includes a flat stage plate52which is laterally slidable along rails50. Two substrate holders18, parallel to each other, are placed horizontally on the stage plate52. After one substrate is transferred between one substrate holder18and the substrate transport device22, the stage plate52is slid laterally and the other substrate is transferred between the other substrate holder18and the substrate transport device22.

As shown inFIGS. 4 through 7, the substrate holder18includes a first holding member (base holding member)54having a rectangular plate shape and made of e.g., vinyl chloride, and a second holding member (movable holding member)58rotatably coupled to the first holding member54through a hinge56which allows the second holding member58to open and close with respect to the first holding member54. Although in this embodiment the second holding member58is configured to be openable and closable through the hinge56, it is also possible to dispose the second holding member58opposite to the first holding member54and to move the second holding member58away from and toward the first holding member54to thereby open and close the second holding member58.

The second holding member58includes a base portion60and a ring-shaped seal holder62. The seal holder62is made of vinyl chloride so as to enable a retaining ring64, which will be described later, to slide well. An inwardly-projecting substrate-side (inner-side) sealing member66is fixed to an upper surface of the seal holder62. The substrate-side sealing member66is placed in pressure contact with a peripheral portion of the surface of the substrate W to seal a gap between the substrate W and the second holding member58when the substrate W is held by the substrate holder18. A holder-side (outer-side) sealing member68is fixed to a surface, facing the first holding member54, of the seal holder62. This holder-side sealing member68is placed in pressure contact with the first holding member54to seal a gap between the first holding member54and the second holding member58when the substrate W is held by the substrate holder18. The holder-side sealing member68is located outwardly of the substrate-side sealing member66.

As shown inFIG. 7, the substrate-side sealing member66is sandwiched between the seal holder62and a first mounting ring70awhich is secured to the seal holder62by fastening tools69a, such as bolts. The holder-side sealing member68is sandwiched between the seal holder62and a second mounting ring70bwhich is secured to the seal holder62by fastening tools69b, such as bolts.

The seal holder62of the second holding member58has a stepped portion at a periphery thereof, and the retaining ring64is rotatably mounted to the stepped portion via a spacer65. The retaining ring64is inescapably held by the first mounting ring70a. This retaining ring64is made of a material having high rigidity and excellent acid corrosion resistance, for example titanium, and the spacer65is made of a material having a low friction coefficient, for example PTFE, so that the retaining ring64can rotate smoothly.

Inverted L-shaped clampers74, each having an inwardly projecting portion and located outside of the retaining ring64, are provided on the first holding member54at equal intervals along a circumferential direction of the retaining ring64. The retaining ring64has outwardly projecting portions64barranged along the circumferential direction of the retaining ring64at positions corresponding to positions of the clampers74. A lower surface of the inwardly projecting portion of each clamper74and an upper surface of each projecting portion64bof the retaining ring64are tapered in opposite directions along the rotational direction of the retaining ring64. A plurality (e.g., four) of upwardly protruding dots64aare provided on the retaining ring64in predetermined positions along the circumferential direction of the retaining ring64. The retaining ring64can be rotated by pushing and moving each dot64afrom a lateral direction by means of a rotating pin (not shown).

When the second holding member58is open, the substrate W is inserted into the central portion of the first holding member54, and the second holding member58is then closed through the hinge56. Subsequently the retaining ring64is rotated clockwise so that each projecting portion64bof the retaining ring64slides into the inwardly projecting portion of each clamper74. As a result, the first holding member54and the second holding member58are fastened to each other and locked by engagement between the tapered surfaces of the projecting portions64bof the retaining ring64and the tapered surfaces of the clampers74. The lock of the second holding member58can be released by rotating the retaining ring64counterclockwise to disengage the projecting portions64bof the retaining ring64from the inverted L-shaped clampers74.

When the second holding member58is locked in the above-described manner, the lower end of the inner downwardly-protruding portion of the substrate-side sealing member66is placed in pressure contact with the peripheral portion of the surface of the substrate W held by the substrate holder18. As a result, the substrate-side sealing member66is uniformly pressed against the substrate W to seal the gap between the substrate W and the second holding member58. Similarly, when the second holding member58is locked, the lower end of the outer downwardly-protruding portion of the holder-side sealing member68is placed in pressure contact with the surface of the first holding member54, whereby the holder-side sealing member68is uniformly pressed against the first holding member54to seal the gap between the first holding member54and the second holding member58.

The dummy substrate DW is held by the substrate holder18in the same manner. Specifically when the second holding member58is open, the dummy substrate DW is inserted into the central portion of the first holding member54, and the second holding member58is then closed through the hinge56. Subsequently the retaining ring64is rotated clockwise so that each projecting portion64bof the retaining ring64slides into the inwardly projecting portion of each clamper74. As a result, the first holding member54and the second holding member58are fastened to each other and locked by engagement between the tapered surfaces of the projecting portions64bof the retaining ring64and the tapered surfaces of the clampers74. The lock of the second holding member58can be released by rotating the retaining ring64counterclockwise to disengage the projecting portions64bof the retaining ring64from the inverted L-shaped clampers74.

When the second holding member58is locked in the above-described manner, the lower end of the inner downwardly-protruding portion of the substrate-side sealing member66is placed in pressure contact with the peripheral portion of the surface of the dummy substrate DW held by the substrate holder18. As a result, the substrate-side sealing member66is uniformly pressed against the dummy substrate DW to seal the gap between the dummy substrate DW and the second holding member58. Similarly, when the second holding member58is locked, the lower end of the outer downwardly-protruding portion of the holder-side sealing member68is placed in pressure contact with the surface of the first holding member54, whereby the holder-side sealing member68is uniformly pressed against the first holding member54to seal the gap between the first holding member54and the second holding member58.

The first holding member54has a protruding portion82in a ring shape corresponding to a size of the substrate W. The protruding portion82has a support surface80which contacts the peripheral portion of the substrate W to support the substrate W. The protruding portion82has recesses84arranged at predetermined positions along a circumferential direction of the protruding portion82.

As shown inFIG. 5, a plurality of electrical conductors (electrical contacts)86(e.g., 12 conductors as illustrated), coupled respectively to wires extending from connection terminals provided on a hand90, are disposed in the recesses84of the protruding portion82. When the substrate W is placed on the support surface80of the first holding member54, ends of the electrical conductors86contact lower portions of the electrical contacts88shown inFIG. 7.

The electrical contacts88, to be electrically connected to the electrical conductors86, are secured to the seal holder62of the second holding member58by fastening tools89, such as bolts. The electrical contacts88each have a leaf spring-like contact portion lying outside the substrate-side sealing member66and projecting inwardly. This contact portion is springy and bends easily. When the substrate W is held by the first holding member54and the second holding member58, the contact portions of the electrical contacts88make elastic contact with the peripheral surface of the substrate W supported on the support surface80of the first holding member54.

The second holding member58is opened and closed by a not-shown pneumatic cylinder and by the weight of the second holding member58itself. More specifically, a through-hole54ais formed in the first holding member54, and the pneumatic cylinder is provided so as to face the through-hole54awhen the substrate holder18is placed on the stage plate52of the substrate loading unit20. The second holding member58is opened by extending a piston rod of the pneumatic cylinder to lift up a pressing rod (not shown) through the through-hole54ato thereby push up the seal holder62of the second holding member58. The second holding member58is closed by its own weight when the piston rod is retracted.

A pair of approximately T-shaped hands90is coupled to the ends of the first holding member54of the substrate holder18. These hands90serve as a support when the substrate holder18is transported and when the substrate holder18is held in a suspended state. In the substrate holder cleaning baths26aand26b, outwardly projecting ends of the hands90are placed on an upper surface of a peripheral wall of each bath, whereby the substrate holder18is suspended in a vertical position. When the substrate holder18is transported, the hands90of the suspended substrate holder18are gripped by the first transporter42of the substrate holder transport device40. Also in the pre-wetting bath28, the pretreatment bath30, the water-cleaning baths32,36a,36b, and36c, the plating baths34aand34b, and the blow bath38, the substrate holder18is suspended with the hands90placed on peripheral walls of these baths.

FIG. 8is a schematic view showing the first substrate holder cleaning bath26aand the second substrate holder cleaning bath26b. As shown inFIG. 8, branch lines106are coupled respectively to the first substrate holder cleaning bath26aand the second substrate holder cleaning bath26b. The branch lines106branch off from a cleaning liquid supply line104, which extends from a cleaning liquid tank100that stores a cleaning liquid therein and is provided with a pump102. The branch lines106are provided with on-off valves108aand108b, respectively. Branch lines114are coupled respectively to the first substrate holder cleaning bath26aand the second substrate holder cleaning bath26b. These branch lines114branch off from a cleaning liquid discharge line112which extends from a cleaning liquid reservoir110. The branch lines114are provided with on-off valves116aand116b, respectively.

In this embodiment, a 30-50 wt % aqueous solution of nitric acid or a 10 wt % aqueous solution of methanesulfonic acid, which is capable of dissolving the Sn—Ag alloy, is used as the cleaning liquid. An aqueous solution of nitric acid having a high concentration necessitates control of the atmosphere for safety reasons, while methanesulfonic acid is free of such a disadvantage and is therefore preferably used.

Branch lines124are coupled respectively to the first substrate holder cleaning bath26aand the second substrate holder cleaning bath26b. These branch lines124branch off from a rinsing liquid supply line122which extends from a rinsing liquid supply source120for supplying a rinsing liquid, such as pure water. The branch lines124are provided with on-off valves126aand126b, respectively. Further, branch lines132, branching off from a water discharge line130, are coupled respectively to the first substrate holder cleaning bath26aand the second substrate holder cleaning bath26b. The branch lines132are provided with on-off valves134aand134b, respectively.

In this embodiment at least one of the first substrate holder cleaning bath26aand the second substrate holder cleaning bath26bis used as a storage bath for storing substrate holders18therein. This can avoid an increase in the footprint of the plating apparatus. When the first substrate holder cleaning bath26ais used as the storage bath, the on-off valves108a,116a,126a, and134aare all closed so that the liquids (the cleaning liquid and the rinsing liquid) will not flow into the first substrate holder cleaning bath26a. When the second substrate holder cleaning bath26bis used as the storage bath, the on-off valves108b,116b,126b,134bare all closed.

A description will now be given of the operation of the plating apparatus in the case where the first substrate holder cleaning bath26ais used as the storage bath and substrate holders18, stored in the first substrate holder cleaning bath26a, are used in a sequence of plating process steps, while the substrate holders18are cleaned with the cleaning liquid in the second substrate holder cleaning bath26bwithout removing the substrate holders18from the plating apparatus. In the case where the second substrate holder cleaning bath26bis used as the storage bath and the substrate holders18are cleaned with the cleaning liquid in the first substrate holder cleaning bath26a, the operation of the plating apparatus is performed in a similar manner, and hence a description thereof will be omitted.

A sequence of plating processes, performed with the use of the substrate holder18stored in the first substrate holder cleaning bath26a, will be described first.

One substrate W is removed by the substrate transport device22from the substrate cassette10mounted to the cassette table12, and the substrate W is placed on the aligner14, where an orientation flat or a notch of the substrate W is aligned in a predetermined direction. After the alignment, the substrate W is transported to the substrate loading unit20by the substrate transport device22.

Two substrate holders18, which are stored in the first substrate holder cleaning bath26a, are simultaneously gripped by the first transporter42, and transported to the substrate loading unit20. The two substrate holders18are lowered in a horizontal position until these substrate holders18are simultaneously placed on the stage plate52of the substrate loading unit20. The pneumatic cylinder is then actuated to open the second holding member58of each of the substrate holders18.

In this state, the substrate W that has been transported to the substrate loading unit20by the substrate transport device22is inserted into the substrate holder18positioned at the center side, and the pneumatic cylinder is reversely actuated to close the second holding member58. Then the second holding member58is locked by means of a locking/unlocking mechanism. After completion of the loading of the substrate W into the one substrate holder18, the stage plate52is slid laterally, and other substrate W is loaded into the other substrate holder18in the same manner. Thereafter, the stage plate52is returned to its original position.

With the above operations, the substrate W is held by the substrate holder18with its front surface (to-be-plated surface) exposed in an opening of the substrate holder18and its peripheral portion sealed by the sealing members66and68which prevent intrusion of a plating solution. The peripheral portion of the substrate W, which is not in contact with the plating solution, is electrically connected to the electrical contacts88. Wires extend from the electrical contacts88to the hand90of the substrate holder18. Therefore, an electric current can be fed to a seed layer200(seeFIG. 2) of the substrate W by connecting a power source to the connection terminal of the hand90.

Next, the two substrate holders18, loaded with the substrates W, are simultaneously gripped by the first transporter42and transported to the first substrate holder cleaning bath26a. The two substrate holders18are lowered in a vertical position and suspended in the first substrate holder cleaning bath26afor temporary storage. The substrate transport device22, the substrate loading unit20, and the first transporter42sequentially repeat the above operations to sequentially remove substrates W from the first substrate holder cleaning bath26a, load the substrates W into substrate holders18, and sequentially suspend the substrate holders18in predetermined positions in the first substrate holder cleaning bath26afor their temporary storage.

Although not shown diagrammatically, instead of the substrate loading unit20on which two substrate holders18are placed in a horizontal position, it is possible to provide a fixing station which supports two substrate holders, which have been transported by the first transporter42, in a vertical position. The substrate holders can be brought into a horizontal position by rotating the fixing station, holding the substrate holders in a vertical position, by 90 degrees. While one locking/unlocking mechanism is provided in this embodiment, it is possible to provide two locking/unlocking mechanisms and to simultaneously perform locking/unlocking of two substrate holders, disposed adjacent to each other, by means of the two locking/unlocking mechanisms.

Two substrate holders18loaded with substrates W, which have been temporarily stored in the first substrate holder cleaning bath26a, are simultaneously gripped by the second transporter44and transported to the pre-wetting bath28, where the two substrate holders18are lowered until they are immersed in a pre-wetting liquid (pure water) in order to enhance the hydrophilicity of the surface of the seed layer200(seeFIG. 2) of each substrate W.

It is also possible to transport the substrate holders18, each loaded with the substrate W, directly to the pre-wetting bath28to immerse the substrates together with the substrate holders18into the pre-wetting liquid by the first transporter42, i.e., without temporarily storing the substrate holders18in the first substrate holder cleaning bath26a.

Next, the two substrate holders18loaded with the substrates W are transported to the pretreatment bath30in the same manner as described above. In the pretreatment bath30, a surface oxide film formed on the seed layer200(seeFIG. 2) of each substrate W is etched away, thereby exposing a clean metal surface. Thereafter, the substrate holders18loaded with the substrates W are transported to the pretreatment solution water-cleaning bath32, where the acid adhering to the surface (to-be-plated surface) of the substrate W is removed.

Thereafter, the two substrate holders18loaded with the substrates W are transported in the same manner to the Cu plating bath34ain which a Cu plating solution is held, and are suspended in the Cu plating bath34a. Copper plating of the surface of each substrate W is carried out in the following manner. While the Cu plating solution is supplied to the Cu plating bath34aand is circulating through the Cu plating bath34a, a plating voltage is applied between the substrate W and an anode (not shown) in the Cu plating bath34aand, at the same time, the paddle is reciprocated parallel to the surface of the substrate W by means of the paddle driving device46. As shown inFIG. 2, a metal206, which is a Cu film, is formed by the copper plating on the exposed surfaces of the seed layer200, lying inside the resist openings202a, in each substrate W.

Like the sealing member204shown inFIG. 2, if the substrate-side sealing member66bridges over those resist openings202awhich lie in the peripheral portion of the surface of the substrate W, the metal206may be deposited abnormally in the resist openings202aover which the substrate-side sealing member66bridges and may reach even the top surface of the resist202, resulting in adhesion of the over-deposited metal207(Cu) to the substrate-side sealing member66. The same problem could occur in the below-described nickel plating and Sn—Ag alloy plating. When an Ni film is formed on the surface of the Cu film by nickel plating, and when an Sn—Ag alloy film is formed on the surface of the Ni film by Sn—Ag alloy plating, a metal206may be deposited abnormally in those resist openings202aover which the substrate-side sealing member66bridges and may reach even the top surface of the resist202, resulting in adhesion of the over-deposited metal207(Ni and an Sn—Ag alloy) to the substrate-side sealing member66.

It is therefore necessary to clean the substrate holder18, periodically or as needed, to remove the metal207(Cu, Ni and/or an Sn—Ag alloy) from the substrate-side sealing member66.

During the copper plating, the substrate holder18is suspended and fixed with the hands90supported on the top of the Cu plating bath34a, and electricity is fed from a plating power source to the seed layer200(seeFIG. 2) of the substrate W through the electrical conductors (electrical contacts)86and the electrical contacts88. Feeding of the electricity is performed in the same manner in below-described nickel plating and Sn—Ag alloy plating.

After the completion of copper plating, the application of the plating voltage, the supply of the plating solution, and the reciprocation of the paddle are stopped. Thereafter, the two substrate holders18loaded with substrates W are simultaneously gripped by the second transporter44, and are transported to the first water-cleaning bath36a, where the substrates W and the substrate holders18are cleaned with pure water by repeating at least twice the operation of supplying pure water into the first water-cleaning bath36aand draining the pure water from the bath36a.

After water cleaning, the substrate holders18loaded with the substrates W are transported in the same manner to the Ni plating bath34bin which an Ni plating solution is stored, and are suspended in the Ni plating bath34b. As necessary, the second transporter44sequentially repeats the above operations to sequentially transport substrate holders18, each loaded with a substrate, to the Ni plating bath34band suspend the substrate holders18at predetermined positions in the Ni plating bath34b.

Nickel plating of the surface of each substrate W is carried out in the following manner. While the Ni plating solution is supplied into the Ni plating bath34band is circulating through the Ni plating bath34b, a plating voltage is applied between the substrate W and an anode (not shown) in the Ni plating bath34band, at the same time, the paddle is reciprocated parallel to the surface of the substrate W by means of the paddle driving device46. An Ni film is formed by the nickel plating on the surface of the Cu film which has been formed by the copper plating.

After the completion of nickel plating, the application of the plating voltage, the supply of the plating solution, and the reciprocation of the paddle are stopped. Thereafter, the two substrate holders18loaded with substrates W after nickel plating are simultaneously gripped by the second transporter44, and are transported to the second water-cleaning bath36b, where the substrates W and the substrate holders18are cleaned with pure water in the same manner as described above.

After water cleaning, the substrate holders18loaded with the substrates W are transported in the same manner to the Sn—Ag alloy plating bath34cin which an Sn—Ag alloy plating solution is stored, and are suspended in the Sn—Ag alloy plating bath34c. As necessary, the second transporter44sequentially repeats the above operations to sequentially transport substrate holders18, each loaded with a substrate, to the Sn—Ag alloy plating bath34cand suspend the substrate holders18at predetermined positions in the Sn—Ag alloy plating bath34c.

Sn—Ag alloy plating of the surface of each substrate W is carried out in the following manner. While the Sn—Ag alloy plating solution is supplied into the Sn—Ag alloy plating bath34cand is circulating through the Sn—Ag alloy plating bath34c, a plating voltage is applied between the substrate W and an anode (not shown) in the Sn—Ag alloy plating bath34cand, at the same time, the paddle is reciprocated parallel to the surface of the substrate W by means of the paddle driving device46. An Sn—Ag alloy film is formed by the Sn—Ag alloy plating on the surface of the Ni film which has been formed by the nickel plating.

After the completion of Sn—Ag alloy plating, the application of the plating voltage, the supply of the plating solution, and the reciprocation of the paddle are stopped. Thereafter, the two substrate holders18loaded with substrates W are simultaneously gripped by the second transporter44, and are transported to the third water-cleaning bath36c, where the substrates W and the substrate holders18are cleaned with pure water in the same manner as described above.

Thereafter, the substrate holders18are transported to the blow bath38, where the substrate holders18are cleaned with water and then air blows the substrate holders18to remove water droplets from the substrates W and the substrate holders18. The substrate holders18are then gripped by the first transporter42and transported to the substrate loading unit20, where the substrate holders18are placed on the stage plate52in the same manner as described above.

The second holding member58of the substrate holder18positioned on the center side is unlocked by means of the locking/unlocking mechanism, and the pneumatic cylinder is actuated to open the second holding member58. The substrate W after plating is then removed from the substrate holder18by the substrate transport device22, and transported to the spin drier16, where the substrate W is spin-dried (drained) by high-speed rotation of the spin drier16. The dried substrate W is returned to the substrate cassette10by the substrate transport device22.

After or in parallel with returning the substrate to the substrate cassette10, the stage plate52is slid laterally and the other substrate is removed from the other substrate holder18. The substrate is then spin-dried by the spin drier16, and the dried substrate is returned to the substrate cassette10.

After returning the stage plate52to the original position, the two substrate holders18, from which the substrates have been removed, are simultaneously gripped by the first transporter42and are returned to predetermined positions in the first substrate holder cleaning bath26ain the same manner as described above. Thereafter, the two substrate holders18, which have been returned to the first substrate holder cleaning bath26a, are simultaneously gripped by the substrate holder transport device40and, in the same manner as described above, are placed on the stage plate52of the substrate loading unit20. Thereafter, the same operations as described above are repeated.

Processes of cleaning the substrate holders18in the second substrate holder cleaning bath26bwill now be described.

One dummy substrate DW is removed from the dummy substrate cassette24, disposed adjacent to the substrate transport device22, by the substrate transport device22and, if necessary, the substrate DW is placed on the aligner14, where an orientation flat or a notch of the dummy substrate DW is aligned in a predetermined direction. The dummy substrate DW is then transported to the substrate loading unit20by the substrate transport device22.

Two substrate holders18stored in the first substrate holder cleaning bath26aare simultaneously gripped by the first transporter42, and transported to the substrate loading unit20. The substrate holders18are lowered in a horizontal position until they are simultaneously placed onto the stage plate52of the substrate loading unit20. The pneumatic cylinder is then actuated to open the second holding member58of each of the substrate holders18.

The dummy substrates DW are then held by the substrate holders18, respectively, in the same manner as the case of the substrate W. When the dummy substrate DW is held by the substrate holder18, a space around the peripheral portion of the dummy substrate DW is sealed off by the sealing members66and68which prevent intrusion of the plating solution into the space. The electrical contacts88of the substrate holder18are located in this sealed space where the cleaning liquid is not permitted to enter.

When the dummy substrate DW is held by the substrate holder18, a substrate contact portion66aof the substrate-side sealing member66is wiped by the surface of the dummy substrate DW, whereby extraneous matter can be rubbed off the substrate contact portion66a. Likewise, a substrate contact portion88aof the electrical contact88is wiped by the surface of the dummy substrate DW, whereby impurities can be rubbed off the substrate contact portion88a. The wiping effect due to contact with the surface of the dummy substrate DW is high especially when the dummy substrate DW is a bare silicon substrate or a substrate having a surface silicon oxide film which, as compared to the substrate W to be plated, has a higher surface hardness and a larger contact area with the substrate contact portion66aof the substrate-side sealing member66or with the substrate contact portion88aof the electrical contact88.

Next, the two substrate holders18, loaded with the dummy substrates DW, are simultaneously gripped by the first transporter42and transported to the second substrate holder cleaning bath26b. The two substrate holders18are lowered in a vertical position until they are suspended in the second substrate holder cleaning bath26b. The substrate transport device22, the substrate loading unit20, and the first transporter42sequentially repeat the above operations to sequentially load dummy substrates DW into substrate holders18which have been stored in the first substrate holder cleaning bath26aand sequentially suspend the substrate holders18in predetermined positions in the second substrate holder cleaning bath26b.

FIG. 8schematically illustrates the second substrate holder cleaning bath26bin which the substrate holders18, each holding the dummy substrate DW, are suspended.

The pump102is then driven and only the on-off valve108b, provided in the branch line106of the cleaning liquid supply line104, is opened to supply a predetermined amount of a cleaning liquid (10 wt % aqueous solution of methanesulfonic acid) into the second substrate holder cleaning bath26bso that the substrate holders18, each holding the dummy substrate DW and suspended in the second substrate holder cleaning bath26b, are immersed in the cleaning liquid. By immersing the substrate holders18in the cleaning liquid, the metal207(seeFIG. 2) adhering to the inner peripheral surface of the substrate-side sealing member66of each substrate holder18is dissolved in the cleaning liquid and is thus removed. While the substrate holders18are immersed in the cleaning liquid, the cleaning liquid is preferably stirred by air bubbling or by means of a paddle.

During cleaning of the substrate holder18with the cleaning liquid, the dummy substrate DW is held by the substrate holder18with a space around the dummy substrate DW sealed off by the sealing members66and68, and the electrical contacts88of the substrate holder18are located in this sealed space where the cleaning liquid does not contact. Thus, the electrical contacts88can be prevented from contacting the cleaning liquid and becoming wet with the cleaning liquid. After keeping the substrate holders18immersed in the cleaning liquid for a predetermined period of time, only the on-off valve116b, provided in the branch line114of the cleaning liquid discharge line112, is opened to discharge the cleaning liquid from the second substrate holder cleaning bath26bso that the cleaning liquid is recovered in the cleaning liquid reservoir110.

Next, only the on-off valve126b, provided in the branch line124of the rinsing liquid supply line122, is opened to supply a predetermined amount of a rinsing liquid (pure water) into the second substrate holder cleaning bath26bso that the substrate holders18are immersed in the rinsing liquid, whereby the substrate holders18are rinsed. After keeping the substrate holders18immersed in the rinsing liquid for a predetermined period of time, only the on-off valve134b, provided in the branch line132of the water discharge line130, is opened to discharge the rinsing liquid from the second substrate holder cleaning bath26bthrough the water discharge line130.

Next, the two substrate holders18after cleaning in the second substrate holder cleaning bath26bare simultaneously gripped by the second transporter44and transported to the pretreatment solution water-cleaning bath32, where the cleaning liquid adhering to the substrate holders18is removed. Thereafter, the substrate holders18are transported to the blow bath38, where the substrate holders18are cleaned with water and then air blows the substrate holders18to remove water droplets from the substrate holders18.

The substrate holders18are then gripped by the first transporter42and transported to the substrate loading unit20, where the substrate holders18are placed on the stage plate52of the substrate loading unit20. In the same manner as in the case of the substrates W, the dummy substrates DW are removed from the substrate holders18by the substrate transport device22, and transported to the spin drier16in a sequential manner, where the dummy substrates DW are spin-dried (drained) by high-speed rotation of the spin drier16. The dried dummy substrates DW are returned to the dummy substrate cassette24by the substrate transport device22.

The two substrate holders18, from which the dummy substrates DW have been removed, are simultaneously gripped by the first transporter42and returned to predetermined positions in the second substrate holder cleaning bath26b. The process of cleaning the substrate holders18in the second substrate holder cleaning bath26bis completed when all the dummy substrates DW are removed from all the substrate holders18and the substrate holders18are returned to the second substrate holder cleaning bath26b.

While both the first substrate holder cleaning bath26aand the second substrate holder cleaning bath26bserve not only as a cleaning unit but also as a storage bath in this embodiment, one of the first substrate holder cleaning bath26aand the second substrate holder cleaning bath26bmay be replaced with a container having no pipes and no valves and provided solely for use as a storage bath. Thus, in this case, all the substrate holders18in the plating apparatus are cleaned in only one of the first substrate holder cleaning bath26aand the second substrate holder cleaning bath26b.

In one embodiment, the substrate holder18to be cleaned is suspended in the second substrate holder cleaning bath26bwith no dummy substrate DW held by the substrate holder18. In another embodiment, the substrate holder18may be suspended in the second substrate holder cleaning bath26bwith the dummy substrate DW held by the substrate holder18immediately after the plated substrate W is removed from the substrate holder18. This embodiment can reduce a time for loading the dummy substrate DW into the substrate holder18.

Because the first substrate holder cleaning bath26aand the second substrate holder cleaning bath26balso serve as the storage bath, they are configured to store therein at least the same number of substrate holders as the number of plating baths. In an initial operating stage of the plating apparatus, the substrate holders18of the plating apparatus are all stored in the first substrate holder cleaning bath26aor the second substrate holder cleaning bath26b. When the plating apparatus is in operation at a maximum operating rate, all the substrate holders18may be in use for continuous operation, with no substrate holder18left in the first substrate holder cleaning bath26aand in the second substrate holder cleaning bath26b. If some (e.g., one-half) of the substrate holders18are cleaned in the second substrate holder cleaning bath26b, main plating operations can be performed by using the remainder of the substrate holders18, though the operating rate of the plating apparatus decreases.

It is also possible to sequentially load the dummy substrates DW into the substrate holders18that have been stored in the first substrate holder cleaning bath26aand/or the second substrate holder cleaning bath26band to perform cleaning of the substrate holders18, each loaded with the dummy substrate DW, in a substrate holder cleaning mode when the plating apparatus is in an idle state in which no substrate is processed.

Though in this embodiment the dummy substrates DW are stored in the dummy substrate cassette24disposed adjacent to the substrate transport device22, it is also possible to mount a substrate cassette10, in which dummy substrates are stored, on the cassette table12when cleaning the substrate holders18. Thus, it is not necessary to provide the dummy substrates in the plating apparatus, and the dummy substrates can be carried into the plating apparatus just before their use for cleaning of the substrate holders18.

The cleaning liquid tank100may be installed either in the plating apparatus, or outside the apparatus as a cleaning liquid supply unit. The cleaning liquid, if it is not reusable for cleaning of substrate holders18, may be discarded without recovering it in the cleaning liquid reservoir110.

FIG. 9illustrates a substrate holder cleaning bath150provided instead of at least one of the substrate holder cleaning baths26aand26b.

The substrate holder cleaning bath150of this embodiment can effectively dissolve and remove a metal207(seeFIG. 2), adhering to the substrate-side sealing member66of the substrate holder18and composed of different types of metals, in particular Cu, Ni, and Sn—Ag alloy in this embodiment, by using different types of cleaning liquids. The use of the substrate holder cleaning bath150can eliminate the use of a plurality of cleaning baths for different types of cleaning liquids, thus avoiding a considerable increase in the footprint of the plating apparatus.

As shown inFIG. 9, the substrate holder cleaning bath150of this embodiment is provided with an overflow bath152. A first cleaning liquid supply line154, a second cleaning liquid supply line156, and a third cleaning liquid supply line158are coupled to the substrate holder cleaning bath150. The first cleaning liquid supply line154is provided for supplying a first cleaning liquid capable of dissolving and removing copper. The first cleaning liquid is, for example, a mixture of 10 wt % aqueous solution of sulfuric acid and 3 wt % aqueous solution of hydrogen peroxide. The second cleaning liquid supply line156is provided for supplying a second cleaning liquid capable of dissolving and removing nickel. The second cleaning liquid is, for example, a 5 wt % aqueous solution of sodium hydroxide. The third cleaning liquid supply line158is provided for supplying a third cleaning liquid capable of dissolving and removing an Sn—Ag alloy. The third cleaning liquid is, for example, a 10 wt % aqueous solution of methanesulfonic acid.

The first cleaning liquid supply line154, the second cleaning liquid supply line156, and the third cleaning liquid supply line158are provided with on-off valves160a,160b, and160c, respectively.

A rinsing liquid supply line162for supplying a rinsing liquid, such as pure water, is coupled to the substrate holder cleaning bath150. This rinsing liquid supply line162is provided with an on-off valve160d. An air supply line164for supplying air into a liquid, such as the first cleaning liquid, in the substrate holder cleaning bath150in order to form bubbles in the liquid, is coupled to the substrate holder cleaning bath150. The air supply line164is provided with an on-off valve160e.

Further, a first cleaning liquid discharge line166, a second cleaning liquid discharge line168, a third cleaning liquid discharge line170, and a water discharge line172are coupled to the substrate holder cleaning bath150. The first cleaning liquid discharge line166is provided for discharging the first cleaning liquid from the substrate holder cleaning bath150, the second cleaning liquid discharge line168is provided for discharging the second cleaning liquid from the substrate holder cleaning bath150, and the third cleaning liquid discharge line170is provided for discharging the third cleaning liquid from the substrate holder cleaning bath150. The first cleaning liquid discharge line166, the second cleaning liquid discharge line168, the third cleaning liquid discharge line170, and the water discharge line172are provided with on-off valves160f,160g,160h, and160i, respectively. An overflow water discharge line174which joins the water discharge line172is coupled to the bottom of the overflow bath152.

Process of cleaning the substrate holders, each having the substrate-side sealing member66(seeFIG. 7) to which a metal207(seeFIG. 2) composed of Cu, Ni, and an Sn—Ag alloy is attached, by using the substrate holder cleaning bath150having the above construction will now be described.

First, the substrate holders, each loaded with a dummy substrate, are suspended in the substrate holder cleaning bath150in the same manner as the above-described manner in which substrate holders18, each loaded with the dummy substrate DW, are suspended in the second substrate holder cleaning bath26b.

Next, only the on-off valve160aof the first cleaning liquid supply line154is opened to supply a predetermined amount of the first cleaning liquid (a mixture of 10 wt % aqueous solution of sulfuric acid and 3 wt % aqueous solution of hydrogen peroxide) into the substrate holder cleaning bath150so that the substrate holders, each holding the dummy substrate and suspended in the substrate holder cleaning bath150, are immersed in the first cleaning liquid and cleaned with the first cleaning liquid. The metal207(mainly its Cu portion), adhering to the substrate-side sealing member66of each substrate holder, is effectively dissolved in the first cleaning liquid and is thus removed. During the cleaning of the substrate holders, if necessary, the on-off valve160eof the air supply line164may be opened to supply air into the first cleaning liquid to form air bubbles in the first cleaning liquid. After keeping the substrate holders immersed in the first cleaning liquid for a predetermined period of time, only the on-off valve160fof the first cleaning liquid discharge line166is opened to discharge the first cleaning liquid from the substrate holder cleaning bath150.

Next, only the on-off valve160dof the rinsing liquid supply line162is opened to supply a predetermined amount of the rinsing liquid (pure water) into the substrate holder cleaning bath150so that the substrate holders are immersed in the rinsing liquid, whereby the substrate holders are rinsed. During the rinsing of the substrate holders, if necessary, the on-off valve160eof the air supply line164may be opened to supply air into the rinsing liquid to form air bubbles in the rinsing liquid. After keeping the substrate holders immersed in the rinsing liquid for a predetermined period of time, only the on-off valve160iof the water discharge line172is opened to discharge the rinsing liquid from the substrate holder cleaning bath150through the water discharge line172.

Next, only the on-off valve160bof the second cleaning liquid supply line156is opened to supply a predetermined amount of the second cleaning liquid (5 wt % aqueous solution of sodium hydroxide) into the substrate holder cleaning bath150so that the substrate holders, each holding the dummy substrate and suspended in the substrate holder cleaning bath150, are immersed in the second cleaning liquid and cleaned with the second cleaning liquid. The metal207(mainly its Ni portion), adhering to the substrate-side sealing member66of each substrate holder, is effectively dissolved in the second cleaning liquid and is thus removed. During the cleaning of the substrate holders, if necessary, the on-off valve160eof the air supply line164may be opened to supply air into the second cleaning liquid to form air bubbles in the second cleaning liquid. After keeping the substrate holders immersed in the second cleaning liquid for a predetermined period of time, only the on-off valve160gof the second cleaning liquid discharge line168is opened to discharge the second cleaning liquid from the substrate holder cleaning bath150.

Next, only the on-off valve160dof the rinsing liquid supply line162is opened to supply a predetermined amount of the rinsing liquid (pure water) into the substrate holder cleaning bath150so that the substrate holders are immersed in the rinsing liquid, whereby the substrate holders are rinsed. After keeping the substrate holders immersed in the rinsing liquid for a predetermined period of time, only the on-off valve160iof the water discharge line172is opened to discharge the rinsing liquid from the substrate holder cleaning bath150through the water discharge line172.

Next, only the on-off valve160cof the third cleaning liquid supply line158is opened to supply a predetermined amount of the third cleaning liquid (10 wt % aqueous solution of methanesulfonic acid) into the substrate holder cleaning bath150so that the substrate holders, each holding the dummy substrate and suspended in the substrate holder cleaning bath150, are immersed in the third cleaning liquid and cleaned with the third cleaning liquid. The metal207(mainly its Sn—Ag alloy portion), adhering to the substrate-side sealing member66of each substrate holder, is effectively dissolved in the third cleaning liquid and is thus removed. During the cleaning of the substrate holders, if necessary, the on-off valve160eof the air supply line164may be opened to supply air into the third cleaning liquid to form air bubbles in the third cleaning liquid. After keeping the substrate holders immersed in the third cleaning liquid for a predetermined period of time, only the on-off valve160hof the third cleaning liquid discharge line170is opened to discharge the third cleaning liquid from the substrate holder cleaning bath150.

Next, only the on-off valve160dof the rinsing liquid supply line162is opened to supply a predetermined amount of the rinsing liquid (pure water) into the substrate holder cleaning bath150so that the substrate holders are immersed in the rinsing liquid, whereby the substrate holders18are rinsed. After keeping the substrate holders immersed in the rinsing liquid for a predetermined period of time, only the on-off valve160iof the water discharge line172is opened to discharge the rinsing liquid from the substrate holder cleaning bath150through the water discharge line172.

Next, as with the substrate holders18after cleaning in the second substrate holder cleaning bath26b, the substrate holders after cleaning are transported to the pretreatment solution water-cleaning bath32(seeFIG. 3), where the cleaning liquid adhering to the substrate holders is removed. Thereafter, the substrate holders are transported to the blow bath38(seeFIG. 3), where the substrate holders are cleaned with water and air blows the substrate holders to remove water droplets from the substrate holders. The dummy substrates are removed from the substrate holders by the substrate transport device22(seeFIG. 3), and then transported to the spin drier16(seeFIG. 3) in a sequential manner, where the dummy substrates are spin-dried (drained) by high-speed rotation of the spin drier16. The dried dummy substrates are returned to the dummy substrate cassette24(seeFIG. 3) by the substrate transport device22. The substrate holders, from which the dummy substrates have been removed, are sequentially returned to predetermined positions in the substrate holder cleaning bath150.

The substrate holder cleaning bath150of this embodiment can perform cleaning of the substrate holder with the use of different types of cleaning liquids capable of effectively dissolving and removing different types of metals adhering to the sealing member of the substrate holder, making it possible to eliminate the use of a plurality of cleaning baths for different types of cleaning liquids and thus to avoid a considerable increase in the footprint of the plating apparatus.

While the present invention has been described with reference to preferred embodiments, it is understood that the present invention is not limited to the embodiments described above, but is capable of various changes and modifications within the scope of the inventive concept as expressed herein.