1. Field of the Invention
The present invention relates to a magnetic film plating apparatus and method, and more particularly to a magnetic film plating apparatus and method which is useful for forming a magnetic film on an exposed surface of a metal layer formed on a surface of a substrate, such as a semiconductor wafer.
2. Description of the Related Art
As a technique for forming a magnetic film on a device, such as an MRAM or a magnetic head, by electroplating, a method is known, for example, which comprises immersing a substrate, which is held in a horizontal position with a surface to be plated (front surface) of the substrate facing downwardly, in a plating solution in a plating tank, and passing a plating current between the substrate and an anode disposed parallel to the substrate while forming a horizontal magnetic field around the substrate by means of electromagnets (or permanent magnets) disposed on opposite sides of the plating tank (see Japanese Patent laid-Open Publication No. H5-17898). Further, it has been proposed to use, besides a main magnet, an auxiliary magnet for correcting a main magnetic field formed by the main magnet so as to provide a magnetic field parallel to a substrate (see Japanese Patent laid-Open Publication No. S61-190091).
The applicant has proposed a plating apparatus for carrying out a sequence of process steps for plating, such as copper plating, on a surface of a substrate such as a semiconductor wafer, comprising a substrate holder for holding a substrate; a substrate attachment/detachment section for attaching and detaching the substrate to and from the substrate holder; a plating tank for carrying out plating; and a substrate holder transport apparatus for transporting the substrate holder (see Japanese Patent No. 3979847). In this plating apparatus, a substrate in a vertical position is immersed in a plating solution in the plating tank. Therefore, this plating apparatus has the advantages of relatively good escape of bubbles during plating, narrow footprint of the apparatus and good suitability for automation of the apparatus.
In the case where a magnetic film is formed by electroplating on a surface (surface to be plated) of a substrate which is held horizontally with the surface facing downwardly and immersed in a plating solution in a plating tank, however, escape of bubbles is generally poor. In addition, such a plating apparatus needs a wide footprint and automation of the apparatus is generally difficult.
In the formation of a magnetic film by electroplating, a ferromagnetic material is sometimes used for an anode. When using a ferromagnetic material for an anode and forming a magnetic film on a surface (surface to be plated) of a substrate by electroplating while forming a magnetic field around the substrate, due to the presence of the anode of ferromagnetic material, magnetic field lines will deviate from a reference direction by a certain angle, making it difficult to equalize the magnetic density in the substrate surface. Such non-uniformity of the magnetic density in the substrate surface affects uniformity of the magnetic anisotropy in the magnetic film formed on the substrate. The use of the auxiliary magnet described in the above-cited patent document is not in consideration of the influence of an anode; and therefore it is considered that when a ferromagnetic material is used for an anode, the presence of the anode (ferromagnetic material) will affect the uniformity of magnetic anisotropy in a magnetic film formed on a substrate.
The present invention has been made in view of the above situation. It is therefore an object of the present invention to provide a magnetic film plating apparatus and method which employs a dip method that allows relatively good escape of bubbles and does not require a wide footprint and which, even when a ferromagnetic material is used for an anode, can form a magnetic film on a substrate surface while minimizing the influence of the anode on the uniformity of magnetic anisotropy in the magnetic film.
In order to achieve the above object, the present invention provides a magnetic film plating apparatus comprising: a plating tank for holding therein a plating solution; an anode vertically disposed in the plating tank at a position to be immersed in the plating solution; a substrate holder for holding a substrate and positioning the substrate opposite the anode; and a magnetic field generator, disposed outside the plating tank, for generating a magnetic field around the substrate held by the substrate holder and positioned opposite the anode.
The plating apparatus employs a dip method that allows relatively good escape of bubbles and does not require a wide footprint, and can form a magnetic film on a substrate surface.
The magnetic field generator is comprised, for example, of an electromagnet disposed around the plating tank.
The magnetic field generator may be comprised of a permanent magnet disposed around the plating tank.
Preferably, a first dummy anode, having a larger size than the substrate and surrounding the circumference of the anode, is disposed on the circumference of the anode.
When a ferromagnetic material, such as nickel, is used for the anode, the first dummy anode can reduce deviation of the magnetic flux in a substrate surface from a reference direction.
The first dummy anode preferably has a rectangular shape.
The first dummy anode is at a right angle to the reference direction of the magnetic flux. Accordingly, the use of the first dummy anode of a rectangular shape can make magnetic field lines in the vicinity of a substrate closer to the reference direction.
Preferably, a second dummy anode is disposed on the opposite side of the substrate from the anode, held by the substrate holder and positioned opposite the anode.
The use of the second dummy anode can reduce inclination of magnetic field lines from the vertical direction toward the normal direction of the substrate.
The second dummy anode preferably has the same shape and size as the sum of the anode and the first dummy anode.
Preferably, the surface of the substrate held by the substrate holder, the anode, the first dummy anode and the second dummy anode are disposed parallel to each other in the plating tank.
Preferably, the substrate held by the substrate holder is disposed at the center of a space in which the magnetic field is formed by the magnetic field generator.
Preferably, a stirring paddle for stirring the plating solution in the plating tank is disposed in the plating tank.
The use of the stirring paddle can make the flow of the plating solution along the surface of the substrate more uniform over an entire substrate surface, making it possible to form a magnetic film (plated film) with a more uniform thickness over the entire substrate surface.
Preferably, an electric field regulation plate for regulating the electric field in the plating tank is disposed in the plating tank.
Preferably, a tray for preventing the plating solution from dropping downward is retractably provided under the substrate holder.
The use of the tray can prevent the plating solution, dropping off the substrate holder, from falling onto an electromagnet and the outside of the plating tank when withdrawing the substrate holder from the plating tank after plating and transporting the substrate holder.
The plating tank is preferably provided with an air bag for fixing the substrate holder in a predetermined position.
The use of the air bag enables the substrate holder to be fixed in a predetermined position without using a magnet which may distribute the magnetic field in the plating tank.
Preferably, exhaust ducts are provided at positions along the side of the magnetic field generator.
By creating flows of air flowing from the plating tank toward the exhaust ducts, and discharging a vapor evaporating from the plating solution with the flows of air, contamination of a substrate with the vapor can be prevented. An arbitrary number of exhaust ducts may be provided.
Preferably, the substrate holder is provided with a notch pin which, when the substrate is held by the substrate holder, enters a notch portion of the substrate to align the direction of the substrate with respect to the substrate holder.
When the substrate is held by the substrate holder after aligning the direction of the notch portion of the substrate with respect to the substrate holder, e.g., by an aligner, the direction of the notch portion of the substrate with respect to the substrate holder can always be made precisely constant.
The present invention also provides a magnetic film plating method comprising: vertically disposing an anode and a substrate opposite each other in a plating solution; and applying a plating voltage between the anode and the substrate while forming a magnetic field around the substrate, thereby forming a magnetic film on a surface of the substrate.
The present invention also provides a plating facility comprising: the magnetic film plating apparatus; an aligner for aligning the direction of a substrate; and a main frame in which the magnetic film plating apparatus and the aligner are housed.
The plating tank of the magnetic film plating apparatus is preferably provided in a plural number in the main frame.
Preferably, one or more of a pre-wetting tank, a pre-soaking tank, a blow tank and a rinsing tank are housed in the main frame.
This enables a series of plating process steps to be carried out successively in the same facility.
Preferably, the plating facility further comprises a substrate holder transport apparatus for transporting the substrate holder of the magnetic film plating apparatus, and the substrate held by the substrate holder is transported between the tanks.
Two substrate holders may be placed laterally slidably and parallel to each other on a substrate attachment/detachment section. This enables the use of a single opening/closing mechanism for opening and closing the two substrate holders and, in addition, can eliminate the need to laterally move the substrate transport apparatus.
According to the present invention, a dip method, which does not require a wide footprint, can be employed and, even when a ferromagnetic material is used for an anode, a magnetic film having magnetic anisotropy can be formed on a substrate surface while minimizing the influence of the anode on the uniformity of the magnetic anisotropy.
Preferred embodiments of the present invention will now be described with reference to the drawings. In the following embodiments, a magnetic film of permalloy (Ni/Fe=80/20%) is formed on a surface (surface to be plated) of a substrate, such as a semiconductor wafer. A plating solution capable of forming permalloy is used. An anode of nickel (Ni), which is a ferromagnetic material, or an insoluble anode (e.g., Ti coated with IrO2 or Ti cladded with 1-μm Pt) may be used. Besides a permalloy magnetic film, a magnetic film of cobalt or a cobalt alloy, for example, can also be formed.
In the clean space 16, there are disposed a substrate transport robot 20 for carrying in and carrying out a substrate in a substrate cassette mounted in the loading/unloading port 18, and for transporting a substrate, an aligner 22 for aligning an orientation flat or a notch of a substrate with a predetermined direction, a cleaning/drying device 24 for cleaning (rinsing) a plated substrate with a cleaning liquid, such as pure water, and rotating the substrate at a high speed to dry the substrate, and a substrate attachment/detachment section 28, as a substrate transfer section, for attaching and detaching substrates between it and two substrate holders 26 (see
The substrate transport robot 20 disposed in the clean space 16 is designed so as to hold a substrate and carry in and carry out the substrate in a horizontal state in which a front face (surface to be plated) of the substrate faces upward. The aligner 22 and the cleaning/drying device 24 are designed so as to hold and process a substrate in a horizontal state in which a front face (surface to be plated) of the substrate faces upward.
In the plating space 14, in the order from the partition plate 12, there are disposed four pair (total eight) of stocker tanks 30 for storing or temporarily storing the substrate holders 26, a pair of pre-wetting tanks 32 for enhancing a hydrophilicity of the substrate surface by immersing and wetting with pure water, a pair of pre-soaking tanks 34 for etching away an oxide film, having a large electric resistance, on a seed layer formed on the surface of the substrate with a liquid chemical, such as sulfuric acid or hydrochloric acid, a pair of blow tanks 36 for dewatering the substrate after rinsing (cleaning), a pair of rinsing tanks 38 for rinsing (cleaning) the plated substrate with pure water, and two pair (total four) of plating tanks 40. In the main frame 10, a pair of service tanks 42 for putting in and taking out the substrate holders 26 and anode holder 222 (see
In this embodiment, as shown in
Lateral to the substrate attachment/detachment section 28 and the above tanks is disposed a substrate holder transport apparatus 46 having a transport rail 44 linearly extending along the substrate attachment/detachment section 28 and the tanks, and a transporter 45 which travels on the transport rail 44 while holding two substrate holders 26. As shown in
To the base end of the arm 48 is vertically mounted a rotating shaft 51 which is rotatable by a rotation mechanism 50, and to the lower end of the rotating shaft 51 is coupled a base end of a horizontally-extending tray 52. The tray 52 opens upward, has a semicircular cross-section and, at its rotating shaft 51 side end, is provided with a drain 53 for discharging downward a plating solution collected in the tray 52. With this structure, when withdrawing the substrate holders 26 from the plating tanks 40 and transporting the substrate holders 26, a plating solution dropping from the lower ends of the substrate holders 26 is received by the tray 52 positioned right under the substrate holders 26. This can prevent the plating solution from falling, e.g., onto electromagnet 112 (magnetic field generator 114) or other devices lying outside the plating tanks 40. The tray 52 can be rotated to the retracted position, shown by the broken lines in
As described above, each substrate holder 26, together with each plating tank 40 and a magnetic field generator 114, comprised of a cylindrical electromagnet 112 disposed around the plating tank 40, constitutes a magnetic film plating apparatus 110 (see
As shown in
The movable holding member 58 has a base portion 58a and, in this embodiment, a ring-shaped support portion 58b, and is made of, for example, a vinyl chloride resin for better slippage against a below-described press ring 62. A ring-shaped sealing member (seal ring) 60 having a substantially channel-shaped transverse cross section with two lips, one being longer than the other, is mounted on a surface of the support portion 58b, which faces the fixed holding member 54, of the moveable holding member 58. The ring-shaped sealing member 60 is open toward the fixed holding member 54. A press ring 62 is rotatably supported on a surface of the moveable holding member 58 on the far side from the fixed holding member 54, and slide plates 64 are jointed to outer circumferential surfaces of the press ring 62. The press ring 62 is made of, for example, titanium that is highly resistant to corrosion in oxidizing environments and has sufficient rigidity.
Inverted L-shaped clampers 70, each having an inward protrusion, are vertically mounted on the fixed holding member 54 at circumferentially equal spaced intervals in positions laterally outward of the slide plates 64. The surfaces of the slide plates 64, and the lower surfaces of the inward protrusions of the clampers 70, which are positioned in covering relation to the surfaces of the slide plates 64, are tapered so as to be slanted oppositely to each other in the rotational direction. Projections 73, which comprise rotary pins threaded into the press ring 62, for example, are mounted on the surface of the press ring 62 respectively in a plurality of locations (e.g., four locations) along the circumferential direction of the press ring 62. The projections 73 are engaged by a rotating mechanism for rotating the press ring 62 in unison with the slide plates 64.
When the movable holding member 58 is open, the substrate W is inserted into the center of the fixed holding member 54. After the movable holding member 58 is closed about the hinge 56, the press ring 62 is turned clockwise to cause the slide plates 64 to slide into the protrusions of the clampers 70, thereby fastening and locking the fixed holding member 54 and the movable holding member 58 to each other through their tapered surfaces. By turning the press ring 62 counterclockwise, the slide plates 64 are removed from the protrusions of the L-shaped clampers 70, unlocking the fixed holding member 54 and the movable holding member 58 from each other. When the movable holding member 58 is locked, a shorter lip 60a (see
A ridge 82 is mounted centrally on and projects from the fixed holding member 54 in a ring shape matching the size of the substrate W. The ridge 82 provides a support surface 80 for abutting against the peripheral edge of the substrate W to support the substrate W thereon. The ridge 82 has a plurality of recesses defined therein at predetermined positions along the circumferential direction thereof. A plurality of (eight in the illustrated embodiment) conductors (electrical contacts) 88 are disposed respectively in the recesses 84 and connected to respective wires extending from external contacts on a below-described hand 98. The conductors 88 have their springy ends exposed on the surface of the fixed holding member 54 laterally of the substrate W when the substrate W is placed on the support surface 80 of the fixed holding member 54.
A support body (see
The movable holding member 58 is opened and closed by a cylinder (not shown) and the weight of the movable holding member 58 per se. Specifically, the fixed holding member 54 has a through-hole 54a, as shown in
In the present embodiment, the press ring 62 is rotated to lock and unlock the movable holding member 58. A locking/unlocking mechanism for locking and unlocking the movable holding member 58 is mounted on the ceiling side. The locking/unlocking mechanism has gripping members disposed in respective positions aligned with the projections 73 of the press ring 62 of the centrally positioned substrate holder 26 placed on the loading plate of the substrate attachment/detachment section 28. The locking/unlocking mechanism is arranged to rotate the press ring 62 when the gripping members are turned about the axis of the press ring 62 with the loading plate of the substrate attachment/detachment section 28 being lifted and the projections 73 being gripped by the gripping members. There is a single locking/unlocking mechanism being used, and after the locking/unlocking mechanism locks (or unlocks) one of two substrate holders 26 placed on the loading plate of the substrate attachment/detachment section 28, the loading plate of the substrate attachment/detachment section 28 is slid horizontally, and the locking/unlocking mechanism locks (or unlocks) the other substrate holder 26.
A pair of substantially T-shaped hands 98 is jointed to an end of the fixed holding member 54 of the substrate holder 26. The stocker tank 30 is designed so as to engage on an upper surface of a surrounding wall with outwardly projecting portions of the hands 98 of each substrate holder 26 to thus support the substrate holders 26 in such a state that the substrate holders 26 are suspended in a vertical direction. The hands 98 of the substrate holder 26 suspended in a vertical direction are gripped by the transporter 45 of the substrate transport apparatus 46 for transporting the substrate holder 26. The pre-wetting tank 32, the pre-soaking tank 34, the blow tank 36, the rinsing tank 38 and plating tank 40 are also designed so as to support the substrate holders 26 on surrounding walls by the hands 98 in such a state that the substrate holders 26 are suspended in a vertical direction.
In plating of a magnetic film, it is sometimes necessary to apply a magnetic field precisely in a predetermined direction with respect to a structure formed on a substrate. For this purpose, it is desired to impart to the substrate holder 26 a misalignment prevention function which, after aligning the direction of a notch portion of a substrate W with respect to the substrate holder 26 by the aligner 22, always makes the direction of the notch portion of the substrate W with respect to the substrate holder 26 precisely constant. In this embodiment, as shown in
Though the two spring members, the first spring member 100 and the second spring member 102, are used in this embodiment, it is also possible to integrate the first spring member 100 and the second spring member 102. Though it is preferred that a rod-like spring member (notch pin) be inserted into the notch portion of a substrate W when the substrate W is held by a substrate holder 26, and the rod-like spring member (notch pin) separate from the notch portion of the substrate W when the holding of the substrate W by the substrate holder 26 is released, it is also possible to allow a stationary pin to be inserted into the notch portion of a substrate without using an elastically deformable member. By thus utilizing the operation of holding the substrate W between the fixed holding member 54 and the movable holding member 58, and causing the elastic members, such as a plate spring, to deform, the misalignment prevention mechanism can be constructed with a relatively simple structure.
The plating tank 40 includes a plating tank body 186 for holding a certain amount of plating solution Q in which a substrate W, held by the substrate holder 26 with its peripheral portion watertightly sealed by the seal member 60 (see
A bottom plate 210 having therein a large number of plating solution passage holes is disposed in the bottom of the plating tank body 186, whereby the interior of the plating tank body 186 is separated into an upper substrate processing chamber 214 and a lower plating solution distribution chamber 212. A downwardly-extending shield plate 216 is mounted to the bottom plate 210.
Thus, in the plating tank 40 of this embodiment, the plating solution Q is introduced into the plating solution distribution chamber 212 of the plating tank body 186 by the actuation of the pump 202, passes through the large number of plating solution passage holes of the bottom plate 210 and flows into the substrate processing chamber 214, flows upwardly approximately parallel to the surface of the substrate W held by the substrate holder 26 and flows into the overflow tank 200. The plating tank 40 is thus constructed so that the plating solution Q can be moved approximately parallel to the surface of the substrate W by actuating the pump 202 when carrying out plating.
A disk-shaped anode 220, conforming to the shape of the substrate W, is held by an anode holder 222 and is disposed in the plating tank body 186 in a vertical position. When the plating solution Q is filled into the plating tank body 186, the anode 220 becomes immersed in the plating solution Q and faces the substrate W held by the substrate holder 26 and disposed at a predetermined position in the plating tank body 186. Also in the plating tank body 186, an electric field regulation plate 224 for regulating an electric field in the plating tank body 186 is disposed between the anode 220 and the substrate holder 26 disposed at a predetermined position in the plating tank body 186. In this embodiment, the electric field regulation plate 224 is comprised of a cylindrical portion 226 and a rectangular flange portion 228, and is made of polyvinyl chloride, which is a dielectric material. The cylindrical portion 226 has such an opening size and axial length as to sufficiently regulate the extent of the electric field. The lower end of the flange portion 228 of the electric field regulation plate 224 reaches the bottom plate 210.
In the plating tank body 186, between the electric field regulation plate 224 and the substrate W, held by the substrate holder 26 and disposed at a predetermined position in the plating tank body 186, is disposed a vertically-extending stirring paddle 232 which reciprocates parallel to the substrate W to stir the plating solution Q between the substrate W and the electric field regulation plate 224. By stirring the plating solution Q between the substrate W and the electric field regulation plate 224 by the stirring paddle 232, ions in the plating solution Q can be supplied uniformly to the surface of the substrate W.
As shown in
It is preferred that the width and the number of the slits 232a be determined such that each strip-shaped portion 232b is as narrow as possible insofar as it has the necessary rigidity so that the strip-shaped portions 232b between the slits 232a can efficiently stir the plating solution and, in addition, the plating solution can efficiently pass through the slits 232a.
In this embodiment, as shown in
As shown in
The magnetic film plating apparatus 110 is provided with a plating power source 250; the anode is connected to the anode 220 via a conducting wire, and the cathode is connected to the substrate W via a conducting wire during plating.
In this embodiment, as shown in
As shown in
To facilitate insertion of the hand 98 into the recess 120a, the width of the recess 120a is somewhat larger than the width of the hand 98. Therefore, in this embodiment, an air bag 130 is provided in one sidewall of the recess 120a of the substrate holder receiver 120. After inserting the hand 98 into the recess 120a, as shown in
In operation of the magnetic film plating apparatus 110, a predetermined amount of plating solution Q having a predetermined composition is first filled into the plating tank body 186 and allowed to circulate. The substrate holder 26 holding a substrate W is lowered to dispose the substrate W at a predetermined position in the plating tank body 186 where the substrate W is immersed in the plating solution Q and held vertically. The anode of the plating power source 250 is connected to the anode 220 and the cathode is connected to the substrate W and, at the same time, electric current is passed through the coil 118 of the electromagnet 112, thereby forming an upwardly directed magnetic field around and approximately parallel to the substrate W held by the substrate holder 26. A plated film, a magnetic film (permalloy) having magnetic anisotropy, is allowed to grow on the surface of the substrate W while stirring the plating solution Q between the electric field regulation plate 224 and the substrate W by the stirring paddle 232, as necessary, by moving the stirring paddle 232 parallel to the substrate W. By actuating the pump 202 of the circulation piping 204, as necessary, during plating, the plating solution Q is circulated while keeping the plating solution Q at a predetermined temperature by cooling or heating it. After a predetermined time has elapsed from the start of plating, the anode 220 and the substrate W are disconnected from the plating power source 250, and the supply of electric current to the coil 118 of the electromagnet 112 and the reciprocation of the stirring paddle 232 are stopped, thereby terminating plating.
A sequence of process steps for plating of a magnetic film by the thus-constructed plating facility of this embodiment will now be described. First, substrates W having a surface seed layer as a feeding layer are placed with their front surfaces (surfaces to be plated) facing upwardly in a substrate cassette, and the substrate cassette is mounted in the loading/unloading port 18. One substrate is taken by the substrate transport robot 20 out of the cassette mounted in the loading/unloading port 18, and the substrate is place on the aligner 22 to align the direction of a notch portion or an orientation flat. After the alignment, the substrate is transported to the substrate attachment/detachment section 28 by the substrate transport robot 20.
In the substrate attachment/detachment section 28, two substrate holders 26 housed in the stocker tanks 30 are simultaneously gripped by the substrate holder holding section 49 of the transporter 45 of the substrate transport apparatus 46 and the arm 48 is raised. The substrate holders 26 are then transported to the substrate attachment/detachment section 28, where the arm 48 is rotated 90 degrees to bring the substrate holders 26 into a horizontal position. Thereafter, the arm 48 is lowered to simultaneously place the two substrate holders 26 on the loading plate of the substrate attachment/detachment section 28, and then the cylinder is actuated to open the movable holding member 58 of the substrate holder 26.
In this state, the substrate, which has been transported by the substrate transport robot 20, is inserted into the substrate holder 26 positioned on the center side, and the cylinder is reversely actuated to close the movable holding member 58, and then the movable holding member 58 is locked by the locking/unlocking mechanism. Misalignment of the direction of the notch portion of the substrate W with respect to the substrate holder 26 upon this operation can be prevented by the first spring member 100 and the second spring member 102, as shown in
Each substrate is thus fixed in each substrate holder 26 with its front surface (surface to be plated) exposed in the opening of the substrate holder 26 and its periphery sealed with the seal member 60 to prevent intrusion of a plating solution thereinto so as to allow electrical connection within the sealed portion, not in contact with the plating solution, with the plurality of electrical contacts 92. The wire 128 from the conductors (electrical contacts) 88 is connected to the hand 98 of the substrate holder 26. Therefore, electricity can be fed to the seed layer of the substrate by electrically connecting the contact terminals 124, 126.
Next, the two substrate holders 26 with the substrates attached thereto are simultaneously gripped by the substrate holder holding section 49 of the transporter 45 of the substrate transport apparatus 46 and the arm 48 is raised. The substrate holders 26 are then transported to the stocker tanks 30, where the arm 48 is rotated 90 degrees to bring the substrate holders 26 into a vertical position. Thereafter, the arm 48 is lowered to simultaneously suspend the two substrate holders 26 in the stocker tanks 30 for temporary storage of the substrate holders 26. The above operations are repeated sequentially to sequentially attach substrates to substrate holders 26, which have been housed in the stocker tank 30, and sequentially suspend the substrate holders 26 with the substrates attached in predetermined positions in the stocker tank 30 for their temporary storage.
The two substrate holders 26 with the substrates attached thereto, which have been temporarily stored in the stocker tanks 30, are simultaneously gripped by the substrate holder holding section 49 of the transporter 45 of the substrate transport apparatus 46 and the arm 48 is raised. The substrate holders 26 are then transported to the pre-wetting tanks 32, where the arm 48 is lowered to immerse the substrate holders 26, e.g., in pure water held in the pre-wetting tanks 32, thereby wetting the surfaces of the substrates to enhance the hydrophilic properties. It is, of course, possible to use any aqueous liquid other than pure water insofar as the liquid can wet the surface of the substrate and replace air in holes with the liquid, thereby enhancing the hydrophilic properties of the substrate surface.
A substrate holder 26 in which is housed a substrate whose electrical contact condition has been determined to be poor by a sensor, provided in the substrate holder 26, for sensing contact between the substrate and the electrical contacts, is kept temporarily stored in the stocker tank 30. This enables continuing plating operations without a stop of the apparatus despite the poor contact between the electrical contacts and the substrate attached to the substrate holder 26. The substrate of poor electrical contact is not subjected to plating. In this case, after substrates are returned to the substrate cassette, the unplated substrate is removed from the substrate cassette.
Next, in the same manner as described above, the two substrate holders 26 with the substrates attached thereto are transported to the pre-soaking tanks 34, and the substrates are immersed in a liquid chemical, such as sulfuric acid or hydrochloric acid, held in the pre-soaking tanks 34 to etch away an oxide film, having a high electrical resistance, from the surface of the seed layer, thereby exposing a clean metal surface. Thereafter, in the same manner as described above, the substrate holders 26 with the substrates attached thereto are transported to the rinsing tanks 38, and the substrate surfaces are rinsed (cleaned) with pure water held in the rinsing tanks 38.
In the same manner as described above, the two substrate holders 26 with the substrates attached thereto are transported after rinsing to the plating tanks 40 filled with a plating solution, and are each suspended and held at a predetermined position in each plating tank 40. When the substrate is held in the plating tank 40, as shown in
After the completion of plating, the application of the plating voltage, the supply of the plating solution, the supply of electric current to the coil 118 of the electromagnet 112 and the reciprocation of the stirring paddle 232 are stopped. Thereafter, the two substrate holders 26 with the substrates after plating attached thereto are simultaneously gripped by the substrate holder holding section 49 of the transporter 45 of the substrate transport apparatus 46, and the arm 48 is raised to withdraw the substrates from the plating solution Q in the plating tanks 40. When thus withdrawing the substrate holders 26 from the plating solution Q in the plating tanks 40, the tray 52 shown in
After returning the tray 52 to the retracted position, the substrate holders 26 are lowered to immerse the substrates in pure water held in the rinsing tanks 38, thereby rinsing (cleaning) the surfaces of the substrates with pure water. Thereafter, the substrate holders 26 with the substrates attached thereto are transported to the blow tanks 36 in the same manner as described above, where water droplets are removed from the substrate holders 26 by air blowing. Thereafter, the substrate holders 26 with the substrates attached thereto are returned to the stocker tanks 30 and are each suspended and held at a predetermined position in the stocker tank 30 in the same manner as described above.
The two substrate holders 26 with the substrates attached thereto, which have been returned to the stocker tanks 30 after plating, are simultaneously gripped by transporter 45 of the substrate transport apparatus 46 and, in the same manner as described above, are placed on the loading plate of the substrate attachment/detachment section 28. The substrate holder 26 in which is housed the substrate whose electrical contact condition has been determined to be poor by the sensor, provided in the substrate holder 26, for sensing contact between the substrate and the electrical contacts, and which has been kept temporarily stored in the stocker tank 30, is also transported and placed on the loading plate.
The movable holding member 58 of the substrate holder 26 positioned on the center side is unlocked by the locking/unlocking mechanism, and the cylinder is actuated to open the movable holding member 58. The substrate after plating is then taken by the substrate transport robot 20 out of the substrate holder 26, and transported to the cleaning/drying device 24, where the substrate is cleaned and then spin-dried by high-speed rotation of the cleaning/drying device 24. The dried substrate is returned by the substrate transport robot 20 to the substrate cassette of the loading/unloading port 18.
After, or in parallel with, returning the substrate, which has been taken out of the one substrate holder 26, to the substrate cassette, the loading plate of the substrate attachment/detachment section 28 is slid laterally and the other substrate is taken out of the other substrate holder 26. The substrate is then treated in the same manner, and the spin-dried substrate is returned to the substrate cassette.
After returning the loading plate of the substrate attachment/detachment section 28 to the original position, the two substrate holders 26, from which the substrates have been taken out, are simultaneously gripped by the substrate holder holding section 49 of the transporter 45 of the substrate transport apparatus 46 and, in the same manner as described above, are returned to the predetermined positions in the stocker tanks 30. Thereafter, two substrate holders 26, which have been returned to the stocker tanks 30, are simultaneously gripped by the substrate holder holding section 49 of the transporter 45 of the substrate transport apparatus 46 and, in the same manner as described above, are placed on the loading plate of the substrate attachment/detachment section 28. Thereafter, the same operations as described above are repeated.
As described hereinabove, according to the plating facility of this embodiment, by setting a substrate cassette, in which substrates are housed, in the loading/unloading port 18 and activating the apparatuses, electroplating using a dip method can be carried out in a fully automatic manner to form a magnetic film (plated film) of, e.g., permalloy, having magnetic anisotropy, on a surface of a substrate.
By arranging a plurality of plating tanks 40, each individually surrounded by the magnetic field generator 114 comprised of the electromagnet 112, as in this embodiment, the formation of a magnetic field parallel to a substrate can be facilitated.
In this embodiment, the magnetic field generator 114 is comprised of the cylindrical electromagnet 112 surrounding the circumference of the plating tank 40. It is also possible to use a magnetic field generator 114a, as shown in
When a common plating solution is used, it is possible to use a plating tank 40a including a plurality of plating tank bodies 186 disposed inside one overflow tank 200a, as shown in
Though a magnetic field generator comprised of an electromagnet, which can adjust a magnetic force, e.g., in the range of 0 to 500 G (0 to 0.05 T), is used in the above embodiments, it is possible to use a magnetic field generator comprised of a permanent magnet. When a magnetic field generator comprised of a permanent magnet is used, the permanent magnet is disposed such that the N pole and the S pole line up vertically.
The plating tank 302 includes a plating tank body 308 for holding therein a certain amount of plating solution Q in which a substrate W, held by the substrate holder 26 with its peripheral portion watertightly sealed by the seal member 60 (see
A disk-shaped anode 318, conforming to the shape of the substrate W, and a first dummy anode 320 surrounding the circumference of the anode 318 are held by a first anode holder 322 and disposed in a vertical position in the plating tank body 308. When the plating solution Q is filled into the plating tank body 308, the anode 318 and the first dummy anode 320 become immersed in the plating solution Q and face the substrate W held by the substrate holder 26 and disposed at a predetermined position in the plating tank body 308. Nickel (Ni), which is a ferromagnetic material, is used for the anode 318. Instead of the nickel anode, it is also possible to use an insoluble anode (e.g., Ti coated with IrO2 or Ti cladded with 1-μm Pt).
In the plating tank body 308, between the anode 318 and the substrate W, held by the substrate holder 26 and disposed at a predetermined position in the plating tank body 308, is disposed a vertically-extending stirring paddle 232 having the same construction as described above, which reciprocates parallel to the substrate W to stir the plating solution Q between the substrate W and the anode 318. By stirring the plating solution Q between the substrate W and the anode 318 by the stirring paddle 232, ions in the plating solution Q can be supplied uniformly to the surface of the substrate W. As with the above-described embodiment, an electric field regulation plate may be disposed between the stirring paddle 232 and the anode 318.
The magnetic field generator 306 comprised of the electromagnet 304 is disposed outside the plating tank 302. The electromagnet 304 comprises a cylindrical yoke 330 and a coil 332 extending circumferentially on the inner circumferential surface of the yoke 330. The magnetic field generator 306 can form a vertical magnetic field parallel to and in the vicinity of the substrate Win the plating tank 302, enabling the formation of a magnetic film, having magnetic anisotropy, on the substrate surface by electroplating. In this embodiment, the coil 332 is divided into an upper coil 332a, a middle coil 332b and a lower coil 332c. Bypassing independent electric currents through the respective coils 332a, 332b and 332c, vertical magnetic fields of different strengths can be formed around vertically upper, middle and lower portions of the substrate W.
In this embodiment, a desired magnetic field can be formed by controlling respective electric currents applied to the coils 332a, 332b and 332c. For example, the magnetic field can be adjusted by, for example, changing the current applied to the middle coil 332b while keeping the currents applied to the upper coil 332a and the lower coil 332c constant. Though the three coils are used in this embodiment, any number of coils may be selected depending on the intended magnetic field, the size of the substrate, etc.
By disposing the coil 332 inside the yoke 330, leakage of magnetic field to the outside of the plating tank 302 can be suppressed. This enables a plurality of plating tanks 40 to be installed in adjacent positions. By making the vertical size of the electromagnet 304 used as the magnetic field generator 306 sufficiently larger than the size of the plating tank 302 and the size of the substrate W, a stable magnetic field can be formed around the substrate W in the plating tank 302. As with the above-described embodiment, the electromagnet 332 comprised of the yoke 330 and the coil 332 is coated with a resin (not shown) resistant to a plating solution so that the electromagnet 304 will not be damaged if the plating solution splatters and adheres to the electromagnet 304.
As shown in
In this embodiment, a second dummy electrode 336, having the same size as or similar size to the size of the sum of the anode 318 and the first dummy anode 320, held by a second anode holder 336, is disposed on the opposite side of the substrate W from the anode 318 and at the same distance from the substrate W as the distance of the anode 318 from the substrate W. Similarly to the above-described first dummy electrode 320, the second dummy anode 336 comprises an anode material, for example nickel, which is entirely coated with a resin to prevent deposition thereon from a plating solution.
In this embodiment, in order to form a vertical magnetic field parallel to the substrate W, the first dummy anode 318 and the second dummy anode 334 are disposed parallel to the substrate W and the anode 318. If they are not parallel to each other, the direction of the magnetic field is unlikely to be uniform in the substrate surface.
When a ferromagnetic material is used for the anode 318 and only the anode 318 is installed opposite the substrate W, magnetic field lines in the surface of the substrate W are attracted toward the anode 318. Accordingly, the magnetic flux density in the surface of the substrate W decreases and variation in the magnetic flux density in the substrate surface becomes larger, resulting in increased deviation of the direction of the magnetic field lines from the reference direction (vertical direction). By disposing the substrate W at the center of the electromagnet 304 and between the anode 318 and the second dummy anode 334, inclination of the magnetic field lines from the vertical direction toward the normal direction of the substrate W can be reduced.
A region, in which magnetic field lines are curved, can be shifted away from the substrate W and the direction of magnetic field lines in the vicinity of the substrate W can be made closer to the reference direction by using the first dummy anode 320 having a larger size. The first dummy anode 320 is at a right angle to the reference direction of the magnetic flux. Accordingly, the use of the first dummy anode 320 in a rectangular shape, as compared to a circular shape, can make magnetic field lines in the vicinity of the substrate closer to the reference direction.
For example, when a substrate W having a diameter of 300 mm is used, an anode 318 whose diameter is somewhat smaller than 300 mm is used. The circumference of the anode 318 is surrounded by a square first dummy anode 320 whose each side has a length of, e.g., 390 mm. On the opposite side of the substrate from the first dummy anode 320 is installed a second dummy anode 334, having the same square shape as the first dummy anode 320, such that the distance between it and the substrate is equal to the distance between the anode 318/the first dummy anode 320 and the substrate. The dummy anodes 320, 334 may not be of a square shape. The thicknesses of the anode 318 and the dummy anodes 320, 334 are equal. The smaller their thickness is, the lower is their effect of attracting magnetic field lines. Therefore, their aspect ratio (diameter or length of each side/thickness) is preferably not less than 45.
Though the anode 318 surrounded by the first dummy anode 320 and the second dummy anode 336 are disposed opposite each other with the substrate W interposed therebetween in this embodiment, it is also possible to dispose only the anode 318, surrounded by the first dummy anode 320, opposite the substrate W without providing the second dummy anode 336. This can also reduce deviation of the magnetic flux in the substrate surface from the reference direction.
When designing the direction of a substrate, the direction of a magnetic field and the direction of the flow of a plating solution in a plating apparatus that generates a magnetic field parallel to a substrate, the following three methods, as shown in
The degree of freedom of the direction of a substrate will now be compared between the three methods. If the angle of a substrate around the X-axis deviates in the A method, the substrate will become non-parallel to the magnetic field. If the angle of the substrate around the Z-axis deviates, the direction of a structure formed on the substrate will deviate with respect to the direction of the magnetic field. On the other hand, even when the angle of the substrate around the Y-axis deviates to some degree, the magnetic field remains parallel to the flow of the plating solution. In view of the fact that it basically suffices if the substrate keeps parallel to an anode, it can be said that the direction of the substrate around the Y-axis has some degree of freedom. With reference to the method B, the direction of a substrate around the Y-axis and the direction around the Z-axis need to be set precisely for the same reasons. The substrate remains parallel to a magnetic field if the angle of the substrate around the X-axis deviates. The substrate, however, becomes non-parallel to the flow of plating solution, which can affect the in-plane uniformity of a plated film. With reference to the method C, the direction of a substrate around the X-axis and the direction around the Z-axis need to be set precisely for the above reasons. If the angle of the substrate around the Y-axis deviates, a plating solution will not hit the substrate uniformly, which may affect the in-plane uniformity of a plated film. In summary, the method B and the method C thus need three-axis adjustment, whereas the method A, which is employed by the magnetic film plating apparatus 110 shown in
As shown in
While the strength of a magnetic field cannot be adjusted when a permanent magnet is used as a magnetic field generator, the use of the electromagnet 304 can easily control the strength of a magnetic field. In this embodiment, the magnetic force can be controlled, e.g., in the range of 0 to 500 G (0 to 0.05 T). If necessary, the electromagnet 304 may be provided with a cooling mechanism.
In this embodiment, as shown in
In this embodiment, a plurality of exhaust ducts 340, each penetrating an upper portion of the yoke 330 at a position slightly below the upper coil 332a and reaching an upper position in the plating tank 302, are provided. By creating flows of air flowing from the plating tank 302 toward the exhaust ducts 340, and discharging a vapor evaporating from the plating solution with the flows of air to the outside of the yoke 330, contamination of a substrate with the vapor can be prevented. An arbitrary number of exhaust ducts may be provided. The air inlets of the exhaust ducts 340 are provided at upper positions in the plating tank 302 at which the inlets do not interfere with movements of the substrate holder 26, the stirring paddle 232 (see
In operation of the magnetic film plating apparatus shown in
As described above, in the magnetic film plating apparatus shown in
While the present invention has been described with reference to the embodiments thereof, it will be understood by those skilled in the art that the present invention is not limited to the particular embodiments described above, but it is intended to cover modifications within the inventive concept.
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