Patent Grant
7393439
The present invention is directed toward microfeature workpiece processing tools having registration systems for locating transport devices and reactors, including reactors having multiple electrodes and/or enclosed reciprocating paddles.
Microdevices are manufactured by depositing and working several layers of materials on a single substrate to produce a large number of individual devices. For example, layers of photoresist, conductive materials, and dielectric materials are deposited, patterned, developed, etched, planarized, and otherwise manipulated to form features in and/or on a substrate. The features are arranged to form integrated circuits, micro-fluidic systems, and other structures.
Wet chemical processes are commonly used to form features on microfeature workpieces. Wet chemical processes are generally performed in wet chemical processing tools that have a plurality of individual processing chambers for cleaning, etching, electrochemically depositing materials, or performing combinations of these processes. Each chamber typically includes a vessel in which wet processing fluids are received, and a workpiece support (e.g., a lift-rotate unit) that holds the workpiece in the vessel during processing. A robot moves the workpiece into and out of the chambers.
One concern with integrated wet chemical processing tools is that the processing chambers must be maintained and/or repaired periodically. In electrochemical deposition chambers, for example, consumable electrodes degrade over time because the reaction between the electrodes and the electrolytic solution decomposes the electrodes. The shapes of the consumable electrodes accordingly change, causing variations in the electrical field. As a result, consumable electrodes must be replaced periodically to maintain the desired deposition parameters across the workpiece. The electrical contacts that contact the workpiece also may need to be cleaned or replaced periodically. To maintain or repair electrochemical deposition chambers, they are typically removed from the tool and replaced with an extra chamber.
One problem with repairing or maintaining existing wet chemical processing chambers is that the tool must be taken offline for an extended period of time to remove and replace the processing chamber. When the processing chamber is removed from the tool, a pre-maintained processing chamber is mounted in its place. The robot and the lift-rotate unit are then recalibrated to operate with the new processing chamber. Recalibrating the robot and the lift-rotate unit is a time-consuming process that increases the downtime for repairing or maintaining processing chambers. As a result, when only one processing chamber of the tool does not meet specifications, it is often more efficient to continue operating the tool without stopping to repair the one processing chamber until more processing chambers do not meet the performance specifications. The loss of throughput of a single processing chamber, therefore, is not as severe as the loss of throughput caused by taking the tool offline to repair or maintain a single one of the processing chambers.
The practice of operating the tool until at least two processing chambers do not meet specifications severely impacts the throughput of the tool. For example, if the tool is not repaired or maintained until at least two or three processing chambers are out of specification, then the tool operates at only a fraction of its full capacity for a period of time before it is taken offline for maintenance. This increases the operating costs of the tool because the throughput not only suffers while the tool is offline to replace the wet processing chambers and recalibrate the robot, but the throughput is also reduced while the tool is online because it operates at only a fraction of its full capacity. Moreover, as the feature sizes of the processed workpiece decrease, the electrochemical deposition chambers must consistently meet much higher performance specifications. This causes the processing chambers to fall out of specification sooner, which results in shutting down the tool more frequently. Therefore, the downtime associated with repairing and/or maintaining electrochemical deposition chambers and other types of wet chemical processing chambers is significantly increasing the cost of operating wet chemical processing tools.
The electrochemical deposition chambers housed in the tool may also suffer from several drawbacks. For example, during electrolytic processing in these chambers, a diffusion layer develops at the surface of the workpiece in contact with an electrolytic liquid. The concentration of the material applied to or removed from the workpiece varies over the thickness of the diffusion layer. In many cases, it is desirable to reduce the thickness of the diffusion layer so as to allow an increase in the speed with which material is added to or removed from the workpiece. In other cases, it is desirable to otherwise control the material transfer at the surface of the workpiece, for example, to control the composition of an alloy deposited on the surface, or to more uniformly deposit materials in surface recesses having different aspect ratios.
One approach to reducing the diffusion layer thickness is to increase the flow velocity of the electrolyte at the surface of the workpiece. For example, some vessels include paddles that translate or rotate adjacent to the workpiece to create a high speed, agitated flow at the surface of the workpiece. In one particular arrangement, the workpiece is spaced apart from an anode by a first distance along a first axis (generally normal to the surface of the workpiece) during processing. A paddle having a height of about 25% of the first distance along the first axis oscillates between the workpiece in the anode along a second axis transverse to the first axis. In other arrangements, the paddle rotates relative to the workpiece. In still further arrangements, fluid jets are directed at the workpiece to agitate the flow at the workpiece surface.
The foregoing arrangements suffer from several drawbacks. For example, it is often difficult even with one or more paddles or fluid jets, to achieve the flow velocities necessary to significantly reduce the diffusion layer thickness at the surface of the workpiece. Furthermore, when a paddle is used to agitate the flow adjacent to the microfeature workpiece, it can create “shadows” in the electrical field within the electrolyte, causing undesirable nonuniformities in the deposition or removal of material from the microfeature workpiece. Still further, a potential drawback associated with rotating paddles is that they may be unable to accurately control radial variations in the material application/removal process, because the speed of the paddle relative to the workpiece varies as a function of the radius and has a singularity at the center of the workpiece.
The reactors in which such paddles are positioned may also suffer from several drawbacks. For example, the electrode in the reactor may not apply or remove material from the workpiece in a spatially uniform manner, causing some areas of the workpiece to gain or lose material at a greater rate than others. Existing devices are also not configured to transfer material to and/or from different types of workpieces without requiring lengthy, unproductive time intervals between processing periods, during which the devices must be reconfigured (for example, by moving the electrode and/or a shield to adjust the electric field within the electrolyte). Another drawback is that the paddles can disturb the uniformity of the electric field created by the electrode, which further affects the uniformity with which material is applied to or removed from the workpiece. Still another drawback with the foregoing arrangements is that the vessel may also include a magnet positioned proximate to the workpiece to control the magnetic orientation of material applied to the workpiece. When the electrode is removed from the vessel for servicing or replacement, it has been difficult to do so without interfering with and/or damaging the magnet.
The present invention is a tool that includes a processing chamber having a paddle device, a transport system for moving workpieces to and from the processing chamber, and a registration system for locating the processing chamber and the transport system relative to each other. The tool includes a mounting module having positioning elements and attachment elements for engaging the chamber and the transport system. The positioning elements maintain their relative positions so that the transport system does not need to be recalibrated when the processing chamber is removed and replaced with another processing chamber.
In a particularly useful embodiment of the tool, the mounting module includes a deck that has a rigid outer member, a rigid interior member, and bracing between the outer member and the interior member. The processing chamber is then attached to the deck. The module further includes a platform that has positioning elements for locating the transport mechanism.
In further useful embodiments, the paddle device in the processing chamber is positioned within a paddle chamber, with tight clearances around the paddle device to increase the fluid agitation, and therefore enhance mass transfer effects at the surface of the workpiece. The paddle device can include multiple paddles and can reciprocate through a stroke that changes position over time to reduce the likelihood for electrically shadowing the workpiece. Multiple electrodes (e.g., including a thieving electrode) provide spatial and temporal control over the current density at the surface of the workpiece. An electric field control element can be positioned between electrodes of the chamber and the process location to circumferentially vary the electric current density in the processing fluid at different parts of the process location, thereby counteracting potential three-dimensional effects created by the paddles as they reciprocate relative to the workpiece.
As used herein, the terms “microfeature workpiece” or “workpiece” refer to substrates on and/or in which microelectronic devices are integrally formed. Typical microdevices include microelectronic circuits or components, thin-film recording heads, data storage elements, microfluidic devices, and other products. Micromachines or micromechanical devices are included within this definition because they are manufactured using much of the same technology that is used in the fabrication of integrated circuits. The substrates can be semiconductive pieces (e.g., doped silicon wafers or gallium arsenide wafers), nonconductive pieces (e.g., various ceramic substrates), or conductive pieces. In some cases, the workpieces are generally round and in other cases, the workpieces have other shapes, including rectilinear shapes.
Several embodiments of integrated tools for wet chemical processing of microfeature workpieces are described in the context of depositing metals or electrophoretic resist in or on structures of a workpiece. The integrated tools in accordance with the invention, however, can also be used in etching, rinsing or other types of wet chemical processes in the fabrication of microfeatures in and/or on semiconductor substrates or other types of workpieces. Several examples of tools and chambers in accordance with the invention are set forth in
A. Embodiments of Integrated Tools with Mounting Modules
The frame 162 has a plurality of posts 163 and cross-bars 161 that are welded together in a manner known in the art. A plurality of outer panels and doors (not shown in
The mounting module 160 is a rigid, stable structure that maintains the relative positions between the wet chemical processing chambers 110, the workpiece supports 113, and the transport system 105. One aspect of the mounting module 160 is that it is much more rigid and has a significantly greater structural integrity compared to the frame 162 so that the relative positions between the wet chemical processing chambers 110, the workpiece supports 113, and the transport system 105 do not change over time. Another aspect of the mounting module 160 is that it includes a dimensionally stable deck 164 with positioning elements at precise locations for positioning the processing chambers 110 and the workpiece supports 113 at known locations on the deck 164. In one embodiment (not shown), the transport system 105 is mounted directly to the deck 164. In an arrangement shown in
The tool 100 is particularly suitable for applications that have demanding specifications which require frequent maintenance of the wet chemical processing chambers 110, the workpiece support 113, or the transport system 105. A wet chemical processing chamber 110 can be repaired or maintained by simply detaching the chamber from the processing deck 164 and replacing the chamber 110 with an interchangeable chamber having mounting hardware configured to interface with the positioning elements on the deck 164. Because the mounting module 160 is dimensionally stable and the mounting hardware of the replacement processing chamber 110 interfaces with the deck 164, the chambers 110 can be interchanged on the deck 164 without having to recalibrate the transport system 105. This is expected to significantly reduce the downtime associated with repairing or maintaining the processing chambers 110 so that the tool 100 can maintain a high throughput in applications that have stringent performance specifications.
B. Embodiments of Dimensionally Stable Mounting Modules
The deck 164 further includes a plurality of positioning elements 168 and attachment elements 169 arranged in a precise pattern across the first panel 166a. The positioning elements 168 include holes machined in the first panel 166a at precise locations, and/or dowels or pins received in the holes. The dowels are also configured to interface with the wet chemical processing chambers 110 (
The mounting module 160 also includes exterior side plates 170a along longitudinal outer edges of the deck 164, interior side plates 170b along longitudinal inner edges of the deck 164, and endplates 170c attached to the ends of the deck 164. The transport platform 165 is attached to the interior side plates 170b and the end plates 170c. The transport platform 165 includes track positioning elements 168c for accurately positioning the track 104 (
The panels and bracing of the deck 164 can be made from stainless steel, other metal alloys, solid cast materials, or fiber-reinforced composites. For example, the panels and plates can be made from Nitronic 50 stainless steel, Hastelloy 625 steel alloys, or a solid cast epoxy filled with mica. The fiber-reinforced composites can include a carbon-fiber or Kevlar® mesh in a hardened resin. The material for the panels 166a and 166b should be highly rigid and compatible with the chemicals used in the wet chemical processes. Stainless steel is well-suited for many applications because it is strong but not affected by many of the electrolytic solutions or cleaning solutions used in wet chemical processes. In one embodiment, the panels and plates 166a-b and 170a-c are 0.125 to 0.375 inch thick stainless steel, and more specifically they can be 0.250 inch thick stainless steel. The panels and plates, however, can have different thicknesses in other embodiments.
The bracing 171 can also be stainless steel, fiber-reinforced composite materials, other metal alloys, and/or solid cast materials. In one embodiment, the bracing can be 0.5 to 2.0 inch wide stainless steel joists, and more specifically 1.0 inch wide by 2.0 inches tall stainless steel joists. In other embodiments the bracing 171 can be a honey-comb core or other structures made from metal (e.g., stainless steel, aluminum, titanium, etc.), polymers, fiber glass or other materials.
The mounting module 160 is constructed by assembling the sections of the deck 164, and then welding or otherwise adhering the end plates 170c to the sections of the deck 164. The components of the deck 164 are generally secured together by the throughbolts 172 without welds. The outer side plates 170a and the interior side plates 170b are attached to the deck 164 and the end plates 170c using welds and/or fasteners. The platform 165 is then securely attached to the end plates 170c, and the interior side plates 170b. The order in which the mounting module 160 is assembled can be varied and is not limited to the procedure explained above.
Returning to
C. Embodiments of Reactors Having Multiple Electrodes and Enclosed Paddle Devices
A paddle chamber 130 is positioned proximate to the virtual electrode location V. The paddle chamber 130 includes a paddle device 140 having paddles 141 that reciprocate back and forth relative to a central position 180, as indicated by arrow R. The paddle chamber 130 also has an aperture 131 defining a process location P. A microfeature workpiece W is supported at the process location P by the workpiece support 113, so that a downwardly facing process surface 109 of the workpiece W is in contact with the processing fluid. The paddles 141 agitate the processing fluid at the process surface 109 of the workpiece W. At the same time, the relative value of the electrical potential (e.g., the polarity) applied to each of the electrodes 121, and/or the current flowing through each of the electrodes 121, may be selected to control a manner in which material is added to or removed from the workpiece W. Accordingly, the paddles 141 can enhance the mass transfer process at the process surface 109, while the electrodes 121 provide for a controlled electric field at the process surface 109. Alternatively, the electrodes 121 may be eliminated when the reactor 110 is used to perform processes (such as electroless deposition processes) that still benefit from enhanced mass transfer effects at the process surface 109.
The reactor 110 includes a generally horseshoe-shaped magnet 195 disposed around the outer vessel 111. The magnet 195 includes a permanent magnet and/or an electromagnet positioned to orient molecules of material applied to the workpiece W in a particular direction. For example, such an arrangement is used to apply permalloy and/or other magnetically directional materials to the workpiece W. In other embodiments, the magnet 195 may be eliminated.
The workpiece support 113, positioned above the magnet 195, rotates between a face up position (to load and unload the microfeature workpiece W) and a face down position (for processing). When the workpiece W is in the face down position, the workpiece support 113 descends to bring the workpiece W into contact with the processing fluid at the process location P. The workpiece support 113 can also spin the workpiece W about an axis generally normal to the downwardly facing process surface 109. The workpiece support 113 spins the workpiece W to a selected orientation prior to processing, for example, when the process is sensitive to the orientation of the workpiece W, including during deposition of magnetically directional materials. The workpiece support 113 ascends after processing and then inverts to unload the workpiece W from the reactor 110. The workpiece support 113 may also spin the workpiece W during processing (e.g., during other types of material application and/or removal processes, and/or during rinsing), in addition to or in lieu of orienting the workpiece W prior to processing. Alternatively, the workpiece support 113 may not rotate at all, e.g., when spinning before, during or after processing is not beneficial to the performed process. The workpiece support 113 also includes a workpiece contact 115 (e.g., a ring contact) that supplies electrical current to the front surface or back surface of the workpiece W. A seal 114 extends around the workpiece contact 115 to protect it from exposure to the processing fluid. In another embodiment, the seal 114 can be eliminated.
The paddle chamber 730 includes a base 733, and a top 734 having an aperture 731 at the process location P. The paddle chamber 730 houses a paddle device 740 having multiple paddles 741 that reciprocate back and forth beneath the workpiece W (shown in phantom lines in
Processing fluid enters the reactor 710 through an inlet 716. Fluid proceeding through the inlet 716 fills the lower portion 719a and the upper portion 719b, and can enter the paddle chamber 730 through a permeable portion 733a of the base 733, and through gaps in the base 733. Some of the processing fluid exits the reactor 710 through first and second flow collectors, 717a, 717b. Additional processing fluid enters the paddle chamber 730 directly from an entrance port 716a and proceeds through a gap in a first wall 732a, laterally across the paddle chamber 730 to a gap in a second wall 732b. At least some of the processing fluid within the paddle chamber 730 rises above the process location P and exits through drain ports 797. Further details of the flow into and through the paddle chamber 730, and further details of the paddle device 740 are described below in Section F and are included in pending U.S. patent application Ser. No. 10/734,098, entitled “Paddles and Enclosures for Enhancing Mass Transfer During Processing of Microfeature Workpieces,” incorporated herein in its entirety by reference and filed concurrently herewith.
The reactor 710 is mounted to a rigid deck 764 in a manner generally similar to that described above with reference to
One feature of the arrangement shown in
The electrodes 721a-721d are coupled to a power supply 828 and a controller 829. The power supply 828 and the controller 829 together control the electrical potential and current applied to each of the electrodes 721a-721d, and the workpiece W. Accordingly, an operator can control the rate at which material is applied to and/or removed from the workpiece W in a spatially and/or temporally varying manner. In particular, the operator can select the outermost electrode 721d to operate as a current thief. Accordingly, during a deposition process, the outermost electrode 721d attracts ions that would otherwise be attracted to the workpiece W. This can counteract the terminal effect, e.g., the tendency for the workpiece W to plate more rapidly at its periphery than at its center when the workpiece contact 115 (
One advantage of the foregoing arrangement is that the multiple electrodes provide the operator with increased control over the rate and manner with which material is applied to or removed from the workpiece W. Another advantage is that the operator can account for differences between consecutively processed workpieces or workpiece batches by adjusting the current and/or electric potential applied to each electrode, rather than physically adjusting parameters of the reactor 710. Further details of multiple electrode arrangements and arrangements for controlling the electrodes are included in the following pending U.S. application Ser. Nos: 09/804,697, entitled “System for Electrochemically Processing a Workpiece,” filed Mar. 2, 2001; 60/476,891, entitled “Electrochemical Deposition Chambers for Depositing Materials Onto Microfeature Workpieces,” filed Jun. 6, 2003; 10/158,220, entitled “Methods and Systems for Controlling Current in Electrochemical Processing of Microelectronic Workpieces,” filed May 29, 2002; and 10/426,029, entitled, “Method and Apparatus for Controlling Vessel Characteristics, Including Shape and Thieving Current for Processing Microelectronic Workpieces,” filed Apr. 28, 2003, all incorporated herein in their entireties by reference.
When the outermost electrode 721d operates as a current thief, it is desirable to maintain electrical isolation between the outermost electrode 721d on the one hand and the innermost electrodes 721a-721c on the other. Accordingly, the reactor 710 includes a first return flow collector 717a and a second return flow collector 717b. The first return flow collector 717a collects flow from the innermost three electrode compartments 822a-822c, and the second return flow collector 717b collects processing fluid from the outermost electrode compartment 822d to maintain electrical isolation for the outermost electrode 721d. By draining the processing fluid downwardly toward the electrodes 721, this arrangement can also reduce the likelihood for particulates (e.g., flakes from consumable electrodes) to enter the paddle chamber 730. By positioning the outermost electrode 721d remotely from the process location P, it can be easily removed and installed without disturbing structures adjacent to the process location P. This is unlike some existing arrangements having current thieves positioned directly adjacent to the process location.
One feature of an embodiment of the reactor 710 described above with reference to
In other arrangements, the electrodes 721 have other locations and/or configurations. For example, in one arrangement, the chamber base 733 houses one or more of the electrodes 721. Accordingly, the chamber base 733 may include a plurality of concentric, annular, porous electrodes (formed, for example, from sintered metal) to provide for (a) spatially and/or temporally controllable electrical fields at the process location P, and (b) a flow path into the paddle chamber 730. Alternatively, the paddles 741 themselves may be coupled to an electrical potential to function as electrodes, in particular, when formed from a non-consumable material. In still other arrangements, the reactor 710 may include more or fewer than four electrodes, and/or the electrodes may be positioned more remotely from the process location P, and may maintain fluid and electrical communication with the process location P via conduits.
D. Embodiments of Reactors Having Electric Field Control Elements to Circumferentially Vary an Electric Field
The elongated paddles 941 can potentially affect the uniformity of the electric field proximate to the circular workpiece W in a circumferentially varying manner. Accordingly, the reactor 910 includes features for circumferentially varying the effect of the thieving electrode (not visible in
The paddle chamber 930 shown in
The fourth wall gap 925d has narrow portions 999a proximate to the 3:00 and 9:00 positions shown in
The electric field control element 1192 also functions as a gasket between the upper portion 1119b and a lower portion 1119a of the reactor 1110, and can replace the gasket 727 described above with reference to
E. Embodiments of Paddles for Paddle Chambers
The agitation provided by the paddles 1241 may also be supplemented by fluid jets. For example, the paddle 1241e (
One feature of the paddles described above with reference to
One aspect of the present invention, is that, whatever shape and configuration the paddles have, they reciprocate within the confines of a close-fitting paddle chamber. The confined volume of the paddle chamber can further enhance the mass transfer effects at the surface of the workpiece W. Further details of the paddle chamber and the manner in which the paddles are integrated with the paddle chamber are described below with reference to
F. Embodiments of Reactors Having Paddles and Reciprocation Schedules to Reduce Electric Field Shielding and Improve Mass Transfer Uniformity
The paddle device 1440 includes a plurality of paddles 1441 positioned between the process location P and the chamber base 1433. The paddle chamber 1430 has a height H1 between the process location P and the chamber base 1433, and the paddles 1441 have a height H2. The tops of the paddles 1441 are spaced apart from the process location P by a gap distance D1, and the bottoms of the paddles 1441 are spaced apart from the chamber base 1433 by a gap distance D2. In order to increase the level of agitation in the paddle chamber 1430 and in particular at the process location P, the paddle height H2 is a substantial fraction of the chamber height H1, and the gap distances D1 and D2 are relatively small. In a particular example, the paddle height H2 is at least 30% of the chamber height H1. In further particular examples, the paddle height H2 is equal to at least 70%, 80%, 90% or more of the chamber height H1. The chamber height H1 can be 30 millimeters or less, e.g., from about 10 millimeters to about 15 millimeters. When the chamber height H1 is about 15 millimeters, the paddle height H2 can be about 10 millimeters, with the gap distances D1 and D2 ranging from about 1 millimeter or less to about 5 millimeters. In yet a further particular example, the chamber height H1 is 15 millimeters, the paddle height H2 is about 11.6 millimeters, D1 is about 2.4 millimeters and D2 is about 1 millimeter. Other arrangements have different values for these dimensions. In any of these arrangements, the amount of flow agitation within the paddle chamber 1430 is generally correlated with the height H2 of the paddles 1441 relative to the height H1 of the paddle chamber 1430, with greater relative paddle height generally causing increased agitation, all other variables being equal.
The plurality of paddles 1441 more uniformly and more completely agitates the flow within the paddle chamber 1430 (as compared with a single paddle 1441) to enhance the mass transfer process at the process surface 109 of the workpiece W. The narrow clearances between the edges of the paddles 1441 and (a) the workpiece W above and (b) the chamber base 1433 below, within the confines of the paddle chamber 1430, also increase the level of agitation at the process surface 109. In particular, the movement of the multiple paddles 1441 within the small volume of the paddle chamber 1430 forces the processing fluid through the narrow gaps between the paddles 1441 and the workpiece W (above) and the chamber base 1433 (below). The confined volume of the paddle chamber 1430 also keeps the agitated flow proximate to the process surface 109.
An advantage of the foregoing arrangement is that the mass transfer process at the process surface 109 of the workpiece W is enhanced. For example, the overall rate at which material is removed from or applied to the workpiece W is increased. In another example, the composition of alloys deposited on the process surface 109 is more accurately controlled and/or maintained at target levels. In yet another example, the foregoing arrangement increases the uniformity with which material is deposited on features having different dimensions (e.g., recesses having different depths and/or different aspect ratios), and/or similar dimensions. The foregoing results can be attributed to reduced diffusion layer thickness and/or other mass transfer enhancements resulting from the increased agitation of the processing fluid.
The processing fluid enters the paddle chamber 1430 by one or both of two flow paths. Processing fluid following a first path enters the paddle chamber 1430 from below. Accordingly, the processing fluid passes through electrode compartments 1422 of an electrode support 1420 located below the paddle chamber 1430. The processing fluid passes laterally outwardly through gaps between compartment walls 1423 and the chamber base 1433. The chamber base 1433 includes a permeable base portion 1433a through which at least some of the processing fluid passes upwardly into the paddle chamber 1440. The permeable base portion 1433a includes a porous medium, for example, porous aluminum ceramic with 10 micron pore openings and approximately 50% open area. Alternatively, the permeable base portion 1433a may include a series of through-holes or perforations. For example, the permeable base portion 1433a may include a perforated plastic sheet. With any of these arrangements, the processing fluid can pass through the permeable base portion 1433a to supply the paddle chamber 1430 with processing fluid; or (if the permeable base portion 1433a is highly flow restrictive) the processing fluid can simply saturate the permeable base portion 1433a to provide a fluid and electrical communication link between the process location P and annular electrodes 1421 housed in the electrode support 1420, without flowing through the permeable base portion 1433a at a high rate. Alternatively (for example, if the permeable base portion 1433a traps bubbles that interfere with the uniform fluid flow and/or electrical current distribution), the permeable base portion 1433a can be removed, and (a) replaced with a solid base portion, or (b) the volume it would normally occupy can be left open.
Processing fluid following a second flow path enters the paddle chamber 1430 via a flow entrance 1435a. The processing fluid flows laterally through the paddle chamber 1430 and exits at a flow exit 1435b. The relative volumes of processing fluid proceeding along the first and second flow paths can be controlled by design to (a) maintain electrical communication with the electrodes 1421 and (b) replenish the processing fluid within the paddle chamber 1430 as the workpiece W is processed.
The workpiece W (e.g., a round workpiece W having a diameter of 150 millimeters, 300 millimeters or other values) is supported by a workpiece support 1513 having a support seal 1514 that extends around the periphery of the workpiece W. When the workpiece support 1513 lowers the workpiece W to the process location P, the support seal 1514 can seal against a chamber seal 1537 located at the top of the paddle chamber 730. Alternatively, the support seal 1514 can be spaced apart from the chamber seal 1537 to allow fluid and/or gas bubbles to pass out of the paddle chamber 730 and/or to allow the workpiece W to spin or rotate. The processing fluid exiting the paddle chamber 730 through the exit gap 1535b rises above the level of the chamber seal 1537 before exiting the reactor 710. Accordingly, the chamber seal 1537 will tend not to dry out and is therefore less likely to form crystal deposits, which can interfere with its operation. The chamber seal 1537 remains wetted when the workpiece support 1513 is moved upwardly from the process location P (as shown in
Because the workpiece W is typically not rotated when magnetically directional materials are applied to it (e.g., in conjunction with use of the magnet 795), the linearly reciprocating motion of the plurality of paddles 741 is a particularly significant method by which to reduce the diffusion layer thickness by an amount that would otherwise require very high workpiece spin rates to match. For example, a paddle device having six paddles 741 moving at 0.2 meters/second can achieve an iron diffusion layer thickness of less than 18 microns in a permalloy bath. Without the paddles, the workpiece W would have to be spun at 500 rpm to achieve such a low diffusion layer thickness, which is not feasible when depositing magnetically responsive materials.
As the linearly elongated paddles 741 described above reciprocate transversely beneath a circular workpiece W, they may tend to create three-dimensional effects in the flow field adjacent to the workpiece W. Embodiments of the invention described below with reference to
Referring first to
Because the support seal 1614 projects downwardly away from the process surface 109 of the workpiece W (i.e., outwardly from the plane of
To counteract the foregoing effect, the outer paddle 1641b has a different (e.g., smaller) size than the inner paddle 1641a so as to be spaced apart from the support seal 1614 by a gap distance D4, which is approximately equal to the gap distance D1 between the inner paddle 1641a and the workpiece W. Accordingly, the enhanced mass transfer effect at the periphery of the workpiece W (and in particular, at the periphery proximate to the 3:00 and 9:00 positions shown in
Any of the paddle devices described above with reference to
Shifting the point about which the paddle device 140 reciprocates reduces the likelihood for forming shadows or other undesirable patterns on the workpiece W. This effect results from at least two factors. First, shifting the central position 180 reduces electric field shadowing created by the physical structure of the paddles 141. Second, shifting the central position 180 can shift the pattern of vortices that may shed from each paddle 141 as it moves. This in turn distributes the vortices (or other flow structures) more uniformly over the process surface 109 of the workpiece W. The paddle device 140 can accelerate and decelerate quickly (for example, at about 8 meters/second2) to further reduce the likelihood for shadowing. Controlling the speed of the paddles 141 will also influence the diffusion layer thickness. For example, increasing the speed of the paddles 141 from 0.2 meters/second to 2.0 meters per second is expected to reduce the diffusion layer thickness by a factor of about 3.
The number of paddles 141 may be selected to reduce the spacing between adjacent paddles 141, and to reduce the minimum stroke length over which each paddle 141 reciprocates. For example, increasing the number of paddles 141 included in the paddle device 140 can reduce the spacing between neighboring paddles 141 and reduce the minimum stroke length for each paddle 141. Each paddle 141 accordingly moves adjacent to only a portion of the workpiece W rather than scanning across the entire diameter of the workpiece W. In a further particular example, the minimum stroke length for each paddle 141 is equal to or greater than the distance between neighboring paddles 141. For any of these arrangements, the increased number of paddles 141 increases the frequency with which any one portion of the workpiece W has a paddle 141 pass by it, without requiring the paddles 141 to travel at extremely high speeds. Reducing the stroke length of the paddles 141 (and therefore, the paddle device 140) also reduces the mechanical complexity of the drive system that moves the paddles 141.
From the foregoing, it will be appreciated that specific embodiments of the invention have been described herein for purposes of illustration, but that various modifications may be made without deviating from the spirit and scope of the invention. For example, features of the paddle devices and paddle chambers described above in the context of electrolytic processing reactors are also applicable to other reactors, including electroless processing reactors. In another example, the workpiece W reciprocates relative to the paddle device. In still a further example, the workpiece W and the paddle device need not move relative to each other. In particular, fluid jets issuing from the paddle device can provide fluid agitation that enhances the mass transfer process. Nevertheless, at least some aspect of the workpiece W and/or the paddle device is activated to provide the fluid agitation and corresponding mass transfer enhancement at the surface of the workpiece W. Accordingly, the invention is not limited except as by the appended claims.
The present application claims priority to pending U.S. Provisional Application No. 60/484,603, filed Jul. 1, 2003; pending U.S. Provisional Application No. 60/484,604, filed Jul. 1, 2003; and pending U.S. Provisional Application No. 60/476,786, filed Jun. 6, 2003, all of which are incorporated herein in their entireties by reference.
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