US20150090599A1

US20150090599A1 - Insoluble Anode With a Plurality of Switchable Conductive Elements Used to Control Current Density in a Plating Bath

Info

Publication number: US20150090599A1
Application number: US14/044,660
Authority: US
Inventors: Jonathan Hander; Demetrius Papapanayiotou; Robert Moon; David Guarnaccia
Original assignee: Tel Nexx Inc
Current assignee: ASM Nexx Inc
Priority date: 2013-10-02
Filing date: 2013-10-02
Publication date: 2015-04-02
Also published as: TW201520377A; WO2015050593A1; TWI551729B

Abstract

This application relates to systems and methods for controlling current density in an electrochemical bath using an anode assembly that comprises a plurality of anodes arranged across a surface of the anode assembly. In one embodiment, each of the anodes may be coupled to a power supply through an intervening electrical switch. A switch controller enables the selection of which anodes should be turned on or off during processing. In this way, current density across the anode assembly can be controlled in a uniform manner by turning on and off select anodes. Turning off a portion of the anodes may lower current density in that region. Likewise, turning on the portion of anodes will increase the current density in that region.

Description

BACKGROUND OF THE INVENTION

The disclosed embodiment relates generally to a method and apparatus for electrochemical deposition, and more particularly to a method and apparatus for electrochemical deposition using an insoluble anode.
Electrochemical deposition, among other processes, is used as a manufacturing technique for the application of films, for example, tin, tin silver, nickel, copper or otherwise to various structures and surfaces, such as semiconductor wafers and silicon work pieces or substrates. An important feature of systems used for such processes is their ability to produce films with uniform and repeatable characteristics such as film thickness, composition, and profile relative to the underlying workpiece profile. Electrochemical deposition systems may utilize an anode to provide current to an electroplating solution that is in contact with the substrate. The characteristics of the film may be influenced by a variety of factors that result in thickness profile across the substrate. For example, the film may be thicker near the substrate edge than in the center or vice versa. The thickness variation may impact the electrical characteristics of the devices being formed on the substrate. Thickness variations may vary from substrate to substrate and process to process and may require hardware reconfigurations of the hardware. Such reconfiguration can be expensive and can require significant down time of the electrochemical deposition tool or sub module for service and process requalification that adversely affects the cost of ownership of the deposition tool. Accordingly, there is a desire for new and improved methods and apparatuses for controlling film thickness in electrochemical deposition tools.

SUMMARY

Broadly, electrochemical deposition may include the transfer of metal ions from a metal source (e.g., anode) in a chemical solution to a substrate (e.g., cathode) that may also be immersed in the solution. The metal ion transfer may be enabled by applying current to the metal source causing metal ions to dissolve into the chemical solution. The metal ions may migrate through the solution and may plate or couple to the substrate. It is sometimes preferable to use an insoluble anode for electrochemical deposition. When this is used, the electrochemical deposition process works as previously described except the metal ions deposited onto the wafer are not replenished by dissolution of the anode. In some instances, the metal ions may not plate uniformly across the substrate due to various chemical, electrical, and mechanical aspects of the plating bath that includes the metal source, substrate, and the chemical solution.
One aspect of the thickness variation may be related to the current density within the plating bath or the solution. The current density may be non-uniformly distributed across the anode due to the physical characteristics of the plating bath, substrate, and/or the anode. Hence, the anode may be designed to control or influence current density at the cathode by optimizing current density uniformity at localized regions of the anode.
In one instance, the anode assembly may be designed to provide current uniformly across the anode by incorporating a plurality of anodes uniformly throughout a surface of the anode assembly. Current density across the anode assembly may be controlled or optimized by selectively turning on or off one or more of the plurality of anodes. The anodes may be controlled by electrical switches that may turn an anode on or off by allowing or restricting current flow from a single power source. The control resolution of the current density may be related to the size or diameter of the anode assembly and the diameter and arrangement of the anodes. Mounting height of each anode with respect to the insulating support piece can also be used to optimize near-anode interactions. The control resolution will be higher as the diameter of the anode decreases and the distribution of the anodes becomes denser. Near-anode interaction can be adjusted by mounting the anodes in a protruded, recessed, or planar fashion with respect to the insulating mounting piece. The higher control resolution and tuned near-anode interaction may enable a more uniform current density across the anode assembly which may result in a more uniform thickness on the substrate.
In one embodiment, the anodes may be coupled to a single power source that can provide a substantially similar amount of current to each of the anodes. However, other chemical, electrical, and/or mechanical factors may result in non-uniform current distribution at the substrate. These non-uniformities result in deposition non-uniformity on the substrate. High edge thickness is the most common deposition non-uniformity pattern observed. Accordingly, a select group of anodes proximate to the edge of the anode assembly may be turned off to decrease the current density at the edge without decreasing current density at the center of the anode assembly.
In another embodiment, one portion of the anodes may be collectively controlled by a single electrical switch and another portion of the anodes may each be individually controlled by a corresponding switch. In this way, at least one group of anodes may be turned on or off at the same time by a single switch while at least one or more individual anodes may be turned on or off by an electrical switch dedicated to that individual anode. The groups of anodes may be covering an area of the anode assembly that may inherently have uniform current density. While the individual anodes may be covering another area of the anode assembly that has a higher degree of current density non-uniformity. For example, a group anodes located near the center of the anode assembly may be controlled by a single switch and anodes near the edge of the anode assembly may be controlled by individual switches. Accordingly, the anodes near the edge may be selectively turned off to minimize the amount of current flowing into the solution. This may compensate for other factors contributing to deposition thickness non-uniformity resulting in a more evenly distributed deposit across the substrate. Hence, the arrangement or location of the anodes can have an impact on current density and deposition distribution across a substrate.
For example, the arrangement of the anodes within the anode assembly may enable various current density control profiles that may impact thickness on the substrate. The control profiles may include, but are not limited to, radial control, quadrant control, and/or top-to-bottom control. Briefly, radial control may include turning off groups of anodes that may be a certain distance from the center of the anode assembly. In this instance, the turned off anodes may form a circle or quasi-circle around the center of the assembly. By forming a circle off turned off anodes, the impact of the turned off anodes can result in relatively uniform deposition across the substrate surface. Radial control may also enable one or more circles of turned off anodes, the circles may be close together or they may be separated by circles of turned on anodes. In another instance, one or more circles of anodes may be so close that they form a single ring of anodes around the center of the anode assembly.
Another form of control may be quadrant control that may organize specific locations or regions to turn off or on at the same time. The geometry or arrangement of the turned off/on anodes is merely limited by the density of the anodes. For example, quadrant control may enable on/off anodes to be arranged in various geometries that may include, but are not limited to, circles, rectangles, lines, triangles, or rhombuses. In short, quadrant control may be used to impact current density in a relatively non-uniform way across the anode assembly. This may include creating localized regions of on or off anodes to account for substrate features. For example, the anodes located above specific die or devices on the substrate may be turned on to impact current density above one or more die. Likewise, the anodes located above the gaps between die may be turned off at the same time.
In another instance, quadrant control may impact current density across a continuous region of the anode assembly. The anode assembly or bath may be configured in way that creates pockets or regions of high or low current density. The anodes in the regions may be turned on or off to raise or lower the current density in that region. For example, the anodes within a certain distance of the anode assembly's edge may be turned off while the remaining anodes may be turned on. Under quadrant control, the on and off anodes may vary by any pattern that may improve current density control or thickness uniformity on the plated substrate.
Another form of anode control can be Top-to-bottom control. For example, the anode assembly may vary the amount of “on” anodes to “off” anodes in a systematic way to control the current density from top to bottom or from side to side of the anode assembly. In one embodiment, this may include having more anodes turned on at the top than at the bottom of the anode assembly. This type of control may be used to address substrate thickness profiles that vary from high to low across the substrate.
Described herein are several embodiments related to the current density control across the anode assembly. Note that this summary section does not specify every embodiment and/or incrementally novel aspect of the present disclosure or claimed invention. Instead, this summary only provides a preliminary discussion of different embodiments and corresponding points of novelty over conventional techniques. For additional details and/or possible perspectives of the invention and embodiments, the reader is directed to the Detailed Description section and corresponding figures of the present disclosure as further discussed below.

BRIEF DESCRIPTION OF THE DRAWINGS

The features within the drawings are numbered and are cross-referenced with the written description. Generally, the first numeral reflects the drawing number where the feature was first introduced, and the remaining numerals are intended to distinguish the feature from the other notated features within that drawing. However, if a feature is used across several drawings, the number used to identify the feature in the drawing where the feature first appeared will be used. Reference will now be made to the accompanying drawings, which are not necessarily drawn to scale and wherein:

FIG. 1 illustrates a simplified block diagram of a single compartment ECD cell with metal-concentrate dosing as described in one or more embodiments of the disclosure.

FIG. 2 illustrates a simplified block diagram of a two-compartment cell with metal-concentrate dosing as described in one or more embodiments of the disclosure.

FIG. 3 illustrates a bottom view of an anode assembly that includes a plurality of anodes as described in one or more embodiments of the disclosure.

FIG. 4 illustrates a bottom view of a portion of an anode assembly indicating which anodes are turned on or off using radial control as described in one or more embodiments of the disclosure.

FIG. 5 illustrates a bottom view of a portion of an anode assembly indicating which anodes are turned on or off using quadrant control as described in one or more embodiments of the disclosure.

FIG. 6 illustrates another bottom view of a portion of an anode assembly indicating which anodes are turned on or off using quadrant control as described in one or more embodiments of the disclosure.

FIG. 7 illustrates another bottom view of a portion of an anode assembly illustrating another embodiment in which anodes are turned on or off using top-to-bottom control as described in one or more embodiments of the disclosure.

FIG. 8 illustrates a simplified block diagram of the power source, switching assembly, and the anode assembly as described in one or more embodiments of the disclosure.

FIG. 9 illustrates a method flow diagram for controlling individual anodes or groups of anodes in the anode assembly as described in one or more embodiments of the disclosure.

DETAILED DESCRIPTION

Techniques disclosed herein include methods and systems for electrochemical deposition (ECD), as well as sub systems, auxiliary modules, and processes that support ECD systems.
Of course, the order of discussion of the different steps as described herein has been presented for clarity sake. In general, these steps can be performed in any suitable order. Additionally, although each of the different features, techniques, configurations, etc. herein may be discussed in different places of this disclosure, it is intended that each of the concepts can be executed independently of each other or in combination with each other. Accordingly, the concepts described in this application can be embodied and viewed in many different ways. For example, techniques for electrochemical deposition can include, but are not limited to, a primary ECD unit, and one or more modules or cells that can generate various chemicals and metal ions to assist with the plating process. There can be various configurations among the different modules. Such modules assist with plating bath controls and provide a set of components that can be combined in various ways depending on specifications of a particular plating application or treatment process.
FIG. 1 illustrates a simplified block diagram 1000 of a single compartment ECD cell with a metal-concentrate dosing scheme. In FIG. 1, plating solution is contained in cell 1003 and reservoir 1020, and can be recirculated, via conduits 1012 and 1013 using pump 1011. The plating solution is replenished via dosing with solutions shown in the dosing array 1006-1009, and delivered via conduit 1005. The single compartment ECD cell can include a substrate 1002 (functioning as the cathode). Substrate 1002 can be plated with SnAg alloy or many other metal alloys that may include, but is not limited to, copper. Dosed species can include some or all of the following: Sn-concentrate solution, Ag-concentrate solution, one or more organic additives, an Ag complexor concentrate, acid, and water. Current through the ECD plating cell can be controlled via the power supply 1004 that can provide the current to the anode assembly 1001. In one embodiment, the anode assembly 1001 may include a plurality of anodes (not shown) that are exposed to the plating solution 1003. The current can dissociate metal ions from the anode assembly and are deposited on the substrate 1002. The anode assembly 1001, opposite wafer 1002, can be an inert anode or insoluble anode.
Two-Compartment Cell with Metal-Concentrate Dosing.
FIG. 2 illustrates a simplified schematic of an insoluble anode two-compartment ECD cell with a metal-concentrate dosing scheme. The cell in FIG. 2 may operate similarly to single cell system described in FIG. 1, in that the entire primary metal ion supply can be delivered through dosing unit 2018. For the cell in FIG. 2, the anolyte may be comprised, in some embodiments, of a simple acid-water solution. In particular embodiments, control of such an anolyte can be accomplished by maintaining a targeted acid concentration. In some embodiments, acid control may be realized by an overflow weir and water dosing mechanism (not shown). Current through the ECD cell or ECD Load can be controlled via the power supply 2007. Electrodissolution of the anode 2001 occurs in the anolyte within compartment 2002.
Using an insoluble anode results in different benefits. By way of a particular example, in some implementations (notably the plating of Sn or Sn-containing alloys) the anolytes (in reservoir 2004 and compartment 2002) can be selected so as to have differing compositions. By way of a specific example, anolyte in reservoir 2004 receives metal ions upon electrodissolution of anode 2001, and may also use a cross-bleed to ensure that all dissolved metal ions cross-over to the plating solution in reservoir 2030. Dosing unit 2018 is then used for supplemental dosing. A given plating solution can be recirculated, via conduits 2016 and 2015, through the ECD cell using pump 2008. Another benefit can be that insoluble anode system does not need to rely on the anolyte in compartment 2002 as a metal ion source. The cell in FIG. 2 then may operate similarly to that in FIG. 1 in that the entire primary metal ion supply can be delivered through dosing unit 2018.
FIG. 3 illustrates a bottom view 3000 of an anode assembly 2001 that includes a plurality of anodes 3001 that may transmit current from the power supply 2007 into the plating solution 2002. The anode assembly 2001 may also include fasteners 3002 along the perimeter that may be used to secure the anode assembly 2001 to a wall of the plating cell shown in FIG. 2.
In the FIG. 3 embodiment, the plurality of anodes 3001 may be distributed in constant density throughout the surface of the anode assembly 2001. The density of the anodes may be based, at least in part, on the process requirements for the substrate 2009 and the bath design. One goal of the constant density embodiment may be to maintain a constant current density across the surface of the anode assembly 2001. In certain instances, the current density may vary and cause high current density pockets that can result in higher thickness non-uniformity on the substrate 2009. Likewise, the anode assembly 2001 may also have low current density pockets. However, by selectively turning on or off individual anodes, or groups of anodes, the relative high or low current density pockets may be eliminated or diminished such that the substrate 2009 thickness non-uniformity is within acceptable limits. Examples of various embodiments will be described in greater detail in the description of the remaining figures.
The anode assembly 2001 may be made of a dielectric material or a conductive material that may or may not be the same conductive material used in the anodes 3001. In one specific embodiment, the anode assembly 2001 may be made of, but is not limited to, niobium, titanium, platinum, gold, carbon, PVDF, PTFE, PP, FFPM, FKM or FFKM. In other embodiments, the conductive material may be copper, tin, silver, or any other metal that may be plated onto a substrate 2009. The anode assembly 2001 can have a diameter that enables metal plating on substrates with diameters of 200 mm or higher.
The anodes 3001 can be placed within the anode assembly 2001 and can be secured by a push-fit tolerance that keeps the anode in position within the anode assembly 2001. The diameter of the anodes 3001 may range between 1 mm to 5 mm. In one specific embodiment, the diameter of the anodes 3001 may be 4.5 mm. The anodes 3001 can be spaced evenly across the anode assembly 2001. A higher anode density provides greater resolution for controlling current density in the plating bath 2002. The FIG. 3 embodiment is merely an example of how the anodes can be arranged in the anode assembly. The arrangement may vary based, at least in part, on the positions of the anodes 3001, on the size of the substrate 2009, the features on the substrate 2009, and the type of metal that may be deposited on the substrate 2009.
In one embodiment, the anodes 3001 may have a surface that is substantially flush with anode assembly 2001. This may mean that the surface of anodes 3001 and a surface of the anode assembly 2001 may be in the same plane. In this way, the current interaction between nearby anodes 3001 may be relatively uniform when they are in the same position. However, the current interaction between nearby anodes 3001 may be varied based, at least part, on the relative positions of the anodes 3001 with respect to the surface of the anode assembly 2001. For example, the surface of the anodes 3001 may be recessed into the anode assembly 2001 so that the surfaces anodes 3001 and the anode assembly 3001 may not be substantially flush. This embodiment may decrease the current interaction between the anodes 3001. In yet another embodiment, the anodes 3001 may be protruding from the anode assembly 2001 which can increase the current interaction between nearby anodes 3001. In some instances, the anodes 3001 may vary in distance from the cathode 1002 across the anode assembly 2001. For example, at least one of the anodes 3001 may be flush with the anode assembly 2001 and at least one other anode 3001 may be recessed into or protruding from the anode assembly 2001. Further, two or more portions of the anodes 3001 may be positioned in flush, recessed, and/or protruding positions with respect to the anode assembly 2001 or in any combination thereof.
The anodes 3001 can be made of a conductive material, preferably a metal, which can be plated onto a substrate 2009. The anodes 3001 may comprise, but are not limited to, Sn (tin) (various alpha-particle grades), Pb (lead) (various alpha particle grades), SnPb, Cu (copper), Ni (nickel), Ag (silver), Bi (bismuth), etc. The metal anodes 3001 can provide the metal ions that can be plated onto the substrate 2009.
In one embodiment, the each of the anodes 3001 can coupled to an electrical switch (not shown) that is electrically coupled to the power supply 2007. The electrical switches can act as a gate for the current flow to the anode and can be programmed to be on or off during processing. The selection of which anodes 3001 that are on or off can impact the current density profile along the anode assembly and/or the plating bath 2002.
In another embodiment, an electrical switch can be coupled to more than one anode 3001 and can turn the anodes 3001 on or off collectively. This grouping arrangement may be done on certain areas of the anode assembly 2001 that are known to have at least a relatively uniform current density. Accordingly, the anodes 3001 in these uniform regions are not likely to be turned on or off without the surrounding anodes 3002 being in the same state. In this way, the number of electrical switches can be reduced to provide some cost savings. However, each of the anodes 3001 in the other non-uniform regions can continue to be controlled by individual switches. As noted above, a single power supply 2007 can provide power to the anodes instead of using multiple power supplies to power each or a group of anodes 3001 in the anode assembly 2001.
The grouping of anodes to a single switch along with additional anodes that have their own switch reduces the number of switches. There is a tradeoff between equipment cost and equipment capability. For example, in certain instances the high resolution capability of using all individually controlled anodes 3001 may not be required to control current density to desired levels. In view of the capability to control individual anodes 3001, the arrangement of “on” or “off” anodes 3001 may vary widely from process to process to obtain a relatively uniform current density. Hence, the anode control strategy may vary from process to process. Broadly, the control strategies can be classified by, but are not limited to, radial control, quadrant control, and/or top-to-bottom control.
Turning now to one radial control embodiment, FIG. 4 illustrates a bottom view 4000 of a portion of an anode assembly 2001 indicating which anodes may be turned on (filled anodes) or off (clear anodes). For the purpose of explanation, FIG. 4 is limited to showing two radial segments 4003, 4004 along the outer edge of the anode assembly 2001. Additional anodes 4002 may be turned off during processing, but they are not shown here in FIG. 4. For ease of illustration, only one quarter of the anode assembly is shown in FIG. 4. The other three quarters of the anode assembly 2001 can have the same configuration as shown in FIG. 4, except that the other quadrants would be rotated at least 90 degrees. However, in other embodiments, the radial pattern across the anode assembly 2001 does not have to be symmetrical to the quadrant shown in FIG. 4.
Broadly, radial control can apply to controlling a group of anodes that can form a radial pattern around the center of the anode assembly 2001 when they are turned on or off. The group of anodes 4003 may be immediately adjacent to each other, such that there no intervening anodes that between them that are in a different state (e.g., on or off). However, in other embodiments the group of anodes 4004 may form a radial pattern, but they may have intervening anodes that have a different state. Further, there may be more than one radial pattern assigned to the anode assembly 2001 at the same time. The plurality of radial patterns can be used to control the current density in a cooperative manner. In that, the current density profile may be adjusted by one group of anodes or two or more groups of anodes working together.
In this embodiment, the radial control strategy targets an outer segment of anodes 4003 and an inner segment of anodes 4004. The outer segment of anodes 4003 form the outer ring of the anodes 3001, in that each of the outermost anodes can be turned off to control current density at the edge of the anode assembly 2001 or the substrate 2009. Additionally, an inner segment of anodes 4004 that are turned off can also be used to control current density in conjunction with the outer segment 4003.
This arrangement can be used to address higher current density around the substrate perimeter. Decreasing the flow of current by turning off the outer segment anodes 4003, the current density can be reduced at the edge of the anode assembly 2001 so that outer edge current density can be closer in magnitude to the current density in other areas of the anode assembly 2001.
Additionally, the current density may also be optimized by turning off the inner segment anodes 4004. In this embodiment, there is a gap of on anodes 4002 that intervene between the inner segment anodes 4004 and the outer segment anodes 4004. Also, the inner segment anodes 4004 may also include intervening anodes 4002 that are turned on as shown in FIG. 4. This arrangement provides a higher magnitude of current to the plating solution 2002 than when the intervening anodes 4002 are turned on. In contrast, a lower magnitude of current would be provided to the plating solutions 2002 when the intervening anodes 4002 are turned off. The number of intervening “on” anodes between “off” anodes may vary by one or more “on” anodes.
In other embodiments, the inner segment anodes 4004 and the outer segment anodes 4003 may be varied radially from the center of the substrate. Such that, the distance from the center of the anode assembly 2001 can vary in distance. For example, the pattern of the outer anode segment 4003 or the inner anode segment 4004 can be moved, radially, closer to the center of the anode assembly 2001.
In addition to radial control, the anodes may be turned on and off based, at least in part, on particular x-y coordinates that may correlate to device features on the substrate 2009 or to a known region of high current density.
FIG. 5 illustrates a bottom view 5000 of a portion of an anode assembly 2001 indicating which anodes are turned on or off using quadrant control. As indicated in the drawing, the dark anodes 5001 can be turned off and the clear anodes 5002 can be turned on based, at least in part, on the location of the anodes 5001, 5002 relative to the die positions or feature positions on the substrate 2009. In this embodiment, the shaded square regions 5003 in FIG. 5, may be representative of die positions on the substrate. Accordingly, the x-y coordinates of the anodes 5002 that correspond to the location of the square regions 5003 can be turned on and the anodes 5001 that correspond to gaps between the square regions 5003 can be turned off. The anodes 5001 that are near the edge, or where there is a region of high current density, may also be turned off, as shown in FIG. 5.
In this embodiment, the incoming substrate 2009 can be aligned to the anode assembly prior to being placed in the plating solution 2002. The alignment can be done using alignment features on the devices on the substrate 2009 or notch alignment using a notch etched into the substrate or aligning based on the position of the wafer identification scribed into the surface of the substrate 2009.
In other embodiments, determining which anodes can be turned on or off can be based on the size and pitch of the device substrates and the size and pitch of the anodes 5001, 5002. However, when the pitch and size of the devices are relatively small compared to the pitch and size of the anodes 5001, 5002, the interior anodes may be turned on and the edge anodes may be turned off as shown in FIG. 6.
FIG. 6A illustrates another bottom view 6000 of a portion of an anode assembly 2001 indicating which anodes are turned on or off using quadrant control in view of the device locations on the substrate 2009. The device locations are indicated by the gray squares 6003 that are over laid on the anode assembly 2001. In this embodiment, the device pitch and size is such that there are few, if any, gaps that are large enough that would warrant turning off any anodes 6001 within the interior of the substrate 2009. In this example, the pitch and size of the anodes 6001 are not small enough to distinguish between the devices and any gaps between the devices on the substrate.
In another embodiment (not shown), select anodes 6001 may be turned off to lower the deposition rate of the metal on the substrate across the substrate. This may enable a plating process that deposits metal at different deposition rates. The select anodes 6001 can be selected based, at least in part, on lowering the current density evenly across the substrate 2009 and thereby lowering the metal deposition rate. The select anodes 6001 may include a pattern, in which every other anode is turned off, or every second anode is turned off, or every third anode is turned off. In another embodiment, an entire row or column may be turned off to lower the current density across the substrate 2009. Further, more than one row and/or column may be turned off at the same time to achieve the lower deposition rate. In fact, at least one row and at least one column of anodes may be turned off to achieve the lower deposition rate. This may be in addition to the anodes 6002 that may have been turned off during the higher deposition rate step at the edge of the substrate 2009.
FIG. 7 illustrates another bottom view 7000 of a portion of an anode assembly 2001 illustrating another embodiment in which anodes are turned on or off using top-to-bottom control. A control strategy of top-to-bottom control could be used to control thickness uniformity across the substrate 2009 from either top-to-bottom or side-to-side. In this way, the anodes may be configured to generate a current density profile that varies from low to high across the substrate 2009. Such that, the current density profile may increase linearly or non-linearly across the substrate 2009.
One way to implement a top-to-bottom current density profile can be to increase or decrease the number of on or off anodes across the anode assembly 2001. As shown in FIG. 7, one or more groups of turned on anodes (anode group 6004, anode group 6005, anode group 6006, anode group 6007, anode group 6008) may be arranged across the anode assembly 2001. The first group on the low current density side may have a relatively small amount of anodes compared to the high current density side that may have larger groups of anodes. For example, in one embodiment, anode group 6004 may include two rows of anodes that are turned on. The adjacent anode group 6005 may have three rows of turned on anodes. In this embodiment, there may be one row of anodes that are turned off between anode group 6004 and anode group 6005. However, in other embodiments, there may be more than one row of turned off anodes. Anode groups 6006, 6007, and 6008 may also increase the number turned on anodes relative the proceeding anode groups 6004, 6005. Although FIG. 7 shows the groups being arranged into a rectangular geometry, the anode groups can take any form (e.g., square, circular, trapezoid) that enables the current density profile to range from low to high across the anode assembly 2001.
In another embodiment, the top-to-bottom control strategy may be combined with the radial and/or quadrant strategy to customize the current density profile across the anode assembly 2001. For example, the top-to-bottom anode arrangement in FIG. 7 may be combined with radial anode arrangement as shown in FIG. 4. Further, the top-to-bottom anode arrangement in FIG. 7 may be combined with quadrant anode arrangement as shown in FIG. 5. Likewise, the radial and quadrant control strategies may also be combined. An example could include an overlay of FIG. 4 and FIG. 5 in some manner. In short, the anode on/off arrangement can be designed using two or more of the control strategies to improve metal thickness non-uniformity on the substrate 2009.
FIG. 8 illustrates a simplified block diagram 8000 of an ECD system that can include an anode power supply 8001, a switch assembly 8002, a switch controller 8003, and the anodes 3001 that can be coupled to switches (not shown) within the switch assembly 8002. For ease of illustration and explanation, the ECD system in FIG. 8 does not show the components listed or described in FIGS. 1 and 2. However, the features described in FIG. 8 can be incorporated into the ECD systems described in FIGS. 1 and 2.
The power supply 8001 can be configured to provide current to one or more switches (not shown) in the switch assembly 8002. Current may be provided in the direct current or alternating current format. Preferably, the direct current can be used to provide a relatively constant current to the plating solution 1003, 2001. The power supply 8001 can regulate the current flow to a target condition and can maintain that target condition to within a tolerance threshold. The power supply can be a battery or receive power from an outside source such as a power outlet or a power distribution box. The power supply can regulate and/transform the incoming power to provide current to the switch assembly 8002 in a manner that is conducive to electrochemical plating. In one specific embodiment, a single power supply 8002 can provide all of the current to the switch assembly 8002 and the anodes 3001.
The switch assembly 8002 can include electrical switches (not shown) that can provide or restrict current from the power supply 8001 to the anodes 3001. The electrical switches may be controlled by switch controller 8003 to turn off or on during substrate 2009 processing. In another embodiment, the electrical switches may regulate the amount of current that can be provided to the anodes 3001 in a more nuanced manner than passing all the current or none of the current. For example, the current regulation may enable each anode to receive three or more amounts of current. In one instance, the first amount may be zero, the second amount may be the maximum current that can be provided by the power supply 8002, and the third amount may be a value between the first and second amounts. In other embodiments, the amount of current provided to the anodes 3001 may vary so that several individual anodes 3001 or several groups of anodes 3001 may be providing different amounts of current at the same time.
In one embodiment, each of the anodes 3001 may be controlled by a single electrical switch. In this way, each of the anodes may be turned on or off independently from other anodes 3001. Accordingly, in this embodiment, the number anodes and the number of electrical switches should be similar. In another embodiment, a group of anodes may be turned on or off by a single electrical switch. For example, the current density near the center of the anode assembly 2001 may be relatively constant and may not require a high degree of anode resolution to maintain uniform current density. Accordingly, a single electrical switch may be coupled to two or more anodes. In one embodiment, the anodes 3001 located within 5 cm of the center of the anode assembly 2001 can be coupled to the single electrical switch. However, each the remaining anodes outside of the 5 cm diameter may be coupled to individual electrical switches.
In other embodiments, a portion of the anodes 3001 may be grouped into two or more groups that can be controlled by a single electrical switch, while each of the remaining anodes may be controlled by a single electrical switch. Generally, the groups of anodes would correspond to regions of the anode assembly 3001 that are likely to have relatively uniform current density. As mentioned above, the individually controlled anodes 3001 may be located in regions in which the current density is not likely to be uniform. For example, the non-uniform regions may be near the edge of the anode assembly 3001 and the uniform regions may be near the center of the anode assembly 3001.
In one embodiment, the switch assembly 8002 may include DIN (Deutsches Institut fur Normung) rail relays that enable each of the electrical switches to be controlled by one signal from the power supply 8001. In this way, the electrical switches that are designated to be turned on will be closed and the electrical switches that are designated to be turned off will be closed. The on/off designation may be enabled by the switch controller 8006. In another embodiment, the switch assembly 8002 may include Double Pole Single Throw electrical switches that can also be controlled by a single signal to turn on/off the electrical switches.
The switch controller 8006 will direct which electrical switches will be open or closed and the duration of when the electrical switches will be opened or closed. The switch controller may include a processor (not shown) and memory (not shown) that contains computer-executable instructions that may be executed by the processor. The switch controller 8006 may also include a communications interface that can send signals to the switch assembly 8002 that specify which electrical switch(s) will be opened or closes.
The memory herein may be provided as a tangible machine-readable medium storing machine-executable instructions that, if executed by a machine, cause the machine to perform the methods and/or operations described herein. The tangible machine-readable medium may include, but is not limited to, any type of disk including floppy disks, optical disks, compact disk read-only memories (CD-ROMs), compact disk rewritables (CD-RWs), magneto-optical disks, semiconductor devices such as read-only memories (ROMs), random access memories (RAMs) such as dynamic and static RAMs, erasable programmable read-only memories (EPROMs), electrically erasable programmable read-only memories (EEPROMs), flash memories, magnetic or optical cards, or any type of tangible media suitable for storing electronic instructions. The machine may include any suitable processing or computing platform, device or system and may be implemented using any suitable combination of hardware and/or software. The instructions may include any suitable type of code and may be implemented using any suitable programming language. In other embodiments, machine-executable instructions for performing the methods and/or operations described herein may be embodied in firmware.
The processor herein may be provided as a computer processor or other logic device that can process computer-executable instructions to render a result that can be provided to memory or other components of the ECD system 9000. The processor may operate as a reduced instruction set computing (RISC) or complex instruction set computing (CISC). However, the processor may be any device that may include one or more arithmetic logic unit(s) (ALU) to generate instructions that can be communicated to the switch assembly 8002.
FIG. 9 illustrates a method flow diagram 9000 for controlling individual anodes 3001 or groups of anodes (e.g., anode group 6004) in the anode assembly 2001. The flow diagram illustrates one embodiment of the method. In other embodiments, the methods may omit or rearrange the order of the steps shown in FIG. 9. Broadly, FIG. 9 pertains to a method for controlling electrochemical deposition on a substrate 2009. More specifically, controlling the amount of current density across the anode assembly 2001 or the substrate 2009 to minimize the thickness non-uniformity of the deposited metal. Current density may be controlled by turning on or off anodes 3001 in an arrangement that minimizes the variation of current density across the anode 2001.
At block 9001, the method 9000 may be implemented by disposing an anode structure 2001 in an electrochemical deposition system 2000 opposite a substrate 2009. The anode structure 2001 can be placed in contact with an electrochemical medium 2002 contained between the anode structure 2001 and the substrate 2009. In one embodiment, the anode structure may be configured with a plurality of anodes 3001 that can provide current to the electrochemical medium 2002. In one embodiment, the anodes 3001 may be arranged uniformly across the anode structure 2001, as shown in FIG. 3. The diameter of the anodes can be between 1 mm and 5 mm.
At block 9002, the method 9000 may be further implemented by providing a plurality of electrically controlled switches (e.g., switch assembly 8002) coupled between a power source 8001 and said plurality of anodes 3001. The electrically controlled switches can couple electrical current from the power source 8001 to one or more of said plurality of anodes 3001. The electrical switches may be configured to be an open circuit during a portion of the electrochemical process and a closed circuit during the plating portion of the electrochemical process implemented on the electro chemical deposition system 2000.
In one embodiment, the plurality of anodes 3001 is coupled exclusively to a corresponding electrical switch. In this way, each of the anodes 3001 may be controlled independently of the other anodes 3001 in the anode structure 2001.
In another embodiment, plurality of anodes 3001 comprises at least one group of anodes 3001 that are coupled to one electrical switch and a portion of anodes that are exclusively coupled to their own electrical switch. For example, anodes 3001 located near the center of the anode structure 2001 may be grouped to the same electrical switch. The grouping enables those anodes 2001 coupled to that single electrical switch to be turned on or off collectively at substantially the same time. The grouping may be based, at least in part, on the regions of the anode structure that typically have a relatively uniform current density during electrochemical processing.
At block 9003, the ECD system 8000 can be enabled to set a first configuration of an on and off state for each of the plurality of anodes 3001. For example, the configuration can be based, at least in part, but is not limited to, a radial control strategy, a quadrant strategy, and/or a top-to-bottom strategy as described above in the description of FIGS. 4-7. For example, the first configuration comprises identifying an on or off state of a first set of at least one of said plurality of anodes 3001 with a first region on the substrate 2009. The identification may be based, at least in part, on analyzing the current density profile across the anode structure 2001 and/or the thickness non-uniformity on the metal deposited on the substrate 2009. In another embodiment, the identification may be based, at least in part, on the location of die or devices that are being formed on the substrate 2009. For example, the embodiment of FIG. 4 shows one way in which the anodes 3001 may be configured to correspond to die or devices on the substrate 2009.
In other embodiments, the electrochemical process may have a multi-step deposition process that can use different power settings for depositing a metal layer on the substrate 2009. The multi-step process may be used to accommodate features on the substrate 2009. For example, different power settings may be used during deposition step to account for via (e.g., hole on the surface of the substrate 2009) aspect ratios or to assist in initiating plating for thin or high resistance seed substrates. In another example, the current density profile or the deposition rate may change as the metal layer grows thicker or that a process condition or hardware feature may change the thickness uniformity over time. Although different power settings may be used to control uniformity, the anodes 3001 on/off configuration may also be reconfigured to account for changes in deposition uniformity over time. For example, the first configuration may similar to the arrangement shown in FIG. 4 that accommodates die position on the substrate 2009. The first deposition may cover substrate features, but the uniformity of the deposition may change once those features are covered or filled. The anodes 3001 may change to a second configuration to compensate to maintain a threshold of thickness non-uniformity. For example, the second configuration may be similar to the anode 3001 arrangement shown in FIG. 2.
In another embodiment, switching between the first configuration and the second configuration may be based, at least in part, on when another substrate 2009 is placed into the chemical plating solution 2010. For example, the first configuration may be used with a first type of substrate and the second configuration may be used with a second type of substrate. In this way, the anode assembly 2001 can be configured for different substrates without having to remove and modify the anode assembly 2001.
At block 9004, the anode arrangement discussed immediately above may be implemented by spatially controlling an anode current from the anode structure 2001 by setting the plurality of electrically controlled switches to the first configuration. As noted above, one embodiment can have the first configuration arranged in the manner as shown in FIG. 4.
At block 9005, the substrate 2009 in may receive an electrochemically deposited film when the power is applied to the anodes in the first configuration and the substrate is exposed to a chemical plating solution (e.g., chemical solution 2010).
Although only certain embodiments of this application have been described in detail above, those skilled in the art will readily appreciate that many modifications are possible in the embodiments without materially departing from the novel teachings and advantages of this invention. Accordingly, all such modifications are intended to be included within the scope of this invention.

Claims

What is claimed is:

1. An anode assembly for use in an electrolytic processing system, comprising:

an anode structure comprising a plurality of anodes;

a plurality of electrically controlled switches arranged to be disposed between a power source and said plurality of anodes, each of said electrically controlled switches being configured to couple electrical current from said power source to one or more of said plurality of anodes; and

a controller coupled to said plurality of electrically controlled switches, and programmed to set said plurality of electrically controlled switches to a pre-determined configuration of on and off-state for each of said plurality of anodes.

2. The anode assembly of claim 1, wherein said pre-determined configuration includes a first set of said electrically controlled switches set to an off-state to disconnect current flow to a first set of said plurality of anodes, and a second set of said electrically controlled switches set to an on-state to connect current flow to a second set of said plurality of anodes.

3. The anode assembly of claim 1, wherein said plurality of anodes are housed within a dielectric member or a conductive member.

4. The anode assembly of claim 3, further comprising:

an electrode disposed behind said dielectric member, and electrically coupled to two or more of said plurality of anodes, said electrode being electrically coupled to one of said plurality of electrically controlled switches.

5. The anode assembly of claim 3, further comprising:

a first electrode disposed behind said dielectric member, and electrically coupled to two or more of said plurality of anodes centrally located in said anode structure, said first electrode being electrically coupled to one of said plurality of electrically controlled switches; and

a second electrode disposed behind said dielectric member, and electrically coupled to two or more of said plurality of anodes peripherally located in said anode structure, said second electrode being electrically coupled to another of said plurality of electrically controlled switches.

6. The anode assembly of claim 1, wherein a first electrically controlled switch is electrically coupled to a first array of said plurality of anodes, and a second electrically controlled switch is electrically coupled to a second array of said plurality of anodes.

7. The anode assembly of claim 1, wherein said plurality of anodes comprise a plurality of insoluble anodes.

8. The anode assembly of claim 1, wherein at least one of a number density or a size of said plurality of anodes are turned on or off across a first dimension of said anode structure.

9. An electrochemical deposition system, comprising:

a cathode;

an anode assembly disposed opposite said cathode;

a power source coupled to said anode assembly and said cathode, and configured to supply an electrical current between said anode assembly and said cathode through an electrochemical medium, wherein said anode assembly comprises:

an anode structure comprising a plurality of anodes, and

a plurality of electrically controlled switches disposed between said power source and said plurality of anodes, each of said electrically controlled switches being configured to couple electrical current from said power source to said one or more of said plurality of anodes; and

10. The anode assembly of claim 9, wherein at least one of said plurality of anodes is positioned at a first axial distance from said cathode, and at least another of said plurality of anodes is positioned at a second axial distance from said cathode.

11. The anode assembly of claim 9, wherein at least one of said plurality of anodes is substantially flush with the anode assembly, recessed into the anode assembly, or protruding from the anode assembly.

12. A method for processing a substrate in an electrochemical deposition system, comprising:

disposing an anode structure in an electrochemical deposition system opposite a substrate, and contacting said anode structure with an electrochemical medium contained between said anode structure and said substrate, said anode structure comprising a plurality of anodes;

providing a plurality of electrically controlled switches coupled between a power source and said plurality of anodes, each of said electrically controlled switches being configured to couple electrical current from said power source to one or more of said plurality of anodes;

determining a first configuration of an on and off-state for each of said plurality of anodes;

spatially controlling an anode current at said anode structure by setting said plurality of electrically controlled switches to said first configuration of said on and off-state of said plurality of anodes; and

electrochemically depositing a film on said substrate.

13. The method of claim 12, further comprising:

determining a second configuration of an on and off-state for each of said plurality of anodes; and

switching from said first configuration to said second configuration of said on and off-state for each of said plurality of anodes.

14. The method of claim 13, wherein said switching is performed during said electrochemically depositing.

15. The method of claim 13, wherein said switching is performed following electrochemically depositing said film on said substrate and electrochemically depositing another film on another substrate.

16. The method of claim 12, wherein said determining said first configuration comprises identifying an on or off-state of a first set of at least one of said plurality of anodes with a first region on said substrate.

17. The method of claim 16, wherein said first region includes one or more dies.

18. The method of claim 12, wherein each of said plurality of anodes is coupled exclusively to a corresponding electrical switch.

19. The method of claim 12, wherein said plurality of anodes comprise at least one group of anodes that are coupled to one electrical switch and a portion of anodes that are exclusively coupled to their own electrical switch.

20. The method of claim 12, wherein each of said plurality of anodes comprise a diameter between 1 mm to 5 mm.