US20060144712A1

US20060144712A1 - Systems and methods for electrochemically processing microfeature workpieces

Info

Publication number: US20060144712A1
Application number: US11/217,686
Authority: US
Inventors: John Klocke
Original assignee: Semitool Inc
Current assignee: Semitool Inc
Priority date: 2003-12-05
Filing date: 2005-08-31
Publication date: 2006-07-06

Abstract

Systems and methods for electrochemically processing microfeature workpieces are disclosed herein. In one embodiment, a method includes flowing a first processing fluid at least proximate to a processing site in a reaction chamber, flowing a second processing fluid at least proximate to an electrode in the reaction chamber, applying an electrical current to the electrode to establish an electrical current flow in the first and second processing fluids, separating the first processing fluid and the second processing fluid with a barrier, and changing a batch of the first and/or second processing fluid after at least five weeks of normal operation.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation-in-part of (a) U.S. patent application Ser. No. 10/729,349 filed on Dec. 5, 2003; (b) U.S. patent application Ser. No. 10/729,357 filed on Dec. 5, 2003; and (c) U.S. patent application Ser. No. 10/861,899 filed Jun. 3, 2004, which is a continuation-in-part of U.S. application Ser. No. (i) 10/729,349 filed on Dec. 5, 2003 and (ii) Ser. No. 10/729,357 filed on Dec. 5, 2003, all of which are incorporated herein by reference. The present application is also related to U.S. patent application Ser. No. ______ (Perkins Coie Docket No. 291958239US) filed on ______, and entitled SYSTEMS AND METHODS FOR ELECTROCHEMICALLY PROCESSING MICROFEATURE WORKPIECES, which is hereby incorporated by reference in its entirety.

TECHNICAL FIELD

This application relates to systems and methods for electrochemically processing microfeature workpieces having a plurality of microdevices integrated in and/or on the workpiece. The microdevices can include submicron features. Particular aspects of the present invention are directed toward methods for changing the processing fluid in wet chemical processing systems.

BACKGROUND

Microelectronic devices, such as semiconductor devices, imagers and displays, are generally fabricated on and/or in microelectronic workpieces using several different types of machines (“tools”). Many such processing machines have a single processing station that performs one or more procedures on the workpieces. Other processing machines have a plurality of processing stations that perform a series of different procedures on individual workpieces or batches of workpieces. In a typical fabrication process, one or more layers of conductive materials are formed on the workpieces during deposition stages. The workpieces are then typically subject to etching and/or polishing procedures (i.e., planarization) to remove a portion of the deposited conductive layers for forming electrically isolated contacts and/or conductive lines.
Tools that plate metals or other materials onto workpieces are becoming an increasingly useful type of processing machine. Electroplating and electroless plating techniques can be used to deposit copper, solder, permalloy, gold, silver, platinum, electrophoretic resist and other materials onto workpieces for forming blanket layers or patterned layers. A typical copper plating process involves depositing a copper seed layer onto the surface of the workpiece using chemical vapor deposition (CVD), physical vapor deposition (PVD), electroless plating processes, or other suitable methods. After forming the seed layer, a blanket layer or patterned layer of copper is plated onto the workpiece by applying an appropriate electrical potential between the seed layer and an anode in the presence of an electroprocessing solution. The workpiece is then cleaned, etched and/or annealed in subsequent procedures before transferring the workpiece to another processing machine.
Conventional single-wafer processing stations generally include a container for receiving a flow of electroplating solution from a fluid inlet. The processing station can include an anode, a plate-type diffuser having a plurality of apertures, and a workpiece holder for carrying a workpiece. The workpiece holder can include a plurality of electrical contacts for providing electrical current to a seed layer on the surface of the workpiece. When the seed layer is biased with a negative potential relative to the anode, it acts as a cathode. In operation, the electroplating fluid flows around the anode, through the apertures in the diffuser, and against the plating surface of the workpiece. The electroplating solution is an electrolyte that conducts electrical current between the anode and the cathodic seed layer on the surface of the workpiece. Therefore, ions in the electroplating solution plate the surface of the workpiece.
The plating machines used in fabricating microelectronic devices must meet many specific performance criteria. For example, many plating processes must be able to form small contacts in vias or trenches that are less than 0.5 μm wide, and often less than 0.1 μm wide. A combination of organic additives such as “accelerators,” “suppressors,” and “levelers” can be added to the electroplating solution to improve the plating process within the trenches so that the plating metal fills the trenches from the bottom up. As such, maintaining the proper concentration of organic additives in the electroplating solution is important to properly fill very small features.
One drawback of conventional plating processes is that the organic additives decompose and break down proximate to the surface of the anode. Also, as the organic additives decompose, it is difficult to control the concentration of organic additives and their associated breakdown products in the plating solution, which can result in poor feature filling and nonuniform layers. Moreover, the decomposition of organic additives produces byproducts that can cause defects or other nonuniformities. To reduce the rate at which organic additives decompose near the anode, other anodes such as copper-phosphorous anodes can be used.
Another technique to compensate for breakdown products and byproducts in conventional tools is to periodically replace the electroplating solution to provide a fresh solution with an acceptable concentration of byproducts. The electroplating solution is changed in either a batch process in which the entire solution is replaced at one time or a bleed-and-feed process in which a portion of the solution is removed and replenished at a constant rate or periodically. In batch processing, the electroplating solution is typically changed every two to five weeks. Consequently, the composition of the electroplating solution is not consistent over the life of each batch because although organic additives are added to the solution to keep the additives within a desired range, byproducts build up in the solution until the electroplating process is unsustainable. Bleed-and-feed processes typically remove and replenish solution at a constant rate such that a complete volume of the solution is changed every ten to twenty days. Because electroplating solution is constantly being removed and replenished, the solution often remains in a consistent intermediate state with undesirable byproducts.
One drawback of conventional batch and bleed-and-feed processes is that the frequent replacement of electroplating solution (necessitated by byproduct buildup) consumes and wastes large amounts of expensive organic additives. A significant portion of the organic additives are wasted when the solution is changed because both good and decomposed additives are removed with the solution and replaced by new additives in the fresh solution.
Another drawback of conventional plating processes is that organic additives and/or chloride ions in the electroplating solution can passivate and/or consume pure copper anodes. This alters the electrical field, which can result in inconsistent processes and nonuniform layers. One existing approach to inhibit organic additives from contacting and passivating the anode is to place a porous barrier between the workpiece and the anode and flow electroplating solution from the anode toward the workpiece during operation and while the tool is idle. This approach, however, only reduces the number of additives that decompose proximate to the anode surface. The approach also includes using a carbon filter to remove byproducts from the solution proximate to the workpiece. The carbon filter, however, generates particles and removes good organic additives in addition to the decomposed additives. Thus, there is a need to improve the plating process to reduce the adverse effects of the organic additives.

SUMMARY

The present invention is directed toward electrochemical deposition chambers with a barrier between processing fluids to mitigate or eliminate the problems caused by organic additives. The chambers are divided into two distinct systems that interact with each other to electroplate a material onto the workpiece while controlling migration of organic additives in the processing fluids across the barrier to avoid the problems caused by the interaction between the additives and the anode. As such, the barrier prevents organic additives from decomposing proximate to the anode and producing byproducts that interfere with the plating process. Moreover, by reducing the decomposition of organic additives, the barrier increases the life of the processing fluids and, accordingly, reduces the frequency at which the processing fluids need to be replaced. This reduces the downtime of the chamber and the volume of organic additives consumed.
The chambers include a processing unit for providing a first processing fluid to a workpiece (i.e., working electrode), an electrode unit for conveying a flow of a second processing fluid different than the first processing fluid, an electrode (i.e., counter electrode) in the electrode unit, and a barrier between the first and second processing fluids. The barrier can be a porous, permeable member that permits fluid and small molecules to flow through the barrier between the first and second processing fluids. Alternatively, the barrier can be a nonporous, semipermeable member that prevents fluid flow between the first and second processing fluids while allowing ions to pass between the fluids. In either case, the barrier separates and/or isolates components of the first and second processing fluids from each other such that the first processing fluid can have different chemical characteristics than the second processing fluid. For example, the first processing fluid can be a catholyte having organic additives and the second processing fluid can be an anolyte without organic additives or with a much lower concentration of such additives.
The barrier provides several advantages by substantially preventing the organic additives in the catholyte from migrating to the anolyte. First, because the organic additives are inhibited from moving into the anolyte, the additives cannot flow past the anode and decompose into products that interfere with the plating process. Second, because the organic additives do not decompose at the anode, the anode is consumed at a much slower rate in the catholyte so that it is less expensive and easier to control the concentration of organic additives in the catholyte. Third, less expensive anodes, such as pure copper anodes, can be used in the anolyte because the risk of passivation is reduced or eliminated.
The barrier in the chamber provides a system that is significantly more efficient and produces significantly better quality products. The system is more efficient because using one processing fluid for the workpiece and another processing fluid for the electrodes allows the processing fluids to be tailored to the best use in each area without having to compromise to mitigate the adverse effects of using only a single processing solution. As such, the tool does not need to be shut down as often to adjust the fluids, and the tool consumes less organic additives and other bath constituents. The system produces better quality products because using two different processing fluids allows better control of the concentration of important constituents in each processing fluid.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically illustrates a system for wet chemical processing of microfeature workpieces in accordance with one embodiment of the invention.
FIGS. 2A-2H graphically illustrate the relationship between the concentration of hydrogen and copper ions in an anolyte and a catholyte during a plating cycle and while the system of FIG. 1 is idle in accordance with one embodiment of the invention.
FIG. 3 schematically illustrates a system for wet chemical processing of microfeature workpieces in accordance with another embodiment of the invention.

DETAILED DESCRIPTION

As used herein, the terms “microfeature workpiece” or “workpiece” refer to substrates on and/or in which microdevices are 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 in much the same manner as integrated circuits. The substrates can be semiconductive pieces (e.g., silicon wafers or gallium arsenide wafers), nonconductive pieces (e.g., various ceramic substrates), or conductive pieces (e.g., doped wafers). Also, the term electrochemical processing or deposition includes electroplating, electro-etching, anodization, and/or electroless plating.
Several embodiments of electrochemical deposition chambers for processing microfeature workpieces are particularly useful for electrolytically depositing metals or electrophoretic resist in and/or on structures of a workpiece. The deposition chambers in accordance with the invention can accordingly be used in systems for 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 embodiments of wet chemical processing systems including electrochemical deposition chambers are set forth in FIGS. 1-3 and the corresponding text to provide a thorough understanding of particular embodiments of the invention. A person skilled in the art will understand, however, that the invention may have additional embodiments or that the invention may be practiced without several of the details of the embodiments shown in FIGS. 1-3.
A. Embodiments of Wet Chemical Processing Systems
FIG. 1 schematically illustrates a system 100 for electrochemical deposition, electropolishing, or other wet chemical processing of microfeature workpieces. The system 100 includes an electrochemical deposition chamber 102 having a head assembly 104 (shown schematically) and a wet chemical vessel 110 (shown schematically). The head assembly 104 loads, unloads, and positions a workpiece W or a batch of workpieces at a processing site relative to the vessel 110. The head assembly 104 typically includes a workpiece holder having a contact assembly with a plurality of electrical contacts configured to engage a conductive layer on the workpiece W. The workpiece holder can accordingly apply an electrical potential to the conductive layer on the workpiece W. Suitable head assemblies, workpiece holders, and contact assemblies are disclosed in U.S. Pat. Nos. 6,228,232; 6,280,583; 6,303,010; 6,309,520; 6,309,524; 6,471,913; 6,527,925; 6,569,297; 6,773,560; and 6,780,374, all of which are hereby incorporated by reference in their entirety.
The illustrated vessel 110 includes a processing unit 120 (shown schematically), an electrode unit 180 (shown schematically), and a barrier 170 (shown schematically) between the processing and electrode units 120 and 180. The processing unit 120 is configured to contain a first processing fluid for processing the microfeature workpiece W. The electrode unit 180 is configured to contain an electrode 190 and a second processing fluid at least proximate to the electrode 190. The second processing fluid is generally different than the first processing fluid, but they can be the same in some applications. In general, the first and second processing fluids have some ions in common. The first processing fluid in the processing unit 120 is a catholyte and the second processing fluid in the electrode unit 180 is an anolyte when the workpiece is cathodic. In electropolishing or other deposition processes, however, the first processing fluid can be an anolyte and the second processing fluid can be a catholyte.
The system 100 further includes a first flow system 112 that stores and circulates the first processing fluid and a second flow system 192 that stores and circulates the second processing fluid. The first flow system 112 may include (a) a first processing fluid reservoir 113, (b) a plurality of fluid conduits 114 to convey a flow of the first processing fluid between the first processing fluid reservoir 113 and the processing unit 120, and (c) a plurality of components 115 (shown schematically) in the processing unit 120 to convey a flow of the first processing fluid between the processing site and the barrier 170. The second flow system 192 may include (a) a second processing fluid reservoir 193, (b) a plurality of fluid conduits 185 to convey the flow of the second processing fluid between the second processing fluid reservoir 193 and the electrode unit 180, and (c) a plurality of components 184 (shown schematically) in the electrode unit 180 to convey the flow of the second processing fluid between the electrode 190 and the barrier 170.
The barrier 170 is positioned between the first and second processing fluids in the region of the interface between the processing unit 120 and the electrode unit 180 to separate and/or isolate the first processing fluid from the second processing fluid. For example, the barrier 170 can be a porous, permeable membrane that permits fluid and small molecules to flow through the barrier 170 between the first and second processing fluids. Alternatively, the barrier 170 can be a nonporous, semipermeable membrane that prevents fluid flow between the first and second flow systems 112 and 192 while selectively allowing ions, such as cations and/or anions, to pass through the barrier 170 between the first and second processing fluids. In either case, the barrier 170 restricts bubbles, particles, and large molecules such as organic additives from passing between the first and second processing fluids.
Nonporous barriers, for example, can be substantially free of open area. Consequently, fluid is inhibited from passing through a nonporous barrier when the first and second flow systems 112 and 192 operate at typical pressures. Water, however, can be transported through the nonporous barrier via osmosis and/or electro-osmosis. Osmosis can occur when the molar concentrations in the first and second processing fluids are substantially different. Electro-osmosis can occur as water is carried through the nonporous barrier with current-carrying ions in the form of a hydration sphere. When the first and second processing fluids have similar molar concentrations and no electrical current is passed through the processing fluids, fluid flow between the first and second processing fluids is substantially prevented.
The illustrated barrier 170 can also be hydrophilic so that bubbles in the processing fluids do not cause portions of the barrier 170 to dry, which reduces conductivity through the barrier 170. Suitable materials for permeable barriers include polyethersulfone, Gore-tex, Teflon coated woven filaments, polypropylene, glass fritz, silica gels, and other porous polymeric materials. Suitable membrane type (i.e., semipermeable) barriers 170 include NAFION membranes manufactured by DuPont°, Ionac® membranes manufactured by Sybron Chemicals Inc., and NeoSepta membranes manufactured by Tokuyuma.
When the system 100 is used for electrochemical processing, an electrical potential can be applied to the electrode 190 and the workpiece W such that the electrode 190 is an anode and the workpiece W is a cathode. The first and second processing fluids are accordingly a catholyte and an anolyte, respectively, and each fluid can include a solution of metal ions to be plated onto the workpiece W. The electrical field between the electrode 190 and the workpiece W may drive positive ions through the barrier 170 from the anolyte to the catholyte, or drive negative ions in the opposite direction. In plating applications, an electrochemical reaction occurs at the microfeature workpiece W in which metal ions are reduced to form a solid layer of metal on the microfeature workpiece W. In electrochemical etching and other electrochemical applications, the electrical field may drive ions in the opposite direction.
One feature of the system 100 illustrated in FIG. 1 is that the barrier 170 separates the first processing fluid in the first flow system 112 from the second processing fluid in the second flow system 192, but allows ions and/or small molecules, depending on the type of barrier 170, to pass between the first and second processing fluids. As such, the fluid in the processing unit 120 can have different chemical and/or physical characteristics than the fluid in the electrode unit 180. For example, the first processing fluid can be a catholyte having organic additives and the second processing fluid can be an anolyte without organic additives or with a much lower concentration of such additives. As explained above in the summary section, the lack of organic additives in the anolyte provides the following advantages: (a) reduces byproducts of decomposed organics in the catholyte; (b) reduces consumption of the organic additives; (c) reduces passivation of the anode; and (d) enables efficient use of pure copper anodes.
The illustrated system 100 further includes a chemical management system 130 (shown schematically) for controlling the composition of the first and second processing fluids and a controller 140 (shown schematically) for operating the chemical management system 130. The chemical management system 130 can be operably coupled to (a) the processing unit 120 and/or the first processing fluid reservoir 113 for monitoring and controlling the concentrations of individual constituents in the first processing fluid, and/or (b) the electrode unit 180 and/or the second processing fluid reservoir 193 for monitoring and controlling the concentrations of individual constituents in the second processing fluid. The chemical management system 130, for example, can add and/or remove individual organic additives, metals, and/or water from the first and/or second processing fluid based on the composition of the fluid or other parameters. In several embodiments, when the anolyte lacks organic additives, the chemical management system 130 may need to add only water to the anolyte. The chemical management system 130 may also need to periodically (a) add organic additives to the catholyte, and (b) add and/or remove water from the catholyte.
The illustrated chemical management system 130 can also replace the first and/or second processing fluid after a predetermined period of time or after the concentration of byproducts in the fluid exceeds a threshold. For example, in one embodiment, the chemical management system 130 replaces a batch of the first and/or second processing fluid after five weeks of normal operation. In one aspect of this embodiment, the chemical management system 130 changes the batch of the first and/or second processing fluid after six weeks. In a further aspect of this embodiment, the system 130 changes the batch of the first and/or second processing fluid after two months. In a further aspect of this embodiment, the system 130 changes the batch of the first and/or second processing fluid after three months. In a further aspect of this embodiment, the system 130 changes the batch of the first and/or second processing fluid after six months. In a further aspect of this embodiment, the system 130 changes the batch of the first and/or second processing fluid after one year.
The chemical management system 130 can also replace the first and/or second processing fluid by removing and replenishing the fluid at a specific rate. For example, in one embodiment, the chemical management system 130 bleeds-and-feeds the first and/or second processing fluid at a rate of less than five percent of the corresponding fluid volume per day. In one aspect of this embodiment, the chemical management system 130 bleeds-and-feeds the first and/or second processing fluid at a rate of three percent or less of the corresponding fluid volume per day. In several embodiments, the chemical management system 130 removes and replenishes ten liters or less of the first and/or second processing fluid per day. In one aspect of these embodiments, the chemical management system 130 removes and replenishes five liters or less of the first and/or second processing fluid per day. In a further aspect of these embodiments, the chemical management system 130 removes and replenishes one liter or less of the first and/or second processing fluid per day. In additional embodiments, the chemical management system 130 may remove and replenish a volume of fluid sufficient only for analysis purposes.
One feature of the system 100 illustrated in FIG. 1 is that separation of the first and second processing fluids extends the useful life of the fluids. For example, in several embodiments, the anolyte can be replaced less frequently because the anolyte lacks organic additives that decompose into byproducts. The catholyte includes organic additives, however, the decomposition rate of the additives in the catholyte is reduced because the additives are separated from the anode. Accordingly, the catholyte and anolyte can be replaced less frequently, which reduces the downtime of the system 100 and the volume of good additives wasted when the fluid is changed.
The system 100 illustrated in FIG. 1 is also particularly efficacious in maintaining the desired concentration of copper ions or other metal ions in the first processing fluid. During the electroplating process, it is desirable to accurately control the concentration of materials in the first processing fluid to ensure consistent, repeatable depositions on a large number of individual microfeature workpieces. For example, when copper is deposited on the workpiece W, it is desirable to maintain the concentration of copper in the first processing fluid (e.g., the catholyte) within a desired range to deposit a suitable layer of copper on the workpiece W. This aspect of the system 100 is described in more detail below.
To control the concentration of metal ions in the first processing solution in some electroplating applications, the system 100 illustrated in FIG. 1 uses characteristics of the barrier 170, the volume of the first flow system 112, the volume of the second flow system 192, and the different acid concentrations in the first and second processing solutions. In general, the concentration of acid in the first processing fluid is greater than the concentration of acid in the second processing fluid, and the volume of the first processing fluid in the system 100 is greater than the volume of the second processing fluid in the system 100. As explained in more detail below, these features work together to maintain the concentration of the constituents in the first processing fluid within a desired range to ensure consistent and uniform deposition on the workpiece W. For purposes of illustration, the effect of increasing the concentration of acid in the first processing fluid will be described with reference to an embodiment in which copper is electroplated onto a workpiece. One skilled in the art will recognize that different metals can be electroplated and/or the principles can be applied to different wet chemical processes in other applications. In additional embodiments, however, the concentration of acid in the first processing fluid may not be greater than the concentration of acid in the second processing fluid, and/or the volume of the first processing fluid may not be greater than the volume of the second processing fluid.
FIGS. 2A-2H graphically illustrate the relationship between the concentrations of hydrogen and copper ions in the anolyte and catholyte during a plating cycle and while the system 100 is idle. FIGS. 2A and 2B show the concentration of hydrogen ions in the second processing fluid (anolyte) and the first processing fluid (catholyte), respectively, during a plating cycle. The electrical field readily drives hydrogen ions across the barrier 170 (FIG. 1) from the anolyte to the catholyte during the plating cycle. Consequently, the concentration of hydrogen ions decreases in the anolyte and increases in the catholyte. As measured by percent concentration change or molarity, the decrease in the concentration of hydrogen ions in the anolyte is generally significantly greater than the corresponding increase in the concentration of hydrogen ions in the catholyte because: (a) the volume of catholyte in the illustrated system 100 is greater than the volume of anolyte; and (b) the concentration of hydrogen ions in the catholyte is much higher than in the anolyte.
FIGS. 2C and 2D graphically illustrate the concentration of copper ions in the anolyte and catholyte during the plating cycle. During the plating cycle, the anode replenishes copper ions in the anolyte and the electrical field drives the copper ions across the barrier 170 from the anolyte to the catholyte. Thus, as shown in FIG. 2C, the concentration of copper ions in the anolyte increases during the plating cycle. Conversely, in the catholyte cell, FIG. 2D shows that the concentration of copper ions in the catholyte initially decreases during the plating cycle as the copper ions are consumed to form a layer on the microfeature workpiece W.
FIGS. 2E-2H graphically illustrate the concentration of hydrogen and copper ions in the anolyte and the catholyte while the system 100 of FIG. 1 is idle. For example, FIGS. 2E and 2F illustrate that the concentration of hydrogen ions increases in the anolyte and decreases in the catholyte while the system 100 is idle because the greater concentration of acid in the catholyte drives hydrogen ions across the barrier 170 to the anolyte. FIGS. 2G and 2H graphically illustrate that the concentration of copper ions decreases in the anolyte and increases in the catholyte while the system 100 is idle. The movement of hydrogen ions into the anolyte creates a charge imbalance that drives copper ions from the anolyte to the catholyte.
One feature of the embodiment illustrated in FIG. 1 is that when the system 100 is idle, the catholyte is replenished with copper because of the difference in the concentration of acid in the anolyte and catholyte. An advantage of this feature is that the desired concentration of copper in the catholyte can be maintained while the system 100 is idle. Another advantage of this feature is that the increased movement of copper ions across the barrier 170 prevents saturation of the anolyte with copper, which can cause passivation of the anode and/or the formation of salt crystals.
The foregoing operation of the system 100 shown in FIG. 1 occurs, in part, by selecting suitable concentrations of hydrogen ions (i.e., acid protons) and copper. In several useful processes for depositing copper, the acid concentration in the first processing fluid can be from approximately 10 g/l to approximately 200 g/l, and the acid concentration in the second processing fluid can be from approximately 0.1 g/l to approximately 1.0 g/l. Alternatively, the acid concentration of the first and/or second processing fluid can be outside of these ranges. For example, the first processing fluid can have a first concentration of acid and the second processing fluid can have a second concentration of acid less than the first concentration. The ratio of the first concentration of acid to the second concentration of acid, for example, can be from approximately 10:1 to approximately 20,000:1. The concentration of copper is also a parameter. For example, in many copper plating applications, the first and second processing fluids can have a copper concentration of between approximately 10 g/l and approximately 50 g/l. Although the foregoing ranges are useful for many applications, it will be appreciated that the first and second processing fluids can have other concentrations of copper and/or acid.
In other embodiments, the barrier can be anionic and the electrode can be an inert anode (i.e. platinum or iridium oxide) to prevent the accumulation of sulfate ions in the first processing fluid. In this embodiment, the acid concentration or pH in the first and second processing fluids can be similar. Alternatively, the second processing fluid may have a higher concentration of acid to increase the conductivity of the fluid. Copper salt (copper sulfate) can be added to the first processing fluid to replenish the copper in the fluid. Electrical current can be carried through the barrier by the passage of sulfate anions from the first processing fluid to the second processing fluid. Therefore, sulfate ions are less likely to accumulate in the first processing fluid where they can adversely affect the deposited film.
In other embodiments, the system can electrochemically etch copper from the workpiece. In these embodiments, the first processing solution (the anolyte) contains an electrolyte that may include copper ions. During electrochemical etching, an electrical potential can be applied to the electrode and/or the workpiece. An anionic barrier can be used to prevent positive ions (such as copper) from passing into the second processing fluid (catholyte). Consequently, the current is carried by anions, and copper ions are inhibited from flowing proximate to and being deposited on the electrode.
The foregoing operation of the illustrated system 100 also occurs by selecting suitable volumes of anolyte and catholyte. Another feature of the embodiment illustrated in FIG. 1 is that the system 100 has (a) a first volume of the first processing fluid in the first flow system 112 and the first processing fluid reservoir 113, and (b) a second volume of the second processing fluid in the second flow system 192 and the second processing fluid reservoir 193. The ratio between the first volume and the second volume can be from approximately 1.5:1 to 20:1, and in many applications is approximately 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1 or 10:1. The difference in volume of the first and second processing fluids moderates the change in the concentration of materials in the first processing fluid. For example, as described above with reference to FIGS. 2A and 2B, when hydrogen ions move from the anolyte to the catholyte, the percentage change in the concentration of hydrogen ions in the catholyte is less than the change in the concentration of hydrogen ions in the anolyte because the volume of catholyte is greater than the volume of anolyte. In other embodiments, the first and second volumes can be approximately the same.
B. Additional Embodiments of Wet Chemical Processing Systems
FIG. 3 schematically illustrates a system 200 for wet chemical processing of microfeature workpieces in accordance with another embodiment of the invention. The system 200 is generally similar to the system 100 described above with reference to FIG. 1. For example, the illustrated system 200 includes an electrochemical deposition chamber 202, a first processing fluid reservoir 113, a second processing fluid reservoir 193, and a chemical management system 130 for monitoring and controlling the individual constituents of the first and/or second processing fluid.
The deposition chamber 202 has a wet chemical vessel 210 (shown schematically) with a processing unit 220 (shown schematically), an electrode unit 280 (shown schematically), and a barrier 170 (shown schematically) between the processing and electrode units 220 and 280. The processing unit 220 of the illustrated embodiment includes a dielectric divider 242 projecting from the barrier 170 toward the processing site and a plurality of chambers 215 (identified individually as 215 a-b) defined by the dielectric divider 242. The chambers 215 a-b can be arranged concentrically and have corresponding openings 244 a-b proximate to the processing site. The chambers 215 a-b are configured to convey the first processing fluid to/from the microfeature workpiece W. In other embodiments, the processing unit 220 may not include the dielectric divider 242 and the chambers 215, or the dielectric divider 242 and the chambers 215 may have other configurations.
The illustrated electrode unit 280 includes a dielectric divider 286, a plurality of compartments 284 (identified individually as 284 a-b) defined by the dielectric divider 286, and a plurality of electrodes 290 (identified individually as 290 a-b) disposed within corresponding compartments 284. The compartments 284 can be arranged concentrically and configured to convey the second processing fluid at least proximate to the electrodes 290. Although the illustrated system 200 includes two concentric electrodes 290, in other embodiments, systems can include a different number of electrodes and/or the electrodes can be arranged in a different configuration.
When the system 200 is used for electrochemical processing, an electrical potential can be applied to the electrodes 290 and the workpiece W such that the electrodes 290 are anodes and the workpiece W is a cathode. The first electrode 290 a provides an electrical field to the workpiece W at the processing site through the portion of the second processing fluid in the first compartment 284 a of the electrode unit 280 and the portion of the first processing fluid in the first chamber 230 a of the processing unit 220. Accordingly, the first electrode 290 a provides an electrical field that is effectively exposed to the processing site via the first opening 244 a. The first opening 244 a shapes the electrical field of the first electrode 290 a to create a “virtual electrode” at the top of the first opening 244 a. This is a “virtual electrode” because the dielectric divider 242 shapes the electrical field of the first electrode 290 a so that the effect is as if the first electrode 290 a were placed in the first opening 244 a. Virtual electrodes are described in detail in U.S. patent application Ser. No. 09/872,151, which is hereby incorporated by reference in its entirety. Similarly, the second electrode 290 b provides an electrical field to the workpiece W through the portion of the second processing fluid in the second compartment 284 b of the electrode unit 280 and the portion of the first processing fluid in the second chamber 230 b of the processing unit 220. Accordingly, the second electrode 290 b provides an electrical field that is effectively exposed to the processing site via the second opening 244 b to create another “virtual electrode.”
In operation, a first current is applied to the first electrode 290 a and a second current is applied to the second electrode 290 b. The first and second electrical currents are controlled independently of each other such that they can be the same or different than each other at any given time. Additionally, the first and second electrical currents can be dynamically varied throughout a plating cycle. The first and second electrodes 290 a-b accordingly provide a highly controlled electrical field to compensate for inconsistent or non-uniform seed layers as well as changes in the plated layer during a plating cycle.
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. Accordingly, the invention is not limited except as by the appended claims.

Claims

1. A method of electrochemically processing microfeature workpieces, the method comprising:

flowing a first processing fluid at least proximate to a processing site in a reaction chamber;

flowing a second processing fluid at least proximate to an electrode in the reaction chamber;

applying an electrical current to the electrode to establish an electrical current flow in the first and second processing fluids;

separating the first processing fluid and the second processing fluid with a barrier; and

changing a batch of the first and/or second processing fluid after at least five weeks of normal operation.

2. The method of claim 1 wherein changing the batch of the first and/or second processing fluid comprises replacing the batch of the first and/or second processing fluid after at least two months of normal operation.

3. The method of claim 1 wherein changing the batch of the first and/or second processing fluid comprises replacing the batch of the first and/or second processing fluid after at least three months of normal operation.

4. The method of claim 1 wherein changing the batch of the first and/or second processing fluid comprises replacing the batch of the first and/or second processing fluid after at least six months of normal operation.

5. The method of claim 1 wherein changing the batch of the first and/or second processing fluid comprises replacing the batch of the first and/or second processing fluid after at least one year of normal operation.

6. The method of claim 1 wherein changing the batch of the first and/or second processing fluid comprises replacing the batch of the first processing fluid after at least five weeks of normal operation.

7. The method of claim 1 wherein separating the first and second processing fluids comprises inhibiting organic additives from passing between the first and second processing fluids with a porous barrier.

8. The method of claim 1 wherein separating the first and second processing fluids comprises separating the flow of the first processing fluid from the flow of the second processing fluid with a semipermeable barrier.

9. The method of claim 1 wherein separating the first and second processing fluids comprises separating the flows of the first and second processing fluids with a nonporous barrier configured to allow either cations or anions to pass through the barrier between the first and second processing fluids.

10. The method of claim 1 wherein:

flowing the first processing fluid comprises flowing a catholyte having a concentration of between approximately 10 g/l and approximately 200 g/l of acid; and

flowing the second processing fluid comprises flowing an anolyte having a concentration of between approximately 0.1 g/l and approximately 1.0 g/l of acid.

11. The method of claim 1 wherein:

flowing the first processing fluid comprises flowing a catholyte having a first concentration of acid; and

flowing the second processing fluid comprises flowing an anolyte having a second concentration of acid, the ratio of the first concentration of acid to the second concentration of acid being between approximately 10:1 and approximately 20,000:1.

12. The method of claim 1 wherein:

flowing the second processing fluid comprises flowing the second processing fluid at least proximate to a plurality of electrodes in the reaction chamber; and

applying the electrical current comprises applying electrical potentials to individual electrodes to establish the electrical current flow in the first and second processing fluids.

13. A method of operating a system for depositing material onto microfeature workpieces, the method comprising:

processing a plurality of microfeature workpieces in an electrochemical deposition chamber, the deposition chamber comprising (a) a processing unit including a first flow system configured to convey a flow of a first processing fluid to the microfeature workpieces, (b) an electrode unit coupled to the processing unit, the electrode unit including a plurality of electrode compartments, a plurality of electrodes in corresponding compartments, and a second flow system configured to convey a flow of a second processing fluid proximate to the electrodes, and (c) a barrier between the processing unit and the electrode unit to inhibit selected matter from passing between the first and second processing fluids; and

replacing a batch of the first and/or second processing fluid after not less than six weeks of processing.

14. The method of claim 13 wherein replacing the batch of the first and/or second processing fluid comprises changing the batch of the first and/or second processing fluid after not less than two months of processing.

15. The method of claim 13 wherein replacing the batch of the first and/or second processing fluid comprises changing the batch of the first and/or second processing fluid after not less than three months of processing.

16. The method of claim 13 wherein replacing the batch of the first and/or second processing fluid comprises changing the batch of the first and/or second processing fluid after not less than six months of processing.

17. The method of claim 13 wherein replacing the batch of the first and/or second processing fluid comprises changing the batch of the first and/or second processing fluid after not less than one year of processing.

18. The method of claim 13 wherein the barrier comprises a porous barrier.

19. The method of claim 13 wherein the barrier comprises a semipermeable barrier.

20. A method of electrochemically processing microfeature workpieces, the method comprising:

flowing a first processing fluid at least proximate to a microfeature workpiece in a reaction chamber;

selectively applying an electrical current to the electrode to establish an electrical current flow in the first and second processing fluids;

removing and replenishing the first and/or second processing fluid at a rate of less than five percent of the corresponding fluid volume per day.

21. The method of claim 20 wherein removing and replenishing the first and/or second processing fluid comprises bleeding and feeding the first and/or second processing fluid at a rate of three percent or less of the corresponding fluid volume per day.

22. The method of claim 20 wherein removing and replenishing the first and/or second processing fluid comprises bleeding and feeding ten liters or less of the first and/or second processing fluid per day.

23. The method of claim 20 wherein removing and replenishing the first and/or second processing fluid comprises bleeding and feeding five liters or less of the first and/or second processing fluid per day.

24. The method of claim 20 wherein removing and replenishing the first and/or second processing fluid comprises bleeding and feeding one liter or less of the first and/or second processing fluid per day.

25. The method of claim 20 wherein removing and replenishing the first and/or second processing fluid comprises analyzing the removed first and/or second processing fluid.

26. The method of claim 20 wherein separating the first and second processing fluids comprises inhibiting organic additives from passing between the first and second processing fluids with a porous barrier.

27. The method of claim 20 wherein separating the first and second processing fluids comprises separating the flow of the first processing fluid from the flow of the second processing fluid with a semipermeable barrier.

28. The method of claim 20 wherein separating the first and second processing fluids comprises separating the flows of the first and second processing fluids with a nonporous barrier configured to allow either cations or anions to pass through the barrier between the first and second processing fluids.

29. The method of claim 20 wherein:

30. The method of claim 20 wherein:

31. The method of claim 20 wherein:

selectively applying the electrical current comprises applying electrical potentials to individual electrodes to establish the electrical current flow in the first and second processing fluids.

32. A method of operating a system for depositing material onto microfeature workpieces, the method comprising:

removing and replenishing four percent or less of the first and/or second processing fluid per day during processing.

33. The method of claim 32 wherein removing and replenishing the first and/or second processing fluid comprises bleeding and feeding three percent or less of the first and/or second processing fluid per day.

34. The method of claim 32 wherein removing and replenishing the first and/or second processing fluid comprises bleeding and feeding ten liters or less of the first and/or second processing fluid per day.

35. The method of claim 32 wherein removing and replenishing the first and/or second processing fluid comprises bleeding and feeding five liters or less of the first and/or second processing fluid per day.

36. The method of claim 32 wherein removing and replenishing the first and/or second processing fluid comprises bleeding and feeding one liter or less of the first and/or second processing fluid per day.

37. The method of claim 32 wherein the barrier comprises a porous barrier.

38. The method of claim 32 wherein the barrier comprises a semipermeable barrier.

39. A system for wet chemical processing of microfeature workpieces, the system comprising:

a processing unit including a first flow system for conveying a flow of a first processing fluid to a microfeature workpiece;

an electrode unit coupled to the processing unit, the electrode unit including an electrode and a second flow system for conveying a flow of a second processing fluid proximate to the electrode;

a barrier between the processing unit and the electrode unit to inhibit selected matter from passing between the first and second processing fluids; and

a controller operably coupled to the processing and/or electrode unit, the controller having a computer-readable medium containing instructions to perform a method comprising—

flowing the first processing fluid at least proximate to the microfeature workpiece;

flowing the second processing fluid at least proximate to the electrode;

applying an electrical current to the electrode to establish an electrical current flow in the first and second processing fluids; and

40. The system of claim 39 wherein the computer-readable medium instruction changing the batch of the first and/or second processing fluid comprises replacing the batch of the first and/or second processing fluid after at least two months of normal operation.

41. The system of claim 39 wherein the computer-readable medium instruction changing the batch of the first and/or second processing fluid comprises replacing the batch of the first and/or second processing fluid after at least three months of normal operation.

42. The system of claim 39 wherein the computer-readable medium instruction changing the batch of the first and/or second processing fluid comprises replacing the batch of the first and/or second processing fluid after at least six months of normal operation.

43. The system of claim 39 wherein the computer-readable medium instruction changing the batch of the first and/or second processing fluid comprises replacing the batch of the first and/or second processing fluid after at least one year of normal operation.

44. The system of claim 39 wherein the barrier comprises a semipermeable barrier that allows either cations or anions to pass through the barrier between the first and second processing fluids.

45. A system for wet chemical processing of microfeature workpieces, the system comprising:

an electrode unit coupled to the processing unit, the electrode unit including a plurality of electrode compartments, a plurality of electrodes in corresponding compartments, and a second flow system for conveying a flow of a second processing fluid proximate to the electrodes;

a barrier between the processing unit and the electrode unit to separate the first and second processing fluids; and

processing a plurality of microfeature workpieces in the processing unit; and

46. A system for wet chemical processing of microfeature workpieces, the system comprising:

flowing the second processing fluid at least proximate to the electrode;

selectively applying an electrical current to the electrode to establish an electrical current flow in the first and second processing fluids; and

47. A system for wet chemical processing of microfeature workpieces, the system comprising:

processing a plurality of microfeature workpieces in the processing unit; and