Removal of by-products from electroplating solutions

Abstract

Systems and methods for electroplating are provided. The electroplating system may include an electroplating tank configured to contain an anode and an electroplating solution, a wafer holder configured to support a wafer in the electroplating tank, a reservoir configured to contain at least a portion of the electroplating solution, a recirculation flow path fluidly connecting the reservoir and the electroplating tank, wherein the recirculation flow path includes a pump and is configured to circulate the electroplating solution between the reservoir and the electroplating tank, and a bubbler fluidly connected to one or more of the electroplating tank, the reservoir, and the recirculation flow path. The bubbler may be configured to generate bubbles in the electroplating solution when the electroplating solution is present in the electroplating system, interfaces with the bubbler, and the bubbler is activated.

Description

[0001] Incorporate by reference

[0002] The PCT request form is filed concurrently with this specification as a part of this application. Each application for which this application claims the benefit or priority of an application identified in a concurrently filed PCT request form is hereby incorporated by reference in its entirety and for all purposes. Background Art

[0003] Electrochemical deposition processes are widely used in the semiconductor industry for metallization in integrated circuit manufacturing. One such application is copper (Cu) electrochemical deposition, which may involve depositing copper lines into trenches and / or vias preformed in a dielectric layer. In this process, a thin adherent metal diffusion barrier film is pre-deposited onto the surface using physical vapor deposition (PVD) or chemical vapor deposition (CVD). A thin copper seed layer is then deposited on top of the barrier layer, typically by a PVD deposition process. The features (vias and trenches) are then electrochemically filled with copper by an electrochemical deposition process, during which the copper anions are electrochemically reduced to copper metal. Summary of the invention

[0004] Details of one or more implementations of the subject matter described in this specification are set forth in the accompanying drawings and the following description. Other features, aspects, and advantages will become apparent from the specification, drawings, and claims. The following non-limiting embodiments are considered part of this disclosure; other embodiments will also be apparent from the entirety of this disclosure and the drawings.

[0005] In some embodiments, an electroplating system may be provided. The electroplating system may include an electroplating tank configured to contain an anode and an electroplating solution, a wafer holder configured to support a wafer within the electroplating tank, a reservoir configured to contain at least a portion of the electroplating solution, a recirculation flow path fluidly connecting the reservoir and the electroplating tank, and the recirculation flow path includes a pump and is configured to circulate the electroplating solution between the reservoir and the electroplating tank, and a bubbler fluidly connected to one or more of the electroplating tank, the reservoir, and the recirculation path, wherein the bubbler is configured to generate bubbles in the electroplating solution when the electroplating solution is present in the electroplating system, interfaces with the bubbler, and the bubbler is activated.

[0006] In some embodiments, the bubbler may include at least one of an aeration stone, one or more jets, one or more nozzles, a propeller, or an impeller.

[0007] In any of the above embodiments, the bubbler may include an aeration stone, and the aeration stone may be constructed of a material that is compatible with the electroplating solution.

[0008] In any of the above embodiments, the material may include one or more of high density polyethylene (HDPE), polypropylene (PP), and polytetrafluoroethylene (PTFE).

[0009] In any of the above embodiments, the material may have a porosity between about 1 millimeter and about 1 micron.

[0010] In any of the above embodiments, the electroplating system may further include a gas source fluidly connected to the bubbler and configured to flow gas toward the aeration stone.

[0011] In any of the above embodiments, the electroplating system may further include a container, and the container may be fluidly connected to one or more of the electroplating tank, the reservoir, or the recirculation flow path, and the container may be configured to receive and hold a first volume of the electroplating solution. The bubbler may also be configured to generate bubbles in the electroplating solution in the container when the container holds the first volume of the electroplating solution and the bubbler is activated.

[0012] In any of the above embodiments, the electroplating system may further include a foam generating unit including a container and a bubbler, and the foam generating unit may be fluidly connected to one or more of the electroplating tank, the reservoir, or the recirculation flow path.

[0013] In any of the above embodiments, the container can be physically separate from but fluidly connected to one or more of the plating tank, the reservoir, or the recirculating flow path.

[0014] In any of the above embodiments, the container can be at least partially positioned in one of the plating tank, the reservoir, or the recirculation flow path.

[0015] In any of the above embodiments, the container can be fluidly positioned between the plating tank and the reservoir.

[0016] In any of the above embodiments, the container may further include a foam outlet configured to allow foam in the container to exit the container through the foam outlet.

[0017] In any of the above embodiments, the container may include a fluid outlet, and the foam outlet may be at a height higher than the fluid outlet.

[0018] In any of the above embodiments, the container may include a fluid inlet, and the foam outlet may be at a height higher than the fluid inlet.

[0019] In any of the above embodiments, the electroplating system may further include a foam moving unit configured to move foam in the container out of the container when the foam is in the container and when the foam moving unit is activated.

[0020] In any of the above embodiments, the foam movement unit includes one or more of a fan, a skimmer, and a vacuum pump.

[0021] In any of the above embodiments, the electroplating system may further include a controller configured to control the bubbler, the controller including control logic for causing the electroplating solution to flow into and be contained in the container, and causing the bubbler to generate bubbles in the electroplating solution in the container.

[0022] In any of the above embodiments, the electroplating system may further include one or more inlet valves configured to control the flow of the electroplating solution into the container. The controller may also be configured to control the one or more inlet valves, and the controller may further include control logic for causing the one or more inlet valves to open to allow the electroplating solution to flow into the container.

[0023] In any of the above embodiments, the system may be further configured to allow the electroplating solution to flow into and out of the container through a common flow path, and one or more inlet valves may be configured to control the flow of the electroplating solution into the container through the common flow path. The one or more inlet valves may also be configured to also control the flow of the electroplating solution out of the container through the common flow path, and the controller may further include control logic for closing the one or more inlet valves to allow the container to contain the electroplating solution in the container.

[0024] In any of the above embodiments, the electroplating system may further include one or more outlet valves configured to control the flow of the electroplating solution out of the container. The controller may be further configured to control the one or more outlet valves, and the controller may further include control logic for closing the one or more outlet valves to allow the container to contain the electroplating solution in the container, and opening the one or more outlet valves to allow the electroplating solution to flow out of the container.

[0025] In any of the above embodiments, the electroplating system can be configured to hold a total working volume of the electroplating solution, and the container can be configured to hold up to 5% of the total working volume of the electroplating solution.

[0026] In any of the above embodiments, the electroplating system may also include a controller configured to control a bubbler, and the controller may include control logic for causing the bubbler to generate bubbles in the electroplating solution during one or more time periods when the electroplating solution is present in the electroplating system and interfaces with the bubbler.

[0027] In any of the above embodiments, the controller may further include control logic for causing the bubbler to generate bubbles in the electroplating solution when the electroplating solution is present in the electroplating system and interfaces with the bubbler for a first time period, and causing the bubbler to repeatedly generate bubbles at a first time interval.

[0028] In any of the above embodiments, the electroplating system may further include a power supply electrically connected to the wafer support and the electroplating tank. The power supply may be configured to apply a voltage to the wafer held by the wafer support, and the controller further includes control logic for causing the power supply to apply a current to the wafer held by the wafer support and the electroplating tank, and measuring a voltage potential between the wafer and the electroplating tank. Causing the bubbler to generate bubbles in the electroplating solution may further be based at least in part on the measured voltage.

[0029] In any of the above embodiments, the controller may further include control logic for determining a change in voltage potential between the wafer and the plating bath, and causing the bubbler to generate bubbles in the plating solution may be further based, at least in part, on the determined change in voltage potential.

[0030] In any of the above embodiments, the electroplating system may further include a controller configured to control the bubbler, and the controller may include control logic for causing the bubbler to continuously generate bubbles in the electroplating solution during wafer electroplating.

[0031] In some embodiments, an electroplating method may be provided. The method may include providing an electroplating solution to an electroplating system, the electroplating system including an electroplating tank configured to contain an anode and an electroplating solution, a wafer support configured to support a wafer using the electroplating tank, and a reservoir configured to contain at least a portion of the electroplating solution. Using a bubbler, bubbling an electroplating fluid by generating bubbles in the electroplating solution to generate foam; and removing the foam from the electroplating system.

[0032] In any of the above embodiments, bubbling may reduce the amount of leveler from the electroplating solution.

[0033] In any of the above embodiments, the foam may include a leveler from the electroplating solution.

[0034] In any of the above embodiments, bubbling may further include flowing the gas toward an aeration stone in the bubbler.

[0035] In any of the above embodiments, the gas may include nitrogen.

[0036] In any of the above embodiments, bubbling can further include agitating the electroplating solution with at least one of one or more jets, one or more nozzles, a propeller, and an impeller.

[0037] In any of the above embodiments, the method may further include flowing the electroplating solution into a container, wherein bubbling occurs in the container, and after bubbling, flowing the electroplating solution from the container to one or more of a reservoir and a plating tank.

[0038] In any of the above embodiments, the method may further include containing a first volume of the electroplating solution in the container during at least the bubbling period.

[0039] In any of the above embodiments, the method may further include causing the foam generated in the container to flow out of the container at least during the frothing period.

[0040] In any of the above embodiments, the method may further include interfacing the electroplating solution with a bubbler.

[0041] In any of the above embodiments, the method may further include electroplating the wafer, and the blistering and the removal may be performed continuously during the electroplating process. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Various embodiments disclosed herein are illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings in which like reference numerals refer to similar elements.

[0043] Figure 1 A first example electroplating system is depicted.

[0044] Figure 2 Depicted Figure 1 A first example system is shown with a schematic cross-sectional view of an electroplating tank.

[0045] Figure 3A A first example foam generating unit is depicted and Figure 3B A second example foam generating unit is depicted.

[0046] Figures 4A to 4E Various example configurations of electroplating systems having separate foam generating units are depicted.

[0047] Figure 5 A first example technique for bubbling an electroplating solution is depicted.

[0048] Figure 6 A second example technique for bubbling the electroplating solution is depicted.

[0049] Figure 7 Describes something like Figure 5 A third technique for bubbling electroplating solutions is described.

[0050] Figure 8 A fourth example technique for bubbling an electroplating solution is depicted.

[0051] Fig. 9 Plotted are through-wafer bump height maps for two electroplating processes.

[0052] Fig. 10A Plotting the recovery time graph for two plating solutions, Fig. 10B Depicted are cross-sectional side views of vias on two wafers. DETAILED DESCRIPTION

[0053] In the following description, numerous specific details are set forth in order to provide a thorough understanding of the embodiments presented. The disclosed embodiments may be practiced without some or all of these specific details. In other cases, well-known process operations are not described in detail to avoid unnecessarily obscuring the disclosed embodiments. Although the disclosed embodiments will be described in conjunction with specific embodiments, it should be understood that they are not intended to limit the disclosed embodiments.

[0054] Introduction and Background

[0055] The manufacture of semiconductor devices often requires the deposition of conductive materials on semiconductor wafers. Conductive materials, such as copper, are often deposited by electroplating onto a metal seed layer that is deposited on the surface of the wafer by various methods, such as physical vapor deposition (PVD) or chemical vapor deposition (CVD). Electroplating is often used to deposit metal into vias and trenches of processed wafers during damascene and dual damascene processes.

[0056] Electroplating is typically performed in a plating bath where the semiconductor wafer is immersed in a plating solution. During the process of plating the wafer, various byproducts and other materials are generated in the plating solution. In conventional electroplating systems, these byproducts and other materials are typically removed using a "drain and feed" technique where the plating solution is replenished with fresh solution and the old solution is disposed of or reconstituted. While it is often desirable to renew a small portion of the solution via the drain and feed method, this is not an economically viable approach for some byproducts and other materials.

[0057] Electroplating processes and equipment are typically executed and designed to minimize and eliminate any bubble formation in the plating system. Many plating solution foams tend to dry on areas of the plating system, such as reservoir walls and features of the plating cell, and condense into crystals (copper sulfate tends to crystallize easily), which can re-enter the plating solution as unwanted particulate contamination of the system, or can be reintroduced and dissolved into the solution, all of which can negatively impact the electroplating. Therefore, electroplating equipment is typically designed to avoid or minimize the generation of bubbles / foam in the plating solution.

[0058] Some electroplating processes produce byproducts in the electroplating solution that negatively impact the electroplating process, and removal of the byproducts requires high, unacceptably high bleed and feed rates to maintain acceptable solution concentrations, which results in large amounts of solution being wasted, leading to high operating costs for the electroplating equipment.

[0059] Described herein are apparatus and techniques for removing unwanted chemical components (e.g., byproducts) from electroplating solutions by bubbling the electroplating solution to produce a foam that captures the unwanted components, and then removing the foam to remove the unwanted components from the electroplating solution. These electroplating systems include a bubbler that generates bubbles at a gas-liquid interface due to, for example, stirring and / or aeration. The bubbler can be an aerator (for example) that flows a gas into the electroplating solution to stir and / or aerate the solution; the bubbler can also be a propeller, an impeller, or a plurality of nozzles or jets. As described above, this bubbling of the electroplating solution is contrary to typical electroplating systems and operations.

[0060] Characteristics of electroplating

[0061] The damascene process is used to form interconnects on integrated circuits (ICs). It is particularly suitable for making copper interconnects. The damascene process involves forming embedded metal lines in trenches and forming trenches and vias in dielectric layers (intermetal dielectrics). In a typical damascene process, a pattern of trenches and vias is etched in a dielectric layer of a semiconductor wafer substrate. A thin diffusion barrier film, such as tantalum, tantalum nitride, or TaN / Ta bilayer, is then deposited on the surface of the wafer by a PVD method, and a copper seed layer is then deposited on top of the diffusion barrier layer. The trenches and vias are then electrically filled with copper, and the wafer surface is planarized to remove excess copper.

[0062] The vias and trenches are filled electrically in an electroplating apparatus, which may include a cathode and an anode immersed in a plating solution containing an electrolyte in a plating reservoir. The cathode of the apparatus is the wafer itself, or more specifically its copper seed layer and, over time, the deposited copper layer. The anode may be a disk composed of, for example, phosphorus-doped copper. The composition of the electrolyte used to deposit the copper may vary, but typically includes sulfuric acid, a copper salt such as CuSO 4 ), chloride ions, and an organic additive. The electrodes are connected to a power source that provides the necessary voltage to electrochemically reduce the copper ions at the cathode, resulting in the deposition of copper metal on the surface of the wafer seed layer.

[0063] The composition of the electroplating solution is selected to optimize the rate and uniformity of electroplating. During the electroplating process, copper salts, as a source of copper cations, also provide conductivity for the electroplating fluid; in addition, in certain embodiments, sulfuric acid enhances the conductivity of the electroplating solution by providing hydrogen ions as charge carriers. In addition, organic additives commonly referred to as promoters, inhibitors or levelers in the art can selectively increase or inhibit the deposition rate of copper (Cu) on different surfaces and wafer features. Chloride (Cl) ions can be used to adjust the effect of organic additives and can be added to the electroplating bath for this purpose. In some embodiments, another halide (e.g., bromide or iodide) is used instead of chloride or in addition to chloride.

[0064] Although not wishing to be bound by any theory or mechanism of action, it is believed that the leveler (alone or in combination with other bath additives) acts as an inhibitor, counteracting the depolarization effect associated with the promoter in some cases, particularly in exposed portions of the substrate, such as the field area of ​​the wafer being processed, and the sidewalls of the features. The leveler can locally increase the polarization / surface resistance of the substrate, thereby slowing down the local electrodeposition reaction in the area where the leveler is present. The local concentration of the leveler is determined to some extent by mass transfer. Therefore, the leveler acts primarily on surface structures with geometric shapes protruding from the surface. This action makes the surface of the electrodeposited layer "smooth". It is believed that in many cases, the leveler reacts or is consumed at a rate equal to or close to the diffusion-limited rate on the substrate surface, and therefore, a continuous supply of the leveler is generally beneficial to maintain uniform electroplating conditions over time.

[0065] Leveler compounds are generally classified as levelers according to their electrochemical functions and effects, and no specific chemical structure or formulation is required. However, levelers generally contain one or more nitrogen, amines, imides or imidazoles, and may also contain sulfur functional groups. Certain levelers include one or more five-membered and six-membered rings and / or conjugated organic compound derivatives. The nitrogen group may form part of the ring structure. In amine-containing levelers, the amine may be a primary, secondary or tertiary alkylamine. In addition, the amine may be an arylamine or a heterocyclic amine. Example amines include, but are not limited to, dialkylamines, trialkylamines, arylalkylamines, triazoles, imidazoles, triazoles, tetrazoles, benzimidazoles, benzotriazoles, piperidines, morpholine, piperazines, pyridines, oxazoles, benzoxazoles, pyrimidines, quinolines and isoquinolines. Imidazoles and pyridines may be particularly useful. Other examples of levelers include Janus Green B and Prussian Blue. Leveler compounds may also include ethoxy groups. For example, the leveler can include a general backbone similar to that found in polyethylene glycol or polyethylene oxide, with an amine fragment functionally inserted into the chain (e.g., Janus Green B). Exemplary epoxides include, but are not limited to, epihalohydrins, such as epichlorohydrin and epibromohydrin, and polyepoxides. Polyepoxide compounds having two or more epoxide moieties linked together by ether-containing bonds may be particularly useful. Some leveler compounds are polymeric, while others are not. Exemplary polymeric leveler compounds include, but are not limited to, polyethylene imine, polyamidoamine, and reaction products of amines with various oxygen epoxides or sulfides. An example of a non-polymeric leveler is 6-mercapto-hexanol. Another example leveler is polyvinyl pyrrolidone (PVP).

[0066] During the process of electroplating wafers, various byproducts and other materials are generated in the plating solution. In conventional electroplating systems, these byproducts and other materials are typically removed using a "drain and feed" technique, where the plating solution is replenished with fresh solution and the old solution is disposed of or reconstituted. While it is often desirable to renew a small portion of the solution via the drain and feed method, this is not an economically viable approach for some byproducts and other materials.

[0067] As described above, it has been found that some electroplating processes produce byproducts in the electroplating solution that have a negative impact on electroplating, but for these processes, the byproducts are produced at high rates, which requires the use of high and undesirable discharge and feed rates to maintain acceptable solution concentrations. These high discharge and feed rates cause a large amount of solution to be wasted. When high discharge and feed rates are used, the operating cost of the electroplating equipment becomes very high. In some embodiments, as discussed below, conventional discharge and feed rates can result in the removal and disposal of about 10% to 20% of the electroplating solution during a 24-hour electroplating process, compared to these high byproduct production rates that can result in the removal of about 100% of the electroplating solution in the same 24-hour electroplating.

[0068] Some such processes use plating solutions containing little or no intentionally added levelers, but the nature of these plating processes, such as the wafer configurations, plating solutions, or chemistries involved, are such that process byproducts are inherently produced in the solution, which act as levelers that adversely affect the plating process by, for example, reducing the performance of the plating solution, reducing bump height, and reducing fill quality. As is well known in the art, for potential plating processes, such as through silicon via ("TSV") applications, the bump height of the filled via provides an indicator of plating performance and, in some cases, degradation of the plating solution due to the presence of unwanted leveler byproducts. The bump height is measured relative to the wafer surface, such that, for example, a bump height of 4 microns (μm) is a via filled 4 μm above the wafer surface. As leveler byproducts accumulate in the plating solution during plating of one or more wafers, the bump heights decrease over time until they reach unacceptable levels.

[0069] In these processes, leveler byproducts are produced at rates that are difficult to remove in an acceptable manner using conventional methods. For example, many conventional substrates used in TSV plating have a via opening area of ​​less than or equal to about 0.5% or 0.7% of the substrate, including 0.1% to 0.2% for some TSV memory applications (e.g., dynamic random access memory, i.e., DRAM), and 0.4% to 0.7% for some TSV logic applications. This is calculated by multiplying the area of ​​a single via by the number of vias on the wafer and then dividing it by the total area of ​​the wafer. In general, via density and byproduct generation scale are synergistic, so that increasing via density leads to a corresponding increase in the scale of byproduct generation. Pattern density in the semiconductor industry is increasing, and for some high pattern density wafers, the via opening area is greater than 0.5%, including approaching or equal to 1% and above 1% to about 2%. It has been found that the rate at which these high pattern density wafers produce leveler byproducts can only be removed at very high drain and feed rates using conventional drain and feed techniques. These wafers can also degrade the plating solution faster because the greater number of vias on the substrate generates more byproducts. In some of these processes, conventional drain and feed techniques are used to remove the required amount of leveler byproducts from the plating solution, which results in replacing 100% of the plating solution in a 24-hour plating process. In contrast, for most plating processes, an acceptable drain and feed amount is to replace 10% to 20% or less of the solution in the same 24-hour plating process.

[0070] The inventors conceived the systems and techniques discussed herein to control the composition of electroplating solutions in a more economical manner.

[0071] definition

[0072] The following terms are used intermittently throughout this disclosure:

[0073] “Substrate”—In this application, the terms “semiconductor wafer,” “wafer,” “substrate,” “wafer substrate,” and “partially fabricated integrated circuit” are used interchangeably. One of ordinary skill in the art will understand that the term “partially fabricated integrated circuit” can refer to a silicon wafer during any of the many stages on which an integrated circuit is fabricated. Wafers or substrates used in the semiconductor device industry typically have a diameter of 200 mm, 300 mm, or 450 mm. In addition, the terms “electrolyte,” “plating bath,” “electrolytic bath,” “bath,” “plating solution,” and “electrolytic solution” are used interchangeably. The workpiece can have a variety of shapes, sizes, and materials. In addition to semiconductor wafers, other workpieces that can utilize the disclosed embodiments include various articles of manufacture, such as printed circuit boards, magnetic recording media, magnetic recording sensors, mirrors, optical elements, micromechanical devices, and the like.

[0074] "Electroplating Cell"—a cell, typically configured to house an anode and a cathode, positioned opposite one another. Electroplating is performed at the cathode of an electroplating cell and refers to the process of using an electric current to reduce dissolved metal cations so that they form a thin, coherent metal coating on the electrode. In certain embodiments, an electroplating system has two compartments, one for housing the anode and the other for housing the cathode. In certain embodiments, the anode compartment and the cathode compartment are separated by a semipermeable membrane that allows for the selective movement of ionic species concentrations across the membrane. The membrane may be an ion exchange membrane, such as a cation exchange membrane. For some embodiments, Nafion TM Versions of (eg, Nafion 324) are suitable for use as such membranes.

[0075] "Anode Chamber"—a chamber within an electroplating cell designed to house an anode. The anode chamber may contain a support for holding the anode and / or providing one or more electrical connections to the anode. The anode chamber may be separated from the cathode chamber by a semipermeable membrane. The electrolyte contained in the anode chamber is sometimes referred to as the anolyte.

[0076] "Cathode Chamber"—a chamber within an electroplating cell designed to house a cathode. Generally in the context of the present disclosure, a cathode is a substrate such as a wafer, e.g., a silicon wafer, having multiple parts of a fabricated semiconductor device. The electrolyte contained in the cathode chamber is sometimes referred to as the catholyte. In many embodiments, the cathode can be removed from the cathode chamber to allow the wafer to be connected to the cathode; the cathode can then be reintroduced into the cathode chamber and immersed in the catholyte. It should be understood that the anode chamber and cathode chamber can also refer to different parts of the same overall structure, such as an electroplating cell. If a membrane is used, the membrane can serve as a separator between the two chambers.

[0077] "Plated solution" (or plating bath, plating electrolyte, bath, plating solution, solution, or primary electrolyte)—a liquid of dissociated metal ions, usually in solution with a conductivity-enhancing solvent such as an acid or base. The dissolved cations and anions are evenly dispersed in the solvent. Electrically, such a solution is neutral. If an electric potential is applied to such a solution, the cations of the solution are attracted to the electrode with the large number of electrons, while the anions are attracted to the electrode with the small number of electrons.

[0078] "Recirculation System"—a system that circulates the electroplating solution back to a central reservoir for subsequent reuse. The recirculation system may be configured to efficiently reuse the electroplating solution and also control and / or maintain the concentration level of metal ions in the solution as desired. The recirculation system may include piping or other fluid conduits and a pump or other mechanism for driving the recirculation.

[0079] "Frothing" or "foaming" - the act of intentionally creating relatively stable bubbles of gas at a gas-liquid interface due to agitation, aeration, boiling, or chemical reaction. Devices specifically configured to froth a liquid are referred to herein as "bubblers."

[0080] "Foam" - A collection of bubbles formed on or in a liquid, which may be stabilized by organic compounds and surfactants and usually formed by effervescence.

[0081] First Example Electroplating System for Forming Foam

[0082] Described herein are apparatus and techniques for removing unwanted components, such as byproducts, from an electroplating solution by bubbling the electroplating solution to form a foam to capture the unwanted components and then removing the foam to remove the unwanted components from the electroplating solution.

[0083] In contrast to conventional electroplating processes, the inventors herein have discovered that frothing an electroplating solution containing unwanted byproducts to produce foam is advantageous because the foam entraps the byproducts. This concept was confirmed in testing, at least in part, because when the foam was allowed to relax, i.e., converted to liquid form, the amount of leveler in the solution increased, indicating that the foam contained a higher proportion of the byproduct plating fluid than the liquid electroplating solution / byproduct mixture. Thus, the inventors recognized that an electroplating system including an apparatus configured to intentionally (and controllably) generate foam from an electroplating solution and then separate the foam from the electroplating solution would advantageously function to preferentially remove unwanted excess byproducts from the electroplating system, thereby reducing the concentration of the unwanted byproducts and reducing the "drain and feed" feed rate.

[0084] The generation of foam can be achieved by using a bubbler. As described herein, a bubbler is used to bubble the electroplating solution to generate foam. The bubbler can have a variety of configurations and can be positioned in the electroplating system in various ways. Examples of bubblers are discussed further below, but in order to provide background on the positioning, configuration, and arrangement of bubblers, a first example electroplating system and the fluid flow within the system will first be discussed.

[0085] Figure 1 A first example electroplating system 100 is depicted having an electroplating tank 102, a reservoir 104 for holding an electroplating solution, an electroplating tank flow loop 106, and an optional recirculation loop 108 for the reservoir 104. At least during an electroplating process, the tank 102 holds an electroplating solution, the reservoir 104 contains the electroplating solution, the electroplating tank flow loop 106 is configured to flow the electroplating solution between the tank 102 and the reservoir 104, and the recirculation loop 108, which is optional in some embodiments, is configured to recirculate the electroplating solution within the reservoir 104 using a first pump 110.

[0086] Figure 2 Depicted Figure 1 A first example system of FIG. 1 is a schematic cross-sectional view of a plating tank. Typically, a plating system includes one or more plating tanks in which wafers are processed. For clarity, Figure 2 Only one plating tank is shown. Figure 2 2, the electroplating bath 214 contains an electroplating solution (having, for example, a composition as provided herein), which is shown at level 216. The catholyte portion of the reservoir is adapted to receive a substrate in the catholyte. Wafer 218 is immersed in the electroplating solution and is held by, for example, a "clamshell" substrate holder 220 mounted on a rotatable spindle 222, which allows the clamshell substrate holder 220 to rotate with the wafer 218.

[0087] Anode 224 is disposed below the wafer in electroplating bath 214 and is separated from the wafer area by membrane 225, preferably an ion selective membrane. For example, Nafion TM Cation Exchange Membrane (CEM). The area below the anode membrane is often referred to as the "anode chamber". The ion-selective anode membrane 225 allows ionic communication between the anode and cathode regions of the electroplating cell while preventing particles generated at the anode from entering the vicinity of the wafer and contaminating the wafer. The anode membrane can also be used to redistribute current during the electroplating process, thereby improving the uniformity of the electroplating. Ion exchange membranes, such as cation exchange membranes, are particularly suitable for these applications. These membranes are typically made of ionomer materials, such as perfluorinated copolymers containing sulfonic acid groups (e.g., Nafion TM ), sulfonated polyimide and other materials known to those skilled in the art as suitable for cation exchange. Suitable Nafion TM Selected examples of membranes include N324 and N424 membranes available from Dupont de Nemours Co.

[0088] During electroplating, ions from the plating solution are deposited on the substrate. The metal ions must diffuse through the diffusion boundary layer and into the through-holes or other features of the wafer. A typical way to assist diffusion is by convective flow of the plating solution provided by the second pump 226. In addition, vibration stirring or sonic stirring members and wafer rotation can be used, which may be conducive to uniform electroplating. For example, a vibration transducer 228 can be attached to a clamshell substrate holder 220.

[0089] During electroplating, in some embodiments, the electroplating solution is continuously supplied from the reservoir to the electroplating tank and from the electroplating tank to the reservoir via a electroplating tank flow loop, which can operate as described herein. Figure 2, the plating solution flows from the reservoir 104 to the plating tank using a second pump 226, enters the tank above the membrane on the cathode side, and then flows upward to the center of the wafer 218 and then flows radially outward through the wafer 218. The plating solution then overflows the plating bath 214 to the overflow reservoir 232. The plating solution then flows back to the reservoir 104, thereby completing the recirculation 106 of the plating solution through the plating tank flow loop, which is partially indicated by the dashed arrow 106.

[0090] Figure 2 Other features of the electroplating system 100 in the embodiment include a reference electrode 234, which is located outside the electroplating bath 214 in a separate chamber 236, which is replenished by overflow from the main electroplating bath 214. Alternatively, in some embodiments, the reference electrode is positioned as close to the substrate surface as possible, and the reference electrode chamber is connected to the side of the wafer substrate or directly below the wafer substrate by a capillary or by another method. In some preferred embodiments, the device also includes a contact sensing lead, which is connected to the periphery of the wafer and is configured to sense the potential of the metal seed layer at the periphery of the wafer but does not transmit any current to the wafer. When electroplating is required at a controlled potential, the reference electrode 234 is generally used. The reference electrode 234 can be one of a variety of commonly used types, such as mercury / mercuric sulfate, silver chloride, saturated calomel or copper metal. In some embodiments, in addition to the reference electrode, a contact sensing lead in direct contact with the wafer 218 can also be used to perform more accurate potential measurements (not shown).

[0091] A DC power supply 238 may be used to control the current flowing to the wafer 218. The power supply 238 has a negative output lead 240 electrically connected to the wafer 218 through one or more slip rings, brushes, and contacts (not shown); alternatively, the negative output lead may be electrically connected to a substrate holder 220, which in turn may be connected to a substrate. A positive output lead 242 of the power supply 238 is electrically connected to an anode 224 located in the electroplating bath 214. The power supply 238, the reference electrode 234, and a contact sensing lead (not shown) may be connected to a system controller 244, which, among other functions, allows modulation of the current and potential provided to the elements of the electroplating bath. For example, the controller may allow electroplating to be performed in both potential-controlled and current-controlled states. The controller may include program instructions specifying the current and voltage levels that need to be applied to the various elements of the electroplating bath, and the times when these levels need to be changed. When a forward current is applied, the power supply 238 biases the wafer 218 to have a negative potential relative to the anode 224. This causes current to flow from anode 224 to wafer 218 and electrochemical reduction (e.g., Cu 2+ +2e － =Cu 0 ) occurs at the wafer surface (cathode), causing a conductive layer (e.g., copper) to be deposited on the wafer surface.

[0092] The system may also include a heater 252 for maintaining the temperature of the plating solution at a specific level. The plating solution may be used to transfer heat to other elements of the plating bath. For example, when the wafer 218 is loaded into the plating bath, the heater 252 and the second pump 226 may be turned on to circulate the plating solution through the plating system 200 until the temperature of the entire device becomes substantially uniform. In one embodiment, the heater is connected to the system controller 244. The system controller 244 may be connected to a thermocouple to receive feedback on the temperature of the plating solution within the plating device and determine whether additional heating is required.

[0093] Return to reference Figure 1 , the recirculation loop 108 may be used for a variety of reasons. It may be advantageous to recirculate the plating solution contained within the reservoir 104 to mix the solution and prevent stagnation in the reservoir. In some embodiments, diluents, make-up solutions (e.g., a portion of a "feed" of new plating solution), and organic additives may also be added directly to the reservoir from various sources, and the recirculation loop 108 may mix the solutions. Figure 1 In the embodiment of the present invention, diluent, replenishing solution and organic additives can be added directly to the reservoir 104 from sources 131, 139 and 157 through pipelines 159, 161 and 163, respectively. Valves 171, 173 and 175 control the dosage of diluent, replenishing solution and additives, respectively. As discussed herein, these items can be used during the discharge and feeding of the electroplating solution. In some cases, although Figure 1 Although not shown, the recirculation loop 108 may include a filter for filtering the electroplating solution in the reservoir 104. Similar to the above, the recirculation loop 108 may also include a heater or cooling unit configured to heat or cool the electroplating solution in the reservoir 104.

[0094] Positioning the bubbler in the first example plating system

[0095] In various embodiments, the bubbler is positioned in fluid communication with one or more elements of the electroplating system such that the bubbler can bubble at least some of the electroplating fluid to produce foam while the electroplating fluid is in the system. In some embodiments, the bubbler can be a separate unit of the system such that it is not part of other system elements. For example, Figure 1 As shown, the bubbler 160 is a separate unit in fluid connection with the reservoir 104 and the recirculation loop 108; the bubbler is not part of the other system elements. In some other embodiments, the bubbler can be part of one or more elements in the system, such as being positioned within the reservoir and configured to bubble the electroplating solution contained in the reservoir.

[0096] like Figure 1As seen more specifically in FIG. 1 , the bubbler 160 is fluidly connected to the reservoir 104 and the recirculation loop 108 via a bubbler flow path 162 (labeled 162 and shown in phantom). The bubbler flow path 162 is configured to allow fluid to flow between the bubbler 160 and the reservoir 104 and between the recirculation loop 108 and the bubbler 160. The direction of flow between these elements can be in either direction and can be unidirectional or multidirectional. For example, representing the bubbler flow path 162 as a directional arrow indicates that the electroplating solution flows from the recirculation loop 108 to the bubbler 160, and from the bubbler 160 to the reservoir 104.

[0097] In some embodiments, the bubbler flow path 162 may have one or more valves at at least one of an intersection or termination point with other elements of the electroplating system. Figure 1 The bubbler flow path 162 in the embodiment has a first valve 164A at one intersection 166A (circled by a dashed ellipse) with the recirculation loop 108, and a second valve 164B (circled by a dashed ellipse) at or near a second intersection 166A with the reservoir 104. Each of these valves is configured to control flow between each of its connected portions. The first valve 164A is configured to control the flow of the electroplating solution between the bubbler flow path 162 and the recirculation loop 108 so that the fluid can flow to only one of these loops at a time. If the first valve is in a diverting position, the fluid can be diverted from the recirculation loop 108 to the bubbler flow path 162. The second valve 164B is configured to limit and stop the flow of fluid between the reservoir 104 and the bubbler flow path 162, so that when fully closed, the second valve 164B prevents the fluid from flowing between the reservoir 104 and the bubbler flow path 162. Figure 1 The intersections shown in are intended to be illustrative and non-limiting examples. For example, the intersection of the bubbler flow path 162 and the recirculation loop 108 may be at different locations along the recirculation loop 108 and other connection arrangements may be used. The valve may be a variety of valve types, such as ball valves, stop valves, butterfly valves, needle valves, plug valves, poppet valves, gate valves, slide valves, and other control valves.

[0098] Bubbler Configuration Example

[0099] The bubbler can be configured to generate foam in different ways. As described above, the bubbler is configured to generate bubbles in the electroplating solution by stirring, aerating, boiling or chemically reacting the electroplating solution at the gas-liquid interface to generate foam, thereby bubbling the electroplating solution. In some embodiments, the generation of foam can be assisted by surfactants and other compounds in the electroplating solution. Once the foam is generated and floats on the surface of the solution, it can be removed from the system in various ways. As discussed below, the bubbler can be configured to bubble the electroplating solution, which is contained by a container or contained by one of the other elements of the electroplating system, such as a reservoir or a tank.

[0100] In some embodiments, the bubbler can be an aerator, such as an aeration stone, which is made of a porous material and is configured to receive gas. The aeration stone does not need to be a mineral-based material, such as a stone, but can be any porous material, such as a ceramic or polymeric material. The aerator can allow gas to pass through it and enter the electroplating solution in contact with the aerator, thereby introducing a large number of separate air flows into the solution through the holes of the aerator and generating a large number of small bubble flows. The gas is flowed through the aerator to aerate the electroplating solution, and in some cases, the electroplating solution is also stirred to generate foam. In some embodiments, the porous material of the aerator may have a size of about 1 micron and about 1 mm between the hole. The aerator can be made of a material compatible with the electroplating chemical, such as high-density polyethylene (HDPE), polypropylene (PP) and polytetrafluoroethylene (PTFE), but other suitable materials can also be used. Compatibility may mean that the electroplating chemical and the aerator will not react adversely with each other, such as the aerator decomposing or releasing unwanted materials into the electroplating solution, or the electroplating solution reacts with the aerator in some way. The aerator may have a porosity of about less than or equal to 1 mm, including between about 1 mm and about 1 micron, of a porous material. The gas flowing through the aerator may contain only nitrogen, only molecular oxygen (O 2 ), only ozone (O 3 ) or a mixture of gases, such as molecular oxygen and nitrogen. Any suitable gas may be used; the above list is not intended to be limiting. In general, the selected gas may be selected to avoid undesirably affecting the properties of the solution.

[0101] In some embodiments, the bubbler may be provided by one or more jets configured to flow a gas such as nitrogen, molecular oxygen, ozone, or a combination of these gases, as described above, or a fluid, such as the electroplating solution itself, into the electroplating solution to aerate and / or agitate the electroplating solution to produce foam. If a portion of the electroplating solution itself is sprayed back into the electroplating solution, the jets may be positioned so that the jets encounter the surface of the solution, thereby allowing air or other gases above the surface to be entrained in the jet and introduced into the solution.

[0102] In some embodiments, the bubbler can be configured to physically agitate the electroplating solution. For example, the bubbler can include a propeller or impeller that is configured to contact the electroplating solution while rotating near the surface of the electroplating solution and generate foam by agitation.

[0103] As described above, in some embodiments, the bubbler can be a part of a foam generating unit that is separated from other elements of the electroplating system but is fluidly connected to other elements. The foam generating unit may include a bubbler and a container configured to hold a certain volume of electroplating solution. In these embodiments, the bubbler is configured to foam the electroplating solution contained in the container to produce bubbles in the electroplating solution contained by the container by, for example, stirring, aerating, boiling or causing the electroplating solution to react chemically at an air-liquid interface to produce bubbles in the electroplating solution contained by the container. In some embodiments, the bubbler may be positioned in the container and configured to contact the electroplating solution contained by the container. For example, one or more aeration stones, propellers or impellers may be positioned in the container to aerate and / or stir the electroplating solution in the container. In some similar examples, the foam generating unit may include one or more flow paths including a bubbler, for example, a flow path including a propeller or an impeller.

[0104] Figure 3A A first example foam generating unit 368A is depicted, which includes a container 370 and a bubbler 360 positioned within the container 370. The container 370 is configured to hold a first volume of a plating solution, indicated by the dark shading and the top level marked as 372. The container may include an inlet 374 and an outlet 376, through which the plating solution can enter and exit the container 370, respectively. Although the inlet 374 and the outlet 376 are shown as being positioned near the bottom of the container 370, such as in an area proximate to the bottom 378 of the reservoir, the inlet 374 and the outlet 376 can be positioned at other locations of the container. For example, the inlet can be on the side of the container and the outlet can be at the bottom of the container; the inlet can be at the top (380) of the container; the inlet can be in an area proximate to the top 380 of the container; the container can have an open top that can be used as an inlet.

[0105] The container 370 is also fluidly connected to at least one other element of the electroplating system, such as the recirculation loop 108 and the reservoir 104, via the bubbler flow path 162. Figure 1 Return to reference Figure 1 , the bubbler 160 marked in this figure can represent this and any other foam generating unit described herein. This representation includes any configuration between the bubbler 160 and the system 100 described above, including the fluid connection between the bubbler 160 / foam generating unit 368A, the reservoir 104, and the recirculation loop 108.

[0106] exist Figure 3AIn the embodiment, the bubbler 360 is located in the container and is configured to aerate and / or stir the electroplating solution in the container to generate foam. Figure 3A The bubbler 360 is an aeration stone as described above, which is fluidly connected to a gas source 382 and is configured to flow a gas (e.g., nitrogen, oxygen, a mixture of these gases, another gas, or another mixture) from the gas source 382 into the container 370 so that the gas can aerate and / or agitate the electroplating solution in the container and produce foam 384 (which is represented by light shading). In this embodiment, the electroplating solution 372 is shown as being interfaced with the bubbler 360 so that they are in contact with each other; the bubbler 360 is also immersed in the electroplating solution 372. There can also be one or more valves 383 or other control elements, such as mass flow controllers, which are configured to control the flow of gas from the gas source 382 to the bubbler 360.

[0107] The container 370 may have a foam outlet 386 configured to allow foam 384 in the container 370 to exit the container 370 through the foam outlet 386. In some embodiments, the foam outlet 386 may be connected to the exhaust port 379 via an exhaust flow path 388. Return to Reference Figure 1 , the exhaust port 179 can also be seen and represents the location where the foam can flow out of the bubbler 160. Generally speaking, the outlet can be located above the surface of the first volume of the electroplating solution. As the foam is generated and increases in volume, the foam can actually force itself out of the outlet 386 and into the exhaust port 379. Alternatively or additionally, the gas can flow into the top of the container 370 and out of the outlet 386, causing the foam in the gas flow path to be actively drawn into the outlet 386 and the exhaust port 379.

[0108] The foam generating unit can be configured in many other ways, e.g. Figure 3B 368B is depicted together with the electroplating solution 372 and the foam 384. The inlet and outlet are not depicted for clarity, but the container may have a plurality of Figure 3A Same inlet and outlet as described. Figure 3BMany examples of different types of bubblers and their positioning are shown; it should be understood that these are illustrative, non-limiting examples, and that the foam generating unit may not include all of these bubblers in one unit, but these multiple examples are provided in one figure for clarity and simplicity. In some embodiments, the bubbler can be a propeller 390 connected to a motor 392 that is configured to agitate the electroplating solution 372 and generate foam. The bubbler can also be an impeller 394 that is located outside the container 370 but is fluidly connected to the container 370 through an impeller flow path 396 and is configured to generate foam 384; in some other embodiments, the impeller 394 can be positioned within the container similar to the propeller 390.

[0109] In some embodiments, the bubbler can be a plurality of nozzles, represented as triangles labeled 398A-E, which can be positioned at different locations inside or outside the container. One or more nozzles can be positioned on the side of the container, such as nozzle 398A, which can be above the fill line of the container 370, and nozzle 398B, which can be below the fill line. One or more nozzles can also be in the bottom 378 or bottom area of ​​the container like nozzle 398C, at the top 380 inside the container 370 or in the top area of ​​the container like nozzle 398D, or outside the container 370 but in the top 380 area of ​​the container 370. So that fluid or gas can flow into the container 370 through the top 380, like nozzle 398E. In some such embodiments, the nozzle can be configured to flow gas from a gas source 382 into the container 370, similar to an aeration stone, so as to aerate and / or agitate the electroplating solution in the container 370. For these nozzles that can be in contact with the electroplating solution, the interface of these nozzles with the electroplating solution may be the interaction of gas or fluid flowing into the electroplating solution.

[0110] In some embodiments, one or more nozzles may be configured to flow the electroplating solution itself into the container 370, and the electroplating solution may be aerated and / or agitated to generate foam. For these nozzles that can cause the electroplating solution to flow out of the nozzles, the interface between these nozzles and the electroplating solution may be the action of the electroplating solution flowing out. In some similar embodiments, the nozzles may be configured to flow the electroplating solution and the gas simultaneously and / or continuously to generate foam. For example, the nozzle may first flow the electroplating solution into the container to stir and generate some foam, and then flow the gas into the container to further generate foam. For these such nozzles, the interface between these nozzles and the electroplating solution may be the action of gas or liquid flowing into the electroplating solution, or the action of the electroplating solution flowing out of the nozzle.

[0111] As mentioned above, it is desirable to remove foam from the electroplating system in order to remove the byproducts trapped in the foam. Figure 3AIn some other embodiments, the foam generating unit may have an element configured to move the foam, such as a foam moving unit configured to move, remove, or assist in removing the foam from the electroplating system. This may include a first element configured to extract the foam, such as a vacuum unit, or a second element configured to move the foam to the foam outlet, such as a skimmer, fan, or blower. A skimmer can be considered a device designed to remove items (e.g. foam) from the surface of a liquid; a skimmer can be a weir-type skimmer, which allows foam floating on the surface of the solution to flow over a weir; a belt-type skimmer uses a belt, running on a motor and pulley system, passing through a plating solution containing foam to pick up the foam from the surface, after passing over a head pulley the belt passes through wiper blades in series, the foam and plating solution are scraped off both sides of the belt and drained; and a mechanical arm or pusher to push the foam. Figure 3B , the foam moving unit is represented as object 3100.

[0112] Instead of a separate unit, in some embodiments, the bubbler can be configured to contact and bubble the plating solution contained in a fluid holding element (e.g., a tank and / or reservoir) of the electroplating system. The plating solution holding body of the reservoir and / or tank can be configured as described above and in Figure 3A and 3B The container of the foam generating unit shown in FIG. 1 is constructed in a similar manner. For example, as described above with respect to Figure 3A and 3B As described above with respect to the container 370, any of the bubblers described above may be positioned and configured to bubble the electroplating solution contained in the plating bath 214 or the overflow reservoir 232. In some cases, such as Figure 3A As shown, aeration stones may be placed in the reservoir, electroplating bath 214 or overflow reservoir 232 of the tank to aerate and agitate the electroplating solution and create foam in these components. Figure 3B Any bubbler shown in, such as a propeller, impeller, or nozzle, can be positioned in and around the reservoir 104, the plating tank 214, or the overflow reservoir 232 to foam the electroplating solution contained in these bodies, as discussed above. For example, a propeller can be positioned in the reservoir to agitate and generate foam within the reservoir. In addition, a nozzle can be positioned on the side, top, or above the reservoir 104, the plating tank 214, or the overflow reservoir 232 to flow gas or plating solution into these fluid retaining bodies to generate foam.

[0113] To remove foam from these fluid holding bodies, the electroplating system can be configured as described above to allow, move, or remove foam from the system. In some embodiments, the fluid holding bodies of the electroplating system, such as the reservoir, the plating bath, and the overflow reservoir, can have the above-described and Figure 3A The foam outlet shown allows the foam to flow out of the fluid retaining body. The fluid retaining body of the electroplating system can also have a foam moving unit, as described above, which is configured to move, remove or assist in removing foam from the electroplating system, which can include a first element configured to extract the foam (e.g., a vacuum unit), or a second element configured to move the foam to the foam outlet, such as a skimmer, fan, or blower.

[0114] In some embodiments, the reservoir can be configured to hold at least 1 liter of plating solution. It has been found that in some such embodiments, for an electroplating system containing a total of about 100 L of plating fluid, periodically bubbling about 1 L of plating solution at specific time intervals can remove a desired amount of byproducts.

[0115] Example configuration of a stand-alone foam generator within an electroplating system

[0116] As described above, the bubbler can be a separate foam generating unit that is fluidly connected to other elements of the electroplating system. Each fluid connection between the foam generating unit and / or bubbler to another element of the electroplating solution can be considered a fluid flow path or conduit that allows fluid to travel between these elements. In some cases, this may be considered a loop. Figures 4A to 4E Various example configurations of electroplating systems having separate foam generating units are depicted. Figure 4A , the electroplating system 400A is configured such that the bubble generating unit 168 including the bubbler (not shown) is directly fluidly connected to the reservoir 104 only, so that the electroplating solution flows between these components through the same bubbler flow path 462A. In some cases, this flow path may not be a loop, such as Figure 4A 462A, while in other cases, the flow path may be a loop only between these two elements, namely the foam generating unit 168 and the reservoir 104. In the depicted example, the electroplating solution may be moved from the reservoir 104 to the foam generating unit 168 via the same fluid flow path used to move the electroplating solution from the foam generating unit 168 to the reservoir 104. Other embodiments may have separate supply / return flow paths to / from the foam generating unit, thereby allowing the electroplating solution to continuously circulate through the foam generating unit. One or more valves, such as two valves 464A and 464B, may control the flow of the electroplating solution through the flow path 462A.

[0117] exist Figure 4B , the electroplating system 400B is configured such that the foam generation unit fluid is connected to the plating tank flow loop 106 and the tank 102 through the bubbler flow path 462B. The system may include one or more valves configured to control the flow of the electroplating solution within the bubbler flow path 462B and between the foam generation unit 168, the plating tank flow loop 106 and the tank 102. For example, similar to Figure 1 , the system 400B includes a first valve 164A at the intersection 166A of the bubbler flow path 462B and the plating tank flow loop 106, which is configured to control the flow of the plating solution between these two elements, thereby controlling the flow between the foam generating unit 168 and the plating tank flow loop 106. The system 400B also includes a second valve 164B at the intersection 166B between the tank 102 and the bubbler flow path 462B, which is configured to control the flow between these two elements, thereby controlling the flow between the tank 102 and the foam generating unit 168. The system 400B can be configured so that the fluid can flow through the bubbler flow path 462B in one or two directions, such as in the direction indicated by the arrow of the bubbler flow path 462B, in the opposite direction, and in either direction.

[0118] exist Figure 4C , the electroplating system 400C is configured such that the bubble generating unit 168 is only fluidly connected directly to the tank 102 via the bubbler flow path 462C. Figure 4A , system 400C includes one or more first valves 164A, which are configured to control the flow of the electroplating solution between the two elements (i.e., the foam generating unit 168 and the tank 102). In some cases, the flow path 462C is not a loop, while in other cases, this flow path may be just a loop between the two elements.

[0119] exist Figure 4D , the electroplating system 400D is configured such that the foam generating unit 168 is directly fluidly connected to the recirculation loop 108 via the bubbler flow path 462D. Figure 4A and 4B , the system 400D includes one or more first valves 164A configured to control the flow of the electroplating solution between the two elements, i.e., the foam generating unit 168 and the recirculation loop 108. In some cases, the flow path 462D is not a loop, while in other cases, the flow path may simply be a loop between the two elements.

[0120] exist Figure 4E In the embodiment, the electroplating system 400E is configured such that the foam generating unit 168 is directly connected to the electroplating tank flow circuit 106 through the bubbler flow path 462E. Figure 4A , 4B Similar to 4D, system 400E includes one or more first valves 164A configured to control the flow of the plating solution between the two elements, i.e., the foam generating unit 168 and the plating tank flow loop 106. In an example, the flow path 462E is not a loop, while in other examples, the flow path can be a loop only between the two elements.

[0121] In all of these example systems, one or more pumps may be used to move the electroplating solution into and out of the bubbler and foam generating unit. Figure 4A In the embodiment of the present invention, pump 463 is positioned in bubbler flow path 462A and is configured to pump the electroplating solution from reservoir 104 to bubble generating unit 168, and from bubble generating unit 168 to reservoir 104. The pump can be positioned in any and all other electroplating systems described herein, including Figures 4A to 4E ,as well as Figure 1 and 2 .

[0122] Although not depicted in these figures, the foam generating unit may also have direct fluid connections to multiple elements in the system, such as reservoirs and tanks, as well as direct fluid connections to all elements in the electroplating system.

[0123] Example Techniques for Foaming Electroplating Solutions

[0124] Various techniques can be used to foam the electroplating solution. Figure 5 A first example technique for bubbling a plating solution is depicted. In block 501, the plating solution is provided to a plating system, which may be any system described herein. In block 503, the plating solution is in the plating system, and a bubbler may bubble the plating solution, such as stirring, aerating and / or bubbling, the plating solution generating bubbles, which in turn generate foam. Such bubbling may be caused by any of the bubblers described above, which bubble the plating solution contained in a reservoir of a foam generating unit or contained in other elements of the plating system, such as a reservoir and a tank. In some embodiments, bubbling may include flowing a gas, which may include nitrogen, into an aeration stone when the bubbler contacts the plating solution.

[0125] As described above, the bubbler interfaces with the electroplating solution during bubbling. In some embodiments, the interface may include causing the electroplating solution to surround and contact at least a portion of the bubbler. For a container of the foam generating unit, this may also include flowing the electroplating solution into the container such that the electroplating solution contacts and / or surrounds the bubbler. In some other embodiments, the interface may include causing a nozzle (e.g., Figure 3BThe nozzles 398D and 398E in the figure allow the gas to flow onto and into the plating solution so that the bubbler interfaces with the plating solution, or allow the nozzles to flow the plating solution into a fluid container such as a container.

[0126] In block 505, the foam may be removed from the system. As described above, this removal may be an independent removal, wherein the pressure and gravity of the generated foam causes the foam to flow out of a container, reservoir, or tank. This removal may also include the foam flowing through a discharge flow path to a drain pipe. As described above, the foaming of the solution generates foam, which captures byproducts in the foam, and the removal of the foam from the system removes unwanted byproducts, such as levelers, from the electroplating system.

[0127] In some embodiments including a foam generating unit, the techniques described herein may also include the operation of flowing the electroplating solution into and out of the foam generating unit. Figure 6 A second example technique for bubbling the electroplating solution is depicted. Here, blocks 601, 603, and 605 are respectively associated with Figure 5 It can be seen that after block 601 and before block 603, block 607 is performed, including flowing the electroplating solution to the foam generating unit; this may include operating a valve and / or moving a pump to allow the electroplating solution to flow to the unit. For example, referring to Figure 4B , the operation block 607 may include opening valve 164B, which allows fluid to flow from tank 102 to bubbler flow path 462B and to foam generating unit 168 .

[0128] In some embodiments, the bubbling of block 603 may further include containing the electroplating solution (e.g., the first volume (e.g., 1 liter)) in a container during the bubbling. After the bubbling and de-bubbling of block 503, the electroplating solution may flow back to another element of the electroplating system, which may in turn include operating a valve and / or a pump, as shown in block 609. For example, still referring to Figure 4B As shown, this may include operating valve 164A so that the plating solution may flow from the bubble generation unit 168 to the plating tank flow circuit 106 through the bubbler flow path 462B.

[0129] The occurrence of electroplating solution bubbling can be based on periodic, time-based intervals, as well as detection and determined conditions of the electroplating system. In some embodiments, the electroplating solution can be bubbled for a specific duration, such as a first time period, such as about 1 minute, 1 to 10 minutes, and 30 minutes. Bubbling can also be repeated at time-based intervals, including the same or different intervals during the process. Figure 7 Describes something like Figure 5 The third technique for bubbling the electroplating solution is described in detail in FIG. 701 , 703 and 705 respectively. Figure 5. After the foaming of block 703 is performed, or after the foam is removed in block 705, block 711 can be executed to start a timer that tracks the next foaming repetition. The timer is monitored and compared to a threshold time, which can be a periodic interval such as 30 minutes, and once the timer reaches the threshold, the foaming and foam removal of blocks 703 and 705 can be repeated. In some embodiments, the threshold time can be between about 2 minutes and about 30 minutes (+ / - 5%); this allows an idle time between foaming of between about 2 minutes and 30 minutes (including 5 minutes). It has been found that for some electroplating processes and solutions, starting foaming between 2 minutes and 30 minutes after the foaming is completed can reduce unwanted byproducts at a high enough and frequent enough rate so that the generated byproducts do not adversely affect the electroplating process. In some embodiments, foaming can occur for about three minutes, then idle for two minutes, followed by foaming for about 3 minutes, and then idle for about two minutes, which can be repeated during electroplating. It has also been found that for some electroplating processes, bubbling 1 liter (L) of plating solution for about 1 to 10 minutes in a plating system containing about 100 L of plating solution can better remove the desired amount of byproducts than conventional drain and feed techniques. For some electroplating systems with 200 L of plating solution, bubbling 2 L of plating solution, including using two containers, each container containing about 1 L of plating solution, for about 1 to 10 minutes can better remove the desired amount of byproducts than conventional drain and feed techniques. In some embodiments, the bubbler can be configured to bubble about 1%, 2%, or 5% of the total volume of the plating solution in the system.

[0130] In some embodiments, bubbling of the electroplating solution may occur based on the determination of voltage changes within the electroplating system. Figure 2 As described above, during wafer electroplating, the DC power supply 238 controls the current flowing to the wafer 218 and other electrical components of the plating tank. The controller includes various program instructions for current and voltage levels, as well as for monitoring and detecting voltage changes on the wafer and other system components. In some cases, the voltage change on the wafer may indicate when the through-holes on the wafer are full, that is, have been satisfactorily plated. Under normal electroplating conditions, when the byproducts in the plating solution are below a certain undesirable threshold, a certain amount of voltage change will occur at a specific time to indicate that the through-holes in the wafer are full.

[0131] When the plating solution has degraded beyond an undesirable threshold, such as when leveler byproducts are at or above a threshold, the voltage on the wafer may change earlier or later, more or less, or both, than expected under normal operation. For example, if there are too many byproducts in the plating solution (so that the desired plating does not occur, for example, the bump height is less than a certain height), the voltage change may occur earlier than under normal plating conditions. The specific voltage signature may depend on the wafer type, TSV size, die layout, and pattern density. For some substrates, bath height degradation may occur when the voltage change is greater than about + / - 10% of the plating solution voltage and there are no byproducts. The system controller is configured to detect such a change, determine whether such a change is above or below the expected change amount, determine whether such a change occurs earlier or later than expected, and based on one or both of these determinations, determine whether the byproducts are exceeding the threshold and causing blistering. In some cases, the threshold amount may be below the actual level at which undesirable plating occurs; this can be accomplished by pre-bubbling the plating solution and removing byproducts before the plating solution reaches undesirable amounts to maintain the plating solution at a desired byproduct level, thereby producing consistent and desired plating on the wafer.

[0132] Figure 8 A fourth example technique for bubbling an electroplating solution is depicted. Blocks 801, 803, and 805 are respectively Figure 5 801, followed by block 815, in which electroplating of the wafer is initiated; the electroplating, as described herein, includes applying a voltage to the wafer and across the electroplating solution. During the electroplating, in block 817, the voltage applied to the wafer is monitored as described above, and in block 819, a change in the voltage can be detected, and in block 821, a determination can be made based on the detected change in voltage whether the byproducts in the system are above a threshold. As described above, the determination includes determining whether the change is above or below an expected amount of change, whether the change occurs earlier or later than expected, or both. If these changes exceed normal expected changes, the byproducts in the electroplating solution may be higher than the desired amount. Once it is determined that the byproducts in the system are above the threshold, the bubbling and foam removal of the electroplating system of blocks 803 and 805 are performed.

[0133] In some embodiments, the electroplating solution can be continuously bubbled during electroplating, including during all desired plating of one and / or more substrates. In some of these embodiments, the electroplating fluid can continuously flow to or interface with a bubbler. This can include continuously flowing the electroplating solution into and out of the vessel while continuously operating the bubbler to bubble the electroplating solution in the vessel. This can also include continuously removing the generated foam from the system. Reference Figure 5 , for example, during electroplating, blocks 503 and 505 may be performed continuously. Figure 6 As another example, during the electroplating process, blocks 607 , 603 , 605 , and 609 may be performed consecutively.

[0134] In some embodiments, the above techniques may include bubbling the plating solution and performing drain and feed operations to remove byproducts and maintain the plating solution at a desired level. Any of the above techniques, such as Figures 5 to 8 The technology in the embodiment of the present invention may also include one or more operations for performing discharge and feeding operations, which may be continuous or periodic operations during the electroplating process. The discharge and feeding operations may also include dilution operations to dilute the solution.

[0135] The above-mentioned techniques and equipment are applicable to various electroplating processes. This includes wafers with high-density features, such as through holes and grooves, which may produce more byproduct levelers than traditional wafers. This can also include electroplating processes for wafers with photoresists, which may be released into the electroplating solution and may have an adverse effect on the electroplating process. The foam produced by bubbling the electroplating solution containing the photoresist material may capture some of these photoresist materials, similar to the foam that captures the leveler. Therefore, bubbling this electroplating solution and removing the foam can remove some unwanted photoresist materials from the electroplating solution, thereby improving the electroplating performance. The above-mentioned techniques and equipment are also applicable to various electroplating solutions, such as those including and can be used for electroplating copper, nickel, tin, Sn, Ag, gold, palladium and cobalt. For example, some TSV fill chemistries might use a plating solution with copper, cobalt, and nickel; some damascene plating uses a plating solution containing copper and cobalt; and plating through resist (e.g., plating onto a wafer with a photoresist) may use a plating solution with copper, nickel, tin, Sn, Ag, gold, palladium, and cobalt.

[0136] Experimental Results

[0137] The above-mentioned techniques and equipment are used to improve the plating performance of the plating system by removing unwanted byproducts. As described above, it is well known in the art that the TSV bump height of the filled through hole provides an indicator of the plating performance and plating solution degradation caused by the presence of unwanted leveler byproducts in some cases. The bump height is measured relative to the wafer surface, for example, a bump height of 4 microns (μm) is a through hole filled 4μm above the wafer surface. Since the leveler byproducts accumulate in the plating solution during the plating of one or more wafers, the bump height decreases over time until they reach an unacceptable level. In some embodiments, the desired bump height is about 4μm, + / -1μm. Fig. 9Plots of wafer through-hole bump height for two electroplating processes are depicted; the horizontal axis is unitless process time and the vertical height is bump height in μm. The first electroplating process was performed without a bubbler and over time the bump height decreased to and below 0 μm, indicating degradation in the electroplating fill process as the via was not completely filled to the top of the wafer. The second electroplating process utilized a bubbler as described herein to bubble the plating solution, produce foam that captures the leveler byproducts, and remove the foam. It can be seen that the use of a bubbler maintains the desired plated bump height within a range of 4 μm + / - 1 μm compared to the electroplating process without a bubbler.

[0138] The above-mentioned technique and apparatus also improve the recovery time of the electroplating solution, which can improve production throughput as well as electroplating performance. In many conventional electroplating systems, the electroplating solution can be recovered and returned to the desired level of byproducts by idling the electroplating solution, i.e., allowing the solution to remain static over time. By using the above-mentioned foaming technique and apparatus, the recovery time of the electroplating solution is reduced, so that the electroplating solution can be used for the electroplating process more quickly, improving production throughput and reducing the waste of the electroplating solution. Fig. 10A Plotting the recovery time graph for two plating solutions, Fig. 10B Depicted are cross-sectional side views of vias on two wafers. Fig. 10A In FIG. 1 , the horizontal axis is time in hours and the vertical axis is bump height in μm, and it can be seen that the plating solution has a recovery time of about 98 hours (hrs) when left idle to reach about 4 microns. Fig. 10B In the figure, the bump heights are 1.6μm, 1.7μm, and 4.0μm at 0, 12, and 98 hours of idle recovery time, respectively. Fig. 10A and 10B As shown, the use of a bubbler will allow the plating solution to recover in approximately 10 hours.

[0139] As used herein, the term "wafer" may refer to a semiconductor wafer or substrate or other similar types of wafers or substrates.

[0140] It should also be understood that the use of ordinal indicators herein, such as (a), (b), (c), ..., is for organizational purposes only and is not intended to convey any particular order or importance to the items associated with each ordinal indicator. For example, "(a) obtaining information about speed and (b) obtaining information about position" would include obtaining information about position before obtaining information about speed, obtaining information about speed before obtaining information about position, and obtaining information about position while obtaining information about speed. However, in some cases, some of the items associated with the ordinal indicators may inherently require a specific order, for example, "(a) obtaining information about speed, (b) determining a first acceleration based on the information about speed, and (c) obtaining position information"; in this example, (a) would require the execution of (b) because (b) depends on the information obtained in (a)-(c), but may be executed before or after (a) or (b).

[0141] Various modifications to the embodiments described in this disclosure will be apparent to those skilled in the art, and the general principles defined herein may be applied to other embodiments without departing from the spirit or scope of the disclosure. Therefore, the claims are not intended to be limited to the embodiments shown herein, but are to be given the broadest scope consistent with the disclosure, the principles and novel features disclosed herein.

[0142] Certain features described in this specification in the context of separate implementations may also be implemented in combination in a single implementation. Conversely, various features described in the context of a single implementation may also be implemented in multiple implementations, either individually or in any suitable subcombination. Furthermore, while features may be described above as functioning in certain combinations and even initially claimed as such, in some cases one or more features may be removed from the claimed combination, and a claimed combination may be directed to a subcombination or variations of a subcombination.

[0143] Similarly, although operations are depicted in a particular order in the accompanying drawings, this should not be understood as requiring such operations to be performed in the particular order shown or in sequence, or performing all the operations shown to achieve the desired result. In addition, the accompanying drawings may schematically depict another example process in the form of a flow chart. However, other operations not depicted may be incorporated into the example process schematically illustrated. For example, one or more additional operations may be performed before, after, at the same time, or between any of the operations shown. In some cases, multitasking and parallel processing may be advantageous. In addition, the separation of various system components in the above-mentioned embodiments should not be understood as requiring such separation in all embodiments, and it should be understood that the described program components and systems can generally be integrated together in a single software product or packaged into multiple software products. In addition, other embodiments are within the scope of the appended claims. In some cases, the actions described in the claims may be performed in different orders and still achieve the desired results.

Claims

1. An electroplating system comprising: an electroplating cell configured to contain an anode and an electroplating solution; a wafer support configured to support a wafer within the electroplating tank; a reservoir configured to contain at least a portion of the electroplating solution; a recirculation flow path fluidly connecting the reservoir and the electroplating tank, wherein the recirculation flow path includes a pump and is configured to circulate the electroplating solution between the reservoir and the electroplating tank; and a bubbler in fluid communication with one or more of: the electroplating tank, the reservoir, and the recirculation flow path, wherein the bubbler is configured to generate bubbles in the electroplating solution when the electroplating solution is present in the electroplating system, interfaces with the bubbler, and is activated, and to generate foam that captures byproducts of electroplating, Wherein the electroplating system is configured to remove the foam and the byproducts captured therein from the electroplating system.

2. The electroplating system according to claim 1, wherein: The bubbler includes at least one of the following: an aeration stone, one or more nozzles, one or more jet ports, a propeller, and an impeller.

3. The electroplating system according to claim 2, wherein: The bubbler comprises an aeration stone, and The aeration stone is composed of a material that is compatible with the electroplating solution.

4. The electroplating system according to claim 3, wherein: The material includes one or more of the following: high density polyethylene (HDPE), polypropylene (PP) and polytetrafluoroethylene (PTFE).

5. The electroplating system according to claim 4, wherein: The porosity of the material is between 1 mm and 1 μm.

6. The electroplating system of claim 3, further comprising a gas source fluidly connected to the bubbler and configured to flow gas toward the aeration stone.

7. The electroplating system of claim 1, further comprising a container, wherein: The container: is fluidly connected to one or more of: the plating tank, the reservoir, or the recirculation flow path, and configured to receive and contain a first volume of the electroplating solution; and The bubbler is further configured to generate bubbles in the electroplating solution in the container when the container contains the first volume of the electroplating solution and the bubbler is activated.

8. The electroplating system according to claim 7 further includes a foam generating unit, wherein the foam generating unit includes the container and the bubbler, wherein the foam generating unit is fluidly connected to one or more of the following: the electroplating tank, the liquid reservoir or the recirculation flow path.

9. The electroplating system of claim 7, wherein the container is physically separated from but fluidly connected to one or more of: the electroplating tank, the reservoir, or the recirculation flow path.

10. The electroplating system of claim 7, wherein the container is at least partially positioned in one of: the electroplating tank, the reservoir, or the recirculation flow path.

11. The electroplating system according to claim 7, wherein: The container is fluidly disposed between the plating tank and the reservoir.

12. The electroplating system of claim 7, wherein the container further comprises a foam outlet configured to allow foam in the container to exit the container through the foam outlet.

13. The electroplating system of claim 12, wherein: The container includes a fluid outlet, and The foam outlet is at a height higher than the fluid outlet.

14. The electroplating system of claim 13, wherein: The container includes a fluid inlet, and The foam outlet is at a height higher than the fluid inlet. 15 . The electroplating system according to claim 7 , further comprising a foam moving unit configured to cause foam in the container to leave the container when the foam is in the container and when the foam moving unit is activated.

16. The electroplating system according to claim 15, wherein: The foam moving unit includes one or more of the following: a fan, a skimmer, and a vacuum pump.

17. The electroplating system of claim 7, further comprising a controller configured to control the bubbler, wherein the controller comprises control logic for: allowing the electroplating solution to flow into and be contained by the container, and The bubbler is caused to generate bubbles in the electroplating solution in the container.

18. The electroplating system of claim 17, further comprising one or more inlet valves configured to control the flow of the electroplating solution into the container, wherein: The controller is further configured to control the one or more inlet valves, and The controller also includes control logic for causing the one or more inlet valves to open to allow the electroplating solution to flow into the vessel.

19. The electroplating system of claim 18, wherein: The system is further configured such that the electroplating solution flows into and out of the container through a common flow path, The one or more inlet valves are configured to control the flow of the electroplating solution into the container through the common flow path, The one or more inlet valves are further configured to also control the flow of the electroplating solution out of the reservoir through the common flow path, and The controller also includes control logic for causing the one or more inlet valves to close to allow the container to contain the electroplating solution therein.

20. The electroplating system of claim 18, further comprising one or more outlet valves configured to control the flow of the electroplating solution out of the container, wherein: The controller is further configured to control the one or more outlet valves, and The controller also includes control logic for: causing the one or more outlet valves to close to allow the container to contain the electroplating solution therein, and The one or more outlet valves are opened to allow the electroplating solution to flow out of the container.

21. The electroplating system of claim 7, wherein: The electroplating system is configured to contain a total working volume of the electroplating solution, and The container is configured to hold up to 5% of a total working volume of the electroplating solution.

22. The electroplating system of claim 1 , further comprising a controller configured to control the bubbler, wherein the controller comprises control logic for causing the bubbler to generate bubbles in the electroplating solution during one or more time periods when the electroplating solution is present in the electroplating system and interfaces with the bubbler.

23. The electroplating system of claim 22, wherein: The controller also includes control logic for: causing the bubbler to generate bubbles in the electroplating solution while the electroplating solution is present in the electroplating system and interacts with the bubbler for a first period of time, and The bubbler is caused to repeatedly generate bubbles at a first time interval.

24. The electroplating system of claim 22, further comprising a power source electrically connected to the wafer support and the electroplating tank, wherein: The power supply is configured to apply a voltage to a wafer held by the wafer holder, The controller also includes control logic for: causing the power supply to apply current to the wafer held by the wafer holder and the electroplating bath, and measuring the voltage potential between the wafer and the electroplating bath, and The causing the bubbler to generate bubbles in the electroplating solution is further based at least in part on the measured voltage.

25. The electroplating system of claim 24, wherein: The controller also includes control logic for determining a change in voltage potential between the wafer and the electroplating bath, and The causing the bubbler to generate bubbles in the electroplating solution is further based at least in part on the determined voltage potential change.

26. The electroplating system of claim 1, further comprising a controller configured to control the bubbler, wherein the controller includes control logic for causing the bubbler to continuously generate bubbles in the electroplating solution during electroplating of a wafer.

27. The electroplating system of claim 1, wherein the foam is configured to float on a surface of the electroplating solution.

28. An electroplating method, the method comprising: A plating solution is provided to an electroplating system, the electroplating system comprising: an electroplating tank configured to contain an anode and an electroplating solution, a wafer support configured to support a wafer within the electroplating tank, and a reservoir configured to contain at least a portion of the electroplating solution, frothing the electroplating solution by generating bubbles in the electroplating solution using a bubbler, thereby generating a foam, wherein the foam captures byproducts of electroplating; and The foam and the byproducts trapped therein are removed from the electroplating system.

29. The method of claim 28, wherein the bubbling reduces the amount of leveler from the electroplating solution.

30. The method of claim 28, wherein the foam comprises a leveler from the electroplating solution.

31. The method of claim 28, wherein: The bubbling further includes flowing the gas toward an aeration stone in the bubbler.

32. The method according to claim 31, wherein: The gas includes nitrogen.

33. The method of claim 28, wherein: The bubbling further comprises agitating the electroplating solution using at least one of: one or more jets, one or more nozzles, a propeller, and an impeller.

34. The method of claim 28, further comprising: flowing the electroplating solution into a container, wherein the bubbling occurs in the container; and After bubbling, the electroplating solution flows from the container to one or more of: the reservoir and the electroplating tank.

35. The method of claim 34, further comprising: A first volume of the electroplating solution is contained in the container during at least the bubbling process.

36. The method of claim 34, further comprising: At least during the foaming process, the foam generated in the container is caused to flow out of the container.

37. The method of claim 28, further comprising interfacing the electroplating solution with the bubbler.

38. The method of claim 28, further comprising electroplating a wafer, wherein the blistering and the removing are performed continuously during the electroplating.

39. The method of claim 28, wherein the foam is configured to float on a surface of the electroplating solution.

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