Electric filling from alkaline electroplating solution

Abstract

SOLUTION: Disclosed is an apparatus and method for electroplating a metal using an alkaline electrodeposition solution or the like. In electric plating, the solution can perform superconformal filling in features of a metal such as the features having critical dimensions of about 20 nm or less. A metal electric plating process can be used in an integrated circuit production. For example, the process can be used to fill trenches and vias in a partially fabricated integrated circuit. The electrically plated metal may be copper. The copper can be electrically plated on a substrate material less noble than copper.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] Incorporation by Reference A PCT application is being filed concurrently herewith as part of this application, and each application identified in that concurrently filed PCT application to which this application claims benefit or priority is incorporated herein by reference in its entirety for all purposes. [Background technology]

[0002] As fabricated integrated circuit features become smaller, there is less room for thicker, more robust seed layers to support copper electroplating, but due to its low resistivity, copper metal is still used for many applications, such as damascene fill in back-end-of-line processes. In some implementations, copper is electroplated onto a less noble material than copper, such as cobalt.

[0003] The background and contextual discussion contained herein is provided solely for the purpose of generally presenting the content of the present disclosure. Much of the present disclosure presents work by the inventors, and merely because such work is discussed in the Background section or presented as content elsewhere herein does not mean that it is admitted to be prior art. Summary of the Invention

[0004] Some aspects of the present disclosure relate to methods for electroplating metal into features of a substrate. Such methods can be characterized by the acts of contacting a substrate with an electroplating solution and electroplating copper metal from the electroplating solution into the features of the substrate. In some implementations, the electroplating solution comprises: Aqueous solutions with a pH greater than 7, Approximately 0.1 to 60 g / L of copper salt dissolved in aqueous solution; Copper(II) complexing ligands, and A combination of an inhibitor and an accelerator selected from the group consisting of: (i) polyallylamine (inhibitor) and thiourea (accelerator), (ii) polyallylamine (inhibitor) and ammonium thiocyanate (accelerator), and (iii) saccharin (inhibitor) and thiourea (accelerator). Includes. In some embodiments, the electroplating solution comprises: Aqueous solutions with a pH greater than 7, Approximately 0.1 to 60 g / L of copper salt dissolved in aqueous solution; copper(II) complexing ligand, an accelerator comprising a thiocyanate; and Inhibitor Includes.

[0005] The electroplating operation may be performed as a superconformal filling of copper metal into features of the substrate. In some cases, the electroplating operation is performed while rotating the substrate in the electroplating solution. In some cases, the electroplating operation is performed while flowing the electroplating solution through a cell containing the substrate.

[0006] In certain embodiments, prior to contacting the substrate with the electroplating solution, the method further comprises annealing the substrate in an inert or reducing atmosphere at a temperature of about 30°C to 600°C for about 30 seconds to 1 hour. In certain embodiments, prior to contacting the substrate with the electroplating solution, the method further comprises annealing the substrate in the presence of a remote reducing plasma while heating the substrate at a temperature of about 30°C to 600°C for about 30 seconds to 1 hour. In certain embodiments, prior to contacting the substrate with the electroplating solution, the method further comprises contacting the substrate with a pretreatment bath for about 1 to 600 seconds. In certain embodiments, the pretreatment bath has a composition different from the composition of the electroplating solution. In certain embodiments, the method further comprises electrically polarizing the substrate in the pretreatment bath. In certain embodiments, the pretreatment bath does not contain any constituent chemicals that are also not present in the electroplating solution. In some implementations, after the pretreatment period, the method further comprises modifying the composition of the pretreatment bath to obtain an electroplating solution.

[0007] In some embodiments, the electroplating operation fills a substrate feature having a critical dimension of about 20 nm or less. In some embodiments, the substrate feature includes a diffusion barrier that is about 1-5 nm thick. By way of example, the diffusion barrier includes tantalum nitride. In particular embodiments, the substrate feature includes a conductive liner that is about 1-5 nm thick. By way of example, the conductive liner includes cobalt, molybdenum, titanium, or any combination thereof.

[0008] In certain embodiments, after contacting the substrate with the electroplating solution, the method further includes the act of holding the substrate at a potential of about 0 to about −1.5 V relative to the copper pseudo reference electrode. By way of example, the substrate is held at a potential of about 0 to about −1.5 V relative to the copper pseudo reference electrode for about 0 to about 10 seconds. In certain embodiments, after contacting the substrate with the electroplating solution, the method further includes the act of controlling the current so that about 0 A flows between the substrate and the electroplating solution.

[0009] In a particular embodiment, the act of electroplating copper metal controls the current to about 0.25 mA / cm on the electroplating surface of the substrate. 2 ~about 40mA / cm 2 In certain embodiments, the act of electroplating copper metal includes controlling the current between the substrate and the electroplating solution so that the current increases from a low value to a high value or decreases from a high value to a low value. For example, the current may be about 1 to about 60 mA / cm on the electroplating surface of the substrate for a time period of about 0.1 seconds to about 10 seconds. 2 and then controlling to decrease the current density on the electroplating surface of the substrate. In certain embodiments, the operation of electroplating copper metal includes controlling the current between the substrate and the electroplating solution using a series of current pulses.

[0010] In certain embodiments, the act of electroplating copper metal includes controlling the potential of the substrate. Certain aspects of the present disclosure include a method for producing a composition comprising the following components: Aqueous solutions with a pH greater than 7, Cu(II) at approximately 0.1–60 g / L, supplied as copper salts dissolved in aqueous solution; Copper(II) complexing ligands, and A combination of an inhibitor and an accelerator selected from the group consisting of: (a) polyallylamine (inhibitor) and thiourea (accelerator), (b) polyallylamine (inhibitor) and ammonium thiocyanate (accelerator), and (c) saccharin (inhibitor) and thiourea (accelerator). The present invention relates to an electroplating solution that can be characterized by: Certain aspects of the present disclosure include a method for producing a composition comprising the following components: Aqueous solutions with a pH greater than 7, Cu(II) at approximately 0.1–60 g / L, supplied as copper salts dissolved in aqueous solution; copper(II) complexing ligand, an accelerator comprising a thiocyanate; and Inhibitor The present invention relates to an electroplating solution that can be characterized by:

[0011] Some electroplating solutions further include a pH adjuster or buffer sufficient to maintain a pH above 7 during electroplating of copper from the electroplating solution. Some electroplating solutions further include a leveler. Some electroplating solutions further include a sacrificial oxidizer.

[0012] In some electroplating solutions, the copper(II) complexing agent is present in the aqueous solution in a concentration sufficient to prevent the precipitation of copper hydroxide.

[0013] Some electroplating solutions further comprise a copper(I) complexing ligand. In some instances, the electroplating solution comprises a component that reduces the ability of the copper(I) ligand to prevent Cu(I) reduction during electroplating.

[0014] These and other features of the present disclosure are presented in more detail below with reference to the associated drawings. [Brief explanation of the drawings]

[0015] [Figure 1]FIG. 1 is a flow chart of an exemplary process that may be used to electroplate metal onto features of a partially fabricated integrated circuit.

[0016] [Figure 2] FIG. 2 is a schematic diagram of an example electroplating cell and a system including the electroplating cell for carrying out methods according to disclosed embodiments. [Figure 3] FIG. 3 is a schematic diagram of an example electroplating cell and a system including the electroplating cell for carrying out methods according to disclosed embodiments. [Figure 4] FIG. 4 is a schematic diagram of an example electroplating cell and a system including the electroplating cell for carrying out methods according to disclosed embodiments.

[0017] [Figure 5] FIG. 5 is an example of a filling profile showing the effect of an electrical waveform, particularly an electrical waveform having an initial current pulse.

[0018] [Figure 6] FIG. 6 shows an example of electron micrographs of cross sections of microfabricated trenches that were partially plated with copper from alkaline electroplating solutions with various combinations of accelerators and suppressors.

[0019] [Figure 7A] FIG. 7A is an example showing the results of two electrochemical techniques for additive screening. [Figure 7B] FIG. 7B is an example showing the results of two electrochemical techniques for additive screening. [Figure 7C] FIG. 7C is an example showing the results of two electrochemical techniques for additive screening. DETAILED DESCRIPTION OF THE INVENTION

[0020] Introduction and Background The present disclosure relates to alkaline electrodeposition solutions and apparatus and methods for electroplating metals using such solutions. In certain embodiments, the solutions are capable of superconformal filling of metals into small features, e.g., features having critical dimensions of about 20 nm or less. The metal electroplating process can be used during integrated circuit fabrication. For example, the process can be used to fill trenches and vias in partially fabricated integrated circuits. In certain embodiments, the metal is copper. In some implementations, the copper is electrodeposited onto a substrate material that is less noble than copper.

[0021] Various embodiments of the present disclosure relate to the electrofill of features in one or more layers of dielectric material. Some embodiments relate to forming conductive lines in a partially fabricated electronic device. In some cases, the electrical fill is performed in a damascene process that fills features having critical dimensions of about 20 nm or less, e.g., 14 nm or less.

[0022] In some embodiments, the features to be electrically filled (e.g., trenches and / or vias in a dielectric material) include a diffusion barrier that can be about 1-5 nm thick. In some cases, the diffusion barrier includes TaN. In some cases, the diffusion barrier is deposited by CVD. In some embodiments, the features to be electrically filled also include a conductive liner that can be about 1-5 nm thick. In some cases, the conductive liner includes cobalt, molybdenum, titanium, or any combination thereof. The conductive liner can include a metal that readily forms an oxide that can be dissolved in acid. The use of such metal liners presents challenges to superconformal filling in conventional acid electroplating solutions.

[0023] As fabricated components become smaller, there is less room for a relatively thick, robust conductive liner to support copper electroplating. However, due to its low resistivity, copper remains the primary current-carrying metal in many integrated circuit designs. As mentioned, in some damascene applications, the critical dimension is 14 nm or less, yet the diffusion barrier and conductive liner are each about 1-5 nm thick.

[0024] Native oxides formed on conductive liners can be quickly removed by typical acidic electroplating solutions and cannot be restored. This problem is exacerbated when the substrate material is less noble than copper, as in the case of cobalt. Copper ions participate in exchange reactions with cobalt or other less noble liner materials. The effects of the acid and the exchange reactions reduce the thickness of the liner. Copper electroplated on such a liner may deposit in some places but not in others.

[0025] In some embodiments, the electroplating process is carried out by applying a cathodic protection potential during immersion, however, this does not always provide sufficient protection.

[0026] In some embodiments, alkaline electroplating solutions are used because alkaline solutions are less likely to dissolve conductive liners such as cobalt. Additionally, certain electroplating solutions employ one or more compounds that complex copper ions. The resulting complexed copper ions are less likely to participate in exchange reactions with cobalt metal or other conductive liner metals.

[0027] However, even with the protection offered by alkaline electroplating solutions such as these, superconformal filling can remain a challenge. The proper selection of electroplating additives, including accelerators and supplemental suppressors and / or levelers, for superconformal filling has been elusive.

[0028] Aspects of the present disclosure relate to (a) defined electroplating solution compositions, (b) substrate liner pretreatments, and / or (c) electrofill processes using defined electroplating process parameters, each of which is addressed herein. In certain embodiments, the disclosed alkaline electrofill solutions enable retention of the substrate metal even if its surface is partially or completely converted to a native oxide. In certain embodiments, the electroplating solutions, apparatus, and processes described herein provide good nucleation of copper on a conductive liner, such as a cobalt liner.

[0029] In certain embodiments of the present disclosure, the copper electrofilling solution includes (a) an alkaline copper ion plating solution, (b) a complexing agent for Cu(II) and / or Cu(I), (c) a buffering agent to maintain alkalinity, and (d) electroplating additives (e.g., accelerators and suppressors).

[0030] In some alkaline electroplating solutions, the accelerator behaves similarly to 3-mercapto-1-propanesulfonic acid (MPS) and / or bis(3-sulfopropyl)disulfide (SPS) in acidic solutions during superconformal electrofilling of copper. Such behavior can include strong adhesion to the copper metal surface during deposition. In addition, the accelerator does not substantially degrade or become incorporated into the growing electrofilled copper layer. Unfortunately, it has been found that SPS and MPS may not function properly in some alkaline solutions.

[0031] Suppressors in alkaline electroplating solutions can behave similarly to suppressors in acidic solutions during superconformal electrofilling of copper. However, suppressors used in alkaline electroplating solutions must be compatible with the accelerators in that solution. Levelers in alkaline electroplating solutions can behave similarly to levelers in acidic solutions during superconformal electrofilling of copper. However, levelers used in alkaline electroplating solutions must work in concert with the accelerators in that solution.

[0032] In certain embodiments, the alkaline electroplating solution includes one or more complexing agents for copper(I) and / or copper(II) ions. In certain embodiments, the alkaline electroplating solution includes one or more sacrificial oxidizers. The sacrificial oxidizers can protect the conductive liner by having a reduction potential that allows the conductive liner to compete with copper deposition, resulting in a current efficiency lower than the unit current efficiency.

[0033] In certain embodiments, prior to copper electroplating in an alkaline solution, the conductive liner on the substrate features is treated to protect the liner from removal upon contact with the alkaline electrofill solution. Such pretreatment may involve contacting the liner with a wet and / or dry environment to chemically reduce or otherwise modify the liner to resist attack by the alkaline electroplating solution.

[0034] In certain embodiments, the pretreatment is a dry process that chemically reduces metal oxides on the liner, thereby increasing the amount of elemental metal in the liner. Examples of dry pretreatments include, for example, high temperature annealing and exposure to a reducing plasma (e.g., a hydrogen-containing plasma).

[0035] In certain embodiments, the pretreatment is a wet protection that reduces metal oxides on the liner or protects the metal liner from alkaline solutions. The wet pretreatment can be performed in the electroplating cell (in-situ) or outside the electroplating cell (ex-situ). In certain embodiments, the wet pretreatment involves applying a reducing potential to the substrate to chemically reduce oxides on the liner present in the solution. In some embodiments, the wet reduction of oxides is performed in a metal-free solution.

[0036] In certain embodiments, depositing copper metal from an alkaline electroplating solution includes applying current pulses and / or voltage ramps to the substrate onto which the copper is to be electroplated. In some cases, a voltage ramp is applied first during the electroplating process.

[0037] Any one or more of the following features may be used alone or in combination with any of the others. 1) Accelerator / suppressor combinations for electroplating copper from alkaline electroplating solutions, for example, onto conductive liners comprising metals less noble than copper; 2) the use of a leveller-mediated diffusion-based mechanism for electrofilling features; 3) Cu(II) and / or Cu(I) ligands in alkaline electroplating solutions; 4) sacrificial oxidizers in alkaline electroplating solutions; 5) the use of pulsed electroplating (e.g., pulsed current applied to the electroplating cell); 6) Use of lamp current waveform during electroplating; 7) Control of mass transport (e.g., by controlling the rotation speed of the rotating electrode and / or the flow rate of the electroplating solution into the electroplating cell), optionally varying mass transport conditions during plating, e.g., to optimize filling across various feature sizes; 8) Use of a wet pretreatment solution, optionally performing the pretreatment in situ on the substrate in the electroplating cell and replacing the pretreatment bath with the electroplating solution; and 9) Use of dry pretreatments to condition the conductive liner before plating.

[0038] The following detailed description describes electrochemical plating, also referred to as "electroplating" or simply "plating." In certain embodiments, electroplating fills features in a semiconductor device partially fabricated on a semiconductor substrate. In this description, the terms "semiconductor wafer" or "semiconductor substrate," or simply "substrate," refer to a substrate having semiconductor material anywhere within its body; it will be understood by those skilled in the art that the semiconductor material need not be exposed. A semiconductor substrate can include one or more dielectric and conductive layers formed on the semiconductor material. Wafers used for semiconductor wafers may be circular semiconductor substrates, which may have diameters of, for example, 200 mm, 300 mm, or 450 mm. However, those skilled in the art will understand that suitable alternative embodiments of what is described herein exist and that the disclosed electroplating operations can be performed on workpieces of various shapes and sizes and made from various materials. In addition to semiconductor wafers, other workpieces that can utilize the disclosed embodiments include various articles such as electronic control displays, backplanes for such displays, and the like. In some embodiments, the wafer may be glass or another non-semiconductor material.

[0039] electroplating solution In various aspects, the electroplating solution of the present disclosure is alkaline and contains copper. In certain embodiments, a substrate electroplated with an alkaline electroplating solution contains a material less noble than copper. For example, the substrate can contain a cobalt liner. Compared to acidic electroplating solutions, alkaline electroplating solutions can be less aggressive in attacking the less noble material on the substrate. Alkaline electroplating solutions can leave a passivating layer of native oxide on the surface of the less noble material. During electroplating or wet pretreatment, the native oxide can be electrochemically reduced in situ rather than being rapidly dissolved by the electrolyte. In some embodiments, the alkaline electroplating solution contains species that complex copper ions, thereby reducing the thermodynamic driving force for galvanic corrosion of the substrate by copper.

[0040] As noted, in certain embodiments, the electroplating solution is alkaline. Thus, in some cases, the pH of the electroplating solution is about 7-14. In some cases, the pH of the electroplating solution is about 8-10.

[0041] As noted, in certain embodiments, the electroplating solution includes copper. In some embodiments, the range of possible copper concentrations is limited by the solubility and / or complexing agent species used in the electroplating solution. In certain embodiments, the concentration of copper ions in the electroplating solution is from about 0.1 to about 2 g / L. In such embodiments, the copper ions may be provided in the form of copper sulfate. In some cases, the concentration of copper ions in the electroplating solution is from about 0.4 to about 1 g / L.

[0042] The alkaline copper-containing electroplating solution may contain any of a variety of additives, some of which are described herein.

[0043] One class of additives is molecules that act as inhibitors, requiring increased polarization before copper can be reduced from solution onto the substrate. Another class includes molecules or elements that act as accelerators, reducing the polarization required to reduce copper from solution against the action of an inhibitor. Another class includes molecules or ions that act as levelers, reducing the activity of accelerators and allowing an accelerated surface to return to a more inhibited state. A further class includes molecules or ions that act as Cu(II) complexing agents, stabilizing copper ions in solution. A further class includes molecules or ions that act as Cu(I) complexing agents, stabilizing reaction intermediates in the Cu(II) → Cu reaction and thus increasing its rate. In some circumstances, Cu(I) complexing agents that increase reaction rate and reduce polarization can also be considered accelerators compared to certain inhibitors, so there may be some overlap between these classes. Yet another class is molecules or ions that act to modify or maintain pH in the alkaline range. Yet another class includes molecules or ions that are sacrificial oxidants that have an electrode reduction potential such that they can effectively compete with copper deposition, resulting in less than unity current efficiencies.

[0044] Inhibitor molecules, or "inhibitors," generally prevent copper from being readily reduced on the substrate. One mechanism by which this can occur is through the chemisorption of molecules on the substrate surface, sterically hindering the access of Cu(II) ions or occupying reactive sites on the substrate. If the substrate is not a copper film, the selected inhibitor will interact with both the unplated substrate surface and the plated copper film.

[0045] Suppressors (alone or in combination with other electroplating solution additives) are surface kinetic polarization compounds that result in a significant increase in the voltage drop across the substrate-electrolyte interface, especially when present in combination with surface chemisorbed halides (e.g., chloride or bromide). In some cases, the halide acts as a chemisorbed bridge between the suppressor molecule and the substrate surface. Suppressors (1) increase the local polarization of the substrate surface in areas where the suppressor is present compared to areas where the suppressor is absent (or present at relatively low concentrations), and (2) generally increase the polarization of the substrate surface. The increased polarization (local and / or global) corresponds to an increase in resistivity / impedance and therefore slower plating at a particular applied potential.

[0046] Inhibitors can be relatively large molecules, sometimes polymers such as polyethers (e.g., paraformaldehyde, polyethylene oxide (PEO), polypropylene oxide (PPO), polyethylene glycol (PEG), polypropylene glycol (PPG), other common polyalkylene glycol (PAG) polymers, copolymers of any of these (including block copolymers), etc.). These polymers and copolymers can be further functionalized with functional groups that can improve solubility or interaction with the substrate. Some examples of inhibitors include polyethylene oxide and polypropylene oxide with sulfur- and / or nitrogen-containing functional groups. Inhibitors can have linear or branched structures, or both. A particular class of inhibitor molecules includes organic chemisorption corrosion inhibitors. Inhibitor molecules with various molecular weights can coexist in an inhibitor solution.

[0047] Due in part to the large size of the suppressors, the diffusion of these compounds into the recessed features can be relatively slow compared to other electroplating solution components.

[0048] In some cases, the suppressor may slowly degrade over time by electrolysis or chemical decomposition in the electroplating solution, but may not become significantly incorporated into the deposited film.

[0049] Aside from their chemical structure, inhibitors can be characterized by specific electrochemical or other physical properties. These include the rate at which the inhibitor exerts its polarization effect and the strength of the polarization effect. Inhibitors increase polarization, making the deposition potential (cathode potential) more negative. The magnitude of the negative change in deposition potential is a measure of the inhibitor's polarization strength. One way to measure the properties of an inhibitor is to conduct an experiment in which a metal (e.g., copper) is plated onto a metal electrode (e.g., cobalt or copper). The experiment begins by plating the metal using a plating solution that does not contain the inhibitor under consideration. Plating can be performed galvanostatically, and the plating potential (e.g., the cathode potential) can be monitored. After plating for a period of time (e.g., until the system reaches a steady state), the inhibitor in question is introduced into the plating solution. During and after this introduction, a constant current is applied, and the electrode potential is measured. The delay until a measurable change in voltage is detected indicates the rate of the inhibitor's effect. The magnitude of the change in voltage (regardless of how quickly it occurs) indicates the "strength" of the inhibitor's effect. In certain embodiments, plating continues for approximately 5-10 minutes after the suppressor is introduced. If there is no detectable potential change during that time period, the suppressor is characterized as slow or ineffective. If the change occurs nearly immediately (e.g., within about 1 second after the suppressor is added), the suppressor is characterized as fast. In certain embodiments, a suppressor is considered to have a strong response if it makes the deposition potential at least about 200 mV more negative compared to the potential exhibited under the same conditions but without the electroplating additive. In certain embodiments, a suppressor is considered to have a weak response if it makes the deposition potential by no more than about 50 mV more negative.

[0050] The results in the table below were obtained using additive addition methods common in the industry. The electrode is first polarized in an electrolyte solution containing metal ions, a pH buffer, and a complexing agent (an aliphatic amine such as ethylenediamine) until a baseline constant current is achieved. After this potential is established, an inhibitor is added, and the magnitude and rate of polarization change are used to characterize the inhibitor as strong / weak and fast / slow, respectively. If an accelerator is subsequently tested, it is added after the inhibitor reaches steady state, and the further magnitude and rate of polarization change are used to characterize the accelerator as strong / weak and fast / slow, respectively. [Table 1-1] [Table 1-2]

[0051] In certain embodiments, any one or more of the suppressors listed above are used in the alkaline electroplating solution. In certain embodiments, polyallylamine ([C3H5NH2] n ) or structurally related polymers are used as suppressors in alkaline electroplating solutions.

[0052] Accelerator molecules allow copper to be reduced more readily on a substrate compared to an inhibited surface, e.g., a surface with an inhibitor species attached. Accelerators (alone or in combination with other electroplating solution additives) are believed to locally reduce the polarization effects associated with the presence of inhibitors, thereby locally increasing the electrodeposition rate. Accelerator molecules may be used in part based on their ability to maintain higher rates of plating in areas where these high rates initiate (relative to areas where the inhibitor dominates the polarization characteristics).

[0053] Electrochemically, accelerators reduce the magnitude of polarization required to deposit copper onto an inhibited substrate. Because the inhibitor molecule is more inhibitory than the accelerator, one possible mechanism of action of the inhibitor involves competition with the inhibitor for binding sites, resulting in higher current densities in regions where the inhibitor is displaced by the accelerator. Another possible mechanism of action is through stabilization of Cu(I) reaction intermediates, which can reduce polarization in regions of the substrate to levels even lower in magnitude than that of an uninhibited surface. Thus, some Cu(I) ligands can act as a form of accelerator. Both of these possible mechanisms of action are possible in parallel.

[0054] The depolarization effect is most pronounced in regions of the substrate surface where the accelerator is most concentrated (i.e., polarization is reduced as a function of the local surface concentration of adsorbed accelerator). Although accelerators can become strongly adsorbed to the substrate surface as a result of the plating reaction and become generally laterally immobile, in some embodiments, the accelerator generally does not significantly incorporate into the film. In such cases, the accelerator can remain on the surface as the metal deposits. As the recesses fill, the local accelerator concentration increases at the surface within the recesses. Accelerators tend to be smaller molecules and exhibit faster diffusion into recessed features compared to suppressors.

[0055] Accelerators can be characterized by certain electrochemical or other physical properties. These include the rate at which the accelerator exerts its effect on polarization and the strength of the accelerator's depolarizing effect. Accelerators reduce polarization, making the deposition potential (cathode potential) more positive. The magnitude of the negative change in deposition potential is a measure of the accelerator's depolarizing strength. One way to measure the accelerator's properties is to conduct an experiment in which a metal (e.g., copper) is plated onto a metal electrode (e.g., cobalt or copper). The experiment begins by plating the metal using a plating solution that does not contain the accelerator under consideration. Plating can be performed galvanostatically, and the plating potential (e.g., the cathode potential) is monitored. After plating for a period of time (e.g., until the system reaches a steady state), the accelerator in question is introduced into the plating solution. During and after this introduction, a constant current is applied, and the electrode potential is measured. The delay until a measurable change in voltage is detected indicates the rate of the accelerator's effect. The magnitude of the change in voltage (regardless of how quickly it occurs) indicates the "strength" of the accelerator's effect. In certain embodiments, plating continues for approximately 5-10 minutes after the accelerator is introduced. If there is no detectable potential change during that time period, the accelerator is characterized as slow or ineffective. If the potential change occurs almost immediately (e.g., within 1 second), the accelerator is characterized as very fast. In certain embodiments, an accelerator is considered to have a strong response if it makes the deposition potential at least approximately 400 mV more positive compared to a solution containing the suppressor and electrolyte but no accelerator. In certain embodiments, an accelerator is considered to have a weak response if it makes the deposition potential no more negative by approximately 50 mV or less.

[0056] A list of accelerators useful in the specific alkalinity of the electroplating solution of this disclosure is presented in the table below. The results in the table were obtained using two types of experiments. One is the additive addition method common in the industry. The electrode is first polarized in an electrolyte solution containing metal ions, a pH buffer, and a complexing agent (ethylenediamine) until a baseline constant current is achieved. After this potential is established, an inhibitor is added, and the magnitude and rate of polarization change are used to characterize the inhibitor as strong / weak and fast / slow, respectively. If an accelerator is subsequently tested, it is added after the inhibitor reaches steady state, and further magnitude and rate of polarization change are used to characterize the accelerator as strong / weak and fast / slow, respectively. The second type of experiment is cyclic voltammetry (CV). By comparing the CV of a fully constituted solution with the CV of a solution containing only the base electrolyte, the difference between the polarizations at a given current can be found. The more polarization required, the stronger the inhibition. [Table 2-1] [Table 2-2]

[0057] As indicated, the alkaline electroplating solution can include an accelerator that is a halide (iodide, bromide, chloride, and / or fluoride). In various embodiments, the halide ions are provided in the electroplating solution as a salt, such as, for example, a salt of an alkali metal, such as NaCl, NaBr, NaI, KCl, KBr, KI, etc. The halide ions may be provided by any of a variety of salts or as an acid, such as HCl, HBr, and HI. Of course, if the acid is neutralized, the salt determined by the base can be, for example, one of the pH adjusters described below.

[0058] Additionally or alternatively, the accelerator may be a pseudohalide. Examples of pseudohalides include cyanide, cyaphide, isocyanide, hydroxide, disulfide, cyanate, isocyanate, fulminate, thiocyanate, isothiocyanate, hypothiocyanate, selenocyanate, azide, nitrite, tetracarbonylcobaltate, trinitromethanide, tricyanomethanide, and trifluoromethanesulfonate (triflate). Any of these halides and pseudohalides may be provided in compounds containing any cationic or organic species. An example of a cation is NH4 + or a substituted ammonium ion, such as a quaternary ammonium ion. In various embodiments, a thiocyanate, such as ammonium thiocyanate or an alkali metal thiocyanate, is present as a promoter.

[0059] Leveling molecules can act by limiting the depolarizing effects of accelerating molecules. Levelers can perform this function particularly on exposed portions of the substrate, such as the field region of the wafer being processed, and on the sidewalls of features. Levelers can act by desorbing or displacing accelerators, preventing them from effectively competing with suppressors for binding sites, embedding accelerators in the plated film, or chemically decomposing them. The local concentration of the leveler is determined in part by mass transport. Levelers are often believed to react or be consumed at the substrate surface at or near the diffusion-limited rate; therefore, a continuous supply of leveler can maintain uniform plating conditions over time.

[0060] The potential role of the leveler in the disclosed alkaline electroplating solution is twofold. First, it controls overplating, ensuring that features that begin to experience accelerated fill do not overshoot to the point where the final uniformity of the plated part is too poor to allow for good downstream planarization. In this role, the leveler can act primarily on surface structures that have geometric shapes that protrude from the surface. This action smooths the surface of the electrodeposited layer. Second, it is a filling mechanism in which the leveler preferentially deactivates accelerators on the field toward the top of the feature, enhancing the system's ability to achieve and maintain superconformal fill.

[0061] Leveler compounds are generally classified as such based on their electrochemical function and effect and do not require a specific chemical structure or formulation. However, levelers often contain one or more nitrogen-containing compounds, such as amines, imides, amides, or imidazoles, and may also contain sulfur functional groups. Certain levelers contain one or more five- 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. Furthermore, the amine may be an arylamine or heterocyclic amine. Exemplary amines include, but are not limited to, dialkylamines, trialkylamines, arylalkylamines, triazoles, imidazoles, triazoles, tetrazoles, benzimidazoles, benzotriazoles, piperidine, morpholine, piperazine, pyridine, oxazoles, benzoxazoles, pyrimidines, quonoline, and isoquinoline. Imidazoles and pyridines may be particularly useful. Other examples of levelers include Janus Green B and Prussian Blue.

[0062] In general, levelers fall into the category of nitrogen-containing heterocyclic compounds, which have one or more heterocyclic moieties as defined herein, such as aromatic heterocycles (e.g., having one or more nitrogen atoms), bicyclic heterocycles (e.g., aromatic bicyclic heterocycles), and various aliphatic heterocycles.

[0063] In certain embodiments, the heterocycle is a cyclic amine. Exemplary cyclic amines are NR 1 R 2 R 3 R can have the formula 1 and R 2 together with the nitrogen atom to which each is attached form a heterocyclyl, and R 3 is hydrogen, hydroxyl, aliphatic, haloaliphatic, haloheteroaliphatic, heteroaliphatic, aromatic, aliphatic-aromatic, heteroaliphatic-aromatic, or any combination thereof. Exemplary cyclic imines are shown in the list below.

[0064] In another embodiment, the heterocycle is a cyclic amide. Exemplary cyclic amides are those having R 3 -C(O)NR 1 R 2 R can have the formula 1 and R 2 together with the nitrogen atom to which each is attached form a heteroaliphatic or heterocyclyl group as defined herein; R 3 are independently aliphatic, haloaliphatic, haloheteroaliphatic, heteroaliphatic, aromatic, aliphatic-aromatic, heteroaliphatic-aromatic, or any combination thereof; or R 1 and R 3 is R 1 together with the nitrogen atom to which it is attached form a heteroaliphatic or heterocyclyl group as defined herein, and R 2 are independently hydrogen, aliphatic, haloaliphatic, haloheteroaliphatic, heteroaliphatic, aromatic, aliphatic-aromatic, heteroaliphatic-aromatic, or any combination thereof; or R 1 and R 2 each is independently hydrogen, aliphatic, haloaliphatic, haloheteroaliphatic, heteroaliphatic, aromatic, aliphatic-aromatic, heteroaliphatic-aromatic, or any combination thereof; 3 is an optionally substituted heterocyclyl or an optionally substituted alkyl-heterocyclyl.

[0065] In another embodiment, the heterocycle is an N-heterocyclic carbene or a cyclic thioalkylaminocarbene (eg, as further described below).

[0066] Non-limiting examples of nitrogen-containing heterocycles include optionally substituted imidazole, optionally substituted triazole, optionally substituted tetrazole, optionally substituted pyrazole, optionally substituted imidazoline, optionally substituted pyrazoline, optionally substituted imidazolidine, optionally substituted pyrazolidine, optionally substituted pyrrole, optionally substituted pyrroline, optionally substituted pyrrolidine, optionally substituted succinimide, optionally substituted thiazolidinedione, optionally substituted oxazolidone, optionally substituted hydantoin, optionally substituted optionally substituted pyridine, optionally substituted piperidine, optionally substituted pyridazine, optionally substituted piperazine, optionally substituted pyrimidine, optionally substituted pyrazine, optionally substituted triazine, optionally substituted oxazine, optionally substituted morpholine, optionally substituted thiazine, optionally substituted thiomorpholine, optionally substituted cytosine, optionally substituted thymine, optionally substituted uracil, optionally substituted thiomorpholine dioxide, optionally substituted indene, optionally substituted indoline, optionally substituted indole, optionally substituted isoindole, optionally substituted indolizine, optionally substituted indazole, optionally substituted benzimidazole, optionally substituted azaindole, optionally substituted azaindazole, optionally substituted pyrazolopyrimidine, optionally substituted purine, optionally substituted benzisoxazole, optionally substituted anthranil, optionally substituted benzisothiazole, optionally substituted benzoxazole, optionally substituted benzthiazole, optionally substituted benzthiadiazole, optionally substituted adenine , optionally substituted guanine, optionally substituted tetrahydroquinoline, optionally substituted dihydroquinoline, optionally substituted dihydroisoquinoline, optionally substituted quinoline, optionally substituted isoquinoline, optionally substituted quinolizine, optionally substituted quinoxaline, optionally substituted phthalazine, optionally substituted quinazoline, optionally substituted cinnoline, optionally substituted naphthyridine, optionally substituted pyridopyrimidine, optionally substituted pyridopyrazine, optionally substituted pteridine, optionally substituted benzoxazine,Examples include optionally substituted quinolinones, optionally substituted isoquinolinones, optionally substituted carbazoles, optionally substituted acridines, optionally substituted phenazines, optionally substituted phenoxazines, optionally substituted phenothiazines, optionally substituted phenoxathiins, optionally substituted quinuclidines, optionally substituted azaadamantanes, optionally substituted dihydroazepines, optionally substituted azepines, optionally substituted diazepines, optionally substituted thiazepines, optionally substituted azocanes, optionally substituted azocines, optionally substituted azonanes, and optionally substituted azecines. Optional substitutions include any substituent such as alkoxy, amide, amine, thioether, thiol, acyloxy, silyl, alicyclic, aryl, aldehyde, ketone, ester, carboxylic acid, acyl, acylhalo, cyano, halogen, sulfonate, nitro, nitroso, quaternary amine, pyridinyl (or pyridinyl where the nitrogen atom is functionalized with an aliphatic or aryl group), alkyl halide, or any combination thereof.

[0067] The heterocycle can also include cations and / or salts of any of these. In some embodiments, the cationic form includes an optionally substituted alkyl bonded to the nitrogen atom of the heterocycle. Exemplary cationic forms include thiazolium, as well as salts thereof. The heterocycle can include one or more substituents (e.g., any of those described herein for aryl or alkyl, such as amine, alkyl, oxo, etc.). Exemplary substituted heterocycles include N-methylpyrrolidone, N-methylimidazole, 2,6-lutidine, and 4-N,N-dimethylaminopyridine. In some embodiments, the heterocycle includes two or more heteroatoms (e.g., two or more of N, O, and / or S).

[0068] In certain embodiments, the leveler is a heterocyclic aromatic compound. A heterocyclic nitrogen-containing aromatic compound is, unless otherwise specified, an aromatic compound containing 5, 6, or 7 membered rings containing 1, 2, 3, or 4 non-carbon heteroatoms (e.g., nitrogen and, optionally, one or more other heteroatoms independently selected from the group consisting of oxygen, phosphorus, sulfur, or halo). In some cases, the heterocyclic aromatic compound is methylated. In some cases, the heterocyclic aromatic compound follows Hückel's 4n+2 rule. In some cases, the additive is a halogen-substituted aromatic compound. A halogen-substituted aromatic compound is an aromatic compound containing at least one halogen bonded to the aromatic ring. As used herein, halogen or halo refers to F, Cl, Br, or I.

[0069] In some embodiments, the leveler is a heterocyclic aliphatic compound. As used herein, "aliphatic" refers to a compound having at least 1 carbon atom and up to 50 carbon atoms (C 1-50 ), e.g., 1 to 25 carbon atoms (C 1-25 ), or 1 to 10 carbon atoms (C 1-10 ), including alkanes (or alkyls), alkenes (or alkenyls), alkynes (or alkynyls), including cyclic versions thereof, and further including straight-chain and branched-chain configurations, as well as all stereoisomers and positional isomers. Heterocyclic aliphatic compounds, unless otherwise specified, are aliphatic compounds containing a 5-, 6-, or 7-membered ring containing 1, 2, 3, or 4 non-carbon heteroatoms (e.g., at least one nitrogen atom and, optionally, one or more other heteroatoms independently selected from the group consisting of oxygen, phosphorus, sulfur, or halo).

[0070] Leveler compounds may also contain alkoxide groups, such as methoxide and ethoxide groups. For example, levelers may contain a general backbone similar to that found in polyethylene glycol or polyethylene oxide, with amine fragments functionally inserted into the chain (e.g., Janus Green B). Leveler compounds may also contain epoxides. Exemplary epoxides include, but are not limited to, epihalohydrins, such as epichlorohydrin and epibromohydrin, and polyepoxide compounds. Polyepoxide compounds with 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, polyethyleneimine, polyamidoamine, and the reaction products of amines with various oxygen epoxides or sulfides. An example of a non-polymeric leveler is 6-mercaptohexanol. Another exemplary leveler is polyvinylpyrrolidone (PVP).

[0071] Levelers that can be used in the alkaline electroplating solutions of the present disclosure include many that have been used in acidic electroplating solutions for conformal fill applications, as well as other compounds. Examples are shown in Table 3.

[0072] superconformal packing In the superconformal filling mechanism, recessed features on a plating surface tend to be plated with metal from the bottom to the top of the feature and from the sidewalls of the feature inward toward the center. By controlling the relative deposition rates within the feature and in the field region, uniform filling is achieved and the incorporation of voids in the electrically filled feature is avoided. The three types of additives mentioned above are useful in achieving superconformal filling, each functioning to selectively increase or decrease polarization at the substrate surface.

[0073] After the substrate is immersed in the electrolyte, the suppressor adsorbs onto the surface of the substrate, particularly in exposed areas such as the field region. During the initial plating stage, there can be a substantial difference in suppressor concentration between the top and bottom of the recessed feature. This difference exists due to the relatively large size of the suppressor molecule and its correspondingly slow transport properties. Over this same initial plating time, the accelerator is expected to accumulate at a low, substantially uniform concentration throughout the plating surface, including the bottom and sidewalls of the feature. Because the accelerator diffuses into the feature more rapidly than the suppressor, the initial ratio of accelerator to suppressor within the feature (particularly at the bottom of the feature) is relatively high. A relatively high initial accelerator:suppressor ratio promotes rapid plating from the bottom of the feature upward and from the sidewalls inward. Meanwhile, the initial plating rate in the field region is relatively slow due to the low accelerator:suppressor ratio. Thus, during the initial plating stage, plating occurs relatively quickly within the feature and relatively slowly in the field region.

[0074] As plating continues, the feature is filled with metal, reducing the surface area within the feature. Because the surface area is reduced and the accelerator remains substantially on the surface, the local surface concentration of accelerator within the feature increases as plating continues. This increase in accelerator concentration within the feature helps maintain the differential plating rates beneficial for superconformal filling.

[0075] In later stages of plating, especially as an overburden deposit, the accelerator can accumulate in certain areas (e.g., above filled features), resulting in faster local plating than desired. A leveler can be used to counteract this effect. The surface concentration of the leveler is greatest in exposed areas of the surface (i.e., not within recessed features), where convection is greatest. The leveler is thought to displace the accelerator, increasing local polarization and potentially reducing the local plating rate in areas of the surface that plate at faster rates than elsewhere on the deposit. In other words, the leveler tends to at least partially reduce or eliminate the influence of the accelerator compound in exposed areas of the surface, particularly in protruding structures. Without the leveler, features tend to overfill, resulting in bumps. Therefore, in later stages of superconformal fill plating, a leveler is beneficial for producing a relatively flat deposit. Note that superconformal fill is sometimes referred to as "bottom-up fill."

[0076] The combined use of suppressors, accelerators, and levelers may enable void-free filling of features from a superconformal and from the inside of the sidewalls while providing a relatively flat deposition surface.

[0077] As described, alkaline copper ion-containing electroplating solutions can include combinations of accelerators and suppressors. In some embodiments, the combinations include a strong and fast (in terms of polarization) accelerator combined with a strong and fast suppressor. In some embodiments, other combinations are used. These include, for example, a strong and slow accelerator used in combination with a strong and fast suppressor, and a weak and fast accelerator used in combination with a weak and slow suppressor. In certain embodiments, the suppressor is strong enough to polarize the electrode surface (field region) and prevent plating there, and the accelerator acts more quickly or strongly within the feature and promotes plating there. The descriptions of strong, fast, weak, and slow polarization effects above, as well as the corresponding tests for establishing these effects, can be applied to the combinations identified herein. Thus, for example, the suppressors and accelerators characterized as strong, weak, fast, and slow in Tables 1 and 2 can be applied to the combinations herein.

[0078] complexing agent Copper(II) complexing agents can be used in alkaline electroplating solutions. Such complexing agents can prevent or reduce the amount of copper hydroxide precipitation. In certain embodiments, the complexing agent prevents copper hydroxide precipitation when the copper ion concentration is relatively high, such as during the preparation of the electroplating solution, or during the administration of a makeup solution containing copper ions to the solution. The complexing agent can also achieve higher polarization and reduce the redox activity of Cu(II) ions, which can help preserve substrates that are less noble than copper. For example, copper(II) complexing agents in alkaline electroplating solutions can prevent or reduce the amount of cobalt removed from a cobalt liner during contact with the alkaline electroplating solution. Copper(II) ligands that can be used in alkaline electroplating solutions include, but are not limited to, linear, cyclic, or polycyclic polyamines, aminocarboxylic acids, alkanolamines, oxycarboxylic acids, cyclic acid imide compounds, and organic phosphonic acids. Some examples of copper(II) complexing agents are listed in Table 3.

[0079] Copper(I) complexing agents can fulfill any one or more of a variety of roles, depending in part on the electrorecharge mechanism being pursued. For example, Cu(I) ligands can stabilize Cu(I) as an intermediate in the copper(II) reduction reaction, allowing the reduction reaction to occur more readily. In this role, Cu(I) ligands can act as accelerators. In another example, Cu(I) ligands can further stabilize the Cu(I) intermediate so that it halts the reaction instead of promoting the complete reduction of Cu(II) to Cu metal. The stabilized Cu(I) can then diffuse away from the electroplated copper surface. In this role, Cu(I) ligands function similarly to sacrificial oxidants (i.e., they hinder copper deposition significantly more in field regions than in features). Copper(I) ligands that can be used in alkaline electroplating solutions include, but are not limited to, molecules and ions considered "soft." Soft ions include H + These ions have a low charge relative to their volume, such as Cu(I), as opposed to ions with a high concentration of charge, such as Cu(I). Such ions include some halides, pseudohalides, cyclic imide compounds, and compounds containing sulfur functional groups, such as thiols, sulfides, disulfides, sulfinic and sulfonic acids, thiocyanates, isothiocyanates, thials (RC(S)H), and sulfones. Some examples of copper(I) complexing agents are listed in Table 3.

[0080] base As mentioned, alkaline electroplating solutions can help preserve passivating oxides on the substrate metal during immersion in the electroplating solution. Compared to acidic electroplating solutions, alkaline electroplating solutions can slow or prevent dissolution of the substrate metal and / or its oxide. For example, two types of bases can be used to generate and maintain alkaline electroplating solutions. The first of these is a base, particularly a hydroxide-containing base, which can be used to adjust the pH of the electroplating solution to a desired range. Strong bases may include, but are not limited to, potassium hydroxide and sodium hydroxide. Weak bases include ammonium hydroxide, tetramethylammonium hydroxide, tetraethylammonium hydroxide, and other quaternary ammonium hydroxides. The second class of bases of interest are buffer systems capable of passively maintaining the electroplating solution in a pH range of interest. The combination of active electroplating solution management with a stronger base and passive electroplating solution management with a buffer system results in a more manufacturable process. Some examples of buffers and pH-adjusting species are listed in Table 3.

[0081] sacrificial oxidant Sacrificial oxidants are species that are more easily reduced from solution than Cu(II). Therefore, sacrificial oxidants provide side reaction pathways and can result in copper deposition current efficiencies less than 100%. These ions or molecules can lead to charging through a differential current efficiency mechanism. In such a mechanism, a concentration or activity gradient is established between the feature and the substrate field such that the ratio of sacrificial oxidant reduction to copper ion reduction is greater over the field than within the feature. The concentration or activity gradient can be generated by the diffusion or use of molecules that promote or suppress side reactions, such as catalysts and inhibitors, respectively.

[0082] Generally, sacrificial oxidants are species with a reduction potential more positive than that of Cu(II) in the solution under consideration. Sacrificial oxidants can be selected by comparing the reduction potential of Cu(II) in the alkaline electroplating solution under consideration with the standard reduction potential of candidate sacrificial oxidants in the solution phase and selecting candidates with reduction potentials in the desired range. The standard reduction potential of Cu(II) is 0.339 V, but this potential decreases substantially when complexed with strong ligands. The standard reduction potential of Cu(II) with ethylenediamine is -0.119 V, and the standard reduction potential of Cu(II) with ethylenediaminetetraacetic acid (EDTA) is -0.216 V. Therefore, species with reactions with solution-phase reactants and products and standard reduction potentials more positive than -0.216 V are potentially interesting as sacrificial oxidants. Some examples of sacrificial oxidants are listed in Table 3. Any one or any combination of these can be used in alkaline electroplating solutions. [Table 3-1] [Table 3-2] [Table 3-3] [Table 3-4] [Table 3-5] [Table 3-6]

[0083] In some cases, the alkaline electroplating solution has a pH of about 8-10, a copper ion concentration of about 0.4-2 g / L, and an accelerator / suppressor combination. In certain embodiments, such alkaline electroplating solutions include thiocyanate as an accelerator. In certain embodiments, such alkaline electroplating solutions include at least one of the following accelerator / suppressor combinations: thiocyanate and polyallylamine, or thiocyanate and polyacrylamide.

[0084] Alkaline electroplating solutions having any one or more of the accelerator / suppressor combinations identified herein may further have a leveler, a copper(II) complexing agent, a copper(I) complexing agent, a buffering agent, a pH adjusting component, a sacrificial oxidizer, or any combination thereof.

[0085] Any one or more of the copper(II) complexing agents identified herein may be used. In certain embodiments, ethylenediamine and / or EDTA are used. Any one or more of the copper(I) complexing agents identified herein may be used. For example, bromides, chlorides, or polyatomic pseudohalides may be used. Any one or more of the buffering agents or pH adjusting components identified herein may be used. In some embodiments, ammonium hydroxide is used to adjust the pH higher. Any one or more of the sacrificial oxidizing agents identified herein may be used. In some embodiments, nitrates are used as sacrificial oxidizing agents.

[0086] Process Flow 1 illustrates a simple process flow 103 including several steps that may be used in an electroplating process using an alkaline electroplating solution, such as any of those disclosed herein. Process flow 103 begins with optional operation 105, which provides a pretreatment of the substrate to be electroplated. In the illustrated embodiment, this pretreatment is a dry pretreatment, which may be performed, for example, as a high-temperature anneal, plasma treatment, or other operation that does not involve contacting the substrate with a liquid. In certain embodiments, the dry pretreatment is performed to reduce oxides on a conductive liner of the substrate, for example, reducing cobalt oxide on cobalt metal. As an example, an oxide-reduction dry pretreatment involves contacting the substrate with a reducing plasma, such as a hydrogen-containing plasma.

[0087] In optional process operation 107, the substrate undergoes a wet pretreatment that involves contacting the substrate, or at least the surface of the substrate, with a liquid. In certain embodiments, the liquid includes a material that provides some protection to the metal liner from removal or degradation when immersed in an alkaline electroplating solution.

[0088] After optional dry and / or wet pretreatment, the substrate is immersed in an alkaline electroplating solution. This may be the operation to which the metallic or conductive liner is most susceptible. The wet and / or dry pretreatment may provide some protection against this attack. Additionally or alternatively, the substrate may be electrically controlled during immersion, such as by preventing current flow between the substrate and the electrolyte or by cathodically biasing the substrate, thereby reducing the risk of attack by the electroplating solution.

[0089] Next, the substrate is optionally exposed to a high current or a strong reducing potential pulse in operation 111. Such an operation may be performed, for example, to facilitate nucleation on the feature walls during the early stages of electroplating.

[0090] Finally, the method electrofills the features on the substrate with copper in operation 113. This electroplating operation is optionally performed at a constant current or potential, or at a ramped current or potential, and / or at a pulsed current or potential.

[0091] Pretreatment The condition of the incoming substrate affects the quality of the metal film electroplated on the substrate. Substrate pretreatment is one way to facilitate the electroplating of a suitable film. As the name suggests, pretreatment is a process performed on the substrate to be electroplated before immersion in the electroplating solution.

[0092] Examples of dry pretreatment processes include annealing and plasma treatment. Examples of wet pretreatment processes include dissolution, prefunctionalization, and in-situ oxide reduction. Some of these techniques can be used in combination.

[0093] Dry pretreatment processes can improve the conductive liner (or other portions of the substrate) by improving the purity, surface functionality, and / or conductivity of the liner prior to introduction into the electroplating solution.

[0094] The annealing process involves heating the substrate in a controlled atmosphere for a controlled period of time, after which the substrate is cooled. In some cases, after annealing, the substrate is exposed to normal atmospheric air. In one example, the annealing process involves heating the substrate to a temperature of about 30 to 600 degrees Celsius for about 30 seconds to 1 hour. An example atmosphere for the annealing process may be forming gas, for example, containing about 0 to 5% hydrogen by volume, with the remainder of the atmosphere being nitrogen. The atmosphere for the annealing process may also be, for example, a nitrogen-containing atmosphere. -9 The atmosphere may be provided at a substantially or moderately reduced pressure ranging from 0.1 Torr to 760 Torr. In some cases, the atmosphere may include one or more inert gases, such as helium, argon, and / or nitrogen. In some cases, the atmosphere may consist solely of one or more inert gases, such as helium, argon, and / or nitrogen.

[0095] In some embodiments, the dry pretreatment modifies the surface of the substrate using plasma. The plasma process can reduce oxides on the surface of the substrate. Some such processes use a reducing plasma. In certain embodiments, the plasma is generated from a gas mixture of hydrogen and a carrier, such as helium. The pressure of the gas mixture can be about 0.1 to 10 Torr, e.g., about 1 to 3 Torr. The plasma is struck in the gas mixture using radio frequency energy input, e.g., having a power of about 0.25 to 5 kW, e.g., about 1 to 3 kW. In certain embodiments, the plasma generation chamber can be separated from the substrate by a perforated barrier (e.g., a showerhead), which can be grounded and cooled to reduce ion flux while allowing hydrogen radical flux. During processing, the substrate can be placed on a heated pedestal below the showerhead. An example of a remote plasma system is described in U.S. Patent No. 9,865,501, issued January 9, 2018, the disclosure of which is incorporated herein by reference in its entirety.

[0096] In certain plasma pretreatment embodiments, the substrate temperature (optionally through control of the pedestal temperature) is maintained between about 30 and 600 degrees Celsius, for example, between about 75 and 250 degrees Celsius. In certain embodiments, the plasma pretreatment is carried out for between about 30 seconds and 60 minutes. The substrate is allowed to cool before contacting the substrate with the normal atmosphere.

[0097] Further examples of dry pretreatments that may be employed prior to electroplating with the alkaline electroplating solutions disclosed herein are provided in U.S. Pat. No. 9,070,750, issued June 30, 2015, U.S. Pat. No. 9,865,501, issued January 9, 2018, U.S. Patent Application Publication No. 2015 / 0299886, published October 22, 2015, and U.S. Patent Application Publication No. 2015 / 0376792, published December 31, 2015, each of which is incorporated herein by reference in its entirety.

[0098] Wet pretreatments can be used alone or in combination with dry pretreatments. As an example, pretreatment prior to immersion in an electroplating solution can involve first annealing and / or plasma treating the substrate, followed by immersion in a pretreatment bath for, for example, about 1 to 600 seconds.

[0099] One type of wet pretreatment involves removing unwanted materials, which may be in the form of a layer of material, from a substrate. An example of such a wet pretreatment is descumming the surface of the incoming substrate using an organic solvent, a mixture of organic solvents, or a mixture of organic solvent and water. As an example, descumming can be performed using isopropyl alcohol, ethanol, acetone, toluene, benzene, or other solvents familiar to those skilled in the art in descumming. Descumming is described, for example, in Menon, VB, et al. (1989), Particle Removal from Semiconductor Wafers Using Cleaning Solvents, in: Mittal, KL (ed) Particles in Gases and Liquids 1, pp. 259-271, Springer, Boston, MA.

[0100] In some embodiments, the wet pretreatment dissolves any incoming oxide or other surface layer. The choice of pretreatment solution depends on the substrate and the material to be removed. In some cases, the pretreatment uses an acidic solution, such as sulfuric acid, hydrochloric acid, or other acid in solution, to provide a pH of 1 to 7.

[0101] In some embodiments, the wet pretreatment adds materials to or modifies the surface of the substrate, for example, through prefunctionalization. In some cases, such wet pretreatment introduces suppressors, accelerators, levelers, copper, ligands, buffer species, or any combination thereof, to the substrate before immersion in the electroplating solution. This pretreatment can allow the molecules contained therein (in the pretreatment solution) to interact with the substrate without competing with other molecules used in the alkaline electroplating solution that are not present in the pretreatment bath. In some cases, this process allows additives to be set within substrate features and / or on field regions in a way that promotes certain electrical filling characteristics, at least early in the plating process.

[0102] In certain embodiments, the wet pretreatment reduces oxides on the substrate in situ. In some examples, the substrate is immersed in an additive-free pretreatment electrolyte bath. During or after immersion, but before electroplating, a reducing potential is applied to the substrate. Such a potential may be less negative than water so that the solvent is not electrolytically decomposed. The reducing potential can reduce native oxides on the surface of the substrate, creating an improved surface for nucleation during a subsequent electroplating operation. In certain embodiments, the reducing pretreatment is performed so that metal does not electroplate onto the substrate.

[0103] In all wet pretreatment processes, the pretreatment can be performed in a separate bath from the electroplating cell, or it can be performed in the same cell, but in a manner that changes the bath composition over time. If the pretreatment is performed in a separate cell or other container, the substrate is removed from the pretreatment bath and rinsed or immediately immersed in the electroplating solution. In some embodiments, where the pretreatment is performed in a container where the solution composition changes from the pretreatment composition to the electroplating composition, some or all of the components of the pretreatment bath can be present at certain concentrations in the final electroplating solution, and additional components can be added at the end of the pretreatment process. For example, a wet pretreatment can be performed in which the substrate is exposed to a reducing potential in a bath containing only the suppressor and buffer species used in the final electroplating solution. After the pretreatment is complete, a concentrated solution containing copper, accelerators, levelers, ligands, suppressors, and buffers in appropriate concentrations can be added and mixed with the solution volume of the pretreatment bath. After the target composition of the electroplating solution is reached, a plating waveform is applied. In some embodiments, the pretreatment bath does not contain any constituent chemicals that are not also present in the electroplating solution.

[0104] As shown, in some embodiments, wet passivation (performed in situ or ex situ with respect to the plating cell) involves applying a reducing potential to the substrate and reducing the oxide while it is in solution. In some implementations, wet oxide reduction is performed in a metal-free solution. In this way, all or much of the reduction current flows to reduce the metal oxide on the substrate surface, with little or no current flowing to reduce the metal ions in the solution phase, a competing reaction that can produce a mixed oxide and reduced metal layer on the surface. In some embodiments, the substrate is initially pretreated in the plating chamber solely for oxide reduction without plating. In this initial stage, the wafer is immersed in a plating cell with a composition similar to the plating electrolyte but without reducible metal ions (e.g., without copper ions), and the wafer is exposed to a reducing potential. After a defined period (elapsed time or current or charge), metal ions are introduced into the plating cell, for example, by mass transfer of plating solution into the plating cell, driven, for example, via a pump, whereupon electroplating begins on the reduced metal liner. During both stages of the process (wet pretreatment and electrofilling), the wafer is held at a reducing potential. During the first stage, the current can be relatively low, since all charge transfer occurs from the reduction of a thin layer of oxide on the wafer surface. During the second stage, the current is relatively high, typical of plating, since charge transfer can now occur with Cu(II) due to reduction provided by the electrolyte.

[0105] Further examples and features of wet pretreatments that may be employed prior to electroplating with the alkaline electroplating solutions disclosed herein are presented in U.S. Patent Application No. 2014 / 0199497, published July 17, 2014, and U.S. Patent Application Publication No. 2015 / 0299886, published October 22, 2015, each of which is incorporated herein by reference in its entirety.

[0106] Plating Process Board Entry The entry of the substrate into the electroplating solution can be controlled. Different entry types can be used depending on the nature of the substrate being plated and its interaction with the additives. In some cases, the entry of the wafer into the alkaline electroplating solution can affect the nucleation of copper on the substrate. Nucleation plays a role in the formation of a good interface between the plated film and the substrate.

[0107] Cold entry is a process in which a substrate is immersed in an alkaline electroplating solution without passing a current; specifically, in cold entry, no current is passed across the substrate and into the electroplating solution. The potential of the substrate can be shifted while maintaining the currentless state. In certain embodiments, the cold entry state is maintained for the entire time the substrate is immersed in the electroplating solution, i.e., from the time the wafer contacts the surface of the electroplating solution until it is fully immersed. In some cases, the cold entry is maintained for about 0 to 10 seconds, e.g., about 0 to 2 seconds.

[0108] In some cases, cold entry allows the electroplating solution to strip unwanted surface coatings from the substrate. In other cases, cold entry facilitates the distribution of additives in the appropriate locations on the substrate. Such distribution can facilitate subsequent superconformal filling.

[0109] In potentiostatic entry, substrate immersion occurs at a controlled substrate potential, for example, between about 0 and -1.5 V relative to the potential of a copper reference electrode or copper pseudo-reference electrode. This potential is maintained for a time sufficient to fully immerse the substrate in the electroplating solution, plus an additional time, for example, between about 0 and 10 seconds, in some embodiments. In certain embodiments, potentiostatic entry is used to cathodically protect the substrate, such as when the substrate metal (e.g., a conductive liner) is less noble than copper.

[0110] Electrical waveform The plating electrical waveform can have characteristics that facilitate plating of high quality films with good filling in features, e.g., high conductivity copper films without gaps or voids. Current control or potential control may be used. Potential control may be suitable for applications where the surface area of ​​the substrate exposed to the solution changes rapidly.

[0111] In some embodiments, the waveform is a single constant current applied to the substrate. In some embodiments, the waveform includes increasing the current, for example, during the first few hundred milliseconds after immersion. This waveform has been found to improve nucleation on the substrate in some cases. In some embodiments, the waveform applied to the substrate includes ramping the current. Ramping the current has been found to result in improved filling in some cases by sweeping a series of currents and potentials, so that each feature on the substrate experiences a current or potential suitable for superconformal filling for a period of time. For some filling mechanisms where contrast is created by a slightly higher concentration of a particular accelerator or copper ion in the feature relative to the field, pulsing the plating potential can improve filling by repeating a small contrast over many events.

[0112] Examples of common types of electrical waveforms include constant current, linear ramps up or down of current, high current pulses followed by constant or linear ramps, as first order mode fill, or long duration pulses with net reducing current separated by longer duration constant current or linear ramps. These waveforms can be under either current or potential control regimes.

[0113] The following provide several examples of electrical waveforms that may be used with alkaline electroplating solutions, any one or more of which may be used in a given electroplating process. 1) During the first approximately 0 to 10 seconds after immersion, the potential of the substrate is controlled to a point between approximately 0 and -1.5 V versus the copper pseudo-reference electrode. 2) For the first 1 to 10 seconds after immersion, the current to the part is controlled at approximately 0 A, allowing the potential to drift freely. 3) During the filling period after immersion, the current to the substrate is approximately 0.25 mA / cm 2 ~40mA / cm 2 This may be a constant current. 4) During the post-immersion filling period, the current to the substrate is electrokinetically controlled and increases from a low value to a high value or from a high value to a low value. In certain embodiments, the current density is between about 4 and about 400 mA / cm. 2. s. In one example, the ramp is approximately 0.25 mA / cm for 0.1 to 10 seconds. 2 ~about 40mA / cm 2 The range may be: 5) During the post-immersion filling period, the current to the substrate is initially controlled at a constant current, e.g., about 1-60 mA / cm, for about 0.1-10 seconds before returning to a galvanostatically or electrokinetically controlled current. 2 In various embodiments, the electroplating waveform includes such an initial high current pulse. 6) During the post-soak loading period, current is applied to the substrate via a series of high and low current pulses with a net reductive duty cycle. In certain embodiments, this current waveform comprises a series of strong and weak reducing pulses and / or one or more strong reducing pulses followed by one or more weak oxidizing (stripping) pulses. 7) In any of Examples 2 to 6, the listed current control may be replaced with potential control. 8) In any of Examples 1-7, in addition to the change in waveform, the rotational speed of the substrate is changed to a higher or lower speed during application of the electrical waveform. 9) In any of Examples 1-7, in addition to the change in waveform, the fluid flow through the plating cell changes higher or lower during application of the electrical waveform.

[0114] material transport Mass transport of alkaline electroplating solutions into substrate features can affect electroplating conditions and results. Apart from the choice of solution species, mass transport can sometimes be controlled by any one or more of the following operating parameters: (a) the flow rate at which the solution passes through the plating cell, (b) the revolutions per minute (RPM) at which the substrate rotates within the plating cell, and (c) the temperature of the electroplating solution, which influences the diffusion of species into the substrate. The flow rate and RPM can be statically or dynamically controlled during the plating process. To practice static control, a constant flow rate and RPM are determined and controlled at that level for the duration of the process. To practice dynamic control, the flow rate and / or RPM are varied during the process to result in different mass transport regimes appropriate for different stages of electroplating. For example, during fill, it may be beneficial to have low-convection, diffusion-limited transport of leveler or sacrificial oxidant to promote contrast between fields and features, while during electroplating of the overburden step, it may be beneficial to have a high flow rate and / or RPM to support a high limiting current and increase process throughput.

[0115] Device FIG. 2 presents an example of a single electroplating cell 201 that can be used to electroplate copper. In certain embodiments, cell 201 can serve as one of the cells in an electroplating platform. Additives (e.g., accelerators, suppressors, and / or levelers) added to the electrolyte can react with the anode in undesirable ways. Therefore, the anode and cathode regions of the electroplating cell can be separated by a membrane, allowing plating solutions of different compositions to be used in each region. The electroplating solution in the cathode region is called the catholyte, and the electroplating solution in the anode region is called the anolyte. Many engineering designs can be used to introduce the anolyte and catholyte into the plating apparatus.

[0116] Referring to FIG. 2, a schematic cross-sectional view of an electroplating apparatus 201 according to one embodiment is shown. An electroplating bath 203 is shown at level 205. The catholyte portion of the vessel is adapted to receive a substrate in catholyte. A wafer 207 is immersed in the plating solution and held, for example, by a "clamshell" substrate holder 209 mounted on a rotatable spindle 211, which allows rotation of the clamshell substrate holder 209 along with the wafer 207. A general description of clamshell-type plating apparatuses having aspects suitable for use in the present invention is described in detail in U.S. Patton et al., U.S. Pat. No. 6,156,167, and U.S. Pat. No. 6,800,187, issued to Reid et al., the disclosures of which are incorporated herein by reference in their entireties.

[0117] An anode 213 is positioned below the wafer in the electroplating bath 203 and is separated from the wafer area by a membrane 215, such as an ion-selective membrane. These membranes can be made of ionomer materials, such as perfluorinated copolymers containing sulfonic acid groups (e.g., Nafion™), sulfonated polyimides, and other materials known to those skilled in the art to be suitable for cation exchange. Examples of suitable Nafion™ membranes include the N324 and N424 membranes available from DuPont de Nemours. The area below the anode membrane is often referred to as the "anode chamber." The ion-selective anode membrane 215 allows ionic communication between the anode and cathode regions of the plating cell while preventing particles generated at the anode from entering and contaminating the vicinity of the wafer. The anode membrane distributes current flow during the plating process, thereby improving plating uniformity. A detailed description of suitable anodic films is provided in US Pat. Nos. 6,146,798 and 6,569,299 issued to Reid et al., both of which are incorporated herein by reference in their entireties.

[0118] During electroplating, ions from the plating solution are reduced on the substrate. The metal ions must diffuse through a diffusion boundary layer into the TSV holes or other features. A typical method to assist diffusion is through convection of the electroplating solution, provided by a pump 217. In addition, vibratory or sonic agitation members can be used, as can wafer rotation. For example, a vibration transducer 208 can be attached to the clamshell substrate holder 209.

[0119] Electroplating solution is continuously provided to the bath 203 by a pump 217. In certain embodiments, the plating solution flows upward through the anode membrane 215 and the diffuser plate 219 to the center of the wafer 207 and then radially outward across the wafer 207. Electroplating solution may also be provided from the side of the plating bath 203 to the anode region of the bath. The electroplating solution then overflows from the plating bath 203 into an overflow reservoir 221. The electroplating solution is then filtered (not shown) and returned to the pump 217, completing the recirculation of the plating solution. In certain configurations of the plating cell, a separate electrolyte circulates through the portion of the plating cell that contains the anode, while mixing with the main plating solution is prevented using a low-permeability or ion-selective membrane.

[0120] The reference electrode 231 is located outside the plating bath 203 in a separate chamber 233, which is replenished by overflow from the main plating bath 203. Alternatively, in some embodiments, the reference electrode is positioned near the substrate surface, and the reference electrode chamber is connected via a capillary or otherwise to the side of or directly beneath the wafer substrate. The reference electrode 231 can be one of a variety of commonly used types, such as mercury / mercury sulfate, silver chloride, saturated calomel, or copper metal. In some embodiments, in addition to the reference electrode, contact sensing leads in direct contact with the wafer 207 can be used for potential measurements (not shown). In some embodiments, the contact sensing leads are connected to the wafer periphery and are configured to sense the potential of the metal seed layer at the wafer periphery but not carry current to the wafer.

[0121] A DC power supply 235 can be used to control the flow of current to the wafer 207. The power supply 235 has a negative output lead 239 electrically connected to the wafer 207 through one or more slip rings, brushes, and contacts (not shown). The positive output lead 241 of the power supply 235 is electrically connected to the anode 213 located within the plating bath 203. The power supply 235, reference electrode 231, and contact sensing leads (not shown) can be connected to a system controller 247, which, among other functions, enables modulation of the current and potential provided to the elements of the electroplating cell. For example, the controller can enable electroplating in a potential-controlled and / or current-controlled regime. The controller can include program instructions specifying the current and voltage levels that need to be applied to the various elements of the plating cell, as well as the times at which these levels need to be changed. When a forward current is applied, the power supply 235 biases the wafer 207 to have a negative potential relative to the anode 213. This causes a current to flow from the anode 213 to the wafer 207, causing an electrochemical reduction reaction to occur on the wafer surface (cathode), resulting in the deposition of a conductive layer (e.g., copper) on the surface of the wafer. An inert or active anode 214 may be placed below the wafer 207 in the electroplating bath 203 and separated from the wafer area by a membrane 215.

[0122] The apparatus may also include a heater 245 for maintaining the temperature of the electroplating solution at a particular level. The electroplating solution may be used to transfer heat to other elements of the plating bath. For example, once a wafer 207 is loaded into the plating bath, the heater 245 and pump 217 may be turned on to circulate the electroplating solution through the electroplating apparatus 201 until the temperature throughout the apparatus is substantially uniform. In one embodiment, the heater is connected to a system controller 247. The system controller 247 may be connected to a thermocouple to receive feedback of the plating solution temperature within the electroplating apparatus and determine the need for additional heating.

[0123] The controller typically includes one or more memory devices and one or more processors. The processor may include a CPU or computer, analog and / or digital input / output connections, stepper motor controller boards, etc. In certain embodiments, the controller controls all of the activity of the electroplating apparatus. A non-transitory machine-readable medium containing instructions for controlling process operations in accordance with the present embodiments may be coupled to the system controller.

[0124] In certain embodiments, there is a user interface associated with the controller 247. The user interface may include a display screen, a graphical software display of equipment and / or process conditions, and user input devices such as a pointing device, a keyboard, a touch screen, a microphone, etc. Computer program code for controlling the electroplating process may be written in any conventional computer-readable programming language (e.g., assembly language, C, C++, Pascal, Fortran, etc.). Compiled object code or scripts are executed by a processor to perform the tasks identified in the program. One example of a plating apparatus that can be used in accordance with embodiments herein is the Lam Research Sabre tool. Electrodeposition can be performed in components that form a larger electrodeposition apparatus.

[0125] 3 shows a schematic diagram of a top view of an exemplary electrodeposition apparatus. Electrodeposition apparatus 300 can include three separate electroplating modules 302, 304, and 306. Electrodeposition apparatus 300 can also include three separate modules 312, 314, and 316 configured for various process operations. For example, in some embodiments, one or more of modules 312, 314, and 316 can be spin-rinse-dry (SRD) modules. In other embodiments, one or more of modules 312, 314, and 316 can be post-electrofill modules (PEMs), each configured to perform functions such as edge bevel removal, backside etching, and acid cleaning of a substrate after the substrate has been processed by one of electroplating modules 302, 304, and 306.

[0126] Electrodeposition apparatus 300 includes a central electrodeposition chamber 324. Central electrodeposition chamber 324 is a chamber that holds chemical solutions used as electroplating solutions in electroplating modules 302, 304, and 306. Electrodeposition apparatus 300 also includes a dosing system 326 that can store and deliver additives for the electroplating solution. A chemical dilution module 322 can store and mix chemicals used as etchants. A filtration and pumping unit 328 can filter the electroplating solution for central electrodeposition chamber 324 and pump it to the electroplating modules.

[0127] The system controller 330 provides the electronic and interface controls necessary to operate the electroplating apparatus 300. The system controller 330 (which may include one or more physical or logical controllers) controls some or all aspects of the electroplating apparatus 300.

[0128] Signals for monitoring the process may be provided by analog and / or digital input connections of the system controller 330 from various process tool sensors. Signals for controlling the process may be output at analog and digital output connections of the process tool. Non-limiting examples of process tool sensors that may be monitored include mass flow controllers, pressure sensors (such as pressure gauges), thermocouples, optical position sensors, etc. Appropriately programmed feedback and control algorithms can be used with data from these sensors to maintain process conditions.

[0129] Hand-off tool 340 can select a substrate from a substrate cassette, such as cassette 342 or cassette 344. Cassette 342 or 344 can be a Front Opening Unified Pod (FOUP). A FOUP is an enclosure designed to securely and safely hold a substrate in a controlled environment and allow the substrate to be removed for processing or measurement by a tool with an appropriate load port and robotic handling system. Hand-off tool 340 can hold the substrate using a vacuum attachment mechanism or some other attachment mechanism.

[0130] The hand-off tool 340 can interface with the wafer handling station 332, the cassettes 342 or 344, the transfer station 350, or the aligner 348. From the transfer station 350, the hand-off tool 346 can access the substrate. The transfer station 350 may be a slot or location that allows the hand-off tools 340 and 346 to pass the substrate through without passing through the aligner 348. However, in some embodiments, the hand-off tool 346 can align the substrate with the aligner 348 to ensure that the substrate is properly aligned on the hand-off tool 346 for accurate delivery to the electroplating module. The hand-off tool 346 can also deliver the substrate to one of the electroplating modules 302, 304, or 306, or to one of three separate modules 312, 314, and 316 configured for various process operations.

[0131] An example of a process operation according to the above-described method may proceed as follows: (1) electrodepositing copper or another material onto a substrate in electroplating module 304, (2) rinsing and drying the substrate with SRD in module 312, and (3) performing edge bevel removal in module 314.

[0132] An apparatus configured to enable efficient cycling of substrates through sequential electroplating, rinsing, drying, and PEM process operations can be useful in embodiments for use in a manufacturing environment. To accomplish this, module 312 can be configured as a spin-rinse dryer and edge bevel removal chamber. In such a module 312, substrates only need to be transferred between electroplating module 304 and module 312 for copper plating and EBR operations. In some embodiments, the methods described herein are performed in a system including an electroplating apparatus and a stepper.

[0133] An alternative embodiment of an electrodeposition apparatus 400 is shown schematically in FIG. 4. In this embodiment, the electrodeposition apparatus 400 has a pair of electroplating cells 407, each containing an electroplating bath, in a paired or multiple "duet" configuration. In addition to electroplating itself, the electrodeposition apparatus 400 can perform various other electroplating-related processes and substeps, such as, for example, spin rinse, spin dry, metal and silicon wet etching, electroless deposition, pre-wet and pre-chemical treatment, reduction, annealing, electroetching and / or electropolishing, photoresist stripping, and surface pre-activation. While the electrodeposition apparatus 400 is shown schematically from a top-down perspective in FIG. 4, and only a single level or "floor" is apparent in the figure, it should be readily understood by those skilled in the art that such an apparatus, e.g., a Lam Sabre™ 3D tool, can have two or more levels "stacked" on top of each other, each potentially having the same or different types of processing stations.

[0134] Referring again to FIG. 4 , substrates 406 to be electroplated are generally fed into the electrodeposition apparatus 400 through a front-end loading FOUP 401 and transported from the FOUP to the main substrate processing area of ​​the electrodeposition apparatus 400 via a front-end robot 402, which can store and move the substrates 406, driven by spindles 403 in multiple dimensions, from one accessible station to another; in this example, two front-end accessible stations 404 and two front-end accessible stations 408 are also shown. The front-end accessible stations 404 and 408 may include, for example, a pre-processing station and a spin-rinse-dry (SRD) station. Lateral movement of the front-end robot 402 from side to side is achieved utilizing a robot track 402a. Each of the substrates 406 may be held by a cup / cone assembly (not shown) driven by a spindle 403 connected to a motor (not shown), which may be attached to a mounting bracket 409. This example also shows four "duets" of electroplating cells 407, for a total of eight electroplating cells 407. A system controller (not shown) may be coupled to the electrodeposition apparatus 400 to control some or all of the properties of the electrodeposition apparatus 400. The system controller may be programmed or otherwise configured to execute instructions according to the processes previously described herein.

[0135] System Controller In some embodiments, the controller is part of a system, and such a system may be used with the apparatus described above. For example, a system may comprise semiconductor processing equipment, including one or more processing tools, one or more chambers, one or more processing platforms, and / or specific processing components (e.g., wafer holders, electrolyte recirculation systems, etc.). These systems may be integrated with electronics and / or logic for controlling system operation before, during, and after semiconductor wafer or substrate processing. Such electronics and / or logic may be referred to as a "controller" and may control various components or subcomponents of one or more systems. The controller may be programmed to control any of the processes disclosed herein, depending on the processing requirements and / or type of system. Such processes may include temperature settings (e.g., heating and / or cooling), pressure settings, current and / or potential settings, flow rate settings, fluid delivery settings, rotation speed settings, substrate immersion settings, position and motion settings, wafer loading and unloading from the tool, and wafer loading and unloading from other transfer tools and / or load locks connected or interfaced with the particular system.

[0136] In broad terms, a controller may be defined as an electronic device having various integrated circuits, logic, memory, and / or software that receives instructions, issues instructions, controls operations, enables composition control of electroplating solutions, enables electroplating, etc. Integrated circuits may include chips in the form of firmware that store program instructions, digital signal processors (DSPs), chips defined as application-specific integrated circuits (ASICs), and / or one or more microprocessors, i.e., microcontrollers, that execute program instructions (e.g., software). Program instructions may be instructions communicated to the controller in the form of various individual settings (or program files) that define operational parameters for performing a particular process on or for a semiconductor wafer or for a system. The operational parameters, in some embodiments, may be part of a recipe defined by a process engineer to accomplish one or more processing steps in the fabrication of one or more layers, materials, metals, oxides, silicon, silicon dioxide, surfaces, circuits, and / or wafer dies.

[0137] In some embodiments, the controller may be part of, coupled to, or a combination of a computer integrated with, coupled to, or otherwise networked to the system. For example, the controller may be in the “cloud” or all or part of a fab host computer system. This allows for remote access of wafer processing. The computer may provide remote access to the system to monitor the current progress of a fabrication operation, review the history of past fabrication operations, review trends or performance criteria from multiple fabrication operations, modify parameters of a current process, configure processing steps following a current process, or initiate a new process. In some examples, a remote computer (e.g., a server) can provide process recipes to the system over a network. Such a network may include a local network or the Internet. The remote computer may include a user interface that allows entry or programming of parameters and / or settings, which are then communicated from the remote computer to the system. In some examples, the controller receives instructions in the form of data. Such data identifies parameters for each processing step performed during one or more operations. It should be understood that the parameters may be specific to the type of process being performed and the type of tool the controller is configured to interface with or control. Thus, as discussed above, the controller may be distributed, for example, by having one or more individual controllers networked together and working together toward a common purpose (such as the processes and controls described herein). An example of a distributed controller for such purposes would include one or more integrated circuits on the electroplating system in communication with one or more integrated circuits located remotely (e.g., at the platform level or as part of a remote computer) and coupled to control the process in the chamber.

[0138] Exemplary systems may include, but are not limited to, a metal electroplating cell or module, a spin rinse chamber or module, a bevel edge etch chamber or module, a plasma etch chamber or module, a deposition chamber or module, a cleaning chamber or module, a physical vapor deposition (PVD) chamber or module, a chemical vapor deposition (CVD) chamber or module, an atomic layer deposition (ALD) chamber or module, an atomic layer etch (ALE) chamber or module, an ion implantation chamber or module, a tracking chamber or module, and any other semiconductor processing system that may be associated with or used in the fabrication and / or manufacturing of semiconductor wafers.

[0139] As noted above, depending on the process step or steps being performed by the tool, the controller may communicate with one or more other tool circuits or modules, other tool components, cluster tools, other tool interfaces, adjacent tools, nearby tools, tools located throughout the fabrication factory, a main computer, another controller, or tools used in material transport to and from tool locations and / or load ports of wafers within the semiconductor device manufacturing factory.

[0140] example Figure 5 presents an example of a filling profile that illustrates the effect of an electrical waveform, specifically an initial high current pulse. The figure shows an electron micrograph of a cross section of a micromachined trench that has been electroplated with copper. When no high current is applied (0.8 mA / cm in this example), 2 ), in this example, poor nucleation was observed, as can be seen in the image above. At higher currents (1.6 mA / cm in this example), 2 ) is applied during the fill period, conformal plating occurs, but nucleation is only tolerated. In this example, best results can be achieved by nucleating at a high current and filling at a low current. See center image.

[0141] In these tests, the substrates included cobalt liner substrates with open dimensions of approximately 20 nm. Each solution shown here had a pH of approximately 9, used a 2:1 molar ratio of ethylenediamine (complexing agent) to Cu(II), used a Cu concentration of 0.5 g / L (from CuSO), and did not use a leveler or sacrificial oxidant.

[0142] Figure 6 presents an electron micrograph of a cross section of a microfabricated trench that was partially electroplated with copper. If the fill is partial, the amount of copper metal inside the feature compared to the amount at the top of the field is an early indicator of the quality of the fill; a thin field and thick bottom plating are desirable. Each solution shown here has a pH of approximately 9, uses a 2:1 molar ratio of ethylenediamine to Cu(II) as the Cu(II) complexing agent, a Cu concentration of 0.5 g / L (from CuSO), no leveler or sacrificial oxidant, and the following accelerator / inhibitor pairs: Image 1 uses benzotriazole as the inhibitor without an accelerator; Image 2 adds ammonium thiocyanate as an accelerator; Image 3 uses high molecular weight polyacrylamide as the inhibitor without an accelerator; Image 4 adds ammonium thiocyanate as an accelerator; Image 5 uses polyallylamine as the inhibitor without an accelerator; and Image 6 adds ammonium thiocyanate as an accelerator. Thiocyanate can act as a Cu(I) complexing agent. In all three systems, packing becomes more pronounced with the addition of promoters. In some systems, the addition of promoters worsens nucleation.

[0143] Figures 7A, 7B, and 7C show the results of two electrochemical techniques for additive screening. Figure 7A is a composite polarization chart of several organic additives. Copper metal was plated onto a test substrate at a constant current, and at a time x, the additive was dosed. Thiourea showed a very fast and very strong acceleration. Saccharin showed a very strong and very fast inhibition. SPS and taurine showed weak and slow acceleration. The x-time values ​​of dose were not consistent in these screens, which is based on observing relatively steady-state polarization.

[0144] The bottom charts in Figures 7B and 7C are cyclic voltammograms. The substrate was immersed at its rest potential, and then the potential was ramped toward a stronger decrease. Once the set point was reached, the potential reversed and returned to its original state. Additives that exhibit a large gap between the forward and reverse scans indicate a large difference in activity between the inhibited and accelerated surfaces. This may be useful for superconformal filling. The 0.1 mM BTA cyclic voltammogram presents an example of a strong hysteresis signal. Hysteresis is necessary for filling, but not sufficient; if the field-to-feature delta between the two scans cannot be achieved, hysteresis is irrelevant.

[0145] conclusion Although the foregoing embodiments have been described in some detail for clarity of understanding, it will be apparent that certain changes and modifications may be practiced within the scope of the appended claims. The embodiments disclosed herein may be practiced without some or all of these specific details. In other instances, well-known process operations have not been described in detail so as not to unnecessarily obscure the disclosed embodiments. Furthermore, while the disclosed embodiments will be described in conjunction with specific embodiments, it will be understood that the specific embodiments are not intended to limit the disclosed embodiments. It should be noted that there are many alternative ways of implementing the processes, systems, and apparatus of the present embodiments. Therefore, the present embodiments should be considered illustrative rather than limiting, and the embodiments should not be limited to the details set forth herein.

Claims

1. 1. A method of electroplating metal into features of a substrate, comprising: contacting the substrate with an electroplating solution; The electroplating solution comprises: an aqueous solution with a pH greater than 7; 0.1 to 60 g / L of a copper salt dissolved in the aqueous solution; copper(II) complexing ligand, an accelerator comprising thiosulfate, and The accelerator and a complementary inhibitor contacting the substrate with the electroplating solution; electroplating copper metal from the electroplating solution into the features of the substrate; A method comprising:

2. 10. The method of claim 1, The method, wherein the copper(II) complexing ligand comprises tartaric acid or citric acid.

3. 10. The method of claim 1, The method, wherein the electroplating solution comprises pyridine.

4. 10. The method of claim 1, The method, wherein the electroplating solution comprises imidazole.

5. 10. The method of claim 1, The method, wherein the feature of the substrate comprises a cobalt-containing liner.

6. 10. The method of claim 1, The method, wherein the feature of the substrate includes a conductive liner that is 1 to 5 nm thick.

7. 10. The method of claim 1, The method, wherein electroplating copper metal comprises bottom-up filling of the copper metal into the features of the substrate.

8. 10. The method of claim 1, The method wherein electroplating copper metal is performed while rotating the substrate in the electroplating solution.

9. 10. The method of claim 1, The method wherein electroplating copper metal is carried out while flowing the electroplating solution through a cell containing the substrate.

10. 10. The method of claim 1, The method further comprises annealing the substrate in an inert or reducing atmosphere at a temperature of 30 to 600° C. for a time period of 30 seconds to 1 hour prior to contacting the substrate with the electroplating solution.

11. 10. The method of claim 1, The method further comprises annealing the substrate in the presence of a remote reducing plasma while heating the substrate at a temperature between 30° C. and 600° C. for a period of 30 seconds to 1 hour prior to contacting the substrate with the electroplating solution.

12. 10. The method of claim 1, The method further comprises contacting the substrate with a pretreatment bath for 1 to 600 seconds prior to contacting the substrate with the electroplating solution.

13. 13. The method of claim 12, The method further comprising electrically polarizing the substrate in the pretreatment bath.

14. 13. The method of claim 12, The method wherein the pretreatment bath does not contain any constituent chemicals that are not also present in the electroplating solution.

15. 15. The method of claim 14, The method further comprising modifying the composition of said pretreatment bath after a pretreatment period to obtain said electroplating solution.

16. 10. The method of claim 1, The method, wherein the feature of the substrate includes a diffusion barrier that is 1 to 5 nm thick.

17. 17. The method of claim 16, The method, wherein the diffusion barrier comprises tantalum nitride.

18. 10. The method of claim 1, The method further comprises, after contacting the substrate with the electroplating solution, holding the substrate at a potential of 0 to −1.5 V relative to a copper pseudo reference electrode.

19. 18. The method of claim 17, The substrate is held at a potential of 0 to -1.5 V versus a copper pseudo reference electrode for a period of 0 to 10 seconds.

20. 10. The method of claim 1, After contacting the substrate with the electroplating solution, the method further comprises controlling a current so that 0 A flows between the substrate and the electroplating solution.

21. 10. The method of claim 1, Electroplating copper metal was performed by controlling the current to 0.25 mA / cm on the electroplating surface of the substrate. 2 ~40mA / cm 2 providing a current density of

22. 10. The method of claim 1, A method in which electroplating copper metal includes controlling the current between the substrate and the electroplating solution so that the current increases from a low value to a high value or decreases from a high value to a low value.

23. 23. The method of claim 22, The current is applied to the electroplated surface of the substrate for a period of 0.1 to 10 seconds at a rate of 1 to 60 mA / cm. 2 and then reducing the current density on the electroplating surface of the substrate.

24. 10. The method of claim 1, The method wherein electroplating copper metal comprises controlling current between the substrate and the electroplating solution using a series of current pulses.

25. 10. The method of claim 1, The method wherein electroplating copper metal includes controlling the potential of the substrate.

26. 10. The method of claim 1, The aqueous solution has a copper ion concentration of 0.1 to 2 g / L.

27. 1. An electroplating solution comprising: an aqueous solution with a pH greater than 7; 0.1 to 60 g / L of a copper salt dissolved in the aqueous solution; copper(II) complexing ligand, an accelerator comprising thiosulfate, and The accelerator and a complementary inhibitor 1. An electroplating solution comprising:

28. 28. The electroplating solution of claim 27, An electroplating solution wherein the copper(II) complexing ligand comprises tartaric acid or citric acid.

29. 28. The electroplating solution of claim 27, The electroplating solution comprises pyridine.

30. 28. The electroplating solution of claim 27, The electroplating solution wherein the suppressor comprises imidazole.

31. 28. The electroplating solution of claim 27, The electroplating solution wherein the copper(II) complexing ligand is present in the aqueous solution at a concentration sufficient to prevent precipitation of copper hydroxide.

32. 28. The electroplating solution of claim 27, The electroplating solution further comprising a pH adjuster or buffer sufficient to maintain the pH above 7 during electroplating of copper from the electroplating solution.

33. 28. The electroplating solution of claim 27, The electroplating solution further comprising a leveler.

34. 28. The electroplating solution of claim 27, The electroplating solution further comprises a copper(I) complexing ligand.

35. 28. The electroplating solution of claim 27, The electroplating solution further comprises a sacrificial oxidizer.

36. 28. The electroplating solution of claim 27, The aqueous solution has a copper ion concentration of 0.1 to 2 g / L.

Images