Composition and method for electrodeposition of nanotwinned copper

Abstract

A copper electroplating solution includes a copper salt, a halide ion source, and a linear or branched polyhydroxyl compound. The copper electroplating solution is used to deposit copper having high density nanotwinned columnar copper grains on a substrate. The linear or branched polyhydroxyl compound can include a reaction product between 2,3-epoxy-1-propanol and an amine alcohol or an ammonium alcohol.

Description

TECHNICAL FIELD

[0001] The present invention generally relates to electrodeposition of nanotwinned copper and to an electrolytic copper plating bath for producing a nanotwinned copper deposit. BACKGROUND

[0002] Electrochemical deposition processes are well established in the manufacture of integrated circuits. In a process commonly referred to as "damascene" processing (pre-passivated metallization), copper lines are formed by electroplating metal into very thin, high-aspect ratio trenches and vias.

[0003] Due to high ductility and electrical conductivity, copper is one of the most fundamental conductors in microelectronic devices. As microelectronic devices advance, there is a continuing need to produce smaller and denser interconnect features. One approach to this goal is to remove solder between two separate substrates that are connected by copper vias, pads, bumps, or pillars, which can be accomplished, for example, by a Cu-Cu hybrid bonding process.

[0004] Nanotwinned copper has attracted attention for use in microelectronics due to the combination of excellent mechanical properties, good electrical conductivity, and unique structure.

[0005] In particular, the mechanical strength of a metal material such as copper generally increases when the size of the crystalline grains is reduced to the nanoscale level. Nanotwinned copper represents ultrafine-grained copper whose grains contain a high density of lamellar nanotwins separated by coherent twin boundaries. By introducing nanoscale twins into the microstructure of copper, properties such as mechanical strength, ductility, electromigration resistivity, and hardness can be improved.

[0006] Some thin metal films at the nanoscale level can even have specific mechanical properties. As a result, materials with nanotwinned crystalline properties have been found to be suitable for applications such as silicon through-holes, semiconductor chip interconnects, package substrate pin-through-holes, metal interconnects (e.g., copper interconnects), or metal materials on substrates.

[0007] Nanotwinned copper can be obtained in a variety of ways, including, for example, sputtering and electrolytic deposition. One of the advantages of sputtering is the high purity of the copper film, with the ability to conform to the preferred orientation of the crystalline grains. Sputtered (111)-oriented nanotwinned copper has been shown to have a high degree of thermal stability and strength. On the other hand, direct current electrolytic plating is extremely compatible with mass production in industry, and electroplated nanotwinned copper can be divided into two groups: equiaxed grain nanotwinned copper and (111)-oriented nanotwinned copper.

[0008] Crystal defects can affect the mechanical, electrical, and optical properties of materials. Twinning can occur in materials in which two parts of the crystal structure are symmetrically related to each other. In face-centered cubic (FCC) crystal structures containing copper, coherent twin boundaries can form as (111) mirror planes, with the typical stacking order of (111) planes reversing from the mirror plane. In other words, adjacent grains are mirrored across the coherent twin boundary in a layered (111)-structure. The twins grow in a layer-by-layer fashion extending along the lateral (111) crystal planes, with twin thicknesses on the nanometer scale, hence the term "nanotwinning." Nanotwinned copper (nt-Cu) exhibits superior mechanical and electrical properties and can be used in a wide range of applications in wafer-level packaging and advanced packaging designs.

[0009] Nanotwinned copper has strong mechanical properties, including high strength and high tensile ductility, compared to copper with conventional grain boundaries. Nanotwinned copper also exhibits high electrical conductivity, which can be attributed to the twin boundaries, resulting in less pronounced electron scattering compared to grain boundaries. In addition, nanotwinned copper exhibits high thermal stability, which can be attributed to the twin boundaries having an order of magnitude lower excess energy than grain boundaries. Further, nanotwinned copper enables high copper atom diffusivity, which is useful for copper-copper direct bonding. Nanotwinned copper also shows high resistance to electromigration, which can be a result of the twin boundaries slowing down electromigration-induced atomic diffusion. Nanotwinned copper exhibits strong resistance to seed etching, which can be important in fine line in redistribution layer applications. Nanotwinned copper also exhibits low impurity incorporation, which results in fewer Kirkendall voids due to solder reactions with nanotwinned copper.

[0010] In some implementations, nanotwinned copper enables direct copper-copper bonding. Such copper-copper bonding can occur at low temperature, moderate pressure, and lower bonding force / time. Typically, deposited copper structures result in rough surfaces. In some implementations, an electro-polishing process can be performed after electrodeposition of nanotwinned copper to obtain a smooth surface prior to copper-copper bonding. With the smooth surface, nanotwinned copper structures can be used for copper-copper bonding with shorter bonding time, lower temperature, and fewer voids.

[0011] U.S. Patent 7,074,315 to Desmaison et al., the subject matter of which is incorporated herein by reference in its entirety, describes a copper electrolyte for depositing a matte copper layer. The electrolytic copper plating bath includes at least one polyhydroxyl compound selected from the group consisting of poly(l,2,3-propanetriol), poly(2,3-epoxy-l-propanol), and derivatives thereof, to produce a copper deposit that is matte and exhibits uniform, slight roughness, thereby providing sufficient bonding of organic coatings without additional pretreatment. However, there is no suggestion to use this copper electrolyte to deposit nanotwinned copper.

[0012] WO 2020 / 092244 to Banik et al., the subject matter of which is incorporated herein in its entirety by reference, describes a copper structure with high density nanotwinned copper deposited on a substrate. Banik does not describe a specific electrolytic copper plating bath, but rather describes plating conditions, including a pulsed current waveform applied between constant current and no current, with the duration of no current applied substantially greater than the duration of constant current applied.

[0013] U.S. Patent 10,566,314 to Yang, the subject matter of which is incorporated herein in its entirety by reference, describes how the optimal copper grain structure for Cu-Cu metal-metal bonding is a columnar grain microstructure. The copper grain microstructure plated by the disclosed inhibitor-only system produces a columnar grain structure due to the plated nanotwinned copper. While columnar grains are mentioned, there is no mention of the (111) copper grain structure of nanotwinned copper.

[0014] Accordingly, there remains a need in the art for an improved electrolytic copper solution for producing nanotwinned copper deposits. Additionally, there remains a need in the art for an improved electrolytic copper solution that can deposit nanotwinned copper with (111) orientation and high percentage of nanotwins. SUMMARY

[0015] It is an object of the present invention to provide an improved copper electroplating solution.

[0016] It is another object of the present invention to provide a copper electroplating solution that is capable of producing nanotwinned copper in the deposit.

[0017] It is yet another object of the present invention to provide (111) oriented nanotwinned copper.

[0018] It is still another object of the present invention to provide a copper deposit with high density nanotwins.

[0019] To this end, in one embodiment, the present invention is generally directed to a copper electroplating solution for producing nanotwinned copper, the copper electroplating solution generally comprising:

[0020] A) a copper salt;

[0021] B) a source of halide ions; and

[0022] C) a linear or branched polyhydroxyl compound.

[0023] In another embodiment, the present invention is also generally directed to a method of producing a copper deposit with high density nanotwins using the copper electroplating solution described herein. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1SEM depicting copper deposits produced according to Comparative Example 1 (30 pm width at 10K magnification).

[0025] Figure 2 SEM depicting copper deposits produced according to Comparative Example 1 (30 pm width at 10K magnification).

[0026] Figure 3 SEM depicting copper deposits produced according to Comparative Example 1 (30 pm width at 10K magnification).

[0027] Figure 4 SEM depicting copper deposits produced according to Comparative Example 1 (30 pm width at 10K magnification).

[0028] Figure 5 SEM depicting copper deposits produced according to Comparative Example 1 (30 pm width at 10K magnification).

[0029] Figure 6 SEM depicting copper deposits produced according to Comparative Example 1 (30 pm width at 10K magnification).

[0030] Figure 7 SEM depicting copper deposits produced according to Comparative Example 1 (30 pm width at 10K magnification).

[0031] Figure 8 SEM depicting copper deposits produced according to Comparative Example 1 (30 pm width at 10K magnification). DETAILED DESCRIPTION

[0032] The inventors of the present invention have discovered that electrodepositing (111) oriented high density nanotwinned copper enables smaller and denser interconnect features between two separate substrates for connecting copper via Cu-Cu hybrid bonding.

[0033] As used herein, unless the context clearly indicates otherwise, “a,” “an,” and “the” refer to both the singular and plural forms.

[0034] As used herein, the term “about” refers to a measurable value such as a parameter, an amount, a duration, and so on, and is intended to include variations of + / - 15% or less, preferably + / - 10% or less, more preferably + / - 5% or less, even more preferably + / - 1% or less, still more preferably + / - 0.1% or less, of the particular value stated, as long as such variations are appropriate to perform the invention described herein. Furthermore, it is to be understood that the value indicated for “about” can itself be approximated, as described herein.

[0035] As used herein, spatially relative terms, such as "beneath", "below", "lower", "above", "upper" and the like, can be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientations depicted in the figures. For example, if a device shown in the figures is inverted, elements described as "below" or "beneath" other elements or features would then be oriented "above" the other elements or features. Thus, the term "below" can encompass both an orientation of above and below. The device can be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.

[0036] As used herein, the terms "comprises" and / or "comprising", and the like are intended to indicate that the features, integers, steps, or elements listed thereafter are present in the composition, article, method, process, or machine defined by the disclosure, but do not, by themselves, delimit the scope of the disclosure, and that one or more other features, integers, steps, or elements can be added.

[0037] As used herein, the terms "substantially" and "essentially" mean that the given element or compound is not detected by ordinary analytical means by those skilled in the art of metal plating baths. Such methods typically include atomic absorption spectroscopy, titration, ultraviolet-visible analysis, secondary ion mass spectroscopy, and other commonly used analytical techniques.

[0038] All amounts are weight percent, unless otherwise specified. All numerical ranges are inclusive and combinable in any order, except where such numerical ranges are limited to add up to 100%.

[0039] The terms "plating" and "deposit" or "deposition" are used interchangeably throughout the specification. The terms "composition" and "bath" and "solution" are used interchangeably throughout the specification. The term "alkyl" means an organic chemical group consisting solely of carbon and hydrogen, and having the general formula CnH2n+1, unless otherwise specified in the description. n H 2n+1 The term "average" is equivalent to the mean value of a sample. All amounts are weight percent, unless otherwise specified. All numerical ranges are inclusive and combinable in any order, except where such numerical ranges are limited to add up to 100%.

[0040] In one embodiment, the present invention generally relates to the electrodeposition of nanotwinned copper, and a copper electroplating solution for producing nanotwinned copper generally comprises:

[0041] A) a copper salt;

[0042] B) a source of halide ions; and

[0043] C) a linear or branched polyhydroxyl compound.

[0044] In a preferred embodiment, the copper salt comprises copper sulfate. Other copper salts that can be used in the composition include copper methane sulfonate, copper pyrophosphate, copper propane sulfonate, and other similar compounds. The concentration of copper sulfate in the electroplating solution is typically in the range of about 1 g / L to 100 g / L, more preferably in the range of about 20 g / L to about 80 g / L, and most preferably in the range of about 40 g / L to about 60 g / L.

[0045] Halo ions can act as a bridge to help certain organic additives adsorb onto the substrate surface. Halo ions include, but are not limited to, chloride ions, bromide ions, iodide ions, and combinations thereof. In one embodiment, the halo ions comprise chloride ions. The concentration of chloride ions in the electroplating solution is typically in the range of about 1 mg / L to 150 mg / L, more preferably about 30 mg / L to about 120 mg / L, and most preferably about 45 mg / L to about 75 mg / L.

[0046] Linear or branched polyols typically have a molecular weight of about 200 g / mol to about 20,000 g / mol, more preferably about 500 g / mol to about 5,000 g / mol, and most preferably about 1,000 g / mol to about 3,000 g / mol. In a preferred embodiment, the linear or branched polyol comprises poly(2,3-epoxy-l-propanol). In one embodiment, the concentration of linear or branched polyol is in the range of about 1 mg / L to about 10,000 mg / L, more preferably about 10 mg / L to about 1,000 mg / L, and most preferably about 50 mg / L to about 600 mg / L.

[0047] Additionally, the electroplating composition can contain an acid to control the conductivity of the plating bath, and suitable acids include sulfuric acid and methane sulfonic acid. In one embodiment, the acid is sulfuric acid. The concentration of acid in the electroplating solution is typically in the range of about 0 g / L to 240 g / L, more preferably in the range of about 10 g / L to about 180 g / L, and most preferably in the range of about 80 g / L to about 140 g / L.

[0048] The present inventors have also surprisingly discovered that the reaction of an amine alcohol or ammonium alcohol with 2,3-epoxy-l-propanol can improve the properties of nanotwinned copper. These polyol initiators from nitrogen-containing species can increase the density of columnar nanotwinned copper and help initiate nanotwinned copper faster than poly(2,3-epoxy-l-propanol).

[0049] Examples of these amine alcohols include, but are not limited to, ethanolamine, diethanolamine, triethanolamine, propanolamine, isopropanolamine, diisopropanolamine, triisopropanolamine, N-methyldiethanolamine, N-ethyldiethanolamine, N- propyldiethanolamine, methylmonoethanolamine, N,N-dimethylethanolamine, N,N- diethylethanolamine, N-propylmonoethanolamine, N-propyldiethanolamine, N- butylethanolamine, N-butyldiethanolamine, N,N-dibutylethanolamine, hydroxyethyl morpholine, 2-piperidinylethanol, diethanolisopropanolamine, N-(2- hydroxyethyl)pyrrolidine, and combinations of the foregoing.

[0050] Further, the amine alcohols can be converted to ammonium salts by quaternization of the nitrogen, for example, with the aid of a methylating agent such as dimethyl sulfate.

[0051] Examples of these amine alcohols include, but are not limited to, ethanolamine, diethanolamine, triethanolamine, propanolamine, isopropanolamine, diisopropanolamine, triisopropanolamine, N-methyldiethanolamine, N-ethyldiethanolamine, N- propyldiethanolamine, methylmonoethanolamine, N,N-dimethylethanolamine, N,N- diethylethanolamine, N-propylmonoethanolamine, N-propyldiethanolamine, N- butylethanolamine, N-butyldiethanolamine, N,N-dibutylethanolamine, hydroxyethyl morpholine, 2-piperidinylethanol, diethanolisopropanolamine, N-(2- hydroxyethyl)pyrrolidine, and combinations of the foregoing.

[0052] In the reaction of the amine alcohol or ammonium alcohol with 2,3-epoxy-l- propanol, the molar ratio of amine to 2,3-epoxy-l-propanol is typically in the range of about 0.01 to 0.50, more preferably in the range of 0.01 to 0.20, and more preferably in the range of 0.01 to 0.10.

[0053] The present inventors have also discovered that the introduction of other organic plating compounds can destroy the ability of the polyhydroxyl compound material to produce nanotwinned copper. These inhibiting compounds include accelerators, brighteners, carriers, wetting agents, and / or leveling agents. Thus, in a preferred embodiment, the plating solution is at least substantially free of any accelerators, brighteners, carriers, wetting agents, and / or leveling agents, or any compounds that can act as accelerators, brighteners, carriers, wetting agents, and / or leveling agents. By "substantially free" is meant that the plating solution contains less than 20 ppm, more preferably less than about 10 ppm, and most preferably less than about 3 ppm, of any compounds that can act as accelerators, brighteners, carriers, wetting agents, and / or leveling agents.

[0054] In a preferred embodiment, the copper electroplating composition of the present invention comprises:

[0055] A) about 40 g / L to about 60 g / L of copper ions;

[0056] B) about 80 g / L to about 140 g / L of sulfuric acid;

[0057] C) about 30 mg / L to about 120 mg / L of chloride ions;

[0058] D) about 300 mg / L to about 500 mg / L of a linear or branched polyhydroxyl compound, wherein the polymer can or can not contain a nitrogen-containing species.

[0059] In another preferred embodiment, the present application consists essentially of a copper electroplating composition capable of electrodepositing copper having a high density of nanotwinned copper, the electroplating composition consisting essentially of:

[0060] A) about 40 g / L to about 60 g / L of copper ions;

[0061] B) about 80 g / L to about 140 g / L of sulfuric acid;

[0062] C) about 30 mg / L to about 120 mg / L of chloride ions;

[0063] D) about 300 mg / L to about 500 mg / L of a linear or branched polyhydroxyl compound, wherein the polymer can or can not contain a nitrogen-containing species.

[0064] "Consists essentially of" means that the composition is free of any additives that have an adverse effect on the ability of the composition to deposit nanotwinned copper.

[0065] The present application also relates in its entirety to a method of electroplating nanotwinned copper on a substrate, the method comprising the steps of:

[0066] A) providing a substrate, at least one anode, and the above-described copper plating bath;

[0067] B) contacting the surface of the substrate and the at least one anode with the copper bath, respectively; and

[0068] C) applying a voltage between the surface of the workpiece and the at least one anode such that a cathodic polarity is imposed on the substrate relative to the at least one anode;

[0069] wherein a copper structure having a high density of nanotwins is deposited on the substrate.

[0070] In some embodiments, the nanotwinned copper structure has a plurality of (111) grain structures. Furthermore, to ensure the success of such a process requiring elevated temperatures and pressures, it is generally preferred to produce electroplated copper that is (111) oriented with >90% nanotwinned columnar copper (nt-Cu) grains. While not being bound by a particular theory, it is hypothesized that when two nanotwinned copper substrates are contacted and exposed to the necessary temperatures and pressures, nanotwinned copper growth will extend between the boundaries of the copper substrates, thereby forming Cu-Cu bonds that extend across the interface.

[0071] The current density is typically in the range of about 0.01 ASD to about 50 ASD, more preferably about 0.5 ASD to about 20 ASD, most preferably about 1 ASD to about 10 ASD. Additionally, the plating solution is preferably agitated, and typically the plating solution is mixed at about 1 rpm to about 2,500 rpm, more preferably about 10 rpm to about 1,200 rpm, most preferably about 50 rpm to about 400 rpm.

[0072] The anode is preferably an insoluble anode.

[0073] The copper is electrodeposited for a period of time to plate copper to a thickness of about 0.1 μιη to about 1,000 μιη, more preferably about 0.3 μιη to about 200 μιη, most preferably about 1 μιη to about 100 μιη.

[0074] Substrates that can be plated with the copper plating solution include, for example, pillars, pads, lines, and vias.

[0075] The presence of the nanotwinned grain structure can be observed using any suitable microscopy technique, such as electron microscopy techniques. The amount of the nanotwinned grain structure in the copper deposit is preferably greater than about 80% nanotwinned columnar copper grains, more preferably greater than about 90% nanotwinned columnar copper grains, based on SEM cross-section estimates.

[0076] As shown in the following examples, the nanotwinned copper structure can be characterized by a plurality of (111) oriented crystalline copper grains containing a majority of nanotwins. In some implementations, the plurality of (111) oriented crystalline copper grains contain a high density of nanotwins. As used herein, "a high density of nanotwins" can refer to a copper structure having greater than about 80% nanotwins and even greater than about 90% nanotwins, as observed using a suitable microscopy technique.

[0077] The crystal orientation of the crystalline copper grains can be characterized using suitable techniques such as electron backscatter diffraction (EBSD) analysis. In some implementations, the crystal orientation mapping can be displayed in inverse pole figure (IPF) mapping. According to the present disclosure, it is preferred that the nanotwinned copper structure contains predominantly (111) oriented grains.

[0078] Comparative Example 1 :

[0079] A copper electrolytic composition containing a solution of 50 g / L copper (II) ions, 100 g / L sulfuric acid, 50 mg / L chloride ions, and 400 mg / L polyethylene glycol (PEG) was prepared and placed in a plating cell. A blanket PVD copper substrate was immersed in the plating cell at 25 °C. The agitation was set to 300 rpm, and a current density of 6 ASD was applied for 500 s in order to plate a 10 μιη copper film.

[0080] As Figure 1SEM cross-sections show the absence of nanotwinned copper in the plated copper film.

[0081] Example 2 :

[0082] The same bath and substrate as described in Comparative Example 1 were prepared; however, the PEG was replaced with 400 mg / L of poly(2,3-epoxy-l-propanol) and electroplating was performed under the same plating conditions. The results show a majority of nanotwinned copper.

[0083] As Figure 2 shown, SEM cross-sections show the presence of a majority of nanotwinned copper in the plated film. The grains are highly columnar and have a high density of intrinsic nanotwins.

[0084] Comparative Example 3 :

[0085] The same bath and substrate as described in Example 2 were prepared, except that 1 mg / L of poly(dithiobispropane sulfonic acid sodium salt) (SPS) was added to the solution (brightener) and electroplating was performed under the same plating conditions. The results show that the addition of a conventional brightener results in a complete loss of nanotwinned copper in the plated film, as seen in Figure 3 .

[0086] Comparative Example 4 :

[0087] The same bath and substrate as described in Example 2 were prepared. However, 5 mg / L of a cationic nitrogen leveler was added to the solution and electroplating was performed under the same plating conditions. As seen in Figure 4 , the addition of a leveler to the plating composition also results in a complete loss of nanotwinned copper.

[0088] Example 5 :

[0089] The same bath as described in Example 2 was prepared and a 70 μm wide substrate was plated with 6ASD to produce 40 μm high pillars. The results show a high density of nanotwinned copper, as seen in Figure 5 .

[0090] Example 6 :

[0091] The same bath as described in Example 5 was prepared and a substrate containing vias was plated. The results show a majority of nanotwinned copper, as seen in Figure 6 .

[0092] Example 7 :

[0093] The additive can be prepared by reacting an amine alcohol or ammonium alcohol with 2,3-epoxy-l-propanol. The general reaction procedure is as follows:

[0094] In an IL round bottom flask, fitted with a thermometer, reflux condenser and magnetic stirrer, to a solution of 2,3-epoxy-1-propanol (2 mol) and N-methyldiethanolamine (0.2 mol) was added dropwise a solution of boron trifluoride etherate (5 mmol) in methanol. The temperature was allowed to rise freely during the exotherm and heated at its maximum temperature for 30 minutes. The reaction was then allowed to cool to below 100°C, water was added to make a 20% w / w solution and stirring was continued for 4 hours. The solution was then filtered and used as is.

[0095] The bath as described in Example 2 was plated using the additive prepared above.

[0096] The results show a faster initiation from the nanotwinning of the copper seed crystals. In addition, a more dense array of nanotwinning columnar growth was observed, as shown in Figure 7 The grain structure of this copper deposit is depicted in Figure 8 as being predominantly in (111) grain orientation.

[0097] From the examples and comparative examples, it can be seen that the copper electroplating composition of the present invention is capable of depositing a plated copper structure comprising a high density of nanotwinning columnar copper grains.

[0098] Finally, it should also be understood that the following claims are intended to cover all of the generic and specific features of the invention herein described and all statements of the scope of the invention which, as a matter of language, might be said to fall therebetween.

Claims

1. A copper electroplating solution comprising: a) 40 to 60 g / L of copper ions; b) 1 to 150 mg / L of chloride ions; c) 10 to 180 g / L of an acid; and d) 1 to 10,000 mg / L of a linear or branched polyhydroxyl compound, wherein the linear or branched polyhydroxyl compound comprises a reaction product between 2,3-epoxy-1-propanol and an amine alcohol or an ammonium alcohol, wherein the copper electroplating solution is capable of depositing nanotwinned copper on a substrate, wherein the copper electroplating solution is free of at least any accelerators, brighteners, carriers, wetting agents, or leveling agents, or any compound that can act as an accelerator, brightener, carrier, wetting agent, or leveling agent, in an amount detectable by atomic absorption spectroscopy, titration, ultraviolet-visible light analysis, or secondary ion mass spectroscopy.

2. The copper electroplating solution of claim 1, wherein the copper ions comprise copper sulfate.

3. The copper electroplating solution of claim 1, wherein the acid comprises sulfuric acid or methane sulfonic acid.

4. The copper electroplating solution of claim 1, wherein the linear or branched polyhydroxyl compound comprises at least one nitrogen atom.

5. The copper electroplating solution of claim 1, wherein the amine alcohol or the ammonium alcohol is selected from the group consisting of ethanolamine, diethanolamine, triethanolamine, propanolamine, isopropanolamine, diisopropanolamine, triisopropanolamine, N-methyldiethanolamine, N-ethyldiethanolamine, N- propyldiethanolamine, methylmonoethanolamine, N,N-dimethylethanolamine, N,N- diethylethanolamine, N-propylmonoethanolamine, N-butylethanolamine, N- butyldiethanolamine, N,N-dibutylethanolamine, hydroxyethylmorpholine, 2- piperidinylethanol, diethanolisopropanolamine, N-(2-hydroxyethyl)pyrrolidine, choline chloride, b-methyl choline chloride, bis(2-hydroxyethyl)dimethylammonium chloride, tris(2-hydroxyethyl)methylammonium chloride, carnitine chloride, (2- hydroxyethyl)dimethyl(3-sulfopropyl)ammonium chloride, and combinations of the foregoing.

6. The copper electroplating solution of claim 1, wherein the copper electroplating solution comprises: a. 80 to 140 g / L of sulfuric acid; b. 30 to 120 mg / L of chloride ions; c. 300 to 600 mg / L of the linear or branched polyhydroxyl compound.

7. A method of electrodepositing copper on a substrate, the method comprising the steps of: a. contacting a surface of the substrate and at least one anode with the copper electroplating solution of claim 1; and b. applying a voltage between the surface of the substrate and the at least one anode such that a cathodic polarity is imposed on the substrate relative to the at least one anode; wherein a copper deposit having a high density of nanotwinned columnar copper grains is deposited on the substrate.

8. The method of claim 7, wherein the nanotwinned copper deposit is (111) oriented.

9. The method of claim 7, wherein the copper deposit comprises greater than 80% nanotwinned columnar copper grains.

10. The method of claim 9, wherein the copper deposit comprises more than 90% nanotwinned columnar copper grains.

11. The method of claim 7, wherein the substrate comprises one or more feature structures selected from the group consisting of pillars, pads, lines, vias, and combinations of one or more of the foregoing.

Images