Improving Photoresist Resolution through Anisotropic Copper Electroplating

Abstract

The substrate is characterized by copper electroplated by a method that includes electroplating copper on a selectively deposited seed layer or a seed layer defined by a photoresist with a copper electroplating composition that contains a selective inhibitor compound and a selective leveling compound capable of anisotropic plating. Optionally, the seed layer can be treated with an aqueous solution of a sulfur-containing promoter prior to copper electroplating.

Description

Technical Field

[0001] The present invention relates to a method for improving the resolution of a photoresist by anisotropically copper electroplating photoresist-defined features. More specifically, the present invention relates to a method for improving the resolution of a photoresist by anisotropically copper electroplating photoresist-defined features, the method being carried out by anisotropically copper electroplating a seed layer of photoresist-defined features of a substrate with an aqueous copper electroplating composition containing a selective inhibitor and a selective leveling agent compound capable of anisotropically copper electroplating, wherein prior to anisotropically copper electroplating the seed layer, the seed layer of the photoresist-defined features may optionally be treated with a solution containing a sulfur-containing promoter compound. Background of the Invention

[0002] The packaging and interconnection of electronic components rely on the ability to create circuit patterns within a dielectric matrix and fill the patterns with a metal (such as copper) that conducts electrical signals. Conventionally, these circuits are built through photoresist patterns, where the process of exposure through a patterned mask and subsequent removal of the exposed material results in the formation of a network of recessed, empty features on a conductive seed. These features can be filled by electroplating with copper on the seed, such that after removal of the photoresist and etch-back of the seed, a conductor pattern is obtained. The features in these circuits typically include lines, pads, vias, pillars, and through-holes of various sizes.

[0003] Typically, plating bath additives that interact with the electroplated deposit during its growth are used to achieve control over fill uniformity and deposit quality. Although the additives adjust many microstructural properties of the deposit, the shape of the plated feature itself is controlled only by the photoresist. In other words, the photoresist contains the copper deposit during its growth and prevents it from taking any shape other than the circuit pattern. If the deposit grows above the height of the photoresist, the expected shape will not be faithfully maintained. In most cases, copper will continue to plate on the photoresist in all directions, a behavior known as isotropic plating growth. This multi-directional expansion compromises the integrity of the circuit, for example, by connecting adjacent features and creating circuit shorts that render the entire structure useless. Thus, in most industrial plating processes, it is required that the photoresist or pattern layer be at least as thick as the target electroplated deposit height.

[0004] In fact, the photoresist used to encapsulate the circuit needs to be even higher than the features themselves to avoid circuit bridging issues, as we are trying to planarize the plating at very different feature heights. Since modern circuits include small and large openings in the photoresist with different diffusion constraints for planarization additives, we have found that achieving the target height for one dimension may mean that we need to plate the other dimension significantly higher. This is especially true for high-frequency and high-power applications, where finer lines for data transmission are integrated with larger features that supply an increased amount of power to more dense components. Thus, current and future applications will continue to exacerbate the need to image finer features in a relatively thicker photoresist layer.

[0005] Due to the natural limitations of plating techniques, these trends lead to significant technical and economic limitations in circuit manufacturing. In particular, the need to fully contain the plated features and address the planarization issues will drive the resolution limits of photoresists, photoimageable materials, and imaging tools. For a 2 μm line and space (L / S) dimension, conventional photoresist materials cannot form trenches deeper than 6 μm on an industrial scale. Chemically amplified photoresists can push the trench depth to 10 μm, but this comes at the cost of increasing the cost of the imageable material by more than two orders of magnitude.

[0006] Therefore, it would be advantageous to develop new circuit plating schemes that allow operation with a photoresist that is thinner than the expected feature height yet still able to maintain the pattern shape across the entire feature height. Doing so will not only increase the resolution or enable greater circuit design flexibility, but also reduce the material cost of the patterned layer by simply reducing the volume of photoresist involved in the process.

[0007] To be able to implement such a process, the metal plating technique needs to be redesigned such that the growth of the plating film occurs anisotropically in a direction perpendicular to the substrate. This is different from the current process, where due to the natural electric field distribution, any deposits not constrained by the patterned layer will grow in several directions simultaneously.

[0008] Therefore, a method for anisotropically electroplating copper for forming photoresist-defined features is needed. Summary of the Invention

[0009] The present invention relates to a method, which comprises:

[0010] a) providing a substrate comprising a seed layer;

[0011] b) optionally selectively applying an aqueous treatment solution comprising a sulfur-containing promoter to the seed layer, wherein the pH of the aqueous treatment solution is 3 or below, or 9 or above;

[0012] c) Provide a copper electroplating composition comprising a copper ion source, an accelerator, an acid, a chloride source, an inhibitor that produces an α-peak curve in the cathodic wave of the voltammogram of the copper electroplating composition on a working electrode, and a leveling agent, wherein the leveling agent is a copolymer of the reaction product of imidazole and butyl diglycidyl ether or a copolymer of the reaction product of imidazole and phenylimidazole;

[0013] d) Contact the substrate comprising the seed layer with the copper electroplating composition; and

[0014] e) Anisotropically electroplate copper on the seed layer of the substrate.

[0015] The present invention further relates to a method comprising:

[0016] a) Provide a substrate comprising a seed layer;

[0017] b) Coat the seed layer with a photoresist;

[0018] c) Image the photoresist to form a pattern on the substrate and selectively expose the seed layer;

[0019] d) Optionally apply an aqueous treatment solution comprising a sulfur-containing accelerator to the exposed seed layer, wherein the aqueous treatment solution has a pH of 3 or less, or 9 or more;

[0020] e) Provide a copper electroplating composition comprising a copper ion source, an accelerator, an acid, a chloride source, an inhibitor that produces an α-peak curve in the cathodic wave of the voltammogram of the copper electroplating composition on a working electrode, and a leveling agent, wherein the leveling agent is a copolymer of the reaction product of imidazole and butyl diglycidyl ether or a copolymer of the reaction product of imidazole and phenylimidazole;

[0021] f) Contact the substrate comprising the seed layer with the copper electroplating composition; and

[0022] g) Anisotropically electroplate anisotropic copper on the seed layer of the substrate.

[0023] The present invention also relates to an article comprising a copper deposit plated to a height at least 2 μm above the surrounding photoresist without causing feature broadening, and comprising non-coherent grain boundaries oriented at 80°-90° relative to the plane of the substrate, and comprising concurrent twinned boundaries oriented at 40°-50° relative to the plane of the substrate.

[0024] The method of the present invention enables anisotropic copper electroplating of features of different shapes and sizes, and maintains the features even when the electroplated layer thickness is significantly higher than the thickness of the photoresist. The method of the present invention enables the formation of features in which a high degree of planarization can be maintained even when different aspect ratios and shapes are combined in a single layer or plating step. After reading the disclosure and examples in this specification, additional advantages of the present invention will be apparent to those of ordinary skill in the art. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 is a voltammogram showing the current (A) of the α-peak and ΔV as a function of the potential (V).

[0026] Figure 2A and 2B are illustrations of an isotropic copper feature and an anisotropic copper feature of the present invention, respectively.

[0027] Figure 3 is an illustration of the surface activation method of the present invention and an anisotropically plated copper feature.

[0028] Figure 4A and 4B are Fourier transform diagrams showing the orientation differences of the incoherent (A) and (111) twin (B) grain boundaries between copper wire features plated with isotropic or anisotropic electroplating formulations.

[0029] DETAILED DESCRIPTION OF THE INVENTION

[0030] As used throughout this specification, unless the context clearly indicates otherwise, the following abbreviations shall have the following meanings: A = ampere; A / dm 2 = ampere per square decimeter; ASD = A / dm 2 ; V = voltage = potential; °C = degree Celsius; g = gram; mg = milligram; L = liter; mL = milliliter; ppm = parts per million; ppb = parts per billion; M = mole per liter; mol = mole; nm = nanometer; μm = micron = micrometer; mm = millimeter; cm = centimeter; EBSD = electron backscatter diffraction; SEM = scanning electron micrograph; DI = deionized; Mw = weight average molecular weight; MES = 2-mercaptoethanesulfonic acid; NaOH = sodium hydroxide; PEG = polyethylene glycol; EO = ethylene oxide; PO = propylene oxide; PR = photoresist; H2SO4 = sulfuric acid; Cu = copper; Ti = titanium; Pt = platinum; and PCB = printed circuit board.

[0031] As used throughout this specification, the terms "bath" and "composition" are used interchangeably. Throughout the specification, "plating" and "electroplating" are used interchangeably. The expression "(hkl)" are Miller Indices and define a specific crystal plane in a lattice. The term "Miller Indices: (hkl)" means the orientation of the surface of a crystal plane defined by considering how a plane (or any parallel plane) of a solid intersects the principal crystal axes (i.e., reference coordinates - such as the x, y, and z axes defined in a crystal, where x = h, y = k, and z = l), where a set of numbers (hkl) quantifies the intercepts and is used to identify the plane. The term "plane" means a two-dimensional surface (having length and width) where a straight line connecting any two points in the plane will lie entirely flat. The term "crystal plane (111) orientation-enriched compound" means a compound that increases the exposure of metal grains (such as copper metal grains) having a crystal plane (111) orientation at the region where the metal contacts the compound. The term "aspect ratio" means the ratio of the height of a feature to the width of the surface on which the feature is plated. As used in this specification, the term "ppm" is equivalent to mg / L. The term "aqueous" or "aqueous-based" means that the solvent is water. An "inhibitor" refers to an organic additive that inhibits the plating rate of a metal during electroplating. A "promoter" means an organic compound that increases the plating rate of a metal, and such compounds are commonly referred to as brighteners. A "leveler" means an organic compound that enables uniform deposition of a metal and can improve the throwing power of an electroplating bath. The term "anisotropic" within the scope of the present invention means directionally or locally dependent - different properties in different directions or parts of a material, such that copper deposits grow mainly in the vertical direction relative to the horizontal direction. The term "isotropic" within the scope of the present invention means non-directional or the same properties that are uniform in different directions or parts of a material, where copper growth occurs substantially equally in the vertical and horizontal directions. The term "morphology" means the physical dimensions of a feature, such as height, length, and width, as well as the surface appearance. Throughout the specification, the terms "composition", "solution", and "activator etchant" are used interchangeably. The term "aperture" means an opening and includes, but is not limited to, perforations, vias, trenches, and through-silicon vias. The articles "a / an" refer to singular and plural. Unless otherwise indicated, all amounts in percentages are by weight. All numerical ranges are inclusive of the end values and can be combined in any order, except in cases where it is apparent that such numerical ranges are limited to a total of 100%.

[0032] The present invention enables anisotropic copper electroplating of features to form anisotropic copper deposits, while forming non-coherent copper grain boundaries that are substantially perpendicular to the substrate or at 90° to the substrate (grain boundaries with an orientation difference between adjacent grains of 0° to 15°, preferably greater than 0° but less than 15°), and twin copper grain boundaries that selectively grow at an inclination angle such as 65° to the substrate (grain boundaries where atoms at the grain boundary are shared by the lattices of two adjacent grains). In contrast, typical copper deposits showing isotropic electroplating growth exhibit non-coherent grain boundaries oriented at less than 80° to the substrate, or do not show non-coherent grain boundaries with a selective orientation at all. Since the anisotropic properties are caused by this selective orientation of non-coherent grain boundaries in the electroplated copper deposits, the properties are less dependent on shape and space. In other words, since anisotropic plating is guided by the internal structure of copper, once started, it is less dependent on continuous surface interactions with plating additives. Thus, the differences in plating additive activity between features of different sizes typically observed in isotropic plating baths are not apparent in anisotropic plating baths. For these reasons, the method of the present invention enables simultaneous anisotropic growth of features having different sizes (i.e., line widths of 1 to 100 μm, preferably a size range of 1 - 10 μm), pitches (i.e., pitches of 1 to 100 μm, preferably a pitch range of 1 - 10 μm), and aspect ratios (i.e., aspect ratios of 0.1 to 5, preferably a pitch of 1 - 5).

[0033] The methods and compositions of the present invention can be used for anisotropic copper electroplating of many substrates, such as but not limited to printed circuit boards and dielectric or semiconductor wafers having a seed layer such as a copper seed layer capable of making the dielectric wafer conductive. Such dielectric wafers include but are not limited to silicon wafers such as single-crystalline silicon, polycrystalline silicon, and amorphous silicon, plastics such as Ajinomoto Build-up Film (ABF), acrylonitrile butadiene styrene (ABS), epoxides, polyimides, polyethylene terephthalate (PET), silica or alumina-filled resins.

[0034] The methods and compositions of the present invention can electroplate anisotropic copper layers or anisotropic copper features, such as circuits, pillars, bond pads, and line space features. The compositions and methods of the present invention can also be used to electroplate copper anisotropically in vias, through-holes, trenches, and TSVs.

[0035] Patterning masks, photo-tools, or imaged photoresist-coated copper features such as circuits, pillars, bond pads, vias, and line features, as well as other raised features of PCBs and dielectric wafers, may or may not be used to define features. Typically, photoresist is imaged to define features on a substrate. Both positive and negative conventional photoresists can be used to image the substrate. The copper electroplating methods and compositions of the present invention enable anisotropic copper deposits such as raised features to be plated to 12 times the height of the imaged photoresist layer and still maintain their morphology, with minimal to no isotropic plating.

[0036] The areas or portions of the substrate to be electroplated with the copper electroplating composition of the present invention include a seed layer, such as a copper seed layer, to render the selected areas or portions of the substrate conductive for copper electroplating. Preferably, the seed layer predominantly has a (111) crystal plane orientation on the surface exposed to the plating bath. Conventional methods known in the art for forming seed layers can be used. Such conventional methods include, but are not limited to, chemical vapor deposition, physical vapor deposition, and electroless metal plating. Preferably, the seed layer is made of copper metal.

[0037] As Figure 1 shown, the copper electroplating composition of the present invention shows a characteristic α-peak curve in the cathodic wave of the voltammogram of the plating bath collected on a working electrode, preferably a Pt working electrode. The more distinct the α-peak of the α-peak curve, the more anisotropic the copper deposit. As Figure 1 shown by the α-peak or α-peak I 最大值 at the apex of the α-peak curve. As Figure 1 shown, the tendency to produce anisotropic growth is quantified by calculating ΔV. ΔV = V2 of α-peak I 最大值 − V of α-peak I 最大值 where V2 of α-peak I 最大值 is the voltage or potential at the apex of the α-peak curve as indicated by the second vertical dashed line in Figure 1 and V of α-peak I 最大值 is the voltage at the intersection of the horizontal dashed line starting from the apex of the α-peak curve with the cathodic wave also indicated by the first vertical dashed line in Figure 1 .

[0038] The α-peak curve in the cathodic wave of the voltammogram as described above is preferably used to select an inhibitor for the copper plating composition to enable plating of anisotropic copper deposits. Various compounds known for their inhibitor activity can be tested to determine their ability to achieve anisotropic copper deposits. If a copper plating composition containing an inhibitor provides a voltammogram curve with an α-peak curve in the cathodic wave, the inhibitor can be used for plating anisotropic copper deposits. The larger the ΔV, the more anisotropic the copper deposit plated from the copper plating composition with a specific inhibitor.

[0039] Figure 2A and 2B The isotropically deposited copper wire of a conventional copper plating bath is shown and compared with the copper wire electroplated from the anisotropic copper plating bath of the present invention. Figure 2A A dielectric substrate 20, such as a silicon wafer, coated with a copper seed layer 22 is shown. Imaging photoresist 24 coats the seed layer 22. The isotropically deposited copper wire 26 shown is deposited within a recess 28 in the imaging photoresist. Three arrows indicate the growth of the copper pillar and its isotropic characteristics, where portions of the wire overlap the imaging photoresist 24, indicating copper deposition in the horizontal direction. The vertical arrow indicates copper growth in the vertical direction simultaneously with the horizontal growth. In contrast, Figure 2B A dielectric substrate 30, such as a silicon wafer, coated with a copper seed layer 32 is shown. Imaging photoresist 34 coats the seed layer 32. The anisotropic copper pillar 36 shown is deposited within a recess 38 in the imaging photoresist. The vertical arrow indicates the anisotropic characteristics of the copper pillar 36, where once the copper growth exceeds the height of the imaging photoresist, copper deposition occurs only in the horizontal direction. There is no horizontal copper growth on the imaging photoresist 34.

[0040] The anisotropic copper plating composition of the present invention is water-based and includes a copper ion source. The copper ion source is a copper salt and includes but is not limited to copper sulfate; copper halides, such as copper chloride; copper acetate; copper nitrate; copper fluoroborate; copper alkylsulfonate; copper arylsulfonate; copper sulfamate; and copper gluconate. Exemplary copper alkylsulfonates include copper (C1-C6) alkylsulfonate and copper (C1-C3) alkylsulfonate. Preferably, the copper alkylsulfonate is copper methanesulfonate, copper ethanesulfonate, and copper propanesulfonate. Exemplary copper arylsulfonates include but are not limited to copper benzenesulfonate, copper phenolsulfonate, and copper p-toluenesulfonate. A mixture of copper ion sources can be used.

[0041] The copper salt can be used in the aqueous anisotropic copper plating bath in an amount that provides a sufficient copper ion concentration to electroplate copper on the substrate. Preferably, the copper salt is present in an amount sufficient to provide 10 g / L to 180 g / L of copper ions in the plating solution, more preferably 20 g / L to 100 g / L of copper ions in the plating solution.

[0042] An acid can be included in the anisotropic copper electroplating bath. The acid includes, but is not limited to, sulfuric acid, fluoboric acid, alkane sulfonic acids such as methanesulfonic acid, ethanesulfonic acid, propanesulfonic acid, and trifluoromethanesulfonic acid, aryl sulfonic acids such as benzenesulfonic acid, phenolsulfonic acid, and toluenesulfonic acid, sulfamic acid, hydrochloric acid, and phosphoric acid. A mixture of acids can be used in the copper electroplating bath. Preferably, the acid includes sulfuric acid, methanesulfonic acid, ethanesulfonic acid, propanesulfonic acid, and mixtures thereof.

[0043] The acid is preferably present in an amount of 1 g / L to 300 g / L, more preferably 5 g / L to 250 g / L, and even more preferably 10 to 150 g / L. Acids are generally commercially available from a variety of sources and can be used without further purification.

[0044] A halide ion source can be included in the anisotropic copper electroplating bath. The halide ion is preferably chloride ion. A preferred chloride ion source is hydrochloric acid. The chloride ion concentration is in an amount of 1 ppm to 100 ppm, more preferably 10 to 100 ppm, and even more preferably 20 to 75 ppm.

[0045] Accelerators include, but are not limited to, 3-mercapto-propane sulfonic acid and its sodium salt, 2-mercapto-ethane sulfonic acid and its sodium salt, and bis-sulfopropyl disulfide and its sodium salt, sodium 3-(benzothiazolyl-2-thio)-propane sulfonate, sodium 3-mercaptopropane-1-sulfonate, sodium ethylenedithiodipropane sulfonate, disodium bis-(p-sulfophenyl)-disulfide, disodium bis-(ω-sulfobutyl)-disulfide, disodium bis-(ω-sulfohydroxypropyl)-disulfide, disodium bis-(ω-sulfopropyl)-disulfide, disodium bis-(ω-sulfopropyl)-sulfide, sodium methyl-(ω-sulfopropyl)-disulfide, sodium methyl-(ω-sulfopropyl)-trisulfide, O-ethyl-dithiocarbonic acid-S-(ω-sulfopropyl)-ester, potassium salt of mercaptoacetic acid, O-ethyl-bis-(ω-sulfopropyl)-ester disodium salt of thiophosphoric acid, trisodium salt of tris-(ω-sulfopropyl)-ester of thiophosphoric acid, (3-sulfopropyl) ester of N,N-dimethyldithiocarbamic acid, sodium salt, potassium salt of (O-ethyl dithiocarbonic acid)-S-(3-sulfopropyl)-ester, 3-[(amino-iminomethyl)-thio]-1-propane sulfonic acid, and sodium salt of 3-(2-benzothiazolylthio)-1-propane sulfonic acid. Preferably, the accelerator is bis-sulfopropyl disulfide or its sodium salt. Preferably, the accelerator is included in the copper electroplating bath in an amount of 1 ppb to 500 ppm, more preferably 50 ppb to 50 ppm, and most preferably 5 ppm to 40 ppm.

[0046] Preferably, inhibitors include, but are not limited to, polyethylene glycol polymers having a weight average molecular weight of 1000 - 6000 g / mol, random and block ethylene oxide - propylene oxide (“EO / PO”) copolymers having a weight average molecular weight of 1000 - 5000 g / mol.

[0047] More preferably, the inhibitor is a diamine core-EO / PO surfactant, which preferably has the following general formula:

[0048]

[0049] which has a weight average molecular weight of 1000-10,000 g / mol and is commercially available from BASF, Mount Olive, NJ as a surfactant; and

[0050]

[0051] which has a weight average molecular weight of 1000-10,000 g / mol and is commercially available from BASF as an R surfactant, where the variables x, x’, x”, x”’, y, y’, y” and y”’ are integers equal to or greater than 1 such that the weight average molecular weight of the copolymer ranges from 1000-10,000 g / mol.

[0052] Most preferably, the diamine-core polymer is terminated with 1 to 4 sulfonic acid groups. The most preferred example is a diamine-core polymer having the following general formula:

[0053]

[0054] where the weight average molecular weight is 1000-10,000 g / mol and the variables x, x”, x”, x”', y, y', y” and y”' are independently integers greater than or equal to 1 to provide a molecular weight range of 1000-10,000 g / mol.

[0055] The inhibitor is preferably included in the copper electroplating bath in an amount of 0.5 g / L to 20 g / L, more preferably 1 g / L to 10 g / L, and even more preferably 1 g / L to 5 g / L.

[0056] Preferably, the leveling agent includes a copolymer of imidazole and butyl diglycidyl ether or a reaction product of imidazole and phenylimidazole. Preferably, such a leveling agent has a weight average molecular weight of 1000 g / mol to 50,000 g / mol. Such a leveling agent can be prepared by methods disclosed in the literature or by methods known to those of ordinary skill in the art.

[0057] The leveling agent is preferably included in the copper electroplating bath in an amount of 0.01 ppm to 100 ppm, more preferably 0.01 ppm to 10 ppm, and even more preferably 0.01 ppm to 1 ppm.

[0058] Optionally, a pH regulator may be included in the composition to maintain the desired pH. One or more inorganic acids and organic acids may be included to adjust the pH of the composition. Inorganic acids include, but are not limited to, sulfuric acid, hydrochloric acid, nitric acid, and phosphoric acid. Organic acids include, but are not limited to, citric acid, acetic acid, alkane sulfonic acids such as methanesulfonic acid. Bases that may be included in the composition include, but are not limited to, sodium hydroxide, potassium hydroxide, ammonium hydroxide, and mixtures thereof.

[0059] The pH of the copper electroplating composition is from 0 to 14, preferably from 0 to 6, more preferably from 0 to 4.

[0060] To provide a conductive substrate for copper electroplating, the substrate of the present invention includes a selectively deposited seed layer, such as a copper seed layer, to render the substrate conductive. The selectively deposited seed layer is then copper plated to provide an anisotropic copper deposit on the selective seed layer. Once the seed layer is copper coated, continuous copper plating results in vertical copper growth with minimal to no horizontal copper deposition. Alternatively, the entire surface of the substrate includes a seed layer coating. A photoresist material is applied on the seed layer and the photoresist is imaged using conventional methods known in the art to form a pattern or feature on the substrate. The photoresist can be one of many conventional photoresists known to those of ordinary skill in the art. The photoresist can be a negative or positive acting photoresist. Due to the anisotropic nature of the copper electroplating composition of the present invention, the thickness of any photoresist applied to the substrate surface can be thinner than the thickness of the electroplated copper layer.

[0061] The substrate can be electroplated with copper by contacting the substrate with the plating composition. The substrate acts as the cathode. The anode can be a soluble or insoluble anode. A sufficient current density is applied and the plating is carried out for a certain period of time to deposit copper having the desired thickness and morphology on the substrate. The current density can range from 0.5 ASD to 30 ASD, preferably from 0.5 ASD to 20 ASD, more preferably from 1 ASD to 10 ASD, and further preferably from 1 ASD to 5 ASD.

[0062] The temperature of the copper electroplating bath during electroplating preferably ranges from room temperature to 65 °C, more preferably from room temperature to 35 °C, and further preferably from room temperature to 30 °C.

[0063] The copper electroplating composition and method of the present invention can anisotropically electroplate fine lines having a width of 1 - 100 μm, or such as 1 - 50 μm, or such as 1 - 5 μm and a height of up to 40 μm.

[0064] Optionally, but preferably, prior to copper electroplating, the seed layer can be treated with an aqueous treatment solution containing one or more sulfur-containing accelerator compounds. The pre-treatment solution for copper electroplating is further capable of anisotropic copper electroplating. The treatment solution can be applied to the selectively deposited seed layer, followed by anisotropic copper electroplating. The aqueous treatment solution has a pH below 3 such as from 0 to less than 3, or above 9 such as greater than 9 to 14.

[0065] Alternatively, a substrate containing a seed layer coating the entire surface of the substrate can be coated with a photoresist, imaged to form a pattern, and the treatment solution can be applied such that the treatment solution contacts the exposed seed at the bottom of the imaged portion of the photoresist. The remaining photoresist is then stripped from the substrate with a conventional photoresist stripper. The treated seed layer is then copper-plated with the copper plating composition of the present invention. Anisotropic copper electroplating occurs on the seed layer treated with the treatment solution, rather than on the untreated seed layer. Optionally, copper electroplating can be performed after applying the treatment solution but before stripping the imaged photoresist from the substrate. After copper electroplating, the photoresist can be stripped from the substrate.

[0066] The sulfur-containing accelerators include many of the accelerators included in the copper plating compositions of the present invention. The accelerators include, but are not limited to, 3-mercapto-propane sulfonic acid and its sodium salt, 2-mercapto-ethane sulfonic acid and its sodium salt, and bis-sulfopropyl disulfide and its sodium salt, sodium 3-(benzothiazolyl-2-thio)-propyl sulfonate, sodium 3-mercaptopropane-1-sulfonate, sodium ethylenedithiodipropane sulfonate, bis-(p-sulfophenyl)-disulfide disodium salt, bis-(ω-sulfobutyl)-disulfide disodium salt, bis-(ω-sulfohydroxypropyl)-disulfide disodium salt, bis-(ω-sulfopropyl)-disulfide disodium salt, bis-(ω-sulfopropyl)-sulfide disodium salt, methyl-(ω-sulfopropyl)-disulfide sodium salt, methyl-(ω-sulfopropyl)-trisulfide disodium salt, O-ethyl-dithiocarbonic acid-S-(ω-sulfopropyl)-ester, potassium salt of mercaptoacetic acid, O-ethyl-bis-(ω-sulfopropyl)-ester disodium salt of thiophosphoric acid, tris-(ω-sulfopropyl)-ester trisodium salt of thiophosphoric acid, N,N-dimethyl dithiocarbamic acid (3-sulfopropyl) ester, sodium salt, (O-ethyl dithiocarbonic acid)-S-(3-sulfopropyl)-ester, potassium salt, 3-[(amino-iminomethyl)-thio]-1-propane sulfonic acid and 3-(2-benzothiazolylthio)-1-propane sulfonic acid, sodium salt. Preferably, the accelerator is 2-mercapto-ethane sulfonic acid and its sodium salt. Preferably, the accelerator is included in the copper plating bath in an amount of 1 ppb to 500 ppm, more preferably 50 ppb to 50 ppm, and most preferably 5 ppm to 40 ppm.

[0067] Optionally, one or more surfactants may be included in the treatment solution of the present invention. Such surfactants include nonionic surfactants, cationic surfactants, anionic surfactants, and amphoteric surfactants. For example, nonionic surfactants may include polyesters, polyethylene oxides, polypropylene oxides, alcohols, ethoxylates, silicon compounds, polyethers, glycosides, and their derivatives; and anionic surfactants may include anionic carboxylates or organic sulfates, such as sodium lauryl ether sulfate (SLES).

[0068] Surfactants may be included in conventional amounts. Preferably, when surfactants are included in the treatment solution of the present invention, they are included in an amount of 0.1 g / L to 10 g / L.

[0069] The treatment solution of the present invention may be applied at a temperature from room temperature to 60 °C, preferably from room temperature to 30 °C, and more preferably the composition is applied to copper at room temperature.

[0070] The treatment solution of the present invention may be applied by dipping a substrate having a seed layer into the solution, by spraying the solution onto the substrate, spin coating, or other conventional methods for applying the solution to the substrate. The treatment solution of the present invention may also be selectively applied to copper. Selective application may be carried out by any conventional method for selectively applying the solution to the substrate. Such selective application includes, but is not limited to, inkjet application, writing pen, eye dropper, polymer stamp with a patterned surface, masks such as imaged photoresist or screen printing.

[0071] Figure 3 Shown are a method of the present invention for applying a treatment solution and anisotropic copper wires deposited according to the method of the present invention. Substrate 40 is coated with a copper seed layer 42, and the copper seed layer is coated with an imaged photoresist 44 having an opening 46 with a height of 3 μm. The portion 48 of the seed layer exposed at the bottom of the opening 46 is treated with a treatment solution containing MES to provide a treated seed layer 50. Then the photoresist is stripped, leaving the treated seed layer 50. Then the treated seed layer is plated with the anisotropic copper electroplating bath of the present invention, where copper wire growth occurs vertically only on the seed layer treated with the treatment solution, and then the remaining copper growth is isotropic to form copper wires 52.

[0072] Figure 4A and 4B The structure of anisotropically plated copper is shown by analyzing the grain boundaries of the cross-section of the wire features electroplated with anisotropic or isotropic copper. Figure 4AIt is a differential Fourier transform diagram of the subtraction of the line features of anisotropic growth (white lines) from the line features of isotropic growth (black lines), showing the orientation of the non-coherent grain boundaries relative to the substrate. The white horizontal line indicates that these grain boundaries of the anisotropic growth lines are preferably oriented at 90° relative to the substrate, which indicates that they reduce the lateral growth of the plated copper and thus ensure anisotropic plating growth. Figure 4B It is a similar differential Fourier transform diagram of the subtraction of the line features of anisotropic growth from the line features of isotropic growth, showing the orientation of the (111)-twin grain boundaries relative to the substrate. The two white diagonal lines indicate that the twin grain boundaries of the anisotropic growth lines are oriented at about 45° relative to the substrate, which indicates that grain growth occurs within the boundaries of the non-coherent grain boundaries via deposition on the (111)-twin plane.

[0073] The article of the present invention includes a copper deposit plated to a height at least 2 μm higher than the surrounding photoresist without causing feature broadening, and the deposit includes non-coherent grain boundaries oriented at 80° - 90° relative to the plane of the substrate and parallel twin grain boundaries oriented at 40° - 50° relative to the plane of the substrate.

[0074] The following examples are included to further illustrate the present invention but are not intended to limit its scope.

[0075] Examples 1 - 2

[0076] Activated on sodium 3-mercapto-propane sulfonate, using a highly anisotropic bath 3, the plating height of a 1 - 100 μm fine line pattern was planarized, compared with non-activated, using an isotropic bath 1.

[0077] Prepare the following two copper electroplating baths:

[0078] Plating bath 1 (isotropic bath):

[0079] 50 g / L Cu(II) ions

[0080] 100 g / L H2SO4

[0081] 50 ppm chloride ions

[0082] 5 ppm sodium polydithiopropane sulfonate

[0083] 2 g / L EO-PO random copolymer with an average MW of 1,100 and hydroxyl end groups

[0084] 5 ppm reaction product of epichlorohydrin and imidazole

[0085] Plating bath 2 (anisotropic bath):

[0086] 50 g / L Cu(II) ions

[0087] 100 g / L H2SO4

[0088] 50 ppm chloride ions

[0089] 40 ppm sodium polydithiopropane sulfonate

[0090] 2 g / L EO-PO random copolymer with an average MW of 1,100 and hydroxyl end groups

[0091] 1 ppm reaction product of butyl diglycidyl ether, imidazole and phenylimidazole

[0092] Plating bath 3 (anisotropic bath):

[0093] 50 g / L Cu(II) ions

[0094] 100 g / L H2SO4

[0095] 50 ppm chloride ions

[0096] 20 ppm sodium polydithiopropane sulfonate

[0097] 2 g / L diamine core EO / PO block copolymer with an average MW of 7,000

[0098] 0.1 ppm reaction product of butyl diglycidyl ether, imidazole and phenylimidazole

[0099] A silicon wafer coated with a 20 nm Ti adhesion layer and a 200 nm conductive Cu seed layer is laminated with a 3 μm thick positive-tone Shipley BPR TM 100PR layer. Fine line patterns are constructed on the PR layer to contain a series of trenches with widths ranging from 6 to 100 μm. These trenches are then plated to a target height of 4.5 μm using either plating bath 1 or plating bath 3. Samples plated with plating bath 1 are wetted with DI water before plating. Samples plated with plating bath 3 are first immersed in a 4 g / L MES solution in water with a pH of 0.7 and then rinsed with DI water before plating. In both cases, electroplating is carried out at a cathode rotation rate of 50 rpm at 2 ASD. After plating, Shipley BPR TMThe stripper removes the PR at 80 °C for 10 minutes to produce a pattern of fine lines. The sample is then exposed to an etch solution containing 84 mL / L of 85% phosphoric acid and 8 mL / L of 45.5% hydrogen peroxide solution to remove the remaining conductive seed crystals that have been protected by the PR. The height of the separated Cu fine lines is measured using a laser profiler from Keyence Corporation. The results summarized in Table 1 show that both plating baths produce highly planarized deposits, where the plating height is uniform regardless of the variation in feature size. These results indicate that anisotropic plating is possible while still obtaining highly planarized deposits over a wide range of line sizes, as typically provided by plating bath 1.

[0100] Table 1

[0101]

[0102] Example 3 - 6.

[0103] Line broadening is performed on MES-activated 1 - 100 μm fine line patterns using highly surface-reactive bath 2, in contrast to non-activation, using non-surface-reactive bath 1

[0104] A silicon wafer coated with a 20 nm Ti adhesion layer and a 200 nm conductive Cu seed crystal is laminated with a PR layer having a thickness of 3 μm. A fine line pattern is constructed on the PR layer to contain a series of trenches with widths ranging from 1 to 100 μm. These trenches are then plated to a target height of 4.5 μm using either plating bath 1 or plating bath 3. In each case, the sample is wetted with DI water before plating, or first immersed in a pH 0.7 solution of 4 g / L MES in water and then rinsed with DI water before plating. In all cases, electroplating is carried out at a cathode rotation rate of 50 rpm at 2 ASD. After plating, the PR is removed in a PR stripper bath to produce a pattern of fine lines. The sample is then exposed to the seed crystal etch solution to remove the remaining conductive seed crystals that have been protected by the PR. The width of the separated Cu fine lines is measured using a laser profiler. The results summarized in Table 2 show that even when the target plating height is significantly higher than the height of the PR layer, plating bath 3 prevents significant line broadening. On the other hand, samples prepared with plating bath 1 show significant line broadening regardless of any pretreatment. In sample regions with small line spacings, this broadening leads to the fusion of adjacent Cu lines.

[0105] Table 2

[0106]

[0107] Examples 7 - 10

[0108] Line broadening is performed on the MES-activated 1 - 100 μm fine line pattern using the highly surface-reactive bath 3, in contrast to no activation, using the non-surface-reactive bath 1

[0109] A silicon wafer coated with a 20 nm Ti adhesion layer and a 200 nm conductive Cu seed layer is laminated with a PR layer having a thickness of 3 μm. A fine line pattern is constructed on the PR layer to contain a series of 100 μ wide trenches. Then the substrate is plated to a target height of 36 μm using plating bath 1 or plating bath 3. Samples plated with plating bath 1 are wetted with DI water before plating. Samples plated with plating bath 3 are first immersed in a 4 g / L MES solution in water at pH 0.7 and then rinsed with DI water before plating. In both cases, electroplating is carried out at a cathode rotation rate of 50 rpm at 2 ASD. After plating, the PR is removed in a PR stripper bath to produce a pattern of fine lines. Then the samples are imaged via SEM. Table 3 shows that samples plated with plating bath 1 resulted in complete line fusion, while samples plated with plating bath 3 did not exhibit any significant line broadening and the plating deposits had grown anisotropically in the shape of the thinner PR pattern.

[0110] Then a fine line pattern is constructed on a 3 μm PR layer of a similar substrate to contain a series of trenches with widths from 1 to 5 μm. Then the substrate is plated similarly using the same process flow as above, with the only difference being a lower plating target height of 6 μm. Table 3 shows that samples plated with plating bath 1 resulted in complete line fusion, while samples plated with plating bath 3 did not exhibit any significant line broadening and the plating deposits grew anisotropically in the shape of the thinner PR pattern.

[0111] Table 3

[0112]

[0113] Examples 11 - 18.

[0114] Effect of surface activation with different plating baths on 100 μm wide lines relative to no surface activation

[0115] A silicon wafer coated with a 20 nm Ti adhesion layer and a 200 nm conductive Cu seed layer was laminated with a PR layer having a thickness of 3 μm. A fine line pattern was constructed on the PR layer to contain a series of grooves 100 μm wide. Then the substrate was plated to a target height of 6 μm using 4 different plating bath formulations. In each case, the sample was wetted with DI water before plating, or first immersed in a pH 0.7 solution of 4 g / L MES in water and then rinsed with DI water before plating. In all cases, electroplating was carried out at a cathode rotation rate of 50 rpm at 10 ASD. After plating, the PR was removed in a PR stripper bath to produce the pattern of fine lines. Then the sample was resin molded and cross-sectioned using argon plasma. Subsequently, SEM imaging was carried out to observe the effect of the plating formulation on the line shape and uniformity. The results are summarized below.

[0116] Examples 11 and 12 were plated with plating bath 3. Example 11 was pretreated with an MES solution, while Example 12 was only pre-wetted with DI water. Example 11 shows a uniform line shape and anisotropic growth along the edges of the line. Example 12 results in a severely non-uniform line shape and anisotropic growth along the edges of the line.

[0117] Examples 13 and 14 were plated with plating bath 2. Example 13 was pretreated with an MES solution, while Example 14 was only pre-wetted with DI water. Example 13 shows a uniform line shape and slight anisotropic growth along the edges of the line. Here, a slightly anisotropic bath is a formulation that produces less line broadening than plating bath 1 and, when plated above the height of the PR, results in a plating deposit growth direction of 75° - 89° relative to the substrate. Example 14 shows a non-uniform line shape and slight anisotropic growth along the edges of the line.

[0118] Examples 15 and 16 were plated with plating bath 4 containing the following:

[0119] 50 g / L Cu(II) ions

[0120] 100 g / L H2SO4

[0121] 50 ppm chloride ions

[0122] 40 ppm sodium polydithiopropane sulfonate

[0123] 2 g / L EO-PO block copolymer with an average MW of 1,100 and hydroxy end groups

[0124] 1 ppm reaction product of butyl diglycidyl ether, imidazole and phenylimidazole

[0125] Example 15 was pretreated with MES solution, while Example 16 was only pre-wetted with DI water. Example 15 shows a uniform line shape and slight isotropic growth along the edges of the line. The slight isotropic bath is a formulation that produces less line broadening than plating bath 1, and when plated above the height of the PR, it results in a plating deposit growth direction of 40° - 74° relative to the substrate. Example 14 shows a non-uniform line shape and isotropic growth along the edges of the line.

[0126] Examples 17 and 18 were plated with plating bath 1. Example 17 was pretreated with MES solution, while Example 18 was only pre-wetted with DI water. Example 17 shows a uniform line shape and strong isotropic growth along the edges of the line. Example 18 shows a uniform line shape and strong isotropic growth along the edges of the line.

[0127] Examples 11 - 18 were cross-sectioned and then analyzed via EBSD to determine the differences in microstructure with increasing anisotropic plating behavior. For this purpose, the length of all grain boundaries in each cross-section was analyzed and divided by the corresponding cross-sectional surface area to obtain the grain boundary density. It was thus found that the more significant the anisotropic growth behavior of the plating bath formulation, the more the twin grain boundary density would increase when the seed crystal was activated with MES solution. This trend is shown in Table 4. Additionally, it was observed that all samples immediately after plating contained Cu deposits with small grains, but the Cu grain size increased at different rates depending on the plating formulation at room temperature. When the samples were cross-sectioned and analyzed, the grain size of the highly isotropic growth Examples 17 - 18 was larger than that of the highly anisotropic Examples 11 - 12. Grain growth can continue until stable grain boundaries, such as twin grain boundaries, are formed. This indicates that the relatively high twin density in Examples 17 - 18 may be the result of subsequent grain growth rather than an inherent tendency of plating bath 1 to produce a high twin grain boundary density. Thus, the data indicate that anisotropic growth is accompanied by a higher tendency to form twin grain boundaries during plating.

[0128] Table 4

[0129]

[0130] The EBSD data were further processed via Fourier analysis to study whether anisotropic growth was accompanied by a change in the grain boundary orientation relative to the substrate. For all non-coherent grain boundaries of the (111)-twin grain boundaries, the Fourier transform plot of Example 11 was subtracted from the plot of Example 18. The resulting difference plot is shown in Figure 4A and 4BAmong them, the horizontal lines indicate the alignment of grain boundaries perpendicular to the plated substrate, while the vertical lines indicate the alignment of parallel grain boundaries. The white lines correspond to the preferred alignment in Example 11 of anisotropic growth, and the black lines correspond to the preferred alignment in Example 18 of isotropic growth. The data show that anisotropic growth is accompanied by the preferred alignment of incoherent grain boundaries perpendicular to the substrate, while anisotropic growth is associated with a less distinct preference. In the case of (111)-twin grain boundaries, the isotropic growth samples show vertical and parallel orientations, while the anisotropic samples show a moderate preference for (111)-twin grain boundaries oriented at approximately 45° relative to the substrate.

[0131] In summary, the twin grain boundary density and Fourier analysis data indicate that anisotropic growth is caused by the preferential deposition or nucleation of new grains on twin grain boundaries. The lower preference for growth on incoherent grain boundaries causes these grain boundaries to tend to fix the deposit along the thickness of the deposit, preventing it from spreading outwards and thus resulting in anisotropic growth. On the other hand, the ability of all grain boundaries to spread laterally along the thickness of the deposit in isotropic samples provides a path for Cu to grow without a preferred direction.

[0132] Examples 19 - 25

[0133] Design a plating bath that responds to surface activation and increases the plating growth angle

[0134] The growth angle of the plating deposit can be adjusted by changing the plating composition. A key variable in the formulation is the choice of inhibitor additive. Therefore, to study the effect of inhibitors on line broadening, different inhibitors were incorporated into a bath containing the following:

[0135] 50 g / L Cu(II) ions

[0136] 100 g / L H2SO4

[0137] 50 ppm chloride ions

[0138] 40 ppm sodium polydithiopropane sulfonate

[0139] 2 g / L inhibitor additive

[0140] Example 19: PEG MW 1,000

[0141] Example 20: Block EO-PO MW 1,100

[0142] Example 21: Block EO-PO MW 1,950

[0143] Example 22: Random EO-PO MW 1,100

[0144] Example 23: Reverse Tetronic, MW 3,750

[0145] Example 24: Reverse Tetronic, MW 5,300

[0146] Example 25: Reverse Tetronic with sulfonated end groups, MW 4,800

[0147] Reaction product of 0.1 ppm butyl diglycidyl ether, imidazole, and phenylimidazole

[0148] Using a Pt rotating working electrode (10 rpm, 10 mV / s scan rate, 25 °C), a general analytical tool for Cu plating baths as Figure 1 shown therein analyzes the formulation via cyclic voltammetry. The more significant the anisotropic growth produced by a given formulation, the more prominent the α-peak feature in the cathodic wave of the CVS will become. Thus, as Figure 1 shown therein, the tendency to produce anisotropic growth is quantified by calculating ΔV. The plating bath from Example 19 produced a ΔV of 0.003 V; Example 20 produced a ΔV of 0.049 V; Example 21 produced a ΔV of 0.076 V; Example 22 produced a ΔV of 0.093 V; Example 23 produced a ΔV of 0.094 V; Example 24 produced a ΔV of 0.095 V; Example 25 produced a ΔV of 0.101 V.

[0149] Examples 26 - 35

[0150] Controlling feature broadening in 1 - 60 μm wide feature patterns with different inhibitor additives

[0151] A silicon wafer coated with a 20 nm Ti adhesion layer and a 200 nm conductive Cu seed layer is laminated with a PR layer having a thickness of 3 μm. A fine line pattern is constructed on the PR layer to contain a series of trenches with widths ranging from 1 to 60 μm. Then these trenches are plated to a target height of 6 μm using 10 different plating bath formulations that differ in the properties of the inhibitor additives:

[0152] 50 g / L Cu(II) ions

[0153] 100 g / L H2SO4

[0154] 50 ppm chloride ions

[0155] 40 ppm sodium polydithiopropanesulfonate

[0156] Reaction product of 0.1 ppm butyl diglycidyl ether, imidazole, and phenylimidazole

[0157] 2 g / L inhibitor additive

[0158] Example 26: Block EO-PO MW 1,100

[0159] Example 27: Block EO-PO MW 1,950

[0160] Example 28: Block EO-PO MW 4,950

[0161] Example 29: Random EO-PO MW 1,100

[0162] Example 30: PEG MW 1,000

[0163] Example 31: PEG MW 6,000

[0164] Example 32: Reverse Tetronic, MW 3,750

[0165] Example 33: Reverse Tetronic, MW 5,300

[0166] Example 34: Reverse Tetronic, MW 7,250

[0167] Example 35: Reverse Tetronic with sulfonated end groups, MW 4,800

[0168] Each sample was rinsed with DI water before plating. In all cases, plating was carried out at a cathodic rotation rate of 50 rpm at 2 ASD. After plating, the PR was removed in a PR stripper bath to produce a pattern of fine lines. The samples were then exposed to Cu and Ti etch solutions to remove the remaining conductive seed crystals that had been protected by the PR. Finally, the width of the plated lines was determined by laser profilometry.

[0169] The results are listed in Table 6. The results show that the reverse Tetronic-type inhibitors are the most effective in minimizing line broadening; while sulfonation of the Tetronic end groups results in the most significant anisotropic plating and little line broadening when plating above the PR.

[0170] Table 6 Effect of inhibitors on fine line broadening (6 μm height, 3 μm PR)

[0171]

[0172] Examples 35 - 39

[0173] Controlling feature broadening in 1 - 60 μm wide feature patterns with different planarizer concentrations

[0174] A silicon wafer coated with a 20 nm Ti adhesion layer and a 200 nm conductive Cu seed crystal is laminated with a PR layer having a thickness of 3 μm. A fine line pattern is constructed on the PR layer to contain a series of grooves with widths ranging from 1 to 60 μm. These grooves are then plated to a target height of 6 μm using 5 different plating bath formulations with different leveling agent additive concentrations:

[0175] 50 g / L Cu(II) ions

[0176] 100 g / L H2SO4

[0177] 50 ppm chloride ions

[0178] 40 ppm sodium polydithiopropane sulfonate

[0179] 2 g / L reverse Tetronic with sulfonated end groups, MW 4,800

[0180] Example 35: Reaction product of 0.1 ppm butyl diglycidyl ether, imidazole, and phenylimidazole

[0181] Example 36: Reaction product of 1 ppm butyl diglycidyl ether, imidazole, and phenylimidazole

[0182] Example 37: Reaction product of 2 ppm butyl diglycidyl ether, imidazole, and phenylimidazole

[0183] Example 38: Reaction product of 5 ppm butyl diglycidyl ether, imidazole, and phenylimidazole

[0184] Example 39: Reaction product of 10 ppm butyl diglycidyl ether, imidazole, and phenylimidazole

[0185] Each sample is rinsed with DI water before plating. In all cases, constant current plating is carried out at a cathode rotation rate of 50 rpm at 2 ASD. After plating, the PR is removed in a PR stripper bath to produce the pattern of fine lines. The samples are then exposed to a seed crystal etch solution to remove the remaining conductive seed crystals that have been protected by the PR. Finally, the width of the plated lines is determined by laser profilometry.

[0186] The results disclosed in Table 7 show that as the concentration of the leveling agent additive decreases, anisotropic plating is most significant. The best results in minimizing the broadening of the plated lines are obtained when the leveling agent concentration is 1 ppm or lower.

[0187] Table 7 Effect of leveling agent concentration on the broadening of fine lines (6 μm height, 3 μm PR)

[0188]

[0189] Examples 40 - 45. Controlling feature broadening in feature patterns 1 - 60 μm wide with surface pre - treatment and different inhibitor additives

[0190] A silicon wafer coated with a 20 - nm Ti adhesion layer and a 200 - nm conductive Cu seed layer was laminated with a PR layer having a thickness of 3 μm. A fine - line pattern was constructed on the PR layer to contain a series of trenches with widths from 1 to 100 μm. Then these trenches were electroplated to a target height of 4.5 μm using 6 different plating bath formulations that differed in inhibitor additives:

[0191] 50 g / L Cu(II) ions

[0192] 100 g / L H2SO4

[0193] 50 ppm chloride ions

[0194] 2 g / L inhibitor additive

[0195] Example 40: Block EO - PO MW 1,100

[0196] Example 41: Block EO - PO MW 1,950

[0197] Example 42: Reverse Tetronic, MW 5,300

[0198] Example 43: Reverse Tetronic with sulfonated end - groups, MW 4,800

[0199] Example 44: Random EO - PO MW 1,100

[0200] Example 45: Reverse Tetronic, MW 7,250

[0201] Each sample was first immersed in a 4 - g / L MES solution in water at pH 0.7 or pH 5.5 and then rinsed with DI water before plating. In all cases, electroplating was carried out at a cathodic rotation rate of 50 rpm at 2 ASD. After plating, the PR was removed in a PR stripper bath to produce the pattern of fine lines. Then the samples were exposed to a Cu and Ti etch solution to remove the remaining conductive seed that had been protected by the PR. Finally, the width of the plated lines was determined by laser profilometry.

[0202] Each sample was first immersed in a 4 g / L solution of MES in water at pH 0.7 or pH 5.5 and then rinsed with DI water before plating. In all cases, electroplating was carried out at a cathode rotation rate of 50 rpm at 2 ASD. After plating, the PR was removed in a PR stripper bath to produce a pattern of fine lines. The samples were then exposed to Cu and Ti etchant solutions to remove the remaining conductive seed crystals that had been protected by the PR. Finally, the width of the plated lines was determined by laser profilometry.

[0203] The results are listed in Tables 8 - 9, showing that seed activation improved the anisotropic plating characteristics of all inhibitors. However, the same patterns were found in Examples 35 - 39 that did not include seed activation. The reverse Tetronic - type inhibitors were most effective in minimizing line broadening, and sulfonation of the reverse Tetronic end chain resulted in the most pronounced anisotropic plating behavior.

[0204] Each sample was first immersed in a 4 g / L solution of MES in water at pH 0.7 or pH 5.5 and then rinsed with DI water before plating. In all cases, electroplating was carried out at a cathode rotation rate of 50 rpm at 2 ASD. After plating, the PR was removed in a PR stripper bath to produce a pattern of fine lines. The samples were then exposed to Cu and Ti etchant solutions to remove the remaining conductive seed crystals that had been protected by the PR. Finally, the width of the plated lines was determined by laser profilometry.

[0205] The results are shown in Tables 8 - 9, showing that seed activation improved the anisotropic plating characteristics of all inhibitors. However, the same patterns found in Examples 35 - 39 that did not include seed activation were also found here. That is, the reverse Tetronic - type inhibitors were most effective in minimizing line broadening, and sulfonation of the reverse Tetronic end chain resulted in the most pronounced anisotropic plating behavior.

[0206] Table 8 Effect of inhibitors on fine line broadening (12 μm height, 3 μm PR, pH = 5.5)

[0207]

[0208] Table 9 Effect of inhibitors on fine line broadening (12 μm height, 3 μm PR, pH = 0.7)

[0209]

[0210] Examples 46 - 48

[0211] Seed activation solution with promoter and wetting agent

[0212] The effect of including a wetting agent in the activation solution to promote planarization on anisotropic plating growth was tested on three different fine line patterns of different line widths. Silicon wafers coated with a 20 nm Ti adhesion layer and a 200 nm conductive Cu seed layer were laminated with a PR layer having a thickness of 3 μm. Fine line patterns were constructed on the PR layer to contain trenches with widths of 7, 20, or 100 μm. The trenches in each pattern were then filled via copper electroplating using plating bath 1, plating bath 2, or plating bath 3. The samples were first immersed in a solution of 4 g / L MES and 1 g / L TN-747 wetting agent in water at pH 0.7 and then rinsed with DI water before plating. The 7 μm fine line pattern was plated to a line height of 9 μm (3X PR height); the 20 μm fine line pattern was plated to a line height of 9 μm (3X PR height); and the 100 μm fine line pattern was plated to a line height of 36 μm (12X PR height). Electroplating was carried out at a cathodic rotation rate of 50 rpm at 2 ASD. After plating, the PR was removed in a PR stripper bath to produce the pattern of fine lines. The samples were then exposed to a Cu and Ti etch solution to remove the remaining conductive seed that had been protected by the PR. The width of the isolated Cu fine lines was determined using a laser profilometer. The results summarized in Table 10 show that anisotropic plating bath 3 prevented the line thickness from increasing beyond the width of the shorter PR trenches. Isotropic plating bath 1 did not prevent the plated lines from fusing when plated above the PR trench height, thus destroying the fine line pattern. Plating bath 2, having intermediate anisotropic behavior, showed a small increase in the fine line width. Line fusing occurred. The wetting agent in the pretreatment solution ensured planarized plating by allowing all parts of the exposed seed to interact with the promoter components. In summary, the data show that the plating bath formulation can be adjusted to control the degree of plating anisotropy.

[0213] Table 10

[0214]

[0215] Examples 49 - 56.

[0216] Effect of activator pH on the shape of plating features

[0217] The control of the fine line filling shape was investigated by adjusting the pH of the pretreatment solution. The same fine line patterns used in Examples 1-2 above were treated with 4 g / L aqueous MES solution having a pH of 0.7, 3, 4, 5.5, 8, 9, 13 or 14 and rinsed with DI water before electroplating. The samples were then electroplated to a target height of 5 μm (1.66X PR height) using plating bath 3. In all cases, electroplating was carried out at a cathode rotation rate of 50 rpm at 2 ASD. After plating, the PR was removed in a PR stripper bath to produce the pattern of the fine lines. The samples were then exposed to a Cu and Ti etch solution to remove the remaining conductive seed crystals that had been protected by the PR. The width of the isolated Cu fine lines was determined using a laser profilometer. The results summarized in Table 11 show that leveling plating can be carried out regardless of the pH of the pretreatment solution. However, the filling shape of the fine lines varied significantly; i.e., high pH promoted a disc-shaped plating shape while low pH promoted a slightly domed shape. More intermediate pH (pH = 4-8) resulted in a more pronounced domed shape. As shown by the following data, this intermediate pH range is not favorable for obtaining the desired filling shape with an anisotropic plating bath formulation. Instead, by maintaining the pH range outside the intermediate range, the anisotropic plating can be further adjusted to reduce the domed profile or induce a disc-shaped profile.

[0218] Table 11

[0219]

[0220] Examples 57-59

[0221] Anisotropic plating during removal of the PR layer after activation and before electrolytic electroplating

[0222] The ability of the anisotropic plating method described herein to maintain feature resolution even in the absence of a patterned layer during plating was investigated. To this end, three plating scenarios were examined to test and compare the anisotropic plating performance with and without a PR layer against a control isotropic run without a PR layer. The same patterned substrates as in Examples 3 - 6 were used. The sample of Example 57 was pretreated with a 4 g / L aqueous MES solution, rinsed with DI water, and the PR layer was removed using a 1:1 dimethyl sulfoxide - γ - butyrolactone mixture prior to plating. The sample of Example 58 was only pretreated with a 4 g / L aqueous MES solution and rinsed with DI water. The sample of Example 59 was only pretreated with DI water. The samples of Examples 57 - 58 were plated with plating bath 3, and the sample of Example 59 was plated with plating bath 1. All three samples were plated at a cathode rotation rate of 50 rpm and a plating target height of 5 μm at 2 ASD. After plating, the PR was removed in a Shipley BPRTM PR stripper bath to produce a pattern of fine lines. The samples were then exposed to a seed etch solution to remove the remaining conductive seeds that had been protected by the PR. The width and height of the separated Cu fine lines were determined using a laser profilometer. The results summarized in Table 12 show that significant line fusing was prevented in the samples of Examples 57 - 58, where anisotropic plating occurred even in the absence of a patterned PR layer during plating. On the other hand, the sample of Example 59 showed significant line fusing at all fine line widths. All samples shown in Table 13 showed good leveling of the plating height within the feature width range.

[0223] Table 12

[0224]

[0225] Table 13

[0226]

Claims

1. A method, comprising: a) providing a substrate comprising a seed layer; b) selectively applying an aqueous treatment solution comprising a sulfur-containing promoter to the seed layer, wherein the aqueous treatment solution has a pH below 3 or above 9; c) providing a copper electroplating composition comprising a copper ion source, a promoter, an acid, a chloride source, an inhibitor that produces an α-peak curve in the cathodic wave of the voltammogram of the copper electroplating composition on a working electrode, and a leveling agent, wherein the leveling agent is a copolymer of imidazole, the reaction product of butyl diglycidyl ether and phenylimidazole; The inhibitor comprises polyethylene glycol having a weight average molecular weight of 1000 - 6000 g / mol, or an EO / PO block copolymer having a weight average molecular weight of 1000 - 5000 g / mol, or an EO / PO random copolymer having a weight average molecular weight of 1000 - 5000 g / mol, or a diamine core EO / PO block copolymer having a weight average molecular weight of 1000 - 10000 g / mol; d) contacting the substrate comprising the seed layer with the copper electroplating composition; and e) electroplating copper anisotropically on the seed layer of the substrate.

2. The method according to claim 1, wherein The diamine core EO / PO block copolymer has the following formula: wherein the weight average molecular weight is 1000 - 10000 g / mol and the variables x, x’, x”, x”’, y, y’, y” and y”’ are integers greater than or equal to 1 to provide a weight average molecular weight of 1000 - 10,000 g / mol.

3. The method according to claim 1, wherein The diamine core EO / PO block copolymer has the following formula: wherein the weight average molecular weight is 1000 - 10000 g / mol and the variables x, x’, x”, x”’, y, y’, y” and y”’ are integers greater than or equal to 1 to provide a weight average molecular weight of 1000 - 10,000 g / mol.

4. The method according to claim 1, wherein The diamine core EO / PO block copolymer has the following formula: wherein the weight average molecular weight is 1000 - 10000 g / mol and the variables x, x’, x”, x”’, y, y’, y” and y”’ are integers greater than or equal to 1 to provide a weight average molecular weight of 1000 - 10,000 g / mol.

5. A method, comprising: a) providing a substrate comprising a seed layer; b) coating the seed layer with a photoresist; c) imaging the photoresist to form a pattern on the substrate and selectively expose the seed layer; d) applying an aqueous treatment solution comprising a sulfur-containing promoter to the exposed seed layer, wherein the aqueous treatment solution has a pH below 3 or above 9; e) providing a copper electroplating composition comprising a copper ion source, a promoter, an acid, a chloride source, an inhibitor that produces an α-peak curve in the cathodic wave of the voltammogram of the copper electroplating composition on a working electrode, and a leveling agent, wherein the leveling agent is a copolymer of imidazole, the reaction product of butyl diglycidyl ether and phenylimidazole; The inhibitor includes polyethylene glycol having a weight-average molecular weight of 1000-6000 g / mol, or an EO / PO block copolymer having a weight-average molecular weight of 1000-5000 g / mol, or an EO / PO random copolymer having a weight-average molecular weight of 1000-5000 g / mol, or a diamine core EO / PO block copolymer having a weight-average molecular weight of 1000-10000 g / mol; f) contacting the substrate comprising the seed layer with the anisotropic copper electroplating composition; and g) electroplating anisotropic copper on the seed layer of the substrate.

6. An article prepared by the method according to claim 1 or 5, comprising a copper deposit having a height of at least 2 μm higher than the surrounding photoresist, and comprising incoherent grain boundaries oriented at 80°-90° with respect to the plane of the substrate, and comprising parallel twin grain boundaries oriented at 40°-50° with respect to the plane of the substrate.

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