TWI699457B - Electroplated copper - Google Patents

Abstract

An electroplated copper metal having certain grain misorientations between adjacent grains at a ＜111＞ crystal plane direction provides for improved properties of the copper. A method of electroplating the copper metal on substrates, including dielectric substrates, is also disclosed.

Description

Copper plating

The present invention relates to copper electroplating and copper electroplating methods, in which copper metal has high tensile strength. More specifically, the present invention relates to copper electroplating and copper electroplating methods, in which copper metal has high tensile strength and has a certain percentage of specific angles between adjacent crystal grains of copper metal with respect to the crystal plane direction <111> Poor orientation to provide high tensile strength copper metal and other improved material properties.

In promoting future applications in the electronics industry, such as artificial intelligence and autonomous vehicles, advanced semiconductor packaging that can achieve high-density circuits, reduce form factors (device size, configuration or physical configuration) and enhance electronic device functions is highly expected Products and processes. In addition to the required smaller package sizes, there is an increasing need for more reliable chip-to-chip, chip-to-circuit board, and end-to-end interconnections. For example, in the past few decades, copper has been used in interconnection applications, such as in the copper redistribution layer (RDL) used to reroute conductive paths in chip packages. As the package size decreases, the demand for reliable thin-line RDL is also increasing. During the thermal cycle test (TCT), due to the thermal stress caused by the difference in the coefficient of thermal expansion (CTE) of copper and adjacent materials during the cycle between the hot and cold chambers, copper cracks in the thin wire RDL have been reported. The way to resolve the rupture problem remains controversial. In conventional printed circuit board (PCB) applications, copper with high elongation is generally known as a better way to solve the cracking problem. However, as the feature size of the electronic components on the PCB decreases and the components become more integrated to micron size or even nanometer size, such as currently occurring in advanced packaging applications, this approach may not be appropriate. There is also another idea that high material strength or high tensile strength, not high elongation, is essential to avoid copper cracking during multiple thermal cycles. The disadvantage of copper with high tensile strength is that such copper may become brittle. One way to solve the cracking problem is to use nano-twinned copper, which is characterized by high tensile strength and high elongation. Although nano-twinned copper may be suitable for solving the problem of copper cracking in RDL, it has been found that nano-twinned copper is not suitable for many plated through-hole applications, such as advanced technology that requires 3D stacking to increase circuit density. Package application. In many such applications, the via filling has not been found to be acceptable, and the surface of the copper deposit has been found to be unacceptably rough and uneven.

Therefore, there is a need for a copper metal that can withstand the thermal stress caused by the difference in CTE between copper and adjacent materials when circulating between a hot chamber and a cold chamber without copper cracking, and can achieve smooth and uniform features in features Copper deposits, even in high circuit density applications.

The present invention relates to copper metal, which contains a twinning fraction of 30% or more of the grain boundary between adjacent copper crystal grains having an orientation difference angle of 55° to 65° with respect to the crystal plane direction <111>.

The present invention also relates to a copper electroplating method, the method comprising: a) providing a substrate; b) providing a copper electroplating bath, the copper electroplating bath includes one or more copper ion sources to provide a concentration of 20 g/L to 55 g One or more reaction products of one or more copper ions, one or more imidazole compounds or one or more 2-aminopyridine compounds and one or more biepoxides, wherein the concentration of one or more reaction products is 2 ppm to 15 ppm; Electrolyte; one or more accelerators, one or more accelerators have a concentration of 0.5 ppm to 100 ppm; and one or more inhibitors, one or more inhibitors have a concentration of 0.5 g/L to 10 g/L; c ) Immersing the substrate in a copper electroplating bath; d) electroplating copper on the substrate to deposit a copper layer on the substrate; and, e) heating the copper layer to a temperature of at least 200°C in an inert atmosphere to provide a copper layer, the copper The layer includes a twinning fraction of 30% or more of the grain boundary between adjacent copper crystal grains having an orientation difference angle of 55° to 65° with respect to the crystal plane direction <111>.

Compared with many conventional copper metals deposited by a copper plating bath or by physical or chemical vapor deposition, the copper metal of the present invention has improved tensile strength. In addition, the copper metal of the present invention has good elongation and low thermal stress. When copper metal is exposed to heat in a high temperature environment (such as TCT) and is present in an annealing process, the properties of the copper metal of the present invention inhibit the copper metal from cracking. The copper metal electroplating composition of the present invention can be used for electroplating the copper metal of the present invention under high current density applications with non-conformal plating, in which copper is simultaneously deposited on the substrate at a faster rate than in holes such as through holes in the substrate. On the surface of the substrate to provide a smooth and uniform copper deposit in the hole and on the surface of the substrate. The method of the present invention can also directly electroplate the copper metal of the present invention on or near the metal seed layer, which is adjacent to or connected to the dielectric or semiconductor material used in the electronic device, wherein the CTE of the material is different No need to consider rupture. The copper metal of the present invention is very suitable for the fine line redistribution layer technology used in advanced packaging, where the redistribution line spacing is reduced and the circuit density is increased.

Unless the context clearly indicates otherwise, the following abbreviations as used throughout this manual shall have the following meanings: A=ampere; A/dm ² = amperage per square decimetre=ASD; DC=direct current; ℃=degree Celsius ;Mmol=millimoles; mg=mg; g=gram; L=liter; mL=ml; ppm=parts per million=mg/L; m=meter; mm=micron (micron)=micrometer =10 ^-6 meters; mm = millimeters; cm = centimeters; nm = nanometers = 10 ^-9 meters; Å = angstroms = 1x10 ^-10 meters; 2.54 cm = inches; MPa = megapascals = N/m ² ; N = Newtons; kV = kilovolts; V = volts = Joules/Coulomb; mA = milliamperes; DI = deionization; mJ = millijoules; Joules = kg(m)/s ² ; kg = kilograms; s = Second; Mw=weight average molecular weight; Mn=number average molecular weight; wt%=weight percentage; XRD=X-ray diffraction; EBSD=electron backscatter diffraction; FE-SEM=field emission scanning electron microscope; EO/PO=ring Ethylene oxide/propylene oxide copolymer; IPF = reverse pole figure; RDL = redistribution layer; N ₂ = nitrogen; pair (vs.) = contrast (versus); eg = for example; ohm-cm = resistance; and L /S=Line spacing or distance between two features or structures, such as for RDL.

As used throughout the specification, the term "plating" refers to metal plating. "Deposition" and "plating" are used interchangeably throughout this manual. The terms "composition" and "bath" are used interchangeably throughout the specification. "Accelerator" refers to an organic additive that increases the plating rate of an electroplating composition and is also used to improve the brightness of copper deposits. "Inhibitors" refer to organic additives that inhibit the plating rate of metals during electroplating. The term "electrolyte" means a chemical compound, such as an acid, that dissociates into ions and is therefore capable of transporting charge. The term "portion" means a molecule or part of a polymer that can include the entire functional group or a part of the functional group as a substructure. The terms "part" and "group" are used interchangeably throughout this specification. The term "hole" means openings, holes, gaps or through holes. The term "aspect ratio" means the thickness of the substrate divided by the aperture of the features in the substrate. The term "grain boundary" refers to the interface between two crystal grains or crystallites in copper metal, where the grain boundary is a two-dimensional defect (2D) in the copper crystal structure. The terms "grain", "crystal" and "microcrystalline" are used interchangeably throughout this manual. The term "differential orientation" means the difference in crystal orientation between two crystal grains or crystallites and a common interface, where the crystal orientation between the two crystal grains or crystallites can be in the range of 0-180°, where 0 ° indicates a perfect crystal without any misorientation. The term "tensile strength" means the resistance to fracture of a material under tension. The term "thermal stress" refers to the stress that occurs due to the thermal expansion of the copper structural member when the temperature of the copper structural member changes. The term "annealing" means a heat treatment that changes the physical and sometimes chemical properties of materials. The term "Miller index: (hkl), [hkl], {hkl} and <hkl>" means the orientation of the crystal plane surface defined by considering how the plane (or any parallel plane) intersects the main crystal axis of the solid ( That is, the reference coordinates defined in the crystal-x, y, and z axes, where x=h, y=k and z=l), and a set of numbers (hkl), {hkl}, and <hkl> quantization intercept And used to identify the surface. The expression "(hkl)" defines a specific crystal plane in the crystal lattice. The expression "[hkl]" defines the specific direction of the crystal plane in the crystal lattice. The expression "{hkl}" defines the set of all faces equal to (hkl) due to the symmetry of the lattice. The expression "<hkl>" defines the set of all directions equal to [hkl] due to the symmetry of the lattice. The term "surface" means a two-dimensional surface (having a length and a width) in which the straight line connecting any two points in the surface will lie completely in it. The term "lattice" means an arrangement of isolated points in a regular pattern, which shows the positions of atoms, molecules or ions in the crystal structure. The term "grain boundary energy" means the energy at the interface between two crystal grains due to the formation of the interface. The term "crystalline domain" means that atoms in a specific space have the same atomic arrangement, crystallinity, orientation, and symmetry. The term "texture (crystalline)" refers to the distribution of the crystal orientation of the copper sample, where these samples with completely random orientation are said to have no obvious texture, and if the crystal orientation is not random but has some better orientations, the sample Has a weak, medium or strong texture, the extent of which depends on the percentage of crystals with better orientation. The term "slip system" refers to a group of symmetrically identical sliding surfaces and related sliding direction families, which are prone to dislocation motion and lead to plastic deformation, in which external forces make parts of the lattice slide along each other, thereby changing the material Geometric structure. The term "pitch" means the frequency of feature positions on the substrate relative to each other. The term "amino" = -NHR, where R is -H (hydrogen) or a straight or branched chain hydrocarbon group. The term "aminoalkyl" = -(C ₁ -C ₄ )-NH-R, where R -H (hydrogen) or a straight or branched chain hydrocarbon group. The term "hydrocarbyl" means hydrogen and carbon functional groups. The term "halide" means chloride, fluoride, bromide and iodide. The term "adjacent" means directly on or beside two structures or materials so that the two structures or materials have a common interface. The article "一 (a/an)" refers to the singular and plural.

As used throughout the specification, the average value of a parameter means the sum of the individual measured values of the parameter divided by the number of measurements used by the parameter. The grain size (spherical equivalent diameter) is calculated based on the calculation that all grains are spherical, where the grain size area = π(d/2) ² , where d = grain diameter. Copper has a hexagonal cubic structure and is the same via symmetry in all directions. The twin fraction of grain length (μm) and texture (crystal) is based on EBSD analysis technology, which is synonymous with FE-SEM. As used throughout the manual, the mechanical tensile test parameters are based on the test procedure IPC-TM-650 obtained from the IPC® Association Connecting Electronics Industries using the INSTRON™ tensile tester. As used throughout the specification, the ratio of the area under the curve of the diffraction peak (111) plane orientation and the diffraction peak (200) plane orientation is based on the XRD analysis of the diffraction intensity (I) to the diffraction angle 2θ (º), such as The Jade 2010 MDI software available from KSA Analytical Systems, Aubrey, TX (KSA Analytical Systems, Aubrey, TX) does the same thing.

All numerical ranges are inclusive and can be combined in any order, but obviously such numerical ranges are limited to a total of 100%.

The present invention relates to copper metal including twins that are 30% or more of the grain boundary between adjacent copper crystal grains having an orientation difference angle of 55° to 65° with respect to the crystal plane direction axis <111> fraction. The twinning fraction is defined as the sum of the grain boundary length (in μm) and the difference in orientation from 55º to 65º divided by all grain boundary lengths (in μm) and relative to a given measurable sample area such as 60 μm×3 μm The ratio of the sum of the orientation differences of 0° to 180° in the observed crystal plane direction <111>.

Preferably, the twinning fraction is 35% or more of the grain boundary between adjacent copper crystal grains having an orientation difference angle of 55° to 65° with respect to the crystal plane direction <111>; more preferably, twinning The fraction is 35% to 55% of the grain boundary between adjacent copper grains with an orientation difference angle of 55° to 65° with respect to the crystal plane direction <111>; further preferably, the twin fraction is relative to the crystal plane The direction <111> has 35% to 52% (for example, 35%, 37%, or 52%) of the grain boundary between adjacent copper crystal grains with an misorientation angle of 55° to 65°. Preferably, the grain boundary between adjacent copper crystal grains has an orientation difference angle of 60° with respect to the crystal plane direction <111>. This misorientation angle is thermodynamically stable, so that the misorientation does not change with time.

Relative to the crystal plane direction <111> The grain boundary between adjacent copper crystal grains with an orientation difference angle of 55° to 65° is a high-angle grain boundary, where the high-angle grain boundary is defined as relative to the crystal plane direction <111 > The angular orientation difference is greater than 10°. The low-angle grain boundary has an orientation difference of 2°-10° with respect to the crystal plane direction <111>. In addition to the high-angle grain boundary orientation difference of 55° to 65° relative to the crystal plane direction <111>, the copper metal of the present invention may include an orientation of less than 55° and greater than 65° relative to the crystal plane direction <111> The twin fraction of the grain boundary between adjacent copper grains with a different angle is less than 30%. Relative to the crystal plane direction <111>, this kind of misorientation angle can range from 0° to less than 55° and greater than 65° to 180°.

The copper metal of the present invention has a texture index (crystalline), also known as a multiple of random distribution (MRD), which is equal to or greater than 2, preferably equal to or greater than 5, such as 5 to 10.5 ( For example, 5.7 to 10.2). The high (111) texture indicates that the present invention has more (111) surfaces that can be used for slippage, because the slip system in copper includes {111} slip surfaces and <110> ({111}<110>) The sliding direction, and therefore the mechanical performance of tensile strength and elongation are improved. The texture index 1 indicates that in the sample with the (111) plane orientation, the random orientation of the (111) plane and fewer copper crystals, so less slippage, which leads to poor mechanical performance of tensile strength and elongation. A texture index greater than 1 indicates that there are more crystals in the sample with (111) plane orientation. Therefore, texture index 2 means that the number of crystals in the sample with (111) plane orientation is 2× more than the number of crystals in the sample with texture index of 1, and texture index 5 means that the sample with (111) plane orientation The number of crystals is 5× of the number of crystals in a sample with a texture index of 1, so as to achieve improved slippage and improved mechanical properties. The additional orientations detected when the MRD is greater than 2 are, for example, (001), (101), (201), (212), (311) and (511), but may have such as less than 5, or such as 0-5, Or a texture index such as 1-4 (for example, 1 to 3.5).

For the copper metal of the present invention, the XRD area ratio of the (111) plane orientation/(200) plane orientation at the diffraction angle 2θ (º) on the diffraction intensity (I) versus the diffraction angle 2θ (º) curve is equal to or Greater than 1. Preferably, the XRD area ratio of (111) plane orientation/(200) plane orientation at the diffraction angle 2θ (º) is greater than or equal to 5. More preferably, the XRD area ratio of (111) plane orientation/(200) plane orientation at the diffraction angle 2θ (º) is 5-31 (for example, 5.3, 21 or 31), which means that copper crystals have a large amount of (111) )surface.

The average crystal grain size (spherical equivalent diameter) of the copper metal of the present invention does not substantially increase when exposed to heat at a high temperature of 200°C or higher, such as found in the annealing process, thus reducing the possibility of copper metal cracking Sex. For example, before annealing, the average crystal grain size (spherical equivalent diameter) of all crystal grains in a copper sample with a misorientation angle of 55° to 65° at the crystal plane direction <111> can be 100 nm and larger. It is preferably 500 nm and larger, more preferably 1-2 μm. After thermal annealing, the average diameter of copper crystal grains with an orientation difference angle of 55° to 65° at the crystal plane direction <111> has a diameter of 100 nm or more, preferably 500 nm or more (spherical equivalent diameter). More preferably, after thermal annealing, the average diameter of copper crystal grains with an orientation difference angle of 55° to 65° at the crystal plane direction <111> has 0.1 μm to 3 μm (for example, 1 μm to 2.5 μm, or Such as 1.4 μm to 2.3 μm) diameter (spherical equivalent diameter); even better, after thermal annealing, the average of copper crystal grains with an orientation difference angle of 55° to 65° at the crystal plane direction <111> The diameter has a diameter of 1 µm to 2.5 µm, preferably 1.5-2.3 µm (spherical equivalent diameter). The small grain size diameter (spherical equivalent diameter) of the copper metal of the present invention can strengthen the material and improve the tensile strength, as evidenced by the Hall-Petch relationship: σ _y (yield stress) = σ ₀ + k ₁ D ^-1/2 where σ _y is the yield strength of the material in Mpa. σ ₀ is the material constant used for the initial stress of dislocation movement, and is 25 MPa for copper. k ₁ is a strengthening factor (a constant specific to each material), which is 0.11 MPa m ^1/2 for copper. D is the average grain size in meters.

The copper metal of the present invention is electroplated by the aqueous acid copper electroplating composition (bath) of the present invention. The aqueous acid copper electroplating composition (bath) of the present invention contains the following (preferably consisting of): a source of copper ions and a source of counter anions; an electrolyte; a leveling agent, containing one or more imidazole compounds or one or more 2-amino groups The reaction product of a pyridine compound and one or more biepoxides (preferably composed of one or more imidazole compounds or the reaction product of one or more 2-aminopyridine compounds and one or more biepoxides); promoter; inhibitor; Dependent but preferred halide ion source; and water.

（I） 其中R₁ 、R₂ 及R₃ 獨立地選自氫原子、直鏈或分支鏈(C₁ -C₁₀ )烷基、羥基、直鏈或分支鏈烷氧基、直鏈或分支鏈羥基(C₁ -C₁₀ )烷基、直鏈或分支鏈烷氧基(C₁ -C₁₀ )烷基、直鏈或分支鏈羧基(C₁ -C₁₀ )烷基、直鏈或分支鏈胺基(C₁ -C₁₀ )烷基或經取代或未經取代的苯基，其中取代基選自羥基、羥基(C₁ -C₃ )烷基或(C₁ -C₃ )烷基。較佳地，R₁ 、R₂ 及R₃ 獨立地選自氫原子；直鏈或分支鏈(C₁ -C₅ )烷基、羥基、直鏈或分支鏈羥基(C₁ -C₅ )烷基或直鏈或分支鏈胺基(C₁ -C₅ )烷基。更佳地，R₁ 、R₂ 及R₃ 獨立地選自氫原子或(C₁ -C₃ )烷基，諸如甲基、乙基或丙基部分。此類化合物的實例為1H-咪唑、2,5-二甲基-1H-咪唑及4-苯基咪唑。Preferably, the imidazole compound has the following general formula:

(I) wherein R ₁ , R ₂ and R _{3 are} independently selected from hydrogen atom, linear or branched (C ₁ -C ₁₀ ) alkyl, hydroxyl, linear or branched alkoxy, linear or branched Hydroxy (C ₁ -C ₁₀ ) alkyl, linear or branched alkoxy (C ₁ -C ₁₀ ) alkyl, linear or branched carboxy (C ₁ -C ₁₀ ) alkyl, linear or branched Amino (C ₁ -C ₁₀ )alkyl or substituted or unsubstituted phenyl, wherein the substituent is selected from hydroxyl, hydroxy (C ₁ -C ₃ )alkyl or (C ₁ -C ₃ )alkyl. Preferably, R ₁ , R ₂ and R _{3 are} independently selected from hydrogen atoms; linear or branched (C ₁ -C ₅ ) alkyl, hydroxyl, linear or branched hydroxy (C ₁ -C ₅ ) alkane Group or straight or branched chain amino (C ₁ -C ₅ )alkyl. More preferably, R ₁ , R ₂ and R _{3 are} independently selected from a hydrogen atom or (C ₁ -C ₃ )alkyl, such as methyl, ethyl or propyl moieties. Examples of such compounds are 1H-imidazole, 2,5-dimethyl-1H-imidazole and 4-phenylimidazole.

The 2-aminopyridine compound of the present invention is a pyridine compound in which carbon-2 of the pyridine ring is substituted with an amino group or an aminoalkyl group.

Preferably, the 2-aminopyridine compound of the present invention has the following formula:

Wherein R ₈ is -H or a straight chain of branched (C ₁ -C ₄ ) alkyl, and R ₉ is -H, straight or branched (C ₁ -C ₄ ) alkyl, halo, straight or branched Chain amino (C ₁ -C ₄ ) alkyl or phenyl, and p is an integer from 0 to 4, wherein when p = 0, the nitrogen of NHR ₈ forms a covalent bond with carbon-2 of the pyridine ring. Preferably, R ₈ is -H or (C ₁ -C ₂ )alkyl, R ₉ is -H of C ₁ -C ₂ )alkyl, amino (C ₁ -C ₂ )alkyl, chloro, And p is an integer of 1-2. More preferably, R ₈ is -H or methyl, R ₉ is -H or methyl, and p is an integer of 1-2. Optimally, R ₈ is -H, R ₉ is -H and p =2. Exemplary compounds of formula (II) are 2-amino-4-methylpyridine, 2-amino-5-methylpyridine, 2-amino-5-chloropyridine, 2-aminopyridine, 2-( 2-aminoethyl)pyridine and 4-(2-aminoethyl)pyridine, of which 2-(2-aminoethyl)pyridine is preferred.

Preferably, the double epoxide has the following formula:

Wherein R ₄ and R _{5 are} independently selected from hydrogen and (C ₁ -C ₄ )alkyl; R ₆ and R ₇ may be different and the same, and are independently selected from hydrogen, methyl or hydroxyl; m=1-6 and n=1-20. Preferably, R ₄ and R ₅ are hydrogen. Preferably, R ₆ and R _{7 are} independently selected from hydrogen, methyl or hydroxyl. More preferably, R ₆ is hydrogen, and R ₇ is hydrogen or hydroxyl. Preferably, m =2-4 and n =1-2. More preferably, m =3-4 and n =1.

The compound of formula (III) includes, but is not limited to, 1,4-butanediol diglycidyl ether, ethylene glycol diglycidyl ether, two (ethylene glycol) diglycidyl ether, glycerol diglycidyl ether, neopentyl glycol Diglycidyl ether, propylene glycol diglycidyl ether, di(propylene glycol) diglycidyl ether, poly(ethylene glycol) diglycidyl ether compound, and poly(propylene glycol) diglycidyl ether compound.

The reaction product (leveling agent) of the present invention can be prepared by various methods known in the art. Generally, one or more imidazole compounds or one or more 2-aminopyridine compounds are dissolved in deionized water at room temperature, and then one or more bisepoxide compounds are added dropwise. The temperature of the bath is then increased from room temperature to about 100°C. Heating is carried out with stirring for 2-5 hours. Then, while stirring for another 8-12 hours, the temperature of the heating bath is reduced to room temperature. The amount of each component can vary, but generally a sufficient amount of each reactant is added to provide a molar ratio of the part derived from the imidazole compound or 2-aminopyridine compound to the part derived from the biepoxide in 1:1 Products in the range of 100:70. The reaction product or copolymer of the present invention is positively charged (cationic) in the acid copper electroplating composition of the present invention.

Generally, the number average molecular weight (Mn) of the reaction product is 200 to 100,000, preferably 300 to 50,000, more preferably 500 to 30,000, but reaction products with other Mn values can also be used. The weight average molecular weight (Mw) value of such reaction products can be in the range of 1000 to 50,000, preferably 5000 to 30,000, but other Mw values can also be used.

Based on the total weight of the plating bath, the amount of the reaction product contained in the copper electroplating bath for plating copper metal of the present invention may be 2 ppm to 15 ppm, preferably 2 ppm to 10 ppm, more preferably 2 ppm to 5 ppm, the best 3 ppm to 4 ppm range.

The copper ion source is a copper salt (preferably water-soluble) and includes, but is not limited to: copper sulfate, such as copper sulfate pentahydrate; copper halide, such as copper chloride; copper acetate; copper nitrate; copper tetrafluoroborate; alkyl Copper sulfonate; copper arylsulfonate; copper sulfamate; copper perchlorate and copper gluconate. Exemplary copper alkane sulfonates include (C ₁ -C ₆ ) copper alkane sulfonate, and more preferably (C ₁ -C ₃ ) copper alkane sulfonate. The preferred copper alkanesulfonate is copper methanesulfonate, copper ethanesulfonate and copper propanesulfonate. Exemplary copper arylsulfonates include, but are not limited to, copper benzenesulfonate and copper p-toluenesulfonate. A mixture of copper ion sources can be used. Preferably, the copper salt is present in an amount sufficient to provide 30 to 60 g/L of copper ions in the plating solution. More preferably, the amount of copper ions is 35 to 50 g/L; most preferably, the amount of copper ions is 35 to 45 g/L.

The electrolyte of the present invention is acidic. Preferably, the pH of the electrolyte is less than or equal to 2; more preferably, the pH is less than or equal to 1. Acidic electrolytes include, but are not limited to, sulfuric acid; acetic acid; fluoroboric acid; alkanesulfonic acid, such as methanesulfonic acid, ethanesulfonic acid, propanesulfonic acid, and trifluoromethanesulfonic acid; arylsulfonic acid, such as benzenesulfonic acid, p-toluenesulfonic acid ; Aminosulfonic acid; Hydrochloric acid; Hydrobromic acid; Perchloric acid; Nitric acid; Chromic acid; and phosphoric acid. A mixture of acids can be used in the copper electroplating composition of the present invention. Preferred acids include sulfuric acid, methanesulfonic acid, ethanesulfonic acid, propanesulfonic acid, hydrochloric acid and mixtures thereof. Sulfuric acid is the best acid. The amount of acid present can be 1 to 400 g/L; preferably 10 g/L to 300 g/L; more preferably 25 g/L to 250 g/L; most preferably 30 g/L to 100 g/L. When sulfuric acid is included in the copper electroplating composition, the preferred concentration range is 40 g/L to 80 g/L, most preferably 40 g/L to 60 g/L. Electrolytes are generally commercially available from a variety of sources and can be used without further purification.

Such an electrolyte may optionally contain a source of halide ions. Preferably, chloride ion and bromide ion are used. Exemplary chloride ion sources include copper chloride, sodium chloride, potassium chloride, and hydrochloric acid. Examples of bromide ion sources are chlorine bromide and bromine water. A wide range of halide ion concentrations can be used in the present invention. Preferably, based on the plating bath, the halide ion concentration is in the range of 0.5 ppm to 100 ppm. More preferably, the content of halide ions is 50 ppm to 80 ppm, most preferably 65 ppm to 75 ppm. Such halide ion sources are generally commercially available and can be used without further purification.

The aqueous acid copper electroplating bath contains an accelerator. Accelerators (also known as brighteners) include but are not limited to N,N-dimethyl-dithiocarbamate-(3-sulfopropyl) ester; 3-mercapto-propylsulfonic acid-(3 -Sulfopropyl) ester; 3-mercapto-propylsulfonate sodium salt; dithio-O-ethyl-S-carbonate and 3-mercapto-1-propanesulfonate potassium salt; bissulfopropyl disulfide Compound; Bis-(sodium sulfopropyl)-disulfide; 3-(benzothiazolyl-S-thio)propyl sulfonate sodium salt; pyridinium propyl sulfobetaine; 1-sodium-3- Mercaptopropane-1-sulfonate; N,N-dimethyl-dithiocarbamate-(3-sulfoethyl) ester; 3-mercapto-ethylpropylsulfonic acid-(3-sulfoethyl) ) Ester; 3-mercapto-ethylsulfonate sodium salt; carbonate-dithio-O-ethyl-S-ester and 3-mercapto-1-ethanesulfonic acid potassium salt; bissulfoethyl disulfide; 3-(benzothiazolyl-S-thio)ethylsulfonic acid sodium salt; pyridinium ethyl sulfobetaine; and 1-sodium-3-mercaptoethane-1-sulfonate. The preferred accelerator of the present invention is N,N-dimethyl-dithiocarbamate-(3-sulfopropyl) ester. Preferably, the content of the accelerator is 0.1 ppm to 1000 ppm. Preferably, the content of the accelerator is 10 ppm to 50 ppm, most preferably 40 ppm to 50 ppm.

Inhibitors include but are not limited to polypropylene glycol copolymers and polyethylene glycol copolymers, including ethylene oxide-propylene oxide ("EO/PO") copolymers and butanol-ethylene oxide-propylene oxide copolymers . The weight average molecular weight of the inhibitor may be in the range of 800-15,000, preferably 900-12,000. Preferably, based on the weight of the composition, the inhibitor is present in the range of 0.5 g/L to 15 g/L; more preferably 1 g/L to 5 g/L.

The electroplating bath can be prepared by combining the components in any order. Preferably, first add inorganic components, such as copper ion source, water, electrolyte and optionally halide ion source, into the bath container, and then add organic components, such as reaction product (leveling agent), accelerator , Inhibitors and any other optional organic components.

According to the method, the hydrated copper electroplating bath of the present invention may contain conventional leveling agents as appropriate, and the limitation is that such leveling agents basically do not damage the structure and function of copper characteristics. Such leveling agents may include those disclosed in Step et al. U.S. Patent No. 6,610,192, Wang et al. U.S. Patent No. 7,128,822, Hayashi et al. U.S. Patent No. 7,374,652, and Hagiwara et al. U.S. Patent No. 6,800,188. Them. However, it is preferable to exclude such leveling agents from the bath.

Plating is preferably carried out at 15°C-65°C; more preferably, electroplating is from room temperature to 50°C; even more preferably from room temperature to 40°C; and most preferably from room temperature to 30°C, of which room temperature is the best.

Preferably, the copper electroplating bath of the present invention is stirred during plating. Stirring methods include but are not limited to: air bubbling, workpiece stirring and impact. Preferably, the stirring speed is 10 cm/sec to 25 cm/sec, more preferably 15 cm/sec to 20 cm/sec.

The substrate is electroplated by immersing the substrate in a bath or by spraying the substrate with the bath so that the substrate is in contact with the plating bath. The substrate can be used as a cathode. The plating bath contains an anode, which can be a soluble anode or an insoluble anode. A potential is applied to the electrode. The current density is preferably 2 ASD to 8 ASD; more preferably 4 ASD to 8 ASD; and most preferably 5 ASD to 7 ASD (for example, 5 ASD to 6 ASD, or 5 ASD to 7 ASD, or 6 ASD to 7 ASD) Within range.

After electroplating the substrate with copper from the water-based acid copper electroplating composition of the present invention, the copper is annealed with the substrate to complete the method of preparing the copper metal of the present invention. Preferably, annealing is performed at 200°C or higher; more preferably 200°C to 260°C; most preferably 230°C to 250°C. Preferably, annealing is carried out for 2 hours to 10 hours; more preferably 5 hours to 8 hours; most preferably 5.5 hours to 6.5 hours. Preferably, annealing is performed in an inert atmosphere, such as a gaseous N ₂ atmosphere. The annealing process basically does not increase the copper grain size.

In addition to the above properties, the copper metal of the present invention also has good mechanical properties of tensile strength (break) and percent elongation (break). Preferably, the tensile strength at break of the copper metal of the present invention is equal to or greater than 330 MPa; more preferably, 330 MPa to 360 MPa. The% elongation at break is greater than or equal to 20% (for example, 20% to 25%; preferably 21% to 23%.

Although the copper metal of the present invention and the method of electroplating copper metal of the present invention can be used for various substrates of copper metallization, preferably, the copper metal of the present invention is electroplated by the method of the present invention to form a thin-line copper RDL for use in a chip package. The method of re-selecting the conductive path, such as the thin line RDL with less than or equal to 10 μm×10 μm; preferably, 5 μm×5 μm; more preferably, less than or equal to 2 μm×2 μm; most preferably, less than or Equal to 1 μm × 1 μm L/S chip package.

In addition to copper plating RDL, the copper electroplating method of the present invention can be used to electroplate the copper metal of the present invention on dielectric substrates and semiconductors with metal seed layers (such as copper seed layers). The dielectric material includes, but is not limited to, thermoplastic resin and thermosetting resin. A particularly preferred dielectric material is polyimide. Semiconductor materials include but are not limited to silicon.

The copper metal electroplating method can be used to non-conformally electroplate the copper metal of the present invention on the surface of the substrate and in the holes such as through holes. Preferably, the hole containing the through hole has a 2:1 or greater; more preferably 4:1 or greater; even more preferably 6:1 or greater, such as a high aspect ratio of 10:1 to 20:1.

The diameter of the hole, such as the through hole, is preferably 0.5 mm to 200 mm, more preferably 1 mm to 50 mm. The depth of the hole may be in the range of preferably 0.5 mm to 500 mm, more preferably 1 mm to 100 mm.

The following examples are included to further illustrate the present invention, but are not intended to limit its scope. Example 1 Leveling agent

Glycerol diglycidyl ether (60 mmol) and 1H-imidazole (100 mmol) were added to a round bottom reaction flask placed in a heating bath at room temperature. Then add 40 mL of deionized water to the flask. The temperature of the heating bath is set to 98°C. The reaction mixture was heated for 5 hours and stirred for another 8 hours at room temperature. The reaction product (reaction product 1) was used without purification. The molar ratio of the part derived from 1H-imidazole to the molar ratio of the ether part is 100:63. Example 2 Leveling agent

Glycerol diglycidyl ether (30 mmol) and a mixture of imidazole compounds (30 mmol) of 1H-imidazole (25 mol%) + 4-phenylimidazole (75% mol) were added to the heating bath at room temperature In the round bottom reaction flask. Then add 40 mL of deionized water to the flask. The temperature of the heating bath is set to 98°C. The reaction mixture was heated for 5 hours and stirred for another 8 hours at room temperature. The reaction product (reaction product 2) was used without purification. The molar ratio of the part derived from the imidazole mixture to the molar ratio of the ether part is 1:1. Example 3 Leveling agent

2-(2-Aminoethyl)pyridine (100 mmol) was added to a round bottom reaction flask placed in a heating bath at room temperature. Then add 40 mL of deionized water to the flask. The temperature of the heating bath is heated to the jacket temperature set at 90°C. Once the bath reached an internal temperature of 76°C-78°C, glycerol diglycidyl ether (100 mmol) was slowly fed into the round bottom reaction flask to ease any exotherm. Under stirring, the reaction mixture was heated for 4 hours by means of the jacket temperature set at 90°C. The reaction mixture was then cooled to 50°C-55°C and sulfuric acid solution was added to dilute the mixture to 40 wt%. The final reaction product (reaction product 3) was cooled to 25°C and then discharged by gravity. The reaction product 3 was used without purification. The molar ratio of the part derived from the imidazole mixture to the molar ratio of the ether part is 1:1. Example 4 Comparison of leveling agents

In a 250 mL round bottom three-necked flask equipped with a condenser and a thermometer, 100 mmol 1H-imidazole and 12 mL deionized water were added, followed by 200 mmol epichlorohydrin. The resulting mixture was heated for 5 hours using an oil bath set at 95°C, and then stirred at room temperature for another 8 hours. Transfer the reaction product to a 200 mL measuring flask, rinse with deionized water and adjust to the 200 mL mark. The reaction product (comparative reaction product) solution was used without further purification. Example 5 Copper electroplating bath of the present invention

含水銅電鍍浴的pH小於1。 實例6 比較銅電鍍浴The following hydrated copper electroplating bath was prepared at room temperature by mixing and stirring the components of the bath in water. Table 1

The pH of the aqueous copper electroplating bath is less than 1. Example 6 Comparison of copper electroplating baths

含水銅電鍍浴的pH小於1。 實例7 藉助於本發明浴1的銅電鍍The following hydrated copper electroplating bath was prepared at room temperature by mixing and stirring the components of the bath in water. Table 2

The pH of the aqueous copper electroplating bath is less than 1. Example 7 Copper electroplating by means of bath 1 of the present invention

A copper blank silicon wafer (size=4 cm×4 cm) with a 1500 Å thick copper seed layer was placed in a plating tank containing the aqueous copper electroplating composition from Bath 1 of Example 5. The pH of the bath during plating was less than 1, and the plating composition was paddle-stirred at a linear velocity of 20 cm/sec during plating. The soluble copper electrode is used as the anode. DC plating was performed at room temperature using a current density of 6 ASD. Copper electroplating is performed until a copper deposit with a thickness of 20 μm is plated on the wafer. The copper deposits were annealed at 230°C for 6 hours in an oven filled with an inert N ₂ atmosphere. After annealing, the copper-plated wafer is cooled to room temperature. Example 8 Copper electroplating with comparative bath

A copper blank silicon wafer (size=4 cm×4 cm) with a 1500 Å thick copper seed layer was placed in a plating tank containing the aqueous copper electroplating composition from the comparative bath of Example 6. The pH of the bath during plating was less than 1, and the plating composition was paddle-stirred at a linear velocity of 20 cm/sec during plating. The soluble copper electrode is used as the anode. DC plating was performed at room temperature using a current density of 6 ASD. Copper electroplating is performed until a copper deposit with a thickness of 20 μm is plated on the wafer. The copper deposits were annealed at 230°C for 6 hours in an oven filled with an inert N ₂ atmosphere. After annealing, the copper-plated wafer is cooled to room temperature. Example 9 Analysis of copper electroplating section

EBSD was used to quantitatively measure the properties of copper deposits from Examples 7 and 8. EBSD reveals the grain size, grain orientation, texture and grain boundary angle.

Cutting 4 mm×8 mm copper-plated wafers (300 mm polysilicon, P/boron, <100>, 0-100 ohm-cm, from Pure Wafer, Ringwood, San Jose, California 2240 Avenue, Zip code 951311 (2240 Ringwood Ave. San Jose CA 951311) and installed on the sample rack. An Argon milling cross-section polishing machine from JEOL USA, Inc., model JEOL IB09010CP was used to polish the surface of each piece and analyze the surface. A FE-SEM (FEI model Helios G3) coupled with an EBSD detector (EDAX Inc. (EDAX Inc.), model Hikari Super, and data analyzed by OIM TM analysis software) was used to collect the diffraction signal from the sample. For grain size analysis, the step size is 0.025 μm (measured every 0.025 μm), in which 10 scans performed at different random sample positions are collected to obtain statistically significant data. For texture analysis, the step size is 0.075 μm (measured every 0.075 μm), and 5 different positions are scanned (statistically significant).

1 and 2 respectively show the EBSD inverse pole diagram (IPF) of the present invention and the comparative example, which show various orientations shown in different tones in each figure. In Figures 1 and 2, the bold black outlines represent the twin fractions of adjacent grain boundaries with an orientation difference angle of 60°±5° in the <111> direction, as indicated by the arrows in each figure. Adjacent grain boundaries having misorientation angles outside the range of 60°±5° are shown by thin non-thick lines. In Figure 1, the misorientation angles beyond the range of 60º±5º are 5º, 40º and 93º, respectively. Compared to Figure 1, the misorientation angle of 60º±5º accounts for 35%, and the other misorientation is outside this range. In Figure 2, the misorientation angles beyond the range of 60º±5º are 23º, 39º and 139º, respectively. Compared with Figure 2, the misorientation angle of 60º±5º only accounts for 15%, and the other misorientation is out of this range. The comparative copper metal of FIG. 2 has an orientation difference angle of 60°±5°, which is less than half of the amount of the copper metal of the present invention of FIG. 1.

As shown in Figures 1 and 2, EBSD is used to determine the difference in orientation between two adjacent grains.

The copper wafers of Examples 7 and 8 were mechanically broken into pieces of about 1 cm×2 cm. Then use double-sided tape to install each piece with the copper side up on the plastic sample holder. The Bruker D8 Advanceq-q X-ray diffractometer (XRD) equipped with a copper sealed source tube and the Vantec-1 linear position-sensitive detector were used to collect diffraction patterns (Bruker AXS Inc.) Madison, Wisconsin Dongxue 5465 Parkway, Zip Code 53711 (5465 East Cheryl Parkway, Madison WI 53711). The tube was operated at 35 kV and 45 mA, and the sample was irradiated with copper K radiation (l=1.541 Å). Use a 3˚ detector window to collect XRD data from 15˚ to 84˚ 2q, where the step size is 0.0256˚ and the collection time is 1 second/step. The analysis was performed using the Jade 2010 MDI software program from KSA Analysis System in Aubrey, Texas.

The mechanical property test is carried out using the INSTRON™ tensile tester 33RR64. First, the test samples were plated on a stainless steel substrate (size 12 cm×12 cm) using the formulations in Examples 7 and 8 under the same plating conditions, and plated at a current density of 6 ASD. Then the plated copper was peeled from the stainless steel plate and cut into strips with a size of 1.3 cm×10 cm. The thickness of the independent copper film is 50 μm. In this test, the INSTRON™ tensile tester 33R4465 is used for the test procedure (IPC-TM-650). The copper strip was annealed in a furnace (Blue M industrial laboratory oven, model 01440A) at 230°C for 6 hours. After allowing the sample to cool to room temperature, the sample is tested in a tensile tester. The extension rate applied was 0.002 inches/minute until the sample broke. Use Bluehill-3 software available from INSTRON® to record data. Table 3 shows the results of the elongation test. The mechanical tensile test shows that the sample of the present invention has improved tensile strength relative to the comparative sample without sacrificing significant elongation performance.

Table 3 shows a comparison of the copper deposits of the present invention with comparison or conventional baths. After thermal annealing, the grain size of the copper deposit of the present invention is about 43% smaller than the copper of the comparative example.

EBSD is also used to measure the copper deposits of the present invention and compare the twin fraction and texture index of copper. The copper deposit of the present invention shows a 35% twin fraction of the grain boundary with a 60°±5° orientation difference between adjacent crystal grains in the crystal plane direction <111>. The texture index of the copper metal of the present invention is 5.7 in the (111) plane orientation. High (111) plane orientation is preferable because the sliding system of copper is {111}<110>. A high (111) surface score can promote slippage easily, which leads to better mechanical performance. On the other hand, in the comparison of copper metals, the (001) plane orientation texture is dominated by a texture index ratio of 5.1, which is not conducive to system slip. The (111) surface and (001) surface are unambiguously the two most important surfaces, or MRD>2 in copper. Therefore, comparing the two planes, for the copper metal of the present invention, the (111) plane is better than the (001) plane.

實例10 本發明之浴2的銅電鍍段的分析XRD also revealed that the copper metal of the present invention has a much higher (111)/(200) ratio than the comparative copper metal. The sample used for the XRD test was a copper film with a thickness of about 5 μm plated on the silicon wafer by the copper bath of Examples 7 and 8. The diffraction peak on the (200) plane orientation is used to determine this ratio because the (200) plane orientation is the second strong diffraction peak after (111). Other diffraction peaks are too weak or undetectable. Record the relationship between the diffraction intensity (I) and the diffraction angle 2θ (º), and plot each sample, as shown in Figure 3. The area under the specific diffraction peak (111) orientation and the diffraction peak (200) orientation is integrated for further quantification. Integrate with Jade 2010 MDI software for XRD system. The results are shown in Table 3. Table 3 Performance comparison

Example 10 Analysis of the copper plating section of bath 2 of the present invention

實例11 本發明之浴3的銅電鍍段的分析Copper metal was plated in the bath 2 on the same type of substrate as disclosed in Example 7 above. The plating conditions are basically the same as those disclosed in Example 7. The properties of copper plated by the copper electroplating composition of Bath 2 disclosed in Table 2 of Example 5 were analyzed according to the method described in Example 9 above. The results of EBSD, XRD, and mechanical tensile test results are disclosed in Table 4 below. Table 4

Example 11 Analysis of the copper electroplating section of bath 3 of the present invention

Copper metal was plated on the same type of substrate as disclosed in Example 7 in Bath 3. The plating conditions are basically the same as those in Example 7. The properties of copper plated by the composition of Bath 3 disclosed in Table 2 in Example 5 were analyzed according to the method described in Example 9 above. The results of EBSD, XRD, and mechanical tensile test results are disclosed in Table 5 below. table 5

Figure 1 is an inverse pole diagram of the copper metal of the present invention, which shows the grain boundaries and grain boundary angles relative to the crystal plane direction <111>, and different orientations; Figure 2 is a comparison of the inverse pole diagrams of copper metal, which shows Show the grain boundary and grain boundary angle relative to the crystal plane direction <111>, and different orientations; and Figure 3 is based on the area of copper metal of the present invention based on the Jade 2010 MDI software program used for data analysis to compare the area of copper X-ray diffraction diagram of diffraction intensity (I) versus 2θ (º) diffraction angle at crystal plane (111) to crystal plane (200).

Claims (7)

A copper metal including a twinning fraction of 30% or more of the grain boundary between adjacent copper crystal grains with an orientation difference angle of 55° to 65° with respect to the crystal plane direction <111>. The copper metal described in item 1 of the scope of the patent application further includes an XRD area ratio of (111) plane orientation/(200) plane orientation at a diffraction angle of 2θ (º) equal to or greater than 1. For the copper metal described in the second item of the scope of patent application, the XRD area ratio of (111) plane orientation/(200) plane orientation at the diffraction angle 2θ (º) is equal to or greater than 5. The copper metal described in item 1 of the scope of patent application, wherein after thermal annealing, the copper crystal grain diameter is 100 nm or more. A method of copper electroplating, comprising: a) providing a substrate; b) providing a copper electroplating bath, the copper electroplating bath includes one or more copper ion sources to provide the concentration of 20 g/L to 55 g/L Copper ion; one or more reaction products of one or more imidazole compounds or one or more 2-aminopyridine compounds and one or more biepoxides, wherein the concentration of the one or more reaction products is 2 ppm to 15 ppm; electrolyte One or more accelerators, wherein the concentration of the one or more accelerators is 0.5 ppm to 100 ppm; and one or more inhibitors, wherein the concentration of the one or more inhibitors is 0.5 g/L to 10 g/ L; c) immersing the substrate in the copper electroplating bath; d) electroplating copper on the substrate to deposit a copper layer on the substrate; and, e) annealing the copper layer in an inert atmosphere to A temperature of at least 200°C to provide a copper layer including 30% or more of the grain boundary between adjacent copper grains with an orientation difference angle of 55° to 65° with respect to the crystal plane direction <111> Big twin fraction. The method described in item 5 of the scope of the patent application, wherein the current density during the copper electroplating is 2 to 8 ASD. According to the method described in claim 5, wherein the substrate includes a dielectric, the dielectric has a metal seed layer adjacent to the dielectric, and wherein the copper layer and the The metal seed layer of dielectric is deposited adjacently.

Images