TW202307270A - A composite and a method for manufacturing a composite of a copper layer and an organic layer - Google Patents

Abstract

The present invention relates to a composite and a method for manufacturing a composite, the method comprises in this order the steps: (i) providing a first pure copper structure having a first copper surface; (ii) contacting the first copper surface with an aqueous alkaline conditioner solution and nano-oxidizing the first copper surface by converting Cu-(0) into Cu-(I) and Cu-(II) oxide species obtaining a uniformly oxidized first copper surface layer having a uniformly oxidized first copper surface; (iii) contacting the uniformly oxidized first copper surface with an aqueous alkaline enhancer solution, comprising at least one oxidizing agent, and oxidizing the uniformly oxidized first copper layer by converting the Cu-(I) oxide species into Cu-(II) oxide species and Cu-(0) oxide species into Cu-(I) oxide species obtaining a controlled oxidized first copper surface layer having a controlled oxidized first copper surface; (iv) providing a first non-conductive organic material; and (v) applying the first non-conductive organic material as a first non-conductive organic material layer onto the controlled oxidized first copper surface to obtain the composite.

Description

Composite of copper layer and organic layer and its manufacturing method

The present invention generally relates to a composite of a copper structure and a non-conductive organic material and a method of manufacturing the same, particularly for the production of wafer/panel level packaging in electronic articles. The method is particularly suitable for fan-out wafer/panel level packaging for the production of electronics. The compound exhibits excellent adhesion and reliability properties.

Recent developments in semiconductor manufacturing technology require microelectronic components to become smaller and the circuits within these components to become denser and denser. In order to reduce the size of these components, the packaging and assembly of these components with circuit boards must become more compact. Heterostructures are considered a key technology to meet current and near future needs. It involves the integration of independently produced components into one package, providing enhanced functionality and improved operating characteristics. In this case, system-in-package (SiP) assemblies allow or increase interconnect density, reduce form factor, and improve efficiency.

Examples of such packages include embedded wafer ball grid array (eWLB) or fan-out wafer-level packaging (FOWLP), which are constructed in which the contacts of the semiconductor die are made through an interposer typically formed on a substrate such as a TSV interposer. A redistribution layer (RDL) redistributes a packaging process over a larger area.

While the FOWLP process sequence varies by manufacturer and package variant, the baseline process is generally similar. An adhesive material is applied to the carrier wafer, and one or more die are placed face down on the adhesive layer. This is followed by wafer-level over-molding, which essentially embeds the die(s) in a molded layer. The next step in the process is debonding, during which the carrier wafer is removed from the newly reconstituted overmolded wafer, thereby exposing the active area of the die. A redistribution layer (RDL) is then formed on the increased area of the overmolding, followed by soldering and finally die separation.

This RDL structure is typically achieved by repeatedly adding metal (such as copper layers) and non-conductive layers (such as build-up layers) onto the wafer surface to reroute the I/O layout into a more spaced footprint. defined. This redistribution requires thin film polymers such as BCB, PI or other organic polymers and metallization such as Cu to rewire the perimeter pads to an area array configuration.

Heterostructures usually require a combination of many different materials such as organic films, metallic Cu and silicon. Due to the differential thermal expansion of these materials, the package can be prone to reliability issues.

It is critical that delamination does not occur during the lifetime of this multilayer structure. Therefore, it is desirable that the adhesion between the copper circuit and the non-conductive layer laminated thereon be as high as possible and remain strong during the lifetime of the respective structure that is part of the electronic article.

However, the non-conductive layer sometimes suffers from insufficient adhesion to the copper surface of the copper layer, resulting in delamination at the interface between the copper layer and the non-conductive layer.

To improve the adhesion between copper layers and non-conductive layers in the production of printed circuit boards (PCBs), it is known to roughen the copper surface.

In WO96/19097, copper surfaces are micro-roughened by using an adhesion-promoting composition comprising hydrogen peroxide, mineral acids, corrosion inhibitors such as triazoles, tetrazoles or imidazoles, and quaternary ammonium surfactants To improve the adhesion of polymer materials.

Unfortunately, strong etchants, even when used with corrosion inhibitors, still result in strongly roughened copper surfaces commonly referred to as micro-roughened copper surfaces. This treatment typically roughly removes copper from the circuit surface, leaving a strongly roughened copper surface, including wide and deep depressions even in the micron range. Therefore, this method is not very suitable for fine-line circuits, especially high-frequency applications or wafer/panel level packaging technology in the production of electronic items, because the loss of copper is too large, and the surface becomes too rough, and the obtained Adhesion is usually too weak.

EP3310137B1 discloses a method of increasing the adhesion strength between a copper surface and an organic layer, wherein in the first step, the copper surface is oxidized to copper oxide and reduced back to metallic copper, and in the second step, a compound comprising aminoazole and The surface is treated with an acidic non-etch protectant aqueous solution of peroxide and finally the organic layer is laminated onto the substrate obtained after the second step.

US 2018/0223412 A1 discloses a roughened copper foil, which can significantly improve the adhesion and reliability to insulating resin. The roughened copper foil has a roughened surface formed by applying redox treatment, wherein the entire copper surface is composed of a mixed phase of Cu metal and _Cu2O .

US 4,816,086 A discloses a composition useful for providing an oxide coating to copper to improve the adhesion between dielectric materials and copper, and a method for providing the oxide surface.

US 4,717,439 A relates to a composition and process for improving the leaching resistance of a copper oxide coating on a copper circuit of a printed circuit board to a solution used in its preparation, the process comprising making the copper oxide of the circuit board Contact with a solution of an amphoteric element containing an acidic oxide such as selenium dioxide.

US 2011/186221 A1 relates to a method for improving the adhesion between copper/copper alloys and resins, such as in multilayer printed circuit boards.

While these methods have particular value in producing multi-layer PCBs to facilitate interlayer adhesion, these methods are not suitable for smaller dimensions, such as where handling/connection has much smaller dimensions and is much more demanding in production and reliability embedded in the die. One example of embedded die is fan-out wafer/panel level packaging, where the die is placed on a wafer carrier and a package is built around it. Fan-out is a preferred packaging method because it is designed to significantly increase I/O density and reduce footprint and profile, in part due to the fact that it is thinner than flip-chip because it does not require a packaging substrate. In fan-out processing, a redistribution layer is partially plated on the die and molding resin. Use a metal or glass wafer carrier that is removed after RDL formation, leaving the RDL and second-level interconnect (SLI) pads open for solder ball connection to the PCB. Warpage is a key processing challenge in fan-out due to the use of molding resins, thinner substrates, and thicker Cu deposition.

Due to further miniaturization, in particular for applications as wafer/panel level packaging and chip molding in the production of electronic items, further improvements to existing methods are generally required so that the adhesion strength is further increased and the reliability of the obtained composites is improved .

OBJECTS OF THE INVENTION Accordingly, it is an object of the present invention to provide an improvement for manufacturing composites, preferably for wafer/panel level packaging, preferably for fan-out wafer/panel level packaging, for the production of electronic articles A method leading to an increased adhesion strength between the surface of the copper layer and the layer of non-conductive organic material and improved reliability of the composite obtained compared to prior art methods.

Another object of the present invention is to provide a more cost-effective and environment-friendly method.

The above objects are solved by a method for manufacturing composites, preferably for wafer/panel level packaging, preferably for fan-out wafer/panel level packaging, for the production of electronic articles, which method in turn comprises The following steps: (i) providing a first pure copper structure having a first copper surface; (ii) contacting the first copper surface with an aqueous alkaline conditioner solution and rendering the first copper surface nano-scaled by converting Cu-(0) to Cu-(I) and Cu-(II) oxide species Oxidation to obtain a uniformly oxidized first copper surface layer having a uniformly oxidized first copper surface; (iii) contacting the uniformly oxidized first copper surface with an aqueous alkalinity enhancer solution comprising at least one oxidizing agent, and by converting the Cu-(I) oxide species to Cu-(II) oxide species and allowing converting Cu-(0) oxide species to Cu-(I) oxide species to oxidize the uniformly oxidized first copper layer, obtaining a controlled oxidized first copper surface layer having a controlled oxidized first copper surface; (iv) providing a first non-conductive organic material, preferably a polyimide-containing resin, a polybenzoxazole-containing resin or an epoxy-containing resin or a mixture thereof; and (v) applying the first non-conductive organic material as a first non-conductive organic material layer onto the oxidized first copper surface, obtaining the composite, Wherein step (ii) is carried out in an electroless manner and the alkaline conditioner aqueous solution includes an inorganic base in a concentration range of 2 to 5 g/L, preferably sodium hydroxide or potassium hydroxide.

Furthermore, this object is solved by a compound comprising (a) A first pure copper structure having a controlled oxidized first copper surface layer comprising Cu-(I) and Cu-(II) oxide species, the Cu-(I) and Cu-(II) oxide species forming comprising Controlled Oxidation of Cu-(I) Oxide Species and Acicular Cu-(II) Oxide Species First Copper Surface Layer Interspersed with the Acicular Cu-(II) Oxide Species ) oxide species, - wherein the Cu-(I) oxide species form a layer thickness of 5 nm to 100 nm, and the acicular Cu-(II) oxide species have a length of up to 500 nm, more preferably 100 nm to 500 nm ; (b) the first non-conductive organic material layer, preferably containing polyimide resin, containing polybenzoxazole resin or containing epoxy resin or a mixture thereof; (c) wherein the first non-conductive organic material layer is attached to the oxidized first copper surface.

It will be clear to those skilled in the art that layer thickness is also understood to be "average layer thickness" since the layer thickness may vary locally but will generally be within the specified range. When "average layer thickness" is sometimes used hereinafter, this means that the local layer thicknesses of the total layer thickness considered may vary, but all local layer thickness values are calculated together and divided by the number of local thickness values to calculate The average layer thickness of the considered layer thickness and is within a given range. The layer thickness can be seen and measured in the FIB pictures of the layers. In other words, Cu-(I) oxide species with a local layer thickness of less than 5 nm or greater than 100 nm can be seen and determined, for example, in the FIB picture of a layer or layer assembly, but if the layer thickness is tied to the total layer thickness Measured, as shown in the FIB picture, the calculated average layer thickness values are within the given range.

If the "average length" of acicular Cu-(II) oxide species is used in the following, it means that according to the above explanation of "average layer thickness", it can be obtained by taking all considered acicular Cu in the FIB picture - Add together the (II) oxide species and measure the length of the considered needle-like Cu-(II) oxide species in the FIB picture.

According to the invention, the first pure copper structure preferably having a first copper surface is part of a substrate selected from the group consisting of: redistribution layer (RDL) structures (more specifically, copper structures of RDL structures is the first copper surface), an integrated circuit (IC) or a copper column structure and/or a copper contact structure of a die (eg on a wafer). This means that the substrate comprises the first pure copper structure with the first copper surface to be provided for the method and to be treated. The invention is particularly suitable for forming a robust composite between the first pure copper structure having the first copper surface as part of the substrate and a layer of non-conductive organic material for excellent mechanical properties, especially for shrinkage dimensions. Furthermore, the present invention is particularly suitable for improving the ductility of the copper layer of the inventive composite, which is significantly improved compared to prior art composites not produced by the present invention.

The method of the invention and the composite of the invention provide increased adhesion strength between a copper structure having a controlled oxidized first copper surface and a layer of non-conductive organic material without aggressive etching or significant removal of copper from the copper structure .

Furthermore, the present invention does not require and does not include an additional reduction step to reduce the copper oxide species back to metallic copper, which reduces the number of process steps, safety costs and time, and avoids the use of reducing agents such as formaldehyde, hydrazine, or other environmentally hazardous reducing agents . The present invention specifically does not provide a surface of a mixed phase of Cu metal and _Cu2O on the entire surface resulting from the reduction step.

Furthermore, the present invention does not require the application of an additional coupling layer comprising, for example, triazole, tetrazole or imidazole prior to the application of the first non-conductive organic material.

Preferably the method of the present invention, wherein the first pure copper structure has a copper content of 99% by weight or higher, preferably 99.9% by weight or higher copper. In this case, pure copper preferably does not contain, preferably does not include other elements other than copper; more preferably substantially does not contain, preferably does not include one, more than one or all elements selected from the group consisting of molybdenum , cobalt, nickel, tungsten and titanium.

Without wishing to be bound by theory, the improved adhesion, ductility and reliability of the composite are based on the combination of steps (ii) and (iii), which allow the first very slow copper oxidation, resulting from a uniform and smooth reaction The uniformly oxidized first copper surface is followed by controlled oxidation during step (iii) of the uniformly oxidized first copper surface obtained during step (ii). Preferably step (iii) is provided directly after step (ii) without any additional steps such as rinsing or cleaning steps, in particular without an acidic impregnation step involving organic or inorganic acids such as formic or sulfuric acid.

This means that in step (ii), the first pure copper structure is made by converting the Cu-(0) surface to Cu-(I) oxide species and Cu-(II) oxide species. Copper surface nano-oxidation, where it is likely that Cu-(I) oxide species are slowly converted to Cu-(II) oxide species, where the Cu-(I) and Cu-(II) oxides still have the same size. Finally, a uniformly oxidized first copper surface layer is formed having a uniformly oxidized first copper surface in which both Cu-(I) and Cu-(II) oxide species are present. The obtained Cu-(I) and Cu-(II) oxide species have a nanocrystalline structure. Cu-(I) and Cu-(II) oxide species are uniformly distributed on the first pure copper structure, wherein Cu-(0) on the first copper surface is transformed. The obtained Cu-(I) and Cu-(II) oxide species are preferably Cu ₂ O, CuO and corresponding hydroxides (such as Cu(OH) ₂ ), more preferably Cu ₂ O and CuO. This uniform transformation is not limited to certain regions of the first copper surface, such as the regions of the copper grain boundaries of the first pure copper structure, but occurs over the entire surface of the first copper surface. Inhomogeneous conversion is undesirable to us and will be prevented by performing step (ii). This means that the initial first copper surface is covered by a uniform copper oxide layer consisting of Cu-(I) and Cu-(II) oxide species, preferably the Cu-(I) and Cu-(II) The oxide species consists of _Cu2O , CuO and corresponding hydroxides (eg Cu(OH) ₂ ), more preferably _Cu2O and CuO.

The aqueous alkaline conditioner used provides very mild oxidation conditions to achieve the slow nano-oxidation in step (ii). Preferably, the aqueous alkaline conditioner solution does not include any intentionally added oxidizing agent, except typically during the preparation and use of the aqueous alkaline conditioner solution, preferably within a temperature range between 15°C and 60°C (at normal atmospheric pressure Bottom) In addition to dissolved air oxygen.

Preferably, the Cu-(I) and Cu-(II) oxide species of step (ii) uniformly oxidize the first copper surface have an average layer thickness from 5 nm to 30 nm or have a layer thickness from 5 nm to 30 nm nm uniform oxidation of the first copper surface layer. This means that after step (ii), the uniformly oxidized first copper surface layer formed in step (ii) has a layer thickness of 5 nm to 30 nm. The Cu-(I) and Cu-(II) oxide species have a nanocrystalline structure, wherein the uniformly oxidized first copper surface layer surface is very uniform, and the Cu-(I) and Cu-(II) ) oxide species have the same length or size respectively. In step (iii), Cu-(I) oxide species are further converted to Cu-(II) oxide species and Cu-(0) is converted to Cu by using an aqueous basic enhancer solution comprising at least one oxidant - (I) oxide species to oxidize the uniformly oxidized first copper surface, obtaining a controlled oxidized first copper surface layer having a controlled oxidized first copper surface. Controlled in this context means that the inventors have found that due to the formation of a dense and uniformly oxidized first copper surface layer in step (ii), also because very small amounts of Cu-(0) are available and convertible to Cu-(I ) oxide species, the oxidizing agent mainly oxidizes the Cu-(I) oxide species into Cu-(II) oxide species. The obtained Cu-(I) oxide species again has a nanocrystalline structure and the obtained Cu-(II) oxide species is now larger crystalline compared to the dense and small Cu-(I) oxide species structure. Thus, conversion of Cu-(I) oxide species to acicular Cu-(II) oxide species occurs, while a small amount of Cu(0) will still be converted to Cu(I) oxide species. The obtained Cu-(I) and Cu-(II) oxide species are preferably Cu ₂ O, CuO and corresponding hydroxides (such as Cu(OH) ₂ ), more preferably Cu ₂ O and CuO.

Although the homogeneously oxidized first copper surface is well covered (by homogeneous oxidation) with the obtained Cu-(I) and Cu-(II) oxide species, it is believed that the aqueous alkaline enhancer solution can still contact the A very small area of the initial first copper surface, or in other words, may be in contact with a small amount of metallic copper of the first copper surface. Therefore, Cu-(I) oxide species are also formed in step (iii), while the Cu-(I) oxide species are mainly converted to acicular Cu-(II) oxide species.

In any case, this first pure copper structure remained unchanged, with no aggressive etching or significant copper removal.

Preferably, after step (iii) of the method of the present invention, the converted Cu-(I) oxide species has a nanocrystalline structure uniformly distributed over the entire surface, and the converted Cu-(II) is oxidized The species is acicular Cu-(II) oxide species, wherein the Cu-(I) oxide species are interspersed with the acicular Cu-(II) oxide species. The Cu-(I) oxide species form a layer thickness of 5 nm to 100 nm in the controlled oxidized first copper surface layer, and the acicular Cu-(II) oxide species have up to 500 nm, More preferably an average length of 100 nm to 500 nm or have a length up to 500 nm, more preferably 100 nm to 500 nm. This means that after step (iii), the controlled oxidized first copper surface layer formed in step (iii) has Cu-(I) oxide species with a layer thickness of 5 nm to 100 nm, and has up to 500 nm, more preferably acicular Cu-(II) oxide species with a length of 100 nm to 500 nm.

In other words, the controlled oxidized first copper surface layer can be considered to have a total thickness of about 5 to about 500 nm, wherein the Cu-(I) oxide species form a layer thickness of 5 nm to 100 nm and the acicular Cu -(II) The oxide species has a length of up to 500 nm, more preferably 100 nm to 500 nm, most preferably 120 nm to 350 nm. The overall (or total) layer thickness of the controlled oxidized first copper surface layer up to 500 nm is mainly determined by the preferred up to 500 nm of the acicular Cu-(II) oxide species after step (iii). The length and layer thickness of the Cu-(I) oxide species after step (iii) is determined preferably from 5 nm to 100 nm. Figure 1 illustrates this controlled oxidized first copper surface layer after step (iii), where dense and uniform Cu-(I) oxide species interspersed with acicular Cu-(II) oxide species can be seen.

Advantageously, the method of the present invention provides a very smooth, nano-roughened, uniformly oxidized first copper surface layer after step (ii) (and also step iii), compared to conventional etching methods which typically result in Very obvious surface roughness or even surface damage usually involves changing the topography of the surface. This is unnecessary, especially not suitable for fine line circuits and high frequency applications. After step (iii) of the method of the present invention, by maintaining a layer thickness of 5 nm to 100 nm of the Cu-(I) oxide species formed in the controlled oxidation first copper surface layer, and the acicular Cu-(II) oxide species (needle morphology) have lengths up to 500 nm, more preferably 100 nm to 500 nm, optimally 120 nm to 350 nm, it is expected that the controlled oxidized first copper surface is "inhomogeneous" of".

Preferably, the layer thickness of the Cu-(I) oxide species formed in step (iii) is 10 to 90 nm, preferably 20 nm to 80 nm.

This mixed structure of the controlled oxidation Cu-(I) and Cu-(II) oxide species is responsible for the improved adhesion and reliability of the composite after step (iii). The controlled oxidized first copper surface layer with the highly non-uniform surface is well suited for the following steps (iv ) and (v).

Interestingly, in step (iii), the conversion of Cu-(I) to Cu-(II) oxide species terminates itself after the conversion of all available Cu-(0). "Available" in this context means the conversion of Cu-(0) to Cu(I) if the aqueous base enhancer solution cannot contact the initial first copper surface through the dense nanocrystalline Cu-(I) oxide species cessation, or in other words, conversion occurs as long as the aqueous alkalinity enhancer solution is in contact with the metallic copper of the first copper surface.

After step (iii), the surface morphology is significantly modified and generally results in needle-like surface morphology of copper-(II) oxide species and nanocrystalline structure of copper-(I) oxide species with very low surface roughness Spend. However, the total surface area is significantly increased compared to the total surface area before and after step (ii). The resulting controlled oxidation of the first copper surface layer (as a result of this transformation) results in the advanced adhesive strength of the composite.

Preferably, step (iii) is performed by self-limited formation of Cu-(II) oxide species such as CuO and/or its hydroxides, preferably CuO. It has been found that if all available Cu-(0) is converted to Cu-(I) oxide species, the formation of Cu-(II) oxide species, preferably acicular Cu-(II) oxide species, also automatically ceases . Self-limiting here means that even though the oxidizing agent is still available, no further conversion from Cu-(I) to Cu-(II) oxide species occurs under the given conditions because the aqueous base enhancer solution is no longer compatible with the first Cu-(II) oxide species. A copper surface is in metallic copper contact, or in other words, it is believed that no Cu-(0) can diffuse from the first copper surface to the controlled oxidized first copper surface.

In general, the surface layer according to steps (ii) and (iii) (which is also considered nano-roughened (because of its nanometer scale)) can be analyzed by atomic force microscopy (AFM), Fourier transform infrared spectroscopy ( FT-IR), focused ion beam high-resolution scanning electron microscopy (FIB high-resolution SEM), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) for research, analysis and measurement. Preferably, the analysis is performed in vertical cross-sections of the respective samples. More preferably, the nano-roughened surface layer thickness is observed and measured by FIB high-resolution SEM and AFM, for example, to determine the maximum layer thickness. The best method is AFM.

The method according to steps (ii) and (iii) is preferably carried out electrolessly. The first copper surface in step (ii) may be immersed in an aqueous alkaline conditioner solution or sprayed onto the surface.

The alkaline conditioning agent aqueous solution nano-oxidizes the first copper surface and transforms it into uniformly oxidized first copper surface, and adjusts the pH and electrochemical potential of the surface.

The aqueous alkaline conditioner used in step (ii) comprises an inorganic base, preferably sodium hydroxide or potassium hydroxide, in a concentration range of 2 to 5 g/L, preferably 2 to 4 g/L. In a preferred embodiment, the aqueous alkaline conditioner used in step (ii) does not include phosphates, organic nitrogen-containing compounds or sulfur-containing compounds. More preferably, the alkaline conditioner aqueous solution used in step (ii) is from 2 to 5 g/L, preferably inorganic alkali in the concentration range of 2 to 4 g/L, preferably sodium hydroxide or potassium hydroxide and water composition.

According to the method of step (ii), wherein the nano-oxidation is preferably carried out at a temperature of 30 to 60° C., preferably 45 to 55° C., for a period of 0.25 min to 6 min. Preferably, the nano-oxidation is performed by soaking process for 0.25 min to 3 min or by spraying process for 3 min to 6 min.

The uniformly oxidized first copper surface treated in step (iii) may be immersed in an aqueous alkalinity enhancer solution, or the aqueous alkalinity enhancer may be sprayed onto the surface.

The alkaline enhancer aqueous solution in the step (iii) includes 2 to 5 g/L, preferably inorganic bases in the concentration range of 2 to 4 g/L, more preferably sodium hydroxide or potassium hydroxide, and the oxidizing agent is Within the concentration range of 10 to 100 g/L, preferably 15 g/L to 40 g/L for soaking, and 40 g/L to 100 g/L for spraying.

In a preferred embodiment, the aqueous alkali enhancer solution used in step (iii) does not include phosphate, organic nitrogen-containing compounds or sulfur-containing compounds. More preferably, the alkaline enhancer aqueous solution used in step (iii) is from 2 to 5 g/L, preferably inorganic alkali in the concentration range of 2 to 4 g/L, preferably sodium hydroxide or potassium hydroxide, 10 Composition of oxidant and water within the concentration range of 100 g/L.

The method according to step (iii), wherein the oxidation in the step is carried out at a temperature of 50 to 80°C, preferably 55°C to 75°C, and lasts for 0.5 min to 20 min, preferably 2 min to 10 min.

Preferably, the temperature in step (ii) is lower than the temperature in step (iii), more preferably, the temperature in step (ii) is 45°C to 55°C and the temperature in step (iii) is 55°C to 75°C.

Step (iii) preferably follows step (ii) directly without further steps (eg washing steps) being applied in between.

The oxidizing agent is preferably selected from the group consisting of chlorites comprising chlorous acid, hypochlorites comprising hypochlorous acid, peroxides comprising hydrogen peroxide, permanganates, perchloric acid perchlorates, persulfates including peroxymonosulfates, peroxodisulfates and their related acids. Preferred chlorites are chlorous acid and alkaline chlorites, most preferably sodium chlorite. A preferred hypochlorite is hypochlorous acid and its salts. A preferred peroxide is hydrogen peroxide. Preferred perchlorates are perchloric acid and its salts. Preferred persulfates are selected from the group consisting of peroxymonosulfates, peroxodisulfates and related acids. The oxidizing agents are present in a total concentration sufficient to accomplish the desired oxidation. After step (ia), copper is present predominantly with oxidation number +2.

In one embodiment of the method of the present invention, a cleaning step (ia) is applied prior to step (ii), wherein the first copper surface is treated with an acidic solution to remove copper oxide and other residues such as grease.

The acidic solution preferably comprises a mineral acid, more preferably sulfuric acid. The concentration of the mineral acid is preferably 3 to 7% by weight of the total solution.

The acidic solution preferably does not include _an oxidizing agent such as _H2O2 .

The acidic solution preferably has a pH value <2, preferably <1.

The cleaning step (ia) is carried out at a temperature of 15 to 25° C. and for a time of 0.25 min to 1 min.

The method of the present invention is preferred, wherein the first non-conductive organic material is polyimide-containing resin, polybenzoxazole-containing resin or epoxy-containing resin or a mixture thereof. In addition, liquid crystal polymers (LCPs) may be used. In one embodiment of the present invention, the first non-conductive organic material layer preferably includes a material selected from the group consisting of: epoxy compounds including epoxy esters and fluorine-containing epoxy resins, photoimaging polyamides Polyimides of amines, cyanate esters, polybenzoxazoles, bismaleimide-triazine compounds, polypropylene ethers and polyolefins, more preferably the first non-conductive organic material layer comprises polyamide-containing Build-up or mold of imide resin.

In one embodiment of the present invention, the first non-conductive organic material layer is substantially free of, preferably free of filler fibers, preferably substantially free of, preferably free of glass fibers.

According to step (v) of the method according to the invention, a first non-conductive organic material is applied as a first non-conductive organic material layer onto the controlled oxidized first copper surface to obtain a composite. Preferably, the composite is obtained by applying step (v) directly to the controlled oxidized first copper surface without requiring any additional treatment steps to treat the controlled oxidized first copper surface, such as cleaning, rinsing, applying Adhesive films are, for example, based on silane compounds, or solutions are applied to prevent leaching, for example solutions containing amphoteric elements forming acidic oxides such as selenium dioxide.

The method of the invention is preferred wherein the first non-conductive organic material is a foil, a dry film such as a dry film stack or a liquid. Preferably, the first non-conductive organic material is a liquid that can be spin-coated or cast by known techniques. Those skilled in the art will appreciate that the liquid organic layer herein is not perfectly fluid, but exhibits a certain viscosity typical in the art. Likewise, those skilled in the art know that dry films are not completely dry, but contain certain amounts of typical solvents.

Preferably, if the first pure copper structure with the first copper surface is part of the substrate, it is selected from the group consisting of copper columnar structures and/or copper contact structures of integrated circuits (IC) or die , the first non-conductive organic material can then be applied in liquid form, by eg spin coating or casting onto the controlled oxidized first copper surface. Preferably, if the first pure copper structure having a first copper surface is part of a substrate selected from the group consisting of redistribution layer (RDL) structures, the first non-conductive organic material may be applied in the form of a foil or a dry film, and laminated to the controlled oxidation first copper surface. Application by spin coating, casting or foil lamination is known to those skilled in the art.

During step (v), the first non-conductive organic material layer is in direct contact with the controlled oxidized first copper surface. Since the copper surface is modified according to the method of the present invention, the adhesion strength between the non-conductive organic material layer and the surface is increased. Preferably, the first non-conductive organic material layer does not include a silane-containing compound as a silane coupling agent.

The method of the present invention is preferred, wherein in step (v) the first layer of non-conductive organic material may be in the form of a coating or in the form of a mold. The layer has a layer thickness of 10 μm or less, preferably 5 μm or less, more preferably 3 μm or less, even better 15 μm or less, most preferably 10 μm or less. The mold has a thickness of 100 μm to 300 μm, preferably 200 μm to 250 μm.

Our experiments have shown the benefit of using a first non-conductive organic material layer (e.g. a build-up layer) exhibiting a layer thickness of 10 μm or less, especially 5 μm or less is highly sensitive to oxygen permeation, especially when subjected to increased temperature hour. This infiltration is highly undesirable as it leads to re-oxidation of the copper. The method of the invention is therefore particularly beneficial for very thin layers of non-conductive organic material, in particular less than 3 μm, in order to prevent undesired re-oxidation of copper to copper oxide.

Preferably, the compound obtained by the method of the present invention can be used as a precursor for further processing in the manufacture of electronic articles (such as smart phones or computers), wherein the compound after further processing can be connected to different electronic components, such as A microchip of sensors or RAM. Thus, the method of the present invention can be used in a heterogeneous package by involving the integration of independently produced components into a package, such as a system-in-package (SiP) assembly, which provides enhanced functionality and Improved operating characteristics.

Preferably, the method of the present invention comprises a further step, wherein the layer of non-conductive organic material of the composite of step (v), more specifically, the layer of non-conductive organic material of the composite comprises a non-conductive outer surface and wherein the method in After step (v), additionally comprise the following steps: (vi) applying a plating resist to the non-conductive outer surface of the composite; (vii) inserting at least one opening through the plating resist, the layer of non-conductive organic material and terminating at the controlled oxidized first copper surface, and optionally inserting traces through the plating resist and terminating at the composite non-conductive The outer surface; (viii) electrochemically depositing a metal or metal alloy layer into the at least one opening and optional traces to create conductive vias and optional conductive lines.

The metal is preferably copper, nickel, gold, silver and metal alloys of these metals.

Therefore, the method of the present invention is preferred, wherein the first non-conductive organic material layer in step (v) is a stacked layer.

After performing step (viii), the method according to steps (ii) to (v) may be repeated, for example 3 to 4 times. In this case, the metal or metal alloy layer (eg copper layer) of step (viii) is provided analogously to the first pure copper structure having a first copper surface of step (i). This periodic sequence is typical for a semi-additive process, and our experiments have shown that the method of the present invention is particularly beneficial for this process.

Therefore, the method of the present invention is preferably used in a semi-additive process to build a redistribution layer structure on the contact structure of the die.

The benefits of the method of the invention have been described above. What has been said above with respect to the method of the invention also applies to the compound of the invention.

The present invention also relates to a complex comprising: (a) a first pure copper structure having a controlled oxidized first copper surface layer comprising Cu-(I) and Cu-(II) oxide species, wherein the converted Cu-(I) oxide species have nano Mi-crystalline structure and the converted Cu-(II) oxide species are acicular Cu-(II) oxide species, wherein the Cu-(I) oxide species are interspersed with the acicular Cu-(II) oxide species ) oxide species, -wherein the Cu-(I) oxide species form a layer thickness of 5 nm to 100 nm in the controlled oxidation first copper surface layer, and the acicular Cu-(II) oxide species have up to 500 nm, preferably 100 nm to 500 nm in length; (b) the first non-conductive organic material layer, preferably containing polyimide resin, containing polybenzoxazole resin or containing epoxy resin or a mixture thereof; (c) wherein the first non-conductive organic material layer is attached to the controlled oxidation first copper surface.

Preferably, the first pure copper structure having the first copper surface is part of the substrate, which is selected from an integrated circuit (IC) or a redistribution layer (RDL) structure of a die, a copper pillar structure and/or a copper contact A group of dot structures.

The invention is further explained by the following figures and non-limiting examples.

EXAMPLES Example Set 1 A. Sample preparation step (i): providing a first pure copper structure having a first copper surface:

Eleven copper foils (5 µm) were plated on top of a stainless steel wafer by using a state-of-the-art ECD Cu plating electrolyte. The foils were peeled off the carrier and annealed at 230° C. for 1 hour under a nitrogen atmosphere. Nine foils were treated with the inventive method (inventive examples 1 to 9) and 2 foils (comparative examples 1 and 2) which did not use the inventive method steps (ii) and (iii) were prepared for comparison. These comparative examples are processed according to the standard process flow in the industry.

In step (ia), cleaned copper foils were obtained by cleaning the copper surfaces of all foils with an aqueous solution containing 5% by weight of sulfuric acid in DI water. This cleaning removes oxides and other compounds, such as rust inhibitors and/or surfactants. After the cleaning, the cleaned copper foils were rinsed with cold water for about two minutes. Thus, the cleaned and rinsed copper foil is obtained.

Subsequently, proceed to step (ii): In step (ii), the foils were immersed in an aqueous alkaline conditioner solution comprising 3.2 g/L NaOH in DI water for 45 seconds at 50°C. Thus, a conditioned copper foil with a uniformly oxidized first copper surface is obtained.

Next, the copper foil obtained after the step (ii) is processed by performing the step (iii).

In step (iii), the conditioned copper foils were treated with an aqueous alkaline enhancer solution comprising 2.5 g/L NaOH and 250 g/l NaClO2 (25% by weight solution) in DI water. The treatment was carried out at 70 °C for different times ranging from 0.5 min to 8 min, resulting in the respective conversion of Cu(0) to Cu(I)-oxide and Cu(I)-oxide to Cu(II)-oxide. Controlled and self-limited conversion, which forms needle-type layers of converted copper with a maximum layer thickness greater than 350 nm. After oxidation in step (iii), the copper foils were rinsed with cold water.

In Fig. 1, a FIB picture according to IE 4 is shown. The picture represents a treatment time of 6 min at 70°C in step (iii). The picture shows the layer thickness of the Cu-(I) oxide species layer, the acicular Cu-(II) oxide species, and the total layer thickness of the controlled oxidized first copper surface layer.

Step (iv): providing a first non-conductive organic material after step (iii): In order to provide a pull-strength-test that requires a stable base layer, FR4 materials based on epoxy resin are used.

Step (v): Applying the first non-conductive organic material as a first non-conductive organic material layer on the controlled oxidized first copper surface, obtaining the composite: Inventive examples 1 to 9 were applied using 20 kp/cm ² The foil is pressed against the organic dielectric material (FR4-like material) with the controlled oxidation side. The same procedure was carried out for Comparative Examples 1 and 2, without using the additional treatment according to the invention. Six foils (inventive examples 1 to 5 and comparative example 1) were exposed to a temperature of 180°C for 3 hours without _N2 protection, and five foils (inventive examples 6 to 9 and comparative example 2) were exposed to In 5 standard lead-free reflow profiles.

The test situation is a known standard test situation showing the quality of the composite molding, eg in the case of mold materials.

B. Adhesion Strength Evaluation: After heat treatment, all foils were tested by using a pull test, the foils were removed from the dielectric material in a 90° orientation and the associated forces were determined. Such testing procedures are known to those skilled in the art.

A summary of the results after heat treatment for 3 h/180° C. without nitrogen blanket is given in Table 1 . sample IE 1 (0.5 min) IE 2 (2 min) IE 3 (4 min) Internet Explorer 4 (6 min) Internet Explorer 5 (8 minutes) CI 1 Average force [Nm/cm] 3.63 4.24 3.77 4.07 3.98 1.68 Table 1. Summary of Adhesive Strength

A summary of the results after heat treatment of five standard lead-free reflow profiles is given in Table 2. sample Internet Explorer 6 (2 min) Internet Explorer 7 (4 minutes) Internet Explorer 8 (6 min) Internet Explorer 9 (8 minutes) CI 2 Average force [Nm/cm] 0.593 0.364 1.050 1.430 0.282 Table 2. Summary of Adhesive Strength

The values in Table 1 show that Inventive Examples 1 and 9 provide significantly improved adhesion strength compared to Comparative Examples 1 and 2.

FIG. 2 shows the adhesion test results of inventive examples IE 2 and IE 4 and comparative example CI 1. In addition, the FIB pictures of IE 2 and IE 4 after step (iii) according to the present invention and CI 1 not processed by the present invention are shown. The controlled oxidized first copper surface layer had a total layer thickness of about 350 nm after 8 min. While the FIB picture of CI 1 does not show a uniform copper oxide surface or a controlled copper oxide surface, the FIB picture of the inventive example shows nanocrystalline Cu-(I) oxide species interspersed with acicular Cu-(II) oxide species.

Figure 3 shows the inventive examples prepared as described above, where the processing temperatures for the different inventive examples were 60°C and 70°C. In each case, the treatment time was 6 min. FIB pictures (a) and (b) show total controlled oxidation of the first copper surface layer depending on the temperature in step (iii) according to the invention (FIB picture (a) at 60°C and (b) at 70°C) . Figure 3c shows the total thickness of the controlled oxidation first copper surface layer. Figure 3d shows the thickness of Cu-(I) oxide species of the controlled oxidation first copper surface layer.

Figure 4 shows the self-limiting behavior in step (iii) of the invention according to the formation of acicular Cu-(II) oxide species over time. It can be seen that the layer thickness of the Cu-(I) oxide seed layer and the total layer thickness of the controlled oxidized first copper surface layer increase very rapidly to a total layer thickness of about 300 nm within the first 3 min and within the step (iii) period remains fairly constant at this point. At 4 and 6 min, FIB pictures of the controlled oxidized first copper surface layer are also shown.

Example Group 2 A. Sample Preparation A wafer substrate with a copper layer was prepared for further processing of the inventive method (Inventive Example - Cu w AP). The comparative examples were not treated according to the method of the invention. In particular, steps (ii) and (iii) of the method of the invention were not carried out (comparative example - Cu).

Step (i): Providing a first pure copper structure having a first copper surface: A copper layer (20 µm deposition thickness) was applied on top of the gold wafer substrate by using a state-of-the-art ECD Cu plating electrolyte (Spherolyte Cu UF 3 process, Atotech). Copper layers were provided by using a standard electrolytic plating tool (Rena) at 25°C and 2 ASD. The resulting copper layer was allowed to self-anneal at room temperature before further processing.

Initially in step (ia), the surface is cleaned with an acidic solution (5% sulfuric acid in water) for 60 seconds at 35°C and rinsed with water for 35 seconds at ambient temperature. This cleaning removes oxides and other compounds, such as rust inhibitors and/or surfactants.

Subsequently, step (ii) is carried out, wherein an aqueous alkaline conditioner is applied to the previously prepared copper layer. In this step, the copper-clad wafer substrate was immersed in a solution of NaOH (3.2 g/L) in water at 50° C. for 30 seconds. Thus, a conditioned copper surface with a uniformly oxidized first copper surface is obtained.

In step (iii), the conditioned copper foil surface was treated with an aqueous alkaline enhancer solution comprising NaOH (2.5 g/L) and 80 g/L sodium chlorite (25% by weight solution) at 70°C for 6 min . The samples were then rinsed with water for 0.5 min at ambient temperature.

Steps (iv) and (v): A polyimide material is provided as the first non-conductive organic material and applied to the controlled oxidized first copper surface of step (iii). The comparative example was without steps (ii) and (iii) and used bare copper foil. The polyimide material (LTC 9320 E07, Fuji Film) was applied by spin coating at 1000 rpm using industry standard processes. Two 6 min prebakes were performed at 105°C, followed by UV curing with 300 mJ. It was further cured at 230° C. for 1 hour under a nitrogen atmosphere.

B. Tensile test and peel strength test: After applying the polyimide material, both examples were further subjected to 2 hours of heat treatment at 230° C., and the resulting composite of copper and polyimide was removed from the gold substrate remove.

The ductility of the composite of the copper layer and the polyimide layer without and with the use of the method of the invention was determined by means of a tensile test. Test strips (12.7 mm width, 100 mm length) were first cut using a JDC Precision Sample Cutter, and then annealed at 120 °C for 1 h in an inert atmosphere. The ductility was determined with a tensile testing device (Zwick Z1.0, force sensor 500 N pneumatic grips with Vulkollan coating). Figure 5 compares the normalized ductility values for composites of copper layers and polyimide layers with and without the method of the invention (comparative example "Cu" and inventive example "Cu w AP" (AP-adhesion promotion)) . For better comparison, the equivalent values were normalized to the comparative example without the inventive method. The shaping of the composite when applying the method of the invention leads to a marked increase in this ductility.

To measure the peel strength, a double-sided polyimide tape was placed on the spin-coated polyimide of the composite. After applying the double-sided tape, a portion of the composite is cut to the size of the tape. Therefore, the composite of polyimide layer and copper layer was transferred to a backplane for mechanical reinforcement and cut into strips of 10 mm width. At the beginning of each peel strip, a blade must be used to separate the part from the polyimide layer, avoiding separation of the copper from the backplane. The polyimide layer of the composite was stretched in the direction perpendicular to the sample orientation and the force required to remove the layer from the underlying copper layer was measured in the absence and presence of the method of the invention. These corresponding results are shown in Figure 5 and reveal a significantly stronger adhesion in the presence of the inventive method (comparative example "Cu" compared to inventive example "Cu w AP" (AP-adhesion promotion)). Although negligible adhesion was observed for the comparative example of a composite of a copper layer and a polyimide layer, larger values were obtained when the method of the invention was applied. For better comparison, these values were normalized to the comparative example, and the inventive method provided about a 4.5-fold improvement.

Figure 1 shows a FIB picture according to the present invention;

Fig. 2 shows the adhesion test results and FIB pictures of the inventive example and the comparative example.

Figures 3(a) to 3(d) show the temperature-dependent thickness of the Cu-(I) oxide species and the total thickness of the controlled oxidized first copper surface layer in step (iii) according to the present invention;

Figure 4 shows the self-limiting behavior of the formation of acicular Cu-(II) oxide species over time according to the present invention;

Figure 5 shows the normalized ductility and normalized peel strength of a composite of copper layer and polyimide layer in the absence and presence of the present invention.

Claims (15)

A method for manufacturing a composite, preferably for wafer/panel level packaging for the production of electronic articles, more preferably for fan-out wafer/panel level packaging, the method comprising the following steps in sequence: (i) providing a first pure copper structure having a first copper surface; (ii) contacting the first copper surface with an aqueous alkaline conditioner solution and rendering the first copper surface nano-scaled by converting Cu-(0) to Cu-(I) and Cu-(II) oxide species Oxidation to obtain a uniformly oxidized first copper surface layer having a uniformly oxidized first copper surface; (iii) contacting the uniformly oxidized first copper surface with an aqueous alkalinity enhancer solution comprising at least one oxidizing agent, and by converting the Cu-(I) oxide species to Cu-(II) oxide species and allowing converting Cu-(0) oxide species to Cu-(I) oxide species to oxidize the uniformly oxidized first copper layer, obtaining a controlled oxidized first copper surface layer having a controlled oxidized first copper surface; (iv) providing a first non-conductive organic material, preferably a polyimide-containing resin, a polybenzoxazole-containing resin or an epoxy-containing resin or a mixture thereof; and (v) applying the first non-conductive organic material as a first non-conductive organic material layer onto the controlled oxidized first copper surface, obtaining the composite, Wherein step (ii) is performed in an electroless manner and the alkaline conditioner aqueous solution includes an inorganic base in a concentration range of 2 to 5 g/L, preferably sodium hydroxide or potassium hydroxide. The method according to claim 1, wherein the uniform oxidized first copper surface layer formed in step (ii) has a layer thickness of 5 nm to 30 nm. If the method of claim 1 or 2, Wherein the controlled oxidation first copper surface layer formed in step (iii) has Cu-(I) oxide species with a layer thickness of 5 nm to 100 nm, and has Cu-(I) oxide species up to 500 nm, more preferably 100 nm to 500 nm long needle-like Cu-(II) oxide species. The method according to claim 3, wherein the layer thickness of the Cu-(I) oxide species formed in step (iii) is 10 to 90 nm, preferably 20 nm to 80 nm. The method of any one of the preceding claims, wherein in step (iii), the conversion of Cu-(I) to Cu-(II) oxide species terminates itself after all Cu-(0) conversion. The method of any one of the preceding claims, wherein the first pure copper structure having the first copper surface is part of a substrate selected from an integrated circuit (IC) or a redistribution layer (RDL) of a die structure, copper pillar structure and/or copper contact structure. The method according to any one of the preceding claims, wherein step (ii) is performed without adding an oxidizing agent to the aqueous alkaline conditioner solution, and the aqueous alkaline conditioner solution does not contain the oxidizing agent, preferably does not contain an oxidizing agent selected from the group consisting of Chlorites of chlorous acid, hypochlorites containing hypochlorous acid, peroxides containing hydrogen peroxide, permanganates, perchlorates containing perchloric acid, peroxymonosulfates, An oxidizing agent from the group consisting of peroxodisulfates and persulfates of related acids is added to the aqueous alkaline conditioner, and the aqueous alkaline conditioner does not contain the oxidizing agent. A method as in any one of the preceding claims, wherein step (iii) is carried out in an electroless manner and the aqueous alkalinity enhancer solution includes an inorganic base in a concentration range of 2 to 5 g/L, preferably sodium hydroxide or hydrogen Potassium oxide, and the oxidizing agent is in the concentration range of 10 to 100 g/L. The method according to any one of the preceding claims, wherein the oxidizing agent is selected from the group consisting of: chlorite comprising chlorous acid, hypochlorite comprising hypochlorous acid, peroxide comprising hydrogen peroxide , permanganate, perchlorate including perchloric acid, persulfate including peroxymonosulfate, peroxodisulfate and their related acids. The method according to any one of the preceding claims, wherein the nano-oxidation in step (ii) is carried out at a temperature of 30 to 60° C. for a period of 0.25 min to 6 min. The method according to any one of the preceding claims, wherein the oxidation in step (iii) is carried out at a temperature of 50 to 80°C for a period of 0.5 min to 20 min. The method of any one of the preceding claims, wherein prior to step (ii), a cleaning step (ia) is performed, wherein the first copper surface is treated with an acidic solution to remove copper oxide. The method according to claim 12, wherein the cleaning step (ia) is carried out at a temperature of 15 to 25° C. for a period of 0.25 min to 1 min. The method of any one of the preceding claims, wherein the non-conductive organic material layer of the composite of step (v) comprises a non-conductive outer surface, and wherein the method additionally comprises the following steps after step (v): (vi) applying a plating resist to the non-conductive outer surface of the composite; (vii) inserting at least one opening through the plating resist, the layer of non-conductive organic material and terminating at the controlled oxidized first copper surface, and optionally inserting traces through the plating resist and terminating at the non-conductive of the composite The outer surface; (viii) electrochemically depositing a metal or metal alloy layer into the at least one opening and optional traces to create conductive vias and optional conductive lines. A complex comprising: (a) a first pure copper structure having a controlled oxidized first copper surface layer comprising Cu-(I) and Cu-(II) oxide species, wherein the converted Cu-(I) oxide species have nano Mi-crystalline structure and the converted Cu-(II) oxide species are acicular Cu-(II) oxide species, wherein the Cu-(I) oxide species are interspersed with the acicular Cu-(II) oxide species ) oxide species, wherein the Cu-(I) oxide species form a layer thickness of 5 nm to 100 nm in the controlled oxidation first copper surface layer, and the acicular Cu-(II) oxide species have a thickness up to 500 nm , preferably 100 nm to 500 nm in length; (b) the first non-conductive organic material layer, preferably containing polyimide resin, containing polybenzoxazole resin or containing epoxy resin or a mixture thereof; (c) wherein the first non-conductive organic material layer is attached to the controlled oxidation first copper surface.

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