TW201326465A - Aqueous composition for etching of copper and copper alloys - Google Patents

Abstract

The present invention relates to an aqueous composition and a process for etching of copper and copper alloys. The aqueous composition comprises Fe3+ ions, an acid and a N-alkoxylated polyamide. The aqueous composition is particularly useful for making of tine structures in the manufacture of printed circuit boards, IC substrates and the like.

Description

Aqueous composition for etching copper and copper alloys

This invention relates to aqueous compositions for etching copper and copper alloys in the manufacture of printed circuit boards, IC substrates, copper-containing semiconductor wafers, and the like, and processes for etching copper and copper alloys.

Forming circuit circuits by etching copper or copper alloy layers produces standard fabrication steps for printed circuit boards, IC substrates, and related devices.

A negative pattern of the circuit is formed by a) applying a resist on the copper layer (eg, a polymeric dry film resist or a metal resist), b) etching away copper that is not covered by the resist And a portion thereof, and c) removing the resist from the remaining copper circuitry.

The etching solution applied for this task is selected from different types of compositions, such as mixtures of oxidizing agents and acids. The two main types of etching solutions are based on acids such as sulfuric acid or hydrochloric acid and contain hydrogen peroxide or Fe ³⁺ ions (added as FeCl ₃ ) as the oxidizing agent. Such etching solutions are disclosed in CFCoombs, Jr., "Printed Circuits Handbook", 5th Edition, 2001, Chapter 33.4.3, pages 33.14 to 33.15 and Chapter 33.4.5, page 33.17.

The ongoing circuit miniaturization of the line width/line spacing values and thicknesses of the etched copper layer does not allow the use of conventional etching solutions, such as those set forth above.

If copper traces are fabricated by a semi-additive process (SAP), the disadvantages of even more known etching solutions are exhibited. Here, the bare dielectric substrate is first coated with a seed layer serving as a conductive layer. The seed layer includes, for example, by electroless plating Copper of the product. Next, a patterned resist layer is formed over the seed layer and a thicker second copper layer is deposited by electroplating into the openings of the patterned resist layer on the seed layer. The patterned resist layer is stripped and the seed layer deposited by electroplating between the copper traces needs to be removed by a differential etching step. The seed layer deposited by electroless plating has a finer grain structure than the second copper layer deposited by electroplating. Different grain structures can produce different etching behaviors for the individual copper layers.

A similar situation exists when a copper trace is fabricated by a modified semi-additive process (m-SAP) in which a thick second copper layer is deposited in the opening of the patterned resist layer on the first thin copper layer. The first copper layer is fabricated by, for example, thinning a copper cladding attached to a dielectric substrate. Also, the first and second copper layers have different grain structures.

The etching solution applied for the differential etching step should remove only the first copper layer between the copper traces without invading the sidewalls of the copper trace deposited by electroplating and the top and underlying first copper layer or copper seed crystal Floor.

An etching solution based on sulfuric acid and hydrogen peroxide would undesirably undercut the first copper layer during etching (Fig. 1), which would result in insufficient adhesion of the copper layer to the dielectric substrate.

Etching solutions based on sulfuric acid and Fe ³⁺ ions typically exhibit an etch behavior as shown in FIG. A wider substrate that is etched with copper can cause an unacceptable short circuit.

The object of the invention

Accordingly, a first object of the present invention is to provide an aqueous composition for etching copper and a copper alloy that forms a rectangular copper feature after etching.

A second object of the invention is to remove Cu ²⁺ ions from the aqueous composition.

The first object is solved by an aqueous composition for etching copper and a copper alloy, the composition comprising an etch of Fe ³⁺ ions, at least one acid, and at least one selected from the group consisting of N-alkoxylated polydecylamines. An additive, the N-alkoxylated polyamine amine system a) is obtained by N-alkoxylation of polyamine with one or more compounds of the formula (I), Wherein R ₁ is hydrogen or a hydrocarbon residue having 1 to 6 carbon atoms and R ₂ is hydrogen or a hydrocarbon residue having 1 to 6 carbon atoms and/or b) by N-alkoxylated indoleamine The polymerization was obtained.

When the aqueous composition of the present invention is applied, a rectangular line shape of the etched copper or copper alloy structure is achieved. Therefore, the risk of short circuit between individual copper or copper alloy structures is minimized. In addition, sufficient adhesion is achieved between the etched copper or copper alloy structure and the underlying dielectric substrate.

The second object of the present invention is solved by a process for etching copper and a copper alloy, the process comprising the steps of: a. providing a substrate having a copper or copper alloy surface, b. providing the substrate with the water of the present invention The composition is contacted in a first tank wherein copper is oxidized to Cu ²⁺ ions during contact and Cu ²⁺ ions are present in the aqueous composition of the invention, c. a portion of the aqueous composition of the invention after contact with the substrate Transferring to a second tank, wherein the second tank includes an anode and a cathode, and d. reducing the Cu ²⁺ ions to copper by applying a current between the anode and the cathode.

Etching a layer of copper or copper alloy using an aqueous composition for etching copper and a copper alloy, the composition comprising Fe ³⁺ ions, at least one acid, and at least one group selected from the group consisting of N-alkoxylated polyamines An etch additive, the N-alkoxylated polyamine amine a) obtained by N-alkoxylation of polyamine with one or more compounds of formula (I), Wherein R ₁ is hydrogen or a hydrocarbon residue having 1 to 6 carbon atoms and R ₂ is hydrogen or a hydrocarbon residue having 1 to 6 carbon atoms and/or b) by N-alkoxylated indoleamine The polymerization was obtained.

Preferably, R ₁ and R ₂ in the compound of formula (I) are preferably hydrogen and methyl. Most preferably, R ₁ and R ₂ are hydrogen.

The N-alkoxylated indoleamine is selected from the group consisting of compounds of formula (II): Wherein R ₃ is hydrogen or methyl, A is a hydrocarbon residue, n is an integer of 2 to 10, more preferably 2 to 5, and m is an integer of 1 to 50, more preferably 1 to 12.

The hydrocarbon residue A is preferably a -CH ₂ - group.

Preferably, the N-alkoxylated indoleamine of formula (II) is selected from the group consisting of ethoxylated β-endoyamine, hexaethoxylated γ-butylide, and octa Oxylated δ-valeroinamide, pentapropoxylated δ-valeroinamide, hexaethoxylated ε-caprolactam and dodecaethoxylated ε-caprolactam.

At least one etching additive obtained by N-alkoxylation of polyamine with one or more compounds of formula (I) is an N-alkoxylated polyamine. Such polymers can be obtained, for example, by expanding a polyamine in an alkylene oxide compound of formula (I) at a temperature in the range of from 10 ° C to 40 ° C, followed by a temperature in the range of from 100 ° C to 160 ° C. The alkylene oxide compound of the formula (I) is further added. A detailed description of the synthetic method is disclosed in DE 913 957.

The N-alkoxylated polydecylamine can be obtained by subjecting the monomer of the formula (II) to ring-opening polymerization at, for example, 260 ° C in an inert atmosphere of nitrogen for about 4 to 5 hours.

The concentration of the at least one etching additive in the aqueous composition is between 0.001 g/l and 10 g/l, more preferably 0.005 g/l to 5 g/l and most preferably between 0.01 g/l and 1 g/l.

Fe ³⁺ ion source of water-soluble salt is selected from Fe ³⁺ ions. The ^preferred source of Fe ³⁺ ions is Fe ₂ (SO ₄ ) ₃ .

The concentration of Fe ³⁺ ions is between 1 g/l and 100 g/l, more preferably 1 g/l to 50 g/l and most preferably between 5 g/l and 40 g/l.

The at least one acid is selected from the group consisting of inorganic acids such as sulfuric acid and organic acids such as methanesulfonic acid. The best acid is sulfuric acid and methanesulfonic acid.

The concentration of the acid (or all acids together if more than one acid is added) is from 10 g/l to 400 g/l, more preferably from 30 g/l to 300 g/l and most preferably from 50 g/l Between 200 g/l.

Optionally, the aqueous composition further comprises one or more of the following: Fe ²⁺ ions, surfactants, corrosion inhibitors (selected from triazoles, benzotriazoles, imidazoles, benzimidazoles, tetrazoles, and isocyanates) , organic sulfur compounds (such as thiourea and sulfosalicylic acid) and polyalkylene compounds (such as polyethylene glycol, polypropylene glycol, polyethylene glycol and polypropylene glycol copolymers and derivatives thereof).

The substrate is preferably treated by spraying the aqueous composition of the present invention onto a substrate. The aqueous composition can be sprayed in a vertical mode or a horizontal mode, depending on the desired device. Alternatively, the substrate can be immersed in the aqueous composition by soaking.

The temperature of the aqueous composition of the present invention during use is between 10 ° C and 60 ° C, more preferably between 20 ° C and 50 ° C and most preferably between 30 ° C and 45 ° C. The contact time depends on the thickness of the copper to be etched and is between 10 s and 360 s, more preferably 20 s to 200 s and most preferably between 30 s and 90 s.

The aqueous composition is enriched in Cu ²⁺ ions during use. At the same time, Fe ³⁺ ions are reduced to Fe ²⁺ ions. Cu ²⁺ ions have a negative impact on the performance of aqueous compositions. Cu ²⁺ ions increase the density and viscosity of the etching solution and thereby negatively affect the etching behavior. For example, the etch rate and sidewall etch performance are reduced. In addition, Cu ²⁺ ion complexes can precipitate. Such precipitates pose a mechanical hazard to the equipment and the surface in contact with the aqueous composition.

In prior art processes, some or all of the added Cu ²⁺ ions are removed by overflowing (removing) the appropriate amount of etching solution and adding (supplying) a fresh etching solution to the remaining solution.

A particular method of removing Cu ²⁺ ions from aqueous solutions is to electrolytically reduce Cu ²⁺ ions to metallic copper.

In principle, electrolysis requires a second tank equipped with an anode and a cathode and a rectifier.

The aqueous composition of the present invention is partially transferred from a first tank in which etching of a copper or copper alloy layer is performed to a second tank equipped for electrolysis. During electrolysis, Cu ²⁺ ions are reduced to metallic copper at the cathode and Fe ²⁺ ions are anodized to Fe ³⁺ ions.

Metal copper can be collected and recycled. In the absence of an electrolytic regeneration cell, it is necessary to continuously add an oxidizing agent (Fe ³⁺ ion) to the etching solution. By applying the above regeneration, the consumed Fe ³⁺ ions are regenerated at the anode (Fe ^{2+ is} oxidized to Fe ³⁺ ) and thus there is no need to add (supply) the oxidant during use of the etching solution.

Halide ions are not preferred in aqueous compositions when used in the process of the present invention because they oxidize during the electrolysis reaction and thereby form dihalogen molecules.

Methods and apparatus that can be used in this process are disclosed in US 2006/0175204 A1. The method involves supplying an etching solution to a hermetic seal or an electrolytic cell having an anode casing, the electrolytic cell comprising a cathode, an inert anode, a member for removing electrolytically deposited copper from the cathode, and for collecting the removed copper and A member that removes the potential applied by copper, wherein the electrolytic cell does not have an ion exchange membrane or membrane.

Another application of the aqueous compositions for etching copper and copper alloys of the present invention is to clean the copper or copper alloy surface prior to other processing steps, such as depositing weldable or bondable surface finishes. Etching cleaning system This is because the copper or copper alloy surface is cleaned, for example, by a copper oxide phase and/or an organic residue, and a portion of the surface of the copper or copper alloy is etched away thereby exposing the "fresh" copper or copper alloy surface, and This applies to other process steps.

Another application of the aqueous composition for etching copper and copper alloys of the present invention is to microscopically roughen the surface of the copper or copper alloy to improve adhesion of the resist material (e.g., photoresist) or solder mask.

Instance

The invention will now be explained by reference to the following non-limiting examples.

A substrate comprising a dielectric layer, a seed layer (obtained by electroless copper plating), and a patterned second copper layer (obtained by electroplating) was used in all examples.

The seed layer not covered by the patterned second copper layer was etched away by spraying different aqueous compositions onto the substrate at an adjusted etch rate of 2 μm/min. The contact time is adjusted to provide the desired copper removal. The sample was rinsed with water and the dry film resist was stripped.

After the nickel layer was deposited on the copper traces during the preparation of the profile to serve as a protective layer, the shape of the line obtained by etching the copper traces was studied by optical microscopy.

Example 1 (comparative)

An aqueous composition consisting of 20 g/l H ₂ O ₂ and 90 g/l sulfuric acid was applied as an etching solution.

The resulting line shape of the copper trace (trace width: 8 μm, trace height: 10 μm) is shown in FIG. The copper trace shows that the trace substrate (i.e., the seed layer obtained by electroless copper plating) is severely undercut. Therefore, copper traces do not have the required It has a rectangular shape and is not sufficiently adhered to the underlying dielectric substrate.

Example 2 (comparative)

An aqueous composition consisting of 5 g/l of Fe ₂ (SO ₄ ) ₃ and 90 g/l of sulfuric acid was applied as an etching solution.

The resulting line shape of the copper trace (trace width: 20 μm, trace height: 10 μm) is shown in FIG. The copper traces show a significant trapezoidal shape. Thus, copper traces do not provide the desired rectangular shape and create a risk of shorting or crosstalk between individual traces.

Example 3

Application of 15 g/l Fe ₂ (SO ₄ ) ₃ , 90 g/l sulfuric acid and 0.1 g/l N-ethoxylated polyamine 6 (by ε-caprolactam-N-ethoxylate) The ring-opening polymerization obtains an aqueous composition of the composition as an etching solution.

The resulting line shape of the copper trace (trace width: 8 μm, trace height: 10 μm) is shown in FIG. The copper trace has a desired rectangular line shape that is sufficiently adhered to the underlying dielectric substrate and does not pose a risk of short circuit.

Figure 1 shows two copper traces obtained by etching using an aqueous composition consisting of sulfuric acid and hydrogen peroxide (comparative example).

Figure 2 shows copper traces obtained by etching using an aqueous composition consisting of sulfuric acid and Fe ³⁺ ions (comparative example).

Figure 3 shows two copper traces obtained by etching using the aqueous composition of the present invention.

Claims (14)

An aqueous composition for etching copper and copper alloys comprising Fe ³⁺ ions, at least one acid, and at least one etching additive selected from the group consisting of N-alkoxylated polydecylamines. An aqueous composition for etching copper and a copper alloy according to claim 1, wherein the N-alkoxylated polyamine is an N-alkoxy group by polyamine using one or more compounds of the formula (I). Gain, Wherein R ₁ is hydrogen or a hydrocarbon residue having 1 to 6 carbon atoms and R ₂ is hydrogen or a hydrocarbon residue having 1 to 6 carbon atoms. An aqueous composition for etching copper and a copper alloy according to claim 1, wherein R ₁ and R ₂ in the formula (I) are selected from the group consisting of hydrogen and methyl. An aqueous composition for etching copper and a copper alloy according to claim 1, wherein the concentration of the at least one etching additive is between 0.001 g/l and 10 g/l. An aqueous composition for etching copper and a copper alloy according to claim 1, wherein the concentration of Fe ³⁺ ions is between 1 g/l and 100 g/l. An aqueous composition for etching copper and a copper alloy according to claim 1, wherein the at least one acid is selected from the group consisting of sulfuric acid and methanesulfonic acid. An aqueous composition for etching copper and a copper alloy according to claim 1, wherein the concentration of the at least one acid is between 10 g/l and 400 g/l. An aqueous composition for etching copper and a copper alloy, comprising Fe ³⁺ ions, at least one acid, and at least one etching additive selected from the group consisting of N-alkoxylated polyamines, wherein the N-alkoxylated poly The guanamine is obtained by the polymerization of the N-alkoxylated indoleamine of the formula (II). Wherein R ₃ is selected from the group consisting of hydrogen and methyl, the A-based hydrocarbon residue, n is an integer from 2 to 10 and m is an integer from 1 to 50. An aqueous composition for etching copper and a copper alloy according to claim 8, wherein the N-alkoxylated indoleamine of the formula (II) is selected from the group consisting of ethoxylated β-endoamine , hexaethoxylated γ-butyrolactam, octaethoxylated δ-valeroinamide, pentapropoxylated δ-valeroinamide, hexaethoxylated ε-caprolactam and ten Diethoxylated ε-caprolactam. An aqueous composition for etching copper and a copper alloy according to claim 8, wherein the concentration of the at least one etching additive is between 0.001 g/l and 10 g/l. An aqueous composition for etching copper and a copper alloy according to claim 8, wherein the concentration of Fe ³⁺ ions is between 1 g/l and 100 g/l. An aqueous composition for etching copper and a copper alloy according to claim 8, wherein the at least one acid is selected from the group consisting of sulfuric acid and methanesulfonic acid. An aqueous composition for etching copper and a copper alloy according to claim 8, wherein the concentration of the at least one acid is between 10 g/l and 400 g/l. A method for etching copper and a copper alloy, comprising the steps of: a. providing a substrate having a copper or copper alloy surface, b. causing the substrate to include Fe ³⁺ ions, at least one acid, and at least one selected from the group consisting of An aqueous composition of an N-alkoxylated polydecylamine etch additive is contacted in a first tank wherein copper is oxidized to Cu ²⁺ ions during contact and the Cu ²⁺ ions are present in the aqueous composition, c. Transferring a portion of the aqueous composition to a second tank after contact with the substrate, wherein the second tank includes an anode and a cathode, and d. the Cu ²⁺ is applied by applying a current between the anode and the cathode The ions are reduced to copper.