WO2014064050A1

WO2014064050A1 - Treatment of preforms containing copper with a mixture containing chlorine-free and carboxyl-free acids and oxidants

Info

Publication number: WO2014064050A1
Application number: PCT/EP2013/071966
Authority: WO
Inventors: Thomas PAASCHE; Henning Urch
Original assignee: Basf Se
Priority date: 2012-10-25
Filing date: 2013-10-21
Publication date: 2014-05-01
Also published as: TW201418521A

Abstract

A method for treating preforms containing copper, wherein an aqueous mixture (M), containing (a.) chlorine-free acids without carboxyl groups, (b.) oxidants, (c.) aqueous solvent and optionally further additives is brought into contact with the preform. The method is inter alia characterized in that the aqueous mixture (M) additionally (e.) contains dissolved copper after etching or pickling and is separated from the preform. The invention also relates to a method for processing the separated aqueous mixture (M), which additionally contains dissolved copper, by electrolysis. The invention further relates to mixtures (MI) containing (a.) from 10 to 40% w/w methane sulphonic acid, (b.) from 10 to 20% w/w hydrogen peroxide and (c.) from 40 to 80% w/w water and to the use thereof for etching or pickling preforms containing copper.

Description

TREATMENT OF FORM BODIES CONTAINING COPPER WITH A MIXTURE

CONTAINING CHLORINE AND CARBOXL-FREE ACIDS AND OXIDIZING AGENTS

description

The present invention relates to a process for the treatment of moldings containing copper with a mixture containing chlorine-free acids without carboxyl groups and Oxidati- onsmittel. Furthermore, the invention also relates to mixtures comprising methanesulfonic acid and hydrogen peroxide. Another object of the invention is the use of such mixtures containing chlorine-free acids without carboxyl groups and oxidizing agents, in particular methanesulfonic acid and hydrogen peroxide, for etching or pickling of moldings containing copper.

Further embodiments of the present invention can be taken from the claims, the description and the examples. It is understood that the features mentioned above and those yet to be explained of the subject matter according to the invention can be used not only in the particular concretely specified combination but also in other combinations without departing from the scope of the invention. Preferred or very preferred are the embodiments of the present invention in which all features have the preferred or very preferred meanings.

Copper and copper alloys are often used as conductive materials in the semiconductor manufacturing field. Copper tracks are often found to be conductive connecting elements of semiconductor structures, for example in integrated circuits on boards.

In the fabrication of semiconductor structures, effective processes, such as wet chemical etching techniques, are required in various process steps to remove copper or copper alloys. This often causes problems, since the removal of the copper is usually uneven and can lead to the formation of surface irregularities or generally problems with anisotropic removal at grain boundaries. For example, it is difficult to create smooth straight edges on isolated structures by uniform removal of copper. There is therefore a need for wet-chemical etching processes which lead to well-defined structures, in particular to structures with smooth surfaces and defined edges, in the removal of copper-containing materials.

In the wet-chemical removal of copper by etching, mixtures containing acids, for example hydrochloric acid, acetic acid, sulfuric acid or nitric acid and oxidizing agents such as pereroxides, persulfates, permanganates, Fe (III) solutions, bromine or Cr (VI) compounds are frequently used.

WO 201 1/0171 19 A2 describes wet-chemical etching processes for removing copper in the processing of semiconductors by means of solutions comprising complexing agents and oxidizing agents in a pH range from 5 to 12. US 2005/0056616 A1 and US 2006/0183056 A1 describe methods for etching copper and copper alloys. With the aid of compositions containing weak and strong complexing agents for copper and oxidizing agents, the surfaces of copper or copper alloys are treated at a pH of 6 to 12.

US 7,465,408 B1 describes methods of etching copper-containing materials by first contacting the material with a first solution which converts a portion of the material to a passivating layer. This first solution contains a peroxide, a first organic acid, and water at a pH of 2 to 6. Subsequently, the passivating coating is contacted with a second solution to remove the passivating film, this second solution being a second contains organic acid and water.

For example, in the manufacture of printed circuit boards, copper is often deposited on an epoxy resin board. On the copper layer, a photoresist (photoresist) is applied and selectively exposed at certain points. Unexposed residues of the photoresist are usually removed in further processing steps with alcoholic solutions. The copper layers, which were under the unexposed photoresist, now also often have to be etched away wet-chemically. Frequently, in industrial processes, aqueous mixtures of CuC, FeC or HCl and hydrogen peroxide are used as etching mixtures for removing or building structures containing copper or for pickling surfaces containing copper. The resulting in these wet chemical etching mixtures contain after removal of the copper in addition to the copper ions a high proportion of chloride ions in the solution and are therefore a simple reprocessing and recovery of copper, for example by electrolysis, because of the formation of chlorine gas, difficult to access.

The object of the present invention was therefore to find processes for the treatment of moldings containing copper, which allow a simple reprocessing and recovery of copper after the treatment. A further object of the invention was to provide wet-chemical etching processes which lead to well-defined structures in the removal of copper-containing materials, in particular to structures with smooth surfaces and defined edges. These objects are achieved by a method for the treatment, preferably for etching or pickling, of moldings containing copper, wherein an aqueous mixture (M) containing (a) chlorine-free acids without carboxyl groups, (b.) Oxidizing agent and (c.) Aqueous Solvent, is brought into contact with the molding. The content of copper of moldings containing copper can vary over a wide range depending on the use of the molding. Frequently, for example, populated boards contain up to 25% by weight of pure copper. In other cases, the layer thickness of the copper is from 20 to 45 μηι thick, which corresponds to about 0.02 wt .-% with an assumed total thickness of a board of 1 mm. In the case of thinner circuit boards, the relative content of copper thus generally increases.

As a rule, such molded articles contain from 0.01% by weight to 50% by weight of copper, based on the total amount of molding. Particularly preferably from 0.01 to 25 wt .-%. Further preferably, the copper occurs in the form of metallic copper or copper alloys with other metals, such as molybdenum.

In a preferred embodiment of the process according to the invention, the chlorine-free acids without carboxyl groups (a.) Are selected from the group of alkylsulfonic acids, tetrafluoroboric acid, sulfuric acid, hexafluorosilicic acid, trifluoroacetic acid, trifluoromethanesulfonic acid. Methanesulfonic acid is particularly preferred as chlorine-free acid without carboxyl groups (a.). In a further preferred embodiment of the process according to the invention, the oxidizing agents (b.) Are selected from the group of peroxide compounds and perborate compounds, preferably from the group consisting of hydrogen peroxide, sodium perborate, barium perborate, carbamate peroxide and urea peroxide, peroxycarboxylic acids such as peramaic acid or peracetic acid. Very particular preference is given to hydrogen peroxide as oxidizing agent (b.).

The component (c.) Contains as an aqueous solvent from 10 to 100 wt .-% water. Preference is given to using water as the aqueous solvent (c.). In addition to water, further polar liquids such as alcohols or ionic liquids may be present in the aqueous solvent.

In a particularly preferred embodiment of the process according to the invention are used as chlorine-free acids without carboxyl group (a.) Alkylsulfonsäuren, especially methanesulfonic acid, as the oxidizing agent (b.) Hydrogen peroxide and as an aqueous solvent (c.) Water.

The aqueous mixture (M) may contain as additional component (d.) Additional additives. Preferred additives (d.) Here are surfactants, complexing agents or corrosion inhibitors. As a rule, surfactants serve to improve the wetting of the molding or of the copper with the aqueous mixture (M). It is possible to use anionic, cationic, nonionic or amphoteric surfactants. The surfactants may also be polymeric surfactants and preferably have a block structure. Surfactants are known to those skilled in the art and knowledgeable in the art and can be purchased commercially. It is preferred to use anionic or nonionic surfactants. For example, alkyl polyglycosides can be used as surfactants. Complexing agents are often used to complex copper ions and thus to accelerate the dissolution process of the copper. Corresponding complexing agents are known to the skilled person from the prior art and his expertise and can be purchased commercially. For example, ethylenediaminetetraacetic acid (EDTA), methylglycine diacetic acid, glutamic acid diacetic acid (GLDA) or nitrilotriacetic acid (NTA) can be used as complexing agent.

As a rule, corrosion inhibitors are used in the treatment of moldings containing copper to prevent or suppress unwanted corrosion effects on materials. Corresponding corrosion inhibitors are known to those skilled in the art and their knowledge and can be purchased commercially. For example, alkyl phosphates, 2-butyne-1,4-diol, propargyl alcohol, ethynylcarbinol alkoxylate, polyethylene lenimin, thiodiglycol ethoxylate can be used as corrosion inhibitors. In a further preferred embodiment of the process according to the invention, the aqueous mixture contains (M)

(A) from 10 to 40% by weight, preferably from 10 to 25% by weight, of the chlorine-free acids without carboxyl groups (a.),

(B) from 1 to 50% by weight, preferably from 10 to 20% by weight, of the oxidizing agent (b.), (C.) from 10 to 89% by weight, preferably from 55 to 80% by weight. -% aqueous solvent

(c), and

(D.) from 0 to 10% by weight of the additional additives (d.),

wherein the quantities are in each case based on the total amount of components (a.), (b.), (c.) and (d.) and the sum of the amounts of all components (a.), (b.), (c. ) and (d.) is 100% by weight. In the mixture (M), in particular before the treatment of the shaped body, particular preference is given to containing no further components apart from the components (a.), (B.), (C.) And optionally (d.).

The total amount of all additives (d.) In the aqueous mixture (M) is, as described above, in the range from 0 to 10% by weight, preferably from 0 to 5% by weight, in particular from 0 to 3% by weight. -%. Surfactants are preferably used in an amount of 0.5 to 2 wt .-%. Complexing agents are preferably used in an amount of 0.5 to 5 wt .-%. Corrosion inhibitors are preferably used in an amount of 0.1 to 1 wt .-%. In general, the aqueous mixture (M) has a pH of from -0.5 to 5, preferably from 0 to 5, particularly preferably from 0 to 3, very particularly preferably from 0 to 2, in particular from 0 to 1 , The pH of the mixture (M) is determined by glass electrode.

In general, the copper contained may be distributed arbitrarily in the molding as long as it at least partially in contact with the aqueous mixture (M) or comes into contact or is brought into contact. Preferably, the copper contained is at least partially on at least one surface of the shaped body. Very particularly preferred as flat layer on one side of the molding or on one or more other metal layers. Particularly preferred on a layer containing molybdenum

Preferably, the molded body is a printed circuit board (board) or printed circuit board.

It was surprisingly found that the necessary etching times in the process according to the invention were comparable to processes in which hydrochloric acid is used. Another advantage of the method according to the invention is therefore that the chlorine-free acids without carboxyl groups, in particular methanesulfonic acid, are significantly less corrosive than hydrochloric acid and nevertheless lead to short processing times and smooth straight surfaces and well-defined edges.

In the context of the process according to the invention for the treatment of shaped bodies containing copper, copper is usually removed from or from the shaped body, preferably metallic copper in the form of copper ions is separated from or from the shaped body.

In a preferred embodiment of the process according to the invention, after the treatment, preferably after etching or pickling, the aqueous mixture (M) additionally contains dissolved copper, preferably in the form of copper ions, and the aqueous mixture is separated from the solid in a further process step. A so-called waste solution is obtained.

Another object of the invention is a process for working up the aqueous mixture (M), which additionally contains (e.) Dissolved copper (waste solution), wherein an electrolysis is carried out on this waste solution to at least partially deposit the dissolved copper as metallic copper. Typical conditions for the electrowinning of copper on stainless steel electrodes are high current densities of 250-1000A / m ² at 0.3-0.4V. The electrode distance is 5 to 50 mm. In this way, a simple and inexpensive process for recovering copper from the waste solutions is feasible. Since the chlorine-free acids without carboxyl groups contain no chlorine, the electrolysis does not cause any disturbing chlorine evolution. It has usually been necessary for companies to transport their waste solutions to an external recycling or disposal company in order to have their recycling or disposal carried out there. With the aid of the method according to the invention, such operations are now able to cost-effectively carry out a work-up of their waste solutions internally and thereby recover copper.

Another object of the present invention are mixtures (MI), containing (a.) From 10 to 40 wt .-% of methanesulfonic acid, (b.) From 10 to 20 wt .-%, preferably from 15 to 20

Wt .-% hydrogen peroxide and (c.) From 40 to 80 wt .-% water. These mixtures can also be excellently mixed with further additives (d.) In the context of the process according to the invention. rens for the treatment of moldings containing copper. As a rule, from 0 to 10% by weight of additives (d.) Are contained in the mixtures. The quantities given in each case relate to the total amount of components (a.), (B.), (C.) And optional (d.) And the sum of the amounts of all components (a.), (B.), (C) , (d.) is 100% by weight.

In particular, these mixtures according to the invention can be used for etching or pickling of shaped bodies containing copper, wherein preferably the copper contained is at least partially located on at least one surface of the shaped body. In a preferred embodiment of the use according to the invention, the shaped body is a circuit board.

The present invention provides processes for the treatment of moldings containing copper which, after treatment, allow easy reprocessing and recovery of copper. Furthermore, wet-chemical etching processes are provided which lead to well-defined structures, in particular to structures with smooth surfaces and defined edges, when removing copper-containing materials.

The invention is explained in more detail by the examples, without the examples limiting the subject matter of the invention.

Examples

The aqueous mixture M1 was obtained by mixing the individual components with water.

M1: 10% by weight of methanesulfonic acid (MSA), 15% by weight of H ₂ O ₂ , 75% by weight of H ₂ O.

As a comparison mixture V1, a mixture of 10 wt .-% MSA and 90 wt .-% H2O was used.

Example 1: Measurement of polarization resistance Rp

The determination of the polarization resistance was carried out in a potential range of ± 5 mV against the corrosion potential (Ecorr) using a scan rate of 0.1 mV / s. The measured potential (E) plotted against the current density (j) was fitted to a straight line, from the slope of the line Rp was determined.

The Rp value indicates the resistance of a metal to the transfer of electrons to an electroactive species in solution. Higher values of Rp mean higher corrosion resistance to uniform corrosion. Lower values thus correlate with a faster dissolution of the metal. Resolution of copper:

For V1, Rp values of 2000 to 14000 Qcm ^{2 were} determined over a period of 20 hours, while mixture M1 reached a value of 4 Qcm ^{2 over} a period of 50 minutes.

Example 2: Measurement of the potential

Measurements of the potential (E: caloric reference electrode saturated with reference cell vs. SCE) versus time or current density show the significantly increased rate of copper dissolution for M1 compared to V1. The value of E for M1 is about +0.22 V while for V1 it is about -0.5 V in a period up to 60 hours.

Example 3: Etching printed circuit boards

On copper coated circuit boards (5 x 2 cm, copper layer thickness 45μηη, on epoxy plastic) geometric patterns were recorded using a waterproof pen.

The following aqueous comparative solutions (VL1-VL5) were prepared:

For VL1 and VL2, the remainder is 100% by weight of water. Furthermore, the following aqueous solutions according to the invention (L6-L15) were prepared:

The remainder to 100% by weight is water at L6 to L15. The copper-coated circuit boards were placed at a temperature of 18 ° C in 100 ml of the respective solution.

The following dissolution times resulted in minutes:

VL1 VL2 VL3 VL4 VL5 L6 L7 L8 L9 L10 L1 1 L12 L13 L14 L15

10 12 50 50 50 12 12 12 24 24 12 12 12 12 12 After visual assessment of the dissolution of the experiment was terminated after the appropriate time to prevent further oxidation of the copper.

The copper-coated circuit boards were further laid at 100 ° C. of the respective solution at a temperature of 18 ° C. for 12 to 50 minutes.

The quality of the solutions was as follows

It is an optical evaluation of the etching quality. It was evaluated whether the geometric patterns after etching were comparable to VL1: o, better: +, or worse: -.

Claims

claims:

1 . Process for the treatment of shaped bodies containing copper, characterized in that an aqueous mixture (M) containing

(a.) chlorine-free acids without carboxyl groups,

(b.) oxidizing agent,

(c.) aqueous solvent,

is brought into contact with the molding.

2. The method according to claim 1, characterized in that the aqueous mixture (M) continues

(d.) contains additional additives.

3. The method according to claim 1 or 2, characterized in that the aqueous mixture (M)

(A) from 10 to 40% by weight of the chlorine-free acids without carboxyl groups (a.).

(B) from 1 to 50% by weight of the oxidizing agent (b.),

(C) from 10 to 89% by weight of aqueous solvent (c), and (D) from 0 to 10% by weight of the additional additives (d.), The amounts given being based on the total amount of components ( a.), (b.), (c.) and (d.) are referred to and the sum of the amounts of all components (a.), (b.), (c.) and (d.) 100 wt. % is.

4. Process according to claims 1 to 3, characterized in that the aqueous mixture (M) has a pH of -0.5 to 5.

5. The method according to claims 1 to 4, characterized in that the copper contained is at least partially located on at least one surface of the shaped body and is brought into contact with the aqueous mixture.

6. Process according to claims 1 to 5, characterized in that the shaped body is a circuit board.

7. Process according to claims 1 to 6, characterized in that the aqueous mixture (M) additionally contains (e.) Dissolved copper after the etching or pickling and is separated from the solid.

8. A process for working up the separated aqueous mixture (M), which additionally contains dissolved copper according to claim 7, characterized in that an electrolysis is performed to at least partially deposit the dissolved copper as metallic copper.

9. Mixtures (MI) containing

(a.) from 10 to 40% by weight of methanesulfonic acid,

(b.) From 10 to 20 wt .-% hydrogen peroxide

(c.) From 40 to 80 wt .-% water.

10. Use of mixtures according to claims 1 to 7 or according to claim 9 for etching or pickling of moldings containing copper.

1 1. Use according to claim 10, wherein the copper contained is at least partially on at least one surface of the molding.

12. Use according to claim 10 or 11, wherein the shaped body is a printed circuit board.