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ORGANIC ADDITIVE SYSTEM for ELECTRODEPOSITION of COPPER FROM ACID COPPER PLATING BATHS

IP.com Disclosure Number: IPCOM000040648D
Original Publication Date: 1987-Dec-01
Included in the Prior Art Database: 2005-Feb-02
Document File: 3 page(s) / 47K

Publishing Venue

IBM

Related People

David, AP: AUTHOR [+2]

Abstract

Electrodeposition of level, bright, and ductile copper deposits onto irregular conducting surfaces, using a range of current densities, is accomplished with an additive plating system which is described in the following. The additive mixture is a chemical composition selected from four classes of chemicals. The first class comprises certain water-soluble polymers which adsorb at the copper plating interface. This group includes polythylene diamine co-adipic acid, polyethylene glycol and polypropylene glycol. The unique characteristic of this group of water soluble polymers is their net positive charge in acidic solution and subsequent very strong adsorption at the copper cathode interface in the presence of previously adsorbed halide ions.

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ORGANIC ADDITIVE SYSTEM for ELECTRODEPOSITION of COPPER FROM ACID COPPER PLATING BATHS

Electrodeposition of level, bright, and ductile copper deposits onto irregular conducting surfaces, using a range of current densities, is accomplished with an additive plating system which is described in the following. The additive mixture is a chemical composition selected from four classes of chemicals. The first class comprises certain water-soluble polymers which adsorb at the copper plating interface. This group includes polythylene diamine co-adipic acid, polyethylene glycol and polypropylene glycol. The unique characteristic of this group of water soluble polymers is their net positive charge in acidic solution and subsequent very strong adsorption at the copper cathode interface in the presence of previously adsorbed halide ions. The function of these polymers is primarily to improve bath throwing power by forming a

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strongly adsorbed film which uniformly limits current over the entire plated surface. It is important that the polymers chosen adsorb with adequate strength to limit current flow only in the presence of a halide ion. Steady-state polarization curves (Fig. 1) show the influence of a polymer and a polymer in the presence of chloride ions upon interfacial currents as a function of applied potential. The concentration of this component in the bath should be between 50 and 500 parts per million (ppm). The second class of chemicals includes the halide ions (fluorine, chlorine, bromine and iodine). The function of the halide ions in the overall formulation is to aid in forming a uniformly adsorbed film by pinning water-soluble polymers to the plated surface. Halide ions should be present in the bath at concentrations between 20 and 200 ppm.

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The third class of compounds includes molecules which exhibit grain refining, ductility promoting, and brightening properties during acid copper electrodeposition. These molecules are of the general structure A-B-C-D, in which A _ _ _ _ is a highly ionized functional group such as SO-3, along with any counter ion such as Na+
. B is an unsubstituted alkane or alkene chain of between two and seven carbons in length. C is a single carbon atom bonded to one or more su...