Low internal stress copper electroplating method
Copper electroplating methods provide low internal stress copper deposits. Concentrations of accelerators in the copper electroplating bath vary as a function of the plating current density and the low internal stress copper deposit is observed as a matt copper deposit.
1. A method comprising:
a) contacting a Hull Cell metal test panel with a composition comprising one or more sources of copper ions, one or more suppressors and an accelerator at a given concentration in a range of 1 ppm and greater;
b) applying a current to the Hull Cell metal test panel for a given period of time over different current densities to electroplate copper on the Hull Cell metal test panel;
c) determining MattCDmax by correlating a current density where the electroplated copper deposit transitions from matt to bright at the given concentration of the accelerator; and
d) electroplating copper with a matt appearance from the composition at the MattCDmax or at a lower current density below the MattCDmax on a substrate at the given concentration of the accelerator or optionally at a greater accelerator concentration than the given accelerator concentration.
2. The method of claim 1 , wherein the accelerator is chosen from one or more of 3-mercaptopropane-1-sulfonic acid, ethylenedithiodipropyl sulfonic acid, bis-(ω-sulfobutyl)-disulfide, methyl-(ω-sulfopropyl)-disulfide, N,N-dimethyldithiocarbamic acid (3-sulfopropyl) ester, (O-ethyldithiocarbonato)-S-(3-sulfopropyl)-ester, 3-[(amino-iminomethyl)-thiol]-1-propanesulfonic acid, 3-(2-benzylthiazolylthio)-1-propanesulfonic acid, bis-(sulfopropyl)-disulfide and alkali metal salts thereof.
3. The method of claim 1 , wherein the one or more sources of copper ions are chosen from copper sulfate and copper alkane sulfonates.
4. The method of claim 1 , wherein the suppressors are chosen from one or more of polyoxyalkylene glycol, carboxymethylcellulose, nonylphenolpolyglycol ether, octandiolbis-(polyalkylene glycolether), octanolpolyalkylene glycolether, oleic acidpolyglycol ester, polyethylenepropylene glycol, polyethylene glycol, polyethylene glycoldimethylether, polyoxypropylene glycol, polypropylene glycol, polyvinylalcohol, stearic acidpolyglycol ester and stearyl alcoholpolyglycol ether.
5. The method of claim 1 , wherein the accelerator concentration ranges from 2 ppm and greater.
6. The method of claim 5 , wherein the accelerator concentration ranges from 3 ppm to 500 ppm.