High purity copper and method of producing high purity copper based on electrolysis
View Patent ↗High purity copper having a purity of 6N or higher, wherein content of each of the respective components of P, S, 0, and C is 1 ppm or less, and nonmetal inclusions having a particle size of 0.5 μm or more and 20 μm or less contained in the copper are 10,000 inclusions/g or less. As a result of using high purity copper or high purity copper alloy as the raw material from which harmful P, S, C, O-based inclusions have been reduced and controlling the existence form of nonmetal inclusions, it is possible to reduce the occurrence of rupture of a bonding wire and improve the reproducibility of mechanical properties, or reduce the percent defect of a semiconductor device wiring formed by sputtering a high purity copper target with favorable reproducibility.
1. A method of producing high purity copper, comprising the steps of:
performing electrolysis using nitric or hydrochloric acid as electrolyte in an electrolytic cell having a partition provided by a diaphragm extending between a cathode and a copper anode of a purity of 5N or less such that a cathode side and an anode side are defined within the electrolytic cell;
during said electrolysis step, extracting the electrolyte from the anode side of the electrolytic cell;
passing the electrolyte extracted during said extracting step through an activated carbon filter; and
immediately supplying the electrolyte passed through the activated carbon filter during said passing step to the cathode side of the electrolytic cell after the electrolyte passes through the activated carbon filter; and
as a result of the electrolysis, electrodepositing copper of a purity of 6N or higher on the cathode.
2. The method of producing high purity copper according to claim 1 , wherein the copper obtained as a result of the electrolysis contains 1 ppm or less of each of P, S, O, and C and contains nonmetal inclusions having a particle size of 0.5 μm or more and 20 μm or less in an amount of 10,000 inclusions/g or less.
3. The method of producing high purity copper according to claim 2 , wherein the copper obtained as a result of the electrolysis contains inclusions of carbon or carbide having a particle size of 0.5 μm or more and 20 μm or less in an amount of 5,000 inclusions/g or less.
4. The method of producing high purity copper according to claim 1 , wherein the copper obtained as a result of the electrolysis contains inclusions of carbon or carbide having a particle size of 0.5 μm or more and 20 μm or less in an amount of 5,000 inclusions/g or less.