Copper electroplating Current density

Current density can be increased without impairing the quaUty of the copper by polishing the cathode surface by brief periodic current reversals (PCR). Reversed current electrolysis, first developed for electroplating, was tested in 1952 for copper refining. Although good results were obtained, no suitable electrical equipment for current reversal was available. The thyristor-controUed siUcon rectifier, introduced in the 1960s, provided a means for... 

A number of bi-electrodes have been studied for application as insoluble anodes in electroplating platinised titanium, Ti-Pt, Ti-Cu and Ti-Ag. Anodic polarisation measurements in various copper, nickel, chromium and tin plating solutions together with passivation current densities are used to discuss performance and suitability. 

The sulphate bath The sulphate bath, the earliest of electroplating solutions and the simplest in composition, contains typically 150-250 g/1 of copper sulphate and 40-120 g/1 of sulphuric acid. The composition is not critical and the higher concentrations are used for plating at higher current densities, normally up to 6 A/dm. ... 

Boyd et al. have electroplated technetiiun under a variety of conditions. Optimum results are obtained at pH 5.5 in the presence of about 10 M fluoride concentration. Yields are higher when copper instead of platimun cathodes are used. At a current density of 100 mA/cm 98.5% of technetiiun is deposited in 2 h. However, yields of 98-99% are obtained at similar current densities even with platinum cathodes, at pH 2 to 5 and fluoride concentrations of 5 x 10 M with plating times of up to 20 h... 

The advantage of the magnetite electrodes lies in the fact that it is possible to electrolyse at an elevated temperature of 70 to 80 °C, which considerably accelerates the chemical oxidation of hypochlorite, and so indirectly increases the current efficiency. However, magnetite electrodes are brittle, their electrical conductivity is low and they do not permit to use current density which exceeds 2 to 3 A per sq. dm. Magnetite electrodes are either in the form of hollow bars or tiles, which are closed at the bottom and electroplated inside with copper. Copper increases the conductivity of the electrode and enables current conductors to be soldered to the top of it without any difficulty. The current efficiency obtained with magnetite electrodes reaches 86 to 90 p. c., and... 

Dopant incorporation and resistance transients in unpatterned films of electroplated copper were studied as a function of bath age and other plating parameters such as current density, agitation, temperature, additive concentration and chloride concentration. Dopant content exhibits a strong dependence on agitation and additive concentration it also depends on current density but to a lesser extent. Chlorine content of the film is independent of chloride content in the bath. Dopant incorporation is independent of bath age. Resistance transients are slower the higher the dopant content of the film. 

Measurements of Rs transients were conducted in order to assess the effect of dopants / plating parameters on the kinetics of the transformation of electroplated copper [8]. Results are shown in Figure 6. For a constant bath temperature, the parameters that affect dopant incorporation the most are current density, rotation speed, and additive concentration. It is seen that an increase in additive concentration and rotation speed leads to a delay in the resistance transformation and to an increase in dopant content. Similarly, an increase in plating current density causes an acceleration of the resistance transformation and a decrease in dopant incorporation. It is thus concluded that dopant content increase causes delays in the resistance transformation of plated copper in accordance with the observations of Harper et al [8]. Results shown in Figs. 7 and 8 corresponding to different bath temperatures as well as plating from three different commercial chemistries are consistent with this correlation. 

Solutions of acid copper sulfate (containing only chloride and carrier) were used as the copper electroplating bath. A piece of titanium mesh (diameter = 55 mm) coated with iridium oxide was used as an insoluble anode. The bath was pumped through the anode to the cathode under 1 l/min and controlled at 25 °C. The cathode rotating speed was maintained at 165 rpm. The copper electrodeposition tests were conducted under different electric field waveforms with an average cathodic current density of 25 to 32 ASF, which was controlled by the cell voltage. Samples were cross-sectioned with a focused ion beam scanning electron microscope (FIB-SEM) to inspect both the quality of the copper deposits in the trenches or via-holes. 

Watanabe and coworkers have found that alloy electrodes are often more efficient than electrodes made of pure metals. They have studies the reduction of CO on copper alloys with nickel, tin, lead, zinc cadmium and mercury [24]. The alloys were all produced by electroplating from mixtures of the metal ions in solution. In the cases of nickel, tin, lead and zinc alloys, current densities and faradaic efficiencies were all found to be greater than those of the pure components. Also product selectivity was found to be a function of the metal alloyed with copper. 

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