No abstract

An electrochemical direct current polarization method was used to investigate characteristics of copper deposition onto silicon from dilute and buffered hydrofluoric acid solutions. The corrosion current density and corrosion potential of silicon were not very sensitive to the Cu2 concentration, up to 1000 parts per billion, in buffered hydrofluoric acid. However, the extent of copper deposition, as measured by total reflection X-ray fluorescence, increased as the Cu' concentration in solution increased. In dilute hydrofluoric acid, Cu2 addition had a significant and systematic effect on the corrosion potential and corrosion current density of silicon. However, in both types of solution, the cathodic current calculated from the measured copper deposition was found to be only a small fraction of the corrosion current (less than 1%). This indicates that the primary cathodic reaction is not copper ion reduction but hydrogen ion reduction. Illumination affected the electrochemical behavior of both p-and n-type silicon in Cu' spiked dilute hydrofluoric acid, but only that of p-type silicon in buffered hydrofluoric acid.

Copper contamination of silicon wafers from 50:1 HF solutions containing 0 to 100 ppb Cu was studied using dc electrochemical techniques. As the level of copper concentration in HF solutions increased, the corrosion current density and corrosion potential of silicon as well as the amount of copper deposition were increased. Upon addition of a nonionic surfactant, the corrosion potential, corrosion current density, and the extent of copper deposition were decreased. However, the levels of deposited copper and surface roughness were dependent on sufactant concentration. When H202 was added to copper-spiked HF solutions, the open-circuit potential of silicon recovered to a value that is characteristic for silicon immersed in a mixture of H,02 and HF indicating the removal of deposited copper on silicon. InfroductionMetallic contamination of silicon wafer surfaces is an important issue because of its harmful impact on the performance of semiconductor devices. The deleterious effects ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 130.113.111.210 Downloaded on 2015-06-30 to IP ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 130.113.111.210 Downloaded on 2015-06-30 to IP

No abstract

Electrochemical impedance spectroscopy was used to probe the mechanism of copper deposition on silicon from dilute hydrofluoric acid solutions. Reaction parameters such as polarization resistance and space-charge capacitance were evaluated using an equivalent circuit model. The electrochemical impedance technique was found to be sensitive to parts per billion levels of Cu2 ion in dilute hydrofluoric acid solutions. An inductive loop appeared in Nyquist plots only when Cu2 ions were present in hydrofluoric acid solutions. Both the polarization resistance and inductance decreased significantly as the solution Cu2 concentration increased. Addition of a nonionic surfactant to hydrofluoric acid solutions significantly altered impedance characteristics of the silicon/solution interface. Total reflection X-ray fluorescence results showed that illumination enhanced deposition of copper on silicon nearly an order of magnitude.