H. Morinaga et al., MECHANISM OF METALLIC PARTICLE GROWTH AND METAL-INDUCED PITTING ON SIWAFER SURFACE IN WET CHEMICAL-PROCESSING, Journal of the Electrochemical Society, 141(10), 1994, pp. 2834-2841
To understand the mechanism of noble-metal adhesion in wet processes,
the behavior of Cu adhesion to the Si surface in various chemical solu
tions, the shape and chemical composition of Cu contaminants adhering
to Si surfaces, the surface microroughness of Si surfaces, and the inf
luence of the type of the substrates are investigated. The results sho
w that Cu ion deposits on the Si surface in the form of metallic parti
cles in wet chemical processing, that Cu deposition in HF solutions ca
uses pits to be formed on the Si surface, and that, on a patterned sub
strate, Cu deposits on the Si surface but not on the SiO2 surface. The
experimental results imply a Cu deposition mechanism. In a dilute HF
solution, the Si surface beneath the Cu particles is etched away to be
come SiF6(2-) and a pit is made. Contamination with noble metals is cr
itical. The mechanism for metal deposition may apply to noble metals i
n general. These metallic impurities must not be introduced into any w
et chemical solution or ultrapure water when a bare Si surface is expo
sed.