MECHANISM OF METALLIC PARTICLE GROWTH AND METAL-INDUCED PITTING ON SIWAFER SURFACE IN WET CHEMICAL-PROCESSING

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.