Requirements of Modern Technology

Abstract

With the increasing size of highly integrated circuits due to their ever increasing complexity — bearing in mind the diminishing dimensions of structures, and diffusion depths, in VLSI and ULSI — the detriment al effect of lattice distortions within the very small and shallow electrically active zones has increased considerably. Most of the lattice distortions are caused by precipitated transition-metal impurities. They are introduced into the wafers by diffusion of unintentional surface contaminants during the large number of process steps required to fabricate a modern device. In order to achieve sufficiently high yields, the number of faulty structures must be reduced drastically. Therefore, the tolerable impurity concentrations shrunk considerably. As a consequence, new specifications limiting the concentrations of impurities in device fabrication were set up. They concern mainly the concentrations of iron, nickel, and copper. In order to control these new specifications the suppliers of polished wafers and their customers had to agree on suitable measurement techniques.