
50 Crystal Growth and Evaluation of Silicon for VLSI and ULSI
a vacancy, or missing atom. This vacancy is occupied in a perfect crystal. The stability of
the surrounding crystal structure assures that the adjacent atom will not simply collapse
around the vacancy. As shown in the gure, the presence of a vacancy distorts the lat-
tice network. The vacancy here is active because of the missing coordination bond of the
neighboring lattice atoms. This vacancy may attract other free ions present in the intersti-
tial positions to ll that vacant portion of the lattice. Agglomeration of such defects may
increase the defect size, as shown in Figure 3.2 ...