Ra. Brown et al., METALLIC IMPURITY GETTERING AND SECONDARY DEFECT FORMATION IN MEGAELECTRON VOLT SELF-IMPLANTED CZOCHRALSKI AND FLOAT-ZONE SILICON, Journal of the Electrochemical Society, 144(8), 1997, pp. 2872-2881
Megaelectron volt (MeV) self-implantation has been investigated as a m
eans of producing buried defect layers for gettering metallic impuriti
es in Czochralski (CZ) and float-zone (FZ) silicon. The properties of
implanted and annealed wafers were studied by generation lifetime (Zer
bst) analysis of transient capacitance data, capacitance-voltage measu
rements, deep-level transient spectroscopy, scanning electron-beam-ind
uced current microscopy, transmission electron microscopy, optical mic
roscopy with preferential chemical etching, and secondary ion mass spe
ctroscopy. We found that metallic contaminants such as Fe and Cu were
effectively gettered to buried extended defect layers formed by implan
tation of ion fluences less than or similar to 1 x 10(15) Si cm(-2). F
or example, the concentration of iron in regions near the buried defec
ts can be reduced to below 10(10) cm(-3) in samples annealed at 900 de
grees C. The region above the damage layer appears to be free of elect
rically active defects, having very high generation lifetime values, a
nd is therefore suitable for device processing. However, the structure
and width of the buried defect band is sensitive to the implanted ion
fluence and the oxygen content of the wafers. For example, the defect
layers formed by high ion fluences (similar to 10(15) cm(-2)) are wid
er in FZ wafers than in CZ wafers. For fluences approximate to 1 x 10(
14) cm(2), dislocations extend from the buried damage band in both dir
ections during annealing and are observed at depths up to 10 mu m. The
se dislocations intersect the wafer surface in both CZ and FZ wafers,
making fluences lower than similar or equal to 5 x 10(14) cm(-2) unsui
table for device fabrication.