A preferred, non-destructive method for characterizing sputter target cleanliness
includes the steps of sequentially irradiating the test sample with sonic energy
predominantly of target sputter track areas; detecting echoes induced by the sonic
energy; and discriminating texture-related backscattering noise from the echoes
to obtain modified amplitude signals. These modified amplitude signals are compared
with one or more calibration values so as to detect flaw data points at certain
positions or locations where the comparison indicates the presence of at least
one flaw. Most preferably, groups of the flaw data pixels corresponding to single
large flaws are bound together so as to generate an adjusted set of flaw data points
in which each group is replaced with a single, most significant data point. The
adjusted set of flaw data point is used to calculate one or more cleanliness factors,
or to plot a histogram, which characterizes the cleanliness of the sample.
