Appeal No. 1998-2342 Page 15
Application No. 08/505,739
a motor responsive to the output signal and operatively connected between the
cathode assembly and the substrate holder so as to move one relative to the other in
accordance with the output signal.
20. A method of maintaining, from substrate to substrate, the uniformity, across the
surface of a substrate, of a film sputtered from a relatively thick sputtering target that
substantially erodes over its life, the method comprising the step of :
sputtering, from a sputtering target of a given design, a film onto a plurality of
substrates at each of a plurality of distances from the target and measuring the film
thickness uniformity across the surfaces of the substrates;
based on film thickness uniformity measurements, empirically deriving
target-to-substrate spacing as a function of target erosion that will cause a film of a
given uniformity to be sputtered onto a substrate from a target of the given design;
sputtering, from a sputtering target of the given design, a film of the given
thickness uniformity across the surface of a first substrate; then
determining the state of erosion of the sputtering target; then
changing target-to-substrate spacing in accordance with the empirically derived
function; then
sputtering a film of the given uniformity across the surface of a second substrate
from the sputtering target.
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