Machine performance and repeatability continue to
improve. However, newer processes are more demanding,
so traditional machine calibrations may not always be
sufficient. New tools that allow machines to be
characterized based on empirical data will help to bridge
this gap. These tools - in the form of personality
parameters - should be tuned at the most sensitive part of
the bond cycle, which is first bond.
Machine-side improvements can only go so far.
Therefore, to achieve portable processes, an understanding
of the variations in the equipment and the material is
impoaant. The variation in material needs to be held to a minimum. Specifications should be in place to ensure that
the normal tolerances do not affect the process portability.
A practical manufacturing approach would be to allow
a narrow range of critical parameter values as opposed to a
single value setting for each. This is already standard
practice in many facilities, but the process could be
improved by restricting the parameters that can be adjusted.
For instance, if capillary dimensional variation is the
concem, only allow the operator to adjust the FAB size.
Ultimately, finer pitch processes will probably require a
combination of several of the methods discussed here. In
the futnre it will also be necessary to revisit some of the
effects this paper dismisses as being less significant.