Methods are disclosed for fabricating spring structures that minimize
helical twisting by reducing or eliminating stress anisotropy in the thin
films from which the springs are formed through manipulation of the
fabrication process parameters and/or spring material compositions. In
one embodiment, isotropic internal stress is achieved by manipulating the
fabrication parameters (i.e., temperature, pressure, and electrical bias)
during spring material film formation to generate the tensile or
compressive stress at the saturation point of the spring material.
Methods are also disclosed for tuning the saturation point through the
use of high temperature or the incorporation of softening metals. In
other embodiments, isotropic internal stress is generated through
randomized deposition (e.g., pressure homogenization) or directed
deposition techniques (e.g., biased sputtering, pulse sputtering, or long
throw sputtering). Cluster tools are used to separate the deposition of
release and spring materials.