The built-in strain in deposited polysilicon films depends on film morphology. The strain may be compressive or tensile. Its magnitude and uniformity may be measured by using surface micro machining with test structures which require a single photomask level and use Euler buckling. Anneal cycles may be used to convert compressive strain to tensile or zero strain. Deposition and anneal cycles may be optimized to produce fine grained polysilicon with isotropic mechanical behavior.
Strain field control can improve yield by reducing surface sticking. This mechanical stiffening is used in, for instance, pressure transducer construction. Built-in and applied axial strain are used to change the resonant frequencies of clamped-clamped beams in a vacuum envelope where quality factors up to 300,000 have been measured.