Open AccessAdhesion of polysilicon microbeams in controlled humidity ambients
Author(s) -
Maarten P. Boer,
P J Clews,
B K Smith,
T A Michalske
Publication year - 1998
Language(s) - English
Resource type - Reports
DOI - 10.2172/658196
Subject(s) - adhesion , relative humidity , atomic force microscopy , humidity , materials science , exponential function , composite material , elasticity (physics) , viscoelasticity , chemistry , nanotechnology , thermodynamics , physics , mathematics , mathematical analysis
The authors characterize in-situ the adhesion of surface micromachined polysilicon beams subject to controlled humidity ambients. Beams were freed by supercritical CO{sub 2} drying. Consistent adhesion results were obtained using a post-treatment in an oxygen plasma which rendered the microbeams uniformly hydrophilic. Individual beam deformations were measured by optical interferometry after equilibration at a given relative humidity (RH). Validation of each adhesion measurement was accomplished by comparing the deformations with elasticity theory. The data indicates that adhesion increases exponentially with RH from 30% to 95%, with values from 1 mJ/m{sup 2} to 50 mJ/m{sup 2}. Using the Kelvin equation, the authors show that the data should be independent of RH if a smooth interface is considered. By modeling a rough interface consistent with atomic force microscopy (AFM) data, the exponential trend is satisfactorily explained