Note to users. If you're seeing this message, it means that your browser cannot find this page's style/presentation instructions -- or possibly that you are using a browser that does not support current Web standards. Find out more about why this message is appearing, and what you can do to make your experience of our site the best it can be.
Fatigue Failure in Polysilicon Not Due to Simple Stress Corrosion Cracking
H. Kahn,R. Ballarini,*J. J. Bellante,A. H. Heuer*
In the absence of a corrosive environment, brittle
materials such as silicon should be immune to cyclic fatigue. However,fatigue effects are well known in micrometer-sized polycrystallinesilicon (polysilicon) samples tested in air. To investigate theorigins of this phenomenon in polysilicon, we developed a fixed-gripfracture mechanics microspecimen but could find no evidence ofstatic
stress corrosion cracking. The environmental sensitivityof the fatigue
resistance was also investigated under cyclic loading.For low-cycle
fatigue, the behavior is independent of the ambientconditions, whether
air or vacuum, but is strongly influencedby the ratio of compressive
to tensile stresses experienced duringeach cycle. The fatigue damage
most likely originates from contactstresses at processing-related
surface asperities; subcriticalcrack growth then ensues during
further cyclic loading. The lowerfar-field stresses involved in
high-cycle fatigue induce reducedlevels of fatigue damage. Under these
conditions, a corrosiveambient such as laboratory air exacerbates the
fatigue process.Without cyclic loading, polysilicon does not undergo
stress corrosioncracking.
Case Western Reserve University, 10900 Euclid Avenue, Cleveland,
OH 44106-7204, USA.
*
To whom correspondence should be addressed: E-mail: rxb7{at}po.cwru.edu
(R.B.); ahh{at}po.cwru.edu(A.H.H.)
Abrupt Temperature Changes in the Western Mediterranean over the Past 250,000 Years.
B. Martrat, J. O. Grimalt, C. Lopez-Martinez, I. Cacho, F. J. Sierro, J. A. Flores, R. Zahn, M. Canals, J. H. Curtis, and D. A. Hodell (2004)
Science
306, 1762-1765
|Abstract »|Full Text »|PDF »
