J. Fruhauf et al., New aspects of the plastic deformation of silicon - prerequisites for the reshaping of silicon microelements, APPL PHYS A, 68(6), 1999, pp. 673-679
New shapes of silicon microelements which can be partially situated outside
the wafer plane can be created by the combination of wet anisotropic etchi
ng and plastic deformation at high temperatures. Therefore new applications
become possible.
In order to characterize the plastic behaviour of the silicon microelements
bending tests in the 3-point manner were carried out at monocrystalline, d
ifferently orientated beams with variation of temperature, bending rate and
maximum bending. Additionally the fracture strength at room temperature of
deformed and undeformed beams was determined. The dislocation content intr
oduced during the deformation was analysed by the etch pit technique.
The deformation is characterized by the formation of dislocations, a pronou
nced yield point effect, and an orientation-dependent strengthening. The yi
eld points depend strongly on temperature. Because of the strong dependence
on the deformation parameters it is possible to create the same amount of
irreversible deformation at different stages of the stress-bend diagrams re
sulting in different dislocation contents and therefore different propertie
s. The analysis of the fracture strength values by means of the Weibull sta
tistics shows a slightly decreased average fracture strength of the deforme
d material in comparison to the undeformed silicon but a strongly increased
Weibull modulus.