New aspects of the plastic deformation of silicon -: prerequisites for the reshaping of silicon microelements

New shapes of silicon microelements which can be partially situated outside the wafer plane can be created by the combination of wet anisotropic etching 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, differently 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 introduced during the deformation was analysed by the etch pit technique. The deformation is characterized by the formation of dislocations, a pronounced yield point effect, and an orientation-dependent strengthening. The yield 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 resulting in different dislocation contents and therefore different properties. The analysis of the fracture strength values by means of the Weibull statistics shows a slightly decreased average fracture strength of the deformed material in comparison to the undeformed silicon but a strongly increased Weibull modulus.