Reshaping as a 3D fabrication technique

In this work, a new micromachining technology, namely reshaping, which combines advantages of two-dimensional IC fabrication with the third dimension of the mechanical world, is investigated in detail. With the new technology, surface micromachined and released polysilicon structures are deformed with external forces and then they are annealed to any desired 3D shape by Joule heating generated by the current through the devices. A similar technique was proposed before, however a detailed investigation is given in this work. Other available 3D fabrication techniques (e.g. LIGA) are expensive and there are still many challenges to overcome. In order to understand the reshaping process, polysilicon layers, whose crystallographical structure was modified by doping and annealing, were utilized. U-shaped cantilever beam microactuators were fabricated, reshaped and tested. Reshaping process was carried out at varying power levels with varying current pulse durations. Experimental results showed that microstructures in the desired shape with the optimized elastic properties can be obtained by controlling recrystallization, grain growth and plastic deformation parameters, which play a major role in reshaping.