Stress control of porous silicon film for microelectromechanical systems

Control of stress in porous silicon (PS) through porosity changes was studied using X-ray diffraction rocking curve measurements. The effect of thermal annealing on the stress was also investigated, which showed the ability to achieve compressive or tensile films in a reversible manner. The effect of stress on the resonant frequency of PS microbeams was studied to understand the impact of PS film stress when used as the structural layer in a microelectromechanical systems sensor. The results indicated that stress is a significant factor in determining resonant frequency, shifting it by up to a factor of 3.6 from the zero stress state, illustrating the need for accurate control.