Mitigating the irreversible deformation with pressure in silicon/porous silicon composite membranes

Due to the low Young's Modulus of porous silicon (PS), Si/PS composite membranes - where the silicon membrane is converted into PS to a certain depth - deform more than silicon membranes and hence MEMS pressure sensors with composite membranes have higher sensitivity. But the Si/PS composite membranes exhibit a smaller range of linear response with applied pressure than silicon membranes with the linear range being less for Si/microPS as compared to Si/macroPS composite membranes. In addition, while the composite membrane deformation saturates at high pressures like silicon membranes, the deformation is irreversible unlike that seen with silicon membranes within reasonable limits. With the possibility that the irreversible deformation could be due to stiction force between the collapsed pore walls at high pressure, we investigate the effect of formation of self-assembled monolayer (SAM) antistiction coating on the performance of Si/PS composite membranes. © 2010 Copyright SPIE - The International Society for Optical Engineering.