Mechanical properties of silicon films and capacitive microsensors.

摘要

Experimental techniques have been developed to study the mechanical properties of boron-doped P;The internal stresses produced by boron diffusion are found to be tensile and nonuniform through the thickness of the diffused layer, which is slightly decreased by the elastic deformation and greatly relieved by the generation of dislocations. The residual stresses are measured to be about 60 MPa. They are nonuniform through the thickness of the diffused layer, and cause the cantilever beams to bend. Annealing is used to flatten the bent beams. The optimum annealing condition is 1100;At room temperature, the P;The Young's modulus of P;An experimental study on silicon-diaphragm buckling is given. It is found that the buckling only occurs in heavily doped diaphragms that are etched from the wafers with drive-in as the last high-temperature process. The flat diaphragms can also become buckled after annealing at high temperature. The buckled diaphragms can be flattened by going through another boron diffusion. The mechanism of the diaphragm buckling is proposed.;A new mode of silicon capacitive microsensors, referred to as "touch mode sensors", is studied, in which the center area of the diaphragm is touched the substrate when certain pressure is applied. This mode of operation has more uniform sensitivity over a wide pressure range and no overload problem.