Determination of mechanical-thermal deformation in the surface micromachined membrane of gas microsensors

We performed a simulation study of the "bimetal" effects for the silicon-silicon oxide membrane suspended in different ways. For this purpose, a commercial COSMOS/M program working with finite element method has been used. We investigated the dependence of the value and orientation of the displacements (upward or downward) of the two-layer type membrane as a function of temperature, temperature gradient, geometrical dimensions, expansion coefficients and type of membrane support. The test structure for this simulation consists of a square SiO/sub 2//Si membrane of 100/spl times/100 /spl mu/m/sup 2/ with 10 /spl mu/m for each layer The connection of the membrane to the bulk silicon was performed as follows: (i) by four horizontal bridges, (ii) by four vertical legs or (iii) by its four edges. From the simulation study, we have obtained the effect of the above variables on the value and orientation of the membrane deformation: (a) the temperature and gradient temperature, layer thickness and rigidity of the material lead to modification of the displacements of the membrane; (b) the type of membrane support leads to modification of the value and orientation of the deformation of the membrane. This study of membrane deformation can be successfully used for designing a new gas structure based on surface micromachining and hopefully with low power consumption and predicted deformation.