Investigation of residual stress effects and modeling of spring constant for RF MEMS switches

Any film which is deposited during the fabrication undergoes some form of stress. It can be either a compressive stress or tensile stress. It is important to have right value of either compressive or tensile stress for the particular application. In this paper we present an investigation of the stresses generated by the gold thin film during the fabrication process of RF MEMS switches. During the fabrication of RF MEMS series switches a small value of tensile stress is intentionally generated so that beam does not lead to stiction after final release. We are also briefly presenting a new mathematical model for calculation of the spring constant of the beam structures. The method we used is based on the Euler-Bernoulli beam equations. The spring constants calculated for two new beam designs were 3.37 N/m and 3.31 N/m respectively.