Thick films of BiSrCaCuO superconductors are grown by spray pyrolysis technique. Annealed films are superconducting with T c (0) at 83K. The microbridges of dimensions 120μm are scribed manually on these films. Application of microwave leads to the appearance of Shapiro steps. The frequency dependent study of critical current show a maxima for an optimum frequency. At this frequency, the critical current shows oscillatory decay with increasing microwave power. The above results indicate microwave absorption at the grain boundaries, leading to nucleation of vortices which eventually decay with increasing microwave power.