YBa2Cu3Ox (YBCO) superconducting thin films were deposited on MgO(100) single-crystal substrates using the metalorganic chemical vapor deposition (MOCVD) method. The microstructure of the YBCO aim was controlled by varying the deposition temperature and pressure. Different shapes and numbers of weak links were observed depending on the microstructure. Bridge-type Josephson junctions of natural grain boundaries were fabricated using photolithography and chemical etching for infrared detection. Effects of the microstructure and microbridge patterns on the IR responsivity of the YBCO thin films were investigated and discussed.