Characterization of molybdenum thin films for micromechanical structures

Characteristics of sputter-deposition, patterning, and sacrificial-layer etching for the formation of free-standing molybdenum structures are described. Stress measurement, etching, and deposition techniques are discussed. It is shown that sacrificial layer material has a strong influence on residual stress, and that long sacrificial layer etching times degrade film quality. For these reasons, aluminum is superior to SiO₂ as a sacrificial layer for molybdenum. Appropriate wet and dry etching processes have been developed for patterning molybdenum and for removing the sacrificial layer. It is found that sputtering current and speed of rotation have little effect on film stress. These and other parameters are characterized so as to give control of film stress as deposited. X-ray diffraction measurements have revealed that the orientation of metal grain is determined by the direction of wafer rotation under the sputtering target