Investigation of domain-related topography formation during chemical mechanical polishing (CMP) of piezoelectric ceramic material

Novel MEMS manufacturing can be expected, if the joining areas of the concerned material components are atomically flat (roughness <0.6 nm). In this case, the assembly should be achieved by direct bonding mechanisms. Accordingly, no additional intermediate layers or undercoatings between the active and passive material components are necessary. The conditioning of piezoelectric ceramic surfaces is usually correlated with the change of the domain morphology, particularly, if very flat surfaces are processed. Ferroelastic interactions and the piezoelectric effect caused by the acting forces during the machining process come into account and change the local polarization distribution of the treated surface area. This local modulation is represented in the resulting surface topography. It might be different from the active domain structure in the surface area after machining by relaxation. The preparation of the highly flattened surface of thin ceramic sheets with least roughness was done using Chemical Mechanical Polishing (CMP). The removal was adjusted to be invariant to the polarization condition of the treated surface area. Thus, the treatment resulted in an optical flat mirror-like surface with roughness below 1 nm. The topography follows the polarization of the ferroelectric domains underneath in a nanometer scale. The present work reports on results of a multiple of investigation techniques, such as FESEM, PFM, SPM and gives a phenomenological interpretation. With the deepened understanding of the preparation process and the related material interactions, it is now possible to treat the surface machining to be domain independent.