Observation of contact holes by atomic force microscopy with a ZnO whisker tip

We have developed a new precise imaging technique for atomic force microscopy (AFM) and observed complicated surface structures of integrated circuit (IC) devices by this technique. This technique consists of a hopping mode operation and use of a zinc oxide whisker as a probing tip with high aspect ratio. In this operation, topographic data of the surface structures are obtained under a constant repulsive force at each measuring point, and after each measurement the probing tip is withdrawn from the surface and moved to the next measuring point. The contact holes with a diameter of ∼1 μm and a depth of 1.5 μm fabricated on IC devices have been successfully imaged in this AFM imaging technique.