Overcoated diamond tips for nanometer-scale semiconductor device characterization

Abstract

Micromachined diamond tips have become the ultimate choice for the electrical probing of semiconductor devices at the nanometer scale because of the required high pressures in the GPa range. Although state-of-the-art full diamond tips (FDTs) show an ultra-high spatial resolution of 1nm, they are suffering from the limited electrical conductivity of the interfacial diamond layer resulting in an overall lower dynamic range. Conventional coated diamond tips (CDTs) on the other hand show a higher electrical conductivity but their core Si tips are prone to breaking off close to the apex due to the high lateral forces during scanning. Therefore, we developed in this work so-called overcoated diamond tips (ODTs) which are combining the advantages of the high mechanical stability of molded FDTs with the higher conductivity of CDTs. The key is the local underetching of a first molded diamond tip and the subsequent growth of a 50–150nm thin boron-doped diamond layer onto the interfacial diamond layer. The resulting ODT structure is attached to a metal cantilever and is used for electrical atomic force microscopy (AFM) measurements. The fabricated ODTs are mechanically stable and show a higher conductivity than FDTs. This work presents the probe and fabrication scheme, shows manufactured probe devices and demonstrates their performance in electrical AFM measurements.