Fabrication of counter electrodes for scanning atomic probe

This paper reports on the fabrication of innovative counter electrodes for the development of a new Scanning Atom Probe (SAP) instrument. A process using thick spin-on dielectrics (BenzoCycloButene), deep reactive ion etching (DRIE) and photolithography (both standard and electroplated) has been developed for the realisation of the counter electrodes. The novel structure is a two-terminal device in the form of a hollow cone shape, with two electrodes separated by a dielectric layer (high breakdown voltage insulator). Different counter electrode design versions are presented, with the focus on the results for the first iteration. Electrical testing of the insulating layer is performed to investigate the material suitability for the operating conditions of the SAP instrument. Details regarding the design and fabrication procedure for the different designs, with emphasis on the process flow for the non standard steps, are also presented.