Purity and resistivity improvements for electron-beam-induced deposition of Pt

Abstract

Electron-beam-induced deposition (EBID) of platinum is used by many researchers. Its main application is the formation of a protective layer and the “welding material” for making a TEM lamella with a focused ion beam thinning process. For this application, the actual composition of the deposition is less relevant, and in practice, both the mechanical strength and the conductivity are sufficient. Another important application is the creation of an electrical connection to nanoscale structures such as nano-wires and graphene. To serve as an electrical contact, the resistivity of the Pt deposited structure has to be sufficiently low. Using the commonly used precursor MeCpPtMe3 for deposition, the resistivity as created by the basic process is 10+5–10+6 higher than the value for bulk Pt, which is 10.6 µΩ cm. The reason for this is the high abundance of carbon in the deposition. To improve the deposition process, much attention has been given by the research community to parameter optimization, to ex situ or in situ removal of carbon by anneal steps, to prevention of carbon deposition by use of a carbon-free precursor, to electron beam irradiation under a high flux of oxygen and to the combination with other techniques such as atomic layer deposition (ALD). In the latter technique, the EBID structures are used as a 1-nm-thick seed layer only, while the ALD is used to selectively add pure Pt. These techniques have resulted in a low resistivity, today approaching the 10–150 µΩ cm, while the size and shape of the structure are preserved. Therefore, now, the technique is ready for application in the field of contacting nano-wires.