Magnetron co-sputtered μm-thick Mo–Cu films as structural material with low heat extension for key parts of high-power millimeter-band vacuum microelectronic devices

Abstract

The development of high-power millimeter and THz-band vacuum microelectronic devices (μVEDs) demands structural materials with special properties. In particular, key components of μVEDs must retain their dimensions when heated while operating at higher power levels. A molybdenum-copper alloy is a promising material, thanks to the low thermal expansion of molybdenum and the remarkable thermal and electrical conductivity of copper. However, such alloys can only be obtained by a limited number of techniques that are rather complicated. Thus, the goal of this work is the implementation of vacuum magnetron co-deposition as a facile method in the fabrication of μm-thick Mo–Cu films. Such films are very promising for the microfabrication of microstrip slow-wave structures for high-power millimeter and THz-band μVEDs. This study is focused on controlling the morphology, resistivity, and roughness of the fabricated thin films by changing the deposition process parameters, such as the sputtered Cu and Mo ratio and substrate temperature.