An important step in the MEMS switch fabrication is the formation of a suspended micron-sized beam. Typically, the beam is made of gold due to its high electrical conductivity and chemical inertness. However, the fabrication process is complicated by poor suitability of Au for chemical etching and deformation of the beam under residual mechanical stress. An additional disadvantage is a high price of gold. Aluminium and its alloys are considered as a promising alternative. In this work, the magnetron-sputtered Al 99.99%, Al–1% Si and Al–1.5% Ti are tested as structural materials for a MEMS switch. We fabricate 1 μm thick beams and investigate surface morphology, electrical resistivity and mechanical properties. Single-layer films of Al 99.99% and Al–1% Si have coarse-grained microstructure with the root-mean-square roughness higher than 50 nm. The multi-step deposition reduces this value to 15 nm without significant deterioration of the resistivity and Young’s modulus. However, multilayer films of Al 99.99% have interlayer voids, which may degrade the switch reliability. Al–1.5% Ti provides much smoother and fine-grained film with plain sidewalls, which results in a higher quality factor of the beams. But this alloy has three times higher electrical resistivity than pure Al. Therefore, fabrication of the beam and transmission line from Al–1.5% Ti will increase insertion loss of the switch. A four-layer film of Al–1% Si is more preferable, since it also has fine microstructure and does not contain interlayer voids, but is close to pure aluminium in terms of resistivity.

MEMS开关制造中的重要步骤是形成悬浮的微米级光束。通常，由于其高电导率和化学惰性，该梁由金制成。然而，由于金对化学蚀刻的适应性差以及在残余机械应力下光束的变形，使得制造过程变得复杂。另一个缺点是金价高。铝及其合金被认为是有前途的替代品。在这项工作中，磁控溅射Al 99.99％，Al-1％Si和Al-1.5％Ti被用作MEMS开关的结构材料。我们制造了1μm厚的梁，并研究了表面形态，电阻率和机械性能。Al 99.99％和Al-1％Si的单层膜具有粗糙的微观结构，其均方根粗糙度高于50 nm。多步沉积将该值减小到15 nm，而电阻率和杨氏模量没有明显降低。然而，Al 99.99％的多层膜具有层间空隙，这可能降低开关可靠性。Al–1.5％Ti可以提供更光滑，更细腻的膜和平坦的侧壁，从而提高光束的品质因数。但是这种合金的电阻率是纯铝的三倍。因此，由Al–1.5％Ti制造光束和传输线会增加开关的插入损耗。Al-1％Si的四层膜是更优选的，因为它还具有良好的微观结构，不包含层间空隙，但在电阻率方面接近纯铝。