S-shaped double-spring structures for high stiffness and spring height

Stress-engineered spring structures have been demonstrated for a variety of innovative applications in nanoelectronics and micro-electromechanical systems (MEMS). They are fabricated by lifting a patterned metal film with internal stress gradient out of the substrate plane using sputtering. As their circular side profile puts a limit on the attainable spring height, non-circular spring shapes are highly desired. Therefore, we have developed a double-spring approach with an S-shape side profile which allows for extreme spring heights while still relying on the same stress-engineered base process without additional lithography steps. In our concept, the lower beam is pushing upwards and the upper beam is pushing downwards which leads to the S-shape. Optional interlocking features allow both springs to lock into a certain position. This paper presents the double-spring approach and demonstrates fabricated structures. Nearly vertical springs illustrate the potential of the technology for applications which require non-circular shapes and extreme heights.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► We have developed double-springs with an S-shape side profile. ► Nearly vertical spring structures can be fabricated by our approach. ► Optional interlocking features allow both springs to lock into a certain position.