Manufacturing integrated MEMS switching devices using electrodeposited NiFe
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The development of magnetic technologies employing microfabricated magnetic structures for the production of integrated electronic components is a driving topic in the electronic industry. Despite the large amount of work reported in the literature towards the production of magnetic devices that can be integrated into conventional silicon technology, the published research has only achieved moderate success. The research presented in this thesis was conducted with the aim to progress towards the production of a magnetic MEMS relay based on electro-deposited NiFe that combines magnetic and electrostatic actuation and that can be integrated in a standard IC processing chain. This work includes a comprehensive design study for the proposed MEMS device and presents the development of the manufacturing processes required for its fabrication. As the theoretical performance of the device is found to be crucially reliant on the mechanical and magnetic properties of the microformed structures, a series of novel test methodologies has been devised and implemented with the aim of acquiring knowledge on the behaviour of the NiFe films. Novel mechanical test routines employing microfabricated test structures are presented and applied to build a systematic and robust system for the characterisation of the electrodeposited films. The quantitative mapping of residual stress at the wafer level using microfabricated test structures has been demonstrated for the first time and applied to optimise processes and tools. A complete fabrication process flow for manufacturing the designed magnetic MEMS switch has been proposed and the fabrication of the actuated section of the switch has been demonstrated, comprising all the functional electric and magnetic components. The fabricated magnetic devices have been tested to monitor their response to an external magnetic force and prove their viability for use in MEMS actuators. Additional work was finally conducted towards the development of a reliable and robust process aimed at increasing the device yield and thus facilitating the eventual commercialisation of magnetic MEMS switches.