(Invited) Magnetic MEMS for Industry 4.0

Abstract

Introduction In the modern manufacturing technology it is necessary to compile a multitude of measurement data. They do not only allow to assure process reliability during fabrication, but also verify the product quality after completing production. Especially in the context of Industry 4.0 it is important to generate, collect and analyze data from various processes. New measurement tasks as well as measuring positions lead to great demands of sensors. It is no longer sufficient to adapt existing sensor systems, it is rather important to develop new sensor manufacturing technologies. To fulfill these requirements the IMPT investigates techniques in the context of the Collaborative Research Centre 653 “Gentelligent Components in Their Lifecycle – Utilization of Inheritable Component Information in Product Engineering”. For a better understanding of the term “Gentelligent” it can be explained that one topic is collecting information using sensors (intelligent) and to store the information for suing to design the next component generation. This is the genetic part of this term. For the genetic part a component inherent magnetic storage system could be used. Thin-film modular sensor family The approach of the modular multifunctional micro sensor family is to get information from the components during their lifecycle. They are able to gather user and maintenance data as well as recycling relevant information through the whole life cycle of the components. A modular design will enable a process optimized fabrication of a micro sensor family measuring magnetic properties, force, strain, and temperature [1, 2]. For realizing this goal, the research starts with the development and investigation of functional layers, which can be used as elementary basic modules for this novel modular micro sensor. Within the scope of this project, magneto-elastic, magneto-resistive, conducting, insulating, as well as temperature sensitive layers were created. In a second step, foil based techniques for thin-film sensors were developed. In this context magneto-resistive and strain gauge sensors were investigated. The benefit of this sensor is a closer connection to the component. E.g. the developed strain gauge sensors are ten times more sensitive than commercial ones. Based on these results we developed a new sputtering system which allows a direct deposition of the functional layers. The main benefit of this system is that the size of the components is not limited from a vacuum chamber of a conventional sputtering system [3]. This means for the sensor itself, intermediate layers, such as carrier substrates or glue, are no longer required. As a result, the measurement errors caused by these layers are eliminated and the sensors fabricated in that way get thinner and closer to the surface of the measurement object. Fig. 1 shows the decreasing of the distance between the sensor and the technical surface depending on the used fabrication techniques for the sensor. Inherent data storage Data storage is one of the indispensable technical assets defined in a framework of Industry 4.0. Among many data storage technologies, inherent magnetic data storage on surfaces of technical components is promising, especially when the components are employed in harsh environments. Comparing with other storage technologies like labels, RFID tags and engraving, the inherent magnetic storage is rewritable and resistant to weathering. High temperatures and high magnetic fields, however, can degrade or even delete magnetically stored data. This limitation can be coped with the use of a medium with higher coercivity than the external magnetic fields that can delete the stored information. As a consequence of higher coercivity, a higher write field is required to magnetize the medium. A design of a flexible write head that is suitable for storage applications on surfaces of technical components, is restricted by head-medium interface criteria, and hence field strength generated from the write head cannot be arbitrary large. To solve this problem, a heat-assisted magnetic recording (HAMR) is proposed as a means to temporarily reduce coercivity of a medium during writing.