Data storage has become an integral part of our lives now. The ever-continuing drive to increase areal density of data recording has led to advances in device scaling—where the challenge is to deliver higher memory readout at high efficiency and lower bit cost. To improve the efficiency and minimize magnetic losses at high operating frequencies (4G,5G &gt;GHz range), there is a need to develop high resistive magnetic thin film coatings with minimum core losses. Soft high moment magnetic (SHMM) alloys such as CoFe, NiFe, CoFeNi, are emerging as top contenders due to their high magnetic moment, high corrosion resistance and low-cost implementation. However, the growth stress in these thin films is a matter of concern, especially at thickness range of 0.5-10um. It can adversely alter their magnetic properties. In such scenarios, sulfur containing surfactants and additives have shown to act as stress relieving agents. During thin film growth, these molecules adsorb in the form of a low surface energy phase and can modify surface thermodynamics of nucleation and grain boundary formation. As shown in Figure 1A and 1B, for low mobility metals like Co, Fe and Ni, the maximum tensile stress is mainly during the grain boundary zipping process. Surfactant adsorption also inhibits hydrogen incorporation in the deposit and controls growth/post-deposition tensile stress evolution along with impacting film properties.<br/><br/>In this talk, we present the effect of saccharin as a surfactant to mediate growth stress and crystal structure of the CoFe/CoFeNi thin film coatings for MEMS applications. Surfactant concentrations were in the range of 0g/L to 2g/L and the growth stress was measured in-situ during the thin film deposition using cantilever-bending methods. Results in Figure 1C show growth stress is a decreasing function of surfactant concentration, as saccharin segregates preferentially at the grain boundaries acting as stress reliever during the zipping process. Effect of surfactant on the deposition rate and film properties will be discussed in detail during the talk.

Surfactant mediated thin film coatings for MEMS applications

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ACS Fall 2022

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