High-performance integrated hard magnets for MEMS applications

Inhalt:
High performance permanent micromagnets for MEMS applications are fabricated from NdFeB powder using a novel powder agglomeration technique by means of atomic layer deposition (ALD). Hard magnetic properties, dimensionality, thermal and chemical stability were investigated for the NdFeB micromagnets. Effect of ALD process temperature on the performance of the fabricated micromagnets was studied. Micromagnets processed at lower ALD temperatures have higher remanence and intrinsic coercivity. In magnetic hysteresis loop measurements of a NdFeB structures a remanence of 292mT and intrinsic coercivity of 899mT has been achieved. ALD bonded NdFeB powder micromagnet of different geometries are fabricated and characterized. Thermal stability of the NdFeB micromagnets was assessed in air and vacuum. Micromagnets survived higher temperatures under vacuum conditions. Additionally, for evaluating the chemical stability, pressure cooker tests were performed with and without passivation layer. Results showed that micromagnets with passivation layer are moisture proof. The constructive results from these experiments confirm that ALD bonded powder micromagnets are well suited for a wide range of applications.