Development of a High Resolution Magnetic Field Position Sensor System Based on a Through Silicon Via First Integration Concept

This paper presents the conception, the fabrication, first characterization results as well as application scenarios for a new position sensor system architecture based on tunnelmagnetoresistive (TMR) technology. The new concept aims for improving the precision of magnetic position sensing by miniaturization of both magnetic scale and magnetic field sensing circuitry. The concept is enabled by though silicon vias (TSVs) which allow to route the signals from the sensing elements though the chip directly to its back side. Since interconnection structures like wire bond loops are avoided at the front side of the sensors the here located sensing elements can be brought into very close distance to the magnetic stimulus. The TSV based chip architecture enables a successful sensor implementation based on hard magnetic CoP poles with a width of 50 μm and a periodic length of 100 μm as well as a corresponding magnetic readout circuitry utilizing TMR junctions with a diameter of 3 μm. The fabricated sensor chips support the readout of two adjacent magnetic scales which are used as incremental and absolute track. Based on that, high precision position measurements with better than 700 nm accuracy and less than 110 nm bidirectional repeatability could be shown on a scale with 25 mm travel length. The system supports true power on functionality, meaning that the absolute position on the full scale is given immediately after power on without any reference check.