Dual-Resonator MEMS Magnetometer Based on Self-Clocking Sigma-Delta Modulation

status: publishe

A Single-side Fabricated Tri-axis (111)-Silicon Micro-Accelerometer with electromechanical Sigma-delta Modulation

This paper presents a novel single-side (111)-silicon (non-SOI) fabricated triaxis capacitive microaccelerometer with a dual quantization electromechanical sigma-delta modulator (EM-ΣΔM) interface circuit. The fully CMOS compatible single-sided micromachining process with toroidal shaped electrical isolation structures is described. A 2.6 mm × 2.6 mm sized triaxis accelerometer was designed and fabricated using only the front side of a 4-in (111) silicon wafer. The interface circuit was based on a front-end ASIC readout circuit and a back-end dual quantization high-order EM-SDM digital circuit implemented on an FPGA. The EM-ΣAM loop adopts a multifeedback noise shaping architecture, for which different numbers of bits for the loop quantization were analyzed. The parameters of the EM-ΣAM loop are optimized by a genetic algorithm. Acceleration sensitivities of 170 mV/g (2785 LSB/g), 142 mV/g (2327 LSB/g), and 26 mV/g (426 LSB/g) were measured in EM-ΣAM closed-loop operation for the in-plane (X/Y) and out-of-plane (Z) axes, respectively. The cross-axis sensitivity was in the order of 1%-6% and the output noise was 0.5 mg-2 mg/√Hz, with a 1-h bias drift of 3-6 mg.status: publishe

Design, Fabrication, and Testing of a Monolithically Integrated Tri-Axis High-Shock Accelerometer in Single (111)-Silicon Wafer

In this paper, a monolithic tri-axis piezoresistive high-shock accelerometer has been proposed that has been single-sided fabricated in a single (111)-silicon wafer. A single-cantilever structure and two dual-cantilever structures are designed and micromachined in one (111)-silicon chip to detect Z-axis and X-/Y-axis high-shock accelerations, respectively. Unlike the previous tri-axis sensors where the X-/Y-axis structure was different from the Z-axis one, the herein used similar cantilever sensing structures for tri-axis sensing facilitates design of uniform performance among the three elements for different sensing axes and simplifies micro-fabrication for the multi-axis sensing structure. Attributed to the tri-axis sensors formed by using the single-wafer single-sided fabrication process, the sensor is mechanically robust enough to endure the harsh high-g shocking environment and can be compatibly batch-fabricated in standard semiconductor foundries. After the single-sided process to form the sensor, the untouched chip backside facilitates simple and reliable die-bond packaging. The high-shock testing results of the fabricated sensor show linear sensing outputs along X-/Y-axis and Z-axis, with the sensitivities (under DC 5 V supply) as about 0.80–0.88 μV/g and 1.36 μV/g, respectively. Being advantageous in single-chip compact integration of the tri-axis accelerometers, the proposed monolithic tri-axis sensors are promising to be embedded into detection micro-systems for high-shock measurement applications