This paper presents a design of microelectromechanical systems (MEMS) accelerometers for sensing sub-1g (g = 9.8 m/s2) acceleration. The accelerometer has a high-density proof mass to suppress the Brownian noise that dominates the output noise of the sensor. The low-temperature (<400 °C) process enables to integrate the accelerometer on the sensing complementary metal-oxide semiconductor circuit by electroplating of gold; a proof mass of 1020 μm × 1020 μm in area with the thickness of 12 μm has been found to suppress the measured noise floor to 0.78 μg/Hz at 300 K, which is nearly one order of magnitude smaller than those of the conventional MEMS accelerometers made of silicon.

This paper reports a novel sensor structure and its evaluation results for an integrated complementary metal oxide semiconductor (CMOS) microelectromechanical systems (MEMS) accelerometer with a wide detection range on a chip. The proposed sensor structure has the following features: i) a layer separation technique between the proof mass and the mechanical suspensions, ii) mechanical stoppers for the proof mass to avoid destruction, and iii) a SiO 2 film underneath the proof mass to prevent stiction and electrical short. Gold was used as the MEMS structure material to reduce the proof mass size and to lower the Brownian noise to below 100 g/ ffiffiffiffiffiffi Hz p . Furthermore, the micro fabrication was carried out below 310 C for the CMOS devices to remain intact. The evaluation results indicate that the Brownian noise was 90.6 g/ ffiffiffiffiffiffi Hz p. Thus, we have confirmed that the proposed MEMS structure has the potential for use in future integrated CMOS-MEMS accelerometers.

No abstract

This paper reports the design and evaluation results of a capacitive CMOS–MEMS sensor that consists of the proposed sensor circuit and a capacitive MEMS device implemented on the circuit. To design a capacitive CMOS–MEMS sensor, a multi-physics simulation of the electromechanical behavior of both the MEMS structure and the sensing LSI was carried out simultaneously. In order to verify the validity of the design, we applied the capacitive CMOS–MEMS sensor to a MEMS accelerometer implemented by the post-CMOS process onto a 0.35-µm CMOS circuit. The experimental results of the CMOS–MEMS accelerometer exhibited good agreement with the simulation results within the input acceleration range between 0.5 and 6 G (1 G = 9.8 m/s2), corresponding to the output voltages between 908.6 and 915.4 mV, respectively. Therefore, we have confirmed that our capacitive CMOS–MEMS sensor and the multi-physics simulation will be beneficial method to realize integrated CMOS–MEMS technology.

No abstract