Takaaki Matsushima

Novel Sensor Structure and Its Evaluation for Integrated Complementary Metal Oxide Semiconductor Microelectromechanical Systems Accelerometer

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 SiO2 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 µg/√Hz. 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 µg/√Hz. Thus, we have confirmed that the proposed MEMS structure has the potential for use in future integrated CMOS-MEMS accelerometers.

A SPICE-based Multi-physics Seamless Simulation Platform for CMOS-MEMS

1 NTT Advanced Technology Corporation 3-1 Wakamiya, Morinosato, Atsugi, Kanagawa 243-0124, Japan Phone: +81-46-240-3068 E-mail: toshifumi.konishi@ntt-at.co.jp 2 Institute of Industrial Science, The University of Tokyo 4-6-1 Komaba, Meguro-ku, Tokyo 153-8904, Japan 3 Institute of Space and Astronautical Science, The Japan Aerospace Exploration Agency 3-1-1 Yoshinodai, Chuoku, Sagamihara, Kanagawa 252-5210, Japan 4 Integrated Research Institute, Tokyo Institute of Technology 4259 Nagatsuta, Midori-ku, Yokohama, Kanagawa 226-8503, Japan

An arrayed accelerometer device of a wide range of detection for integrated CMOS–MEMS technology

This paper reports the design and experimental results of an arrayed accelerometer device in 3 × 3 format that can detect wide range of acceleration between 1G and 20G (1G = 9.8 m/s2). Implemented in a single chip has been performed by gold electroplating for integrated complementary metal oxide semiconductor–microelectromechanical systems (CMOS–MEMS) technology. An equivalent circuit of a MEMS accelerometer has been developed with an electrical circuit simulator to demonstrate the mixed-behavior of the arrayed sensor device and sensing CMOS circuits. Mechanical and electrical crosstalk between the arrayed elements is analyzed on the electrical field distributions. Experimental results show that the resonant frequency and readout capacitance as a function of applied acceleration have been well explained by the results of the multi-physics simulation. As a result, it is confirmed that the proposed device is applicable to an integrated CMOS–MEMS arrayed accelerometer.

A capacitive CMOS?MEMS sensor designed by multi-physics simulation for integrated CMOS?MEMS technology

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.

A 0.1 G-to-20 G integrated MEMS inertial sensor

This paper presents a novel integrated MEMS inertial sensor with a wide range of acceleration from 0.1 G to 20 G (G = 9.8 m/s2) and with a design suitable for CMOS integration. Owing to the high-density of post-processed gold and the multi-metal layer technology, we have implemented different types of single-axis MEMS capacitive inertial sensors on a single chip of 4 × 4 mm2 in area to obtain a wide sensing range. The estimated Brownian noise was between 82.4 nG/Hz1/2 and 1.11 µG/Hz1/2. The experimental results show that the MEMS sensor has higher sensing resolution than those of conventional MEMS accelerometers.

A dual-axis MEMS inertial sensor using multi-layered high-density metal for an arrayed CMOS-MEMS accelerometer

This paper reports a novel dual-axis MEMS inertial sensor that utilizes multi-layered electroplated gold. All the MEMS structures are made by gold electroplating that is used as post-CMOS process. Due to the high density of gold, the Brownian noise on the proof mass becomes lower than those made of other materials in the same size. The miniaturized MEMS accelerometer can be integrated in an arrayed CMOS-MEMS accelerometer to detect a broad range of acceleration on a single sensor chip.

Sub-1G MEMS accelerometer

This paper reports a sub-1G detectable MEMS accelerometer formed by the multilayer metal intended for post-CMOS process. High density of gold enables to minimize the footprint of the proof mass without compromising the sensitivity subjected to thermal-mechanical noise. The requirements of a low-G accelerometer have been studied in terms of the fabrication process and the device structure. The Brownian noise of the accelerometer is designed to be 2.24 μg/√Hz (at RT) for a proof mass of 1020 μm × 1020 μm × 12 μm, and the estimated actual value is 5.44 μg/√Hz. Sub-1G sensing has also been demonstrated by measuring the capacitance shift as a function of the input acceleration.

A tri-axis MEMS capacitive sensor using multi-layered high-density metal for an integrated CMOS-MEMS accelerometer

This paper reports a novel tri-axis microelectro-mechanical systems (MEMS) capacitive sensor utilizing multi-layer electroplated gold. The high density of gold has enabled us to minimize the Brownian noise and hence to reduce the footprint of the proof mass. To optimize the flexibility of the mechanical springs for tri-axis motions, we have newly developed multi-layered metal spring structures. All the MEMS structures have been made by gold electroplating, used as a post complementary metal-oxide semiconductor (CMOS) process, and thereby the MEMS sensors can be implemented as integrated CMOS-MEMS accelerometers.

A 1mG-to-20G Integrated MEMS Inertial Sensor

We report an integrated MEMS (micro-electro-mechanical systems) inertial sensor with the sensing range from 1mG to 20G (G = 9.8 m/s2), which is suitable to realize integrated CMOS (complementary-metal-oxide semiconductor)-MEMS accelerometers. By utilizing the high-density of gold and the electroplating process, we have implemented five sets of single-axis MEMS capacitive inertial sensors on a silicon die of 4 mm × 4 mm to obtain a wide sensing range from 1mG to 20G. The measured Brownian noise is ranged from 82.4 nG/Hz1/2 to 1.11 μG/Hz1/2, which shows the feasibility of high-resolution sensing.

A Sub-1G Tri-axis MEMS Capacitive Sensor for Integrated CMOS-MEMS Accelerometers

This paper reports a novel sub-1G tri-axis microelectromechanical systems (MEMS) capacitive sensor by employing the high-density of gold for the proof mass. All the MEMS structures have been fabricated by post complementary metal-oxide semiconductor (CMOS) process such that the sensor can be implemented as integrated CMOS-MEMS accelerometers. We demonstrate the capacitance shift as a function of input acceleration in X-, Yand Zaxis, and the experimentally obtained Brownian noise have been below 1 G/Hz 1/2 (G = 9.8 m/s 2 ).