Monolithic integration of capacitive sensors using a double-side CMOS MEMS post process (original) (raw)
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Journal of Micromechanics and Microengineering, 2009
This study presents a process design methodology to improve the performance of a CMOS-MEMS gap-closing capacitive sensor. In addition to the standard CMOS process, the metal wet-etching approach is employed as the post-CMOS process to realize the present design. The dielectric layers of the CMOS process are exploited to form the main micro mechanical structures of the sensor. The metal layers of the CMOS process are used as the sensing electrodes and sacrificial layers. The advantages of the sensor design are as follows:
Japanese Journal of Applied Physics, 2014
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/s 2), 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 Review of MEMS based Capacitive Pressure Sensor
This paper presents a review of the capacitive pressure sensor. Firstly, the different types of sensors available are compared. For applications requiring high sensitivity and very low effects due to temperature, the capacitive sensor is preferred. Various methods to change the capacitance are also compared, which leads to the conclusion that the method involving changing the distance between the plates has the highest sensitivity. The different diaphragms available are also compared in this paper. The result of the comparison shows that the square diaphragm is most suitable. Further study shows that the diaphragm with a bossed structure has the highest sensitivity and the lowest nonlinearity. After the structural analysis, the pull-in effect phenomenon present during anodic bonding is also studied. The analysis of the pull-in effect showed that the dimension of the sensor should be chosen such that the electrodes do not stick during the anodic bonding. Different capacitive sensing schemes are also shown in this paper. The parasitic capacitances and the noise are major factors limiting the performance of the sensor. So the sources and methods to mitigate such effects are also presented. The ASICs available for the conversion of the capacitance to voltage or digital output are compared based on different parameters.
Design and Simulation of MEMS Capacitive Pressure Sensor
Employing the MEMS technology, high sensitivities and resolutions have been achieved. Capacitive sensing uses the diaphragm deformation-induced capacitance change. In this paper, the design and simulation of conventional slotted and touch mode MEMS capacitive pressure sensor is proposed. The designed sensors are composed of a polysilicon diaphragm that deflects due to pressure applied over it, is accounted for modeling. The simulation results shows that the slotted MEMS capacitive pressure sensor achieves good sensitivity where as the touch mode MEMS capacitive pressure sensor achieves good linearity and large operating pressure range. The proposed MEMS capacitive pressure sensor demonstrated with diaphragm of side length 20 μm, gap depth 2 m is being modelled. The sensor exhibit a linear response for the pressure applied between 0 to 50 MPa. The simulation is carried out for different types of MEMS capacitive pressure sensor using COMSOL Multiphysics.
2013
Micro-electromechanical systems (MEMS) have received a great deal of attention in recent years. This is due to the great promise of increased miniaturization and Performance of MEMS devices over conventional devices. MEMS pressure sensors currently dominate the market for greater than atmospheric pressure sensors. In this paper, a theoretical and finite elements analysis (FEA) solution for Micro-electromechanical systems (MEMS) pressure sensor to evaluate capacitance for before and after touch point is proposed. By looking at MEMS devices, when the diaphragm starts touching the fixed electrode by applying loads, it will have a major effect on the overall of the capacitance. Therefore, one should consider the effect of touch mode capacitance value in the system to evaluate good linearity, large operating pressure range and large overload protection at output. As of so far the evaluation for capacitance value of touch point and after touch point has not been evaluated in the literatures. This paper presents the new analytical formula to approach for including the touchdown effect capacitance value of Microsystems. The proposed MEMS capacitive pressure sensor demonstrated diaphragm with radius of m 180 , the gap depth of m 5. 0 and the sensor exhibit linear response with pressure from 0.01 Mpa to 1.7 Mpa.
MEMS Capacitive Pressure Sensors: A Review on Recent Development and Prospective
—Recently MEMS Capacitive Pressure Sensor gains more advantage over micromachined piezoresistive pressure sensor due to high sensitivity, low power consumption, free from temperature effects, IC compatibility, etc,. The spectrum of capacitive pressure sensor application is increasing, hence it is essential to review the path of technological development and further prospective of micromachined capacitive pressure sensor. This paper focuses on the review of various types of capacitive pressure sensor principle, MEMS materials used in fabrication, procedures adopted in microfabrication for silicon and polymer material diaphragm, bonding and packaging techniques used. Selected result on capacitive sensitivity, effect of temperature on capacitive sensitivity was also presented. Finally, the development of smart sensor was discussed. MEMS Capacitive pressure sensor, Review on pressure sensor, CDPS, MEMS Fabrication, MEMS Material, pressure sensor, MEMS (Micro Electro Mechanical System)
Journal of Micromechanics and Microengineering, 2007
This study presents a novel CMOS-MEMS out-of-plane linear accelerometer. This capacitance-type accelerometer contains specially designed gap-closing sensing electrode arrays with on-chip fully differential sensing circuits. Moreover, the comb-finger electrodes have the characteristics of the high fill factor and sub-micron gap to increase the sensing capacitance. Thus, the sensitivity and signal-to-noise ratio can be further improved. This study has established a post-CMOS wet-etching process to realize the accelerometer with sensing electrodes of the sub-micron gap in the out-of-plane direction. The present accelerometer has been demonstrated using the standard TSMC 2P4M process plus the post-release technique. The measurement results demonstrate that the accelerometer has a sensitivity of 1.14 mV g −1 , and a nonlinearity of 3.4%.
Energy Harvesting and Systems, 2021
In this paper, the improvement of the sensitivity of a capacitive MEMS pressure sensor is investigated. The proposed spring for the sensor can increase the sensitivity. Silicon is used as the substrate and gold and aluminium nitrate are used as the diaphragm and the dielectric layer, respectively. The dimensions of the diaphragm are 150 µm × 150 µm, which is suspended by four springs. The air gap between the diaphragm and the top electrode is 1.5 µm. The proposed structure is an efficient sensor for the pressures in the range of 1–20 kPa. By using the proposed design, the sensitivity of the MEMS sensor in 18 kPa has improved to 663 (× 10−3 pF/kPa).
MEMS Capacitive Accelerometer: A Review
2023
Micro-electro-mechanical systems sensors are integrated systems used in many fields such as consumer electronics, the automobile industry, and biomedical, and their dimensions change between micrometers and millimeters. MEMS capacitive accelerometers are the most widely used sensor type among MEMS accelerometer sensors. As a result of the external force applied to the capacitive accelerometer sensor, the proof mass inside the sensor moves, and the capacitive change is measured as an electrical signal using reading circuits. In this review paper, general information about MEMS sensors is given, and a comprehensive review is made of MEMS capacitive accelerometers. In the study, the dynamic circuit of the MEMS capacitive accelerometer is given, and the calculation of the important values for the mechanical and electronic structure during the design of the capacitive MEMS accelerometer is explained. In addition, information about the readout circuits used to convert the capacitive change to voltage is given. Finally, the fabrication processes used to produce the final product are explained, and the studies on sample fabrication processes found in the literature are mentioned.