Fabrication of Monolithic Integrated Bimaterial Resonant Uncooled IR Sensor

2013 ◽  
Vol 543 ◽  
pp. 176-179 ◽  
Author(s):  
D.Q. Zhao ◽  
Xia Zhang ◽  
P. Liu ◽  
F. Yang ◽  
C. Lin ◽  
...  
Keyword(s):  
Silicon Nitride ◽  
Hole Mobility ◽  
Micro Electro Mechanical System ◽  
Cmos Process ◽  
Standard Cmos Process ◽  
Ir Sensor ◽  
Cantilever Structure ◽  
Cmos Mems ◽  
On Chip ◽  
Micro Cantilever

In this work we studied the fabrication of a monolithic bimaterial micro-cantilever resonant IR sensor with on-chip drive circuits. The effects of high temperature process and stress induced performance degradation were investigated. The post-CMOS MEMS (micro electro mechanical system) fabrication process of this IR sensor is the focus of this paper, starting from theoretical analysis and simulation, and then moving to experimental verification. The capacitive cantilever structure was fabricated by surface micromachining method, and drive circuits were prepared by standard CMOS process. While the stress introduced by MEMS films, such as the tensile silicon nitride which works as a contact etch stopper layer for MOSFETs and releasing stop layer for the MEMS structure, increases the electron mobility of NMOS, PMOS hole mobility decreases. Moreover, the NMOS threshold voltage (Vth) shifts, and transconductance (Gm) degrades. An additional step of selective removing silicon nitride capping layer and polysilicon layer upon IC area were inserted into the standard CMOS process to lower the stress in MOSFET channel regions. Selective removing silicon nitride and polysilicon before annealing can void 77% Vth shift and 86% Gm loss.

Method for Achieving CMOS MEMS Accelerometers with Excellent Built-in Thermal Stability and Reduced Charge Damage

2012 ◽  
Vol 1415 ◽  
Author(s):  
Klaus Y. J. Hsu ◽  
Siew Seong Tan
Keyword(s):  
Thermal Stability ◽  
Stress Gradient ◽  
Dry Etching ◽  
Detection Sensitivity ◽  
Cmos Process ◽  
Excellent Thermal Stability ◽  
Mems Accelerometers ◽  
Out Of Plane ◽  
Cmos Mems ◽  
On Chip

ABSTRACTCapacitive CMOS MEMS sensors are usually defined by anisotropic dry etching processes (RIE and DRIE). These processes can provide clean and vertical sidewall geometry. However, during the dry-etching processes, charges are added to the gate electrodes of the on-chip MOSFET’s through metal pads and micro-structures, and the voltage may be raised to the level of breaking down the gate oxide, which leads to large leakage current and fails the circuit. On another hand, the thin spring beams in capacitive CMOS MEMS accelerometers suffer from in-plane curling and out-of-plane curling caused by stress gradient. Furthermore, the stress in the layers of MEMS structure is a function of temperature. Therefore, the in-plane curling and out-of-plane curling vary with temperature, leading to varying electrode coupling area in the sensing beams. This in turn causes variation in the sensitivity and the DC offset of sensors, meaning that usually the thermal stability of CMOS MEMS capacitive accelerometers is very poor. To cope with these problems, this work develops a new wafer-level post-CMOS process for fabricating thermally stable capacitive accelerometers. The resultant MEMS structures have high aspect ratio (e.g. 2-2.5 μm gaps versus 57 μm depth) and are insensitive to residual stress as well as temperature change. Excellent thermal stability was achieved intrinsically by making the crystalline Si layer in the sensors thick. Moreover, this process totally avoids the charge damage problem during the dry-etching procedure. For demonstration, an accelerometer sensor was fabricated by using the proposed process and was integrated with an on-chip sensing circuit in commercial 0.35 μm 2P4M CMOS process. High detection sensitivity of 595 mV/g and very low thermal variation of 1.68 mg/°C were successfully achieved.

scholarly journals Detection of cracks in Micro structured Cantilever Beam using Wavelet Transforms

2020 ◽  
Vol 8 (6) ◽  
pp. 501-505
Keyword(s):  
Wavelet Transform ◽  
Cantilever Beam ◽  
Wavelet Transforms ◽  
Micro Electro Mechanical System ◽  
Mems Devices ◽  
Device Structure ◽  
Time Frequency ◽  
Cantilever Structure ◽  
Small Change ◽  
Micro Cantilever

Wavelet Analysis, the improved version of Fourier transform is used to investigate and analyze the variant transient signals in time-frequency domain with higher accuracy and precision. Wavelet theory found its promising application in various fields not limited to Physics, Biology, Geophysics, Engineering and Medicine which becomes a common tool to analyze data. In this work we present new insight using wavelet transform to detect the cracks present in micro structured cantilever beam which found its application in various Micro Electro Mechanical System (MEMS) devices such as Transducers, Sensors, Switches, Actuators and Probes. Even a small change in microstructure will reflect in its dynamic output, so it is desired to locate the presence of cracks or damages over the device structure accurately. The modeling of such microstructure is designed and simulated using COMSOL Multiphysics. The displacement (Static Response) and stress of the beam for simulated damage were analyzed by wavelet transform using MATLAB. The obtained results highlights this method of analysis provides accurate location and effect of the crack over the Micro cantilever structure.

scholarly journals Research on a CMOS-MEMS Infrared Sensor with Reduced Graphene Oxide

Sensors ◽  
2020 ◽  
Vol 20 (14) ◽  
pp. 4007 ◽  
Author(s):  
Shu-Jung Chen ◽  
Bin Chen
Keyword(s):  
Graphene Oxide ◽  
Reduced Graphene Oxide ◽  
Complementary Metal Oxide Semiconductor ◽  
Oxide Semiconductor ◽  
Cmos Process ◽  
Ir Absorption ◽  
Long Distance ◽  
Ir Sensor ◽  
Reduced Graphene ◽  
Cmos Mems

In this research, a new application of reduced graphene oxide (rGO) for a complementary metal-oxide-semiconductor (CMOS)-MEMS infrared (IR) sensor and emitter is proposed. Thorough investigations of IR properties including absorption and emission were proceeded with careful calibration and measurement with a CMOS thermoelectric sensor. The thermocouples of the sensor consist of aluminum and n-polysilicon layers which are fabricated with the TSMC 0.35 μm CMOS process and MEMS post-process. In order to improve the adhesion of rGO, a sensing area at the center of the membrane is formed with an array of holes, which is easy for the drop-coating of rGO material upon the sensing region. To evaluate the performance of the IR sensor with rGO, different conditions of the IR thermal radiation experiments were arranged. The results show that the responsivity of our proposed CMOS-MEMS IR sensor with rGO increases by about 77% compared with the sensor without rGO. For different IR absorption incident angles, the measurement of field of view shows that the CMOS-MEMS IR sensor with rGO has a smaller view angle, which can be applied for the application of long-distance measuring. In addition, characteristics of the proposed thermopile are estimated and analyzed with comparisons to the available commercial sensors by the experiments.

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