Design, simulation and fabrication of piezoresistive microcantilevers using standard multi user MEMS process (original) (raw)
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The present study investigates Joule heating in piezoresistive microcantilever sensors. Joule heating and thermal deflections are a major source of noise in such sensors. This work uses analytical and numerical techniques to characterise the Joule heating in 4-layer piezoresistive microcantilevers made of silicon and silicon dioxide substrates but with the same U-shaped silicon piezoresistor. A theoretical model for predicting the temperature generated due to Joule heating is developed. The commercial finite element software ANSYS Multiphysics was used to study the effect of electrical potential on temperature and deflection produced in the cantilevers. The effect of piezoresistor width on Joule heating is also studied. Results show that Joule heating strongly depends on the applied potential and width of piezoresistor and that a silicon substrate cantilever has better thermal characteristics than a silicon dioxide cantilever.
Minimizing the Development Steps of Piezoresistive Microcantilever Using MEMS Micromachining
The conventional photolithography of crystalline silicon techniques is limited to two-dimensional and structure scaling. It is also requiring a lot of time and chemical involves for the whole process. These problems can be overcome by using laser micromachining, which a technique capable of producing three-dimensional (3D) structure and simultaneously avoiding the needs for photomasks. This paper reported the use of RapidX-250 excimer laser micromachine with 248 nm KrF to create in-time mask design and assisting ifabrication of piezoresistive microcantilever structures.Laser micromachining parameters is investigated in order to fabricate the microcantilever, which can be used in multiple applications including acceleration, vibration, bio/chemical detections and also in energy harvesting. Preliminary result shows that the fabricated sensor able to define the differences force and acceleration given regarding the unique electrical characteristic on fabricated piezoresistor.
This paper reports on the development of a piezoresistive microcantilever sensor read-out circuitry to detect acceleration, biological or chemical activities. Laser micromachining technique is used in fabricating the piezoresistive microcantilever sensor as well as assisting in the cantilever beam and piezoresistor shape formation. In order to test the sensor performance, a Wheatstone bridge which acts as resistive sensor is integrated with three other resistors and the fabricated sensor. A set of amplifier circuit consisting of INA128 is developed to amplify and extract the electrical signal component of the bridge circuit. The resistance and output voltage characteristic of the Wheatstone bridge is investigated, where the percentages difference between the calculated and measured output voltage is very low and similar to each other. The sensor response to vibration is also studied using an electro-dynamic vibration system. The system is designed specifically to enable the accessibility of a small resistivity change due to outside reaction.
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Journal of Physics: Conference Series, 2014
One the major requirements for sensing devices is its sensitivity. This paper presents the design, analysis and simulation of various types of MEMS based microcantilevers shapes and their influence on sensing sensitivity. A commercial finite element analysis software ANSYS is used to analyze the designs. Six different analytical model of the microcantilever were investigated for its Equivalent (von-Mises) stress, maximum deflection and fundamental resonant frequency. Finally, the best sensitive structure is then identified. It is found that the trapezoidal design microcantilever would have significant sensing advantages compared to other remaining microcantilever shape.
Simulation and design of piezoelectric microcantilever chemical sensors
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This paper presents an analytical modeling of a piezoelectric multi-layer cantilever used as a micro-electro-mechanical-system (MEMS) chemical sensor. Selectively coated microcantilevers have been developed for highly sensitive chemical sensor applications. The proposed piezoelectric chemical sensor consists of an array of multi-layer piezoelectric cantilevers with voltage output in the millivolt range that replaces the conventional laser-based position-sensitive detection systems. The sensing principle is based upon changes in the deflection induced by environmental factors in the medium where a microcantilever is immersed. Bending of the cantilever induces the potential difference on opposite sides of the piezoelectric layer providing an information signal about the detected chemicals. To obtain an application specific optimum design parameters and predict the cantilever performance ahead of actual fabrication, finite element analysis (FEM) simulations using CoventorWare (a MEMS design and simulation program) were performed. Analytical models of multi-layer cantilevers as well as simulation concept are described. Both mechanical and piezoelectric simulation results are carried out. The cantilever structures are analyzed and fabrication process steps are proposed.
2008
Microcantilevers that thermally sense the topography of the sample with the ability of electrostatic actuation enable a highly parallel implementation where multiple cantilevers scan the media. Microcantilevers with integrated sensors are used for a variety of applications viz. calorimetry, thermal dip pen lithography, thermal metrology, room temperature chemical vapor deposition in addition to high density data storage application. The dynamics of these cantilevers is governed by a complex interplay of mechanical, thermal, electrostatic and interatomic forces. Such dynamics are analyzed in this paper for operating conditions that are practical for high density data storage applications (¿ Tb=in2) and imaging. Models for a thermo-mechanical cantilever that are tractable for real-time applications as well as a comprehensive characterization of the relevant physical effects and methods for identifying model parameters are developed. The efficacy of the paradigm developed is proven by a comparison with experimental data.
IEEE Sensors Journal, 2000
Microelectromechanical systems (MEMS)-based cantilever beam sensors for microfluidics applications with on-chip temperature sensors for temperature drift compensation were developed. The stress induced on gold surface with polysilicon piezoresistive sensing is demonstrated. In principle, adsorption of biochemical species on a functionalized surface of the microfabricated cantilever will cause surface stress and, consequently, cantilever bending. The sensing mechanism relies on the piezoresistive properties of the doped polysilicon wire encapsulated in the beam. The beam is constructed through multiusers MEMS Process (PolyMUMPs) foundry with postprocessing silicon etching. Bending analysis is performed so that the beam tip deflection can be predicted. The piezoresistor designs on the beams were varied, within certain constraints, so that the sensitivity of the sensing technique could be measured by external read-out circuit. The mass detection of 0.0058-0.0110 g is measured by the beam resistor series as a balanced Wheatstone bridge configuration. The voltage output of the bridge is directly proportional to the amount of bending in the MEMS cantilever. The temperature dependency and sensor performance have been characterized in experiments. Compensation by resisters on the substrate significantly reduces the temperature dependence.