Thin Film Polymer Stress Measurement Using Piezoresistive Anisotropically Etched Pressure Sensors

1995 ◽  
Vol 390 ◽  
Author(s):  
David J. Monk ◽  
Mahesh Shah
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
Pressure Sensor ◽  
Stress Measurement ◽  
Applied Pressure ◽  
Pressure Sensors ◽  
Film Stress ◽  
Polymeric Coating ◽  
Stress Effect ◽  
Parylene C

ABSTRACTStresses in thin polymer films have been studied for some time by using wafer bowing, bending beams, microstructure release, and laser holographic techniques. An alternative technique for measuring stresses in thin films is discussed in the following paper. Piezoresistive anisotropically etched single crystal silicon pressure sensors are sensitive not only to applied pressure, but also to applied package stress. Deposited passivation materials, like silicone gels and polyimides, have been observed to change the sensitivity of the pressure sensor. In the current work, a thin, conformal polymeric coating (parylene C) is being developed for these pressure sensors. This thin film has been observed to reduce the sensitivity of the device as a function of the film thickness and modulus and the silicon thickness and modulus. The parylene C thin films exhibit a consistent change in film stress during annealing indicating a modification to polymer crystallinity and a corresponding change in material properties. Qualitatively, the electrical output on the pressure sensor compares favorably with measurements taken using wafer bowing. Experimental DMA and TMA work has been performed to determine the modulus (7.84 × 105 psi) and CTE (39 ppm/°C at 25 °C) of the material. However, literature values of modulus (4.1 × 105 psi) have been used with finite element analysis to model the stress effect more accurately for the thin conformal coating on the pressure sensor device. These results indicate that the sensitivity of the pressure sensor will be reduced approximately quadratically as a function of the polymer coating thickness. An empirical function has been derived to estimate sensitivity loss as a function of substrate (i.e., initial diaphragm material) modulus and thickness and coating modulus and thickness.

Development of circuit solution and design of capacitive pressure sensor array for applied robotics

2020 ◽  
Vol 8 (4) ◽  
pp. 296-307
Author(s):  
Konstantin Krestovnikov ◽  
Aleksei Erashov ◽  
Аleksandr Bykov
Keyword(s):  
Pressure Sensor ◽  
Output Signal ◽  
Sensor Array ◽  
Applied Pressure ◽  
Pressure Sensors ◽  
Fine Tuning ◽  
Capacitive Pressure Sensor ◽  
Cell Parameters ◽  
Linear Pattern ◽  
Sensor Structure

This paper presents development of pressure sensor array with capacitance-type unit sensors, with scalable number of cells. Different assemblies of unit pressure sensors and their arrays were considered, their characteristics and fabrication methods were investigated. The structure of primary pressure transducer (PPT) array was presented; its operating principle of array was illustrated, calculated reference ratios were derived. The interface circuit, allowing to transform the changes in the primary transducer capacitance into voltage level variations, was proposed. A prototype sensor was implemented; the dependency of output signal power from the applied force was empirically obtained. In the range under 30 N it exhibited a linear pattern. The sensitivity of the array cells to the applied pressure is in the range 134.56..160.35. The measured drift of the output signals from the array cells after 10,000 loading cycles was 1.39%. For developed prototype of the pressure sensor array, based on the experimental data, the average signal-to-noise ratio over the cells was calculated, and equaled 63.47 dB. The proposed prototype was fabricated of easily available materials. It is relatively inexpensive and requires no fine-tuning of each individual cell. Capacitance-type operation type, compared to piezoresistive one, ensures greater stability of the output signal. The scalability and adjustability of cell parameters are achieved with layered sensor structure. The pressure sensor array, presented in this paper, can be utilized in various robotic systems.

CMOS-MEMS Based Current Mirror MOSFET Embedded Pressure Sensor for Healthcare and Biomedical Applications

2013 ◽  
Vol 647 ◽  
pp. 315-320 ◽  
Author(s):  
Pradeep Kumar Rathore ◽  
Brishbhan Singh Panwar
Keyword(s):  
Pressure Sensor ◽  
Biomedical Applications ◽  
Circuit Simulation ◽  
Applied Pressure ◽  
Pressure Sensors ◽  
Cmos Technology ◽  
Current Mirror ◽  
Sensing Element ◽  
Pressure Sensing ◽  
Cmos Mems

This paper reports on the design and optimization of current mirror MOSFET embedded pressure sensor. A current mirror circuit with an output current of 1 mA integrated with a pressure sensing n-channel MOSFET has been designed using standard 5 µm CMOS technology. The channel region of the pressure sensing MOSFET forms the flexible diaphragm as well as the strain sensing element. The piezoresistive effect in MOSFET has been exploited for the calculation of strain induced carrier mobility variation. The output transistor of the current mirror forms the active pressure sensing MOSFET which produces a change in its drain current as a result of altered channel mobility under externally applied pressure. COMSOL Multiphysics is utilized for the simulation of pressure sensing structure and Tspice is employed to evaluate the characteristics of the current mirror pressure sensing circuit. Simulation results show that the pressure sensor has a sensitivity of 10.01 mV/MPa. The sensing structure has been optimized through simulation for enhancing the sensor sensitivity to 276.65 mV/MPa. These CMOS-MEMS based pressure sensors integrated with signal processing circuitry on the same chip can be used for healthcare and biomedical applications.

Micromachined Pressure Sensors on Optical Fiber Tip

2009 ◽  
Vol 74 ◽  
pp. 149-152
Author(s):  
X.M. Zhang ◽  
M. Yu ◽  
Silas Nesson ◽  
H. Bae ◽  
A. Christian ◽  
...  
Keyword(s):  
Optical Fiber ◽  
Pressure Sensor ◽  
Linear Response ◽  
Applied Pressure ◽  
Pressure Sensors ◽  
Outer Diameter ◽  
Sensor Element ◽  
Batch Fabrication ◽  
In Vitro Measurements

This paper reports the development of a miniature pressure sensor on the optical fiber tip for in vitro measurements of rodent intradiscal pressure. The sensor element is biocompatible and can be fabricated by simple, batch-fabrication methods in a non-cleanroom environment with good device-to-device uniformity. The fabricated sensor element has an outer diameter of only 366 μm, which is small enough to be inserted into the rodent discs without disrupting the structure or altering the intradiscal pressures. In the calibration, the sensor element exhibits a linear response to the applied pressure over the range of 0 - 70 kPa, with a sensitivity of 0.0206 μm/kPa and a resolution of 0.17 kPa.

Experimental Evaluation of the Probe Test for Measuring Thin Film Adhesion

2003 ◽  
Author(s):  
David A. Dillard ◽  
Caleb Scott ◽  
Kris Mount ◽  
Dingying Xu ◽  
Kai-Tak Wan ◽  
...  
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
Finite Element ◽  
Experimental Evaluation ◽  
Polymeric Coating ◽  
Finite Element Analyses ◽  
Film Adhesion ◽  
Thin Film Adhesion ◽  
Probe Test ◽  
Interfacial Fracture Energy

A probe test is proposed to quantify the adhesion of thin films and coatings. Using a micromanipulator, a tungsten probe is advanced into the edge of a polymeric coating. Debonds initiate at the loading point and propagate into semicircular cracks at the interface as the probe slides under the coating. The size of the debond is related to the interfacial fracture energy; poorer adhesion results in larger debonds for a given probe displacement. Approximate closed-form and finite element analyses of the geometry have been conducted, along with a significant number of experiments on as-produced and environmentally-conditioned specimens. The technique is showing considerable promise for characterizing coating adhesion, and has certain advantages over existing techniques for certain application.

Measurement of Thin-Film Stress, Stiffness, and Strength Using an Enhanced Membrane Pressure-Bulge Technique

2003 ◽  
Vol 795 ◽  
Author(s):  
Aaron J. Chalekian ◽  
Roxann L. Engelstad ◽  
Edward G. Lovell
Keyword(s):  
Thin Films ◽  
Microelectromechanical Systems ◽  
Applied Pressure ◽  
High Strength ◽  
Film Stress ◽  
Intrinsic Stress ◽  
Positive Pressure ◽  
Bulge Test ◽  
Thin Film Stress ◽  
The One

ABSTRACTAccurate mechanical properties of thin films are essential for viable design and fabrication of semiconductor devices and microelectromechanical systems. Relevant properties of thin films such as intrinsic stress, biaxial modulus, and fracture strength can be significantly different than their corresponding bulk values, and much more difficult to measure. However, such data can be obtained from the pressure-deflection response of clamped freestanding membranes, i.e., the so-called pressure-bulge test. Experimental challenges include membrane leakage prevention, ensuring proper structural boundary conditions, and accurately measuring applied pressure and transverse displacements simultaneously. In addition to these issues, most previously-developed pressure-bulge instruments rely on vacuum pump loadings. Such tools are limited by the one-atmosphere differential pressure over the membrane, which is inadequate for burst testing of high-strength films. Consequently, an enhanced pressure-bulge tool has been developed and will be described in this paper. It incorporates positive pressure to overcome the one-atmosphere load limitation, improved edge constraints, and the ability to test an array of membrane windows across a single substrate.

A pressure-deformation analytical model for rectangular diaphragm of MEMS pressure sensors

2017 ◽  
Vol 31 (05) ◽  
pp. 1750046
Author(s):  
Wu Zhou ◽  
Dong Wang ◽  
Huijun Yu ◽  
Bei Peng
Keyword(s):  
Pressure Sensor ◽  
Applied Pressure ◽  
Influence Factors ◽  
Pressure Sensors ◽  
Superposition Method ◽  
Uniform Load ◽  
Pressure Sensitive ◽  
Partial Load ◽  
Mems Pressure Sensors ◽  
Measured Pressure

Rectangular diaphragm is commonly used as a pressure sensitive component in MEMS pressure sensors. Its deformation under applied pressure directly determines the performance of micro-devices, accurately acquiring the pressure–deflection relationship, therefore, plays a significant role in pressure sensor design. This paper analyzes the deflection of an isotropic rectangular diaphragm under combined effects of loads. The model is regarded as a clamped plate with full surface uniform load and partially uniform load applied on its opposite sides. The full surface uniform load stands for the external measured pressure. The partial load is used to approximate the opposite reaction of the silicon island which is planted on the diaphragm to amplify the deformation displacement, thus to improve the sensitivity of the pressure sensor. Superposition method is proposed to calculate the diaphragm deflections. This method considers separately the actions of loads applied on the simple supported plate and moments distributed on edges. Considering the boundary condition of all edges clamped, the moments are constructed to eliminate the boundary rotations caused by lateral load. The diaphragm’s deflection is computed by superposing deflections which produced by loads applied on the simple supported plate and moments distributed on edges. This method provides higher calculation accuracy than Galerkin variational method, and it is used to analyze the influence factors of the diaphragm’s deflection, includes aspect ratio, thickness and the applied force area of the diaphragm.

Identification of the Failure Mechanism of a Thin Film on a Thick Substrate by Means of Synchrotron X-Ray Topography Combined with Transmission Electron Microscopy

1987 ◽  
Vol 108 ◽  
Author(s):  
D. Goyal ◽  
W. Ng ◽  
A. H. King ◽  
J. C. Bilello
Keyword(s):  
Thin Film ◽  
Electron Microscopy ◽  
Thin Films ◽  
Transmission Electron Microscopy ◽  
Film Thickness ◽  
Film Stress ◽  
Silicon Substrates ◽  
X Ray ◽  
Transmission Electron ◽  
Thick Substrate

ABSTRACTWe have used synchrotron x-ray topographic techniques to study the stresses in thin films formed upon silicon substrates either by evaporation or sputtering. It is found that the film stress generally decreases with increasing film thickness for evaporated films, but film delamination occurs at a well defined film thickness. Transmission electron microscope studies have been performed on the same specimens in order to reveal what mechanisms are involved with the delamination of the films.

scholarly journals Fabrication of Pressure Sensor Using Electrospinning Method for Robotic Tactile Sensing Application

Nanomaterials ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 1320
Author(s):  
Tamil Selvan Ramadoss ◽  
Yuya Ishii ◽  
Amutha Chinnappan ◽  
Marcelo H. Ang ◽  
Seeram Ramakrishna
Keyword(s):  
Pressure Sensor ◽  
Applied Pressure ◽  
Pressure Sensors ◽  
Open Circuit ◽  
Tactile Sensing ◽  
Base Materials ◽  
Sensing Applications ◽  
Electrospinning Method ◽  
Base Polymer ◽  
External Stimuli

Tactile sensors are widely used by the robotics industries over decades to measure force or pressure produced by external stimuli. Piezoelectric-based pressure sensors have intensively been investigated as promising candidates for tactile sensing applications. In contrast, piezoelectric-based pressure sensors are expensive due to their high cost of manufacturing and expensive base materials. Recently, an effect similar to the piezoelectric effect has been identified in non-piezoelectric polymers such as poly(d,l-lactic acid (PDLLA), poly(methyl methacrylate) (PMMA) and polystyrene. Hence investigations were conducted on alternative materials to find their suitability. In this article, we used inexpensive atactic polystyrene (aPS) as the base polymer and fabricated functional fibers using an electrospinning method. Fiber morphologies were studied using a field-emission scanning electron microscope and proposed a unique pressure sensor fabrication method. A fabricated pressure sensor was subjected to different pressures and corresponding electrical and mechanical characteristics were analyzed. An open circuit voltage of 3.1 V was generated at 19.9 kPa applied pressure, followed by an integral output charge (ΔQ), which was measured to calculate the average apparent piezoelectric constant dapp and was found to be 12.9 ± 1.8 pC N−1. A fabricated pressure sensor was attached to a commercially available robotic arm to mimic the tactile sensing.

scholarly journals Modeling of a square-shape ZnO, ZnS and AlN membrane for mems capacitive pressure-sensor applications

2020 ◽  
Vol 11 ◽  
pp. 14
Author(s):  
Ahmad Dagamseh ◽  
Qais Al-Bataineh ◽  
Zaid Al-Bataineh ◽  
Nermeen S. Daoud ◽  
Ahmad Alsaad ◽  
...  
Keyword(s):  
Thermal Stress ◽  
Pressure Sensor ◽  
Membrane Structure ◽  
Applied Pressure ◽  
Pressure Sensors ◽  
Membrane Thickness ◽  
Capacitive Pressure Sensor ◽  
The Finite Element Method ◽  
Sensor Applications ◽  
Opposite Behavior

In this paper, mathematical modeling and simulation of a MEMS-based clamped square-shape membrane for capacitive pressure sensors have been performed. Three types of membrane materials were investigated (i.e. Zinc Oxide (ZnO), Zinc Sulfide (ZnS) and Aluminum Nitride (AlN)). Various performance parameters such as capacitance changes, deflection, nonlinearity, the sensitivity of the membrane structure for different materials and film-thicknesses have been considered using the Finite Element Method (FEM) and analytically determined using the FORTRAN environment. The simulation model outperforms in terms of the effective capacitance value. The results show that the membrane deflection is linearly related to the applied pressure. The ZnS membrane provides a capacitance of 0.023 pico-Farad at 25 kPa with a 42.5% relative capacitance changes to reference capacitance. Additionally, the results show that for ZnO and AlN membranes the deflection with no thermal stress is higher than that with thermal stress. However, an opposite behavior for the ZnS membrane structure has been observed. The mechanical and capacitance sensitivities are affected by the membrane thickness as the capacitance changes are inversely proportional to the membrane thickness. Such results open possibilities to utilize various materials for pressure sensor applications by means of the capacitance-based detection technique.

scholarly journals Thin film stress and microstructure analysis by energy-dispersive diffraction

2014 ◽  
Vol 70 (a1) ◽  
pp. C724-C724
Author(s):  
Christoph Genzel
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
Residual Stress ◽  
Film Growth ◽  
High Energy ◽  
Energy Dispersive ◽  
Film Stress ◽  
Ex Situ ◽  
Near Surface

The most important advantage of energy dispersive (ED) diffraction compared with angle dispersive methods is that the former provides complete diffraction patterns in fixed but arbitrarily selectable scattering directions. Furthermore, in experiments that are carried out in reflection geometry, the different photon energies E(hkl) of the diffraction lines in an ED diffraction pattern can be taken as an additional parameter to analyze depth gradients of structural properties in the materials near surface region. For data evaluation advantageous use can be made of whole pattern methods such as the Rietveld method, which allows for line profile analysis to study size and strain broadening [1] or for the refinement of models that describe the residual stress depth distribution [2]. Concerning polycrystalline thin films, the features of ED diffraction mentioned above can be applied to study residual stresses, texture and the microstructure either in ex-situ experiments or in-situ to monitor, for example, the chemical reaction pathway during film growth [3]. The main objective of this talk is to demonstrate that (contrary to a widespread opinion) high energy synchrotron radiation and thin film analysis may fit together. The corresponding experiments were performed on the materials science beamline EDDI at BESSY II which is one of the very few instruments worldwide that is especially dedicated to ED diffraction. On the basis of selected examples it will be shown that specially tailored experimental setups allow for residual stress depth profiling even in thin films and multilayer coatings as well as for fast in situ studies of film stress and microstructure evolution during film growth.

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