Fabrication of SiC MEMS Pressure Sensor Based on Novel Vacuum-Sealed Method (original) (raw)
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The Fifth International Conference on Advanced Semiconductor Devices and Microsystems, 2004. ASDAM 2004., 2004
Characterization of cubic 3C(fJ)-SiC samples for pressure sensors and micro-electromechanical system (MEMS) applications is reported in this paper. Polycrystalline 3C(fJ)-SiC thinjilms have been deposited on oxidized Si by low pressure chemical vapor deposition (LPCVD) to obtain bi-layer structures [Si(lOO)/SiO;lpoly 3C-SiCj. The films have been preliminary characterized by atomic force microscopy (AFM) and surface photovollage spectroscopy (SPS) and then ohmic contacts have been optimized by transmission line method (TLM) analyses performed at diff erent temperatures focusing the attention on the evaluation of the bulk resistivity (p), the spec ifi c contact resistivity (pJ.
Design, analysis and fabrication of 4H–SiC diaphragm for piezoresistive MEMS pressure sensor
ISSS Journal of Micro and Smart Systems, 2021
A diaphragm-based MEMS pressure sensor, suitable for harsh environments, was designed, simulated, analyzed and virtually fabricated on p -type SiC epitaxial semi-insulating 4H–SiC substrate to measure the external pressure in the range of 0–8 MPa using device simulation software. The critical component of the pressure sensor is a thin flat square SiC diaphragm with an area of 1500 µm × 1500 µm and thickness of 75 µm. The area and thickness were optimized by performing computer simulation using the finite element method of simulation. The p -type SiC resistors were virtually fabricated in Wheatstone bridge configuration on top of the SiC diaphragm to convert the mechanical stress signal, generated due to external pressure into an electrical output voltage signal. The 4H–SiC MEMS pressure sensor was virtually fabricated on high-purity semi-insulating SiC substrate by dry etching method and its sensitivity was obtained at 2.42 µV/V/KPa for the operating pressure range. A thin SiC diaph...
High Reliability of MEMS Packaged Capacitive Pressure Sensor Employing 3C-SiC for High Temperature
Energy Procedia, 2015
This study develops the prototype of a micro-electro-mechanical systems (MEMS) packaged capacitive pressure sensor employing 3C-SiC diaphragm for high temperature devices. The 3C-SiC diaphragm is designed with the thicknesses of 1.0 μm and the width and length of 2.0 mm x 2.0 mm. The fabricated sensor is combined with a reliable stainless steel o-ring packaging concept as a simple assembly approach to reduce the manufacturing cost. There is an o-ring seal at the sensor devices an advantageous for high reliability, small size, lightweight, smart interface features and easy maintenance services. The stability and performance of the prototype devices has been tested for three test group and measured by using LCR meter. The prototypes of MEMS capacitive pressure sensor are characterized under static pressure of 5.0 MPa and temperatures up to 500°C in a stainless steel chamber with direct capacitance measurement. At room temperature (27°C), the sensitivity of the sensor is 0.0096 pF/MPa in the range of pressure (1.0-5.0 MPa), with nonlinearity of 0.49%. At 300°C, the sensitivity is 0.0127 pF/MPa, and the nonlinearity of 0.46%. The sensitivity increased by 0.0031 pF/MPa; corresponding temperature coefficient of sensitivity is 0.058%/°C. At 500°C, the maximum temperature coefficient of output change is 0.073%/°C being measured at 5.0 MPa. The main impact of this work is the ability of the sensor to operate up to 500°C, compare to the previous work using similar 3C-SiC diaphragm that can operates only 300°C. The results also show that MEMS packaged capacitive pressure sensor employing 3C-SiC is performed high reliability for high temperature up to 500°C. In addition, a reliable stainless steel o-ring packaging concept of MEMS packaged capacitive pressure sensor.
Journal of Engineering, 2014
This paper discusses the mechanical and electrical effects on 3C-SiC and Si thin film as a diaphragm for MEMS capacitive pressure sensor operating for extreme temperature which is 1000 K. This work compares the design of a diaphragm based MEMS capacitive pressure sensor employing 3C-SiC and Si thin films. A 3C-SiC diaphragm was bonded with a thickness of 380 μm Si substrate, and a cavity gap of 2.2 μm is formed between the wafers. The MEMS capacitive pressure sensor designs were simulated using COMSOL ver 4.3 software to compare the diaphragm deflection, capacitive performance analysis, von Mises stress, and total electrical energy performance. Both materials are designed with the same layout dimensional with different thicknesses of the diaphragm which are 1.0 μm, 1.6 μm, and 2.2 μm. It is observed that the 3C-SiC thin film is far superior materials to Si thin film mechanically in withstanding higher applied pressures and temperatures. For 3C-SiC and Si, the maximum von Mises stres...
Wafer Bonding of SiC-AlN at Room Temperature for All-SiC Capacitive Pressure Sensor
Micromachines, 2019
Wafer bonding of a silicon carbide (SiC) diaphragm to a patterned SiC substrate coated with aluminum nitride (AlN) film as an insulating layer is a promising choice to fabricate an all-SiC capacitive pressure sensor. To demonstrate the bonding feasibility, a crystalline AlN film with a root-mean-square (RMS) surface roughness less than ~0.70 nm was deposited on a SiC wafer by a pulsed direct current magnetron sputtering method. Room temperature wafer bonding of SiC-AlN by two surface activated bonding (SAB) methods (standard SAB and modified SAB with Si nano-layer sputtering deposition) was studied. Standard SAB failed in the bonding, while the modified SAB achieved the bonding with a bonding energy of ~1.6 J/m2. Both the microstructure and composition of the interface were investigated to understand the bonding mechanisms. Additionally, the surface analyses were employed to confirm the interface investigation. Clear oxidation of the AlN film was found, which is assumed to be the fa...
Low Stress Polycrystalline SiC Thin Films Suitable for MEMS Applications
Journal of The Electrochemical Society, 2011
This paper details the development of low residual stress and low stress gradient unintentionally doped polycrystalline SiC (poly-SiC) thin films. The films were deposited in a large-volume, low-pressure chemical vapor deposition (LPCVD) furnace on 100 mm-diameter silicon (Si) wafers using dichlorosilane (SiH 2 Cl 2 ) and acetylene (C 2 H 2 ) as precursors. We found that the flow rate of SiH 2 Cl 2 could be used to control the residual film stress in the as-deposited films. Wafer curvature measurements for 2m−thickfilmsindicatedthattensilestressrangingfrom4to55MPaacrossa25waferboathadbeenachieved.Avarietyofmicromachinedstructuresincludinglateralresonantstructures,stresspointersandcantileverswerefabricatedforcharacterizationofthedepositedSiCfilms.TheaverageYoung′smoduluswasfoundtobe403GPa.Residualstressmeasurementswereconsistentwiththoseobtainedusingawafercurvaturetechnique.Interferometricmeasurementsofcantileverbeamsindicatedstressgradientswithanupperboundof52MPa/mfor2 m-thick films indicated that tensile stress ranging from 4 to 55 MPa across a 25 wafer boat had been achieved. A variety of micromachined structures including lateral resonant structures, stress pointers and cantilevers were fabricated for characterization of the deposited SiC films. The average Young's modulus was found to be 403 GPa. Residual stress measurements were consistent with those obtained using a wafer curvature technique. Interferometric measurements of cantilever beams indicated stress gradients with an upper bound of 52 MPa/m for 2m−thickfilmsindicatedthattensilestressrangingfrom4to55MPaacrossa25waferboathadbeenachieved.Avarietyofmicromachinedstructuresincludinglateralresonantstructures,stresspointersandcantileverswerefabricatedforcharacterizationofthedepositedSiCfilms.TheaverageYoung′smoduluswasfoundtobe403GPa.Residualstressmeasurementswereconsistentwiththoseobtainedusingawafercurvaturetechnique.Interferometricmeasurementsofcantileverbeamsindicatedstressgradientswithanupperboundof52MPa/mfor2 m-thick films with tensile stress less than 55 MPa.
3C-SiC HeteroEpitaxial Films for Sensors Fabrication
Advances in Science and Technology, 2008
Silicon Carbide (SiC) is a very promising material for the fabrication of a new category of sensors and devices, to be used in very hostile environments (high temperature, corrosive ambient, presence of radiation, etc.). The fabrication of SiC MEMS-based sensors requires new processes able to realize microstructures on bulk material or on the SiC surface. The hetero-epitaxial growth of 3C-SiC on silicon substrates allows one to overcome the traditional limitations of SiC microfabrication. This approach puts together the standard silicon bulk microfabrication methodologies with the robust mechanical properties of 3C-SiC. Using this approach we were able to fabricate SiC cantilevers for a new class of pressure sensor. The geometries studied were selected in order to study the internal residual stress of the SiC film. X-Ray Diffraction polar figure and Bragg-Brentano scan analysis were used to check to crystal structure and the orientations of the film. SEM analysis was performed to analyze the morphology of the released MEMS structures.
Demonstration of 3C-SiC MEMS Structures on Polysilicon-on-oxide Substrates
MRS Proceedings, 2010
Silicon carbide has robust mechanical, electrical, and chemical properties which make it an attractive material candidate for micro- and nano-electromechanical systems (MEMS and NEMS). 3C-SiC films grown via a polysilicon seed-layer CVD-deposited on an oxide coated (111) Si substrate offers an innovative method to overcome the residual film stress issues associated with 3C-SiC heteroepitaxy and the difficulties of fabricating structures from 3C-SiC films. The oxide plays a dual role by permitting film relaxation with respect to the supporting substrate and functioning as a MEMS release layer, allowing MEMS structures such as cantilevers and diaphragms, to be easily fabricated from the 3C-SiC film. The impact of the oxide layer on the relaxation of the film stress was investigated by comparing direction-sensitive MEMS stress sensors fabricated from 3C-SiC films grown via a polysilicon-on-oxide-coated-substrate and a polysilicon-on-crystalline Si substrate. Scanning Electron Microscop...
Bulletin of Materials Science, 2015
Low-temperature plasma enhanced chemical vapour deposition (PECVD) deposited silicon carbide (SiC) thin films are promising materials for the development of high-temperature working microelectromechanical system (MEMS) owing to their excellent mechanical properties, non-corrosive nature and ability to withstand high temperature. However, the surface roughness of such thin films is the main obstacle to achieve thicker thin films for MEMS applications as the surface becomes more rougher with the increase in the thickness of PECVD SiC thin films. Therefore, in this present study, thicker SiC thin films were deposited by PECVD process by using CH 4 and SiH 4 as the precursor gases in the presence of Ar as the carrier gas and two process parameters, i.e., radio frequency (RF) power with mixed frequency condition and flow ratio of silane to methane were varied by keeping the temperature and pressure constant to investigate the influence of these parameters on the growth rate, surface roughness and morphology of SiC thin films. It was observed that both the RF power (with the mixed frequency condition) and flow ratio of SiH 4 /CH 4 can control the growth rate, surface roughness and morphology of the PECVD SiC thin films. Higher the carbon content in the thin films the surface became more smoother, whereas the surface became for rougher by increasing the RF power.