1. UKM Learning and Research Repository
2. PHD Thesis / Tesis PHD
3. Institute of Microengineering and Nanoelectronics / Institut Kejuruteraan Mikro dan Nanoelektronik (IMEN)

Title:	(3C-SiC) silicon carbide mems capacitive pressure sensor for high temperature applications
Authors:	Noraini Marsi (P63136)
Supervisor:	Burhanuddin Yeop Majlis, Prof. Dato' Dr.
Keywords:	Silicon carbide Pressure sensor Thin film Silicon substrate
Issue Date:	3-Jul-2015
Description:	This research focuses on the development of (3C-SiC) silicon carbide MEMS capacitive pressure sensor for high temperature applications. A packaged MEMS capacitive pressure sensor materials that operates at pressure up to 5.0 MPa and temperature up to 500 °C is developed. The diaphragm employs a single-crystal 3C-SiC thin film which is back-etched from its silicon substrate. A photosensitive ProTEK PSB is used as a polymeric protection layer to reduce the processing steps. The single-crystal 3C-SiC-on-Si wafer was supplied by Queensland Micro and Nanotechnology Center (QMNC), Griffith University. The fabrication of the diaphragm, the bottom substrate and the bonding process between the two electrodes was fabricated using bulk micromachining techniques. The 3C-SiC diaphragm with thicknesses of 1.0 μm and dimensional layout of 2.0 mm x 2.0 mm square shapes. The packaging of the MEMS capacitive pressure sensor is made up of four elements: a 3C-SiC diaphragm, silicon substrate, stainless steel o-ring and vacuum clamped. Two high temperature aluminium wires are bonded to the top and bottom plates. The simple and rugged package is thought to be more practical over ceramic package for operation at extreme environment such as inside the combustion engine. Nitrogen gas is used to vary the pressure from 1-5 MPa, which is measured by the pressure gauge. The MEMS capacitive pressure sensor is wrapped with stainless steel chamber heater from room temperature (27 °C) to 500 °C, which is monitored by the thermocouple. The LCR meter is used to directly measure the value of the capacitance from the top and bottom plates. The results were compiled together with CoventorWare and COMSOL 4.3a simulation with experimentally measured data of capacitance versus an externally applied pressure at 27 °C, 300 °C and 500 °C. It is clear that simulated data at three different temperatures exhibits the best linearity due to the ideal conditions, whereas the experimental data show higher non-linearity with a downward curve at temperature above 300 °C. The results also compare with similar works that also employs a single-crystal 3C-SiC-on-Si with ceramic package. At a critical temperature of 500 °C and the pressure of 1-5 MPa, MEMS capacitive pressure sensor has the linearity of 0.94%, hysteresis of 3.13% and the sensitivity of 0.82 pF/MPa. The previous work has the following performance at the critical temperature of 400 °C and a pressure of 1100-1760 Torr (0.15-0.23 MPa) i.e. linearity of 2.1%, hysteresis of 3.7% and sensitivity of 7.7 fF/Torr(1.02 pF/MPa). It is clear that we achieve better sensitivity, hysteresis and non-linearity albeit operating at higher temperature and much higher pressure range. The main impact of this work is the ability MEMS capacitive pressure sensor to operate up to 500 °C and to measure pressure of 5 MPa to surpass the performance of previous work at lower temperature and pressure. In addition, this MEMS capacitive pressure sensor has stainless steel o-ring packaging with a direct assembly approach to reduce manufacturing cost and easy installation and maintenance at extreme environment.,Ph.D.
Pages:	233
Publisher:	UKM, Bangi
Appears in Collections:	Institute of Microengineering and Nanoelectronics / Institut Kejuruteraan Mikro dan Nanoelektronik (IMEN)

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