A MEMS packaged capacitive pressure sensor employing 3C-SiC with operating temperature of 500 °C
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This study develops the prototype of a micro-electro-mechanical systems (MEMS) packaged capacitive pressure sensor employing 3C-SiC thin film as a diaphragm. The details of the design and fabrication steps involved bulk micromachining process. The 3C-SiC-on-Si wafer is back-etched the bulk Si to leave 3C-SC thin film by applied ProTEK PSB coating as a newly photosensitive layer. The ProTEK PSB is exposed into desired pattern of MEMS capacitive pressure sensor and the exposed pattern is developed by developer (ethylene lactate). The photosensitive can be stripped off with strong combination acid such as 2-(1-methoxy)propyl acetate, ethyl acetoacetate and photoacid generator which is attack the exposed ProTEK PSB while unexposed ProTEK PSB areas remain contact the alignment on the wafer surfaces. The prototypes of a MEMS capacitive pressure is packaged for high temperature up to 500 àand characterized under static pressure of 5.0 MPa in a stainless steel chamber with direct capacitance measurement using LCR meter. The diaphragm of 3C-SiC thin film has the thicknesses of 1.0 孠and the size of 2.0 mm נ2.0 mm. At room temperature (27 é, the sensitivity of the sensor is 0.00962 pF/MPa in the range of (1.0-5.0 MPa), with nonlinearity of 0.49 %. At 300 ì the sensitivity is 0.0127 pF/MPa, and nonlinearity of 0.46 %. The sensitivity increased by 0.0031 pF/MPa, corresponding temperature coefficient of sensitivity is 0.058 %/î At 500 ì the maximum temperature coefficient of output change is 0.073 %/àbeing red at 5.0 MPa. The main impact of this work is the ability of the sensor to operate up to 500 ì compare to the previous work using similar 3C-SiC diaphragm that can operates only 400 î In addition, a reliable stainless steel o-ring packaging concept is proposed as a simple assembly approach to reduce the manufacturing cost. There is an o-ring seal a this sensor is designed for high reliability, small size, lightweight, smart interface featured and easy cleaning service in the field which is relatively easy to replace without the need for special skill or tools in short period of time.
Microelectronics and Integrated Circuits
Microelectromechanical Systems (MEMS)