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MEMS Very Low Capacitive Pressure Sensor Based on CMOS Process
(Sensor Kapasitif Bertekanan Sangat Rendah-MEMS Berasaskan Proses CMOS)
Muhamad Ramdzan Buyong*, Norazreen Abd Aziz & BurhanuddinYeopMajlis
Institute of Microengineering and Nanoelectronics (IMEN), Universiti Kebangsaan Malaysia
43600 UKM Bangi, Selangor D.E., Malaysia
Received: 16 July 2010 / Accepted: 3 September 2010
ABSTRACT
The CMOS standard process with advantage of simplicity in term of design
and fabrication process compatibility has triggered the invention of MEMS very
low capacitive pressure sensor, (MEMS-VLCPS). In this paper the
development of the whole structure of MEMS-VLCPS that involves the
design simulation, fabrication and testing is described. The novelty of this
work lies in the design and fabrication process itself. A new technique in
fabricating thin sensor membrane of VLCPS using seal-off techniques
is also presented. The physical structure of the membrane consists of parallel
plate. The top plate acts as the flexible electrode membrane and the bottom
plate acts as the counter electrode membrane. Both plates are separated by
absolute air gap with fixed end at both sides. As a result, it was found that
the etch-opening holes of 0.8 μm and seal-off
thickness of 4000 Å gave the optimum sealing surface. The percentage of
relative capacitance change is extracted from the reference capacitance
measurement. Air gap thickness of 0.3 μm gives
the highest percentage of PRCC showing that smaller air gap
thickness provides a larger change in capacitance value.
Keywords: CMOS; MEMS; very low capacitive pressure sensor
ABSTRAK
Proses piawai CMOS dengan kelebihannya dalam meringkaskan kesesuaian reka bentuk dan proses fabrikasi mencetuskan penciptaan sensor kapasitif bertekanan sangat rendah MEMS (MEMS-VLCPS).
Di dalam kertas ini, pembangunan keseluruhan struktur MEMS-VLCPS yang melibatkan simulasi reka bentuk, fabrikasi dan uji kaji dibentangkan. Novelti penyelidikan ini terletak pada reka bentuk dan proses fabrikasinya yang tersendiri. Satu teknik baru dalam fabrikasi membran nipis sensor MEMS-VLCPS menggunakan teknik litupan juga diperkenalkan. Struktur fizikal membran terdiri daripada plat selari. Plat atas bertindak sebagai membran elektrod boleh lentur manakala plat bawah bertindak sebagai membran elektrod dengan pengimbang. Kedua-dua plat dipisahkan oleh rongga udara dengan kedua-duanya melekat pada sisi tepi. Melalui hasil pencirian, didapati bukaan rongga punar 0.8 μm dan ketebalan litupan sebanyak 4000 Å menghasilkan permukaan tertutup yang optimum. Peratusan perubahan kapasitan relatif, PRCC diperoleh melalui pengukuran kapasitan rujukan. Rongga udara berketebalan sebanyak 0.3 μm memberikan nilai PRCC paling tinggi yang menggambarkan rongga udara yang kecil menghasilkan perubahan yang besar dalam kapasitan.
Kata kunci: CMOS; MEMS; sensor tekanan kapasitif yang sangat rendah
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*Corresponding author; email: muhdramdzan@yahoo.com
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