Sains Malaysiana 40(3)(2011): 259–266

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

Diserahakan: 16 Julai 2010 / Diterima: 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 telah 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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*Pengarang untuk surat-menyurat; email: muhdramdzan@yahoo.com