Fabrication of capacitive absolute pressure sensor using Si-Au eutectic bonding in SOI wafer

Abstract

Abstract.A capacitive absolute pressure sensor was fabricated using a large deflected diaphragm with a sealed vacuum cavity formed by removing handling silicon wafer and oxide layers from a SOI wafer after eutectic bonding of a silicon wafer to the SOI wafer. The deflected displacements of the diaphragm formed by the vacuum cavity in the fabricated sensor were similar to simulation results. Initial capacitance values were about 2.18pF and 3.65pF under normal atmosphere, where the thicknesses of the diaphragm used to fabricate the vacuum cavity were 20 and 30 , respectively. Also, it was confirmed that the differences of capacitance value from 1000hPa to 5hPa were about 2.57pF and 5.35pF, respectively.

Research of MEMS pressure sensor stability with PDA-NFL circuit

“…The geometry of assembly structure for pressure sensor chip PDA-NFL has a significant influence on the errors, because the RMS relaxation from all kinds of chip-to-body bonding has effect by time and temperature changing (the second factor about long-term stability from the Introduction). It is possible to consider different types of chip PDA-NFL micro-assembly and other MEMS in general before the moment of connection with metal, ceramic, plastic or other materials cases [80,81]: hydrophilic or hydrophobic direct bonding of silicon [82], anodic bonding [83], coupling through glass (frit) [84,85], eutectic [86,87], adhesive bonding [88,89], reactive compound [90,91], thermal compression [92,93] or laser-assisted coupling [94]. There are also rather exotic micro-assembly technologies, such as in the design of the PS 3 [95].…”

Wafer-Level Vacuum Packaging of Smart Sensors

“…Au 0.82 Si 0.18 eutectic bonding, originally developed and adopted as a die attach process [53], has more recently been demonstrated for transfer printing of light emitting diodes (LEDs) [54] and as a wafer bonding method for absolute pressure sensors [55], a MEMS Pirani vacuum gauge with CMOS elements [56,57,58], and other MEMS and smart sensors using surrogate wafers [56,57,58,59,60,61,62,63,64,65,66]. In this approach, Au is deposited by evaporation, sputtering, or electroplating.…”