Micro thermal shear stress sensor based on vacuum anodic bonding and bulk-micromachining

This paper describes a micro thermal shear stress sensor with a cavity underneath, based on vacuum anodic bonding and bulk micromachined technology. A Ti/Pt alloy strip, 2$\mu $m$\times $100$\mu $m, is deposited on the top of a thin silicon nitride diaphragm and functioned as the thermal sensor element. By using vacuum anodic bonding and bulk-si anisotropic wet etching process instead of the sacrificial-layer technique, a cavity, functioned as the adiabatic vacuum chamber, 200$\mu $m$\times $200$\mu $m$^{ }\times $400$\mu $m, is placed between the silicon nitride diaphragm and glass (Corning 7740). This method totally avoid adhesion problem which is a major issue of the sacrificial-layer technique.