Silicon pressure sensor integrates resonant strain gauge on diaphragm

Micromachined Resonant Sensors— an Overview

“…The vacuum encapsulation can be achieved in principal on three levels: (a) on the single device level using, eg, vacuum-encapsulated resonant strain gages [11,37,42], (b) on a chip level using, eg, wafer-bonding techniques [76±78], or (c) on the packaging level using hermetic packages [79]. In the following, different fabrication processes found in the literature for vacuum encapsulation of single resonant elements will be briefly discussed.…”

“…Ikeda et al [42,80] made monocrystalline silicon resonators inside on-chip vacuum cavities. The devices are fabricated using selective growth of a series of silicon epitaxial layers with different doping concentrations in combination with selective wet etching and a hydrogen evacuation technique.…”

“…Micromachined resonant pressure sensors are commercially available from Yokogawa Electric in Japan [81] and Druck in the UK [135]. The Yokagawa device [42,81] with two vacuum-encapsulated H-shaped silicon resonators on a silicon membrane has been described briefly in Section 1.4.3. It features a guaranteed accuracy of +0.075% and +0.1% stability for 24 months of operation [81].…”

Surface micromachining for microelectromechanical systems

“…The implementation of wafer-level packaging schemes to seal and protect micromechanical elements prior to dicing (sawing of wafer into individual die) is an important development. Early efforts to microencapsulate resonant silicon structures with wafer-level microfabricated vacuum shells showed promise [151]. These shell processes were later adapted to vacuum-encapsulated polysilicon MEMS devices [152].…”

A thermal micro pressure sensor: its characteristics and application to pressure measurement in a minute package

“…Various micro sensors have been developed and proposed for pressure detection and may be roughly classified as follows: (i) The aforementioned resonant type (1). One of its shortages is the low sensitivity in pressure regime lower than 1Pa.…”