Preloaded linear beam vibration sensor and its manufacturing method
AssigneeTokyo Gas Co., Ltd.
InventorsSean S. Cahill, Walter Shoeys, Kenichi Nakamura
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Abstract
A method is described for manufacturing a miniaturized accelerometer having a narrow bandwidth and behaving as a switch sensitive only to low frequencies such as are contained in earthquakes. The method includes provision of an unbalanced see-saw beam assembly composed of beams 2 and masses 3 at opposite ends of the beams 2. The beams 2 have their suspension at a location with slightly different distances from the masses 3 along a line parallel to and vertically offset from the line connecting centers of gravity of the masses 3.
Claims2
A method for manufacturing a preloaded linear beam vibration sensor including an unbalanced see-saw type see-saw beam having its suspension at an intermediate portion thereof and a mass at each end thereof, comprising the steps of:
- providing a substrate;
- depositing on said substrate an oxide film;
- integrally making on said substrate, via a polysilcon film deposited on said oxide film, a see-saw beam comprising two parallel beams, two masses connecting said beams at respective ends and hinge posts extending from said beams at a location spaced different distances from said masses;
- depositing an oxide film on said see-saw beam;
- forming on said oxide film covering said hinge posts, via a polysilcon film, hinges which cover said hinge posts;
- etching part of said substrate underlying said see-saw beam to form a space permitting pivotal movement of said see-saw beam;
- and
- removing said oxide film covering said see-saw beam and said hinge posts to allow said beam to move freely within said hinges.
A method for manufacturing a preloaded linear beam vibration sensor including an unbalanced see-saw type see-saw beam having its suspension at an intermediate portion thereof and a mass at each end thereof, comprising the steps of:
- providing a substrate;
- depositing on said substrate an oxide film;
- integrally making on said substrate, via a polysilicon film deposited on said oxide film, a see-saw beam comprising, two parallel beams, two masses connecting said beams at respective ends and hinge posts extending from said beams at a location spaced different distances from said masses;
- depositing an oxide film on said see-saw beam;
- forming on said oxide film, via a polysilicon film, hinges which cover said hinge posts;
- providing a lubricant layer of silicon nitride (SiN.sub.x) between said hinge posts and said hinges;
- etching part of said substrate underlying said see-saw beam to form a space permitting pivotal movement of said see-saw beam;
- and
- removing said oxide film covering said see-saw beam and said hinge posts to allow said beam to move freely within said hinges.
Dependencies are inferred from the claim text.