Micromachined differential pressure transducers
First Claim
1. A micromachined differential pressure transducer comprising:
- (a) a substrate having top and bottom sides;
(b) a deformable membrane mounted to and sealed at its peripheral edges to the top of the substrate and spaced from the substrate at its central portion to define a cavity which is sealed between the membrane and the substrate, the bottom of the cavity in the substrate being spaced from the membrane to allow normal deflections of the membrane but providing an overpressure stop for membrane deflection toward the substrate to prevent damage to the membrane;
(c) at least one channel leading from a remote position in the substrate to the cavity to provide communication therefrom to the cavity;
(d) an overpressure stop mounted to the top of the substrate and having a bridge portion spanning the membrane and spaced therefrom to allow normal deflections of the membrane while providing an overpressure stop to prevent displacements of the membrane away from the substrate which would damage the membrane, the spacing between the overpressure stop bridge and the membrane and between the membrane and the bottom of the cavity being less than about 10 micrometers; and
(e) means for sensing the deflections of the membrane.
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Accused Products
Abstract
Microminiature pressure transducers are formed on semiconductor substrates such as silicon and include a membrane which spans a cavity over the substrate, with the membrane being mounted to and sealed to the substrate at the peripheral edges of the membrane. The bottom of the cavity forms an overpressure stop to prevent over deflections of the membrane toward the substrate. An overpressure stop formed as a bridge of a material such as nickel extends above the membrane and is spaced therefrom to allow the membrane to deflect freely under normal pressure situations but prevent over deflections. The thickness of the polysilicon membrane and the spacing between the membrane and the overpressure stops is preferably in the range of 10 micrometers or less, and typically in the range of one micrometer. The overpressure stop bridge is formed utilizing deep X-ray lithography to form a well-defined bridge structure. The gap between the membrane and the bottom surface of the bridge is established with a sacrificial layer, such as a polyimide film, which dissolves in a solvent. The transducer is formed utilizing processing techniques which do not affect the performance of the membrane as a pressure sensor and which allow the substrate to have further micromechanical or microelectronic devices formed thereon.
153 Citations
19 Claims
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1. A micromachined differential pressure transducer comprising:
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(a) a substrate having top and bottom sides; (b) a deformable membrane mounted to and sealed at its peripheral edges to the top of the substrate and spaced from the substrate at its central portion to define a cavity which is sealed between the membrane and the substrate, the bottom of the cavity in the substrate being spaced from the membrane to allow normal deflections of the membrane but providing an overpressure stop for membrane deflection toward the substrate to prevent damage to the membrane; (c) at least one channel leading from a remote position in the substrate to the cavity to provide communication therefrom to the cavity; (d) an overpressure stop mounted to the top of the substrate and having a bridge portion spanning the membrane and spaced therefrom to allow normal deflections of the membrane while providing an overpressure stop to prevent displacements of the membrane away from the substrate which would damage the membrane, the spacing between the overpressure stop bridge and the membrane and between the membrane and the bottom of the cavity being less than about 10 micrometers; and (e) means for sensing the deflections of the membrane. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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14. A micromachined differential pressure transducer comprising:
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(a) a single crystal silicon substrate having top and bottom sides; (b) a deformable polycrystalline silicon membrane mounted to and sealed at its peripheral edges to the top of the substrate and spaced from the substrate at its central portion to define a cavity which is sealed between the membrane and the substrate, the bottom of the cavity in the substrate being spaced from the membrane to allow normal deflections of the membrane but providing an overpressure stop for membrane deflection toward the substrate to prevent damage to the membrane, the membrane having a thickness of about 10 micrometers or less; (c) at least one channel leading from a remote position in the substrate to the cavity to provide communication therefrom to the cavity; (d) an overpressure stop formed of electroplated metal mounted to the top of the substrate and having a bridge portion spanning the membrane and spaced therefrom to allow normal deflections of the membrane while providing an overpressure stop to prevent displacements of the membrane away from the substrate which would damage the membrane, the spacing between the overpressure stop bridge and the membrane and between the membrane and the bottom of the cavity being less than about 10 micrometers; and (e) means for sensing the deflections of the membrane. - View Dependent Claims (15, 16, 17, 18, 19)
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Specification