BACKGROUND

Technical Field

This application is directed to a capacitive pressure sensor, and in particular, a capacitive pressure sensor having an expanded dynamic range.

Description of the Related Art

Capacitive pressure sensors rely on a variation in capacitance to detect a condition, such as a gas or fluid pressure. The accuracy of a capacitive sensor over various pressure ranges is constrained by the dynamic range of the sensor. The capacitive responsiveness of a capacitive pressure sensor deteriorates outside certain pressure ranges. Consequently, the sensor may be deemed unreliable beyond the pressure ranges. Whereas the capacitive sensor may be accurate when used to measure a pressure value within its dynamic range, it becomes less reliable for measuring another pressure value outside of the dynamic range. Widening or increasing the dynamic range of capacitive pressure sensors is, therefore, desirable as it results in reliable pressure measurements over a wider pressure range.

BRIEF SUMMARY

In an embodiment, a capacitive pressure sensor includes a first capacitive plate having a first side and a second side and a second capacitive plate having a first side and a second side, where the second side of the second capacitive plate is separated from the first side of the first capacitive plate by a dielectric between the first and second capacitive plates. In an embodiment, a capacitive pressure sensor includes a diaphragm adjacent to the second side of the first capacitive plate, where the diaphragm includes a volume of material having a base adjacent to the second side of the first capacitive plate. In an embodiment, the diaphragm is movably responsive to pressure such that an increase in the pressure causes the diaphragm to flex toward the first capacitive plate, causing a distance between the first and second capacitive plates to shorten and thereby increasing a capacitance between the first and second capacitive plates. In an embodiment, the diaphragm has a hollowed volume within an interior of the diaphragm operative to increase a flexibility of the diaphragm in response to the pressure.

In an embodiment, a capacitive pressure sensor includes a base plate adjacent to the first side of the second capacitive plate. In an embodiment, a capacitive pressure sensor includes vertical interconnect access channels extending through the base plate and terminating at the second capacitive plate providing access to the second capacitive plate for reading the capacitance of the capacitive pressure sensor. In an embodiment, a capacitive pressure sensor includes a bonding layer disposed at a periphery of the diaphragm and the base plate for bonding the diaphragm to the base plate.

In an embodiment, the hollowed volume extends longitudinally at least partially through the diaphragm between the periphery of the diaphragm and a necked region that is disposed in the base of the diaphragm. In an embodiment, the necked region has a central axis transverse to the base of the diaphragm and the necked region is not hollowed. In an embodiment, the bonding layer includes quartz bonding. In an embodiment, at least one of the first side of the first capacitive plate and the second side of the second capacitive plate is contoured to increase a surface area of the at least one of the first side of the first capacitive plate and the second side of the second capacitive plate that is exposed to the other of the first side of the first capacitive plate and the second side of the second capacitive plate.

In an embodiment, the hollowed volume comprises globules of vacuum or air dispersed within the interior of the diaphragm. In an embodiment, at least one of the first capacitive plate and the second capacitive plate is metalized with hafnium or hafnium oxide. In an embodiment, at least one of the first capacitive plate and the second capacitive plate includes tantalum and is metalized with a tantalum oxide coating thereon. In an embodiment, at least one of the first capacitive plate and the second capacitive plate is metalized to amplify the capacitance between the first and second capacitive plates. In an embodiment, the diaphragm is a fused silica wafer with the first capacitive plate deposited thereon.

In an embodiment, a capacitive pressure sensor includes a first capacitive plate having a first side and a second side and a second capacitive plate having a first side and a second side, where the second side of the second capacitive plate is separated from the first side of the first capacitive plate by a dielectric disposed between the first and second capacitive plates. In an embodiment, a capacitive pressure sensor includes a diaphragm adjacent to the second side of the first capacitive plate, where the diaphragm is movably responsive to pressure on the diaphragm and operative to flex toward the first capacitive plate and cause a distance between the diaphragm and the first capacitive plate to shorten, thereby increasing a capacitance between the first and second capacitive plates. In an embodiment, at least one of the first side of the first capacitive plate and the second side of the second capacitive plate is contoured to increase a surface area of the at least one of the first side of the first capacitive plate and the second side of the second capacitive plate that is exposed to the other of the first side of the first capacitive plate and the second side of the second capacitive plate.

In an embodiment, the at least one of the first capacitive plate and the second capacitive plate is contoured in the shape of a cone, an inverted cone, a curved cone, or an inverted curved cone. In an embodiment, the at least one of the first side of the first capacitive plate and the second side of the second capacitive plate is contoured such that the increased surface area is operative to widen the capacitive response of the capacitive pressure sensor for measurement of pressure over a wider range of pressures. In an embodiment, the first side of the first capacitive plate is contoured with a first shape and the second side of the second capacitive plate is contoured with a second shape that is an inversion of the first shape. In an embodiment, the second shape is not an inversion of the first shape. For example, the second shape may be different than the first shape and the inversion thereof.

In an embodiment, a pressure sensing device includes a first capacitive pressure sensor that is exposed to an external environmental pressure, where the first capacitive pressure sensor has a first capacitive response having a first dynamic range over a first pressure range. In an embodiment, the first capacitive pressure sensor is configured to sense a first pressure being exerted upon the first capacitive pressure sensor, and output, based on the sensed first pressure, a first signal representative of a first pressure measurement of the first capacitive pressure sensor. In an embodiment, a pressure sensing device includes a second capacitive pressure sensor that is exposed to the external environmental pressure, where the second capacitive pressure sensor has a second capacitive response different than the first capacitive response and the second capacitive response having a second dynamic range over a second pressure range that is different than the first pressure range. In an embodiment, a pressure sensing device includes more than two capacitive pressure sensors.

In an embodiment, the second capacitive pressure sensor is configured to sense a second pressure being exerted upon the second capacitive pressure sensor and output, based on the sensed second pressure, a second signal representative of a second pressure measurement of the second capacitive pressure sensor. In an embodiment, a pressure sensing device includes control circuitry configured to receive the first and second signals from the first and second capacitive pressure sensors, determine, based on the first and second signals and the first and second pressure ranges, whether to output the first or second pressure measurement as a measurement of the environmental pressure, and in response to the determination, output the measurement of the environmental pressure.

In an embodiment, determining whether to output the first or second pressure measurement includes identifying the first and second pressure measurements based on the first and second signals, respectively, and identifying one of the first pressure range and the second pressure range that includes at least one of the first pressure measurement, the second pressure measurement, or a pressure value that is a function of the first and second pressure measurements. In an embodiment, determining whether to output the first or second pressure measurement includes outputting the first pressure measurement as the measurement of the environmental pressure if the first pressure range includes the at least one of the first pressure measurement, the second pressure measurement, or the pressure value, or outputting the second pressure measurement if the second pressure range includes the at least one of the first pressure measurement, the second pressure measurement, or the pressure value.

In an embodiment, determining whether to output the first or second pressure measurement includes selecting one of the first pressure measurement, the second pressure measurement, or a pressure value that is a function of the first and second pressure measurements, if the selected one of the first pressure measurement, the second pressure measurement, or the pressure value is less than a threshold pressure, outputting the first pressure measurement, and if the selected one of the first pressure measurement, the second pressure measurement, or the pressure value is greater than the threshold pressure, outputting the second pressure measurement.

In an embodiment, a pressure sensing device includes an interdigital capacitor including a first conductor having a first side and a second side, where the first conductor has a first plurality of fingers extending longitudinally from the first side of the first conductor. In an embodiment, the interdigital capacitor includes a second conductor having a first side and a second side, where the second conductor has a second plurality of fingers extending longitudinally from the second side of the second conductor. In an embodiment, the second plurality of fingers is interleaved with the first plurality of fingers with a dielectric therebetween.

In an embodiment, a pressure sensing device includes a diaphragm adjacent to the second side of the first conductor, where the diaphragm is movably responsive to pressure such that an increase in the pressure causes the diaphragm to flex onto the first conductor, causing a distance between the first and second conductors to shorten and thereby increase a capacitance between the first and second conductors.

