MEMS capacitive pressure sensor

A method of operating a pressure sensor, comprising:

• measuring an external pressure using a first pressure sensor element having a capacitive MEMS pressure sensor having a deformable top electrode, and a fixed bottom electrode spaced by a first cavity portion, wherein the top electrode deforms in response to a pressure difference between the external pressure and an internal cavity pressure;
• measuring the internal cavity pressure using a second pressure sensor element housed within a second cavity portion, wherein the first and second cavity portions are connected to define a combined sealed cavity;
• and
• combining the external and internal pressure measurements, such that the second pressure sensor element output provides calibration of the first pressure sensor output,
• wherein:
• the second cavity portion has a rigid top cover,
• a detection routine uses a capacitance input of the first pressure sensor element with data on the internal cavity pressure provided by the second pressure sensor element,
• the first and second cavity portions are side-by-side over a Complementary Metal-Oxide Semiconductor (CMOS) integrated circuit,
• the top electrode comprises tungsten and a silicon nitride capping layer is applied on the top electrode,
• the bottom electrode is made of a metal and an isolation layer is provided over the bottom electrode such that the isolation layer is between the bottom electrode and the first cavity.

A method of manufacturing a pressure sensor, comprising:

• forming a first pressure sensor element comprising a capacitive MEMS pressure sensor having a deformable top electrode, and a fixed bottom electrode spaced by a first cavity portion;
• forming a second pressure sensor element housed within a second cavity portion, and forming a rigid top cover over the second cavity portion;
• and
• connecting the first and second cavity portions to define a combined sealed cavity,
• wherein:
• the combined sealed cavity is formed via a sacrificial etch, by deposition of a sacrificial layer and subsequent removal of the sacrificial layer,
• the first and second cavity portions are side-by-side over a Complementary Metal-Oxide Semiconductor (CMOS) integrated circuit,
• the top electrode comprises tungsten and a silicon nitride capping layer is applied on the top electrode,
• the bottom electrode is made of a metal and an isolation layer is provided over the bottom electrode, such that the isolation layer is between the bottom electrode and the first cavity,
• the sacrificial layer is silicon oxide, and
• a second pressure sensor element output provides calibration of a first pressure sensor output.

A pressure sensor, comprising:

• a first pressure sensor element having an output and comprising a capacitive Micro Electro Mechanical Systems (MEMS) pressure sensor having a deformable top electrode, and a fixed bottom electrode spaced by a first cavity portion, wherein the top electrode deforms in response to a pressure difference between an external pressure and an internal cavity pressure;
• and
• a second pressure sensor element having an output and housed within a second cavity portion,
• wherein:
• the second cavity portion has a rigid top cover, wherein the first and second cavity portions are connected to define a combined sealed cavity,
• the second pressure sensor element is configured and arranged with the first pressure sensor element output, such that the second pressure sensor element output provides calibration of the first pressure sensor output,
• the second pressure sensor element measures the internal cavity pressure,
• a detection routine uses a capacitance input of the first pressure sensor element with data on the internal cavity pressure provided by the second pressure sensor element,
• the first and second cavity portions are side-by-side over a Complementary Metal-Oxide Semiconductor (CMOS) integrated circuit,
• the top electrode comprises tungsten and is positioned on a silicon nitride membrane,
• a silicon nitride passivation layer is applied on the top electrode such that the top electrode is between the silicon nitride membrane and the silicon nitride passivation layer, and
• the bottom electrode is made of a metal and an isolation layer is provided over the bottom electrode such that the isolation layer is between the bottom electrode and the first cavity.

A pressure sensor, comprising:

• a first pressure sensor element having an output and comprising a capacitive Micro Electro Mechanical Systems (MEMS) pressure sensor having a deformable top electrode, and a fixed bottom electrode spaced by a first cavity portion, wherein the top electrode deforms in response to a pressure difference between an external pressure and an internal cavity pressure;
• and
• a second pressure sensor element having an output and housed within a second cavity portion,
• wherein:
• the second cavity portion has a rigid top cover,
• the first and second cavity portions are connected to define a combined sealed cavity,
• the second pressure sensor element is configured and arranged with the first pressure sensor element output, such that the second pressure sensor element output provides calibration of the first pressure sensor output,
• the second pressure sensor element measures the internal cavity pressure,
• a detection routine uses a capacitance input of the first pressure sensor element with data on the internal cavity pressure provided by the second pressure sensor element,
• the first and second cavity portions are side-by-side over a Complementary Metal-Oxide Semiconductor (CMOS) integrated circuit,
• the top electrode comprises tungsten and a silicon nitride capping layer is applied to the top electrode,
• the bottom electrode is made of a metal and an isolation layer is provided over the bottom electrode such that the isolation layer is between the bottom electrode and the first cavity,
• the second pressure sensor element comprises a Pirani gauge, and
• the Pirani gauge is realized as a surface micromachined silicon Pirani device that is arranged as a wire with gaps between the wire and side heat sinks.