Monolithic MEMS platform for integrated pressure, temperature, and gas sensor

A monolithic MEMS platform, comprising:

• a semiconductor substrate comprising one or more transistor devices and a temperature sensor;
• a dielectric layer disposed over the semiconductor substrate and having a cavity disposed within an upper surface of the dielectric layer;
• a plurality of metal interconnect layers arranged within the dielectric layer and comprising a first pressure sensor electrode extending along a bottom surface of the cavity;
• a MEMS substrate comprising a conductive semiconductor material disposed onto the upper surface of the dielectric layer, wherein the MEMS substrate comprises a second pressure sensor electrode disposed over the cavity and first gas sensor electrode electrically isolated from the second pressure sensor electrode;
• and
• a polymer having a dielectric constant that varies depending upon a presence of a liquid or gas in a surrounding ambient environment, which is disposed between the first gas sensor electrode and a second gas sensor electrode.

A method of forming a monolithic MEMS platform, comprising:

• performing CMOS processes to form a temperature sensor and a plurality of devices within a substrate;
• forming a dielectric structure over the substrate, wherein the dielectric structure surrounds a plurality of metal interconnect layers and a cavity defined by sidewalls of the dielectric structure coupled between an upper surface of the dielectric structure and a recessed surface of the dielectric structure facing away from the substrate, and wherein a first pressure sensor electrode for a MEMS pressure sensor comprises a metal interconnect layer disposed along the recessed surface and between the sidewalls of the dielectric structure;
• bonding a MEMS substrate to the upper surface of the dielectric structure;
• patterning the MEMs substrate to concurrently define a second pressure sensor electrode for the MEMs pressure sensor and a first gas sensor electrode for a MEMS gas sensor;
• and
• forming a polymer over the first gas sensor electrode.