MEMS integrated pressure sensor and microphone devices and methods of forming same

A method for forming a micro-electromechanical (MEMS) device comprising:

• providing a MEMS wafer, wherein a portion of the MEMS wafer is patterned to provide a first membrane for a pressure sensor device;
• bonding a carrier wafer to the MEMS wafer;
• forming a first sealed cavity on a first surface of the first membrane for the pressure sensor device;
• forming first and second MEMS structures by patterning a MEMS substrate of the MEMS wafer, wherein the first MEMS structure is disposed over the first membrane;
• forming a polysilicon layer over a surface of the MEMS wafer opposing the carrier wafer, wherein a portion of the polysilicon layer is disposed over the first MEMS structure and is patterned to provide a second membrane for a microphone device;
• bonding a cap wafer to the polysilicon layer to form a second sealed cavity including the second MEMS structure;
• and
• exposing the second membrane for the microphone device and a second surface of the first membrane for the pressure sensor device to an ambient environment.

A method for forming a micro-electromechanical (MEMS) device comprising:

• providing a MEMS wafer, wherein a portion of the MEMS wafer is patterned to provide a first membrane for a first MEMS device and a second membrane for a second MEMS device;
• bonding a carrier wafer to a first side of the MEMS wafer to form a second sealed cavity, wherein a first surface of the second membrane is exposed to a sealed pressure level of the second sealed cavity;
• bonding a cap wafer to a second side of the MEMS wafer opposite the first side to form a first sealed cavity;
• exposing both surfaces of the first membrane to an ambient environment;
• and
• exposing a second surface of the second membrane to the ambient environment.