Sensors are commonly used in a variety of applications, including electronics, automotive and consumer goods, among others. Some types of sensors comprise a membrane, lamella or other suitable structure that flexes, deforms or otherwise moves in response to a physical quantity to be sensed or measured. One example of such a sensor is a pressure sensor, which can sense or measure pressure related to a gas, fluid, mechanical or other force. The flexure, deformation and/or movement of the moveable portion of the sensor (e.g., the membrane, lamella or other structure) can be sensed by a variety of technologies, including capacitive, piezoresistive, piezoelectric, electromagnetic, optical or some other technology, and the related pressure determined therefrom. For example, a pressure sensor can comprise a flexible membrane that flexes or otherwise deforms when a pressure is present. The flexure of the membrane can be detected capacitively by an electrode arranged proximate the membrane, as a capacitance between the membrane and the electrode changes as the membrane sags or expands.
Regardless of type, sensors often operate as parts of larger systems and therefore may be integrated within these systems. In some applications, such as automotive airbag sensors, a pressure sensor can be integrated within the airbag application-specific integrated circuit (ASIC). As the processes for manufacturing ASICs develop and evolve, it can be challenging to integrate manufacture of the sensors with the ASIC without increasing the complexity of or having to alter the fundamental manufacturing processes. For example, many ASICs are constructed using CMOS (complementary metal-oxide-semiconductor) technologies, and integrating pressure sensor construction into suitable CMOS processes can be complicated and/or expensive, sometimes requiring changes to the conventional processing steps or techniques or requiring additional steps. For example, one attempt to integrate pressure sensor structure comprising a polycrystalline silicon lamella required at least five mask planes and a complicated process for removing the sacrificial layer between the lamella and the substrate to enable the lamella to flex or move and could not be successfully integrated in a CMOS process.
USPTO Backgrounds
USPTO Backgrounds