Pressure sensing device with stepped cavity to minimize thermal noise

摘要

A pressure sensing element may include a diaphragm and a stepped cavity. The pressure sensing element may include a plurality of piezoresistors, which are operable to generate an electrical signal based on an amount of deflection of the diaphragm in response to a sensed pressure of the fluid. The pressure sensing element may be mounted onto a housing substrate using an adhesive so that a portion of the adhesive is attached to walls of a first cavity and to a step surface of the stepped cavity to redistribute thermally induced stresses on the pressure sensing element. The stepped cavity may be included in a MEMS pressure sensing element to reduce or eliminate thermal noise, such as temperature coefficient of offset voltage output (TCO).

主权项

1. An apparatus, comprising:
a pressure sensing element including:
a stepped cavity formed into a base surface of the pressure sensing element, by a plurality of walls of a first cavity, a step surface, a plurality of walls of a second cavity, and a bottom surface of a diaphragm; anda plurality of piezoresistors on a top surface of the diaphragm;at least one substrate; and an adhesive that connects the substrate to the base surface such that the walls of the first cavity and the step surface of the stepped cavity are adhered to at least a portion of the adhesive; wherein the adhesive further comprises: a base portion; an outer fillet portion integrally formed with the base portion, the outer fillet portion adjacent the at least one outer surface when the pressure sensing element is connected to the at least one substrate; and an inner fillet portion integrally formed with the base portion, the inner fillet portion substantially disposed in the first cavity when the pressure sensing element is connected to the at least one substrate.