Polysilicon on sapphire oil-less pressure sensor

A method of producing a pressure sensor assembly comprising:

• forming a polysilicon strain gauge pattern on a first surface of a sapphire isolation member;
• bonding the sapphire isolation member to a support structure to form a region between the first surface of the sapphire isolation member and the support structure with the polysilicon strain gauge pattern formed within the region;
• and
• positioning the pressure sensor within a cavity of a header such that a second surface of the sapphire isolation member is positioned to interface with fluid within a fluid pathway to the pressure sensor assembly.

A process control measurement system comprising:

• a housing;
• a header positioned within the housing, the header including a cavity and the pressure sensor assembly including a fluid pathway to the cavity;
• a pressure sensor positioned in the cavity and configured to sense a pressure of process fluid through the fluid pathway, the pressure sensor including:
• a support structure;
• a sapphire isolation member, formed of a single crystal sapphire element, coupled to the support structure and forming a region between a first surface of the sapphire isolation member and the support structure, a second surface of the sapphire isolation member positioned to interface with fluid within the fluid pathway, the sapphire isolation member configured to be deflected by pressure from the fluid within the fluid pathway;
• electrical leads extending through the support structure;
• and
• a polysilicon strain gauge pattern positioned in the region on the first surface of the sapphire isolation member and coupled to the electrical leads, wherein the polysilicon strain gauge pattern is configured to generate electrical signals indicative of the pressure of the fluid within the fluid pathway when the sapphire isolation member deflects responsive to the pressure.