Thermal fluid sensor with encapsulated fluid region

A fluid sensor for sensing a concentration or composition of a fluid, the fluid sensor comprising:

• a semiconductor substrate comprising separate first and second semiconductor substrate sections, a first etched portion and a second etched portion;
• a dielectric region located on the semiconductor substrate, wherein the dielectric region comprises a first dielectric membrane, and a second dielectric membrane;
• wherein the first semiconductor substrate section comprises the first etched portion and the first dielectric membrane provided on the first etched portion, and the second semiconductor substrate section comprising the second etched portion and the second dielectric membrane provided on the second etched portion;
• two temperature sensing elements on or within the first dielectric membrane and two temperature sensing elements on or within the second dielectric membrane;
• an output circuit configured to measure a differential signal between the two temperature sensing elements of the first dielectric membrane and the two temperature sensing elements of the second dielectric membrane;
• and
• wherein the first dielectric membrane is exposed to the fluid and the second dielectric membrane is isolated from the fluid;
• and
• wherein the fluid sensor comprises an exposed region exposed to the fluid, and a sealed region sealed and isolated from the fluid, wherein:
• the first dielectric membrane and the first etched portion are in the exposed region;
• and
• the second dielectric membrane and the second etched portion are in the sealed region.

A fluid sensor for sensing a concentration or composition of a fluid, the fluid sensor comprising:

• a semiconductor substrate comprising integral first and second semiconductor substrate sections, a first etched portion and a second etched portion, wherein the first etched portion and the second etched portion are separated from one another by a portion of the semiconductor substrate;
• a dielectric region located on the semiconductor substrate, wherein the dielectric region comprises a first dielectric membrane, and a second dielectric membrane;
• wherein the first semiconductor substrate section comprises the first etched portion and the first dielectric membrane provided on the first etched portion, and the second semiconductor substrate section comprising the second etched portion and the second dielectric membrane provided on the second etched portion;
• two temperature sensing elements on or within the first dielectric membrane and two temperature sensing elements on or within the second dielectric membrane;
• an output circuit configured to measure a differential signal between the two temperature sensing elements of the first dielectric membrane and the two temperature sensing elements of the second dielectric membrane;
• and
• wherein the first dielectric membrane is exposed to the fluid and the second dielectric membrane is isolated from the fluid;
• and
• wherein the fluid sensor comprises an exposed region exposed to the fluid, and a sealed region sealed and isolated from the fluid, wherein:
• the first dielectric membrane and the first etched portion are in the exposed region;
• and
• the second dielectric membrane and the second etched portion are in the sealed region.