Extremely low cost pressure sensor realized using deep reactive ion etching

An absolute pressure sensor comprising:

• a first silicon layer comprising a diaphragm having a top and a bottom;
• an insulator layer covering the bottom of the diaphragm;
• and
• a second silicon layer below the insulator layer and comprising a sidewall extending from the insulator layer on the bottom of the diaphragm, the sidewall having an interior side forming a backside cavity having a backside opening, the interior side substantially orthogonal to the diaphragm;
• and
• a block covering the backside opening such that a hermetic seal is formed.

An absolute pressure sensor comprising:

• a diaphragm having a top and a bottom;
• a sidewall extending from the bottom of the diaphragm, the sidewall having an interior side forming a backside cavity having a backside opening, the interior side substantially orthogonal to the diaphragm;
• and
• a block covering the backside opening such that a hermetic seal is formed,
• wherein the block is glass, and
• wherein the glass block is covered with metal over the backside opening.

A silicon wafer comprising:

• a plurality of pressure sensors, each pressure sensor comprising:
• a diaphragm having a top and a bottom;
• and
• a sidewall extending from the bottom of the diaphragm, the sidewall having an interior side formed using a deep reactive ion etch and forming a backside cavity having a backside opening, the interior side substantially orthogonal to the diaphragm,
• wherein the plurality of pressure sensors includes approximately at least twenty-thousand pressure sensors,
• and wherein the silicon wafer is a 150 mm (6 inch) wafer.

A pressure sensor apparatus comprising:

• exactly one pressure sensor in a housing, the exactly one pressure sensor comprising:
• a diaphragm having a top and a bottom;
• and
• a sidewall extending from the bottom of the diaphragm, the sidewall having an interior side formed using a deep reactive ion etch and forming a backside cavity having a backside opening, the interior side substantially orthogonal to the diaphragm,
• wherein the diaphragm is less than 350 microns in length, and
• the diaphragm accounts for more than 10 percent of an area of the exactly one pressure sensor.

A pressure sensor comprising:

• a diaphragm having a top and a bottom;
• a sidewall extending from the bottom of the diaphragm, the sidewall having an interior side forming a backside cavity having a backside opening, the interior side substantially orthogonal to the diaphragm;
• a cap attached to the top of the diaphragm;
• a first electrode attached to the top of the diaphragm;
• and
• a second electrode attached to an underside of the cap,
• wherein the cap and diaphragm form a reference cavity, and
• wherein the first electrode and the second electrode form a capacitor.

A pressure sensor comprising:

• a diaphragm having a top and a bottom;
• a sidewall extending from the bottom of the diaphragm, the sidewall having an interior side forming a backside cavity having a backside opening, the interior side substantially orthogonal to the diaphragm;
• a cap attached to the top of the diaphragm;
• a plurality of resistors in the top of the diaphragm,
• wherein the cap and diaphragm form a reference cavity, and
• wherein the plurality of resistors form a piezoresistive sensing circuit.

A pressure sensor comprising:

• a first silicon layer comprising a diaphragm;
• an insulator layer below the first silicon layer;
• a second silicon layer below the insulator layer and having a backside cavity defined by a sidewall, a backside opening, and a portion of the insulator layer below and directly in contact with the diaphragm,
• wherein the backside cavity is formed using a deep reactive ion etch and the sidewall is substantially orthogonal to the diaphragm,
• wherein the backside opening is non-rectangular.

A pressure sensor comprising:

• a first silicon layer having a top side and a bottom side and comprising a diaphragm;
• an insulator layer having a top side and a bottom side, the top side in contact with the bottom side of the first silicon layer;
• a second silicon layer having a top side and a bottom side, the top side in contact with the bottom side of the insulator layer and having a backside cavity defined by a sidewall, a portion of the bottom side of the insulator layer, and a backside opening in the bottom side of the second silicon layer,
• wherein the backside cavity is formed using a deep reactive ion etch and the sidewall is substantially orthogonal to the diaphragm.