Method for manufacturing a semiconductor pressure sensor
AssigneeSTMicroelectronics S.r.l.
InventorsFlavio Francesco Villa, Gabriele Barlocchi, Pietro Corona, Benedetto Vigna, Lorenzo Baldo
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Abstract
Method for manufacturing a semiconductor pressure sensor, wherein, in a silicon substrate, trenches are dug and delimit walls; a closing layer is epitaxially grown, that closes the trenches at the top and forms a suspended membrane; a heat treatment is performed so as to cause migration of the silicon of the walls and to form a closed cavity underneath the suspended membrane; and structures are formed for transducing the deflection of the suspended membrane into electrical signals.
Claims20
A method for manufacturing a semiconductor pressure sensor, comprising the steps of:
- providing a wafer comprising a bulk region of semiconductor material;
- forming a membrane above and at a distance from said bulk region;
- forming a closed cavity between said membrane and said bulk region;
- and
- forming structures for transducing the deflection of said membrane into electrical signals;
- wherein, said step of forming a membrane comprises the steps of:
- etching a plurality of first trenches in said bulk region, said first trenches delimiting a plurality of first walls of semiconductor material;
- epitaxially growing, starting from said first walls, a closing layer of semiconductor material, said closing layer closing said trenches at the top and forming said membrane;
- and
- carrying out a heat treatment, thereby causing migration of the semiconductor material of said first walls and forming a closed cavity.
A method of fabricating a capacitive pressure sensor comprising:
- providing a silicon wafer;
- forming a sensor capacitor in a sensor area of the silicon wafer, wherein said step of forming the sensor capacitor includes:
- forming a plurality of sensor trenches, each sensor trench being separated from an adjacent sensor trench by a first column having a first width;
- epitaxially growing a sensor membrane from the first columns, the sensor membrane fully covering the sensor trenches;
- and
- annealing the sensor area such that the first columns migrate toward the sensor membrane and the plurality of the sensor trenches merge into a sensor cavity underlying the sensor membrane;
- and
- forming a reference capacitor in a reference area of the silicon wafer, wherein said step of forming the reference capacitor includes:
- forming a plurality of reference trenches, each reference trench being separated from an adjacent reference trench by a second column having a second width;
- epitaxially growing a reference membrane from the second columns, the reference membrane fully covering the reference trenches;
- and
- annealing the reference area to partially thin down the second columns;
- and
- oxidizing the second columns to form an insulating region underlying the reference membrane.
A method of forming a pressure sensor including:
- providing a silicon wafer;
- forming a plurality of sensor trenches in the silicon wafer, each sensor trench being separated from an adjacent sensor trench by a column;
- epitaxially growing a sensor membrane from the columns, the sensor membrane fully covering the sensor trenches;
- and
- heating the silicon wafer such that the columns migrate toward the sensor membrane and the plurality of sensor trenches merge into a sensor cavity underlying the sensor membrane;
- and
- forming a piezoresistive element at a periphery of the sensor membrane.
Dependencies are inferred from the claim text.