SEMICONDUCTOR GAS SENSOR DEVICE AND MANUFACTURING METHOD THEREOF
A semiconductor gas sensor device includes a first cavity that is enclosed by opposing first and second semiconductor substrate slices. At least one conducting filament is provided to extend over the first cavity, and a passageway is provided to permit gas to enter the first cavity. The sensor device may further including a second cavity that is hermetically enclosed by the opposing first and second semiconductor substrate slices. At least one another conducting filament is provided to extend over the second cavity.
1 . A semiconductor gas sensor device, comprising:
a doped semiconductor substrate of a first semiconductor slice,
a first insulating layer placed above said doped semiconductor substrate,
a part of at least one first cavity formed inside said first insulating layer and said doped semiconductor substrate and extending inside said doped semiconductor substrate to a first depth,
at least one conductive filament placed over said part of the at least one first cavity in a bridge way,
a conductive metal layer placed at the ends of at least one filament for making electrical contact,
another doped semiconductor substrate of a second semiconductor slice comprising another part of the at least one first cavity and being placed above said first semiconductor slice so as to form and close said at least one first cavity, said another doped semiconductor substrate comprising at least one hole in correspondence of the first cavity for the inlet of gas to detect.
2 . The semiconductor gas sensor device according to claim 1 , wherein the first semiconductor slice comprises:
parts of the first cavity and a second cavity formed inside said first insulating layer and said doped semiconductor substrate and extending inside said doped semiconductor substrate to the first depth,
a first pair of conductive filaments and a second pair of conductive filaments placed inside said respective first and second cavities in a bridge way, said first and second pairs of conductive filaments being respectively the variable resistors and the reference resistors of a Wheatstone bridge,
the conductive metal layer being placed at the ends of each filament of the first and the second pairs of conductive filaments for making electrical contact,
said another doped semiconductor substrate comprising other parts of the first and second cavities and being placed above said first semiconductor slice so as to form said first and a second cavities and hermetically close the second cavity and close the first cavity, said another doped semiconductor substrate comprising at least one hole in correspondence only of the first cavity for the inlet of the gas to detect.
3 . The semiconductor gas sensor device according to claim 2 , wherein said another doped semiconductor substrate comprises two holes in correspondence only of the first cavity for the inlet of the gas to detect.
4 . The semiconductor gas sensor device according to claim 1 , wherein the integrated gas sensor device comprises a second insulating layer placed above and around said at least one conductive filament.
5 . The semiconductor gas sensor device according to claim 1 , wherein the first and second semiconductor slices are joined together by an adhesive.
6 . The semiconductor gas sensor device according to claim 5 , wherein the adhesive is glass frit.
7 . A method for manufacturing a semiconductor gas sensor device, comprising:
forming a doped semiconductor substrate of a first semiconductor slice,
forming a first insulating layer above said doped semiconductor substrate,
forming a part of at least one first cavity inside said first insulating layer and said doped semiconductor substrate so that said part of at least one first cavity extends inside said doped semiconductor substrate to a first depth,
forming at least one conductive filament over said part of the at least one first cavity in a bridge way,
forming a conductive metal layer at the ends of at least one filament for making electrical contact,
forming another doped semiconductor substrate of a second semiconductor slice,
forming the other part of the at least one first cavity with said another doped semiconductor substrate,
forming at least one hole in correspondence of said other part of the at least one first cavity for the inlet of gas to detect,
placing the second semiconductor slice above said first semiconductor slice so as to form and close said at least one first cavity.
8 . The method according to claim 7 , with respect to the first semiconductor slice, further comprises:
forming parts of the first cavity and a second cavity inside said first insulating layer and said doped semiconductor substrate so that said parts of the first and second cavities extend inside said doped semiconductor substrate to the first depth,
forming a first pair of conductive filaments and a second pair of conductive filaments inside said respective first and second cavities in a bridge way, said first and second pairs of conductive filaments being respectively the variable resistors and the reference resistors of a Wheatstone bridge,
forming the conductive metal layer on the ends of each filament of the first and second pairs of conductive filaments for making electrical contact,
forming other parts of said first and second cavities with said another doped semiconductor substrate,
forming at least one hole only in correspondence of said other part of the first cavity for the inlet of gas to detect,
placing the second semiconductor slice above said first semiconductor slice so as to form said first and second cavities and hermetically close the second cavity and close the first cavity.
9 . The method according to claim 8 , with respect to the another doped semiconductor substrate, further comprising forming two holes in correspondence only of the first cavity for the inlet of the gas to detect.
10 . The method according to claim 7 , further comprising forming a second insulating layer above and around said at least one conductive filament.
11 . The method according to claim 7 , wherein placing the first semiconductor slice over the second semiconductor slice comprises joining the first semiconductor slice and the second semiconductor slice using an adhesive.
12 . The method according to claim 11 , wherein the adhesive is glass frit.
13 . A sensor, comprising:
a first substrate including a first cavity;
a first conductive filament extending over said first cavity on a first bridge way;
first conductive contacts at each end of the first conductive filament;
a second substrate placed above said first substrate and configured to enclose said first cavity; and
a passageway extending through at least one of the first and second substrates and into said first cavity for permitting passage of a gas to be detected by the sensor.
14 . The sensor of claim 13 , further comprising:
the first substrate including a second cavity;
a second conductive filament extending over said second cavity on a second bridge way;
second conductive contacts at each end of the second conductive filament; and
the second substrate further configured to hermetically enclose said second cavity.
15 . The sensor of claim 13 , further comprising:
a third conductive filament extending over said first cavity on a third bridge way;
a fourth conductive filament extending over said second cavity on a fourth bridge way;
the first through fourth conductive filaments electrically connected to form a Wheatstone bridge circuit.