Flow sensor

Claim 2

A flow sensor, comprising: a thin film heater suspended in air by thin film dielectric; a pair of thin film heat sensors suspended in air by thin film dielectric and disposed on opposite sides of the heater; means for operating the heater at a temperature elevated above ambient, thus creating a no-flow temperature gradient in the air above and adjacent to the heater, the temperature within the no-flow gradient making a transition between the elevated temperature and substantially ambient temperature; the sensors being located sufficiently close to the heater to be located substantially within the no-flow temperature gradient; and the heater and the sensors being substantially thermally isolated so that a primary path of heat between the heater and the sensors is air.

Claim 3

A flow sensor, comprising: a thin film heater; a pair of thin film heat sensors; a semiconductor body supporting the heater and sensors with at least a major portion of the heater and sensors held out of contact with the body by thin film dielectric and with the sensors disposed on opposite sides of the heater; means for operating the heater at a temperature elevated above ambient, thus creating a no-flow temperature gradient in the air above and adjacent to the heater, the temperature within the no-flow gradient making a transition between the elevated temperature and substantially ambient temperature; the sensors being located sufficiently close to the heater to be located substantially within the no-flow temperature gradient; and the heater and the sensors being substantially thermally isolated so that a primary path of heat between the heater and the sensors is air.

Claim 4

A flow sensor, comprising: a thin film heater; a pair of thin film heat sensors; a semiconductor body supporting the heater and sensors with at least a major portion of the heater and sensors held out of contact with the body by thin film dielectric and with the sensors disposed on opposite sides of the heater; means for operating the heater at a temperature elevated above ambient, thus creating a no-flow temperature gradient in the air above and adjacent to the heater, the temperature within the no-flow gradient making a transition between the elevated temperature and substantially ambient temperature; the sensors being located sufficiently close to the heater to be located substantially within the no-flow temperature gradient; and the heater and the sensors being substantially thermally isolated so that a primary path of heat between the heater and the sensors is air.

Claim 5

A flow sensor, comprising: a thin film heater; a pair of thin film sensors; a semiconductor body with a depression therein; thin film means connecting the heater and the sensors to the body and bridging the depression so that at least a major portion of the heater and the sensors are out of contact with the body and with the sensors disposed on opposite sides of the heater; means for operating the heater at a temperature elevated above ambient, thus creating a no-flow temperature gradient in the air above and adjacent to the heater, the temperature within the no-flow gradient making a transition between the elevated temperature and substantially ambient temperature; the sensors being located sufficiently close to the heater to be located substantially within the no-flow temperature gradient; and the heater and the sensors being substantially thermally isolated so that a primary path of heat between the heater and the sensors is air.

Claim 6

A flow sensor, comprising: a thin film heater; a pair of thin film sensors; a semiconductor body with a depression therein; thin film means connecting the heater and the sensors to the body and bridging the depression so that at least a major portion of the heater and the sensors are out of contact with the body and with the sensors disposed on opposite sides of the heater; means for operating the heater at a temperature elevated above ambient, thus creating a no-flow temperature gradient in the air above and adjacent to the heater, the temperature within the no-flow gradient making a transition between the elevated temperature and substantially ambient temperature; the sensors being located sufficiently close to the heater to be located substantially within the no-flow temperature gradient; and the heater and the sensors being substantially thermally isolated so that a primary path of heat between the heater and the sensors is air.

Claim 7

The apparatus of claim 1, 2, or 3 wherein the sensors are located from the heater at a preferred distance which, when contrasted to an alternate distance, provides a substantially greater change in the heat being delivered to the sensors for a given change in flow rate.

Claim 8

The apparatus of claim 1, 2, or 3 wherein the proximal edges of the sensors are located from the near edges of the heater at a distance within the range of approximately 5 microns to approximately 25 microns.

Claim 9

The apparatus of claim 1, 2, or 3 wherein the heater and each sensor comprise a resistive element having a pattern of resistive material formed in lines having a line width, the lines being separated by substantially a line width, the sensors being separated from the heater by a distance in the range of approximately one line width to approximately five line widths.

Claim 10

The apparatus of claim 1, 2, or 3 wherein the thin film heater and sensors each comprise a permalloy element.

Claim 11

The apparatus of claim 7 wherein each permalloy element has a resistance in the range of approximately 200 ohms to approximately 2000 ohms at approximately 25 degrees Centigrade.

Claim 12

The apparatus of claim 7 wherein each permalloy element has a thickness in the range of approximately 800 angstroms to approximately 1600 angstroms.

Claim 13

The apparatus of claim 3 wherein the means connecting the heater and the sensors to the body comprises a dielectric encapsulating the heater and the sensors.

Claim 14

The apparatus of claim 10 wherein the dielectric has a thickness in the range of approximately 0.8 micron to approximately 1.2 microns.

Claim 15

The apparatus of claim 10 wherein the dielectric comprises silicon nitride.

Claim 16

A flow sensor comprising: a thin film heater encapsulated in thin film dielectric; a pair of thin film sensors encapsulated in thin film dielectric, the sensors being disposed on opposite sides of the heater; a semiconductor body with a depression therein; the encapsulated heater and sensors forming at least one thin film member bridged across the depression so that at least a major portion of the heater and the sensors are out of contact with the semiconductor body; means for operating the heater at a temperature elevated above ambient, thus creating a no-flow temperature gradient in the air above and adjacent to the heater, the temperature within the no-flow gradient making a transition between the elevated temperature and substantially ambient temperature; the sensors being located sufficiently close to the heater to be located substantially within the no-flow temperature gradient; and the heater and the sensors being substantially thermally isolated so that a primary path of heat between the heater and the sensors is air.

Claim 17

A flow sensor comprising: a thin film heater encapsulated in thin film dielectric; a pair of thin film sensors encapsulated in thin film dielectric, the sensors being disposed on opposite sides of the heater; a semiconductor body with a depression therein; the encapsulated heater and sensors forming at least one thin film member bridged across the depression so that at least a major portion of the heater and the sensors are out of contact with the semiconductor body; means for operating the heater at a temperature elevated above ambient, thus creating a no-flow temperature gradient in the air above and adjacent to the heater, the temperature within the no-flow gradient making a transition between the elevated temperature and substantially ambient temperature; the sensors being located sufficiently close to the heater to be located substantially within the no-flow temperature gradient; and the heater and the sensors being substantially thermally isolated so that a primary path of heat between the heater and the sensors is air.

Claim 18

A flow sensor comprising: a semiconductor body having a depression formed into a first surface of the body; a thin film heater encapsulated in thin film dielectric; a pair of thin film sensors encapsulated in thin film dielectric, the thin film sensors being disposed on opposite sides of the heater; the encapsulated heater and sensors forming at least one thin film member, the at least one thin film member being attached to the first surface at least at one location in order to suspend at least a major portion of the heater and sensors over the depression; means for operating the heater at a temperature elevated above ambient, thus creating a no-flow temperature gradient in the air above and adjacent to the heater, the temperature within the no-flow gradient making a transition between the elevated temperature and substantially ambient temperature; the sensors being located sufficiently close to the heater to be located substantially within the no-flow temperature gradient; and the heater and the sensors being substantially thermally isolated so that a primary path of heat between the heater and the sensors is air.

Claim 19

A flow sensor comprising: a semiconductor body having a depression formed into a first surface of the body; a thin film heater encapsulated in thin film dielectric; a pair of thin film sensors encapsulated in thin film dielectric, the thin film sensors being disposed on opposite sides of the heater; the encapsulated heater and sensors forming at least one thin film member, the at least one thin film member being attached to the first surface at least at one location in order to suspend at least a major portion of the heater and sensors over the depression; means for operating the heater at a temperature elevated above ambient, thus creating a no-flow temperature gradient in the air above and adjacent to the heater, the temperature within the no-flow gradient making a transition between the elevated temperature and substantially ambient temperature; the sensors being located sufficiently close to the heater to be located substantially within the no-flow temperature gradient; and the heater and the sensors being substantially thermally isolated so that a primary path of heat between the heater and the sensors is air.

Claim 20

The apparatus of claim 13 or 14 wherein the sensors are located from the heater at a preferred distance which, when contrasted to an alternate distance, provides a substantially greater change in the heat being delivered to the sensors for a given change in flow rate.

Claim 21

The apparatus of claim 13 or 14 wherein the proximal edges of the sensors are located from the near edges of the heater at a distance within the range of approximately 5 microns to approximately 25 microns.

Claim 22

The apparatus of claim 13 or 14 wherein the heater and each sensor comprise a resistive element having a pattern of resistive material formed in lines having a line width, the lines being separated by substantially a line width, the sensors being separated from the heater by a distance in the range of approximately one line width to approximately five line widths.

Claim 23

The apparatus of claim 13 or 14 wherein the thin film heater and sensors each comprise a permalloy element.

Claim 24

The apparatus of claim 18 wherein each permalloy element has a resistance in the range of approximately 200 ohms to approximately 2000 ohms at approximately 25 degrees Centigrade.

Claim 25

The apparatus of claim 18 wherein each permalloy element has a thickness in the range of approximately 800 angstroms to approximately 1600 angstroms.

Claim 26

The apparatus of claim 13 or 14 wherein the dielectric has a thickness in the range of approximately 0.8 micron to approximately 1.2 microns.

Claim 27

The apparatus of claim 13 or 14 wherein the dielectric comprises silicon nitride.

Claim 28

The apparatus of claim 13 or 14 wherein: the semiconductor body comprises (100) silicon having a (100) plane and a [110] direction; the heater and sensors lie in a plane substantially parallel to the (100) plane; and the means connecting the heater and sensors to the body have a configuration oriented at a non-zero angle to the [110] direction.

Claim 29

The apparatus of claim 23 wherein the non-zero angle is substantially 45 degrees.

Claim 30

The apparatus of claim 13 or 14 wherein the heater and both sensors are located on a single member.

Claim 31

A flow sensor, comprising: a thin film heater; a pair of thin film sensors; a semiconductor body with a depression therein, the semiconductor body comprising (100) silicon having a (100) plane and [110] directions; the heater and sensors lying in a plane substantially parallel to the (100) plane; thin film means connecting the heater and the sensors to the body and bridging the depression so that at least a major portion of the heater and the sensors are out of contact with the body and with the sensors disposed on opposite sides of the heater, the means connecting the heater and the sensors to the body having a configuration oriented at a non-zero angle to the [110] direction; means for operating the heater at a temperature elevated above ambient, thus creating a no-flow temperature gradient in the air above and adjacent to the heater, the temperature within the no-flow gradient making a transition between the elevated temperature and substantially ambient temperature; the sensors being located sufficiently close to the heater to be located substantially within the no-flow temperature gradient; and the heater and the sensors being substantially thermally isolated so that a primary path of heat between the heater and the sensors is air.

Claim 32

A flow sensor, comprising: a thin film heater; a pair of thin film sensors; a semiconductor body with a depression therein, the semiconductor body comprising (100) silicon having a (100) plane and [110] directions; the heater and sensors lying in a plane substantially parallel to the (100) plane; thin film means connecting the heater and the sensors to the body and bridging the depression so that at least a major portion of the heater and the sensors are out of contact with the body and with the sensors disposed on opposite sides of the heater, the means connecting the heater and the sensors to the body having a configuration oriented at a non-zero angle to the [110] direction; means for operating the heater at a temperature elevated above ambient, thus creating a no-flow temperature gradient in the air above and adjacent to the heater, the temperature within the no-flow gradient making a transition between the elevated temperature and substantially ambient temperature; the sensors being located sufficiently close to the heater to be located substantially within the no-flow temperature gradient; and the heater and the sensors being substantially thermally isolated so that a primary path of heat between the heater and the sensors is air.

Claim 33

The apparatus of claim 26 wherein the non-zero angle is substantially 45 degrees.

Claim 34

The apparatus of claim 27 wherein the thin film heater and sensors each comprise a permalloy element.

Claim 35

The apparatus of claim 28 wherein each permalloy element has a resistance in the range of approximately 200 ohms to approximately 2,000 ohms at approximately 25 degrees centigrade.

Claim 36

The apparatus of claim 29 wherein the thin film means connecting the heater and the sensors to the body comprises a dielectric encapsulating the heater and the sensors.

Claim 37

The apparatus of claim 30 wherein the dielectric has a thickness in the range of approximately 0.8 micron to approximately 1.2 microns.

Claim 38

The apparatus of claim 31 wherein the dielectric comprises silicon nitride.

Claim 39

The apparatus of claim 26 wherein the thin film heater and sensors each comprise a permalloy element.

Claim 40

The apparatus of claim 33 wherein each permalloy element has a resistance in the range of approximately 200 ohms to approximately 2,000 ohms at approximately 25 degrees centigrade.

Claim 41

The apparatus of claim 34 wherein the thin film means connecting the heater and the sensors to the body comprises a dielectric encapsulating the heater and the sensors.

Claim 42

The apparatus of claim 35 wherein the dielectric has a thickness in the range of approximately 0.8 micron to approximately 1.2 microns.

Claim 43

The apparatus of claim 36 wherein the dielectric comprises silicon nitride.

Claim 44

The apparatus of claim 26 wherein the thin film means connecting the heater and the sensors to the body comprises a dielectric encapsulating the heater and the sensors.

Claim 45

The apparatus of claim 38 wherein the dielectric has a thickness in the range of approximately 0.8 micron to approximately 1.2 microns.

Claim 46

The apparatus of claim 39 wherein the dielectric comprises silicon nitride.

Claim 47

A flow sensor comprising: a thin film heater encapsulated in thin film dielectric; a pair of thin film sensors encapsulated in thin film dielectric, the sensors being disposed on opposite sides of the heater; a semiconductor body with a depression therein; and the encapsulated heater and sensors forming two thin film members bridged across the depression so that at least a major portion of the heater and the sensors are out of contact with the semiconductor body, approximately one half of the heater and approximately one half of each sensor being located on each member.

Claim 48

A flow sensor comprising: a thin film heater encapsulated in thin film dielectric; a pair of thin film sensors encapsulated in thin film dielectric, the sensors being disposed on opposite sides of the heater; a semiconductor body with a depression therein; and the encapsulated heater and sensors forming two thin film members bridged across the depression so that at least a major portion of the heater and the sensors are out of contact with the semiconductor body, approximately one half of the heater and approximately one half of each sensor being located on each member.

Claim 49

A flow sensor comprising: a semiconductor body having a depression formed into a first surface of the body; a thin film heater encapsulated in thin film dielectric; a pair of thin film sensors encapsulated in thin film dielectric, the thin film sensors being disposed on opposite sides of the heater; and the encapsulated heater and sensors forming two thin film members attached to the first surface at least at one location in order to suspend at least a major portion of the heater and the sensors over the depression, approximately one half of the heater and approximately one half of each sensor being located on each member.

Claim 50

A flow sensor comprising: a semiconductor body having a depression formed into a first surface of the body; a thin film heater encapsulated in thin film dielectric; a pair of thin film sensors encapsulated in thin film dielectric, the thin film sensors being disposed on opposite sides of the heater; and the encapsulated heater and sensors forming two thin film members attached to the first surface at least at one location in order to suspend at least a major portion of the heater and the sensors over the depression, approximately one half of the heater and approximately one half of each sensor being located on each member.

Claim 51

The apparatus of claim 41 or 42 wherein the heater is operated at a temperature elevated above ambient, thus creating a no-flow temperature gradient in the air above and adjacent to the heater, the temperature within the no-flow gradient making a transition between the elevated temperature and substantially ambient temperature, the sensors being located sufficiently close to the heater to be located substantially within the no-flow temperature gradient.

Claim 52

The apparatus of claim 41 or 42 wherein the sensors are located from the heater at a preferred distance which, when contrasted to an alternate distance, provides a substantially greater change in the heat being delivered to the sensors for a given change in flow rate.

Claim 53

The apparatus of claim 41 or 42 wherein the proximal edges of the sensors are located from the rear edges of the heater at a distance within the range of approximately 5 microns to approximately 25 microns.

Claim 54

The apparatus of claim 41 or 42 wherein the heater and each sensor comprise a resistive material formed in lines having a line width, the lines being separated by substantially a line width, the sensors being separated from the heater by a distance in the range of approximately one line width to approximately five line widths.

Claim 55

The apparatus of claim 41 or 42 wherein the thin film heater and sensors each comprise a permalloy element.

Claim 56

The apparatus of claim 47 wherein each permalloy element has a resistance in the range of approximately 200 ohms to approximately 2000 ohms at approximately 25 degrees centigrade.

Claim 57

The apparatus of claim 41 or 42 wherein each member has a thickness in the range of approximately 0.8 micron to approximately 1.2 microns.

Claim 58

The apparatus of claim 49 wherein the dielectric comprises silicon nitride.

Claim 59

The apparatus of claim 41 or 42 wherein: the semiconductor body comprises (100) silicon having a (100) plane and a [110] direction; the heater and sensors lie in a plane substantially parallel to the (100) plane; and the thin film members connecting the heater and sensors to the body have a configuration oriented at a non-zero angle to the [110] direction.

Claim 60

The apparatus of claim 51 wherein the non-zero angle is substantially 45 degrees.

Claim 61

The apparatus of claim 41 or 42 wherein the two thin film members are connected by an interconnect.

Claim 62

The apparatus of claim 41 or 42 wherein the heater and the sensors are substantially thermally isolated so that a primary path of heat between the heater and the sensors is air.

Claim 63

The apparatus of claim 54 wherein the heater is operated at temperature elevated above ambient, thus creating a no-flow temperature gradient in the air above and adjacent to the heater, the temperature within the no-flow gradient making a transition between the elevated temperature and substantially ambient temperature, the sensors being located sufficiently close to the heater to be located substantially within the no-flow temperature gradient.

Claim 64

The apparatus of claim 54 wherein the sensors are located from the heater at a preferred distance which, when contrasted to an alternate distance, provides a substantially greater change in the heat being delivered to the sensors for a given change in flow rate.

Claim 65

The apparatus of claim 54 wherein the proximal edges of the sensors are located from the near edges of the heater at a distance within the range of approximately 5 microns to approximately 25 microns.

Claim 66

The apparatus of claim 54 wherein the heater and each sensor comprise a resistive material formed in lines having a line width, the lines being separated by substantially a line width, the sensors being separated from the heater by a distance in the range of approximately one line width to approximately five line widths.

Claim 67

The apparatus of claim 54 wherein: the semiconductor body comprises (100) silicon having a (100) plane and a [110] direction; the heater and sensors lie in a plane substantially parallel to the (100) plane; and the thin film members connecting the heater and sensors to the body have a configuration oriented at a non-zero angle to the [110] direction.

Claim 68

The apparatus of claim 59 wherein the non-zero angle is substantially 45 degrees.