Semiconductor device, in particular semiconductor sensor and method for its fabrication

Claim 2

An integrated semiconductor device, comprising: a semiconductor body (20) with a first surface (36) having a predetermined orientation with respect to a crystalline structure in the semiconductor body, the semiconductor body having a depression (30) formed into the first surface of the body; a layer (29) of thin film material covering at least a portion of the first surface (36); and diaphragm means (32) comprising the layer (29) of thin film material and further comprising a transducer element (22, 24, 26), characterized i n that the diaphragm means forms a slotted diaphragm (32) substantially covering the depression (30); the slotted diaphragm (32) comprises at least one slot (82) sized and oriented so that, in the fabrication of the device, an anisotropic etch placed on the slot will undercut the diaphragm (32) and form the depression (30); the transducer element (22, 24, 26) is substantially supported by the diaphragm (32) and, therefore, substantially thermally and physically isolated from the semiconductor body (20).

Claim 3

A device according to claim 1, characterized in that the semiconductor body (20) comprises (100) silicon and has a (100) plane and a [110] direction, the first surface (36) of the semiconductor body being substantially parallel to the (100) plane; and the slot (82) is oriented at substantially 45 degrees to the /1107 direction and extends across the depression (30) at the approximate center of the depression.

Claim 4

A device according to claim 1 or 2, characterized in that the transducer element (22, 24, 26) is a static electric element, a thermal-to-electric transducing element, or an electric-to-thermal element.

Claim 6

A device according to claim 3 or 4 for use as a flow sensor, characterized b y a thin film heater (26) supported over the depression (30) by the diaphragm (32), approximately half of the heater being located on each side of the slot (82).; and a pair of thin film heat sensors (22, 24) supported by the diaphragm (32), the thin film sensors being disposed on opposite sides of the heater (26).

Claim 7

A device according to claim 5, characterized in that the heater (26) 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; and that the sensors (22, 24) are located sufficiently close to the heater (20) to be located substantially within the no-flow temperature gradient.

Claim 8

A device according to claim 5 or 6, characterized in that the proximal edges of the sensors (22, 24) are located from the near edges of the heater (26) at a distance within the range of approximately 5 microns to approximately 25 microns.

Claim 10

A device according to claim 8, characterized in that the permalloy element has a thickness in the range of approximately 800 angstroms to approximately 1,600 angstroms.

Claim 12

A device according to claim 10, characterized in that the dielectric material has a thickness in the range of approximately 0.8 micron to approximately 1.2 microns.

Claim 17

A method according to claim 15, characterized by the steps of: providing a semiconductor body (20) comprising (100) silicon and having a (100) plane and a [110] direction, the first surface (36) of the semiconductor body being substantially parallel to the (100) plane; providing a layer (29) of thin film material of which the diaphragm is comprised onto the first surface (36); exposing an area of the first surface through a slot in the layer of thin film material, the slot being oriented at substantially 45 degrees to the /T107 direction, the slot having a length which determines the maximum width of the depression as measured along the slot oriented at substantially 45 degrees to the /110% direction; and applying an anisotropic etch to the exposed surface area to undercut the diaphragm and create the depression.

Claim 18

A method according to claim 16 for fabricating a slotted diaphragm semiconductor device comprising a slotted diaphragm (32) of thin film material substantially covering a depression (30) etched into a first surface (36) of a semiconductor body (20), the depression being bounded at the first surface by a substantially square configuration comprising four substantially perpendicular boundary edges (111, 113), each of the four substantially perpendicular boundary edges being substantially in line with or substantially perpendicular to a [110] direction in the semiconductor body, the method comprising the steps of: providing a semiconductor body comprising (100) silicon and having a (100) plane and a [110] direction, the first surface of the semiconductor body being substantially parallel to the (100) plane; exposing first and second areas of the first surface through first and second slots in the layer of thin film material, the first and second slots being located on a line oriented at substantially 45 degrees to the [110] direction, each of the first and second slots comprising a first end located at a maximum width of the depression as measured along the line oriented at substantially 45 degrees to the /11-07 direction, each of the first and second slots having a second end located so that each of the first and second slots extends only a portion of the distance across the maximum width of the depression as measured along the line oriented at substantially 45 degrees to the [110] direction; exposing third, fourth, fifth and sixth areas of the first surface through third, fourth, fifth and sixth slots oriented substantially in line with or substantially perpendicular to the [110] direction, there being one of the third, fourth, fifth and sixth slots located at the substantial center of each of the four boundary edges, each of the third, fourth, fifth and sixth slots having a length sufficient to permit undercutting of the diaphragm when an anisotropic etch is placed on each of the six slots; and applying the anisotropic etch to the exposed surface areas to undercut the diaphragm and create the depression.