DE102006050041B4 - Radiation sensor with an array of several thermopiles on a substrate with membrane surfaces - Google Patents

Abstract

Radiation sensor, in particular infrared sensor, with an array (22) of several thermopiles (5) on a substrate with membrane surfaces (10a, 10b), wherein the membrane surfaces (10a, 10b) first membrane surfaces (10a) for thermopiles (5) with an 8-sided Molds and second diaphragm surfaces (10b) for electronics having a square shape which form a regular array with sides of the square second diaphragm surfaces (10b) being disposed on sides of the 8-cornered first diaphragm surfaces (10a), the thermopiles (5) each formed of series-connected thermocouples (7) and each on one of the first membrane surfaces (10a) with an absorber (9) are arranged, and wherein the second membrane surfaces (10b) of adjacent first membrane surfaces (10a) laterally by webs ( 15) are separated as heat sinks, which are arranged below the second membrane surfaces.

Description

State of the art

The invention relates to a radiation sensor, in particular infrared sensors, with an absorber for the radiation to be measured and a plurality of thermocouples for measuring a heating of the absorber caused by the absorbed radiation.

Radiation sensors of the type mentioned above are known from the prior art. The schematic structure of such a radiation sensor is in 1 shown. The radiation sensor 1 usually contains a substrate 2 with a membrane 10 , on whose surface several thermocouples 7 connected in series, and one on the membrane 10 formed, radiation 8th absorbent absorber 9 , The thermocouples 7 themselves consist alternately of a first thermal material and a second thermal material. Two contacting thermocouples made of different thermal materials 7 make a thermocouple together. A multitude of thermocouples in series forms a so-called thermopile 5 , At the two ends of the so coupled thermocouples are electrical connection fields 3 arranged.

In the area of the transition from the first thermal material to the second thermal material, a thermal contact is formed in each case 4a . 4b , Here are the thermocouples 7 arranged so that so-called "hot" thermal contacts 4a in the self-supporting area of the membrane 10 from the absorber 9 to be covered. On the other hand, the so-called "cold" thermal contacts 4b in the edge region of the membrane 10 or in the substrate 2 supported, by the absorber 9 uncovered area arranged so that these "cold" thermal contacts 4b due to the good thermal conductivity of the substrate 2 opposite the "hot" thermal contacts 4a have a lower temperature. In 1 is the front wall of the substrate 2 Drawn not shown to the membrane 10 or to better recognize the recess arranged thereunder.

When rays 8th on the sensor 1 arrive, the absorber heats up 9 stronger than the rest of the sensor 1 , and as a result, a temperature gradient forms. This temperature gradient between the absorber 9 and the remaining sensor region induces a voltage difference in each thermocouple due to the Seebeck effect, which can be measured as a small signal voltage. Because a whole series of thermocouples in series to a thermopile 5 are switched accordingly increases the resulting total signal voltage of a thermopile 5 , This signal voltage can be applied to the two electrical connection panels 3 be tapped.

To further enhance the sensor signal on the smallest possible chip area, various measures have been proposed. For example, this is off DE 103 21 639 A1 an infrared sensor is known in which a support body is provided with a support surface for receiving an absorber element, wherein the support body surface has a recess whose extent corresponds to at least 45% of the support surface. According to the above-mentioned document, an optimized area utilization is thereby achieved.

Next will be in DE 198 43 984 A1 describes the manufacture of a radiation sensor comprising an array of thermopiles and absorbers. The individual field units are each arranged above an opening, wherein the openings are separated by vertically extending, steep-walled webs.

A similar structure of a radiation sensor is described in DE 101 44 343 A1 proposed. It is also explained in this document that a plurality of sensor units can be arranged on a membrane of a single chip. In this case, the membrane is arranged over a recess which is bounded laterally completely by side walls, wherein at least one side wall is arranged at an angle β between 80 ° and 100 ° to the membrane.

From the DE 103 21 639 A1 is a radiation sensor with an array of several thermopiles known. The DE 103 20 357 A1 describes sensor elements which are arranged on hexagonal carriers. The JP H01-259 227A discloses a manufacturing method of a thermopile structure wherein a hexagonal hole is formed in a silicon single crystal by anisotropic etching.

Typically, according to the prior art, a thermopile array consists of area units that have a round or rectangular, often square shape. In each case a thermopile is applied to these surface units, so that the entirety of the thermopiles is arranged in a rectangular grid on a chip.

Disclosure of the invention

The object according to the invention with the features of the independent claim has the advantage over the previously known prior art that a significant saving in the total area required for a thermopile array can be achieved. This advantageously results in a noticeable reduction in the production costs of radiation sensors on the basis of Microsystem technology, as they are largely determined by the space required.

With the same sensitivity of the sensors, d. H. at the same total area of the absorber, the same number, the same thickness and the same minimum length of the thermocouples and the same heat capacity of the membrane, advantageously decreases in a sensor according to the invention, the space requirement significantly: By the arrangement of the thermopiles or the associated membrane surface after z. B. hexagonal symmetry reduces the area requirement for non-consideration of the area for the electronics by about 30% for a 4 × 4 array, and already by about 40% for a 16 × 16 array.

Expedient developments emerge from further dependent claims and from the description.

drawing

Embodiments of the invention are illustrated in the drawings and are explained in more detail below. Show it:

The 1 a radiation sensor as known from the prior art in a perspective view,

the 2a an example of a sensor unit with a thermopile on a hexagonal membrane surface in plan view,

the 2 B a section of an array for hexagonal membrane surfaces in plan view,

the 3a an embodiment of a sensor unit with a thermopile on an 8-cornered membrane surface in plan view, and

the 3b a section of an array for 8-sided membrane surfaces with additional membrane surfaces for the electronics in plan view.

The radiation sensor according to the invention is based on the knowledge that through the use of arrays of hexagonal or 8-angular membrane surfaces, on each of which a sensor unit, d. H. a thermopile and, where appropriate, electronics for this purpose, a reduction in the area required by the radiation sensor with the same sensitivity can be achieved in comparison with quadrangular membrane surfaces. The advantage of the radiation sensor according to the invention over previously known radiation sensors can also be expressed alternatively in that with the same total area of the membrane and otherwise identical conditions, a higher sensitivity of the sensor is achieved.

2a shows an example of a sensor unit with a thermopile 5 on a hexagonal membrane surface 10a in plan view. On the hexagonal membrane surface 10a is first a thermopile 5 , formed by many series-connected thermocouples 7 , recognizable. These series-connected thermocouples are advantageous 7 arranged in a cross or star shape. As already explained, adjacent thermocouples 7 through thermal contacts 4a . 4b electrically connected to each other. The "hot" thermal contacts 4a in the middle region of the membrane surface 10a be through an absorber 9 covered, which is also on the membrane surface 10a is arranged. The in the edge region of the membrane surface 10a arranged "cold" thermal contacts 4b stay away from the absorber 9 uncovered. At the two ends of the chain of thermocouples 7 are electrical connection fields 3 intended to decrease the signal voltage. Such a membrane surface 10a is bounded laterally by webs 15 that are below the membrane surface 10a are arranged. These webs serve as heat sinks and carry the heat away from the membrane surface 10a ,

If one assigns several of those just described and in 2a illustrated 6-angular membrane surfaces 10a without any space in an array 20 on, this results in a regular hexagonal arrangement as in 2 B shown. For clarity, are in 2 B only the individual membrane surfaces 10a without further components on the membrane surfaces 10a shown. It is stated that in addition to the membrane surfaces 10a also the thermopiles 5 even in hexagonal symmetry in an array 20 are arranged. The membrane surfaces 10a are not in on one 2a arranged substrate.

In one embodiment of the present invention is according to 3a an 8-cornered membrane surface 10a proposed. Because the geometric shape of the membrane surface 10a Here is the essential difference from the above example, the above explanations to other components on the 6-sided membrane surface 10a on the now 8-angular membrane surface 10a be taken over.

Also the 8-angular membrane surfaces 10a for the thermopiles 5 can become an array 22 be formed with a regular arrangement, wherein - as in 3b shown - to each 8-cornered membrane surface 10a an additional membrane surface 10b is available. This additional, in this example square membrane surface 10b lends itself to the electronics, if the electronics not together with the other components on the 8-cornered membrane surface 10a can or should be arranged. Also the membrane surface 10b for the electronics is laterally separated from adjacent membrane surfaces 10a through bars 15 that are below the membrane surface 10b are arranged.

Incidentally, in all embodiments, the webs 15 , yes as heat sinks under the individual membrane surfaces 10a . 10b for thermopiles 5 and / or electronics are arranged at their edge regions, have a thickness which is equal to or smaller than the thickness of the substrate, depending on requirements or production method. In the case of webs 15 with the same thickness as the substrate is also a particularly strong mechanical stability of the membrane surfaces 10a . 10b achieved.

However, in many cases it is sufficient if the bars 15 have a certain minimum thickness smaller than substrate thickness. It is important in any case that the thickness of the webs 15 at least so great that a sufficient heat dissipation is ensured. For this are the bars 15 under the membrane surfaces 10a . 10b connected to each other and ultimately to the substrate, so that the heat from the membrane surfaces 10a . 10b can flow to the substrate.

Finally, it should be noted that the absorber is advantageous 9 the geometry of the respective membrane surface 10a can be adjusted. This is the way the absorber points 9 even an octagonal shape.

Claims (5)

Radiation sensor, in particular infrared sensor, with an array ( 22 ) of several thermopiles ( 5 ) on a substrate with membrane surfaces ( 10a . 10b ), wherein the membrane surfaces ( 10a . 10b ) first membrane surfaces ( 10a ) for Thermopiles ( 5 ) with an octagonal shape and second membrane surfaces ( 10b ) for electronics having a square shape, which form a regular array, with sides of the square second membrane surfaces ( 10b ) on the sides of the 8-angular first membrane surfaces ( 10a ), the thermopiles ( 5 ) in each case from series-connected thermocouples ( 7 ) are formed and in each case on one of the first membrane surfaces ( 10a ) with an absorber ( 9 ) are arranged, and wherein the second membrane surfaces ( 10b ) of adjacent first membrane surfaces ( 10a ) laterally by webs ( 15 ) are separated as heat sinks, which are arranged below the second membrane surfaces. Sensor according to claim 1, characterized in that the webs ( 15 ) are formed thinner than the thickness of the substrate. Sensor according to claim 1, characterized in that the webs ( 15 ) have a thickness as the thickness of the substrate. Sensor according to one of the preceding claims, characterized in that the series-connected thermocouples ( 7 ) are arranged in a cross or star shape. Sensor according to one of the preceding claims, characterized in that the absorber ( 9 ) has an octagonal shape.

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