Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
  • G01K7/00—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements
  • G01K7/02—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements using thermoelectric elements, e.g. thermocouples
  • G01K7/028—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements using thermoelectric elements, e.g. thermocouples using microstructures, e.g. made of silicon
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
  • G01J5/00—Radiation pyrometry, e.g. infrared or optical thermometry
  • G01J5/10—Radiation pyrometry, e.g. infrared or optical thermometry using electric radiation detectors
  • G01J5/12—Radiation pyrometry, e.g. infrared or optical thermometry using electric radiation detectors using thermoelectric elements, e.g. thermocouples

Definitions

• the invention relates to a microstructured thermal sensor, in particular an infrared sensor, according to the preamble of the independent claims.
• thermoelectric sensors such as those used in security technology, system engineering or household appliance technology, measure the temperature of a body using the infrared radiation it emits.
• pyroelectric, bolometric and thermoelectric sensors A fundamental distinction is made between so-called pyroelectric, bolometric and thermoelectric sensors.
• thermoelectric sensors it is known to implement them using thin-film technology, for example on polyimide film.
• Microstructured thermal sensors based on silicon technology are also already known.
• thermocouples running on the surface of the largely self-supporting membrane in the form of conductor tracks, which are alternately formed from a first and a second material, so that in the area in which these two materials touch, Thermal contacts arise.
• the first material is aluminum while the second material is poly-silicon.
• a microstructured thermal sensor in the form of an infrared sensor by initially producing a thin self-supporting membrane on a silicon substrate, for example with the aid of a sacrificial layer technique or another etching process low thermal conductivity is thermally decoupled from a substrate underneath, so that the membrane heats up more than the substrate when infrared radiation is incident.
• a large number of microstructured sensor elements or thermocouples are then located on the membrane, which thermoelectrically convert a temperature difference between the center of the membrane and the substrate into an electrical signal proportional thereto.
• the material combinations platinum / polysilicon, aluminum / poly-silicon or p-doped poly-silicon / n-doped poly-silicon are used for the thermocouples realized on the self-supporting membrane in the form of conductor tracks.
• the material combination poly-silicon / aluminum which is mainly used in bulk micromechanics, has the advantage that it is CMOS compatible.
• thermocouples gold also being suitable for bulk micromechanics.
• the object of the present inventions was to implement a microstructured thermal sensor which is improved compared to known microstructured thermal sensors with regard to sensitivity and stability at higher temperatures.
• the microstructured thermal sensor according to the invention has the advantage that the structure of the conductor tracks on the support body and / or the special choice of materials for the thermocouple results in increased temperature sensitivity without any major changes to the previous manufacturing process are required for microstructured thermal sensors.
• the layout of the generated conductor tracks of the thermocouples and / or the material used to deposit these conductor tracks is modified.
• thermocouple that is to say the combination of platinum or aluminum with doped or undoped polySilicon-Germanium, ensures that the microstructured thermal sensor produced has a significantly increased temperature stability compared to known thermal sensors in which For example, aluminum with poly-silicon can be used as the material for the thermocouple.
• thermocouple can now also prevent migration effects and thus stability problems of the microstructured thermal sensor obtained at temperatures greater than 200 ° C, as is often the case with sensors based on poly-silicon and aluminum as thermocouple material is.
• aluminum which has been widely used to date, is a very good heat conductor, which means that the thermoelectric effectiveness of the thermocouple manufactured with it is relatively low, whereas platinum can be used at temperatures up to 400 ° C on the one hand, and by a factor compared to aluminum 3 has lower thermal conductivity.
• polycrystalline, doped or undoped poly-silicon germanium in contrast to polycrystalline silicon, has a thermal conductivity which is 3 to 8 times lower and therefore also leads to a significantly increased thermoelectric effectiveness of the thermocouple produced.
• thermocouple a particularly high increase in sensitivity and particularly good temperature stability of the thermal sensor is achieved by combining the novel, meandering or undulating layout of the microstructured conductor tracks on the surface of the support body with the special materials for the thermocouple described.
• thermocouple for example as an infrared sensor
• the materials mentioned for the thermocouple can be combined with one another, it being possible for the semiconductor to be material p-doped or n-doped.
• thermoelectrically Since with microstructured thermal sensors a temperature difference between so-called “hot” and “cold” contacts is converted thermoelectrically into a measurable electrical voltage, the "cold” points must either be a constant temperature, or this temperature must be known or referenced relative to the temperature of the "hot” contact. So-called thermistors in hybrid technology have hitherto usually been integrated on the support body for the thermocouple, since the materials used are aluminum and polysilicon Determining this reference temperature is often not sensitive enough.
• thermoelectric material When using platinum as the thermoelectric material, it is now advantageously possible in this context to integrate or integrate a high-precision, resistive temperature measuring element in the same manufacturing step as the corresponding conductor track or supply line on the silicon chip or the support body carrying the thermocouple to deposit. This eliminates the need for an additional thermistor.
• the design of the conductor tracks in the form of meandering or wave-shaped conductor tracks running on the supporting body further offers the possibility of designing only the conductor track with the lower internal resistance than meandering, since the material has a high electrical resistance due to the meandering shape or wave form increased noise voltage comes.
• the meandering or wave-shaped conductor tracks can run both next to one another and at least in regions overlap or overlap, these then having to be electrically insulated from one another by suitable insulation layers made of oxides, for example. If sufficient space is available, it is generally advantageous to run the conductor tracks next to one another.
• thermocouple produced on the surface of a support body in the form of applied conductor tracks running next to one another.
• the invention is initially based on an infrared sensor, as has already been proposed in application DE 100 09 593.3.
• the infrared sensor proposed there is modified in two ways.
• an at least largely self-supporting membrane made of a poorly heat-conducting material such as an oxide, a nitride or a combination of both materials is first produced on a good heat-conducting material such as silicon as the substrate, as already proposed in DE 100 09 593.3.
• This at least largely self-supporting membrane which then serves as a support body 12 for a thermocouple 20 to be applied thereon, preferably consists of silicon dioxide, silicon nitride or porous silicon.
• thermocouples 20 arranged in series, in a cruciform or star-shaped arrangement are produced on the surface of this supporting body 12, whereby according to the figure, which shows only a single one of these thermocouples 20, a first material 13 is first provided on the supporting body 12 in the form of a first, meandering conductor track 15 and then a second material 14 in the form of a second, likewise meandering conductor track 16.
• the first conductor track 15 and the second conductor track 16 run, as shown in the figure, at least largely parallel to one another.
• first material 13 and the second material 14 touch in the area of a first thermal contact 10 and a second thermal contact 11, and that further leads 17 to the thermocouple 20 are provided, which are formed analogously to the second conductor track 16 and have been applied so that the thermocouple 20 can be electrically connected or controlled via these leads 17 in a manner known per se with electronic components (not shown).
• the figure also shows that the first thermal contact 10 is exposed to a first temperature T 1 and the second thermal contact 11 is exposed to a second temperature T 2.
• the temperature T2 is the actual temperature to be detected or measured by the microstructured thermal sensor 5, while the temperature T -] _ is either kept at least approximately constant or alternatively can be determined by means of an additional measuring device.
• the temperature T] _ of the first thermal contact 10 (“cold" thermal contact) serves as the reference temperature for the temperature to be measured T2 of the second thermal contact 11 ("hot” thermal contact).
• the width of the conductor tracks 14, 15 and the feed lines 17 is moreover between 20 nm and 200 ⁇ m, preferably between 1 ⁇ m and 20 ⁇ m.
• the first and second conductor tracks 15, 16 and their meandering structure were produced, and the supply lines 17 were produced in a known manner by sputtering or vapor deposition of the respective materials 13, 14, for example using PECVD (“Physically Enhanced Chemical Vapor Deposition) or LPCVD (Low Pressure Chemical Vapor Deposition ").
• PECVD Physical Enhanced Chemical Vapor Deposition
• LPCVD Low Pressure Chemical Vapor Deposition
• the first material is 13 n-doped poly-silicon germanium with a thermal conductivity of 3 to 8 W / km.
• the second material 14 is platinum with a thermal conductivity of 70 W / km.
• the supply lines 17 are each designed analogously to the second conductor track 16 in the form of a platinum conductor track, so that there are two thermal contacts 10, 11, each of which is formed by the material combination of platinum / poly-silicon-ger anium.
• first conductor track 14 and the second conductor track 15 can also run in regions or completely one above the other and, apart from the thermal contacts 10, 11, to be electrically insulated from one another.
• the electrical insulation is ensured by an oxidic, electrically insulating intermediate layer between the conductor tracks 15, 16.
• thermal contacts 10, 11 a plurality of thermal contacts can also be provided, which are arranged in the manner of a thermal chain or a thermal column. Then there are at least two the thermal contacts exposed to different temperatures.
• part of an additional measuring device in the form of a conductor track for determining the first temperature T ] is additionally generated or integrated on the support body 12.
• the integration of a conventional thermistor on the surface of the support body 12 in the area of the first thermal contact 10 can then be dispensed with.
• this measuring device is then realized in that in an environment of the first thermal contact 10 an additional reference conductor made of platinum is provided as a sensitive component of this measuring device, which via corresponding feed lines is also used with evaluation means known per se for determining a temperature-dependent electrical resistance of this reference conductor. is switched.
• This reference conductor track is, for example, analogous to the feed line 17 or the second conductor track 16.
• this measuring device can also be implemented in that a section of the second conductor track 16 or the supply lines 17 is used as a reference conductor track and is connected with corresponding evaluation means for determining the temperature-dependent electrical resistance of this part of the conductor track.
• This possibility of integrating an additional reference conductor track on the support body 12 or the possibility of using a part of the second conductor track 16 or the feed line 17 as a reference conductor track on the support body 12 results for measuring or monitoring the temperature T 1 from the suitability of platinum for high-precision resistive temperature measurement.
• thermocouple 20 With regard to further details on the structure of the thermocouple 20 and the function and the further structure of the thermocouple 5 according to the figure, reference is made to the application DE 100 09 593.3, in which this thermal sensor 5, apart from the special layout of the conductor tracks 15, 16 of the thermocouple 20 and the special choice of materials for the thermocouple 20, in the form of an infrared sensor.

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• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Spectroscopy & Molecular Physics (AREA)
• Chemical & Material Sciences (AREA)
• Crystallography & Structural Chemistry (AREA)
• Radiation Pyrometers (AREA)
• Photometry And Measurement Of Optical Pulse Characteristics (AREA)
• Measuring Temperature Or Quantity Of Heat (AREA)

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• 2000
  • 2000-07-11 DE DE10033589A patent/DE10033589A1/de not_active Ceased
• 2001
  • 2001-06-07 WO PCT/DE2001/002145 patent/WO2002004905A1/de active Application Filing
  • 2001-06-07 JP JP2002509730A patent/JP2004503743A/ja active Pending
  • 2001-06-07 EP EP01947197A patent/EP1198699A1/de not_active Withdrawn
  • 2001-06-07 US US10/070,973 patent/US6863438B2/en not_active Expired - Fee Related

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