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WO2005029007A1 - Capteur de masse d'air a pellicule chaude presentant une structure de support et un gradient de porosite sous la membrane de detection, et procede de production correspondant - Google Patents

Capteur de masse d'air a pellicule chaude presentant une structure de support et un gradient de porosite sous la membrane de detection, et procede de production correspondant Download PDF

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Publication number
WO2005029007A1
WO2005029007A1 PCT/EP2004/052007 EP2004052007W WO2005029007A1 WO 2005029007 A1 WO2005029007 A1 WO 2005029007A1 EP 2004052007 W EP2004052007 W EP 2004052007W WO 2005029007 A1 WO2005029007 A1 WO 2005029007A1
Authority
WO
WIPO (PCT)
Prior art keywords
sensor
air mass
membrane
sensor chip
film air
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/EP2004/052007
Other languages
German (de)
English (en)
Inventor
Uwe Konzelmann
Tobias Lang
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Robert Bosch GmbH
Original Assignee
Robert Bosch GmbH
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Robert Bosch GmbH filed Critical Robert Bosch GmbH
Publication of WO2005029007A1 publication Critical patent/WO2005029007A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
    • G01F1/00—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow
    • G01F1/68—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow by using thermal effects
    • G01F1/684—Structural arrangements; Mounting of elements, e.g. in relation to fluid flow
    • G01F1/6845—Micromachined devices

Definitions

  • a defined air mass must be supplied in many processes. These include, in particular, combustion processes that take place under controlled conditions, such as the combustion of fuel in automotive internal combustion engines with subsequent catalytic exhaust gas purification. Hot air mass sensors are used to measure the air mass flow rate.
  • the membrane must be made as thin as possible so that the greatest possible proportion of the heat flow emitted by the heating element on the sensor membrane is released into the air and is not dissipated via the silicon of the sensor chip. Furthermore, a cavern is formed for insulation below the membrane in the hot film air mass sensors currently used. Since the sensor chip is housed in a carrier structure, the cavern is completely sealed off and there is no air exchange with the surroundings. This further increases the insulating effect of the cavern.
  • a disadvantage of the sensor chips currently used is that the mechanical stability of the sensor chip is only maintained by the frame surrounding the sensor membrane. In addition, the membrane itself is sensitive to mechanical influences.
  • the solution according to the invention provides for a support structure made of porous silicon to be arranged below the membrane in order to support the membrane.
  • the porosity of the welding structure directly underneath the membrane should be chosen as high as possible.
  • the porosity of the support structure directly below the sensor membrane is preferably in the range of less than 0.7, a porosity of 1 meaning that there is no silicon oxide, while a porosity of 0 means pure silicon oxide.
  • the porous layer preferably comprises a highly porous layer, which is followed by a layer with decreasing porosity. The thickness of the highly porous layer is carried out in such a way that a sufficient insulating effect is built up overall.
  • the highly porous layer has a thickness of preferably at most 200 ⁇ m, more preferably of at most 100 ⁇ m and in particular of at most 30 ⁇ m. From this thickness, the porosity of the smear structure is reduced as the distance from the sensor membrane increases. This ensures that the amount of heat stored in the smtz structure can be better delivered to the sensor chip surrounding the smtz structure. Overall, the thickness of the sealing structure takes up only part of the thickness of the sensor chip. This means that the Slitz structure is limited on the top by the sensor membrane and on all other sides by the material of the sensor chip. Both the sensor chip and the scratch structure preferably consist of silicon.
  • the sensor membrane is preferably made of silicon oxide and provided with a silicon metride coating.
  • a heating element and two temperature sensors are arranged on the sensor membrane for measuring the air mass flow.
  • the temperature sensors are installed in front of and behind the heating element in the direction of flow. With a constant heat flow emitted by the heating element, the air mass flow can be determined from the temperature difference between the two temperature sensors.
  • further temperature sensors for measuring the ambient air temperature can also be arranged on the sensor chip.
  • two heating elements are arranged on the sensor membrane. Furthermore, there are temperature sensors in front of and behind the heating elements in the direction of flow. To determine the air mass flow flowing over the sensor chip, the temperature profile in the air flow is kept constant by varying the heat flow supplied. Depending on the heat flow or the heating power supplied, the air mass flow can be determined.
  • further temperature sensors can also be arranged on the sensor chip in order to measure the air temperature.
  • the at least one heating element and the temperature sensors and the conductor tracks for supplying voltage or for recording the measurement data are preferably made of platinum.
  • Another material for manufacturing the at least one heating element, the temperature sensors and the conductor tracks is silicon carbide, which has a high mechanical and thermal stability.
  • the temperature sensors preferably work as resistance thermometers. However, it is also possible to use temperature sensors in the form of thermocouples.
  • FIG. 1 shows a detail from a hot film air mass sensor according to the prior art in a perspective view
  • FIG. 2 shows a section through a sensor chip designed according to the invention
  • Figure 3 shows a detail of a hot film air mass sensor with thermopiles in a perspective view. variants
  • FIG. 1 shows a detail from a hot film air mass sensor according to the prior art in a perspective view.
  • a hot air mass mass sensor 1 is arranged in a measuring channel, not shown here.
  • the direction of the air mass to be measured is identified by an arrow designated by reference number 15.
  • the air flows around the hot film air mass sensor 1, which comprises a sensor chip 3 with a sensor membrane 4.
  • the sensor chip 3 which is preferably made of silicon, is accommodated in a receptacle 7 of a carrier structure 5.
  • the air in the cavern 6 has an insulating effect due to its low thermal capacity compared to silicon and its low thermal conductivity.
  • a fluidically favorable form of the hot film air mass sensor 1 is obtained in that the carrier structure 5 has a rounded leading edge 14 on the inflow side of the air.
  • the leading edge 14 can also have any other aerodynamically favorable inflow profile known to the person skilled in the art. These include in particular elliptical and parabolic profiles.
  • the sealing surfaces 9 of the receptacle 7 are provided with a circumferential chamfer 10.
  • An air flow into the cavern 6 below the sensor membrane 4 is avoided by the sealing surfaces 9, which are in contact with the side surfaces 19 of the sensor chip 3. This avoids that when the hot film air mass sensor 1 overflows, part of the air flow passes under the sensor chip 3 through a gap between the support structure 5 and the sensor chip 3.
  • the sensor chip 3 is preferably arranged in the carrier structure 5 such that the top 21 of the carrier structure 5 and the top 18 of the sensor chip 3 form a plane.
  • the alignment of the sensor chip 3 in the carrier structure 5 takes place with the aid of a gap 17 below the sensor chip 3.
  • the gap 17 serves as tolerance compensation, the distance from the bottom 8 to the top 21 of the carrier structure 5 having to be greater than the distance from the underside 20 from the thickened areas 16 surrounding the sensor membrane 4 Top side 18 of the sensor chip 3.
  • the sensor chip 3 is fastened in the carrier structure 5 by means of an adhesive, not shown in FIG. 1. When gluing, make sure that no glue gets into the cavern 6 below the sensor membrane 4.
  • the amount of adhesive is to be dimensioned such that the top 18 of the sensor chip 3 and the top 21 of the carrier structure 5 form a plane.
  • a heating element 11, a first temperature sensor 12 and a second temperature sensor 13 are arranged on the sensor membrane 4 transversely to the flow direction 15 of the air.
  • the temperature of the air is first measured with the first temperature sensor 12, in the further course the air overflowing the hot film air mass sensor 1 is heated at the heating element 11 with a constant heat flow and finally the temperature is measured again with the second temperature sensor 13 ,
  • the air mass flowing over the hot film air mass sensor 1 is directly inversely proportional to the temperature difference between the first temperature sensor 12 and the second temperature sensor 13 when the heat flow is supplied and the specific heat capacity is constant.
  • the heating element 11 is attached to the sensor membrane 4. Because of the small thickness of the sensor membrane 4, only a small proportion of the heat given off by the heating element 11 is transported to the sensor chip 3 by heat conduction. A further reduction in the heat conduction from the sensor membrane 4 to the sensor chip 3 is achieved in that the sensor membrane 4 is preferably made of silicon oxide. Compared to the sensor chip 3, which is preferably made of silicon, silicon oxide has a lower thermal conductivity. In order to prevent the ingress of air moisture or condensed water from the air flowing over the hot film air mass sensor 1, the upper side 18 of the sensor membrane 4 is provided with a silicon nitride coating, which at the same time improves the mechanical stability of the membrane surface.
  • FIG. 2 shows a sensor chip designed according to the invention.
  • the sensor chip 3 designed according to the invention comprises a sensor membrane 4 which rests on a frame structure 22.
  • the support structure 22 has a height h which is lower than the thickness d of the sensor chip 3. In this way, the support structure 22 is enclosed on the top 18 of the sensor chip 3 by the sensor membrane 4 and on all other sides by the material of the sensor chip 3 , The fact that the support structure 22 on all Pages is completed, it is ensured that no air can flow under the sensor membrane 4.
  • the support structure 22 is designed such that the porosity of the support structure 22 decreases with increasing distance from the sensor membrane 4. Directly under the sensor membrane 4, the smta structure 22 has a high porosity in order to improve the thermal decoupling of the sensor membrane 4 from the sensor chip 3.
  • the highly porous layer is made so thick that a sufficient insulation effect is being built up overall. As the thickness of the structure 22 increases, the porosity is reduced with increasing distance from the sensor membrane 4. This ensures that the heat stored via the support structure 22 can be better released to the sensor chip 3.
  • the dynamic behavior of the sensor can already be influenced during the manufacture of the sensor chip 3.
  • two heating elements 11.1, 11.2 are arranged on the sensor membrane 4 and a first temperature sensor 12 in the flow direction 15 in front of each heating element 11.1, 11.2 and a second temperature sensor 13 behind each heating element 11.1, 11.2.
  • the direction of flow of the sensor chip 3 is identified by the arrow identified by reference numeral 15.
  • further temperature sensors 23 are arranged on the sensor chip 3 in the embodiment variant shown in FIG.
  • the heating element 11.1, 11.2 can also be formed around a temperature sensor 12, 13 or a temperature sensor around a heating element 11.1, 11.2.
  • a heating element 11 and two temperature sensors 12, 13 corresponding to the embodiment variant shown in FIG. 1 can also be arranged in the sensor membrane 4, which is supported by the structure 22. Furthermore, any other combination of heating elements 11, 11.1, 11.2 and temperature sensors 12, 13 is possible, with which the air mass flow can be determined via the heat flow emitted by heating element 11, 11.1, 11.2 and the temperature difference at temperature sensors 12, 13.
  • the heating elements 11, 11.1, 11.2 and temperature sensors 12, 13, 23, like the conductor tracks used for the voltage supply and for the transmission of the electrical signals on the sensor chip 3, are preferably made of platinum.
  • Resistance thermometers made of platinum, for example PT 100, are used in particular as temperature sensors 12, 13, 23. puts. In addition to temperature sensors as resistance thermometers, thermocouples are also suitable.
  • FIG. 3 shows a section of a hot film air mass sensor with thermopiles in a perspective view.
  • thermopile 25 a heating element 11 and a second thermopile 26 are arranged on the upper side 18 of the sensor chip 3 in the direction of flow 15. The voltage supply of the heating element 11 and the data transmission of the thermopiles 25, 26 takes place via electrical contacts 27.
  • the porous seat structure 22 below the sensor membrane 4 is preferably produced by an etching process.
  • a base wafer which is preferably made of silicon
  • the mask is interrupted where the structure 4 is to be created.
  • porous silicon is produced at the point where the mask is interrupted.
  • the thermal conductivity is set via the current strength during the anodization, the hydrogen fluoride concentration, the substrate doping or the etching duration or pause duration between two etching processes.
  • the mask made of silicon nitride is removed.
  • the porous silicon is oxidized. The pores are closed by a silicon nitride coating. Finally there is a coating with platinum and a silicon oxide top layer.
  • the gradient of the porosity can be adjusted by adapting the current density with increasing etching depth.
  • the support structure 4 can also be formed as a column or web structure made of silicon oxide.
  • appropriate structures are first created in the silicon wafer by plasma etching, the structures are oxidized and then sealed with silicon oxide. Finally, there is also a coating with platinum and silicon oxide.
  • a silicon nitride cover layer can be applied both to the sensor chip 3 with the support structure 4 made of porous silicon oxide and to the sensor chip 3 with the column or web structure.
  • a gradient can be generated in the support structure 4 by increasing the material density.

Landscapes

  • Physics & Mathematics (AREA)
  • Fluid Mechanics (AREA)
  • General Physics & Mathematics (AREA)
  • Measuring Volume Flow (AREA)
  • Investigating Or Analyzing Materials Using Thermal Means (AREA)

Abstract

L'invention concerne un capteur de masse d'air à pellicule chaude comprenant une puce de détection (3) pourvue d'une membrane de détection (4). Selon l'invention, au moins un élément chauffant (6) et deux capteurs de température (7) sont disposés sur la membrane de détection (4). Une structure de support poreuse (11) est logée sous la membrane de détection (4), la porosité de cette structure de support diminuant à mesure que la distance par rapport à la membrane de détection (4) augmente.
PCT/EP2004/052007 2003-09-22 2004-09-02 Capteur de masse d'air a pellicule chaude presentant une structure de support et un gradient de porosite sous la membrane de detection, et procede de production correspondant Ceased WO2005029007A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE2003143792 DE10343792B4 (de) 2003-09-22 2003-09-22 Heissfilmluftmassensensor mit poröser Stützstruktur und Porositätsgradient unter der Sensormembran sowie Herstellungsverfahren
DE10343792.4 2003-09-22

Publications (1)

Publication Number Publication Date
WO2005029007A1 true WO2005029007A1 (fr) 2005-03-31

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PCT/EP2004/052007 Ceased WO2005029007A1 (fr) 2003-09-22 2004-09-02 Capteur de masse d'air a pellicule chaude presentant une structure de support et un gradient de porosite sous la membrane de detection, et procede de production correspondant

Country Status (2)

Country Link
DE (1) DE10343792B4 (fr)
WO (1) WO2005029007A1 (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2013030198A1 (fr) * 2011-08-31 2013-03-07 Hahn-Schickard-Gesellschaft für angewandte Forschung e.V. Capteur d'écoulement pour déterminer un paramètre d'écoulement et procédé pour déterminer ledit paramètre

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE112017000359B4 (de) 2016-01-13 2024-11-21 Analog Devices International Unlimited Company Luftdurchflusssensor für lüftergekühlte Systeme

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2002042723A1 (fr) * 2000-11-23 2002-05-30 Robert Bosch Gmbh Capteur d'ecoulement
WO2002081363A2 (fr) * 2001-04-07 2002-10-17 Robert Bosch Gmbh Procede pour produire un composant a semi-conducteur et composant a semi-conducteur obtenu selon le procede

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE10046622B4 (de) * 2000-09-20 2010-05-20 Robert Bosch Gmbh Verfahren zur Herstellung einer Membransensoreinheit sowie Membransensoreinheit

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2002042723A1 (fr) * 2000-11-23 2002-05-30 Robert Bosch Gmbh Capteur d'ecoulement
WO2002081363A2 (fr) * 2001-04-07 2002-10-17 Robert Bosch Gmbh Procede pour produire un composant a semi-conducteur et composant a semi-conducteur obtenu selon le procede

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2013030198A1 (fr) * 2011-08-31 2013-03-07 Hahn-Schickard-Gesellschaft für angewandte Forschung e.V. Capteur d'écoulement pour déterminer un paramètre d'écoulement et procédé pour déterminer ledit paramètre
EP2869039A1 (fr) * 2011-08-31 2015-05-06 Hahn-Schickard-Gesellschaft für angewandte Forschung e.V. Capteur de flux destiné à la détermination d'un paramètre d'écoulement et son procédé de détermination
EP2869041A1 (fr) * 2011-08-31 2015-05-06 Hahn-Schickard-Gesellschaft für angewandte Forschung e.V. Capteur de flux destiné à la détermination d'un paramètre d'écoulement et son procédé de détermination
EP2869040A1 (fr) * 2011-08-31 2015-05-06 Hahn-Schickard-Gesellschaft für angewandte Forschung e.V. Capteur de flux destiné à la détermination d'un paramètre d'écoulement et son procédé de détermination

Also Published As

Publication number Publication date
DE10343792B4 (de) 2014-12-18
DE10343792A1 (de) 2005-04-14

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