WO2002048702A2 - Material sensor with protective layer - Google Patents

Material sensor with protective layer Download PDF

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Publication number
WO2002048702A2
WO2002048702A2 PCT/IB2001/002393 IB0102393W WO0248702A2 WO 2002048702 A2 WO2002048702 A2 WO 2002048702A2 IB 0102393 W IB0102393 W IB 0102393W WO 0248702 A2 WO0248702 A2 WO 0248702A2
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Prior art keywords
protective layer
layer
sensor according
measuring
sensor
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PCT/IB2001/002393
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German (de)
French (fr)
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WO2002048702A3 (en
Inventor
Felix Mayer
Mark Hornung
René Hummel
Original Assignee
Sensirion Ag
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Application filed by Sensirion Ag filed Critical Sensirion Ag
Priority to AU2002220975A priority Critical patent/AU2002220975A1/en
Publication of WO2002048702A2 publication Critical patent/WO2002048702A2/en
Publication of WO2002048702A3 publication Critical patent/WO2002048702A3/en

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
    • G01N27/02—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance
    • G01N27/22—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating capacitance
    • G01N27/223—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating capacitance for determining moisture content, e.g. humidity
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
    • G01N27/02—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance
    • G01N27/04—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance
    • G01N27/12—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance of a solid body in dependence upon absorption of a fluid; of a solid body in dependence upon reaction with a fluid, for detecting components in the fluid
    • G01N27/121—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance of a solid body in dependence upon absorption of a fluid; of a solid body in dependence upon reaction with a fluid, for detecting components in the fluid for determining moisture content, e.g. humidity, of the fluid

Definitions

  • the invention relates to a sensor for measuring a concentration of a substance in a gas or a liquid according to the preamble of claim 1.
  • the task is therefore to better isolate a sensor of the type mentioned at the outset from external influences, but its sensitivity should not be impaired. This task is claimed by the sensor
  • a protective layer is therefore arranged above, in particular directly on, the measuring layer, which consists partly or entirely of a polymer permeable to the substance to be measured. It has been shown that such a coating can increase the life of the sensor in a corrosive environment.
  • interdigital electrodes are provided which are arranged on the semiconductor substrate and over which the measuring layer lies.
  • the electrodes are already protected by the measuring layer, it surprisingly shows that the protective layer achieves an advantageous effect in that the protective layer also develops a protective effect for the measuring layer.
  • Polyorganosiloxanes have proven to be a particularly advantageous polymer material since they have a relatively good permeability, in particular for smaller molecules, especially for water.
  • polyorganosiloxanes have a tendency to form chemical bonds with the surface of the measuring layer or other parts of the sensor, which leads to passivation and stabilization of the sensor.
  • Fig. 1 shows a section through a preferred embodiment of the sensor according to the invention
  • Fig. 2 shows a section through the embodiment of FIG. 1 on a circuit board.
  • FIG. 1 A preferred embodiment of the sensor according to the invention is shown in FIG. 1. It has a semiconductor substrate 1 as a substrate, on which an electrode arrangement comprising two interdigital electrodes 2, 3 is integrated in a known manner.
  • a measuring layer 4 which in the present embodiment consists of a polymer or a ceramic, lies on the electrode arrangement.
  • a measuring circuit is also integrated on the semiconductor substrate 1, with which the capacitance between the interdigital electrodes 2, 3 can be measured.
  • the measuring layer 4 is designed such that it absorbs moisture from the environment. Their dielectric constant, and thus the capacitance between the interdigital electrodes 2, 3, is therefore dependent on the ambient humidity. The moisture in the environment can thus be measured by the capacitance measurement.
  • the measuring layer 4 is not in direct contact with the surroundings, but is completely covered with a protective layer 5.
  • This protective layer serves to protect the sensor. It is described in more detail below.
  • the protective layer consists at least partially, preferably completely, of a polyorganosiloxane, ie a silicone, such as that available under the registered trademark Elastosil from the company Wacker Chemie GmbH, Germany.
  • Elastosil E50 is particularly suitable.
  • a typical thickness of the protective layer 5 is 1-2 mm. Protection can improve with increasing thickness, but an excessively high thickness affects the response time of the sensor. However, protective effects can already be observed with relatively small layer thicknesses, which is attributed to the fact that the polyorganosiloxane enters into chemical connections with the sensor and thereby passivates it.
  • a preferred thickness range for the protective layer 5 is 50 ⁇ m to 2 mm.
  • polyorganosiloxanes in the protective layer 5 has the advantage in a moist environment, and in particular in a moisture sensor, that only a little water is stored in the layer due to the hydrophobic properties of this material. Nevertheless, the layer is permeable to water molecules.
  • Particularly suitable materials are:
  • Polysilicones such as polyphenylmethylsiloxane from Supelco, Silicone OV-17, Eccocoat S7003 from Emerson & Cuming,
  • polyurethanes such as polyether urethane PEUT from Supelco,
  • - polyimide such as Bectron from BASF
  • - cellulose derivatives such as ethyl cellulose from BASF
  • PET polyethylene terephthalate
  • Polysulfone such as UDEL from Amoco Chemicals, acrylic-based polymers such as polyethyl methacrylate PMMA, from Aldrich No. 18.223-0 [9011-14-7],
  • Epoxides such as araldite, Polyglycol like PEG from Aldrich no. 20,244-4 [25322-68-3],
  • the protective layer 5 is applied after the actual sensor has been completed and the measuring layer 4 has been applied. Suitable methods are spraying, “spinning”, dip coating of a solution, for example of monomers with subsequent polymerization.
  • the layers can also be brushed on, or one can Polymerization takes place from the gas phase, and further processes are coatings in wave or river baths.
  • the interdigital electrodes 2, 3 are arranged on the lower side of the measuring layer 4 and the protective layer 5 on the upper side.
  • the protective layer 5 is in contact with the measuring layer and passivates its surface.
  • the extension of the protective layer 5 should be at least large enough to cover the active area of the measuring layer 4, but is preferably larger, so that it also covers and passivates regions of the semiconductor substrate 1 adjacent to the measuring layer 4. It is also conceivable to cover the entire semiconductor substrate, as shown in FIG. 2.
  • the substrate 1 was placed on a base 8, e.g. a printed circuit board, the electrical contact between the base 8 and the semiconductor substrate 1 being ensured by means of bonding wires 9.
  • the bonding wires 9 and a part of the semiconductor substrate 1 are covered by a protective compound 10, which, however, leaves the part of the substrate covered by the measuring layer 4 free.
  • the measuring layer 4 and the other parts of the semiconductor substrate 1 are covered with the protective layer 5.
  • the protective layer not only protects the actual area of the Measuring layer 4, but also other parts of the semiconductor substrate that would otherwise be delivered unprotected from the environmental influences or that would have to be protected with complex measures.
  • the protective layer 5 also extends over parts of the base 8 adjacent to the semiconductor substrate 1, so that the side edges of the semiconductor substrate are also protected.
  • the protective layer 5 lies directly on the measuring layer 4.
  • the electrode arrangement consists of two electrodes arranged on the opposite surfaces of the measuring layer 4, the upper electrode coming between the measuring layer 4 and the protective layer 5.
  • 1 is a moisture sensor.
  • the same technology can also be used to manufacture a sensor for measuring the concentration of other substances in gas or liquid, e.g. a sensor for volatile hydrocarbons, as described in H. Baltes, D. Lange and A. Koll in "The electronic nose in lilliput", IEEE Spectrum 35, no. 9 (1998).
  • a suitable measuring layer must be arranged on or in the substrate, the properties of which (e.g. dielectric constant or conductivity) depend on the concentration to be measured. Appropriate techniques are known to the person skilled in the art.
  • the protective layer increases the service life and accuracy of the sensor, and the medium to be measured is better shielded from the sensor.
  • a protective layer 11 is arranged between the interdigital electrodes 2, 3 and the measuring layer 4. This consists of a gas-tight, non-oxidizing material. It can be seen that the arrangement of such a layer improves the service life and reliability of the sensor.
  • the protective layer 11 can be at least partially made of a suitable metal, in particular a noble metal, such as gold. However, it can also have a non-oxidizing dielectric or consist of a non-oxidizing dielectric. Preferred non-oxidizing dielectrics are silicon nitride and silicon oxide. If the protective layer is not conductive, it can extend over all interdigital electrodes 2, 3 at the same time, otherwise, as shown in FIG. 1, it is arranged individually over each interdigital electrode. While preferred embodiments of the invention are described in the present application, it should be clearly pointed out that the invention is not limited to these and can also be carried out in other ways within the scope of the following claims.

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  • Chemical & Material Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Electrochemistry (AREA)
  • Physics & Mathematics (AREA)
  • Health & Medical Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Biochemistry (AREA)
  • General Health & Medical Sciences (AREA)
  • General Physics & Mathematics (AREA)
  • Immunology (AREA)
  • Pathology (AREA)
  • Investigating Or Analyzing Materials By The Use Of Fluid Adsorption Or Reactions (AREA)
  • Investigating Or Analyzing Materials By The Use Of Electric Means (AREA)

Abstract

A sensor for measuring the concentration of a material in a gas or a fluid, in particular a humidity sensor, is arranged on a semiconductor substrate (1). A measuring layer (4) is arranged on the substrate (1) the properties of which are dependant upon the concentration to be measured. A protective layer (5) is arranged over the measuring layer, which at least partially comprises a polymer, permeable to the material to be measured, preferably a polyorganosiloxane. An improvement in working life, in particular in corrosive environments may be achieved by means of the protective layer.

Description

Stoffsensor mit Schutzschicht Fabric sensor with protective layer
Hinweis auf verwandte AnmeldungenReference to related applications
Diese Anmeldung beansprucht die Priorität der Schweizer Patentanmeldung 2454/00, die am 15. Dezember 2000 eingereicht wurde und deren ganze Offenbarung hiermit durch Bezug aufgenommen wird.This application claims priority from Swiss Patent Application 2454/00, which was filed on December 15, 2000, the entire disclosure of which is hereby incorporated by reference.
Technisches GebietTechnical field
Die Erfindung betrifft einen Sensor zum Messen einer Konzentration eines Stoffes in einem Gas oder einer Flüssigkeit gemäss Oberbegriff von Anspruch 1.The invention relates to a sensor for measuring a concentration of a substance in a gas or a liquid according to the preamble of claim 1.
Hintergrundbackground
Sensoren dieser Art sind z.B. zur Messung von Feuchte oder organischen Verbindungen bekannt. So wird in US 4 429 343 ein Feuchtesensor beschrieben, welcher eine Messschicht aus einem Polymer- aufweist . Diese Messschicht ist auf einem Halbleitersubstrat mit Elektrodenanordnung angeordnet. Die Dielektrizitätskonstante der Messschicht und somit die Kapazität der Elektrodenanordnung ändert sich in Abhängigkeit des Wassergehalts der Messschicht. H. Baltes, D. Lange und A. Koll beschrieben in „The elec- tronic nose in lilliput", IEEE Spectrum 35, no. 9 (1998), Seiten 35 - 38 einen Detektor für flüchtige Kohlenwasser- Stoffe. Auch hier ist eine Messschicht aus einem geeigneten Polymer vorgesehen, deren Eigenschaften von der zu messenden Konzentration abhängen.Sensors of this type are e.g. known for measuring moisture or organic compounds. US Pat. No. 4,429,343 describes a moisture sensor which has a measuring layer made of a polymer. This measuring layer is arranged on a semiconductor substrate with an electrode arrangement. The dielectric constant of the measuring layer and thus the capacitance of the electrode arrangement changes depending on the water content of the measuring layer. H. Baltes, D. Lange and A. Koll described in "The electronic nose in lilliput", IEEE Spectrum 35, no. 9 (1998), pages 35-38, a detector for volatile hydrocarbons Measuring layer made of a suitable polymer is provided, the properties of which depend on the concentration to be measured.
Werden derartige Sensoren einer korrosiven Umgebung ausgesetzt, so kann es zu Veränderungen kommen, die deren Funktionalität beeinträchtigen. Andererseits besteht bei verschiedenen Anwendungen, z.B. im Medizinalbereich, der Wunsch, das zu messende Medium möglichst gut vo Sensor abzuschirmen, so dass eine Kontamination des Mediums vermieden wird.If such sensors are exposed to a corrosive environment, changes can occur that impair their functionality. On the other hand, in various applications, for example in the medical field, there is a desire to have the medium to be measured as good as possible shield the sensor so that contamination of the medium is avoided.
Darstellung der ErfindungPresentation of the invention
Es stellt sich deshalb die Aufgabe, einen Sensor der eingangs genannten Art besser von äusseren Einflüssen zu isolieren, jedoch soll seine Empfindlichkeit nicht beeinträchtigt werden. Diese Aufgabe wird vom Sensor ge äss AnspruchThe task is therefore to better isolate a sensor of the type mentioned at the outset from external influences, but its sensitivity should not be impaired. This task is claimed by the sensor
1 erfüllt.1 fulfilled.
Erfindungsgemäss ist also über, insbesondere direkt auf, der Messschicht eine Schutzschicht angeordnet, die teilweise oder ganz aus einem für den zu messen- den Stoff permeablen Polymer besteht. Es zeigt sich, dass durch eine derartige Beschichtung die Lebensdauer des Sensors in korrosiver Umgebung erhöht werden kann.According to the invention, a protective layer is therefore arranged above, in particular directly on, the measuring layer, which consists partly or entirely of a polymer permeable to the substance to be measured. It has been shown that such a coating can increase the life of the sensor in a corrosive environment.
In einer bevorzugten Ausführung sind Interdi- gitalelektroden vorgesehen, die auf dem Halbleitersub- strat angeordnet sind und über denen die Messschicht liegt. Obwohl die Elektroden schon durch die Messschicht geschützt sind, zeigt es sich überraschenderweise, dass durch die Schutzschicht ein vorteilhafter Effekt erreicht wird, indem die Schutzschicht auch eine Schutzwirkung für die Messschicht entwickelt.In a preferred embodiment, interdigital electrodes are provided which are arranged on the semiconductor substrate and over which the measuring layer lies. Although the electrodes are already protected by the measuring layer, it surprisingly shows that the protective layer achieves an advantageous effect in that the protective layer also develops a protective effect for the measuring layer.
Als besonders vorteilhaftes Polymermaterial haben sich Polyorganosiloxane (Silikone) herausgestellt, da diese insbesondere für kleinere Moleküle, vor allem für Wasser, eine relativ gute Permeabilität aufweisen. Ausserdem haben Polyorganosiloxane die Tendenz, mit der Oberfläche der Messschicht oder anderen Teilen des Sensors chemische Bindungen einzugehen, was zu einer Passi- vierung und Stabilisierung des Sensors führt.Polyorganosiloxanes (silicones) have proven to be a particularly advantageous polymer material since they have a relatively good permeability, in particular for smaller molecules, especially for water. In addition, polyorganosiloxanes have a tendency to form chemical bonds with the surface of the measuring layer or other parts of the sensor, which leads to passivation and stabilization of the sensor.
Kurze Beschreibung der Zeichnungen Weitere Vorteile und Anwendungen der Erfindung ergeben sich aus der nun folgenden Beschreibung anhand der Figuren. Dabei zeigen:Brief description of the drawings Further advantages and applications of the invention emerge from the following description with reference to the figures. Show:
Fig. 1 einen Schnitt durch eine bevorzugte Ausführung des erfindungsgemässen Sensors undFig. 1 shows a section through a preferred embodiment of the sensor according to the invention and
Fig. 2 einen Schnitt durch die Ausführung nach Fig. 1 auf einer Leiterplatte.Fig. 2 shows a section through the embodiment of FIG. 1 on a circuit board.
Wege zur Ausführung der ErfindungWays of Carrying Out the Invention
Eine bevorzugte Ausführung des erfindungsgemässen Sensors ist in Fig. 1 dargestellt. Er besitzt ein Halbleitersubstrat 1 als Substrat, auf dem in bekannter Weise eine Elektrodenanordnung aus zwei Interdigitalelek- troden 2, 3 integriert ist. Auf der Elektrodenanordnung liegt eine Messschicht 4, welche in der vorliegenden Ausführung aus einem Polymer oder einer Keramik besteht. Auf dem Halbleitersubstrat 1 ist ferner eine Messschaltung integriert, mit der die Kapazität zwischen den Interdigi- talelektroden 2, 3 gemessen werden kann.A preferred embodiment of the sensor according to the invention is shown in FIG. 1. It has a semiconductor substrate 1 as a substrate, on which an electrode arrangement comprising two interdigital electrodes 2, 3 is integrated in a known manner. A measuring layer 4, which in the present embodiment consists of a polymer or a ceramic, lies on the electrode arrangement. A measuring circuit is also integrated on the semiconductor substrate 1, with which the capacitance between the interdigital electrodes 2, 3 can be measured.
Die Messschicht 4 ist so ausgestaltet, dass sie Feuchtigkeit aus der Umgebung aufnimmt. Ihre Dielek- trizitätskonstante, und somit die Kapazität zwischen den Interdigitalelektroden 2, 3, ist deshalb abhängig von der Umgebungsfeuchte. Durch die Kapazitätsmessung kann also die Feuchte der Umgebung gemessen werden.The measuring layer 4 is designed such that it absorbs moisture from the environment. Their dielectric constant, and thus the capacitance between the interdigital electrodes 2, 3, is therefore dependent on the ambient humidity. The moisture in the environment can thus be measured by the capacitance measurement.
Im Sensor gemäss Fig. 1 steht die Messschicht 4 nicht direkt mit der Umgebung in Kontakt, sondern sie ist vollständig mit einer Schutzschicht 5 bedeckt. Diese Schutzschicht dient dem Schutz des Sensors. Sie wird im Folgenden genauer beschrieben.In the sensor according to FIG. 1, the measuring layer 4 is not in direct contact with the surroundings, but is completely covered with a protective layer 5. This protective layer serves to protect the sensor. It is described in more detail below.
In einer bevorzugten Ausführung besteht die Schutzschicht mindestens teilweise, vorzugsweise vollständig aus einem Polyorganosiloxan, d.h. einem Silikon, wie es z.B. unter dem eingetragenen Markennamen Elastosil der Firma Wacker Chemie GmbH, Deutschland vertrieben wird. Besonders geeignet ist Elastosil E50.In a preferred embodiment, the protective layer consists at least partially, preferably completely, of a polyorganosiloxane, ie a silicone, such as that available under the registered trademark Elastosil from the company Wacker Chemie GmbH, Germany. Elastosil E50 is particularly suitable.
Eine typische Dicke der Schutzschicht 5 beträgt 1 - 2 mm. Mit zunehmender Dicke kann sich der Schutz verbessern, wobei jedoch eine übermässig hohe Dik- ke die Reaktionszeit des Sensor beeinträchtigt. Schutzeffekte lassen sich jedoch bereits bei relativ geringen Schichtdicken beobachten, was darauf zurückgeführt wird, dass das Polyorganosiloxan chemische Verbindungen mit dem Sensor eingeht und diesen dadurch passiviert. Ein bevorzugter Dickenbereich für die Schutzschicht 5 ist 50 μm bis 2 mm.A typical thickness of the protective layer 5 is 1-2 mm. Protection can improve with increasing thickness, but an excessively high thickness affects the response time of the sensor. However, protective effects can already be observed with relatively small layer thicknesses, which is attributed to the fact that the polyorganosiloxane enters into chemical connections with the sensor and thereby passivates it. A preferred thickness range for the protective layer 5 is 50 μm to 2 mm.
Die Verwendung von Polyorganosiloxanen in der Schutzschicht 5 hat bei feuchter Umgebung, und insbeson- dere bei Feuchtesensoren, den Vorteil, dass aufgrund der hydrophoben Eigenschaften dieses Materials nur wenig Wasser in der Schicht gespeichert wird. Dennoch ist die Schicht durchlässig für Wassermoleküle.The use of polyorganosiloxanes in the protective layer 5 has the advantage in a moist environment, and in particular in a moisture sensor, that only a little water is stored in the layer due to the hydrophobic properties of this material. Nevertheless, the layer is permeable to water molecules.
Es können jedoch auch andere Polymermateria- lien verwendet werden, insbesondere Elastomere. Diese haben eine besonders hohe Gaspermeation (z.B. für H2O, CO2 , O2 oder N2) •However, other polymer materials can also be used, in particular elastomers. These have a particularly high gas permeation (e.g. for H2O, CO2, O2 or N2) •
Besonders geeignete Materializen sind:Particularly suitable materials are:
- Polysilikone (Silikonkautschuk) wie Poly- phenylmethylsiloxan von Supelco, Silicone OV-17, Eccocoat S7003 von Emerson & Cuming,Polysilicones (silicone rubber) such as polyphenylmethylsiloxane from Supelco, Silicone OV-17, Eccocoat S7003 from Emerson & Cuming,
- Polyurethane wie Polyetherurethan PEUT von Supelco,- polyurethanes such as polyether urethane PEUT from Supelco,
- Polyimid wie Bectron von BASF, - Zellulose-Derivate wie Ethylcellulose von- polyimide such as Bectron from BASF, - cellulose derivatives such as ethyl cellulose from
Aldrich Nr. 24, 749-3 [9004-57-3],Aldrich No. 24, 749-3 [9004-57-3],
- Polyethylenterephtalat (PET) ,- polyethylene terephthalate (PET),
- Polysulfon (PSF) wie UDEL von Amoco Chemicals, - Acrylbasierte Polymere wie Poly ethyl- methacrylat PMMA, von Aldrich Nr. 18,223-0 [9011-14-7],Polysulfone (PSF) such as UDEL from Amoco Chemicals, acrylic-based polymers such as polyethyl methacrylate PMMA, from Aldrich No. 18.223-0 [9011-14-7],
- Epoxide wie Araldit, - Polyethylglykol wie PEG von Aldrich Nr. 20,244-4 [25322-68-3],Epoxides such as araldite, Polyglycol like PEG from Aldrich no. 20,244-4 [25322-68-3],
- Polyvynilpyrrolidon wie Povidone PVP von Aldrich Nr. 23,425-7 [9003-38-8], - Parylen- polyvinyl pyrrolidone such as Povidone PVP from Aldrich No. 23,425-7 [9003-38-8], - parylene
Die Aufbringung der Schutzschicht 5 erfolgt nach Fertigstellung des eigentlichen Sensors und Aufbringen der Messschicht 4. Geeignete Verfahren sind Sprühen, „Spinning", TauchbeSchichtung einer Lösung, z.B. von Mo- nomeren mit anschliessender Polymerisation. Die Schichten können auch aufgepinselt werden, oder es kann eine Polymerisation aus der Gasphase erfolgen. Weitere Verfahren sind Beschichtungen im Wellen- oder Flussbad.The protective layer 5 is applied after the actual sensor has been completed and the measuring layer 4 has been applied. Suitable methods are spraying, “spinning”, dip coating of a solution, for example of monomers with subsequent polymerization. The layers can also be brushed on, or one can Polymerization takes place from the gas phase, and further processes are coatings in wave or river baths.
Bei der Anordnung nach Fig. 1 sind auf der unteren Seite der Messschicht 4 die Interdigitalelektro- den 2 , 3 und auf der oberen Seite die Schutzschicht 5 angeordnet . In diesem Falle steht die Schutzschicht 5 in Kontakt mit der Messschicht und passiviert deren Oberfläche. Die Ausdehnung der Schutzschicht 5 sollte mindestens so gross sein, dass sie die aktive Fläche der Messschicht 4 überdeckt, vorzugsweise ist sie jedoch grö- sser, so dass sie auch an die Messschicht 4 angrenzende Bereiche des Halbleitersubstrats 1 abdeckt und passi- viert. Es ist auch denkbar, das ganze Halbleitersubstrat abzudecken, wie dies in Fig. 2 dargestellt ist. Hier wurde das Substrat 1 auf einer Unterlage 8, z.B. einer Leiterplatte, angeordnet, wobei der elektrische Kontakt zwischen Unterlage 8 und Halbleitersubstrat 1 über Bonding- Drähte 9 gewährleistet ist. Die Bonding-Drähte 9 und ein Teil des Halbleitersubstrats 1 sind von einer Schutzmasse 10 bedeckt, die jedoch den mit der Messschicht 4 bedeckten Teil des Substrats freilässt. Die Messschicht 4, sowie die übrigen Teile des Halbleitersubstrats 1 sind mit der Schutzschicht 5 bedeckt.1, the interdigital electrodes 2, 3 are arranged on the lower side of the measuring layer 4 and the protective layer 5 on the upper side. In this case, the protective layer 5 is in contact with the measuring layer and passivates its surface. The extension of the protective layer 5 should be at least large enough to cover the active area of the measuring layer 4, but is preferably larger, so that it also covers and passivates regions of the semiconductor substrate 1 adjacent to the measuring layer 4. It is also conceivable to cover the entire semiconductor substrate, as shown in FIG. 2. Here the substrate 1 was placed on a base 8, e.g. a printed circuit board, the electrical contact between the base 8 and the semiconductor substrate 1 being ensured by means of bonding wires 9. The bonding wires 9 and a part of the semiconductor substrate 1 are covered by a protective compound 10, which, however, leaves the part of the substrate covered by the measuring layer 4 free. The measuring layer 4 and the other parts of the semiconductor substrate 1 are covered with the protective layer 5.
In der Ausführung nach Fig. 2 schützt die Schutzschicht nicht nur den eigentlichen Bereich der Messschicht 4, sondern auch noch weitere Teile des Halbleitersubstrats, die ansonsten ungeschützt den Umgebungseinflüssen ausgeliefert wären oder mit aufwendigen Mass- nahmen geschützt werden müssten. Die Schutzschicht 5 er- streckt sich auch über an das Halbleitersubstrat 1 angrenzende Teile der Unterlage 8, so dass die Seitenkanten des Halbleitersubstrats ebenfalls geschützt sind.In the embodiment according to FIG. 2, the protective layer not only protects the actual area of the Measuring layer 4, but also other parts of the semiconductor substrate that would otherwise be delivered unprotected from the environmental influences or that would have to be protected with complex measures. The protective layer 5 also extends over parts of the base 8 adjacent to the semiconductor substrate 1, so that the side edges of the semiconductor substrate are also protected.
In der Ausführung nach Fig. 1 liegt die Schutzschicht 5 direkt auf der Messschicht 4 auf. Es ist jedoch z.B. auch denkbar, dass die Elektrodenanordnung aus zwei, an den gegenüberliegenden Oberflächen der Messschicht 4 angeordneten Elektroden besteht, wobei die obere Elektrode zwischen die Messschicht 4 und die Schutzschicht 5 zu liegen kommt. Der Sensor gemäss Fig. 1 ist ein Feuchtesensor. Mit gleicher Technologie kann jedoch auch ein Sensor zur Messung der Konzentration anderer Stoffe in Gas oder Flüssigkeit hergestellt werden, z.B. ein Sensor für flüchtige Kohlenwasserstoffe, wie beschrieben in H. Bal- tes, D. Lange und A. Koll beschreiben in „The electronic nose in lilliput", IEEE Spectrum 35, no. 9 (1998) .In the embodiment according to FIG. 1, the protective layer 5 lies directly on the measuring layer 4. However, it is e.g. it is also conceivable that the electrode arrangement consists of two electrodes arranged on the opposite surfaces of the measuring layer 4, the upper electrode coming between the measuring layer 4 and the protective layer 5. 1 is a moisture sensor. However, the same technology can also be used to manufacture a sensor for measuring the concentration of other substances in gas or liquid, e.g. a sensor for volatile hydrocarbons, as described in H. Baltes, D. Lange and A. Koll in "The electronic nose in lilliput", IEEE Spectrum 35, no. 9 (1998).
Je nach zu messendem Stoff ist eine geeignete Messschicht auf bzw. im Substrat anzuordnen, deren Eigenschaften (z.B. dielektrische Konstante oder Leitfähig- keit) von der zu messenden Konzentration abhängen. Entsprechende Techniken sind dem Fachmann bekannt . Durch die Schutzschicht wir die Lebensdauer und Genauigkeit des Sensor erhöht, und das zu messende Medium wird besser vom Sensor abgeschirmt . In der Ausführung nach Fig. 1 ist zwischen den Interdigitalelektroden 2, 3 und der Messschicht 4 eine Schutzschicht 11 angeordnet. Diese besteht aus einem gasdichten, nicht-oxidierenden Material. Es zeigt sich, dass die Anordnung einer solchen Schicht die Lebensdauer und Zuverlässigkeit des Sensors verbessert.Depending on the substance to be measured, a suitable measuring layer must be arranged on or in the substrate, the properties of which (e.g. dielectric constant or conductivity) depend on the concentration to be measured. Appropriate techniques are known to the person skilled in the art. The protective layer increases the service life and accuracy of the sensor, and the medium to be measured is better shielded from the sensor. In the embodiment according to FIG. 1, a protective layer 11 is arranged between the interdigital electrodes 2, 3 and the measuring layer 4. This consists of a gas-tight, non-oxidizing material. It can be seen that the arrangement of such a layer improves the service life and reliability of the sensor.
Die Schutzschicht 11 kann mindestens teilweise aus einem geeigneten Metall, insbesondere einem Edel- metall, wie z.B. Gold, bestehen. Sie kann jedoch auch ein nicht-oxidierendes Dielektrikum aufweisen oder aus einem nicht-oxidierenden Dielektrikum bestehen. Bevorzugte nicht-oxidierende Dielektrika sind Siliziumnitrid und Si- liziumoxid. Falls die Schutzschicht nicht leitend ist, kann sie sich über alle Interdigitalelektroden 2, 3 gleichzeitig erstrecken, ansonsten wird sie, wie in Fig. 1 dargestellt, über jeder Interdigitaleketrode einzeln angeordnet . Während in der vorliegenden Anmeldung bevorzugte Ausführungen der Erfindung beschrieben sind, ist klar darauf hinzuweisen, dass die Erfindung nicht auf diese beschränkt ist und in auch anderer Weise innerhalb des Umfangs der folgenden Ansprüche ausgeführt werden kann . The protective layer 11 can be at least partially made of a suitable metal, in particular a noble metal, such as gold. However, it can also have a non-oxidizing dielectric or consist of a non-oxidizing dielectric. Preferred non-oxidizing dielectrics are silicon nitride and silicon oxide. If the protective layer is not conductive, it can extend over all interdigital electrodes 2, 3 at the same time, otherwise, as shown in FIG. 1, it is arranged individually over each interdigital electrode. While preferred embodiments of the invention are described in the present application, it should be clearly pointed out that the invention is not limited to these and can also be carried out in other ways within the scope of the following claims.

Claims

Patentansprüche claims
1. Sensor zum Messen einer Konzentration eines Stoffes in einem Gas oder einer Flüssigkeit, insbe- sondere Feuchtesensor, mit einem Halbleitersubstrat (1) und einer auf oder im Halbleitersubstrat (1) angeordneten Messschicht (4) , deren Eigenschaften von der zu messenden Konzentration abhängen, dadurch gekennzeichnet, dass über der Messschicht (4) eine Schutzschicht (5) angeordnet ist, wobei die Schutzschicht (5) ein für den Stoff permeables Polymer aufweist oder daraus besteht.1. Sensor for measuring a concentration of a substance in a gas or a liquid, in particular moisture sensor, with a semiconductor substrate (1) and a measuring layer (4) arranged on or in the semiconductor substrate (1), the properties of which depend on the concentration to be measured , characterized in that a protective layer (5) is arranged above the measuring layer (4), the protective layer (5) having or consisting of a polymer permeable to the substance.
2. Sensor nach Anspruch 1, wobei das Polymer ein Polyorganosiloxan aufweist oder daraus besteht.2. Sensor according to claim 1, wherein the polymer comprises or consists of a polyorganosiloxane.
3. Sensor nach einem der vorangehenden An- Sprüche, dadurch gekennzeichnet, dass das Polymer einen3. Sensor according to one of the preceding claims, characterized in that the polymer is a
Kautschuk aufweist oder daraus besteht, und insbesondere dass das Polymer einen Silikonkautschuk aufweist oder daraus besteht.Has or consists of rubber, and in particular that the polymer has or consists of a silicone rubber.
4. Sensor nach einem der vorangehenden An- Sprüche, wobei das Polymer mindestens einen Stoff ausgewählt aus der Gruppe umfassend Polysilikone, Polyurethane, Polyimid, Zellulose-Derivate, Polyethylenterephtalat, Polysulfon, Acrylbasierte Polymere, Epoxide, Polyethyl- glykol, Polyvynilpyrrolidon und Parylen aufweist oder daraus besteht.4. Sensor according to one of the preceding claims, wherein the polymer has at least one substance selected from the group comprising polysilicones, polyurethanes, polyimide, cellulose derivatives, polyethylene terephthalate, polysulfone, acrylic-based polymers, epoxies, polyethylene glycol, polyvinyl pyrrolidone and parylene or consists of it.
5. Sensor nach einem der vorangehenden Ansprüche, wobei die Schutzschicht (5) direkt auf der Messschicht (4) aufliegt, und insbesondere dass die Schutzschicht (5) chemisch an die Messschicht (4) gebunden ist. 5. Sensor according to one of the preceding claims, wherein the protective layer (5) rests directly on the measuring layer (4), and in particular that the protective layer (5) is chemically bound to the measuring layer (4).
6. Sensor nach einem der vorangehenden Ansprüche, wobei die Schutzschicht (5) eine Dicke von weniger als 2 mm, vorzugsweise im Bereich zwischen 50 μm und 2 mm, aufweist.6. Sensor according to one of the preceding claims, wherein the protective layer (5) has a thickness of less than 2 mm, preferably in the range between 50 microns and 2 mm.
7. Sensor nach einem der vorangehenden An- Sprüche, wobei die dielektrische Konstante oder der elektrische Widerstand der Messschicht (4) von der zu messenden Konzentration abhängt und der Sensor Elektroden zur Messung der dielektrischen Konstante bzw. des elektrischen Widerstands aufweist.7. Sensor according to one of the preceding claims, wherein the dielectric constant or the electrical resistance of the measuring layer (4) depends on the concentration to be measured and the sensor electrodes for Measurement of the dielectric constant or the electrical resistance.
8. Sensor nach Anspruch 7, wobei die Elektroden auf dem Halbleitersubstrat integrierte Interdigitale- lektroden sind und die Messschicht (4) über den Interdi- gitalelektroden angeordnet ist.8. Sensor according to claim 7, wherein the electrodes on the semiconductor substrate are integrated interdigital electrodes and the measuring layer (4) is arranged above the interdigital electrodes.
9. Sensor nach einem der vorangehenden Ansprüche, wobei auf einer ersten Seite der Messschicht (4) Interdigitalelektroden und auf einer zweiten Seite der Messschicht (4) die Schutzschicht (5) angeordnet sind.9. Sensor according to one of the preceding claims, wherein on a first side of the measuring layer (4) interdigital electrodes and on a second side of the measuring layer (4) the protective layer (5) are arranged.
10. Sensor nach Anspruch 9, wobei die Interdigitalelektroden auf dem Halbleitersubstrat (1) integriert sind.10. Sensor according to claim 9, wherein the interdigital electrodes are integrated on the semiconductor substrate (1).
11. Sensor nach einem der Ansprüche 9 oder 10, wobei zwischen den Interdigitalelektroden und der11. Sensor according to one of claims 9 or 10, wherein between the interdigital electrodes and the
Messschicht (4) eine Schutzschicht aus nicht-oxidieren- dem, gasdichten Material, angeordnet ist, und insbesondere dass die Schutzschicht (11) ein metallisches Edelmetall und/oder ein nicht-oxidierendes Dielektrikum auf- weist oder daraus besteht, vorzugsweise Gold, Siliziumoxid und/oder Siliziumnitrid.Measuring layer (4) is a protective layer made of non-oxidizing, gas-tight material, and in particular that the protective layer (11) has or consists of a metallic noble metal and / or a non-oxidizing dielectric, preferably gold, silicon oxide and / or silicon nitride.
12. Sensor nach einem der vorangehenden Ansprüche, wobei die Schutzschicht (5) eine grössere Ausdehnung als die Messschicht (4) besitzt und an die Mess- Schicht (4) angrenzende Bereiche des Halbleitersubstrats (1) abdeckt .12. Sensor according to one of the preceding claims, wherein the protective layer (5) has a greater extent than the measuring layer (4) and covers regions of the semiconductor substrate (1) adjacent to the measuring layer (4).
13. Sensor nach einem der vorangehenden Ansprüche, wobei der Sensor eine Unterlage (8) zur Aufnahme des Halbleitersubstrats (1) aufweist, wobei die Schutz- schicht sich über mindestens einen Teil des Halbleitersubstrats (1) und mindestens einen Teil der Unterlage (8) erstreckt . 13. Sensor according to one of the preceding claims, wherein the sensor has a base (8) for receiving the semiconductor substrate (1), the protective layer covering at least part of the semiconductor substrate (1) and at least part of the base (8) extends.
PCT/IB2001/002393 2000-12-15 2001-12-10 Material sensor with protective layer WO2002048702A2 (en)

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EP2287596A1 (en) * 2009-08-11 2011-02-23 Sensirion AG Sensor with glob-top and method for manufacturing the same
US7923823B2 (en) 2007-01-23 2011-04-12 Infineon Technologies Ag Semiconductor device with parylene coating
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Cited By (7)

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Publication number Priority date Publication date Assignee Title
US7923823B2 (en) 2007-01-23 2011-04-12 Infineon Technologies Ag Semiconductor device with parylene coating
US8110906B2 (en) 2007-01-23 2012-02-07 Infineon Technologies Ag Semiconductor device including isolation layer
WO2010079206A1 (en) * 2009-01-08 2010-07-15 Eads Deutschland Gmbh Accumulating moisture sensor
EP2287596A1 (en) * 2009-08-11 2011-02-23 Sensirion AG Sensor with glob-top and method for manufacturing the same
WO2014146959A1 (en) * 2013-03-18 2014-09-25 Robert Bosch Gmbh Humidity sensor with water-permeable protective layer and method for protecting the sensor using the protective layer
FR3041758A1 (en) * 2015-09-29 2017-03-31 Commissariat Energie Atomique DEVICE AND METHOD FOR QUANTIFYING A GASEOUS ENTITY FLOW WITHIN A POROUS MEDIUM
WO2017055249A1 (en) * 2015-09-29 2017-04-06 Commissariat A L'energie Atomique Et Aux Energies Alternatives Device and method for quantifying a flow of a gaseous entity within a porous medium

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