EP1425573A1 - Detecteur de gaz chrome-titane-oxyde-semi-conducteur et procede permettant de le produire - Google Patents

Detecteur de gaz chrome-titane-oxyde-semi-conducteur et procede permettant de le produire

Info

Publication number
EP1425573A1
EP1425573A1 EP02779286A EP02779286A EP1425573A1 EP 1425573 A1 EP1425573 A1 EP 1425573A1 EP 02779286 A EP02779286 A EP 02779286A EP 02779286 A EP02779286 A EP 02779286A EP 1425573 A1 EP1425573 A1 EP 1425573A1
Authority
EP
European Patent Office
Prior art keywords
metal oxide
oxide semiconductor
layer
gas sensor
semiconductor gas
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.)
Withdrawn
Application number
EP02779286A
Other languages
German (de)
English (en)
Inventor
Harald BÖTTNER
Jürgen WÖLLENSTEIN
Gerd KÜHNER
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.)
Fraunhofer Gesellschaft zur Forderung der Angewandten Forschung eV
Original Assignee
Fraunhofer Gesellschaft zur Forderung der Angewandten Forschung eV
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 Fraunhofer Gesellschaft zur Forderung der Angewandten Forschung eV filed Critical Fraunhofer Gesellschaft zur Forderung der Angewandten Forschung eV
Publication of EP1425573A1 publication Critical patent/EP1425573A1/fr
Withdrawn legal-status Critical Current

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Classifications

    • 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
    • G01N27/125—Composition of the body, e.g. the composition of its sensitive layer

Definitions

  • the invention relates to a metal oxide semiconductor gas sensor which has a chromium-titanium oxide (CTO) layer as the sensor-active metal oxide thin layer and a method for its production.
  • CTO chromium-titanium oxide
  • Metal oxide semiconductor gas sensors are known and are used in many areas for the detection of particles in air.
  • Semiconductor gas sensors generally consist of a sensor-active metal oxide layer which is arranged on a substrate, the sensor-active layer being connected to at least one electrode.
  • the previous sensors are preferably constructed in such a way that contact electrodes are applied directly to an inert carrier.
  • the sensor-active layer is then deposited on the contact electrodes.
  • an integrated heating tongue provided, the z. B. can be arranged on the back of the substrate.
  • a thin Si0 2 layer is provided, which can be applied directly to the substrate.
  • promoters / catalysts are often also used in a targeted manner. Sensors modified in this way are used for a large number of gases.
  • DE 44 24 342 AI describes a sensor array with metal oxide semiconductor gas sensors which are operated as resistance elements, the sensor-active layer being an SnO 2 layer which has been applied by means of thin-film technology. Further such thin-film gas sensors are also described in DE 197 10 456.8 AI and in DE 197 18 584.3 AI.
  • Sn0 2 , TiO, ZnO, Fe x O y , Zr0 2 , Ga 2 0 3 , CuO, In0 3 and W0 3 are recommended as metal oxide materials which are suitable for thin-film technology
  • the sensor-active layer which layer consists of a mixed oxide, namely chromium-titanium oxide (CTO).
  • CTO chromium-titanium oxide
  • sensors which have a CTO layer as the sensor-active layer do not Have structuring options in the ⁇ m range. This means that these gas sensors cannot be introduced as microelectronic components in suitable circuits.
  • Another object is to provide a suitable method for producing metal oxide semiconductor gas sensors of this type which have a mixed oxide as the sensor-active layer.
  • the invention thus relates to a metal oxide semiconductor gas sensor which has a chromium-titanium oxide layer as the sensor-active metal oxide thin layer.
  • a gas sensor which has a CTO thin layer as the sensor-active layer, has hitherto not been known from the prior art.
  • gas sensors with CTO layers as microelectronic components can now also be incorporated in corresponding circuits.
  • the thin-film sensor according to the invention with the CTO layer has a layer thickness of 10 nm to 1 ⁇ m. The layer thickness is preferably selected so that it is in the range from 100 to 500 nm.
  • the sensor according to the invention in thin-film technology differs significantly from the previously known sensor of WO 01/38867 AI, which although also has a CTO layer as a sensor-active layer, the morphology of which, however, originates from the field of thick-film technology. This means that its use for microelectronics is not possible.
  • the mixed oxide is present as a single-phase material in a corundum structure, the phase advantageously corresponding to that of the sensors in thick-film technology.
  • the gas sensor with the CTO thin layer according to the invention can have up to 40 at% titanium in the cation sublattice.
  • the gas sensors according to the invention with the CTO thin layers have specific sheet resistances of approximately 10 k ⁇ to 10 M ⁇ , preferably a few 100 k ⁇ , at operating temperatures of approximately 350 °.
  • the CTO layer of the gas sensor according to the invention can of course contain catalysts or promoters, as is already known from the prior art.
  • Silicon is preferably used as substrate, with Si0 2 as insulator and Al 2 O 3 or quartz glass.
  • the thin-film gas sensor according to the invention with the CTO layer can also have a passivation layer which is arranged between the substrate and the CTO layer. Is preferred for the According gas sensor Si0 2 used as a passivation layer.
  • the passivation layer can have a thickness of 100 nm to 1 ⁇ m.
  • the thin-film gas sensor according to the invention is not subject to any restrictions. In principle, all structures known to date from the prior art for producing electrodes can also be used for the thin-film gas sensor according to the invention. It is preferred here if the sensor is designed as a contact pad on the substrate. With regard to the design of this contact pad and the corresponding materials, reference is made to DE 44 24 342 Cl. Reference is expressly made to the disclosure content of this document.
  • the invention further includes the possibility of interconnecting a plurality of sensors to form a sensor array.
  • a sensor array For this purpose, reference is also made to the aforementioned DE 44 24 342 Cl and to DE 197 10 4568 AI and DE 197 18 584.3.
  • the possibilities shown therein for the formation of sensor arrays and their structuring also apply to the gas sensor according to the invention described above.
  • the invention also includes a method for producing the metal oxide semiconductor gas sensor described above.
  • the metal layers are applied one above the other by means of thin-film techniques known per se, and that annealing then takes place. It does not matter which layer is applied first. It can have both the chrome layer on it the titanium layer and the titanium layer are applied to the chrome layer. Surprisingly, the inventors were able to show that if the metal layers are applied one above the other as in the above process, interdiffusion, reaction and crystal growth take place simultaneously. It should be emphasized here that the method according to the invention leads to a single-phase material with a corundum structure.
  • Thin-film processes such as thermal evaporation or sputtering can be used to build up the layers.
  • methods such as MOCVD and MBE-derived methods are also very suitable.
  • the choice of the individual layer thickness to one another is essential both for presetting the ratio of chromium to titanium and for the formation of the homogeneous mixed oxide according to the invention.
  • the layer thicknesses of the individual metal layers are preferably in the range from 2 to 200 nm, preferably in the range from 5 to 75 nm.
  • Layers can be made directly from the molecular data ten and the density of the metals. This makes it possible to cover the concentration range of up to 40 at% titanium, which is important for sensitive layers, in the cation sublattice.
  • the layer thickness ratios are limited by the need to ensure a homogeneous mixing of the metals with a subsequent annealing process, both by interdiffusion of the metals, and by complete oxidative control of the annealing process for complete oxidation to CTO.
  • the coating process itself must be carried out in such a way that the coating adheres to substrates suitable for sensory applications.
  • the coating rates are in the range of 10-20 nm / min.
  • the total layer thicknesses depend on the total resistances to be achieved in the 10 to 100 ⁇ range at the usual use temperature of these layers as gas sensors. These are temperatures of up to 500 ° C.
  • a further special feature of the method according to the invention is the tempering, which, in comparison to the temperatures of up to 1300 ° C. necessary for the formation of homogeneous mixed crystals, is a low-temperature method.
  • This low-temperature process which is suitable down to temperatures down to 850 ° C, is possible because, compared to the prior art, the above-mentioned deposition processes result in a much closer molecular contact between the partners involved than in the usual solid-state reaction between the specified ones also nanoscale proportions of the separated oxides Cr 2 0 3 and Ti0 2 .
  • the main difference from the prior art with regard to the formation of the CTO is that interdiffusion, reaction and crystal growth take place simultaneously.
  • the Te - per time is around 12h.
  • the layer thickness increases with the annealing.
  • the annealing can take place both under a controlled atmosphere in a conventional diffusion furnace and with a Rapid Thermal Annealing Equipment.
  • the processes are proven on the one hand by adhesion studies using temperature shock in liquid nitrogen (detachment of layers not according to the invention) on the other hand by electron microscopy, preferably by scanning electron microscopy (SEM) combined with energy dispersive X-ray analysis (EDX), the latter method for determining the elemental composition.
  • SEM scanning electron microscopy
  • EDX energy dispersive X-ray analysis
  • the crystal structure can be verified by conventional ⁇ / 2 ⁇ X-ray examinations. Within the detection limits, these show none of the metals and only single-phase material in the expected crystal structure: corundum structure.
  • the annealed layers in a suitable sensor layout have specific sheet resistances of approximately 10 ⁇ to a few M ⁇ , preferably a few 100 k ⁇ Operating temperatures of approx. 350 ° C.
  • FIG. 1 shows the schematic structure of a thin-film gas sensor according to the invention.
  • FIG 3 shows the course of resistance over time of a CTO sensor element according to the invention.
  • 1 shows the basic structure in a schematic form of a sensor according to the invention. 1 does not contain the necessary electrodes for operating the sensor.
  • 1 consists of a silicon substrate on which a 1 ⁇ m thick SiO 2 layer has been deposited.
  • the CTO layer has a thickness of a few 100 nm and was deposited using the method according to the invention, as explained above in the description. 1 shows a possible embodiment only by way of example. It is also possible to build up the layer structure on other substrates suitable for the gas sensor application, such as A1 2 0 3, in its usual designs including sapphire.
  • the invention naturally also includes all other embodiments in which the individual sensor is connected in the form of an array.
  • the configurations in the form of an array described there are also possible with the sensor according to the invention.
  • a preferred embodiment consists in an array with Sn0 2 with and without catalyst, with W0 3 with and without catalysts and also 2 Os with and without catalysts, mainly designed for oxide layers in thin-film technology. Combinations are also possible as an array on a chip with sensitive layers that have been applied using conventional thick-film techniques.
  • FIG. 2 now shows an SEM image of a thin-film CTO surface according to the invention.
  • 2 was annealed at 900 ° C in synthetic air. Crystals of the order of 50 nm to 200 nm connected to surfaces can be seen.
  • the CTO surface has a uniform structure both in the transverse fracture and in the grain size and grain size distribution on the surface. In tests, the applicant was able to show that such layers withstand the adhesion test (LN 2 shock test).
  • Fig. 3 shows the resistance curve over time combined with a sensor layout according to DE 197 18 584 when exposed to different target gases in synthetic air (50% relative humidity) at an operating temperature of 420 ° C.
  • the high sensitivity of the sensor exposure to ammonia should be emphasized.
  • the slow one Setting the basic resistance after exposure to ammonia is not sensor-related. This means that only the desorption properties of the measurement equipment used here are reproduced.
  • the layers according to the invention are furthermore characterized by a typically low sensitivity to moisture at various ammonia concentrations.
  • Fig. 4 shows the influence of the relative air humidity at various ammonia concentrations on the resistance of a CTO sensor at an operating temperature of 380 ° C.
  • the ammonia concentration has been varied from 0-100 ppm and the relative humidity from 0-70%.
  • the typical properties compared to the usual target gases such as methane, CO, NO, H 2 and ammonia combined with the low moisture sensitivity enables further embodiments together with a moisture sensor in an array.
  • Such a combination gives the possibility of using the combined sensor reaction from sensitivity to the corresponding targets together with the low moisture sensitivity via a second exclusive moisture-sensitive sensor to determine the target concentration quantitatively by subsequent evaluation.

Landscapes

  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • Physics & Mathematics (AREA)
  • Health & Medical Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Analytical Chemistry (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)

Abstract

L'invention concerne un détecteur de gaz métal-oxyde-semi-conducteur et un procédé permettant de le produire. Ledit détecteur comprend une fine couche de métal-oxyde, active en termes de détection, appliquée sur un substrat, qui est en contact avec au moins une électrode. La fine couche de métal-oxyde, active en termes de détection, se présente sous forme de couche de chrome-titane-oxyde (CTO), de 10 nm à 1 νm d'épaisseur. Les couches de chrome et de titane sont appliquées par superposition mutuelle, par des techniques de couches minces, puis sont durcies par trempe.
EP02779286A 2001-09-12 2002-09-02 Detecteur de gaz chrome-titane-oxyde-semi-conducteur et procede permettant de le produire Withdrawn EP1425573A1 (fr)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
DE10144900 2001-09-12
DE10144900A DE10144900B4 (de) 2001-09-12 2001-09-12 Verfahren zur Herstellung eines Metalloxid-Halbleitergassensors
PCT/EP2002/009763 WO2003023387A1 (fr) 2001-09-12 2002-09-02 Detecteur de gaz chrome-titane-oxyde-semi-conducteur et procede permettant de le produire

Publications (1)

Publication Number Publication Date
EP1425573A1 true EP1425573A1 (fr) 2004-06-09

Family

ID=7698760

Family Applications (1)

Application Number Title Priority Date Filing Date
EP02779286A Withdrawn EP1425573A1 (fr) 2001-09-12 2002-09-02 Detecteur de gaz chrome-titane-oxyde-semi-conducteur et procede permettant de le produire

Country Status (4)

Country Link
US (1) US7406856B2 (fr)
EP (1) EP1425573A1 (fr)
DE (1) DE10144900B4 (fr)
WO (1) WO2003023387A1 (fr)

Families Citing this family (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US8646311B1 (en) 2007-11-09 2014-02-11 Atmospheric Sensors Ltd. Sensors for hydrogen, ammonia
DE102011106685A1 (de) 2011-07-06 2013-01-10 Deutsches Zentrum für Luft- und Raumfahrt e.V. Verfahren zur Herstellung von P-halbleitenden TiO2-Nanoröhren
DE102011080690B4 (de) 2011-08-09 2021-02-04 Deutsches Zentrum für Luft- und Raumfahrt e.V. NO2 selektiver Sensor mit Al-dotierten TiO2 Sensorelektroden
US20130142942A1 (en) * 2011-11-17 2013-06-06 Abbott Diabetes Care Inc. Methods of Making a Reference Electrode for an Electrochemical Sensor
GB2520251A (en) * 2013-11-12 2015-05-20 Emma Newton Hand held device for the detection of trace gases
US11275051B2 (en) 2016-03-23 2022-03-15 Vaon, Llc Metal oxide-based chemical sensors
US10132769B2 (en) * 2016-07-13 2018-11-20 Vaon, Llc Doped, metal oxide-based chemical sensors
US11203183B2 (en) 2016-09-27 2021-12-21 Vaon, Llc Single and multi-layer, flat glass-sensor structures
US11243192B2 (en) 2016-09-27 2022-02-08 Vaon, Llc 3-D glass printable hand-held gas chromatograph for biomedical and environmental applications
WO2018160650A1 (fr) 2017-02-28 2018-09-07 Vaon, Llc Capteurs chimiques à base d'oxyde de métal à dopage bimétallique
WO2020213223A1 (fr) * 2019-04-16 2020-10-22 パナソニックセミコンダクターソリューションズ株式会社 Procédé de commande de capteur de gaz et dispositif de détection de gaz

Family Cites Families (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB8704873D0 (en) 1987-03-02 1987-04-08 Atomic Energy Authority Uk Sensors
US4967589A (en) * 1987-12-23 1990-11-06 Ricoh Company, Ltd. Gas detecting device
DE4424342C1 (de) 1994-07-11 1995-11-02 Fraunhofer Ges Forschung Sensorarray
GB9526393D0 (en) * 1995-12-22 1996-02-21 Capteur Sensors & Analysers Gas sensing
DE19710456C1 (de) * 1997-03-13 1998-08-13 Fraunhofer Ges Forschung Dünnschicht-Gassensor
DE19718584C1 (de) 1997-05-05 1998-11-19 Fraunhofer Ges Forschung Sensor zur Detektion von oxidierenden und/oder reduzierenden Gasen oder Gasgemischen
GB9823428D0 (en) 1998-10-26 1998-12-23 Capteur Sensors & Analysers Materials for solid-state gas sensors
EP1067377A3 (fr) 1999-06-23 2001-09-26 Siemens Aktiengesellschaft Détecteur de gaz
FR2796879B1 (fr) * 1999-07-30 2001-10-05 Inst Textile De France Procede pour le recyclage de bandes magnetiques par extrusion
DE19944140A1 (de) * 1999-09-15 2001-03-29 Schulze Loewen Automaten Geldbetätigtes Gerät
DE19944410C2 (de) 1999-09-16 2001-09-20 Fraunhofer Ges Forschung Vorrichtung zur Halterung einer zu heizenden Mikrostruktur und Verfahren zur Herstellung der Vorrichtung
GB9927689D0 (en) 1999-11-23 2000-01-19 Capteur Sensors & Analysers Gas sensors

Non-Patent Citations (1)

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Title
See references of WO03023387A1 *

Also Published As

Publication number Publication date
US7406856B2 (en) 2008-08-05
DE10144900B4 (de) 2005-08-04
US20040231974A1 (en) 2004-11-25
WO2003023387A1 (fr) 2003-03-20
DE10144900A1 (de) 2003-04-10

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