DE102012011079A1 - Pyroelectric infrared detector for detecting infrared radiation in e.g. technical area, has overlay structure formed by arranging lower metal electrode, film and upper metal electrode above other on substrate - Google Patents

Abstract

The detector has a free standing support structure made of ferroelectric-polymer. An overlay structure is formed by arranging a lower metal electrode (2), a poly (vinylidene fluoride-trifluoroethylene) film (3) and an upper metal electrode (4) above the other on a substrate (1), where the film is formed as a pyroelectric material. The substrate is formed as a polyethylene terephthalate film or a polyimide film, where a thickness of the substrate is smaller than 5 mm. The upper and lower electrodes are designed as a stripy electrode i.e. semi-transparent metallic film. An independent claim is also included for a method for manufacturing a pyroelectric infrared detector.

Description

The invention relates to a non-cooled infrared detector, namely a pyroelectric infrared detector with a free-standing support structure of a ferroelectric polymer or a manufacturing method of such an infrared detector.

A so-called infrared detector can detect or measure an infrared radiation and thus finds a wide application in various technical fields, such. A pyroelectric infrared detector is a temperature-controlled detector based on the fact that the spontaneous polarization of a ferroelectric material can have a pyroelectric effect with a change in temperature. Such a detector absorbs infrared radiation through its pyroelectric material and converts its thermal energy into an electrical signal. This can be used to determine if infrared radiation is present. The pyroelectric detector is a non-cooled detector that has excellent performance. Due to its light weight and simple structure, it is applicable in various infrared detection technologies. For example, lead zirconate titanate (abbreviation: PZT) ceramics, lithium tantalate (abbreviation: LiTaO3) single wafer and triglycine sulfide (abbreviation: TGS) are all excellent pyroelectric materials. But such materials have problems in the process of their manufacture and processing, such as. B. complicated production technology, high costs, low homogeneity and finished product quota. Furthermore, their application is very limited because the infrared detector is very prone to crash. Moreover, since PZT ceramics contain lead, their manufacture and processing can pollute the environment. Therefore, it is necessary to develop novel pyroelectric materials which are excellent in performance, easy processability, high intensity and environmental friendliness. Poly (vinylidene fluoride-trifluoroethylene) [Abbreviation: P (VDF-TrFE)] represents a ferroelectric material with superior performance, its manufacturing process is simple and environmentally friendly. This material can thus be used in the research, development and manufacture of non-cooled infrared detectors.

The invention is based on the object to produce an environmentally friendly, low-cost pyroelectric infrared detector easy. This object is achieved by a pyroelectric infrared detector with the features of claim 1 and a manufacturing method with the features of claim 8. Further advantageous embodiments of the invention will become apparent from the respective dependent claims.

According to the invention, a pyroelectric infrared detector with a ferroelectric polymer is provided, which has a freestanding support structure. The overlay structure is formed in the order of at least one lower metal electrode, at least one poly (vinylidene fluoride trifluoroethylene) film [abbreviation: P (VDF-TrFE)] as a pyroelectric material and at least one upper metal electrode stacked on a soft substrate of the infrared detector ,

The P (VDF-TrFE) film as a pyroelectric material for an infrared detector has the advantages, e.g. A low manufacturing temperature, a small heat capacity, a simple manufacturing technique, a good environmental friendliness and a stand-alone support structure, etc., and the film can overcome the shortcomings that a traditional infrared detector requires a substrate material having a large heat capacity and a thermal insulation structure. Film materials, e.g. As polyethylene terephthalate, can be used as a substrate in the preparation of the P (VDF-TrFE) film. However, this substrate is ultimately removed from the final product, so that this manufactured pyroelectric infrared detector is a detector having a freestanding support structure with a P (VDF-TrFE) film.

The P (VDF-TrFE) film as the pyroelectric material of the infrared detector has a thickness of 60-2000 nm and is represented in a form P (VDF _x -TrFE _y ), wherein the molar ratio of VDF (vinylidene fluoride) of the P (VDF-TrFE) material x%, and TrFE (trifluoroethylene) y%. X and y satisfy the conditions that is x + y = 100, 50 ≤ x ≤ 100, 0 ≤ y ≤ 50, and its chemical formula is [- (CH2-CF2) _x - (CHF-CF2) _y -] n.

According to an advantageous embodiment of the invention, the substrate of the pyroelectric infrared detector consists of a polyethylene terephthalate film or polyimide film, and it is soft and easily separable, the thickness of which is smaller than 5 mm. According to an advantageous embodiment of the invention, the lower electrode in the form of a strip-shaped metal electrode or in a width of 0.2-2.5 mm and a thickness of 20-100 nm designed. The top electrode, which is a 20-50 nm thick semitransparent film, is also a 0.1-2.5 mm wide strip metal electrode. When using different metal materials for making the upper electrode, the thickness of the film should be set so that the electrical resistance of the film is about 188 Ω / □. The upper electrode can also be made by sputtering ion radiation or by thermal evaporation.

According to a further advantageous embodiment of the invention, the upper electrode which is under the P (VDF-TrFE) film and the lower electrode which lies on this film are arranged crossing one over the other, in particular orthogonally crossing, the P (VDF -FEFE) film is located between the two electrodes. The overlay portion of the two electrodes together with the intervening corresponding portion of the P (VDF-TrFE) film together form the structure of a capacitor, which is considered to be a sensitive element of the infrared detector. Here, the P (VDF-TrFE) film is the dielectric material of the capacitor.

According to a further advantageous embodiment of the invention, the lower and the upper electrode made of metal or alloy, for. As lead, gold, silver, platinum, nickel, nickel-cadmium or ferronickel.

• – ein Substrat aus einem weichen Polyethylenterephthalatfilm oder einem Polyimidfilm bereitzustellen,
• – auf einer ersten Seite (Vorderseite) des Substrats mindestens eine streifenförmige untere Metallelektrode auszubilden,
• – durch eine Drehschmiermethode einen P(VDF-TrFE)-Film als pyroelektrisches Material des Infrarotdetektors auf der unteren Metallelektrode aufzulegen,
• – auf dem P(VDF-TrFE)-Film mindestens eine streifenförmige obere Metallelektrode zu gestalten, die die untere Elektrode übereinander kreuzt, insbesondere orthogonal kreuzt, wobei der P(VDF-TrFE)-Film zwischen den zwei Elektroden angeordnet wird, und der Überlagerungsteil der oberen und der unteren Elektrode mit dem dazwischen eingebetteten entsprechenden Teil des P(VDF-TrFE)-Films zusammen die Struktur eines Kondensators bildet, die einem sensitiven Element des Infrarotdetektors entspricht,
• – mit einer Ionen-Ätzentechnik, insbesondere Ätzen von Sauerstoffplasma, die zweite Seite (Rückseite) des Substrats, die keinen P(VDF-TrFE)-Film hat, so zu ätzen, um eine freistehende Unterstützungsstruktur für den Infrarotdetektor zu bilden.

Furthermore, a production method according to the invention is specified for the production of an abovementioned pyroelectric infrared detector, the method comprising the following steps:

• To provide a substrate of a soft polyethylene terephthalate film or a polyimide film,
• On at least one strip-shaped lower metal electrode on a first side (front side) of the substrate,
• By applying a P (VDF-TrFE) film as a pyroelectric material of the infrared detector on the lower metal electrode by a rotary lubrication method,
• To form on the P (VDF-TrFE) film at least one strip-shaped upper metal electrode which crosses over the lower electrode, in particular crosses orthogonally, the P (VDF-TrFE) film being placed between the two electrodes, and the overlay part the upper and lower electrodes together with the corresponding part of the P (VDF-TrFE) film embedded therebetween, together form the structure of a capacitor corresponding to a sensitive element of the infrared detector,
• Etching with an ion etching technique, in particular etching of oxygen plasma, the second side (back side) of the substrate, which does not have a P (VDF-TrFE) film, to form a freestanding support structure for the infrared detector.

• – eine bestimmte Menge von P(VDF-TrFE)-Materialien, die in der Regel als Granulat oder Trituration erhältlich sind, abzuwiegen,
• – diese Materialien als sensitives Elementenmaterial des Detektors in einem Lösungsmittel, z. B. Methyl Ethyl Keton oder Diethyl-Carbonat, aufzulösen, und dann durch eine Drehschmiermethode den P(VDF-TrFE)-Film erzeugen,
• – den erzeugten P(VDF-TrFE)-Film auszuglühen. Der Ausglühenprozess dauert in einem Temperaturbereich von 130–140 ☐ ungefähr 2–8 Stunden an.

The P (VDF-TrFE) film is prepared by the following procedure:

• To weigh a certain amount of P (VDF-TrFE) materials, which are usually available as granules or triturations,
• - These materials as a sensitive element material of the detector in a solvent, eg. Methyl ethyl ketone or diethyl carbonate, and then produce the P (VDF-TrFE) film by a rotary lubricating method,
• - annealing the generated P (VDF-TrFE) film. The annealing process continues in a temperature range of 130-140 □ for about 2-8 hours.

The ion etching technique described above is to be carried out in the following steps:
before etching, with at least one mask covering the rear side of the substrate without the P (VDF-TrFE) film so as to leave the partial area of the rear side of the substrate corresponding to a coverage area of the sensitive element on the front side an etching window is formed by arranging the mask. Through the etching window, the substrate material is etched to realize a free-standing support structure of the infrared detector. In this case, the substrate material in the window area can be completely or partially removed.

• 1) Die Fertigungstechnik des Detektors ist einfach und kostenniedrig, somit können die Produktstabilität und die Fertigproduktquote erhöht werden, und der Herstellungsprozess sowie der Detektor selbst bringen keine Umweltverschmutzung mit sich.
• 2) Der Detektor hat eine gute Stabilität und Zuverlässigkeit bzw. eine hohe Empfindlichkeit, und keine Abkühlung muss im Betrieb des Detektors vorgenommen werden.
• 3) Die Detektormaterialien können in Array-Komponenten vorgesehen werden, damit ein Vermessen von der Vision des Infrarot-Ziels verwirklicht werden kann.
• 4) Das Gestalten des Detektors weisen eine große Diversifikation und starke Integrierbarkeit auf und können mit Detektoren in anderen Wellenbereichen leicht zusammengeschaltet werden.

A P (VDF-TrFE) infrared detector with a freestanding support structure made by this method has the following advantages:

• 1) The detection technology of the detector is simple and low cost, thus the product stability and the finished product quota can be increased, and the manufacturing process as well as the detector itself does not cause environmental pollution.
• 2) The detector has good stability and reliability, and high sensitivity, and no cooling is required during operation of the detector.
• 3) The detector materials can be provided in array components so that a measurement of the vision of the infrared target can be realized.
• 4) The design of the detector has great diversification and high integrability, and can be easily interconnected with detectors in other wavebands.

The present invention will be explained below with reference to the figures. Show it:

1 a schematic representation of a detector according to the invention, and

2 : a schematic representation of the manufacturing process of the detector.

LIST OF REFERENCE NUMBERS

1

substratum

2

lower electrode

3

P (VDF-TrFE) film

4

upper electrode

5

mask

6

sensitive element

7

Ätzenfenster

In 1 (a) For example, a pyroelectric infrared detector is schematically illustrated, which is a substrate 1 , a lower electrode 2 and an upper electrode 4 includes. The two electrodes 2 and 4 forms with a P (VDF-TrFE) film embedded between them 3 together a sensitive element of the infrared detector, which can detect infrared radiation. It shows 1 (b) the supervision of a sectional view of the detector.

• 1) Bereitstellung des Substrats 1: Das Substrat 1 wird mit einer Dicke von kleiner als 5 mm bereitgestellt, hier wird z. B. ein Polyethylenterephthalatfilm oder Polyimidfilm mit einer Dicke von 2.5 mm als das Substrat 1 verwendet.
• 2) Bereitstellung der unteren Elektrode 2: Auf einer ersten Seite (Vorderseite) des Substrats 1 wird ein Aluminiumfilm durch Verdampfung als die untere Elektrode 2 plattiert, diese wird streifenförmig bzw. 1.2 mm breit und 100 nm dick gestaltet, siehe 2(a).
• 3) Bereitstellung des P(VDF-TrFE)-Films 3: Zuerst wird eine Menge von P(VDF-TrFE)-Materialien abgewogen, die in der Regel als Granulat oder Trituration zu bekommen sind. Das Molverhältnis von Granulat oder Trituration ist z. B. 70:30 (mol%). Granulat oder Trituration wird in einem Lösungsmittel, Diethyl-Carbonat oder Methyl Ethyl Keton, aufgelöst, die Stoffkonzentration des Lösungsmittels ist z. B. 2.5%wt. Dann wird auf der Vorderseite des Substrats 1, worauf die unterer Elektrode 2 angeordnet worden ist, ein P(VDF-TrFE)-Film 3 als pyroeletrische Materialien durch eine Drehschmiermethode aufgelegt, dessen Dicke beträgt z. B. 60–2000 nm, siehe 2(b).
• 4) Bereitstellung der oberen Elektrode 4: Mit Verdampfungsbeschichtungstechnik wird die obere Elektrode 4 aus einem Aluminiumfilm hergestellt, wodurch diese mit der unteren Elektrode 2 und dem P(VDF-TrFE)-Film 3 eine Kondensatorstruktur bildet, siehe 2(c). Dabei ist die obere Elektrode 4 ebenfalls streifenförmig und 0.4 mm breit zu gestalten, sie sollte auch halbtransparent sein und eine Dicke von 20 nm aufweisen. Die obere Elektrode 4 und die untere Elektrode 2 kreuzen sich übereinander, insbesondere in einer orthogonalen Kreuzform, der Überlagerungsteil der beiden Elektroden 2 und 4 bildet zusammen mit dem dazwischen liegenden P(VDF-TrFE)-Film 3 ein sensitives Element 6 des Detektors.
• 5) Verwirklichung der freistehenden Struktur: Mit einer Ionen-Ätzentechnik, wie z. B. Ätzen von Sauerstoffplasma, wird das das sensitive Element 6 abstützende Substrat 1 geätzt, siehe 2(d). Vor dem Ätzen, wird die Rückseite des Substrats 1, worauf kein P(VDF-TrFE)-Film 3 ist, mit zwei Metallmasken 5 derart verdeckt, dass eine Teilfläche der Rückseite, die einem Abdeckungsbereich des sensitiven Elements 6 auf der Vorderseite des Substrats 1 entspricht, freigelassen wird, indem die Anordnung der zwei Metallmasken 5 ein Ätzenfenster 7 bildet. Im Bereich des Ätzenfensters 7 werden die Substratmaterialien des Substrats 1 ganz oder zum Teil geätzt. Dadurch wird eine freistehende Unterstützungsstruktur für den Infrarotdetektor verwirklicht. Mit einer Ätzenleistung von 300 W und einer Ätzenzeit von 3 Minuten kann ein 2.5 mm dickes Polyethylenterephthalatsubstrat 1 in dem oben dargestellten Verfahren geätzt werden, siehe 2(e).

Such an infrared detector can be manufactured in the following embodiment:

• 1) Provision of the substrate 1 : The substrate 1 is provided with a thickness of less than 5 mm, here is z. A polyethylene terephthalate film or polyimide film having a thickness of 2.5 mm as the substrate 1 used.
• 2) Provide the lower electrode 2 : On a first side (front) of the substrate 1 becomes an aluminum film by evaporation as the lower electrode 2 plated, this is designed strip-shaped or 1.2 mm wide and 100 nm thick, see 2 (a) ,
• 3) Provide the P (VDF-TrFE) film 3 First, a lot of P (VDF-TrFE) materials are weighed, which are usually obtained as granules or triturations. The molar ratio of granules or trituration is z. B. 70:30 (mol%). Granules or trituration is dissolved in a solvent, diethyl carbonate or methyl ethyl ketone, the substance concentration of the solvent is z. B. 2.5% wt. Then it will be on the front of the substrate 1 , whereupon the lower electrode 2 has been arranged, a P (VDF-TrFE) film 3 placed as pyroeletric materials by a rotary lubrication method whose thickness is z. B. 60-2000 nm, see 2 B) ,
• 4) Provide the upper electrode 4 : With evaporative coating technique becomes the upper electrode 4 made of an aluminum film, making this with the lower electrode 2 and the P (VDF-TrFE) film 3 forms a capacitor structure, see 2 (c) , Here is the upper electrode 4 It should also be semi-transparent and have a thickness of 20 nm. The upper electrode 4 and the lower electrode 2 cross each other, in particular in an orthogonal cross shape, the overlay part of the two electrodes 2 and 4 forms together with the intervening P (VDF-TrFE) film 3 a sensitive element 6 of the detector.
• 5) Realization of the freestanding structure: With an ion etching technique, such. As etching of oxygen plasma, this becomes the sensitive element 6 supporting substrate 1 etched, see 2 (d) , Before etching, the back of the substrate 1 , whereupon no P (VDF-TrFE) movie 3 is, with two metal masks 5 obscured such that a partial surface of the back, which is a coverage area of the sensitive element 6 on the front of the substrate 1 corresponds, is released by the arrangement of the two metal masks 5 an etching window 7 forms. In the area of the etching window 7 become the substrate materials of the substrate 1 completely or partially etched. Thereby, a free-standing support structure for the infrared detector is realized. With an etching power of 300 W and an etching time of 3 minutes, a 2.5 mm thick polyethylene terephthalate substrate 1 etched in the method outlined above, see 2 (e) ,

Claims (11)

A pyroelectric infrared detector comprising a free-standing support structure of a ferroelectric polymer, characterized in that the detector has a superposition structure arranged in the order of at least one lower metal electrode ( 2 ), at least one poly (vinylidene fluoride-trifluoroethylene) film [abbreviation: P (VDF-TrFE)] ( 3 ) as a pyroelectric material and at least one upper metal electrode ( 4 ) on top of each other on a substrate ( 1 ) of the infrared detector is formed. Pyroelectric infrared detector according to claim 1, characterized in that the substrate ( 1 ) is a polyethylene terephthalate film or polyimide film and has a thickness of less than 5 mm. Pyroelectric infrared detector according to claim 1, characterized in that the P (VDF-TrFE) film ( 3 ) has a thickness of 60-2000 nm, wherein the molar ratio of VDF (vinylidene fluoride) of the P (VDF-TrFE) material is x%, and TrFE (trifluoroethylerte) y%, and where x + y = 100, including 50 ≤ x ≤ 100 and 0 ≤ y ≤ 50. Pyroelectric infrared detector according to claim 1, characterized in that the lower electrode ( 2 ) is a strip-shaped electrode, which is provided in a width of 0.2-2.5 mm and a thickness of 100 nm and can be provided by sputtering of ion radiation or by thermal evaporation. Pyroelectric infrared detector according to claim 1, characterized in that the electrode ( 4 ) a strip-shaped electrode which is provided in the form of a semi-transparent metal film having a width of 0.4 mm and a thickness of 20-50 nm and can be provided by sputtering ion radiation or by thermal evaporation. Pyroelectric infrared detector according to claim 4 or 5, characterized in that the upper electrode ( 4 ) and the lower electrode ( 2 ) are crossed over one another, in particular orthogonally crossing, whereby the P (VDF-TrFE) film ( 3 ) between the two electrodes ( 2 ) and ( 4 ) is located. Pyroelectric infrared detector according to claim 4 or 5, characterized in that the upper electrode ( 4 ) and the lower electrode ( 2 ) can each be made of lead, gold, silver, platinum, nickel, nickel-cadmium or ferronickel. Manufacturing method of a pyroelectric infrared detector described in claim 1, in which - a substrate ( 1 ) of the infrared detector is provided from a polyethylene terephthalate film or polyimide film, - on a first side of the substrate ( 1 ) at least one lower metal electrode ( 2 ) is provided by a rotary lubrication method a P (VDF-TrFE) film ( 3 ) as infrared-sensitive material on the first side of the substrate ( 1 ) and / or the lower metal electrode ( 2 ) is placed on the P (VDF-TrFE) film ( 3 ) at least one upper metal electrode ( 4 ) is provided so that the lower electrode ( 2 ) and the upper electrode ( 4 ), crossing one another, in particular orthogonally crossing, whereby the P (VDF-TrFE) film ( 3 ) between the two electrodes ( 2 ) and (4), whereby an overlay part of the electrodes ( 2 ) and ( 4 ) with the P (VDF-TrFE) film between them ( 3 ) together a sensitive element ( 6 ) of the infrared detector, - with an ion etching technique, in particular etching of oxygen plasma, a second side of the substrate ( 1 ), which are not compatible with the sensitive element ( 6 ) is etched so as to realize a free-standing support structure of the infrared detector. The manufacturing method according to claim 8, wherein the P (VDF-TrFE) film ( 3 ) is provided such that a P (VDF-TrFE) material in a solvent, e.g. As methyl ethyl ketone or diethyl carbonate, is dissolved, then a rotary lubrication method for generating the P (VDF-TrFE) film ( 3 ) and the completed P (VDF-TrFE) film ( 3 ) can anneal. The manufacturing method according to claim 8, wherein the P (VDF-TrFE) film ( 3 ) is annealed in a temperature range of 120-140 □ and for 2 to 8 hours. The manufacturing method according to claim 8, wherein the ion etching technique comprises the steps of: - before etching, with at least one mask ( 5 ) the second side of the substrate ( 1 ), which without the sensitive element ( 6 ), is covered in such a way that a partial area of the second side corresponding to a coverage area of the sensitive element ( 6 ) on the first side is released, with an etching window ( 7 ) by arranging the mask ( 5 ), - the substrate ( 1 ) in the region of the etching window ( 7 ) etched in whole or in part.

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