WO2021224213A1

WO2021224213A1 - Micromechanical radiation detector, micromechanical spectrometer and method for measuring radiation

Info

Publication number: WO2021224213A1
Application number: PCT/EP2021/061633
Authority: WO
Inventors: Clemens Mart; Thomas KÄMPFE; Sophia EßLINGER
Original assignee: Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V.
Priority date: 2020-05-04
Filing date: 2021-05-04
Publication date: 2021-11-11
Also published as: DE102020205599A1

Abstract

The invention relates to a micromechanical radiation detector, to a detector array having micromechanical radiation detectors and to a method for detecting radiation. The radiation detector comprises: - a Fabry-Pérot interferometer element (1), which has an optical resonance chamber (4) and at least one actuator (2); and - a pyroelectric sensor element (3). The at least one actuator (2) has a first electrode layer (E1), an active layer (9) and a second electrode layer (E2), which are designed and arranged to mechanically deform the actuator (2), when a voltage is applied to the active layer (9) by means of the first electrode layer (E1) and the second electrode layer (E2), such that the distance between a first reflection surface and a second reflection surface, by which reflection surfaces the resonance chamber (4) is formed, can be set and/or changed in a defined way. The pyroelectric sensor element (3) has a pyroelectric layer (13) and is designed to sense, by means of the pyroelectric layer (13), a temperature change, which is caused by the absorption of electromagnetic radiation, transmitted through a radiation-transmissive substrate (5) into the resonance chamber (4), at the second reflection surface according to the wavelength of the electromagnetic radiation, according to the distance w and/or according to a change in the distance w.

Description

Micromechanical radiation detector, micromechanical spectrometer and method for radiation measurement

The present invention relates to a micromechanical radiation detector, a micromechanical detector array and a method for radiation measurement, in particular for the spectrometric measurement of infrared radiation.

Up to now, spectrometers have been constructed from discrete optical elements and require moving parts or various assemblies, which are a Prevent miniaturization and require a high level of maintenance. Radiation detectors can nowadays be manufactured in miniaturized form, but such detectors do not offer any way of gaining information about the spectral composition of an irradiated electromagnetic radiation. Pyroelectric radiation sensors also have the disadvantage that they can only detect electromagnetic radiation that is pulsed in order to generate the temperature change required for the pyroelectric measuring principle. Usually, therefore, an electrically pulsed radiation source is used or a temporally continuous radiation is pulsed by means of an external, movable mechanical pulse shaper, also called a chopper or shutter. However, such pulse shapers are prone to failure and cannot be miniaturized.

The present invention is therefore based on the object of overcoming these disadvantages and providing an easy-to-manufacture micromechanical radiation detector, an easy-to-manufacture micromechanical detector array and a method for measuring radiation with which electromagnetic radiation can be detected quickly and efficiently.

This object is achieved according to the invention by a micromechanical radiation detector according to claim 1, a detector array according to claim 11 and a method according to claim 12. Advantageous embodiments and developments are each described in the dependent claims.

A micromechanical radiation detector has a Fabry-Perot interferometer element with at least one actuator and a pyroelectric sensor element. The Fabry-Perot interferometer element has an optical resonance space formed with a first reflective surface and a second reflective surface, which can also be referred to as an optical resonator, in which the first reflective surface is formed on a surface of a substrate that is permeable to radiation for an electromagnetic radiation to be detected is and is plane-parallel at a distance w to the second Re is arranged flexion surface. The at least one actuator is formed on the second reflection surface of the resonance chamber and has a first electrode layer, an active layer and a second electrode layer, which are formed and arranged, the actuator when an electrical is applied To mechanically deform voltage to the active layer via the first electrode layer and the second electrode layer in such a way that the distance w between the first reflective surface and the second reflective surface of the resonance chamber can be set and / or changed in a defined manner. The pyroelectric sensor element has a pyroelectric layer and is designed to use this pyroelectric layer to detect a temperature change caused by absorption of an electromagnetic radiation to be detected that is transmitted or radiated into the resonance space through the radiation-permeable substrate second reflection surface depending on the wavelength l of the electromagnetic radiation to be detected, the distance w and / or a change in the distance w is effected. The radiation detector can thus be used to efficiently determine an intensity and / or a wavelength l of electromagnetic radiation. Compared to electrostatic drives with spring suspensions, the actuator of the radiation detector can be manufactured more efficiently and there is no snap-in effect. The operating voltage is lower than that of electrostatic drives, and because the distance w can be set quickly and easily, the radiation detector can achieve short response and measurement times. The radiation detector can be operated without external moving parts and can be designed as a monolithic component. As a result, both an increase in reliability and a miniaturization can be achieved. The term "planparal lel" is to be understood here in particular as a completely parallel alignment of the reflective surfaces in which their surface normals are not offset from one another, ie by 0 °, that is, run parallel Reflection surfaces are slightly tilted against each other, so their surface normals are tilted against each other by up to 5 ° ge.

If the distance w or the resonator length w of the resonance space meets the (simplified) resonance condition for electromagnetic radiation with the wavelength l through the radiation-permeable substrate, preferably perpendicularly, into the resonance space: w oc ml / [4 n cos (0)] with n: refractive index of the resonance medium in the resonance space w: distance between the reflective surfaces l: wavelength of the incident electromagnetic radiation Q: angle of incidence of the incident electromagnetic radiation m: natural number m> 0, a constructive multiple interference occurs in the resonance space for this wavelength and the resonance space forms an optical resonator. The radiation of wavelength l is transmitted from the resonance chamber and absorbed on the second reflective surface, whereby the second reflective surface is warmed up.

The resonance condition can be achieved by changing the distance w along the optical axis of the resonance space, i.e. H. perpendicular to the reflective surfaces, can be changed in a defined manner. The resonance space can thus be used as a variable optical band-pass filter, with which a central wavelength of the first interference order (m = 1) can usually be transmitted. If the resonance condition is no longer met, the radiation is no longer transmitted by the resonance chamber and the second reflective surface is no longer heated. The temperature change at the second reflection surface is therefore dependent on the respective wavelength l of the electromagnetic radiation emitted and the distance w or its change. The temperature change causes a charge separation on the electrodes or conductor layers of the pyroelectric sensor element due to the pyroelectric effect and thus a measurable current flow that can be detected with the radiation detector and used to determine the intensity and / or the wavelength l of the electromagnetic radiation can be.

For a precise setting and change of the distance w of the least one actuator can be designed, for example, as a bending beam, which is arranged with a longitudinal axis parallel to an edge of the second reflective surface. A bending beam can be understood to mean an actuator that is cuboid with a rectangular active layer that has a length-to-width ratio of at least 2 to 1, preferably at least 5 to 1, particularly preferably at least 15 to 1. The active layer can be arranged and formed plane-parallel to the second reflection surface be to contract or expand when an electrical voltage is applied, preferably along a longitudinal axis of the bending beam, that the actuator deforms or bends along the optical axis of the resonance chamber and thereby the distance w between the first reflection

5 surface and the second reflection surface increases or decreases. Such bending beams can be controlled very easily and quickly. In addition, they are mechanically very robust and, compared to spring suspensions, can be miniaturized more easily and manufactured directly on a substrate without complex joining processes.

10

The second surface of the resonance chamber can preferably be formed with a flat surface of the first electrode layer of the at least one actuator. That is to say, the resonance space can have a first reflection surface on a flat surface of the radiation-permeable substrate and

15 of a second reflective surface can be formed on a flat surface of the first electrode layer of the at least one actuator. In this way, the deformation of the actuator can be transferred directly to the resonance chamber. Particularly preferably, the first and second reflection surfaces can be polygonal, preferably square, and congruent with one another

20 forms and arranged, wherein at least one actuator is arranged on the second reflective surface in the region of each side or edge of the second reflective surface, which is designed as a bending beam and is arranged with a longitudinal axis parallel to the respective side or edge of the second reflective surface . As a result, the distance w can be used in the entire surface area of the Re

25 flexion surfaces can be changed particularly precisely and uniformly and a high degree of parallelism of the reflection surfaces can be achieved.

The bending beam can be formed, for example, with a first electrode layer and a second electrode layer, the different layers

Blocks, compositions and / or mechanical properties aufwei sen, whereby a deformation or bending of the actuator can be caused along the optical axis of the resonance chamber. In this application, an electrode layer can be understood to mean an electrically conductive layer or an electrically conductive layer stack which

35 or which has an electrical conductivity of at least IO ⁸ S / m within Has nes temperature range that can be achieved on the active layer by the temperature change of the second reflective surface, for example at a temperature of 20 ° C. In particular, an electrically conductive layer is to be understood as a layer made of a material which has an electrical conductivity of more than 10 ⁶ S / m at a temperature of 20 ° C. A layer stack of an electrode layer can have a conductor layer and at least one carrier layer, wherein the conductor layer is formed on a surface of the active layer and / or the piezoelectric layer and the at least one carrier layer can be formed on a surface of the conductor layer opposite the active layer . The bending beam can accordingly be formed with a first electrode layer and a second electrode layer, in which the conductor layer and / or the carrier layer of the first and second electrode layers each have different layer thicknesses, materials and / or mechanical properties, so that deformation or Bending of the actuator along the optical axis of the resonance space can be caused. A conductor layer can, for example, consist of Ti tantalum nitride, TiN, tantalum nitride, TaN, tantalum carbonitride, TaCN, tantalum aluminum nitride, TaAlN, ruthenium, Ru, ruthenium oxide, RuO, titanium, Ti, titanium aluminum nitride, TiAIN, platinum, Pt, iridium, Ir, iridium oxide, IrO, or molybdenum, Mo, or another electrically conductive material.

Alternatively or additionally, the bending beam can be formed with an active layer, the composition and / or mechanical properties of which change continuously or gradually in the direction of the optical axis of the resonance chamber or the longitudinal axis of the bending beam in such a way that the active layer and thus change the at least one actuator deforms or bends in the direction of the optical axis of the resonance chamber when an electrical voltage is applied to the active layer. Such an active layer can be achieved, for example, by a gradient in the doping of the active layer or a corresponding multilayer structure of the active layer.

The bending beam can advantageously be arranged with a longitudinal axis parallel to an edge and / or the surface of the pyroelectric sensor element. The pyroelectric sensor element can thus through the actuator are also thermally insulated, whereby a greater heating or greater temperature change of the active sensor surface can be achieved. The pyroelectric sensor element can be in the form of a straight prism or cuboid, ie shaped with a polygonal, preferably square, base of the pyroelectric layer and preferably arranged centrally on or on the second reflective surface, with the sides or edges of the pyroelectric sensor element parallel to the sides or edges of the second reflection surface can be arranged. The at least one bending beam can accordingly be arranged between an outer side or outer edge of the pyroelectric sensor element and a side or edge of the second reflective surface with a longitudinal axis parallel to the respective sides or edges of the pyroelectric sensor element and the second reflective surface.

Both the at least one actuator and the pyroelectric sensor element can preferably be arranged in the plane of the second reflection surface. The second reflective surface can be formed with a flat surface of the first electrode layer of the at least one actuator, in particular a carrier layer of the first electrode layer of the at least one actuator, and a first electrode layer of the pyroelectric sensor element, in particular a carrier layer of the first electrode layer of the pyroelectric sensor element .

Particularly preferably, the radiation detector can have a first electrode layer, on the surface of which the second reflective surface is formed and which is structured or spatially separated vertically from the second reflective surface in such a way that a first electrode layer of the min at least one actuator and a first electrode layer of the pyroelectric sensor element are formed. The first electrode layer of the at least one actuator and a first electrode layer of the pyroelectric sensor element can thus be formed in a plane parallel to the reflection surfaces and have the same composition and the same layer thickness, since they are gebil det from the same first electrode layer. With such a first electrode layer, the production of the Detector can be significantly simplified, since only a single electrode layer has to be formed and structured. In addition, a very high degree of parallelism between the actuator and the pyroelectric sensor element and the reflective surfaces can be achieved. Analogously, the radiation detector can have a second electrode layer, which is formed on a surface of the active layer of the at least one actuator and the piezoelectric layer of the piezoelectric sensor element opposite the first electrode layer and is structured or spatially separated vertically to the second reflection surface in such a way that with the second electrode layer of the radiation detector electrically insulated from one another, a second electrode layer of the at least one actuator and a second electrode layer of the pyroelectric sensor element are formed.

The optical and geometric properties of the resonance space can be designed to meet the resonance condition for the electromagnetic radiation to be detected. The electromagnetic radiation to be detected can be an electromagnetic radiation in the infrared range between 0.78 pm and 1000 miti, in particular an electromagnetic radiation in the near infrared range between 0.78 pm and 3.0 pm and / or in the medium infrared range between 3 , 0 pm and 50 pm. The radiation-permeable substrate can accordingly be designed to transmit electromagnetic radiation in the infrared range, in particular in the near and / or mid-infrared range, into the resonance space. The substrate can, for example, be made of silicon, Si, germanium, Ge, gallium arsenide, GaAs, silicon germanium, SiGe, indium phosphide, InP, silicon carbide, SiC. It can also have one or more functional layers on a surface opposite the first reflective surface that is or are transparent to the electromagnetic radiation to be detected, such as an anti-reflective coating for improved radiation coupling of the electromagnetic radiation to be detected into the substrate .

The first reflective surface and the second reflective surface can be designed as flat mirrors that are partially transparent to the electromagnetic radiation to be detected, so that they are in the wavelength range of the detecting electromagnetic radiation, e.g. B. in the infrared range, in particular special in the near and / or mid-infrared range, can form an optical resonator. The first reflective surface and the second reflective surface can have degrees of reflection between 85% and 98% in the wavelength range of the electromagnetic radiation to be detected. The substrate and the first reflective surface can be made of Si, Ge,

GaAs, SiGe, InP or SiC can be formed. The second reflection surface can be on a surface of a doped semiconductor such as polycrystalline Si, SiGe or Ge with dopants, such as. B. boron, B, aluminum, AI, gallium, Ga, In dium, In, phosphorus, P, arsenic, As, antimony, Sb, bismuth, Bi or metals such as aluminum, AI, copper, Cu, cobalt, Co, Nickel, Ni, molybdenum, Mo, tantalum, Ta, and / or titanium, Ti, be formed. If the second reflective surface is formed on the first electrode layer, in particular a carrier layer of the first electrode layer, the respective electrode layer and / or carrier layer can accordingly be made from one of the aforementioned materials. It can also be provided that the first carrier layer is designed as a Bragg reflector. A Bragg reflector can be designed as a multi-layer stack or multilayer of high and low refractive index 1/4 layers. Bragg reflectors can be designed as Si-SiGe multilayers, for example.

The resonance chamber can be designed as an optical air-gap resonator, the distance w between the first and the second reflective surface in egg nem wavelength range of the electromagnetic radiation to be detected treatment, for. B. in the infrared range, especially in the near and / or medium infrared range, adjustable or changeable. The distance w can, for example, be adjustable or changeable in a range which is between 0.5 pm and 35 pm. As a result, the radiation detector can be used in particular for a spectrometric gas analysis. Instead of air, other gaseous, liquid and / or solid resonance media can also be provided in the resonance space. With a defined resonance medium, the thermal properties of the radiation detector can be set or controlled in a targeted manner. The resonance space can contain, for example, air, nitrogen or noble gases as a resonance medium, ie be filled with these, or be formed with a vacuum, so that the thermal insulation of the micromechanical actuator from the rest of the radiation detector can be improved.

It can be provided that the resonance chamber is formed by means of a first flat sacrificial layer, which is formed in a defined area on the radiation-permeable substrate and, after the formation of the at least one actuator and the pyroelectric sensor element or the first electrode layer, on a surface opposite the substrate first sacrificial layer wet chemical, z. B. by wet etching or hydrofluoric vapor etching was removed. Such a sacrificial layer can, for example, consist of silicon dioxide and be deposited by means of atomic layer deposition (ALD), laser beam evaporation (pulsed laser deposition, PLD), chemical vapor deposition (CVD) or physical vapor deposition (PVD). The etchant for the wet chemical removal can reach the sacrificial layer via passages in the first electrode layer or intermediate spaces which are formed between the at least one actuator and the pyroelectric sensor element. By removing the sacrificial layer, a well-defined cavity is created between the radiation-permeable substrate, the min least one actuator and the pyroelectric sensor element or between the substrate and the first electrode layer, which forms the resonance space. Resonance spaces that are formed by means of such a sacrificial layer can therefore have particularly precise measurements and an extremely high parallelism of the reflection surfaces aufwei sen.

The actuator can advantageously be designed as a piezoelectric, flexoelectric or electrostrictive actuator, in which the active layer is formed with or from a piezoelectric, flexoelectric and / or electrostrictive material. In this application, a piezoelectric material can be understood as a dielectric material without an inversion center in the symmetry of the crystal structure, which is mechanically deformed when an electrical voltage is applied, ie when an electrical field is applied, ie has an inverse piezo effect. Electrostrictive materials can be dielectric materials that, when an electrical voltage is applied, deform through a mechanical voltage that is proportional to the square of the field strength, regardless of their crystal structure of the electric field applied by means of the electric voltage. Under flexoelectric materials dielectric materials are to be understood, which deform regardless of their crystal structure when an electrical voltage is applied, if this causes an electrical field gradient in the material.

A subgroup of piezoelectric materials can be pyroelectric materials in which the electrical polarization changes due to a change in temperature and a change in the surface charges acts. Pyroelectric materials can in turn comprise a subgroup of ferroelectric materials in which the polarization of the electrical polarization can be reversed by applying an electrical voltage.

A pyroelectric sensor element can be designed as a plate capacitor with a first electrode layer, a pyroelectric layer as a capacitor medium and a second electrode layer. The pyroelectric layer can be formed with or from one or more pyroelectric and / or ferroelectric materials. The pyroelectric layer of the pyroelectric sensor element and the active layer of the at least one actuator can advantageously be formed with or from one or more pyroelectric and / or ferroelectric materials, for example from doped hafnium oxide, HfC> ₂ , a mixed hafnium oxide or combinations of this. Possible dopants in the doped hafnium oxide include aluminum, Al, silicon, Si, germanium, Ge, yttrium, Y, scandium,

Sc, gadolinium, Gd, strontium, Sr, lanthanum, La, niobium, Nb, barium, Ba, cerium, Ce, neodymium, Nd, samarium, Sm, erbium, Er, and / or ytterbium, Yb, can be used. The active layer and the pyroelectric layer can preferably be formed in a plane parallel to the reflective surfaces and / or be formed with or from the same material or the same materials.

The radiation detector particularly preferably has an active layer which is formed with or made of a pyroelectric and / or ferroelectric material in a plane parallel to the second reflection surface and is structured or spatially separated vertically to the second reflection surface in such a way that the active Layer of the radiation detector is an active one Layer of the at least one actuator and a pyroelectric layer, electrically insulated therefrom, of the pyroelectric sensor element are formed. The active layer of the at least one actuator and the pyroelectric layer of the pyroelectric sensor element can therefore have the same composition and the same layer thickness, since they are formed with the same active layer. Such an active layer of the radiation detector enables a significantly simpler and more precise production of the radiation detector, since only a single active layer has to be formed and structured in order to form the at least one actuator and the pyroelectric sensor element.

For simple manufacture and handling, the radiation detector can have a first electrode layer, an active layer and a second electrode layer, each of which is parallel to the second reflective surface and structured or spatially separated vertically to the second reflective surface in such a way that the first electrode layer of the Radiation detector, the active layer of the radiation detector and the second electrode layer of the radiation detector of the at least one actuator and electrically insulated therefrom, the pyroelectric sensor element are formed. That is, the at least one actuator and the pyroelectric sensor element can have a first electrode layer, an active or piezoelectric layer and a second electrode layer, each of which has the same composition and the same layer thickness, since they were each formed with the same layer. Thus, only a single first electrode layer, a single active layer and a single second electrode layers have to be formed and structured on the substrate for the production of the detector in order to produce the at least one actuator and the pyroelectric sensor element. To further simplify production, the first electrode layer and the second electrode layer can have the same composition or be formed with or from the same materials.

Furthermore, for efficient electrical contacting of the radiation detector, it can be provided that the substrate is designed to be electrically conductive. The radiation detector can have a first electrode layer, an active layer and a second electrode layer, the first The electrode layer is formed on the second reflection surface and in direct contact with the electrically conductive substrate, and the first electrode layer, the active layer and the second electrode layer are structured or spatially separated in defined areas vertical to the second reflection surface in such a way that these layers the at least one actuator and the pyroelectric sensor element are electrically insulated therefrom, and the at least one actuator and the pyroelectric sensor element can be electrically contacted independently of one another via the electrically conductive substrate and the second electrode layer. For this purpose, the substrate can be electrically contactable, for example, around the Fabry-Perot interferometer element in Randbe range of the substrate, ie it can be formed there free of coatings. The first electrode layer, the active layer and the second electrode layer can in particular be structured in such a way that the previously described shapes and / or arrangements of actuators and pyroelectric sensor element are formed in the radiation detector. The electrode layers, the active layer and / or the pyroelectric layer can be formed for example by means of atomic layer deposition (ALD), laser beam evaporation (pulsed laser deposition, PLD), chemical gas phase deposition (CVD) and / or physical gas phase deposition (PVD) and by means of lithographic processes, wet chemical processes or dry etching processes.

In one embodiment it can be provided that the radiation detector has a control unit which is designed to condition and / or recondition the active layer of the at least one actuator and / or the pyroelectric layer of the pyroelectric sensor element. The control unit can alternatively or additionally be designed to increase the piezoelectric effect of the active layer of the at least one actuator and / or to increase the pyroelectric effect of the pyroelectric layer of the pyroelectric sensor element.

The expression of the piezoelectric and / or the pyroelectric effect can depend on the electrical history of the respective active or pyroelectric layer. With the control unit, the active layer of the at least one actuator and / or the pyroelectric Layer of the pyroelectric sensor element, a defined electrical history can be impressed by applying a defined electrical voltage or voltage sequence to the respective layer. This can be done once, for example, when the sensor element is put into operation, at regular intervals determined by the control electronics or after a defined number of switch-on processes (conditioning) and / or after a certain operating time or after a certain number of switch-on processes (Reconditioning). In this way, possible degradation processes can be compensated and a high reproducibility of the radiation detection guaranteed. The voltage or voltage sequence can be generated with an integrated pulse generator or a waveform generator and can include, for example, square, sine, triangular or sawtooth waveforms in a frequency range between 10 Hz and 1 MHz.

With the control unit, certain voltages or voltage sequences can be applied to the active layer of the at least one actuator and / or pyroelectric layer of the pyroelectric sensor element, with which the piezoelectric or pyroelectric effect of the respective layer can be enhanced. The piezoelectric and / or pyroelectric effect can be increased, for example, by means of a preferably sinusoidal or co-sinusoidal alternating voltage (cycles), the lower limit of which exceeds the coercive field strength of the piezoelectric or pyroelectric material of the respective layer and the upper limit of which is below the breakdown field strength of the piezoelectric or pyroelectric material of the respective layer lies. In the case of active and / or pyroelectric layers made of doped hafnium oxide HfC> 2 or hafnium oxide mixed oxides, the lower limit value can, for example, be in a range between 0.7 MV / cm and 1.5 MV / cm and the upper limit value in a range between 3 MV / cm and 3.5 MV / cm. The alternating voltage can be applied to the respective layer ^{for 10 1} to 10 ^{6 periods before the radiation measurement.} Alternatively or additionally, the pyroelectric effect of the pyroelectric sensor element can also be increased by means of a direct voltage that is applied to the pyroelectric sensor element during the measurement. The pyroelectric coefficient in Si-doped hafnium oxide HfC> 2 can, for example, by applying a direct voltage of 1.5 V to up to can be increased to -140 pC / m ^{2 K.}

Since only temperature changes can be detected with the pyroelectric sensor element, the electromagnetic beam to be detected can

5 treatment can be an externally pulsed or time-modulated radiation. If such radiation is detected with the radiation detector at a time-constant set distance w, conclusions can be drawn from the amplitude of the measurement signal of the pyroelectric sensor element about the magnitude of the temperature change and thus the intensity of the electromagnetic beam

10, whose wavelength l fulfills the resonance condition for the set distance w. The measurement can be repeated for different intervals w that are set to be constant over time, so that a spectrum of the electromagnetic radiation to be detected can be reconstructed from the individual measurements given a sufficient number of measurements

15 can. The distances w can each be set within a range that lies within or corresponds to the free spectral range of the resonance space. The free spectral range FSR can be defined as the distance between two transmission maxima for which the transmission condition is met in the Fabry-Perot cavity or in the resonance space. For

20 the transmission _{maxima m} and A _{m + i} , this is, for example, a free spectral range FSR = 2w / [m (m + l)].

So that the radiation detector can also detect unpulsed or unmodulated electromagnetic radiation that is constant over time, it can be provided

25 it can be seen that the actuator is designed to continuously and preferably uniformly change or tune the distance w in a defined tuning range Aw. The pyroelectric sensor element can be designed accordingly to continuously detect the temperature change during the change in the distance w. With such dynamism

BO's operation of the radiation detector allows very short measurement times to be achieved, since lengthy setting times for the distance w are not required. In addition, an external modulation of the electromagnetic radiation to be detected can be bypassed and thus an external pulse shaper can be dispensed with.

35

The tuning range Aw can typically be in the free spectral range of the resonance space. It can at least correspond to the width of an interference peak of electromagnetic radiation, for whose wavelength l, preferably the central wavelength, the resonance condition in the resonance space can be met, and can correspond at most to the free spectral range of the resonance space. The distance w can be changed by applying a preferably sinusoidal or cosinusoidal alternating voltage to the active layer of the at least one actuator. The distance w can be changed in the tuning range Aw within half a period of the alternating voltage. An alternating current can be detected on the pyroelectric sensor element, the amplitude of which is used as a measurement signal. From the measured amplitude curve, calibration methods in which the measured amplitude curve is compared, for example, with one or more amplitude curves of a known reference radiation, can then be used to reconstruct the spectrum of the radiation to be detected for the respective tuning range Aw. As a result, the radiation detector can also be used to determine the spectrum of a time-constant, unpulsed or unmodulated electromagnetic radiation.

In one embodiment it can be provided that the radiation-permeable substrate has a wavelength-selective optical layer on a surface opposite the first reflection surface, which is designed to transmit electromagnetic radiation of a defined wavelength l or electromagnetic radiation of a defined narrow-band wavelength range. As a result, only the wavelength selected by means of the wavelength-selective optical layer or the selected narrow-band wavelength range, that is to say a monochromatic or approximately monochromatic electromagnetic radiation, can be transmitted through the substrate into the resonance chamber. Alternatively, the substrate can be designed as a wavelength-selective substrate which transmits electromagnetic radiation of a defined wavelength l or a defined narrow-band wavelength range into the resonance space.

A narrow-band wavelength range can be a wavelength range in which the intensity of an interference peak of a wavelength detectable with the radiation detector, preferably a central wavelength, is more than 1%, preferably more than 2%, particularly preferably more than 3%, of the maximum intensity of the interference peak. A wavelength detectable with the radiation detector can in particular be a wavelength for which the resonance condition can be met in the tuning range Aw of the resonance space. With such a radiation detector, electromagnetic radiation to be detected of the respectively selected wavelength or a wavelength of the respectively selected narrowband wavelength range can be detected particularly reliably and quickly.

In the case of externally pulsed radiation, the radiation of the respective wavelength can be detected at a distance w set to be constant over time, which fulfills the resonance condition for the respective wavelength. In the case of unpulsed or unmodulated radiation, the radiation of the respective wavelength can be detected by continuously changing or tuning the distance w in a tuning range Aw, the tuning range Aw being a continuous range that has both a spacing w and spacings w, in which the resonance condition for the selected wavelength or the selected narrowband wavelength range is met, as well as distances w, at which the resonance condition for the selected wavelength or the selected narrowband wavelength range is not met. If the distance w is continuously changed or tuned in this tuning range Aw, at least one temperature change can be brought about on the second reflection surface. The tuning range Aw can be run through several times during the change in distance, for example by applying an alternating voltage to the active layer of the at least one actuator, so that a chopper effect can be generated by the repeated temperature changes. Due to the sharply defined pass band of the wavelength-selective optical layer, a temperature change with a high gradient can be achieved, so that the tuning range Aw can be passed through with a frequency in the range from 5 kHz to 5 MHz. Accordingly, an alternating current can be detected on the pyroelectric sensor element, the amplitude of which can serve as a measurement signal. The radiation detector can thus be optimized for a specific wavelength and operated without an external pulse shaper. The narrower the tuning range is chosen, the faster the tuning range can run through and the electromagnetic radiation to be detected is detected.

In one embodiment it can also be provided that the radiation-permeable substrate has a broadband bandpass filter or an edge

5 filter, which can also be referred to as a long-pass or high-pass filter, has. This filter can be designed, undesirable resonance wavelengths, z. B. low resonance wavelengths below a certain wave gears _min , to hide, ie to block, so that these wavelengths are not transmitted into the resonance space.

10

A detector array has at least two micromechanical radiation detectors whose second reflection surfaces, preferably without overlapping, are each aligned in one spatial direction. The radiation detectors can be arranged offset to one another or preferably arranged in such a way

15 be that the second reflection surfaces are each arranged in a plane. The radiation detectors can for example be attached to a common carrier or chip. Alternatively, the radiation detector can have a substrate which is permeable to radiation for the electromagnetic radiation to be detected, on the surface of which the second reflection surface

20 surfaces of the radiation detectors can be arranged and designed. That is to say, the radiation detectors can be designed on a common substrate. Tilting of the radiation detectors can thereby be avoided and production of the detector array can be facilitated.

The radiation detectors can each be angeord net at defined positions and have Fabry-Perot interferometer elements that are identical to one another. Electromagnetic radiation to be detected can thus be spatially resolved and / or detected in a spectrally resolved manner.

BO In one embodiment, the radiation detectors can be optimized for the detection of electromagnetic radiation with different wavelength ranges so that, for example, a multispectral detector array for IR spectroscopy (infrared spectroscopy) or multispectral thermal imaging can be formed. The radiation detectors can do this

35 each adjustable or tunable in different areas have resonance spaces, ie the distances w of the resonance spaces can each be adjustable and / or changeable in different areas.

In a further embodiment, the radiation detectors can each have a wavelength-selective optical layer on a surface of the radiation-permeable substrate opposite the first reflection surface, which is designed to each have an electromagnetic radiation of a defined wavelength l or an electromagnetic radiation of a defi

10 ned narrow band wavelength range to transmit. The wavelength-selective optical layers can each transmit the identical wavelength l or the identical narrow-band wavelength range or transmit different wavelengths l or different narrow-band wavelength ranges. The respective wavelengths or

15 narrow-band wavelength ranges can, for example, be characteristic absorption or transmission lines or bands of a certain material, so that qualitative and quantitative material determination measurements can be carried out with the detector array. The respective absorption or transmission lines or bands can be used simultaneously

20 can be detected, so that the material determination can be carried out not only in a non-contact and non-destructive manner, but also extremely quickly. Alternatively, the number of radiation detectors and the wavelengths or narrow-band wavelength ranges of the respective wavelength-selective optical layers can be adapted to the wavelength range of a

The resulting electromagnetic radiation can be adapted or distributed over it in such a way that the spectrum of the electromagnetic radiation to be detected can be reconstructed from the measurements of the individual radiation detectors. The advantage here again lies in the simultaneous and therefore very rapid, but also very precise radiation measurement.

BO

In a method for radiation measurement, an electromagnetic radiation to be detected is passed through a substrate which is radiation-permeable for the electromagnetic radiation to be detected into a resonance space formed with a first reflection surface and a second reflection surface

35 of a Fabry-Perot interferometer element transmitted, the first Re flexionsfläche with a surface of the radiation-permeable substrate is formed plane-parallel at a distance w from the second reflection surface. The distance w is set and / or changed in a defined manner by means of at least one actuator. The actuator is designed for this on the second reflective surface of the resonance chamber and has a first electrode layer, an active layer and a second electrode layer, which are designed to mechanically deform the actuator when an electrical voltage is applied to the active layer in such a way that the distance w is adjustable and / or can be changed in a defined manner. A temperature change is detected by means of a pyroelectric sensor element, which occurs due to an absorption of the electromagnetic radiation to be detected on the second reflection surface depending on the wavelength l of the electromagnetic radiation to be detected, the distance w and or a change in the distance w or is effected. For this purpose, the pyroelectric sensor element has a pyroelectric layer and is designed to detect the temperature change by means of this pyroelectric layer. The intensity and / or the wavelength l of the electromagnetic radiation is or are determined from the temperature change, the distance w and / or the change in the distance w over time.

The described method can in particular be carried out with the described radiation detector or the described detector array, that is, the described radiation detector and the described detector array are set up for carrying out the described method.

Exemplary embodiments of the invention are shown in the drawings and are explained below with reference to FIGS. 1 to 8.

Show it:

1 shows a schematic illustration of a sectional view of an example of a micromechanical radiation detector,

2 in a schematic representation a plan view of an example of a micromechanical radiation detector, 3 shows the transmission behavior of an example of a micromechanical radiation detector as a function of the incident wave length,

4 shows a schematic illustration of a top view of an example of a micromechanical detector array,

5 shows a schematic illustration of a sectional view of an example of a micromechanical detector array,

6 in a schematic representation a top view of a further example of a micromechanical detector array,

7 shows, in a schematic representation, an electrical circuit of a control unit, and FIG

8 shows a schematic illustration of a production method for an example of a micromechanical radiation detector.

In Figures 1 and 2, an example of a micromechanical radiation detector is shown in a schematic representation. FIG. 1 shows a sectional view and FIG. 2 shows a plan view of the radiation detector. In Fi gur 2 the sectional plane of the sectional view shown in Figure 1 is indicated with a dashed line. The direction of incidence of the electromagnetic radiation to be detected on the micromechanical radiation detector is indicated in FIG. 1 with arrows. Recurring features are provided with identical reference numerals in FIGS. 1 and 2, as well as in the following figures.

The micromechanical radiation detector has a Fabry-Perot interferometer element with at least one actuator 2 and a pyroelectric sensor element 3. The Fabry-Perot interferometer element has an optical's resonance space 4, which is provided with a first reflection surface, which can also be referred to as a resonance surface, and a second reflection surface or resonance surface and lateral boundaries 6 of a first sacrificial surface. Layer OS1 is formed, wherein the first and the second reflection surface are arranged plane parallel at a distance w from one another and the first reflection surface is formed on a surface of a substrate 5 which is transparent to radiation for an electromagnetic radiation to be detected. The at least one actuator 2 is formed on the second reflective surface of the resonance chamber 4 and has a first electrode layer E1, an active layer 9 and a second electrode layer E2, which are formed and arranged, the at least one actuator 2 when an electrical voltage is applied to mechanically deform the active layer 9 via the first electrode layer E1 and the second electrode layer E2 in such a way that the distance w between the first reflective surface and the second reflective surface of the resonance chamber 4 can be set and / or changed in a defined manner. The pyroelectric sensor element S has a pyroelectric layer IS and is designed to detect a temperature change by means of this pyroelectric layer 13, this temperature change being caused by an absorption of an electromagnetic to be detected transmitted or radiated into the resonance space 4 through the radiation-permeable substrate 5 Radiation at the second reflection surface is caused as a function of the wavelength l of the electromagnetic radiation to be detected, the distance w and / or a change in the distance w.

In the example of Figures 1 and 2, the at least one actuator 2 is designed as a flexural beam with a polygonal, plane-parallel to the second reflective surface on ordered active layer 9, which contracts or expands when an electrical voltage is applied, so that the actuator 2 through the contraction or expansion along the optical axis of the resonance space 4 is deformed or deflected and the distance w between the first reflective surface and the second reflective surface increases or decreases as a result.

In the example shown, the resonance chamber 4 is formed with a first and a second reflection surface, which are square and congruently shaped and arranged to one another. The second reflection surface is formed with or on a flat surface of the first electrode layer E1 of the at least one actuator 2. In this way, the deformation of the at least one actuator 2 can act directly on the resonance chamber 4. In the example shown, the radiation detector has four actuators 2 which are designed as bending beams and are each arranged with a longitudinal axis parallel to an edge of the second reflective surface of the resonance chamber 4. As a result, the distance w can be set or changed with a particularly high degree of parallelism of the reflection surfaces. However, other shapes of the reflective surfaces and numbers or arrangements of the min least one actuator 2 are also possible.

The pyroelectric sensor element 3 is also square in the example shown and arranged centrally on the second reflective surface of the resonance space 4, the second reflective surface being formed with or on a flat surface of a first electrode layer El of the pyroelectric sensor element. The actuators 2 are each arranged with a longitudinal axis parallel to an outer edge and surface of the pyroelectric sensor element 3 and thereby thermally isolate the pyroelectric sensor element 3 so that a higher temperature change can be achieved in the pyroelectric layer 13 of the pyroelectric sensor element 3. However, other shapes and arrangements of the pyroelectric sensor element 3 and the at least one actuator 2 are also possible, please include.

In the example in FIGS. 1 and 2, the at least one actuator 2 is formed with a first electrode layer E1 and a second electrode layer E2, which have different layer thicknesses from one another in order to form a flexible beam which, when the active layer 9 expands or contracts, along the optical The axis of the resonance chamber 4 is deformed or sagged. The first electrode layer E1 preferably has a layer thickness less than 300 nm, while the second electrode layer E2 preferably has a layer thickness greater than 300 nm. The active layer 9 can have a layer thickness between 10 nm and 1000 nm, preferably between 20 nm and 100 nm.

Alternatively, the bending beam can also be formed with a first electrode layer E1 and a second electrode layer E2, which have different compositions and / or mechanical properties, or with an active layer 9, the composition and / or mechanical properties of which are in Direction of the optical axis of the resonance chamber 4 or the longitudinal axis of the bending beam continuously or step by step, for example through a gradient in the doping of the active layer 9 or a corresponding multilayer structure, such that the active layer 9 and thus the at least one actuator 2 change when an electrical voltage is applied deformed or deflected on the active layer 9 in the direction of the optical axis of the resonance chamber 4.

In the example of FIGS. 1 and 2, the electrode layers E1 and E2 of the at least one actuator 2 and the pyroelectric sensor element S are formed from an electrically conductive layer stack, each of which has a conductor layer 8, 10 and a carrier layer 7, 11. The conductor layers 8, 10 are each arranged on a surface of the active layer 9 or the piezoelectric layer 13 and the carrier layers 7, 11 are each on a surface of the respective conductor layer 8 opposite the active layer 9 or the piezoelectric layer 13 , 10 trained. As electro denschichten, however, individual layers or layer stacks with other layer sequences and / or layer compositions, such as. B. electrically conductive Bragg reflectors can be used. The second reflective surface is formed on or with a surface of the carrier layer 7 of the first electrode layer E1 of the at least one actuator 2 and the pyroelectric sensor element 3. The conductor layers 8, 10 in the example shown in Figures 1 and 2 are made of titanium nitride, TiN, but can also consist of tantalum carbonitride, TaCN, tantalum aluminum nitride, TaAlN, ruthenium, Ru, ruthenium oxide, RuO, titanium, Ti, titanium aluminum nitride, TiAlN, platinum, Pt, iridium, Ir, iridium oxide, IrO, or molybdenum, Mo, or another suitable electrically conductive material.

In the example of FIGS. 1 and 2, the electrode layers E1 and E2, the active layer 9 and the pyroelectric layer 13 are formed from layers which the entire radiation detector has in each case. That is, the radiation detector has a first electrode layer E1, an active layer 9 and a second electrode layer E2, which are each arranged parallel in a plane to the reflective surfaces and are structured or spatially separated vertically to the second reflective surface in such a way that with the first electrode layer El, the active layer 9 and the second electrode layer E2 des Radiation detector of the at least one actuator 2 and electrically insulated therefrom, the pyroelectric sensor element S are formed. The first electrode layer E1, the second electrode layer E2 and the active layer 9 of the radiation detector can each be formed in just a single manufacturing step, which significantly simplifies the manufacture of the radiation detector. In addition, the active layer 9 of the actuator 2 and the pyroelectric layer IS of the pyroelectric sensor element 3 are formed in the same plane and have the same composition and layer thickness, so that a high degree of parallelism of the layers with respect to the reflection surfaces can be achieved. In the example of Figures 1 and 2, the active layer 9 of the actuator 2 and the pyroelectric layer 13 of the pyroelectric sensor element 3 are formed from or with doped hafnium oxide, HfC> 2, a mixed hafnium oxide or combinations of these, the dopants in the doped Hafnium oxide aluminum, AI, silicon, Si, germanium, Ge, yttrium, Y, scandium, Sc, gadolinium, Gd, strontium, Sr, lanthanum, La, niobium, Nb, barium, Ba, cerium, Ce, neodymium, Nd, samarium , Sm, Erbium, Er, and / or or Ytterbium, Yb, can be.

Alternatively, only the first electrode layer E1, the second electrode layer E2 and / or the active layer 9 can be designed as a layer of the radiation detector in the radiation detector and arranged parallel to the reflection surfaces and vertically structured or spatially separated in such a way that the respective layer the first electrode layer E1, the second electrode E2 or an active layer 9 of the at least one actuator 2 and electrically insulated therefrom the first electrode layer E1, the second electrode layer E2 or a pyroelectric layer 13 of the pyroelectric sensor element 3 forms. The layers E1, E2, 9 of the at least one actuator 2 and the layers E1, E2, 13 of the pyroelectric sensor element 3 can alternatively also have different compositions and / or layer thicknesses and / or be produced in separate manufacturing steps. The at least one actuator 2 can be designed as a piezoelectric, flexoelectric or electrostrictive actuator, in which the active layer 9 is formed with or from a piezoelectric, flexoelectric and / or electrostrictive material. The pyroelectric sensor element S can be designed as a plate capacitor with a first electrode layer El, a pyroelectric layer IS as the capacitor medium and a second electrode layer E2, the pyroelectric layer 13 being formed with or from one or more pyroelectric and / or ferroelectric materials can be. The sensor area of the pyroelectric sensor element 3, ie the area of the pyroelectric layer 13 of the pyroelectric sensor element 3, can have an area between 100 μm ² and 2 mm ² .

In the example of FIGS. 1 and 2, the resonance chamber 4 is designed as an optical air gap resonator, the distance w of which can be set or changed in a range between 0.5 μm and 35 μm. As a result, the radiation detector can be used in particular for the detection of electromagnetic radiation in the near and medium infrared range. However, radiation detectors with resonance chambers 4 can also be produced which are formed with other resonance media, such as vacuum, nitrogen or noble gases, or the spacing w of which can be set and / or changed in other areas. The resonance space 4 can be formed, for example, by means of a sacrificial layer. An example of a method for producing a micromechanical radiation detector is described in FIG.

In the example of FIGS. 1 and 2, the radiation-permeable substrate 5 is designed in such a way that it transmits the electromagnetic radiation to be detected into the resonance chamber 4 and has a first reflective surface on one surface, which is a flat, partially permeable mirror with a degree of reflection between 85 % and 98% is formed in the wavelength range of the electromagnetic radiation to be detected. For this purpose, the radiation-permeable substrate can consist, for example, of Si, Ge, GaAs, SiGe or InP. The second reflection surface is formed on a surface of a carrier layer 7 of the first electrode layer E1 in such a way that it forms a flat, partially transparent mirror with a reflectance between 85% and 98% in the wavelength range of the electromagnetic radiation to be detected. The carrier layer 11 is for this purpose, for example, made of polycrystalline Si, SiGe or Ge with dopants, such as. B. boron, B, aluminum,

AI, gallium, Ga, indium, In, phosphorus, P, arsenic, As, antimony, Sb, bismuth, Bi, o- which also metals such as aluminum, Al, copper, Cu, cobalt, Co, nickel, Ni, Mo lybdenum, Mo, tantalum, Ta, and / or titanium, Ti, are formed. For simple manufacture of the radiation detector, the carrier layers 7, 11 and the conductor layers 8, 10 in the example shown each have the same composition, but they can also be made of different materials.

For efficient electrical contact, the radiation detector in the case of FIGS. 1 and 2 is ausgebil det with a radiation-permeable substrate 5 which is electrically conductive, such as, for. B. a substrate made of Si, Ge, GaAs, SiGe or InP. The first electrode layer E1 of the radiation detector is formed both on the second reflection surface and in direct contact with the electrically conductive substrate 5. The first electrode layer El, the active layer 9 and the second electrode layer E2 are also structured or spatially separated in defined areas Gl, G2, G3, G4 vertical to the second reflection surface in such a way that the first electrode layer El, the active layer 9 and the second electrode layer E2 of the radiation detector of the at least one actuator 2 and electrically insulated therefrom with the first electrode layer El, the active layer 9 and the second electrode layer E2 of the radiation detector the pyroelectric sensor element 3 are formed, the at least one actuator 2 being formed via the electrically conductive Sub strat 5, Kl and at least one first contact K2 on the second electrode layer E2 can be electrically contacted and the pyroelectric sensor element 3 can be electrically contacted independently via the electrically conductive substrate 5, Kl and at least one second contact K3 on the second electrode layer E2 . For direct electrical contact, the electrically conductive substrate 5 is designed without coatings in an edge region K1 of the substrate 5 around the Fabry-Perot interferometer element. However, alternative electrical contacts between the at least one actuator 2 and the pyroelectric sensor element 3 are also possible.

The radiation detector of the example of FIGS. 1 and 2 can have a control unit, not shown in FIGS. 1 and 2, which is designed to close the active layer 9 of the at least one actuator 2 and / or the pyroelectric layer 13 of the pyroelectric sensor element 3 condition and / or recondition. Alternatively or additionally, the Control unit can also be designed to increase the piezoelectric effect of the active layer 9 of the at least one actuator 2 and / or to increase the pyroelectric effect of the pyroelectric layer IS of the pyroelectric sensor element 3. This can be achieved, for example, by applying a voltage or voltage sequence to the active layer 9 of the at least one actuator 2 and / or the pyroelectric layer 13 of the pyroelectric sensor element 3. An example for the conditioning or reconditioning and the amplification of the piezoelectric or pyroelectric effect is described in the example of FIG. 7, which shows an example of an electrical circuit of a control unit.

In the example of FIGS. 1 and 2, the electromagnetic radiation to be detected can be broadband, external, preferably uniform, pulsed or temporally modulated radiation or broadband, temporally continuous, unpulsed or unmodulated radiation. An externally pulsed or modulated radiation can be detected with the radiation detector at a time constant set distance w of the resonance chamber 4, since the temperature change on the second reflection surface in the case of resonance is caused by the increasing and decreasing intensity of the electromagnetic radiation to be detected . From the amplitude of the measurement signal of the py roelectric sensor element 3, conclusions can be drawn about the magnitude of the temperature change and thus the intensity of the electromagnetic radiation whose wavelength l meets the resonance condition for the set distance w. The measurement can be repeated for different intervals w set to be constant over time, so that, given a sufficient number of measurements, a wavelength-dependent intensity spectrum of the electromagnetic radiation to be detected can be reconstructed from the individual measurements. The distances w can each be set within a range which lies within or corresponds to the free spectral range of the resonance space 4.

Time-constant, unpulsed or unmodulated electromagnetic radiation can be detected with the radiation detector by a temperature change is generated by changing the distance w of the resonance chamber 4, so the radiation detector is operated dynamically. The min- At least one actuator 2 of the example of FIGS. 1 and 2 is therefore designed to continuously, and preferably uniformly, change or tune the distance w of the resonance chamber 4 in a defined continuous tuning range Aw. The pyroelectric sensor element 3 is designed accordingly to continuously detect the change in temperature of the second reflection surface during the change in the distance w. The tuning range Aw can lie in the free spectral range of the resonance space or correspond to it. In the example of FIGS. 1 and 2, the change in the distance w is generated by applying a preferably sinusoidal or cosinusoidal alternating voltage to the active layer 9 of the at least one actuator 2. An alternating current is then detected at the pyroelectric sensor element 3, the amplitude of which is used as a measurement signal. The spectrum of the radiation to be detected in the respective tuning range Aw is reconstructed from the measured amplitude curve using calibration methods in which the measured amplitude curve is compared, for example, with one or more amplitude curves of a known reference radiation.

The radiation detector of the example of FIGS. 1 and 2 also has an optional functional layer 12 on a surface of the radiation-permeable substrate 5 which is opposite or opposite to the first reflection surface. This can, for example, be an antireflection layer for improved radiation coupling of the radiation to be detected into the substrate 5 and / or a wavelength-selective optical layer 12 which is formed, an electromagnetic radiation of a defined wavelength l or an electromagnetic radiation of a defined narrow-band wavelength range in to transmit the substrate 5 and thus into the resonance space 4. As an alternative to a wavelength-selective optical layer 12, the radiation-permeable substrate 5 can also be designed as a wavelength-selective substrate which only transmits electromagnetic radiation of a defined wavelength l or a defined narrow-band wavelength range into the resonance chamber 4.

In the case of externally pulsed radiation, the wavelength selected in each case by means of the wavelength-selective optical layer or a wavelength length of the narrowband wavelength range selected in each case by means of the wavelength-selective optical layer can be detected at a distance w set to be constant over time and which fulfills the resonance condition for this wavelength. In the case of an unpulsed or unmodulated radiation, the corresponding wavelength can be detected by continuously changing or tuning the distance w in a tuning range Aw. The tuning range Aw is a continuous range that includes both a distance w or distances w at which the resonance condition for the selected wavelength or a wavelength of the selected narrow-band wavelength range is met, as well as distances w at which the The resonance condition for the selected wavelength or a wavelength of the selected narrow-band wavelength range is not met. If the distance w is continuously changed or tuned in this tuning range Aw, at least one temperature change is brought about on the second reflection surface.

The tuning range Aw is passed through several times in the example shown in FIGS. 1 and 2 by applying an alternating voltage to the active layer 9 when the distance w is changed, so that a chopper effect is generated by the temperature changes that occur repeatedly. Accordingly, an alternating current is detected on the pyroelectric sensor element, the amplitude of which is used as the measurement signal. The radiation detector can thereby be optimized for a wavelength or selected narrowband wavelength range selected by means of the wavelength-selective optical layer 12 and can be operated without external pulse shapers.

As an alternative or in addition to the functional layer 12, the radiation-permeable substrate 5 can also have a broadband bandpass filter or an edge filter. Such filter layers can be formed, un desired resonance wavelengths, for. B. low resonance wavelengths un below a certain swell _min , hide, ie to blockie ren.

In Figure 3, the transmission behavior of an example of a Strahlungsde detector is shown as a function of the incident wavelength. Here- only a specific, narrow-band wavelength range B1 is allowed to pass through. If a distance between the reflective surfaces of the Fabry-Perot interferometer is now changed, its transmission wavelength is within (Tli) or outside (Tla) of the transmitted area Bl. turned off.

In FIGS. 4 and 6, two examples of detector arrays 14 are shown in a schematic plan view. The detector arrays 14 each have at least two micromechanical radiation detectors whose reflective surfaces, preferably without overlap, are each aligned in one spatial direction. The radiation detectors can be formed in a plane of a radiation-permeable substrate or can be attached to a plane plane of a carrier or chip 15. The radiation detectors can each be arranged at defined positions, be formed identically to one another or have Fabry-Perot interferometer elements with different free spectral ranges of the resonance chambers 4 and / or different wavelength-selective optical layers 12, so that an electromagnetic radiation to be detected is spatially resolved and / or or can be detected in a spectrally resolved or wavelength-optimized manner.

FIG. 4 shows, for example, a detector array 14 that can be used as an imaging detector array. The radiation detectors are arranged in a plurality of rows in a matrix 16. The electrical connections of the actuators 2 and the pyroelectric sensor elements 3 are each connected to bond pads 17, 18, which can be contacted by wires with a housing.

In FIG. 6, the detector array is applied to a CMOS chip (complementary metal-oxide-semiconductor) or a carrier 15 which has a CMOS circuit. This CMOS circuit can, for example, have electrical components for controlling the actuators 2 and / or reading out the measurement signals from the pyroelectric sensor elements 3. The CMOS circuit can in particular be an amplifier or electrical current or voltage sources 19 and multiplexer 20 for controlling the actuators gates 2, as well as analog switch 21 and current, voltage or transimpe dance amplifier 22 and analog-to-digital converter 23 for reading the pyro electrical sensor elements S included. Furthermore, interface electronics 24 and bond pads and / or electrical components of the control device can be part of the CMOS chip.

In Figure 5, a cross section of a further example of a micromechanical detector array 14 is shown in a schematic representation. The second reflection surfaces of the radiation detectors of the detector array 14 are each arranged on a flat surface of an electrically conductive, radiation-permeable substrate 5 of the detector array 14 and forms. The direction of incidence of the electromagnetic radiation to be detected is indicated in FIG. 6 with arrows. The detector array 14 is attached to a CMOS chip 15. As in the example in FIG. 4, this can have a CMOS circuit for radiation detection and / or electrical components for conditioning, reconditioning and / or amplifying the piezoelectric or pyroelectric effect. The electrical contacts between the electrically conductive, radiation-permeable substrate 5 and the CMOS chip 15 can be made by means of "solder bumps"

25, but also by means of wire bond connections 35. The entire component comprising detector array 14 and CMOS chip is placed in an optional housing G and electrically contacted by means of solder bumps 25 or wire bonds.

FIG. 7 schematically shows an example of an electrical circuit of a control unit. The characteristics of the pyroelectric and piezoelectric effect can depend on the electrical history of the respective material. Therefore, the radiation detector and / or the detector array can have a control device which is designed to condition the active and / or the pyroelectric layer 9, 13 or layers and / or to recondition and / or the piezoelectric rule effect of the active layer 9 or layers and / or the pyroelectric effect of the pyroelectric layer 13 or layers to increase hen. The control unit can have a special circuit that is integrated into the pyroelectric sensor element S and is designed to conduct one or more electrical pulses or pulse trains to the piezoelectric layer 9 and / or pyroelectric layer IS or layers. The implementation of such a circuit is shown schematically in FIG. An electrical signal is generated by an integrated pulse generator or waveform generator 26 which is electrically connected to a control circuit 27. The generated electrical waveform or pulse sequence can be changed ver by an amplifier 28 in their amplitude or offset voltage. The amplitude of the generated waveform or pulse sequence rises above the coercive field strength of the piezoelectric and / or pyroelectric material with or from which the respective layer 9, 13 is formed, which in the case of doped hafnium oxide or hafnium oxide mixed oxides in the area is between 0.7 MV / cm to 1.5 MV / cm. The amplitude is lower than the breakdown field strength of the material in the range between 3 MV / cm to 3.5 MV / cm. As a result, the piezoelectric and / or pyroelectric effect of the respective layer can be increased.

Possible pulse trains include square, sine, triangular or sawtooth waveforms in a frequency range from 10 Hz to 1 MHz. The electrical connection is established with the aid of a first analog switch or multiplexer 29. As a result, the pulse sequence or waveform is passed on to a pyroelectric sensor element 3 or an actuator 2, which is selected with the aid of a second analog switch or multiplexer 30. The pulse sequence or waveform can be applied to the respective layer ^{with 10 to 10 6 periods.} This can, for example, take place once when the sensor element is put into operation, and / or at regular time intervals specified by the control electronics, or after a specified number of switch-on processes (conditioning). Furthermore, after a certain operating time or after a certain number of switch-on processes, the conditioning can be repeated, ie reconditioning, in order to compensate for possible degradation processes of the piezoelectric and / or pyroelectric material. By switching the first analog switch or multiplexer 29, the measurement signal of the pyroelectric sensor element 3 after conditioning or Reconditioning can be read out. For this purpose, the pyroelectric sensor element S is connected to an amplifier circuit 31 and an analog-digital converter 32 and the digital control circuit 33 and connection pads 34. Alternatively, the pyroelectric sensor element 3 can also be electrically connected to the first analog switch or multiplexer 29 directly via a connection pad.

In certain pyroelectric and / or ferroelectric materials, the expression of the pyroelectric effect is also dependent on the electric field. In order to increase the pyroelectric coefficient, a direct voltage can therefore also be applied to the pyroelectric layer 13 of the pyroelectric sensor element 3. For this purpose, a DC voltage source is connected in series with the amplifier circuit 31. The pyro-electrical coefficient of Si-doped hafnium oxide HfC> 2 can be increased to a coefficient of -140 pC / m ² K, for example, at a direct voltage of 1.5 V.

In Figure 8, a production method of an example of a micromechanical radiation detector is shown schematically. The method comprises the following steps, the numbering of which is identical to the numbering of the respective representations in FIG. 8:

1. Deposition of a first sacrificial layer OS1 on a flat surface of an electrically conductive, radiation-permeable substrate 5 using an ALD, CVD or PVD process

2. Structuring or partial removal of the first sacrificial layer OS1 with a lithographic method, so that the first sacrificial layer has the dimensions or the base area of a resonance space 4

3. Deposition of a first carrier layer 7 on the first sacrificial layer OS1 and the radiation-permeable substrate 5 using an ALD, CVD or PVD method

4. Deposition of a first conductor layer 8, an active layer 9 and a second conductor layer 10 on the first carrier layer 7 using an ALD, CVD and / or PVD method

5. Deposition of a second carrier layer 11 and a second sacrificial Layer OS2 on the second conductor layer 10 with an ALD, CVD and / o the PVD method

6. Structuring or partial removal of the second sacrificial layer OS2 with a lithographic process in areas G3 in FIGS Isolate the outer edges of the pyroelectric sensor elements 3 to be formed electrically from one another, and in edge regions Gl, G2 in FIGS. 1 and 2 around the outer edges of the actuators 2 to be formed

7. Removal of the second carrier layer 11 and the second conductor layer 10 with a wet chemical etching process or a vapor etching process in areas G3 in FIGS. 1 and 2, which form the second conductor layer 10 and the second carrier layer 11 of the actuators 2 to be formed and the pyroelectric Sensor element 3 on the outer edges of the pyroelectric sensor element 3 to be bil ding electrically isolate from each other, as well as in edge areas Gl, G2 in Fig. 1 and 2 around the outer edges of the actuators 2 to be formed, so that electrical contacts K2, K3 for the actuators to be formed 2 and the sensor element 3 to be formed are formed

8. Removal of the second sacrificial layer OS2 using a wet chemical etching process, a steam etching process or a dry etching process

9. Deposition of a third sacrificial layer OS3 using an ALD, CVD and / o the PVD process

10. Structuring the third sacrificial layer OS3 with a lithographic process and removal of the carrier layers 7, 11, conductor layers 8, 10 and the active layer 9 in one or more etching steps with a wet chemical etching process, a vapor etching process and / or a dry etching process in areas G4 in 1 and 2, which electrically isolate the actuators 2 to be formed and the pyroelectric sensor element 3 to be formed paral lel to the outer edges of the active layer 9, 13 of the pyroelectric sensor element 3 to be formed, and in areas G2 in FIGS 2 parallel to the outer edges of the actuators 2 to be formed and edge regions K 1 in FIGS. 1 and 2 of the substrate 5 permeable to radiation

11. Removal of the first sacrificial layer OS1 and the third sacrificial layer OS3 in a wet chemical etching process or a vapor etching process, with the removal of the first sacrificial layer OS1, a resonance space 4 between the electrically conductive substrate 5 and the first carrier layer 7 is formed

12. Application of optional functional layers 12 on a surface of the radiation-permeable substrate 5 opposite the resonance chamber 4.

The respective layers are preferably designed as planar layers or can be planarized after their formation.

Features of the various exemplary embodiments disclosed only in the exemplary embodiments can be combined with one another and claimed individually, regardless of the respective example shown.

Claims

1. Micromechanical radiation detector comprising a Fabry-Perot interferometer element (1) with at least one actuator (2) and a pyroelectric sensor element (S), wherein the Fabry-Perot interferometer element (1) is formed with a first reflective surface and a second reflective surface optical resonance chamber (4), the first reflection surface being formed on a surface of a substrate (5) which is transparent to radiation for an electromagnetic radiation to be detected and is arranged plane-parallel at a distance w from the second reflection surface, the at least one actuator (2) is formed on the second reflection surface of the resonance chamber (4) and has a first electrode layer (El), an active layer (9) and a second electrode layer (E2), which are formed and arranged, the actuator (2) when applying a gene electrical voltage to the active layer (9) via the first electrode layer (El) and the second electrode layer icht (E2) to be mechanically deformed in such a way that the distance w can be set and / or changed in a defined manner, the pyroelectric sensor element (S) has a pyroelectric layer (IS) and is designed to detect a temperature change by means of the pyroelectric layer (13) which is transmitted by absorption of an electromagnetic radiation to be detected, which is transmitted through the radiation-permeable substrate (5) into the resonance space (4), to the second reflection surface depending on the wavelength l of the electromagnetic radiation to be detected, the distance w and / or a change in the distance w is effected.

2. Radiation detector according to claim 1, characterized in that the at least one actuator (2) is designed as a bending beam which is arranged with a longitudinal axis parallel to an edge of the second Reflexi onsfläche and / or with a longitudinal axis parallel to egg ner edge and / or surface of the pyroelectric sensor element (3) is arranged.

3. Radiation detector according to claim 2, characterized in that the first electrode layer (El) and the second electrode layer (E2) of the at least one actuator (2) have different layer thicknesses, compositions and / or mechanical properties.

4. Radiation detector according to one of claims 2 or 3, characterized in that the bending beam is formed with the active layer (9) whose composition and / or mechanical properties are in the direction of the optical axis of the resonance chamber (4) or the longitudinal axis of the Bending beam change continuously or step by step in such a way that the active layer (9) and thus the at least one actuator (2) deform when an electrical voltage is applied to the active layer (9) in the direction of the optical axis of the resonance chamber (4).

5. Radiation detector according to one of the preceding claims, characterized in that the at least one actuator (2) is designed as a piezoelectric, flexoelectric and / or electrostrictive actuator (2), the active layer (9) with or from a piezoelectric, flexoelectric and / or electrostrictive material is formed.

Radiation detector according to claim 5, characterized in that the active layer (9) of the at least one actuator (2) and / or the pyroelectric layer (13) of the pyroelectric sensor element (3) with or made of a pyroelectric and / or ferroelectric material, in particular with or is / are formed from a doped hafnium oxide or a hafnium mixed oxide.

7. Radiation detector according to claim 5 or 6, characterized in that the radiation detector has an active layer which is formed with or from a pyroelectric and / or ferroelectric material in a plane parallel to the second reflective surface and is so structured and / or vertical to the second reflective surface It is spatially separated that the active layer (9) of the at least one actuator (2) and a pyroelectric layer (13) of the pyroelectric sensor element (3) electrically isolated therefrom are formed with the active layer (9) of the radiation detector.

8. Radiation detector according to one of claims 5 to 7, characterized in that the radiation detector has a control unit which is designed to include the active layer (9) of the at least one actuator (2) and / or the pyroelectric layer (13) of the To condition and / or recondition pyroelectric sensor element (3), to increase the piezoelectric effect of the active layer (3) of the at least one actuator (2) and / or to increase the pyroelectric effect of the pyroelectric layer (13) of the pyroelectric sensor element (3) increase.

9. Radiation detector according to one of the preceding claims, characterized in that the actuator is designed to continuously change the stand w in a tuning range Aw.

10. Radiation detector according to one of the preceding claims, characterized in that the substrate (5) is designed to be wavelength-selective or has a wavelength-selective optical layer (12), so that electromagnetic radiation with a defined wavelength l or a defined narrowband wavelength range in the Resonance chamber (4) is transmitted.

11. Detector array having an arrangement of micromechanical radiation detectors according to one of claims 1 to 10.

12. Radiation measurement method in which An electromagnetic radiation to be detected is transmitted through a substrate (5) that is radungsransparent for the electromagnetic radiation to be detected into a resonance space (4) of a Fabry-Perot interferometer element (1) formed with a first reflective surface and a second reflective surface, the first reflective surface with a surface of the radiation-permeable substrate (5) at a distance w from the second reflective surface is formed, the distance w between the first reflective surface and the second reflective surface of the resonance chamber (4) is set and / or defined by means of at least one actuator (2) is changed, wherein the actuator (2) is formed on the second reflection surface of the resonance chamber (4) and has a first electrode layer (El), an active layer (9) and a second electrode layer (E2), which are formed out, the actuator (2) derar when an electrical voltage is applied to the active layer (9) t mechanically deform so that the distance w can be set and / or changed in a defined manner, a temperature change is detected by means of a pyroelectric sensor element (S) which is caused by absorption of the electromagnetic radiation to be detected on the second resonance surface as a function of the Wavelength l of the electromagnetic radiation, the distance w and / or a change in the distance w be acts, wherein the pyroelectric sensor element (S) has a pyroelectric layer (IS) and is formed, the temperature change by means of the pyroelectric layer (13 ), and from the temperature change, the distance w and / or the change in the distance w, the intensity and / or wavelength l of the electromagnetic radiation to be detected is / are determined.