Core-shell structure for bolometer detector

Abstract

The present invention relates to a core-shell structure for a bolometer detector, wherein - The core (1) is made of a metal element and forms an absorber element for incident electromagnetic radiation to be detected; - The shell (2) is made of an optical dielectric material and covers the metal core, The above core / shell structure provides a thermometer function for measuring the temperature of the absorbent.

Description

Technology Field

[0001] The present invention relates to a photodetector, specifically a bolometric detector used primarily in the long wavelength and THz regions of infrared light. The present invention relates particularly to an optical antenna designed for use in infrared photodetectors and intended for use in detection arrays for imaging applications. Detectors used in thermal or infrared imaging are traditionally implemented in the form of an array of basic detectors that form image points or pixels in one or two dimensions. Accordingly, pixels are basic detectors assembled into a 1D or 2D array to capture an image of a scene, and the pixel size or pixel period is the period of the 1D or 2D array of pixels forming a focal plan array (FPA).

[0002] The present invention relates particularly to a core-shell structure that supports two basic functions of a bolometer: (1) a function of absorbing incident electromagnetic radiation by an optical antenna constituting the core, and (2) a function of measuring the temperature of an absorber by the thermal properties of the shell (e.g., electrical resistance that changes with temperature). Background Technology

[0003] A bolometer is used to measure the power of incident electromagnetic radiation. As illustrated in FIG. 1, the bolometer consists of an assembly comprising a support substrate (S) holding a Read Out Integrated Circuit (ROIC embedded within the support substrate (S)) and a reflector (R), an element (10) for absorbing incident radiation, and a temperature measuring element (20) in thermal contact with the absorbor, which is positioned away from the reflector (R) and typically at the 1 / 4 position of the incident wavelength where the electric field of the standing wave is maximum. The heat generated by the absorbor (10) due to the incident radiation enables the heat generation of the temperature measuring element and the measurement of this heat generation. This measurement is provided by the ROIC. To ensure thermal insulation of the assembly of the absorbor element and the temperature measuring element, they are suspended under vacuum over the substrate (S) via thermally insulating arms (40). These arms also provide mechanical support and electrical connection between the thermometer and the ROIC. FIG. 1 schematically illustrates such a bolometer detector. A support substrate (S) typically includes means for sequentially addressing basic detectors and means for electrically exciting and preprocessing electrical signals generated from these basic detectors.

[0004] These detectors primarily utilize silicon technology and operate at room temperature. This enables their manufacturing and operation at a very advantageous cost compared to other photodetectors, such as quantum detectors, which require cooling for long-wavelength detection.

[0005] To measure thermometer temperature, detectors such as those described in WO-A-2021009421 use changes in physical parameters of a suitable material or material assembly(s) that vary with temperature, typically around 300K. In the specific case of the most commonly used bolometer detectors, this physical parameter is electrical resistivity, but other parameters such as dielectric constant values, polarization, thermal expansion, and refractive index may also be used.

[0006] Therefore, basic detectors or resistive microbolometers are commonly used, particularly in civilian applications (home automation, automotive driving or flight assistance, night vision, fire detection, etc.).

[0007] These microbolometers are particularly suitable for infrared detection, more specifically for the 8-14 μm spectral range (also referred to as LWIR or Band III), which corresponds to one of the atmospheric transmission bands where heat emission from objects or organisms can be observed at approximately room temperature.

[0008] These bolometers can operate at room temperature, that is, without needing to be cooled to very low temperatures, in contrast to detection devices referred to as "quantum detectors" or "cooled detectors" that operate only at very low temperatures.

[0009] Such microbolometers comprise a membrane in the form of an absorber-thermistor assembly consisting of an absorber element layer, a temperature-measuring element or thermistor layer forming good thermal contact with the absorber element, and a support substrate on which the membrane floats. The microbolometer also includes thermally insulating arms and electrical connection elements to electrically contact the temperature-measuring element with contact pads on the support substrate. The support substrate, for example made of silicon, provides mechanical rigidity to the resistance reading circuits of the microbolometer and the temperature-measuring element. The support substrate is typically covered with a reflector to form a standing wave with the incident radiation. It is worth noting that even without a reflector, it can provide reflections that are sufficiently large for some applications. The absorption of incident photon flux by the absorber tends to increase its temperature according to Joule's law. The thermistor enables the electrical measurement of this temperature. Thermal insulation of the absorber-thermistor assembly with respect to the support substrate (by means of a thermal insulation arm and an insulating vacuum maintained around the absorber-thermistor assembly) improves the sensitivity of the device by increasing the temperature rise of the absorber-thermistor assembly for a given photon flux.

[0010] In the prior art, the absorber element may consist of a thin metal layer, but it is important to note that other components of the floating membrane (thermometer, insulating arm) also contribute to absorption, albeit to a small extent. A thermistor is a resistor composed of a material, for example, vanadium oxide (VOx) or amorphous silicon (a-Si), which is generally selected due to the large change in resistivity with temperature. The thermal insulating arm consists of mechanical and electrical links, for example, exhibiting low thermal conductance, and positions the absorber-thermistor assembly in a floating state in an insulating vacuum on a substrate holding a reflector.

[0011] To obtain a field of view for these detectors, a scene is captured on an array of basic detectors through a suitable optical system. To acquire electrical signals that form an image of the temperature reached by each basic detector, electrical stimulation tuned by the ROIC is applied to each basic detector or each row of these detectors. This signal is processed somewhat finely by the ROIC and then optionally processed by an external electronic device to generate an image of radiation emitted from the observed scene, commonly referred to as a thermal image.

[0012] Currently available microbolometers are primarily limited by trade-offs between velocity and sensitivity and reduced pixel spacing.

[0013] The operation of a bolometer can be divided into the following three stages:

[0014] 1. Incident radiation is absorbed by an infrared radiation absorber that is insulated from the outside world (excluding the thermometer), and heat is generated accordingly.

[0015] 2. This heat is transferred to a thermometer placed in good thermal contact with the absorbent.

[0016] 3. The measurement of the temperature rise (ΔT) of a thermometer is a measurement of the incident flux power (Pinc), which makes it a photodetector.

[0017] Therefore, to increase the sensitivity of a bolometer, the temperature of the thermometer must be increased. That is, for a given absorber, the thermal resistance (Rth) of the thermal insulation (insulating arm, vacuum, and radiation) separating it from the outside world must be increased, and the temperature difference with the support is ΔT = Rth Pinc, where Pinc is the incident power. On the other hand, to increase the speed of the bolometer, the thermal resistance must be reduced, because the time constant (τ) of the bolometer is denoted as τ = Rth Cth, where Cth is the thermal capacity of the absorber-thermometer assembly. Thus, the design of a bolometer is based on a trade-off between speed and sensitivity with a merit factor of ΔT / τ = Pinc / Cth. Therefore, it is desirable to minimize the thermal capacity (Cth) to shift this trade-off toward a faster and / or more sensitive bolometer.

[0018] As previously mentioned, bolometers currently available on the market take the form of absorber-thermometer assemblies, typically consisting of a membrane (continuous or structured) covering the largest possible portion of the pixel to optimize absorption; this results in a significant value for the thermal capacity (Cth) of the assembly. Consequently, the trade-off between speed and sensitivity results in slow bolometers (acquisition frequency 30–50 Hz) and low sensitivity (NETD 40–50 mK). NETD stands for Noise Equivalent Thermal Difference. This parameter corresponds to the smallest temperature difference detectable in the scene by the detector. To reduce thermal capacity, WO2021009421 proposed that the surface of the thermometric material be less than 0.4 times the surface of the membrane, and that a recess be formed (i.e., within the absorber) in the region without the thermometric material. Such membranes reduce thermal capacity for a constant thermal resistance. However, this literature does not propose any solution for the surface problems of the arm (Rth) and membrane (ΔT) respectively, which constrains the trade-off between speed and sensitivity, especially for small pixel sizes.

[0019] Current practice also involves reducing pixel size from approximately 50–100 μm in the 1990s to about 10 μm today. This allowed for a reduction in detector size (leading to lower manufacturing costs). In the same manner, the number of pixels was increased. Progress is slow with this practice, which has persisted for decades, because every time a new pixel spacing value is introduced, the trade-off between velocity and sensitivity must be completely re-evaluated. As the number of pixels in a detector array increases, the incident electromagnetic energy flux per detector decreases. Therefore, to maintain pixel sensitivity, the space occupancy of the absorber must be increased while the pixel area is reduced. This makes it difficult to provide thermally insulated arms that meet the desired velocity-sensitivity trade-off.

[0020] Literature FR-A-2 977 937 proposes a bolometer detector for the thermal detection of incident radiation in a given spectral band, comprising a support substrate and a microbolometer assembly of a given size arranged in an array form, wherein each microbolometer comprises a membrane floating on the support substrate by means of a support element, the membrane comprises an absorber element for the incident radiation, and a thermometric element in thermal contact with the absorber and is electrically insulated from the absorber element. It also comprises an electrical connection element between the support substrate and the thermometric element. The absorber element is composed of a metal-insulator (dielectric)-metal (MIM) structure comprising a stack of three overlapping layers having a submicron thickness, namely a first metal layer, a dielectric material layer, and a second metal layer. This MIM structure is adapted to form an optical antenna and to generate plasmon resonance with the incident radiation for at least one wavelength of the spectral band, and the microbolometer surface covered by the membrane is less than half of the total surface of the microbolometer.

[0021] In such bolometers, the MIM structure is better excited when the formed antenna is placed at one of the maximum values ​​of the magnetic field of the standing wave generated by the reflector, that is, the shortest one is placed at half the length of the reflector wavelength. This distance is not compatible with conventional microbolometers.

[0022] In Marina Yakovleva's paper "Novel concepts for theoretical and applied problems of electromagnetism. Part 1: Absolute representation of the fields in the spacetime map. Part 2: Low-volume optical antennas for bolometer applications", Electromagnetism. Universite Paris-Saclay, 2021. English. NNT: 2021UPASP129.tel-03679218, an insulator-metal-insulator (IMI) structure is described as an excellent optical antenna for infrared absorption in bolometers. The structure studied consists of a gold layer sandwiched between two dielectric materials (insulators), one of which is a silicon membrane, and the top layer is air or vacuum. The studied behavior of this test structure was generalized to other materials through general laws of physics. Analysis results show that the IMI structure can be used in the form of a periodic array of IMI antennas located at a distance of about λres / 4 (i.e., typically 2.5 μm for the 8-14 spectral band) over a reflector held by a substrate, and that total absorption can be obtained by an antenna acting as an electromagnetic radiation absorber element extending over part of the antenna period.

[0023] Although different types of optical antennas (MIM structures with different geometric structures) have been studied, none provide satisfactory results regarding the reduction of antenna volume and the consequent reduction in thermal capacity.

[0024] Consequently, the objective of the present invention is to provide a design of a structure that provides a small footprint within a pixel, which is suitable for precise temperature measurement and allows the electromagnetic radiation absorber element to maintain a low thermal capacity while providing space for more efficient thermal insulation arms.

[0025] For this purpose, the first object of the present invention is a core-shell structure for a bolometer detector, wherein

[0026] - The core is composed of a metal element to form an absorber element for incident electromagnetic radiation to be detected, and

[0027] - The shell consists of an optical dielectric material covering a metal core, and

[0028] The above core / shell structure provides a thermometer function for measuring the temperature of the absorbent.

[0029] Advantageously, the core-shell structure is a structure that supports the two basic functions of a bolometer:

[0030] (1) A function of absorbing incident electromagnetic radiation by an IMI (Insulator-Metal-Insulator) antenna composed of metal elements forming a core, and

[0031] (2) Function to measure the temperature of the absorbent.

[0032] Preferably, this core-shell structure is suspended on a substrate covered with a reflector. However, the core / shell structure may be placed on a wider support structure, for example, a structured membrane, or even, the lower part of the shell may be part of such a support.

[0033] The IMI antenna is a metallic part of a core-shell structure and provides the absorption function of the core-shell structure.

[0034] Advantageously, the optical antenna enables absorption within a core-shell structure. However, at resonance, the optical antenna concentrates the electromagnetic field into a small volume around it, which, on the one hand, increases absorption within the metal (Joule effect), and on the other hand, increases absorption within the dielectric material (e.g., shell) when the imaginary part of the refractive index of this optical dielectric material has a non-zero value.

[0035] The outer part of the core-shell structure (i.e., the shell), made of an optical dielectric material, may continuously cover all sides of the IMI antenna or may cover only a part thereof.

[0036] Optical dielectric materials refer to materials in which the real part of the permittivity has a positive value in the wavelength band of interest (frequencies greater than 10 THz). In addition, these materials allow charge to flow when a low-frequency (less than 10 kHz) bias voltage is applied. Semiconductor materials are representative optical dielectric materials, as described, for example, for doped silicon in the literature S. Basu, BJ Lee, and ZM Zhang, Infrared Radiative Properties of Heavily Doped Silicon at Room Temperature, Journal of Heat Transfer, 132, 023301 (2010), doi: 10.1115 / 1.4000171.

[0037] Optical dielectric materials provide both functions of a core-shell structure: field confinement for superior absorption and electrical resistance for thermometers.

[0038] The core-shell structure according to the present invention provides an optical antenna with significantly reduced volume and occupied area while maximizing thermal contact between a shell and a metal core that provide a temperature measurement function. Since the shell is in good thermal contact with the absorber element, this core-shell structure provides reliable measurement of the IMI antenna temperature.

[0039] A bolometer equipped with an IMI antenna has maximum sensitivity when the antenna is located at a distance of about 1 / 4 wavelength from the bolometer reflector, which is compatible with current bolometer technology.

[0040] The core-shell structure has characteristics that are configurable, in particular, according to the following:

[0041] Types of metals constituting metal elements;

[0042] Geometric shape of the above metal element;

[0043] Types of optical dielectric materials constituting the shell;

[0044] The thickness of the shell covering the electromagnetic radiation absorber element.

[0045] Core-shell structured IMI antennas provide multiple degrees of freedom to adjust antenna characteristics according to the needs of the intended application.

[0046] The geometric shape of the IMI antenna defines the spectral response. The length (L) of the IMI antenna (length of the metal element) allows for the definition of a resonant wavelength (λres) that can be approximated by the following equation:

[0047] λres 2L * neff, where neff is the effective refractive index of the mode.

[0048] In its simplest geometric form, the IMI antenna takes the shape of a parallelepiped bar with a rectangular, square, or elliptical cross section. The absorption of the antenna depends on its width and thickness. These parameters are controlled as a function of the period value of the antenna array to absorb 100% of the incident radiation at resonance (critical coupling conditions).

[0049] The selection of the metal for the core also affects the resonance wavelength and peak width.

[0050] The above metals are metals that support surface plasmon polariton (SPP) modes, such as silver, gold, copper, aluminum, doped aluminum, aluminum alloys, titanium, and titanium nitride. Aluminum is preferred for silicon technology in bolometers.

[0051] The core-shell structure has the following form:

[0052] A rod shape designed for applications requiring sensitivity to the polarization of incident light, or a cross, "L" shape, "V" shape, disc, or square shape designed for applications requiring insensitivity to the polarization of incident light.

[0053] The core-shell structure according to the present invention provides an optical antenna having a reduced length. The optical dielectric material is characterized by an optical index with a real part greater than 1. Since this material surrounds the IMI antenna, the effective refractive index (neff) of the mode is significantly increased compared to an IMI antenna without a shell, and accordingly, the length of the IMI antenna is shortened for a given resonant wavelength. The higher the real part of the refractive index of the optical dielectric material, preferably higher than 1.5, the smaller the antenna length becomes.

[0054] As a result, the length of the core-shell structure according to the present invention is reduced compared to a standalone IMI antenna, while the occupied area increases slightly but remains at a negligible level (i.e., a few percent of the pixel area).

[0055] Since the shell is a layer of optical dielectric material, it can also provide a temperature measurement function. This shell, which forms good thermal contact with the core, provides a core-shell structured thermometer function either alone or in combination with the core.

[0056] According to one embodiment of the present invention, a metal element provides a temperature measurement function by means of electrical characteristics of the metal element, such as electrical resistance that changes with temperature.

[0057] According to one embodiment of the present invention, the shell provides a temperature measurement function by means of electrical properties of the optical dielectric material forming the shell, such as electrical resistance that changes with temperature. The optical dielectric material may be selected from materials whose resistivity changes significantly with temperature, namely optical dielectric materials having an appropriate resistance temperature coefficient (TCR), such as amorphous silicon. The thermometer function is provided by the electrical resistance of the optical dielectric material forming the shell that changes with temperature.

[0058] According to another embodiment of the present invention, a thermometer function is provided by modifying the electrical and optical properties of the shell and / or core by modifying at least a portion of the optical dielectric material, for example, the shell portion closest to the IMI antenna, through treatments such as heat treatment, doping, or alloying. This portion has a temperature measurement function for other portions of the shell extending to the support, electrical access path, and insulating arm.

[0059] Optical dielectric materials preferably have a refractive index greater than 1.5, such as germanium, silicon, silicon / germanium alloys, or vanadium oxide. From an electromagnetic perspective, Si, Ge, and Si / Ge are the most advantageous materials, and from a TCR perspective, VOx is the most advantageous material.

[0060] Furthermore, the shell covering the IMI antenna may have a constant thickness. Changing the shell thickness changes the effective refractive index (neff) of the mode, the volume of the optical antenna, and consequently the thermal capacity of the bolometer incorporating the core-shell structure. Thus, the thickness of the optical dielectric material layer is within the range of 0 to several hundred nanometers, typically when the antenna cross-section of the IMI antenna is small and typically several tens of nanometers.

[0061] Controlling the shell thickness provides high flexibility in core-shell structural design for bolometer applications. The shell thickness is a free parameter that allows the definition of the following:

[0062] (1) Thermal capacity of a core-shell structure according to the desired application,

[0063] (2) The electrical resistance of the thermometer when the shell material forms the thermistor element.

[0064] In addition, the thickness of the shell may not be uniform.

[0065] According to one embodiment of the present invention, the core-shell structure has an electrical insulator interposed between a metal core and an optical dielectric material shell, forming a double shell structure. Such a core-shell structure is referred to as a double shell structure. This electrical insulator layer enables more precise measurement of the electrical resistivity of the shell by reducing the portion of current circulating within the metal. In practice, without this insulating layer, the measurement of the electrical resistivity of the shell is affected by the metal element (core): a significant portion of the measured current circulates within the metal rather than in the shell.

[0066] The electrical insulating layer is implemented by introducing a thin layer of insulating dielectric material, such as SiOx, SiNx, AlOx, ZnS, ZnSe, or other materials exhibiting similar electrical properties, between a metal core and an optical dielectric material shell. In this way, the measurement current circulates only within the shell; and since the TCR of the shell material is higher than the TCR of the metal, the influence of temperature during measurement will be stronger.

[0067] It is important to note that the introduction of nitride or oxide-based electrical insulating materials significantly alters the electromagnetic behavior of the core-shell structure. In fact, the refractive index of these materials is lower than that of germanium (n > 4) or silicon (n > 3.7) (typically between 1.4 and 2). This results in the amplification of the electromagnetic field within the insulating material, while adversely affecting other materials within the core-shell system. Furthermore, some of these materials, particularly SiO2, have a near-zero permittivity at specific wavelengths (8 to 14 µm) within the spectral range of thermal imaging equipment. This is the ENZ effect, which suppresses the resonance of the optical antenna, thereby enabling the suppression of absorption in the core-shell structure. This effect can be useful for blocking absorption in specific spectral bands. Conversely, in the case of a germanium shell, it is preferred to use other materials, such as silicon, for electrical insulation between the shell and the core (IMI antenna). The silicon-germanium heterojunction exhibits a large discontinuity in the valence band for thermal energy kT, allowing holes to be retained within the germanium shell.

[0068] As mentioned above, depending on whether the optical dielectric material has a suitable TCR, the shell of the core-shell structure can provide a thermometer function, but this temperature measurement function can also be provided in other ways. In fact, the shell and / or core can provide a temperature measurement function by the following:

[0069] - PN junction and Schottky junction

[0070] - Thermoelectric effect (Seebeck effect)

[0071] - Pyroelectric effect.

[0072] Therefore, if the optical dielectric material of this shell is a semiconductor (e.g., silicon or germanium), it is possible to provide a Schottky junction between the metal of the IMI antenna and the optical dielectric material of the shell by locally treating this material. This enables temperature measurement by utilizing the exponential dependence of the current measured at a given voltage with respect to temperature.

[0073] In a core-shell structure with a double shell, the PN junction between the two shells, formed by N-type doping of the inner shell (electrical insulator) and P-type doping of the outer shell (optical dielectric material), enables precise measurements due to the same exponential dependence of current on temperature. In this case, the bandgap change can be coupled with the doping change, such as in an N-type doped silicon-P-type doped germanium heterojunction.

[0074] As mentioned earlier, integrating a temperature measurement function into the shell offers two significant advantages:

[0075] - Since heat generation (Joule effect emission, the depth of which is limited by the skin effect) is localized across the entire surface of the metal core (antenna IMI), thermal contact between the metal core and the shell is optimized. It should also be noted that if the optical dielectric material is an absorber (where the imaginary part of the refractive index is not zero), heat generation is localized within the "thermometer" itself.

[0076] In any case, because the thickness is thin, the temperature inside the shell is uniform on a constant measurement time scale. Consequently, the temperature rise of the IMI antenna caused by absorbed infrared radiation can be precisely measured, for example, by measuring the electrical resistance of the shell, and this electrical resistance depends on the geometric shape of the shell and the type of optical dielectric material (intrinsic properties, degree of doping) constituting the shell.

[0077] Advantageously, the optical dielectric material layer or shell surrounding the metal element can also be used as a mechanical support and allows the IMI antenna to be held in a fixed position relative to other antennas (maintaining coupling with them) and to be held in a fixed position relative to the reflector within the bolometer detector (position relative to the formed standing wave).

[0078] The optical dielectric material of the shell can be configured to form extensions beyond both ends of the core-shell structure to provide mechanical support and insulation functions for the core-shell structure.

[0079] Accordingly, the shell exhibits a form extending along the longitudinal axis of the optical antenna beyond both ends of the antenna to extend the mechanical function of the optical antenna, contribute to the thermal insulation of the core-shell, and enable electrical connection between the temperature measurement element and the readout integrated circuit. These extensions may be implemented with a geometric shape different from that of the shell (e.g., different cross-section, different length, or different shape) and / or so that the optical dielectric material has modified electrical and / or thermal properties (e.g., by doping the optical dielectric material to control the thermal resistivity of the material).

[0080] Furthermore, the extensions of the shell allow the core-shell structure to be connected to support elements to maintain it within a plane at a fixed distance above the reflector.

[0081] IMI antennas with a rod shape are used in applications requiring such polarization sensitivity because their response is highly sensitive to the polarization of the incident light.

[0082] For applications requiring insensitivity to the polarization of incident light, the core-shell structure according to the present invention can exhibit sensitivity to both components of the electric field within the structural plane, such as a structure having a shape such as a cross, "L", "V", a disc, or a square, as can be seen in FIG. 13.

[0083] The core-shell structure according to the present invention provides an advanced method for developing a bolometer detector with enhanced integration potential.

[0084] The second object of the present invention is a bolometer detector for detecting electromagnetic radiation, characterized by including a support substrate and at least one core-shell structure per pixel, wherein the core-shell structure is composed of a metal element forming an electromagnetic radiation absorber element, the metal element forms the core of the core-shell structure, and the shell is composed of an optical dielectric material covering the metal element, the core / shell structure provides a thermometer function for measuring the temperature of the absorber, and the core-shell structure is floated on the support substrate by means of a support means.

[0085] Accordingly, the structure and form of the core-shell structure according to the present invention advantageously provide a bolometer detector in which the pixel area occupied by the absorber element is significantly reduced compared to a conventional bolometer detector, and this enables the use of multiple optical antennas within the same detector, and thereby within the same pixel.

[0086] When the pixel size is larger than or close to the operating wavelength, the bolometer may include two or more core-shell structures within a single pixel.

[0087] In a core-shell structure, extensions of the shell enable electrical connection between the core / shell structure and the read integrated circuit integrated on the substrate.

[0088] The detector includes electrical connection elements for connecting the core-shell structure to a support substrate comprising a read integrated circuit (ROIC) embedded within a support for temperature reading within the core-shell structure. The substrate elements for the core-shell structure include thermal isolation arms and pillars comprising at least an electrically conductive material to ensure electrical contact between the temperature measuring element and the electrical connection pads of the ROIC.

[0089] The insulating arm is a high thermal resistance element that enables the maintenance of the floating structure, electrical connection between the ROIC and the core-shell structure thermometer element, and thermal insulation. The pillar is a vertical structure that (1) positions the floating structure (the core-shell structure of the present invention) at the correct distance from the reflector (R) and (2) enables electrical contact between the insulating arm and the ROIC. The pillar is generally metallic. Pillars are present at at least two corners of the pixel corresponding to the two electrical contacts required for measurement, and these also ensure the stability of the floating structure.

[0090] Electrical connections and, more generally, thermal insulation arms absorb incident radiation. This is considered a drawback of conventional bolometers. The insulation arm reduces optical absorption due to the funneling effect, which concentrates the electromagnetic field near the antenna. The funneling effect may also lead to a reduction in optical leakage through the substrate. This reduction in parasitic absorption and leakage increases useful absorption, thereby increasing the heat generated by the thermometer. In other words, an improved signal is expected.

[0091] As mentioned earlier, changes in the thickness of the side layer of the optical dielectric material forming the shell cause changes in the antenna volume, which in turn causes changes in the bolometer thermal capacity.

[0092] The integrated structure of this core-shell architecture optimizes the following:

[0093] a. Reduction in the volume of the "hot" portion of the bolometer, i.e., the heat capacity. The IMI antenna forming the core portion of the core-shell structure has a smaller volume than that of conventionally presented bolometer absorber antennas or bolometer absorbers of the latest technology. As a result, the detector according to the present invention can re-examine the trade-off between speed and sensitivity to derive a faster detector, a more sensitive detector, or a faster and more sensitive detector.

[0094] b. Optimization of thermal contact between the absorber element (the "core" part of the core-shell system) and the thermometer (the "shell" part of the same system).

[0095] c. Possibility of increased thermal resistance of the insulating arm due to widened free space within the pixel.

[0096] d. Possibility of reducing pixel size while maintaining both absorption efficiency close to 1 and efficient thermal insulation at resonance thanks to sufficient clearance around the core-shell structure.

[0097] e. Possibility of placing multiple core-shell structures within each pixel to expand the detection area and / or to respond to various wavelengths.

[0098] f. The pixel area occupied by the absorber element is significantly reduced compared to conventional bolometer detectors, providing more space for the isolation arm. This last point is important as it facilitates pixel pitch reduction, which is a major goal for all manufacturers.

[0099] This volume reduction is very useful as it decreases by orders of magnitude compared to existing commercial products, and consequently, the thermal capacity of the detector is also reduced.

[0100] The spectral response of a bolometer, which was nearly flat in conventional structures, can be structured through the present invention. Structuring according to requirements is possible by combining multiple antennas.

[0101] For example, various applications can be envisioned, such as (1) a multispectral camera (or "color" camera) in the infrared region, and (2) the removal of parts of the spectrum that are considered troublesome during imaging in the MWIR band (3 - 5 μm) (e.g., the band around 4.2 μm due to CO2 absorption).

[0102] At resonance, under critical coupling conditions, the absorption rate of the antenna reaches 100% of the incident power per period, compared to 70-80% of the current bolometer. Critical coupling is a condition where the incident power is equal to the absorbed power, so that the power reflected in the far field becomes zero. For a given incident power and antenna period, this condition can be achieved by adjusting the geometric parameters of the core-shell structure, such as the IMI antenna cross-section (its width and thickness) and shell thickness.

[0103] For applications requiring polarization insensitivity, the simplest parallelepiped bar-shaped antenna can be replaced with an antenna that responds to both components of the electric field within the structural plane, such as an antenna having a shape like a cross, "L", "V", a disc, or a square. Even in such cases, the concept of the core-shell structure presented in this invention is applicable with the same advantages as described for simple antennas.

[0104] The bolometer detector of the present invention is an electromagnetic radiation sensor, which is primarily for infrared imaging in the 8-14 µm wavelength band, commonly referred to as thermal imaging. These may also be used in other wavelength bands, for example, the 3 to 5 µm band (the transparent window of the atmosphere), the 20-30 µm band for imaging cold objects, or in the terahertz (THz) region.

[0105] Another object of the present invention is a method for manufacturing a bolometer detector according to the present invention. Such a manufacturing method comprises the following steps:

[0106] A: A step of manufacturing a read-through integrated circuit (ROIC) on a silicon wafer constituting a support substrate;

[0107] B: Step of depositing pillars;

[0108] C: Optionally, a step of depositing a reflector;

[0109] D: Step of depositing a sacrificial layer;

[0110] E: A step of depositing contacts on anchor elements and depositing a dielectric material layer to form the internal part of the shell;

[0111] F: A step of depositing one or more metal elements (metal element 1) forming an antenna;

[0112] G: A step of depositing a new dielectric material layer on a metal element to completely cover the metal element and form a shell around the metal element;

[0113] H: Step for defining insulation arms;

[0114] I: Step to remove the victim layer. Brief explanation of the drawing

[0115] Other features and advantages of the present invention will become clear by reading the following description, which is illustrated by the drawings: [Fig. 1] Schematic diagram of a bolometer detector illustrating various basic functions for the operation of a bolometer detector according to the prior art; [Fig. 2] Front perspective view of a core-shell structure according to one embodiment of the present invention; [Fig. 3] Side perspective view of a cut core-shell structure having a double shell according to another embodiment of the present invention; [Fig. 4] Schematic diagram illustrating the relative positions of the mirror (and substrate) of the core-shell structure according to Fig. 2; [Fig. 5] Front perspective view of an example of a bolometer detector according to the present invention including four core-shell structures per pixel; [Fig. 6a] Graph showing the absorption spectrum as a function of incident radiation wavelength of an aluminum IMI antenna placed 2.5 μm above the reflector; [Fig. 6b] A graph showing the areal filling factor of an IMI antenna within the antenna period at critical coupling as a function of structural area (w * l) for an aluminum IMI antenna with various geometric parameters placed 2.5 μm above the reflector; [Fig. 7a] Graph showing the absorption spectrum as a function of incident radiation wavelength of a core-shell structure having a 100 nm Ge shell placed 2.5 μm above the reflector; [Fig. 7b] Area occupancy of the core-shell structure within the antenna period at critical coupling, structural area (w tot * l tot Graph shown as a function of ), where w tot = w + 2*h includes the core width and both shell thicknesses, and length l tot The same applies to = l + 2*h; [Fig. 8a] Graph showing the change in IMI antenna resonance length and core-shell structure length as a function of shell thickness; [Fig. 8b] Graph showing different variations in IMI antenna length as a function of shell thickness; [Fig. 8c] Graph showing the area occupancy of the core-shell structure within the antenna period as a function of shell thickness; [Fig. 9] Graph showing the volume of the core-shell structure as a function of shell thickness; [Fig. 10] Graph showing the normalized electrical resistance of the shell as a function of shell thickness; [Fig. 11] Graph showing the absorption spectra of different metals forming a core of a core-shell structure with a germanium shell 100 nm thick; [Fig. 12a] A graph showing the change in the real part (neff) of the effective refractive index of the excited mode as a function of shell thickness for various permittivityes of the shell-forming material; [Fig. 12b] A graph showing the change in the imaginary part (neff) of the effective refractive index of the excitation mode as a function of shell thickness for various permittivityes of the shell-forming material; [Fig. 13] Examples of various forms of a core-shell structure according to the present invention; and [Fig. 14] Steps of a method for manufacturing an example of a bolometer detector according to the present invention. Specific details for implementing the invention

[0116] To clarify the detailed specifications, various terms are explained here:

[0117] FIG. 2 shows a schematic diagram of a core-shell structure (A) according to the present invention. The core (1) is a metal element and is a metal part of an IMI antenna that forms an electromagnetic radiation absorber. The shell (2) is made of an optical dielectric material and completely covers the metal core (1). The shell (2) provides a thermometric function, and according to one embodiment of the present invention, the optical dielectric material is selected to form a thermometric element and has a high TCR for this purpose.

[0118] This core-shell structure is used in a bolometer detector that operates in a manner similar to that described in schematic FIG. 1, where the core-shell structure replaces the conventionally used membrane by including all the main layers (e.g., absorber and thermometer). This detector includes electrical connection elements that connect the core-shell structure (A) to a support substrate (S). This support substrate (S) is made of silicon to ensure mechanical rigidity to the detector and includes a read integrated circuit (ROIC) embedded within the support (S) for polarization and temperature reading of the core-shell structure (A). The support elements for the core-shell structure (A) include a thermal insulating arm (4) and a pillar (5) (as illustrated in the example of FIG. 5), which include at least an electrically conductive material to ensure electrical contact between the electrical contact pad (PC) of the read integrated circuit on the support substrate and the temperature measuring element. The insulating arm (4) is a high thermal resistance element that enables the maintenance of the floating structure, its thermal insulation, and electrical connection between the ROIC and the thermometer element of the core-shell structure (A). The pillar (5) is a vertical structure that (1) positions the floating structure (the core-shell structure of the present invention) at an appropriate distance from the reflector (R) located on the substrate (S), and (2) enables electrical contact between the insulating arm (4) and the ROIC. These are generally metallic. To ensure the stability of the floating structure, the pillar (5) is present at at least two corners of the pixel.

[0119] The support substrate (S) may be covered with a mirror-like reflector (R) that is deposited on top of the ROIC and used to form a standing wave with the incident radiation. This is typically made of metal. This reflector is spaced apart from the core-shell structure (A) by a distance d, which is typically around λres / 4, where λres is the operating wavelength of the detector.

[0120] An example of a bolometer detector according to the present invention is illustrated in FIG. 5. It includes four core-shell structures (A) within a single pixel: the pixel period is twice as large as the antenna period. The shell (2) is made of an optical dielectric material and has an extension (2a) for contacting an insulating arm (4), thereby ensuring mechanical support of the core-shell structure (A), thermal insulation, and electrical connection between the core-shell structure (A) and the ROIC.

[0121] According to another embodiment of the present invention, the core-shell structure (A') of FIG. 3 has a core-double shell structure. The second shell (3) is an electrical insulator placed between the metal core (1) and the optical dielectric material shell (2). In the core-shell structure (A), as a significant portion of the measurement current circulates within the metal core (1) rather than the shell (2), the measurement of the electrical resistivity of the shell can be altered by the presence of the metal core (1). Consequently, the electrical insulator layer (3) provides a more accurate measurement of the electrical resistivity of the shell.

[0122] Electrical insulation is provided between the core (1) and the shell (2) using SiOx, SiNx, or AlO. x This can be implemented by introducing a thin layer of an electrically insulating dielectric material, such as ZnS, ZnSe, or other electrically insulating materials. In this way, the measurement current circulates only within the shell (2), and the influence of temperature on the measurement becomes stronger because the TCR of the shell material is higher than the TCR of the metal.

[0123] The core element of the core-shell structure (A) or core-double shell structure (A') constitutes an IMI antenna and responds to the electrical component of the electromagnetic field surrounding it. These IMI antennas exhibit maximum sensitivity when at a distance d of approximately 1 / 4 of the operating wavelength relative to the reflector (R). Since the distance d is d = λ / 4, structure A or A' is compatible with existing bolometer technology.

[0124] The spectral response of the IMI antenna of structure A is defined by its geometric design. The length L of the metal core (1) (IMI antenna) defines the resonant wavelength λres, which can be approximated as follows: λres 2L*neff, where neff is the effective refractive index in the corresponding mode. It is worth noting that the properties of both metallic and optical dielectric materials affect the resonance wavelength (which affects neff) and the resonance width.

[0125] The cross-section of the metal core (1) is the product of its thickness (t) and width (w) and defines the absorption of the IMI antenna. The cross-section can be adjusted according to the antenna period value to exhibit complete absorption of incident electromagnetic radiation (critical coupling condition) at the operating resonance wavelength. The antenna period is the period of the antenna array to cover the sensitive area at the corresponding wavelength. This area can be a pixel, a group of pixels, or the entire FPA. If the antenna period is greater than or equal to the pixel size, only one antenna exists per pixel. The critical coupling condition is the condition where the incident power is equal to the absorbed power, so that the reflected power is equal to zero. For a given incident power and antenna period, this condition can be achieved by adjusting the geometric parameters of the core-shell structure, such as the IMI antenna cross-section (its width and thickness) and the shell thickness. If the antenna period is smaller than the pixel size, several antennas may be placed at each pixel to maintain complete absorption (nearly 100%). However, to simplify the device structure, fewer antennas per pixel may be used, which leads to incomplete absorption of incident radiation, but even in this case, the core-shell structure will still function as a bolometer.

[0126] FIG. 6a shows a shell-less reflector (R) positioned at a distance d=2.5 μm above the reflector (R), arranged in a 7.7 μm periodic array, with a length of 4.059 μm, a width and thickness of 60 nm (cross-sectional 60x60 nm). 2 It shows the absorption spectrum for a periodic array of IMI antennas including an aluminum core (1) (IMI antenna) having ). This IMI antenna (metal core (1) surrounded by vacuum) exhibits a critical coupling condition at a resonant wavelength of 10 μm. The area of ​​the antenna (0.24 μm) 2 ) occupies about 0.4% of the period area.

[0127] In FIG. 6b, it can be seen that the area occupied by the IMI antenna is negligible (less than 1%) compared to the antenna period. However, its length represents a major portion of the IMI antenna period (53% of the previous example, see paragraph

[0104] ), which may limit the introduction of multiple of this type of IMI antennas for each pixel in the case of pixels larger than the wavelength (see paragraph

[0103] ) and / or for multispectral applications.

[0128] Antenna occupancy is the ratio of the antenna area to the antenna period area (the product of the period in the x-axis direction and the period in the xy-axis direction, typically the square of the period).

[0129] Figure 6b shows the area share relative to the structural area (structural area relative to the periodic area) for a periodic array of IMI antennas at critical coupling of a resonant wavelength of 10 µm. The antenna has a square cross-section (equal width and thickness), is shell-free, and the distance from the reflector to the antenna is 2.5 µm (the width and thickness (w=t) change as the period changes to maintain critical coupling), and the antenna length is adjusted by a few percent to maintain the resonant wavelength at 10 µm).

[0130] The core-shell structure according to the present invention can reduce this length while maintaining a very low occupancy rate of the pixel surface. In fact, if an optical dielectric material having a high refractive index, such as silicon or germanium, is introduced near the IMI antenna (metal core (1)), the effective refractive index (neff) can be significantly increased, thereby shortening the length of the IMI antenna. It is worth noting that in most cases (i.e., when the shell is thicker than tens of nanometers depending on the material's refractive index), the overall length of the core-shell structure is shortened despite the addition of dielectric material layers at both ends.

[0131] Figure 7a shows the absorption spectrum for a periodic array of a core-shell structure with a period of 8 μm, an aluminum core (IMI antenna) with a length of 2.8 μm, a width and thickness of 60 nm, a shell made of germanium with a thickness of 100 nm, and a distance from the reflector to the core-shell of 2.5 μm. This IMI antenna exhibits a critical coupling condition at a resonant wavelength of 10 μm.

[0132] The occupancy rate of the core-shell structure is the ratio of the core-shell occupied area (footprint, upper or lower surface) to the core-shell periodic area (square of the period). FIG. 7b shows the area occupancy rate relative to the structural area (structural area relative to the periodic surface) for a periodic array of core-shell structures at a critical coupling of 10 μm resonant wavelength. The metal core (1) has a square cross-section (equal width and thickness). The shell thickness is 100 nm, it is made of Ge, and the distance from the reflector to the structure is 2.5 μm. Again, as the period value changes to maintain critical coupling, different IMI core widths and thicknesses (w=t) also change, and the antenna length is adjusted by a few percent to maintain the resonant wavelength at 10 μm while the shell thickness is 100 nm. The area of ​​the core-shell structure (0.728 μm) 2 ) occupies 1.2% of the pixel area.

[0133] Figure 8a illustrates the device length as a function of shell thickness for a core-shell structured periodic array. This is a core-shell periodic array optimized for a 10 µm resonant wavelength, with a core made of Al and a shell made of Si, a period of 8 µm, and positioned 2.5 µm above the reflector. This figure shows three curves:

[0134] Curve 1: Length of a metal core corresponding to a 10 μm resonant wavelength as a function of shell thickness when the core cross-section is kept constant at w = t = 45 nm.

[0135] Curve 2: Total length of the core-shell structure corresponding to a 10 μm resonant wavelength as a function of shell thickness when the core cross-section is kept constant at w = t = 45 nm.

[0136] Curve 3: Length of the metal core corresponding to a 10 μm resonant wavelength as a function of shell thickness, when the sides of the square cross-section (w=t) of the core are changed to maintain the critical coupling condition (complete absorption), and the cross-section of the core (IMI antenna) changes from w = t = 45 nm when the shell thickness is 0 to w = t = 100 nm when the shell thickness is 300 nm.

[0137] FIG. 8b illustrates the resonant antenna length as a function of shell thickness for a core-shell structured periodic array. This is a core-shell periodic array optimized for a 10 µm resonant wavelength, with a core made of Al and a shell made of Si, a period of 8 µm, and positioned at a distance of 2.5 µm above the reflector. This figure shows two curves:

[0138] Curve 1: Length of the metal core corresponding to a 10 μm resonant wavelength as a function of shell thickness when the core cross-section is kept constant at w = t = 45 nm (identical to Curve 1 in Fig. 8a).

[0139] Curve 2: Corresponds to a "sandwich-like" structure in which the shell layer exists only on the top and bottom of the metal core and there is no shell on the sides. The length of the metal core corresponding to the 10 μm resonance wavelength of the sandwich-like structure is plotted as a function of the shell thickness. To maintain the critical coupling condition, the sides of the square cross-section (w=t) of the metal core change from w = t = 45 nm when the shell thickness is 0 to w = t = 53 nm when the shell thickness is 300 nm.

[0140] FIG. 8c shows the area share of the core-shell structure as a function of the thickness of the silicon layer forming the shell (2) that embeds the aluminum antenna as the core (1) at a critical coupling of 10 μm resonant wavelength.

[0141] For the same core-shell structure embodiment, at a resonant wavelength of 10 μm, it can be seen that the change in IMI antenna length (Figs. 8a and 8b) and the occupancy of the core-shell structure (Fig. 8c) are functions of the thickness of the silicon layer forming the shell (2) that encloses the aluminum IMI antenna, which is the core (1). It should be noted that while the occupancy increases slightly, the length of the IMI antenna (metal core portion) can be shortened by a factor of more than two. Consequently, the structural area does not exceed 4% of the square of the antenna period.

[0142] A change in the thickness of the shell (2) forming the optical dielectric material changes the volume of the antenna thus implemented and further changes the thermal capacity of the bolometer detector. When the cross-section of the antenna IMI is low (typically tens of nm), a large change in thermal capacity is possible as the thickness of the shell (2) varies between 0 and 300 nm. This provides high flexibility to the antenna concept to match the thermal capacity required for the intended application.

[0143] Figure 9 shows the total volume of a core-shell structure antenna as a function of shell thickness. This example demonstrates that the thermal capacity of the shell varies by more than two orders of magnitude. This volume is typically 10 µm 3 It is still much lower than the volume of conventional technology.

[0144] As previously mentioned, the shell (2) covering the metal core (1) provides a temperature measurement function either alone (e.g., electrical resistance dependence with temperature) or in conjunction with the core (e.g., temperature dependence of current passing through a Schottky diode at the metal (core) / semiconductor (shell) interface). Consequently, this core-shell structure offers two significant advantages.

[0145] First, since the shell covers the core (1) integrally at the place where heat is generated (the Joule effect emission that is depth-limited by the skin effect) (in the embodiment of FIG. 2), the thermal contact between the core and the shell is optimal.

[0146] Second, when the optical dielectric material is also an absorber (where the imaginary part of the refractive index is not zero), the corresponding heat generation is also located within the temperature measuring device itself. This corresponds to the absorption of photons incident into the dielectric volume. This is related to electronic transitions or phonon excitation between two states (defects, free carriers) existing within the dielectric material.

[0147] In the measurement time constant scale, the internal temperature of the shell (2) is uniform because its thickness is thin.

[0148] Measurement of electrical resistance in the shell (2) leads to an accurate and reliable measurement of the temperature rise of the IMI antenna (metal core (1)) heated under infrared radiation. This electrical resistance depends on the geometric design of the shell and the properties (intrinsic properties, degree of doping) of the material used to form it.

[0149] As can be seen in Fig. 10, the possible resistance of the shell (Rnom = R / ρ), normalized by the resistivity (ρ) of the material used, is expressed as a function of the shell thickness. It can be observed that this electrical resistance varies by nearly four orders of magnitude when the shell thickness varies between 0 and 300 nm. The high possible range of shell thickness and the high dynamics associated with various materials for the shell enable further control of this resistance value for the specifications of the ROIC.

[0150] Furthermore, when multiple antennas are placed within the same pixel for a single temperature measurement, the variety of possible electrical connections of these antennas increases the dynamics observed in Fig. 10.

[0151] Considering the bolometer detector of FIG. 5, four core-shell structures (A) are arranged within the same pixel and have a thermometer resistance of R. These structures (A) can be connected in series for a total resistance of 4R, in parallel for a total resistance of R / 4, or in a mixed arrangement such as series-parallel for a resistance of R. In this example of installation, the type of antenna connection provides a difference of an order of magnitude in the dynamics of the resistance to be measured by the ROIC.

[0152] Figure 11 shows the absorption spectra for different metals forming a core of a core-shell structure, having a germanium shell with a thickness of 100 nm.

[0153] FIG. 12a shows the real part of the effective refractive index (neff) of the excited mode as a function of shell thickness for various permittivity values ​​of the shell-forming material, and FIG. 12b shows the imaginary part of the effective refractive index (neff) of the excited mode as a function of shell thickness for various permittivity values ​​of the shell-forming material.

[0154] IMI antennas in the form of parallelepiped bars forming the core of a core-shell structure are highly sensitive to the polarization of incident radiation regardless of the shape of the cross-section. They exhibit a maximum response when aligned with the direction of the electrical component of the incident electromagnetic field. However, when aligned orthogonally, the response is zero. They are highly efficient for imaging applications that require sensitivity to polarization (e.g., detection of artifacts within a natural background).

[0155] For applications requiring polarization insensitivity, the core-shell structure according to the present invention may exhibit sensitivity to two components of the electric field within the structural plane, such as a structure having a shape such as a cross, "L", "V", a disc (d), or a square (g). As illustrated in FIG. 13, in this case, the core-shell structure can be applied to these complex shapes while having the same advantages as described above for simple shapes. The core may have a cross, L, or V shape covered by a shell, as in (a), (b), and (c). The L and V shapes may be formed by the core / shell structure of this shape. The antenna (core) may be formed from two metal rods separated by a small gap, as exemplified in (e) for an L-shaped antenna and (f) for a V-shaped antenna in FIG. 13.

[0156] FIG. 14 illustrates various steps of a method for manufacturing a bolometer detector comprising at least one core-shell structure according to the present invention. The manufacturing method comprises the following steps:

[0157] A: A step of manufacturing a read integrated circuit on a silicon wafer constituting a support substrate (S);

[0158] B: Step of depositing a pillar element (5);

[0159] C: Optionally, a step of depositing a reflector (R);

[0160] D: Step of depositing and planarizing a sacrificial layer (CS);

[0161] E: A step of depositing a contact (PC) on the upper part of the pillar element (5) and depositing a dielectric material layer to form the lower part of the shell (2);

[0162] F: A step of depositing one or more metal elements to form an incident electromagnetic radiation absorber element;

[0163] G: A step of locally depositing another dielectric material layer on a metal element to cover a metal element as a core (1) of the core / shell structure implemented in this way and to form a shell (2) on the metal element;

[0164] H: Step of defining the insulating arm (4);

[0165] I: Step to remove the victim layer (CS).

Claims

Claim 1 A core-shell structure for a bolometer detector, wherein the core (1) is made of a metal element and forms an absorber element for incident electromagnetic radiation to be detected; and the shell (2) is made of an optical dielectric material and continuously covers all sides of the metal core, and the core / shell structure provides a thermometer function for measuring the temperature of the absorber. Claim 2 In claim 1, the core-shell structure is a core-shell structure having characteristics that can be configured depending, in particular, the type of metal constituting the metal element, the geometric shape of the metal element, the type of optical dielectric material constituting the shell, and the thickness of the shell. Claim 3 The core-shell structure of claim 1 or 2, wherein the core-shell structure is a rod shape designed for applications requiring sensitivity to the polarization of incident light; or a core-shell structure in the shape of a cross, "L", "V", disc, or square designed for applications requiring insensitivity to the polarization of incident light. Claim 4 A core-shell structure characterized in that, in any one of claims 1 to 3, the metal of the core (1) portion is a metal that supports surface plasmon polariton modes, such as silver, gold, copper, aluminum, doped aluminum, aluminum alloy, or titanium nitride. Claim 5 A core-shell structure according to any one of claims 1 to 4, characterized in that the metal element provides a temperature measurement function by means of an electrical characteristic of the metal element, such as electrical resistance that changes with temperature. Claim 6 A core-shell structure according to any one of claims 1 to 4, wherein the shell (2) provides a temperature measurement function by means of electrical properties of the optical dielectric material forming the shell (2), such as electrical resistance that changes with temperature. Claim 7 A core-shell structure according to any one of claims 1 to 4, wherein the shell (2) and / or the core (1) provide a temperature measurement function by - a PN junction and / or a Schottky junction, - a thermoelectric effect (Seebeck effect), or - a pyroelectric effect. Claim 8 A core-shell structure according to any one of claims 1 to 7, wherein the optical dielectric material has an optical refractive index greater than 1.5, such as germanium, silicon, a silicon / germanium alloy, or vanadium oxide. Claim 9 A core-shell structure according to any one of claims 1 to 8, wherein the core-shell structure further comprises an electrical insulator layer (3) interposed between the metal core (1) and the optical dielectric material shell (2) to form a double shell structure. Claim 10 A core-shell structure according to claim 9, wherein the electrical insulator layer (3) interposed between the metal core (1) and the dielectric optical material shell (2) is an insulating dielectric material such as SiOx, SiNx, AlOx, ZnS, or ZnSe. Claim 11 A core-shell structure according to any one of claims 1 to 10, wherein the optical dielectric material of the shell (2) is configured to form an extension beyond both ends of the core-shell structure to provide mechanical support and thermal insulation functions to the core-shell structure. Claim 12 A core-shell structure according to claim 11, wherein the extension (2a) is implemented in a geometric shape different from the geometric shape of the shell, and / or is implemented in a dielectric material having modified electrical and / or thermal properties. Claim 13 A bolometer detector for detecting electromagnetic radiation comprising a support substrate (S), wherein the bolometer detector comprises at least one core-shell structure according to any one of claims 1 to 12 per pixel, and wherein the core-shell structure is floated on the support substrate (S) by means of a support means. Claim 14 A bolometer detector according to claim 12, wherein the extension (2a) of the shell (2) within the core-shell structure enables electrical connection between the core / shell structure and a read integrated circuit integrated on the support substrate (S). Claim 15 A bolometer detector according to claim 12 or 13, characterized in that when the pixel size is larger than or close to the operating wavelength, the bolometer may include two or more core-shell structures within a single pixel. Claim 16 A method for manufacturing a bolometer detector according to any one of claims 12 to 14, comprising: A: manufacturing a readout integrated circuit on a silicon wafer constituting a support substrate (S); B: depositing a pillar element (5); C: optionally, depositing a reflector (R); D: depositing and planarizing a sacrificial layer (CS); E: depositing a contact (PC) on the pillar element (5) and an optical dielectric material layer to form a lower part of a shell (2); F: depositing one or more metal elements to form an incident electromagnetic radiation absorber element; G: locally depositing on a metal element of another optical dielectric material layer and forming a shell (2) around the metal element as a core (1) of a core / shell structure thus implemented; H: defining an insulating arm (4); I: removing the sacrificial layer (CS).

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