Method of manufacturing a device for detecting electromagnetic radiation comprising a getter material

Abstract

The invention relates to a method for manufacturing a detection device comprising at least one thermal detector (20) covered by a mineral sacrificial layer (14, 15), at least one getter portion (13) covered by a carbonaceous sacrificial layer (17), and a thin encapsulation layer (31) surrounding the thermal detector and the getter portion. The manufacturing method comprises a step of creating a via (16) extending through the mineral sacrificial layer (14, 15) and opening onto the substrate (10), and a step of depositing a carbonaceous sacrificial layer (17) so as to cover the getter portion (13) located in the via (16) and to completely fill the via (16).

Description

TECHNICAL FIELD

[0001] The field of the invention is that of a device for detecting electromagnetic radiation, in particular infrared or terahertz radiation, comprising at least one thermal detector encapsulated in a sealed cavity, a getter material also being located in the sealed cavity. The invention is particularly suitable for use in the field of infrared and thermal imaging. BACKGROUND

[0002] A device for detecting electromagnetic radiation, such as infrared or terahertz radiation, can comprise a matrix of thermal detectors, each of which comprises an absorption portion capable of absorbing the electromagnetic radiation to be detected.

[0003] In order to ensure the thermal insulation of the thermal detectors, the absorption portion generally takes the form of a membrane suspended above the substrate by anchoring columns and thermally insulated from the substrate by support arms. These anchoring columns and support arms also have an electrical function, electrically connecting the suspended membrane to a reading circuit generally located in the substrate.

[0004] The reading circuit generally takes the form of a CMOS circuit. It allows control signals to be applied to the thermal detectors, as well as reading detection signals produced by the thermal detectors in response to the absorption of the electromagnetic radiation to be detected. The reading circuit comprises various levels of electrical interconnection formed by metal lines, which are separated from each other by dielectric layers called intermetallic layers. At least one electrical connection pad of the reading circuit is provided on the substrate, so that it is possible to make contact with the substrate from the outside of the detection device.

[0005] Document EP2581339A1 describes an example of a detection device, the encapsulation structure of which comprises two cavities communicating with each other, a first cavity in which the thermal detectors are located and a second cavity in which a getter material is located, which ensures the pumping of the gas inside the cavity. However, this arrangement of two cavities defined by the same encapsulation structure results in a particularly small active area of the getter material, which can lead to a decrease in the performance of the detection device, and also results in a lack of suitability for cases where the same sealed cavity contains a plurality of thermal detectors.

[0006] Document EP3239670A1 describes a method for manufacturing a detection device by a mineral sacrificial layer, which is then removed by wet chemical etching. A portion of the getter material is located under the absorption membrane and is protected from the effects of the wet chemical etching by a thin carbon- containing sacrificial layer, which is then removed by dry chemical etching. The thin carbon- containing sacrificial layer can in particular be made of amorphous carbon or polyimide. However, on the one hand, it is necessary to improve the mechanical strength of the stack obtained at various stages of the manufacturing method, in particular during the planarization step, and, on the other hand, it is necessary to strengthen the protection of the getter material during the removal of the mineral sacrificial layer by wet chemical etching. SUMMARY

[0007] The aim of the present invention is to remedy at least partially the drawbacks of the prior art, more particularly to propose a method of manufacturing a device for detecting electromagnetic radiation, comprising the following steps:

[0008] o producing at least one thermal detector on the substrate, the at least one thermal detector being covered by at least one mineral sacrificial layer made of a mineral material able to be removed by a first chemical etching;

[0009] o producing a getter portion made of a metallic material having a gettering effect on the substrate, the getter portion being covered by a carbonaceous sacrificial layer made of a carbonaceous material which is inert to the first chemical etching and able to be removed by a second chemical etching;

[0010] o producing a thin encapsulation layer comprising a top portion located on the mineral sacrificial layer and on the carbonaceous sacrificial layer, and a peripheral portion extending through the mineral sacrificial layer and surrounding the thermal detector and the getter portion;

[0011] o removing the mineral sacrificial layer by the first chemical etching;

[0012] o removing the carbonaceous sacrificial layer by the second chemical etching.

[0013] According to the invention, the getter portion is arranged in contact with the substrate and at a distance from the thermal detector in a plane parallel to the substrate.

[0014] Moreover, the step of producing the carbonaceous sacrificial layer is performed after the step of producing the thermal detector, which comprises:

[0015] • producing a through hole extending through the mineral sacrificial layer and leading to the substrate. The getter portion is located in the through hole, at a distance from a lateral boundary defined by the mineral sacrificial layer and delimiting the through hole in a plane parallel to the substrate. In other words, the getter portion is not in contact with the mineral sacrificial layer surrounding it.

[0016] • depositing the carbonaceous sacrificial layer to cover the getter portion located in the through hole and surround it in a plane parallel to the substrate and to fill the through hole completely. In other words, the mineral sacrificial layer covers and is in contact with the free face of the getter portion in a plane parallel to the substrate and along an axis orthogonal to the substrate. The getter portion is located on the substrate and encapsulated by the carbonaceous sacrificial layer.

[0017] Finally, the top portion of the thin encapsulation layer is located on the mineral sacrificial layer and on the carbonaceous sacrificial layer.

[0018] Hereafter are certain preferred but non-limiting aspects of the method.

[0019] The getter portion can be arranged between the thermal detector and the peripheral portion of the thin encapsulation layer.

[0020] The peripheral portion can comprise an inner surface oriented towards the thermal detector and in contact with the carbonaceous sacrificial layer.

[0021] The mineral sacrificial layer and the carbonaceous sacrificial layer can have a top face that is coplanar with the substrate.

[0022] The mineral material can comprise at least silicon oxide or silicon nitride, and the first chemical etching can be a gas-phase hydrofluoric acid etching.

[0023] The carbonaceous material can be chosen from amorphous carbon and polyimide, and the second chemical etching can be a dry etching by oxygen plasma.

[0024] The metal material having a gettering effect can be chosen from titanium, zirconium, vanadium, chromium, cobalt, iron, manganese, palladium, barium and / or aluminium, and alloys of these metals.

[0025] The method can comprise creating at least one first release vent and at least one second release vent through the top portion of the thin encapsulation layer, the first release vent opening into the mineral sacrificial layer and the second release vent opening into the carbonaceous sacrificial layer.

[0026] The first release vent and the second release vent can be created before the first chemical etching, the carbonaceous sacrificial layer underlying the top portion of the thin encapsulation layer being in contact with the mineral sacrificial layer.

[0027] The thin encapsulation layer can further comprise an internal portion extending from the top portion in the direction of the substrate and located between the mineral sacrificial layer and the carbonaceous sacrificial layer, such that the carbonaceous sacrificial layer underlying the top portion of the thin encapsulation layer is in contact with the top portion, the peripheral portion and the internal portion of the thin encapsulation layer.

[0028] The step of creating the second release vent can comprise, in addition to forming at least one second release vent opening into the carbonaceous sacrificial layer, forming at least one vent perpendicular to the internal portion, said at least one vent at least partially interrupting the interruption of the physical link between the inner wall and the top portion, thereby ensuring, after the second chemical etching, the communication between the first space in which the thermal detector is located and the second space in which the getter portion is located.

[0029] The internal portion can be in contact with a carbonaceous portion arranged in contact with the substrate and made of a carbonaceous material that is inert to the first chemical etching and removable by the second chemical etching, such that the second chemical etching ensures the removal of the carbonaceous sacrificial layer and the release of the getter portion and ensures the removal of the carbonaceous portion and the communication between the first space in which the thermal detector is located and the second space in which the getter portion is located.

[0030] A plurality of thermal detectors can be simultaneously produced, each of the plurality of thermal detectors comprising a membrane adapted to absorb electromagnetic radiation to be detected, the membrane being suspended over a substrate by anchoring columns and being thermally insulated from the substrate by a support arm.

[0031] Furthermore, a top portion of the thin encapsulation layer can be located on and in contact with the mineral sacrificial layer, and can be located on and in contact with the carbonaceous sacrificial layer. BRIEF DESCRIPTION OF DRAWINGS

[0032] Other aspects, objectives, advantages and features of the application will become more apparent from the following detailed description of preferred embodiments of the application, given by way of non-restrictive example only and with reference to the accompanying drawings, in which:

[0033] Figures 1A-1F is a schematic partial cross-sectional view of different steps of a method for manufacturing a detection device according to a first embodiment;

[0034] Figures 2A-2F is a schematic partial cross-sectional view of different steps of a method for manufacturing a detection device according to a second embodiment;

[0035] Figures 3A-3E is a schematic partial cross-sectional view in cross-section of different steps of a method for manufacturing a detection device according to a variant of the second embodiment. DETAILED DESCRIPTION

[0036] In the rest of the drawings and of the description, identical references denote identical or similar elements. Furthermore, the various elements are not shown to scale in order to improve the clarity of the drawings. Moreover, the various embodiments and variants are not mutually exclusive and can be combined with each other. Unless otherwise stated, the terms "substantially", "approximately" and "about" mean within 10%, preferably within 5%. Furthermore, unless otherwise stated, the term "between" and its equivalent means inclusive of the boundaries.

[0037] The present application relates to a method for manufacturing a device for detecting electromagnetic radiation adapted to detect infrared or terahertz radiation. It comprises at least one thermal detector intended to be located in a sealed cavity, and a material having a gettering effect, the material being located on a substrate inside the sealed cavity. This material having a gettering effect is a material exposed to the atmosphere of the sealed cavity and is able to carry out gas pumping by absorption and / or adsorption. The material is a metal which can be chosen from titanium, zirconium, vanadium, chromium, cobalt, iron, manganese, palladium, barium and / or aluminium, or is an alloy of these metals, such as TiZrV.

[0038] The manufacturing method comprises a step of producing the thermal detector by at least one sacrificial layer called mineral sacrificial layer. This mineral sacrificial layer is made of a mineral or inorganic material. Here is a silicon-based dielectric material which also allows to produce an intermetallic dielectric layer of the reading circuit, i.e. an electrically insulating material, whose dielectric constant or relative dielectric constant is for example lower than or equal to 3.9, allowing to limit the parasitic capacitance between interconnections. This mineral material does not comprise any carbon chain and can be silicon oxide SiOx or silicon nitride Si x N y , or an organosilicon material such as SiOC, SiOCH, or a fluoride glass type material such as SiOF. The mineral sacrificial layer can be removed by wet chemical etching, such as a chemical etching in the form of an acidic medium, for example using a gaseous hydrofluoric acid (HF vapor). "Wet etching" generally means that the etchant is in a liquid or gaseous phase, here preferably gaseous.

[0039] The manufacturing method also comprises a step for producing a sacrificial layer called carbonaceous sacrificial layer and able to protect the getter material during the step of wet chemical etching, such as HF vapor etching, performed to remove the mineral sacrificial layer. This carbonaceous sacrificial layer comprises a carbonaceous material, i.e. a material formed of at least one type of chemical substance comprising carbon atoms. It can thus involve a mineral material such as amorphous carbon, optionally of the DLC (Diamond Like) type, or an organic material such as polyimide. Carbon of the DLC type is an amorphous carbon with a high rate of hybridization of the carbon sp 3 . Preferably, the carbonaceous material does not contain any silicon, thus avoiding any residue at the end of the step of removing this sacrificial layer. The carbonaceous sacrificial layer is thus substantially inert with respect to the wet chemical etching performed to remove the mineral sacrificial layer. "Substantially inert" means that the carbonaceous material hardly reacts, or only slightly reacts, with the etchant used in the step of removing the mineral sacrificial layer, so that at the end of this removal step, the carbonaceous sacrificial layer still completely covers the getter material. The carbonaceous sacrificial layer can also be removed by chemical etching, such as dry chemical etching, whose etchant is for example oxygen contained in a plasma.

[0040] Figures 1A-1FThe various steps of the method for manufacturing a detection device according to the first embodiment are illustrated. Only a portion of the detection device is displayed. By way of example, the thermal detectors 20 are here adapted to detect infrared radiation in the LWIR (for Long Wavelength Infrared) range, the wavelengths of which are of the order of 8 to 14 pm. The detection device comprises one or more thermal detectors 20, here preferably a matrix of identical thermal detectors 20, located in the same sealed cavity 1, connected to a reading circuit located in a substrate 10, hence called reading substrate. The thermal detectors 20 thus form sensitive pixels, which are arranged periodically and which can have a lateral dimension in the plane of the reading substrate 10 of the order of a few tens of microns, for example equal to about 10 pm or less.

[0041] A three-dimensional direct coordinate system XYZ is defined here and in the remainder of the description, in which the XY plane is substantially parallel to the plane of the reading substrate 10 and the Z axis is oriented in the direction of the thermal detectors 20 along a direction substantially orthogonal to the plane of the reading substrate 10. The terms "vertical" and "vertically" are understood with respect to an orientation substantially parallel to the Z axis and the terms "horizontal" and "horizontally" are understood with respect to an orientation substantially parallel to the (X, Y) plane. Furthermore, the terms "bottom" and "top" are understood with respect to a position increasing when moving away from the reading substrate 10 along the +Z direction.

[0042] Reference is made to Figure 1A The matrix of thermal detectors 20 is produced on the reading substrate 10 so that the thermal detectors are covered by the mineral sacrificial layer 15.

[0043] The reading substrate 10 is silicon-based and is formed from a carrier substrate containing a reading circuit (not shown) adapted to control and read the thermal detectors 20. The reading circuit here takes the form of a CMOS integrated circuit. This reading circuit comprises in particular portions of electrically conductive lines separated from each other by an intermetallic insulation layer made of a dielectric material, for example a silicon-based mineral material such as silicon oxide SiO x or silicon nitride SiN x .

[0044] The reading substrate 10 can comprise a reflector 11 placed towards each thermal detector 20. The reflector 11 can be formed from a portion of the electrically conductive lines of the last interconnection level, made of a material adapted to reflect the electromagnetic radiation to be detected. Said reflector is towards the absorbing film 21 of the thermal detector 20 and is intended to form a quarter-wave interference cavity related to the electromagnetic radiation to be detected.

[0045] Finally, the readout substrate 10 includes a protective layer 12 to specifically cover the top intermetallic insulating layer. This protective layer 12 corresponds to an etch stop layer made of a material that is substantially inert to the chemical etchant (e.g., HF medium in gaseous form) subsequently used to remove the mineral sacrificial layers 14, 15. Therefore, the protective layer 12 forms a sealed and chemically inert layer that is electrically insulating to prevent any short circuits between the anchor posts 22. Thus, the protective layer can prevent the underlying intermetallic insulating layer from being etched during this step of removing the mineral sacrificial layers 14, 15. The protective layer may be formed of alumina or aluminum nitride, aluminum trifluoride, or unintentionally doped amorphous silicon.

[0046] A thermal detector 20 is then formed on the readout substrate 10. These formation steps are the same as or similar to those described, particularly in document EP3239670A1. Here, the thermal detector 20 is a microbolometer, each of which includes an absorption film 21, i.e., an absorption film capable of absorbing the electromagnetic radiation to be detected, which is suspended above the readout substrate 10 by anchor posts 22 and thermally insulated from the readout substrate by support arms. The absorption film 21 is typically obtained by surface micromachining techniques, which include forming the anchor posts 22 through a first mineral sacrificial layer 14, and forming a thermally insulating arm and the absorption film 21 on the top surface of the first sacrificial layer. Each absorption film 21 also includes a temperature transducer, such as a thermistor material, which is connected to the readout circuitry by providing electrical connections disposed in the thermally insulating arm and the anchor posts 22. Next, a second mineral sacrificial layer 15 is deposited, which preferably has the same properties as the first mineral sacrificial layer 14. The mineral sacrificial layer 15 covers the mineral sacrificial layer 14 and the thermal detector 20.

[0047] refer to Figure 1B A carbon-containing sacrificial layer 17 is generated, which covers the getter material placed on the read substrate 10 and is in contact with the read substrate.

[0048] For this purpose, vias 16 extending through the mineral sacrificial layers 14, 15 and leading to the readout substrate 10 are created by photolithography and etching. Preferably, the vias 16 do not lead to any part of the thermal detectors 20. Thus, the thermal detectors 20 remain completely covered by the mineral sacrificial layers 14, 15. The vias 16 are defined in the XY plane by a lateral boundary 16.1 defined by the mineral sacrificial layers 14, 15. Its lateral dimension is larger than the lateral dimension of the desired getter portion 13. For example, for a getter portion 13 with a width of tens to hundreds of micrometers, or even millimeters, such as approximately 100 μm, the width of the via 16 can be tens to hundreds of micrometers, such as approximately 150 μm. Therefore, the distance in the XY plane between the getter portion 13 and the lateral boundary 16.1 of the via defines the protection dimension of the carbon-containing sacrificial layer 17 for the getter portion 13 during HF vapor etching. If the carbon-containing sacrificial layer 17 is not a thin layer with a protection size of approximately 0.5 μm as shown in document EP3239670A1, then the protection size may be tens or hundreds of micrometers.

[0049] A getter portion 13 is then created, located within the via 16 and placed on the read substrate 10, where it contacts the read substrate. For this purpose, a thin layer of getter material is deposited, extending to contact the read substrate 10. This thin layer of getter material may also extend to the top surface of the mineral sacrificial layer 15 and to the lateral boundary 16.1 of the via 16. Then, portions of the thin getter layer located on the top surface of the mineral sacrificial layer 15 and the lateral boundary 16.1 of the via 16 are removed, for example, by localized etching. The peripheral region of the thin getter layer on the read substrate 10 that contacts the lateral boundary 16.1 is also removed, so that only the central portion remains. Therefore, this central portion is located on the read substrate 10 and at a non-zero distance from the mineral sacrificial layers 14, 15 in the XY plane. In other words, the getter portion 13 is offset relative to the thermal detectors 20 in the XY plane, and it is not positioned relative to (i.e., perpendicular to) them along the Z-axis as in document EP3239670A1, but rather neither fully nor partially positioned. Therefore, the getter portion 13 is located at a certain distance from the thermal detectors 20 (i.e., from the absorber membrane and anchor post) in the XY plane, and thus at a non-zero distance from them in the XY plane.

[0050] The via 16 is then completely filled with a carbon-containing sacrificial layer 17 that completely covers the getter portion 13. If the thickness of this layer allows for complete filling of the via 16, it is referred to as a thick layer. Therefore, it can be made of polyimide or amorphous carbon, in this case, polyimide. Thus, the carbon-containing sacrificial layer 17 covers the getter portion 13 along the Z-axis and completely surrounds it in the XY plane. Therefore, the carbon-containing sacrificial layer 17 will be able to ensure protection of the getter portion 13 during chemical etching (e.g., with HF acid in the gas phase), subsequently during the removal of the mineral sacrificial layers 14, 15. The protection dimension in the XY plane may then be approximately tens to hundreds of micrometers. The portion of the carbon-containing sacrificial layer 17 covering the mineral sacrificial layer 15 is then removed to obtain a planar top surface defined by the mineral sacrificial layer 15 and the carbon-containing sacrificial layer 17.

[0051] refer to Figure 1C The thin encapsulation layer 31 of the encapsulation structure 30 is then produced in a manner similar to that described in document EP3239670A1. The various thin layers of the encapsulation structure 30 are transparent to the electromagnetic radiation to be detected. Using conventional photolithography, the mineral sacrificial layers 14 and 15 are then locally etched until the surfaces leading to the readout substrate 10, and even to the getter portion 13, are not covered. Nevertheless, the etched areas here surround the thermal detector 20 and at least part of the getter portion 13 in the form of continuous and closed peripheral trenches.

[0052] Then, a thin encapsulation layer 31 (here, amorphous silicon) is conformally deposited, for example, using chemical vapor deposition (CVD), extending over the mineral sacrificial layer 15 and the carbon-containing sacrificial layer 17 and into the trench. The thin encapsulation layer 31 includes a top portion 31.1 (also referred to as a top wall) extending over and spaced from the thermal detector 20 and the getter portion 13, and a peripheral portion 31.2 (also referred to as a peripheral wall) continuously surrounding the thermal detector 20 and the getter portion 13 in the XY plane and subsequently defining the sealing cavity 1 in the XY plane. Thus, the top wall 31.1 is located on and in contact with the mineral sacrificial layer 15 and the carbon-containing sacrificial layer 17. The peripheral wall 31.2 is positioned preferably with its inner surface oriented toward the thermal detector 20 in contact with the carbon-containing sacrificial layer 17.

[0053] Then, vias 32.1, 32.2 forming release vents are created in the thin encapsulation layer 31 by photolithography and etching. These release vents are designed to allow various sacrificial layers to drain from the cavity. The first vent 32.1 is positioned along the Z-axis opposite to the mineral sacrificial layers 14, 15 and placed on, for example, the absorbent film 21. Preferably, at least one second vent 32.2 is positioned along the Z-axis opposite to the carbon-containing sacrificial layer 17.

[0054] refer to Figure 1D Here, a first chemical etching suitable for removing the two mineral sacrificial layers 14, 15 is performed using a wet chemical etching process involving vapor-phase hydrofluoric acid etching. The products of the chemical reaction are discharged through a first release vent 32.1. This wet chemical etching is isotropic, resulting in the suspension of the absorbent film 21 and the release of the anchoring post 22. The first chemical etching is selective, thus not removing the carbon-containing sacrificial layer 17, thereby completely protecting the getter portion 13 from HF vapor etching. Therefore, the carbon-containing sacrificial layer 17 is released, meaning its surface, which initially contacted the mineral sacrificial layers 14, 15, is now free. It covers the getter portion 13 and completely surrounds it in the XY plane. Therefore, the top wall 31.1 of the thin encapsulation layer 31 partially rests on the carbon-containing sacrificial layer 17.

[0055] refer to Figure 1E A second chemical etching is performed to remove the carbon-containing sacrificial layer 17, thereby releasing the getter portion 13. This chemical etching is a dry chemical etching, where the etchant is oxygen present in the plasma. This dry chemical etching is isotropic, preserving the integrity of the released structure while facilitating the entry of the etchant into the cavity through release vents 32.1 and 32.2. Therefore, the getter portion 13 is released, leaving it with a free (uncoated) surface, thus exposed to the atmosphere of the cavity.

[0056] refer to Figure 1F A sealing layer 33 is deposited on a thin encapsulation layer 31, having sufficient thickness to ensure that the various release vents 32.1, 32.2 are sealed, i.e. blocked. The sealing layer 33 is transparent to the electromagnetic radiation to be detected and can be made of germanium with a thickness of approximately 1.7 μm. An anti-reflective layer 34 is then deposited to allow optimized transmission of electromagnetic radiation through the encapsulation structure 30. This anti-reflective layer 34 can be made of zinc sulfide with a thickness of approximately 1.2 μm. This results in a sealed cavity 1 under vacuum or low pressure, in which the thermal detector 20 and the getter portion 13 are housed.

[0057] Then, the chemical adsorption of the getter portion 13 is activated by appropriate heat treatment of the detection device in an oven or drying oven, thereby causing the getter material to react with the residual gas molecules present in the sealed cavity 1 to form a stable compound. This results in a continuous or reduced vacuum level within the sealed cavity 1, thereby extending the service life of the detection device.

[0058] Therefore, the manufacturing method allows for the acquisition of a detection device comprising one or more thermal detectors 20 and getter portions 13, all located within the sealed cavity 1. The getter portion 13 is located in the XY plane at a distance from the thermal detectors, i.e., at a non-zero offset relative to the thermal detectors 20, and preferably between the thermal detectors 20 and the peripheral wall 31.2 of the thin encapsulation layer 31. It is protected by a thick carbon-containing sacrificial layer to prevent first chemical etching, which, together with the mineral sacrificial layers 14 and 15, contributes to supporting the thin encapsulation layer 31 along the Z-axis.

[0059] During the successive CMP steps to planarize the top surfaces of the various deposited mineral sacrificial layers 14, 15, mechanical retention of the mineral sacrificial layers 14, 15 is maintained. This thereby avoids the mechanical fragility mentioned in document EP3239670A1, which highlights the configuration where the getter portion 13 is located below the thermal detector 20 and protected by a thin carbon-containing sacrificial layer made of polyimide. In fact, in the context of this invention, the mineral sacrificial layers 14, 15 are not located on the carbon-containing sacrificial layer 17, which is located in the through-holes 16 extending through the mineral sacrificial layers 14, 15.

[0060] Furthermore, as long as the getter portion 13 is protected by a thick carbon-containing sacrificial layer rather than a thin one, the integrity of the getter portion 13 is also maintained, allowing for a much larger protection size. In the context of this invention, the carbon-containing sacrificial layer 17 is a thick (not thin) layer that completely surrounds the getter portion 13 in the XY plane. It can be made of polyimide or amorphous carbon. The protection size can be approximately tens or even hundreds of micrometers, which significantly improves the protection of the getter portion 13. It is used to ensure support of a portion of the thin encapsulation layer 31 during deposition. Furthermore, the getter portion 13 is not positioned facing the absorber film 21 as in document EP3239670A1, which allows for the use of a larger area of ​​getter material. Moreover, the getter material can be selected solely based on its chemisorption properties, rather than on the complementary properties of the optical reflector. Therefore, getter materials with high chemisorption performance can be selected.

[0061] Figures 2A-2F The various steps of a method for manufacturing a detection device according to a second embodiment are shown. Only a portion of the detection device is shown. The main difference between this embodiment and the embodiments described above is that the thin encapsulation layer 31 includes an inner portion 31.3 (also referred to as an inner wall) located between the mineral sacrificial layers 14, 15 and the carbon-containing sacrificial layer 17, and ensures physical protection of the carbon-containing sacrificial layer 17 relative to the first chemical etching.

[0062] refer to Figure 2AA matrix of thermal detectors 20 is generated on the readout substrate 10, such that they are covered by the mineral sacrificial layer 15. This step is similar to the reference step. Figure 1A The steps described herein differ in that a getter portion 13 is formed on the protective layer 12 prior to the deposition of the mineral sacrificial layer 14 and the formation of the absorber film 21. Therefore, the getter portion 13 is positioned offset in the XY plane relative to the thermal detector 20 and is covered by the two mineral sacrificial layers 14, 15. However, it should be noted that the formation of the getter portion 13 can also be achieved here after the formation of the absorber film 21 and the deposition of the sacrificial layer 15.

[0063] refer to Figure 2B Then, in a similar reference Figure 1B The aforementioned method produces a thin encapsulation layer 31 of the encapsulation structure 30. However, the inner wall 31.3 extends in the XY plane to separate the carbon-containing sacrificial layer 17 from the mineral sacrificial layers 14, 15. Therefore, it has a surface that contacts the mineral sacrificial layers 14, 15, and an opposing surface that contacts the carbon-containing sacrificial layer 17. It is positioned in contact with the readout substrate 10 and connects to the top wall 31.1 of the thin encapsulation layer 31 along the Z-axis. Thus, the inner wall 31.3 and the outer wall 31.2 define a sealed space 1.2 separated from the space 1.1 where the thermal detector 20 is located.

[0064] Then, vias 32.1 are formed in the thin encapsulation layer 31 by photolithography and etching. These vias form first release vents designed to allow the mineral sacrificial layers 14, 15 to drain from the cavity. These first vents 32.1 are positioned along the Z-axis opposite to the mineral sacrificial layers 14, 15, for example, above the absorber film 21. Preferably, no second vent 32.2 leading to the carbon-containing sacrificial layer 17 is formed at this stage.

[0065] refer to Figure 2C Here, a first chemical etching is performed using wet chemical etching with HF vapor to remove the two mineral sacrificial layers 14 and 15. The products of the chemical reaction are discharged through the first release vent 32.1. Therefore, unlike the first embodiment, the carbonaceous sacrificial layer 17 is completely protected by the physical protection provided by the inner wall 31.3. In the case where wet chemical etching causes partial etching of the carbonaceous sacrificial layer 17, the carbonaceous sacrificial layer is completely retained here.

[0066] refer to Figure 2DThen, one or more second release vents 32.2 are created, which are designed to allow the carbon-containing sacrificial layer 17 to be discharged from the space 1.2 where the carbon-containing sacrificial layer 17 is located. These second vents 32.2 are positioned along the Z-axis opposite to the carbon-containing sacrificial layer 17. At least one second vent 32.2 is positioned perpendicular to the inner wall 31.3 to continuously or partially disconnect the physical connection between the inner wall and the top wall 31.1. This step is performed by photolithography and etching using photoresist 18, which is subsequently removed. The photoresist 18 has viscosity properties that prevent it from penetrating into the vents 32.1.

[0067] refer to Figure 2E A second chemical etching is performed to remove the carbon-containing sacrificial layer 17 and release the getter portion 13. This chemical etching is a dry chemical etching, where the etchant is oxygen present in the plasma. The etching products from the carbon-containing sacrificial layer 17 are essentially discharged through the second vent 32.2. Therefore, there is communication between the space 1.1 where the thermal detector 20 is located and the space 1.2 where the getter portion 13 is located.

[0068] refer to Figure 2F Then, a sealing layer 33 is deposited on the thin encapsulation layer 31 to ensure the sealing (i.e., blocking) of the various release vents 32.1, 32.2. Next, an anti-reflective layer 34 is deposited. Then, the chemisorption of the getter portion 13 is activated by heat treatment.

[0069] Therefore, by creating a sealed space 1.2, which is formed, in particular, by the inner wall 31.3 of the thin encapsulation layer 31, and with the carbon-containing sacrificial layer 17 and the resulting getter portion 13 located within this sealed space, the carbon-containing sacrificial layer 17 is prevented from being degraded by wet chemical etching (in this case, HF vapor etching), and the protection of the getter portion 13 relative to this etching is further improved. This embodiment is particularly advantageous when the carbon-containing sacrificial layer 17 can react slightly with the etchant used in the first chemical etching.

[0070] Figures 3A-3E Various steps of a method for manufacturing a detection device according to a variant of the second embodiment are shown. Only a portion of the detection device is shown. This variant differs from the second embodiment in that the device is used to ensure communication between the space 1.1 where the thermal detector 20 is located and the space 1.2 where the carbon-containing sacrificial layer 17 and the getter portion 13 are located.

[0071] refer to Figure 3AOn and in contact with the read substrate 10 between the thermal detector 20 and the getter portion 13, a portion of another carbon-containing sacrificial layer 17, referred to as the carbon-containing portion 19, is pre-formed. This carbon-containing portion 19 is made of a carbon-containing material that is substantially inert to the first chemical etching (here, HF vapor etching) and can be removed by a second chemical etching (here, O2 plasma). It can be made of the same material as the carbon-containing sacrificial layer 17 or a different material. In this example, the carbon-containing portion 19 is made of amorphous carbon, and the carbon-containing sacrificial layer 17 is made of polyimide. The thin encapsulation layer 31 includes an inner wall 31.3 similar to that described in the second embodiment, but it contacts the carbon-containing portion 19 and connects to the top wall 31.1 along the Z-axis.

[0072] refer to Figure 3B Here, a first chemical etching is performed using wet chemical etching with HF vapor etching to remove the two mineral sacrificial layers 14, 15. The products of the chemical reaction are discharged through the first release vent 32.1. As long as the carbon-containing portion 19 is inert relative to the HF vapor etching, there is no interruption in the physical connection between the inner wall 31.3 and the readout substrate 10. Therefore, the carbon-containing sacrificial layer 17 remains completely retained.

[0073] refer to Figure 3C Then, one or more second release vents 32.2 are created, which are designed to allow the carbon-containing sacrificial layer 17 to be discharged from the space 1.2 where the carbon-containing sacrificial layer 17 is located. These second vents 32.2 are positioned along the Z-axis opposite to the carbon-containing sacrificial layer 17. However, with Figure 2D The difference is that no vents positioned perpendicular to the inner wall 31.3 are created, thus interrupting the physical connection between the inner wall and the top wall 31.1. The interruption of the physical connection is ensured by removing the carbon-containing portion 19.

[0074] refer to Figure 3D A second chemical etching is performed to remove the carbon-containing sacrificial layer 17 and release the getter portion 13, but also removes the carbon-containing portion 19. The etching product from the carbon-containing sacrificial layer 17 is discharged through the second vent 32.2. Therefore, there is a connection between the space 1.1 where the thermal detector 20 is located and the space 1.2 where the getter portion 13 is located. This connection is not achieved through the absence of a physical connection between the inner wall 31.3 and the top wall 31.1, but rather through the absence of a physical connection between the inner wall 31.3 and the readout substrate 10. This absence of a physical connection may be continuous or discontinuous along the inner wall 31.3.

[0075] refer to Figure 3EThen, a sealing layer 33 is deposited on the thin encapsulation layer 31 to ensure the sealing (i.e., blocking) of the various release vents 32.1, 32.2. Next, an anti-reflective layer 34 is deposited. Then, the chemisorption of the getter portion 13 is activated by heat treatment.

[0076] Specific embodiments have just been described. Various modifications and variations will be apparent to those skilled in the art.

[0077] Therefore, generally, as shown in the two embodiments, the step of generating the getter portion 13 can be performed before or after the step of generating the thermal detector 20. Furthermore, the getter portion 13 can extend laterally in the XY plane such that the peripheral wall 31.2 contacts the getter portion, thereby improving the adhesion between the package structure 30 and the readout substrate 10.

Claims

1. A method for manufacturing an apparatus for detecting electromagnetic radiation, comprising the following steps: o At least one thermal detector (20) is generated on a substrate (10), the at least one thermal detector being covered by at least one mineral sacrificial layer (14, 15) made of a mineral material that can be removed by a first chemical etching; o Creates vias (16) that extend through the mineral sacrificial layers (14, 15) and into the substrate (10); o generates a getter portion (13) made of a metallic material with a getter effect, the getter portion being disposed on and in contact with the substrate (10), and being at a certain distance from a thermal detector (20) in a plane parallel to the substrate (10); • The getter portion (13) is located in the through hole (16) at a certain distance from the lateral boundary (16.1), which is defined by the mineral sacrificial layer (14, 15) and defines the through hole (16) in a plane parallel to the substrate (10); o produces a carbon-containing sacrificial layer (17) made of a carbon-containing material that is inert to the first chemical etching and can be removed by the second chemical etching. • To cover the getter portion (13), and to surround the getter portion in a plane parallel to the substrate, and to completely fill the through-hole (16); o produces a thin encapsulation layer (31), the thin encapsulation layer comprising: a top portion (31.1) and a peripheral portion (31.2); The top portion is located on the mineral sacrificial layer (15) and the carbon-containing sacrificial layer (17); the outer portion extends through the mineral sacrificial layers (14, 15) and surrounds the thermal detector (20) and the getter portion (13); o Remove the mineral sacrificial layers (14, 15) by the first chemical etching; o The carbon-containing sacrificial layer (17) is removed by the second chemical etching.

2. The method according to claim 1, wherein, The getter portion (13) is disposed between the thermal detector (20) and the outer portion (31.2) of the thin encapsulation layer (31).

3. The method according to claim 1, wherein, The peripheral portion (31.2) includes an inner surface oriented toward the thermal detector (20) and in contact with the carbon-containing sacrificial layer (17).

4. The method according to claim 1, wherein, The mineral sacrificial layer (15) and the carbon-containing sacrificial layer (17) have coplanar top surfaces opposite to the substrate (10).

5. The method according to claim 1, wherein, The mineral material comprises at least silicon oxide or silicon nitride, and the first chemical etching is a gas-phase hydrofluoric acid etching.

6. The method according to claim 1, wherein, The carbon-containing material is selected from amorphous carbon and polyimide, and the second chemical etching is a dry etching performed by oxygen plasma.

7. The method according to claim 1, wherein, The metal material having a gas-getting effect is selected from titanium, zirconium, vanadium, chromium, cobalt, iron, manganese, palladium, barium and / or aluminum, as well as alloys of these metals.

8. The method according to claim 1, wherein, The method includes generating at least one first release vent (32.1) and at least one second release vent (32.2) through the top portion (31.1) of the thin encapsulation layer (31), the first release vent (32.1) leading to the mineral sacrificial layer (15) and the second release vent (32.2) leading to the carbonaceous sacrificial layer (17).

9. The method according to claim 8, wherein, The first release vent (32.1) and the second release vent (32.2) are formed prior to the first chemical etching, and the carbon-containing sacrificial layer (17) below the top portion (31.1) of the thin encapsulation layer (31) is in contact with the mineral sacrificial layer (15).

10. The method according to claim 8, wherein, The thin encapsulation layer (31) further includes an inner portion (31.3) extending from the top portion (31.1) toward the substrate (10) and located between the mineral sacrificial layers (14, 15) and the carbon-containing sacrificial layer (17), such that the carbon-containing sacrificial layer (17) below the top portion (31.1) of the thin encapsulation layer (31) contacts the top portion (31.1), the outer portion (31.2) and the inner portion (31.3) of the thin encapsulation layer (31).

11. The method according to claim 10, wherein, The step of generating the second release vent (32.2) includes, in addition to forming at least one second release vent (32.2) leading to the carbon-containing sacrificial layer (17), forming at least one vent (32.2) perpendicular to the inner portion (31.3), the at least one vent at least partially interrupting the physical connection between the inner wall (31.3) and the top portion (31.1), thereby ensuring communication between the first space (1.1) where the thermal detector (20) is located and the second space (1.2) where the getter portion (13) is located after the second chemical etching.

12. The method according to claim 10, wherein, The inner portion (31.3) is in contact with the carbon-containing portion (19), which is configured to contact the substrate (10) and is made of a carbon-containing material that is inert to the first chemical etching and can be removed by the second chemical etching, such that the second chemical etching removes the carbon-containing sacrificial layer (17) and releases the getter portion (13), and removes the carbon-containing portion (19) and forms a connection between the first space (1.1) where the thermal detector (20) is located and the second space (1.2) where the getter portion (13) is located.

13. The method according to claim 1, wherein, Simultaneously, multiple thermal detectors (20) are generated, each of which includes a membrane adapted to absorb the electromagnetic radiation to be detected, the membrane being suspended above the substrate (10) by anchor posts (22) and thermally insulated from the substrate by support arms.

14. The method according to claim 1, wherein, The top portion (31.1) of the thin encapsulation layer (31) is located on and in contact with the mineral sacrificial layer (15), and is located on and in contact with the carbon-containing sacrificial layer (17).

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