Electromagnetic radiation detection device and manufacturing method

Abstract

The invention relates to a device (1) for detecting electromagnetic radiation, comprising at least one detector placed in a cavity (2) formed by an encapsulation structure comprising an anchor strut (21) and a support strut (22), the at least one anchor strut being connected to the at least one detector, the support strut being connected to the at least one detector, and the support strut being connected to the at least one detector. And the supporting pillar (22) is mounted at the top of the anchoring pillar (21). Advantageously, the support pillar (22) has a portion (220) extending above at least one side face (210) of the anchoring pillar (21). The invention also relates to a method for manufacturing such a device (1).

Description

Technical Field

[0001] The present invention relates to a device for detecting electromagnetic radiation, particularly infrared or terahertz radiation, comprising at least one thermal detector (e.g., a microbolometer) enclosed in a cavity. The invention is particularly applicable to the fields of infrared or terahertz imaging, thermal imaging, presence detection, and even gas detection. Background Art

[0002] Devices for detecting electromagnetic radiation (e.g., infrared or terahertz) typically comprise a matrix of thermal detectors, each of which consists of a thin film capable of absorbing the electromagnetic radiation to be detected and a temperature transducer, such as a thermistor. To ensure thermal isolation of the temperature transducer from the reading substrate on which the detector is fabricated, the absorbing film is typically suspended above the substrate by anchoring struts and thermally isolated from the substrate by thermally insulating arms. These anchoring struts and thermally insulating arms also serve an electrical function, connecting the absorbing film to the reading circuitry, which is typically incorporated into the substrate.

[0003] To ensure the best working state of the thermal detector, a lower pressure level may be required. For this purpose, the thermal detector is usually encapsulated individually or in multiples in at least one vacuum or reduced pressure sealed cavity.

[0004] Among the various technologies used to package thermal detectors (integrated in a sealed housing, sealed assembly with a second substrate, and sealed by thin layer deposition), the technology of forming a packaging structure by a thin layer and a sealed cavity defined by a reading substrate is particularly suitable for large-scale, low-cost manufacturing of radiation detection devices.

[0005] Document FR2003858 describes an example of such a packaging method for manufacturing a detection device 1, as Figure 1 As shown, the thermal detector of the device is placed in a cavity 2 formed by a packaging structure on a reading substrate 100. The method uses two layers of mineral sacrificial layers to produce, in sequence, a thermal detector connected to an anchoring pillar 21, followed by the upper part of the packaging structure. These sacrificial layers are then removed by chemical vapor etching. The upper part of the packaging structure is composed of a thin layer 23 (called an encapsulation layer) and a thin layer 24 (called a sealing layer), the purpose of which is to close the vent 230 used to remove the sacrificial layer. In this example, the encapsulation layer 23 extends all the way to the surface above the thermal detector and the non-etched portion of the second sacrificial layer. It also extends continuously to the vertical portion to form a support pillar 22 for the encapsulation layer, which is located on the anchoring pillar 21. An electrical isolation layer 3 is further provided between the anchoring pillar 21 and the support pillar 22 to electrically isolate the thermal detector supported by the anchoring pillar 21.

[0006] The support struts of the package structure have the particular function of maintaining the mechanical integrity of the package structure, as the package structure is subject to the atmospheric pressure outside the cavity. Therefore, the support struts serve to withstand compressive forces. A disadvantage of this solution is that the interface layer between the support struts and the anchor struts does not adhere strongly to the anchor struts. Therefore, if the package structure is subjected to traction forces (typically caused by mechanical stresses between the reader substrate and the package structure), the support struts can detach from the anchor struts.

[0007] Therefore, it is necessary to provide a method for manufacturing a packaging structure to improve the mechanical strength of the packaging structure. The purpose of the present invention is to meet this demand.

[0008] In particular, the present invention aims at a detection device which improves the mechanical strength of the package structure and in particular limits the risk of detachment between the support pillars of the package structure and the anchoring pillars supporting the detector. Another object of the invention is a method for producing such a device.

[0009] Other objects, features and advantages of the present invention will become apparent after studying the following description and the accompanying drawings. It should be understood that the present invention also has other advantages. Summary of the Invention

[0010] To achieve this purpose, according to one embodiment, an electromagnetic radiation detection device is provided, which includes at least one detector, which is arranged in a cavity formed by a packaging structure, and the packaging structure includes anchoring pillars (wherein at least one anchoring pillar is connected to at least one detector) and supporting pillars, which are located above the anchoring pillars.

[0011] Advantageously, the support strut has a portion extending to at least one side of the anchor strut.

[0012] This increases the contact surface between the support strut and the underlying structure, thereby improving adhesion. Furthermore, the support strut, through its portion extending to the side of the anchoring strut, is at least partially in direct contact with the anchoring strut. This direct contact generally provides greater adhesion than indirect contact achieved through an electrically insulating layer inserted between the anchoring strut and the support strut (as disclosed in document FR2003858). Mechanical strength is also improved.

[0013] During the development of the present invention, it was observed that the electrical isolation layer, typically composed of a stack of multiple thin layers, can delaminate or detach from the anchoring posts under the influence of traction forces associated with the mechanical stress differential between the reader substrate and the package structure. This likelihood of delamination is particularly pronounced when the isolation layer comprises a large number of thin layers of varying properties and thicknesses.

[0014] To improve interlayer adhesion and avoid delamination, those skilled in the art may consider optimizing solutions, for example, by modifying the properties of the various layers of the barrier layer, or by improving the surface preparation and / or deposition methods of the various layers. These conventional solutions are generally available to those skilled in the art. However, they are still not very effective and, therefore, are not included within the scope of the present invention.

[0015] Therefore, according to the present invention, the innovative connection between the anchoring pillars and the supporting pillars can significantly improve the mechanical strength of the packaging structure of the electromagnetic radiation detection device.

[0016] Another aspect of the present invention relates to a method of manufacturing such an electromagnetic radiation detection device, comprising:

[0017] - providing a substrate;

[0018] - forming a first sacrificial layer on the substrate;

[0019] - forming anchoring struts through the first sacrificial layer;

[0020] - placing at least one detector over the first sacrificial layer and forming a connection between the at least one detector and at least one of the anchoring posts;

[0021] - forming a second sacrificial layer over the first sacrificial layer, the at least one detector, and the anchoring posts;

[0022] - forming a second opening in the second sacrificial layer above the anchoring post, the second opening extending to at least one side of the anchoring post and preferably extending into the first sacrificial layer;

[0023] - filling said second opening with at least one filling material to form a support strut positioned above the anchor strut;

[0024] - forming an encapsulation layer made of an encapsulation material on the second sacrificial layer and at least a portion of the support pillars;

[0025] - forming at least one vent hole in the encapsulation layer, the vent hole leading to the second sacrificial layer;

[0026] - removing the second and first sacrificial layers through the at least one vent hole, thereby forming a cavity around the at least one detector;

[0027] - forming a sealing layer made of a sealing material on the encapsulation layer to block the at least one vent hole and preferably to seal the cavity. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The objects, goals, features and advantages of the present invention will be best understood from the detailed description of the embodiments of the present invention, which are illustrated in the following drawings, in which:

[0029] Figure 1 An electromagnetic radiation detection device according to the prior art includes a packaging structure;

[0030] Figure 2A 、 Figure 3A 、 Figure 4A 、 Figure 5A 、 Figure 6A 、 Figure 7A 、 Figure 8A and Figure 9A The steps of manufacturing an electromagnetic radiation detection device according to an embodiment of the present invention are schematically illustrated along a first cross section;

[0031] Figure 2B 、 Figure 3B 、 Figure 4B 、 Figure 5B 、 Figure 6B 、 Figure 7B 、 Figure 8B and Figure 9B The corresponding embodiment according to the present invention is schematically illustrated along different cross sections. Figure 2A 、 Figure 3A 、 Figure 4A 、 Figure 5A 、 Figure 6A 、 Figure 7A 、 Figure 8A and Figure 9A The manufacturing steps shown in;

[0032] Figure 10A 、 Figure 11A and Figure 12A The steps of manufacturing an electromagnetic radiation detection device according to another embodiment of the present invention are schematically illustrated along a first cross section;

[0033] Figure 10B 、 Figure 11B and Figure 12B The corresponding embodiment according to another embodiment of the present invention is schematically illustrated in cross section. Figure 10A 、 Figure 11A and Figure 12A The manufacturing steps shown in;

[0034] 13A to 13D Different schemes for manufacturing an electromagnetic radiation detection device according to different embodiments of the present invention are schematically illustrated in the form of top views;

[0035] Figure 14A and Figure 14B The electromagnetic radiation detection device according to another embodiment of the present invention is schematically illustrated. Figure 14B and Figure 14A corresponds to the cross section XX shown in;

[0036] Figure 15 A variant of manufacturing an electromagnetic radiation detection device according to an embodiment of the present invention is schematically illustrated in a top view.

[0037] In the cross-sectional views, the cutting planes are indicated as (AA, BB, ..., XX) and intersect with the cutting planes in the corresponding figures. The accompanying drawings are given as examples and do not limit the invention. They constitute schematic diagrams of principles intended to facilitate understanding of the invention and are not necessarily consistent with the proportions of actual applications. In particular, in the schematic diagrams, the thickness and / or size of the different layers, patterns and raised elements do not represent the actual situation. For the sake of clarity, only a single supporting strut mounted on a single anchoring strut is shown in each figure. It will be understood that the detection device typically includes a plurality of supporting struts and anchoring struts. DETAILED DESCRIPTION

[0038] Before starting to describe the embodiments of the present invention in detail, the following will describe the optional functions that can be used in combination or alternately:

[0039] According to one example, the device further comprises an intermediate structure located between the supporting struts and the anchoring struts, said intermediate structure having:

[0040] - an isolation arm configured to support at least one detector,

[0041] - At least one overhang located at the periphery of the upper surface of the anchoring strut.

[0042] According to one example, a portion of the support strut bypasses or passes through at least one overhang. This portion of the support strut, bypassing or passing through the overhang, contacts the side of the anchor strut below the overhang. Thus, the support strut is mechanically anchored below the overhang. The overhang contributes to enhancing the mechanical strength of the support strut, thereby strengthening the mechanical strength of the package structure.

[0043] According to one example, the portion of the support strut includes a first portion located at the at least one overhang, having a first dimension La along a reference direction x or y, and a second portion located outside the at least one overhang and extending to at least one side of the anchoring strut, having a second dimension Lb along the reference direction x or y, such that the second dimension Lb is strictly greater than the first dimension La. Thus, after passing the overhang, the portion of the support strut widens laterally of the anchoring strut. The widened second portion thus forms a stop (butée) against the overhang, preventing the support strut from being pulled relative to the anchoring strut.

[0044] According to one example, the portion of the support strut forms a keying structure with at least one overhang of the intermediate structure, such as a dovetail or sawtooth structure. The portion of the support strut engages the overhang. This can be in the form of a groove that fits the overhang, or more generally, in the form of a mechanical assembly utilizing the overhang.

[0045] According to one example, at least a second portion of the portion of the support strut is in contact with at least one side of the anchor strut.

[0046] According to one example, the first and second portions of the portion of the support strut are in contact with at least one side of the anchoring strut, thereby improving the adhesion of the portion of the support strut to the anchoring strut.

[0047] According to one example, a first portion of the portion of the support strut contacts an upper surface of the anchor strut, thereby further improving adhesion between the portion of the support strut and the anchor strut.

[0048] According to one example, the portion of the supporting strut extends to a first side surface (located on a first side) and a second side surface (located on a second side opposite to the first side) of the anchoring strut. Mechanical strength is further enhanced.

[0049] According to one example, the cavity is enclosed by an encapsulation layer made of encapsulation material carried on a supporting pillar and a sealing layer made of sealing material on the encapsulation layer, and the supporting pillar is at least partially formed only by the encapsulation layer or formed by the encapsulation layer and the sealing layer together, so that the supporting pillar only contains encapsulation material or contains encapsulation material and sealing material.

[0050] According to one example, the cavity is laterally delimited by a peripheral wall extending substantially vertically between the reading substrate and the encapsulation layer. The peripheral wall is typically based on the material (typically based on SiO2) of the sacrificial layer used to form the cavity.

[0051] According to one example, the cavity is sealed.

[0052] According to one example, the height of the cavity is less than or equal to 10 μm, or even less than 5 μm (for example, if only the vacuum packaging function is required).

[0053] According to one example, the thickness of the thin encapsulation layer is less than or equal to 800 nm.

[0054] According to one example, the supporting and / or anchoring struts are arranged in a matrix.

[0055] According to one example, a thermal detector includes an absorbing film suspended above a reader substrate by anchoring posts.

[0056] According to one example, the method further includes forming an intermediate structure between the support pillar and the anchor pillar after forming the first sacrificial layer and before forming the second sacrificial layer, the intermediate structure having:

[0057] - a spacer arm configured to support at least one detector, said spacer arm forming a connection between said at least one detector and at least one of the anchoring struts;

[0058] - There is at least one overhang around the periphery of the upper surface of the anchoring post.

[0059] According to one example, forming the second opening includes:

[0060] - an anisotropic etch configured to extend the second opening below and vertically align with the at least one overhang,

[0061] - an isotropic etch configured to extend the second opening below the at least one overhang and abut against at least one side of the anchoring strut, so that after filling the second opening, the portion of the supporting strut has a first portion at the at least one overhang (the first portion having a first dimension La along a reference direction x or y), and a second portion, the second portion being located below the at least one overhang and on at least one side of the anchoring strut and having a second dimension Lb along the reference direction x or y, such that the second dimension Lb is strictly greater than the first dimension La.

[0062] According to one example, the method further includes, after forming the intermediate structure, forming a first opening in the intermediate structure, wherein the first opening partially exposes the upper surface of the anchoring post and passes through at least one overhang portion of a periphery of the anchoring post.

[0063] According to one example, the second opening in the second sacrificial layer is configured so that the second opening at least partially passes through the first opening. Thus, during the subsequent filling process, this portion of the support strut passes through the overhang and directly contacts the upper surface and side surfaces of the anchor strut. This enhances the mechanical strength and adhesion of the support strut to the anchor strut.

[0064] According to one example, the second opening is filled at least partially during the formation of the encapsulation layer by conformally depositing the encapsulation layer on the second sacrificial layer and in the second opening, such that at least one filling material includes the encapsulation material. This can limit the number of steps required for filling and forming the encapsulation layer, allowing them to be at least partially completed simultaneously.

[0065] According to one example, the second opening is at least partially filled during the sealing layer formation process, i.e., the sealing layer is deposited on the encapsulation layer, so that the at least one filling material includes an encapsulation material and a sealing material. This can limit the number of steps required for filling and forming the sealing layer, so that they can be at least partially completed simultaneously.

[0066] According to one example, the second opening is filled with a filling material different from the encapsulation material before the encapsulation layer is formed, so that the filling material can be selected based on its adhesion properties without considering its optical properties.

[0067] According to one example, the filler material is selected to be the same as or based on the material of the anchoring struts.

[0068] It is understood that, unless mutually incompatible, all of the above optional features can be combined to form embodiments not necessarily illustrated or described. The present invention obviously does not exclude such implementations. The features and advantages of one aspect of the present invention (e.g., an apparatus or method) can be applied to other aspects of the present invention with appropriate modifications.

[0069] The present invention generally relates to an electromagnetic radiation detection device suitable for detecting infrared or terahertz radiation, and a method for manufacturing such a device. The detection device comprises at least one detector, preferably a matrix of thermal detectors, positioned within a sealed cavity. The matrix of thermal detectors is preferably formed as a periodic network. Each thermal detector is a photosensitive detector and forms a detection pixel suitable for detecting the relevant electromagnetic radiation.

[0070] Within the scope of the present invention, the cavity is delimited in its lower part by a reading substrate and in its upper part by an encapsulation structure comprising one or more thin layers transparent to the electromagnetic radiation to be detected, including in particular a thin encapsulation layer and a thin sealing layer for the vent. The encapsulation structure also comprises anchoring struts and supporting struts located above the anchoring struts, all of which support the upper layer of the encapsulation structure.

[0071] The cavity is further laterally bounded by a peripheral wall that extends continuously around the thermal detector matrix. As described below, the peripheral wall generally corresponds to a non-etched portion of the sacrificial layer.

[0072] The term "surmount" (French: "surmount") means located "above." Specifically, a support strut being "surmounted" by an anchor strut means that the support strut is located above the anchor strut along at least one common line or direction in the z-direction in the figures. For the purposes of this invention, a first element that exceeds a second element in height cannot be considered "surmounted" by a second element unless it is located directly above the second element.

[0073] The phrase "on the side" (Sur un flanc in French) means in direct contact with the side. In particular, a portion of a support strut "extending to the side of an anchor strut" means that portion is in direct contact with the side of the anchor strut. A first element arranged parallel to a second element does not "extend to the side of the second element" within the meaning of the present invention if the first element does not directly contact the second element.

[0074] A thin layer is a layer formed by microelectronic material deposition techniques, preferably having a thickness of less than or equal to 10 micrometers. Furthermore, a thin layer is considered transparent when its transmittance at the central wavelength of the electromagnetic radiation spectral range to be detected is greater than or equal to 50%, preferably 75%, or even 90%.

[0075] It should be noted that, within the scope of the present invention, the terms "on", "over", "covering", "under", "opposite to", and their equivalents do not necessarily mean "in contact with". Thus, for example, depositing, transferring, bonding, assembling, or applying a first layer onto a second layer does not necessarily mean that the two layers are in direct contact, but rather means that the first layer at least partially covers the second layer, either by directly contacting the second layer or by being separated from the second layer by at least one other layer or at least one other element.

[0076] Furthermore, a layer may also consist of a plurality of sub-layers of the same material or sub-layers of different materials.

[0077] The so-called substrate, film, or layer "based on" material A refers to a substrate, film, or layer composed only of this material A, or a substrate, film, or layer composed of this material A and other materials (such as doping elements or alloy elements).

[0078] The following describes several embodiments of the present invention for implementing the continuous steps of the manufacturing method. Unless explicitly mentioned, the adjective "continuous" does not necessarily mean (even though this is usually preferred) that the steps follow each other immediately, and intermediate steps can separate them.

[0079] Furthermore, the word "step" refers to a part of performing a method and may also refer to a series of sub-steps.

[0080] Furthermore, the term "step" does not necessarily imply that the operations performed in that step are performed simultaneously or consecutively. In particular, some operations of a first step may be interrupted by operations in other steps, and then the remaining operations of the first step may be continued. Thus, the term "step" does not necessarily refer to a single, indivisible operation that is performed over time and in a sequential order of method stages.

[0081] "Selective etching relative to" or "etching selectively to" means that the etching is configured to remove material A or layer A relative to material B or layer B, and the etching rate of material A is greater than the etching rate of material B. Selectivity is the ratio of the etching rate of material A to the etching rate of material B, denoted by S. A:B . Selective S A:B A ratio of 10:1 means that the etching rate of material A is 10 times that of material B.

[0082] The drawings show an orthogonal coordinate system preferably comprising x, y and z axes. If only a single coordinate system is shown in the same set of drawings, this coordinate system applies to all drawings in the set.

[0083] In this patent application, "thickness" is preferably used for layers or films, and "height" is preferably used for devices or structures. The thickness is measured along the normal direction of the main extension plane of the layer or film. Thus, a layer or film usually has a thickness along the z-axis. The packaging structure or pillar has a height along the z-axis. Relative terms such as "on...", "above...", "below...", "below..." refer to positional relationships along the z-axis. "Lateral" dimensions refer to dimensions along the xy direction of the plane. "Lateral extension" or "laterally" refers to extension in one or more directions along the xy plane.

[0084] When an element is “vertically aligned” or “facing” another element, it means that both elements are located on the same line perpendicular to the plane in which the lower or upper surface of the substrate mainly extends, that is, on the same line in the vertical direction in a cross-sectional view.

[0085] The terms "substantially", "about" and "approximately" refer to an error of ±10%, preferably ±5%. In addition, the terms "between..." and equivalent expressions mean that, unless otherwise specified, the endpoint values are included.

[0086] Figures 2A to 9A According to a first cross-sectional view (AA, CC, . . . , OO) an embodiment of a device for detecting infrared radiation with a wavelength between 8 μm and 14 μm is shown, which device comprises a microbolometer type detector. Figures 2B to 9B According to the corresponding Figures 2A to 9A The other cross-sectional views shown, BB, DD, ..., PP, etc., illustrate the same embodiment of the device.

[0087] like Figure 2A 、 Figure 2BAs shown, the first step consists in forming, in a known manner, the anchoring pillars 21 on a substrate 100, which preferably comprises a readout circuit based on CMOS (Complementary Metal Oxide Semiconductor) transistors, referred to as readout substrate 100. The readout circuit of substrate 100 generally comprises at least one metallization layer including conductive portions 101 (generally made of copper) flush with the surface of substrate 100. In this case, these conductive portions 101 serve to electrically connect the anchoring pillars 21 to the readout circuit of substrate 100.

[0088] On the reading substrate 100, a barrier layer 110, for example made of silicon nitride (SiN), can be formed to prevent copper diffusion. Then, a protective layer 120 is formed, for example made of aluminum nitride (AlN) or aluminum oxide (Al2O3). This protective layer has electrical insulation properties and is chemically inert to hydrofluoric acid (HF). The function of this layer 120 is to protect the substrate 100 during the subsequent hydrofluoric acid vapor etching step to remove the sacrificial layer and form the cavity of the device.

[0089] Subsequently, a first sacrificial layer 20a, preferably made of silicon dioxide (SiO2), is formed on the protective layer 120. The first sacrificial layer 20a is then opened by local etching using a photolithographic pattern, the photolithographic pattern corresponding to the position of the anchoring pillar 21 above the conductive portion 101. The shape of the photolithographic pattern can be circular, square or rectangular and substantially determines the cross-section of the anchoring pillar 21 in the xy plane. The etching extends through the layers 120 and 110 to expose the conductive portion 101. Before filling the opening of the first sacrificial layer 20a, it is preferred to first deposit a barrier layer (not shown, for example made of TiN) and then perform a step of depositing a conductive material layer (for example made of tungsten (W) or copper (Cu)). A chemical mechanical polishing (CMP) step is then performed to remove the material deposited on the upper surface of the first sacrificial layer 20a and form the upper surface 211 of the anchoring pillar 21. At this stage, anchoring posts 21 are formed in the form of metal pillars (plots metalliques in French), typically having dimensions or diameters of approximately 0.5 μm along the x and / or y axes and a height of approximately 1.8 μm along the z axis. These anchoring posts 21 are electrically connected to the readout circuitry of substrate 100. The upper surface 211 of the anchoring posts 21 is substantially flush with the upper surface of the first sacrificial layer 20a. The upper surface 211 may be slightly recessed relative to the upper surface of the first sacrificial layer 20a as a result of the CMP polishing operation, which preferably removes the metal material of the anchoring posts 2 (relative to the SiO2 of the sacrificial layer 20a). For example, this recess is approximately 70 nm, less than 4% of the height of an anchoring post having a height of 1.8 μm. The side surfaces 210 of the anchoring posts 21 are in contact with the first sacrificial layer 20a.

[0090] like Figure 3A 、 Figure 3BAs shown, a wafer 310, for example, circular, octagonal, square or rectangular, is formed on the upper surface 211 of each metal pillar 21. The wafer 310 is advantageously made of TiN to serve as a barrier to the diffusion of metal atoms in the metal pillar. Its thickness is typically between 20 nm and 50 nm. Its size or diameter along the x and / or y direction is typically larger than the size or diameter of the anchoring pillar 21. Preferably, it is aligned with the center of the anchoring pillar 21. Thus, a first overhang is formed relative to the anchoring pillar 21. The wafer 310 overhangs the anchoring pillar 21 laterally by a distance of tens to hundreds of nanometers. The first overhang may extend a distance greater than or equal to 50 nm, for example 100 nm or 200 nm.

[0091] like Figure 4A 、 Figure 4B As shown, a stack of layers 301, 302, and 303 is formed on a wafer 310 and the upper surface of the first sacrificial layer 20a, and then structured by etching to form an intermediate structure 3 including the thermal insulation arms 30. Therefore, the intermediate structure 3 includes the wafer 310 and the stack of structured layers 301, 302, and 303. The intermediate structure 3 is used to be inserted between the bottom anchoring pillar 21 and the supporting pillar above.

[0092] The insulating arms 30 are generally narrow, with a width in the y direction of, for example, between 0.1 μm and 0.3 μm, typically 0.18 μm. In this case, the insulating arms 30 include a conductive layer 302 of TiN with a thickness of approximately 7 nm, which is inserted between two amorphous silicon (a-Si) dielectric layers 301 and 303, each of which has a thickness of typically between 15 nm and 50 nm. In the central region of the wafer 310, before depositing the layer 302, the layer 301 is removed so that the conductive layer 302 is electrically connected to the anchoring pillar 21. In a known manner, the insulating arms 30 are used to support an absorbing film (not shown) capable of absorbing infrared radiation. The absorbing film typically includes a temperature measuring transducer, such as a thermistor, capable of measuring the temperature of the absorbing film. In a known manner, the film and the thermistor constitute a thermal detector known as a microbolometer.

[0093] The stack of layers 301, 302, and 303 is configured to retain a portion of these three layers 301, 302, and 303 mounted on and around the wafer 310. This allows for mechanical and electrical connection between the thermally insulating arms 30 and the anchoring posts 21. Advantageously, the stack of these three layers 301, 302, and 303 extends laterally beyond the periphery of the wafer 310, partially resting on the first sacrificial layer 20a. This lateral extension is typically approximately 0.2 μm. This allows for the formation of an overhang 31 of the intermediate structure 3. The overhang 31 of the intermediate structure 3 overhangs the side 210 of the anchoring posts 21 by a lateral distance typically between 0.4 μm and 0.6 μm.

[0094] As described in document FR2999805, after forming the intermediate structure 3, a thermal detector is usually formed at the end of the insulating arm 31. The thermal detector is usually composed of a microbolometer comprising an absorbing film and a temperature measuring transducer connected to the anchoring support 21.

[0095] like Figure 5A 、 Figure 5B As shown, after the intermediate structure 3 is formed, a first opening 300 is formed on the stack of layers 301, 302, 303, and 310. This opening 300 is usually made by photolithography and etching techniques. The shape of the opening 300 in the xy plane can be square, rectangular, circular, elliptical, or other shapes. The opening 300 can be made by an etching process that can simultaneously etch amorphous silicon (a-Si) and titanium nitride TiN-based layers 301, 302, 303, and 310 (selective to the material of the metal column of the anchoring pillar 21). This etching can be achieved by an RIE (reactive ion etching) method using a fluorine-containing chemical agent. The etching parameters can be easily adjusted by those skilled in the art.

[0096] like Figure 5A As shown, the opening 300 is preferably formed on the overhang 31, spanning the upper surface 211 of the anchoring post 21. In this way, a portion of the upper surface 211 of the anchoring post 21 is advantageously exposed. This exposed portion of the anchoring post 21 can then form an advantageous direct contact with the supporting post, thereby improving the adhesion between the supporting post and the anchoring post 21. In this case, the opening 300 extends vertically aligned with the first sacrificial layer 20a. The lateral extension of the opening 300 along the y-direction on the first sacrificial layer 20a can be approximately 0.2 μm to 0.4 μm. The lateral extension of the opening 300 along the y-direction above the anchoring post 21 can be approximately 0.1 μm to 0.2 μm. In this way, a sufficient contact surface can be maintained between the metal pillar 21 and the intermediate structure 3.

[0097] exist Figure 5A , the opening 300 extends along the y-direction onto the first sacrificial layer 20a beyond the overhang 31. Thus, the continuity of the overhang 31 along the x-direction is interrupted. The opening 300 spans the intermediate structure 3. According to another embodiment, not shown, a peripheral portion of the overhang 31 may be present around the opening 300. This peripheral portion preserves the continuity of the overhang 31 along the x-direction. In this case, the opening 300 is located inside the intermediate structure 3. In any case, the opening 300 is located on the first sacrificial layer 20a, preferably on the upper surface 211 of the anchoring post 21.

[0098] Figure 5B It is along Figure 5A The cross section of plane HH is shown as Figure 5BAs shown, the opening 300 is preferably opened in the middle of the overhang 31, leaving portions 31a and 31b (in the y direction) of the overhang 31. These portions 31a and 31b of the overhang 31 will then advantageously form stops for the support struts, counteracting traction forces in the +z direction.

[0099] like Figure 6A 、 6B As shown, a second sacrificial layer 20b is first formed on the first sacrificial layer 20a, on the intermediate structure 3, and on the thermal detector. The second sacrificial layer 20b is preferably formed of the same material as the first sacrificial layer, in this example, SiO2. The second sacrificial layer 20b is then partially opened by etching above the anchoring post 21 to form a second opening 200. The second opening 200 is typically formed by an etching process that selectively etches the second sacrificial layer 20b relative to the material of the intermediate structure 3 and the metal post of the anchoring post 21. The second opening 200 extends transversely, perpendicularly aligned with the overhang 31 of the intermediate structure 3, and longitudinally to the entire height of the second sacrificial layer 20b, exposing a portion of the upper surface 211 of the anchoring post 21 that was already exposed prior to the formation of the first opening 300. Advantageously, the second opening 200 extends into the first sacrificial layer 20a along the side 210 of the anchoring post 21, with the opening portion 201a located below the overhang 31 abutting against the side 210 of the anchoring post 21. The opening portion 201a is typically formed by anisotropic etching of the first opening 300 along the z-direction. The etching can be performed using RIE using a fluoride-based plasma chemistry. In this case, the etching parameters need to be adjusted so that the etching rates of the SiO2 of the first and second sacrificial layers 20a and 20b are sufficiently different from the etching rates of the amorphous silicon of the layers 303 and 301. Typically, the etching parameters are adjusted to obtain a selectivity S of greater than 20:1, preferably greater than 50:1, for example, about 80:1. SiO2:a-Si At this stage, the second openings 200, 201a expose a portion of the upper end surface 211 and side surface 210 of the anchoring strut 21. Alternatively, the second openings 200, 201a can be filled to form a support strut, as shown below. This allows a portion of the support strut to contact the upper surface 211 and side surface 210 of the anchoring strut 21. This improves the adhesion of the support strut to the anchoring strut 21.

[0100] according to Figure 7A and Figure 7BIn the preferred embodiment shown, second opening 200 is enlarged using an isotropic etching method, for example, by wetting with a partially diluted aqueous solution of buffered HF. This isotropic etching allows second opening 200 to extend below the unetched overhangs 31a and 31b during the formation of first opening 300. Consequently, this opening extension 201b exposes a larger surface area of the side 210 of anchoring strut 21. This allows support struts subsequently formed in openings 200 and 201b to directly contact the wider anchoring strut 21. Furthermore, opening extension 201b advantageously extends below and abuts overhangs 31a and 31b. Consequently, support struts subsequently formed in openings 200 and 201b can effectively abut overhangs 31a and 31b. This allows the support struts to form an embedded structure within intermediate structure 3, further enhancing mechanical strength along the +z direction.

[0101] like Figure 8A and Figure 8B As shown, the second openings 200 and 200 b continue to be filled to form support posts above the anchoring posts 21 .

[0102] According to this embodiment, an electrically isolating layer 231 (e.g., an Al2O3 layer) that is inert to HF is first deposited on the surface of the second opening and the second sacrificial layer 20b. The layer 231 can be deposited by ALD (atomic layer deposition). A conformal deposition of the Al2O3 layer 231 can be obtained by ALD type deposition. Therefore, the thickness of the layer 231 is essentially constant, typically between 20 nm and 40 nm. The function of this layer 231 is to electrically isolate the supporting pillars from the intermediate structure 3 and the anchoring pillars 21, and the intermediate structure and the anchoring pillars are electrically connected to the thermal detector. The Al2O3 layer 231 deposited on the upper surface of the second sacrificial layer 20b can be removed by photolithography and etching steps. Part of the layer 231 at the boundary of the opening on the upper surface of the second sacrificial layer 20b can be retained. This part typically extends from 250 nm to 500 nm.

[0103] An encapsulation layer 23 made of amorphous silicon is then conformally deposited in the second opening, on layer 231 and on the surface of the second sacrificial layer 22b. The uniform thickness of the encapsulation layer 23 is between 200 nm and 800 nm. The encapsulation layer 23 made of amorphous silicon is deposited to a thickness sufficient to partially or completely fill the second opening, particularly in the portion of the opening extending in contact with the underlying anchoring pillar 21. This encapsulation layer 23 continuously forms the upper portion of the encapsulation portion of the encapsulation structure and at least partially forms the supporting pillars of the encapsulation structure.

[0104] like Figure 9A 、 Figure 9BAs shown, vent holes 230 are first etched through the encapsulation layer 23. These vent holes 230 lead to the second sacrificial layer 20b. HF vapor chemical etching is then performed to remove the two sacrificial layers 20a, 20b made of SiO2 through the vent holes 230. In this way, the cavity 2 is formed. A sealing layer 24 is then formed to block the vent holes 230, and the filling of the second opening is optionally completed. In this embodiment, the support pillar 22 is formed at the same time as the encapsulation layer 23 and the sealing layer 24 are formed. This makes it possible to omit a step in the method specifically for filling the second opening to form the support pillar 22. In this case, the support pillar 22 includes an encapsulation material and an optional sealing material.

[0105] The sealing layer 24 is typically formed using a secondary vacuum deposition technique, such as vacuum evaporation of the material to be deposited. Consequently, the cavity 2 is sealed under reduced pressure. This allows the thermal detector (e.g., a microbolometer) in the cavity 2 to operate optimally. The sealing layer 24 is made of a sealing material that is transparent to the radiation to be detected, such as germanium (Ge) for infrared range detection devices. In this example, an antireflection layer 25 made of zinc sulfide (ZnS) is preferably deposited on the surface of the sealing layer 24 to improve the transmittance of infrared radiation through the assembly of the two layers 24 and 25. This forms the detection device 1 including a packaging structure surrounding the sealed cavity 2. The packaging structure includes a support pillar 22, the lower portion 220 of which contacts the underlying anchor pillar 21. In this example, the lower portion 220 of the support pillar 22 includes a first portion 220a extending through the overhang 31 and a second portion 220b located below the overhang 31. The first portion 220a contacts the upper surface of the anchor pillar 21. This improves the adhesion of support strut 22 to anchor strut 21. Second portion 220b contacts side 210 of anchor strut 21. This further improves the adhesion of support strut 22 to anchor strut 21. First portion 220a has a first dimension La along the x-axis, while second portion 220b has a second dimension Lb along the x-axis that is strictly larger than first dimension La. This allows portion 220 to form a stop against overhang 31. The mechanical traction strength of support strut 22 on anchor strut 21 is further enhanced.

[0106] Different variants of the device 1 and the manufacturing method will be described and explained below. Only the features that differ from the first embodiment will be described and explained. The other features are considered to be the same as those of the first embodiment.

[0107] like Figure 10A and 10BAs shown, according to one option, the filling of the second opening and the formation of the encapsulation layer are carried out separately. The filling of the second opening can use one or more filling materials that are different from the encapsulation material. In this case, the encapsulation layer no longer extends into the support pillar 22. The encapsulation layer can be made in a subsequent step after the support pillar is formed, and its material is different from the material used for the support pillar. This embodiment makes it possible to independently select the material for forming the support pillar on the one hand and the material for forming the encapsulation layer on the other hand. An advantage of this embodiment is that the support pillars of the encapsulation structure can be made of a material that has good adhesion to the material of the anchoring terminal. The encapsulation layer can be made of an optically transparent material, for example made of amorphous silicon, for use in radiation detectors with wavelengths between 8 and 14 μm.

[0108] The support pillars 22 can be made of tungsten, just like the anchoring pillars 21. This ensures good adhesion between the support pillars 22 and the anchoring pillars 21. Alternatively, a chromium layer 40 is pre-deposited conformally in the second opening. The chromium layer 40 is in direct contact with the exposed portion of the anchoring pillar 21. The thickness of the chromium layer 40 ranges from 100 nm to 200 nm. A thicker tungsten layer, for example, with a thickness between 200 nm and 800 nm, can then be deposited to fill the second opening. Thus, the support pillars 22 can consist of a relatively thin chromium layer 40 and a thicker tungsten portion 41. In this case, the chromium layer 40 serves to further improve adhesion between the anchoring pillars 21 and the support pillars 22. Therefore, the material of the support pillars 22 can be selected based on their adhesion properties rather than their optical properties. In this embodiment, the support pillars 22 do not necessarily comprise a material that is transparent to the radiation to be detected. Furthermore, in this embodiment, the support pillars 22 do not necessarily include an electrically isolating layer that is inert to HF, as the electrical isolation between the encapsulation layer and the intermediate structure 3 and anchoring pillars 21 can advantageously be formed in a subsequent step. In fact, providing such an electrically isolating layer between the anchoring struts 21 and the supporting struts 22 may degrade the sought-after adhesion properties.

[0109] Chemical mechanical polishing (CMP) is typically used to remove material deposited on the upper surface of the second sacrificial layer 20b and form the upper surface 221 of the support pillar 22. In this case, the upper surface 221 of the support pillar 22 is substantially flush with the upper surface of the second sacrificial layer 20b.

[0110] like Figure 11A 、 Figure 11BAs shown, a layer 231 made of an electrically isolating material (e.g., aluminum oxide (Al2O3) with a thickness between 20 nm and 100 nm) is deposited on the surface of the second sacrificial layer 20b and the upper surface 221 of the support pillar 22. The Al2O3 layer 231 deposited on the upper surface of the second sacrificial layer 20b can be removed by photolithography and etching steps. A portion of the layer 231 on the upper surface of the second sacrificial layer 20b located at the boundary of the upper surface 221 of the support pillar 22 can be retained. This portion can typically extend from 250 nm to 500 nm. The function of the isolation layer 231 is to electrically isolate the support pillar 22 from the encapsulation layer 23 (which is conductive in itself) made of amorphous silicon. In this case, the support pillar 22 is electrically connected to the anchor pillar 21 and the detector.

[0111] Then, an encapsulation layer 23 made of amorphous silicon is deposited on the surface of the layer 231 and the second sacrificial layer 22b. The uniform thickness of the encapsulation layer 23 is between 200 nm and 800 nm. In this case, the encapsulation layer 23 is mainly flat.

[0112] The following method is the same as the previous embodiment, including forming the vent hole 230, removing the sacrificial layers 20a, 20b by HF vapor chemical etching, and depositing the sealing layer and the anti-reflection layer 24, 25. Figure 12A and 12B shown.

[0113] Different variations of a support strut including a lower portion in contact with at least one side of an anchoring strut will be described and illustrated below.

[0114] Figure 13A 、 Figure 13B 、 Figure 13C Some variations of the formation of the first opening 300 are shown in top view, which determines the shape of the second opening 200 and ultimately the shape of the lower portion of the support post. Figure 13A Shown is a reference Figure 5A 、 Figure 5B In the case described above, the first opening 300 is located in the xy plane projection, spans the overhang 31 of the underlying anchoring pillar 21, and extends laterally along the y-axis to above the first sacrificial layer. In this case, the first opening 300 extends to both sides of the overhang 31, breaking the continuity of the overhang 31. Figure 13B The case where the first opening includes two opening portions 300a and 300b located on two overhangs 31a and 31b is shown. Figure 13A Compared with the case shown in Figure 1, the contact area between the support and anchor pillars has doubled. The adhesion and mechanical strength between the support and anchor pillars have been improved. Figure 13ASimilarly, the first opening portion 300a extends laterally to a first overhang 31a. The first overhang 31a is located on a first side of the intermediate structure 3. The second opening portion 300b extends laterally to a second overhang 31b. The second overhang 31b is located on a second side of the intermediate structure 3, preferably opposite the first side. This balances the distribution of traction forces on the intermediate structure. Figure 13C The case where the first opening includes two opening portions 300a and 300b inside the overhangs 31a and 31b is shown. In this case, the opening portions 300a and 300b do not extend beyond the overhangs 31a and 31b in the Y direction. The continuity of each overhang 31a and 31b is maintained. The rigidity of the intermediate structure is optimized. However, Figure 13A and Figure 13B This opening method requires a higher lithographic resolution than the case shown. Figure 13D A second opening pattern 200 is shown superimposed on the first opening portions 300a and 300b. In a preferred embodiment, the second opening pattern 200 extends laterally beyond the sides 210 of the anchoring struts 21, but remains confined to the perimeter of the overhangs 31a and 31b of the intermediate structure. Thus, the lateral volume of the support struts remains limited.

[0115] Electrical contact region 410 (the region where the TiN of layer 302 contacts the TiN of wafer 310, see for example Figure 4A and Figure 4B cross-section) can:

[0116] - or embedded in the footprint of the anchoring struts defined by the side 210

[0117] (This situation is shown in the figure),

[0118] - or suspended on anchoring posts defined by the side faces 210 while still embedded in the package of the die 310 (a situation not shown in the figures).

[0119] Figure 14A and Figure 14BAn embodiment is shown in cross section which includes only the formation of the second opening and does not include the formation of the first opening. In this embodiment, the intermediate structure is not etched. The second opening passes through the periphery of the overhang 31 during the anisotropic etching process, and then passes under the overhang 31 during the isotropic etching process to contact the side 210 of the anchoring pillar. In order to facilitate the extension of the second opening to below the overhang 31, the width of the overhang 31 along y is reduced when the intermediate structure is formed. In this embodiment, the overhang 31 extends laterally relative to the side 210 of the anchoring pillar 21 to form an overhang, and the lateral extension distance is preferably between 0.2μm and 0.3μm. In order to form the second opening 200, an opening pattern including a first lateral extension portion 200a and / or a second lateral extension portion 200b is generally used, such as Figure 15 These lateral extensions 200a and / or 200b extend beyond the periphery of the overhangs 31a and 31b and directly extend to above the first sacrificial layer.

[0120] The anisotropic etching step along the z-direction can selectively etch the material of the intermediate structure over the entire thickness of the second sacrificial layer, while etching only a portion of the thickness of the first sacrificial layer in the extended portion, with the etching depth typically being between 200 nm and 800 nm.

[0121] By anisotropically etching using reactive ion etching (RIE), the etched portion of the first sacrificial layer is vertically aligned with the outer periphery of the overhang of the intermediate structure. Consequently, the distance between this etched portion and the side of the anchoring post is approximately 0.2 μm to 0.3 μm, which corresponds to the amount of overhang formed with the side of the anchoring post. In this case, wet isotropic etching is typically used so that the second opening extends below the lower surface of the overhang by a distance at least equal to the distance between the anisotropic etch fronts of the side of the anchoring post. This can be achieved by adjusting the wet etching time. Providing additional etching time to clear a larger surface area of the side of the anchoring post is particularly advantageous. This allows for a wider range of direct contact between the support post and the anchoring post.

[0122] This embodiment saves at least one step dedicated to forming the first opening. However, in this embodiment, the support strut does not contact the upper surface of the anchoring strut. In this embodiment, the portion 220 of the support strut 22 includes a first portion 220a that bypasses the overhang 31 and a second portion 220b below the overhang 31. Only the second portion 220b contacts the side 210 of the anchoring strut 21. The first portion 220a has a first dimension La along the y-direction, and the second portion 220b has a second dimension Lb along the y-direction, and the second dimension Lb is strictly larger than the first dimension La. This enables the portion 220 to form a stop against the overhang 31. In this way, the mechanical pulling strength of the support strut 22 on the anchoring strut 21 is improved.

[0123] In summary, it is clear that the proposed apparatus and method provide a particularly effective solution for improving the adhesion of a package structure by directly contacting the support struts with the anchor struts. This physical contact between the struts can significantly enhance the mechanical robustness of the package structure. The support struts can also abut against the bottom surface of the overhanging portion of the intermediate structure, thereby increasing the traction strength of the package structure.

[0124] The present invention is not limited to the above-described embodiments.

[0125] For multiple support pillars on the corresponding anchoring pillar, each support pillar preferably includes a lower portion that is in contact with the underlying anchoring pillar. Other options are possible, for example, only a portion of the support pillars include a lower portion that is in contact with the underlying anchoring pillar, for example, one out of every two support pillars, or a staggered arrangement or any other arrangement that can be determined by a person skilled in the art based on the present description. The cavity formed in the packaging structure can generally accommodate a so-called "trap" material for capturing residual gas in the cavity to improve the reliability and service life of the detection device. The support pillars and / or the anchoring pillars may include other layers, for example, a barrier layer for the diffusion of TiN metal atoms.

Claims

1. A device (1) for detecting electromagnetic radiation, comprising at least one detector, which is arranged in a cavity (2) formed by an encapsulation structure, the encapsulation structure comprising anchoring struts (21) and supporting struts (22), wherein at least one of the anchoring struts is connected to the at least one detector, the supporting struts (22) being located above the anchoring struts (21), the device (1) being characterized in that the supporting struts (22) have a portion (220) extending to at least one side (210) of the anchoring struts (21).

2. The device (1) according to the preceding claim, comprising an intermediate structure (3) between the supporting struts (22) and the anchoring struts (21), the intermediate structure (3) having: an isolation arm (30) configured to support the at least one detector; at least one overhang (31) located on the periphery of the upper surface (211) of the anchoring pillar (21), The portion (220) of the support strut (22) surrounds the at least one overhang (31) or passes through the at least one overhang (31).

3. The device (1) according to the preceding claim, wherein the portion (220) of the support strut (22) comprises: A first portion (220a) located at the at least one overhang (31), the first portion having a first dimension La along a reference direction (x, y), and a second portion (220b) outside the at least one overhang (31) and extending to at least one side (210) of the anchoring strut (21), the second portion having a second dimension Lb along the reference direction (x, y), and the second dimension Lb being strictly greater than the first dimension La.

4. The device (1) according to the preceding claim, wherein at least the second portion (220b) of the portion (220) of the supporting strut (22) is in contact with at least one side (210) of the anchoring strut (21).

5. The device (1) according to the preceding claim, wherein the first portion (220a) and the second portion (220b) of the portion (220) of the supporting strut (22) are in contact with at least one side (210) of the anchoring strut (21).

6. The device (1) according to any one of the three preceding claims, wherein the first portion (220a) of the portion (220) of the supporting strut (22) is in contact with the upper surface (211) of the anchoring strut (21).

7. The device (1) according to any one of the preceding claims, wherein the portion (220) of the support strut (22) extends to a first side (210a) of the anchor strut (21) located on a first side, and extends to a second side (210b) of the anchor strut (21) located on a second side opposite to the first side.

8. The device (1) according to any one of the preceding claims, wherein the cavity (2) is enclosed by an encapsulation layer (23) made of an encapsulation material on the support pillar (22) and a sealing layer (24) made of a sealing material covering the encapsulation layer (23), wherein: The support pillar (22) is at least partially composed only of the encapsulation layer (23) or of the encapsulation layer (23) and the sealing layer (24), so that the support pillar (22) contains a single encapsulation material or contains both encapsulation material and sealing material.

9. A method of manufacturing a device (1) for detecting electromagnetic radiation as claimed in any one of the preceding claims, comprising providing a substrate (100); forming a first sacrificial layer (20a) on the substrate (100); forming an anchoring pillar (21) through the first sacrificial layer (20a); placing at least one detector above the first sacrificial layer (20a) and forming a connection between the at least one detector and at least one of the anchoring pillars (21); forming a second sacrificial layer (20b) on the first sacrificial layer (20a), on the at least one detector, and on the anchoring pillar (21); forming a second opening (200) in the second sacrificial layer (20b) above the anchoring post (21), the second opening (200) extending to at least one side (210) of the anchoring post (21), preferably extending into the first sacrificial layer (20a); filling the second opening (200) with at least one filler material to form a support strut (22) positioned above the anchor strut (21); forming an encapsulation layer (23) made of an encapsulation material on the second sacrificial layer (20b) and at least a portion of the support pillars (22); forming at least one vent hole (230) in the packaging layer (23), wherein the vent hole (230) leads to the second sacrificial layer (20b); removing the second sacrificial layer (20b) and the first sacrificial layer (20a) through the at least one vent hole (230) to form a cavity (2) around the at least one detector; as well as A sealing layer (24) made of a sealing material is formed on the encapsulation layer (23) to close the at least one vent hole (230).

10. The method according to the preceding claim, further comprising: After forming the first sacrificial layer (20a) and before forming the second sacrificial layer (20b), an intermediate structure (3) is formed between the support pillar (22) and the anchor pillar (21), the intermediate structure (3) having: an isolation arm (30) configured to support the at least one detector, the isolation arm (30) forming a connection between the at least one detector and at least one of the anchoring struts (21); At least one overhanging portion (31, 31a, 31b) is located around the upper surface (211) of the anchoring pillar (21); The step of forming the second opening (200) comprises: Anisotropic etching configured to extend the second opening (200) below the at least one overhang (31, 31a, 31b) and vertically align therewith; Isotropic etching is configured to extend the second opening (200) to below the at least one overhang (31) and against at least one side (210) of the anchoring pillar (21), so that after filling the second opening (200), the portion (220) of the supporting pillar (22) has: a first portion (220a) at the at least one overhang (31) and a second portion (220b) located below the at least one overhang (31) and on at least one side (210) of the anchoring pillar (21), the first portion (220a) having a first dimension La along a reference direction (x, y), the second portion (220b) having a second dimension Lb along the reference direction (x, y), and the second dimension Lb being strictly larger than the first dimension La.

11. The method according to any one of claims 9 to 10, further comprising: After forming the intermediate structure (3), forming a first opening (300) in the intermediate structure (3), wherein the first opening (300) partially exposes the upper surface (211) of the anchoring pillar (21) and passes through at least one overhang (31) around the anchoring pillar (21); The second opening (200) is formed in the second sacrificial layer (20b) in such a manner that the second opening (200) at least partially passes through the first opening (300).

12. A method according to any one of claims 9 to 11, wherein the filling of the second opening (200) is at least partially achieved during the formation of the encapsulation layer (23) by conformally depositing the encapsulation layer (23) on the second sacrificial layer (20b) and in the second opening (200), so that at least one filling material includes an encapsulation material.

13. A method according to the preceding claim, wherein the filling of the second opening (200) is at least partially achieved during the formation of the sealing layer (24) by depositing the sealing layer (24) on the encapsulation layer (23) so that the at least one filling material includes an encapsulation material and a sealing material.

14. The method according to any one of claims 9 to 11, wherein the filling of the second opening (200) is completed before the encapsulation layer (23) is formed using a filling material different from an encapsulation material.

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