Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
  • G01J5/00—Radiation pyrometry, e.g. infrared or optical thermometry
  • G01J5/02—Constructional details
  • G01J5/0205—Mechanical elements; Supports for optical elements
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
  • G01J5/00—Radiation pyrometry, e.g. infrared or optical thermometry
  • G01J5/02—Constructional details
  • G01J5/0225—Shape of the cavity itself or of elements contained in or suspended over the cavity
  • G01J5/024—Special manufacturing steps or sacrificial layers or layer structures
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
  • G01J5/00—Radiation pyrometry, e.g. infrared or optical thermometry
  • G01J5/02—Constructional details
  • G01J5/04—Casings
  • G01J5/041—Mountings in enclosures or in a particular environment
  • G01J5/045—Sealings; Vacuum enclosures; Encapsulated packages; Wafer bonding structures; Getter arrangements
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
  • G01J5/00—Radiation pyrometry, e.g. infrared or optical thermometry
  • G01J5/10—Radiation pyrometry, e.g. infrared or optical thermometry using electric radiation detectors
  • G01J5/20—Radiation pyrometry, e.g. infrared or optical thermometry using electric radiation detectors using resistors, thermistors or semiconductors sensitive to radiation, e.g. photoconductive devices

Definitions

• Devices for detecting electromagnetic radiation may comprise a matrix of thermal detectors each comprising a membrane capable of absorbing the electromagnetic radiation to be detected and containing a thermometric transducer such as a thermistor material.
• a thermometric transducer such as a thermistor material.
• the absorbent membranes are usually suspended above the substrate via anchoring pillars and are thermally insulated from these this by thermal insulation arms. These anchoring pillars and thermal insulation arms also have an electrical function by connecting the absorbent membranes to the reading circuit generally placed in the substrate.
• thermal detectors are generally confined, or encapsulated, alone or in groups, in at least one hermetic cavity under vacuum or at reduced pressure.
• a hermetic cavity delimited with the reading substrate by an encapsulation structure formed of layers thin is a technique particularly suited to the high-volume, low-cost manufacturing of radiation detection devices.
• the document FR2003858 describes an example of such an encapsulation process for the manufacture of a detection device 1, illustrated here in Figure 1, the thermal detectors of which are arranged in a cavity 2 formed within a structure of encapsulation on the reading substrate 100.
• the method uses two mineral sacrificial layers to successively produce the thermal detectors connected to the anchoring pillars 21, then the upper part of the encapsulation structure. These sacrificial layers are then removed by chemical vapor etching.
• the upper part of the encapsulation structure is formed by a thin layer 23 called encapsulation and by a thin layer 24 called sealing aimed at closing the vents 230 used to remove the sacrificial layers.
• the encapsulation layer 23 extends here continuously above the thermal detectors and on the surface of a non-etched portion of the second sacrificial layer. It also extends continuously in vertical portions to form support pillars 22 of the encapsulation structure which are positioned in support of the anchoring pillars 21.
• An electrically insulating layer 3 is also provided between the pillars of anchor 21 and the support pillars 22, to electrically isolate the thermal detectors supported by the anchor pillars 21.
• the support pillars of the encapsulation structure have the particular function of maintaining the mechanical integrity of the encapsulation structure which is subjected to the forces of the atmospheric pressure outside the cavity.
• the support pillars are therefore designed to withstand compressive forces.
• a disadvantage of this solution is that the layer at the interface between the support pillars and the anchor pillars does not have strong adhesion with the anchor pillars. Consequently, if the encapsulation structure is subjected to a tensile force, the support pillars can separate from the anchor pillars. Such traction forces can typically be induced by differential mechanical stresses existing between the reading substrate and the encapsulation structure.
• An objective of the invention is to meet this need.
• an object of the invention is a detection device making it possible to improve the mechanical strength of the encapsulation structure, in particular limiting the risk of separation between support pillars of the encapsulation structure and pillars of anchor supporting the detectors.
• Another object of the invention is a method for producing such a device.
• a device for detecting electromagnetic radiation comprising at least one detector arranged within a cavity formed by an encapsulation structure, said encapsulation structure comprising pillars anchoring pillars, at least one of which is connected to the at least one detector, and support pillars surmounting said anchoring pillars.
• the support pillars have a portion extending over at least one side of the anchoring pillars.
• the support pillars are at least partially in direct contact with the anchoring pillars, via the portion extending on the side of the anchoring pillars.
• This direct contact offers an adhesion force typically greater than indirect contact via a layer of electrical insulation interposed between the anchoring pillars and the support pillars, as disclosed by document FR2003858.
• Mechanical strength is further improved.
• the electrical insulation layer typically formed by a stack of thin layers, could delaminate or detach from the anchoring pillar under the effect of a tensile force linked to the presence of a differential mechanical stress between the substrate of reading and encapsulation structure. Delamination of the insulation layer is all the more likely when it includes a large number of layers of different nature and of small thickness.
• the original connection between the anchoring pillars and the support pillars according to the invention thus advantageously makes it possible to significantly improve the mechanical strength of the encapsulation structure of the electromagnetic radiation detection device.
• Another aspect of the invention relates to a method of manufacturing such a device for detecting electromagnetic radiation, comprising:
• Figures 13A to 13D schematically illustrate in top view manufacturing variants of a device for detecting electromagnetic radiation, according to different embodiments of the present invention.
• the portion of the support pillars comprises a first part at the level of the at least one overhang having a first dimension La in a reference x or y direction, and a second part beyond the at least one overhangs on at least one side of the anchoring pillars and having a second dimension Lb in said reference x or y direction, such that the second dimension Lb is strictly greater than the first dimension La.
• the portion of the support pillars s It thus widens at the level of the side of the anchoring pillars, after passing at the level of the overhang.
• the second enlarged part thus forms a stop against the overhang preventing traction of the support pillars with respect to the anchoring pillars.
• the first and second parts of the portion of the support pillars are in contact with at least one side of the anchoring pillars.
• the adhesion of the portion of the support pillars with the anchoring pillars is improved.
• the first part of the portion of the support pillars is in contact with the upper face of the anchoring pillars.
• the adhesion of the portion of the support pillars with the anchoring pillars is further improved.
• the support and/or anchoring pillars are arranged in a matrix fashion.
• the method further comprises, after formation of the first sacrificial layer and before formation of the second sacrificial layer, a formation of an intermediate structure between the support pillars and the anchoring pillars, said structure intermediate presenting:
• the formation of the second opening comprises
• An anisotropic engraving configured to extend the second opening under and directly above the at least one overhang
• An isotropic engraving configured to extend the second opening under the at least one overhang and against the at least one side of the anchoring pillars, so that, after filling of said second opening, the portion of the support pillars has a first part at the level of the at least one overhang having a first dimension La in a reference x or y direction, and a second part below the at least one overhang on the at least one side of the pillars of anchoring and having a second dimension Lb in said reference x or y direction, such that the second dimension Lb is strictly greater than the first dimension La.
• the method further comprises, after forming the intermediate structure, forming a first opening in the intermediate structure, said first opening partly exposing the upper face of the anchoring pillars and passing through the at least one overhang around the anchoring pillars.
• the invention generally relates to an electromagnetic radiation detection device adapted to detect infrared or terahertz radiation, and a method of manufacturing such a device.
• the detection device comprises at least one detector, preferably a matrix of thermal detectors located in a hermetic cavity.
• the array of thermal detectors forms a preferably periodic network.
• Each of the thermal detectors is an optically sensitive detector, and forms a detection pixel adapted to detect the electromagnetic radiation of interest.
• the cavity is delimited in its lower part by the reading substrate and in its upper part by an encapsulation structure which comprises one or more thin layers transparent to the electromagnetic radiation to be detected, including in particular a layer thin encapsulation and a thin layer of vent sealing.
• the encapsulation structure further comprises anchoring pillars and support pillars surmounting the anchoring pillars, all of these pillars making it possible to support the upper layers of the encapsulation structure.
• a preferably orthonormal reference frame comprising the x, y, z axes is shown in the attached figures.
• this reference applies to all the figures on this sheet.
• a stack of layers 301, 302, 303 is formed on the wafer 310 and on the upper face of the first sacrificial layer 20a, then structured by etching so as to form an intermediate structure 3 comprising an arm thermal insulation 30.
• the intermediate structure 3 thus comprises the wafer 310 and the structured stack of layers 301, 302, 303.
• This intermediate structure 3 is intended to be inserted between the underlying anchoring pillar 21, and a support pillar above.
• the thermal insulation arm 30 is generally narrow with a width along y of for example between 0.1 pm and 0.3 pm, typically 0.18 pm.
• the thermal insulation arm 30 here comprises an electrically conductive layer 302 in TiN, approximately 7 nm thick, interposed between two dielectric layers 301, 303 in amorphous silicon (a-Si), each having a thickness typically between 15 nm and 50 nm.
• a-Si amorphous silicon
• the layer 301 is removed before depositing the layer 302 so that the conductive layer 302 is electrically connected to the anchoring pillar 21.
• the arm of thermal insulation 30 is intended to support an absorbent membrane (not illustrated) capable of absorbing infrared radiation.
• This absorbent membrane can typically comprise a thermometric transducer such as a thermistor capable of measuring the temperature of the absorbent membrane.
• the membrane and the thermistor form a thermal detector called a micro bolometer.
• the structuring of the stack of layers 301, 302, 303 is configured so as to keep a portion of these three layers 301, 302, 303 straddling the wafer 310 and on the periphery of the wafer 310. This makes it possible to obtain a mechanical and electrical connection between the thermal insulation arm 30 and the anchoring pillar 21.
• This stacking portion of the three layers 301, 302, 303 advantageously extends laterally beyond the periphery of the wafer 310, in part on the first sacrificial layer 20a. This lateral extension is typically of the order of 0.2 pm. It makes it possible to form an overhang 31 of the intermediate structure 3.
• the overhang 31 of the intermediate structure 3 forms an overhang with respect to the flank 210 of the anchoring pillar 21, over a lateral distance typically between 0.4 pm and 0.6 pm.
• a first opening 300 is made in the stack of layers 301, 302, 303, 310.
• This opening 300 is typically made by photolithography and engraving.
• the shape of the opening 300, in the xy plane, can be square, rectangular, circular, oblong or other.
• This opening 300 can be produced by an etching capable of simultaneously etching the layers 301, 302, 303, 310 based on amorphous silicon a-Si and titanium nitride TiN, selectively to the material of the metal pad of the anchoring pillar 21.
• Such etching can be obtained by an RIE (reactive ion etching) etching process using fluorinated chemical agents.
• the engraving parameters can be adjusted without difficulty by a person skilled in the art.
• the opening 300 is preferably made at the level of a overhang 31, straddling the upper face 211 of the anchor pillar 21. Part of the upper face 211 of the anchor pillar 21 is thus advantageously exposed. This exposed part of the anchor pillar 21 will subsequently make it possible to advantageously form direct contact with the support pillar, thus improving the adhesion between the support pillar and the anchor pillar 21.
• the opening 300 extends here to the plumbness of the first sacrificial layer 20a.
• the lateral extension along y of the opening 300 above the first sacrificial layer 20a can be of the order of 0.2 pm to 0.4 pm.
• the lateral extension along y of the opening 300 above the anchoring pillar 21 can be of the order of 0.1 pm to 0.2 pm. This makes it possible to maintain a sufficient contact surface between the metal pad 21 and the intermediate structure 3.
• the opening 300 extends along y on the first sacrificial layer 20a beyond the overhang 31.
• the continuity along x of the overhang 31 is thus interrupted.
• the opening 300 straddles the intermediate structure 3.
• a peripheral part of the overhang 31 can remain around the opening 300.
• the continuity along x of the overhang 31 is preserved for this peripheral part.
• the opening 300 is in this case internal to the intermediate structure 3. It opens in all cases onto the first sacrificial layer 20a, and preferably onto the upper face 211 of the anchoring pillar 21.
• a second sacrificial layer 20b is first formed on the first sacrificial layer 20a, on the intermediate structure 3 and on the thermal detectors.
• the second sacrificial layer 20b is preferably of the same nature as the first sacrificial layer, here in SiO2.
• the second sacrificial layer 20b is then opened locally by etching above the anchoring pillars 21.
• This second opening 200 is typically produced by an etching capable of etching the second sacrificial layer 20b selectively to the materials of the intermediate structure 3 and of the stud. metal of the anchoring pillar 21.
• This second opening 200 extends laterally directly above the overhangs 31 of the intermediate structure 3, and vertically over the entire height of the second sacrificial layer 20b, so as to expose the part of the upper face 211 of the anchoring pillar 21 previously exposed by the formation of the first opening 300.
• the second opening 200 is extended along the flank 210 of the anchoring pillar 21, here in the first sacrificial layer 20a, by an opening part 201a located under the overhang 31, against the flank 210 of the anchoring pillar 21.
• the opening 201a is typically formed by anisotropic etching along z through the first opening 300. The etching can be done by RIE presenting plasma chemistry based on fluorinated species.
• the etching parameters will be adjusted so that the respective etching speeds of the SiO2 of the first and second sacrificial layers 20a, 20b on the one hand, and of the amorphous silicon of the layers 303, 301 are sufficiently distinct.
• the etching parameters will be adjusted so as to obtain an SsiO2:a-si selectivity greater than 20:1, preferably greater than 50:1, for example of the order of 80:1.
• the second opening 200, 201a here makes it possible to expose the part of the upper face 211 of the anchoring pillar 21 and part of the side 210 of the anchoring pillar 21.
• the second opening 200, 201a can be filled to form the support pillar as illustrated below.
• the support pillar then has a part in contact with the upper face 211 of the anchor pillar 21 and the side 210 of the anchor pillar 21.
• the adhesion of the support pillar on the anchor pillar 21 is already improved.
• the second opening 200 is widened by an isotropic etching process, for example wet etching based on a partially diluted aqueous solution of buffered HF.
• This isotropic engraving makes it possible to extend the second opening 200 under the overhang parts 31a, 31b not engraved during the formation of the first opening 300.
• This opening extension 201b thus makes it possible to discover a larger surface area of the side 210 of the pillar anchor 21.
• the support pillar subsequently formed in this opening 200, 201b thus presents direct contact with the more extended anchor pillar 21.
• the opening extension 201b advantageously extends under and against the overhang parts 31a, 31b.
• the support pillar subsequently formed in this opening 200, 201b thus advantageously abuts against the overhang parts 31a, 31b.
• the support pillar thus forms an engagement with the intermediate structure 3.
• the mechanical strength in traction along +z is further improved.
• the second opening 200, 200b is then filled to form a support pillar surmounting the anchoring pillar 21.
• an electrically insulating layer 231 which is inert to HF, for example a layer of AI2O3, is first deposited in the second opening and on the surface of the second sacrificial layer 20b.
• Layer 231 can be deposited by ALD (Atomic Layer Deposition).
• a deposit of the ALD type makes it possible to obtain a conformal deposit of layer 231 of Al2O3.
• Layer 231 thus has a substantially constant thickness, typically between 20 nm and 40 nm.
• This layer 231 has the function of electrically insulating the support pillar from the intermediate structure 3 and the anchoring pillar 21, electrically connected to the thermal detectors. Photolithography and etching steps make it possible to remove the layer 231 of Al2O3 deposited on the upper face of the second sacrificial layer 20b. A part of the layer 231 located at the edge of the openings, on the upper face of the second sacrificial layer 20b, can be retained. This part can typically extend over 250 nm to 500 nm.
• An encapsulation layer 23 of amorphous silicon is then deposited conformally in the second opening, on the layer 231 and on the surface of the second sacrificial layer 22b.
• the encapsulation layer 23 may have a uniform thickness of between 200 nm and 800 nm.
• the deposition of this encapsulation layer 23 in amorphous silicon can be done with a thickness sufficient to partially or completely fill the second opening, in particular at the level of the opening extension in contact with the anchoring pillar 21 underlying.
• This encapsulation layer 23 continuously forms the upper part of the encapsulation structure and at least partly the support pillar of the encapsulation structure.
• vents 230 are first etched through the encapsulation layer 23. These vents 230 open onto the second sacrificial layer 20b. A chemical attack in H F vapor is then carried out to remove the two sacrificial layers 20a, 20b in SiO2, through the vents 230. A cavity 2 is thus formed. A sealing layer 24 is then formed to close the vents 230, and possibly to complete the filling of the second opening.
• the support pillar 22 is formed simultaneously with the formation of the encapsulation layer 23 and the formation of the sealing layer 24. This saves a process step dedicated to filling the second opening for the formation of the support pillar 22.
• the support pillar 22 here comprises the encapsulation material and possibly the sealing material.
• the sealing layer 24 is typically formed by a secondary vacuum deposition technique such as vacuum evaporation deposition of the material to be deposited. Cavity 2 is thus sealed under reduced pressure. This allows optimal operation of thermal detectors such as micro-bolometers housed within cavity 2.
• the sealing layer 24 is made of a sealing material transparent to the radiation that we wish to detect, for example germanium (Ge) for a detection device in the infrared range.
• An anti-reflective layer 25, here made of zinc sulphide (ZnS), is preferably deposited on the surface of the sealing layer 24 to improve the transmission of infrared radiation through all of the two layers 24, 25.
• a detection device 1 comprising an encapsulation structure around a hermetic cavity 2 is thus formed.
• the encapsulation structure comprises a support pillar 22 comprising a lower portion 220 in contact with the underlying anchoring pillar 21.
• the portion 220 of the support pillar 22 comprises a first part 220a passing through the overhang 31, and a second part 220b under the overhang 31.
• the first part 220a is in contact with the upper face of the anchoring pillar 21. This improves the adhesion of the support pillar 22 on the anchor pillar 21.
• the second part 220b is in contact with the flank 210 of the anchor pillar 21. This further improves the adhesion of the support pillar 22 on the anchoring pillar 21.
• the first part 220a has a first dimension La along x
• the second part 220b has a second dimension Lb along x strictly greater than the first dimension La. This makes it possible to form a stop for the portion 220 against the overhang 31.
• the mechanical tensile strength of the support pillar 22 on the anchoring pillar 21 is further improved.
• the filling of the second opening and the formation of the encapsulation layer are carried out separately.
• the second opening can be filled with one or more filling materials other than the encapsulation material.
• the encapsulation layer no longer extends here within the support pillar 22.
• the encapsulation layer can be produced at a later stage, after formation of the support pillars, and in a material different from that used for the pillars. support.
• This embodiment makes it possible to independently choose the materials used to form the support pillars on the one hand, and the encapsulation layer on the other hand.
• This embodiment advantageously makes it possible to form support pillars of the encapsulation structure in a material offering good adhesion with the material of the anchoring pads.
• the encapsulation layer can be made of optically transparent materials, for example amorphous silicon for a radiation detector between 8 and 14 pm in length. wave.
• the support pillars 22 can be made of tungsten like the anchor pillars 21. This makes it possible to obtain good adhesion between the support pillar 22 and the anchor pillar 21.
• a layer 40 of chrome is previously deposited correctly in the second opening. This chrome layer 40 is in direct contact with the exposed parts of the anchoring pillars 21.
• This chrome layer 40 may have a thickness of between 100 nm and 200 nm. A thick deposit of tungsten, for example with a thickness of between 200 nm and 800 nm, then makes it possible to fill the second opening.
• the support pillar 22 can thus comprise a relatively thin layer 40 of chrome and a thick part 41 of tungsten.
• the chrome layer 40 here has the function of further improving the adhesion between the anchoring and support pillars 21, 22.
• the support pillar 22 can therefore be made of materials chosen for their adhesion properties, independently of their optical properties.
• the support pillar 22 does not necessarily include materials transparent to the radiation to be detected.
• the support pillar 22 does not necessarily comprise an electrically insulating and HF inert layer because the electrical insulation between the encapsulation layer and the intermediate structure 3 and the anchoring pillar 21 can be advantageously formed at a later stage. In fact, providing such a layer of electrical insulation between the anchoring pillar 21 and the support pillar 22 can degrade the adhesion properties which are sought here.
• CMP Chemical mechanical polishing

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• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Spectroscopy & Molecular Physics (AREA)
• Engineering & Computer Science (AREA)
• Manufacturing & Machinery (AREA)
• Photometry And Measurement Of Optical Pulse Characteristics (AREA)
• Measurement Of Radiation (AREA)

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• 2022
  • 2022-11-29 FR FR2212455A patent/FR3142546B1/fr active Active
• 2023
  • 2023-11-28 EP EP23813739.2A patent/EP4627303A1/de active Pending
  • 2023-11-28 KR KR1020257021268A patent/KR20250112875A/ko active Pending
  • 2023-11-28 JP JP2025531166A patent/JP2025537944A/ja active Pending
  • 2023-11-28 WO PCT/EP2023/083425 patent/WO2024115517A1/fr not_active Ceased
  • 2023-11-28 CN CN202380081563.5A patent/CN120476294A/zh active Pending

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