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    • 专利摘要:
    A method of producing a bolometric detector (100) comprising: - performing a stack, on an interconnection level (20) of a read circuit, comprising a sacrificial layer disposed between a support layer (32) and a etching stop layer (29), the sacrificial layer comprising a mineral material; - Making a via (38) conductor through the stack such that it is in contact with a conductive portion (21) of said interconnection level; depositing a conductive layer on the support layer and the via; etching the conductive layer and the support layer, forming a bolometer membrane (54) electrically connected to the via via a remaining portion (44) of the conductive layer which covers an upper part (40) of the via; - Removal of the sacrificial layer by a selective chemical etching, and such that the membrane is suspended via via.
    公开号:FR3066321A1
    申请号:FR1754060
    申请日:2017-05-09
    公开日:2018-11-16
    发明作者:Patrick Leduc；Sebastien CORTIAL；Stephane Pocas；Jean-Jacques Yon
    申请人:Commissariat a lEnergie Atomique CEA；Commissariat a lEnergie Atomique et aux Energies Alternatives CEA；
    IPC主号:
    专利说明:

    METHOD FOR PRODUCING A BOLOMETRIC DETECTOR
    DESCRIPTION
    TECHNICAL FIELD AND PRIOR ART The invention relates to the field of electromagnetic radiation detectors with bolometers or micro-bolometers, intended for the detection of radiation in the “thermal” or infrared field.
    In this document, the term “bolometer” is used generically whatever the dimensions of the bolometer, and therefore denotes a bolometer or a micro-bolometer of micrometric dimensions.
    A bolometer detector, or bolometric detector, generally comprises a set of bolometers arranged on the surface of a support substrate by forming a matrix. Each of the bolometers is intended to provide thermal information relating to a pixel of an image supplied by the detector.
    Each bolometer comprises a suspended membrane mechanically and electrically connected to the substrate by means of long narrow beams called holding arms and connected to electrically conductive pillars ensuring the suspension of the membrane. The assembly is placed in an airtight enclosure, for example a housing under very reduced pressure, so as to suppress the thermal conductance of the surrounding gas.
    During the operation of the detector, the membrane of each bolometer heats up by absorbing the incident radiation from the observed thermal scene, this radiation being transmitted and focused on the bolometer matrix by suitable optics at the level of the matrix focal plane. This membrane comprises a thermal-electrical transduction device, an electrical characteristic of which (for example the resistivity) changes appreciably when the temperature changes, generating for example a variation of current, that is to say an electrical signal, when this material is under constant polarization, the amplitude of which depends on the flux of the incident radiation. The signal obtained corresponds to the temperature image of the detector. Such a thermal-electrical transduction device corresponds, for example, to a layer of transducer material, for example a metal oxide (VOX, NiOx, TiOx) or amorphous silicon (a-Si), or to a diode or a transistor.
    The conventional methods of manufacturing such detectors, of the “above IC” or “MEMS on top” type, include steps implemented directly from the surface of a substrate generally made of silicon and comprising a plurality of electronic circuits forming the detection circuit. reading or ROIC (“Read Out Integrated Circuit”), in a so-called monolithic way. This term “monolithic” designates a continuous sequence of operations implemented from the same substrate, following the manufacturing process of the read circuit.
    The bolometer manufacturing steps are generally implemented to collectively produce several detectors, for example between a few tens and a few hundred on the same substrate.
    During these stages, the elements of the bolometers fulfilling the functions of radiation absorption, optical-thermal transduction and thermal-electrical transduction are placed on the surface of a sacrificial layer intended to form a building base and to be eliminated at the end of the process by a suitable process which does not attack the other elements (the structural and active organs) of the structure. The sacrificial layer generally corresponds to an organic layer of polyimide which is then eliminated by combustion in an oxygenated plasma.
    The dielectric or semi-conductive layers which form the elements of the detection structure are conventionally made of silicon oxide (SiO), silicon nitride (generically noted SiN), or else amorphous silicon, as described for example in the document. EP 0 828 145 A1. These materials can be deposited at a relatively low temperature and are inert with respect to the process for removing the organic sacrificial layer implemented under oxygenated plasma, that is to say are not not etched by oxygenated plasma.
    After the etching of the sacrificial layer, the bolometer membranes remain suspended above the substrate without any other contact or attachment than their holding arms.
    The bolometers are for example produced by forming a matrix with a repeating step (distance separating the centers of two neighboring bolometers and arranged on the same line or the same column of the matrix) equal to 17 μm, or even of the order of 12 pm or 10 pm.
    In order to be able to carry out “far infrared” (LWIR) detection, the detector generally comprises a quarter-wave plate or cavity formed between the membrane and a reflector arranged on the surface of the substrate, so as to obtain maximum absorption. of the detector for wavelengths near 10 µm. Thus, in order to connect and maintain the membrane at a suitable distance from the reflector and with good mechanical support, the electrically conductive pillars produced are rather complex and of considerable size, and are formed through a thick layer of polyimide ( thickness generally between 2 pm and 2.5 pm) forming the sacrificial layer, the thickness of this sacrificial layer of polyimide corresponding to the desired membrane - reflector distance.
    In document EP 2 743 659 A1, it has been proposed to integrate the bolometers in part into the “back-end” (or “BEOL” for “Back End Of Line”) layers of the bolometer reading circuit. The acronym BEOL designates the stages of manufacture of all the metallic interconnections implemented at a relatively low temperature, typically below about 400 ° C., which are characteristic of the end of standard microelectronic manufacturing processes. The purpose of this so-called "MEMS-in-CMOS" approach is to use certain BEOL provisions, which are mature on an industrial level, to integrate part of the bolometer elements. In particular, metallized vias obtained according to a “damascene” process are produced to form the electrically conductive pillars of the bolometers, and one of the IMDs (“Inter-Metal-Dielectrics”, or inter-metal dielectrics), comprising for example SiO which is a standard material in microelectronics, is used as a sacrificial layer on which the membranes of the bolometers are produced. The elimination of such a sacrificial layer requires the use of hydrofluoric acid in the vapor phase (HFv). Consequently, all the materials constituting the bolometer are chosen from those which are inert with respect to this chemically very aggressive process, that is to say among the materials not impacted by this etching.
    By integrating the bolometers into the BEOL, the last photolithographic levels of the ROIC normally used to conduct electrical contact at the surface of the passivation layer at the top of the BEOL are also used to produce the electrically conductive pillars of the bolometers . It is therefore saved several lithographic levels among all the levels necessary for the manufacture of bolometers, hence a significant saving on the costs of manufacturing these bolometers. In addition, the electrically conductive pillars of cylindrical shape thus produced benefit from the drawing rules of the CMOS die, that is to say a diameter equal to approximately 0.5 μm, which represents a very significant gain in compactness compared to the electrically conductive pillars generally produced. in "above IC" technology which generally occupies an area of approximately 3x3 pm2. This gain in space can constitute a decisive advantage in a context of reducing the pitch of the bolometric matrix detectors.
    In the structure described by document EP 2 743 659 A1, the electrical connection between the electrically conductive pillars and the metal present in the membrane of the bolometer to ensure the absorption of electromagnetic radiation can be obtained indirectly via a support layer of the membrane which contains amorphous silicon. However, the electrical resistivity of this non-metallic amorphous silicon layer is very high compared to metal and introduces, despite its small thickness, a parasitic electrical resistance in series with the thermal - electrical transducer element, which penalizes the sensitivity of micro-detectors.
    To overcome this limitation, document EP 2 743 659 A1 also describes another embodiment in which an electrical contact is provided through the support layer of the amorphous silicon membrane by virtue of an opening formed through this support layer, for s to overcome the drawbacks indicated above. This contact, and therefore the opening in which this contact is made, must be inscribed in the cross section of the electrically conductive pillar so that the metallic layer present in the bolometer membrane can create reliable electrical continuity with the metal that constitutes the pillar. electrically conductive. This arrangement reveals two critical points: - the definition of contact by photolithography and its alignment on the electrically conductive pillar is very delicate or even impossible when the diameter of the electrically conductive pillar is reduced to the minimum dimension authorized by the photolithography means, which is one of the main interests of this “MEMS in CMOS” construction of the bolometer. Indeed, to register a contact inside a section of diameter equal to 0.5 pm requires the use of advanced lithography means not available in a typical BEOL line, - the contact is made through the silicon layer amorphous whose thickness is generally equal to 50 nm. The topography generated must not create any discontinuity in the metal layer of the bolometer deposited in the contact. This layer, which is necessarily very thin (typically 10 nm) since it also has a radiation absorber function in the bolometric membrane, will be ineffective in covering the flanks of the contact etched in the support layer of amorphous silicon.
    Furthermore, another drawback of this solution is the addition of a level of lithography and etching for the production of the opening in which the contact must be made, which represents an additional manufacturing cost.
    STATEMENT OF THE INVENTION
    An object of the present invention is to propose a method for producing a bolometric detector in which the bolometer or bolometers are produced partly within the BEOL of the electronic reading circuit of the detector, and which eliminates the drawbacks described above which relate to the electrical contact between the membrane of a bolometer and at least one of the electrically conductive pillars to which the membrane of this bolometer is suspended.
    For this, the invention proposes a method for producing a bolometric detector comprising at least the implementation of the following steps: - producing a stack of layers on an electrical interconnection level of an electronic circuit for reading the detector, the stack comprising at least one sacrificial layer disposed between a support layer and a first etching stop layer, the first etching stop layer being disposed between the sacrificial layer and said electrical interconnection level, and the sacrificial layer comprising at least one mineral material capable of being selectively etched with respect to the support layer and the first etching stop layer; production of at least one electrically conductive via passing through at least the stack of layers such that at least one electrically conductive material of the via is in contact with at least one electrically conductive portion of said level of electrical interconnection connected to the electronic circuit of reading ; - deposit of at least one electrically conductive layer on the support layer and the via; - Etching of the electrically conductive layer and of the support layer, forming a bolometer membrane electrically connected to the electrically conductive via by at least a remaining portion of the electrically conductive layer which covers at least an upper part of the via; - Removal of the sacrificial layer by chemical etching which the first etching stop layer and the support layer resist, and such that the membrane is suspended via the via.
    In this process, the bolometer (s) are produced on an electrical interconnection level of the electronic reading circuit and using a mineral sacrificial layer, and are therefore partly integrated within the BEOL of this circuit.
    In addition, since the electrically conductive layer is deposited directly on the electrically conductive via serving as a pillar for suspending the membrane, and because the electrically conductive via is produced after having formed the support layer, the electrical contact between the electrically conductive layer the membrane and the electrically conductive via is produced directly between these two elements, without the presence of semiconductor material between them.
    This process makes it possible to form a direct electrical connection between the electrically conductive via and the electrically conductive layer of the membrane which benefits from a smaller footprint because it is not necessary to provide a large contact surface of the pillar electrically. conductor to achieve alignment with an opening which would be formed through the support layer as in the prior art. The electrically conductive via can therefore be produced with smaller dimensions than in the prior art, for example with a diameter or a dimension side of the order of 0.5 μm.
    In addition, since the electrical contact between the electrically conductive via and the electrically conductive layer is not formed in an opening passing through the support layer, a small thickness of the electrically conductive layer does not represent a drawback for the reliability of the contact. .
    Finally, with respect to the process requiring the creation of an opening through the support layer of the membrane to make contact between the electrically conductive pillar and the electrically conductive layer of the membrane, the process according to the invention also makes it possible to eliminate a level of photolithography and etching due to the absence of such an opening in this process.
    The method according to the invention makes it possible to obtain excellent electrical continuity between the reading circuit and the bolometer membrane because the electrical connection between the reading circuit and the electrically conductive material of the membrane is formed only of electrically conductive materials. .
    The above advantages are obtained whatever the material of the support layer. The stack of layers may further comprise a second etching stop layer such that the support layer is disposed between the second etching stop layer and the sacrificial layer, the method being able to further comprise, between the production of the via and the deposition of the electrically conductive layer, the implementation of the following steps: - removal, for example by mechanical-chemical polishing, of a layer of electrically conductive material formed on the second etching stop layer during production of the via, then - removal of the second etching stop layer, and the electrically conductive layer can be deposited such that the remaining portion of the electrically conductive layer also covers lateral flanks of the upper part of the uncovered via (or placed naked or revealed) by removing the second etching stop layer.
    Because the upper part of the electrically conductive via "protrudes" from the support layer, and therefore that the mechanical maintenance of the support layer by the via is carried out under this upper part, the mechanical maintenance of the support layer, and therefore of the membrane, to the electrically conductive via is improved. In addition, since the remaining portion of the electrically conductive layer covers, in addition to the upper face of the via, the lateral flanks of this upper part of the via, the contact surface between this portion of the electrically conductive layer and the via electrically conductive increases, and the electrical contact between the electrically conductive layer and the electrically conductive via is therefore improved.
    The support layer may comprise at least one dielectric material or a material of which at least one electrical parameter varies as a function of its temperature. Thus, the support layer provides an electrical insulation or thermal-electrical transduction function within the bolometer membrane.
    The method can also comprise, before the sacrificial layer is removed, the production of at least one infrared radiation absorbing element intended to be detected by the detector, on the membrane.
    In this case, the absorbing element can comprise at least one MIM structure (or “Metal - Insulator - Metal”). Other types of absorbing elements can be produced on the membrane. The expression “MIM structure” designates a stack comprising at least one dielectric element disposed between an upper metallic element and a lower metallic element, and capable of achieving selective absorption of certain wavelengths according to the dimensions and the materials of the structure. MIM.
    The electrically conductive layer can be etched such that a plurality of remaining portions of said electrically conductive layer form bolometer electrodes and resistive portions capable of absorbing infrared radiation intended to be detected by the detector.
    The method may further comprise, between the etching of the electrically conductive layer and the etching of the support layer (the support layer being etched after the electrically conductive layer), the deposition of a first layer of thermal-electrical transduction on the portions remaining from the electrically conductive layer and on the support layer. Such a first thermal-electrical transduction layer can be deposited on the electrically conductive layer and on the support layer. In addition to the electrical connection between the conductive layer and the thermal-electrical transduction layer, this arrangement also makes it possible to compensate for a bimetallic strip effect occurring between the portions of the electrically conductive layer and the support layer.
    The first thermal-electrical transduction layer may comprise at least one material resistant to chemical etching used to remove the sacrificial layer. In this case, this first thermal-electrical transduction layer can also serve to protect the electrically conductive layer from the etching solution used to etch the sacrificial layer.
    The method can also comprise, after the deposition of the first thermal-electrical transduction layer, the deposition of a second thermal-electrical transduction layer on the first thermal-electrical transduction layer and whose thickness is greater than that of the first thermal-electrical transduction layer. In this case, the signal to noise ratio of the conversion of the absorbed thermal energy into electrical energy carried out within the detector is improved. The second thermal-electrical transduction layer may comprise at least one material resistant to chemical etching used to remove the sacrificial layer.
    This second thermal-electrical transduction layer can then be etched in order to form one or more portions of thermometric material on the membrane, for example a central portion of thermometric material.
    The method can be such that: - the support layer comprises amorphous silicon, and / or - when a first thermal-electrical transduction layer is deposited, the first thermal-electrical transduction layer comprises amorphous silicon, and / or - when a second thermal-electric transduction layer is deposited, the second thermal-electric transduction layer comprises amorphous silicon.
    BRIEF DESCRIPTION OF THE DRAWINGS
    The present invention will be better understood on reading the description of exemplary embodiments given purely by way of indication and in no way limiting, with reference to the appended drawings in which: - Figures IA to IN represent steps of a method of making d 'A bolometric detector, object of the present invention, according to a first embodiment; - Figure 2 shows a bolometric detector obtained by implementing an embodiment process, object of the present invention, according to a second embodiment.
    Identical, similar or equivalent parts of the different figures described below have the same reference numerals so as to facilitate the passage from one figure to another.
    The different parts shown in the figures are not necessarily shown on a uniform scale, to make the figures more readable.
    The different possibilities of realization (variants and embodiments) must be understood as not being mutually exclusive and can be combined with one another.
    DETAILED PRESENTATION OF PARTICULAR EMBODIMENTS
    A method of producing an infrared bolometric detector 100 according to a first embodiment is described below in connection with Figures IA to IN.
    The device 100 produced in this first embodiment comprises a plurality of thermal detectors, of the micro-bolometer type, which are produced from a semiconductor substrate 10, for example of silicon, on and / or in which is integrated an electronic reading circuit 12 produced in CMOS technology. The reading circuit 12 reads the variation in electrical characteristic induced by the heating of each of the bolometers, and also the polarization of the bolometers.
    The electronic reading circuit 12 includes semiconductor layers 13 (“Front End” part) in which transistors, diodes, capacitors and other electronic devices of the MOS type are made, enabling electronic functions to be implemented. of the read circuit 12. One or more electrical interconnection levels 14 (“Back End” part) connecting in particular functional blocks of the read circuit 12 to each other and intended to form input / output links of the reader circuit 12 , are produced on the semiconductor layers 13 of the read circuit 12.
    The last level of electrical interconnection intended to form the electrical contacts of the reading circuit 12 is not yet carried out at the stage shown in FIG. IA. In FIG. 1A, the reference 14 can therefore designate a single level of electrical interconnection, corresponding both to the first level of electrical interconnection and to the penultimate level of electrical interconnection, or else several levels of interconnection electrical stacked from the first level of electrical interconnection (the one in contact with the semiconductor layers 13) to the penultimate level of electrical interconnection. The last level of electrical interconnection will be carried out such that it integrates the bolometers intended to be produced in a suspended manner above the reading circuit 12 and provides the electrical connections between the inputs of the reading circuit 12 accessible from the levels d electrical interconnection 14 and the bolometer output electrical connections. This last level of electrical interconnection is also carried out in order to form electrical connection pads of the reading circuit 12 accessible from the outside, that is to say which can be contacted electrically from the outside of the detector 100.
    As a variant, it is possible to use several (for example 2 or 3) of the last electrical interconnection levels to form the mechanical support means of the bolometers and the means of electrical connection between the inputs of the reading circuit 12 and the connections bolometers output.
    FIG. 1B represents the penultimate electrical interconnection level 20 produced, forming part of the electrical interconnection levels 14 and on which the bolometers of the detector 100 are intended to be produced. This level of electrical interconnection 20 comprises in particular a metal line 21 of which portions 16 (a single portion 16 is shown in FIG. 1B) are electrically and locally connected, by means of electrically conductive vias 22, or vertical connections, and possibly via the lower electrical interconnection level (s), to the electronic MOS devices of the read circuit 12. At least part of these portions 16 are intended to be electrically connected to the bolometers of the detector 100. Outside the vias 22 which provide the electrical connections with the lower electrical interconnection level, the electrical interconnection level 20 is electrically isolated from the metal line of the lower electrical interconnection level by a dielectric layer 27, called inter-metal dielectric (also called IMD , or "Inter-Metal Dielectric"), which is a mineral material and for example composed of undoped silicon oxide (also called USG, or “Undoped Silica Glass”) or of an oxide of lower dielectric permittivity, such as SiOF, SiOC, SiOCH, etc.
    The electrical interconnection level 20 may also include other portions (not shown in FIG. 1B) of the metal line 21, connected or not connected to the lower electrical interconnection level, intended not to be connected to the bolometers but to be used for example in the production, at least in part, of connection pads used for testing and wired wiring of the read circuit 12 and of the detector 100 in general.
    Different technical options are possible for making the vias 22 and the metallic line 21 of the penultimate electrical interconnection level 20 (and also the metallic lines and the vias of the other electrical interconnection levels 14). A first possibility consists in making the metal line 21 from aluminum advantageously inserted between two layers of titanium or titanium nitride, and in making the vias 22 in tungsten. A second possibility is to produce the metal line 21 and the vias 22 in copper according to a damascene process comprising filling the trenches formed in the dielectric layer 27, or intermetal dielectric, with copper. It may be a simple damascene process in which the vias 22 and then the metal line 21 are carried out in two successive damascene steps, or else a double damascene process as shown in FIG. 1B, in which the embodiments of the metal line 21 and vias 22 are integrated into a "continuous" manufacturing process. The heart of these elements 21 and 22 is formed by portions of copper 23 produced by electrolysis of a copper salt in solution (ECD deposition). The lower faces and the lateral faces of these copper portions 23 are further coated by a set of conductive layers, for example of tantalum nitride 24, of tantalum 25 and of copper 26, advantageously produced by ionizing sputtering (also called iPVD ) in order to improve the recovery of these deposits on the vertical sides. The tantalum layer 25 forms a barrier layer preventing the diffusion of copper 23 and 26 in the inter-metal dielectric Y1 and towards the semiconductor layers 13 of the reading circuit 12 where this copper would otherwise create electrical faults, especially in the transistors and diodes. The tantalum nitride layer 24 is generally intended to improve the adhesion of the tantalum layer 25 to the surface of the inter-metal dielectric 27. The copper layer 26 serves as both a cathode and a germination layer for growth electrolytic copper portions 23. The level of the interconnection level 20 on the surface of the inter-metal dielectric 27 is obtained by a chemical mechanical polishing process (CMP) controlled by a barrier layer 28 for example based on SiO2.
    An insulating dielectric layer 29 covers the barrier layer 28 and the upper faces of the different portions of the metal line 21. This layer 29 here corresponds to a bilayer formed by the stacking of a first layer disposed on the barrier layer 28 and a second layer covering this first layer. The first layer of this stack is intended to form a diffusion barrier vis-à-vis the copper of the metal line 21, and comprises for example silicon nitride. The second layer of the stack forms an etching stop layer capable of resisting HFv etching which will be implemented later on when the membranes of the bolometers are released, which will therefore protect the level of electrical interconnection 20 during the bolometers released. This second layer of the stack comprises for example AI2O3 or AIN.
    In the following figures, the metal line 21 and the vias 22 are shown in less detail than in Figure IB in order to facilitate reading of these figures.
    A sacrificial layer 30, comprising at least one mineral material such as SiO2, is deposited on the layer 29 (FIG. 1C). The thickness (dimension along the axis Z) of the sacrificial layer 30 is for example between approximately 1 μm and 5 μm. The thickness of the sacrificial layer 30 is in particular chosen as a function of the absorption properties desired with respect to infrared radiation intended to be received and absorbed by the bolometers of the detector 100. This thickness is for example chosen so that the space freed by the subsequent etching of the sacrificial layer 30 forms a quarter-wave cavity under the membrane of the bolometers (in particular when the detector 100 is intended to detect infrared radiation whose wavelength belongs to example at band III (between 8 to 12 pm)). The thickness of the sacrificial layer 30 can be adjusted, after its deposition, via the implementation of a CMP type planarization.
    As shown in FIG. ID, a support layer 32 is then deposited on the sacrificial layer 30. The support layer 32 can comprise at least one material sensitive to temperature, for example whose resistivity varies substantially with temperature. In this case, the support layer 32 comprises for example amorphous silicon deposited by CVD. As a variant, the support layer 32 may comprise at least one material forming an electrical insulator or provided with a high resistivity. Thus, in addition to amorphous silicon, the support layer 32 can include SiC, AI2O3, ΓΑΙΝ, etc. In all cases, the material or materials of the support layer 32 are inert with respect to the HFv etching which will be implemented subsequently during the etching of the sacrificial layer 30, that is to say capable of resist (not be etched) the chemical etching solution (s) used to etch the sacrificial layer 30. Thus, the material of the sacrificial layer 30 is capable of being selectively etched with respect to the support layer 32 and the first etching stop layer 29.
    In addition, the support layer 32 can correspond to a stack of several different materials, for example a bilayer, such that the lower layer of this stack (that in contact with the sacrificial layer 30) protects the other upper layer (s) from this stack. during the etching of the sacrificial layer 30. The thickness of the support layer 32 is for example between approximately 10 nm and 100 nm.
    A second etching stop layer 34 is then deposited on the support layer 32 (FIG. IE). This layer 34 is intended to stop an ablation process, or planarization, which will be implemented later to remove an excess of conductive material formed during the production of electrically conductive vias connecting the bolometers to the metal line 21, and this in order to prevent degradation of the layer 32 during this removal of conductive material. The layer 34 comprises at least one material resistant to mechanical and / or chemical and / or ionic abrasion which will be used, preferably corresponding to at least one material already used during the production of the elements found in the layers of semiconductor 13, such as for example SiN and / or SiO. The layer 34 has for example a thickness of between approximately 20 nm and 100 nm.
    Electrically conductive vias 38 are then produced through the stack of layers previously formed on the electrical interconnection level 20. In FIGS. 1F to 1H, the production of a single electrically conductive via 38 is described. However, several electrically conductive vias are produced through this stack. The number of these vias 38 depends on the number of bolometers that the detector 100 is intended to have. These electrically conductive vias 38 are intended to ensure the electrical connections between the bolometers of the detector 100 and the reading circuit 12, and also to ensure the mechanical maintenance in suspension of the membranes of the bolometers.
    As shown in FIG. 1F, an opening 36 is etched through the stack formed from the layers 34, 32, 30 and 29 previously produced. This opening 36 forms an access to the metal line 21 and is intended for making one of the electrically conductive vias 38. The shape and the dimensions of the section of the opening 36, in a plane of the layers 34, 32, 30 and 29 at the interfaces of these layers crossed by this opening 36, define the shape and the dimensions of the via 38 which will be produced in this opening 36, this shape possibly being for example circular or polygonal, the diameter or a dimension of one side of this opening can be equal to approximately 0.5 μm. The opening 36 is then filled with one or more electrically conductive materials, thus forming the electrically conductive via 38. A thin barrier layer, comprising for example TiN, is for example deposited against the walls of the opening 36 (at the bottom and against the side walls), then the empty volume remaining in the opening 36 is filled with another electrically conductive material, for example tungsten deposited by CVD. The barrier layer present at the bottom of the opening 36, between the metal line 21 and the other electrically conductive material disposed in the opening 36, makes it possible to avoid a chemical reaction which may occur between the electrically conductive material (for example copper) of the metal line 21 and this other electrically conductive material (for example tungsten) deposited in the opening 36. This barrier layer present against the side walls of the opening 36 also makes it possible to improve the adhesion of said other electrically conductive material deposited in opening 36.
    Alternatively, the metallization of the electrically conductive via 38 can be carried out using copper. The different embodiments of the metal line 21 and the vias 22 described above can be applied for the production of the electrically conductive via 38.
    After the deposition of the electrically conductive material or materials in the opening 36, a layer 39 of this or these electrically conductive materials deposited to form the electrically conductive via 38 is present on the layer 34 (FIG. IG). A removal step, for example by CMP, is implemented in order to remove this layer 39, the layer 34 serving as a stop layer for this removal (FIG. 1H).
    The layer 34 is then removed (FIG. 11), for example by the implementation of chemical etching in an aqueous medium offering a very good selectivity of etching with respect to the support layer 32 underlying the layer 34 and vis-à-vis the electrically conductive material or materials of the electrically conductive via 38. Such an etching uses for example an etching solution of BOE type (“Buffered Oxide Etch”, or etched buffered oxide) having an HF base. diluted. The etching agents are chosen such that the support layer 32 is not etched by these etching agents which can be of the same nature as those which will be used later to etch the sacrificial layer 30. This etching of the layer 34 reveals an upper part 40 of the electrically conductive via 38 (symbolically delimited from the rest of via 38 by a dotted line) whose lateral flanks are not covered, at this stage of the process by any material. The thickness of this upper part 40 is equal to that of the layer 34.
    An electrically conductive layer 42 is then deposited on the support layer 32 and also covering the upper part 40 of the electrically conductive via 38, and in particular the upper face and the lateral faces of this upper part 40 of the electrically conductive via 38 (FIG. IJ) . The layer 42 comprises for example TiN. This covering of the upper part 40 of the electrically conductive via 38 by the layer 42 increases the contact surface between the conductive material of the layer 42 and the conductive material or materials of the via 38, and thus improves the electrical conduction between the pillar formed by via 38 and layer 42. When the membrane of the bolometer produced is released by etching the sacrificial layer 30, the fact that the support layer 32 surrounds via 38 at a level located under this upper part 40 of via 38 will increase the robustness mechanics of the assembly.
    The bolometer is then completed by carrying out the various optical-thermal and thermal-electrical transduction elements on the support layer 32, by etching the support layer 32 (and any other layers deposited on the support layer 32) to form the membrane of the bolometer, and by etching the sacrificial layer 30 in order to release this membrane.
    In the first embodiment described here, layer 42 is etched such that the remaining portions of this layer form electrodes 44 of the bolometer directly in contact with the conductive material or materials of vias 38 (a single electrode 44 is shown in the figure 1K). Other remaining portions of the layer 42 form resistive portions 46 capable of absorbing the infrared radiation intended to be detected by the detector 100. The portions of the support layer 32 made of amorphous silicon which are not covered by the electrodes 44 and the resistive portions 46 will form regions of thermal-electrical transduction of the bolometer.
    As shown in FIG. IL, a thermal-electrical transduction layer 48, called the first thermal-electrical transduction layer, is deposited on the remaining portions 44, 46 of the layer 42 and on the parts of the support layer 32 not covered by these portions 44, 46. This layer 48, comprising for example amorphous silicon, is intended to ensure, with the support layer 32 (because the latter is also made of amorphous silicon in this first embodiment), the conversion into electrical energy infrared radiation that will be received by the bolometer. In addition, the layers 32 and 48 make it possible to compensate for a bimetallic strip effect occurring between the portions 46 of the electrically conductive layer and the support layer 32.
    A second thermal-electrical transduction layer 50 is then deposited on the layer 48 (FIG. IM). Advantageously, this layer 50 comprises amorphous silicon and has a thickness greater than that of the layer 48 and that of the support layer 32.
    This second layer 50 is etched so that at least one remaining part 52 of this layer 50 is capable of forming at least one thermal-electrical transduction element of the bolometer. In the first embodiment described here, the remaining part 52 forms a central thermometric element of the membrane 54. Advantageously, the parts of the second layer 50 located on the zones intended to form the holding arms of the membrane 54 are removed during this etching, which provides the membrane 54 with high thermal insulation. The etching process of the second layer 50 can advantageously have recourse to an etching stop layer, which in particular makes it possible to properly control the thickness in the holding arms.
    The layers 48 and 32 are then etched according to the desired pattern to form the membrane 54 of the bolometer and the holding arms of the membrane 54. Finally, the sacrificial layer 30 is etched chemically and selectively with respect to the materials of the layers 32 , 48, 50 and 29, thus releasing the membrane 54 which is suspended thanks to the vias 38 (Figure IN).
    The infrared thermal detector 100 obtained is formed of a central element comprising, in addition to the absorbing elements 46 produced for example in the form of metallic ribbons, thermometric elements corresponding to the superimposed portions of temperature-sensitive materials from the three layers 32, 48, 52 whose total thickness is substantially greater than the sum of the thicknesses of the layers 32 and 48. In this case, it follows a reduction in the electrical noise of the thermometric elements according to a law inversely proportional to the thickness of the thermometric elements . This central element is electrically and mechanically connected to the electrically conductive vias 38 by means of arms formed by the superposition of the materials of the layers 32, 42 and 48, the thickness of these arms being substantially less than that of the central element. It follows a reduction in the thermal conductance of these arms and consequently better thermal insulation of the central element and a gain in sensitivity of the detector 100. At the end of the process, the bolometer (s) produced are placed in an airtight enclosure.
    According to a second embodiment, the support layer 32 can be used to form the thermometric element of the bolometer of the detector 100, and the absorber element of the detector can be formed by one or more MIM structures (Metal - Insulator - Metal) produced on the bolometer membrane. FIG. 2 represents a detector 100 obtained by implementing a method according to this second embodiment, the reference 56 designating a MIM structure which is formed of a lower metal portion 58, of a dielectric portion 60 and of a portion upper metallic 62. A dielectric portion 64, comprising a dielectric material capable of withstanding the final HF etching such as, for example, AIN or AI2O3, is disposed between the lower metallic portion 58 and the layer 32 in order to electrically insulate the thermometric element formed by the layer 32 from the lower metal portion 58. This dielectric portion 64 is for example produced by depositing a layer of the material of this portion 64 prior to the deposition of the materials of the MIM structure 56, and etched at the same time as the materials forming the MIM structure 56. In this second embodiment, the MIM structure 56 is formed say side on the etched layer 32 forming the bolometer membrane. Here, the part of the layer 32 forming the membrane ensures thermal - electrical transduction within the bolometer. The MIM 56 structure makes it possible in particular to carry out a selective absorption of the wavelengths.
    As in the first embodiment, the electrical connection between the conductive material present in the bolometer membrane and the detector reading circuit is ensured by means of the electrodes 44 which directly cover the electrically conductive vias 38.
    In general, the implementation of the steps previously described in connection with Figures IA to IJ makes it possible to form a base for receiving the various elements of the bolometers, that is to say the elements carrying out the optical - thermal and thermal transductions - electric inside the bolometer. The different configurations of these elements described in document EP 2 743 659 A1 can be applied to form the detector 100.
    The production method described above can be applied for the production of a detector 100 comprising a single bolometer or several bolometers.
    权利要求:
    Claims (10)
    [1" id="c-fr-0001]
    1. Method for producing a bolometric detector (100) comprising at least the implementation of the following steps: - producing a stack of layers (29, 30, 32, 34) on an electrical interconnection level (20 ) an electronic reading circuit (12) of the detector (100), the stack comprising at least one sacrificial layer (30) disposed between a support layer (32) and a first etching stop layer (29), the first etching stop layer (29) being disposed between the sacrificial layer (30) and said electrical interconnection level (20), and the sacrificial layer (30) comprising at least one mineral material capable of being selectively etched vis -with respect to the support layer (32) and the first etching stop layer (29); - Production of at least one electrically conductive via (38) passing through at least the stack of layers (29, 30, 32, 34) such that at least one electrically conductive material of the via (38) is in contact with at least an electrically conductive portion (21) of said electrical interconnection level (20) connected to the electronic reading circuit (12); - depositing at least one electrically conductive layer (42) on the support layer (32) and the via (38); - Etching of the electrically conductive layer (42) and of the support layer (32), forming a bolometer membrane (54) electrically connected to the via (38) by at least one remaining portion (44) of the electrically conductive layer (42 ) which covers at least an upper part (40) of the via (38); - Removal of the sacrificial layer (30) by chemical etching to which the first etching stop layer (29) and the support layer (32) resist, and such that the membrane (54) is suspended via the via (38).
    [2" id="c-fr-0002]
    2. Method according to claim 1, in which the stack of layers (29, 30, 32, 34) further comprises a second etching stop layer (34) such that the support layer (32) is disposed between the second etching stop layer (34) and the sacrificial layer (30), the method further comprising, between the creation of the via (38) and the deposition of the electrically conductive layer (42), the implementation of the steps following: - removal of a layer of electrically conductive material (39) formed on the second etching stop layer (34) during the production of the via (38), then - removal of the second etching stop layer (34), and in which the electrically conductive layer (42) is deposited such that the remaining portion (44) of the electrically conductive layer (42) also covers lateral flanks of the upper part (40) of the via (38) uncovered by removing the second etch stop layer ( 34).
    [3" id="c-fr-0003]
    3. Method according to one of the preceding claims, wherein the support layer (32) comprises at least one dielectric material or a material of which at least one electrical parameter varies as a function of its temperature.
    [4" id="c-fr-0004]
    4. Method according to one of the preceding claims, further comprising, before the removal of the sacrificial layer (30), the production of at least one element (56) absorbing infrared radiation intended to be detected by the detector (100 ), on the membrane (54).
    [5" id="c-fr-0005]
    5. Method according to claim 4, in which the absorbing element comprises at least one MIM structure (56).
    [6" id="c-fr-0006]
    6. Method according to one of the preceding claims, in which the electrically conductive layer (42) is etched such that a plurality of remaining portions of said electrically conductive layer (42) form bolometer electrodes (44) and resistive portions (46) capable of absorbing infrared radiation intended to be detected by the detector (100).
    [7" id="c-fr-0007]
    7. Method according to one of the preceding claims, further comprising, between the etching of the electrically conductive layer (42) and the etching of the support layer (32), the deposition of a first layer (48) of thermal transduction -electric on the remaining portions (44, 46) of the electrically conductive layer (42) and on the support layer (32).
    [8" id="c-fr-0008]
    8. The method of claim 7, wherein the first layer (48) of thermal-electrical transduction comprises at least one material resistant to chemical etching used to remove the sacrificial layer (30).
    [9" id="c-fr-0009]
    9. Method according to one of claims 7 or 8, further comprising, after the deposition of the first layer (48) of thermal-electrical transduction, the deposition of a second layer (50) of thermal-electrical transduction on the first layer (48) of thermal-electrical transduction and whose thickness is greater than that of the first layer (48) of thermal-electrical transduction.
    [10" id="c-fr-0010]
    10. Method according to one of the preceding claims, in which: - the support layer (32) comprises amorphous silicon, and / or - when a first layer (48) of thermal-electrical transduction is deposited, the first layer ( 48) of thermal-electrical transduction comprises amorphous silicon, and / or - when a second layer (50) of thermal-electrical transduction is deposited, the second layer (50) of thermal-electrical transduction comprises of amorphous silicon.
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    同族专利:
    公开号 | 公开日
    FR3066321B1|2019-06-14|
    CN109000807A|2018-12-14|
    EP3401657A1|2018-11-14|
    US20180331155A1|2018-11-15|
    US10797103B2|2020-10-06|
    KR20180123638A|2018-11-19|
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    DE10058864A1|2000-11-27|2002-06-06|Siemens Ag|Production of a micromechanical structure used for integrated sensor arrays comprises applying an auxiliary layer and a membrane to a substrate to cover contact surfaces|
    EP2743659A1|2012-12-17|2014-06-18|Commissariat à l'Énergie Atomique et aux Énergies Alternatives|Method for manufacturing an infrared detection device|WO2022023658A1|2020-07-29|2022-02-03|Lynred|Method for producing an infrared imaging micro-bolometer and associated micro-bolometer|FR2752299B1|1996-08-08|1998-09-11|Commissariat Energie Atomique|INFRARED DETECTOR AND MANUFACTURING METHOD THEREOF|
    FR2883417B1|2005-03-16|2007-05-11|Ulis Soc Par Actions Simplifie|BOLOMETRIC DETECTOR, INFRARED DETECTION DEVICE USING SUCH A DETECTOR AND METHOD FOR MANUFACTURING SAME|
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    JP5218460B2|2010-03-26|2013-06-26|セイコーエプソン株式会社|Pyroelectric detector, pyroelectric detector and electronic device|
    FR2977937B1|2011-07-15|2013-08-16|Centre Nat Rech Scient|BOLOMETRIC DETECTOR WITH IMPROVED PERFORMANCES|
    FR3009865B1|2013-08-22|2015-07-31|Commissariat Energie Atomique|BOLOMETRIC DETECTOR WITH REINFORCED THERMALIZATION COMPENSATION BOLOMETER|CN106124067B|2016-07-18|2019-01-18|上海集成电路研发中心有限公司|Infrared acquisition pixel structure and preparation method thereof, mixing image device|
    WO2018018709A1|2016-07-28|2018-02-01|上海集成电路研发中心有限公司|Infrared detector pixel structure and preparation method therefor|
    FR3070096B1|2017-08-08|2021-09-17|Commissariat Energie Atomique|METHOD OF MANUFACTURING A DETECTION DEVICE WITH TWO SUBSTRATES AND SUCH A DETECTION DEVICE|
    FR3113125A1|2020-07-29|2022-02-04|Lynred|METHOD FOR MAKING AN INFRARED IMAGING MICRO-BOLOMETER AND ASSOCIATED MICRO-BOLOMETER|
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    CN113639879A|2021-10-13|2021-11-12|北京北方高业科技有限公司|Preparation method of infrared microbridge detector with multilayer structure and infrared microbridge detector|
    法律状态:
    2018-05-28| PLFP| Fee payment|Year of fee payment: 2 |
    2018-11-16| PLSC| Search report ready|Effective date: 20181116 |
    2019-05-31| PLFP| Fee payment|Year of fee payment: 3 |
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    2021-05-31| PLFP| Fee payment|Year of fee payment: 5 |
    优先权:
    申请号 | 申请日 | 专利标题
    FR1754060A|FR3066321B1|2017-05-09|2017-05-09|METHOD FOR PRODUCING A BOLOMETRIC DETECTOR|
    FR1754060|2017-05-09|FR1754060A| FR3066321B1|2017-05-09|2017-05-09|METHOD FOR PRODUCING A BOLOMETRIC DETECTOR|
    US15/968,863| US10797103B2|2017-05-09|2018-05-02|Method for producing a bolometric detector|
    EP18170940.3A| EP3401657A1|2017-05-09|2018-05-04|Method for manufacturing a bolometric detector|
    KR1020180052762A| KR20180123638A|2017-05-09|2018-05-08|Method For Producing A Bolometric Detector|
    CN201810433331.2A| CN109000807A|2017-05-09|2018-05-08|Method for manufacturing bolometer detector|
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