Method of manufacturing a multispectral filter for electromagnetic radiation

Abstract

Method for manufacturing a multispectral filter for electromagnetic radiation The invention relates to a method for manufacturing a multispectral filter for electromagnetic radiation comprising at least two color filters, each filter comprising a first reflective layer, a second reflective layer, a layer of Fabry-Pérot cavity dielectric material, the thickness of the dielectric layer of the two color filters being different and each of the two filters being opposite a photoelectric transducer.The method comprises the following steps: Deposition on a substrate, called the handle substrate, of a resin layer; Three-dimensional structuring of the resin layer by lithography so as to obtain at least two resin patterns of different heights, at least one of the patterns having a maximum reference height; Deposition of a layer made in the dielectric material intended to form the dielectric patterns of the Fabry-Pérot cavities and planarization by removal of the dielectric material with selective stopping at the top of the highest resin pattern; Transfer of the planarized face of the handle substrate onto the upper face of a carrier substrate; Removal of the handle substrate and the resin so as to release at the surface at least two dielectric patterns of Fabry-Pérot cavities of different thickness and deposition of a reflective layer on the at least two dielectric patterns of Fabry-Pérot cavities, forming the second reflective layer.Figure to be published with the abstract: [Fig. 13].

Description

Title of the invention: Method for manufacturing a multispectral filter for electromagnetic radiation TECHNICAL FIELD OF THE INVENTION

[0001] The technical field of the invention is that of spectral filtering, in particular for imaging applications and the production of colored filters for CMOS type image sensors, liquid crystal display devices or light-emitting diodes. The invention can also be implemented in light-emitting devices.

[0002] The present invention relates to a method of manufacturing a multispectral filter for electromagnetic radiation. TECHNOLOGICAL BACKGROUND OF THE INVENTION

[0003] A spectral filter or a color filter makes it possible to filter light by wavelength, so as to provide information on the intensity of the light in certain wavelengths. Several color filters can be combined so as to form, for example, red-green-blue filters (RGB in English terminology) which provide information on the intensity of these three colors.

[0004] In particular, metal / dielectric color filters are known, made from a Fabry-Pérot cavity. These filters comprise one or more dielectric (or possibly semiconducting) cavities formed between two thin metal films having a metal mirror function so as to form a Fabry-Pérot cavity. An example of this type of filter is described in document US6031653. Generally, the metal / dielectric stacks are different depending on the position on the optoelectronic component (an image sensor for example). The transmission of the filter is adjusted by adjusting the thickness of the cavity. Thus, in operation, a portion of the incident light corresponding to the wavelength of the filter is transmitted through it in the form of a colored beam, while the remainder of the incident light is reflected.Generally speaking, the thickness of the dielectric layer fixes the transmitted central wavelength, while the thickness of the metal layers allows the transmission spectral width to be adjusted. Furthermore, the use of several Fabry-Pérot cavities allows the spectral profile of the filter transmission to be modified. A filter of this type is made using conventional semiconductor manufacturing techniques. Thus, to obtain a red-green-blue filter, it is necessary to form at least one dielectric cavity whose thickness must have three different values. This entails significant technological constraints, in particular at least one masking and then etching step for each. dielectric cavity made.

[0005] It has also been shown that it is possible to use a network of multispectral filters for imaging directly produced on an array of optical sensors using a CMOS-compatible manufacturing technique (bottom-up approach in English terminology). These techniques are described in particular in document EP2522968.

[0006] More recently, the feasibility of optically functional devices following the creation of Fabry-Pérot cavities above a CMOS image sensor device has also been described (see document WO2019 / 239139).

[0007] All the solutions mentioned above require numerous successive lithography and etching steps to produce the different thicknesses of dielectric layers to ensure the filtering of the different colors.

[0008] Furthermore, when etching structures, various phenomena can lead to profile deformations, etching non-uniformities generated by “ARDE” (for “Aspect Ratio Dependent Etching” according to English terminology) effects or to degraded surface qualities. However, it is important to maintain the AR (for “Aspect Ratio”) form factor for devices such as multispectral filters. Summary of the invention

[0009] The invention offers a solution to the problems mentioned above, by proposing a method for manufacturing a multispectral filter for electromagnetic radiation making it possible to avoid the successive steps of lithography and etching of dielectric material for producing the different thicknesses of dielectrics and to obtain improved profiles and surface qualities.

[0010] To do this, the invention relates to a method for manufacturing a multispectral filter for electromagnetic radiation, said filter comprising at least two color filters, each filter comprising a first reflective layer, a second reflective layer, a layer of Fabry-Pérot cavity dielectric material between the first reflective layer and the second reflective layer, the thickness of the dielectric layer of the two color filters being different and each of the two filters being opposite a photoelectric transducer, said method comprising the following steps: • Deposition on a substrate, called a handle substrate, of a layer of resin; • Three-dimensional structuring of the resin layer by lithography of so as to obtain at least two resin patterns of different heights, at least one of the patterns having a maximum reference height, the height being measured perpendicular to the plane of the substrate; • Deposition of a layer made in the dielectric material intended to form the dielectric patterns of the Fabry-Pérot cavities, said layer of dielectric material covering all of the resin patterns, having an upper surface each point of which is located at a height relative to the substrate greater than the maximum reference height; • Planarization by removal of the dielectric material with selective stopping at the top of the highest resist pattern; • Transfer of the planarized face of the handle substrate onto the upper face of a substrate, called the carrier substrate, comprising at least two photoelectric transducers, each of said patterns being opposite a photoelectric transducer, a reflective layer intended to form the first reflective layer of the two color filters being positioned at the transfer interface between the handle substrate and the carrier substrate; • Removal of the handle substrate; • Removal of the resin so as to release at least two dielectric patterns of Fabry-Pérot cavities of different thickness on the surface; • Deposition of a reflective layer on the at least two Fabry-Pérot cavity dielectric patterns, forming the second reflective layer of the two color filters.

[0011] Thanks to the invention, the Fabry Pérot cavities are produced on a temporary support substrate, called a handle substrate, by filling a 3D resin structure previously produced by 3D lithography obtained in one step making it possible to avoid the numerous successive steps of lithography and etching of dielectric material forming the core of the cavities. The support substrate is then transferred to a substrate supporting the optoelectronic components of interest. Another advantage of the invention consists in not vertically transferring the patterns into the dielectric material forming the cores of the Fabry-Pérot cavities via a conventional etching approach and thus making it possible to maintain good surface quality and the desired form factor.

[0012] In addition to the characteristics which have just been mentioned in the preceding paragraph, the method of the invention may have one or more complementary characteristics among the following, considered individually or according to all technically possible combinations: • the structuring step is followed, before the deposition of the layer made in the dielectric material intended to form the dielectric patterns of the Fabry-Pérot cavities, by a step of conformal deposition of an encapsulation layer on the resin patterns. • the lithography used for the structuring step is a grayscale lithography. the reflective layer intended to form the first reflective layer of the color filters is previously deposited on the carrier substrate above the photoelectric transducers. a layer of dielectric material is deposited on said reflective layer of the carrier substrate so as to ensure a dielectric / dielectric contact when the planarized face of the handle substrate is transferred to the upper face of the carrier substrate. The method according to the invention comprises a step of producing alignment marks, said alignment marks being produced in the handle substrate or in the resin layer, alignment marks also being present in the carrier substrate so as to ensure that each of the resin patterns is placed opposite a photoelectric transducer. The method according to the invention comprises a step of depositing a stop layer prior to the step of depositing the resin layer, the removal of the handle substrate stopping on said stop layer and being followed by the removal of the stop layer so as to release the structured resin layer on the surface. According to a first variant, the method according to the invention comprises a step of producing air walls separating the dielectric patterns from Fabry-Pérot cavities. According to a second variant, the method according to the invention comprises a step of producing walls of material having an optical refractive index strictly lower than the refractive index of the dielectric material intended to form the dielectric patterns of the Fabry-Pérot cavities, said walls separating the dielectric patterns of the Fabry-Pérot cavities. The method according to the invention comprises, in addition to the production of at least two color filters, each filter comprising a first reflective layer, a second reflective layer, a layer of Fabry-Pérot cavity dielectric material between the first reflective layer and the second reflective layer, the production of at least one other color filter comprising a first reflective layer, a second reflective layer, a layer of Fabry-Pérot cavity dielectric material, said to be of a second type, between the first reflective layer and the second reflective layer, the dielectric material of this other color filter being different from the dielectric material of the two color filters.Advantageously, said step of three-dimensional structuring of the resin layer by lithography is carried out so as to obtain a free location in which the dielectric material intended to form the pattern of the Fabry-Pérot cavity of a second type is deposited.

[0013] The invention and its various applications will be better understood upon reading the following description and examining the accompanying figures. BRIEF DESCRIPTION OF THE FIGURES

[0014] The figures are presented for information purposes only and in no way limit the invention. • [Fig.l] shows a schematic representation of a block diagram of the method according to a first embodiment of the invention; [Fig.2], [Fig.3], [Fig.4], [Fig.5], [Fig.6], [Fig.7], [Fig.8], [Fig.9], [Fig.10], [Fig.11], [Fig.12] and [Fig.13] illustrate the steps of the method of [Fig.l]; • [Fig. 14] shows a schematic representation of a block diagram of the method according to a second embodiment of the invention; [Fig.15], [Fig.16], [Fig.17], [Fig.18], [Fig.19], [Fig.20], [Fig.21], [Fig.22], [Fig.23], [Fig.24], [Fig.25], [Fig.26], [Fig.27], [Fig.28], [Fig.29], [Fig.30], [Fig.31], [Fig.32] and [Fig.33] illustrate the steps of the process of [Fig.14]; • [Fig.34] shows a schematic representation of a block diagram of the method according to a third embodiment of the invention; • [Fig.35], [Fig.36], [Fig.37], [Fig.38] and [Fig.39] illustrate the steps of the process of [Fig.34]; • [Fig.40] shows a schematic representation of a block diagram of the method according to a fourth embodiment of the invention; • [Fig.41], [Fig.42] and [Fig.43] illustrate the steps of the process of [Fig.40] • [Fig.44] shows a schematic representation of a block diagram of the method according to a fifth embodiment of the invention; • [Fig.45], [Fig.46], [Fig.47], [Fig.48] and [Fig.49] illustrate the steps of the process in [Fig.44]. DETAILED DESCRIPTION

[0015] The figures are presented for information purposes only and in no way limit the invention

[0016] It should be recalled first that, generally and well known to those skilled in the art, a metal / dielectric type color filter made from a Fabry-Pérot cavity is obtained by dimensioning the thickness of the dielectric layer formed between the two metal layers. If the filtering of several colors is sought on the same component, it is then necessary to be able to obtain a dielectric thickness of variable thickness on this same component.

[0017] This dimensioning is for example carried out using an electromagnetic calculation program such as the Abeles matrix transfer formalism or a diffraction calculation for pixels whose size is close to the wavelength such as the Fourier Expansion Modal Method formalism or rigorous analysis by coupled waves (RCWA according to English terminology).

[0018] These calculation programs make it possible to determine the optimal parameters of the metal-dielectric stacks for each pixel. The calculation takes into account in particular the thicknesses of the metal and dielectric layers as well as their indices, the spectrum and the angular distribution of the incident light. For example, in the case of Fabry-Pérot filters, the central wavelength of the filter is determined approximately by the following formula:, _ Ihn.cos 0 + ¢. m-^r^

[0019] where • h is the thickness of the cavity, i.e. approximately the thickness of the dielectric layer • m, a positive integer between 1 and 10, is the order of the cavity, • n is the effective index of the cavity, and •<pl et q> 2 are the phase shifts on reflection on metal mirrors (determined by the nature of the materials involved and the wavelength considered), • 0 is the angle of incidence of the incident light on the filter (counted from from the perpendicular to the filter surface).

[0020] Once the cavity order is chosen, the angle of attack is known, the index and the phase shifts are known, all that remains is to determine an approximate thickness h so that the cavity is centered on a particular wavelength. Once the filtering function is calculated for each filter and each wavelength, the thicknesses h of the dielectrics are then adjusted according to the desired performance (search for a good signal-to-noise ratio, maximum transmission, etc.).

[0021] Another more empirical method consists of calculating, for several thicknesses h, the response of the stack and choosing h such that the resonance peak of the filter (Xres) is positioned in accordance with the specifications.

[0022] [Fig.l] shows a schematic representation of a block diagram of a method 100 according to a first embodiment of the invention.

[0023] The first step 101 of the method 100 illustrated in [Fig.2] consists of depositing on a substrate 200, called the handle substrate, a so-called stop layer 201 which will serve as a stop layer during the subsequent release steps. The substrate 200 may for example be a Si substrate, a Silicon On Insulator SOI substrate or a glass or sapphire substrate. The stop layer 201 may for example be a layer of dielectric material such as SiN. Advantageously, this first step 101 also comprises a sub-step of production of alignment marks 203, said alignment marks being produced in the handle substrate 200. We will see later that these alignment marks 203 are all the more useful for small pixels or in the case of using insulation walls. These marks 203 are produced by techniques known to those skilled in the art such as lithography and etching techniques.

[0024] The second step 102 illustrated in [Fig.3] consists of depositing a layer of resin then structuring said resin layer 204 in three dimensions. The 3D structuring is carried out by a lithography step. This lithography can preferably be a grayscale lithography or Grayscale according to the English electronic or optical terminology (followed by stabilization of the Grayscale resin by thermal or ultraviolet process).Other lithography techniques such as two-photon lithography or nano-imprinting can also be used to produce the resin structure 204. The structure 204 comprises a plurality of 3D patterns 204Ai (here 4 patterns 204A1, 204A2, 204A3 and 204A4). It is possible to freely set the dimensions of each pattern in the three directions of the Oxyz space (where Oxy is the plane of the figure, the Oy axis being in the direction perpendicular to the plane of the substrate 200 and the Oz axis being in the direction perpendicular to the plane of the figure).

[0025] For illustration purposes, [Fig.4] shows an image of 3 3D patterns zl, z2 and z3 of different dimensions obtained by structuring a layer of resin.

[0026] According to the invention, it is appropriate to have at least two resin patterns 204Ai of different heights (here the 4 patterns each have different heights). Among all of these patterns 204Ai, one of them, here the pattern 204A1, has a maximum height Hmax, called reference, the height being measured perpendicular to the plane of the substrate 200 along the axis Ox. We will return to the determination of the heights of each pattern 204Ai in the remainder of the description.

[0027] Advantageously, the method 100 according to the invention comprises a third step 103 illustrated in [Fig. 5] consisting of carrying out a conformal deposition of an encapsulation layer 205 on the resin patterns 204Ai. The material of the encapsulation layer 205 may be for example Al2O3 or SiO2 and the deposition will preferably be carried out by a low-temperature deposition technique such as atomic layer deposition (ALD). Advantageously, the material of the encapsulation layer 205 has an optical index close to (or even identical to) the optical index of the dielectric material used for the patterns of the Fabry-Pérot cavities which will be defined in the following. It will be noted that the material of the encapsulation layer 205 may also be a metal deposited in a conformal manner.

[0028] For each resin pattern 204Ai, we will note Hres(i) the height of the pattern, the height being measured perpendicular to the plane of the substrate. Thus, for pattern 204A1, Hres(l) is here equal to the reference height Hmax.

[0029] If the method 100 according to the invention comprises the encapsulation step 103, Hres(i) includes both the thickness of the resin 204 but also the thickness of the encapsulation layer 205; in the absence of step 103, Hres(i) is formed solely by the thickness of the pattern 204Ai.

[0030] The method 100 according to the invention then comprises a step 104 illustrated in [Fig.6] aimed at depositing a layer 206 made of the dielectric material intended to form the dielectric patterns of the Fabry-Pérot cavities. The layer 206 of dielectric material covers all of the resin patterns 204Ai. In other words, it has an upper surface 219 (not necessarily planar) each point of which is located at a height, relative to the handle substrate, greater than the maximum reference height Hmax. Thus, the layer 206 completely fills the voids between the resin patterns 204Ai and is located in its entirety above the highest resin pattern 204A1 of the structure. The material of the layer 206 is preferably but not limited to a material transparent in the visible range such as an organic material of the polymer or inorganic type (oxide, silicon nitride, alumina, etc.).It should be noted that the invention is not limited to the visible range and that other materials transparent to other wavelengths, in the infrared for example (for example using silicon), can be used. We will see in another embodiment that the invention can also be applied to several materials to cover a wider spectral range. It should be noted that this step could be carried out in the absence of the encapsulation layer (i.e. directly on the 3D resin patterns 204Ai): however, the advantage of the encapsulation layer is to prevent possible deformation of the resin patterns, the latter being likely to liquefy from certain temperatures (i.e. for example during the deposition of the layer 206): therefore, the encapsulation layer makes it possible to maintain the 3D structure during the deposition of the layer 206.Another advantage of the encapsulation layer is to facilitate the deposition of the layer 206, in particular if the materials of the layers 204 and 206 are very different (for example, organic on one side and inorganic on the other). Depositing the layer 206 directly on the patterns 204Ai could indeed pose adhesion problems. To overcome this difficulty, it is possible to choose an encapsulation layer material 205 suitable for receiving the dielectric material of the layer 206.

[0031] The method 100 then comprises in [Fig.7] a step of planarization of the layer 206 produced in the dielectric material intended to form the dielectric patterns of the Fabry-Pérot cavities so as to form a surface-planarized layer 207 by removal of the dielectric material from the layer 206. The planarization step can be carried out by an etch-back type etching step possibly followed by a CMP (Chemical Mechanical Polishing) step. The planarization is carried out with a stop on the encapsulation layer 205 located at its highest level (i.e. at the level of the reference height of the pattern 204A1). It will be noted that in the absence of the encapsulation layer 205, the planarization would stop directly on the pattern 204A1. One of the advantages of the presence of the encapsulation layer is that the latter protects the 3D resin patterns 204Ai which can be made in a softer material without being damaged.

[0032] Hdiel(i) is the height of the dielectric material of the layer 206 above the pattern 204Ai. For all the patterns 204Ai corresponding to a future pixel of the filter, the sum Hdiel(i)+Hres(i) must be constant and equal. The height Hdiel(i) corresponds to the thickness of the dielectric layer of the i-th Fabry-Pérot cavity and can be determined according to the methods mentioned above (depending on the specifications for the desired filtering): thus, by subtraction, between the constant height Hdiel(i)+Hres(i) given whatever the value of i and the height Hdiel(i), the height Hres(i) of each 3D resin pattern to be manufactured in step 102 is obtained (where appropriate taking into account the thickness of the encapsulation layer 205).

[0033] Step 106 of the method 100 shown in [Fig.8] consists of turning over the device 209 obtained at the end of step 105 to transfer the planarized face of the device 209 formed by the handle substrate onto the upper face 212 of a substrate, called the carrier substrate 210.

[0034] The carrier substrate 210 comprises a substrate 211 in which alignment marks 213 are made. These alignment marks 213 will be placed opposite the alignment marks 203 of the device 209. On the substrate 211 are formed a plurality of photoelectric transducers (at least two) 214Ai, each delimited by dotted lines (here 4 photoelectric transducers 214A1, 214A2, 214A3 and 214A4 are shown). The photoelectric transducers can operate either as a collector of light coming from the filters or as an emitter of light towards the filters. If they are collectors, the transducers can be for example CMOS type photodiodes. In the case of emitters, the transducers can be, for example, LED diodes, QLED diodes or LASER diodes, the emitters in this case having a broader emission spectrum than that of the corresponding Fabry-Pérot cavities.The carrier substrate 210 also comprises, above the transducers 214Ai, a reflective layer 215 intended to form the first reflective layer (or mirror layer) of the Fabry-Pérot color filters. In the embodiment of [Fig.8] and in a non-limiting manner, there is placed above the reflective layer 215, a dielectric layer 216 intended to. promote the transfer of the planarized surface 208 of the dielectric layer 207. In the event of the presence of this dielectric layer 216, it is appropriate to take into account the thickness of this layer in the value of Hdiel(i) for the dimensioning of the 3D resin patterns 204Ai.

[0035] When transferring the planarized face 208 of the device 209 formed by the handle substrate onto the upper face 212 of the carrier substrate 210, the alignment marks (respectively 203 and 213) are advantageously used so that each of the 3D resin patterns 204Ai faces a photoelectric transducer 214Ai. In other words, the patterns 204A1, 204A2, 204A3 and 204A4 face the transducers 214A1, 214A2, 214A3 and 214A4 respectively. As mentioned above, it is possible to dispense with the use of the alignment marks for pattern sizes of sufficiently large dimensions. On the other hand, a fine alignment will preferentially result in the presence of the alignment marks 203 and 213.

[0036] Step 107 of the method 100 shown in [Fig.9] is the extension of step 106 and aims to bond the planarized surface 208 of the dielectric layer 207 to the surface 212 of the dielectric layer 216.

[0037] According to an alternative not shown, it would be possible to dispense with the presence of the dielectric layer 216 on the support substrate 210 and provide a distribution of the reflective layer into two reflective layers, one which would be present on the device 209 formed by the handle substrate and the other such as the layer 215 illustrated in [Fig.8]. In this case, the bonding between the handle device 209 and the support substrate 210 will be done via a bonding between the two reflective layers (metal / metal bonding instead of a dielectric / dielectric bonding). According to this variant as in the previous embodiment, the reflective layer intended to form the first reflective layer of the two color filters is positioned at the transfer interface between the handle substrate and the carrier substrate.

[0038] According to [Fig. 10], the method 100 according to the invention comprises a step 108 of removing the handle substrate 200 with a stop on the stop layer 201 which serves as a protective layer for the resin patterns 204Ai. This operation can be carried out for example by etching, CMP type polishing or grinding type grinding.

[0039] The method 100 then comprises: • a step 109 of removing the stop layer 201 illustrated in [Fig.l 1], for example by a dry or wet etching process so as to release the resin on the surface. • A step 110 of removing the resin 204 (and therefore all of the patterns 204Ai) illustrated in [Fig. 12] with a stop on the encapsulation layer 205, for example by a chemical etching technique of the stripping type; we see here another advantage of the encapsulation layer 205 which facilitates removal selective of the resin 204 with respect to the dielectric material of the layer 206.

[0040] Step 110 makes it possible to release on the surface a plurality (at least two) of dielectric patterns 217Ai of Fabry-Pérot cavities of different thickness: here, five patterns 217A1, 217A2, 217A3, 217A4 and 217A5 are represented. Provided that the thickness of each resin pattern has been well chosen and taking into account, where appropriate, the thickness of the encapsulation layer 205 and the dielectric layer 216, each pattern 217Ai can form the core of a Fabry-Pérot cavity (including at the location where there was no resin which gives rise to the dielectric pattern 217A5; in this case, it is also appropriate to provide at this location a photoelectric transducer 214A5 on the substrate 211).

[0041] As illustrated in [Fig. 13], the method 100 according to the invention then comprises a step 111 of depositing a reflective layer 218 on the dielectric patterns 217Ai of the Fabry-Pérot cavity (here on the encapsulation layer 205 covering the filters, it being understood that removal of this layer 205 is also possible). This reflective layer 218 forms the second reflective layer of the color filters Fi of the Fabry-Pérot cavity type obtained according to this step (here five filters F1 to F5). Each filter Fi is formed by a part of the first reflective layer 215, the dielectric pattern 217Ai and a part of the reflective layer 218. Each filter Fi faces a corresponding transducer (i.e. a pixel) 214Ai. The reflective layer 218 is for example deposited conformally by chemical vapor deposition (CVD) or physical vapor deposition (PVD).Preferably, the layer 218 is deposited continuously on all of the dielectric patterns 217Ai, including on the sides of the latter. Advantageously, the thickness of the reflective layer 218 will be controlled to be constant, at least on the top of the patterns but also preferentially on the sides (hence the advantageous use of a conformal deposition). As already mentioned, it can be seen here that the five color filters obtained by the method 100 according to the invention have dimensions freely fixed along the three axes Ox, Oy and Oz, the thickness measured along the Oy axis fixing the desired resonance peak and the other dimensions along the Ox and Oz axes being able to be freely fixed according to the confinement of the desired light and possible space constraints.

[0042] [Fig. 14] shows a schematic representation of a block diagram of a method 300 according to a second embodiment of the invention. As already mentioned above, this second embodiment uses several dielectric materials for the production of the Fabry-Pérot cavities so as to cover a wider spectral range, for example visible and infrared.

[0043] The method 300 comprises a first step 301 illustrated in [Fig. 15] identical to step 101 of [Fig. 2], the references 200, 201 and 203 being respectively replaced by references 400, 401 and 403.

[0044] The second step 302 illustrated in [Fig. 16] consists of depositing a layer of resin 404 and then structuring said layer of resin 404 in three dimensions. The 3D structuring is carried out by a lithography step. This lithography may preferably be a grayscale lithography or Grayscale according to the English electronic or optical terminology (followed by stabilization by thermal or ultraviolet process of the Grayscale resin). Other lithography techniques such as two-photon lithography or nano-imprinting may also be used for producing the resin structure 404. The structure 404 comprises a plurality of 3D patterns 404Ai (here 6 patterns 404A1, 404A2, 404A3, 404A5, 404A6 and 404A7).It is possible to freely fix the dimensions of each pattern in the three directions of the Oxyz space (where Oxy is the plane of the figure, the Oy axis being in the direction perpendicular to the plane of the substrate 200 and the Oz axis being in the direction perpendicular to the plane of the figure).

[0045] According to the invention, it is appropriate to have at least two resin patterns 404Ai of different heights (here the 4 patterns each have different heights). Among all of these patterns 404Ai, at least one of them, here the patterns 404A1 and 404A5, has a maximum height Hmax, called reference, the height being measured perpendicular to the plane of the substrate 400 along the axis Ox. The determination of the heights of each pattern 404Ai has already been explained above with reference to the first embodiment of the method according to the invention. According to this second embodiment and unlike [Fig.3], we observe here that the step of depositing and structuring the resin has left a location 419 free on the stop layer 401. We will see later that this location 419 is reserved for the subsequent creation of a second type of Fabry-Pérot cavity using a dielectric material other than that provided at the locations of the patterns 404Ai.

[0046] Advantageously, the method 300 according to the invention comprises a third step 303 illustrated in [Fig. 17] consisting of carrying out a conformal deposition of an encapsulation layer 405 on the resin patterns 404Ai and on the free location 419. The material of the encapsulation layer 405 may be for example A12O3 or SiO2 and the deposition will preferably be carried out by a low-temperature deposition technique such as an atomic layer deposition (ALD) (“Atomic Layer Deposition” according to the English terminology).

[0047] The method 300 according to the invention then comprises a step 304 illustrated in [Fig. 18] aimed at depositing a layer 406 made in the dielectric material intended to form the dielectric patterns of the Fabry-Pérot cavities of the first type. The layer 406 of dielectric material covers all of the resin patterns 404Ai as well as the location 419 which is completely filled with dielectric material. In other words terms, it has an upper surface 427 (not necessarily flat) each point of which is located at a height, relative to the handle substrate, greater than the maximum reference height Hmax. Thus, the layer 406 completely fills the voids between the resin patterns 204Ai and is located in its entirety above the highest resin pattern 404A1 of the structure. The material of the layer 406 is preferably but not limited to a material transparent in the visible range such as an organic material of the polymer or inorganic type (oxide, silicon nitride, alumina, etc.).

[0048] The method 300 then comprises in [Fig. 19] a step of planarization of the layer 406 made in the dielectric material intended to form the dielectric patterns of the Fabry-Pérot cavities of a first type so as to form a surface-planarized layer by removing the dielectric material from the layer 406. The planarization step can be carried out by an etch-back type etching step possibly followed by a CMP (Chemical Mechanical Polishing) step. The planarization is carried out with a stop on the encapsulation layer 405 located at its highest level (i.e. at the level of the reference height of the patterns 404Al and 404A5).

[0049] Step 306 of the method 300 shown in [Fig.20] consists of turning over the device 409 obtained at the end of step 305 to transfer the planarized face 408 of the device 409 formed by the handle substrate onto the upper face 412 of a substrate, called the carrier substrate 410.

[0050] As in the first embodiment, the carrier substrate 410 comprises a substrate 411 in which alignment marks 213 are made. These alignment marks 413 will be placed opposite the alignment marks 403 of the device 409. On the substrate 411 are formed a plurality of photoelectric transducers (at least two) 414Ai, each delimited by dotted lines (here 7 photoelectric transducers 414A1, 414A2, 414A3, 414A4, 414A5, 414A6 and 414A7 are shown). The carrier substrate 410 further comprises, above the transducers 414Ai, a reflective layer 415 intended to form the first reflective layer (or mirror layer) of the Fabry-Pérot color filters. In the embodiment of [Fig.20] and in a non-limiting manner, a dielectric layer 416 is placed above the reflective layer 415, intended to promote the transfer of the planarized surface 408 of the dielectric layer 406.

[0051] When transferring the planarized face 408 of the device 409 formed by the handle substrate onto the upper face 412 of the carrier substrate 410, the alignment marks (respectively 403 and 413) are advantageously used so that each of the 3D resin patterns 404Ai and the free location 419 faces a photoelectric transducer 414Ai. In other words, the patterns 404A1, 404A2, 404A3, 404A5, 404A6 and 404A7 are respectively opposite the transducers 414A1, 414A2, 414A3, 414A5, 414A6 and 414A7. The free location 419 is opposite the transducer 414A4.

[0052] Step 307 of the method 300 shown in [Fig.21] is the extension of step 306 and aims to bond the planarized surface 408 of the dielectric layer 406 to the surface 412 of the dielectric layer 416.

[0053] According to [Fig.22], the method 300 according to the invention comprises a step 308 of removing the handle substrate 400 with a stop on the stop layer 401 which serves as a protective layer for the resin patterns 404Ai. This operation can be done for example by etching, CMP type polishing or grinding type grinding.

[0054] The method 300 then comprises a step 309 of removing the stop layer 401 illustrated in [Fig.23], for example by a dry or wet etching method so as to release the resin patterns 404Ai and the free location 419 on the surface.

[0055] According to steps 310 to 312 of the method 300 according to the invention, a photolithography operation is carried out by starting by depositing or spreading a hard mask layer 420 (in SiO2 for example) above the patterns 404Ai and the free location 419. A photosensitive resin layer 421 is then spread on the hard mask layer ([Fig.24]). A lithography operation known to those skilled in the art makes it possible to open (opening 422) the resin layer 421 vertically above the free location 419 provided for the production of a Fabry-Pérot cavity of a second type ([Fig.25]). The opening 422 is then transferred from the resin layer 421 into the hard mask 420 by etching ([Fig.26]) so that the opening 422 vertically overhangs the free location 419. The resin layer is then removed.

[0056] According to step 313 of method 300 illustrated in [Fig.27], two dry etching steps are carried out in order to remove the part 423 of the encapsulation layer 405 opposite the opening 422 and the dielectric material intended to form the Fabry-Pérot cavities of the first type filling the free location 419. The etching step of the dielectric material stops on the reflective layer 415 so as to form an empty opening 425 in the free location 419.

[0057] The method 300 according to the invention then comprises a step 314 illustrated in [Fig.28] aimed at depositing a layer 424 made of the dielectric material intended to form the dielectric pattern of at least one Fabry-Pérot cavity of a second type. The layer 424 of dielectric material here covers the entirety of the hard mask 420 and completely fills the opening 425 by overflowing from it. In other words, the layer 424 has an upper surface 426 (not necessarily planar) each point of which is located at a height, relative to the handle substrate, greater than the maximum reference height Hmax to which the height hHM of the hard mask 420 is added. The material of the layer 424 may be an organic dielectric material or inorganic.

[0058] The method 300 then comprises in [Fig.29] a planarization step 315 with stopping on the hard mask 420, of the layer 424 made in the dielectric material intended to form the dielectric patterns of the Fabry-Pérot cavities of a second type so as to eliminate the excess dielectric material above the hard mask 420 and to planarize the upper surface of the dielectric volume filling the opening 425 thus forming a dielectric pattern 426 of the electrical cavity of a second type. The planarization step can be carried out by a reactive dry etching step of the RIE type (Reactive Ion Etching in English) or a chemical mechanical polishing step CMP (Chemical Mechanical Polishing according to the English terminology).

[0059] According to a first variant of the method 300, the latter comprises a step 316 illustrated in [Fig. 30] consisting of selectively removing the hard mask 420 so as to allow an excess thickness hsup of the pattern 426 to protrude above the structured resin layer 404. This first variant applies when the optical index of the dielectric material intended to form the Fabry-Pérot cavities of a second type is such that the thickness of the cavities of a second type must be greater than the height Hmax of the resin layer 404. Advantageously, the thickness hsup of the pattern 426 is less than or equal to the thickness hHM of the hard mask 420 (the two thicknesses are substantially equal in [Fig. 30]).

[0060] The method 300 then comprises a step 317 of removing the resin 404 (and therefore all of the patterns 404Ai) illustrated in [Fig.31] with a stop on the encapsulation layer 405, for example by a chemical etching technique of the stripping type.

[0061] Step 317 makes it possible to release on the surface the dielectric patterns 417Ai of Fabry-Pérot cavities of a first type (here, the six patterns 417A1, 417A2, 417A3, 417A5, 417A6 and 417A7 are represented) in addition to the dielectric pattern 426 of a Fabry-Pérot cavity of a second type. Provided that the thickness of each resin pattern has been well chosen and taking into account, where appropriate, the thickness of the encapsulation layer 405 and the dielectric layer 416, each pattern 417Ai can form the core of a Fabry-Pérot cavity of a first type and the pattern 426 forms the core of a Fabry-Pérot cavity of a second type.

[0062] As illustrated in [Fig.32], the method 300 according to the invention then comprises a step 318 of depositing a reflective layer 418 on the dielectric patterns 417Ai of Fabry-Pérot cavity of a first type (here on the encapsulation layer 205 covering the patterns) and on the dielectric pattern 426 of cavity of a second type. This reflective layer 418 forms the second reflective layer of the color filters Fi of Fabry-Pérot cavity type obtained according to this step: here six filters F1, F2, F3, F5, F6 to F7 of a first type and one filter F4 of a second type). It is understood that we have illustrated this mode through the production of a single filter of the second type but it is also possible to obtain several filters of the second type (in particular by leaving several locations left free during step 301 represented in [Fig. 16]). Each cavity of a first type uses the same dielectric material and has a predetermined thickness allowing specific filtering. The cavity F4 of a second type uses another dielectric material and, thanks to this different material, allows specific spectral filtering different from the cavities of the first type.

[0063] Each Fi filter is formed by a portion of the first reflective layer 415, the dielectric pattern and a portion of the reflective layer 418. Each Fi filter faces a corresponding photoelectric transducer 414Ai. The reflective layer 418 is for example conformally deposited by chemical vapor deposition (CVD) or physical vapor deposition (PVD).

[0064] A second variant of the method 300 can be envisaged following the planarization step 315, when the optical index of the dielectric material intended to form the Fabry-Pérot cavities of a second type is such that the thickness of the cavities of a second type HFp2 must be less than the height Hmax of the resin layer 404.

[0065] The method then comprises a step 316' illustrated in [Fig.33] following step 315 and consisting of selectively etching the second type dielectric material with respect to the hard mask 420 until the thickness hFP2 of the desired pattern 426' is obtained. Once this step has been carried out, the hard mask 420 is removed and the following steps are identical to steps 317 to 318 (removal of the resin and deposition of a reflective layer forming the second reflective layer of the first and second type Fabry-Pérot cavity type color filters).

[0066] [Fig.34] shows a schematic representation of a block diagram of a method 500 according to a third embodiment of the invention. This third embodiment is particularly suitable when the dimensions of the pixels and therefore of the color filters are reduced, typically of the order of the wavelength of the light. The spatial overlap of the light contributions from one Fabry-Pérot cavity to another can degrade the efficiency of the overall device. This "crosstalk" phenomenon has already been observed for photoelectric transducers (i.e. CMOS sensors). In recent years, pixel dimensions have continued to reduce, in order to offer high-resolution sensors, particularly for smartphones. This reduction in pixel dimensions has two very distinct consequences: • The total amount of incident light arriving at each pixel decreases, meaning that fewer and fewer photons reach the photosensitive component. The collection and proper guidance of each photon within the component to the sensor is all the more important to ensure good sensor efficiency. • As the pixel size approaches the length of the light to be collected, diffraction comes into play, increasing optical and spatial losses in the device.

[0067] Accompanying the issues related to the reduction of pixel dimensions, the angle of incidence with which light enters the Fabry-Pérot cavity is also an element that should not be neglected. Indeed, when oblique light rays reach the surface of the cavities, a certain portion of the light passes through the physical edge of the filter, to end its course in the neighboring cavity. This unwanted, parasitic contribution distorts the light collection at the device scale, and is another important source in the "crosstalk" from one pixel to another.

[0068] The first five steps 501 to 505 are identical to the first five steps 101 to 105 of the method illustrated in figures 2, 3, 4, 6 and 7 (for the sake of simplification, the same references are used for the elements common to figures 2, 3, 4, 6 and 7).

[0069] The sixth step 506 of the method 500 is illustrated in [Fig.35] consists of depositing or spreading on the planarized layer 207 of the dielectric material intended to form the patterns of the Fabry-Pérot cavities and the encapsulation layer 205, a layer of photosensitive or electrosensitive resin 601.

[0070] The method 500 according to the invention then comprises in [Fig.36] a photolithography step 507 consisting of creating trenches 602 aligned with the edges of the future Fabry-Pérot cavities. To do this, the photo or electrosensitive resin layer 601 is exposed using lithography equipment, in order to define on its surface a regular trench grid after development of the resin (open spaces in the resin up to the dielectric material 207 or up to the encapsulation layer 205).

[0071] The top view of [Fig.36] shows the regular grid of the resin trenches 602, the parts of the dielectric layer 207 seen through the trenches 602 and the part of the encapsulation layer 205 corresponding to the resin pattern 204A1. It should be noted that the representation of the patterns in the form of squares is given for illustrative purposes only. As explained several times above in the description, the dimensions of the patterns can be different from one pattern to another and there is no requirement that the pattern be square in top view (it could be a rectangular pattern for example).

[0072] The method 500 according to the invention then comprises in [Fig.37] a photolithography step 508 consisting of transferring by dry or wet etching the trenches or open spaces 602 previously made in the layer 207 of material di electrical of the future Fabry-Pérot cavities with stop on the encapsulation layer 205 of the structured resin layer 204. This transfer makes it possible to produce an identical grid in the dielectric layer 207 with trenches 603 substantially aligned on the sides of the encapsulation layer 205. Each transferred trench thus defines the outer edges of each filter cavity. The remainder of the surface resin 601 possibly not consumed at the end of the etching is removed if necessary, for example by a stripping-type cleaning process (step 509 illustrated in [Fig.38]). It should be noted that the dimension of the trenches 603 thus opened in the dielectric material 207 may be taken into account, if necessary, in the lateral dimensioning (size) of the future Fabry-Pérot cavities.

[0073] Steps 510, 511, 512, 513 and 514 are respectively identical to steps 106, 107, 108, 109 and 110 illustrated in Figures 8 to 12 and make it possible to obtain the device illustrated in [Fig. 39]. This device is almost identical to the device of [Fig. 13] except that it comprises air gaps 603 having a low optical index and which serve as a confinement barrier for the light within the Fabry-Pérot cavities. As in [Fig. 13], the reflective layer 218 forms the second reflective layer of the Fabry-Pérot cavity type color filters Fi obtained according to this step (here six filters F1 to F6). Each Fi filter is formed by a portion of the first reflective layer 215, the dielectric pattern and a portion of the reflective layer 218. Each Fi filter faces a corresponding transducer (i.e. a pixel).

[0074] Thanks to this third embodiment and the presence of the “air-gaps” 603, the previously mentioned “crosstalk” problems are considerably limited when the dimensions of the Fabry-Pérot cavities become of the order of the wavelength of the light, thus increasing the efficiency of the overall device. The air slice surrounding each Fabry-Pérot cavity therefore makes it possible to achieve a multispectral filtering device using Fabry-Pérot cavities isolated from each other. It should be noted that advantageously, air slices can also surround the photoelectric transducers also subject to the same crosstalk problems.

[0075] A fourth embodiment of the method according to the invention may consist of replacing the air gaps with optical isolation walls, said walls being made of materials with a low optical refractive index, said walls surrounding the Fabry-Pérot cavities so as to limit the "crosstalk" between them. It will be noted that this type of solution ("air-gap" or isolation wall) has already been implemented around photoelectric transducers (photodiode) but not at the filter level as proposed in the present invention. It will be possible to use for the materials of the isolation walls materials having an optical index of between 1.25 and 1.4 (such as Low-n polymer reference SLS-B047A from Fujifilm™ with an index n = 1.25 at 550nm). Advantageously, it is advisable to use a polymer with an optical index between 1.25 and 1.4 (knowing that the average optical index of a polymer is around 1.5). Usually, these are polymers with fluorinated groups. A large number of materials of this type already exist for optical applications. Examples of polymers with fluorinated groups include Poly(hexafluoropropylene oxide), Fluorinated Ethylene Propylene, Poly(tetrafluoroethylene) or Poly(octafluoropentyl acrylate). Examples of non-fluorinated polymers such as Poly(methyl hydro siloxane) or Hydroxypropyl cellulose can also be mentioned.

[0076] The method 700 according to this fourth embodiment is represented in [Fig.40]. The first eight steps 701 to 709 are respectively identical to the first eight steps 501 to 509 of the method 500 previously described.

[0077] Step 710 illustrated in [Fig.41] consists of depositing or spreading a material 800 with a low optical index (i.e. an optical index strictly lower than the optical index of the dielectric material of the layer 207 intended to form the Fabry-Pérot cavity). The material 800 fills the trenches 603 previously created. It will be noted, as is the case in [Fig.41], that the filling with the material 800 can be done with excess above the surface formed by the resin patterns 204 and the encapsulation layer 205.

[0078] Step 711 illustrated in [Fig.42] consists of planarizing the surface by removing the excess material 800 to leave the latter only in the trenches 603.

[0079] The top view of [Fig.42] shows the regular grid of the trenches filled with material 800, the parts of the dielectric layer 207 seen through the trenches 602 and the part of the encapsulation layer 205 corresponding to the resin pattern 204A1.

[0080] Steps 712, 713, 714, 715 and 716 are respectively identical to steps 106, 107, 108, 109 and 110 illustrated in Figures 8 to 12 and make it possible to arrive at the device illustrated in [Fig.43]. This device is almost identical to the device of [Fig.39] except that the air gaps are replaced by trenches filled with material 800 having a lower optical index than that of the dielectric material used for the Fabry-Pérot cavities and which serves as a confinement barrier for the light within said cavities. As in [Fig.39], the reflective layer 218 forms the second reflective layer of the Fabry-Pérot cavity type color filters Fi obtained according to this step (here six filters F1 to F6). Each Fi filter is formed by a portion of the first reflective layer 215, the dielectric pattern and a portion of the reflective layer 218. Each Fi filter faces a transducer (i.e.a corresponding pixel).

[0081] As mentioned previously, the presence of the walls made of material 800 aims to reinforce the optical efficiency of the Fabry-Pérot filter cavities thanks to the integration of these optical isolation and confinement walls in each cavity.

[0082] It can be seen that in the previous embodiment, the insulating walls are produced after the deposition of the dielectric material intended to form the core of the Fabry-Pérot cavities. According to a fifth embodiment of the method according to the invention (method 900 in [Fig.44]), it is also possible to start by carrying out the deposition of the low optical index material and structuring it into insulating walls before the production and structuring of the dielectric material defining the Fabry-Pérot cavities.

[0083] The first three steps 901, 902 and 903 of the method 900 are respectively identical to steps 101, 102 and 103 of the method 100 illustrated in Figures 2, 3 and 5.

[0084] Step 904 illustrated in [Fig.45] consists of depositing or spreading the material 718 with a low optical index (i.e. an optical index strictly lower than the optical index of the dielectric material intended to form the Fabry-Pérot cavity and not yet deposited) on the encapsulation layer 205.

[0085] Step 904 is followed by step 905 illustrated in [Fig.46] during which the layer 718 is planarized with a selective stop at the top of the encapsulation layer 205. This planarization step can be carried out by an etch-back type etching step possibly followed by a CMP (Chemical Mechanical Polishing) step.

[0086] The method 900 then comprises a step 906 illustrated in [Fig.47] consisting of depositing or spreading a layer of photo- or electro-sensitive resin 719 above the planarized layer 718 of low optical index material.

[0087] The following step 907 illustrated in [Fig.48] aims to expose said resin layer 719 to a photolithography system to structure a network in the form of a grid of lines 720 after the development of the resin, the lines being arranged directly above the edges or sides of the future Fabry-Pérot cavities (here, the lines are aligned with the sides of the encapsulation layer 205).

[0088] The method 900 then comprises a step 908 illustrated in [Fig.49] in which a dry or wet etching of the planarized layer 718 of low optical index material is carried out by transferring the lines 720 of resin previously produced in the layer 718. A grid of lines 721 of the low optical index material is thus formed, identical to the grid of resin obtained at the end of step 907.

[0089] It will be noted that the dimension (width) of the lines forming the insulation walls, thus transferred into the low optical index material, can be taken into account, if necessary, in the lateral dimensioning (size) of the Fabry-Pérot cavities.

[0090] The following steps 909, 910, 911, 912, 913, 914, 915 and 916 of the method 900 are identical to steps 104, 105, 106, 107, 108, 109, 110 and 111 of the method 100 according to the invention and make it possible to arrive at a device such as that presented in [Fig.43].

Claims

Claims

1. Method (100) for manufacturing a multispectral filter for electromagnetic radiation, said filter comprising at least two color filters (Fi), each filter comprising a first reflective layer (215), a second reflective layer (218), a layer of dielectric material (207) of Fabry-Pérot cavity between the first reflective layer (215) and the second reflective layer (218), the thickness of the dielectric layer of the two color filters being different and each of the two filters (Fi) being opposite a photoelectric transducer (214Ai), said method comprising the following steps: - Deposition (102) on a substrate (200), called handle substrate, of a layer of resin (204); - Three-dimensional structuring (102) of the resin layer (204) by lithography so as to obtain at least two resin patterns (204Ai) of different heights, at least one of the patterns having a maximum reference height (Hmax), the height being measured perpendicular to the plane of the substrate (200); - Deposition (104) of a layer (206) made in the dielectric material intended to form the dielectric patterns of the Fabry-Pérot cavities, said layer (206) of dielectric material covering all of the resin patterns (204Ai) while having an upper surface (219) each point of which is located at a height relative to the handle substrate (200) greater than the maximum reference height (Hmax); - Planarization (105) by removal of the dielectric material with selective stopping at the top of the highest resin pattern; - Transfer (106, 107) of the planarized face (208) of the handle substrate onto the upper face (212) of a substrate (210), called the carrier substrate, comprising at least two photoelectric transducers (214Ai), each of said patterns being opposite a photoelectric transducer, a reflective layer (215) intended to form the first reflective layer of the two color filters being positioned at the transfer interface between the handle substrate and the carrier substrate; - Removal (108) of the handle substrate (200); - Removal (110) of the resin (204) so ​​as to release on the surface at least two dielectric patterns (217Ai) of Fabry-Pérot cavities of different thickness; - Deposition (111) of a reflective layer (218) on the at least two dielectric patterns of Fabry-Pérot cavity, forming the second reflective layer of the two color filters.

2. Method according to claim 1 characterized in that the structuring step is followed, before the deposition of the layer produced in the dielectric material intended to form the dielectric patterns of the Fabry-Pérot cavities, by a step of conformal deposition of an encapsulation layer on the resin patterns.

3. Method according to one of the preceding claims, characterized in that the lithography used for the structuring step is a grayscale lithography.

4. Method according to one of the preceding claims, characterized in that the reflective layer intended to form the first reflective layer of the color filters is previously deposited on the carrier substrate above the photoelectric transducers.

5. Method according to the preceding claim, characterized in that a layer of dielectric material is deposited on said reflective layer of the carrier substrate so as to ensure a dielectric / dielectric contact when transferring the planarized face of the handle substrate onto the upper face of the carrier substrate.

6. Method according to one of the preceding claims, characterized in that it comprises a step of producing alignment marks, said alignment marks being produced in the handle substrate or in the resin layer, alignment marks also being present in the carrier substrate so as to ensure that each of the resin patterns is placed opposite a photoelectric transducer.

7. Method according to one of the preceding claims, characterized in that it comprises a step of depositing a stop layer prior to the step of depositing the resin layer, the removal of the handle substrate stopping on said stop layer and being followed by the removal of the stop layer so as to release the structured resin layer on the surface.

8. Method according to one of the preceding claims, characterized in that that it includes a step of producing air walls separating the dielectric patterns of Fabry-Pérot cavities.

9. Method according to one of claims 1 to 7, characterized in that it comprises a step of producing walls of material having an optical refractive index strictly lower than the refractive index of the dielectric material intended to form the dielectric patterns of the Fabry-Pérot cavities, said walls separating the dielectric patterns of the Fabry-Pérot cavities.

10. Method according to one of the preceding claims, characterized in that it comprises, in addition to the production of at least two color filters, each filter comprising a first reflective layer, a second reflective layer, a layer of Fabry-Pérot cavity dielectric material between the first reflective layer and the second reflective layer, the production of at least one other color filter comprising a first reflective layer, a second reflective layer, a layer of Fabry-Pérot cavity dielectric material, said to be of a second type, between the first reflective layer and the second reflective layer, the dielectric material of this other color filter being different from the dielectric material of the two color filters.

11. Method according to the preceding claim, characterized in that said step of three-dimensional structuring of the resin layer by lithography is carried out so as to obtain a free location in which the dielectric material intended to form the pattern of the Fabry-Pérot cavity of a second type is deposited.

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