MULTISPECTRAL FILTER MATRIX WITH CURVED FABRY-PEROT FILTERS AND METHOD FOR MANUFACTURING

Description

DOMAINE TECHNIQUE DE L'INVENTION

[0001] The technical field of the invention is that of spectral filtering, in particular for imaging applications and the production of color filters, infrared filters or other filters of longer wavelengths depending on the appropriate metal and cavity material, 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 multispectral filtering matrix and methods of manufacturing such a matrix. ARRIERE-PLAN TECHNOLOGIQUE DE L'INVENTION

[0003] A spectral filter or a color filter allows light to be filtered by wavelength, in order to provide information on the intensity of light in certain wavelengths. Several color filters can be combined to form, for example, red-green-blue (RGB) filters 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 semiconductor) 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 rest of the incident light is reflected.Generally speaking, the thickness of the dielectric layer determines the central transmitted 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's transmission to be modified. A filter of this type is produced 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.

[0005] However, even though wavelength selectivity can be achieved by varying the cavity thickness, a Fabry-Pérot cavity filter is also very sensitive to the angle of incidence. The [ Fig. 1 ] presents the spectral response of a color filter to an electromagnetic wave, for a fixed dielectric layer thickness and different angles of incidence of the electromagnetic wave.

[0006] Many studies have been conducted to address this sensitivity deficiency of filters to the angle of incidence of electromagnetic waves. One way to reduce sensitivity, described in the following article: "Non-iridescent Transmissive Structural Color Filter Featuring Highly Efficient Transmission and High Excitation Purity. Sci Rep 4, 4921 (2014)", Shrestha, V., Lee, SS., Kim, ES. et al., is to use multiple cavities with a higher index cavity material. The authors of the article used the fact that the angle-dependent fractional wavelength shift is determined by the refractive index of the cavity: ∂ λ 0 λ 0 ∂ θ ∝ cos θ sin θ n 2 − sin θ 2 , where θ is the angle of incidence of the electromagnetic wave and n is the refractive index of the cavity. The proposed solutions reduce the angle sensitivity, but they require several lithography and etching steps for their fabrication.

[0007] Another way to reduce angular sensitivity is proposed in document US4466699A which describes a Fabry-Pérot filter with two plates of curved surfaces or, more particularly, aspherical surfaces which are movable relative to each other along an axis. The curved surfaces make it possible to have an angle of incidence of the radiation which is not perpendicular to the surface at every point on the surface. The curvature of the plates is chosen such that the error introduced by the fact that the angle of incidence is not perpendicular is compensated by the difference in distance between the plates, to obtain the desired wavelength at the output of the filter.

[0008] However, the Fabry-Pérot filter proposed in document US4466699A allows the spacing between the plates to be varied to obtain one wavelength at a time and not several wavelengths at a time. In addition, since the filter has a variable distance between the plates, it cannot be used in imaging, and in particular at microelectronics dimensions with CMOS image sensors, due to manufacturing constraints. US 2011 / 0043823 A1 describes another example of a prior art multispectral filtering matrix. RESUME DE L'INVENTION

[0009] The invention offers a solution to the problems mentioned above, by proposing a matrix comprising Fabry-Pérot filters making it possible to obtain several wavelengths, insensitive to the variation of the angle of incidence of electromagnetic radiation and usable in CMOS technology.

[0010] One aspect of the invention relates to a multispectral filtering matrix for an electromagnetic wave, the matrix comprising at least a first and a second optoelectronic element, each optoelectronic element comprising a color filter and a photoelectric transducer opposite said filter, each color filter forming a Fabry-Pérot cavity comprising a first reflective layer, a second reflective layer and a layer of Fabry-Pérot cavity dielectric material between the first reflective layer and the second reflective layer, the layer of dielectric material comprising: a lower surface, in contact with the first reflective layer, the lower surface being curved; an upper surface in contact with the second reflective layer, the upper surface being curved; the thicknesses of the two layers of dielectric material of the two color filters being different.

[0011] Thanks to the invention, the transmission of the color filters is independent of the angle of incidence of an incident electromagnetic wave, which makes it possible to obtain a desired wavelength for each filter only by varying the thicknesses of the dielectric layers without worrying about the angles of incidence. In addition, the matrix comprises Fabry-Pérot cavity filters used for imaging in microelectronics, and in particular in CMOS technologies.

[0012] In addition to the characteristics which have just been mentioned in the preceding paragraph, the matrix according to a first aspect of the invention may have one or more complementary characteristics among the following, considered individually or according to all technically possible combinations: for each color filter: the first reflective layer has a curved lower surface and a curved upper surface of the same radius of curvature, the upper surface of the first reflective layer being in contact with the lower surface of the dielectric material layer; the second reflective layer has a curved lower surface and a curved upper surface of the same radius of curvature, the lower surface of the second reflective layer being in contact with the upper surface of the dielectric material layer. the radii of curvature of the lower surface and the upper surface of the dielectric material layer of each color filter are strictly greater than 300 nm. for each color filter, the curvatures of the lower surface and the upper surface of the dielectric material layer of each color filter are both convex or both concave.the curved profile of the lower surface of the dielectric material layer of at least one color filter among the first and second color filters is defined by the following equation: . y = R y ∗ 1 − x f ∗ Sx m 1 n + h Cri 1 and the curved profile of the upper surface of said layer is defined by the following equation: y = R y ∗ 1 − x f ∗ Sx m 1 n + hi + h Cri 1 in a reference frame (O,X,Y,Z) of space, O being the origin of the lower surface of the first reflective layer; With: hi the thickness of the layer of dielectric material of said filter, h Cri1 the thickness, along the Y axis, of the first reflective layer of the filter, Ry the radius of curvature of the lower surface and of the upper surface of the layer of dielectric material along the Y axis for x=0, m and n respectively a natural integer and a non-zero natural integer, With f*Sx the radius of curvature of the lower surface and of the upper surface of the layer of dielectric material along the X axis, Sx being the size, along the X axis, of the photoelectric transducer opposite the filter and f a constant; the curved profile of the lower surface of the layer of dielectric material of at least one color filter among the first and second color filters is defined by the following equation: z = R z ∗ 1 − x f ∗ Sx m − y f ∗ Sy n 1 k + h Cri 1 And the curved profile of the upper surface of said dielectric material layer of the color filter is defined by the following equation: z = R z ∗ 1 − x f ∗ Sx m − y f ∗ Sy n 1 k + h i + h Cri 1 In a reference frame (O,X,Y,Z) of space, O being the origin of the lower surface of the first reflective layer of the filter, With: hi the thickness of the layer of dielectric material of said filter, h Cri1 the thickness, along the Y axis, of the first reflective layer of the filter, RZ the radius of curvature of the lower surface and the upper surface of the layer of dielectric material along the Z axis, m and n respectively a natural integer and a non-zero natural integer, With f*Sx the radius of curvature of the lower surface and the upper surface of the layer of dielectric material along the X axis, Sx being the size, along the X axis, of the photoelectric transducer opposite the filter and f a constant, With f*Sy the radius of curvature of the lower surface and the upper surface of the layer of dielectric material along the Y axis, Sy being the size, along the Y axis, of the photoelectric transducer opposite the filter.for each color filter, when the curvatures of the lower surface and the upper surface of the dielectric material layer are both convex, the curvature of the upper surface and the lower surface of the dielectric material layer is chosen so as to focus the electromagnetic wave on the transducer opposite said filter. This characteristic possibly makes it possible to do without a microlens, which is usually used in imaging to focus the electromagnetic waves received by a filter towards the transducer.

[0013] A second aspect of the invention relates to a method of manufacturing a multispectral filtering matrix according to the invention in which the thickness of the layer of dielectric material of the first color filter is less than the thickness of the layer of dielectric material of the second color filter and the production of the first and second color filters comprises the following steps: Deposition on a substrate carrying a resin layer; Structuring the resin layer, to obtain a first resin pattern defining a first pattern area and a second resin pattern defining a second pattern area, each resin pattern having a curved upper surface, the first and second pattern areas defining an overall pattern area; Conformal deposition of a first reflective layer on the overall pattern area, forming the first reflective layers of the first and second color filters; Conformal deposition of a first layer of dielectric material on the overall pattern area, the first layer of dielectric material having a thickness equal to the thickness of the Fabry-Pérot cavity dielectric material layer of the first filter; Deposition of a photosensitive resin layer on the overall pattern area; Removal, by photolithography, of the portion of the photosensitive resin layer covering the second pattern area, Conformal deposition of a second layer of dielectric material on the second pattern area, the total thickness of the second layer of dielectric material and the first layer of dielectric material of the second pattern area being equal to the thickness of the dielectric material layer of the second color filter;Removing the photosensitive resin layer, so as to release on the surface the first layer of dielectric material from the first pattern area forming the layer of Fabry-Pérot cavity dielectric material of the first color filter; Conformal deposition of a second reflective layer on the overall pattern area, forming the first reflective layers of the first and second color filters.

[0014] A third aspect of the invention relates to a method of manufacturing a multispectral filtering matrix according to the invention in which the thickness of the layer of dielectric material of the first color filter is greater than the thickness of the layer of dielectric material of the second filter and the production of the first and second color filters comprises the following steps: Deposition on a substrate carrying a resin layer; Structuring the resin layer to obtain a first resin pattern defining a first pattern area and a second resin pattern defining a second pattern area, each resin pattern having a curved upper surface, the first and second pattern areas defining an overall pattern area; Conformal deposition of a first reflective layer on the overall pattern area, forming the first reflective layers of the first and second color filters; Conformal deposition of a first layer of dielectric material on the overall pattern area, the first layer of dielectric material having a thickness equal to the thickness of the Fabry-Pérot cavity dielectric material layer of the first filter; Deposition of a photosensitive resin layer on the overall pattern area;Removal by photolithography of the part of the photosensitive resin layer covering the second pattern area, Removal of a thickness of the dielectric material layer from the second pattern area to obtain the thickness of the dielectric material layer of the second filter; Removal of the photosensitive resin layer so as to release on the surface the first dielectric material layer of the first pattern area forming the Fabry-Pérot cavity dielectric material layer of the first color filter; Conformal deposition of a second reflective layer on the overall pattern area, forming the first reflective layers of the first and second color filters. ;

[0015] Thanks to the second and third aspects of the invention, the lithography and etching steps are limited compared to the state of the art, in particular when several dielectric materials make up the Fabry-Pérot cavity.

[0016] A fourth aspect of the invention relates to a method for manufacturing a multispectral filtering matrix according to the invention in which the thickness of the layer of dielectric material of the first color filter is less than the thickness of the layer of dielectric material of the second filter and the production of the first and second color filters comprises the following steps: Deposition on a substrate carrying a resin layer; Structuring the resin layer to obtain a first resin pattern defining a first pattern area and a second resin pattern defining a second pattern area, each resin pattern having a curved upper surface, the first and second pattern areas defining an overall pattern area; Conformal deposition of a first reflective layer on the overall pattern area, forming the first reflective layers of the first and second color filters; Deposition of a layer of dielectric material on the overall pattern area, said layer of dielectric material having a substantially planar upper surface; Deposition of a second resin layer on the overall pattern area;Structuring the second resin layer, to obtain a first and second resin pattern of the second resin layer respectively in the first and second pattern area, each resin pattern of the second resin layer having a curved upper surface; Transferring the first and second resin pattern of the second resin layer into the dielectric material layer to obtain the dielectric material layer of the first filter in the first pattern area and the dielectric material layer of the second filter in the second pattern area; Conformal deposition of a second reflective layer on the overall pattern area, forming the first reflective layer of the first and second color filters. ;

[0017] Thanks to the fourth aspect of the invention, the different thicknesses of the layers of dielectric material of the filters are obtained in a single etching step.

[0018] In addition to the characteristics which have just been mentioned in the preceding paragraph, the method according to a second, third and fourth aspect of the invention may have one or more complementary characteristics among the following, considered individually or according to all technically possible combinations: The resin structuring step is carried out in three dimensions. The resin structuring step is carried out by Grayscale lithography. Grayscale lithography makes it possible to obtain a non-necessarily flat shape of the resin patterns and makes it possible to shape the resin into different curved shapes, for example.

[0019] The invention and its various applications will be better understood by reading the following description and examining the accompanying figures. BREVE DESCRIPTION DES FIGURES

[0020] The figures are presented for information purposes only and in no way limit the invention. There [ Fig.1 ] is a spectral response representation of a state-of-the-art Fabry-Pérot cavity filter, as a function of the angle of incidence of an incident electromagnetic wave. The [ Fig. 2 ] is a diagram of a matrix, according to the invention, of two optoelectronic elements respectively comprising two different color filters. The [ Fig. 3a ] presents the spectral response of a first color filter, for different angles of incidence of an electromagnetic wave incident on the first filter of the [ Fig. 2 ]. There [ Fig. 3b ] presents the spectral response of a second color filter, different from the first filter, for different angles of incidence of an electromagnetic wave incident on the second filter of the [ Fig. 2 ]. There [ Fig. 4 ] is a detailed diagram of an optoelectronic element of the matrix according to the first aspect of the invention. The [ Fig. 5 ] is a block diagram of a method of manufacturing the matrix and in particular the color filters according to a second aspect of the invention. The [ Fig. 6], [Fig. 7], [Fig. 8 ], [ Fig. 9], [Fig. 10], [Fig. 11 ], [ Fig. 12], [Fig. 13], [Fig. 14 ], [ Fig. 15 ] illustrate the steps of the process of the [ Fig. 5 ] according to the second aspect of the invention, The [ Fig. 16 ] is a block diagram of a method of manufacturing the matrix and in particular the color filters according to a third aspect of the invention. The [ Fig. 17 ] illustrates a step of the method according to the third aspect of the invention. The [ Fig. 18 ] is a block diagram of a method of manufacturing the matrix and in particular the color filters according to the fourth aspect of the invention. The [ Fig. 19] , [Fig. 20 ], [ Fig. 21], [Fig. 22 ] illustrate steps in the process of the [ Fig. 18 ] according to the fourth aspect of the invention. DESCRIPTION DETAILLEE

[0021] The figures are presented for information purposes only and in no way limit the invention.

[0022] 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.

[0023] 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 coupled wave analysis (RCWA according to English terminology).

[0024] These calculation programs allow the optimal parameters of metal-dielectric stacks to be determined 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: λ res = 2 hn . cos θ m − ϕ 1 + ϕ 2 2 π Or 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 Φ1 and Φ2 are the phase shifts on reflection on the metal mirrors (determined by the nature of the materials involved and the wavelength considered), θ is the angle of incidence of the incident light on the filter (counted from the perpendicular to the surface of the filter).

[0025] Once the cavity order has been chosen, the angle of attack known, the index and the phase shifts 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 has been 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.).

[0026] 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 (λres) is positioned in accordance with the specifications.

[0027] A first aspect of the invention relates to a multispectral filtering matrix, for at least one electromagnetic wave.

[0028] The electromagnetic wave received by the matrix can include wavelengths in the visible, infrared (near, medium or far) or microwave range.

[0029] In the following, the terms “Multispectral Filtering Matrix” and “Matrix” will be confused.

[0030] The matrix comprises at least two optoelectronic elements.

[0031] There [ Fig.2 ] is an example of a matrix 10 of two optoelectronic elements (E 1 , E2) each comprising a color filter F i and a transducer T i opposite said color filter F i.

[0032] The terms "color filter" and "filter" will be confused in the rest of the article.

[0033] A color filter F i is a filter that transmits only the said color when it receives an electromagnetic wave.

[0034] Each filter F i comprises a first reflective layer C r1i , a second reflective layer C r2i and a layer of dielectric material C FPi between the two reflective layers (C r1i, C r2i ).

[0035] The terms "Fabry-Pérot cavity dielectric material layer", "dielectric material layer" and "dielectric layer" will be confused in the rest of the article.

[0036] According to the invention, the thicknesses (h 1 ,h 2 ) of the two layers of dielectric material C FPi of the two filters (F 1 , F 2 ) are different. Thus, when each filter F i receives an incident electromagnetic wave, it transmits a wavelength λ res_i depending on the thickness hi of its dielectric layer C FPi according to the formula cited previously: λ res _ i = 2 h i . n . cos θ m − ϕ 1 + ϕ 2 2 π

[0037] In the example of the [ Fig. 2 ], the thickness h 1 of the dielectric layer C FP1 of the first filter F 1 is greater than the thickness h 2 of the dielectric layer C FP2 of the second filter F 2

[0038] There [ Fig. 3a ] is a representation of the spectral responses of the first filter F 1 for a thickness h 1 of the dielectric layer at C FP1 equal to 100 nm and for several angles of incidence θ of an incident electromagnetic wave. We thus note that for an angle of incidence θ equal to 0°, 20° and 40°, the spectral responses of the first filter F 1 are substantially identical and therefore do not depend on the angle of incidence of the wave.

[0039] There [ Fig. 3b ] is a representation of the spectral responses of the second filter F 2 for a thickness h 2 of the dielectric layer at C FP1 equal to 120 nm and for several angles of incidence θ of an incident electromagnetic wave. We thus note that for an angle of incidence θ equal to 0°, 20° and 40°, the spectral responses of the second filter F 2 are also substantially identical and therefore do not depend on the angle of incidence of the wave.

[0040] We notice in the [ Fig. 3a] et [Fig. 3b ] that the two wavelengths transmitted by the first filter F 1 and the second filter F 2 , respectively, are very different, given the two different thicknesses (h 1 , h 2 ) of the two dielectric layers (C FP1 , C FP1 ) of the two filters.

[0041] When the matrix 10 comprises at least three optoelectronic elements E i , at least two optoelectronic elements E i respectively comprise two different filters F i. The third optoelectronic element E 3 may comprise a filter F 3 identical to one of the two other filters F i of the two other optoelectronic elements E i or a filter F 3 different from the two optoelectronic elements.

[0042] By "two different filters" is meant two filters having two different respective dielectric layer thicknesses.

[0043] “Two identical filters” means two filters having two respective identical dielectric layer thicknesses.

[0044] For example, a 10-array RGB matrix might include 50% green color filters, 25% red color filters, and 25% blue color filters.

[0045] According to an embodiment not shown, the matrix 10 comprises a number C x L of optoelectronic elements E i , C representing the number of columns of the matrix 10 and L representing the number of rows of the matrix 10.

[0046] L and C are two natural numbers strictly greater than 0. At least one of the natural numbers L or C is greater than or equal to 2.

[0047] The structure of each optoelectronic element E i is shown in detail in the [ Fig. 4 ].

[0048] Each optoelectronic element E i is a pixel.

[0049] Each optoelectronic element E i can comprise, in addition to the filter F i and the transducer T i , a carrier substrate Si on which the different layers are produced.

[0050] Each reflective layer (Cr 1i ,Cr 2i ) of each filter F i is preferably made of metal and has a metal mirror function. The metal is for example silver.

[0051] The upper S1 sup_i and lower S1 inf_i surfaces of the first reflective layer Cr 1i of each filter F i are curved.

[0052] The upper S2 sup_i and lower S2 inr_i surfaces of the second reflective layer Cr 2i of each filter F i are also curved.

[0053] For each filter F i , each layer of dielectric material C FPi has a lower surface at the contact S inf_i of the first reflective layer Cr 1i and an upper surface S sup_i at the contact of the second reflective layer Cr 2i .

[0054] Here, the lower surface S inf_i of the dielectric layer C FPi is in contact with the upper surface S1 sup_i of the first reflective layer Cr 1i . The radius of curvature of the upper surface S1 sup_i of the first reflective layer Cr 1i is equal to the radius of curvature of the lower surface S inf_i of the dielectric material layer C FPi .

[0055] Similarly, the upper surface S sup_i of the dielectric layer C FPi is in contact with the lower surface S2 inr_i of the second reflective layer Cr 2i . The radius of curvature of the upper surface S2 inr_i of the second reflective layer Cr 2i is equal to the radius of curvature of the upper surface of the dielectric material layer C FPi .

[0056] For each color filter F i , the curvatures of the lower surface S inf_i and the upper surface S sup_i of the dielectric material layer C FPi are both convex. In this embodiment, the curvatures of the lower surface S1 inf_i and the upper surface S1 sup_i of the first reflective layer Cr 1i and the curvatures of the lower surface S2 inr_i and the upper surface S2 sup_i of the second reflective layer Cr 2i are all four convex.

[0057] When the upper surfaces S2 sup_i and lower surfaces S2 inr_i of the second reflective layer Cr 2i of a filter F i are convex, the filter F i makes it possible to focus the electromagnetic wave on the transducer T i opposite said filter F i , unlike a conventional state-of-the-art filter which requires a microlens above the Fabry-Pérot cavities in order to focus an incident wave.

[0058] Preferably, the radius of curvature of the lower surface S inf_i and of the upper surface S sup_i of the layer of dielectric material C FPi of each color filter F i is strictly greater than 300 nm.

[0059] The dielectric material of the dielectric material layer C FPi of each color filter F i is preferably but not limited to a material transparent in the visible range such as an organic material of the photosensitive polymer type modeled then hardened, or an inorganic material (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.

[0060] Each filter F i behaves like a material with a constant refractive index of 1.46, which is close to the refractive index of SiO 2 which is 1.47 in the visible spectrum.

[0061] The thickness hi of the layer of dielectric material C FPi of each color filter F i is preferably constant along said layer C FPi . In other words, the radius of curvature of the upper surface S sup_i and the radius of curvature of the lower surface S inf_i of the layer of dielectric material C FPi are identical.

[0062] In the case of figures 3a et 3b , the thickness hi of a dielectric layer C FPi of each filter F i is respectively equal to 100nm and 120nm.

[0063] According to another embodiment, each color filter F i has a thickness h diel_i (x,y) depending on the position x on the X axis and the position y on the Y axis.

[0064] According to one embodiment, the curved profile of the lower surface S inf_i of the dielectric layer C FPi of at least one filter F i is defined by the following equation in a reference frame (O,X,Y) of a reference frame (O,X,Y,Z) of space, with O the origin of the lower surface of the first reflective layer S1 inf_i: y = R y ∗ 1 − x f ∗ Sx m 1 n + h Cri 1 .

[0065] And the curved profile of the upper surface S sup_i of the dielectric material layer C FP is defined by the following equation: y = R y ∗ 1 − x f ∗ Sx m 1 n + hi + h Cri 1

[0066] h Cri1 is the thickness of the first reflective layer Cr 1i of said filter F i .

[0067] hi is the thickness of the layer of dielectric material C FPi of said filter F, preferably along the Y axis.

[0068] R y is the radius of curvature of the bottom surface along the Y axis for x=0.

[0069] m and n are respectively a natural number and a non-zero natural number.

[0070] For example, m = 1.8 and n = 0.8.

[0071] The term f*Sx is the radius of curvature of the lower surface S inf_i and the upper surface S sup_i of the dielectric material layer C FPi along the X axis.

[0072] S x is the size, along the X axis, of the optoelectronic element E i .

[0073] S x is a positive real number, for example equal to 2000 nm or 5000 nm.

[0074] f is a constant that defines the radius of curvature of the lower surface S inf-i and the upper surface S sup_i of the dielectric material layer C FPi along the X axis.

[0075] Preferably, the constant f is between 0.4 and 1. For example, f is 0.5.

[0076] According to another embodiment of a three-dimensional filter, the curved profile of the lower surface S inf_i of the dielectric layer C FPi of at least one filter Fi is defined by the following equation: z = R z ∗ 1 − x f ∗ Sx m − y f ∗ Sy n 1 k + h Cri 1

[0077] The curved profile of the upper surface S sup_i of the dielectric layer C FPi is defined by the following equation: z = R z ∗ 1 − x f ∗ Sx m − y f ∗ Sy n 1 k + h i + h Cri1 .

[0078] Rz is the radius of curvature of the bottom surface along the Z axis.

[0079] S y is the size, along the Y axis, of the element . SZ is a positive real number.

[0080] f is a constant that defines the radius of curvature of the lower surface S inf_i and of the upper surface S sup_i along the X axis and along the Y axis.

[0081] Preferably, f is between 0.4 and 1. For example, f is 0.5.

[0082] The term f*Sx is the radius of curvature of the lower surface S inf_i and the upper surface S sup_i of the dielectric material layer C PFi along the X axis.

[0083] The term f*Sy is the radius of curvature of the lower surface S inf_i and the upper surface S sup_i of the dielectric material layer C PFi along the Y axis.

[0084] k is a non-zero natural number. The photoelectric transducers T i can operate either as collectors of the light coming from the filters or as emitters of light towards the filters. If they are collectors, the transducers can be, for example, CMOS photodiodes. If they are 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.

[0085] A second aspect of the invention relates to a method 200a for manufacturing a multispectral filtering matrix 10 in which the thickness h 1 of the layer of dielectric material C FP1 of the first color filter F 1 is less than the thickness h 2 of the layer of dielectric material C FP2 of the second filter F 2 .

[0086] The figure [ Fig.5 ] is a block diagram of the method 200a for manufacturing the multispectral filtering matrix 10 according to the second aspect of the invention and in particular of the steps for producing the first F 1 and the second F 2 color filters.

[0087] The first step 201 of the method 200a according to the second aspect of the invention, illustrated in [ Fig. 6 ], consists of depositing a layer of resin 301 on a carrier substrate 300. The carrier substrate 300 may for example be an Si substrate, a Silicon on Insulator SOI substrate (for “Silicon On Insulator” according to English terminology) or a glass or sapphire substrate.

[0088] The second step 202 of the method 200a, illustrated in [ Fig. 7 ], consists of structuring the resin layer 301 to obtain at least a first resin pattern M 1 defining a first pattern zone Z 1 and a second resin pattern M 2 defining a second pattern zone Z 2 .

[0089] Each resin M i pattern has a curved top surface.

[0090] The first Z 1 and second Z 2 pattern area define an overall Z pattern area.

[0091] The structuring is carried out, for example, in two dimensions or preferably in three dimensions.

[0092] The resin structuring can be carried out by a lithography method. This lithography can preferably be an electronic or optical grayscale lithography (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 for the production of the resin structure. It is possible to freely fix the dimensions and the curvature of the upper surface of each resin pattern in the three directions of space (O, X, Y, Z).

[0093] The third step 203 of the method 200a according to the second aspect of the invention, illustrated in [ Fig. 8 ], consists of depositing, in a conforming manner, a first reflective layer 302 on the overall area of ​​patterns Z. The first reflective layer 302 completely covers the first M 1 and second M 2 resin patterns and forms the first reflective layer Cr 1i of each color filter F i.

[0094] Each reflective layer is preferably continuously deposited on the first M 1 and second M 2 resin patterns by plasma-enhanced chemical vapor deposition (PECVD), physical vapor deposition (PVD), pulsed laser ablation deposition (PLD) or atomic thin film deposition (ALD) for example.

[0095] The fourth step 204 of the method 200a according to the second aspect of the invention, illustrated in [ Fig. 9 ], consists of depositing, in a conforming manner, a first layer 303 of dielectric material on the overall area of ​​patterns Z.

[0096] The first layer 303 of dielectric material is preferably deposited continuously according to the conformal deposition methods cited above and completely covers, indirectly, the first M 1 and second M 2 resin patterns.

[0097] The first layer 303 of dielectric material has a thickness equal to the thickness h 1 of the layer of dielectric material C FP1 of the Fabry-Pérot cavity of the first filter F 1 .

[0098] The fifth step 205 of the method 200a according to the second aspect of the invention, illustrated in [ Fig. 10 ], consists of depositing a layer of resin such as a photosensitive resin 304 on the overall area of ​​patterns Z. The photosensitive resin is preferably a photosensitive polymer.

[0099] The method 200a according to the second aspect of the invention may comprise a sixth step 206, illustrated in [ Fig. 11 ], consisting of using mask 305 to expose the portion of the photosensitive resin layer 304 covering the second pattern area Z 2 so that the portion of the exposed resin layer can then be selectively etched.

[0100] The seventh step 207 of the method 200a according to the second aspect of the invention, illustrated in [ Fig. 12 ], consists of removing the part of the photosensitive resin layer 304 covering the second pattern zone Z 2.

[0101] The eighth step 208 of the method 200a according to the second aspect of the invention, illustrated in [ Fig. 13 ], consists of depositing a second layer 306 of dielectric material on the second zone Z 2 of patterns, to form with the part of the first layer 303 of the second zone Z 2 of patterns, the layer of dielectric material C FP2 of Fabry-Pérot cavity of the second color filter F 2 .

[0102] Thus, the total thickness of the second layer 306 of dielectric material and of the first layer 303 of dielectric material of the second zone Z 2 of patterns is equal to the thickness h 2 of the layer of dielectric material C FP2 of the second filter F 2 .

[0103] The ninth step 209 of the method 200a according to the second aspect of the invention, illustrated in [ Fig. 14 ], consists of removing the layer of photosensitive resin not removed in the seventh step 207, so as to release on the surface the layer of dielectric material C FP1 of the Fabry-Pérot cavity of the first filter F 1 .

[0104] The tenth step 210 of the method 200a according to the second aspect of the invention, illustrated in [ Fig.15 ], consists of depositing a second reflective layer 307 on the overall area Z of patterns to respectively form the second reflective layer C FP2 of the first F 1 and second F 2 color filters.

[0105] A third aspect of the invention relates to a method 200b for manufacturing a multispectral filtering matrix 10 in which the thickness h 1 of the layer of dielectric material C FP1 of the first color filter F 1 is greater than the thickness h 2 of the layer of dielectric material C FP2 of the second filter F 2 .

[0106] The figure [ Fig.16 ] is a block diagram of the method 200b for manufacturing the multispectral filtering matrix 10 according to the third aspect of the invention and in particular the steps of producing the first F 1 and the second color filters F 2.

[0107] The method 200b according to the third aspect of the invention comprises first 201, second 202, third 203, fourth 204, fifth 205, sixth 206 and seventh 207 steps identical to the steps of the method 200a according to the second aspect of the invention.

[0108] The eighth 208b step of the method according to the third aspect of the invention, illustrated in [ Fig. 17 ], consists of removing a thickness of the first layer 303 of dielectric material from the second zone Z 2 to obtain the thickness h 2 of the layer of dielectric material C FP2 of the Fabry-Pérot cavity of the second filter F 2 .

[0109] The method 200b according to the third aspect of the invention then comprises the ninth 209 and tenth 210 steps identical to those of the method 200a according to the second aspect of the invention.

[0110] A fourth aspect of the invention relates to a method 200c for manufacturing the multispectral filtering matrix 10 in which the thickness h 1 of the layer of dielectric material C FP1 of the first color filter F 1 is less than the thickness h 2 of the layer of dielectric material C FP2 of the second filter F 2 .

[0111] The figure [ Fig.18 ] is a block diagram of a method of manufacturing the multispectral filtering matrix 10 according to a fourth aspect of the invention and in particular the steps of producing the first F 1 and the second F 2 color filters.

[0112] The method 200c according to the fourth aspect of the invention comprises the first 201, second 202 and third 203 steps identical to those illustrated for the method 200a according to the second aspect of the invention.

[0113] The fourth step 204c of the method according to the fourth aspect of the invention, illustrated in [ Fig. 19 ], consists of depositing a layer 308 of dielectric material on the overall pattern area, said layer 308 having a flat upper surface.

[0114] The fifth step 205c of the method 200c according to the fourth aspect of the invention, illustrated in [ Fig. 20 ], consists of depositing a second layer 309 of resin on the overall area Z of patterns.

[0115] The sixth step 206c of the method 200c according to the fourth aspect of the invention, illustrated in [ Fig. 21 ], consists of structuring, preferably in three dimensions, the second resin layer 309, to obtain a first M' 1 pattern in the first pattern zone Z 1 and a second M' 2 pattern in the second pattern zone Z 2. The resin structuring is carried out according to the same methods as those cited in the second step of the method 200a according to the second aspect of the invention.

[0116] Each resin pattern M' i of the second resin layer 309 has a curved upper surface.

[0117] The average heights of the two resin patterns M' 1 , M' 2 of the second resin layer 309, relative to the flat surface of the layer 308 of dielectric material, are different.

[0118] The height of the first pattern M' 1 of the second resin layer 309 is less than the height of the second pattern M' 2 of the second resin layer 309.

[0119] The seventh step 207c of the method 200c according to the fourth aspect of the invention, illustrated in [ Fig. 22 ], consists of transferring the first M' 1 and second M' 2 resin patterns from the second resin layer 309 into the dielectric material layer 308, to obtain the dielectric material layer C FP1 of the first filter F 1 in the first pattern area and the dielectric material layer C FP2 of the second filter F 2 in the second pattern area Z 2.

[0120] Pattern transfer is preferably achieved by etching, non-selectively and at a constant speed.

[0121] The method 200c according to the fourth aspect of the invention further comprises the tenth 210 step of the method 200a according to the second aspect of the invention.

Claims

1. A multispectral filtering matrix (10) for an electromagnetic wave, the matrix including at least a first (E1) and a second (E2) optoelectronic element, each optoelectronic element (Ei) comprising a colour filter (Fi) and a photoelectric transducer (Ti) facing said filter (Fi), each colour filter (Fi) forming a Fabry-Perot cavity including a first reflective layer (Cr1i), a second reflective layer (Cr2i) and a Fabry-Perot cavity layer of dielectric material (CFPi) between the first reflective layer (Cr1i) and the second reflective layer (Cr2i), the layer of dielectric material (CFPi) including : - a lower surface (Sinf_i), in contact with the first reflective layer (Cr1i); the lower surface (Sinf_i) being curved; - an upper surface (Ssup_i) in contact with the second reflective layer (Cr1i), the upper surface (Ssup_i) being curved; the thicknesses of the two layers of dielectric material of the two colour filters being different.

2. The multispectral filtering matrix (10) according to the preceding claim, characterised in that, for each colour filter (Fi): - The first reflective layer (Cr1i) has a curved lower surface (S1inf_i), and a curved upper surface (S1sup_i), having the same radius of curvature, the upper surface of the first reflective layer (S1sup_i) being in contact with the lower surface (Sinf_i) of the layer of dielectric material (CFPi); - The second reflective layer (Cr2i) has a curved lower surface (S2inf_i) and a curved upper surface (S2sup_i) with the same radius of curvature, the lower surface (S2inf_i) of the second reflective layer being in contact with the upper surface (Ssup_i) of the layer of dielectric material (CFPi).

3. The multispectral filtering matrix (10) according to any of the preceding claims, characterised in that the radii of curvature of the lower surface (Sinf_i) and of the upper surface (Ssup_i) of the layer of dielectric material (CFPi) of each colour filter (Fi) are strictly greater than 300 nm.

4. The matrix (10) according to any of the preceding claims, characterised in that, for each colour filter (Fi), the curvatures of the lower surface (Sinf_i) and of the upper surface (Ssup_i) of the layer of dielectric material (CFPi) of each colour filter (Fi) are both convex or both concave.

5. The matrix (10) according to any of the preceding claims, characterised in that the curved profile of the lower surface (Ssup_i) of the layer of dielectric material (CFPi) of at least one colour filter (Fi) of the first (F1) and second (F2) colour filters is defined by the following equation: y = R y ∗ 1 − x f ∗ Sx m 1 n + h Cri1 and in that the curved profile of the upper surface (Sinf_i) of said layer is defined by the following equation: y = R y ∗ 1 − x f ∗ Sx m 1 n + hi + h Cri1 In a (O,X,Y,Z) reference frame in space, with O being the origin of the lower surface of the first reflective layer (S1inf_i) of the filter Fi; With: - hi the thickness of the layer of dielectric material (CFPi) of said filter (Fi), - hCri1 the thickness, along the axis Y, of the first reflective layer (Cr1i) of the filter (Fi), - Ry is the radius of curvature of the lower surface (Sinf_i) and the upper surface (Ssup_i) of the layer of dielectric material (CFPi) along the axis Y for x=0, - m and n respectively a natural number and a non-zero natural number, - with f*Sx the radius of curvature of the lower surface (Sinf_i) and of the upper surface (Ssup_i) along the axis X, Sx being the size, along the axis X, of the photoelectric transducer (Ti) facing the filter (Fi) and f is a constant.

6. The matrix (10) according to any of claims 1 to 4, characterised in that the curved profile of the lower surface (Ssup_i) of the layer of dielectric material (CFPi) of at least one colour filter (Fi) from among the first (F1) and second (F2) colour filters is defined by the following equation: z = R z ∗ 1 − x f ∗ Sx m − y f ∗ Sy n 1 k + h Cri1 and in that the curved profile of the upper surface (Sinf_i) of said layer is defined by the following equation: z = R z ∗ 1 − x f ∗ Sx m − y f ∗ Sy n 1 k + hi + h Cri1 In a (O,X,Y,Z) reference frame in space, with O being the origin of the lower surface of the first reflective layer (S1inf_i) of the filter Fi; with: - hi the thickness of the layer of dielectric material (CFPi) of said filter (Fi), - hCri1 the thickness, along the axis Y, of the first reflective layer (Cr1i) of the filter (Fi), - Rz is the radius of curvature of the lower surface (Sinf_i) and of the upper surface (Ssup_i) of the layer of dielectric material (CFPi) along the axis Z, - m and n respectively a natural number and a non-zero natural number, - with f*Sx the radius of curvature of the lower surface (Sinf_i) and the upper surface (Ssup_i) of the layer of dielectric material (CFPi) along the axis X, Sx being the size, along the axis X, of the photoelectric transducer (Ti) facing the filter (Fi) and f is a constant, - with f*Sy the radius of curvature of the lower surface (Sinf_i) and the upper surface (Ssup_i) of the layer of dielectric material (CFPi) along the axis Y, Sy being the size, along the axis Y, of the photoelectric transducer (Ti) facing the filter (Fi).

7. The matrix (10) according to one of the preceding claims, characterised in that, for each colour filter (Fi), the curvatures of the lower surface (Sinf_i) and of the upper surface (Ssup_i) of the layer of dielectric material (CFPi) are both convex, the curvature of the upper surface (Ssup_i) and the lower surface (Sinf_i) of the layer of dielectric material (CFPi) being chosen so as to focus the electromagnetic wave on the transducer (Ti) facing said filter (Fi).

8. A method (200a) for manufacturing a multispectral filtering matrix (10) according to any of the preceding claims, characterised in that the thickness (h1) of the layer of dielectric material (CFP1) of the first colour filter (F1) is less than the thickness (h2) of the layer of dielectric material (CFP2) of the second colour filter (F2), and making the first (F1) and second (F2) colour filters includes the following steps of: - Depositing (201) a resin layer (301) onto a carrier substrate (300); - Structuring (202) the resin layer (301) to obtain a first resin pattern (M1) defining a first pattern zone (Z1) and a second resin pattern (M2) defining a second pattern zone (Z2), each resin pattern (Mi) having a curved upper surface, the first and second pattern zones defining an overall pattern zone (Z); - Conformally depositing (203) a first reflective layer (302) onto the overall pattern zone, forming the first reflective layer (Cr1i, Cr2i) of the first (F1) and second (F2) colour filters; - Conformally depositing (204) a first layer (303) of dielectric material onto the overall pattern zone, the first layer of dielectric material (303) having a thickness equal to the thickness (h1) of the Fabry-Perot cavity layer of dielectric material (CFP1) of the first filter (F1); - Depositing (205) a photosensitive resin layer (304) onto the overall pattern zone; - Removing (207), by photolithography, the part of the photosensitive resin layer (304) covering the second pattern zone (Z2), - Conformally depositing (208) a second layer (306) of dielectric material onto the second pattern zone (Z2), the total thickness of the second layer (306) of dielectric material and of the first layer (303) of dielectric material of the second pattern zone (Z2) being equal to the thickness (h2) of the layer of dielectric material (CFP2) of the second colour filter (F2); - Removing (209) the photosensitive resin layer, so as to release the first layer of dielectric material of the first pattern zone forming the Fabry-Perot cavity layer of dielectric material (CFP1) of the first colour filter (F1) at the surface; - Conformally depositing (210) a second reflective layer (307) onto the overall pattern zone (Z), forming the reflective layers (Cr1i, Cr2i) of the first (F1) and second (F2) colour filters.

9. A method (200b) for manufacturing a multispectral filtering matrix (10) according to any one of claims 1 to 7, characterised in that the thickness (h1) of the layer of dielectric material (CFP1) of the first colour filter (F1) is greater than the thickness (h2) of the layer of dielectric material (CFP2) of the second colour filter (F2), and making the first (F1) and second (F2) colour filters includes the following steps of: - Depositing (201) a resin layer (301) onto a carrier substrate (300); - Structuring (202) the resin layer (301) to obtain a first resin pattern (M1) defining a first pattern zone (Z1) and a second resin pattern (M2) defining a second pattern zone (Z2), each resin pattern (Mi) having a curved upper surface, the first and second pattern zones defining an overall pattern zone (Z); - Conformally depositing (203) a first reflective layer (302) onto the overall pattern zone, forming the first reflective layer (Cr1i, Cr2i) of the first (F1) and second (F2) colour filters; - Conformally depositing (204) a first layer (303) of dielectric material onto the overall pattern zone, the first layer of dielectric material (303) having a thickness equal to the thickness (h1) of the Fabry-Perot cavity layer of dielectric material (CFP1) of the first filter (F1); - Depositing (205) a photosensitive resin layer (304) onto the overall pattern zone (Z); - Removing (207), by photolithography, the part of the photosensitive resin layer (304) covering the second pattern zone (Z2), - Removing (208b) a thickness of the layer of dielectric material of the second pattern zone (Z2) to obtain the thickness (h2) of the layer of dielectric material (CFP1) of the second filter (F2); - Removing (209) the photosensitive resin layer (304), so as to release the first layer of dielectric material of the first pattern zone (Z1) forming the Fabry-Perot cavity layer of dielectric material (CFP1) of the first colour filter (F1) at the surface; - Conformally depositing (210) a second reflective layer (307) onto the overall pattern zone forming the first reflective layer (Cr1i, Cr2i) of the first (F1) and second (F2) colour filters.

10. A method (200c) for manufacturing a multispectral filtering matrix (10) according to any one of claims 1 to 7, characterised in that the thickness (h1) of the layer of dielectric material (CFP1) of the first colour filter (F1) is less than the thickness (h2) of the layer of dielectric material (CFP2) of the second colour filter (F2), and making the first and second colour filters includes the following steps of: - Depositing (201) a resin layer (301) onto a carrier substrate (300); - Structuring (202) the resin layer (301), to obtain a first resin pattern (M1) defining a first pattern zone and a second resin pattern (M2) defining a second pattern zone, each resin pattern (Mi) having a curved upper surface, the first and second pattern zones defining an overall pattern zone; - Conformally depositing (203) a first reflective layer (302) onto the overall pattern zone, forming the first reflective layer (Cr1i, Cr2i) of the first (F1) and second (F2) colour filters; - Depositing (204c) a layer of dielectric material (308) onto the overall pattern zone, said layer of dielectric material having a planar upper surface; - Depositing (205c) a second resin layer (309) onto the overall pattern zone; - Structuring (206c) the second resin layer (309), to obtain a first (M'1) and second (M'2) resin pattern of the second resin layer (309) in the first and second pattern zone, respectively, each resin pattern (M'i) of the second resin layer (309) having a curved upper surface; - Transferring the first (M'1) and second (M'2) resin patterns of the second resin layer (309) into the layer of dielectric material (308) to obtain the layer of dielectric material (CFP1) of the first filter (F1) in the first pattern zone and the layer of dielectric material (CFP2) of the second filter (F2) in the second pattern zone (Z2); - Conformally depositing (210) a second reflective layer (302) onto the overall pattern zone, forming the first reflective layer (Cr1i, Cr2i) of the first (F1) and second (F2) colour filters.

11. The method of any one of claims 8 to 10, characterised in that the step of structuring (202) the resin layer is performed by Grayscale lithography.