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    • 专利摘要:
    The invention relates to a method for manufacturing a substrate (40) for surface-enhanced Raman diffusion, the method comprising the following steps: - production of a carrier structure (2) at least one microstructured pattern (5) comprising a vertex (8) and sidewalls (7); - Deposition of a multilayer (10) on the carrier structure (2), the multilayer (10) comprising at least two metal layers (13) and a spacer layer (14) disposed between the two metal layers (13), each layer interlayer (14) being made of a selectively etchable material with respect to the metal layers (13); etching a portion of the multilayer deposited on the top of the microstructured pattern to expose ends of each layer of the multilayer ; - Selective etching of the ends (18) of the intermediate layers (14) so as to form cavities (20) between the ends (19) of two successive metal layers (13).
    公开号:FR3031394A1
    申请号:FR1550009
    申请日:2015-01-05
    公开日:2016-07-08
    发明作者:Stefan Landis；Vincent Reboud
    申请人:Commissariat a lEnergie Atomique CEA；Commissariat a lEnergie Atomique et aux Energies Alternatives CEA；
    IPC主号:
    专利说明:

    [0001] FIELD OF THE INVENTION The field of the invention is that of processes for manufacturing substrates that can be used to implement surface enhanced Raman scattering (SERS) methods. The invention also relates to a surface enhanced Raman diffusion substrate. STATE OF THE PRIOR ART Exalted Raman Surface Diffusion (SERS) is one of the most promising detection techniques for identifying and characterizing molecules. This technique involves depositing the molecules of interest on a substrate having a rough metal surface. The metal surface on which the molecules of interest are fixed is then illuminated by a monochromatic light. The molecules then emit a Raman signal characteristic of these molecules, which makes them detectable and identifiable. However, the Raman signal emitted by the molecules has a much lower intensity than the intensity of the monochromatic light with which the molecules have been illuminated. To remedy this problem, it has been found that the roughness of the metal surface of the substrate carrying the molecules of interest makes it possible to exalt the Raman signal emitted by the molecules of interest by the excitation of localized plasmons of the metal. (electromagnetic exaltation) and charge transfer between the metal and the adsorbed molecule (chemical effect). This exaltation thus makes it possible to specifically detect adsorbed samples with extremely low concentrations and / or very short times. 303 13 94 2 This exaltation can be done through "hot spots" ("hot spots" in English). These hot spots are areas of the substrate at which the electromagnetic field is located and intense. For this, the hot spots generally have dimensions smaller than the wavelength of the monochromatic light. The prior art thus knows methods for producing hot spots on the surface of a substrate. These hot spots can be formed by cavities or peak effects. Thus, the document Appl. Phys. Lett. 97, 063106 2010, Nanoletters, 9, 4505, 2009 describes hot spots formed by spikes. The document Nano Lett. 11, 2538, 2011; J. Vac. Sci. Technol. B 27, 2640 (2009) describes hot spots formed by cavities. However, prior art hot spot forming methods employ structuring technologies that can achieve very high spatial resolutions and are therefore complex and expensive. In addition, they generally do not produce substrates having a high density of hot spots, so that the increase in light intensity emitted by the molecules of interest is limited. DESCRIPTION OF THE INVENTION The purpose of the invention is to overcome the drawbacks of the state of the art by proposing a method for manufacturing a surface-enhanced Raman diffusion substrate which is not aggressive and which is simple to implement. and which allows a constant increase in the light intensity emitted by the molecules on the entire substrate. Another object of the invention is to propose a method for manufacturing a surface-enhanced Raman diffusion substrate that is reproducible and reliable, which allows a strong increase in the luminous intensity emitted by the molecules of interest and which presents a high density of hot spots. Another object of the invention is to propose a method for manufacturing a surface-enhanced Raman-diffusion substrate which makes it possible to simultaneously produce a large number of identical substrates. To do this, a first aspect of the invention relates to a method for manufacturing a surface-enhanced Raman diffusion substrate, the method comprising the following steps: (a) producing a carrier structure on an upper surface of a carrier, the carrier structure having at least one microstructured pattern, the microstructured pattern having a top and side walls, the side walls extending in a secant direction to the direction of the upper surface; - (b) depositing a multilayer on the carrier structure, the multilayer having at least two metal layers and an intermediate layer disposed between the two metal layers, each intermediate layer being made of a material that can be etched selectively with respect to the metal layers ; (c) etching a portion of the multilayer deposited on the top of the microstructured pattern so as to expose ends of each layer of the multilayer; - (d) selectively etching the ends of the intermediate layers so as to form cavities between the ends of two successive metal layers. Thus, the method firstly produces a carrier structure whose dimensions, typically between 50 nm and 100 μm, do not directly make it possible to obtain the function of exaltation of the electromagnetic field, but which is easy to achieve by the known techniques. On this supporting structure, other structures are produced with much smaller characteristic dimensions which this time make it possible to exalt the electromagnetic field. These second structures are made by successive deposition of metal layers and interlayers so as to form a multilayer which matches the shape of the carrier structure. The clipping of the portion of the multilayer deposited on the upper part of each pattern of the carrier structure is then locally carried out. The alternation of the layers of the multilayer is then exposed to the air so that one has access to each of the layers of the multilayer. The intermediate layers of the multilayer can then be selectively and partially etched so as to form cavities between the ends of two successive metal layers. The method thus makes it possible to obtain micrometric patterns surrounded by metal pins of nanometric dimensions, separated between two by cavities of nanometric dimensions. The method is particularly advantageous since it makes it possible to easily produce metal pins of nanometric dimensions separated by cavities of nanometric dimensions without resorting to aggressive etching processes. In addition, the width of the pins and cavities is very well controlled since it is determined by the thickness of the deposited layers. This thickness is easy to control.
    [0002] The method thus makes it possible to easily obtain a substrate enabling the electromagnetic field to be reinforced. The intensity of the electromagnetic field obtained thanks to the substrate thus formed can thus be between 10 times and several thousand times greater than that obtained with the substrates of the prior art.
    [0003] The method according to the invention may also have one or more of the following characteristics taken individually or in any technically possible combination. Advantageously, the intermediate layer is a dielectric layer, because the dielectric layers do not absorb or little plasmon generated on the surface of the metal. The substrate thus produced will thus allow better surface exaltation. In addition, the dielectric layers can be easily etched selectively with respect to the metal layers, which is advantageous in step (d) of the method.
    [0004] Advantageously, each microstructured pattern has a height of between 50 nm and 100 μm, which makes it easy to manufacture the microstructured pattern using known methods.
    [0005] Advantageously, each metal layer of the multilayer has a thickness of between 1 angstrom and 50 nm. The thickness of the metal layers of the multilayer will condition the width of the metal pins on the surface of the substrate. Advantageously, each interlayer of the multilayer has a thickness of between 1 angstrom and 20 nm. The thickness of the interlayers will condition the width of the cavities between the metal pins.
    [0006] Advantageously, the multilayer has a thickness less than the height of the microstructured pattern, which makes it possible to update all the layers during the step (c) of clipping.
    [0007] Advantageously, the layers of the multilayer are deposited according to a conformal deposition technique, which makes it possible to have a multilayer of constant thickness over the entire surface of each microstructured pattern. The step (c) of etching is then facilitated.
    [0008] Advantageously, the side walls of the microstructured pattern extend in a direction which forms an angle strictly less than 90 ° with a direction normal to the upper surface of the support, which makes it easier to produce conforming deposits on the pattern.
    [0009] According to various embodiments, the etching carried out during the step may be performed by chemical mechanical polishing or by dry etching. A second aspect of the invention relates to a surface-enhanced Raman scattering substrate comprising: a support having a top surface; a supporting structure disposed on the upper surface of the support, the supporting structure comprising at least one microstructured pattern, the microstructured pattern comprising a crown and side walls, the lateral walls extending in a direction intersecting with the direction of the upper surface; ; a multilayer disposed on the side walls of the microstructured pattern, the multilayer comprising at least two metal layers and an interlayer disposed between the two metal layers, the interlayer being made of a material that can be etched selectively with respect to the metal layers, each metal layer having one end, the intermediate layer having one end recessed from the end of the surrounding metal layers so that the ends of two successive metal layers form metal pins separated by a cavity. Such a substrate has multiple hot spots at the cavities situated between the ends of the metal layers, which makes it possible to strongly exalt the Raman signal emitted by the molecules of interest deposited on this substrate by the excitation of localized plasmons of the metal (exaltation by electromagnetic effect). Such a substrate therefore makes it possible to increase the luminous intensity emitted by molecules of interest which are deposited on its surface so that it allows a faster detection of these molecules of interest.
    [0010] The substrate according to the second aspect of the invention may have one or more of the following features taken individually or in any technically possible combination.
    [0011] Advantageously, the side wall of the microstructured pattern comprises faces separated by edges, which makes it possible to create a strengthening of the electromagnetic field by a peak effect and therefore to increase the exaltation of the Raman signal emitted by the molecules.
    [0012] Advantageously, the carrier structure comprises several microstructured patterns forming a periodic grating, which makes it possible to increase the density of hot spots on the surface of the substrate, and to homogenize their distribution on the substrate. The exaltation of the Raman signal generated by the substrate is thus greater and more homogeneous. Advantageously, the metal layers have different thicknesses from each other, which makes it possible to obtain a progressive index gradient so that the substrate will then have resonances at several incident wavelengths. Advantageously, the multilayer comprises several intermediate layers, the intermediate layers having different thicknesses from each other, which makes it possible to obtain a progressive index gradient so that the substrate will then have resonances at several incident wavelengths. . Advantageously, each microstructured pattern has a height of between 50 nm and 100 μm. Advantageously, each metal layer of the multilayer has a thickness of between 1 angstrium and 50 nm, preferably between 10 nm and 50 nm. Advantageously, each interlayer of the multilayer has a thickness of between 1 angstrium and 20 nm, preferably between 10 nm and 20 nm. Advantageously, each cavity has a depth of between 1 angstrium and 200 nm, and preferably between 10 nm and 100 nm. BRIEF DESCRIPTION OF THE FIGURES Other characteristics and advantages of the invention will emerge on reading the detailed description which follows, with reference to the appended figures, which represent: FIGS. 1a to 1e, the steps of a method according to an embodiment of the invention; FIGS. 2c to 2e, steps of a method according to another embodiment of the invention; FIGS. 3a and 3b, microstructured patterns that can be used in a method according to one embodiment of the invention; 303 13 94 8 - Figures 4d and 4e, alternative steps to the steps shown in Figures 1d and; - Figure 5a, a schematic representation of a substrate according to one embodiment of the invention; Figure 5b is an enlarged view of part E of the substrate of Figure 5a; FIG. 6, a curve representing the reflectivity of a substrate according to one embodiment of the invention for an incident wavelength of 785 nm, as a function of the height H1 of the metal pins of this substrate, when these pins are metal have a width W1 = 40 nm, and the air gaps 10 between these pins having a depth P0 = 40 nm and a width W0 = 7.3 nm; FIG. 7, a diagram representing the evolution of the reflectivity of a substrate according to one embodiment of the invention for an incident wavelength of 785 nm, as a function of the width W 1 of the metal pins of this FIG. substrate and the width WO of the cavities between these metal pins, when these metal pins have a height H1 = 100 nm and that the cavities have a depth P0 = 40 nm; FIG. 8, a diagram representing the evolution of the reflectivity of a substrate according to one embodiment of the invention for an incident wavelength of 785 nm, as a function of the height H 1 of the metal pins of this substrate and the height H1-P0 of the cavities between these metal pins, when these metal pins have a width W1 = 40 nm and the cavities have a width W2 = 7.3 nm; Figures 9a and 9b are top views of substrates according to a first and a second embodiment of the invention; FIGS. 10a and 10b, top views of substrates according to two other embodiments of the invention; - Figure 11, a top view of a substrate according to another embodiment of the invention; FIG. 12 is a sectional view of a microstructured pattern of a substrate according to one embodiment of the invention; FIG. 13, the resulting reflectivity curve of an incident wave at 785 nm on the substrate of FIG. 12, as a function of the inclination angle α of the side walls of the microstructured patterns of this substrate in cases where the microstructured pattern is covered only by a gold metal layer (curve A) and in the case where the microstructured pattern is covered with a multilayer comprising two gold metal layers of 40 nm in thickness and two interlayers in oxide of silicon of 20 nm thickness, the cavities between the metal pins having a depth of 100 nm PO; FIGS. 14a to 14f, views of a substrate according to one embodiment of the invention during a method of producing this substrate; FIGS. 15a to 15d, views of a substrate according to another embodiment during a method of producing this substrate; FIGS. 16a and 16b, views of a substrate during steps (102) and (103) of a method according to one embodiment of the invention; - Figures 16c and 16d, views of another substrate during steps (102) and (103) of a method according to one embodiment of the invention.
    [0013] DETAILED DESCRIPTION OF AT LEAST ONE EMBODIMENT FIGS. 1a to 1e show the various steps of a method according to one embodiment of the invention.
    [0014] This method comprises a first step 101 for producing a carrier structure 2 on an upper surface 4 of a support 3. According to various embodiments, the support 3 may be made of silicon, metal or glass.
    [0015] The carrier structure 2 comprises at least one microstructured pattern 5, and preferably several microstructured patterns 5. Each microstructured pattern preferably has dimensions of between 50 nm and 100 μm. Each microstructured pattern 5 has an upper portion 8, also called "top" or "ridge" and a side wall 7, also called "sidewall". The side wall 7 of the microstructured units 5 preferably extends in a secant direction to the upper surface 4 of the support 3. The microstructured patterns 5 may have different shapes.
    [0016] Thus, according to an embodiment shown in FIG. 1b, each microstructured pattern 5 may have a parallelepiped shape. In this case, each microstructured pattern 5 comprises: an upper wall 8 extending in a direction substantially parallel to the upper surface 4 of the support; - A side wall 7 extending in a direction substantially perpendicular to the upper surface 4 of the support 3. The side wall 7 has four faces 11 separated from each other by edges 12.
    [0017] However, the microstructured patterns could also have other shapes. Thus, with reference to FIG. 3a, each microstructured pattern 5a could comprise several parts, having different heights from each other. This gives a microstructured pattern that has a staircase shape. Referring to Figure 3b, each microstructured pattern 5b could have a dome shape, or a shape of triangle, pyramid, or more complex shapes. According to various embodiments, the microstructured patterns of the carrier structure may all have the same shape, as shown in Fig. 1b, or they may have different shapes, as shown in Figs. 3a and 3b.
    [0018] The carrier structure 2 is preferably made of polymers. Indeed, the polymers have the advantage of not or very little absorb the plasmonic resonance of metals, so they will not reduce the exaltation of the local electromagnetic field. According to different embodiments, the carrier structure may be made of acrylic-based polymers, polyhydroxystyrene (PHS) based polymers or methyl methacrylate (MMA) based polymers. Acrylic bases make it possible to have a better adhesion of the metal layers to their surfaces and a better mechanical resistance for the subsequent steps. In addition, the cited polymers have the advantage of supporting the following steps of the process. The supporting structure can be achieved by different techniques depending on the material that constitutes it. Thus, when the carrier structure is made of polymer, the step of producing the carrier structure may comprise the following sub-steps: - formation of a polymer layer 9, for example by spin coating (or spin-coating); coating "in English); - Formation of microstructured patterns 5, for example by lithography nanoimpression (or "nanoimprint lithography" in English), photolithography, electronic lithography, lithography in the ultraviolet etrème, interferential lithography or by laser writing.
    [0019] With reference to FIG. 1c, the method then comprises a step 102 for deposition of a multilayer 10 on the supporting structure 2. The multilayer 10 matches the shape of the carrier structure so that it is deposited on the upper part 8 of the The multilayer 10 thus comprises portions 15 which extend in a secant direction to the upper surface 4 of the support and other parts which extend in a direction substantially parallel to the surface. upper 4 of the substrate. The multilayer 10 comprises at least two metal layers 13, two successive metal layers 13 being separated by an intermediate layer 14. In fact, the metal layers have a so-called "plasmonic" response when they are subjected to a specific electromagnetic radiation. The metal layers are preferably made of one of the following materials: gold, silver, copper, aluminum. According to different embodiments, the metal layers can all be made of the same material, or they can be made at least two by two with the same material. We can then have different pairs of metal layers in the multilayer which would make it possible to operate the device at different wavelengths. Furthermore, the metal layers can all have the same thickness or they can have different thicknesses. which makes it possible to obtain a gradual index gradient. Indeed, by adjusting the thicknesses of each layer, the equivalent optical index of the multilayer can be varied between the optical index of the metal layers and that of the intermediate layers, as long as the sum of the thickness of a metal layer and the thickness of an interlayer remains lower than the incident wavelength. The substrate thus formed will then have resonances at several incident wavelengths. The intermediate layers 14 are made of a material that can be etched selectively with respect to the metal layers. According to different embodiments, the intermediate layers may all be made of the same material, or they may be made of different materials from each other. In the latter case, all the intermediate layers are preferably made of a material which can be etched selectively with respect to the metal layers, either at the same time or one after the other with different processes. Then we can consider having different cavity depths and thus adjust the operation and / or resonance of the substrate thus obtained. According to a preferred embodiment, the intermediate layers consist of a dielectric material. Indeed, the dielectric materials do not absorb or little plasmon generated on the surface of the metal layers. For example, silicon oxide, alumina, hafnium oxide, silicon nitride, titanium oxide, etc. can be chosen as the dielectric material. Moreover, the intermediate layers can all have the same thickness or they may have different thicknesses, which allows to obtain a gradual index gradient. The substrate thus formed will then have resonances at several incident wavelengths. One could also consider making the intermediate layers in metal materials. However, in this case, the depth of the cavities dug in the intermediate layers will have to be greater than in the previous embodiment, so that the intermediate layer does not absorb the plasmon generated on the surface of the metal layers.
    [0020] The layers of the multilayer are preferably deposited by a conformal deposition method so that the thickness of the multilayer is substantially the same over the entire surface of the microstructured patterns. This can be done by depositing the layers of the multilayer by physical vapor deposition, using an inclined bombardment beam, rotating the sample. During the deposition step of the multilayer, the first layer deposited on the microstructured patterns, which will be called "inner layer" 39, may be a metal layer or it may be a spacer layer. Similarly, the last deposited layer, which will be called "outer layer" 31, may be a metal layer or it may be a spacer layer. The fact that the outer layer 31 has an intermediate layer makes it possible to protect the active metal layer from subsequent processes and / or the risks of chemical reaction with the atmosphere or of mechanical scratch-type damage during handling of the substrate. With reference to FIG. 1d, the method then comprises a step 103 of etching a part of the multilayer deposited on the upper part 8 of each microstructured pattern 5. This step is called a "clipping step". Indeed, it comprises a step of etching the portion of the multilayer deposited on the crest of each of the microstructured patterns. This step may also include a step of etching a portion of the peak of each microstructured pattern. In the embodiment of FIG. 1d, the part 16 of the multilayers deposited on the upper surface 8 of the microstructured patterns is etched. For this, one can for example engrave the regions of the multilayer which are parallel to the upper surface 4 of the support, while etching slower regions of the multilayer which are inclined relative to the upper surface 4 of the support. It can be used for this purpose a spacer etching technique (or "spacer patterning" in English). This etching step 103 can also be performed by chemical mechanical polishing (or CMP for "Chemical Mechanical Planarization"). At the end of this step, columns 17 extending in a direction intersecting with the upper surface 4 of the support 3 are obtained, each column 17 comprising alternating metal layers and intermediate layers. The upper ends 18 of each metal layer and the upper ends 19 of each interlayer are exposed to air and are therefore accessible for the next steps of the process.
    [0021] Alternatively, with reference to FIG. 4d, this step 103 for etching the portions of the multilayer disposed on the upper portion 8 of the microstructured patterns may also include a step of etching the horizontal portions 24 of the multilayer disposed on the surface 4 of the support. Thus, not only is access to the upper ends 18 and 19 of the intermediate layers and metal layers, but also to their lower ends 22 and 23, which will be useful for performing a double etching step, as will be seen later. with reference to Figure 4e.
    [0022] Referring to Figure 1 e, the method then comprises a step 104 of selective etching of a portion of the intermediate layers 14 so as to form air cavities 20 between the ends 19 of two successive metal layers 13. More specifically, during this step, the ends 18 of the intermediate layers 14 are etched selectively with respect to the ends 19 of the metal layers 13 so that, at the end of this step, the ends 19 of the metal layers are separated by This etching step is partial so as to retain part of the intermediate layers between the metal layers, which makes it possible to hold the metal layers in place without collapsing on top of one another and also to have air cavities of controlled depth. The technique used to selectively etch the interlayers depends on the material chosen for the interlayers and for the metal layers. According to various embodiments, the technique chosen may be a dry or wet etching technique.
    [0023] Alternatively, with reference to FIG. 4e, the selective etching step 104 may be a double etching step during which the upper ends 18 of the intermediate layers, but also the lower ends 22 of the intermediate layers, are selectively etched. This results in twice as many metal pins and twice as many cavities: in fact, as before, vertical metal pins 21 separated by vertical air cavities and horizontal metal pins 26 separated by air cavities are obtained. 25 horizontal. As before, this double etching step can be performed by dry or wet etching. The method makes it possible to manufacture a substrate 40 that can be used in the context of surface enhanced Raman detection. Indeed, microstructured patterns 5 are obtained on the surface of the substrate 5 surrounded by metal pins 21, 26 of nanometric dimensions, separated by air cavities of equally nanometric dimensions. Each air cavity obtained at the end of the process preferably has a width of between 1 angstrom and 20 nm and a depth of between 10 nm and 100 nm. Each metal pin obtained at the end of the process preferably has a width between 10 nm and 50 nm. The method may then comprise a step of depositing molecules of interest on the surface of the substrate thus obtained. The molecules of interest are then deposited on the surface of the metal pins and in the air cavities. The materials chosen to make the carrier structure may be chosen according to their surface energy so as to control the deposition of the molecules which will then be deposited on the substrate. It is thus possible to promote the deposition of the molecules at certain places of the substrate rather than at other places. The invention is not limited to the embodiment described above. Thus, as represented in FIGS. 2c to 2e, the method described with reference to FIGS. 1a to 1a could also comprise, following the step 102 of deposition of the multilayer 10, an additional step 102bis of deposition of a dielectric material. in the spaces 28 formed between the microstructured patterns 5 covered by the multilayer 10. This dielectric material 27 makes it possible to fill the empty space between the microstructured patterns, which makes the step of clipping by chemical mechanical polishing easier and more controllable. . Furthermore, since this void space is filled, the residues formed during the clipping step will not fit in the void spaces and may subsequently be easily removed by surface cleaning processes. Otherwise, the removal of these residues may be impossible or very complicated and they may interfere with the proper functioning of the substrate. The dielectric material 27 deposited in the spaces 28 may be, for example, silicon oxide or silicon nitride. The subsequent steps 103, 104 of the process are identical to those described above. The method according to the invention is particularly advantageous since it makes it possible to obtain metal pins separated by cavities of precisely controllable dimensions. Indeed, the width w1 metal pins 21 obtained is controlled by controlling the thickness of the deposited metal layers 13. Likewise, the width w 0 of the air cavities 20 is controlled by controlling the thickness of the deposited intermediate layers 14. The width of the pins and cavities and therefore easily and precisely controllable since the thickness of the deposited layers is also. Moreover, the depth PO of the air cavities is controllable by controlling the etching of the end of the intermediate layers 20 which is also easily controllable. In addition, when the intermediate layer is of dielectric material, the method does not use an aggressive etching step since said interlayer can be easily etched by dry etching or chemical etching.
    [0024] Sizing of metal pins and cavities: A method of dimensioning metal pins 21 and cavities 20 which separate them will now be described with reference to Figures 5a and 5b.
    [0025] The dimensions chosen for the pins and the cavities are essential to obtain a resonance of the electromagnetic field. These dimensions can be determined according to the method explained below.
    [0026] We first choose the incident wavelength of the monochromatic light that will be sent to the molecules to be detected. This incident wavelength may be chosen according to the molecules to be detected and / or according to the equipment available to the user. In this embodiment, for example, an incident wavelength of 785 nm is chosen.
    [0027] The materials which will constitute the metal layers and the intermediate layers of the multilayer 10 are then selected. These materials can be chosen according to the available deposition methods, and / or for reasons of chemical affinities with the molecules to be detected, and / or depending on the absorption properties of these materials vis-à-vis the incident wavelength. In this embodiment, it is chosen, for example, to produce gold metal layers and interlayers of SiO 2.
    [0028] The method then comprises a step of dimensioning the cavities 20 and metal pins 21 as a function of the incident wavelength chosen and the materials chosen for the multilayer. Indeed, it is possible to determine the dimensions of the pins and cavities so that the substrate has a resonance at the incident wavelength. For this, we determine the dimensions of the cavities 20 and pins 21 which minimize the reflectivity of the substrate and therefore maximize the strengthening of the electromagnetic field. One can for example use a method called "rigorous coupled wave analysis" or a method called "finite difference time domain" (or FDTD for "finite difference time domain"). "). These methods make it possible to simulate the reflectivity of a surface according to its geometry and its composition. Thus, FIG. 6 thus represents the evolution, as a function of the height H1 of the metal pins, of the reflectivity of a structure comprising an alternation of gold and silica layers for an incident wavelength of 785 nm, when the metal pins have a width W1 = 40 nm, the cavities have a width WO of 7.3 nm and a depth PO of 40 nm. It can be seen that the structure obtained may have a minimum of reflectivity for a height H1 equal to 99 nm or 187 nm, or 275 nm. One can therefore choose one of these heights for the metal pins H1. FIG. 7 represents another simulation performed by a rigorous coupled wave analysis (RCWA) method in which: the incident wavelength is fixed at 785 nm, the metal layers are made of gold, the interlayers consist of silica, the height H1 of the pins is set at 100 nm; the depth PO of the cavities is set at 40 nm. This time we look at the evolution of the reflectivity of the substrate as a function of the width W1 of the pins and the width WO of the cavities. It can be seen that the minimum reflectivity is reached when W1 and WO respect the following logarithmic law: W0 = 439 In (W1) -1909, with W1 and WO in microns. FIG. 8 represents another simulation carried out in which this time the widths W1 of the pins and those W0 of the cavities have been fixed and optimum heights are sought so as to have the minimum of reflectivity. Thus, this simulation has been carried out by a rigorous coupled wave analysis method (RCWA) in which: the incident wavelength is fixed at 785 nm, the metal layers consist of gold, - the interlayers consist of silica, - the width of the pins is set at 40 nm; the width of the cavities is fixed at 7.3 nm. These simulations thus make it possible to determine: the width W1 of the pins and therefore the thickness of the deposited metal layers; the width WO of the cavities and therefore the thickness of the deposited intermediate layers; the height H1 of the pins and therefore the height of the microstructured patterns at the end of step 103; the depth PO of the cavities and therefore the duration of etching of the end of the intermediate layers. Simulations can also be performed to determine the number of layers in the multilayer. These simulations are identical to those presented previously except that instead of taking into consideration only two metal layers and a spacer layer, a greater number of layers are taken into consideration so as to identify or not modes of coupling between the layers. 13 94 19 different repetitions of layers, which could or might not change the optimal geometries. The optimum thickness of the multilayer 10 is thus deduced therefrom. Choice of the carrier structure: The method then comprises a step of determining the carrier structure. The carrier structure preferably comprises several microstructured patterns on which the multilayer will be deposited. These microstructured patterns 5 can be isolated from each other as shown in Fig. 9a or they can form a grating as shown in Fig. 9b. Having microstructured patterns that form a network allows for a higher density of hot spots. The shape of each microstructured pattern 5 can also be determined by simulating the response that the substrate will have depending on the shape chosen. These simulations can also be performed with a rigorous coupled wave analysis method or a finite difference time domain method. Thus, with reference to FIGS. 10a and 10b, the shape of the side walls 7 of the microstructured units 5 is preferably chosen so that the side walls 7 comprise faces 11 separated by ridges 12. these ridges 12 are determined so that the supporting structure, once covered by the multilayer 10, generates a strengthening of the electromagnetic field by peak effect in areas 28 located near the edges 12. More specifically, the metal layer outer surface 31 of the multilayer which covers the microstructured patterns also forms edges 29 where the side wall 7 of the microstructured patterns form ridges 12. The edges 29 of the outer metal layer 31 thus generate spike effects and therefore zones 28 of strengthening of the electromagnetic field. Furthermore, with reference to FIG. 11, the spacing between two adjacent microstructured patterns can also be determined, by simulations with electromagnetic computation software, so as to optimize the coupling effects between adjacent microstructured patterns so as to increase the strengthening of the electromagnetic field. More precisely, by optimizing the distance between the edges 29 of the outer metal layer 31 surrounding two adjacent microstructured patterns, it is still possible to optimize the strengthening of the electromagnetic field by coupling the peak effect generated by the edges 29 and the confinement of the electromagnetic field. created in the space 30 formed between these two edges 29. This optimization of the distance dl between the edges 29 of the outer metal layer 31 is preferably performed using an electromagnetic calculation software. This distance d1 is preferably between 1 nm and 50 nm. Once the distance d1 is set, as the thickness of the multilayer 10 has been fixed previously during the step of dimensioning the cavities and the pins, the distance d2 is deduced between the edges 12 of two adjacent microstructured units 5.
    [0029] With reference to FIG. 12, the angle formed between the lateral walls 7 of each microstructured pattern 5 and a reference axis 32 perpendicular to the upper surface 4 of the support can also be optimized so as to minimize the reflectivity of the substrate thus formed. . Thus, FIG. 13 represents the evolution of the resulting reflectivity of an incident wave at 785 nm as a function of the angle α: of a pyramid-shaped microstructured pattern covered by a 160 nm gold layer (curve A); a microstructured pattern 5 in the form of a pyramid covered by a multilayer 10 comprising two stacks each comprising: a metal layer 13 made of 40 nm gold; an interlayer 14 made of silicon oxide 20 nm thick; a gold metal layer 40 nm thick. The cavities 20 formed between two successive metal pins 21 each having a depth PO of 100 nm (curve B). It can be seen in this figure that as the angle α increases, the reflectivity of the substrate decreases. Indeed, the microstructured patterns which have side walls inclined relative to the normal to the plane of the support have the advantage, that after selective etching of the end of the intermediate layers relative to the ends of the metal layers, the formed cavities present non-parallel openings to the surface 4 of the support 3 which allows optimum use of the substrate if the incident monochromatic wave is not emitted in a direction normal to the upper surface of the support. Indeed, the coupling between the incident wave and each cavity strongly depends on the angle between the opening of the cavity and the direction of the monochromatic wave. The reflectivity decreases as the angle of the pyramid increases. This phenomenon is all the more marked for lo structures with cavities. It is also possible to make a carrier structure projecting from the surface of the support as shown in FIGS. 14a to 14f, or it may be chosen to produce a carrier structure dug in the support or in a layer deposited on the support, such as shown in Figures 15a to 15d. In the case of a projecting supporting structure, hot spots are created by the gaps formed between the multilayers deposited on two adjacent microstructured patterns as shown in FIGS. 14e and 14f. The distance dp1 between these multilayers can be calculated so as to optimize the amplification of the electromagnetic field 20 in this zone. In the case of an excavated carrier structure, hot spots are created by peak effect at the upper end 36 of the ridges separating two adjacent microstructured patterns. The width dc of this edge 36 is also calculated so as to optimize the amplification of the electromagnetic field obtained. Sizing of the Carrier Structure: The dimensions of the carrier structure and the materials constituting it can be chosen so that the carrier structure forms a photonic crystal. This photonic crystal will enhance the optical coupling between the surface of the sample (with nano-gaps) and the incident laser. In practice, the photonic crystal can be dimensioned with calculation software and it allows the incident laser to arrive on the surface at almost normal incidence to be redirected in the plane of the substrate, which considerably increases the interaction length between the incident laser and our nangaps. Dimensioning of microstructured patterns: Once the shape of the carrier structure has been determined, the method comprises a step of determining the dimensions of the microstructured patterns of the carrier structure. The choice of these dimensions does not necessarily require a reinforcement calculation of the electromagnetic waves, outside the height of these patterns which is determined so as to have the desired height H1 for the metal pins. The other dimensions of the microstructured patterns are preferably determined as a function of: the technological capacity of the processes used to produce these patterns during step 101; the technological capacity of the etching processes used during step iO3; the technological capacity of the deposition processes for their ability to planarize an existing structure if the deposited thickness is too great. Indeed, if the microstructured patterns are too high; it is more complicated to have a consistent deposit over the entire height of each pattern because each deposition step, especially if it is performed by PVD or evaporation, is not perfectly consistent and there is a slight deformation of the shape the resulting structure after each deposit and therefore as and when filing there may be a planarization of the structure which is not sought.
    [0030] Furthermore, with reference to FIGS. 16c and 16d, the height of the microstructured units 5 is preferably chosen such that after deposition of the multilayer, the highest point 37 of the first layer deposited will be higher than the highest point. bottom 38 of the last deposited layer. Thus, after the clipping step, all layers of the multilayer will be updated. Otherwise, shown in Figures 16a and 16b, a portion of the layers of the multilayer will not be used for the manufacture of the cavities, since: - either they will be completely removed during the clipping step. This is the case if the clipping is done along line A; - Or they will not be used at all because completely covered by other layers. This is the case if the clipping is done along line B.
    [0031] Naturally, the invention is not limited to the embodiments described with reference to the figures and variants could be envisaged without departing from the scope of the invention.
    权利要求:
    Claims (17)
    [0001]
    REVENDICATIONS1. A method of manufacturing a substrate (40) for surface-enhanced Raman scattering, the method comprising the steps of: (a) providing a carrier structure (2) on an upper surface (4) of a carrier (3) , the carrier structure (2) having at least one microstructured pattern (5), the microstructured pattern (5) having a crown (8) and side walls (7), the side walls (7) ro extending in one direction secant in the direction of the upper surface (4); (b) deposition of a multilayer (10) on the carrier structure (2), the multilayer (10) having at least two metal layers (13) and an interlayer (14) disposed between the two metal layers (13) each interlayer (14) being made of a selectively etchable material with respect to the metal layers (13); (c) etching a portion of the multilayer (10) deposited on the top (8) of the microstructured pattern (5) so as to expose ends (18, 19) of each layer (13, 14) of the multilayer (10); (d) selectively etching the ends (18) of the spacer layers (14) to form cavities (20) between the ends (19) of two successive metal layers (13). 25
    [0002]
    2. Method according to the preceding claim, wherein the intermediate layer (14) is a dielectric layer.
    [0003]
    3. Method according to one of the preceding claims, wherein each microstructured pattern (5) has a height between 50 nm and 100 30 m.
    [0004]
    4. Method according to one of the preceding claims, wherein the multilayer (10) has a thickness less than the height of the microstructured pattern.
    [0005]
    5. Method according to one of the preceding claims, wherein the layers (13, 14) of the multilayer (10) are deposited according to a conformal deposition technique.
    [0006]
    6. Method according to one of the preceding claims, wherein the side walls (7) of the microstructured pattern (5) extend in a direction which forms an angle (a) strictly less than 900 with a normal direction to the upper surface. of the support.
    [0007]
    7. Method according to one of the preceding claims, wherein the etching performed in step (c) is performed by chemical mechanical polishing.
    [0008]
    8. Substrate (40) for surface enhanced Raman scattering comprising: a support (3) having an upper surface (4); a carrier structure (2) disposed on the upper surface (4) of the carrier (3), the carrier structure (2) having at least one microstructured pattern (5), the microstructured pattern (5) having a vertex (8) and side walls (7), the side walls (7) extending in a direction secant to the direction of the upper surface; a multilayer (10) disposed on the side walls (7) of the microstructured pattern (5), the multilayer (10) comprising at least two metal layers (13) and an interlayer (14) disposed between the two metal layers (13); ), the intermediate layer (14) being made of a material that can be etched selectively with respect to the metal layers (13), the interlayer (14) having an end (18) set back from the end (19) of the metal layers (13) surrounding it so that the ends (19) of two successive metal layers form metal pins separated by a cavity (20).
    [0009]
    9. Substrate (40) according to the preceding claim, wherein the interlayer (14) is a dielectric layer.
    [0010]
    10. Substrate (40) according to one of claims 8 or 9, wherein the side wall (7) of the microstructure pattern (5) has faces (11) separated by edges (12).
    [0011]
    11. Substrate (40) according to one of claims 8 to 10, wherein the carrier structure (2) comprises a plurality of microstructured patterns (5) forming a periodic network.
    [0012]
    12. Substrate (40) according to one of claims 8 to 11, wherein the metal layers (13) have different thicknesses from each other.
    [0013]
    13. Substrate (40) according to one of claims 8 to 12, wherein the multilayer (10) comprises a plurality of intermediate layers (14), the spacer layers (14) having different thicknesses from each other.
    [0014]
    14. Substrate (40) according to one of claims 8 to 13, wherein each microstructured pattern (5) has a height between 50 nm and 100 pm.
    [0015]
    15. Substrate (40) according to one of claims 8 to 14, wherein each metal layer (13) has a thickness between 1 angstrom and 50 nm, preferably between 10 nm and 50 nm.
    [0016]
    16. Substrate (40) according to one of claims 8 to 15, wherein each interlayer (14) of the multilayer has a thickness between 1 angstrom and 20 nm, preferably between 10 nm and 20 nm.
    [0017]
    17. Substrate (40) according to one of claims 8 to 16, wherein each cavity has a depth between 1 angstrom and 200 nm, and preferably between 10 nm and 100 nm.
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    同族专利:
    公开号 | 公开日
    US20160195475A1|2016-07-07|
    JP2016136138A|2016-07-28|
    EP3040710A1|2016-07-06|
    US9632032B2|2017-04-25|
    FR3031394B1|2020-06-05|
    EP3040710B1|2020-08-05|
    引用文献:
    公开号 | 申请日 | 公开日 | 申请人 | 专利标题
    US20110140209A1|2007-05-29|2011-06-16|Hong Wang|Multi-layer micro structurefor sensing substance|
    KR20110097354A|2010-02-25|2011-08-31|한국과학기술원|Multi layer nanogap structure and its manufacturing method|
    US20130038870A1|2011-08-14|2013-02-14|Industrial Technology Research Institute|Surface-enhanced raman scattering substrate and a trace detection method of a biological and chemical analyte using the same|
    JP2012518288A|2009-02-18|2012-08-09|ヨーロピアン・ナノ・インヴェスト・アーベー|Nanoplasmon parallel lithography|FR3031395B1|2015-01-05|2017-07-21|Commissariat Energie Atomique|METHOD FOR MANUFACTURING SUBSTRATE FOR EXTENDED SURFACE RAMAN DIFFUSION AND SUBSTRATE|
    JP2020041942A|2018-09-12|2020-03-19|王子ホールディングス株式会社|Substrate for analysis|
    US11150191B2|2019-03-01|2021-10-19|The Board Of Regents Of The University Of Oklahoma|Automatic, real-time surface-enhanced raman scatteringanalysis|
    US11092551B2|2019-10-17|2021-08-17|International Business Machines Corporation|Staircase surface-enhanced raman scattering substrate|
    法律状态:
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    2016-07-08| PLSC| Search report ready|Effective date: 20160708 |
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    优先权:
    申请号 | 申请日 | 专利标题
    FR1550009|2015-01-05|
    FR1550009A|FR3031394B1|2015-01-05|2015-01-05|METHOD FOR MANUFACTURING A SUBSTRATE FOR SURFACE-ENHANCED RAMAN DIFFUSION|FR1550009A| FR3031394B1|2015-01-05|2015-01-05|METHOD FOR MANUFACTURING A SUBSTRATE FOR SURFACE-ENHANCED RAMAN DIFFUSION|
    EP16150012.9A| EP3040710B1|2015-01-05|2016-01-04|Method for manufacturing a substrate for surface-enhanced raman scattering|
    JP2016000709A| JP2016136138A|2015-01-05|2016-01-05|Method of manufacturing substrate for surface-enhanced raman spectrography|
    US14/988,122| US9632032B2|2015-01-05|2016-01-05|Method for manufacturing a substrate for surface-enhanced Raman spectography|
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