Patent Application
20220111562
The invention generally relates to the production of structures of micrometric or nanometric size, to form microelectronic, optical or optoelectronic devices, as well as micromechanical or electromechanical devices. An advantageous application of the invention relates to the field of methods for manufacturing a master for the manufacture of at least a portion of a nanoimprint mould.
More particularly, the invention finds a particularly advantageous application in the manufacture of a master for forming moulds or mould parts, in order to mould aspherical microlenses, advantageously of low, or even very low curvature. These microlenses can in turn be intended for applications of light collection, imaging and light guiding, in transmission or in reflection, for example.
An advantageous application of the invention relates to the field of methods for manufacturing at least a portion of a nanoimprint mould.
Another application of the present invention is to directly manufacture a microlens, optionally without implementing any one of a mould part and a master.
There are many techniques for manufacturing microlenses.
Among these techniques, micro-jet imprinting and thermal creep are now very advanced techniques that are used in industry to produce high optical quality microlenses. These techniques are more qualitative than quantitative when it comes to achieving an accurate surface profile. For example, the thermal creep of photo-resin (See for example the article by N. T. Gordon and al., entitled “Application of microlenses to infrared detector arrays”, in the journal Infrared Phys., 30, 6, 599-604, 1991) and imprinting by micro-jets are based on delicate physicochemical phenomena involving a balancing of the surface tensions involved, which greatly limits the choice of surface profiles potentially obtained by these techniques.
On the contrary, laser ablation (See, for example, the article by F. Chen and al., Entitled “Simple fabrication of closed-packed IR microlens arrays on silicon by femtosecond laser wet etching”, in the journal Applied Physics A, (2015) 121: 157-162), two-photon polymerisation and direct laser writing techniques allow to obtain a very large choice of surface profiles. However, these techniques are sequential, which does not make them adapted in terms of cost and efficiency on an industrial scale.
The use of RIE (for “reactive ion etching”) etching (See for example the article by R. Yamazaki and al., entitled “Microlens for uncooled infrared array sensor”, in the journal Electronics and Communications in Japan, 96, 2, 2013) and the use of proton lithography are, in turn, considered to be expensive techniques, especially if they are used to produce polymer microlenses.
More recently, moulding and imprinting techniques such as those generally referred to by their names “hot embossing”, “imprinting” and “injection moulding” have been increasingly used to produce microlenses. The principle of manufacture is to fill a mould with a material (typically a polymer) and detach the material from the mould. The microlenses potentially obtained in this way can be hemispherical or spherical in shape. Depending on the type of substrate on which the moulding is made, silicon or glass (or quartz) substrate, the applications may concern, respectively, the wavelength range of infrared (IR) or that of visible light.
The manufacturing methods by imprinting require the availability of moulds which can, in turn, be manufactured for example using the techniques mentioned in the following publication: “Journal of Optics A: Pure and Applied Optics 8”, issue 7, pages 407-429, published in 2006. As a general rule, the standard techniques implemented by the microelectronics industry are most often preferred, because they are very reliable and the integration of the microlenses into the final components, typically electronic components of transistor type, is facilitated.
A known method for manufacturing a mould by microelectronic techniques is described below with reference to
Optionally, the relief patterns of the mould can be created directly in the silicon 103 without resorting to the intermediate silica layer 102. In this case, the etching solution is a mixture of hydrofluoric acid (HF) and nitric acid (HNO3) as reported in 2009 in an article in the journal Optics Express, Volume 17, Edition 8, pages 6283 to 6292 (2009).
If the mould manufacturing methods briefly described above are suitable for obtaining, as shown, spherical or hemispherical patterns, it is on the other hand difficult to obtain lenses called aspherical lenses of desired shapes or lenses with large radii of curvature (diameter very much greater than the sweep) with these methods. However, the production of masters of aspherical microlenses is generally required in many applications. These aspherical lenses indeed usually have much better optical properties. In particular, the spherical lenses, unlike aspherical lenses, induce optical aberrations, the rays passing through the centre of the lens not converging at exactly the same point as those passing through the edges. This causes blurring at large apertures and a widening of the focus spot that cannot be ignored in most applications.
It is then necessary to use lasers and techniques called “laser machining” or laser ablation, already mentioned above, which alone are likely to be able to create the necessary complex profiles with, however, the major disadvantage that each microlens must then be individually shaped. These techniques are for example described in the article “Spherical and Aspheric Microlenses Fabricated by Excimer Laser LIGA-like Process”, by Yung-Chun Lee, and al., Published in 2006 in the journal “Journal of Manufacturing Science and Engineering”, 129, 126-134.
An object of the present invention is therefore to provide a method for producing a structure having at least one curved pattern which allows to limit, or even eliminate, at least some of the problems set out above.
The other objects, features and advantages of the present invention will become apparent upon examining the following description and the accompanying drawings. It is understood that other advantages can be incorporated.
To achieve this purpose, according to one embodiment, the present invention provides a method for producing a structure having at least one pattern, for example to manufacture a master for a nanoimprint mould, the method comprising the following steps:
Thus, the free surface of the base layer is deformed due to the at least partial filling of the spaces between the reliefs of each plurality. The volume of material displaced in particular in line with the reliefs during the deformation of the base layer is at most equal to the volume of the spaces defined between the reliefs. By applying conventional microelectronic techniques, it is possible to perfectly control the volume of these spaces. Consequently, the volume of material displaced is a fortiori also well controlled; however, the shape, the curvature and the sweep of the formed pattern depend in particular on the volume of the displaced material. The shape, the curvature and the sweep of the formed pattern are therefore perfectly controllable.
The pattern thus formed can advantageously have an aspherical curvature, which is preferably low (<10−2 μm−1), or even very low (<10−6 μm−1).
Thanks to the method according to the invention, it is possible to manufacture a nanoimprint mould. This mould can then be used for moulding microlenses which have an aspherical curvature, which is preferably low (<10−2 μm−1), or even very low (<10−6 μm−1).
Furthermore, the manufacturing method as introduced above is advantageously simple, rapid, operable in a single series of steps on the scale of a wafer, and compatible with the standard techniques of microelectronics.
Another aspect of the present invention relates to a method for manufacturing at least one nanoimprint mould using a master manufactured by implementing the method as introduced above. Thus, the present invention provides for the use of a master manufactured by implementing the method as introduced above, for the manufacture of at least one nanoimprint mould.
Another aspect of the present invention relates to a method for manufacturing at least one microlens by nanoimprinting, using a nanoimprint mould manufactured by transferring at least one pattern from a master manufactured by implementing the method as introduced above. Thus, the present invention provides for the use of a nanoimprint mould manufactured by transferring at least one pattern from a master manufactured by implementing the method as introduced above, for the manufacture of at least one microlens per nanoimprint.
Another aspect of the present invention relates to a method for manufacturing at least one nanoimprint mould part manufactured by implementing the method as introduced above. The present invention provides for the use of the nanoimprint mould part manufactured by implementing the method as introduced above, for the manufacture of at least one microlens by nanoimprinting from said part.
Another aspect of the present invention relates to a method for manufacturing a lens, or microlens, by implementing the method as introduced above. This other aspect of the invention is in particular advantageous for reflective optics applications. For this purpose, provision can indeed be made to make the polymer, on the basis of which the base layer is made, reflective by depositing on the polymer, at low temperature, a metal or dielectric thin layer, so as to optimise the reflection.
The purposes, objects, as well as the features and advantages of the invention will become more apparent from the detailed description of an embodiment thereof which is illustrated by the following accompanying drawings wherein:
The drawings are given by way of examples and are not limiting of the invention. They constitute schematic principle representations intended to facilitate the understanding of the invention and are not necessarily on the scale of practical applications. In particular, the relative dimensions of the various layers and reliefs are not representative of reality. In
Before starting on a detailed review of embodiments of the invention, optional features which can possibly be used in combination or alternatively are listed below:
These base layer deposition techniques are advantageously simple, rapid and operable in a single step or series of steps at the scale of a wafer;
It is specified that in the context of the present invention, the term “on”, “surmounts”, “covers” or “underlying” or their equivalents do not necessarily mean “in contact with”. Thus, for example, the deposition of a first layer on a second layer does not necessarily mean that the two layers are directly in contact with one another, but this means that the first layer at least partially covers the second layer by being either directly in contact therewith, or by being separated therefrom, for example by at least one other layer or at least one other element.
In the context of the present invention, the thickness of a layer, as well as the depth or the height of a cavity or of a relief is taken in a direction perpendicular to a front face of a substrate on which the layer rests or at which the cavity or relief is formed. The thickness, height and depth are thus taken in a direction perpendicular to the main plane wherein the substrate and the layer extend. In the figures, the thickness, height and depth are taken in the direction Z as illustrated in
Likewise, when it is indicated that a material is deposited in line with at least a portion of a substrate, this means that this material and at least this portion of the substrate are both located on the same line perpendicular to the main plane of the substrate, in other words on the same line oriented vertically in the figures.
In the context of the present invention, the term “pattern” denotes a local variation of a free surface of a base layer having an analogue profile, that is to say with a continuous variation of the tangents of the profile shape, as illustrated for example in
“Nanoimprinting” means any lithography technique wherein a hard mould is applied to the surface of a material, in order to leave therein, in a resin, or equivalently a polymer, the imprint of a structure of a micrometric or even a nanometric size.
“Master” means an element bearing an imprint or pattern that is in negative in a mould obtained by direct copying of the master. Thus, the master has at least one pattern which is reproduced in negative in the mould. The mould is then used to transfer this negative to another layer, for example to form a microlens. The pattern formed in this other layer corresponds to the negative of the pattern carried by the mould. Advantageously, the pattern carried by the same mould is transferred to a very large number of layers.
A film or a layer based on a material A, means a film or a layer comprising this material A and possibly other materials.
A layer of “uniform” thickness means a layer having a constant thickness in a direction perpendicular to the tangent at each point of one of its two main faces.
“Conformal” means a layer geometry which has the same thickness, within manufacturing tolerances, despite changes in layer direction, for example at the sidewalls of a pattern.
“Microlens” means a small lens, generally with a diameter less than 5 mm, or even less than or equal to 2 mm, and which may reach around ten micrometres, and one of the dimensions (diameter or sweep) of which is less than 1 mm.
The present invention can allow to directly or indirectly manufacture microlenses such as that 10 illustrated in
A first embodiment of the invention is described below with reference to
This first embodiment describes in particular a method 100 for manufacturing a master 1 for a nanoimprint mould, but it is understood that the description which is given below also applies mutatis mutandis to describe a method 100 for manufacturing a part of a nanoimprint mould and/or a method 100 for manufacturing a lens. These three variations of the method for producing a structure 1 having at least one curved pattern 6 indeed provide, for the first one, for the production of a master for a nanoimprint mould as structure 1, for the second one, for the production of a part of a nanoimprint mould as structure 1, and, for the third one, for the production of a lens as structure 1.
With reference to the aforementioned figures, the method 100 for manufacturing the master 1 for a nanoimprint mould first comprises a step of providing 110 a structured substrate 2.
The substrate 2 is for example based on a material selected from: silicon, germanium, glass, silicon nitride, etc. More generally, the substrate 2 is selected from a material which, on the one hand, can be structured as described below and which, on the other hand, withstands the temperatures and other stresses undergone during the implementation of the method according to the invention. This last stress is not strongly limiting given that the temperatures to which the substrate 2 will be subjected during the method 100 according to the invention are generally not necessarily high. Typically, for a pattern created from a layer of polymer, such as a resin, the temperatures to which the substrate is subjected do not exceed 400° C.
In the exemplary embodiments described below, the substrate comprises a silicon wafer, which may have a diameter of eight inches, or even more. As will be seen below, such a wafer advantageously offers a sufficient working surface to manufacture several masters in a single implementation of the method according to the invention.
More particularly, the substrate 2 comprises a front face 20 which is partly and preferably only partly structured. Thus, the front face 20 of the substrate comprises, or consists of, at least one structured portion 21 and another unstructured portion 22.
Each structured portion 21 comprises a plurality of reliefs 3 which define spaces 4 therebetween. On the same substrate 2, several structured portions 21 can be provided each comprising a plurality of reliefs 3 which is specific thereto. The other portion 22 of the front face 20 of the substrate 2 is free of reliefs. It is preferably substantially flat. When several pluralities of reliefs 3 are provided, each occupying a structured portion 21 of the front face 20 of the substrate 2, the other portion 22 of the front face 20 can extend integrally around each structured portion 21 and around the assembly formed by the plurality of structured portions. Thus, each structured portion can be surrounded on all sides by a portion 22 of the front face 20 of the substrate 2 which is free of reliefs. Consequently, at least two pluralities of reliefs 3 structuring the front face of the substrate define second spaces therebetween. Each second space is larger, for example at least ten times larger, than the space defined between the reliefs 3 of the same plurality. In general, the structuring of the front face 20 of the substrate 2 is preferably carried out using known methods in microelectronics, such as photolithography, and more particularly the deep relief microelectronic manufacturing methods (for example hard mask and method Bosch®).
As shown in
Each cavity 41 may have a height, or more particularly here a depth, greater than 10 μm, preferably greater than 100 μm. Each cavity 41 can also have at least one transverse dimension comprised between 20 and 200 μm, preferably comprised between 50 and 100 μm. Each cavity 41 can be in the shape of a hole, for example of circular section; in which case, the transverse dimension of the cavity 41 corresponds to its diameter. When a cavity 41 forms a hole, the latter may be through or blind. Alternatively or in addition, each cavity 41 can be in other shapes, such as the shape of a hole of oblong or polygonal, for example rectangular or square section, the shape of a groove closed or not on itself and crossing or not at least one other groove.
The plurality of reliefs 3 as illustrated in
The reliefs 31 as illustrated in
In general, it may be preferable for the structuring of the front face 20 of the substrate 2 to be configured so that the spaces 4, 41 (and 42, See
The structuring of the front face 20 of the substrate 2 can therefore be advantageously carried out by well-known and controlled microelectronic techniques, and of industrial efficiency because they allow the entire front face 20 of the substrate 2 to be treated at once.
Once the structured substrate 2 has been provided 110, the manufacturing method 100 according to the invention comprises a step of depositing 120 a base layer 5 on the front face 20 of the substrate 2.
Preferably, this base layer 5 is formed from a material based on one of a polymer, such as a resin, and a glass. It should be noted here that a polymer and a glass have in common that they can be viscoelastically deformed, in particular when they are brought above their glass transition temperature Tg. Glass, generally stiffer than a polymer, will be preferred for the manufacture of patterns 6 of lower curvature. Other materials may be considered which are known to be deformable in this way, and within temperature ranges compatible with maintaining the integrity of the substrate 2.
The base layer 5 is more particularly deposited at least in line with the reliefs 3 of each plurality; it preferably extends beyond said reliefs for reasons which will be explained below when the notion of mesh size is introduced. Thus, in a non-limiting manner, the base layer 5 can extend in line with the entire front face 20 of the substrate 2. The deposition 120 of the base layer 5 is performed so that, at least before its deformation, the base layer 5 has a thickness for example comprised between 20 and 200 μm.
It is preferable that the base layer 5 as deposited 120, and before its deformation, is uniform; its thickness is constant over its entire extent, within manufacturing tolerances. In this way, the shape of the pattern 6 formed can be better, or more easily, controlled, insofar as it is then not necessary to integrate into the method according to the invention, the management of the influence that would, a non-uniformity, and in particular a variation in thickness, of the base layer 5 as deposited 120, have on the shape of the formed pattern 6.
The step 120 of depositing the base layer 5 can comprise either one of the following steps:
The deposition 120 of the base layer 5 can therefore be advantageously carried out by well-known and controlled deposition techniques, and of industrial efficiency, allowing in particular to treat the entire front face 20 of the substrate at once.
The deposition 120 of the base layer 5 by depositing a dry film by lamination is preferably carried out under vacuum.
Various dry films based on various polymers are marketed today which can be used according to the manufacturing method 100 of the invention. For example, mention can be made of: the MX5000™ series from DuPont™ or the A2023 film from Nagase Gmbh. The manufacturers of such films generally characterise the parameters which are of interest for the implementation of the method according to the present invention, such as their viscoelastic parameter(s), their deposition parameter(s) and their thickness.
The aforementioned deposition techniques can, by their sole embodiment, bring the base layer 5 to temperature, or even pressure conditions, allowing it 130 to be deformed, in particular viscoelastically, after the deposition 120, or even including during the deposition 120.
Alternatively or in addition, it is considered to subject at least the base layer 5 to a sufficient temperature, or even to a controlled surrounding pressure, to induce its viscoelastic deformation, or else also its plastic deformation.
More particularly, the base layer 5 is either deposited solid, before being heated, or deposited “hot”. The couple [temperature T, time t] of the deformation of the base layer 5 is selected so as to allow to fill, if necessary partially, the spaces 4. The higher the temperature, the shorter the filling time, this time can vary from 1 min to a few hours, even 1 day or a few days. A temperature of at least 10° above the glass transition temperature Tg will be selected (to induce the viscoelastic deformation). Advantageously, a temperature T between 10 and 40° C. above the glass transition temperature Tg will be selected, but it is possible to go beyond this insofar as there is no degradation of the material of the base layer 5 and/or the substrate. For the highest temperatures, rather a viscous flow will be obtained (but the viscous flow remains comprised in the viscoelastic deformations).
Furthermore, as indicated above, the step of depositing 120 the base layer 5 and the step of allowing 130 the material of the base layer 5 to at least partially fill the at least one of the spaces 4, preferably all the spaces, defined between the reliefs of the same plurality by an at least viscoelastic deformation of the base layer 5, can be carried out under different pressure conditions. More particularly, while the deposition step 120 is preferably carried out under vacuum, step 130 can, in turn, be carried out at a higher pressure, and in particular at ambient pressure. This step 130 can be carried out under a flow of compressed air or nitrogen. Thus, an air pressure differential between the second face 50 of the base layer 5, this second face 50 defining the free surface of the base layer 5, and the first face of the base layer 5 located facing the front face 20 of the substrate 2 is created. This differential assists the viscoelastic deformation of the free surface 50 of the base layer 5.
Thus, the step of allowing 130 the material of the base layer 5 to at least partially fill the at least one of the spaces 4, preferably all the spaces, defined between the reliefs 3 of the same plurality by an at least viscoelastic deformation of the base layer 5 may or may not require a positive action (a rise in temperature in particular). This need or its absence is to be determined at least according to the viscoelastic parameters, the deposition parameters and the thickness of the base layer 5. When no positive action is required, it is sufficient to allow the base layer 5 as deposited 120 to evolve freely and naturally for a certain time.
Typically, the temperatures to be considered are comprised between −20° C. and 400° C., and more particularly comprised between 20° C. and 200° C., for polymers. They are comprised between 300° C. and 700° C. for glass (depending on their composition). It should also be noted that the shape of the pattern 6, before reaching the balance of the surface tensions involved, changes over time in a very dependent manner on the temperature to which the base layer 5 is subjected: generally, the higher the temperature, the faster the change in the shape of the pattern 6.
As stated above, the filling of the spaces 4 defined between the reliefs of the plurality of reliefs 3 structuring the front face 20 of the substrate 2 is related to the deformation, which is in particular viscoelastic, of the base layer 5, which flows into the spaces 4 left free between the reliefs 3.
Several observations immediately appear as to the deformation of the free surface 50 of the layer 5.
First, the free surface 50 must remain continuous; its deformation must not lead to its rupture. To ensure this, the thickness of the layer 5, the temperature to which it is brought to be deformed and/or the time that is left for the base layer 5 to be deformed are all parameters to be taken into consideration.
It also appears, in particular by comparing
Whether one proceeds by balancing the surface tensions involved or by interrupting the deformation at a selected moment before stabilisation, the curvature of the pattern 6 formed depends at least on the viscoelastic, or else plastic parameters of the base layer 5. To some extent, these parameters in turn depend on the deposition parameters of the base layer 5.
From these considerations, it follows that, for each plurality of reliefs 3, the number, shape and spatial distribution of the reliefs 3 are to be configured at least according to the viscoelastic, or else plastic parameters and to the deposition parameters of the base layer 5. It is the set of these parameters which determines the curvature of the formed pattern 6 whether it is stabilised or not.
It is also possible to play on the composition of the base layer 5: thus the base layer 5 can consist not of a single layer but of a stack of two or more layers of different materials selected from glass and polymers and whose properties among which at least one of their thickness and their glass transition temperature Tg are different. Thus, a considerably increased number of possibilities for implementing the method is obtained, for adaptation to each need and each objective, in particular in terms of curvature and/or size of the pattern. Indeed, it is possible to optimise, by simulation or empirically, the various method parameters: choice of materials, thicknesses of the layers, temperature and pressure, etc., to induce the deformation. Advantageously, the layers flowing the least (viscoelastic, even viscous) will be placed at the bottom of the stack (that is to say on the side of the front face 20 of the substrate 2), and the more elastic layer(s) on top of the stack.
Whether one proceeds by balancing the surface tensions or by interrupting the deformation at a selected moment, it is preferable that the free surface 50 of the base layer 5 is sufficiently stiff or stiffened to maintain its shape. For the production of a master, it is preferable that the free surface 50 of the base layer 5 is sufficiently stiff or stiffened to allow the subsequent manufacture of a mould.
The deposition parameters 120 of the base layer 5, as well as the temperature, or else pressure parameters wherein the base layer 5 is maintained during the filling of the spaces 4 (the latter parameters being able to change over time) influence the more or less stiff state of the free surface 50 of the base layer 5, once the balance of the surface tensions has been reached or when the deformation is interrupted. This stiffness may be sufficient to ensure that the shape of the pattern 6 formed is maintained. Otherwise, the method 100 may further comprise, once the pattern 6 has been formed, a step of stiffening, at least on the surface, the base layer.
When the material of the base layer 5 is a polymer, the stiffening step can comprise providing the polymer, at least on the surface of the base layer 5, in a glassy, solid or rubbery state. The crosslinking of the polymer can be obtained either by application of a luminous flux, for example by UV (ultra-violet) treatment, or by heat treatment. When the viscoelastic material is glass, the stiffening step can comprise bringing the glass, at least to the surface of the base layer, into a glassy state. When a stiffening step is not necessary, it means that the material of the base layer 5 is already in one of the aforementioned states without the need for positive action.
The pattern 6 of the master 1 as manufactured by implementing the method 100 according to the embodiment which has just been described with reference to
Other optional steps of the manufacturing method 100 according to the invention are described below, in particular with reference to
As illustrated in
As illustrated in
More particularly, the master 1 is thus prepared in additional steps comprising in particular the grafting on the finish layer 7 of non-stick layers and/or the transfer of the pattern 6 in transfer layers generally comprising organic elements and intended to form an intermediate mould. The non-stick layers are provided to prevent unwanted tearing when the transfer layers of the pattern 6 are peeled from the master 1.
Moreover, it is advantageous that the finish layer 7 is based on silicon oxide or silicon nitride because such a layer is impermeable to the organic elements composing the transfer layers; this prevents migration of these organic elements into the structure 1. This is also advantageous because the grafting of non-stick layers is facilitated on this type of material.
At this stage, the master 1 manufactured by implementing the manufacturing method 100 according to the first variation of the invention is prepared in order to manufacture a nanoimprint mould intended for example for the manufacture of microlenses such as the one illustrated in
The mesh size can define the extent over which the layer 5 must be deposited, in a centred manner, in line with and beyond the reliefs 3, to avoid undesirable edge effects during the deformation of the base layer 5. When several pluralities of reliefs 3 structure the front face 20 of the substrate 2, the mesh size can further define the distance to be placed between these pluralities to prevent the deformation of the base layer 5 at a plurality from influencing on the deformation of the base layer 5 at any other plurality. Thus, when several pluralities of reliefs structure the front face of the substrate, each plurality should be sufficiently spaced from any other plurality, if it is desired that each plurality define the curvature of the pattern 6 that it generates without any other influence, in a self-controlled manner.
It should be noted that, if the geometry of the pattern can be controlled by adjusting the reliefs of a plurality and their surface density, it is still possible to compensate for a possible impact of the method at the scale of the substrate. This impact can be related, for example, to a thermal expansion effect or to a volume shrinkage related to the crosslinking of the polymer. The compensation for this impact can be achieved by a local correction of patterns 6 formed from, for example, an empirical study consisting in converging, from trials/errors, to the optimal solution.
Two other embodiments of the method according to the invention will now be described, in terms of what distinguishes them from the embodiment described above, and with reference to
The reliefs 3 illustrated in
According to the embodiment illustrated in
Once the structured substrate 2 has been provided 110, as before, the base layer 5 is deposited at least in line with the plurality of reliefs 3.
Unlike the embodiment illustrated in
Thanks to the method 100 according to the embodiments described above, it is possible to manufacture a master for the manufacture of a mould part, a mould part for nanoimprinting microlenses, and ultimately a lens such as that illustrated in
The invention exploits the viscoelastic, and potentially also plastic, deformation of a free surface 50 of a base layer 5 based on polymer or glass by filling cavities 41, 42 or spaces defined between the reliefs 31 on which the base layer 5 is deposited 120. The shape, the curvature and the sweep of each pattern 6 formed depend on the density of the cavities 41, 42 and/or reliefs 31, on the viscoelasticity of the base layer 5 and on the deposition parameters of the base layer 5. The volume of material displaced is proportional to the volume of the cavities 41, 42 or of the spaces defined between the reliefs 31, but the shape of the pattern 6 is in turn more related to the density of the cavities 41, 42 and/or reliefs 31 on a given mesh size. The mesh size depends on the materials and conditions under which the method 100 is implemented. If the pattern 6 as generated is of aspherical shape, with low, or even very low curvature, its shape ratio can be further accentuated via an imprinting-etching step on a new substrate. The shape factors then further depend on the etching method and the materials involved. In particular, if the etching selectivity between the resin of the base layer 5 and the substrate is strictly greater than 1, the curvature will be reduced. Conversely, if the etching selectivity between the resin of the base layer 5 and the substrate is strictly less than 1, the curvature will be increased.
The manufacturing method 100 according to the invention allows to manufacture in parallel a plurality of patterns 6 on a substrate 2 in the shape of a wafer eight inches in diameter, or even more, potentially in just a few minutes. When the structure 1 obtained has several patterns 6, it is possible that the latter have been formed so as to have a predetermined relative position with respect to one another. In this case, the structure 1 comprising several patterns 6 can be used as such, for example, when the structure 1 is a master, in order to manufacture a mould allowing the simultaneous nanoimprinting of a plurality of microlenses having said predetermined relative position relative to each other. Alternatively, a structure 1 comprising several patterns 6 can be subjected to a cutting aiming at separating the patterns 6 from each other, for example, when the structure 1 is a master, to use each of them for the manufacture of a mould part and, consequently, in the manufacture of a microlens.
Another aspect of the present invention indeed relates to the use of a master 1 manufactured by implementing the method 100 according to one of the embodiments described above, for the manufacture of at least one nanoimprint mould.
According to another aspect, the invention relates to a method for manufacturing at least one nanoimprint mould by moulding from a master 1 manufactured by implementing the method 100 according to one of the embodiments described above.
According to another aspect, the invention relates to the use of a nanoimprint mould manufactured according to a method for manufacturing at least one nanoimprint mould by moulding from a master 1 manufactured by implementing the method 100 according to one of the embodiments described above, for the manufacture of at least one microlens 10 by nanoimprinting.
The structure 1 produced according to the method 100 of the invention indeed finds application in the manufacture of microlenses or three-dimensional shapes with low, or even very low curvature. The structure 1 can indeed be used as a mould comprising the pattern 6 formed by the method 100 according to the invention. The microlenses or three-dimensional shapes manufactured using such a mould can be made from a permanent polymer transparent to the visible wavelengths for visible imaging or from a polymer used as an etching mask for manufacturing lenses from silicon for applications related to infrared imaging.
It is still possible, thanks to the method 100 according to the invention, to manufacture three-dimensional shapes in a layer of polymer deposited on a reflective substrate to make reflection optics. The use of a non-reflective substrate to make reflection optics is also considered by providing to cover it with a thin reflective layer (which is typically metallic, for wavelengths in the visible, for example).
It is also possible, thanks to the method 100 according to the invention, to manufacture curved substrates which can be used as a handle to transfer flexible components requiring a certain curvature thereon in order to have an optimal or improved operation. This is for example the case with imagers or video sensors, such as CCD (for “Charge-Coupled Device”) sensors, thus allowing to have curved detectors. The curvature is then induced by the support substrate manufactured with the method 100 according to the invention. Furthermore, the manufacture of the sensor can be made on a flat substrate, the sensor then being transferred on the support substrate. This can allow to relieve some stresses in the manufacture of the sensor, and in particular some stresses in the manufacture of the optics associated with the sensor, which no longer necessarily needs to be curved.
The invention is not limited to the embodiments previously described and extends to all embodiments covered by the claims.
For example, if the figures illustrate reliefs 31 and cavities 41 which are all identical, whether for the same plurality or different pluralities of reliefs 31 and cavities 41, 42, it is understood that the reliefs 31 and the cavities 41, 42 may be of various shapes and sizes, whether within the same plurality or from one plurality to another.
For example, the reliefs 31 and the cavities 41, 42 of the same plurality may have different heights or depths. This allows great freedom in the shape of the pattern 6 obtained in the end.
For example, the cavities 41, 42 and/or the reliefs 31 can form concentric rings of diameters which are different from each other.
| Number | Date | Country | Kind |
|---|---|---|---|
| 18 56929 | Jul 2018 | FR | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2019/069829 | 7/23/2019 | WO | 00 |
