Greyscale lithography mask

Abstract

Title: Grayscale Lithography Mask The invention relates to a grayscale lithography mask (1) for diffracting the illumination radiation of a photosensitive resin (20). The illumination radiation, of wavelength λ, is emitted by a light source having a coherence σ and a numerical aperture NA. The mask extends primarily along a horizontal plane (XY) perpendicular to a principal direction of the illumination radiation from the photosensitive resin through the mask. The mask comprises a plurality of areas opaque to the radiation, the plurality of opaque areas comprising first opaque areas and second opaque areas, the first opaque areas being arranged in a grid of steps P1 in the horizontal plane and the second opaque areas being arranged in a grid of steps P2 in the horizontal plane, such that P1

Description

Title of the invention: Greyscale lithography mask technical field

[0001] The present invention relates to the field of photolithography, more specifically to grayscale lithography. The invention relates particularly to the mask used in this technique. It relates in particular to the fabrication of hierarchical three-dimensional structures, that is to say, structures exhibiting several levels of structuring. STATE OF THE ART

[0002] Three-dimensional structures, and more particularly structures with several levels of structuring, have been the subject of numerous studies in recent years which have demonstrated their interest in applications as diverse as anti-reflection devices, self-cleaning surfaces, hydrophobic or hydrophilic surfaces or even functional surfaces for biodetection.

[0003] Several lithography techniques exist for the fabrication of such structures, including structures with microstructuring and nanostructuring. Among these techniques are, for example, nanoimprint lithography (US 8636937 B2, US 2012 / 0268822 Al), selective-repetitive lithography (see, for example, US 11037794 B2), and lithography using block copolymers (KR102523636 Bl).

[0004] These various techniques are, however, not entirely satisfactory because they require numerous lithography steps. For example, to achieve the different levels of structuring by nanoimprinting, several master molds (commonly referred to as "master" molds) must be manufactured and used during the 3D structure fabrication process. With regard to repeated selective lithography, it is necessary to protect the structures formed after each structuring step with a mask or protective layer. Finally, lithography using block copolymers only allows for nanostructuring and must be combined with another lithography technique to achieve microstructuring.

[0005] There is therefore a need to simplify the manufacturing of structures with multiple levels of structuring. The present invention aims to meet this need. SUMMARY

[0006] To achieve this objective, a first aspect of the invention relates to a greyscale lithography mask intended to diffract insolation radiation from a photosensitive resin, the insolation radiation having been emitted by a light source having a coherence of θ and a numerical aperture of NA, the insolation radiation having a wavelength of X, the mask extending mainly along a horizontal plane defined by a first direction and a second direction, the horizontal plane being perpendicular to a principal direction of the insolation radiation of the photosensitive resin through the mask. According to the invention, the mask comprises a plurality of areas opaque to the radiation, the plurality of opaque areas comprising first opaque areas and second opaque areas, the first opaque areas being arranged according to a grid of steps Pi in the horizontal plane and the second opaque areas being arranged according to a grid of steps P2 in the horizontal (XY) plane, such that Pi<PRayieigh et P2> PRayieigh, with n __ 1 <_• Z •Rayleigh ~ l+a NA '

[0007] PRayieigh is the threshold below which a grating of pitch P does not diffract the incident radiation (zero-order diffraction), and above which it does diffract it (first-order or higher diffraction). Thus, within the mask according to the invention, there is at least one grating of opaque zones that allow the radiation to pass through without diffracting it and at least one grating of opaque zones that diffract the radiation.

[0008] It has become apparent that combining these two types of networks allows in a single step the resin layer to be exposed in such a way that the latter, once developed, presents two levels of structuring: a first level of structuring, called microstructuring, induced by the network of first opaque zones, and a second level of structuring, called nanostructuring, induced by the network of second opaque zones.

[0009] Of course, it is possible to add other networks of opaque areas in order to add levels of structuring to the final resin layer.

[0010] The invention thus makes it possible to form complex and precise shapes in the resin layer, in a single lithography and resin development cycle. The invention therefore simplifies the manufacturing of structures with multiple levels of structuring.

[0011] A second aspect of the invention relates to a method for exposing a photosensitive resin comprising the following steps: a. provide a photosensitive resin, b. expose the photosensitive resin to insolation radiation emitted by a light source having a coherence of 0 and a numerical aperture of NA, the insolation radiation having a wavelength K c. the exposure of the photosensitive resin to insolation radiation through a mask according to the first aspect of the invention.

[0012] The advantages of the mask according to the first aspect of the invention apply mutatis mutandis to the process according to the second aspect of the invention. BRIEF DESCRIPTION OF THE FIGURES

[0013] The aims, objects, features and advantages of the invention will become clearer from the detailed description of an embodiment thereof, which is illustrated by the following accompanying drawings in which:

[0014] [Fig. 1A] Figures IA in 1D represent greyscale lithography masks and scanning electron microscope views of resins exposed through these masks and then developed. Figures IA and IB relate to the fabrication of 3D structures having platforms at different heights.

[0015] [Fig.1B]

[0016] [Fig.1C] Figures IC and 1D relate to the manufacture of 3D microlenses having a dome shape.

[0017] [Fig.1D]

[0018] [Fig.2A] [Fig.2B] [Fig.2C] [Fig.2D] [Fig.2E] [Fig.2F] [Fig.2G] [Fig.2H] Figures 2A to 2H illustrate an example in which the mask comprises two regular lattices with Pi <PRayieigh, P2—PRayleigh et P2=2*Pj.

[0019] [Fig. 3A] [Fig. 3B] [Fig. 3C] [Fig. 3D] [Fig. 3E] [Fig. 3F] [Fig. 3G] [Fig. 3H] Figures 3A to 3H illustrate an example in which the mask comprises two regular arrays of opaque areas with Pi<PRayieigh, P2> PRayieigh and P2=3*P!

[0020] [Fig.4A] [Fig.4B] [Fig.4C] [Fig.4D] [Fig.4E] Figures 4A to 4E illustrate an example in which the mask comprises two regular arrays of opaque areas with P1 <PRayleigh, P2—Pkayleigh et P2—2,5Pi

[0021] [Fig. 5A] [Fig. 5B] [Fig. 5C] [Fig. 5D] [Fig. 5E] Figures 5A to 5E illustrate an example in which the mask comprises three regular arrays of opaque areas with Pl <PRayleigh, P2» P2—PRayleigh et P2=2:| P1 et P3=3î|'Pi

[0022] [Fig.6A] [Fig.6B] [Fig.6C] [Fig.6D] [Fig.7A] [Fig.7B] [Fig.7C] [Fig.7D] [Fig.7E] [Fig.8A] [Fig.8B] [Fig.8C] [Fig.8D] [Fig.9A] [Fig.9B] [Fig.9C] [Fig.9D] Figures 6A to 9D illustrate an example in which the mask comprises an irregular network of opaque areas with a local increase in pitch.

[0023] [Fig.1OA] [Fig.1OB] [Fig.1OC] [Fig.1OD] Figures 10A to 10D illustrate an example in which the mask comprises an irregular network of opaque areas with local decrease in pitch.

[0024] [Fig.llA] [Fig.llB] [Fig.llC] [Fig.llD] [Fig.llE] [Fig.llF][Fig.llG] Figures 1 IA to 1 IG illustrate an example in which the mask includes an overlay of an irregular network of opaque zones with Pi<PRayieigh et d’un réseau régulier de zones opaques avec P2> PRayieigh.

[0025] [Fig. 12A] [Fig. 12B] [Fig. 12C] [Fig. 12D] [Fig. 12E] [Fig. 12F] Figures 12A to 12F illustrate an example in which the mask comprises the superposition of an irregular lattice with Pi<PRayieigh et d’un réseau régulier en forme de croix avec P2> PRayieigh-

[0026] [Fig. 13A] [Fig. 13B] [Fig. 13C] [Fig. 13D] [Fig. 13E] [Fig. 13F] [Fig. 13G] [Fig. 13H] Figures 13A to 13H illustrate an example in which the mask comprises a superposition of an irregular lattice with Pi<PRayieigh et de deux réseaux réguliers avec P2, P3> PRayieigh, one of which is in the shape of a cross.

[0027] [Fig. 14] The [Fig. 14] is a cross-sectional view of a greyscale lithography mask being used for the exposure of a photosensitive resin.

[0028] The drawings are given by way of example and are not limiting of the invention. They constitute schematic representations of principle intended to facilitate understanding of the invention and are not necessarily to scale with practical applications. In particular, the dimensions are not representative of reality. DETAILED DESCRIPTION

[0029] Before proceeding with a detailed review of embodiments of the invention, optional features that may be used in combination or alternatively are listed below:

[0030] According to one embodiment, the step size Pi is constant over the entire network of first opaque zones. It is also possible for the step size Pi to vary within the network of first opaque zones, while satisfying the condition Pi over the entire network <PRayieigh-Selon un mode de réalisation, le pas P2 est constant sur tout le réseau de deuxièmes zones opaques. Il est également possible que le pas P2 varie au sein du réseau de deuxièmes zone opaques, tout en vérifiant sur tout le réseau la condition P2> PRayieigh-

[0031] For example, Pi can be between 100 and 300 nm. The first opaque zones also have a first characteristic dimension CD1 (typically the side of the square in the case of square opaque zones). CD1 can, for example, be greater than 40 nm and / or less than Pi.

[0032] For example, P2 may be greater than 300 nm. The second opaque zones also exhibit a second characteristic dimension CD2. CD2 may, for example, be greater than 40 nm and / or less than P2.

[0033] Preferably, P2 is at least 1.5 times greater than Pp, preferably at least twice greater.

[0034] According to one embodiment, the first opaque zones are substantially identical to each other. In particular, the first opaque zones may be identical to each other in shape and dimensions.

[0035] According to one embodiment, the first opaque zones have distinct dimensions. In particular, they may have distinct shapes or dimensions. This can notably allow for microstructuring of the exposed resin layer, for example, dome-shaped microstructuring.

[0036] According to one embodiment, the second opaque zones are substantially identical to each other. In particular, the second opaque zones may be identical to each other in shape and dimensions.

[0037] According to one embodiment, some of the first opaque zones and the second opaque zones are at least partially confused.

[0038] According to an example, P2=2*m*Pb m being an integer.

[0039] According to an example, P2=3*m*Pb m being an integer.

[0040] According to an example, P2=2.5*m*Pb m being an integer.

[0041] According to one embodiment, the plurality of opaque zones further includes third opaque zones organized according to a step network P3 in the horizontal plane (XY), P3 being distinct from Pi and P2.

[0042] According to an example, P3>PRayieigh.

[0043] According to an example, P3=3*n*Pb n being an integer.

[0044] According to one embodiment, the plurality of opaque zones admits at least one first plane of symmetry perpendicular to the horizontal plane.

[0045] According to one embodiment, the second opaque zones have at least one first plane of symmetry perpendicular to the horizontal plane. This allows for nanostructuring of the resin with a plane of symmetry.

[0046] According to one embodiment, the first opaque zones have at least one first plane of symmetry perpendicular to the horizontal plane. This allows for microstructuring of the resin with a plane of symmetry.

[0047] According to one embodiment, the plurality of opaque zones admits at least a second plane of symmetry perpendicular to the first plane of symmetry and to the horizontal plane.

[0048] According to one embodiment, the second opaque zones admit at least one second plane of symmetry perpendicular to the first plane of symmetry and to the horizontal plane. This makes it possible to achieve a nanostructuring of the resin having two planes of symmetry.

[0049] According to one embodiment, the first opaque zones have at least one second plane of symmetry perpendicular to the first plane of symmetry and to the horizontal plane. This allows for a micro-structuring of the resin with two planes of symmetry.

[0050] According to an example, PI is less than or equal to 300 nm, for example equal to 200 nm.

[0051] According to one example, P2 is greater than or equal to 400 nm, for example equal to 400 nm, 500 nm or 600 nm.

[0052] In the context of the present invention, a resin is defined as an organic or organo-mineral material that can be shaped by exposure to a beam of electrons, photons, X-rays, a beam of light in the ultraviolet, extreme ultraviolet (EUV) or deep ultraviolet (Deep UV) range, typically in the wavelength range of 193 nm to 248 nm, the emission lines of a mercury lamp, namely: 365 nm for the I line, 435 nm for the G line and 404 nm for the H line.

[0053] The invention applies equally to positive resins, i.e., those whose exposed part becomes soluble in the developer and where the unexposed part remains insoluble, and to negative resins, i.e., those whose unexposed part becomes soluble in the developer and where the exposed part remains insoluble.

[0054] The contrast of a resin, commonly denoted y, reflects the effectiveness of the behavior referred to in the literature as the "threshold" behavior of the resin. The greater the contrast, the smaller the dose variation required for the resin to transition from a state in which it cannot be developed to a state in which it can be developed (or vice versa for a negative resin). The value of the contrast y of a resin, whether positive or negative, is generally determined by the slope of the curve according to the following equation: e_t(Ai), where e is the film thickness (e0D). resin after exposure and development, e0 is the initial resin film thickness, D is the applied exposure dose and Do is the dose at which the full film thickness is developed.

[0055] The "nature" of a material such as a resin means its chemical composition, that is to say, the nature and proportion of the species constituting the material. Two layers are considered to be made of the same resin if they have the same chemical composition.

[0056] In this description, the dose is defined as the amount of energy received by a resin per unit area. This energy can be in the form of photons (photolithography) for a photosensitive resin. It is then the product of the intensity of the incident light radiation (generally expressed in Watts / m²) and the exposure time (expressed in seconds). The dose is then usually expressed in Joules per m², or more often in millijoules (mJ) per cm² (10⁴ m²) or even in mJ / m². This energy can also be in the form of electrons (electron lithography) for an electrosensitive resin. The dose is then usually expressed in coulombs per m², or more often in microcoulombs (pC) per cm² (10² m²), or in pC / m².

[0057] A parameter "approximately equal to / greater than / less than" a given value means that this parameter is equal to / greater than / less than the given value, to within 20% or 10% of that value. A parameter "approximately between" two given values ​​means that this parameter is at least equal to the smaller of the given values, to within 20% or 10% of that value, and at most equal to the larger of the given values, to within 20% or 10% of that value.

[0058] In this patent application, the terms thickness for a layer and height for a structure or device will be preferred. The thickness is measured in a direction normal to the principal plane of extension of the layer, and the height is measured perpendicular to the horizontal XY plane. Thus, a layer typically has a thickness in the so-called vertical Z direction when it extends primarily along the horizontal XY plane. The relative terms "on," "under," and "below" preferentially refer to positions measured in the vertical Z direction.

[0059] A first object of the present invention relates to a photolithography mask particularly adapted to greyscale lithography.

[0060] Greyscale lithography is a photolithography technique that allows the creation of three-dimensional (3D) microstructures in a single lithographic and development step. It is particularly used in the fabrication of optical microelements, MEMS (microelectromechanical systems), MOEMS (microoptoelectromechanical systems), microfluidic devices, and textured surfaces.

[0061] This technique is based on varying the thickness along a dimension Z over which a photosensitive resin is exposed by modulating the dose of ultraviolet (UV) received by the resin in space. Once the exposed portions have developed, the resin exhibits a 3D structure (seen by scanning electron microscopy (SEM) and shown in Figures IB and ID) and can, for example, serve as a mold for the fabrication of 3D microstructures.

[0062] The ultraviolet dose received locally by the resin can be modulated, in particular, by adjusting the dimensions and positioning of opaque areas present on the lithography mask (Figures IA and IC). These opaque areas are typically created by depositing chromium on a glass mask.

[0063] Greyscale lithography thus makes it possible to obtain 3D microstructures with a characteristic height ranging from ten to several hundred micrometers.

[0064] The mask according to the present invention will now be described with reference to the figures and in particular to [Fig. 14].

[0065] The mask 1 extends mainly along a plane (in the example horizontal) XY defined by the first direction X and the second direction Y. More precisely, it has a top face 11 and a bottom face 12 each extending substantially parallel to the horizontal plane XY.

[0066] When using the mask 1, its lower face 12 is positioned opposite an upper face 21 of a resin layer 20, which may also be referred to as resin 20. The upper face 21 of the resin layer 20 also extends parallel to the horizontal plane XY. The resin layer 20 typically rests on a support substrate 40. An underlayer 30 may be interposed between the support substrate 40 and the resin layer 20.

[0067] When using the mask 1, the resin layer 20 is exposed to radiation 50 through the mask 1. The radiation 50 is emitted by a light source (not shown) having a coherence 0 and a numerical aperture NA.

[0068] This radiation 50 has a principal direction substantially perpendicular to the horizontal plane XY. The radiation 50 has a wavelength X. It may be monochromatic radiation, in which case X will correspond to the single emitted wavelength. However, it may also be polychromatic radiation, in which case the wavelength X of the radiation is considered to be its principal wavelength, typically the one at which the light intensity is highest, or its average wavelength.

[0069] Radiation 50 is typically UV (ultraviolet) radiation; it can therefore be radiation emitted in a wavelength range from approximately 100 nm to approximately 400 nm, for example 365 nm. However, it can also be radiation with wavelengths outside this range. Generally, but not limited to, radiation emitted in a wavelength range from approximately 90 nm to approximately 500 nm can be considered.

[0070] Ideally, the resin 20 used has at least one of the following characteristics: a. A substantially linear response between the radiation dose to which it is exposed and the thickness over which it is exposed. b. A sufficiently low contrast, for example less than 2, to allow the implementation of greyscale lithography, but sufficiently high, for example greater than 1, to avoid excessively long exposure times. Advantageously, the contrast is between 1.1 and 1.5. c. Good film-forming properties, guaranteed for example by the presence of a film-forming agent in its composition. d. Weak inhibition of dissolution.

[0071] Examples of resins that can be used in the context of the invention include resins produced by Micro Resist Technology bearing the commercial references ma-P 1215G, ma-P 1225G and ma-P 1275G.

[0072] The following paragraphs aim to describe mask 1 more precisely with reference to the figures, for example to [Fig.2A].

[0073] The mask according to the invention comprises a plurality of opaque zones. It also comprises transparent zones.

[0074] Transparent areas correspond to regions of mask 1 whose composition is transparent to radiation 50, while opaque areas correspond to regions of mask 1 whose composition is opaque to radiation 50. An area is considered opaque, for example, when it blocks at least 90% of the incident radiation 50. An area is considered transparent when it transmits at least 60% of the incident radiation 50.

[0075] For example, mask 1 can be a glass mask with chromium deposits. The opaque areas then correspond to the areas of mask 1 where chromium has been deposited, while the transparent areas correspond to the areas that remained free of chromium.

[0076] According to the principle of greyscale lithography, for a given region of the mask 1, the surface density D of the opaque areas within this region determines the radiation dose received by the region of the underlying resin layer 20 and therefore, consequently, the thickness e over which this region of the resin layer 20 is exposed by the radiation 50. This density D is typically modulated from one region to another of the mask so as to spatially modulate the exposed thickness in the resin layer 20.

[0077] For a given region of the mask 1, the surface density D of the opaque areas is the ratio between the surface area of ​​the region occupied by the opaque areas and the total surface area of ​​the region. These surfaces can, for example, be evaluated at the lower face 12 of the mask 1, on which the material deposits (for example, chromium) forming the opaque areas are typically made.

[0078] According to the present invention, the plurality of opaque zones comprises at least two networks of opaque zones formed respectively of first opaque zones 100 and second opaque zones 200. It is understood that the plurality of opaque zones may comprise other networks of opaque zones having distinct pitches (see below).

[0079] The first opaque zones 100 are distributed in the horizontal plane XY according to a step network Pb which can be designated first step Pb The first opaque zones 100 have a first characteristic dimension CDL When the first opaque zones 100 are square in shape, CD1 corresponds to the side of this square.

[0080] The second opaque zones 200 are distributed in the horizontal plane XY according to a grid of spacing P2, which can be designated second spacing P2. The second opaque zones 200 have a second characteristic dimension CD2. When the second opaque zones 200 are square in shape, CD2 corresponds to the side of this square.

[0081] The first step P1 and the second step P2 also satisfy the following conditions: P1<PRayieigh et P2> PRayieigh, with:

[0082] [Math.l] o ___ 1 * <1 * Rayleigh “ 1+ <t AA

[0083] o being the coherence and NA the numerical aperture of the light source emitting the radiation 50.

[0084] Rayleigh is designated as the Rayleigh pitch. This is the threshold below which a grating of pitch P does not diffract the incident radiation (zero-order diffraction), and above which it does diffract it (first-order or higher-order diffraction). This constant is specific to the characteristics of the light radiation 50 and the light source emitting it.

[0085] For example, for incident radiation emitted at a wavelength X = 365nm and a source of coherence o = 0.7 and numerical aperture NA = 0.7, PRayieigh is equal to 306 nm.

[0086] Thus, in the areas where the first opaque zones 100 are located, the mask 1 does not diffract the incident radiation 50. The radiation 50 is transmitted to the resin 20 without undergoing diffraction. The transmitted dose depends on the density of opaque zones in these areas. It can therefore be modulated by varying the pitch Pi and the dimension CDi of the first opaque zones 100. The network of first opaque zones thus makes it possible to define a first level of structuring.

[0087] It is possible that all the first opaque zones 100 are arranged according to a grid with a constant pitch Pi and thus form a regular grid (see, for example, [Fig. 2A]). The regions of the resin exposed by radiation 50 passing through the first opaque zones 100 then exhibit, once developed, a planar average profile. By average profile, we mean the profile that does not take into account the nanostructuring described above.

[0088] It is also possible that the step size Pi varies within the network of first 100 opaque zones, while satisfying the condition Pi <PRayieigh- Le profil moyen des régions de la résine insolées par le rayonnement 50 traversant les premières zones opaques 100 n’est alors pas constant. Il peut par exemple présenter une forme générale convexe.

[0089] It is also possible that the micro-structuring is defined by several networks of opaque zones and not only the first network of opaque zones 100. These different networks all having pitches less than PRayieigh are then organized so as to form the desired average profile in the resin.

[0090] The network of first opaque zones 100 - and possible other networks of opaque zones satisfying P <PRayieigh - permet ainsi de définir la forme générale de la résine une fois développée. Ce premier niveau de structuration peut être qualifié de microstructuration.

[0091] Conversely, in areas where the second opaque zones are located, the mask 1 diffracts the incident radiation 50. This diffraction causes the diffracted incident radiation 50 to concentrate on certain areas of the resin 20, leading to locally higher doses of radiation than in other areas. These local variations in radiation doses, once the resin is exposed, create variations in thickness within the resin. This results in a structuring of the resin. This second level of structuring can be described as nanostructuring.

[0092] It is possible that all the second opaque zones 200 are arranged according to a constant pitch network P2 and thus form a regular network.

[0093] It is also possible that the step P2 varies within the network of second opaque zones 200, while verifying the condition P2>PRayieigh-

[0094] It is also possible that the nanostructuring is defined by several networks of opaque zones and not only the second network of opaque zones 200. These different networks all having pitches greater than or equal to PRayieigh are then organized so as to form the desired nanostructuring in the resin.

[0095] The figures also illustrate the case of opaque areas of square shape in the horizontal XY plane, but it is understood that other shapes are possible. The opaque areas can, for example, be rectangular, circular, triangular, hexagonal, oval, or even cross-shaped.

[0096] Several opaque zone configurations will now be described with reference to Figures 2A to 14H.

[0097] Example 1: two regular lattices with P i <P Rayleigh * P 2 P Rayleigh _ et P 2 =2*P 1

[0098] Les figures 2A à 2H illustrent le cas d’un masque 1 comprenant un réseau régulier de premières zones opaques 100 dont le pas Pi vérifie Pi<PRayieighainsi qu’un réseau régulier de deuxièmes zones opaques 200 dont le pas P2 vérifie P2> PRayieigh- Figure [2A] is a general view of the mask, while Figures 2B and 2C are enlargements of the mask centered respectively on a first opaque zone 100 and a second opaque zone 200. In this example, the second opaque zones 200 each coincide with a single first opaque zone 100. The second opaque zones 200 do not overflow into other first opaque zones 100.

[0099] In this example, the first opaque zones 100 have a square shape with side CD1 and the second opaque zones 200 have a square shape with side CD2.

[0100] In this example, we have also fixed the following condition: P2=2*Pi.

[0101] More specifically, to carry out the simulations, the following values ​​were fixed: Pi = 300 nm, P2 = 600 nm, CD1 = 150 nm and CD2 = 200 nm.

[0102] Figures 2D to 2H are simulation results illustrating the resin obtained after exposure to 50 radiation through mask 1 of [Fig. 2A] and after development. [Fig. 2D] is a top view of the resin layer and [Fig. 2E] a perspective view. Figures 2F and 2G (enlargement of [Fig. 2F]) are cross-sectional views of the resin layer along section AA shown in [Fig. 2D]. [Fig. 2H] is an enlargement of the cross-sectional view of the resin layer along section BB shown in [Fig. 2D].

[0103] It is observed that the regular network of first opaque zones 100 allows for a general plateau shape due to the uniform insolation induced by this regular network. Furthermore, the regular network of second opaque zones 200 creates a regular structuring of this plateau, observable in each of Figures 2D to 2H. Peaks 25 and troughs 26 are thus observed on the surface of the resin layer 20. A peak-to-trough height is defined, measured along the vertical direction Z between the bottom of the troughs 26 and the top of the peaks 25. A first peak-to-trough height hi is measured at section AA ([Fig. 2G]) and a second peak-to-trough height h2 is measured at section BB ([Fig. 2H]). The values ​​hi = 85 nm and h2 = 160 nm are recorded. This demonstrates the nanostructuring caused by the network of second opaque zones 200.

[0104] Example 2: two regular lattices with P i <P Raviejgh ■ P 2 E Ravieigh et P 2 = 3 *Pi

[0105] Figures 3A to 3H illustrate the case of a mask 1 comprising a regular array of first opaque zones 100 whose pitch Pi satisfies Pi <PRayieighainsi qu’un réseau régulier de deuxièmes zones opaques 200 dont le pas P2 vérifie P2> PRayieigh- La [Fig.3A] is a general view of the mask while figures 3B and 3C are enlargements of the mask centered respectively on a second opaque zone 200 and on four first opaque zones 100. In this example, the second opaque zones 200 are each coincided with a first opaque zone 100 and are also partially coincided with the eight immediately adjacent first opaque zones 100.

[0106] In this example, the first opaque zones 100 have a square shape with side CD1 and the second opaque zones 200 have a square shape with side CD2.

[0107] In this example, we have also fixed the following condition: P2=3*Pi.

[0108] More specifically, to carry out the simulations, the following values ​​were fixed: Pi = 200 nm, P2 = 600 nm, CD1 = 118.4 nm and CD2 = 200 nm.

[0109] Figures 3D to 3H are simulation results illustrating the resin obtained after exposure to 50 radiation through mask 1 of [Fig. 3A] and after development. [Fig. 3D] is a top view of the resin layer and [Fig. 3E] a perspective view. Figures 3F and 3G (enlargement of [Fig. 3F]) are cross-sectional views of the resin layer along section AA shown in [Fig. 3D]. [Fig. 3H] is an enlargement of the cross-sectional view of the resin layer along section BB shown in [Fig. 2D].

[0110] As in the previous example, the regular network of first opaque zones 100 allows obtaining a general plateau shape and the regular network of second opaque zones 200 a regular structuring of this plateau observable on each of the figures 2D to 2H. This time we note hi=600 nm ([Fig.3G]) and h2 = 614 nm ([Fig.3H]).

[0111] The two preceding examples illustrate how it is possible, by imposing that P2 is a multiple of Pi (P2=2*P1,P2=3*P1...), to create a regular nanostructure, with peaks 25 of the same height over the entire surface of the resin 20.

[0112] Example 3: two regular lattices with P i <P Ravieigh ■ P 2 E Ravieigh _ et P 2 = 2^5 *Pi

[0113] Figures 4A to 4E illustrate the case of a mask 1 comprising a regular array of first opaque zones 100 whose pitch Pi satisfies Pi <PRayieighainsi qu’un réseau régulier de deuxièmes zones opaques 200 dont le pas P2 vérifie P2> PRayieigh- Fig. 4A is a general view of mask 1 while Fig. 4B is an enlargement of mask 1 centered on a second opaque zone 200. In this example, the second opaque zones 200 are, alternately, partially coincident with four or six first opaque zones 100 (see figures 4A and 4B: Fig. 4B is for example centered on a second opaque zone 200 coincident with four first opaque zones 100).

[0114] In this example, the first opaque zones 100 have a square shape with side CD1 and the second opaque zones 200 have a square shape with side CD2.

[0115] In this example, we have also fixed the following condition: P2=2.5*Pi.

[0116] More specifically, to carry out the simulations, the following values ​​were fixed: Pi = 200 nm, P2 = 500 nm, CD1 = 118 nm and CD2 = 295 nm.

[0117] Figures 4C to 4E are simulation results illustrating the resin obtained after exposure to 50 radiation through mask 1 of [Fig. 4A] and after development. [Fig. 4C] is a perspective view of the resin layer. Figures 4D and 4E are cross-sectional views of the resin layer along section AA and section BB respectively, as shown in [Fig. 4A].

[0118] As in the previous examples, the regular network of first opaque zones 100 makes it possible to obtain a general plateau shape and the regular network of second opaque zones 200 a regular structuring of this plateau observable on each of the figures 4C to 4E.

[0119] Due to the condition P2=2.5*Pi, we observe main peaks 25 and secondary peaks 25', lower than the main peaks 25. According to the AA section, we thus define a peak-to-trough height hi for the main peaks 25 (hi = 247 nm) and a peak-to-trough height hf for the secondary peaks 25' (h / = 163 nm).

[0120] This example thus illustrates how it is possible, by imposing that P2 is a multiple of Pi modulo 0.5*Pi (P2=2.5*P1,P2=3.5*P1...), to create a regular nanostructure, with peaks 25, 25' of two different heights on the surface of the resin 20.

[0121] Example 4: three regular lattices with P AT <P Ravieigh ^J^^Ps^P Rayleigh _ et P 2 = 2ÎPi__etP3 = 3ÎPi

[0122] Figures 5A to 5E illustrate the case of a mask 1 comprising a regular array of first opaque zones 100 whose pitch Pi satisfies Pi <PRayieighainsi qu’un réseau régulier de deuxièmes zones opaques 200 et un réseau régulier de troisièmes zones opaques 300 dont les pas respectifs P2 et P3 vérifient P2> PRayieighet P3>P Rayieigh- La [Fig.5A] is a general view of mask 1 while la [Fig.5B] is an enlargement of mask 1 centered on a third opaque zone 300.

[0123] In this example, the first opaque zones 100 have a square shape with side CD1, the second opaque zones 200 have a square shape with side CD2 and the third opaque zones 300 have a square shape with side CD3.

[0124] In this example, the following conditions were also set: P2 = 2*Pi and P3 = 3*Pi.

[0125] More precisely, to carry out the simulations, the following values ​​were set: Pi = 200 nm, P2 = 400 nm, P2 = 600 nm, CD1 = 118 nm, CD2 = 236 nm and CD3 = 355 nm.

[0126] Figures 5C to 5E are simulation results illustrating the resin obtained after exposure to 50 radiation through mask 1 of [Fig. 5A] and after development. [Fig. 5C] is a perspective view of the resin layer. Figures 5D and 5E are cross-sectional views of the resin layer along section AA and section BB respectively, as shown in [Fig. 5A].

[0127] As in the previous examples, the regular network of first opaque zones 100 makes it possible to obtain a general plateau shape. The regular structuring of this plateau, observable in each of Figures 5C to 5E, is this time due to the regular network of second opaque zones 200 as well as the regular network of third opaque zones 300.

[0128] The presence of two opaque zone networks with a pitch greater than the Rayleigh number allows for a more complex nanostructure than in the case of a single opaque zone network satisfying this condition. In particular, we observe main peaks 25 and secondary peaks 25', which are lower than the main peaks 25.

[0129] This example thus illustrates how it is possible, by using several networks of opaque zones having a pitch greater than the Rayleigh pitch, to create a regular nanostructure, with peaks 25, 25' of different heights on the surface of the resin 20.

[0130] Example s _ 5, 6, 7 and 8 irregular network with local increase in pitch

[0131] Figures 6A to 6D illustrate a mask 1 ([Fig. 6A]) whose density of opaque areas is modulated so that, once developed, the resin has a dome shape (Figures 6B, 6C, 6D). The following three examples combine this principle with the principle of the present invention to carry out nanostructuring on a first dome-shaped structure.

[0132] Figures 7A to 7E illustrate the case of a mask 1 comprising a network of first opaque zones 100 whose variable pitch Pi satisfies Pi <PRayieighdans tout le réseau.Le masque 1 comprend par ailleurs un réseau de deuxièmes zones opaques 200 dont le pas P2 vérifie P2> PRayieigh.

[0133] In this example, the first opaque zones 100 have a square shape with variable side length CD1, and the second opaque zones 200 have a square shape with possibly variable side length CD2. Furthermore, CD2 is larger than CD1 in this example.

[0134] Figure 7A is a general view of the mask. Figures 7B to 7E are simulation results illustrating the resin obtained after exposure to 50 radiation through mask 1 of Figure 7A and after development. Figure 7C is a perspective view of the resin layer and Figure 7B is a side view. Figures 7D and 7E are cross-sectional views of the resin layer along section AA and section BB respectively, as shown in Figure 7A.

[0135] The network of first opaque zones 100 provides a general dome shape, and the network of second opaque zones 200 results in a nanostructure of the dome, observable in each of Figures 7B to 7E. The fact that, in this example, CD2 is greater than CD1 induces a nanostructure in the form of peaks 25. These peaks 25 are protruding from the general dome shape induced by the network of first 100 opaque zones.

[0136] Two other very similar examples are illustrated in figures 8A to 8D on the one hand and 9A to 9D on the other hand. These examples differ from the previous example in the positioning of the second opaque zones 200 on mask 1. In the example illustrated in Figures 8A to 8D, the second opaque zones are distributed regularly across the entire surface of mask 1. The simulation results (Figures 8B, 8C, 8D) show the formation of as many peaks 25 as there are second opaque zones 200. In the example illustrated in Figures 9A to 9D, the second opaque zones 200 are aligned along axes parallel to a diagonal of mask 1. The simulation results (Figures 9B, 9C, 9D) show the formation of as many peaks 25 or crests 25 as there are rows of second opaque zones 200. In both cases, nanostructuring is added to the dome-like microstructuring induced by the network of first opaque zones 100.

[0137] Example 9: Irregular network with local decrease in pitch

[0138] Another example is illustrated in Figures 10A to 10D ([Fig. 1OA]: general view of the mask, [Fig. 1OB]: perspective view of the exposed and developed resin, Figures 10C and 10D: views along sections AA and BB). It differs from the two previous examples in that CD2 is smaller than CD1. The nanostructuring caused by the second opaque zones results this time in hollows 26. These hollows 26 are set back from the general dome shape induced by the network of first opaque zones 100.

[0139] Example 10: Superposition of an irregular lattice with P i <p raviejgh et d’un réseau régulier avec p 2>P Rayleigh

[0140] Figures 1 IA to 11F illustrate the case of a mask 1 comprising an irregular array of first opaque zones 100 whose variable pitch Pi satisfies Pi <PRayieigh sur tout le réseau ([Fig. 1 IB]), ainsi qu’un réseau régulier de deuxièmes zones opaques 200 dont le pas P2 vérifie P2> PRayieigh ([Fig.l IA]). The [Fig.l IC] is a general view of the mask, which corresponds to the superposition of the two networks illustrated in figures 11A and 11B.

[0141] In this example, the first opaque zones 100 have a square shape with variable side CD1 and the second opaque zones 200 have a square shape with side CD2.

[0142] Figures 11D to 1IG are simulation results illustrating the resin obtained after exposure to radiation 50 through mask 1 of [Fig. 1IC] and after development. [Fig. 1D] is a perspective view of the resin layer 20. [Fig. 1E] is a cross-sectional view of the resin layer along section AA shown on [Fig. 11C]. Figures 11F and 11G (enlargement of [Fig. 11F]) are cross-sectional views of the resin layer along section BB shown on [Fig. 1 IC].

[0143] The network of first opaque zones 100 allows obtaining a general dome shape and the network of second opaque zones 200 a nanostructuring of the dome (see peaks 25) observable on each of the figures 11D to 11F.

[0144] It is also noted that the relative arrangement of the opaque zone networks causes strong transmission of radiation 50 at the center of the resin layer 20, thus locally inducing a thin resin layer (see [Fig. 1F] in particular: thickness of 515 nm). The resulting hollow 26 defines an intermediate structuring level that can be exploited to create certain complex shapes.

[0145] Example 11: Superposition of an irregular lattice with P i <p raviejgh et d’un réseau régulier en forme de croix avec p 2>P Rayleigh

[0146] Another very similar example is illustrated in Figures 12A to 12F. In this example, the second opaque zones 200 are not regularly distributed over the entire surface of mask 1 as in the previous example, but are distributed in such a way as to form a cross (see [Fig. 12A]). Mask 1 ([Fig. 12C]) is thus formed by the superposition of this regular cross-shaped network satisfying P2>PRayieigh ([Fig. 12A]) and the irregular network of first opaque zones satisfying Pi <PRayieigh-

[0147] The simulation results show not only the dome microstructuring induced by the first network of opaque zones, but also a nanostructuring of this dome whose shape follows the general shape of the network of second opaque zones 200 (see on [Fig.12D] the ridges 25 also forming a cross).

[0148] Fig. 12E is a cross-sectional view of the resin layer along section AA shown in Fig. 12C. Fig. 12F is a cross-sectional view of the resin layer along section BB shown in Fig. 12C.

[0149] Example 12: Superposition of an irregular lattice with P i <p rayleigh et de deux réseaux réguliers avec p 2 . 3>P Ravieigh – one of which is cross-shaped

[0150] Another example is illustrated in Figures 13A to 13G. Compared to the previous example, a regular network of 300 opaque third zones whose step P3 satisfies P3 >PRayieigh ([Fig.13B]) has been added.

[0151] Again, the network of first opaque zones 100 gives a general dome shape to the resin 20, while the two networks of opaque zones with a pitch greater than the Rayleigh spacing induce nanostructuring of this dome. The regular network of the third zone induces the presence of regular peaks over the entire surface of the resin, while the regular cross network induces a structure also in the shape of a cross (see [Fig.l3E] in particular).

[0152] Through the different embodiments described above, it appears that the present invention allows the formation in a layer of photosensitive resin of a double structuring according to various patterns.

[0153] The invention is not limited to the embodiments previously described and extends to all embodiments covered by the invention.

Claims

Demands

1. A greyscale lithography mask (1) for diffracting radiation from a photosensitive resin (20), the radiation having been emitted by a light source having a coherence of 0 and a numerical aperture of NA, the radiation having a wavelength of X, the mask (1) extending mainly along a horizontal plane (XY) defined by a first direction (X) and a second direction (Y), the horizontal plane (XY) being perpendicular to a principal direction of the radiation from the photosensitive resin (20) through the mask (1), the mask (1) comprising a plurality of areas opaque to the radiation, the plurality of opaque areas comprising first opaque areas and second opaque areas,the first opaque zones being organized according to a grid of steps Pi in the horizontal (XY) plane and the second opaque zones being organized according to a grid of steps P2 in the horizontal (XY) plane, such that Pi<PRayieigh et P2> Rayleigh, with n __L 1 Rayleigh ~ l+o- NA,

2. Mask (1) according to the preceding claim, wherein the first opaque areas are substantially identical to each other.

3. Mask (1) according to claim 1, wherein the first opaque areas have distinct dimensions from each other.

4. Mask (1) according to any one of the preceding claims, wherein the second opaque areas are substantially identical to each other.

5. Mask (1) according to any one of the preceding claims, wherein some of the first opaque areas and the second opaque areas are at least partially confused.

6. Mask (1) according to any one of the preceding claims, wherein P2=2*m*Pi, m being an integer.

7. Mask (1) according to any one of claims 1 to 5, wherein P2=3*m*Pi, m being an integer.

8. Mask (1) according to any one of claims 1 to 5, wherein P2=2.5*m*Pi, m being an integer.

9. Mask (1) according to any one of the preceding claims, wherein the plurality of opaque areas further comprises

10.

11.

12.

13.

14.

15.

16. third opaque zones organized according to a P3 step network in the horizontal (XY) plane, P3 being distinct from Pi and P2. Mask (1) according to the preceding claim, wherein P3>PRayieigh-Mask (1) according to any one of the two preceding claims, wherein P3=3*n*Pi, n being an integer. Mask according to any one of the preceding claims in which the plurality of opaque zones admits at least one first plane of symmetry perpendicular to the horizontal plane. A mask according to the preceding claim, wherein the plurality of opaque zones admits at least one second plane of symmetry perpendicular to the first plane of symmetry and to the horizontal plane. A mask according to any one of the preceding claims, wherein P1 is less than or equal to 300 nm, for example, equal to 200 nm. A mask according to any one of the preceding claims, wherein P2 is greater than or equal to 400 nm, for example, equal to 400 nm, 500 nm, or 600 nm. A process for exposing a photosensitive resin (20) comprising the following steps: • provide a photosensitive resin (20), • expose the photosensitive resin (20) to insolation radiation emitted by a light source having a coherence θ and a numerical aperture NA, the insolation radiation having a wavelength X, the exposure of the photosensitive resin (20) to insolation radiation through a mask (1) according to any one of the preceding claims.

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