Deposition Process Based on Stencil Mask and Application to the Fabrication of Tags Supporting Multi-Functional Traceable Codes

Abstract

A chemical gas phase deposition process comprises steps of providing a high vacuum chamber, and inside the high vacuum chamber: positioning a substrate surface; positioning a mask parallel to the substrate surface, whereby the mask comprises one or more openings; adjusting a gap of determined dimension between the substrate surface and the mask; and orienting a plurality of chemical precursor beams of at least one precursor species towards the mask with line of sight propagation, each of the plurality of chemical precursor beams being emitted from an independent punctual source, and molecules of the chemical precursor pass through the one or more mask openings to impinge onto the substrate surface for deposition thereon. At least a part of the chemical precursor molecules decompose on the substrate surface at a decomposition temperature. The process further comprises adjusting a temperature of the substrate surface greater or equal to the chemical precursor molecule decomposition temperature, thereby remaining greater than a mask temperature, and maintaining the mask temperature below the decomposition temperature, thereby causing a decomposition of the chemical precursor and a growth of a film on the substrate surface, but not on the mask; and heating the substrate surface using a heating device.

Claims

1. A tag device comprising a multi-functional material thin film, comprising a plurality of structures that provide a plurality of independent physical quantities, each of which is patterned to the intent of being measured by one or more measuring techniques, wherein each of the plurality of structures exhibit a specific signal in response to a selected measurement technique, wherein each of the plurality of structures has an outer size in the order of nanometres to centimetres.

2. The tag device of claim 1, wherein the plurality of structures comprises a plurality of three-dimensional (3D) structures of different thickness and sizes, wherein each of the plurality of 3D structures displays a plurality of varying properties depending on the chemical composition, size, shape or interface combinations of heterostructures.

3. The tag device of claim 2, wherein the three-dimensional (3D) structures are 3D dots, wherein each dot provides hundreds of different values.

4. The tag device of claim 2, wherein said varying properties are at least one of: colour iridescence, reflectivity, light scattering, wettability, electrical conductivity, piezoelectricity, ferroelectricity, magnetism.

5. The tag device of claim 1, wherein structures having size at different scales are present on the same tag.

6. The tag device of claim 1, wherein the multifunctional material thin film is an oxide thin film, or a semiconductor material thin film or a ceramic thin film.

7. The tag device of claim 1 comprising a partition arranged with a plurality of regions, each region comprising structures of different sizes and/or providing physical quantities of different nature, that can be measured by different readers; wherein the tag device preferably comprises more than four regions.

8. The tag of claim 7, wherein one of the plurality of regions has overt authentication features, one has covert anti-counterfeiting features, one has forensic anti-counterfeiting feature, one has power generation functionality, one or more regions have ultra-covert authentication features enabled by a plurality of possible reading methods.

9. The tag of claim 7, wherein one of the plurality of regions display uniform or graded properties taken amongst the list comprising: thickness, colour and electrical conductivity, said properties being the properties of a material that are further modifiable by light irradiation or by a chemical process to achieve additional features that contribute to enhance traceability, anti-forgery or cryptographic functionalities.

10. The tag device of claim 8, wherein the overt authentication feature is a holographic feature.

11. The tag device of claim 7, wherein each region comprises a plurality of structures at various scales, wherein each of the plurality of regions display different functional properties that can be read through different reading techniques within the same region, wherein in each region are embedded from more than 1 up to millions of codes, preferably wherein a first region can be identified by naked eye and comprises structures having a size in the order of from millimetres to centimetres, a second region can be identified by a reader and comprises structures having a size in the order of from 10 micrometre to below 1 millimetre, a third region comprises structures having a size in the order of from 1 to 10 micrometres, and at least a fourth region comprises structures having a size in the order of from 1 nanometre to below 1 micron.

12. The tag device of claim 1, wherein the plurality of independent physical structures are obtained by a chemical gas phase deposition process comprising the steps of: providing a high vacuum chamber; positioning a substrate surface inside the high vacuum chamber; positioning a mask parallel to the substrate surface, the mask including one or more openings; providing a gap of determined dimension between the substrate surface and the mask to introduce a temperature difference between the substrate surface and the mask, wherein said gap is adjustable; and orienting a plurality of chemical precursor beams of at least one precursor species towards the mask with line of sight propagation, each of the plurality of chemical precursor beams being emitted from an independent punctual source, and molecules of the chemical precursor pass through the one or more mask openings to impinge onto the substrate surface for deposition thereon, at least a part of the chemical precursor molecules decompose on the substrate surface at a decomposition temperature; and adjusting a temperature of the substrate surface greater or equal to the chemical precursor molecule decomposition temperature to remain greater than a mask temperature, and maintaining the mask temperature below the decomposition temperature, thereby causing a decomposition of the chemical precursor and a growth of a film on the substrate surface, but not on the mask, heating the substrate surface using a heating device; wherein the chemical gas phase deposition process is operated under vacuum conditions below 10.sup.5 mbar; wherein the substrate surface is positioned between the heating device and the mask and the distance of the mask to the substrate is smaller than the distance of the mask to the precursor sources.

13. The tag device of claim 12 obtained by the chemical gas phase deposition process in a single step.

14. The tag device of claim 12 wherein the chemical gas phase deposition process further comprises a post deposition process of laser irradiation on at least a part of the film formed on the substrate surface, thereby enabling to selectively pattern at morphological level or at the crystalline phase level.

15. The tag device of claim 12, wherein the chemical precursor molecules are selected form the group consisting of metal alkoxides or derivatives thereof, or beta-diketone, metal alkyls; preferably wherein the chemical precursor molecules are titanium dioxide, titanium tetraisopropoxide, copper bis(2,2,6,6-tetrametyl-3,5-heptanedionate, LINbO.sub.3, or dimethyl zinc.

16. Use of the tag of claim 1 in an authentication process involving a step of reading the tag by naked eye or by an optical reader, said optical reader being preferably selected from the group consisting of a dvd player, a blue ray player, a Smartphone and a digital camera, whereby the tag is illuminated with a plurality of different monochromatic illumination wavelengths or with white light filtered by at least one filter, and/or by an instrument selected from the group consisting of Ohm-meter, spectral reflectometre, spectral Ellipsometre, micro-Raman, AFM, STM reader, wherein each of the reading provides a different output.

17. Use of the tag device of claim 1 in a book-cipher-like encrypting method, comprising providing at least two identical tags, which are unique and not forgeable, wherein one of the two identical tags is used as key-code.

18. A packaging for a tag device according to claim 1, wherein the tag device is provided on a thin metallic foil sealing a container and that is torn apart when the container is open, or wherein the tag device is embedded in polymer foils, or it is directly melted into a material, or it is deposited onto an electronic device.

19. The packaging of claim 18, wherein the tag device is melted into a material, said material being a transparent media, wherein the multifunctional thin film material is capable of withstanding high temperatures and has a high refractive index.

20. The packaging of claim 18, wherein the tag is deposited onto an electronic device, said electronic device being a CMOS camera, a sensor or any other integrated circuit with direct vertical/monolithic integration.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0131] The invention will be better understood through the detailed description of example embodiments of the invention and in light of the accompanying FIGS., wherein

[0132] FIG. 1 contains an illustration of a deviation of deposition through stencil mask from the ideal case, due to blurring and clogging;

[0133] FIG. 2 contains a schematic disposition within a vacuum chamber of a substrate heater, a substrate, a mask and a precursor flow distribution unit;

[0134] FIG. 3 shows in a) and b) deposition from two different precursor sources resulting either in separated or superimposed flows leading to either separated or superimposed deposit.; an in c) and d) example of deposits superimposed or not obtained by depositing through a single aperture from 10 neighbouring punctual sources;

[0135] FIG. 4 illustrates different chemical precursor molecule flows as a function of the number of active sources, resulting in different impinging rate gradients and graded growth rates on the substrate;

[0136] FIG. 5 is an illustration of different chemical precursor molecular species for a ternary oxide thin film (3 elements: Ti, Nb, Zr+oxygen) with graded flows, resulting in graded chemical composition across the substrate;

[0137] FIG. 6 contains a graph of a typical growth rate GR obtained from a single precursor decomposition as a function of surface temperature T;

[0138] FIG. 7 illustrates main radiative heat flows exchanged in the deposition system;

[0139] FIG. 8 shows an MF-CODE divided in several regions; and

[0140] FIG. 9 illustrates several examples of known printed codes.

[0141] Same reference numbers will be used throughout the description to designate same of similar features.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS OF THE INVENTION

[0142] FIG. 3 describes the effect of the mask/substrate-to-be-covered gap to deposit 3D structures. Schemas a) and b) shows the deposit from two punctual sources PA and PB through a mask (SM) on a substrate Su through two different openings. Depending on the distance p between apertures, on dimension apertures d and on mask-subtrate gap g, the flows from the two sources can either remain separated (image a) or partially superimpose (image b) or almost fully superimpose. If precursors for different elements are used in the two sources, such deposition process allows obtaining in a single step separated deposits of different elements with different thicknesses, or co-deposition of different elements with varying chemical composition and thickness within the deposit or thin film structure.

[0143] Pictures c) and d) shows TiO.sub.2 deposit AFM profiles for the deposition from 10 neighbouring Ti precursor sources through a single triangular deposit for a substrate mask gap g of about 80 m and a source plane-substrate distance of about 15 cm. For a 1 m triangular opening OM (left image), the deposits from the 10 different sources are separated (image c) while for a 5 m triangular opening, the deposits from the 10 different sources partially overlap. The dimension of the aperture is reported as a white line triangle on the deposit profile for comparison.

[0144] FIG. 2 describes the set-up assembly and the relative disposition of the various components. Within a vacuum-pumped chamber, a radiative substrate heater (RH), a substrate to be deposited on (Su), a (stencil) mask (SM) and a precursor flow distribution system (GD). The precursor flow distribution system is represented here for 3 precursors (labelled PA, PB and PC) and precursor beams are emitted with Knudsen effusion (symbolized as EffK) from a plurality of precursor sources, S.sub.i. Here the sources are represented alternating precursors and disposed on a ring, but any over configuration is acceptable depending on the targeted result. The sources have a small diameter in comparison to the distance h (they are considered as point sources). The gap-mask distance g is small in comparison to the distance precursor source-substrate h. The sources can accommodate different chemical precursor (other number of precursors than the 3 represented here can be used) and can be turned on or off independently.

[0145] FIG. 4 describes, for the example, the system depicted in FIG. 2 for which 18 groups of sources are used alternating for 3 different precursors. Some configurations to achieve chemical precursor flow gradients across the whole substrate simply by shutting on and off some of the sources for a given precursor are reported. Very different distributions can be achieved and only some configurations are reported as examples. The number of active source group, C, is varied from 1 to 6, resulting in different flow gradients with a varied maximal flow ratio, RF, along the major gradient diameter (highlighted in the small 3D-views in each case). If all the six source groups for a given species are turned on, a homogeneous deposition results. The main graphic shows the modelled precursor flow (line) as a function of the position along the major flow gradient diameter on the substrate, with additionally, some scaled deposit thickness measurements (obtained experimentally in this configuration. Some photographs of these deposited wafers are shown at the top of the picture).

[0146] FIG. 5 shows an example of a ternary graded deposit obtained on a wafer, from 3 precursors (titanium tetra-isopropoxide, zirconium tetra-butoxoxide, niobium tetra-ethoxide dimethyl aminoethoxide). The map on the left corresponds to the deposit thickness. On the ternary diagram represented on the right, experimentally measured chemical composition are presented for the 4 different precursor diameters highlighted on the thickness map. The full lines correspond to flow model simulation while dots are experimental points. Such results demonstrate that the presented system is suitable to achieve combinatorial production of coating/devices all with different properties in a single deposition step.

[0147] FIG. 6 presents a typical growth rate variation (GR) as a function of the surface temperature (T) on which the deposition takes place. Generally, below an offset temperature Tlim, no deposition takes place (regime label: ND). With increasing T, a chemical reaction limited regime (regime label: CL) is achieved, in which the growth rate is independent of impinging precursor flow. With further increasing temperature, a mass limited regime (regime label: ML) is achieved: the transition between the chemical reaction limited and the mass transfer limited regime as well as the growth rate in the mass transfer limited regime depend on the impinging precursor flow. The higher the impinging precursor flow

[0148] (F1<F2<F3<F4), the higher the transition temperature and the higher the mass limited growth rate.

[0149] In the present invention, a difference of temperature T is observed between substrate and mask. The ideal case is presented as situation A: a mass transport regime is achieved on the substrate surface at surface Ts(A) (all the chemical precursor molecules are decomposed (growth rate GR(A)) and no deposition (growth rate Gm(A)=0) is achieved on the mask surface at temperature Tm(A) (below Tlim). In this optimal case, diffusion (bouncing of molecules) between the substrate surface and the mask is avoided resulting in optimal resolution with limited (or no) halo blurring effects.

[0150] In a less favoured situation B, deposition occurs also only on the substrate, but in the chemical reaction limited regime, meaning that some unreacted molecules can bounce between mask and substrate, and contribute to blurring.

[0151] In another less favoured situation C, a smaller temperature difference between substrate (temperature Ts(C)) and mask (temperature Tm(C)) is obtained. The deposition occurs both on substrate and mask, but deposition rate on substrate GR(C) is much higher than on mask (Gm(C)).

[0152] FIG. 7 describes the preferred method to obtain a temperature difference between mask and substrate. The substrate is heated by a radiative heater RH, that emits towards the substrate a heat flow E.sub.H. At equilibrium, the substrate reaches a temperature Ts and emits a radiative heat flow Es towards the mask. The mask receives this heat flow on one side and re-emits a heat flow E.sub.M on both side, so that it reaches at equilibrium a temperature Tm smaller than Ts. Tm (in K) is less than 0.9 Ts (in K). The deposition system makes use of liquid nitrogen cooled cryo-panels (CP).

[0153] Same reference numbers will be used throughout the description to designate identical or similar features.

[0154] FIG. 8 shows the MFT-CODE divided in several regions each containing different structures/information at various x-y scales (for example from a few mm to few cm in region 1, from 10 to few hundreds of microns in region 2, from 1 to 10 microns in region 3 and from nano-metric to sub-micrometric scale in region 4), and from nano-metric to several microns in z scales. More regions can be envisaged. Each region could display different functional properties possibly checked by a specific/different measuring/reading device and be attributed to a different specific type of customer. Reading of several multifunctional properties, even within the same region, could be selectively attributed to different customers through different reading techniques.

[0155] More than 1 code up to several millions of codes for smallest features can be embedded in a given region. The MFT-Code should contain in preference a macroscopic region that can be identified by naked eye with, one that can be identified by a highly available reader (smart-phone), and one or more further regions with a higher security level and a huger amount of (encrypted) information.

[0156] The MFT-Code of FIG. 8 is produced with the preferred technique of CB VD.

[0157] In FIG. 8, Region 1 corresponds to structures in x-y from several hundreds of microns to few mm with a z thickness from few nm to several microns. In this region, some structures are visible by naked eyes (ex-letters, numbers, logos, etc. . . . ). They are written as non deposited region or as thicker or thinner deposit than the background, which consists either on an homogeneous deposit or on a graded composition deposit.

[0158] In FIG. 8, Region 2 represents a region where structures with lateral dimensions in the tens of microns scale are produced. These structures can have any shape, different deposits of different shapes can be deposited, fully separated or partially overlapping to generate complex patterns.

[0159] In FIG. 8, Region 3 represents a region where deposits with lateral dimensions in the micrometric scale are produced. Deposits can have any shape, different deposits of different shapes can be deposited, fully separated or partially overlapping. Overlapping structures can form a network.

[0160] In FIG. 8 Region 4 represents a region where deposits with lateral dimensions in the sub micrometric scale are produced.

[0161] Complex colour patterns are achieved and several optical microscope pictures are provided. In Region 1 on the left, we have a vertical varying colour (rainbow pattern due to Bragg mirrors) varying from IR (infra-Red) to UV (Ultra-Violet) spectrum.

[0162] In Region 1 on the right, we have from top to bottom complex patterns in colours with stereo-effects leading to the impression of 3D topography, a photonic crystal with dots of different colours (thickness) with a few microns resolution, a uniform coating. We also have a complex pattern on the edge with varying colours (between 5 to 10 that can be distinguished by naked eye on the picture) and thin film thickness.

[0163] In Region 2 we have different patterns displaying a huge variety of colours and shapes with scales of the order of tens of microns.

[0164] In Region 3 we have different patterns displaying a huge variety of colours and shapes with scales of the order of 1 micron.

[0165] In Region 3 we have different patterns displaying no colour variation (Scanning Electron Microscopy picture) but different shapes with scales below 1 micron.

[0166] The invention provides a process which combines a stencil mask, and more in general a mask, with a chemical precursor in a vacuum deposition process, involving a chemical precursor transported in the molecular flow regime, i.e., with oriented beams, effused by several independent punctual sources that is decomposed on a heated substrate. A temperature dependent chemical reaction leads to precursor decomposition at the substrate surface to form a thin film. The invention has an advantage in that the deposition process is modulated as a function of the precursor flow and the substrate temperature.

[0167] If stencil masks have been extensively used to achieve direct patterned thin films in prior art, none of the prior art processes allows to achieve the advantages of the invention as described in sections A to J. The described configurations of the invention allow a very powerful multi-functional thin film material parallel printing with resolution down to the sub micrometre scale and the possibility to achieve such structures in a very cost effective mass production process that can be reconfigured easily to provide a multitude of different structures and properties on a same substrate surface.

[0168] The CBVD equipment according to the present invention has the additional favourable characteristic, compared to previous standard CBE deposition reactors, consisting of a precursor delivering unit based on the geometrical distribution of many point sources around the substrate, that enables the generation of independently controlled flow gradients for different precursors across the substrate [62]. This competitive advantage enables the deposition of complex (3-Dimensional, multi-elements, chemical composition gradients) structured oxide films, using a stencil mask, in one step [63,64].

[0169] The particularity of the set up described in the invention is that a small band gap g is maintained between the substrate and the mask (see FIG. 2). This gap ensures that there is no direct thermal exchange between substrate and mask, and as the system is maintained under vacuum conditions, thermal exchange by convection is negligible. Consequently, the only thermal exchanges between mask and substrate are radiative. As shown on FIG. 7, the mask receives heat radiative flow from the substrate on one side, and dissipates it on two sides, so at system equilibrium, its temperature Tm is smaller than the substrate temperature Ts. Such a difference in temperature can also be achieved in transient phases (out of thermal equilibrium) such as achieved by pulsed lasers, rapid thermal annealing or as a result of different optical absorption medium of substrate and mask (silicon is transparent to IR, while oxides are not and the reverse is true for visible wavelengths).

[0170] The film deposition on the substrate results from surface decomposition reactions of precursor molecules brought to the substrate as molecular beams. These precursor molecules are typically for oxide deposition metal alkoxides or derivatives (for instance, titanium tetraisopropoxide), -diketone compounds (for instance, copper bis(2,2,6,6-tetramethyl-3,5-heptanedionato), metal alkyls (for instance, dimethyl zinc), etc. . . . . Generally, the deposition growth rate depends on precursor impinging flow and on substrate to be covered temperature as presented in Error! Reference source not found. Therefore, due to the substrate difference between substrate and mask, it is possible to obtain a mass transfer limited deposition on the substrate (i.e. almost all impinging precursor molecules decompose) without any deposition on the mask or very limited one. In the less favoured case of chemical reaction limited growth on the substrate or on insufficient temperature difference between mask and substrate, the deposition rate on the substrate is still much higher than on the mask. The mass transfer regime on the substrate is to be preferred to optimise deposit structure resolution as it limits the number of un-reacted molecules that may bounce between substrate and mask and contribute to a halo deposit around the structure (see FIG. 1).

[0171] The precursor molecules are emitted from small sources that can be considered as punctual from a combinatorial gas delivering system (GD, see FIG. 2). This special design allows the generation of precursor flow gradients on the substrate, which can induce different chemical composition of incident precursor flow at a given substrate point when several precursor compounds are used (see FIG. 5).

[0172] The controlled gap g maintained between substrate and mask allows in combination with stencil mask opening design and position of active precursor sources to obtain different thickness deposits through a single mask apertures or different chemical composition deposits (see FIG. 2).

[0173] Several advantages are further achieved by the inventive process as described in the following sections A to H.

[0174] A.

[0175] The introduction of a gap of controlled dimension between the stencil mask and the substrate surface to introduce a temperature difference between the two surfaces, allows obtaining a growth rate difference between the stencil mask and the substrate surface, up to total deposition selectivity on the substrate. Keeping the stencil mask at a lower temperature than at the substrate surface avoids deposition on the stencil mask, thereby extending the lifetime of the mask, promoting reusability of the mask, and brings the possibility to achieve high aspect ratio patterned thin films as mask apertures are not getting clogged as a function of time.

[0176] B.

[0177] The introduction of the gap of controlled dimension further enables, with a plurality of point-like sources, to obtain different chemical beams emitted in different angular directions from different precursor sources. As a result very complex patterns may be achieved with a single orifice, as all the chemical beam pass through this orifice. Among others, the inventive process allows to respond to a quote of co-deposition of different structures with either different thickness or chemical composition, possibly also achieving controlled chemical composition gradients at different scales down to sub-micrometre scale.

[0178] C.

[0179] Several layers of thermal shielding can be used, by interposing several surfaces between the substrate surface and the stencil mask, to increase temperature gradient and improve selectivity. This improved selectivity can also be achieved by adding blocking precursors blown tangentially to the stencil mask such that they impinge exclusively on the mask surface and not on the substrate.

[0180] D.

[0181] The inventive process achieves a mass transport limited regime on the substrate surface and no deposition on the stencil mask surface is one of the key factors to achieve neat border avoiding diffusion/bouncing of unreacted molecules between the substrate and the stencil mask back surface that can lead to blurring and low resolutions structures. The second key factor is to have point-like sources, whereby source diameter is small in comparison to the distance of the source to the substrate to improve resolution and/or shape of the structures achieved through the stencil mask opening/apertures.

[0182] E.

[0183] Thin films structures achieved through the stencil mask can be varied in size by simple variation of the ratio between g and h, where g is the stencil mask to substrate surface distance and h is the stencil mask to source distance. Modulation during the growth of this distance allows high flexibility in shapes and sizes of the thin film patterns.

[0184] F.

[0185] In a particularly advantageous example embodiment, combinatorial at macro, i.e., full wafer, or sub-micro-level is coupled to the shadow mask deposition process by controlling either chemical flows species impinging rate and/or temperature on the substrate with previously described arrangements to achieve in a controlled way a plurality of very different materials (chemical composition, structures shapes and sizes and interfaces) on the substrate surface. This allows a huge variability of structures depending on the substrate position and flow conditions even with the same mask and improved combinatorial methodology for material properties investigation allowing variation not only at the chemical composition level, but also at the (nano)-size, shape or interfaces interactions level.

[0186] G.

[0187] In a further particularly advantageous example embodiment, a part of the produced thin film is modified by laser irradiation either during deposition or in a post deposition process. In opposition to standard laser marking resulting in a visible or invisible mark, the present irradiation process provides a densification or phase transition resulting in a wider range of functionalities variation, including, but not limited to, optical properties such as optical thickness and/or refractive index, electrical conductivity, wettability, 3D-topography, etc.

[0188] H.

[0189] Different packaging is available. In particular, the tag can be achieved on very thin metallic foils to provide a sealing solution that will be torn apart when a container is open (tamper-evidence solution). In alternative, the tag can be embedded in polymer foils if a more robust solution is required or directly melted into a material such a glass bottle or different other transparent media as the tag can withstand high temperatures and the thin film material has a higher refractive index (n=2.4 for TiO.sub.2 for example in comparison to n=1.5 for polymers or glass). Finally, the tag deposition process is CMOS compatible and/or standard microelectronics processes compatible. Hence the process can be achieved directly onto a device such as a CMOS camera, a sensor or any other integrated electronic/photonic/etc circuit with direct vertical/monolithic integration. This process is highly desirable to achieve embedded cyber-security functionality and connection to the internet with cryptography protocols. This description is added as an additional advantage, but should have been trivial from an expert in the field from following description.

[0190] I.

[0191] The multifunctional material constituting the tag can provide further functionalities such as sensing, energy harvesting or more complex functionalities. Among others, we disclose the possibility to use the tag to do chemical composition analysis of samples such as liquids looking at the pattern/properties variation of the tag in contact with such a sample. Hence the features of the tag can be directly integrated within more complex devices in a single step further reducing production costs shared between several functionalities. This description is added as an additional advantage, but should have been trivial from an expert in the field from following description.

[0192] J.

[0193] The multifunctional material properties can be read by a plurality of different readers/analysis methods. The exact reading technique can be made private and could evolve with time or as a function of different customers/users. Because of this evolving reading technique, we coined a new technical term, namely an ultra-covert solution that will make more difficult forgery. This description is added as an additional advantage, but should have been trivial from an expert in the field from following description.

[0194] The invention generally provides a tag device, which equivalently designates a code, a tag, an etiquette, a mark, or a dedicated device that will be called MFT-CODE (Multi-Functional Traceable Code) in the following, merging the concept of the different tracking codes (QR, Datamatrix, flash-code among others) with authentication and the security concept of anti-counterfeiting features. Unlike previously discussed state of the art for traceability, i.e., tracking codes that have only a 2 dimensional pattern and display a limited colour variation, mainly black and white, we provide a solution with increased dimensionality such as a 3D topography, with z variation, and a plurality of different functionalities/properties mapping based on various physical and chemical measurable properties (iridescent colours, reflectivity variation, light scattering, wettability variation, electrical conductivity variation, piezoelectricity, ferro-electricity, magnetism, and most of the physical/chemical properties displayed by multi-functional materials). Our advantage is that a single layer is required and that the various effects cannot be separated in various independent solutions, thus providing a higher degree of security.

[0195] The proposed approach to achieve the described MFT-CODE is through the use of a high-resolution patterned thin film, layer, or coating of a multi-functional material such as a semiconductor, ceramic or other material on a substrate. A preferred disclosed solution is with a multi-functional oxide thin film.

[0196] Such properties mapping will provide a highly secure solution that displays most of the anti-counterfeiting features today available on the market, but simultaneously, to avoid duplications of the MFT-CODE or counterfeited lecture of the same and furthermore contains a huge quantity of organized information in its high-resolution pattern.

[0197] The proposed MFT-CODE is thus able to address all the challenges reported for traceability, security and cyber-security in a single object: it contains a huge quantity of information, obtained by miniaturization of organized patterns and/or structures with lateral dimensions from cm size down to the sub-micrometre or even down to nano level, provides a high level of security, most of the available existing solutions for anti-counterfeiting tags, and provides a hardware cryptographic key solution able to provide in a fraction of second several thousands/millions of different codes in a highly secured way. A possible encrypting method is related to book cipher where two identical tags are used as code-keys, but other methods are also available.

[0198] An important feature of the MFT-CODE according to the invention is the possibility to achieve different size and/or functions of the features distributed on a partition of the MFT-CODE allowing different reading techniques, privileging either availability, cost, and/or transportability of the reader, or increased security depending on the investigated region of the MFT-CODE.

[0199] Further from all these security solutions, we may also propose an investigation related to the size of the proposed mark and/or patterns, namely a multi-reader solution. Actually, there are all the possible sizes available: larger ones are of interest for naked eye identification, but nearly no information is contained at this scale. On the opposite approach, nano solutions are used to achieve invisible codes that can be identified only with special equipment, in order to increase security. However, such small marks/tags can be very complicated to find if no reference is provided. The idea to provide in a single solution different scales may help in reinforcing the security and in finding rapidly where the information/security tag is with simple visual references embedded in the MFT-CODE.

[0200] In particular, referring to FIG. 8 which represents an MFT-Code, the MFT-Code comprises a Region 1 where a uniform deposit or a deposit with macro-graded properties is achievedwith regards to one up to all the displayed functional propertiesthat can be modified in a second processing step. Said modifications in a second step could be achieved by beam irradiation (laser, electron, ions, etc. . . . ) or by any other method (mechanical machining, chemical etching or functionalisation, or any other method) to modify selectively one or more of the functional properties of the MFT-CODE. The preferred disclosed modification technique is through induced crystalline phase transition or by chemical composition changing of the MFT-CODE material. Said region would be principally used for further customisation of the MFT-CODE in a second step by a different actor not involved in the main tag manufacturing. Laser-induced phase transition is the preferred method. In particular, this region is highly suitable to embed a coloured aesthetic logo or a tracking number/code. Naked eye patterns such as holographic or other diffractive features may also be embedded using optical properties variation related to crystalline phase variation and/or material densification or chemical composition shifts. In particular, varying selectively the multi-functional film optical thickness (densification through crystalline phase shift) could allow achieving a wavelength reflected light intensity selectivity/modulation with increased sensitivity to a wide number of different selected wavelengths. In other words, modulation of the irradiation (or other additional process) conditions to modify the thin film leads to different patterns with different wavelength sensitivity. Electrical conductivity modulation may also be achieved for example with TCO that display a different conductivity as a function of the crystalline phase (like TiO.sub.2 doped with Nb where anatase displays a different electrical conductivity in comparison to rutile or with other materials like ZnO:Al or vanadium oxide phase transition). Several other functionalities like catalysis or bio-compatibility also strongly depend on the phase for a given material.

[0201] LiNbO.sub.3 is also an interesting material due to its ability to be used as holography data storage medium.

[0202] The preferred reader for this Region 1 is a Smartphone, but naked eye is also suitable to identify features such as colour patterns. Also a multi-meter, e.g., ohm-meter, or any other low cost reader, such as CD or DVD readers, is suitable to identify other pattern properties. Droplets of various liquids may also be used to test the surface wettability or the catalytic properties such that the result is made apparent to the naked eye or to a Smartphone or other low cost readers or measuring devices.

[0203] A further reader could be provided by any microelectronic device in which the tag could be integrated (vertical integration or by different packaging solution).

[0204] Referring again to FIG. 8, in the second, third and fourth (and any further number) regions, i.e., Region 2, Region 3 and Region 4, a higher resolution of the pattern is achieved with progressive resolution improvement. A parallel printing method is proposed to avoid limited serial printing/marking techniques throughput that are getting time consuming and less precise and cost efficient as the features scale decreases. In this region, the pattern is preferably achieved by direct growth of a multi-functionally patterned thin film with an additive printing method and/or technology. In particular, we propose to use shadow masks in combination with a vacuum deposition technique involving chemical precursor decomposition to achieve selective deposition through the control of either energy or impinging species flows on the substrate. In comparison to the state of the art, we propose to achieve a cost effective mass production of all-different MFT-CODES with a bijective relation between a code and an object/concept/person/information (one code that is unique to each single object). This feature cannot be achieved in prior art with parallel printing as a different mask should be manufactured for each

[0205] MFT-CODE resulting in an extremely expensive manufacturing process. Instead of varying the mask feature, the invention proposes to vary either the provided energy to induce precursor deposition or the impinging species (precursor, co-reactive species) flows on the substrate that can be easily modulated in the disclosed configuration, achieving a combinatorial generation of the MFT-CODES and of their properties.

[0206] At high resolution (sub-micron), the MFT-CODE displays similar features as CD or DVD, but instead of having a binary code, the multi-functionality allows to achieve hundreds of different values for each dot leading to improved security and number of arrangements.

[0207] At nanometre level, self assembly (auto-organized) features could also be introduced exploiting precursor diffusivity variation as a function of the deposition conditions (energy and chemical precursor flows, temperature, etc. . . . ) to embed further security into the patterns. In opposition to the nano-inks achieved patterns, regular patterns could be obtained. This is considered as an advantage as nano-inks only provide random nano-patterns containing no information or security in comparison to ordered patterns. Such self-assembly effects have a huge impact on functional properties such as light diffusion, catalytic activity, etc. Furthermore, they cannot be easily identified by reverse-engineering and improve the number of the parameters/combinations to something beyond analysis investigation.