FR3037002A1 - ELECTRONIC DOCUMENT COMPRISING A MICROCIRCUIT AND A DEVICE DETECTING MICROWAVE EXPOSURE - Google Patents

Abstract

Electronic document (10) comprising a microcircuit (8) and a device (1) able to detect exposure to a dose of microwave radiation less than a dose affecting the microcircuit (8).

Description

The present invention relates to an electronic document comprising a microcircuit and a device adapted to detect exposure to microwave radiation, in order to detect an exposure of the microcircuit to microwave radiation. In the field of electronic documents, it is known to integrate a microcircuit. The term "electronic document" means documents or objects intended to contain information relating to the user, this information being written on the document itself and on the microcircuit. Such a microcircuit conventionally offers secure functions of information storage and calculation. These functions are typically used to store confidential information, such as information about the bearer of said document, biometric material or even cryptographic material for carrying out checks to test the integrity, authenticity and provenance of the document. secure and data it stores. A known application of such an electronic document is the production of an identity document, such as an identity card, or a transport document, such as a passport, associated with a carrier, and which makes it possible to authenticate said carrier, during an identity check, for example when crossing a border. Controls using a microcircuit provide a high level of security and moreover, advantageously, to automate the performance of controls. Therefore, such controls are increasingly used. Now it appears that exposure of such a microcircuit to microwave radiation, can permanently affect the microcircuit, and a dose of microwave radiation adapted can make the microcircuit inoperative. This is done moreover without otherwise visibly affecting the electronic document integrating the microcircuit. This can be exploited by a fraudster who is thus able to render inoperative the microcircuit of an electronic document 3037002 2 and simply by means of a utensil spilled, in that it is present in most kitchens. In the case of application of an identity document, a faulty microcircuit does not prohibit the verification of identity or crossing, for example the crossing of the border. On the contrary, the procedure generally provides that the identity verification is, in such a case, carried out on the basis of "manual" controls only, without the "electronic" controls using the microcircuit. Also, an inoperative microcircuit is detrimental, in that the level of security attached to the identity verification is very much reduced in such a case. Also, it is highly sought for an electronic document comprising a microcircuit and a device capable of detecting exposure to microwave radiation of the device and thus the microcircuit. The device of such a document is typically able to be modified by exposure to microwave radiation and to keep a trace, persistently, and advantageously visible to the naked eye. Advantageously, the device is shaped to react to a dose of microwave radiation less than a dose affecting the microcircuit. Moreover, since exposure to microwave radiation is not necessarily fraudulent, a characterization of the dose of microwave radiation received is advantageous in that it makes it possible to evaluate the intention behind the exposure. . The invention relates to an electronic document comprising a microcircuit and a device capable of detecting exposure to a dose of microwave radiation less than a dose affecting the microcircuit. According to another characteristic, the device comprises a sensitive element made of an electrically conductive material, able to be modified by exposure to a said dose. According to another characteristic, the sensitive element is disposed near the microcircuit, preferably superimposed on the microcircuit. According to another characteristic, the microcircuit is characterized by a fineness of etching, and the sensing element has at least one characteristic dimension less than or equal to a hundred times the fineness. According to another characteristic, the characteristic dimension is the thickness, and said thickness of the electrically conductive material is between a few nanometers and a few micrometers, preferably between 10 nm and 4 μm. According to another characteristic, the sensing element comprises, in a direction transverse to the thickness, at least one contour comprising at least one acute projection, a projection having at least one characteristic dimension. According to another characteristic, the sensitive element 15 further comprises a second projection, and the characteristic dimension is the distance between the projections. According to another characteristic, the sensitive element comprises at least two protrusions, having stepped respective extension dimensions, in order to characterize a dose of microwave radiation received. According to another characteristic, at least one contour is shaped according to a fractal shape. According to another characteristic, the sensing element comprises, in a direction transverse to the thickness, at least two tracks, and the characteristic dimension is the spacing between said at least two tracks and / or the width of a track. According to another characteristic, the sensitive element comprises a plurality of tracks arranged concentrically.

According to another characteristic the sensitive element comprises a metallic material having a high electrical conductivity, preferably a high thermal conductivity, and still preferably selected from Cu, Au, Ag.

According to another characteristic, the device further comprises a heat-sensitive component disposed near the sensitive element. According to another characteristic the device further comprises a control, reproducing, at least partially, the shape of the sensitive element, and insensitive to said microwave radiation. According to another characteristic, the device further comprises a second sensitive element, capable of being modified by exposure to a dose of microwave radiation greater than a dose affecting the microcircuit. The invention further relates to a method of manufacturing such an electronic document wherein the sensing element is obtained by inkjet printing with a conductive ink. Other characteristics, details and advantages of the invention will emerge more clearly from the detailed description given below for information in connection with drawings in which: FIG. 1a shows an electronic document, and FIG. An exploded view of such a document, - Figure 2 illustrates an embodiment, based on at least one projection, - Figures 3-5 illustrates the erosion of the projections and the staging principle, - Figure 6 illustrates a principle of producing a fractal curve, - Figures 7 and 8 illustrate two successive refinements of a fractal curve, Figure 9 illustrates another embodiment, based on tracks, - Figure 10 illustrates a mode of realization, comprising concentric tracks.

Before starting, the notation used for the reference signs should be specified. The same number represents the same element. A single digit can be used to designate an element generically. This figure 35 may be supplemented by a letter or a second digit in order to specify a particular occurrence of such an element. Thus the number 4 is used to designate a projection. A protrusion 4 generically represents all the protrusions. The projection 4a, 4i or 42 designates a particular declination of a projection. The same letter, respectively the same second number, refers to the same declination. Thus 6 generically denotes the extension dimension of a projection 4. 6b, respectively 63, denotes the extension dimension of the projection 4b, respectively 43. The invention relates to an electronic document 10. An example of such an electronic document is shown in FIGS. 1a and 1b. This is a card 10 comprising a body formed of a plurality of plastic layers 101 to 106. A module 30 is integrally secured in a cavity 31 of the body. This module comprises a microcircuit 8 and metal contacts 32 serving as an interface with an external terminal. According to the invention there is added to the electronic document 10 a device 1 able to detect exposure to microwave radiation. An electronic document 10 is typically based on a thin support, generally formed of at least one sheet of paper, cardboard, plastic or equivalent material capable of being formed into a sheet. In addition to at least one microcircuit 8, it may further comprise an antenna 9 composed of conductive turns and inserted into the support.

As previously described, a microcircuit 8 can be degraded, possibly to the point of rendering it unusable, by exposure to microwave radiation. Also, an electronic document 10 is advantageously provided with at least one device 1 capable of detecting that the device 30 1, and by extension the microcircuit 8, has been exposed to microwave radiation. Without exposure, the cause of a failure or failure of the microcircuit 8 may come from another cause. If it is detected that the device 1 has been exposed, it can be assumed that the microcircuit 8 has also been subjected to exposure and presumably to the same exposure. The device 1 may be disposed at any point of the electronic document 10. A conventional source of microwave radiation, in the form of a domestic microwave oven, does not allow to achieve highly focused radiation. Moreover, the mode of use of such an oven, requiring the global insertion of the entire electronic document leads to an overall exposure. Also an exposure affecting the microcircuit 8 is likely to affect the entire electronic document 10, including the device 1. However, the previous assumption is all the more just that the device 1 is disposed near the microcircuit 8 In order to prevent a more focused microwave radiation source from affecting the microcircuit 8 without affecting the detector device 1, the device 1 is advantageously arranged as close as possible to the microcircuit 8. A particularly advantageous arrangement consists in superimposing the device 1 above or below the microcircuit 8. This preferred feature is possible for embodiments where the device 1 has a very small thickness.

The location of the device 1, relative to the microcircuit 8, makes it possible to assume that the microcircuit 8 is subjected to the same exposure, as the device 1. This is all the more certain that the device 1 is close to the microcircuit 8 and therefore presumably exposed to the same 25 doses. The estimation or characterization of the dose received by the device 1 is thus indicative of the dose received by the microcircuit 8. The device 1 advantageously makes it possible to detect exposure to a dose of microwave radiation less than a dose affecting the microcircuit 8. Thus assuming that the device 1 receives the same dose as the microcircuit 8, the device 1 makes perceptible the exposure of the document before the microcircuit 8 is affected. Thus, even if exposure to a dose insufficient to affect the microcircuit 8, this exposure can be detected. The dose affecting the microcircuit 8 can be any dose producing a permanent effect, or not, on the microcircuit 8 and therefore any dose at least equal to a dose modifying the behavior of the microcircuit 8, relative to its nominal operation. In the case described below, where the device 1 is configured in several staggered detectable doses, at least one of these detectable doses is less than the dose affecting the microcircuit 8. In general, a microcircuit 8 may be characterized by a finesse of engraving. This fineness of etching is indicative of the minimum dimension (thickness, width, for example) of the conductive tracks internal to the microcircuit 8. The fineness is a known indicator of the resistance of an electronic circuit to a radiation, whether it be nuclear, cosmic or microwave origin. As the fineness with the evolution of electronic technologies decreases and the component density increases, so does the resistance of radiation. In order to detect an exposure, the device 1 comprises a sensitive element 2. This sensitive element 2 is electrically conductive in order to be sensitive to microwaves and to be able to be modified by such exposure. It is the sensitive element 2, sensitive part of the device 1, which is more particularly disposed near the microcircuit 8. Advantageously, this sensitive element 2 is shaped so as to be sensitive for a dose lower than the dose affecting the microcircuit 8 This conformation comprises the choice of the constituent material, its dimensions, as well as the shape or forms. For the dimensions, the sensing element 2 has one or more dimensions, which one qualifies as characteristic. According to an important characteristic such a characteristic dimension of the sensitive element 2 is related to the fineness of the microcircuit 8. Thus, if it is considered that the sensitive element 2 is composed of a material having the same sensitivity to the micro As the microcircuit 8, for the sensitive element 2 to react at a dose less than one integration of electronics to the dose affecting the microcircuit 8, it is appropriate that at least one of the characteristic dimensions of the element sensitive 2 is less than or equal to the fineness, this fineness being expressed as a dimension.

In practice, mainly because of the methods usable for producing such a sensitive element 2, it is difficult to realize this characteristic. Thus for a typical fineness of 40 nm, it is very difficult to make a sensitive element having such a characteristic dimension, for example the thickness, less than or equal to 40 nm. However, a microcircuit 8 is conventionally protected from exposure to microwaves by its packaging which achieves a significant attenuation. Also with this attenuation in mind, at least one of the characteristic dimensions of the sensing element 2 should be less than or equal to the fineness multiplied by the attenuation. This makes it possible to retain the advantageous property of detection by the device 1 for a dose less than the dose affecting the microcircuit 8. A typical attenuation being equal to one hundred, it is possible to accept a characteristic dimension less than or equal to one hundred times the finesse. In a known manner, a microwave radiation acts mainly at the boundaries of an element, on its edges, in limit of matter. Also the characteristic dimension (s) is / are measured between two edges, material limit, for example in thickness or in width. Several embodiments of a device 1 will now be described, forming edges remote from this characteristic dimension. According to one embodiment, the characteristic dimension is the thickness. In this case the sensitive element 2 is a thin film. Its thickness is typically between a few nanometers and a few micrometers, depending on the fineness considered. Preferably, for a conventional fineness for a conventional microcircuit, equal to 40 nm, the thickness is between 40 nm and 4 pm.

However, the invention is not limited to the dimensions mentioned above. The trend towards miniaturization of microcircuits and engraving fineness, as well as the mastery of printing technologies, will undoubtedly allow a fineness of etching of less than 40 nm, for example 10 nm. The thickness may then be between 10 nm and 4 pm. According to another embodiment, alternative or complementary to the previous one, the characteristic dimension is transverse to the thickness, either according to the width or the length. In this embodiment the characteristic dimension is realized by means of the form and can take at least two variants. This shape is illustrated in front view in Figures 2-10.

According to a first variant, said shape comprises at least one contour comprising at least one acute projection. A projection has an extension dimension 6, and the characteristic dimension is the extension dimension 6. The characteristic dimension may still be the distance between two projections. As illustrated in front of FIG. 2, a device 1 comprises an electrically conductive sensitive element 2. This sensitive element 2 has a shape that can be modified by exposure to microwaves. In order to be able to be controlled and thus to reveal such exposure to microwave radiation, the modification of the sensing element 2 is advantageously persistent in order to persist, at least between the moment of exposure and the moment when the Device 1 is controlled. A modification visible to the naked eye is not mandatory, but advantageously facilitates the control in that no specific tools are necessary to detect an exposure.

A sensitive element 2, under the effect of exposure to microwave radiation, becomes the seat of induced currents. The circulation of these currents causes a first thermal effect, heating the sensitive element 2. This heating 3037002 10 may be a first cause of modification. This heating may cause desiccation, combustion, or a melting of the sensitive element 2. These various effects may cause deformations, cracks, fractures, which are most often irreversible and thus advantageously ensure a persistence of the modification. According to one characteristic, the contour (s) 3 limiting the sensitive element 2 comprises (s) at least one acute projection 4. This is illustrated in Figure 2 showing an exemplary embodiment. Here a device 1 comprises a sensitive element 2 substantially shaped as a ring. This ring is limited by an outer contour 3e and an inner contour 3i. The material is between the two contours 3i, 3e. The sensing element 2 may comprise a plurality of outer contours 3e in that it may be composed of several disjoint parts. The sensing element 2 may comprise several internal contours 3i, spaced apart by a characteristic dimension, in that such a portion may comprise at least one recess.

The outer contour 3e comprises an illustrative projection 4e. The inner contour 3i comprises an illustrative projection 4i. In both cases, internal or external, a protrusion is protruding or outgoing, in that it extends out of the contour 3e, 3i, away from the material, or in a normal outgoing to the contour 3e, 3i . A projection 4 may have any shape. A protrusion 4 is advantageously acute in that its opening angle 5, or angle in which the projection 4 fits, is acute. Thus the opening angle 5i of the projection 4i is acute and the opening angle 5e of the projection 4e is acute. The opening angle 5 is preferably less than 90 °. At least one such projection 4 is advantageous, relative to a contour 3 smoother, less angular, in that a tip, such that the end of such a projection 4 35 promotes the modifications of the sensitive element 2. It appears Indeed, the "corners" both incoming and outgoing, are as many obstacles to the circulation in the sensitive element 2 of currents induced by microwave radiation. Thus, an outgoing corner such as a projecting end 4 forms a trap for the induced currents. The difficulty of running the current leads to an increase in the temperature rise. A re-entrant wedge forms a dielectric, which together with the two zones of the sensitive element 2 located on either side, forms a capacitor. Circulating currents, and this with difficulty, tend to crack such a capacitor.

These various effects combine to produce a heating, which produces and / or promotes local melting and / or evaporation phenomena. This can still lead to plasma appearances. This can cause microcracks at first. Then, by the induced currents, sparks appear within the same sensitive element 2. Indeed, when a microcrack is formed, a spark creates an ionized gas that reduces suddenly the electrical resistance of the sensing element 2. The air in the immediate vicinity of the sensing element 2 then allows the formation of a plasma. This plasma is conductive and visible in the form of a spark. Plasma again forms a conductive circuit with any conductor nearby: the sensitive element 2, the metal tracks of a microcircuit, any antenna tracks 9, etc. This then leads to an even greater spark and so on. This phenomenon allows the generated current to exit the sensitive element 2 with increased energy, allowing it to modify / degrade the surrounding materials, including the sensitive element 2 itself.

The advantage of a protrusion 4 is to form on the one hand a tip at its end and on the other hand reentrants on its sides. A main mode of modification / degradation of the sensitive element 2 consists of erosion of the projections 4.

This is more particularly illustrated with reference to FIGS. 3-5. Figures 3-5 illustrate, in front view, a sensitive element 2, a contour portion 3 comprises three projections 4a, 4b, 4c. The material is located below the 3037002 contour 3 in the plane of the figures. The projections 4 each have a different extension dimension 6. Thus, from left to right, the projection 4a is the smallest and has a small extension dimension 6a, the projection 4b is intermediate or medium and has an intermediate or intermediate extension dimension 6b, and the projection 4c is the larger and has a large dimension of extension 6c. Thus, the dimensions 6a-c of the projections 4a-c are staggered.

It appears an embodiment in which the characteristic dimension is defined by the extension dimension 6. This mode is associated with the modification of the sensing element 2 by erosion. It still appears an embodiment in which the characteristic dimension is defined between the distance between two protrusions 4. This mode is associated with the modification of the sensitive element 2 by breakdown. Figure 3 shows the initial state, before exposure to microwave radiation. The peaks of the projections 4a-c are well formed and protruding. Figure 4 shows the degradation of the projections 4a-c under the effect of the exposure of the sensitive element 2 to the microwave radiation. The various phenomena previously described (heating, breakdown, microcrack, plasma, spark, etc.) combine to produce an erosion effect tending to blunt the outgoing and protruding tips that are the ends of the projections 4a-c, eliminating any roughness or roughness, in order to smooth the shape of the contour to the maximum 3. The sensitive element 2 is exposed to a given dose of microwave radiation, such as to cause erosion removing a quantity of material over a height A of each of the projections 4a-c. It is assumed that this height A is substantially independent of the respective height or extension dimension 6a-c of each protrusion 4a-c and constant from one projection to the other. Figure 5 shows the result. The projection 4c has its point blunted by erosion and is found rounded, its initial extension dimension 6c is reduced by a dimension 3037002 13 A to become equal to 6c '. The projection 4b also sees its point blunted by erosion and is rounded again, its initial extension dimension 6b is reduced by one dimension A to become equal to 6b '. The projection 4a also sees its blunt tip. Its initial expansion dimension 6a, less than or equal to the dimension A is reduced by one dimension A and vanishes. The smallest projection 4a disappears under the erosive effect caused by the exposure. The doses of microwave radiation are cumulative. A further exposure, or prolongation of the previous exposure, carrying a higher dose of microwave radiation, would result in increased erosion, removing a quantity of material over a height greater than A. This would ultimately lead to at a disappearance of the average projection 4b. By continuing even longer exposure, accompanied by a dose of microwave radiation even greater, the disappearance of the large projection 4c could be obtained. It follows that for a given dose of microwave radiation, in relation to the dose affecting a microcircuit 8 that it is desired to detect by means of a device 1 associated with said microcircuit 8, it is possible to associate a quantity of material effectively removed by erosion under the effect of the exposure and thus to associate a dimension A.

It is then possible to size at least one projection 4 of the device 1, according to an extension dimension 6 substantially equal to the dimension A. Thus, if this projection 4 disappears during an exposure, this is indicative of a receiving, by the device 1, a dose of radiation at least equal to the given microwave radiation dose, associated with said dimension A. By associating this extension dimension 6 / dimension A with a characteristic dimension correlated with the fineness of the microcircuit 8, it is possible to detect whether the microcircuit 8 is or has been affected. Also according to another feature, it is possible to provide a device 1 with at least two projections 4, having respectively stepped extension dimensions 6. These stepped dimensions, like the dimensions 6a-c of the projections 4a-c of FIGS. 3-5, make it possible to form a scale making it possible to characterize a dose of microwave radiation received.

Thus with the three protrusions 4a-c, it is possible to perform a dose characterization scale at four intervals: 1) no significant erosion is found indicating that the dose is very low, 2) the small protrusion 4a is totally eroded, and the mean protrusion 4b and the large protrusion 4c are partially eroded indicating that the dose is higher, 3) the small protrusion 4a and the average protrusion 4b are totally eroded, and the large protrusion 4c is partially eroded indicating that the dose is even higher and 4) the three protuberances 4a-c are totally eroded indicating that the dose is very high. According to an advantageous embodiment, at least one of said at least one contour 3 is shaped according to a fractal shape 16,17. Such a fractal shape 16, 17 is advantageous in that it makes it possible on the one hand to produce an outline 3 comprising a large number of projections 4, and on the other hand, such a fractal shape makes it possible to integrate into one and the same contour 3 protrusions 4 of different dimensions, staggered. The principle of producing a fractal curve is known and is briefly recalled in relation to FIG. 6. The principle consists in replacing a segment 11, as illustrated on the left-hand part of FIG. 6 by a replacement form. , which can be chosen from a wide variety of shapes, an example of which is illustrated on the right side of FIG. 6. According to one possible embodiment, the shape is such that the segment 11 is kept identical to itself for its ends. , in the form of segments 12,15. Its middle part is replaced by a pattern, here for example triangular, formed by the segments 13, 14, forming a projection 41. The replacement shape retains the two ends identical to those of the initial segment 11. It can thus take the place of the initial segment 11. The replacement form advantageously comprises at least one (here three) segment. This allows a recurrent application of the replacement principle, to each of the new segments thus created. The figure used here is regular: equilateral triangle 5, and occupies the central third of the initial segment 11. Segments 12-15 all have the same length, equal to one-third of the length of the initial segment 11. This is not mandatory, but facilitates recurring application, however, each of the new segments 12-15 can in turn be replaced. by a new form of replacement comprising four sub-segments. Thus, starting from a basic figure, for example an equilateral triangle, which is called a figure of rank 0, it is possible, by applying the previous transformation to each of the three sides / segments, to obtain a star. with 6 branches, which is designated figure of rank 1, comprising twelve segments. It is possible to repeatedly apply the transformation to each of the twelve newly obtained segments.

FIG. 7 shows a detail of a fractal curve 16, as obtained at a rank n, with here n at least equal to 3. The fractal structure is advantageous in that it reveals several levels of projections 41- 43, of respective dimensions 61-63 staggered. Indeed one can note the presence of large projections 41 of extension dimension 61, simultaneously with the presence of projections 62 smaller, extension dimension 62, still simultaneously with the presence of projections 43 even smaller, dimension extension 63.

The application to the fractal curve 16 of rank n of FIG. 7 of a new transformation, or successive refinement, makes it possible to obtain the fractal curve 17 of rank n + 1 illustrated in FIG. 8. This curve 17 comprises the same projections 41-43 as before, to which is added a new level of projections, even more reduced, with a new projection segment. The example illustrated here is a fractal curve 16,17, called ile or Koch flake. It is a fractal curve 3037002 16 possible among a large number. The use of a fractal curve 16, 17 advantageously makes it possible to combine in a reduced space different projections 41-43 of different sizes 61-63.

Thus, according to one embodiment, a n-order fractal curve 16 comprises simultaneously n dimension levels 61-63 stepped with projections 41-43. In order to simplify the reading of the eroded projection (s) by exposure, according to one embodiment, the fractal curve 16,17 forming the outline 3 of the sensing element 2 may advantageously be developed in different ranks. For example, a "snowflake" with six branches may comprise a branch developed at rank 1, another branch developed at rank 2, and so on.

This makes it possible to locate the level of erosion more quickly by observing which branch is affected. In order to have a good sensitivity to microwave radiation, the sensitive element 2 is advantageously thin. This increases the concentration of the induced currents and thus the heating of the sensing element 2 and thus all the effects tending to modify the sensing element 2. Moreover, a small thickness of the sensing element 2 increases its capacity to deform . The sensing element 2 has an extension 25 substantially in the plane of the figures. Its thickness is measured perpendicular to the plane of the figures. Such a small thickness is advantageous and constitutes an important advantage for the device 1 allowing its integration into thin supports, such as paper sheet, cardboard or plastic card and if necessary in superposition with the microcircuit 8. This is important for the envisaged applications: electronic document, identity document, microcircuit card, etc., where the supports are thin.

The sensing element 2, in order to ensure its electrical conduction, comprises a conductive material. In order to have good sensitivity to microwave radiation, this material should have a high electrical conductivity. In order to react to the microwave radiation by a significant modification / degradation, it is appropriate that this material still has a high thermal conductivity. This material may, in one embodiment, be a metallic material. According to a preferred embodiment, a material combining these three characteristics is advantageously chosen from copper, Cu, gold, Au or silver Ag. The similarity of materials used between the sensitive element 2 of the device 1 and the tracks of the microcircuit 8, guarantees similar microwave radiation behaviors and thus allows a characteristic dimension directly comparing with the fineness. Depending on the desired microwave radiation sensitivity, the electrical or thermal conductivities may be varied. For this, it is possible to vary the material used. It is of course possible to make mixtures / alloys of different materials. It is also possible to vary the amount of material, for example by varying the thickness of the material or the thickness of the sensitive element 2. According to a second variant, alternative or complementary to the first variant, more particularly illustrated in FIGS. Figures 9 and 10, the shape of the sensing element 2 comprises at least two tracks 18. The characteristic dimension is the spacing 20 between said at least two tracks 18 and / or the width 19 of a track 18. According to a In one embodiment, more particularly illustrated in FIG. 10, the sensing element 2 comprises a plurality of tracks 18 arranged concentrically. The shape of the tracks 18 can be arbitrary: rectangular, triangular, circular or elliptical, as illustrated. It is of course possible to combine the two variants by arranging at least one protrusion 5 on at least one of the contours 3 formed by the edges of a track 18. In order to facilitate the reading of the modification undergone by the element 2, it is advantageous to include in the 3037002 18 device 1 a figure indicative of the initial shape of the sensitive element 2 before exposure. Thus, it is possible, to detect the magnitude and / or location of erosion, to compare the initial form before exposure with the final form after exposure and erosion. This comparison is advantageously simplified if both forms can be visible at the same time and advantageously close together, to facilitate a visual comparison. This is possible by means of a control 7. The device 1 10 advantageously comprises such a control 7, reproducing, at least partially, the shape of the sensitive element 2, but is not sensitive to microwave radiation. Thus, the control 7 remains identical to itself, including following the exposure, and thus makes it possible to represent the initial shape of the sensitive element 2 by providing a reference for a comparison. For this, the control 7 is made by means of a material with little or no electrical conductor, little or no thermal conductor. This material is advantageously non-metallic. One embodiment of these features is to use a conventional ink, the control 7 being made by any printing means. A witness 7 reproduces all or part of the shape of the sensitive element 2. It thus reproduces all or part of one or more of said at least one contour 3. A control 7 25 can also be made in several parts, a part reproducing a portion of the sensing element 2, such as a first contour 3, and another portion reproducing another portion of the sensing element 2. A control 7 has any dimension and orientation. However, in order to facilitate the comparison with the sensitive element 2, according to a preferred embodiment, a control 7 is made of the same size and in the same orientation as the sensitive element 2. A control 7 can be moved away, see even separated on a different support of the electronic document 10. According to an embodiment illustrated in FIG. 1, a control 7, formally similar to the associated sensing element 2, is disposed in the immediate vicinity of its associated sensitive element 2. in an electronic document 10. According to another possible embodiment, a control 7 is supplied separately to the control service, as a control tool, independently of the electronic document 10. In order to take advantage of the heating produced by the exposure of the sensitive element 2, it is still possible to have a thermo sensitive component near the sensitive element 2. The thermo-sense component The target is such that it is modified, advantageously persistently, and advantageously in a visible manner, under the effect of a heating that the boundary sensitive element 2 transmits to it. Such a component can thus comprise a thermosensitive material which can thus change color or reveal a pattern, thus revealed by heat. An addition in the device 1 of such a thermally sensitive component makes it possible, during an exposure, to obtain an additional modification of the device 1. This modification can make it possible to redundate the detection of an exposure obtained elsewhere. Alternatively, this modification, using another physical principle, may make it possible to perform exposure detection in another dose range. For example, a dose that is too low to cause detectable erosion, however, causes heating of the sensing element 2 which can be detected and stored by means of the thermally sensitive component. In some embodiments, the sensing element 2 has been described as a (very) thin film comprising a conductive material and having a characteristic shape.

Such a conductive film can be made by any means. A particularly suitable embodiment consists of an ink jet printing, with a special ink in that it is conductive. This known technology employs nanoparticles comprising at least one electrically conductive material inserted into the ink. The conductive material advantageously comprises a metallic material having a high electrical conductivity, preferably also a high thermal conductivity, and more preferably 3037002 selected from Cu, Au, Ag. The printing technique allows here to produce a sensitive element 2 of the shape to meet the desired shape and size characteristics. The presence of conductive material in the ink ensures that the sensing element 2 thus printed is conductive. According to this embodiment by printing, the thickness is important. Achieving 40 nm thick printing is possible but technically delicate and expensive. Also taking into account an attenuation factor, typically one hundred, provided by the packaging of the microcircuit 8, which as described above makes it possible to increase the thickness of the sensitive element 2 by the same amount, is advantageous. . Achieving a 4-μm thick print uses more common and much cheaper technologies.

Claims (16)

REVENDICATIONS1. Electronic document (10) comprising a microcircuit (8), characterized in that it further comprises a device (1) able to detect exposure to a dose of microwave radiation less than a dose affecting the microcircuit (8). 10 2. Electronic document (10) according to claim 1, wherein the device (1) comprises a sensitive element (2) made of an electrically conductive material, capable of being modified by exposure to the microwave radiation dose less than a dose affecting the microcircuit (8) and is disposed near the microcircuit (8). An electronic document (10), according to claim 2, wherein the microcircuit (8) is characterized by a fineness of etching, and wherein the sensing element (2) has at least one characteristic dimension less than or equal to one hundred times the finesse. The electronic document (10) according to claim 3, wherein the characteristic dimension is the thickness of the electrically conductive material. 5. Electronic document (10) according to claim 4, wherein said thickness is between a few nanometers and a few micrometers, preferably between 10 nm and 4 pm. An electronic document (10) according to any one of claims 2 to 5, wherein the sensing element (2) comprises, in a direction transverse to the thickness, at least one contour (3) having at least one projection (4) acute, wherein a projection (4) has an extension dimension which is at least one dimension characteristic of the sensing element. 3037002 22 The electronic document (10) according to claim 6, wherein the sensing element (2) further comprises a second projection (4), and wherein the characteristic dimension is the distance between said at least two projections (4). 8. Electronic document (10) according to claim 7, wherein the sensing element (2) comprises at least two protrusions (4), having respective extension dimensions (6) staggered, to characterize a dose of micro radiation - received wave. 9. Electronic document (10) according to any one of claims 6 to 8, wherein at least one of said at least one contour (3) is shaped in a fractal form. 10. Electronic document (10) according to any one of claims 3 to 9, wherein the sensing element (2) comprises in a direction transverse to the thickness, at least two tracks (18), and has a characteristic dimension which is the spacing (20) between said at least two tracks (18) and / or the width (19) of a track. An electronic document (10) according to claim 10, wherein the sensing element (2) comprises a plurality of tracks (18) disposed concentrically. 12. Electronic document (10) according to any one of claims 2 to 11, wherein the sensitive element (2) comprises a metallic material having a high electrical conductivity, preferably a high thermal conductivity, and more preferably selected from Cu , Au, Ag. An electronic document (10) according to any one of claims 2 to 12, wherein the device (1) further comprises a thermally sensitive component disposed near the sensing element (2). 3037002 23 14. Electronic document (10) according to any one of claims 2 to 13, wherein the device (1) further comprises a control (7) reproducing, at least partially, the shape of the sensitive element (2), and insensitive to said microwave radiation. An electronic document (10) according to any one of claims 2 to 14, wherein the device (1) further comprises a second sensing element, capable of being modified by exposure to a microwave radiation dose greater than a dose affecting the microcircuit (8). A method of manufacturing an electronic document (10) according to any one of claims 2 to 15, wherein the sensing element (2) is obtained by inkjet printing with a conductive ink.