GB2265753A

GB2265753A - Ionizing ray microimaging device

Info

Publication number: GB2265753A
Application number: GB9305606A
Authority: GB
Inventors: Marc Cuzin; Pierre Jeuch
Original assignee: Commissariat a lEnergie Atomique CEA
Current assignee: Commissariat a lEnergie Atomique et aux Energies Alternatives CEA
Priority date: 1992-04-01
Filing date: 1993-03-18
Publication date: 1993-10-06
Anticipated expiration: 2013-03-18
Also published as: FR2689684A1; GB9305606D0; FR2689684B1; DE4310622A1; GB2265753B

Abstract

The device constitutes a bidimensional detector comprising semiconductor solid material (2) able to transform incident ionizing radiation directly into electric charges and incorporating a detection zone (4) defined in a central region of the solid material, (2) and a connection zone located at the periphery of the detection zone. At least one charge collection system (10) comprises an array of conductive metal electrodes located on the first face of the material (2) and, in the detection zone, formed as parallel microstrips, the spacing (10a) of the electrodes widening out in the connection zone so as to be compatible with a connection by microspheres. Reading circuits (14) for said charges are electrically connected to the collection system (10) by microspheres. <IMAGE>

Description

2265753 Ionizing ray microimaging device.

DESCRIPTION

The invention relates to a device for microimaging high resolution ionizing rays or radiation and for use in non-destructive inspection, control or testing. The ionizing rays to which the invention applies are X or gamma rays.

By radiographic projection or tomographic reconstruction, the imaging of ionizing rays makes it possible to study living or non-living matter and consequently permits the non-destruc- tive analysis of the internal structure of irradiated objects having variable masses and dimensions.

The obtaining of high resolution images requires an extremely small ionizing ray source, which corresponds to a bundle of parallel rays. Such a condition is satisfied in the case of synchrotron beams.

The device according to the invention is more particularly intended for radiological microimaging and microtomography of generally biological structures irradiated with low energy sources of below 5 keV, metal alloys irradiated with average energy sources generally between 5 and 15 keV and also composite structures (of the ceramic or fibrous type) irradiated with energy sources above 15 keV. Therefore the imaging device according to the invention can be used in numerous fields of application, namely in the medical, biological and indust- rial fields.

In industry, the invention e.g. applies to the car, space, nuclear, building construction and similar fields.

2 More specifically, the device according to the invention relates to the detection part of the ionizing radiation.

Conventional ionizing ray imaging devices using photosensitive films, image intensifiers, radiological screens coupled to photosensitive cameras make it possible, possibly in real time, to obtain good quality images, but whose spatial resolution is a few dozen micrometres.

This resolution, partly due to the diffusion of light of the layer for converting the X or gamma rays into light is some- times reduced by the use of needle scintillating structures (e.g. CsI crystals in radiological image intensifiers) or structures whose shape is subsequently produced. In the latter case, the resolution levels are approximately 100 jim.

In addition, the conventional imaging devices cannot be used when it is wished to analyse faults in a material of approximately 1 micrometre.

Another known bidimensional imaging method used in nuclear medicine consists of carrying out a barycentric reconstruction using the Anger principle. For this purpose, a large photo- multiplier array with a diameter of approximately 70 mm recovers the photons from a thick scintillator (CsI crystal), which transforms the incident X radiation into light and the localization of said light spot is reconstructed by a resistance bridge associating the outputs of the different photomultipliers.

When the sought spatial resolution is about 10 micrometres, use is made for barycentric reconstruction of a microstriptype electrode array, the electrodes being arranged parallel to one another. For example, microstrips arranged with a spacing of 25 to 50 jum permit a localization to within 5 jum of the X- material interaction.

Such a system is in particular described in Nuclear Instruments and Methods in Physics Research A305, 1991, pp.173-176 by 1. Hietanen et al "Beam test results of an ion-implanted silicon strip detector on a 100mm wafer". It uses microstrips formed by ion implantation in silicon. This barycentric imaging method unfortunately makes use of complex and cumbersome technological means.

When the interest is centered on microscopic structures, use is made of integrated detection devices, based on the direct conversion of ionizing rays into electric charges under an electric field. Thus, it is possible to eliminate the lateral diffusion of the energy trapped by the detection device.

In these devices, use is more particularly made of directly irradiated charge coupled devices (CCD's), which make it possible to obtain a spatial resolution of about 10 micrometres. These CCD's are generally formed in silicon.

A commercial, bidimensional CCD has pixels of approximately 7 jum and the detection of the ionizing radiation in the silicon substrate consequently permits an accurate localization, but only for low energy gamma or X photons, i.e. with an energy of,<5keV. Therefore the number of its applications is consequently limited.

Moreover, the circuits for reading the charges created in the substrate and associated with these detectors are also exposed to radiation and therefore age badly.

The imaging device according to the invention is based on the principle of the barycentric localization of the energy of the radiation received by a semiconductor material in a volume of average size 10 to 20 p. This principle is more particularly described in US-A-4,411,059. In the latter, the detection of gamma radiation takes place by PIN diodes formed in silicon. The detection takes place with the aid of row electrodes and column electrodes on either side of the semiconductor layers.

On producing these electrodes in the form of parallel microstrips separated by a spacing of 5 p it would be possible to locate the detection zone by barycentric reconstruction. An accuracy of 10% on the spacing of the electrodes corresponds to a localization of better than 1 micrometre on the radiation impact point. Therefore this method would permit a micrometric localization of the ionizing rays.

As for charge coupled devices, if the reading circuits are exposed to ionizing rays they age very badly.

In the case of row and column electrodes positioned very close together, the known imaging devices do not make it possible to read the charges collected by these electrodes using appro- priate reading circuits, because the spacing of the electrodes is not compatible with a connection by wires welded by microspheres or any other means.

The invention is therefore directed at a novel gamma or X ray imaging device making it possible to obviate the disadvan- tages referred to hereinbefore. In particular, said device ensures a micrometric imaging. In addition, said device can be of small size and is relatively simple to manufacture.

More specifically, the invention relates to a device for the microimaging of ionizing rays comprising:

A) a bidimensional detector incorporating a solid semiconductor material able to transform incident ionizing radiation into electric charges and having a first and a second parallel faces, a detection zone defined in a central region of the solid material, a connection zone located on the periphery of the detection zone, at least one first charge collection system constituted by an array of conductive metal electrodes located on the first face of the material and having, in the detection zone, parallel microstrips, the spacing of the elec- trodes widening into the connection zone so as to be compatible with a connection by microspheres and B) first circuits for reading the said charges, electrically connected to the first collection system by hybridization by microspheres in the connection zone.

The term microspheres is understood to mean strips spaced by:!10 p. In particular, the spacing of the electrodes in the detection zone is <5 pm and the microstrips have a width of 4 31m.

In the connection zone, the spacing of the electrodes is k.10 pm and can extend to 1000 11m. Thus, it is compatible with a connection by microspheres.

In the microimaging device according to the invention, the detection and measurement functions are separate and carried out by separate, hybridized components. Moreover, it can be used with radiation sources having an energy level above 15 keV and therefore has a wide range of applications.

It differs from known barycentric detection devices by the use of an undoped semiconductor material having a high electrical resistance, either in the form of a solid material, or in the form of a film deposited on an electrically'insulating substrate.

Moreover, as the reading circuits are located outside the detection zone, their premature aging by irradiation is preven5 ted.

A solid semiconductor material detector according to the invention can be used both for gamma or X rays of low energy (4 5keV) and for rays having a high energy level (4 15keV). However, a detector having a semiconductor film deposited on an insulating substrate is intended solely for the detection of very soft gamma or X rays, whose energy levels are below 5keV.

This film can be gas or liquid phase epitaxied or can be deposited by chemical vapour deposition (CVD) and all variants thereof, e.g. MOCVD. In principle, said film has a thickness of 1 to 50 pm, so as to be able to stop the gamma or X rays with an energy level of 45keV.

The insulating substrate can be made from any random electrically insulating material serving also as a thermal insulant.

As the insulating substrate it is possible to use ceramics such as alumina, silica, glasses, polymers, etc.

The semiconductor material of the detector according to the invention must be able to transform the ionizing rays into electric charges. In particular, said material must be able to transform a gamma or X photons into several hundred pairs of electrons- holes. This semiconductor material must consequently have a high electrical resistivity, preferably exceeding 10 3 ohm.metre.

7 The semiconductor material can be made from any known semiconductor material such as germanium, silicon, binary, ternary or quaternary alloys of III and V elements or II and VI elements of the periodic classification of elements. Preferably, the semiconductor is made from silicon, GaAs or CdTe having a high electrical resistivity.

According to the invention, the imaging device can incorporate one or two charge collection systems on either side of the semiconductor material and coinciding with one another. In this case second charge reading circuits must be electrically connected to the second collection system by hybridization by microspheres in the connection zone.

According to the invention, the collection of the charges by a row electrode or a column electrode can be carried out on the entire size of the detector, the latter then functioning in photon by photon counting. In this case, the second charge collection system is constituted by a uniform conductive layer deposited on the complete detector.

Preferably, each of the two charge collection systems is for- med, in the detection zone, by parallel, metal, conductive microstrips, the microstrips of the first and second systems intersecting in directions forming between them an angle of 60 to 900.

Advantageously, both the common electrode and the strip electr- odes of the two systems can be subdivided transversely into two, which then gives access to a higher photon counting rate and/or to an improvement in the spatial resolution of the device.

The reading of the electric charges formed in the semiconductor 8 material by each row and column must take place with the aid of reading circuits having a very low noise level, because the charge corresponding to a detected gamma or X photon is distributed over several measuring channels (columns and tows).

In addition, these reading devices are located in the immediate vicinity of the detection zone, but outside the latter so as not to be irradiated.

In order to improve the thermal noise performance characteristics of the reading circuits by lowering the same, a cooling system can be provided and can consist of a Peltier effect structure.

According to the invention, the reading circuits are hybridized on the semiconductor material thus permitting the obtaining of a small imaging device. These reading circuits have in particular integrated transistors of the MOS type serving as amplifiers, each transistor being associated with an electrode.

Preferably, the outputs of these transistors are connected to electrical resistors, which are interconnected. Thus, it is possible to reconstruct the localization of the incident beam according to the Anger principle.

According to the invention, the reading circuits of the first and second electrode systems (e.g. row electrodes and column electrodes) can be located on either side of the semiconductor material. However, it is possible to place these reading circuits on the same face of the semiconductor material. In this case, holes can be provided in the semiconductor material to permit the passage of conductors from one material face to the other.

The invention is described in greater detail hereinafter relative to nonlimitative embodiments and the attached drawings, wherein show:

Fig. 1 diagrammatically and in perspective a microimaging device according to the invention using hybridized reading circuits.

Fig. 1A a variant of the electrodes of the detector according to the invention.

Fig. 2 a longitudinal sectional view of the device of fig. 1.

Fig. 3 diagrammatically and in plan view a device according to the invention using reading circuits integrated onto the detection semiconductor material.

Fig. 4 diagrammatically and in perspective a variant of the device according to the invention using hybridized reading circuits.

Fig. 5 diagrammatically and in perspective another variant of the imaging device according to the invention using a common electrode.

Fig. 6 diagrammatically and in longitudinal section another variant of the device according to the invention in which the reading circuits are located on the same side of the semiconductor material.

Fig. 7 diagrammatically, partially and in section, another variant of the device according to the invention using a semi- conductor film for detection purposes.

With reference to figs. 1 and 2, the X or gamma ionizing ray imaging device according to the invention comprises a bidimensional detector formed by a detecting plate 2 made from a solid semiconducting material, whose central part 4 constitutes the detection zone or the zone intended for imaging. The periphery of the semiconductor material 2 is intended for the reading circuits.

According to the invention, the semiconductor material 2 is of silicon, gallium arsenide or cadmium telluride with a high electrical resistivity, typically exceeding 103 ohms.cm. The semiconductor plate 2 has a typical thickness of 100 to 400 pm. It ensures the transformation of the ionizing radiation 6 striking the upper face of the plate 2 into electronhole pairs, which are collected by two arrays of electrodes, respectively 8 and 10, directly deposited on the upper and lower surfaces of the semiconductor 2.

In a solid semiconductor, detection takes place solely on the principle of photoelectric interaction, so that the spatial resolution is at an optimum.

In the imaging zone 4, the electrodes 8 are in the form of microstrips oriented parallel to one another in a direction x and the electrodes 10 are in the form of microstrips oriented parallel to one another in a direction y, perpendicular to the direction x. Therefore the electrodes 8 and 10 define detection rows and columns in the imaging zone 4.

These electrodes 8 and 10 are made, in the case shown, from a conductive metal and in particular aluminium, chromium, silver, tungsten, gold, etc. They are produced e.g. by metal deposition using cathodic sputtering according to the lift- off method (irradiation of a photosensitive resin through a mask representing the image of the electrodes to be produced, development of the resin, deposition of the metal coating and then dissolving of the resin).

In the detection zone, the electrodes have a width of 0.2 to 1.5 pm, a spacing of 2 to 10)1m and a thickness of 10 to 300 nm.

In the embodiment shown, the detection or imaging zone 4 has, in plan view, the shape of a square, whose side dimension is below 1 mm. For example, an image zone 4 of 300x3OO ym 2 can supply an image of 500x5OO pixels (elementary display points) after barycentric reconstruction for the pixels (image points whose dimensions are fixed by the intersection of a 2 row and a column of the detection zone) of 0.6xO.6)am It would obviously also be possible to envisage a rectangular 2 detection zone of a few mm Barycentric methods permit a localization of the incident beam on the detector better than 1 micrometre. They permit the use of a detector like that shown in fig. 1, at least ten times smaller than those used up to now in the field of gamma or X imaging.

According to the invention, the bidimensional detector has a connection or reading zone 11 on the periphery of the detection zone 4. In said zone 11, the spacing of the electrodes 8 and 10 exceeds that of the electrodes in the detection zone and is typically between 100 and 1000 p. This increase in the spacing of the electrodes in the connection zone can be brought about in different ways.

For example, at their end outside the detection zone 4, the electrodes 8 can have lateral branches 8a perpendicular to the direction x. The ends of the lateral branches 8a can be aligned along the diagonal z of the detector in order to increase the spacing thereof. In the same way, the electrodes 10 can have at their ends branches 10a perpendicular to the direction y and whose spacing exceeds that of the microstrips in the detection zone.

The branches 8a,10a of the electrodes 8,10 can also be oriented in a direction forming an obtuse angle with the direction x, as shown in fig. 1A. The branches 8a,10a can be arranged in fan-like manner instead of parallel to one another.

It is also possible to envisage any other arrangement of the branches 8a, 10a of the electrodes 8,10 increasing their spacing in the connection zone 11, so as to be compatible with a hybridization by microspheres.

At one out of two corners of at least the upper surface of the semiconductor plate 2 and in the connection zone 11, there are integrated circuits 12 connected in accordance with a hybridization method to the branches 8a of the conductive electrodes 8 used for the reading of the electrical signals supplied by said electrodes.

In the same way, at at least one corner out of two of the lower surface of the semiconductor plate 2 and in the connec- tion zone 11 there are integrated circuits 14 connected according to the hybridization method to the branches 10a of the electrodes 10 used for the reading of the electrical signals supplied by said electrodes.

13 - The hybridization of the bidimensional detector and the reading circuits can take place by means of an indium ball or sphere connection system 16. The connection of the circuits 12j14, respectively to the conductive electrodes 8,10, is brought about at the periphery of the semiconductor material 2, where the spacing of the connections has been sufficiently increased to be compatible with this hybridization method. Thus, the detection and reading functions are separate and can be optimized independently of one another.

In the variant shown in figs. 1 and 2, the electrodes 8 are arranged in two groups 19,20, each connected to a reading circuit 12. In the same way, the electrodes 10 are subdivided into two groups, each connected to a reading circuit 14.

The reading circuits 12,14 have amplifiers respectively 18 and 20 with a very low noise level, located in the immediate vicinity of the detection zone 4. To each electrode 8 is connected an amplifier 18 and to each electrode 10 is connected an amplifier 20. These amplifiers are in particular MOS transistors produced on a silicon substrate separate from that of the detector. These reading amplifiers 18,20 can be simultaneously read (which corresponds to the embodiment shown in fig. 1) or optionally read independently of one another.

The localization of the incident beam 6 and therefore the treatment of the signals supplied by the amplifiers 18 and 20 is carried out by dedicated circuits respectively 22,24, positioned as far away as possible from the detection zone 4 and in particular outside the semiconductor 2. These dedi cated circuits are e.g. those known under the name charge reading registers sold by THOMSON (TMS).

According to the invention, with each amplifier can be associated a dedicated treatment or processing circuit. However, it is preferable to only use two dedicated circuits, as shown in fig. 1. In this case, the current outputs of the amplifiers of the same group (here 19 and 21) will be interconnected by a resistance bridge 26.

This arrangement can be more clearly gathered from fig. 3, which shows in plan view a detector according to the invention in which the reading circuits are integrated into the solid semiconductor 2 and not hybridized as shown in figs. 1 and 2.

The following description will only relate to the system of rows and their reading circuits, but it is obvious that the column electrodes and their associated reading circuits located on the other face of the semiconductor 2 can be arranged in accordance with the same principle.

In fig. 3, the upper electrodes parallel to the direction x carry the reference 28 and are only in the form of microstrips parallel to one another and to the direction x.

Each of the transistors 18 is connected to a row electrode 28 and said transistors have their outputs interconnected by the resistance bridge 26, so that there are only two output signals -u and +u for the row electrodes x and I, and 1 2 for the column electrodes y. The relationship of the signals respectively of the rows and columns makes it possible to directly localize the impact point of the incident beam on the detector and is calculated by the dedicated circuits 22,24.

The electrical signals supplied by the reading circuits 12 and 14 respectively give, in time coincidence, the abscissa x and the ordinate y of the interaction point of the radiation - is - with the detector and in known manner.

Apart from the shape of the electrodes, fig. 3 differs from figs. 1 and 2 through the use of a single external dedicated circuit 22, because the row electrodes 28 and consequently the transistors 18 are not subdivided into two groups.

As shown in fig. 4, it is possible to subdivide the upper electrodes and lower electrodes into two equal parts in the direction y perpendicular to the microstrips. Thus, it is possible to obtain respectively four groups 28,30,32 and 34 of upper electrodes, each associated with a reading circuit 12 identical to those described hereinbefore. The detection, subdivided into four sectors in this way, permits an improvement of the spatial resolution or the counting rate.

As shown in fig. 5, it is also possible to use one of the two electrode systems, e.g. that supported by the upper face of the semiconductor 2, in the form of a common electrode 38 covering the entire size of the detection zone 4 of the detector. Under these conditions, the detector operates on a photon by photon counting basis. This common electrode 38 is obviously connected at the output to an amplifier 18 located outside the detection zone 4, e.g. integrated into the semiconductor.

The lower electrode array can be arranged in the manner shown in fig. 1, or can be subdivided into sectors as shown in fig.

4. In addition, the common electrode 4 can be subdivided into two equal parts in a direction perpendicular to the direction x, which gives access to a twice higher counting rate.

In figs. 1 to 5, the reading circuits respectively 12 and 14 of the row electrodes and column electrodes were respectively located on the lower and upper faces of the semiconductor 2, respectively coated with the row electrodes and the column electrodes.

However, as shown in fig. 6, it is also possible to arrange the reading circuits 12 of the row electrodes on the lower face of the detector 2. To this end, holes 40 are formed on the periphery of the semiconductor 2 and completely traverse the same. These holes are filled with a conductive material 42 making it possible to connect the electrodes 8 to sockets 44 formed on the lower face of the semiconductor 2 and used for connecting a reading circuit 12.

In the embodiment shown in fig. 6, the reading circuits 12 are hybridized circuits, connected via indium spheres 16 to the sockets 44.

The holes 40 can be produced by laser or ultrasonics and metallization of said holes is carried out either by chemical deposition, or by vapour phase transport. Under these conditions, the reading circuits 12 and 14 respectively of the rows and columns can be formed on the same chip connected to the semi- conductor 2. The connection of the conductive columns and rows to the reading circuits 12,14 is ensured in the same way as in fig. 1.

The detector according to the invention shown in figs. 1 to 6 uses as the detection material a solid semiconductor sub- strate 2. It thus made it possible to detect gamma or X radiation with an energy level below 5 keV, an energy level between 5 and 15 keV, or an energy level above 15 keV.

Moreover, a cooling device 46 (cf. figs. 1 and 2) can be provided for improving the performance characteristics of the amplifiers by reducing the thermal noise. This device is in particular necessary for imaging rays with an energy level above 5 keV. This cooling device consists of Peltier effect circuits.

In the case of very soft gamma or X rays, i.e. with an energy below 5keV, it is possible to produce the detector according to the invention in the manner shown in fig. 7. This detector 10 has an electrically and thermally insulating substrate 48, e.g. of alumina, on the upper surface of which is produced the lower electrode system 10. These column electrodes can be made from tungsten or chromium in accordance with the liftoff procedure and have the shapes shown in figs. 1 and 4.

The array of electrodes 10 is covered with an amorphous silicon layer 50 or a layer of any other semiconductor material having a high resistivity and a thickness of a few micrometres. This layer 50 constitutes the detection layer of the ionizing radiation ensuring the transformation thereof into electrical 20 charges.

On the upper surface of the detecting layer 50 are provided the row electrodes 8 oriented, at least in the detection zone, perpendicular to the column electrodes 10 and produced in the manner described hereinbefore (figs. 1 to 4).

In fig. 7, the row 12 and column 14 reading circuits are connected by hybridization to the detection layer 50. They can obviously be integrated into the layer 50. Moreover, these circuits can be located either on the same side of the semiconductor layer 50, or respectively on the upper surface of the layer 50 and on the flank, as shown in fig. 7. Moreover, these circuits are located on the same side of the substrate 48. According to the invention, these reading circuits are located on the periphery of the detection layer 50.

The reading amplifiers integrated into the detection semiconductor (fig. 3) or hybridized (figs. 1 and 2) are constituted by NMOS and/or PMOS transistors in accordance with microelectronic procedures.

In place of using two arrays of metal electrodes, in the manner described hereinbefore, it is possible to localize the incident X or gamma radiation by using only a single electrode array, e.g. the upper electrode array 8, associated with resistive connections. In this case, it is merely necessary to add to the upper metal electrodes in known manner resistive lines formed e.g. by ion diffusion into a semiconductor material differing from that of the detector, each end then being connected to an amplifier in order to localize on the metal line the impact point of the gamma or X radiation.

The determination of the impact of the incident radiation when using a resistive connection is carried out in the manner described in US-A-4,411,059.

Claims

1. A device for the microimaging of ionizing rays comprising.:

A) a bidimensional detector incorporating a solid semiconductor material (2,50) able to transform incident ionizing radia- tion (6) into electric charges and having a first and a second parallel faces, a detection zone (4) defined in a central region of the solid material, a connection zone located on the periphery of the detecton zone, at least one first charge collection system (10) constituted by an array of conductive metal electrodes located on the first face of the material and having, in the detection zone, parallel microstrips, the spacing (10a) of the electrodes widening into the connection zone so as to be compatible with a connection by microspheres and B) first circuits (14) for reading the said charges, electrically connected to the first collection system by hybridization by microspheres in the connection zone.

2. Device according to claim 1, characterized in that a second charge collection system (8,28,38) is located on the second face of the material and at least facing the metal microstrips of the first system and in that second reading circuits (12) of said charges are electrically connected by hybridization by microspheres to the second collection system in the connection zone.

3. Device according to claim 2, characterized in that the second charge collection system (8,28) consists of an electrode array having, in the detection zone, parallel, conductive metal microstrips oriented perpendicular to the conductive microstrips of the first collection system.

4. Device according to claim 1, characterized in that the microstrips have a spacing of:S5 jim.

5. Device according to claim 1, characterized in that the spacing of the electrodes in the connection zone is alOum.

6. Device according to claim 1, characterized in that the semiconductor material is a solid material (2) or a film (50) deposited on an electrically insulating substrate.

7. Device according to claim 1, characterized in that the semiconductor material (2,50) is made from silicon, gallium arsenide or cadmium telluride with high electrical resistivity.

8. Device according to claim 3, characterized in that the conductive microstrips of the first (10) and/or second (8,28) system are transversely subdivided into two identical portions.

9. Device according to claim 2, characterized in that the first and second reading circuits (12,14) are placed on two opposite faces of the semiconductor material.

10. Device according to claim 2, characterized in that the first and second reading circuits (12,14) are placed on the same face of the solid material, holes (40) being made in said material to ensure the passage of the electrical conductors (42) to the other face of the material, intended for the electrical connection of the circuits (12) installed on said other face.

11. Device according to claim 3, characterized in that the first and/or second reading circuits incorporate transistors (18) serving as amplifiers, each transistor being associated with an electrode.

12. Device according to claim 11, characterized in that the transistors of the first and/or second reading circuits (12,14) have outputs electrically interconnected by electrical resistors (26).

13. Device according to claim 3, characterized in that the conductive microstrips of the second collection system, in the detection zone, are associated with microstrips diffused in the semiconductor material (2) of high electrical resistivity.

14. Device according to claim 3, characterized in that the electrodes of the first and/or second collection system have, outside the detection zone, branches (8a,10a) widened from microstrips respectively of the first and/or second system and used for the connection of the microstrips to the asso15 ciated reading circuits.