Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
  • H01L31/18—Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
  • H01L31/02—Details
  • H01L31/0232—Optical elements or arrangements associated with the device
  • H01L31/02322—Optical elements or arrangements associated with the device comprising luminescent members, e.g. fluorescent sheets upon the device

Definitions

• the invention relates to a method for producing a radiation detector comprising a photosensitive receiver associated with a radiation converter.
• the invention also relates to a tool for producing a radiation detector and a method of implementing this tool.
• the fields of application of this type of detector are, for example, the detection of X-rays used for radiology: radiography, fluoroscopy, mammography, as well as non-destructive testing and safety.
• the invention will be described in connection with an X-ray detector. It is understood that the invention can be implemented in any type of detector for which the photosensitive receiver is not directly sensitive to the radiation to be detected, and for it is therefore necessary to interpose a radiation converter between an input window of the detector and the photosensitive receiver.
• Such radiation detectors are known for example from French patent FR 2 605 166 in which a sensor formed of amorphous silicon photodiodes, forming the photosensitive receiver, is associated with a radiation converter.
• the photosensitive sensor is generally made from photosensitive elements in the solid state arranged in matrix or in line.
• the photosensitive elements are made from semiconductor materials, most commonly mono-crystalline silicon for CCD or CMOS type sensors, polycrystalline silicon or amorphous silicon.
• a photosensitive element comprises at least one photodiode, a phototransistor or a photo resistance. These elements are deposited on a substrate, usually a glass slab.
• the photosensitive sensor is associated with a radiation converter which comprises a layer of a scintillating substance.
• This substance has the property, when excited by such radiation, to emit radiation of longer wavelength, for example, visible or near-visible light, to which the sensor is sensitive.
• the light emitted by the radiation converter illuminates the photosensitive elements of the sensor which perform a photoelectric conversion and deliver electrical signals exploitable by appropriate circuits.
• the radiation converter will be called a scintillator in the following description.
• Certain scintillating substances of the alkaline halide or rare earth oxysulfide family are frequently used for their good performance.
• sodium or thallium doped cesium iodide depending on whether it is desired to emit at about 400 nanometers or about 550 nanometers respectively, is known for its high X-ray absorption and for its excellent fluorescence efficiency. It is in the form of thin needles that are grown on a support. These needles are substantially perpendicular to this support and they partially confine the light emitted towards the sensor. Their fineness conditions the resolution of the detector.
• Lanthanum and gadolinium oxysulfides are also widely used for the same reasons.
• scintillator reported In a first configuration, called the scintillator reported, scintoid Matrix substance is deposited on a support that the radiation to be detected must cross before reaching the sensor. The whole is then stuck on the sensor.
• a second configuration In a second configuration, called direct deposition, the sensor serves as a support for the scintillating substance which is then in direct and intimate contact with the sensor. The scintillating substance is then covered with a protective sheet. Both configurations have advantages and disadvantages.
• An advantage of the first configuration, said scintillator reported is that the sensor and the scintillator are assembled if they have been successfully tested which improves the overall production efficiency.
• the invention seeks to improve the manufacture of a radiation detector made according to the first configuration and more specifically, the invention seeks to improve the bonding used in the assembly of the scintillator and the sensor.
• This bonding is currently carried out using a glue specially designed for its optical properties and in particular for its optical transparency at the wavelengths emitted by the scintillator.
• a glue specially designed for its optical properties and in particular for its optical transparency at the wavelengths emitted by the scintillator.
• a silicone-based gel is used.
• the quality of the image delivered by the sensor depends on the thickness of the glue layer used. Indeed, the light radiation generated by the scintillator must pass through the adhesive layer before being absorbed by the sensor. The dispersion of the radiation will be even lower as the thickness of the adhesive layer will be thin.
• the dispersion of the radiation essentially influences the resolution of the image which must remain homogeneous over the entire surface of the image.
• the glue is currently deposited by screen printing on one or both elements to be assembled.
• the adhesive layer In the case of scintillators based on cesium iodide, the adhesive layer must have a minimum thickness in order to allow good mechanical adhesion and sufficient coating by the glue of cesium iodide needles. The coating of the cesium iodide needles is important to ensure the quality of the optical interface between the scintillator and the glue.
• the purpose of the invention is to simplify the production of detectors obtained by gluing a scintillator onto a sensor.
• the subject of the invention is a method for producing a radiation detector comprising two elements: a photosensitive receiver and a scintillator transforming the radiation into a radiation to which the photosensitive sensor is sensitive, the scintillator being fixed by gluing on the photosensitive receiver, characterized in that it consists in implementing a film of adhesive protected on each of its faces by a protective film and in that it consists in following the following operations:
• the invention also relates to a tool for producing a radiation detector as described above, characterized in that the tool comprises an enclosure whose interior can be evacuated, in that Inside the enclosure are arranged a plate on which is placed the first element and cylinders to maintain the second element away from the first element. This tool is more precisely used to bring the second element into contact with the glue film.
• Another object of the invention is a method of implementing the tool described above, characterized in that it consists of:
• Another advantage of the invention is the improvement of the modulation transfer frequency by reducing the thickness of the glue joining the photosensitive receiver and the scintillator. Indeed, by depositing glue by screen printing, the minimum possible thickness is of the order of 40 .mu.m. On the other hand, there are protected glue films with a thickness of 12 ⁇ m which makes it possible to bring the scintillator closer to the detector and thus to improve the modulation transfer frequency. In addition, the tolerance on the protected adhesive film is much narrower than the tolerance on the thickness of a glue deposit by screen printing, which improves the homogeneity of the modulation transfer frequency.
• Yet another advantage of the invention is that the process is carried out at room temperature. This makes it possible to guard against harmful effects due to possible differences between coefficients of thermal expansion of the elements to be assembled by means of the glue film.
• FIG. 1 represents a radiation detector used in radiology whose scintillator comprises cesium iodide
• FIG. 2 represents another radiation detector used in radiology, the scintillator of which comprises gadolinium oxysulfide
• FIG. 3 represents a radiation detector comprising an intermediate element between the scintillator and the sensor
• Figure 4 shows a radiation detector where the scintillator is optically coupled to the sensor via a lens
• FIG. 5 represents a tool for producing a radiation detector.
• FIG. 1 represents a radiation detector comprising a photosensitive sensor 1 comprising a substrate 2, for example formed of a glass slab, supporting photosensitive elements 3.
• a photosensitive sensor 1 comprising a substrate 2, for example formed of a glass slab, supporting photosensitive elements 3.
• Each photosensitive element 3 is mounted between a line conductor and a column conductor so that it can be addressed.
• the conductors are not visible in Figure 1 for the sake of simplification.
• the photosensitive elements 3 and the conductors are generally covered with a passivation layer 4 intended to protect them from moisture.
• the radiation detector also includes a scintillator
• the scintillator 5 optically coupled with the sensor 1.
• the optical coupling is produced by means of an adhesive film 6.
• the scintillator 5 comprises a layer of scintillating substance 7, represented with a needle structure, deposited on a support 8.
• the support 8 thus carries the scintillating substance
• the scintillating substance 7 belongs to the family of alkaline halides such as cesium iodide which is particularly sensitive to wet oxidation.
• an input window 10 is placed on the scintillator 5 without being fixed on it.
• the radiation passes through the inlet window 10 upstream of the scintillator 5.
• a seal 1 1 moisture-tight fixed the inlet window 10 to the sensor 1 or more precisely to its substrate 2.
• the main advantage of the implementation In place of a separate entrance window 10 of the scintillator support 5 is to improve the radiation detector's tightness with respect to the ambient air to which the cesium iodide is particularly sensitive.
• the material of the inlet window 10 is chosen so that its coefficient of thermal expansion is close to that of the substrate 2. This makes it possible to use a rigid seal 1 1 having a good watertight seal. humidity.
• FIG. 2 represents another radiation detector used in radiology, the scintillating substance 7 of which comprises a rare earth oxysulfide such as, for example, gadolinium oxysulfide or lanthanum oxysulfide.
• This radiation detector comprises the same elements as the radiation detector shown in FIG. 1 with the exception of the input window 10.
• the scintillator 5 made with rare earth oxysulfide uses a plastic binder. conferring a good intrinsic seal. It is therefore not necessary to strengthen the tightness of the entire radiation detector.
• the input window function is performed directly by means of the support 8 of the scintillator 5. This support is for example made of an aluminum alloy.
• This alloy has a coefficient of thermal expansion greater than that of a substrate 2 made of glass.
• the sealing gasket 1 1 connects the support 8 to the substrate 2. Due to the difference in the coefficient of expansion between the support 8 and the substrate 2, use will be made of a flexible gasket 1, for example a silicone-based one, which by nature is less moisture-tight than a rigid seal 1 1 as described with the aid of Figure 1.
• a method for implementing the invention consists of using a film of adhesive protected on each of its faces by a protective film and to sequence the following operations: • removing a protective film, • roll the glue film on the first of the elements (scintillator 5 or photosensitive sensor 1),
• the rolling of the adhesive film on the first element is made between two rollers in order to eliminate any air bubble between the element and the adhesive film.
• the adhesive film is cut according to the dimensions of the first element.
• This cutting can for example be done using a cutter that can cut the glue film to the exact dimensions of the first element.
• the contacting of the second element with the adhesive film is done under vacuum.
• This vacuum process is well suited to rare earth oxysulfides which have a smooth appearance.
• scintillators belonging to the family of alkaline halides such as cesium iodide
• vacuum bonding is less necessary. Indeed, this family of scintillating substance has a microporous appearance allowing to naturally eliminate any air bubbles retained between the film and the scintillator 5.
• the glue film is based on acrylic.
• FIG. 3 represents a radiation detector similar to that of FIG. 1 in which an optical fiber network 30 has been inserted between the photosensitive sensor 1 and the scintillator 5.
• the optical coupling between the photosensitive sensor 1 and the optical fiber network 30 is produced by means of an adhesive film 61.
• the optical coupling between the scintillator 5 and the optical fiber grating 30 is produced by means of an adhesive film 62.
• the two glue films 61 and 62 can be implemented according to a process according to the invention. It is also possible to implement such an optical fiber network 30 in a radiation detector as described in FIG. 2, where the scintillating substance 7 is directly placed on the input window 8.
• the optical fiber network 30 enables to guide the radiation from the scintillator 5 to the photosensitive sensor 1.
• the optical fiber grating 30 can be replaced by an electro-magnetic material. optics based on amorphous selenium allowing the amplification of the radiation from the scintillator 5.
• FIG. 4 represents a radiation detector comprising an optical device 40 making it possible to focus the radiation coming from the scintillator 5 towards the photosensitive sensor 1.
• This radiation detector further comprises a blade 41 transparent to the radiation coming from the scintillator 5 and forming the photosensitive receiver .
• the optical coupling between the blade 41 and the scintillator 5 is achieved by means of the adhesive film 6 which can be set up according to a method according to the invention.
• FIG. 5 represents a tool for producing a radiation detector.
• the tool comprises a body 30 which with a fabric 31 form an enclosure whose interior can be evacuated, for example by means of a channel 32 intended to be connected to a vacuum pump not shown in the figure.
• a plate 33 on which is placed the first element, for example the scintillator 5, and cylinders 34 for holding the photosensitive receiver 1 away from the scintillator 5.
• jacks 34 are shown in the high position. They thus keep the photosensitive receiver 1 away from the scintillator 5.
• the photosensitive receiver 1 is positioned inside a countersink formed in a support 35 placed on the cylinders 34.
• the photosensitive receiver 1 is held on the support 35 by fingers 36 integral with the support 35. To ensure correct relative positioning of the photosensitive receiver 1 and the scintillator 5, the support is centered with respect to the body 30.
• the gluing time is for example of the order of a few minutes.

Applications Claiming Priority (2)

Publications (1)

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ID=36046930

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• 2005
  • 2005-09-23 FR FR0509777A patent/FR2891401B1/fr not_active Expired - Fee Related
• 2006
  • 2006-09-07 JP JP2008531666A patent/JP2009509151A/ja active Pending
  • 2006-09-07 WO PCT/EP2006/066116 patent/WO2007036417A1/fr active Application Filing
  • 2006-09-07 EP EP06793314A patent/EP1927140A1/de not_active Withdrawn
  • 2006-09-07 US US12/065,758 patent/US8044480B2/en not_active Expired - Fee Related
• 2008
  • 2008-02-12 IL IL189468A patent/IL189468A0/en unknown

Non-Patent Citations (1)

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