Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L27/00—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate
  • H01L27/14—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components 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
  • H01L27/144—Devices controlled by radiation
  • H01L27/146—Imager structures
  • H01L27/14601—Structural or functional details thereof
  • H01L27/1462—Coatings
  • H01L27/14621—Colour filter arrangements
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L27/00—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate
  • H01L27/14—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components 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
  • H01L27/144—Devices controlled by radiation
  • H01L27/146—Imager structures
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L27/00—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate
  • H01L27/14—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components 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
  • H01L27/144—Devices controlled by radiation
  • H01L27/146—Imager structures
  • H01L27/14601—Structural or functional details thereof
  • H01L27/1462—Coatings
  • H01L27/14623—Optical shielding
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L27/00—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate
  • H01L27/14—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components 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
  • H01L27/144—Devices controlled by radiation
  • H01L27/146—Imager structures
  • H01L27/14601—Structural or functional details thereof
  • H01L27/14625—Optical elements or arrangements associated with the device
  • H01L27/14627—Microlenses
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L27/00—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate
  • H01L27/14—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components 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
  • H01L27/144—Devices controlled by radiation
  • H01L27/146—Imager structures
  • H01L27/14683—Processes or apparatus peculiar to the manufacture or treatment of these devices or 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
  • H01L31/02325—Optical elements or arrangements associated with the device the optical elements not being integrated nor being directly associated with the device
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
  • H04N25/00—Circuitry of solid-state image sensors [SSIS]; Control thereof
  • H04N25/70—SSIS architectures; Circuits associated therewith
  • H04N25/76—Addressed sensors, e.g. MOS or CMOS sensors

Definitions

• the invention relates to photosensitive sensors, in particular electronic image sensors in CMOS integrated circuit technology, comprising photosensitive pixels of small dimension.
• FIG. 1 shows a simplified embodiment of an electronic camera 10 using an image sensor 12 of the CMOS type comprising a photosensitive surface 14 of pixels 16.
• the electronic camera comprises a non-telecentric system for reasons of compactness having a lens 18 and a diaphragm 20 focusing the light of the images targeted by the camera on the photosensitive surface 14 of the electronic sensor 12.
• Rays of light r1 close to the optical axis ZZ 'of the optical system, have an incidence substantially perpendicular to the photosensitive surface 14 of the sensor while rays r2, r3 distant from said optical axis ZZ' arrive at the edges of the sensor with a certain inclination ⁇ with respect to a normal to this photosensitive surface 14.
• a photosensitive area 22 of the pixel is located at the bottom of each of these wells. Good focusing of the light on the photosensitive area of the pixel is necessary, on the one hand, to obtain good pixel efficiency and, on the other hand, to recover some of the unused light arriving around the pixels.
• current image sensors comprise a network of micro-lenses, each of the micro-lenses of the network, associated with a respective pixel, focusing the incident light on a pixel and around the pixel, on the area photosensitive 22 of the pixel.
• FIG. 2 shows a detailed view of the image sensor 12 of FIG. 1 comprising an array of microlenses 30 having one microlens 32 per pixel.
• the purpose of micro-lens 32 is to focus the light arriving at the level of a pixel 16 on a photosensitive zone 22 situated in the background of the pixel.
• the size of the smallest pixels of the order of 5 to 10 micrometers in width L for a depth H of the pixel of the same order, lies within the limit dimensions of the size of the microlenses achievable.
• Such an array of micro-lenses 30 makes it possible to obtain a better efficiency of the image sensor in a region of the sensor close to the optical axis ZZ ′ but this efficiency decreases as one moves away from this optical axis towards the periphery of the sensor. Indeed (see FIG. 2), the rays r1 close to the optical axis ZZ ', substantially parallel to this axis, are well focused on the photosensitive part 22 of the pixel, while rays r2, r3 distant from the center of the sensor 12 have an inclination ⁇ relative to a normal the surface of the sensor.
• the inclination ⁇ of the light rays is all the more important as the targeted pixels are distant from the optical axis ZZ ′, the focusing area of the rays r2, r3 progressively moving towards the edges of the pixels. At the periphery of the sensor, the rays are no longer focused on the photosensitive zone 22 of the pixels but on the edges of the pixel well which then provides less electrical charges for the same light intensity received by the pixel.
• Another important drawback of the sensors of the prior art lies in the fact that the rays r2, r3 distant from the optical axis, arriving obliquely on the photosensitive surface, can reach the sensitive zone of the neighboring pixel causing on this neighboring pixel a modulation parasitic or crosstalk by a ray of light which is not intended for it.
• the pixels of the optical sensors do not have opaque lateral optical partitions, the side walls are relatively transparent and the oblique rays of light can scan adjacent pixels.
• the invention provides a photosensitive sensor, in particular in CMOS technology, comprising a substrate having a network of pixels forming a photosensitive surface receiving light rays, characterized in that it comprises, in the path of the light rays, a holographic layer having a recorded hologram, the holographic layer having an optical function corresponding to the inverse of a spatial diffusion function so as to bring the rays closer to normal luminous arriving on the layer under dispersed oblique incidences.
• the function of approximation to normal of the photosensitive surface acts to concentrate towards a pixel the incident rays arriving on a surface surrounding the pixel.
• the invention also relates to a method of producing a photosensitive sensor, in particular in CMOS technology, comprising a substrate having an array of pixels forming a sensitive surface receiving light rays, characterized in that one deposits, on the surface of the sensor, in the path of light rays, a holographic layer having a recorded hologram, the holographic layer having an optical function corresponding to the inverse of a spatial diffusion function so as to bring the rays closer to normal luminous arriving on the layer under dispersed oblique incidences.
• a support layer of the hologram is deposited on the surface of the sensor and then the hologram is recorded on the holographic layer secured to the sensor.
• the holographic layer comprising the hologram is produced separately, then the layer is transferred onto the substrate of the photosensitive sensor.
• the holographic layer supported for example by a substrate transparent to light, comprises a holographic pattern recorded in its volume. The saved pattern produces the desired optical function.
• the holographic layer can be produced on a polycarbonate or polyester film, on a glass slide or on any other holographic support by transmission.
• FIG. 3 shows an image sensor according to the invention comprising a holographic layer on the sensor
• FIG. 4a shows a holographic recording in the mass of the holographic layer
• FIG. 4b shows a holographic recording in relief on the holographic layer
• FIG. 5 shows a first alternative embodiment of the image sensor of Figure 3.
• FIG. 6 shows another embodiment of the image sensor according to the invention.
• FIG. 3 represents a first embodiment of an electronic image sensor 40 according to the invention used for example in an electronic camera.
• the image sensor essentially comprises a substrate 42 having an array of pixels 44 in CMOS technology forming a photosensitive surface and a holographic layer 48, deposited on the substrate 42, producing a desired optical function.
• the method for producing the image sensor according to the invention comprises at least the following steps: - producing on the substrate 42 the array of pixels 44, using CMOS technology, forming the photosensitive surface;
• the holographic layer 48 includes a holographic interference pattern producing the desired optical function.
• a hologram having an optical function tending to bring towards a normal to the surface of the holographic layer 48 the light rays r1, r2, r3 arriving on the layer under dispersed oblique incidences can, for example, be obtained by producing holographic patterns in the mass of the holographic layer of a series of interferences between two waves of coherent light, each of the interferences being produced by interference of a first wave arriving for example from one side of the layer with a determined angle with respect to this layer and of a second wave arriving from the other side of the layer with an angle of interference with respect to the surface of the layer which will be changed at each interference, the variation of this interference angle sweeping a solid angle of the scattered oblique incident waves which it is desired to approximate to the normal to the surface of the layer.
• rays of light r1, r2, r3, coming from the optics of the camera arrive with an oblique angle angle incidence, relative to normal at the surface of the image sensor, varying according to the position of arrival of the rays on the sensitive surface of the sensor.
• the rays r1, r2, r3 passing through the holographic layer are brought closer to the normal to the sensitive surface of the sensor.
• the rays arriving at the pixels located near the edges of the sensor and having the greatest inclination relative to the normal of the sensor are brought closer to this normal by the optical action of the holographic layer 48.
• Hologram recording can be performed in the volume of a photosensitive holographic layer.
• FIG. 4a shows such a recording of the holographic pattern in the mass of the holographic layer 48 of the image sensor of FIG. 3 according to the invention.
• a photosensitive layer 54 is exposed to two coherent light waves V1 and V2 producing an interference pattern 58 in the photoresist layer 54.
• the holographic pattern 58 produces the desired optical function.
• the recording of the hologram in the holographic layer can be carried out in other known ways, namely:
• FIG. 4b shows such a type of recording during which a holographic pattern 60 in relief is stamped by compression of the surface of a thermoplastic layer 62 fixed on a support 56, by a matrix of hard material comprising a complementary pattern in relief of the pattern to be printed.
• the support 56 can also be the substrate 42 of the electronic image sensor.
• the embodiment of the image sensor of FIG. 3 according to the invention brings a marked improvement in performance compared to the sensors of the prior art by an effect of channeling the light rays towards the sensitive areas of the pixels in particular an improvement in the ratio signal to noise of the electronic signal generated by the sensor.
• FIG. 5 represents a variant of the embodiment of the image sensor of FIG. 3 providing a further improvement in the efficiency of the pixels.
• the holographic layer in addition to the effect of approximation to a normal to the sensor of the light rays towards the sensitive zone of the pixels, has another additional effect of concentration of the rays towards the sensitive zone 22 of the pixels.
• rays r4, r5, r6 light up parts surrounding the sensitive zone of the pixels which do not produce electric charges useful for the generation of the electric signal representing the image.
• an image sensor 70 comprises the substrate
• the function concentrating optic of the holographic layer acting to concentrate the incident rays arriving on a surface surrounding the pixel towards a pixel.
• FIG. 6 shows another embodiment of the photosensitive sensor 80 according to the invention comprising a holographic layer 82 having the records of the holographic patterns of the layers of the embodiments previously described.
• the holographic layer comprising the hologram is produced separately, then is transferred to the substrate 42 of the photosensitive sensor.
• a photosensitive sensor 80 according to the invention comprises at least the following manufacturing steps:
• the rays r4, r5, r6 arriving on a surface surrounding the pixel can be concentrated, in this variant of FIG. 6, by the holographic layer, towards the sensitive area of the pixel.
• the holographic interference pattern is the result of the combination of two waves in coherent light in the sensitive layer, a first incident wave coming directly from the coherent light source and a second wave coming from the same source but illuminating the object of which wants to record the hologram corresponding to the desired optical function. It is a natural recording.
• the hologram can be of synthetic type.
• the holographic interference pattern can be produced by computer calculation, which has the advantage of being able to obtain holographic patterns corresponding to optical functions which cannot be obtained using a natural registration.
• Synthetic holograms are used to perform optical functions of frequency filtering, display or for the production of optical elements. Recordings of holographic patterns can also be obtained by combining natural holograms and synthetic holograms.
• the hologram recorded in the holographic layer of the image sensor according to the invention allows flexibility and ease of obtaining different optical functions necessary for the optical sensors. But other possibilities are also offered by holograms such as color filtering of color cameras.
• the holographic layer in addition to the optical functions of the embodiments described, includes optical filtering functions of the three fundamental colors red, green and blue.
• the holographic layer comprises a hologram producing an optical function for filtering infrared rays which are not useful for the camera.
• the application of the sensor according to the invention is not limited to the image sensors of the cameras.
• light is transmitted to a photosensitive pixel via an optical fiber, the output end of which is located opposite this pixel. The light travels in the optical fiber by reflection on the walls of the fiber.
• the light exiting at the end of the fiber has a non-zero angle with respect to the normal to the sensitive area of the pixel.
• the holographic layer, as described in the invention brings the light at the output of the fiber closer to this normal at the sensitive area of the pixel with the advantages mentioned above.

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• Engineering & Computer Science (AREA)
• Physics & Mathematics (AREA)
• Power Engineering (AREA)
• General Physics & Mathematics (AREA)
• Electromagnetism (AREA)
• Condensed Matter Physics & Semiconductors (AREA)
• Computer Hardware Design (AREA)
• Microelectronics & Electronic Packaging (AREA)
• Signal Processing (AREA)
• Multimedia (AREA)
• Solid State Image Pick-Up Elements (AREA)
• Holo Graphy (AREA)
• Diffracting Gratings Or Hologram Optical Elements (AREA)
• Photometry And Measurement Of Optical Pulse Characteristics (AREA)
• Blocking Light For Cameras (AREA)

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• 2000
  • 2000-12-28 FR FR0017229A patent/FR2819101B1/fr not_active Expired - Fee Related
• 2001
  • 2001-12-20 JP JP2002554888A patent/JP2004523888A/ja active Pending
  • 2001-12-20 CN CNA018216714A patent/CN1484863A/zh active Pending
  • 2001-12-20 IL IL15652701A patent/IL156527A0/xx unknown
  • 2001-12-20 KR KR10-2003-7008658A patent/KR20030082557A/ko not_active Application Discontinuation
  • 2001-12-20 US US10/451,666 patent/US20040051806A1/en not_active Abandoned
  • 2001-12-20 EP EP01994936A patent/EP1360728A1/de not_active Withdrawn
  • 2001-12-20 CA CA002432528A patent/CA2432528A1/fr not_active Abandoned
  • 2001-12-20 WO PCT/FR2001/004115 patent/WO2002054500A1/fr not_active Application Discontinuation

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