• 专利附录
  • 专利说明
  • 权利要求
  • 类似技术
  • 同族专利
  • 引用文献
  • 法律状态
  • 优先权
    • 专利摘要:
    The integrated backlit illumination image sensor comprises at least one pixel (PIX) comprising a semiconductor active region (1) having a first face (10) and a second face (11) and containing a photodiode (3), a lens convergent (L) located opposite the first face (10) of said active region (10) and configured to direct the light rays (r1) arriving on the lens (L) towards a central zone (12) of the active region ( 1). The active region (1) comprises at least one diffractive element (5) having an optical index different from the optical index of the active region (1) and located at least partly in said central zone (12) at the level of the one of said faces (10, 11) of the active region.
    公开号:FR3056333A1
    申请号:FR1658898
    申请日:2016-09-22
    公开日:2018-03-23
    发明作者:Axel Crocherie；Pierre Emmanuel Marie MALINGE
    申请人:STMicroelectronics Crolles 2 SAS；
    IPC主号:
    专利说明:

    ® FRENCH REPUBLIC
    NATIONAL INSTITUTE OF INDUSTRIAL PROPERTY © Publication number: 3,056,333 (to be used only for reproduction orders)
    ©) National registration number: 16 58898
    COURBEVOIE © Int Cl 8 : H 01 L 27/146 (2017.01), H 04 N 5/33
    A1 PATENT APPLICATION
    ®) Date of filing: 22.09.16. © Applicant (s): STMICROELECTRONICS (CROLLES ©) Priority: 2) SAS Simplified joint stock company - FR. @ Inventor (s): CROCHERIE AXEL et MALINGE PIERRE EMMANUEL MARIE. (43) Date of public availability of the request: 23.03.18 Bulletin 18/12. ©) List of documents cited in the report preliminary research: Refer to end of present booklet (© References to other national documents ® Holder (s): STMICROELECTRONICS (CROLLES 2) related: SAS Simplified joint-stock company. ©) Extension request (s): ©) Agent (s): CASALONGA.
    IMAGE SENSOR WITH IMPROVED QUANTUM EFFICIENCY FOR INFRARED RADIATION.
    FR 3 056 333 - A1 _ The integrated rear-face illumination image sensor comprises at least one pixel (PIX) comprising an active semiconductor region (1) having a first face (10) and a second face (11) and containing a photodiode (3), a converging lens (L) located opposite the first face (10) of said active region (10) and configured to direct the light rays (r1) arriving on the lens (L) towards a central area ( 12) of the active region (1).
    The active region (1) comprises at least one diffracting element (5) having an optical index different from the optical index of the active region (1) and located at least partially in said central area (12) at the level of the one of said faces (10, 11) of the active region.


    i
    Improved quantum efficiency image sensor for infrared radiation
    Embodiments of the invention relate to optical image sensors, in particular rear-facing illumination image sensors, and in particular to improving the quantum efficiency of this type of sensor.
    The quantum efficiency of an image sensor is the ratio between the number of electronic charges collected and the number of photons incident on an active region of an image sensor, for example a photodiode. This quantity is used to characterize the light sensitivity of an image sensor.
    The quantum efficiency of near infrared optical signals, that is to say light rays whose wavelength is between 700 nanometers and 1000 nanometers, is low, and this due to the low absorption of these wavelengths by the silicon of the photosensitive regions of the sensors.
    There are ways to improve the quantum efficiency of rear-facing illumination image sensors for near-infrared wavelengths.
    One solution is to increase the optical path traveled by light rays in silicon by reflection phenomena, for example on metal levels located in the interconnection part (commonly known to those skilled in the art under the acronym). -saxon BEOL: “Back End Of Lines) behind the active area, or on insulating trenches delimiting the active area.
    However, these methods remain insufficient, in particular because of the small thicknesses of silicon used in the most compact image sensors.
    Thus, according to one embodiment, an image sensor is proposed having an improved quantum efficiency for infrared light rays.
    According to one aspect, an integrated rear-face illumination image sensor is proposed comprising at least one pixel comprising a semiconductor active region having a first face or rear face and a second face and containing a photodiode, a converging lens located in look at the first face of said active region and configured to direct the light rays arriving on the lens towards a central zone of the active region.
    According to a general characteristic of this aspect, the active region comprises at least one diffracting element having an optical index different from the optical index of the active region (such as for example an oxide) and located at least partly in said central zone at the level of one of said faces of the active region.
    Thus, by producing a specific diffracting element at least in part in said central zone, the optical path traveled by light rays in silicon is further increased due to the numerous diffractions resulting from the location of this diffracting element.
    The sensor can also comprise at least one level of metal opposite the second face of the active region, coated in an insulating region and optically coupled with the diffracting element.
    Thus, the effect of the diffracting element is further increased by the presence of at least one level of metal which reflects the rays diffracted by the diffracting element.
    According to one embodiment, said at least one diffracting element may comprise a trench of insulating material located in the active region at the level of said first face of the active region.
    According to another embodiment, compatible with the previous embodiment, said at least one diffracting element may comprise a trench of insulating material located in the active region at the level of said second face of the active region.
    Said at least one diffracting element may also comprise a line of polysilicon produced on the second face of the active region. The front face of the active region conventionally comprising a thin oxide protective layer, there is always a difference in index between the diffracting element and its surrounding medium.
    According to one embodiment, said at least one diffracting element extends in a single direction parallel to the first and to the second face and is located at least partially in the central zone of the active region.
    The sensor may include several diffracting elements, at least one of which is located at least partially in the central area of the active region.
    At least some of the diffracting elements may be integral so as to form a single and same diffracting pattern extending in several directions.
    According to another aspect, a system is proposed, for example of the type forming a smart mobile telephone or a digital photographic camera, comprising at least one integrated image sensor as defined above, Other advantages and characteristics of the the invention will appear on examining the detailed description of embodiments, in no way limiting, and the appended drawings in which:
    - Figures 1 to 7 schematically illustrate embodiments of the invention.
    FIG. 1 schematically illustrates a pixel PIX of an integrated image sensor CAP of the rear face illumination type (BSI: “Back Side Illumination” according to the Anglo-Saxon name well known to those skilled in the art), and the Figure 2 is a sectional view along the torque line II-II of Figure 1.
    The pixel PIX comprises an active region 1, comprising a first face 10, or rear face, and a second face 11, or front face. The active region 1 is isolated from the adjacent pixels by deep isolation trenches 2 (DTI: "Deep Trench Isolation" in English).
    The active region 1 conventionally comprises a photodiode 3. The photodiode 3 is here of the pinched type (“pinned” in English) vertical, that is to say a photodiode comprising a doped region for example of type N encompassed in another region doped, for example, of the P type, and extending vertically in the active region 1, that is to say in 3056333 in a direction going from the front face 10 towards the rear face 11.
    The pixel PIX comprises a first insulating region 40, produced on the rear face 10 of the active region, and on which there is a converging lens L, able to converge incident rays rl towards a central zone 12 of the active region 1 comprising photodiode 3.
    The pixel PIX comprises a second insulating region 41 encompassing several levels of metal belonging for example to an interconnection part (BEOL) of the integrated circuit containing the sensor CAP. These metal levels can allow interconnections between different components of the sensor (not shown for simplification purposes), and certain metal levels M, located opposite the second face of the active region, also serve as reflectors in order to reflect towards active region 1 any light rays passing through it.
    The rear face 10 of the active region supports a diffracting element 5, produced within the active region 1 and partly in the central region 12 and capable of diffracting the incident rays coming from the lens L.
    The diffracting element 5 here comprises a shallow trench 50 made in the active region 1 and comprising an insulating material.
    Thus, for example, when an incident light ray rl arrives on the lens L, it is directed towards the central zone 12 of the active region 1. When it meets the diffracting element 5, it is diffracted in the active region 1 by a multitude of diffracted rays r2, r3, r4 at different angles.
    For example, the diffracted ray r4 is reflected a first time against the deep insulation trenches 2 towards the front face 11 of the active region 1. Then, the diffracted ray r4 crosses the active region 1 until it meets a line of metal of the level of metal M coated in the second insulating region 41. The ray is then reflected a second time towards the active region 1, in which it can be reflected again on the deep trenches 2, and / or be absorbed.
    Thus, the diffracting element 5 advantageously contributes to increasing the optical path of the incident rays passing through the lens L.
    Indeed, the combined effects of the diffracting element 5, the isolation trenches 2, and the metal level M allow a particularly long optical path, and therefore a great improvement in the absorption of photons by the active region 1. The quantum efficiency of the CAP image sensor is therefore improved.
    The inventors have in particular observed that this type of sensor allows absorption of infrared radiation up to three times greater than the absorption of infrared radiation of a similar sensor but lacking a diffracting element.
    It should be noted here that the totality of the incident rays does not meet the diffracting element 5. However, the lens L being a converging lens configured to direct the incident rays towards the central zone 12 of the active region, and the element being partly located in this central zone 12, the majority of the incident rays will meet the diffracting element 5.
    FIG. 3 illustrates an embodiment in which the diffracting element 5 comprises a shallow isolation trench 51 which is not located at the rear face 10 of the sensor as described above, but in the active region at from the front 11.
    Thus, an incident ray rl arriving on the sensor will first pass through the active region 1 before being diffracted by the diffracting element 5. The majority of the diffracted rays r4, r5, r6 by the diffracting element 5 are therefore reflected a first time by a metal line from the metal level M to the active region 1, where they can be reflected a second time against the deep isolation trenches 2 and / or absorbed.
    It is also possible that an incident ray crosses the active region 1 and is then reflected a first time by a metal line from the metal level M towards the diffracting element before meeting the diffracting element 5 and being diffracted in the active region 1 into a plurality of diffracted rays which will be reflected a second time against the deep isolation trenches 2 and / or absorbed.
    This embodiment is also compatible with a pixel comprising a planar type photodiode.
    It should be noted that it is entirely possible to provide a diffracting element comprising both an insulating trench located at the rear face 10 and an insulating trench located at the front face 11.
    FIG. 4 illustrates an embodiment of the invention, in which the diffracting element 5 comprises a line of polysilicon 52 produced on the front face of the active region 1, between the active region 1 and the metal level M. La front face 11 of the active region 1 conventionally comprising a thin oxide protective layer, there is indeed a difference in index between the diffracting element 5 and the front face 11.
    This embodiment has the same advantages from an optical point of view as the embodiment described above and illustrated in FIG. 2 and could be combined with the embodiments illustrated in FIGS. 2 and / or 3.
    However, this embodiment of FIG. 4 is particularly advantageous from the point of view of the production method. Indeed, the line of polysilicon material 52 is produced according to the same process used to produce elements of other electronic components, such as for example charge transfer grids involved in the operation of the pixel (not shown for simplification purposes ). This polysilicon line is therefore a fictitious grid ("dummy spoils" according to the Anglo-Saxon name well known to those skilled in the art).
    Although image sensors comprising pixels comprising a single diffracting element have been presented here, it would also be possible, as illustrated in FIG. 5, to produce a plurality of diffracting elements 60, 61, 62 in the active region 1, according to one of the embodiments presented previously and illustrated in FIGS. 1 to 4.
    Since the majority of the light rays arrive in the central zone 12, at least one of the diffracting elements, here element 61, is partly located in the central region 12. The other two diffracting elements 60 and 62 are produced in parallel on both sides of the diffracting element 61
    The CAP image sensors described above and illustrated in FIGS. 1 to 5 can conventionally be integrated into an optical system comprising a shutter, conventionally in a digital camera or in a smart cell phone ("Smartphone", in English).
    Figures 6 and 7 illustrate systems comprising CAP image sensors comprising PIX pixels according to an embodiment of the invention. Figure 6 illustrates a digital camera APN and Figure 7 illustrates a TPI smart cell phone. The camera and the mobile phone include a CAP image sensor according to an embodiment of the invention.
    The application examples of the invention are not limited to those illustrated in FIGS. 6 and 7, and those skilled in the art will be able to apply the embodiments of the invention described above and illustrated in FIGS. 1 to 5 to d other known systems.
    The embodiments presented here are in no way limiting. In particular, although there has been shown here in connection with FIG. 5 an image sensor comprising a plurality of diffracting elements 60, 61, 62 distinct and parallel, it would be entirely conceivable to have several diffracting elements s 'extending in distinct directions, and / or being mutually joined so as to form one and the same pattern.
    权利要求:
    Claims (9)
    [1]
    1. Integrated rear-face illumination image sensor comprising at least one pixel (PIX) comprising a semiconductor active region (1) having a first face or rear face (10) and a second face (11) and containing a photodiode (3), a converging lens (L) located opposite the first face (10) of said active region (10) and configured to direct the light rays (rl) arriving on the lens (L) towards a central zone (12 ) of the active region (1), characterized in that the active region (1) comprises at least one diffracting element (5) having an optical index different from the optical index of the active region (1) and located at least in part in said central area (12) at one of said faces (10, 11) of the active region.
    [2]
    2. Sensor according to claim 1, further comprising at least one metal level (M) opposite the second face of the active region, coated in an insulating region (41) and optically coupled with the diffracting element (5) .
    [3]
    3. Sensor according to claim 1 or 2, wherein said at least one diffracting element (5) comprises a trench (50) of insulating material located in the active region (1) at said first face (10) of the region active (1).
    [4]
    4. The sensor of claim 1, 2 or 3, wherein said at least one diffracting element (5) comprises a trench (51) of insulating material located in the active region (1) at said second face (11) of the active region (1).
    [5]
    5. Sensor according to one of the preceding claims, wherein said at least one diffracting element (5) comprises a line of polysilicon (52) produced on the second face (11) of the active region.
    [6]
    6. Sensor according to one of the preceding claims, wherein said at least one diffracting element (5) extends in a single direction parallel to the first face (10) and to the second face (11) and is located at least partly in the central area (12) of the active region (1).
    [7]
    7. Sensor according to one of the preceding claims, comprising several diffracting elements (60, 61, 62), one of which (61)
    At least 5 is located at least partly in the central zone (12) of the active region (1).
    [8]
    8. The sensor of claim 7, wherein at least some of the diffracting elements are integral so as to form a single and same diffracting pattern extending in several directions.
    [9]
    9. System comprising at least one integrated image sensor (CAP) according to one of claims 1 to 8.
    10. The system of claim 9, of the type forming a smart mobile phone (TPI) or a digital camera (APN).
    1/3
    2/3
    CAP
    3/3
    TPI
    CAP
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    引用文献:
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    US20110164156A1|2009-07-24|2011-07-07|Masao Hiramoto|Image pickup device and solid-state image pickup element|
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    US8716823B2|2011-11-08|2014-05-06|Aptina Imaging Corporation|Backside image sensor pixel with silicon microlenses and metal reflector|
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    US20200227458A1|2019-01-11|2020-07-16|Semiconductor Components Industries, Llc|Image sensors with diffractive lenses in a semiconductor substrate|
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    法律状态:
    2017-08-21| PLFP| Fee payment|Year of fee payment: 2 |
    2018-03-23| PLSC| Search report ready|Effective date: 20180323 |
    2018-08-22| PLFP| Fee payment|Year of fee payment: 3 |
    2019-08-20| PLFP| Fee payment|Year of fee payment: 4 |
    2021-06-11| ST| Notification of lapse|Effective date: 20210506 |
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    FR1658898|2016-09-22|
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    US16/414,409| US10475836B2|2016-09-22|2019-05-16|Image sensor with improved quantum efficiency for infrared radiation|
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