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WO2024210832A1 - Détecteur de lumière infrarouge et procédé correspondant de détection de lumière infrarouge - Google Patents

Détecteur de lumière infrarouge et procédé correspondant de détection de lumière infrarouge Download PDF

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Publication number
WO2024210832A1
WO2024210832A1 PCT/SG2024/050209 SG2024050209W WO2024210832A1 WO 2024210832 A1 WO2024210832 A1 WO 2024210832A1 SG 2024050209 W SG2024050209 W SG 2024050209W WO 2024210832 A1 WO2024210832 A1 WO 2024210832A1
Authority
WO
WIPO (PCT)
Prior art keywords
substrate
infrared light
photodetector
light detector
light
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
PCT/SG2024/050209
Other languages
English (en)
Inventor
Todd Bishop
Johannes Wild
Mike King
Nicola Macri
Michael Hirmer
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Ams Osram Asia Pacific Pte Ltd
Original Assignee
Ams Osram Asia Pacific Pte Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Ams Osram Asia Pacific Pte Ltd filed Critical Ams Osram Asia Pacific Pte Ltd
Publication of WO2024210832A1 publication Critical patent/WO2024210832A1/fr
Anticipated expiration legal-status Critical
Pending legal-status Critical Current

Links

Classifications

    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10F—INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION
    • H10F77/00—Constructional details of devices covered by this subclass
    • H10F77/40—Optical elements or arrangements
    • H10F77/413—Optical elements or arrangements directly associated or integrated with the devices, e.g. back reflectors
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J5/00—Radiation pyrometry, e.g. infrared or optical thermometry
    • G01J5/02—Constructional details
    • G01J5/08—Optical arrangements
    • G01J5/0801—Means for wavelength selection or discrimination
    • G01J5/0802—Optical filters
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J5/00—Radiation pyrometry, e.g. infrared or optical thermometry
    • G01J5/10—Radiation pyrometry, e.g. infrared or optical thermometry using electric radiation detectors
    • G01J5/20—Radiation pyrometry, e.g. infrared or optical thermometry using electric radiation detectors using resistors, thermistors or semiconductors sensitive to radiation, e.g. photoconductive devices
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10F—INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION
    • H10F30/00—Individual radiation-sensitive semiconductor devices in which radiation controls the flow of current through the devices, e.g. photodetectors
    • H10F30/20—Individual radiation-sensitive semiconductor devices in which radiation controls the flow of current through the devices, e.g. photodetectors the devices having potential barriers, e.g. phototransistors
    • H10F30/21—Individual radiation-sensitive semiconductor devices in which radiation controls the flow of current through the devices, e.g. photodetectors the devices having potential barriers, e.g. phototransistors the devices being sensitive to infrared, visible or ultraviolet radiation

Definitions

  • the invention relates to an infrared light detector . It further relates to a corresponding method of sensing infrared light .
  • Prior-art infrared light detectors usually comprise a die with a silicon substrate into/onto which a photodetector is integrated or embedded . On top of the photodetector there is a number of optical layers ( coatings ) deposited which form an infrared bandpass filter .
  • the filter deposition process requires dedicated materials and processing steps during production .
  • An obj ective of the invention is to provide a low-cost infrared light detector which is easy to manufacture . Furthermore, a corresponding method of sensing infrared light with such an infrared light sensor shall be given .
  • the obj ective is met by an infrared sensor according to claim 1 .
  • the invention provides an infrared light detector, comprising
  • a photodetector arranged on or at the front side of the substrate , wherein the photodetector is configured for backside illumination, and wherein the substrate is configured to act as an infrared bandpass filter .
  • the basic idea of the invention is to create a low-cost infrared (IR) light detector with a standard photodetector arranged on or embedded into a semiconductor substate or die , in particular made of silicon ( Si ) , and with a build-in infrared bandpass filter .
  • the processed side of the substrate with the photodetector and associated circuits around is pointing downwards , in particular to a printed circuit board or similar, such that backside illumination of the photodetector is established .
  • Light hitting the top side of the die will travel through the substrate and generate a photocurrent in the photodetector .
  • the substrate acts as an IR pass filter, where the lower cut-of f frequency is determined by the die thickness . Higher die thickness will generally shift the cut-of f wavelength to higher values .
  • the photodetector comprises a back surface which is transparent for infrared light , wherein the back surface faces the substrate . Therefore, ef ficient backside illumination is enabled .
  • the photodetector comprises a front surface which is covered by a light barrier .
  • the light barrier preferably covers the complete area of the photodetector and may extend beyond .
  • Said light barrier preferably is opaque at least for visible light . This way it is assured that the backside IR illumination is the predominant mode of illumination, while frontside illumination (with light not passing the substrate and therefore not being IR filtered) is attenuated or suppressed or preferably completely blocked .
  • the light barrier on the photodetector comprises a back surface which faces the photodetector and is reflective for infrared light , such that IR light which would otherwise escape from the photodetector is reflected back .
  • a mirror can be added on the front side (which now is actually the back side ) of the die to further enhance the IR sensitivity .
  • a mirror can be added on the front side (which now is actually the back side ) of the die to further enhance the IR sensitivity .
  • gold from flip chip bumping as a light shield and reflector over the photodetector to lock light and further increase IR response .
  • Flip Chip Bumping is the metallization of the die front side and solder ball placement to enable the die interconnect to take place on the front side .
  • the die is then " flipped" and mounted upside down onto the board circuit .
  • the metalli zation to form the top side contacts that receive the solder ball is used for the top side light shield and reflector .
  • the substrate is configured to let pass spectral components in the IR range , in particular in the range from 850 nm to 1 . 200 nm .
  • the passband may be narrower than said range .
  • the substrate comprises or consists of a semiconductor material , in particular silicon .
  • the substrate has a preferred thickness in the range from 100 pm to 750 pm, in particular from 100 pm to 300 pm .
  • a light barrier with an aperture opening in the region of the photodetector is expediently arranged on the back side of the substrate .
  • Said light barrier preferably is opaque at least for visible and infrared light .
  • a back side ( top side ) optical aperture can adj ust the level and characteristics of light reaching to the photodiode .
  • the front side of the substrate faces a printed circuit board or similar .
  • electric circuits may be arranged on the front side of the substrate adj acent to or around the photodetector, said circuits preferably being electrically and mechanically connected to the printed circuit board (PCB ) by a number of solder balls .
  • PCB printed circuit board
  • solder balls instead of a PCB an ASIC may be used .
  • solder balls copper pillars may be used .
  • An IR light detector according to the present disclosure may be part of various electronic devices , such as infrared sensors , proximity sensors , and IR communication receivers .
  • Possible sensor applications include :
  • ambient light sensing and/or f licker detection with the help of an IR sensor according to the present disclosure may be of particular interest .
  • the invention also comprises a method of sensing infrared light with an infrared light detector of the kind described above, wherein a light source is arranged in front of the back side of the substrate , wherein light from light source is guided through and optically filtered by the substrate to provide backside illumination of the photodetector, while preferably frontside illumination is blocked .
  • the invention makes use of the substrate thickness to control and filter the incident light .
  • Replacing the prior-art front side filter with back side illumination of the photodetector will reduce the product cost associated with filter material , filter deposition process , packaging process , and yield loss .
  • the overall cost of an IR light detector according to the disclosure is much cheaper compared to a module with additional external filters and bond wires .
  • the overall system complexity will be reduced .
  • the si ze of the IR detector may also be reduced because Wafer Level Chip Scale Package (WL-CSP) can be used, which basically means bare die with solder bumps , f lipped .
  • WL-CSP Wafer Level Chip Scale Package
  • FIG . 1 schematically shows a cross-sectional view of a prior art infrared (IR) light detector .
  • FIG . 2 schematically shows a cross-sectional view of an IR light detector according to the invention .
  • FIG . 3 shows a diagram with various graphs of signal ratios over wavelengths obtained from frontside illumination and backside illumination of a light detector .
  • FIG . 4 shows a diagram with various graphs of signal ratios over wavelengths obtained from backside illumination of a light detector, illustrating the impact of surface resistivity .
  • FIG . 5 shows a diagram with various graphs of signal ratios over wavelengths obtained from backside illumination of a light detector, illustrating the effect of substrate thickness with respect to absorption .
  • FIG. 6 shows a variation of the diagram in FIG. 5 with a differently scaled y-axis (ordinate) , illustrating a shift of a lower cut-off frequency with varying substrate thickness.
  • FIG. 1 schematically shows a cross-sectional view of a priorart infrared (IR) light detector, or briefly IR detector 2.
  • the IR detector 2 comprises a wafer or die 4 with a front side 6 (here: top side) and a back side 8 (here: bottom side) .
  • the die 4 comprises a substrate 10, preferably a semiconductor substrate, in particular a silicon substrate.
  • a photodetector 12 on the front side 6 there is a photodetector 12, in particular a photodiode, integrated and partially embedded into or arranged on the substrate 10.
  • Adjacent to or around the photodetector 12 there may be a metallic circuit layer 14 arranged on the front side 6 of the substrate 10.
  • the circuit layer 14 may be wire-bonded to a printed circuit board or the like.
  • the photodetector 12 is intended to sense the IR portion of light 20 incident on the front side 6 of the IR detector 2, namely on the front surface 16 of the photodetector 12, as indicated by the arrows. Therefore, an IR filter 18 is arranged in front (here: on top) of the photodetector 12.
  • the IR filter 18 is an optical filter with an IR bandpass characteristic. That is, IR light with a wavelength within a passband, in particular from 850 nm to 1.200 nm, may pass while light with a wavelength outside the passband is blocked or attenuated.
  • the IR filter 18 is deposited on the photodetector 12 by way of a coating process. This involves additional steps and material during the production of the IR detector 2.
  • FIG. 1 schematically shows a cross-sectional view of an IR detector 2 according to the invention.
  • the die 4 with the integrated photodetector 12 is flipped (by 180°) such that front side 6 with the photodetector 12 faces away from the light source 22, and the back side 8 faces the light source 22. That is, light 20 from the light source 22 is incident on the back side 8 of the die 4 , passes through the substrate 10 , and then reaches the photodetector 12 from the back side 8 .
  • the substrate 10 unavoidably attenuates the passing light to some extent, it also acts as an IR bandpass , allowing IR light to pass while wavelengths outside the IR passband are blocked or attenuated . Therefore, the photodetector 12 is illuminated from the back side 8 by the IR portion of the incident light 20 .
  • the IR detector 2 comprises a waver or die 4 with a front side 6 (here : bottom side ) and a back side 8 (here : top side ) .
  • the die thickness 24 is indicated by a double-headed arrow .
  • the die 6 comprises a substrate 10 , preferably a semiconductor substrate , in particular a silicon substrate .
  • a photodetector 12 on the front side 6 there is a photodetector 12 , in particular a photodiode, integrated and partially embedded into or arranged on the substrate 10 .
  • Adj acent to or around the photodetector 12 there may be a metallic circuit layer 14 arranged on the front side 6 of the substrate 10 .
  • the photodetector 12 is configured for backside illumination . Therefore , the photodetector 12 is intended and arranged to sense the IR portion of light 20 impacting on the back side 8 of the IR detector 2 , passing through the substrate 10 , and then reaching the back surface 26 of the photodetector 12 , as indicated by the arrows .
  • the substrate 10 acts as an IR (bandpass ) filter . That is , IR light with a wavelength within a passband, in particular from 850 nm to 1 .
  • 200 nm may pass , while light with a wavelength shorter than the lower limit ( lower cut-of f wavelength) or longer than the upper limit (upper cut-of f wavelength) of the passband is blocked or considerably attenuated .
  • circuits of the metallic circuit layer 14 around the photodetector 12 may be connected via a number of solder balls 30 to a printed circuit board 28 ; with said top side contacts there is no need for bond wires .
  • a (here : top side ) optical barrier or light barrier 32 with an aperture may optionally be arranged of the back side 8 of the die 4 , such that the aperture opening 36 is preferably centered with respect to the photodetector 12 .
  • the size ( area ) of the aperture opening 36 limits the amount of light 20 reaching the photodetector 12 .
  • the surrounding light barrier 32 may be of any suitable opaque material .
  • the light barrier 32 is configured such that an entire spectral range for which the photodetector 12 is sensitive including visible and IR light ( and preferably beyond) is blocked .
  • a light barrier 38 or light shield arranged on the front side 6 (here : bottom side ) of the die 4 , covering at least the front surface 16 of the photodetector 12 .
  • the light barrier 38 is configured such that an entire spectral range for which the photodetector 12 is sensitive including visible and IR light ( and preferably beyond) is blocked Hence, it is assured that essentially only the light 20 of interest from the back side 8 reaches the photodetector 12 while the light from the front side 6 which might distort the measurement is blocked .
  • any suitable opaque material and any suitable means of fixation may be used for the light barrier In a situation wherein the front side 6 of the die 4 is arranged in close proximity to an opaque printed circuit board 28 , a housing, or similar light shielding element , the light barrier 38 may be omitted .
  • the light barrier 38 may also act as or comprise an internal reflector for incident light from the back side 8 . That is , the back surface 40 of the light barrier 38 which faces the front surface 16 of the photodetector 12 may be reflective for IR light . For example , this is achieved by a metal sheet . This means that IR light passing the photodetector 12 that would otherwise be absorbed and lost in the light barrier 38 is reflected back into the photodetector 12 and may enhance the sensed signal .
  • the substrate 10 which is usually made of or comprises substantial amounts of semiconductor material such as silicon, has a suitable thickness , preferably in the range from 100 pm to 750 pm .
  • FIG . 3 shows simulation results with respect to the spectral response of an IR detector 2 according to FIG . 2 with frontside illumination (i . e . illumination from below with no light barrier 38 and without dedicated optical filters applied) versus backside illumination ( as described above ) for two dif ferent substrate thicknesses .
  • the resistivity of the substrate is set to 10 mOhm cm .
  • the signal strength for backside illumination is weaker than for frontside illumination but still quite usable in the IR range from 850 nm to 1 . 200 nm. More importantly, the transmissivity of the substrate 10 coincides with said band of wavelengths without the need for additional optical filters .
  • FIG . 4 shows simulation results with respect to the spectral response of an IR detector 2 according to FIG . 2 with backside illumination for two dif ferent substrate thicknesses and two dif ferent resistivities .
  • the photodetector 12 is illuminated from the backside .
  • FIG . 5 shows simulation results with respect to the spectral response of an IR detector 2 according to FIG . 2 with backside illumination for two dif ferent substrate thicknesses .
  • the photodetector 12 is illuminated from the backside , and the substrate resistivity is set to 10 mOhm cm .
  • FIG . 6 shows the same two graphs as in FIG . 5 , albeit with a logarithmically scaled y-axis .
  • the photodetector 12 is illuminated from the backside , and the substrate resistivity is set to 10 mOhm cm .
  • IR filter 18 light 20 light source 22 die thickness 24 back surface 26 printed circuit board 28 solder ball 30 light barrier 32 aperture opening 36 light barrier 38 back surface 40 signal ratio SR wavelength W

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Spectroscopy & Molecular Physics (AREA)
  • Photometry And Measurement Of Optical Pulse Characteristics (AREA)

Abstract

Un détecteur de lumière infrarouge à faible coût (2) comprend un substrat (10) ayant un côté avant (6) et un côté arrière (8), et un photodétecteur (12) disposé sur le substrat ou sur le côté avant (6) du substrat (10), le photodétecteur (12) étant configuré pour un éclairage arrière, et le substrat (10) étant configuré pour agir comme un filtre passe-bande infrarouge.
PCT/SG2024/050209 2023-04-03 2024-04-01 Détecteur de lumière infrarouge et procédé correspondant de détection de lumière infrarouge Pending WO2024210832A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US202363493840P 2023-04-03 2023-04-03
US63/493,840 2023-04-03

Publications (1)

Publication Number Publication Date
WO2024210832A1 true WO2024210832A1 (fr) 2024-10-10

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PCT/SG2024/050209 Pending WO2024210832A1 (fr) 2023-04-03 2024-04-01 Détecteur de lumière infrarouge et procédé correspondant de détection de lumière infrarouge

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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20090032894A1 (en) * 2007-07-11 2009-02-05 Cubic Corporation Flip-Chip Photodiode
US20160126381A1 (en) * 2013-05-22 2016-05-05 Shih-Yuan Wang Microstructure enhanced absorption photosensitive devices
US20180247968A1 (en) * 2015-11-06 2018-08-30 Artilux Corporation High-speed light sensing apparatus iii

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20090032894A1 (en) * 2007-07-11 2009-02-05 Cubic Corporation Flip-Chip Photodiode
US20160126381A1 (en) * 2013-05-22 2016-05-05 Shih-Yuan Wang Microstructure enhanced absorption photosensitive devices
US20180247968A1 (en) * 2015-11-06 2018-08-30 Artilux Corporation High-speed light sensing apparatus iii

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