WO2011048170A1 - Détecteur de térahertz comprenant une antenne à couplage capacitif - Google Patents

Détecteur de térahertz comprenant une antenne à couplage capacitif Download PDF

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Publication number
WO2011048170A1
WO2011048170A1 PCT/EP2010/065843 EP2010065843W WO2011048170A1 WO 2011048170 A1 WO2011048170 A1 WO 2011048170A1 EP 2010065843 W EP2010065843 W EP 2010065843W WO 2011048170 A1 WO2011048170 A1 WO 2011048170A1
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WIPO (PCT)
Prior art keywords
antenna
thermal
thz
detector
operative
Prior art date
Application number
PCT/EP2010/065843
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English (en)
Inventor
David Goren
Thomas Morf
Israel Berger
Danny Elad
Original Assignee
International Business Machines Corporation
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Filing date
Publication date
Priority claimed from US12/903,235 external-priority patent/US8354642B2/en
Application filed by International Business Machines Corporation filed Critical International Business Machines Corporation
Priority to CN2010800473984A priority Critical patent/CN102575961A/zh
Publication of WO2011048170A1 publication Critical patent/WO2011048170A1/fr

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Classifications

    • 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
    • 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
    • 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
    • G01J5/0215—Compact construction
    • G01J5/022—Monolithic
    • 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
    • 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
    • G01J5/0837—Microantennas, e.g. bow-tie
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q15/00—Devices for reflection, refraction, diffraction or polarisation of waves radiated from an antenna, e.g. quasi-optical devices
    • H01Q15/0006—Devices acting selectively as reflecting surface, as diffracting or as refracting device, e.g. frequency filtering or angular spatial filtering devices
    • H01Q15/0013—Devices acting selectively as reflecting surface, as diffracting or as refracting device, e.g. frequency filtering or angular spatial filtering devices said selective devices working as frequency-selective reflecting surfaces, e.g. FSS, dichroic plates, surfaces being partly transmissive and reflective
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q15/00—Devices for reflection, refraction, diffraction or polarisation of waves radiated from an antenna, e.g. quasi-optical devices
    • H01Q15/0006—Devices acting selectively as reflecting surface, as diffracting or as refracting device, e.g. frequency filtering or angular spatial filtering devices
    • H01Q15/0013—Devices acting selectively as reflecting surface, as diffracting or as refracting device, e.g. frequency filtering or angular spatial filtering devices said selective devices working as frequency-selective reflecting surfaces, e.g. FSS, dichroic plates, surfaces being partly transmissive and reflective
    • H01Q15/004—Devices acting selectively as reflecting surface, as diffracting or as refracting device, e.g. frequency filtering or angular spatial filtering devices said selective devices working as frequency-selective reflecting surfaces, e.g. FSS, dichroic plates, surfaces being partly transmissive and reflective using superconducting materials or magnetised substrates
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q19/00—Combinations of primary active antenna elements and units with secondary devices, e.g. with quasi-optical devices, for giving the antenna a desired directional characteristic
    • H01Q19/10—Combinations of primary active antenna elements and units with secondary devices, e.g. with quasi-optical devices, for giving the antenna a desired directional characteristic using reflecting surfaces
    • H01Q19/108—Combination of a dipole with a plane reflecting surface
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q9/00—Electrically-short antennas having dimensions not more than twice the operating wavelength and consisting of conductive active radiating elements
    • H01Q9/04—Resonant antennas
    • H01Q9/16—Resonant antennas with feed intermediate between the extremities of the antenna, e.g. centre-fed dipole
    • H01Q9/28—Conical, cylindrical, cage, strip, gauze, or like elements having an extended radiating surface; Elements comprising two conical surfaces having collinear axes and adjacent apices and fed by two-conductor transmission lines
    • 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
    • G01J2005/0077—Imaging

Definitions

  • the present invention relates to the field of semiconductor imaging devices, and more particularly relates to a monolithic passive THz detector.
  • THz radiation imaging is currently an exponentially developing research area with inherent applications such as THz security imaging which can reveal weapons hidden behind clothing from distances of ten meters or more; or medical THz imaging which can reveal, for example, skin cancer tumors hidden behind the skin and perform fully safe dental imaging. Constructing prior art THz detectors is typically a challenging endeavor since both radiation sources and radiation detectors are complex, difficult and expensive to make.
  • THz radiation is non- ionizing and is therefore fully safe to humans unlike X-ray radiation.
  • THz imaging for security applications uses passive imaging technology, namely the capabilities of remote THz imaging without using any THz radiation source thus relying solely on the very low power natural THz radiation which is normally emitted from any room temperature body according to well-known black body radiation physics.
  • Passive THz imaging requires extremely sensitive sensors for remote imaging of this very low power radiation.
  • Prior art passive THz imaging utilizes a hybrid technology of superconductor single detectors cooled to a temperature of about 4 degrees Kelvin which leads to extremely complex (e.g., only the tuning of the temperature takes more than 12 hours before any imaging can take place) and expensive (e.g., $100,000 or more) systems.
  • a detector is desirable that can be used to detect THz radiation and that has much lower potential cost compared with existing superconducting solutions.
  • Passive THz imaging requires three orders of magnitude higher sensitivity compared with passive infrared (IR) imaging, which is a challenging gap.
  • a THz radiation detector comprises a plurality of antenna arms separated from a suspended platform by an isolating thermal air gap.
  • the detector functions to concentrate THz radiation energy into the smaller suspended MEMS platform (e.g., membrane) upon which a thermal sensor element is located.
  • the THz photon energy is converted into electrical energy by means of a pixilated antenna using capacitive coupling in order to couple this focused energy across the thermally isolated air gap and onto the suspended membrane on which the thermal sensor is located.
  • the detector mechanism achieves a much stronger, focused THz induced thermal heating of the suspended membrane such that this thermal signal becomes much stronger than the detector temperature noise, even when the detector operates at room temperature. This much higher thermal signal to thermal noise is then converted into a much higher electrical signal to electrical noise by the thermal sensor element.
  • a terahertz (THz) detector comprising a dielectric substrate, an antenna fabricated on the substrate, a suspended platform comprising a thermal sensor operative to receive THz radiation focused by the antenna via capacitive coupling and operative to convert the received THz radiation to an electrical signal and wherein the capacitive coupling provides thermal isolation between the antenna and the thermal sensor.
  • THz terahertz
  • a terahertz (THz) detector comprising a dielectric substrate, an antenna fabricated on the substrate and operative to receive THz radiation, a load resistor capacitively coupled to the antenna and a suspended platform comprising a thermal sensor thermally isolated from the antenna and thermally coupled to the resistor and operative to convert THz radiation focused by the antenna to an electrical signal.
  • THz terahertz
  • a method of detecting terahertz (THz) radiation comprising providing an antenna fabricated on a dielectric substrate and operative to receive THz radiation energy, capacitively coupling THz radiation energy received by the antenna to a resistor, thermally coupling heat generated by the resistor to a suspended platform comprising a thermal sensor thermally isolated from the antenna and thermally coupled to the resistor and converting THz radiation incident on the thermal sensor to an electrical signal.
  • THz terahertz
  • Fig. 1 is a diagram illustrating an example embodiment of a passive THz radiation detector
  • Fig. 2 is a circuit diagram illustrating an equivalent circuit for the THz radiation detector of Figure 1;
  • Fig. 3 is a diagram illustrating a metal pattern layer of a wide bandwidth reflector structure of the detector
  • Fig. 4 is a diagram illustrating several layers of the wide bandwidth reflector structure of the detector
  • Fig. 5 is a diagram illustrating a side view of the THz radiation detector of Figure 1 ;
  • Fig. 6 is a circuit diagram of a first example embodiment of the thermal sensor of the THz detector
  • Fig. 7 is a circuit diagram of a second example embodiment of the thermal sensor of the THz detector.
  • Fig. 8 is a circuit diagram of a third example embodiment of the thermal sensor of the THz detector
  • Fig. 9 is a circuit diagram of a fourth example embodiment of the thermal sensor of the THz detector
  • Fig. 10 is a diagram illustrating a second example embodiment of a passive THz radiation detector
  • Fig. 11 is a diagram illustrating an example 2x2 pixel matrix using the THz radiation detector of Figure 10;
  • Fig. 12 is a diagram illustrating an expanded view of an example THz detector including holding arm structure and suspended thermal sensor;
  • Fig. 13 is a diagram illustrating a side view of the THz radiation detector of Figure 10.
  • Fig. 14 is a diagram illustrating a side view of the holding arm portion of the THz radiation detector.
  • FIG. 1 A diagram illustrating an example embodiment of a passive THz radiation detector is shown in Figure 1.
  • the THz radiation detector embodiment generally referenced 10, comprises antenna bars 12, capacitive coupling gaps 18, suspended platform 16, resistor 22, thermal sensing element 24, holding arm 14 and substrate 28.
  • the etched areas denoted 29 provide isolation to other surrounding detectors.
  • the THz detector 10 utilizes an electromagnetic coupling technique whereby the optical energy (i.e. THz energy) is first absorbed by the antenna 12 (which in this specific example comprises a cross dipole bow-tie type antenna) which functions to convert it to electrical energy that is then capacitive ly coupled to the thermally isolated, released thermal sensor element (e.g., a diode, transistor, etc.). Capacitively coupling the antenna to the thermal sensor element provides thermal isolation of the sensor from the antenna.
  • a plurality of detectors are arranged to receive THz radiation energy in a 2D array configuration.
  • THz radiation energy received in each pixel of the 2D imaging array whose size, in one example embodiment, is on the order of several hundred microns (e.g., 300 microns square) and concentrated at each pixel at a frequency on the order of 1 THz into a much smaller suspended MEMS platform (of the order of tens microns) on which the THz detector is situated (so that the complete suspended thermally isolated MEMS structure has minimal thermal mass and thermal conductivity).
  • this is achieved by means of converting the THz photon energy into electrical energy using a pixilated antenna and by using capacitive coupling to couple this focused antenna energy across the thermally isolated air gap and into the suspended platform on which the thermal sensor is located.
  • This method achieves focused THz induced thermal heating of the suspended platform so that this THz induced thermal signal becomes much stronger than the detector temperature noise, even when the detector operates at room temperature.
  • This higher thermal signal to thermal noise is then converted into a signal having a larger electrical signal to noise ratio by the sensing active device (e.g., transistor).
  • a thermal conductance discontinuity (e.g., capacitance coupling gap 18) is created between the antenna and the relatively small suspended platform by means of the MEMS process.
  • capacitive coupling to focus the antenna energy onto an isolated sub- pixel floating platform 16 can be used with a variety of on-chip pixilated antennas, such as the antenna shown in Figure 10 which has higher bandwidth. Focusing the THz energy via the antenna 12 aids in filtering out competing received infrared radiation, since the infrared radiation not being received by the antenna is absorbed by the small suspended platform 16 whose size is substantially smaller than the pixel size.
  • the capacitive coupling can be increased by combining several silicon process back end of line (BEOL) metal levels to form the capacitors and by using interdigitized (i.e. comb like) structures to increase the capacitor area.
  • the detector provides impedance matching between the pixilated antenna 12 and the thermal sensor across the coupling capacitance.
  • An antenna with reactive impedance is preferably used that cancels the coupling capacitance at the bandwidth of interest. This can be achieved, for example, by using the bow-tie dipole antenna 12 whose length is larger than half a wavelength and is also possible by an appropriate design of the antenna shown in Figure 10.
  • the higher than half wavelength antenna also provides a high impedance of several hundred ohms which aids in matching the antenna to the thermal sensor element across the given impedance of the coupling capacitor.
  • the impedance matching between the antenna and the thermal sensor element is achieved by capacitively coupling the signal into a matched resistor, preferably made of polysilicon.
  • a matched resistor preferably made of polysilicon.
  • this approach is modified to permit separating the two different polarizations of the received THz radiation. This can be useful to identify polarized radiation such as obtained from reflection by flat surfaces.
  • the cross bow-tie type antenna shown in Figure 1 comprises two orthogonal bow-tie antennas 12 whose shape and length are designed to form a bit reactive impedance over the desired THz imaging spectrum.
  • the energy from the antennas is then capacitively coupled to the sub-pixel suspended platform 16 which remains after the etching process.
  • stronger capacitive coupling can be achieved by using several BEOL metal layers of the silicon process connected by dense vias at the edge of the antenna and the platform (not shown).
  • the platform 16 comprises a suspended, thermally isolated platform with the thermal sensing element (e.g., transistor, diode, etc.) located on it.
  • the platform is designed with dimensions typical for existing infra-red detectors.
  • the platform is connected to the silicon substrate 28 by a holding arm 14.
  • the holding arm defines the thermal resistance which, together with the platform thermal capacitance, tunes the platform to have the desired thermal time constant appropriate for video imaging (i.e. about 70 milliseconds or less).
  • the detector shown in Figure 1 is one example embodiment whereby the thermal flow discontinuity between the antenna and the tiny platform is enabled by the MEMS process.
  • the detector of Figure 1 illustrates the option of having the holding arm run inside one of the bow-tie trapezoids. It is appreciated that other
  • the holding arm run diagonally outside of the antenna.
  • the holding arm may go in a big circle around the antenna until it reaches the silicon substrate, which results in much lower thermal conductance of the holding arm.
  • antenna types include spiral antennas, toothed antennas and slotted antennas. Although it is not critical which antenna type is used, it is preferred that the energy from the antenna is not directly coupled to the detector but rather is capacitively coupled to permit thermal isolation of the thermal sensor element.
  • the capacitance coupling between the suspended, thermally isolated, platform and the antenna arms can be significantly increased if the length over which they are made parallel to each other is increased.
  • the coupling capacitor located on the platform edges can be constructed with a saw-tooth (i.e. comb like) edge structure, and the antenna bar shape is adapted to have a complimentary saw-tooth edge structure, such that the structure becomes an interdigitized capacitor structure. This adds significantly to the coupling surface between the coupling capacitor and the antenna, without adding much to the capacitor area (i.e. without adding to the coupling capacitor's thermal capacitance).
  • the same technique can be used if several BEOL metal levels are used to form the coupling capacitor.
  • the same coupling capacitance can be increased by making the parallel spacing between the antenna and the platform smaller. This, however, depends on the quality of the MEMS process being used. A better MEMS process allows this spacing to decrease without the risk of having an electrical short between the antenna and the coupling capacitance metals in the platform.
  • FIG. 2 A circuit diagram illustrating an equivalent circuit for the THz radiation detector of Figure 1 is shown in Figure 2.
  • the detector generally referenced 50, comprises a plurality of antenna bars 52 (e.g., cross dipole bow-tie type antenna), coupling capacitors 54, heating element (e.g., resistor) 56 and thermal sensor 58 thermally coupled to resistor 56.
  • the resistor comprises a polysilicon resistor and the thermal sensor element comprises an SOI transistor which is located on the suspended platform 16 ( Figure 1).
  • the areas designated 24 comprise the diffusion regions of this transistor.
  • the size of the transistor is made relatively small is located at one corner between the cross shaped polysilicon wires.
  • the portion referenced 28 comprises the supporting silicon wafer substrate.
  • the bow-tie antenna resides directly on the silicon wafer as is where the MEMS post-processing is only used to release the small suspended platform both from below and from above. Due to the high dielectric constant and associated losses of the silicon, however, some undesired THz energy reflection may occur close to the antenna.
  • the silicon wafer is back etched from below the antenna to form the large openings using Deep Reactive Ion Etch (DRIE) etching wherein the buried oxide layer (BOX) of the SOI silicon process is used as an etch- stop.
  • DRIE Deep Reactive Ion Etch
  • BOX buried oxide layer
  • the bow-tie antenna bars thus preferably are constructed within a pure silicon oxide area without any silicon below them.
  • the antenna is then still within the same oxide and buried oxide layers which are not separated from the surrounding silicon wafer. Note that in one embodiment, the entire region below the two dimensional array of active pixels is etched using well- known deep reactive-ion etching (DRIE) techniques.
  • DRIE deep reactive-ion etching
  • RIE Reactive Ion Etching
  • a high bandwidth backside reflector plane is added to the pixilated antennas wafer.
  • This backside reflector is on a second plate, parallel to the THz detector chip and separated by a particular distance from its back side using a dedicated spacer. If a back metallic surface is placed with a given separation distance from the antenna, it functions as an effective reflector at the one frequency in which the separation distance equals a quarter of the corresponding wavelength (calculated in the dielectric medium between the antenna and the reflecting metal plane). This is sufficient if it is desired to have a good narrowband reflector at a given frequency. For high bandwidth applications (i.e. frequency ratio about 1 : 1.5 or even greater than 1 :2 or 1 :3), however, an efficient reflector throughout this whole bandwidth is required.
  • a back reflector comprising several metallic layers is constructed, each patterned as an array of metal cross shapes as shown in Figure 3, wherein all layers are constructed within the same background dielectric constant of the packaging material.
  • Figure 3 illustrates a top down view of a single metal patterned layer of the high bandwidth reflector structure.
  • Such a 2D ordered array of cross shapes functions as a filter reflecting back radiation whose half wavelength is smaller than the cross bar length, and permitting radiation with longer wavelengths to pass through.
  • This is similar to the shapes used in a Yagi-Uda antenna.
  • Any rod element of a Yagi-Uda antenna can operate as a reflector or a director depending on its length relative to the half wavelength length of the dipole antenna element itself.
  • the back reflector of a Yagi-Uda antenna is therefore somewhat longer than half a wavelength, and the front directors are shorter than half a wavelength.
  • a plurality of parallel layers of the type patterned as in Figure 3 are combined to form a stack of layers as shown in Figure 4 wherein the cross arm lengths become longer as we move to layers further from the pixilated antennas wafer plane.
  • Each of these patterned layers has a separation distance from the pixilated antenna plane which is equal to a quarter of a wavelength where the cross arm length in this same patterned layer is adapted to be somewhat longer than half the same wavelength. This rule of thumb serves as a guideline for the tuning and optimization of this structure within an
  • EM solver analysis application after which the patterned layer design is somewhat amended to consider the existing interaction between the elements of different lengths.
  • the readout of several pixels is electrically combined together, which yields higher sensitivity (i.e. a higher signal to noise ratio) in the lower THz frequencies but at the cost of reduced resolution in the higher THz frequencies.
  • This technique can be
  • the video rate used has a relatively low frame rate of about 15 Hz (in order to have the largest possible integration time in each sensing device to achieve the largest possible signal to noise ratio) the available "dead" time between frames can be used to alternatively display both the image with a small pixel size (i.e. higher resolution) and the image with a large pixel size (i.e. higher sensitivity and higher penetration through clothing). Both images are combined in the eye of the user viewing the image to create a higher quality image having both high resolution and high
  • This same technique can be used to form a continuous function between the two extremes of small and large pixel size, by displaying many image frames during the sensor integration time, where some images have small pixels and some of them have the combined larger pixels. By varying the ratio of image frames shown with the larger pixels, one can sweep through the trade off between resolution and
  • FIG. 5 A diagram illustrating a side view of the THz radiation detector of Figure 1 is shown in Figure 5.
  • the detector, generally referenced 100 comprises bow-tie antenna bars 126, suspended platform 128, silicon substrate 102 and reflector 120.
  • the bow-tie (or any other type) antenna bars 126 are constructed on the silicon substrate 102 and comprise metal 104 (e.g., aluminum or copper) over silicon oxide dielectric (BOX) 112.
  • metal 104 e.g., aluminum or copper
  • BOX silicon oxide dielectric
  • the suspended platform 128 structure comprises silicon oxide dielectric layer 114, silicon thermal sensor element (e.g., sensing transistor body or bulk wafer) layer 116, polysilicon layer 118, silicon oxide dielectric (BOX) 108 and metal (e.g., aluminum or copper) 106.
  • the high bandwidth reflector 120 comprises dielectric layer 122 and multiple layers of metal mesh patterns 124.
  • the opening under the antenna and suspended platform is constructed using the well-known technique of Deep Reactive Ion Etch (DRIE) etching.
  • DRIE Deep Reactive Ion Etch
  • the suspended platform is separated from the antenna bars by a capacitive coupling gap 110.
  • FIG. 6 A circuit diagram of a first example embodiment of the thermal sensor of the THz detector is shown in Figure 6.
  • the thermal sensor element 60 comprises an MOS transistor 62 operating in sub-threshold region.
  • Thermal energy thermally coupled from the resistor 56 ( Figure 2) causes an electrical signal to be generated in the transistor which is then amplified and processed by read-out circuitry.
  • FIG. 7 A circuit diagram of a second example embodiment of the thermal sensor of the THz detector is shown in Figure 7.
  • the thermal sensor element 70 comprises a forward biased diode 72.
  • Thermal energy thermally coupled from the resistor 56 ( Figure 2) causes an electrical signal to be generated in the diode which is then amplified and processed by read-out circuitry.
  • FIG 8. A circuit diagram of a third example embodiment of the thermal sensor of the THz detector is shown in Figure 8.
  • the thermal sensor element 80 comprises a forward biased bipolar transistor junction 82. Thermal energy thermally coupled from the resistor 56 ( Figure 2) causes an electrical signal to be generated in the bipolar transistor which is then amplified and processed by read-out circuitry.
  • FIG. 9 A circuit diagram of a fourth example embodiment of the thermal sensor of the THz detector is shown in Figure 9.
  • the thermal sensor element 90 comprises a resistive bolometer 92. Thermal energy thermally coupled from the resistor 56 ( Figure 2) causes an electrical signal to be generated in the bolometer which is then amplified and processed by read-out circuitry.
  • FIG. 10 A diagram illustrating a second example embodiment of a passive THz radiation detector is shown in Figure 10.
  • the detector shown in Figure 10 is similar to that of Figure 1 with the major difference being the type of on-chip antenna used.
  • the antenna has a square toothed shape.
  • the detector, generally referenced 130 comprises a plurality of antenna arms 132 (four in this example), silicon substrate 144 surrounding the antenna 130, suspended platform 136, holding arm 138, sensor signals 142 and read-out circuit 140.
  • antenna protrusions 134 approximately the length of the suspended platform, capacitively couple the thermal energy focused by the antenna to corresponding coupling capacitors (not shown) on the suspended platform across an isolation gap surrounding the suspended platform.
  • the energy coupled across the gap heats a resistor which is sensed by a thermal sensor (not shown) constructed on the suspended platform.
  • the output of the sensor is processed by the read-out circuitry 140 for display or further post-processing.
  • the imaging matrix generally referenced 150, comprises a plurality of detectors 152 (four in this example embodiment), sensor signal lines 154 and read-out circuitry 156. Each detector comprises antenna arms 157, suspended platform 160 and holding arm 158. The output of the sensors located on the platforms is input to the read-out circuit 156 for display or further post-processing. Note that in one embodiment, the pixel array is surrounded by dummy pixel rows and columns.
  • FIG. 12 A diagram illustrating an expanded view of an example THz detector including holding arm structure and suspended thermal sensor is shown in Figure 12.
  • the example detector generally referenced 170, comprises a plurality of antenna bars 172 (four in this example), suspended platform 174 and holding arm 186.
  • the suspended platform 174 comprises coupling capacitors 178 along the four edges of the platform wherein the capacitors are formed from the thermally isolated air gaps 176 surrounding the platform, cross shaped polysilicon resistor 180 which heats the entire platform and thermal sensor 182.
  • Holding arm 186 is attached to the silicon substrate 188 and functions to support the suspended platform.
  • Sensor output signals 184 are routed from the thermal sensor along the holding arm to the read-out circuit (not shown).
  • FIG. 13 A diagram illustrating a side view of the THz radiation detector of Figure 10 is shown in Figure 13.
  • the detector generally referenced 190, comprises antenna arms 191 and suspended platform 193.
  • the antenna arms comprise BOX layer 204, silicon dioxide layers 200, 196, polysilicon portion 208, metal portion 212, metal layer 194 and oxide layer 192.
  • the suspended platform comprises BOX layer 206, silicon dioxide layer 202, polysilicon layer 218, silicon dioxide layer 198 and metal portions 212.
  • FIG. 14 A diagram illustrating a side view of the holding arm portion of the THz radiation detector is shown in Figure 14.
  • the holding arm generally referenced 220, comprises BOX layer 224, silicon dioxide layer 225, silicon nitride layer 227, polysilicon sensor signal lines 228, silicon nitride layer 226 and silicon dioxide layer 222.
  • the corresponding black body power temperature sensitivity per degree Kelvin is given as
  • ⁇ is the efficiency of the detector
  • r ⁇ env is the efficiency of the environment (i.e. anything other than the detector).
  • the value of 0.3 is reasonable to assume at this stage.
  • G t,h which yields a required holding arm thermal conductivity of 1.243 x 10 ⁇ 7 Watt I °K assuming a detector temperature of 315 degrees Kelvin (40 degrees Celsius). Note that better results are obtained when the detector is cooled somewhat and maintained, using a closed cycle system, at a fixed temperature somewhat lower than room temperature.
  • micron x 50 micron which can be (in principle) as low as 10 micron x 10 micron, thereby reducing the electrical noises by a factor of 625 and the thermal fluctuation noise by a factor of 25.

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

Abstract

La présente invention concerne un détecteur de rayonnement THz (10) qui comprend plusieurs bras d'antenne (12) séparés d'une plateforme suspendue (16) par un espace d'air thermiquement isolé (18). Le détecteur concentre l'énergie du rayonnement THz dans la plateforme MEMS suspendue plus petite (par ex., membrane) sur laquelle se trouve un élément de détection thermique (24). L'énergie photonique THz est convertie en énergie électrique au moyen d'une antenne à pixels à l'aide d'un couplage capacitif dans le but de coupler cette énergie focalisée sur l'espace d'air thermiquement isolé et sur la membrane suspendue sur laquelle se trouve le capteur thermique.
PCT/EP2010/065843 2009-10-23 2010-10-21 Détecteur de térahertz comprenant une antenne à couplage capacitif WO2011048170A1 (fr)

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Application Number Priority Date Filing Date Title
CN2010800473984A CN102575961A (zh) 2009-10-23 2010-10-21 包括电容耦合天线的太赫兹检测器

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US25420709P 2009-10-23 2009-10-23
US61/254,207 2009-10-23
US12/903,235 US8354642B2 (en) 2010-10-13 2010-10-13 Monolithic passive THz detector with energy concentration on sub-pixel suspended MEMS thermal sensor
US12/903,235 2010-10-13

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WO2011048170A1 true WO2011048170A1 (fr) 2011-04-28

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US8872112B2 (en) 2011-10-02 2014-10-28 International Business Machines Corporation Hybrid THz imaging detector with vertical antenna and sub-pixel suspended MEMS thermal sensor and actuator
US8957378B2 (en) 2011-10-02 2015-02-17 International Business Machines Corporation Nano-tip spacers for precise gap control and thermal isolation in MEMS structures
CN102590095A (zh) * 2012-01-20 2012-07-18 中国科学院上海技术物理研究所 二维摆镜扫描的太赫兹被动式成像***
CN102680091A (zh) * 2012-06-12 2012-09-19 中国科学院上海微***与信息技术研究所 一种太赫兹波的高速探测方法及装置
GB2507306A (en) * 2012-10-25 2014-04-30 Ibm An antenna-coupled bolometer device for sensing electromagnetic radiation
US9105551B2 (en) 2013-02-18 2015-08-11 Commissariat à l'énergie atomique et aux énergies alternatives Method for making an imager device
FR3016997A1 (fr) * 2014-01-30 2015-07-31 Commissariat Energie Atomique Detecteur de rayonnement photonique comportant un reseau d'antennes et un support resistif en spirale
EP2902758A1 (fr) * 2014-01-30 2015-08-05 Commissariat à l'Énergie Atomique et aux Énergies Alternatives Détecteur de rayonnement photonique comportant un réseau d'antennes et un support résistif en spirale
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EP3246675A4 (fr) * 2015-01-14 2018-09-26 Hamamatsu Photonics K.K. DÉTECTEUR BOLOMÈTRE À THz
US10393649B2 (en) 2015-01-14 2019-08-27 Hamamatsu Photonics K.K. THz bolometer detector
CN107946401A (zh) * 2017-08-30 2018-04-20 中国科学院上海技术物理研究所 一种室温拓扑绝缘体太赫兹探测器及制备方法

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