CN204128692U - The infrared imaging detector of a kind of pixel cell and formation thereof - Google Patents
The infrared imaging detector of a kind of pixel cell and formation thereof Download PDFInfo
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- CN204128692U CN204128692U CN201420575717.4U CN201420575717U CN204128692U CN 204128692 U CN204128692 U CN 204128692U CN 201420575717 U CN201420575717 U CN 201420575717U CN 204128692 U CN204128692 U CN 204128692U
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Abstract
The utility model disclose a kind of pixel cell and thus pixel cell form infrared imaging detector.This pixel cell comprises the supporting layer set gradually, bonded layer, dielectric layer, photosensitive unit layer, sensing circuit layer and microlens layer from the bottom to top, described sensing circuit layer and photosensitive unit layer are positioned at the same face of silicon substrate, described microlens layer is positioned at the another side of silicon substrate, described photosensitive unit is the micro-nano structure by conducting metal or semi-conducting material manufacturing, and be positioned at pixel cell center, described photosensitive unit be read out circuit ring around, and to interconnect with sensing circuit.This infrared imaging detector is made up of the pixel cell distributed in two-dimensional array.The back side of the present utility model lenticule contributes to improving fill factor, curve factor, and then improves the responsiveness of device; The thermal mass of micro-nano structure photosensitive unit is very little, can significantly improve the response speed of detector; Preparation technology is simple, is conducive to reducing costs.
Description
Technical field
The utility model belongs to infrared detection technique field, relates to the back illumination infrared detecting pixel unit with the photosensitive unit of micro-nano structure, the not refrigerant infrared imaging detector be made up of this pixel cell.
Background technology
The current not refrigerant infrared imaging detector based on micro-metering bolometer principle all adopts front lit thermosensitive film absorbing detection mode.Fig. 1 is the pixel vertical cross-section diagram of the micro-metering bolometer detector of lighting system work in the past.Infrared absorption layer 12 containing photo-conductive film is suspended in silicon substrate 21 surface containing sensing circuit (ROIC) by the supporting bridge leg 13 of both sides, supporting leg 13 surface also makes the two ends of photosensitive unit be connected with the electrical pickoff 14 of ROIC respectively containing conductive electrode simultaneously, forms electric loop.Infrared radiation changes into heat after inciding and photosensitive unit being absorbed and the resistance of sensitive thin film is changed, and this variable quantity is read out circuit and detects.A large amount of pixel cell composition two-dimensional array forming surface array detector, can realize staring infrared imaging.
Infrared absorption layer containing photo-conductive film in dot structure in Fig. 1 does not directly contact with silicon substrate but is suspended on silicon substrate, its objective is reduction thermal conductance, strengthens the temperature rise after light absorption, obtain higher photoresponse rate.Realize high frame rate detection to obtain the fast response time, the low thermal mass multi-layer film structure that infrared absorption layer 12 often adopts thickness to be less than 1 micron, the unabsorbed infrared light of part returns infrared absorption layer after being reflected by the metal level 11 of substrate surface simultaneously.Making it to form quarter-wave resonance cavity with the spacing of metal level 11 by controlling infrared absorption layer 12, the absorptivity of more than 80% can be obtained near resonance wavelength.But the elemental area that the dot structure of Fig. 1 is certain because supporting leg occupies, therefore the fill factor, curve factor of detector is not high, the capacity usage ratio of infrared light is low, and the thermal mass of infrared absorption layer is still comparatively large simultaneously, limits the further raising of response speed.The technology improved adopts three-decker, intermediate second layer is increased for placing supporting leg as passed through in US Patent No. P6144030, upper strata infrared absorption layer is connected with the supporting leg of the below second layer by short and thin support column, for the pixel cell of 30 μm × 30 μm, fill factor, curve factor can higher than 85%.But the structure complicated process of preparation of this improvement, poor reliability, cost is difficult to reduce.
Utility model content
The utility model provides the infrared imaging detector of a kind of pixel cell and formation thereof, and object is the fill factor, curve factor and the response device rate that improve detector, improves reliability, and reduces production cost.
A kind of pixel cell that the utility model provides, it is characterized in that, it comprises the supporting layer set gradually from the bottom to top, bonded layer, dielectric layer, photosensitive unit layer, sensing circuit layer and microlens layer, described sensing circuit layer and photosensitive unit layer are positioned at the same face of silicon substrate, described microlens layer is positioned at the another side of silicon substrate, described photosensitive unit is the micro-nano structure by conducting metal or semi-conducting material manufacturing, and be positioned at pixel cell center, described photosensitive unit be read out circuit ring around, and interconnect with sensing circuit, described lenticule is used for the infrared light of incidence coalescence can focus to photosensitive unit, photosensitive unit is used for absorbing and detection infrared light.
Described micro-nano structure can be nano dot, nano wire, nano rod, or star, polygon or fractal graph nanostructured.
Technique scheme can adopt following any one or appoint a several mode improve: be provided with isolation channel around (one) described photosensitive unit, isolate for the silicon substrate of photosensitive unit and surrounding is carried out heat, make simultaneously electrode lead portion unsettled be reduced by lead-in wire heat conduction loss; (2) described support layer surface is provided with cavity array, and cavity inside surface is coated with metallic reflective coating, for not absorbed by photosensitive unit but the light arriving pocket surfaces is reflected back photosensitive unit, absorbs to realize strengthening; (3) described photosensitive unit surrounding has cone tank, makes pixel center region form a taper table top wide at the top and narrow at the bottom, and the infrared light that the side of this taper table top is used for lenticule is assembled reflects and makes it enter into described photosensitive unit; (4) electrical interconnection is carried out by the electrical pickoff of the sensing circuit in electrode wires and pixel cell in described photosensitive unit two ends, described photosensitive unit both sides are provided with antenna, antenna is for collecting the part infrared resonance radiation collection converging to taper table top, produce surface current, and near nano wire, excite the electromagnetic field intensity of enhancing, to improve the receptivity of nano wire to resonance infrared radiation; (5) described photosensitive unit is nano wire, and nano wire both sides are provided with dipole antenna, and the two-arm of dipole antenna is vertical with nano wire, and the load point in the middle of cover antenna; (6) described antenna is logarithm antenna, helical aerials or butterfly antenna.
The utility model provides the infrared imaging detector be made up of above-mentioned pixel cell, and this infrared imaging detector is made up of the pixel cell distributed in two-dimensional array.
The structure of the back illumination micro-nano structure detector that the utility model provides and there is such beneficial effect: (1) back side lenticule contributes to improving fill factor, curve factor, and then improves the responsiveness of device; (2) thermal mass of micro-nano structure photosensitive unit is very little, can significantly improve the response speed of detector; (3) preparation technology is simple, is conducive to reducing costs.
Accompanying drawing explanation
Fig. 1 is the vertical cross-section diagram of traditional single pixel of uncooled IRFPA detector;
Fig. 2 is the vertical cross-section diagram of the single pixel of a kind of back illumination non-refrigeration infrared detector of the present utility model;
Fig. 3 is the front view (FV) (not containing passive support sheet) of the detector pixel array formed with two-dimensional array form dense arrangement;
Fig. 4 is a kind of vertical cross-section diagram of isolating the single pixel of back illumination uncooled IRFPA detector of cavity and spherical reflector with heat of the present utility model;
Fig. 5 is the vertical cross-section diagram with the single pixel of back illumination uncooled IRFPA detector of taper table top on a kind of active of the present utility model;
Fig. 6 is the vertical cross-section diagram with the single pixel of back illumination uncooled IRFPA detector of isolation annular groove on a kind of active of the present utility model;
Fig. 7 is a kind of sub-wavelength or front plan view of the infrared photosensitive unit of nano wire with dipole antenna coupling;
Fig. 8 is a kind of sub-wavelength or front plan view of the infrared photosensitive unit of nano wire with butterfly antenna coupling;
Fig. 9 is a kind of sub-wavelength or front plan view of the infrared photosensitive unit of nano wire with helical aerials coupling;
Figure 10 is the fabrication processing figure of a kind of micro-nano structure non-refrigeration infrared detector that the utility model example provides.
Embodiment
Below in conjunction with accompanying drawing, embodiment of the present utility model is described further.It should be noted that at this, the explanation for these embodiments understands the utility model for helping, but does not form restriction of the present utility model.In addition, if below in described each embodiment of the utility model involved technical characteristic do not form conflict each other and just can mutually combine.
Fig. 2 is the vertical cross-section diagram of the single pixel of a kind of infrared eye.This pixel forms primarily of slim silica-based active 200 and passive support sheet 210 two parts bonding, and the pixel cell structure therefore from the bottom up after bonding contains successively: supporting layer 21, bonded layer 22, photosensitive unit 23, dielectric layer 24, sensing circuit (ROIC) layer 25 and silicon microlens layer 26.
Supporting layer 21 material can be silicon, pottery or optical glass, preferred optical glass; The material of bonded layer 22 can be organic or inorganic bonded adhesives, solder etc.; Dielectric layer 24 plays insulation and passivation, and material used is the dielectric material with low thermal conductivity coefficient, preferred silicon dioxide.Photosensitive unit 23 is for having the conducting metal of thermistor characteristic as Pt, Ti, Ni etc., or the micro-nano structure that semiconductor makes as materials such as vanadium oxide (VOx), amorphous silicon and Si-Ge.The micro-nano structure of the utility model indication refers to have at least a direction to be of a size of the planar structure of nanometer scale in the plane being parallel to substrate surface, as simple nano dot, nano wire, nano rod, the nanostructured figure of complicated shape also can be comprised as star, polygon or fractal graph etc.
Belong to infrared transmission passage around the circle of pixel center certain limit or square region, the distribution of sensing circuit should avoid these regions, in order to avoid stop that infrared light converges to photosensitive unit 23.Sensing circuit layer is positioned at the side of silica-based active 200 on the surface, and its depth range is generally within 3-4 micron, and microlens layer 26 is in the opposite side surface of silica-based active 200, and its crown height is generally within 5 microns.(be generally square because the Pixel Dimensions of detector is less, the length of side tens to tens microns), for obtaining the focused spot of diffraction limit, fast lenticule should be adopted, therefore silicon substrate 200 need be thinned to the thickness of 10-50 micron, then make lenticule thereon and be coated with optical film as antireflective film or filter coating.
Fig. 3 is formed the front view of pel array (from the unilateral observation of passive support sheet using micro-nano structure detector as pixel cell by two dimensional form dense arrangement, but not containing passive support sheet), wherein nano wire photosensitive unit 23 occupies the very small size of each pixel center, the two ends of nano wire are connected with the electrical pickoff 32 of sensing circuit by metallic film lead-in wire 31, realize the electrical interconnection with sensing circuit.
Fig. 4 is another embodiment, be that cavity 20 is contained in region relative with photosensitive unit 23 on support chip 210 with the difference of Fig. 2 embodiment, the inside surface of cavity 20 also can be coated with metallic reflective coating 27, its effect is that unabsorbed for photosensitive unit infrared radiation is reflected back photosensitive unit 23, strengthens the absorptivity to infrared light.Another effect of cavity 20 is the heat conduction loss reducing photosensitive unit outside surface.The surface configuration of cavity can be spheric, aspheric surface shape, or other shapes of V-type or optimal design.
Fig. 5 is another embodiment, is with the difference of Fig. 2 and Fig. 4, and the surrounding of photosensitive unit 23 has isolation channel 30, and its effect reduces the heat conduction loss of photosensitive unit 23 by silicon substrate and metal lead wire.And its support chip 210 still adopts the structure same with Fig. 2 and Fig. 3 embodiment.The degree of depth of isolation channel is generally several microns to tens microns, and width is 1-3 microns.
Fig. 6 is the modified node method of Fig. 5 embodiment, is from the different of Fig. 5, and the surrounding of photosensitive unit 23 adopts the cone tank structure of inclination, and it has the thermal conductance loss function of attenuating photosensitive unit 23 by surrounding equally.Simultaneously cone tank makes pixel center region form a taper table top wide at the top and narrow at the bottom, and photosensitive unit is on the narrow table top of taper platform.Because wide conical bottom mask has larger area, therefore the infrared light more assembled by lenticule can be collected incide photosensitive unit, the reflection of conical surface lateral wall by more convergence of rays to photosensitive unit.
Fig. 7 is a kind of front plan view (time not containing support chip) of nano wire detector pixel of integrated optics antenna.Optical antenna is for strengthening the capacity gauge to particular resonance spectral coverage infrared radiation.Photosensitive unit 23 (as nano wire) is as the material to sensitive for infrared radiation, and electrical interconnection is carried out by electrode wires 31 and the electrical pickoff 32 of the ROIC in this pixel in its two ends.Nano wire both sides have the two-arm of dipole antenna 33 perpendicular, and the load point in the middle of cover antenna.Antenna will converge to the part infrared resonance radiation collection of taper table top 34, produce surface current, and near nano wire, excite the electromagnetic field intensity of enhancing thus improve nano wire to the receptivity of resonance infrared radiation.Antenna structure form on table top 34 can be various, as can butterfly antenna 33 as shown in Figure 8, or the helical aerials 33 shown in Fig. 9, or other antenna forms are as logarithm antenna etc.Different antennas has different spectral responses and polarity response, can select as required.The dirigibility of antenna-coupled is also same antenna structure or multiple antenna structure to combinationally use, and realizes multispectral section or the detection of selectivity spectral coverage.
The material that above-mentioned various antenna uses can adopt metal, conductive compound or semiconductor, wherein metal preferably gold (Au), conductive compound preferential oxidation indium tin (ITO), the preferred highly doped silicon of semiconductor.By the design of antenna parameter, the antenna mode of infrared band can be excited, produce the enhancing field intensity concentrated at antenna load point, the strong absorption of generation causes local temperature to rise by the photosensitive unit at this place, thus causes electrical quantity to change and be read out circuit detection.Under antenna-coupled, the size of photosensitive unit can be reduced to tens or tens nanometer scale, still has larger light capacity gauge.
The utility model for the embodiment of Fig. 4 to Fig. 6, design based on wafer scale step of preparation process as shown in Figure 10.According to the structure of device, the preparation of wafer is divided into active and passive support sheet two class, can make simultaneously, then adopt bonding techniques to be bonded together by two kinds of wafers.
Main processing step comprises:
(1) make ROIC circuit: adopt twin polishing silicon wafer as the substrate of device, make ROIC circuit at a side surface of silicon wafer;
(2) make the photosensitive element array of micro-nano structure: make photosensitive unit in the central area of each pixel, form photosensitive-cell array, and make dielectric layer on its surface;
(3) the hot isolation channel in side makes: employing dry method or wet processing corrode the silicon materials part around photosensitive unit in each pixel, forms the hot isolation channel array in rectangle or V-type cross section.
(4) passive support sheet (simultaneously can carry out with above-mentioned 1-3 step) is made: adopt silicon or glass substrate, a surface of support chip makes the spill corresponding with photosensitive-cell array or V-type array of cavities, and is coated with metallic reflective coating at cavity inside surface;
(5) bonding design producing: figuratum side makes bonding pattern on silicon chip and glass sheet respectively, and bonding material can be polymkeric substance, solder or metal etc.;
(6) silicon wafer and glass support sheet bonding: be bonded together after silicon wafer has the side of figure and support chip is aimed at, bonding pattern can be selected and glued joint the form such as bonding or solder bond;
(7) bonding pad is thinning: the silicon layer of silicon wafer side in bonding pad is thinned to the thickness of 10-50 micron;
(8) make lenticule be coated with surface optics rete: position corresponding with opposite side photosensitive unit on thinning makes microlens array, subsequently at microlens array plated surface optical film layer as antireflective film or filter coating etc.
(9) section and encapsulation: bonding pad is cut into little chip, tests and selects qualified little chip for encapsulation.
The utility model is not only confined to above-mentioned embodiment; persons skilled in the art are content disclosed in the utility model; other multiple embodiment can be adopted to implement the utility model; therefore; every employing project organization of the present utility model and thinking; do the design that some simply change or change, all fall into the scope of the utility model protection.
Claims (9)
1. a pixel cell, it is characterized in that, it comprises the supporting layer set gradually, bonded layer, dielectric layer, photosensitive unit layer, sensing circuit layer and microlens layer from the bottom to top, described sensing circuit layer and photosensitive unit layer are positioned at the same face of silicon substrate, described microlens layer is positioned at the another side of silicon substrate, described photosensitive unit is the micro-nano structure by conducting metal or semi-conducting material manufacturing, and be positioned at pixel cell center, described photosensitive unit be read out circuit ring around, and to interconnect with sensing circuit.
2. pixel cell according to claim 1, is characterized in that, described micro-nano structure is nano dot, nano wire, nano rod, or star, polygon or fractal graph nanostructured.
3. pixel cell according to claim 1, is characterized in that, is provided with isolation channel around described photosensitive unit.
4. pixel cell according to claim 1, is characterized in that, described support layer surface is provided with cavity array, and cavity inside surface is coated with metallic reflective coating.
5. pixel cell according to claim 1, it is characterized in that, described photosensitive unit surrounding has cone tank, make pixel center region form a taper table top wide at the top and narrow at the bottom, the infrared light that the side of this taper table top is used for lenticule is assembled reflects and makes it enter into described photosensitive unit.
6. pixel cell according to claim 5, it is characterized in that, electrical interconnection is carried out by the electrical pickoff of the sensing circuit in electrode wires and pixel cell in described photosensitive unit two ends, described photosensitive unit both sides are provided with antenna, antenna is for collecting the part infrared resonance radiation collection converging to taper table top, produce surface current, and near nano wire, excite the electromagnetic field intensity of enhancing, to improve the receptivity of nano wire to resonance infrared radiation.
7. pixel cell according to claim 6, is characterized in that, described photosensitive unit is nano wire, and nano wire both sides are provided with dipole antenna, and the two-arm of dipole antenna is vertical with nano wire, and the load point in the middle of cover antenna.
8. pixel cell according to claim 6, is characterized in that, described antenna is helical aerials or butterfly antenna.
9. the infrared imaging detector be made up of described pixel cell arbitrary in claim 1 to 5, is characterized in that, this infrared imaging detector is made up of the pixel cell distributed in two-dimensional array.
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105527026A (en) * | 2014-09-29 | 2016-04-27 | 华中科技大学 | Pixel unit, infrared imaging detector provided with pixel unit and manufacturing process |
| CN106356416A (en) * | 2016-11-28 | 2017-01-25 | 中国电子科技集团公司第十三研究所 | High-speed photoelectric detector chip and manufacturing method thereof |
| CN110095426A (en) * | 2019-04-12 | 2019-08-06 | 华中科技大学鄂州工业技术研究院 | A kind of infrared gas sensor based on infrared emission and detection integrated chip |
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2014
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Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105527026A (en) * | 2014-09-29 | 2016-04-27 | 华中科技大学 | Pixel unit, infrared imaging detector provided with pixel unit and manufacturing process |
| CN105527026B (en) * | 2014-09-29 | 2019-04-12 | 华中科技大学 | A kind of infrared imaging detector of pixel unit and its composition |
| CN106356416A (en) * | 2016-11-28 | 2017-01-25 | 中国电子科技集团公司第十三研究所 | High-speed photoelectric detector chip and manufacturing method thereof |
| CN110095426A (en) * | 2019-04-12 | 2019-08-06 | 华中科技大学鄂州工业技术研究院 | A kind of infrared gas sensor based on infrared emission and detection integrated chip |
| CN110095426B (en) * | 2019-04-12 | 2022-01-07 | 华中科技大学鄂州工业技术研究院 | Infrared gas sensor based on infrared emission and detection integrated chip |
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