CN104993199A - Ultrathin terahertz medium high frequency broad band filter and manufacturing method for the same - Google Patents
Ultrathin terahertz medium high frequency broad band filter and manufacturing method for the same Download PDFInfo
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Abstract
The invention discloses an ultrathin terahertz medium high frequency broad band filter and a manufacturing method for the same. The ultrathin terahertz medium high frequency broad band filter, from the bottom to the top, successively comprises one layer or multiple layers of amorphous medium films and one layer or multiple layers of metal films, wherein the amorphous medium film is etched into a periodical graph structure which is either a square or a circular. The metal film is directly adhered on the surface of the amorphous medium film, and the shapes of the metal film and the amorphous medium film are consistent. The terahertz medium high frequency broad band filter disclosed by the invention has a relatively thin thickness, can reduce the insertion loss brought by a traditional substrate material and can prevent the fabry-perot resonating caused by a resonant cavity constituted by the substrate in the terahertz wave band. The ultrathin terahertz medium high frequency broad band filter disclosed by the invention is simple in structure and easy in manufacture, and has relatively broad bandpass width, wherein the center frequency of the bandpass can cover the whole terahertz wave band. If a plurality of terahertz filters are superposed, a terahertz filter having steeper responding wave form and good out-of-band rejection performance is obtained.
Description
Technical field
The invention belongs to Terahertz Technology field, be specifically related to a kind of ultra-thin Terahertz medium-high frequency broadband filter and preparation method thereof.
Background technology
THz wave is last wave band not yet obtaining Application and Development well in all electromagnetic waves, is often called as in " Terahertz gap ".THz wave is between microwave and infrared waves, and being commonly referred to as frequency is 0.1-10THz, and wavelength is the electromagnetic wave of 3000-30 μm of this scope.THz wave has the physical characteristic of the uniquenesses such as pulse is narrow, photon energy is low, penetrability is strong, makes it have broad application prospects in fields such as spectroscopic imaging, biomedicine and environmental science, astrophysics, safety monitoring and quality control, material science, the communication technologys.
Along with the acquisition of the stable high-power THz source in broadband, non-brake method terahertz detection technology comes into one's own gradually.2005, the A.W. Lee etc. of Massachusetts Polytechnics arranges as detector with uncooled microbolometer focal plane array, build the terahertz imaging system of real-time continuous ripple, confirm that the feasibility of micro-metering bolometer for terahertz imaging is (see A.W. Lee, " Real-time; continuous-wave terahertz imaging by use of a microbolometer focal-plane array ", Optics Letters, 30 (19): 2563-2565 (2005) documents).The electromagnetic wave energy of radiation is mainly converted into heat by the operation principle of uncooled microbolometer, makes the electric property of detector sensitive material change and be detected.Therefore, in order to improve the sensitivity of system, the THz wave of more wide spectrum should be allowed as far as possible to enter probe unit, be converted into more heat.Meanwhile, in order to improve the signal to noise ratio of system, also answer other wave band of filtering (as ultraviolet, visible ray, infrared, microwave etc.) electromagnetic interference.So broadband terahertz filter is the key technology promoting terahertz detector performance.
Because nature lacks effective Terahertz responsive materials, there is an artificial composite structure for the extraordinary electromagnetic response character not available for natural material, i.e. electromagnetism Meta Materials (Metamaterial is called for short Meta Materials), once proposition, cause the extensive attention of academia and industrial quarters soon.Meta Materials can provide highly controlled electromagnetic response, and its response range can contain light wave, infrared, the wave band such as Terahertz, millimeter wave.Utilize Meta Materials, perfect lens, stealthy cape, the perfect particular device such as absorber, perfect filter of electromagnetic wave can be realized.
Frequency-selective surfaces (frequency selective surfaces, being called for short FSS) structure is one of study hotspot in Meta Materials field, each periodic unit of FSS is equivalent to a passive resonator, by this passive resonator periodic arrangement, can carry out space filtering to electromagnetic wave.It is that the second order band of square four open-types of bilayer of 0.25THz leads to terahertz filter that Mingzhi Lu etc. reports a kind of centre frequency, this filter adopts thickness to be that the single crystal quartz crystal of 165 μm is as dielectric substrate, at 227-283GHz, there is second order bandpass characteristics, insertion loss is about 2dB(see Mingzhi Lu, " Second-order bandpass terahertz filter achieved by multilayer complementary metamaterial structures ", Optics Letters, 36 (7): 1071-1073 (2011) documents).For this FSS Structure Filter based on metal-dielectric-metal structure, the loss of backing material and thickness affect larger on the response characteristic of FSS structure.The substrate thickness of FSS structure and resonance frequency are roughly linear, thickness is thinner, frequency is higher (see Mingzhi Lu, " Second-order bandpass terahertz filter achieved by multilayer complementary metamaterial structures ", Optics Letters, 36 (7): 1071-1073 (2011) documents).So, if selected the less quartz of THz wave loss as substrate, preparation Dai Tong center is the FSS Structure Filter of 3THz, resonance peak is led in order to avoid producing unnecessary band near design wave band, i.e. forming method Fabry-Perot-type resonance, the thickness of quartz substrate should be thinned to about 20 μm.Obviously, the processing and use of giving filter are brought great difficulty by so thin quartz substrate.
In order to solve the various problems that typical backing material brings to FSS filter, such as Fabry-Perot resonance, insertion loss etc., a kind of solution removes substrate, realizes the FSS all-metal construction at the linerless end.The implementation method of traditional all-metal construction is: spin coating photoresist in one piece of quartz substrate, develops after photoetching resonant shape unit.Then, the deposition techniques thickness such as electron beam evaporation are adopted to be approximately the low stress metal of 10 μm, as copper or nickel.Then, ultrasonic stripping, obtains the metal structure of resonant shape.Finally, by chemical corrosion release back quartz substrate.Adopt in this way, D.W. the people such as Porterfield successfully produces operating center frequency and is positioned at the terahertz filter based on cross structure of 585GHz-2.1THz (see D.W. Porterfield, " Resonant metal-mesh bandpass filters for the far infrared ", Applied Optics, 33 (25): 6046-6052 (1994) documents).Regrettably, the stripping technology of this thick metal (~ 10 μm), all requires higher to the spin coating thickness of photoresist and exposure imaging.And, simple resonant shape structure can only be realized, for the graphic structure of complexity, be then difficult to realize.If design the terahertz filter of more high frequency, resonant shape size will reduce, and for the stripping technology of thicker metal, will more be difficult to realize its required precision.
Terahertz filter involved by prior art is only limitted to the low-frequency band (< 1THz) of Terahertz, and its responsive bandwidth is also narrower.So far, also not there is at the medium-high frequency wave band (3-6THz) of Terahertz the terahertz filter of broadband response.Because the thickness of the backing material of traditional terahertz filter based on FSS structure is large, the problems such as negative Fabry-Perot resonance, insertion loss are large will be brought to filter thus.If reduce the thickness of substrate, owing to being subject to the restriction of conventional backing material mechanical performance, the processing and use of giving filter are brought great difficulty.And for the all-metal construction at traditional linerless end, then need to peel off thick metal, so also can only large, the simple resonant shape of structure of processing dimension, limit its application at Terahertz medium-high frequency filter.As can be seen here, existing filter construction and manufacturing technology all constrain the development of Terahertz medium-high frequency broadband filter.
In addition, in non-brake method Terahertz passive detection field, in order to improve the sensitivity of detection, take into account the signal to noise ratio of detector, need terahertz filter can have optionally broadband through performance at terahertz wave band, effectively stop that other frequency range is electromagnetic to be passed through.Therefore, efficient Terahertz medium-high frequency broadband filter is urgently developed in this area.
Summary of the invention
For the deficiencies in the prior art, the invention provides a kind of ultra-thin Terahertz medium-high frequency broadband filter, significantly reduce the insertion loss brought by backing material, eliminate the Fabry-Perot resonance caused by traditional thicker substrate, inhibit the generation of unnecessary resonance frequency band.
Technical scheme of the present invention is: a kind of ultra-thin Terahertz medium-high frequency broadband filter, comprise one or more layers amorphous media film and one or more layers metallic film from the bottom to top successively, wherein, described amorphous media film is etched to square or round central a kind of periodic pattern structure; Described metallic film is directly attached to the surface of amorphous media film, and metallic film is identical with the shape of amorphous media film.
Further, described amorphous media film is a kind of in the middle of silicon nitride, silica, silicon oxynitride film or their composite membrane, its thickness is 10nm-10 μm, and optimum is 100nm, 200nm, 300nm, 400nm, 500nm, 600nm, 700nm, 800nm, 900nm, 1000nm, 1200nm, 1500nm, 1800nm, 2000nm.
Further, described metallic film is Al, Au, Ti, TiN
x , TiSi
x , TiW
x , W, WSi
x , Ni, NiSi
x , Ta, TaN
x , a kind of in the middle of Fe, Pt, Cu, Ag, Cr, NiCr or their compound, the thickness of metallic film is 5nm-4000nm, and optimum is 50nm, 100nm, 120nm, 150nm, 180nm, 200nm, 220nm, 250nm, 300nm, 350nm, 400nm, 450nm, 500nm, 550nm, 600nm, 650nm, 700nm.
Present invention also offers a kind of manufacture method of ultra-thin Terahertz medium-high frequency broadband filter, comprise the steps:
(1) twin polishing substrate is cleaned;
(2) utilize reactor, deposit one or more layers amorphous media film in the one side of substrate;
(3) at surperficial spin coating one deck photoresist of amorphous media film, and toast;
(4) to photoresist exposure, after development, the periodic structure figure of photoresist is obtained;
(5) adopt reactive ion etching, obtain the periodic structure figure with square or round central a kind of shape;
(6) removing residue photoresist, obtains the periodic structure figure of the amorphous media film with square or round central a kind of shape;
(7) step (1)-(3) are repeated to the another side of described substrate;
(8) exposure imaging, obtains the fenestration figure at the back side;
(9) remove residue photoresist by reactive ion etching amorphous media film, back must be arrived and to window graphic structure;
(10) adopt lithographic method, the substrate of photoetching step (9) obtained etches, and obtains the amorphous media film with periodic structure figure;
(11) on the surface of amorphous media film, utilize reactor, deposit one or more layers metallic film, obtain having square or round in the middle of a kind of shape ultra-thin Terahertz medium-high frequency broadband filter.
In the manufacture method of a kind of ultra-thin Terahertz medium-high frequency broadband filter of the present invention, twin polishing substrate used is in step (1) twin polishing monocrystalline substrate, wherein, when step (10) adopts dry etching, twin polishing substrate used is a kind of twin polishing monocrystalline substrate in the middle of silicon (100) or silicon (111), silicon (110); When step (10) adopts wet etching, twin polishing substrate used is silicon (100) twin polishing monocrystalline substrate, the corrosive liquid used is the KOH aqueous solution, wherein, the concentration of the KOH aqueous solution is 10wt.% – 60wt.%, and optimum is 10wt.%, 15wt.%, 20wt.%, 25wt.%, 30wt.%, 33.3wt.%, 35wt.%, 40wt.%; Adopt a kind of method in the middle of water-bath, oil bath or air bath to control the reaction temperature of wet etching, its range of reaction temperature is 30 DEG C – 120 DEG C, and optimum is 60 DEG C, 65 DEG C, 70 DEG C, 75 DEG C, 80 DEG C, 85 DEG C, 90 DEG C; The time of wet etching is 0.5 – 20h, and optimum is 3h, 4h, 5h, 6h, 7h, 8h, 9h, until silicon (100) the twin polishing monocrystalline substrate described in step (1) is etched completely.
In the manufacture method of a kind of ultra-thin Terahertz medium-high frequency broadband filter of the present invention, in step (2), the reactor that preparation amorphous media film adopts is plasma enhanced chemical vapor deposition (PECVD) system, or low-pressure chemical vapor deposition (LPCVD), aumospheric pressure cvd (APCVD), electron beam evaporation, vacuum thermal evaporation, one in the middle of magnetic control sputtering system.When using plasma strengthens chemical vapour deposition (CVD), its operating frequency is that high frequency, low frequency or High-frequency and low-frequency are alternately used in combination.Prepared amorphous media film is silicon nitride (SiN
x ) or silica (SiO
x ), silicon oxynitride (SiO
x n
y ) a kind of in the middle of film or their composite membrane, as the support film of ultra-thin Terahertz medium-high frequency broadband filter, its thickness is 10nm – 10 μm, and optimum is 100nm, 200nm, 300nm, 400nm, 500nm, 600nm, 700nm, 800nm, 900nm, 1000nm, 1200nm, 1500nm, 1800nm, 2000nm.
In the manufacture method of a kind of ultra-thin Terahertz medium-high frequency broadband filter of the present invention, in step (5) with (9), the reacting gas that described reactive ion etching adopts is CF
4, CHF
3, C
3f
8, SF
6, NF
3central a kind of F base gas or their compound.
In the manufacture method of a kind of ultra-thin Terahertz medium-high frequency broadband filter of the present invention, in step (6) with (9), the method removing residue photoresist is: adopt acetone, butanone, methyl alcohol, a kind of in the middle of ethanol or their compound as adhesive remover, by ultrasonic, remove remaining photoresist.
In the manufacture method of a kind of ultra-thin Terahertz medium-high frequency broadband filter of the present invention, in step (10), the method for etching twin polishing substrate is the one in the middle of dry etching or wet etching.
In the manufacture method of a kind of ultra-thin Terahertz medium-high frequency broadband filter of the present invention, in step (11), preparing the reactor that metallic film adopts is one in the middle of electron beam evaporation, vacuum thermal evaporation, magnetron sputtering, metal-organic chemical vapor deposition equipment (MOCVD) system.The metal of prepared metallic film is Al, Au, Ti, TiN
x , TiSi
x , TiW
x , W, WSi
x , Ni, NiSi
x , Ta, TaN
x , a kind of in the middle of Fe, Pt, Cu, Ag, Cr, NiCr or their compound, the thickness of metallic film is 5nm – 4000nm, and optimum is 50nm, 100nm, 120nm, 150nm, 180nm, 200nm, 220nm, 250nm, 300nm, 350nm, 400nm, 450nm, 500nm, 550nm, 600nm, 650nm, 700nm.
Compared with prior art, the present invention has following beneficial effect:
(1) ultra-thin Terahertz medium-high frequency broadband filter provided by the invention is made up of very thin amorphous media film and the metal film that is deposited on its surface, can greatly reduce the insertion loss brought by thicker backing material, the Fabry-Perot resonance caused by the substrate that tradition is thicker can also be eliminated, inhibit the generation of unnecessary resonance frequency band;
(2) ultra-thin Terahertz medium-high frequency broadband filter provided by the invention, can by modes such as the cell size of adjustment graphic structure and duty ratio, change graphics shape or material parameters, the band controlling filter leads to centre frequency and bandwidth, thus covers whole terahertz wave band (0.1 – 10THz).Especially, at Terahertz medium-high frequency wave band, the band pass filter of broadband, high-permeability can be obtained;
(3) ultra-thin Terahertz medium-high frequency broadband filter provided by the invention, can also use by multiple similar filter being carried out superposition, making filter shape more steep, thus obtaining better Out-of-band rejection performance;
The structure of ultra-thin Terahertz medium-high frequency broadband filter provided by the invention is simple, making is easy.Its main processing technology comprises exposure, development, PECVD, reactive ion etching (RIE), wet etching, electron beam evaporation etc., is the routine of semiconductor applications, ripe processing technology, reliable and stable.
Accompanying drawing explanation
The Periodic Building Unit schematic diagram of Fig. 1 to be centre frequency that the present invention proposes be ultra-thin broadband filter of 3.8THz.A in Fig. 1 is its planar structure schematic diagram, and P is the square unit cycle length of side 72 μm, and W is the intermediate etch square length of side 52 μm; B in Fig. 1 is its cross-sectional view.Wherein, 1 is metallic film, and 2 is SiN
x supporting Media film.
Fig. 2 is the centre frequency that the present invention proposes is in the ultra-thin broadband filter of 3.8THz, SiN
x the optical microscope photograph of support film.Wherein, the b in Fig. 2 is the enlarged drawing of a.
Fig. 3 is the centre frequency that the present invention proposes is in the broadband filter of 3.8THz, the photo after wet etching silicon substrate.Wherein, a in Fig. 3 is the picture surface of the periodicity square grid structure in front, and whole filter construction figure face is of a size of 5mm × 5mm; B in Fig. 3 is the structure graph windowed in the back side, and opening surface is of a size of 7mm × 7mm.Comprise the silicon substrate framework of figure surrounding, whole sample is of a size of 10mm × 10mm.
The process chart of Fig. 4 to be centre frequency that the present invention proposes be ultra-thin broadband filter of 3.8THz.Wherein, a in Fig. 4 deposits layer of sin for adopting PECVD
x film support film; B is at SiN
x surperficial spin coating one deck photoresist of film support layer, baking post-exposure development, obtains periodically square grid structure; C etches SiN for adopting RIE
x film, and remove photoresist; Silicon substrate overturns by d, deposits another layer of sin at another side PECVD
x film; E is at this SiN
x another layer photoetching glue of the surperficial spin coating of film, baking post-exposure development, must arrive the result windowed in the back side; F etches SiN for adopting RIE
x film, and remove photoresist; G is wet etching, is corroded by silicon substrate, structure release, obtains the SiN with periodic structure figure
x support film; H is for adopting electron beam evaporation technique, depositing metal films; I is the ultra-thin Terahertz medium-high frequency broadband filter structure obtained.
Fig. 5 be according to the present invention make centre frequency be the actual test result of the ultra-thin broadband filter of 3.8THz and the contrast of simulation result.
Fig. 6 is under square structure, when the metal film of the filter that the present invention proposes changes NiCr into by Al, and the results contrast of the Terahertz response characteristic of filter.
Fig. 7 is under identical material parameter, when the metal of filter that the present invention proposes and the shape of dielectric film change into round by square, and the results contrast of the Terahertz response characteristic of filter.
Fig. 8 be when material parameter and square shape identical, when the metal of filter that the present invention proposes and W and the P parameter of the graphic structure of dielectric film change, the results contrast of the Terahertz response characteristic of filter.
Fig. 9 is that what make according to the present invention is the superimposed measured results of multiple filters of the ultra-thin broadband filter of 3.8THz centre frequency.Wherein, a in Fig. 9 is the number of filter of superposition when being respectively 1,2,3,4, the schematic diagram of superposition filter; B in Fig. 9 is the number of filter of superposition when being respectively 1,2,3,4, the test result of different superposition filters.
Embodiment
For ease of understanding the present invention, it is as follows that the present invention enumerates embodiment.Those skilled in the art should understand, described embodiment is only help to understand the present invention, should not be considered as concrete restriction of the present invention.
The embodiment of the present invention adopts the ultra-thin SiN of good mechanical performance
x film is as the backing material of filter.Meanwhile, the embodiment of the present invention, by adopting square graphic structure, obtains Terahertz medium-high frequency broadband filter, has the advantages such as good pass band width is large, Out-of-band rejection performance is good.And square structure is easy to manufacture, mechanical stability is high.
The manufacture method of ultra-thin Terahertz medium-high frequency broadband filter provided by the invention, adopts conventional micro fabrication manufacture.The embodiment of the present invention is 72 μm × 72 μm with the unit cycle, center etching size is 52 μm × 52 μm (as shown in fig. ia), the logical centre frequency of band is 3.8THz, bandwidth is 2.6THz(2.1THz – 4.7THz) square structure (square grid) be example, concrete manufacture method is described, those skilled in the art can according to the terahertz filter with the logical centre frequency of other band and bandwidth of other size of content production of this specification.
Embodiment
Centre frequency is a broadband filter of 3.8THz, is made by the following method:
Step 1: cleaning silicon (100) twin polishing substrate;
In this step, cleaning process is: first substrate is put into acetone soln ultrasonic cleaning 10 – 15min; Take out substrate, then put into absolute ethyl alcohol ultrasonic cleaning 10 – 15min; Take out substrate, then use deionized water rinsing 2 – 4 times, until clean up, finally with nitrogen, substrate is dried up.
Step 2: adopt PECVD, deposit the passive amorphous SiN of one deck in the one side of silicon substrate
x dielectric film;
In this step, PECVD is adopted to deposit SiN
x the process conditions of film are: RF operating frequency is high frequency 13.56MHz, low frequency 380KHz, and the two is used alternatingly; Reacting gas is SiH
4and NH
3, ventilation flow rate ratio SiH
4: NH
3=1:5; Depositing temperature is 250 DEG C; Amorphous SiN
x the deposit thickness of film is 1 μm.
Step 3: at SiN
x surperficial spin coating one deck photoresist of film, and toast;
In this step, first sample is placed 120 DEG C of baking 20min in an oven, remove the moisture on surface; Then, spin coating photoresist, and be placed on 100 DEG C of baking 3min on hot plate;
Step 4: exposure imaging, obtains front periodically square structure graph;
In this step, adopt ultraviolet photolithographic technology to expose photoresist, obtain periodically square structure graph after development, the dimension of picture in the front of whole filter construction is for 5mm × 5mm(is as shown in a in Fig. 3);
Step 5: adopt reactive ion etching (RIE) etching period square grid structure graph;
In this step, RIE etches SiN
x the process conditions of film are: etching reaction gas is CHF
3, gas flow is 20sccm, and etch rate is 60nm/min, and etch period is 20min; Spend quarter 20%, make the SiN that structure graph is exposed
x film is etched completely, until substrate silicon surface.
Step 6: the structure etched is carried out ultrasonic in acetone, removes remaining photoresist.
Step 7: step 1 – 3 is repeated to the another side of twin polishing silicon substrate;
Step 8: exposure imaging, obtains the fenestration figure at the back side;
In this step, aimed at by twin polishing silicon substrate with plane of exposure described in step 4, adopt ultraviolet photolithographic technology to expose photoresist, obtain planless fenestration after development, the fenestration at the back side is of a size of 7mm × 7mm(as shown in the b in Fig. 3).
Step 9: by reactive ion etching and go residue photoresist step, must arrive back and to window graphic structure;
Step 10: adopt wet etching, graph substrate step 9 obtained is corroded, obtains the SiN with periodic structure figure
x support film;
In this step, first the graph substrate that step 9 obtains is cut into 10mm × 10mm(as shown in Figure 3).Wherein, the periodicity square structure in front and the fenestration at back are all positioned in the middle of cut substrate.In wet etching subsequently, the SiN that edge does not etch
x prevention silicon substrate is etched by film; The silicon substrate be not etched, as frame structure, is convenient to subsequent step and is operated filter.
The process conditions of wet etching are: corrosive liquid is the 33.3 wt.% KOH aqueous solution, and etching reaction temperature is 75 DEG C; Adopt water-bath or oil bath to control reaction temperature, etch period about 6h, until silicon substrate etching completely, finally leave SiN
x support film and silicon frame (as shown in Figure 3).
Step 11: at SiN
x the surface of support film, deposition layer of metal aluminium (Al) film, obtains ultra-thin Terahertz medium-high frequency broadband filter.
In this step, adopt electron beam evaporation process, in the SiN with periodic structure figure that step 10 obtains
x surface deposition a layer thickness of support film is the Al film of 200nm.
According to above-mentioned steps 1 to 11, prepare the ultra-thin Terahertz medium-high frequency broadband filter shown in Fig. 1,2 and 3.Wherein, centered by Fig. 1, frequency is the schematic diagram of the broadband filter periodic structure unit of 3.8THz.Centered by Fig. 2, frequency is the SiN of the broadband filter of 3.8THz
x the optical microscope photograph of support film.Centered by Fig. 3, frequency is the broadband filter of 3.8THz, the front after wet etching silicon substrate and back side photo.Centered by Fig. 4, frequency is the process chart of the broadband filter of 3.8THz.
The Supporting Media film of the ultra-thin Terahertz medium-high frequency broadband filter that the present invention proposes is not particularly limited, except silicon nitride (SiN
x ) film, can also be the silica (SiO of other thickness and component
x ) film, silicon oxynitride (SiN
x o
y ) a kind of in the middle of film or their composite membrane, or amorphous silicon (a-Si) film, polyimides, other polymer, iron oxide (FeO
x ), titanium oxide (TiO
x ), titanium nitride (TiN
x ), vanadium oxide (VO
x ), vanadium nitride (VN
x ), GaAs (GaAs), aluminium oxide (AlO
x ), hafnium oxide (HfO
x ), hafnium aluminum oxide (HfAlO
x ) a kind of in the middle of known in the industry other dielectric film such as film or their composite membrane.The metal level of the ultra-thin Terahertz medium-high frequency broadband filter that the present invention proposes also is not particularly limited, and can be metal A l, Au, Ti, TiN
x , TiSi
x , TiW
x , W, WSi
x , Ni, NiSi
x , Ta, TaN
x , a kind of in the middle of Fe, Pt, Cu, Ag, Cr, NiCr or their compound.The ultra-thin lower layer support film of Terahertz medium-high frequency broadband filter that the present invention proposes and the figure of upper strata metal are also not particularly limited, can be square, other round or known in the industry shape Terahertz response pattern in the middle of one.
Analyze through following, the ultra-thin Terahertz medium-high frequency broadband filter that provable the present invention proposes, can under the prerequisite keeping mechanical stability, effectively to the THz wave of specific wavelength carry out selectivity broadband through, be the terahertz filter of function admirable.
CST microwave studio software is used to emulate filter structure.During emulation, as shown in Figure 1, box structure unit cycle P=72 μm, intermediate etch square length of side W=52 μm, square grid structure width is 20 μm to filter Periodic Building Unit.Simulation parameter is: SiN
x the dielectric constant of support film is 4, and loss angle tangent is 0, and thickness is 1 μm; The conductivity of metal layer A l is 3.56 × 10
7s/m.In addition, use the far infrared assembly of the Spectrum400 Fourier infrared spectrograph of PerkinElmer company, filtering performance test is carried out to the ultra-thin broadband filter that the centre frequency of embodiment making is 3.8THz.
Fig. 5 is the centre frequency that embodiment makes is the actual test result of single ultra-thin broadband filter under vertical incidence (incidence angle is 0 °) condition and the comparison diagram of simulation result of 3.8THz.Wherein, simulation result (Fig. 5) shows, and the centre frequency of single terahertz filter is 3.9THz, and the logical central permeate rate of band reaches 99%.By comparison, test result (Fig. 5) shows, the centre frequency of single terahertz filter is 3.8THz, and the logical central permeate rate of band is 93%.SiN when considering emulation
x what adopt is lossless condition parameter, and the SiN that actual fabrication obtains
x there is certain loss.And the conductivity of metal layer A l is due to surface oxidation, and realistic conductivity is also lower than ideal value, also can bring certain loss.In addition, test also finds, at 3.0THz, 2.5THz, 1.7THz, 1.3THz place, has occurred some little absworption peaks, mainly because the impact of testing background water in air, carbon dioxide etc.Fig. 5 result clearly shows, simulation result and measured result are substantially identical, and they all prove: filter provided by the invention has excellent Terahertz medium-high frequency wideband filtered performance.
Figure 6 – 8 shows filter material and the impact of structural parameters change on the Terahertz response performance of device.Wherein, Fig. 6 shows, and when the square structure of filter is constant, when the metal film of filter changes the low NiCr of conductivity into by the Al that conductivity is high, the centre frequency of filter is constant, but transmitance weakens.Fig. 7 shows, and when the material parameter of filter is constant, but when the shape of the metal film of filter and dielectric film changes into round by square, the 3.8THz centre frequency of filter is constant, but frequency band narrows; And in 4 higher – 10THz frequency ranges, all there is obvious change in response frequency and transmitance.Fig. 8 shows, and when the material parameter of filter, film thickness and square shape invariance, but when W and the P parameter of its graphic structure changes, corresponding change all occurs for the centre frequency, frequency band etc. of filter; Wherein, when W and P parameter increases, response frequency moves to Terahertz low frequency, and on the contrary, when W and P parameter reduces, response frequency is then to Terahertz high-frequency mobile.Figure 6 – 8 result shows, for terahertz filter provided by the invention, can by the change of structure and material parameter, and the centre frequency of filter and frequency band etc. are regulated, makes it to meet different application requirements.
It should be noted that the band of terahertz filter provided by the invention leads to the loss at centre frequency place very low, be about 0.3dB, much smaller than traditional multilayer based on FSS Structure Filter (being about 2dB).This illustrates, the terahertz filter of the FSS structure based on ultra-thin support film provided by the invention, can reduce insertion loss effectively.In addition, the three dB bandwidth of terahertz filter provided by the invention is 2.6THz(2.1-4.7THz), half-peak breadth (FWHM) is 68%, illustrates that terahertz filter provided by the invention has broadband through performance at the medium-high frequency wave band (3-6THz) of Terahertz.In addition, be about-5.3dB at 6 – 12THz wave band Out-of-band rejections, terahertz filter provided by the invention be described, in terahertz wave band, except design through except frequency range, do not have other resonance to occur through peak.So, effectively can eliminate the Fabry-Perot resonance caused by traditional thicker substrate, suppress the generation of unnecessary resonance frequency band.
On the basis of single ultra-thin broadband filter, the multiple similar terahertz filter that we are also tested for embodiment makes superposes, and obtains the Terahertz through performance of new superposition filter.The structural representation of the terahertz filter of superposition, as shown in a in Fig. 9, is namely stacked the front of the back of top filter and below filter, obtains the combining structure of new filter.The test result of relevant superposition filter is as shown in the b in Fig. 9.B display in Fig. 9, if 2 filters are superimposed, the logical centre frequency of band is constant, transmitance is then 83%, and loss is about 0.8dB, and three dB bandwidth is 1.5THz(2.6-4.1THz), half-peak breadth (FWHM) is 39%, is about-10dB at 6 – 21THz wave band Out-of-band rejections; When 3 filter constructions are superposed, the transmitance of new filter is 72%, and loss is about 1.4dB, and three dB bandwidth is 1.0THz(3.0-4.0THz), half-peak breadth (FWHM) is 26%, is about-15dB at 6 – 21THz wave band Out-of-band rejections; If 4 filter constructions are superposed, it is constant that the band of new filter leads to centre frequency, and transmitance is then 62%, loss is about 2.0dB, three dB bandwidth is 0.9THz(3.1-4.0THz), half-peak breadth (FWHM) is 24%, is about-18dB at 6 – 21THz wave band Out-of-band rejections.Form shown in table 1 embodies the performance parameter contrast of the different wavenumber filter of superposition more intuitively.All in all, along with the increase of number of the filter of superposition, it is constant that the band of new filter leads to centre frequency, and be 3.8THz, but its transmitance reduces gradually, loss increases; Three dB bandwidth reduces, and half-peak breadth reduces; Waveform is more steep, and Out-of-band rejection performance is improved.
Table 1: when the number of the filter of superposition is respectively 1,2,3,4, the contrast of the test performance index of different superposition filters.
The above embodiment only have expressed the embodiment of the application, and it describes comparatively concrete and detailed, but therefore can not be interpreted as the restriction to the application's protection range.It should be pointed out that for the person of ordinary skill of the art, under the prerequisite not departing from technical scheme design, can also make some distortion and improvement, these all belong to the protection range of the application.
Claims (10)
1. a ultra-thin Terahertz medium-high frequency broadband filter, it is characterized in that, comprise one or more layers amorphous media film and one or more layers metallic film from the bottom to top successively, wherein, described amorphous media film is etched to square or round central a kind of periodic pattern structure; Described metallic film is directly attached to the surface of amorphous media film, and metallic film is identical with the shape of amorphous media film.
2. a kind of ultra-thin Terahertz medium-high frequency broadband filter according to claim 1, it is characterized in that, described amorphous media film is a kind of in the middle of silicon nitride, silica, silicon oxynitride film or their composite membrane, and its thickness is 10nm-10 μm.
3. a kind of ultra-thin Terahertz medium-high frequency broadband filter according to claim 1, it is characterized in that, described metallic film is Al, Au, Ti, TiN
x , TiSi
x , TiW
x , W, WSi
x , Ni, NiSi
x , Ta, TaN
x , a kind of in the middle of Fe, Pt, Cu, Ag, Cr, NiCr or their compound, the thickness of metallic film is 5nm-4000nm.
4. the manufacture method of a kind of ultra-thin Terahertz medium-high frequency broadband filter according to any one of claim 1-3, is characterized in that, comprise the steps:
(1) twin polishing substrate is cleaned;
(2) utilize reactor, deposit one or more layers amorphous media film in the one side of substrate;
(3) at surperficial spin coating one deck photoresist of amorphous media film, and toast;
(4) to photoresist exposure, after development, the periodic structure figure of photoresist is obtained;
(5) adopt reactive ion etching amorphous media film, obtain the periodic structure figure with square or round central a kind of shape;
(6) removing residue photoresist, obtains the periodic structure figure of the amorphous media film with square or round central a kind of shape;
(7) step (1)-(3) are repeated to the another side of described substrate;
(8) exposure imaging, obtains the fenestration figure at the back side;
(9) remove residue photoresist by reactive ion etching amorphous media film, back must be arrived and to window graphic structure;
(10) adopt lithographic method, the substrate of photoetching step (9) obtained etches, and obtains the amorphous media film with periodic structure figure;
(11) on the surface of amorphous media film, utilize reactor, deposit one or more layers metallic film, obtain having square or round in the middle of a kind of shape ultra-thin Terahertz medium-high frequency broadband filter.
5. the manufacture method of a kind of ultra-thin Terahertz medium-high frequency broadband filter according to claim 4, it is characterized in that, twin polishing substrate used is in step (1) twin polishing monocrystalline substrate, wherein, when step (10) adopts dry etching, twin polishing substrate used is a kind of twin polishing monocrystalline substrate in the middle of silicon (100) or silicon (111), silicon (110); When step (10) adopts wet etching, twin polishing substrate used is silicon (100) twin polishing monocrystalline substrate, the corrosive liquid used is the KOH aqueous solution, wherein, the concentration of the KOH aqueous solution is 10wt.% – 60wt.%, and adopt a kind of method in the middle of water-bath, oil bath or air bath to control the reaction temperature of wet etching, its range of reaction temperature is 30 DEG C – 120 DEG C, the time of wet etching is 0.5 – 20h, until twin polishing monocrystalline substrate is etched completely.
6. the manufacture method of a kind of ultra-thin Terahertz medium-high frequency broadband filter according to claim 4, it is characterized in that, in step (2), the reactor that preparation amorphous media film adopts is plasma reinforced chemical vapor deposition system, or low-pressure chemical vapor deposition, aumospheric pressure cvd, electron beam evaporation, vacuum thermal evaporation, one in the middle of magnetic control sputtering system; When using plasma strengthens chemical vapour deposition (CVD), its operating frequency is that high frequency, low frequency or High-frequency and low-frequency are alternately used in combination; Prepared amorphous media film is a kind of in the middle of silicon nitride or silica, silicon oxynitride film or their composite membrane, and as the support film of ultra-thin Terahertz medium-high frequency broadband filter, its thickness is 10nm – 10 μm.
7. the manufacture method of a kind of ultra-thin Terahertz medium-high frequency broadband filter according to claim 4, is characterized in that, in step (5) with (9), the reacting gas that described reactive ion etching adopts is CF
4, CHF
3, C
3f
8, SF
6, NF
3central a kind of F base gas or their compound.
8. the manufacture method of a kind of ultra-thin Terahertz medium-high frequency broadband filter according to claim 4, it is characterized in that, in step (6) with (9), the method removing residue photoresist is: adopt acetone, butanone, methyl alcohol, a kind of in the middle of ethanol or their compound as adhesive remover, by ultrasonic, remove remaining photoresist.
9. the manufacture method of a kind of ultra-thin Terahertz medium-high frequency broadband filter according to claim 4, is characterized in that, in step (10), the method for etching twin polishing substrate is the one in the middle of dry etching or wet etching.
10. the manufacture method of a kind of ultra-thin Terahertz medium-high frequency broadband filter according to claim 4, it is characterized in that, in step (11), preparing the reactor that metallic film adopts is one in the middle of electron beam evaporation, vacuum thermal evaporation, magnetron sputtering, metal-organic chemical vapor deposition equipment system, and the metal of prepared metallic film is Al, Au, Ti, TiN
x , TiSi
x , TiW
x , W, WSi
x , Ni, NiSi
x , Ta, TaN
x , a kind of in the middle of Fe, Pt, Cu, Ag, Cr, NiCr or their compound, the thickness of metallic film is 5nm – 4000nm.
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