CN104993199B - A kind of ultra-thin Terahertz medium-high frequency broadband filter and preparation method thereof - Google Patents
A kind of ultra-thin Terahertz medium-high frequency broadband filter and preparation method thereof Download PDFInfo
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Abstract
The invention discloses a kind of ultra-thin Terahertz medium-high frequency broadband filter and preparation method thereof, wave filter includes one or more layers amorphous media film and one or more layers metallic film successively from the bottom to top, wherein, described amorphous media film is etched to square or a kind of round central 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.Terahertz broadband filter provided by the invention has relatively thin thickness, and Fabry Perot caused by the resonator for can weaken insertion loss that typical substrate material brings, avoiding being made up of substrate in terahertz wave band resonates.Filter construction provided by the present invention is simple, easy to manufacture, and its bandpass center frequency can cover whole terahertz wave band, while has wider band logical bandwidth.If multiple terahertz filters are superimposed, can meet with a response the terahertz filter that waveform is more steep, Out-of-band rejection performance is more excellent.
Description
Technical field
The invention belongs to Terahertz Technology field, and in particular to a kind of ultra-thin Terahertz medium-high frequency broadband filter and its
Preparation method.
Background technology
THz wave is last wave band that development and application well are not yet obtained in all electromagnetic waves, is commonly referred to as
" Terahertz gap ".For THz wave between microwave and infrared waves, it is 0.1-10THz to be commonly referred to as frequency, and wavelength is
The electromagnetic wave of 3000-30 μm of this scope.THz wave has unique physics such as pulse is narrow, photon energy is low, penetrability is strong
Characteristic, make its spectroscopic imaging, it is biomedical with environmental science, astrophysics, safety monitoring and quality control, material science,
The fields such as the communication technology have broad application prospects.
With the acquisition of the stable high-power THz source in broadband, non-brake method terahertz detection technology is gradually taken seriously.
2005, A.W. Lee of Massachusetts Polytechnics etc. were arranged as detector with uncooled microbolometer focal plane array, are built
The terahertz imaging system of real-time continuous ripple, it was confirmed that micro-metering bolometer is used for the feasibility of terahertz imaging（Referring to A.W.
Lee, “Real-time, continuous-wave terahertz imaging by use of a microbolometer
focal-plane array”, Optics Letters, 30(19):2563-2565 (2005) document）.Non-brake method micrometering
The electromagnetic wave energy of radiation is mainly converted into heat by the operation principle of bolometer, makes the electrical property of detector sensitive material
It can change and be detected.Therefore, in order to improve the sensitivity of system, the THz wave of more wide spectrum should be allowed to enter as far as possible
Probe unit, it is converted into more heats.Meanwhile in order to improve the signal to noise ratio of system, it should also filter out other wave bands（Such as ultraviolet,
Visible ray, infrared, microwave etc.）The interference of electromagnetic wave.So broadband terahertz filter is lifting terahertz detector performance
One key technology.
Because nature lacks effective Terahertz responsive materials, a kind of extraordinary electromagnetism with not available for natural material
The artificial composite structure of response property, i.e. electromagnetism Meta Materials（Metamaterial, abbreviation Meta Materials）, once proposition, soon
Cause the extensive attention of academia and industrial quarters.Meta Materials can provide highly controllable electromagnetic response, and its response range can be with
Cover the wave band such as light wave, infrared, Terahertz, millimeter wave.Utilize Meta Materials, it is possible to achieve perfect lens, stealthy cape, electromagnetic wave
The particular devices such as perfect absorber, perfect wave filter.
Frequency-selective surfaces（Frequency selective surfaces, abbreviation FSS）Structure is in Meta Materials field
One of study hotspot, FSS each periodic unit is equivalent to a passive resonator, and this passive resonator is periodically arranged
Row, space filtering can be carried out to electromagnetic wave.It is the double-deck square of 0.25THz that Mingzhi Lu etc., which report a kind of centre frequency,
The second order band logical terahertz filter of four open-types, it is 165 μm of single crystal quartz crystal as medium that the wave filter, which uses thickness,
Substrate, there is second order bandpass characteristics in 227-283GHz, insertion loss is about 2dB（Referring to Mingzhi Lu, " Second-
order bandpass terahertz filter achieved by multilayer complementary
metamaterial structures”, Optics Letters, 36(7):1071-1073 (2011) document）.For this
Kind of FSS Structure Filters based on metal-dielectric-metal structure, the response of the loss and thickness of backing material to FSS structures
Characteristic has a great influence.The substrate thickness of FSS structures and the substantially linear relation of resonant frequency, thickness is thinner, and frequency is higher（Referring to
Mingzhi Lu, “Second-order bandpass terahertz filter achieved by multilayer
complementary metamaterial structures”, Optics Letters, 36(7): 1071-1073
(2011) document）.So if less quartz, which is lost, to THz wave in selection is used as substrate, preparation bandpass center is 3THz
FSS Structure Filters, in order to avoid design wave band near produce unnecessary band logical resonance peak, that is, form Fabry-Perot
Luo Gongzhen, the thickness of quartz substrate should be thinned to about 20 μm.Obviously, so thin quartz substrate by the processing of wave filter and
Using bringing great difficulty.
In order to solve the various problems that typical backing material is brought to FSS wave filters, such as Fabry-Perot resonance,
Insertion loss etc., a kind of solution method are to remove substrate, realize the FSS all-metal constructions of no substrate.Traditional all-metal construction
Implementation method be：The spin coating photoresist in one piece of quartz substrate, develop after photoetching resonant shape unit.Then, using electronics
The technology deposit thickness such as beam evaporation is about 10 μm of low stress metal, such as copper or nickel.Then, ultrasound is peeled off, and obtains resonance figure
The metal structure of shape.Finally, back quartz substrate is discharged by chemical attack.In this way, D.W. Porterfield
Et al. successfully produce the terahertz filter based on cross structure that operating center frequency is located at 585GHz-2.1THz（Ginseng
See D.W. Porterfield, " Resonant metal-mesh bandpass filters for the far
infrared”, Applied Optics, 33(25):6046-6052 (1994) document）.Regrettably, this thick metal
（~10 μm）Stripping technology, spin coating thickness and exposure imaging to photoresist are required to higher.Moreover, it can only realize simple
Resonant shape structure, for the graphic structure of complexity, then it is difficult to realize.If design the terahertz filter of higher frequency, resonance
Dimension of picture will reduce, and for the stripping technology of thicker metal, be more difficult in realizing its required precision.
Terahertz filter involved by prior art is only limitted to the low-frequency band of Terahertz（＜ 1THz）, moreover, it rings
Answer bandwidth also narrower.So far, also not in the medium-high frequency wave band of Terahertz（3-6THz）Terahertz with broadband response
Wave filter.Because the thickness of the backing material of traditional terahertz filter based on FSS structures is big, wave filter band thus will be given
Carry out the problems such as negative Fabry-Perot resonates, insertion loss is big.If reduce the thickness of substrate, due to by conventional substrate
The limitation of the mechanical property of materials, great difficulty will be brought to the processing of wave filter and use.And for traditional no substrate
All-metal construction, then need to peel off thick metal, thus also can only big, the simple in construction resonant shape of processing dimension, limit it
In the application of Terahertz medium-high frequency wave filter.As can be seen here, existing filter construction constrains Terahertz with manufacturing technology
The development of medium-high frequency broadband filter.
In addition, in non-brake method Terahertz passive detection field, in order to improve the sensitivity of detection, the noise of detector is taken into account
Than, it is necessary to which terahertz filter can effectively prevent other frequencies in the selective broadband through performance of terahertz wave band
Section electromagnetic wave passes through.Therefore, efficient Terahertz medium-high frequency broadband filter is urgently developed in this area.
The content of the invention
In view of the shortcomings of the prior art, the present invention provides a kind of ultra-thin Terahertz medium-high frequency broadband filter, effectively
The insertion loss brought by backing material is reduced, the Fabry-Perot as caused by traditional thicker substrate is eliminated and resonates, suppression
The generation of unnecessary resonance frequency band is made.
The technical scheme is that：A kind of ultra-thin Terahertz medium-high frequency broadband filter, includes successively from the bottom to top
One or more layers amorphous media film and one or more layers metallic film, wherein, described amorphous media film is etched
Into square or a kind of round central periodic pattern structure；Described metallic film is directly attached to the table of amorphous media film
Face, and metallic film is identical with the shape of amorphous media film.
Further, the amorphous media film be silicon nitride, silica, among silicon oxynitride film it is a kind of either
Their composite membrane, its thickness be 10nm-10 μm, it is optimal for 100nm, 200nm, 300nm, 400nm, 500nm, 600nm,
700nm、800nm、900nm、1000nm、1200nm、1500nm、1800nm、2000nm。
Further, the metallic film is Al, Au, Ti, TiN x 、TiSi x 、TiW x 、W、WSi x 、Ni、NiSi x 、Ta、
TaN x , a kind of or their compound among Fe, Pt, Cu, Ag, Cr, NiCr, the thickness of metallic film is 5nm-
4000nm, it is optimal for 50nm, 100nm, 120nm, 150nm, 180nm, 200nm, 220nm, 250nm, 300nm, 350nm,
400nm、450nm、500nm、550nm、600nm、650nm、700nm。
Present invention also offers a kind of preparation method of ultra-thin Terahertz medium-high frequency broadband filter, including following step
Suddenly：
（1）Clean twin polishing substrate；
（2）Using reactor, one or more layers amorphous media film is deposited in the one side of substrate；
（3）In one layer of photoresist of surface spin coating of amorphous media film, and toast；
（4）Photoresist is exposed, after development, obtains the periodic structure figure of photoresist；
（5）Using reactive ion etching, the periodic structure figure with square or a kind of round central shape is obtained；
（6）Remaining photoresist is removed, obtains the cycle with square or a kind of amorphous media film of round central shape
Property structure graph；
（7）To the another side repeat step of the substrate（1）—（3）；
（8）Exposure imaging, obtain the fenestration figure at the back side；
（9）By reactive ion etching amorphous media film and remaining photoresist is removed, obtains back windowing graphic structure；
（10）Using lithographic method, by step（9）The substrate of obtained photoetching performs etching, and obtains having periodically
The amorphous media film of structure graph；
（11）On the surface of amorphous media film, using reactor, one or more layers metallic film is deposited, is had
The ultra-thin Terahertz medium-high frequency broadband filter of square or a kind of round central shape.
In a kind of preparation method of ultra-thin Terahertz medium-high frequency broadband filter of the present invention, in step（1）In it is used
Twin polishing substrate be twin polishing monocrystalline substrate, wherein, work as step（10）During using dry etching, two-sided throwing used
Light substrate is silicon（100）Or silicon（111）, silicon（110）A kind of central twin polishing monocrystalline substrate；Work as step（10）Using wet
When method etches, twin polishing substrate used is silicon（100）Twin polishing monocrystalline substrate, the corrosive liquid used are that KOH is water-soluble
Liquid, wherein, the concentration of the KOH aqueous solution is 10wt.% -60wt.%, it is optimal for 10wt.%, 15wt.%, 20wt.%, 25wt.%,
30wt.%、33.3wt.%、35wt.%、40wt.%；Wet etching is controlled using a kind of method among water-bath, oil bath or air bath
Reaction temperature, its range of reaction temperature is 30 DEG C -120 DEG C, it is optimal be 60 DEG C, 65 DEG C, 70 DEG C, 75 DEG C, 80 DEG C, 85 DEG C, 90
℃；The time of wet etching is 0.5-20h, and optimal is 3h, 4h, 5h, 6h, 7h, 8h, 9h, until step（1）Described silicon
（100）Twin polishing monocrystalline substrate is etched completely.
In a kind of preparation method of ultra-thin Terahertz medium-high frequency broadband filter of the present invention, in step（2）In, prepare
The reactor that amorphous media film uses is plasma enhanced chemical vapor deposition（PECVD）System, or low pressure chemical
Vapour deposition（LPCVD）, aumospheric pressure cvd（APCVD）, electron beam evaporation, vacuum thermal evaporation, magnetic control sputtering system work as
In one kind.When using plasma strengthens chemical vapor deposition, its working frequency is that high frequency, low frequency or high frequency and low frequency are handed over
For being used in mixed way.Prepared amorphous media film is silicon nitride（SiN x ）Either silica（SiO x ）, silicon oxynitride
（SiO x N y ）A kind of or their composite membrane among film, the branch as ultra-thin Terahertz medium-high frequency broadband filter
Support film, its thickness be 10nm -10 μm, it is optimal for 100nm, 200nm, 300nm, 400nm, 500nm, 600nm, 700nm,
800nm、900nm、1000nm、1200nm、1500nm、1800nm、2000nm。
In a kind of preparation method of ultra-thin Terahertz medium-high frequency broadband filter of the present invention, in step（5）With（9）
In, the reacting gas that described reactive ion etching uses is CF4、CHF3、C3F8、SF6、NF3A kind of central F bases gas is either
Their compound.
In a kind of preparation method of ultra-thin Terahertz medium-high frequency broadband filter of the present invention, in step（6）With（9）
In, the method for removing remaining photoresist is：Using a kind of or their compound among acetone, butanone, methanol, ethanol
As adhesive remover, by ultrasound, remaining photoresist is removed.
In a kind of preparation method of ultra-thin Terahertz medium-high frequency broadband filter of the present invention, in step（10）In, carve
The method for losing twin polishing substrate is one kind among dry etching or wet etching.
In a kind of preparation method of ultra-thin Terahertz medium-high frequency broadband filter of the present invention, in step（11）In, system
The reactor that standby metallic film uses is electron beam evaporation, vacuum thermal evaporation, magnetron sputtering, metal-organic chemical vapor deposition equipment
（MOCVD）One kind among 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 or their compound among Fe, Pt, Cu, Ag, Cr, NiCr, the thickness of metallic film
Spend for 5nm -4000nm, it is optimal for 50nm, 100nm, 120nm, 150nm, 180nm, 200nm, 220nm, 250nm, 300nm,
350nm、400nm、450nm、500nm、550nm、600nm、650nm、700nm。
Compared with prior art, the invention has the advantages that：
（1）Ultra-thin Terahertz medium-high frequency broadband filter provided by the invention is by very thin amorphous media film and deposition
Metal film on its surface is formed, and can greatly reduce the insertion loss brought by thicker backing material, moreover it is possible to eliminate by
Fabry-Perot caused by the substrate of conventional thicker resonates, it is suppressed that the generation of unnecessary resonance frequency band；
（2）Ultra-thin Terahertz medium-high frequency broadband filter provided by the invention, can be by adjusting the list of graphic structure
Elemental size and dutycycle, change the mode such as graphics shape or material parameter, control the bandpass center frequency and bandwidth of wave filter, from
And cover whole terahertz wave band（0.1–10THz）.Especially, in Terahertz medium-high frequency wave band, broadband, high-permeability can be obtained
Bandpass filter；
（3）Ultra-thin Terahertz medium-high frequency broadband filter provided by the invention, can also be by multiple similar filters
Ripple device is overlapped use, makes filter shape more steep, so as to obtain more preferable Out-of-band rejection performance；
The structure of ultra-thin Terahertz medium-high frequency broadband filter provided by the invention is simple, it is easy to make.It is main
Processing technology includes exposure, development, PECVD, reactive ion etching（RIE）, wet etching, electron beam evaporation etc., be partly to lead
Conventional, the ripe processing technology in body field, it is reliable and stable.
Brief description of the drawings
Fig. 1 is that the Periodic Building Unit for the ultra-thin broadband filter that centre frequency proposed by the present invention is 3.8THz shows
It is intended to.A in Fig. 1 is its planar structure schematic diagram, and P is 72 μm of the square unit cycle length of side, 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 be SiN x Supporting Media film.
Fig. 2 is SiN in the ultra-thin broadband filter that centre frequency proposed by the present invention is 3.8THz x Support film
Optical microscope photograph.Wherein, the b in Fig. 2 is a enlarged drawing.
Fig. 3 is in the broadband filter that centre frequency proposed by the present invention is 3.8THz, after wet etching silicon substrate
Photo.Wherein, a in Fig. 3 be positive periodicity square grid structure picture surface, whole filter construction figure face size
For 5mm × 5mm；B in Fig. 3 is the structure graph of back side windowing, and the size of opening surface is 7mm × 7mm.Including figure surrounding
Silicon substrate framework, the size of whole sample is 10mm × 10mm.
Fig. 4 is the process chart for the ultra-thin broadband filter that centre frequency proposed by the present invention is 3.8THz.Wherein,
A in Fig. 4 is to deposit layer of sin using PECVD x Film support film；B is in SiN x One layer of the surface spin coating of film support layer
Photoresist, post-exposure development is toasted, obtains periodicity square grid structure；C is to etch SiN using RIE x Film, and remove photoetching
Glue；D deposits another layer of sin for silicon substrate is overturn, in another side with PECVD x Film；E is in the SiN x The surface spin coating of film
Another layer of photoresist, post-exposure development is toasted, obtain the result of back side windowing；F is to etch SiN using RIE x Film, and remove
Photoresist；G is wet etching, and silicon substrate is corroded, structure release, obtains the SiN with periodic structure figure x Support
Film；H is using electron beam evaporation technique, deposited metal film；I is obtained ultra-thin Terahertz medium-high frequency broadband filter
Structure.
Fig. 5 is the actual test result for the ultra-thin broadband filter that the centre frequency made according to the present invention is 3.8THz
With the contrast of simulation result.
Fig. 6 is that when the metal film of wave filter proposed by the present invention changes NiCr into by Al, wave filter is too under square structure
The results contrast of hertz response characteristic.
Fig. 7 is that the metal of wave filter proposed by the present invention and the shape of dielectric film are by side under identical material parameter
When type changes round into, the results contrast of the Terahertz response characteristic of wave filter.
Fig. 8 is the metal and medium of wave filter proposed by the present invention in the case of material parameter and square shape identical
When W the and P parameters of the graphic structure of film change, the results contrast of the Terahertz response characteristic of wave filter.
Fig. 9 be according to the present invention make be centre frequency 3.8THz ultra-thin broadband filter multiple wave filters
Superimposed measured result.Wherein, when the number of wave filters of a in Fig. 9 to be superimposed is respectively 1,2,3,4, it is superimposed wave filter
Schematic diagram；When the number of wave filters of the b to be superimposed in Fig. 9 is respectively 1,2,3,4, the test knot of different superposition wave filters
Fruit.
Embodiment
For ease of understanding the present invention, it is as follows that the present invention enumerates embodiment.Those skilled in the art are it will be clearly understood that the implementation
Example is only to aid in understanding the present invention, is not construed as the concrete restriction to the present invention.
The embodiment of the present invention uses the ultra-thin SiN of good mechanical performance x Backing material of the film as wave filter.Together
When, the embodiment of the present invention obtains Terahertz medium-high frequency broadband filter, has good passband by using square graphic structure
With the advantages that roomy, Out-of-band rejection performance is good.Moreover, square structure is easily fabricated, mechanical stability is high.
The preparation method of ultra-thin Terahertz medium-high frequency broadband filter provided by the invention, using the micro Process work of routine
Skill manufactures.For the embodiment of the present invention using the unit cycle as 72 μm of 72 μ m, center etching size is 52 μm of 52 μ m（Such as a in Fig. 1
It is shown）, bandpass center frequency is 3.8THz, with a width of 2.6THz（2.1THz–4.7THz）Square structure（Square grid）Exemplified by,
Illustrate specific preparation method, those skilled in the art there can be it according to the other sizes of content production of this specification
The terahertz filter of its bandpass center frequency and bandwidth.
Embodiment
A kind of centre frequency is 3.8THz broadband filter, is made by the following method：
Step 1：Clean silicon（100）Twin polishing substrate；
In this step, cleaning process is：First place the substrate into 10-15min of ultrasonic cleaning in acetone soln；Take out substrate,
It is then placed in 10-15min of ultrasonic cleaning in absolute ethyl alcohol；Take out substrate, then with deionized water rinsing 2-4 times, until cleaning is dry
Only, finally substrate is dried up with nitrogen.
Step 2：Using PECVD, one layer of amorphous SiN to play a supportive role is deposited in the one side of silicon substrate x Dielectric film；
In this step, SiN is deposited using PECVD x The process conditions of film are：RF operating frequency is high frequency
13.56MHz, low frequency 380KHz, the two is used alternatingly；Reacting gas is SiH4And NH3, ventilation flow rate ratio SiH4:NH3=1:5；
Depositing temperature is 250 DEG C；Amorphous SiN x The deposit thickness of film is 1 μm.
Step 3：In SiN x One layer of photoresist of surface spin coating of film, and toast；
In this step, sample is first placed into 120 DEG C of baking 20min in an oven, removes the moisture on surface；Then, spin coating
Photoresist, and it is placed on 100 DEG C of baking 3min on hot plate；
Step 4：Exposure imaging, obtain positive periodicity square structure graph；
In this step, photoresist is exposed using ultraviolet photolithographic technology, periodicity square structure graph is obtained after development, it is whole
The positive dimension of picture of individual filter construction is 5mm × 5mm（As shown in a in Fig. 3）；
Step 5：Using reactive ion etching（RIE）Etching period square grid structure graph；
In this step, RIE etchings SiN x The process conditions of film are：Etching reaction gas is CHF3, gas flow is
20sccm, etch rate 60nm/min, etch period 20min；Spend quarter 20% so that the exposed SiN of structure graph x Film
It is etched completely, until substrate silicon surface.
Step 6：The structure etched is subjected to ultrasound in acetone, removes remaining photoresist.
Step 7：To the another side repeat step 1-3 of twin polishing silicon substrate；
Step 8：Exposure imaging, obtain the fenestration figure at the back side；
In this step, twin polishing silicon substrate is aligned with plane of exposure described in step 4, using ultraviolet photolithographic technology to photoetching
Glue exposes, and planless fenestration is obtained after development, the size of the fenestration at the back side is 7mm × 7mm（Such as the b institutes in Fig. 3
Show）.
Step 9：By reactive ion etching and remaining photoresist step is gone, obtains back windowing graphic structure；
Step 10：Using wet etching, the graph substrate that step 9 is obtained is corroded, and acquisition has periodic structure
The SiN of figure x Support film；
In this step, the graph substrate for first obtaining step 9 is cut into 10mm × 10mm（As shown in Figure 3）.Wherein, it is positive
Periodicity square structure and the fenestration at back are respectively positioned among cut substrate.In subsequent wet etching, edge is not carved
The SiN of erosion x Film will prevent silicon substrate from being etched；The silicon substrate not being etched is easy to subsequent step to filter as frame structure
Ripple device is operated.
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；
Using water-bath or oil bath controlling reaction temperature, etch period 6h or so, until silicon substrate etching is complete, SiN is finally left x Support
Film and silicon frame（As shown in Figure 3）.
Step 11：In SiN x The surface of support film, deposit layer of metal aluminium（Al）Film, obtain in ultra-thin Terahertz
High-frequency wideband wave filter.
In this step, using electron beam evaporation process, in the SiN with periodic structure figure that step 10 obtains x Branch
The surface of support film deposits the Al films that a layer thickness is 200nm.
According to above-mentioned steps 1 to 11, the ultra-thin Terahertz medium-high frequency broadband filter shown in Fig. 1,2 and 3 is prepared.Its
In, frequency is the schematic diagram of 3.8THz broadband filter periodic structure unit centered on Fig. 1.Frequency is centered on Fig. 2
The SiN of 3.8THz broadband filter x The optical microscope photograph of support film.Frequency is 3.8THz broadband centered on Fig. 3
Wave filter, front and back side photo after wet etching silicon substrate.Frequency is 3.8THz broadband filter centered on Fig. 4
Process chart.
The Supporting Media film of ultra-thin Terahertz medium-high frequency broadband filter proposed by the present invention is not particularly limited, and is removed
Silicon nitride（SiN x ）Film, it can also be other thickness and the silica of component（SiO x ）Film, silicon oxynitride（SiN x O y ）It is thin
A kind of or their composite membrane among film, or non-crystalline silicon（a-Si）Film, polyimides, other polymer, oxygen
Change iron（FeO x ）, titanium oxide（TiO x ）, titanium nitride（TiN x ）, vanadium oxide（VO x ）, vanadium nitride（VN x ）, GaAs（GaAs）, oxidation
Aluminium（AlO x ）, hafnium oxide（HfO x ）, hafnium aluminum oxide（HfAlO x ）Film etc. in the industry one kind among known other dielectric films or
Person is their composite membrane.The metal level of ultra-thin Terahertz medium-high frequency broadband filter proposed by the present invention is not also limited especially
System, can be metal Al, Au, Ti, TiN x 、TiSi x 、TiW x 、W、WSi x 、Ni、NiSi x 、Ta、TaN x 、Fe、Pt、Cu、Ag、Cr、
A kind of or their compound among NiCr.Under ultra-thin Terahertz medium-high frequency broadband filter proposed by the present invention
Layer support film and the figure of upper strata metal are also not particularly limited, and can be squares, round or be known other in the industry
One kind among the Terahertz response pattern of shape.
Through following analysis, provable ultra-thin Terahertz medium-high frequency broadband filter proposed by the present invention, can keep
On the premise of mechanical stability, selective broadband transmission effectively is carried out to the THz wave of specific wavelength, is function admirable
Terahertz filter.
Filter structure is emulated using CST microwave studio softwares.During emulation, filter period construction unit is such as
Shown in Fig. 1, the box structure unit cycle P=72 μm, intermediate etch square length of side W=52 μm, square grid structure width is 20 μ
m.Simulation parameter is：SiN x The dielectric constant of support film is 4, loss angle tangent 0, and thickness is 1 μm；Metal layer A l conductance
Rate is 3.56 × 107S/m.In addition, using PerkinElmer companies Spectrum400 Fourier infrared spectrographs it is remote red
Outer component, the ultra-thin broadband filter for being 3.8THz to the centre frequency that embodiment makes are filtered performance test.
Fig. 5 be embodiment make centre frequency be 3.8THz single ultra-thin broadband filter in vertical incidence（Enter
Firing angle is 0 °）Under the conditions of actual test result and simulation result comparison diagram.Wherein, simulation result（Fig. 5）It has been shown that, it is single too
The centre frequency of hertz wave filter is 3.9THz, and bandpass center transmitance is up to 99%.By comparison, test result（Fig. 5）Show,
The centre frequency of single terahertz filter is 3.8THz, and bandpass center transmitance is 93%.SiN during in view of emulation x Use
It is lossless condition parameter, and the SiN that actual fabrication obtains x There is certain loss.Moreover, metal layer A l electrical conductivity is due to table
Face aoxidizes, and realistic conductivity is also lower than ideal value, also brings along certain loss.In addition, test also found,
At 3.0THz, 2.5THz, 1.7THz, 1.3THz, there are some small absworption peaks, be primarily due in testing background air
The influence of water, carbon dioxide etc..Fig. 5 results clearly show that simulation result is coincide substantially with measured result, and they are all proved：This
The wave filter that invention provides has excellent Terahertz medium-high frequency wideband filtered performance.
Fig. 6-8 shows the influence of filter material and structural parameters change to the Terahertz response performance of device.Wherein, scheme
6 displays, when the square structure of wave filter is constant, the metal film of wave filter changes the low NiCr of electrical conductivity into by the high Al of electrical conductivity
When, the centre frequency of wave filter is constant, but transmitance weakens.Fig. 7 shows, when the material parameter of wave filter is constant, but filters
When the metal film of ripple device and the shape of dielectric film change round into by square, the 3.8THz centre frequencies of wave filter are constant, but
Frequency band narrows；Moreover, in 4 higher -10THz frequency ranges, response frequency and transmitance occur significantly to change.Fig. 8 shows
Show, when W the and P parameters of the material parameter of wave filter, film thickness and square shape invariance, but its graphic structure change
When, corresponding change occurs for the centre frequency of wave filter, frequency band etc.；Wherein, when W and P parameters increase, response frequency is to terahertz
Hereby low frequency moves, on the contrary, when W and P parameters reduce, response frequency is then to Terahertz high-frequency mobile.Fig. 6-8 results show, right
In terahertz filter provided by the invention, can by the change of structure and material parameter, centre frequency to wave filter and
Frequency band etc. is adjusted, and is allowed to meet different application requirements.
It is worth noting that, the loss at the bandpass center frequency of terahertz filter provided by the invention is very low, about
0.3dB, much smaller than traditional multilayer based on FSS Structure Filters（About 2dB）.This explanation, it is provided by the invention based on super
The terahertz filter of the FSS structures of thin support film, can be effectively reduced insertion loss.In addition, it is provided by the invention too
The three dB bandwidth of hertz wave filter is 2.6THz（2.1-4.7THz）, half-peak breadth（FWHM）For 68%, illustrate it is provided by the invention too
Medium-high frequency wave band of the hertz wave filter in Terahertz（3-6THz）With broadband through performance.In addition, outside 6-12THz wave band bands
Suppress to be about -5.3dB, illustrate terahertz filter provided by the invention, in terahertz wave band, except the transmission frequency range of design
Outside, occur without other resonance through peak.Thus it is possible to effectively eliminate the method cloth as caused by traditional thicker substrate
In-Perot resonance, suppress the generation of unnecessary resonance frequency band.
On the basis of single ultra-thin broadband filter, we be also tested for embodiment make it is multiple it is similar too
Hertz wave filter is overlapped, and obtains the Terahertz through performance of new superposition wave filter.The knot of the terahertz filter of superposition
Structure schematic diagram is stacked the back of top wave filter and the front of lower section wave filter as shown in a in Fig. 9, obtains new filter
The combining structure of ripple device.The test result of related superposition wave filter is as shown in the b in Fig. 9.B in Fig. 9 shows, if 2
Wave filter is superimposed, and bandpass center frequency is constant, and transmitance is then 83%, and loss is about 0.8dB, three dB bandwidth 1.5THz
（2.6-4.1THz）, half-peak breadth（FWHM）It is about-10dB in 6-21THz wave bands Out-of-band rejections for 39%；When 3 wave filter knots
When structure is overlapped, the transmitance of new wave filter is 72%, and loss is about 1.4dB, three dB bandwidth 1.0THz（3.0-4.0THz）,
Half-peak breadth（FWHM）It is about-15dB in 6-21THz wave bands Out-of-band rejections for 26%；If 4 filter constructions are overlapped,
The bandpass center frequency of new wave filter is constant, and transmitance is then 62%, and loss is about 2.0dB, three dB bandwidth 0.9THz（3.1-
4.0THz）, half-peak breadth（FWHM）It is about-18dB in 6-21THz wave bands Out-of-band rejections for 24%.Form shown in table 1 is more directly perceived
Ground embodies the performance parameter contrast of different wavenumber filters of superposition.All in all, with superposition wave filter number increasing
Add, the bandpass center frequency of new wave filter is constant, is 3.8THz, but its transmitance gradually reduces, loss increase；Three dB bandwidth
Reduce, half-peak breadth reduces；Waveform is more steep, and Out-of-band rejection performance is improved.
Table 1：When the number of the wave filter of superposition is respectively 1,2,3,4, the test performance index of different superposition wave filters
Contrast.
Embodiment described above only expresses the embodiment of the application, and its description is more specific and detailed, but simultaneously
Therefore the limitation to the application protection domain can not be interpreted as.It should be pointed out that for one of ordinary skill in the art
For, on the premise of technical scheme design is not departed from, various modifications and improvements can be made, these belong to this
The protection domain of application.
Claims (8)
1. a kind of ultra-thin Terahertz medium-high frequency broadband filter, it is characterised in that include one or more layers successively from the bottom to top
Amorphous media film and one or more layers metallic film, wherein, described amorphous media film is etched to square or circle
A kind of periodic pattern structure among type；Described metallic film is directly attached to the surface of amorphous media film, Er Qiejin
It is identical with the shape of amorphous media film to belong to film；The amorphous media film is silicon nitride, silica, silicon oxynitride film are worked as
In a kind of or their composite membrane, its thickness be 10nm-10 μm；The metallic film is Al, Au, Ti, TiNx、
TiSix、TiWx、W、WSix、Ni、NiSix、Ta、TaNx, a kind of among Fe, Pt, Cu, Ag, Cr, NiCr or they answer
Compound, the thickness of metallic film is 5nm-4000nm.
2. a kind of preparation method of ultra-thin Terahertz medium-high frequency broadband filter according to claim 1, its feature exist
In comprising the following steps：
(1) twin polishing substrate is cleaned；
(2) reactor is utilized, one or more layers amorphous media film is deposited in the one side of substrate；
(3) in one layer of photoresist of surface spin coating of amorphous media film, and toast；
(4) photoresist is exposed, after development, obtains the periodic structure figure of photoresist；
(5) reactive ion etching amorphous media film is used, obtains the periodicity knot with square or a kind of round central shape
Composition shape；
(6) remaining photoresist is removed, obtains the periodicity knot with square or a kind of amorphous media film of round central shape
Composition shape；
(7) to another side repeat step (1)-(3) of the substrate；
(8) exposure imaging, the fenestration figure at the back side is obtained；
(9) by reactive ion etching amorphous media film and remaining photoresist is removed, obtains back windowing graphic structure；
(10) lithographic method is used, the substrate for the photoetching that step (9) is obtained performs etching, and obtains with periodic structure
The amorphous media film of figure；
(11) on the surface of amorphous media film, using reactor, one or more layers metallic film is deposited, is obtained with square
A kind of or ultra-thin Terahertz medium-high frequency broadband filter of round central shape.
3. a kind of preparation method of ultra-thin Terahertz medium-high frequency broadband filter according to claim 2, its feature exist
In, twin polishing substrate used is twin polishing monocrystalline substrate in step (1), wherein, when step (10) uses dry method
During etching, twin polishing substrate used is a kind of twin polishing monocrystalline silicon lining among silicon (100) or silicon (111), silicon (110)
Bottom；When step (10) uses wet etching, twin polishing substrate used is silicon (100) twin polishing monocrystalline substrate, is made
Corrosive liquid is the KOH aqueous solution, wherein, the concentration of the KOH aqueous solution is 10wt.% -60wt.%, using water-bath, oil bath or sky
A kind of reaction temperature of method control wet etching among gas bath, its range of reaction temperature is 30 DEG C -120 DEG C, wet etching
Time be 0.5-20h, until twin polishing monocrystalline substrate is etched completely.
4. a kind of preparation method of ultra-thin Terahertz medium-high frequency broadband filter according to claim 2, its feature exist
In, in step (2), the reactor that uses of amorphous media film is prepared as plasma reinforced chemical vapor deposition system, or
Person be low-pressure chemical vapor deposition, aumospheric pressure cvd, electron beam evaporation, vacuum thermal evaporation, among magnetic control sputtering system
One kind；When using plasma strengthens chemical vapor deposition, its working frequency is that high frequency, low frequency or high frequency replace with low frequency
It is used in mixed way；Prepared amorphous media film be silicon nitride either silica, one kind among silicon oxynitride film or
It is their composite membrane, as the support film of ultra-thin Terahertz medium-high frequency broadband filter, its thickness is 10nm -10 μm.
5. a kind of preparation method of ultra-thin Terahertz medium-high frequency broadband filter according to claim 2, its feature exist
In in step (5) and (9), the reacting gas that described reactive ion etching uses is CF4、CHF3、C3F8、SF6、NF3It is central
A kind of F bases gas either their compound.
6. a kind of preparation method of ultra-thin Terahertz medium-high frequency broadband filter according to claim 2, its feature exist
In in step (6) and (9), the method for removing remaining photoresist is：Using one kind among acetone, butanone, methanol, ethanol
Either their compound, by ultrasound, removes remaining photoresist as adhesive remover.
7. a kind of preparation method of ultra-thin Terahertz medium-high frequency broadband filter according to claim 2, its feature exist
In in step (10), the method for etching twin polishing substrate is one kind among dry etching or wet etching.
8. a kind of preparation method of ultra-thin Terahertz medium-high frequency broadband filter according to claim 2, its feature exist
In in step (11), preparing reactor that metallic film uses as electron beam evaporation, vacuum thermal evaporation, magnetron sputtering, metal
One kind among organic chemical vapor deposition system, the metal of prepared metallic film is Al, Au, Ti, TiNx、TiSix、
TiWx、W、WSix、Ni、NiSix、Ta、TaNx, a kind of or their compound among Fe, Pt, Cu, Ag, Cr, NiCr,
The thickness of metallic film is 5nm -4000nm.
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