CN1464298A - Mini type infrared ray gas analysis apparatus - Google Patents
Mini type infrared ray gas analysis apparatus Download PDFInfo
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- CN1464298A CN1464298A CN 02122353 CN02122353A CN1464298A CN 1464298 A CN1464298 A CN 1464298A CN 02122353 CN02122353 CN 02122353 CN 02122353 A CN02122353 A CN 02122353A CN 1464298 A CN1464298 A CN 1464298A
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Abstract
The miniature infrared gas analyzer includes mainly a miniature infrared emitter unit; a miniature infrared collimator to convert the infrared ray from the infrared emitter unit into parallel infrared ray beam; a band-pass and spatial filter with at least one pass band including the absorption spectrum band and allowing infrared beam within some specific geometric zone to pass through; a frequency-modulating filter unit passing only one narrow absorption spectrum band of the tested gas in some time; a sensing unit for judging the concentration and sort of the tested gas based on the obtained spectrum strength; and a microcomputerized control unit with I/O interface. The miniature infrared gas analyzer consists of miniature elements manufactured via silicon micro machining technology, has low power consumption and low cost, and is suitable for qualitative and quantitative analysis of infrared absorption spectrum of various gases.
Description
Technical field
The present invention relates to a kind of gas analyzing apparatus, particularly a kind of mini type infrared ray gas analysis apparatus based on the silicon micromachining technology manufacturing.
Background technology
Present gas measuring device, main flow is the solid-state sensor that utilizes metal oxide (tin oxide) to be done, the resistance variations that (it typically is 300～400 ℃) produced with gas reaction when high temperature is as the sensing principle.Can be subdivided into traditional type and little machining type (Micromachined) again.The power consumption that difference of them only terminates in little machining type is lower, is applicable to the application of portable product, yet the fiduciary level (Reliability) of little machining type gas sensing device is still the problem that is difficult to overcome most.
No matter but be traditional type or little machining type, its maximum shortcoming is all arranged, promptly can't effectively do gas and differentiate (differentiation gaseous species), with carbon monoxide and alcohol is example, the both can react with tin oxide, in case sense gas, can't differentiate it is that carbon monoxide or alcohol are caused.The sensitivity of solid state gas sensing device is lower in addition, is subject to the interference (as humidity and temperature etc.) of environment, and material long period of operation under the environment of high temperature also has aging problem.
The infrared gas sensing device that utilization infrared absorption spectrum technology is developed can solve the difficulty that above-mentioned solid state gas measuring device is run into.See also Fig. 1, it is the characteristic for the gas with various infrared absorption spectrum.Find that by knowing among Fig. 1 the pairing absorbing wavelength of gas with various has sizable gap (CO for example
2Be 4.3 μ m, CO is 4.7 μ m), be can satisfy quite meticulous spectrum to differentiate with the various narrow-band bandpass filters (Narrow Bandpass Filter) of present optical coating made.
Yet known infrared gas sensing rating of set consumption is big, is because traditional resistance wire infrared light sources joule power is big.Have again, various narrow-band bandpass filter efficient with the optical coating made are low, and the wave length shift that environmental effect caused also is a big problem, if will detect multiple gases simultaneously, then necessary construction multi-group bandpass filter, these some problems make it cost an arm and a leg and are unfavorable for promoting.See also United States Patent (USP) numbering 5,852,308,5,468,962,5,861,545.
In view of this, the present invention will propose a brand-new mini type infrared ray gas analysis apparatus.
Summary of the invention
The present invention will provide a kind of mini type infrared ray gas analysis apparatus, makes its tool low-power, is applied to the technical matters of the qualitative and quantitative test of all gases cheaply with solution.
It is such solving the problems of the technologies described above the technical scheme that is adopted:
A kind of mini type infrared ray gas analysis apparatus, mainly include an infra-red ray transmitting unit, it is characterized in that: this infra-red ray transmitting unit is to utilize thermal resistance wire blackbody radiation principle to launch the mini type infrared ray transmitter unit of the infrared spectrum of a broadness, also comprises following micro element simultaneously:
One infrared ray with the infra-red ray transmitting unit outgoing becomes the infrared ray collimating mirror of parallel infrared light beam;
One screening comprises at least one gas absorption spectra to be measured at an interior infrared ray wave band, and the logical and spatial filter of the band that only allows the infrared light beam in particular geometric zone to pass through;
Together the time only allows the frequency modulation filter unit that the narrow frequency wavelength of single gas absorption spectra to be measured passes through, and based on Fabry-Perot interferometer principle, utilizes the length of electric field controls optical resonant cavity;
One differentiates the concentration of gas to be measured and the sensing cell of kind;
One as the microcomputer control unit of exporting/go into interface control;
This infra-red ray transmitting unit comprises:
The miniature thermal resistance infrared transmitter that one silicon micromachining technology is made, according to the principle of blackbody radiation, emission to all the winds comprises the radius of various wave bands;
One stablizes the equitemperature driving circuit of miniature thermal resistance infrared actuator temperature, is not subjected to the influence of room temperature drift, and influences the luminous exitance of specific wavelength, reduces the sensitivity that measures;
This miniature thermal resistance infrared transmitter comprises:
One crystal orientation is 100 silicon substrate, has first and second surface;
The V-type groove that one silicon anisotropy etching is made is formed at first or second surface of this silicon substrate;
One suspension thin plate is formed on this V-type groove;
One thermal resistance material is made in this suspension thin plate;
One black matrix material, it is the most surperficial to be made in the suspension thin plate, to increase the emittance of optical radiation;
This thermal resistance material is silicon, the platinum of high-temperature coefficient;
This black matrix material is that Jin Hei and platinum are black;
This band is logical to be comprised with spatial filter:
One crystal orientation is 100 silicon substrate, has first and second surface;
The logical optical thin film of one band is made in the first surface of silicon substrate, the infrared spectrum wave band beyond at least one gas to be measured of filtering;
One metallic film with geometry in particular opening is made on the logical optical thin film of band as spatial filter;
The V-type groove that one silicon anisotropy etching is made, this V-type channel opening is formed at the second surface of silicon substrate, and this V-type channel erosion wears silicon substrate so that V-type groove plinth exposes the geometry in particular opening that band leads to optical thin film and metallic film spatial filter;
The logical optical thin film of this band is that the multilayer dielectric material is formed; This multilayer dielectric layer basic composition unit is the high and low dielectric material of refraction coefficient of a pair of refraction coefficient;
This metallic film spatial filtering modulator material is Ti/Au or Cr/Au, and wherein Ti or Cr are as adhesion layer;
This frequency modulation filter unit comprises:
The miniature frequency modulation wave filter that one silicon micromachining technology is made changes the infrared ray absorbing wavelength of the length of optical resonant cavity with screening desire detecting gas with electric field controls;
One provides the driving oscillatory circuit of a direct current voltage and a small alternating voltage, makes this miniature frequency modulation wave filter have the function of wavelength screening and optical modulator concurrently;
This miniature frequency modulation wave filter comprises:
One silicon insulation course silicon substrate, the silicon monoxide insulation course is divided into positive and reverse side two silicon wafers with this silicon insulation course silicon substrate;
One suspension mechanical structure, this suspension mechanical structure comprise a thin-slab construction and at least one elongated leg, and first end points of this at least one elongated leg is to be connected with thin-slab construction, and second end points of this at least one elongated leg then is connected at least one fixed area;
At least one spacing block connects this at least one fixed area and its front silicon wafer;
One clearance is formed between this suspension mechanical structure and front silicon wafer surface, and the initial distance of this clearance is the height decision by at least one spacing block;
One first catoptron is made in thin-slab construction central authorities;
One floating electrode is made on the thin-slab construction, and this floating electrode is to electrically connect with extraneous by at least one elongated leg and at least one fixed area;
One fixed electorde is made in the front silicon wafer surface, be positioned under the floating electrode, with this floating electrode apart from this clearance;
One resonant cavity V-type groove is made in the silicon wafer of front, is positioned under first catoptron, and the square flat bottom of this resonant cavity V-type groove exposes and is positioned at the middle insulating layer of silicon oxide of silicon insulation course silicon substrate;
At least one anti-glutinous V-type groove of being stained with is made in the silicon wafer of front, is positioned under this at least one elongated leg;
One back side groove is made in the reverse side silicon wafer, and positive alignment is in first catoptron, and this back side groove flat bottom exposes and is positioned at the middle insulating layer of silicon oxide of silicon insulation course silicon substrate;
One second catoptron is made on the groove flat bottom of the back side;
The sandwich structure that this suspension mechanical structured material is formed for silicon-rich silicon nitride, polysilicon and silicon-rich silicon nitride in regular turn;
This floating electrode material is a polysilicon;
This spacing block material is polysilicon or amorphous silicon;
This first and second catoptron is by many high reflectivity mirror to high index of refraction/low refraction coefficient dielectric material made;
This sensing cell comprises:
The miniature hot detector that one silicon micromachining technology is made;
The one phase-locked circuit that reads compares the electric AC signal of miniature hot detector output and the modulating frequency of this driving oscillatory circuit, with the assorted ratio of the news that improve the sensing signal, and can exempt the noise problem that environmental effect (temperature variation) causes;
This miniature hot detector comprises:
One crystal orientation is 100 silicon substrate, has first and second surface;
The V-type groove that one silicon anisotropy etching is made is formed at first or second surface of silicon substrate;
One suspension thin plate is formed on the V-type groove;
At least one thermopair is made in the suspension thin plate, and the thermo-contact district of this at least one thermopair is positioned at the middle body of suspension thin plate, and the cold joint of this at least one thermopair touches the district and is positioned on the silicon substrate of V-type groove edge;
One black matrix material is made in the suspension thin sheet surface, increases the absorption of optical radiation;
This thermopair comprises first and second thermocouple material, and this first and second thermocouple material is that N type and P type silicon semiconductor constitute, or a silicon semiconductor and metallic conductor formation;
This black matrix material is that Jin Hei or platinum are black.
The invention relates to a kind of design of mini type infrared ray gas analysis apparatus, comprising: an infra-red ray transmitting unit, utilize thermal resistance wire blackbody radiation principle, launch the infrared spectrum of a broadness; One infrared ray collimating mirror becomes the infrared ray of this infra-red ray transmitting unit outgoing into parallel infrared light beam; Logical and the spatial filter of one band, screening comprises at least one gas absorption spectra to be measured at an interior infrared ray wave band, and only allows the infrared light beam in particular geometric zone to pass through; One frequency modulation filter unit, its principle is the Fabry-Perot interferometer, utilizes the length of electric field controls optical resonant cavity, the same time only allows the narrow frequency wavelength of single gas absorption spectra to be measured to pass through; Reach a sensing cell, differentiate the concentration and the kind of gas to be measured according to the narrow frequency Wavelength strength of this incident; And a microcomputer control unit, as exporting/go into interface control.
About this infra-red ray transmitting unit, comprise: the miniature thermal resistance infrared transmitter that a silicon micromachining technology is made, principle according to blackbody radiation, emission to all the winds comprises the radius of various wave bands, and equitemperature (resistance) driving circuit, stablize the temperature of this miniature thermal resistance infrared transmitter, be not subjected to room temperature drift and influence the luminous exitance of specific wavelength, reduce the sensitivity that measures.
Logical and the spatial filter about this band, comprising: a crystal orientation has first and second surface for the silicon substrate of (100); The logical optical thin film of one band is made in the first surface of this silicon substrate, the infrared spectrum wave band beyond at least one gas to be measured of filtering; One metallic film with geometry in particular opening is made on the logical optical thin film of band as spatial filter; And the V-type groove of a silicon anisotropy etching making, this V-type channel opening is formed at the second surface of silicon substrate, and this V-type channel erosion wears silicon substrate so that this V-type groove plinth exposes the geometry in particular opening that band leads to optical thin film and metallic film spatial filter.
About frequency modulation optics filter unit, comprising: the miniature frequency modulation wave filter that a silicon micromachining technology is made, utilize electric field controls to detect the infrared ray absorbing wavelength of gas with the screening desire with the length that changes optical resonant cavity; And one drive oscillatory circuit, and a direct current voltage and a small alternating voltage are provided, and makes this miniature frequency modulation wave filter have the function of wavelength screening and optical modulator concurrently.
About sensing cell, comprising: the miniature hot detector that a silicon micromachining technology is made; And the phase-locked circuit that reads, the electric AC signal of this miniature hot detector output and the modulating frequency of this driving oscillatory circuit are compared, with the assorted ratio of the news that improve the sensing signal, and can exempt environmental effect (temperature variation) thus the noise problem that causes has solved and makes its tool low-power, is applied to the technical matters of the qualitative and quantitative test of all gases cheaply.
The present invention is simple in structure, and this microminiaturization infrared ray gas analysis apparatus comprises: an infra-red ray transmitting unit, utilize thermal resistance wire blackbody radiation principle, and launch the infrared spectrum of a broadness; One infrared ray collimating mirror becomes the infrared ray of this infra-red ray transmitting unit outgoing into parallel infrared light beam; Logical and the spatial filter of one band, screening comprises at least one gas absorption spectra to be measured at an interior infrared ray wave band, and only allows the infrared light beam in particular geometric zone to pass through; One frequency modulation filter unit, its principle is the Fabry-Perot interferometer, utilizes the length of electric field controls optical resonant cavity, the same time only allows the narrow frequency wavelength of single gas absorption spectra to be measured to pass through; Reach a sensing cell, differentiate the concentration and the kind of gas to be measured according to the narrow frequency Wavelength strength of this incident; And a microcomputer control unit, as exporting/go into interface control; Based on the various micro elements of silicon micromachining technology manufacturing meeting low power consumption and requirement cheaply, being applied to the qualitative and quantitative test of all gases infrared absorption spectrum, and the tool practicality.
Description of drawings
Fig. 1 is a gas with various infrared absorption spectrum characteristic synoptic diagram.
Fig. 2 is the functional block diagram of mini type infrared ray gas analysis apparatus of the present invention.
Fig. 3 is that each assembly of mini type infrared ray gas analysis apparatus of the present invention is arranged synoptic diagram.
Fig. 4 a is the plan structure synoptic diagram of the miniature thermal resistance infrared transmitter of the embodiment of the invention.
Fig. 4 b is that Fig. 4 a is along the cross-sectional view shown in the A-A line.
Fig. 5 a is another embodiment plan structure synoptic diagram of miniature thermal resistance infrared transmitter of the present invention.
Fig. 5 b is that Fig. 5 a is along the cross-sectional view shown in the A-A line.
Fig. 6 is the logical sectional structure synoptic diagram with spatial filter of miniature band of the present invention.
Fig. 7 is the miniature frequency modulation Filter Structures of an embodiment of the invention cut-open view.
Fig. 8 a is the plan structure synoptic diagram of embodiment of the invention minisize thermoelectric heap detector.
Fig. 8 b is that Fig. 8 a is along the cross-sectional view shown in the A-A line.
Fig. 9 a is the plan structure synoptic diagram of another embodiment of minisize thermoelectric heap detector of the present invention.
Fig. 9 b is that Fig. 9 a is along the cross-sectional view shown in the A-A line.
Embodiment
See also Fig. 2, it is the functional block diagram (Functional Blocks) of mini type infrared ray gas analysis apparatus of the present invention.Comprise: an infra-red ray transmitting unit 10, utilize thermal resistance wire blackbody radiation principle, launch the infrared spectrum of a broadness; One infrared ray collimating mirror (IR Collimator) 20 becomes the infrared ray of dispersing of these infra-red ray transmitting unit 10 outgoing into parallel infrared light beam; Logical and the spatial filter (Bandpass and Spatial Filter) 30 of one band, screening comprises at least one gas absorption spectra to be measured at an interior infrared ray wave band, and only allows the infrared light beam in particular geometric zone to pass through; One frequency modulation filter unit 50, its principle is the Fabry-Perot interferometer, utilizes the length of electric field controls optical resonant cavity, the same time only allows narrow frequency (Narrow Band) wavelength of single gas absorption spectra to be measured to pass through; Reach a sensing cell 60, differentiate the concentration and the kind of gas to be measured according to the narrow frequency Wavelength strength of this incident; And a microcomputer control unit 70, as exporting/go into interface control.
In order to clearly demonstrate the entity schematic construction of functional block diagram shown in Figure 2, see also Fig. 3, it is that each assembly of mini type infrared ray gas analysis apparatus of the present invention is arranged synoptic diagram.Infra-red ray transmitting unit 10 comprises thermal resistance (Thermo-Resistive) infrared transmitter (IREmitter) 10a and an equitemperature (resistance) the driving circuit 10b that a silicon micromachining technology is made, this miniature thermal resistance infrared transmitter 10a can be considered as a pointolite, principle according to blackbody radiation (Black-Body Radiation), to all the winds launch infrared spectrum, by an infrared ray collimating mirror 20, the maximum cone-shaped beam of being collected (pyramid zone that light 11 is contained) is become parallel beam 21.The material that this infrared ray collimating mirror 20 was suitable for is for 3-5 μ m or 2-8 μ m has good penetrance such as silicon, signle crystal alumina (Saphire) and magnesium fluoride etc.
Logical and the spatial filter 30 of one miniature band comprises: the metal level 34 of logical blooming 33, one circles of a band or square aperture is as spatial filter.The major function of the logical blooming 33 of this band is the spectral band beyond at least one gas to be measured of filtering.This spatial filter 34 only allows this circle or the square aperture of the light beam 21 of part by this metal level 34, and promptly the zone contained of light 12 its objective is the resonant cavity area that cooperates following miniature frequency modulation wave filter 50a.
One miniature frequency modulation wave filter 50a, utilize electric field controls with the length that changes the Fabry-Perot resonant cavity to screen specific narrow frequency optical wavelength (the infrared ray absorbing wavelength of desire detecting gas), this driving oscillatory circuit 50b provides a direct current voltage V
0Reach a small alternating voltage Δ Vsin ω t, make this frequency modulation wave filter 50a have the function of wavelength screening and optical modulator (Modulator) concurrently.
One miniature hot detector 60a, the intensity of this narrow frequency optical wavelength that detecting frequency modulation wave filter 50a is screened, the one phase-locked circuit 60b that reads compares the AC signal I (ω) of this ultrared sensing device 60a output and the modulating frequency ω of this driving oscillatory circuit 50b, assorted with the news that improve the sensing signal than (S/N Ratio), and can exempt the noise problem that environmental effect (temperature variation) causes.
For manufacture that more clearly demonstrates the micro element that utilizes the silicon micromachining technology making shown in Fig. 3 and the superiority that is different from traditional element, below will describe in detail with plurality of units.
Miniature thermal resistance infrared transmitter (Micro Thermo-Resistive IR Emitter)
Utilizing heating resistor to produce ultrared mode is according to the blackbody radiation principle, can confirm the relation of optical radiation emittance (Exitance) maximal value and temperature T and wavelength X to be described below formula (1) by Webster shifting theorem (Wien ' s Displacement Law)
λT＝2897.8(μm?K) (1)
The normal person is at 37 ℃, the wavelength of maximum emittance is 9.35 μ m, as the infrared absorption spectrum that is applied to gas (3～5 μ m or 2-8 μ m), the temperature that can infer thermal resistance wire must can obtain enough optical radiation emittances up to more than the hundreds of ℃, this makes that traditional thermal resistance wire infrared transmitter power consumption is quite big, and is to utilize manpower to make one by one, and the quality keyholed back plate is difficult for, increase the difficulty that back segment is proofreaied and correct, this all is to make its expensive reason.And utilize silicon micromachining technology just can solve the problem of power consumption, and (see also J.S.Shie by the problem that the silicon semiconductor processing procedure produce in batches to solve the quality keyholed back plate, Bruce C.S.Chou, and Y.M.CHen, High performance Pirani Vacuumgauge, J.Vac.Sci.Tech, A, 13 (6) 1995 pp.2972-2979.).
See also Fig. 4 a, it is the plan structure synoptic diagram for the miniature thermal resistance infrared transmitter of the present invention 10a.And Fig. 4 b be for Fig. 4 a along the cross-sectional view shown in the A-A line.Wherein, one crystal orientation is the silicon substrate 100 of (100), one suspension thin plate (Membrane) 101, support and be fixed in the edge of a V-type groove 106 by four elongated legs 102, the formation of this V-type groove 106 is to finish by the definition of etching window 105 and silicon anisotropy etching (Anisotropic Etching) technology.This thin-slab construction 101 and this elongated leg 102 are made up of dielectric material 101a and 101b, and this dielectric material 101a and 101b are generally monox and silicon nitride common in the manufacture of semiconductor or the two is arranged in a combination.At these thin-slab construction 101 internal productions one thermal resistance material 103 is arranged, it typically is thermistor material such as silicon, the platinum etc. of high-temperature coefficient (Temperature Coefficient of Resistance).The most surperficial black matrix material 104 of then making of suspension thin plate it typically is extremely thin metallic film, and for example gold black (Gold-Black) and platinum black (Platinum-Black) are so as to increasing the emittance of optical radiation.
Miniature thermal resistance infrared transmitter forming shown in Fig. 4 a and Fig. 4 b by suspension structure, can effectively reduce heat-conduction value, therefore its value only needs quite little joule power just to be enough to produce the goodish thermal effect that adds usually between 1 μ W/ ℃～10 μ W/ ℃.Illustrate, the polysilicon thermal resistance wire is 1K Ω, is 1mA by electric current, can produce the power of 1mW, if the heat-conduction value of miniature thermal resistance infrared transmitter is 3 μ W/ ℃, the temperature of the thin-slab construction 101 that then suspends will reach more than 300 ℃, and this good thermal efficiency is that traditional element is beyond one's reach.Simultaneously, this elongated leg 102 is fairly good for the thermal insulation of 100 of this suspension thin-slab construction 101 and substrates, and should can be considered as isothermal region by suspension thin-slab construction 101, and this substrate 100 then is in room temperature.Simultaneously, the area of thin-slab construction 101 is quite little (～mm * mm), so can be considered as pointolite, can quite simplify by this design for subsequent optical path.Control by an equitemperature (resistance) driving circuit 10b is arranged again, can stablize the temperature of this suspension thin-slab construction 101, be not subjected to room temperature drift and influence the luminous exitance of specific wavelength, reduce the sensitivity that measures.
See also Fig. 5 a, it is the plan structure synoptic diagram of another embodiment of the miniature thermal resistance infrared transmitter of the present invention.And Fig. 5 b be for Fig. 5 a along the cross-sectional view shown in the A-A line.Structure and Fig. 4 a shown in Fig. 5 a and Fig. 5 b and Fig. 4 b difference only are to utilize back side anisotropy etching to form this V-type groove 106, and all the other processing procedures and design all communicate, and do not give unnecessary details at this.
Logical and the spatial filter (Micro Bandpass and Spatial Filter) of miniature band
Known optical band pass filter is to make optical thin film at an optical substrate (for example quartz glass), its quality requirements is that optical substrate and optically coated material are for desired optics channel penetrance good (low absorption coefficient), particularly the thickness of optical substrate is much larger than optical thin film, therefore determined that more light intensity absorbs, therefore, high-quality optical substrate is played the part of important factor.Simultaneously, for gas infrared absorption spectrum (3～5 μ m or 2～8 μ m) frequency range, the infrared optical substrate of high penetration is rare especially and expensive.For this reason, the present invention proposes a minisize band-pass filter to solve the above problems.
See also Fig. 6, it is the logical sectional structure synoptic diagram with spatial filter 30 of the miniature band of the present invention.Wherein, 31 is the silicon substrate of a crystal orientation for (100), and the one side of this silicon substrate 31 is manufactured with the logical blooming 33 of a band, and the logical blooming 33 of this band is that the multilayer dielectric material is formed.Multilayer dielectric layer basic composition unit is the high and low dielectric material of refraction coefficient of a pair of refraction coefficient, it typically is TiO
2/ MgF
2And its thickness t satisfies nt=λ/4 respectively, and wherein n is a refraction coefficient, and λ is the centre wavelength by frequency range.The V-type groove 32 that one silicon anisotropy etching forms has been removed the silicon substrate 31 of part, and the logical blooming 33 of the band that exposes part and form a film (Diaphragm) structure 35, this measure can be got rid of silicon substrate 31 for the absorption of special spectrum (for example visible light etc.).The arrange in pairs or groups screening of a last spatial filter 34, be the geometric areas that infrared ray passes through, the making of this spatial filter 34 then is the metallic pattern of the manufacture of semiconductor program of a standard with plated film and etching mode made, this metal material is generally Ti/Au or Cr/Au, and wherein Ti or Cr use as adhesion layer.
Miniature frequency modulation wave filter (Micro Tunable Filter)
Common frequency modulation wave filter is based on Fabry-Perot interferometer (being called for short the FP interferometer) principle, but mainly be modulation (traditional modulation mode is for the utilizing the piezoelectric modulation) optical resonant cavity (Resonant Cavity) that utilizes two high reflectivity mirror to form, when resonant cavity length satisfies the half integer multiple m/2 (m represents exponent number) of specific wavelength of light, the light pulse of output has very narrow halfwidth (FWHM FullWidth of Half Maxilmum) characteristic, is widely used in optical communication and various light spectrum detecting apparatus.Yet utilize traditional process technology and assembling be can't produce and possess broad modulation (Free SpectralRange, FSR) the FP interferometer of spectral characteristic, main cause by the length of resonant cavity too big (FSR is inversely proportional to resonant cavity length) caused.Utilize the miniature frequency modulation wave filter of micro-processing technology made can solve this problem, its spectrum modulation scope can be up to 1～2 μ m, such result makes it have the spectrometer function that is equivalent to as grating (Grating) beam split and (sees also United States Patent (USP) numbering 5,550,375), this is that traditional F P interferometer is beyond one's reach, and also is the characteristic of the maximum of miniature frequency modulation optical filter.The present invention is used in the main reason that infrared spectrum detects with it especially.Moreover the batch process low cost also is a great reason like low power consumption and the silicon semiconductor.
See also Fig. 7, it is the structure cut-open view of the miniature frequency modulation wave filter of embodiment of the invention 50a.Comprise: a silicon substrate 500, this silicon substrate 500 is to be a silicon insulation course silicon wafer (Silicon OnInsulator, SOI), there is silicon monoxide insulation course 500b that this silicon substrate 500 is divided into front silicon wafer 500c (claim not only element silicon wafer Device Wafer) and reverse side silicon wafer 500a (but also claiming to hold under the arm to put silicon wafer Handle Wafer) in the middle of this silicon substrate 500.
One suspension mechanical structure 501 is with silicon wafer 500c surface distance one clearance 506, front.This suspension mechanical structure 501 comprises a thin-slab construction 502, four elongated legs 504 and four support fixation zones 505.One end points of elongated leg 504 is connected with thin plate 502, another end points of elongated leg 504 then is connected in this fixed area 505, this fixed area 505 is to connect and be fixed in this silicon wafer 500c surface, front by a spacing block 514 (Spacer), and the thickness of spacing block 514 is the starting altitude of this clearance 506.
One first catoptron 510 is made in this thin-slab construction 502 central authorities; One floating electrode 503 is made on this thin-slab construction 502, is connected to fixed area 505 and electrically connects with the external world by elongated leg 504.
One fixed electorde 512 is made in silicon wafer 500c surface, front, and its position is positioned under this floating electrode 503.
A plurality of V-type grooves 507,508 are made in the positive 500c silicon wafer, comprise the resonant cavity V-type groove 508 that is positioned at these first catoptron, 510 belows, and anti-glutinous (Anti-Sticking) V-type groove 507 of being stained with that is positioned at elongated leg 504 belows, resonant cavity V-type groove 508 square flat bottom expose the insulating layer of silicon oxide 500b that is positioned at silicon substrate 500 centres; Reach a back side V-type groove 509 and be made among the reverse side silicon wafer 500a, positive alignment is in this first catoptron 510, and back side V-type groove 509 square flat bottom expose the insulating layer of silicon oxide 500b that is positioned at silicon substrate 500 centres; And one second catoptron 511, be made in this back side V-type groove 509 square flat bottom.
Wherein, the optical resonant cavity of frequency modulation optical filter of the present invention, promptly be by first catoptron 510 that is made on the thin-slab construction 502, and the square flat bottom of resonant cavity V-type groove 508 (being connected in second catoptron 511 of the square flat bottom of back side V-type groove 509), the optical resonant cavity of the two plane mirrors that constituted.
The length of optical resonant cavity of the present invention is to combine face type Micrometer-Nanometer Processing Technology (sacrifice polysilicon layer technology) and build micro-processing technology (etching of monocrystalline silicon anisotropy) made, the length of optical resonant cavity be front silicon wafer 500c and clearance 506 both thickness and, it determines to be the thickness of front silicon wafer 500c usually, this thickness can obtain different specification (0.3～100 μ m) by commercial silicon insulation course silicon wafer (SOI) supplier, therefore quite has elasticity, selection by suitable 500c thickness, broad spectrum modulation scope can be obtained, the spectral characteristic of light resolution can be satisfied again.
Design and fabrication by floating electrode 503 and fixed electorde 512, can utilize mode modulation first catoptron 510 and 511 optical resonance cavity lengths of second catoptron of electric field attracts, it is by the making of sacrifice layer and follow-up etching action definition that clearance 506 between floating electrode 503 and the fixed electorde 512 makes, and therefore can comply with the different different clearances 506 of requirement definition.Also because this spacing is defined its common thickness＜3 μ m, so only need the lower voltage just can modulation optical resonance cavity length by sacrificial layer thickness.
Anti-be stained with the below that glutinous V-type groove 507 is made in elongated leg 504, be stained with glutinous (Sticking) mutually because of what surface tension that etching liquid produces caused in order to avoid elongated leg and silicon wafer 500c surface, front, bottom.
Except above-mentioned advantage, first catoptron 510 and second catoptron 511 have the excellent depth of parallelism.And the special microstructure design of this frequency modulation wave filter, make it be not limited to the influence of substrate 500 effects, only need just can make the frequency modulation wave filter (being same as the design concept of aforesaid minisize band-pass filter) that is applicable to gas infrared absorption spectrum wave band of the present invention by the selection of first catoptron 510 and second catoptron, 511 materials.
Wherein, the production method of this fixed electorde 512 is that the impurity that utilizes the mode of High temperature diffusion or implanting ions to finish on silicon wafer 500c surface, front oozes assorted.Wall 514 materials are polysilicon, and the sandwich structure that this physical construction 501 is made up of trilaminate material is respectively silicon-rich silicon nitride (SiliconRich Nitride), polysilicon and silicon-rich silicon nitride.Wherein silicon-rich silicon nitride has goodish mechanical rigid and quite low hot unrelieved stress and (sees also Bruce C.S.Chou et al., Fabrication ofLow-Stress Dielectric Thin-Film for Microsensor AppliCations, IEEE ElectronDevice Letters, Vol.18,1997, p.599-601.), therefore be suitable as most MIniature machinery structure high-quality, high stability.Polysilicon in the middle of being positioned at is then simultaneously as the conductor material of physical construction and floating electrode 503.First and second catoptron 510,511 is made height reflection, a low-loss catoptron of multilayer dielectric material.Multilayer dielectric layer basic composition unit is the high and low dielectric material of refraction coefficient of a pair of refraction coefficient, it typically is MgF
2/ TiO
2And its thickness t satisfies nt=λ/4 respectively, and wherein n is a refraction coefficient, and λ is the centre wavelength of institute's modulation spectrum.
Miniature hot detector
The advantage of hot detector (thermal resistance Bolometer, burnt electric Pyrometer and thermoelectric Thermopile) is suitable broadness and smooth spectral response characteristic (Broad and Flat Spectral Response), quite be suitable as the correction of spectrum, but shortcoming be element responsiveness (Responsivity, V/W) relatively poor.
Along with the development of the 1980's silicon micromachining technology, have the suspension thin-slab construction (thin-slab construction can reduce thermal capacitance) of height insulation effect (low thermal conductance), make the thermoelectric pile element responsiveness (responsivity, V/W) and the speed of response significantly promote.Therefore, the development of miniature hot detector has had more significant progress.Minisize thermoelectric heap detector particularly, the advantage of thermoelectric pile element is that itself does not consume any power, therefore, can exempt any voltage noise that is coupled into from the power supply supply, this advantage be other resistor-type (bolometric) infrared element can't be obtained.Moreover, because therefore the electric current very little (even being 0) of the thermoelectric pile element of flowing through itself, also can be ignored by the low frequency noise (l/f noise) of the material that drive current caused.When not having radiation incident, the thermo-contact district and the cold contact region of thermopair can be considered as isothermal, therefore, the environment temperature drift is to the influence of this kind element, also more than little to the resistor-type infrared element.So this kind element is suitable for portable and ambient operation, and do not need extra temperature regulating device.
See also Fig. 8 a, it is the plan structure synoptic diagram of embodiment of the invention minisize thermoelectric heap detector 60a.And Fig. 8 b be for Fig. 8 a along the cross-sectional view shown in the A-A line.Thermoelectric pile element 60a comprises: the silicon substrate 600 of a crystal orientation (100); And a suspension thin plate 601, be formed on the substrate 600, have a plurality of thermopair 603.Thermo-contact district 604 is the middle bodies that are positioned at suspension thin plate 601, and cold contact region 605 is in peripheral part of suspension thin plate 601.
By a plurality of etching window 606 definition, but etching forms the V-type groove 607 of suspension thin plate 601 belows, to constitute the structure of suspension thin plate 601.The most surperficial black matrix material 602 of then making of suspension thin plate 601 it typically is extremely thin metallic film, and for example gold black (Gold-Black) and platinum are deceived (Platinum-Black), to increase the absorptivity of optical radiation.
Suspension thin plate 601 comprises one first dielectric layer 600a, one first thermopair 603a, one second dielectric layer 600b, one second thermopair 603b, one the 3rd dielectric layer 600c, and wherein this first, second and third dielectric layer 600a, 600b, 600c are generally monox and silicon nitride common in the manufacture of semiconductor or the two is arranged in a combination; First and second thermopair 603a, 603b material are constituted by N type and P type silicon semiconductor, or a silicon semiconductor and a metallic conductor constitute.
See also Fig. 9 a, it is the plan structure synoptic diagram of another embodiment of minisize thermoelectric heap detector of the present invention.And Fig. 9 b be for Fig. 9 a along the cross-sectional view shown in the A-A line.Structure and Fig. 8 a shown in Fig. 9 a and Fig. 9 b and Fig. 8 b difference only are to utilize back side anisotropy etching to form this V-type groove 607, and all the other processing procedures and design all communicate, and do not give unnecessary details at this.
The specific embodiment that is proposed in the detailed description of embodiment is only in order to convenient explanation technology contents of the present invention, but not with narrow sense of the present invention be limited to the foregoing description, under the situation that does not exceed spirit of the present invention and claim, the many variations of being done is implemented, and still belongs to scope of the present invention.
In sum, the certain tool advance of the present invention, practicality have met the application for a patent for invention important document, so propose application for a patent for invention in accordance with the law.
Claims (18)
1, a kind of mini type infrared ray gas analysis apparatus, mainly include an infra-red ray transmitting unit, it is characterized in that: this infra-red ray transmitting unit is to utilize thermal resistance wire blackbody radiation principle to launch the mini type infrared ray transmitter unit of the infrared spectrum of a broadness, also comprises following micro element simultaneously:
One infrared ray with the infra-red ray transmitting unit outgoing becomes the infrared ray collimating mirror of parallel infrared light beam;
One screening comprises at least one gas absorption spectra to be measured at an interior infrared ray wave band, and the logical and spatial filter of the band that only allows the infrared light beam in particular geometric zone to pass through;
Together the time only allows the frequency modulation filter unit that the narrow frequency wavelength of single gas absorption spectra to be measured passes through;
One differentiates the concentration of gas to be measured and the sensing cell of kind;
One as the microcomputer control unit of exporting/go into interface control.
2, mini type infrared ray gas analysis apparatus according to claim 1 is characterized in that: this infra-red ray transmitting unit comprises:
The miniature thermal resistance infrared transmitter that one silicon micromachining technology is made;
One stablizes the equitemperature driving circuit of miniature thermal resistance infrared actuator temperature.
3, mini type infrared ray gas analysis apparatus according to claim 2 is characterized in that: this miniature thermal resistance infrared transmitter comprises:
One crystal orientation is 100 silicon substrate, has first and second surface;
The V-type groove that one silicon anisotropy etching is made is formed at first or second surface of this silicon substrate;
One suspension thin plate is formed on this V-type groove;
One thermal resistance material is made in this suspension thin plate;
One black matrix material, it is the most surperficial to be made in the suspension thin plate.
4, mini type infrared ray gas analysis apparatus according to claim 3 is characterized in that: this thermal resistance material is silicon, the platinum of high-temperature coefficient.
5, mini type infrared ray gas analysis apparatus according to claim 3 is characterized in that: this black matrix material is that Jin Hei and platinum are black.
6, mini type infrared ray gas analysis apparatus according to claim 1 is characterized in that: this band is logical to be comprised with spatial filter:
One crystal orientation is 100 silicon substrate, has first and; The surface;
The logical optical thin film of one band is made in the first surface of silicon substrate, the infrared spectrum wave band beyond at least one gas to be measured of filtering;
One metallic film with geometry in particular opening is made on the logical optical thin film of band as spatial filter;
The V-type groove that one silicon anisotropy etching is made, this V-type channel opening is formed at the second surface of silicon substrate, and this V-type channel erosion wears silicon substrate so that V-type groove plinth exposes the geometry in particular opening that band leads to optical thin film and metallic film spatial filter.
7, mini type infrared ray gas analysis apparatus according to claim 6 is characterized in that: the logical optical thin film of this band is that the multilayer dielectric material is formed; This multilayer dielectric layer basic composition unit is the high and low dielectric material of refraction coefficient of a pair of refraction coefficient.
8, mini type infrared ray gas analysis apparatus according to claim 6 is characterized in that: this metallic film spatial filtering modulator material is Ti/Au or Cr/Au, and wherein Ti or Cr are as adhesion layer.
9, mini type infrared ray gas analysis apparatus according to claim 1 is characterized in that: this frequency modulation filter unit comprises:
The miniature frequency modulation wave filter that one silicon micromachining technology is made changes the infrared ray absorbing wavelength of the length of optical resonant cavity with screening desire detecting gas with electric field controls;
One provides the driving oscillatory circuit of a direct current voltage and a small alternating voltage.
10, mini type infrared ray gas analysis apparatus according to claim 9 is characterized in that: this miniature frequency modulation wave filter comprises:
One silicon insulation course silicon substrate, the silicon monoxide insulation course is divided into positive and reverse side two silicon wafers with this silicon insulation course silicon substrate;
One suspension mechanical structure, this suspension mechanical structure comprise a thin-slab construction and at least one elongated leg, and first end points of this at least one elongated leg is to be connected with thin-slab construction, and second end points of this at least one elongated leg then is connected at least one fixed area;
At least one spacing block connects this at least one fixed area and its front silicon wafer;
One clearance is formed between this suspension mechanical structure and front silicon wafer surface, and the initial distance of this clearance is the height decision by at least one spacing block;
One first catoptron is made in thin-slab construction central authorities;
One floating electrode is made on the thin-slab construction, and this floating electrode is to electrically connect with extraneous by at least one elongated leg and at least one fixed area;
One fixed electorde is made in the front silicon wafer surface, be positioned under the floating electrode, with this floating electrode apart from this clearance;
One resonant cavity V-type groove is made in the silicon wafer of front, is positioned under first catoptron, and the square flat bottom of this resonant cavity V-type groove exposes and is positioned at the middle insulating layer of silicon oxide of silicon insulation course silicon substrate;
At least one anti-glutinous V-type groove of being stained with is made in the silicon wafer of front, is positioned under this at least one elongated leg;
One back side groove is made in the reverse side silicon wafer, and positive alignment is in first catoptron, and this back side groove flat bottom exposes and is positioned at the middle insulating layer of silicon oxide of silicon insulation course silicon substrate;
One second catoptron is made on the groove flat bottom of the back side.
11, mini type infrared ray gas analysis apparatus according to claim 10 is characterized in that: the sandwich structure that this suspension mechanical structured material is formed for silicon-rich silicon nitride, polysilicon and silicon-rich silicon nitride in regular turn.
12, mini type infrared ray gas analysis apparatus according to claim 10 is characterized in that: this floating electrode material is a polysilicon.
13, mini type infrared ray gas analysis apparatus according to claim 10 is characterized in that: this spacing block material is polysilicon or amorphous silicon.
14, mini type infrared ray gas analysis apparatus according to claim 10 is characterized in that: this first and second catoptron is by many high reflectivity mirror to high index of refraction/low refraction coefficient dielectric material made.
15, mini type infrared ray gas analysis apparatus according to claim 9 is characterized in that: this sensing cell comprises:
The miniature hot detector that one silicon micromachining technology is made;
The one phase-locked circuit that reads compares the electric AC signal of miniature hot detector output and the modulating frequency of this driving oscillatory circuit.
16, mini type infrared ray gas analysis apparatus according to claim 15 is characterized in that: this miniature hot detector comprises:
One crystal orientation is 100 silicon substrate, has first and second surface;
The V-type groove that one silicon anisotropy etching is made is formed at first or second surface of silicon substrate;
One suspension thin plate is formed on the V-type groove;
At least one thermopair is made in the suspension thin plate, and the thermo-contact district of this at least one thermopair is positioned at the middle body of suspension thin plate, and the cold joint of this at least one thermopair touches the district and is positioned on the silicon substrate of V-type groove edge;
One black matrix material is made in the suspension thin sheet surface.
17, mini type infrared ray gas analysis apparatus according to claim 16, it is characterized in that: this thermopair, comprise first and second thermocouple material, this first and second thermocouple material is that N type and P type silicon semiconductor constitute, or a silicon semiconductor and metallic conductor formation.
18, mini type infrared ray gas analysis apparatus according to claim 16 is characterized in that: this black matrix material is that Jin Hei or platinum are black.
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| Application Number | Priority Date | Filing Date | Title |
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| CN 02122353 CN1464298A (en) | 2002-06-14 | 2002-06-14 | Mini type infrared ray gas analysis apparatus |
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| Application Number | Priority Date | Filing Date | Title |
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| CN 02122353 CN1464298A (en) | 2002-06-14 | 2002-06-14 | Mini type infrared ray gas analysis apparatus |
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Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102213673A (en) * | 2010-04-09 | 2011-10-12 | 中国科学院微电子研究所 | MEMS infrared emission gas-sensitive sensor |
| CN102539370A (en) * | 2011-11-11 | 2012-07-04 | 西安交通大学 | Filtering method for Fourier transform infrared spectrum online analysis of multi-component gas |
| CN103896203A (en) * | 2014-03-24 | 2014-07-02 | 苏州宏态环保科技有限公司 | MEMS infrared light source and preparation method thereof |
| CN104285500A (en) * | 2012-05-08 | 2015-01-14 | 剑桥Cmos传感器有限公司 | Infrared emitter and NDIR sensor |
| CN105241966A (en) * | 2014-07-09 | 2016-01-13 | 中国石油化工股份有限公司 | Multi-component gas detection device |
| CN107990989A (en) * | 2017-12-21 | 2018-05-04 | 南京方旭智芯微电子科技有限公司 | Thermopile IR detector and preparation method thereof |
| CN113495059A (en) * | 2020-04-04 | 2021-10-12 | 江苏物联网研究发展中心 | Infrared gas sensor and preparation method thereof |
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2002
- 2002-06-14 CN CN 02122353 patent/CN1464298A/en active Pending
Cited By (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102213673A (en) * | 2010-04-09 | 2011-10-12 | 中国科学院微电子研究所 | MEMS infrared emission gas-sensitive sensor |
| CN102213673B (en) * | 2010-04-09 | 2013-03-20 | 中国科学院微电子研究所 | MEMS infrared emission gas-sensitive sensor |
| CN102539370A (en) * | 2011-11-11 | 2012-07-04 | 西安交通大学 | Filtering method for Fourier transform infrared spectrum online analysis of multi-component gas |
| CN102539370B (en) * | 2011-11-11 | 2014-06-04 | 西安交通大学 | Filtering method for fourier transform infrared spectrum online analysis of multi-component gas |
| CN104285500A (en) * | 2012-05-08 | 2015-01-14 | 剑桥Cmos传感器有限公司 | Infrared emitter and NDIR sensor |
| CN104285500B (en) * | 2012-05-08 | 2017-11-28 | Ams传感器英国有限公司 | RF transmitter and NDIR sensors |
| CN103896203A (en) * | 2014-03-24 | 2014-07-02 | 苏州宏态环保科技有限公司 | MEMS infrared light source and preparation method thereof |
| CN105241966A (en) * | 2014-07-09 | 2016-01-13 | 中国石油化工股份有限公司 | Multi-component gas detection device |
| CN107990989A (en) * | 2017-12-21 | 2018-05-04 | 南京方旭智芯微电子科技有限公司 | Thermopile IR detector and preparation method thereof |
| CN113495059A (en) * | 2020-04-04 | 2021-10-12 | 江苏物联网研究发展中心 | Infrared gas sensor and preparation method thereof |
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