CN1464298A - Miniature Infrared Gas Analysis Device - Google Patents

Abstract

A miniature infrared gas analysis device mainly comprises an infrared emission unit, and is characterized in that the infrared emission unit is a miniature infrared emission unit; also included are the following microelements: an infrared collimating lens for converting the infrared rays emitted from the infrared emitting unit into parallel infrared beams; a band-pass and spatial filter for screening an infrared band including at least an absorption spectrum of a gas to be measured and allowing only infrared beams of a specific geometric region to pass therethrough; the frequency modulation filtering unit only allows the narrow-band wavelength of the absorption spectrum of a single gas to be detected to pass through at the same time; a sensing unit for determining the concentration and type of the gas to be detected according to the incident narrow-band wavelength intensity; a microcomputer control unit as an input/output interface; the micro-devices manufactured by the silicon micro-processing technology are applied to qualitative and quantitative analysis of infrared absorption spectra of various gases so as to meet the requirements of low power consumption and low cost, and have practicability.

Description

Mini type infrared ray gas analysis apparatus

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 example₂Be 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-redray 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-redray 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 frequencymodulation 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 asensing cell 60, differentiate the concentration and the kind of gas to be measured according to the narrow frequency Wavelength strength of this incident; And amicrocomputer 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-redray transmitting unit 10 comprises thermal resistance (Thermo-Resistive) infrared transmitter (IREmitter) 10a and an equitemperature (resistance) thedriving circuit 10b that a silicon micromachining technology is made, this miniature thermal resistanceinfrared 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 infraredray 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 infraredray 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 thespatial filter 30 of one miniature band comprises: themetal 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.Thisspatial filter 34 only allows this circle or the square aperture of thelight beam 21 of part by thismetal level 34, and promptly the zone contained of light 12 its objective is the resonant cavity area that cooperates following miniature frequencymodulation wave filter 50a.

One miniature frequencymodulation 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 drivingoscillatory circuit 50b provides a direct current voltage V₀Reach a small alternating voltage Δ Vsin ω t, make this frequencymodulation wave filter 50a have the function of wavelength screening and optical modulator (Modulator) concurrently.

One miniaturehot detector 60a, the intensity of this narrow frequency optical wavelength that detecting frequencymodulation wave filter 50a is screened, the one phase-lockedcircuit 60b that reads compares the AC signal I (ω) of thisultrared sensing device 60a output and the modulating frequency ω of this drivingoscillatory 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 TiO₂/ MgF₂And 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: asilicon substrate 500, thissilicon substrate 500 is to be a silicon insulation course silicon wafer (Silicon OnInsulator, SOI), there is siliconmonoxide insulation course 500b that thissilicon substrate 500 is divided intofront silicon wafer 500c (claim not only element silicon wafer Device Wafer) and reverseside silicon wafer 500a (but also claiming to hold under the arm to put silicon wafer Handle Wafer) in the middle of thissilicon substrate 500.

One suspensionmechanical structure 501 is withsilicon wafer 500c surface distance oneclearance 506, front.This suspensionmechanical 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 withthin plate 502, another end points of elongated leg 504 then is connected in this fixedarea 505, this fixedarea 505 is to connect and be fixed in thissilicon wafer 500c surface, front by a spacing block 514 (Spacer), and the thickness ofspacing block 514 is the starting altitude of thisclearance 506.

Onefirst 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 fixedarea 505 and electrically connects with the external world by elongated leg 504.

Onefixed electorde 512 is made insilicon 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 ofsilicon oxide 500b that is positioned atsilicon substrate 500 centres; Reach a back side V-type groove 509 and be made among the reverseside silicon wafer 500a, positive alignment is in thisfirst catoptron 510, and back side V-type groove 509 square flat bottom expose the insulating layer ofsilicon oxide 500b that is positioned atsilicon substrate 500 centres; And onesecond 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 byfirst 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 insecond 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 befront silicon wafer 500c andclearance 506 both thickness and, it determines to be the thickness offront 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 fixedelectorde 512, can utilize mode modulationfirst 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 thatclearance 506 between floating electrode 503 and thefixed electorde 512 makes, and therefore can comply with the differentdifferent 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 andsilicon wafer 500c surface, front, bottom.

Except above-mentioned advantage,first catoptron 510 andsecond 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 ofsubstrate 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 offirst catoptron 510 and second catoptron, 511 materials.

Wherein, the production method of this fixedelectorde 512 is that the impurity that utilizes the mode of High temperature diffusion or implanting ions to finish onsilicon wafer 500c surface, front oozes assorted.Wall 514 materials are polysilicon, and the sandwich structure that thisphysical 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 MgF₂/ TiO₂And 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: thesilicon substrate 600 of a crystal orientation (100); And a suspensionthin plate 601, be formed on thesubstrate 600, have a plurality of thermopair 603.Thermo-contact district 604 is the middle bodies that are positioned at suspensionthin plate 601, andcold contact region 605 is in peripheral part of suspensionthin plate 601.

By a plurality ofetching window 606 definition, but etching forms the V-type groove 607 of suspensionthin plate 601 belows, to constitute the structure of suspension thin plate 601.The most surperficialblack matrix material 602 of then making of suspensionthin 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.

Suspensionthin plate 601 comprises onefirst dielectric layer 600a, one first thermopair 603a, onesecond dielectric layer 600b, onesecond thermopair 603b, one the 3rddielectric layer 600c, and wherein this first, second and thirddielectric 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)

Translated fromChinese

1、一种微型红外线气体分析装置，主要包括有一红外线发射单元，其特征是：该红外线发射单元为利用热阻丝黑体辐射原理发射出一宽广的红外线光谱的微型红外线发射单元，同时还包括以下微型元件：1. A miniature infrared gas analysis device mainly includes an infrared emitting unit, which is characterized in that: the infrared emitting unit is a miniature infrared emitting unit that emits a broad infrared spectrum by utilizing the principle of thermal resistance wire black body radiation, and also includes the following Micro components:一将红外线发射单元出射的红外线变成平行红外线光束的红外线准直镜；An infrared collimating mirror that converts the infrared rays emitted by the infrared emitting unit into parallel infrared beams;一筛选包含至少一待测气体吸收光谱在内的一红外线波段，并且只允许特定几何区域的红外线光束通过的带通与空间滤波器；A band-pass and spatial filter that screens an infrared band that includes at least one absorption spectrum of the gas to be measured, and only allows infrared beams in a specific geometric region to pass through;一同一时间仅允许单一待测气体吸收光谱的窄频波长通过的调频滤波单元；A frequency modulation filter unit that only allows the narrow-band wavelength of the absorption spectrum of a single gas to be measured to pass through at the same time;一判别待测气体的浓度与种类的感测单元；A sensing unit for distinguishing the concentration and type of the gas to be measured;一作为输出/入界面控制的微电脑控制单元。A microcomputer control unit as an I/O interface control.2、根据权利要求1所述的微型红外线气体分析装置，其特征是：该红外线发射单元包括：2. The miniature infrared gas analysis device according to claim 1, characterized in that: the infrared emitting unit includes:一硅微加工技术制作的微型热阻红外线发射器；A miniature thermal resistance infrared emitter made by silicon micromachining technology;一稳定微型热阻红外线发射器温度的等温度驱动电路。An isothermal drive circuit for stabilizing the temperature of the miniature thermal resistance infrared emitter.3、根据权利要求2所述的微型红外线气体分析装置，其特征是：该微型热阻红外线发射器包括：3. The miniature infrared gas analysis device according to claim 2, characterized in that: the miniature thermal resistance infrared emitter comprises:一晶向为100的硅基板，具有第一及第二表面；A silicon substrate with a crystal orientation of 100 has a first surface and a second surface;一硅异方性蚀刻制作的V-型槽形成于该硅基板的第一或第二表面；A V-groove formed by silicon anisotropic etching is formed on the first or second surface of the silicon substrate;一悬浮薄板，形成于该V-型槽上；a suspended thin plate formed on the V-groove;一热阻材料，制作于该悬浮薄板中；a thermal resistance material made in the suspended thin plate;一黑体材料，制作于悬浮薄板最表面。A blackbody material is made on the outermost surface of the suspended thin plate.4、根据权利要求3所述的微型红外线气体分析装置，其特征是：该热阻材料为高温度系数的硅、白金。4. The micro-infrared gas analysis device according to claim 3, characterized in that: the thermal resistance material is silicon or platinum with a high temperature coefficient.5、根据权利要求3所述的微型红外线气体分析装置，其特征是：该黑体材料为金黑及白金黑。5. The micro-infrared gas analysis device according to claim 3, characterized in that: the black body material is gold black and platinum black.6、根据权利要求1所述的微型红外线气体分析装置，其特征是：该带通与空间滤波器包括：6. The micro-infrared gas analysis device according to claim 1, characterized in that: the band-pass and spatial filter includes:一晶向为100的硅基板，具有第一及第；表面；A silicon substrate with a crystal orientation of 100, having first and second surfaces;一带通光学薄膜制作于硅基板的第一表面，滤除至少一待测气体以外的红外线光谱波段；A band-pass optical thin film is fabricated on the first surface of the silicon substrate to filter out at least one infrared spectral band other than the gas to be measured;一具有特定几何形状开口的金属薄膜作为空间滤波器，制作于带通光学薄膜上；A metal thin film with openings in a specific geometric shape is used as a spatial filter, which is fabricated on a bandpass optical thin film;一硅异方性蚀刻制作的V-型槽，该V-型槽开口形成于硅基板的第二表面，该V-型槽蚀穿硅基板以致V-型槽方形底部暴露出带通光学薄膜与金属薄膜空间滤波器的特定几何形状开口。A V-shaped groove made by silicon anisotropic etching, the opening of the V-shaped groove is formed on the second surface of the silicon substrate, and the V-shaped groove is etched through the silicon substrate so that the square bottom of the V-shaped groove exposes a bandpass optical film Specific geometry openings with metal thin film spatial filters.7、根据权利要求6所述的微型红外线气体分析装置，其特征是：该带通光学薄膜是多层介电质材料所组成；该多层介电层基本组成单位为一对折射系数高与折射系数低的介电材料。7. The micro-infrared gas analysis device according to claim 6, characterized in that: the bandpass optical film is composed of multilayer dielectric materials; the basic composition unit of the multilayer dielectric layer is a pair of high refractive index and A dielectric material with a low index of refraction.8、根据权利要求6所述的微型红外线气体分析装置，其特征是：该金属薄膜空间滤波器材料为Ti/Au或Cr/Au，其中Ti或Cr作为附着层。8. The micro-infrared gas analysis device according to claim 6, characterized in that: the metal film space filter material is Ti/Au or Cr/Au, wherein Ti or Cr is used as the adhesion layer.9、根据权利要求1所述的微型红外线气体分析装置，其特征是：该调频滤波单元包括：9. The miniature infrared gas analysis device according to claim 1, characterized in that: the frequency modulation filter unit includes:一硅微加工技术制作的微型调频滤波器，以电场控制改变光学共振腔的长度以筛选欲侦测气体的红外线吸收波长；A micro-frequency modulation filter made by silicon micro-processing technology, using electric field control to change the length of the optical resonant cavity to screen the infrared absorption wavelength of the gas to be detected;一提供一直流电压及一微小的交流电压的驱动振荡电路。A drive oscillator circuit that provides a DC voltage and a small AC voltage.10、根据权利要求9所述的微型红外线气体分析装置，其特征是：该微型调频滤波器包括：10. The miniature infrared gas analysis device according to claim 9, characterized in that: the miniature FM filter comprises:一硅绝缘层硅基板，一氧化硅绝缘层将该硅绝缘层硅基板分为正面与反面两硅晶片；A silicon insulating layer silicon substrate, a silicon oxide insulating layer divides the silicon insulating layer silicon substrate into two silicon wafers, the front and the back;一悬浮机械结构，该悬浮机械结构包含一薄板结构及至少一细长支脚，该至少一细长支脚的第一端点是与薄板结构连接，该至少一细长支脚的第二端点则连接于至少一固定区域；A suspended mechanical structure, the suspended mechanical structure includes a thin plate structure and at least one elongated leg, the first end point of the at least one elongated leg is connected to the thin plate structure, and the second end point of the at least one elongated leg is connected to at least one fixed area;至少一分隔块，连接该至少一固定区域与其正面硅晶片；at least one partition block, connecting the at least one fixed area and its front side silicon wafer;一空气间隙，形成于该悬浮机械结构与正面硅晶片表面间，该空气间隙的起始距离是由至少一分隔块的高度决定；an air gap formed between the suspended mechanical structure and the surface of the front silicon wafer, the initial distance of the air gap is determined by the height of at least one spacer;一第一反射镜制作于薄板结构中央；A first reflector is fabricated in the center of the thin plate structure;一浮动电极制作于薄板结构上，该浮动电极是通过至少一细长支脚及至少一固定区域与外界作电性连接；A floating electrode is fabricated on the thin plate structure, and the floating electrode is electrically connected to the outside through at least one elongated leg and at least one fixed area;一固定电极，制作于正面硅晶片表面，位于浮动电极正下方，与该浮动电极距离该空气间隙；a fixed electrode, made on the surface of the front silicon wafer, located directly below the floating electrode, and separated from the floating electrode by the air gap;一共振腔V-型凹槽制作于正面硅晶片中，位于第一反射镜正下方，该共振腔V-型凹槽方形平坦底部暴露出位于硅绝缘层硅基板中间的氧化硅绝缘层；A resonant cavity V-shaped groove is made in the front silicon wafer, located directly below the first reflector, and the square flat bottom of the resonant cavity V-shaped groove exposes the silicon oxide insulating layer located in the middle of the silicon insulating layer silicon substrate;至少一防沾黏V-型凹槽，制作于正面硅晶片中，位于该至少一细长支脚正下方；At least one anti-sticking V-shaped groove formed in the front side silicon wafer, located directly below the at least one elongated leg;一背面凹槽，制作于反面硅晶片中，正对准于第一反射镜，该背面凹槽平坦底部暴露出位于硅绝缘层硅基板中间的氧化硅绝缘层；A backside groove, made in the backside silicon wafer, is aligned with the first reflector, and the flat bottom of the backside groove exposes the silicon oxide insulating layer located in the middle of the silicon insulating layer silicon substrate;一第二反射镜，制作于背面凹槽平坦底部上。A second reflecting mirror is fabricated on the flat bottom of the back groove.11、根据权利要求10所述的微型红外线气体分析装置，其特征是：该悬浮机械结构材料依序为富硅氮化硅、多晶硅及富硅氮化硅所组成的三明治结构。11. The micro-infrared gas analysis device according to claim 10, characterized in that: the suspended mechanical structure material is a sandwich structure composed of silicon-rich silicon nitride, polysilicon and silicon-rich silicon nitride in sequence.12、根据权利要求10所述的微型红外线气体分析装置，其特征是：该浮动电极材料为多晶硅。12. The micro-infrared gas analysis device according to claim 10, characterized in that: the material of the floating electrode is polysilicon.13、根据权利要求10所述的微型红外线气体分析装置，其特征是：该分隔块材料为多晶硅或非晶硅。13. The micro-infrared gas analysis device according to claim 10, characterized in that: the material of the partition block is polycrystalline silicon or amorphous silicon.14、根据权利要求10所述的微型红外线气体分析装置，其特征是：该第一及第二反射镜，是由多对高折射系数/低折射系数介电材料所制作的高反射率反射镜。14. The micro-infrared gas analysis device according to claim 10, characterized in that: the first and second mirrors are high-reflectivity mirrors made of multiple pairs of high-refractive-index/low-refractive-index dielectric materials .15、根据权利要求9所述的微型红外线气体分析装置，其特征是：该感测单元包括：15. The miniature infrared gas analysis device according to claim 9, characterized in that: the sensing unit includes:一硅微加工技术制作的微型热侦测器；A miniature heat detector made by silicon micromachining technology;一锁相读取电路，将微型热侦测器输出的电交流讯号与该驱动振荡电路的调制频率作比对。A phase-locked reading circuit compares the electric AC signal output by the miniature heat detector with the modulation frequency of the driving oscillation circuit.16、根据权利要求15所述的微型红外线气体分析装置，其特征是：该微型热侦测器包括：16. The miniature infrared gas analysis device according to claim 15, characterized in that: the miniature heat detector comprises:一晶向为100的硅基板，具有第一及第二表面；A silicon substrate with a crystal orientation of 100 has a first surface and a second surface;一硅异方性蚀刻制作的V-型槽形成于硅基板的第一或第二表面；A V-shaped groove made by silicon anisotropic etching is formed on the first or second surface of the silicon substrate;一悬浮薄板，形成于V-型槽上；a suspended sheet formed on the V-groove;至少一热电偶，制作于悬浮薄板中，该至少一热电偶的热接触区位于悬浮薄板的中央部分，该至少一热电偶的冷接触区位于V-型槽边缘的硅基板上；at least one thermocouple fabricated in the levitation sheet, the thermal contact area of the at least one thermocouple is located in the central part of the levitation sheet, and the cold contact area of the at least one thermocouple is located on the silicon substrate at the edge of the V-shaped groove;一黑体材料，制作于悬浮薄板表面。A black body material is made on the surface of the suspended thin plate.17、根据权利要求16所述的微型红外线气体分析装置，其特征是：该热电偶，包含第一及第二热电偶材料，该第一及第二热电偶材料为N型及P型硅半导体构成，抑或一硅半导体与一金属导体构成。17. The miniature infrared gas analysis device according to claim 16, characterized in that: the thermocouple includes first and second thermocouple materials, and the first and second thermocouple materials are N-type and P-type silicon semiconductors Composition, or a silicon semiconductor and a metal conductor.18、根据权利要求16所述的微型红外线气体分析装置，其特征是：该黑体材料为金黑或白金黑。18. The miniature infrared gas analysis device according to claim 16, characterized in that: the black body material is gold black or platinum black.

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