TW490554B - Miniaturized infrared gas analyzing apparatus - Google Patents

Abstract

A miniaturized infrared gas analyzing apparatus is formed by composing various miniaturized components (infrared source, frequency modulated filter and thermal sensor) based on silicon micro-machining, so as to satisfy the requirements of low power consumption and low cost, and be applied in the fixed quantity and fixed quality analysis for different infrared gas absorbing spectrum. The miniaturized infrared gas analyzing apparatus includes: an infrared transmitting unit for transmitting a wide infrared spectrum by using a thermal resistor filament blackbody radiation theory; an infrared collimating lens for converting the infrared transmitted by the infrared transmitting unit into parallel infrared beams; a band-pass and space filter for screening an infrared band including at least a to-be-tested gas absorbing spectrum, and only allowing infrared beam of specific geometric area to pass; a frequency modulated filter unit theoretically based on a Fabry-Perot interferometer, and using electrical field to control the length of optical resonant chamber, so as to allow the narrow band-pass wavelength of only one to-be-tested gas absorbing spectrum to pass at one time; and a sensing unit for determining the concentrations and types of the to-be-tested gas based on the injected narrow band-pass wavelength strength; and a microcomputer control unit used for out/input interface control.

Description

490554 V. Description of the Invention (l) Field of the Invention The present invention relates to an infrared gas analysis device, and more particularly, to a miniature infrared gas analysis device 'based on Shixi micro-machining technology, and a method for designing and manufacturing its components. [Description of Known Technology] The current gas sensing device is mainly a metal oxide (a solid-state sensor made by oxidation, which reacts with a gas at a high temperature (which is usually 3,000 to 4,000)). The generated resistance change is used as a sensing principle. It can be subdivided into traditional and micromachined. The difference between the two is only limited to the low power consumption of the micromachined type, which is suitable for the application of portable products, but micromachined Reliability of the gas sensor is still the most difficult problem to overcome. However, whether it is traditional or micro-machined, it has its biggest disadvantage, that is, it cannot effectively do gas identification (differentiate gas types), and use carbon monoxide. Take alcohol as an example. 'Both react with tin oxide. Once the gas is sensed, it cannot be identified as being caused by carbon monoxide or alcohol. In addition, solid-state gas sensors are less sensitive' and are more susceptible to environmental interference (such as Humidity and temperature, etc.), and the material will have aging problems in long-term operation under high temperature environment. Infrared gas developed using infrared absorption spectroscopy technology 技术Chase measuring device can solve the difficulties encountered by the above solid-state gas sensing device. Please refer to

Page 5 490554 V. Description of the invention (2) See Figure 1 ′, which shows the characteristics of the infrared absorption spectra of different gases. From Figure 1, it can be clearly found that there is a considerable gap between the absorption wavelengths corresponding to different gases (for example, C02 is 4 · 3um, and C0 is 4 · 7um). Narrow Bandpass Filter) can satisfy quite fine spectral distinction. However, the conventional infrared gas detection device consumes large power due to the large Joule power of the conventional resistance wire infrared light source. In addition, the yield of various narrow-band pass filters made with optical coatings is low, and the wavelength drift caused by environmental effects is also a major problem. If multiple gases are to be detected at the same time, multiple sets of bandpasses must be constructed. Filters, these problems make the price f expensive and not conducive to popularization. See U.S. Patent Nos. 5,852,30 & Attachment 1), 5,468,962 (Attachment 2), 5,86 1 545 (Attachment 3). In view of this, the present invention will propose a brand-new miniature infrared gas separation device, based on silicon micro-machining (Si Micromachining) technology, f types of miniature elements (infrared light source, bandpass and spatial filter, frequency modulation f Wave device and thermal sensor) to meet the requirements of low power consumption and low cost: for the qualitative and quantitative analysis of the infrared absorption spectrum of various gases. SUMMARY OF THE INVENTION Therefore, the object of the present invention is to provide a micro-infrared gas analysis device manufactured based on silicon micromachining technology π, and to provide its design and manufacture

490554 V. Description of the invention (3) Method. According to one object of the present invention, the design of the analysis device. Including the principle of integrated radiation, it emits a wide mirror and emits the infrared emitting unit beam; an infrared beam outside the infrared band including the bandpass and spatial filter spectrum passes; an FM filter interferometer that uses the electric field to control the light to a single standby Measure the gas absorption spectrum element according to the incident narrow-band wavelength class; and a microcomputer control unit according to one of the purposes of the present invention, including: a silicon micro-machining technology to produce a black body light emission principle, radiating light to all sides; and an isothermal The temperature of a specific wavelength of light emitted by a thermal resistance infrared transmitter is reduced to a miniature infrared gas = external line emission unit, which uses the infrared spectrum of f in the thermal resistance knife; an infrared and quasi-infrared emitted infrared rays become parallel infrared rays. Contains at least one gas to be detected

The length of the sub / vibration L is the same as that of the narrow-band wavelength at the same time; and the intensity of a sensing unit is used to determine the concentration and species of the gas to be measured as the input / output interface control. About this infrared emitting unit. Including a miniature thermal resistance infrared transmitter, according to the Bafang emission, it includes various waveband (resistance) driving circuits to stabilize the miniature, which is not affected by room temperature drift and affects the sensitivity of low measurement. ^ θ

According to one object of the present invention, the present invention relates to the bandpass and spatial filter. The method includes: a silicon substrate with a crystal orientation of (100) having first and second surfaces; a band-pass optical film made on the first surface of the silicon substrate and filtering out at least one infrared spectral band except for a gas to be measured; A metal thin film with a specific geometric opening is used as a spatial filter, and is fabricated on the band-pass optical film.

Page 7 490554

Formed on the second surface of the silicon substrate, the v-groove etched through the silicon substrate so that the square bottom of the V-groove exposed the specific geometric opening of the filter between the band-pass optical film and the metal thin film. According to an object of the present invention, it relates to the FM optical filter unit. Including: a micro-frequency modulation filter manufactured by silicon micro-processing technology, the use of electric field approval to change the length of the optical resonant cavity to screen the infrared absorption wavelength of the gas to be measured; and a drive oscillation circuit, which provides a DC voltage and a small The parental voltage makes the micro-frequency wave modulator have the function of the wavelength modulator of the optical disc.

According to an object of the present invention, it relates to the sensing unit. Including: a miniature thermal detector manufactured by a stone evening micromachining technology; and a phase-locked read circuit, which detects the miniature thermal heat as an output electric alternating current signal and the modulation frequency of the driving oscillation circuit of the patent application scope item g Compare to improve the signal-to-noise ratio of the sensing signal, and to avoid noise problems caused by environmental effects (temperature changes). [Description of Examples]

Please refer to FIG. 2, which is a functional block diagram (Functionai Blocks) of the miniature infrared gas analysis device of the present invention. Including: an infrared emission unit 10, using the principle of thermal resistance wire blackbody radiation, emits a broad spectrum of external lines; an infrared collimator (1 ^ C0lima tor) 20, the external line emission unit 1〇 The divergent infrared light emitted by the beam becomes a beam of parallel infrared light; a bandpass and spatial filter (Bandpass and Spatial Pilter 〇30, screening one including at least one absorption spectrum of the gas to be measured)

490554 V. Description of the invention (5) = Outside line band, and only infrared beams with a specific geometric area are allowed =, an FM filter unit 50, the principle of which interferes with 1, the electrical% controls the length of the optical resonant cavity, only one measurement is allowed at the same time The narrow-band (NarrOw Band) wavelength of the volume absorption spectrum passes; and one get, Unit 60, determines the concentration of the gas to be measured based on the incident narrow-band wavelength intensity &

= Kind, and a microcomputer control unit 70 as an input / output interface control. X In order to clearly illustrate the physical schematic structure of the functional block diagram shown in FIG. 2, please refer to FIG. 3, which is a miniature infrared gas analysis device of the present invention. Schematic diagram of each component arrangement. The infrared emission unit includes a silicon micro-processing, thermal resistance (T herm 〇-Resistive) infrared emitter (I r Emitter) 10a and a temperature (resistance) driving circuit. The thermal resistance infrared emitter 10 a can be regarded as a point light source. According to the principle of Black-Body Radiation, it emits infrared spectrum in all directions. Through an infrared collimator 20, the collected maximum cone beam ( The pyramidal area covered by the ray 11 becomes a parallel beam 21. Suitable materials for the infrared collimator 20 are those having a good transmittance for 3 ~ 5um or 2 ~ 8um, such as Shi Xi, single crystal oxide (Sap h i r e), and fluoride town. A miniature band-pass, spatial filter, and wave filter 30 includes a band-pass optical film 3 3 ′ and a circular or square-opened metal layer 34 as a space wave filter. The main function of the band-pass optical film 33 is to filter out spectral bands other than at least one gas to be measured. The spatial filter 34 allows only part of the light beam 21 to pass through the circular or square opening of the metal layer 34, that is, the area covered by the light 12, and the purpose is to cooperate with the following micro-FM filter 50a Cavity area. 490554 V. Description of the invention (6) A miniature FM filter 50a, which uses electric field control to change the length of the Fabry-Perot resonant cavity to screen a specific narrow-band optical wavelength (to detect the infrared absorption wavelength of a gas). The driver The vibration surplus circuit 5 0 b provides a DC voltage VG and a small AC voltage Δ V si η ω t, so that the frequency-modulated wave generator 50 0 a has both a function of wavelength screening and an optical modulator (M odu 1 ator). A miniature thermal detector 60a detects the intensity of the narrow-band light wavelength screened by the FM filter 50a, and a phase-locked read circuit 60b compares the AC signal I ( ω) and the modulation frequency ω of the driving oscillation circuit 50b to improve the signal-to-noise ratio (s / N Rat io) of the sensing signal, and to avoid noise problems caused by environmental effects (temperature changes). In order to more clearly illustrate the manufacturing method of the micro-components produced by the silicon micro-processing technology shown in FIG. 3 and the advantages of the micro-components compared to the traditional components, the following will describe them in detail in several units.

Micro Thermo-Resistive IR Transmitter

Emitter), the way that the 3 I heating resistor generates infrared light is based on the black body radiant% light s early Wis Displacement Law (Wiens Displacement Law) can confirm: the maximum value of the two emission degrees (Exi tance) and the temperature τ and wavelength The relationship is described by the following formula (1) λΤ ~ 2897 · 8 (um K) rη

Page 10 490554 V. Description of the invention (7) " The wavelength of the maximum output of a normal person at 37C is 9.35um. When applied to the infrared absorption spectrum of a gas (3 ~ 5um or 2 ~ 8um), you can imagine the heat The temperature of the resistance wire must be as high as a few hundred ° C above to get enough light to radiate 'radiance'. This makes the traditional thermal resistance wire infrared emitters consume considerable power. ^ It is manufactured by humans one by one. Quality control It ’s not easy, and it is difficult to increase the difficulty of the rear section, which is why it is expensive. The use of silicon micromachining technology can solve the problem of power consumption, and solve the problem of quality control through the mass production of Shixi Semiconductor process. Please refer to Annex 4 JS Shie, Bruee CS Chou, and YM CHen, High performance Pirani Vacuum gauge, J. Vac. Sc i. Tech. A, 13 (1995) 2972-2979 ·. Please refer to FIG. 4a, which is a schematic plan view of a miniature thermal resistance infrared emitter 10a according to the present invention. Fig. 4b is a schematic cross-sectional structure view taken along line AA in Fig. 4a. Among them, a Shixi substrate 100 with a crystal orientation of (100), a suspension sheet (Membrane) 101, supported by four slender legs 102, and fixed to the edge of a V-shaped groove 106, The formation of the V-shaped groove 106 is completed by the definition of the etching window 105 and the Anisotropic Etching technology. The thin plate structure 101 and the elongated legs 102 are composed of dielectric materials 101a and 101b. The dielectric materials 1013 and 10113 are usually silicon oxide and silicon nitride or two The combination of the permutations. A thermal resistance material 103 is produced inside the thin plate structure 101, which is usually a temperature resistance coefficient (Temperature Coefficient of Resistance) thermistor material such as silicon, platinum, and the like. A blackbody material 104 is produced on the outermost surface of the suspended sheet, which is usually a very thin metal film, such as gold black

490554 V. Description of the Invention (8) (Gold-Black) and Platinum-Black (upper-injection). k) In order to increase the light radiation, the miniature thermal resistance infrared emitter shown in Figure 4 can effectively reduce the heat conduction value by the formation of a suspension structure. Its value is usually k1uW / ~ 10uW / ° c, so only a relatively small amount is needed. Joule power is enough to produce a fairly good heating effect. For example; polycrystalline silicon thermal resistance wire is 1K Ω, with a current of 1mA, it can generate lmW power. If the thermal conductivity of the miniature thermal resistance infrared transmitter is 3uW / ° C, the temperature of the suspended thin plate structure 10 will reach 30. Above 0 ° C, this good thermal efficiency cannot be reached by traditional components. At the same time, 'the elongated leg 102 is quite good in thermal insulation between the suspended sheet structure 100m and the substrate 1000, and the suspended sheet structure 1 can be regarded as an exclusive temperature area, and the substrate 100 Is at room temperature. At the same time, the area of the thin plate structure 101 is relatively small (~ mm × mm), so it can be regarded as a point light source, which can simplify the design of subsequent light paths. Furthermore, through the control of a first-temperature (resistance) driving circuit 10b, the temperature of the floating sheet structure 10m can be stabilized without being affected by room temperature drift to affect the light emission at a specific wavelength, and the measurement accuracy can be reduced. Please refer to FIG. 5a, which is a schematic plan view of another embodiment of the miniature thermal resistance infrared emitter of the present invention. Fig. 5b is a schematic cross-sectional structure view taken along line AA in Fig. 5a. The difference between the structure shown in Figs. 5a and 5b and Figs. 4a and 4b is only that the V-shaped groove 106 is formed by using anisotropic etching on the back surface, and the rest of the processes and designs are the same, and details are not described herein. '' Micro Bandpass and Spatial Filter

490554 V. Description of Invention (9)

Filter) The conventional optical band-pass filter is made on an optical substrate (such as quartz glass to make optical films, and its quality requirement is that the optical substrate and the optical plating material have good transmittance for the required optical channel ( Low absorption coefficient), especially because the thickness of the optical substrate is much larger than the optical film, so it determines the absorption of more light intensity. Therefore, the optical substrate of high quality plays an important role = 丄 At the same time, for the gas infrared absorption spectrum (3 ~ 5um or 2 ~ 8um) bandwidth, infrared optical substrate with high transmittance is scarce and expensive. A miniature band-pass filter is proposed for the invention to solve the above problem. Please refer to FIG. 6, which is A cross-sectional structural schematic diagram of the micro-bandpass and the space filter according to the present invention, wherein 31 is a silicon-based film with a crystal orientation of (100), and a band-pass optical film 33 is produced on one side. The band-pass light, 33 series Evening layer; 丨 Composed of dielectric materials. The basic composition of multilayer dielectric layers is single

Ti〇 /: f is a dielectric material with a high refractive index and a low refractive index, which is usually a number ;, 甬, ft i, and the degree t respectively satisfy ^ and Μ, where η is a refractive system ί =: silicon substrate 31 ′ Whereas, a part of the band-pass light i (Diaphragm) structure 35 is exposed, which can remove 1 ^; absorption of a specific spectrum (such as visible light, etc.).捭 Matching-The filtering of the spatial filter 34, that is, for the "infrared rays" that pass through. The production is-standard semiconductor process. 夂: The metal pattern made by the film η, the metal plating

Ti / Au or Cr / Au, Ml φτ: ^ r φ ^, middle Ti or Cr is used as an adhesion layer.

Page 13 490554 V. Description of the Invention (ίο) Micro Frequency Tuning Furnace (Micr ο Unab 1 e F i 11 er) The common frequency tuning chirp is based on the principle of Fabry-Perot interferometer (FP interferometer for short). It mainly uses two high-reflectance mirrors to tune (the traditional modulation method is modulation by piezoelectric materials) optical resonant cavity (Resonant Cavity) 'When the length of the resonant cavity meets a half-integer multiple of the specific light wavelength m / 2 (m represents the order) when the light pulse output has a very narrow FWHM Full Width of Half Maximum

Used in optical communication and various spectrum detection equipment. However, traditional processing techniques and assembly methods cannot be used to produce FP interferometers with a wide spectral range (pree spectral range, FSR) spectral characteristics. The main reason is that the resonant cavity length is too large (FSR is inversely proportional to the resonant cavity length). This problem can be solved by using a micro-frequency modulation filter manufactured by micro-processing technology. Its spectral modulation range can be as high as 2um. This result makes it equivalent to a spectrometer function such as Grating (see Appendix 5). U.S. Patent No. 5, 5, 50, 3 75), which cannot be achieved by traditional FP interferometers, is also the biggest feature of miniature FM optical filters and wave behavior. It is the most important reason why the present invention uses it for infrared spectrum detection. In addition, low power consumption and low cost of silicon semiconductor-like batch production are also a major reason.

Please refer to FIG. 7 ′, which is a cross-sectional view of a structure of a miniature FM filter 50a according to an embodiment of the present invention. Including: a silicon substrate 500, the silicon substrate 500 is a silicon wafer insulation wafer (Silicon ON Insulator, SOI), a silicon oxide insulation layer 500b in the middle of the silicon substrate 500 The silicon substrate 500 is divided into front silicon

Page 14 490554 V. Description of the invention (11) Wafer 5 0c (also known as Device Silicon wafer) and reverse silicon wafer 5 0a (also known as Handle Wafer) Guangyi suspension mechanical structure 501, an air gap of 506 from the surface of the front silicon wafer 500c. The suspension mechanical structure 501 includes a thin plate structure 502, four slender legs 504, and four support fixing areas 505. One of the known points of the slender foot 504 is connected to the thin plate 502, and the other end of the slender foot 504 is connected to the far fixed area 5 0 5 'The fixed area 5 05 is through a partition 514 ( Spacer) is connected and fixed to the surface of the front silicon wafer 500c, and the thickness of the partition block 5 1 4 is the starting height of the air gap 5 06. A first reflecting mirror 5 1 0 is made in the center of the thin plate structure 50 2; a floating electrode 50 3 is made on the thin plate structure 5 0 2, and is connected to the fixed area 5 0 5 through the elongated foot 5 0 4 to communicate with the outside. Make electrical connections. A fixed electrode 512 is formed on the surface of the front silicon wafer 500c, and its position is directly below the floating electrode 503. A plurality of V-shaped grooves 50 7, 5 0 8 are fabricated on the front surface 50 0c silicon wafer, including a resonant cavity v_-shaped groove Mg located below the 4 first reflector 51 °, and the elongated leg 504 The anti-sticking v-shaped groove 50 7 below, the square flat bottom of the resonant cavity V-shaped groove 508 exposes the silicon oxide insulating layer 500b in the middle of the silicon substrate 500; and a back surface v The —-shaped groove 509 is fabricated in the reverse Shi Xi wafer 500a, which is aligned with the first mirror 51 ^, and the back V-shaped groove 509 square flat bottom exposes the silicon substrate 500. The middle silicon oxide insulating layer 500b and a second reflecting mirror 51i are formed on the square flat bottom of the V-shaped groove 509 on the back surface. The optical resonant cavity of the FM optical filter of the present invention is

490554 V. Description of the invention (12) The first mirror 5 1 〇 on the special plate structure 5 〇 2 and the square flat bottom of the resonant cavity V-shaped groove 5 08 (connected to the v-shaped concave on the back) The second reflecting mirror 5 n) of the square flat bottom of the slot 509 is a two-plane mirror-type optical resonant cavity. ^ The length d of the optical resonant cavity of the present invention is made by combining the surface microfabrication technology (polycrystalline silicon sacrificial layer technology) and the body micromachining technology (single-crystal silicon anisotropic surname,). The thickness of the wafer 500c and the two air gaps 5 0 6 is the sum of the thicknesses, which is usually determined by the thickness of the front silicon wafer 5 0 c. This thickness can be supplied by commercial silicon insulation silicon wafers (s0). The quotient obtains different specifications (03 ~ 10011111), so it is quite flexible. Through the choice of an appropriate thickness of 500c, a wide spectrum modulation range can be obtained, and the spectral characteristics of the light resolution can be satisfied. The design and production of the floating electrode 50 3 and the fixed electrode 51 2 can be adjusted by the electric field attraction method. The length of the optical resonant cavity between the first reflection mirror 51 and the second reflection mirror 5η 'floating electrode 5 03 and the fixed electrode 5丨 2 the space between 5 6 production 疋 is defined by the production of the sacrificial layer and subsequent etching operations, so different gaps 5 0 6 can be defined according to different needs. Also, because the pitch is defined by the thickness of the sacrificial layer, which is usually <3um in thickness, the length of the optical cavity can be adjusted with a lower voltage. Anti-adhesion V-shaped groove 507 is made under the slender feet 504 to avoid mutual adhesion between the slender feet and the bottom silicon wafer 500c surface due to the surface tension caused by the etching liquid. (Sticking). In addition to the aforementioned advantages, the first mirror 5 1 0 and the second mirror 5 11 have excellent flatness. And the special microstructure design of the FM filter

Page 16 490554 V. Description of the invention (13) The plan 'makes it not limited to the effect of the substrate 500 effect. It only needs to pass the selection of the materials of the first mirror 510 and the second mirror 511, and it can be manufactured and applied. The FM filter in the gas infrared absorption spectrum band of the present invention (same design concept as the aforementioned miniature band-pass filter). Wherein, the method for manufacturing the fixed electrode 5 1 2 is impurity doping on the surface of the front silicon wafer 500 c by means of high temperature diffusion or ion implantation. The material of the spacer layer 514 is polycrystalline silicon. The mechanical structure 501 is a sandwich structure composed of three layers of materials, namely silicon-rich silicon nitride (S i 1 i con ^ i ch N 11 rl de), polycrystalline silicon, and Silicon-rich silicon nitride. Among them, silicon-rich silicon nitride has fairly good mechanical rigidity and relatively low thermal residual stress (see Annex 6: Bruce CS Chou et al., A method of fabricating low-stress dielectric thin fiim for microsensors applications, IEEE Electron Device Lettei: sl8'1 9 9 7, p.5 9 9- 6 0 1 ·), so it is most suitable as a high-quality, high-stability micromechanical structure. The polycrystalline silicon in the middle serves as a conductive material for both the mechanical structure and the floating electrode 503. The first and second reflections 1 5 11 are high reflection and low loss mirrors made of multilayer dielectric materials. The basic unit of the multilayer dielectric layer is a pair of dielectric materials with a high refractive index and a low refractive index, which is usually MgVTi02. And its thickness t 2 is equal to nt = and / 4, where n is the refractive index and the miniature thermal detector whose spectrum is modulated

490554 V. Description of the invention (14) The advantages of thermal detectors (Bolometer, Pyrometer and Thermopile) are that they have broad and flat spectral response characteristics, which are quite suitable for the spectrum. Correction, but the disadvantage is that the responsivity (V / W) of the component is poor. With the development of Shixi micro-machining technology in the 1980s, the suspended sheet structure (thin plate structure can reduce heat capacity) with a high thermal insulation effect (low thermal conductivity), so that the responsivity of thermopile components (reSp0nSiVity, V / W) And the response rate is greatly improved. As a result, the development of miniature thermal detectors has come a long way. Especially for miniature thermopile detectors, the advantages of thermopile components are that they do not consume any power, so they can avoid any voltage noise coupled from the power supply. This advantage is other bolometric infrared elements. Out of reach. Furthermore, since the current flowing through the thermopile element itself is small (or even 0), the low frequency noise (1 / f noise) of the material caused by the driving current can also be ignored. When there is no radiation incident, the thermocouple = hot contact area and cold contact area can be regarded as isothermal. Therefore, the effect of environmental temperature drift is much smaller than that of resistive infrared components. Therefore, the components are suitable for portable and room temperature operation, and do not require additional temperature control

Referring to FIG. 8a, it is a top view-structure diagram of a miniature thermopile detection crya according to an embodiment of the present invention. FIG. 8b is a schematic diagram of the structure of FIG. 8a along the line aa. The // 1 stacker element 60a includes: a crystalline orientation (100) Shi Xi, and a suspended sheet 601 formed on the substrate 600, and there are several thermocouples 603. The thermal contact zone 604 is located in the suspended sheet 601 &amp;

490554 V. Description of the invention (15) The central part, and the cold contact area 605 is the surrounding part of the suspended sheet 60. With the definition of a plurality of etching windows 60 6, a V-shaped groove 60 7 ′ of the suspended sheet 6 ^ can be etched to form the structure of the suspended sheet 601. A black body material 602 is made on the most suspended surface, which is usually a very thin gold plate film, such as Gold-Black and Platinum-Black, so as to increase the absorption of light radiation. It includes a first dielectric layer 600a, a thermoelectric layer 600b, a second thermocouple 6003b, and a third dielectric: gas; the first, second, and third dielectric layers are usually It is a combination of semiconductor manufacturing process, it and nitride, or both. 3 i i ί A ί pair of materials is composed of N-type and P-type Shi Xi conductors, or a silicon conductor and a metal conductor. Then P 汊 # 如 ί S 5 is another embodiment of the miniature thermopile debt detector of the present invention: a schematic diagram. And ′ is shown in FIG. 9 &amp; The structures shown in Figs. 9a and 9b are different from those of Figs. 8a and 8b and -i ratio phase z-plane anisotropic etching is used to form the V-shaped groove 607. The remaining processes and e are connected in white, and are not described herein. The specific application proposed in the detailed description of the embodiments: Ϊ: within the technology of 5 rounds, instead of narrowly limiting the present invention to the scope of the patent application above | implementation of various changes, which still belongs to the scope of the present invention .

Page 19 490554 V. Description of the invention (16)

ΙΙϋϋΙΙ Page 20 490554

Brief description of drawings [Explanation of drawings] Figure 1 shows the infrared absorption spectrum characteristics of different gases. Fig. 2 is a functional view of the miniature infrared gas analysis device of the present invention. Fig. 3 is a diagram showing the arrangement of each component of the miniature infrared gas analysis device of the present invention. Figure 4a is a schematic diagram of a miniature thermal resistance infrared emitter according to an embodiment of the present invention. Illustration. The structure is a schematic view of the cross-sectional structure shown in FIG. 4a along the line AA. Fig. 5a is a schematic diagram showing the structure of a miniature thermal resistance infrared transmitter according to the present invention. The top view of the power money embodiment is the cross-section shown in FIG. 5a along the line AA. FIG. 6 is a micro-bandpass and spatial filtering view of the present invention. ^ Photograph-elevation 7 is a micro-FM filter of the embodiment of the present invention. Don't think about it. , This is a miniature thermoelectric benefit of the embodiment of the present invention; The top view of the shell is shown in Fig. 8b, which is a judgment along the line AA in Fig. 8a. Fig. 9a is a schematic diagram of the micro thermopile detection of the present invention. Schematic diagram. ,, °. Top view of another embodiment FIG. 9b is a schematic view of the four-side structure shown in FIG. 9a along the AA line. [Explanation of symbols] 10 10a Infrared emitting unit Thermal resistance type infrared emitter

490554 on page 21 Simple illustration 10b ~ Isothermal drive circuit 11 ~ Infrared light 12 ~ Infrared light 100 ~ Silicon substrate m ~ Suspension sheet 102 ~ Slim legs 103 ~ Thermal resistance material 104 ~ Black body material 105 ~ Etching window 106 ~ V-groove 20 ~ Infrared collimator 21 ~ Parallel beam 30 ~ Micro bandpass and space filter 31 ~ Silicon substrate 32 ~ V-groove 33 ~ Bandpass optical film 34 ~ Metal thin film space filter 35 ~ Levitation optics Membrane area 50 ~ FM filter unit 50a ~ Miniature Fabry-Per 〇t FM filter 50b ~ Drive oscillation circuit 5 0 0 ~ Silicon insulation layer Silicon wafer 5 0 0a ～ Reverse cut wafer 5 0 0b ～ Silicon oxide insulation Floor

Page 22 490554 Brief description of the diagram 5 0 0 c ~ front silicon wafer 5 0 1 ~ suspension mechanical structure 5 0 2 ~ thin plate structure ^ 5 0 3 ~ floating electrode-5 0 4 ~ slender feet 5 0 5 ~ suspension Mechanical structure fixing area 5 0 6 ~ Air gap 5 0 7 ~ Anti-stick V-shaped groove 508 ~ Resonant cavity V-shaped groove 509 ~ Back V-shaped groove 5 1 0 ~ First reflector φ 5 1 1 ~ Second reflector 5 1 2 ~ Fixed electrode 5 1 3 ~ Insulation layer 514 ~ Polycrystalline broken material 6 0 ~ Sensing unit 6 0 a ~ Micro thermopile detector 6 0 b ~ Phase-locked read circuit 6 0 0 to broken substrate 6 0 0 a to first dielectric layer 6 0 0 b to second dielectric layer 600 c to third dielectric layer 601 to suspended sheet 6 0 2 to black body material

490554 on page 23 Simple illustration 6 0 3 ~ thermocouple 6 0 3a ~ first thermocouple conductor 6 0 3b ~ second thermocouple conductor 6 0 4 ~ hot contact area 6 0 5 ~ cold contact area 6 0 6 ~ Etched window 607 ~ V-groove

Page 24

Claims (1)

490554 6. Scope of patent application j A miniature infrared gas analysis device. Includes: • An infrared emission unit, which uses the principle of thermal resistance wire blackbody radiation, to emit a wide infrared spectrum; x an infrared collimator, which transforms the infrared rays emitted by the infrared emission unit into parallel infrared beams; a bandpass and space filter , Screening an infrared band including at least one absorption spectrum of the gas to be measured and allowing only infrared beams of a specific geometric region to pass; An FM filter unit, based on the principle of the Fabry-Perot interferometer, uses an electric field to control the length of the optical resonant cavity, and allows only a narrow frequency wavelength of a single gas absorption spectrum to pass at the same time; and a sensing unit, based on the intensity of the narrow frequency wavelength Determining the concentration and type of the gas to be measured; and a microcomputer control unit for output / input interface control. 2. The infrared emitting unit according to item 1 of the scope of patent application, further comprising: a miniature thermal resistance infrared emitter manufactured by Ishiba Micromachining Technology, which emits radiant light in various directions in all directions according to the principle of blackbody radiation; and Constant temperature (resistance) driving circuit to stabilize the temperature of the miniature thermal resistance infrared emitter 'is not affected by room temperature drift and affects specific The light emission degree of the wavelength reduces the measurement sensitivity. 3. The miniature thermal resistance infrared emitter according to item 2 of the patent application scope, comprising: a silicon substrate with a crystal orientation of (100), having first and second surfaces; Page 25 490554 VI. Scope of patent application ---- Shi Xi Anisotropy 14 _ 7-shaped groove is formed on the first or second surface of the silicon substrate; a suspended thin plate is formed on the v- On the groove; a thermal resistance material is made in the suspension sheet; and a black body material is made on the outermost surface of the suspension sheet to increase the light radiation output. 4. If the thermal resistance material in item 3 of the patent application range is silicon or platinum with high temperature coefficient. 5 · = Declares that the blackbody material in item 3 of the patent scope is gold black and platinum 6 · =! Ί f Fan, the bandpass and spatial filter around item 1, including: 2 = 向 为 (1 ( (H)) a silicon substrate having first and second surfaces; a f optical film is fabricated on the first surface of the silicon substrate, and filtered to an infrared spectrum band other than y a gas to be measured; A metal film with an opening in the shape is used as a spatial filter, and is fabricated on the band-pass optical film; and Shi Xi 1 :! 生 # The groove is formed on the second surface of the soil plate. , The V-shaped groove etched through the silicon substrate so that the square-shaped bottom of the ^ -shaped groove exposed the specific geometric opening of the band-pass optical film and the metal 7 滤波器 hollow filter. • The band-pass optical film according to item 6 of the patent is composed of a multilayer dielectric shell. The basic composition unit of the multilayer dielectric layer is a pair of dielectric materials having a low refractive index and a low refractive index. 8. If the metal thin film space filter is claimed as item 6 of the patent scope, the material 490554 6. The scope of patent application is Ti / Au or Cr / Au, where Ti or Cr is used as the adhesion layer. 9. For example, the FM filter unit of the scope of patent application, further includes: a micro FM filter manufactured 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 And a driving oscillation circuit, which provides a DC voltage and a small AC voltage, so that the miniature frequency-modulated wave modulator has the functions of wavelength screening and optical modulator. 10. Such a miniature FM filter as claimed in item 9 of the scope of patent application. Including: a silicon insulation layer Shi Xi substrate (S 0 I), a silicon oxide insulation layer cuts the silicon insulation The edge silicon substrate is divided into two front and back silicon wafers; a suspension mechanical structure including a thin plate structure and at least one elongated leg, and the first end of the at least one elongated leg is connected to the thin plate structure Connected, the second end of the at least one slender foot is connected to at least one fixed area; at least one partition block is connected to the at least one fixed area and the front silicon wafer, and an air gap is formed in the suspension mechanical structure The initial distance between the air gap and the surface of the front silicon wafer is determined by the height of the at least one partition; A first reflector is made in the center of the thin plate structure; a floating electrode is made on the thin plate structure, and the floating electrode is electrically connected to the outside through the at least one elongated leg and the at least one fixed area; Page 490 554 6. The scope of the patent application: The solid electrode is made on the front surface of the wafer, directly below the floating electrode, and the air gap is away from the floating electrode. A resonant cavity V-shaped groove is made in the front silicon wafer. Located directly below the first reflector, the square flat bottom of the cavity V-shaped groove of the resonant cavity exposes the two edge layers of the oxide stone in the middle of the silicon insulation layer silicon substrate; &lt; at least one anti-stick V-shaped cavity A groove is made in the front broken wafer, directly under the at least one elongated leg; and; a lunar groove is made in the reverse stone wafer, and is aligned with the first reflector and the back groove The flat bottom exposes the silicon oxide insulating layer located in the middle of the silicon substrate of the Shixi insulating layer; and a second reflector is formed on the flat bottom of the back groove. 11 · If the suspension mechanical structure of item No. 丨 0 of the patent application scope, the materials are in order of s 4 222, s 4 s, 2 s s, 2 s, 2 s, 2 s, 2 s, 2 s, 2 s, 2 s, 2 s, 2 s, 2 2 s structure. Xin Erming 1 2 · As for the floating electrode of the scope of application for patent, Shi Xi. , J Ma Xijing 13. 14. For example, at least one partition block of the patent application scope No. 10 spar or amorphous silicon. The material is multiple 15. For example, the first and the second reflection systems of the tenth patent application range are made of a plurality of pairs of high-refractive index / low-refractive index dielectric materials and reflectivity mirrors. The sensing unit according to item 1 of the patent application scope includes: a micro thermal detector made of silicon micro-processing technology; and Page 28 490554, Apply for patent Fanyuan Liusuo 'to compare the electric frequency of this micro-heat detector and / or the scope of the patent application, and compare the modulation frequency of the driving oscillator circuit to improve the sensing. The signal-to-noise ratio of the signal, and can eliminate noise problems caused by environmental effects (temperature changes). 1 6 · A miniature thermal detector as described in item 15 of the scope of patent application, including a broken substrate with a crystal orientation of (100) and having first and second surfaces. A groove is formed on the first or second surface of the Shi Xiji plate; a suspended thin plate is formed on the V-shaped groove; at least one thermocouple is made in the suspended thin plate, and the heat of the at least one thermocouple is The contact area is located in the center of the suspended sheet, and the cold contact area of G to = a thermocouple is located on the two exposed plates of the V-shaped groove; a black body material is made on the surface of the suspended sheet to increase light radiation Absorption. 17, Please refer to the at least one thermocouple in item 16 of the scope of interest, including type -I, or ... and the body and the second and 18. U the black body material in the scope of the patent, item 16, is gold black or White 第 29 页