WO2002088699A1 - Procede de fabrication d'un filtre de diffusion de gaz faisant intervenir un capteur de gaz photoacoustique - Google Patents

Procede de fabrication d'un filtre de diffusion de gaz faisant intervenir un capteur de gaz photoacoustique Download PDF

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Publication number
WO2002088699A1
WO2002088699A1 PCT/JP2002/004286 JP0204286W WO02088699A1 WO 2002088699 A1 WO2002088699 A1 WO 2002088699A1 JP 0204286 W JP0204286 W JP 0204286W WO 02088699 A1 WO02088699 A1 WO 02088699A1
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WO
WIPO (PCT)
Prior art keywords
gas diffusion
silicon layer
diffusion filter
gas
porous silicon
Prior art date
Application number
PCT/JP2002/004286
Other languages
English (en)
Japanese (ja)
Inventor
Hisatoshi Fujiwara
Nobuaki Honda
Takashi Kihara
Original Assignee
Yamatake Corporation
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Yamatake Corporation filed Critical Yamatake Corporation
Publication of WO2002088699A1 publication Critical patent/WO2002088699A1/fr

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
    • G01N29/22—Details, e.g. general constructional or apparatus details
    • G01N29/24—Probes
    • G01N29/2418—Probes using optoacoustic interaction with the material, e.g. laser radiation, photoacoustics
    • G01N29/2425—Probes using optoacoustic interaction with the material, e.g. laser radiation, photoacoustics optoacoustic fluid cells therefor
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
    • G01N21/1702—Systems in which incident light is modified in accordance with the properties of the material investigated with opto-acoustic detection, e.g. for gases or analysing solids
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
    • G01N21/1702—Systems in which incident light is modified in accordance with the properties of the material investigated with opto-acoustic detection, e.g. for gases or analysing solids
    • G01N2021/1704—Systems in which incident light is modified in accordance with the properties of the material investigated with opto-acoustic detection, e.g. for gases or analysing solids in gases

Definitions

  • the present invention relates to a method for manufacturing a gas diffusion filter for a photoacoustic gas sensor, wherein the gas diffusion filter incorporated in the photoacoustic gas sensor can be easily and integrally provided on the Si substrate forming the cavity of the photoacoustic gas sensor.
  • Those photoacoustic gas sensor utilizes the phenomenon called the particular type of gas to thermal expansion by absorbing infrared of a specific wavelength, which detects a specific kind of gas, for example, C 0 2 concentration in the mixed gas such as air It is.
  • a specific kind of gas for example, C 0 2 concentration in the mixed gas such as air It is.
  • this type of photoacoustic gas sensor basically has a cavity 1 into which gas is introduced as shown in FIG. 3, a light source 2 for intermittently irradiating infrared rays into the cavity 1, and a cavity 1 as described above.
  • a microphone 3 that forms part of the wall surface (ceiling surface) and responds to the sound pressure in the cavity 1.
  • the cavity 1 is formed by etching a Si substrate transparent to infrared light to form a predetermined space, and further provided with a gas passage 4 for introducing gas into the cavity 1.
  • the gas passage 4 is usually provided with a gas diffusion filter 5.
  • the gas diffusion filter 5 has a large number of fine ventilation holes, and restricts the flow of gas so that the flow of gas (air) between the inside of the cavity 1 and the outside thereof is prevented. While maintaining the above, it plays a role of changing the sound pressure in the cavity 1 according to the thermal expansion of the gas due to the absorption of the infrared light described above.
  • the gas diffusion filter 5 plays the following two roles. One of them is to act as a large airflow resistor against a sudden pressure change (sound pressure) generated in the cavity 1 due to infrared pulse irradiation, and to keep the inside of the cavity 1 substantially closed to produce sound. This function prevents pressure from being transmitted to the outside of cavity 1. The other is that it does not act as an airflow resistor against slow pressure changes (sound pressure) in the cavity 1 caused by changes in the external environment such as temperature and atmospheric pressure. This function keeps the air open.
  • a porous sintered body (ceramic), a stainless steel frit, or the like is mainly used as the gas diffusion filter 5 of this type.
  • the gas diffusion filter 5 is incorporated as a spacer or the like in the cavity 1.
  • a porous sintered body in the case of a porous sintered body, its porosity greatly depends on the sintering conditions and the like, and it cannot be denied that the dispersion of the filter characteristics is large.
  • a porous sintered body is used as the gas diffusion filter 5
  • a similar problem occurs when stainless steel frit is used, and the controllability and reproducibility of its porosity are very poor. For this reason, in mass-producing high-quality photoacoustic gas sensors with stable sensor characteristics, a major problem remains in how to realize a gas diffusion filter with stable filter characteristics. Disclosure of the invention
  • An object of the present invention is to solve the above-mentioned problems, and an object of the present invention is to provide a method of manufacturing a gas diffusion filter for a photoacoustic gas sensor, which can easily mass-produce a gas diffusion filter having stable filter characteristics and good controllability.
  • a gas diffusion filter for a photoacoustic gas sensor according to the present invention.
  • Luyu's manufacturing method focuses on porous silicon, which has excellent controllability of porosity, and anodizes the gas flow channel formation site on the Si substrate that forms the cavity of the photoacoustic gas sensor. It is characterized in that a porous silicon layer is formed, and the porous silicon layer is used as a gas diffusion filter.
  • the porous silicon layer is selectively removed by etching, and the remaining polysilicon is selectively removed. It is characterized in that the glass layer is used as a gas diffusion filter. In other words, the thickness (filter length) of the gas diffusion filter is adjusted by selective etching and removal of the porous silicon layer.
  • the formation of the porous silicon layer by anodic oxidation of the Si substrate is carried out, for example, by masking the periphery of the gas flow passage formation site in the Si substrate with a photosensitive polyimide or the like, and forming the back side of the Si substrate.
  • the Si substrate is used as an anode
  • a cathode is immersed in hydrofluoric acid together with the Si substrate, and a current of a predetermined density is applied between the anode (Si substrate) and the cathode, whereby the S This is performed by anodizing the gas flow channel formation portion of the i-substrate over a predetermined depth.
  • the selective etching of the porous silicon layer can be performed by, for example, masking a portion of the porous silicon layer where a gas diffusion filter is formed with a metal film or the like, using a weakly alkaline etching solution such as a 1% aqueous solution of NaOH, or drying. : More done.
  • FIGS. 1A to 1C are exploded views showing a method for manufacturing a gas diffusion filter for a photoacoustic gas sensor according to an embodiment of the present invention.
  • FIG. 2 is a diagram showing a relationship between specifications required for a gas diffusion filter and a porous silicon layer formed by anodizing Si.
  • FIG. 3 is a diagram showing a schematic configuration of a photoacoustic gas sensor. BEST MODE FOR CARRYING OUT THE INVENTION
  • FIG. 1A to 1C show a method of manufacturing a gas diffusion filter according to this embodiment in a stepwise manner.
  • the gas diffusion filter is interposed between, for example, a pair of upper and lower cell members (not shown) each having a concave space, and airtightly connects the pair of cell members to each other to provide the cavity (sample chamber) of the photoacoustic gas sensor.
  • the pair of cell members and the spacer 11 are formed, for example, by etching an Si substrate into a predetermined shape.
  • the spacer 11 has a square shape with a side of 4 mm, for example, as shown in FIG. 1A, and a square penetration with a side of 2 mm at the center of a Si chip having a thickness of 300 m. It is composed of holes 12 formed.
  • a 1 is vapor-deposited to a thickness of 0.3 m, or A 1 Is heat-treated at about 500 ° C. in a vacuum. This AI film is used as an electrode contact at the time of anodic oxidation described later.
  • the photosensitive polyimide When the photosensitive polyimide is formed as a 25-passage, the photosensitive polyimide is removed over a width of 500 xm. After that, use the photosensitive polyimide as a mask to design the Si chip. As shown in FIG. 1B, the porous silicon layer 13 is formed by anodic oxidation.
  • the anodic oxidation of the Si chip is performed by mechanically covering the back side of the Si chip on which the A1 film is formed as described above, or by covering the Si chip with a tape or the like and protecting the Si chip by a cathode.
  • the electrode is immersed in hydrofluoric acid together with an electrode (not shown) used as an electrode, and a current of a predetermined density is applied between these electrodes using the Si chip as an anode.
  • the anodic oxidation of the Si chip is performed at a current density of, for example, 100 mA / cm 2 for about 30 minutes, whereby the porous silicon layer 13 having a depth of about 100 / m is formed.
  • photosensitive polyimide is used as the mask of the Si chip, but it goes without saying that a noble metal or other polymer material may be used.
  • the porous silicon layer 13 By forming the porous silicon layer 13 by anodic oxidation of the Si chip (spacer 11), the porous silicon layer 13 is embedded in the upper surface of the Si chip, for example, 500 A gas passage 14 having a depth of approximately 100 m is formed in a groove over a width of m. Then, the porous silicon layer 13 functions as a gas diffusion filter for the gas flowing through the gas passage 14.
  • the porous silicon layer 13 may be used as it is as a gas diffusion filter, but it is generally desirable to adjust the path length (the thickness of the filter) to have desired filter characteristics.
  • a resist is applied on the metal film.
  • the resist film is patterned by photolithography to leave a resist film only in a region of the porous silicon layer 13 which is to be left as a gas diffusion filter.
  • the metal film is etched with nitric acid to form a mask.
  • the porous silicon layer 1 is etched using a weak alkaline etching solution composed of, for example, a 1% aqueous solution of NaH. 3 is selectively etched.
  • a weak alkaline etching solution composed of, for example, a 1% aqueous solution of NaH. 3 is selectively etched.
  • FIG. 1C only the mask portion of the porous silicon layer 13 is left over a predetermined length, for example, a length of 0.1 mm.
  • a gas diffusion filter whose thickness is adjusted is realized.
  • the Si chip (spacer 11) is handled alone, and the Si chip is anodized and a gas diffusion filter composed of a porous silicon layer 13 is attached to the Si chip (spacer 11). It was described as being formed integrally with 1). However, actually, at the stage of the Si wafer in which a plurality of Si chips are collectively formed, the porous silicon layer 13 is formed following the formation of the through-holes 12 described above, and if necessary, the porous silicon layer 13 is formed. After selectively etching the glass silicon layer 13 and adjusting its path length (filter thickness), it is desirable to cut out individual Si chips (spacers 11) from the above Si wafer .
  • the porous silicon layer 13 was selectively etched using a weak etching solution consisting of a 1% aqueous solution of NaOH, but the bolus silicon layer 13 was dry-etched. It is of course possible to adjust the path length (the thickness of the filter).
  • the method for manufacturing a gas diffusion filter in which a gas diffusion filter composed of the porous silicon layer 13 is integrally formed on one surface of the spacer 11 composed of the Si chip Since only the porous silicon layer 13 is formed by anodic oxidation of the Si chip, its manufacture is very easy. Moreover, the porosity of the porous silicon layer 13 accompanying the anodic oxidation of Si can be controlled by controlling the current density under the known resistance (specific resistance) of the Si substrate (Si chip). It can be easily adjusted. Further, by controlling the time of the anodic oxidation, the formation depth of the porous silicon layer 13 can be easily and accurately adjusted. Further, the thickness (filter length) of the porous silicon layer 13 by etching is very easy to adjust, and dimensional control can be performed with high precision.
  • a gas stripping filter having desired filter characteristics can be simplified and refined. It can be manufactured well.
  • a gas diffusion filter can be formed for a plurality of sensors 11 (Si chips) at once as an Si wafer, stable quality with uniform filter characteristics can be achieved. There is an advantage that the gas diffusion filter can be manufactured with good mass productivity.
  • the filter characteristics required for the gas diffusion filter are determined according to the specifications of the cavity in the photoacoustic gas sensor, specifically, the gas diffusion coefficient and the pressure loss coefficient of the capital as shown in FIG.
  • the porosity (porosity) of the porous silicon layer 13 forming the gas diffusion filter is closely related to the gas diffusion coefficient and the pressure loss coefficient. Therefore, the above-described anodic oxidation conditions may be adjusted in accordance with these specifications to form the porous silicon layer 13 having a desired porosity.
  • the gas diffusion coefficient greatly depends on the filter length of the gas diffusion filter. Therefore, the length of the porous silicon layer 13 whose porosity has been adjusted (controlled) as described above may be adjusted by etching, thereby producing a gas diffusion filter having desired filter characteristics.
  • a spacer 11 is interposed between a pair of upper and lower cell members each provided with a concave space, and airtightly connects the pair of cell members to form a cavity (sample chamber) of the photoacoustic gas sensor. It was described that a gas diffusion filter was formed at the beginning. However, when a cavity is formed by directly joining the pair of cell members without using a spacer, a gas diffusion filter may be formed on the joint surface of the cell members. The formation width and depth of the glass layer 13 may be determined according to the specifications required for the gas diffusion filter. In short, the present invention may be variously modified without departing from the gist thereof. Can be implemented. Industrial applicability
  • the Si substrate forming the cavity of the photoacoustic gas sensor The porous silicon layer is formed by anodic oxidation of the portion where the gas flow channel is formed, and this porous silicon layer is used as a gas diffusion filter, or the porous silicon layer is selectively removed by etching. Since the layer is used as a gas diffusion filter, a gas diffusion filter for a photoacoustic gas sensor can be easily manufactured with good mass productivity, and its characteristics can be manufactured with high quality, which has a great practical advantage.

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  • Physics & Mathematics (AREA)
  • Biochemistry (AREA)
  • General Physics & Mathematics (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Chemical & Material Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Pathology (AREA)
  • General Health & Medical Sciences (AREA)
  • Health & Medical Sciences (AREA)
  • Immunology (AREA)
  • Optics & Photonics (AREA)
  • Investigating Or Analysing Materials By Optical Means (AREA)
  • Investigating Or Analyzing Materials By The Use Of Ultrasonic Waves (AREA)
  • Sampling And Sample Adjustment (AREA)
  • Optical Measuring Cells (AREA)

Abstract

L'invention concerne un procédé destiné à la fabrication en masse simple et aisément contrôlable d'un filtre de diffusion de gaz présentant des caractéristiques de filtre stabilisées. Ledit procédé consiste à anodiser les parties d'un passage de flux de gaz (14) destinées à recevoir des cavités d'un capteur de gaz photoacoustique dans une puce Si (11), de manière à former des couches de silicium poreuses (13) servant de filtre de diffusion de gaz formé d'un bloc à l'intérieur du passage de flux de gaz. Ledit procédé consiste par ailleurs à retirer sélectivement ladite couche de silicium poreuse par gravure de manière à utiliser la partie restante de la couche de silicium poreuse en tant que filtre de diffusion de gaz.
PCT/JP2002/004286 2001-04-27 2002-04-26 Procede de fabrication d'un filtre de diffusion de gaz faisant intervenir un capteur de gaz photoacoustique WO2002088699A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP2001-132484 2001-04-27
JP2001132484A JP2002328118A (ja) 2001-04-27 2001-04-27 光音響ガスセンサ用ガス拡散フィルタの製造方法

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WO2002088699A1 true WO2002088699A1 (fr) 2002-11-07

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP5546111B2 (ja) * 2007-06-29 2014-07-09 キヤノン株式会社 超音波探触子、該超音波探触子を備えた検査装置
FI20125665L (fi) * 2012-06-15 2013-12-16 Vaisala Oyj Anturi ja menetelmä ankariin olosuhteisiin tarkoitetun anturin yhteydessä

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH06194343A (ja) * 1992-09-30 1994-07-15 Gec Marconi Ltd ガス分析装置
JPH09127066A (ja) * 1995-09-04 1997-05-16 Cerberus Ag 光音響ガスセンサおよびその使用方法
WO1999000659A1 (fr) * 1997-06-30 1999-01-07 Honeywell Inc. Detecteur de gaz opto-thermique micro-usine

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH06194343A (ja) * 1992-09-30 1994-07-15 Gec Marconi Ltd ガス分析装置
JPH09127066A (ja) * 1995-09-04 1997-05-16 Cerberus Ag 光音響ガスセンサおよびその使用方法
WO1999000659A1 (fr) * 1997-06-30 1999-01-07 Honeywell Inc. Detecteur de gaz opto-thermique micro-usine

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
TAKASHI KIHARA ET AL.: "Hikari onkyoshiki CO2 sensor no micromachining gijutsu ni yoru kogataka no kensho", SAVEMATION REVIEW, vol. 19, no. 2, 1 August 2001 (2001-08-01), pages 30 - 34, XP002954465 *

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