JPH0418258B2 - - Google Patents

Description

[Detailed description of the invention]

[[Industrial Application Field]] The present invention relates to a gas detection element capable of detecting a special gas that spontaneously ignites at a concentration of several percent when mixed with other gases such as air, and a method for manufacturing the same. [[Prior art]] Monosilane (SiH ₄ ) and dichlorosilane (SiH ₂ As special gases such as Cl ₂ ), trichlorosilane (SiHCl ₃ ), phosphine (PH ₃ ), diborane (B ₂ H ₆ ) and arsine (AsH ₃ ) are used in large quantities, these special gases Accidents resulting in spontaneous ignition due to leakage into the air and fires are increasing. [[Problems with Prior Art]] Conventionally, to detect such gases, measuring instruments have been used that measure the presence and concentration of gases based on spectral components. However, such measuring instruments require time and effort for adjustment and measurement, and are completely unsuitable for detecting gas leaks that do not know when they will occur and must be detected early. For this reason, a gas detection element that can easily detect such a special gas is desired, but such a gas detection element is currently not available. [[Means for solving the problem]] The present inventor conducted various experiments in order to obtain a gas detection element capable of detecting special gases, and found that platinum, stannic oxide, and antimony trioxide were combined into Sb/Sn=
Mix at a composition ratio of 1 to 8 mol% and Pt/Sn = 1 to 8 mol%, sinter in an atmosphere of air or antimony oxide gas at 600 to 850°C, and further add 25 to 400 ppm.
A gas detection element is composed of a metal oxide semiconductor element in which a silane compound is dispersed and supported on the element surface by exposure to a silane-based gas atmosphere such as monosilane, and a means for heating this semiconductor element. By heating the semiconductor element to 200 to 400°C, we have discovered a gas detection element suitable for detecting special gases and a method for manufacturing the same. [[Function]] The gas detection element according to the present invention can detect special gases at low concentrations and with selectivity, and
It can also be used as an alcohol gas detection element in an environment where no special gas exists. [[Example]] Hereinafter, a gas detection element according to the present invention and a method for manufacturing the same will be explained using experimental examples. [Experimental example 1] Chloroplatinic acid ( _{H 2}
PtCl ₆ ) aqueous solution is added so that Pt/Sn=1 to 8 mol %, and dispersed well by ultrasonication. This aqueous dispersion solution is placed in a vacuum freeze dryer and rapidly frozen and dried at -40°C. Next, antimony trioxide (Sb ₂ O ₃ ) was added to this dried sample.
Add so that Sn = 1 to 8 mol%, and use a mortar to
Mix for a minute. Add isopropyl alcohol to this mixed sample to make a paste, apply it to an alumina porcelain tube with an electrode attached, and let it air dry. This dried element was exposed to the atmosphere for 700 minutes.
It is placed in a quartz tube in an air oxidation atmosphere (hereinafter referred to as air atmosphere) set at ±5°C and fired for 15 minutes. Next, a heater is inserted and attached to the alumina porcelain tube of this fired element, electricity is applied to this heater to heat the element to 300±50°C, and the element is aged in this heated state for 12 hours in air. Furthermore, the aged element is heated to 325±5℃.
The device is stabilized by heating it to 100% and exposing it to a SiH ₄ gas atmosphere with a gas concentration of 100 ppm for 10 minutes, and as a post-treatment, a silane compound from the SiH ₄ gas is dispersedly supported on the device surface. Thereafter, the element was heated to 300±50°C with a heater and aged in air for 12 hours. In this way, the composition ratios of Pt, SnO ₂ and Sb ₂ O ₃ were varied, and four gas detection elements were manufactured for each composition ratio. Then, these gas detection elements are heated by energizing the heater so that the element temperature becomes 325°C.
In clean air at 25℃ and each concentration
100ppm hydrogen ( _H2 ), carbon monoxide (CO), ammonia ( _NH3 ), methane ( _CH4 ), ethylene ( _C2
H ₄ ), ethane (C ₂ H ₆ ), isobutane (iC ₄ H ₁₀ ),
The resistance value was measured by exposing it to isopropyl alcohol (iC ₃ H ₇ OH) and monosilane (SiH ₄ ) gases, and from the measurement results, the resistance value in air (R ₀ ) and the resistance value in each gas (Rg ) was _calculated , and the average values of the four elements at each composition ratio were as shown in Table 1.・And from this measurement result, for SiH ₄ gas
When we calculated the ratio of R ₀ /Rg to the maximum R ₀ /Rg for other gases, that is, the SN ratio, we obtained the results shown in the SN ratio column of Table 1.
When we calculated the SN ratio between R ₀ /Rg for iC ₃ H ₇ OH gas and the maximum R ₀ /Rg for other gases except SiH ₄ gas, we found the following in the SN ratio column of Table 1. The results are shown below. Furthermore, among the gas detection elements shown in Table 1, the resistance change characteristics for various gases of elements with composition ratios of Pt/Sn = 2 mol% and Sb/Sn = 4 mol% are as shown in Figure 1. The minimum of R ₀ is Pt/Sn = 2 mol%,
The maximum of 15KΩ and R ₀ of the element with Sb/Sn = 4 mol% is
For elements with Pt/Sn=5 mol% and Sb/Sn=2 mol%
The resistance was 373KΩ, and the former element had the maximum SN ratio, and the latter element had the minimum SN ratio. In addition, the composition ratio of Pt/Sn is 0.5 mol% and 10
mol% or more, and Sb/Sn=0.5 mol% and 10
When we fabricated devices with a mol% or more of SiH4 gas using the above manufacturing method and measured their characteristics with respect to various gases, we found that most of these devices had a SN ratio of SiH ₄ gas relative to other gases.
It showed 1.5 or less. In addition, in the above manufacturing method, the firing temperature is 500~
When I tried changing it in the range of 1000℃, it was 600 to 850
In the device fired in the temperature range of °C, the SN ratio of SiH ₄ gas to other gases was 1.5 or more, but at other temperatures the SN ratio decreased to 1.5 or less. Furthermore, by varying the heating temperature of the element, the S/N ratio of SiH ₄ gas relative to other gases was 200~
At 400°C, most of them showed a value of 1.5 or higher, but outside this temperature range, many of the elements showed a tendency for the S/N ratio to drop significantly. Furthermore, when the SiH ₄ gas concentration in the post-treatment step was varied, the responsiveness to SiH ₄ gas was reduced in the elements that were subjected to post-treatment, that is, surface treatment, at 400 ppm or more. This is thought to be because the amount of the silane compound intended for dispersion and support is excessive, resulting in a layered structure.
In addition, elements post-treated at 25 ppm or less have a change ratio (time-dependent characteristics) when repeatedly exposed to SiH ₄ gas.
showed a tendency to worsen. Note that, in addition to SiH ₄ gas, a silane-based gas such as SiH ₂ Cl ₂ gas may be used as the gas for the post-treatment process. For example, elements post-treated with SiH ₂ Cl ₂ gas,
Although it differs depending on the composition ratio, there is a tendency for the selectivity to SiH ₄ gas to be somewhat improved compared to those post-treated with SiH ₄ gas. As a result of this experiment, Pt, SnO ₂ and Sb ₂ O ₃ were
Elements mixed with a composition ratio of Sn = 1 to 8 mol% and Sb/Sn = 1 to 8 mol%, fired in an air atmosphere at 600 to 850°C, and further post-treated in a 25 to 400 ppm silane gas. By heating to 200 to 400°C, a gas detection element can be obtained that is selective to special gases such as SiH ₄ and selective to alcohol gas in gases that do not contain special gases. It has been found.

[Experiment example 2]

An aqueous H ₂ PtCl ₆ solution is added to SnO ₂ so that Pt/Sn=1 to 8 mol %, and the mixture is well dispersed by ultrasonication. This aqueous dispersion solution is placed in a vacuum freeze dryer and rapidly frozen and dried at -40°C. next,
Sb ₂ O ₃ was added to this dried sample as Sb/Sn=1 to 8.
Add to the desired mol% and mix in a mortar for 30 minutes. Add isopropyl alcohol to this mixed sample to make a paste, apply it to an alumina porcelain tube with an electrode attached, and let it air dry. On the other hand, an alumina boat containing 2.5 mg of antimony oxychloride (SbOCl) was sealed in a quartz tube with an inner diameter of 40 mm and an electric furnace insertion portion of 50 cm set at 700±5°C for 30 minutes, creating an antimony oxidation gas atmosphere inside the quartz tube. do. Then, the air-dried element was sealed in a quartz tube in an antimony oxidation gas atmosphere set at 700±5°C, and fired for 15 minutes. Next, a heater is inserted and attached into the alumina porcelain tube of this fired element, electricity is applied to this heater to heat the element to 300±50°C, and the element is aged in the air for 12 hours in the heated state. Further, the aged device is heated to 325±5° C. with a heater and exposed for 10 minutes in an SiH ₄ gas atmosphere with a concentration of 100 ppm to disperse and support the silane compound on the device surface, thereby stabilizing the device. After that, the element is heated to 300℃ with a heater.
Heat to ±50°C and age in air for 12 hours. In this way, the composition ratios of Pt, SnO ₂ and Sb ₂ O ₃ were varied, and four gas detection elements were manufactured for each composition ratio. Then, these gas detection elements are heated by energizing the heater so that the element temperature becomes 325°C.
In clean air at 25℃ and each concentration
100ppm _H2 , CO _{, NH3} , _CH4 , _C2H4 , _{C2H6 ,}
The resistance was measured by exposing it to iC ₄ H ₁₀ , iC ₃ H ₇ OH, and SiH ₄ gases. From this measurement result, in the air
When the ratio R ₀ /Rg between R ₀ and Rg in each gas was determined, the average values of the four elements at each composition ratio were as shown in Table 2. From these measurement results, for SiH ₄ gas
When we calculated the SN ratio between R ₀ /Rg and the maximum value of R ₀ /Rg for other gases, we obtained the results shown in Table 2.
The results are shown in the SN ratio column, and the SN ratio between R ₀ /Rg for iC ₃ H ₇ OH gas and R ₀ /Rg for other gases except SiH ₄ gas is the highest.
When the ratio was determined, the results were shown in the SN ratio column of Table 2. In addition, among the gas detection elements in Table 2, the composition ratio is
The resistance change characteristics of the element with Pt/Sn = 2 mol% and Sb/Sn = 4 mol% against various gases are shown in Figure 2, and the minimum R ₀ is Pt/Sn = 2 mol%, Sb/
The maximum of 50KΩ and R ₀ of the element with Sn = 4 mol% is Pt/
For an element with Sn=8 mol% and Sb/Sn=8 mol%
1.3MΩ, minimum S/N ratio Pt/Sn=4 mol%, Sb/
The R ₀ of the element with Sn = 4 mol % was 374 KΩ, and the R ₀ of the element with Pt/Sn = 8 mol % and Sb/Sn = 4 mol %, which had the maximum S/N ratio, was 645 K Ω. In addition, the composition ratio of Pt/Sn is 0.5 mol% and 10
mol% or more, and Sb/Sn is 0.5 mol% and 10
When devices containing more than mol% of SiH 4 gas were manufactured using the above manufacturing method, the S/N ratio of SiH ₄ gas to other gases decreased to around 1.5 or lower in many of these devices. In addition, when the firing temperature was varied in the above manufacturing method, the elements fired in the range of 600 to 850℃ were
Although the S/N ratio of SiH ₄ gas relative to other gases is 1.5 or more, the S/N ratio of devices fired at temperatures below 550°C or above 900°C decreased to below 1.5 in most cases. Next, we fabricated devices by varying the amount of SbOCl to create an antimony oxide gas atmosphere inside the quartz tube.
The S/N ratio of SiH ₄ gas to other gases was greater than 1.5. Furthermore, when an antimony oxidation gas atmosphere was created using Sb ₂ O ₃ instead of SbOCl, Sb ₂ O ₃ was reduced to 0.25
Devices fabricated in an atmosphere created by firing ~7.5mg showed similar results as above. As a result, the antimony oxidation gas atmosphere becomes Sb ₂
Converted to the number of moles of O ₃ 2×10 ^-9 to 3×10 ^-8 mol/
It was found that the antimony compound can be created by firing an amount of antimony compound in an amount of ^cm3 . Furthermore, when we varied the SiH ₄ gas concentration in the post-treatment process, we found that the elements surface-treated with 400 ppm or more
The responsiveness to SiH ₄ gas decreased, and the elements surface-treated with 25 ppm showed a tendency for the aging characteristics to deteriorate. Further, the post-treatment time varies depending on the gas concentration, but a range of about 1 to 30 minutes is appropriate. In addition, when the heating temperature of the element was changed,
The S/N ratio for SiH ₄ gas was mostly 1.5 or higher between 200 and 400°C, but outside this temperature range, most of the devices showed a tendency to drop significantly. Note that, as in Experimental Example 1, a silane-based gas such as SiH ₂ Cl ₂ may be used as the gas for the post-treatment process. As a result of this experiment, Pt, SnO ₂ and Sb ₂ O ₃ were
Mixed with a composition ratio of Sn = 1 to 8 mol% and Sb/Sn = 1 to 8 mol%, fired in an antimony oxidation gas atmosphere at 600 to 850°C, and further post-treated in 25 to 400 ppm silane gas. By heating the element to 200 to 400℃ and using it, a gas detection element can be obtained that has selectivity for special gases such as _SiH4 , and also has selectivity for alcohol gas in gases that do not contain special gases. It turned out that it was possible.

[Table] [[Effects]] According to the present invention, there is provided a gas detection element that has selectivity for special gases and can be used to detect low concentration special gases against dangers such as leakage, and its manufacture. Furthermore, in an environment where special gases cannot exist, it is possible to create a gas detection element that is selective to alcohol gas.

[Brief explanation of drawings]

FIG. 1 is a diagram showing resistance change characteristics for various gases of an example of a gas detection element manufactured according to Experimental Example 1 and FIG. 2 according to Experimental Example 2 of the present invention.

Claims (1)

[Scope of Claims] 1. Using stannic oxide as a main material, platinum as a catalyst, and antimony trioxide as a stabilizer, the composition ratio is Pt/Sn = 1 to 8 mol% and Sb/Sn = 1 to 8 mol%. 1. A gas detection element comprising: an element having a silane compound from a silane-based gas dispersedly supported on the element surface; and means for heating the element to 200 to 400°C. 2 Add stannic oxide to Pt/Sn chloroplatinic acid aqueous solution
The first step is to add Sb/Sn so that it is 1 to 8 mol% and to disperse it well, and the second step is to mix antimony trioxide to the sample produced in the first step so that Sb/Sn is 1 to 8 mol%. A third step is to add an organic solvent to the sample produced in the second step, make it into a paste, apply it to an insulator with electrodes, and dry it. A method for producing a gas detection element, comprising a fourth step of firing the element in a silane gas atmosphere, and a fifth step of exposing the element fired in the fourth step to a silane-based gas atmosphere of 25 to 400 ppm. 3 Adding stannic oxide to Pt/Sn chloroplatinic acid aqueous solution
The first step is to add Sb/Sn so that it is 1 to 8 mol% and to disperse it well, and the second step is to mix antimony trioxide to the sample produced in the first step so that Sb/Sn is 1 to 8 mol%. A third step involves adding an organic solvent to the sample produced in the second step, making it into a paste, applying it to an insulator with electrodes, and drying it.The device produced in the third step is exposed to antimony oxide gas at 600 to 850°C. A method for manufacturing a gas detection element, comprising a fourth step of firing in an atmosphere, and a fifth step of exposing the element fired in the fourth step to a silane-based gas atmosphere of 25 to 400 ppm. 4. The antimony oxidation gas atmosphere is created by firing an antimony compound in an amount of 2×10 ^-9 to 3×10 ^-8 mol/cm ³ in terms of the number of moles of antimony trioxide. A method for manufacturing a gas detection element according to scope 3. 5. The method for manufacturing a gas detection element according to claim 4, wherein the antimony compound is antimony oxychloride. 6. The method for manufacturing a gas detection element according to claim 4, wherein the antimony compound is antimony trioxide.