JPH061251B2 - Silane gas detection element - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas detecting element for selectively detecting a special gas that spontaneously ignites at a concentration of several% when contact-mixed with another gas such as air.

[0002]

2. Description of the Related Art Monosilane (SiH ₄ ), dichlorosilane (SiH ₄ ) which spontaneously ignites and burns at a concentration of several% when contacted or mixed with other gases such as air in semiconductor factories, chemical factories and laboratories. ₂ Cl ₂ ), trichlorosilane (SiHCl ₃ ), phosphine (PH ₃ ), diborane (B ₂ H ₆ ), arsine (AsH ₃ ), etc. are used in large quantities, and these special gases are being used. Accidents that spontaneously ignite and become a fire by leaking into the air are increasing. Therefore, a gas detecting element capable of detecting such a special gas at a low concentration is desired, but such a gas detecting element is not found at present.

In view of these points, the present inventor has conducted various experiments to obtain a gas detection element capable of detecting a special gas such as a silane-based gas. As a result of this experiment, when the gas detecting element based on the invention of Japanese Patent Application No. 57-226510 previously applied was provided with a heating means such as a heater and the gas detecting element was heated by this heating means, it was higher than the silane-based gas. It has been found that a gas detection element having selectivity can be obtained. In other words, stannous oxide (SnO ₂ ) and chloroplatinic acid (H
₂ PtCl ₆ ) and antimony oxychloride (SbOCl) as P
A mixture of t / Sn = 4 mol% and Sb / Sn = 6 mol% was applied on an alumina porcelain tube provided with a pair of electrodes, and the air atmosphere was set at 700 ± 5 ° C. Also, a device was manufactured by firing for 15 minutes in a quartz tube in an antimony oxidizing gas atmosphere obtained by firing 4.0 mg of SbOCl, and a heater as a heating means was inserted into the alumina porcelain tube of this device. Then, the heater is energized to heat the gas detection element to 260 ° C., and the concentration of carbon monoxide (CO), methane (CH ₄ ), ethylene (C ₂ H ₄ ), ethane in clean air at 25 ° C. and 100 ppm, respectively. (C ₂ H ₆ ),
Measure the resistance value (Ro) in air and the resistance value (Rg) in each gas by exposing it to each gas of hydrogen (H ₂ ), ammonia (NH ₃ ), ethyl alcohol (EtOH) and monosilane (SiH ₄ ). Then, Ro / Rg, that is, the SN ratio was determined. An example of these results is shown in Table 1. A gas detection element (element A) having an initial resistance value Ro of 135 KΩ was fired in an air atmosphere, and an initial resistance value Ro was fired in an antimony oxidizing gas atmosphere.
Table 1 shows the gas detection element (element B) having a value of 74 KΩ.

[0004]

[Table 1]

Incidentally, the resistance value of these gas detecting elements in the clean air after being exposed to SiH ₄ gas is 28 K for the element A.
Ω Further, the element B dropped to 16.5 KΩ. Further, when these gas detection elements were exposed to the above gases to examine the characteristics of Ro / Rg, the second Ro / Rg was S in element A.
36 for iH ₄ gas, 5.8 for EtOH gas, and 1.1-3.6 for other gases.
Then, 33 for SiH ₄ gas and 6.3 for EtOH gas.
And 1.1 to 3.8 for the other gases, respectively. In addition, after the third time, the resistance values in both the element A and the element B in the clean air show a slight increase or decrease and hardly change, and Ro / Rg for SiH ₄ gas is 27 to 1
No. 8 and Ro / Rg for other gases showed a tendency similar to or lower than the above. Further, the element was manufactured by changing the composition ratio of the element and the firing temperature, and an experiment was conducted by changing the element temperature. The Ro / Rg for SiH ₄ gas was 110 to 300 for the first time and 30 to 5 for the second time.
From the 0th and 3rd times onward, 16 to 35 were shown, and Ro / Rg for other gases was 1/4 to 1/6 or less of SiH ₄ gas.

From the above experiment, stannic oxide, antimony oxychloride and platinum were added to Sb / Sn = 2 to 8 mol%, Pt
/ Sn = 2 to 10 mol% and mixed at a composition ratio of 600 to 85
If a heating means is provided to the element fired in an air atmosphere at 0 ° C. or in an antimony oxidizing gas atmosphere, and the element is heated to 200 to 400 ° C. by the heating means and used, the silane-based gas can be detected with high selectivity. It has been found that a gas detection element basically having is obtained. Further, it was found that this gas detection element had a large change with time in Ro / Rg, that is, the SN ratio with respect to the silane-based gas. On the other hand, the gas detection element after being exposed to the silane-based gas once It was found that although the resistance value itself of No. 1 decreased, the change with time of the S / N ratio decreased and it tended to be stable. The present inventor, based on the points found from the above experimental results, further conducted an experiment to obtain a gas detection element with little change over time. As a result, stannic oxide, antimony oxychloride and platinum were mixed with Sb / Sn = 2. ˜8 mol%, Pt / Sn = 2 to 10 mol%, and mixed and burned in an air atmosphere at 600 to 850 ° C. or in an antimony oxidizing gas atmosphere.
Furthermore, by exposing to a silane-based gas atmosphere to disperse and support silane from the silane compound on the device surface, and then performing heat aging at 200 to 400 ° C. in air,
A gas detection element was obtained in which silicon oxide was discontinuously supported on the element surface, had a high selectivity for silane-based gas, and had a good SN ratio change over time.

The present invention will be further described below with reference to examples.

EXAMPLES Example 1 SnO ₂ was treated with an aqueous solution of chloroplatinic acid (H ₂ PtCl ₆ ) to obtain Pt / Sn =
Add 4 mol% and disperse well by ultrasonic wave. This dispersion aqueous solution is rapidly frozen at -40 ° C, then set in a vacuum freeze dryer and dried. Next, SbOC1 is added to the dried sample so that Sb / Sn = 4 mol%, and mixed in a mortar for 30 minutes. Isopropyl alcohol is added to this mixed sample to form a paste, which is applied to an alumina porcelain tube to which an electrode is attached and naturally dried. The dried element is put in a quartz tube in an air atmosphere set at 700 ° C. ± 5 ° C. and baked for 30 minutes. Next, a heater was inserted into the alumina porcelain tube of this fired element and attached, and the heater was energized to remove the element
Heat to 0 ° C ± 50 ° C, and in this heated state, in air 1
Aging for 2 hours. Next, the element which has been aged is heated to 325 ° C. ± 5 ° C. by a heater, and a silane gas having a monosilane (SiH ₄ ) gas concentration of 100 ppm is adsorbed on the surface to dispersively carry it to stabilize the element. . Then, heat the element to 300 ℃ ± 50 ℃.
And aging in air for 12 hours. Silicon oxide is discontinuously supported on the surface of the obtained device. The gas detection element manufactured in this manner is heated by energizing a heater so that the element temperature becomes 325 ° C., and the concentration is 100% in clean air at 25 ° C.
ppm monosilane (SiH ₄ ), ethyl alcohol (EtO
H), carbon monoxide (CO), and 1000 ppm of hydrogen (H ₂ ), methane (CH ₄ ), ethylene (C ₂ H ₄ ), ethane (C ₂ H ₆ ), and ammonia (NH ₃ ) in each gas. Then, the resistance value was measured by exposure to air, and the ratio Ro / Rg, that is, the SN ratio, of the resistance value (Ro) in air and the resistance value (Rg) in each gas was obtained. The results shown in Table 2 were obtained.

[0008]

[Table 2]

When the resistance change characteristic of this gas detecting element with respect to the SiH ₄ gas concentration was measured, the characteristic shown in FIG. 1 (A) was obtained. Next, in order to obtain an effective component ratio and a firing temperature range of this gas detecting element, the component ratios were set to Pt / Sn = 1,2,4,8,10,12 mol% and Sb / Sn = by the above manufacturing method. 1,2,4,6,8,10 mol%, calcination temperature in air atmosphere is 550,600,700,8
50,900 ° C., element temperature when exposed to silane gas atmosphere is 150,200,325,500,850 ° C., and silane gas concentration is 10,25,100,500,100.
A gas detection element was manufactured by changing the amount to 0.1 and 1500 ppm, respectively. Then, with respect to these gas detection elements, in a state where the element temperature is heated to 325 ° C. by a heater,
The resistance value (Ro) in air at 25 ° C and the resistance value (Rg) in SiH ₄ gas were measured respectively, and from the measurement results, Ro / R
g, that is, the SN ratio was obtained. In addition, each gas detection element
Repeatedly exposed to 100 ppm SiH ₄ gas from the above air, and the resistance value Rg after the first exposure to SiH ₄ gas and the resistance value R _{10 after the 10th} exposure, the change ratio with time R
₁₀ / Rg was determined. Table 3 shows this component ratio, the firing temperature, and the measurement results.

[0010]

[Table 3]

Of these gas detection elements, Pt /
Sn = 4 mol%, Sb / Sn = 6 mol%, air atmosphere firing temperature 700 ° C. for 30 minutes, silane gas atmosphere element temperature 32
FIG. 2 shows changes with time when a gas detection element manufactured at a silane gas concentration of 100 ppm at 5 ° C. for 10 minutes was repeatedly exposed to 100 ppm of SiH ₄ . In addition, in FIG. 2, (a) is a resistance value in clean air at 25 ° C., and (b) is 1 at 25 ° C.
It is a resistance value in 00 ppm SiH ₄ gas.

Example 2 An aqueous solution of H ₂ PtCl ₆ was added to SnO _{2 so} that Pt / Sn = 4 mol%, and well dispersed by ultrasonic waves. This dispersion aqueous solution is rapidly frozen at -40 ° C, then set in a vacuum freeze dryer and dried. Then add Sb to this dried sample
OCl was added to Sb / Sn = 4 mol% and mixed in a mortar for 30 minutes. Isopropyl alcohol is added to this mixed sample to form a paste, which is applied to an alumina porcelain tube to which an electrode is attached and naturally dried. On the other hand, an alumina boat on which 2.5 mg of SbOC1 is placed is placed in a quartz tube having an inner diameter of 40 mm and an electric furnace insertion portion of 50 cm set at 700 ° C. ± 5 ° C. for 30 minutes to make the quartz tube an antimony oxidizing gas atmosphere. Next, the above naturally dried element is sealed in the quartz tube in the antimony oxidizing gas atmosphere set at 700 ± 5 ° C. and baked for 30 minutes. Next, a heater was inserted into the alumina porcelain tube of the fired element and attached, and the heater was energized to turn the element at 300 ° C. ± 50.
The mixture is heated to 0 ° C. and aged in the air for 12 hours in the heated state. Next, use a heater to remove the element that has been aged.
The device is stabilized by heating at 5 ° C. ± 5 ° C. and adsorbing silane gas having a monosilane (SiH ₄ ) gas concentration of 100 ppm on the surface in a dispersed manner. afterwards,
Heat the element to 300 ° C ± 50 ° C with a heater and
Time aging. Silicon oxide is discontinuously supported on the surface of the obtained device. The gas detection element manufactured in this way is heated by a heater so that the element temperature becomes 325 ° C., and in the atmosphere of 25 ° C., the concentration of SiH ₄ , EtOH, C in each of 100 ppm is 100%.
The resistance value was measured by exposing to O, H ₂ , CH ₄ , C ₂ H ₄ , C ₂ H ₆ , and NH ₃ gases, and Ro / Rg was determined.
The results are shown in.

[0013]

[Table 4]

When the resistance characteristic of this gas detecting element with respect to the SiH ₄ gas concentration was measured, the characteristic shown in FIG. 1 (B) was obtained. Next, in order to make the inside of the quartz tube an atmosphere of antimony oxidizing gas, the amount of SbOCl in the above manufacturing method was set to 0.2.
5, 0.5, 1.0, 2.5, 5.0, 7.5 mg to produce a gas detection element, the resistance value (Ro of the gas detection element in clean air at 25 ℃ atmosphere ) And 100 ppm
Resistance value (Rg) in SiH ₄ gas was measured, and Ro / Rg
I asked. The results are shown in Table 5.

[0015]

[Table 5]

In order to create an atmosphere of antimony oxidizing gas in the quartz tube, antimony trioxide (S) is used instead of SbOC1.
b ₂ O ₃ ) and the amount of Sb ₂ O ₃ is 0.25, 0.5, 1.
Gas detection elements were manufactured by the same manufacturing method as described above by changing to 0, 2.5, 5.0, 7.5 mg, and Ro and Rg of these gas detection elements were measured by the same method as described above. Ro / Rg was determined. The results are shown in Table 6.

[0017]

[Table 6]

Further, in the above manufacturing method, the component ratio is Pt.
/ Sn = 1,2,4,8,10 mol%, Sb / Sn = 1,
2,4,6,8,10 mol%, firing temperature in an antimony oxidizing gas atmosphere is 550,600,700,850,
900 ° C, element temperature 150 in silane gas atmosphere,
200,325,500,850 ° C, and silane gas concentration of 10,25,100,500,1000,1500
A gas detection element was manufactured by changing each to ppm. The amount of SbOC1 was set to 2.5 mg to create an antimony oxidizing gas atmosphere in the quartz tube, and it was created at the same temperature as each firing temperature. And for these gas detection elements,
Resistance value Ro in clean air at 25 ° C and S of 100ppm in the state heated by the heater so that the element temperature becomes 325 ° C.
The resistance value Rg in iH ₄ gas was measured, and Ro / Rg (SN ratio) was determined from the measurement results. Further, each gas detection element was repeatedly exposed to 100 ppm SiH ₄ gas from clean air at 25 ° C., and the above resistance value Rg when exposed to SiH ₄ gas for the first time and resistance value R ₁₀ at the 10th time The change ratio with time R ₁₀ / Rg was determined from. The results of this measurement are shown in Table 7.

[0019]

[Table 7]

Among these gas detecting elements, Pt /
Sn = 4 mol%, Sb / Sn = 6 mol%, SbOCl 2.5 mg
Is fired at 700 ° C. for 30 minutes in an antimony oxidizing gas atmosphere, and is fired at 700 ° C. for 30 minutes, and then 325
A gas detection element manufactured by exposing it to an atmosphere with a silane gas concentration of 100 ppm for 10 minutes at an element temperature of ℃
FIG. 3 shows the change with time when repeatedly exposed to m of SiH ₄ . In FIG. 3, (a) is a resistance value in clean air at 25 ° C., and (b) is a resistance value in 100 ppm SiH ₄ gas at 25 ° C. In the above examples, the element was heated with a heater to expose the element after firing to the silane gas atmosphere in order to disperse and support the silane compound on the element surface. However, instead of heating the element with the heater, the silane gas atmosphere was changed to 150 Even if the element which was not heated was exposed to a temperature of up to 850 ° C., a gas detection element having the same characteristics as those of the above-mentioned experimental examples was obtained. Further, the time for firing the element in the air atmosphere or the antimony oxidizing gas may be 5 to 60 minutes, and the time for exposing the element after firing to the silane gas atmosphere may be 2 to 60 minutes. It may be performed in a constant temperature bath or the like, and aging of the element may be performed in a constant temperature bath instead of heating with a heater. Further, as a solvent for making the mixed sample into a paste, 25 wt% of β-terpineol, butyl carbitol acetate 72 as well as isopropyl alcohol were used.
An organic solvent such as wt% or ethyl cellulose 3% may be used. As a base for applying the paste-like sample, a porcelain tube or a tubular or plate-like insulator that can withstand firing may be used. An infrared light bulb or the like may be used. The atmosphere of the antimony oxidizing gas may be created by using a solid or gas of antimony trichloride (SbCl ₃ ) or hydrogen antimonide (SbH ₃ ) gas, and the atmosphere of the silane gas is dichlorosilane (SiH ₂ Cl ₂ ) or ethoxysilane (SiH ₂ Cl ₂ ). (C ₂ H ₅ O) ₄ Si), silicon tetrachloride (SiC
l ₄ ), chloromethylsilane ((CH ₃ ) ₂ SiCl ₂ ) or the like.

[0021]

As described above, according to the present invention, stannic oxide, antimony oxychloride and platinum are mixed with S.
b / Sn = 2 to 8 mol% and Pt / Sn = 2 to 10 mol% were mixed and burned in an air atmosphere at 600 to 850 ° C. or in an antimony oxidizing gas atmosphere. Since the silane compound was dispersed and supported, and this element was heated to 200 to 400 ° C. in air to discontinuously support silicon oxide on the surface, it has high selectivity for silane-based gas, and It is possible to provide a gas detection element having a favorable change over time.

[Brief description of drawings]

FIG. 1 is an S of a silane gas detection element according to an embodiment of the present invention.
iH ₄ is a graph showing a gas concentration versus resistance change characteristic.

FIG. 2 is a graph showing aging characteristics of the silane gas detection element according to Example 1 of the present invention.

FIG. 3 is a graph showing aging characteristics of a silane gas detection element according to Example 2 of the present invention.

[Explanation of symbols]

A: Device manufactured according to Example 1. B: Device manufactured according to Example 2. a: Resistance value in clean air at 25 ° C. b: Resistance value in 100 ppm SiH ₄ gas at 25 ° C.

Claims (1)

[Claims] 1. The composition ratio of stannic oxide, antimony oxychloride and platinum is Sb / Sn = 2 to 8 mol%, Pt / Sn = 2.
10 to 10 mol%, a silane compound from a silane-based gas is dispersed and carried on the surface of the element in an element that has been baked at a temperature of 600 to 800 ° C., and the element is heated to 200 to 400 ° C. in air.
A silane gas detection element, characterized in that the silicon oxide is discontinuously supported by being heated to the temperature.