JPH0458906B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a gas detection element that can selectively detect special gases such as silane gases, and a method for manufacturing the same. [Prior art] Monosilane (SiH ₄ ), dichlorosilane (SiH ₂
Cl ₂ ), trichlorosilane (SiHCl ₃ ), phosphine (PH ₃ ), diborane (B ₂ H ₆ ) and arsine (AsH ₃ )
etc., several percent when mixed with other gases such as air.
As a gas detection element capable of detecting a special gas that spontaneously combusts at a concentration of We have proposed a metal oxide semiconductor gas detection element with a composition of (SnO ₂ ), palladium (Pb), and antimony compound (Sb compound) and post-treated in a silane gas atmosphere. This SnO ₂ -Pb-Sb compound gas detection element is
When exposed to 10 ppm SiH ₄ gas, the SN ratio is about 5, the response time is around 150 seconds, and 10 ppm of SiH ₄ gas is used for 100 ppm of ethyl alcohol (EtOH).
The gas selectivity of R(EtOH 100ppm)/R(SiH ₄
10ppm) = approximately 0.5. [Objective and solution] The object of the present invention is to provide a gas detection element that has a quick response time, good gas selectivity, and can selectively detect special gases, and a method for manufacturing the same.
The main material is activated stannic oxide (SnO ₂ ) obtained by pre-calcining SnO ₂ to _which tin SnO 2 or stannic chloride (SnCl ₄ ) has been added, and palladium (Pb) is used as a catalyst.
Pb/Sn=0.1~ using antimony (Sb) as a stabilizer
A metal oxide semiconductor having a composition ratio of 8 mol% and Sb/Sn = 0.5 to 8 mol% and treated in a 20 to 400 ppm silane-based gas atmosphere and this metal oxide semiconductor heated to 200 to 400°C. It is characterized by comprising a heating means for heating. Further, the manufacturing method is characterized by having the following steps. Add SnCl ₄ to SnO ₂ SnCl ₄ /SnO ₂ = 0 to 20 mol%
Activated SnO ₂ is created by pre-calcining in an air atmosphere at 600 to 900°C. A palladium oxide (PbCl ₂ ) solution is added to the activated SnO ₂ so that Pb/Sn=0.1 to 8 mol % and dispersed, followed by drying. An Sb compound is added to the sample so that Sb/Sn=0.5 to 8 mol% and mixed. An organic solvent is added to the sample to form a paste, which is applied to an insulator provided with a pair of electrodes and dried. The device is fired for 5 to 30 minutes in air or antimony oxidation gas atmosphere at 600 to 850°C. The device is treated with 20 to 400 ppm silane gas for 5 to 30 minutes by CVD method. The device is heated and aged. [Effect] SnCl ₄ was added at SnCl ₄ /SnO ₂ = 0 to 20 mol%
By using activated SnO ₂ obtained by pre-calcining SnO ₂ as the main material, it has the effect of reducing sensitivity to gases other than special gases and increasing responsiveness to special gases. [Example] Hereinafter, the gas detection element of the present invention and the manufacturing method thereof will be explained with reference to Examples. Gas detection elements of Examples 1 to 10 were manufactured by the following manufacturing method. Note that the number of gas detection elements manufactured in each example was eight. First, stannic chloride SnCl ₄ is added to stannic oxide SnO ₂
The solution was mixed so that SnCl ₄ /SnO ₂ = 0 to 10 mol%, heated linearly in the air to a predetermined temperature of 600 to 900°C, and baked at the predetermined temperature for 30 minutes (hereinafter, this baking was (Calcination) to create activated SnO ₂ . Next, a palladium chloride _PbCl2 solution is added to the activated _SnO2 so that Pb/Sn=0.1 to 8.0 mol% to create a mixed aqueous solution. In addition, the PbCl ₂ solution is
It is created by adding, for example, a 0.2% hydrochloric acid aqueous solution to _PbCl2 . This mixed aqueous solution is stirred using an ultrasonic stirrer to disperse Pb well. Thereafter, this dispersed mixed solution was set in a vacuum freeze dryer and dried at −40°C.
Dry samples are prepared by rapid freeze-drying at temperatures below ℃. Then, antimony oxychloride (SbOCl) is added to this dry sample so that Sb/Sn=1.0 to 8 mol%, and mixed in a mortar for about 30 minutes to obtain a mixed sample. In addition, Pb of each mixed sample in Examples 1 to 10,
The composition ratio of Sb and Sn is as shown in the table below. Isopropyl alcohol, which is an organic solvent, is added to this mixed sample to form a paste-like mixed sample, which is applied onto an alumina porcelain tube having a pair of electrodes so as to cover between the pair of electrodes, and then air-dried. Next, this air-dried element is fired for 10 or 15 minutes in a quartz tube set at 700°C in an antimony oxidation gas atmosphere. This antimony oxidation gas atmosphere is as shown in the firing atmosphere in the table below.
It was prepared by placing 2.5 mg of SbOCl on an alumina boat and placing it in a quartz tube (inner diameter 4 cm, electric furnace insertion part 50 cm) set at 700°C for 30 minutes to evaporate it. Then, a heater is attached to the element after firing, and electricity is applied to the heater to heat the element to 300±50°C, and the first aging is performed for 10 hours in the atmosphere. Furthermore, the element that has undergone the first aging is heated to 325±5℃ using a heater, and then placed in the air.
The _CVD method (chemical
A metal oxide semiconductor is obtained by dispersing Si oxide on the surface of the device using a vapor deposition method. Finally, this element is heated to 300±50℃ using a heater.
The gas detection element of each example was completed by heating to 100% and performing a second aging in the atmosphere for 12 hours. In addition, in order to compare with Examples 1 to 10, Example 11 is a comparative gas detection element manufactured by the above manufacturing method using SnO ₂ that has not been pre-fired without using activated SnO ₂ . be. The resistance value Ro in the atmosphere was measured for each of the eight gas detection elements of Examples 1 to 11 manufactured in this way, and the average value of the eight elements was determined for each example. The results shown are obtained.

【table】

[Table] In both the above measurements and the measurements described below, the gas detection elements of each example were heated to 325±10° C. with a heater. Next, each element of Examples 1 to 11 was exposed to hydrogen (H ₂ ), methane (CH ₄ ),
Ethylene (C ₂ H ₄ ), ethane (C ₂ H ₆ ), isobutane (iC ₄ H ₁₀ ), ammonia (NH ₃ ), carbon monoxide (CO), isopropyl alcohol (iPA), ethyl alcohol (EtOH), At a concentration of 10 ppm in each test gas atmosphere and air,
They were sequentially exposed to a test gas atmosphere containing SiH ₄ gas, and the resistance value Rg and response time in each test gas were measured. From these measurement results, the average values of the 8 elements for the SN ratio, that is, Ro/Rg, and response time for each sample gas were determined for each experimental example, and the results shown in the table were obtained. From this result, the gas detection elements of Examples 1 to 10 have a higher sensitivity to SiH ₄ gas than the element of Example 11.
Although there is not much change in the S/N ratio, the S/N ratio for other gases has decreased to about 2/3 to 1/2, indicating that the selectivity of SiH ₄ gas has greatly improved. . In addition, the selectivity of SiH ₄ for iPA

The relationship between [R(iPA)/R(SiH ₄ )] and the firing temperature when pre-calcining the activated SnO ₂ was determined from Examples 3 and 6 to 8, and is as shown in FIG. In addition, the response time to SiH ₄ is from Example 1 to
10 is approximately 1/2 the time compared to Example 11, which indicates a significant improvement. In addition, Example 1~
Activation created by pre-calcining only SnO ₂ from 5.
It can be seen that although the response time is sufficiently fast even when SnO ₂ is used, the response time is even faster when activated SnO ₂ is used, which is pre-calcined by adding SnO ₄ to SnO ₂ . The relationship between SnCl ₄ /SnO ₂ and response time when creating this activated SnO ₂ is shown in Figure 2, and from this Figure 2,
It can be seen that the amount of SnCl ₄ added has a large effect up to about 20 mol% relative to SnO ₂ . Further, FIG. 3 shows the response characteristics of one gas detection element of Example 3 as a representative example of the response characteristics for each sample gas. By the way, various conditions in the above manufacturing method are as follows. The pre-calcination time at a predetermined temperature to create activated SnO ₂ ranges from 10 minutes to several hours. The mixed aqueous solution may be dried by natural drying or the like. In this case, compared to the case of rapid freeze-drying,
The dispersion state of Pb tends to become uneven, and the product yield decreases. Sb added to the dry sample includes SbOCl and Sb ₂ O ₃
Sb compounds such as
A range of 0.5 to 8 mol% is suitable. Outside this range, the activity of Pb in the element may be impaired or Ro may become small. When the above quartz tube is used, the antimony oxidation gas atmosphere when firing the element is 0.25 to 10 mg.
An atmosphere created by placing an Sb compound such as SbOCl or antimony trioxide Sb ₂ O ₃ in an atmosphere at a temperature of 600 to 850° C. for 5 to 60 minutes is used. The amount of Sb compound in this case is 1×10 ^-9 in terms of the number of moles of Sb ₂ O ₃
~4.5×10 ⁻⁸ mol/cm ³ . Note that the firing of the element may be performed in an air atmosphere. In this case, there is no difference except that when devices are manufactured continuously, the variation in resistance value between manufacturing rods becomes larger than when the devices are manufactured in an antimony oxidation gas atmosphere. Further, the temperature and time for firing the device are in the range of 600 to 850° C. and 5 to 30 minutes in either antimony oxidation gas or air atmosphere. Outside this range, the activity of Pb decreases. Dispersion treatment of metal oxide semiconductors by CVD method is
Silane gas such as SiH ₂ Cl ₂ may be used, and the concentration range of the silane gas is 20 to 400 ppm. Concentrations outside this range reduce selectivity to specialty gases. Note that the treatment temperature and time at this time are in the range of 150 to 850°C for 5 to 30 minutes. The first aging may be omitted, and the second aging is preferably performed for 10 hours or more. Further, the heating temperature range of the gas detection element during gas detection is 200 to 400°C. Outside this range,
The response time to special gases is slower and
Selectivity decreases. [Effects] According to the present invention, there is an effect that a gas detection element capable of detecting a low concentration special gas with good selectivity and a fast response time and a method for manufacturing the same can be obtained.

[Brief explanation of the drawing]

Figures 1 to 3 are diagrams showing the characteristics of the gas detection element according to the present invention, and Figure 1 shows selectivity and activation.
Figure 2 shows the relationship between the pre-calcination temperature of SnO ₂ and SnCl ₄ /
Figure 3 shows the relationship between SnO ₂ and response time in Example 3.
The response characteristics of one of the elements to each gas are shown.

Claims (1)

[Claims] 1. Activated stannic oxide obtained by pre-calcining stannic oxide to which stannic oxide or stannic chloride has been added.
Main material: tin, palladium as catalyst, antimony as stabilizer, Pb/Sn=0.1-8 mol%, Sb/Sn=
It consists of a metal oxide semiconductor having a composition ratio of 0.5 to 8 mol% and treated in a silane-based gas atmosphere of 20 to 400 ppm, and a heating means for heating this metal oxide semiconductor to 200 to 400°C. Characteristic gas detection element. 2 Adding stannic chloride to stannic oxide as SnCl ₄ /SnO ₂
= 0 to 20 mol%, 600 to 900℃
The first step is to create activated stannic oxide by pre-calcining in an atmospheric atmosphere, and to add a palladium chloride solution to the activated stannic oxide.
A second step of adding Pb/Sn to a concentration of 0.1 to 8 mol%, dispersing it, and drying it; and adding an antimony compound to the sample prepared in the second step.
A third step is to add and mix Sb/Sn so that it is 0.5 to 8 mol%. An organic solvent is added to the sample prepared in the third step to form a paste, and this is applied to an insulator with a pair of electrodes. a fourth step of coating and drying; a fifth step of firing the element created in the fourth step for 5 to 30 minutes in the air at 600 to 850°C or an atmosphere of antimony oxidation gas; and a fifth step of firing the element in the fifth step. The device was manufactured using the CVD method.
A method for manufacturing a gas detection element, comprising: a sixth step of treating with ~400 ppm silane gas for 5 to 30 minutes; and a seventh step of heating and aging the element produced in the sixth step. 3 The antimony oxidation gas atmosphere is created by placing an antimony compound of 1×10 ^-9 to 4.5×10 ^-8 mol/cm ³ in terms of the number of moles of antimony trioxide in an atmosphere at 600 to 850°C for 5 to 60 minutes. A method for manufacturing a gas detection element according to claim 2, wherein the gas detection element is produced.