JPS62213822A - Treatment of gas containing arsine - Google Patents

Abstract

PURPOSE:To remove arsine from gas containing arsine by retaining oxygen of more than specified rate in gas containing arsine and contacting the same with heated activated carbon. CONSTITUTION:Oxygen is added to gas containing AsH3 such as off-gas exhausted out of semi-conductor manufacturing process at a rate of mol more than 1.5 times of AsH3 to be sent into a reaction tube filled with activated carbon. At that time, activated carbon is preheated with a heater wound to the reaction tube, so that reaction temperature may be set within a range of more than 40 deg.C and less than the decomposition temperature of AsH3.

Description

Detailed Description of the Invention [Industrial Application Field 1] The present invention is applicable to MO-CVD equipment for epitaxial films fJTi of Group I-V compound semiconductors in the semiconductor industry, and ion implantation equipment for doping silicon substrates. The present invention relates to a method for processing arsine-containing gas that efficiently removes arsine contained in exhaust gas and the like.

[Conventional technology] Arsine (ASH) is used in the semiconductor industry, chemical industry, etc.
3) Metal hydrides such as phosphine (PH3) are highly toxic gases with extremely low permissible concentrations, and A
The Sf-h permissible concentration is 0.05+)I)I. Therefore, it is difficult to remove As1(s) from the exhaust gas containing AsH3 to below the permissible concentration, and various methods have been proposed, but none of them can be said to be an efficient removal method.

For example, chemical cleaning methods using solutions containing oxidizing agents such as potassium permanganate, sodium hypochlorite, and ferric chloride have a poor removal effect on low-concentration ASHHz, and furthermore, it is difficult to dispose of the absorbent solution containing arsenic. It takes.

In addition, adsorption methods using activated carbon, zeolite, etc., and removal methods using adsorbents carrying oxidizing agents, do not have high removal rates or can reduce Ast-h per unit of adsorbent. It cannot be said that the removal ability is sufficient.

On the other hand, the darkness of AS H3 that can be removed by the adsorption power of activated carbon is 1llff, and although it varies depending on the pressure, it is the number W [% to 10 wt% of the weight Bk of activated carbon. ) It is difficult to completely remove ASH3 and regenerate activated carbon that has adsorbed lx using the general heating regeneration method, so in order to safely process it,
It is necessary to dispose of ASH3 after decomposing it with a solution containing an oxidizing agent. In addition, adsorbents in which ferric chloride is supported as a main agent on activated carbon, diatomaceous earth, etc., or copper oxide,
In reactive adsorption methods that use adsorbents that support metal compounds as second and third components in addition to gold amides such as manganese oxide or oxides, the removal capacity for As H3 is generally 5 times the adsorbent's own weight. ~20 W[%], and required an operation to support it on activated carbon.

Due to these circumstances, there is a strong demand for an efficient removal method that has a high removal rate of As H3 and a large removal capacity.

[Problems to be Solved by the Invention] In view of the above circumstances, the present inventors conducted intensive research to develop an efficient method for removing arsine. It was found that when the As H3 concentration in the scum was brought into contact with activated carbon, the As H3 concentration in the scum was significantly reduced.

The present invention was developed based on the above knowledge, and
Let the concentration of 113 be efficiency<0. It is an object of the present invention to provide a method for removing ASH3 that can reduce O to 5 ppm or less and also allows easy handling of the activated carbon used for removal.

[Means for Solving the Problems 1] The present invention achieves the above-mentioned object, and its gist is that oxygen gas is present in an arsine-containing gas in an amount of 1.5 times or more mole relative to arsine, and at 40°C or higher. , a method for treating an arsine-containing gas which is brought into contact with activated carbon at a temperature below the decomposition temperature of arsine.

[Specific structure and operation of the invention] The present invention will be explained in detail below.

Semiconductor! In Il manufacturing, the presence of 02 is extremely disliked, so 02 is added to the As H3-containing gas discharged from the process.
is often not included.

In the method of the present invention, a predetermined amount of 02 is present with respect to As th in the exhaust gas containing As H3, and activated carbon is used as a catalyst to react and remove A at a predetermined temperature.
S) (Since a predetermined amount of 02 is required to remove z, and arsenic and arsenic trioxide are detected in surface analysis of J3 and used activated carbon, the following reaction is being carried out in parallel. think about something.

/JAS H3+302→4AS +68204AS
+302→2AS 203 (2As +13 +302→As 203 +3H2
0) The arsenic compounds remaining in activated carbon after use include arsenic with a high boiling point (sublimation point 615°C) and hisotrioxide (boiling point 46°C).
5°C), the vapor pressure at room temperature is low, and used activated carbon can be safely handled without further post-treatment such as oxidation treatment.

The activated carbon used in the present invention can be any activated carbon. For example, the υJ limit of the type and brand of commercially available activated carbon made from coal, petroleum coke, coconut shell, etc., or molecular sieve carbon with 3 to 5 pores that is recently used for various purposes, etc. do not have.

In addition, the oxygen supplied to make the predetermined m exist is air,
l! Both enriched air and pure oxygen can be used, and their m
is 1.5 times the mole or more of As H3 contained in the exhaust gas,
In particular, it is preferable to add it in an amount of 1.8 times the mole or more. If the amount is less than 1.5 times the mole, there will be a shortage of oxygen. However, even if the molar ratio of oxygen to arsine is three times or more, the removal efficiency of ASH3 does not increase much. However, As
If combustible gas coexists in the H3-containing gas and enters the explosive range due to the addition of Mi, a large excess of air may be added to avoid this. If the arsine-containing gas contains 1.5 times or more mole of oxygen gas relative to arsine from the beginning, it is not necessary to add oxygen gas.

The reaction temperature ranges from 40°C or higher to the decomposition temperature of As H3 or lower, with a range of 50 to 200°C being particularly preferred. This reaction proceeds even at room temperature, but at temperatures below 40°C, the reaction rate is close and the contact time needs to be extended, which is not only impractical, but also leaves As H3 physically adsorbed on the activated carbon. This makes handling of used activated carbon difficult. The reaction rate accelerates as the reaction temperature increases. For example, at 200°C, the contact time is about 2 seconds and the As1-N1 degree is 0. O becomes less than 5 ppm, AS N3 breaks through, and As1'3 in the outflow gas
Approximately 45% of ASI-13 in the activated carbon type seedlings is removed by the time the WJ degree becomes Q, O5 ppm or less. When the reaction temperature exceeds the decomposition temperature (230 to 240°C) of As) (11), arsine decomposes, so this reaction can also be used to remove arsine. A reaction temperature of ℃ or higher is required, and economic efficiency is lost.

In addition, the contact time is 0.5~ in terms of 20℃ lat ■.
The time is 200 seconds, but in practice, about 1 to 120 seconds is preferable.

Naturally, the longer the contact time, the more arsine can be removed.
There is a correlation between the reaction temperature maintained at 05 ppm+ or less and the contact time; the higher the reaction temperature within a predetermined temperature range, the shorter the contact time.

When carrying out the method of the invention on an industrial scale, Δ51
13, including the ASN311 degree in the gas contained, the gas Iδ to be treated, the reaction temperature, and the contact time, the economic conditions f1
All you have to do is select.

[Example] Next, the present invention will be explained by showing examples and comparative examples.

Example 1 A stainless steel reaction tube with an inner diameter of 10Ill and a length of 40tJ was filled with 16 to 20 meshes of activated carbon (Hokuetsu Tanso, Hokuetsu Y-10), and was introduced into the reaction tube while flowing N2. After heating and activation at 170° C. for 4 hours using a wrapped tape heater, the heater was turned off and cooled. Next, before supplying arsine-containing gas (hereinafter referred to as raw material gas), the reaction tube was preheated to nearly 50°C, and AS N3:
0.49%, N2:8.84%, 02:1.4%, H
-: Room temperature raw material gas consisting of 9.8%: 255cc/
A+in was introduced at a pressure of 0.3 at 5F/aiG and flowed out from the outlet of the reaction tube. After the raw material gas was supplied, the temperature rose due to the heat of reaction, so the output of the heater wound around the reaction tube was lowered to adjust the reaction temperature to about 50°C.

After starting to feed the raw material gas, the AsN3 gas that flows out at any time
．． 02, N2, N21! When I measured the degree, it was 63
Astra: 0.05+1 Ilm(
Release allowable concentration) or less, 02:0.74±0.03%, H
z: ND (however, the lower limit of detection was 0.02%). However, at 650 minutes As +13: 0.5pE1m
.

(3.5111 in 370 minutes) became III, and a breakthrough was detected. Thereafter, when the supply of raw material gas was stopped and only N2 was introduced, the degree of As1-hcJ in the outflowing N2 gas was less than 10-odd Q, 2flf1m. This indicates that ASI3 was not substantially desorbed from the activated carbon after breakthrough, and that Ast 13 was not removed by physical adsorption.

From the above results, Asl.13 can be removed to below the allowable concentration. The removal capacity (hereinafter referred to as removal capacity) per 100g of activated carbon (A, C) is 18.8 (+As l-h /10
0(l AC.

In addition, the analysis of ASI-13 is based on AS+3 detection alarm meter (
The 02, N2, and To12 analyzes were conducted by the TCD-GC method.

Comparative Example 1 Activated carbon Y-10: 13.7 g was used, and using the same reaction tube as in Example 1, it was activated by heating and cooled to room temperature. Then, without preheating the reaction tube, ASHHz: 0.51%, N2
A raw material gas at room temperature of 242 CC/l1in consisting of : 88.3%, 02: 1.4%, and 1-1c: 9.8% was fed into the reaction tube at a pressure of 0.3 Ky/dG. The temperature of the reaction tube was maintained within the range of 17°C to 28°C. meanwhile,
Until 410 minutes had elapsed from the start of feeding, ASI3: Below the allowable concentration, 02: About 0.92%, but after 430 minutes, AsN3: 3.3pE)m, and a breakthrough was detected. After that, when the supply of raw material gas was stopped and only N2 was introduced, the As831 degree in the flowing N2 was 1
The temperature exceeded 001)l)l, and no decrease in temperature was observed for more than ten minutes thereafter. This is the adsorbed ΔSSi201
It shows that the parts are attached and detached.

From the above results, when the temperature is room temperature, even though there is sufficient 02, the oxidation of arsine is insufficient and ASf-h is physically adsorbed on the shell, and the removal vessel is 12.5 (JASth/
100 (IAc).

Comparative Example 2 Activated carbon (Hokuetsu Carbon Y-10): 3.92G inner needle: 4.
The mixture was filled into a stainless steel reaction tube of 4 mm+ length: 55 c#I, heated and activated in the same manner as in Example 1, and cooled to room temperature. Next, As 1-13: 0.5%, N2: 9
0%, 1-1e: 9.5% of raw material gas containing no 02 at room temperature was introduced into the reaction tube at 50° C. at a rate of 250 cc/sin. ASI-+ until 55 minutes after the start of feeding
3: The concentration was below the allowable level, but after 60 minutes, 1 pf
)11 or more, a breakthrough was detected, and the As@3 removal ability was 5.8Q AS +3 /100o AC. After that, the supply of raw material gas is stopped and N
2 was fed, (7) As l-h in the outflow N2
'a degree was 2001) l) 1 or more.

Example 2 Molecular sieve carbon 5A (Narita Pharmaceutical Molcibon HGY-31
8') 16-24 mesh broken product: 3.90 inner diameter:
A reaction tube of 4.4 mm in length and 55 cm in length was filled with the mixture, and the mixture was heated and activated in the same manner as in Example 1, and then allowed to cool. The reaction tube was then preheated to about 80°C and As h :0,
47%, 02:1.34%, N
A raw material gas at room temperature consisting of 2:89.2% and f-1e:9.0% was fed at a rate of 266 cc/1n. After feeding, the voltage of the heater was adjusted so that the reaction temperature did not rise above 80°C. Up to 105 minutes after the start of feeding, As+3: below the allowable limit, 02: 0.75%, but As+3: 2.51)r)l was detected after 115 minutes. Thereafter, only N2 was passed in the same manner as in Example 1, but the AS +3 in the outflowing N2 was 0.15 pp- or less. Also, in this case, the removal ability is 11 (1: AS
It was Hz/100 (J AC).

Example 3 Using the molecular sieve carbon of Example 2: 3.65+I+, As
+3: 0.5%, 02: 5.2%, N2: 8
4.8%, He:9.5% raw material gas at 250cc/
The procedure was the same as in Example 2, except that the injection was carried out at n+in.

The AS N3 concentration in the effluent gas was below the permissible limit until 110 minutes after the start of the supply, but after 115 minutes, As +-
+3: 2 ppm was detected. In this case, ASH3
Removal capacity is 12.3Q -As l-h /100g・
It is AC. This shows that even if the degree of Oz'lA in the raw material gas is increased, the removal ability does not change much.

Example 4 Using activated carbon (Hokuetsu Carbon Y-10): 13.450, A
Sth: Q, 98%, Oz: 2.5%, N2 near 7
．． 9%, l-1e: 18.6% raw material gas at 152CC
The procedure was the same as in Example 1 except that the flow rate was 1/1 lin. AS in the outflow gas until 1050 minutes after the start of supply
I-13 was below the allowable concentration, 02:1.11%, but A3H3:2.51)Ellll was detected after 1080 minutes. In this case, removal ability = 37, Ba ・ASH3
/1000° AC.

Example 5 Activated carbon (Hokuetsu Tanso Y-10): /1. After preheating the reaction tube to about 140°C using OQ, Δ5t-h: 0.47
%, 02: 1', 0%, N2: 89.3%
, 1-18:9.2% was introduced at room temperature, and the reaction tube was adjusted to 140° C., but the same procedure as in Example 1 was carried out. ASH3: Permissible 81 until 280 minutes after the start of feeding
degree or less, 02:0.41%, llz:ND,
As +3:2ppn+ was detected 300 minutes later. In this case, the removal capacity is 28.4! J・AS +3
/100 (1 AC.

Example 6 Activated carbon (Hokuetsu Carbon Y-10): 3.81 (using J, after preheating the reaction tube to about 200°C, ASI-+3: 0.49
%, 02: 1.37%, N2: 88.8%, He:
255 cc/si of room temperature raw material gas consisting of 9.3%
The procedure was the same as in Example 1, except that the reaction temperature was adjusted to 200°C. 420 minutes after the start of sending, ASH
3: Below permissible concentration, 02: 0.69%, N2: ND
However, As +3:51) DI was detected after 450 minutes. In this case, the removal ability is 45o ・As l
-13/100Q ・AC.

Example 7 After preheating the reaction tube to about 14.0°C using activated carbon (Hokuetsu Carbon Y-10>3.90), AsH2: 0.48%,
02: 0.75%, N2: 89.6%, 1-1e:
The procedure was the same as in Example 5 except that a room temperature raw material gas containing 9.2% was introduced. G41, A until 275 minutes after the start of feeding
s1-13 below allowable concentration, 02: 0.11%, H2:
ND, but after 300 minutes As H3: 2.5p
po+ was detected. In this case, ASi13 removal ability crab28
．． O(+ ・ASH3/10017AC.

[Effects] As described above, the method for treating AS 83-containing gas of the present invention has a large ability to remove AsH2, and moreover, the removed As, as highly toxic ASt13, is mostly activated carbon. Since the activated carbon is not adsorbed or remains, post-processing of the activated carbon becomes easy, and this will greatly contribute to the progress of the semiconductor industry, which uses AsH2 extensively.

Claims (1)

[Claims] 1. A method for treating an arsine-containing gas, which comprises causing the arsine-containing gas to contain oxygen gas in an amount of 1.5 times or more moles relative to arsine, and contacting the arsine-containing gas with activated carbon at a temperature of 40° C. or higher and arsine thermal decomposition temperature or lower.