JPH05237334A - Method for removing silane - Google Patents

Abstract

PURPOSE:To remove silane mixed into the preceding stage of a NH3 removing process by reaction and decomposition. CONSTITUTION:A silane removing process using as a silane removing agent at least one of manganese oxide, copper oxide and iron oxide is installed in the preceding stage of a NF3 removing process. The inflow of silane to a silane removing part is detected by the temp. rise and gas collected on the way to the silane removing part is analyzed or a material which is reacted with silane to discolor is arranged in a window part installed in a part of the silane removing part, to detect the life of a silane removing agent.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for removing silane in the preceding step in order to safely remove NF ₃ in a system that handles NF ₃ and silane simultaneously.

[0002]

2. Description of the Related Art NF ₃ has been attracting attention as a rocket fuel in the aerospace field, and as a dry cleaning agent for a CVD apparatus or a dry etching agent in an LSI manufacturing process in the semiconductor industry field in recent years. In particular, as a dry etching agent, compared with a perfluorocarbon type etching agent such as CF _{4, the} dry etching agent has an advantage that the degree of contamination of the LSI is extremely small, and it has been increasingly used.

However, NF ₃ is extremely stable in the atmosphere and has a TLV of 10 p, which is only slightly soluble in water.
Since it is a toxic gas of pm, when using it,
When discharging the unused gas, it is always necessary to remove it. On the other hand, NF ₃ has a strong reactivity with silane used at the same time in the CVD apparatus, and there is a demand for a method of safely using and removing these gases in the same system.

NF ₃ is a very stable gas near room temperature, does not react with chemical substances such as acids and alkalis, is hardly absorbed by water, and has no suitable adsorbent. Can not be removed by a traditional method. But NF ₃
Starts to decompose into N ₂ and active F atom at 180 ° C or higher, 4
It has a sufficiently high decomposition rate at 00 ° C or higher.

[0005] That is, an effective method for processing NF ₃ is decomposed to NF ₃ at a high temperature of at least 400 ° C., occurs F
Most of the NF ₃ removal methods developed so far for industrial use are based on this principle, which involves reacting atoms with a suitable substance. For example, a method of using a substance that forms a volatile fluoride such as Si, W, and Mo as a substance that reacts with F (Japanese Patent Publication No. 63-48570), activated carbon such as C
Method of using carbon source to generate F ₄ gas (Japanese Patent Publication No. 2-30
No. 731).

[0006]

By the way, silane is often used as a raw material gas in the film forming step before the cleaning and etching steps in semiconductor manufacturing, which is the main application of NF ₃ . Since NF ₃ and silane gas can form an explosive mixture by mixing, the equipment and system are designed with care so that these gases used in the film forming process and the cleaning and etching process never mix with each other. Yes, but after all the same CV
Since the gas source is connected through a pipe because it is used in the D device or the like, it cannot be said that there is absolutely no possibility of mixing due to erroneous operation of the valve or the like. If the explosive air-fuel mixture formed by such an unexpected situation flows into the NF ₃ abatement device having a high temperature reactor that provides a place for the NF ₃ abatement reaction, there is a risk of explosion there. No suitable backup system has been proposed so far to eliminate such dangers.

[0007]

Means for Solving the Problems As a result of earnest studies in view of the above situation, the present inventors have arranged a chemical agent for removing silane before the NF ₃ abatement device having a high temperature part, and in the unlikely event that N
Even if the mixture of F ₃ and silane is introduced into the NF ₃ abatement device while it is still formed, the silane component can be removed from the mixture to safely remove NF _3. It provides a method. Also,
Provided is a method capable of warning a dangerous situation by automatically detecting the presence of silane in the NF ₃ removal line, and further, automatically managing the life of the agent for removing silane. It also provides a method of obtaining.

That is, the present invention is a method for removing silane, characterized in that, in the step of removing NF ₃ , the silane mixed in the step is reacted and removed with the removing agent before the step. Manganese oxide, copper oxide,
Characterized by comprising at least one or more agents selected from iron oxide, detecting the inflow of silane into the silane removal section by increasing the temperature, and further analyzing the gas collected from the middle of the silane removal section. To detect the life of the silane removal agent, and to detect the life of the silane removal agent by arranging a substance that changes color by reacting with silane in a window provided in a part that can be observed from the outside in a part of the silane removal section. This is a method for removing silane.

In the present invention, as a result of diligent studies on the silane-removing agent, the present inventors have found that an agent consisting of at least one selected from manganese oxide, copper oxide and iron oxide is very useful for such purpose. The present invention has been discovered and has reached the present invention. That is, a chemical agent consisting of at least one selected from manganese oxide, copper oxide, and iron oxide can not only remove silane even in a completely dry state, but at the same time, it can be discharged from a cleaning process or an etching process such as semiconductor manufacturing. As a result, they have found that the present invention has the advantage that the silane removal capability is hardly adversely affected even by a cleaning or etching product gas such as SiF ₄ accompanied by undecomposed NF ₃ .

The oxides used in the present invention include Mn ₃ O ₄ , Mn ₂ O ₃ and MnO ₂ as manganese oxide, Cu ₂ O and CuO as copper oxide, and FeO and F as iron oxide.
e ₃ O ₄ and Fe ₂ O ₃ are preferred.

As a chemical agent for removing silane, potassium permanganate or the like is generally known as an oxidizing agent.
Further, metasilicates, alkalis, etc. are also known, but since they all have the ability to remove silane in the presence of water, they are either wet or semi-dry type removal methods, and silanes placed before the NF ₃ abatement system It is very uncomfortable as a removal device. This is because the water held by the silane removal agent enters the NF ₃ abatement part as a partial pressure of steam at that temperature together with the gas flowing into the NF ₃ abatement device, but at this time, due to the action of F atoms and water vapor, the temperature becomes high. This is because the metal of the reactor material is corroded remarkably.

In the present invention, the substance called silane includes monosilane consisting of one silicon atom, disilane containing two silicon atoms, and fluorosilane, chlorosilane, and bromosilane in which hydrogen atoms of these silanes are partially replaced by halogen atoms. It also includes various types.

Further, if silane continues to be mixed in the NF ₃ removal line, the silane removal agent provided by the present invention can avoid the immediate danger, but since the ability of the agent is limited, the silane removal ability will eventually be reached. Can be lost and put in danger. Therefore, a mechanism is required to detect such a dangerous state and inform the operator.
The present invention also provides a method for the detection mechanism. That is, since a chemical consisting of at least one selected from manganese oxide, copper oxide, and iron oxide generates heat due to the reaction with silane, the temperature sensor catches the temperature rise due to the heat generation, and the NF ₃ abatement line is supplied with silane. It is possible to detect that the is mixed in very early. For example, in the case of the NF ₃ —SiH ₄ —N ₂ system, the explosion lower limit SiH ₄ concentration is said to be 0.66%, but even in the case of 0.5% SiH _{4 having} a lower concentration than this, the temperature is 30 ° C.
It shows the above temperature rise and can be easily detected.

A signal detected by the temperature sensor can be used to activate an alarm device such as a lamp or a buzzer to promptly inform an operator of a dangerous state, and the silane or / and NF ₃ main valve can be automatically operated. It is also possible to shut off automatically to eliminate the cause of the dangerous condition.

In the above-mentioned silane contamination detection mechanism for the NF ₃ abatement line, it is practical to set the temperature level at which the alarm is output to a value obtained by adding the error width to the temperature fluctuation width in the normal state. Is. Therefore, a situation may occur in which silane is mixed but its concentration is low and the temperature level at which an alarm is output is not reached. When left as it is, the ability of the silane removal agent is lost without noticing and the function as a safety device is not fulfilled. Therefore, a mechanism for detecting such a situation is also required, and the present invention also provides a method therefor. It is a thing. That is, when the ability of the silane removing agent is lost, the silane flows out to the downstream side, so a measure can be taken by analyzing this silane. However, in this case, if the gas at the outlet of the silane removal section is analyzed, it is dangerous to take measures in advance because the silane is detected and the silane flows into the NF ₃ removal reaction section at the same time. Therefore, it is necessary to determine the sampling position of the analysis gas in the middle of the silane removal section so that even if some of the chemicals on the upstream side of the silane removal section lose their ability, the remaining chemicals on the downstream side still retain their ability. is there. As a specific method of analysis, an appropriate one may be selected from gas chromatography, IR absorptiometry, potentiostatic electrolysis and the like depending on the conditions.

Further, as a method for confirming the ability of the silane-removing agent, in addition to the above-mentioned method, the present invention also provides a method for arranging a reagent whose color changes due to a reaction with silane so that it can be observed from the outside in the silane-removing portion. By the way. The color-changing agent may be selected from those that change color by the action of silane, and HgCl ₂ or the like is useful. The color-changing reagent can be used as it is or in the form of being dissolved in water and attached to a carrier such as silica gel, porous alumina, or filter paper.

[0017]

EXAMPLES The present invention will be specifically described below with reference to examples.
It Example 1 CuO and Mn₂O₃Balls at a weight ratio of 30:70
Charge in a mill, mix while crushing, and then press-mold.
The product was crushed and adjusted into particles having a diameter of about 3 mm. This
On the pipe wall at the same distance from the gas inlet and outlet pipes at both ends
Measuring gas sampling pipe and internal temperature
With an inner diameter of 24 mm and a length of 500 mm equipped with a thermocouple for
140g was filled in a stainless steel tube to make a silane removal column.
It was NF from one port of the column at room temperature₃= 2%
Flow the remaining N2 gas mixture at a flow rate of 250 cc / min.
Then, when the gas that came out from the other mouth was analyzed, NF
₃= 2% and there was no change. In addition, the temperature in the column
There was no change. Next, NF ₃= 2%, SiH_Four= 2
%, Balance N₂Mixed gas at a flow rate of 250 cc / min
The gas flowing out from the other mouth was analyzed,
F₃= 2%, SiH_Four<10 ppm (below the detection limit)
there were. The internal temperature is highest near the gas inlet, 166 ° C.
(22 ° C. before the start of the experiment).

SiH supplied_FourThe integrated value of 1.0L
Gas was sampled from the hole in the center of the column.
NF when analyzed₃= 2%, SiH_Four= 0.12%
there were. At the same time, the outlet gas sampled at the same time
The composition is NF₃= 2%, SiH _Four<10ppm, no change
won.

Example 2 A glass window made of quartz was provided near the gas sampling port of the stainless steel tube of Example 1, and HgCl ₂ powder was placed inside the window so that it could be observed from the outside. Other conditions are Example 1
When the integrated value of the supplied SiH ₄ reached 0.4 L, the color of the powder changed from white to Hg ₂ C.
l ₂ changes to yellow and is upstream of the position of the window, that is, 1 /
Two of the drugs broke through indicating that SiH ₄ was detected.

Example 3 Supply gas NF ₃ = 2%, SiH ₄ = 0.5%, balance N ₂
When the same procedure as in Example 1 was carried out except that the mixed gas was No. 1, the temperature inside the column was 58 ° C. at the maximum (22 ° C. at the initial stage).
It showed a temperature change sufficient to detect H ₄ .

Example 4 In the same experimental apparatus as in Example 1, at room temperature, a mixed gas of NF ₃ = 2%, SiH ₂ Cl ₂ = 2% and the balance N _{2 was} supplied from one port of the column at a flow rate of 250 cc / min. Analysis of the gas flowing out from the other mouth of the sink showed that NF ₃ = 2%, Si
H ₂ Cl ₂ <10 ppm (below the lower limit of detection).

Example 5 In the same experimental apparatus as in Example 1, at room temperature, a mixed gas of NF ₃ = 2%, SiH ₂ F ₂ = 2% and the balance N _{2 was} supplied from one port of the column at a flow rate of 250 cc / min. When the gas flowing out from the other mouth of the flow was analyzed, NF ₃ = 2%, SiH
₂ F ₂ <10 ppm (below the lower limit of detection).

Example 6 Fe ₂ O ₃ and Mn ₂ O ₃ were mixed in a ball mill at a weight ratio of 30:70 while being crushed, and then pressed and crushed to obtain particles having a diameter of about 3 mm. It was adjusted. this,
The same stainless steel tube as in Example 1 was filled with 140 g to obtain a silane removal column. 250 cc / mi of a mixed gas of NF ₃ = 2% and the balance N ₂ from one port of the column at room temperature.
When the gas flowing at the flow rate of n and flowing out from the other mouth was analyzed, NF ₃ = 2%, which was not changed. There was also no change in the temperature inside the column. Then NF ₃ = 2%, S
iH ₄ = 2%, the remaining N ₂ mixed gas at 250 cc / mi
When the gas flowing at the flow rate of n and flowing out from the other port was analyzed, NF ₃ = 2% and SiH ₄ <10 ppm (below the lower limit of detection). The highest internal temperature reached 134 ° C near the gas inlet (22 ° C before the start of the experiment).

SiH supplied_FourThe integrated value of 1.0L
Gas was sampled from the hole in the center of the column.
NF when analyzed₃= 2%, SiH_Four= 0.87%
there were. At the same time, the outlet gas sampled at the same time
The composition is NF₃= 2%, SiH _Four<10ppm, no change
won.

Comparative Example The same stainless steel tube as in Example 1 was filled with 140 g of KMnO _4, and NF ₃ = 2% from one mouth at room temperature, SiH ₄
= 2%, the remaining N ₂ mixed gas was flowed at a flow rate of 250 cc / min, and the gas coming out from the other port was analyzed. NF ₃ = 2%, SiH ₄ = 2%, and the removal effect was recognized. There wasn't. There was no change in the temperature in the column.

Further, Na ₂ Si is used instead of KMnO _4.
Similar tests were conducted on O ₃ and soda lime (Ca (OH) ₂ + NaOH), but no removal effect was observed.

[0027]

EFFECTS OF THE INVENTION According to the present invention, in the step of removing NF ₃ , it is possible to detect silane contamination in advance and remove it, and it is possible to avoid the risk of explosion due to contamination. ..

Claims (5)

[Claims] 1. A method for removing silane, characterized in that, in the step of removing NF ₃ , the silane mixed in the step is reacted and removed with a removing agent in the preceding stage of the step. 2. Manganese oxide as a silane removal agent,
The method for removing silane according to claim 1, wherein the method comprises at least one chemical selected from copper oxide and iron oxide. 3. The method for removing silane according to claim 1, wherein the inflow of silane into the silane removing section is detected by an increase in temperature. 4. The method for removing silane according to claim 1, wherein the life of the silane-removing agent is detected by analyzing a gas collected from the silane-removing section. 5. The life of the silane removal agent is detected by arranging a substance that changes color by reacting with silane in a window portion provided in a portion that can be observed from the outside in a part of the silane removal portion. The method for removing silane according to claim 1.