JP2823486B2 - NF (3) processing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION In addition to rocket fuels, NF ₃ has recently attracted attention as a dry etching agent or fluorinating agent for LSIs.
Contamination of perfluorocarbon-based LSI substrate occurring during etching compared with the etching agent, such as F ₄ has advantages such that very little. On the other hand, NF ₃ is extremely stable in the atmosphere, is slightly soluble in water, and has a TL
It is a toxic gas of V10 ppm, and when it is used, its treatment is always required when exhausting residual gas and the like. The present invention relates to a method for treating such a gas containing NF ₃ .

[0002]

2. Description of the Related Art As a method for treating NF ₃ , we have used various metals such as Si, their non-oxide compounds and NF ₃ at 200 ° C. to 800 ° C.
And proposed a method for collecting the obtained fluoride gas. (Japanese Patent Publication No. Sho 63-48570) Among these reactants, metal Si is particularly reactive and inexpensive, and the reaction product (SiF ₄ ) has a sufficient vapor pressure at room temperature.
Therefore, SiF _{4, which} can be easily discharged from the system, has a feature that it can be completely treated with an alkali, and it can be said that SiF ₄ is most suitable for NF ₃ treatment.

However, in this treatment method, when oxygen coexists in NF ₃ , the surface of Si is oxidized by oxygen and NF ₃
Since the processing speed decreases, the reaction temperature must be raised to obtain the required processing speed, which requires extra heat energy for the processing, and the material required for the reactor is also of high quality. There was a problem.

The present invention has been made in view of such a point, and an object of the present invention is to provide a method for treating NF ₃ which does not decrease the NF ₃ treatment speed even when oxygen coexists.

[0005]

[Means for Solving the Problems] As a result of studying the above-mentioned problems, the present inventors have found that a small amount of a chemical on the Si surface can be used as an agent capable of treating NF ₃ gas containing oxygen while utilizing the advantages of Si. The present invention was found to be effective when the metal Cu was impregnated as a catalyst.

[0006] Metallic Cu itself is NF under heating.
_ThreeCan be decomposed, but only plain NF _ThreeUsed as a treatment agent for
There is a problem. For example, NF for plain Cu_ThreeAnd react
When the solid fluoride (CuF_TwoWhich generates this
NF because it covers the surface of Cu_ThreeDiffusion is hindered,
The rate goes down. CuF_TwoPowder may block the reactor
And so on. On the other hand, Si is NF_ThreeAfter processing
Reaction product is gaseous SiF_FourIt becomes like plain Cu
NF_ThreeWhere oxygen coexists
In this case, the problem described in the previous section is included. Like this
This is a perfect NF by itself_ThreeUnable to process
The present inventors have successfully combined Si and Cu.
We succeeded in creating new functions by combining
Was.

Although the details of the mechanism of the NF ₃ decomposition reaction of Si with Cu attached to the surface are unknown, at least Cu
Can be said to act as a catalyst from the following two points. That is, when NF ₃ is decomposed by the chemical, NF ₃ is treated by hundreds or thousands of times of the chemical equivalent of Cu attached thereto, and the decomposition product at that time is SiF ₄ and reacts. The main agent is Si. Further, the catalytic effect of Cu is very high in that it lasts until substantially the entire amount of Si is consumed.
The magnitude of the treatment capacity of the agent with respect to the O ₂ coexisting NF ₃ exhaust gas does not depend much on the method of attaching Cu, for example, as described in (a) to (d) below. If it is in the state, the effect will be exhibited.

[0008] Since the treatment capacity of the chemical for the NF ₃ exhaust gas coexisting with O ₂ depends on the amount of Cu impregnated per unit amount of Si, it should be adjusted within the following range of the optimum amount of impregnation. That is, the amount of Cu to be attached to the Si surface is at least 0.01% by weight in terms of weight ratio, and if it is less than this, a sufficient effect on the treatment of NF ₃ exhaust gas containing oxygen cannot be expected. On the other hand, it can be said that there is essentially no upper limit of the amount of Cu, but when Cu is attached by the method shown in this specification, if over 2.0 wt%, Cu covers the Si surface, and NF ₃ and Si Contact is hindered and the treatment effect is reduced. In treating NF ₃ exhaust gas with oxygen, the amount of Cu that maximizes the treatment rate is 0.05 to 0.4 wt%, and even if a large amount of Cu is added unnecessarily, the effect corresponding to it cannot be expected and it is uneconomical. Therefore, the upper limit of the amount of Cu to be applied should be 2.0% in practical use. The amount of Cu impregnated by weight ratio is NF
The value gradually increases as Si reacts with ₃ and consumes Si (since Cu is not consumed). Needless to say, the amount of Cu impregnated here refers to the drug in the initial state. Absent.

Various commonly known methods can be applied to deposit Cu on the Si surface. For example,
(a) a method of plating Cu on a Si surface by an electroless method,
(b) a method in which metal Cu and Si are mixed and heat-treated in an inert atmosphere such as N ₂ to form an alloy with Cu on the Si surface; (c)
Mixing the cuprous and Si chloride N ₂ atmosphere 400 to 500 ° C.
And (d) a method of spraying Cu on the Si surface. However, any method is effective.

[0010] Further, as an embodiment of the present invention, from the viewpoint that the internal space of the reactor should be used effectively, it is desirable to use a method in which only necessary and sufficient Cu is attached as a catalyst to the surface of Si as a main agent. However, even in the method in which Si and Cu are simply simultaneously charged into the reactor, an active catalyst region as shown in (b) is formed at the contact portion between the Si particles and the Cu particles, which is effective for treating NF ₃ exhaust gas coexisting with O _2. Is still the same.

[0011]

The present invention will be described in more detail with reference to the following Examples, but it should not be construed that the invention is limited thereto.

Comparative Example 1 A 1/2 inch Ni pipe was used as a reactor and was horizontally fixed in an annular furnace. The reaction agent used was one having Si particles sieved to adjust the particle diameter to 3 mm to 5 mm. A zone having a length of about 100 mm of the reactor was filled with about 11 g of the reactant and heated by a heater. As a simulated exhaust gas (NF ₃ =
2%, N ₂ = 98%) and (NF ₃ = 2%, O ₂ = 2
%, N ₂ = 96%) was flowed at 1 liter / min, and the NF ₃ concentration of the outlet gas was analyzed 10 minutes after the treatment was started. (The gas concentration is a volume ratio.
Table 1 shows the results. Note that SiF ₄ having a concentration corresponding to the decomposed NF ₃ was detected in components other than NF _{3 in the} outlet gas.

If O ₂ = 0%, NF ₃ is easily decomposed by Si, but if O ₂ coexists in NF ₃ , the TLV value becomes 1
It is very difficult to treat to 0 ppm or less, and this comparative example was not achieved even at a temperature of 800 ° C. If the NF ₃ of the treated gas is reduced to 10 ppm or less, the reactor becomes large in order to secure the reaction time, and the installation space, manufacturing cost, and running cost become uneconomical.

Example 1 Table 1 shows the results of experiments conducted in the same manner as in Comparative Example 1 except that Si to which Cu was added under various conditions was used as a reactant. According to the method described above, the Cu
(a) to (d).

Impregnation method (a): The bath of CuSO ₄ .5H ₂ O and Rossell salt was adjusted to pH = 12.3 with NaOH,
After immersion of the grains, the grains were reduced by adding HCHO and plated with Cu. Si particles were taken out, washed with water, dried and used.

Impregnation method (b): Si particles and Cu powder were mixed in the same amount and heat-treated at 900 ° C. for 1 hour in an N ₂ atmosphere to form a Cu alloy layer on the Si surface. A material obtained by removing excess Cu powder by sieving was used.

Impregnation method (c): The same amount of Si particles and CuCl were mixed and heat-treated at 450 ° C. for 1 hour in an N ₂ atmosphere to form a reduced Cu layer on the Si surface. Excess CuCl powder was used after sieving.

Adhesion method (d): Si particles obtained by plasma-spraying Cu were used.

[0019]

[Table 1]

COMPARATIVE EXAMPLE 2 The composition of the supplied gas was as follows: (NF ₃ = 2%, N ₂ = 98%), the supply gas flow rate: 1 liter / min, temperature : NF ₃ in the outlet gas was continuously analyzed at 700 ° C. until about 80% of the drug was consumed. The result is shown in FIG.

In this comparative example in which O ₂ = 0%, NF ₃ was easily decomposed simply with Si, and NF ₃ was not detected in the outlet gas initially (3 ppm>). As the Si was consumed, a space was created above the drug filling section of the horizontally arranged reactor, and NF ₃ short-passing this space was detected in the outlet gas, and its concentration gradually increased. . However, the supplied NF ₃ (inlet concentration = 2
0000 ppm) means that even when 80% of the charged amount of Si is consumed 8 hours after the start of the treatment, most of the Si is still decomposed, and NF ₃ is efficiently decomposed by a small amount of Si. Is shown.

COMPARATIVE EXAMPLE 3 The composition of the supplied gas was determined using Si-only particles as a drug and using the same apparatus as in Comparative Example 1: (NF ₃ = 2%, O ₂ = 2%, N ₂ = 96)
%), Supply gas flow rate: 1 liter / min, temperature: 70
The outlet gas NF ₃ was continuously analyzed at 0 ° C. until about 80% of the drug was consumed. The result is shown in FIG.

[0023] In this comparative example the NF ₃ O ₂ coexist NF ₃ concentration in the outlet gas at the beginning of 200ppm or even there Si Plain is difficult to completely decomposing NF ₃ for coexistence of O ₂ It indicates that there is.

Example 2 The chemicals used in Example 1 prepared by the Cu impregnation method (a) (plating method) were supplied to the same apparatus as in Comparative Example 1 in the supply gas composition: (NF
₃ = 2%, O ₂ = 2%, N ₂ = 96%), supply gas flow rate: 1 liter / min, temperature: 700 ° C. The outlet gas NF ₃ was consumed until about 80% of the drug was consumed. Analyzed continuously. The result is shown in FIG.

From the present embodiment, it can be seen that Cu impregnated S
i The effect of even if the O ₂ = 2% coexistence, O ₂ = S 0%
It can be seen that NF ₃ can be decomposed as efficiently as in the case of i-only (Comparative Example 2). Moreover, this Cu catalytic effect continues until at least 80% or more (perhaps the entire amount) of Si is consumed.

[0026]

According to the present invention, it has become possible to remove the NF ₃ exhaust gas containing oxygen at a low temperature without lowering the processing speed.

[Brief description of the drawings]

FIG. 1 shows the treatment results of NF ₃ exhaust gas of Example 2 and Comparative Examples 2 and ₃ .

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-7-762 (JP, A) JP-A-5-192538 (JP, A) JP-A-2-273511 (JP, A) JP-A 63-762 12322 (JP, A) (58) Field surveyed (Int. Cl. ⁶ , DB name) B01D 53/34, 53/54, 53/68

Claims (1)

(57) [Claims] 1. A method for treating exhaust gas, which comprises contacting an exhaust gas containing NF ₃ as a harmful component with a treating agent to remove NF ₃ from the exhaust gas, wherein the treating agent has a weight ratio of 0.01 to 2. processing method of NF _3, which comprises using a 0 wt% of Si was impregnated with Cu.