JP5423594B2 - Method for removing fluorine-containing compound gas - Google Patents

Description

  In particular, the present invention relates to a method for removing a fluorine-containing compound gas in a gas used for etching or cleaning in a semiconductor manufacturing, a liquid crystal manufacturing, and a solar cell manufacturing, using a remover.

Fluorine-containing compound gases such as carbon tetrafluoride fluorine (CF ₄ ) gas and sulfur hexafluoride (SF ₆ ) gas are used for etching gas and cleaning for removing silicon and tungsten in semiconductor manufacturing, liquid crystal manufacturing and solar cell manufacturing. Used as a gas.

  Many of these fluorine-containing compound gases have high ozone depletion potential (ODP) and global warming potential (GWP), and have recently become a major problem internationally. Therefore, when these gases are used, it is always necessary to decompose and remove them when exhausting the residual gas.

Many of the fluorine-containing compound gases are extremely stable in the atmosphere and are only slightly soluble in water, and therefore cannot be removed by conventional decomposition and removal techniques such as a removal device using an alkaline chemical or a wet scrubber. Also, there is a removal technology by decomposition using combustion gas, but there are undecomposed components remaining though gas decomposition, and generation of fluoride gas such as HF and SiF ₄ after decomposition and removal The problem of having to do arises.

On the other hand, for the fluorine-containing compound gas, a method in which the removing agent is decomposed and removed by heating is adopted in part. These removing agents are mainly composed of calcium compounds such as CaO, CaCO ₃ , and Ca (OH) ₂ and are fixed as calcium fluoride (CaF ₂ ) as shown in the following reaction formulas (1) to (3). In addition to the main component, alumina (Al ₂ O ₃ ) may be mixed and used as a catalyst in order to promote decomposition of the fluorine-containing compound gas. In this case, if the calcium compound fixes the fluorine component as calcium fluoride, the activity of alumina as a catalyst is maintained. However, after the calcium compound becomes calcium fluoride, the alumina itself is also represented by the following reaction formula (4). As shown in the formula, aluminum fluoride (AlF ₃ ) is generated by the fluorine-containing compound gas, or even if it reacts with the fluorine component generated by the decomposition of the fluorine-containing compound gas, aluminum fluoride (AlF ₃ ) is generated and covered. Poisoned and loses its effectiveness as a catalyst. (Patent Documents 1 to 3)
CF ₄ + 2CaO → 2CaF ₂ + CO ₂ (1)
CF ₄ + 2CaCO ₃ → 2CaF ₂ + 3CO ₂ (2)
CF ₄ + 2Ca (OH) ₂ → 2CaF ₂ + CO ₂ + 2H ₂ O (3)
3CF ₄ + 2Al ₂ O ₃ → 4AlF ₃ + 3CO ₂ (4)
In the method in which these removing agents are removed by heating, the removing agent is converted into calcium fluoride (CaF ₂ ) or aluminum fluoride (AlF ₃ ) as the removal process proceeds, and the ability to remove fluorine-containing compound gas is lost. Therefore, it is necessary to replace the remover periodically.

  Furthermore, fluorine-containing compound gases used for cleaning and etching in semiconductor manufacturing, liquid crystal manufacturing, or solar cell manufacturing increase in consumption with the increase in wafer diameter and liquid crystal size, and contain these. The exhaust gas also increases. Therefore, it is necessary to efficiently remove a large amount of the fluorine-containing compound gas contained in the exhaust gas.

  However, generally used fluorine-containing compound gas removal agents have a small amount of fluorine-containing compound gas that can be removed per unit mass of the removal agent (unit treatment amount), and the removal agent must be replaced frequently. There is a problem of not becoming. Replacement of the fluorine-containing gas removal agent is performed by removing the filling cylinder filled with the removal agent from the exhaust gas removal device, opening each of the filling cylinders, taking out the used removal agent, and refilling the unused removal agent. , Takes time and effort.

  On the other hand, the time and labor required to replace the removing agent can be reduced by enlarging the filling cylinder or using a plurality of filling cylinders. However, in these methods, there is a problem of an increase in cost, such as an increase in the amount of removal agent used due to the fact that the equipment is large-scale and a plurality of filling cylinders are required. That is, when the filling cylinder is made larger, the filling cylinder heater is also enlarged, and the power consumption is also increased. In addition, the removal with a plurality of filling cylinders requires a plurality of filling cylinders and a plurality of separate filling cylinder heaters associated therewith.

Japanese Patent No. 3789277 Japanese Patent No. 4156312 Japanese Patent No. 4457648

  As described above, in the method of removing the fluorine-containing compound gas by heating the removal agent, the time and labor required to replace the removal agent in the filling cylinder has been reduced by the response from the equipment side. An increase problem occurs.

  Therefore, in order to reduce the time and labor that can suppress the increase in cost, the present invention provides a method for removing the fluorine-containing compound gas by heating the removing agent, in the fluorine-containing compound gas having an increased unit treatment amount of the fluorine-containing compound gas. It aims to provide a removal method.

  As a result of intensive studies to solve such problems, the present inventor, in a method for removing a fluorine-containing compound gas by heating a fluorine-containing compound gas remover comprising a mixture of a calcium compound and alumina as a component, Discovered that the mixing mass ratio and unit treatment amount differ depending on the treatment flow rate (gas flow rate passed through the removal agent), and the removal agent with a different mixing mass ratio is used to increase the unit treatment amount of the entire removal agent As a result, the present invention was reached.

  More specifically, it can be seen that there is a difference between the mixing mass ratio at which the unit throughput is maximum when the processing flow rate is small and the mixing mass ratio at which the unit processing amount is maximum when the processing flow rate is large. After passing a gas containing a fluorine-containing compound gas through a removal agent having a mixture mass ratio that maximizes the unit throughput when the treatment flow rate is small, a mixture mass ratio that maximizes the unit throughput when the treatment flow rate is large It has been found that the amount of the unit treatment is increased by passing through the removing agent in comparison with the case of passing through the removing agent having the same mixing mass ratio.

  That is, the present invention has at least a first removal step and a second removal step in which a fluorine-containing compound gas is removed using a mixture containing a calcium compound and alumina as a removal agent, and the mixture is used as a removal agent. Furthermore, the mass ratio (Al / (Al + Ca)) of aluminum atoms to the sum of calcium atoms and aluminum atoms in the mixture (Al / (Al + Ca)) is greater than the mixture of the second removal step (first mixture) than the mixture of the first removal step (first mixture). Fluorine, characterized in that a gas containing a fluorine-containing compound gas is brought into contact with the first mixture in the first removal step and then brought into contact with the second mixture in the second removal step. A method for removing contained compound gas is provided.

  Furthermore, in both the first mixture and the second mixture, the mass ratio of aluminum atoms to the sum of calcium atoms and aluminum atoms in the mixture (Al / (Al + Ca)) is in the range of 0.1 or more and 0.8 or less. Therefore, the present invention provides a method for removing a fluorine-containing compound gas.

  According to the present invention, in a method of removing a dry removal agent by heating to a high temperature in a single filling cylinder, the unit treatment amount of the removal agent to be used can be increased, and the replacement frequency of the removal agent can be reduced.

The schematic of the experimental flow of removal of fluorine-containing compound gas is shown.

  Hereinafter, the contents of the present invention will be described in detail.

The fluorine-containing compound gas to be removed is CF ₄ , SF ₆ , C ₄ F ₈ , C ₃ F ₈ , C ₅ F ₈ , C ₄ F ₆ , C ₂ F ₆ , C ₃ F ₆ , CHF ₃ , CH ₃ F, CH ₂ F _{2 and the} like can be mentioned.

Examples of the calcium compound include Ca (OH) ₂ , CaCO ₃ , and CaO.

As alumina (Al ₂ O ₃ ), a commercially available product can be used, or boehmite AlO (OH) is heated to 500 ° C. or more (reaction formula: 2AlO (OH) → 2Al ₂ O ₃ + H ₂ O) What can be obtained can be used.

  The first and second mixtures used in the present invention are prepared by mixing calcium compound and alumina, adding water to calcium compound and alumina, mixing, granulating with a granulator, and drying to remove moisture. Can be obtained.

  The average particle size of the first and second mixtures is preferably φ2 mm or more and φ8 mm or less, more preferably φ4.5 mm or more and φ5.5 mm or less in order to improve gas flowability and unit throughput. If the diameter is less than 2 mm, the pressure loss becomes large and the passage of gas may be hindered. If the diameter exceeds 8 mm, the reaction does not proceed to the inside of the remover and the unit throughput may be reduced.

  The mixing mass ratio A of the first and second mixtures is a formula using the mass of calcium atoms (Ca) contained in the calcium compound and the mass of aluminum atoms (Al) contained in the alumina: A = Al / (Ca + Al ) Represents the value obtained. The mixing mass ratio A is larger in the second mixture than in the first mixture. Furthermore, the mixing mass ratio A is preferably 0.1 ≦ A ≦ 0.8. When A <0.1, the reaction rate with the fluorine-containing compound gas is too low to increase the unit treatment amount. When 0.8 <A, the removal agent is easily pulverized and pulverized. May prevent the passage of gas.

  The temperature when the removing agent and the fluorine-containing compound gas are brought into contact with each other is preferably 500 ° C. or higher and 900 ° C. or lower. If it is less than 500 ° C., a sufficient reaction rate cannot be obtained, and as a result, unreacted fluorine-containing compound gas may remain and be discharged as an outlet gas. If the temperature exceeds 900 ° C, the strength of the stainless steel, which is the material of the filling cylinder, may be lost in a short period of time due to corrosion by the fluorine-containing compound gas.

  The concentration of the fluorine-containing compound gas to be removed is not limited, but in consideration of the load on the material of the filling cylinder and the temperature control of the filling cylinder due to the reaction heat of the fluorine-containing compound and the removing agent, it is 5 vol% or less. It is preferable to dilute with an inert gas such as helium gas, neon gas, argon gas, or nitrogen gas so that it is preferably 2 vol% or less, more preferably 1 vol% or less.

  Hereinafter, the present invention will be described specifically by way of examples.

  FIG. 1 shows a schematic diagram of an experimental flow used in this example. From the cylinder 1 filled with the gas to be removed and the cylinder 2 filled with nitrogen gas (B grade manufactured by Taiyo Nippon Sanso Co., Ltd., which is high-purity nitrogen gas with an oxygen concentration of less than 1 ppm by volume) Filler cylinder 3 (made of stainless steel, inner diameter 30 mm, length 500 mm, removal agent) heated to 600 ° C. by filling cylinder heater 4 as a nitrogen dilution gas at a predetermined flow rate by adjusting the flow rate (not shown in the figure) Is introduced from the upper part of the total filling length of 300 mm) and brought into contact with the removing agent, and a part of the gas discharged from the lower part of the filling cylinder 3 of the filler is converted into a Fourier transform infrared absorption spectrometer 5 (made by MIDAC (model) In IGA-2000)), the fluorine gas-containing compound gas is analyzed at an analysis lower limit of 1 ppm. Based on the analysis result, the removal state of the fluorine gas-containing compound gas can be confirmed. The value obtained from the formula: (1- (removal target gas concentration in exhaust gas / removal target gas concentration in introduced nitrogen dilution gas)) × 100 is defined as a removal rate (%), and the removal rate is 99.9% or less. The total flow rate of the gas to be removed that was introduced up to this time was taken as the processing amount of the filling cylinder.

The fluorine-containing compound gas to be removed is CF ₄ , SF ₆ , C ₄ F ₈ , C ₃ F ₈ , C ₅ F ₈ , C ₄ F ₆ , C ₂ F ₆ , C ₃ F ₆ , CHF ₃ , CH ₃ F or CH ₂ F ₂ is used (each gas uses a semiconductor gas for etching and cleaning having a purity of 99.9% or more manufactured by Taiyo Nippon Sanso Corporation).

The calcium compound and a mixture of alumina removers, calcium compound, Ca _{(OH) 2} (Niimi Chemical Industries Ltd. industrial slaked lime), CaCO ₃ (Shiraishi Calcium Salton 3200 Co., Ltd.), or using CaO . CaO was mixed with Ca (OH) ₂ (industrial slaked lime manufactured by Niimi Kagaku Kogyo Co., Ltd.) and alumina, and then heated at 800 ° C. for 1 hour to release moisture, thereby forming CaO (Ca (OH) ₂ → CaO + H ₂ O). AA100 manufactured by DK Fine Co., Ltd. was used as the alumina.

The mixture of calcium compound and alumina uses a calcium compound and alumina in an amount corresponding to a predetermined mixing mass ratio, and 30% of the total mass is added and mixed, and the granulator (Electric Mincer G manufactured by Hyogo / Miki Trading Center) is mixed. -50) and then dried at 150 ° C. for 2 hours to remove moisture. To obtain a mixture of CaO as the calcium compound, Ca (OH) ₂ is used as the raw material of the calcium compound, and the mixture is obtained in the same manner as described above except that the temperature is set to 800 ° C.

  After drying, a granular remover having an average particle size of 4.5 mm to 5.5 mm was obtained by sieving.

  A removal agent having a predetermined mixing mass ratio is divided into two layers, an upper part and a lower part, and filled in the filling cylinder 3, and the nitrogen dilution gas introduced into the filling cylinder 3 comes into contact with the upper removal agent, Contact with remover.

[Examples 1 to 3, Comparative Examples 1 and 2]
In the above experimental flow, CF ₄ was used as the gas to be removed, the flow rate was adjusted to 0.01 L / min, the nitrogen gas was adjusted to 1 L / min, and the nitrogen dilution gas was supplied to the filling cylinder 3. As the remover, a mixture of CaO and alumina was used, and a mixture having a mixing mass ratio A of 0.3 at the top and a mixing mass ratio A of 0.5 at the bottom was used. Of the filling length of 300 mm, the upper filling length was changed to 240 (Example 1), 270 (Example 2), 285 mm (Example 3), 300 mm (Comparative Example 1), 0 mm (Comparative Example 2), The lower filling length was also adjusted accordingly and an experiment was conducted for each.

The results are shown in Table 1. The processing amount of the filling cylinder is 5.70 L in Example 1, 5.95 L in Example 2, 5.55 L in Example 3, 4.95 L in Comparative Example 1, 4.30 L in Comparative Example 1, and the mixed weight. Compared with the case where only the ratio A = 0.3 is filled (Comparative Example 1) and the case where only the mixing weight ratio A = 0.5 is filled (Comparative Example 2), in the case of Examples 1 to 3, one filled cylinder It can be confirmed that the per-process amount is increasing.

[Examples 4 to 33]
In the above experimental flow, instead of CF ₄ , SF ₆ (Examples 4 to 6), C ₄ F ₈ (Examples 7 to 9), C ₃ F ₈ (Examples 10 to 12), instead of CF ₄ , C ₅ F ₈ (example _13~15), C 4 _{F 6} (example _16~18), C 2 _{F 6} (example _19~21), C 3 _{F 6} (example 22 to 24), CHF ₃ (example 25-27), except using _CH 3 F (example 28 to 30), _CH 2 _{F 2} (example 31 to 33) respectively, it was performed in the same manner as in example 1-3.

The results are shown in Table 2. It can be confirmed that various fluorine-containing compound gases can be removed.

[Examples 34 to 39]
Similar to Examples 1 to 3 except that Ca (OH) ₂ (Examples 34 to 36) and CaCO ₃ (Examples 37 to 39) are used instead of CaO for the calcium compounds of the upper and lower removers, respectively. Went to.

  The results are shown in Table 3. The processing amount of the filling cylinder was 5.75 L in Example 34, 5.90 L in Example 35, 5.55 L in Example 36, 5.50 L in Example 37, 5.94 L in Example 38, and Example 39. It was 5.54 L, and it was confirmed that various calcium compounds could be removed. In the case of Examples 34 to 39, compared with the case where only the mixing weight ratio A = 0.3 was filled (Comparative Example 1). It can be confirmed that the processing amount per cylinder is increasing.

[Examples 40 to 42]
The type of calcium compound used, CaCO ₃ (Example 40) into CaO and bottom to top, CaO (Example 41) CaCO ₃ and lower in the upper, Ca _(OH) into CaO and bottom to top ₂ (Example 42 ) Was performed in the same manner as in Example 2 except that.

The results are shown in Table 3. The processing amount per one filling cylinder was 5.93 L in Example 40, 5.90 L in Example 41, and 5.92 L in Example 42, both of which were obtained using Example 2 using only CaO as the calcium compound. Similar results were obtained. It can be confirmed that the same effect can be obtained even when different types of calcium compounds are used in the upper and lower removers.

[Example 43, Comparative Example 3]
The flow rate of CF ₄ is 0.03 L / min, the flow rate of nitrogen gas is 3 L / min, and the upper filling length is 180 (Example 43) and 300 (Comparative Example) out of the total filling length 300 mm in the filling cylinder 3. The same procedure as in Example 2 was carried out except that the lower filling length was adjusted accordingly.

  The results are shown in Table 4. The processing amount of the filling cylinder is 3.70 L in Example 43 and 3.45 L in Comparative Example 3, and even when the flow rate in this example is filled with only the mixing weight ratio A = 0.3 (Comparative Example 3). In comparison, in the case of Example 43, it can be confirmed that the processing amount per one filling cylinder is increased.

[Example 44, comparative example 4]
The flow rate of CF ₄ is 0.10 L / min, the flow rate of nitrogen gas is 10 L / min, and the upper filling length is 60 (Example 44) and 300 (Comparative Example) out of the total filling length 300 mm in the filling cylinder 3. Example 4 was performed in the same manner as in Example 2 except that the lower filling length was adjusted accordingly.

The results are shown in Table 4. The processing amount of the filling cylinder is 2.40 L in Example 44 and 0.90 L in Comparative Example 4, and even when only the mixing weight ratio A = 0.3 is filled at the flow rate in this example (Comparative Example 4). In comparison, in the case of Example 44, it can be confirmed that the processing amount per one filling cylinder is increased.

[Examples 45 to 47, Comparative Examples 5 and 6]
The flow rate of CF ₄ is 0.005 L / min, the flow rate of nitrogen gas is 1 L / min, and the upper filling length of the total filling length 300 mm in the filling cylinder 3 is 60 (Example 45), 30 (Example) 46), 15 (Example 47), 300 (Comparative Example 5) and 0 mm (Comparative Example 6), and the same procedure as in Example 2 was performed except that the lower filling length was adjusted accordingly.

The results are shown in Table 5. The processing amount of the filling cylinder is 5.71 L in Example 45, 5.94 L in Example 46, 5.55 L in Example 47, 4.95 L in Comparative Example 5, and 4.29 L in Comparative Example 6, and this example Also in the flow rate in Example 4, compared with the case where only mixing weight ratio A = 0.3 is filled (Comparative Example 5) and the case where only mixing weight ratio A = 0.5 is filled (Comparative Example 6), Examples 45-47. In this case, it can be confirmed that the processing amount per one filling cylinder is increased.

[Examples 48 to 50, Comparative Examples 7 and 8]
The flow rate of CF ₄ is 0.015 L / min, the flow rate of nitrogen gas is 1 L / min, and the upper filling length is 60 (Example 48) and 30 (Example) among the total filling length 300 mm in the filling cylinder 3. 49), 15 (Example 50), 300 (Comparative Example 7), 0 mm (Comparative Example 8), and the same procedure as in Example 2 except that the lower filling length was adjusted accordingly.

The results are shown in Table 6. The processing amount of the filling cylinder is 5.12 L in Example 48, 5.34 L in Example 49, 4.95 L in Example 50, 4.36 L in Comparative Example 7, and 3.75 L in Comparative Example 8, and this example In comparison with the case where only the mixing weight ratio A = 0.3 is filled (Comparative Example 7) and the case where only the mixing weight ratio A = 0.5 is filled (Comparative Example 8), the flow rates in Examples 48 to 50 are also compared. In this case, it can be confirmed that the processing amount per one filling cylinder is increased.

[Comparative Examples 9 to 11]
Example 1 except that the mixing weight ratio A of the upper and lower removing agents is smaller in the lower part than in the upper part, and the mixing weight ratio A is set to 0.5 for the upper part and 0.3 for the lower part, respectively. Performed in the same manner as ˜3.

The results are shown in Table 7. The amount of processing per one filling cylinder is 4.25 L when the upper filling length is 240 mm (Comparative Example 9), 4.26 L when the upper filling length is 270 mm (Comparative Example 10), and the upper filling length. Is 4.21 L when 285 mm (Comparative Example 11), and the mixing weight ratio A of the upper and lower removing agents in Examples 1 to 3 is 0.3 when the mixing weight ratio A is 0.3 and 0.5 at the lower part, respectively. It can be confirmed that the processing amount per one filled cylinder is small compared to the case where the removing agent is filled.

  The present invention is particularly useful as a fluorine-containing compound gas remover in gases exhausted and used for etching and cleaning in semiconductor manufacturing, liquid crystal manufacturing, and solar cell manufacturing.

1 ... cylinder (gas to be removed)
2 ... bomb (nitrogen gas)
3 ... remover filling cylinder 4 ... filling cylinder heater 5 ... Fourier transform infrared absorption spectrometer

Claims (2)

In a method of removing fluorine-containing compound gas using a mixture containing a calcium compound and alumina as a remover,
At least a first removal step and a second removal step using the mixture as a removal agent;
Furthermore, the mass ratio (Al / (Al + Ca)) of aluminum atoms to the sum of calcium atoms and aluminum atoms in the mixture is greater than the mixture of the first removal step (first mixture) (second mixture). The mixture) is larger,
A method for removing a fluorine-containing compound gas, comprising bringing a gas containing a fluorine-containing compound gas into contact with a first mixture in a first removal step and then bringing the gas into contact with a second mixture in a second removal step. In both the first mixture and the second mixture, the mass ratio of aluminum atoms to the sum of calcium atoms and aluminum atoms in the mixture (Al / (Al + Ca)) is in the range of 0.1 or more and 0.8 or less. The method for removing a fluorine-containing compound gas according to claim 1.

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