JPH09157852A - Vacuum vapor-phase reactor and treatment of its waste gas - Google Patents

Abstract

PROBLEM TO BE SOLVED: To decontaminate a cleaning gas such as gaseous ClF3 and to easily clean a reaction chamber without using a dry decontaminator in a vacuum vapor-phase reactor using a water-sealed pump, with respect to the vacuum vapor-phase reactor and the treatment of its waste gas. SOLUTION: In the vacuum vapor-phase reactor having a mechanism for feeding gaseous ClF3 to remove the reaction product depositing in a reaction chamber 1, a water-sealed pump 10 with at least the impeller, side plate and intermediate wallboard formed with a corrosion-resistant metallic material such as stainless steel and Ni-base metal is provided in a gas exhaust pipe 6 after the mechanical booster pump 7 to discharge air, and the gaseous CIF3 and gasified reaction product are decontaminated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to chemical vapor deposition (c) of thin films necessary for manufacturing semiconductor devices or solar cells.
chemical vapor deposition:
The present invention relates to a reduced pressure gas phase reactor for forming by applying the CVD method and an exhaust gas treatment method thereof.

Currently, when forming a thin film as described above,
A reduced pressure gas phase reaction device is often used, in which the reaction chamber is depressurized, the mean free path of gas molecules is increased, and a thin film is formed by surface reaction to improve film thickness uniformity. During the formation, a thin film is deposited not only on the substrate but also in the reaction chamber, so it is necessary to clean it.

In this case, to perform cleaning by wet cleaning, it is very troublesome to go through the steps of lowering the temperature of the CVD furnace, disassembling the apparatus, cleaning the wet apparatus, assembling the apparatus, and raising the temperature of the CVD furnace.

In order to avoid this complication, cleaning
It is said that dry cleaning using NF ₃ gas or ClF ₃ gas as a gas is adopted, and in particular, dry cleaning using ClF ₃ gas can be easily performed because a plasma generator is unnecessary.

However, in the dry cleaning using ClF ₃ gas, there is a problem that mixing with a hydrogen-based film-forming gas is dangerous, so that there is a problem that it must be avoided, and in the exhaust gas treatment thereof. However, since there is a problem that it cannot be diluted and discharged into the atmosphere and requires a dedicated expensive detoxification device, these problems must be solved, and according to the present invention, Can meet.

[0006]

2. Description of the Related Art FIG. 9 is an explanatory view of a main part of a reduced pressure gas phase reactor for explaining a conventional technique.

In the figure, 1 is a reaction chamber, 2 is a thin film forming gas supply pipe, 3 is a furnace cleaning gas supply pipe, 4 is a SiH ₄ cylinder, 5 is a ClF ₃ cylinder, 6 is a gas exhaust pipe, 7 is a mechanical booster pump (vacuum pump), 8 is an oil rotary pump (vacuum pump), 9 is an ejector pump, 10 is a water ring pump, 11 is a gas exhaust pipe, 12
A and 12B are switching valves, and 13 is a dry abatement device dedicated to ClF ₃ gas. Although not shown, the supply pipe 2 is provided with a required number of valves, a mass flow controller, and the like, and is connected with an N ₂ gas supply system for purging and dilution.

According to the apparatus shown in FIG. 9, (1) formation of a polycrystalline silicon thin film using SiH ₄ gas as a source gas (2) case of performing in-furnace cleaning using ClF ₃ gas as a cleaning gas explain.

(A) A semiconductor wafer (not shown) is set at a predetermined position in the reaction chamber 1, and the switching valve 1
2A is open and the switching valve 12B is closed.

(B) The vacuum pump system consisting of the mechanical booster pump 7 and the oil rotary pump 8 is operated to evacuate the reaction chamber 1 to the ultimate vacuum level to reduce the pressure.

(C) The thin film forming gas supply pipe 2 is used to perform sufficient purging with N ₂ gas.

(D) The reaction chamber temperature is 620 ° C., the reaction chamber pressure is 0.3 Torr, and the SiH ₄ flow rate is 90.
A polycrystalline silicon thin film is formed on the semiconductor wafer as [sccm].

At this time, an ejector pump 9 and a water seal pump 10 are provided up to an exhaust duct (not shown) connected to the collecting scrubber, and an exhaust gas treatment system is constituted by them. It functions as a simple and inexpensive abatement device for SiH ₄ gas, and as a final-stage vacuum pump that is easy to maintain.

(E) After about 36 minutes, a polycrystalline silicon thin film having a thickness of, for example, 400 nm is grown. Therefore, evacuation and purging with N ₂ gas are sufficiently performed again. A semiconductor wafer whose surface is covered with a polycrystalline silicon thin film is taken out of the reaction chamber 1.

The operations (A) to (E) are repeated 20 to 30 times, and when the total film thickness of the polycrystalline silicon film attached to the wall surface in the reaction chamber 1 becomes 10 [μm], The inside of the furnace is cleaned with ClF ₃ gas as described in (2) above.

(A) The switching valve 12A is closed and the switching valve 12B is opened, and the vacuum pump system consisting of the mechanical booster pump 7 and the oil rotary pump 8 is operated to evacuate the reaction chamber 1 to the ultimate vacuum level. To reduce the pressure. Of course, in this case, no semiconductor wafer is set in the reaction chamber 1.

(B) Furnace cleaning gas supply pipe 3
Is used to perform sufficient purging with N ₂ gas.

(C) The temperature of the reaction chamber is 620 [° C.], the pressure in the reaction chamber is 1.7 [Torr], the ClF ₃ gas flow rate is 200 [sccm], and the N ₂ gas flow rate is 5 [slm]. The unnecessary polycrystalline silicon film attached to the inner wall and jigs is removed by etching.

By the etching according to the above conditions, the polycrystalline silicon film having a thickness of 10 μm attached to the inner wall of the reaction chamber 1 can be completely removed in 2 hours.

In carrying out the cleaning, the introduction of ClF ₃ gas under reduced pressure or the dilution with an inert gas depends on the partial pressure of ClF ₃ gas or the ambient temperature. This is because corrosion of the stainless steel of the flange material and the viton ring of the seal material may significantly progress, and is to be suppressed.

By the way, ClF ₃ used for cleaning
If the gas is discharged into the atmosphere as it is, it reacts with water to produce compounds such as HF, HCl, and Cl ₂ .
In order to prevent this, the reduced pressure gas phase reactor shown in FIG.
Detoxification is performed using a dry type detoxification device 13 dedicated to ClF ₃ gas.

FIG. 10 is an explanatory view of essential parts showing a part of a reduced pressure gas phase reaction apparatus for explaining another conventional technique.
The same symbols as those used in FIG. 9 represent the same parts or have the same meanings.

In the apparatus shown in FIG. 10, SiH ₄ gas, which is a source gas for forming a thin film, is removed by using a dry type abatement apparatus 14 as in the case of removing ClF ₃ gas. .

The removal of the SiH ₄ gas for forming the thin film should be carried out not only by using the dry removal device 14 described with reference to FIG. 10 but also by using the ejector pump 9 and the water seal pump 10 shown in FIG. Is also known (if necessary,
(See JP-A-55-34158).

According to the conventional technique, the exhaust gas of the Si-based film forming gas causes a combustion reaction with the air sucked from the ejector pump 9 immediately before the water seal pump 10 to produce SiH ₄ +.
Due to the reaction of 2O ₂ → SiO ₂ + 2H ₂ O, almost S
Change to iO ₂ and H ₂ O, that is, S with explosive properties
iH ₄ becomes safe and minute quartz glass particles and water.

These products are pumped from the ejector pump 9 to a water ring pump 10, where the water ring pump 10
Functions as a vacuum pump having an exhaust rate of 100 [m ³ / hour], and safely treats the reaction products such as Si dust generated in the reaction chamber 1 together with the quartz glass particles by using a water seal.

The ejector pump 9 and the water ring pump 1
In the technique of removing the source gas by using 0, for example, (1) the concentration of SiH ₄ supplied into the reaction chamber 1 can be increased to 100% depending on the case.

(2) Compared with the conventional oil rotary pump,
It is possible to increase the concentration of SiH ₄ that can be introduced to about 100 times.

(3) The maintenance frequency can be reduced to 1/100, and the danger can be eliminated.

(4) The ultimate pressure can be made equal to or lower than that of the conventional device.

(5) Since the scrubber is a single-purpose scrubber against explosive gas and toxic gas, it is possible to save labor in a factory facility.

(6) Compared with an ordinary chemical plant, the device can be downsized and the space gain is large. It has many advantages and is a very attractive method.

[0033]

In the conventional reduced pressure gas phase reaction apparatus described with reference to FIG. 9, the water sealing pump 10 and the dry type detoxifying apparatus 13 are switched valves 12A and 12B.
When the cleaning gas is removed, the gas exhaust pipe 6 associated with the water ring pump 10 serves as a decompression system, and the gas exhaust pipe 11 associated with the dry abatement device 13 is operated. Is an atmospheric pressure system.

Therefore, in order to avoid danger, the switching timing and sequence of the switching valves 12A and 12B are very complicated. In addition, the dry type abatement device 13
Space is required, and the cost for exchanging the adsorbent is required, and its running cost cannot be ignored.

In the conventional reduced pressure gas phase reaction apparatus described with reference to FIG. 10, since the dry type abatement apparatus is used for both the cleaning gas and the thin film forming gas, both of the gas exhaust lines 6 and 11 are large. Since it is an atmospheric pressure system, the switching timing and sequence of the switching valves 12A and 12B are simpler than those of the conventional reduced pressure gas phase reaction apparatus shown in FIG.

However, since a dry type abatement device 14 for removing the gas for forming the thin film must be added,
The occupied space becomes larger, and the running cost also rises.

In the invention disclosed in Japanese Patent Laid-Open No. 55-34158, since the thin film forming gas is removed by using the ejector pump and the water ring pump, the switching valve switching timing and sequence are used. However, it is impossible to clean the reaction chamber and the like by using a cleaning gas such as ClF ₃ gas.

The reason is, of course, that the ClF ₃ gas is a corrosive gas, so that when it is exhausted with a water seal pump, it reacts with the seal water in the water seal pump to produce hydrofluoric acid or hydrochloric acid, The purpose is to corrode and damage metal parts.

The present invention relates to a reduced pressure gas phase reactor using a water ring pump, without using a dry type abatement device.
Enables the removal of cleaning gas such as F ₃ gas,
Try to facilitate cleaning of the reaction chamber.

[0040]

In the present invention, a water ring pump is used in a depressurized gas phase reactor, and the exhaust gas is removed by using the water ring pump. As a cleaning gas for the reaction chamber, ClF ₃ gas is used. However, if water is used as it is, the water ring pump will be damaged if it is removed. Therefore, it is basically necessary to construct the water ring pump with a corrosion resistant material or to dilute the ClF ₃ gas sufficiently. ing.

From the above, in the reduced pressure gas phase reaction apparatus and the exhaust gas treatment method thereof according to the present invention, (1)
A vacuum pump (for example, a mechanical booster) is used in a reduced pressure gas phase reactor having a mechanism for feeding and cleaning ClF ₃ gas in order to remove a reaction product attached to the inside of the reaction chamber (for example, the reaction chamber 1). -Gas exhaust line after pump 7 and oil rotary pump 8) (for example, gas exhaust pipe 6)
At least the impeller, the side plate, and the intermediate wall plate, which are inserted into the exhaust pipe to remove the ClF ₃ gas and the gasified reaction product, are made of a corrosion-resistant metal material selected from stainless steel or Ni-based metal. A water ring pump (for example, a water ring pump 10), or

(2) In the above (1), an ejector pump (for example, an ejector pump 9) which is connected immediately before the water ring pump and which dilutes the ClF ₃ gas and the gasified reaction product with the sucked gas is used. Is it characterized by being prepared,
Or,

(3) In the above (1) or (2), at least the roughing or auxiliary vacuum pump of the vacuum pumps is a dry pump or an oil rotary pump (for example, the oil rotary pump 8: see FIG. 7). Characterized by being either, or

[0044] (4) a reaction chamber (e.g., reaction chamber 1) and the step of performing cleaning by fed the ClF ₃ gas in order to remove reaction products adhering to the inside, ClF ₃ gas discharged from said reaction chamber And a water ring pump (for example, the water ring pump 10) in which the gasified reaction product is inserted into a gas exhaust line (for example, the gas exhaust pipe 6) after the vacuum pump (for example, the mechanical booster pump 7 and the oil rotary pump 8). )
Diluting the metal at the inlet to a concentration that does not corrode the metal, and taking in the diluted ClF ₃ gas and the gasified reaction product into the sealed water in the water seal pump for detoxification. Or including a process, or

[0045] (5) a reaction chamber (e.g., reaction chamber 1) and the step of performing cleaning by fed the ClF ₃ gas in order to remove reaction products adhering to the inside, ClF ₃ gas discharged from said reaction chamber And the gasified reaction product is inserted into a gas exhaust line (for example, the gas exhaust pipe 6) subsequent to the vacuum pump (for example, the mechanical booster pump 7 and the oil rotary pump 8) and a liquid sealing tank (for example, the liquid sealing tank 16: (See Figure 8)
And a water-sealing pump (for example, a water-sealing pump 18:
8)) to introduce an alkaline substance (for example, caustic soda) into the sealing liquid to neutralize the acid wastewater and remove the harm, or

(6) In the above (4) or (5), the ClF ₃ gas and the gasified reaction product are diluted with the gas sucked by the ejector pump connected immediately before the water seal pump. Feature or

(7) In the above (4), (5) or (6), a dry pump or an oil rotating device which constitutes a vacuum pump interposed between the reaction chamber and the water seal pump to perform vacuuming It is characterized in that rough pumping or the like is performed by a pump (for example, an oil rotary pump 8: see FIG. 7).

By adopting the above means, it is possible to remove ClF ₃ gas, which is a cleaning gas, and gasification reaction products, and a thin film, without attaching a dry abatement device to the reduced pressure gas phase reactor. Since the removal of the reactive gas for formation can be carried out by the water ring pump, the removal cost can be reduced and the occupied area of the reduced pressure gas phase reactor can be reduced, and It is possible to easily avoid the risk that the ClF ₃ gas and the hydrogen-based film forming gas are mixed.

[0049]

BEST MODE FOR CARRYING OUT THE INVENTION As described above, when the ClF ₃ gas is removed by using the water ring pump in the reduced pressure gas phase reactor, the corrosion of the water ring pump poses a problem. Conducted an experiment on it.

FIG. 1 is an explanatory view of the main part of a reduced pressure gas phase reaction apparatus used in an experiment. The same symbols as those used in FIG. 9 represent the same parts or have the same meaning. 1
The difference between the reduced pressure gas phase reaction apparatus shown in Fig. 9 and the reduced pressure gas phase reaction apparatus shown in Fig. 9 is that the reduced pressure gas phase reaction apparatus shown in Fig. 1 does not have a dry abatement device.

In the experiment, the reaction chamber 1 was composed of two mechanical booster pumps 7 and 15, an ejector pump 9 and a water ring pump 10 in a reduced pressure gas phase reactor capable of cleaning with ClF ₃ gas. ClF ₃ gas was introduced into the vacuum pump unit, and the durability of the water ring pump 10 was examined.

The conditions for flowing ClF ₃ gas are: ClF ₃ gas flow rate 200 [sccm], N ₂ gas flow rate 28 [liter / minute], and air 50 [liter / minute], and at the inlet of the water seal pump 10. ClF ₃ gas concentration at 0.24
It is [%]. Air is introduced by the ejector pump 9, and the amount of sealing water in the water sealing pump is 15
[L / min].

Here, in order to carry out the acceleration test, continuous operation was carried out in a state where there was no deposit on the inner wall of the reaction chamber 1, that is, in a state where cleaning was not performed.

FIG. 2 is a table in which the results obtained in the experiment are summarized in a table. The types of the water-sealed pumps shown in FIG. 2, that is, the conventional type, the main part BC type, and the all stainless type are concrete. For the details, refer to FIG. In addition, in each drawing, the notation BC is C as seen in the JIS standard.
u, Sn, and Zn alloys, and SUS, SCS, and FC in FIG. 3 represent stainless steel, stainless casting, and cast iron, respectively, as shown in JIS standards, and the numerical values following the abbreviations. Indicates the types of materials, and those having different numerical values have subtle differences in the chemical composition of the alloy and have properties corresponding to the composition.

In the conventional water ring pump, the impeller (impeller) is made of stainless steel, but the intermediate wall plate and the side plates are made of cast iron.

As shown in FIG. 2, the ultimate pressure of the reaction chamber 1 in the reduced pressure gas phase reactor was initially 0.03 [To.
rr], which deteriorated to 0.18 [Torr] after introducing 277 [liters] of ClF ₃ gas, and although not shown in the table, at this time, the suction port pressure of the ejector pump 9 is It rose from 6 [Torr] to 8 [Torr].

From these results, the performance of the water ring pump 10 is clearly deteriorated, and therefore, when disassembling and observing the surface, corrosion is observed in the cylinder, and this is a main part particularly affecting exhaust performance. Of the impeller, middle wall plate and side plate,
Corrosion of 0.4 [mm] at the maximum was observed in the intermediate wall plate and the side plate, and it was found that the exhaust speed decreased due to the increase in clearance.

This is one in which cast iron was corroded by hydrofluoric acid or hydrochloric acid produced by the reaction of ClF ₃ gas with the sealing water in the water sealing pump 10.

Next, the case of using a BC type water ring pump will be described. This is a BC2 alloy which is said to have high corrosion resistance to hydrofluoric acid, that is, Cu, Sn, Z.
The alloy of n was used as a material for the impeller, the intermediate wall plate, and the side plate.

As shown in FIG. 2, the ultimate pressure of the reaction chamber 1 in the reduced pressure gas phase reactor was initially 0.02 [To.
rr], which deteriorated to 0.10 [Torr] after introducing 178 [liters] of ClF ₃ gas. Also, although not shown in the table, the ejector pump 9
The inlet pressure of No. 1 increased from 4 [Torr] to 15 [Torr].

Since the results show that the performance of the water ring pump 10 was obviously deteriorated, disassembly and surface observation revealed that all of the impeller, the intermediate wall plate and the side plate were
A maximum corrosion of 0.1 mm was observed.

Next, the case of using the all-stainless type water ring pump will be described. In this water ring pump, all of the impeller, the intermediate wall plate and the side plate are made of SCS14 which is a kind of stainless steel. is there.

As shown in FIG. 2, the ultimate pressure of the reaction chamber 1 in the reduced pressure gas phase reactor was initially 0.02 [To.
rr], and 313 [liters] of ClF ₃ gas was introduced over a period of about 26 [hours], but the ultimate pressure was 0.012.
It was [Torr], and so-called pump down was not seen.

When disassembled and the surface was observed, the impeller,
A black film that seems to be an oil film was attached to the side plate, but SC
Since no corrosion was observed in S14 itself, it was confirmed that this water ring pump can be used as a ClF ₃ gas detoxifying device and a vacuum pump.

The continuous operation of this all-stainless steel water ring pump for about 26 hours is equivalent to an apparatus operating period of about 3 months in consideration of the actual cleaning frequency and cleaning time of the reaction chamber 1. Considering the necessity of periodical overhaul due to the essential fluid wear of the above, it was shown that the water ring pump can be used for more than about 3 months, and it is clearly worth the cost. Is.

Further, although it leads to an increase in cost, a Ni-based alloy having corrosion resistance to both hydrofluoric acid and hydrochloric acid, in other words, a Ni-based corrosion-resistant alloy, for example, commercially available Ni or Ni-Cu alloy, Monel (trade name). , Ni-Cr alloy, Inconel (trade name), Ni-Mo
Alloy Hastelloy (trade name)
If at least one of these is adopted as the main motion part,
Corrosion due to strong acid can be almost ignored, and ClF is an overhaul period determined by the degree of damage due to fluid wear.
It can be used as a vacuum pump and an abatement device when cleaning the reaction chamber 1 with ₃ gases.

Based on the above experimental results, in the present invention, Cl
In a reduced pressure gas phase reactor equipped with a function of introducing F ₃ gas to carry out cleaning of a reaction chamber, a vacuum pump, that is, a gas from a mechanical booster pump 7 and an oil rotary pump 8 in FIG. Impeller in the exhaust line,
ClF ₃ gas can be removed over a practical period by inserting the water ring pump 10 made of stainless steel or Ni alloy into the main operating parts such as the intermediate wall plate and the side plate. It was

In the above experiment, since the structure of the vacuum pump unit was two mechanical booster pumps and one water seal pump with an air ejector, in the experiment of the conventional type and the main type BC water seal pump, The mechanical booster pump was strongly affected by the back pressure, the exhaust speed was interlocked and deteriorated, and as a result, the ultimate pressure of the reaction chamber 1 immediately deteriorated.

In order to avoid this, by using a dry pump or an oil rotary pump as a roughing pump or an auxiliary pump as a pre-stage pump of the water ring pump 10, the exhaust speed of the water ring pump 10 deteriorates. However, the vacuum pump is not affected by the back pressure, the ultimate pressure of the reaction chamber 1 does not change, and the film formation is not hindered. Therefore, if the parts are regularly replaced, It is possible to remove the pest for a realistic period by using a water ring pump of the type.

Other means for enabling a realistic period of harm removal using a conventional water ring pump are the flow rate of the inert gas for diluting the ClF ₃ gas, the amount of air introduced from the ejector, and the water ring. It is sufficient to delay the progress of metal corrosion by further diluting the ClF ₃ gas by increasing at least one of the amount of circulating water in the pump.

In order to sufficiently dilute the ClF ₃ gas with an inert gas, an enormous amount of the inert gas is required. Therefore, as a means for avoiding this, a water-sealing pump of a liquid circulation system is used. By using an alkaline substance such as caustic soda in the sealing liquid tank, ClF ₃ gas can neutralize the hydrofluoric acid and hydrochloric acid generated by the reaction with the sealing water, and it is also possible to suppress metal corrosion. is there.

As described above, the water ring pump is cleaned together with SiH ₄ gas, which is a Si-based film forming gas, for cleaning.
ClF ₃ gas, which is a gas, can be removed if it is sufficiently diluted, and when doing so, it is not necessary to provide a gas exhaust line for the source gas for manufacturing the target product and a branch line. become.

In this case, the reaction chamber and the water ring pump are set to 1: 1.
If it corresponds, it is only necessary to attach an interlock mechanism to prevent the film forming gas and ClF ₃ gas from flowing at the same time, for example, a mechanism in which normally open and normally on pneumatic valves are interlocked. The safety is extremely high.

The timing of switching between film formation and cleaning may be after the purge time required to return the reaction chamber 1 to atmospheric pressure and open it. Even in the case of processing with the sealing pump 10, there is no problem if simultaneous film formation and simultaneous cleaning in each reaction chamber 1 are encouraged.

In addition to the above-mentioned experiments, in order to know the extent of the corrosion progress of the water-sealed pump material when ClF ₃ gas was introduced, the test piece was immersed in a hydrofluoric acid + hydrochloric acid (HF + HCl) solution to obtain its corrosion resistance. Was investigated.

Here, as the test piece, BC2, SCS
Four types, 14 and SUS316, Monel were adopted.

It is necessary to set the mixing ratio of the hydrofluoric acid + hydrochloric acid solution to a value close to the value that is actually generated, and the measured values of the HF gas and HCl gas concentrations measured at the water seal pump outlet side. It was decided based on.

FIG. 4 shows that the water ring pump is supplied with 250 ClF ₃ gas.
[Sccm] (condition A) and 50 [sccm]
It is the figure which summarized the measured result of HF gas and HCl gas sampled at the exit side when introducing by applying the two conditions of (condition B).

In order to dilute the ClF ₃ gas, 270 [liter / min] of air and N ₂ gas are introduced together.
The expected concentration of ClF ₃ gas on the inlet side is 925 [ppm]
(Condition A) and 185 [ppm] (Condition B).

From the result of actual measurement, the ratio to ClF ₃ gas was obtained. HCl gas was 0.054 and HF gas was 0.
Assuming 432, only this value is exhausted as exhaust gas without being dissolved in the sealed water in the water seal pump.

Assuming that the ClF ₃ gas is completely dissolved in the sealed water in the water seal pump, the HCl solution should have the same concentration as the ClF ₃ gas, and the HF solution should be produced three times the concentration of the ClF ₃ gas. However, since the HCl gas and the HF gas are actually discharged as described above, the HCl concentration and the HF concentration in the actual sealed water in the water seal pump are ClF ₃ : HCl: HF. It is estimated that = 1: (1-0.054) :( 3-0.432) = 1: 0.946: 2.568≈1: 1: 2.7.

Therefore, hydrochloric acid (HCl solution) and hydrofluoric acid (H
It is appropriate that the mixing ratio with the F solution) is 1: 2.7. However, HCl for the ClF ₃ concentration in the above formula
The concentrations of HF and HF are local, and in fact, it is considered that the HF and HF are immediately diluted with the constantly changing running water, and the HF is discharged to a lower concentration.

In the experiment, the concentration in the mixed solution of hydrochloric acid and hydrofluoric acid with the mixing ratio of 1: 2.7 was changed by 0.2 [%] between 0.2 [%] and 1 [%]. What and 2
A test piece having a change of 2% from [%] to 10% was prepared, and a test piece of 20 mm square was dipped for 2 hours.

The corrosion resistance was evaluated by measuring the change in weight before and after dipping in a mixed solution of hydrochloric acid and hydrofluoric acid, and by SEM (sca).
Ning electron microscop
y) was used for the surface observation.

In the above experiment, in order to bring the state as close as possible to the actual state, bubbling of air at about 5 [liter / min] into the mixed solution, and the test piece sometimes being brought into contact with the air were also performed. is there. The test pieces used were ultrasonically cleaned in advance with butyl acetate in order to remove oils and fats.

FIG. 5 shows that the concentration of the hydrochloric acid + hydrofluoric acid mixture solution is 0.2.
It is a diagram showing the relationship of the weight change of each test piece in the case of [%] ~ 1 [%], and FIG. 6 shows the concentration of the hydrochloric acid + hydrofluoric acid mixture solution of 0.2 [%] ~ It is a diagram showing the relationship of the weight change of each test piece in the case of 10 [%].

The degree of progress of metal corrosion is proportional to the concentration of the acidic solution, and is also substantially proportional to the immersion time. Therefore, by increasing the concentration of the hydrochloric acid + hydrofluoric acid mixed solution, the same result as when the immersion is performed for a long time can be expected.

Regarding the results observed from FIGS. 5 and 6, although there are some variations due to the improper bubbling method, the overall tendency can be grasped.

In a durability test conducted with an actual water-sealed pump, good results were obtained in the stainless steel SCS14. When the concentration became 0.4% or more, a weight change appeared, and SE
When observed according to M, generation of holes and surface roughness were observed.

In contrast, SUS3 of the same stainless steel
No. 16 showed a weight change after the concentration became 2% or more, and it was found that the corrosion resistance was superior to that of SCS14.

Monel metal, which is a Ni alloy, is
Even if the concentration reaches 10%, the weight does not change and SEM
Even when observed by, the surface was slightly rough.

In BC2, corrosion does not progress so much only by immersion, but by bubbling air, the corrosion becomes severe, and the weight change already appears at a concentration of 0.2%.

From the above, even if the water ring pump adopts SCS14 made of stainless steel for the impeller, the intermediate wall plate and the side plate, there is a possibility that the pump may be down due to corrosion when it is operated for a long time. I know that there is.

The possibility of pump down is cost
It has been confirmed that SUS316 is less than that, although it is tied up, and that Ni alloys such as Monel metal are hardly corroded.

[0095]

【Example】

First Embodiment In the reduced pressure gas phase reactor shown in FIG. 1, the water ring pump 10 has a normal structure in which an impeller, an intermediate wall plate and side plates are made of SCS14 which is a kind of stainless steel as a material. It was adopted.

Air is introduced from the ejector pump 9 at a flow rate of 50 [liter / min], and N ₂ gas for dilution is introduced at a flow rate of 23 [liter / min] without passing through the reaction chamber 1. Then, the ClF ₃ concentration at the inlet of the water ring pump 10 was set to 0.24% as in the above experiment. Also,
The amount of sealing water is 15 [liters / minute].

According to the present embodiment, the harm of SiH ₄ gas is removed,
Also, the removal of ClF ₃ gas can be achieved to the same extent as when a dry removal device is used.
Regarding corrosion such as 0, as in the previous experiment,
There is no problem at all.

Second Embodiment FIG. 7 is an explanatory view of the main part of a reduced pressure gas phase reaction apparatus for explaining another embodiment of the present invention. The same symbols as those used in FIG. They represent the same part or have the same meaning.

The difference between the second embodiment and the first embodiment is that the water ring pump 10 is made of cast iron and is similar to the conventional one, and the structure of the vacuum pump is mechanical.
It is composed of the booster pump 7 and the oil rotary pump 8, and in order to prevent the water ring pump 10 from being corroded, a large amount of diluting gas is flowed to dilute the cleaning gas.

Using this reduced pressure gas phase reactor, a polycrystalline silicon thin film was formed and the reaction chamber was cleaned.

(1) Formation of polycrystalline silicon thin film Temperature in reaction chamber 1: 620 [° C.] Pressure in reaction chamber 1: 0.2 [Torr] Source gas: SiH ₄ SiH ₄ gas flow rate: 50 [sccm]

(2) Regarding cleaning At the start point: the film thickness of the deposit on the inner wall of the reaction chamber 1 is 10 [μm]
Cleaning gas: ClF ₃ Reaction chamber 1 temperature: 620 [° C] Reaction chamber 1 pressure: 2.0 [Torr] Cleaning gas: ClF ₃ ClF ₂ gas flow rate: 250 [sccm] Diluting gas : N ₂ N ₂ gas flow rate: 5 [slm]

By performing the cleaning of (2), the polycrystalline silicon film having a thickness of 10 μm can be completely removed in about 1 hour.

In this embodiment, since the water ring pump 10 is made of cast iron, in order to prevent corrosion caused by ClF ₃ gas, air is introduced at a flow rate of 100 [liter / min] during cleaning, and the reaction is further performed. N ₂ gas for dilution was introduced at a flow rate of 160 [liter / min] without passing through the chamber 1, and the ClF ₃ concentration at the inlet of the water ring pump 10 was set to 0.09 [%].

In this embodiment, since the oil rotary pump 8 is used as the vacuum pump which is the preceding stage of the water ring pump 10, even if the water ring pump 10 is pumped down, it is hardly affected by the back pressure. Therefore, it is possible to reduce the risk that the pressure in the reaction chamber 1 fluctuates.

Third Embodiment FIG. 8 is an explanatory view of a main part of a reduced pressure gas phase reaction apparatus for explaining another embodiment of the present invention. The symbols used in FIG. 1 and FIG. The same symbol represents the same part or has the same meaning. For the sake of simplicity, only the exhaust gas treatment system is shown in FIG.

In the figure, 16 is a sealing liquid tank, 17 is a heat exchanger for cooling the sealing liquid, 18 is a water sealing pump main body, 19 is a sealing liquid circulation line, and 20 is a pH sensor.

A titanium nitride thin film was formed and the reaction chamber was cleaned using this reduced pressure gas phase reactor.

To form a titanium nitride thin film, a source
TiCl ₄ gas is used as the gas. In this case, not only the ClF ₃ gas used as the cleaning gas but also the TiCl ₄ gas is corrosive.

Therefore, when exhausted by a normal water-sealed pump, the water-sealed pump reacts with the sealed water to generate hydrochloric acid, which significantly increases the reactivity with respect to metal, and the water-sealed pump is discharged in a short period of time. In such a case, it is preferable to use a water-sealing pump of a liquid-circulation circulation system as shown in the figure, because the metal part of the above is damaged by corrosion.

In general, the performance of a water ring pump is greatly affected by the temperature of the liquid seal, so that the water ring pump of the liquid ring circulation system
For the purpose of suppressing the temperature rise of the circulating sealing liquid, it is necessary to install a cooling mechanism in the sealing liquid tank or the sealing liquid circulation line. In the third embodiment, the heat exchanger 17 is used as the cooling mechanism in the sealing liquid tank 16.
Is provided.

Although not shown in the figure, caustic soda as an alkaline substance was mixed into the sealing liquid maintained at a constant temperature while adjusting the input amount, and hydrochloric acid wastewater generated in the sealing liquid was mixed with acid.
Neutralizes by alkali reaction. In order to adjust the input amount of caustic soda, the pH detected by the pH sensor 20
Use values. In this way, even if the water ring pump 18 is made of cast iron, the damage due to corrosion is reduced, so that it is possible to maintain the practicality comparable to that using a corrosion resistant material.

The reaction formula for growing a titanium nitride film using TiCl ₄ gas is 2TiCl ₄ + N ₂ + 4H ₂ → 2TiN + 8HCl, and since hydrogen gas is used, mixing with ClF ₃ gas is avoided. It is necessary.

In this embodiment, since the reaction chamber 1 and the water seal pump body 18 are made to correspond to each other in a one-to-one relationship, hydrogen gas and Cl
It is easy to form an interlock so that the F ₃ gas and the F ₃ gas do not flow simultaneously.

As is clear from the above description, in this embodiment, the water sealing pump of the sealing liquid circulation system is used to neutralize the acid waste water by the alkaline substance and remove the reactive gas for forming the thin film. Since it is possible to remove both harm and gas for cleaning, a normal cast iron pump can be used as the water ring pump.

[0116]

EFFECTS OF THE INVENTION In the reduced pressure gas phase reaction apparatus and the method for treating exhaust gas thereof according to the present invention, a mechanism for feeding ClF ₃ gas for cleaning in order to remove the reaction products adhering to the reduced pressure reaction chamber is provided. In a decompression gas-phase reactor, the ClF ₃ gas and gasified reaction products are removed by a water-sealing pump made of a corrosion-resistant metal material, or a large amount of diluting gas is passed to seal the water. The concentration of ClF ₃ gas or the like is remarkably reduced at the inlet of the pump, or the acid wastewater is neutralized by adding an alkaline substance to the sealing liquid tank of the water sealing pump to neutralize the acid wastewater.

By adopting the above-mentioned constitution, the depletion of ClF ₃ gas which is a cleaning gas and the gasified reaction product, and the thin film without attaching a dry detoxification device to the depressurized gas phase reactor. Since the removal of the reactive gas for formation can be carried out by the water ring pump, the removal cost can be reduced and the occupied area of the reduced pressure gas phase reactor can be reduced, and It is possible to easily avoid the risk that the ClF ₃ gas and the hydrogen-based film forming gas are mixed.

[Brief description of the drawings]

FIG. 1 is an explanatory view of essential parts showing a reduced pressure gas phase reaction apparatus used in an experiment.

FIG. 2 is a table summarizing the results obtained in the experiment.

FIG. 3 is a table in which the specific contents of the types of water-sealed pumps shown in FIG. 2, that is, the conventional type, the main part BC type, and the all stainless type are summarized in a table.

FIG. 4 is a table in which the actual measurement results of HF gas and HCl gas sampled on the outlet side by introducing ClF ₃ gas into a water ring pump are summarized in a table.

FIG. 5: Concentration of hydrochloric acid + hydrofluoric acid mixed solution is 0.2 [%] to 1
It is a diagram showing the relationship of the weight change of each test piece in the case of [%].

[Fig. 6] Concentration of hydrochloric acid + hydrofluoric acid mixed solution is 0.2 [%] to 1
It is a diagram showing the relationship of the weight change of each test piece in the case of 0%.

FIG. 7 is an explanatory view of a main part of a reduced pressure gas phase reaction apparatus for explaining another embodiment of the present invention.

FIG. 8 is a principal part explanatory view showing a reduced pressure gas phase reaction apparatus for explaining another example of the present invention.

FIG. 9 is a principal part explanatory view showing a reduced pressure gas phase reaction apparatus for explaining a conventional technique.

FIG. 10 is an explanatory view of a main part showing a part of a reduced pressure gas phase reaction apparatus for explaining another conventional technique.

[Explanation of symbols]

1 Reaction chamber 2 Gas supply pipe for forming thin film 3 Gas supply pipe for cleaning inside furnace 4 SiH ₄ cylinder 5 ClF ₃ cylinder 6 Gas exhaust pipe 7 First mechanical booster pump (vacuum pump) 8 Oil rotary pump 9 Ejector Pump 10 Water-sealing pump 11 Gas exhaust pipe 12A Switching valve 12B Switching valve 13 ClF ₃ Dry detoxification device for gas 14 Dry detoxification device 15 Second mechanical booster pump 16 Encapsulation tank 17 Heat for cooling encapsulation liquid Exchanger 18 Water seal pump main body 19 Seal liquid circulation line 20 pH sensor

Continuation of front page (51) Int.Cl. ⁶ Identification number Office reference number FI Technical display location H01L 21/304 341 B01D 53/34 134A (72) Inventor Naoki Sakamoto 1015 Kamiodanaka, Nakahara-ku, Kawasaki-shi, Kanagawa Fujitsu (72) Inventor Toru Tsurumi, 1015 Kamiodanaka, Nakahara-ku, Kawasaki-shi, Kanagawa, Fujitsu Limited (72) Inventor, Hirokazu Yamanishi 1015, Ueda, Nakahara-ku, Kawasaki, Kanagawa (72) Inventor, Fujitsu Hiroyuki Kamata 1015 Kamiodanaka, Nakahara-ku, Kawasaki-shi, Kanagawa, Fujitsu Limited (72) Inventor Yoshiyasu Sato 1015, Kamikodanaka, Nakahara-ku, Kawasaki, Kanagawa Prefecture, Fujitsu Limited (72) Inventor, Abe Kazuhide Aizu-Wakamatsu, Fukushima Prefecture Tamachi Industrial Park No. 4 Fujitsu Tohoku Electronics Co., Ltd. (72) Inventor Kei Omatsu 30 Miyake-cho, Moriyama City, Shiga Prefecture Shinko Seiki Co., Ltd. (72) Inventor Hideo Yamamoto 30 Miyake-cho, Moriyama City, Shiga Prefecture Shinko Seiki stock Within the company (72) inventor Nobuhiro Nishimura Moriyama City, Shiga Prefecture Miyake-cho, 30 address Shinko Seiki shares in the company

Claims (7)

[Claims] 1. A depressurized gas phase reactor having a mechanism for feeding and cleaning ClF ₃ gas to remove reaction products adhering to the inside of the reaction chamber, through a gas exhaust line after a vacuum pump. Water for which at least the impeller, the side plate and the intermediate wall plate, which are inserted and exhausted to remove the ClF ₃ gas and the gasified reaction product, are made of a corrosion-resistant metal material selected from stainless steel or Ni-based metal. A reduced pressure gas phase reaction apparatus comprising a sealing pump. 2. An ejector pump connected immediately before the water ring pump to dilute the ClF ₃ gas and the gasified reaction product with the sucked gas.
The reduced pressure gas phase reactor described. 3. The reduced pressure gas phase reaction apparatus according to claim 1, wherein at least the roughing or auxiliary vacuum pump of the vacuum pumps is either a dry pump or an oil rotary pump. 4. A step of feeding ClF ₃ gas for cleaning to remove a reaction product adhering to the reaction chamber, and a step of cleaning the ClF ₃ gas discharged from the reaction chamber and the gasified reaction product. A step of sufficiently diluting the water at the inlet of a water seal pump inserted in a gas exhaust line after the vacuum pump so that the metal is not corroded, and the diluted ClF ₃ gas and the gasified reaction product. A method of treating exhaust gas in a reduced pressure gas phase reaction apparatus, comprising the step of taking in the sealed water in the water seal pump to remove the harm. 5. A step of feeding ClF ₃ gas for cleaning in order to remove the reaction product adhering to the reaction chamber, and cleaning the ClF ₃ gas and the gasified reaction product discharged from the reaction chamber. It is inserted into the gas exhaust line after the vacuum pump and guided to a water sealing pump of a liquid sealing circulation system that has a liquid sealing tank and a heat exchange mechanism, and mixes alkaline substances into the liquid sealing to neutralize acid wastewater and remove it. A method for treating exhaust gas in a reduced pressure gas phase reaction apparatus, comprising: 6. An ejector connected immediately before the water ring pump.
The exhaust gas treatment method in a reduced pressure gas phase reaction apparatus according to claim 4 or 5, wherein the ClF ₃ gas and the gasified reaction product are diluted with the gas sucked by the pump. 7. A dry pump or an oil rotary pump, which constitutes a vacuum pump interposed between the reaction chamber and the water-sealed pump to perform vacuuming, and performs roughing or the like. Or a method for treating exhaust gas in the reduced pressure gas phase reactor according to item 6.