JPH0972493A - Trap for dry vacuum pump rear stage - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a long life trap to collect condensed gas which is not condensed in a dry vacuum pump but cured or liquefied at an ordinary temperature and an ordinary pressure or at a value approximately equal thereto. SOLUTION: Condensing plates 171 , 172 ..., 176 and 277 , and 279 are mounted on a center shaft 15 erected on the bottom of a housing 11 as the numbers of spacers 16 is regulated and a gap therebetween is gradually decreased. Further, the opening areas of the flow passage parts 181 , 182 , 183 and 287 , 288 , and 289 of the respective condensing plates are gradually decreased. Further, a cooling gas introduction port 21 is formed in the vicinity of a gas introduction port 12.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a trap installed after a dry vacuum pump in a vacuum exhaust line, and more particularly to a trap in which a condensate is uniformly formed in the entire interior.

[0002]

_2. Description of the Related Art Among semiconductor manufacturing processes, SiN _x (silicon nitride) is manufactured by low pressure CVD (chemical vapor deposition) using SiH ₂ Cl ₂ (dichlorosilane) and NH ₃ (ammonia) as source gases. ) Al is formed by NH ₄ Cl (ammonium chloride) gas, which is a by-product when forming a film, or an etching gas containing Cl (chlorine).
The AlCl ₃ (aluminum chloride) gas produced as a by-product when the (aluminum) film is subjected to reactive ion etching has a property of solidifying at room temperature and atmospheric pressure or in the vicinity thereof. Figure 10 shows a vapor pressure curve S of AlCl _3, right vapor pressure curve S, for example, AlCl ₃ is the point A (300 ° C.,
Although the gaseous phase in the time of generation as to generate at 10 ² Pa), which left the steam pressure curve S in the process leading to the outside, for example, point B is close to normal temperature and normal pressure (50 ℃, 10 ⁵ P
When it becomes a), it will be in a solid state.

Exhaust gas containing unreacted etching gas and AlCl ₃ gas produced as a by-product in the above reactive ion etching is usually sent to a scrubber of an exhaust treatment facility by a vacuum pump in a low vacuum region for processing. At this time, in the oil rotary vacuum pump which has been conventionally used, the exhaust gas was dissolved in the oil, the condensate corroded the pump member, and the condensate was stuck inside the pump to cause a difficulty in starting. Instead, dry vacuum pumps that do not use oil in the compression chamber have been adopted. Since the dry vacuum pump reaches a very high temperature (for example, 100 to 300 ° C.) due to the compression heat of the exhaust gas, the conventional oil rotary vacuum pump condenses inside A.
lCl ₃ can be discharged in the gas phase, the maintenance cycle is significantly extended, and the operating rate is dramatically improved.

On the other hand, however, there are problems such as AlCl ₃ condensing and blocking in the piping from the dry vacuum pump to the exhaust scrubber, and shortening the life of the exhaust scrubber.

Therefore, there is an attempt to solidify and separate by providing a trap for collecting AlCl ₃ gas in a pipe between the dry vacuum pump and the exhaust scrubber. FIG. 11 is a vertical sectional view of a conventional trap 90. A gas inlet 92 is provided on the bottom surface of a cylindrical housing 91 having a bottom, and an end face plate 93 provided with a gas outlet 94 is airtightly attached to the upper opening. Further, nine condensing plates 97 are equidistantly provided on the center shaft 95 fixed to the bottom surface, one end of which is in contact with the inner wall of the housing 91, and a gas flow path formed between the other end and the inner wall of the housing 91. The parts 98 are mounted alternately on opposite sides and the gas is trapped in the trap 9
As shown by the arrow, the inside of 0 rises in a zigzag shape and flows. A cooling water jacket 99 is attached to the outer periphery of the housing 91.
The inner wall and the condenser plate 97 are cooled.

When the trap 90 is installed in an exhaust gas line containing AlCl ₃ , for example, the gas introduced into the trap 90 through the gas inlet 92 collides with the condenser plate 97 and the inner wall of the housing 91 to be cooled and condensed and solidified. However, this condensation occurs intensively on the condensation plate 97 closest to the gas inlet 92 and the inner wall of the housing 91, and the adhered matter C is generated. FIG. 11 also shows the generation state of the adhered matter C. When the trap 90 is clogged with the adhered matter C, the trap 90 reaches the end of its life, so the operation is stopped.
Although the adherent C of lCl ₃ is to be taken out, the amount of solid AlCl _{3 that} can be collected is extremely small compared to the volume of the trap 90, and the time to reach the end of life is much shorter than expected. There is.

When the AlCl ₃ gas is in the viscous flow region and has a high flow velocity, a gas that passes through without colliding with the condenser plate 97 and the inner wall of the housing 91 is generated. This is confirmed by the fact that the adhered substance C is thinly formed in the gas outlet 94. In order to cope with this, if the area of the condenser plate 97 is increased, the trap 90 becomes large, and if the attachment interval of the condenser plate 97 is narrowed, clogging is likely to occur and the life of the trap 90 is further shortened.

[0008]

The present invention has been made in view of the above problems, and condenses a condensed gas which is not condensed in a dry vacuum pump but is condensed at room temperature / normal pressure or in the vicinity thereof to be solidified or liquefied. It is an object of the present invention to provide a trap that is installed in a subsequent stage of a dry pump that is a trap for the purpose of being difficult to be blocked by condensed solidified matter and that does not allow condensed gas to pass through.

[0009]

[Means for Solving the Problems] The above object is to install a single or a single unit for condensing the condensed gas in the exhaust gas by installing it in the latter stage of the dry vacuum pump and forming a flow path of the exhaust gas in the housing. In the trap for the latter stage of the dry vacuum pump to which a plurality of condenser plates are attached, the resistance of the flow passage between the gas inlet provided in the housing and the gas outlet may be gradually increased. And a trap for the latter stage of the dry vacuum pump.

[0010]

[Function] Since the flow path resistance of the gas in the trap is gradually increased from the gas inlet to the gas outlet, the condensed gas is uniformly condensed in the trap, and the adhered matter is biased in the trap. Generate without. Further, since the flow path resistance is large in the vicinity of the gas outlet, the passage of condensed gas is suppressed.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A trap for the latter stage of a dry pump according to an embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a vertical cross-sectional view of the trap 10 for condensing the AlCl ₃ gas described above, which is installed at the subsequent stage of a dry vacuum pump that discharges the AlCl ₃ gas without condensing it inside. FIG. 2 shows [2]-in FIG.
[2] It is sectional drawing of a line direction. That is, the trap 10
Is a gas inlet 12 on the bottom of a cylindrical housing 11 with a bottom.
And an end face plate 13 provided with a gas outlet 14 is airtightly attached to the upper opening. Housing 1
In the first embodiment, a predetermined number of spacers 16 are inserted into and intervened on the center shaft 15 fixed to the bottom surface, and nine condensing plates 17 ₁ , 17 ₂ , 17 ₃ , 17 ₄ , 17 are provided.
₅ , 17 ₆ and 27 ₇ , 27 ₈ and 27 ₉ are sequentially assembled from the gas introduction port 12 side and assembled, and tightened by a nut 19 screwed to the top of the center shaft 15. A nut 19 is inserted and screwed directly below the condensing plate 17 ₁ . In addition, FIG.
FIG. 27 is a perspective view of the assembly of ₁ , 17 ₂ , ..., 27 ₈ , 27 ₉ .

Referring to FIGS. 2 and 3, the condensing plate 17 ₁ is formed by cutting out a half-moon shaped gas flow path portion 18 ₁ from a disc, and the condensing plates 17 ₂ , 17 ₃ , ..., 17 ₆ Is also the same. Three upper disk-shaped condensing plates 27 ₇ , 27 ₈ , 2
No. 7 ₉ has circular holes of the same area formed in each of them as gas flow passage portions 28 ₇ , 28 ₈ and 28 ₉ . Then, the flow path portions 18 ₁ , 18 ₂ , 18 ₃ , 18 ₄ , 1 of each condensing plate
8 ₅ , 18 ₆ and 28 ₇ , 28 ₈ , 28 ₉ are alternately arranged on the opposite side with respect to the center shaft 15.

Further, between the bottom surface of the housing 11 and the upper end surface plate 13, between the bottom surface of the housing 11 and the condensing plate 17 ₁ , there are about 11 spacers 16 which are condensed with the condensing plate 17 _1. Spacer 16 between plate 17 ₂
There eight minute intervals, condenser plates 17 ₂ and 3 pieces of Between the condensing plate 17 _3, 2 pieces of each between the condenser plates 17 ₃ to condenser plates 27 _7, condenser plates 27 from the condenser plate 27 ₇ The distances up to ₉ are one, and the distance between the condenser plate 27 ₉ and the end face plate 13 is about two. That is, these intervals are attached so as to gradually decrease from the gas inlet 12 toward the gas outlet 14, and the AlCl ₃ gas is condensed and solidified and collides with the condenser plates 17 and 27 as the partial pressure thereof decreases. The intervals are narrowed so that the probability is high.

Further, referring to FIG. 2, the maximum radial length a ₁ of the flow passage portion 18 ₁ of the adhesion plate 17 _{1 and} the flow passage portions of the condensing plates 17 ₂ , 17 ₃ , ..., 17 ₆ are shown. 18 ₂ ,
18 ₃ , ..., 18 ₆ are similarly defined as a ₂ , a
Regarding ₃ , ₆ , a ₆ , the flow path portions 18 ₁ , 18 ₂ , ..., 18 are provided with the relationship of a ₁ > a ₂ > a ₃ = a ₄ = a ₅ = a _6.
The opening area of ₆ is set to decrease gradually, and the adhesion plate 27
_7, 27 _8, 27 channel section 28 ₇ of the circular holes in the _9,
The opening areas of 28 ₈ and 28 ₉ are further reduced significantly. In this manner, the gas flow on the gas inlet 12 side is relatively stable, and the vortex flow is generated on the gas outlet 14 side to facilitate turbulent flow. The collision probability is increased, and the gas is prevented from passing through between the condenser plates 27.

In the first aspect, "the resistance of the flow passage is gradually increased" means that one spacer 16 is provided between the condenser plates 27 ₇ , 27 ₈ and 27 ₉ as described above. and at regular intervals, that between the condenser plates 27 ₉ and the end face plate 13 thereon which is increased to approximately interval corresponding to two of the spacer 16,
In addition, there are some places where the flow passage resistances are made equal to each other and the flow passage resistances are partially reduced by providing equal opening areas of the flow passage portions 18 and 28. It means that the flow path resistance is gradually increased as a whole while reaching the gas outlet port 14.

Further, in the vicinity of the gas inlet 12,
A cooling gas introduction port 21 is provided on the side wall of the housing 11, and an inert gas such as N ₂ (nitrogen) gas is introduced for cooling.

The trap 10 of the embodiment is constructed as described above, and its operation will be described below.

Referring to FIG. 1, the exhaust gas containing AlCl ₃ gas fed from the gas inlet 12 is the gas inlet 1
Introduced from the second internal diameter to a sufficiently large inner diameter of the trap 10 in being decelerated, diffuse across the exhaust gas is from the cooling gas inlet 21 is cold N ₂ gas simultaneously introduced at several times the flow rate of AlCl ₃ gas , Reduce the temperature. Although the partial pressure of AlCl ₃ is also reduced by the introduction of N ₂ gas, as can be understood from the fact that the pressure of the vapor pressure curve S in FIG. 10 is shown on a logarithmic scale, this amount of N ₂ gas is used. Even if introduced, the condensation behavior of AlCl ₃ gas is not significantly affected.

Next, the exhaust gas mixed with the N ₂ gas collides with the condenser plate 17 ₁ closest to the gas inlet 12 and the inner wall of the housing 11 in the vicinity thereof, and heat is exchanged to lower the temperature. AlCl ₃ gas molecules are condensed and adhere to the condensing plate 17 ₁ and its vicinity.

Then, the gas ascends in the trap 10 as shown by the arrows while colliding with the inner walls of the condenser plates 17 and the housing 11 and condensation of AlCl ₃ gas molecules by heat exchange. During this time, the intervals between the condenser plates 17 and the opening area of the half-moon shaped flow passage portions 18 are gradually narrowed, and vortices are generated after passing through the flow passage portions 18 to disturb the flow. As a result, the frequency of collision of AlCl ₃ gas molecules with each condensing plate 17 is increased, and the AlCl ₃ gas molecules are condensed and approach the gas outlet 14 while reducing the partial pressure.

On the gas outlet 14 side, each condensing plate 27
Is narrower, and the flow path portion 28 of the circular hole has a smaller opening area. Therefore, the frequency of gas collision is further increased, and the AlCl ₃ gas molecules having a reduced partial pressure are further condensed. The residual gas is discharged from the gas outlet 14.

As a result, as shown in FIG. 4 which is a sectional view corresponding to FIG. 1, AlCl ₃ adhered matter C is formed relatively evenly from the gas introduction port 12 of the trap 10 to the upper part of the inside thereof, and the adhered amount is large. Becomes On the other hand, no adhesion of AlCl ₃ was observed at the gas outlet 14, indicating that none of the AlCl ₃ gas molecules passed through. That is, a clear difference is observed in the adhesion state of AlCl ₃ as compared with the trap 90 of the conventional example of FIG.

Although the embodiment of the present invention has been described above, the present invention is not limited to this, and various modifications can be made based on the technical idea of the present invention.

For example, in this embodiment, AlCl ₃
The case of condensing and solidifying the gas is illustrated, but the trap of the present invention installed in the latter stage of the dry vacuum pump is AlCl ₃
Other than NH ₄ Cl (ammonium chloride), GaCl ₃
(Gallium chloride), AlBr ₃ (aluminum bromide),
In addition, although it is not condensed and solidified in the dry vacuum pump,
It can be applied to a gas that solidifies at or near room temperature and atmospheric pressure, or can be applied to water vapor that liquefies at or near room temperature and atmospheric pressure even if it does not stick in the trap.

For example, N which is a by-product in the exhaust line of a CVD vacuum device for forming a SiN _x insulating film on a semiconductor substrate.
Although H ₄ Cl gas was discharged, a large amount of NH ₄ Cl was fixed inside the trap 10 of the present invention installed after the dry vacuum pump in this exhaust line after a long time had passed. Further, almost no adhesion was observed at the gas outlet 14, indicating that the trap 10 has a high collection efficiency.
On the other hand, in the conventional trap which uses the same casing and does not gradually increase the flow path resistance, NH ₄ Cl adheres to the gas outlet port even though it has a short life until it is blocked, and it passes through without being aggregated. It was suggested that NH ₄ Cl was present.

Further, in the present embodiment, the condensing plate 17
_1, 17 _2, ..., 17 ₆ channel sections 18 _that is cut out in half-moon shape, 18 _2, ..., 18 ₆ and a disk-shaped with a condenser plates 27 _7, 27 _8, 27 ₉ of a circular hole Flow path portion 28 ₇ ,
While a combination of these as 28 _8, 28 _Sep disc shape with the shape of the condenser plates and the channel section may be any shape other than these. Moreover, you may assemble with the condensing plate of the same shape.

Further, in this embodiment, the condenser plate 17
The intervals of ₁ , 17 ₂ , ..., 17 ₆ , 27 ₇ , 27 ₈ , 27 ₉ are attached in a gradually decreasing manner as shown in FIG.
The opening areas of 8 ₁ , 18 ₂ , ..., 18 ₆ , 28 ₇ , 28 ₈ , 28 ₉ were also set to gradually decrease, but the intervals between these condensing plates and the ratio of gradually decreasing the opening area of the flow path part were fixed. Are set to grow evenly in the trap 10. And this means the type of gas to be condensed, the partial pressure, the temperature,
Since it varies depending on the flow velocity and the like, it cannot be unconditionally determined and is set to an optimum value by trial and error.

In the present embodiment, the condenser plates 17 and 27 are attached to the center shaft 15 standing on the bottom surface of the bottomed cylindrical housing 11, but as shown in FIG.
A trap having a structure in which the bottom surface side of the housing 31 is hermetically sealed by the end face plate 33 and the condenser plates 37 and 47 are attached to the center shaft 35 fixed to the end face plate 33 via the spacer 36 may be used. The gas inlet 32, the gas outlet 34, and the cooling gas inlet 41 are provided at the positions shown in FIG. If the inside of the trap 30 is blocked by the adhered matter, the condenser plates 37 and 47 in the solid line position can be pulled out together with the end face plate 33 from the housing 31 as shown by the one-dot chain line, so that the adhered matter is recovered and the trap 30 is regenerated. Is easy. Of course, the end face plate 33 may be attached to the upper surface side of the housing 31 and the center shaft 35 may be fixed to this and pulled out in the opposite direction. In that case, the gas outlet 34
Will be attached to the side wall of the housing 31.

Further, in this embodiment, the condenser plate 17,
Although 27 is attached to the center shaft 15, it may be fixed to the inner wall of the housing 11, and the condensing plates 17 and 27 are disc-shaped, but may be three-dimensional cylindrical or cap-shaped.

In this embodiment, the condenser plate 17,
Although 27 is arranged in a direction orthogonal to the general flow direction of the gas from below to above trap 10, it may be arranged in any other direction so as to obtain the optimum fixed state. For example, the schematic vertical cross-sectional view of FIG. 6 shows an example in which a condensing plate 57 is arranged in the housing 51 of the trap 50 in parallel with the general flow direction of gas indicated by an outline arrow. The schematic vertical cross-sectional view of FIG. 7 shows an example in which the cohesive plate 67 is arranged in the housing 61 so that the gas repeats the forward flow and the reverse flow in the trap 60 with respect to the general gas flow direction. is there.
Similarly, the schematic vertical sectional view of FIG. 8 shows an example in which the condensing plate 77 is arranged in the housing 71 of the trap 70 so as to exist as a part of the inverted conical surface, and the gas introduced from the gas inlet 72 is entirely The gas flows obliquely to the flowing direction of the gas.
In addition, the schematic vertical cross-sectional view of FIG.
This is an example of arranging. In each of the examples of FIGS. 6 to 9, each condenser plate is installed so as to narrow the interval from the gas inlet port to the gas outlet port and gradually increase the flow path resistance.
6 to 9, the gas inlets and the gas outlets are denoted by the same reference numerals as the gas inlet 12 and the gas outlet 14 of the embodiment, and the cooling gas inlet is omitted. are doing.

Further, in the present embodiment, the trap 10 is placed vertically and the gas is made to flow from the lower side to the upper side. However, the structure may be made such that the gas is made to flow from the upper side to the lower side, or the trap 10 may be placed horizontally. . Further, although the trap 10 has a cylindrical shape, it may have a rectangular tube shape.

In this embodiment, the cooling gas inlet 21 is provided to cool the entire gas with the inert N ₂ gas, but the cooling gas may not be needed depending on the type of gas to be condensed.

In this embodiment, the material of the trap 10 is not specified, but aluminum or aluminum alloy having good thermal conductivity is a preferable choice.

Further, by installing two traps 10 of this embodiment in parallel and switching and using them, the adhered substances can be recovered from the closed trap without stopping the exhaust gas line.

[0036]

As described above, according to the trap for the latter stage of the dry vacuum pump of claim 1 of the present invention, a gas which is easily solidified or liquefied at room temperature and normal pressure or in the vicinity thereof, for example, AlCl ₃ gas is discharged. When it is installed in the exhaust line, AlCl ₃ is efficiently collected, and a sticking substance is formed over the entire inside of the trap with little unevenness, so that the total length of the trap can be shortened and the clogging member is not blocked. Longer life. Further, as a result, the life of the entire exhaust line is extended, the frequency of maintenance is reduced, and the work is simplified.

According to the trap for the latter stage of the dry vacuum pump of claim 4, the number of spacers can be changed to adjust the intervals of the condensing plates, and the condensing plates can be replaced or condensing plates having different shapes can be combined. As a result, the collection efficiency can be improved and the adhered matter can be formed evenly inside the trap.

According to the trap for the latter stage of the dry vacuum pump of claim 5, since the cooling gas can be introduced to sufficiently lower the temperature of the entire gas, the cooling equipment for the condenser plate and the inner wall of the housing is unnecessary. Or significantly reduce the load on the cooling equipment (refrigerant flow rate and temperature difference).

[Brief description of drawings]

FIG. 1 is a vertical sectional view of a trap for a latter stage of a dry vacuum pump according to an embodiment.

FIG. 2 is a sectional view taken along the line [2]-[2] in FIG.

FIG. 3 is a perspective view showing the assembly of the condenser plate in the embodiment.

FIG. 4 is a cross-sectional view corresponding to FIG. 1, showing a generation state of adhered substances.

FIG. 5 is a vertical cross-sectional view showing a modified example of attachment of a condenser plate.

FIG. 6 is a schematic vertical cross-sectional view showing a modified example of the arrangement of condenser plates.

FIG. 7 is a schematic vertical cross-sectional view showing a modified example of the arrangement of condenser plates.

FIG. 8 is a schematic vertical sectional view showing a modified example of the arrangement of the condenser plate.

FIG. 9 is a schematic vertical sectional view showing a modified example of the arrangement of the condenser plate.

FIG. 10 is a vapor pressure curve of aluminum chloride.

FIG. 11 is a vertical cross-sectional view of a trap of a conventional example, showing a state of adhered substances.

[Explanation of symbols]

 10 Trap for Dry Vacuum Pump Second Stage of Example 11 Housing 12 Gas Inlet Port 13 End Face Plate 14 Gas Outlet Port 16 Spacer 17 Condensing Plate 18 Passage Portion 21 Cooling Gas Inlet 27 Condensing Plate 28 Passage Portion C Adherent

Claims (7)

[Claims] 1. A dry vacuum pump, which is installed at a subsequent stage of the dry vacuum pump and is provided with a condenser plate or a plurality of condenser plates for condensing condensed gas in the exhaust gas by forming an exhaust gas passage in the housing. In the trap for the latter stage of the vacuum pump, the resistance of the flow passage between the gas inlet provided in the housing and the gas outlet is gradually increased gradually, and the trap for the latter stage of the dry vacuum pump is characterized. . 2. An end face plate on the gas inlet side of the housing between the gas inlet and the gas outlet.
The trap for the latter stage of the dry vacuum pump according to claim 1, wherein the interval between the condenser plate and the end face plate on the gas outlet side of the housing is gradually reduced. 3. The area of the flow passage portion formed by the condenser plate and the housing or the passage portion opened in the condenser plate tends to have an area between the gas inlet port and the gas outlet port. The trap for the latter stage of the dry vacuum pump according to claim 1 or 2, wherein the trap is gradually reduced. 4. The condenser plate is attached to a shaft with one or a plurality of spacers interposed, and it is possible to change an interval between the condenser plates and a kind of the condenser plate. The trap for the latter stage of the dry vacuum pump according to any one of claims 1 to 3. 5. The gas condensing plate is attached to the shaft fixed to the gas inlet side end face plate or the gas outlet side end face plate, and the gas inlet side end face plate or the gas outlet side end. The trap for the latter stage of the dry vacuum pump according to any one of claims 1 to 4, which can be inserted into the housing together with the face plate and taken out from the housing. 6. The trap for the latter stage of the dry vacuum pump according to claim 1, wherein a cooling gas introduction port is provided near the gas introduction port of the housing. 7. The gas according to claim 1, wherein the condensing gas is a gas such as aluminum chloride gas, ammonium chloride gas, or water, which solidifies or liquefies at room temperature / normal pressure or in the vicinity thereof. Trap for the latter stage of the dry vacuum pump.