JP3539446B2 - By-product trap device and cleaning method thereof - Google Patents

Description

[0001]
[Industrial applications]
The present invention traps products and by-products during film formation and by-products generated during cleaning of a process device from a process device to a vacuum pump, thereby preventing clogging of the vacuum pump and exhaust system. The present invention relates to a by-product trap device capable of cleaning without removing a pipe and a cleaning method thereof.
[0002]
[Prior art]
One of processes performed in a vacuum in a semiconductor manufacturing process is film formation by CVD, and one typical example thereof is the formation of a Si ₃ N ₄ film. An example of the chemical formula of this reaction can be represented by Formula (1).
3SiH ₂ Cl ₂ + 10NH ₃ → Si ₃ H ₄ + 6H ₂ + 6NH ₄ Cl (1)
At this time, NH ₄ Cl is generated as a by-product in addition to the target Si ₃ N ₄ film.
[0003]
This by-product sublimes at 340 ° C. at normal pressure. However, in a temperature range lower than that, the solid becomes solid and the reaction vessel (since the film is formed in a space of 700 to 900 ° C., the temperature of the reaction vessel is naturally considered to be higher than the sublimation point of NH ₄ Cl). Also, a large amount of the gas adheres to the inner wall of the vacuum exhaust system piping and the rotor of the vacuum pump, which lowers the temperature of the vacuum pump and causes the vacuum pump to stop operating.
[0004]
Si ₃ N _4, which is a target product of film formation, also adheres to the inner wall of the reaction vessel, the vacuum pumping system pipe, and the vacuum pump rotor, but the amount is smaller than that of NH ₄ Cl. The clogging of the pump is predominantly due to NH ₄ Cl.
[0005]
The product Si ₃ N _4, which is a product accumulated on the inner wall of the reaction vessel, increases in thickness as the number of times of film formation increases, peels off from the inner wall and falls on the wafer being formed, causing contamination. For this reason, in plasma CVD or the like, cleaning is performed using an NF ₃ gas every several times of film formation to remove Si ₃ N ₄ attached to the wall. At this time, cleaning is performed according to the reaction formulas (2) to (4).
Cleaning during _{Si 3 N 4 + NF 3 +} SiH 4 + NH 3 + N 2 → Si x F y + reaction byproducts ₊ N 2 (2)
Case 1
Si _x F _y + NF ₃ + reaction byproducts _{→ (NH 4) 2 SiF 6} + X (3)
Case 2
SiH ₄ + 2NH ₃ + 2NF ₃ → (NH ₄ ) ₂ SiF ₆ + X (4)
[0006]
At this time, (NH ₄ ) ₂ SiF ₆ is generated as a by-product. This substance also vaporizes at about 300 ° C. at normal pressure, but is solid in a temperature range below that and adheres to the vacuum exhaust pipe and the vacuum pump as described above. In particular, when a by-product adheres to the vacuum pump and breaks down, the production line stops, causing serious damage. For this reason, many production lines of CVD apparatuses are provided with a by-product trap device between the CVD apparatus and the vacuum pump so as to prevent by-products from adhering to the vacuum pump as much as possible.
[0007]
[Problems to be solved by the invention]
However, in the conventional by-product trapping device, when by-products accumulate, the vacuum evacuation is stopped, the vacuum evacuation is removed from the exhaust pipe, and water washing (NH ₄ Cl, (NH ₄ ) ₂ SiCl ₆ are all water-soluble). To remove the adhered products, and then installed in a pipe and evacuated again. Therefore, "disassembly" and reassembly of the exhaust system piping, labor of vacuum leak and re-evacuation are required, and once the vacuum system is opened to the atmosphere, it takes a long time to return to the original degree of vacuum. And productivity such as baking is required.
[0008]
SUMMARY OF THE INVENTION It is an object of the present invention to provide a by-product trap device that can clean by-products and efficiently trap by-products without "blowing" the evacuation system.
[0009]
[Means for Solving the Problems]
The present invention has been made to solve the above problems, and is provided in an exhaust system of a film forming apparatus to solidify products and / or by-products contained in exhaust gas of the film forming apparatus in a trap section. A trap device body for collecting, a heater provided on the trap device body and heating a solidified product and / or by-product, and a product connected to the trap device via a valve and heated and vaporized And / or a cleaning exhaust system for exhausting by- products, a heater for heating the heated and vaporized products and / or by-products flowing in the cleaning exhaust system, and forcibly cooling the trap section. A cooling means for cooling a trap portion during film formation and fixing a product and / or by-product to the trap portion, and heating the trap portion during cleaning to discharge the product and / or by-product. Become There.
[0010]
In another aspect of the present invention, a pump device for sucking the inside of the trap device body to reduce the pressure is provided in the cleaning and exhausting system.
The cleaning and exhaust system may be provided with a gas supply device for supplying an inert gas such as air or N2 gas into the inside of the trap device body to forcibly exhaust gas of a by-product. Further, a trapping step of cooling the trap portion of the trap device body to solidify products and / or by-products contained in the exhaust gas of the film forming device into the trap portion, and heating the trap device body, Vaporizing the solidified products and / or by-products and exhausting the heated and vaporized products and / or by-products by a cleaning and exhaust system connected to the trap device via a valve. You may have it.
Here, the above-described cleaning step may be performed in a state where the inside of the trap device main body is suctioned to reduce the pressure .
[0011]
[Action]
In the present invention, in a trap device main body, products and / or by-products are efficiently solidified and collected in a cooled trap portion, and after being sublimated or decomposed by heating with a heater, they are passed through a valve. It is discharged out of the system by the cleaning exhaust system connected.
[0012]
In another aspect of the present invention, a cooling medium passage for forcibly cooling the trap portion is formed in the trap device body.
Further, in another aspect of the present invention, the sublimation temperature is lower than the normal pressure by the pump device that sucks the inside of the trap device body and lowers the pressure, so that the same cleaning effect is obtained by lowering the heating temperature by the heater.
Incidentally, by forcing exhausting by-product gas by inert gas, such as air or N ₂ gas, cleaning exhaust system of the pump is not required.
[0013]
【Example】
FIG. 1 shows a by-product trap device of the present invention. The apparatus and method of the present invention will be described with reference to FIG.
The by-product trap device is a CVD device 1 that is a film forming device, a main exhaust (vacuum) pump 2 connected to the CVD device 1, and is interposed between the two devices. A trap device main body 3 (hereinafter, abbreviated as main body) for fixing and trapping contained products and by-products. Valves V ₁ and V ₂ are arranged on pipes 4 and 5 connecting the main body 3 and the CVD apparatus 1 and between the main body 3 and the main exhaust pump 2, respectively.
[0014]
CVD apparatus 1, the valve _{V 1,} the main body 3, the valve _{V 2,} the main exhaust pump 2, a main (for film formation) exhaust system A for forming a film smoothly is formed. Downstream of the main exhaust pump 2, an abatement device 6 for treating harmful substances contained in exhaust gas is provided.
A branch pipe 7 is provided in the middle of a pipe 4 connecting the main body 3 and the valve V ₁ , connected to a sub-exhaust (vacuum) pump 8 via a valve V ₃ , and further connected to an abatement apparatus 6. The pipe 9 extending from the branch pipe 7 and valve V ₃ to the auxiliary exhaust pump 8, and a heater 10 is mounted. The main body 3, the branch pipe 7, the valve V ₃ , the pipe 9, and the sub exhaust pump 8 constitute a cleaning exhaust system B.
[0015]
FIG. 2 is a cross-sectional view of the main body 3, in which a trap plate 12 for actively trapping by-products is attached inside a case 11, and both the inner surface of the case 11 and the trap plate 12 are provided. Is the trap section. A cooling jacket 13 is formed in the case 11, and a cooling pipe 14 for supplying cooling water is connected to the cooling jacket 13. A heater 15 (see FIG. 1) for heating the entire body 3 and the trap plate 12 is attached to the case 11. The main body 3 and the heater 15 of the cleaning / exhaust system B may be provided with a ribbon heater or a heating element may be sprayed on the main body and the exhaust system piping.
[0016]
Hereinafter, the operation of the trap device configured as described above will be described.
During film formation, the main exhaust system A for film formation is used by opening the valves V ₁ and V ₂ and closing V ₃ . At this time, water, liquid nitrogen, or the like is caused to flow through the cooling pipe 14 to lower the temperature of the trap portion, thereby making it easier to capture by-products. Usually, water is sufficient.
In the apparatus having the configuration as shown in the figure, the degree of vacuum inside the main body 3 is considered to be in the order of 10 to 10 ^-1 Torr. In a vacuum state, since the sublimation temperature of the by-product is lower than that at normal pressure, the by-product can be captured by actively cooling the trap portion. As shown in FIG. 3 (edited by The Chemical Society of Japan, Basic Handbook of Chemistry 2, Maruzen 1984, P2-111), the sublimation temperature of NH ₄ Cl is about 210 ° C. at 10 Torr from the theoretical value ⁽¹⁾ .
[0017]
In this way, by-products causing clogging of the pump are trapped from the exhaust gas, so that by-products fly to the exhaust system piping and the pump section after the trap device main body 3 are significantly reduced. Thereby, clogging of the pump can be eliminated, and failure of the pump → stop → stop of the film forming line can be eliminated.
[0018]
At a point in time when the film forming process has been performed to some extent, the trap device main body 3 is cleaned at a time when the film forming process is not being performed. At this time, the valves V ₁ and V ₂ are closed, the valve V ₃ is opened, and the vacuum pump 2 of the cleaning system B is operated. At this time, the heater 15 of the main body 3 is turned on, the temperature of the trap portion is raised to a temperature equal to or higher than the sublimation point, and the main body 3 is evacuated. In this manner, by sublimating the main body 3, sublimation or decomposition gasification can be performed in a lower temperature range than the atmospheric pressure state (at about 210 ° C. at 10 Torr, the temperature at this time is about 220 to 300 ° C.). Is enough).
[0019]
At the same time, the temperature of the pipes 7 and 9 of the exhaust system B is increased so that by-products do not adhere to the pipes. The temperature of the pipe at this time is ideally about 220 to 300 ° C., but even if the temperature is lower than that, adhesion of by-products is extremely small. If the by-product is NH ₄ Cl as shown in the formula (1), it is decomposed by sublimation to form NH ₃ and HCl. These gases are rendered harmless by the abatement system and released into the atmosphere.
[0020]
In FIG. 1, the main vacuum pump is shown as a dry roots pump, and the sub vacuum pump is shown as an oil rotary pump which is less expensive than the roots pump. In the film forming process, an oil rotary pump in which the oil flows backward is not preferable, and it is not necessary to use an expensive roots pump for cleaning only the main body. However, both the vacuum pump 1 and the vacuum pump 2 may be roots pumps or oil rotary pumps. Further, the vacuum pump may be other than the roots pump and the oil rotary pump as described herein.
[0021]
In the case of FIG. 1, there is a concern that by-products may adhere to the sub-vacuum pump (oil rotary pump) used for exhaust for cleaning. However, if the temperature of the pipe is increased until immediately before the vacuum pump, exhaust gas is introduced into the pump. The gas temperature does not drop significantly even if gas enters, so that adhesion here is small.
In such a case you do not want to use the sub-vacuum pump 8 for exhaust cleaning concerns the deposition, as shown in FIG. 4, the compressor 16 is provided through the valve V ₄ between the body 3 and the valve V _2, This may be supplied with an inert gas, such as air or N _2. In this case, the temperature of the trap portion sublimation point, or by-products above the temperature decomposed and gasified, and V _3, V ₄ closing the valves V _1, V ₂ and the open, non such as air or N ₂ By flowing the active gas, the by-product gas is transferred to the abatement device, and the by-product trap device is washed. From the viewpoint of cost, the flowing gas is sufficient.
[0022]
In the above, the case where the by-product is NH ₄ Cl has been mainly described. However, even when the by-product is (NH ₄ ) ₂ SiF ₆ or AlCl ₃ , the trapping method and the cleaning method are the same. is there.
[0023]
【The invention's effect】
As described above, during film formation in which by-products that cause clogging of the vacuum pump are generated, the by-products are actively collected by lowering the temperature of the by-product trap device body and the vacuum is removed. Reduce the occurrence of clogging of the pump and extend the life of the pump. On the other hand, when the film is not formed, the inside of the main body is set to a high temperature and a low pressure, and the by-product is cleaned in-line in a temperature range lower than the normal pressure without removing the main body from the main exhaust line. Therefore, when the by-product trap device of the present invention is attached to a film forming apparatus, the operation rate increases, which leads to an improvement in film forming productivity.
[Brief description of the drawings]
FIG. 1 is a schematic view showing one embodiment of a by-product trap device of the present invention.
FIG. 2 is a sectional view of a trap device main body.
FIG. 3 is a diagram showing a relationship (theoretical value) between a degree of vacuum and a sublimation temperature.
FIG. 4 is a schematic diagram showing another embodiment of the by-product trap device at the time of cleaning.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 CVD apparatus 2 Main exhaust pump 3 Trap device main body 8 Sub exhaust pump 10 Heater 11 Case 12 Trap plate 14 Cooling pipe 15 Heater 16 Compressor A Main exhaust system B Cleaning exhaust system

Claims (2)

A trap device main body that is attached to an exhaust system of the film forming device and solidifies and traps products and / or by-products contained in the exhaust gas of the film forming device in a trap portion;
A heater provided on the trap device main body, for heating the solidified product and / or by-product;
A cleaning exhaust system connected to the trap device via a valve to exhaust heated and vaporized products and / or by-products;
A heater for heating the heated and vaporized products and / or by-products flowing in the cleaning and exhaust system;
Cooling means for forcibly cooling the trap portion,
During film formation, the trap portion is cooled to fix products and / or by-products thereon, and during cleaning, the trap portion is heated to discharge products and / or by-products. By-product trapping device. 2. The trap device according to claim 1, wherein the cleaning / exhaust system is provided with a pump device that sucks the inside of the trap device body to reduce the pressure.

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