JPH0864582A - Semiconductor wafer treatment equipment - Google Patents

Abstract

PURPOSE: To prevent semiconductor wafer contamination due to the swirl of particles in a chamber, by setting a specific break filter made of ceramics, in the gas flowing-out vent of a preliminary chamber in which a treatment equipment for a wafer to be treated is temporarily carried from the outside and held. CONSTITUTION: A wafer W is carried in a preliminary chamber 2. By closing a partition, the inside of the chamber 2 is kept airtight, and then turned into the state of reduced pressure by exhausting the air through a gas exhaust vent 10. The same atmospheric gas as a treatment chamber 1 is introduced in the chamber 2 through a gas flowing-out vent 12 where a break filter made of ceramics is arranged which is stretched and installed in the chamber 2 and has an average thin hole diameter smaller than or equal to 5μm. Thus a gas introducing process for substituting the inside of the preliminary chamber 2 by the gas in the treatment chamber 1 is ended. Since the gas flows into the preliminary chamber 2 through the break filter made of ceramics, the gas flow rate can be finely adjusted, and the semiconductor wafer contamination due to the swirl of particles in the chamber can be prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor wafer processing apparatus used for various kinds of processing of semiconductor wafers, and more specifically, it has a processing chamber for semiconductor wafers, a predetermined gas exhaust port and a gas inlet port, and is capable of depressurizing. The present invention relates to a semiconductor wafer processing apparatus including a preliminary chamber.

[0002]

2. Description of the Related Art In a semiconductor manufacturing process, a semiconductor wafer is processed under various conditions such as a reduced pressure or a gas atmosphere having a composition different from the atmosphere. Conventionally, in such a processing step, usually, a wafer to be processed is first stored in the atmosphere in the load side preliminary chamber for introducing a wafer, then the gas in the preliminary chamber is discharged to reduce the pressure, and then, if necessary. It is general that a processing atmosphere gas is introduced into the preliminary chamber so that the atmosphere of the processing chamber is substantially the same as that of the processing chamber continuous with the preliminary chamber, and then the wafer is transferred from the preliminary chamber to the processing chamber for processing. The processed wafer that has been processed in the processing chamber is transferred to the unload-side preliminary chamber for taking out the processed wafer. In this case, as the unload-side preliminary chamber, the load-side preliminary chamber accommodating the wafer to be processed is also used as the unload-side preliminary chamber, or it is provided separately from the processing chamber in the same manner as the load-side preliminary chamber. That method is adopted. Further, the unload-side preliminary chamber in which the wafer to be processed is transferred and stored is previously held under the same atmospheric condition as the atmospheric condition in the processing chamber. Finally, the processed wafers stored in the unload side spare chamber are evacuated in advance if the spare chamber has a harmful atmosphere.
Atmosphere or a gas such as nitrogen gas is introduced into the preliminary chamber to take out the processed wafer. The above-mentioned load side preliminary chamber and unload side preliminary chamber are generally called load locks, and can be normally held under reduced pressure such as vacuum. As described above, the load lock chamber, that is, the preliminary chamber, is adjusted to the external atmosphere when the wafer to be processed is carried in from the outside or the processed wafer is carried out to the outside. Normally, the preliminary chamber is provided with a gas introduction port. Therefore, it is possible to release a depressurized state such as a vacuum by introducing gas.

Gas is introduced by means of a valve to release the above depressurized state. In order to prevent particles such as fine dust from flying up in the spare chamber, conventionally, the gas introduction speed is such that the valve is slowly opened. The slow vent method is adopted to reduce the. However, no matter how carefully the valve is opened and closed, at the moment when the valve is opened from the decompressed state such as vacuum, there is a sudden change in the pressure and the particles fly up into the load lock chamber, and the particles adhere to the wafer surface. There was a problem of being polluted. Therefore, in recent years, for the purpose of buffering the pressure, a gas introduction port provided on the wall surface of the load lock chamber, a metal or an element made of a porous resin film such as Teflon is attached and operated. This element is generally called a break filter.

[0004]

However, even in a preparatory chamber using the above-mentioned break filter made of metal or a porous resin film such as Teflon, it is possible to prevent particle contamination of semiconductor wafers as desired. There is a demand for a semiconductor wafer processing apparatus that cannot do so and has less pollution. SUMMARY OF THE INVENTION It is an object of the present invention to solve the above problems in a semiconductor wafer processing apparatus, and in particular, to prevent the particles from rising when releasing the depressurized state in the preparatory chamber and prevent the semiconductor wafer from being contaminated. For the above-mentioned purpose, the inventors have diligently studied the gas introduction operation to the preliminary chamber, and when using a break filter made of a conventional metal or a porous resin film such as Teflon, the following problems I found out. That is, (1) Since the pore diameter of the conventional metal or Teflon porous membrane filter that is generally used is relatively large, the pressure buffering effect is small and it is not possible to completely prevent the particles from flying up. (2) When a corrosive gas is used in the processing chamber, it is difficult to completely block the diffusion of the corrosive gas from the processing chamber into the load lock. Therefore, a metal break filter or a mounting metal such as a screw is used. Parts are easily corroded. (3) Since the break filter is attached only to the introduction port and the effective area of the filter is small, pressure loss is large and it takes time to return to the external pressure. (4) In particular, a filter made of a resin porous membrane such as Teflon has a problem in strength, pressure fluctuation cannot be reduced more than a predetermined value, and particles rise up. The inventors have further earnestly studied on the basis of the above findings to improve the method for introducing gas into the auxiliary chamber, which has a sufficient buffering effect against pressure fluctuations, and as a result, have completed the present invention.

[0005]

According to the present invention, a semiconductor wafer processing chamber and at least one spare chamber are hermetically connected by a connecting portion having a partition wall that can be opened and closed, and
The spare chamber is airtightly isolated from the outside by a partition that can be opened and closed, and at least a gas discharge means and a gas introducing means are provided in the spare chamber, and the gas introducing means is provided in an internal space of the spare chamber. A semiconductor wafer processing apparatus having at least one extended gas outlet, and a ceramic break filter having a ceramic layer having an average pore diameter of 0.2 μm or less is arranged at the gas outlet. Provided.

In this case, although it depends on the size of the preliminary chamber, it is preferable that the length of the break filter is 50 mm or more in total, either in single or in plural. Further, it is preferable that the break filter is arranged in parallel with a surface of a wafer housed in the preliminary chamber. Further, it is preferable that the gas introduced into the preliminary chamber is in a laminar flow state by the break filter.

[0007]

The present invention is configured as described above, and when the semiconductor wafer is transferred to the processing chamber, the auxiliary chamber which is a load lock chamber for temporarily carrying in and out the wafer to be processed is held from the outside.
Since the gas flows out through a fine-grain ceramic break filter, the gas flow rate can be adjusted minutely, the pressure fluctuation can be buffered, and the particles such as dust in the room can be prevented from flying up. Can be protected from pollution. Further, by arranging the ceramic break filter at a predetermined position, it is possible to make the gas outflow into the preliminary chamber be in a laminar flow state, similarly to suppress the particle soaring as much as possible and prevent the semiconductor wafer from being contaminated. it can.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the drawings. However, the present invention is not limited to the following examples. FIG. 1 is a schematic explanatory view of an example of a semiconductor wafer etching processing apparatus using a chlorine-based gas according to an embodiment of the present invention. The semiconductor wafer etching processing apparatus of FIG. 1 includes a processing chamber 1, a load side preliminary chamber 2 for loading a processing target wafer and unload side preliminary chambers 3 for unloading a processing wafer, which are arranged on both sides of the processing chamber 1. Two
There are two load lock chambers, and the auxiliary chambers 2 and 3 are hermetically connected to the processing chamber 1 by connecting portions 4 and 5, respectively. Partitions 6 and 7 that can be opened and closed are provided on each of the connecting portions 4 and 5.
Are arranged, and when the partition walls 6 and 7 are open, the load side and unload side auxiliary chambers 2 and 3 are in air-tight communication with the processing chamber 1, respectively, while in the closed state, they are in air-tightness with the processing chambers. To be isolated. The processing chamber 1 is a cylindrical body whose upper and lower ends are closed, and a reaction gas supply pipe 8 having a valve is installed on the upper surface and an exhaust pipe 9 is installed on the lower surface. Further, in each of the auxiliary chambers 2 and 3, gas outlets 10 and 11 and gas outlets 12 and 13 in which a break filter made of ceramic is arranged are arranged.

Next, an example of a wafer processing step using the semiconductor wafer etching apparatus shown in FIG. 1 will be described. First, an openable / closable partition wall (not shown) provided in the load side auxiliary chamber 2 is opened to communicate with the external space,
After the wafer W to be processed is loaded into the preparatory chamber 2, the partition wall is closed again to keep the preparatory chamber 2 airtight, and then the preparatory chamber 2 is evacuated through the gas exhaust port 10 to a depressurized state.
Then, the same atmosphere gas as that of the processing chamber 1 is introduced into the preliminary chamber 2 from the gas outlet 12 which is extended and installed in the preliminary chamber 2 and in which the ceramic break filter is arranged. The first gas introduction step of substituting the gas in the processing chamber 1 is completed. The first gas introduction step may be performed at the same time as the exhaust gas decompression step, or by introducing the replacement gas without installing an exhaust means such as a gas exhaust port in the load side auxiliary chamber 2. The gas in the auxiliary chamber 2 may be replaced by only natural exhaust.

Next, an openable / closable partition wall 6 provided in a connecting portion 4 for air-tightly connecting the load side auxiliary chamber 2 and the processing chamber 1
Is opened, the load side preliminary chamber 2 and the process chamber 1 are communicated with each other, the wafer W to be processed is transferred into the process chamber 1 and placed on a predetermined susceptor, and then the partition wall 6 is closed again to load the load side. The preliminary chamber 2 and the processing chamber 1 are airtightly isolated from each other. afterwards,
A chlorine-based gas is supplied from the reaction gas supply pipe 8 into the processing chamber 1 to etch the wafer W. After the etching process, the openable / closable partition wall 7 provided in the connecting portion 5 that connects the unload-side preliminary chamber 3 and the processing chamber 1 is opened to communicate the unload-side preliminary chamber 3 and the processing chamber 1 with each other. The processed wafer W that has been subjected to the etching process is transferred into the unload-side preliminary chamber 3 together with the atmospheric gas in the processing chamber 3, and then the partition wall 7 is closed again to hermetically seal the unload-side preliminary chamber 3 and the processing chamber 1, respectively. Quarantine. Next, the unload-side auxiliary chamber 3 is evacuated from the gas in the auxiliary chamber 3 through the gas discharge port 11 to bring it into a depressurized state such as a vacuum. Thereafter, while evacuation if necessary, gas is introduced from the gas outlet 13 which is extended and installed in the spare chamber 3 and in which a ceramic break filter is arranged, and the inside of the unload side spare chamber 3 is replaced with a safe atmosphere gas. The second gas introduction step is completed. Finally, the unload side spare room 3
An openable and closable partition wall (not shown) provided in the open space is opened to communicate with the external space, the processed wafer W is taken out to the external space, and then the partition wall is closed again.

FIG. 2 is a schematic explanatory view of the unload side spare chamber. In FIG. 2, the unload-side preliminary chamber 3 is provided with an openable / closable partition wall 7 communicating with the processing chamber and an openable / closable partition wall 15 communicating with the external space. A gas introduction pipe 16 continuous from an outdoor gas supply source is connected to the upper space of the room. A cylindrical break filter 17 made of ceramic is connected to the open end of the introduction pipe 16.
In this case, the outer diameter of the cylindrical ceramic break filter 17 is usually preferably 10 mm or more. In addition, the gas outflow surface area is 15 regardless of the shape of the break filter.
It is preferable to set it to 00 mm ² . The length of the ceramic break filter 17 can be appropriately selected depending on the equivalent diameter of the break filter, the gas outflow surface area, the diameter of the wafer to be processed, the size of the processing chamber, and the like. Normally,
It preferably has a length of 50 mm or more, and more preferably 50 mm to 100 mm. When a plurality of break filters are installed, it is preferable that the total length of the plurality of break filters is 50 mm or more. The length of the ceramic break filter 17 is 5
This is because when the thickness is 0 mm or less, the pressure loss is large, it takes time to replace the atmospheric gas, and the gas cannot be supplied to the wafer surface in a laminar flow state, causing particles to fly up. The cylindrical ceramic break filter 17
May close half of the outer peripheral surface of the cylinder, for example, the upper half peripheral surface, and allow the gas to flow out only from the remaining half peripheral surface. The load side auxiliary chamber can also be configured in substantially the same manner as the above unload side auxiliary chamber.

In the present invention, regardless of the shape and structure of the gas outflow portion, the total length of the gas outflow portion of the break filter is preferably 50 mm or more as described above, and from that portion. Is preferably constructed so that the gas flows out uniformly. When using a plurality of break filters, the gases flowing out from the respective filters are arranged so as to be in a laminar flow state. For example, a plurality of them are arranged so as to be parallel to each other, or arranged in a straight line. By configuring as described above, it is possible to introduce the outflow gas into the auxiliary chamber in a laminar state in all directions,
The outflow gas flows as if sweeping the surface of the wafer carried into the preliminary chamber with a broom, and the soaring of particles is suppressed as much as possible. At the same time, it is possible to prevent the particles from falling and adhering to the wafer surface even if the particles fly up.

The ceramic break filter of the present invention has an average pore diameter of 0.5 μm or less, preferably 0.2 μm.
It has the following ceramic layers: This is because when the average pore diameter of the ceramic layer is larger than 0.5 μm, the outflow gas is jetted out vigorously, and the particles do not flow in a laminar flow state but rise up. On the other hand, if the average fine pore diameter is smaller than 0.1 μm, the pressure loss is large, and it takes a long time to introduce the gas into the auxiliary chamber and replace the atmosphere gas, which is not preferable. However, in this case, the time required for gas replacement can be adjusted by adjusting the gas outflow surface area in consideration of the filter length, the number of filters arranged, and the size of the preliminary chamber. The ceramic constituting the ceramic break filter of the present invention has an average pore diameter of 0.5 μm or less,
The thickness is preferably 0.2 μm or less, and is a ceramic material having corrosion resistance to the gas for treatment and heat resistance, and can be appropriately selected from known ceramic materials. Usually, ceramic materials such as alumina, silicon carbide and quartz glass are preferably used. Especially when alumina is used, its purity is 99%.
The above is preferable.

Example 1 (Fabrication of Ceramic Break Filter) FIG. 3 is a partial cross-sectional structure explanatory view of an example of the ceramic break filter of the present invention used in this example. In FIG. 3, the diameter 1
A ceramic filter 20 (manufactured by Toshiba Ceramics Co., Ltd., trade name Membrane Rocks) having an alumina ceramic layer having an average pore diameter of 0.2 μm on the surface of an alumina ceramic cylinder having a length of 9 mm and a length of 50 mm is provided at both ends thereof. Stainless steel (S
Disks 22 and 22 made of US316L) were arranged to form a hollow cylinder closed at both ends. Into this hollow cylinder closed at both ends, a stainless pipe 23 was inserted into the internal space through the disk 22 from one closed end. The end of the pipe 23 in the hollow portion of the ceramic filter 20 is closed, and the peripheral surface of the pipe 23 located in the hollow portion is provided with 6 holes 24 of about 2 mm at a constant interval in the axial direction. Similarly, a total of 24 holes 24 'are provided on the peripheral surface at positions shifted by a predetermined distance in the axial direction and shifted by 90 degrees in the rotational direction of the shaft. Ceramic break filter 1 configured and formed as described above
7, the gas flowing into the pipe 23 is
It was possible to flow out from Nos. 4 and 24 'into the hollow portion of the ceramic filter 20, and to uniformly jet out from the outer peripheral surface through the ceramic filter 20. Incidentally, in order to more completely prevent the corrosion of the metal parts such as the disk 22 and the pipe 23, the metal parts may be subjected to anticorrosion treatment such as thermal spraying of ceramics.

(Formation of Preliminary Chamber) FIG. 4 is a conceptual explanatory view in which a ceramic break filter is arranged in the preliminary chamber housing. FIG. 5 is an explanatory diagram showing the positional relationship between the ceramic break filter and the semiconductor wafer in the auxiliary chamber housing. In FIG. 4, when the ceramic break filter 17 formed as described above is set in the upper part of the pre-chamber housing 30, the wafer W having a diameter of 6 inches is set on the wafer cassette 31, the break filter 17
Were arranged so as to be located right above the center of the wafer W (see FIG. 5). Further, the gas introduction pipe 32 is connected to the pipe 23 of the break filter 17 through the valve V1, and the inside of the housing 30 and the gas discharge pipe 33 are connected to each other, and the gas discharge pipe 33 is connected.
A valve V2 is disposed in the gas exhaust pipe 33, and a fine adjustment valve V3 is disposed in the gas exhaust pipe 33 by bypassing the valve V2. Further, a pressure gauge P for measuring the internal pressure of the housing is provided.

(Depressurizing and Pressurizing Operation in Preparatory Chamber) A wafer W having a diameter of 6 inches was set on a cassette 31 in the preparatory chamber housing 30 formed as described above. Next, the break filter 17 was set so as to be right above the center of the wafer. Next, from the gas exhaust pipe 33 to the housing 30
The inside was evacuated to 5 × 10 ^-2 Torr. After that, high-purity nitrogen gas was circulated from the gas introduction pipe 32 through the valve V1 at a constant gas flow rate, the high-purity nitrogen gas was introduced from the break filter 17 into the housing 30, and the pressure was increased to atmospheric pressure. The relationship between the pressure in the housing 30 and the gas flow rate at this time is shown in FIG. After the above operation, the wafer W was taken out, and the number and size of particles adhering to the surface of the wafer W were measured by the wafer surface defect inspection apparatus. Similarly, the operation was repeated 3 times, and the average value of the results is shown in Table 1.

Examples 2 to 4 The preparatory chamber was operated in the same manner as in Example 1 except that the lengths of the filters were 50 mm, 200 mm and 300 mm. Regarding the adhesion of particles on the wafer, only the total number was measured, and the results are shown in Table 1.

Comparative Example 1 The same operation as in Example 1 was carried out except that the break filter 17 was not arranged in the gas introduction pipe 32 but the gas was introduced directly into the housing 30 from the end of the gas introduction pipe 32. Example 2
Similarly to the above, only the total number of particles attached on the wafer was measured, and the results are shown in Table 1.

[0019]

[Table 1]

Comparative Example 2 The same operation as in Example 1 was carried out except that a metal break filter having a length of 100 mm and an average pore diameter of 3 μm was used. The results are shown in Table 1.

Example 5 The same apparatus as in Example 1 was used, except that the high-purity nitrogen gas was introduced from the gas inlet pipe 32 through the valve V1 so that the pressure in the preparatory chamber was kept constant so that the gas flow rate was constant. The procedure was as in Example 1. The relationship between the pressure in the housing 30 and the gas flow rate at that time is shown in FIG. Further, the particle adhesion on the wafer was measured in the same manner as in Example 1, and the results are shown in Table 2.

[0022]

[Table 2]

Examples 6 to 8 The preparatory chamber was operated in the same manner as in Example 5 except that the lengths of the filters were 50 mm, 200 mm and 300 mm. Regarding the adhesion of particles on the wafer, only the total number was measured, and the results are shown in Table 2.

Comparative Example 3 The same operation as in Example 5 was carried out except that the break filter 17 was not arranged in the gas introduction pipe 32 and the gas was introduced directly into the housing 30 from the end of the gas introduction pipe 32. Only the total number of particles deposited on the wafer was measured, and the results are shown in Table 2.

Comparative Example 4 The same operation as in Example 5 was carried out except that a metal break filter having a length of 100 mm and an average pore diameter of 3 μm was used. The results are shown in Table 2.

Ninth Embodiment Using the same apparatus as in the first embodiment, the pressure in the spare chamber is increased so that the flow rate increases proportionally with time from the initial stage to the middle stage of supplying high-purity nitrogen gas from the gas introduction pipe 32 through the valve V1. The same operation as in Example 1 was performed except that the operation was performed. The relationship between the pressure in the housing 30 and the gas flow rate at that time is shown in FIG. Table 3 shows the results of particle adhesion on the wafer.

[0027]

[Table 3]

Examples 10 to 12 The preparatory chamber was operated in the same manner as in Example 9 except that the lengths of the filters were 50 mm, 200 mm and 300 mm. Only the total number of particles deposited on the wafer was measured, and the results are shown in Table 3.

Comparative Example 5 The same operation as in Example 9 was carried out except that the break filter 17 was not arranged in the gas introduction pipe 32 but the gas was introduced directly into the housing 30 from the end of the gas introduction pipe 32. Only the total number of particles deposited on the wafer was measured, and the results are shown in Table 3.

Comparative Example 6 The same operation as in Example 9 was carried out except that a metal break filter having a length of 100 mm and an average pore diameter of 3 μm was used. Table 3 shows the results.

As is clear from the above Examples and Comparative Examples, when the ceramic break filter of the present invention having a fine average pore size is used to boost the pressure in the auxiliary chamber, it goes without saying that no filter is used. It can be seen that the adhesion of particles is extremely reduced as compared with the metal filter, and the rising of particles is suppressed. It can also be seen that the longer the ceramic break filter is, the more gradually the particles are attached. Further, the time required for introducing gas from the reduced pressure and returning it to normal pressure is short and practical.

[0032]

According to the semiconductor wafer processing apparatus of the present invention, a predetermined ceramic break filter is set at the gas outlet of the load lock chamber for temporarily carrying in / out the wafer to be processed from the outside and holding it. Since the buffering effect at the time of fluctuation is exhibited, and the gas can be made to flow into the preliminary chamber in a laminar flow state, it is possible to prevent the semiconductor wafer from being contaminated due to the rising of particles in the preliminary chamber, which is a problem in the conventional method. In addition, the time required to increase the pressure from the reduced pressure in the preliminary chamber is short, which is industrially useful.

[Brief description of drawings]

FIG. 1 is a schematic explanatory diagram of a semiconductor wafer etching processing apparatus according to an embodiment of the present invention.

FIG. 2 is a schematic explanatory diagram of an unload-side auxiliary chamber according to an embodiment of the present invention.

FIG. 3 is a partial cross-sectional structural explanatory view of a ceramic break filter used in an example of the present invention.

FIG. 4 is a conceptual explanatory view in which the ceramic break filter of the present invention is arranged in a preliminary chamber housing.

FIG. 5 is an explanatory diagram showing an example of the positional relationship between the ceramic break filter and the semiconductor wafer in the auxiliary chamber housing of the present invention.

FIG. 6 is a diagram showing a relationship between a pressure and a gas flow rate when a gas flow rate of the ceramic break filter according to an embodiment of the present invention is kept constant and the pressure in the auxiliary chamber housing is increased from a reduced pressure to an atmospheric pressure.

FIG. 7 is a diagram showing a relationship between a pressure and a gas flow rate when a gas flow rate is made to flow from a ceramic break filter in one embodiment of the present invention at a constant flow rate to increase the pressure in the pre-chamber housing from a reduced pressure to an atmospheric pressure.

FIG. 8 is a diagram showing a case in which the ceramic break filter according to an embodiment of the present invention is circulated so that the flow rate increases proportionally with time from the initial stage to the middle stage of supply, and the pressure inside the pre-chamber housing is increased from the reduced pressure to the atmospheric pressure. It is a relationship diagram of the pressure and the gas flow rate.

[Explanation of symbols]

 1 Processing Room 2 Load Side Spare Room 3 Unload Side Spare Room 4, 5 Connection Chamber 6, 7, 15 Partition 8 Reaction Gas Supply Pipe 9 Exhaust Pipe 10, 11, 33 Gas Discharge Pipe 12, 13 Gas Outlet 16, 32 Gas introduction pipe 17 Ceramic break filter 20 Ceramic filter 21 Gasket 22 Disc 23 Pipe 24 Hole 30 Preliminary chamber housing 31 Wafer cassette W Wafer V1, V2, V3 Valve P Pressure gauge

Claims (4)

[Claims] 1. A semiconductor wafer processing chamber and at least one preliminary chamber are airtightly connected by a connecting portion having a partition wall that can be opened and closed, and the preliminary chamber is airtightly isolated from the outside by an opening and closing partition wall. In addition, at least a gas discharging means and a gas introducing means are provided in the spare chamber, and the gas introducing means has at least one gas outlet extending into the internal space of the spare chamber. A semiconductor wafer processing apparatus, wherein a ceramic break filter having a ceramic layer having an average pore diameter of 0.5 μm or less is arranged at the outlet. 2. The semiconductor wafer processing apparatus according to claim 1, wherein the total length of the break filters is 50 mm or more. 3. The semiconductor wafer processing apparatus according to claim 1, wherein the break filter is arranged parallel to a surface of a wafer housed in the preliminary chamber. 4. The semiconductor wafer processing apparatus according to claim 1, wherein gas is introduced into the preliminary chamber in a laminar flow state by the break filter.