JP2009092038A - Vertical screw vacuum pump - Google Patents

Abstract

The present invention provides a vacuum pump capable of preventing operation from being hindered and reducing the frequency of maintenance by preventing intrusion of massive reaction products into an exhaust chamber.
A vertical screw vacuum pump used in a semiconductor manufacturing process, wherein a pair of screw rotors are rotatably fixed in a housing with a rotating shaft vertical, and an air intake port is a side surface from an upper end surface of the housing. And at least a part of the screw rotor when viewed from above, an exhaust port is opened at the lower part of the housing, and the intake port and the exhaust port are always connected by the housing and the pair of screw rotors. A recess for accommodating a reaction product is provided in a housing inner peripheral portion at a lower end portion of the intake port at a position until the exhaust chamber is closed by the intake side housing and a pair of screw rotors. .
[Selection] Figure 2

Description

  The present invention relates to a screw-type vacuum pump used in a semiconductor manufacturing process for semiconductor products, electronic parts, and the like. A reaction product falling from a reaction chamber of a semiconductor manufacturing apparatus to an inlet of a screw-type vacuum pump is a screw-type vacuum pump. It is related with the structure which makes it difficult to enter into the exhaust chamber.

In a manufacturing process of a semiconductor product, a film such as a poly-Si film, a silicon nitride film, or a silicon oxide film is formed on the surface of an object to be processed.
In forming these films, a chemical vapor deposition apparatus (CVD), an etching apparatus or the like is generally used.
For example, when a film is formed using the above-described chemical vapor deposition apparatus (CVD), a quartz boat loaded with a large number of objects to be processed is accommodated in the reaction chamber of the apparatus, and the reaction chamber is subjected to a reduced pressure and heating environment. To make. A source gas such as SiH4, SiH2Cl2, NH3 is supplied from the source gas supply system to form a reaction product film such as a poly-Si film or a silicon nitride film on the surface of the object to be processed. Further, the process gas (gas) supplied to the reaction chamber in such a chemical vapor deposition apparatus (CVD) or etching apparatus is exhausted from the reaction chamber by a vacuum pump.

By the way, it is known that a raw material gas such as SiH4, SiH2Cl2, and NH3 causes a chemical reaction in a reaction chamber to produce a solid powdery reaction product.
Further, in this reaction product, for example, a reaction product is generated due to a change in physical conditions such as a pressure increase from a reduced pressure state and a temperature decrease from a high temperature state, and further the powdery reaction product. It is known that there are those that aggregate to form a massive solid.

When such a reaction product is generated, the reaction product enters into the vacuum pump together with the processed process gas (gas), which causes a problem in the operation of the vacuum pump.
The applicant of the present application has made extensive studies on this problem and has proposed the invention described in Patent Document 1 (Japanese Patent Application Laid-Open No. 2004-36547).

The previously proposed invention will be described with reference to FIGS. FIG. 8 is a front sectional view of a main part showing a schematic internal structure of the vacuum pump, and FIG. 8 is a sectional view of the vacuum pump of FIG.
As shown in the figure, the vacuum pump 100 includes a casing 103 formed with an intake port portion 101 and an exhaust port 102 connected to an exhaust pipe (not shown) connected to the reaction chamber. In the casing 103, screw rotors 104 and 105 are accommodated in parallel so as to mesh with each other in a non-contact meshing state with a predetermined clearance (a minute gap).

Between the casing 103 and the screw rotors 104, 105, bearings 106, 107, 108, 109 and seal members 110, 111, 112, 113 for sealing the shaft holes are provided.
Synchronous gears 114 and 115 that are integrally attached to the screw rotors 104 and 105 are provided, and a driving means 116 such as a motor is provided at one end of the screw rotor 105.

Further, the screw rotors 104 and 105 have a predetermined clearance with respect to the inner wall surface 103a of the casing 103, for example, an outer diameter dimension and an axial length separating a gap of 50 microns.
A plurality of spiral working chambers are formed that are partitioned by the meshing portions of the casing 103 and the screw rotors 104 and 105, and the working chambers move in the axial direction of the rotating shaft by the rotation of the screw rotors 104 and 105. It is configured.

  In addition, the intake port portion 101 has one end connected to an exhaust pipe (not shown) connected to the reaction chamber and the other end connected to the intake port 101b of the casing, and the intake port 101b. And a net-like reaction product trap 117 arranged immediately before. The intake pipe 101a in the vicinity of the trap 117 is provided with a storage chamber 101c for storing the reaction product 118.

In the vacuum pump 100 configured as described above, when the screw rotors 104 and 105 are rotated by the driving means 116 such as a motor, the working chamber partitioned by the meshing portion of the casing 103 and the screw rotors 104 and 105 is inhaled. It moves from the port 101b side to the exhaust port 102 side.
Thereby, the process gas (gas) in the working chamber sucked from the suction port 101 b is transferred to the exhaust port side and exhausted from the vacuum pump 100.

At this time, the above-described reaction product 118 is captured by the net-like reaction product trap 117, and intrusion into the vacuum pump is suppressed. In particular, the reaction product 118 that is so massive as to hinder the operation of the vacuum pump is captured by the reaction product trap 117.
In addition, the reaction product attached and deposited inside the reaction chamber or the exhaust pipe connecting the reaction chamber and the vacuum pump may be separated into a massive reaction product 118 and fall inside the intake pipe 101a. However, since the storage chamber 101c is provided, it is captured in the storage chamber 101c.

In this way, since the reaction product 118 is prevented from entering the inside of the vacuum pump, it is possible to avoid a situation in which the screw rotors 104 and 105 cannot rotate and the vacuum pump becomes inoperable.
JP 2004-36547 A

In the vacuum pump 100 described above, since the reaction product trap 117 is disposed immediately before the intake port 101b, a space for arranging the reaction product trap 117 is required. There is a problem that the arrangement space becomes large.
Further, when the storage chamber 101c for storing the reaction product 118 is filled with the trapped reaction product 118, when the reaction product is cleaned, the storage chamber 101c cannot be seen from the intake port. When it is arranged, a special tool for cleaning is required, and it is difficult to confirm whether or not the remaining reaction product remains.

  In particular, when a cantilevered screw vacuum pump that supports the screw rotor only at one shaft end is placed vertically, the intake port must be formed on the screw end surface in order to reduce the placement space and not deteriorate conductance. If the reaction product sucked into the exhaust chamber is a fine powder, it is unlikely to cause a major problem in vacuum pump operation even if it is sucked. However, the exhaust connected between the reaction chamber or the reaction chamber and the vacuum pump is difficult. When the bulk reaction product peeled from the pipe was sucked, the air inlet was formed on the end face of the screw, so that it dropped directly into the exhaust chamber, which hindered the operation of the empty pump.

  The present invention has been made on the basis of the above problems, and in particular, by preventing the intrusion of bulk reaction products into the vacuum pump, there is no hindrance to the operation of the vacuum pump, and the arrangement space is small. In addition, it is an object of the present invention to provide a vertical screw vacuum pump that can be easily maintained.

The present invention has been made to achieve the above object, and a vertical screw vacuum pump according to the present invention is a vertical screw vacuum pump used in a semiconductor manufacturing process, in which a pair of screw rotors has a rotating shaft. The intake port is open from the upper end surface to the side surface of the housing and is opened at a position overlapping at least a part of the screw rotor as viewed from above. An exhaust port is opened at a lower portion of the housing, and the housing and the pair of screw rotors are partitioned so that the intake port and the exhaust port do not always communicate with each other, and the exhaust chamber is closed by the intake side housing and the pair of screw rotors. A recess for accommodating the reaction product is provided in the inner peripheral portion of the housing at the lower end of the intake port. By adopting such a configuration, it is not necessary to provide a trap for accommodating the reaction product as a separate member from the housing, and the vacuum pump can be reduced in size.
In particular, for a vertical screw vacuum pump in which a screw rotor is cantilevered by placing a bearing only at the lower shaft end, a rotor shaft support member such as a bearing is not disposed on the intake side, so the upper end of the housing The inlet shape of the part can be freely selected, and the vacuum pump can be made smaller.
In addition, since a hollow for accommodating the reaction product is provided in the inner peripheral portion of the housing at the lower end of the intake port, even if a lump of reaction product falls on the upper surface of the screw rotor, the centrifugal force due to the rotation of the rotor causes It is blown to the housing side, and a lump of reaction products can be collected in the recess.
In addition, when a screw-type vacuum pump that exhausts by volume compression is used as the reaction chamber side pump of the two-stage screw vacuum pump, the intake port is located at the position of the present invention and a recess is provided, It is not necessary to provide a trap, and the space for arranging the pump on the reaction chamber side, which is large, can be reduced.

The vertical screw type vacuum pump according to the present invention has an upper end surface of the screw rotor so as to cover an overlapping portion between the intake port arranged at a position overlapping with a part of the screw rotor as viewed from above in the vertical direction and the upper end surface of the screw rotor. And a baffle plate was placed between the air intake. With such a configuration, it is possible to prevent a large lump of reaction product from dropping directly into the exhaust chamber of the vacuum pump by the baffle plate. The baffle plate may have a shape that makes it easy for the reaction product to fall into the recess for containing the reaction product, for example, a structure having a groove inclined to the recess, or the reaction generation on the upper surface of the baffle plate It is good also as a structure which can deposit an object.
In particular, for a vertical screw vacuum pump that cantilever-supports a screw rotor by placing a bearing only at the lower shaft end, the upper end surface of the screw rotor is not fixed via the bearing, so during operation If a mass of reaction product is caught between the rotors or between the housing and the rotor, contact may occur between the rotors or between the housing and the rotor, which may cause a failure. Although it was difficult to arrange at a position overlapping with a part of the rotor, it was facilitated by preventing the product lump from dropping directly into the exhaust chamber by the baffle plate.
In addition, when a screw-type vacuum pump that compresses and exhausts as a pump on the reaction chamber side of the two-stage screw vacuum pump is used, the clearance between the upper and lower end surfaces of the screw rotor and the housing is reduced. With this configuration in which the objects are less likely to enter the exhaust chamber, it is possible to reduce failures due to the biting of reaction products.

In the screw-type vacuum pump according to the present invention, the air inlet formed in the upper end portion is provided at a position overlapping with at least a recess for accommodating the reaction product when viewed from vertically above. By adopting such a configuration, the reaction product accumulated in the recess for containing the reaction product can be removed using a suction machine or the like without removing the upper end housing, and can be maintained and repaired. Disassembly and assembly work can be simplified. Further, since the reaction product can be visually removed from the upper portion of the intake port, it is possible to prevent the reaction product from being accidentally dropped into the exhaust chamber.
In particular, for a vertical screw vacuum pump that cantilever-supports a screw rotor by placing a bearing only on the lower shaft end, the distance between the recess for housing the reaction product and the end surface of the housing can be shortened, It becomes easier to remove the reaction product.

  According to the first aspect of the present invention, there is no need to provide a trap for accommodating the reaction product as a separate member from the housing, and the vacuum pump can be made compact.

  According to the invention of claim 2, it is possible to prevent a large lump of reaction product from dropping directly into the exhaust chamber of the vacuum pump by the baffle plate. Furthermore, by the centrifugal force due to the rotation of the screw rotor and the rotation of the rotor, the mass of reactive organisms that have fallen on the upper end surface of the screw rotor can be guided to the hollow side for containing the reaction product, and the fall into the exhaust chamber can be prevented. Can be suppressed.

  According to the invention of claim 3 of the present application, the reaction product accumulated in the recess for accommodating the reaction product can be visually removed from above using a suction machine or the like, and can be decomposed during maintenance and repair. -The assembly work can be simplified, and the reaction product can be prevented from being accidentally dropped into the exhaust chamber.

Embodiments of a vacuum pump according to the present invention will be described below with reference to the drawings. FIG. 5 is a sectional view schematically showing an embodiment of a two-stage screw type vacuum pump according to the present invention.
Here, the first screw-type vacuum pump (first vacuum pump, rotary rotor pump, cantilever rotary pump, pre-stage vacuum pump or booster pump) 1A of FIG. 5 will be described with reference to FIGS. To do.
FIG. 1 is a cross-sectional view schematically showing an embodiment of a first screw vacuum pump (first vacuum pump, rotary rotor pump, cantilever rotary pump, pre-stage vacuum pump or booster pump) 1A. FIG. 2 is a cross-sectional view taken along the line AA in FIG.
As shown in the figure, the first screw-type vacuum pump 1A includes a pair of screw rotors 102 and 103 arranged vertically, and the pair of screw rotors 102 and 103 is housed inside an exhaust chamber housing 171. ing. A housing (exhaust chamber housing) 171 forming the exhaust chamber is constituted by the rotor housing 104, the upper end housing 172, and the bearing housing 173.

  A plurality of working chambers 107 are formed by the pair of screw rotors 102 and 103 and the exhaust chamber housing 171. The working chamber 107 sucks process gas (reaction product gas) from an intake port 153 formed in the rotor housing 104 and the upper end housing 172, and process gas (reaction product gas) as the pair of screw rotors 102 and 103 rotates. Is exhausted from an exhaust port (exhaust port) 154 formed on the side surface of the rotor housing 104.

  The screw rotors 102 and 103 and the exhaust chamber housing 171 are partitioned so that the intake port 153 and the exhaust port (exhaust port) 154 do not always communicate with each other. The exhaust chamber 168 is separated by the screw rotors 102 and 103 on the intake side and the exhaust chamber housing 171. In the position until the intake side is closed, a recess 173 for accommodating a reaction product is provided at the lower end of the intake port 153 formed in the rotor housing 104. Further, a baffle plate 174 is arranged at the intake port 153 above the screw rotors 102 and 103 so that a lump of reaction products does not fall directly into the exhaust chamber 168.

  Between the screw rotors 102 and 103 and the exhaust chamber housing 171, there is a minute gap including the end surfaces of the screw rotors 102 and 103, but the second screw-type vacuum pump that is disposed on the atmosphere side and requires an air sealing function. The gap may be larger than that.

  Further, the second screw vacuum pump (the latter stage vacuum pump or the main stage pump) has a large power for exhausting to the atmosphere by being volume-compressed and exhausted by the first screw type vacuum pump (first stage vacuum pump or booster pump) 1A. Tap pump) 1B can be reduced in size and energy is saved.

  The screw rotor 102 includes a rotor member 156 and a rotating shaft member 105. The rotor member 156 is made of an aluminum material, and the rotary shaft member 105 is made of an iron material. The rotor member 156 is a hollow rotor, and a cylindrical member 157 made of an iron-based material is shrink-fitted or cold-fitted in the hollow portion. In this way, the cylindrical member 157 made of an iron-based material is shrink-fitted or cold-fitted to the rotor member 156 made of an aluminum-based material, so that the aluminum-based material is more iron-based when the temperature rises. Even if the thermal expansion is greater, the compression of the iron-based material and the expansion of the aluminum-based material due to shrink fitting or cold fitting are buffered, and a gap is less likely to be generated between the rotor member 156 and the cylindrical member 157. Further, the joint surface between the rotor member 156 and the cylindrical member 157 has a cylindrical shape so that the rotational axes of both members can be easily aligned. A step portion 166 is provided at the lower end of the cylindrical member 157 so that the relative position in the axial direction of the rotor member 156 does not change. Further, a taper that becomes narrower toward the upper part is provided on the inner periphery of the cylindrical member 157, and a taper having the same shape as the taper of the cylindrical member 157 that becomes thinner toward the end also at the upper end of the rotary shaft member 105 is provided. It is. Then, the rotating shafts of the rotor member 156 and the cylindrical member 157 are made to coincide with each other by bringing the tapered portions of the cylindrical member 157 and the rotating shaft member 105 into pressure contact with each other. The cylindrical member 157 and the rotating shaft member 105 are the same iron-based material, and there is almost no difference in the amount of thermal expansion due to a temperature change. The cylindrical member 157 and the rotating shaft member 105 are brought into pressure contact with each other by disposing a disc spring 158 between the upper surface of the cylindrical member 157 and a bolt 159 fastened to the upper end of the rotating shaft member 105. A lid 160 is fastened to the upper end portion of the screw rotor 102 so that reactive organisms do not accumulate in the hollow portion of the rotor member 156.

  Similarly, the screw rotor 103 includes a rotor member 161 and a rotating shaft member 108. The rotor member 161 is made of an aluminum material, and the rotary shaft member 108 is made of an iron material. The rotor member 161 is a hollow rotor, and a cylindrical member 162 made of an iron-based material is shrink-fitted or cold-fitted in the hollow portion. In this way, the cylindrical member 162 made of an iron-based material is shrink-fitted or cold-fitted to the rotor member 161 made of an aluminum-based material, so that when the temperature rises, the aluminum-based material is more iron-based material. Even if the thermal expansion is greater than that, the compression of the iron-based material and the expansion of the aluminum-based material due to shrink fitting or cold fitting are buffered, and it is possible to make it difficult to form a gap between the rotor member 161 and the cylindrical member 162. Further, the joint surface between the rotor member 161 and the cylindrical member 162 is formed in a cylindrical shape so that the rotation axes of both members can be easily aligned. A step portion 167 is provided at the lower end of the cylindrical member 162 so that the relative position in the axial direction with the rotor member 161 does not change. Further, a taper that narrows toward the upper part is provided on the inner periphery of the cylindrical member 162, and further, a taper having the same shape as the taper of the cylindrical member 162 that becomes thinner toward the end part is also provided at the upper end of the rotary shaft member 108. is there. Then, the rotating portions of the rotor member 161 and the cylindrical member 162 are made to coincide with each other by pressing the taper portions of the cylindrical member 162 and the rotating shaft member 108 together, and further, the rotating shaft of the rotating shaft member 108 is also made to coincide. The cylindrical member 162 and the rotating shaft member 108 are the same iron-based material, and there is almost no difference in the amount of thermal expansion due to temperature change. The cylindrical member 162 and the rotary shaft member 108 are brought into pressure-contact with each other by disposing a disc spring 163 between the upper surface of the cylindrical member 162 and a bolt 164 fastened to the upper end of the rotary shaft member 108. A lid 165 is fastened to the upper end portion of the screw rotor 103 so that reactive organisms do not accumulate in the hollow portion of the rotor member 161.

  The screw rotors 102 and 103 can be rotated at a high speed by increasing the resonance frequency by providing a lightweight aluminum-based material and a hollow portion like the screw rotors 102 and 103 to make the screw rotors 102 and 103 as light as possible. . As a result, the first vacuum pump (previous vacuum pump or booster pump) can be reduced in size and the sealing performance can be improved, so that the first vacuum pump (previous vacuum pump or booster pump) with good exhaust efficiency can be configured. .

  In the screw rotor 102, a rotary shaft portion 105 of the rotor is rotatably supported in a rotor housing 104 by bearings 106 and 101 provided at an upper portion below the rotary shaft portion 105 and a bearing 123 provided at a lower portion. . In order to prevent process gas (reaction product gas) in the exhaust chamber from leaking to the bearing side and accumulating on the bearing or contaminating the lubricating oil between the bearing 106 and the exhaust chamber 168, the lubricating oil on the bearing side 106 is further exhausted. A shaft seal 169 is provided so as not to leak to the chamber 168 side. The bearings 106, 101, 123 are pressurized by a disc spring (not shown).

  Similarly, in the screw rotor 103, the rotating shaft portion 108 of the rotor can be rotated in the rotor housing 104 by bearings 109 and 110 provided at the upper portion below the rotating shaft portion 108 and a bearing 124 provided at the lower portion. It is supported. In order to prevent process gas (reaction product gas) in the exhaust chamber from leaking to the bearing side and accumulating on the bearing or contaminating the lubricating oil between the bearing 109 and the exhaust chamber 168, the lubricating oil on the bearing side 109 is further exhausted. A shaft seal 170 is provided so as not to leak to the chamber 168 side. The bearings 109, 110, and 124 are pressurized by a disc spring (not shown) or the like.

  The outer rings of the bearings 106 and 101 are press-fixed to the inner periphery of a cylindrical bearing support member 175 made of an iron-based material, and the outer peripheral portion of the bearing support member 175 is press-contacted to a bearing housing 175 made of an aluminum-based material. It is fixed. A projecting portion 180 is formed at the lower end of the bearing support member 175 in the radial direction of the rotary shaft so as to be easily positioned in the axial direction with respect to the outer ring of the bearing and the bearing housing 175. Similarly, the outer rings of the bearings 109 and 110 are pressure-fixed to a bearing support member 177 made of an iron-based material, and the bearing support member 177 is pressure-fixed to a bearing housing 176 made of an aluminum-based material. A projecting portion 181 is formed at the lower end of the bearing support member 177 in the radial direction of the rotary shaft so that the bearing support member 177 can be easily positioned in the direction with respect to the outer ring of the bearing and the bearing housing 176. In this way, it is fixed to the bearing housing 176 made of an aluminum-based material having a different thermal expansion coefficient through the bearing support members 175 and 177 having the same thermal expansion coefficient as the outer rings of the bearings 106, 101, 109, and 110. By doing so, it is possible to prevent a gap from being changed between the outer rings of the bearings 106, 101, 109, and 110 and the bearing support members 175 and 177.

  Further, the bearing housing 176 is formed with a hollow portion 182 for thermally insulating the bearings 106, 101, 109, 110 and the exhaust chamber 168. Thus, heat between the exhaust chamber 168 and the bearings 106, 101, 109, 110 is prevented so that heat such as compression heat of the exhaust gas generated in the exhaust chamber 168 is not transmitted to the bearings 106, 101, 109, 110. Providing a space in the conduction path makes it difficult for heat to be transferred to the bearings 106, 101, 109, and 110, and prevents breakage due to the high temperature of the bearings 106, 101, 109, and 110. By providing the hollow portion 182 around the bearings 106, 101, 109, and 110, a heat conduction path through which heat is transmitted to the bearings 106, 101, 109, and 110 through the bearing housing 176 can be lengthened, so that a more heat insulating effect can be obtained. improves. Further, when a reaction product gas that becomes solid at low temperature flows, the vacuum pump is operated by setting the flow path of the reaction product gas (intake port 153 → exhaust chamber 168 → exhaust port 154) to a high temperature so that the reaction product does not accumulate. However, there is an effect of preventing the heat around the exhaust chamber 168 maintained at a high temperature by the hollow portion 182 from being transmitted to the bearings 106, 101, 109, and 110.

  The rotor housing 104, the upper end housing 172 and the bearing housing 173 constituting the exhaust chamber housing 171 are made of the same aluminum material as the rotor member 161 made of an aluminum material, and have the same thermal expansion coefficient. This prevents the gap between the screw rotors 102 and 103 and the exhaust chamber housing 171 from changing with temperature. Further, since the exhaust chamber housing 171 is made of an aluminum-based material, the heat conductivity is good and the heat generated near the exhaust port 153 can be easily transferred to the intake port 154 side, and the temperature of the exhaust chamber 168 can be made uniform.

  A heat transfer plate 183 made of an aluminum material for controlling the temperature in the exhaust chamber 168 is in close contact with the periphery of the rotor housing 104. A passage 184 for flowing a cooling medium (water or the like) or a heating medium (high-temperature and high-pressure steam or the like) is formed in the heat transfer plate, and heating and cooling are performed with these media. For example, when exhausting a reaction product gas that solidifies at a high temperature such as tungsten, the exhaust chamber needs to be maintained at a low temperature, and cooling water is supplied to the path 184.

A cooling plate 185 made of an aluminum-based material is disposed at a position at the lower end of the bearing housing 176 and in contact with a heat conduction path through which heat is transferred to the bearings 106, 101, 109, 110 via the bearing housing 176. When the bearings 106, 101, 109, and 110 cannot be sufficiently maintained at a low temperature only by the hollow portion 182, the amount of heat conducted to the bearings 106, 101, 109, and 110 can be reduced by arranging the cooling plate 185. Therefore, the temperature rise of the bearings 106, 101, 109, 110 can be suppressed.
The cooling plate 185 is provided with a cooling path 186 for allowing a medium such as cooling water to flow, thereby further improving the cooling efficiency.

  Further, the cooling plate 185 is in contact with the motor housing 187, and the motor 113 can be cooled. Further, a second cooling plate 188 is in close contact with the outer periphery of the motor housing 187, and the motor 113 is also cooled by the second cooling plate 188. Further, the second cooling plate 188 is formed with a cooling path 189 for flowing a medium such as cooling water, thereby further improving the cooling efficiency.

  A timing gear 111 is provided at the lower end portion of the rotating shaft portion 105, and a timing gear 112 is provided at the lower end portion of the rotating shaft portion 108. When the timing gears 111 and 112 mesh with each other, the screw rotors 102 and 103 are engaged. Are configured to rotate in a non-contact manner synchronously.

  A permanent magnet type rotor 150 of the motor 113 is fixed between the bearing 110 and the timing gear 112 of the rotating shaft portion 108, and canned by a can 151. When the vacuum pump is driven and the inside of the exhaust chamber 168 is evacuated, the motor 113 side is also evacuated, so the can 151 prevents the rotor 150 side from being separated from the atmosphere, thereby preventing atmospheric leakage to the exhaust chamber 168. . Further, when the pressure of the exhaust port 153 becomes higher than the atmospheric pressure at the start of operation, the process gas in the exhaust chamber 168 may leak to the motor 113 side. In this case, the process gas can be prevented from leaking to the atmosphere due to the motor being canned. An electromagnet stator 152 of the motor 113 is fixed outside the can 151, and the rotational speed of the screw rotor 103 is controlled by an inverter. Furthermore, the screw rotors 102 and 103 are configured to rotate in a non-contact manner synchronously by transmitting the rotational motion to the screw rotor 102 via the timing gears 111 and 112.

  The timing gears 111 and 112 are housed in an oil chamber 127 in which lubricating oil 126 partitioned by an oil housing 125 is stored. The timing gears 111 and 112 are configured to be supplied with lubricating oil by a lubricating oil supply means (not shown). Further, by changing the axial thickness of the timing gears 111 and 112 and aligning the bottom surfaces in the axial direction, the lubricating oil blown from the timing gear 111 to the timing gear 112 due to the centrifugal force of rotation is exchanged with the timing gear 112. Stopped at the stepped portion, the meshing portion with the timing gears 111 and 112 is lubricated.

Next, the second screw type vacuum pump (rotary rotor type pump, cantilever type rotary pump, rear vacuum pump or main pump) 1B of FIG. 5 will be described with reference to FIGS.
FIG. 3 is a sectional view schematically showing an embodiment of the second screw type vacuum pump (rotary rotor type pump, cantilever type rotary pump, rear vacuum pump or main pump) 1B. 4 is a cross-sectional view taken along the line BB in FIG.
As shown in the figure, the screw type vacuum pump 1 B includes a pair of screw rotors 202 and 203 arranged vertically, and the pair of screw rotors 202 and 203 are housed inside an exhaust chamber housing 271. The exhaust chamber housing 271 includes a rotor housing 204, an upper end housing 272, and a bearing housing 276.

  A plurality of working chambers 207 are formed by the pair of screw rotors 202 and 203 and the exhaust chamber housing 271. The plurality of working chambers 207 suck process gas (reaction product gas) from an intake port 253 formed in the upper end housing 272 and transfer the process gas (reaction product gas) as the pair of screw rotors 202 and 203 rotate. Then, the air is exhausted from an exhaust port (exhaust port) 254 formed on the side surface of the lower end of the rotor housing 204.

  At the upper end of the upper end housing 272, that is, the cantilevered screw rotors 202, 203 having the structure described below, an exhaust port 154 of the first screw type vacuum pump 1A and an intake port 253 of the second screw type vacuum pump 1B are provided. A pulsation prevention space 290 for buffering the pulsation is formed when the intermediate pressure between the two pulsates. For example, when the atmospheric pressure is suddenly exhausted from the vacuum state as an extreme case, the maximum pressure of the pulsation becomes equal to or higher than the atmospheric pressure (in some cases, more than several times the atmospheric pressure), and the exhaust port 154 of the first screw type vacuum pump 1A. And pulsation between the suction port 253 of the second screw type vacuum pump 1B and process gas leaks to the bearing 109 side of the first screw type vacuum pump 1A having a low pressure, causing a failure. Further, when a pulsation with a large pressure change occurs in the intermediate pressure, in the case of cantilever screw rotors such as the first screw vacuum pump 1A and the second screw vacuum pump 1B, the screw rotor is biased in the bending direction. A force is generated, causing contact between the screw rotor or between the screw rotor and the housing, causing damage. In particular, the first screw-type vacuum pump has a plurality of working chambers formed in parallel, for example, a pair of screw rotors such as three, four, four, and six, and is exhausted by volume compression. The pressure of each working chamber at the exhaust end face is different, and the force in the direction of bending with respect to the screw rotor increases. The second screw-type vacuum pump has a structure in which both screw rotors are single and exhausted without volume compression. Since the shaft diameter is smaller than the screw rotor of the first screw-type vacuum pump, Compared with the vacuum pump, the force in the direction of bending with respect to the screw rotor is not so great.

  A trap member 291 is disposed in the pulsation prevention space 290 formed in the upper end housing 272 so as to partition the intake port 253 and the exhaust chamber 268 so that reaction products do not enter the exhaust chamber 268. The trap member 291 has a hollow structure that tapers from the lower end to the upper end, and is configured such that reaction products accumulate in a groove 292 formed between the upper end housing 272 and the trap member 291. By configuring the upper end housing 272 as a side housing in which the upper surface flange and the air inlet 253 are formed, the reaction product accumulated in the groove portion 292 can be cleaned only by removing the upper surface flange.

  A small gap is formed between the screw rotors 202 and 203 and at least the rotor housing 204.

  The screw rotor 202 includes a rotor member 256 and a rotating shaft member 205. The rotor member 256 and the rotating shaft member 205 are made of an iron-based material. The rotor member 256 is a hollow rotor, and a taper that narrows toward the upper part is provided on the inner periphery of the rotor member 256, and further, the taper of the rotor member 256 that becomes narrower toward the end also on the upper end of the rotary shaft member 205. A taper of the same shape is provided. Then, the rotating shafts of the rotor member 156 and the rotating shaft member 205 can be easily matched by press-contacting the tapered portions of the rotor member 256 and the rotating shaft member 205 with each other. The rotor member 256 and the rotating shaft member 205 are the same iron-based material, and there is almost no difference in the amount of thermal expansion due to temperature change. The rotor member 256 and the rotary shaft member 205 are pressure-contacted by a tapered portion by disposing a disc spring 258 between the hollow inner upper surface of the rotor member 256 and the bolt 259 fastened to the upper end of the rotary shaft member 205. . A lid 260 is fastened to the upper end portion of the screw rotor 202 so that reactive organisms do not accumulate in the hollow portion of the rotor member 256.

  Similarly, the screw rotor 203 includes a rotor member 261 and a rotating shaft member 208. The rotor member 261 and the rotating shaft member 208 are made of an iron-based material. The rotor member 261 is a hollow rotor, and is provided with a taper that becomes narrower toward the upper part of the inner periphery of the rotor member 261. Further, the upper end of the rotary shaft member 208 becomes thinner toward the end, and the taper of the rotor member 261 is reduced. A taper of the same shape is provided. Then, the rotating shafts of the rotor member 261 and the rotating shaft member 208 can be easily matched by pressing the tapered portions of the rotor member 261 and the rotating shaft member 208 together. The rotor member 261 and the rotating shaft member 208 are the same iron-based material, and there is almost no difference in the amount of thermal expansion due to temperature change. The rotor member 261 and the rotary shaft member 208 are pressure-contacted by a tapered portion by disposing a disc spring 264 between the hollow inner upper surface of the rotor member 261 and the bolt 264 fastened to the upper end of the rotary shaft member 208. . A lid 265 is fastened to the upper end portion of the screw rotor 203 so that reactive organisms do not accumulate in the hollow portion of the rotor member 261.

In the first screw-type vacuum pump, in order to obtain the exhaust capacity, the screw rotor becomes large, and the weight of the rotating part becomes heavy. However, the exhaust chamber 168 in operation is in the vicinity of the molecular flow region, and the gap between the screw rotor and between the screw rotor and the rotor casing can be widened. Therefore, even a material having a large thermal expansion coefficient can be used. Therefore, the screw rotor of the first screw type vacuum pump is optimally made of an aluminum-based material that has a large thermal expansion coefficient but is lightweight.
On the other hand, the second screw type vacuum pump has a smaller exhaust capacity than the first screw type vacuum pump, so the screw rotor part is small, but it needs a sealing function to suppress the backflow of the atmosphere. It is necessary to narrow the gap between the screw rotor and the rotor casing. Therefore, the screw rotor of the second screw-type vacuum pump is optimally an iron-based material having a high density but a low thermal expansion coefficient.

  In the screw rotor 202, the rotary shaft portion 205 of the rotor is rotatably supported in the rotor housing 204 by bearings 206 and 201 provided in the upper portion below the rotary shaft portion 205 and a bearing 223 provided in the lower portion. . In order to prevent the process gas (reaction product gas) in the exhaust chamber from leaking to the bearing side and accumulating on the bearing between the bearing 206 and the exhaust chamber 268, the lubricating oil on the bearing side 206 is further removed. A shaft seal 269 is provided so as not to leak to the exhaust chamber 268 side. The bearings 206, 201, and 223 are pressurized by a disc spring (not shown).

  Similarly, in the screw rotor 203, the rotary shaft portion 208 of the rotor can be freely rotated in the rotor housing 204 by the bearings 209 and 210 provided in the upper portion below the rotary shaft portion 208 and the bearing 224 provided in the lower portion. It is supported. In order to prevent the process gas (reaction product gas) in the exhaust chamber from leaking to the bearing side and accumulating on the bearing between the bearing 209 and the exhaust chamber 268, the lubricating oil on the bearing side 209 is further removed. A shaft seal 270 is provided so as not to leak to the exhaust chamber 268 side. The bearings 206, 201, and 223 are pressurized by a disc spring (not shown) or the like.

The outer rings of the bearings 206 and 201 are fixed to the inner periphery of a cylindrical bearing support member 275 made of an iron-based material, and the outer peripheral portion of the bearing support member 275 is pressed against a bearing housing 276 made of an iron-based material. It is fixed. At the lower end of the bearing support member 275, a protrusion 280 is formed in the radial direction of the rotary shaft so as to be easily positioned with respect to the outer ring of the bearing and the bearing housing 276 in the rotary shaft direction. Similarly, the outer rings of the bearings 209 and 210 are press-fixed to a bearing support member 277 made of an iron-based material, and the bearing support member 277 is press-fixed to a bearing housing 276 made of an iron-based material. At the lower end of the bearing support member 277, a protruding portion 281 is formed in the radial direction of the rotary shaft so as to be easily positioned with respect to the outer ring of the bearing and the bearing housing 276 in the rotary shaft direction. The bearing support members 275 and 277 are disposed so as to support the bearing in the empty portion 282 described later.
Thus, by fixing the outer ring of the bearings 206, 207, 209, 210 to the bearing housing 276 via the bearing support members 275, 277, the hollow portion 282 and the bearings 206, 207, 209, 210 are connected in series in the rotation axis direction. The axial length of the vacuum pump can be shortened without being arranged in the above.

  Further, the bearing housing 276 is formed with a hollow portion 282 for thermally insulating the bearings 206, 207, 209, 210 and the exhaust chamber 268. Thus, heat between the exhaust chamber 268 and the bearings 206, 207, 209, 210 is prevented so that heat such as compression heat of the exhaust gas generated in the exhaust chamber 268 is not transmitted to the bearings 206, 207, 209, 210. By providing a space in the conduction path, it becomes difficult for heat to be transferred to the bearings 206, 207, 209, and 210, and breakage due to a high temperature of the bearings 206, 207, 209, and 210 can be prevented. By providing the hollow portion 282 around the bearings 206, 207, 209, and 210, a heat conduction path through which heat is transmitted to the bearings 206, 207, 209, and 210 via the bearing housing 176 can be lengthened, so that a more heat insulating effect can be obtained. improves. Further, when the reaction product gas is exhausted, it is necessary to operate the vacuum pump with a high temperature in the path (intake port 253 → exhaust chamber 268 → exhaust port 254) through which the reaction product gas flows so that the reaction product does not accumulate. However, there is an effect that heat around the exhaust chamber 268 maintained at a high temperature by the hollow portion 282 is prevented from being transmitted to the bearings 206, 207, 209, and 210.

  The rotor housing 204, the upper end housing 272, and the bearing housing 276 constituting the exhaust chamber housing 271 are made of the same iron-based material as the rotor member 161 made of an iron-based material, and have the same thermal expansion coefficient. Thus, the gap between the screw rotors 202 and 203 and the exhaust chamber housing 271 is prevented from changing with temperature.

  A heat transfer plate 283 made of an aluminum material for controlling the temperature in the exhaust chamber 268 is in close contact with the periphery of the rotor housing 204. A passage 284 for flowing a cooling medium (water or the like) or a heating medium (high-temperature high-pressure steam or the like) is formed in the heat transfer plate 283, and heating / cooling is performed with these media. For example, when exhausting a reaction product gas that solidifies at a high temperature and low temperature (temperature close to normal temperature) such as tungsten, the exhaust chamber needs to be maintained at a low temperature, and cooling water is supplied to the path 284. In this way, the heat transfer plate 283 made of an aluminum material having a thermal conductivity better than that of an iron material is brought into close contact with the rotor housing 204 to equalize the temperature of the rotor housing 204.

A cooling plate 285 made of an aluminum-based material is disposed at a position at the lower end of the bearing housing 276 and in contact with a heat conduction path through which heat is transferred to the bearings 206, 207, 209, and 210 via the bearing housing 276. When the bearings 206, 207, 209, and 210 cannot be sufficiently maintained at a low temperature only by the hollow portion 282, the cooling plate 285 is disposed to reduce the amount of heat conducted to the bearings 206, 207, 209, and 210. Therefore, the temperature rise of the bearings 206, 207, 209, and 210 can be suppressed.
The cooling plate 285 is provided with a cooling path 286 for allowing a medium such as cooling water to flow, thereby further improving the cooling efficiency.

  Further, the cooling plate 285 is in contact with the motor housing 287, and the motor 213 can be cooled. Further, a second cooling plate 288 is in close contact with the outer periphery of the motor housing 287, and the motor 213 is also cooled by the second cooling plate 288. The second cooling plate 288 is provided with a cooling path 289 for allowing a medium such as cooling water to flow, thereby further improving the cooling efficiency.

  A timing gear 211 is provided at the lower end portion of the rotating shaft portion 205, and a timing gear 212 is provided at the lower end portion of the rotating shaft portion 208. When the timing gears 211 and 212 mesh with each other, the screw rotors 202 and 203 are engaged. Are configured to rotate in a non-contact manner synchronously.

  A permanent magnet type rotor 250 of the motor 213 is fixed between the bearing 210 of the rotating shaft portion 208 and the timing gear 212, and canned by a can 251. When the exhaust port 254 side of the second screw type vacuum pump is clogged, the pressure in the vicinity of the exhaust port 254 may become higher than the atmospheric pressure, and the process gas in the exhaust chamber 268 leaks to the motor 213 side. In this case, since the motor 213 is canned, the process gas can be prevented from leaking to the atmosphere. An electromagnet stator 252 of the motor 213 is fixed outside the can 251 and the rotational speed of the screw rotor 203 is controlled by an inverter. Furthermore, the screw rotors 202 and 203 are configured to rotate in a non-contact manner synchronously by transmitting the rotational motion to the screw rotor 202 via the timing gears 211 and 212.

  The timing gears 211 and 212 are accommodated in an oil chamber 227 in which lubricating oil 226 partitioned by an oil housing 225 is stored. The timing gears 211 and 212 are configured to be supplied with lubricating oil by a lubricating oil supply means (not shown). Furthermore, by changing the axial thickness of the timing gears 211 and 212 and aligning the bottom surfaces in the axial direction, the lubricating oil blown from the timing gear 211 to the timing gear 212 by the centrifugal force of rotation is exchanged with the timing gear 212. Stopped by the stepped portion, the meshing portion with the timing gears 211 and 212 is lubricated.

  Since some reaction product gases tend to solidify when the pressure increases, an inert gas is injected into the exhaust chamber on the side of the rotor housing 204 of the second screw vacuum pump 1B disposed on the atmosphere side. An inert gas injection path 295 is provided for diluting the reaction product gas to make it difficult to produce a reaction product.

  Finally, referring to FIG. 5, the exhaust port 154 of the first screw type vacuum pump 1A and the intake port 253 of the second screw type vacuum pump 1B are connected in series and the vertical two-stage screw type vacuum pump 300 is connected. The configuration will be described.

As shown in FIG. 5, the exhaust path formed by the exhaust port 154 of the first screw-type vacuum pump 1A, the intake port 253 of the second screw-type vacuum pump 1B, and the intermediate pipe 301 is horizontal. By disposing, the exhaust port 154 of the first screw type vacuum pump 1A and the intake port 253 of the second screw type vacuum pump 1B can be connected with almost no decrease in conductance.
Further, the exhaust port 154 of the first screw-type vacuum pump 1A and the intake port 253 of the second screw-type vacuum pump 1B may be connected without using the intermediate pipe 301.

When repairing or maintaining the screw rotor part, the fastening between the bearing housing and the rotor housing of each of the first screw type vacuum pump and the second screw type vacuum pump is released, and the upper part of the rotor housing together with the rotor housing. By removing the upper end housing and the like disposed on the screw rotor portion, the screw rotor portion can be easily exposed to the operator, so that workability is improved and assembly is facilitated.

  It can be applied to a rotary rotor type fluid pump, a cantilever type rotary fluid pump, a rotary rotor type vacuum pump, a cantilever type rotary vacuum pump, and the like. In particular, it can be applied to a cantilever screw vacuum pump for exhausting process gas used in semiconductor manufacturing processes, and in particular, to a multi-stage cantilever screw vacuum pump in which a plurality of cantilever screw vacuum pumps are connected in series. .

It is sectional drawing which shows typically embodiment of the 1st screw type vacuum pump of the two-stage screw type vacuum pump which concerns on this invention. It is AA sectional drawing of FIG. It is sectional drawing which shows typically embodiment of the 2nd screw type vacuum pump of the two-stage screw type vacuum pump which concerns on this invention. It is BB sectional drawing of FIG. It is sectional drawing which shows typically embodiment of the two-stage screw type vacuum pump which concerns on this invention. It is explanatory drawing which showed the prior art. FIG. 7 is a side view of FIG. 6.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1A 1st screw type vacuum pump 102,103 Screw rotor 104 Rotor housing 105 Rotary shaft member 101,106,109,110,123,124 Bearing 107 A working chamber is formed 113 Motor 111,112 Timing gear 125 Oil housing 126 Lubricating oil 150 Rotor 151 Can 152 Stator 153 Intake port 154 Discharge port (exhaust port)
156 Rotor member 157 Cylinder member 166 Stepped portions 158 and 163 Disc springs 159 and 164 Bolt 160 and 165 Lid 168 Exhaust chamber 169 and 170 Shaft seal 171 Exhaust chamber housing 172 Upper end housing 173 Bearing housing 174 Baffle plates 175 and 177 Bearing support member 182 Hollow part 183 Heat transfer plate 184 Path 185 Cooling plate 186, 189 Cooling path 188 Second cooling plate

Claims (3)

A vertical screw vacuum pump used in a semiconductor manufacturing process, wherein a pair of screw rotors are rotatably fixed in a housing with a rotating shaft vertical, and an intake port is opened from an upper end surface to a side surface of the housing, It opens at a position that overlaps at least a part of the screw rotor as viewed from above, and an exhaust port is opened at the lower part of the housing so that the intake port and the exhaust port do not always communicate with each other between the housing and the pair of screw rotors. Partitioned,
A vertical installation characterized in that a recess for accommodating a reaction product is provided in a housing inner peripheral portion at a lower end portion of the intake port at a position until the exhaust chamber is closed by the housing on the intake side and a pair of screw rotors. Screw type vacuum pump.   A baffle plate is disposed between the upper end surface of the screw rotor and the intake port so as to cover an overlapping portion between the upper end surface of the screw rotor and the intake port disposed at a position overlapping with a part of the screw rotor as viewed from above vertically. The vertical screw vacuum pump according to claim 1, wherein the vertical screw vacuum pump is provided.   The vertical screw-type vacuum according to claim 1 or 2, wherein the intake port formed in the upper end portion is provided at a position overlapping with at least a recess for accommodating a reaction product when viewed from above vertically. pump.

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