JP2009197643A - Cryopump and evacuation method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the burden of maintenance work such as an exchange of panels by prolonging a service life of a cryopanel. <P>SOLUTION: This cryopump 10 alternately performs a cryopumping process for discharging gas by adsorbing discharged gas containing a first and a second gases to an adsorbent and a re-generating process for discharging gas by desorbing the adsorbed gas from the adsorbent. The cryopump 10 comprises a first adsorbent 50 and a second adsorbent 52. In the first adsorbent 50, the adsorption quantity per unit weight of a gas having a larger residual rate in the re-generating process in the first and the second gases is larger than the adsorption quantity per a unit weight of the other gas having a smaller residual rate. In the second adsorbent 52, the adsorption quantity per a unit weight of a gas having a larger residual rate in the re-generating process in the first and the second gases is smaller than the adsorption quantity per a unit weight of the other gas having a smaller residual rate. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a cryopump and a vacuum exhaust method.

  The cryopump is a vacuum pump that traps and exhausts gas molecules by condensation or adsorption onto a cryopanel cooled to a very low temperature. The cryopump is generally used to realize a clean vacuum environment required for a semiconductor circuit manufacturing process or the like.

For example, Patent Document 1 describes a cryopump in which activated carbon having a thermal conductivity of about 0.01 w / cmK or more is attached to a panel. According to this, a cryopump having a high exhaust capacity capable of reliably and efficiently adsorbing hydrogen, helium, etc. without increasing the size of the pump is provided. In this cryopump, activated carbon is affixed to the surface on the back side of the cryopanel plate as viewed from the opening where the chevron baffle is provided.
JP 2005-54689 A

  The cryopump is a so-called built-in vacuum pump, and the exhaust performance gradually decreases as the accumulation of exhausted gas proceeds. For this reason, the regeneration process which discharges | emits the gas molecule trapped on the cryopanel surface outside is performed with an appropriate frequency. The exhaust performance of the cryopump is usually recovered through a regeneration process. However, there is also a gas having a relatively large ratio remaining in the adsorbent even after the regeneration treatment. Such a difficult-to-regenerate gas is generated by, for example, a chemical change in the exhaust process. When the exhausted gas contains a difficult-to-regenerate gas, the exhaust performance cannot be sufficiently recovered by the regeneration process, so that the lifetime of the cryopanel is shortened. As a result, the frequency of maintenance work such as replacement with a new cryopanel increases.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a cryopump and a vacuum exhaust method capable of realizing a long life of a cryopanel and reducing a maintenance work burden such as panel replacement.

  One embodiment of the present invention is a cryopump. The cryopump alternately performs a cryopumping process for exhausting the exhausted gas containing the first and second gases by adsorbing the adsorbent on the adsorbent and a regeneration process for desorbing and discharging the adsorbed gas from the adsorbent. To do. The cryopump includes a first adsorbent and a second adsorbent. The first adsorbent has an adsorption amount per unit weight of a gas having a large residual ratio in the regeneration treatment among the adsorbed first and second gases, and an adsorption amount per unit weight of a gas having a smaller residual ratio. Bigger than. The second adsorbent has an adsorption amount per unit weight of a gas having a large residual ratio in the regeneration treatment among the adsorbed first and second gases, and an adsorption amount per unit weight of a gas having a smaller residual ratio. Smaller than.

  According to this aspect, the first adsorbent has an adsorption performance superior to the hardly regenerated gas than the second adsorbent. For this reason, the hardly regenerated gas is accumulated in the first adsorbent, and accumulation in the second adsorbent is reduced. Therefore, the influence on the lifetime of the second adsorbent is reduced, and the second adsorbent can be used for a long time. Further, practically, if the maintenance work necessary for accumulating the hardly regenerating gas is performed only on the first adsorbent, it is sufficient for practical use, and therefore the work load can be reduced.

  Another aspect of the present invention is a cryopump. This cryopump is used in a vacuum exhaust system of an ion implantation apparatus. The cryopump includes a first adsorbent in which the adsorption amount per unit weight of the dopant gas used in the ion implantation process is larger than the adsorption amount per unit weight of the non-condensable gas, and the dopant gas used in the ion implantation process. A second adsorbent whose adsorption amount per unit weight is smaller than the adsorption amount per unit weight of the non-condensable gas.

  A further aspect of the present invention is a cryopanel structure. The cryopanel structure is formed in a portion different from the first adsorption region and the first adsorption region that selectively adsorbs the first gas molecule, and the second gas molecule different from the first gas molecule. And a second adsorption region that selectively adsorbs.

  A further aspect of the present invention is a cryopanel structure. The cryopanel structure includes a first adsorbent having a maximum peak in the pore diameter distribution curve as a first pore diameter, and a second fine particle having a maximum peak in the pore diameter distribution curve smaller than the first pore diameter. And a second adsorbent having a pore diameter.

  A further aspect of the present invention is a vacuum evacuation method. This method includes a cryopumping process in which exhaust gas including the first and second gases is adsorbed on the adsorbent and exhausted, and a regeneration process in which the adsorbed gas is desorbed from the adsorbent and discharged. In the cryopumping step, the exhaust gas is exhausted by using the first adsorbent and the second adsorbent together. The first adsorbent has an adsorption amount per unit weight of a gas having a large residual ratio in the regeneration step among the adsorbed first and second gases, and an adsorption amount per unit weight of a gas having a smaller residual ratio. Bigger than. The second adsorbent has an adsorption amount per unit weight of a gas having a large residual ratio in the regeneration step among the adsorbed first and second gases, and an adsorption amount per unit weight of a gas having a smaller residual ratio. Smaller than. This method is a maintenance that selectively replaces the first adsorbent when the residual amount in the first adsorbent of the gas having a large residual ratio in the regeneration step among the first and second gases exceeds a reference. A process may be further included.

  ADVANTAGE OF THE INVENTION According to this invention, the work burden of the maintenance of a cryopump can be reduced.

  The cryopump according to the present embodiment includes a first adsorption region that is suitable for adsorption of hardly regenerated gas. The first adsorption region may be formed so as to selectively adsorb the hardly regenerated gas. Further, the first adsorption region may be formed so as to be more excellent in the performance of hardly regenerating gas than the other adsorption regions. The cryopump includes a second adsorption region formed at a site different from the first adsorption region, and the second adsorption region is formed so as to adsorb gas that is substantially completely removed in the regeneration process. May be. The adsorption region is formed, for example, by providing an adsorbent on the cryopanel surface. In the cryopump according to the present embodiment, for example, different types of adsorbents are provided in the divided areas, and a plurality of adsorption areas having different adsorption performances are formed.

The cryopump includes a first cryopanel that is cooled to a first cooling temperature level, and a second cryopanel that is cooled to a second cooling temperature level lower than the first cooling temperature level. May be. In the first cryopanel, gas having a low vapor pressure at the first cooling temperature level is captured by condensation and exhausted. For example, a gas having a vapor pressure lower than a reference vapor pressure (for example, 10 ⁻⁸ Pa) is exhausted. In the second cryopanel, gas having a low vapor pressure at the second cooling temperature level is captured by condensation and exhausted. An adsorption region is formed on the surface of the second cryopanel in order to capture non-condensable gas that does not condense even at the second temperature level due to high vapor pressure.

  Since the cryopump is a so-called built-in vacuum pump, a regeneration process for discharging the gas accumulated inside to the outside at an appropriate frequency is executed. For regeneration, the temperature of the cryopanel is raised to a temperature higher than the operating temperature of the cryopanel (for example, room temperature), the gas condensed or adsorbed on the panel surface is re-released and discharged to the outside, and the operating temperature of the cryopanel again. This is a process of cooling. As the temperature rises, the gas captured by condensation on the cryopanel surface is vaporized, and the gas captured by adsorption is desorbed and released into the pump container. Usually, prior to the regeneration process, the cryopump is separated from the exhaust target volume by closing the gate valve. The re-released gas is discharged through the discharge port of the cryopump, for example, by driving an attached roughing pump.

  The gas accumulated in the cryopump is normally exhausted substantially completely by the regeneration process, and when the regeneration is completed, the cryopump is restored to the specified exhaust performance. However, a part of the exhausted gas has a relatively high ratio of remaining in the adsorbent even after the regeneration process. For example, in a cryopump installed for evacuation of an ion implantation apparatus, it was observed that a sticky substance adheres to activated carbon as an adsorbent. It was difficult to completely remove the adhesive substance even after the regeneration treatment. This adhesive substance is considered to be caused by organic outgas discharged from the photoresist coated on the substrate to be processed. Alternatively, it may be caused by a toxic gas used as a dopant gas, that is, a raw material gas in the ion implantation process. There is a possibility that it may be caused by other by-product gas in the ion implantation process. There is a possibility that these gases are combined to produce an adhesive substance.

  In the ion implantation process, most of the exhausted gas is hydrogen gas. The hydrogen gas is discharged to the outside substantially completely by regeneration. Of the exhausted gas, the amount of hardly regenerated gas is very small. Therefore, the influence of the hardly regenerating gas on the exhaust performance of the cryopump in one cryopumping process is slight. However, as the cryopumping process and the regeneration process are repeated, the hardly regenerated gas is gradually accumulated in the adsorbent, and the exhaust performance is lowered. When the exhaust performance falls below the allowable range, maintenance work is required. For example, the adsorbent is exchanged together with the cryopanel, or the adsorbent is subjected to a chemically difficult-to-regenerate gas removal process. Thus, the difficult-to-regenerate gas shortens the life of the adsorbent and increases the frequency of maintenance work.

  Therefore, the cryopump according to the embodiment of the present invention is configured to accumulate the hardly regenerated gas in a part of the cryopanel. The cryopump may be provided with a cryopanel or adsorbent dedicated to the hardly regenerating gas, or may be provided with a cryopanel or adsorbent that is relatively excellent in the ability to adsorb hardly regenerating gas. Thereby, accumulation | storage of the hardly reproducible gas to another cryopanel is reduced. Therefore, the influence on the exhaust performance of these panels is reduced, and the shortening of the cryopanel life is also suppressed. Moreover, since the object of the required maintenance work can be limited to the hardly regenerated gas panel, the work load can be reduced.

  Here, the difficult-to-regenerate gas is, for example, a gas that has not been completely discharged to the outside of the pump when the discharge of the predetermined gas (for example, hydrogen) to the outside of the cryopump is substantially completed in the predetermined regeneration process. . Moreover, even if it passes through the regeneration process adjusted so that predetermined | prescribed gas may be discharged | emitted completely out of a cryopump, it can be said that the gas whose residue in an adsorbent exceeds a reference | standard is a difficult regeneration gas. For example, organic outgas from a resist or other coating applied to the wafer surface may also have a high residual ratio in the adsorbent during the regeneration process. In addition, a toxic dopant gas used in the ion implantation process can also be a difficult-to-regenerate gas.

  A cryopump according to a specific example of this technical idea is a cryopump suitable for use in an evacuation system of an ion implantation apparatus. The cryopump includes a first adsorbent in which the adsorption amount per unit weight of the dopant gas used in the ion implantation process is larger than the adsorption amount per unit weight of the non-condensable gas, and the dopant gas used in the ion implantation process. A second adsorbent in which the adsorption amount per unit weight is smaller than the adsorption amount per unit weight of the non-condensable gas.

  Another example is a cryopump suitable for use in a vacuum exhaust system of a substrate processing apparatus. For example, the substrate processing apparatus processes a substrate coated with a resist with a process gas. The cryopump is a first adsorbent in which the adsorption amount per unit weight of the organic gas released from the resist is larger than the adsorption amount per unit weight of the process gas, and the adsorption per unit weight of the organic gas released from the resist. And a second adsorbent whose amount is smaller than the adsorption amount per unit weight of the process gas.

  The resist is, for example, an organic resist made of an organic material. The process gas may be a reactive process gas that chemically reacts directly with the processing target (for example, the substrate) or the resist on the surface thereof. Alternatively, the process gas may be a gas for assisting the introduction of the reactive gas into the processing target. When the substrate processing apparatus is a sputtering apparatus, the process gas is an inert gas such as argon. When the substrate processing apparatus is an ion implantation apparatus, the process gas is, for example, hydrogen gas or dopant gas. An organic gas can be released from the resist by the interaction between the process gas and the resist during the process. Further, outgas can be released from the resist by a vacuum environment even when not in process. This organic gas can include, for example, aromatics, straight chain hydrocarbons, alcohols, ketones, ethers, and the like.

  The difficult-to-regenerate gas is not limited to the organic gas from the resist and the dopant gas used for the ion implantation process. For example, depending on the process, the process gas itself may be a hardly regenerating gas. In addition, the gas released from the coating other than the resist on the substrate may be a hardly regenerating gas.

  Therefore, the cryopump performs a cryopumping process for exhausting the exhausted gas including the first and second gases by adsorbing the adsorbent on the adsorbent, and a regeneration process for desorbing and discharging the adsorbed gas from the adsorbent. It is comprised so that it may carry out alternately and may be provided with the 1st adsorbent and the 2nd adsorbent. The first adsorbent has an adsorption amount per unit weight of a gas having a large residual ratio in the regeneration treatment among the adsorbed first and second gases, and an adsorption amount per unit weight of a gas having a smaller residual ratio. Larger adsorbents. The second adsorbent has an adsorption amount per unit weight of a gas having a large residual ratio in the regeneration treatment among the adsorbed first and second gases, and an adsorption amount per unit weight of a gas having a smaller residual ratio. Smaller adsorbents.

  Further, the present invention can be rephrased as a technical idea of forming a plurality of adsorption regions having different adsorption performances for different gases in a cryopump. In a typical cryopump, activated carbon is selected based on a design concept that a single type of activated carbon is commonly used in the entire cryopanel. For example, the cryopump is formed in a portion different from the first adsorption region and the first adsorption region that is significantly superior in the adsorption performance of the first gas molecule, and the second gas different from the first gas molecule. A cryopanel structure comprising: a second adsorption region that is significantly superior in molecule adsorption performance. Thereby, the efficient vacuum exhaust according to the component structure of exhaust gas is attained. For example, by accumulating a gas that exhibits adhesiveness with the adsorbent in a part of the adsorbent, it is possible to prevent the adsorbing performance from being reduced due to the other adsorbent being covered with the adhesive substance.

  For example, the cryopanel structure is formed in a portion different from the first adsorption region formed by the first adsorbent that selectively adsorbs the first gas molecules and the first adsorption region. A second adsorption region formed by a first adsorbent that selectively adsorbs second gas molecules different from the gas molecules. Alternatively, the cryopanel structure has a first adsorption region formed by the first adsorbent having a maximum peak in the pore size distribution curve as the first pore diameter, and a portion different from the first adsorption region. And a second adsorption region formed by a second adsorbent having a maximum peak in the pore diameter distribution curve as a second pore diameter smaller than the first pore diameter. . Here, the first pore diameter may be selected corresponding to the molecular diameter of the first gas molecule, and the second pore diameter may be selected corresponding to the molecular diameter of the second gas molecule. In addition to the first adsorption region and the second adsorption region, a third adsorption region for the third gas molecule may be further formed.

  FIG. 1 is a diagram schematically showing an ion implantation apparatus 1 and a cryopump 10 according to an embodiment of the present invention. The ion implantation apparatus 1 includes an ion source unit 2, a mass analyzer 3, a beam line unit 4, and an end station unit 5. The ion source unit 2 is configured to ionize an element to be implanted into the substrate surface and extract it as an ion beam. The mass analyzer 3 is provided downstream of the ion source unit 2 and is configured to select necessary ions from the ion beam. The beam line unit 4 is provided downstream of the mass analyzer 3 and includes a lens system that shapes the ion beam and a scanning system that scans the substrate with the ion beam. The end station unit 5 is provided downstream of the beam line unit 4 and includes a substrate holder that holds a substrate to be subjected to ion implantation processing, a drive system that drives the substrate with respect to the ion beam, and the like. The

  Further, the ion implantation apparatus 1 is provided with a vacuum exhaust system 6. The evacuation system 6 is provided to maintain a desired high vacuum (for example, higher than 10 −5 Pa) from the ion source unit 2 to the end station unit 5. The vacuum exhaust system 6 includes cryopumps 10a, 10b, and 10c. For example, the cryopumps 10 a and 10 b are attached to the cryopump mounting opening on the vacuum chamber wall surface of the beam line unit 4 for evacuating the vacuum chamber of the beam line unit 4. The cryopump 10 c is attached to a cryopump mounting opening in the vacuum chamber wall surface of the end station unit 5 for evacuating the vacuum chamber of the end station unit 5.

  The cryopumps 10a and 10b are attached to the beam line unit 4 via gate valves 7a and 7b, respectively. The cryopump 10c is attached to the end station unit 5 through a gate valve 7c. Hereinafter, the cryopumps 10a, 10b, and 10c are collectively referred to as the cryopump 10 and the gate valves 7a, 7b, and 7c are collectively referred to as the gate valve 7 as appropriate. When the cryopump 10 is regenerated, the gate valve 7 is closed. During the operation of the ion implantation apparatus 1, the gate valve 7 is opened, and the cryopump 10 evacuates. The beam line unit 4 and the end station unit 5 may each be configured with an evacuation system 6 so as to be evacuated by one cryopump 10. Further, the vacuum exhaust system 6 may be configured such that the beam line unit 4 and the end station unit 5 are exhausted by a plurality of cryopumps 10 respectively.

  The evacuation system 6 may further include a turbo molecular pump and a dry pump for making the ion source unit 2 high vacuum. Further, the vacuum exhaust system 6 may include a roughing pump for exhausting the beam line unit 4 and the end station unit 5 from the atmospheric pressure to the operation start pressure of the cryopump 10 in parallel with the cryopump 10.

The gas present in the beam line unit 4 and the end station unit 5 and the introduced gas are exhausted by the cryopump 10. Most of the exhausted gas is usually hydrogen gas. Further, the exhausted gas includes a toxic gas used as a dopant gas. When the element to be implanted into the substrate is, for example, boron, for example, boron trifluoride (BF ₃ ) is used as the dopant gas. For example, phosphine (PH ₃ ) is used as a dopant gas when phosphorus is implanted. When arsenic is implanted, for example, arsine (AsH ₃ ) is used as a dopant gas. It is also conceivable that the by-product gas in the ion implantation process is included in the exhaust gas.

  FIG. 2 is a cross-sectional view schematically showing the cryopump 10 according to the embodiment of the present invention. The cryopump 10 is attached to the vacuum chamber 80. The vacuum chamber 80 is a vacuum chamber of the beam line unit 4 or the end station unit 5 (see FIG. 1), for example. The cryopump 10 includes a refrigerator 12, a panel structure 14, and a heat shield 16. The panel structure 14 includes a plurality of cryopanels 42, and these panels are cooled by the refrigerator 12. A cryogenic surface for trapping and exhausting gas by condensation or adsorption is formed on the panel surface.

  The cryopump 10 shown in FIG. 2 is a so-called vertical cryopump. The vertical cryopump is a cryopump in which the refrigerator 12 is inserted along the axial direction of the heat shield 16. The present invention can also be applied to a so-called horizontal cryopump. The horizontal cryopump is a cryopump in which the second cooling stage of the refrigerator is inserted and arranged in a direction (usually an orthogonal direction) intersecting the axial direction of the heat shield 16.

  The refrigerator 12 is a Gifford McMahon refrigerator (so-called GM refrigerator). The refrigerator 12 is a two-stage refrigerator and includes a first cooling stage 22 and a second cooling stage 24. The refrigerator 12 is connected to the compressor 20 via a pipe 18, and a working fluid such as helium supplied from the compressor 20 is adiabatically expanded in the interior thereof to the first cooling stage 22 and the second cooling stage 24. Generates cold. The second cooling stage 24 is cooled to a lower temperature than the first cooling stage 22. The second cooling stage 24 is cooled to about 10K to 20K, for example, and the first cooling stage 22 is cooled to about 60K to 100K, preferably about 80K to 100K.

  The heat shield 16 is fixed to the first cooling stage 22 of the refrigerator 12 in a thermally connected state, and the panel structure 14 is thermally connected to the second cooling stage 24 of the refrigerator 12. It is fixed. For this reason, the heat shield 16 is cooled to the same temperature as the first cooling stage 22, and the panel structure 14 is cooled to the same temperature as the second cooling stage 24.

  The heat shield 16 is provided to protect the panel structure 14 and the second cooling stage 24 from ambient radiant heat. The heat shield 16 is formed in a bottomed cylindrical shape having an opening 26 at one end. The opening 26 is defined by the inner surface of the end of the cylindrical side surface of the heat shield 16.

  On the other hand, a closed portion 28 is formed at the other end of the heat shield 16 opposite to the opening 26, that is, at the other end of the pump bottom. The closing portion 28 is formed by a flange portion extending radially inward at the end of the cylindrical side surface of the heat shield 16 on the pump bottom side. Since the cryopump 10 shown in FIG. 2 is a vertical cryopump, the flange portion is attached to the first cooling stage 22 of the refrigerator 12. Thereby, a cylindrical internal space 30 is formed inside the heat shield 16. The refrigerator 12 projects into the internal space 30 along the central axis of the heat shield 16, and the second cooling stage 24 is inserted into the internal space 30.

  In the case of a horizontal cryopump, the closing portion 28 is normally completely closed. The refrigerator 12 is disposed so as to protrude into the internal space 30 along a direction orthogonal to the central axis of the heat shield 16 from the opening for attaching the refrigerator formed on the side surface of the heat shield 16. The first cooling stage 22 of the refrigerator 12 is attached to the opening for attaching the refrigerator of the heat shield 16, and the second cooling stage 24 of the refrigerator 12 is arranged in the internal space 30. The panel structure 14 is attached to the second cooling stage 24. The panel structure 14 may be attached to the second cooling stage 24 via a panel attachment member having an appropriate shape.

  The shape of the heat shield 16 is not limited to a cylindrical shape, and may be a cylindrical shape having any cross section such as a rectangular tube shape or an elliptical cylinder shape. Typically, the shape of the heat shield 16 is similar to the shape of the inner surface of the pump case 34. Further, the heat shield 16 may not be configured as an integral cylinder as illustrated, and may be configured so as to form a cylindrical shape as a whole by a plurality of parts. The plurality of parts may be arranged with a gap therebetween.

  A baffle 32 is provided in the opening 26 of the heat shield 16. The baffle 32 is provided at a distance from the panel structure 14 in the central axis direction of the heat shield 16. The baffle 32 is attached to the end of the heat shield 16 on the opening 26 side, and is cooled to a temperature similar to that of the heat shield 16. The baffle 32 is, for example, a louver or chevron. The baffle 32 may be formed concentrically, for example, when viewed from the vacuum chamber 80 side, or may be formed in other shapes such as a lattice shape. A gate valve 7 (see FIG. 1) is provided between the baffle 32 and the vacuum chamber 80.

  The heat shield 16, the baffle 32, the panel structure 14, and the first cooling stage 22 and the second cooling stage 24 of the refrigerator 12 are accommodated in the pump case 34. The pump case 34 is formed by connecting two cylinders having different diameters in series. The large-diameter cylindrical side end of the pump case 34 is opened, and a flange portion 36 for connection to the vacuum chamber 80 is formed extending outward in the radial direction. In addition, the small-diameter cylindrical side end of the pump case 34 is fixed to the refrigerator 12. The cryopump 10 is airtightly fixed to the cryopump connection opening of the vacuum chamber 80 via the flange portion 36 of the pump case 34, and an airtight space integral with the internal space of the vacuum chamber 80 is formed.

  Both the pump case 34 and the heat shield 16 are formed in a cylindrical shape and are arranged coaxially. Since the inner diameter of the pump case 34 is slightly larger than the outer diameter of the heat shield 16, the heat shield 16 is disposed with a slight gap between the inner surface of the pump case 34.

  The panel structure 14 is disposed in the internal space 30 of the heat shield 16. The panel structure 14 includes a panel mounting member 40 and a plurality of cryopanels 42a, 42b, and 42c. Hereinafter, the cryopanels 42a, 42b, and 42c may be collectively referred to simply as the panel 42. The panel attachment member 40 is a bottomed cylindrical member having one end opened and the other end closed by a disk portion 44. The disk portion 44 has a surface facing the inside of the panel attachment member 40 fixed to the second cooling stage 24 of the refrigerator 12, and the panel attachment member 40 is disposed so as to surround the second cooling stage 24. Yes. The other surface of the disc portion 44 faces the opening 26 of the heat shield 16 and is arranged in parallel to the opening 26.

  A plurality of panels 42 are attached to the cylindrical side surface of the panel structure 14 at intervals. Three panels 42 are provided, and an uppermost panel 42 a and two lower panels 42 b and 42 c are provided at equal intervals along a direction perpendicular to the opening 26 in order from the side closer to the opening 26 of the heat shield 16. It has been. The plurality of panels 42 are all formed in the same shape, and are in the shape of a truncated cone side surface or an umbrella shape. The panel 42 is formed to extend radially outward from the cylindrical side surface of the panel mounting member 40, and away from the opening 26 of the heat shield 16 as it extends radially outward. For this reason, the surface of the panel 42 is disposed obliquely with respect to the opening 26 so as to move away from the opening 26 of the heat shield 16 as it goes radially outward from the central axis of the heat shield 16.

  For example, activated carbon is bonded to the surface of the panel structure 14 as an adsorbent for adsorbing gas. The first activated carbon 50 is bonded to the entire surface 46a of the surface of the uppermost panel 42a facing the opening 26 (hereinafter, this surface is appropriately referred to as “panel front surface”) 46a. The second activated carbon 52 is bonded to the entire area of the panel front surfaces 46b and 46c of the lower panels 42b and 42c.

  The first activated carbon 50 uses the maximum peak in the pore diameter distribution curve as the first pore diameter. The first pore diameter is selected according to the molecular diameter of the hardly regenerated gas contained in the exhausted gas. For example, the maximum peak of the pore diameter of the first activated carbon 50 is selected in accordance with the molecular diameter of the organic gas released from the resist applied to the substrate. The maximum peak of the pore diameter of the first activated carbon 50 may be selected in correspondence with the molecular diameter having the maximum composition ratio in the molecular diameter distribution of the organic gas. Alternatively, for example, the maximum peak of the pore diameter of the first activated carbon 50 may be selected corresponding to the molecular diameter of any one of boron trifluoride, phosphine, and arsine.

  On the other hand, the second activated carbon 52 sets the maximum peak in the pore diameter distribution curve to the second pore diameter smaller than the first pore diameter. The second pore diameter is selected according to the molecular diameter of the non-condensable gas. The second pore diameter is selected from, for example, any of rare gases, specifically, for example, corresponding to the molecular diameter of hydrogen gas.

  FIG. 3 is a diagram illustrating an example of pore diameter distribution curves of the first activated carbon 50 and the second activated carbon 52. The horizontal axis in FIG. 3 indicates the pore diameter of the activated carbon, and the vertical axis indicates the pore volume. The pore distribution shown in FIG. 3 is, for example, a Log differential pore volume distribution, but instead of this, an integrated pore volume distribution, a differential pore volume distribution, or a differential pore volume distribution can be used. . The pore distribution is calculated by, for example, the BJH method based on, for example, an isothermal adsorption curve of nitrogen gas at a liquid nitrogen temperature.

  As shown in FIG. 3, the first activated carbon 50 has a maximum pore diameter peak at about 30 mm, and the second activated carbon 52 is about 20 mm smaller than the maximum pore diameter peak of the first activated carbon 50. Has a maximum pore diameter peak. Thus, the first activated carbon 50 and the second activated carbon 52 have different adsorption characteristics because the maximum peak of the pore diameter is different. It is considered that the first activated carbon 50 and the second activated carbon 52 have different adsorption characteristics with respect to gases having different molecular diameters. Since the first activated carbon 50 has a relatively large pore diameter peak and the second activated carbon 52 has a relatively small activated carbon peak, the first activated carbon 50 has an organic outgas or ion implantation having a relatively large molecular diameter. It is considered that the second activated carbon 52 is excellent in the adsorption performance of the rare gas having a relatively small molecular diameter.

  Therefore, for the first activated carbon 50, the adsorption amount per unit weight of the dopant gas used for the organic outgas and ion implantation treatment is larger than the adsorption amount per unit weight of the non-condensable gas. For the second activated carbon 52, the adsorption amount per unit weight of the dopant gas used in the organic outgas and ion implantation treatment is smaller than the adsorption amount per unit weight of the non-condensable gas. In other words, with respect to the first activated carbon 50, the adsorption amount per unit weight of the dopant gas having a large residual ratio in the regeneration process among the exhausted gases is the adsorption amount per unit weight of the gas of the non-condensable gas having a small residual ratio. Bigger than. As for the second activated carbon 52, the adsorption amount per unit weight of the dopant gas having a large residual ratio in the regeneration treatment among the exhausted gases is smaller than the adsorption amount per unit weight of the non-condensable gas having a small residual ratio. Become. As a result, the hardly regenerated gas can be accumulated in the first activated carbon 50. In addition, the amount of adsorption per unit weight of the adsorbent is, for example, the amount of adsorption under a reference condition (for example, a standard state). Further, the adsorption amount of the gas may not be compared per unit weight of the adsorbent, and may be compared per unit volume or per unit specific surface area, for example.

  The activated carbon bonded to each panel 42 is formed in a cylindrical shape, for example. The side surfaces of the activated carbon are bonded to the panel surface in such a posture that the central axis is parallel to the opening 26. A large number of activated carbons are adhered in a state of being closely arranged on the surface of the panel 42. The shape of the adsorbent may not be a cylindrical shape, and may be, for example, a spherical shape, other shaped shapes, or an indefinite shape. The arrangement of the adsorbent on the panel may be a regular arrangement or an irregular arrangement.

  Since the panel front surface 46 of the uppermost panel 42a directly faces the opening 26 and the baffle 32, gas molecules that have passed through the opening 26 and the baffle 32 fly along a linear path. In other words, the gas molecules that have passed through the baffle 32 reach the panel front surface 46 directly without being disturbed by other panels. For this reason, the panel front surface 46 of the uppermost panel 42 a has a relatively higher exhaust speed per unit area than other portions of the panel structure 14. In contrast, the lower panels 42b and 42c basically do not reach the gas molecules that have passed through the opening 26 and the baffle 32 through a linear flight path. For example, the gas molecules reach the lower panels 42b and 42c only after they collide with other panels, the heat shield 16 and the like and are reflected, for example, many times. For this reason, the contribution of the lower panels 42b and 42c to the exhaust speed is relatively low. Therefore, by providing the first activated carbon 50 on the uppermost panel 42 a that is relatively excellent in exhaust efficiency, the dopant gas can be more efficiently accumulated on the first activated carbon 50.

  In other words, it is desirable to provide the first suction region in a portion exposed when viewed from the opening 26. In addition, it is desirable to provide the second suction region in a portion that is not exposed when viewed from the opening 26. Therefore, for example, an adsorbent that is relatively superior in the adsorption characteristics of the non-condensable gas may be provided on the back surface of the panel 42 as viewed from the opening 26.

  In the present embodiment, the cryopanel having the first adsorption region is configured to be detachable from the panel structure 14. Specifically, the uppermost panel 42a is detachably attached to the panel attachment member 40. The uppermost panel 42a is attached to the panel attachment member 40 with bolts or the like, for example, and can be detached from the panel attachment member 40 as necessary. In this way, when the hardly regenerated gas is accumulated in the first adsorbent exceeding the predetermined standard, it can be easily replaced with another panel having a new adsorbent. The lower panels 42b and 42c may also be detachably attached to the panel attachment member 40 in the same manner as the uppermost panel 42a. Alternatively, the lower panels 42b and 42c may be fixedly attached to the panel attachment member 40 by, for example, soldering.

  In the present embodiment, the first adsorbent for the difficult-to-regenerate gas is provided on the single cryopanel 42a. That is, a single type of adsorbent is provided in one cryopanel 42 so that the adsorption characteristics are different for each panel. For example, the first activated carbon 50 is bonded to the uppermost panel 42a, and the second activated carbon 52 is bonded to the lower panels 42b and 42c. Accordingly, since only the cryopanel 42a having the first adsorbent can be selected and replaced, maintenance work can be easily performed. Note that the type of adsorbent may be different for each panel unit composed of a plurality of cryopanels 42. In this case, the panel unit may be configured to be detachable from the panel structure 14.

  As a modification of the above-described embodiment, for example, an adsorbent such as zeolite formed so as to selectively adsorb specific gas molecules may be used. For example, an adsorbent that selectively adsorbs a dopant gas used in the ion implantation process may be used as the first adsorbent, and an adsorbent that selectively adsorbs a non-condensable gas may be used as the second adsorbent. Good. In this case, the first adsorbent may be provided on the uppermost panel 42 a of the panel structure 14, and the second adsorbent may be provided on the lower panels 42 b and 42 c of the panel structure 14.

  Further, a plurality of types of adsorbents formed so as to selectively adsorb each of the plurality of types of dopant gases may be provided in the panel structure 14. For example, the upper panel 42a of the panel structure 14 is provided with an adsorbent that selectively adsorbs boron trifluoride, an adsorbent that selectively adsorbs phosphine, and an adsorbent that selectively adsorbs arsine. Also good. Similarly, a plurality of types of adsorbents formed so as to selectively adsorb each of a plurality of types of rare gases may be provided in the panel structure 14. For example, the lower panels 42b and 42c of the panel structure 14 may each be provided with an adsorbent that selectively adsorbs hydrogen, an adsorbent that selectively adsorbs neon, and an adsorbent that selectively adsorbs xenon. Good. When an adsorbent adapted to a specific gas is provided as described above, an adsorbent for adsorbing another gas, such as activated carbon, may be installed in the panel structure 14 and used together.

In the above-described embodiment, a plurality of types of adsorbents are used by paying attention to the gas residual ratio in the adsorbent when the regeneration process is performed, but a plurality of types of adsorbents are used from other viewpoints. Also good. For example, as the first adsorbent, the adsorption amount per unit weight of the first gas whose cooling temperature is lower than a predetermined adsorption equilibrium pressure (for example, 10 ⁻⁸ Pa) is relatively high. Alternatively, an adsorbent larger than the adsorption amount per unit weight of the second gas having a low temperature may be used. As the second adsorbent, the adsorption amount per unit weight of the first gas whose cooling temperature is lower than a predetermined adsorption equilibrium pressure is relatively high, and the second gas whose cooling temperature is relatively low is used. An adsorbent smaller than the amount adsorbed per unit weight may be used.

  In this case, the first adsorbent may be provided on the surface of the cryopanel having a relatively large heat input by radiation, and the second adsorbent may be provided on the surface of the cryopanel having a relatively small heat input by radiation. For example, a first adsorbent is provided on the cryopanel surface exposed to the cryopump opening surface, and a second adsorbent is provided on the cryopanel surface shielded from the cryopump opening surface by another cryopanel or the like. May be. In this way, the cryopanel that tends to be relatively high temperature is provided with an adsorbent that is suitable for gas that is adsorbed even at high temperatures. Therefore, it is possible to optimize the exhaust performance against the influence of radiant heat from the outside of the cryopump.

  In the present embodiment, a plurality of types of adsorbents having different surface properties of the adsorbent by varying the pore size distribution are used. By varying the surface properties of the adsorbent, different adsorption performance is realized for each adsorbent. However, the method of making the surface properties different is not limited to this, and for example, the specific surface area (that is, the surface area per unit weight) of the adsorbent may be made different, or the adsorption characteristics may be made different. The adsorption characteristics of the adsorbent are represented by, for example, a gas phase isothermal adsorption curve. The gas-phase isothermal adsorption curve is a plot of the amount of adsorption against the above relative pressure at a constant temperature. The gas-phase isothermal adsorption curve is measured by a method specified in JIS K 1474, for example.

  Here, different types of adsorbent (for example, activated carbon) means that at least one of the properties of the adsorbent is significantly different. Significantly different is, for example, that there are differences that exceed the error for certain properties when comparing two adsorbents. In the present embodiment, when there is a significant difference in the adsorption performance for different gases, the type of adsorbent is considered to be different.

  When the cryopump 10 is operated, first, the vacuum chamber 80 is roughly evacuated to about 1 Pa using another appropriate roughing pump before the operation. Thereafter, the cryopump 10 is operated. The first cooling stage 22 and the second cooling stage 24 are cooled by driving the refrigerator 12, and the heat shield 16, the baffle 32, and the panel structure 14 that are thermally connected thereto are also cooled.

  The cooled baffle 32 cools gas molecules flying from the vacuum chamber 80 toward the inside of the cryopump 10, and exhausts gas (for example, moisture) whose vapor pressure is sufficiently low at the cooling temperature to condense on the surface. To do. A gas whose vapor pressure does not become sufficiently low at the cooling temperature of the baffle 32 passes through the baffle 32 and enters the heat shield 16. Among the gas molecules that have entered, the gas whose vapor pressure is sufficiently low at the cooling temperature of the panel structure 14 is condensed on the surface of the panel structure 14 and exhausted. The gas whose vapor pressure is not sufficiently lowered even at the cooling temperature is adsorbed and exhausted by the adsorbent which is bonded to the surface of the panel structure 14 and cooled. In this way, the cryopump 10 can reach the desired degree of vacuum inside the vacuum chamber 80.

  In particular, in the cryopump 10 used in the evacuation system of the ion implantation apparatus, the gas having a relatively large molecular diameter such as an organic gas or a dopant gas among the gases that have entered the heat shield 16 is the upper panel 42a. It is mainly adsorbed on the first activated carbon 50. A gas having a relatively small molecular diameter, such as hydrogen gas, is mainly adsorbed by the second activated carbon 52 of the lower panels 42b and 42c. In this way, the cryopumping process is performed.

  When the cryopumping process is continuously performed, exhaust gas is accumulated inside the cryopump. A regeneration process is performed to discharge the accumulated gas to the outside. First, the cryopump 10 is separated from the vacuum chamber 80 by closing the gate valve 7. Next, the temperature of the cryopanel 42 is raised. The cryopanel 42 is heated to a temperature (for example, room temperature) higher than the cooling temperature in the cryopumping process. As the temperature rises, the gas captured by condensation on the cryopanel surface is vaporized, and the gas captured by adsorption is desorbed and re-released into the pump container. The re-released gas is discharged to the outside through a discharge port (not shown) of the cryopump 10 by driving an attached roughing pump, for example. Thereafter, the cryopanel 42 is re-cooled to the operating temperature in the cryopumping process. The regeneration process is completed by re-cooling. The gate valve 7 is opened and the cryopumping process is started again. In this way, the cryopumping process and the reproduction process are alternately performed.

  In the present embodiment, maintenance processing is performed on the cryopanel 42 as necessary. For example, the maintenance process is performed when it is assumed that the residual amount of the organic gas from the resist or the dopant gas used in the ion implantation process on the first activated carbon 50 exceeds the standard. For example, when the cumulative amount of the target gas such as the dopant gas exceeds a reference value, it may be determined that the residual gas amount of the activated carbon exceeds the reference. Alternatively, when the accumulated time of the cryopumping process exceeds the reference value, it may be determined that the residual gas amount of the activated carbon exceeds the reference value. These reference values can be appropriately set by experiments or the like in consideration of the amount of adsorption to the adsorbent. In this maintenance process, for example, the cryopanel 42a having the first activated carbon 50 is replaced. Alternatively, a gas removal process for chemically removing the residual gas may be performed. In the present embodiment, since the hardly regenerated gas is accumulated on the first activated carbon 50, only the cryopanel 42a having the first activated carbon 50 needs to be selectively subjected to maintenance processing. For this reason, maintenance work can be simplified. Note that a maintenance process may be additionally performed on the cryopanel having the second activated carbon 52.

  As described above, in the present embodiment, the first activated carbon 50 adsorbs better than the second activated carbon 52 with respect to difficult-to-regenerate gases such as organic gases from resist and toxic gases used for ion implantation. Has performance. The first activated carbon 50 is bonded to the front surface of the uppermost panel 42 a exposed to the opening 26 of the cryopump 10. For this reason, the hardly regenerated gas is accumulated in the first activated carbon 50. Therefore, accumulation of difficult-to-regenerate gas on the second activated carbon 52, which is excellent in adsorption performance of non-condensable gas such as hydrogen gas, is reduced. Therefore, the exhaust performance of the cryopump 10 can be maintained by the second activated carbon 52. At the same time, the influence on the service life of the second activated carbon 52 is reduced, and the second activated carbon 52 can be used for a long time. Further, if the maintenance work required for accumulating the hardly regenerated gas is performed only on the first adsorbent, it will be practically sufficient, so the work burden can be reduced.

  In the above, this invention was demonstrated based on the Example. It will be understood by those skilled in the art that the present invention is not limited to the above-described embodiment, and various design changes are possible, various modifications are possible, and such modifications are within the scope of the present invention. By the way.

  For example, an exposed surface other than the cryopanel 42 in the panel structure 14 may be used as the adsorbent application surface. For example, the disk portion 44 of the panel mounting member 40 may be used as one of the panels. In this case, an adsorbent may be provided on the surface of the disk portion 44 facing the opening 26. It should be noted that the adsorbent provided in the disc portion 44 may be the same as or different from the adsorbent on the panel front surface 46 of the uppermost panel 42a.

  You may employ | adopt the panel arrangement | positioning different from the above-mentioned embodiment. For example, the panel spacing may be the same for all panels or may be different. For example, each of the plurality of panels 42 may be arranged so that the panel interval becomes narrower as the position of the panel moves away from the opening 26. In this way, it is possible to improve the gas flowability at the site of the panel structure 14 adjacent to the opening 26 and increase the exhaust speed. At the same time, the adsorption area can be increased by arranging the panels relatively densely at the part of the panel structure 14 far from the opening 26, so that a sufficient gas occlusion amount can be ensured.

  Moreover, you may employ | adopt the panel 42 of a shape different from the above-mentioned embodiment. For example, the orientation of the panel 42 may be parallel to the opening 26 or may be inclined so as to approach the opening 26 as it extends radially outward. In order to increase the surface area of the panel that functions as the adsorption region, the orientation of the panel is preferably oblique rather than parallel to the opening 26.

  The shape of the panel 42 may be different for each panel. For example, the length of the panel 42 in the radial direction may be varied, and the length may be increased or decreased as the distance from the opening 26 increases. Moreover, the shape when the panel 42 is viewed from the opening 26 side may not be circular, and may be other shapes such as a polygonal shape. The number of panels 42 is not limited to three, and may be any number.

  In the panel structure 14, a third adsorption region having different properties from the first adsorption region and the second adsorption region may be formed. Moreover, you may form so that a property may change continuously from a 1st adsorption | suction area | region to a 2nd adsorption | suction area | region. Further, the formation of the adsorption region may be performed by surface processing on the panel surface other than providing the adsorbent on the panel surface. For example, the adsorption region may be formed by modifying the panel surface to be porous, for example.

It is a figure which shows typically the ion implantation apparatus and cryopump which concern on one Embodiment of this invention. It is sectional drawing which shows typically the cryopump which concerns on one Embodiment of this invention. It is a figure which shows an example of the pore diameter distribution curve of a 1st activated carbon and a 2nd activated carbon.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 Cryopump, 12 Refrigerator, 14 Panel structure, 16 Heat shield, 26 Opening part, 28 Blocking part, 32 Baffle, 42a Top panel, 42b Lower panel, 50 1st activated carbon, 52 2nd activated carbon

Claims (12)

A cryopump that alternately performs a cryopumping process for exhausting the exhausted gas containing the first and second gases by adsorbing to the adsorbent and a regeneration process for desorbing and discharging the adsorbed gas from the adsorbent. There,
First adsorption in which the adsorption amount per unit weight of the gas having a large residual ratio in the regeneration process among the adsorbed first and second gases is larger than the adsorption amount per unit weight of the gas having the smaller residual ratio. Agent,
The second adsorption in which the adsorption amount per unit weight of the gas having a large residual ratio in the regeneration treatment among the adsorbed first and second gases is smaller than the adsorption amount per unit weight of the gas having the smaller residual ratio. And a cryopump. The first adsorption region formed at a site where gas molecules that have entered the cryopump can reach via a linear flight path, and the gas molecules that have entered the cryopump do not reach the linear pumping path. A cryopanel structure including a second adsorption region formed in the site,
The cryopump according to claim 1, wherein the first adsorption region is formed by a first adsorbent, and the second adsorption region is formed by a second adsorbent.   The cryopump according to claim 2, wherein the cryopanel structure is configured to be detachable from the first suction region.   The exhaust gas includes a non-condensable gas and a dopant gas used for ion implantation, and the first adsorbent has an adsorption amount per unit weight of the dopant gas that is greater than an adsorption amount per unit weight of the non-condensable gas. The cryopump according to claim 1, wherein the second adsorbent has an adsorption amount per unit weight of the dopant gas smaller than an adsorption amount per unit weight of the non-condensable gas.   The first adsorbent selectively adsorbs a gas having a large residual ratio in the regeneration process out of the first and second gases, and the second adsorbent regenerates out of the first and second gases. The cryopump according to claim 1, wherein a gas having a small residual ratio is selectively adsorbed.   The cryopump according to claim 1, wherein the first adsorbent has a maximum peak pore diameter in the pore diameter distribution curve larger than that of the second adsorbent. A cryopump used in a vacuum exhaust system of an ion implanter,
A first adsorbent in which the adsorption amount per unit weight of the dopant gas used for the ion implantation process is larger than the adsorption amount per unit weight of the non-condensable gas;
A cryopump comprising: a second adsorbent in which the adsorption amount per unit weight of the dopant gas is smaller than the adsorption amount per unit weight of the non-condensable gas. A cryopump used in a vacuum exhaust system of a substrate processing apparatus for processing a substrate coated with a resist with a process gas,
A first adsorbent in which the adsorption amount per unit weight of the organic gas released from the resist is larger than the adsorption amount per unit weight of the process gas;
And a second adsorbent having an adsorption amount per unit weight of the organic gas smaller than an adsorption amount per unit weight of the process gas.   A first adsorption region that selectively adsorbs the first gas molecules and a second gas molecule that is formed at a site different from the first adsorption region and that is different from the first gas molecules are selectively adsorbed. A cryopanel structure comprising: a second adsorption region.   A first adsorbent having a maximum peak in the pore diameter distribution curve as a first pore diameter, and a second adsorbent having a maximum peak in the pore diameter distribution curve as a second pore diameter smaller than the first pore diameter. A cryopanel structure. A vacuum evacuation method including a cryopumping process for adsorbing and exhausting a gas to be exhausted containing first and second gases to an adsorbent and a regeneration process for desorbing and discharging the adsorbed gas from the adsorbent. And
The cryopumping process
First adsorption in which the adsorption amount per unit weight of the gas having a large residual ratio in the regeneration step among the adsorbed first and second gases is larger than the adsorption amount per unit weight of the gas having the smaller residual ratio. Agent,
The second adsorption in which the adsorption amount per unit weight of the gas having a large residual ratio in the regeneration step among the adsorbed first and second gases is smaller than the adsorption amount per unit weight of the gas having the smaller residual ratio. A vacuum evacuation method characterized by exhausting a gas to be exhausted together with an agent.   It further includes a maintenance step of selectively exchanging the first adsorbent when the residual amount in the first adsorbent of the gas having a large residual ratio in the regeneration step among the first and second gases exceeds the standard. The vacuum evacuation method according to claim 11.

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