CN116368298A

CN116368298A - Cryopump and inlet restrictor for cryopump

Info

Publication number: CN116368298A
Application number: CN202180074311.0A
Authority: CN
Inventors: J·卡塞洛
Original assignee: Edwards Vacuum LLC
Current assignee: Edwards Vacuum LLC
Priority date: 2020-11-02
Filing date: 2021-10-26
Publication date: 2023-06-30
Also published as: GB2600479A; TW202227717A; GB202017345D0; JP2023546494A; WO2022090923A1; KR20230097024A; EP4237686A1; US20230392838A1; IL302376A

Abstract

A restrictor for restricting the flow rate of gas flowing into a cryopump and the cryopump are disclosed. The restrictor is configured to be installed in an inlet of the cryopump, the restrictor comprising: an inlet means for providing a gas flow path into the cryopump; a shielding plate mounted to at least partially shield the gas flow path through the inlet member; and an intermediate member coupling the shielding plate to the inlet member, the intermediate member including at least one aperture defining at least one gas flow path into the cryopump. The shielding plate is configured to shield the gas flow path through the inlet member such that when installed on the cryopump, there is no direct line of sight path through the inlet member to a cryopanel within the cryopump.

Description

Cryopump and inlet restrictor for cryopump

Technical Field

The field of the invention relates to cryopumps and to an inlet restrictor for cryopumps.

Background

A restrictor plate or throttle plate may be used to limit the flow of gas into the cryopump in order to limit the pumping speed of the pump and maintain a desired pressure in the process chamber, for example, in a PVD physical vapor deposition process. These restrictor plates have conventionally been provided with a plurality of orifices having different geometries through which the class II and III gases enter the pump, and the size and number of these orifices control the flow rate or velocity. A potential problem with plates having holes or orifices is that during viscous flow or continuous flow, the orifices have a line-of-sight view of the second stage cryopanel in the pump and this increases the radiant heat load and may result in preferential gas pumping at these sites. Preferential gas pumping may cause gas molecular columns condensed as "frost" to grow upward from the second stage cryogenic panel toward the plate opening, particularly during high gas flow rates. As the columns become farther from the cryogenic panel, they become hotter, receive increased radiation load, and may begin to degas, thus raising the pressure in the chamber. The increased second stage temperature due to the radiation load and/or the hotter gas column causes the vapor pressure of the class II gas to rise and the pressure in the pump/chamber to rise. The class II gas is a gas such as nitrogen that condenses at the temperature of the second stage cryopanel of the cryopump, while the class III gas does not condense at these temperatures and is typically captured by the adsorbent on the cryopanel.

Fig. 1 shows an example of a cryopump with a throttle plate or restrictor plate 5 according to the prior art. Restrictor plate 5 is placed across the inlet of the pump and includes a plurality of orifices 7 through which gas flows into the pump. The size of the orifice is selected for the desired pumping speed of the pump. The pump is a cryogenic pump and has a chiller unit 15, the chiller unit 15 having a first chiller heat station 10 connected to an inner housing of the pump, which is insulated from an outer housing of the vacuum vessel 9. It also has a second stage heat station 11 connected to a second stage cold panel 12 and other adsorbent cold panels 13. The upper cryogenic panel 12 will experience a frost accumulation 14 on its upper surface, with a particular accumulation forming a peak at a location corresponding to the aperture 7. A potential problem with uneven frost accumulation and radiant heat loading is that the pressure inside the chamber takes longer to recover and may require regeneration more quickly.

It would be desirable to provide a cryopump in which the time between regenerations increases and the pressure recovery time inside the chamber decreases.

Disclosure of Invention

A first aspect provides a restrictor for restricting the flow rate of gas flowing into a cryopump, the restrictor being configured to be installed in an inlet of the cryopump, the restrictor comprising: an inlet means for providing a gas flow path into the cryopump; a shielding plate mounted to at least partially shield the gas flow path through the inlet member; and an intermediate component coupling the shielding plate to the inlet component, the intermediate component including at least one aperture defining at least one gas flow path into the cryopump; wherein the shielding plate is configured to shield the gas flow path through the inlet member such that when installed on the cryopump, there is no direct line of sight path through the inlet member to a cryopanel within the cryopump.

In some embodiments, the inlet member is located in a plane parallel to and offset from the baffle such that when mounted on the cryopump, the inlet member is located between the pumping chamber of the cryopump and the baffle.

The inventors have recognized problems associated with conventional restrictor plates mounted on the inlet of cryopumps and have addressed these problems by providing a two-stage restrictor having an inlet member axially displaced from a baffle. The shield shields the inlet member from gas entering the pump through the inlet, forcing gas around the shield and through the intermediate member to the gas flow path through the inlet member. Thus, gas entering the cryopump is diverted around the shielding member through at least one aperture in the intermediate member and into the flow path through the inlet member. In this way, the direct line of sight of the inlet is separated from the cryogenic panel by the shielding element and the preferential pumping path provided by the aperture looking directly into the cryogenic panel is avoided.

In some embodiments, the inlet member has an annular form that delimits an orifice that defines the gas flow path. The annular form of the inlet member forming a single orifice achieves a more uniform flow across the cross-sectional area of the inlet and helps to inhibit preferential accumulation of frost at specific sites on the cryogenic panel.

In some embodiments, the intermediate member comprises a plurality of apertures.

The intermediate member may be provided with a single aperture extending around the surface of the coupling shield and the inlet member, or it may have a plurality of apertures. The size of the pores and/or the number of pores may be selected to limit the flow to a desired amount, depending on the requirements of the cryopump. Where multiple apertures are present, selecting both the size and number of apertures may enable precise control of the flow rate.

In some embodiments, a surface of the intermediate member including the at least one aperture is at an angle between 120 ° and 60 ° to the shield.

Advantageously, the intermediate member is angled relative to the shield and the inlet member such that the aperture is not directly visible to the cryogenic panel. In this regard, it may be advantageous that it is at an angle between 60 ° and 120 ° to the plane of the shielding plate, and in some embodiments it is advantageously substantially perpendicular to the shielding plate.

In some embodiments, the intermediate member comprises a cylinder.

In some embodiments, the outer perimeter of the inlet member extends beyond the outer perimeter of the shield.

An advantageous geometry of the shielding plate and the inlet member may be such that the shielding plate does not extend as far as the outer perimeter of the inlet member, but rather extends further than the outer perimeter of the orifice of the inlet member. In this way, the orifice is directly blocked by the blocking plate, but a path is provided for the gas to enter the pump around the edge of the blocking plate and then through the intermediate member.

While the geometry of the shield and inlet member may take a variety of forms, such as rectangular, square, or oval, in some embodiments the shield and the inner member have a generally circular outer perimeter.

The circular cross-section of the cryopump generally facilitates a more uniform flow.

In some embodiments, the at least one aperture of the intermediate component is configured to restrict flow into the cryopump to a predetermined flow rate.

The size and/or number of aperture(s) of the intermediate component may be selected according to the desired flow rate of the process being carried out in the chamber evacuated by the cryopump.

A second aspect provides a cryopump comprising: a pump inlet; a refrigerating unit; a cryogenic panel configured to be cooled by the refrigeration unit; and is also provided with

Comprising a flow restrictor according to the first aspect, the flow restrictor being mounted in an inlet of the cryopump such that the flow restrictor restricts the flow of gas into the inlet.

A third aspect provides a method of upgrading a cryopump, comprising: removing a throttle plate mounted across an inlet of the cryopump for restricting flow into the cryopump; and replacing the throttle plate with a restrictor according to the first aspect.

Further particular and preferred aspects are set out in the accompanying independent and dependent claims. Features of the dependent claims may be combined with features of the independent claims as appropriate and in combinations other than those explicitly set out in the claims.

Where a device feature is described as being operable to provide a function, it will be appreciated that this includes the device feature providing that function or being adapted or configured to provide that function.

Drawings

Embodiments of the invention will now be further described with reference to the accompanying drawings, in which:

FIG. 1 shows a cryopump and restrictor plate according to the prior art;

FIG. 2 illustrates a flow restrictor according to an embodiment;

FIG. 3 shows a top view of the flow restrictor with the shielding removed;

FIG. 4 illustrates a top view of a flow restrictor and cryopump including the flow restrictor in accordance with embodiments; and is also provided with

Fig. 5 shows a view from the interior of the pump towards the inlet of the restrictor, according to an embodiment.

Detailed Description

Before any embodiments are discussed in more detail, an overview will first be provided.

Embodiments provide a throttle plate, sputtering plate, or restrictor utilizing an indirect orifice/opening scheme arranged to inhibit preferential pumping or radiation of class II gases from adversely affecting a second stage frost or cryogenic panel. The idea is to allow integral type II gas storage on the second stage cryogenic panel, thereby increasing the amount of type II gas that can be stored. In this regard, if the gas is pumped uniformly, more gas may be stored, and if one zone accumulates condensed gas faster than the other zones, the partial pressure of the gas within the pump will increase.

The flow restrictor of the embodiment acts as an orifice (with one or more openings) and allows the class II and III gases to enter the pump at a rate or speed controlled by the size and number of orifices. Which is arranged such that the orifice is at an angle to the pump inlet and does not provide a direct line of sight to the cryogenic panel.

The cryopump is configured such that the restrictor operates at a temperature of 45K to 110K, i.e. it is connected to the first stage of the two-stage refrigeration apparatus. In an embodiment, the restrictor is mounted on the inner wall of the pumping chamber cooled by the first stage heat station. The second stage cryogenic panel operates between 8K and 16K and may have charcoal or similar adsorbent material for class III gas pumping. The second stage cryogenic panel may or may not be configured to separate the class II gas from the adsorbent material for the class III gas. In this regard, in the embodiment of fig. 4, the panel 13 may include a low temperature panel covered by charcoal obscured by the upper low temperature panel 12.

The restrictor adjusts the pump speed for both class II and class III gases to match the (PVD) process gas flow rate and achieve the predicted pressure within the vacuum chamber. The amount of openings or orifices should be carefully designed so that the pump provides a predictable and consistent pumping rate. When a restrictor is used in the pump inlet, a higher vacuum is achieved below the restrictor opening and a lower vacuum is achieved on the chamber side.

Restrictor or throttle plate pumps are mainly used in viscous flow or continuous flow conditions, such as in physical vapor deposition PVD processes. For viscous flow to the restrictor, any opening/orifice having a line of sight to or directly "looking" into the second stage cryopanel of the pump may result in preferential gas pumping. Radiant heat loads are always present within the cryopump, but proper shielding may mitigate the effects on the second stage. Most cryopumps have a much higher refrigeration capacity in the first stage, so it is advantageous to intercept the heat load at the restrictor. The second stage of most cryopumps has less refrigeration capacity and should be protected from high heat loads and uneven gas loads. In the case of preferential gas pumping through the inlet opening/orifice, the line-of-sight path grows "spikes" and over time these prevent the performance of the pump. Thus, suppressing the viscous flow of gas through the restrictor in a direct line into the second stage is beneficial for increased pumping performance.

In this regard, the cryopump is a "trap" pump, so any gas that is cryogenically pumped onto its surface (below its vapor pressure) will remain trapped until the cryopanel "regenerates" or warms up to release it to a pressure relief valve/roughing valve. All cryopumps have a finite amount of gas that can be pumped before the pump's pressure degrades rendering it unusable for the desired process. When a particular process has a very high flow rate of class II gases, the pump stores these gases as frost on the second stage plate, and when the frost reaches the restrictor or the condensing gases (frost) become too hot, the pump will not operate as intended. The time between regenerations is mainly controlled by the maximum storage capacity of the pump for the class II gas and the gas flow rate. Capture is important to the pump user because increased capture reduces the frequency of regeneration. Providing a more uniform capture increases the amount of gas that can be captured before the effect of condensing gas inhibits pump performance to the point where regeneration is required.

The restrictor plate or throttle plate of the embodiments has a top plate or shield plate, which may be circular, but may be any shape. The shielding plate may be smaller than the inlet plate with a "spacer" or intermediate member in between that separates the two plates by a sufficient amount to allow the class II gas to enter the cryopump. The flow path through the spacer may be at substantially 90 ° to the pump inlet. A "spacer" or intermediate member separates the shield and the inlet plate and provides a path for the gas diverted by the shield to flow between the two plates and across the outer edge of the inlet plate through the opening in the inlet plate into the pump. The opening may be circular, but it may be any shape. A top plate or shield may be suspended over the "spacer" to further prevent radiation and unwanted gases from entering the cryopump.

A restrictor configured in this manner achieves reduced radiant heat load and provides integral frost pumping without the disadvantages of line of sight or preferential gas pumping. This reduction in uneven gas loading and radiation on the second stage cryogenic panel keeps the second stage cryogenic panel cooler and increases gas capture capacity.

This restrictor is designed such that the gas is directed through the opening/orifice, which may be any shape in the intermediate spacer. This arrangement achieves random gas pumping and provides for a substantially uniform integral frost accumulation over the entire surface area of the second stage cryopanel. Such integral gas pumping is advantageous in inhibiting frost on the second stage cryogenic panel from contacting the warmer first stage radiant shield or restrictor.

The shielding is important to maximize or at least increase the type II gas frost pumping and radiation abatement, thereby achieving longer time between regenerations.

Fig. 2 shows a flow restrictor 40 according to an embodiment. In this embodiment, the flow restrictor 40 has a circular cross-section and comprises a shielding plate 1, said shielding plate 1 being mounted via a lower surface 1A on an intermediate member 3, the intermediate member 3 being in the form of a cylinder with an aperture 3A around the longitudinal surface. The intermediate part 3 is mounted on the inlet part 2, which inlet part 2 comprises a projection 4 for mounting the restrictor 40 on the inner wall of the cryopump.

A restrictor 40 is installed at the inlet of the cryopump and restricts flow into the pump. The shield 1 shields the cryopanel within the cryopump from view of the inlet of the pump, while the aperture 3A provides a path for gas to flow into the pump through an orifice in the middle of the inlet part 2. This provides a substantially uniform flow across the cross section of the gas flow path provided by the orifice in the component 2. The size and number of apertures 3A may be selected to limit the flow of gas into the pump to a speed that may be required to maintain the pressure within the pump at a desired rate.

Fig. 3 shows a view of the pump from the top of the restrictor with the shielding 1 removed. This shows an inlet member 2 with an orifice 2A, the orifice 2A providing a gas flow path into the pump. The upper surface of the intermediate spacer member 3 is shown.

Fig. 4 illustrates a cryopump with a restrictor mounted thereon according to an embodiment. The flow restrictor is also shown in side and top view with the shield 1 in place.

The cryopump has a refrigerator unit 15, which refrigerator unit 15 cools a first stage refrigerator heat station 10 for cooling a housing on which a flow restrictor 40 is mounted and a second stage refrigerator heat station 11 for cooling an upper low temperature panel 12 and other low temperature panels 13. These lower cryogenic panels may be coated with an adsorbent material for adsorbing group III gases. The upper panel 12 protects the lower panel 13 from the type II gases condensed on the upper panel 12.

This figure shows the accumulation of condensed type II gas in the form of frost 14, the frost 14 being formed from gas molecules trapped on the cryogenic panel 12. This illustrates how with the restrictor in place there is a uniform accumulation of frost, allowing significantly more gas to be captured before the frost reaches the restrictor. Having a more uniform gas flow and corresponding uniform trapping and frost accumulation allows for an increase in time between regenerations, in some embodiments, up to 50%.

Fig. 5 shows a bottom view of the restrictor, showing the cryogenic boss or foot 4 for mounting the restrictor on the inner housing of the cryopump. Fig. 5 also shows the shielding viewed through the aperture 2A in the inlet part 2. As can be seen, the shutter 1 completely shields the orifice 2A from the direct line of sight path between the inside and the outside of the pump.

The restrictor 40 of the embodiments is adapted to be mounted within the inlet of the cryopump, and in some embodiments, on the inner wall of the pump housing. In an embodiment, the cryopump may be upgraded by: any existing throttle plate is removed and the restrictor 40 of the embodiment is placed in the inlet such that the flow of gas entering the pump is diverted around the baffle plate via the intermediate member to the orifice in the inlet member, thereby providing a uniform flow of gas across the cross section of the pump inlet.

Although illustrative embodiments of the present invention have been disclosed in detail herein with reference to the accompanying drawings, it is to be understood that the invention is not limited to the precise embodiments described, and that various changes and modifications may be effected therein by one skilled in the art without departing from the scope of the invention as defined by the appended claims and their equivalents.

Reference numerals

1. Shielding plate

Lower surface of 1A shielding plate

2. Inlet part

2A orifice

3. Intermediate part

Voids in the 3A intermediate part

4. Low Wen Tutai

5. Restrictor plate

9. Vacuum container

10. First stage heat station

11. Second stage heat station

12. Low temperature panel

13. Low temperature panel with adsorbent

14. Cream

14a frost peak

15. Refrigerating unit

40. Flow restrictor

Claims

1. A restrictor for restricting a flow rate of gas flowing into a cryogenic pump, the restrictor configured to be installed in an inlet of the cryogenic pump, the restrictor comprising:

an inlet means for providing a gas flow path into the cryopump;

a shielding plate mounted to at least partially shield the gas flow path through the inlet member; and

an intermediate member coupling the shielding plate to the inlet member, the intermediate member including at least one aperture defining at least one gas flow path into the cryopump;

wherein the method comprises the steps of

The shielding plate is configured to shield the gas flow path through the inlet member such that when installed on the cryopump, there is no direct line of sight path through the inlet member to a cryopanel within the cryopump.

2. The flow restrictor of claim 1, wherein the inlet member has an annular form that delimits an orifice defining the gas flow path.

3. A restrictor according to claim 1 or 2 wherein the intermediate member comprises a plurality of apertures.

4. A restrictor according to any preceding claim wherein the surface of the intermediate member comprising the at least one aperture is at an angle between 120 ° and 60 ° to the shield.

5. The flow restrictor of claim 4, wherein the surface of the intermediate member including the at least one aperture is substantially perpendicular to the shielding plate.

6. A restrictor according to any preceding claim wherein the intermediate member comprises a cylinder.

7. A restrictor according to any preceding claim wherein the outer periphery of the inlet member extends beyond the outer periphery of the shield.

8. The restrictor of claim 7, wherein an outer perimeter of the shield extends beyond a perimeter of the aperture of the inlet member.

9. A restrictor according to any preceding claim wherein the shield and the inner member have a substantially circular outer perimeter.

10. A restrictor according to any preceding claim wherein the at least one aperture of the intermediate member is configured to restrict flow into the cryopump to a predetermined flow rate.

11. A cryopump, comprising:

a pump inlet;

a refrigerating unit;

a cryogenic panel configured to be cooled by the refrigeration unit; and

a restrictor according to any preceding claim mounted in an inlet of the cryopump such that the restrictor restricts the flow of gas into the inlet.

12. A method of upgrading a cryopump, comprising:

removing a throttle plate mounted across an inlet of the cryopump for restricting flow into the cryopump; and

a restrictor according to any preceding claim in place of the throttle plate.