VALVES FOR CHARGED PARTICLE BEAM MICROSCOPE, VALVE MEMBER AND CHARGED PARTICLE BEAM MICROSCOPE

A valve for a charged particle beam microscope comprises: a valve seat comprising an opening; and a valve member comprising a valve member body and a sealing ring on a first surface of the valve member body. The valve member is movable between a first position where the sealing ring seals around the opening and a second position where the valve member is spaced apart from the opening. The valve member further comprises an electrically conducting shielding member extending at least at a side surface of the valve member body facing the opening in the second position.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims benefit under 35 U.S.C. § 119 to German Application No. 10 2023 118 986.7, filed Jul. 18, 2023. The entire disclosure of this application is incorporated by reference herein.

FIELD

The present application relates to valves for charged particle beam microscopes, valve members of such valves and to corresponding charged particle beam microscopes.

BACKGROUND

Charged particle beam microscopes are a type of microscopes in which a charged particle beam, for example an electron beam or an ion beam, is guided to a sample, and the interaction between the charged particle beam and the sample is used for generating an image. Examples of charged partial beam microscopes are transmission electron microscopes (TEMs) and scanning electron microscopes (SEM). For increasing throughput, such microscopes may also use more than one charged particle beam, for example in so called Multi-SEMs (MSEM).

Generally, such charged particle beam microscopes include a charged particle beam source for generating the charged particle beam, components to focus the charged particle beam on the sample, for example magnets, and one or more detectors to detect the response, which may for example include reflected charged particle beams, scattered charged particle beams, secondary charged particles like Auger electrons or also other kinds of radiation like x-ray radiation generated.

In most types of charged particle beam microscopes, the charged particle beam is at least for the most part guided through a vacuum onto the sample. At a charged particle beam source, usually an ultra high vacuum (UHV) is used (1×10−9mbar or better), while in other parts of a charged particle beam microscope the beam may pass through a high vacuum (e.g. 1×10−6mbar or better) because this level of vacuum is sufficient.

A valve is used in some configurations to separate a first chamber where the charged particle beam is generated from a second chamber where the sample resides. As an example,FIG.6shows a columnar arrangement of a charged particle beam microscope60including an upper chamber61and a lower chamber62. As indicated by arrows, both upper chamber61and lower chamber62may be evacuated to generate a vacuum therein.

Upper chamber61includes a cathode63which generates a charged particle beam, e.g. electrons. The charged particle beam leaves upper chamber61and enters lower chamber62via a channel (pressure stage)64. A pressure in lower chamber62is, as mentioned above, higher than in upper chamber61(e.g. UHV in upper chamber61, high vacuum in lower chamber62).

The charged particle beam is focused onto a sample68via an objective lens67. Detectors66serve for detecting the signal, e.g. scattered particles, secondary particles and/or radiation, as mentioned above. Around detector66, the pressure again may be higher than in lower chamber62, e.g. 1×10−5mbar or less. It should be noted that pressures here are given only by way of example and may vary depending on the implementation.

A valve65is provided which may be used to separate upper chamber61from lower chamber62. For example, in case of a loss of vacuum in lower chamber62, valve65may be closed, to preserve the vacuum in upper chamber61and protect cathode63. Also, when charged particle beam microscope is not in use or when the sample is changed, valve65may be closed.

FIGS.5A and5Bshow an example of a conventional valve used in such charged particle beam microscopes in schematic side views for comparison purposes.FIG.5Ashows the valve in an open position, andFIG.5Bshows the valve in a closed position. The valve shown inFIGS.5A and5Bincludes a valve seat12with an opening11. In operation, a charged particle beam16, for example an electron beam, passes through opening11between the above-mentioned chambers. Furthermore, the valve includes a valve member having a valve member body13and a sealing ring14like an O-ring on a first surface of valve member13. In an open position, valve member body13is retracted, such that opening11is open. In a closed position, valve member body13presses sealing ring14against the circumference of opening11, thus sealing the opening.

An electrical contact spring (not shown) may be provided at a side surface of valve member body13. In the closed position, the electrical contact spring, which is electrically conducting, is in electrical contact with valve seat12, and in the open position the electrical contact spring is in electrical contact with a portion which sometimes is referred to as “valve garage” and is generally referred to as a valve housing member herein, and which provides a kind of housing for the valve member. This serves to bring the valve member to a certain electric potential, for example ground in the closed position or an acceleration voltage for the charged particle beam, for example in the Kilovolt range, in the open position.

SUMMARY

An electrical contact spring may deteriorate over time, for example by corrosion and/or mechanical wear, leading to an undefined potential of the valve member. Furthermore, in the open position shown inFIG.5A, sealing ring14may be charged by charged particle beam16. Such effects may lead to a certain deflection of the charged particle beam16, which may deteriorate image quality or lead to an unstable image position, i.e. to image drift. Furthermore, the electrical contact spring may for example corrode. Furthermore, particles may be generated by the movement and the moving contact between the electrical contact spring and valve seat12or a housing, respectively.

The present application generally relates to valves which may be used in charged particle beam microscopes to separate areas from each other in a gas-tight manner, for example upper chamber61and lower chamber62ofFIG.6. Other parts of such charged particle beam microscopes may be implemented in any conventional manner, andFIG.6shows merely a simple non-limiting example.

According to a first aspect, a valve for a charged particle beam microscope is provided, comprising: a valve seat comprising an opening; and a valve member comprising a valve member body and a sealing ring on a first surface of the valve member body, wherein the valve member is movable between a first position where the sealing ring seals around the opening and a second position where the valve member is spaced apart from the opening, wherein the valve member further comprises an electrically conducting shielding member extending at least at a sized surface of the valve member body facing the opening in the second position.

In some embodiments, the shielding member may prevent a charging of the sealing ring in the second position.

The second position may be offset from the first position in a direction parallel to a plane in which the opening is provided. The sealing member may for example be made of a metal.

The shielding member may extend to a height at least corresponding to a height of the sealing ring above the first surface in the second position. In some embodiments, this may provide a good shielding of the sealing ring.

The sealing ring may for example be an O-ring made of a rubber material.

The shielding member may be attached to the second surface of the valve member body opposite the first surface. In some embodiments, this may give some resiliency to the arrangement of the shielding member coupled to the valve member body.

The valve may further comprise a valve housing member which extends below the valve member. In such an embodiment, the shielding member may be configured to electrically contact at least a conducting part of the valve housing member in the second position. This may allow for a biasing of the valve member in the second position via the valve housing member and for shielding member. For example, the valve housing member may be configured to be set to a high voltage potential at least when the valve member is in the second position, such that the valve member is biased with the high voltage potential in the second position via the shielding member.

Furthermore, the shielding member may be configured to electrically contact a conducting portion of the valve seat when the valve member is in the first position. In this way, in the first position the valve member may be biased via the valve seat, for example to a ground potential if the valve seat is configured to be set to a ground potential at least when the valve is in the first position.

In addition, the valve member may include an electrical contact spring at a further side surface thereof, which is configured to receive a first voltage in the first position and a second voltage in the second position, for example the high voltage and ground potential mentioned above. The first voltage may be a high voltage, and the second voltage may correspond to ground.

The valve seat may comprise a further shielding member around the opening, where the sealing ring is configured to abut against the further shielding member in the first position and shielded by the shielding member in the second position. This further shielding member in some embodiments may provide an additional shielding for the sealing ring.

This further shielding member may also be used independently from the shielding member, such that in a second aspect a valve for a charged particle beam microscope is provided, comprising: a valve seat comprising an opening, and a shielding member around the opening; and a valve member comprising a valve member body and a sealing ring on the first surface of the valve member body, wherein the valve member is movable between a first position where the sealing ring abuts against the shielding member to seal around the opening and a second position where the valve member is spaced for apart from the opening and the sealing ring is shielded by the shielding member.

The valve may further comprise a flexible electrically conducting wire coupled to the valve member body, via which the valve member may be biased, for example to the first and/or second voltage mentioned above. This may also be used independently or in combination with the above features, such that in a third aspect a valve for a charged particle beam microscope is provided, comprising: a valve seat comprising an opening; and a valve member comprising a valve member body and a sealing ring on a first surface of the valve member body, wherein the valve member is movable between a first position where the sealing ring seals around the opening and a second position where the valve member is spaced apart from the opening, and a flexible electrically conducting attached to the electrically conducting attached to the valve member body for biasing the valve member.

Furthermore, an electrical contact may be provided adjacent to the valve seat, such that the valve member contacts the electrical contact in the second position. This may also serve for biasing the valve member in the second position and may also be used independently from some of the features above. In this respect, the electrical contact may form part of a recess where the valve member is positioned when in the second position. According to a fourth aspect a valve for a charged particle beam microscope is provided, comprising: a valve seat comprising an opening, and an electrical contact adjacent to the valve seat; and a valve member comprising a valve member body and a sealing ring on a first surface of the valve member body, wherein the valve member is movable between a first position where the sealing ring seals around the opening and a second position where the valve member is spaced apart from the opening and contacts the electrical contact.

In order to reduce friction and particle generation by friction, a suitable vacuum compatible lubricant may be provided at portions where the valve member comes to sliding contact with other parts like the valve housing member. For example, the lubricant may be provided where the shielding member electrically contacts a conducting part of the valve housing member or where the electrical contact spring at the further side surface comes into contact with other elements. The lubricant may be based on a fluoropolymer or a silicone grease. The lubricant may be highly inert, i.e. not prone undergoing chemical reactions, and therefore in some embodiments may also protect against corrosion. For example, suitable lubricants may be based on polyfluoroethylene (PFE) with a viscosity of the order of 250-300 mm2/s at 20° C., a TOC (degassing) value of at or below 20 ng/mg when at 200° C. for 2 min as analyzed by GC-MS (combine gas chromatography and mass spectrometry).

This may also be independent from the above, such that according to a fifth aspect a valve for a charged particle beam microscope is provided, comprising: a valve seat comprising an opening; and a valve member comprising a valve member body and a sealing ring on a first surface of the valve member body, wherein the valve member is movable between a first position where the sealing ring seals around the opening and a second position where the valve member is spaced apart from the opening, and a lubricant at least one point of sliding contact between the valve member and a further part of the valve.

According to further aspects, corresponding valve members are provided. According to a further aspect, a charged particle beam microscope comprising any of the valves discussed above is provided.

DETAILED DESCRIPTION

In the following, various embodiments of valves and valve members for charged particle beam microscopes will be discussed. The valves and valve members discussed may in particular separate a first chamber where a charged particle beam like an electron beam is generated from a second chamber where the sample is provided, for example to preserve a vacuum. As an example, the valves discussed may be used as valve65in the charged particle beam microscope ofFIG.6described above.

Features from different embodiments may be combined to form further embodiments. For example, different embodiments may include different modifications compared to the comparative example discussed in the introductory portion with respect toFIGS.5A-5D, and these variations may be used independently or in various combinations with each other. On the other hand, in a single embodiment shown in the figures and described herein more than one such variation may be present, and also in this case the variations may be used independently from each other or in combination.

In the figures, like components are designated with the same reference numerals and will not be describe repeatedly.

FIG.1Ais a side view of a valve according to an embodiment in an open position, andFIG.1Bis a side view of the valve ofFIG.1Ain a closed position.FIGS.1E and1Fshow perspective views of example implementations of the valve ofFIGS.1A and1B.

The valve ofFIGS.1A,1B, include a valve seat12with an opening11. In operation, a charged particle beam16, for example an electron beam, passes through opening11.

The valve further comprises a valve member including a valve member body13, a sealing ring14disposed on a first side of the valve member body13, and a shielding15. As can be seen inFIG.1B, in the closed position (also referred to as first position herein) sealing ring14seals around opening11, for example to prevent a vacuum loss.

Shielding member15is made of an electrically conducting material, for example a metal or metal alloy, and extends on a side of valve member body13which faces opening11and charged particle beam16in the open position if the valve member (also referred to as second position herein) ofFIG.1A. Shielding15extends above the first surface, such that sealing ring14is shielded from the charged particle beam16, which in some embodiments may prevent charging of sealing ring14.

As can been inFIGS.1A and1B, shielding15may be attached to second side of valve member body13opposite the first side (where sealing ring14is provided), such that shielding member15is fixed in a spring-like manner. In the closed position ofFIG.1B, as shown shielding member15then abuts against valve seat12and establishes an electrical contact to valve seat12. Valve seat12in the closed position may for example be set to a ground potential, and this contact of shielding member15to valve seat12contributes to also setting the valve member to ground potential.

As in conventional systems, as shown inFIGS.1C and1D, the valve may also include a valve housing member17which extends, in the figure, below the valve member. As shown inFIG.1C, also in this case in the closed position shielding member15abuts against valve seat12.

Moreover, in some embodiments, as shown inFIG.1Din the open position shielding member15may press against valve housing member17, such that in the open position shielding member15may be biased via valve housing member17, for example to a high voltage potential. In other embodiments, in the open position shielding member15is not in contact with valve housing member17in the open position.

Furthermore, the valve member ofFIGS.1E and1Fhas an electrical spring contact18at a side thereof, which in the embodiment ofFIGS.1E and1Fis formed with shielding member15in one piece. In other embodiments, an implementation using separate pieces or elements for shielding member15may be used. Electrical spring contact18serves to additionally provide the conventional contacting for biasing the valve member, as explained in the introductory portion with respect toFIGS.5C and5D, see electrical spring contact18thereof. In this case, the biasing via shielding member15as shown inFIGS.1B,1Cfor the contact to the valve seat and inFIG.1Dfor the contact to valve housing member17provides an additional contact to the conventional contact via electrical spring contact18.

FIGS.2A and2Billustrate a valve according to a further embodiment, whereFIG.2Ashows the open case where the valve member is in the second position, andFIG.2Bshows the closed case where opening11is sealed.

Instead of the shielding15provided in the embodiment ofFIG.1A-1Khere a further shielding21is provided which extends from valve seat12and surrounds opening11. In the position shown inFIG.2A, further shielding21is interposed between the sealing ring14and the charged particle beam16, such that a charging of sealing ring14is prevented or at least reduced. In the first state shown inFIG.2B, sealing ring14abuts against further shielding21, thus sealing opening11.

In some embodiments, further shielding21may be combined with shielding15discussed previously.

Furthermore, in the embodiment ofFIGS.2A and2Ban electrically conducting member20is attached to valve member body13. Using electrically conducting member20, the valve member may be securely biased to a high voltage or to ground in some embodiments. In some embodiments, electrically conducting member20may be a flexible member like a wire or a cable like a ribbon cable. In other embodiments, electrically conducting member20may be fully or partially rigid, for example with a flexible contact or rolling contact remote from the valve member.

FIGS.3A and3Billustrate a valve according to a further embodiment.FIG.3Ashows the second position (open position), andFIG.3Bshows the first position (close position).

Here, a valve seat32is provided which has a recess31, into which sealing ring14is positioned in the open case ofFIG.3A, such that sealing ring14is shielded from charged particle beam16. Additionally, an electrically conducting element33is provided, against which valve member body13abuts in the second position, thus providing an electrical contact for biasing the valve member. Note that in the embodiment ofFIGS.3A and3Bshielding member15is provided and has the function as explained with reference toFIGS.1A-1K, in particular abuts against valve seat32in the first position ofFIG.3Bwhere the sealing ring14is pressed against valve seat32to seal around opening11. Nevertheless, the recess and the electrical contact element33ofFIGS.3A and3Bmay be provided independently from shielding member15.

In further embodiments, together with the embodiments discussed above or independently thereon, a lubricant is used at points where a sliding electrical contact is established. This is illustrated inFIGS.4A and4B.FIG.4AreproducesFIG.1D. Reference numeral40indicates where shielding member15comes into sliding contact with valve housing member17, which may correspond to the contact established by protrusion19, as shown inFIGS.1H and1J.FIG.4Bshows a top view where electrical spring contact18comes into contact with valve housing member17or any other point, and as indicated by reference numeral41here also a lubricant may be used. The lubricant may protect from mechanical abrasion and generation of particles. Such an abrasion, besides problems which may generated by free particles in the charged particle beam microscope itself, may increase the surface of the corresponding contact elements like electrical spring contact18or shielding member15, which in turn may increase an oxidation or other chemical reaction, which may reduce the quality of the electrical contact. For example, shielding15may be made of copper, bronze, or brass (like chromed brass), and in charged particle beam microscope NOCl gas may react with such metal to form copper chloride, which may provide an electrical isolation. Such NOCl gas is used as processing gas to locally etch structures in the samples via the electron beam, but may also inadvertedly react with other components in the device.

Suitable lubricants include fluoropolymers like so called TEM oil, or silicone grease based lubricants. [Examples include APIEZON® high vacuum grease or silicone high vacuum grease by Plano GmbH, or Lit-Oil 300 or 500 oils from the Zeiss Material catalog.

Therefore, various embodiments herein may increase the reliability of biasing of the valve member and/or may provide a shielding for a sealing ring, which may in some embodiments prevent or mitigate a deterioration of image quality or image position drift of the charged particle beam microscope.