Thermally regulated enclosure for charged particle instrument

Abstract

A charged particle instrument system includes a charged particle instrument, an instrument housing, and a thermal conditioning system. The charged particle instrument includes a vacuum enclosure, a charged particle source disposed within the vacuum enclosure, and a magnetic assembly. The charged particle source is configured to generate a charged particle beam that propagates along an axis and interacts with a specimen. A magnetic assembly is disposed within the vacuum enclosure and is configured to direct the charged particle beam toward the specimen. The instrument housing defines an interior volume and is configured to receive at least a portion of a charged particle instrument therein. The thermal conditioning system includes a temperature conditioner in thermal communication with the charged particle instrument to adjust a temperature of the charged particle instrument and in thermal communication with the instrument enclosure to adjust a temperature of air within the interior volume of the enclosure.

Description

Background Art

[0001] The present disclosure relates to a charged particle instrument, such as a transmission electron microscope (TEM), a scanning transmission electron microscope (STEM), a scanning electron microscope (SEM), and / or a focused ion beam (FIB) instrument, etc. The instrument typically has a specimen chamber in which the specimen is disposed during an operation (e.g., imaging, milling, etc.). Charged particles (such as electrons) are directed to the specimen to perform an operation on the specimen. The performance of the instrument may be affected by the environment in which the instrument is located. Summary of the invention

[0002] Charged particle instruments are highly sensitive, and the performance of the instrument may be affected by environmental aspects. For example, ambient noise and temperature fluctuations near the instrument may affect the instrument. Most instruments are located in a conditioning room to control temperature and ambient noise. However, accurately regulating the temperature of the entire room can be expensive. Therefore, the present disclosure provides a structure for reducing the effects of temperature fluctuations on charged particle instruments, thereby allowing for relaxation of room temperature control requirements and / or improving the performance of charged particle instruments.

[0003] In one embodiment, a charged particle instrument system includes a charged particle instrument, an instrument housing, and a thermal regulation system. The charged particle instrument includes a vacuum housing and a charged particle source disposed within the vacuum housing. The charged particle source is configured to generate a charged particle beam that propagates along an axis and interacts with a sample. The instrument housing defines an internal volume and is configured to receive at least a portion of the charged particle instrument therein. The thermal regulation system includes a temperature regulator that is thermally connected to the charged particle instrument to adjust the temperature of the charged particle instrument and is thermally connected to the instrument housing to adjust the temperature of air within the internal volume of the instrument housing.

[0004] In another embodiment, a charged particle instrument system includes a charged particle instrument, an instrument housing configured to receive at least a portion of the charged particle instrument, and a thermal regulation system. The charged particle instrument includes a vacuum housing, a charged particle source disposed in the vacuum housing, a magnetic assembly disposed in the vacuum housing, and a controller operably coupled to the charged particle source and the magnetic assembly. The charged particle source is configured to generate a charged particle beam that propagates along an axis and interacts with a sample. The magnetic assembly is configured to guide the charged particle beam toward the sample. The instrument housing includes a plurality of surfaces that define a closed internal volume and are configured to reduce the effects of ambient noise on the charged particle instrument. The thermal regulation system is configured to adjust the temperature of the magnetic assembly and adjust the temperature of the air in the instrument housing.

[0005] In yet another embodiment, an instrument housing for use with a charged particle instrument having a thermal regulation system includes a plurality of surfaces defining an interior volume of the instrument housing, the interior volume being configured to receive at least a portion of the instrument therein. A heat exchanger is disposed within the interior volume. The heat exchanger is configured to be fluidically coupled to the thermal regulation system of the charged particle instrument such that the thermal regulation system of the charged particle instrument is configured to adjust the temperature of air within the interior volume.

[0006] Other aspects of the disclosure will become apparent by consideration of the detailed description and accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 A longitudinal cross-sectional elevation view of a charged particle microscope according to an embodiment of the present disclosure is schematically shown.

[0008] Figure 2 It is limited Figure 1 Shown is an enlarged and more detailed view of the magnetic components of the specimen chamber of a charged particle microscope.

[0009] Figure 3 A charged particle instrument system according to an embodiment of the present disclosure is schematically shown.

[0010] Figure 4 An instrument housing according to an embodiment of the present disclosure is shown.

[0011] Figure 5A A thermal circuit according to an embodiment of the present disclosure is schematically shown.

[0012] Figure 5B A thermal circuit according to another embodiment of the present disclosure is schematically shown.

[0013] Fig. 6A is a graph showing the measurement results of the instrument housing adjustment with the heat exchanger turned off.

[0014] Figure 6B is a graph showing the measurement results of the instrument housing adjustment with the heat exchanger turned on.

[0015] Figure 7 is a graph showing the modeled transfer function between room air temperature and enclosure air temperature.

[0016] Fig. 8A is a graph showing measured temperature over time with the heat exchanger turned off.

[0017] Figure 8B is a graph showing measured temperature over time with the heat exchanger turned on. DETAILED DESCRIPTION

[0018] Before explaining any embodiments of the present disclosure in detail, it should be understood that the present disclosure is not limited in its application to the details of construction and arrangement of components set forth in the following description or shown in the following drawings. The present disclosure is capable of other embodiments and can be practiced or carried out in various ways.

[0019] Some instruments, such as charged particle instruments, are sensitive to changes in the environment of the instrument. This sensitivity is also known as background drift. One source of background drift is changes in the ambient air temperature, and achieving background drift requirements can be difficult. Sensitivity to changes in ambient air temperature can be reduced by using an enclosure in which the instrument is positioned. The enclosure acts as a low-pass filter to reduce the effects of temperature changes. However, even using an enclosure cannot always meet background drift requirements.

[0020] Such instruments typically include a cooling system that circulates water to cool the instrument during operation. The cooling water has a much higher temperature stability than a typical room (e.g., the ambient environment) in which the instrument is located. Therefore, it is desirable to better couple the air in the housing and the cooling water by conditioning the air in the housing. The basic principle is to implement passive conditioning of the air in the housing by installing a heat exchanger (such as a fin-tube heat exchanger) in the housing (e.g., on the inner wall of the housing or in the housing air). The heat exchanger has a significant surface area in contact with the housing air and is coupled to the existing cooling water system. Therefore, additional thermal coupling is generated between the housing air and the cooling water system, thereby improving the effectiveness of the housing as a low-pass filter by reducing the DC gain between the ambient air temperature and the housing air temperature.

[0021] The stability of the air temperature within the enclosure can be further improved by actively controlling the temperature of the air. Active control can be achieved by adding an inline water heater to the water supply to the heat exchanger. The heater can raise the water temperature to provide a control margin. A temperature sensor is positioned to sense the enclosure air, and the water temperature can be controlled so that the temperature of the enclosure air is further stabilized.

[0022] Improving housing temperature stability has a positive impact on drift as well as other areas of instrument performance such as corrector astigmatism, monochromator drift, and coma drift. Additionally, cooling the housing air provides the benefit of additional cooling of the microscope. Cooling of the microscope can reduce drift after inserting a sample into the microscope because the cooled microscope is closer in temperature to the sample.

[0023] Figure 1is a highly schematic depiction of an embodiment of a charged particle instrument, shown as a microscope M, with which the present disclosure may be implemented; more specifically, it shows an embodiment of a transmission-type microscope M, which in this case is a TEM / STEM, but may include any other type of electron-based microscope, or an ion-based microscope, a proton-based microscope, or any other type of charged particle microscope, charged particle milling instrument, etc. Figure 1 In the embodiment of the present invention, within a vacuum housing 2, an electron source 4 (which may generally be referred to herein as a charged particle source) generates an electron beam B, which propagates along an optical axis B' (which may generally be referred to herein as a charged particle beam axis) and passes through an optical illuminator 6 for guiding / focusing the electrons (or other charged particles) onto a selected portion of a sample S (which may, for example, be (locally) thinned / flattened). A deflector 8 is also depicted, which may (among other things) be used to achieve a scanning motion of the beam B. Although a transmission electron microscope M is described in detail herein, the present disclosure is applicable to any type of charged particle instrument M. The charged particle instrument M may include other types of charged particle microscopes or milling instruments, such as a scanning electron microscope (SEM), a focused ion beam (FIB), etc. Therefore, the beam B may be an ion beam, a proton beam, or any other type of charged particles.

[0024] The sample S is held on a sample holder H which can be positioned with multiple degrees of freedom by a positioning device / stage A which moves a carriage A' to which the sample holder H is (removably) attached; for example, the sample holder H may include fingers that can be moved (especially) in the XY plane (see the depicted Cartesian coordinate system; in general, movements parallel to Z and tilting about X / Y will also be possible). Such movement allows different parts of the sample S to be irradiated / imaged / inspected by an electron beam B traveling along an optical axis B' (in the Z direction) (and / or allows scanning movements to be performed as an alternative to beam scanning). If desired, an optional cooling device (not depicted) can be brought into close thermal contact with the sample holder H, for example to maintain the sample holder (and the sample S thereon) at a cryogenic temperature.

[0025] The electron beam B will interact with the specimen S in such a way that various types of "stimulated" radiation will be emitted from the specimen S, including (for example) secondary electrons, backscattered electrons, X-rays and optical radiation (cathodoluminescence). If desired, one or more of these radiation types can be detected with the aid of an analysis device 22, which can be, for example, a combined scintillator / photomultiplier tube or an EDX (energy dispersive X-ray spectroscopy) module. In this case, images can be constructed using essentially the same principles as in a scanning electron microscope (SEM). However, alternatively or in addition, one can study electrons that pass through (through) the specimen S, exit / emit from the specimen and continue to propagate along the optical axis B' (essentially, although usually with some deflection / scattering). This transmitted electron flux enters an imaging system (projection lens) 24, which will typically include various electrostatic / magnetic lenses, deflectors, correctors (such as an stigmator), etc. In normal (non-scanning) TEM mode, the imaging system 24 may focus the transmitted electron flux onto a phosphor screen 26, which may be retracted / withdrawn (as schematically indicated by arrow 26') if necessary so as to keep it away from the optical axis B'. An image (or diffraction pattern) of (a portion of) the specimen S will be formed on the screen 26 by the imaging system 24, and this may be viewed through a viewing port 28 located in a suitable portion of the wall of the vacuum enclosure 2. In some embodiments, the viewing port 28 may be located away from the wall of the vacuum enclosure 2. The retraction mechanism of the screen 26 may, for example, be mechanical and / or electrical in nature, and is not depicted here.

[0026] As an alternative to viewing the image on screen 26, one can instead exploit the fact that the depth of focus of the electron flux leaving the imaging system 24 is typically large (e.g., about 1 meter). Thus, various other types of analysis / sensing devices, such as TEM camera 30, STEM camera 32, and / or spectroscopic equipment 34, can be used downstream of screen 26.

[0027] At the TEM camera 30, the electron flux may form a static image (or diffraction pattern) which may be processed by the controller 20 (which may include a processor, memory, and inputs and outputs) and displayed, for example, on a display device (not depicted), such as a flat panel display. When not needed, the TEM camera 30 may be retracted / withdrawn (as schematically indicated by arrow 30') so as to keep it away from the optical axis B'.

[0028] The output from the STEM camera 32 can be recorded as a function of the (X,Y) scanning position of the beam B on the specimen S, and an image can be constructed that is a "map" of the output from the STEM camera 32 as a function of X,Y. The STEM camera 32 may include a single pixel having a diameter (e.g., 20 mm or any other suitable diameter), as opposed to the matrix of pixels characteristically present in the TEM camera 30. In addition, the STEM camera 32 will typically have a higher speed than the TEM camera 30 (e.g., 10 pixels per second). 2 images) at much higher acquisition rates (e.g., 10 6 Again, when not needed, the STEM camera 32 may be retracted / withdrawn (as schematically indicated by arrow 32') so as to keep it clear of the optical axis B' (although such retraction is not necessary where the STEM camera 32 is embodied as, for example, a donut-shaped annular dark field camera; in such cameras, the central aperture would allow flux to pass when the camera is not in use).

[0029] As an alternative (in addition) to imaging using the TEM camera 30 and the STEM camera 32 , one may also call upon a spectroscopic device 34 , which may be, for example, an electron energy loss spectroscopy (EELS) module.

[0030] It should be noted that the order / position of items 30 , 32 and 34 is not critical and many possible variations are envisaged. For example, the spectroscopic device 34 may also be integrated into the imaging system 24 .

[0031] It should be noted that the controller 20 is connected to the various components shown via control lines (buses) 20'. This controller 20 can provide a variety of functions, such as synchronizing actions, providing set points, processing signals, performing calculations, and displaying messages / information on a display device (not depicted). Needless to say, the (schematically depicted) controller 20 can be (partially) located inside or outside the vacuum housing 2 and can have an integral or composite structure as desired.

[0032] The skilled person will appreciate that the interior of the vacuum enclosure 2 need not be kept under a strict vacuum; for example, in a so-called "ambient TEM / STEM", a background atmosphere of a given gas is intentionally introduced / maintained within the vacuum enclosure 2. The skilled person will also appreciate that, in practice, it may be advantageous to limit the volume of the vacuum enclosure 2 so that, where possible, it substantially surrounds the optical axis B', taking the form of a small tube (e.g., of about 1 cm in diameter) through which the employed electron beam passes, but widened to accommodate structures such as the source 4, the sample holder H, the screen 26, the TEM camera 30, the STEM camera 32, the spectroscopic equipment 34, etc.

[0033] The microscope M may include a retractable X-ray CT module 40, which can be advanced / retracted by means of a positioning system 42 in order to place / remove it in the path of the beam B (see arrow 44). In the particular configuration shown here, the module 40 includes a fork-like frame on which are mounted: a target T and an X-ray detector D. The target T is arranged above the plane of the sample S. The X-ray detector D is arranged below the plane of the sample S.

[0034] The microscope M also includes a magnetic assembly 50 defining a sample chamber 52 (which may also be referred to herein as a vacuum chamber 52). The magnetic assembly 50 is disposed between the optical illuminator 6 and the imaging system 24 in the direction of the optical axis B'. (For example, the upper end of the magnetic assembly 50 may be the lower end of the optical illuminator 6, and the lower end of the magnetic assembly 50 may be the beginning of the imaging system 24.) The sample holder H is in an imaging position (at Figure 2 ) is received in the sample chamber 52. The imaging position is the position where the sample S is imaged. The electron beam B intersects the sample S at the imaging position. The optical axis B' passes through the magnetic assembly 50. The optical axis B' may be aligned with the center of the magnetic assembly 50 or close to the center of the magnetic assembly 50.

[0035] In some examples, magnetic assembly 50 may overlap with either or both of illuminator 6 and imaging system 24. For example, one or more lenses of the illuminator may be positioned in magnetic assembly 50 for directing a charged particle beam toward a specimen.

[0036] like Figure 2As best shown in , the magnetic assembly 50 includes any number of pieces of magnetic material arranged to shape the magnetic field and direct the flux, the pieces of magnetic material forming a yoke 59. For example, as shown, the yoke 59 includes a first pole piece 56, a second pole piece 58, a yoke housing 60, a first yoke plate 62, and a second yoke plate 64, each of which includes a magnetic material of relatively high magnetic permeability (compared to its surroundings, such as air) that concentrates the magnetic field lines 61 into one or more magnetic circuits (closed loops). The magnetic field lines 61 guide the electron beam B (or another charged particle beam) along the optical axis B' at the specimen S. For example, the magnetic material may include iron, nickel-iron alloy, cobalt-iron alloy, or any combination thereof. Other magnetic materials may also be used. The choice of material depends primarily on its maximum magnetic saturation and its remanence. Different pieces of the yoke 59 may be formed of different magnetic materials or the same magnetic material as desired. The pieces of the yoke 59 may be integrated (in any combination) into fewer monolithic components. For example, the yoke housing 60 can be integrated with one or both of the first yoke plate 62 and the second yoke plate 64 (e.g., formed as one piece); the first pole piece 56 and / or the second pole piece 58 can be integrated with one or both of the first yoke plate 62 and the second yoke plate 64; etc. Any one or more of the pieces of the yoke 59 can also be separated (in any combination) into more single-piece components. For example, any of the pieces of the yoke 59 can be formed from two separate pieces or more separate pieces.

[0037] The magnetic assembly 50 also includes at least one coil 54 . Figure 2 One coil 54 is shown in the figure, however any number of coils 54 may be used, such as two, three, four or more. In the charged particle microscope M, the charged particles are focused by an electric field or a magnetic field. In the embodiment shown, a magnetic field is used. The coil 54 carries a wire winding that is rotationally symmetrically positioned around the optical axis B' of the microscope M. The coil 54 is excited by a current of, for example, several amperes. As will be described in more detail herein, cooling of the coil 54 is used. When excited, the coil 54 generates a strong magnetic field in the axial direction (i.e., coaxially parallel to the optical axis B') on the optical axis B' of the microscope M. Since the magnetic field is non-divergent, it inherently has a component in the radial direction (i.e., perpendicular to the optical axis B'). These radial components grow linearly with the distance to the optical axis B', and their net effect is that the charged particles are deflected toward the optical axis B', which is linearly proportional to the distance of these particles to the optical axis B'. Therefore, this magnetic field acts as a circular focusing lens. The focusing strength of the magnetic lens is proportional to the sum of the square of the axial magnetic field and the length of the axial magnetic field (as measured along the optical axis B'). Therefore, in order to obtain a magnetic lens (i.e., to produce a lens effect), the magnetic field is concentrated in a small area on the optical axis B' by the yoke 59 around the coil 54 to direct and focus its magnetic flux to an imaging position on the optical axis B'. The imaging position can be only a few millimeters in length.

[0038] Thus, the magnetic assembly 50 at least partially contributes to providing desired magnetic conditions at the specimen S (and thus at the specimen holder H in the imaging position), sometimes in combination with other components external to the magnetic assembly 50. The concentrated magnetic field lines 61 in the magnetic material (and in particular the outermost portions of the concentrated magnetic field lines 61) define a specimen chamber volume 66 in which the specimen holder H is disposed in the imaging position.

[0039] The accuracy of the microscope M described herein may be negatively affected by, among other things, ambient noise and temperature fluctuations. Therefore, the present disclosure provides an instrument system 100 that is intended to counteract temperature fluctuations and / or ambient noise in the room in which the microscope M is located. Figure 3 is a schematic diagram illustrating an instrument system 100. The instrument system 100 includes a microscope M (or another charged particle instrument), a thermal regulation system 104 coupled to the microscope M, and an instrument housing 108 in which the microscope M is disposed. The thermal regulation system 104 provides temperature regulation (e.g., cooling) for the microscope M, and in the illustrated embodiment, the thermal regulation system 104 is operably coupled to the instrument housing 108 to provide thermal regulation to adjust (e.g., stabilize) the temperature of air within the instrument housing 108.

[0040] refer to Figure 3 5, the thermal regulation system 104 includes a thermal loop 116 that circulates a working fluid, such as water or a water-glycol solution, to adjust the temperature of the air within the microscope M and the instrument housing 108. The thermal regulation system 104 includes a temperature regulator, such as a cooler 112, which can be disposed outside the instrument housing 108. When the working fluid circulates through the cooler 112, the cooler 112 can operate to adjust the temperature of the working fluid. The thermal loop 116 thermally couples the cooler 112 to the microscope M. The working fluid can be circulated to adjust the temperature of various components of the microscope M. In the illustrated embodiment, the thermal loop 116 is thermally connected to the magnetic assembly 50, and more particularly to the coil 54, to inhibit overheating of the magnetic assembly 50 during operation of the microscope M and provide temperature stability to the microscope M (e.g., minimize drift due to room temperature changes). In other words, the magnetic assembly 50 is cooled by the thermal regulation system 104. The thermal loop 116 can also be thermally connected to the controller 20 to adjust the temperature of the electronic components within the controller 20 (e.g., cooling). The thermal circuit 116 may also be thermally connected to other components of the microscope M (such as the electron source 4), depending on the need to adjust the temperature of the components (eg, cool them) during operation of the microscope M.

[0041] In the illustrated embodiment, the cooler 112 may operate under the principle of a vapor compression cycle or any other suitable thermodynamic process configured to remove heat from the thermal loop 116 and discharge the heat to any place outside the housing 108. Therefore, in one example, the cooler 112 may include a compressor, a condenser, an expansion valve, and an evaporator (not shown) configured in a loop according to the known principles of the vapor compression cycle. In this example, the evaporator (not shown) is in thermal contact with the thermal loop 116 to cool the working fluid in the thermal loop 116 when the working fluid is thermally connected to the cooler 112 and circulates through the cooler 112. In addition, the thermal regulation system 104 may include a pump (not shown) to circulate the working fluid around the thermal loop 116. In other examples, the cooler 112 may have any other suitable components for removing heat from the thermal loop 116 and discharging the heat to any place outside the housing 108. Therefore, when the working fluid circulates through the cooler 112, the cooler 112 can operate to extract heat out of the working fluid. In this embodiment, the thermal regulation system 104 is operable to cool both the microscope M and the air within the housing 108. In another embodiment, the temperature regulator of the thermal regulation system 104 may additionally or alternatively include a heater 114. The heater 114 introduces heat into the working fluid to adjust the temperature of the air within the housing 108, thereby adjusting (e.g., stabilizing) the temperature of the air within the instrument housing 108. The heater 114 may be actively controlled (e.g., by the controller 20) to adjust the temperature of the air within the instrument housing 108. For example, the heater 114 may introduce heat into the working fluid to increase the temperature of the working fluid. In one example, the temperature of the working fluid may be increased to above the temperature of the air within the housing 108 to heat the air. However, in another example, the temperature of the working fluid may be maintained below the temperature of the air within the housing 108. In this embodiment, heating the working fluid provides a control margin while still utilizing the working fluid to cool the temperature of the air within the housing 108. Therefore, the amount of cooling of the temperature of the air within the housing 108 may be controlled by controlling the amount of heat added to the working fluid.

[0042] In the illustrated embodiment, the thermal regulation system 104 is a passive system. Therefore, the cooler 112 is not actively controlled to remove (or introduce) the desired amount of heat from the working fluid. The thermal regulation system 104 is independent of the temperature of the microscope M or the temperature of the air in the instrument housing 108. However, in other embodiments, the thermal regulation system 104 can be actively controlled. In such an embodiment, the thermal regulation system 104 can further include one or more temperature sensors to detect the temperature of the air, microscope M, or working fluid in the instrument housing 108. Such a thermal regulation system 104 may also include a controller (e.g., controller 20 or a separate dedicated controller) or communicate with the controller to adjust the cooling rate or set temperature of the cooler 112 to achieve the desired temperature of the air or microscope M in the instrument housing 108. It should be understood that passive control or active control can be applied to a thermal regulation system that implements refrigeration or heating. Therefore, the thermal regulation system 104 may include any combination of a passively controlled refrigeration system, a passively controlled heating system, an actively controlled refrigeration system, and / or an actively controlled heating system.

[0043] Continue to refer Figure 3 and Figure 4, the instrument housing 108 defines an interior volume 120, in which the microscope M is disposed. More specifically, the vacuum housing 2 of the microscope M is disposed within the interior volume 120. The instrument housing 108 includes a front surface 124, a rear surface 128 opposite the front surface 124, a first side surface 132 extending between the front and rear surfaces 124, 128, a second side surface 136 opposite the first side surface 132, and an upper surface 140 coupled to the upper surfaces 124, 128, 132, 136 of the front, rear, and side surfaces. The instrument housing 108 of the illustrated embodiment has a height of approximately 3.5 meters measured between the upper surface 140 and the floor, and the instrument housing defines a floor area of ​​approximately 1.5 meters by 1.5 meters. In other embodiments, the height may be 2.0 meters to 4.0 meters, or may be 3.0 meters to 4.0 meters, or may be at least 2.0 meters, or may be at least 3.0 meters. The floor area may be at least 1.0 meter by 1.0 meter. Thus, the enclosed volume (i.e., height multiplied by floor area) may be between 2.0 m^3 and 9.0 m^3, or more specifically between 4.0 m^3 and 9.0 m^3, or more specifically between 5.0 m^3 and 9.0 m^3, or more specifically between 6.0 m^3 and 9.0 m^3, or more specifically between 7.0 m^3 and 8.0 m^3, or may be 9.0 m^3 or less. In some embodiments, the instrument housing 108 includes a lower surface (not shown) opposite to the upper surface 104, which defines a floor area. In other embodiments, the instrument housing 108 may include more or less surfaces, depending on the desired shape of the instrument housing 108. The size of the internal volume 120 of the instrument housing 108 is set to accommodate the microscope M (e.g., the vacuum housing 2). In some embodiments, it may be desirable that the internal volume 120 is only slightly larger than the microscope M to reduce the total footprint of the instrument system 100. Reducing the volume of the interior volume 120 reduces the amount of air conditioned by the thermal conditioning system 104, which can result in a higher efficiency in conditioning the air temperature. The instrument system 100 (i.e., including the instrument housing 108) can be positioned within a room in which the microscope M is to be used. In some embodiments, the instrument housing 108 can be formed of or include a sound damping material, such as open cell insulation, foam insulation, rock wool, or glass wool. Thus, the instrument housing 108 operates as a sound-reducing acoustic enclosure and reduces the effects of ambient noise on the microscope M during operation.

[0044] In the illustrated embodiment, at least one heat exchanger 144 is disposed within the instrument housing 108 and is in thermal communication with the thermal conditioning system 104 such that the thermal conditioning system 104 can adjust (e.g., cool or heat) the temperature of the air within the interior volume 120 of the instrument housing 108. In some embodiments, the heat exchanger 144 is coupled to a wall of the housing 108 to adjust (e.g., cool or heat) the temperature of the housing 108. In the illustrated embodiment, the heat exchanger 144 is a fin tube heat exchanger. The fin tube heat exchanger 144 of the illustrated embodiment may include 34 tubes having a diameter of 20 mm and a length of 1800 mm, thereby providing a 3.8 m 2 The total surface area of ​​the fin tube heat exchanger 144 can have a convective heat transfer coefficient of 5W / m2 / K and the ability to absorb 114W. In other embodiments, the heat exchanger 144 can be a plate heat exchanger, a plate-fin heat exchanger, or other type of heat exchanger capable of being thermally connected to the air. The instrument housing 108 of the illustrated embodiment includes a plurality of heat exchangers 144, but any number of heat exchangers 144 can be used. A plurality of heat exchangers 144 are supported within the interior volume 120 of the instrument housing 108. More particularly, the heat exchanger 144 can be coupled to the side surfaces 132, 136 of the instrument housing 108, but any position in thermal contact with the air in the interior volume 120 is possible. Each of the plurality of heat exchangers 144 is fluidly coupled to the thermal circuit 116. Therefore, the circulation of the working fluid in the thermal circuit 116 adjusts the temperature of the heat exchanger 144, which in turn adjusts the temperature of the air within the interior volume 120. The number and / or size of the heat exchangers 144 may be selected based on the amount of cooling desired within the instrument housing 108. For example, the instrument housing 108 may also include heat exchangers 144 coupled to the rear surface 128, the upper surface 140, and / or the front surface 124 of the instrument housing 108. Furthermore, depending on the size of the heat exchangers, the instrument housing 108 may include multiple heat exchangers 144 coupled to a single surface.

[0045] The thermal conditioning system 104 described above may utilize a plurality of heat exchangers 144 to cool the air within the instrument housing 108. In some embodiments, the plurality of heat exchangers 144 may directly cool the instrument housing 108, such as the side surfaces 132, 136 of the instrument housing 108 (as compared to cooling only the air within the instrument housing 108). In such an embodiment, the side surfaces 132, 136 of the instrument housing 108 may be in thermal communication with the heat exchangers 144 and / or may be fluidly coupled to the thermal loop 116 to function as a heat exchanger. The effects of room temperature changes are reduced before the air within the instrument housing 108 is affected by directly cooling the side surfaces 132, 136 of the instrument housing 108. In yet another embodiment, the instrument housing 108 may be heated via the heater 114 to allow the temperature of the air within the instrument housing 108 to be adjusted. As previously described, the heater 114 may heat the working fluid to allow the temperature of the working fluid to be controlled while maintaining the temperature of the working fluid below the temperature of the air within the instrument housing 108. Alternatively, the heater 114 may heat the working fluid to a point where the temperature of the air within the instrument housing is increased. If the heater 114 is utilized, the heat exchanger 144 may be coupled to the side surfaces 132, 136 to adjust the temperature of the instrument housing 108 and / or may be supported so as to be in thermal communication with the air inside the instrument housing 108. Finally, in yet another embodiment, the instrument housing 108 may be designed so that a natural air flow circulates within the instrument housing 108 to uniformize the temperature of the air within the instrument housing. The instrument housing may also include an air flow generator (not shown), such as a fan, to circulate air within the instrument housing 108 to uniformize the temperature of the air.

[0046] Reference now Figure 5A and Figure 5B , the thermal loop 116 of the thermal regulation system 104 will be described in more detail. The thermal loop 116 thermally couples the cooler 112 to both the microscope M and the heat exchanger 144 within the instrument housing 108. In one embodiment, the microscope M and the heat exchanger 144 are arranged in parallel within the thermal loop 116 ( Figure 5A ). In other words, the flow of the working fluid is split between the microscope M and the heat exchanger 144 to adjust the temperature of the microscope M and the temperature of the heat exchanger 144 simultaneously. In some embodiments, the flow of the working fluid through the microscope M and through the heat exchanger 144 can be controlled independently of each other. In another embodiment, the microscope M and the heat exchanger 144 are arranged in series within the thermal circuit 116 so that the temperature of the microscope M is adjusted before the temperature of the heat exchanger 144, or vice versa ( Figure 5B). The heat exchanger 144 and the microscope M can have any position relative to each other within the thermal circuit 116, as long as the heat exchanger 144 and the microscope M are cooled by the same cooler 112. In other embodiments, a cooler for the microscope M and a separate cooler for the heat exchanger 144 can be used.

[0047] In operation, the instrument system 100 reduces the effects of temperature fluctuations (such as temperature fluctuations within the room in which the microscope M is used) on the accuracy of the microscope M. Because the microscope M is located within the instrument housing 108, the thermal regulation system 104 only needs to adjust the temperature of a relatively small volume of air within the interior volume 120 (e.g., rather than a much larger volume of air within the room). Therefore, the requirements for the stability of the air temperature within the room itself can be relaxed.

[0048] refer to Fig. 6A and Figure 6B , cooling or heating the air within the instrument housing 108 adjusts (e.g., stabilizes) the air surrounding the microscope M, so that fluctuations in the air temperature inside the instrument housing 108 are reduced, and fluctuations in the air temperature outside the instrument housing 108 are less likely to affect the performance of the microscope M. Fig. 6A 1 is a graph of temperature differences over time without using the heat exchanger 144. The graph includes a first curve P1 showing the room air temperature and a second curve P2 showing the air temperature within the instrument housing 108. When the room temperature increases, the temperature of the air within the instrument housing 108 also increases, but remains lower than the room temperature. Fig. 6A The second curve P2 further shows that the air temperature within the instrument housing 108 continues to increase over time, which will continue to affect the performance of the microscope M. Figure 6B 1 is a graph of temperature differences over time when the heat exchanger 144 is used to condition (e.g., cool) the air within the instrument housing 108. The graph also includes a first curve P1 showing the room air temperature and a second curve P2 showing the air temperature within the instrument housing 108. When the room temperature increases, the air temperature within the instrument housing 108 also increases, but is lower than the temperature without the heat exchanger 144. Fig. 6A Differently, when heat exchanger 144 is used, the air in instrument housing 108 also reaches a steady state. Fig. 6A and Figure 6B , use of the heat exchanger 144 shows a 7% improvement in DC gain based on temperature and a 22% improvement in DC gain based on heat load.

[0049] Figure 7A graph of the modeled transfer function between the air temperature in the room and the air temperature in the instrument housing is shown. Curve P3 shows the transfer function without the use of the heat exchanger 144 and represents a DC gain of 0.5. Curve P4 shows the transfer function with the use of the heat exchanger 144 and represents a DC gain of 0.32. Curve P5 shows the transfer function of the housing wall and represents a DC gain of 0.06. Therefore, when considering the transfer function from the room air temperature to the housing air temperature with and without the heat exchanger 144, the DC gain can be reduced by a factor of 1.6. This means that the air inside the housing 108 has become 1.6 times less sensitive to temperature changes than the air in the room. The modeled best improvement in performance is obtained by directly cooling the side surfaces 132, 136 of the instrument housing 108, which results in a modeled DC gain that can be reduced by a factor of 8. When the side surfaces 132, 136 of the instrument housing 108 are directly cooled, the disturbance (i.e., the changing room temperature) is reduced before the housing air is affected by it. Significant improvements in DC gain can also be obtained using other cooling methods. The system described herein can provide an improvement in DC gain of between 20% and 50%, and more particularly 36% as tested. If the area of ​​the heat exchanger 144 is twice the area resulting in a 36% improvement, the DC gain can be improved by 54%. The improvement in stability based on DC gain also results in an improvement in the accuracy of the microscope M to achieve a background drift specification of a maximum of 0.5nm / min. For a temperature fluctuation of 0.4 degrees, the background drift of the system described herein in various embodiments is 0.35nm / min, compared to 0.8nm / min without the system. Adjustment can also include reducing the time it takes to reach a steady-state air temperature within the instrument housing 108 after the microscope M is turned on. In an embodiment where the instrument housing 108 includes sound damping material, the accuracy of the microscope M is further improved because ambient noise is less likely to affect the microscope M.

[0050] Fig. 8A and Figure 8B Measured temperature results are shown for the magnetic assembly 50, the air within the instrument housing 108, the room air temperature, and the cooling inlet of the objective lens. Fig. 8A shows measurements made without the use of heat exchanger 144, and Figure 8B Measurements taken with the heat exchanger 144 are shown. As shown by curves P6a and P6b, the use of the heat exchanger 144 reduced the temperature of the magnetic assembly 50 by approximately 0.9 degrees Celsius. As shown by comparing curves P7a and P7b, the use of the heat exchanger 144 also reduced the temperature of the air within the instrument housing 108 by approximately 2.5 degrees Celsius. As shown by curves P8a / P8b and P9a / P9b, respectively, the temperature of the room air and the cooling inlet of the objective lens did not experience significant changes.

[0051] In some embodiments, the instrument housing 108 is manufactured and / or sold separately from the microscope M and the thermal regulation system 104. The instrument housing 108 includes a heat exchanger 144 and can be retrofitted to the microscope M and the thermal regulation system 104. The retrofit may include fluidly coupling the heat exchanger 144 to the thermal loop 116. After the retrofit, the microscope M is received within the instrument housing 108, and the heat exchanger 144 is thermally connected to the thermal regulation system 104. In such an embodiment, the instrument housing 108 may or may not include sound damping material. However, the instrument housing 108 is thermally coupled to the existing thermal loop 116 of the microscope.

[0052] Thus, the present disclosure provides, among other things, a charged particle microscope M having a thermal circuit 116 for cooling the microscope M and stabilizing the temperature of air within an instrument housing 108 in which the microscope M is disposed. Various features and advantages of the present disclosure are set forth in the appended claims.

Claims

1. A charged particle instrument system, comprising: A charged particle instrument comprising vacuum housing, and a charged particle source disposed within the vacuum housing, The charged particle source is configured to generate a charged particle beam that propagates along the axis and interacts with the specimen; an instrument housing defining an interior volume, the instrument housing being configured to receive at least a portion of the charged particle instrument therein; and A thermal regulation system includes a temperature regulator in thermal communication with the charged particle instrument to regulate the temperature of the charged particle instrument and in thermal communication with the instrument housing to regulate the temperature of air within an interior volume of the instrument housing.

2. The charged particle instrument system of claim 1 , further comprising an electronic controller configured to control the operation of the charged particle instrument, wherein: The electronic controller is thermally coupled to the temperature regulator to be cooled by the temperature regulator.

3. The charged particle instrument system according to claim 1, wherein: The enclosure is an acoustic enclosure configured to reduce the effects of ambient noise on the charged particle instrument.

4. The charged particle instrument system according to claim 1, wherein: The thermal regulation system circulates a working fluid between the temperature regulator, a heat exchanger disposed within the instrument housing, and the charged particle instrument.

5. The charged particle instrument system according to claim 4, wherein: The thermal regulation system includes a controller configured to adjust a temperature of the working fluid based on a desired temperature of air within the instrument enclosure and a detected temperature of the air within the enclosure.

6. The charged particle instrument system according to claim 4, wherein: The working fluid is water.

7. The charged particle instrument system according to claim 4, wherein: The heat exchanger within the instrument housing includes a fin-tube heat exchanger.

8. A charged particle instrument system, comprising: A charged particle instrument, comprising: Vacuum housing, a charged particle source disposed within the vacuum housing, The charged particle source is configured to generate a charged particle beam that propagates along the axis and interacts with the specimen, a magnetic assembly disposed within the vacuum housing, the magnetic assembly being configured to direct the charged particle beam toward the sample, and a controller operably coupled to the charged particle source and the magnetic assembly; an instrument housing configured to receive at least a portion of the charged particle instrument, the instrument housing comprising a plurality of surfaces defining an enclosed interior volume of the instrument housing and configured to reduce the effects of ambient noise on the charged particle instrument; and A thermal regulation system is in thermal communication with the instrument housing and with the magnetic assembly, the thermal regulation system being configured to regulate a temperature of the magnetic assembly and to regulate a temperature of air within the instrument housing.

9. The charged particle instrument system according to claim 8, wherein: The thermal regulation system comprises: a cooler, the cooler being arranged outside the housing of the instrument, a working fluid configured to circulate within the thermal regulation system, and A heat exchanger is disposed within the instrument housing and is in thermal communication with the cooler.

10. The charged particle instrument system according to claim 9, wherein: The chiller is controlled independently of the temperature of the air within the instrument housing.

11. The charged particle instrument system according to claim 9, wherein: The heat exchanger disposed within the instrument housing includes a fin-tube heat exchanger.

12. The charged particle instrument system of claim 9, wherein: The heat exchanger is a first heat exchanger of a plurality of heat exchangers.

13. The charged particle instrument system of claim 9, wherein: The working fluid includes water.

14. The charged particle instrument system of claim 9, wherein: The heat exchanger disposed in the instrument housing is disposed outside the vacuum housing.

15. The charged particle instrument system of claim 9, wherein: The thermal regulation system defines a thermal circuit through which the working fluid flows between the cooler, the heat exchanger disposed in the instrument housing, and the magnetic assembly, and wherein the heat exchanger and the magnetic assembly disposed in the instrument housing are disposed in parallel within the thermal circuit.

16. The charged particle instrument system of claim 9, wherein: The instrument is a transmission microscope.

17. An instrument housing for use with a charged particle instrument having a thermal regulation system, the instrument housing comprising: a plurality of surfaces defining an interior volume of the instrument housing, the interior volume being configured to receive at least a portion of the instrument therein; and a heat exchanger disposed within the interior volume and in thermal communication with air in the interior volume, Wherein the heat exchanger is configured to be fluidly coupled to the thermal regulation system of the charged particle instrument such that the thermal regulation system of the charged particle instrument is configured to adjust the temperature of air within the internal volume.

18. The instrument housing according to claim 17, wherein: The heat exchanger comprises a fin-tube heat exchanger.

19. The instrument housing of claim 17, further comprising acoustic damping configured to reduce the effects of ambient noise on the charged particle instrument.

20. The instrument housing of claim 17, wherein: The instrument housing is retrofittable onto the charged particle instrument.

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